Content:
Presentation type:
SSS – Soil System Sciences

EGU24-11742 | ECS | Orals | SSS5.2 | Arne Richter Awards for Outstanding ECS Lecture

Digging into the Future: The transition between bedrock and soil as an underexplored frontier zone in geoscience 

Daniel Evans

Terrestrial environments and their ecosystems demand healthy, sustainable, and resilient soils. Over the past couple of decades, significant efforts have been made to safeguard global soils, yet the materials and resources responsible for soil formation have been widely overlooked.  The transition from bedrock to soil – a zone often described as ‘soil parent material’ – holds an exciting yet untapped potential for helping us address some of the largest environmental challenges, including climate change and the biodiversity crisis. In this award lecture, I will present a strand of my research programme ‘Building Tomorrow’s Soils’ which seeks to establish how soil parent materials enhance the sustainability, health, and resilience of soil systems. First, with a focus on carbon sequestration, I will highlight how the bedrock–soil transition zone has the potential to be a long-term store of organic carbon. I will then present research which shows that some soil parent materials release petrogenic (i.e. rock-derived) organic carbon into soils. These understudied inputs of organic carbon to soils are currently absent from most, if not all, soil carbon models, which threatens our ability to optimize soil carbon management in the long-term. Finally, I will argue that developing a mechanistic understanding about this transition zone – this underexplored material which is neither rock nor soil in structure and function, but a blend of both – requires a similarly cross-disciplinary approach.

How to cite: Evans, D.: Digging into the Future: The transition between bedrock and soil as an underexplored frontier zone in geoscience, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11742, https://doi.org/10.5194/egusphere-egu24-11742, 2024.

EGU24-12483 | Orals | MAL32-SSS | Philippe Duchaufour Medal Lecture

Beasts, Balances and Boundaries in Soil Science 

Jan Willem Van Groenigen

This is both an exciting and a challenging time to be a soil scientist. Societal interest in soil is thriving because of its pivotal role in food security, climate change, and biodiversity. But this interest comes with serious responsibilities, within the context of a scientific climate dominated by perverse incentives for funding and publishing. In this Philippe Duchaufour lecture I would like to reflect on some of the balances we should aim for, and the boundaries we should acknowledge, as soil scientists. I will do this for field of climate-related soil research; for the role of soil ecology in the transition towards sustainable agriculture; as well as for academic publishing.

The soil takes center stage in discussions regarding climate change mitigation. However, the focus is mostly on large-scale carbon sequestration (LSCS). There almost seems to be a dichotomy within the scientific community regarding the potential and desirability of LSCS, with exceedingly optimistic assessments finding their way to policy documents, and more critical publications on the limits or usefulness of LSCS apparently ignored. I will highlight some fundamental boundaries to large scale carbon sequestration, notably the amount of carbon available through photosynthesis. As a possible way forward, I will stress the importance of focusing on improving soil functioning rather than on increasing the carbon stock size.

The need for a transition towards more sustainable forms of agriculture while maintaining high productivity is broadly acknowledged within the scientific community. Such forms of agriculture should both include a high degree of circularity as well as a larger reliance on the benefits that soil biota provide. However, these two aspects are often not studied in relation to each other.  Earthworms provide an instructive case in this respect. It is clear that they are beneficial to crop growth – the literature even suggests an overall increase of 25% in crop yield in the presence of earthworms. Yet, this number is not realistic as many primary earthworm studies do not represent realistic systems. In particular, we should not claim that earthworms can compensate for the removal of nutrients through harvest. This can only be done through replenishment of nutrients from elsewhere – preferably in a circular manner. I will discuss how earthworms and other biota could positively affect nutrient recycling in future agricultural systems that will receive new, circular forms of soil amendments.  

Finally, scientific publishing is in crisis. Scientific articles are in many ways the basic building blocks of scientific careers, and yet the publishing process is overstretched and flawed. This is mostly related to imbalances: especially between those who pay and those who earn; and between those who write and those who review. I will highlight some of these imbalances, which are to some extend geographic, and will discuss to what extent switching to an open publishing model will resolve them. I will end with some thoughts on how to improve the publishing process, including a call for more cooperation between editors across journals to keep scientific publishing viable.

How to cite: Van Groenigen, J. W.: Beasts, Balances and Boundaries in Soil Science, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12483, https://doi.org/10.5194/egusphere-egu24-12483, 2024.

SSS0.1 – Inter- and Transdisciplinary Sessions

EGU24-180 | ECS | Orals | ITS1.23/SSS0.1.4

Developing a Rangeland Carbon Tracking and Monitoring System Using Remote Sensing Imagery Coupled With a Modeling Approach 

Yushu Xia, Jonathan Sanderman, Jennifer Watts, Megan Machmuller, Stephanie Ewing, Andrew Mullen, Charlotte Rivard, and Haydee Hernandez

Rangelands play a crucial role in providing various ecosystem services and have significant potential for carbon sequestration. However, monitoring soil organic carbon (SOC) stocks in rangelands is challenging due to the large size of ranches and the high spatial variability influenced by climate and management factors. To address these challenges, we have developed the Rangeland Carbon Tracking and Management (RCTM) system, which integrates remote sensing inputs, survey data sources, and both empirical and process-based SOC models. In this work, we will introduce the structure of RCTM v1.0, its data input requirements, data processing pipelines, and the resulting data outputs. Additionally, we will discuss the high-resolution soil moisture data layers, baseline SOC maps, and the targeted field sampling plan generated through an empirical digital soil mapping approach. The Bayesian calibration and validation scheme for obtaining grassland plant functional type (PFT)-specific parameters using flux tower network data will also be explained. After calibration, the RCTM system generated estimates of rangeland carbon fluxes across PFTs (R2 between 0.6 and 0.7) and surface depth SOC stocks (R2 = 0.6) with moderate accuracy at the regional scale. The visualization of modeling results associated with long-term rangeland C dynamics at different scales will be demonstrated using the Google Earth Engine platform to inform management decisions and policymaking.

How to cite: Xia, Y., Sanderman, J., Watts, J., Machmuller, M., Ewing, S., Mullen, A., Rivard, C., and Hernandez, H.: Developing a Rangeland Carbon Tracking and Monitoring System Using Remote Sensing Imagery Coupled With a Modeling Approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-180, https://doi.org/10.5194/egusphere-egu24-180, 2024.

Soil erosion is a widespread environmental challenge with far-reaching implications for agricultural productivity, water quality and ecosystem health. Addressing this complex issue requires the use of modelling tools that empower diverse stakeholders, such as researchers and decision-makers, to simulate soil erosion systems under different scenarios. For these tools to be effective, not only they need to make good predictions, but they need to be accessible and educational, so users, regardless of their technical skills and modelling expertise, can understand and even more importantly, trust the model. In traditional soil erosion modelling, the primary emphasis to build trust is by demonstrating the model’s ability to replicate past observations, and less attention is given to build trust by providing an educational and exploratory experience. We introduce a project that aims at democratizing soil erosion modelling, making it more accessible and trustworthy to researchers, educators, decision-makers, and local communities. Leveraging the versatility and accessibility of Jupyter Notebooks, we are developing iMPACT-erosion, a soil erosion modelling toolbox to support education, land management and informed decision making. A series of dedicated Notebooks not only explain and simulate the main soil erosion processes but guides users through the main steps to enhance the credibility of the model results, i.e. sensitivity analysis, model calibration, uncertainty analysis, model evaluation and scenario analysis. The integration of interactive visualization enhances this experience by facilitating exploration of both the model configuration and the soil erosion system's response under different scenarios/decisions. This model development approach is not confined to the field of soil erosion and offers the potential to facilitate knowledge transfer and collaboration between model developers and decision makers in various domains.

How to cite: Peñuela, A.: Democratizing soil erosion modelling: A Jupyter Notebook approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1907, https://doi.org/10.5194/egusphere-egu24-1907, 2024.

EGU24-3186 | ECS | Orals | ITS1.23/SSS0.1.4

Prediction of soil phosphorus sorption capacity in agricultural soils using mid-infrared spectroscopy.  

Sifan Yang, Blánaid White, Fiona Regan, Nigel Kent, Rebecca Hall, Felipe de Santana, and Karen Daly

             Advice for phosphorus (P) fertilisation based on soil testing using extractive methods but does not consider P sorption processes. Traditional soil P sorption capacity examined from a Langmuir isotherm batch experimental design, which is time-consuming, labour intensive and expensive. Mid-infrared (MIR) spectroscopy is a rapid analysis technique that can potentially replace the extractive technique traditionally used in soil analysis. The objective of this work was to predict the isothermal parameter of P sorption maximum capacity (Smax, mg·kg-1) from MIR spectroscopy.

              This study created spectral libraries from benchtop (Bruker) and handheld (Agilent) MIR spectrometers by scanning samples in two particle sizes, < 0.100 mm (ball-milled) and < 2 mm. The four spectral libraries created used an archive of samples with a database of sorption parameters where soils were classified into low and high sorption capacities using a threshold value of Smax = 450.03 mg·kg-1. To assess the optimal algorithmic method with highest Smax prediction accuracy, regression models were based on the partial least squares (PLS) regression, Cubist, support vector machine (SVM) regression and random forest (RF) regression algorithms. After the first derivative Savitzky-Golay smoothing, Bruker spectroscopies with both soil particle sizes yielded ‘excellent models’, with SVM predicting Smax values with high accuracy (RPIQVal = 4.50 and 4.25 for the spectral libraries of the ball-milled and <2mm samples, respectively). In comparison, the Agilent handheld spectrometer produced spectra with more noise and less resolution than the Bruker benchtop spectrometer. Unlike Bruker, for Agilent MIR spectroscopy, more homogeneous samples after ball-milling resulted in a higher accurate Smax prediction. For Agilent spectroscopy of ball-milled samples, an ‘approximate quantitative model’ (RPIQVal = 2.74) was obtained from the raw spectra using the Cubist algorithm. However, for Agilent spectroscopy of < 2 mm samples, the best performing Cubist algorithm can only achieve a ‘fair model’ (RPIQVal = 2.23) with the potential to discriminate between high and low Smax values.

              The results suggest that the Bruker bench-top spectrometer can predict the Langmuir Smax value with high accuracy without the need to ball-mill samples, highlighting the availability of the MIR spectrometer as a rapid alternative method for understanding soil P sorption capacity. However, for handheld spectrometers, the Agilent instruments can only make approximate quantitative predictions of Smax for ball milled samples. For <2mm samples, Agilent can only be used to classify low and high sorption capacity soils.

How to cite: Yang, S., White, B., Regan, F., Kent, N., Hall, R., de Santana, F., and Daly, K.: Prediction of soil phosphorus sorption capacity in agricultural soils using mid-infrared spectroscopy. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3186, https://doi.org/10.5194/egusphere-egu24-3186, 2024.

This study employs the PHYGROW simulation model to assess the 40-year dynamics of arid grassland in Jordan, focusing on the Leaf Area Index (LAI) as a pivotal indicator of vegetation health. The observed results reveal a notable decline in LAI over the study period, with the highest recorded value in 2005 (2.27) and a subsequent reduction to 1.68 in 2021. Rigorous statistical analyses, including regression analysis, confirm the significance of this downward trend, prompting further investigation into potential contributing factors such as changes in climate, land use, and soil conditions.

 

Interannual variability analysis identifies specific years marked by noteworthy LAI fluctuations, providing insights into the dynamic responses of the arid grassland ecosystem. Comparison with concurrent climate data underscores the intricate relationship between LAI trends and environmental variables. The study emphasizes the importance of continuous monitoring and understanding the underlying drivers of vegetation dynamics in arid regions.

The observed decrease in LAI holds implications for the overall health and resilience of the ecosystem, highlighting the need for informed decision-making in sustainable land management practices. These findings contribute significantly to the broader understanding of arid land dynamics, guiding future research and collaborative efforts with experts in related fields. Such collaborations are essential for enhancing the robustness and applicability of the results, ultimately informing conservation and resource management strategies tailored to the unique challenges of arid environments.

How to cite: Alhamad, M. N. and Abdullah, S.: Simulation Modeling of Arid Grassland Dynamics in Jordan: A 40-Year Analysis of Leaf Area Index Trends, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4117, https://doi.org/10.5194/egusphere-egu24-4117, 2024.

In the Sahel region, landscape configuration is closely linked to factors such as climate, ecology, soil composition, agronomy, livestock, and biology. Over the past decades, significant changes in these factors have been observed, including shorter rainy seasons, irregular precipitation, a decrease in biomass productivity, and rapid population growth, negatively impacting local agricultural and pastoral systems. In response to this pressure, mitigation strategies have been implemented to contribute to the improvement of local food, nutritional, and economic security. Agroforestry systems, involving a combination of trees, shrubs, crops, and animals in the same plot, represent one of these strategies. Therefore, characterizing these systems in the current context of climate change is crucial for sustainable natural resource management.

In this study, three agroforestry landscapes of the Senegalese Sahel were described, spanning a bioclimatic gradient from the Louga region (Ouarkhokh) in the north to the Fatick region (Niakhar) in the center, and the Tambacounda region (Koussanar) in the south. The data utilized included satellite imagery synthesis (Sentinel-2 and Spot), landscape variables (rainfall, evapotranspiration, biomass, and vegetation), spectral indices (NDVI, NDRE, GNDVI), and field data on land use and woody cover. The methodology consisted of three main approaches: (i) landscape stratification involving Sentinel image segmentation in 2021, selection of relevant landscape variables, and mixed discriminant factor analysis to establish landscape heterogeneity; (ii) land use and land cover mapping through supervised pixel-based classification using a Random Forest (RF) machine learning classifier with 500 trees; (iii) floristic diversity analysis by assessing floristic composition and calculating diversity indices (i.e., Shannon, Pielou, and Simpson indices).

Landscape stratification identified seven classes with distinct landscape characteristics. Classes (1, 2, and 4) in the Ouarkhokh site had lower average biomass, rainfall, and actual evapotranspiration values than classes (3 and 4) in the Niakhar site. Similarly, classes (5, 6, and 7) in the Koussanar area had higher average biomass, rainfall, and actual evapotranspiration values than the first two sites. Land use mapping showed vegetation predominance in the Ouarkhokh site, significance in the Koussanar site, and low presence in the Niakhar area. Other identified units (cultivated areas, built-up areas, water, and bare land) were dominant in the Niakhar area, present in the Koussanar site, and low in the Ouarkhokh area. Likewise, vegetation dominated in classes 1, 5, 6, and 7. Class 1 was exclusively found in Ouarkhokh, while classes 5, 6, and 7 were located in the Koussanar site. The majority of cultivated surfaces were in class 3, exclusively located in the Niakhar area. Species richness was higher in the Niakhar area (60 species, 21 families) and lower in the Koussanar area (56 species, 16 families) and Ouarkhokh area (31 species, 13 families). This landscape distribution of land use, landscape classes, and identified species highlights the influence of anthropogenic, soil-related, and climatic factors specific to each site.

How to cite: sylla, D., Diouf, A. A., and Ndao, B.: Variation of woody plants diversity and land use along a bioclimatic gradient of agroforestry landscapes in Senegalese Sahel, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5133, https://doi.org/10.5194/egusphere-egu24-5133, 2024.

The landscape-scale evaluation and modeling of the impact of agricultural management and climate change on soil-derived ecosystem services requires soil information at a spatial resolution addressing individual agricultural fields. A pattern recognition approach is presented that generates a nationwide data product. It agglomerates the multivariate soil parameter space into a limited number of functional soil process units (SPUs) that facilitate operating agricultural process models. Each SPU is defined by a multivariate parameter distribution along its depth profile from 0 to 100 cm. It has a depth resolution of 1 cm and a spatial resolution of 100 m. The methodological approach is based on an unsupervised classification procedure involving remote sensing, cluster analysis, and machine learning. It accounts for differences in variable types and distributions and involves genetic algorithm optimization to identify those SPUs with the lowest internal variability and maximum inter-unit difference with regards to both, their soil characteristics and landscape setting. The high potential of the method is demonstrated for the agricultural soil landscape of Germany. It can be applied to other landscapes and ecosystem contexts.

How to cite: Ließ, M.: A pattern recognition approach to generate soil process units for ecosystem modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5461, https://doi.org/10.5194/egusphere-egu24-5461, 2024.

EGU24-5750 | ECS | Orals | ITS1.23/SSS0.1.4

Identifying landscape hot and cold spots of soil greenhouse gas fluxes by combining field measurements and remote sensing data 

Elizabeth Wangari, Ricky Mwanake, Tobias Houska, David Kraus, Gretchen Gettel, Ralf Kiese, Lutz Breuer, and Klaus Butterbach-Bahl

Upscaling chamber measurements of soil greenhouse gas (GHG) fluxes from point scale to landscape scale remain challenging due to the high variability in the fluxes in space and time. This study measured GHG fluxes and soil parameters at selected point locations (n = 268), thereby implementing a stratified sampling approach on a mixed-landuse landscape (∼ 5.8 km2). Based on these field-based measurements and remotely sensed data on landscape and vegetation properties, we used random forest (RF) models to predict GHG fluxes at a landscape scale (1 m resolution) in summer and autumn. The RF models, combining field-measured soil parameters and remotely sensed data, outperformed those with field-measured predictors or remotely sensed data alone. Available satellite data products from Sentinel-2 on vegetation cover and water content played a more significant role than those attributes derived from a digital elevation model, possibly due to their ability to capture both spatial and seasonal changes in the ecosystem parameters within the landscape. Similar seasonal patterns of higher soil/ecosystem respiration (SR/ER–CO2) and nitrous oxide (N2O) fluxes in summer and higher methane (CH4) uptake in autumn were observed in both the measured and predicted landscape fluxes. Based on the upscaled fluxes, we also assessed the contribution of hot spots to the total landscape fluxes. The identified emission hot spots occupied a small landscape area (7 % to 16 %) but accounted for up to 42 % of the landscape GHG fluxes. Our study showed that combining remotely sensed data with chamber measurements and soil properties is a promising approach for identifying spatial patterns and hot spots of GHG fluxes across heterogeneous landscapes. Such information may be used to inform targeted mitigation strategies at the landscape scale.

How to cite: Wangari, E., Mwanake, R., Houska, T., Kraus, D., Gettel, G., Kiese, R., Breuer, L., and Butterbach-Bahl, K.: Identifying landscape hot and cold spots of soil greenhouse gas fluxes by combining field measurements and remote sensing data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5750, https://doi.org/10.5194/egusphere-egu24-5750, 2024.

EGU24-5949 | ECS | Posters on site | ITS1.23/SSS0.1.4

The Joint FAO/IAEA Center and the Soil Fertility Project: Integrating Nuclear and Related Techniques for Modelling to Support Practical Decision Management Support 

Magdeline Vlasimsky, Gerd Dercon, Hami Said Ahmed, Sarata Daraboe, Yusuf Yigini, Yuxin Tong, Yi Peng, Franck Albinet, Maria Heiling, and Christian Resch

The Soil Fertility (SoilFer) project, led by the Land and Water Division at FAO, seeks to enhance agricultural practices and resilience globally, starting with five countries (Guatemala, Honduras, Zambia, Kenya, and Ghana). The project collaborates with governments and relevant national partners to establish comprehensive national monitoring and mapping systems for soil management, catering to the diverse needs of agriculture stakeholders. The Soil and Water Management Laboratory at the Joint FAO/IAEA Center serves as a crucial hub for advancing research and technical expertise in soil and water management using nuclear and related techniques. Through its multifaceted approach in collaboration with the Land and Water Division, the laboratory contributes significantly to the SoilFer project, through the development and implementation of technical training programs for and expert advising on the application of Mid-Infrared Spectroscopy (MIRS), Cosmic Ray Neutron Sensor (CRNS), and Gamma Ray Spectroscopy (GRS) to soil monitoring and mapping.

The integration of MIRS, CRNS, and GRS technologies within the SoilFer project forms a robust framework for soil monitoring and mapping, as MIRS has been shown to provide detailed insights into soil composition and carbon content, CRNS offers real-time data on soil moisture dynamics, and GRS contributes to the analysis of radioactive isotopes and elemental composition. Given the integrated nature of landscape processes, the adoption of technological approaches must mirror this complexity. Interconnected ecological, hydrological, and geological processes within landscapes necessitate a holistic and integrated technological framework. This approach ensures that diverse data streams, derived from technologies such as remote sensing, geographic information systems (GIS), and advanced sensor networks, can be harmoniously synthesized. Only through such integration can a comprehensive understanding of landscape dynamics be achieved, facilitating informed decision-making and sustainable management practices across multifaceted environmental systems. The project emphasizes the seamless integration of these advanced technologies with soil monitoring and mapping systems, ensuring a comprehensive and effective approach to soil management practices, while improving national capacity and stakeholder engagement in data-based decision making. 

The key objectives of the SoilFer project encompass the development of robust national soil information systems, the implementation of decision support systems targeting soil health, and the promotion of sustainable soil management practices. By fostering collaboration and knowledge exchange, the project aspires to build technical, increase agricultural resilience and ensure food security in the participating countries.

How to cite: Vlasimsky, M., Dercon, G., Said Ahmed, H., Daraboe, S., Yigini, Y., Tong, Y., Peng, Y., Albinet, F., Heiling, M., and Resch, C.: The Joint FAO/IAEA Center and the Soil Fertility Project: Integrating Nuclear and Related Techniques for Modelling to Support Practical Decision Management Support, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5949, https://doi.org/10.5194/egusphere-egu24-5949, 2024.

EGU24-6126 | Posters on site | ITS1.23/SSS0.1.4

NewLife4Drylands Protocol for dryland restoration in Protected Areas: an innovative tool to support restoration activities. 

Serena D'Ambrogi, Francesca Assennato, Rocco Labadessa, Paolo Mazzetti, Valentina Rastelli, Nicola Riitano, and Cristina Tarantino

Land degradation processes have experienced a significant increase in recent decades, a trend that is projected to escalate further in the absence of any intervention. The need of adopting practices to contain, mitigate and restore degraded land have been stressed also by the new European Mission 'A Soil Deal for Europe'. To guide and support restoration actions, through a common and effective framework, an efficient monitoring approach and an adaptive ecological restoration process is needed. 

The NewLife4Drylands LIFE project provides a Protocol for design, implementation, and maintenance of restoration activities based on Nature-Based Solutions (NBS) within drylands. The Protocol, developed following the principles and inputs of some international restoration standards (SER, IUCN), is based on the identification and monitoring of degradation processes exploiting remote sensing capabilities, with the aim to integrate data derivation procedures into ecological restoration and maintenance activities. The Protocol is supported by a Decision-Making web-tool guiding trough the degradation processes, NBS along with indices/indicators with the aim to reduce the knowledge effort and helps in prioritizing options. 

The Newlife4drylands experience highlighted the heterogeneity and complexity of degradation processes, as resulted from a selected set of degraded pilot sites within Mediterranean Protected Areas, together with the issue for harmonization and standardization of ecological/physical indicators, especially those derived from satellite observations, when used as proxies of land degradation. The integrated use of both available field data (for short-term monitoring) and satellite data (for medium and long-term monitoring) have been explored to identify indicators for evaluating the effectiveness of planned restoration actions. This approach is geared, towards fostering adaptive and collaborative management of the ecological restoration process. 

Therefore, the Protocol acts as support tool for decision-makers, including public administration of Protected Areas, as well as technicians and planners. The proposed approach aims to raise awareness about the needs of drylands and opportunities provided by NBS. It serves as a guide for the identification of specific/local NBS for the restoration of drylands, beginning with the identification of degradation processes.

How to cite: D'Ambrogi, S., Assennato, F., Labadessa, R., Mazzetti, P., Rastelli, V., Riitano, N., and Tarantino, C.: NewLife4Drylands Protocol for dryland restoration in Protected Areas: an innovative tool to support restoration activities., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6126, https://doi.org/10.5194/egusphere-egu24-6126, 2024.

EGU24-6475 | Posters on site | ITS1.23/SSS0.1.4

Introducing the ’miniRECgap’ package with GUI-supported R-scripts for simple gap-filling of Eddy Covariance CO2 flux data 

Alina Premrov, Jagadeesh Yeluripati, and Matthew Saunders

The Eddy covariance (EC) is a well-known technique used (among others) to investigate the ecosystem exchange of greenhouse gasses (GHGs) between the biosphere and the atmosphere (Burba et al., 2007), often required in studies on soil-plant-atmosphere interactions and GHG emissions/removals from different soil systems. The long data records from EC measurements often experience data gaps due to various reasons (BaldocchiI, 2003) resulting in  many gap-filling methods being developed over the past decades. This study is introducing the new ’miniRECgap’ (Premrov, 2024) computational tool, which is using so-called ‘classic’, traditional robust and validated modelling approaches for gap-filling the missing EC CO2 flux measurements,  based on the application of environmental temperature and light response functions (Lloyd and Taylor, 1994; Rabinowitch, 1951) in combination with empirical/semi-empirical parameter-optimisation. ‘miniRECgap’ is a very small R package that operates in a user-friendly way via GUI (Graphical User Interface) supported scripts. It is purposely designed to be simple, operating in only 5 steps. The application of ‘miniRECgap’ will be demonstrated using EC CO2 flux data from an Irish peatland site Clara Bog. Due to its simplicity, it is thought that the new tool may be beneficial for new R users and that it may allow for easier and less time-consuming testing of the potential suitability of ‘classic’ empirical/semi-empirical gap-filling on different datasets.

 

Acknowledgements

The authors are grateful to the Irish Environmental Protection Agency (EPA) for funding the CO2PEAT project (2022-CE-1100) under the EPA Research Programme 2021-2030.

 

References

BaldocchiI, D.D. (2003) Assessing the eddy covariance technique for evaluating carbon dioxide exchange rates of ecosystems: past, present and future.  9, 479-492.

Burba, G., Anderson, D., Amen, J., (2007) Eddy Covariance Method: Overview of General Guidelines and Conventional Workflow, AGU Fall Meeting Abstracts, pp. B33D-1575.

Lloyd, J., Taylor, J.A. (1994) On the temperature dependence of soil respiration. Functional Ecology 8, 315-323.

Premrov, A., (2024) miniRECgap. R package  with GUI suported scripts for gap-filling the of Eddy Covariance CO2 flux data.  Copyright: Trinity College Dublin. URL:  'miniRECgap package will be uploaded on GitHub in near future'.

Rabinowitch, E.I. (1951) Photosynthesis and Related Processes. Interscience Publishers.

How to cite: Premrov, A., Yeluripati, J., and Saunders, M.: Introducing the ’miniRECgap’ package with GUI-supported R-scripts for simple gap-filling of Eddy Covariance CO2 flux data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6475, https://doi.org/10.5194/egusphere-egu24-6475, 2024.

EGU24-6832 | ECS | Posters on site | ITS1.23/SSS0.1.4

A Comprehensive Assessment of the AquaCrop Model in drylands: Performance Examination and Sensitivity Analysis 

Ahmed S. Almalki, Marcel M. El Hajj, Kasper Johansen, and Matthew F. McCabe

The AquaCrop model is a powerful tool for crop monitoring, providing a daily estimation of soil-crop-atmosphere dynamics. The model requires a substantial number of input variables and parameters, highlighting the need for identifying those that significantly influence model outputs. Sensitivity analysis is a vital method for this purpose. A key objective of this study is to examine the performance of the AquaCrop model in simulating wheat yield and irrigation water requirement in drylands under two scenarios: first running the model employing a minimal amount of in situ data, and second using all available in situ data. A second focus is to analyze the sensitivity to all crop and soil related input variables and parameters. To do this, a pilot-scale study was undertaken, focusing on a commercial farm in the Al-Jouf province of Saudi Arabia. The farm comprised 200 center-pivot fields of mainly wheat crops. In situ data was collected to calibrate the model for two consecutive growing seasons (2019-2020 and 2020-2021). Using the variance-based Sobol technique, the sensitivity of the AquaCrop model outputs, particularly wheat yield and irrigation water requirement, to crop and soil related input variables and parameters was examined, as were the influential and non-influential inputs on these outputs. Results showed that the second scenario (all data) outperformed the first (minimal data), demonstrating more accurate wheat yield predictions with rRMSE values of 17% and 21% for the 2019-2020 and 2020-2021 growing seasons, respectively. Regarding irrigation water requirement estimations, the second scenario also exhibited lower rRMSE values of 20% and 19% for the same growing seasons. Results also demonstrated that the sensitivity indices of variables and parameters varied with model outputs and growing seasons. By synthesizing inputs sensitivities under different conditions, the influential input variables and parameters were distinguished. Overall, six variables and parameters held significant influence on the analyzed model outputs based on their total-order sensitivity indices. These included duration from sowing to senescence (senescence), duration from sowing to harvesting (maturity), duration from sowing to yield formation (HIstart), base temperature below which growth does not progress (Tbase), minimum air temperature below which pollination failure begins (Tmin_up), and shape factor describing reduction in biomass production (fshabe_b). It was revealed that most variables and parameters were non-influential, which might allow them to be fixed within their ranges to optimize model calibration. The research represents the performance assessment and sensitivity analysis of the AquaCrop model over a desert farming system and offers guidelines for model calibration by delivering information on influential and non-influential input variables and parameters.

How to cite: Almalki, A. S., El Hajj, M. M., Johansen, K., and McCabe, M. F.: A Comprehensive Assessment of the AquaCrop Model in drylands: Performance Examination and Sensitivity Analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6832, https://doi.org/10.5194/egusphere-egu24-6832, 2024.

EGU24-8466 | Posters on site | ITS1.23/SSS0.1.4

Metamodel simulation of carbon fluxes across an eroding and pristine blanket bog in Scotland 

Bhaskar Mitra, Jagadeesh Yeluripati, James Cash, Linda Toca, Mhairi Coyle, and Rebekka Artz

Accurately quantifying carbon dynamics in peatlands is critical to assess their role in regulating global climate. Within hotspots of peatland degradation, such as in Europe and South-east Asia, skilful assessment of the spatial and temporal impacts of climate change and different land management options is required to meet emissions reductions targets and improve regional management planning.

To address this challenge, a random forest-based metamodel was evaluated to assess its utility in simulating various greenhouse gas (CO2) emission components, including Net Ecosystem Exchange (NEE), Gross Primary Productivity (GPP), and Ecosystem Respiration (ER) across two Scottish peatlands. The metamodel mimicked the complex Wetland-DNDC model at a higher level of abstraction with increased efficiency and lower computational time.

While Wetland-DNDC also simulates NEE, GPP and ER, it typically involves a considerable number of parameters related to soil properties, climate data, vegetation characteristics, biogeochemical processes, hydrology, nutrient cycling, and microbial activity. Many of these parameters (more than 100) are challenging to measure in the field, and literature values are often adopted, which may not necessarily reflect local site conditions. In essence, this multidimensional parameter space introduces high uncertainties in modelling carbon fluxes.

In contrast, random forest-based metamodel preserved the key relationships between NEE and input variables (air and soil temperature, water table, precipitation, vegetation, and soil properties) as described in the Wetland-DNDC model with lower parameter requirements (less than 20) and increased accuracy. Similar unique relationships were established for GPP and ER. The random forest-based metamodel represented the Wetland-DNDC model  within the spectrum of input values and parameters across which it was simulated.

The simulation was conducted in two locations across Scotland with contrasting contemporary carbon dynamics: a near natural blanket bog in Cross Lochs, Forsinard, currently functioning as a resilient net carbon dioxide sink (UK-CLS; Lat. = 58.37, Long. = -3.96; altitude = 207 m) and an eroding oceanic blanket bog located in the Cairngorms, currently net emitting carbon dioxide (UK-BAM; Lat. = 56.92, Long. = -3.15, altitude = 642 m). The simulation was validated against eddy covariance flux measurements under varying climate conditions.

In contrast to Wetland-DNDC (R2 = 0.43), the metamodel provided a much-improved fit to the 1:1 line for NEE (R2 = 0.83). Model accuracy was slightly lower for the former (RMSE = 0.72) compared to its metamodel version (RMSE = 0.699). Similar trends were observed for GPP and ER simulations. At a monthly resolution, Wetland-DNDC-derived NEE, GPP, and ER consistently deviated by more than 20% from the eddy covariance-derived estimates, whereas its metamodel version showed deviations of less than 10%. Currently, work is in progress to incorporate management and drought simulation within a metamodel framework, as well as to upscale carbon fluxes from tower to landscape resolution.

The simulation of carbon fluxes using the metamodel-based approach holds the promise of enhancing emission reporting to Tier 3 standards and offers a hopeful avenue for modelling carbon dynamics in peatlands.

How to cite: Mitra, B., Yeluripati, J., Cash, J., Toca, L., Coyle, M., and Artz, R.: Metamodel simulation of carbon fluxes across an eroding and pristine blanket bog in Scotland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8466, https://doi.org/10.5194/egusphere-egu24-8466, 2024.

EGU24-10001 | Orals | ITS1.23/SSS0.1.4

MIR spectroscopy combined with meteorological data can estimate soil compaction risks in top and subsoils. 

Felipe de Santana, Rebecca Hall, Longnan Shi, Victoria Lowe, Jim Hodgson, and Karen Daly

Soil compaction is an important physical characteristic that affects agricultural productivity by increasing soil density, which reduces the volume of a given soil mass. Due to the higher compaction, plant roots find resistance in penetrating deeply into the soil, limiting their access to essential nutrients and moisture, impacting the plant health with lower levels of N, P and K, resulting in lower productivity. Soil compaction can also reduce soil porosity, aeration, carbon mineralisation/sequestration and increasing the production of greenhouse gases through denitrification in anaerobic sites. Besides that, soil compaction can cause surface runoff and erosion, increasing the risk of flooding and soil loss. A partial recuperation of compacted soils is an expensive and labour-intensive task. In addition, agricultural land expansion for crops is limited. Hence, mapping agricultural areas at risk of soil compaction is essential to implement strategies to mitigate the adverse effects of soil compaction.

Soil particle size and soil drainage were used to classify topsoil's (T) compaction risk class. For subsoil (S) soils (after horizon A), the subsoil particle size, packing density (bulk density + 0.009 * clay (%)), soil drainage and field capacity days were used to estimate the compaction risks. The main problem of this strategy is that these analyses are expensive and time-consuming, i.e., soil particle size analysis requires an average time of 1 month per 100 samples and costs ~ 40.00 per sample. Bulk density analysis costs ~ € 7.00 per sample and is also time-consuming; consequently, bulk density values are mainly predicted using pedo-transfer functions in mapping studies.

To speed up the analysis and minimise the costs, vibrational spectroscopy combined with chemometrics was used to determine soil particle size and bulk density. Both parameters were combined with field capacity days (obtained from 104 national wide meteorological stations) and drainage class (obtained from Irish - Environmental Protection Agency) to map soil compaction risk areas in the northern half of the Republic of Ireland with a resolution of 4 km2 (2x2km) and 1 km2 grid for regional and periurban regions, respectively (Tellus achieve). To confidentially map these regions, spectral control charts based on PCA were used to identify unrepresentative sample spectra based on the spectral models used. Only samples classified as representative were predicted by the spectral models. Using this strategy, we could predict ~ 90% (T) and ~66% (S) compaction risks in non-peat soils. The prediction results showed that ~33% (T) and ~43% (S) were classified as high risks of compaction, ~19% (T) and ~23% (S) as moderate, and ~37% (T) and <1% (S) as low risks or other classes.

How to cite: de Santana, F., Hall, R., Shi, L., Lowe, V., Hodgson, J., and Daly, K.: MIR spectroscopy combined with meteorological data can estimate soil compaction risks in top and subsoils., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10001, https://doi.org/10.5194/egusphere-egu24-10001, 2024.

EGU24-10906 | Posters virtual | ITS1.23/SSS0.1.4

SDG 15.3.1 indicator at local scale for monitoring land degradation in protected areas 

Cristina Tarantino, Mariella Aquilino, Saverio Vicario, Rocco Labadessa, Vito Emanuele Cambria, Christos Georgiadis, Marcello Vitale, Francesca Assennato, and Paolo Mazzetti

In the framework of the NewLife4Drylands LIFE Preparatory project (LIFE20 PRE/IT/000007, 2021-2024) the estimation of SDG 15.3.1 indicator [1], adopted in the UNCCD’s Good Practice Guidance [2], was applied for evaluating Land Degradation (LD) in different Mediterranean Protected Areas (PA). To effectively support PAs managers, joint effort was made in the evaluation of SDG 15.3.1 indicator at the local scale by using satellite Remote Sensing data in the computation of the three main sub-indicators as trend in Land Cover (LC), Primary Production (PP) and Soil Organic Carbon (SOC) stock. Where feasible, local scale sub-indicators were not sourced from open-access global/European databases due to their lack of accuracy at the site scale [3]. LD was estimated not only for the whole PA but also for specific LC classes of interest, considering additional sub-indicators related to pressures and threats affecting the class. This study focuses on the dryland Alta Murgia (IT9120007) PA, in southern Italy, and the wetland Nestos River Delta (GR1150001) PA, in Greece. For Alta Murgia site, featuring semi-natural dry grassland habitats of community interest that are frequently subjected to fire events during the summer season, the Burn Severity (BS) index was included. BS trends were measured by assessing the difference in pre/post–fire Normalized Burn Ratio (NBR) index from Landsat data during summer. Baseline data from 2004, coinciding with the establishment of a National Park within PA, was compared with 2018 for validating field data availability. Nestos River Delta hosts the largest natural riparian forest in Greece and is frequently subjected to hydrological cycle modifications, involving water scarcity due to both inappropriate river management and climate change, in turn hampering the transport of nutrient-rich sediments and the enrichment of soils being at risk of aridification. Within this framework, Hydroperiod and Soil Salinity indices were considered for LD and specific impacts on aquatic vegetation LC. Baseline data from 2017, after the dry climate conditions of 2016-2017, was compared with 2021 for validating field data availability. Both in Alta Murgia and Nestos, LC mappings were obtained by a data-driven pixel-based approach considering Landsat/Sentinel-2, respectively, multi-seasonal imagery and a multi-class Support Vector Machine (SVM) classifier trained with data from in-field campaigns and historical orthophotos interpretation. Time series of MSAVI from Landsat (which replaced standard NDVI for its soil correction benefits [4]) and PPI from Sentinel-2 by Copernicus services, respectively, were used to track grassland PP trends. Lastly, for SOC stock trends, the open-source Trends.Earth QGIS plugin [5], incorporating customized LC data and global SoilGrids product, was adopted to supplement local data limitations. According to its specification, the SDG 15.3.1 indicator was computed by integrating all the sub-indicators according to the principle “one out, all out” obtaining the 3-classes output mapping (Degradation, Improvement, Stable). The findings can support the monitoring and evaluation of LD, guiding protective measures aligned with the Agenda 2030 for Sustainable Development. They, also, highlight the importance of the integration of local scale data and sub-indicators within the UNCCD methodology.

References

[1] https://unstats.un.org/sdgs/metadata/files/Metadata-15-03-01.pdf

[2]https://www.unccd.int/publications/good-practice-guidance-sdg-indicator-1531-proportion-land-degraded-over-total-land

[3] https://doi.org/10.3390/rs13020277

[4] https://doi.org/10.3390/rs12010083

[5] http://trends.earth/docs/en

 

How to cite: Tarantino, C., Aquilino, M., Vicario, S., Labadessa, R., Cambria, V. E., Georgiadis, C., Vitale, M., Assennato, F., and Mazzetti, P.: SDG 15.3.1 indicator at local scale for monitoring land degradation in protected areas, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10906, https://doi.org/10.5194/egusphere-egu24-10906, 2024.

EGU24-11219 | ECS | Posters on site | ITS1.23/SSS0.1.4

Exploring soil organic carbon dynamics through a multi-model simulation of multiple long-term experiments  

Matteo Longo, Ilaria Piccoli, Antonio Berti, Michela Farneselli, Vincenzo Tabaglio, Domenico Ventrella, Samuele Trestini, and Francesco Morari

Agricultural system models are widely recognized as valuable tools for identifying best management practices and addressing the challenges posed by climate change. In this context, the use of model ensembles has been recently recommended for their enhanced performance and accuracy. However, assessing their effectiveness over a large geographical area, such as national scale is often currently lacking. This study focuses on simulating soil organic carbon (SOC) dynamics using an ensemble of models comprising DSSAT, CropSyst, EPIC, and APSIM models, utilizing data derived from five Long-Term Experiments (LTEs) spread across a north-to-south pedoclimatic range transect in Italy. This region is of particular importance as it represents a significant hotspot for climate change. The LTEs featured a robust array of 63 unique experimental protocols, incorporating variation effect in fertilization rates, cropping rotations, and tillage prescriptions. This resulted in a total of 2184 years of simulated data for each model. The dataset employed included SOC stocks and crop yield and biomass. Models underwent independent calibration, with crop and SOC parameters selected based on expert knowledge. Main crop cultivars, such as maize, soybean, sugarbeet, and wheat, were further categorized and calibrated by maturity classes. A similar approach was used for cover crops. The extensive dataset enabled a nuanced exploration of the models’ performance across varied agro-ecological contexts. The models proved capable of accurately reproducing the varied pedo-climatic conditions of the Italian peninsula, contributing to the advancement of our understanding of SOC dynamics.

How to cite: Longo, M., Piccoli, I., Berti, A., Farneselli, M., Tabaglio, V., Ventrella, D., Trestini, S., and Morari, F.: Exploring soil organic carbon dynamics through a multi-model simulation of multiple long-term experiments , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11219, https://doi.org/10.5194/egusphere-egu24-11219, 2024.

EGU24-11605 | Orals | ITS1.23/SSS0.1.4

A Geospatial Overview of Agricultural Long-Term Field Experiments across Europe 

Cenk Donmez, Carsten Hoffmann, Nikolai Svoboda, Tommy D'Hose, Xenia Specka, and Katharina Helming

Long-Term Field Experiments (LTEs) are agricultural infrastructures for studying the long-term effects of different management practices and soil and crop properties in changing climate conditions. These experiments are essential to examine the impact of management and environment on crop production and soil resources on different soil textures and types. Some of those LTEs have average times of 20-50 years, even more than 100 years. These infrastructures are thus scientific heritages with high values of agricultural data; however, LTE-related information was difficult to find since it was scattered. To close this gap, we developed a geospatial data infrastructure, including an LTE overview map to compile and analyze the meta-information of the LTEs across Europe. The map provides a spatial representation of LTEs and the meta-information, collected by extensive literature review and factsheets in collaboration with BonaRes and EJPSoil projects, clustered in different categories (management operations, land use, duration, status, etc.) (Grosse et al. 2021; Donmez et al., 2022; Blanchy et al., 2023; Donmez et al., 2023). A threshold filter with a minimum duration of 20 years was applied, which results in a total of 500 LTEs across Europe and included into the map. The clusters of LTEs were geospatially analyzed to provide inputs for the agricultural sector, scientists, farmers and policy-makers. The fertilization treatment was the major research theme of collected and studied LTEs, followed by crop rotation and tillage trials. Bringing the meta information of dispersed LTEs through the development of the LTE overview map is expected to help developing a mutual management framework of efficient agricultural production by revealing the LTE potential internationally. This will contribute to scaling up the agricultural practices from site to landscape level for increasing the climate change adaptation to agricultural yield and management.

References

Donmez C., Schmidt M., Cilek A., Grosse M., Paul C., Hierold W., Helming K., (2023): Climate Change Impacts on Long-Term Field Experiments in Germany. https://doi.org/10.1016/j.agsy.2022.103578. Vol.205, 103578. Agricultural Systems.

Blanchy G., D’Hose T., Donmez C., Hoffmann C., Makoschitz L., Murugan R., O’Sullivan L., Sanden T., Spiegel A., Svoboda N., Boltenstern S.Z., Klummp K., (2023): An open-source database of European long-term field experiments. https://doi.org/10.1111/sum.12978  Soil Use and Management

Donmez C., Blanchy G., Svoboda N., D’Hose T., Hoffmann C., Hierold W., Klummp K., (2022): Provision of the metadata of European Agricultural Long-Term Experiments through BonaRes and EJP SOIL Collaboration. Data in Brief. https://doi.org/10.1016/j.dib.2022.108226.

Grosse, M., Ahlborn, M.C., Hierold, W. (2021): Metadata of agricultural long-term experiments in Europe exclusive of Germany. Data in Brief 38, https://doi.org/10.1016/j.dib.2021.107322

How to cite: Donmez, C., Hoffmann, C., Svoboda, N., D'Hose, T., Specka, X., and Helming, K.: A Geospatial Overview of Agricultural Long-Term Field Experiments across Europe, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11605, https://doi.org/10.5194/egusphere-egu24-11605, 2024.

EGU24-12129 | Posters on site | ITS1.23/SSS0.1.4

Soil water holding capacity as descriptor of soil health at district scale – a sensitivity study 

Thomas Weninger, Irene Schwaighofer, Florian Darmann, Thomas Brunner, and Peter Strauss

The proposal for the European Soil Monitoring Law includes an integrated value of soil water holding capacity to be determined as a proxy for soil quality for whole soil districts. As this is a relatively new but interesting approach, a number of details of the assessment procedure remain open at the current stage of formulation. The aim of this study is to quantify the effects of the choice of different options on the overall result, focusing on the delineation of soil districts in different sizes, the detailed definition of the respective soil property, and the treatment of sealed areas.

High-resolution data for soil hydrological properties for two Austrian provinces are used as a basis, including different approaches to calculate soil water holding capacity. The size of the study area corresponds to the maximum size of a soil district as proposed. Thus, a variation of three size levels is possible, namely the whole area, major river catchments, and agro-geographical sub-units. The term soil water holding capacity is basically defined in the proposed EU Directive, but several options for its determination are possible. We used two different pedotransfer functions to derive soil water holding capacity values and an additional method based on averaging results from randomly located sampling points. Soil sealing is a major threat to hydrological soil functionality, and its assessment over large areas is still not standardized. Here, the European LUISA land use/land cover dataset for 2020 (1 km resolution) and a national dataset with higher resolution are used. Both datasets are optionally overlaid with the Copernicus imperviousness layer involves gradual information about surface imperviousness.

By combining all these factors with each other, different ways were evaluated to determine the target value of soil water holding capacity integrated on a regional scale. Differences in the results and their sensitivity to input variations are quantified to inform policy decisions in the implementation of the European Soil Monitoring Law in the member states.

How to cite: Weninger, T., Schwaighofer, I., Darmann, F., Brunner, T., and Strauss, P.: Soil water holding capacity as descriptor of soil health at district scale – a sensitivity study, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12129, https://doi.org/10.5194/egusphere-egu24-12129, 2024.

Soil erosion constitutes an increasing threat to soil productivity and food security. This work describes the potential of using Artificial Neural Networks (ANN) for upscaling soil loss outputs from medium to low scale. The Revised Universal Soil Loss Equation (RUSLE) model was implemented to calculate soil loss rates in two scales in Crete, Greece. Specifically, the RUSLE model was applied in six (6) watersheds across the island using medium spatial resolution satellite images (5m), namely Planetscope. These results were used to feed an ANN model to upscale the mesoscale outputs (5m) to regional outputs (30m-island level). The ANN system was trained using spatial environmental parameters such as the Normalized Difference Vegetation Index, Digital Elevation Model, and topographical slope angle. This "optimized" soil loss derivative later made it possible to compare it with the corresponding final derivative of Crete (regional spatial scale), which emerged from the straightforward processing of RUSLE model with the more "coarse" and generalized data as estimated from the  Landsat-8 satellite images (30m). The statistics revealed that the detailed and high-quality soil loss data, as derived from the upscaling process, provide more precise and reliable results.

How to cite: Alexakis, D. D. and Polykretis, C.: Using Artificial Neural Networks to upscale soil erosion model results from local to regional scale. An example from Crete, Greece., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14678, https://doi.org/10.5194/egusphere-egu24-14678, 2024.

EGU24-15537 | ECS | Orals | ITS1.23/SSS0.1.4

Integrating UAV data and soil-crop modelling for Enhanced Soil Health Monitoring 

Nikolaos-Christos Vavlas, Lammert Kooistra, Fenny van Egmond, and Gerlinde De Deyn

The necessity of soil health monitoring is paramount in reversing soil degradation and promoting sustainable farming. Including cover crops in the crop rotation is one of the sustainable soil management practices contributing to soil health. Cover crops contribute to soil health by nutrient retention and carbon accumulation during their growth and return of organic matter to the soil upon their incorporation. During monitoring, the sampling frequency can change from annual in the case of SOC to weekly or daily for fertilization and irrigation. Remote sensing techniques offer a solution, enabling the monitoring of vegetation over time and space, thereby enhancing our understanding of the impact of cover crops on the main crop. However, this technology makes it possible to see the surface of the field which can assist with the above-ground changes of the system. Process-based modelling and data assimilation can subsequently link the above-ground component with soil functions. In-situ data collection that includes crop characteristics such as biomass and N-uptake is essential both for transforming remote sensing data into crop characteristics and for calibrating models. Using Unmanned Aerial Vehicles (UAVs) can potentially collect data at high frequency, which can be used to enhance soil process modelling. The development of this UAV-based method has the potential to be scaled up to a satellite level in the future.

In our research, we have combined the study of nutrient cycling and the effect of cover crops on soil health. To achieve this, we have used the WOFOST-SWAP-ANIMO model to simulate the varying influence of cover crop monocultures and mixtures on Soil Organic Carbon (SOC) and Nitrogen cycling in a 7-year crop rotation on sandy soil. The model simulates vegetation characteristics such as biomass, leaf area index, and yield, as well as soil moisture and mineral Nitrogen concentrations. This will give us a good estimation of the vegetation input into the soil as well as the nutrient uptake from both cover crops and main crops. Soil sampling is also important to model calibration/validation to be able to simulate the N dynamics of biological activity under the surface. Our findings suggest that the model, in conjunction with UAV data and field sensors, can effectively monitor soil health indicators crucial for field management practice selection, such as the Carbon cycle and Nitrogen use efficiency.

How to cite: Vavlas, N.-C., Kooistra, L., van Egmond, F., and De Deyn, G.: Integrating UAV data and soil-crop modelling for Enhanced Soil Health Monitoring, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15537, https://doi.org/10.5194/egusphere-egu24-15537, 2024.

EGU24-18038 | Orals | ITS1.23/SSS0.1.4

Empowering soil health in Mediterranean environments through collaborative stakeholder engagement: insights from Sardinian Living Lab of the InBestSoil project 

Valentina Mereu, Gianluca Carboni, Alessio Menini, Marta Canu, Marco Dettori, Giulia Urracci, and Serena Marras

Preserving soil health and enhancing the ecosystem services that soil produces is of primary importance in European strategies and policies. More than 60% of the European soils are unhealthy due to unsustainable land use, pollution, climate change, and extreme events. This causes loss of ecosystem services, costing the EU at least €50 billion annually. Collaboration among businesses, policymakers, public administration, and the scientific community is crucial to develop practices that recognize the essential role of soils in sustaining livelihoods, biodiversity, and climate regulation.

In this framework, the Horizon Europe funded project InBestSoil (https://inbestsoil.eu/) aims to co-create a framework for investments in soil health preservation and restoration by developing a system for the economic valuation of the ecosystem services provided by healthy soil and the impacts of soil interventions, and its incorporation into business models and incentives. To achieve this, InBestSoil has selected 7 existing Soil Health Lighthouses (LHs) and 2 Soil Health Living Labs (LLs, in different maturity stages) covering four land uses (agricultural, forestry, urban, mining) across four biogeographic regions over Europe. The LLs are collaborative initiatives focused on co-creating knowledge and innovations, while LHs represent individual sites known for exemplary performance. The LL1, located in Sardinia (Italy), is coordinated by the CMCC Foundation and Agris Sardegna Research Agency. It focuses on Mediterranean agricultural soils and aims addressing the challenges related to climate change and extreme events, soil pollution, land abandonment, and water scarcity. It includes 2 LHs on conservation agriculture managed by Agris and 9 Living Lab Experimental Sites (LLES), which evaluate the introduction of sustainable soil practices. The LHs included in the LL are two Long-Term Experiments (>20 years) on conservation agriculture (reduced and no tillage versus conventional tillage) on durum wheat in rotation with legumes, in soils with different fertility levels that are representative of Mediterranean cereal farming conditions. Conservation agriculture is among the most promising climate-smart agricultural practices because it contributes to both climate change mitigation and adaptation objectives while helping to maintain and increase farmers' incomes. However, it is important both to acquire additional information to assess the medium- to long-term effects of these practices in different environments and cropping systems as well as to disseminate the scientific evidence and support the wider application of these practices in the Mediterranean region.

The LHs aim to provide scientific evidence and disseminate knowledge and experience gained in the long-term application of conservation agriculture in Mediterranean agricultural systems.  Moreover, in the selected 9 LLES, located in different areas and including cereal, olive tree and vineyard farms, soil samplings and analyses are being conducted to measure soil indicators and provide information to assess the economic evaluation of ecosystem services provided by soils managed with sustainable agricultural practices, primarily including conservation agriculture.

We aim to create a permanent space of discussion on the topic of soil health, involving all relevant actors, from farmers to researchers to policy makers, in order to identify common solutions and innovations that can face the economic and environmental challenges the Mediterranean agriculture is facing.

How to cite: Mereu, V., Carboni, G., Menini, A., Canu, M., Dettori, M., Urracci, G., and Marras, S.: Empowering soil health in Mediterranean environments through collaborative stakeholder engagement: insights from Sardinian Living Lab of the InBestSoil project, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18038, https://doi.org/10.5194/egusphere-egu24-18038, 2024.

Mountain grasslands play a pivotal role in delivering both economic and cultural ecosystem services, including food production, carbon sequestration, the provision of clean water, and preserving local traditions. However, these ecosystems are facing increasing threats from climate change around the world. Among the main challenges is the intensification of extreme precipitation events. They can aggravate the process of soil erosion and trigger landslides in mountain grasslands, with possible negative consequences on both ecosystems and human activities. However, the high variability of these ecosystems, as well as their wide distribution, makes it complex to adequately map their locations and investigate possible soil erosion hotspots, especially under future scenarios with varied rainfall regimes. In this context, the use of remote sensing technologies and modeling approach could open new frontiers to investigate critical areas and therefore guide mitigation solutions. The satellite Earth Observation (EO) through international space missions, coupled with cloud-based data analysis platforms like Google Earth Engine (GGE), facilitates ecosystem mapping at a resolution and frequency previously inaccessible. Furthermore, the utilization of multi-temporal models for potential soil erosion analysis in present and future scenarios can enhance our understanding of erosion dynamics attributed to climate change. In this research, we first map at high resolution the global mountain grasslands distribution taking advantage of Sentinel-based EO’s products. In such locations, we evaluate the multi-temporal soil erosion dynamics caused by water employing diverse climate scenarios (RUSLE model; 2015 vs. 2070-RCP8.5). Our findings indicate a potential global escalation in soil erosion within mountain grasslands, notably in South America and Africa, alongside identifiable localized hotspots. Remote sensing-based research paired with a modeling approach aimed at mapping critical areas and analyzing environmental challenges in ecosystems is therefore imperative. Such investigations not only delineate vulnerable regions but also guide targeted solutions crucial for safeguarding these ecosystems and their ecosystem services in the face of climate change.

How to cite: Straffelini, E., Luo, J., and Tarolli, P.: Satellite-based remote sensing and multitemporal modeling approach for mapping soil erosion hotspots in global mountain grasslands under climate change, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18161, https://doi.org/10.5194/egusphere-egu24-18161, 2024.

Peatland restoration and rehabilitation action has become more widely acknowledged as a necessary response to mitigating climate change risks and improving global carbon storage. Peatland ecosystems require restoration timespans on the order of decades and thus cannot be dependent upon the shorter-term monitoring often carried out in research projects. Hydrological assessments using geospatial tools provide the basis for planning restoration works as well as analysing associated environmental influences. “Restoration” encompasses applications to pre- and post-restoration scenarios for both bogs and fens, across a range of environmental impact fields. A scoping review was carried out to identify, describe, and categorise current process-based modelling uses in peatlands in order to investigate the applicability and appropriateness of eco- and/or hydrological models for northern peatland restoration. Two literature searches were conducted using the Web of Science entire database in September 2022 and August 2023. Of the final 211 papers included in the review, models and their applications were categorised according to this review’s research interests in 7 distinct categories aggregating the papers’ research themes and model outputs. Key themes emerging from topics covered by papers in the database included: modelling restoration development from a bog growth perspective; the prioritisation of modelling GHG emissions dynamics as a part of policymaking; the importance of spatial connectivity within or alongside process-based models to represent heterogeneous systems; and the emerging prevalence of remote sensing and machine learning techniques to predict restoration progress with little physical site intervention. Based on this assessment, CoupModel, DigiBog, and MPeat2D were calibrated for the case of Abbeyleix Bog, Co. Laois, Ireland (ongoing with results expected before April 2024). The exploration of subsequent simulations to represent varying peatland restoration conditions is discussed from an ecohydrological lens.

How to cite: Silva, M.: Ecohydrological modelling on peatlands: scoping review and application of three process-based models to Irish raised bog restoration, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18533, https://doi.org/10.5194/egusphere-egu24-18533, 2024.

Carbon use efficiency has recently been proposed as a central parameter that promotes soil organic carbon storage based on data assimilation with a global soil organic carbon database and a vertical, microbial explicit soil organic carbon model (Tao et al., 2023). In this research, we present a sensitivity study with a vertical soil organic carbon model, COMISSION v2.0 (Ahrens et al., 2020), that not only models microbial interactions explicitly but also represents organo-mineral interactions with a maximum capacity, Qmax, to form mineral-associated organic carbon (MAOC).

The COMISSION model represents the formation of MAOC from microbial necromass and dissolved organic carbon analogous to Langmuir sorption. Empirical studies have provided Qmax parameterizations derived from quantile or boundary line regressions with clay and silt content. For the sensitivity study, we vary Qmax along the full range of observed Qmax values while simultaneously varying carbon use efficiency (CUE). Our results highlight that CUE and Qmax promote soil organic carbon storage to similar degrees along their respective observed ranges. The remaining parameters of the COMISSION model were kept at their calibrated values from a multi-site calibration with soil organic carbon, mineral-associated organic carbon, and radiocarbon profiles (Ahrens et al., 2020). While Qmax and CUE are of similar importance for promoting soil organic carbon storage, they also interact in promoting SOC storage. Higher Qmax values strengthen the promotion of soil organic carbon storage with higher CUE. This positive interaction results from higher microbial necromass with higher CUE and the subsequent association of microbial necromass on mineral surfaces mediated through Qmax. The sensitivity study revealed that CUE is the dominant driver for microbial biomass levels. Qmax affects microbial biomass only to a small degree through 'competition' between mineral surfaces and microbial biomass for dissolved organic carbon. While the effect of Qmax on microbial biomass is small, the relationship between Qmax and microbial biomass is generally negative. At the lower end of the tested range of carbon use efficiencies (CUE < 0.15), further model experiments reveal that imposing a stronger microbial limitation of depolymerization can lead to a negative relationship between CUE and soil organic carbon storage.

Overall, our results highlight that in soil organic carbon models with microbial interactions and a limited capacity to form organo-mineral associations, both processes can be of similar importance in promoting soil organic carbon storage. The current debate in the observational realm, whether there is indeed an upper limit for mineral-associated organic carbon formation, can spark a similar debate in the modeling realm on how to represent mineral-associated organic carbon formation in models mechanistically.

 

References

Ahrens B, Guggenberger G, Rethemeyer J et al. (2020) Combination of energy limitation and sorption capacity explains 14C depth gradients. Soil Biology and Biochemistry, 148, 107912.

Tao F, Huang Y, Hungate BA et al. (2023) Microbial carbon use efficiency promotes global soil carbon storage. Nature, 618, 981-985.

Funding acknowledgment: Bernhard Ahrens has received funding through the AI4SoilHealth project. The AI4SoilHealth project has received funding from the European Union's Horizon Europe research and innovation programme under grant agreement No. 101086179.

How to cite: Ahrens, B. and Chettouh, M. A.: Carbon use efficiency and mineralogical capacity are of similar importance for promoting soil organic carbon stocks, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18844, https://doi.org/10.5194/egusphere-egu24-18844, 2024.

EGU24-19814 | ECS | Posters on site | ITS1.23/SSS0.1.4

Performance of the DNDC in Estimating CO 2 and N 2 O emissions of Integrated Crop-Livestock Systems 

Priscila S Matos, Johnny R Soares, Maria C S Carvalho, Beata E Madari, Bruno J R Alves, Claudia P Jantalia, Antônio C R Freitas, Bhaskar Mitraa, and Jagadeesh Yelupirati

Integrated crop-livestock (ICL) systems can have a complex of effects on soil properties that can influence greenhouse gas emissions (GHG). The ICL aim to capture atmospheric CO2 and sequester it in the soil, holding promise for reducing GHG emission intensity from livestock products. Moreover, modeling N2O emissions can help assess the potential impact of N management on the ICL system to optimize the sustainability of agriculture production. Field data were obtained from an ICL experiment of EMBRAPA-Rice and Beans, located on Capivara farm, Santo Antônio de Goiás/GO, Brazil (16°28´S; 49°17´W; 823 m alt.). The ICL experiment was evaluated for four years (2013-2016) with the following crop rotation sequence: pasture-fallow-maize, fallow-soybean, maize-fallow-maize, and beans-fallow. The N2O data was obtained from the 2013-14 season, which was measured in a static chamber during maize cultivation. The experiment consisted of 9 treatments (N sources and rates) with 5 replicates. The N2O was measured in 30 sampling events over almost 100 days. The daily N2O fluxes from the treatments control (No N), urea (UR), calcium ammonium nitrate (CAN), and ammonium sulfate (AS) at an N rate of 150 kg/ha were used to parametrize the DNDC. Model crop and soil parameters were adjusted to better simulate maize production and N2O emission according to observed data. DNDC simulated CO2 emissions, quantified as Net Ecosystem Exchange (NEE), were validated against CO2 emissions derived from eddy-covariance data, using statistical parameters such as R2, RMSE, MAE, and Bias. While data refinement is ongoing, preliminary findings indicate that DNDC shows promise for estimating CO2 emissions IPS under tropical conditions The DNDC had a satisfactory performance in predicting N2O emission in the ICL system, resulting in a significant correlation with the observed data (r = 0.63, p < 0.001), MAE of 0.024, and RMSE of 0.036. The average daily N2O-N emission observed was 0.026 kg ha-1 day-1 and simulated was 0.025 kg ha-1 day-1. The UR, CAN and AS applications showed a peak of N2O emission on 31th day after sowing (2 days after fertilization) corresponding to 0.175, 0.217, and 0.163 kg ha-1 day-1, respectively, where the model simulated N2O peaks of 0.151, 0.123, and 0.173 kg ha-1 day-1. The accumulated N2O emissions were 0.513, 1.148 1.738, and 0.890 kg ha-1 for control, UR, CAN, and AS respectively, in which the simulated by DNDC were 0. 778, 1.612, 1.391, and 1.755 kg ha-1. In general, the model had a good fit with daily N2O emissions, but it tended to overestimate the N2O emission from UR and AS, and underestimate from CAN. Further model parametrization and calibration may be necessary to better predict N2O and CO2 emissions. The DNDC satisfactory simulated the N2O emissions from different N sources applied to ICL system, which can be used to evaluate the potential emissions and mitigation according to N management in ICL.

How to cite: Matos, P. S., Soares, J. R., Carvalho, M. C. S., Madari, B. E., Alves, B. J. R., Jantalia, C. P., Freitas, A. C. R., Mitraa, B., and Yelupirati, J.: Performance of the DNDC in Estimating CO 2 and N 2 O emissions of Integrated Crop-Livestock Systems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19814, https://doi.org/10.5194/egusphere-egu24-19814, 2024.

EGU24-19820 | ECS | Posters on site | ITS1.23/SSS0.1.4

The LOESS project to boost soil health literacy across Europe: The case of Italy 

Marco Peli, Arianna Dada, Francesca Barisani, Vera Ventura, Michèle Pezzagno, Stefano Barontini, and Giovanna Grossi

The Horizon Europe project LOESS ‘Literacy boost through an Operational Educational Ecosystem of Societal actors on Soil health’ officially started in June 2023 involving twenty partner organizations in fifteen countries across Europe, lead by the WILA Bonn Science Shop. The final goal of the project is to raise awareness on the importance of soil and of its functions and to increase soil literacy across Europe. To do so, the first step of the project activity is designed to map and connect multiple actors in Communities of Practice (CoPs) at the national level, and engage them to provide an overview of the current level of soil related knowledge and teaching programmes and materials, in order to identify the gap between this material and the educational needs amongst different levels of the society (from pupils to students to citizens).

The Italian chapter is led by two university research groups with different expertise (civil and environmental engineering at the University of Brescia on one hand and social sciences at the University of Sassari on the other) and one NGO (Controvento) whose mission is children not-formal education. The Italian CoP, led by the University of Brescia, is composed of 62 members from both the higher education and the research community, as well as from the primary and secondary education levels (teachers and pupils), from the productive sectors (farmers and spatial planners), from the politics world (local administrators) and from the civil society (NGOs and associations).

This contribution presents the activities performed so far, viz the stakeholder mapping, the creation of the CoP and its first meetings and the community-based participatory activity which was organized on the World Soil Day 2023.

How to cite: Peli, M., Dada, A., Barisani, F., Ventura, V., Pezzagno, M., Barontini, S., and Grossi, G.: The LOESS project to boost soil health literacy across Europe: The case of Italy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19820, https://doi.org/10.5194/egusphere-egu24-19820, 2024.

EGU24-20664 | Posters on site | ITS1.23/SSS0.1.4

A framework for setting soil health targets and thresholds in agricultural soils  

Amanda Matson, Maria Fantappiè, Grant A. Campbell, Jorge F. Miranda-Vélez, Jack H. Faber, Lucas Carvalho Gomes, Rudi Hessel, Marcos Lana, Stefano Mocali, Pete Smith, David Robinson, Antonio Bispo, Fenny van Egmond, Saskia Keesstra, Nicolas P.A. Saby, Bozena Smreczak, Claire Froger, Azamat Suleymanov, and Claire Chenu

Soil health is a key concept in worldwide efforts to reverse soil degradation, but to be used as a tool to improve soils, it must be definable at a policy level and quantifiable in some way. Soil indicators can be used to define soil health and quantify the degree to which soils fulfil expected functions. Indicators are assessed using target and/or threshold values, which define achievable levels of the indicators or associated soil functions. However, defining robust targets and thresholds is not a trivial task, as they should account for differences in soil type, climate, land-use, management, and history, among other factors.

We assessed (through theory and stakeholder feedback) four approaches to setting targets and thresholds: fixed values based on research, fixed proportions of natural reference values, values based on the existing range (e.g. lower quartile of the observed distribution), and targets based on relative change (e.g. a 20% increase of the indicator’s value). Three approaches (not including relative change) were then further explored using case study examples from Denmark, Italy, and France, which highlighted key strengths and weaknesses of each approach. Here, we present a selection of the assessment and case study results, as well as a framework, which facilitates both choosing the most appropriate target/threshold method for a given context, and using targets/thresholds to trigger follow-up actions to promote soil health.  

How to cite: Matson, A., Fantappiè, M., Campbell, G. A., Miranda-Vélez, J. F., Faber, J. H., Gomes, L. C., Hessel, R., Lana, M., Mocali, S., Smith, P., Robinson, D., Bispo, A., van Egmond, F., Keesstra, S., Saby, N. P. A., Smreczak, B., Froger, C., Suleymanov, A., and Chenu, C.: A framework for setting soil health targets and thresholds in agricultural soils , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20664, https://doi.org/10.5194/egusphere-egu24-20664, 2024.

EGU24-21616 | Posters on site | ITS1.23/SSS0.1.4

Searching for pedotransfer functions to predict sorption of pharmaceuticals from soil properties 

Pierre Benoit, Charline Godard, Marjolaine Deschamps, Nathalie Bernet, Ghislaine Delarue, Valenti Serre, and Claire-Sophie Haudin

In the context of recycling organic waste products or irrigation by treated wastewaters (re-use), the fate of human and veterinary pharmaceuticals in agricultural soils and consequent ground-water contamination are influenced by many factors, including soil properties controlling sorption and dissipation processes (Verlicchi et al., 2015, Mejías et al., 2021, Rietra et al., 2022). Sorption coefficients are among the most sensitive parameters in models used for risk assessment. However, for different classes of pharmaceuticals, the variations in sorption among different soil types are poorly described and understood (Kodesova et al., 2015). Here we reviewed sorption parameters for different classes of pharmaceuticals and their variation with selected soil properties. We also evaluated the sorption isotherms for three pharmaceuticals, ofloxacin, tetracycline, diclofenac and a bactericide,  riclocarban and ten soils from temperate and tropical regions, and assessed the impact of soil properties on Freundlich equation parameters Kf and n. Batch experiments were set up adapting OECD protocol and using initial concentration ranges from 5 to 1000 μg/L. For strongly sorbed molecules, namely ofloxacin, tetracycline and triclocarban, there were strong technical constraints for the quantification of equilibrium concentrations by LC-MS-MS. We used this knowledge from both literature review and experimental data to build pedotransfer functions that allow predicting sorption parameters for a wide range of soils. Sorption of ionizable pharmaceuticals was, in many cases, highly affected by soil pH and CEC whereas soil organic matter content remained a driving factor of sorption for neutral molecular forms.


References:
Kodesova, R., et al. (2015) Science of the Total Environment 511, 435–443.
Mejías, C. et al. (2021) Trends in Environmental Analytical Chemistry 30, e00125.
Rietra, R.P.P.J., et al. (2024) Heliyon 10 (2024) e23718.
Verlicchi, P. & Zambello, E., (2015) Science of The Total Environment 538, 750–767

How to cite: Benoit, P., Godard, C., Deschamps, M., Bernet, N., Delarue, G., Serre, V., and Haudin, C.-S.: Searching for pedotransfer functions to predict sorption of pharmaceuticals from soil properties, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21616, https://doi.org/10.5194/egusphere-egu24-21616, 2024.

EGU24-22341 | Posters on site | ITS1.23/SSS0.1.4

Transport and bioaccessibility of nano-contaminants in Brazilian latosol through pore water evaluation 

Aline de Andrade, Marco A. Z. Arruda, Sophie Miguel, Stéphanie Reynaud, and Javier Jiménez-Lamana

Plastic production worldwide has increased from 1.5 million tons in 1950 to 390.7 million tons in 2021.1 Nanoplastics (NPTs) have been considered an emergent contaminant entering the environment without any control since they can be formed by the degradation of large-sized plastic inadequately disposed of and considering that only 9% are effectively recycled.2 Just as the NPTs, nanoparticles (NPs) are considered emergent contaminants, and their application in different industrial products raises concern regarding the NPs entering the environment matrices.3 The soil bioaccessibility is an important parameter when considering the contaminants assessment evaluation with biological soil phase, and the study of soil liquid solution, which is called the soil pore water, can elucidate not only the bioaccessibility but also NPTs and NPs mobility, fate, and stability.4 The NPTs’ and NPs’ concentrations in the range of ng L-1 might be a limitation for their evaluation. However, spICP-MS can provide information on size, number concentration, and mass concentration, even in environmental conditions.5 In this study, a typical Brazilian soil used for plant cultivation (Latosol) was employed, and the soil moisture was controlled according to the field capacity determined in advance. Polystyrene (PS) nanoparticles with gold core and silver NPs (AgNPs), considering their abundance in different goods, were used as model nano-contaminants. The soil pore water was collected in two sampling points through a low-pressure lysimetric method using Rhizon® samplers once a week for 45 days of the experiment. In addition, the soil moisture was controlled by monitoring and adding more water to maintain the soil humidity, considering the three field capacity percentages studied. Results showed a downward trend in the number of particles detected in successive collections over time for both nano-contaminants. However, they also demonstrated different behaviours between them. The NPTs were bioaccessible in the pore water after the first days from the beginning of the experiments, and their concentration decreased constantly. At the same time, the NPs presented an inconstant transport through the soil column, gradually becoming bioaccessible. Finally, the concentration proved to be an important and decisive parameter, bringing essential discussion regarding the nano-contaminant's increasing concentration and behaviour in an environmental matrix, demonstrating the necessity to comprehend their interactions with the soil and between each other.

 

1 S. Maity, R. Guchhait, M. B. Sarkar and K. Pramanick, Plant. Cell Environ., 2022, 45, 1011–1028.
2 P. Zhou, L. Wang, J. Gao, Y. Jiang, M. Adeel and D. Hou, Soil Use Manag., 2023, 39, 13–42.
3 Q. Abbas, B. Yousaf, Amina, M. U. Ali, M. A. M. Munir, A. El-Naggar, J. Rinklebe and M. Naushad, Environ. Int., 2020, 138, 105646.
4 M. Di Bonito, N. Breward, N. Crout, B. Smith and S. Young, in Environmental Geochemistry, Elsevier, 2008, pp. 213–249.
5 J. Jiménez-Lamana, L. Marigliano, J. Allouche, B. Grassl, J. Szpunar and S. Reynaud, Anal. Chem., 2020, 92, 11664–11672.

How to cite: de Andrade, A., Arruda, M. A. Z., Miguel, S., Reynaud, S., and Jiménez-Lamana, J.: Transport and bioaccessibility of nano-contaminants in Brazilian latosol through pore water evaluation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22341, https://doi.org/10.5194/egusphere-egu24-22341, 2024.

EGU24-467 | Orals | ITS4.6/SSS0.1.5

Nature-based solutions for leveed river corridors 

Matt Chambers, Dave Crane, Charles van Rees, Matt Shudtz, Craig Landry, Susana Ferreira, Don Nelson, Burton Suedel, Brock Woodson, and Brian Bledsoe

Climate driven changes in hydrologic regimes are increasing riverine flood risks in many parts of the world. Societies that have historically relied on structural flood management infrastructure, e.g., levees and dams, may face significant challenges as these types of infrastructure can be expensive and politically difficult to retrofit for non-stationary and uncertain future flood hazards. Hybridizing conventional infrastructure systems with nature-based solutions (NbS) can help communities adapt to non-stationarity and improve flood resilience. However, despite advances in the academic literature, NbS have failed to become mainstream in many societies. The United States (US) is no exception and has an extensive history of engineering rivers with structural systems to support immediate-term economic growth and with limited consideration for non-stationarity. For example, there are thousands of kilometers of continuously leveed river corridors in the US and many of these levees were built as close to river banks as possible to maximize the commercial prospects of flood protected land use. Such levees are relatively sensitive to non-stationarity and the communities they protect are becoming increasingly vulnerable to climate change-driven flooding. Our research focuses on how to bridge the gap between the scientific development of NbS and implementation in professional practice. We are doing so by example, with levee setbacks on America’s longest river -- the Missouri -- and in collaboration with the US’s primary action agency of flood risk management -- the US Army Corps of Engineers. Setbacks are implicitly an adaptation strategy that buffer a community against uncertainty and non-stationarity by providing additional room for floodwater conveyance. Unfortunately, they are fraught with social and political challenges because -- as a form of managed retreat -- they require some community members to relinquish private property rights so that the broader community can have greater flood protection. Critical to bridging the gap between levee setback research and implementation is understanding the performance of setbacks at scale and the development of simple and repeatable methods for designing setbacks to successfully deliver multiple ecosystem services. The most fundamental of which is how to “size” a setback – in other words – how big of a floodplain reconnection is required to achieve a desired improvement in flood protection services? In this talk, we will discuss sizing methodologies for achieving multiple services, as well as practical engineering, social, ecological, and administrative constraints that have arisen in the process of translating NbS research to practice. The example of levee setbacks on American rivers is particularly useful because it affords experimentation with repeatability (given the thousands of kilometers of continuously leveed river corridors) and the spatial scale of reconnection required to achieve multiple benefits (given the massive size of many levees and floodplains). The results of which may be relatable to many engineered river corridors around the world and will hopefully support mainstreaming NbS in other social and political contexts.

How to cite: Chambers, M., Crane, D., van Rees, C., Shudtz, M., Landry, C., Ferreira, S., Nelson, D., Suedel, B., Woodson, B., and Bledsoe, B.: Nature-based solutions for leveed river corridors, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-467, https://doi.org/10.5194/egusphere-egu24-467, 2024.

As urbanization and climate change continue to pose significant challenges for cities worldwide, green roofs (GRs) has emerged as a viable sustainable solution for supporting traditional infrastructure in managing stormwater runoff. Although their hydrological behavior has been sufficiently documented in literature, conflicting results emerge regarding the potential variations in their retention capacity (RC) over the medium and long-term. Based on preliminary investigations, this research aimed at assessing medium-term changes in the hydrological performance of two experimental GRs (GR1 and GR2), further investigating the potential role played by precipitation severity. The GRs, located in Southern Italy and consisting of three layers (vegetation, substrate and drainage), were set up in 2017 and monitored for two operational periods, 2017-2019 and 2022-2023. The measurements gathered between 2017 and 2019 provide valuable insights into the initial performance of the GRs and their ability to retain water during the early years of operation. Data collected in 2022 and 2023 instead reflect the retention capacity of the GRs after a few years of operation. A total of 29 mild precipitation events were collected during both periods and for both GRs, detecting from the monitoring data their cumulative precipitation (P) and runoff (R) with the objective of assessing the RC (RC = 1 - R/P). Based on the preliminary findings, it appears that there is an overall decline in the RC for both GR1 and GR2, without significant differences between the two. The Aging Indexes (AI) were calculated for GR1 and GR2, representing the average reduction of the runoff coefficient (RC) over time. GR1, which has a drainage layer composed of expanded clay, exhibited an AI of 12%. On the other hand, GR2, characterized by a drainage layer made of MODI' plastic panel filled with expanded clay, exhibited a slightly higher AI of 13%. Further analysis revealed that within each dataset, two groups were identified based on a threshold determined by the growth coefficient g(T) of the precipitation events. For the group of events with g(T) values above 0.12 (sample size of 14), the AI values were 15% and 16% for GR1 and GR2, respectively. On the other hand, the group of events with g(T) values equal to or lower than 0.12 (sample size of 15) experienced AI values of 10% and 11% for GR1 and GR2, respectively. These findings suggest that as the growth coefficient g(T) increases, indicating higher return periods T, the AI and consequently the reduction in hydrological performance of GRs also increase. The highly possible increase in the future of extreme precipitations would pose a considerable limit to the spread of this kind of sustainable drainage infrastructures. However, additional modeling investigations focused at detecting the effects of alternative GRs designs and materials on their long-lasting average hydrological performance would be essential for making informed decisions and investments.

How to cite: D'Ambrosio, R. and Longobardi, A.: Assessing the Medium-Term Changes in Hydrological Performance of Green Roofs: The Influence of Precipitation Severity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1019, https://doi.org/10.5194/egusphere-egu24-1019, 2024.

EGU24-1035 | ECS | Posters on site | ITS4.6/SSS0.1.5 | Highlight

Multi-scale analysis of green infrastructure morphology for climate change adaptation 

Lou Valide, Pierre-Antoine Versini, and Olivier Bonin

Nature-based Solutions, even if not identified as such, are becoming more and more popular in land planning, especially in cities. Conserving and restoring green infrastructure in urban context is now recognised as being a good practice in the face of climate change adaptation: ecosystem services provided by green spaces can help reduce urban heat island effect and risks of flood, improve resilience of ecosystems to preserve biodiversity and enhance human well-being through access to nature. Simultaneously, cities have to face another challenge: containing land take and urban expansion. The European Commission, in its Roadmap to a Resource Efficient Europe (2011), claimed the “aim to achieve no net land take by 2050”, a goal already transcribed in French law since 2021. Hence, the competition for land use which already existed between housing, industry, roads and recreational purposes will only become fiercer and have to include a new competitor: Nature-based Solutions. In this context, the ability of optimizing the implementation of such solutions – through the different scales at which they provide ecosystem services (building, neighbourhood, city and landscape) – is becoming primordial. Where should we conserve or restore green spaces in priority to ensure the providing of the ecosystem services needed for urban climate change adaptation? This question implies a multi-scale spatial analysis of the impact of green infrastructures on cities. To do so, the question of urban form is tackled by focusing on what is between buildings and streets, where green infrastructure can be deployed and woven into the urban fabric. To establish a multi-scale typology of green infrastructures based on their morphologies, classical approaches are combined with mathematical tools such as fractal analysis for characterizing their dispersion or graph theory for characterizing their connections, essential when studying biodiversity issues. This typology, associated with ecosystem services and biodiversity assessment for different French case studies (including the conurbations of Niort and Dijon), could help understand how to spatially implement Nature-based Solutions within cities, and be integrated into land-planning scenarios.

How to cite: Valide, L., Versini, P.-A., and Bonin, O.: Multi-scale analysis of green infrastructure morphology for climate change adaptation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1035, https://doi.org/10.5194/egusphere-egu24-1035, 2024.

EGU24-2018 | ECS | Posters on site | ITS4.6/SSS0.1.5

WebGIS for Marine Coastal Ecosystems: A Dynamic Interface for Communicating and Collaborating on Nature-Based Solutions in Climate Change Mitigation and Adaptation 

Jéssica Uchôa, Catarina Fonseca, Rafaela Tiengo, Bruna Almeida, and Artur Gil

As the global community grapples with the complex challenges of climate change, the integration of nature-based solutions (NBS) has emerged as a critical strategy. This work introduces a Web Geographic Information System (WebGIS) designed to showcase and communicate the results of initiatives focused on NBS within the scope of the Marine Coastal Ecosystems Biodiversity and Services in a Changing World (MaCoBioS) project. The platform serves as an interface for decision-makers and stakeholders, providing a spatially contextualized visualization of geospatial data related to marine and coastal ecosystems, climate risks, and adaptation. The MaCoBioS webGIS is based on an open-source platform, using JavaScript and the Leaflet map library to showcase key scenarios developed for case study ecoregions. The platform allows remote access to data irrespective of geographical constraints and is capable of integrating multidisciplinary data, ensuring a comprehensive and up-to-date view of evolving climate-related scenarios. The MaCoBioS webGIS not only facilitates the identification, evaluation, and direction of potential solutions to extant and emergent issues but also affords public access and participation. It serves as a foundational platform for prospective local and regional areas monitoring and management. By integrating qualitative information with scientific data, the aim is to present the results clearly and in a straightforward language, to reach a broader audience, including those who may not have specialized expertise. In so doing, it establishes the groundwork for future initiatives, promoting collaboration and leveraging cutting-edge technology for the betterment of coastal communities and ecosystems. In summary, the webGIS not only serves as a powerful tool for visualizing geospatial data but also acts as an effective means of communication and collaboration. By promoting informed decision-making, and supporting initiatives related to climate change and NBS, the platform contributes to the collective effort in addressing the complexities of our changing climate.

How to cite: Uchôa, J., Fonseca, C., Tiengo, R., Almeida, B., and Gil, A.: WebGIS for Marine Coastal Ecosystems: A Dynamic Interface for Communicating and Collaborating on Nature-Based Solutions in Climate Change Mitigation and Adaptation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2018, https://doi.org/10.5194/egusphere-egu24-2018, 2024.

The Great Green Wall (GGW) is a multibillion-dollar African initiative to combat desertification in the Sahel by restoring 100 million hectares of degraded land. The idea of a physical green wall of trees has now been developed into the implementation of scattered green zones throughout arid areas, providing sustainable reforestation, revegetation, and land management. In West Africa, the most important climate feature is the West African Monsoon (WAM), which brings rainfall over the Sahel during the Northern Hemisphere summer. Climate dynamics associated with WAM changes could also play a role on the Atlantic Tropical Cyclones (ATCs) formation and variability. The potential climate impacts of the most recent GGW plan on northern Africa and tropical Atlantic have not yet been adequately evaluated, raising concerns about unforeseen climate ramifications that could affect stability in northern Africa and impact on the ATC variability. Here, we use a high-resolution (~13 km) regional climate model to evaluate the climate impacts of four GGW scenarios with varying vegetation densities under two extreme emission pathways (low and high). Higher vegetation density GGW scenarios under both emission pathways show enhanced rainfall, reduced drought lengths and decreased summer temperatures beyond the GGW region relative to the cases with no GGW. However, all GGW scenarios show more extreme hot days and heat indices in the pre-monsoonal season. Furthermore, in spite of a strong variation in the African Easterly Waves activity, no significant changes are found in terms of ATCs frequency, intensity, meridional motion and translation speed over the North Atlantic area. Small changes in the TC densities are found in front of the cost of West Africa,  in the eastern side of the Main Development Region. These findings highlight the GGW's contrasting climatic effects, emphasizing the need for comprehensive assessments in shaping future policies.

 

How to cite: Ingrosso, R. and Pausata, F. S.: On the climate impacts of four different Great Green Wall scenarios on the northern Africa and the Atlantic Tropical Cyclones variability., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2883, https://doi.org/10.5194/egusphere-egu24-2883, 2024.

Given the local pollution near the school in Follonica(Gr)-Italy, specifically at the Gora river’s mouth, students have designed a study (IBSE method) of the chemical and ecological indicators of the river's situation. Analyzing the city's history about climate, the changes of the water regime and the shape of the river during the XX century, they have measured the indicators (physical and chemical parameters of the water, Extended Biotic Index). Creating a website and an interactive map of the river, they have communicated the situation to the local authorities, so the school has become involved in the "Pecora River Agreement", a local project aiming to the redevelopment of the river ecosystem. Students make proposal: plants in the riverbank, activities to sensitize local community and monitoring through ecological index for the future of the city.

How to cite: severi, A.: Requalify our river: from a school project to a city project, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3616, https://doi.org/10.5194/egusphere-egu24-3616, 2024.

The recently released IPCC Mitigation report placed agroforestry as one of the top three Agriculture, Forestry and Other Land Use (AFOLU) mitigation pathways, noting that it delivers multiple biophysical and socioeconomic co-benefits such as increased land productivity, diversified livelihoods, reduced soil erosion, improved water quality, and more hospitable regional climates, concluding there is ‘high confidence’ in agroforestry’s mitigation potential at field scale. As such, agroforestry is one of the most cited nature-based solutions in development strategies and in reporting of nationally determined contributions (NDC),  both for its potential mitigation benefits, but not least for the adaptation, resilience and livelihood benefits it can provide, across scales from agro-industrial farming to small farmer holdings. Here we present recent global and regional estimates of above- and below-ground biomass on agricultural land based upon IPCC Tier 1 estimates and compare results with an updated carbon density map based on remote sensing, with results indicating the methodology and initial estimations are robust. Two future scenarios are evaluated to estimate carbon sequestration potential of increasing tree cover on agricultural land: 1.) incremental change and 2.) systematic change to agroforestry. Estimates of above- and below ground biomass carbon were combined with a remote sensing-based tree cover analysis to estimate the increase in biomass. Global increases (4-6 Pg C for incremental change; 12-19 Pg C for systematic change) highlight substantial mitigation potential. Increasing global tree cover on agricultural land by 10% would sequester more than 18 Pg C over a decade. South America has the highest potential, followed by Southeast Asia, West and Central Africa, and North America. Brazil, Indonesia, Philippines, India, the United States and China are among the top countries. Additionally, we provide an overview and analysis of the unique and significant contribution agroforestry can provide in mountainous regions and in reducing pressure on irrecoverable carbon.

How to cite: Zomer, R., Xu, J., Spano, D., and Trabucco, A.: Nature-Based Solutions: Evaluating the global carbon sequestration potential of agroforestry and increased tree cover on agricultural land., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6018, https://doi.org/10.5194/egusphere-egu24-6018, 2024.

EGU24-6169 | ECS | Orals | ITS4.6/SSS0.1.5

Modelling CO2 flows from extensive green roofs within the TEB (town energy balance) urban canopy model 

Aurélien Mirebeau, Cécile de Munck, Stephan Weber, Aude Lemonsu, and Valéry Masson

To mitigate climate change impacts in cities, nature-based solutions are broadly promoted due to their supposed benefits for biodiversity, rainwater management, evaporative cooling, and sequestration of carbon. Among existing solutions, green roofs show the advantage of tackling the lack of space available for greening in urban areas. But green roofs are still underdeveloped due to their cost and the lack of scientific knowledge around their potential, especially for carbon sequestration. Quantifying the various contributions of green roofs using reliable scientific approaches is a major challenge. Thus, it is essential to build a numerical model capable of simulating green roofs development and functioning at city scale in order to provide information to decision-makers with relevant indicators.

 

Here, the urban canopy model Town Energy Balance (TEB) with the module TEB-GREENROOF is used to model green roofs. The TEB-GREENROOF model, evaluated in previous study for heat and water transfers, is improved by activating the photosynthesis model ISBA-A-gs in order to represent the CO2 exchanges of the vegetation implemented on the green roof. The modelling is informed by 6 years of continuous CO2 flux data on a non-irrigated extensive green roof located in Berlin (Germany) in partnership with the Technische Universität Braunschweig. In order to evaluate and improve the thermal, hydrological and respiration characteristics of the ISBA-A-gs model on a green roof, an initial simulation is carried out by forcing the monthly evolution of the leaf area index (LAI) by LAI data estimated experimentally. The model is then applied with a dynamic calculation of LAI in order to enable it for simulations of roof greening scenarios on a city-wide scale under any climate with no information on the LAI.

 

Results show that the model is able to estimate the annual net ecosystem exchange of the Berlin green roof and to correctly reproduce the CO2 fluxes for both diurnal cycles and annual variation under climate variability, with drier years showing less carbon sequestration.

How to cite: Mirebeau, A., de Munck, C., Weber, S., Lemonsu, A., and Masson, V.: Modelling CO2 flows from extensive green roofs within the TEB (town energy balance) urban canopy model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6169, https://doi.org/10.5194/egusphere-egu24-6169, 2024.

EGU24-6608 | Orals | ITS4.6/SSS0.1.5

Nature-based solutions for erosion mitigation : insights from a systematic review for the Andean region 

Veerle Vanacker, Armando Molina, Miluska Rosas, Vivien Bonnesoeur, Francisco Román-Dañobeytia, Boris Ochoa-Tocachi, and Wouter Buytaert

The Andes Mountains stretch over about 8900 km and cross tropical, subtropical, temperate and arid latitudes. More than 85 million people lived in the Andean region by 2020, with the northern Andes being one of the most densely populated mountain regions in the world. The demographic growth and a stagnating agricultural productivity per hectare led to an expansion of the total agricultural land area, either upward to steep hillsides at high elevations covered by native grassland-wetlands ecosystems, or downward to lands east and west of the Andes covered by tropical and subtropical forests. Land use and management have significantly altered the magnitude and frequency of erosion events. 

This study systematically reviews the state of evidence on the effectiveness of interventions to mitigate soil erosion by water and is based on Andean case studies published in gray and peer-reviewed literature. After screening 1798 records, 118 empirical studies were eligible and included in the quantitative analysis on soil quality and soil erosion. Six indicators were pertinent to study the effectiveness of natural infrastructure: soil organic carbon and bulk density of the topsoil, soil loss rate and run-off coefficient at the plot scale, and specific sediment yield and catchment-wide run-off coefficient at the catchment scale. The protection and conservation of natural vegetation has the strongest effect on soil quality, with 3.01 ± 0.893 times higher soil organic carbon content in the topsoil compared to control sites. Soil quality improvements are significant but lower for forestation and soil and water conserva- tion measures. Soil and water conservation measures reduce soil erosion to 62.1 % ± 9.2 %, even though erosion mitigation is highest when natural vegetation is maintained.

Further research is needed to evaluate whether the reported effectiveness holds during extreme events related to, for example, El Niño–Southern Oscillation.

 

 

 

How to cite: Vanacker, V., Molina, A., Rosas, M., Bonnesoeur, V., Román-Dañobeytia, F., Ochoa-Tocachi, B., and Buytaert, W.: Nature-based solutions for erosion mitigation : insights from a systematic review for the Andean region, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6608, https://doi.org/10.5194/egusphere-egu24-6608, 2024.

EGU24-7898 | ECS | Posters on site | ITS4.6/SSS0.1.5

Nature-based Solutions on privately owned land: Stakeholder engagement matters 

Marion Wallner, Thomas Thaler, Arthur Schindelegger, and Katharina Gugerell

To tackle hydrometeorological extreme events and adapt to climate change, Nature-based Solutions (NbS) are widely considered a promising approach. Yet, their implementation remains challenging. One key reason is that NbS require a lot more land than grey infrastructure – making their implementation dependent on privately owned land and prone to cause or exacerbate conflicts of interest over land use. This request of privately owned land widens the numbers of actors involved in the decision-making process. For this very reason, the realisation of NbS highlights the necessity of meaningful stakeholder engagement. However, in the past, technical mitigation measures were traditionally enforced top down by engineers within the public administration at national or regional level. Stakeholder engagement thus fundamentally changes the way how risk managers and citizens collaborate and is often reported to not live up to its expectations. Therefore, this study will address the role of stakeholder engagement as a decisive factor for the implementation of NbS on privately owned land. More specifically, it aims (i) to analyse what approaches to stakeholder engagement are currently employed on the side of flood risk authorities and (ii) to evaluate how stakeholder engagement processes account for conflicts of interest over land use. For this purpose, a qualitative research design approach will be exerted. This will involve desk research to identify areas in Austria where NbS on privately owned land have already been (and will be) implemented, semi-structured interviews with public water authorities and workshops in our case study site – the Lafnitz catchment in Austria. Lessons learnt will be compared with those of five other regions across Europe, as our study is embedded in the EU Horizon Project “Land4Climate” (Utilization of private land for mainstreaming Nature-based Solutions in the systemic transformation towards a climate-resilient Europe, HORIZON-MISS-2022-CLIMA-01-06). By doing so, our research will provide hands-on knowledge on NbS implementation and foster its mainstreaming across the European Union.

How to cite: Wallner, M., Thaler, T., Schindelegger, A., and Gugerell, K.: Nature-based Solutions on privately owned land: Stakeholder engagement matters, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7898, https://doi.org/10.5194/egusphere-egu24-7898, 2024.

Idea and Objectives: The health and well-being of urban populations are increasingly under pressure from climate change, for example, due to temperature extremes resulting in heat stress. The demand for heat mitigation is particularly high for urban areas in humid, tropical climates, as they are affected by heat stress already today, and for which a further amplification of heat stress is expected. For the case of Hue, a humid tropical Central-Vietnamese city, based on a typology of selected green-blue infrastructure elements, potential benefits for the regulation of outdoor temperature and outdoor thermal comfort are systematically virtually implemented and modelled. In order to promote acceptance of greening interventions by the public in Hue, citizen demands and preferences towards urban green elements, including potential co-benefits, are considered in this study, and in so-doing, best practices for local action shall be identified.

 

Background: Vietnam is a country that faces multiple challenges. Climate change is anticipated to exacerbate natural hazard risks, i.e., of flooding, storms, and prolonged periods of extreme heat, which are known to increase the risk of mortality, particularly among vulnerable groups. This is compounded by ongoing, rapid urban growth, that urgently necessitates safeguarding urban ecosystem services to facilitate climate change adaptation, and to support human health and well-being. Elements of the urban green-blue infrastructure are typically regarded as efficient nature-based interventions for the delivery of often multiple ecosystem services, including benefits for urban heat mitigation, i.e., the improvement of outdoor thermal comfort. Accordingly, such measures are increasingly being funded, politically recognised and implemented in Southeast Asian countries, including Vietnam. However, specifically for Vietnam, certain knowledge gaps remain with respect to the effectiveness of greening interventions for heat mitigation under local conditions, as well as in regard to ensuring the implementation of locally relevant and thus sustainable and resilient nature-based solutions.

How to cite: Sumfleth, L., Scheuer, S., Nguyen, L., and Haase, D.: Urban green-blue infrastructure as nature-based solutions for urban heat adaptation in Hue city, Central Vietnam – Potential impacts in contrast to citizen demands for urban greenery, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7963, https://doi.org/10.5194/egusphere-egu24-7963, 2024.

EGU24-8569 | ECS | Posters on site | ITS4.6/SSS0.1.5

Reference evapotranspiration sensitivity to climatic variables in Genoa, Italy.  

Komal Jabeen and Anna Palla

  Reference evapotranspiration sensitivity to climatic variables in Genoa, Italy.

  • Komal*, A. Palla

Department of Civil Chemical and Environmental Engineering, University of Genova, Montallegro 1, Genoa, Italy

*Corresponding author email: komal.jabeen@edu.unige.it

To develop nature-based solutions for sustainable urban water management, it is important to understand the effect of climatic variables over Reference Evapotranspiration (ET0). The aim of this study is to observe the effect of variation in independent meteorological variables in estimation of ET0 through Penman Montieth Equation for a green roof experimental site located in Genoa, Italy. Sensitivity of ET0 along the year is investigated by using relative changes in the dependent variable (ET0 in mm/day) against relative changes in the following independent variables: maximum temperature (Tmax in °C), solar radiation (Rs in MJ/m²/day), wind velocity (U in m/s), maximum relative humidity (RHmax in %) while keeping all other dependent variables constant. Reference evapotranspiration at daily scale was assessed by the Penman–Monteith equation according to the guidelines given in FAO irrigation and drainage paper 56.

     

A dimensionless sensitivity coefficient, SCX for each independent variable, X, is defined as follows:

where the subscripts Base refers to the observed set of dependent variables while the subscript X refers to the subset including the modified dependent variable. The modified variables are built according to a matrix of 40 values characterized by a 5% increase.

In the daily analysis, the SC average values for T, Rs and U are positive while for RHmax is negative. According to the results, FAO-56 is highly sensitive to the value of Rs as confirmed by the average value of SC equal to 0.3147) that means every 5% increase in Rs would result in 31.47% rise in the rate of ET0 on average annually. Average value of SC for Tmax was 0.1641, for RH max was -0.0951 and for U was found to be 0.2063. SC values were ranked as Rs > U > T max > RHmax but this impact of increase or decrease does not work identically all through the year since all the SC coefficients show seasonality. In particular, for summer season the sensitivity of ET0 is higher for Rs and Tmax as the intensity and duration of incoming solar radiation is high while the effect of windspeed is negligible in summer, contrary in winter season, ET0 is negatively affected by Rs and Tmax.  follows the pattern of  but it varies in magnitude. The effect of wind is quite noticeable in winter when windspeed is generally higher in Genoa with respect to temperature and solar radiation becoming the ET0 driving factor.  As Genoa is a coastal city and the climate is mainly humid, the effect of maximum relative humidity is almost constant all through the year. This study can serve as a baseline to understand the sensitivity of FAO Penman equation across different urban zones of Italy and consequently to understand the hydrologic performance nature-based solution under climate change.

How to cite: Jabeen, K. and Palla, A.: Reference evapotranspiration sensitivity to climatic variables in Genoa, Italy. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8569, https://doi.org/10.5194/egusphere-egu24-8569, 2024.

EGU24-8691 | ECS | Posters on site | ITS4.6/SSS0.1.5

Development of wind and fire risk indices for climate-mitigation forestry 

Els Ribbers, Hanna Lee, Priscilla Mooney, Helene Muri, Lei Cai, Jin-Soo Kim, and Lars Nieradzik

Afforestation has long been discussed as a nature-based climate mitigation solution. Although it could be an economic, green, and safe climate mitigation method, several studies suggest the possibility of unforeseen consequences depending on how it is implemented. An important aspect to be taken into account when designing af- and reforestation plans is the risk of damage to the new forest system in the face of climate warming. Recent studies have already shown an increase in both wind and fire damage risks in northern latitudinal forests related to climate warming, with strong winds leading to breakage of individual branches as well as in the knock-over of individual trees or even entire forest areas.

However, the forest system is complex, with a high number of feedback loops between different types of damage and between forest structure and ecological parameters. A few examples: Trees that are weakened by damage from pest outbreaks and snowfall are more susceptible to damage from wind and fire; Gaps in the forest that are created by management or damage both increase wind flow due to an eddy effect and create new forest edges with poorly adapted trees, increasing the risk of wind-throw.

Due to this complexity, the resilience to damage and therefore ability of forests to mitigate climate on a regional scale are still poorly understood. Understanding this complexity requires model work and extensive literature research, as most studies only focus on a few aspects of the forest system, such as the management type or wind effects. The aim of the study is therefore to develop adequate and future-proof wind- and fire risk indices that boreal forest managers can use to improve management strategies to make climate-mitigation forests more effective, resilient and damage resistant.

To do this, output from the Weather Research and Forecasting (WRF) model is used in combination with data on damage, forest management and forest structure to shed some light on possible feedbacks between forest systems and climate on a small-scale basis, in this case 3kmx3km. This information is then used to expand the Canadian Forest Fire Weather Index (FWI) to include ecological, management-related and forest structural parameters. As the structure of the existing FWI is climate-based, the wind risk index will be based on the developed fire risk index.

Our preliminary results show that wind damage was most common and extensive in the south-western coastal area of Norway over the last two decades. In contrast, fire damage was most prevalent in the south, with increased damage extent in the south-west of the country. Furthermore, the FWI shows that under an afforestation scenario in Norway, the mountainous region will have the highest frequency of days with medium to high danger of forest fires under climate warming. In this presentation we will discuss these preliminary results, as well as the methodology we will be using to develop the risk indices. Policymakers and forest owners alike will be able to use the risk indices to make the climate-mitigation forests more resilient against damage in a warming climate.

How to cite: Ribbers, E., Lee, H., Mooney, P., Muri, H., Cai, L., Kim, J.-S., and Nieradzik, L.: Development of wind and fire risk indices for climate-mitigation forestry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8691, https://doi.org/10.5194/egusphere-egu24-8691, 2024.

The proliferation of climate-induced stressors has deterred countries' green spaces (GS), which in turn degrade and deplete natural green barriers. Hence, Urban Green Infrastructure (UGI) modelling is grabbing global attention perceiving it as a nature-based mitigation/adaptation strategy to enhance the resilience of urban areas to fight climatic risks. UGI protects and improves the socio-ecological wellness of urban and rural regions. This research intends to investigate thirteen sustainable UGI indicators and their functional linkage with the five vital taxonomies of nature-based green solutions (at the neighborhood level) under a community participatory (CP) approach; out of ten GS elements and twenty-two sustainable UGI indicators developed by the author in his earlier research study [2-5]. It is to develop a sustainable UGI indicator-based framework (tailored to the native-built context) for climate-resilient urbanisation.

The results of the in-depth household survey (192 questionnaires), executed in three KP districts, Charsadda, Peshawar, and Mardan, and results were generated through Relative Importance Index (RII) and Interquartile Range Technique (IQR) show a very good level of coefficient alpha (α) value, (α = 0.7) — an acceptable threshold level [6, 7]. Furthermore, this study acknowledges key GS taxonomies that have achieved RII value ≥ 0.72. This performs a pivotal role in quality improvement and strengthening the resilience (health) of the respective UGI indicators. This scientific research study provides a foundation for an eco-regional paradigm in KP territory that paves the way for an effective implementation of green urbanism to naturally ameliorate the vulnerability to potential climatic stresses (like flooding, drought, the UHI effect) and disastrous impacts on the socio-ecological wellness.

Keywords: sustainable green infrastructure (GI) indicators; participatory planning (PP); nature-based green initiatives; climate change (CC); socio-ecological wellness; KP, Pakistan

References

1. Mell, I. C., Henneberry, J., Hehl-Lange, S., & Keskin, B. (2013). Promoting urban greening: Valuing the development of green infrastructure investments in the urban core of Manchester, UK. Urban Forestry & Urban Greening, 12(3), 296–306. http://dx.doi.org/10.1016/j.ufug.2013.04.006

2. Rayan, M., Gruehn, D., Khayyam, U., (2021b). Green infrastructure planning. A strategy to safeguard urban settlements in Pakistan. In: Jafari, M., Gruehn, D., Sinemillioglu, H., Kaiser, M. (Eds.), Planning in Germany and Iran. Responding Challenges of Climate Change through Intercultural Dialogue. Mensch und Buch Verlag. Berlin, pp. 197–220.

3. Rayan, M., Gruehn, D., & Khayyam, U. (2021a). Green infrastructure indicators to plan resilient urban settlements in Pakistan: Local stakeholder’s perspective. Urban Climate, 38, 100899. https://doi.org/https://doi.org/10.1016/j.uclim.2021.100899

4. Rayan, M.; Gruehn, D.; Khayyam, U (2022a). Frameworks for Urban Green Infrastructure (UGI) Indicators: Expert and Community Outlook toward Green Climate-Resilient Cities in Pakistan. Sustainability 2022,14, 7966. https://doi.org/10.3390/su14137966.

5. Rayan, M.; Gruehn, D.; Khayyam, U (2022b). Planning for Sustainable Green Urbanism: An Empirical Bottom-Up (Community-Led) Perspective on Green Infrastructure (GI) Indicators in Khyber Pakhtunkhwa (KP), Pakistan. Int. J. Environ. Res. Public Health 2022, 19, 11844. https://doi.org/10.3390/ijerph191911844

6. Cortina, J. M. What is coefficient alpha? An examination of theory and applications. J. Appl. Psychol (1993).

7. Peterson, R. A. A Meta-analysis of Cronbach’s Coefficient Alpha. J. Consum. Res (1994).

8. Wu, J., & Wu, T. (2012). Sustainability indicators and indices: an overview. Handbook of Sustainability Management, 65–86. http://dx.doi.org/10.1142/9789814354820_0004

How to cite: Rayan, M., Gruehn, D., and Khayyam, U.: Community-driven sustainable green infrastructure (GI) indicators to plan an eco-friendlier and climate-resilient city-state in Khyber Pakhtunkhwa (KP), Pakistan., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8806, https://doi.org/10.5194/egusphere-egu24-8806, 2024.

EGU24-9173 | ECS | Orals | ITS4.6/SSS0.1.5

Opportunities to Restore and Protect Coastal Ecosystems with Enhanced Interdisciplinary Management - The Mediterranean Model. 

Maria Makaronidou, Vito Emanuele Cambria, Evangelia Korakaki, Christos Georgiadis, and Nikos Petrou

Coastal zone ecosystems’ global importance is the primary driver of the wide scientific efforts for their restoration and protection. Over the past three decades, there has been a growing global momentum in the pursuit of initiatives aimed at conserving nature. Regardless of the wide scientific interest, and despite the notable exposure of these ecosystems to degradation and deterioration, numerous habitats, and species, in Europe, have 'vulnerable', or 'near threatened' conservation status. Even in the most favourable circumstances, factors including strong human pressure, urbanization and agriculture, and climate change, exhilarate the current, already, negative trends indicators, related to biodiversity and their associated ecosystem functions and services provision. This project proposes a set of existing and emerging methodologies and solutions for the restoration, conservation, and management practices, which are crucial to improving these profoundly delicate ecosystems in the Mediterranean and similar environmental contexts.

Traditional and innovative ecological restoration solutions have been designed and applied in two such areas along the Greek and Italian coasts, ‘Nestos Delta’ and ‘Bosco di Palo Laziale’, respectively, to improve the conservation status of 'Pannonian-Balkanic turkey oak-sessile oak forests' (habitat 91M0), ‘Alluvial forests with Alnus glutinosa and Fraxinus excelsior’ (habitat 91E0), and 'Mediterranean temporary ponds' (*3170) that have been increasingly exposed to climate change and inappropriate forest and water management.

Analogous, ecological restoration practices include selective trimming of encroaching shrub vegetation (and alien invasive shrubs in the Nestos area), remote-controlled irrigation system, origin-controlled and pathogen-free forestry nursery, ex-situ micro-propagation and in-situ reinforcement of keystone plant populations. An in-depth assessment and quantification of abiotic and biotic factors of the sites' ecosystems were preliminarily conducted to tailor these interventions to the habitats' geo-morphological, climatic, pedological, and physiological conditions.

The EU project LIFE PRIMED (LIFE17 NAT/GR/000511), operates at the Delta of River Nestos in Greece, and the Forest of Palo Laziale in Italy. The results in both areas, thus far, have demonstrated that the collaborative development of innovative water harvesting systems, coupled with adaptation measures, has the potential to enhance water resilience in already degraded forest ecosystems. To date, the project has successfully tackled the effects of escalating irregular rainfall patterns on Mediterranean coastal habitats by implementing a hydraulic system and a wellpoint-based water distribution network in Palo Laziale and Nestos Delta, respectively.

Monospecific approaches for climate and human-related phenomena, such as extreme weather events and agriculture pressure, are disfavoured. Therefore, the LIFE PRIMED project, comprised of an interdisciplinary team of Botanists, Zoologists, Foresters, and Environmental Engineers, has developed and delivered Nature-based transnational, ecosystem-oriented holistic solutions that will have the potential to be replicable and transferable with the greatest aim to recover dysfunctional, poorly managed coastal forest areas, across the Mediterranean region.

How to cite: Makaronidou, M., Emanuele Cambria, V., Korakaki, E., Georgiadis, C., and Petrou, N.: Opportunities to Restore and Protect Coastal Ecosystems with Enhanced Interdisciplinary Management - The Mediterranean Model., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9173, https://doi.org/10.5194/egusphere-egu24-9173, 2024.

EGU24-11439 | ECS | Orals | ITS4.6/SSS0.1.5 | Highlight

Assessing the vulnerability to climate change of tree species for urban afforestation 

Cristiano Gala, Gabriele Curci, Loretta Pace, Alessandro Marucci, and Dina Del Tosto

Nature-based solutions are now a key part in climate change adaptation, particularly for urban environments. The integration of natural systems within the urban fabric has the potential to increase cities’ resilience to the predicted changes in climate. Urban forests are one of the most used methods for adding ecosystem services to an urban environment and at the same time address urban-specific climate change challenges such as heat-island effect, intense rainfall and water management. However, the effects of climate change in the long-term on urban forests are not often taken into account when planning interventions such as afforestation. Species selection for urban forests should, among other factors, be based on an assessment of local future climatic conditions, so to ensure the long-term viability of the project. Here we propose a methodology easily applicable to any place in Europe. We use data from interpolated publicly available climate datasets and species distribution data from the European Tree Atlas in order to analyse climatic niches for tree species in Italy. These climatic ranges are then compared to local climatic data, obtained from homogenised time-series measured by a weather station in the city of L’Aquila. The results are summarised in a suitability matrix providing vulnerability scores for each species based on predicted climate changes for the local area. The analysis ranks the species which are less vulnerable to projected future climate conditions. The application to the pilot area of L’Aquila suggests that some species already present will still be suitable also in future climate (e.g. Quercus pubescens) while others will not (e.g. Quercus petraea), and species not traditionally present may become suitable (e.g. Quercus ilex). The importance of obtaining accurate local climate data from observations is a key aspect for municipalities to consider as results of this analysis are greatly dependent on this.

How to cite: Gala, C., Curci, G., Pace, L., Marucci, A., and Del Tosto, D.: Assessing the vulnerability to climate change of tree species for urban afforestation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11439, https://doi.org/10.5194/egusphere-egu24-11439, 2024.

EGU24-13018 | ECS | Orals | ITS4.6/SSS0.1.5

Leveraging the co-benefits of large tree protection to inform nature-based management of a forest ecosystem 

Tessa Maurer, Patricia Manley, Christopher Anderson, Nicholas Povak, Philip Saksa, Anu Kramer, and Zachary Peery

In fire-adapted forests around the world, nature-based solutions (NbS) are increasingly used as a tool to promote resilience to catastrophic fire through actions like fuels reduction and prescribed burning. This work also has many potential co-benefits, including climate change mitigation through stable carbon storage and biodiversity through habitat protection. One key mechanism for realizing both of these co-benefits is the protection of large and ancient trees, keystone components that sequester a disproportionate amount of carbon and serve as unique habitat for old forest associated species, many of which are declining or at risk of extinction. However, climate change poses a substantial risk to both tree recruitment and survival, either directly (temperature and drought tolerance) or indirectly (wildfire and insect occurrence). These impacts are not fully understood in the scientific literature nor, as a result, fully accounted for in the design of NbS management projects.

Therefore, to help inform near-term NbS restoration priorities, we investigated how a changing climate will impact the retention of large trees on the landscape and the ecosystem functions they support. Focusing on the Sierra Nevada, California, USA, a biophysically diverse and at-risk mountain ecoregion, we evaluated the intersection of current and future climate with large tree occurrence and two critical functions: carbon storage and habitat for the California spotted owl (Strix occidentalis occidentalis; CSO), an old growth associated species whose core population is limited to the Sierra Nevada and that requires large trees for nesting habitat. We mapped large trees across the Sierra Nevada, evaluated the climatic drivers of large tree biogeography, and forecasted how conditions supportive of large tree populations might shift geographically in the future under two emission levels (RCP 4.5 and 8.5). Using a bivariate fuzzy logic approach, we mapped the joint probability of current CSO occupancy and carbon storage and then evaluated future climate vulnerabilities and associated management strategies. We found that carbon and CSO occupancy corresponded closely with the current distribution of large trees in the Sierra, primarily at mid-elevations in the central Sierra. Similarly, we found that these mid-elevation montane forests are likely to continue to support large trees and CSO habitat and carbon storage through mid-century (e.g., consistent with "monitor" and "protect" climate-informed management strategies). Conversely, climate conditions in the southern Sierra and the upper elevations of the central Sierra are likely to constrain the persistence and recruitment of large trees, affecting the potential to recruit CSO habitat and enhance the carbon storage of higher elevation forests. 

We hope these findings will encourage the design of and investment in climate-informed NbS projects, and we propose that this method could be used in other ecosystems to jointly assess the climate change mitigation and biodiversity impacts of NbS-based management.

How to cite: Maurer, T., Manley, P., Anderson, C., Povak, N., Saksa, P., Kramer, A., and Peery, Z.: Leveraging the co-benefits of large tree protection to inform nature-based management of a forest ecosystem, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13018, https://doi.org/10.5194/egusphere-egu24-13018, 2024.

Modern cities are highly vulnerable to the adverse effects of climate change, primarily due to the escalating frequency of extreme weather events, including heatwaves. The current state of knowledge leaves no doubt that these effects are exacerbated by ongoing urbanization, leading to the continuous sealing of surfaces and a decrease in green areas in urbanized regions, contributing to the formation of Urban Heat Islands (UHI). These phenomena result in urban space degradation, causing economic, environmental, and demographic losses. Consequently, implementing solutions to enhance cities' resilience to climate threats should be a priority for local governments. Crucial in this context is the development of blue-green infrastructure, with a specific emphasis on micro-retention and the improvement of biologically active surfaces and vegetation habitat conditions. The implementation of such solutions, especially in the face of increasing extreme weather events, is essential for ensuring the sustainable development of smart cities.

This paper will present the results of research on the spatiotemporal distribution of the effectiveness of various components of blue-green infrastructure on a city-wide scale (including: river valleys, forests, urban parks, squares, pocket parks, and larger water bodies) in mitigating the UHI phenomenon in Wrocław, Poland. The study assesses the potential of blue-green infrastructure to mitigate the impact of heatwaves on the population most vulnerable to such threats. As an indicator of urbanized areas' vulnerability to the negative health effects of UHI, we focused on the population aged over 65. The research aims to provide crucial insights into how blue-green infrastructure can be optimized to effectively reduce UHI impacts and minimize health risks, especially within the most vulnerable age groups. This operation constitutes one of the initial stages in creating a prototype of a digital twin of the urban environment of Wrocław. The ultimate goal is to model information about blue-green infrastructure for the purpose of optimizing spatial policy in the context of adapting urbanized areas to climate change. This approach aligns with the Destination Earth initiative developed within the framework of the European Green Deal and EU Digital Strategy.

In the research, data integration was performed using various sources, including multispectral imagery from PlanetScope SuperDove, thermal data from ECOSTRESS LST, point clouds from airborne laser scanning (ALS), Topographic Objects Database (BDOT10k), and demographic data from municipal databases. Importantly, the utilized data are openly accessible and free of charge under the principles of Open Science, enabling the replication of procedures in other cities in Poland and, after identification and adjustment of relevant local data, numerous cities worldwide. In Wrocław, the project aims to provide support in creating and modifying existing and new planning documents, including local spatial development plans, the general plan, and the commune development strategy. This action supports the adaptation of local spatial policy to the growing needs of adaptation to climate change. The research is conducted within the program "Implementation Doctorate – 6th edition" by the Ministry of Education and Science.

How to cite: Budzik, G., Kowalczyk, T., Krajewski, P., Lebiedzińska, M., and Soszyńska, A.: Assessing spatiotemporal distribution of the effectiveness of Blue-Green Infrastructure in mitigating the Urban Heat Island phenomenon in Wroclaw, Poland under the Digital Twin concept for spatial policy optimization, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13070, https://doi.org/10.5194/egusphere-egu24-13070, 2024.

EGU24-17239 | ECS | Posters on site | ITS4.6/SSS0.1.5

NBS for secondary wastewater effluents infiltration based on soil and woodchips as drainage material: laboratory study    

Pauline Louis, Laurent Lassabatère, Arnold Imig, and Rémi Clément

Wastewater management and treatment are key points in maintaining the quality and the sustainability of water resources. To preserve receiving  water environments, efforts are being conducted to improve the  treatment efficiency . Soil infiltration can therefore be used as a  nature-based solution tertiary treatment, in some areas without surface  water available, or with supplementary water bodies’ protection  regulations. Secondary wastewater effluents (SWE) infiltration surfaces mainly consist of infiltration trenches or flood-meadows. Among the main issues encountered with soil infiltration, two can be highlighted:  the possible low hydraulic conductivity induced by soil clogging, on the  one hand, and the use of non-renewable draining materials such as  pebbles or gravel to ensure the distribution of water in trenches, on  the other hand. In France, in order to overcome those issues,  stakeholders are now considering the replacement of the gravel with  woodchips, a renewable biodegradable material, also prone to  biodiversity in soils. It has been demonstrated through a previous field study that the use of woodchips in infiltration trenches helps maintain infiltration over time, and even improves their performance. However, understanding the underlying mechanisms remains a significant scientific challenge. To better understand the soil and woodchip evolution processes, four columns were set up in a laboratory and fed with secondary treated effluents from a wastewater treatment plant.

 These four columns (with a diameter of 37 cm) are composed as follows:

  • a) Column #1: 80 cm of soil,
  • b) Column #2: 40 cm of wood chips and 40 cm of soil,
  • c) Column #3: 80 cm of soil inoculated with a selection of earthworms ,
  • d) Column #4: 40 cm of wood chips and 40 cm of soil, inoculated with a selection of earthworms .

During the presentation, hydraulic monitoring of the columns will be presented (inlet and outlet flow, column weight monitoring), showing the evolution of the infiltration rate. To analyze the evolution of physical properties within the columns, including parameters like saturated hydraulic conductivity, a modeling study was carried out using Comsol Multiphysics. Specifically, the Richards model (van Genuchten-Mualem) was employed to simulate and understand the changes occurring over time. The models fit the data well. They mainly show that the soil columns (1 and 3) tend to clog early if the hydraulic loads are too excessive. This is reflected by a reduction of hydraulic conductivity at saturation and porosity. In comparison, columns with wood chips seem to maintain their properties, with no major difference between columns with or without earthworms, after two years of monitoring. These results will be compared to the monitoring of physicochemical parameters of the inflow and outflow waters from the columns, allowing for a better understanding of the processes involving woodchips, soil, and macrofauna.

How to cite: Louis, P., Lassabatère, L., Imig, A., and Clément, R.: NBS for secondary wastewater effluents infiltration based on soil and woodchips as drainage material: laboratory study   , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17239, https://doi.org/10.5194/egusphere-egu24-17239, 2024.

EGU24-18619 | ECS | Posters on site | ITS4.6/SSS0.1.5

Nature-Based Solutions for stormwater management: A case study with Multi-Hydro in Parc Molière, France 

Ismael Ávila Vasconcelos, Pierre-Antoine Versini, and Igor da Silva Rocha Paz

Over the last few decades, the urban hydrological cycle has undergone significant changes due to the influence of the built environment, resulting in rapid runoff and increased risk of flooding. Faced with these challenges, nature-based solutions (NBS) are emerging as an appropriate response, especially in densely populated areas, facing the impacts of climate change and biodiversity loss. The application of green infrastructures, as evidenced by Parc Molière in Les Mureaux, France, with its 700 trees, 11,500 m² of flowerbeds, 8,700 m² of grassland and 5,000 m² of gardens, represents a sustainable approach to urban stormwater management. By reintroducing extensive impermeable areas to the open air, Parc Molière strengthens biodiversity, facilitates animal movement, promotes air cooling and reduces urban heat islands, while also modifying hydrological behavior. Carried out in the framework of the LIFE ARTISAN project, this study uses the Multi-Hydro software, developed at the École des Ponts ParisTech, to computationally model the Parc Molière area in two different scenarios: before and after the creation of the green spaces. Based on a fully distributed and physical hydrological model, Multi-Hydro is able to illustrate the influence of NBS by comparing the obtained simulations with instrumented hydrological data. The results should demonstrate that the NBS have a significant impact on peak flow and total runoff volume, mitigating the negative effects in an urban hydrological scenario.

How to cite: Ávila Vasconcelos, I., Versini, P.-A., and da Silva Rocha Paz, I.: Nature-Based Solutions for stormwater management: A case study with Multi-Hydro in Parc Molière, France, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18619, https://doi.org/10.5194/egusphere-egu24-18619, 2024.

EGU24-18701 | ECS | Orals | ITS4.6/SSS0.1.5 | Highlight

A multi-ecosystem service assessment for urban climate adaptation in Singapore  

Emma Ramsay, Leanne Tan, Yuan Wang, and Perrine Hamel

Nature-based solutions are an important tool to adapt to climate change in cities. Green spaces including nature reserves, parks and green streetscapes are essential to mitigate urban heat and also provide important recreation opportunities that benefit peoples physical and mental health. Effectively planning climate resilient and liveable cites thus requires quantitative, spatially explicit information about these ecosystem services. Such data are especially important in dense cities where vacant land is limited and trade-offs must be made to prioritise certain services. Here we present a multi-ecosystem service assessment for Singapore using the urban InVest models to evaluate urban cooling and urban nature access. We generate future greening scenarios based on policy targets to plant one million trees and increase the land area of parks by 50% by 2030 and compare ecosystem service provision for each scenario when either cooling or nature access is maximised in the spatial configuration of scenarios. We compare the benefits and trade-offs achieved by each scenario and explore the potential to quantify these through health indicators. Finally, we discuss how multi-ecosystem service assessment cans be integrated into urban planning and the implications for cities in an uncertain climate future.

How to cite: Ramsay, E., Tan, L., Wang, Y., and Hamel, P.: A multi-ecosystem service assessment for urban climate adaptation in Singapore , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18701, https://doi.org/10.5194/egusphere-egu24-18701, 2024.

EGU24-18875 | Orals | ITS4.6/SSS0.1.5

Suitability assessment of the location for the Natural Based Solution application on drainage systems 

Milica Vranešević, Milica Knežević, Radoš Zemunac, and Maja Meseldžija

The introduction of Natural Based Solution (NBS) into sustainable agricultural practices is a key issue on which the balancing of intensive agricultural activities with environmental protection depends. In lowland areas with intensive agricultural production, occurrences of extreme amounts of excess water, caused by climate change, increase the need for efficient drainage systems. Within the comprehensive framework of drainage system improvement, NBS are emerging as key and versatile interventions. The principal challenge lies in reconciling these solutions with the prevalent technical paradigms in both land reclamation and agriculture. The most important change is the strategic integration of the use of riparian buffers as supplementary melioration measures in delineated areas, especially aimed at reducing the inflow of excess water into the canal network. Deciding where to implement NBS for better drainage systems comes down to assessing the risks that may occur as a consequence to natural resources such as water and soil. When the implementation of NBS determines the crucial factors and evaluates them effectively, then it can categorize and map the optimal places where improvement of the drainage system is possible and efficient. In this study the aim was to delineate suitable zones for implementing nature-based solutions along watercourses through the application of Geographic Information System (GIS) methodology. By overlaying different layers, including pedological and geomorphological maps, digital terrain models indicating land slope, land use classifications, and drainage classes, it is intended to analyze and identify optimal locations. Some of the characteristic drainage systems in Vojvodina have been selected to provide a relevant case study illustrating how GIS can be applied to demonstrate the potential of nature-based solutions in improving drainage systems. This approach not only enhances the efficiency of the existing drainage systems. It also provides insights for strategic afforestation and the increase of biodiversity in agricultural areas.

How to cite: Vranešević, M., Knežević, M., Zemunac, R., and Meseldžija, M.: Suitability assessment of the location for the Natural Based Solution application on drainage systems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18875, https://doi.org/10.5194/egusphere-egu24-18875, 2024.

The main concern with public policies and strategies for integrating nature-based solutions is to facilitate access to innovative interventions to reach cities and communities that are more sustainable and climate resilient. However, there is an impediment to linking information on the results of projects and the expected impact of the European Commission in the framework programmes for research funding. Here we show how projects targeting nature-based solutions help to implement and review public policies under the EU Strategy for Adaptation to Climate Change 2013 – 2020 and European Green Deal. These policies have a positive impact in various areas, especially in green transition, with the potential to analyse the link between the scientific results of nature-based projects and the strategic orientations of research and innovation. We focused on the evaluation of 150 projects funded at the Horizon 2020 and Horizon Europe level, within three main programmes that provide funding for projects based on nature, resilience and adaptation to climate change: (1) Climate action, Environment, Resource Efficiency  and Raw Materials, (2) Climate, Energy and Mobility and (3) Food, Bioeconomy, Natural Resources, Agriculture and Environment. The main analyzed elements are the number and type of partners, the level of funding, the main objectives of the projects, types of nature-based solutions and their distribution by geographical regions in Europe. This analysis leads to the filling in the existing knowledge of the results that produce science, so that it can be exploited throughout the community. Our results consist in (1) overview of climate challenges in EU R&I framework programmes Horizon 2020 and Horizon Europe, (2) Main NBS designed by European R&I organizations, (3) NBS for climate resilience implemented through EU R&I funding in Horizon 2020 and Horizon Europe, (4) NBS for climate resilience – key pathways of knowledge valorization for ecosystem restoration, preservation and management. Overall, they show that the aspects analyzed in the selected funded projects support the development of nature-based solutions and what are the main actions that lead to long-term impact.

How to cite: Barbu, G.-R. and Niță, M.-R.: Nature-based solutions for climate resilience in EU R&I framework programmes Horizon 2020 and Horizon Europe, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19213, https://doi.org/10.5194/egusphere-egu24-19213, 2024.

Rural European landscapes are increasingly faced with the interlinked and cascading hazards of flooding and drought, exacerbated by both unsustainable land use practices and climate change. Sponge measures are particularly promising for addressing such multi-hazard risk from a participatory and social-ecological perspective. Sponge measures are nature-based solutions (NbS) that preserve, restore, enhance or create ecosystems to increase landscape and soil water retention while providing co-benefits for people and nature through biodiversity and ecosystem services. As NbS, they interact in complex ways with the socio-ecological systems (e.g. watershed boundaries) in which they are implemented. Thus, participatory processes are needed to ensure a systemic and interdisciplinary understanding of impacts while capturing diverse stakeholder values and interests. NbS design and planning often lacks 1) a shared understanding of the spatially-explicit impacts of NbS on the social-ecological system among stakeholders; 2) consideration of a broad spectrum of impacts as (co-)benefits and trade-offs; and 3) consideration of scales beyond the immediate measure and within diverging future scenarios.

As a promising approach to address these shortcomings, we propose the use of geodesign - an iterative framework for multidisciplinary, stakeholder-driven, and context-sensitive spatial decisions based on the integration of stakeholder inputs, geospatial data, and technology to generate real-time feedbacks and inform smart decision-making. This process also can support participation through fostering shared understandings and reconciling stakeholder conflicts. Despite promising applications in urban and landscape planning, knowledge is lacking on how and with what impacts geodesign can be applied to facilitate the planning of sponge measures at landscape scale. The aim of our research is to assess the utility of geodesign in the context of adaptive sponge measures by combining a systematic literature review with practical application of geodesign in two European catchments faced with increasing risk of hydrometeriological extremes. The review will quantify the adoption and past effectiveness of geodesign practices in similar landscape planning contexts. Based on these insights, a geodesign approach will be developed and implemented within the EU SpongeScapes project (spongescapes.eu) in selected case studies to generate future scenarios to increase landscape resilience against climate change. We present the research plan, including initial hypotheses and preliminary findings as conducted within the context of ongoing PhD research. With the increasing implementation of NbS in Europe in response to unfolding climate change and its consequences, our research will provide insights into the potential benefits and limitations of geodesign to improve their co-design, support policy creation, and inform decision-making.

How to cite: Jajeh, S., Anderson, C. C., and Albert, C.: Collaborative planning of nature-based solutions for climate resilience at landscape scale: exploring the potential of geodesign, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19504, https://doi.org/10.5194/egusphere-egu24-19504, 2024.

Nature-Based Solutions as a tool to reduce coastal risks have gained in popularity in the last 10 years. However, in France, their development still faces some limits and oppositions from local populations and stakeholders. The main reasons for this are the lack of knowledge and feedback, and the fear of being less protected with against floods with Nature-Based Solutions than with sea walls. This work will present the example of Criel-sur-Mer, in the North of France, where a project of restoration of intertidal habitats to reduce coastal risks is currently discussed and capitalize on feedbacks from three finalized projects from the Netherlands and England.

This study is part of a PhD work on the mobilization of Nature-Based Solutions in coastal protection projects. This presentation is based: on field trips conducted between March and April in the Netherlands and England, on the sites of Hedwige & Prosperpolder (Netherlands, Belgian border), Freiston Shore and Abbotts Hall (England), and in September 2022 and March 2024 in Criel-Sur-Mer (France); on semi-structured interviews conducted with stakeholders on those sites; on semi-structured interviews conducted with 39 coastal engineers and environmentalists between June and August 2023 in Artelia, the engineering firm in charge of the project of intertidal habitats restoration in Criel-sur-Mer; and on observative participation to a public consultation workshop with local actors and stakeholders for the project of Criel-sur-Mer.

The cross-study of the three Dutch and English projects gives us useful examples of the effectiveness of Nature-Based Solutions used as a tool to reduce coastal risks, that can be reused to enrich the project of Criel-sur-Mer. As the two English projects have been finalized in 2002, they are a source of extensive feedback on the evolution of intertidal ecosystems with managed realignment and their efficiency facing storms. The Dutch example started in 2005, but was finalized only in 2023, as it faced numerous social and political oppositions. These projects can thus be used as feedback on governance, project structuration and finding the right balance between different interests for the Criel-sur-Mer example.

How to cite: d'Avdeew, M.: Nature-Based Solutions for coastal risks protection: lessons learned from Dutch and English examples, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20731, https://doi.org/10.5194/egusphere-egu24-20731, 2024.

EGU24-20974 | Orals | ITS4.6/SSS0.1.5

Role of blue and green spaces in mitigating heat stress and providing biodiversity co-benefits in India’s cities  

Jagdish Krishnaswamy, Kiran Chandrasekharan, Dhananjayan Mayavel, and Ravi Jambhekar

Cities and urbanizing spaces combine heat stress from both heat island effect due to the built environment as well as global warming.  India with its high rate of urbanization is no exception. However, many Indian cities have blue and green spaces with various levels of protection from land-use and land-cover change. 

Blue and green spaces (BGS) are potentially nature-based solutions for mitigating heat stress through evaporation and transpiration besides sequestering carbon and as a habitat for urban biodiversity.  The effectiveness of BGS in mitigating heat stress depends on size, shape, weather, and climate variables, especially humidity.  

We use satellite derived land surface temperature (LST) to quantify and map negative temperature anomalies (cooling) with respect to spatial average across the city in years with different levels of summer temperature, especially due to El Nino.   We analyse the diverse types of blue and green spaces in three metropolitan cities in India and classify them in terms of biodiversity value (using e-bird data and other published sources). 

Cooling more than few degrees Celsius with respect to city wide averages from blue and green infrastructure has been observed and is much higher if compared to nearby built areas.  The geometry and landscape ecology of existing urban blue and green infrastructure can help inform future planning for blue and green spaces as adaptation in a warming urban environment. 

How to cite: Krishnaswamy, J., Chandrasekharan, K., Mayavel, D., and Jambhekar, R.: Role of blue and green spaces in mitigating heat stress and providing biodiversity co-benefits in India’s cities , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20974, https://doi.org/10.5194/egusphere-egu24-20974, 2024.

SSS1 – History, Education and Society of Soil Science

EGU24-758 | ECS | Orals | EOS4.4

Méditerranée 2000: Nurturing climate & ocean awareness 

Pimnutcha Promduangsri, Pariphat Promduangsri, and Estelle Bellanger

Humans have been suffering increasingly from the escalating impacts of climate and ocean change.  Well known examples are droughts, flooding, wildfires, acidification, heatwaves, sea-level rise, extreme storms and biodiversity loss.  If global average temperature rises by more than 1.5°C above pre-industrial levels, multiple climate tipping points will be triggered, and indeed, some already are.  This is and will be devastating for people around the world, especially those in coastal areas.  Thus, the need for immediate and informed action has become urgent.

This presentation will outline some of the many concrete, local actions in the area of climate and ocean, undertaken by Méditerranée 2000 (Med2000), an environmental association in the South of France.  Since 1989, the association has committed its efforts and educational programs to promoting sustainable development.  Each year, the association educates more than 25,000 young people and adults, led by a team of ten specialized speakers.  Med2000’s initiatives include awareness campaigns about climate and ocean change, hands-on educational activities in local schools and events for the general public.

How to cite: Promduangsri, P., Promduangsri, P., and Bellanger, E.: Méditerranée 2000: Nurturing climate & ocean awareness, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-758, https://doi.org/10.5194/egusphere-egu24-758, 2024.

Academic researchers have long been advocates of various causes in the public arena; their public advocacy to take normative positions regarding various moral, political or social issues is not new. Today, however, in the face of the many challenges facing our society, the question of researchers' public positions, particularly in relation to the environment and climate change, is being raised anew. A number of climate scientists are committed in a variety of ways, from signing op-eds to participating in the work of NGOs or think tanks, supporting legal actions or writing blog posts. In addition, the development of traditional and social media has significantly increased the public exposure of these researchers. At the same time, serious questions are being raised within the research community. Many of its members are debating the ways in which researchers can engage in such public advocacy, its advisability, and even its very principle. However, these debates are currently taking place in informal settings and, given the extensive individual experience of a number of colleagues, it is probably time to engage in this discussion in a more collective and organised way, as is done in other research communities.

Here are some examples of questions that might be discussed. How can researchers engage in public advocacy safely and responsibly? What is the role of the scientist versus the expert versus the citizen versus the activist? Can a researcher be neutral when taking a public stance? What is the risk of appearing naive, manipulated or irrelevant? How should researchers deal with vested interests and private actors? Should the climate community research geoengineering? For whom should researchers develop climate services?

Because addressing these issues involves a tension between personal values that may go beyond those shared by the scientific community, they are essentially novel ethical questions. Some may be so intimidating that many researchers choose not to engage publicly. Care must therefore be taken to organise the exchange properly, for example by creating safe internal spaces for debate or by inviting experts from other disciplines.

The French CNRS Ethics Committee has recently published on opinions on these issues[1], which I will use as a starting point for a broader discussion.


[1]  https://comite-ethique.cnrs.fr/en/comets-opinion-freedom-and-responsibility-academic-researchers-public-advocacy/

How to cite: Guilyardi, E.: Freedom and Responsibility: the Ethics of Academic Researchers’ Public Advocacy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1344, https://doi.org/10.5194/egusphere-egu24-1344, 2024.

EGU24-2053 | Orals | EOS4.4

Perceiving Cape-Town-Geoethics (CTG) through Symbolic Universes (SU) 

Martin Bohle, Rika Preiser, and Eduardo Marone

Cultural milieus determine the worldviews and practices of individuals and groups, including the reception of norms that guide them. Semiotic Cultural Psychological Theory (SCPT) methods, such as Symbolic Universes (SU), describe relationships of reception, worldviews and practice, which also applies to geo-philosophical matters [1]. This essay outlines how geoethics, for example, the Cape Town Geoethics (CTG), might be received in different cultural milieus.

The Cape Town Statement on Geoethics was proposed in 2016 at the 36th IGC [2] and is the most accessible resource on geoethics. It bundles various concepts in a Kantian/Aristotelian virtue ethics framework, illustrated, for example, by the Geoethical Promise [3].

The SU method describes the understanding, insights, and behaviour of groups of people expressing their respective cultural milieus. Extensive fieldwork identified five SU for people of European (Western) cultures [4]. The SUs called "Ordered Universe", "Interpersonal Bond", "Caring Society", "Niche of Belongingness", and "Others' World" categorise milieus, for example, in terms of relation to power and institutions or sources of trust. They corroborated with the Kohlberg hierarchy of the level of societal coordination [5] that is applicable to associate CTG and the worldviews of individuals and groups [6].

Comparing CTG and SU indicates: (1) CTG resonates most positively with people of the cultural milieu “Ordered Universe” (highest Kollberg level); (2) in other milieus, the reception of the CTG will be “measured”; (3) reception will be adverse for the milieu “Others' World” (lowest Kohlberg level). Hence, considering the quantitative distribution of SUs (in Europe), European citizens' reception of CTG is likely restrained.

Given complex-adaptive social-ecological systems of the World and Nature couple world views, human practices, and societal and natural systems [7] (see example: [8]), whether variants of CTG “fitted to different milieus” should be developed is of practical relevance. The perception of norms and their acceptance or rejection is a system feature, of which geoethics should not be agnostic.

[1] Bohle M (2019) “Homo Semioticus” Migrating Out of Area? In: Salvatore S, et al. (eds) Symbolic Universes in Time of (Post)Crisis. Springer Berlin Heidelberg, Cham, pp 295–307

[2] Di Capua G, et al. (2017) The Cape Town Statement on Geoethics. Ann Geophys 60:1–6. https://doi.org/10.4401/ag-7553

[3] Matteucci R, et al. (2014) The “Geoethical Promise”: A Proposal. Episodes 37:190–191. https://doi.org/10.18814/epiiugs/2014/v37i3/004

[4] Salvatore S, et al (2019) The Cultural Milieu and the Symbolic Universes of European Societies. In: Salvatore S, et al. (eds) Symbolic Universes in Time of (Post)crisis. Springer, Cham, pp 53–133

[5] Kohlberg L (1981) The Philosophy of Moral Development: Moral Stages and the Idea of Justice. Harber & Row, San Francisco

[6] Bohle M, Marone E (2022) Phronesis at the Human-Earth Nexus: Managed Retreat. Front Polit Sci 4:1–13. https://doi.org/10.3389/fpos.2022.819930

[7] Preiser R, Woermann M (2019) Complexity, philosophy and ethics. In: Galaz V (ed) Global Challenges, Governance, and Complexity. Edward Elgar Publishing., Cheltenham, pp 38–62

[8] Talukder B, et al. (2023) Complex Adaptive Systems-Based Conceptual Framework for Modeling the Health Impacts of Climate Change. J Clim Chang Heal 100292. https://doi.org/10.1016/j.joclim.2023.100292

How to cite: Bohle, M., Preiser, R., and Marone, E.: Perceiving Cape-Town-Geoethics (CTG) through Symbolic Universes (SU), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2053, https://doi.org/10.5194/egusphere-egu24-2053, 2024.

EGU24-2607 | Posters on site | EOS4.4

Geoethics literacy:  Clarifying values, principles and behaviour 

David Crookall, Pimnutcha Promduangsri, and Pariphat Promduangsri

Learning about geoethics is not easy partly because the area is relatively new (having emerged in the early 2010s), the concepts are sometimes difficult to fathom and geoethics touches on such a wide area of geoscience phenomena and on such a variety of human issues.

Learning through active, participatory engagement has been developing since the 1960s, and is now deployed, albeit sporadically, across the full educational and training spectrum (from the humanities, through the social sciences to the hard sciences).  Methods that have developed in this learning paradigm include project work, internships, experiential learning, simulation/gaming, values clarification and many more.  We contend that participatory methods are an effective way in which to learn, as supported by much research.

Our poster invites you to participate in a game-like, values clarification exercise.  We have developed a new version of an exercise that we have used in several places (Austria, Costa Rica, France, online) to unravel the knotty relations among values, principles and behaviours related to geoethical issues and dilemmas.

It is possible to play alone, but it is more enlightening and engaging to play in pairs or small groups.  Please bring a friend or two to our poster and participate in our exercise.  The basic process of the exercise can be adapted to your own specific areas of interest.  We look forward to seeing you – please bring a pencil.

(This poster was originally intended as a workshop in a short course, but our SC proposal was declined.)

How to cite: Crookall, D., Promduangsri, P., and Promduangsri, P.: Geoethics literacy:  Clarifying values, principles and behaviour, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2607, https://doi.org/10.5194/egusphere-egu24-2607, 2024.

EGU24-3568 | Posters on site | EOS4.4

Exploring the horizon of geosciences through the lens of geoethics 

Silvia Peppoloni and Giuseppe Di Capua

Geosciences play an indispensable role in the functioning of contemporary societies. Nevertheless, the technological aspects associated with the practical application of geoscientific knowledge, should not overshadow the fundamental contribution of geosciences to shaping human thought. Geosciences have not only influenced but continue to shape our perception of the world, its interrelationships, and evolution.

The ongoing ecological crisis, with its environmental, social, cultural, economic, and geopolitical implications, has stemmed from an imprudent trajectory in human development. Regrettably, there have been instances where geosciences have contributed to this irresponsible path. This oversight has led to an undervaluation of the social and cultural significance inherent in geological disciplines and the crucial role they can play in addressing current global challenges to support human societies.

Geoethics, as the ethics of responsibility towards the Earth system, is grounded in the comprehensive understanding provided by geoscientific knowledge of the complexity of reality. It stands out as the optimal tool for cultivating a new perspective on geosciences, recognizing them as fundamental disciplines crucial for addressing global environmental challenges. This recognition extends beyond technical considerations, emphasizing their cultural significance. By virtue of their epistemological foundations, the geosciences collectively represent an invaluable reservoir of knowledge for human civilization. They are indispensable for redefining the intricate relationship that binds us, as humans, to the Earth.

For this reason, geoethical thought should serve as a complementary element to knowledge in the education of geoscientists. It aims to furnish them with a principled framework and ethical values, offering guidance for any application of geoscientific knowledge to the natural environment and human communities. Additionally, geoethical thought is the ground on which to set a shared, global ethical foundation, facilitating the advancement of our interactions with nature. It seeks to actualize an ecological humanism that forms the basis for human well-being and a more sustainable development of socio-ecological systems. The geoethical perspective redefines the cultural significance and objectives of the geosciences. Geoeducation and communication emerge as fundamental tools for bridging the gap between geosciences and society. They play a crucial role in promoting geoscientific knowledge, highlighting not only its scientific value in providing technical solutions to the ecological crisis but also emphasizing the philosophical dimension of geosciences, the geosophy of living consciously and responsibly within the Earth system.

How to cite: Peppoloni, S. and Di Capua, G.: Exploring the horizon of geosciences through the lens of geoethics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3568, https://doi.org/10.5194/egusphere-egu24-3568, 2024.

EGU24-3586 | Posters on site | EOS4.4

An infrastructure for researching on geoethics and facilitating its international promotion 

Giuseppe Di Capua and Silvia Peppoloni

The development of the theoretical foundations of geoethics and its practical applications have had a notable boost in recent years, seeing the involvement of a growing number of scholars from different disciplines. This has increasingly necessitated the creation of spaces where reflections, discussions, results, and study materials can be shared. The network of scholar relationships has progressively developed physical and conceptual spaces for discussions. The goal has been to sustain conceptual consistency in geoethical thinking by anchoring reflections in the discipline's historical evolution and fostering further developments through open analysis, welcoming contributions from diverse disciplinary backgrounds. Today, what can be defined as a research infrastructure on geoethics and the promotion of its contents possesses a complex structure, serving as a convergence point for various cultural and scientific experiences.

At the core of this infrastructure lies the International Association for Promoting Geoethics - IAPG (https://www.geoethics.org), established in 2012. It consists of an Executive Committee, national sections, and Task Groups focusing on specific topics within geoethics. More recently, two new entities have augmented this infrastructure: i) the Commission on Geoethics of the International Union of Geological Sciences (IUGS), established in February 2023, that is the supporting branch of the IAPG to the IUGS and the IUGS body that officially deals with geoethics and social geosciences for the Union; ii) the Chair on Geoethics of the International Council for Philosophy and Human Sciences (CIPSH, an organization operating under the umbrella of UNESCO), established in December 2023, with the aim of expanding and reinforcing an international research network of institutions, not-governmental organizations, and individual scholars to foster interdisciplinary initiatives for bridging geosciences, humanities, and social sciences through geoethics.

The research infrastructure on geoethics has been enriched over time with two editorial initiatives: a) SpringerBriefs in Geoethics series by Springer Nature (https://www.springer.com/series/16482), founded in 2020 and supported by the IAPG, that envisions a series of short publications that aim to discuss ethical, social, and cultural implications of geosciences knowledge, education, research, practice and communication; b) the Journal of Geoethics and Social Geosciences (https://www.journalofgeoethics.eu/), a diamond open access publication of the National Institute of Geophysics and Volcanology (Rome, Italy) and supported by the IAPG, founded in 2021.

Finally, the research infrastructure on geoethics is complemented by the School on Geoethics and Natural Issues (the “Schola”), founded in 2019 (https://www.geoethics.org/geoethics-school). The “Schola” is a place for teaching and learning of the principles and values of geoethics in the light of the philosophy and history of Earth sciences. The intent is to provide background knowledge and the evaluation skills necessary to understand the complex relationship between human action on ecosystems and the decisions geoscientists make in the discipline that impact society, including improving the awareness of professionals, students, decision-makers, media operators, and the public on an accountable and ecologically sustainable development.

How to cite: Di Capua, G. and Peppoloni, S.: An infrastructure for researching on geoethics and facilitating its international promotion, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3586, https://doi.org/10.5194/egusphere-egu24-3586, 2024.

The ocean has started to attract more attention in the recent past with the notions of Blue Economy and Blue Growth becoming rallying points for a new frontier for investments [1]. Many countries and institutions prepare policy papers promising to end poverty, a push for new technologies and profits to fund the development. A recent systematic review of the literature [2], however, found no trace of articulated ethics and justice notions in midst of all the lofty hope and hype surrounding the often blurred concepts. The increasing financialisation of technological developments accelerated through digitalisation and the internet are creating increasing injustices to humans and harm to nature. But, as Rushkoff argues [3], the possibilities for feedback and more circular reasoning have potential to teach everybody that there is no escape from the natural world, thus weaning us from the hyperbole of permanent exponential growth. Here it is argued that critically engaged ocean and geo-sciences with their inherent message of a changing planet through deep time can contribute to debunking the ahistorical promise of fixing self-created problems by starting on a presumed ‘clean slate’. We frequently observe a pattern of wanting to solve the damage provoked by one technology with more technology, e.g. deep sea mining [4] or further technology development in fisheries and aquaculture [5]. At country level, these deliberately disruptive industrial approaches often pay little attention to working with the affected small-scale wild food producers who account for a quarter of global production. Instead, harnessing a combination of traditional and indigenous knowledges and providing intelligible access to the sciences holds significant potential for less destructive pathways. That would also be consonant with the promotion of knowledge co-creation during the UN Ocean Decade in pursuit of a vision of ‘the science we need for the ocean we want’. Practice of co-creation will require some rethinking of the self-image of many sciences and adaptations to typical project formulation and flows. In return, this is expected to produce valuable new insights in addition to opportunities for cooperation and blue justice as steps towards transformations based on ethical principles.

 

[1] World Bank. (2016). Oceans 2030: Financing the blue economy for sustainable development. Blue Economy Development Framework, Growing the Blue Economy to Combat Poverty and Accelerate Prosperity. World Bank Group, Washington DC.

[2] Das, J. (2023). Blue Economy, Blue Growth, Social Equity and Small-scale Fisheries: A Global and National Level Review. Studies in Social Science Research, 4(1):45 p. DOI: https://doi.org/10.22158/sssr.v4n1p38

[3] Rushkoff, D. (2022). Survival of the richest. Escape fantasies of the tech billionaires. Scribepublications, UK, ISBN 978-1-915590-24-4, 212 p.

[4] Zenghui Liu, Kai Liu, Xuguang Chen, Zhengkuo Ma, Rui Lv, Changyun Wei, Ke Ma. (2023). Deep-sea rock mechanics and mining technology: State of the art and perspectives. International Journal of Mining Science and Technology, 33(9):1083-1115. https://doi.org/10.1016/j.ijmst.2023.07.007.

[5] FAO. (2022). The State of World Fisheries and Aquaculture 2022: Towards Blue Transformation. Rome, FAO. doi:10.4060/cc0461en

How to cite: Nauen, C. E.: Can geosciences help inserting social justice notions into Blue Economy narratives?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4054, https://doi.org/10.5194/egusphere-egu24-4054, 2024.

Science indicates that human impact on the planet's climate is clear. Over the past 30 years, climate change has shifted from being primarily a scientific concern to emerging as one of the defining environmental challenges within our society. However, science alone cannot guide us on how to address this crisis. This challenge is also about how we envision living together, what we collectively value, and the level of risk we are prepared to assume. It fundamentally pertains to the kind of society we aspire to, making education a pivotal component. Inspired by the Paris Agreement, the time has arrived for Climate Change Education. It derives its momentum from the aspirations and mobilization of the youth, making it the most potent transformative action in response to climate change.

Climate Change Education comes with unique and exciting opportunities. Firstly, it offers a chance to learn about science in general and climate science specifically, drawing from authoritative sources like IPCC reports. Secondly, it provides an avenue to acquire life skills, humanities knowledge, and insights into global citizenship, imparting a holistic perspective to the young generation on a global scale. Lastly, it fosters critical thinking, hopeful hearts, and empathy in an ever-evolving educational landscape. However, Climate Change Education presents numerous challenges as it strives to balance the development of cognitive, emotional, and practical aspects within existing educational systems. Educators need to be prepared for this unique combination of ‘head’, ‘heart’, and ‘hands’.

The mission of the Office for Climate Education (OCE) is precisely to empower educators in preparing young generations with a robust understanding of climate change and the skills needed to act as global citizens in a changing world. The OCE, driven by collaboration between climate science and educational communities, develops sets of pedagogical resources, offers teacher professional development opportunities, and facilitates networks of practice worldwide. As a pivotal participant in the newly established Greening Education Partnership, the OCE serves as a bridge between the global landscape of IPCC-based science and the specific needs of local primary and secondary educational systems in over 20 countries.

How to cite: Guilyardi, E. and Wilgenbus, D.: Exciting times for Climate Change Education – from global opportunities to local challenges, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6101, https://doi.org/10.5194/egusphere-egu24-6101, 2024.

The National Association of State Boards of Geology (ASBOG) plays an essential role in supporting the licensing of applied geoscientists in more than 30 states in the United States [1] through promulgating model law, rules, and regulations for professional licensure, [2] by developing and implementing the Fundamentals of Geology (FG) and Practice of Geology (PG) exams, and [3] by providing related educational materials.  The content of the FG and PG exams is driven substantially by the results of Task Analysis Surveys (TAS) taken by practicing geologists and academic geologists.  Before 2023, the exams included content related to ethics reflected in the earlier TAS analytical summaries;  however, ethics content is not included in the 2023 TAS or, reportedly, in the current FG or PG exams.
     ASBOG has a history of including applied ethics in its products and organizational structure.  There is a "Code of Conduct/Harassment Policy and Performance Guidelines" for the ASBOG organization on its website (ASBOG.org).  The "Professional Geologist Model Licensure Law" states that each applicant must "submit a signed statement that the applicant has read and shall adhere to any code of professional conduct/ethics and rules established by the Board..." and that the application "be signed and sworn to by the applicant before a notary public" (ASBOG 2017, lines 844-847).  Its "Model Rules and Regulations" includes a sample "Code of Ethics" for licensed professional geologists (ASBOG 2019, p. 27-29).  
     Geoscience professional organizations in the US and internationally affirm the fundamental importance of ethics in academic and applied geoscience.  Virtually all professional organizations relevant to applied-geoscience practice in the United States (e.g., AAPG, AGI, AGU, AIPG, AEG, ASBOG, GSA, SIPES...) have some form of ethics code that their members are obligated to know and adhere to.  The International Association for the Promotion of Geoethics (IAPG -- www.geoethics.org) curates a list of codes of ethics/professional practice and provides publications and educational opportunities supporting geoethics.  Another essential resource is the "Teaching Geoethics" website (serc.carleton.edu/geoethics -- Mogk and Bruckner, 2014-23).
     Robert Tepel (1995) described the essential connection between licensure laws and professional ethics.  To the extent that there is a lack of ethics content in the current 2023 TAS, candidate handbook, exam preparation resources, and FG and PG exams, ASBOG sends a message that applied ethics might not be a core competency for licensed geoscientists -- a message for which there is essentially no support among geoscience professional organizations.
          I suggest that ASBOG collaborate with IAPG and other relevant organizations to address the problems or concerns that resulted in the reported elimination/reduction of ethics content in the application, preparation, and implementation of its FG and PG exams.  Licensed professional geoscientists must continue to understand that geoethics is foundational for their work within society.  For references and resources, visit CroninProjects.org/EGU-Geoethics2024/.

How to cite: Cronin, V.: The need to include ethics content in professional licensure exams in the US (and worldwide), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6136, https://doi.org/10.5194/egusphere-egu24-6136, 2024.

EGU24-6573 | ECS | Orals | EOS4.4

Proposal for a Geoethics Code for the Geoscientist Community of Chile 

Hernán Bobadilla, Luisa Pinto Lincoñir, Pablo Ramirez, Thiare González, José Benado, Nilda Lay, Tania Villaseñor, Millarca Valenzuela, Mohammad Ayaz Alam, and Alejandro Pérez

The proposal of the Geoethics Code (hereinafter “Code”) of the Geological Society of Chile arises as a strategic objective of the Geoethics Group within this institution. The Code encapsulates the principles and values that ethically guide and protect the professional decisions of geoscientists in Chile to protect society and the environment. Likewise, it establishes standards of conduct from the personal to the environmental dimension of professional and scientific practice. Consequently, the Code serves as a valuable tool to the geoscientist community in Chile, facilitating reflection and decision-making within an ethical framework.

Grounded in the principles and values defined by the Geoethics Group of the Geological Society of Chile and the Cape Town Geoethics Declaration of the International Association Promoting Geoethics (IAPG) from 2016 (Di Capua et al., 2017), the Code is built upon four titles: a) Professional and scientific work; b) Geosciences and its relationship with society; c) Geosciences and its relationship with the environment; and d) Contribution to new generations of scientists and professionals in Geosciences.

The construction strategy of the Code underscores the pivotal role of the Chilean geoscientist community. Thus, the Code proposal was enriched through consultations, including surveys, meetings, discussions, and seminars, engaging the Geoscientist Community of Chile to understand their perspectives on pertinent topics and challenges. Furthermore, consultations and reflections were conducted to validate the Code proposal before and during the XVI Chilean Geological Congress in 2023. Ultimately, the Code underwent validation with experts from the IAPG, including geoscientists representing Latin America. Consequently, the Code authentically represents the concerns and challenges of the national geoscientific community while also resonating with the international geoscientific community.

Financing

This project is sponsored by the Geological Society of Chile.

Acknowledgements

To the geoscientist community of Chile, the IAPG experts and other professionals who have participated in the process of construction and reflection on the titles of the proposed Geoethics Code.

References

Di Capua, G., Peppoloni, S., Bobrowsky, P.T., 2017. The Cape Town Statement on Geoethics. Annals of Geophysics, 60, Fast Track 7: Geoethics at the heart of all geoscience. doi: 10.4401/ag-7553.

Keywords

Geoethics Code, Principles and Values, IAPG, Geoscientist Community.

How to cite: Bobadilla, H., Pinto Lincoñir, L., Ramirez, P., González, T., Benado, J., Lay, N., Villaseñor, T., Valenzuela, M., Alam, M. A., and Pérez, A.: Proposal for a Geoethics Code for the Geoscientist Community of Chile, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6573, https://doi.org/10.5194/egusphere-egu24-6573, 2024.

EGU24-6593 | ECS | Posters on site | EOS4.4

Invitation to a research project on geography and climate education 

Pimnutcha Promduangsri

Educational approaches around the world are shaped by diverse geographical factors, including topography, climate, distance, urbanization and societal characteristics.  As a consequence, the methods employed for climate change education (CCedu) are expected to vary according to these geographical factors.

The United Nations Educational, Scientific and Cultural Organization (UNESCO) emphasizes the crucial role of CCedu in fostering an understanding of and effective response to the impacts of the climate crisis.  The Intergovernmental Panel on Climate Change (IPCC) highlights the importance of a globally conscious population for effectively addressing and adapting to climate change challenges.

However, rather than exploring the concept of CCedu or its effectiveness, my research project will focus on identifying the influence of geographical factors on climate change education/literacy.  In the long run, this project could potentially contribute to improving the effectiveness of CCedu.  I invite participants to visit my poster to discuss, share ideas and collaborate on this research project.

How to cite: Promduangsri, P.: Invitation to a research project on geography and climate education, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6593, https://doi.org/10.5194/egusphere-egu24-6593, 2024.

Environmental (in)justice arising from Climate change and urbanization exhibit uneven distributions, specifically impacting disadvantaged communities. While studies in the USA highlight the elevated heat exposure faced by low-income and ethnic minority groups, similar insights are lacking for other countries. This knowledge gap impedes a comprehensive understanding of environmental (in)justice experienced by various socio-economic and ethnic groups and hampers the identification of inadequacy in urban planning policies.

This research seeks to bridge the gap between social and environmental sciences to address environmental (in)justice by establishing a link between extreme heat (at both regional and country level) and socio-economic disparities for Australia and New Zealand. Using remotely sensed satellite data for Land Surface temperature mapping for summer (night time) and Census data of countries, the analysis explores various socio-economic indicators—such as education levels, age demographics, and the proportion of foreign populations.

Australia and New Zealand serve as pertinent case studies due to their distinct socio-economic landscapes and Indigenous populations. By recognizing the unequal distribution of urban heat and its disproportionate impact on vulnerable communities, there emerges a critical mandate to prioritize equitable urban planning policies. This research underscores the urgency for policymakers and urban planners to prioritize environmental justice interventions and integrate strategies that aim to reduce race and class disparities concerning urban heat. The findings also serve as a template for similar analyses globally; fostering inclusive, equitable and resilient urban landscapes.

How to cite: Chawla, J. and Benz, S.: Examining Race and Class Disparities in Urban Heat in Australia and New Zealand: Towards Environmental Justice in Urban Planning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6662, https://doi.org/10.5194/egusphere-egu24-6662, 2024.

EGU24-7655 | Orals | EOS4.4

Delivering Critical Raw Materials: Ecological, Ethical and Societal Issues 

Richard Herrington and Sarah Gordon

Leaders across geographical and political boundaries are united behind a pledge to deliver a net zero carbon world by 2050.  Society’s conundrum is that mining is an essential part of that delivery, yet is an activity regarded by many as unpalatable. Projects that have fallen short on ecological, ethical, or social grounds, serve to confirm to many that mining is currently not an industry to be trusted, rather than being the industry that could and should be empowering significant societal development.

Examples of societal failure include the incidents around the 2012 miners’ strike at the Marikana platinum mine in South Africa which escalated into violence and loss of life.  Failure on ethical grounds was most recently highlighted by the settlement of corruption claims in the Democratic Republic of Congo (DRC) where international mining company staff bribed country officials to secure “improper business advantages.”  Ecological failures are all too common and most visible in the failure of tailings storage facilities such as the 2015 Mariana (Brazil), 2019 Brumadinho (Brazil), and 2022 Jagersfontein (South Africa) dam disasters.

The challenge for those who explore, extract, and process the raw materials so vital for the energy transition, is to do so whilst delivering on true Sustainability right from the start of any project.  Mining disasters are rarely a surprise.  The proactive management of both threats and opportunities is therefore key to the urgent delivery of materials to secure our net zero future in a responsible manner.  We must ensure that this delivery is achieved by projects with wholly net positive outcomes for the environment and people.

How to cite: Herrington, R. and Gordon, S.: Delivering Critical Raw Materials: Ecological, Ethical and Societal Issues, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7655, https://doi.org/10.5194/egusphere-egu24-7655, 2024.

EGU24-8075 | Orals | EOS4.4

Can landslides provide geosystem services? 

Martin Mergili, Christian Bauer, Andreas Kellerer-Pirklbauer-Eulenstein, Jana Petermann, Hanna Pfeffer, Jörg Robl, and Andreas Schröder

The concepts of biodiversity and ecosystem services, focusing on the diversity of life and the services provided to humans by such diversity, in interaction with abiotic ecosystem components, are well established. Only recently, geosciences have started to challenge this rather biocentric view by highlighting that geodiversity – understood as the diversity of minerals, rocks, geological structures, soils, landforms, and hydrological conditions – provides substantial services to society and should be treated as equal partner to biodiversity. It was proposed to use the more general term natural services or, where geodiversity is much more relevant than biodiversity, geosystem services. Even though the term geosystem services is more and more employed in literature, it evolves only slowly into a commonly used concept with a clearly defined meaning. Interpretations range from all services associated with geodiversity which are independent of interactions with biotic nature, to the restriction to subsurface services. None or few of these concepts, however, include risks as negative services, or as costs of services, which is surprising as this would enable a more integrated vision on human-nature relationships. Only very recently, the potential of geosystem service maps to highlight both services and risks related to geomorphological processes was pointed out.

This work picks up landslides as a type of geomorphological process and landform, which is rather negatively connotated in society and associated with risks rather than with chances. We use landslides to develop a broader understanding of geosystem services, together with the common understanding of hazards and risks. We will (i) present a sound and integrated conceptual framework to consider landslides within the field of tension between risks and resources, and (ii) highlight a case study where landslides are used as cultural geosystem services for environmental education in the context of UNESCO Global Geoparks, which are considered important instruments for conserving and promoting geodiversity.

How to cite: Mergili, M., Bauer, C., Kellerer-Pirklbauer-Eulenstein, A., Petermann, J., Pfeffer, H., Robl, J., and Schröder, A.: Can landslides provide geosystem services?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8075, https://doi.org/10.5194/egusphere-egu24-8075, 2024.

EGU24-10646 | Posters virtual | EOS4.4

Protects and Heats 

Walter Tavecchio

The project “Protects and Heats” aims to safeguard the environment, to reduce the carbon dioxide emissions and the risk of collapse of buildings affected by earthquakes.

This is a new way to heat and cool buildings and at the same time mitigate the seismic vibrations.

 

The logic of the project is to create a discontinuity (Moat) in the ground in front of the structures to be protected, similar to damping methods that are implemented to dampen the vibrations produced by mechanical machines and without compromising the stability of the buildings themselves.

The project involves the construction of a double row of aligned micro piles and the insertion of HDPE and steel pipes inside the vertical drilling holes.

Closed circuit geothermal probes will be positioned, inside some vertical holes, with a low enthalpy closed circuit geothermal system.

The method of the project is achieved by combining two types of technologies:

-   The first concerns the interposition, between the direction of the seismic waves and the buildings, of a damping barrier.

The vertical barrier starting from the topographic surface will be positioned outside the buildings, generally orthogonal to the direction of the seismic waves.

-  The second concerns the installation of geo-exchange pipes, in the holes.

How to cite: Tavecchio, W.: Protects and Heats, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10646, https://doi.org/10.5194/egusphere-egu24-10646, 2024.

EGU24-12918 | Orals | EOS4.4

The most consequential ethical decision for geoscience  

Emlyn Koster and Philip Gibbard

A geological definition of the Anthropocene, shorthand for humanity’s cumulative disruption of the Earth-Human Ecosystem, looms as the planet-and-people focused UN approaches its Summit of the Future in New York City on 22-23 September 2024. The International Union of Geological Sciences (IUGS) “aims to promote development of the Earth sciences through the support of broad-based scientific studies relevant to the entire Earth system”. With the UN recently declaring that the planet is in peril and in need of a rescue plan, Anthropocene considerations with a geoethical lens are urgently needed.

Each potential new interval in the Geological Time Scale begins with a working group mandated by the International Stratigraphic Commission (ICS), in the case of the Anthropocene also by its Subcommission on Quaternary Stratigraphy (SQS). The Anthropocene Working Group (AWG) was formed in 2009. In 2010, its first chair Jan Zalasiewicz with co-authors Mark Williams, Will Steffen and Paul Crutzen recognized that “the Anthropocene represents a new phase in both humankind and of the Earth, when natural forces and human forces become intertwined, so that the future of one determines the fate of the other”. In 2015, the AWG’s second and current chair Colin Waters with ten co-authors posed the question "Can nuclear weapons fallout mark the beginning of the Anthropocene Epoch?" in the Bulletin of the Atomic Scientists. This was affirmed in 2019 and the AWG presented its recommendation to the SQS in early 2024. The remaining review and decision steps are the ICS and IUGS. Reflecting concerns of other geoscience scholars as well as of other professions and an anxious public, an opposing mindset advocates for an Anthropocene event that spans the cumulative and ongoing environmental impacts of Homo sapiens. It views Geological Time Scale protocols as unsuitable for archaeological and contemporary developments, regards unemotive references to humanity’s most abhorrent invention as distasteful, and visualizes the Anthropocene Event as valuably informing a new zeitgeist for our troubled world.

In 1950 astronomer Fred Hoyle anticipated that humanity’s first view of the Earth from space would revolutionize the course of history. Insofar as a ‘giant leap of mankind’ did not result from NASA’s Apollo 1969 lunar mission with its estimated 600 million viewers, the Anthropocene Event fuels an opportunity for geoscience to inform a realistic outlook during NASA’s upcoming Artemis lunar mission. With unique knowledge of once pristine environments, current climate change and incipient sea level rise, ongoing biodiversity loss and ecosystem disruption, finite energy and mineral resources, the geoscience profession should arguably have already become a crucial asset in this troubled world.

How to cite: Koster, E. and Gibbard, P.: The most consequential ethical decision for geoscience , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12918, https://doi.org/10.5194/egusphere-egu24-12918, 2024.

EGU24-13965 | Orals | EOS4.4

Ocean Futures: A New Paradigm and Teaching in the Age of Ocean Change 

Susanne Neuer, Stephanie Pfirman, Roberta Martin, Katie Kamelamela, Amy Maas, and Nick Bates

The new School of Ocean Futures (oceans.asu.edu) at Arizona State University (Tempe, AZ, USA) has embarked on a novel way of teaching ocean science with a forward-looking philosophy that centers on the current and future states of the ocean. While situated in Arizona State University’s main campus, it leverages the location of its two offshore campuses, the Center of Global Discovery and Conservation Science in Hilo, Hawaii, and the Bermuda Institute of Ocean Sciences (BIOS) in Bermuda. The Ocean Futures programs combine aspects of traditional ocean science teaching with ocean stewardship, partnerships, and Indigenous knowledge, and focus on the communities that live with the ocean and are affected by its rapid change. In this presentation we will introduce the curriculum of the new degree, as well as the challenges encountered, and best practices learned. Novel courses include “Introduction to Ocean Futures”, a capture course that aims at increasing the interdisciplinary knowledge of oceans, while actively seeking to increase diversity and retention in the field via inclusive pedagogical practices, the historical context of oceanography and an emphasis on developing a mindset of empowerment for change. It is followed by “Ocean Communities”, a course that immerses students through an ethnobotanical lens in global mountain to ocean cultural connections, while elaborating on how various human communities engage, exchange, and build relationships with regional resources. The students will receive hands-on aquatic knowledge through field courses at BIOS, the Sea of Cortez, Hawaii, and Antarctica. The curriculum culminates with an ocean workshop and capstone course that will allow the students to work directly with partners to address real-world challenges facing coastal communities and marine systems.

 

 

How to cite: Neuer, S., Pfirman, S., Martin, R., Kamelamela, K., Maas, A., and Bates, N.: Ocean Futures: A New Paradigm and Teaching in the Age of Ocean Change, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13965, https://doi.org/10.5194/egusphere-egu24-13965, 2024.

In the Anthropocentric era, the human-driven climate crisis has become a serious global issue. To mitigate the impacts of climate change, it is crucial for humans to adopt a more sustainable way of living. Human behaviors are shaped by their culture, where religious beliefs play important roles. As a result, people turned to religions for addressing with climate change issues.

Seeming to be unrelated, religions and climate issues have found connections through social systems and communication. By endowing climate issues with religions meanings, religions are able to resonate with the ecological crisis and take meaningful actions. Through this "resonance," religions contribute to climate issues by shaping worldviews, establishing sustainable habits, initiating actions, and influencing policies.

Religious communities have recognized the severity of the human-driven climate crisis. Their call for action reflects the fact that Taiwanese society has failed to respond to the climate crisis due to its endless pursuit of consumerism. To deal with the challenges, religious communities have advocated for “Ecological Conversion”, which persuade people to save the nature for the sake of God.

How religions can empirically contribute to environment issues has been a long-discussed topic. However, previous literatures only focus on the Western-Christian World. Countries with religious beliefs other than Judeo-Christian ethics are seldom discussed. To explore the relationship between religion and climate in Asian contexts, this research will focus on Taiwan, a multicultural country with various religions.

Using the sample data from the 2020 Taiwan Social Change Survey, this study aims to explore the relationship between religion and climate by conducting factor analysis and ordinary least squares regressions.

The evidence reveals a weak connection between religions and people's climate attitudes in Taiwan. Among all the religions in Taiwan, Buddhists and Christians tend to have the most eco-friendly attitudes. The social networks within these two religious communities foster an eco-friendly atmosphere, which highlights the importance of environmental conservation. However, when it comes to peoples’ willingness to pay, faith holders are less likely to show their supports.

By illustrating the religion-climate relationship in Taiwan, this study demonstrates how these two fields intersect in a non-Western society. It also provides implications for how religions can inspire people's willingness to engage in environmental conservation efforts.

How to cite: Tsui, C. H.: Do religions matter? The empirical study of the religion-climate relation in Taiwan, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14027, https://doi.org/10.5194/egusphere-egu24-14027, 2024.

EGU24-14752 | Posters on site | EOS4.4

Towards sustainable management of georesources: the importance of Cooperation Projects to boost education on responsible and sustainable mining. The example of the SUGERE and GEODES projects. 

Giovanna Antonella Dino, Susanna Mancini, Dolores Pereira, Manuela Lasagna, Francesca Gambino, Guido Prego, Domingos Gonçalves, Aida Jacinto, Daud Jamal, Josè Loite, Hélio Nganhane, Nelson Rodrigues, and Pedro Dinis

Sustainable and responsible management of geo-resources requires a rethinking and redesign of our production and consumption patterns. Awareness of the natural environment as a common good to be preserved, and knowledge of the close link between the natural environment and the socio-economic system are prerequisites for a profound change in human attitudes at both individual and societal levels. In this context, training and education of all actors involved in the management of geo-resources is an indispensable starting point for the acquisition of critical, ethical, and conscious thinking and the technical skills necessary to solve local problems and initiate sustainable development.

The present research focuses on two consequential ERASMUS+ projects: SUGERE and GEODES. Both had the common goal of the international standardization of Higher Education training and teaching in Earth Sciences and Mining Engineering.

SUGERE (Sustainable Sustainability and Wise Use of Geological Resources) was successfully completed in September 2023, involved 3 European universities (from Portugal, Spain, and Italy) and 6 non-European universities (from Mozambique, Cape Verde, and Angola). The objective was to enhance capacity building for the responsible and sustainable use of geological resources by supporting the didactic organization and standardization of 5 degree courses at Bachelor, Master and Doctorate levels in Earth Sciences and Mining Engineering. Both online and face-to-face training sessions were organized in European and African universities.

GEODES, started in June 2023, represents the continuation of the SUGERE project and involves a total of 9 partners. The same 3 European universities and 6 African institutions, formally attributing teaching and training roles to 2 universities that participated in SUGERE, already achieved a good standard in terms of infrastructures and have long teaching experience in the field of geosciences, and receiving 4 young institutions from less favored regions of Angola and Mozambique.

SUGERE and GEODES projects aim to strengthen the role of geosciences in the development of up-to-date strategies for the sustainable management of natural resources and to implement new collaborations thanks to an international network focused on local economic and social development and respect for the natural environment in the geological-mining context. The culture of sustainability and the deepening of skills in the field of geological mining form the basis for the development of the critical thinking necessary for local problem solving, the acquisition of ethical values and the technical skills that underpin sustainable development.

Deepening technical skills in geomining from a sustainable perspective is crucial for developing critical thinking and acquiring ethical values necessary for solving local problems. SUGERE and GEODES contribute to this outcome with a solid network of research, training, sharing and exchange of expertise and research activities between European and non-European universities interested in mining issues. A careful analysis of the local economic development of the countries involved in the projects is required to achieve the most effective methods for the exploration and sustainable exploitation of underground georesources.

 

How to cite: Dino, G. A., Mancini, S., Pereira, D., Lasagna, M., Gambino, F., Prego, G., Gonçalves, D., Jacinto, A., Jamal, D., Loite, J., Nganhane, H., Rodrigues, N., and Dinis, P.: Towards sustainable management of georesources: the importance of Cooperation Projects to boost education on responsible and sustainable mining. The example of the SUGERE and GEODES projects., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14752, https://doi.org/10.5194/egusphere-egu24-14752, 2024.

Since time immemorial, nature, and by extension the ocean, have made positive contributions to the health of mankind. Whether it be fertile soil, pollination, medicine, taking part in mindfulness activities, or food, we as a species depend on the many services provided by the natural world.  Our environment can be linked to some fundamental determinants of health, such as clean air, clean water, and balanced nutrition, and emotional wellbeing.  Therefore, any environmental degradation as a result of climate change has undeniable tangible and intangible effects on human health all over the globe, and this is especially true in relation to mental health in populations occupying Large Ocean Island States (LOIS).   As climate change has led to an increase in extreme weather events, and the accompanying devastation, there has been a corresponding decrease in health and quality of life.  This presentation will explore how the impact of climate change and its corresponding impact on the ocean has enduring impacts, both physiologically and mentally.   Therefore, all of the processes and recommendations to combat climate
change will have important co-benefits to mental and physical health, and help to build resilience in the face of the dearth of resources faced by LOIS. This lack of resources must be urgently addressed, and solutions can be explored by fostering collaboration between mental health professionals and climate scientists to collect sufficient data. The resulting findings can be used to expedite access to the funds needed to implement the necessary levels of mitigation and adaptation specifically tailored to the infrastructural realities of LOIS.

How to cite: Alvarez de la Campa, S.: Climate Change, Ocean Health and Quality of Life - An Inextricable Connection in Large Ocean Island States, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16730, https://doi.org/10.5194/egusphere-egu24-16730, 2024.

EGU24-17346 | Posters on site | EOS4.4

The importance of making geoethics a central concern of Sri Lankan education strategy 

Giuseppe Di Capua and Udaya Gunawardana

Like numerous regions worldwide, Sri Lanka faces significant environmental challenges that endanger its biodiversity, natural resources, and the well-being of its population. Predominant issues encompass water and air pollution, land degradation, deforestation, improper waste disposal, consequences of climate change, disaster risks, as well as the loss of biodiversity and geodiversity. The nexus between political, economic, and social factors contributes to these geo-environmental challenges, often exacerbated by the politicization of the environmental issues in Sri Lanka. However, it is crucial to acknowledge that human activities primarily drive these conditions. Gunnar Myrdal’s Soft State theory asserts that despite the existence of multiple governing bodies, regulations, and laws, humans strategically transcend the environment leading to the depletion of geo-environmental resources within a context of strong societal inequalities, particularly in developing countries influenced by the historical conditioning of colonial interests by developed nations. A philosophical exploration of this issue emphasizes the pivotal role of human indifference towards the environment and natural resources in causing these challenges. To address this issue effectively, a transformation in people's attitudes is imperative, and education emerges as the most potent tool for this purpose. However, a careful analysis of Sri Lanka's primary and secondary school curricula reveals an absence of a dedicated discipline addressing the philosophical and social dimensions of the geo-environmental matter. In light of this, the incorporation of subjects such as geoethics, which specifically addresses the ethical problems in the human-environment interaction, becomes paramount. Integrating geoethics into the educational framework, particularly at primary and secondary levels, stands as the foundation of a sustainable and responsible strategic approach to many societal and environmental problems. This educational strategy should envision as the most important solution to mitigate the majority of geo-environmental problems in Sri Lanka, fostering environmentally sensitive and responsible citizens.

How to cite: Di Capua, G. and Gunawardana, U.: The importance of making geoethics a central concern of Sri Lankan education strategy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17346, https://doi.org/10.5194/egusphere-egu24-17346, 2024.

EGU24-17614 | Orals | EOS4.4

Choice Question (MCQ) Peer Construction for Training Students as Climate Change decision-makers or Knowledge Spreaders 

Gérard Vidal, Charles-Henri Eyraud, Carole Larose, and Éric Lejan

After more than 40 years of reasoned alerts from the scientific community directed towards society, with minimal impact, a recent surge in the size and frequency of extraordinary climatic events has begun to reshape the perspectives of ordinary citizens. This situation underscores the challenge of directly influencing society with scientific evidence or models, emphasizing the crucial role of universities in training students who will occupy intermediate or elevated positions that may impact society at large.

While "Climate Fresk" has gained widespread popularity in higher education institutions as an effective tool for raising awareness about climate change and the intricate processes affecting our global earth ecosystem, concerns have arisen at the university level. The repetition of "Climate Fresk" or similar tools may be perceived as greenwashing practices, as university students are already well-acquainted with the issue. Hence, there is a need to surpass mere awareness in higher education.

As TASK Change Leaders at ENS-Lyon, we explored pedagogical and assessment tools provided by Sulitest. This initiative, extends beyond climate and ocean changes, it places a significant emphasis on various topics, including Sustainable Development Goals, earth limits, and driving processes of climate change. One of the major interest of the approach is to address all disciplines (scientific or non scientific).

We built a three-step strategy involving:

  • Administering a positioning test to enable students to assess their performance relative to the institution and the wider community.

  • Utilizing the looping tool from Sulitest, wherein small teams of students generate Multiple Choice Questions accompanied by a list of academic publications validating the terms of their questions. Subsequently, these questions are discussed in large interdisciplinary open groups, compelling students to articulate questions and answers intelligible across all disciplines.

  • Participating in the TASK to receive an assessment of their proficiency in sustainable development, evaluated by an external body.

This strategy, particularly the second step, empowers students to assume the role of a teacher or knowledge spreader in the face of a diverse peer community. It serves as a simulation of their potential future roles as educators, knowledge spreaders or decision-makers, instilling an understanding of the importance of providing validated sources and the challenges associated with crafting questions and answers comprehensible to all, preparing them for future teaching or decision-making scenarios. A notable byproduct is the creation of valuable pedagogical resources in a "connectivist MOOC flavor."

Beyond the training benefits, membership in the TASK Change Leaders group provides opportunities for discussions on the sustainability of education, green education, and competency frameworks, to apply to ourselves the concepts we are teaching.

How to cite: Vidal, G., Eyraud, C.-H., Larose, C., and Lejan, É.: Choice Question (MCQ) Peer Construction for Training Students as Climate Change decision-makers or Knowledge Spreaders, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17614, https://doi.org/10.5194/egusphere-egu24-17614, 2024.

EGU24-20953 | Posters on site | EOS4.4

Shaping Thriving Ocean Futures – Education to advance healthy coastal communities and marine systems 

Susanne Neuer, Stephanie Pfirman, Roberta Martin, Katie Kamelamela, Amy Maas, Andrew Peters, and Nick Bates

The new Ocean Futures program at Arizona State University (Tempe, AZ, USA) prepares students to become coastal and marine stewards, community leaders, innovators, and researchers capable of shaping the future of the world's oceans.  The program is taught and mentored by faculty and community leaders in an environment that supports our students’ individual and collaborative strengths, creativity, and diversity.  Students learn and work across disciplines, exploring global and local ocean dynamics, ecosystems, and stressors, engaging with community contexts and livelihoods, and advancing culturally-appropriate, reciprocal stewardship.  In support of ASUʻs mission of embeddedness and linking innovation to public value, graduates of the School of Ocean Futures are equipped with the knowledge and skills to work with diverse communities and partners to create innovative solutions for our changing world.

The School of Ocean Futures educational goal is to build student capacity to apply knowledge of coastal and marine systems coupled with community partnerships to help shape thriving futures, both locally and globally.  Students engage in research and work with partners in Arizona, the Bermuda Institute of Ocean Sciences (BIOS) in Bermuda, the Center of Global Discovery and Conservation Science in Hilo, Hawaii, the Sea of Cortez, and Antarctica.

Ocean Futures education at ASU is based on an innovative “cascade” curriculum.  The cascade starts with core classes in Introduction to Ocean Futures and Ocean Communities, followed by foundational courses in sciences and mathematics, an upper-level core class in Oceanography, electives focused on partnerships, stewardship, and advanced problem-solving, and culminates in an applied workshop and capstone course where students work with partners to transfer knowledge to action in addressing problems facing coastal communities and marine systems.

How to cite: Neuer, S., Pfirman, S., Martin, R., Kamelamela, K., Maas, A., Peters, A., and Bates, N.: Shaping Thriving Ocean Futures – Education to advance healthy coastal communities and marine systems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20953, https://doi.org/10.5194/egusphere-egu24-20953, 2024.

Fifty years ago, Peter Berg developed a way to locate yourself within your bio-region, starting with your watershed. To begin, trace your water from precipitation to tap—and back to precipitation. Then, how much rain fell in your area last year? How much water does your household consume per month? What percentage of your town’s water supply goes to households? to manufacturing? to farming? to golf courses? to mining operations? to extinguishing fires? What pollutants affect your water supply? Once you can map your local water supplies, consider how manufacturing transistors, operating data storage centers and streaming videos impact international waters. With awareness of our daily lives’ impacts on local and international waters, we can create realistic limits.  

How to cite: Singer, K.: Mapping water from our tap to the watershed: A first step toward ecological limits  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21221, https://doi.org/10.5194/egusphere-egu24-21221, 2024.

This ongoing project integrates the concept of science diplomacy, conducting an in-depth exploration of the intricate interrelations among geo-bio-cultural diversity and its pivotal role in peace building, risk management, and climate action in Colombian cities and territories. Leveraging geodiversity assessment and its correlation with biodiversity, we explore how the bio-geo duplex interacts with ethnic diversity in Colombia. The aim is to develop initiatives aligned with the ancestral knowledge of indigenous, African-descended, farmers, and mixed-Colombian communities across cities and territories withing the geoethics concept.
In the realm of science diplomacy, our emphasis lies in cultivating international collaboration and knowledge exchange to tackle intricate societal challenges. We seek to foster dialogue and cooperation among traditional and nontraditional actors, advocating for the integration of scientific expertise with local and indigenous knowledge. The study provides a comprehensive analysis, considering historical, environmental, economic, social, and political contexts. It sheds light on how these interactions unfold and their diverse representations across Colombia, including the Caribbean, Pacific, and Andean regions.

How to cite: Marin-Ceron, M. I.: Science Diplomacy with Nontraditional Actors: Enhancing Geo-Bio-Cultural Diversity in Colombian Cities and Territories, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22117, https://doi.org/10.5194/egusphere-egu24-22117, 2024.

EGU24-410 | ECS | Orals | EOS3.1 | Highlight

Family-Friendly Conferences in the Geosciences 

Elena Päffgen, Leonie Esters, and Lisa Schielicke

Participation in (inter-) national conferences, seminars, and workshops such as the EGU General Assembly is important for professional exchange and personal networking, especially for early career scientists. Enabling scientists with family obligations to take part in conferences will increase gender equity and diversity, as women remain to be the main caregivers in most families.

The questions of family planning and kickstarting a professional career arise simultaneously in almost any field. What makes this particularly challenging for young families in academia is that this line of work frequently requires for parents to move, making traditional forms of supportive caregiving by extended family members often unavailable. The vital role conference attendance plays for an academic career only aggravates that challenge. Therefore, a lack of opportunities to attend conferences and workshops clearly puts young parents at a disadvantage, especially young women in academia.

The Project for Family-Friendly Conferences has been initiated by Leonie Esters and Lisa Schielicke from the Department of Geosciences at the University of Bonn in April 2023. Elena Päffgen joined as a research assistant (WHK) later the same year. With an initial duration of one and a half years the project is funded by the Gleichstellungsbüro (office for equal opportunities) of the university. Our principal goal is to find out, how conference and workshop participation can be made more family-friendly.

The present work analyses an online survey with 245 participants who were interviewed on the topic of family-friendly conferences. The survey was addressed to all scientists with a focus on geosciences, 58% of all participants claimed to have children, while 42% were childless. 61 comments expressing wishes and needs of parents and guardians we received from the participants underscore the urgency of the matter. Key concerns of the participants were clear communication (e.g., whether children could be brought along to the events in question), awareness among event-organizers, and easy access to financial assistance (e.g. for babysitting). For instance, more hybrid events, on-site childcare and designated family-friendly activities at conferences were named as possible improvements. However, considering that families and their challenges are diverse, a wide array of offers and flexibility are required to address their needs.

Our project aims to educate the wider academic community on family-specific challenges. Based on the results of this survey, we will provide conference organizers with guidelines to improve family-friendliness of conferences and facilitate their exchange among each other. Additionally, we want to keep parents informed about the offers for families that are already in place at conferences in our field of study. Overall, we are convinced that outcomes of our project will be beneficial for conference and workshop organizers likewise as for researchers who are parents and will contribute to gender equity and diversity in academia.

Children, parents and guardians are particularly welcome to the poster presentation and discussion.

If you would like to participate in our survey: https://www.empirio.de/s/VxLGGLxWv2

 

 

How to cite: Päffgen, E., Esters, L., and Schielicke, L.: Family-Friendly Conferences in the Geosciences, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-410, https://doi.org/10.5194/egusphere-egu24-410, 2024.

The European Geosciences Union (EGU) is the leading organisation supporting Earth, planetary and space science research in Europe, upholding and promoting the highest standards of scientific integrity, open science and open access research. EGU’s vision is to realise a sustainable and just future for humanity and the planet through advances in Earth, planetary and space sciences.

The EGU awards and medals programme acknowledges distinguished scientists every year for their exceptional research contribution to the Earth, planetary and space sciences. Furthermore, it recognises the awardees as role models for the following generation of early-career scientists, encouraging geoscience research. 

Except for EGU council and award committee members everyone (including non-EGU members) is eligible for receiving an EGU award. Nominations need to be submitted by EGU members online by 15 June every year. Each EGU medal or award is selected through a rigorous assessment of the candidates and their merits through the respective committee. The procedures for nomination, selection of candidates and the time schedule are described in detail on the EGU website. 

EGU is committed to recognizing scientific excellence providing equal opportunities. The processes and procedures that lead to the recognition of excellence must be transparent and free of biases. However, establishment of clear and transparent evaluation criteria and performance metrics to provide equal opportunities to researchers across gender, continents and ethnic groups can be challenging since the definition of scientific excellence is often elusive. 

The purpose of this presentation is to share the experiences and efforts of the European Geosciences Union to ensure equal opportunities. The presentation will showcase data and statistics to provide constructive directions towards the objective of offering equal opportunities to researchers from diverse demographic backgrounds.

How to cite: Blunier, T.: Equality of opportunities in EGU recognitions: The EGU Awards Committee experience, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1620, https://doi.org/10.5194/egusphere-egu24-1620, 2024.

EGU24-9435 | ECS | Orals | EOS3.1 | Highlight

Navigating parenthood as an early career scientist: insights and challenges from hydrological sciences 

Diana Spieler, Lina Stein, and Rodolfo Nóbrega

Combining an academic career with caretaking responsibilities is an often-overlooked challenge. Juggling the workload, conference attendance, or the potential requirement to move to a new job all become more demanding when children or other caretaking responsibilities are a part of your life. We, members of the Young Hydrology Society (YHS), wanted to hear some views from academic parents in hydrology. What are the challenges they face, what is their advice to other parents and what systematic changes would they like to see? This non-scientific initiative gathered responses from academics within the hydrology community from different parts of the world at different career stages, including PhD candidates, postdoctoral researchers, assistant professors, and group leaders. The survey revealed diverse challenges and strategies employed by academic parents to balance their professional and personal lives. We identified a complex interplay of personal, institutional, and cultural factors that influence these experiences in academia. A common theme across responses was the strategic timing of parenthood, often aligned with phases of planning security, such as after having won a longer-term grant. Despite the varying international backgrounds, many responses highlighted the supportive role of national policies, particularly in countries like Sweden, which offer substantial parental support and flexible work arrangements. However, challenges such as reduced research productivity, lack of support to attend conferences, and the need to relocate were frequently mentioned as limiting factors for career development and progression. Among the strategies employed to minimise these challenges, we highlight adjusting work schedules, reducing workloads, and relying on support from partners and extended family. Childcare distribution varied, with many striving for an equitable split between partners, though this was often influenced by career demands and cultural standards or expectations. The responses also contained suggestions for systemic improvement, including extended childcare facilities at conferences, more flexible job contracts, and institutional support for parents, particularly during fieldwork and conferences. While there are notable advancements in some areas, there remains a significant need for systemic changes to better support academic parents and ensure a more inclusive and equitable academic environment. It is fundamental to highlight, however, that the results of this initiative do not capture the entire spectrum of experiences faced by those with caretaking responsibilities, and that our survey is likely to be biased towards ECS who still were engaged and successful in their work. We aim to release these results as a series of blog posts on the YHS webpage (https://younghs.com/blog/) to disseminate this topic with the main aim of offering valuable reassurance to current and future parents in academia facing similar challenges.

How to cite: Spieler, D., Stein, L., and Nóbrega, R.: Navigating parenthood as an early career scientist: insights and challenges from hydrological sciences, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9435, https://doi.org/10.5194/egusphere-egu24-9435, 2024.

EGU24-9557 | Orals | EOS3.1

Diversity at a Small Geoscience Conference 

Alice Lefebvre and Renée Bernhard

Conferences are places where intellectual and communication standards are shown. Ultimately, they can contribute to create a sense of belonging or inadequateness. However, several analyses of specific diversity measures have demonstrated that large conferences often lack diversity in terms of gender, geographic location or race. The present contribution presents an analysis of the gender, country of affiliation and student status of the participants and presenters during four instances of a small European geoscience conference, as well as the length of presentation and number and tone of questions of the latest instance of this conference. We found that women make up about one-third of participants, session chairs, invited keynote speakers, and presenters (oral and poster) on average, but percentages vary greatly from one year to the next. Students represent around 30% of participants, but over 40% of poster presenters and 28% of long presentations. In total, only half of the participants asked a question, and most of the questions were asked by senior men. Around 25% of the questions were asked with a friendly tone; the remainder were neutrally asked. Friendly questions were asked more frequently after keynote lectures and long presentations than following short talks. We suggest concrete actions that can be taken to promote the development of an inclusive and supportive environment at small conferences.

How to cite: Lefebvre, A. and Bernhard, R.: Diversity at a Small Geoscience Conference, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9557, https://doi.org/10.5194/egusphere-egu24-9557, 2024.

EGU24-10508 | ECS | Posters on site | EOS3.1 | Highlight

An Evaluation of the ADVANCEGeo Partnership Bystander Intervention Model 

Blair Schneider, Christine Bell, Stefanie Whitmire, Horinek Hannah, Meredith Hastings, Rebecca Barnes, Allison Mattheis, Billy Williams, and Erika Marin-Spiotta

The ADVANCEGeo Partnership program, funded by a National Science Foundation ADVANCE award in 2017, was designed to empower geoscientists to transform workplace climate, and has been recently adapted to other STEMM disciplines as well. To date, the ADVANCEGeo Partnership has led over 230 workshops to institutions across the USA and Europe, in both virtual and in-person formats. A main strategy of ADVANCEGeo for organizational climate change is to enact interventions at the individual and collective level through behavior change education informed by intersectionality and ethics of care frameworks. The program uses a community-based model for bystander intervention and workplace climate education designed to give members of the academic community the knowledge and tools to identify, prevent, and mitigate harm from exclusionary behaviors that directly affect the retention of historically excluded groups in STEMM. 

Evaluation data from 81 workshops held between 2018-2022 were analyzed using a transtheoretical framework of behavioral change. All of these workshops used a consistent structure and length of presentation (averaging 2.5 hours overall). Thirty six workshops were conducted in-person (44%) and forty five workshops were conducted virtually (56%) using the Zoom platform. The workshops were conducted for a variety of audiences, including institutional leadership, academic departments, professional societies, research groups, and student groups. Each workshop included the same core components, though some materials in the presentation portion were tailored to the needs of the audience as requested. Evaluation results show positive increases in participant knowledge, satisfaction, and intent to change behavior directly after the workshop. An additional follow up survey that was disseminated approximately 6 months after the workshop provides evidence of longitudinal behavior change. These results demonstrate that the ADVANCEGeo Bystander Intervention model design successfully shifts behaviors in workshop participants, with an aim to create more positive workplace climates for all seeking to be a part of STEMM.

How to cite: Schneider, B., Bell, C., Whitmire, S., Hannah, H., Hastings, M., Barnes, R., Mattheis, A., Williams, B., and Marin-Spiotta, E.: An Evaluation of the ADVANCEGeo Partnership Bystander Intervention Model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10508, https://doi.org/10.5194/egusphere-egu24-10508, 2024.

EGU24-11929 | ECS | Orals | EOS3.1 | Highlight

Promoting and Supporting Equity, Diversity, Inclusion, and Accessibility: A Collaborative Approach in the Hydrogeological Community and Beyond 

Luka Vucinic, Viviana Re, Barbara Zambelli, Theresa Frommen, Fatima Ajia, and Shrikant Limaye

The International Association of Hydrogeologists (IAH) is a scientific and educational charitable organisation for scientists, engineers, water managers and other professionals working in the fields of groundwater resources planning, management and protection. Comprising various commissions and networks, IAH engages in activities such as contributing to groundwater science, outreach, education, and training. While IAH takes meaningful steps towards equity, diversity, inclusion, and accessibility, recognising the importance of putting these principles into practice, it is essential to acknowledge that there are still numerous challenges and barriers that need to be addressed. It is worth noting that IAH shares similar challenges with many other organisations and associations in navigating the path towards greater equity, diversity, and inclusion. Therefore, the establishment of a dedicated working group became imperative to address and overcome these challenges effectively.

The Socio-Hydrogeology Network (IAH-SHG), an official IAH network, aims to integrate social sciences into hydrogeological research, and has two active working groups: the Working Group on Groundwater and Gender, and the newly established Equity, Diversity, Inclusion, and Accessibility (EDIA) Working Group. This group is designed to further enhance the EDIA landscape within the IAH and beyond. It is the result of collaborative endeavours, extensive discussions, and productive meetings within the IAH and IAH-SHG, and it builds on the work and experience of the Working Group on Groundwater and Gender and the IAH-SHG in general. We will showcase the key insights gained from our IAH-SHG experiences and demonstrate how we applied these lessons to facilitate the establishment of the EDIA Working Group.

By harnessing the power of collective effort, the EDIA Working Group aims to foster a positive impact that resonates throughout the IAH and wider hydrogeological community. We will present our experience regarding the pivotal role of networks, such as IAH-SHG, in advancing equity, diversity, inclusion, and addressing barriers within the geosciences. We will also share our plans for collaboration with other IAH commissions, networks, IAH members, and other individuals (i.e. membership in the IAH is not a prerequisite for individuals interested in joining the IAH-SHG or any of its working groups), as well as ideas and recommendations for new and innovative strategies to identify and overcome barriers. Furthermore, we will share the EDIA Working Group's experience so far, providing insights that may be valuable for other associations, organisations, and groups facing similar challenges.

How to cite: Vucinic, L., Re, V., Zambelli, B., Frommen, T., Ajia, F., and Limaye, S.: Promoting and Supporting Equity, Diversity, Inclusion, and Accessibility: A Collaborative Approach in the Hydrogeological Community and Beyond, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11929, https://doi.org/10.5194/egusphere-egu24-11929, 2024.

EGU24-12182 | ECS | Orals | EOS3.1 | Highlight

Is my teaching gender-fair? A self-assessment questionnaire. 

Sílvia Poblador, Maria Anton-Pardo, Mireia Bartrons, Xavier Benito, Susana Bernal, Eliana Bohorquez Bedoya, Miguel Cañedo-Argüelles, Núria Catalán, Isabel Fernandes, Anna Freixa, Ana Genua-Olmedo, Elisabeth León-Palmero, Anna Lupon, Clara Mendoza-Lera, Ada Pastor, Pablo Rodríguez-Lozano, Aitziber Zufiaurre, and María del Mar Sánchez-Montoya

The study of inland waters - Limnology - is full of fascinating women who have vastly contributed to our understanding of these valuable ecosystems. Although women’s visibility was low during the early years of Limnology, it has increased over time. Nowadays, women represent half of the early-career limnologists in Europe. However, as in many other fields, their scientific contributions have been traditionally neglected from schools to universities (i.e., the Matilda effect). The project “Gender LimnoEdu”, developed by the Gender&Science AIL group and funded by EGU (2020), aims to increase the visibility of women in Limnology and related subjects - such as Ecology, Hydrology or other Geosciences - in academic courses and lectures. We have created a set of online ready-to-use resources: (1) a self-evaluation form to detect gender biases and raise self-awareness for teachers of Limnology and Geosciences courses (the form is applicable to a wide range of courses and disciplines), (2) teaching nutshells highlighting key female limnologists (and their history) to help lecturers to acknowledge the role of women in Limnology in their courses, and (3) a complete teaching unit about the past and present situation of women in the field of Limnology. All these resources are freely available (https://www.genderlimno.org). Here, we will present this toolbox of resources and guide you on how to use them for your teaching needs. Moreover, we will share the preliminary results of the self-evaluation form to showcase how gender-fair Limnology lessons in high-education courses are. We welcome everybody to take it! https://www.genderlimno.org/gender-fair-lessons.html

How to cite: Poblador, S., Anton-Pardo, M., Bartrons, M., Benito, X., Bernal, S., Bohorquez Bedoya, E., Cañedo-Argüelles, M., Catalán, N., Fernandes, I., Freixa, A., Genua-Olmedo, A., León-Palmero, E., Lupon, A., Mendoza-Lera, C., Pastor, A., Rodríguez-Lozano, P., Zufiaurre, A., and Sánchez-Montoya, M. M.: Is my teaching gender-fair? A self-assessment questionnaire., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12182, https://doi.org/10.5194/egusphere-egu24-12182, 2024.

Many universities openly pledge commitments to improving diversity, with science, technology, engineering, and math (STEM) fields receiving significant attention. Despite these efforts, geoscience remains one of the least diverse fields in STEM. This recognition has prompted an increase in studies stressing the systemic lack of representation across the field and the barriers that exist for those within. However, much of this work has been limited by the use of demographic datasets that have been either passively collected or derived from government sources. Constraints include country-specific data collection policies, failures to collect field-specific data, and the absence of additional information necessary for intersectional analysis. Advancing diversity, equity, and inclusion (DEI) in our field requires meaningful datasets that clearly identify social inequalities. Limited, incomplete, or anecdotal data are too easily dismissed by those in power, stalling constructive efforts.

In Canada, demographic data is not regularly collected at academic institutions and is seldom field-specific. This absence of data undermines efforts to identify the current state of diversity in the field and prioritise initiatives for improvement. Collecting comprehensive demographic data is a crucial step in determining whether progress is evident. It can also help to highlight areas of concern, especially in fields lacking in diversity, such as geoscience. To address this absence of data, we disseminated a 22-question demographic survey to 35 academic geoscience departments across Canada in late 2022.

We received 482 eligible responses to the survey, accounting for approximately 20% of the research population. Overall, men make up a slight majority across all respondents (53%), and the percentage of individuals who identify as white (73%) is greater than the national average (67%). Additionally, results shows that research students (MSc and PhD) are a diverse group, while salaried positions (postdoc, research staff and faculty) lack diversity in a wide range of categories including, gender, race, LGBTQ+, Indigeneity, and disability. Moreover, tenured positions are overwhelmingly occupied by white men, with racial inequalities prominent in the data.

These data highlight several areas of concern in the academic career path. The transition from research student to salaried research remains a clear area of concern, while the tenure process appears to continually favour white able-bodied cisgender men. Moreover, the representation of Indigenous persons and those with self-identified disabilities remains very low. Solutions require institutional changes to recruitment, tenure applications, postdoctoral hiring, field work design, and mentoring practices. Importantly, they also require changes to how we collect and analyse demographic datasets in geoscience, as a continued reliance on data that is passively collected or obtained from government sources will continue to limit our abilities to identify areas of concern and create effective strategies.

How to cite: Jess, S., Heer, E., and Schoenbohm, L.: Active demographic data collection in geoscience: results, implications, and recommendations from a survey of Canadian academia  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12643, https://doi.org/10.5194/egusphere-egu24-12643, 2024.

EGU24-13028 | Orals | EOS3.1

Embedding EDI in Geoscience Publications – Examples from the AGU  

Matthew Giampoala, Mia Ricci, and Paige Wooden

The American Geophysical Union understands an expansive and inclusive geoscience community is key to furthering knowledge about the Earth and the universe and finding solutions to current societal challenges. Though the geosciences have historically been dominated by a few homogenous groups, the collaborative and global nature of our science impels us to change our systems to include historically marginalized voices. Supported by AGU’s 2018 Diversity and Inclusion Strategic Plan, in 2023, AGU Publications signed the Joint Commitment for Action on Inclusion and Diversity in PublishingSignatories agree to collect self-reported gender and race/ethnicity data, develop baselines, and set minimum standards for inclusion. We provide a demographic overview of our authors, reviewers, and editors over time, detail how we collect data while following privacy laws, and discuss how data informs our DEIA strategies. We provide reports to our journal editors who set baselines and develop journal goals. We launched various initiatives to increase diversity and equity and decrease bias in peer review processes, and used the data to assess outcomes of these initiatives. In addition, we present examples of policy and structural changes we have implemented to weave DEIA in the scientific publishing environment, including our equitable approach to Open Access, our Community Science Exchange, and the recently launched Inclusion in Global Research policy to improve equity and transparency in research collaborations.

How to cite: Giampoala, M., Ricci, M., and Wooden, P.: Embedding EDI in Geoscience Publications – Examples from the AGU , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13028, https://doi.org/10.5194/egusphere-egu24-13028, 2024.

EGU24-14684 | Posters on site | EOS3.1

Nakkihomma: attitudes towards and distributions of academic household work 

Katja Anniina Lauri, Xuefei Li, Paulina Dukat, Nahid Atashi, Laura Karppinen, Katrianne Lehtipalo, Anna Lintunen, Dmitri Moisseev, Janne Mukkala, Tuomo Nieminen, Rosa Rantanen, Timo Vesala, Ilona Ylivinkka, and Hanna Vehkamäki

The equality and work well-being group at the Institute for Atmospheric and Earth System Research (INAR) at the University of Helsinki conducted a survey about academic household work (AHW) tasks among the institute’s staff in autumn 2023. The main aim of the survey was to find out how different AHW tasks are divided among the staff members and how the staff members consider these tasks.

Before the actual survey, we asked the staff to list tasks they consider AHW (nakkihomma in Finnish; direct translation: Frankfurter task). A few examples of AHW tasks we got: sending calendar invitations for meetings, making coffee for others, helping to organize social events at the institute, emotional service work (being involved in discussion with colleagues or students about their personal affairs or problems). For the survey, we grouped the proposed tasks in three categories (number of tasks in parentheses): research-related tasks (3), society-related tasks (4) and community-related tasks (29). The last category was further divided into four subcategories: tasks related to meetings (7), social events (6) and facilities (9), and miscellaneous (7). We asked which tasks the staff members consider as AHW, and how frequently they are committed to each task.

We received a total of 91 answers to the survey. This corresponds to 33% of our staff, but according to the background information we collected, the different groups in terms of gender, career stage, language status (Finnish/non-Finnish speaker) and staff group (research/technical/administrative) were represented well.

The general attitude towards AHW was surprisingly positive: 57% of respondents had a positive attitude while 35% had a neutral attitude. Senior research staff members use a considerable amount of time participating in different committee meetings while early-career researchers do not so much; however, they do a great deal of practical duties related to meetings. Furthermore, we found out that a lot of emotional service work is being done. Interestingly, early career researchers do not consider this generally as AHW while senior researchers do. Male staff members contribute more to technical writing and guiding tasks while female staff use more of their time in emotional service work and general collective AHW tasks. Finnish speakers contribute more to writing and guiding tasks while non-Finnish speakers are more frequently committed in “catering” AHW like making coffee. Technical and administrative personnel generally contribute more to AHW than research staff.

We hope that the results of this survey will help us developing a more equitable and inclusive atmosphere in our institute by enabling us to pay more attention in distributing AHW tasks in a more equal and just manner.

How to cite: Lauri, K. A., Li, X., Dukat, P., Atashi, N., Karppinen, L., Lehtipalo, K., Lintunen, A., Moisseev, D., Mukkala, J., Nieminen, T., Rantanen, R., Vesala, T., Ylivinkka, I., and Vehkamäki, H.: Nakkihomma: attitudes towards and distributions of academic household work, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14684, https://doi.org/10.5194/egusphere-egu24-14684, 2024.

EGU24-16168 | Posters on site | EOS3.1

Inclusive excellence at the ERC: latest actions and results of sustained measures 

Claudia Jesus-Rydin, Luis Fariña-Busto, and Eystein Jansen

The European Research Council (ERC), Europe’s premiere funding agency for frontier research, views equality of opportunities as an essential priority and a vital mission to ensure fairness in the review process. The ERC monitors various demographic data yearly on every call and has taken actions to tackle imbalances and potential implicit and explicit biases.

The presentation focuses on ERC general historical data for the three individual funding schemes: Starting Grant, Consolidator Grant and Advanced Grant. Demographic geosciences data of proposals and grants, disaggregated by gender and country, is presented. After more than 14 years of existence and various specific actions to tackle societal imbalances, ERC data provides an insight of the impact of various actions.

In the first framework programme (FP7, 2007-2013), 25% of applicants were women. In the last years (Horizon 2020, 2014-2020), this percentage increased by 4%, with 29% of women applying for ERC grants. In the same periods of time, the share of women as grantees has also increased from 20% to 29%. In the last years, men and women enjoy equal success rates (data for non-binary applicants is also presented).

The most recent actions taken by the ERC to address gender and diversity (including disabilities and neo-colonialism) in its operations and processes are also presented.

The ERC knows that work to ensure inclusive excellence and equality of opportunities is never-ending. This presentation analyses the institutional efforts critically and discusses possible steps to consolidate the accomplished results.

How to cite: Jesus-Rydin, C., Fariña-Busto, L., and Jansen, E.: Inclusive excellence at the ERC: latest actions and results of sustained measures, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16168, https://doi.org/10.5194/egusphere-egu24-16168, 2024.

EGU24-17197 | ECS | Orals | EOS3.1

Science Sisters: Interviews with diverse role models on career paths and academic life 

Marina Cano, Iris van Zelst, and Hinna Shivkumar

Science Sisters is a YouTube interview series and podcast hosted by Dr. Iris van Zelst. Lighthearted in tone, it explores different career paths, academic life, and science communication in the planetary and geosciences. The majority of the guests on the episodes are female and/or non-white to show a diverse range of role models in STEM and celebrate women in science. Together with the guest, Iris goes into the highs and lows of being a researcher and discusses issues in academia, such as the lack of permanent jobs in science and sexism. So far, two seasons of Science Sisters have been produced with topics including ethical fieldwork, switching careers, science communication, postdoc life, leadership, women in science, job applications, postdoc hopping, outreach, publishing, feeling incompetent, astronaut training, toxic academia, and how to build a research group.

Here, we present the project and some of the choicest nuggets of wisdom from the guests about academic life and careers. We also discuss the production phase of the series, highlighting for instance the considerations that go into selecting topics and guests, and the postproduction phase of editing and uploading the videos.

In addition, we present how we use Science Sisters as a way to start conversations in our own institutes. We organise a parallel seminar series where we watch the premieres of the episodes live on YouTube and afterwards have a discussion on the episode topic with the episode guest attending online. This has resulted in a greater understanding of each other and more cohesion within the institute. Early career scientists in particular say that Science Sisters is extremely useful to learn about life as a researcher and they enjoy the chatty, entertaining quality of the interviews.

How to cite: Cano, M., van Zelst, I., and Shivkumar, H.: Science Sisters: Interviews with diverse role models on career paths and academic life, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17197, https://doi.org/10.5194/egusphere-egu24-17197, 2024.

EGU24-18544 | ECS | Orals | EOS3.1

Time’s up, bottom-up! A successful bottom-up approach for diversity and inclusions at Utrecht University 

Manon Verberne, Jana R. Cox, Frances E. Dunn, Merel Postma, and Tina Venema

Young Women of Geoscience (YWOG) is a group of young professionals (PhDs, postdocs, assistant professors and supporting staff) at Utrecht University with the aim to inspire, connect and support women and historically underrepresented groups in the field of geosciences, by creating an equal and inclusive working environment. We do this by opening up conversations and creating a safe and positive space for discussion. Now in our seventh year, the committee has established itself as a constant and stable presence within the faculty with regular events and initiatives that can easily be organized from our reputable base.

Our regular events consist of meet-and-greet sessions with senior staff members, that are well-attended by a variety of colleagues, which result in inspiring conversations. Additionally, book give-aways combined with book discussions are a recurring event, where books on diversity, inclusions and climate change are used to open conversations. These events often engage individuals who may not have initially identified with the committee's target audience, but afterwards their interest was sparked. In recent years we also organized successful events due to requests from staff members. Parenting during COVID was a successful online event with a panel discussion consisting of colleagues sharing tips and struggles. Additionally, this year we organized an event on pronouns, reaching a wide audience, from PhDs to supporting staff, professors and the faculty dean. It was also this session, with informative presentations and lively discussion, that led to immediate action from higher level staff on practical matters concerning pronouns in the workplace.

Our experience highlights the importance of a bottom-up approach in instigating meaningful change. The pronouns event is a prime example of this, opening the eyes of many attendees and making people feel the urgency for action. The event stemmed from a need within the faculty. However, to be able to organize such an event there must be a platform to do so. We have the opportunity to organize many events helped by funding through an Equality, Diversity and Inclusion (EDI) scheme and an internal award won by the committee. We aim to continue with the regular events like the meet-and-greets and book shares, and hope to organize more events that are based on the needs in the faculty to open conversations. YWOG's experience demonstrates the efficacy of a bottom-up approach, emphasizing the importance of diverse perspectives in fostering substantial changes toward a more inclusive working environment. The committee looks forward to sharing its experiences, connecting with other faculties and universities, and inspiring collective efforts to promote diversity and inclusion within geosciences.

How to cite: Verberne, M., Cox, J. R., Dunn, F. E., Postma, M., and Venema, T.: Time’s up, bottom-up! A successful bottom-up approach for diversity and inclusions at Utrecht University, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18544, https://doi.org/10.5194/egusphere-egu24-18544, 2024.

EGU24-20027 | Orals | EOS3.1

Planning virtual and hybrid events: steps to improve inclusion and accessibility 

Aileen Doran, Victoria Dutch, Bridget Warren, Robert A. Watson, Kevin Murphy, Angus Aldis, Isabelle Cooper, Charlotte Cockram, Dyess Harp, Morgane Desmau, and Lydia Keppler

Over the last decade, the way we communicate and engage with one another has changed on a global scale. It is now easier than ever to network and collaborate with colleagues worldwide. But, the COVID-19 pandemic led to a rapid and unplanned move to virtual platforms, resulting in several accessibility challenges and the inadvertent exclusion of several people during online events. While virtual/hybrid events have strong potential to facilitate new opportunities and networks for everyone, they are also greatly positioned to increase the inclusion of groups traditionally excluded from purely in-person conferences. However, early and careful planning is needed to achieve this, with inclusion and accessibility considered from the start. Including a virtual element in a conference does not automatically equal inclusion or accessibility. Without effective planning, virtual and hybrid events will replicate many biases and exclusions inherent to in-person events.

This presentation will share lessons learned from previous events’ successes and failures, based on the combined experiences of several groups and individuals who have planned and run such events. This presentation is based on an EGU Sphere article, of the same title, that aims to provide guidance on planning online/hybrid events from an accessibility viewpoint based on the authors experiences. The goal of this presentation is to initiate discussion on event accessibility and inclusion and to help generate new ideas and knowledge from people outside of the authors network. Every event is unique and will require its own accessibility design, but early consideration is crucial to ensure everyone feels welcome and included. Our suggested accessibility considerations have been broken down into three stages of event planning: 1) Pre-event planning, 2) on the day/during the event, and 3) after the event.

Ensuring accessibility and inclusivity in designing and running virtual/hybrid events can help everyone engage more meaningfully, resulting in more impactful discussions including groups with limited access to in-person events. However, while this article is intended to act as a starting place for inclusion and accessibility in online and hybrid event planning, it is not a fully comprehensive guide. As more events are run, it is expected that new insights and experiences will be gained, helping to continually update standards.

How to cite: Doran, A., Dutch, V., Warren, B., Watson, R. A., Murphy, K., Aldis, A., Cooper, I., Cockram, C., Harp, D., Desmau, M., and Keppler, L.: Planning virtual and hybrid events: steps to improve inclusion and accessibility, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20027, https://doi.org/10.5194/egusphere-egu24-20027, 2024.

EGU24-20337 | Posters on site | EOS3.1

The stagnation of low percentage of female scientists in Japan and JpGU's initiatives 

Rie Hori and Chiaki Oguchi

The percentage of female scientists in Japan is 17.5% in the 2021 survey. This percentage is the lowest among OECD countries. The percentages of female doctoral students in science and engineering graduate programs nationwide are 21.0% and 19.2%, indicating a gap between the percentage of female prospective researchers and the percentage of women actually employed. It is pointed out that this is due to gender bias at the time of recruitment. On the other hand, the percentage of female members of JpGU remains around 20%, which is higher than the average in Japan, but still low compared to the percentage of female geoscientists in EGU and AGU. One of the reasons for the low number of female scientists in Japan is the low percentage of female students entering science and engineering fields in Japan (27% in science and 16% in engineering). The Science Council of Japan's Subcommittee on Gender and Diversity in Science and Engineering analyzed this problem and pointed out that its cause lies in the environment of education system during elementary and junior high schools (Opinion of SCJ, 2023). In Japan, the following factors are considered to have contributed to the decline in the number of female students going on to study science and engineering, even though surveys such as PISA (2018) and TIMSS (2019) show that both male and female 15-year-olds have equal academic achievement and interested in science and mathematics in the early education stage. (1) The percentage of female science teachers in junior high school and above is significantly lower than in the OECD countries → Few role models. (2) Often exposed to obvious “implicit bias” that has no evidence to support it (for example, girls are not good at mathematics. Science and engineering professions are not suitable for girls).

JpGU and Japanese universities actively conduct outreach programs for female junior igh and high school students every year to foster future female scientists. However, only a small percentage of them in whole Japan participate in such events, and these initiatives does not give us a full solution.

How to cite: Hori, R. and Oguchi, C.: The stagnation of low percentage of female scientists in Japan and JpGU's initiatives, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20337, https://doi.org/10.5194/egusphere-egu24-20337, 2024.

EGU24-22185 | Posters on site | EOS3.1

Signatures of Equality, Diversity and Inclusivity at EGU General Assemblies 

Johanna Stadmark, Alberto Montanari, and Caroline Slomp

The EGU recognises the importance of equality, diversity, and inclusion as a crucial foundation for scientific research to address fundamental scientific questions and societally relevant environmental challenges. The increasing diversity of our membership in all its facets fosters collaborative research and discovery that benefits humanity and our planet.

Since its founding, the EGU has worked to ensure equitable treatment for everyone in the community with the goal of increasing diversity. In autumn 2018, the EGU Council established a working group whose aim is to promote and support equality, diversity, and inclusion (EDI) in the Earth, planetary, and space sciences, with a focus on EGU activities. Less than three years later, the EDI group was upgraded into a committee and has delivered numerous actions.

The most recent achievements of EDI@EGU are the Champion(s) for Equality, Diversity and Inclusion Award that is bestowed to recognize excellent contributions to put into exemplary practice the principles of EDI. Furthermore, the EDI Committee is currently working on a new travel support scheme to promote diversity at the EGU General assemblies.

The above actions resulted in a more diverse attendance at EGU General Assemblies along the years. The total number of presenters has increased over the time period 2015-2023, and this increase was observed throughout all career stages. The proportion of women presenters has increased from 2015 to 2023. A similar trend was observed for the convenors, an increase in total numbers over the years and a higher proportion of women in 2023 than in 2015.

In the hybrid meeting in 2023 both early career scientists and more senior scientists to a higher extent participated physically in the meeting than online. While there were no differences in how women and men participated (online or physically), there are differences connected to the country affiliations. More than half of participants from countries in most of western Europe attended in Vienna, while participants from North America and Asia attended online.

Since EGU General Assembly is the largest geosciences conference in Europe understanding the demographic evolution and their participation to EGU activities, including the GA, of various groups is an important tool for EGU governing body to draw targeted actions to ensure that the current procedures are fair and that all in the community are being and feeling included. We therefore aim to analyse the changes in demographics with regards to gender, career stage as well as to geographical distribution of the presenters and convenors also in coming years to better understand the potential impacts of meetings organized online or physically, or as a combination of both these modes.

How to cite: Stadmark, J., Montanari, A., and Slomp, C.: Signatures of Equality, Diversity and Inclusivity at EGU General Assemblies, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22185, https://doi.org/10.5194/egusphere-egu24-22185, 2024.

SSS2 – Soil Erosion and Conservation

Land degradation is a primary form of global environmental deterioration. Soil erosion and land desertification are common land degradation processes in many regions. In this research, we take the Zhuoshui River basin in central Taiwan as the study area, and investigate the environmental sensitivity of different land use/land cover to land degradation subjected to historical and future climate scenarios. In order to understand the quality of land resources in the study area, we used the evaluating framework of the Mediterranean Desertification and Land Use (MEADALUS) model with revisions according to the localized mountainous characteristics in central Taiwan, and calculated the Environmentally Sensitive Areas Index (ESAI) of the study area. The ESAI is comprised of five indicators, which include climate, soil, vegetation, management, and landslide indicators. For the climate index, observed data from 2001 to 2020 of weather factors were used in the historical scenarios. On the other hand, data of weather factors generated by MIRCO5 GCM considering RCP2.6 and RCP8.5 scenarios in near-term and long-term time scales were used for the climate indicator in the future scenarios. The results depict the spatial variation of environmental sensitivity to land degradation in the Zhuoshui River basin using numerical values ranging from 1 to 2, where higher values correspond to more severe degradation. It is evident that the upper reaches of the Zhuoshui River exhibit lower degrees of land degradation due to dense vegetation, higher elevations, and limited human presence. In contrast, the downstream areas show a higher trend of land degradation, with the wet season exhibiting lower degradation trends compared to the dry season. Furthermore, there is a slight upward trend in land degradation since 2015, primarily attributed to climate indicators, as soil and vegetation indicators, as well as anthropogenic management indicators, show no significant changes. The land degradation index shows relatively subtle differences between future scenarios and historical scenarios, with land degradation index variations ranging from -13% to 22%. Negative values in the degradation index differences indicate an improvement in the degree of degradation, while positive differences denote an exacerbation of land degradation. According to the land use distribution in the Zhuoshui River basin, the land degradation trends for forests and national parks show relatively consistent variations between the dry and wet seasons. However, in the middle and lower reaches of the basin, apart from the RCP85 scenario for the long-term period, the other three scenarios exhibit higher differences in land degradation index changes for agricultural and urban areas compared to historical values. The research provides a reference for preventing continued land degradation and conserving terrestrial ecosystems and biodiversity in the study area.

How to cite: Wang, Y.-C. and Lu, Y.-H.: Evaluating the environmental sensitivity to land degradation: a case study in central Taiwan, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8, https://doi.org/10.5194/egusphere-egu24-8, 2024.

EGU24-44 | ECS | Posters on site | SSS2.1

Application of Dempster-Schafer theory for predicting ephemeral gullies with remote sensing data 

Solmaz Fathololoumi, Hiteshkumar B. Vasava, Prasad Daggupati, and Asim Biswas

Mapping Ephemeral Gullies (EGs) is essential for enhancing the management and conservation of natural and agricultural resources. This study aimed to devise a novel approach utilizing the Dempster-Shafer (D-S) theory to achieve more accurate EGs mapping. To accomplish this, a high-resolution satellite image and ground data collected during a field visit to the Niagara region in Canada were utilized. Firstly, spectral features that effectively identify EGs were extracted from the satellite imagery. Subsequently, three machine learning classifiers including the artificial neural network (ANN), support vector machine (SVM), and random forest (RF) were employed to generate the EGs map. Finally, the D-S theory was applied to integrate the outcomes from these classifiers, aiming for a more precise EGs map. The results highlighted that the most significant variable importance was attributed to the Normalized Near-Infrared (NIR) (18%) and Soil line (15%). The average producer and user accuracies for the EGs and non-EGs classes across the three classifiers were 0.53 and 0.67, and 0.97 and 0.95, respectively. Incorporating the D-S theory enhanced these accuracy values by 0.15 and 0.19 for EGs and 0.02 and 0.02 for non-EGs. Furthermore, the overall accuracies for the EGs maps generated by the ANN, SVM, RF, and D-S theory models were 94%, 93%, 95%, and 97%, respectively. The results of this study showed that D-S theory is useful for improving the EGs mapping using remote sensing data.

How to cite: Fathololoumi, S., B. Vasava, H., Daggupati, P., and Biswas, A.: Application of Dempster-Schafer theory for predicting ephemeral gullies with remote sensing data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-44, https://doi.org/10.5194/egusphere-egu24-44, 2024.

EGU24-190 | ECS | Orals | SSS2.1

Effects of the Initial Soil Moisture Contents on Rill Erodibility and Critical Shear Stress of the Clay-rich Soils   

selen deviren saygin, Fikret Ari, Cagla Temiz, Sefika Arslan, Mehmet Altay Unal, and Gunay Erpul

Rill erosion is one of the most significant water erosion types in the agricultural areas as a complex type of concentrated flow erosion process. And, it is known that hydraulic conditions are closely related to rill development in terms of the initial soil moisture contents. However, the impact of the subsoil hydrology on sediment discharge potentials is somewhat entangled. Thus, many recent studies point out that the change in soil erosion depends on hydrological conditions in the subsoil and suggest that the evaluation of those changes would increase the success of soil erosion estimates to more efficiently manage natural resources. This study was aimed to investigate the effects of different soil moisture settings (referred as dry, saturated and drainage) on rill erodibility (Kr) and critical shear stress (τcr) values of the soils as the significant variables of process-based WEPP model, and the relations between basic soil properties (e.g. particle size distribution, aggregate stability, soil mechanical cohesion, organic matter etc.) and these model variables for the heavy textured 12 soil types (clay contents change between 33 and 52 %). Flume experiments were performed by using a V-shaped mini-flume apparatus, which was 0.046 m wide, 0.5 m long, and 0.12m deep, specifically designed for rill experiments. Two V-shaped channels with a length of 0.2 m were cemented to the flumes, one on each side. The soil samples were packed in boxes to attain natural bulk densities of the soils after passing through a 2 mm screen opening. The slope steepness was set to 3% for the slope bed and the flow rate was controlled with a flow meter from 0.10 L min-1 to 0.65 L min-1. Within the scope of the study, the mechanical soil cohesion values of the soils were determined by the fluidized bed approach. Obtained results clearly showed that the initial moisture contents had significant effects on sediment concentrations. The lowest Kr values were observed for the drainage condition in all soils while the highest Kr value was obtained for the soils with higher clay than silt content in the saturated conditions. Under dry conditions, on the contrary, the latter reversed and there was the highest Kr value for the soils having higher silt contents than clay. The inverse relationship between Kr and τcr was very pronounced and the highest τcr value was measured under drainage conditions. In addition, it was observed that there were significant correlations between rill erodibility (Kr) and silt contents and mechanical soil cohesion variables of the soils. Conclusively, rill erodibility potential of the soils observed under concentrated flow conditions had statistically close relationships with initial moisture conditions and primary physical soil properties (p<0.01). The research findings experimentally confirmed that variations in subsoil hydrology would play a crucial role in new generation studies of process-based modelling of the rill erosion.

Key words: Rill erodibility, critical shear stress, WEPP, initial soil moisture content

Acknowledgements: This work was supported by the Scientific and Technological Research Council of Turkey [TUBİTAK-3001, Project no: 118O111].

How to cite: deviren saygin, S., Ari, F., Temiz, C., Arslan, S., Unal, M. A., and Erpul, G.: Effects of the Initial Soil Moisture Contents on Rill Erodibility and Critical Shear Stress of the Clay-rich Soils  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-190, https://doi.org/10.5194/egusphere-egu24-190, 2024.

EGU24-890 | ECS | Posters on site | SSS2.1

 Soil Hydrophobicity Effects on Soil Erosion: Interplay between Hydrological and Mechanical Effects 

Mahboobeh Fallah, Marco Van De Wiel, and Ran Holtzman

 

Soil erosion poses a significant threat to agricultural and natural resources. Soil water repellency (SWR), namely the resistance to wetting due to hydrophobicity, has become widespread due to variety of processes including droughts, wildfires, pollution and greywater irrigation. Recent studies showed that that SWR exerts a strong effect on soil erosion by its hydrological impact: reduction in infiltration implies increase in overland flow, the driving force for erosion. Another, much less explored and more complex effect of SWR on erosion is through its impact on soil cohesion and strength, the resisting force for erosion. Here, we focus on the combined effects of SWR on erosion. We compile the published experimental data of erosion in hydrophobic soils, which provides contradictory evidence of both increase and decrease of erosion with increasing SWR. We find that while drought- and fire-induced SWR predominantly increases erosion, there is no clear trend for pollution-induced SWR, suggesting that pollution can improve the soil’s resistance to erosion, and that this mechanical effect of SWR is stronger than the hydrological effect of increased overland flow. We establish a rational connection between the SWR and its hydrological and mechanical effects on erosion through a simple 1D numerical model. The results of the model indicate that the net erosional impacts of SWR depends on the balance between the soil hydrological and soil mechanical effects of SWR. The key insights obtained from literature and this straightforward model enhanced our understanding of the dual nature of SWR's influence on soil erosion dynamics.

Keywords: Cohesion, Erodibility, Hydrophobicity, Hydrology, Runoff, Soil Erosion

How to cite: Fallah, M., Van De Wiel, M., and Holtzman, R.:  Soil Hydrophobicity Effects on Soil Erosion: Interplay between Hydrological and Mechanical Effects, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-890, https://doi.org/10.5194/egusphere-egu24-890, 2024.

As a result of intensive agricultural practices, cultivated soils of the European loess belt can experience high levels of degradation by erosive runoff. Given the sometimes severe and costly on- and off-site impacts, the agricultural community is urged to adopt alternative cropping techniques to mitigate runoff and erosion. Several cropping practices related to conservation agriculture are known for their ability to mitigate surface flows, but the magnitude of their effectiveness is associated with a wide variability due to environmental or management factors. The influence of these factors on the practices’ effectiveness is still poorly understood in quantitative terms. We therefore quantitatively reviewed the effectiveness of three common conservation farming practices at controlling runoff and soil loss. A systematic search was performed, focused on the plot scale and the Western European context, and meta-analyses were carried out on the 35 collated relevant studies involving 239 individual trials (plot-years). Two different approaches suitable for hierarchically structured datasets were used for the meta-analyses: hierarchical nonparametric bootstrapping and linear random effects models. Both methods yielded very similar outcomes, but the lack of primary data sometimes restricted the ability to account for all hierarchical levels of the dataset in the random effects models. We found that, on average, winter cover crops decrease cumulative seasonal (autumn-winter) runoff by 68% and soil erosion by 72% compared to a bare soil. The level of stubble tillage on the control plot, the number of successive years of cover cropping, and the maximum vegetation cover reached are three key variables explaining the mitigation effect of winter cover crops. In potato crops, tied-ridging (=(micro)basin tillage) cut cumulative seasonal (spring-summer) overland flow by a mean of 70% and soil loss by 92% compared to conventional furrows, but no moderators could be identified to explain the variability across studies or trials. Conservation (non-inversion) tillage techniques alleviate cumulative seasonal runoff by 27% and associated sediments losses by 66% on average, but a publication bias is strongly suspected for this meta-dataset. These mitigation effects are much greater for spring crops than for winter crops, and increase over time since ploughing stopped. The type of conservation tillage schemes also affects the capacity to attenuate surface flows. Intensive non-inversion tillage schemes based on multiple (powered) tillage operations turns out to be the least effective at reducing both water and soil losses. The best performing scheme against runoff appears to be a deep non-inversion tillage (-61%), while against erosion it would be a direct drilling system (-82%). Coarser-textured soils (sandy loam) also respond slightly better to conservation tillage than (clay-)loams. Although several factors could partly explain the effectiveness of two of the three conservation practices considered in this study, there remains a high (unexplained) variability between trial effect sizes, thus not attributable to sampling variability. Meanwhile, this review provides farm advisors or policy makers with guidance on the conditions in which such conservation practices are expected to achieve the greatest benefits.

How to cite: Clement, T., Bielders, C., and Degré, A.: Effectiveness of conservation tillage, tied-ridging, and winter cover crops at controlling runoff and soil loss in the Western European context: a meta-analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2129, https://doi.org/10.5194/egusphere-egu24-2129, 2024.

EGU24-3077 | ECS | Orals | SSS2.1

Spatial distribution of fallout 137Cs and 239+240Pu in Equatorial and Southern Hemisphere soils 

Gerald Dicen, Florianne Guillevic, Pierre-Alexis Chaboche, Katrin Meusburger, Pierre Sabatier, Olivier Evrard, and Christine Alewell

Past nuclear weapons testing and nuclear power plant accidents resulted in the ubiquitous deposition of radionuclides in the environment. While the risks associated with radionuclide contamination are apparent, these fallout radionuclides (FRNs) provide the privileged markers (“golden spikes”) of the Anthropocene stratigraphic layers. The onset of their emissions in the 1950s coincided with the “Great Acceleration”, which is characterized by large-scale shifts in the biophysical and socio-economic aspects of the Earth System, including an increase in soil degradation, triggered mainly by land-use change. Among the host of FRNs deposited globally, 137Cs has been the most commonly used and 239+240Pu is a new emerging tracer and chronological marker to assess soil erosion and/or chronology of sediment deposition.

In this meta-analysis, we compiled existing 137Cs and 239+240Pu data analyzed from undisturbed soils in the literature to get an overview of the spatial distribution and constraints of fallout 137Cs and 239+240Pu in Equatorial and Southern Hemisphere soils, as well as the possible sources of these FRNs through their isotopic ratios. A database composed of 1087 reference cores was built from the literature published on Equatorial and Southern hemisphere soils.

Aside from the cores collected from the north equatorial regions, high 137Cs inventories were also found in reference soils collected at the 40-50° S latitudinal band, which were mostly from South America. On the other hand, high 239+240Pu inventories were found at the 20-30° S latitudinal band, but this was influenced by the unusually high inventories measured from the French Polynesia, where many nuclear weapons testing occurred. The 240/239Pu atomic ratios indicated that sources other than the global fallout (240/239Pu = 0.18) contributed to the reference inventories in the Southern Hemisphere. As some areas lacked measurements, specific points where additional data could be obtained were identified through a GIS-based approach to represent the entire land surface areas of interest adequately. Together with new measurements, the compiled reference soil data will be used to construct a detailed baseline map of 137Cs and 239+240Pu fallout mainly for regional soil erosion assessments.

How to cite: Dicen, G., Guillevic, F., Chaboche, P.-A., Meusburger, K., Sabatier, P., Evrard, O., and Alewell, C.: Spatial distribution of fallout 137Cs and 239+240Pu in Equatorial and Southern Hemisphere soils, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3077, https://doi.org/10.5194/egusphere-egu24-3077, 2024.

EGU24-3799 | ECS | Orals | SSS2.1

Identification of thresholds to conduct efficient soils and water conservation strategies against erosion impacts: new insights from a modelling prospective in Normandy (France) 

Aurélien Maurié, Edouard Patault, Jérôme Ledun, Marielle Deman, and Matthieu Fournier

Erosion is recognized as a major threat worldwide and can be dramatically observed in Northwestern France as a consequence of water runoff. Recent regional studies in Normandy suggested that off-site erosion and runoff impacts led to significant economic costs over the last 25 years. Even if the regional planning strategy against erosion and runoff impacts could be seen as effective with a cost-benefice balance greater than 1, this strategy will no longer be as effective by 2050 due to climate change effects in the near future. To address this issue and conduct efficient land and water degradation neutrality strategies, local stakeholders now have to identify complementary strategies based on the deployments of nature-based solutions. However, there is a lack of references on the effectiveness of these complementary strategies.

In this study, we conducted a modelling exercise with the WaterSed model at the regional scale (12,318 km²) aiming to: (i) quantify the hydro-sedimentary transfers reaching the karstic systems throughout the 15,000 sinkholes distributed across the territory, (ii) established the first regional cartography of vulnerability of sinkholes to runoff and erosion, and (iii) to evaluate the effectiveness of strategies considering nature-based solutions to prevent land and ground water degradation.

The model was calibrated and validated using data of hydro-sedimentary transfer monitoring station on a local catchment. Multiples scenarios were explored (impacts of different nature-based solutions densities, localization of grasslands, ploughing of grass lands, soil and water conservation techniques, etc.) using semi-automatic positioning algorithm.

The WaterSed model provided specific outputs like volume of runoff (m3) and volume of sediments (t) reaching the karstic system for different designed storms. The mean runoff per sinkhole was estimated between 7,700 and 23,200 m3 and the mean volume of sediment reached between 0.8 and 4.7 t per sinkhole.

Our results suggest that increasing the density of nature-based solutions from 2 to 8 per km² can reduce from 0.5 to 1.3 % the runoff volume and from 5 to 15 % the sediment load reaching the sinkholes. Our results also suggest that a complement of 20 m to 250 m of grassland upstream a sinkhole can reduce the sediment load from 5 to 13 % and the runoff from 0.5 to 1.5 %. Our results suggest that the localization of ploughed-up grasslands can have a significant impact on the generation of hydro-sedimentary transfers (up to 10 % more sediment discharge).

The results of this modeling exercise provided: (i) the first regional cartography of vulnerability of the 15,000 sinkholes to runoff and erosion, and (ii) local thresholds and valuable references to build and conduct efficient land and ground water degradation neutrality strategies with stakeholders.

How to cite: Maurié, A., Patault, E., Ledun, J., Deman, M., and Fournier, M.: Identification of thresholds to conduct efficient soils and water conservation strategies against erosion impacts: new insights from a modelling prospective in Normandy (France), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3799, https://doi.org/10.5194/egusphere-egu24-3799, 2024.

The middle reaches of the Yellow River (MYR) cover a significant portion of the Loess Plateau, rendering it among the most heavily impacted regions by soil erosion globally. Consequently, the MYR are characterized by high-intensity soil and water conservation measures, such as terracing and silt check dams, which exert a profound impact on soil erosion and sediment transport in this region. However, there is currently no accurate and clear assessment of sediment interception and sediment reduction contributions for large-scale and complex cascading silt check dams. This study enhances the Revised Universal Soil Loss Equation (RUSLE) model by coupling the processes of soil erosion, slope sediment production, and channel sediment transport. The study evaluates the slope erosion and sediment production through the combination of RUSLE and the Sediment Connectivity Index (IC). Additionally, it calculates the sediment interception and sediment output in the channel based on silt check dams sediment interception efficiency. Accurate classification of complex cascading silt check dams is crucial for assessing their sediment reduction contributions. The research employs a flow-based method for precise dam classification and incorporates the latest terracing distribution data to accurately assess the sediment reduction contributions of high-intensity engineering measures in the MYR. The research findings indicate: (1) The average annual soil erosion rate in the MYR from 1981 to 2017 is 13.32±31.94 t ha-1 yr-1, with moderate to severe soil erosion covering 15.1% of the area. (2) Over the past 40 years, there has been an overall decreasing trend in soil erosion in the MYR, with a significant reduction covering 8.65% of the area. Significant decreases in soil erosion began to appear after 2000, with an average annual soil erosion rate reduction of 0.34 t ha-1 yr-1. (3) Based on the cascading situation of silt check dams, the 2187 large silt check dams in the MYR are classified into 6 categories. Taking the initial siltation year as an example, for basins controlled by silt check dams, the sediment output rate without silt check dams is 3.444 t ha-1 yr-1, while with silt check dams, the sediment output rate is 0.468 t ha-1 yr-1, achieving a sediment reduction contribution of 86.4%. The upcoming tasks include: (1) investigating the interannual fluctuations in sediment reduction attributed to silt dams and validating the model; (2) formulating diverse scenario assumptions to evaluate the sediment reduction contributions from engineering measures and vegetation restoration. This study seeks to precisely evaluate the impact of high-intensity soil and water conservation measures on mitigating soil erosion and sediment transport in the MYR, offering insights for regional soil and water conservation practices and sustainable management.

How to cite: Huang, Y., Gao, G., and Wang, Y.: Effect of high intensity soil and water conservation engineering measures on soil erosion and sediment transport, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4527, https://doi.org/10.5194/egusphere-egu24-4527, 2024.

The Western Ghats are in the final stage of weathering. Hence, the Laterite, clay, and Saprolite layers can vary to depths greater than 50 meters. Thus, the Western Ghats have unique hillslope hydrology, with more than three-quarters of rainfall entering the subsurface flow, thus developing well-networked sub-surface conduits. These sub-surface conduits help maintain slope stability of the Shayadris' (Western Ghats) laterites, which are usually exposed to high-intensity rainfall for longer durations during the monsoon season. The slope failures and floods in 2018, 2019 and 2020 are due to Catchment Fragmentation leading to a disturbed hydrological cycle in both surface and subsurface levels. 

A unique observation showed that most of the landslides (mostly toe failures) were concentrated near the Harangi reservoir and had a valley stream connecting to the reservoir. During field observations in these slope failure sites, soil pipe was observed in the crest of the landslide scarp for most of the accessible locations. The slope failures could be due to backflows in the soil pipes during heavy rainfall and mismanagement of dam gates. Observations from local residents who had witnessed the slope fail gave an idea of backflows in these slopes, which they locally termed as JALASPHOTA – The burst of groundwater up these soil slopes. During field observations post-monsoon, streams were visible at the surface of the scarp through these soil pipes after the landslide. 
GSD of Lateritic soils of Kodagu is Clay, sandy clay, sand-silt clay, clayey sand, sand-silt-clay and clayey sand. A slow-moving landslide was observed on the highway connecting to Mangalore, where more clay content was observed. 
Juvenile and fully developed soil pipes were observed at the landslide scarp, and slopes with fully mature soil pipes were observed to have more runout distance. 
A few case studies of how catchment Fragmentation has disturbed the sub-surface hydrology, leading to slope failure, are discussed in this study. 

How to cite: Manjunath, K.: Field Observations of Soil Piping and associated disasters in the Western Ghats region of Karnataka (Kodagu district) , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4633, https://doi.org/10.5194/egusphere-egu24-4633, 2024.

EGU24-4784 | ECS | Orals | SSS2.1

Quantifying above-ground biomass, SOC and erosion using a new detailed crop pattern map including double and triple cropping in the Yangtze River basin using the PESERA model 

Jichen Zhou, Jantiene Baartman, Yinan Ning, João Carvalho Nunes, Lihua Ma, and Xuejun Liu

Soil erosion represents a primary threat to soil systems with adverse implications for ecosystem services, crop production, potable water, and carbon storage. While numerous studies have quantified the spatial distribution of Above-Ground Biomass (AGB), soil erosion, and Soil Organic Carbon (SOC) in the Yangtze River Basin (YRB) in China, limited attention has been given to assessing the contributions of different land use types and especially crop types to AGB, soil erosion, and SOC. In most studies, cropland is taken as a land use class, while detailed crop types and rotation patterns, and their effect on soil erosion and SOC, vary significantly. In this study, we used the Metronamica model to generate a detailed crop rotation and distribution map across the YRB and subsequently employed the PESERA model to simulate the spatial distribution of AGB, soil erosion, and SOC on a monthly basis. PESERA model simulations indicate an average soil erosion rate across the entire YRB of 7.7 t/ha/yr, with erosion hotspots concentrated in the Sichuan Basin and the central-southern regions. The southwestern region and western Sichuan show elevated levels of AGB and SOC, while the eastern plains display lower levels. Erosion rates are lowest in areas designated as artificial land, pasture and grassland, whereas cropland and fruit trees experience the highest erosion rates. In terms of crop types, the highest erosion rates and lowest AGB are observed in fallow and potato cultivation, while the lowest erosion rates and highest AGB are found in rice-wheat rotation fields. To the best of our knowledge, this is the first study including detailed crop types and patterns into account while evaluating their effect on relatively large scale (i.e. YRB). These findings can help to develop sustainable soil management and (cropping) conservation strategies.

How to cite: Zhou, J., Baartman, J., Ning, Y., Carvalho Nunes, J., Ma, L., and Liu, X.: Quantifying above-ground biomass, SOC and erosion using a new detailed crop pattern map including double and triple cropping in the Yangtze River basin using the PESERA model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4784, https://doi.org/10.5194/egusphere-egu24-4784, 2024.

EGU24-6779 | Orals | SSS2.1

Predicting soil erosion under climate change: Using climate data to forecast future climate change scenarios and RUSLE2 modeling to estimate soil erosion on agricultural lands in the United States 

Mahsa Ghorbani, Racha El Kadiri, Henrique Momm, Daniel Yoder, Vieira Dalmo, Ronald Bingner, Robert Wells, Giulio Ferruzzi, and Christophe Darnault

Soil erosion is one of the major processes of land degradation. Climate change, marked by alterations in the precipitation spatial and temporal patterns as well as rainfall amounts projected to increase, is expected to exacerbate soil erosion and loss of soil in the agricultural landscape. Understanding soil loss using physically-based water erosion prediction models and improving knowledge of soil erosion of agricultural lands under future climate change scenarios is critical to developing best management practices for the conservation of soil resources as well as to inform decision and policy makers. This study aims at investigating the impacts of future climate changes on soil erosion in the United States. By integrating up-to-date climate datasets this study characterized differences and current trends in precipitation with respect to climate change and applied a climate model ensemble based on the CMIP6 climate scenarios to predict the future climate. These data are downscaled with machine learning algorithms. It also estimates soil erosion in different soil-climate-agricultural management systems from predicted precipitation under future climate change scenarios using the Revised Universal Soil Loss Equation, Version 2 (RUSLE2). Research findings on the impacts of future climate change scenarios on soil erosion in agricultural landscapes will allow the development of climate-driven best management practices and conservation agriculture techniques as well as inform decision and policy makers to reduce soil loss, therefore protecting the limited soil and water resources, and contributing to a sustainable agricultural production and food security.

How to cite: Ghorbani, M., El Kadiri, R., Momm, H., Yoder, D., Dalmo, V., Bingner, R., Wells, R., Ferruzzi, G., and Darnault, C.: Predicting soil erosion under climate change: Using climate data to forecast future climate change scenarios and RUSLE2 modeling to estimate soil erosion on agricultural lands in the United States, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6779, https://doi.org/10.5194/egusphere-egu24-6779, 2024.

EGU24-6852 | Orals | SSS2.1

Revised Universal Soil Loss Equation, Version 2 (RUSLE2) Development: Advanced science components and web-based user interface for use in conservation planning 

Christophe Darnault, Mahsa Ghorbani, Gizem Genc Kildirgici, Avinash Kethineedi, Bigyan Ghimire, Jon Calhoun, Henrique Momm, Daniel Yoder, Vieira Dalmo, Ronald Bingner, Robert Wells, and Giulio Ferruzzi

The Revised Universal Soil Loss Equation, Version 2 (RUSLE2) is the water erosion prediction tool for use by the USDA National Resources Conservation Service (NRCS) for all conservation planning in the United States. USDA NRCS utilizes the Integrated Erosion Tool (IET) that combines RUSLE2 with USDA data sets for soil, climate, and agricultural management. The Agricultural Research Service (ARS) is the USDA’s research agency charged with the development of the RUSLE2 model. RUSLE2 is an advanced computer model that estimates rill and interrill erosion by water, combining empirical and process-based science, for use on personal computers. This research aims at improving RUSLE2 science components, including the development of a web-based user interface for RUSLE2, for use by USDA NRCS. Advanced science components will be developed to quantify rainfall and land management effects on spatial and temporal variability of dynamic soil properties in agricultural watersheds in the United States, with emphasis on the assessment of soil erodibility and the risk of soil erosion under climate change. State-of-the-art technologies needed to measure, identify, and link dynamic soil erodibility to soil loss in the agricultural landscape, such as machine learning algorithms, remote sensing, and non-intrusive visualization and imaging technologies will provide advanced science components for RUSLE2. For the development of a web-based RUSLE2 modeling system, a new cloud based infrastructure is being deployed using the Amazon Web Services (AWS) platform, which will support online databases for climate, soil, and agricultural management data. A new database structure is being designed for RUSLE2, to support server based erosion calculations. AWS services will also provide web servers, spatial databases, geoprocessing capabilities, cooperative source code development and all compute and storage resources. These research findings and products will help understand how climate change and modern management practices impact soil erodibility dynamics. Improvements to RUSLE2 technology will lead to advances in determining soil loss across agricultural landscapes through improved physically based water erosion models. New web-based tools will provide best management practices for soil and water resources conservation under changing environments, contributing to sustainable agriculture and food security, while ensuring environmental health.

How to cite: Darnault, C., Ghorbani, M., Genc Kildirgici, G., Kethineedi, A., Ghimire, B., Calhoun, J., Momm, H., Yoder, D., Dalmo, V., Bingner, R., Wells, R., and Ferruzzi, G.: Revised Universal Soil Loss Equation, Version 2 (RUSLE2) Development: Advanced science components and web-based user interface for use in conservation planning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6852, https://doi.org/10.5194/egusphere-egu24-6852, 2024.

EGU24-9422 | Orals | SSS2.1

Assessing soil erosion in a small agricultural catchment in Austria using OSL-dating, modelling, 137Cs and field measurements: a critical comparison 

Ronald Pöppl, Chris Renschler, Bruno Abatti, Nadine Asimus, Sabine Kraushaar, Peter Strauss, and Markus Fuchs

Soil erosion causes severe on- and off-site effects, such as reductions in soil depth, eutrophication of water bodies, loss of organic matter, and clogging and smothering of riverine habitats. Attempts to assess water-induced soil erosion by water include modelling, measuring/monitoring, the use of tracers, and dating. All of these approaches have shown to have shortcomings (Parsons, 2019). The main objective of this research is to assess soil erosion in a small agricultural catchment (HOAL, Lower Austria) using modelling, OSL-dating, 137Cs and field measurements and to compare the gained results in the light of the shortcomings of each method. The study has been conducted in a small catchment (ca. 66 ha), located in the Northern foothills of the Eastern Alps in Austria (i.e. an area intensively agriculturally used since the Middle Ages). The catchment elevation ranges from 268 to 323 m a.s.l. and has a mean slope angle of 8 %. The lithology mainly consists of Tertiary marly to sandy deposits which are superimposed by Quaternary sediments (e.g. loess). The climate in this region is characterized as humid. The results of this study reveal significant – partly even dramatic - differences in soil erosion rates as derived from the different assessment methods. Details as well as a critical method comparison will be provided at the EGU General Assembly 2024.

References:
Parsons, A. J. (2019). How reliable are our methods for estimating soil erosion by water? Science of the Total Environment, 676, 215-221.

How to cite: Pöppl, R., Renschler, C., Abatti, B., Asimus, N., Kraushaar, S., Strauss, P., and Fuchs, M.: Assessing soil erosion in a small agricultural catchment in Austria using OSL-dating, modelling, 137Cs and field measurements: a critical comparison, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9422, https://doi.org/10.5194/egusphere-egu24-9422, 2024.

EGU24-9512 | ECS | Orals | SSS2.1

AI-driven insights into soil health and soil degradation in Europe in the face of climate and anthropogenic challenges 

Mehdi H. Afshar, Amirhossein Hassani, Milad Aminzadeh, Pasquale Borrelli, Panos Panagos, David A. Robinson, and Nima Shokri

A healthy soil supports life on Earth through maintaining ecosystems that provide food, feed and fibre whilst supporting Earth system functions such as waste recycling, climate, flood, and water regulation. The intensification of anthropogenic activities and climate challenges pose serious threats to soil health (Hassani et al., 2021), exacerbating the processes of soil degradation that are putting at risk soil management, biodiversity, and food security.

This study thus aims at enhancing our understanding of the state and changes of soils by combining machine learning methods with a comprehensive series of climate and environmental variables. We employ machine learning methods to analyze the relationships between soil health indicators and a wide range of climatic parameters, and chemical, physical, and biological soil attributes in Europe. Capitalizing on the LUCAS (Land Use/Cover Area frame statistical Survey) topsoil database (2009-2018) and digital soil mapping techniques, our preliminary results highlight the regions across Europe showing consistent decline in soil nutrients and carbon content, signaling potential risks of soil degradation. The proposed framework enables us to understand, document and respond to soil changes in ecosystems under different land management and climate scenarios. This contributes to devising necessary action plans for sustainable soil management and preservation.

This research is part of the project AI4SoilHealth (Accelerating collection and use of soil health information using AI technology to support the Soil Deal for Europe and EU Soil Observatory) funded Horizon Europe (Grant No. 101086179).

 

Reference

Hassani, A., Azapagic, A., Shokri, N. (2021). Global Predictions of Primary Soil Salinization Under Changing Climate in the 21st Century, Nat. Commun., 12, 6663. https://doi.org/10.1038/s41467-021-26907-3.

How to cite: H. Afshar, M., Hassani, A., Aminzadeh, M., Borrelli, P., Panagos, P., Robinson, D. A., and Shokri, N.: AI-driven insights into soil health and soil degradation in Europe in the face of climate and anthropogenic challenges, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9512, https://doi.org/10.5194/egusphere-egu24-9512, 2024.

EGU24-10802 | Orals | SSS2.1

Hydrosedimentary functioning of a lowland field with both surface and subsurface drainage. 

Arthur Gaillot, Olivier Cerdan, Sébastien Salvador-Blanes, Pierre Vanhooydonck, Thomas Grangeon, Marc Desmet, and Célestine Delbart

Erosion is one of the most important threats for soil. Over the long term, soil erosion can have serious on-site (e.g. decrease in agricultural yield) and off-site impacts in morphogenic zones but also important off-site (e.g. mudflow) impacts in plains. Much more efforts have been devoted to study erosion processes in morphogenic zones that have naturally higher erosion rates than plains. However, the intensification of agriculture during the latter part of the 20th century significantly altered landscapes and increased hydrosedimentary connectivity in agricultural plains. The off-site consequences are numerous: mudflows, increasement a river turbidity, siltation in rivers, transfers of pollutants associated with sediments, etc. Generally, in temperate climate, the main source of sediments is the surface runoff that occurs on fields during winter or spring but in lowland areas the subsurface drainage network is a supplementary pathway for runoff and sediments. The few studies that have quantified erosion over a complete hydrological year show subsurface drainage contribution to erosion is very variable. It is still difficult to propose a hierarchy and to quantify factors affecting soil erosion by subsurface drainage. In this study, suspended solids (SS) concentration and water flow of a lowland field have been measured during two consecutive years both at the outlets of surface and subsurface drainage networks. SS yield was 0.49 t ha-1 and 1.08 t ha-1 in 2019–2020 and 2020–2021, respectively. During 2019–2020 and 2020–2021, subsurface drainage contribution to the total runoff was 46% and 21%, respectively and its contribution to SS yield was 9% and 11%, respectively. High temporal resolution measurements of SS concentrations showed the suspended sediment concentration increased at the outlet of both surface and subsurface drains from the first to the second year. These variations and the increase of surface runoff rate suggest a shift in water and sediment connectivity at the field scale. Based on water tracing, water balance and analysis of rainfall characteristics, the main driver is likely cropping practices. This study confirms the majority of sediment exports occurs during a short period, cause by only few runoff event of winter and adds a new quantification of hydrosedimentary fluxes in a surface and subsurface drained field separating surface and subsurface drainage contribution. It also shows that in hydromorphic drained areas, despite the very slight slope, surface runoff can represent the major pathway for soil erosion. Adapted soil tillage practices must be developed to preserve the agricultural production capacity of the fields, maintaining water exports, while simultaneously reducing sediment exports.

How to cite: Gaillot, A., Cerdan, O., Salvador-Blanes, S., Vanhooydonck, P., Grangeon, T., Desmet, M., and Delbart, C.: Hydrosedimentary functioning of a lowland field with both surface and subsurface drainage., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10802, https://doi.org/10.5194/egusphere-egu24-10802, 2024.

EGU24-10943 | ECS | Posters on site | SSS2.1

Study about perception of soil compaction in grasslands: what can be learnt to foster sustainability and policy intervention? 

Manjana Puff, Glenda Garcia-Santos, and Andreas Bohner

The study of the sustainable strategies at regional level complies with the current European Green deal to monitor soil compaction. However, recent studies showed that the implementation of sustainable practices by farmers that are useful for an ecological transition can be slow down by development and technology transfer capacity and or an attitude of resistance of farmers themselves to innovations.

In the context of soil compaction in grasslands, we studied the influence of different management strategies (use of cattle and machinery) and the farmers’ perception of soil compaction. The studied bio-physical indicators in the top soil were organic carbon, plant indicators, bulk density, soil texture, plant indicators, infiltration capacity, water repellence, water content and electrical conductivity at the surface level of permanent grasslands in a total of 16 grasslands in the time period 2022-24 within Görtschitztal and Magdalensberg in south Austria (Carinthia).

First results showed correlation between the use of cattle and number of entries in the field with heavy machinery and the increase of the bulk density, though always within low levels of compaction and at the surface. We also found cases of mismatch perception of soil compaction, which may hinder sustainable practices in the future. The results of this study may serve to increase understanding about the theoretical factors influencing the farmer’s perception of soil compaction problems, providing a valuable addition to the available literature. In terms of policy implications, a clear picture of the factors underlying the dynamics of farmer’s perception can be useful in the future to better targeting policy measures tailored to encourage sustainable practices and innovations in the agricultural sector. We show possible directions affecting perceptions at farmer-based level.

How to cite: Puff, M., Garcia-Santos, G., and Bohner, A.: Study about perception of soil compaction in grasslands: what can be learnt to foster sustainability and policy intervention?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10943, https://doi.org/10.5194/egusphere-egu24-10943, 2024.

EGU24-12285 | Orals | SSS2.1

Comparison of soil erosion rates by wind and water in a semi-arid loess soil  

Itzhak Katra, Meni Ben-Hur, and Smadar Tanner

Soil erosion is a significant process in the loss of soil/land resources, degradation and desertification. Traditionally, wind and water erosions have been studied and modelled separately. A quantitative sediment flux measure from a specific soil due to both water and wind erosion is lacking. The study aimed to drive such erosion rates in a semi-arid loess soil that is subjected to both forces of erosion. Soil samples from top-and sub-layers of the soil were analyzed for physical and chemical properties, including characteristics of soil aggregation. We performed targeted laboratory experiments using a boundary layer wind-tunnel for wind erosion and rainfall simulator for water erosion. Rates of sediment flux that were calculated for the topsoil and the subsoil revealed an opposite trend between water and wind erosion. This indicates that soil erodibility strongly depends on the erosional force applied rather than a certain soil property. The study conducted in a semi-arid region and may serve as a case study under climate change scenarios, in which more (non-arid) regions will be subjected to increase soil erosion.    

How to cite: Katra, I., Ben-Hur, M., and Tanner, S.: Comparison of soil erosion rates by wind and water in a semi-arid loess soil , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12285, https://doi.org/10.5194/egusphere-egu24-12285, 2024.

EGU24-12401 * | ECS | Orals | SSS2.1 | Highlight

Towards a unifying approach of land degradation in Europe 

Remus Pravalie, Pasquale Borrelli, Panos Panagos, Mihai Niculiță, Georgeta Bandoc, Cristian Patriche, and Bogdan Roșca

The impact of land degradation on the environment is multidimensional and is fundamentally influenced by various land degradation processes, which usually interact spatially in a convergent manner. However, the spatial pattern of multiple converging (co-occurring) land degradation pathways remains largely unexplored in Europe. To address the synergistic (convergent) nature of land degradation, in this work we modelled and mapped the spatial pattern of twelve interacting processes in agricultural/arable environments of Europe. Therefore, using state-of-the-art and large-scale datasets that were modelled via appropriate GIS (Geographic Information System) techniques, we performed an unprecedented investigation on land multi-degradation in 40 European countries. Essentially, we found that up to 27%, 35% and 22% of pan-European agricultural/arable landscapes are synergistically affected by one, two and three land degradation processes, while 10–11% of continental agricultural/arable environments are cumulatively threatened by four and at least five co-occurring processes. Our multi-process framework can be a valuable scientific tool for complex modelling of land degradation, but also for applying various agricultural, climate or sustainable development policies at European level.

How to cite: Pravalie, R., Borrelli, P., Panagos, P., Niculiță, M., Bandoc, G., Patriche, C., and Roșca, B.: Towards a unifying approach of land degradation in Europe, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12401, https://doi.org/10.5194/egusphere-egu24-12401, 2024.

EGU24-12976 | ECS | Posters on site | SSS2.1

A piping erosion susceptibility map of Europe 

Anita Bernatek-Jakiel, Matthias Vanmaercke, Jean Poesen, Anna Biernacka, Pasquale Borrelli, Anastasiia Derii, Joanna Hałys, Joseph Holden, Gergely Jakab, Michał Jakiel, Panos Panagos, Dawid Piątek, Taco H. Regensburg, Jan Rodzik, Estela Nadal-Romero, Mateusz Stolarczyk, Els Verachtert, Patryk Wacławczyk, and Wojciech Zgłobicki

Soil erosion represents a crucial environmental issue worldwide that threatens land, freshwater, and oceans. Subsurface erosion by soil piping occurs in almost all climatic zones of the world and in various soil types. Its occurrence changes the conditions for controlling measures to reduce soil degradation. However, it remains one of the most overlooked soil erosion processes, and its global and regional recognition is poorly documented. This project aims to construct a piping erosion susceptibility map of Europe in order to identify locations affected by this process, and where specific erosion control measures should be taken. Firstly, we compiled a database of soil piping-related features, i.e. pipe roof collapses (PCs) and pipe outlets in the European Union and the UK that consists of 6841 locations having piping-related features (6171 PCs and 670 outlets), among which the location of 88% features is known at a resolution of 25 m. Then, this database is used to model the susceptibility of soils to piping erosion at the European scale. We applied the logistic regression model using the scikit-learn library in Python. The following environmental factors are tested: topography (such as slope and height difference), pedology (content of silt, clay, sand, and coarse fragments), land use and land cover, and climate (such as effective precipitation). Our preliminary result clearly shows that it is feasible to accurately identify the European hotspots susceptible to piping erosion, based on a combination of land use, topographic and soil variables (AUC >0.75). The presented map is an important step towards incorporating subsurface soil erosion into regional and global soil erosion models.

 

This research is part of a project “Building excellence in research of human-environmental systems with geospatial and Earth observation technologies” funded by the European Union’s Horizon 2020 research and innovation programme under grant agreement No 952327. The research has also been supported by a grant from the Faculty of Geography and Geology under the Strategic Programme Excellence Initiative at Jagiellonian University.

How to cite: Bernatek-Jakiel, A., Vanmaercke, M., Poesen, J., Biernacka, A., Borrelli, P., Derii, A., Hałys, J., Holden, J., Jakab, G., Jakiel, M., Panagos, P., Piątek, D., Regensburg, T. H., Rodzik, J., Nadal-Romero, E., Stolarczyk, M., Verachtert, E., Wacławczyk, P., and Zgłobicki, W.: A piping erosion susceptibility map of Europe, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12976, https://doi.org/10.5194/egusphere-egu24-12976, 2024.

EGU24-13351 | Posters on site | SSS2.1

Novel use of portable gamma sensors to rapidly assess soil status and recovery in degraded East African agro-pastoral land 

Will Blake, Aloyce Amasi, Claire Kelly, Shaun Lewin, Francis Mkilema, Furaha Msale, Kelvin Mtei, Linus Munishi, Mona Nasseri, Patrick Ndakidemi, and Alex Taylor

Soil resources in East African agro-pastoral lands are being rapidly depleted by erosion, threatening food, water and livelihood security. Here we explore the utility of innovation in portable gamma sensors to rapidly assess soil health via proxy measurement of soil organic matter (SOM) providing visual information that enables local communities to take action to mitigate land degradation before it reaches a critical tipping point.

This study is grounded in the outcomes of an integrated, interdisciplinary approach to support co-design of land management policy tailored to the needs of specific communities and places. The work has shown that limitations to delivering socially acceptable and environmentally desirable solutions can be addressed by (1) closing fundamental gaps between the evidence bases of different disciplines and indigenous knowledge and (2) addressing, through participatory action, the implementation gap between science-based recommendations, policy makers and practitioners. Key adaptations implemented in the study region include new bylaws to enforce altered grazing regimes, grassland recovery and tree planting.

Against this context, we report a first trial of a portable gamma spectrometer to rapidly assess spatial variability in soil health using total and radionuclide-specific gamma emissions from naturally occurring radioisotopes as a proxy for soil organic matter. A Medusa MS-700 portable gamma spectrometer was deployed on foot across a landscape of known variability in soil health status encompassing a spectrum of impact from severely gullied soil/subsoil, heavily grazed surface soil, recovered grazed soil (ca 3 years exclusion of livestock) and conservation agriculture plots. In-situ field results showed a clear gradient in raw total gamma count rate with sample areas in each zone at 1200 ± 100, 980 ± 70, 814 ± 60 and 720 ± 60 counts per second across the above four areas respectively.  Correlations between radioisotope-specific gamma spectrometer data and organic matter (range 15 ± 2 to 30 ± 3 g kg-1 from degraded land to conservation agriculture) were evaluated to explore the dominant control on sensor response. Further comparisons are made to major and minor element geochemistry. Feedback from local Maasai community members who participated in the research further underpins the value of the sensor as a qualitative assessment tool e.g. using visual colour coding in the live data feed in the field. Quantitative comparison of sensor and laboratory data will permit development of protocols for airborne (drone) gamma spectrometry that offers community scale evaluation of grazing pressure on soil health to inform livestock future exclusion policy in common land prone to soil erosion.

How to cite: Blake, W., Amasi, A., Kelly, C., Lewin, S., Mkilema, F., Msale, F., Mtei, K., Munishi, L., Nasseri, M., Ndakidemi, P., and Taylor, A.: Novel use of portable gamma sensors to rapidly assess soil status and recovery in degraded East African agro-pastoral land, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13351, https://doi.org/10.5194/egusphere-egu24-13351, 2024.

EGU24-13949 | ECS | Orals | SSS2.1

A GIS-modeling strategy to locate vulnerable agricultural fields and prioritize conservation efforts across the Midwest United states. 

Eduardo Luquin, Brian Gelder, Daryl Herzmann, Emily Zimmerman, David James, Kelsey Karnish, and Richard Cruse

To appropriately place soil conservation measures, locating the most vulnerable areas prone to soil erosion is required. Available tools to locate vulnerable areas are tedious to use and time-consuming, and most water erosion estimations are based on empirical models with limited applicability. The present study takes advantage of two large-scale soil and water conservation tools available for the Midwest U.S.: the Daily Erosion Project (DEP) and the Agricultural Conservation Planning Framework (ACPF).

In this study, we will showcase a recently developed large scale modeling approach implemented in the Midwest U.S. that currently downscales DEP from Hydrologic Unit Code (HUC) 12 (~90 km2) average estimation of hillslope runoff and soil loss into a much finer resolution, a field and pixel scale. The DEP uses the Water Erosion Prediction Project (WEPP) and simulates hundreds of thousands of hillslopes across the Midwest, covering the wide range of factors including topography, climate, soils and land use and management.

This presentation will introduce the newly developed quantitative soil erosion assessment tool (named OFEtool - Overland Flow Element tool) that uses geographic information systems (GIS) and a physical-based model with real climate data (DEP). The OFEtool analyzes a watershed and groups areas with similar attributes, such as slope, soil type, land use, and management practices (information provided by the ACPF). Following watershed analysis, the tool uses DEP simulations to obtain average hillslope soil erosion or deposition rates for these grouped characteristics. Finally, it associates and assigns these rates to the respective areas within the watershed.

The current version of the tool is used by the ACPF to locate the most vulnerable fields across the watershed for conservation planning scenarios to prioritize interventions in fields and specific areas with the highest erosion rates. The applicability of the tool will be shown for the state of Iowa (approximately 145,746 square kilometers). Preliminary results corroborate spatial variability of soil erosion within watersheds and Major Land Resource Areas (MLRA). The presentation will also provide new insights into the main factors governing soil erosion in Iowa (climate, soils, topography, land use and management).

 

References

Gelder, B., Sklenar, T., James, D., Herzmann, D., Cruse, R., Gesch, K., & Laflen, J. (2018). The Daily Erosion Project – daily estimates of water runoff, soil detachment, and erosion. Earth Surface Processes and Landforms, 43(5), 1105–1117. https://doi.org/10.1002/esp.4286

Daily Erosion Project. (n.d.). Retrieved January 9, 2024, from https://www.dailyerosion.org/

Tomer, M. D., Porter, S. A., James, D. E., Boomer, K. M. B., Kostel, J. A., & McLellan, E. (2013). Combining precision conservation technologies into a flexible framework to facilitate agricultural watershed planning. Journal of Soil and Water Conservation, 68(5). https://doi.org/10.2489/jswc.68.5.113

Agricultural Conservation Planning Framework. (n.d.). Retrieved January 9, 2024, from https://acpf4watersheds.org/

How to cite: Luquin, E., Gelder, B., Herzmann, D., Zimmerman, E., James, D., Karnish, K., and Cruse, R.: A GIS-modeling strategy to locate vulnerable agricultural fields and prioritize conservation efforts across the Midwest United states., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13949, https://doi.org/10.5194/egusphere-egu24-13949, 2024.

EGU24-14123 | Posters on site | SSS2.1

Improved interrill erosion prediction by considering the impact of the near-surface  

Bin Wang, Yujie Wang, and Chenfeng Wang

The mechanism of the interrill erosion process is still unclear under complex conditions. Spatio-temporal variations of the near-surface hydraulic gradient are a common occurrence; however, few attempts have been made to characterize the near-surface hydraulic gradient for erosion prediction. Therefore, the objective of this study is to determine the influence of exogenic erosional forces (rainfall, overland flow, and seepage) on interrill erosion processes by considering the impact of the near-surface hydraulic gradient. Five near-surface hydraulic gradients (70% of field capacity, field capacity, saturated, artesian seepage at 20 cm and 40 cm of the hydrostatic pressure head) were applied in clay loam soil at two representative slope gradients of 8.75% and 17.63% under three rainfall intensities of 30, 60, and 90 mm h-1. The results showed that the near-surface hydraulic gradient was the dominant factor in the interrill erosion process in addition to rainfall intensity (I), runoff (Q), and slope gradient (S). There was a significant improvement in the prediction accuracy of the interrill erosion rate when the factor of near-surface hydraulic gradient was introduced into the interrill erosion prediction equation based on the Water Erosion Prediction Project (WEPP) concept. The R2 and NSE values were 22.36% to 210.00% higher than those of existing empirical equations (main parameters: I, I&S, I&Q, I&S&Q). The correlation matrix results indicated that the flow velocity was a key hydraulic parameter for predicting the interrill erosion rate. The interrill erosion rate was predicted well by a simple power function of the flow velocity, although this relationship lacks clear physical meaning. We also found that the interrill erosion rate increased as a power function with the runoff depth, rainfall intensity, hydrostatic pressure head and slope gradient. Considering the integrated effect of the exogenic erosional dynamics on the interrill erosion, a power function that included the physical description of the hydrodynamic parameters, rainfall intensity and hydrostatic pressure head was used to predict the interrill erosion rate. The results of this research provide new insights into developing process-based and mechanistic models for interrill erosion processes.

How to cite: Wang, B., Wang, Y., and Wang, C.: Improved interrill erosion prediction by considering the impact of the near-surface , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14123, https://doi.org/10.5194/egusphere-egu24-14123, 2024.

EGU24-14241 | Posters on site | SSS2.1

Impact of near-surface hydraulic gradient on the interrillerosion process 

Yujie Wang, Bin Wang, Chenfeng Wang, and Yunqi Wang

The impact of near-surface hydraulic gradients on interrill erosion is still obscure. The objective of this study is to distinguish the dominant interrill erosion process in areas impacted by near-surface hydraulic gradients. A series of rainfall simulations were conducted on a clay loam soil subjected to near-surface hydraulic gradients that shifted from drainage/saturation conditions to seepage conditions under three rainfall intensities (30, 60 and 90 mm hr−1) and two slope gradients (5 and 10). The results showed significant differences in soil loss between all the treatments. The sediment concentrations for seepage conditions were 0.57 to 7.02 times greater than those for drainage conditions. The correlation analysis indicated that the near-surface hydraulic gradient was a governing factor affecting interrill erosion. The critical flow rate was larger than 90 mm hr−1, suggesting that thin sheet flow does not have sufficient power to detach soil particles without raindrop impact. Furthermore, the detachment rates by raindrop impact were 1.12 to 4.60 times greater for seepage conditions than for drainage conditions. As the near-surface hydraulic gradient shifted from drainage conditions to seepage conditions, it transitioned from transport-limited to detachment-limited, and the contribution of interrill erosion to overall erosion increased from 20.19 to 75.30%. The critical point of dominant interrill erosion process transition existed between saturation (SA) and artesian seepage in 20 cm of hydrostatic pressure head (SP20). The results emphasize the importance of the near-surface hydraulic gradients’ impact on the interrill erosion process. Further investigations need to be verified in different soil types, steeper slopes and natural storms.

How to cite: Wang, Y., Wang, B., Wang, C., and Wang, Y.: Impact of near-surface hydraulic gradient on the interrillerosion process, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14241, https://doi.org/10.5194/egusphere-egu24-14241, 2024.

EGU24-15313 | ECS | Orals | SSS2.1

Parent material modulated effects of soil degradation on fertility and organic carbon of tropical cropland soils in Eastern Africa 

Laura Summerauer, Fernando Bamba, Bendicto Akoraebirungi, Ahurra Wobusobozi, Travis W. Drake, Clovis Kabaseke, Daniel Muhindo, Landry Cizungu Ntaboba, Leonardo Ramirez-Lopez, Johan Six, Daniel Wasner, and Sebastian Doetterl

Deforestation for cropland expansion in the sloping landscapes along the East African Rift system causes severe soil erosion and thus the loss of fertile, organic rich topsoil. However, the varying effect of land degradation in the region on soils developed from different parent material - which may influence soil fertility and carbon stabilization - are still largely unknown. To examine these factors, we compared soil organic carbon (SOC) and soil fertility indicators in undisturbed forest topsoils with cropland hillslope topsoils along a chronosequence after deforestation (2–7, 10–20, 20–40, > 60 years of cropping, land abandonment) on mafic (South Kivu, Democratic Republic of Congo) and felsic parent material (western Uganda). From previous studies, we expected higher soil fertility and SOC contents and therefore slower degradation on mafic soils due to the higher amounts of clay and pedogenic metal phases which stabilize SOM and thus further maintain soil fertility.
However, we found similar SOC contents on both parent materials and a consistent decrease with time after deforestation. SOC values were significantly lower in soils that were cleared more than 60 years ago, compared to cropland which was cleared 2–7 years ago and nearby undisturbed forest topsoils (0–10 cm soil depth). While the effective cation exchange capacity (ECEC) positively correlated with SOC in soils on felsic parent material, this was not observed in soils with mafic parent material, where it correlated with mineralogical proxies (total reserves in bases). In both regions, SOC did not correlate with clay content. Mid-Holocene carbonate volcanism appears to have offset soil degradation in the felsic region, contributing to higher pH and ECEC and impeding land abandonment due to the maintenance of acceptable soil fertility levels. Surprisingly, abandoned cropland sites in the mafic region still had an average SOC content of 14–29 g kg-1 in topsoils, likely due to strong fixation of SOC with reactive metal phases; however, they were characterized by extremely low pH values and high Al3+ mobility, combined with low available nutrient status.
Our results emphasize that soil fertility and carbon stabilization are reliant on the mineral composition of the underlying parent material, even in deeply weathered soils of the humid tropics. Soil organic matter in degraded tropical cropland soils does not appear to be a reliable indicator of soil fertility.

How to cite: Summerauer, L., Bamba, F., Akoraebirungi, B., Wobusobozi, A., Drake, T. W., Kabaseke, C., Muhindo, D., Cizungu Ntaboba, L., Ramirez-Lopez, L., Six, J., Wasner, D., and Doetterl, S.: Parent material modulated effects of soil degradation on fertility and organic carbon of tropical cropland soils in Eastern Africa, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15313, https://doi.org/10.5194/egusphere-egu24-15313, 2024.

Olive tree plantations, an ancient and traditional crop in the Mediterranean region, have become erosion-prone due to their soil management and location. Many olive groves are often planted on slopes, where soil management often keeps the soil bare by conventional tillage and/or herbicide use. Further, the natural conditions of the region as long drought periods followed by intensive rainfall episodes, intensify the susceptibility to erosion. As a result of these factors, soil erosion has become a major threat to the sustainability of olive cultivation in southern Spain.

On-site soil erosion measurements through conventional methods usually do not exceed one decade and present several discrepancies among them and with modelling outcomes. Here, we aim to use fallout radionuclide (FRN) inventories (137Cs, 239+240Pu) together with 3D reconstruction of surface levels to estimate soil erosion rates at appropriate temporal and spatial scales for the last 55-60 years and/or from the beginning of tree plantation. Twelve soil cores up to 40 cm depth were taken across olive groves and in identified reference sites, and the model MODERN (Modelling Deposition and Erosion rates with RadioNuclides) (Arata et al., 2016) was used to estimate soil erosion rates from 1960. For the geomorphological reconstruction, manual measurements were taken to recreate the historical soil surface using the germination point in the olive trees as a reference point to the current soil surface. Both methods allowed us to estimate and understand past erosion processes and possible long-term trends.

The radiochemical analysis content of 137Cs, 239+240Pu inventories and its correlation with a geomorphological reconstruction on selected olive tree fields under different soil management in southern Spain will be presented.

 

Arata, L., Meusburger, K., Frenkel, E., A’Campo-Neuen, A., Iurian, A.-R., Ketterer, M. E., Mabit, L., & Alewell, C. (2016). Modelling Deposition and Erosion rates with RadioNuclides (MODERN) – Part 1: A new conversion model to derive soil redistribution rates from inventories of fallout radionuclides. Journal of Environmental Radioactivity, 162–163, 45–55. https://doi.org/10.1016/j.jenvrad.2016.05.008

How to cite: Moreno Romero, G., Alewell, C., and Borrelli, P.: Land degradation due to soil erosion in the Mediterranean olive groves: A comparison of 137Cs, 239+240Pu radionuclides and 3D reconstruction of surface levels, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16310, https://doi.org/10.5194/egusphere-egu24-16310, 2024.

EGU24-16461 | ECS | Orals | SSS2.1

Improving our understanding of sediment and dissolved solids export in Mediterranean croplands: comparative analysis of the response of watersheds with contrasting characteristics 

Mikel Percaz, Iñigo Barberena, Miguel A Campo-Bescós, Rafael Giménez, and Javier Casalí

Adequately assessing the export of sediments and dissolved solids at the outlet of representative watersheds provides extremely interesting information on the behavior of these watersheds, with important environmental and management implications. To this end, the Government of Navarre (Spain) began to implement in 1995 a network of five watersheds representative of different agricultural and forestry conditions in Navarre. La Tejería and Latxaga watersheds, occupy about 200 ha each in a humid sub-Mediterranean climate and are almost completely cultivated with winter grain. Oskotz Principal watershed comprises 1,688 ha under sub-Atlantic climate, most of it covered with forest (61%) whereas the remaining area is covered by pastures and arable land. Within the Oskotz watershed, a 434 ha sub-watershed almost fully covered with forest namely Oskotz Forested, is also monitored. Landazuria watershed covers an area of 480 ha being its climate dry Mediterranean. Over 88% of the watershed area is cultivated, with about 60% of the total cultivated area under pressurized irrigation systems. The rest of the cultivated surface is rainfed agriculture. Average anual suspended sediment concentration are 182 mg/L for La Tejería, and 38, 12, 12, and 30 (median) for Latxaga, Oskotz Principal, Oskotz Forested and Landazuria, respectively. Average anual exported sediment are 4.3 ± 3.7, 1.4 ± 1.7, 1.2 ± 0.9, 0.7 ± 0.6 and 0.3 ± 0.5 Mg/ha for the same watersheds. The average annual export of dissolved solids for the same watersheds is 1.1, 1.1, 2.2, 1.9 and 2.2 Mg/ha.

As for 2010, the 5,500 ha Cemborain river basin (583 mm of precipitation at its outlet) has been incorporated into the monitoring, with the intention of understanding the behavior of a much larger and more complex basin. The dominant land uses are forestry and scrubland (70% of the basin), while cultivated soils cover about 25% of the surface area. The data corresponding to this basin, still very preliminary, are presented for the first time and contextualized in this work. The mean suspended sediment concentrations in Cemboráin are 120 mg/l, with a great temporal variability, increased by suspiciously high values in summer, possibly due to the presence in the samples of various residues instead of sediments. The average sediment export at the outlet of the basin is 3 kg/ha/day in the winter months (January to March), which is 5.0 and 2.8 times lower than those found in La Tejería and Latxaga watersheds (the most similar in terms of climate and soils) for the same period. The average export of dissolved solids was 2.2 kg/ha/day, a figure 3.7 and 4.6 times lower than those found in La Tejería and Latxaga watersheds, respectively. Practically all exports in Cemborain have occurred between December and March. The low sediment export figures are consistent with what is to be expected given that the soil is much more protected than in the cereal basins.

How to cite: Percaz, M., Barberena, I., Campo-Bescós, M. A., Giménez, R., and Casalí, J.: Improving our understanding of sediment and dissolved solids export in Mediterranean croplands: comparative analysis of the response of watersheds with contrasting characteristics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16461, https://doi.org/10.5194/egusphere-egu24-16461, 2024.

EGU24-17090 | ECS | Posters on site | SSS2.1

Hillslope-channel coupling and geomorphic processes in a sub-humid badlands landscape: Evidence from 10 years of high-spatial resolution topography and hydrologic record 

Manel Llena, Jesús Revuelto, Álvaro Gómez-Gutiérrez, J. Ignacio López-Moreno, M. Paz Errea, Esteban Alonso-González, and Estela Nadal-Romero

Badlands landscapes are usually subjected to high erosion rates and soil degradation, representing the main source of fine sediments in some catchments, especially in Mediterranean regions. High erosion rates imply high sediment transfer downstream, with associated environmental and management implications. Coupling between hillslope and channel processes has been proved as a critical factor in the evolution of badlands landscapes. This work examines the hillslope-channel coupling and geomorphic processes in a sub-humid badlands landscape using a 10-year dataset of high-resolution topography in relation with hydro-meteorological drivers. Study catchment (0.45 km2) is located in the Central Southern Pyrenees. Topographic datasets were obtained through multi-temporal surveys (i.e., seasonally and annually) carried out by means of Terrestrial Laser Scanner (TLS) and Structure from Motion (SfM) photogrammetry. Hydrologic records were obtained from a gauging station located at the catchment outlet while rainfall was recorded in three tipping-bucket distributed along the study area. The study analyses the relationships between the hillslope erosion and the main-channel incision processes, and how they interact to shape the badlands landscape over time in relation with the hydro-meteorological registers. The study also highlights the importance of high-resolution topography in understanding erosion and the complex interactions between hillslope and channel processes, and the need for continued monitoring to better understand the long-term geomorphic and hydrological processes in these areas.


This work is supported by the MOUNTWATER (TED2021-131982B-I00) research project funded by the MICINN-Plan de Recuperación, Transformación y Resiliencia and the EU-NextGenerationEU.

How to cite: Llena, M., Revuelto, J., Gómez-Gutiérrez, Á., López-Moreno, J. I., Errea, M. P., Alonso-González, E., and Nadal-Romero, E.: Hillslope-channel coupling and geomorphic processes in a sub-humid badlands landscape: Evidence from 10 years of high-spatial resolution topography and hydrologic record, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17090, https://doi.org/10.5194/egusphere-egu24-17090, 2024.

EGU24-17115 | Orals | SSS2.1

Comparison of national and regional assessments of soil loss rate by water erosion: an application to the Tuscany region (Italy). 

Eduardo Medina-Roldán, Gabriele Buttafuoco, Lorenzo Gardin, Romina Lorenzetti, and Fabrizio Ungaro

Soil erosion, in its various forms, has been identified as one of the major soil threats worldwide because it is one of the most significant forms of land degradation (soil truncation, loss of fertility, slope instability, etc.) and loss of soil- based ecosystem services; causing irreversible effects on the poorly renewable soil resource. The Revised Universal Soil Loss Equation (RUSLE) is one of the most widespread adopted empirical model approaches for assessing long-term average soil loss rate by water erosion. The assessed soil loss rate is an indicator that describes (or measures) the state of the soil erosion in a specific area (field, catchment, region, country) which we are interested in. The quality of this indicator relies on the scale which it represents and its required data. Many European countries, such as Italy, do not have harmonised national soil erosion databases at the different scales required by decision makers (regional, provincial, local) and national scale assessments have been carried out using EU data (JRC 2015, LUCAS 2018). However, national scale assessments are not often coherent with the more detailed information available at regional scale for some Italian regions in which RUSLE based potential soil erosion maps have been produced. Although it would be predictable, it is of particular interest to assess how reliable a national scale assessment can be in providing information on the state of soil erosion at a regional scale. A regional soil database is available for the Tuscany region (IT) and it is suitable for soil erosion assessment at regional scale. In this context, within the framework of the EJP SOIL project SERENA, the study was aimed at comparing three RUSLE applications carried out i) at regional scale by means of the available regional soil/climate/digital terrain model data; ii) at national scale by means of the same datasets upscaled at country level; iii) at national scale based on datasets actually available for all the Italian territory.

This scale effect is likely due to 2 components. First, the spatial density and quality of the observations needed to estimate the RUSLE factors. To this regard, soil and climate data quality and availability are usually higher for small territories than for the whole national territory. Secondly, the reference scale adopted for the aggregation and spatialization of the data, which is particularly important for the LS factor. These two reasons lead to a lower reliability of the RUSLE applications at national scale as compared to a regional one. The assessment at the regional scale of the soil loss rate using the Tuscany Region dataset was used as reference to evaluate the results obtained with the other two datasets at the same regional scale. Such comparisons were made using both the differences among the erosion maps, and through statistical indices that measure the deviations between the reference map and the other spatial products.

How to cite: Medina-Roldán, E., Buttafuoco, G., Gardin, L., Lorenzetti, R., and Ungaro, F.: Comparison of national and regional assessments of soil loss rate by water erosion: an application to the Tuscany region (Italy)., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17115, https://doi.org/10.5194/egusphere-egu24-17115, 2024.

EGU24-18768 | ECS | Posters on site | SSS2.1

Bridging the Gap: A Multilevel Approach to Soil Health Assessment across Various Land Uses 

Niklas Schmücker, Peter Lehmann, Patrick Duddek, Norbert Kirchgessner, Andrea Carminati, and Madlene Nussbaum

To address the challenge of soil degradation among different land uses, development of precise indicators that accurately reflect the current state of soil health is crucial. Soil structural attributes, such as the volume of percolating pores and the connectivity of the pore network are inextricably linked to processes such as nutrient dynamics, carbon cycling, root penetration, biological activity, and rainfall partitioning. Hence, they play a significant role in determining the soil susceptibility to erosion and offer great potential as soil health indicators. These attributes are directly reflected in the hydraulic properties of the soil, particularly in its capacity for water infiltration and retention. Notably, high rates of infiltration and drainage are associated with the presence of well-connected macropores. However, these structural attributes typically have to be quantified using costly and time-consuming imaging methods, while obtaining accurate estimates in lab and field experiments has proven challenging. Our multilevel approach is designed to link directly measured structural attributes (macropore volume and connectivity) to standard field or lab measurements.

More specifically, macropore volume and connectivity were quantified using X-ray imaging across diverse land use types, including arable land, grassland, and forest. Structural characteristics were then correlated with key hydraulic properties, such as water retention and both saturated and unsaturated hydraulic conductivity, measured using the Hyprop system. We further compared the imaged and measured hydraulic properties with predictions from the European soil texture-based pedotransfer function EUPTF, to contrast texture- and structure-related soil hydraulic properties. As an additional exploratory angle, we related mid-infrared (MIR) spectral reflectance to our previously obtained hydraulic property data, to evaluate if MIR could serve as a less laborious alternative to traditional lab-based analyses. Finally, to develop applicable user-friendly and sensitive indicators, we correlated our findings with the classifications from in-situ Visual Evaluation of Soil Structure (VESS) and infiltration experiments.

Preliminary results of X-ray CT data and Hyprop measurements revealed significant differences in the volumetric fraction and drainage capacity of macropores as well as in the saturated hydraulic conductivity between arable land, grassland, and forest. Forest soil showed the largest drainage capacity of macropores, but also the largest variability between samples. Despite exhibiting similar pore size distributions, arable land samples showed, as a result of tillage, larger pore connectivity than grassland. Larger connectivity did, interestingly, not result in larger hydraulic conductivity of macropores. 

Our novel multilevel approach reveals clear distinction of land use regarding the complex interplay between soil structural continuity, soil texture, and hydraulic behavior. Such knowledge is crucial in formulating sensitive, quantifiable, and scalable indicators for soil health evaluation and management. These indicators are instrumental for creating more accurate models, for designing sensitive monitoring networks and ultimately advancing sustainable practices in agriculture, forestry, and environmental conservation.

How to cite: Schmücker, N., Lehmann, P., Duddek, P., Kirchgessner, N., Carminati, A., and Nussbaum, M.: Bridging the Gap: A Multilevel Approach to Soil Health Assessment across Various Land Uses, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18768, https://doi.org/10.5194/egusphere-egu24-18768, 2024.

The Government of Navarre (Spain) began to implement in 1995 a network of five watersheds representative of different agricultural and forestry conditions in Navarre. In this paper we focus on 4 of them. La Tejería and Latxaga watersheds occupy about 200 ha in a humid sub-Mediterranean climate and are almost completely cultivated with winter grain. Oskotz Principal watershed comprises 1,688 ha under sub-Atlantic climate, most of it covered with forest (61%) whereas the remaining area is covered by pastures and arable land. Within the Oskotz watershed, a 434 ha sub-watershed almost fully covered with forest namely Oskotz Forested, is also monitored.

Ten-minute data on flow (Q), water turbidity (T) and the most important meteorological variables are recorded in all the watersheds. Samples are collected daily to determine the concentration of suspended sediments (SSC) and various dissolved substances.  In addition, and since 2006, during particularly heavy rainfall-runoff events, another parallel sampling is activated to determine the sedimentogram in much greater detail. The number of samples taken depends on the Q and T variations detected.

For this study, events have been selected that meet the following requirements: i) there is a clear raising flow phase and a clear decreasing flow phase; ii) at least six samples have been collected and processed throughout the event for SSC determination; iii) the linear regression between Q and T yields a value of r2> 0.75. From this regression equation it is possible to obtain a very detailed sedimentogram (tenminute basis).

A total of 30 events meet the requirements, 7 in La Tejería, 9 in Latxaga, 5 in Oskotz Forestal and 9 in Oskotz Principal.  Hysteresis is observed in all of them. In the cereal watersheds, 75% of the hysteresis curves are of hourly character, that is, with the peak of the sedimentogram located in the rising part of the hydrograph. In these watersheds, the remaining 25% correspond to curves with a complex structure linked to the occurrence of several flow peaks in the same event, which will require further study. In the Oskotz Forestal watershed 3 of the curves are clockwise and two are "eight" shaped, while in Oskotz Forestal 8 of the nine curves are clockwise and one is "eight" shaped.

These preliminary results suggest that in the cereal watersheds the main sediment sources are in the proximity to the watershed outlet, probably in the same channels. In the Oskotz watersheds, the main sources are also mostly located in the vicinity of the outlet, although occasionally other sources far from the outlet are also activated, mainly in the forest watershed.

 

How to cite: Casali, J., Otazu, M., Barberena, I., Campo-Bescós, M. A., and Giménez, R.: Analysis of high-resolution flow vs. suspended sediment concentration curves to determine sediment sources in agricultural and forestry watersheds with contrasting characteristics , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18835, https://doi.org/10.5194/egusphere-egu24-18835, 2024.

EGU24-19354 | ECS | Orals | SSS2.1

Soil loss due to sugar beet harvesting is an underestimated but significant soil erosion process in mechanized agricultural systems. 

Philipp Saggau, Fritjof Busch, Joachim Brunotte, Rainer Duttmann, and Michael Kuhwald

Soil loss due to crop harvesting (SLCH) is a globally occurring, but underestimated process that contributes to soil degradation, adversely affecting soil functionality and fertility. In northern Europe, sugar beets play a crucial role for SLCH due to their high production rates, yet there is a lack of research in commercial mechanized farming of sugar beets. The aim of this study is to measure SLCH for sugar beets using typical commercial harvesters and identify relationships to crop and soil variables. Therefore, sugar beets and soil samples were collected for 14 sampling sites between 2018 and 2020 in Northern Germany.

The results show that SLCH is in average 0.064 kg per kg sugar beet (SLCHspec), which corresponds to a loss of 5.7 Mg ha-1 harvest-1 (SLCHcrop). These numbers are higher than former comparable studies and 83.9 % higher than SLCH estimates by sugar beet factories. In addition, we found that i) SLCH considerably varies among years, fields, but also within fields, ii) the most influential drivers for SLCH are soil water content and clay content, iii) soil properties impact SLCH differently in dependence to soil water content, iv) SLCH of sugar beets can lead to significant nutrient and soil organic carbon losses. Thus, the results underline that SLCH is an important and underestimated determinant of soil erosion processes, which urgently needs to be considered in models and estimates additionally to concurrent processes like water, wind and tillage erosion. This is important for the adaptation of soil conservation measures in order to reduce ongoing soil degradation, especially in highly mechanized agriculture.

How to cite: Saggau, P., Busch, F., Brunotte, J., Duttmann, R., and Kuhwald, M.: Soil loss due to sugar beet harvesting is an underestimated but significant soil erosion process in mechanized agricultural systems., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19354, https://doi.org/10.5194/egusphere-egu24-19354, 2024.

EGU24-20092 | ECS | Posters on site | SSS2.1

A novel soil erosion apparatus for high-velocity surface erosion and fissure-containing soil-structure interfaces 

Chenghao Chen, Wenbin Huang, and Shengshui Chen

Soil erosion is a natural geomorphological process, consisting of soil particle transport in the presence of water runoff. Despite its inherency, intensive human activity as well as acute climate change has led to an acceleration of soil erosion, and this becomes a major threat to environment and sustainability. In recent years, a rapid increase of rainfall frequency at the global scale enhances the production of surface runoff, thus yielding an active surface flow with higher velocity. Wetting-dry cycle induced by climate shifts also contributes to a vast distribution of fissure-containing surfaces, especially on soil-structure interfaces. Erosion triggered in this position can be detrimental, as the structure may lose its resilience against flood and earthquake, or even fails to maintain its gravitational stability. We herein introduce a novel laboratory-scale apparatus designed to investigate the surface erosion under high flow velocity, as well as the erosion of soil-structure interfaces featuring fissures. Our apparatus comprises three modules: a water circulation system, a testing chamber, and a set of data acquisition module. The testing chamber accommodates specimens measuring up to 24×80×80 mm with adjustable fissure widths. Monitoring module of particle removal and transport is emphasized in our study. With the reliable performance regarding repeatability tests using clayey soil, we found that the size of fissure significantly impacts the soil loss process, while its effect on the overall degree of erosion is minor. At different flow velocity intervals, similar successive steps, which involve alteration of single particle detachment and particle aggregate removal were witnessed at the soil surface. This was further validated by images captured by high speed camera and particle removal collection results. We believe that despite the simple framework of test apparatus, it is of great potential to further explore the surface erosion mechanism and the fissure development between soil-structure interfaces.

How to cite: Chen, C., Huang, W., and Chen, S.: A novel soil erosion apparatus for high-velocity surface erosion and fissure-containing soil-structure interfaces, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20092, https://doi.org/10.5194/egusphere-egu24-20092, 2024.

EGU24-20133 | ECS | Posters on site | SSS2.1

Study on the Regulatory Role of Vegetative Measures in the Development of Gravity Erosion 

Yunqi Wang, Bin Wang, and Yujie Wang

In natural environments, the occurrence of gravity erosion on slopes with vegetation is influenced by various external driving factors. Some are primarily controlled by the water field, such as rainfall infiltration, water level fluctuations, and freeze-thaw cycles, affecting the effective stress of the soil. Others are influenced by external loads transmitted to the soil through plants, affecting the original stress balance conditions, such as self-weight or wind force control. Additionally, extreme physical processes, such as wildfires and subsurface erosion, can degrade the soil strength and reduce the anti-sliding force. The investigations and experiments were conducted in the Chongqing section of the Three Gorges Reservoir Area in China. The triggering mechanisms and development patterns of gravity erosion on vegetated slopes under the influence of multiple factors were summarized from both field surveys and numerical models. Using remote sensing interpretation and numerical simulation, we estimated the potential volume of gravity erosion in the Chongqing section of the Three Gorges Reservoir Area in China. The research results indicate that the triggering factors for gravity erosion induced by rainfall and water level fluctuations are related to the soil entering the saturation process through the structural interface of the upper soil layer. This process leads to a reduction in matrix suction or the occurrence of positive pore water pressure. The essence of this phenomenon is the decrease in effective stress. The long-term instability of the surface soil layer in fire-affected areas is primarily due to the combined effects of root strength degradation and recovery, resulting in the deterioration of the overall shear strength of the soil. Wind disasters causing gravity erosion are attributed to local stress concentration and significant deformation induced by external loads, leading to traction and compression. Building upon the study of gravity erosion triggering mechanisms, the developmental process of gravity erosion was authentically reconstructed using aerial DEM and three-dimensional numerical models. The gravity erosion volume was estimated with a simulation accuracy of up to 92%. Additionally, the estimation of gravity erosion volume was extended to a regional scale, obtaining the potential gravity erosion volume in the Chongqing section of the Three Gorges Reservoir Area, with an estimated accuracy ranging from 35% to 60%. A protective solution utilizing vegetation measures is proposed to address gravity erosion induced by various external factors. For layered forested shallow slopes, consider permeable drainage through structural interfaces to address prolonged rainfall. For steep slopes with high wind exposure, consider the canopy-root plate type of afforestation species. In areas affected by fire disturbance, replanting and maintenance should be considered before the prone period of landslides. For riverbank slopes experiencing fluctuations in water levels, consider planting regenerative live stakes in the upper-middle part between the alert water level and the normal water level. Activate landslide disaster warnings when water levels drop rapidly.

How to cite: Wang, Y., Wang, B., and Wang, Y.: Study on the Regulatory Role of Vegetative Measures in the Development of Gravity Erosion, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20133, https://doi.org/10.5194/egusphere-egu24-20133, 2024.

EGU24-21528 | Posters on site | SSS2.1

Mitigating muddy flooding in a changing climate. 

Neil Brannigan, Donal Mullan, Karel Vandaele, and Conor Graham

Soil erosion by water and muddy flooding significantly threaten agricultural productivity and broader environmental health. This issue is widespread in the European Loess Belt, especially in Flanders, Belgium. The off-site impacts of muddy flooding – notably on water quality, ecosystems, and infrastructure – are catastrophic. Encouragingly, existing mitigation strategies that combine curative measures and farming practices have effectively managed soil loss and sediment transport. However, climate change is expected to greatly exacerbate these impacts, likely rendering existing mitigation measures insufficient. Despite a well-recognised need for adaptation, there is a continued lack of research dedicated to designing effective mitigation strategies for arable catchments facing an increased frequency and magnitude of muddy flood events in future. Our study explores adapting these measures for improved resilience to climate change, with a focus on a heavily impacted catchment in Limburg, Belgium. A modelling approach was used to predict future muddy flooding scenarios from 2021 to 2100, employing a novel methodology to select and downscale appropriate climate models for site-specific, daily resolution future climate scenarios. Soil erosion projections were generated using the WEPP model for four hillslopes under each climate scenario, while Erosion3D illustrated spatial erosion patterns across the catchment. Various likely land use choices and potential mitigation strategies under future climatic conditions were evaluated, with strategies shortlisted based on efficacy and farmer practicability. Our findings indicate a considerable increase in erosion magnitude and muddy flooding duration between 2041-2100 under current land management practices, with a marked increase in high-magnitude events. Conservation tillage emerged as the most effective strategy for 2021-2040, followed by no tillage for 2061-2080. Mixing summer crops with winter wheat is highly effective until 2080, but banning summer crops in vulnerable fields is necessary for 2081-2100. These findings underscore the need for better data – especially long-term muddy flood measurements – and enhanced public education on these issues, thereby offering insights applicable to other affected regions.

How to cite: Brannigan, N., Mullan, D., Vandaele, K., and Graham, C.: Mitigating muddy flooding in a changing climate., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21528, https://doi.org/10.5194/egusphere-egu24-21528, 2024.

Soil erosion, a global challenge with profound consequences, impacts soil nutrient depletion, land degradation, agricultural productivity, runoff, and geological hazards. Our study assesses soil erosion and land use changes in the Beas Valley, Kullu, Himachal Pradesh, situated in the Western Himalayas. Employing diverse datasets and a comprehensive methodology, we scrutinize the intricate interactions of climate, soil, topography, and land use to comprehend and mitigate soil erosion risks. Data sources include rainfall data from the Climate Research Unit at the University of East Anglia, soil data from the Food and Agriculture Organization, Digital Elevation Model (DEM) data from the Shuttle Radar Topography Mission, and Landsat satellite imagery. We utilize the Revised Universal Soil Loss Equation (RUSLE) for soil erosion assessment, which includes factors like erosivity (R-factor), erodibility (K-factor), slope and flow accumulation (LS-factor), vegetation cover (C-factor), and conservation practices (P-factor).To bolster the credibility of our findings, we complement our methodology with field observations and interviews. These on-ground assessments and stakeholder insights provide practical context and verification for our research. This interdisciplinary approach yields crucial insights into soil erosion and land use changes in the Beas Valley, enriching our understanding of soil erosion in this fragile Himalayan ecosystem. Our findings offer vital support for informed land management decisions and conservation efforts.

 

Keywords: Soil erosion assessment, Himalayan, RUSLE, GIS and Remote Sensing

How to cite: Maurya, S., Singh, V., Chand, K., and Mishra, P.: Assessment of the spatial distribution of soil erosion using the RUSLE model and field survey study - A case study of Beas Valley, Kullu, India, Western Himalaya , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-135, https://doi.org/10.5194/egusphere-egu24-135, 2024.

Soil erosion causes worldwide land degradation. Long term monitoring of soil erosion is costly and labor intensive. Multiple models using Cs-137 fallout from atomic bomb tests are developed to retrospectively estimate average soil erosion since 1954. However, those models have not been rigorously validated due to the lack of compatible long-term measured soil loss data and thus their usefulness has been seriously challenged. Using 70 years of rare soil loss data measured in two small watersheds of <0.78 ha during 1954 and 2015, the author found that all theoretical models overestimate mean net soil erosion rates by at least 400%, and further confirmed that a key assumption of the homogeneous Cs-137 transfer from rainwater to soil during fallout is invalid and a critical process of the enhanced Cs-137 loss and redistribution during transfer is overlooked. The enhanced Cs-137 uptake by suspended sediment during transfer was responsible for about 8 times more enriched Cs-137 loss in sediment, to which Cs-137 inventory and erosion estimation are extremely sensitive. A new mass balance model is developed to include the dynamic uptake of Cs-137 by suspended sediment in surface runoff and losses of Cs-137 in both runoff solution and uptake by plants. The new model reduced overestimation of soil erosion to about 30%.  The finding of the enhanced radionuclide loss with suspended sediment during transfer is also valid to other fallout radionuclides such as Pb-210 and Be-7, which have been widely used in soil erosion estimation. Taking into account the enhanced radionuclides loss by suspended sediment during fallout will substantially lower soil loss estimation by all fallout radionuclides. 

How to cite: Zhang, X. C. J.: Evaluating and improving cesium-137 technology for estimating soil redistribution using soil loss data measured during 1954-2015, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4180, https://doi.org/10.5194/egusphere-egu24-4180, 2024.

EGU24-10794 | ECS | PICO | SSS2.2

Correlating different evaluation methods for SWC as support for soil processes modelling  

Agnese Innocenti, Veronica Pazzi, and Riccardo Fanti

Soil erosion modelling has a large sensitivity to soil water content as it greatly affects soil erodibility. Knowing soil moisture and water content along a soil profile can help to understand the soil ability to absorb water before runoff occurs, then, to predict runoff and potential erosion.

This study presents a combined approach of direct and indirect methods to monitor soil moisture content on a slope, with the goal of using this data in the future for modelling water erosion processes in soils.

Generally, soil moisture data used for erosion models can be acquired through direct methods (e.g., gravimetric method, time or frequency domain reflectometry, moisture sensors) and/or indirect methods (meteorological data, remote sensing, electrical conductivity).

In this research project, an experiment was carried out with the aim of combining direct and indirect methods to maximize the information on the rate of change of soil moisture in a 9*9 m plot by exploring depths from 0 to 50 cm. We used the water content sensor, SoilVUE10 by Campbell, recently released on the market, and based on Time Domain Reflectometry (TDR) technology conjointly with the Electrical Resistivity Tomography (ERT). Moisture sensors are known to create a disturbance in the ground, while geophysical techniques such as ERT are indirect, non-destructive measurements. Furthermore, they have the great advantage of being able to investigate a significantly larger area than classic humidity sensors.

The conductivity varied in average between 0.02 and 0.08 S/m with a little more evident relationship between the values measured with the two methods in deeper layers than at soil surface (i.e., r=0.31 at -30cm).

Overall, further investigations will be conducted, the ERT system needs data acquisition integration, i.e., remote data acquisition so that much more data can be acquired (at least one data set per day). The moisture values acquired by the SoilVUE10 probe require further analysis and comparison, possibly with other TDR probes. Furthermore, it may be necessary to install a surface moisture sensor capable to improve data acquisition even for the first 10cm soil layer.

How to cite: Innocenti, A., Pazzi, V., and Fanti, R.: Correlating different evaluation methods for SWC as support for soil processes modelling , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10794, https://doi.org/10.5194/egusphere-egu24-10794, 2024.

EGU24-11138 | ECS | PICO | SSS2.2

Experimental simulation of soil erosion in the context of climate change in NW France. 

Gabriel Portzer, Jean-Louis Grimaud, Albert Marchiol, Olivier Stab, Jean-Alain Fleurisson, Samuel Abiven, Simon Chollet, Yara Maalouf, Nicole Khoueiry, and Neda Yadari

This study focuses on the evolution of soil erosion rates on artificial covers for low level radioactive waste in the context of climate change. The objective is to test the impacts on erosion of (i) increasing rainfall intensities during storms and (ii) decreasing soil moisture content before storms. The “Centre de stockage de la Manche” (CSM) in Normandy, France, where Low-Level Nuclear waste are stored and monitored for the next centuries, is used as a reference case. There, climatic models anticipate an increase of temperature and seasonality (i.e., dryer Summers and wetter conditions from Fall to Spring) in the next centuries.

First, the soils of the CSM are sampled to be characterized. The densities, moisture, grainsize distribution and organic content of the soil are measured. We find that these values are rather homogeneous at the scale of the CSM. Second, a series of experimental rainfall simulations is performed on the CSM soils, focusing of rates and distribution of erosion processes. We simulate rainfall events of decennial, centennial, millennial and decamillennial intensities on 18° slopes, corresponding to the steeper banks of the CSM. Using the capacities of the climatic chambers at the Ecotron Lab in Nemours, France, we further test several soil moistures, i.e., very wet, moderately wet and dry, before simulating rainfall events. Finally, each experiment is repeated several times to assess the “memory” effect of topography on erosion. We quantify erosion by measuring sediment concentrations in run-off water collected at the outlet of the model and using topographic acquisitions performed using photogrammetry.

The experimental results are compared with estimations based on the Revised Universal Soil Loss Equation. Some propositions for upscaling, which could be used for assessing hypothetical future increase in soil loss in the CSM, are discussed.

How to cite: Portzer, G., Grimaud, J.-L., Marchiol, A., Stab, O., Fleurisson, J.-A., Abiven, S., Chollet, S., Maalouf, Y., Khoueiry, N., and Yadari, N.: Experimental simulation of soil erosion in the context of climate change in NW France., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11138, https://doi.org/10.5194/egusphere-egu24-11138, 2024.

EGU24-11387 | PICO | SSS2.2

Methodology for Spatially Distributed Rainfall Erosivity Calculations at the Conterminous United States to Support Soil Erosion Studies 

Henrique Momm, Robert Wells, Thomas Seever, Racha ElKadiri, and Ron Bingner

Research and action agencies in the US work collaboratively to develop and use soil erosion technology to support the development of field-specific conservation plans. These tools and accompanying databases are applied in all counties throughout the country covering a wide range of natural and anthropogenic physical conditions. Climate, particularly precipitation, constitutes one of the key drivers directly related to soil detachment and transport. Observations spanning over 30 years have demonstrated that estimated long-term average annual soil loss in agricultural fields is the result of the cumulative effect of many small and moderate-sized storms along with the impact of occasional severe ones. In the Revised Universal Soil Loss Equation version 2 (RUSLE2) technology, the effect of rainfall is represented by the rainfall runoff erosivity index R. This index is designed to serve as an estimation of the potential storm energy specific to each location. In this study, we propose and evaluate a methodology to generate continuous surfaces of monthly R for the continental US from discrete 15-min precipitation data. Over 2000 stations covering more than 50 years of 15-min precipitation data were used. Storm identification algorithms were implemented and evaluated through comparison with existing tools. Outlier events were identified and removed using a 50-year recurrent interval calculated for each station. Using 30-years of recorded data, a custom universal kriging algorithm was employed to generate a smooth continuous surface as a raster grid. This step included a boxcox transformation of the station data, directional variogram fitting, and the removing of external trends using elevation, long-term annual precipitation totals, and distance to the coast. Predicted surfaces were compared with existing RUSLE2 surfaces for the same time period with great level of agreement. The proposed methodology is intended to be comprehensive and reproductible such that it can serve as a template for future updates of erosivity maps for the entire continent at a county-scale. This methodology provides the means for future systematic updates to the RUSLE2 climate database to account for climatic changes and to support continued national efforts in reducing soil erosion and conserving natural resources. 

How to cite: Momm, H., Wells, R., Seever, T., ElKadiri, R., and Bingner, R.: Methodology for Spatially Distributed Rainfall Erosivity Calculations at the Conterminous United States to Support Soil Erosion Studies, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11387, https://doi.org/10.5194/egusphere-egu24-11387, 2024.

EGU24-17727 | ECS | PICO | SSS2.2

QAnnAGNPS: a new plugin in QGIS to facilitate the use of AnnAGNPS 

Iñigo Barberena, Miguel A Campo-Bescós, and Javier Casalí

AnnAGNPS (ANNualized AGricultural NonPoint Source model) is a watershed-scale hydrologic model designed to analyze the impact of non-point pollutants in predominantly agricultural watersheds. It has capabilities that make it unique and indispensable on the world scene, such as an integrated simulation of all types of erosion and all major sources of non-point agricultural pollution. However, AnnAGNPS does not currently have a graphical user interface that allows the user to perform the simulation in a simple way. It is in this context that QAnnAGNPS has been created. QAnnAGNPS is a model developed in QGIS and written in Python 3 that fulfills two general functions. The first is to provide a simple to use graphical user interface to run AnnAGNPS. The second is to incorporate extra functionalities to the model, which are already included in similar hydrological models. The plugin has been used in the simulation of the Latxaga basin, a 207-hectare cereal basin located in Navarra (northern Spain). Its use has allowed to verify that QAnnAGNPS is able to perform the AnnAGNPS simulation and to visualize the results in a simpler way than the original one.

How to cite: Barberena, I., Campo-Bescós, M. A., and Casalí, J.: QAnnAGNPS: a new plugin in QGIS to facilitate the use of AnnAGNPS, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17727, https://doi.org/10.5194/egusphere-egu24-17727, 2024.

Water erosion is a current issue, especially in hilly and areas, where driving force such as surface runoff and subsurface flow can mobilize large amounts of sediment to rivers. In fact, how and at which timescale, seasonality precipitation is turned into runoff or streamflow (Q) it is difficult to be predicted without calibrating site-specific models. The potential soil erosion can be assessed through the study of the relationships between sediment sources and sinks in a watershed (i.e., sediment connectivity assessment) and associated suspended sediment (SS) transport in rivers. On the other hand, sediment connectivity, defined as structural (from a geomorphological point of view) and functional connectivity (considering forcing processes), can be evaluated by the using of specific indexes (e.g., Index of connectivity – IC).  SS transport processes are intermittent processes fluctuating over a large range of temporal and spatial scales, making it challenging to develop predictive models applicable across timescales and rivers. While temporal variability in sediment transport is explained by the concept of “effective timescale of connectivity”; the mechanism behind this variability remains unknown. Here we used a data-driven approach considering two years of monitoring Q and SS to develop and demonstrate a proof of concept for automating the classification of event-based sediment dynamics by using a machine learning approach.  For each storm event we i) calculate the sediment connectivity (extreme rainfall events also are considered) and ii) define the link between sediment transport and deposition by considering SS transport as a fractal system (i.e. fractal storage time distributions in streams). Fractals are here used to describe and predict patterns over different temporal scales of dynamics in SS   The statistic and dynamics of Q, SSCs and associated grain size distribution, at event based, were considered by assessing their probability distribution function, Fourier power spectra, and the machine-learning classification of hysteresis index. Indeed, by approaching SS transport dynamics as a fractal system, it is assumed that patterns of variation in SS transport exist over different timescales, while linkages across those temporal scales are expressed as fractal power-laws. The study site, located near Florence in the Chianti area, is a 1 Km2 agricultural watershed with different types of land cover and characterize by a first-order mixed bedrock and alluvial stream channels. The area was mapped at high resolution with a Drone LIDAR scanner and equipped with a submersible laser diffraction particle size analyser (LISST) for long-term measuring suspended particle size and its volume concentration. Preliminary results showed a robust correlation between sediment connectivity, land cover, and sediment connectivity. Q-SS information flows exhibit seasonally varying behaviour consistent with dominant runoff generation mechanisms (catchment connectivity in wet to dry season). However, the timing and the magnitude of runoff also reflect considerable catchment heterogeneity, likely attributable to differences in baseflow contributions from different lithologies, and variation in of preferential flow paths (land use/land cover).  In conclusion, this study allowed to analyse a small catchment area in term of sediment connectivity and related sediment transport to identify potential areas of (dis)connectivity in the basin.

How to cite: Barbadori, F., Pelacani, S., and Raspini, F.: Investigating water erosion dynamics through connectivity based on fractal approaches: A case study in the Chianti area (Florence, Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18276, https://doi.org/10.5194/egusphere-egu24-18276, 2024.

EGU24-19497 | ECS | PICO | SSS2.2

SoilPulse – Towards FAIR soil process data! 

Jonas Lenz, Jan Devátý, and Conrad Jackisch

Soil processes are known to stretch over many scales – some processes, like erosion, are of particular interest due to their quick and complex characteristics with high impact. The analysis of soil erosion processes is challenging through heterogeneous field situations, involved spatio-temporal scales and by a reconfiguration of the system itself. Various experimental procedures and analytical methods were developed, which can analyze erosion processes. But because the procedures are driven by specific model assumptions which in effect also relate to a plethora of central state variables and parameters, the data of different groups are rarely compatible. Interoperability is hindered further through inhomogeneous data structures and a lack of metadata.

Within the NFDI4Earth pilot SoilPulse (soilpulse.github.io) we are developing an interactive metadata generator which shall assist researchers to make their soil process related data sets reusable by humans and machines. Instead of forcing the user to adhere to a defined metadata standard, the tool semi-automatically and interactively builds a translation procedure i) to map various existing data structures to a common scheme and ii) to feedback valuable but missing information to be provided by the researcher. While treating a dataset the researcher is aided by visualizations of the data in relation to other datasets which are already made machine readable through SoilPulse, allowing to easily discover non-plausible data and errors within the dataset. Once treated the dataset can be queried along with other datasets through a common interface and can be linked to erosion models through an API.

 

The PICO presentation demonstrates the functionality of the SoilPulse metadata generator prototype and invites attendees to apply it themselves on their data sets. As SoilPulse is in active development we highly appreciate comments, hints and impulses to further improve the tool!

How to cite: Lenz, J., Devátý, J., and Jackisch, C.: SoilPulse – Towards FAIR soil process data!, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19497, https://doi.org/10.5194/egusphere-egu24-19497, 2024.

EGU24-20845 | PICO | SSS2.2

An integrated GIS tool for gully erosion modelling  

Michael Maerker, Samuel Pelacani, Adel Omran, and Aleksey Sidorchuk

Gully erosion seriously affects the landscape and human life in different ways by destroying agricultural land and infrastructures, altering the hydraulic potential of soils, or affecting the water quality and quantity. Due to climate change, the negative effects of gully erosion are likely to increase in future, threatening especially low-income agricultural regions. In the past decades, quantitative methods have been proposed to simulate and predict gully erosion at different scales. However, gully erosion is still underrepresented in modern GIS-based modelling and simulation approaches. Therefore, we developed a tool to assess gully erosion dynamics. This tool comprises the data preparation, modelling and output analysis of the modelling phase as well as the visualization of the results. The modelling procedure is based on Sidorchuk’s gully simulation model. The tool was developed using phyton and the QGIS environment.

 

How to cite: Maerker, M., Pelacani, S., Omran, A., and Sidorchuk, A.: An integrated GIS tool for gully erosion modelling , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20845, https://doi.org/10.5194/egusphere-egu24-20845, 2024.

EGU24-21549 | PICO | SSS2.2

Comparing radar-raingauge precipitation-merging-methods for soil erosion modelling support 

Sandro Moretti, Rossano Ciampalini, Andrea Antonini, Alessandro Mazza, Samantha Melani, Alberto Ortolani, Ascanio Rosi, and Samuele Segoni

Radar-based rainfalls are currently used for process monitoring from remote in a large panel of domaines including hydrology and soil erosion modelling. Nevertheless, such data may include systemic and natural perturbations that need to be corrected before using these data. To encompass this problem, adjustments based on raingauge observations are frequently adopted. Here, we analysed the performance of different radar-raingauge merging procedures using a regional raingauge-radar network (Tuscany, Italy) focusing on a selected number of rainfalls events.

The computational methods adopted were: 1) Kriging with External Drift (KED) interpolation (Wackernagel 1998), 2) Probability-Matching-Method (PMM, Rosenfeld et al., 1994), and 3) an Adjusted kriging mixed method exploiting the conditional merging (ADj) process (Sinclair-Pegram, 2005). The latter made available by DPCN (Italian National Civil Protection Department), while methods 1) and 2) were applied on recorded raingauge rainfalls over the regional territory at 15’ time-step, and CAPPI (Constant Altitude Plan Position Indicator) reflectivity data from the Italian radar network at 2000/3000/5000 m at 5’ and 10’.

The comparisons between the three rainfall fields were based on the analyses of variance, Cumulative Distribution Function (CDF), and explicative coefficients such as BIAS, RMSE (Root Mean Square Error), MAD (Median Absolute Deviation). In average, rainfalls showed a moderate variability between the methods. Comparing CDFs, slight differences were detected between KED and ADj with bias mostly pronounced in lower quantiles, while more marked differences are observed in higher quantiles for the ADj-PMM methods. The analyses presented different spatial patterns depending on the applied procedure, closer to the radar data when using ADj, and more reflecting the gauge’s data structure when adopting KED. The probabilistic method (PMM) had the advantage to account for gauge data while preserving the spatial radar patterns, thus confirming interesting perspectives. Globally, the KED method provided more accurate coverage in the calculation by better compensating for local topographical shadows in the data, while ADJ confirmed the more detailed product in terms of time resolution (e.g. 5minute res.).

How to cite: Moretti, S., Ciampalini, R., Antonini, A., Mazza, A., Melani, S., Ortolani, A., Rosi, A., and Segoni, S.: Comparing radar-raingauge precipitation-merging-methods for soil erosion modelling support, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21549, https://doi.org/10.5194/egusphere-egu24-21549, 2024.

EGU24-3323 | ECS | Posters on site | SSS2.3

Innovations in Hydrological Modeling: A Standalone Approach to GAML Equation Enhancement for Runoff and Sediment Yield Estimation Using WEPP model 

Vijayalakshmi Suliammal Ponnambalam and Nagesh Kumar Dasika

Accurate estimation of infiltration rates is crucial for hydrological modeling, impacting predictions of runoff, sediment transport, and related phenomena. Various infiltration models, categorized as empirical, semi-empirical, and physically based, have been developed to compute cumulative infiltration and infiltration rates for these purposes. Because of its simplicity and accuracy, the Green–Ampt (GA) infiltration equation has been widely used for simulating 1-D (vertical) infiltration into the soil. The modification of GA equation by Mein and Larson for steady rainfall conditions (GAML,1973., etc.,) is widely employed in different hydrological modeling software such as ANSWERS (Areal Nonpoint Source Watershed Environment Response Simulation), CREAMS (Chemicals, Runoff, and Erosion from Agricultural Management Systems), and WEPP (Water Erosion Prediction Project), suggests the versatility of the model approach. However, its assumption of a sharp wetting front and uniform soil moisture content tends to overestimate low-flow runoff events. The present study proposes a simple, standalone methodology to refine the GAML equation employed for infiltration calculations in the WEPP model. The advantage of the WEPP model is that it can simulate runoff and soil loss events on an hourly, daily, monthly, annual, and event scale; Spatial and temporal distribution of soil loss and deposition can be estimated, and hillslope to watershed scale studies can be performed. Refinement entails estimating hydraulic conductivity (K) and soil moisture (ϴ) distribution in vertical and horizontal (2D) soil matrices before and after ponding scenarios as a linear equation of infiltration. A new algorithm was developed based on the refined GAML (R-GAML) parameters to estimate revised ponding time and infiltration rates based on experimental results, enhancing the accuracy of runoff predictions. Laboratory experiments on sand, clay, and sandy clay soils are utilized to estimate the soil infiltration parameters. The WEPP model was then employed to simulate runoff for a small agricultural watershed with the outlet at T. Narasipura station (of Cauvery River, India). The R-GAML and conventional GAML equations were used for runoff simulation and validated with the observed runoff data. The overestimation of low-flow runoff events using the conventional GAML was substantially reduced by the newly developed method, and the performance of R-GAML versus GAML was evaluated using correlation coefficient (0.937, 0.905), RMSE (16.471, 35.905), and NSE (0.968, 0.915) performance matrices for the Indian context.  Furthermore, this research aims to extend i) runoff and sediment yield (SY) simulation using the R-GAML equation from the field scale to the river basin scale (upscaling), ii) study the impact of Land Use and Land Cover (LULC) change on runoff and SY production by multi-site and multi-temporal calibration approach using the WEPP model. The findings offer valuable insights for urban planners in designing drainage networks, for agricultural water management in scheduling reservoir water release, and for deriving Best Management Practices (BMPs) in the Cauvery basin, which faces transboundary challenges due to rising water demand.

How to cite: Suliammal Ponnambalam, V. and Dasika, N. K.: Innovations in Hydrological Modeling: A Standalone Approach to GAML Equation Enhancement for Runoff and Sediment Yield Estimation Using WEPP model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3323, https://doi.org/10.5194/egusphere-egu24-3323, 2024.

EGU24-6562 | ECS | Posters virtual | SSS2.3

Development of observation model for predicting the phenomena of Rill and Gully erosion using Machine learning 

Harsha Vardhan Kaparthi and Alfonso Vitti

I am a doctoral candidate in University of Trento (first year) in Earth Observation at the Department of Civil, Environmental and Mechanical Engineering. My administrative University is Sapienza University of Rome and I am writing to express my interest in presenting my research in developing the strategies to predict Rill and Gully erosion in EGU general assembly 2024.

Soil moisture plays a major role in assisting crop productivity and weather forecasting to satisfy the ever-growing demands for land resources.

Soil erosion mechanics involve fluid (water/wind) detachment or entrainment followed by transport of soil particles and subsequent deposition as soil sediment. Soil movement by water often starts when a raindrop impacts the soil surface and initiates splash erosion, i.e., raindrops break aggregates into finer soil particles, displacing those particles and aggregates to create depressions in the soil surface. It depends on rainfall intensity, soil erodibility, and field slope among other factors. 

Various factors affecting soil erosion, including soil slope and length or supporting control practices like contour rows, strip cropping, and terrace systems, were recognized as independent factors influencing soil erosion by their inclusion in regional soil-loss equations. Water Erosion Prediction Project has been used to predict soil loss in a range of environments such as rangeland and forest for simulating runoff and sediment yield from the untreated watershed with good accuracy using continuity equation :

(dG/dx)  =  Dr + Di 

G = sediment load (kg·s-1· m-1)

x = distance down slope (m)

D= rill erosion rate (+for detachment, - for deposition)

D= interrill sediment delivery (kg·s−1·m−2).

Water Erosion Prediction Project relates sediment load in the runoff to the distance downslope as a function of the interrill and rill erosion rates calculated on a daily time step. Interrill erosion is the process of sediment delivery to more concentrated flow in rills, but rill erosion depends on the potential detachment capacity as limited by the sediment transport capacity of runoff in the rill. Soil loss through interrill and rill erosion is associated with the factor known as Revised Universal Soil Loss Equation (RUSLE), formulated as :

A  = R∗K∗Ls∗C∗P

A is the annual soil loss due to erosion [t/ha year];

R the rainfall erosivity factor;

K the soil erodibility factor;

LS the topographic factor derived from slope length and slope gradient;

C the cover and management factor; and

P the erosion control practice factor.

The limitations of RUSLE are that it only accounts for soil loss through sheet and rill erosion and ignores the effects of gully erosion. 

The objective is to generate gully erosion susceptibility maps (GESMs) by applying three machine learning algorithms to identify the area of the basin with respect to total area, which prones to have higher or lower susceptiblity to gully erosion.

These erosions require Persistent Monitoring with the combination of three main elements. High resolution, Revisit rate and global coverage. The models can be developed using GIS or R software and from SAR technologies.

Considering my academic performance so far, I hope to have this opportunity to present in EGU assembly, as I am confident that I will be able to meet your expectations.

Thanking you.

How to cite: Kaparthi, H. V. and Vitti, A.: Development of observation model for predicting the phenomena of Rill and Gully erosion using Machine learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6562, https://doi.org/10.5194/egusphere-egu24-6562, 2024.

EGU24-6677 | Posters on site | SSS2.3

Enhanced Ephemeral Gully Erosion Science within AnnAGNPS  

Ronald Bingner, Robert Wells, Henrique Momm, and Martin Locke

Concentrated runoff increases erosion and moves fine sediment and associated agrichemicals from upland areas to stream channels. Ephemeral gully erosion on croplands in the U.S. may contribute more of the sediment delivered to the edge of the field then from sheet and rill erosion. Typically, conservation practices developed for sheet and rill erosion are also expected to treat ephemeral gully erosion, but science and technology are needed to account for the separate benefits and effects of practices on each of the various sediment sources.

Watershed modeling technology has been widely developed to aid in evaluating conservation practices implemented as part of a management plan, but typically lacks the capability to identify how a source, such as sheet and rill erosion, ephemeral gully erosion, or channel erosion, is specifically controlled by a practice or integrated practices. The U.S. Department of Agriculture’s Annualized Agricultural Non-Point Source pollutant loading model, AnnAGNPS, has been developed to determine the effects of conservation management plans on erosion and provide sediment tracking from all sources within the watershed, including sheet and rill, ephemeral gully, and channel erosion. 

This study describes the ephemeral gully erosion capabilities within the AnnAGNPS model and discusses research needs to further improve these components for integrated conservation management planning.  Conservation management planning by agencies within the U.S. and by international organizations requires a systematic approach when determining the extent of ephemeral gully erosion impacts on a field, watershed, or national basis, and/or to predict recurring or new locations of ephemeral gullies prior to their development.  This technology provides the capability to separate the impact of ephemeral gullies on erosion from other sources and then evaluate the impact of targeted practices to control erosion at the source and subsequent downstream resources.

How to cite: Bingner, R., Wells, R., Momm, H., and Locke, M.: Enhanced Ephemeral Gully Erosion Science within AnnAGNPS , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6677, https://doi.org/10.5194/egusphere-egu24-6677, 2024.

EGU24-7471 | ECS | Posters virtual | SSS2.3

Comparing different approaches to measure erosion by concentrated flow in a rainfed agroecosystem in SE Spain: Field inventory vs RPAS 

Efraín Carrillo-López, Adolfo Calvo Cases, Pedro Pérez Cutillas, and Carolina Boix-Fayos

Concentrated-flow erosion and sheet erosion are main drivers of soil loss in Mediterranean agroecosystems with soft lithologies. Morphologies of concentrated-flow erosion were assessed in a terraced rainfed almond crop (Prunus dulcis Mill.) located on Tertiary marls in SE Spain, using two methodologies: i) field inventory and ii) photogrammetry through images taken with RPAS (Remotely Piloted Aircraft System). Both methods were applied to compare their results within one year after three major rainfall events. For the application of the field inventory, each morphology was divided longitudinally, measuring their dimensions (width, length and depth) to estimate the volume of mobilized material following the shape of each division. RPAS images were processed to obtain digital elevation models (DEMs) and orthophotos, which were subsequently used to identify erosional morphologies and calculate the volume of mobilized material through variation in height and resolution of the DEMs. Sampling for soil’s bulk density was carried out to convert volume into mass. Differences between second and first inventory or flight (period 1), and between third and second ones (period 2) were calculated to estimate sediment yield rates.

Erosional morphologies, identified with both methodologies, were: i) rills, mainly along terraces; ii) gullies, mainly on the edges of terraces; and iii) mass movements, only on the edges of the terraces. Moreover, a fourth form not described in previous studies was identified, called mixed erosion: a joint action of laminar and concentrated flow under extreme rainfall conditions. This form appeared at the base of gullies and, occasionally, connecting gullies.

In period 1, gullies showed higher median sediment yield than rills, both with field inventory (1,3 ± 1,7 y 0,22 ± 0,11 t ha-1 y-1, respectively), and photogrammetry (1,37 ± 1,01 y 0,24 ± 0,2 t ha-1 y-1, respectively). While, in period 2, mixed forms and gullies were more erosive than rills and mass movements, both with field inventory (8,8 ± 0,9, 2,4 ± 1,9, 0,54 ± 0,48 and 1,1 ± 0,8 t ha-1 y-1, respectively), and photogrammetry (1,7 ± 1,1, 1,2 ± 0,9, 0,23 ± 0,18 and 0,15 ± 0,11 t ha-1 y-1, respectively).

69, 16 and 50 % of the rills, gullies and mass movements, respectively, identified through inventory method were also identified with RPAS images. In contrast, all of the mixed erosional morphologies identified in the field survey were vissible in the RPAS images. The proportion of rills and gullies identified simultaneously with both methods increased in successive samplings, likely due to the increased intensity of the successive rainfall events, resulting in more easily identifiable features. Finally, for those morphologies identified with both methods, the RPAS sediment yield estimations were 40 – 50 % higher than those made by inventory method, probably due to the difference in resolution between methods.

The mixed form of erosion and the gullies showed a high erosive potential, involving a great environmental threat on this kind of agroecosystems. At a relatively low cost, RPAS, through its greater resolution, can help to get more reliable values of concentrated erosion rates in rainfed agroecosystems than field inventories.

How to cite: Carrillo-López, E., Calvo Cases, A., Pérez Cutillas, P., and Boix-Fayos, C.: Comparing different approaches to measure erosion by concentrated flow in a rainfed agroecosystem in SE Spain: Field inventory vs RPAS, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7471, https://doi.org/10.5194/egusphere-egu24-7471, 2024.

EGU24-7648 | ECS | Posters on site | SSS2.3

Analysis of some gully control techniques for the conservation of olive cropped landscapes in Southern Spain 

Paula González Garrido, Adolfo Peña, Tom Vanwalleghem, and Juan Vicente Giráldez

The current evolution of climate in Southern Europe, apparently enhances the frequency and persistence of rainless spells, with interspersed short and intense rainfall events. Both circumstances exacerbate the soil erosion episodes, particularly in the olive cropped landscapes, with the consequent risk of soil productivity loss and the dispersion of pollutants. The most common erosion form, gully erosion, act as preferential ways for the removal and dispersal of runoff and sediments.

Although the near-future climate scenarios are uncertain, new and more effective integrated management systems need to adopted to preserve both the food generation potential, and the environment.

The purpose of this work is to analyze some techniques for the assessment of the gully erosion, from the photo-interpretation of the sequence of historical photograms, including Machine Learning methods to avoid the subjectivity of the observer, to the acquisition of new multi-spectral images with UAV. The nest step is the selection of the optimal location of the prevention, such as cover crops and vegetative barriers, and control, like check-dams for the interception of runoff and sediments.

The final outcome of the proposed techniques is the use of the fill-and spill concept to enhance an intermittent connectivity in the gully networks with the additional advantage of the increased biodiversity in the landscapes.

How to cite: González Garrido, P., Peña, A., Vanwalleghem, T., and Giráldez, J. V.: Analysis of some gully control techniques for the conservation of olive cropped landscapes in Southern Spain, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7648, https://doi.org/10.5194/egusphere-egu24-7648, 2024.

EGU24-12354 | Posters on site | SSS2.3

Event Based Modeling of Ephemeral Gully Development in Agricultural Fields 

Dalmo Vieira, Robert Wells, Daniel Yoder, and Ronald Bingner

Ephemeral gullies (EGs) are channels that form in low parts of the field where runoff concentrates, and are often responsible for considerable soil loss from agriculture fields. Unfortunately, predicting the gradual development of gullies in response to storm events remains challenging. The United States Department of Agriculture has developed several modeling tools to predict the location and dimensions of ephemeral gullies and the resulting soil loss. The tool described herein combines precise geospatial determination of EG pathways with soil erosion and delivery calculations for both those pathways and the contributing hillslopes.

Considering the vital importance of determining runoff concentration for EG development, high-resolution (0.5 ~ 3 m) terrain elevation data are processed with specialized geospatial tools to determine topography-driven surface runoff patterns and define swales where concentrated flows occur.  This creates integrated surface drainage descriptions defining hillslope areas where sheet-and-rill erosion predominates, and swales where EG gullies may develop. This results in detailed flow maps covering entire fields, optionally considering oriented roughness created by crop rows on flow distribution.  These data, along with topography-derived parameters and spatial distributions of soil types and vegetation cover, form the digital landscape description for erosion modeling.

The magnitude, frequency, and seasonal distribution of storms are represented by a synthetic series of events derived from long-term climate databases created for the RUSLE2 (Revised Universal Soil Loss Equation, version 2) model.  Runoff for each storm event is estimated with RUSLER (RUSLE2-Raster), a two-dimensional (2D) raster implementation of RUSLE2 technology that calculates runoff and sheet-and-rill soil loss for all flow paths covering a field.  The RUSLER calculation provides the spatial and temporal distribution of incoming runoff and sediment loads necessary for the calculation of erosion and deposition in the EG channels.

The channel flow and sediment transport model EphGEE (Ephemeral Gully Erosion Estimator) employs an excess shear stress approach to determine where flow erosive forces cause soil detachment and transport, and where deposition occurs.  EphGEE also calculates the rates at which channels locally deepen and widen, thus predicting how channel geometry evolves during each storm, which depends strongly on knowledge of soil erodibility parameters. EphGEE attempts to estimate how erodibility parameters vary in time and with depth using management operations data available from RUSLE2 databases. In most cases, however, field data and parameter calibration are still necessary.

This modeling approach has been applied to monitored fields in the United States.  It was successful in determining runoff and concentrated flow paths, resulting in good predictions of locations where gullies form and how they connect to runoff-generating areas.  For tilled fields where a less erodible soil layer exists, the model provides good approximations of gully depths and widths. For no-till and pasture-to-crop transitions, where EG cross-sectional shapes may be dependent on how erodibility varies with soil depth, better data or prediction methods are needed to improve model performance.

How to cite: Vieira, D., Wells, R., Yoder, D., and Bingner, R.: Event Based Modeling of Ephemeral Gully Development in Agricultural Fields, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12354, https://doi.org/10.5194/egusphere-egu24-12354, 2024.

EGU24-12394 | Posters on site | SSS2.3 | Highlight

Automatic generation of topologically connected gully networks for integrated erosion control in sloping olive orchards 

Adolfo Peña, Paula González-Garrido, Ana María Laguna, and Antonio Miguel Gámiz

The severe erosion problems affecting large areas of olive groves on slopes in Andalusia (Spain), whose soil losses exceed 40 kg m-2an  in extreme rainfall events, require an integrated watershed management run by landowners and state or regional agencies.

The most common, and most severe erosion form is gully erosion. Gullies act as preferential ways through which soli particles with adsorbed nutrients and agrochemical substances spread downslope moved by surface runoff, what implies a great water loss.

During the last four years a cooperative innovation project between the University of Cordoba and two joint venture groups to (i) evaluate the extent of the soil loss in selected slopes, (ii) estimate the density and location of check-dams to intercept the water and sediment flows; (iii) design a novel type of modular dams; and (iv) complement th conservation works with new cover crops mixtures.

A by-product of this project is the development of an automatic model for the spatiotemporal evolution of gully networks based on the D8 flow direction algorithm, and a network branches detection scheme to accumulate flow identifying the final outlet.

This model has been successfully applied to two olive cropped slopes of Southern Spain.

The innovative proposal has allowed for: (a) Generation of the DEM (Digital Elevation Model) for hydrological modeling of watersheds and determination of gullies and areas vulnerable to erosion; (b) Development of algorithms for a topologically connected network of gullies to establish the areas of origin of soil loss and sediment deposition (c) Protection and correction of ephemeral and deep gullies in pilot plots by means of dikes of modular pieces, vegetation covers in crop roads, protection of roads and vulnerable areas through native plantations, and burying of pruning remains; (d) Monitoring and follow-up of measures from LiDAR sensors on board UAVs and soil analysis before and after extreme events.

These initiatives have already been successfully tested in several projects in which the University of Cordoba participates, such as the CPI INNOLIVAR project and the HIDROLIVAR Operational Group and will be implemented in new study basins where excellent results are expected due to the fragility of steep slope olive groves in very degraded soils.

How to cite: Peña, A., González-Garrido, P., Laguna, A. M., and Gámiz, A. M.: Automatic generation of topologically connected gully networks for integrated erosion control in sloping olive orchards, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12394, https://doi.org/10.5194/egusphere-egu24-12394, 2024.

EGU24-14301 | ECS | Posters on site | SSS2.3

Quantification Studies on Ephemeral Gully Erosion 

Ximeng Xu

Ephemeral gullies (EGs) are major contributors to sediment loss and land degradation on cultivated lands. EG is an important linear erosion feature, often occurring at mid-slope position, that can be greatly influenced by upslope and lateral inflow. This study quantified the ephemeral gully erosion influenced by the upslope and lateral inflow, and the results showed that upslope and lateral inflow both contributed to the runoff connectivity of the EG channel and lateral rills in the EG system. For these simulated conditions, upslope inflow contributions to total runoff and soil loss were 62–78% and 65–81%, respectively, while lateral inflow only contributed around 10%. The contribution differences could be attributed to flow hydrodynamic characteristics in that shear stress and stream power in the EG channel were 4.9–8.6 times greater than those on the lateral slopes. From sheet flow to rill flow and EG channel flow, the flow regime gradually shifted from laminar and subcritical flow to turbulent and supercritical flow. The flow force, power, and energy correspondingly increased as the flow regime changed toward turbulent and supercritical. Both field monitoring and indoor simulation displayed the additional sediment delivery caused by upslope sediment-laden flow, verifying the transport-dominated sediment regime in EG systems. In field observations, the sediment increment coefficient (SIC, ratio of net sediment delivery caused by upslope sediment-laden flow to the total sediment delivery) on an event scale varied from 4.6% to 88.6%. In indoor simulations, the SIC changed from 24.9% to 87.5%. The SIC linearly decreased as the sediment concentration of upslope inflow increased. Field monitoring showed complicated phenomena because of natural random variations. SIC also generally decreased as the sediment concentration of upslope inflow increased. Laboratory simulations verified the field monitoring results of extreme rainfall events with large rainfall amounts and intensities. In future studies, multiple morphological criteria defining EG under various environments are urgently needed. Similar to the continuous sediment transport equations for rill erosion, continuous sediment transport equations for EG erosion need to be developed.

How to cite: Xu, X.: Quantification Studies on Ephemeral Gully Erosion, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14301, https://doi.org/10.5194/egusphere-egu24-14301, 2024.

EGU24-20 | ECS | Orals | HS9.2

Effect of Sampling Design on Characterizing Surface Soil Fingerprinting Properties. 

Maria Luna, Alexander Koiter, and David Lobb

Purpose: The characterization of soil properties is an important part of many different types of agri-environmental research including inventory, comparison, and manipulation studies. Sediment source fingerprinting (i.e., tracing) is a method that is increasingly being used to link sediment sources to downstream sediment. There is currently not a standard approach to characterizing sources and the different approaches to sampling have not been well assessed.

Methods: Grid, transect, and likely to erode sampling designs were used to characterize the geochemical, colour, grain size distribution, and soil organic matter content at two sites under contrasting land uses (agricultural and forested). The impact of the three sampling designs on fingerprint selection, source discrimination, and mixing apportionment results was evaluated using a virtual mixture.

Results: The sampling design had a significant impact on the characterization of the two sites investigated. While the number and composition of the fingerprints selected varied between sampling designs there was strong discrimination between sources regardless of the sampling approach. There were deviations in the expected apportionment results, but the overall patterns were similar across the three sampling designs.

Conclusions: Despite having an impact on the characterization of sources, the sampling design used ultimately had little impact on the conclusions drawn from the final apportionment results. Continued work at the watershed scale is needed to fully evaluate the importance of source sampling on the sediment source fingerprinting approach.

How to cite: Luna, M., Koiter, A., and Lobb, D.: Effect of Sampling Design on Characterizing Surface Soil Fingerprinting Properties., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20, https://doi.org/10.5194/egusphere-egu24-20, 2024.

EGU24-1585 | ECS | Orals | HS9.2

Understanding spatial and temporal functioning of temporary storage areas to improve their flood mitigation effectiveness 

Martyn T. Roberts, Josie Geris, Paul D. Hallett, and Mark E. Wilkinson

Temporary Storage Areas (TSAs), such as bunds, offline ponds and leaky barriers represent a nature-based solution that can offer additional storage during storm events. They are designed to intercept and attenuate surface runoff, thereby addressing various catchment challenges, including flooding, water scarcity, and soil erosion. Soil infiltration is a key TSA outflow, particularly for more common small to medium storm events, meaning TSA functioning may vary between sites with different soil properties and be time-variable due to the dynamic nature of soil structure. The lack of understanding of TSA functioning in space and time represents a major knowledge gap and acts as a limiting factor for the widespread implementation of TSAs. To address these challenges, there is a need for a TSA analysis approach that allows for the systematic evaluation of TSA functioning.  The overall aim of this study was to enhance understanding of TSA functioning and explore variability in functioning with space and time. Specifically, the objectives were to: (i) develop a systematic data-based method for characterising the functioning of various TSA types; and (ii) assess the effect of spatial and temporal soil variability on TSA functioning and flood mitigation effectiveness.

 

Here we present the TSA Drainage Rate Analysis tool (TSA-DRA tool), a new data-based mechanistic approach that utilises only rainfall and water level to characterise drainage of individual TSAs. Results from a multi-site TSA assessment in the UK revealed time-variable functioning, especially at lower levels when soil infiltration is the dominant outflow. We explored this further by assessing changes in soil physical properties (bulk density, macroporosity and saturated hydraulic conductivity) at two TSA sites. These sites shared the same TSA type (bund) and had similar volumes (~250 m3) and soils (Cambisols). However, they differed in land use (winter wheat vs spring barley and blackcurrants) and TSA surface area (800 m2 vs 2800 m2). Soil cores were taken across three spatial zones: (1) TSA active zone (<10% full) – inundated for the longest time; (2) full zone (>50% full) – active during large storms; and (3) Field zone – field control points outside the wetted footprint. This assessment was then repeated for significant temporal events e.g., post-harvest, growing season and post-flood. Results show significant soil structure variations over time and space, with degradation more pronounced in soils within the TSA wetted footprint due to inundation. While tillage effectively reset topsoil structure at one site, its impact was negligible at the other site due to variations in land management, coupled with high sedimentation post-flooding, altering near-surface soil texture. Results from a modelling exercise suggest that well-structured soils with higher infiltration rates can improve TSA effectiveness during a large storm event by reducing the volume and frequency of overflow compared to a degraded soil. Gaining insights into spatial and temporal variations in TSA functioning is crucial for optimising both current and future TSA designs and maintenance regimes.

How to cite: Roberts, M. T., Geris, J., Hallett, P. D., and Wilkinson, M. E.: Understanding spatial and temporal functioning of temporary storage areas to improve their flood mitigation effectiveness, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1585, https://doi.org/10.5194/egusphere-egu24-1585, 2024.

This study examined the sediment characteristics of areas where landslides occurred due to heavy rains between 2014 and 2019. A total of 5 types of geology in two geographic regions in Japan were examined using LiDAR LP topography data before and after the disasters occurred to estimate the changes in elevation. In addition, the volume of sediment runoff for each case was estimated for watershed areas ranging from 0.01 up to 0.1 km2. The influence of geological differences on the sediment runoff volume within the basin using indicators such as the density of landslide occurrence, landslide volume, and watershed erosion intensity was also assessed. The results showed that, for all geology types, as the watershed area increases, the relief ratio decreases and the sediment runoff volume increases; however, the magnitude of this increase in sediment runoff volume differs depending on the underlying geology. In addition, the density of landslide occurrence was high in plutonic and metamorphic rocks. The landslide volume and the total eroded sediment volume within a watershed can be regressed using the linear equation y=ax. Since the average total eroded sediment volume within a watershed is approximately twice that of the landslide volume, there is a proportional relationship of 1:2. The relationship between the relief ratio and watershed erosion intensity shows that the watershed erosion intensity increases gradually as the relief ratio increases, and the rate of increase is larger in plutonic rocks (granite and granodiorite) than in the other groups. Metamorphic rocks had a relatively low watershed erosion intensity; these geological differences are reflected in differences in the degree of erosion of stream beds and banks by flood flows.

How to cite: Akita, H.: Comparison and analysis of the influence of geological differences on sediment runoff volumes from watersheds -case study of plutonic and metamorphic rocks in two sediment disasters in Japan-, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1808, https://doi.org/10.5194/egusphere-egu24-1808, 2024.

EGU24-1817 | Posters on site | HS9.2

TRACING 2021-2024 – Feedback on international events to develop novel strategies of sediment tracing in catchments and river systems 

Olivier Evrard and the TRACING Event organisers and participants

Several innovative techniques have been developed recently opening up new avenues to establish the assessment of sediment flux in the critical zone. These innovative techniques include the tracing or “fingerprinting” methods to identify the sources and quantify the dynamics of sediment and particle-bound contaminants. However, the use of these techniques is often associated with several methodological and statistical limitations, that are often reported although rarely addressed in the framework of concerted actions taken at the level of the international scientific community.

This presentation will present the main outcomes of the Thematic School organised in 2024 and the Scientific Meeting Days organised in 2022 and 2023 as a follow-up of a first training week organised in 2021 to bring together international experts working on these topics together. Based on the publication of an opinion paper (https://link.springer.com/article/10.1007/s11368-022-03203-1), new strategies to publish and disseminate sediment tracing databases will be presented. An example of formatted dataset will be given, with the objective to test research hypotheses based on multiple datasets adopting the same format of data/meta-data. Other perspectives regarding improvements of the sediment fingerprinting method in terms of modelling, tracer options and selection will also be presented.

How to cite: Evrard, O. and the TRACING Event organisers and participants: TRACING 2021-2024 – Feedback on international events to develop novel strategies of sediment tracing in catchments and river systems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1817, https://doi.org/10.5194/egusphere-egu24-1817, 2024.

EGU24-3919 | ECS | Orals | HS9.2

Exploring the sediment redistribution dynamics of a data-scarce catchment in southwestern Ethiopia using the USPED model and gully erosion threshold indices 

Haftu Yemane, Bart Vermeulen, Berhane Grum, Jantine Baartman, Ton Hoitink, and Martine van der Ploeg

Soil erosion has on– and off-site detrimental effects, including decreased soil quality and sediment buildup in reservoirs. Predicting and monitoring soil erosion is challenging due to the spatio-temporal variation of its triggering factors. Therefore, developing and successfully implementing appropriate intervention measures requires a thorough understanding of its redistribution at the catchment scale. However, many previous soil erosion prediction models have been calibrated/validated based on sediment yield at catchment outlets. This approach does not provide any insight into the sources and sinks of erosion and deposition within the catchments. Furthermore, this approach has limited applicability in regions with no (limited) measured data. Therefore, exploring spatial patterns of erosion and deposition using the recent advances in remote sensing and GIS technologies is advisable. This research integrates the semi-distributed Unit Stream Erosion Deposition (USPED) model, and gully erosion threshold indices, described by stream power index (SPI) and topographic wetness index (TWI), to evaluate the sediment redistribution dynamics of a sub-humid catchment located in Omo-basin in southwestern Ethiopia. The catchment (~77 km2) has a rugged topography with an average slope of 35.8 %. It consists of four primary types of land use and cover (LUC): rangelands (20%), forest areas (19%), built-up areas (7%) and cultivated lands (54%). The (preliminary) results revealed that the gentle and mild slopes contribute more (53%) to the overall annual catchment soil loss (42.5 t.ha-1) from the hillslope. This is because the sediment deposited in the downstream sinks remobilizes, shifting an erosion-limited to a transport-limited system. Moreover, the total contribution of rangelands and forest areas is comparable to that of cultivated lands. Therefore, by focusing our management efforts on these areas, instead of the steeper slopes, we can make a greater impact on the overall sustainability of the catchment.

How to cite: Yemane, H., Vermeulen, B., Grum, B., Baartman, J., Hoitink, T., and van der Ploeg, M.: Exploring the sediment redistribution dynamics of a data-scarce catchment in southwestern Ethiopia using the USPED model and gully erosion threshold indices, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3919, https://doi.org/10.5194/egusphere-egu24-3919, 2024.

EGU24-4719 | Posters on site | HS9.2

An approach for the reduction of the sediment volume transported by debris flow from the high-sloping reach of a debris-flow channel 

Carlo Gregoretti, Matteo Barbini, Martino Bernard, Mauro Boreggio, Sandival Lopez, and Massimiliano Schiavo

Usual works for the reduction of the sediment volume transported by debris flows are the retention basins. Retention basins are usually built on the intermediate and low-sloping reaches of the debris-flow channels or at their end, where the terrain slope is usually not high. When the space required for trapping all the sediment volume is not available or the upper part of the basin must be protected deposition areas can be used. The deposition area is a retention basin without the downstream berm, to be placed in the high-sloping reach of a debris-flow channel. Therefore, it is proposed an approach for the progressive reduction of the sediment volume transported by debris flow: an in-series combination of deposition areas in the high-sloping reaches of the channel, and retention basins in the intermediate low-sloping reaches of the flow path.

An application of such approach is shown for the design of the control works on Ru Secco Creek at the purpose of defending the resort area and the village of San Vito di Cadore (Northeast Italian Alps).

How to cite: Gregoretti, C., Barbini, M., Bernard, M., Boreggio, M., Lopez, S., and Schiavo, M.: An approach for the reduction of the sediment volume transported by debris flow from the high-sloping reach of a debris-flow channel, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4719, https://doi.org/10.5194/egusphere-egu24-4719, 2024.

EGU24-5507 | Posters on site | HS9.2

Impacts of rainfall variability on river discharges and suspended discharges : A Case Study in Chenyulan Watershed, Taiwan 

Wen-Shun Huang, Jinn-Chyi Chen, Kuo-Hua Chien, Yue-Ting Lia, and Fan Wu

In this study, the variations of rainfall, river discharges and suspended sediment discharges were analyzed in the Chenyulan watershed in Nantou County, central Taiwan. The hydrological data, such as rainfall, daily discharges and daily suspended sediment discharges, was collected based on Neimaopu hydrology station during the period from 1972 to 2020. The yearly costs of structure conservation to prevent sediment disasters and slope hazard events were implemented in the watershed between 1999 and 2020 as well. The Rating Curve Method with the formula Qs=aQb is adopted to estimate sediment discharges with the corresponding discharge events. The impact factors that caused the variation of discharges and suspended sediment discharges were also analyzed to provide the references for the influence of geological and hydrological changes on sediment yielded on slope and following suspended sediment discharges in the rivers in the watershed. The analyzed results show that the suspended sediment discharges in 1972-1989 are less than the average value in 1990-2009 at the same discharges. The suspended sediment discharges in 2010-2020 are gradually reverted to that in 1972-1989. The causes of decreasing the suspended sediment discharges in last decade are analyzed, including: 1. The variations of rainfall were gradually calmed in last decade; 2. the loose soil on slopes in the watershed caused by Chi-Chi earthquake became concreted with time; 3. the landslide and debris flow disasters obviously decreased in last decade and the soil yield from slopes has slowed down; 4. the local government involved a lot of money to build the conservation structures in upstream creeks to trap the loose soil and control the volume of sediments from flowing into rivers.

How to cite: Huang, W.-S., Chen, J.-C., Chien, K.-H., Lia, Y.-T., and Wu, F.: Impacts of rainfall variability on river discharges and suspended discharges : A Case Study in Chenyulan Watershed, Taiwan, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5507, https://doi.org/10.5194/egusphere-egu24-5507, 2024.

EGU24-5559 | ECS | Posters on site | HS9.2

Impact of dam construction on suspended sediment load alteration 

Zahra Karimidastenaei, Hamid Darabi, and Ali Torabi Haghighi

Impact of dam construction on suspended sediment load alteration

Zahra Karimidastenaei a*, Hamid Darabi b, Ali Torabi Haghighi a

 

a Water, Energy and Environmental Engineering Research Unit, University of Oulu, P.O. Box 4300, FIN-90014 Oulu, Finland.

bDepartment of Geosciences and Geography, University of Helsinki, Helsinki, Finland

*Corresponding author: Email: zahra.karimidastenaei@gmail.com

 

Abstract

Climate change and human activities have always impacted the fluvial processes, encompassing floods, soil erosion, sedimentation, and sediment transport in rivers, resulting in huge environmental concerns. Dynamics analysis of suspended sediment concentration (SSC) is a determining factor in the sediment budgets, and it has an important role in water resources management. In the current research, the relationship of the suspended sediment (SS) with precipitation (R) and flow discharge (Q) has been analyzed to assess the impact of Saveh Dam on the SSC during 1971-1982 and 1983-1994 as pre and 1995-2006 and 2007-2018 as post-impact periods in the Ghareh-chay basin, Iran. To quantify the spatio-temporal variation of SSC (due to climate change and anthropogenic activities such as dam construction and land use changes), a new measure Δα-based approach was introduced. The newly developed approach, referred to as the Δα-based method, was formulated by calculating the angle between (or the change in the slope of) the optimal Precipitation-Sediment (P-S) and Flow-Sediment (F-S) fit lines. This calculation is conducted spatially, encompassing both upstream and downstream locations, and temporally, by comparing data from different periods. The findings showed that Δα for the Precipitation-Sediment (P-S) relationship between upstream and downstream increased significantly after the Saveh dam commissioning. Initially, Δα was measured at 2.69 degrees and 1.35 degrees for the two pre-impact periods upstream and downstream, respectively. However, these values rose to 5.65 degrees and 9.39 degrees in the corresponding post-impact periods. Based on these results, it is evident that the notable changes in Δα for the Precipitation-Sediment relationship between upstream and downstream indicate the dam's impact on the Suspended Sediment Concentration (SSC) patterns in the Ghareh-chay river. The relatively short distance between the upstream and downstream gauge stations further supports the conclusion that these observed changes in Δα are directly attributable to the dam's influence, significantly altering sediment dynamics in the river system.

Keywords: Saveh dam; dynamics analysis; pre- and post-impacted; quantitative approach, sediment rating curve

 

Fig. 1. Location of the study area

How to cite: Karimidastenaei, Z., Darabi, H., and Torabi Haghighi, A.: Impact of dam construction on suspended sediment load alteration, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5559, https://doi.org/10.5194/egusphere-egu24-5559, 2024.

EGU24-5752 | ECS | Posters on site | HS9.2

Exploring Remote Sensing Methodologies for River Bed Grain Size: Insights from a Mountainous Watershed Study in Val Camonica, Italy 

Matteo Benetti, Payam Heidarian, Riccardo Bonomelli, and Marco Pilotti

The measurement of river bed grain size has become an integral aspect of fieldwork in river geomorphology and regional ecology. Over the past years, various authors have proposed remote sensing methodologies to assess grain size based on ground and aerial images. With the burgeoning applications of small unmanned aerial systems (SUAS) in geomorphology, there is a burgeoning interest in leveraging these remote sensing granulometry methods for SUAS imagery. However, a dearth of studies exists that systematically investigate spatially consecutive images yielding grading curves or specifications over extensive areas within mountainous watersheds.

This study focuses on the granulometry of the mountainous watershed in Val Camonica, located in northern Italy, employing a drone for initial photographic documentation. The study incorporates the BaseGrain software for importing drone spatially consecutive images and extracting granulation curves from the photographed areas. Additionally, the study encompasses the utilization of Structure-from-Motion (SfM) photogrammetry within a Ground Control Points (GCP) workflow to scale the drone-acquired photos. The precision of this scaling is systematically validated by comparing photos with scaling images including meter using BaseGrain software. The precision of AGISOFT software, employed in the SfM-photogrammetry process, is also critically evaluated by itself with different numbers of benchmarks.

Results indicate that, despite the non-professional nature of the instrumentation, the acquisition of high-resolution images is feasible. These images enable the generation of Digital Elevation Models (DEMs) with accuracies ranging between 2 and 3 cm, contingent upon the number of ground control points. The granulation curve, extracted through BaseGrain, exhibits acceptable accuracy within meter-scale resolution. This research contributes valuable insights into the potential of SUAS-based remote sensing granulometry for mountainous watersheds and underscores the importance of methodological precision for reliable results in river geomorphology studies.

How to cite: Benetti, M., Heidarian, P., Bonomelli, R., and Pilotti, M.: Exploring Remote Sensing Methodologies for River Bed Grain Size: Insights from a Mountainous Watershed Study in Val Camonica, Italy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5752, https://doi.org/10.5194/egusphere-egu24-5752, 2024.

EGU24-7560 | ECS | Posters on site | HS9.2

Impact Analysis of Series of Groundsills on the Fluvial Stability and Geomorpholog 

Pohsuan Lin, Tsungyu Hsieh, Kuowei Liao, Kailun Wei, and Guanyu Lin

To mitigate riverbed erosion both longitudinally and transversely, control water flow, and stabilize riverbanks, the use of groundsills has become a widely adopted engineering method. For large conservation areas, using a series of groundsills is standard practice. However, the sediment transport in rivers is a dynamic process, and the implementation of series groundsills can cause discontinuities in the longitudinal corridor of the river, leading to damage to the ecological environment and landscape. Although there is considerable consensus on various aspects of series of groundsills, current research primarily focuses on the influence of the configuration of groundsills (such as height and width) on sediment downstream. Therefore, this project aims to estimate the trends in sediment transport through scaled experiments and numerical simulations. Results shown that according to the analysis results, neither the Q5 nor Q95 criteria are met in the proposed plan for the complete removal of the groundsills. This project believes that the complete removal of the groundsills may have a drastic impact on the environment, potentially leading to unstable conditions, and thus requires careful evaluation. The design of openings in the groundsills is an effective ecological adjustment project. Regarding the design of the opening height, this project suggests considering two factors: one is to reduce the similar damming effect caused by lowering the elevation, and the other is the gathering of water flow. It is a trade-off between these two factors. Increasing the depth of the opening may benefit the ecology but could lead to unintended erosion due to concentrated water flow, and vice versa.According to the analysis results, neither the Q5 nor Q95 criteria are met in the proposed plan for the complete removal of the fixed-bed structure. This project believes that the complete removal of the fixed-bed structure may have a drastic impact on the environment, potentially leading to unstable conditions, and thus requires careful evaluation. The design of openings in the fixed-bed structure is an effective ecological adjustment project. Regarding the design of the opening height, this project suggests considering two factors: one is to reduce the similar damming effect caused by lowering the elevation, and the other is the gathering of water flow. It is a trade-off between these two factors. Increasing the depth of the opening may benefit the ecology but could lead to unintended erosion due to concentrated water flow, and vice versa. he proposed plans can optimize benefits for both upstream and downstream water conservation, and protect downstream objectives by managing sediment transport.

Keywords: series groundsill, ecology, sustainable management, sediment transport

How to cite: Lin, P., Hsieh, T., Liao, K., Wei, K., and Lin, G.: Impact Analysis of Series of Groundsills on the Fluvial Stability and Geomorpholog, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7560, https://doi.org/10.5194/egusphere-egu24-7560, 2024.

EGU24-7827 | Orals | HS9.2

Impacts of check dams: a monitoring experience along a mountain watercourse 

Alessio Cislaghi, Dario Bellingeri, Vito Sacchetti, Emanuele Morlotti, and Gian Battista Bischetti

Torrential dynamic is a complex combination of natural processes along a mountain watercourse, including sediment deposition and erosion that cause cross-section occlusions and streambank failure, respectively. Thus, monitoring and managing sediments are fundamental activities for the maintenance in mountain watersheds. To regulate the sediment transport, a common countermeasure is the check dam, designed to control the sediment movement along the watercourse (Piton et al., 2017). Building check dams is complex and expensive, especially in mountain watercourse. These structures largely modify the surrounding environment and landscape; however, if well designed, check dams are very effective solutions to mitigate the potential losses due to flood, debris flood, and debris flow.

This study presents the monitoring of a stretch of a mountain watercourse over several years in an Alpine environment. The observed dominant process was the sediment deposition that has been countered by the construction of a slot check dam. The torrential dynamic has been strongly influenced by this in-channel structure, exacerbating the change of cross-sectional and longitudinal profiles (width and depth of the cross-sections, longitudinal profile, and bed granulometry) not only in proximity of the structure, but also along the observed overall stretch (downstream and upstream). The monitoring consists in measuring the hydrological response during rainfall events and assessing the geomorphic change using digital elevation models differencing (2010, 2014, 2021, 2023). The last topographic surveys were conducted immediately after the construction of the slot check dam and immediately after the first severe debris flood occurred several months later.

The results of monitoring show a clear geomorphic evolution along the observed stretch, contrary to the previously detected tendency of sediment dynamics and, moreover, a different hydrological response at downstream of the structure. As expected, sediments were trapped upstream of the structure, whereas a severe erosion removed the armoring layer bringing to light several bed sills at downstream.

This study underlines how artificial works have a spatially distributed effects on geomorphological change, on hydraulic behaviour, and in some cases on the flood hazards (also far from the structure). Thus, the prediction of geomorphological change, even if qualitative, is extremely important to improve the effectiveness of the check dam in managing sediment dynamics. In addition, sharing this information is essential to support designers (showing practical examples) in planning works not only focusing on the structural and hydraulic perspectives, but also from a geomorphological point of view, which is often neglected.

Piton, G., Carladous, S., Recking, A., Tacnet, J.M., Liébault, F., Kuss, D., Quefféléan, Y., Marco, O., 2017. Why do we build check dams in Alpine streams? An historical perspective from the French experience: A Review of the Subtle Knowledge of 19th Century Torrent-Control-Engineers. Earth Surf. Process. Landforms 42, 91–108. https://doi.org/10.1002/esp.3967

How to cite: Cislaghi, A., Bellingeri, D., Sacchetti, V., Morlotti, E., and Bischetti, G. B.: Impacts of check dams: a monitoring experience along a mountain watercourse, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7827, https://doi.org/10.5194/egusphere-egu24-7827, 2024.

EGU24-8068 | ECS | Posters on site | HS9.2

The new Austrian standard ÖNORM B4800 for torrent control work 

Georg Nagl, Johannes Hübl, and Jürgen Suda

Austria has a wide variety of protection structures at different condition levels due to the long tradition of torrent control works in the Austrian Alps. This has resulted in a large stock of protection structures and load models. In order to standardise the design of technical structures based on the Eurocode, including torrential processes, snow avalanches and rock fall, an interdisciplinary working group (ON-K-256) was established. The standardisation for torrential processes covers the definition and classification, the impact on structures, the design of structures, and the operation, monitoring and maintenance. These parts are based on and interact with EN 1990 (the basis of structural design), EN 1992-1-1 (the design of concrete structures), EN 1997-7 (geotechnical design) and the related documents for the Austrian national specifications. For torrential mass wasting processes with high variability in the concentration of solids, modern protection concepts are scenario-oriented. To optimize the mitigation measures for a multi-stage system, a functional chain must be implemented. This chain should have different structures to perform various functions such as dosing, filtering, and energy dissipation. When designing these torrential mitigation structures, it is necessary to simplify the model parameters, stress model, and load distribution. For debris flows, a standardized stress model combines the static and dynamic loads of debris flow impact on structures. This model was calibrated using available impact measurements of real debris flows and is in good agreement with common engineering design methods in Austria for debris flow impact on torrential barriers. The proposed method enables practitioners to design debris flow countermeasures with limited data availability.

How to cite: Nagl, G., Hübl, J., and Suda, J.: The new Austrian standard ÖNORM B4800 for torrent control work, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8068, https://doi.org/10.5194/egusphere-egu24-8068, 2024.

EGU24-8164 | ECS | Posters on site | HS9.2 | Highlight

Reconstructing the Flood History of Nan Ancient City: Insights from Sedimentary Analysis 

Prapawadee Srisunthon, Alex Berger, Alex Fuelling, Mubarak Abdulkarim, Damien Ertlen, Daniela Mueller, Jakob Wilk, Meike Reubold, and Frank Preusser

Monsoon-induced floods have played a pivotal role in shaping the fortunes of Asian civilizations and communities over the millennia, and their far-reaching consequences persist to this day. This study delves into the floodplain east of Nan ancient city, a city during Lan Na period in northern Thailand dating back to the 13th century AD. Our primary objective was to unravel the source direction of a catastrophic flood event in 1818 AD, which ultimately led to the city's relocation. Our sedimentological analyses revealed a diverse range of deposition. An innovative provenance study using mid-infrared spectroscopy (MIRS), conducted for the first time in this region, indicated a significant contribution from eastern tributaries not from the Nan River. Only two of the nine sediment cores (WTR and HH2) presented evidence of Nan River sediment. Optically stimulated luminescence (OSL) dating revealed a striking pattern: modern floods dominated the shallow depths (ca. 0-1.10 m) of all cores, while deeper layers exhibited unexpectedly older ages, exceeding 11,000 years. This finding aligns with climate data from multiple proxies, suggesting that Nan ancient city, akin to neighboring e.g. Kingdom of Angkor, endured a dry period. Based on these comprehensive findings, we postulate that the 1818 AD flood catastrophe originated from the east. The deluge may have been triggered by rainfall during an extended dry spell, when the parched and compacted soil's permeability was severely diminished. This sudden surge of water swiftly transported the sediment, ultimately inundating and devastating the city. The insights gained from this study are a reminder of the profound impact of monsoon-related floods on human settlements in Asia. By understanding the conceptions between sedimentology, provenance, and climate, we can better comprehend the historical and ongoing challenges posed by these natural disasters and advance strategies for sustainable development in vulnerable regions.

Keywords: flood sediment, monsoon, Southeast Asia,  provenance analysis, OSL dating, Lan Na, Nan, Thailand

How to cite: Srisunthon, P., Berger, A., Fuelling, A., Abdulkarim, M., Ertlen, D., Mueller, D., Wilk, J., Reubold, M., and Preusser, F.: Reconstructing the Flood History of Nan Ancient City: Insights from Sedimentary Analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8164, https://doi.org/10.5194/egusphere-egu24-8164, 2024.

EGU24-8675 | ECS | Posters on site | HS9.2

Assessment of flash flood impacts in a mountain basin: an integrated approach for the management of channel control works 

Francesco Piccinin, Lorenzo Martini, Sara Cucchiaro, Giacomo Pellegrini, Eleonora Maset, Alberto Beinat, Tommaso Baggio, Federico Cazorzi, and Lorenzo Picco

In mountain basins, the predominant approach to control the supply and transport of large volumes of sediment involves the installation of hydraulic structures within the channel network. While torrent control works are fundamental in reducing flash flood impacts, their effectiveness during time need regular monitoring and maintenance. However, few studies have proposed a workflow based on simple factors and criteria collected in the field to prioritize management interventions of torrent control works in a mountain basin. In this work, the aims are to assess the effectiveness of the hydraulic structures and to quantify their impact on sediment continuity in the Vegliato mountain basin (Italy), affected by a flash flood event occurred on the 30th July 2021. First, rainfall data from 2019 to 2022 are analyzed to detect and characterize the event that caused the flash flood. The assessment of post-event status and functionality of the control works is done using a novel Maintenance Priority index (MPi), distinguishing the structures that no longer fulfil their role and providing an overview on the maintenance and re-planning of the management system. These results integrate the analysis of multi-temporal High Resolution Topography (HRT) data deriving from LiDAR surveys. DEMs of Difference (DoDs) are generated to map the geomorphic changes occurred during the event, quantifying the sediment fluxes impacting on the control works and viceversa. The role of torrent control works is also analyzed in terms of continuity of the sediment cascade applying a novel parameter, the Sediment (dis)Continuity Ratio (SCR), which assesses the capability of the torrent control works system in intercepting and storing a sediment mass fraction constituting the cascade (obtained by DoD) and identifies the hydraulic structures that contribute or limit the sediment (dis)continuity along the channel network.

The application of the MPi indicates that the 16% of the control works should be given the highest maintenance priority (MPi = 1). The 45% of the hydraulic structures exhibit 0.63 ≤ MPi ≤ 0.88 and are in need of intervention to ensure the durability of the structures themselves. On the other hand, 12% of the control works require re-planning operations (0.25 ≤ MPi ≤ 0.50) due to their good structural condition but low functionality. Eventually, the 25% of the structures show MPi = 0 and are in the lowest range of priority for the interventions. These results were also corroborated by the DoD results, which supported the MPi. The analysis of the SCR shows how several torrent control works, especially the ones located in the upper part of the catchment, promote continuity (SCR from -100 to -0.1). On the other hand, several structures in the middle part of the main channel show positive SCR values, therefore promoting discontinuity. The highest values of SCR are found in the downstream and wider part of the main channel.

Finally, the workflow composed of different methodologies adopted in this work provides a detailed overview of the interaction between sediment dynamics and torrent control works and represent a useful tool to develop effective management decisions and plans.

How to cite: Piccinin, F., Martini, L., Cucchiaro, S., Pellegrini, G., Maset, E., Beinat, A., Baggio, T., Cazorzi, F., and Picco, L.: Assessment of flash flood impacts in a mountain basin: an integrated approach for the management of channel control works, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8675, https://doi.org/10.5194/egusphere-egu24-8675, 2024.

EGU24-9330 | Orals | HS9.2

(Dis)connected mountain headwaters: advocating for a paradigm shift in sediment management strategies 

Tomáš Galia, Václav Škarpich, and Tereza Macurová

Beyond land-use alterations at the catchment scale, numerous mountain catchments across Europe have experienced significant morphological changes and shifts in sediment transport dynamics over the past two centuries, largely attributable to the implementation of torrent control structures. A notable example is the mountainous part of the Czech Carpathians, where a comprehensive sediment management regime was introduced at the turn of the 19th and 20th centuries. This approach, based on methodologies established in the Austrian Alps, encompassed the installation of check dams and artificial bank stabilizations. Such practices have remained predominant in these areas, with certain catchments smaller than 25 km² exhibiting substantial portions of their stream lengths stabilized through sequences of consolidation check dams, bed sills, and riprap bank stabilizations.

However, it is crucial to consider the distinct nature of external factors influencing rainfall-runoff processes and sediment supply in the 19th century. This period was marked by the end of the Little Ice Age and a higher prevalence of deforested areas, linked with active gully development. Given the contemporary context of extensive reforestation and subtly altered hydroclimatic conditions, the appropriateness of continuing such 'hard and intensive' management strategies for local streams warrants reassessment.

Consequently, a sediment deficit in both mountain channels and foothill gravel-bed rivers has been observed. It resulted in channel transformation with sediment coarsening, the loss of gravel bars (as vital habitats), and, in some instances, channel incision into the bedrock. This situation necessitates a reconsideration of sediment-control strategies within the frameworks of fluvial continuum and sediment (dis)connectivity, particularly since these headwaters function as primary sediment sources. Without modifying these management approaches, enhancing the hydromorphological state of streams and rivers in the Czech Carpathians remains a formidable challenge.

How to cite: Galia, T., Škarpich, V., and Macurová, T.: (Dis)connected mountain headwaters: advocating for a paradigm shift in sediment management strategies, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9330, https://doi.org/10.5194/egusphere-egu24-9330, 2024.

EGU24-9807 | ECS | Posters on site | HS9.2

Quantifying Sediment Dynamics in an Alpine River Catchment using a 10Be Tracing Method  

Chantal Schmidt, David Mair, Fritz Schlunegger, Brian McArdell, Marcus Christl, and Naki Akçar

In this study, we quantify the spatial variation in sediment generation for the c. 12 km2 large Gürbe catchment situated at the northern margin of the Swiss Alps. We particularly trace the sediment transfer from the hillslope to the channel network in the headwaters, and finally to the depositional fan at the downstream end of the catchment. Mapping shows that sediment production in the Gürbe catchment occurs through three primary mechanisms: (1) overland flow erosion generating sand and silt, contributing to the generation of suspension loads; (2) shallow and deep-seated landslides linked to the main channel, both supplying a mixture of gravel, boulders, and silt/sand during floods, thus generating sediment for both the bedload and suspension load of the Gürbe River; and (3) incision of the river into glacial till in the upper headwaters and into landslides farther downstream. The bedrock of the Gürbe catchment comprises Molasse, Flysch, and Quaternary deposits, posing challenges in tracing the origin of the material and estimating the relative importance of the various processes for sediment generation.  However, previous research has shown that the cosmogenic 10Be concentration can differ for various sediment sources (Cruz Nunes et al. 2015; e.g.). Therefore, we measured 10Be concentrations in the sand fraction (0.25 – 2 mm) in the main channel and in the tributaries, aiming to capture suspension load signals generated through overland flow erosion and landslides. As a novel approach, we also determined the bulk 10Be concentration of gravels (2 – 10 cm) collected from the same sampling locations in the Gürbe channel, in the three tributaries as well as from the landslide tongues reaching into the Gürbe. The results point to three different conclusions: First, there exists a clear difference between the signals measured in the sand fraction and the gravel samples. In particular, the 10Be concentrations in the sand fraction are two to four times higher than those measured in the gravel at the same sites. This grain size dependence aligns with previous findings by Puchol et al. (2014). Second, the sand samples in the main channel show a downstream decrease in 10Be concentration, thereby reflecting the supply of material from the tributaries and particularly from the landslides with low 10Be concentrations. Third, bulk gravel samples reveal a larger variability in 10Be concentrations than the sand samples at the same locations. This suggests that the supply and downstream transport of the coarse-grained bedload material occurs more episodic than the generation and transfer of the suspension load. 

 

REFERENCES 

Cruz Nunes, F., Delunel, R., Schlunegger, F., Akçar, N., & Kubik, P. (2015): Bedrock bedding, landsliding and erosional budgets in the Central European Alps. Terra Nova, 27(5), 370-378.

Puchol, Nicolas; Lavé, Jérôme; Lupker, Maarten; Blard, Pierre-Henri; Gallo, Florian; France-Lanord, Christian (2014): Grain-size dependent concentration of cosmogenic 10Be and erosion dynamics in a landslide-dominated Himalayan watershed. In: Geomorphology 224, S. 55–68.

How to cite: Schmidt, C., Mair, D., Schlunegger, F., McArdell, B., Christl, M., and Akçar, N.: Quantifying Sediment Dynamics in an Alpine River Catchment using a 10Be Tracing Method , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9807, https://doi.org/10.5194/egusphere-egu24-9807, 2024.

Land-use specific sediment source apportionment using compound specific isotopic tracers occurs with challenges from both contributions from aquatic  and particulate organic matter sources. Additionally, compound specific tracers have often occurred with co-linearity. Challenging our current understanding of erosion processes, previous studies using compound-specific isotopic tracers regularly indicate forests as the dominant source of sediment. We hypothesized that this estimation may be attributed to misclassifying particulate organic matter as a sediment contribution from forests.

This study is based in Lake Baldegg (Lucerne, Switzerland) and utilizes the δ13C values of lignin-derived methoxy groups and alkane average chain length as an additional land-use-specific tracer to δ13C fatty acids. Three Suess corrections using different tracer residence times are applied to constrain the changing δ13C values of CO2 in the atmosphere over the last 130 years. To identify changes in sediment sources over the last 130 years, contributions of particulate organic matter are determined, and subsequently removed to apportion only the mineral associated soil fraction. To determine the confidence which can be applied to the model’s output, the model's performance is evaluated with 300 mathematical mixtures. The potential misclassification of forest contributions is investigated by merging particulate organic matter and forest sources to simulate tracers which are unable to discriminate between these two sources.

The incorporation of δ13C values of lignin methoxy groups and alkane average chain length as additional tracers successfully expands the problematic one-dimensional mixing line.  Mathematical mixtures demonstrate the improvement of the model’s performance when using both the average chain length and δ13C values of lignin-derived methoxy groups as an additional tracer. Furthermore, they also demonstrate an underestimation of arable contribution. Changes in dominant sediment sources (Forest: pre-1990, Pasture: 1910-1940, Arable: post-1940) highlight the influence of policy-induced land-use changes. Additionally, the study reveals a 37% overestimation of forest contributions to the sediment core due to the inability to discriminate between particulate organic matter and forest sources.

The use of δ13C values of lignin methoxy groups as an additional tracer enables the identification of critical points in the 130-year sediment history of Lake Baldegg. We emphasize the importance of incorporating multiple Suess corrections to constrain the effect of multiple turnover times of tracers. While merging forest and particulate organic matter sources did not alter the dominant source over the last 130 years, it highlighted the need of separating these sources for more accurate apportionment. The study contributes valuable insights to sediment dynamics and land-use impacts, offering guidance for environmental management strategies.

How to cite: Cox, T., Laceby, P., Greule, M., Keppler, F., and Alewell, C.: Using stable carbon isotopes of lignin derived methoxy groups to investigate the impact of historical land use change on sediment/particulate matter dynamics , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10471, https://doi.org/10.5194/egusphere-egu24-10471, 2024.

EGU24-16053 | ECS | Posters virtual | HS9.2

Hydrological and Sediment Transport Regime on Rivers in the Balkans: The Case of the Seman River in Albania 

Alban Doko, Axel Bronstert, and Till Francke

Hydrological and sediment transport regime are important in water resource management. Aim of this study is to identify the flow regime and the suspended sediment transport in a Mediterranean River Basin. Precipitation, temperature, soil, land use, discharges and suspended sediment concentration are used to quantify runoff and sediment yields at daily scales. WASA-SED (Water Availability in Semi-Arid environments – SEDiments) a spatially semi distributed model it is developed to simulate the flow and sediment transport in Seman Basin. Sediment deposits in Seman Basin contribute to a significant annual loss in the water storage capacity of the dams. Runoff and suspended sediments in Mediterranean hill slopes are closely related to rainfall intensities and land surface cover. This study gives a valuable approach in improving the prediction of flow and sediment transport in Mediterranean River Basin.

Keywords:
Flow, Sediment transport, WASA-SED, Mediterranean River Basin

How to cite: Doko, A., Bronstert, A., and Francke, T.: Hydrological and Sediment Transport Regime on Rivers in the Balkans: The Case of the Seman River in Albania, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16053, https://doi.org/10.5194/egusphere-egu24-16053, 2024.

EGU24-16690 | ECS | Orals | HS9.2

Sediment Source Identification in a Southern Brazilian Watershed: Utilizing Geochemical Properties and Spectral Signatures with Mixing Models 

Mélory Araujo, Gema Guzmán, José Alfonso Gómez, Alexander Koiter, Stefan Nachtigall, and Pablo Miguel

 

One of the main impacts of water erosion within a watershed is the downstream deposition of sediments in watercourses and decrease in water quality, esigning and implementing effective soil and water conservation practices to address these impacts requires a soil conservation practices. Increasingly, researchers are using sediment source fingerprinting methods which use physical, biological, and geochemical attributes of the soil and sediments as tracers (Tiecher et al., 2015). Identifying sediment sources enables targeted corrective measures, but tracer selection and fingerprinting feasibility are ongoing debates among experts (Lizaga et al., 2020; Owens et al., 2022).

This study focuses on identifying sediment sources to develop erosion mitigation plans in a 33.3 km² rural river basin, in southern Brazil, crucial for supplying the municipality of Pelotas. Three primary sediment sources were identified: annual crops, perennial forage (pastures), and gutters (river channels). Samples were collected from the surface horizon (0-20 cm) of agricultural land and perennial pastures. Gutter samples were collected from the underground horizon, where active erosion processes were taking place. In total, 116 source samples were obtained. Nine sediment samples were collected from six sites across the study area every two months during 2021-2022, forming three collections for each sub-area of the river basin (A1, A2, and A3). Traditional fingerprinting methods, utilizing geochemical tracers, total organic carbon, and color coefficient tracers in the visible spectrum, were employed to analyze the soil of the contributing area and the sediments. The FingerPro (v1.1; Lizaga, 2018) mixture model was applied to evaluate the contributions of sediment sources to the collected sediment.

This communication presents preliminary results of 37 tracers: 22 geochemical elements, 14 color coefficients, and total organic carbon. Data processing, using FingerPro, was conducted separately by sub-area and sediment collection. Tracer selection involved a-two sequential statistical tests: 1) Kruskal-Wallis (KW) selects tracers with significant differences between at least two sources and 2) Discriminant Function Analysis (DFA) selects optimal tracers that effectively discriminate between the three sediment sources.

The results obtained demonstrated that the selected tracers for each sub-area varied considerably. For example, the tracer selection procedure for sub-area A1 resulted only in total organic carbon as a viable tracer while the number tracers selected for the other two sub-areas were seven and five, for A2 and A3, respectively. Notably, the varying sets of tracers being selected for each sub-area indicate that the heterogeneity in soil properties is an important consideration in sediment source fingerprinting studies. Combining samples from the whole river basin may distort sediment dynamics. Tailored approaches are crucial for accurate understanding and management.

Acknowledgements

This study was made possible by the generous support of Brazil-CAPES through a doctoral scholarship (Finance Code 001).

References

Lizaga et al. 2020. Consensus ranking as a method to identify non-conservative and dissenting tracers in fingerprinting studies

Lizaga. 2018. fingerPro 1.1.

Owens, P. N. 2022. Sediment source fingerprinting: are we going in the right direction?.

Tiecher et al. 2015. Combining visible-based-color parameters and geochemical tracers to improve sediment source discrimination and apportionment 

How to cite: Araujo, M., Guzmán, G., Gómez, J. A., Koiter, A., Nachtigall, S., and Miguel, P.: Sediment Source Identification in a Southern Brazilian Watershed: Utilizing Geochemical Properties and Spectral Signatures with Mixing Models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16690, https://doi.org/10.5194/egusphere-egu24-16690, 2024.

EGU24-16692 | Posters on site | HS9.2

Pre-event conditions and rainfall–runoff characteristics drive suspended sediment source variability 

Núria Martínez-Carreras, Jean François Iffly, and Laurent Pfister

Most of the total sediment load transported in river systems is carried in suspension. Therefore, if we are to reduce soil erosion and sediment export, it is essential to determine suspended sediment sources and the drivers of its mobilisation into the river network. In this study, we combined the monitoring of suspended sediment fluxes and the sediment fingerprinting approach to test if pre-event conditions and rainfall-runoff characteristics drive suspended sediment source variability in catchments under a semi-oceanic climate. The sedimentological response to storm runoff events was studied in seven nested sub-catchments of the Attert River basin (0.4 - 245 km2), which have contrasting geological bedrock (sandstone, marls and shale) and land uses (forest, cropland and grassland). We collected stream water samples during storm runoff events (~30 events per catchment) using automatic water samplers to measure suspended sediment fluxes. In parallel, time-integrated suspended sediment and sediment sources samples (i.e., from different land use types) were collected and analysed in the laboratory (geochemistry, colour and organic properties) to determine the sediment origin using the sediment fingerprinting approach. Each sampled event was parameterized to describe rainfall, runoff, sediment transport and the relative contribution of each land use type to the sampled suspended sediment. Next, we assessed the relationships between variables. We found higher significant correlations between suspended sediment loads and runoff parameters (i.e., peak discharge and event runoff) than between suspended sediment loads and rainfall parameters (i.e., event precipitation, antecedent rainfall, and maximum rainfall intensity). Peak discharge for single events was found to be the best predictor of sediment loads in the studied catchments. We show that most events exhibit clockwise hysteretic loops between discharge and suspended sediment concentration in all studied catchments. We attribute this finding to the erosion or remobilization of sediment previously deposited on the channel bed or an adjacent area. During most of these events with clockwise hysteretic loops, sediment source apportionment presented a consistent pattern.

How to cite: Martínez-Carreras, N., Iffly, J. F., and Pfister, L.: Pre-event conditions and rainfall–runoff characteristics drive suspended sediment source variability, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16692, https://doi.org/10.5194/egusphere-egu24-16692, 2024.

EGU24-17307 | ECS | Orals | HS9.2

Sediment contribution of shallow landslides and flux connectivity of transfer paths in mountainous areas under climate change projections. A case study for the Saldes River basin (Pyrenees, Spain) 

Stephania Rodriguez, Marcel Hürlimann, Vicente Medina, Ona Torra, Raül Oorthuis, and Càrol Puig Polo

In the context of soil erosion modeling, coarse-grained sediments present considerable challenges, particularly concerning sediment production and quantification. This study proposes a module-based quantification approach that integrates different coarse-grained production processes, where one of the main outputs is the source area delimitation and the quantification of mobilizable sediment.

The present study focuses on analyzing shallow landslides and various scenarios of sediment transport to the nearest fluvial system, by implementing the newly developed “Random Connect” code. This code calculates the accumulated volume that travels from the source areas into the fluvial system based on the connectivity index. The chosen case study is the Saldes River basin in the Pyrenees (Spain) The outlet point of this basin is La Baells water reservoir, presently facing siltation challenges arising from sediment transport across the entire drainage area. Reported by CEDEX (2002), the sediment yield delivered to a La Baells Reservoir from the entire drainage area was 4.54 Mg ha−1yr−1 in 2002. In this sense, this water reservoir is utilized for calibrating and validating our model. The quantification of sediment in water reservoirs does not allow to separate the contributions of the different erosive processes at the basin, thus highlighting the importance of the study of the river section to better understand the sediment production.

For model calibration, field surveys were conducted to ascertain the connectivity index to the main river, identify (dis)connectivity factors, and measure fluvial and sediment grain characteristics. Comparing model output with field data enables determination of sediment transport potential and the maximum sediment quantity that can reach the main river. Depending on the connectivity threshold, the results of sediment reaching the main river for a critical rainfall event can vary between 250000 to 10000 m3.

Assessing sediment at the river cross-section helps in defining the principal coarse-grained production phenomena, such as shallow landslides, rock falls and debris flows. Grain characterization of sediment is necessary to study sediment mobilization through a hydrological-driven module. The main objective is to track coarse-grained sediment until it reaches the water reservoir and identify the meteorological and physical factors that trigger the process.

A historical baseline of sediment production has been determined for the Saldes River basin, based on historical landslide inventories, previous triggering events, and meteorological scenarios for the current climate. The assessment considers the impact of climate change in Spain at different timelines based on return periods. The rate of sediment production is determined by analyzing critical climate change scenarios, resulting in values below and above the baseline. This analysis places special emphasis on extreme climate events and the projection of mean annual precipitation.

How to cite: Rodriguez, S., Hürlimann, M., Medina, V., Torra, O., Oorthuis, R., and Puig Polo, C.: Sediment contribution of shallow landslides and flux connectivity of transfer paths in mountainous areas under climate change projections. A case study for the Saldes River basin (Pyrenees, Spain), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17307, https://doi.org/10.5194/egusphere-egu24-17307, 2024.

EGU24-20102 | ECS | Posters on site | HS9.2

Deglaciation and debris flow dynamics: how does the glacier retreat affect debris flow activity in High Mountain Asia?  

Varvara Bazilova, Leon Duurkoop, Jacob Hirschberg, Tjalling de Haas, and Walter Immerzeel

Debris flows are fast-moving masses of rock, soil, and water, which occur in mountain areas all over the world. Debris flows achieve maximum discharges that are many times greater than those associated with floods and are therefore often hazardous to people and infrastructure. Contrary to the general expectations that climate change will increase the magnitude and frequency of the debris flows, recent assessments have shown that under certain conditions future climate may increase the sediment transport capacity, but could also favor a reduction of the sediment supply and, therefore, reduce debris-flow activity.  The impact of glacier retreat together with future climate conditions on debris-flow catchments is not yet fully understood, but it is expected to increase due to uncovered glacial till, increased hillslope instabilities and an increase in peak rainfall intensities. We aim to quantify the effect of the changes in water availability (changes in precipitation regime, but also glacier meltwater) together with the subsequent landscape changes in climatically contrasting catchments in High Mountain Asia (HMA) on the frequency and magnitude of debris flows. We address it by further extending the sediment cascade model (SedCas), expanding the available hydrological response units to bedrock, vegetated and glaciated parts of the catchment. We further investigate (1) how sediment yield and debris flow magnitude-frequency change over time, and (2) how deglaciation and catchment greening (changes of land cover) affect debris flow activity for different climate regions across High Mountain Asia. We find that in the case study of sediment-unlimited catchments, from 1950 to 2022, glacier retreat increases the water supply. That, in combination with the warming temperatures (and therefore the change in the partitioning of the solid and liquid precipitation) and the decrease in number of extreme precipitation events, results in a decrease in the debris-flow activity. These preliminary results show that changes are not consistent across HMA and highly depend on the climatic regime and elevation. Our findings shed light on the debris flow and flood hazard in the data-scarce areas of HMA and highlight the importance of considering regional climate conditions for hazard assessment in addition to region-wide estimation of glacier retreat. The future development will investigate the sediment-limited conditions. 



How to cite: Bazilova, V., Duurkoop, L., Hirschberg, J., de Haas, T., and Immerzeel, W.: Deglaciation and debris flow dynamics: how does the glacier retreat affect debris flow activity in High Mountain Asia? , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20102, https://doi.org/10.5194/egusphere-egu24-20102, 2024.

EGU24-20399 | Orals | HS9.2

Accumulation of water and sediments upstream of Tuscan check dams 

Federico Preti, Sara Pini, Giorgio Cassiani, Andrea Dani, Yamuna Giambastiani, Luca Peruzzo, and Luigi Piemontese

Faced with a decline in water resources due to precipitation reduction and variability, it is fundamental to identify potential natural "reservoirs" and quantify their water retention capacity. This study examined approaches to estimate the water content rapidly and systematically in the sediment upstream of check dams at different scales, even with limited input data.

The study was conducted in the northern part of Tuscany, with a specific focus on the Casentino Valley. After gathering the necessary databases and information, an estimation model was developed using QGIS Model Designer, and geophysical surveys were performed using Electrical Resistivity Tomography (ERT).

The QGIS-based model relies on limited input data, including the geographical positioning of weirs, the hydrographic network, and a Digital Terrain Model (DTM) of the study area. This method provides useful initial approximate estimates of the water resources in the study area. The ERT surveys revealed varying patterns depending on the lithology of different areas, but a clear discontinuity between the sediment wedge and the original riverbed was observed, confirming the effectiveness of this tool in analyzing each individual structure. With the data obtained through the databases, it was also possible to conduct an analysis on the relationship between the original slope and the compensation slope of sediment wedges, and the distance between check dams located on the same river reach.

In the perspective of utilizing these natural reservoirs, possible maintenance interventions are proposed, especially on the existing spillways, to make a portion of the available water usable, accompanied by an assessment of potential implications. In the future, implementing the outlined procedures and integrating them with other tools could provide support for evaluating and utilizing these "hidden water resources."

How to cite: Preti, F., Pini, S., Cassiani, G., Dani, A., Giambastiani, Y., Peruzzo, L., and Piemontese, L.: Accumulation of water and sediments upstream of Tuscan check dams, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20399, https://doi.org/10.5194/egusphere-egu24-20399, 2024.

EGU24-20482 | Posters on site | HS9.2

Advancing sediment fingerprinting techniques: The importance of considering sediment mixtures data in tracer selection 

Leticia Gaspar, Borja Latorre, Ivan Lizaga, and Ana Navas

Sediment fingerprinting has become a key tool to identify and quantify sediment sources within a catchment. The technique involves statistical testing of a range of properties of source materials to identify a set of tracers that can effectively discriminate between different potential sources before estimating the source contributions with unmixing models. However, despite its increasing popularity among researchers, there is a lack of standardized procedures for tracer selection, which is crucial to estimating a reliable contribution of sediment sources. The most widespread methodology consisted of an initial mass conservation test, usually termed range test (RT), followed by the use of Kruskal-Wallis (KW) and discriminant function analysis (DFA) tests. However, KW and DFA even though identifies the best combination of tracers that provide the maximum discrimination between sources, do not incorporate the information of the sediment mixtures in the analysis. Novel methods highlight the importance of selecting the right tracers for each individual mixture and avoid the inclusion of tracers out of consensus or with non-conservative behavior by using consensus ranking (CR) and consistent tracer selection (CTS) methods. This contribution addresses the role of selecting appropriate tracers, demonstrating their impact on the results of the unmixing model. The main objectives are to emphasize the importance of considering the information provided by the sediment mixture in the selection of tracers and to pay attention to the impact of having sediment mixtures with values below the detection limit of the tracer being selected for source discrimination. A set of experimental and real sediment mixtures were selected to explore the different tracer selection methods, comparing the tracers selected and the contribution of sources obtained using the FingerPro unmixing model. We present the results of rigorously testing methodologies with the aim of understanding and assessing the suitability of each tracer selection method to select a combination of statistical and process-based criteria to select appropriate sediment properties for the unmixing models. Our findings highlight the importance of considering the information on the sediment mixture information for the selection of potential tracers, an aspect often neglected by conventional methods. This oversight can result in biased findings due to the use of tracers that are either not coherent or not conservative.

How to cite: Gaspar, L., Latorre, B., Lizaga, I., and Navas, A.: Advancing sediment fingerprinting techniques: The importance of considering sediment mixtures data in tracer selection, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20482, https://doi.org/10.5194/egusphere-egu24-20482, 2024.

EGU24-21734 | Orals | HS9.2

Measures to mitigate torrential hazards in a typical alpine catchment area in Slovenia 

Jost Sodnik, Matjaž Mikoš, and Nejc Bezak

Various sediment-related disasters such as flash floods, debris flows and landslides can occur in an alpine torrential catchment area. To protect infrastructure and human life, various structural and non-structural (grey, green and hybrid infrastructure) protection measures can be used to mitigate torrential risks. An overview is given of the protective measures constructed near the Krvavec ski resort in north-western Slovenia (Central Europe). In May 2018, an extreme debris flood occurred in this area, causing considerable economic damage. After the event in May 2018, various field investigations (e.g. geological and topographical surveys) and modeling applications (e.g. hydrological modeling, debris flow) were carried out to prepare the necessary input data for the design of protective measures against such disasters in the future — due to climate change, further disasters are expected in this torrential catchment area. Compensatory measures include the engineering works of local streams, the construction of a large silt check dam for sediment retention, the construction of several smaller retention dams and the construction of 16 flexible net barriers with an estimated retention volume of ~8000 m3 to control erosion. A comprehensive monitoring system was also set up in the study area to observe and monitor potential future extreme events. This monitoring system includes measurements of corrosion of flexible nets, estimation of concrete abrasion on retention dams, regular geodetic surveys with small drones (UAV) and hydro-meteorological measurements with rain gauges and water level sensors. The recent extreme floods of August 2023 also hit this part of Slovenia, and this combination of technical countermeasures withstood the event and prevented large amounts of coarse debris from being transported to the downstream section and destroying infrastructure, as was the case in a less extreme event in May 2018. Therefore, such mitigation measures can also be used in other torrential catchment areas in the alpine environment.

How to cite: Sodnik, J., Mikoš, M., and Bezak, N.: Measures to mitigate torrential hazards in a typical alpine catchment area in Slovenia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21734, https://doi.org/10.5194/egusphere-egu24-21734, 2024.

SSS3 – Soil as Records in Time and Space

EGU24-1649 | ECS | PICO | GM7.3

Dunes on the north-eastern Tibetan Plateau as influenced by climate change: a remote sensing study of the past 5 decades  

Lukas Dörwald, Frank Lehmkuhl, Janek Walk, Xiaoping Yang, Deguo Zhang, Andreas Baas, Lucie Delobel, Bruno Boemke, and Georg Stauch

Dunes react quickly to climatic changes, with the main drivers being the dominating wind regime (e.g. magnitude and direction), precipitation, and temperature. Further, human impact can alter dune movement by fixation of active dunes through greening projects, or reactivation of stationary ones through overgrazing by animals. The north-eastern Tibetan Plateau shows a high variability of climatic parameters like wind, temperature, and precipitation within a high elevation environment, situated between the mid-latitude westerlies and the East Asian Summer monsoon. The presented studies asses active barchan dunes in different climatic settings, from the arid southern margins of the Badain Jaran Desert, to the humid Zoige Basin.

Since climate stations on the Tibetan Plateau are rare and their measurements often cover only a short time span, climatic changes were studied from ERA-5 reanalysis data, dating back to the 1950s. These metrics were processed via cloud computing, using Google Earth Engine, and were then compared to dune migration rates, which were deduced from optical satellite imagery. Here, the CORONA KH-4B images from the late 1960s, the Landsat archives, and up-to-date high resolution data (GeoEye and WorldView) were used. The Normalized Difference Vegetation Index (NDVI) was implemented to observe changes in vegetation. As a newly tested metric, dune field density changes were calculated, in order to investigate dynamics of dense dune field setting.

Over 500 dunes were mapped and analyzed in total within four focus-areas for comparative purposes. The results highlight a wide range of different behavioral patterns of dunes within the environment of the north-eastern Tibetan Plateau. This showcases how dunes can be influenced by and linked to climatic changes.

How to cite: Dörwald, L., Lehmkuhl, F., Walk, J., Yang, X., Zhang, D., Baas, A., Delobel, L., Boemke, B., and Stauch, G.: Dunes on the north-eastern Tibetan Plateau as influenced by climate change: a remote sensing study of the past 5 decades , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1649, https://doi.org/10.5194/egusphere-egu24-1649, 2024.

EGU24-1752 | PICO | GM7.3

A conceptual model for alluvial fan formation and development  

Frank Lehmkuhl and Lewis A. Owen

The development of alluvial fans is sensitive to environmental change and, thus, alluvial fans provide essential archives for reconstructing Quaternary paleoenvironmental conditions, particular climate, hydrology, and tectonics. Although alluvial fans have been studied across the globe for over a century, there is no unifying scheme/framework or model to consider their complete variety and mode of formation. By reviewing the global spatial and temporal range of alluvial fan types and data from selected key dryland regions, we are able to develop a conceptual scheme/framework for their geomorphology and formation, and thus aid in their application for Quaternary climate and environmental change studies. This approach suggests that there are three main regimes for alluvial fan geomorphology and formation: Type I) microscale mountain alluvial fans, small in size and extent (radius < a few 100 m); Type II) mesoscale (radius

How to cite: Lehmkuhl, F. and Owen, L. A.: A conceptual model for alluvial fan formation and development , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1752, https://doi.org/10.5194/egusphere-egu24-1752, 2024.

EGU24-2355 | PICO | GM7.3

Monitoring and simulating dryland soil salinization and assessing the impact of climate change and global warming on soil salinity processes over the past three decades in the Bajestan playa (NE Iran) 

Azra Khosravichenar, Mehdi Aalijahan, Saeedreza Moazeni-Noghondar, Anthony R. Lupo, Alireza Karimi, Mathias Ulrich, Naser Parvian, Aboozar Sadeghi, and Hans von Suchodoletz

Dryland soil salinization strongly affects soil properties, with severe consequences for regional ecology, agriculture and the aeolian dust dynamics. Given its climate-sensitivity it forms a serious environmental hazard, and to cope with this challenge during current global warming it needs to be better understood.

The Bajestan Playa, located in the heavily salinization-affected drylands of Iran, is home to several protected areas and serves as a crucial source of regional dust emissions. Consequently, soil salinization in this region affects both local ecosystems and societies but was not systematically studied yet.

Using an unprecedented comprehensive approach, we systematically monitored regional soil salinity from 1992 to 2021 through a combination of remote sensing, on-site field measurements, and laboratory analyses. We linked these data with regional and global climatic information to achieve three main objectives: (i) understanding the spatio-temporal dynamics of soil salinity, (ii) assessing the impact of regional and global climate changes on salinization processes, and (iii) exploring the potential applications of our approach for future soil salinity studies.

Our high-resolution annual data over three decades have provided significantly deeper insights into soil salinization dynamics. Furthermore, this pioneering, multidisciplinary research showcases substantial potential for future applications in other salinity-affected drylands forming a foundational knowledge base to address the consequences of ongoing global climate change.

How to cite: Khosravichenar, A., Aalijahan, M., Moazeni-Noghondar, S., R. Lupo, A., Karimi, A., Ulrich, M., Parvian, N., Sadeghi, A., and von Suchodoletz, H.: Monitoring and simulating dryland soil salinization and assessing the impact of climate change and global warming on soil salinity processes over the past three decades in the Bajestan playa (NE Iran), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2355, https://doi.org/10.5194/egusphere-egu24-2355, 2024.

The lower fourth member of the Paleogene Shahejie Formation (Es4L) in Bonan sag, Bohai Bay Basin, East China was taken as an important target for oil and gas exploration in Shengli oilfield. Bonan sag is one of several sag in the Bohai Bay Basin, located in north-east China. Paleogene deposits are characterized by red rock layers, formed under a hot-warm and arid climate. Four depositional systems were developed in the Bonan sag. Among them, the fan delta developed in the central part of the study area, consisting of gray-white fine glutenite with poor sorting and rounding. The braided river delta is developed in the southern part with large lithofacies. The lithology shows some light gray conglomerate, pebbly sandstone, sandstone and small amount of mudstone. Floodplain facies is mainly developed in the inundated plain that in some weather conditions have the characteristics of shallow lake facies. However, a number of questions remain unanswered about the disparate presence of evaporites, the diverse colors of the mudstones and the varying levels of total organic carbon (TOC) in the area. These disparities can be seen in the many oscillations in TOC content, from the source of the sediments in the upper relief to the flood lacustrine plain. Consequently, given to this conditions, the depositional system which occurs in the area remains unclear from previous works. However, looking at the distribution of the sediments in an apparently short distance of less than 50km from the south to the North of sag, suggests that they are more likely to be terminal fan deposits. Terminal fans are an architectural system for draining and depositional process from high relief to flood plain, with gradual discharge of water through infiltration and evaporation. Although some researchers have conducted studies on terminal fans around the world, the concept remains unfamiliar and deserves to be more elucidated. This approach postulates to be useful to better understanding the sedimentary deposits in the Bonan sag and must be reviewed for similar hydrocarbon explorations elsewhere.

How to cite: Mioumnde, A. P., Zhang, L., and Yan, Y.: Paleoenvironment and Depositional Analysis of a Paleogene Formation: Terminal Fan Sedimentation Approach for Reservoir Quality Study in the Lower Shahejie Fourth Member, Bonan sag, China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2604, https://doi.org/10.5194/egusphere-egu24-2604, 2024.

 In view of the problem that the Cretaceous favorable sedimentary facies belt in Kedong structural belt in the southwest depression of the Tarim Basin is not clear, in order to reduce the uncertainty of the research on the spatial and temporal distribution of source sink sedimentary systems in low drilling density areas, the applicability of sedimentary forward modeling in the Tarim Basin is explored. Based on existing geochemical data, statistical analysis of trace elements and rare earth elements is conducted to explore the ancient sedimentary environment during the sedimentation process of the Cretaceous Kizilsu Group, which is a prerequisite for conducting sedimentary forward modeling. By comprehensively utilizing drilling, seismic and other data, combined with previous research results, DionisosFlow sedimentary forward simulation software is applied to clarify the development characteristics of sedimentary systems. The results show that based on different element abundances, ratios, and sedimentary markers, the study of ancient sedimentary environments shows that the ancient climate is mainly characterized by semi humid, semi dry, and dry hot climate conditions; During the sedimentation period of the Kizilsu Group, the overall water depth was relatively shallow, and the ancient redox environment was a shallow underwater oxidation environment. The favorable paleoenvironmental conditions and abundant material sources provide favorable conditions for the development of shallow water delta sedimentary systems. The Kizilsu Group mainly develops braided river delta sediments in the northern gentle slope zone, with front edge sediments as the main type. The southern steep slope zone develops alluvial fans and fan delta sedimentary systems, and the central part develops shoreline shallow lake facies sediments. The western Kunlun Mountains in the south are the main source of material supply, while the Maigaiti ancient uplift in the north is the secondary source of material supply. The ancient uplift during the sedimentation period of the Kizilsu Group has a blocking effect on the delta that flows into the lake, dividing the southern fan delta and lake sedimentary system from the northern braided river delta and lake sedimentary system.

How to cite: Zhang, Y. and Zhang, L.: Application of Sedimentary Forward Simulation in the Kezilesu Group of the Kedong Structural Belt, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2738, https://doi.org/10.5194/egusphere-egu24-2738, 2024.

EGU24-3400 | ECS | PICO | GM7.3

Small endorheic basin sediments along a climatic gradient as paleoenvironmental archives 

Itzhak Raish, Joel Roskin, Shlomy Vainer, and Revital Bookman

 

Understanding and quantifying the natural variability and evolution of past climate systems require the use of datasets that are considerably long, continuous, and of broad spatial coverage. However, common terrestrial proxies, specifically in low- and mid-latitude could be puzzling due to the diversity of climate systems that records a mixed and regionally wide signal that fails to detect the short-term and transitional climate variability. In Holocene records, which are often used to study human-environment interactions, these resolutions are critical.

Here we explore the potency of deposits that are filling endorheic (internally drained) basins of not more than several km2 in size to serve as paleoenvironmental archives. We focus on three sites spread along a steep, ~150 km long climatic gradient in Israel that are influenced by several atmospheric circulation patterns. Core-drilled sediments acquired from such basins have undergone sequential analyses to characterize their textural, geochemical, and luminescence properties. Optically stimulated luminescence (OSL) dating, applied to construct a chronological framework, is coupled with port/pulsed OSL (POSL) analyses, mainly to analyze sedimentation trends and target samples for OSL dating.

The geomorphic and sedimentological responses to environmental perturbations of the late Quaternary are reflected distinctly in each site. Changes in depositional environments that occur throughout all sites often point to similar regional climatic trends, and are partly synchronous with established climatic events.  The compiled interpretation from several sites along a given climatic transect is anticipated to form a robust regional paleoenvironmental framework that can serve a wide range of Quaternary studies.

How to cite: Raish, I., Roskin, J., Vainer, S., and Bookman, R.: Small endorheic basin sediments along a climatic gradient as paleoenvironmental archives, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3400, https://doi.org/10.5194/egusphere-egu24-3400, 2024.

EGU24-5535 | ECS | PICO | GM7.3

The formation and development of nebkhas based on chronology and sedimentology in the Ordos Plateau, northern China 

Yue Du, Ruijie Lu, Luo Ma, Dongxue Chen, and Yingna Liu

The Ordos Plateau lies on the northwest margin of the East Asian monsoon region as well as the farming-pastoral ecotone in northern China, with a wide distribution of nebkhas. The formation and development of nebkhas in this region are closely related to natural envi ronmental conditions and human activities. However, the processes of nebkhas formation and development under natural and anthropogenic influence still remain unclear. In this study, four typical nebkhas in the Ordos Plateau were selected after detailed field investigations. Chronology and sedimentary features of the formation and development of nebkhas were studied based on optically stimulated luminescence (OSL) dating, lithology, grain size, etc. The results demonstrated that modern nebkhas had formed since at least ~0.59 ka in the southwest of the Ordos Plateau, followed by the middle region, at least ~0.34 ka, and later in the south and north regions, at least ~0.10 ka. There were thin layers of weakly-developed paleosols at ~0.32-0.25 ka, peaks in the silt and fine sand content and lower deposition rates, about 0.37-0.46 cm/a, indicating a relatively humid climate and weak aeolian activities. After ~0.10 ka, aeolian activities intensified and the nebkhas widely developed with a higher deposition rate, ~0.45-5.21 cm/a. Nebkhas in the study region developed primarily over paleo-channels or paleosol layers. Very fine sand and fine sand were dominant composition on grain size of nebkha sediments; saltation was a main means for the particle movements, indicating near-source accumulation for nebkha sediments. In recent decades, local farmers are used to adding nebkhas deposits to the soil of irrigation areas to improve the soil quality and alleviate soil salinization. Such agricultural activities, together with land reclamation, have accelerated the demise of the nebkhas in the Ordos Plateau.

How to cite: Du, Y., Lu, R., Ma, L., Chen, D., and Liu, Y.: The formation and development of nebkhas based on chronology and sedimentology in the Ordos Plateau, northern China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5535, https://doi.org/10.5194/egusphere-egu24-5535, 2024.

EGU24-5537 | ECS | PICO | GM7.3

Estimation of aeolian sediment volume in the middle reaches of the Yarlung Zangbo River based on GPR and LiDAR 

Jianyu Ling, Rongyi Qian, Xu Liu, Zhibo Huang, Ding Wang, Ketong Hu, and Jinhang Zhang

Sand control is one of the most important components of environmental protection. In the middle reaches of the Yarlung Zangbo River, the phenomenon of desertification is becoming serious, which has a great impact on the local ecological environment protection and economic development. The accurate estimation of the volume of aeolian sediment is of great significance to the formulation of the treatment plan. However, most of the existing studies are based on remote sensing interpretation to estimate the area of aeolian sediment, and the research on the volume of aeolian sediment is relatively weak. To make up for this research gap and provide reliable basic information for sand control in the middle reaches of the Yarlung Zangbo River, we carried out research on estimation of aeolian sediment volume based on GPR and LiDAR. The experimental area of this study is located in Zhanang County in the middle reaches of the Yarlung Zangbo River, with an area of approximately 1.8 km2. We set up six GPR survey lines in the experimental area and obtained the bottom interface and corresponding average elevation of aeolian sediment. Subsequently, high-precision surface elevation of the study area was obtained by LiDAR, and the average surface elevation was calculated. Then we obtained the average thickness of the aeolian sediment is 3.25 m by subtraction of the average surface elevation and the elevation of the aeolian sediment bottom interface. Finally, we determined that the volume of aeolian sediment in the experimental area was about 5,850,000 m3. Our study has realized the volume estimation of typical aeolian sediment area in the middle reaches of Yarlung Zangbo River, which has important guiding significance for sand control.

How to cite: Ling, J., Qian, R., Liu, X., Huang, Z., Wang, D., Hu, K., and Zhang, J.: Estimation of aeolian sediment volume in the middle reaches of the Yarlung Zangbo River based on GPR and LiDAR, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5537, https://doi.org/10.5194/egusphere-egu24-5537, 2024.

Climate change continues to impact diverse ecosystems. Drylands stand out as particularly vulnerable environments, as they are highly responsive to key indicators of change. The sensitivity and response time of these regions remain largely unknown, underscoring the need for a deeper understanding of their systems.

Arid regions are considered optimal for Earth Observation based research, primarily due to factors such as minimal anthropogenic disturbance, sparse vegetation cover, and low cloud coverage. These attributes make drylands advantageous for studying and monitoring the impact of climate change, providing valuable insights into these vulnerable ecosystems.

Southern Mongolia stands out as an especially well-suited study area to test novel approaches and to detect land surface changes over both space and time. The basin of Orog Nuur was selected in this study to observe long-term environmental changes, building on significant prior studies conducted around the drainage basin.

Our approach emphasizes the utilization of state-of-the-art earth observation technology to unveil the dynamics of desert ecosystems. This involves cloud-based processing, such as Google Earth Engine and the German High Performance Data Analytics (HPDA) platform “terrabyte”. Throughout the project, we will apply various multispectral and active SAR techniques spanning 50 years to monitor geomorphological processes, ecosystem changes and ongoing surface dynamics linked to climate change indicators. Some of important pillars of the long-term time series analysis can be listed as greening and precipitation events, lake level dynamics, dune movement rates, mapping of sedimentological, geomorphological provinces and aeolian coverage, in order to understand frequency-magnitude relationships.

The findings will be supported by a series of fieldworks covered by UAS campaigns and auxiliary ground-truth sensors, ensuring the accuracy of our estimations by in-situ measurements. Based on the derived surface characteristics, various ecosystems will be defined, and a high-level ecosystem integrity model will be developed. Ultimately, our model aims to represent the intactness, functioning and structure of the different ecosystems within arid regions. Additionally, due to our high temporal study concept, the model will serve as the base for quantifiable measurements of the responsiveness and adaptiveness of the ecosystems.

Having a model for ecosystem intactness not only help to preserve fragile ecosystems but also strengthens the resilience and adaptive capacity of communities. Furthermore, the transferability of our framework to other drylands may also lead to a comprehensive understanding of the arid characteristics.

Keywords: Earth Observation, arid regions, dryland, remote sensing, climate change, impact, geomorphological process, ecological modelling, land surface dynamics

How to cite: Arisoy, B., Ullmann, T., and Stauch, G.: Desert Sensing – Characterizing recent surface dynamics in arid regions through high-performance data analytics of multi-sensor Earth Observation archives and in situ records, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10337, https://doi.org/10.5194/egusphere-egu24-10337, 2024.

Mineral dust aerosol particles are tiny soil particles mobilized and entrained into the atmosphere by wind. Suspended in the atmosphere and transported away from source regions by prevailing wind systems, dust aerosol alters the Earth’s radiation budget, stimulates cloud and precipitation formation processes, and modulates the carbon cycle as it may enhance bio-productivity due to its mineralogical composition. In the light of the manifold dust feedbacks with relevance to the climate, knowledge on the atmospheric pathway of dust from source to sink is essential for accurate climate simulations. Thereby, the spatio-temporal variability of dust source activity, and consequent dust production and entrainment into the atmosphere is of particular interest as dust emission marks the beginning of the atmospheric dust cycle. Although crucial for the understanding of the climate system, detailed knowledge on the interannual variability of dust source characteristics (i.e., emissivity and their susceptibility to wind erosion) and activity (i.e., occurrence frequency of dust emission events and emission fluxes) is still somewhat limited. In particular the impact of changing environmental conditions on dust sources and their emission variability is not fully understood yet and requires further research. This is also of importance in order to assess the spatially and temporally changing contribution of dust sources to the local and regional atmospheric dust burden and related dust feedbacks.

This presentation will provide an overview of different dust source types, their key characteristics, and their response to environmental changes due to climate change with regard to emission flux and dust source activity. It will include examples from remote sensing approaches and dust modelling in order to examine the interannual variability in a changing climate.

How to cite: Schepanski, K.: Mineral dust in the climate system: Dust source types and their response to environmental changes in a changing climate, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11443, https://doi.org/10.5194/egusphere-egu24-11443, 2024.

Aeolian-Fluvial interactions range from aeolian- to fluvial-dominated processes, often resulting in unique morphologies and complex stratigraphies along dunefield margins. In the Northwestern Negev dunefield (Israel) desert, a key factor influencing transitions from aeolian- to fluvial-domination, is the basin size. While medium-sized (40-200 km2) and large (>200 km2) basins were breached before or during the early Holocene, small basins are still dammed by dunes. Often their surficial and buried palaeochannel is comprised of a sequence of remain of dune-dammed water bodies in the form of fossilized playas. Unlike medium and large basins, where incision exposes Aeolian-Fluvial deposits after the dune-dam breaching, small dune-dammed fluvial systems necessitate sampling techniques such as drilling into continuously aggrading Aeolian-Fluvial deposits to reconstruct the stratigraphy and interpret paleoclimate and palaeoenvironmental records. We demonstrate the potential of a SUERC Portable-OSL (port-OSL) for interpreting palaeo-records in small dune-dammed basins.

The Shivta-East basin (3.3 km2) was hand-augered along an ephemeral stream's propagation path into the dunefield, at three disconnected playa-like sediments of seasonal dune-dammed waterbodies. At each dune-dammed waterbody sediments, samples were taken at 15-25 cm intervals and analyzed using the port-OSL reader. Their estimated ages were interpolated according to a calculated regional linear regression based on the northwestern Negev dunefield luminescence age database. This regression, generated by training a data set of thirty-two aeolian sand samples, analyzed for both OSL dating and port-OSL Net counts, accounts for 72% of the age variability, with a standard error of 3.4 ka between the model and the data. Due to the absence of modern-day OSL dated samples, the regression line was reconstructed for the LGM until the early Holocene. The regression model enables dating of the Last Glacial Maximum, Heinrich-1, and Younger Dryas sand incursions, previously described as the main active periods of the aeolian system.

K-means cluster analysis based on the port-OSL signals, reveals three distinct clusters, which points to alternations of the sedimentary units, between sand and fluvial sourced fine-grained sediments. The three clusters are understood to reflect both the mineralogical composition and burial age of the deposits. The overlying cluster mainly consists of fine-grained sediments deposited in the dune-dammed waterbody, while the other two units are sandy deposits.

Interpolation of the sandy samples from all three playas along the palaeochannel in the linear regression demonstrates that during the Heinrich-1 and Younger Dryas events, an aeolian-dominated environment dune-dammed the fluvial system, enabling aeolian sand deposition. Later, coevally with the fluvial system's propagation into the second (middle) dune-dammed waterbody, aeolian domination persisted until the Early Holocene generating the third and upstream dune-dammed waterbody.

This study demonstrates the potential and limitations of the port-OSL reader combined with statistical methods for chrono-stratigraphic analysis of hand-augered samples collected from an altering depositional environment. The ability to rapidly estimated depositional ages and associated palaeoclimatic periods highlights the potential for further exploration of the port-OSL reader in different environmental settings.

How to cite: Greenbaum, N., Robins, L., and Joel, R.: Regional Depositional Age Assessment using Portable-OSL of Hand-Augered Aeolian-Fluvial Deposits along a chain of Small Dune-Dammed Basins in the Northwestern Negev Dunefield Margins, Israel , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12423, https://doi.org/10.5194/egusphere-egu24-12423, 2024.

The Great Central Desert of Iran, located at the center of the Iranian plateau, bears valuable but scattered geological and geomorphological archives. However, the scarcity of data on the paleoenvironment and paleolandscape of this area is attributed to challenging accessibility and harsh climatic conditions. The Khur area in the eastern edge of the Iranian Central desert was selected for this investigation due to its distinctive geomorphological features and improved accessibility.
This study aims to delineate Late Pleistocene-Holocene landscape evolution in central Iran by utilizing sedimentary and morphostratigraphical evidence of aeolian-fluvial sequences. In a first step, geomorphological features were mapped based on satellite imagery, digital elevation models, geological maps and field observations. Subsequently, localities for excavator sections were deduced from these findings, guaranteeing accessibility and further ensuring their incorporation of anticipated stratigraphic key features, including contact zones of distinct geomorphological environments. Stratigraphic description of the excavated profiles was recorded, and sedimentary logs were drawn.
The preliminary results reveal complex interactions of Aeolian, fluvial, and lacustrine morphodynamics during the Late Pleistocene and Holocene. Seven landform groups including aeolian dunes and interdune areas, sandy mud flat, alluvial fans and fluvial plains, dissected fan toe with backward erosional valleys were recognized. Within these, five interfingering sedimentary units were identified based on distinctive geometry and layering and their internal facies distribution: Fluvial flood deposits, well to poorly-sorted alluvial deposits, aeolian sand deposits, fluvially reworked marl (fine-grained mud), paleosol horizons.
In summary, repeatedly changed depositional environments and cyclical climatic changes, where dune development took place during phases of increasing aridity, whereas non-aeolian deposition and paleosol formation might have occurred during more humid conditions and more stable paleosurfaces.
Luminescence dating, sedimentological and geochemical analyses, will determine climatic cycles, sedimentary environments and landscape evolution history.

How to cite: Rashidi Koochi, Z., Büdel, C., Torabi, M., Baumhauer, R., and Fuchs, M.: Towards Late Pleistocen-Holocene stratigraphy and landscape evolution of Khur area, Central IranTowards Late Pleistocen-Holocene stratigraphy and landscape evolution of Khur area, Central Iran, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12653, https://doi.org/10.5194/egusphere-egu24-12653, 2024.

EGU24-13466 | ECS | PICO | GM7.3

Reconstructing timeframes, processes and environmental implications of Late Quaternary aeolian Parna deposition in south-eastern Australia 

Felix Lauer, Samuel Marx, Anthony Dare-Edwards, and Jan-Hendrik May

Sedimentary sequences with major aeolian dust contribution blanket the flat to hilly landscapes of eastern New South Wales. Originally identified by Butler in 1956 within the Riverine Plain and adjoining hills, these widespread clay-rich sediments were termed "Parna”. Parna – which has often been compared to loess – is thought to be fine-grained sediment generated through exogenic processes in arid environments and transported as stable aggregates by prevailing westerly winds during the Quaternary. The primary hypothesized source regions for Parna are arid and semi-arid river and lake systems situated in the western Murray-Darling Basin. Despite the prolonged critical discourse surrounding the concept and terminology of Parna, investigations addressing unresolved questions have been limited, with absolute dating of the aeolian sequences being restricted to only a few sites.

Given the complexity of the Parna sequences resulting from the interaction of aeolian, hillslope and pedological processes, we choose a multimethodological approach combining field observations, grain size analysis, geochronological and geochemical methods to investigate the processes and time frames of sedimentation and sediment provenance. Results of optically stimulated luminescence (OSL) dating for several Parna sites in the Wagga Wagga (Beattie 1972) and Yass region, show age estimates reaching back 150,000 years. Sedimentological parameters are used to distinguish between material derived from local hillslope and aeolian input. Geochemical characteristics will help to trace sources and pathways of the aeolian material. Advancing our understanding of the Parna concept, implying large-scale deposition but also deflation of aeolian material, is one component of reconstructing Quaternary landscape development and environmental conditions in south-eastern Australia.

Butler, B.E., 1956. Parna-an aeolian clay. Australian Journal of Science, 18(5), 145-151.

Beattie, J.A., 1972. Groundsurfaces of the Wagga Wagga Region, New South Wales. C.S.I.R.O Soil. Pub Australia. No. 28.

How to cite: Lauer, F., Marx, S., Dare-Edwards, A., and May, J.-H.: Reconstructing timeframes, processes and environmental implications of Late Quaternary aeolian Parna deposition in south-eastern Australia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13466, https://doi.org/10.5194/egusphere-egu24-13466, 2024.

EGU24-15208 | PICO | GM7.3

Optically stimulated luminescence dating of loess sequences in the Tibetan Plateau and their palaeoenvironmental implications 

Shengli Yang, Li Liu, Qiong Li, Pushuang Li, and Yuanlong Luo

The Tibetan Plateau (TP) is extremely sensitive to climate change. Widely loess deposits distributed in the Tibetan Plateau are important archives for studying the past environmental changes of the Tibetan Plateau. However, little information is understood due to the poorly age constrained of the TP loess. In this study, we use the single-aliquot regenerative dose optically stimulated luminescence (OSL) method, and the post-infrared infrared stimulated luminescence protocol (pIRIR) to date the well-preserved loess–paleosol sequences in the eastern TP and discuss the applicability and reliability of OSL dating of the TP loess for establishing a reliable numerical age framework. We found that quartz OSL signal of TP loess is dominated by fast component, and the equivalent dose can be measured by SAR method. The growth curve shapes and saturation dose shows that the quartz OSL signal in this region saturated at ~200~230 Gy. The prior-IR stimulation plateau test, dose recovery, recycling ratio and recuperation indicated that pIR200IR290 could be used for the equivalent dose estimation of potassium feldspar. Our results contribute to an improved understanding of the TP dust history and paleoenvironmental changes in the Last Glacial cycles.

How to cite: Yang, S., Liu, L., Li, Q., Li, P., and Luo, Y.: Optically stimulated luminescence dating of loess sequences in the Tibetan Plateau and their palaeoenvironmental implications, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15208, https://doi.org/10.5194/egusphere-egu24-15208, 2024.

EGU24-21074 | PICO | GM7.3

Holocene linear dune accumulation in the western Thar desert, India.  

Shashank Nitundil, Abi Stone, Aayush Srivastava, and Komal Songara

The densely populated Thar Desert in the northwestern part of the Indian subcontinent contains a complex spatial pattern of now vegetated dune morphologies. There is a growing dataset of luminescence ages that demonstrates a dominance of Holocene dune dynamics in the preserved record (e.g., Srivastava et al, 2020; Parida et al., 2023; Nitundil et al., 2023). This region is undergoing rapid change in recent decades with widespread flattening of dunes for agricultural land, which is fed by the Indira Gandhi Canal that provides water for irrigation.

 

Our work has developed a training set of >40 samples with published luminescence ages to create a calibration approach for the signals measured using portable luminescence readers (POSL) (Nitundil et al., 2023). Other POSL signal characteristics, such as IRSL:BSL ratios are a good indicator that the Thar sands have a broadly common sedimentary provenance, as well as transport processes and post-depositional histories of mineral weathering. During this work, a rigorous exploration of sediment properties, including moisture content and presence of carbonate was undertaken, and from this, guiding principles for building a calibration curve were developed.

 

Vegetated linear dunes have been sampled in five regions along a ~75 km north-south transect in the western Thar. The POSL calibration has been applied to determine estimated ages for three dunes at the second most northerly site, to shallow depths (2 m) (Nitundil et al., 2023), and from multiple profiles within two dunes at each of three other sites along the transect (a further 19 shallow, 2 m profiles). Fieldwork in September 2023 focussed on obtaining close to full dune vertical profiles via auguring (~10 m depth) from three sites, as well as exploring dynamics across and along a dune using ~0.8 m hand dug pits. This presentation will highlight key findings from the calibration exercise, and present POSL-based ages estimates across the western Thar to explore what they reveal about Holocene dune accumulation in this region. 

 

References

Nitundil, S., et al. (2023) Applicability of using portable luminescence reader for rapid age-assessments of dune accumulation in the Thar desert, India. Quat. Geochron. 78, 101468.

Parida, S. et al. (2023) Luminescence Dating of Dunes in the Western Thar Desert:  New Data and Regional Synthesis. XXI INQUA Congress, 14-20th July 2023, Rome, Italy.

Srivastava, A., et al. (2020) Holocene palaeoenvironmental changes in the Thar Desert: An integrated assessment incorporating new insights from aeolian systems. Quat. Sci. Rev. 233, 106214.

 

How to cite: Nitundil, S., Stone, A., Srivastava, A., and Songara, K.: Holocene linear dune accumulation in the western Thar desert, India. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21074, https://doi.org/10.5194/egusphere-egu24-21074, 2024.

EGU24-21086 | PICO | GM7.3

S.A.N.D.S. - Surface Archaeology on the Namib Desert Surface.  

Abi Stone, Dominic Stratford, Ted Marks, Rachel Bynoe, Kaarina Efraim, Eugene Marais, Rachel Smedley, and George Leader

The hyper-arid Namib Sand Sea (NSS) represents a significant challenge to human occupation, yet, despite these challenges, Early Stone Age (ESA) and Middle Stone Age (MSA) tools are found across this landscape. Whilst surface scatters are hindered by a lack of clear stratigraphy, they provide a spatially integrated record of the structuring of landscape use through time and relationships to sources of raw material and water. Omitting such sites leads to bias in our interpretations of early hominin distribution. We are investigating how and why early hominins were moving into the northern NSS, starting with two interdune pan sites: Namib IV (Leader et al., 2023) and Narabeb. Here we set out the context of these archaeological sites, the stratigraphies observed and our emerging luminescence chronologies for the sedimentary sequences.

 

To establish the palaeoenvironmental context of the lithics (both ESA and MSA) and fossil fauna at Namib IV we dug a series of test pits to explore the sedimentological record. The Namib IV surface has a complex meso-topography with a spatially-patchy, resistant calcareous surface unit, and our test pits reveal a similarly complex sedimentary record across space. This includes the preserved remnant of an aeolian slip face, and elsewhere a number of horizontally bedded units beneath surface calcareous layers. 13 samples from Namib IV were selected for luminescence dating, using pIRIRSL feldspar methods, anticipating ages close to quartz saturation (e.g. Stone et al. (2010) in this region). Narabeb contains predominantly MSA lithics. North (~2 km) of the artifact collection area is a prominent ‘ledge’ of interbedded muds and sands, previously dated using quartz OSL (Stone et al., 2010). We dug two small geotrenches associated with surface calcareous exposures, taking samples for pIRIRSL dating along with two sampling points in the lower unconsolidated dune flank. We also date a sample from the Stone et al. (2010) sequence using pIRIRSL (K fieldspar) to revise the saturated quartz luminescence age estimate.

 

References

Leader, G.M., Bynoe, R., Marks, T., Stone, A., Efraim, K., Stratford, D., Marais, E. (2023) Revisiting the Acheulean at Namib IV in the Namib Desert, Namibia. Journal of Field Archaeology 48(5), 380-394.

Stone, A., Thomas, D.S.G., Viles, H.A. (2010) Late Quaternary palaeohydrological changes in the northern Namib Sand Sea: new chronologies using OSL dating of interdigitated aeolian and water-lain interdune deposits. Palaeogeography, Palaeoclimatology, Palaeoecology 288 (1-4), 35-53.

How to cite: Stone, A., Stratford, D., Marks, T., Bynoe, R., Efraim, K., Marais, E., Smedley, R., and Leader, G.: S.A.N.D.S. - Surface Archaeology on the Namib Desert Surface. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21086, https://doi.org/10.5194/egusphere-egu24-21086, 2024.

Suspended sediment load in rivers has a crucial impact on the river water quality, soil erosion, irrigation activities, and dam or reservoir operations. Dam construction in a river reduces the runoff, which increases the deposition of suspended sediment on the river course and ultimately leads to a change in the river channel morphology. Thus, suspended sediment load prediction is significant for planning and sustainable management of the riverine ecosystem. Researchers have used various physical models, such as sediment rating curves (SRC), SWAT, HEC-RAS, HEC-HMS, etc., for predicting suspended sediment load. Recently, researchers have used machine learning models to predict suspended sediment load in different hydroclimatic regions worldwide. In this study, we used five different machine learning models, such as ElasticNetCV, Multi‑Layer Perceptron (MLP) Regressor, Extreme Gradient Boosting (XGB) Regressor, Light Gradient-Boosting Machine (LGBM) Regressor and Linear Regression (LR), for predicting suspended sediment load in a downstream station of Godavari River Basin (GRB). The GRB is the largest Indian peninsular river basin, covering more than 0.3 million square kilometers of area. We used the 'Lazy Predict' Python library to achieve better results for machine-learning modeling. The data was collected for the period of 1970–2018 and divided into two parts, viz. pre-1990 and post-1990, to consider the dam effects on the downstream regions of the GRB. Performance evaluation revealed that the Multi‑Layer Perceptron (MLP) Regressor performed very significantly, with an r-square value of 0.71 and 0.74, respectively, for pre-1990 and post-1990. The developed models offer a valuable resource for decision-makers, environmental scientists, and water resource managers seeking to proactively manage sediment-related issues in river systems, ultimately fostering sustainable water quality and ecosystem health.

How to cite: Kundu, S., Swarnkar, S., and Agarwal, A.: Application of Machine-Learning Based Models for Prediction of Suspended Sediment Load in the Indian Peninsular River Basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1117, https://doi.org/10.5194/egusphere-egu24-1117, 2024.

EGU24-1900 | Orals | GM5.3 | Highlight

Large Scale Modification of the Salton Sea Shoreline to Reduce the Potential for Dust Emissions 

John Gillies, Eden Furtak-Cole, and George Nikolich

The Salton Sea in California’s Imperial and Riverside counties is a large endorheic lake with significant areas of exposed shoreline.  The exposed shoreline and surrounding desert are potential sources of wind-blown dust that can contribute to degraded air quality as the emissions create high concentrations of particulate matter ≤10 µm in aerodynamic diameter (i.e., PM10), which is a federally regulated pollutant in the USA.  The Salton Sea’s water surface height is lowering at an accelerating rate.  The decreasing volume of water leads to increased shoreline exposure with the potential for high wind speed events to cause dust emissions. This increases the potential for degradation of air quality with respect to PM10 mass concentrations within the basin potentially elevating the health risk to the surrounding population.  The State of California has implemented the Salton Sea Management Plan that has several phases of development to protect air quality and ecosystem values at the Salton Sea.  California Department of Water Resources (DWR) began a series of projects at the Salton Sea designed to limit dust emissions from shoreline areas deemed vulnerable to wind erosion and dust emissions based on evaluation of soil textural properties and in situ measurements of PM10 emissivity.  To protect sandy surfaces vulnerable to wind erosion, surface roughening based on the super-positioning of non-erodible roughness elements onto the exposed sediments of the shoreline has been implemented.  The non-erodible elements are bales of straw sourced from agricultural producers in the vicinity.  They are rectangular prisms of dimensions 0.41 m high, 1.12 m long, and 0.55 m wide. 

To evaluate the effectiveness of the roughness arrays, designed initially to offer 95% reduction in sand transport and dust emissions compared to the unprotected surface, computational fluid dynamics modeling was carried out to quantify the reduction in surface shear stress and dust emission potential due to the presence of the roughness.  In addition, in situ measurements of sand flux and PM10 concentrations were collected to corroborate the simulation results.  Air flow across the roughness array for three freestream wind speeds and three wind direction angles was simulated using CFD in OpenFOAM.  The mean shear stress reduction compared to the surface without roughness for the three freestream wind speeds and wind directions was 62% (±1%), 66% (±0.2%), and 79% (±1%), for 225°, 270°, and 315° wind directions, respectively.  The greatest probability for high wind speed events is expected from the wind direction range 225° to 315°. The mean reduction in total PM10 emission for these three conditions were: 73% (±4%), 85% (±2%), and 80% (±2%).  In situ measurements suggest control effectiveness is even greater as saltation has not been recorded within the roughness for the range of observed wind speed, and there is no indication that PM10 has been emitted from the protected surfaces.  This suggests that large size superposed roughness has effectively modified the dust emission potential of these susceptible surfaces and provides the protection needed to ensure that the exposed shoreline does not contribute to the regional PM10 burden.

How to cite: Gillies, J., Furtak-Cole, E., and Nikolich, G.: Large Scale Modification of the Salton Sea Shoreline to Reduce the Potential for Dust Emissions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1900, https://doi.org/10.5194/egusphere-egu24-1900, 2024.

Sand mining has accelerated in recent years primarily due to population increase and rapid urbanization. To meet demand, the rate of sand extraction often exceeds the rate of natural replenishment with serious environmental consequences. In this review paper, the Vietnamese Mekong Delta (VMD), a global hotspot for sand mining with a prolonged history of intensive riverbed extraction, is used as a representative case study to highlight the extent and compounded impacts of this activity. Sand mining budgets from literature present significant discrepancies, with estimates for the entire delta varying from around 8.5 to 42.2 Mm3/yr. These variances can be attributed to the challenges in the actual measurement of mining rates and the deployment of disparate methods across studies. Moreover, the widespread practice of illegal sand mining in the region further exacerbates the mismatch in budget calculations. Consequences of such mining activities manifest as deeply-incised riverbeds leading to riverbank and coastal erosion. Moreover, the massive sediment removal has resulted in river water level reductions, disrupted hydrological connectivity, and diminished floodplain inundation. The augmented backwater effect, a result of riverbed lowering, amplifies saltwater intrusion in dry seasons. While the physical and hydrological impacts have received attention, studies on the ecological and societal ramifications remain sparse. These impacts, further magnified by factors like upstream dams, irrigation infrastructures, excessive groundwater extraction, and sea-level rise (SLR), present a multifaceted challenge. This paper concludes by advocating for the adoption of remote sensing-based approaches for effective mapping of sand mining activities, and implementation of sustainable sand harvesting practices to balance developmental needs with environmental conservation.

How to cite: Park, E.: Sand mining in the Mekong Delta: Extent and compounded impacts, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2678, https://doi.org/10.5194/egusphere-egu24-2678, 2024.

EGU24-4096 | ECS | Orals | GM5.3

Assessing river corridor changes after anthropogenic vegetation removal: an object-based mapping approach 

Katarina Pavlek, Mateo Gašparović, and Ronald E. Poeppl

The development of remote sensing technologies and image classification methods has facilitated research on changes in river channels and floodplains by automating mapping of land cover and geomorphic units. In often highly heterogeneous river environments, object-based approaches proved sensible, since they are based on objects produced by image segmentation rather than on individual pixels.

This study uses object-based image analysis to investigate land cover and river channel dynamics in the managed corridor of the Orljava River in the Pannonian basin (Croatia). In the last decade, the river has been affected by anthropogenic removal of riparian vegetation to increase channel capacity, which was followed by a big flood event. Five river corridor classes (water, bare soil, sparse vegetation, dense vegetation, and shadows) were classified based on RGB and near-infrared (NIR) aerial images in the period 2011-2021. A digital surface model generated from the images was used to separate bare river channel units (“river sediments”) from bare soil in the floodplain and to define high vegetation, while agricultural land was classified manually. The accuracy of the produced maps was between 85 and 93%, except for the year 2014 which lacked the NIR band. Based on classified river corridor units, changes in channel morphology were further analysed in GIS. The two main phases of river corridor changes were caused by the occurrence of a big flood in 2014. In 2011-2014, immediately after the flood, a significant increase in the area of water and river sediments was recorded, mostly at the expense of bare riverbanks and adjacent agricultural land. Large in-channel bars have formed due to sediment accumulation, as well as significant channel migration has been recorded. Contrarily, in 2014-2021 lower discharges allowed gradual channel narrowing and stabilisation, characterised by the spread and growth of vegetation in the river corridor.

Observed changes in channel morphology and vegetation succession are natural processes related to actively meandering rivers. However, it has been shown that extensive bank erosion during the flood and subsequent land cover dynamics were primarily triggered by anthropogenic removal of riparian vegetation exemplifying how inadequate and isolated river management decisions may increase bank erosion and lead to a loss of agricultural land in floodplain areas.

How to cite: Pavlek, K., Gašparović, M., and Poeppl, R. E.: Assessing river corridor changes after anthropogenic vegetation removal: an object-based mapping approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4096, https://doi.org/10.5194/egusphere-egu24-4096, 2024.

EGU24-4572 | ECS | Posters on site | GM5.3

Human impact on grain size variations of river gravel bars in the western Himalaya: Insights from a UAV survey 

Narendra K. Patel, Fritz Schlunegger, David Mair, Pitambar Pati, and Ariel Henrique Do Prado

Downstream variation in bed material size was investigated over a stretch of the Yamuna River in the western Himalayan region in India. Data on grain size distribution along rivers are critical for understanding river systems and material transport. Flow regulation caused by dam construction can alter sediment transport mechanisms, generating morphological changes. Using an uncrewed aerial vehicle (UAV), we investigated precise grain size variation along the Yamuna River and its tributaries in the Siwalik region, from Lakhwar Dam to Hathni Kund Barrage. All photos were collected via UAV survey.

On these datasets, grain size variation was observed across dams. The upper Yamuna River's bed-load sediments are becoming finer-grained downstream. Since the dam barrier and low flow energy force large particles to remain above the dam, smaller particles are found downstream of the dam. During the survey, evidence of mining in several locations along the river suggests the influence of anthropogenic activity in the regions. Accordingly, this study sheds light on the potential consequences of dam construction on material transportation. We observed that dams work as a barrier for coarse grain particles, which may have an impact on the dam in the near future. Field evidence and preliminary processed data indicate that the size of the gravel bar along the river course has been modified by many human interventions (hydroelectric dams, barrages, mining).

How to cite: Patel, N. K., Schlunegger, F., Mair, D., Pati, P., and Prado, A. H. D.: Human impact on grain size variations of river gravel bars in the western Himalaya: Insights from a UAV survey, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4572, https://doi.org/10.5194/egusphere-egu24-4572, 2024.

Already at the end of the 19th century, initial approaches were carried out to estimate the extent of anthropogenic mass transfer by humans on a global scale. In the course of the proposal of a new geological epoch, the Anthropocene, which is controversially discussed since the 2000s, anthropogenic geomorphological changes have received new attention. According to this concept, humans are moving more rocks and sediments worldwide than natural processes, with a supposed exponential increase in the mid 20th century. Along with agriculture, mining activities are among the most important anthropogenic transformations of the earth's surface. Mining landscapes have become at many locations an integral part of landform development and a crucial element of the technosphere. In the framework of the Anthropogenetic Geomorphology, humans are considered as geomorphological agents, creating a variety of landforms, for which at the same time new classifications are needed.

In the present project an interdisciplinary environmental-historical approach is used to examine the question of when, how and to which extent humans have modified the relief landscape. As study area, the Harz Mountains in Northern Germany were selected, which represents one of the most important historical mining areas in Central Europe, especially for silver, lead and copper. They are a key region for the interconnectedness of human-nature interactions, which are reflected in a genetically complex landscape development. Humans have influenced the landscape of the Harz Mountains already since prehistorical times to varying extents. Distinct phases of landscape transformation will be distinguished in this study. However, one of the most significant landscape changes took place in the Early Modern Period, when the Harz became one of the largest industrial areas in Central Europe with some of the deepest shafts worldwide at that time and large-scale underground excavations. The main driver for the exploitation of ores was the interlinkage with the global metal trade and the arise of new economic and political systems during the Renaissance, whereas the mining operations mainly relied on the local availability of certain resources such as wood and water. The energetic base for the underground mining, reaching up to almost 1000 m below the earth surface, was the Upper Harz Water Management System, the largest historical energy supply system for mining, designated as UNESCO-World-Heritage site in the year 2010.

In a case study in the St. Andreasberg Mining District (West-Harz) as one of the centers of silver mining, the physical landscape changes are systematically examined in the context of litho-geomorphological, ecological and cultural-political aspects and in their spatio-temporal patterns. The focus of the study presented here lies on the type and dimension of subterranean relief changes in the lithosphere in connection with the correlating transformation of the reliefsphere and the hydrological system in the catchment area of the Oder-Sieber River system. The mining landscape is composed of anthropogenic landform assemblages, consisting of heterogeneous compositions of lithogenic, geomorphological, biogenic and aquatic elements, which are representative for the Upper Harz mining landscape.

 

How to cite: Iturrizaga, L. and Ließmann, W.: Anthropogenic landscape transformations and geomorphological landform assemblages in the context of historical mining in the Harz Mountains (Germany): Case study Sankt Andreasberg Mining District , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6818, https://doi.org/10.5194/egusphere-egu24-6818, 2024.

EGU24-9614 | ECS | Posters on site | GM5.3 | Highlight

The influence of anthropogenic topographic changes on geomorphological processes in the city of Rome (Italy) 

Michele Delchiaro, Francesca Vergari, Carlo Esposito, and Maurizio Del Monte

The urban landscape of the city of Rome exhibits a discernible urban-rural gradient, characterized by a diminishing anthropic impact from the central historic city to the outskirts and peri-urban zones, marked by increased open spaces and green areas. In the Aeterna Urbs, the Anthropocene epoch has seen significant urbanization and infrastructure development, frequently leading to profound alterations or complete obliteration of natural landscapes. The distinctive anthropogenic changes observed in Rome, characterized by their unique features, are not confined to the city; they are also evident in other contexts, underscoring commonalities and interconnections in how human activity shapes the landscape. In this regard, the city of Rome stands as an exemplar, offering a unique opportunity to delve into the human-induced changes and their impact on the natural geomorphological processes. However, despite their critical importance in understanding human-landscape interactions and the associated geomorphological risks, the role of human activity as a morphogenetic agent along the urban-rural gradient remains inadequately understood. This study addresses the tricky understanding of human-induced geomorphic changes, particularly on erosion, transport, and sedimentation processes, which pose threats to ecosystem functioning and impede efficient land use. The Malagrotta extraction area in Rome, Italy, characterized by a mining landscape of ridge removal, hillslope terracing and valley filling, offers a unique opportunity to assess the impact of topographical alterations on the geomorphic system. The investigation employs the widely accepted functional relationship between drainage area (A in m2) and slope (S in m/m) to delineate local process domains and facilitate the interpretation of process interactions. The slope-area function is applied to the same watershed across different periods using digital elevation models, offering insights into the evolving geomorphic dynamics influenced by human activities.

How to cite: Delchiaro, M., Vergari, F., Esposito, C., and Del Monte, M.: The influence of anthropogenic topographic changes on geomorphological processes in the city of Rome (Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9614, https://doi.org/10.5194/egusphere-egu24-9614, 2024.

The Bonneville Salt Flats, a landscape characterized by a perennial halite crust and seasonal flooding in western Utah, USA, provides a natural laboratory for advancing understanding of the processes that create and change dynamic saline environments. A decade of interdisciplinary research on the Bonneville Salt Flats has resulted in a new understanding of the salt's history, the functioning of the salt crust ecosystem, and the role that humans play in shaping this landscape. Sedimentological analyses of cores collected across the salt has changed our understanding of the history of the landscape, including evidence of extensive erosion after Pleistocene Lake Bonneville, the surprisingly young age of the oldest salt (~5.4 cal ka BP), and historical and ongoing crust halite dissolution. 16S rRNA gene and metagenomic analysis of the salt crust reveals a complex and robust microbial and archaeal ecosystem within the salt, hosting a wide range of metabolic pathways that actively cycle C, N, and S through the landscape. A long-term environmental observation station established at the center of the salt crust provides a robust new record of landscape processes, weather data, and eddy covariance flux measurements that have helped to constrain the energy and water budgets and highlight the sensitivity of ecosystem-scale surface conductance in the absence of vegetation to atmospheric drying. Arial and spaceborne remote sensing data show the impacts of over a century of human activities on landscape composition and texture, including groundwater extraction for potash mining, intensive surface modification, and land use associated with high-speed vehicle racing on the salt. Brine extraction and attempted mitigation have resulted in salinity and salt crust extent decreases over the last several decades, potentially limiting future landscape uses. The intricate interconnection of the human-natural system has enabled the exploration of variations in mental models influencing decision-making, attribution of blame, and the feasibility of adaptive management in dynamic landscapes serving diverse and conflicting needs. Integration of science with art has expanded the nature of the inquiry and led to new ways of thinking about human connections to a seemingly barren, but truly alive, place. All of these new insights into saline landscapes and the role that human land use and climate change play in altering processes are significant to understand as water delivered to closed basin saline lakes globally is in decline, potentially leading to an expansion of exposed salt-encrusted landscapes.

How to cite: Bowen, B.: A decade of interdisciplinary research on the dynamics of surface processes and landscape change at the Bonneville Salt Flats, Utah, USA, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9915, https://doi.org/10.5194/egusphere-egu24-9915, 2024.

EGU24-11466 | Posters on site | GM5.3

The impact of anthropogenic activities on the geomorphological evolution of the Taro River over the last 70 years 

Vittoria Scorpio, Alessandra Cervizzi, and Sharon Pittau

Human pressures, in response to economic development and population growth, have been one of the main drivers of river systems changes especially since the second half of the last century. In the European context, anthropogenic impacts mainly concern with catchment land use changes, in-stream gravel mining, and in-channel works construction. The reconstruction of the past evolutionary trajectories and the temporal analysis of driving factors is considered fundamental to understand present river conditions, to support channel network management and to anticipate future changes.

The aim of this study is to investigate the anthropogenic factors that have impacted the geomorphological evolution of the Taro River (Northern Apennines, Italy) over the last 70 years.

Traditional methods based on multi-temporal orthophoto (1954, 1976, 1988, 1994 and 2020) analysis in GIS environment were used for studying historical channel changes along a channel segment 90 km long. Analyses of anthropogenic factors that may have influenced changes in the active channel included: (i) analysis of land use changes at the catchment scale, (ii) quantification of gravel mining activities, and (iii) analysis of in-channel work constructions.

Results showed that between 1954 and 1976 the Taro River channel width decreased by 39% on average, mainly in response to gravel mining activities, and subsequently to the increase of works into the channel. To the contrary, as a result of mining activities abandonment in the early 1980s, and of the occurrence of an extreme flood event in 1982, an increase of 18% in the active channel width was observed in 1988. The decreases in active channel width in the last 30 years (since the end of the 1980s) were correlated with the increase in forested areas in the catchment and with the increasing degree of stabilization of channel banks.

These studies are fundamental to identify management solutions in degraded rivers and to anticipate impacts in such rivers still featuring poorly impacted channel morphologies.

How to cite: Scorpio, V., Cervizzi, A., and Pittau, S.: The impact of anthropogenic activities on the geomorphological evolution of the Taro River over the last 70 years, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11466, https://doi.org/10.5194/egusphere-egu24-11466, 2024.

This study contributes to the topic of land surface degradation due to touristic activity by documenting examples of trail impacts related to initial trail development and high-intensity visitor usage. Our observations are based on a case study from the tropical Andes - Peru’s Rainbow Mountain (also named Vinicunca or Montaña de Siete Colores), which became a world-renowned tourist destination in recent years (after 2015/2016). The topic is important, as such high-mountain settings are very fragile, and degradation can occur rapidly – with long-term repercussions, as these landscapes tend not to recover quickly.

The main objectives of the study were to: (1) characterise and map different types of impacts related to direct visitor pressure, (2) document and evaluate activities aimed at limiting degradation while enhancing visitors’ experience, and (3) propose a conceptual model of trail functioning in the tropical high-mountain environment. Data were collected using ground-based surveys, unmanned aerial vehicle (UAV) and high-resolution satellite images.

Eight processes were responsible for transformation of the land surface: (1) trampling, (2) abrasion/shearing by visitors and service animals, (3) transformation of water and sediment circulation, (4) water erosion, (5) freeze-thaw cycles, (6) dry-wet cycles, (7) aeolian activities, and (8) mass movements. The five main trail impacts clearly visible in the landscape just after 1–2 seasons of intensive recreational use were: trail widening, trail incision, formation of braided trail networks, development of muddy sections, and development of informal (visitor-created) trails.

The hiking path was characterised by a width below 2 m and a low incision (<0.1 m incision on 80% of its length). The equestrian path was much wider (up to 17 m) and slightly more incised (<0.3 m incision on 69% of its length). The width of the multi-use path was up to 24 m. We suggest that the location of the trail in relation to the main geomorphological elements of the landscape (valley bottom vs slopes) and trail alignment to the terrain gradient have an essential impact on trail functioning and degradation. Specifically, trail sections routed through flat terrain and without lateral restrictions tend to widen and develop muddy sections, while sections routed parallel to steep slopes were prone to incision. Trails transverse to the terrain gradient were better drained but often developed into several parallel paths.

Undertaken trail management aimed to reduce negative visitor impacts and improve their safety and satisfaction. Successful measures included hardening the trail tread and marking the trail edges, which limited visitor dispersion and stabilised trail conditions. Partially successful actions involved installing artificial drainage (only partly preventing muddy section development) and providing separate paths for pedestrians and equestrians. After this change, the pedestrian trail was narrow and stable, but the equestrian path continued to degrade. Attempts to change visitor traffic patterns by relocating parking and abandoning a section of the trail were unsuccessful, as the new road and parking, and a new additional trail segment further degraded the landscape. Moreover, geomorphological processes continued to transform the abandoned trail section.

This study was funded by National Science Centre, Poland, project 2021/43/B/ST10/00950

How to cite: Tomczyk, A. and Ewertowski, M.: Land surface changes in response to touristic activity in the fragile, high-mountain environment: a case study of Vinicunca (Rainbow Mountain) in Andes, Peru, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12407, https://doi.org/10.5194/egusphere-egu24-12407, 2024.

Palaeochannels offer a glimpse into the history of a landscape. In the context of shifting perspectives from traditional hard engineering to soft nature-based measures, modern flood risk management could benefit from an understanding of the natural processes and features preserved within palaeochannels, which have otherwise been hidden by a legacy of engineering and land management on the river and floodplain. This study uses geophysical surveying techniques to bridge the gap between surface topography LiDAR data and sediment core data, in order to investigate the evolution of past rivers and tidal inlets in the Somerset Levels coastal plain and inland wetlands in southwest England. Case studies from a range of palaeochannels across the Somerset Levels are presented to identify the advantages and limitations of applying the methodology to a coastal plain and wetland dominated by Holocene alluvium and increasing human influence over the past several centuries. Four river systems represent both tidally dominated and inland freshwater conditions: a large tidal creek system within predominantly clay sediment; an inland river system traversing a peat wetland which was the former course of a major drainage network before intentional diversion; and two systems at the transition between tidal and freshwater influence.

Two-dimensional subsurface profiles derived from electrical resistivity tomography (ERT), shallow seismic refraction traverses, and ground penetrating radar (GPR) are used to laterally connect one-dimensional vertical sediment core data, and then integrated with the surface topography LiDAR data to construct channel and floodplain cross-sectional models. Past geomorphological processes – such as lateral migration, channel adjustment, and avulsion – are revealed in the preserved channel sediments, indicating responses to the contemporary climatic and anthropogenic conditions. Geophysical survey designs for identifying fluvial-geomorphological processes and features within palaeochannels are discussed, along with the need to adapt survey design for best resolution and depth in different, peat-dominated or clay-dominated, sedimentary settings. ERT is shown to consistently provide excellent depth penetration and estimations of channel extent. High resolution GPR data at the near-surface can be used in tandem with available core data to delineate the channel fill and bank geometry and calibrate depth estimations.

Flow conditions are reconstructed quantitatively using palaeohydrological drainage equations based on cross-sectional area values derived from the geophysical profiles. This avoids reliance on oversimplified cross-section estimates based upon surface parameters such as width and meander length, and one-dimensional depth estimates from core profiles. Existing hydraulic and drainage regime equations are tested against flow gauge data and channel measurements from active rivers to obtain optimal parameters for palaeohydrological calculations. These parameter estimates also benefit from on-the-ground channel parameter measurements in tandem with topographic remote-sensing. Hence, this study proposes a novel methodology that integrates geophysical surveying within palaeohydrological estimation techniques to improve models over long timescales of past fluvial environments that have been modified by humans.

How to cite: Anthony, J.: A geophysical study of palaeochannels on the Somerset Levels coastal plain and wetland to explore river landscape evolution., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12508, https://doi.org/10.5194/egusphere-egu24-12508, 2024.

EGU24-13659 | ECS | Orals | GM5.3

Testing a low-complexity model to decompose the multitemporal dynamics of soil erosion and sediment delivery in agricultural catchments 

Francis Matthews, Panos Panagos, Arthur Fendrich, and Gert Verstraeten

Testing and improving the capacity of soil erosion and sediment delivery models to simulate the response of soil erosion to the intra-annual dynamics of climatic drivers and disturbances (e.g., vegetation clearcutting, tillage events, wildfires) is critical to understand intolerable soil loss and catchment sediment yields. Here, we approach the trade-off between the need for model simplicity and temporally dynamic predictions by testing the ability of a low-complexity, spatially distributed model (WaTEM/SEDEM), to decompose the 15-day dynamics of soil erosion and sediment yield. A standardised RUSLE parameterisation and model implementation routine was applied to four arable-dominated catchments in North-West Europe with open-access validation data. We firstly show that when applied to simulate the multitemporal dynamics of sediment delivery, a standard assumption of a temporally static transport capacity within the model structure mostly cannot adequately replicate the multitemporal variability of sediment delivery. Instead, optimising a 5-parameter splines curve to determine the temporal profile of the transport capacity coefficient (ktc) based on the monthly average sediment yield improved the model performance and revealed clear seasonality in the sediment transport efficacy. Despite simulating similar temporally aggregated sediment yields, the introduction of seasonal dynamics into the transport capacity further caused a net reduction in the magnitudes of the spatially distributed sediment fluxes, compared to a temporally lumped approach. Published catchment observations infer this seasonality in sediment transport efficiency to attribute abundant vegetative boundaries in summer and increased soil crusting and runoff promotion in winter. Models operating at temporally aggregated timescales should account for the possibility of decoupling in time and space between gross erosion and sediment delivery related to these alternations between transport- and detachment-limited sediment transport capacity states. Despite the complexities and uncertainties involved in the temporal downscaling of WaTEM/SEDEM, we show the utility of this approach to: 1) link optimised multitemporal parameters to key missing model information components which may reduce error in gross erosion predictions (e.g. more consideration of antecedent soil conditions), 2) form a basis for strategically adding physical process-representation, with a focus on maintaining low model complexity while improving predictive skill, and 3) better understand the interdependencies between spatial fluxes and multitemporal dynamics when undertaking model predictions at large spatial and temporal scales.

How to cite: Matthews, F., Panagos, P., Fendrich, A., and Verstraeten, G.: Testing a low-complexity model to decompose the multitemporal dynamics of soil erosion and sediment delivery in agricultural catchments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13659, https://doi.org/10.5194/egusphere-egu24-13659, 2024.

Tailings are a by-product of the processing of minerals. Tailings can be highly erodible and transportable via fluvial processes and are commonly stored in ‘tailings dams’ which are a feature of many mine sites. These dams and their impounded material will become permanent geomorphic features in the post-mining landscape. The question examined here is - can tailings dams ever be walk-away structures? Tailings dams can fail by both catastrophic and gradual failure. Catastrophic failure occurs when there is a large scale rapid structural failure of the dam wall. Gradual failure occurs over time by slow infilling of the dam and the erosion of the dam wall. This can lead to overtopping of the dam wall and gully incision and failure of the wall and release of sediment to the environment. To understand failure modes and risk profile, computer based Landscape Evolution Models (LEMs) can be used. LEMs have become common tools to quantify risk for mine waste rock dumps and waste repositories.  LEMs provide detailed information on erosion rates, type of erosion and where erosion is likely to occur. They inform long-term behaviour which allows designs to be tested and improved. Here they are used to assess tailings dams where the strengths and weaknesses of different tailings dams designs are examined across a range of climates and material settings. The results show that if well-designed and assuming a well understood climate, a dam can be sufficiently robust to last centuries. However, failure can occur under different climate settings. Modelling also demonstrates that upon failure water quality will be affected for many centuries post-breach if no remedial work is conducted. Longer term, the tailings can be contained if there is maintenance and or an increase in the dam wall height over time or a more robust dam wall constructed to manage extreme events.

How to cite: Hancock, G. and Coulthard, T.: Assessing tailings dam long-term failure risk using computer based Landform Evolution Models , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14575, https://doi.org/10.5194/egusphere-egu24-14575, 2024.

EGU24-15250 | ECS | Posters on site | GM5.3

Legacy effects of post-storm silvicultural treatments on plot-scale soil erosion in a subalpine headwater catchment of the Italian Alps 

Kenta Koyanagi, Giovanna Nordio, Andrea Andreoli, Enrico Tomelleri, Ronald Pöppl, and Francesco Comiti

Wind-disturbed mountain forests are often subject to artificial deadwood extraction and tree planting to accelerate the recovery of timber resources. However, little is known about to what degree and extent those post-storm silvicultural treatments modify the surface processes of wind-affected hillslopes. This study aims to understand how post-storm silvicultural treatments affect soil erosion from wind-disturbed mountain forests by coupling monitoring and modeling approaches. We continuously collected and measured soil losses from four 4.5-m-wide and 6.0-m-long bounded field plots located on wind-disturbed hillslopes with a slope angle of 45 % in a subalpine headwater of the Italian Alps during the vegetation periods from 2021 to 2023. The dominant ground cover of four plots resulting from altered post-storm interventions is characterized by residual deadwood, native herbs, 20-year-old plantation, and 5-year-old plantation, respectively. During 75 analyzed storm events, average soil loss from the native herbs-covered plot (2.4 t ha-1; SD: ±3.5 t ha-1) was the smallest, followed by plots covered with residual deadwood (mean±SD: 3.1±2.9 t ha-1), 20-year-old plantation (mean±SD: 3.5±5.2 t ha-1), and the 5-year-old plantation (mean±SD: 4.5±4.2 t ha-1). Moreover, linear regression models (p-value < 0.001) indicated that two plantation plots potentially yield 2-fold sediment of naturally regenerating deadwood and herbs-covered plots as storm rainfall depth increases. Our three-year field observations highlight the persistent impact of post-storm forest management activities in accelerating soil erosion potentially even 20 years after their implementation. In the next step, the Water Erosion Prediction Project (WEPP) model will be used to further investigate the effect of human treatments on hydrology and sediment transport in storm-affected mountain areas.

How to cite: Koyanagi, K., Nordio, G., Andreoli, A., Tomelleri, E., Pöppl, R., and Comiti, F.: Legacy effects of post-storm silvicultural treatments on plot-scale soil erosion in a subalpine headwater catchment of the Italian Alps, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15250, https://doi.org/10.5194/egusphere-egu24-15250, 2024.

As the number and quality of satellite data detecting the Earth increases, a significant number of research fields are using these images, providing increasingly interesting results that were previously unimaginable. In this study, we extract the coastline from satellite images captured over a long period of time and analyze how the location of the coastline has changed in time and space.

Recently, many studies have attempted similar analyzes. However, the resolution of the image is low, so the results tend to be unreliable, as they often produce trend results of less than cm per year. Therefore, in this study, we first analyzed how reliable the trend results are depending on the amount of data, even if the resolution is low.

We also present a method to obtain the location of the coastline from reference points fixed behind the coast by linearly fitting nearby coastline points to reduce the error of coastline points extracted from satellite images. This method obtains the coastline position as the distance to the intersection of the base line and the fitting line and obtains the coastline gradient as the angle of the fitting line.

This method was applied to Wonpyeong-Chogok Beach located in the East Sea of the Korean Peninsula to analyze how the coastline has evolved over the past five years from 2019 to 2023, when coastal structures were built. On this beach, which has a total length of 2.9 km, three submerged detached breakwaters, two emerged detached breakwaters, and three groynes were built to reduce beach erosion. Reference points are located about 100 m behind the circular line that best fits the coastline, and the direction of base line is fixed to face the center of the fitting circle. Behind the emerged detached breakwater, the rate of change is up to 6.2m per year, and even in areas where structures have not yet been installed, there is a slight forward trend (0.4m/yr) due to the influence of beach nourishment. The standard deviation of the coastline position data for each base line ranges from 4.0m to 10.6m. Recently, Lim et al. (2022) presented the relationship between the standard deviation of the coastline data and sand grain size, and compared to the sand grain size results collected in the field, the grain size value was shown to be larger. The reason is that if the annual mean coastline is not maintained and continues to advance, the standard deviation increases. Considering this effect, the results are compared with observed sand gain size data. Therefore, it will be interesting to see how feasible it is to estimate the sand grain size from the analysis of long-term shoreline data obtained from satellite data, as in the results of this study.

 

 

Reference

Lim, C., Kim, T.-K., Kim, J.-B., and Lee, J.-L. (2022). A study on the influence of sand median grain size on the short-term recovery process of shorelines. Front. Mar. Sci. 9. doi: 10.3389/fmars.2022.906209

How to cite: Kim, E. H. and Lee, J. L.: Shoreline Change Analysis After Construction of Coastal Structures in Wonpyeong-Chogok Beach by Satellite Image Process, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16648, https://doi.org/10.5194/egusphere-egu24-16648, 2024.

EGU24-18146 | ECS | Orals | GM5.3

Natural dynamic vs anthropogenic transformations of the AlUla oasis, NW Arabia, during the Holocene: a combination  of geoarchaeology and geomatic approaches 

Amaury Fernandes, Laurent Lespez, Gourguen Davtian, Hatem Djerbi, Claude Rouvier, Sophie Costa, Eric Andrieux, and Louise Purdue

Oases are man-made environment in response to hydro-climatic constraints of dryland. They form landscapes of natural origin that have been modified and exploited by the agro-pastoral practices of human societies. The oasis of AlUla, in Northwestern Saudi Arabia, is settled at least since the beginning of the Bronze Age. This oasis is located at the foot of the Harrat al-Uwayrid formation which separates the sandy deserts of northern Arabia from the Red Sea. AlUla has a long history of occupation, notably through the development of major archaeological sites such as the Late Bronze Age site of Dadan, the Nabataean site of Hegra, and the old towns of AlUla and Al Mabyat from the Islamic period. Recent research has also revealed the development of agro-pastoral activities since the Neolithic and hydroagricultural development from the Late Bronze Age onwards.

The aim of this research is to reconstruct the landscape of the AlUla oasis and thus to find out in what environmental framework these agro-pastoral societies developed. It also aims to study the role of climatic changes in the natural dynamics that have formed the geomorphology of the oasis (aeolian, fluvial, slopes processes and formations) and to determine the impact of human development. These objectives are to provide answers about the understanding of the current organization of geomorphological objects and their evolution/transformation through the Holocene and thus the interactions between societies and their environment that have produced them. This work has also enabled us to produce quantitative data on the volumes of earth moved/excavated since the rampant urbanization of the oasis, and to identify the practices (quarrying vs. levelling) and geomorphological environment most affected by these earthworks.

To achieve these objectives, we have produced a diachronic geomorphological map covering the AlUla oasis and its margins, with the aim of tracing the natural history of the oasis from its current state back to the Neolithic/Early Holocene. This realization of this map is based on a combination of geomatics methods, using a DEM produced by LiDAR data (2018, 40 cm accuracy), orthophotographs (2018, 10 cm accuracy), remote sensing with satellite images (1965-2024 Google, Bing, Corona), geological data (1:500,000) and fieldwork in order to inventory landforms and determined their organization and their chronology (C14, OSL).

Our results show a long-term trend towards aridification since the second half of the Holocene and an increase in human pressure since the Bronze Age. This last observation result from the initiation and expansion of agricultural practices supported by earthworks which have led to the development of levees along wadis, agricultural terraces and anthroposols. These anthropogenic forms associated with numerous excavations have greatly modified the initial topography and therefore the geomorphology of the oasis, from the Bronze age but with an astonishing and constant acceleration over the last thirty years. This demonstrates that the natural dynamics which have prevailed during the Holocene are progressively replaced by the impact of human societies, acting as an agent of erosion in the oasis environment in NW Arabia during the Anthropocene.

How to cite: Fernandes, A., Lespez, L., Davtian, G., Djerbi, H., Rouvier, C., Costa, S., Andrieux, E., and Purdue, L.: Natural dynamic vs anthropogenic transformations of the AlUla oasis, NW Arabia, during the Holocene: a combination  of geoarchaeology and geomatic approaches, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18146, https://doi.org/10.5194/egusphere-egu24-18146, 2024.

EGU24-18350 | Orals | GM5.3

Quantifying human impact during industrialisation on the evolutionary trajectory of Vosgian streams (NE France): the value of documentary archives  

Timothée Jautzy, Nicolas Jacob-Rousseau, Salomé Berthier--Laumond, Margaux Claudepierre, Gilles Rixhon, and Laurent Schmitt

The anthropogenic pressure on European rivers has greatly intensified since the Industrial Revolution through channelisation, rectification, and building of dams and weirs. Against this background, focusing on the Vosges Mountains (NE France) is particularly relevant since it is the most densely populated mountain range in France. The Vosgian hydrographic network was accordingly impacted by widespread human modifications. No less than ~5000 hydraulic structures (HS) mostly involving weirs were built across the main streams draining the massif. Contrary to large rivers (e.g. the Rhine), the edification periods of these HS in smaller catchments remains largely unknown yet, thereby impeding a precise chronological reconstruction of the main phases of human pressure and environmental trajectories.

 

In this study, we aim to gain insight into the spatio-temporal anthropisation of three main streams draining the southern part of the Vosges, i.e. the Fecht, Vologne and Moselotte, and to evaluate their historical morphodynamic adjustments from the end of the 18th century onwards. We took advantage of the abundant paper archives, i.e. written reports, plans…, from the “Ponts et Chaussées” administration, which collected at the local scale every official request to build HS along and across streams from the 18th to the 20th century. Firstly, we characterised and mapped every weir and levee along the three studied streams to produce an updated database of the present distribution of HS. Secondly, we analysed the archives to date the construction (and in some cases deconstruction) of the HS. Finally, we reconstructed the diachronic evolution of the channel pattern, from an ancient topographical map (1866) and two orthophotos (1951, 2018). Our results allow a first quantification of human impacts: the year of construction (terminus ante-quem) could be assigned to 7%, 38% and 59% of the weirs currently present in the Fecht, Vologne and Moselotte, respectively. Most of them were probably built in the middle of the 19th century. Importantly, we also evidence a spatio-temporal correlation between the construction of HS and the simplification of the channel pattern. Although the use of historical documents has several limitations (e.g. loss, destruction, unavailability), we demonstrate that they are valuable archives that usefully complement field observations and investigations.

How to cite: Jautzy, T., Jacob-Rousseau, N., Berthier--Laumond, S., Claudepierre, M., Rixhon, G., and Schmitt, L.: Quantifying human impact during industrialisation on the evolutionary trajectory of Vosgian streams (NE France): the value of documentary archives , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18350, https://doi.org/10.5194/egusphere-egu24-18350, 2024.

EGU24-19923 | Posters on site | GM5.3 | Highlight

Reading the sedimentary archives in the Danube floodplain downstream of Vienna (Austria) 

Michael Weissl, Diana Hatzenbühler, Christian Baumgartner, and Michael Wagreich

Many human interventions in river systems, e.g., river channelization, hydropower dams, or restoration measures, affect geomorphological and sedimentological settings. Anthropogenic impact can lead to alterations in stream dynamics and sedimentary imbalances, as recorded in the sediments of large riverplains.

In the project “From Romans to the Anthropocene, from Carnuntum to Vienna: An Urban Anthropocene Field Lab” (WWTF ESR20-027) we explore long-term urban and geomorphological transformations within the Danube floodplain between Vienna (Austria) and Bratislava (Slovakia). Combining historical and sedimentological methods, our research focuses on the development of a very old settlement area within the transition zone between eastern and Central Europe.

Extensive river engineering, starting in the 19th century, was a precondition for Vienna’s development as a residence and metropolis. This includes extensive river training and the construction of flood control structures. After a long period of river engineering and the construction of many hydro-power dams along the upper Danube, around 2000 the local removal of river bank fortifications started and also the restoration of fluvial dynamics primarily within our study area downstream of Vienna, in the free-flowing river section of the Donau-Auen National Park.

Fine overbank deposits record river dynamics through climatic and anthropogenic drivers. Reading the sequence of alluvial deposits allows us to understand the human impact on floodplain morphology. The great advantage of analyzing sedimentary archives is the temporal depth they offer: we can evaluate the conditions prior to river training (~200 years ago), the effects of engineering measures (e.g. river channelization, construction of hydropower stations), and recent restoration measures as well.

The characterization of sediment archives, including sediment dating (radioactive isotopes, OSL, dendrochronology), provides information on major flooding events, changes in the flow regime, and the dynamics of sedimentation. For investigations into sedimentary processes and river morphology downstream of Vienna, it is also necessary to have a look not only at the present state of a trained river but also at the former, near-natural situation of the riverscape. Therefore, comparisons of changing river morphologies before, during, and after the erection of dams and weirs are a requirement.

 

How to cite: Weissl, M., Hatzenbühler, D., Baumgartner, C., and Wagreich, M.: Reading the sedimentary archives in the Danube floodplain downstream of Vienna (Austria), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19923, https://doi.org/10.5194/egusphere-egu24-19923, 2024.

The interdisciplinary project, titled 'Living together or apart? Unravelling the development, internal organization, and social structure of a complex Bronze Age tell settlement at Toboliu, western Romania,' seeks to analyse Bronze Age settlement activity in Toboliu, located in the easternmost Carpathian Basin. Key aspects of the study include associated land-use and landscape evolution, making the reconstruction of the tell's surroundings a focal point. The study area is dominated by loess and significantly influenced by both modern and prehistoric agricultural practices. Thus, it is a major challenge to differentiate between landscape features caused by natural soil-landscape formation processes and human activity especially for the investigated period. Within this context we focussed our research on closed depressions surrounding the tell and investigated two hypotheses regarding their formation: i) closed depressions result from human activities (such as daub extraction pits) and ii) formed through natural soil-geomorphological processes (like loess dolines or periglacial relicts). Based on core drillings, we made use of Optically Stimulated Luminescence (OSL), radiocarbon-supported, and palynological chronostratigraphical analyses. In addition, we took advantage of spatial analysis involving a high-resolution LIDAR elevation model, multispectral WorldView-3 imagery, and magnetographic data to thoroughly testing both hypotheses. Our results suggest that the examined closed depressions exhibit characteristics reminiscent of specific periglacial relict forms, more commonly known from northern European landscapes. Details will be discussed within the presentation.

How to cite: Zickel, M., Nett, J. J., Röpke, A., and Reimann, T.: Unraveling Geomorphological Processes and Anthropogenic Activity at the Eastern Border of the Carpathian Basin: Insights from the Bronze Age Tell site Toboliu, Romania, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1638, https://doi.org/10.5194/egusphere-egu24-1638, 2024.

In antiquity, the development of techniques to collect and store water was fundamental to sustain life in arid regions. One way to overcome the problem of water supply in the desert was to construct water reservoirs and cisterns which collect surface runoff during rare rain events. Indeed, open reservoirs and rock-cut cisterns are widely spread over the arid zone of the Negev Highlands / Israel. They were an important component of human activity in the area. Today, they can serve as sedimentary archives for archaeological and paleoenvironmental reconstruction. Here we provide the final assessment of a large-scale optically stimulated luminescence (OSL) dating project of water installations in the arid Negev Highlands. By sampling spoil piles, feeding channels, and accumulation of sediments within reservoirs and cisterns, the construction, the phases of maintenance and abandonment were dated. The significance of these results for reconstructing the history of human activity in the region is discussed.

How to cite: Fuchs, M., Junge, A., and Lomax, J.: Chronology of ancient water installations and the history of human activity in the Negev Highlands, Israel , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2124, https://doi.org/10.5194/egusphere-egu24-2124, 2024.

EGU24-4080 | PICO | GM5.4

Holocene overbank sedimentation in Central Europe between natural and human drivers – the Weiße Elster River (Central Germany) 

Hans von Suchodoletz, Azra Khosravichenar, Pierre Fütterer, Christoph Zielhofer, Birgit Schneider, Tobias Sprafke, Christian Tinapp, Alexander Fülling, Lukas Werther, Harald Stäuble, Michael Hein, Ulrich Veit, Peter Ettel, Ulrike Werban, and Jan Miera

Up to several meters thick fine-grained Holocene overbank deposits are ubiquitously found in most Western and Central European lowland floodplains. However, the interplay of different possible causes for their formation are not well understood yet. Most authors suggest human-induced deforestation as the main precondition for sediment mobilisation and transport from the slopes to the floodplain, generally regarding overbank sediments as human-derived ‘legacy sediments’. In contrast, others suggest a stronger influence of climatic factors. This current research gap is caused by often missing well-resolved fluvial chronostratigraphies and spatio-temporal information about former human activity within the studied catchments. To fill this gap we exemplarily studied Holocene overbank sedimentation and possible human or natural drivers in the meso-scale Weiße Elster catchment in Central Germany by using a comprehensive geoarchaeological approach: On the one hand, we applied numerical dating as well as sedimentological and micromorphological analyses to Holocene overbank sediments along three floodplain transects. On the other hand, we built up an unprecedented systematic spatio-temporal database of former human activity within the catchment from the Neolithic until the Early Modern Ages. Together with published paleoclimatic data, this database allowed an unprecedented, systematic comparison of Holocene overbank sedimentation phases with possible human and natural external controls. Our data show that some overbank sedimentation phases were directly linked with human activities in the affected site sub-catchments, whereas others were not. Instead, all phases were clearly linked with natural factors, i.e. hydroclimatic fluctuations. This difference with most former studies could possibly be explained by previously often limited numerical dating of the fluvial sediments and by largely missing spatio-temporally well-resolved regional settlement records, hindering a precise temporal link of fluvial sedimentation with former human settlement. Furthermore, this difference could possibly also be explained by a relatively high natural sensitivity of the landscape dynamics in the Central German lowlands, showing a subcontinental climate, towards external controls.

 

How to cite: von Suchodoletz, H., Khosravichenar, A., Fütterer, P., Zielhofer, C., Schneider, B., Sprafke, T., Tinapp, C., Fülling, A., Werther, L., Stäuble, H., Hein, M., Veit, U., Ettel, P., Werban, U., and Miera, J.: Holocene overbank sedimentation in Central Europe between natural and human drivers – the Weiße Elster River (Central Germany), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4080, https://doi.org/10.5194/egusphere-egu24-4080, 2024.

The Austronesian population, which consists of approximately 0.4 billion people, is widely spread across the Pacific and Indian Ocean islands. Extensive research over several decades has led to an academic consensus that the Austronesian population originated from Taiwan and the southeastern coast of mainland China. However, the exact manner in which the Austronesian ancestors arrived in Taiwan and subsequently dispersed to other oceanic regions remains a mystery. By analyzing the last deglacial sea-level rise, neotectonic activities, and resulting ancient environmental changes, as well as comparing the characteristics of middle Neolithic remains (dating back approximately 7.4-4ka) between the Taiwan Strait, we have proposed the existence of a “proto-Austronesian culture” in the early Holocene (around 11.7ka~7.4ka). This culture was centered around the nearshore area of the Taiwan Strait and Taiwan Shoal region. As sea levels gradually rose, the Austronesian ancestors’ habitat became increasingly submerged, compelling them to retreat to the inshore highlands on both sides of the Taiwan Strait. The Austronesian relics discovered on both sides of the Taiwan Strait, such as Dabenken, Keqiutou, and Fuguodun, among others, are actually branches of the Austronesian ancestors, inheriting their marine ecological characteristics. The scarcity of Neolithic artifacts older than 7.4ka on both sides of the Taiwan Strait can be attributed to a “survivor bias” phenomenon. It is plausible that numerous early Holocene relics of the “proto-Austronesian culture” remain submerged in the nearshore area of the Taiwan Strait and Taiwan Shoal, eagerly awaiting discovery through submarine archaeological exploration.

How to cite: Zhang, K. and Zhang, S.: Unraveling the Origins and Dispersal of Austronesian Culture by the last deglacial sea-level rises and paleoenvironmental changes: Insights from the Taiwan Strait, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4518, https://doi.org/10.5194/egusphere-egu24-4518, 2024.

EGU24-8532 | ECS | PICO | GM5.4

Application of shallow geophysical methods and machine learning for detecting remains of early medieval settlements in south-eastern Poland. 

Szymon Oryński, Artur Marciniak, Piotr Berezowski, Paweł Banasiak, and Justyna Cader

Poland's landscape is a testament to its deep-rooted agricultural history, characterized by ancient field systems echoing the spatial layouts in Celtic fields throughout Europe. These intricate and expansive layouts pose a significant challenge for archaeologists and researchers dedicated to uncovering the secrets of the past. The focus of this study is to meticulously explore and analyze these extensive field systems, which often cover large areas and require a detailed and systematic approach. To navigate this complex task, researchers employed cutting-edge deep learning neural networks (DLNN), particularly the U-Net model. This approach involved semantic segmentation of data derived from Airborne Laser Scanning (ALS) to automate the identification of these significant archaeological sites. The team successfully identified hundreds of ancient sites across Poland by harnessing the power of ALS data combined with thorough desk-based analysis.

The research concentrated on specific sites in southern Poland, namely in the areas around Trzebinia and Jaworzno. Various geophysical methods were utilised here, including Magnetometry and the Slingram Electromagnetic Induction Method. These techniques aimed to confirm the existence of preliminary archaeological features in the region. The researchers conducted Magnetic Gradiometry and Electromagnetic Measurements across different terrains, including cultivated fields and forests. They specifically targeted relict embankments that once delineated old fields. The findings from these investigations were striking. The geophysical profiles of the two studied areas revealed significant differences. In the first area in a current crop field, researchers observed point-like, strong anomalies in both vertical magnetic gradient and electrical conductivity. In contrast, the wooded study area exhibited weaker but continuous anomalies, suggesting the presence of buried burnt clay formations. A key aspect of this research was integrating Ground Conductivity assessments with vertical magnetic gradient evaluations. This approach was crucial in correlating data from both methods. At the first site, variations in conductivity at different depths hinted at geological transitions or man-made structures beneath the surface. Meanwhile, at the second site, resistivity patterns suggested an anthropogenic alteration of water conditions, possibly resembling an artificial fault.

Integrating a machine learning system into this research process marked a significant advancement. It facilitated the automated segmentation of ALS data, greatly enhancing the efficiency of detecting and mapping cultural resources over large areas. Combined with traditional geophysical methodologies, this innovative approach provided a non-invasive means of identifying potential archaeological objects. This was crucial for the effective management and preservation of heritage sites. In summary, this comprehensive interdisciplinary study represents a fusion of advanced technological solutions with traditional geophysical methods. It offers valuable new insights into detecting and interpreting archaeological features, potentially revolutionizing the field of archaeological exploration and heritage conservation. The research highlights the importance of integrating diverse methodologies to uncover the intricacies of our past, ultimately contributing to a deeper understanding of human history and its impact on the landscape.

How to cite: Oryński, S., Marciniak, A., Berezowski, P., Banasiak, P., and Cader, J.: Application of shallow geophysical methods and machine learning for detecting remains of early medieval settlements in south-eastern Poland., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8532, https://doi.org/10.5194/egusphere-egu24-8532, 2024.

EGU24-10076 | PICO | GM5.4

Palaeoenvironmental changes and human-environment interactions in the surroundings of La Silla del Papa, SW Spain 

Dominik Brill, Simon Matthias May, Maike Norpoth, Anna Pint, Lyudmila Shumilovskikh, Kira Raith, Gilles Rixhon, Pierre Moret, Helena Jiménez-Vialás, Ignasi Grau-Mira, Iván García-Jiménez, Dirce Marzoli, César León-Martín, Klaus Reicherter, and Helmut Brückner

The surroundings of the Strait of Gibraltar in southern Iberia are well known as a crossroads for population movements, cultural exchange and trade from Late Prehistory to Modern Times. However, questions remain about how this historical development has impacted the environment. The settlement of La Silla del Papa, an important hillfort located in the Sierra de la Plata in southern Andalusia (Cádiz), and its territory represent an ideal location for long-term studies of human-environment interactions. It was occupied throughout the entire Iron Age, replaced by the coastal town of Baelo Claudia during Roman times, and reoccupied in the early Middle Ages. Therefore, the geoarchaeological investigations in the surroundings of La Silla del Papa within the framework of the interdisciplinary project “Archeostraits” aimed at constraining the ecological conditions and human-environment interactions during the Mid- and Late Holocene and during the most important human occupation phases. Our investigations included sedimentological, geochemical, chronological (OSL, 14C-AMS, diagnostic pottery), microfaunal and palynological analyses of nine sediment profiles as well as nine vibracores from the catchment of the Río del Cachón, a small river originating in the Sierra de la Plata, just below La Silla del Papa. Our results document an early Mid-Holocene open marine embayment in what is now the lower floodplain, which rapidly transformed into a coastal lagoon and later into freshwater-dominated wetlands. After ~2100 BP, fluvial and alluvial deposition considerably increased, suggesting high anthropogenic impact on the local landscape during the Roman or post-Roman times. Palynological results reveal fluctuating agricultural and pastoral activities and suggest two distinct periods of landscape opening between 7000-6000 BP and during the Phoenician and Iron Age period.

How to cite: Brill, D., May, S. M., Norpoth, M., Pint, A., Shumilovskikh, L., Raith, K., Rixhon, G., Moret, P., Jiménez-Vialás, H., Grau-Mira, I., García-Jiménez, I., Marzoli, D., León-Martín, C., Reicherter, K., and Brückner, H.: Palaeoenvironmental changes and human-environment interactions in the surroundings of La Silla del Papa, SW Spain, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10076, https://doi.org/10.5194/egusphere-egu24-10076, 2024.

EGU24-12670 | PICO | GM5.4

Prehispanic agricultural terrace-settlement systems: an integrative approach to study land use and settlement dynamics in the southern Peruvian Andes 

Julia Meister, Christoph Binder, Laura Dietrich, Philipp Godde, Fernando Leceta, Mike Lyons, Erik Marsh, Markus Reindel, and Christian Mader

An impressive relic of the scale of human-environment interaction and land modification in prehispanic South America are agricultural terraces, covering slopes across the Andes and of which only a fraction is still in use nowadays. Despite the ubiquity of agricultural terraces in the Andes, there is a lack of systematic studies that combine the investigation of farming terraces, land use history, and settlement patterns, preventing a comprehensive understanding of prehispanic socio-economic-ecological systems and human-environmental interactions. Our project develops and applies an integrative and interdisciplinary methodological approach to the study of prehispanic Andean terrace agricultural systems and associated settlements, providing reliable data on the dynamics of land use-settlement systems through time and space. Our methodological approach consists of the application of a variety of archaeological and geoscientific methods, including archaeological and geomorphological surveys, archaeological excavations, drone surveys, mapping using satellite imagery and high-resolution digital elevation models, geographic information system applications, soil testing, phytolith and starch analysis, numerical dating, and calculations of food supply capacity and labour requirements.

We apply these to the prehispanic site of Cutamalla (3,300 m asl) in the southern Peruvian Andes, which serves as an ideal and pioneering case study. Previous research has focused primarily on the settlement of Cutamalla, particularly through large-scale archaeological excavations, but less attention has been paid to the extensive farming terraces surrounding the settlement and the close relationship between agricultural and settlement activities. By analyzing both the terrace and settlement levels, we take a new perspective and introduce the term agricultural terrace-settlement system for such complexes. Our results show that the residential occupation of Cutamalla and the use of the surrounding farming terraces coincided: the agricultural terrace-settlement system was intensively used for a relatively short period of about 200 years (~250–40 BCE) during the Formative Late Paracas and transitional Initial Nasca periods. There is no evidence of reoccupation of the site and subsequent reuse of the agricultural system. Our data also document the large extent of agricultural terraces around Cutamalla (221 ha) and that maize was likely a major crop grown there. Finally, we place these findings in their broader socio-economic and ecological context. Cutamalla was an important regional center and economic hub during a very dynamic period characterized by significant population growth and increased violence. Not only a more humid climate, but probably also forced collective labor were cornerstones of substantial agricultural production in Cutamalla and the region.

How to cite: Meister, J., Binder, C., Dietrich, L., Godde, P., Leceta, F., Lyons, M., Marsh, E., Reindel, M., and Mader, C.: Prehispanic agricultural terrace-settlement systems: an integrative approach to study land use and settlement dynamics in the southern Peruvian Andes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12670, https://doi.org/10.5194/egusphere-egu24-12670, 2024.

EGU24-14063 | PICO | GM5.4

Deciphering Hidden Ancient Human Physical and Chemical Markers through pOSL and  pXRF Analysis: A Case Study at Tel Burna 

Oren Ackermann, Martin Janovský, Polina Nikolskaia, Jan Fišer, Yaakov Anker, Yamm Anker, Tziona Ben-Gedalya, Aharon Friedman, Michal Hejcman, and Itzhaq Shai

As archeological sites are not isolated islands, they exert horizontal and vertical influence on their surrounding area. Therefore understanding the impact of these sites on their periphery becomes crucial.  Soil and sediments, as reliable historical archives, provide a unique opportunity to investigate these processes. Recent research has demonstrated that not all markers of human activity are visible, and a combination of physical and chemical methods, including pOSL and pXRF analysis, can provide insights into hidden past human signatures.

Core drills conducted at the footslope of Tel Burna In Israel's archaeological site revealed an anthropogenic unit buried within the valley. This unit also contains a layer indicative of heightened anthropogenic activity, which could either signify the remnants of an ancient field's surface or the site's abandonment, followed by rapid site erosion. Given that these drills spanned from the slope of the Tell to the valley below, we were able to track the sediment's properties from the top of the site down to the valley. It was shown that the anthropogenic influence reduced with distance from the site, resulting in increasingly intricate patterns, suggesting multiple sources of sedimentation—both natural and anthropogenic. Furthermore, the study revealed a cycle of deposits that were transported to the site from the adjacent valley through human material transport activities to be subsequently eroded back into the valley due to natural processes. In summary, the ancient archeological site during its occupation and abandonment is still a physical feature that has been contributing to the landscape cycling processes.

How to cite: Ackermann, O., Janovský, M., Nikolskaia, P., Fišer, J., Anker, Y., Anker, Y., Ben-Gedalya, T., Friedman, A., Hejcman, M., and Shai, I.: Deciphering Hidden Ancient Human Physical and Chemical Markers through pOSL and  pXRF Analysis: A Case Study at Tel Burna, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14063, https://doi.org/10.5194/egusphere-egu24-14063, 2024.

EGU24-15442 | PICO | GM5.4

A submerged Late Pleistocene hunting structure in the Western Baltic Sea 

Jacob Geersen, Marcel Bradtmöller, Jens Schneider von Deimling, Peter Feldens, Jens Auer, Philipp Held, Arne Lohrberg, Ruth Supka, Jasper Hoffmann, Berit Valentin Eriksen, Wolfgang Rabbel, Hans-Jörg Karlsen, Sebastian Krastel, David Heuskin, David Brandt, and Harald Lübke

After the retreat of the Weichselian glaciers, Northern Europe was populated by highly mobile hunter-gatherer groups. Traces of these societies are difficult to find, hampering our understanding of their life. Some remote basins of the western Baltic Sea, however, only drowned in the Holocene, and it has recently been postulated, that they preserve architectures from the Stone Age, that did not survive on land. In 2021 we documented the Blinkerwall, a stonewall megastructure located in 21 m water depth in the Bay of Mecklenburg, Germany. Shipborne and autonomous underwater vehicle hydroacoustic data as well as optical images show that the wall is composed of about 1700 stones, predominantly less than 1 m in height, placed side by side over 971 m in a way that argues against a natural origin by glacial transport or ice push ridges. Combining this information with sedimentological samples, radiocarbon dates, and a geophysical reconstruction of the paleo-landscape, we suggest that the wall was likely used as a drive lane for hunting during the late Pleistocene or earliest Holocene. Ranging among the oldest hunting structures on Earth and the largest Stone Age structures in Europe, the Blinkerwall will become important for understanding subsistence strategies, mobility patterns, and inspire discussions concerning the territorial development in the Western Baltic Sea region.

How to cite: Geersen, J., Bradtmöller, M., Schneider von Deimling, J., Feldens, P., Auer, J., Held, P., Lohrberg, A., Supka, R., Hoffmann, J., Eriksen, B. V., Rabbel, W., Karlsen, H.-J., Krastel, S., Heuskin, D., Brandt, D., and Lübke, H.: A submerged Late Pleistocene hunting structure in the Western Baltic Sea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15442, https://doi.org/10.5194/egusphere-egu24-15442, 2024.

EGU24-16626 | PICO | GM5.4

Micromorphological insights within the Middle Pleistocene-Holocene cave sediment record of Grotta Romanelli, Italy. 

Guido Stefano Mariani, Pierluigi Pieruccini, Davide Susini, Luca Forti, Ilaria Mazzini, and Raffaele Sardella

Grotta Romanelli (Apulia, southern Italy) is a key-site in Mediterranean archaeology. In the long history of excavations since the early 20th century, its sedimentary archive has revealed important information about human frequentation, vertebrate faunas, and environmental changes, inside a time frame which includes the Middle Pleistocene (ca. 350 ka BP) and the Early Holocene (ca 11 ka BP). The peculiarity of the sedimentary succession, which consists of fine- to very fine-grained sediments with weakly-developed or massive sedimentary structures, determined a thorough micromorphological investigation. Indeed, these sedimentary structures are often associated with human-settled cave environments. Thus, the micromorphological analysis is of utmost importance for determining the sedimentary and geomorphological context of an archaeological site. In this respect, we present for the first time the results at a more detailed scale of the depositional environments of Grotta Romanelli, in order to understand the role of sedimentary, post-depositional and anthropogenic processes in the formation of the stratigraphy of the cave.

The micromorphological investigation highlights several microfacies associated with the finer-grained sediments. The sediments within the deposit is mainly allochthonous as evidenced by the abundance of aeolian quartz and remnants of leached soils, thus indicating erosion and transport into the cave. Moreover, the characterisation of the microfacies suggests runoff and standing water processes as main agents of the internal redistribution of material. This also includes, albeit to a lesser extent, phases of biological activity, as well as phases of relative surface stability and anthropogenic contributions. Anthropogenic inputs are mainly related to fire activity and food exploitation, such as charcoal, charred plant tissue, and burnt bones. Notwithstanding the extensive volume of sediments excavated during historical archaeological campaigns, especially in the mid-frontal sectors, results show that anthropogenic inputs are not restricted to specific areas within the cave, due to its dimensions, rather they are sporadically scattered across the microfacies.

How to cite: Mariani, G. S., Pieruccini, P., Susini, D., Forti, L., Mazzini, I., and Sardella, R.: Micromorphological insights within the Middle Pleistocene-Holocene cave sediment record of Grotta Romanelli, Italy., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16626, https://doi.org/10.5194/egusphere-egu24-16626, 2024.

EGU24-20000 | PICO | GM5.4

New stable isotope geochemical approach documents grain production and manuring in the High Middle Ages 

Martin Janovský, Laszlo Ferenczi, and Jakub Trubač

Isotope analysis, particularly for the determination of δ13C and δ15N in archaeobotanical remains, is a recognized method within the field of archaeology. Until now, the primary focus of these analyses has been on archaeobotanical remains directly related to dietary practices. The significant impact of the Cistercian Order on the European agricultural landscape, and its far-reaching ecological consequences, has been well documented. However, the use of isotopic analysis for determining land-use based on present-day soils remains unexplored. The study at hand focuses on a Cistercian court, utilized from the 13th to the 15th century. The lands of this court, along with its surrounding regions, have been extensively surveyed. The isotopic analysis of the anthropogenically influenced soils is compared to approximately 400 archaeobotanical, soil, and sediment samples collected globally. The comparative analysis reveals the potential to ascertain through the presence of the C3 cycle and evidence of medieval fertilization, that the area was used for cereal cultivation and fertilization. The results of our study indicate that the medieval Cistercians employed the landscape primarily for grain production rather than pastoralism.

How to cite: Janovský, M., Ferenczi, L., and Trubač, J.: New stable isotope geochemical approach documents grain production and manuring in the High Middle Ages, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20000, https://doi.org/10.5194/egusphere-egu24-20000, 2024.

EGU24-20312 | ECS | PICO | GM5.4

Plant-wax biomarkers and their isotopes reveal complex relationships between climate, vegetation and fire during collapse of Indus Valley Civilization 

Deepak Jha, James Blinkhorn, Valerie Schwab-Lavric, Verónica Zuccarelli Freire, Jana Ilgner, Hema Achyuthan, Nicole Boivin, Ravindra Devra, S. Yoshi Maezumi, Gerd Gleixner, Patrick Roberts, and Michael Petraglia

Climate variability, especially monsoonal rainfall, has significantly shaped habitable areas for human populations in South Asia in the past just as it does today. Instances of climate-driven social disruptions and population movements are evident worldwide, as evidenced for example in the Classic Maya and the Indus Valley Civilization (IVC). However, climate change can manifest in very different ways in terms of vegetation and fire regimes, with important implications for regional environmental histories as well as socio-political patterns. As such, it is essential to develop a comprehensive understanding of the intricate interplay between climate, vegetation, fire, and archaeological evidence relating to changes in settlement patterns and continuities. Insights derived from such studies offer a foundation to explore and comprehend present and future human-environment interactions.

Here we present multi-proxy time-series datasets derived from a 2.25-meter geological trench known as ‘Jankipura,’ located within the semi-arid Thar Desert. Jankipura, located near Didwana Lake, holds prehistoric importance, being surrounded by major archaeological sites in the Thar Desert. It is also a part of the Didwana Palaeolithic Complex, surrounded by the IVC, Jodhpura-Ganeshwar, and Ahar-Banas cultural regions. The chronology of the Jankipura trench is constructed based on four 14C AMS dates ranging from 183 to 4656 cal yr. BP, aligning with the Mature phase of the IVC – a period characterized by population migration and a severe reduction in settlement density. Our analysis encompasses measurements of sediment total organic and bulk carbon isotope (d13Cbulk) composition, alongside examinations of plant-wax molecular distributions (n-alkanes and fatty acids). Additionally, we analyzed the δ13C and δ2H values of long-chain n-alkanes (C27, C29, C31, and C33) and fatty acids (C26, C28, C30, and C32) extracted from the sediment samples.

Our study also involved the assessment of macro-charcoal concentrations (>125 µm, differentiating grass from wood) to reconstruct the climate-vegetation-fire relationships during and after a major period of disruption of the IVC. The findings highlight an dry phase between 4656 and 2932 cal yr. BP, characterized by a mixed C3-C4 vegetational landscape with limited fire episodes. A significant fire episode took place during the period from 2932 to 1960 cal yr. BP, suggesting dry conditions supported by abundant C4 vegetation. Between 1960 and 183 cal yr. BP, three minor fire events occurred amid fluctuating rainfall conditions and a landscape dominated by mixed C3-C4 vegetation. The identified macro-charcoal predominantly comprised woody fragments over grass fragments. Notably, an increasing trend in isotope values, reaching its peak in macro-charcoal, is observed between 183 cal yr. BP and the present, signifying increased aridity compared to the mature phase of the IVC.

Although the study is based on a single trench, our observation of a weak relationship between vegetation and fire suggests that the reconstructed fire events may have originated from anthropogenic activities. This sheds light on the significance of vegetation, especially the utilization of wood, during the Mature phase of the IVC. We recommend generating more records from this region to better comprehend the spatio-temporal interaction of the IVC population with the environment.

How to cite: Jha, D., Blinkhorn, J., Schwab-Lavric, V., Zuccarelli Freire, V., Ilgner, J., Achyuthan, H., Boivin, N., Devra, R., Maezumi, S. Y., Gleixner, G., Roberts, P., and Petraglia, M.: Plant-wax biomarkers and their isotopes reveal complex relationships between climate, vegetation and fire during collapse of Indus Valley Civilization, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20312, https://doi.org/10.5194/egusphere-egu24-20312, 2024.

EGU24-21345 | ECS | PICO | GM5.4

Holocene relative sea-level changes and coastal dynamics in Southern Latium, Italy: an interdisciplinary investigation  

Claudia Caporizzo, Giuseppe Aiello, Vincenzo Amato, Pietro P.C. Aucelli, Diana Barra, Andrea Gionta, Giuseppe Corrado, Gaia Mattei, Gerardo Pappone, Roberta Parisi, Paola Petrosino, Marcello Schiattarella, and Matteo Vacchi

Understanding the historical changes in Relative Sea Level (RSL) and coastal responses in stable regions is crucial for unraveling the intricate relationship between natural dynamics and human adaptation. This interdisciplinary study seeks to explore the Holocene sea-level fluctuations in the stable area of Southern Latium, shedding light on how past societies adapted to coastal changes.
The study area, located in the historical Sinus Formianus, between the Fondi and Garigliano coastal plains, played a key role in ancient times. Formia, a strategic monitoring point for the Tyrrhenian Sea, was a thriving commercial hub during Roman occupation. During this period, the coastal stretch 
from Formia to Gaeta witnessed substantial urbanization, leaving behind well-preserved remnants visible today in submerged or semi-submerged coastal structures along the present shoreline.

This study reconstructs the Holocene morpho-evolution and RSL changes in the study area by creating a geodatabase following international guidelines for sea-level markers (SLMs). A comprehensive dataset of 52 SLMs was compiled from direct geoarchaeological measurements, stratigraphic and palaeoecological interpretations of new borehole data, and reinterpreting bibliographic information. Archaeological site selection involved analyzing bibliographic, cartographic, and video materials for ruins' details and dating. Additionally, public institutions provided access to an unpublished stratigraphic dataset from five deep boreholes drilled between Fondi and Formia plains in 2023. 
Three samples were collected from the stratigraphic columns of the analyzed boreholes in Formia Plain and dated using the radiocarbon dating technique. One sample, derived from a lagoonal deposit, presented an age exceeding the dating technique's accuracy range and older than 54 ka BCE. Despite this, the dating provided valuable information on the initiation of backshore formation. The other two dated samples, derived from a second drilling and collected inside layers of peat deposits, were interpreted as Terrestrial Limiting Points (TLPs) defining an upper limit of -4.20 m MSL for the RSL position at about 7.5 ka BP.
Accordingly, based on the collected data, between 8.0 and 7.5 ka BP, the sea level in the study area rose from -23 to -5 m at a rate of 25 mm/yr. Subsequently, the rate slowed to less than 5 mm/yr, stabilizing at its current position. In particular, the results coming from the geoarchaeological surveys suggest that the local sea level during the Roman period (I century BCE) was no higher than - 0.55 ± 0.29 m MSL. 
Overall, the RSL data included in the geodatabase highlights the tectonic stability of this sector during the last 2.0 ka, testified by the position of the SLMs in accordance with the GIA models and supported by the determination of average vertical ground movements rates of -0.017 ± 0.23 mm/yr.

Finally, the interplay between new data from geoarchaeological surveys, bibliographic sources, and LiDAR-based geomorphological analysis allowed the creation of a paleogeographic scenario for the study area in the 1st century CE. This highlights the significant landscape modifications induced by anthropic activities during that period.

How to cite: Caporizzo, C., Aiello, G., Amato, V., Aucelli, P. P. C., Barra, D., Gionta, A., Corrado, G., Mattei, G., Pappone, G., Parisi, R., Petrosino, P., Schiattarella, M., and Vacchi, M.: Holocene relative sea-level changes and coastal dynamics in Southern Latium, Italy: an interdisciplinary investigation , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21345, https://doi.org/10.5194/egusphere-egu24-21345, 2024.

SSS4 – Soil Biology, Microbiology and Biodiversity

EGU24-105 | ECS | Orals | SSS4.1

Liming effects on microbial carbon use efficiency and its potential consequences for soil organic carbon stocks 

Julia Schroeder, Claudia Damatirca, Tobias Bölscher, Claire Chenu, Lars Elsgaard, Christoph C. Tebbe, Laura Skadell, and Christopher Poeplau

The allocation of metabolised carbon (C) between soil microbial growth and respiration, i.e. C use efficiency (CUE) is crucial for SOC dynamics. The pH was shown to be a major driver of microbial CUE in agricultural soils and therefore, management practices to control soil pH, such as liming, could serve as a tool to modify microbial physiology. We hypothesised that raising soil pH would alleviate CUE-limiting conditions and that liming could thus increase CUE, thereby supporting SOC accrual. This study investigated whether CUE can be manipulated by liming and how this might contribute to SOC stock changes. The effects of liming on CUE, microbial biomass C, abundance of microbial domains, SOC stocks and OC inputs were assessed for soils from three European long-term field experiments. Field control soils were additionally limed in the laboratory to assess immediate effects, accounting for lime-derived CO2 emissions (δ13C signature). The shift in soil pHH2O from 4.5 to 7.3 with long-term liming reduced CUE by 40%, whereas the shift from 5.5 to 8.6 and from 6.5 to 7.8 was associated with increases in CUE by 16% and 24%, respectively. The overall relationship between CUE and soil pH followed a U-shaped (i.e. quadratic) curve, implying that in agricultural soils CUE may be lowest at pHH2O = 6.4. The immediate CUE response to liming followed the same trends. Interestingly, liming increased microbial biomass C in all cases. Changes in CUE with long-term liming contributed to the net effect of liming on SOC stocks. Our study confirms the value of liming as a management practice for climate-smart agriculture, but demonstrates that it remains difficult to predict the impact on SOC stocks due its complex effects on the C cycle.

How to cite: Schroeder, J., Damatirca, C., Bölscher, T., Chenu, C., Elsgaard, L., Tebbe, C. C., Skadell, L., and Poeplau, C.: Liming effects on microbial carbon use efficiency and its potential consequences for soil organic carbon stocks, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-105, https://doi.org/10.5194/egusphere-egu24-105, 2024.

EGU24-1301 | ECS | Posters on site | SSS4.1

Thermodynamic indicators decipher the molecular composition of organic matter in phase transition 

Philipp Maurischat, Michael Seidel, Oliver Donnerhack, Patrick Liebmann, and Georg Guggenberger

With promising methods such as ultrahigh-resolution mass spectrometry (FT ICR MS), soil scientists have more opportunity than ever to gain a comprehensive picture of the composition and transformation of soil organic matter (SOM).  With soils as central mediators for carbon capture and storage this understanding is key when it comes to tackling major challenges, such as climate change and soil health. However, as novel techniques are often imported from other scientific fields, the evaluation and interpretation of data with regard to the heterogeneous pedosphere often remains a major challenge. For FT ICR MS, several commonly used indices were developed from empirical observations of the deep ocean. While these indices seem statistically transferable from ocean DOM to the terrestrial realm, there is legitimate concern that no causality ultimately ensures this applicability. Indices are needed that allow interpretation of the data from a conceptual perspective. Viewing SOM as a thermodynamically driven mediator of energy fluxes in the soil food web provides an opportunity to put a foot on the ground of data analysis with more general applicability. We aim to show that bioenergetic and thermodynamic molecular indices allow a better understanding of soil organic matter transformation by comparing FT ICR MS samples from complex, mixed sources and single source endmembers.

We investigated the molecular composition of stream DOM and soil leachates along a biome gradient between alpine meadow and alpine steppe, including a chronosequence of degradation in the southern Tibetan Nam Co watershed. Our results suggest a certain match of commonly used DOM molecular indices, such as the ‘island of stability‘, the ‘degradation index‘ and the ‘terrestrial index‘, applied to marine settings for terrestrial DOM and SOM. However, when comparing SOM and DOM phase transitions within endmember sources, we noted inconsistencies. In contrast, indicators representing the bioenergetics of organic matter composition, such as the ‘nominal oxidation state of carbon’ and the ‘Gibbs free energy for carbon oxidation’, show good agreement for the key phase transition between SOM and DOM. These results provide reasonable evidence in line with conceptual understanding, such as more oxidised DOM and SOM in degraded areas and generally less oxidised molecular formulae in mainly allochthonous stream DOM compared to extracted SOM. Our data support the notion that bioenergetic and thermodynamic indicators may be a way forward to better understand the complex nature of organic matter transformation in soils with FT ICR MS. These indicators can serve as important building blocks for molecular fingerprinting.

How to cite: Maurischat, P., Seidel, M., Donnerhack, O., Liebmann, P., and Guggenberger, G.: Thermodynamic indicators decipher the molecular composition of organic matter in phase transition, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1301, https://doi.org/10.5194/egusphere-egu24-1301, 2024.

Chemical quality of plant residues, which are the source of dissolved organic C (DOC), determine the molecular structure, notably functional group polysaccharides in DOC, and the origins of DOC-polysaccharide, which transitioned from plant- to microbial-derived as decomposition progressed. The microbial-derived DOC-polysaccharides contribute to soil organic C (SOC) stabilization, but what factor associated with the residue chemical quality regulates the origin of the DOC-polysaccharides remains unknown. Balanced DOC and dissolved N (DN) (DOC-and-DN) stoichiometry of microbial substrates as indicated by DOC-to-DN ratio enhances microbial C use efficiency (CUE). The CUE indicates the production of microbial-derived DOC compounds. We hypothesized that DOC-and-DN stoichiometry in soils receiving plant residues was a key factor controlling the origin of DOC-polysaccharides. The objectives of this study were to determine 1) DOC-to-DN ratio during decomposition, 2) relationships of DOC-to-DN ratio and microbial metabolic quotient (qCO2 - inverse of CUE), and 3) relationships of qCO2 and DOC-to-DN ratio with DOC-polysaccharides. This study employed data from year 13 of a long-term field experiment on the effect of annual application of varying quality residues on decomposition processes in sandy soils. During the early stage of decomposition (week 0-2), DOC-to-DN ratio of N-rich groundnut stover (GN) residue decreased, in contrast to low-N rice straw (RS), and dipterocarp leaf litter (DP) and medium-N tamarind leaf+petiole litter (TM). During the intermediate stage (week 2-8), GN and RS had increasing ratios, as opposed to DP and TM. Groundnut-treated soil had lower average ratio (6.8±2.6) than TM, RS and DP (10.7±4.4, 12.1±5.4, 14.1±7.2, respectively). Positive influences of the ratio on qCO2 in the three medium-to-low-N soils (R2 = 0.60** - 0.74**) indicated that the ratio had significant control on the CUE. The qCO2, in turn, had significant influence (non-linear relationship) on DOC-polysaccharides (R2 = 0.30*).  In the early stage (high qCO2), it decreased (indicating the increase of CUE) corresponding to the decreases in DOC-polysaccharides indicating that these were plant-derived. The qCO2 decreased further beyond the threshold of 0.00026 mg CO2-C kg-1 microbial biomass C h-1 whichmarked the beginning of the intermediate stage (low qCO2), corresponding to an increase in microbial-derived DOC-polysaccharides.  This increase signified the change in their origin. Negative influence of DOC-to-DN ratio on DOC-polysaccharides (R2 = 0.36*) during the intermediate stage showed that the increased ratios caused the decreases in DOC-polysaccharides. Our results identified DOC-and-DN stoichiometry in residues-treated soils as a prominent factor controlling the origin of the DOC-polysaccharides. Imbalanced DOC-and-DN stoichiometry in low-N residues, i.e., higher DOC-to-DN ratios than microbial biomass C-to-N ratios, brought about the decrease in microbial-derived DOC-polysaccharides during the later stage. Soil management via organic inputs requires careful consideration of changes in DOC-and-DN stoichiometry which can affect SOC accumulation.

How to cite: Poosathit, R. and Vityakon, P.: Stoichiometry of dissolved organic matter controls the origin of polysaccharides in dissolved organic carbon in sandy soils receiving contrasting-quality plant residues, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2590, https://doi.org/10.5194/egusphere-egu24-2590, 2024.

Microbial carbon use efficiency (CUE) is a vital physiological parameter in assessing soil carbon turnover. Yet, how microbial communities with distinct trophic strategies regulate soil microbial CUE has remained elusive. Based on the oligotrophic: copiotrophic framework, we here explored the role of microbial taxa with different trophic strategies in mediating microbial CUE (determined by a 13C-labeling approach) along the vegetation primary succession in the Hailuogou glacier retreat area of the southeastern Tibetan Plateau. Soil microbial CUE ranged from 0.54 to 0.72 (averaging 0.62 ± 0.01 across all samples), increasing markedly along the vegetation succession. Microbial assemblies with distinct trophic strategies were crucial regulators of soil microbial CUE. Specifically, microbial CUE increased with microbial oligotroph: copiotroph ratios, with oligotroph-dominated stages having a higher microbial CUE than copiotroph-dominated ones. The prevalence of oligotrophic members would therefore be linked to the high soil microbial CUE at late successional stages. Given that oligotrophs predominate in soils with more recalcitrant carbon and because of their higher microbial CUE, we speculate that oligotrophs are likely to promote carbon sequestration in soils. In addition, the responses of soil microbial CUE to fungal oligotroph: copiotroph ratios were stronger than to bacterial ones. Fungal taxa may play a particularly pronounced role in shaping microbial CUE relative to bacterial members. Overall, our results highlighted close associations between microbial trophic strategies and CUE and provide direct evidence regarding how microbial trophic strategies regulate soil microbial CUE. This study is a significant step forward for elucidating the physiological mechanisms regulating microbial CUE and has significant implications for understanding microbial-mediated carbon cycling processes.

How to cite: Ma, S., Zhu, W., Wang, W., Li, X., Sheng, Z., and Wanek, W.: Microbial assemblies with distinct trophic strategies drive changes in soil microbial carbon use efficiency along vegetation primary succession in a glacier retreat area of the southeastern Tibetan Plateau, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3903, https://doi.org/10.5194/egusphere-egu24-3903, 2024.

EGU24-5128 | ECS | Posters on site | SSS4.1

Identification of plant, bacterial and fungal necro mass markers in soil organic matter via ultrahigh resolution mass spectrometry 

Konstantin Stumpf, Carsten Simon, and Oliver Lechtenfeld

Soil organic matter (SOM) plays a central role in the global carbon cycle, influencing for example soil fertility, biodiversity, and erosion. Recent theories predict that SOM is a blend of plant metabolites and their breakdown products, perpetually undergoing recycling and transformation driven by soil organisms such as fungi and bacteria. However, our understanding of SOM remains incomplete due to its complex chemical composition. Particularly, we lack distinct metabolite information for the majority of these compounds or sources, hampering the analysis of SOM structure, it’s genesis, as well as mechanistic understanding of soil processes. Non-targeted analysis by ultrahigh resolution mass spectrometry, foremost Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS), has substantially advanced our understanding of organic matter complexity in soils and allows to gain a representative picture through the use of liquid chromatography (LC). To address the above knowledge gaps, we employed LC-FT-ICR-MS for the investigation of three primary types of necromass (maize litter, bacterial and fungal necromass) extracts, as well as aqueous SOM extracts obtained from arable topsoils (2 – 20 cm depth). Water-soluble SOM fractions can be seen as a transition state between higher molecular weight structures in soils like bio- or necromass and its decomposition end products like carbon dioxide or methane.

We employed an LC methodology capable of separating dissolved organic matter (DOM) across a broad polarity spectrum, including highly polar compounds that are typically lost during commonly employed solid-phase extraction. Our results show significant differences between farmyard manure-amended (FYM) and unamended (UF) soil DOM according to its nominal carbon oxidation state (NOSC), saturation and molecular mass, that are most prominent for the highly polar fraction of SOM. We assigned intricate markers derived from bacterial, fungal or plant necromass that indicated higher potential necromass contribution to FYM than UF soil DOM, in line with higher microbial activity in these soils. We found that necromass markers contribute most to the CHNO formula class in soil DOM, thereby explaining structural differences between FYM and UF samples.

The outcomes of our research represent an initial stride towards the identification of novel molecular markers intrinsic to soil DOM, its thermodynamic properties and N content. In the long term, these techniques will enable not only the detection of shifts in the molecular composition of soil DOM during substrate decomposition but also the recognition of alterations in structural motifs that are associated with specific necromass types. This advancement holds promise for enhancing our understanding of soil DOM dynamics and therefore may hold important implications for soil and ecosystem management.

How to cite: Stumpf, K., Simon, C., and Lechtenfeld, O.: Identification of plant, bacterial and fungal necro mass markers in soil organic matter via ultrahigh resolution mass spectrometry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5128, https://doi.org/10.5194/egusphere-egu24-5128, 2024.

EGU24-5432 | ECS | Orals | SSS4.1

Quantifying amino acid and amino sugar biomarkers in a single approach to estimate necromass from soil archaea, bacteria, fungi, and plants 

Erika Salas, Markus Gorfer, Dragana Bandian, Stephanie A. Eichorst, Hannes Schmidt, Julia Horak, Simon K.-M. R. Rittmann, Christa Schleper, Barbara Reischl, Thomas Pribasnig, Jan Jansa, Christina Kaiser, and Wolfgang Wanek

Soil organic matter is the largest carbon (C) pool in terrestrial ecosystems, and it is largely composed of microbial necromass. Microbes contribute to the long-term C storage in soils by incorporating C from plants into their biomass and, consequently, microbial necromass becomes stabilized mostly in mineral associated organic matter. So far, most studies have focused on tracing microbial necromass using amino sugar biomarkers, while plant contributions to soil organic matter are predominantly traced using lignin or long-chain alkanes. Glucosamine and muramic acid are amino sugars commonly used as biomarkers of fungal and bacterial necromass, respectively. Amino acids, such as D-enantiomers and non-proteinogenic amino acids have also been used though rarely as microbial and/or plant necromass tracers. For instance, meso(D,L)-diaminopimelic acid can be found in the peptidoglycan peptide chain of gram-negative bacteria, while hydroxyproline is commonly found in glycoproteins of plant cell walls. Currently, only very few studies have measured amino sugars alongside primary and secondary amino acids as biomarkers of plant and microbial necromass. In this study, we propose a new method that allows the simultaneous exploration of microbial and plant residue biomarkers using a single run via 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) derivatization, followed by ultra-high performance liquid chromatography (UHPLC) and Orbitrap high resolution mass spectrometry. For this, we analysed 121 species of archaea, bacteria, fungi and plants. We were able to quantify amino acids and amino sugar biomarkers in the biomass of all taxonomic groups, as well as compare how these biomarker contents varied between broad taxonomic groups. We confirmed the biomarker potential of non-proteinogenic amino acids and amino sugars using indicator species analysis as well as supervised multivariate approaches, such as random forest and partial least squares discriminant analysis (PLS-DA). Our results showed that hydroxyproline is a biomarker specific for plants, while L,L-diaminopimelic acid can be used alongside muramic acid as biomarkers specific for bacteria. Talosaminuronic acid represents a biomarker specific for archaea, while glucosamine was a biomarker indicative of archaea, bacteria and fungi, being absent in plants. Our results showcase an unparalleled approach to trace both plant and microbial contributions to soil organic matter which will help improve our understanding of how different organic matter sources contribute to soil carbon formation and stabilization. This approach also allows the quantitation of plant versus microbial contributions to the continuum from litter decomposition to soil organic matter formation though microbial processing, the contribution of plant, fungal and bacterial organic matter to mineral-associated organic matter (MaOM) versus particulate organic matter (POM), and to soil macro- and microaggregate formation.

How to cite: Salas, E., Gorfer, M., Bandian, D., Eichorst, S. A., Schmidt, H., Horak, J., Rittmann, S. K.-M. R., Schleper, C., Reischl, B., Pribasnig, T., Jansa, J., Kaiser, C., and Wanek, W.: Quantifying amino acid and amino sugar biomarkers in a single approach to estimate necromass from soil archaea, bacteria, fungi, and plants, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5432, https://doi.org/10.5194/egusphere-egu24-5432, 2024.

EGU24-5842 | Posters on site | SSS4.1

Microbial Mechanisms Governing the Reduction of CH4 Emission in Coastal Wetlands under Elevated CO2 Conditions 

Hojeong Kang, Yerang Yang, Genevieve Noyce, and Patrick Megonigal

Elevated levels of CO2 are known to enhance CH4 emissions from wetlands due to the combined effects of increased plant biomass and greater carbon availability for methanogens. However, recent findings have demonstrated a decrease in CH4 emissions under elevated CO2 conditions in coastal wetlands, primarily attributed to the oxygen priming effect. Despite this knowledge, direct evidence elucidating the microbial processes underlying this reduction remains elusive. In this study, we employed mRNA-based analysis to identify the active microorganisms responsible for CH4 dynamics.

Under elevated CO2 conditions, we observed lower methanogen abundances compared to ambient CO2 levels, suggesting that the oxygen priming effect inhibited the activity of methane-producing microbes. Intriguingly, no significant differences were found for methanotrophs, whose impact on wetland sediments may be minimal. Additionally, there was no notable change in the abundance of dsrA genes, indicating that the reduction in CH4 emission was not a result of carbon substrate competition with sulfate reducers. This research contributes valuable insights into the microbial mechanisms governing CH4 emissions in coastal wetlands under elevated CO2 conditions.

How to cite: Kang, H., Yang, Y., Noyce, G., and Megonigal, P.: Microbial Mechanisms Governing the Reduction of CH4 Emission in Coastal Wetlands under Elevated CO2 Conditions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5842, https://doi.org/10.5194/egusphere-egu24-5842, 2024.

EGU24-6079 | Posters on site | SSS4.1

Spatial modelling of microbial interactions and carbon dynamics in soils 

Xavier Raynaud and Naoise Nunan

Soil hosts a large diversity of microorganisms, that are responsible for the transformation, storage in the soil and release of carbon (C) to the atmosphere. These transformations of C are realized by individual cells that all belong to a metabolic interaction network, i.e. a network of interactions within which cells from different species compete for, transform and exchange resources. Soil C respiration, soil C storage and soil Carbon Use Efficiency are all outcomes of the functioning of this metabolic interaction network. Understand the functioning of metabolic interaction networks is thus essential to understand the cycling of C in soils.

We present a spatially explicit, individual based, model of microbial interactions in which cells are able to take up some resources, transform them into other products, which are released into the environment. Each cell is assumed to have a spatially limited impact on their environment. In this contribution, using different model parametrizations, we explore the interplay between spatial distribution of cells, resource diversity and microbial diversity, and show how the spatial distribution of cells can be a strong modulator of the functioning of metabolic networks in soils.

How to cite: Raynaud, X. and Nunan, N.: Spatial modelling of microbial interactions and carbon dynamics in soils, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6079, https://doi.org/10.5194/egusphere-egu24-6079, 2024.

EGU24-6520 | Orals | SSS4.1

Expanding Understanding: Investigating the Information Value of Calorespirometric Ratio in Dynamic Processes of Soil Microbial Growth Using Calorimetry 

Thomas Maskow, Shiyue Yang, Eliana Di Lodovico, Alina Rupp, Christian Fricke, Anja Miltner, and Matthias Kästner

The preservation of soil services and functions is sustained by the catalytic activity of microbial communities. These communities use energy and carbon – especially for microbial growth – from the transformation of organic matter (OM).  A fraction of this OM is assimilated as carbon source for growth (anabolism). Another fraction is oxidized and the resulting electrons are transferred to various terminal acceptors to derive the energy for growth (catabolism). The distribution of carbon and energy into anabolism and catabolism determines carbon use efficiency (CUE) and energy use efficiency (EUE). Accurate quantification of the relationships between carbon and energy fluxes relies on key parameters like the metabolic heat (Qm),  calorespirometric ratio (CR), carbon dioxide evolution rate (CER), the apparent specific growth rate (μapp), and the degree of anaerobicity (ηA).

However, determining these parameters faces challenges at technical (sample size and instrument sensitivity) and experimental (thermal disturbance, sample aeration) levels impacting the precise quantification of energy and carbon flux relationships. To address these challenges under controlled conditions, we examined microbial turnover processes in a model arable soil amended with a readily metabolizable substrate (glucose). We utilized three commercial isothermal microcalorimeters (IMC)  with volume-related thermal detection limits (LODV) ranging from 0.05 to 1 mW L-1.

Comparison between three IMCs were conducted to figure out the influence of LODV on measuring accuracy. Calorimetric experiments (half ampoules were closed and half were aerated for 5 minutes on selected days) were compared to explore the effect of oxygen limitation and thermal perturbation on the calorimetric signal. CER was monitored by measuring the additional heat resulting from CO2 absorption in NaOH solution used as CO2 trap. The range of errors associated with calorimetrically derived μapp, Qm, and CR was determined experimentally and compared with the requirements for quantifying CUE and ηA from a theoretical perspective.

Significant differences in Qm and µapp were observed between IMCs which have the lowest and highest LODV. IMC with the lowest LODv provided the most accurate results. Opening ampoules for gas exchange did not significantly impact Qm. However, regular ampoule opening during calorimetrically derived CER measurements led to notable measurement errors for CER due to strong thermal perturbation of the signal. If established models are used to calculate CUE and ηA from CR, unrealistically high values are obtained and the accuracy of CR do not fit to the requirements.

There are two ways to cope with this problem. On the one hand, new thermodynamic balance models need to be developed that dispense with the error-prone CR value. On the other hand, new calorespirometric methods must be developed to determine the CR value more reliably. Initial results for both approaches will be presented. 

How to cite: Maskow, T., Yang, S., Di Lodovico, E., Rupp, A., Fricke, C., Miltner, A., and Kästner, M.: Expanding Understanding: Investigating the Information Value of Calorespirometric Ratio in Dynamic Processes of Soil Microbial Growth Using Calorimetry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6520, https://doi.org/10.5194/egusphere-egu24-6520, 2024.

EGU24-7984 | ECS | Orals | SSS4.1

The potential and challenges of dynamic models for investigating microbial processes in soil using the Calorespirometric Ratio 

Martin-Georg Endress, Fatemeh Dehghani, Evgenia Blagodatskaya, and Sergey Blagodatsky

Soil microbes obtain carbon (C), energy and nutrients from their environment to grow and to sustain themselves. Some of the matter and energy entering microbial metabolism leaves the soil system, e.g., as CO2 and heat, while some is recycled via microbial death and turnover. All these matter and energy flows are intimately coupled according to stoichiometric relationships and the laws of thermodynamics, and unraveling the details of this coupling is essential for our understanding of soil functions mediated by microbes such as nutrient cycling and carbon storage.

The ratio of heat to CO2 release, the so-called Calorespirometric Ratio (CR), obtained from soil incubation experiments with substrate amendment has been shown to hold valuable information about the major active metabolic pathways of the microbial community and the C and energy use efficiency. However, due to the complex and obscure nature of the soil system, measured CR values always require mechanistic models of the underlying processes for proper interpretation.

Here, we illustrate both the potential and the limitations of simple dynamic bioenergetic models for explaining experimental CR data and formulating testable hypotheses. For example, we highlight how such models may reveal shifts in metabolic pathways during growth and give clues about the dominant microbial sources of CO2 and heat in the absence of easily degradable C substrates, e.g., during maintenance and turnover, based on observed temporal CR patterns.

At the same time, the CR framework and associated models face important challenges. First, the CR represents the black box sum of all heat and COproducing processes, and this complication can lead to different conclusions being drawn from the same data. Based on experiments with glucose amended soil, we explain how the CR pattern observed during the retardation phase after glucose depletion might be interpreted as resulting from either the decomposition of SOM or the formation of necromass or a combination of both. While this challenge prevents a definitive interpretation based on CO2 ­and heat data alone, it can nonetheless play a vital role in informing and designing future experiments.

Second, evaluating the temporal patterns of the CR relies on synchronous measurements of heat and CO2. In contrast, these two quantities are often measured separately in experiments, and their different diffusion rates may also cause a delay of CO2 relative to heat in the case of simultaneous measurement. We demonstrate that even small shifts in the relative timing can cause a characteristic artificial pattern in observed CR data, with initially high CR values followed by a pronounced drop. We finally indicate how this issue may be accounted for in the structure of the dynamic models.

In summary, we present two major challenges – the black box nature of CR and shifts in relative timing – that arise from the interpretation of experimental rates of heat and CO2 release using mechanistic dynamic models, and we show how these issues may be addressed, and even leveraged, to advance our understanding of microbial processes in soil.

How to cite: Endress, M.-G., Dehghani, F., Blagodatskaya, E., and Blagodatsky, S.: The potential and challenges of dynamic models for investigating microbial processes in soil using the Calorespirometric Ratio, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7984, https://doi.org/10.5194/egusphere-egu24-7984, 2024.

EGU24-8685 | ECS | Orals | SSS4.1

Insights into the role of the environmental setting versus microbial actors for soil carbon cycling 

Daniel Wasner, Joerg Schnecker, Xingguo Han, Aline Frossard, Erick Zagal Venegas, and Sebastian Doetterl

Soil microbes perform important functions in the soil organic carbon (SOC) cycle and soil microbial decomposition activity is a major determinant of the carbon budget of a soil. It is well-established that soil microbial physiology is directly affected by temperature and moisture. However, it is less clear to what extent the environmental setting (i.e. long-term climatic conditions, soil physicochemistry) vs. the microbial actors (i.e. soil bacterial and fungal community composition) control the cycling of SOC in the absence of strong direct physiological constraints such as temperature and moisture limitation.

To address this knowledge gap, we used 35 grassland topsoils (0 – 10 cm) from 10 WRB major soil groups along a north-south transect in Chile, which ranged from arid steppe to tundra. We compiled climatic data and relevant physicochemical soil properties, together with an in depth characterization of OM quality. We then incubated the soils for 1 week in conditions favorable for microbial activity (20 °C, 50 % of water holding capacity). After incubation, we quantified soil microbial carbon and nitrogen, enzyme kinetics of three groups of relevant extracellular enzymes, basal heterotrophic respiration as well as microbial growth rates and carbon use efficiencies by incorporation of 18O into DNA. In addition, we characterized the microbial actors by DNA extraction and Illumina barcoding of a region of the 16S rRNA gene (bacteria) and a section of the ITS region (fungi). Finally, to investigate how strongly the measured microbial SOC functions were linked with the environmental setting vs. the microbial actors, we applied three different cross-validated regression approaches.

The resulting data highlights the links between environment, microbial community composition and SOC cycle functions under conditions without direct temperature and moisture limitation. Our findings show that the environmental setting controlled the amount of microbial biomass, and in extension biomass dependent SOC cycle functions such as heterotrophic respiration. In  contrast, microbial community composition was a better predictor of SOC cycle functions that are independent of microbial biomass such as carbon use efficiency and relative microbial growth rates. These insights help to disentangle the roles of the environmental setting and the microbial actors in the context of microbial SOC cycle functions.

How to cite: Wasner, D., Schnecker, J., Han, X., Frossard, A., Zagal Venegas, E., and Doetterl, S.: Insights into the role of the environmental setting versus microbial actors for soil carbon cycling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8685, https://doi.org/10.5194/egusphere-egu24-8685, 2024.

EGU24-8948 | Orals | SSS4.1

Thermodynamic control of microbial turnover of organic substrates in soils 

Anja Miltner, Matthias Kästner, Thomas Maskow, Marcel Lorenz, and Sören Thiele-Bruhn

Microbial turnover of organic substrates is a key process in soil organic matter formation and turnover. As microorganisms require both carbon and energy for growth and maintenance, carbon and energy fluxes in soils are tightly coupled. On the level of cellular metabolism, the substrates have to be allocated to catabolism and anabolism according to the requirements of the cells. In the soil system, additional processes have to be considered such as multiple substrate use, recycling of biomass components, interaction between different organisms and abiotic processes. As most of the energy flux in catabolism is created by the reduction of the terminal electron acceptors, the availability of the electron acceptors strongly affects carbon use efficiency and energy use efficiency. Here, we present a thermodynamic concept that combines experimental approaches of calorimetry and turnover mass balances paving the way for a better understanding of microbially mediated organic matter turnover and stabilization in soil.

Mass balances in soil systems need to be set up for exemplary substrates using isotope labelled compounds. They should be combined with information on energy fluxes, which can be obtained using calorimetric methods for thermodynamic calculations. Recently, calorimetric methods have been introduced into soil studies, e.g. differential scanning calorimetry or isothermal reaction calorimetry. Alternatively, enthalpies of combustion or formation must be known or estimated, e.g. based on the nominal oxidation state of the substrates and reaction products. All of these methods have their strengths and weaknesses, which need to be considered when assessing and interpreting the results. From a thermodynamic perspective, it is crucial to define the system boundaries and to use thermodynamic state variables such as reaction enthalpy, entropy and Gibbs free energy. If applied properly, the predictive power of thermodynamics can be fully utilized for process evaluation. In particular, this approach will enable us to identify whether a particular process is thermodynamically feasible or not under the given conditions.

In summary, linking mass balances and thermodynamics will allow us to better understand and predict soil organic matter turnover and sequestration.

How to cite: Miltner, A., Kästner, M., Maskow, T., Lorenz, M., and Thiele-Bruhn, S.: Thermodynamic control of microbial turnover of organic substrates in soils, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8948, https://doi.org/10.5194/egusphere-egu24-8948, 2024.

EGU24-9988 | Orals | SSS4.1

It’s the little things that count – how microbial dynamics affect simulation results of the systemic soil model BODIUM 

Sara König, Ulrich Weller, Thomas Reitz, Julius Diel, Ute Wollschläger, and Hans-Jörg Vogel

Mechanistic simulation models are essential tools for predicting soil functions such as nutrient cycling, water filtering and storage, productivity, and carbon storage as well as the complex interactions between these functions. Most soil functions are driven or affected by soil microorganisms. Yet, biological processes are often neglected in soil function models or only implicitly considered in form of unspecific, effective rate parameters. This can be explained by the high complexity of the soil ecosystem with its dynamic and heterogeneous environment, and by the range of temporal and spatial scales at which these processes take place.

We integrated different microbial processes and feedbacks into our systemic soil model BODIUM (König et al., 2023) and tested the sensitivity of soil functions such as productivity and nutrient cycling to these microbial aspects at the scale of soil profiles. This includes flexible C:N ratios, carbon use efficiency, nitrogen fixation, feedback with root exudation, and the dynamics of different functional groups such as fungi and bacteria. We observed a high sensitivity of our simulation outcomes to microbial parameters related to the microbial component, such as the exudation rate or fungal/bacterial resistance to environmental conditions. This shows the high relevance of microbial processes for soil functions at the field scale, but also indicates that the process description should be further improved.  In process-based models, a high sensitivity of parameters is often a sign for an instable process description relying too much on site-specific calibration instead of mechanistic understanding.

We will discuss how to improve this, but also further extensions, including an approach that accounts for the spatial distribution of microorganisms within the pore space.

 

König, S., Weller, U., Betancur-Corredor, B., Lang, B., Reitz, T., Wiesmeier, M., Wollschläger, U., & Vogel, H.-J. (2023). BODIUM—A systemic approach to model the dynamics of soil functions. European Journal of Soil Science, 74(5), e13411. https://doi.org/10.1111/ejss.13411

How to cite: König, S., Weller, U., Reitz, T., Diel, J., Wollschläger, U., and Vogel, H.-J.: It’s the little things that count – how microbial dynamics affect simulation results of the systemic soil model BODIUM, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9988, https://doi.org/10.5194/egusphere-egu24-9988, 2024.

EGU24-10414 | ECS | Posters on site | SSS4.1

Kill’em all? Interactions of predatory Myxobacteria with soil microbes – an in vitro and microcosm perspective on their role in the soil microbial food-web. 

Marc Piecha, Mandip Tamang, Michael Pester, Miriam van Bommel, Liliane Ruess, Morten Streblow, Jonas Woyde, Verena Groß, Mathilde Borg Dahl, Anne Reinhard, Haitao Wang, and Tim Urich

Soil is one of the most complex ecosystems, being an elementary source for food and resources needed by humankind. Despite its pivotal role in shaping and transforming this complex ecosystem, the soil microbial food-web is still poorly understood, which stands also true for matter and energy fluxes to higher trophic levels. A group of microbiome predators that has recently come more into focus are the Myxobacteria. They are famous for their predatory life style and might thus influence microbial death, growth and turnover in the soil environment via predation and an elaborate arsenal of secondary metabolites. To shed light on their role in the soil food-web, we investigated their predatory behavior and interactions with potential prey and predators using in vitro and in situ approaches. 

We tested the predation spectra in vitro with binary interaction assays of four different Myxobacteria (Haliangium ochraceum, Myxococcus virescens, Myxococcus fulvus, Corallococcus coralloides) with 16 different prey bacteria isolated from soils. The in vitro assay showed that each Myxobacterium had species-specific prey spectra. While Haliangium ochraceum and Myxococcus virescens showed the strongest predation effects on prey bacteria, the Corallococcus coralloides strain lysed the fewest prey bacteria. Taken together, not a single bacterium of the tested ones was resistant to lysis. Remarkably, also strains of the never before tested phyla Gemmatimonadota and Veruccomicrobiota can be lysed by Myxobacteria.

To shed light on (inter)actions of Myxobacteria with microbiome members in situ, a 32 day long microcosm study with an agricultural soil was performed, manipulating (a) the carbon source and (b) the grazing pressure of higher trophic levels, via the addition of fungivorous and bacterivorous nematodes, respectively. We applied quantitative PCR and quantitative metatranscriptomics microbiome profiling of 80 samples to shed light of the impact of aforementioned manipulations of C-source and grazers on the microbiome. Three-Domain SSU rRNA profiling showed that myxobacteria were highly abundant (up to 20%) in the used agricultural soil. In contrast, fungal abundance was much lower (1.5 %), while Protozoa, i.e. dominated by Amoebozoa and Cercozoa, were much more abundant than fungi (5 %). This suggests a microbial food-web dynamic in this agricultural soil that was heavily dominated by a bacterial, and not fungal channel. As expected, the abundance and composition of Myxobacteria were not affected by addition of fungivorous Nematodes, but it was surprising that this was also true for adding bacterivorous nematodes. We speculate that Myxobacteria reduce predation pressure of nematodes by utilizing secondary metabolites, while in turn killing enough prey bacteria for their own metabolism and growth. Consequently, the high abundance of Myxobacteria suggests a substantial contribution of their (predatory) activity on matter and energy fluxes in these microcosms. In a next step, we will integrate the metatranscriptomics results with organic matter and energy fluxes via flux-web modelling.

In conclusion, the in vitro assays showed that Myxobacteria killed all prey bacteria. This, together with their high abundance and resistance to predation from higher trophic levels in the in situ microcosm suggest Myxobacteria as important players in the agricultural soil food web.

How to cite: Piecha, M., Tamang, M., Pester, M., van Bommel, M., Ruess, L., Streblow, M., Woyde, J., Groß, V., Borg Dahl, M., Reinhard, A., Wang, H., and Urich, T.: Kill’em all? Interactions of predatory Myxobacteria with soil microbes – an in vitro and microcosm perspective on their role in the soil microbial food-web., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10414, https://doi.org/10.5194/egusphere-egu24-10414, 2024.

Electron transfer reactions are central to the transformation of energy in the environment and play an important role in biogeochemical element cycling. In soils, one of the main drivers of carbon cycling is the activity of organisms that utilize the energy stored in soil organic matter by extracting electrons from organic carbon and transferring them to various electron acceptors. Yet, our understanding of this process is incomplete and the response of the soil carbon pool to climate change remains one of the primary sources of uncertainty in projections of atmospheric carbon dioxide concentrations.

Here, I discuss how we can track electron transfer reactions in soil and relate them to bioenergetic descriptors to elucidate controls on soil heterotrophic respiration. I will use two examples from my research to illustrate this:  first, I show how to characterize the redox properties of solid phase electron acceptors on the basis of reaction thermodynamics. I focus on iron minerals which are abundant solid phase electron acceptors in many soils. Using mediated electrochemistry, I quantified differences in the reactivity and energetics of synthetic iron minerals and variations in mineral redox properties during microbial mineral reduction. Second, I demonstrate how we can assess effects of mineral redox reactivity on anaerobic microbial respiration in a redox-dynamic floodplain soil. To this end, I link the kinetics of electron transfer to electron acceptors to the rate of microbial carbon dioxide production in a series of soil incubations. These two examples provide inspiration on how to integrate the redox reactivities and energetics of electron acceptors into bioenergetic frameworks.

How to cite: Aeppli, M.: Electron transfer reactions and their role in soil carbon cycling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10556, https://doi.org/10.5194/egusphere-egu24-10556, 2024.

EGU24-11690 | Orals | SSS4.1

From energy to soil organic matter 

Yakov Kuzyakov, Chaoqun Wang, and Anna Gunina

We developed a new concept of soil organic matter (SOM) formation and microbial utilization of organic carbon (C) and energy: microorganisms use most of the organics entering the soil as energy rather than as a C source, while SOM accumulates as a residual by-product because the microbial energy investment in its decomposition exceeds the energy gain. So, the energy use efficiency (EUE) is at least as important as the carbon use efficiency (CUE). The microbial EUE depends on the nominal oxidation state of carbon (NOSC) of organic compounds, which is the exact proxy of energy content: The energy content per C atom (enthalpy of combustion) increases by 108 kJ mol−1 C per one NOSC unit. The NOSC in litter remaining by decomposition decreases, and the energy content increases. Consequently, the NOSC of the remaining compounds drops to −0.3 units, and the oxidation decreases due to the residual accumulation of aromatic and aliphatic compounds, and entombment of the necromass. Preferential recycling of energy-rich reduced (lipids, aromatics, certain amino acids, amino sugars) and the microbial degradation of oxidized compounds (carboxylic acids) enrich energy content in remaining SOM. This explains why SOM is not fully mineralized (thermodynamically unfavorable). Energy from litter activates decomposers to mine nutrients stored in SOM (the main function of priming effects) because the nutrient content in SOM is 2–5 times higher than that of litter. Thus, the energy captured by photosynthesis is the main reason why microorganisms utilize organic matter, whereby SOM is merely a residual by-product of nutrient storage and a mediator of energy fluxes. For the first time we assessed the NOSC of microbial biomass in soil (−0.52) and calculated the corresponding energy content of −510 kJ mol−1 C, whereas bacteria contain less energy per unit of C than fungi. We linked CUE and EUE considering the NOSC of microbial biomass and element compositions of substrates utilized by microorganisms. The microbial EUE is always lower than CUE. This is one of the reasons why microbial growth is more limited by energy than by C. Based on the comparison of processes of C and energy utilization for cell growth and maintenance, we concluded that the two main mechanisms behind lower EUE versus CUE are: (i) microbial recycling: C can be microbially recycled, whereas energy is always utilized only once, and (ii) chemical reduction of organic and inorganic compounds: Energy is used for reduction, which is ongoing without C utilization.

Gunina A, Kuzyakov Y 2022. From energy to (soil organic) matter. Global Change Biology 28 (7), 2169-2182
Wang C, Kuzyakov Y 2023. Energy use efficiency of soil microorganisms: Driven by carbon recycling and reduction. Global Change Biology 29, 6170-6187

How to cite: Kuzyakov, Y., Wang, C., and Gunina, A.: From energy to soil organic matter, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11690, https://doi.org/10.5194/egusphere-egu24-11690, 2024.

EGU24-12150 | ECS | Posters on site | SSS4.1

Effect of passive warming (soil translocation) on 18O CUE and soil enzyme activity along a tropical forest elevational gradient 

Bin Song, Aiwei Huang, Kevin Z.Mganga, Juuso Tuure, Christopher Poeplau, Xuhui Luo, and Kristiina Karhu

The impact of global warming on soil processes is a critical area of concern. Limited studies have investigated soil organic carbon (SOC) dynamics' adaptation to warming. This poses a great challenge in assessing and understanding terrestrial C cycle response to climate change. Carbon Use Efficiency (CUE), indicating the proportion of metabolized organic C allocated to microbial biomass growth, is a pivotal regulator governing the fate of soil C. Moreover, our understanding of fundamental drivers of microbial CUE is largely elusive and inconclusive, especially in tropical ecosystems.

To address these knowledge gaps, we translocated top soil samples (10 cm deep soil cores) from two higher elevation sites (Vuria, 2000 m a.s.l, and Ngangao, 1800 m a.s.l) to a lower site (Macha, 1600 m a.s.l) along a moist montane rain forest gradient in Taita Hills, Kenya. Utilizing an 18O-water tracing approach, we examined the changes in microbial CUE in response to approximately three years of experimental warming. We also measured enzyme activities and conducted a 6-month laboratory incubation (15°C and 25°C) to study temperature sensitivity in native and translocated samples.

Our hypotheses were: (i) Both microbial CUE and C related enzyme activities would decrease, however, N- and P- cycle enzyme would increase along an altitudinal gradient toward the top of the Taita Hills, primarily governed by soil C and N availability; (ii) passive warming by soil translocation would result in higher CUE in translocated soils compared to native soils; (iii) At lower temperatures, soil microbial CUE is expected to decrease due to microbes allocating increased energy towards synthesis of enzymes involved in nutrient acquisition, while reducing C investment towards their growth.

Initial findings have revealed significant distinctions in enzyme activity profile due to elevation and temperature effects. Specifically, β-glucosidase and acid phosphatase activities increased and decreased along the elevation, respectively. Consistent with our hypothesis, enzyme activities and microbial CUE were higher in translocated soil than native soil. The six-month incubation had a similar effect on translocated soils and lower temperature increased the microbial CUE. In summary, our study indicates that passive warming alters microbial temperature adaption and underscores the influential role of soil enzyme activities in regulating microbial CUE. We suggest that soil microbiome at lower temperature indicates greater need for nutrients and energy. Our results highlight the need to investigate a wide variety of temperature influence on tropical soils in order to better understand and predict how the changing climate will affect C and nutrient cycling.

How to cite: Song, B., Huang, A., Z.Mganga, K., Tuure, J., Poeplau, C., Luo, X., and Karhu, K.: Effect of passive warming (soil translocation) on 18O CUE and soil enzyme activity along a tropical forest elevational gradient, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12150, https://doi.org/10.5194/egusphere-egu24-12150, 2024.

EGU24-13165 | ECS | Posters on site | SSS4.1

Both soil minerals and organic material contribute to the energy content of soil – Insights from an artificial soil experiment and calorimetric analyses 

Marcel Lorenz, Christian Fricke, Klaus Kaiser, Elvira Sieberger, Thomas Maskow, and Sören Thiele-Bruhn

The thermodynamic perspective on soil systems gets more and more in the research focus and has the potential to take us a substantial step toward a holistic understanding of soil organic matter (SOM) turnover and stabilization. An integral part of new bioenergetic concepts and models is the energy content of SOM, but its determination particularly in mineral soils is challenging. One of the most promising techniques in this respect is thermogravimetry combined with differential scanning calorimetry (TG-DSC), where the heat of combustion is related to the mass losses of soil material during a temperature ramp from 50 to 1000°C under an oxidative atmosphere. Heat and mass changes in the range from 180-600°C are usually interpreted as the result from the exothermic reaction of SOM and thus used to obtain the energy content (combustion enthalpy, ∆CH) of SOM. Overlapping exo- and endothermic reactions by other non-oxidizing processes (e.g. dehydroxylation/-carboxylation and desorption of soil minerals etc.) in that temperature range are often neglected because their distinction and quantification from the rather strong exothermic oxidation reactions from SOM is challenging.

To investigate this, we determined the ∆CH of an organic substrate (cellulose) and soil minerals (quartz sand, quartz silt, goethite, illite, montmorillonite) 1) individually, 2) intensively mixed in the dry state, and 3) intensively mixed after several wetting-drying cycles. Furthermore, the minerals were mixed to create a silt loam texture and combined with cellulose to mimic an artificial soil. Calorimetric analyses were conducted using a TG-DSC coupled with a mass spectrometer (MS) to analyze the evolved gases during combustion.

First results show that the ∆CH value obtained by TG-DSC is lower for the organic substrate compared to reference values obtained by combustion calorimetry as the standard method. Furthermore, ∆CHdiffers when mineral compounds are mixed with cellulose indicating that thermal reactions by mineral soil compounds affect the determination of the energy content by the TG-DSC standard procedure described above. This is supported by the analyses of the pure mineral compounds, which revealed that all investigated minerals show exothermic and/or endothermic side reactions in the range from 180-600°C affecting the TG-DSC signal. In dependence on the mineral composition of the soil, the energy content of SOM by the classical TG-DSC approach can be substantially over- or underestimated.

From this first data set, we identified options to improve both the measurement and the data evaluation procedures. Building on this, we aim to develop a procedure for the accurate measurement of the energy content of SOM in (mineral) soils by TG-DSC(-MS), taking into account the contribution of mineral oxidation and the effect of organo-mineral associations on the energetic signatures derived from the thermograms. This is crucial if energy flows and sinks in soil systems are to be quantified to better understand OM turnover and stabilization in soil.

How to cite: Lorenz, M., Fricke, C., Kaiser, K., Sieberger, E., Maskow, T., and Thiele-Bruhn, S.: Both soil minerals and organic material contribute to the energy content of soil – Insights from an artificial soil experiment and calorimetric analyses, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13165, https://doi.org/10.5194/egusphere-egu24-13165, 2024.

EGU24-14773 | ECS | Posters on site | SSS4.1

Investigation of thermal reactions and energy content of building blocks of soil organic matter using simultaneous thermal analyses 

Christian Fricke, Marcel Lorenz, Thomas Maskow, Sören Thiele-Bruhn, and Gabriele Schaumann

Soils are multi-component, open systems and play a decisive role in natural energy and matter fluxes, e.g. in the storage and bioenergetic control of carbon. A key component in this system is soil organic matter (SOM), as it determines the functionality of the soil. SOM is formed by building blocks from biomass, plant and animal detritus. Therefore, SOM itself is a complex, supramolecular mixture of different components. This property complicates the thermodynamic characterization of SOM and consequently the determination of the energy content. The latter is an important piece of the puzzle for a thermodynamic description of energy fluxes in soil systems, which is necessary for a holistic understanding of SOM turnover and stabilization.

In soil science, simultaneous thermal analysis (STA) is used to determine the energy content of SOM. The soil sample is heated in crucibles in a defined temperature program (e.g. 30-1000 °C, 10 °C/min) under an oxidative atmosphere. During heating, the mass loss (thermogravimetry, TG) and heat flux caused by SOM combustion (dynamic scanning calorimetry, DSC) are measured simultaneously. The STA data can be used to determine the energy content of the SOM during combustion and to identify SOM fractions of different thermal stability.

To develop a deeper understanding of the reactions taking place during STA of SOM, we investigated the combustion of building blocks of SOM and examined the influence of different crucible setups (Al2O3 with and without lid, Pt-Rh-Al2O3 with lid) on the measured energy content. The selection of building blocks included well-defined compounds like glucose, cellulose, chitin, etc. and complex compounds like maize straw, peptidoglycan, humic acid and lignin (organosolv). The STA was coupled with an evolved gas analyzer (mass spectrometer, MS) to draw also conclusions about the combustion reactions of the building blocks by monitoring H2O and CO2.

Our results show two main points: First, the crucible setup has a huge impact on the measured energy content. A better thermal conductivity (Pt-Rh > Al2O3) and the use of a lid lead to an increase in the measured energy content. Secondly, we observe two distinguishable thermal reactions for most of the building blocks, which were mainly revealed by the release of H2O and CO2. The first reaction is a decomposition at low temperatures (< 400 °C) with the formation of char, which was then further oxidized at higher temperatures (> 400 °C). The change in the ratio between the H2O- and CO2-MS signal allows a clear allocation of different thermal reactions.

In summary, the investigation of building blocks of SOM by STA coupled with MS provides a better understanding of the combustion of SOM in soil samples and thus allows a more reliable interpretation of the measured energy contents. Further STA studies should focus on the interaction between SOM building blocks and soil minerals to identify other possible thermal reactions that could affect the measured energy content.

How to cite: Fricke, C., Lorenz, M., Maskow, T., Thiele-Bruhn, S., and Schaumann, G.: Investigation of thermal reactions and energy content of building blocks of soil organic matter using simultaneous thermal analyses, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14773, https://doi.org/10.5194/egusphere-egu24-14773, 2024.

EGU24-15343 | ECS | Orals | SSS4.1

Labile substrate availability affects interactions and function in degrader communities: Insights from a combined experimental and modelling approach 

Moritz Mohrlok, Ksenia Guseva, Lauren Alteio, Julia Berger, Lilian Kaufmann, Julia Mor Galvez, Dave Sirbu, and Christina Kaiser

Bacterial communities that degrade chitin in soils often exhibit “social” behavior, where different strains fulfill different functional roles. “Degraders” produce extracellular enzymes that attack and cleave the complex biopolymer, releasing the monomer N-acetylglucosamine (NAG) as a public good. This compound can be readily taken up by both degraders and “exploiters”. The latter do not contribute directly to the degradation process but might in turn produce different substances that can be utilized by other members. “Scavengers” do not utilize NAG themselves but live mostly off metabolites secreted by the other strains. Our work aimed to investigate what effect the addition of a readily available C compound, like NAG, has on these interactions in such a system. Based on the results of a wet-lab experiment using a model bacterial consortium, we hypothesized that adding labile C leads to domination of the exploiter-strain though competitive exclusion. This in turn results in the breakdown of positive interactions, and a loss of diversity and functionality of the community. To further investigate this, we designed an ordinary differential equation (ODE) consumer-resource model, consisting of different linked pools representing the experiment. By parametrizing this model based on our respiration measurements and simulating the system over time, we were able to reproduce most of the observed experimental patterns in silico. When there was no NAG added to the system, the model matched the measured respiration when we included several positive interactions (such as crossfeeding or division of labor). This resulted in a more diverse community that degraded chitin more efficiently than the degrader-strain in monoculture. When NAG was added, the exploiter-strain outcompeted the other strains quickly, resulting in a loss of their potential function for the community. Through this combined experimental and modelling approach, our work shows that the addition of excess labile C to degrader communities in soil can alter interactions between bacteria, possibly leading to a loss of biodiversity and function.

How to cite: Mohrlok, M., Guseva, K., Alteio, L., Berger, J., Kaufmann, L., Mor Galvez, J., Sirbu, D., and Kaiser, C.: Labile substrate availability affects interactions and function in degrader communities: Insights from a combined experimental and modelling approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15343, https://doi.org/10.5194/egusphere-egu24-15343, 2024.

EGU24-15875 | ECS | Orals | SSS4.1

Changes in the microbial control of C and N cycling in future subarctic tundra soils 

Agnieszka Rzepczynska, Johannes Rousk, and Lettice Hicks

Arctic climate warming will affect microbially-controlled nutrient cycling through elevated nutrient availability and changes in vegetation productivity and composition. Plant-derived C inputs will serve as a microbial energy and C source, while the inorganic N released from soil organic matter (SOM) could . Albeit controlled by different mechanisms, increased C and N availability may each stimulate microbes to degrade more SOM, creating positive climate change feedbacks. Simultaneously, microbes provide the main pathway to sequester and stabilize C and N in SOM through growth and subsequent necromass formation, termed the “microbial pump”, generating a negative climate change feedback. Combining estimates of microbial growth, biomass, and biogeochemical rates allows for the calculation of Carbon Use Efficiency (CUE) and Nitrogen Use Efficiency (NUE). Analyzing NUE relative to CUE may elucidate microbial resource limitation. Resultantly, NUE exceeding CUE indicates microbial N-limitation, and suggests that microbes sequester N in SOM. Conversely, CUE exceeding NUE suggests microbial C-limitation and points towards microbial C sequestration in SOM. In addition, the strength of the microbial C and N pumps can be estimated by assessing microbial growth along with microbial C and N retention times, providing insights into how long resources will be retained in the microbial biomass. These tools contribute to a comprehensive understanding of whether resources will be liberated through decomposition or sequestered via the microbial pump.

Here, we investigated microbial responses to changes in resource availability associated with future climate change in a subarctic tundra heath. We used additions of mineral N and litter in the field to mimic the effects of elevated nutrient availability and shrubification on microbial growth rates (radio-isotope tracing), C and gross N mineralisation rates (gas chromatography and 15N pool dilution methods, respectively), and microbial community size was estimated with phospholipid fatty acids.

We found that field N-fertilization generally decreased microbial NUE, and that the resulting NUE/CUE ratio was close to 1, thereby pointing towards alleviated microbial N-limitation. Field N-fertilization also accelerated N-cycling but had no significant effects on C retention times. Conversely, litter addition in the field led to NUE exceeding CUE, implying the induction of microbial N-limitation, and it slowed C turnover times, but had no significant effect on N turnover times. When N and litter were applied together, similar CUE and NUE values, but accelerated C and N turnover times were observed. Overall, fungal contribution to resource cycling diminished across all field treatments, evident from a reduced fungal-to-bacterial growth ratio compared to the control treatment.

These findings highlight that changes in nutrient availability impact microbial C and N cycling independently and emphasize that the microbial resource limitation may be altered by the substrate stoichiometry. Additionally, our results suggest that while microbial N cycling is likely to accelerate, thus weakening the microbial N pump, microbial C cycling may be impeded and microbial C pump strengthened. Overall, these observations align with projections of more fertile and productive subarctic ecosystems in the future, and underscore the potential for microbial C sequestration even under altered resource availability. 

How to cite: Rzepczynska, A., Rousk, J., and Hicks, L.: Changes in the microbial control of C and N cycling in future subarctic tundra soils, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15875, https://doi.org/10.5194/egusphere-egu24-15875, 2024.

Microbial communities in soil play a pivotal role in nutrient cycling and organic matter decomposition, relying on carbon (C) and energy sources for growth. The allocation of these substrates, crucial for their metabolic activities, is influenced by environmental conditions. We hypothesize a close linkage between carbon and energy fluxes in soil, with environmental conditions shaping substrate requirements and activities, thereby influencing Carbon Use Efficiency (CUE) and Energy Use Efficiency (EUE).

To establish the link between matter and energy fluxes, we employed artificial soil consisting of a sand, clay, and silt mixture as a simplified system, with cellulose as the only added substrate. This model system allowed us to investigate the relationship between C and energy fluxes without a large background of soil organic matter background (SOM). Experimental conditions included three different water contents (10%, 14.4% and 19%), two ratios of added carbon (C) to nitrogen (N) (C/N = 18 and C/N = 9), and two temperature regimes (7  and 20 ). Mineralization (measured by GC-TCD) and residual cellulose (measured by phenol sulphuric acid assay) were quantified on sampling days, while continuous monitoring of heat production rate (P) was monitored using isothermal microcalorimeter (i.e. TAM Air).

Results revealed a clear correlation between environmental conditions and microbial activities. Higher moisture levels led to increased CO2 production, heat generation, and cellulose degradation. Similarly, lower N supply (higher C/N ratio) exhibited the same trend. Decreased temperatures resulted in minimal CO2 evolution and heat production rates and diminished cellulose degradation.

Analysis of CUE over time indicated a decline, possibly due to biomass recycling and additional respiration. Surprisingly, little apparent effect of water content or N supply on CUE was observed. CUE in the two temperature treatments show similar decreasing trends, but CUE is at an overall higher level at 7°C. EUE remained relatively stable over time but tended to decrease under conditions of environmental stress, such as extreme water content or N limitation. However, high variability is observed, and no statistical significance can be found.

An energy balance framework is being developed and will be used to calculate CUE from a theoretical perspective. Comparisons between experimentally derived CUE and theoretically calculated values will prompt a re-evaluation of the underlying assumptions and a call for refined theoretical protocols. In summary, our findings suggest that environmental conditions significantly influence cellulose degradation. However, a clear correlation between CUE and EUE requires further analyses and experimental improvements. This study contributes to our understanding of the intricate relationships between carbon and energy fluxes in soil microbial systems and emphasizes the need for nuanced analyses in future research.

How to cite: Yang, S., Rupp, A., Miltner, A., Maskow, T., and Kästner, M.: Linking mass balances and thermodynamic energy balances at different water contents, temperature and nutrient supply in simplified model systems with artificial soils, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16129, https://doi.org/10.5194/egusphere-egu24-16129, 2024.

EGU24-16811 | Orals | SSS4.1

Prospects and challenges of simulating organic matter turnover and stabilization in soil systems 

Holger Pagel, Thilo Streck, Ahmet Sircan, and Stefano Manzoni

Understanding the turnover and stabilization of soil organic matter (SOM) is the key to highly productive agriculture and to climate change mitigation. Understanding and predicting biogeochemical matter and energy flows in soil systems is challenging due to persisting knowledge gaps regarding biological and energetic controls of SOM turnover and limited knowledge integration of informative data with process-based models. We present modeling concepts of microbially explicit soil organic matter models and shed light on integrating trait-based ecological frameworks in process-based models and the use of advanced data-model fusion approaches. We highlight some insights from applying process-based models and challenges we need to address to acquire robust predictions.

How to cite: Pagel, H., Streck, T., Sircan, A., and Manzoni, S.: Prospects and challenges of simulating organic matter turnover and stabilization in soil systems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16811, https://doi.org/10.5194/egusphere-egu24-16811, 2024.

EGU24-17226 | ECS | Orals | SSS4.1

Dynamics of soil microbial carbon storage compounds in low fertility landscapes 

Orpheus Butler, Stefano Manzoni, and Charles Warren

Intracellular storage of carbon (C) by soil micro-organisms is emerging as a key process that influences soil biogeochemical cycling and the broader function of terrestrial ecosystems. One likely role of intracellular C storage is to serve as a stoichiometric buffer against nutritional imbalances in the microbial substrate. Such a function would make storage compounds vital to the long-term function of ecosystems associated with strongly weathered, low fertility soils, yet there have been few studies of intracellular carbon storage in such ecosystems. We examined the dynamics of two putative storage compounds (triacylglycerol [TAG] and polyhydroxybutyrate [PHB]) across two natural soil fertility gradients in eastern Australia. Across all sites and samples, absolute quantities of storage compounds ranged from 0 to 173 µg C g soil-1 in the case of TAG and 0 to 56 µg C g soil-1 for PHB. When standardized to total soil organic C, quantities of storage compounds tended to be markedly higher than those observed in prior studies of temperate and/or agricultural soils. Allocation to storage compounds followed strong trends across natural gradients of soil fertility and tended to peak in phosphorus-deficient and/or retrogressive ecosystems. Across soils of differing parent material, allocation to C storage was highest in infertile soils derived from phosphorus-depleted sandstone and ironstone compared to soils derived from shale and basalt. Likewise, allocation to C storage increased throughout ~700k years of soil development across a strongly weathered podzolic dune chronosequence. Dynamics of community-level C storage allocation were evidently underpinned by a combination of assemblage-level processes, most notably changes in the relative abundance of TAG-rich, C-limited fungal taxa, and physiological plasticity on the level of individual P-limited bacterial cells. Our findings are largely consistent with the surplus/reserve storage framework and highlight the importance of storage compounds for the function of oligotrophic ecosystems and as a major pool of C in soil.

How to cite: Butler, O., Manzoni, S., and Warren, C.: Dynamics of soil microbial carbon storage compounds in low fertility landscapes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17226, https://doi.org/10.5194/egusphere-egu24-17226, 2024.

EGU24-18651 | Orals | SSS4.1

Using metabolic flux modeling to disentangle anabolic and catabolic contributions to soil heat dissipation 

Guodong Shao, Xin Xu, Callum C. Banfield, Lingling Shi, Kyle Mason-Jones, Weichao Wu, and Michaela A. Dippold

Metabolic flux analysis is an integrated experimental and computational approach for quantitative understanding of biochemical reaction networks with particular relevance in systems biology. Mass and energy flows through soil microbial metabolism are subject to the laws of thermodynamics. Carbon (C) allocation through central metabolic pathways (e.g. glycolysis, pentose phosphate, and Entner-Doudoroff) can be reconstructed by 13C-labelling coupled to metabolic flux analysis (13C-MFA) by tracing specific C atoms from within substrate molecules into metabolic products such as carbon dioxide (CO2) or fatty acids. However, mass flow calculated via 13C-MFA alone cannot fully characterise microbial carbon use. Here, we took the novel approach of coupling MFA with microcalorimetry, to also take bioenergetic constraints into account. We coupled energetics and mass flow on a metabolic level by selecting optimal sets of isotopomer tracers. Fifteen position-specific or uniformly 13C-labelled isotopomers - four alanine, seven glucose, and four glutamic acid ones – were added to a Luvisol (in total 4 folds of the microbial biomass C), and we analyzed substrate-derived 13CO2 fluxes as well as heat dissipation via isothermal microcalorimetry.

Our results demonstrate that the temporal dynamics of catabolic CO2 release resembles that of the heat dissipation, i.e. peak respiration and peak heat dissipation were reached approximately 18 h after substrate addition, irrespective of whether the substance entered the central metabolic pathway at the monosaccharide level (glucose), at the pyruvate level (alanine) or in the citric acid cycle (glutamic acid). This indicates that heat dissipation in the initial growth period was strongly dominated by catabolic processes. However, whereas 13CO2 release leveled off during the 36 hours of incubation, the heat dissipation remained above its original level, suggesting that anabolic processes increasingly contribute to the heat dissipation in the later phases of incubation. Glucose isotopomer utilization indicated dominance of the pentose phosphate and Entner Douderoff pathways over glycolysis, suggesting a high activity of fast-growing organisms with considerable C allocation to anabolism. The dominance of this anabolic C use in the later stage of the incubation was confirmed by the isotopomer utilization of alanine and glutamic acid. This study shows that the heat dissipation of growing microbial communities under high C supply is closely linked to their catabolic CO2 release, whereas slow, potentially recycling-based growth after resource depletion releases energy more via anabolic reactions. We furthermore demonstrated that coupled MFA and calorespirometry provides a powerful tool to differentiate among metabolic contributions to the energy use of soil microbial communities in different growth phases.

How to cite: Shao, G., Xu, X., Banfield, C. C., Shi, L., Mason-Jones, K., Wu, W., and Dippold, M. A.: Using metabolic flux modeling to disentangle anabolic and catabolic contributions to soil heat dissipation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18651, https://doi.org/10.5194/egusphere-egu24-18651, 2024.

EGU24-19075 | ECS | Orals | SSS4.1

Global distribution and drivers of microbial carbon use efficiency for projecting soil organic carbon fates under a changing climate: A meta-analysis 

Qing-Fang Bi, Bernhard Ahrens, Thomas Wutzler, Markus Reichstein, and Marion Schrumpf

Comprehending the factors influencing microbial carbon use efficiency (CUE), and where CUE is most optimal to soil organic carbon (SOC) storage, are crucial for managing microbial roles in SOC sequestration and model prediction. Yet, establishing a direct mathematical relationship between CUE and SOC might be challenging, with global distributions and controls remaining unresolved, particularly in response to various global changes. Here, we leverage a global synthesis of CUE measurements by 18O-microbial DNA growth, and observed an average CUE across all biomes at 0.3, with the highest in temperate grasslands and deeper soils, and the lowest in tropical forests. Random forest analysis identified climates (aridity index and mean annual temperature: MAT) and soil properties (pH, bulk density and soil C:N ratio) as primary drivers influencing CUE. However, microbial biomass size overall exhibited a smaller effects on CUE, despite its substantial impact in each land use type. We then review how these drivers affecting CUE values may be altered by warming, soil fertilization, altered precipitation and elevated carbon dioxide. Notably, nitrogen additions plays a big role in increasing CUE and promoting SOC contents, while warming effects depend on time-scale, with long-term warming potentially leading to SOC losses with a lower CUE and growth. Moreover, we found that the CUE–SOC relationship varies across different climates, greatly driven by MAT and soil properties. Higher CUE promots SOC per fine fraction (clay+silt) across the major data points, contrasting with a negative relationship in a subarctic study, where pH is the primary determinate. Consequently, there might be no simple linear relationship between CUE and C in microbial biomass and soil. We conclude by discussing the integration of CUE into SOC models and the necessity of incorporating interactions between CUE and individual drivers for predicting soil carbon-climate change scenarios. Our study underscores the importance of considering microbial CUE and other microbial processes for improving projections of SOC dynamics.

How to cite: Bi, Q.-F., Ahrens, B., Wutzler, T., Reichstein, M., and Schrumpf, M.: Global distribution and drivers of microbial carbon use efficiency for projecting soil organic carbon fates under a changing climate: A meta-analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19075, https://doi.org/10.5194/egusphere-egu24-19075, 2024.

EGU24-19954 | ECS | Orals | SSS4.1

Microbial phenology in high-alpine environments: the influence of plant dynamics and physiological stress in a changing climate.  

Adam T. Ruka, Johannes Schweichhart, Jiří Doležal, Kateřina Čapková, Travis B Meador, Roey Angel, Rosa Paulina Calvillo Medina, Zuzana Chlumská, Vojtěch Lanta, Nadine Praeg, Paul Illmer, and Klára Řeháková

Alpine biomes experience harsh environmental conditions and short growing seasons, which necessitate interspecific and intraspecific interactions among plants and soil microbes to ensure the stability of diversity and ecosystem multifunctionality. With strong seasonal dynamics in alpine regions, including snow cover, snowmelt, and drought, “hot moments” of biogeochemical activity occur when pulses of nutrients dictate microbial processes across the biome. However, within the rhizosphere, microbial processes are promoted or deterred during phases of plant growth, senescence, and nutrient allocation, leading to a more nuanced seasonal pattern of soil microbes. Indeed, these factors lead to a general microbial phenology of soil processes and community composition. Yet, shifted climatic regimes due to warming likely cause these relationships to be strained, potentially resulting in physiological stress among plants and microbes. Therefore, our research focuses on the coupling or decoupling of plant and microbial parameters across seasonal changes in the Austrian Alps by assessing stoichiometric ratios of shared nutrients such as carbon (C), nitrogen (N) and phosphorus (P), along with microbial diversity. 

Using elevation gradients, the corresponding influence of plants, soil chemistry, and environmental conditions upon microbial phenology can be assessed in two different biomes: undeveloped subnival zones and nutrient-rich alpine meadows.  Furthermore, by combining methods for assessing biological soil parameters, such as chloroform fumigation extraction, enzymatic assays, and respiration measurements, with amplicon DNA sequencing, we can observe broad microbial community responses such as increased biomass (Cmic) in different seasons related to plant-specific interactions while identifying microbial taxa (fungal and bacterial) that indicate nutrient limitations in conjunction with ratios of enzymatic activity. Additionally, by measuring plant nutrient concentrations in distinct plant organs, we can infer which physiological processes among plant species most closely correspond with changes in broad microbial parameters and rhizosphere diversity.

Therefore, we propose that certain aspects of microbial phenology are generalizable, such as increased N cycling during winter and spring months, while the temporal optima for C cycling is more plant-specific. Furthermore, we present results from the rarely studied snow-covered winter months, in which the mineralization of C, P, and chitin degradation are highest. In total, these studies demonstrate a thorough analysis of plant-microbial interactions in alpine ecosystems which are subject to significant change within the coming decades.

How to cite: Ruka, A. T., Schweichhart, J., Doležal, J., Čapková, K., Meador, T. B., Angel, R., Calvillo Medina, R. P., Chlumská, Z., Lanta, V., Praeg, N., Illmer, P., and Řeháková, K.: Microbial phenology in high-alpine environments: the influence of plant dynamics and physiological stress in a changing climate. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19954, https://doi.org/10.5194/egusphere-egu24-19954, 2024.

EGU24-21168 | Orals | SSS4.1

What taxon-specific growth measurements reveal about microbial growth strategies in natural soil communities 

Andreas Richter, Dennis Metze, Alberto Canarini, Lucia Fuchslueger, Hannes Schmidt, and Christina Kaiser

Heterotrophic microorganisms decompose soil organic matter to assimilate organic compounds that provide energy and carbon for growth and maintenance. The growth of microbial communities is thus at the heart of the carbon cycle, and understanding how microbial growth is controlled is arguably of paramount importance for understanding global carbon cycling in the present and future climate. 

Most information on microbial growth comes from work with pure cultures (population level) or from studies of microbial community growth, while understanding the growth of individual microbial taxa in natural communities is poorly studied and understood. However, with the advent of new stable isotope probing techniques based on 18O from labelled water, it is now possible to look beyond the community level to the growth of individual populations of microorganisms in complex soil communities. In addition, recent advances in labelling growing microbial taxa without the addition of liquid water, the so-called ‘vapor qSIP', allow us to analyze microbial growth in complex communities without changing environmental conditions, a prerequisite for studying the behavior of microbial communities in climate change experiments.

We report here on two climate change experiments in which we performed taxon-resolved growth measurements under different environmental conditions. Our results show the following:

(1) Contrary to our expectations, changing environmental conditions (e.g., soil warming and drought) led to a change in the number of actively growing bacterial taxa, but not in their growth rates. Among other things, this challenges the paradigm developed from a plethora of measurements of microbial community growth that microbial physiology is accelerated by higher temperatures.

(2) Many microbial taxa were only actively dividing in specific climate change treatments, i.e., under specific environmental conditions. We conclude that the realized ecological niche of bacteria appears to be much smaller than community growth measurements suggest. Testing, for example, the temperature niche of individual populations (with presumably different functional traits) may therefore lead to very different predictions of soil functions in a future climate.

(3) Compared to estimates of total soil microbial community composition (e.g., amplicon sequencing of the 16S rRNA gene), the actively growing community is more sensitive to changes in environmental conditions, allowing a more accurate prediction of community structure in a future climate and its functional roles in biogeochemistry.

Overall, measuring taxon-resolved population growth rates of complex communities provides a novel, more nuanced and sophisticated picture of soil ecosystems, which may help to develop better predictions of structural and functional changes in microbial ecosystems in a future climate.

How to cite: Richter, A., Metze, D., Canarini, A., Fuchslueger, L., Schmidt, H., and Kaiser, C.: What taxon-specific growth measurements reveal about microbial growth strategies in natural soil communities, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21168, https://doi.org/10.5194/egusphere-egu24-21168, 2024.

EGU24-21170 | ECS | Posters on site | SSS4.1

Tracking 13C into soil organic matter through the mycorrhizal fungal pathway under nutrient addition 

Kaydee S. Barker, Matthew L. Meehan, David Johnson, Richard D. Bardgett, and Clare H. Robinson

Arbuscular mycorrhizal (AM) fungi are ubiquitous plant symbionts that mediate soil organic matter (SOM) formation through nutrient exchange and the accumulation of their own biomass and necromass. Recent studies suggest that microbial necromass, including fungal necromass, may account for upwards of half of SOM carbon, but the specific contribution of AM necromass remains unknown. Additionally, how land management impacts AM-mediated SOM is not well understood, especially in grasslands where AM fungi are prevalent and play a key role in regulating plant diversity and ecosystem function. We grew Lolium perenne with four treatments: (1) an inoculation of AM spore-rich sandy soil, (2) an application of nitrogen-phosphorus-potassium (NPK) fertilizer, (3) a combination of spore-rich soil and NPK, and (4) a control. We isotopically labelled plants with 13C-CO2 before incubating the roots and AM hyphae in place, and are measuring 13C in SOM, plant and microbial pools, and released CO2 at multiple timepoints over 6 months to track C through decomposition. Our preliminary results show that both 13C and 13C-CO2 respiration were lower for fertilizer treatments compared to control and inoculation-only treatments during the first month of incubation. This demonstrates that even a small one-time NPK application may influence subsequent decomposition of root and AM tissues at the end of the growing season. The lower amounts of 13C respiration may be due to differences in plant carbon to nitrogen ratios, leading to higher microbial carbon use efficiency, or NPK addition may have inhibited the growth of AM hyphae, leading to decreased available 13C in the soil. These hypotheses will be investigated further with additional measurements as outlined above. By using stable isotope tracing into biomarkers, SOM pools, and soil respiration, our study will shed light on the contribution of AM and associated root necromass to SOM carbon and provide needed insight for conscious grassland management.

How to cite: Barker, K. S., Meehan, M. L., Johnson, D., Bardgett, R. D., and Robinson, C. H.: Tracking 13C into soil organic matter through the mycorrhizal fungal pathway under nutrient addition, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21170, https://doi.org/10.5194/egusphere-egu24-21170, 2024.

EGU24-588 | ECS | Orals | SSS4.2

Relating bush encroachment density of savanna soils in the Kalahari district in Botswana to soil organic matter stocks and quality. 

José María García de Castro Barragán, Nnyaladzi Batisani, Flora Pule-Meulenberg, Lawrence Akanyang, José María de la Rosa Arranz, M. Rocio Reinoso Limones, and Heike Knicker

Bush encroachment is a form of rangeland degradation. It is characterized by a shift from herbaceous to woody plant dominance, which has reduced indigenous plant and animal biodiversity and it’s a significant problem in southern African savannas, particularly in Botswana, Namibia and South Africa. Overgrazing by cattle on the one hand and the loss of a large part of large herbivores on the other hand, have been identified as main contributor to imbalance of this delicate ecosystem. The present study aimed to investigate bush encroachment effects on soil organic matter (SOM) in areas of low, medium, and high bush density in a farmed area of the Botswana’s savanna. Bush encroachment is expected to have significant effects on soil properties. It is assumed to decrease soil organic C concentration as well as contents of macro and micro nutrients. To investigate such possible impacts, a sampling was realized during the dry season in various plots with varying encroachment densities (Senegalia mellifera). The analysis included standard soil parameters, (pH, electrical conductivity, cation exchange capacity; elemental composition, and bulk density) the composition of the SOM was characterized by solid-state nuclear magnetic resonance spectroscopy. The preliminary results of these analysis revealed only small differences between sites with low, medium, and high levels of bush encroachment. This suggests that the impact of bush encroachment on savannah’s SOM is lower than expected and may not be directly related to bush density. Further research will compare the obtained data with data obtained during the wet season to obtain a better understanding of the SOM dynamics and the impact of encroachment on soil degradation.

Acknowledgement: The authors would like to express their gratitude to the European Commission for the financial support of this research within the European Framework Program for Research and Innovation Horizon 2020 (Grant No. 101036401).

How to cite: García de Castro Barragán, J. M., Batisani, N., Pule-Meulenberg, F., Akanyang, L., de la Rosa Arranz, J. M., Reinoso Limones, M. R., and Knicker, H.: Relating bush encroachment density of savanna soils in the Kalahari district in Botswana to soil organic matter stocks and quality., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-588, https://doi.org/10.5194/egusphere-egu24-588, 2024.

EGU24-1115 | Posters on site | SSS4.2

The impact of the Russian-Ukrainian war on the soil-surface water interactions 

Vita Strokal, Yevhenii Berezhniak, Olena Naumovska, and Svitlana Palamarchuk

This research aims to discuss and reflect on the main consequences of the Russian-Ukrainian war on the soil, and water resources of Ukraine. For the soil resources, the main outcomes are as follows: 1) approximately 35% of the Ukrainian territories have been experiencing soil destruction processes due to the war implications – 130 thousand km2 of the land is mined or damaged; part of the agricultural land for growing crops is not suitable, especially in regions (oblasts) such as Kharkiv, Mykolaiv, Kherson, Zaporizhzhia, Kyiv, and Chernihiv (according to the state report on May 2023); 2) as a result of the damaged Kakhovka Hydropower Dam, losses of crop yields on the part of the Kherson region consist of 100 thousand tons, 31 irrigation systems are left without access to water supply in the southern part of Ukraine. Degradation of soil has impacts on water pollution via polluted runoff and erosion.

For the water resources, the main outcomes are as follows: 1) 724 hydrotechnical systems (hydraulic structures), 160 of treatment and sewage systems (water treatment and sewage facilities), and 22 dams are destroyed leading to water pollution; 2) up to 90% of the irrigation system in the south of Ukraine is lost, and 67% less fishing due to damaged or destroyed hydraulic systems; 3) the disruption of the Kakhovka Hydropower Dam has resulted in the flooded areas: water from the dammed reservoir was flushed and flooded the surrounded areas with polluted soils and households, a lot of pollutants was released into the water from untreated human waste, products of animals, around 31 water supply and drainage facilities were affected, 13 villages left without centralized water supply, and 4 landfills of solid household waste became flooded.

In our research, we analyzed the implications of the Russian-Ukrainian war on the state of soil and water resources and explored their interactions. We identified the main consequences of the Russian aggression such as the loss of soil productivity, the reduction of food production potentials, and the reduction of water safety and availability. The cause-and-effect relationships of risks are discussed. These relationships can become a threat and lead to the deterioration of the population's supply of food and safe water, and the spread of infectious diseases.

Keywords: soil resources; water resources; the Russian-Ukrainian war; soil destruction, the deterioration of food and safe water.

 

How to cite: Strokal, V., Berezhniak, Y., Naumovska, O., and Palamarchuk, S.: The impact of the Russian-Ukrainian war on the soil-surface water interactions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1115, https://doi.org/10.5194/egusphere-egu24-1115, 2024.

EGU24-3156 | ECS | Orals | SSS4.2

Elucidation of the interplay between roots and microorganisms in the organic N transformation in the rhizosphere of maize 

Guoting Shen, Andrey Guber, Alexandra Kravchenko, and Evgenia Blagodatskaya

Mechanisms of nitrogen (N) acquisition in the rhizosphere often include microbial immobilization of mineral N and its further transformation into organic compounds. Therefore, visualization and quantification of organic N distribution and their correlation with N-related enzymatic hotspots helps to reveal the role of roots in plant-microbial interplay related to N cycling. In this study, time-lapse leucine aminopeptidase (LAP) zymography and amino-mapping were coupled to reveal amino-N distribution both in the soil and distinct root segments of Zea mays L. A strong overlap between amino-N content and LAP activity in seminal and lateral root tips, as well as seminal roots, highlighted the intricate interplay between plants and microorganisms in N acquisition. Remarkably, we also uncovered a significant decoupling of LAP activity from amino-N in lateral roots and bulk soil. The distinct patterns in different root parts provided a perspective on the major origins of enzyme production in the rhizosphere. Endogenous LAP production by roots and root-associated microbes in seminal roots and root tips contrasted with the reliance on exogenous rhizosphere microorganisms for enzyme activity in lateral roots. This finding not only advances our understanding of N acquisition but also opens up the new avenues for discussion on the ecological roles of different root segments in shaping the rhizosphere environment.

How to cite: Shen, G., Guber, A., Kravchenko, A., and Blagodatskaya, E.: Elucidation of the interplay between roots and microorganisms in the organic N transformation in the rhizosphere of maize, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3156, https://doi.org/10.5194/egusphere-egu24-3156, 2024.

Substantial progress has been made in estimating and mapping soil organic carbon stocks, but the quantification of carbon stock change rates still needs exploration in numerous soil and management combinations. In this research, the soil organic carbon (SOC) changes and soil organic matter (SOM) composition in the long-term experiment (established in 1989, Tartu, Estonia) with sandy loam soil were studied. The experiment involves three-field crop rotation (potato-spring wheat-spring barley) with two fertilization regimes: (1) mineral fertilisation (N rates 0, 40, 80, 120 and 160 kg ha-1) and (2) same mineral fertilisation treatments with farmyard manure amendment. During 1989–2017, every spring the soil samples were taken from the 0-20 cm soil layer, and SOC concentration was measured by dry combustion. In 2017, the size fractionation of soil samples was also performed. In 2022, the soil samples were also taken from the area surrounding the experimental site, which has not been cultivated since the experiment was established and has been as permanent grassland (GR). Soil mineral-associated organic matter (MAOM fraction;<63 µm) of permanent grasslands is considered to be saturated with C thus the GR was used to estimate the MAOM-C saturation potential in treatments.

The SOC stock increased (0.08–0.18 Mg ha-1 y-1 depending on N fertiliser rate) only in manure treatments. In GR treatment the SOC stock remained unchanged. Without manure, the SOC stock decreased in range from -0.15 to -0.26 Mg ha-1 y-1. N fertilization had a positive effect on SOC stock. Initially, 27% of total SOC stock is related to particulate organic matter (POM fraction, 63-2000 µm) and 73% to MAOM fraction. Without manure, the proportion of C related to POM fraction decreased during 28 years to 21%, while in treatments with manure, it remained stable (28%). POM fraction plays an important role in plant nutrient supply, thus a higher proportion of C related to POM fraction in treatments with manure indicates sustainable nutrition conditions for plants and all soil biota. The MAOM-C concentrations in treatments without manure varied from 17.8 to 19.4 mg g-1 and were lower compared to treatments with manure (21.0–21.8 mg g-1). The MAOM-C of GR was 20.7 mg g-1 indicating that the soil is nearly saturated in manure treatments.  However, treatments without manure are far from saturation and have considerable potential for additional MAOM-C sequestration, varying between 3.0-6.8 Mg ha-1 depending on N fertilization. Soil organic matter fractionation into POM and MAOM fractions allows us to assess the soil's properties for sustainable plant production, and actual C sequestration capabilities, and provide crucial recommendations for effective management strategies.

How to cite: Kauer, K. and Astover, A.: Soil organic carbon change after 28 years of fertilisation in temperate conditions of Estonia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3449, https://doi.org/10.5194/egusphere-egu24-3449, 2024.

EGU24-3910 | ECS | Posters on site | SSS4.2

Microrespiration: A field method for measuring microbial activity in arable soils 

Franziska Weinrich

Microrespiration: A field method for measuring microbial activity in arable soils

Franziska Weinrich1, Katharina Keiblinger1, Christoph Rosinger1,2 Gernot Bodner2

1Institute of Soil Research, Department of Forest- and Soil Sciences, University of Natural Resources and Life Sciences (BOKU), Vienna, Austria (franziska.weinrich@students.boku.ac.at)

2Institute of Agronomy, Department of Crop Sciences, University of Natural Resources and Life Sciences (BOKU), Vienna, Austria

The debate on soil health is more topical than ever. Large-scale soil monitoring is therefore an important tool for assessing the state of soil health. In this context, relatively simple yet reliable methods are needed to accompany lab-based analytics of different soil health indicators, such as microbial activity. Microbial activity is a useful parameter because most soil processes are mediated by soil microorganisms. The aim of this study is to develop a simple and affordable field test for broad applicability of measuring microbial activity in arable soils. The method was tested for sensitivity to different arable management systems and effects of land use as well as the influence of soil texture.

The principle of the field method is based on the colour change of a pH-indicator due to the acidic reaction with CO2 that is released during soil respiration. For this purpose, 13 agricultural sites with varying soil texture, three management systems as well as two types of land use (arable and natural vegetation) were examined. Pioneer management is characterized by management aiming for an increase of soil health by applying conservational or regenerative practices, Standard management involves state of common knowledge practices and the Reference, representing a different land use, is provided by a semi-natural vegetation strip.

The method was developed for different amounts of soil, moisture conditions, incubation periods and substrates (glucose powder, milled straw, milled alfalfa). For the validation of the field method, the colour change of the indicator (evaluated by means of RGB data) is compared to respiration measurements with gas chromatography in the laboratory. Additionally, microbial biomass carbon and ergosterol concentrations as well as their ratio were determined to evaluate changes in the abundance of the microbial community and bacteria vs. fungi composition.

The results show that the continuous colour change of the indicator is highly correlated with the CO2 concentrations measured in the laboratory (r2 = 0.62; p < 0.001). Furthermore, the metabolic quotient and the colour change correlate well with each other (r2 = 0.72; p < 0.001). The differentiation between agricultural management systems (Pioneer vs. Standard) is not so clear, land use however can clearly be distinguished with this method.  The influence of soil texture on the results of the field test is clearly visible. However, it is not possible to derive an indication on the microbial community composition with this method.

The performance of the field method leads to reasonable results and proves to be suitable for the simple determination of microbial activity in arable soils. After further improvement, this method provides a rather simple and affordable tool for soil health monitoring of arable soils.

How to cite: Weinrich, F.: Microrespiration: A field method for measuring microbial activity in arable soils, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3910, https://doi.org/10.5194/egusphere-egu24-3910, 2024.

The land use changes and environmental pollution brought by urbanization are important aspects of global change. Cities provide a unique "natural laboratory" for people to understand the impact of human-nature composite ecosystems on global change and their response processes. Unlike natural soils, human activities during urbanization directly or indirectly affect the formation and development of soils. Generally, urban soils have a higher organic carbon content compared to agricultural soils and some natural soils, making them an important carbon reservoir in urban ecosystem carbon cycles. The urban-rural gradient method based on urbanization intensity provides a possibility for studying the response of Soil Organic Carbon (SOC) storage to urbanization on a global scale. Here, we define Urban Intensity (UI) as the proportion of impervious surface area within each 1x1 square kilometer (ranging from 0 to 100%). We first analyzed the trends of SOC storage along the UI gradient globally and in different climate zones, distinguishing the contributions of natural and socio-economic factors through multiple linear regression and residual quantification. The study found that as UI increases, SOC storage undergoes phased changes, with natural and socio-economic factors contributing differently in each urbanization stage and climate zone. For example, globally, when UI is low (UI ≤ 0.25) and high (0.75 < UI ≤ 1), SOC storage tends to decrease with increasing UI, while at medium intensity (0.25 < UI ≤ 0.75), SOC storage shows an increasing trend. Globally, changes in socio-economic factors (population, GDP) are the main drivers of SOC storage changes during urbanization. Particularly at low and medium urbanization intensities, socio-economic contributions reach 98% and 89%, respectively. However, as urbanization intensity increases, the driving role of natural factors becomes more apparent, contributing over 40% in areas of high urbanization intensity.

How to cite: Xu, F. and Li, S.: Trends and drivers of the soil organic carbon stocks along the urban-rural gradients globally, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4361, https://doi.org/10.5194/egusphere-egu24-4361, 2024.

EGU24-4405 | Orals | SSS4.2

Quantifying Soil Quality in Dryland Regions as A Key Step in Phosphate Mining Restoration 

Tarin Paz-Kagan, Arnon Karnieli, and Yaron Ziv

Mining is crucial in driving economic development but entails extensive environmental damage, such as soil degradation and water and air pollution. Mining activity impacts the soil quality, often making it unable to support ecosystem function and structure and reducing its ecological resilience. Soil degradation reduces physical, chemical, and biological (PBC) soil properties. The current study aims to apply the soil quality index (SQI) to quantify soil restoration success in an open-pit phosphate mine in Israel’s hyper-arid environment. In this regard, we evaluated an ecological restoration practice that includes topsoil refilling compared to the adjacent undisturbed natural system. We used transformed and standardized scorings of 11 PBC soil properties that were further statistically integrated into overall SQI values. Our results revealed significant differences between the restoration practice areas and the nearby natural areas, with a higher soil quality value in the latter. It is proposed that the topsoil restoration method is mainly affected by soil biological indicators, such as soil organic matter, soil proteins, and polysaccharides related to biocrust development, and, to a lesser extent, by physical properties (primarily infiltration rate, followed by available water content). The former properties encourage the biocrust establishment, which is essential for soil surface stabilization. This, in turn, affects the water infiltration, nutrient availability, and erosion rates. The chemical indicators showed no significant differences between most sites for the overall soil quality. In conclusion, our results reflect a slow recovery of the SQI in the restored sites, demonstrating that achieving the quality of the natural areas requires a long-term recovery process. Moreover, the physio-biological indicators were more suitable for reliably estimating mining restoration practices in dryland areas. Our approach could have broader implications for evaluating the ecological restoration success in hyper-arid environments.

How to cite: Paz-Kagan, T., Karnieli, A., and Ziv, Y.: Quantifying Soil Quality in Dryland Regions as A Key Step in Phosphate Mining Restoration, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4405, https://doi.org/10.5194/egusphere-egu24-4405, 2024.

EGU24-5424 | ECS | Orals | SSS4.2

Stoichiometry of soil organic matter and microbial functional traits altered after 5 years of maize monoculture 

María Martín Roldán, Doris Vetterlein, Mika Tarkka, and Evgenia Blagodatskaya

The long-term transformation of organic matter in agroecosystems is modulated by soil properties and functional traits of plants and microorganisms, and is an indicator of soil quality. We studied how contrasting soil texture (loamy vs sandy) and two plant genotypes (a wild type, WT and a mutant deficient in root hairs, rth3) altered organic matter through microbial functioning in a field experiment after 5 years of maize monoculture. Our hypotheses were that (1) loamy rather than sandy soil will promote a larger OM storage; and (2) root-hairs, entailing a higher root-soil interface and water retention in the rhizosphere, boosting microbial processes and OM fluxes, will increase OM content not only in the rhizosphere but in the long-term, also in the bulk soil. To address these hypotheses, plots were filled with homogenized soil, being sandy soil a mix of 16.7 % loam with quartz sand, and the two maize genotypes. After 5 years of monoculture, soil was collected at the early maize growth stage of BBCH19, in the first 20 cm and the 20 to 40 cm depths. We determined stoichiometric ratios of total (TOC/TN) and labile (DOC/DON) fractions of soil organic matter, and microbial eco-physiological indexes related to OM transformation and sustainability, i.e. respiration-to-biomass ratio, qCO2, and microbial-to-total organic C ratio, Cmic:Corg.  The 5- and 7-times larger C supply in loamy vs sandy soil, for WT and rth3, respectively was explained by 40% more efficient C metabolism, i.e. less C losses through respiration per biomass unit, by 90% lower specific labile C content (DOC:Cmic ratio) and by 60% faster microbial turnover (µmax-1) in the former. As the TN content was only 3.1 and 4.2 times larger in loamy than sandy soil for WT and rth3 respectively, the resulting C:N ratio was 1.7- times greater for loamy than sandy soil, indicating more unbalanced stoichiometry in the former for both genotypes. Remarkably, the C and N content increased 20 and 36 %, respectively, after 5 years of maize monoculture, in the plots under root hair-deficient mutant than under wild type maize resulting in significantly larger C storage at rth3-plots in loamy soil. This may be explained by the reported higher exudates production by rth3 under the field conditions. Soil depth up to 40 cm did not show big differences in the capacity for C storage, likely due to similar root density in both depths. Concluding, loamy soil showed a higher capacity of C storage through microbial turnover and sandy soil demonstrated larger C losses through DOC compounds and respiration after 5 years of maize monoculture. Finally, carbon availability was not the limiting factor in sandy soil for microbial growth, but rather other factors such as soil water holding capacity, or OM fluxes from rhizosphere to bulk soil.

How to cite: Martín Roldán, M., Vetterlein, D., Tarkka, M., and Blagodatskaya, E.: Stoichiometry of soil organic matter and microbial functional traits altered after 5 years of maize monoculture, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5424, https://doi.org/10.5194/egusphere-egu24-5424, 2024.

EGU24-5596 | ECS | Posters on site | SSS4.2

Assessing climatic, hydrogeological, and anthropogenic factors shaping sustainable soil management: A case study in northern Germany 

Vahid Sobhi Gollo, Amirhossein Hassani, Peter Fröhle, and Nima Shokri

Sustainable soil and land management which is vital for security of natural resources and food production is a complex task due to the wide range of parameters influencing soil quality and health (1,2). Various parameters, including climatic variables such as precipitation, evaporation, and, in coastal regions, sea level rise and saltwater intrusion (3), hydrogeological factors like groundwater table levels influencing evaporative fluxes (4), groundwater salinity, and soil properties as well as anthropogenic factors such as fertilization and land use, play important roles in sustainable soil management and health. In this study, we gathered diverse climatic, hydrogeological, and anthropogenic data within an intensive food production and natural preservation study area situated in North Sea adjacent northern Germany to explore the complex interplay of parameters affecting soil health and characterize the impact of these variables on sustainable soil management. The area is characterized by predominantly flat terrain with fertile soils utilized for agriculture and grazing. Additionally, it contains protected areas such as forests. Due to significant variations in land use and soil properties across the region, we categorized the area into subgroups for robust comparability. This involved dividing the region into agricultural, grassland, and forest areas, each identified by specific characteristics, such as crop production, meadow type, fertilization method, and soil nutrient holding capacity. Additional parameters including precipitation, evaporation, and leakage were factored into a groundwater recharge model for the area. Statistical analysis and machine learning algorithms were employed to assess the interrelations among these parameters affecting sustainable soil management. Recognizing these interrelations, we adapted our model to potential future scenarios and discussed how hypothetical alterations to parameters such as groundwater recharge and added fertilizer could impact land management in the study area. Our findings are applicable to areas employing similar land management practices, offering insights into the vulnerabilities and potentials of these regions in the face of a changing climate and are useful for implementing mitigation measures against land degradation and preventing the loss of fertile soil.

 

1. Hassani, A., Azapagic, A., Shokri, N. (2020). Predicting Long-term Dynamics of Soil Salinity and Sodicity on a Global Scale, Proc. Nat. Sci., 117(52), 33017-33027, https://doi.org/10.1073/pnas.2013771117

2. Hassani, A., Azapagic, A., Shokri, N. (2021). Global Predictions of Primary Soil Salinization Under Changing Climate in the 21st Century, Nat. , 12, 6663. https://doi.org/10.1038/s41467-021-26907-3

3. Nevermann, H., Gomez, J.N.B., Fröhle, P., Shokri, N. (2023), Land loss implications of sea level rise along the coastline of Colombia under different climate change scenarios, Clim. Risk Manag., 39, 100470, https://doi.org/10.1016/j.crm.2022.10047

4. Sadeghi, M., Shokri, N., Jones, S.B. (2012). A novel analytical solution to steady-state evaporation from porous media. Water Resour. Res., 48, W09516, https://doi.org/10.1029/2012WR012060

How to cite: Sobhi Gollo, V., Hassani, A., Fröhle, P., and Shokri, N.: Assessing climatic, hydrogeological, and anthropogenic factors shaping sustainable soil management: A case study in northern Germany, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5596, https://doi.org/10.5194/egusphere-egu24-5596, 2024.

The conversion of open fields to greenhouse cultivation leads to an increase in the amount and frequency of fertilization, as well as an increase in tillage intensity, which significantly affects soil organic carbon turnover and sequestration. In this study, four types of soils were selected in the coastal area of southeast China based on a sequence of greenhouse cultivation years of 0, 8, 18, and 36. The study fractionated the soil into four organic fractions: free mineral-associated organic carbon (f-MAOC), occluded mineral-associated organic carbon (o-MAOC), free particulate organic carbon (f-POC), occluded particulate organic carbon (o-POC), using particle size and density separation. The organic carbon content and natural abundance of 13C were measured for each of these fractions, as well as for the bulk soil. Key findings include a significant increase in bulk soil organic carbon with extended greenhouse cultivation, although differences between 18 and 36 years were not significant (27.4 g kg-1 and 31.7 g kg-1 respectively). o-MAOC and o-POC contents increased initially, then declined after 18 years. Notably, f-POC content significantly rose after 36 years, reaching 9.91 g kg-1. The δ13C values for f-MAOC, o-MAOC, and f-POC showed similar increasing trends, peaking after 18 years. The carbon flow analysis revealed the main carbon turnover pathway from f-POC to o-MAOC, with reverse transfers occurring after 18 and 36 years. It highlighted a saturation limit in the sequestration capacity of occluded organic carbon and significant accumulation of labile organic carbon due to long-term greenhouse cultivation. These findings offer new insights into carbon management in agricultural soils.

How to cite: Tian, Y., Liu, J. J., and Lu, S.: The impact of converting open-field cultivation to greenhouse cultivation on the accumulation of organic carbon in coastal soil, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7247, https://doi.org/10.5194/egusphere-egu24-7247, 2024.

EGU24-7709 | Posters on site | SSS4.2

How biochar suspension influences soil microbial activity and phosphorus availability 

Iryna Loginova, Nataliya Bilyera, Callum Banfield, Denis Kutoley, Yakov Kuzyakov, and Michaela A. Dippold

Biochar (BC) application to soil is a method of long-term carbon (C) sequestration in croplands. Along with contribution to climate change mitigation, agronomic benefits of biochar are widely accepted. Amelioration and nutritive benefits of biochar are mainly attributed to high applications rates, which may not be viable for farmers. We suggest a new approach: band application, which implements biochar in modern intensive crop rotations and optimizes both C and nutrients cycles (i.e. phosphorus (P)).

As maize is globally one of the most widely planted crops, corncobs (CC) may be utilized for BC production. Corncob biochar (CC BC) may be implemented into the farming practice as suspension with liquid phosphorus solution jointly applied in band in the close proximity to seeds.

We conducted an incubation experiment to evaluate the short-term effects (within 32 days) of corncob biochar and inorganic P application on P availability and microbial activity in a loamy Luvisol.

Corncobs were pyrolyzed to biochar (350oC; 0.2-0.3oC s-1), grinded (<200 µm), suspended and mixed with phosphate solution (as monopotassium phosphate). We compared liquid phosphorus (P) and joint P and BC application (BC+P) to control (water). The application rates were: 30 kg ha-1 P (200 mg kg-1 P) and 300 kg ha-1 BC (0.2% w/w). Soil was sampled on day 7, 14, and 32 to measure pH, available P, enzyme kinetics, microbial biomass C, N, and P.

Despite the alkaline pH of BC (pH 8.7), application of BC+P and P decreased soil pH (5.6-5.7) compared to soil in control (5.8). Acidifying effect of suspensions was attributed to used phosphate source and may differ for others. BC+P did not alter soil P availability compared to solely P applied. Thus, dynamics of soil available P within 32 days was mainly attributed to soil processes but not the BC effect.

Higher basal respiration in amended soil compared to control within first 7 days indicates that physiological status of microorganisms was affected by P and BC+P application. But this was independent on changes in microbial biomass C and dissolved organic C. Microbial biomass-specific activity of beta-glucosidase and leucine aminopeptidase (but not acid phosphatase) in BC+P soil were lower compared to only P application, that may be caused by adsorbing properties of BC. The application BC+P increased the catalytic efficiency (Ka) of all enzymes compared to only P, which indicates the positive effect of biochar on enzymatic efficiency of soil.

Sole P application resulted in acceleration of P immobilization on day 32, as microbial molar C:N:P ratio for only P (18:2:1) differed from control and BC+P (35:3:1 and 36:4:1, accordingly). Principal Component Analysis revealed that BC+P treatment differed from the control and solely P applied at all time points.

To conclude, joint application of corncob biochar suspension and phosphorus solution may not only increase soil P availability, but prevent high P immobilization by microorganisms and facilitate higher enzyme efficiency to potentially increase nutrient availability for seedlings in the application bands.

How to cite: Loginova, I., Bilyera, N., Banfield, C., Kutoley, D., Kuzyakov, Y., and Dippold, M. A.: How biochar suspension influences soil microbial activity and phosphorus availability, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7709, https://doi.org/10.5194/egusphere-egu24-7709, 2024.

EGU24-7713 | Posters on site | SSS4.2

Status of soil health after 18 years of systematic tillage 

Barbara Simon, Györgyi Gelybó, Igor Dekemati, Hanaa M.I. Tharwat, Maxwell Maimela Modiba, and Márta Birkás

Carbon sequestration in our soils in the form of stable, humus materials is one of the most important tasks of our time, which can be monitored by tests carried out in long-term cultivation experiments. In our research, our objective was to determine the soil physical (0-10, 10-20, 20-30 and 30-40 cm depth: bulk density, soil moisture content), chemical (0-20 cm: pH(H2O), pH(KCl), soil organic carbon) and biological properties (0-20 cm: abundance, biomass, species composition of earthworms, soil microbial respiration – SMR). Out of the six soil cultivation methods (no-till, loosening, shallow and deep cultivation, disking and ploughing), we selected three (no-till – NT; shallow cultivation – SC, and ploughing – P) for our experiment. Based on our results, we can say that there was significant difference among the treatments in bulk density in the top layer (0-10 cm) (NT > SC, P), and NT was significantly greater than P in the deeper layers (10–20, 20–30, 30–40 cm). Soil moisture content was only significantly different in the lowest examined layer (30-40 cm), ie. P > SC = NT. The soil organic carbon content (0-10cm) of the investigated treatments was the highest in NT (2.5%), followed by SC (2.4%) and P (2.0%). Soil microbial respiration was significantly greater in NT than in SC and P. The abundance and biomass of earthworms was the highest in the NT treatment (189 ind m-2, 41.26 g m-2), which was followed by SC (125 ind m-2, 36.9 g m-2) and then by P (48 ind m-2, 7.4 g m-2). Thus, NT offers beneficial habitat for earthworms and microorganisms, high SOC storage capacity, whereas the physical parameters tend to be less convenient due to soil compaction in our experiment. Therefore, SC can offer an alternative approach for sustainable soil tillage.

How to cite: Simon, B., Gelybó, G., Dekemati, I., M.I. Tharwat, H., Maimela Modiba, M., and Birkás, M.: Status of soil health after 18 years of systematic tillage, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7713, https://doi.org/10.5194/egusphere-egu24-7713, 2024.

EGU24-7955 | ECS | Orals | SSS4.2 | Highlight

Soil health increases primary productivity across Europe 

Ferran Romero, Maëva Labouyrie, Alberto Orgiazzi, Cristiano Ballabio, Panos Panagos, Arwyn Jones, Leho Tedersoo, Mohammad Bahram, Carlos Guerra, Nico Eisenhauer, Dongxue Tao, Manuel Delgado-Baquerizo, Pablo García-Palacios, and Marcel van der Heijden

The role of soil health in regulating primary productivity at large scale across different land-use types remains poorly understood. This hinders our ability to predict the impact of soil degradation on essential ecosystem services such as food provision and climate regulation. To address this gap, we conducted a pan-European observational field study using data from 588 sites and 27 countries to investigate the link between soil health (a composite index based on soil properties, biodiversity, and plant disease control) and primary productivity across three major land-use types: woodlands, grasslands, and croplands. We found that soil health in woodlands was 31.4% higher than in grasslands, and 76.1% higher than in croplands. We further observed that soil health was positively linked to cropland and grassland productivity at the continental scale. Woodland productivity was linked to climate conditions rather than to soil health status. We observed that soil organic carbon and the richness of Acidobacteria, Firmicutes, and Proteobacteria had a positive effect on primary productivity. Among microbial functional groups, we found that nitrogen-fixing bacteria and mycorrhizal fungi positively related to primary productivity in croplands and grasslands, while plant pathogens showed a negative relationship. Together, our results point to the importance of soil biodiversity and soil health for maintaining primary productivity across contrasting land-use types.

How to cite: Romero, F., Labouyrie, M., Orgiazzi, A., Ballabio, C., Panagos, P., Jones, A., Tedersoo, L., Bahram, M., Guerra, C., Eisenhauer, N., Tao, D., Delgado-Baquerizo, M., García-Palacios, P., and van der Heijden, M.: Soil health increases primary productivity across Europe, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7955, https://doi.org/10.5194/egusphere-egu24-7955, 2024.

EGU24-8176 | ECS | Posters on site | SSS4.2

AI-driven spatiotemporal quantification and prediction of soil salinity at European scale using the LUCAS database 

Mohammad Aziz Zarif, Amirhossein Hassani, Panos Panagos, Inma Lebron, David A. Robinson, and Nima Shokri

Soil salinization, referring to the excessive accumulation of soluble salt in soils, adversely influences nutrient cycling, microbial activity, biodiversity, plant growth and crop production thus affecting soil health and ecosystem functioning. Soil salinity quantification is a major step toward mitigation of its effects. Therefore, developing quantitative tools to predict soil salinity at regional and continental levels under different boundary conditions and scenarios is crucial for sustainable soil management and security of natural resources (1-3). This study proposes an AI-driven soil salinity quantification and projection approach focused on EU soils using a set of environmental covariates which consist of soil properties, terrain attributes, climate, and remotely sensed variables. The soil salinity point data which was used for model training and validation, expressed as electrical conductivity, was obtained from the LUCAS survey for the years 2015 and 2018. The novelty of this work lies in the careful integration of LUCAS data point with AI-driven models aiming to produce soil salinity maps for EU soils. Different AI algorithms including Random Forest, LightGBM, and XGBoost were used in this study enabling us to evaluate the performance of each algorithm in predicting soil salinity across EU with the XGBoost algorithm producing the most accurate results. Feature engineering technique was applied to reduce the models’ collinearity; thus 17 covariates were selected as the most important model variables influencing soil salinity from the initial 34 covariates investigated in our analysis. The output of the predictive model will be a gridded dataset illustrating the spatial and temporal (yearly) distribution of soil salinity across the EU, accompanied by the corresponding uncertainty maps with the spatial resolution of 1-km. This information is crucial for identifying regions with elevated salinity levels and formulating necessary action plans to mitigate the situation.

References

  • Hassani, A., Azapagic, A., Shokri, N. (2020). Predicting Long-term Dynamics of Soil Salinity and Sodicity on a Global Scale, Proc. Nat. Acad. Sci., 117(52), 33017-33027, https://doi.org/10.1073/pnas.2013771117
  • Hassani, A., Azapagic, A., Shokri, N. (2021). Global Predictions of Primary Soil Salinization Under Changing Climate in the 21st Century, Nat. Commun., 12, 6663. https://doi.org/10.1038/s41467-021-26907-3
  • Shokri-Kuehni, S.M.S., Raaijmakers, B., Kurz, T., Or, D., Helmig, R., Shokri, N. (2020). Water Table Depth and Soil Salinization: From Pore-Scale Processes to Field-Scale Responses. Water Resour. Res., 56, e2019WR026707, https://doi.org/10.1029/2019WR026707

How to cite: Zarif, M. A., Hassani, A., Panagos, P., Lebron, I., Robinson, D. A., and Shokri, N.: AI-driven spatiotemporal quantification and prediction of soil salinity at European scale using the LUCAS database, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8176, https://doi.org/10.5194/egusphere-egu24-8176, 2024.

EGU24-8568 | ECS | Posters virtual | SSS4.2

Prospects of returning radioactively contaminated lands in the northern part of Ukraine to economic use 

Volodymyr Illienko, Olga Kosarchuk, Alla Klepko, Dmytro Lazarev, and Mykola Lazarev

About tens thousands hectares of agricultural land in the norther part of Ukraine cannot be used for agricultural production under the Law 'On the Legal Regime of the Territory Affected by Radioactive Contamination as a Result of the Chornobyl Disaster' since 1986 only in Zhytomyr Oblast. Additionally, due to Russia's aggressive military actions, large areas of Ukraine (currently near 800 thousands ha) are unable to carry out agricultural work. It may take over minimum ten years to clear the territories of mines. In these circumstances, revision of the actual contamination levels of lands may help to increase the share of agricultural lands in Ukraine. But before the economic use of these lands, it is essential to conduct a survey to determine the level of soil contamination with radionuclides and assess the radiological situation. This data will form the basis to decide whether the previously contaminated lands can be returned to economic use.

We conducted the radiological surveys, where the radiation background indicators were measured in 2023 in Narodychi and Vyazivka using modern devices that allow automatic registration of routes with GPS reference and marking of gamma background parameters. We recorded from 200 to 600 points on each field to build maps of the spatial distribution of soil radioactive contamination. The Narodychi community in Zhytomyr Oblast provided 30 field plots marked as 'radioactive land' in the State Land Cadastre of Ukraine. These plots include 23 agricultural lands covering an area of over 1400 hectares and 7 floodplain meadows of the Uzh and Zherev rivers covering 1200 hectares. The levels of radioactive contamination in the soil were determine on the agricultural lands, specifically with regards to 137Cs, 90Sr, and partially 238-240Pu isotopes. The maps were constructed to determine the density of radioactive contamination of soil in each field based on the obtained results.

We concluded, that the density of 137Cs, 90Sr and 238-240Pu contamination in the agricultural lands around the settlements of Narodychi and Vyazivka did not exceed the lower limit of the criteria for their classification as an unconditional (mandatory) resettlement zone. Specifically, cesium, strontium and plutonium isotopes did not exceed 555 kBq/m2, 111 kBq/m2 and 3.7 kBq/m2, respectively. While the criteria for assignment to the guaranteed voluntary resettlement zone are limited to cesium isotopes from 185 to 555 kBq/m2, strontium from 5.55 to 111 kBq/m2, or plutonium from 0.37 to 3.7 kBq/m2 (according to Article 2 of the Law of Ukraine "On the Legal Regime of the Territory Affected by Radioactive Contamination as a Result of the Chornobyl Disaster"). Accordingly, all surveyed land should lose its status as 'radioactive land' and can be returned to economic use.

We acknowledge the National Research Foundation of Ukraine for the financial support of this research (Project number 2022.01/0188).

How to cite: Illienko, V., Kosarchuk, O., Klepko, A., Lazarev, D., and Lazarev, M.: Prospects of returning radioactively contaminated lands in the northern part of Ukraine to economic use, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8568, https://doi.org/10.5194/egusphere-egu24-8568, 2024.

EGU24-8602 | ECS | Orals | SSS4.2

Glucose Release Controlled by Sugar Transporters in Wheat Plant Modulates Microbial Growth and Enzyme Activity Around the Root 

Mehdi Rashtbari, Seyed Sajjad Hosseini, Ahmad Samir Azimi, Markus Schemmel, Zheng Zhou, Lingyue Han, Daguang Cai, and Bahar S. Razavi

Soil microbial communities are the main regulators of ecosystem services and are vital for carbon and nutrient cycling. Root exudates play a crucial role in shaping soil microbial assembly and hence, influencing biogeochemical processes that impact plant growth. Here, we hypothesized that continuous wheat cultivation would lead to lower glucose release, resulting in lower microbial growth, activity, and biomass. For the first time in situ glucose imaging was optimized for studying these interactions in the field - using installed root windows in the first (W1) and third (W3) wheat after break crop plots. Root and leaf samples were collected to determine the expression of sugar transporter genes using transcriptomics. Soil microbial respiration (characterized by Substrate Induced Growth Respiration (SIGR)) and enzyme kinetics (measured by fluorometric microplate assays of 4-methylumbelliferone (MUF) and 7-amino-4-methyl coumarin (AMC)) were measured in rhizosphere, root affected and bulk soil samples to assess C, N, and P acquisition.

W3 had the lowest proportion of hotspots for glucose release with 1.35 % of the total soil surface area, indicating a 17.7 % decline compared to W1. Also, we found that the expressions of functional orthologous genes of SWEET1a in wheat roots were significantly upregulated in W3 compared to W1. Furthermore, total microbial biomass dropped by 11.8 and 4.8 % in W3 in the rhizosphere and bulk soils compared to W1, respectively. The growing microbial biomass in the rhizosphere soil of W1 was about five times higher than W3. For β-glucosidase activity, soil samples from W1 had a higher maximum velocity of enzyme activity (Vmax) compared to W3 samples, in all studied compartments (rhizosphere, root affected and bulk soil samples). Lower glucose release in W3 highlights the importance of root exudates in shaping rhizosphere interactions and microbial community dynamics in response to continuous wheat cultivation. Also, differences in SWEET gene expression in wheat roots and leaves, indicates shifts in nutrient uptake and resource allocation strategies. This decline in glucose release observed under W3 compared to W1 underscores the significance of root exudates in shaping rhizosphere interactions.

Overall, the shift in glucose release is linked to altered root physiology and exudation processes, potentially reflecting the plant's strategy to create a less favorable environment for ambuscade and opportunistic pathogens. Hence, this study provides novel insights into the complex interactions between continuous wheat cultivation, root exudation, microbial dynamics, gene expression, and enzymatic activities.

How to cite: Rashtbari, M., Hosseini, S. S., Azimi, A. S., Schemmel, M., Zhou, Z., Han, L., Cai, D., and Razavi, B. S.: Glucose Release Controlled by Sugar Transporters in Wheat Plant Modulates Microbial Growth and Enzyme Activity Around the Root, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8602, https://doi.org/10.5194/egusphere-egu24-8602, 2024.

EGU24-8831 | ECS | Orals | SSS4.2

Evaluation of the relation between soil biomass of arbuscular mycorrhizal fungi and glomalin-related soil protein in conservation agriculture 

Stamatios Thomopoulos, Lars Elsgaard, Lars Juhl Munkholm, and Sabine Ravnskov

Arbuscular mycorrhizal fungi (AMF) are indicators of soil health and are associated with various soil benefits, primarily linked to glomalin accumulation from hyphal turnover. However, the direct connection between glomalin-related soil protein (GRSP) and AMF has been questioned. In addition, conservation agriculture (CA) stands out as a pivotal plant production system that promotes agricultural sustainability and enhances soil quality.  In particular, the combination of minimal soil disturbance with residue retention has been linked with alterations in microbial biomass. The study aimed to explore the correlation between various fractions of GRSP and fatty acid fractions in the soil, along with examining the long-term impact of conservation agriculture practices on AMF biomass and GRSP content. Findings revealed a positive correlation between easily extractable (EE) GRSP and phospholipid fatty acid (PLFA) 16:1ω5, while no significant correlations were found for difficultly extractable (DE) or total GRSP fractions. These results highlight the complexity of GRSP dynamics and the need for further research on different fractions and their relation to AMF biomass. Additionally, the study demonstrated that mechanical soil management had a more significant impact on AMF hyphal biomass and EE-GRSP compared to residue management. Direct seeding, a reduced tillage approach, led to higher hyphal biomass and EE-GRSP, indicating AMF sensitivity to tillage intensity. This suggests that tillage practices exert a more substantial influence on AMF abundance and GRSP content than residue management.

How to cite: Thomopoulos, S., Elsgaard, L., Juhl Munkholm, L., and Ravnskov, S.: Evaluation of the relation between soil biomass of arbuscular mycorrhizal fungi and glomalin-related soil protein in conservation agriculture, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8831, https://doi.org/10.5194/egusphere-egu24-8831, 2024.

EGU24-10503 | Orals | SSS4.2

Unraveling the relationship between rural farm household wealth, carbon storage, and soil quality in Namibia's Zambezi Region 

Alexandra Dr. Sandhage-Hofmann, Foerster Mira, Amatotsero Vanessa, Börner Jan, Gebrekidan Bisrat, and Amelung Wulf

A significant portion of smallholder farming systems in Sub-Saharan Africa are marked by significant heterogeneity in both biophysical and socio-economic conditions. Resource access and the patterns of resource allocation at household level are often co-determined by wealth. We hypothesized that wealth plays a pivotal role in the effect of future-oriented farm management on soil organic carbon storage (SOC) and soil quality. To test this hypothesis, we conducted a study involving 42 households categorized in three wealth classes (high, medium, low) based on farm-household survey data from the Namibian Zambezi region. Soil samples were collected up to a depth of 1 m with a focus on soil organic carbon and nitrogen throughout the soil profile. Topsoils were additionally analyzed for texture, cation exchange capacity (CEC), pH, and available phosphorus; field size was measured. A follow-up survey wave captured information on crop species, yield, and soil management practices.

Results of the survey showed, that farmers of our study area typically burn their field regularly before the cultivation period. With rare exceptions no farmer fertilized their fields, neither with mineral fertilizer nor with manure. Results indicated that relatively wealthier farmers had larger fields, yet intriguingly, their yields per hectare were not higher than for farmers in lower wealth terciles. Notably, the Arenosols, which are widespread in the Zambezi region, had lower sand and higher clay and silt contents among the relatively wealthier farmers. Moreover, high wealth class showed significantly higher soil organic carbon and nitrogen concentrations in the topsoils compared to medium and low wealth classes along with CEC values. Though, no such a trend was observed for available phosphorous and pH. The elevated levels of soil organic carbon and nitrogen of relatively wealthy farmers persisted consistently up to a depth of 1 meter. These results indicate that the soils of farmers in the high wealth class have inherently better soil conditions. Contrary to our hypothesis, the wealthier farmers did not seem to invest more in land management in order to improve soil conditions. Instead, historically they seem to have been more inclined to settle on the more fertile soils in the Zambezi region of Namibia and benefit from larger fields and thus higher quality natural resources.

How to cite: Dr. Sandhage-Hofmann, A., Mira, F., Vanessa, A., Jan, B., Bisrat, G., and Wulf, A.: Unraveling the relationship between rural farm household wealth, carbon storage, and soil quality in Namibia's Zambezi Region, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10503, https://doi.org/10.5194/egusphere-egu24-10503, 2024.

EGU24-10649 | ECS | Posters on site | SSS4.2

Long-Term Effects of Chabazite-Zeolite Tuff Amendments on Soil Quality in Arable and Perennial Cropping Systems 

Giacomo Ferretti, Christoph Rosinger, Eugenio Diaz-Pines, Thomas Weninger, Orracha Sae-Tun, Barbara Faccini, Massimo Coltorti, and Katharina Keiblinger

The use of natural zeolites to enhance soil properties has gained popularity, but there are limited long-term data on its effects. This study evaluates the Soil Quality Index (SQI) in three agricultural soil systems, 6-10 years post-application of chabazite zeolite. These soils had different management practices: intensive arable (cereals), intensive perennial (pear), and organic perennial (olive).

In the arable system, chabazite was applied at rates of 5, 10, and 15 kg m-2, compared to unamended soil. Perennial systems were tested at 5 kg m-2. Analysis of 25 soil parameters related to soil health was conducted at each site, including soil physic-chemical properties (bulk density, pH, electrical conductivity, cation exchange capacity, C-N-P species), biological properties (microbial C-N-P, enzyme activity) and gaseous emissions (CO2, N2O and NH3 fluxes). Principal Component Analysis (PCA) was performed to determine the SQI using a linear scoring method.

In the arable-cereal field, chabazite increased the SQI significantly from ~0.3 to ~0.6, but no clear dose effect was evident. The SQI also rose significantly in perennial fields thanks to the use of chabazite zeolites. Different indicators have been selected by the PCA at each site, suggesting that chabazite addition impacted soil quality differently in each cropping system.

Overall, this research underscores chabazite zeolite potential to boost soil health, indicating a substantial enhancement in soil quality post-amendment.

How to cite: Ferretti, G., Rosinger, C., Diaz-Pines, E., Weninger, T., Sae-Tun, O., Faccini, B., Coltorti, M., and Keiblinger, K.: Long-Term Effects of Chabazite-Zeolite Tuff Amendments on Soil Quality in Arable and Perennial Cropping Systems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10649, https://doi.org/10.5194/egusphere-egu24-10649, 2024.

EGU24-13121 | Orals | SSS4.2 | Highlight

Bridging the Soil Health Data Gap: informing prioritization of soil data collection efforts 

Ester Miglio, Fabrizio Albanito, Simone Sala, and Pete Smith

The sampling and analysis or visual examination of soil to assess its health status are widely practiced from plot to national scales. However, available data are often not made easily accessible and new data are not always shared with the wider public, creating a partial understanding of soil processes and health status across different geographies, as well as a misuse of resources.

To address these challenges, Varda has created an interactive digital soil platform, named SoilHive, which provides an overview of existing soil data across the globe, facilitates the identification of soil data gaps across regions, and supports soil data sharing and interoperability.

To facilitate the identification of functional soil data gaps, Varda created a visualization tool to enable users to identify the extent to which the data available in their selected regions of interest allow them to characterize key soil characteristics and functions, starting with soil health. To this end, Varda collaborated with a team at the Aberdeen University to define a minimum set of indicators and associated soil properties, covering diverse soil degradation processes and ecosystem services, to describe soil health at the local level with a focus on agricultural settings. SoilHive users will be able to select a region of interest and verify how many of those indicators are available to characterize soil health: the gap between the available data and the required data will be marked as the "Soil Health Data Gap" and described as the percentage of data over the total number of indicators.

This Soil Health Data Gap could facilitate the identification of those regions where data collection efforts should be intensified, informing the prioritization of actions aimed at bridging existing gaps while expanding the availability of soil data. Several proposed activities to address this gap include targeted soil mining activities to collect historical and non-digitized soil data, advocating for data-sharing collaborations among diverse stakeholders, and organizing brand-new soil sampling campaigns. Moreover, additional soil health definitions could be used to provide the user with different representations of soil health data gaps, in line with these definitions.

Closing the existing Soil Health Data Gaps bears significant importance, as it empowers us to deepen our comprehension of soil health dynamics. By expanding soil data transparency across all sectors and stakeholders, we would gain the ability to make well-informed decisions regarding optimal soil management practices, efficiently allocate resources, and strive to enhance soil health for the betterment of both present and future generations.

How to cite: Miglio, E., Albanito, F., Sala, S., and Smith, P.: Bridging the Soil Health Data Gap: informing prioritization of soil data collection efforts, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13121, https://doi.org/10.5194/egusphere-egu24-13121, 2024.

EGU24-13198 | ECS | Orals | SSS4.2

Microbial resistance in rhizosphere hotspots under biodegradable and non-degradable microplastic amendment: Community and functional sensitivity 

Bahar S. Razavi, Bin Song, Siyi Shang, Feng M. Cai, Zihao Liu, Jie Fang, Na Li, and Jonathan M. Adams

The annual global production of plastics is currently nearly 400 million tons, leading to widespread concern regarding the quantity of degradation-resistant plastics entering terrestrial environments. Farmland soils are a major sink for microplastics (MPs, size <500 μm) owing to the wide use of plastic film mulching. Although the influence of MPs on soil parameters has been investigated, the response of microbiomes to soil microenvironments with contrasting limiting factors, particularly in flooded soil environments such as rice paddies, remains unknown. Using zymography and high-throughput sequencing, we conducted an experiment with polylactide (PLA) and polyvinyl chloride (PVC) MPs to compare the effects of biodegradable and conventional MPs on rice growth, exoenzyme kinetics, and microbial communities. Both conventional and biodegradable MPs significantly inhibited rice growth, possibly by affecting nutrition. Compared with the control soils, both PLA- and PVC-amended soils exhibited higher enzyme activity in the hotspots. The enzymatic resistance to MPs was higher in ‘coldpots’ with PVC addition compared to that in PLA and control treatments. 
Bacterial biomass increased but diversity declined in PLA-amended soils, possibly because PLA particles act as carbon input inhabited the population of bacteria. Our findings suggest that co-occurrence networks among bacteria were strengthened by the addition of both MPs, with an increase in microbial functionality resilience and enhanced competition with neighboring roots for nutrient mining. This competition for nutrients may 
adversely affect plant growth. 

How to cite: Razavi, B. S., Song, B., Shang, S., Cai, F. M., Liu, Z., Fang, J., Li, N., and Adams, J. M.: Microbial resistance in rhizosphere hotspots under biodegradable and non-degradable microplastic amendment: Community and functional sensitivity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13198, https://doi.org/10.5194/egusphere-egu24-13198, 2024.

EGU24-13244 | ECS | Posters virtual | SSS4.2

Promoting Carbon Storage and Health in Urban Soils through Sustainable Management Practices   

Atefeh Movassagh, Bibiana Betancur Corredor, and Martin Hamer

Sustainable urban soil management is becoming increasingly crucial due to its vital role in climate and water regulation and its significant potential for storing soil organic carbon (SOC). This significance is emphasized considering the ongoing urbanization and climate change issues. Although SOC is influenced by many factors, such as soil type and climate fluctuations (temperature, precipitation patterns), on a regional scale, land use and management practices (e.g., fertilization, irrigation) can have a more significant impact on SOC storage and the balance of soil-atmosphere carbon fluxes. However, there is still a limited understanding of the amount of humus content in urban soils and the effects of urban development and management practices on soil health and carbon storage. We investigated how management practices in urban green spaces influence soil carbon storage as the primary indicator of soil health.

The present study was carried out in the Bonn-Rhein-Sieg area, as the region is vital in terms of sustainable urban and regional development with a high population density (Rhein-Sieg district: 338.4, Bonn: 520.9 inhabitants/km2) in Germany. A survey was conducted with owners and managers of urban private (e.g., allotment and backyard garden) and public green spaces on the practices for the most common vegetation types (e.g., lawn, vegetable, ornamental). In the autumn and winter of 2022, 248 soil samples (0–20 cm depth) were collected from 95 private and public green spaces in the study area and analyzed for physiochemical and biological properties. Multivariate Analysis of Variance (MANOVA) was performed to assess the effects of different management practices on soil properties.

Our results indicate that the average SOC stock in public green areas (94.67 Mg ha-1) is substantially higher than in private ones (house garden 67.72 Mg ha-1, allotment garden 73.15 Mg ha-1). Moreover, urban green spaces with vegetables (91.66 Mg ha-1) and ornamentals (85.05 mg ha-1) show greater SOC stock levels when comparing vegetation types (lawn 62.48 Mg ha-1). Significant differences in SOC are also found for various management practices. Specifically, the monthly fertilization schedule resulted in higher SOC levels (127.37 Mg ha⁻¹) compared to the yearly fertilization schedule (76.88 Mg ha⁻¹). Additionally, the use of organic fertilizers contributed to increased SOC levels (84.40 Mg ha⁻¹) in contrast to mineral fertilizer applications (65.31 Mg ha⁻¹). The average SOC stock in all the studied urban green spaces (85 mg ha-1) was higher than the average SOC stock in arable soils in Germany (47.30 Mg ha-1). The higher SOC in the region could be due to vegetation types and fertilization frequencies, which show statistically significant effects (p-value <0.001). Other management practices (e.g., irrigation type and frequency) did not show a significant effect. Our findings highlight the significance of soil management practices, particularly in selecting vegetation types and determining fertilization frequency, as essential factors influencing urban SOC.

How to cite: Movassagh, A., Betancur Corredor, B., and Hamer, M.: Promoting Carbon Storage and Health in Urban Soils through Sustainable Management Practices  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13244, https://doi.org/10.5194/egusphere-egu24-13244, 2024.

EGU24-14456 | Orals | SSS4.2

Effect of Alternative Dryland Crops on Soil Microbial Communities 

Sadikshya Dangi, Brett Allen, Jay Jabro, Tatyana Rand, Joshua Campbell, and Rosalie Calderon

Soil microbial community composition associated with novel rotation crops could contribute to increased yield to subsequent crops and an important factor influencing the composition of the rhizosphere microbiome. However, the effect of alternative dryland crops on soil microbial community composition is not clear in the northern Great Plains (NGP). The objective of this study therefore was to evaluate the effects of oilseed crops Ethiopian mustard (Brassica carinata A.) or camelina (Camelina sativa L.) or a 10-species forage/cover crop (CC) mix and fallow on soil microorganisms. A field study was conducted from 2014 to 2020 in the northern Great Plains, USA and was designed as a randomized complete block with three replications in a no-tillage system. Results showed that total bacterial proportion was significantly higher in camelina and fallow compared to CC and carinata. Total fungal proportion was significantly higher under CC mix compared to camelina and fallow. Fungal to bacterial ratio was significantly higher in CC and carinata compared to fallow. Fungi are often considered a good indicator of soil health while bacteria are crucial in soil functions. The changes in specific microbial communities due to crop-related alterations might play a key role in the yield of subsequent crop. Mechanisms responsible for these differences will be discussed.

How to cite: Dangi, S., Allen, B., Jabro, J., Rand, T., Campbell, J., and Calderon, R.: Effect of Alternative Dryland Crops on Soil Microbial Communities, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14456, https://doi.org/10.5194/egusphere-egu24-14456, 2024.

EGU24-15886 | Orals | SSS4.2

Understanding the Complexity: A Meta-Analysis of the Impact of Land Use Intensification on Soil Fauna in Global Agroecosystems 

Bibiana Betancur Corredor, Andrey Zaitsev, and David Russell

Increased land use intensity, especially the transition from extensive to intensively managed agroecosystems, is frequently referred to as one of the primary causes of the decline in global biodiversity and is thought to be the primary force influencing soil biodiversity. For appropriate land management in the face of future land use change, it is essential to comprehend how soil biodiversity responds to various land use regimes. Still, there is a great deal of uncertainty regarding the consistent responses of various taxonomic groups to intensification of land use.

We systematically assessed and quantified through meta-analysis the effects of various forms of land use intensification on soil organisms in global agroecosystems (192 studies included, 3190 pairwise observations comparing intensified land use to undisturbed ecosystems across 59 countries) and analyzed the dependence of these effects on abiotic factors such as soil properties (organic matter, pH, nutrient and water availability, texture) and climatic zone.

We observed a substantial decline in springtails abundance (-34%) and species richness (-16%), while earthworms experience a positive abundance trend (+217%) but a reduction in species richness (-12%). Enchytraeids exhibit a negative impact on abundance (-32%) with no effect on species richness. Mites show a positive increase in abundance (+129%), but a significant reduction in species richness (-50%). Nematodes, on the other hand, experience a negative impact on abundance (-7%) with no effect on species richness.

Focusing specifically on earthworms, we observed varying effects depending on the specific forms of intensification employed. Positive impacts on earthworm abundance are observed with agroforestry (+60%), cover crops, low input cropping (+113%), managed grasslands (+52%), vegetable gardens (+52%), and pastures (+218%). Conversely, negative effects are noted in arable cropland (-24%), orchards (-35%), specialty crops (-61%), crop livestock integration (-13%), and managed forests (-95%). Furthermore, the analysis reveals that the intensification effects on earthworm abundance vary across different climatic zones, with significant impacts observed in zones A and C. Higher intensification effects are noted in areas with greater mean annual precipitation, higher soil pH, finer soil textures (clayey, loamy, and silty), and increased organic matter content.

This comprehensive exploration sheds light on the intricate dynamics between land-use intensification and soil fauna, providing valuable insights for sustainable land management practices tailored to different ecological contexts.

How to cite: Betancur Corredor, B., Zaitsev, A., and Russell, D.: Understanding the Complexity: A Meta-Analysis of the Impact of Land Use Intensification on Soil Fauna in Global Agroecosystems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15886, https://doi.org/10.5194/egusphere-egu24-15886, 2024.

EGU24-18198 | ECS | Posters on site | SSS4.2

Earthworm populations and their drivers in agroecosystems across Europe: land use, soil properties, climatic factors 

Marion Mittmannsgruber, Guénola Peres, Rajasekaran Murugan, and Johann Zaller

Earthworms are a crucial part of soil biodiversity and indicate soil health, as they constitute the majority of soil macrofauna affecting various soil functions and ecosystem services. Among the most important drivers of the size and diversity of earthworm populations is land use, especially agriculture. It is widely known that agricultural activities such as tillage, fertilization or the use of agrochemicals directly and indirectly affect earthworms. However, it is rarely investigated to what extent soil properties and climatic factors interact with the influence of agricultural activities. To study this, we analysed datasets of earthworm surveys across 35 European countries covering various agricultural sectors, various soil types and climatic regions including mediterranean, oceanic, and continental climates, across several altitudinal ranges. Investigations were performed within the project MINOTAUR within the European Joint Programme Soil. Data on earthworm abundance and biodiversity in agroecosystems was collated from public sources containing FAIR (findability, accessibility, interoperability, and reusability) data such as GBIF, Edaphobase, datadryad, or zenodo, including many historical and non-English studies to prevent a publication bias. Moreover, long-term ecological research sites were sampled for earthworms as part of the project. The greatest challenge in collating earthworm data was to find meta-data regarding agricultural activities, soil properties and climatic data of the study sites. Moreover, data quality varied considerably, often lacking standard vocabulary, consistent species nomenclature, and details on sampling designs. Thus, preliminary outcomes of our analysis are (i) the need for data harmonization in biodiversity monitoring, (ii) the inclusion of a minimal set of meta-data regarding soil properties, land use intensity, and sampling methodology in order to be able to examine the drivers of earthworm populations in agricultural systems. After a tedious data harmonization process we will analyse our data using structural equation models, to determine which factors had the biggest impacts on earthworm abundance and biodiversity. Using this information, we can better understand earthworm population developments, and promote strategies to foster soil protection and earthworm biodiversity on a European scale.

How to cite: Mittmannsgruber, M., Peres, G., Murugan, R., and Zaller, J.: Earthworm populations and their drivers in agroecosystems across Europe: land use, soil properties, climatic factors, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18198, https://doi.org/10.5194/egusphere-egu24-18198, 2024.

EGU24-18278 | ECS | Orals | SSS4.2

Soil health and microbial diversity in fruit chestnut groves affected by ink disease  

William Trenti, Mauro De Feudis, Gloria Falsone, Livia Vittori Antisari, Federico Puliga, Giulia Tabanelli, Alessandra Zambonelli, and Fausto Gardini

Soil is one of the most diverse and complex natural systems at global scale and is involved in several reactions of formation, development, and breakdown of chemicals, many of these depending on soil microorganisms.

According to the combination of soil forming factors, soil properties show a large horizontal and vertical variability, which can have a huge impact on soil microbial communities. However, relatively few investigations have been carried out to associate the changes in soil microbial community with the variations of soil properties across the genetic horizons and along depth.

In Italy, chestnut groves used to be key sources of products in mountain regions. Recent socio-economic changes have led to the progressive abandonment of this land use, producing degradation of the landscape and increased hydrogeologic risk. Now, programs for the restoration of this activity collide with outbreaks of illnesses such as ink disease, which is caused by Oomycetes present in the soil. In this framework, the physicochemical and biological features of soils play a crucial role in the distribution and assessment of the risk and severity of this disease.

The objective of this study was to correlate the diversity and eco-functionality of the microbial communities with soil properties and health indicators along depth and across a transect including chestnut trees with and without symptoms of ink disease.

The study area was a fruit chestnut grove located in the Apennine mountains south of Bologna, Italy. Soil profiles were opened along a transect ranging from a chestnut tree showing ink disease symptoms (INK1) to two subsequent chestnut trees with no visible symptoms (INK2 and INK3). In each profile, the horizons were described and sampled; to assess spatial variability, three minipits were opened around each profile, and their horizons were also described and sampled. Each horizon was also sampled in sterility. The samples were then analyzed for physicochemical and biological parameters, and total DNA was extracted to perform a taxonomic analysis.

Results showed that some physicochemical parameters, while presenting a trend with depth, also presented a trend with distance from the diseased tree: pH and base saturation decreased near this tree, while C:N and C:P increased, as well as water-extractable organic carbon. The taxonomic analysis showed that, while no substantial variation was detected in the bacterial composition of INK2 and INK3, INK1 showed a higher prevalence of phyla involved in the organic matter cycle (Acidobacteriota and Proteobacteria). Regarding the fungal population, in INK2 and INK3 the main trophic group was soil saprotrophs, while in INK1 the most frequent were short- and medium-distance ectomycorrhizae, which often indicate plant stress. Shannon index showed that bacterial diversity increased with depth while fungal diversity decreased. In both cases the profile near the diseased tree presented the least diversity. No difference was detected between the profiles in soil health indicators, such as organic matter content and microbial biomass and its activity, and these were not correlated with microbial diversity. These results suggest that taxonomic analysis of soil microorganisms could integrate traditional indicators in assessing soil and ecosystem health.

 

How to cite: Trenti, W., De Feudis, M., Falsone, G., Vittori Antisari, L., Puliga, F., Tabanelli, G., Zambonelli, A., and Gardini, F.: Soil health and microbial diversity in fruit chestnut groves affected by ink disease , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18278, https://doi.org/10.5194/egusphere-egu24-18278, 2024.

EGU24-18424 | Posters on site | SSS4.2

Finding the optimum tillage and cover crop system for optimizing microbial soil health and nutrient cycling 

Martin Schneider, Sabine Huber, Niklas Bruhn, Markus Gorfer, Sophie Zechmeister-Boltenstern, Gernot Bodner, and Katharina Keiblinger

Soil ecosystem services and soil health criteria, such as nutrient cycling, carbon (C) sequestration and water regulation, needs to be maintained and improved to meet our environmental, social and economic demands for the future within the frameworks of global change, population growth and economic independency.

This study investigated variations of soil physical, nutritional and microbial properties due to differing cover cropping systems within the first year. The experiment was located on an ongoing long-term tillage field trial in Hollabrunn, Austria. For 18 years, soils were cultivated either conventional (plough), reduced (grubber), minimized (disk-harrow) or by direct-seeding. Beside the fallow treatment, two mixtures of cover crops were selected. The 23 kg ha-1 standard mixture contained 65 % buckwheat (Fagopyrum esculentum), 22 % scorpion-weed (Phacelia tanacetifolia) and 13 % mustard (Brassica juncea). The 35 kg ha-1 advanced mixture contained 14 different species with 19 % Fabaceae and 15 % Brassicaceae. Soils were sampled after sowing of the cover crop in september and in the following june after sowing soybean.

Intensive tillage systems increase mineralization, aeration, redox potential and rooting within the upper most ploughing (Ap) horizon, while decreasing water holding capacity and soil aggregation. However, the higher frequency of machinery passes favors soil compaction in the layer below and limits deep rooting. Reduced tillage systems might provide a less disturbed soil structure, supporting the soil microbiology. In contrast, the reduced aeration and minimized mechanical breakdown should increase water availability, which often is the most critical factor for soil life.

The current results indicated, that soil water contents and aggregate stability was enhanced in the two least intensive treatments. The microbial C and nitrogen (N), dissolved C and N, ergosterol, extracellular enzyme activities (EEA) and the organic C pool were significantly higher with minimized and no-till. This indicated a larger amount of substrates, generating a more active and larger microbial community in the latter.

The vegetative soil coverage between the main crops is another driving factor controlling water and nutrient availability by withdrawal, fixation, mobilization and by feeding the soil rhizosphere.

After one period, cover crop-related effects were found, as the standard mixture had higher EEA, indicating a lower nutrient availability. Larger organic, inorganic and total C pools were found in the advanced mixture. Only the microbial phosphorus (P) was higher in the advanced mixture and no effect was found for microbial C and N. Higher availability of N and P in the advanced mixture due to the higher proportion of Fabaceae and Brassicaceae and their strong mobilizing effect was indicated by the higher ratio of C- to N-allocating EEA and a lower ratio of N- to P-allocating EEA. The fallow treatment was in between both cover crops and seemed to provide considerable amounts of nutrients and water to the main crop, in the first spring.

A combination of minimized or no-tillage and a diverse cover crop seemed to by promising for improving soil health, but characterizing the microbial community by 16S rRNA and ITS is still in progress.

How to cite: Schneider, M., Huber, S., Bruhn, N., Gorfer, M., Zechmeister-Boltenstern, S., Bodner, G., and Keiblinger, K.: Finding the optimum tillage and cover crop system for optimizing microbial soil health and nutrient cycling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18424, https://doi.org/10.5194/egusphere-egu24-18424, 2024.

EGU24-19809 | Posters on site | SSS4.2

Implementation of a pioneer program for soil monitoring and assessment of factors influencing soil biodiversity in Austria 

Johann Zaller, Marion Mittmannsgruber, Edith Gruber, Elisabeth Wiedenegger, Dmytro Monoshyn, Yoko Muraoka, Kathrin Pascher, Stefan Schindler, and Rajasekaran Murugan

Systematic monitoring of soil biodiversity and soil health is still in its infancy in Europe. In Austria, there are several active biodiversity monitoring programs such as the BINATS Biodiversity-Nature-Safety or ÖBM-K Austrian Biodiversity Monitoring of the Cultural Landscape projects. However, these projects focus on habitat diversity, vascular plants, grasshoppers, butterflies and wild bees, but have not taken soil organisms into account. This is surprising, as soils are among the most species-rich habitats and intact soils are the basic prerequisite for the integrity of ecosystems. Healthy soils also play an important role in buffering extreme climate events such as heavy rainfall or drought, or sequester carbon. The aim of the BodenBiodiv project is to close this glaring data gap for Austria and to identify the causes of various indicators of soil biodiversity in the agricultural landscape. As part of objective 1, systematic monitoring of earthworms in the agricultural landscape will be established in 200 quadrants (625 x 625 m) throughout Austria, which are part of the BINATS and ÖBM-K monitoring programs. Lists of the earthworm species present, their abundance and biomass as well as a distribution map are being compiled. In addition, a manual for future surveys on national monitoring of soil biodiversity will be compiled using harmonized terminology as a supplement to the existing monitoring manuals in Austria. Objective 2 deals with the analysis of factors that determine the occurrence of earthworms. For this purpose, site characteristics (land use, altitude) and soil properties (pH value, nutrient concentrations, moisture content, carbon content, soil microorganisms) as well as and management practices are associated with the recorded earthworm parameters and the available biotope mapping of the plots. Objective 3 is to compile a first Red List of earthworms in Austria. BodenBiodiv focuses on indicators of the status of species and biotope types; genetic diversity is also to be determined later on the basis of backup samples. The comprehensive data set from different climatic regions in Austria, from lowlands to high alpine areas, BodenBiodiv also enables the assessment of the influence of climatic variables on soil biodiversity. By incorporating data from existing biodiversity monitoring programs, we can expand our understanding of the interactions between below-ground and above-ground biodiversity.

How to cite: Zaller, J., Mittmannsgruber, M., Gruber, E., Wiedenegger, E., Monoshyn, D., Muraoka, Y., Pascher, K., Schindler, S., and Murugan, R.: Implementation of a pioneer program for soil monitoring and assessment of factors influencing soil biodiversity in Austria, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19809, https://doi.org/10.5194/egusphere-egu24-19809, 2024.

EGU24-20583 | Orals | SSS4.2

Multi-year dynamics of soil structural stability under contrasting farming practices in a belgian organic field experiment 

Frédéric Vanwindekens, Brieuc Hardy, Morgan Abras, Simon Sail, and Bruno Huyghebaert

At the heart of agro-ecosystems lie soils, essential components profoundly affected by intensive farming practices and global changes across various regions in Europe. This impact manifests as a loss of biodiversity, a decline in organic matter content, and heightened susceptibility to erosion. Recognizing these challenges, certain farmers are embracing innovative approaches to enhance soil quality, such as conservation farming and organic farming. These two systems differ significantly in their weed management practices, with conservation farming relying on synthetic herbicides and reduced tillage, while organic farming predominantly employs tillage.

To assess soil structural stability, we developed a new measurement protocol, the QuantiSlakeTest. This low-tech method operates on the principle of continuous quantitative measurement, evaluating the disintegration of a soil sample submerged in water. The resulting curves are normalized, and synthetic indicators, including relative weights at stabilization, time to reach maximum relative weight post-immersion, diverse slopes, and area under the curve, facilitate the comparison of various treatments.

Building on previous research demonstrating the relevance of this approach and the influence of tillage on soil structural stability (Vanwindekens & Hardy, 2023), our study employed the QuantiSlakeTest to highlight the annual evolution of soil structure stability over three years following the implementation of an organic cropping system trial in Gembloux (Wallonia, Belgium). Initiated in 2019, the trial involved converting a conventional 6 ha field to a seven-year rotation of organic farming. The three compared cropping systems differed in weed control, fertilization, and tillage practices. Soil samples were collected in early spring of 2020, 2021, and 2022 from various crops in the trial, including winter cereals, spring cereals, legumes, and maize, with cover crops or even uncovered after a winter ploughing.

Our main findings reveal a gradual differentiation of soil structural stability indicators during the first three years of cultivation. Cropping systems based on reduced tillage practices demonstrated a positive impact on soil structural stability, particularly in the third studied year (2022), while reference systems exhibited lower rates. These results confirm previous studies. We also detect a slight positive impact of legumes, cover crops, and/or crop associations, even in the two cropping systems with ploughing (2022). Further analyses, to be conducted over the seven years rotation will shed additional light on the dynamics of soil structural stability.

Frédéric M. Vanwindekens and Brieuc F. Hardy (2023). The QuantiSlakeTest, measuring soil structural stability by dynamic weighing of undisturbed samples immersed in water, SOIL, 9, 573–591, https://doi.org/10.5194/soil-9-573-2023

How to cite: Vanwindekens, F., Hardy, B., Abras, M., Sail, S., and Huyghebaert, B.: Multi-year dynamics of soil structural stability under contrasting farming practices in a belgian organic field experiment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20583, https://doi.org/10.5194/egusphere-egu24-20583, 2024.

EGU24-21191 | Orals | SSS4.2

Novel Soil Decomposition Sensor: Field Studies and Design Improvements 

Madhur Atreya, Taylor Sharpe, Shangshi Liu, Rebecca Killick, Mengyi Gong, Kelly Verhaalen, Anupam Gopalakrishnan, Noah Smock, Isabella Sarralde, Mac Bean, Jessica Davies, John Quinton, Richard Bardgett, Jason Neff, Evan Thomas, and Greg Whiting

 

The sensing of soil microbial and enzymatic activity continues to be a challenge, as current techniques are typically limited to the laboratory, and are time and labor intensive. In addition, such offsite assessments are not necessarily reflective of in situ bio-chemical-physical processes. We previously presented a novel printed decomposition sensor comprising a poly(hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and carbon composite material, wherein the sensor response correlated with the microbial activity in incubated soils [1]. In field trials carried out in the Yorkshire Dales (UK) these devices showed a clear correlation with measured soil microbial biomass carbon. These sensors consisted of a single fuse-like resistive element and as such were subject to stochastic effects in soil, requiring large numbers of devices to be used in order to address variability in field measurements. Here, we present a novel hardware solution to mitigate these stochastic effects by parallelizing multiple printed sensing elements on custom printed circuit boards (PCBs). The first instantiation of this approach showed to be effective at smoothing out sensor response in potato farms in the Upper Midwest region of the United States. In order to further shape the signal response of these decomposition sensors, we explored different parallel topologies by varying the number of sensing elements, element width, and element length. We discuss the advantages and disadvantages of these different topologies.


[1] Atreya, M.; Desousa, S.; Kauzya, J.; Williams, E.; Hayes, A.; Dikshit, K.; Nielson, J.; Palmgren, A.; Khorchidian, S.; Liu, S.; Gopalakrishnan, A.; Bihar, E.; Bruns, C. J.; Bardgett, R.; Quinton, J. N.; Davies, J.; Neff, J. C.; Whiting, G. L. A Transient Printed Soil Decomposition Sensor Based on a Biopolymer Composite Conductor. Adv. Sci. 2022, 2205785, 1–10. https://doi.org/10.1002/advs.202205785.

How to cite: Atreya, M., Sharpe, T., Liu, S., Killick, R., Gong, M., Verhaalen, K., Gopalakrishnan, A., Smock, N., Sarralde, I., Bean, M., Davies, J., Quinton, J., Bardgett, R., Neff, J., Thomas, E., and Whiting, G.: Novel Soil Decomposition Sensor: Field Studies and Design Improvements, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21191, https://doi.org/10.5194/egusphere-egu24-21191, 2024.

Soil health is pivotal for maintaining environmental sustainability and plays a vital role in supporting diverse ecosystems, agricultural productivity, and overall human well-being. The interplay of climate change and anthropogenic (human-induced) activities can exert substantial influence on soil health, giving rise to a spectrum of challenges. In recent years, a growing body of scientific evidence indicates that climate change will adversely affect soil health. This impact manifests through the decline in soil organic matter, the degradation of soil structure, and an increased vulnerability to erosion and other forms of deterioration. Human activities, particularly pollution and widespread habitat degradation, further exacerbate these effects. Additionally, ongoing misuse of soil contributes to its continued degradation, resulting in adverse consequences such as diminished biodiversity, decreased agronomic productivity, reduced input efficiency, and heightened rural poverty.

Consequently, a paradigm shift is imperative, with a focus on adopting sustainable agricultural systems. This involves a need to restore soil health instead of contributing to its decline, actively mitigating and adapting to climate change rather than exacerbating it, promoting negative emission farming instead of being a source of greenhouse gases and transforming land into a significant carbon sink rather than a source. To deal effectively with the challenge of soil health in the context of climate and human-induced change, it is essential to adopt a global approach. This means integrating sustainable land management practices, formulating effective policies and encouraging global cooperation. These measures are essential to ensure the long-term health and productivity of our soils.

How to cite: Chabbi, A.: Unlocking the crucial interplay between soil health, climate change and global stewardship, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21813, https://doi.org/10.5194/egusphere-egu24-21813, 2024.

EGU24-22474 | Orals | SSS4.2

Using Treated Wastewater Sludge to Improve Soil and Growth characteristics of Rain-fed Wheat under Semi-Arid Conditions 

Lena Abou Jaoude, Rabi H. Mohtar, Farah Kamaleddine, Razan Dbaibo, Rania Bou Said, Imad Keniar, and Sandra F. Yanni

Sludge is an increasingly growing concern in Lebanon given the absence of proper treatment and disposal methods. As a solution, this two-years study proposes the valorization of sludge as an organic amendment on soil cultivated with rainfed wheat (Triticum icaversea) and itsimpact on soil properties, microbial activity, wheat yield and grain quality. Baseline characterization of sewage sludge collected from secondary treatment plant (SS) and tertiary treatment plant (TS) in Bekaa, Lebanon, showed that both sludge types can be classified as suitable for restricted agricultural use (Class B), which cannot be used on soils to grow fruits or vegetables that are eaten raw as per the Lebanese guidelines for sludge use. Post-harvest analysis of the amended soils revealed a significant enhancement in organic matter (OM), organic carbon (OC), soil moisture, wheat yield and grain quality in both seasons SS and TS amended soils compared to the control. All the tested heavy metals were much lower than the allowable limits for agricultural soils, except for zinc (Zn).  Wheat biomass and grain quality assessment revealed a significant increase of 30% in grain yield in both treated soils (SS: 74 g/m2, TS: 81 g/m2) compared to the control (46 g/m2). Notably, TS treatment exhibited the highest protein content (14.5%) and ash (1.9%) in the first season, while both SS and TS treatments showed a significant increase in grain moisture in the second season. Soil microbial analysis were not consistent in the two seasons, but showed a potential risk of total coliforms contamination with SS application in the second season. This research provides valuable insights into the positive effects of sewage sludge application on soil fertility, microbial communities, and wheat grain quality. The findings emphasize the potential benefits of sewage sludge in sustainable agriculture, underscored by numerical improvements in various parameters. Although promising soil quality improvement and yield increase were observed in this study, further research is still needed to assess the potential soil microbial contamination and heavy metal accumulation over the long term.

How to cite: Abou Jaoude, L., H. Mohtar, R., Kamaleddine, F., Dbaibo, R., Bou Said, R., Keniar, I., and F. Yanni, S.: Using Treated Wastewater Sludge to Improve Soil and Growth characteristics of Rain-fed Wheat under Semi-Arid Conditions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22474, https://doi.org/10.5194/egusphere-egu24-22474, 2024.

EGU24-591 | ECS | Orals | SSS4.3

The application of hydrochar promotes soil microbial growth and enhances sunflower yield, altering the nutritional composition of the seeds 

Francisco Jesús Moreno Racero, Rocío Reinoso, Laura Gismero Rodríguez, Enrique Martínez Force, Miguel Ángel Rosales Villegas, and Heike Knicker

In recent decades, the potential use of chars, such as biochar or hydrochar, as soil amendments to enhance plant growth, has garnered significant interest. However, understanding potential toxic impact of these materials on soil and plants remains an area requiring further exploration. In this study, the effect of applying hydrochar (HC) derived from chicken manure on the yield and nutritional quality of sunflower (Helianthus annuus L.) seeds was assessed under both well-irrigated and water deficit (WD) conditions. To address it, the HC was applied to a Cambisol at rates of 3.25 and 6.5 t ha-1. Mineral fertilizer treatments with equivalent total nitrogen contributions as the amendment were included for comparison. Sunflower plants were cultivated in pots under two irrigations conditions (60 and 30% of the soil water holding capacity). After 77 days of cultivation, the plants were harvested, and the content of macro- and micronutrients, heavy metals in both seeds and leaves, as well as the seed fatty acid composition, were analyzed. Additionally, soil nutrient contents were assessed post-experiment

Initially, HC application did not cause a noticeable change in soil nutrient composition. However, both HC applications demonstrated high productivity under well-irrigated conditions. Likewise, under WD conditions, the best yields were achieved with a HC dose of 6.5 t ha-1. Conversely, the composition of the different fatty acids in the seed oil remained unaffected by the treatments and irrigation conditions. Nonetheless, seed nutrient content was notably affected, particularly in plants treated with 6.5 t ha-1. Under well-irrigated conditions, the seeds of these plants exhibited decreased K and P levels, along with higher levels of toxic elements and heavy metals such as Al, Ba, Cd, Pb, and Sr. Under WD conditions, the impact of the treatment on heavy metals contents was less pronounced, but there was a marked reduction of seed macronutrient content (Ca, K, Mg, P and S). Notably, plants treated with 6.5 t ha-1 of HC under well-irrigated conditions exhibited a preferential accumulation of Al and Sr in the seeds, leading to the lowest concentrations of these toxic elements in their leaves. The accumulation of these metals in the seeds was accompanied by a decline of both elements in the soil after 77 days of experiment under this irrigation condition, suggesting plant uptake. Given that the concentration of both elements did not increase after the application of HC at the beginning of the experiment, it is presumed that these changes are due to a potential role of HC involved in heavy metals mobilization. Following qPCR analysis this may be related to microbial activity since the soils treated with 6.5 t ha-1 of HC exhibited a higher abundance of 16S rRNA and ITS gene copies related to bacteria and fungi, respectively, along with an increased dehydrogenase activity. Our findings highlight that the impact of char amendment on soil systems should not be seen as a simple linear process but has to be evaluated considering the complex interactions between climatic conditions, application rate, plant physiology and microbial activity.

How to cite: Moreno Racero, F. J., Reinoso, R., Gismero Rodríguez, L., Martínez Force, E., Rosales Villegas, M. Á., and Knicker, H.: The application of hydrochar promotes soil microbial growth and enhances sunflower yield, altering the nutritional composition of the seeds, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-591, https://doi.org/10.5194/egusphere-egu24-591, 2024.

EGU24-976 | ECS | Orals | SSS4.3

Rooted in the city: Unveiling the hidden world of Quercus cerris enzymatic activity in urban soils  

Anna Gillini, Nataliya Bilyera, Dalila Trupiano, Iryna Loginova, Michaela Dippold, and Gabriella Stefania Scippa

 

The intricate interaction between human activities and the repercussions of climate change has made urban ecosystem health and biodiversity—both vital to human survival and well-being—particularly vulnerable. Recent research has spotlighted the frequently underestimated but crucial role that interactions between plant roots and several biotic and abiotic components of soil play in affecting urban biodiversity and ecosystem dynamics.

We conducted a controlled experiment to investigate this relatively obscure aspect of the urban environment. The experiment has been done with young plantlets of Quercus cerris and three urban soils collected from distinct sites in the city of Campobasso (Italy). We selected three sites in the city to clearly show a specific gradient of urbanization and vegetation fragmentation. Q. cerris young plants were grown in the rhizoboxes packed with three urban soils for two weeks to evaluate the impact of soil-plant interactions on the possible enzymes’ release by the roots and root-harboring microorganisms. The spatial distribution of three enzymes, namely acid phosphatase (P-cycle), β-glucosidase (C-cycle), and leucine aminopeptidase (N-cycle), was mapped and detected in each soil region (i.e., bulk soil and rhizosphere longitudinal surface) using a 2-D soil zymography technique.

The zymogram analysis revealed that the enzyme activities in soils differed spatially along the urbanization gradient, with the more urbanized soil having the highest levels of enzymatic activity and hotspot presence.

The root activity toward the exudation correlated with the highest enzymatic activity, that futrther lead to more intensive turnover of soil organic matter in soil. This could be linked to the exudation of roots to regulate plant growth in unfavorable conditions or to the rhizodeposition of substrates to change soil composition. 

Further in-depth analyses of the physical and chemical properties of the soil, along with the profiling and characterization of the microbial community composition, are currently underway in order to obtain a better understanding of the role of root enzymatic activities and their consequences on the biogeochemical processes in urban soils.

How to cite: Gillini, A., Bilyera, N., Trupiano, D., Loginova, I., Dippold, M., and Scippa, G. S.: Rooted in the city: Unveiling the hidden world of Quercus cerris enzymatic activity in urban soils , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-976, https://doi.org/10.5194/egusphere-egu24-976, 2024.

Glucose is one of the major primary metabolites in the plant root exudates to mediate the cross-talk between plants and microbes, but their contribution to drought resistance of plants is largely unknown. To test this, we inoculated arbuscular mycorrhizal fungi (AMF) in soybean, quantified rhizospheric microbial hotspots, visualized glucose exudation pattern, and analyzed microbial activities, such as kinetic properties of β-glucosidase and acid phosphomonoesterase enzymes, and microbial biomass phosphorus.

Drought reduced glucose exudation, mainly allocated to root tips under optimum conditions, and narrowed the rhizosphere enzymatic hotspot by three times. However, AMF inoculation enhanced glucose exudation compared to non-mycorrhizal plants, and enlarged enzymatic hotspot area by 53% under drought condition. Despite the 50% reduction in β-glucosidase and acid phosphomonoesterase activities owing to water deficit, AMF symbiont triggered up to 36% enzyme activities in correlation with the non-mycorrhizal ones. Therefore, the drought resistance of these two enzymes was enhanced by up to 63% in mycorrhizal plants. The biomass of microbial phosphorus increased by 45% under drought conditions in plants inoculated with AMF.

Overall, the greater resistance of enzyme activities to drought in AMF-inoculated than in non-mycorrhizal suggest that microorganisms associated with mycorrhizal root have higher capability to react to altered abiotic environmental conditions than those associated with non-mycorrhizal roots. The mycorrhization induced an interactive regulation of soybean glucose exudation and rhizosphere expansion for enzyme activities. This contributed to the resistance of microbial functions (e.g., enzyme expression) to drought stress in AMF-inoculated than in non-mycorrhizal soybean. AMF-inoculation suppressed adverse drought effects on plant and microbial nutrient mining, which has substantial implications for controlling microbial roles in organic matter decomposition and P cycling.

Keywords: glucose imaging, arbuscular mycorrhiza fungi, soybean, hotspot, drought resistance

How to cite: Hoang Thi Thu, D.: Overlapping locality between rhizosphere and mycorrhizosphere regulates glucose exudation pattern in rhizosphere and enzyme distribution, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1017, https://doi.org/10.5194/egusphere-egu24-1017, 2024.

EGU24-1765 | ECS | Orals | SSS4.3

Forest microbiomes and aboveground forest functioning  

Mark Alan Anthony and the ICP Forests Microbiome Collaboration

Forest soils and roots harbor hyper-diverse microbiomes which strongly shape the growth and development of plant communities. How the biodiversity and functional capacities of the microbiome influence emergent ecosystem functioning is an important next frontier in the biogeosciences with implications for conservation, ecosystem management, and microbiome engineering. Directly testing hypotheses between microbiome diversity and forest functioning has been obstructed by a lack of paired data on microbiomes and in situ observations of forest growth and health. Here, I will synthesize findings from two large-scale European forest soil and root sampling efforts where we identified features of the mycorrhizal fungal, soil fungal, and bacterial communities linked to variation in forest tree growth and nutrition. We sampled roots and/or soils across 285 forest monitoring plots spanning 18 European countries, sequenced full-length fungal ITS and prokaryotic 16S amplicons to relate microbiomes to high resolution observations of tree growth, foliar nitrogen and phosphorus content, and aboveground carbon stocks. We show that the composition, richness, and traits of both root and soil inhabiting symbiotrophic fungal guilds is tightly linked to variation in tree growth, nutrition, and aboveground biomass carbon stocks while the biodiversity of free-living microbiomes was not tightly coupled to these key metrics of aboveground forest functioning. We also produced a roster of fungal biodiversity and compositional traits which are strong positive and negative bioindicators of forest carbon storage and nutrition. These large-scale observations lay important groundwork for experimental studies and demonstrate that soil microbiomes capture unique variation in emergent forest functions that cannot be explained by other physical, chemical, and biological properties.

How to cite: Anthony, M. A. and the ICP Forests Microbiome Collaboration: Forest microbiomes and aboveground forest functioning , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1765, https://doi.org/10.5194/egusphere-egu24-1765, 2024.

EGU24-1800 | ECS | Posters on site | SSS4.3

Spatio-temporal distribution of enzyme activities with covered and mixed straw incorporation 

Shang Wang, Huadong Zang, Yadong Yang, Zhaohai Zeng, and Bahar Razavi

The rhizosphere and detritusphere are hotspots of soil enzyme-mediated microbial processes, but little is known about their spatiotemporal distribution and interaction, especially under various straw application strategies. Here, we used an in situ method (i.e. zymography) to investigate the distribution of enzyme activities in the maize rhizosphere and straw detritusphere after straw application (no straw, straw mulching and straw mixed). The surroding of straw was considered as detritusphere. Furthermore, the root and shoot performance of maize and soil chemical properity were also monitored in the study. The plant height, shoot weight, and root surface density of straw mulching were 60.4%, 159.6%, and 19.2% higher than that of straw mixed (p < 0.05), which indicate straw mixed returning lead to a stronger competition between plant root and soil microorganism for nutrients. SOC, TN, DOC and DON in the topsoil of straw mulching returning were 97.2%, 27.0%, 186.7% and 175.0% higher than that of straw mixed, respectively (p < 0.05). Moreover, both straw mulching and mixed returning has a positive effect on soil surface enzyme activities. Higher enzyme activities in detritusphere was observed with straw mulching than straw mixed returning (p < 0.05). The higher enzyme activities in the rhizosphere of straw mulching on day 15 can be defined by the increase of C release caused by root growth. This inturn can promote the process of microbial and nutrient cycling, and enhance rhizosphere enzyme activity. These results revealed that straw mulching decreases nutrients competition between root and microorganism and increases the C- and N-acquiring enzyme activities in detritusphere.

How to cite: Wang, S., Zang, H., Yang, Y., Zeng, Z., and Razavi, B.: Spatio-temporal distribution of enzyme activities with covered and mixed straw incorporation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1800, https://doi.org/10.5194/egusphere-egu24-1800, 2024.

The response of soil carbon release to global warming is largely determined by the temperature sensitivity of soil respiration, yet how this relationship will be affected by increasing atmospheric nitrogen deposition is unclear. Here, we present a global synthesis of 686 observations from 168 field studies to investigate the relationship between nitrogen enrichment and the temperature sensitivity of soil respiration. We find that the temperature sensitivity of total and heterotrophic soil respiration increased with latitude. In addition, for total and autotrophic respiration, the temperature sensitivity responded more strongly to nitrogen enrichment with increasing latitude. Temperature and precipitation during the Last Glacial Maximum were better predictors of how the temperature sensitivity of soil respiration responds to nitrogen enrichment than contemporary climate variables. The tentative legacy effects of paleoclimate variables regulate the response through shaping soil organic carbon and nitrogen content. We suggest that careful consideration of past climate conditions is necessary when projecting soil carbon dynamics under future global change.

How to cite: Tian, P.: Past climate conditions predict the influence ofnitrogen enrichment on the temperature sensitivityof soil respiration, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1953, https://doi.org/10.5194/egusphere-egu24-1953, 2024.

EGU24-2546 | ECS | Orals | SSS4.3

Soil zymography: a decade in microbial hotspot imaging and future challenges 

Nataliya Bilyera and Yakov Kuzyakov

Soil zymography represents a non-invasive methodology facilitating the in situ visualization and localization of potential enzyme activities in soil. Due to universality and simplicity of zymography method, it has been widely used to visualize the hidden microbial and root life in soil, which is a very heterogeneous and “dark” environment.

Following the pioneering use of fluorogenic substrates for enzyme activity visualization in soil, a significant methodological advancement occurred within the subsequent decade. Our primary focus is to highlight the progress in the last 10 years, with respect to the spectrum of enzyme activity imaging, zymography resolution, standardization and hotspot identification. Specifically, we emphasize the integration of zymography with the visualization of soil acidification, root exudation, pore distribution, nutrient and water movements. Although the majority of applications so far have centered on enzyme activities in the rhizosphere to reveal plant-soil-microbial interactions, we present the case studies to identify soil heterogeneity and microbial activity also in biopores, detritusphere and other hotspots.

We present not only the advancements made but also the current possibilities, challenges, and the potential directions of soil zymography. This technique finds applications across natural and agricultural ecosystems, both in field settings and laboratory studies, capable of scaling from the entire root system (dm) down to microbial communities (μm).

In the decade ahead, the future of enzyme research, particularly zymography imaging, will continue to broaden the scope of microbial studies and hotspot localization. This expansion will involve integrating with disciplines such as (bio)chemical, physico-chemical, microbial cell imaging, and isotope applications, facilitating a deeper understanding of soil processes and microbial interactions.

How to cite: Bilyera, N. and Kuzyakov, Y.: Soil zymography: a decade in microbial hotspot imaging and future challenges, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2546, https://doi.org/10.5194/egusphere-egu24-2546, 2024.

EGU24-3022 | ECS | Posters on site | SSS4.3

Top-down effects of crust-eating macro-arthropods on biocrust microtopography and carbon cycling 

Nevo Sagi, Amir Sagy, Vincent Felde, and Dror Hawlena

Biological soil crusts (biocrusts) are key regulators of soil C and N cycling, soil erosion, and water (re)distribution in drylands. Nevertheless, huge knowledge gaps exist about one core aspect of biocrust ecology, namely how these processes are affected by biocrust-eating macro-arthropods. We addressed this knowledge gap by exposing biocrusts to varying levels of isopod crustivory (i.e. grazing intensity), and quantifying the consequences for CO2 efflux, C fixation and microtopography. Biocrust CO2 efflux decreased with increasing crustivory and recovered after several wetting events. Crustivory had a negative effect on biocrust C fixation, but only after the CO2 efflux recovered to pre-crustivory levels. Biocrust surface roughness increased with increasing crustivory to a peak and then began to decrease, implying that varying levels of crustivory may have opposing consequences for water infiltration and runoff generation. Our findings suggest that macro-crustivores may play a key role in regulating biocrust ecological functioning, introducing a whole new line of crustivory research that will be instrumental in conceptualizing various ecosystem dynamics in drylands.

How to cite: Sagi, N., Sagy, A., Felde, V., and Hawlena, D.: Top-down effects of crust-eating macro-arthropods on biocrust microtopography and carbon cycling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3022, https://doi.org/10.5194/egusphere-egu24-3022, 2024.

Tropical rainforests on low-phosphorus (P) soils are highly biodiverse and productive, playing a crucial role in climate change mitigation. However, the adaptation mechanisms of tropical rainforest dominated by trees associated with different mycorrhizal symbioses (arbuscular mycorrhizal (AM) and ectomycorrhizal fungi (ECM)) to P-deficient environments remain unclear. Through a 10-year field experiments with nitrogen (N) and P additions in AM- and ECM-dominated stands, we first investigated leaf nutrient content and resorption efficiencies of eight species in each stand. We further explored how litter, soil, and microbes maintain P supply to plants. We found that both AM- and ECM-dominated forests are P-limited. AM-dominated forest exhibited higher soil phoD gene abundance and fungal diversity, while ECM-dominated forest displayed higher soil phosphatase activity. Regression and random forest analyses revealed that AM-dominated forest employ diverse P-acquisition strategies, including increased foliar P resorption efficiency, soil phosphatase activity, and fungal diversity. In contrast, ECM-dominated forest preferred to enhance soil phosphatases activity and mineralize moderately liable P, thereby alleviating P limitation. These findings show joint influence of litter, soil, and microorganisms on plant P acquisition, and P-regulated processes vary by mycorrhizal types. Our study enhances understanding of the effects of global change on biogeochemical processes in tropical rainforests.

How to cite: Yu, Q.: Differential adaptative strategies to phosphorus limitation in tropical rainforests dominated by trees associated with arbuscular and ectomycorrhizal fungi, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3313, https://doi.org/10.5194/egusphere-egu24-3313, 2024.

EGU24-6598 | ECS | Orals | SSS4.3

Why, where, and when are there anoxic microsites in the rhizosphere – a microfluidic approach 

Emily Lacroix, Giulia Ceriotti, Daniel Garrido-Sanz, Sergey Borisov, Jasmine Berg, Christoph Keel, Pietro de Anna, and Marco Keiluweit

For decades, biogeochemists have speculated that roots are key drivers of anoxic microsites – anomalous volumes of oxygen depletion – in upland soils. Rhizosphere-associated anoxic microsites are hypothesized to regulate plant contaminant uptake, nutrient availability, and the fate of root-derived carbon. However, despite the potential importance of rhizosphere-associated anoxic microsites, it remains unclear why, when, and where anoxic microsites form in the rhizosphere. Here, we pair planar optical oxygen sensors with microfluidic devices mimicking a soil structure to map the distribution of oxygen in a young wheat rhizosphere. We filled microfluidic devices with i) sterile; ii) wheat symbiont-inoculated, and iii) whole-soil community-inoculated nutrient solutions. As a result, we were able to determine root oxygen consumption vs. microbial oxygen consumption over space (i.e., at different root physiological features) and time (i.e., day/night cycles). We will show that i) intense root respiration within the root tip may drive anoxic microsite formation, even in the absence of microbial respiration; ii) microbial colonization of lateral root emergence may drive localized oxygen depletion in older root sections, and iii) overall rhizosphere oxygen depletion has a predictable, diurnal cycle dictated by the plant’s photosynthetically active period. Our findings are the first to link root physiology to anoxic microsites, providing a strong basis for future studies of anoxic microsites in field soils. 

How to cite: Lacroix, E., Ceriotti, G., Garrido-Sanz, D., Borisov, S., Berg, J., Keel, C., de Anna, P., and Keiluweit, M.: Why, where, and when are there anoxic microsites in the rhizosphere – a microfluidic approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6598, https://doi.org/10.5194/egusphere-egu24-6598, 2024.

EGU24-7619 | ECS | Posters on site | SSS4.3

Coexistence patterns of biocrust-vascular plant in the Loess Plateau 

Yali Ma, Li Ma, Liping Yang, Siqing Wang, Hongyu Jiang, Yuhan Qi, Qianhai Ye, and Ning Chen

Biological soil crust (biocrust) widely distributes in the Loess Plateau, which is the most typical loess platform worldwide, and a cultural origin of China. Since 1999, the Loess Plateau experienced heavily restorations, costed hundreds of billions Chinese Yuan. Even so, we have no clear idea of how do major biological components – biocrust, grass, and shrub coexist together therein, which can greatly affect restoration practices. To that end, this study combined field survey, reference compiling and remote sensing data to identify coexistence patterns of biocrusts and vascular plants (grass and shrub) on the Loess Plateau. A total of 262 data points had been collected. We found that precipitation, surface temperature and solar radiation were the major drivers in the Loess Plateau, and there were three coexistence patterns, namely high biocrust-vascular mixed state under high annual rainfall and surface temperature of 10-12°C, biocrust-dominated state under low rainfall condition and low biocrust-vascular mixed state under low surface temperature situation. Furthermore, we found that high biocrust-vascular mixed and biocrust-dominated states appeared to be alternative states along annual rainfall gradient. This study discovered coexistence patterns of biocrust-vascular plant in the Loess Plateau for the first time, and can guide future restoration and conservation in the region. This is crucial for achieving sustainable development and ecological safety of north China.

How to cite: Ma, Y., Ma, L., Yang, L., Wang, S., Jiang, H., Qi, Y., Ye, Q., and Chen, N.: Coexistence patterns of biocrust-vascular plant in the Loess Plateau, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7619, https://doi.org/10.5194/egusphere-egu24-7619, 2024.

EGU24-9749 | ECS | Posters on site | SSS4.3

Spatial organization of a soil cyanobacterium and its cyanosphere through GABA/Glu signaling to optimize mutualistic nitrogen fixation 

Corey Nelson, Pavani Dadi, Dhara D. Shah, and Ferran Garcia-Pichel

Soil biocrusts are characterized by the spatial self-organization of resident microbial populations at small scales. The cyanobacterium Microcoleus vaginatus, a prominent primary producer and pioneer biocrust former, relies on a mutualistic carbon (C) for nitrogen (N) exchange with its heterotrophic cyanosphere microbiome, a mutualism that may be optimized through the ability of the cyanobacterium to aggregate into bundles of trichomes. Testing both environmental populations and representative isolates, we show that the proximity of mutualistic diazotroph populations results in M. vaginatus bundle formation orchestrated through chemophobic and chemokinetic responses to Gamma-aminobutyric acid (GABA) / Glutamate (Glu) signals. The signaling system is characterized by: 1) high GABA sensitivity (nM range) and low Glu sensitivity (µM - mM); 2) GABA and Glu are produced by the cyanobacterium as an autoinduction response to N deficiency; and 3) interspecific signaling by heterotrophs in response to C limitation. Further, it crucially switches from a positive to a negative feed-back loop with increasing GABA concentration, thus setting maximal bundle sizes. The unprecedented use of GABA/Glu as an intra- and interspecific signal in the spatial organization of microbiomes highlights the pair as truly universal infochemicals.

How to cite: Nelson, C., Dadi, P., Shah, D. D., and Garcia-Pichel, F.: Spatial organization of a soil cyanobacterium and its cyanosphere through GABA/Glu signaling to optimize mutualistic nitrogen fixation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9749, https://doi.org/10.5194/egusphere-egu24-9749, 2024.

EGU24-10710 | ECS | Posters virtual | SSS4.3

Biological soil crusts as hotspots of managed soils in mesic environments 

Corinna Gall, Julia Katharina Kurth, Karin Glaser, Ulf Karsten, Juliette Ohan, Michael Schloter, Thomas Scholten, Stefanie Schulz, and Steffen Seitz

Biological soil crusts, or “biocrusts”, are biogeochemical hotspots that significantly influence ecosystem processes in arid environments. Biocrusts play an important ecological role in the pedosphere and can improve nutrient availability and fertility, influence plant germination, increase biogeochemical cycling, keep and enhance water availability at the soil surface, increase soil aggregate stability, and protect the soil surface by counteracting soil erosion from water and wind. Although they cover large areas, particularly in managed sites with frequent anthropogenic disturbance, their importance in mesic environments is not in the focus of research so far. As in arid regions, biocrusts can significantly affect soil nutrients, soil degradation as well as the water balance here; however, their persistence may differ. The essential requirements for biocrust development include bare soil and a minimum amount of light. These conditions act as a starting point for biocrust establishment and succession in mesic environments and can either occur in special habitats such as sand dunes or mining heaps or be created by disturbing or removing layers of vegetation and litter. Recent studies have found mesic biocrusts mostly at managed, anthropogenically impacted sites such as monospecific forest plantations, broadleaf-mixed forests under heavy machining, and agricultural fields.

Based on their ecological functions, biocrusts bear the potential to act as novel tools for sustainable soil management. They have already been explored as possible means to restore degraded soils such as in the rehabilitation of salt heaps and burned forests. As a consequence of global climate change with a larger frequency of extreme weather events such as heavy rainfalls or extended droughts, soils will become more vulnerable and require new forms of management. Accordingly, biocrusts could make a significant contribution considering their partly high abundance in managed mesic environments. As the study of biocrusts in mesic environments is still in its infancy, further elaboration on their dynamics, distribution, and potential impacts on ecosystem services is needed. Therefore, we call for interdisciplinary physical, biological, microbiological, chemical, and applied soil science research with a special focus on biocrusts of managed soils from mesic environments, to better understand their impact on overall ecosystem health and resilience, particularly due to climate change.

How to cite: Gall, C., Kurth, J. K., Glaser, K., Karsten, U., Ohan, J., Schloter, M., Scholten, T., Schulz, S., and Seitz, S.: Biological soil crusts as hotspots of managed soils in mesic environments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10710, https://doi.org/10.5194/egusphere-egu24-10710, 2024.

EGU24-11067 | ECS | Posters on site | SSS4.3

Evaluation the efficiency of different application method of Fe aminochelates compared to FeSO4 on yield and quality traits of oleic Sunflower (Helianthus annuus L.) in a calcareous soil 

Mina Alipour Babadi, Mojtaba Norouzi Masir, Abdol Amir Moezzi, Mehdi Taghavi, Afrasyab Rahnama, and Bahar S. Razavi

In modern and sustainable approaches, it is necessary to address the nutrient deficiencies that limit agriculture productions.­ Routine inorganic fertilizers such as FeCl2 and FeSO4, are not effective in correcting iron (Fe) deficiency due to their chemical nature and rapid conversion of soluble Fe forms into unavailable Fe (III)-oxide or hydroxide forms, particularly under lime conditions. Recently, organic complexing agents such as amino acids have been considered important due to increasing nutrient bioavailability in the soils as well as improving plant stress tolerance for more yield. It is hypothesized that the use of ecofriendly Fe (II)-amino acid chelates can increase Fe uptake by plant as such products have the potential to form relatively stable complexes with minerals as "aminochelates". Aminochelate fertilizers are the latest novelties regarding plant nutrition in agricultural production systems. Amino chelates provide higher bioavailability and absorption of micronutrients due to effective ingredients with no environmental side effects. Here, we investigate the effects of Fe aminochelates as Fe sources on the yield of sunflower (Helianthus annuus L.) plants in field condition. We made use of synthesized Fe (glycine)2 [Fe (Gly)2] and Fe (methionine)2 [Fe (Met)2] amino chelates for seed priming, fertigation and foliar application on plant leaves. This experiment showed that all methods of Fe aminochelates application, especially foliar feeding, can increase shoot iron content and improve nutritional quality of sunflower in Fe-deficient soils. We observed the higher effectiveness of Fe aminochelates compared to FeSO4 on increasing plant growth parameters, grain and oil yield, biomass production and activity of antioxidant enzymes. Overall, our results suggested that application of Fe aminochelates can be considered as an effective approach to overcome the plant Fe deficiency and improve the yield of plant in calcareous soil. Future experiments will investigate the effects of aminochelates on soil biological parameters and soil enzymes activity in rhizospheres using imaging techniques.

Key words: Aminochelates; antioxidant enzymes; grain yield; iron deficiency; nutrient uptake

 

How to cite: Alipour Babadi, M., Norouzi Masir, M., Moezzi, A. A., Taghavi, M., Rahnama, A., and Razavi, B. S.: Evaluation the efficiency of different application method of Fe aminochelates compared to FeSO4 on yield and quality traits of oleic Sunflower (Helianthus annuus L.) in a calcareous soil, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11067, https://doi.org/10.5194/egusphere-egu24-11067, 2024.

EGU24-11099 | Posters on site | SSS4.3

Soil fertilization alters spatial and temporal distribution of amino-N in the rhizosphere of maize 

Evgenia Blagodatskaya, Guoting Shen, and Andrey Guber

Despite an importance and relatively high abundance of organic N in soil, it is uncertain how the distribution of organic N is affected by mineral N availability in the course of root development. We visualized amino-N content in seminal and lateral roots of maize (Zea mays L.) grown under reduced and full fertilization at the 4- and 6-leaves phases.  The intensity of amino-N hotspots was fertilization-, growth phase- and root-specific. Under reduced fertilization, amino-N content decreased in all root parts at the 6- versus the 4-leaves phase. Under full fertilization, the content of amino-N increased in seminal roots and lateral root tips but it decreased in seminal root tips with root growth. This suggests a potential functional differentiation of seminal and lateral root tips in the N-acquisition strategy in the course of plant growth. 

How to cite: Blagodatskaya, E., Shen, G., and Guber, A.: Soil fertilization alters spatial and temporal distribution of amino-N in the rhizosphere of maize, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11099, https://doi.org/10.5194/egusphere-egu24-11099, 2024.

EGU24-11732 | ECS | Posters on site | SSS4.3

High soil metal contents override climate impacts on biogeochemical dynamics in bulk and rhizosphere soils of a metal-hyperaccumulating plant 

Carolina Vergara Cid, Natalia Sanchez, Sören Drabesch, Ines Merbach, Evgenia Blagodatskaya, and E. Marie Muehe

Plant roots can modify soil organic matter decomposition, regulating carbon (C) and nitrogen (N) fluxes and storage. Several biotic (e.g., plant species, soil microbiome) and abiotic factors (e.g., nutrient availability, temperature, environmental stressors) can influence the extent of changes in nutrient cycling driven by roots. For instance, metal contamination and climate change can trigger changes in plant and microbial growth and activity, impacting soil biogeochemical processes. Given that future climatic conditions may boost metal mobility in soils and root exudation, the coupling of both disturbances may likely impact nutrient cycling more severely than either single factor. However, little is known about the impacts of coupled climate change and soil contamination on nutrient cycling facilitated by the rhizosphere of a metal hyperaccumulating plant, which is especially relevant in phytoremediation.

To investigate whether and to which extent climate induces modifications of nutrient and metal availability affecting microbiome dynamics and functioning in bulk and rhizosphere soils, we set up a greenhouse pot study with the model metal hyperaccumulating plant Arabidopsis halleri. Three agricultural soils with natural contents of the common non-metabolically useful heavy metal Cd (low 0.2 ppm Cd, medium 1 ppm Cd, and high 14 ppm Cd) were exposed to today’s and future climatic conditions (according to IPCC RCP 8.5: +4º C and +400 ppmv CO2). 

Future climatic conditions enhanced plant growth in all soils producing between 1.6 to 2.8 times more shoot, with plants growing overall less on the high-Cd soil. Future climatic conditions increased shoot Cd accumulation only in soil with medium-Cd content but not low and high-Cd. Increased organic matter decomposition indicated by higher hydrolytic enzyme activity and N mineralization was found in the low-Cd soil under future conditions. Nevertheless, root activity was the main driver in producing changes in soil nutrient fluxes and metal availability in metal contaminated soils. Overall, increasing metal concentration negatively affected soil carbon microbial biomass and the microbial metabolic quotient; however, the decline was significantly more pronounced in the rhizosphere of medium-Cd and high-Cd soils. In addition, hydrolytic enzyme activities involved in C and N cycling were higher in medium-Cd and high-Cd soils, as well as the plant metal content and metal availability in the rhizospheres. These findings indicate a higher maintenance cost for microorganisms in the rhizosphere of contaminated soils, which may respond to higher nutrient demand from plants and a higher portion of assimilated C allocated to alleviate heavy metal toxicity. As soil metal contamination increased, less microbial N biomass and higher N mineralization were found in the rhizosphere, suggesting an adjustment in microbial activity to plant needs and lower capacity for N immobilization in soils.

We conclude that although climate change can significantly affect overall plant responses and boost organic matter decomposition in soils with low metal content, climate impacts on soil microbial community dynamics and biogeochemical processes are overridden in soils with high metal contents, which trigger higher C and N demand by plant and stressed microorganisms and may imply a decrease in C and N soil storage.

How to cite: Vergara Cid, C., Sanchez, N., Drabesch, S., Merbach, I., Blagodatskaya, E., and Muehe, E. M.: High soil metal contents override climate impacts on biogeochemical dynamics in bulk and rhizosphere soils of a metal-hyperaccumulating plant, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11732, https://doi.org/10.5194/egusphere-egu24-11732, 2024.

EGU24-11977 | Posters on site | SSS4.3

Synergistic Effects of Raised Temperature and CO2 on Strategists of Soil Enzyme and Microbial Communities 

Bin Song, Zhenhua Yu, Yuchao Wang, Jonathan Adams, and Bahar Razavi

The effects of global warming and CO2 influence on soil processes and crop growth are a major area of concern. Rhizosphere soil enzymes, mostly produced by microbes, play a pivotal role in enhancing soil nutrient accessibility for plant assimilation. Knowledge about the responses and adaptations related to the nutrient acquisition in space of microbial communities to increased temperature and CO2 re remaining deficient. Here, we grew soybean in rhizobox mesocosms under raised temperature (+2 ℃, ET) and CO2 (+300 ppm, ECO2) and the combination (ECO2+ ET). ECO2 increased the enzymatic hotspot area from 1.8 to 3.3% of soil, while ET increased enzyme activities by 2.5%-8.7%. Notably, the combined influence of ECO2 and ET synergistically amplified both the scope (increasing by 5.3% to 10.1%) and intensity (escalating by 35.4% to 67.3%) of three concurrent enzymes. Compared to ambient, rhizosphere communities in ECO2 were dominated by the keystone taxa of r-strategists, Acidobacteria, Proteobacteria, and Ascomycota. Conversely, ET shifted the microbial community to K- selection by increasing the relative abundance of Basidiomycota and Actinobacteria. Meanwhile, ECO2+ ET promoted the relative abundance of bacterial keystone species (Acidobacteria, Proteobacteria, and Actinobacteria) and fungi (Ascomycota and Basidiomycota) of the total community. These observations emphasize the potentially key role of enzyme hotspot areas in mediating climate change responses. Changes in the activity and extent of enzymes observed under the experimental treatments suggest a shift in balance towards a mixed r and K strategy in the hotspot microbiota. The microbial communities showed clear shifts in composition of the structure in response to the treatments, with changes in taxonomic composition, network structuring, and the balance between r and K-designated species.

How to cite: Song, B., Yu, Z., Wang, Y., Adams, J., and Razavi, B.: Synergistic Effects of Raised Temperature and CO2 on Strategists of Soil Enzyme and Microbial Communities, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11977, https://doi.org/10.5194/egusphere-egu24-11977, 2024.

EGU24-12561 | Posters on site | SSS4.3

Rhizosphere microbial activities in response to combined effects of drought and microplastic  

Ali Feizi, Duyen T.T. Hoang, Bahar S. Razavi, and Sandra Spielvogel

The human’s well-being is challenged by various global issues such as environmental pollution and climate change. While plastic waste, particularly microplastic, is an emerging environmental pollution, drought becomes a more frequent natural hazard to cropping system.

Two hypotheses were proposed in this research as (i) drought is more dominated as compared to microplastic existence regulating microbial activities; (ii) the effects of microplastic on enzyme activities and distribution are enzyme specific and depends on microplastic types. Zymography was acquired to demonstrate the distribution of β-glucosidase (GLU) and acid phosphatase (APT) within soybean rhizosphere amended with either biodegradable microplastics or nondegradable microplastics. In addition, enzyme activities of GLU, APT, leucine aminopeptidase (LEU), and microbial biomass phosphorus (MBP) were assayed to prove the hypotheses. Five-time lower hotspot percentage in dry soil than moist soil regardless of microplastic types implied an overwhelming impacts of water stress as compared to microplastics on the microbial degradation of soil organic matter in the plant-soil ecosystem. A shortened rhizosphere extent was found in microplastic treatments also demonstrated its negative influence on rooted microbial activities. In conclusion, the co-influence of two distinguished abiotic factors should increase the complexity of plant-microbe association and unpredicted regulation of nutrient and C flux in the crop land.

Keywords: rhizosphere, enzyme activities, microbial biomass, drought, zymography

How to cite: Feizi, A., Hoang, D. T. T., Razavi, B. S., and Spielvogel, S.: Rhizosphere microbial activities in response to combined effects of drought and microplastic , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12561, https://doi.org/10.5194/egusphere-egu24-12561, 2024.

EGU24-13285 | Orals | SSS4.3

Abiotic soil matrix, rather than microbial community composition, determines litter C cycling 

Kyle Mason-Jones, Kira Ingenhoven, S. Emilia Hannula, G. F. (Ciska) Veen, and Wim H. van der Putten

Microorganisms are the primary agents of litter decomposition in the detritusphere, and are considered potentially powerful levers for influencing soil biogeochemical transformation of plant C into soil organic matter (SOM). However, it remains unclear whether soil microbial activity is primarily constrained by the microbial community composition or by the abiotic soil habitat in which they live. We explored the relative importance of abiotic and biotic factors in litter carbon (C) cycling by reinoculating five sterilized agricultural soils from the Netherlands with six contrasting soil microbial communities from a gradient of land-use intensity. Admixing of subsurface horizons (representing older SOM) and the addition of synthetic ferrihydrite (as an iron oxide representative) were included as additional abiotic manipulations. 16S and ITS amplicon sequencing confirmed that the contrasting communities successfully colonized the sterilized soils and retained strong signatures of their source inoculum during a laboratory incubation of nine months. Nevertheless, basal respiration of SOM and the mineralization of isotopically (13C) labelled litter (Lolium perenne) was overwhelmingly determined by the abiotic soil matrix, most notably the source soil and mixing of subsurface horizons. Ferrihydrite, in contrast, had little effect. These observations were extended by quantification of mineral nitrogen as well as 13C incorporation into particulate and mineral-associated SOM fractions. The findings provide strong experimental support for the responsiveness of C cycling to soil abiotic habitat factors, irrespective of community structure.

How to cite: Mason-Jones, K., Ingenhoven, K., Hannula, S. E., Veen, G. F. (., and van der Putten, W. H.: Abiotic soil matrix, rather than microbial community composition, determines litter C cycling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13285, https://doi.org/10.5194/egusphere-egu24-13285, 2024.

EGU24-13344 | Orals | SSS4.3

Metabolic responses to hotspot-forming processes: growth modes and their ecological consequences 

Michaela A. Dippold, Callum C. Banfield, and Kyle Mason-Jones

Hotspots are characterized by an increased availability of nutritional elements compared to the surrounding bulk soil, which enhances microbial activity. However, the shifts in nutrient stoichiometry, when hotspot formation is initiated by a non-microbial organic matter source (rhizodeposits, litter, feces & mucus, percolating dissolved organic matter), are highly hotspot-specific. This results in contrasting microbial dynamics in the rhizo-hyphosphere, the detritusphere, the drilosphere and further biopores of soil animals, and in preferential flow pathways.

Experiments and models of microbial growth-death dynamics have recently improved our understanding of how element stoichiometry shapes element allocation in microbial metabolism. This holds specifically true for to the two contrasting pathways of microbial growth – intracellular element storage versus the investment of C, nutrients and energy in replicative microbial growth. Both growth modes involve synthesis of organic polymers – either storage or structural cellular polymers. However, the nature of these two types of polymers is highly contrasting with regards to their elemental but also their molecular diversity, such that the two growth modes generate distinct differences in the molecular compositon of the cellular biomass. We can therefore expect that the stoichiometric differences of nutrient hotspots will drive differences in the molecular diversity of the microbial biomass, and so ultimately the successively accumulating necromass.

Whereas controlled incubation experiments demonstrate how element allocation to storage and replicative growth depends on nutrient stoichiometry, we lack an understanding of how growth modes are distributed among hotspots in situ. Besides developing this conceptual understanding, we aim to shed light on the implications of differences in cell physiology among hotspots, which includes i) the turnover rate of microbial biomass due to contrasting resistance to stress (e.g. starvation), ii) the molecular composition of the microbial cells and iii) the resulting chemical properties and molecular diversity of necromass. These factors strongly influence the formation rates, qualities and persistence of necromass-derived soil organic matter arising in these hotspots. Furthermore, the accrual of organic matter shapes microbial resource availability, including element stoichiometry, in the hotspot, as well as the physico-chemical microbial habitat properties. In consequence, a feedback loop between microbial growth- and turnover-based organic matter formation and the initial processes, that trigger the hotspot formation elaborates. Thus, although hotspot formation is always initiated by non-microbial organic matter input, the characteristics of the established soil hotspots are ultimately linked to the microbial necromass’ molecular and elemental diversity, which is the direct product of the hotspots’ microbial metabolism and growth mode. This study aims to relate the nutrient enriching processes (rhizodeposits, litter, feces & mucus, percolating DOM) and soil-intrinsic feedbacks to the dominant microbial growth modes and resulting properties of the organic matter in soil hotspots. 

How to cite: Dippold, M. A., Banfield, C. C., and Mason-Jones, K.: Metabolic responses to hotspot-forming processes: growth modes and their ecological consequences, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13344, https://doi.org/10.5194/egusphere-egu24-13344, 2024.

EGU24-13836 | ECS | Orals | SSS4.3

Consumption of methane by a landfill cover soil under variable moisture and temperature conditions 

Christina Lam, Stephanie Slowinski, Mehdi Ramezanzadeh, Laura Hug, Nathanael Willms, Philippe Van Cappellen, and Fereidoun Rezanezhad

Landfills are one of the largest anthropogenic sources of methane (CH4), and hot-spots of CH4 emissions in landfill cover soils can enrich microbes that oxidize CH4 to carbon dioxide (CO2). CH4 oxidation rates are modulated by multiple variables including soil moisture and temperature, although the interactive effects of these factors on CH4 oxidation rates have not been well-studied. Here, we conducted a closed-headspace batch experiment with cover soil from a former landfill in Ontario, Canada to measure CH4 consumption and CO2 efflux rates associated with variations in soil moisture and temperature simultaneously. Soil samples were incubated under a factorial design of 5 soil moisture contents ranging from 11 to 47% WFPS (water-filled pore space), and 6 temperatures ranging from 1 to 35°C. At each temperature and WFPS combination, CH4 (812 nmol) was spiked into the headspace, and headspace CH4 and CO2 concentrations were measured over 2 hours to calculate CO2 efflux and CH4 consumption rates. The maximum CO2 efflux rate was observed at the maximal WFPS and temperature conditions of this experiment (92 nmol h-1 g dry wt.-1 at 47% WFPS and 35°C), while the maximum CH4 consumption rate was observed at intermediate WFPS and temperature conditions (1.9 nmol h-1 g dry wt.-1 at 25% WFPS and 25°C). The CO2 efflux observed is primarily attributed to the oxidative degradation of soil organic matter. A diffusion-reaction model was fit to the observed data to represent the effects of temperature and soil WFPS on the CH4 consumption and CO2 efflux rates. The model predicted similar optimal conditions as those observed for both the CH4 consumption and the CO2 efflux rates. The modeling and experimental results show that the dominant controls on optimal soil moisture for CH4 consumption are moisture limitation of microbial activity and of gas (CH4 and oxygen) diffusion, versus the interactive effects of moisture limitation of gas (oxygen) diffusion and of solute mobility for CO2 effluxes. These results provide insight into how seasonal changes in soil moisture and temperature could impact CH4 oxidation rates, and therefore also net CH4 emissions, in landfill cover soils and other environments.

How to cite: Lam, C., Slowinski, S., Ramezanzadeh, M., Hug, L., Willms, N., Van Cappellen, P., and Rezanezhad, F.: Consumption of methane by a landfill cover soil under variable moisture and temperature conditions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13836, https://doi.org/10.5194/egusphere-egu24-13836, 2024.

EGU24-13923 | ECS | Posters on site | SSS4.3

A urea-based symbiotic transfer of nitrogen in biological soil crusts 

Ana Mercedes Heredia-Velasquez, Soumyadev Sarkar, Finlay Warsop Thomas, and Ferran Garcia-Pichel

Crucial to the establishment of biological soil crusts is a mutualistic exchange of C for N between pioneer filamentous non-heterocystous cyanobacteria of the Microcoleus type and a selected group of heterotrophic diazotrophs (for example, Massilia sp.) that come together in the so-called “cyanosphere”. In other such C for N mutualisms, N is transferred between species in the form of amino acids, and potential losses to adventitious bacteria are prevented by sequestering the diazotrophs into specialized structures. Yet, in the Microcoleus symbiosis no such structures exist, and only proximity achieved through chemotaxis is known to optimize the exchange. How is specificity then achieved?  We posited that the exchange might occur through urea, because it is the preferred N source for growth in Microcoleus. We show using cultures that members of the cyanosphere excrete urea when growing in symbiosis with Microcoleus at low concentration but sustained rates, but not when growing on their own diazotrophically. Consistently, Microcoleus can grow on urea down to the micromolar range, unlike other cyanobacteria that need much higher concentrations to grow. We also show that Massilia overexpresses the genes for the urea cycle (production of urea) when in symbioses, but not otherwise, and that Microcoleus overexpresses genes for urea uptake and utilization when in symbiosis. Microcoleus contains a rare set of enzymes for urea utilization (allophanase and urea carboxylase), that, unlike the widespread urease, allow it to process urea at very low concentrations. Hence, it seems that with the combination of these unique biochemical and regulatory capacities, low concentration urea can effectively transfer N in a partner-specific way, dodging potential losses of N to most other bacteria that can only use urease. We discuss the importance of these findings for the ecology and restoration of biological soil crusts.

 

How to cite: Heredia-Velasquez, A. M., Sarkar, S., Warsop Thomas, F., and Garcia-Pichel, F.: A urea-based symbiotic transfer of nitrogen in biological soil crusts, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13923, https://doi.org/10.5194/egusphere-egu24-13923, 2024.

We are currently revisiting a study by Flechtner, Johansen, and Belnap (2008) on the algae of biological soil crusts on San Nicolas Island.  A total of 200+ strains have been newly isolated, of which 78 cyanobacterial strains have been sequenced, representing 26 different species.  Of these 26 species, 23 appear to be phylogenetically new to science.  Several isolates show distinctive biogeography, belonging to genera recently described from Brazil. We found evidence of three species of the heterocytous genus Atlanticothrix, two species of Pycnacronema, and one species of Konicacronema.  Our species are morphologically consistent with species of these genera, but molecularly are clearly separated, particularly on the basis of ribosomal gene trees and analysis of the 16S-23S internal transcribed spacer region. There are presently no known vectors for transmission of taxa from the Atlantic Forest in Brazil to San Nicolas Island, or vice versa.  Wind patterns from Africa are known to bring dust from that continent to both South America and North America, but winds in the western hemisphere blow out into the Pacific Ocean in a westerly direction and do not cross the equator.  This suggests that at some time in the distant past, these microbes may have been seeded from Africa to North America, but have been in place long enough to become independent distinctive lineages worthy of recognition as different species from their southern hemisphere congeners. As preliminary evidence supporting an African origin for soil crust taxa, other workers have reported cyanobacterial genera in Africa (Pseudoacaryochloris, Aliterella, and Atlanticothrix) that also occur on San Nicolas Island. Future work will explore the cyanobacterial flora of all the Channel Islands as well as coastal southern California which could serve as a colonization source for cyanobacteria on the islands.

How to cite: Johansen, J. and Jusko, B.: Discovery of new cyanobacterial species from crusted soils of San Nicolas Island, California, from genera previously restricted to Brazil and Africa., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14115, https://doi.org/10.5194/egusphere-egu24-14115, 2024.

EGU24-14182 | Orals | SSS4.3

Revealing cyanosphere microbial diversity of terrestrial cyanobacteria 

Nicole Pietrasiak, Brianne Palmer, Estelle Couradeau, and Jason Stajich

The cyanosphere contains heterotrophic microorganisms living within the exopolysaccharide sheath of cyanobacteria and serves as an interface between the cyanobacteria and their surrounding ecosystem. The symbiosis between the cyanobacterial host and its cyanosphere microbes spans the mutualistic-antagonistic spectrum. Understanding these relationships will predict the success of terrestrial cyanobacteria and the ecosystem services they provide including primary production in often oligotrophic environments. However, our understanding of the microbial diversity within the cyanosphere is limited. In this study, we used metagenomic sequencing to construct 528 metagenome-assembled genomes (MAGs) from the cyanosphere microbes associated with 50 unialgal terrestrial Cyanobacteria cultures, spanning 12 orders. We found that the composition of cyanosphere microbial communities was unique between Cyanobacteria hosts and was largely influenced by environmental (habitat, precipitation, and temperature) and phylogenetic variables (host order). Alphaproteobacteria was the most common cyanosphere microbial class and Bosea, Devosia, Hyphomicrobium, Mesorhizobium, and Sphingomonas were core genera found across all habitats. Interestingly, the nitrogen-fixing cyanobacterial order, Nostocales, contained the highest diversity of cyanosphere bacteria, many of which have the genomic potential also to fix atmospheric nitrogen. Given the observed variations in the cyanosphere microbial communities across different hosts, future considerations for ecological assessments and cyanobacterial restoration efforts must extend beyond the cyanobacteria to encompass their associated microbial communities.

How to cite: Pietrasiak, N., Palmer, B., Couradeau, E., and Stajich, J.: Revealing cyanosphere microbial diversity of terrestrial cyanobacteria, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14182, https://doi.org/10.5194/egusphere-egu24-14182, 2024.

EGU24-14268 | ECS | Posters on site | SSS4.3

Distribution of biological soil crusts in the Tibetan Plateau 

Zhixin Zhou, Ning Chen, Li Ma, Liping Yang, Hongyu Jiang, and Siqing Wang

Biological soil crust (biocrust) is regarded as a self-organizing principle, and widely distributes in the Tibetan Plateau, which is a crucial ecological security area of China and water towel of Asia. Unfolding biocrust distribution in the region is critical to maintain ecosystem functions and services therein. However, we know little about explicit distribution of biocrust in the Tibet Plateau. To that end, this study combined field survey, reference compiling and random forest algorithm to explore the spatial distribution of biocrusts on Tibetan Plateau and the associated driving factors. A total of 203 data points had been collected. We found that the biocrusts cover up to 20% of the soil surface in the Tibetan Plateau and mainly cover the Qaidam Basin and the northern Tibetan Plateau, but less in the Qiangtang Plateau and the southeastern Tibetan Plateau.The dominating factors affecting biocrust distribution are soil clay content, altitude, average temperature of the hottest season, pH, and soil organic carbon content. Specifically, biocrust acclimatization is positively affected by lower soil clay content and elevation, hotter quarter temperatures (especially greater than 8°C), and greater pH, while negatively affected by higher soil organic carbon content. Overall, this study sheds light on biocrust distribution in the Tibetan Plateau, and will significantly expand our understandings of biocrusts.

How to cite: Zhou, Z., Chen, N., Ma, L., Yang, L., Jiang, H., and Wang, S.: Distribution of biological soil crusts in the Tibetan Plateau, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14268, https://doi.org/10.5194/egusphere-egu24-14268, 2024.

EGU24-14324 | ECS | Posters virtual | SSS4.3

Effects of Elevated Temperature on Microbial Growth and Enzyme Kinetic During Transition from Rhizosphere to Root-Detritusphere 

Seyed Sajjad Hosseini, Mehdi Rashtbari, Amir Lakzian, and Bahar S. Razavi

Microbial growth and enzyme activity depend on carbon availability, which strongly differs in rhizosphere and root-detritusphere. Elevated temperature is expected to intensify enzymatic processes in these spheres. However, the response of soil enzyme activity to elevated temperature may be influenced by microbial growth, driven by variations in carbon availability. Therefore, our study investigated the response of enzyme kinetic parameters to elevated temperature during transition from rhizosphere to root-detritusphere and potential linkage to microbial growth. For this purpose, we measured active microbial biomass (AMC) and growth rate (µ) through substrate-induced growth respiration, as well as kinetic parameters of ꞵ-glucosidase (GLU) in rhizosphere (six weeks after planting) and root-detritusphere (four weeks after shoot cutting) of wheat at two different temperatures, 20 ᵒC and 30 ᵒC.

At both temperatures, a higher µ was observed in the root-detritusphere compared to the rhizosphere. Elevated temperatures significantly enhanced µ by 2.13 and 2.23 times in the rhizosphere and root-detritusphere, respectively. Additionally, AMB in root-detritusphere was lower than in the rhizosphere at both temperatures. Notably, at 30 ᵒC, AMB in the rhizosphere and root-detritusphere was 4.7 and 2.9 times lower than that at 20 ᵒC, respectively. The lower AMB in root-detritusphere and higher temperature, results from microbial starvation caused by rapid substrate uptake and fast growth. At 20 ᵒC, Vmax of GLU in root-detritusphere was higher than in rhizosphere, whereas at 30 ᵒC, the trend was reversed. Elevating the temperature from 20 ᵒC to 30 ᵒC within the rhizosphere resulted in an increase of 98% in the Vmax of GLU. Conversely, in the root-detritusphere, this temperature shift led to a reduction of 29% in the Vmax of GLU. The findings indicate that a reduction in AMB within the root-detritusphere leads to a downregulation of enzyme production. However, enzyme production in the rhizosphere is intricately regulated by both living roots and soil microorganisms, rendering it unaffected by changes in AMB.

How to cite: Hosseini, S. S., Rashtbari, M., Lakzian, A., and Razavi, B. S.: Effects of Elevated Temperature on Microbial Growth and Enzyme Kinetic During Transition from Rhizosphere to Root-Detritusphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14324, https://doi.org/10.5194/egusphere-egu24-14324, 2024.

Arbuscular mycorrhizal fungi (AMF) affect both plant nutrition and soil physical properties, including soil water retention and hydraulic conductivity. However, much less is known about the preferences of AMF for proliferation into soils of different (physical) natures, i.e. soil textures. To investigate this, we designed a pot trial with tomato in which AMF had access to root-free soil patches of different textures. We hypothesized that AMF would prefer fine-textured soils over coarse-textured soils because a finer textured soil is comparatively moist (which most fungi prefer) and contains a greater share of low-weight particles (less growth resistance) than a coarse-textured soil.

We inoculated tomato plants with the fungus Rhizopagus irregularis grown in 4L pots filled with a quartz sand: loam mixture (1:1 w/w). The loam is a calcareous alluvial loam obtained from the C-horizon with a pH of 7.5, low in organic matter (0.05% Corg), 42.72% sand, 44.22% silt, 13.06% clay and is highly P-fixing. The self-propagated fungal inoculum used was based on this loamy soil and, therefore, inoculation did not compromise the soil texture of the potting mix. Each pot received three ingrowth cores covered in root-excluding nylon mesh (37 µm) containing either pure quartz sand (grain size 0.3 – 1.0 mm), pure loam soil or a 1:1 mixture of the two (as in the main pot). To cause variance in soil hyphae development, we applied two treatments. On the one hand, half of the pots contained the tomato cultivar 76R and the other half its related rmc mutant, which is known to show reduced mycorrhizal colonization. On the other hand, we subjected half of the pots to two weeks of terminal drought to slow down plant and fungal growth, while the other half of the pots were kept under ample moisture. After harvest, we measured root colonization and plant nutrient uptake to verify the viability of the mycorrhizal symbioses. From the ingrowth cores, we extracted AMF hyphae and determined their length. As traits known to be affected by functional hyphae and plant activity as well as soil desiccation, we also measured aggregate stability indices in soils from the ingrowth cores.

According to our expectations, we found that the 76R tomatoes, which were able to develop a viable symbiosis, had higher tissue P and N mass fractions in their dry matter than the rmc tomatoes.  Against our expectations, the 76R plants were more sensitive to drought when exposed to it and had significantly lower biomass than the rmc plants and the 76R plants maintained under ample moisture. Furthermore, we illustrate our findings on hyphal length density and aggregation and discuss them with regard to the preferences of AMF to populate the soils with different textures. We answer whether our hypothesis must be confirmed or denied and deduce some potential ecological consequences of our findings.

How to cite: Jacob, E., Camenzind, T., and Bitterlich, M.: The modulation of plant nutrition and soil properties by mycorrhizal fungi and their preferences for the soil texture they encounter, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15871, https://doi.org/10.5194/egusphere-egu24-15871, 2024.

EGU24-16663 | Orals | SSS4.3

Nutrient and Water Availability Modulate the Destabilization of Mineral-Associated Organic Matter in the Rhizosphere 

Marco Keiluweit, Mariela Garcia Arredondo, Sherlynette Castro, Malak Tfaily, and Zoe Cardon

Soils are the largest and most dynamic carbon reservoir in terrestrial environments, with most carbon stored as mineral-associated organic matter (MAOM). It has recently been shown that MAOM is effectively destabilized by reactive compounds released by plant roots and associated microbes. It is well known that quantity and quality of rhizodeposits dramatically change in response to nutrient or water stress, with unclear consequences for rates of plant root-driven MAOM destabilization. Here we show that altered rhizodeposition in response to environmental stressors affects rates of root-driven MAOM destabilization. Well-controlled growth chamber experiments with Avena sativa (common oat) allowed us to test the individual and interactive effects of nitrogen, phosphorus, and water limitations on the fate of 13C-labeled MAOM over a 10-week period. At the end of the experiment, total MAOM mineralization was strongly correlated with root biomass, which generally declined with nutrient and water limitations. However, under P limitations, root-driven MAOM mineralization was greatest during the initial growth stages (vegetative), whereas N limitations resulted in greater rates of MAOM mineralization during later growth stages (flowering). Drought treatments, when compared to their corresponding optimal watering treatments, produced the least MAOM destabilization. To test whether temporal changes in MAOM destabilization rates can be explained by differences in rhizodeposition intensity and composition, we analyzed rhizodeposits collected throughout the experiment via high-resolution mass spectrometry. This study demonstrates that MAOM mineralization is regulated not just by the inherent stability of MAOM against microbial attack, but also depends on plant water and nutrient availability within the whole plant-soil system as well as plant physiological and phenological stages. Through such feedback, changes in soil nutrient and water status (e.g. via altered precipitation or fertilizer application) can be expected to cause plant-induced alterations to the size of the otherwise stable, mineral-associated soil carbon reservoir.

How to cite: Keiluweit, M., Garcia Arredondo, M., Castro, S., Tfaily, M., and Cardon, Z.: Nutrient and Water Availability Modulate the Destabilization of Mineral-Associated Organic Matter in the Rhizosphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16663, https://doi.org/10.5194/egusphere-egu24-16663, 2024.

EGU24-16883 | ECS | Orals | SSS4.3

Temperature increases the versatility of belowground plant-microbiota interactions in cold climates 

Dina in 't Zandt, Anna Aldorfová, Mária Šurinová, Michiel H. in ‘t Zandt, Vigdis Vandvik, and Zuzana Münzbergová

The ongoing change in climate extensively alters belowground interactions between plants and microbiota. Alterations in plant-microbiota interactions have significant implications for the functioning of ecosystems. To predict ecosystem change and protect vulnerable systems, it is therefore crucial to understand how climate shapes belowground plant-microbiota interactions. We test how prokaryote and fungal rhizosphere and root-associated communities of the perennial grass Festuca rubra are affected by temperature and precipitation in cold climate settings. We found that microbial communities were strongly shaped by temperature and to a lesser extent by precipitation. Temperature decreased relative habitat specialisation of the rhizosphere community and the fungal root-associated community. These effects were mediated by an increase in forb cover and a decrease in soil pH with temperature. Our findings indicate that with a rise in temperature in cold environments, plant-microbiota interactions become more versatile and adapted to a broader range of environmental conditions.

How to cite: in 't Zandt, D., Aldorfová, A., Šurinová, M., in ‘t Zandt, M. H., Vandvik, V., and Münzbergová, Z.: Temperature increases the versatility of belowground plant-microbiota interactions in cold climates, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16883, https://doi.org/10.5194/egusphere-egu24-16883, 2024.

EGU24-20430 | ECS | Posters on site | SSS4.3

Harnessing biocrust-isolated bacteria from semiarid soils to promote plant growth in ecological restoration 

Beatriz Roncero-Ramos, Carlotta Pagli, Lisa Maggioli, Eloisa Pajuelo, Yolanda Canton, and Miriam Muñoz-Rojas

Restoration of drylands is crucial to reverse global land degradation because these areas cover around 40% of the Earth surface and host one third of the world population. Restoration efforts are often unsuccessful in drylands and alternative approaches need to be developed, i.e., biocrust-based restoration, to promote plant growth and increase soil fertility and stability. In this research, we cultured several biocrust-forming organisms to inoculate them on degraded soils. We designed a more effective inoculum based on biocrust-forming heterotrophic bacteria with plant growth promotion properties (PGP) and key enzymatic activities. We hypothesised that inoculation of native seeds with a consortium of selected heterotrophic bacteria would enhance seed germination and establishment. We sampled incipient and developed biocrusts from three study sites located in semi-arid areas from SE Spain, and isolated 48 bacterial strains. We performed a screening within the bacterial collection to find those strains with key PGP properties and enzymatic activities. Specifically, we analysed their capacity to fix N2, solubilize P and K, produce biofilms, auxins and siderophores, and the extracellular activity of DNAse, amylase, protease, catalase, and lipase. Then, we assessed the best performing bacterial strains for co-culturing to avoid possible antagonistic effects and identified them by sequencing the 16S rRNA gene. The next step of this project will focus on assessing the effects of seed pelleting with the best-performing consortium on germination and establishment of native plants.

How to cite: Roncero-Ramos, B., Pagli, C., Maggioli, L., Pajuelo, E., Canton, Y., and Muñoz-Rojas, M.: Harnessing biocrust-isolated bacteria from semiarid soils to promote plant growth in ecological restoration, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20430, https://doi.org/10.5194/egusphere-egu24-20430, 2024.

EGU24-20825 | ECS | Orals | SSS4.3

Effect of ZnO nanoparticles on the bacterial community and other soil health parameters 

Zoya Javed, Gyan Datta Tripathi, and Kavya Dashora

The rapid growth of metallic nanoparticles (such as ZnO) in the present time increases the risk of the contamination of soil because it is the sink for all the nanoparticles, intentionally or unintentionally, and affects the microorganism productivity and damages the soil health. Zinc oxide nanoparticles are widely used in agriculture and other industries at the current time. Our study aimed to evaluate the toxicological effects of zinc oxide nanoparticles on the bacterial diversity of soil. A microcosm experiment was conducted by mixing the 1000 µg/gm of ZnO nanoparticles in the soil. After 60 days, the effect of zinc oxide nanoparticles on bacterial diversity was determined using Illumina MiSeq sequencing of 16S rRNA genes. The soil's physiochemical characteristics, such as C, H, and N content, were analyzed and compared with non-treated samples. Dehydrogenases (DH) and fluorescein diacetate (FDA) were assayed as the soil health indicator.  Results have shown that the relative abundances of the dominant and agriculturally significant phyla, namely, Proteobacteria and Actinobacteria, were altered in the presence of Zinc Oxide nanoparticles. However, it was also observed that Zinc oxide nanoparticles showed negligible effects at the phylum level. The dissolution of ZnO nanoparticles was also estimated with the help of ICP-MS, which was 870 µg/gm after 60 days. DH activity was higher and FDA activities were lowered compared to the non-treated soil.

How to cite: Javed, Z., Tripathi, G. D., and Dashora, K.: Effect of ZnO nanoparticles on the bacterial community and other soil health parameters, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20825, https://doi.org/10.5194/egusphere-egu24-20825, 2024.

EGU24-20849 | Orals | SSS4.3

Impact of Copper oxide nanoparticles on soil isolated Bacillus megaterium   

Gyan Datta Tripathi, Zoya Javed, and Kavya Dashora

Bacillus megaterium is a plant growth-promoting bacteria that performs various activities like producing hydrolytic enzymes in the soil such as protease and xylanase, releasing various growth hormones and other bioactive compounds that inhibit the plant pathogenic microbes in the soil. These microorganisms are not only part of the rhizosphere but instrumental in activities such as soil conditioning and nutrient cycling. But as the modernization of agriculture practices comes up with new age agrochemicals, called nano-agrochemicals, the concerns of toxicity also increased. These nano agrochemicals (such as CuO nanoparticles) have several advantages over the traditional chemicals, however, several properties like small size, lower dissolution, and potential to alter soil properties such as pH, raise serious threats to the soil beneficial microbes. It is also estimated that the accumulation of nanoparticles in the soil may become available for microbial ecosystems and cause toxicity with unique mechanisms, eg contact mode toxicity. Copper oxide nanoparticles are integral to new-era agrochemicals like nano-pesticides, nano-fertilizers, etc. There are mixed reviews on the toxicity of CuO nanoparticles on soil owing to diverse microbiota. Our in vitro studies were focused on the analysis of the size and dose-dependent impact of nanoparticles on the plant growth-promoting species  Bacillus megaterium at cellular, morphological as well as Indole acetic acid (IAA) production potential. Our study reveals that the small dose (0.05mg/ml) of copper oxide is not harmful to the microbes because copper is one of the essential elements However at upper concentration around 0.5mg to 1 mg/ml was significantly toxic for the Bacillus megaterium. The size-dependent toxicity on IAA production was also tested with the two different sizes of the CuO nanoparticles and the results were not significantly different.  

 

How to cite: Tripathi, G. D., Javed, Z., and Dashora, K.: Impact of Copper oxide nanoparticles on soil isolated Bacillus megaterium  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20849, https://doi.org/10.5194/egusphere-egu24-20849, 2024.

EGU24-21104 | ECS | Posters virtual | SSS4.3

Biological soil crusts stabilize degraded soils of the Brazilian Pampa affected by sandization 

carla webber, Ulisses F. Bremer, Ruhollah Tagizadeh-Mehrjardi, Bettina Weber, Aline Rosa, Thomas Scholten, and Steffen Seitz

Biological soil crusts (biocrusts) are a main factor in the protection of arid and semiarid ecosystems. They are key contributors to soil stabilization and erosion control through the aggregation of particles and the provision of a continuous surface cover. In the Brazilian Pampa, vegetation disturbance and soil degradation led to an expansion of sandization areas. These areas are quickly covered by biocrusts, which show the same soil-stabilizing effects as in other geographic regions but have not been investigated in this biome before.

The present study aims to expand our knowledge on the occurrence of biocrusts in sandization areas of the Brazilian Pampa and to analyse their distribution patterns related to the local topography. We focused on two research sites, where the presence of biocrusts seemed essential for soil protection. At these sites, first, the different biocrust types were assessed and a taxonomic survey was conducted. Second, UAV-based imagery was created to classify the communities. A random forest approach was applied to understand the relation between biocrust abundance and topography.

We observed that biocrusts are widespread in areas prone to sandization, with a coverage of approximately 25% of the surface area. They are mostly dominated by cyanobacteria, but also bryophytes play a key role. In this study, the cyanobacterial genus Stigonema was predominant at both study sites, while Campylopus pilifer was the dominating moss species. The mapping confirmed all major biocrust types including rolling, pinnacled, rugose, and smooth crusts. The biocrust distribution was influenced by local topography, but also the establishment of vascular plants. Slope and aspect had a strong influence on biocrust development, but the presence of protective topographic positions against atmospheric influences most prominently facilitated their occurrence.

This pilot study proved that biocrusts can play a key role as ecosystem engineers in the Brazilian Pampa with a positive effect on general vegetation growth and soil stabilization. Despite their significant impact in sandization areas, biocrusts are not in the focus of research, yet, and should be further studied to constrain future soil degradation.

How to cite: webber, C., Bremer, U. F., Tagizadeh-Mehrjardi, R., Weber, B., Rosa, A., Scholten, T., and Seitz, S.: Biological soil crusts stabilize degraded soils of the Brazilian Pampa affected by sandization, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21104, https://doi.org/10.5194/egusphere-egu24-21104, 2024.

Plant derived organic matter (OM), entering soils either as aboveground plant litter or via belowground rhizodeposition or dead roots, undergoes microbial mineralization and transformation and finally ends up in various soil OM (SOM) pools. With two major solid SOM pools besides dissolved OM, namely particulate OM (POM) and mineral-associated OM (MAOM), the initially plant dominated OM is progressively transformed into microbial OM during decomposition. However, as mineral soils comprise highly heterogeneous systems over a wide range of spatial and temporal scales, the microbial transformation of plant OM and the formation of SOM is highly variable in time and space as well. Processes controlling the persistence of SOM are especially determined at nm to µm scales at biological highly active biogeochemical interfaces. Thus, plant litter and roots form distinct soil hot spots for interactions between microbiota, OM and mineral particles that are thought to control the long-term fate of soil carbon. The detritusphere and rhizosphere thus represent soil volumes that host the complex interplay of biological, chemical and physical soil processes that determine the fate of SOM. We will highlight the intricate connection between the transformation of plant derived OM via microbial processing and soil structure formation that lead to the build-up of persistent SOM.   

How to cite: Mueller, C. W.: Plants, microorganisms and soil minerals, how the persistence of soil organic carbon is regulated at microscale interfaces, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21758, https://doi.org/10.5194/egusphere-egu24-21758, 2024.

EGU24-21779 | ECS | Orals | SSS4.3

Biocrusts, ecological indicators in the Australian rangelands 

Wendy Williams, Than Myint Swe, Maria Vega, Colin Driscoll, Robyn Cowley, Peter O’Reagain, Andries Potgieter, Yan Zhao, Paul Dennis, and Susanne Schmidt

The Australian rangelands that cover around 70% of the country (~6 million km2) are inhabited by some of the most extensive and diverse biocrusts globally. These regions are predominately managed as natural grazing lands. Across northern Australia where the climate is influenced by the monsoon (wet season) biocrusts dominated by cyanobacteria and liverworts occupy the interspaces between grass plants as a coherent layer that binds the upper millimetres of soil and forms a living cover of photoautotrophic (cyanobacteria, algae, lichens and bryophytes), and heterotrophic (bacteria, fungi and archaea) organisms. During the dry season biocrusts are inactive, then recover at the onset of the wet season, actively participating in nitrogen and carbon fixation and accumulation. To identify the role of biocrusts as ecological indicators, we modelled their distribution, diversity and function across microhabitats. We also determined how biocrust community dynamics had been influenced by long-term fire and grazing management regimes.

At Victoria River Research Station (Kidman Springs, NT), after 30 years of fire research we compared managed burning practices at 2, 4 or 6-yearly intervals on two soil types (calcarosol, vertosol). Biocrusts were resilient and recovered rapidly from fire, where diversity and genetic function altered seasonally, between soil types, and fire regimes. Post-fire, after a wet season (cattle excluded), biocrusts recovered with significantly more carbon and nitrogen in the surface soils of cooler fire treatments every four years.  

At Wambiana Cattle Station (QLD), grazing trials have been established for 25 years. When paddocks were rested from cattle grazing every second year, biocrusts in duplex soils recovered to levels comparable to ungrazed natural sites. In red-yellow earths, there were biocrust hotspots that provided protection to the soil surfaces when there was a loss of grass cover during drought. Biocrust diversity and function differed between soil type and management (moderate and heavy stocking).

This research demonstrates that the top centimetre of biocrust-rich soil is central to ground cover integrity and is essential to soil nutrient cycling and fertility. Biocrusts are an important indicator for overall vegetative recovery post fire, grazing and drought disturbances. The principles of land cover condition based on landscape function should include biocrust presence as a metric that describes landscape resilience, as opposed to bare unprotected ground. Importantly, land managers can apply this research to grazing practices that show that giving the land rest periods timed to coincide with the wet season allows time for biocrust organisms to recover from disturbance.

How to cite: Williams, W., Myint Swe, T., Vega, M., Driscoll, C., Cowley, R., O’Reagain, P., Potgieter, A., Zhao, Y., Dennis, P., and Schmidt, S.: Biocrusts, ecological indicators in the Australian rangelands, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21779, https://doi.org/10.5194/egusphere-egu24-21779, 2024.

The presence of multiple layers of red paleosol in loess strata poses challenges due to its high hardness, which hinders easy collapse when encountering water. This characteristic significantly affects the measurement results of the collapsible amount of loess strata. However, there is currently a lack of reports on the control effect of paleosol on collapsibility, resulting in a deficiency in the theoretical basis for the scientific selection of collapsibility in these strata. This paper aims to address this gap by analyzing the differences in self-weight collapsibility between indoor and outdoor conditions under various paleosol layers in different areas and strata. The analysis is based on statistical results from immersion tests conducted in the Loess Plateau. Furthermore, the research focuses on two test sites in Xi'an and conducts large-scale immersion tests, considering measurements such as water diffusion, changes in water content, soil pressure, and cumulative collapsibility under different test conditions. The study investigates the influence of paleosol layers on water infiltration and their role in controlling total weight collapse.The final results indicate that the presence of a paleosol layer prevents collapsibility from transferring to the lower layer and inhibits water infiltration, thereby reducing total collapsibility. Discrepancies between measured and calculated collapsibility values are positively correlated with the number of ancient soil layers. This research provides valuable insights into the collapsibility mechanism of paleosol-loess strata.

How to cite: Lin, L.:  Effects of paleosol on collapsibility of loess sites under immersion test conditions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-209, https://doi.org/10.5194/egusphere-egu24-209, 2024.

EGU24-1343 | Posters on site | SSS4.4

Soil Structural Stability Influenced by Land Management 

Maysoon Mikha, Timothy Green, Tyler Untiedt, and Gary Hergret

Soil structure is an important factor in regulating soil ecological functions and soil chemical, physical, and biological properties. This study evaluated soil structural stability from three locations within the central Great Plains (USA) under different management practices.  The study sites consisted of Alternative Crop Rotation (ACR) and Long-Term Tillage (LTT) near Akron, Colorado, and Knorr-Holden (KH) near Mitchell, Nebraska.  Tillage treatments consisted of no-tillage (NT), reduced tillage (RT), conventional tillage (CT), and moldboard plow (MP). Commercial mineral fertilizer (F) was used as a nitrogen source in ACR and LTT sites while manure (M) plus F treatments were used in KH.  Soil structural stability was evaluated using four indices, aggregate stability index (ASI), mean weight diameter (MWD), geometric mean diameter (GMD), and fractal dimension (FD).  At 0-15 cm depth, intensive tillage (CT and MP) in ACR and LTT, reduced (P < 0.05) ASI by 46.7%, MWD by 21.0% and GMD by 8.4% and increased FD by 0.77% compared with NT and RT treatments.  The addition of manure increased (P < 0.05) ASI by 72.2%, MWD by 65.6%, GMD by 32.8%, and reduced FD by 5.5% compared with tillage treatments in ACR and LTT.  Although FD was negatively correlated with MWD and GWD; it provides information not captured by ASI and complements MWD and GWD.  The indices presented in this study, including FD, are effective in measuring soil structural stability and should be considered further in management decisions to sustain soil resources and enhance economic returns.

How to cite: Mikha, M., Green, T., Untiedt, T., and Hergret, G.: Soil Structural Stability Influenced by Land Management, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1343, https://doi.org/10.5194/egusphere-egu24-1343, 2024.

The demand for ground improvement of marine sediments has been risen in construction of offshore infrastructures, including wharves, embankments and breakwaters. In recent years, microbially induced carbonate precipitation (MICP) has developed rapidly and become an alternative technology for increasing soil strength and limiting soil erosion. Silty sand is widely distributed in offshore areas throughout the world. The high salinity of seawater may have an impact on the bacterial activity, while the fine particles in silty sand would affect the transportation of cementation solution and the formation of carbonate precipitation. In this study, attentions are paid to the application of MICP on improvement of marine silty sand properties, as well as the factors influencing the hydraulic conductivity and strength of the bio-cemented soil. Multi-gradient domestication tests on Sporosacina pasteurii were carried out to ensure the bacterial and urease activities in seawater environment. It was found that the bacterial concentration and urease activity after five-gradient domestication in seawater reached 98.5% and 92.8% of those in the deionized water environment, respectively. The permeability, unconfined compressive strength (UCS) and content of carbonate precipitation of bio-cemented specimens were measured. The MICP treatment on silty sand with seawater resulted in an increase of UCS to 700 kPa and a reduction of permeability by an order of magnitude, corresponding to a carbonate content of 8%. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were performed to investigate the types and distributions of carbonate crystals. The results indicated the formation of calcium carbonate and magnesium carbonate crystals due to the interaction between carbonate ions and calcium and magnesium ions in seawater. The precipitations were distributed on the surfaces of soil particles and near particle contact points, affecting the soil microstructure and thus the strength and permeability. The influences of concentration and injection rate of cementation solution on the efficiency of MICP were demonstrated and the recommended values were given. This study may provide a possible solution for improvement of engineering properties of marine silty sand foundations.

How to cite: Tang, Y. and Cai, S.: Study on methodology and efficiency of microbially induced carbonate precipitation on improvement of marine silty sand, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2980, https://doi.org/10.5194/egusphere-egu24-2980, 2024.

EGU24-6823 | ECS | Orals | SSS4.4

The role of root mucilage and Extracellular Polymeric Substances in shaping soil structure and maintaining plant-soil contact 

Sara Di Bert, Konstantina Papadopoulou, Patrick Duddek, Andrea Carminati, and Pascal Benard

The hydraulic properties of the rhizosphere are essential for understanding root-soil interactions. Diverging from common assumptions in soil modelling, which often equate rhizosphere properties with those of bulk soil, research shows that the rhizosphere is distinct in its physical, biological, and chemical attributes.

There is a broad agreement on the role of mucilage and extracellular polymeric substances (EPS) in modifying soil water dynamics in the rhizosphere. However, the mechanisms of how these substances interact with the soil matrix and impact its hydraulic properties remain unclear. In this study, we assessed the forces exerted by Xanthan gum, used as a stand-in for EPS, maize root mucilage, and water - formed liquid bridges on particle pairs.

Forces were quantified for 1 microL liquid bridge between a pair of glass beads — one standing on a precision balance and the other fixed to a static stand. While the water bridges broke upon drying due to capillary forces, mucilage and Xanthan gum formed resilient filaments that maintain connectivity and tensile forces between the glass beads. The continuous recordings of weight changes by the balance provided crucial data for quantifying the force exerted on the beads during drying.

Our results show that both Xanthan gum and maize mucilage liquid bridges exert tensile strengths that are substantially greater than those of water bridges. The polymer solutions initially behave similarly to water, but the forces exerted on particle pairs deviate as the solutions dry, becoming progressively stronger. The tensile strength of water reaches around 10-1 mN, while maize and Xanthan gum are respectively 1 and 2 order of magnitudes bigger. This increase is caused by the stretching of the polymer network and the development of elastic forces.

The significant aggregating force observed in our study suggests that EPS and mucilage play a crucial role on the mechanics of the root-soil interface. They contribute to soil structure formation in the rhizoshere and to maintain root and soil contact as roots shrink in drying soils.

 

How to cite: Di Bert, S., Papadopoulou, K., Duddek, P., Carminati, A., and Benard, P.: The role of root mucilage and Extracellular Polymeric Substances in shaping soil structure and maintaining plant-soil contact, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6823, https://doi.org/10.5194/egusphere-egu24-6823, 2024.

EGU24-8747 | ECS | Posters on site | SSS4.4

Correlations between microbial activity and soil texture in Hungarian soils 

Orsolya Szécsy, Márk Rékási, Anita Szabó, and Nóra Szűcs-Vásárhelyi

As part of a national survey, 129 soil samples were taken countrywide across Hungary, in order to be representative of both soil types and intensity of cultivation of the country. The bulk samples were taken from 20 points of the diagonals of each sampling parcel, from the 0-30 cm surface layer. Among other soil physical parameters, samples were classified into soil textures based on the Arany yarn number. Microbial measurements were selected so that they could give an overall look at the actual biological soil state.

 

Our goal was to find out, whether we could detect correlations between soil texture, and clay content in particular with the measured microbial parameters regarding such a heterogeneous and large group of natural soil samples.

 

Biological activity of the soil samples were evaluated applying three tests: fluorescein-diacetate (FDA) and sucrose (invertase) enzyme activity tests as well as substrate induced respiration (SIR) measurement. The FDA test is suitable for estimating the soil’s microbial activity. The hydrolysis of FDA is based on the process of several soil enzymes hydrolysing colourless fluorescein-diacetate added to the soil. Released coloured fluorescein can be measured by spectrophotometry. Determination of sucrose (invertase) enzyme activity is founded on quantitative measurement of reducer monosaccharides emerging from the hydrolysis of sucrose. This test provides information on the carbohydrate metabolism processes in the soil. The most important indicator of soil biological activity is the degree of soil respiration that can be measured through the quantitative analysis of the CO2 produced by the decomposition of organic matter. Substrate induced respiration (SIR) method is based on a so-called respiration answer given by the microbial biomass in the presence of an easily utilisable substrate (glucose) being in saturated concentration. Statistical analysis of the data was performed with the programme StatSoft Statistica (Version 12 and 13).

 

The results showed that according to the Kruskal-Wallis tests, correlations could be detected between soil texture and all three microbial parameters. Microbial activity raised in accordance with increasing clay content. It could therefore be verified that although microbiological state and activity of the soil is affected by several environmental factors, FDA and sucrose activity as well as SIR in our samples all depend on the content of clay minerals of the soil, as these can produce favourable conditions for the accumulation of enzymes. This research was funded by TDR project (KEOP-6.3.0/2F/09-2009-0006).

How to cite: Szécsy, O., Rékási, M., Szabó, A., and Szűcs-Vásárhelyi, N.: Correlations between microbial activity and soil texture in Hungarian soils, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8747, https://doi.org/10.5194/egusphere-egu24-8747, 2024.

Freeze-thaw cycling can influence microbial physiological states including microbial dormancy and resuscitation, and enzyme activities. These factors are essential to the mechanisms that control soil carbon and nutrition dynamics mediated by microbes. Warming-induced thawing may also cause changes in microbial functional diversity and stability. However, it remains a significant challenge to integrate these responses within microbial ecological models, which impedes the precision of carbon-nutrient-climate feedback projections. Here, we depict the dynamics of freezing and thawing soil, as well as the microbial and enzymatic functions in response to freeze-thaw processes within the Microbial-ENzyme Decomposition (MEND) model. The simulation was conducted in the Qingzang alpine grassland with field observations and comprehensive parameterization. Our findings suggest that microbial data potentially enhance confidence in model simulations. We also demonstrate that the relative substrate availability affects the trade-off between enzyme synthesis and metabolic flux. The results can deepen our understanding of microbial acclimation to freeze-thaw cycling and how they respond to soil organic carbon decomposition in permafrost ecosystems. 

How to cite: Qi, S. and Wang, G.: Freeze-thaw processes regulate microbial controls on soil organic carbon decomposition in Qingzang alpine grasslands, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9003, https://doi.org/10.5194/egusphere-egu24-9003, 2024.

EGU24-10743 | Orals | SSS4.4

How is microbial metabolic power distributed throughout the soil pore network? 

Naoise Nunan, Maëlle Maestrali, Haotian Wu, Steffen Schwitzer, and Xavier Raynaud

Soil microbial communities live within a complex three dimensional pore network, the properties of which constrains microbial life and activity. The physical structure of soil, and the associated pore network, limit microbial access to resources. It also determines micro-environmental conditions (e.g. redox conditions) that can affect microbial use of the available resources and the rates at which they use energy. Whilst the distributions of different types of activities (CO2 production, enzyme activities) in the pore network have received some attention, the rate at which microbial communities use the energy available to them, i.e. metabolic power, has received little. Energy is required for most aspects of microbial functioning and the rate at which this energy is used determines the extent to microbial functioning proceeds.

Linking the energy available to the rate at which it is processed at the pore scale may help us to better understand how microbial growth and C dynamics are constrained by the physical environment in soil. In order to do so, we collected data from papers in which isotopically-labelled organic substrate was added to pores with different neck diameters and calculated the microbial community catabolic rates, the Gibbs energies of the reactions in oxic and anoxic conditions. This allowed us to estimate the distribution of microbial metabolic power in the pore network and of carbon use efficiency using the approach in LaRowe and Amend (American Journal of Science, Vol. 315, March, 2015,P.167–203, DOI 10.2475/03.2015.01). We then compare the calculations with laboratory measurements of the distribution of carbon use efficiency at the pore scale.

 

How to cite: Nunan, N., Maestrali, M., Wu, H., Schwitzer, S., and Raynaud, X.: How is microbial metabolic power distributed throughout the soil pore network?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10743, https://doi.org/10.5194/egusphere-egu24-10743, 2024.

EGU24-11174 | ECS | Orals | SSS4.4

Linking progressive SOC depletion to degradation of soil structure: Where does it fail first? 

Franziska B. Bucka, Julien Guigue, Christopher Just, Saniv Gupta, Vincent J.M.N.L. Felde, Stephan Peth, and Ingrid Kögel-Knabner

Soil organic carbon (SOC) depletion is often a result of human land use, which is intensified by climate change. As SOC is closely linked to the stabilization of soil structure, the loss of SOC in a soil may induce soil structure breakdown and turnover processes that are not yet well understood.

In order to study soil structure turnover with respect to OC loss, we designed an incubation experiment with soil microcosms that allowed OC loss by leaching and microbial respiration, while avoiding any mechanical disturbance.

We incubated intact soil cores of an arable Luvisol from Loess deposits in southeastern Germany for 300 days at constant water tension and 25 °C to promote microbial activity. During incubation, CO2 release from the microcosms was monitored. A subset of the microcosms was sampled monthly to assess the effect of progressive OC depletion on the stability and architectural features of the soil structure.

The incubation resulted in a reduction of the initial OC (11.2 mg g-1) by approx. 20% and a narrower C:N ratio, corresponding to a reduced OC coverage of the mineral surfaces (1.7 m² g-1 to 0.9 m² g-1, as determined by N2-BET). Despite the OC reduction, the aggregate size distribution (as determined by both wet and dry sieving) did not change significantly, although there was a trend toward a reduction in the mean weight diameter of the aggregates. The mechanical stability of isolated soil aggregates (as determined by dry crushing) even increased slightly with lower OC content in the bulk soil. Microscopic analysis of resin-embedded soil aggregates revealed a lower bulk density in the center, suggesting a progressive carbon depletion from the outside to the inside of the soil aggregates.

These observations highlight that early stage OC depletion along with reduction of OC-covered mineral surface area, without additional mechanical influence, does not immediately lead to the degradation of soil structure. This suggests the existence of OC storage sites that are not susceptible to OC loss by leaching or microbial degradation. In contrast, the sites of initial OC loss may not contribute to the structural stability of a soil.

How to cite: Bucka, F. B., Guigue, J., Just, C., Gupta, S., Felde, V. J. M. N. L., Peth, S., and Kögel-Knabner, I.: Linking progressive SOC depletion to degradation of soil structure: Where does it fail first?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11174, https://doi.org/10.5194/egusphere-egu24-11174, 2024.

EGU24-12707 | Posters on site | SSS4.4

Fire effects on soil structure and hydraulic conductivity 

Markus Berli, Rose M. Shillito, Dani Or, Jeremy J. Giovando, Jay Pak, Nawa Pradhan, René A. Vermeeren, Ian E. Floyd, and Sean McKenna

Fire-induced changes in soil structure and hydraulic conductivity reduce infiltration and increase the likelihood for post-fire flooding and debris flows. Current post-fire hydrology models, however, cannot take fire-induced soil structure changes into account. The goal of this study was to review current understanding of fire-induced changes in soil structure and their post-fire persistence. Specifically, we seek to quantify how fire-induced soil structure changes affect soil hydraulic conductivity.

Changes in soil structure vary widely with the definition of structure. We focused on literature describing fire-induced changes to soil aggregate stability and onset of loss of aggregation followed by formation of surface crust. Generally, aggregate stability tends to increase with increasing soil temperature up to approximately 200°C. Beyond 200˚C, aggregate stability decreases due to changes or loss of soil organic matter (the main binding agent). Evidence suggests that aggregate stability may decrease for soil temperatures as low as 100˚C due to rupture doe to rapid water evaporation within the aggregates. The loss of soil aggregation can promote erosion or formation of surface crust from fine soil particles. Often, fire-induced soil crusts are related to high soil surface temperatures. Literature data show that fire-induced changes in soil structure may persist for a decade after the burn. We developed a conceptual model to describe soil surface structure life cycle in fire-prone ecosystems.

The effects of aggregate deterioration (and recovery) on saturated hydraulic conductivity (Ks) of the soil can be captured by the model of Bonetti et al. (2021). Calculations show that aggregate deterioration leads to a decrease in Ks by a few orders of magnitude (depending on soil texture). Additionally, post-fire soil crusting effects on infiltration were captured by calculating an effective hydraulic conductivity (Rawls et al.,1990) showing a decrease in hydraulic conductivity by one to two orders of magnitude. Moreover, results suggest that fire-induced aggregate deterioration combined with crust formation can reduce the hydraulic conductivity of a soil surface by three to four orders of magnitude. Even without explicit consideration of documented effects of wildfire on soil hydrophobicity, we illustrate the important impact of fire-induced changes in soil structure on infiltration, flooding and debris flow.

How to cite: Berli, M., Shillito, R. M., Or, D., Giovando, J. J., Pak, J., Pradhan, N., Vermeeren, R. A., Floyd, I. E., and McKenna, S.: Fire effects on soil structure and hydraulic conductivity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12707, https://doi.org/10.5194/egusphere-egu24-12707, 2024.

EGU24-14526 | Posters on site | SSS4.4

Effects of Plant Growth-Promoting Rhizobacteria (PGPR) on Saltwater Evaporation: A Case Study Using Bacillus Subtilis 

Yan Jin, Jing Yan, Bridget Knight, and Wenjuan Zheng

Plant growth-promoting rhizobacteria (PGPR) are known for their ability to enhance plant tolerance to abiotic and biotic stresses, including drought and salinity. Additionally, PGPR have been shown to mediate changes in physical properties and hydrological functions of soil. In previous studies, we demonstrated that Bacillus subtilis FB17 (trade name UD1022, a PGPR), could increase soil water retention, preserve continuity of the liquid phase in drying soils, and decrease evaporation. These effects are attributed to production of extracellular polymeric substances (EPS), which are capable of mediating local/micro scale changes in water retention and flow dynamics in soil. We have since extended our study to investigate the potential influence of UD1022 on saltwater evaporation from sand. Specifically, we are comparing evaporation of saltwater, at concentrations 0 (pure water), 10 and 20 ppt, from UD1022-treated sand columns and controls (without treatment). Measurements include temporal changes in cumulative evaporation and evaporation rate, as well as recording surface salt precipitation patterns. Preliminary results from experiments with pure water and 20 ppt saltwater show significant differences in evaporation of pure water between the treated and control columns, however, treatment effects on the evaporation of 20-ppt saltwater were much less pronounced. A preliminary experiment evaluating effects of salt concentration on pellicle formation showed that biofilm formation was suppressed with increasing salinity, presumably, leading to the insignificant effect in reducing evaporation. Nevertheless, images from light and scanning electron microscopes show an earlier onset of salt precipitation on the surface of UD1022-treated sand than control sand, hinting on the potentially very complex interactions between UD1022 and salt precipitation and their effects on evaporation. Additional on-going experiments at lower salt concentrations will allow better mechanistic understanding on how PGPR may mediate changes in salt precipitation and saltwater evaporation in porous media.

How to cite: Jin, Y., Yan, J., Knight, B., and Zheng, W.: Effects of Plant Growth-Promoting Rhizobacteria (PGPR) on Saltwater Evaporation: A Case Study Using Bacillus Subtilis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14526, https://doi.org/10.5194/egusphere-egu24-14526, 2024.

EGU24-15099 | ECS | Orals | SSS4.4

Biological soil crusts regulate evaporation dynamics and energy partitioning over terrestrial surfaces 

Minsu Kim, Milad Aminzadeh, Samuel Bickel, Nima Shokri, and Bettina Weber

Biological soil crusts (hereafter, biocrusts) occurring in drylands modify near-surface soil properties which influences land-atmosphere interactions and exchanges of energy and matter. Yet, the impact of biocrusts on soil evaporation lacks a mechanistic understanding of the biological processes that modify the crusts’ physical properties. We used controlled laboratory experiments, field observations, and mechanistic modelling to determine the impact of biocrusts on evaporation dynamics and subsurface thermal regimes. Our experiments were conducted with bare soil and different types of biocrusts along the ecological succession of the Succulent Karoo desert, South Africa. The preliminary results highlight how different thermal and radiative properties of the crusts affect evaporation rates and heat transfer into the soil layers beneath. Furthermore, active water uptake and storage by biocrust organisms result in water redistribution, which shapes energy balance during diurnal cycles. We conclude from the mechanistic model that biocrusts can accelerate the vertical transport of substrates at the cost of evaporative water loss. Thus, biocrusts may have evolved to modify soil physical properties for balancing nutrient turnover and water usage in global drylands highlighting their crucial roles in regulating mass and energy exchanges over terrestrial surfaces.

How to cite: Kim, M., Aminzadeh, M., Bickel, S., Shokri, N., and Weber, B.: Biological soil crusts regulate evaporation dynamics and energy partitioning over terrestrial surfaces, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15099, https://doi.org/10.5194/egusphere-egu24-15099, 2024.

As an opaque medium, soil conceals processes beneath its surface, posing a challenge for direct observation. To overcome this limitation, scientists employ imaging techniques based on radiation types capable of penetrating the soil, offering insights into its internal structures. While X-ray imaging is the most commonly used method due to its widespread availability, our focus lies on neutron imaging, an alternative and complementary modality.

The distinctive advantage of neutron imaging lies in its heightened sensitivity to light elements, particularly hydrogen, and its greater penetration depth in many metals compared to X-rays. Hydrogen's significance emerges in studying the distribution of water and organic matter within soils. While the spatial and temporal resolution of neutron imaging falls slightly short of laboratory-based X-ray imaging, it operates within the same order of magnitude. Neutron imaging, often flux-limited, has prompted methodological advancements to enable time-series experiments in two and three dimensions on a scale pertinent to soil studies.

Our efforts have concentrated on refining methods for conducting time-sensitive experiments, and we have pioneered the concurrent use of neutron and X-ray imaging. This dual modality approach enhances the reliability of quantitative analysis by leveraging the advantages of images from the two modalities. Quantitative analysis has been a primary focus, leading to the development of correction methods that substantially enhance the accuracy of gravimetric water content quantification based on gray levels in acquired images. The exceptional sensitivity to hydrogen enables the quantification of water content even in unresolved pores, showcasing the primary advantage of neutron imaging. Incorporating advanced denoising techniques further diminishes uncertainties in the results.

Beyond imaging-related innovations, our current endeavors extend to the provision of dedicated sample environments for porous media experiments. This new equipment encompasses balances, pumps, and signal-logging devices integrated into the instrument control system. This integration improves experiment control and facilitates the logging of metadata associated with each image.

In this presentation, we offer a comprehensive overview of applications benefiting from these developments, showcasing the state-of-the-art performance of neutron imaging techniques in porous media research. Our commitment to refining methodologies, advancing quantitative analysis, and providing specialized sample environments underscores our dedication to pushing the boundaries of neutron imaging for a deeper understanding of soil processes.

How to cite: Kaestner, A.: Unveiling Subsurface Secrets: Advances in Neutron Imaging for Soil Research, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15669, https://doi.org/10.5194/egusphere-egu24-15669, 2024.

EGU24-16045 | ECS | Orals | SSS4.4

Effects of mucilage on soil gas diffusion 

Adrian Haupenthal, Patrick Duddek, Mathilde Knott, Andrea Carminati, Hermann Jungkunst, Eva Kroener, and Nicolas Brüggemann

Gas exchange in the soil is determined by the size and connectivity of air-filled pores. Root mucilage can partially reduce air-filled pore connectivity and thus reduce gas diffusivity. However, it remains unclear to what extent mucilage affects soil pore connectivity and tortuosity. The aim of this study was to gain a better understanding of gas diffusion processes in the rhizosphere by explaining the geometric alterations of the soil pore space induced by mucilage.

We quantified the effect of a root mucilage analogue collected from chia seeds without intrinsic respiratory activity on oxygen diffusion at different water contents during wetting-drying cycles in a diffusion chamber experiment. In addition, we used X-ray computed tomography (CT) imaging to visualize the distribution of air and water in the pore space, and quantified the connectivity of the gas phase. Furthermore, we used environmental scanning electron microscopy (ESEM) to visualize mucilage bridges in the dry soil samples.

Quantification of oxygen diffusion showed that mucilage decreased the gas diffusion coefficient in dry soil without affecting air-filled porosity. Without mucilage, a hysteresis in gas diffusion coefficient during a drying-rewetting cycle could be observed for fine sandy soil as well as silt and clay soils. The effect diminished with increasing mucilage content. CT imaging indicated a hysteresis in the connectivity of the gas phase during a drying-rewetting cycle for samples without mucilage. This effect was attenuated with increasing mucilage content. Electron microscopy showed that mucilage forms membrane-like liquid bridges during drying. With increasing mucilage content cylindrical structured are created and at high content interconnected structures are observed throughout the pore space, thereby progressively reducing the connectivity of the gas phase.

Our results suggest that the release of mucilage into the soil may be a plant adaptation strategy to balance soil oxygen availability and water content.

How to cite: Haupenthal, A., Duddek, P., Knott, M., Carminati, A., Jungkunst, H., Kroener, E., and Brüggemann, N.: Effects of mucilage on soil gas diffusion, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16045, https://doi.org/10.5194/egusphere-egu24-16045, 2024.

EGU24-16463 | ECS | Orals | SSS4.4

Soil bioturbation – how habitat climatic constraints shape biophysical processes 

Siul Ruiz, Paul Hallett, and Dani Or

Soil bioturbation is the physical movement and alteration of soil by fauna and plants. It plays a central role in soil formation at long time scales and shapes soil structure at hydrologic time scales that affects many soil physical processes and ecosystem services. Varying biomes act as hosts to a variety of ‘ecosystem engineers’ that have developed unique strategies for generating habitats and appreciable soil biopores. For example, earthworms and plant roots generate biopores in moist soil via penetration-expansion (and some ingestion) processes. Other organisms such as ants or termites excavate soil by displacing soil particles with their limbs. We present an overview of biophysical processes associated with soil bioturbation driven by various biological agents and biomechanical  strategies (e.g. penetrators vs excavators). The study highlights the critical role of soil moisture and texture in modulating and shaping the various biomechanical strategies and activity time windows. We explore the implications that regional environmental factors play in locally favoring particular bioturbation processes, which can be used to identify the likelihood of a specific bioturbation agents occurrence in a given region. The overview highlights the relative impact of soil bioturbation on soil structure formation by comparison with conventional tillage processes (restricted to arable lands). Ultimately, this work endeavors to open discussions that can aid in reducing intensive mechanized tillage and help guide sustainable land use initiatives by capitalizing on the biological agents present in the environment.   

How to cite: Ruiz, S., Hallett, P., and Or, D.: Soil bioturbation – how habitat climatic constraints shape biophysical processes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16463, https://doi.org/10.5194/egusphere-egu24-16463, 2024.

EGU24-17397 | ECS | Posters on site | SSS4.4

Root hairs facilitate root water uptake across soil textures – a numerical study 

Patrick Duddek, Mutez Ali Ahmed, Mathieu Javaux, Jan Vanderborght, Goran Lovric, Andrew King, and Andrea Carminati

By substantially increasing the surface area of roots available for soil resource capture, root hairs have been hypothesised to facilitate root water uptake, particularly in dry soil conditions. However, existing experimental and computational studies have shown that the effect of root hairs on water uptake cannot be generalised across soils and plant species.

The objective of our study is to investigate to what extent and under which soil conditions root hairs facilitate root water uptake. Ultimately we aim to gain a mechanistic understanding of the effect of root hairs on root water uptake across soil textures.

We scanned maize (Zea Mays L.) roots grown in two soil types (loamy and sandy soil) using synchrotron-based X-ray CT. We utilized an image‐based modelling approach to simulate water flow through the soil-root continuum by solving the flow equations numerically. This approach allowed us to incorporate rhizosphere properties (e.g. root-soil contact) and root hair shrinkage into the image-based model.

Experimental and numerical results show that under dry soil conditions (-1 to -0.1 MPa) root hairs attenuate the gradient in soil matric potential across the rhizosphere. This results in a more effective water extraction compared to a hairless root. Our model revealed that the effect of hairs is determined by soil properties (e.g. soil porosity), root hair traits (e.g. length and density) and the capacity of hairs to remain turgid under drought stress. Compared to densely packed fine textured soils, the effect of hairs is more pronounced in coarse textured soils and loosely packed fine textured soil. This is explained by the steeper hydraulic conductivity curves of these soils.

In conclusion, our results show that the effect of root hairs is determined by root-soil contact, which depends on soil properties, and root hair shrinkage.

How to cite: Duddek, P., Ahmed, M. A., Javaux, M., Vanderborght, J., Lovric, G., King, A., and Carminati, A.: Root hairs facilitate root water uptake across soil textures – a numerical study, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17397, https://doi.org/10.5194/egusphere-egu24-17397, 2024.

EGU24-17648 | ECS | Posters on site | SSS4.4

Exploring the interplay of shoot to root hydraulic conductance in varying soil water contents 

Samantha Spinoso Sosa, Benjamin Hafner, Ruth Adamczewski, and Mohsen Zare

Understanding how plants regulate their hydraulic systems in response to varying soil conditions is crucial for comprehending water fluxes in the soil-plant-atmosphere continuum. This study examines hydraulic conductance in maize plants grown in loamy soil under different soil water contents. We hypothesize that plants actively adjust both aboveground and belowground hydraulic conductance in response to soil texture and moisture to balance their water loss with water uptake.

Maize plants were grown in loamy soil with varying moisture levels, simulating optimal and water-stressed conditions. Pre-germinated seeds were planted in PVC pots (10 cm diameter, 24 cm height). At different growth stages (2, 3, 4 and 6 weeks), shoots were delicately separated from the roots. We assessed both total aboveground (Kab) and belowground hydraulic conductance (Kbe). The Kbe was determined by subjecting soil and roots to incremental pressure increases in a pressure pot, collecting the sap to derive water flow at a given pressure. To calculate the total aboveground hydraulic conductance (Kab,tot), effective internal aboveground xylem hydraulic conductance (Kab,xyl), and stomatal conductance (Kab,sto), we measured transpiration, leaf water potential, temperature, and vapor pressure.

In optimal conditions (OC), our initial findings show a linear increase during the initial growth stage in both above- and belowground conductance, followed by deceleration at the late developmental stage. Significantly,  Kbe surpassed  Kab,tot by over two orders of magnitude. It's worth noting that although Kab,xyl displayed a higher magnitude in our measurements, exceeding Kbe , the Kab,sto took precedence as the primary controlling factor when considering the overall soil-plant hydraulics. Under water-stressed conditions, plants exhibited an overall increase in hydraulic conductance with growth, where Kbe once again surpassed Kab,tot by over two orders of magnitude. However,  Kab,tot values were approximately half of those obtained in OC. Notably,  Kab,xyl decreased with plant age but remained greater than  Kbe. These results provide valuable insights into the intricate interplay between root and shoot hydraulic conductance. This research contributes to our understanding of how plants dynamically regulate their hydraulic systems under varying soil conditions, contributing to the broader knowledge of the soil-plant-atmosphere continuum.

How to cite: Spinoso Sosa, S., Hafner, B., Adamczewski, R., and Zare, M.: Exploring the interplay of shoot to root hydraulic conductance in varying soil water contents, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17648, https://doi.org/10.5194/egusphere-egu24-17648, 2024.

EGU24-20510 | Posters on site | SSS4.4

Influence of cropping and fertilization on soil macropore characteristics in a long-term field study 

John Koestel, Jumpei Fukumasu, and David Nimblad-Svensson

It is known that soil organic carbon (SOC) is positively correlated with soil aggregation and total porosity. Similarly simple relationships between SOC content and abundance of pores in specific diameter ranges seem however elusive. In this study, we used X-ray tomography to investigate if this may be explained by treatment-specific differences in biopore forming agents, in other words soil faunal communities and root growth. We therefore compared the pore and biopore network characteristics in the topsoil of an ongoing long-term field experiment in Ultuna, Sweden, which was started in 1956. We selected three contrasting treatments that had led to significantly different SOC contents, ranging from 0.9 to 2.1% in weight, namely: a bare fallow and two cropped plots with two different fertilization treatments, mineral N-fertilizing with Ca(NO3)2 and farm yard manure (FYM). Sixteen undisturbed soil cores were sampled in eight small (ø 22.5 mm; height 65.5 mm) and eight large (ø 65.5 mm; height 74.8 mm) columns from each treatment, respectively (48 samples in total). The results of our study are in line with empirical knowledge that soil treatments associated with increased carbon contents exhibit larger porosities. However, we observed that the abundance and size distribution of biopores at different scales exhibited treatment-specific differences that cannot be explained with SOC content differences alone. Instead, they must have been caused by distinct root morphologies (or complete absence of roots) and/or by differences in soil faunal communities. Our study demonstrates that simple relationships between soil organic matter content and soil macropore network properties must not be taken for granted.

How to cite: Koestel, J., Fukumasu, J., and Nimblad-Svensson, D.: Influence of cropping and fertilization on soil macropore characteristics in a long-term field study, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20510, https://doi.org/10.5194/egusphere-egu24-20510, 2024.

EGU24-21045 | ECS | Posters on site | SSS4.4

Meta-analysis of soil pore size distribution and its relationship with various soil properties and land management 

Haotian Wu, Maelle Maestrali, Maik Lucas, Xavier Raynaud, Naoise Nunan, and Steffen Schweizer

The size distribution of soil pores is an important key characteristic of soil systems influencing soil functions such as the cycling of water as well as organic matter storage and dynamics. There is a lack of information about the pore size distribution considering a wide variety of soils and whether various soil characteristics pre-dominantly influence specific pore size ranges. Especially, pores with a diameter < 100 µm serve as a key driver of soil water holding capacity and as a habitat for soil microorganisms involved in the decomposition of organic matter. Here, we aim to contribute to the identification of size patterns in the soil pore size distribution and its relationships with soil biogeochemical matter cycles. In our contribution, we will present insights into our literature-based meta-analysis approach enabling relative comparisons by the integration of pore size distributions across different soils using a water retention curve model. To disentangle the effects of soil texture, soil type, organic matter content, and land management on soil pore size distribution, we used multivariate regression, path analysis, and random forest feature importance. By building a quantitative framework of interrelated controls on soil pore size distribution, we aim to discuss the current understanding of the soil pore network and its ecological functions.

How to cite: Wu, H., Maestrali, M., Lucas, M., Raynaud, X., Nunan, N., and Schweizer, S.: Meta-analysis of soil pore size distribution and its relationship with various soil properties and land management, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21045, https://doi.org/10.5194/egusphere-egu24-21045, 2024.

EGU24-21211 | Orals | SSS4.4

Characterization of soil aggregates in green bioswales in relation to carbon sequestration, aggregate stability, and microbial activity 

Maha Deeb, Peter M. Groffman, Matthew Amato, Zhongqi Cheng, and Daniel Giménez

Green Infrastructure (GI) plays a crucial role in reducing stormwater runoff and providing ecological benefits in urban areas. Aggregation is a key process in many soil functions as it influences carbon storage, greenhouse gas emissions, nutrient cycling, hydraulic properties, and biotic activity. In this study, we investigated soil aggregation processes and stability in GI.

Soil samples were collected from six bioswale sites in New York City that had two different designs - streetside infiltration swales and enhanced tree pits. The soil samples were taken from the inlet, center, and outlet positions (relative to stormwater input) of each site. These samples were then tested for 1) macro and micro aggregate sizes; 2) distribution of soil organic carbon (SOC) and nitrogen; 3) aggregate stability; and 4) microbial biomass and activity relevant to carbon and nitrogen cycles in macroaggregates.

Our results showed that 60% g/g of the soil aggregates at these GI sites were smaller than 2 mm and had high structural stability. Microaggregates between 1-2 mm had the highest SOC and accounted for 60% g/g of all microaggregate size classes. GI aggregates are formed from the breakdown of macroaggregates into intermediate microaggregates. The newly formed microaggregates contained more stable SOC than macroaggregates and bonds within microaggregates were stronger than bonds grouping microaggregates, which is not consistent with a classical model of aggregate formation in natural soils. Microbial biomass and activity were correlated with the carbon and nitrogen content of aggregates and with GI type, allowing for the identification of microbial hot spots. These results suggest that aggregation processes in human-engineered soils included in GI play an important role in sustaining carbon and nitrogen cycles.

How to cite: Deeb, M., Groffman, P. M., Amato, M., Cheng, Z., and Giménez, D.: Characterization of soil aggregates in green bioswales in relation to carbon sequestration, aggregate stability, and microbial activity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21211, https://doi.org/10.5194/egusphere-egu24-21211, 2024.

EGU24-1653 | Orals | SSS4.5

Short-term impact of irrigation on soil microbiome in a Mediterranean maize cropping system 

Carla S. S. Ferreira, Pedro R. Soares, André Pereira, Pedro Mendes-Moreira, and Lyudmyla Symochko

Soil is a complex environment, where microorganisms play a crucial role in the maintenance of soil structure, nutrient cycling and thus soil quality, relevant for croplands productivity. Soil microbial activity, however, is largely determined by water availability, and both are affected by agricultural management. This study aims to investigate the impact of irrigation, i.e. different amount of water and application scheduling, on soil microbial biomass and functional structure of soil microbiome (number of microorganisms in various ecological-trophic groups) in a Mediterranean maize farm. In 2023, six irrigation treatments were applied in a maize farm located in the Mondego Agricultural Valey, centre region of mainland Portugal. The irrigation treatments included three different amounts of water per week applied with drip irrigation: i) 100 mm, the average optimal amount over the last 30 years, based on APSIM crop model), ii) 55 mm, selected to simulate water scarcity conditions, and iii) the amount recommended by the local farmers’ association, based on weekly weather forecast and water balance modelling (ranged between 24 mm and 66 mm over the study period). The water was applied once or split in two applications during the week in different treatments. Each treatment was applied in triplicated plots, each plot covering five maize rows and extending over 10 m length. Nine composite soil samples (0-15 cm depth) per treatment were collected immediately before and after the irrigation period (~ 6 to 17 weeks after sowing). The soil samples were analyzed in sterile conditions using solid growth media: Nutrient Agar, Agar-Agar, Jensens Medium, Soil Agar, and Czapek-Dox Medium. The serial dilutions of the samples were provided until the suspension contained a microorganism titer within the range of 10−3–10−5 CFU/mL. The content of general microbial biomass (Сmic) in the soil was determined using the rehydration method. The results show that after the irrigation period, Cmic increased between 14% to 48%. The number of different nitrogen fixing bacteria and ammonifiers (nitrogen-mineralizing bacteria) increased, whereas the number of micromycetes, spore forming bacteria, oligotrophic, and pedotrophic bacteria groups decreased in all the treatments, which are good indicators about soil quality. Generally, these changes are slightly higher in the treatments where irrigation was applied twice instead of once a week (e.g. 28-31% vs 20-34% increase in nitrogen fixing bacteria, and 33-50% vs 12-36% decrease in oligotrophic bacteria - often associated to nutrient-poor soils). This highlights the relevance of providing a more uniform soil moisture content over the crop season (through smaller amounts of water, applied more often) to support soil microbial communities. Microbial biomass was lowest in plots receiving the less water (55 mm per week), but it was similar between plots receiving 100 mm of water per week and adjusting the amount of water to the recommendations of local farmers’ association. Long term average data would be useful to support decision on the amount of water to apply in areas where technical recommendations are not available. Adequate irrigation management in croplands can support soil biodiversity.

How to cite: Ferreira, C. S. S., Soares, P. R., Pereira, A., Mendes-Moreira, P., and Symochko, L.: Short-term impact of irrigation on soil microbiome in a Mediterranean maize cropping system, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1653, https://doi.org/10.5194/egusphere-egu24-1653, 2024.

EGU24-3298 | ECS | Posters on site | SSS4.5

Metagenomic insights into microbial structure and metabolism in alpine permafrost on the Tibetan Plateau 

Luyao Kang, Yutong Song, Rachel Mackelprang, Linwei Wu, and Yuanhe Yang

Permafrost, characterized by its frozen soil, serves as a unique and ecologically significant habitat for diverse microorganisms. Understanding the intricacies of their community structure and functional attributes is crucial for predicting the response of permafrost ecosystems to climate change. However, large-scale evidence regarding microbial profiles and their differences across soil strata remains limited. Here we analyze microbial structure and metabolic potential in permafrost deposits based on 16S rRNA and metagenomic data obtained from a ∼1,000 km permafrost transect on the Tibetan Plateau. We find that microbial communities exhibit apparent discrepancy in structure among soil depth, with a decline in alpha diversity and an increase in spatial variation along soil profile. Microbial assemblages are primarily governed by dispersal limitation and drift, with dispersal limitation being more pronounced in permafrost layer. We also observe that functional genes related to reduction reactions, including nitrate reduction, denitrification, polysulfide reduction, sulfide reduction, tetrathionate reduction, Fe reduction, and methanogenesis, are enriched in the permafrost layer. Taxa involving in redox reactions are more diverse in the permafrost layer and contribute highly to community-level metabolic profiles, reflecting higher redox potential and more complicated trophic strategies for microorganisms in permafrost deposits. These findings provide new insights into the large-scale stratigraphic profiles of microbial community structure and biogeochemical processes and laying the groundwork for future endeavors that elucidate microbial responses to environmental change in permafrost regions.

How to cite: Kang, L., Song, Y., Mackelprang, R., Wu, L., and Yang, Y.: Metagenomic insights into microbial structure and metabolism in alpine permafrost on the Tibetan Plateau, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3298, https://doi.org/10.5194/egusphere-egu24-3298, 2024.

The transition from dry-to-wet soils is often characterized by an acceleration of the nitrogen (N) cycle, representing a period of interest to biogeochemists studying future N cycling responses to global changes. In particular, wetting dry soils can produce large emission pulses of nitric oxide (NO; an air pollutant at high concentrations) and nitrous oxide (N2O; a powerful greenhouse gas), but the mechanisms governing the N losses remain unresolved. The asynchronous timing of when N becomes bioavailable and when ecosystem N sinks activate (e.g., plant N uptake) post wetting has often been used to explain why N is lost when dry soils wet up. However, other factors directly affecting nitrifying communities may also contribute to the emissions. For instance, ammonia oxidizing bacteria (AOB) may be favored over ammonia oxidizing archaea (AOA) in NH4+-rich environments that are typically observed in dry soils. Because AOB may process N less efficiently than AOA, shifts in nitrifier activity may help promote gaseous N losses.

 

To better understand mechanisms for gaseous N loss, we studied drylands in southern California that can experience >6 months without rain, as well as other drylands where we added or excluded precipitation during the dry summer or wet winter seasons. We also selectively inhibited AOA and AOB communities to measure their contributions to soil N emissions. Excluding precipitation during the winter prior to collecting soils did not affect NO emissions, but either adding or excluding precipitation during the summer did; NO emissions after adding extra rainfall (95 ± 6 µg NO g soil-1; p = 0.01) or excluding rainfall (105 ± 22 µg NO g soil-1; p = 0.006) were significantly higher than the control (41 ± 6 µg NO g soil-1), with over 50% of the emissions controlled by AOB. While most of the effects of manipulating precipitation were observed on NO emissions, N2O increased only when we excluded precipitation in the winter wet season, averaging 0.58 ± 0.40 µg N-N2O g soil-1. Using isotopologues of N2O coupled with chloroform fumigations to slow microbial activity, we found that N retention and loss trade off as dry conditions intensify. Altogether, our measurements suggest that that shifts in precipitation patterns can favor AOB-derived NO emissions when dry soils are wetted at the end of the dry season, suggesting that shifts in nitrifier activity from the legacies of past precipitation can also help explain why N is lost when dry soils are wetted.

How to cite: Homyak, P.: Soil nitrogen cycling in dry lands: Precipitation legacy effects on microbial N loss pathways, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4788, https://doi.org/10.5194/egusphere-egu24-4788, 2024.

EGU24-5211 | ECS | Posters on site | SSS4.5

Temperature regulates microbial carbon use efficiency effects on soil organic carbon storage 

Zhaoyang Luo, Jianning Ren, and Simone Fatichi

Microbial carbon use efficiency (CUE), describing the partitioning of microbe assimilated carbon into microbial growth and respiration, is commonly used in soil carbon models to link microbial activities with the consumption of soil organic carbon (SOC). However, the role of CUE in regulating SOC storage remains debated. Previous studies have reported that a higher CUE could not only favour SOC formation through microbial necromass accumulation, but also trigger SOC losses because an enhancement in enzyme production facilitates SOC decomposition. The former leads to a positive relationship between CUE and SOC, while the latter leads to a negative one. Temperature dependencies introduce additional uncertainties while exploring the SOC-CUE relationship since temperature affects both SOC decomposition and CUE. Based on the meta-analysis and numerical simulations with a mechanistic model (T&C), we examined the relationship between CUE, SOC storage and temperature. Numerical results recover the expected SOC storage decrease with increasing temperature when temperature effects are isolated; however, an increase of SOC storage with decreasing CUE is found once temperature effects are discounted, indicating that SOC storage increase with increasing CUE is likely a by-product of temperature dependencies. In addition, we show that CUE variability plays a more important role in affecting SOC storage at lower temperature. Our study helps refine the understanding of SOC responses in a warming climate.

How to cite: Luo, Z., Ren, J., and Fatichi, S.: Temperature regulates microbial carbon use efficiency effects on soil organic carbon storage, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5211, https://doi.org/10.5194/egusphere-egu24-5211, 2024.

EGU24-5313 | ECS | Orals | SSS4.5

Context-dependent benefits of ectomycorrhiza on Aleppo pine seedling performance under ecologically relevant settings  

Stav Livne- Luzon, Lior Herol, Tamir Klein, and Hagai Shemesh

Droughts significantly impact forests, with long-term forest existence largely depending on seedling recruitment. However, seedling establishment under natural conditions is often limited by numerous interacting factors such as water availability, competition with herbaceous vegetation, and interaction with ectomycorrhizal fungi (EMF). We performed two greenhouse experiments to examine these factors and their interacting effects on the establishment of Aleppo pine seedlings. In both experiments, Geopora, a genus known to colonize seedlings in dry habitats, predominantly colonized the seedlings' roots, regardless of the EMF inoculum's origin. EMF inoculation enhanced seedling height, biomass, and branch number. However, under combined drought and competition, EMF had no growth impact. When facing competition or consistent water scarcity, EMF's positive effects decreased. Interestingly, during intermittent drought periods (resource pulses), EMF benefits persisted even in severe drought. This discrepancy in pine performance across treatments highlights the complexity of benefits provided to seedlings by EMF under ecologically relevant settings.

 

How to cite: Livne- Luzon, S., Herol, L., Klein, T., and Shemesh, H.: Context-dependent benefits of ectomycorrhiza on Aleppo pine seedling performance under ecologically relevant settings , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5313, https://doi.org/10.5194/egusphere-egu24-5313, 2024.

EGU24-6731 | Orals | SSS4.5 | Highlight

Comprehensive geospatial assessment of the soil microbiome’s response to temperature and moisture in interior Alaska, USA 

Robyn Barbato, Stacey Doherty, Theodore Letcher, Dragos Vas, and Julie Parno

As global temperatures rise, soil fractions of organic matter are being subjected to microbial degradation, particularly in high latitude regions.  Concurrently, permafrost perched below active layer soils is thawing at unprecedented rates, significantly altering landscapes and ecosystem trajectories by changing subsurface conditions and vegetation characteristics. Our aim was to investigate an Alaskan soil microbiome’s response to changes in temperature and water potential because they are well established factors that influence microbial activity and could be predicted using remote sensing data and weather forecasts.  The extent of microbial change in the seasonally thawed active layer remains poorly understood.  To address this, we studied the physical and microbiological properties of two permafrost-affected surface soils in interior Alaska primarily composed of deciduous forests, coniferous forests, and woody wetlands.  We collected soils for laboratory incubation studies where we measured respiration and microbial taxonomy from replicate microcosms experiencing four temperatures and five matric potentials.  Soil respiration rates from the soils varied according to temperature and moisture, with soils exposed to warmer, wetter conditions exhibiting the highest respiration rates (e.g. 0.23 or 0.70 µg C-CO2 g-1 dry soil h-1) and soils exposed to colder, drier conditions exhibiting lower respiration rates (e.g. 0.03 or 0.1 µg C-CO2 g-1 dry soil h-1).   In the field, we measured soil temperature, moisture, and respiration at the sites where the soils were initially collected.  Surface soil temperatures measured at the sites ranged from -25°C in the winter months to +25°C in the summer months.  These values were compared to geospatial estimates of temperature and soil moisture that were used to calculate soil respiration rates.  The estimated respiration values will be compared to field measurements to determine the efficacy of the model.  Additionally, respiration estimates will be calculated under a future climate scenario.  These findings have important implications for developing accurate forecasts of microbial community assemblages during thaw in that location should be considered as a strong influencing factor. 

How to cite: Barbato, R., Doherty, S., Letcher, T., Vas, D., and Parno, J.: Comprehensive geospatial assessment of the soil microbiome’s response to temperature and moisture in interior Alaska, USA, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6731, https://doi.org/10.5194/egusphere-egu24-6731, 2024.

Increasing industrial activity has led to a growing risk of cadmium (Cd) accumulations and biomagnifications in plants and humans. Arbuscular mycorrhizal fungi (AMF) have been extensively studied as a soil amendment technique due to their capability to reduce the accumulation of Cd in plant tissues. However, a quantitative and data-based consensus has yet to be reached on the effect of AMF on host plant growth, Cd uptake, and tolerance. Here, a meta-analysis was conducted to quantitatively evaluate the impact of AMF using 2079 individual observations from 157 articles. The research showed that adding AMF to the plants stopped the accumulation of Cd in the shoots and roots and increased biomass, phosphorus (P), and catalase (CAT) in the leaves compared to the control. Yet these effects varied with different mycorrhizal colonization rates, AMF species, plant families and functional types, and soil Cd contents. Mycorrhizal colonization rates positively correlate with changes in biomass and P content in shoots and roots, and CAT and proline in leaves, while showing no significant correlation with Cd concentration in plant tissues. Plants inoculated with Funneliformis caledonium exhibited greater biomass accumulation, while those inoculated with Rhizophagus irregularis showed higher P uptake. Mycorrhizal Legumes demonstrated the most significant reduction in Cd concentration among the plant families, whereas Compositae exhibited the highest increase in biomass, P content, and CAT. In addition, soils with intermediate and high Cd levels were more favorable for AMF to promote plant biomass accumulation. This study shows that AMF can help plants become more resistant to environments with excessive Cd. It also talks about how to manage and use them as bio-inoculants for farming and environmental restoration.

 

 

Acknowledgments

This research received funding from the National Key Research and Development Program of China (No. 2022YFC3701303) and the National Natural Science Foundation of China (Grant Nos. U2344228).

 

How to cite: Tan, Q., Wei, R., Hu, H., and Guo, Q.: Role of arbuscular mycorrhizal fungi behind the plant ameliorated tolerance against cadmium stress: A global meta-analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6946, https://doi.org/10.5194/egusphere-egu24-6946, 2024.

Drought resulting from extended periods of limited precipitation have a substantial impact on soil pH, microbial biomass, and soil derived nutrients for plant growth. A long-term integrated crop, beef, and soil health research project at the Dickinson Research Extension Center is designed around a no-till diverse multi-crop rotation (spring wheat, cover crop, corn, pea-barley, sunflower). In this crop and animal production system, beef cattle graze the pea-barley, corn, and 13-specie cover crop to document microbial, fungal, and nutrient change over time and space. Precipitation during the first five-year crop rotation was normal to slightly above normal. However, the second five-year rotation was drier than normal resulting in nutrient concentration, reduced microbial biomass, and pH decline. Potential nitrogen mineralization of soil organic matter (SOM) in the crop rotation suggests that 8.4 mg N/kg of soil are mineralized for each 1.0% increase in SOM. The mean SOM content of soils in the study is 3.97%. For rain-fed crops, periods of reduced precipitation inhibit soil nutrient solubilization and translocation that negatively impacts a complex system of soil microbial respiration, fungal activity, plant nutrient supply, crop yield, and animal grazing days. The extent of soil drying in 2017 compared to moist soil in 2019 and somewhat drier soil in the 2020 cropping season will be presented. With drying, soil pH declined as soluble salt became more concentrated resulting in a more acidic condition. Naturally, reduced precipitation contributes to minimized plant and root growth, which contributed to reduced SOM content and nitrogen mineralization. For most of the crops in the diverse crop rotation, the percent of microbial active carbon, organic C : N ratio, and organic N : inorganic N ratio declined. Ward Lab Haney Test results for 24-hour microbial respiration provide measurements of microbial community and organismal diversity. Mean microbial biomass under drought conditions (2017), in the crop rotation, was 1,637 ng/g of soil. With the return to normal precipitation (2019) soil microbial biomass was 4,804 ng/g of soil; a 193.5% increase. While total microbial biomass increased with return to normal precipitation in 2019, arbuscular mycorrhizal fungi (AMF) did not reestablish in sunflower, cover crop, corn, and spring wheat-control, and only slight levels of AMF were measured in the pea-barley and spring wheat-rotation crops. Declining soil pH effects mineral nutrient availability among copper, manganese, zinc, and aluminum. At pH levels less than 5 (strongly acidic), aluminum availability becomes toxic to plants. Drought effected soil pH in this integrated systems research declined 9.5% to a mean crop pH value of 5.95, which at this pH level aluminum is sufficiently hydrated to be non-toxic. Return to normal precipitation (2019) increased the crop rotation pH mean to 6.58.

How to cite: Landblom, D., Senturklu, S., and Cihacek, L.: Effect of Drought and Subsequent Precipitation (2016-2020) on Soil pH, Microbial Biomass, and Plant Nutrient Change in the Semi-Arid Region of Western North Dakota, USA, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7094, https://doi.org/10.5194/egusphere-egu24-7094, 2024.

A large amount of research has demonstrated that global warming leads to changes in the structure and function of soil microbial communities. Despite the large number of studies which have identified soil microbes as key drivers of biogeochemical processes, little is known about the trade-offs between soil microbial activities under environmental change and how this will affect soil biogeochemistry.

To this end, we currently develop high throughput methodology to measure growth, respiration, extracellular polymeric substance (EPS), extracellular enzyme activity (EEA) and carbon use efficiency (CUE) in pure cultures of a wide range of bacterial isolates. In response to resource quality (concentration, lability, stoichiometry), temperature and oxygen stress, we will assess trade-offs between key microbial catabolic and anabolic processes. The methodology will finally be applied to soils collected from the Achenkirch forest warming experiment in Austria to examine how complex communities and isolates from long-term warming and control soils express trait trade-offs. Isolates will be selected and checked to cover the most actively growing microbes in control and warmed soils using the qSIP method. The purpose of this study is to gain a deeper understanding of the anabolic and catabolic transitions of soil microbes under the influence of warming and, consequently, to predict the potential biogeochemical impacts of long-term warming on forest soils.

How to cite: Li, Y., Li, T., A. Eichorst, S., A. Anthony, M., and Wanek, W.: Trade-offs between growth, carbon use efficiency, and the production of extracellular polymeric substance and soil enzymes of soil microbes under long-term warming with different resource complexities, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7945, https://doi.org/10.5194/egusphere-egu24-7945, 2024.

EGU24-8012 | ECS | Posters on site | SSS4.5

Continental-scale β diversity of bacteria and fungi vary differentially with soil pH in forests 

Changjiang Huang and Xuhui Zhou

Abstract:  The soil microbiota is crucial for regulating biogeochemical cycles, including soil carbon (C) dynamics and nutrient cycling. However, how climate, plants, and soil properties influence the microbiome in forests at a continental scale remains unclear, hampering us from better understanding forest C-climate change feedback. Here, we investigated the spatial patterns of microbial diversity across China’s forests and explored the factors controlling microbial β diversity and network complexity. Our results showed that bacterial and fungal β diversity were strongly influenced by soil pH and climate. To further investigate the environmental preference of the microbial networks, we classified the zero-radius operational taxonomic units (zOTUs) into five groups ranging from acidic to alkaline soils. Co-occurrence network analysis revealed that the topological structure of the bacterial network (e.g., edge and degree) increased with pH and had a negative relationship with β diversity but not with fungal diversity. Soil fungi exhibit greater β diversity with network complexity (i.e., degree and betweenness) than bacteria at pH < 5.1 and vice versa in neutral and alkaline soils (pH > 5.5). Within the pH range of 5.1-5.5, the bacteria-fungi network exhibited the most increased network complexity but the lowest fungal β diversity, with significant positive correlations found between fungal β diversity and soil properties. Furthermore, 46 bacterial core species were identified and shown to be significantly correlated with soil pH. These findings highlight the critical role of soil pH in driving soil microbial β diversity across China’s forests and reveal the effects of pH thresholds on changes in the soil microbial network and core species.

Keywords: Bacterial diversity, fungal diversity, network analysis, forest 

How to cite: Huang, C. and Zhou, X.: Continental-scale β diversity of bacteria and fungi vary differentially with soil pH in forests, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8012, https://doi.org/10.5194/egusphere-egu24-8012, 2024.

EGU24-15868 | ECS | Orals | SSS4.5 | Highlight

Drought intensity shapes legacy effects on grassland plant and soil microbial communities and their response to a subsequent drought 

Natalie J. Oram, Nadine Praeg, Richard D. Bardgett, Fiona Brennan, Tancredi Caruso, Paul Illmer, Johannes Ingrisch, and Michael Bahn

Drought has long-lasting legacy effects on grassland ecosystem functioning, which can manifest as shifts in soil microbial community structure and function and plant productivity that persist long after a drought passes. Increasing drought intensity causes abrupt shifts in plant productivity, plant-soil carbon and nitrogen dynamics, and soil microbial communities. However, very little is known about the role that drought intensity plays in the formation of drought legacies, and in plant and microbial responses to a subsequent drought. In a two-year experiment, we studied soil legacies associated with drought intensity in two model grassland plant communities with contrasting resource acquisition strategies (i.e., a fast- and a slow-strategy community). In the first year of the experiment, communities experienced a gradient of increasing drought intensity from well-watered to severely drought-stressed. In the second year, we determined soil microbial community composition and function, and plant community above-ground biomass in response to a subsequent drought. We found that the drought in the first year affected soil prokaryote and fungal community composition, microbial network structure, and soil function in the following growing season, and these effects were dependent on the past drought’s intensity. Soil drought legacy effects significantly altered plant community resilience to the subsequent drought: increasing intensity of the initial drought reduced plant community productivity resistance in slow-strategy plant communities, and decreased productivity overshoot seven weeks after re-wetting in fast-strategy plant communities. Our study shows that drought intensity causes distinct legacies in soil microbial community composition and function and alters the resilience of plant productivity to subsequent drought.

How to cite: Oram, N. J., Praeg, N., Bardgett, R. D., Brennan, F., Caruso, T., Illmer, P., Ingrisch, J., and Bahn, M.: Drought intensity shapes legacy effects on grassland plant and soil microbial communities and their response to a subsequent drought, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15868, https://doi.org/10.5194/egusphere-egu24-15868, 2024.

EGU24-16307 | Orals | SSS4.5 | Highlight

Land use intensity has a stronger effect on the temperature sensitivity of soil microbial carbon cycling processes than long-term climate change. 

Luiz Domeignoz-Horta, Matthew McLaughlin, Marcelo Soares Fontes, David Sebag, Marie-Liesse Aubertin, Eric Verrecchia, Ansgar Kahmen, Daniel Nelson, Anna-Liisa Laine, Pascal Niklaus, Klaus Butterbach-Bahl, and Ralf Kiese

Microbes are responsible for the cycling of carbon (C) in soils, and predicted changes in soil C stocks under climate change are highly sensitive to shifts in the mechanisms thought to control microbial physiological response to warming. Two mechanisms have been proposed to explain the long-term effects of warming on microbial physiology: microbial thermal acclimation and changes in the quantity and quality of substrates available for microbial metabolism. However, studies disentangling these two mechanisms and assessing how land use affects them are lacking. To disentangle the drivers of changes in microbial physiology in response to long-term climate change, we sampled soils from a 10-year old global change and land use intensity experiment at the Pre-Alpine Terrestrial Environmental Observatories (TERENO project). The global change treatment includes a warming of 2oC and a reduction in precipitation of about 450 mm. We took soil samples at different time-points during the spring season and depths. We performed short-term laboratory incubations over a range of temperatures to measure the relationships between temperature sensitivity of physiology (growth, respiration, carbon use efficiency with the 18O-H2O method) and we characterized the quantity and quality of soil organic matter with the ramped thermal rock-eval pyrolysis at different depths. In this ongoing project, we did not observe thermal acclimation of microbial respiration, growth or CUE to climate change. However, fertilization had the strongest effect on the temperature sensitivity of microbial respiration. In the next steps of this project, we will determine whether climate change and/or land use intensity has an effect on soil organic carbon fractions with different residence times. Our preliminary results show that land use intensity has an overriding effect on the temperature sensitivity of microbial processes compared to long-term climate change.

How to cite: Domeignoz-Horta, L., McLaughlin, M., Soares Fontes, M., Sebag, D., Aubertin, M.-L., Verrecchia, E., Kahmen, A., Nelson, D., Laine, A.-L., Niklaus, P., Butterbach-Bahl, K., and Kiese, R.: Land use intensity has a stronger effect on the temperature sensitivity of soil microbial carbon cycling processes than long-term climate change., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16307, https://doi.org/10.5194/egusphere-egu24-16307, 2024.

EGU24-18381 | ECS | Orals | SSS4.5

Cropping system modulates the effect of drought on ammonia-oxidizing communities 

Ari Fina Bintarti, Elena Kost, Dominika Kundel, Rafaela Feola Conz, Paul Mäder, Hans-Martin Krause, Jochen Mayer, Martin Hartmann, and Laurent Philippot

The severity of drought is predicted to increase across Europe due to climate change. Droughts can substantially impact terrestrial nitrogen (N) cycling and the corresponding microbial communities. Here, we investigated how ammonia-oxidizing bacteria (AOB), archaea (AOA), and comammox (complete ammonia oxidizers) respond to simulated drought in a rain-out shelter experiment in the DOK long-term field trial comparing different organic and conventional agricultural practices since 1978. This study is part of the MICROSERVICES (BiodivERsA) project aiming to understand and predict the effects of climate change on crop-associated microbiomes and their ecosystem functions. We monitored the diversity, the composition, and the abundance of ammonia-oxidizers for five months by Illumina-based amplicon sequencing and quantitative real-time PCR using the amoA gene as molecular marker.

We found that the effect of drought varied depending on the ammonia-oxidizing community and also on the agricultural practices. The community structures of AOA and comammox were more strongly affected by drought than the AOB community structure. Drought also had a stronger impact on the community structure in the biodynamic (organic) cropping system than in both the mixed and mineral-fertilized conventional systems. The abundance of ammonia oxidizers was also influenced by drought, with comammox clade B exhibiting the strongest sensitivity to drought. The drought effect on the community abundance was more prominent in the biodynamic and mixed-conventional systems than in the mineral-fertilized conventional system. We further found a significant interaction between drought and agricultural practices on the abundance of all groups of ammonia-oxidizers except AOB. Overall, our study showed that the impact of drought on ammonia oxidizers was modulated by agricultural practices and varied with time as well as among members of ammonia-oxidizers. These results underscore the significance of agricultural management practices in influencing the response of nitrogen cycling and the corresponding communities to drought.

How to cite: Bintarti, A. F., Kost, E., Kundel, D., Conz, R. F., Mäder, P., Krause, H.-M., Mayer, J., Hartmann, M., and Philippot, L.: Cropping system modulates the effect of drought on ammonia-oxidizing communities, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18381, https://doi.org/10.5194/egusphere-egu24-18381, 2024.

EGU24-19061 | ECS | Posters on site | SSS4.5

Effects of elevated CO2 on soil microbial communities in a tropical understory forest in the Central Amazon 

Crisvaldo Souza, Lucia Fuchslueger, Nathielly Pires Martins, Iokanam Sales Pereira, Alacimar Viana Guedes, Bruno Takeshi Tanaka Portela, Maria Pires Martins, Juliane G. Menezes, Joana Séneca, Sabrina Garcia, Amanda Rayane Macambira Damasceno, Alberto Vicentini, David M. Lapola, and Carlos Alberto Quesada

Soil microbial communities are central to understanding interactions between soil and climate change by controlling  major carbon and nutrient fluxes, such as organic matter formation and decomposition. In addition, soil microbial communities respond sensitively to climate change and  can control the magnitude and direction of potential soil feedback to climate.

Tropical forests have a crucial role as carbon sink to reduce elevated atmospheric CO2 (eCO2), but they rely on soil microbial communities to access nutrients from organic matter. However, especially in tropical areas, the effects of increasing atmospheric CO2 on soil microbial community composition are still not fully understood. Studies, primarily conducted in temperate regions, demonstrate that eCO2 concentrations can cause changes in the structure and activity of soil microbial communities responsible for decomposing organic matter. Additionally, the richness of some microorganism species is relatively sensitive and decrease under eCO2, potentially leading to changes in the abundance of specific microbial taxa. Consequently, this could change nutrient mineralization rates, affecting primary production rates, and subsequently plant organic matter quality and inputs to soil.

Here we used an Open-Top Chamber (OTC) experiment to expose the understory vegetation in a tropical lowland forest to eCO2 (+200 ppm above ambient), and tested the impacts of eCO2 on soil microbial (fungal, bacterial, and archaeal) community structure using 16SrRNA amplicon sequencing. Two soil collections were conducted in eight OTCs (four eCO2 and four ambient control OTCs), in September 2019 before the CO2 increase and in September 2021 after two years of CO2 increment. Our results showed a significant decrease in microbial biomass carbon and phosphorus pools in response to eCO2 and a strong tendency of decreased DNA concentrations corroborating a potential decrease in soil microbial biomass. In addition, our data will provide insights in the diversity of microorganisms in Amazonian soil, and allow to better understand soil microbial community responses and feedbacks of tropical forests to eCO2 and consequences for soil carbon and nutrient cycling.

How to cite: Souza, C., Fuchslueger, L., Pires Martins, N., Sales Pereira, I., Viana Guedes, A., Tanaka Portela, B. T., Pires Martins, M., Menezes, J. G., Séneca, J., Garcia, S., Macambira Damasceno, A. R., Vicentini, A., Lapola, D. M., and Quesada, C. A.: Effects of elevated CO2 on soil microbial communities in a tropical understory forest in the Central Amazon, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19061, https://doi.org/10.5194/egusphere-egu24-19061, 2024.

EGU24-19132 | ECS | Orals | SSS4.5

Microbial growth in a warming Arctic: Exploring controls and temperature responses in permafrost soils 

Cornelia Rottensteiner, Victoria Martin, Alberto Canarini, Hannes Schmidt, Leila Jensen, Julia Horak, Moritz Mohrlok, Carolina Urbina Malo, Willeke A'Campo, Luca Durstewitz, Julia Wagner, Rachele Lodi, Niek Speetjens, George Tanski, Michael Fritz, Hugues Lantuit, Gustaf Hugelius, and Andreas Richter

Permafrost soils are particularly vulnerable to climate warming. With ~1,500 Gt Carbon (C), they store a significant proportion of global soil C. Organic matter that was frozen and thus unavailable for microbial decomposition for millennia, is now thawing. How much of this permafrost C is decomposed will be determined by microbial activities and the partitioning of assimilated C to microbial growth (potential C stabilization) or microbial respiration (C loss). Our current knowledge on the controls of microbial growth and respiration in permafrost soils is, however, limited.

The objective of this study was to analyze microbial growth and respiration in permafrost soils and to explore soil organic matter composition, microbial community composition and various soil parameters as potential drivers. We collected 81 soil samples from four soil layers (organic, mineral, cryoturbated, permafrost) and three lowland tundra polygon types (low-center, flat-center, high-center) in Arctic Canada. We used pyrolysis-GC-MS fingerprinting to characterize soil organic matter composition and amplicon sequencing (16S, ITS1) to identify archaeal, bacterial, and fungal community composition. Temperature responses (Q10) were analyzed in an 8-week laboratory incubation experiment, subjecting soil aliquots to 4 °C and 14 °C. Microbial growth was determined by 18O-H2O-incorporation into DNA and microbial respiration by gas analysis.

Soil organic matter composition differed between soil layers along a gradient of degradation and C content. Organic matter complexity and diversity decreased with the level of decomposition. We found distinct soil organic matter composition for each polygon type, including all soil layers, suggesting different decomposition pathways, induced by differences in vegetation and soil water regime. Anoxic conditions in low-center polygons resulted in more archaea and distinct fungal communities. Microbial community composition differed among all soil layers, with particularly more fungi in organic soils. Microbial mass-specific growth and respiration differed among polygons and soil layers, and both increased with warming. Overall, temperature responses (Q10) were higher for respiration than for growth, implying that microbes are less efficient in using C for growth. Linear mixed effect models revealed that soil organic matter composition and microbial community composition were good predictors for mass-specific growth at field and warmed conditions. Mass-specific respiration was best explained by microbial community composition. Our predictors, however, did not explain the temperature responses.

Our results indicate that under warming, microbes allocated more C to respiration, leading to increased greenhouse gas emissions per unit of carbon taken up. We found these results while including all soil layers and polygon types, suggesting these responses to be representative for lowland Arctic ecosystems. Moreover, we could show that organic matter composition and microbial community composition are good predictors for microbial growth and respiration, thus deserving more attention in future studies.

This study is part of the EU H2020 project “Nunataryuk”.

How to cite: Rottensteiner, C., Martin, V., Canarini, A., Schmidt, H., Jensen, L., Horak, J., Mohrlok, M., Urbina Malo, C., A'Campo, W., Durstewitz, L., Wagner, J., Lodi, R., Speetjens, N., Tanski, G., Fritz, M., Lantuit, H., Hugelius, G., and Richter, A.: Microbial growth in a warming Arctic: Exploring controls and temperature responses in permafrost soils, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19132, https://doi.org/10.5194/egusphere-egu24-19132, 2024.

EGU24-19328 | ECS | Posters on site | SSS4.5

Disentangling the impacts of soil management practices on nitrogen mineralization and inorganic nitrogen accumulation during soil drying events 

Eduardo Vázquez, Nikola Teutscherová, and Marta Benito

The biogeochemical cycling of nitrogen (N) in drylands ecosystems depends strongly on the alternance dry-wet cycles caused by seasonal nature of rainfall pulses. While during the dry periods the soil organic matter (SOM) mineralization is limited and inorganic N (Ninorg) is accumulated in soil because the low diffusion of ions and low N uptake by plant and microbes, the rewetting enhances the diffusion of ions and causes a pulse of N transformations and N2O emissions. Therefore, the understanding of the processes involved in the accumulation of Ninorg is crucial. In this study we combined a field and a laboratory study to disentangle the role of soil management practices on N mineralization and Ninorg accumulation in soils under drought conditions in Spain. First, we evaluated the N mineralization and Ninorg accumulation during summer fallow in a full-factorial field experiment comparing the effect of tillage (no-tillage (NT) vs traditional tillage (TT)) and liming. Second, we performed a soil drying experiment under controlled conditions using soil from the same field experiment to distinguish the impacts of management practices via changes in soil biogeochemical properties (mainly soil organic matter (SOM) and pH) and via soil microenvironmental conditions (soil water availability and temperature).

In the field experiment, Ninorg was accumulated in soils along the summer fallow (from May to July) while the evaluated enzymatic activities (β-glucosaminidase, Leucine aminopeptidase, BAA protease, Casein protease, L-glutaminase and Urease) and the abundance of chiA, pepA and apr genes were significantly reduced during the summer fallow. We observed a significant and positive interaction between NT and liming in the accumulation of Ninorg which may suggest higher risk of N losses upon rewetting. The higher Ninorg accumulation is linked to a similar synergistic effect of both practices on the activity of L-Asparaginase, L-glutaminase and Urease. The higher SOM, pH and less extreme microenvironmental conditions observed in soils managed by NT and liming can explain this synergistic effect. No effect of the treatments in the abundance of the evaluated genes was observed. In the soil drying experiment under controlled conditions where the differences caused by the microenvironmental conditions were excluded, we observed a positive effect of NT and liming on Ninorg accumulation along the drying experiment (29 days of drying). However, no interaction between NT and liming on the Ninorg accumulation was observed. This suggest that the synergistic effect observed in the field experiment was caused by the microenvironmental conditions rather than by changes in biogeochemical properties. Similar circumstance was observed in the analyzed enzymatic activities and chiA abundance (positive effect of NT and liming but without synergistic response) confirming the previous observation. In summary, our results suggest that the combination of NT and liming increases synergistically the accumulation of Ninorg in soil during summer fallow because of their positive effect on soil microenvironmental conditions rather than on soil biogeochemical properties

How to cite: Vázquez, E., Teutscherová, N., and Benito, M.: Disentangling the impacts of soil management practices on nitrogen mineralization and inorganic nitrogen accumulation during soil drying events, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19328, https://doi.org/10.5194/egusphere-egu24-19328, 2024.

EGU24-20534 | Posters on site | SSS4.5

Cover crop diversification alters microbial life-death cycle and enhances carbon sequestration in agricultural soil 

Alexander König, Christoph Rosinger, Katharina Keiblinger, Sophie Zechmeister-Boltenstern, Anke Herrmann, and Erich Inselsbacher

Sequestering atmospheric CO2 within soil organic matter via shifts in agricultural practices represents a compelling strategy for enhancing soil ecosystem services and mitigating global change. Traditionally, the perception of soil carbon (C) stability is focused on intrinsic characteristics of organic matter inputs, such as lignin content. However, recent studies challenge this perspective, proposing a more effective approach centered on managing how the soil microbiome processes C inputs (Sokol et al., 2019; Poeplau et al., 2019).

This shift prompts an exploration into the intricate connection between aboveground plant communities and belowground diversity of the microbiome, as well as the associated metabolic processes governing C sequestration. Building on this, Lehmann et al. (2020) presented a theoretical framework that interprets the persistence of C in soil as a consequence of interactions between the molecular variability of organic matter input and the spatio-temporal microbial heterogeneities within the soil system. This perspective underscores the need for a comprehensive understanding of the dynamic interplay shaping C sequestration, moving beyond static views of organic matter stability.

Therefore, within the EnergyLink framework various microbial markers were investigated to shed light on potential physiological changes at a microbial level across several European agricultural field sites with different cover crop management types. Specifically, to discern shifts in microbial necromass composition and quantity, we focused on amino sugars (galactosamin, gluctosamine, mannosamine and muramic acid). To evaluate effects on potential growth rates, we quantified 14C incorporation into ergosterol for fungi and 14C-leucine incorporation for bacteria. Comprehending changes in uptake strategies, we examined extracellular enzyme activities for different nutrient classes. Additionally, we determined C:N:P ratio for bulk soil and microbial biomass. Here we present first results and discuss implications of diversified cover crops on soil carbon properties.

How to cite: König, A., Rosinger, C., Keiblinger, K., Zechmeister-Boltenstern, S., Herrmann, A., and Inselsbacher, E.: Cover crop diversification alters microbial life-death cycle and enhances carbon sequestration in agricultural soil, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20534, https://doi.org/10.5194/egusphere-egu24-20534, 2024.

EGU24-197 | ECS | Orals | BG3.23

Non-living respiration: another breath in the soil 

Clémentin Bouquet, Benoit Keraval, Gaël Alvarez, Mounir Traïkia, Fanny Perrière, Sandrine Revaillot, Anne-Hélène Le Jeune, Hermine Billard, Sébastien Fontaine, and Anne-Catherine Lehours

Containing about three times more carbon (C) than the atmosphere (600-800 PgC) or the Earth’s vegetation, soils are crucial C pools for climate change mitigation. The CO2 flux (~110 PgC yr1) from soils is the largest terrestrial C source to the atmosphere and is about ten times the annual emissions from burning fossil fuels (IPCC 2021). A small change in soil CO2 flux can significantly alter the atmospheric CO2 concentrationand potentially amplify global warming.A complete and reliable identification of soil processes likely to affect soil C balance and CO2 flux is essential to predict future atmospheric CO2 concentrations.

The current scientific consensus is that the dominant component of the soil CO2 flux is heterotrophic microbial respiration. However, this paradigm is challenged by recurrent observations of substantial and persistent CO2 emissions in soil microcosms where sterilization treatments (e.g. γ-irradiations) reduced microbial activities to an undetectable level. To address this shortcoming, we postulated that non-cellular respiratory pathways in soils are capable of performing the complete oxidation of organic matter to CO2. This hypothesis was enhanced (i) by the detection of an isotopic signature of soil CO2 flux (δ13C-CO2 up to −75.4 ± 2.8 ‰) incompatible with a cell-derived respiration and (ii) by the release of 13C-CO2 in sterilized soils supplied with 13C-glucose (Maire et al. 2013; Kéraval et al. 2016; 2018).

Overall our work highlights that non-cellular respiration accounts for 16 to 48 % of CO2 fluxes from sterilized soils worldwide with contrasted physical and chemical properties. We have also demonstrated that sterilized soils have a high and persistent potential for electron transfer and form self-sustaining systems that can maintain CO2 emissions for more than 6 years without external input. Furthermore, untargeted metabolite profiling carried out using proton nuclear magnetic resonance (1H NMR) spectroscopy revealed that non-living soils have an orderly exometabolome dynamics supporting the idea that non-stochastic scenarios mimicking biochemical transformations (i.e. Krebs cycle, fermentation) occurred in sterilized soils (Bouquet, Keraval et al. in prep).

  • Maire, V. et al, 2013. An unknown oxidative metabolism substantially contributes to soil CO2emissions, Biogeosciences, 10, 1155–1167, https://doi.org/10.5194/bg-10-1155-2013,
  • Kéraval, B., et al, 2016. Soil carbon dioxide emissions controlled by an extracellular oxidative metabolism identifiable by its isotope signature, Biogeosciences, 13, 6353–6362, https://doi.org/10.5194/bg-13-6353-2016, 2016
  • Kéraval, B. et al, 2018. Cellular and non-cellular mineralization of organic carbon in soils with contrasted physicochemical properties. Soil Biol. Biochem. 125, 286–289. doi:10.1016/j. soilbio.2018.07.02
  • Bouquet, C., et al. in prep. Non-living respiration : another breath in the soil

How to cite: Bouquet, C., Keraval, B., Alvarez, G., Traïkia, M., Perrière, F., Revaillot, S., Le Jeune, A.-H., Billard, H., Fontaine, S., and Lehours, A.-C.: Non-living respiration: another breath in the soil, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-197, https://doi.org/10.5194/egusphere-egu24-197, 2024.

EGU24-2201 | ECS | Orals | BG3.23

An innovative soil mesocosm system for studying the effect of soil moisture and background NO contribution on soil surface trace gas fluxes  

Logapragasan Subramaniam, Florian Engelsberger, Benjamin Wolf, Michael Dannenmann, and Klaus Butterbach-bahl

This research investigates the complex dynamics of how soil NO concentrations and soil moisture affect the exchange of greenhouse gases between soils and the atmosphere. To this end, we have developed and tested an automated soil mesocosm system (AU-MES), which allows for dynamically change of headspace and soil NO concentrations, measures trace and greenhouse gas fluxes based on a dynamic chamber approach, and observes and manipulates key soil and environmental metrics such as temperature, light conditions, or moisture.

Initial a brief phase of soil-only incubation experiments demonstrated the influence of soil moisture and soil and headspace NO concentrations of 400 ppbv on gas emissions. We observed that under low soil moisture conditions (30% water-filled pore space), nitrification was favored, as indicated by increased emissions of NO (at zero NO concentration 0.191 kg N ha-1 and at high NO concentration 0.180 kg N ha-1) and NO2 (at zero NO concentration 0.002 kg N ha-1 and at high NO concentration 0.001 kg N ha-1). In contrast, under higher soil moisture conditions (50% water-filled pore space), we observed increased N2O (at zero NO concentration 0.149 kg N ha-1and at high NO concentration 0.147 kg N ha-1) and CO2 (at zero NO concentration 0.122 t C ha-1 and at high NO concentration 0.110 t C ha-1)fluxes, suggesting that denitrification may become more important. These results, particularly under soil rewetting and fertilizer application, illustrate the complex interplay between soil nitric oxide concentrations, moisture levels, microbial activities, and gas emissions.

In summary, the AU-MES system is a valuable tool for investigating soil-atmosphere gas interactions and the effects of various environmental elements on these processes. Our research provides important insights into how nitric oxide may affect soil processes and trace gas exchange at the soil-atmosphere interface.

Keywords
Automated soil mesocosm system, nitric oxide, gas concentrations, headspace purging, soil purging

How to cite: Subramaniam, L., Engelsberger, F., Wolf, B., Dannenmann, M., and Butterbach-bahl, K.: An innovative soil mesocosm system for studying the effect of soil moisture and background NO contribution on soil surface trace gas fluxes , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2201, https://doi.org/10.5194/egusphere-egu24-2201, 2024.

EGU24-2971 | ECS | Posters on site | BG3.23

Viral lifestyles modulate prokaryotic community structure and function in thermokarst lakes 

Yutong Song and Yuanhe Yang

Microbes determine the fate of carbon (C) and nitrogen (N) released by rapidly thawing permafrost, with viruses that infect them mediating this process via lysis and metabolic reprogramming. However, little is known about whether and how viruses with different lifestyles modulate microbial community and ecological functions, particularly in thermokarst lakes where studies for viruses were pretty scarce. Here, we conducted metagenome deep sequencing on sediment samples obtained from 60 thermokarst lakes along a 1,100 km permafrost transect, and recovered 4,161 viral and 2,805 microbial genomes from above 3 Tb data, as well as predicted their interactions and functions. We found that viral lifestyles were coupled with microbial life-history strategies along nutrient gradients. Virus-host interactions were more specialized in temperate viruses dominant samples than those in virulent viruses prevailing samples. Further functional predictions revealed that virus-encoded auxiliary metabolic genes (AMGs) exhibited more diverse and higher abundance in virulent viruses dominant community than those in temperate viruses predominant community. What count was that viruses could reduce methane (CH4) emissions from thermokarst lakes via virus-encoded mmoB genes. Overall, these findings highlight the crucial impact of viral life-history strategies on microbial community and key ecosystem function in climate-sensitive thermokarst habitats.

How to cite: Song, Y. and Yang, Y.: Viral lifestyles modulate prokaryotic community structure and function in thermokarst lakes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2971, https://doi.org/10.5194/egusphere-egu24-2971, 2024.

EGU24-4353 | Orals | BG3.23

Soil microsites controls N2O production and emission in undisturbed soils 

Zhifeng Yan and Baoxuan Chang

Soil structures regulate the production and emission of N2O from soils mainly through influencing substrate availability and gas diffusion. However, the respective impacts of substrate availability and gas diffusion and their response to moisture changes remain elusive. This study conducted laboratory incubation experiments with disturbed (sieved) and undisturbed (intact) soil cores under different soil moisture levels (i.e., 40, 60, 80 and 100% water filled pore space (WPFS)). Soil N2O fluxes were continuously monitored over a 21-day incubation period, during which O2 concentration profile was occasionally measured and relative soil gas diffusivity was measured at the end of experiments. The results show that the N2O fluxes from the disturbed soil cores were 2~25 times higher, respectively, than those from undisturbed cores, which are similar to field observations. Nevertheless, the difference in the relative soil gas diffusivity between them was not obvious, especially under high moisture conditions. Therefore, the overestimated soil N2O emission from sieved soil experiments was attributed to increased C availability caused by disturbance rather than changes in gas diffusivity. Additional incubation experiments with 15N tracing further demonstrated the key impacts of soil microsites on N2O production and emission. Overall, this study highlighted the physical protection of soil microsites on carbon sequestration and N2O mitigation.

How to cite: Yan, Z. and Chang, B.: Soil microsites controls N2O production and emission in undisturbed soils, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4353, https://doi.org/10.5194/egusphere-egu24-4353, 2024.

Global warming can significantly impact soil CH4 uptake in subtropical forests due to changes in soil moisture, temperature sensitivity of methane-oxidizing bacteria (MOB), and shifts in microbial communities. However, the specific effects of climate warming and the underlying mechanisms on soil CH4 uptake at different soil depths remain poorly understood. To address this knowledge gap, we conducted a soil warming experiment (+4°C) in a natural forest. From August 2020 to October 2021, we measured soil temperature, soil moisture, and CH4 uptake rates at four different soil depths: 0-10 cm, 10-20 cm, 20-40 cm, and 40-60 cm. Additionally, we assessed the soil MOB community structure and pmoA gene (with qPCR) at the 0-20 cm depth. Our findings revealed that warming significantly enhanced soil net CH4 uptake rate by 12.28%, 29.51%, and 61.05% in the 0-10, 20-40, and 40-60 cm soil layers, respectively. The warming also led to reduced soil moisture levels, with more pronounced reductions observed at the 20-40 cm depth compared to the 0-20 cm depth. At the 0-10 cm depth, warming increased the relative abundance of upland soil cluster α and decreased the relative abundance of Methylocystis, but it did not significantly increase the pmoA gene copies. Our structural equation model indicated that warming directly regulated soil CH4 uptake rate through the decrease in soil moisture, rather than through changes in the pmoA gene and MOB community structure at the 0-20 cm depth. In summary, our results demonstrate that warming enhances soil CH4 uptake at different depths, with soil moisture playing a crucial role in this process. Under warming conditions, the drier soil pores allow for better O2 and CH4 penetration, thereby promoting more efficient activity of MOB. This increased CH4 uptake in subtropical forests has the potential to mitigate the effects of global warming.

How to cite: Zhang, L., Lin, W., and Guo, J.: Exploring the impact of soil warming on methane uptake at different soil depths in a subtropical forest: unraveling the role of decreased water content, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4918, https://doi.org/10.5194/egusphere-egu24-4918, 2024.

EGU24-5323 | ECS | Orals | BG3.23

The influence of glyphosate on soil CO2 respiration and microbial communities structure in histosol and fluvisol 

Adam Furtak, Anna Szafranek-Nakonieczna, Andrzej Górski, and Anna Pytlak

Carbon dioxide is the most important among all greenhouse gases and microbial respiration is one of the fundamental soil processes, that contribute to atmospheric CO2 pool. Many factors influence the respiration of soil microbiota. With regard to agricultural soils, the most discussed are the type of cultivation and fertilisation. Much less attention is paid to herbicides, which are widely used and comprise a frequent contaminant of the soil environment. The most commonly used herbicide worldwide is glyphosate (GFP). In 2018, annual  GFP consumption exceeded 8.25 x 108 kg and is still increasing. GFP is a foliar herbicide that is used in agriculture in the form of commercial formulations (GFC). Due to imprecise dosing, leaf washoff or with plant necromass, GFC reaches the soil environment where can potentially modulate activity and abundance of soil microorganisms. Possible modes of action include toxicity (e.g. due to inhibition of the shikimate pathway) or stimulation due to the fact that GFP is biodegradable and can potentially be a source of all major biogenic elements C, N and P. Due to the widespread use of GFC in agriculture, it may be an important driver of soil-related CO2 emissions, but knowledge in this area is still fragmentary.  

In the current study, a wide range of GFP and GFC (0 – 10 000µg g-1) doses were used to determine its effect on microbial respiration in two agriculturally used soils (histosol and fluvisol). In parallel, the qualitative and quantitative composition of the soil microbial community was studied. Pure glyphosate (GFP) and a commercial formulation (GFC) containing adjuvants in addition to glyphosate were tested.

For both soils, the exposure to GFP and GFC resulted in an increase in microbial respiration. However, this effect was greater for GFC, indicating the important role of adjuvants in shaping the environmental effect of the herbicides used. In accordance with the respiration results, a significant increase in the total bacteria count was found in both studied soils. Qualitatively, communities' structures were not significantly transformed, even under the influence of high doses of the tested preparations.

How to cite: Furtak, A., Szafranek-Nakonieczna, A., Górski, A., and Pytlak, A.: The influence of glyphosate on soil CO2 respiration and microbial communities structure in histosol and fluvisol, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5323, https://doi.org/10.5194/egusphere-egu24-5323, 2024.

EGU24-5799 | Orals | BG3.23

Stable-isotope probing identifies microorganisms actively degrading DMSP in anaerobic saltmarsh sediments 

Özge Eyice, Susan Hawthorne, Stephania Tsola, Ornella Carrión, and Jonathan Todd

Billions of tons of dimethylsulfoniopropionate (DMSP) are produced every year in marine and coastal ecosystems such as saltmarshes and estuaries. DMSP has far-reaching roles in global carbon and sulfur cycling, also as an osmotolerant and signalling molecule. Furthermore, the microbial degradation of DMSP contributes significantly to the formation of dimethylsulfide (DMS) and methanethiol (MT), other abundant organosulfur compounds with ecological significance. Particularly, in anaerobic sediments, microbial DMS and MT degradation leads to the formation of methane, a powerful greenhouse gas. However, research to date has predominantly focused on aerobic settings, revealing diverse groups of microbes and enzymes mediating DMSP degradation. DMSP concentrations in anaerobic ecosystems and microbial populations underlying DMSP breakdown have never been studied, prohibiting improvements in our understanding of global carbon and sulfur cycles. To address this key knowledge gap, we applied stable-isotope probing combined with 16S rRNA sequencing to identify the active DMSP-degraders in anaerobic saltmarsh sediments.

We collected sediments from a 5-10 cm depth of Medway Saltmarshes (UK) using 3.5cm Perspex corers. We transferred the samples to the laboratory and measured in situ DMSP concentrations of 7.7 (±0.5) μmol g−1 wet sediment. In line with the in situ concentrations, we set up replicated incubations anaerobically with 8 μmol g−113C- and 12C-labelled DMSP, and applied stable-isotope probing combined with 16S rRNA sequencing.

We observed immediate degradation of DMSP in the sediment incubations and DMS production, suggesting the existence of a resident microbial community actively carrying out this process. A total of 48 μmol/g 13C- or 12C-DMSP was amended and a total of 34 (±3.2) μmol/g DMS was produced in the incubations over 12 days.  DNA was extracted and ultracentrifugation was applied to separate heavy and light DNA fractions for downstream analysis. 16S rRNA sequencing of the fractions from 13C and 12C-labelled DNA demonstrated significant enrichment of the family Nitrincolaceae within the order Oceanospirillales in 13C-heavy fractions compared to 13C- light and 12C-heavy fractions (P<0.05). Their relative abundance increased from 2% (±1.3) to 27.2% (±9.1). This demonstrates that they are the active DMSP degraders in anaerobic saltmarsh sediments.

This is the first study quantifying significant concentrations of DMSP in anaerobic saltmarsh sediments and demonstrating Nitrincolaceae to be the active DMSP-degraders. Our findings not only broaden our understanding of microbial carbon and sulfur cycling but also highlight a previously overlooked route to methane formation in anaerobic saltmarsh sediments.  Our study underscores the need to identify microbial communities and pathways of DMSP breakdown across diverse anaerobic settings.

How to cite: Eyice, Ö., Hawthorne, S., Tsola, S., Carrión, O., and Todd, J.: Stable-isotope probing identifies microorganisms actively degrading DMSP in anaerobic saltmarsh sediments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5799, https://doi.org/10.5194/egusphere-egu24-5799, 2024.

EGU24-6777 | Posters on site | BG3.23

Development of an online O2-CO2 soil profile probe for flux estimations 

Martin Maier, Laurin Osterholt, and Elad Levintal

Reliable and accurate measurements of gas fluxes between soil and atmosphere are fundamental to calculate global greenhouse gas budgets. Chamber methods and the eddy covariance method are the most often used methods to measure soil-atmosphere gas fluxes. The gradient method can provide additional information about the localization of gas production within the soil profile. Using this approach gas fluxes in the soil profile are calculated by multiplication of the vertical concentration gradient of a gas in the soil by the effective gas diffusion coefficient of the soil. Technical progress in the field of small gas sensors has made it possible to integrate online CO2 sensors into soil gas profile monitoring systems, which greatly facilitates soil CO2 monitoring. While soil CO2 fluxes have been widely studied during the last decade, the “forgotten half” of this respiratory flux, the counter wise flux of atmospheric oxygen (O2) into the soil is rarely investigated, although it is known that O2 availability is the key for many soil processes.

Our objective was to develop and test a soil gas profile probe for online CO2 and O2 measurements with high temporal resolution that allows (1) soil–atmosphere flux estimation and (2) estimation of soil respiration profiles for both CO2 and O2 including (3) the apparent respiratory coefficient (CO2 efflux divided by O2 influx).

We developed a multilevel O2-CO2 profile probe with small build-in online sensors in multiple depths. The design was based on a modified version of a recently developed CO2 profile probe (Osterholt and Maier, 2020, Osterholt et al 2023). The probe consists of one 3D print segment per depth each containing one small NDIR CO2 and one O2 sensor. Extensive laboratory tests with different O2 sensors were necessary to exclude, or identify and quantify, possible biases in the O2 measurements due to expected environmental changes during field measurements (such as barometric pressure, soil temperature and relative humidity). The segments can be combined to probes of different length. For the installation of the sampler a hole has to be drilled, into which the sampler is inserted. We present first results from laboratory experiments and a field experiment, focusing on methodological issues and the technical performance of the measuring system.

Acknowledgements: This research was supported by the German Research Foundation (DFG, MA 5826/4‑1 project number: 535470615)

Osterholt, L. and Maier, M.: Development of an in-situ CO­2 gradient sampler, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7272, https://doi.org/10.5194/egusphere-egu2020-7272,  2020.

Osterholt, L.; Kolbe, S.; Maier, M. (2022): A differential CO2 profile probe approach for field measurements of soil gas transport and soil respiration #. In J. Plant Nutr. Soil Sci. 185 (2), pp. 282–296. DOI: 10.1002/jpln.202100155.

How to cite: Maier, M., Osterholt, L., and Levintal, E.: Development of an online O2-CO2 soil profile probe for flux estimations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6777, https://doi.org/10.5194/egusphere-egu24-6777, 2024.

EGU24-7425 | ECS | Orals | BG3.23

Hysteretic response of N2O reductase activity to soil pH variations after application of lime to an acidic agricultural soil 

Camille Rousset, Iheb Ouerghi, Florian Bizouard, Henri Brefort, Marjorie Ubertosi, Mustapha Arkoun, and Catherine Hénault

Nitrous oxide (N2O) contributes to increasing the greenhouse effect and is also involved in stratospheric ozone depletion. In soil and water, N2O reductase catalyses the reduction of N2O into the inert form N2 and is then considered as a key environmental enzyme. N2O reductase activity is known to be affected by acidic conditions (Samad et al. 2016) and the application of liming materials to acidic soils is now proposed as a solution for mitigating soil N2O emissions (Barton et al. 2013).

During a one-year laboratory experiment, we studied the functioning of N2O reductase after the application of calcium carbonates to an acidic soil with initially a very low capacity to reduce N2O. The functioning of N2O reductase was characterised through anaerobic incubations using the acetylene inhibition technique combined with a logistic model to determine the main enzyme functioning characteristics (latency, maximal rate).

Both changes in soil pH and soil capacity to reduce N2O were rapidly observed after the application of lime materials. The activity of N2O reductase was observed to be efficient throughout the experiment even when the soil had returned to initial acidic conditions, revealing a hysteretic response of N2O reductase to pH variations. Nevertheless, some signs of lower N2O reductase activity over time were observed mainly after 200 days of applying lime materials. Altogether, these results suggest that, in this soil condition, the beneficial impact of the application of liming materials on N2O emissions could last longer than this on soil pH.

Keywords: Climate change mitigation · N2O reductase · Soil · pH · Lime application · Logistic modelling

 

References:

Barton, L. et al. (2013) Is liming soil a strategy for mitigating nitrous oxide emissions from semi-arid soils? Soil Biology and Biochemistry 62, doi: 10.1016/j.soilbio.2013.02.014

Samad, M. S. et al. (2016) High-resolution denitrification kinetics in pasture soils link N2O emissions to pH, and denitrification to C mineralization. Plos One 11, doi: 10.1371/journal.pone.0151713  

 

Acknowledgements: The authors gratefully acknowledge funding for the NatAdGES project from the “Investissement d’Avenir” program, ISITE-BFC project (contract ANR-15-IDEX-0003), the European Regional Development Fund (FEDER), the public investment bank (BPI France) and the CMI-Roullier.

How to cite: Rousset, C., Ouerghi, I., Bizouard, F., Brefort, H., Ubertosi, M., Arkoun, M., and Hénault, C.: Hysteretic response of N2O reductase activity to soil pH variations after application of lime to an acidic agricultural soil, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7425, https://doi.org/10.5194/egusphere-egu24-7425, 2024.

EGU24-8889 | ECS | Orals | BG3.23

Using 15N isotope and microbiome analysis to understand N2O production and consumption processes. 

Mohit Masta, Mikk Espenberg, Jaan Pärn, and Ülo Mander

Nitrous oxide is a potent greenhouse gas which is involved in stratospheric ozone depletion. Even though nitrogen cycle has been studied for a long time, it is still challenging to understand specific N2O production and consumption processes. This is due to the complexity and heterogeneity of soil, wherein multiple processes can take place simultaneously. Isotopic composition of N2O can help us solve this and provide useful information on evaluating N2O sources and calculate global budgets. N2O is a linear molecule and its understanding at molecular scale can provide major insights into partition of its source processes. The N2O site preference (SP), which is the difference in δ15N between N2O molecules substituted with 15N at the central and the peripheral position, has proved to be a major tool to tackle this problem. The objective of this study is to use isotopic and microbial research for N2O sources and process partitioning. We will bring some examples from our recent studies in the lab and in a drained peatland forest.

 

During our lab study based on peat soil from a floodplain fen, we observed bacterial denitrification was a major source of N2O emissions under flooded conditions. We observed this using 15N isotopic mapping technique, which helped separate multiple active processes. We applied a similar method in-situ on a drained peatland in southeastern Estonia and described hybrid N2O formation, where one N atom of the N2O molecule was taken from NH4 and the other N molecule from another source such as organic N, was the dominant source of N2O emissions. The isotopic mapping and molecular enrichment of 15N during our experiment showed that. The isotopic mapping initially suggested nitrification as a major source, but on further investigation of 15N enrichment, we found the presence of hybrid processes (15N nitrogen from two pools or processes). Furthermore, we studied the genetic potential for major N2O processes (denitrification, nitrification, dissimilatory nitrate reduction to ammonium (DNRA)) and combined these with the isotope results, and this integrated approach is an important tool to partition N2O processes. When using 15N tracers, the isotopic technique can partition the sources (nitrate or ammonia) of N2O. Hence, using the isotopic mapping of natural abundances and 15N tracers to partition the source, we can get initial insights into N2O sources and processes together. Isotopic mapping is still under development and further research is required as it also has a problem of overlapping of processes.

How to cite: Masta, M., Espenberg, M., Pärn, J., and Mander, Ü.: Using 15N isotope and microbiome analysis to understand N2O production and consumption processes., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8889, https://doi.org/10.5194/egusphere-egu24-8889, 2024.

The dynamics of soil carbon (C) emissions along with their biogeochemical and environmental control have garnered increasing attention. However, the role of methane (CH4) in soil organic carbon (SOC) modelling has been relatively underexplored compared to carbon dioxide (CO2), and the omission of microbial processes may prevent us from accurately modelling CH4 dynamics under environmental changes. Here, we incorporated an explicit microbial CH4 module into the Microbial-ENzyme Decomposition (MEND) model and evaluated it against a sub-version with the first-order kinetics (First-order) and the previous MEND (MEND_old) model. We conducted a rigorous calibration and validation of MEND with high-resolution CO2 and CH4 efflux observations across two soil types and five different oxygen (O2) fluctuation conditions. Beyond precisely capturing soil CO2 and CH4 effluxes, the model could also effectively simulate the relative contents of microbial biomass and enzymes. The multi-model comparison further revealed that the inclusion of new processes did not necessarily enhance model performance if microbes were not perceived as explicit state variables. Our results demonstrated that adopting microbial functional groups as drivers of soil CH4 cycle could provide a basis for testing hypotheses on microbially mediated CH4 processes and their responses to environmental changes. With the availability of diverse data and the development of genetic technologies, our modelling framework present here will empower ecologists and governments to perceive and intervene in global warming from underlying biogeochemical mechanisms rather than predictions.

How to cite: Wang, G. and Zhou, S.: Representing explicit microbial processes enhances methane modeling under oxygen fluctuation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9741, https://doi.org/10.5194/egusphere-egu24-9741, 2024.

Drylands, constituting approximately 56% of the Earth's terrestrial surface, stand as the largest biome. Despite their vast expanse, our understanding of soil trace gas emissions from these regions remains limited. This knowledge gap arises from an uneven distribution of soil trace gas flux measurements across continents. While North American and East Asian drylands have been extensively studied, reports from other drylands are scarce. This lack of information hinders our ability to effectively constrain the atmospheric budget of reactive carbon and nitrogen gases and to develop predictive models for changes in soil trace gas emissions amid ongoing global environmental changes.

To address this gap, we conducted a comprehensive study in the Negev Desert, Israel, utilizing an array of seven automatic soil static chambers coupled to two infrared gas analyzers. This allowed us to measure soil emissions of methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2) near-continuously every 15 minutes over three rainless months, measuring ~5000 individual soil fluxes. Our focus was on bare soils with varying organic carbon content (0.2%, 0.5%, and 0.6%) and nitrogen content of ~0.1%.

Our findings reveal significant diurnal variations in both CO2 and N2O emissions. CO2 emissions peaked at noon (1318.2±440.4 µg C m-2min-1) and reached their lowest point at midnight (373.4±228.8 µg C m-2min-1). In contrast, soil N2O flux was highest at 9:00 (0.07±0.02 µg N m-2min-1) and lowest at 21:00 (0.03±0.01 µg N m-2min-1). Soil CH4 flux exhibited minimal variation, with maximum and minimum emissions of 0.43±0.24 and 0.16±0.09 µg C m-2min-1, respectively.

Notably, the distinct peak emission times for CO2 and N2O suggest different underlying mechanisms for the production of these gases in the soil. Furthermore, we observed a strong correlation between soil CO2 emissions and soil water fluxes, while all gaseous fluxes correlated with the organic carbon content of soils. This emphasizes the role of water and soil organic carbon as primary driving factors for trace gas production in desert soils during rainless periods. Specific mechanisms of soil trace gases production in dry desert soils, however, will require further research.

How to cite: Gelfand, I. and Grabovsky, V. I.: During the rainless season, arid soils exhibited large diurnal fluctuations in carbon and nitrous oxides emissions, while displaying a uniform pattern of methane emissions throughout the day. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10301, https://doi.org/10.5194/egusphere-egu24-10301, 2024.

EGU24-11695 | ECS | Posters on site | BG3.23

Microbial nitrogen cycle in sub-tropical peatland cloud forest and wetland ecosystems of Réunion Island 

Fahad Kazmi, Ülo Mander, Reti Ranniku, Maarja Öpik, Kaido Soosaar, Kuno Kasak, Claudine Ah-Peng, and Mikk Espenberg

Peatlands play an essential role in the regulation of carbon and nitrogen cycles. Nitrogen-rich peatlands under warm and dry conditions can be a source of N2O, a potent greenhouse gas. Research on microbial activity, particularly in relation to N2O emissions in sub-tropical peatlands and wetlands, is very limited. In the current study, we investigated two peatland cloud forest sites in Reunion Island, namely Plaine des Cafres (characterized by dominant species Erica reunionensis and Alsophila glaucifolia) and Forêt de Bébour (featuring Erica reunionensis exclusively), alongside one RAMSAR wetland site located in Saint Paul. Both cloud forest sites were located at an altitude of 1500-1600 m, while the wetland was at an altitude of 4 m. to clarify the microbial dynamics of the nitrogen cycle in sub-tropical peatland cloud forests and wetlands.

DNA extraction was performed on these samples, followed by quantification of genes associated with the nitrogen cycle using quantitative polymerase chain reaction (qPCR). Analyses are ongoing for plant samples. In addition, soil samples underwent analyses to assess levels of ammonium (NH4+-N) and nitrate (NO3-N). Soil N2O fluxes were determined by collecting gas samples from the chamber headspace of static soil chamber systems at 20-minute intervals during one-hour sessions. The concentration of N2O was determined from gas samples using a gas chromatographer (Shimadzu, 2014).

All sites emitted negligible soil N2O fluxes (mean: 0.9 µg N m−2 h−1). However, a substantial amount of soil NH4+-N was found across all sites (mean: 77.2 mg/kg). The forests dominated by Erica reunionensis showed the highest values (mean: 106 mg/kg). Soil NH4+-N significantly correlated with the abundance of the nifH gene (R2 = 0.7, p<0.05). This indicates a high potential for microbial nitrogen fixation in all sites. Soil NO3-N varied significantly among different ecosystems. The cloud forests dominated by Erica reunionensis showed the highest values (mean: 139 mg/kg) as compared to the mixed forest (mean: 53.7 mg/kg) and the wetland site (mean: 2.53 mg/kg). Archaeal amoA gene abundance and proportion in soil were higher (p<0.05) in cloud forest sites than in wetland sites, positively correlating with NO3-N (R2 = 0.7, p<0.05). This reveals an archaeal nitrification potential in cloud forests. The nir:amoA ratio, as well as the nirS gene proportion, was significantly higher in the wetland (p<0.05), indicating the anaerobic denitrification potential, which explains the low NO3-N values there. Meanwhile, low soil N2O fluxes in the cloud forest soils can be attributed to the high abundance and proportions of nosZI-type denitrifiers.

The canopy soil from Erica reunionensis had a higher abundance of nirK and nosZI genes than Alsophila glaucifolia's canopy soil (P<0.05). However, it was the opposite in the case of fungal nirK abundance. The presence of denitrification genes in the canopy indicates an aboveground potential denitrification pathway in the cloud forests of the Réunion island. 

How to cite: Kazmi, F., Mander, Ü., Ranniku, R., Öpik, M., Soosaar, K., Kasak, K., Ah-Peng, C., and Espenberg, M.: Microbial nitrogen cycle in sub-tropical peatland cloud forest and wetland ecosystems of Réunion Island, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11695, https://doi.org/10.5194/egusphere-egu24-11695, 2024.

EGU24-12260 | Posters on site | BG3.23

The influence of herbicides on greenhouse gases emissions from soil: a bibliometric analysis 

Anna Pytlak, Adam Furtak, and Anna Szafranek-Nakonieczna

Agriculture is an important factor shaping gas exchange in the soil-atmosphere system. An important mechanism of agricultural impact is through the modulation of the living conditions of soil microorganisms responsible for the biological formation and utilisation of greenhouse gases. In this respect, agrochemicals play an important role. Fertilisers in particular have received much attention to date. The effects of soil supplementation, particularly with mineral nitrogen-containing fertilisers or organic fertilisers, on the microbial communities responsible for GHG transformation are well documented. Far less attention has been paid to other categories of agrochemicals, including herbicides. Meanwhile, the intensification of agriculture and the introduction of herbicide-resistant, transgenic crops involves the introduction of huge quantities of these chemicals (in the thousands of tonnes per year) into the environment. As a result of inaccurate dosing and with dead plant biomass, these compounds end up in the soil environment. The current paper presents a synthesis of information on the current state of knowledge regarding the effects of 4 commonly used herbicides worldwide (glyphosate, glufosinate, atrazine and 2,4-D) on the cycles of the most important greenhouse gases. VOS wiever software, equipped with text mining functionality was used to construct and visualise co-occurrence networks of important terms extracted from a body of scientific literature. An analysis of bibliographic databases for co-occurrence of key words such as "methane", "nitrous oxide", "carbon dioxide" and "greenhouse gas" - separately for each of the studied herbicides revealed that knowledge in this area is scarce and fragmentary. In the context of effects on greenhouse gas balance, only a few papers were recorded for glyphosate and atrazine and none for glufosinate or 2,4-D. In view of increasing global warming and the intensification of agricultural activity, it is important to complete the knowledge in this area.

Acknowledgements

This work was supported by the Project “Effect of glyphosate on the biological methane oxidation in agricultural soils”, no. 2021/41/B/NZ9/03130 which was financed by National Science Centre Poland.

How to cite: Pytlak, A., Furtak, A., and Szafranek-Nakonieczna, A.: The influence of herbicides on greenhouse gases emissions from soil: a bibliometric analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12260, https://doi.org/10.5194/egusphere-egu24-12260, 2024.

EGU24-12641 | Posters on site | BG3.23

Groundwater changes affect soil CO2 dynamics 

Stefan Seeger, Faisal Hayat, Talat Saeidi, and Martin Maier

Soils play a central role in the global carbon (C) cycle and can be a major source or sink of greenhouse gases. The highest concentrations and turnover of soil C is typically found in the top soil (0-0.5m depth). Yet, the total amount stored of soil organic carbon (SOC) in the subsoil (e.g. 0.5-3m) can be large and could be mobilized when soil environmental conditions change. These could be slow changes due to global climate change e.g. in subsoil moisture or temperature affecting subsoil respiration, but also more abrupt changes e.g. subsoil SOC mineralization after a decline in the groundwater level when prior submerged SOC gets exposed to higher O2 levels.

Our objective was (1) to study the effect of a changing groundwater level on soil CO2 concentration dynamics and (2) to test if the gradient method is a suitable tool to identify subsoil respiration effects.

For this pilot study we used a multilevel soil CO2 profile probe that allowed simultaneous online monitoring of soil CO2 concentration at different depth (Osterholt et al 2022), and calculation of the depth distribution of the soil respiration profile based on the gradient method (Maier & Schack-Kirchner, 2014). The CO2 probe and additional sensors were installed in a large (3 m diameter) lysimeter field station with sandy soil where the groundwater table was kept constant for >10 years at 0.8m depth. During the study period the ground water table was changed several times between 0.3-1.0m depth directly inducing effects on the CO2 concentration itself (piston flow) and also on the soil respiration profile (enhanced mineralization after groundwater level drops), which would not have been observed by pure chamber measurements at the surface.

 

Osterholt, L.; Kolbe, S.; Maier, M. (2022): A differential CO2 profile probe approach for field measurements of soil gas transport and soil respiration #. In J. Plant Nutr. Soil Sci. 185 (2), pp. 282–296. DOI: 10.1002/jpln.202100155.

Maier, M., & Schack-Kirchner, H. (2014). Using the gradient method to determine soil gas flux: A review. Agricultural and Forest Meteorology, 192–193, 78–95. https://doi.org/10.1016/j.agrformet.2014.03.006

How to cite: Seeger, S., Hayat, F., Saeidi, T., and Maier, M.: Groundwater changes affect soil CO2 dynamics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12641, https://doi.org/10.5194/egusphere-egu24-12641, 2024.

EGU24-12997 | ECS | Posters on site | BG3.23

Two decades of micrometeorological measurements show dynamic drivers of springtime N2O emissions 

Leah Brown, Ian B. Strachan, David Pelster, Stuart Admiral, Luc Pelletier, Brian Grant, Ward Smith, and Elizabeth Pattey

Nitrous oxide (N2O) is a potent greenhouse gas with a global warming potential 265 times that of carbon dioxide and the ability to destroy stratospheric ozone. Agricultural soils contribute over two-thirds of anthropogenic N2O emissions. Field observations in temperate climates have commonly shown N2O emission peaks occurring in the spring during a period of snow melt and soil thaw. This freeze-thaw period typically accounts for approximately 35% of annual N2O emissions, however, current understanding of its drivers is based off of relatively short observation periods. The analysis of such data over decadal time spans is therefore needed to improve our understanding of key drivers. Here, we report on 21 years (2002-2022) of micrometeorological N2O flux data from a field site in Ottawa, Ontario. Correlation analyses were conducted between the N2O flux during the spring thaw period and variables that are commonly considered drivers. Little to no correlation was seen from linear or multilinear regressions across a range of meteorological, management, and soil variables. The non-linear response of non-growing season cumulative N2O emissions to cumulative freezing degree-days was consistent with previous studies (Wagner-Riddle et al., 2017). However, in isolating freezing degree-days we may be neglecting other possible controls. These results show that the relationship of N2O flux with environmental variables may be related to complex, potentially non-linear, interactions between agricultural practices, weather, soil quality, and other variables. We will further examine the data using other multivariate statistical methods to further investigate potential drivers of these non-growing season emissions with a focus on those emissions occurring specifically during the spring thaw. As these relationships are used in nitrification/denitrification models, improved understanding is still needed to accurately simulate these processes, which is imperative to improving nitrogen budgets and ultimately achieving climate goals.

How to cite: Brown, L., Strachan, I. B., Pelster, D., Admiral, S., Pelletier, L., Grant, B., Smith, W., and Pattey, E.: Two decades of micrometeorological measurements show dynamic drivers of springtime N2O emissions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12997, https://doi.org/10.5194/egusphere-egu24-12997, 2024.

EGU24-13087 | ECS | Orals | BG3.23

Belowground methane cycling along a stream-to-edge transect in the Lompolojänkkä fen 

Lukas Kohl, Salla A. M. Tenhovirta, Iikka Haikarainen, Mari Pihlatie, Markus Greule, Frank Keppler, and Annalea Lohila

Lompolojänkkä is a nutrient-rich fen located in western Lapland. The site has been the focus of detailed methane flux measurements, which revealed high spatial variability along a transect from the central stream to the edge of the peatland. Surprisingly, the highest fluxes did not occur in the center of the peatlands, but rather at the halfway point between the center and the edge of the peatland, likely due greater oxygen transport by turbulent water flow at the center of the peatland. In this study, we aim to quantify the contribution of hydrogenotrophic and acetoclastic methanogenesis, the fraction of methane oxidized prior to emission to the atmosphere, and the location (depth) of these processes in the peat profile. We further investigate if these processes differ in space along a the stream-to-edge transect and time with the progress of the growth season. To quantify these processes, we collected pore water samples from 15 depth profiles at 20 to 100 cm depth. In these samples we quantified concentrations of dissolved methane, its carbon and hydrogen isotope values, and a suite of geochemical measures. We find that locations close to the central stream are characterized by high methane concentrations at depth, which decrease steeply towards the surface, indicating that high rate of methane are produced at depth but oxidized prior to reaching the surface. Sites located at the edge of the peatland, in contrast, show low methane concentrations throughout the peat profiles, indicating that small amounts of methane are produced relatively close to the surface. Stable carbon and hydrogen isotope values add additional complexity to our understanding of the methane dynamics. Methane oxidation is associated with strong increases in both δ13C and δ2H values in the residual methane and would therefore be indicated by an increase in both isotope values from deep to shallow peat layers. Such a pattern, however, was only detected close to the central stream, where approximately 50% of methane was oxidized prior to reaching the surface. In most other transect points, we found that δ13C increased from deep to shallow layers, whereas δ2H showed the opposite trend, indicating the mixing of hydrogenotrophic methane produced in deep peat layers with acetoclastic methane produced in the rooting zone. An isotope mixing model indicated that that the fraction of hydrogenotrophic methane increased from center to edge of the site (from 45 to 30% at 100 cm depth in June) and with the advancing growth season (32 to 0% in September). In contrast, we typically find less than 15% hydrogenotrophic methane in shallow layers. We note that these numbers are associated with significant external uncertainty stemming from poor certainty about mixing model parameters. Overall, our data demonstrates high and temporal spatial heterogeneity of methane production and oxidation within a single site. We demonstrate the additional information gained methane dual isotope analysis, and reveals how δ13C profiles alone can be ambiguous and misleading.

How to cite: Kohl, L., Tenhovirta, S. A. M., Haikarainen, I., Pihlatie, M., Greule, M., Keppler, F., and Lohila, A.: Belowground methane cycling along a stream-to-edge transect in the Lompolojänkkä fen, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13087, https://doi.org/10.5194/egusphere-egu24-13087, 2024.

EGU24-13690 | ECS | Orals | BG3.23

17-Years of Soil Gas Sampling for Assurance Monitoring at an Onshore CCS Demonstration Site in Victoria, Australia 

Kexin Zhang, Svetlana Stevanovic, Zibo Zhou, and Wendy Timms

Carbon capture and storage (CCS) projects aim to capture carbon dioxide (CO2) from hard-to-abate industries and the existing energy industry, for permanent storage in suitable geological formations. CCS technologies offer promising solutions to achieve net-zero emissions and ease the transition towards clean energy. Environmental monitoring is employed to demonstrate minimal influences on the near-surface environment by the CCS operation and provides assurance to the regulators and local communities. Soil gas monitoring is one of the techniques available for monitoring onshore sequestration sites.

The Otway International Test Centre (OITC), Australia’s first demonstration site for deep-well CO2 injection, has demonstrated over 95,000 tonnes of CO2 sequestration into a depleted gas reservoir and a deep saline aquifer. Due to the unique regulatory framework under which the site is permitted, a requirement of the site’s EPA license for the injection of CO2 into the subsurface is soil gas monitoring, which commenced prior to the first injection in 2008. At the OITC, soil gas samples were collected at more than 100 sites across a study area of 3.8 km2 from a 1-meter depth, with soil gas baseline values established in 2007 and 2008. The samples were analysed for major gas concentrations (i.e., oxygen (O2), nitrogen (N2), CO2 and methane (CH4)), 13C analysis on CO2, and selected samples were tested for tracer, including sulphur hexafluoride (SF6), Krypton (Kr) and Xeon (Xe). Based on available data, the injection operations at the OITC have no undesirable impacts on the near-surface environment and, when managed appropriately, CCS operations can be conducted with a high level of confidence.

The 17-year soil gas data from the OITC shows high year-to-year variabilities in soil gas CO2 concentrations, posing a major challenge to ensure robust soil gas baseline monitoring. For this reason, the use of soil gas monitoring for regulatory processes is not supported, however, as a general site check and as a means to garner community confidence, it has proven to be useful. To address the challenge of this naturally occurring variability, a multi-step verification process has been implemented to enhance confidence in identifying or ruling out anomalies. This process incorporates tracer analysis, baseline analysis, and adapted analysis methodologies demonstrated in research papers, such as the process-based analysis. Furthermore, research was conducted to review the evolution of soil gas science in the CCS industry and to optimise the monitoring strategies with data collected from the OITC as a case study.  Valuable lessons highlighted the efficacy of risk-based monitoring adjacent to identified storage formations. For example, monitoring near relatively high-risk legacy wells with compromised well integrity or for highly faulted regions with great geological uncertainty. Risk-based monitoring that includes several locations with higher temporal resolution is supported for future large-scale CCS sites.

How to cite: Zhang, K., Stevanovic, S., Zhou, Z., and Timms, W.: 17-Years of Soil Gas Sampling for Assurance Monitoring at an Onshore CCS Demonstration Site in Victoria, Australia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13690, https://doi.org/10.5194/egusphere-egu24-13690, 2024.

EGU24-14300 | ECS | Posters on site | BG3.23

Hot spots and hot moments of N2O fluxes explained by monthly dynamics of soil microbiome in drained peatland forest 

Mikk Espenberg, Zane Ferch, Fahad Ali Kazmi, Jordi Escuer-Gatius, Sharvari Sunil Gadegaonkar, Reti Ranniku, Martin Maddison, Kaido Soosaar, Jaan Pärn, and Ülo Mander

The nitrogen (N) cycle involves intricate interactions affected by the spatial and temporal variability. Hot moments, occurring short-lived across seasons, significantly contribute to temporal nitrous (N2O) emission fluctuations. Likewise, N2O emissions exhibit localized spatial variability as hot spots. Year long monthly based studies of soil N cycle microbiome dynamics in peatland forests are unknown. This study investigates the relationship between soil microbial communities and N2O gaseous fluxes within a drained peatland forest throughout a year. Key research questions are: how are the genes responsible for N cycling in the peatland spatially and temporally distributed?; what patterns are there between soil characteristics (e.g., soil water content, soil temperature and pH) and N cycling gene abundances?

Soil samples from 12 sites within a drained peatland forest in south-eastern Estonia were collected over a year and analysed for their physical and chemical properties and the abundance of genes associated with N cycling. Quantitative polymerase chain reaction was used to evaluate the bacterial and archaeal community abundances by quantifying the abundances of specific 16S rRNA genes and to evaluating the abundances of 10 genes associated with N cycling: denitrification (nirS, nirK, nosZ clade I, nosZ clade II, and fungal nirK), nitrification (bacterial, archaeal, and comammox amoA), DNRA (nrfA), and N fixation (nifH). This data was paired with N2O flux data collected in automatic dynamic gas chambers throughout the study period.

Spatial variations apparent in the soil's chemical and physical composition reveal distinct vegetation and microbial communities across the area. Archaeal 16S rRNA, along with genes associated with N cycling (fungal nirK, nosZI, bacterial and comammox amoA), exhibited correlations with N2O emissions. Archaeal 16S rRNA, bacterial amoA, fungal nirK, and nosZI were positively correlated with N2O emissions. Throughout the year, water table levels and volumetric water content significantly influenced both N2O emissions and the abundance of N cycling genes. The site encompasses specific areas with consistently higher N2O emissions (hot spots) and periodic peaks in emissions (hot moments) due to the combined interplay of physical, chemical, and genetic attributes within the peatland soil.

How to cite: Espenberg, M., Ferch, Z., Kazmi, F. A., Escuer-Gatius, J., Gadegaonkar, S. S., Ranniku, R., Maddison, M., Soosaar, K., Pärn, J., and Mander, Ü.: Hot spots and hot moments of N2O fluxes explained by monthly dynamics of soil microbiome in drained peatland forest, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14300, https://doi.org/10.5194/egusphere-egu24-14300, 2024.

EGU24-14918 | Posters on site | BG3.23

Simultaneous Quantification of Soil Water States, Water Fluxes, Greenhouse Gases and BVOC Exchange between soil and atmosphere during transient conditions 

Efstathios Diamantopoulos, Hai Anh Nguyen, Frederic Leuther, and Anke Nölscher

Biogenic volatile organic compounds (BVOCs) are a diverse group of chemicals emitted from living organisms. These compounds are involved in a variety of ecological processes, as well as the formation of aerosols and ozone, which can impact air quality and climate. Recent studies suggest that BVOCs can be released and taken up by soil through biotic and abiotic pathways in high amounts. In this work, we simultaneously quantified the BVOCs exchange between , soil water evaporation fluxes, and matric potential under transient conditions (drying-rewetting experiments). The experiment was conducted with 250 cm³ soil cores (n=4) packed with sieved soil (loamy sand, bulk density: 1.6g/cm³) taken from agricultural topsoil. Aluminum chambers (1L in volume) were attached to the top of the soil cylinders and gas with different BVOCs concentrations was applied at the inlet. At the outlet, the analysis of BVOCs mixing ratios and BVOCs emission was done with a Proton Transfer Reaction – Time of Flight – Mass Spectrometry (PTR-ToF-MS). In addition, a Greenhouse Gas Analyzer (GGA) was used for monitoring the fluxes of methane, carbon dioxide, and water vapor. The analysis of soil water retention curves was done with a Hydraulic Property Analyzer (HYPROP). The results showed a strong negative correlation between ambient mixing ratios and soil emission rates of water-soluble BVOCs when the soil was wet. As the soil moisture fell below a threshold of 0.18 m3m-3 volumetric water content, BVOCs emission negatively correlated to soil water content. The more frequently the soil was rewetted, the more BVOCs could be taken up by wet soil. In conclusion, the study suggests that the BVOCs mixing ratio in the ambient air was the dominant driving factor of the BVOCs emission rate in disturbed soil samples from agricultural land use. Lastly, soil water content affected BVOCs emission mainly when the soil was dry.

How to cite: Diamantopoulos, E., Nguyen, H. A., Leuther, F., and Nölscher, A.: Simultaneous Quantification of Soil Water States, Water Fluxes, Greenhouse Gases and BVOC Exchange between soil and atmosphere during transient conditions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14918, https://doi.org/10.5194/egusphere-egu24-14918, 2024.

EGU24-15503 | ECS | Posters on site | BG3.23

Differences of nitrogen cycle microbes and nitrous oxide emissions from natural and degraded tropical peatland sites in Malaysia 

Laura Kuusemets, Ülo Mander, Maarja Öpik, Lulie Melling, Kaido Soosaar, Kuno Kasak, and Mikk Espenberg

Tropical peatlands in Southeast Asia are severe threats due to rapid changes in land-cover. Estimates suggest that approximately 25% of natural peatlands in Malaysia have been converted for large-scale agro-industrial development in the last two decades, primarily driven by the rapid expansion of oil palm cultivation. These intense and rapid land-use changes contribute to adverse ecological impacts, including increased greenhouse gas (GHG) emissions, soil degradation, deforestation and the loss of biodiversity. The aim of the study was to assess the genetic potential of nitrogen (N) transformation processes by quantifying functional marker genes of N cycle and measuring nitrous oxide (N2O) emissions from natural tropical peatland and oil palm plantation. This was conducted to understand the effect of land-cover changes on microbial N transformation processes and gaseous N emissions, using the closed chamber method and quantitative polymerase chain reaction (qPCR) analysis. N2O emissions were measured in the natural tropical peatland forest in Maludam (Sarawak, Malaysia) and in the oil palm plantation on peat soil in Betong (Sarawak, Malaysia) in September 2022. qPCR was used to measure the abundance of bacterial and archaeal specific 16S rRNA, nitrification (AOB, AOA and COMAMMOX amoA genes), denitrification (nirK, nirS, nosZ clade I and nosZ clade II genes) and dissimilatory nitrate reduction to ammonium (DNRA; nrfA gene) marker genes in the collected soil, litter and leaf samples.

The average soil N2O emissions were relatively higher from the oil palm plantation, ranging from 2.04 to 131.9 µg N m-2 h-1. Soil N2O emissions from the natural peatland forest were negligible. Quantification of N cycle genes revealed variations in the microbiome between natural peatland and deep-drained oil palm plantation. The microbial analysis showed that the archaeal abundance in leaves did not vary significantly between the two sites, but the abundance of bacteria in leaves was higher in the oil palm plantation. The abundance of denitrifying microorganisms was significantly higher in the natural peatland soil compared to the peat soil in the oil palm plantation. However, the abundances of bacterial amoA and archaeal amoA were found to be lower in the soil of natural site compared to the soil in oil palm plantation, suggesting a higher genetic potential of nitrification in the oil palm plantation. In addition, microbes possessing the archaeal amoA gene seemed to be the primary nitrifiers in the soil of oil palm plantation. The study’s findings indicate that hydrological interventions cause significant changes in the microbial N cycle and N2O emissions of tropical peatlands.

How to cite: Kuusemets, L., Mander, Ü., Öpik, M., Melling, L., Soosaar, K., Kasak, K., and Espenberg, M.: Differences of nitrogen cycle microbes and nitrous oxide emissions from natural and degraded tropical peatland sites in Malaysia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15503, https://doi.org/10.5194/egusphere-egu24-15503, 2024.

Wetting of dry soil after prolonged drought triggers emissions of N-oxides (nitric oxide; NO and nitrous oxide; N2O) and this post-wetting burst may contribute disproportionately to annual soil N-oxides emissions in drylands. During the wetting, nitrification and denitrification were shown to be the major sources of soil N-oxides emissions. Several abiotic reactions involving the nitrification intermediates- e.g. nitrite (NO2-), however, may also contribute to the production of N-oxides in soils. The contribution of these abiotic reaction to N-oxides emissions, despite potential importance is not well quantified. To quantify and partition the contribution of abiotic and biotic processes to post-wetting N-oxides emissions in drylands, we measured soil NO and N2O production in a laboratory incubation with live and gamma-irradiated soils. Samples were collected under canopies of dominant local (Acacia tortilis) and invasive (Prosopis juliflora) trees, as well as from bare soils outside the canopy cover.

We found that that while the overall dynamics of soil NO and N2O emissions were similar in gamma irradiated and live soils under both P. juliflora and A. tortilis trees, as well as in bare soils, the magnitudes and rates of emissions exhibited significant disparities. In particular, gamma irradiated soils under A. tortilis canopies after eight hours’ incubation, emitted ~10 times less NO (~5 ng N g-1) and ~4 times less N2O (~10 µg N g-1) compared to the live soils. While gamma irradiated soils under P. juliflora canopies emitted ~2 times less NO (~7 ng N g-1) and similar N2O (~7 µg N g-1) compared to the live soils, and in the bare soils, ~9 times less NO (~5 ng N g-1) and similar N2O (~10 µg N g-1). Our findings suggest that both biotic and abiotic pathways contribute to N-oxides production following dry soil wetting, however, the relative contribution is dependent on the landscape position and affected by plant presence and species. Specifically, abiotic processes contributed 10% to soil NO and 25% to N2O production in soils beneath A. tortilis canopies and between 10% and 75% in the bare soils. In soil under P. juliflora canopies abiotic processes contributed five times more to the NO production (50%) while N2O production was solely from abiotic activity.

How to cite: Yagle, I. and Gelfand, I.: Quantification and partitioning the contributions of abiotic and biotic processes to soil N-oxides emissions in the Dead Sea valley, Israel., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16201, https://doi.org/10.5194/egusphere-egu24-16201, 2024.

EGU24-17269 | ECS | Orals | BG3.23

Genome-resolved metagenomics of tropical peatland ammonia-oxidising archaea 

Frazer Midot, Kian Mau Goh, Kok Jun Liew, Sharon Yu Ling Lau, and Lulie Melling

Nitrogen cycling, a critical biogeochemical process in ecosystems, involves a complex microorganism network. In nitrification, ammonia oxidation is mainly governed by ammonia-oxidizing archaea (AOA) in acidic soil. Limited information exists about these taxa in tropical peatlands. This genome-centric metagenomic study aimed to identify key taxa and their functional potential driving nitrification in tropical peatlands. After cleaning Illumina reads, draft bins were created, refined, reassembled, and decontaminated through various strategies, involving both semi-supervised and unsupervised binners, including deep-learning-based approaches. This process resulted in 271 medium to high-quality archaeal metagenome-assembled genomes (MAGs). Five near-complete high-quality AOA MAGs were constructed. Phylogenomic analyses placed the AOA MAGs in the Nitrosotalea genus within the Nitrosopumilaceae family. Comparisons to reference genomes using average amino acid identity (AAI) and average nucleotide identity (ANI) suggested these MAGs might represent separate Nitrosotalea species. Besides core ammonia monooxygenase (amoCAB), these Nitrosotalea MAGs also encoded for nitrite reductase (nirK), ferredoxin-nitrite reductase (nirA) and nitric oxide reductase (norQ) that could also lead to the production of nitrous oxide (N2O), a potent greenhouse gas. These tropical peatland autotrophic Nitrosotalea MAGs fixed carbon with the hydroxypropionate/hydroxybutyrate pathway and survive in low pH environments through flagellar motility, various transport proteins, substrate acquisition and pH regulation systems for oxidising ammonia. Genomic analyses of candidate taxa can provide a thorough understanding of important biogeochemical functions as critical baseline information to assess microorganism resilience and response to anthropogenic-induced land use change.

How to cite: Midot, F., Goh, K. M., Liew, K. J., Lau, S. Y. L., and Melling, L.: Genome-resolved metagenomics of tropical peatland ammonia-oxidising archaea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17269, https://doi.org/10.5194/egusphere-egu24-17269, 2024.

EGU24-17493 | ECS | Orals | BG3.23

Differences in the uptake of biogenic volatile organic compounds (BVOCs) between habitat types and peat layers in boreal peatlands 

Aino Korrensalo, Cleo Davie-Martin, Elisa Männistö, James Blande, and Riikka Rinnan

Biogenic volatile organic compounds (BVOCs) released by boreal vegetation have a net cooling impact on climate, both in the boreal and Arctic regions. While boreal forests play a major role in this process, the release and uptake of BVOCs in peatlands is poorly understood, even though they cover up to 28% of the boreal region. Furthermore, soil BVOC sinks and sources are an understudied component of the boreal BVOC budget. Recently, microbial uptake of BVOCs has been found to regulate BVOC release from the soil into the atmosphere. In peatlands, methane emissions from the peat are known to be controlled by microbial oxidation within the living mosses, but it is unknown whether similar uptake occurs with BVOCs.

Our aim was to quantify the release and uptake of BVOCs across different boreal peatland habitats. We collected peat samples, including the living moss layer, from four peatland habitats varying in fertility, wetness, and vegetation composition (bog hollow, bog hummock, fen, bog peat). The samples were split into the living moss layer, as well as the oxic and anoxic peat layers, above and below the water table, respectively. First, we investigated the potential uptake of peat-derived BVOCs in the living moss layer by incubating the peat and moss layers in glass jars both separately and together with other layers from the same habitat. Next, we quantified the uptake of four specific compounds by introducing 13C-labeled BVOCs into jars containing peat or moss layers. The magnitude and compound composition of BVOCs was measured with proton transfer reaction–time of flight–mass spectrometry (PTR-TOF-MS).

Contrary to our expectations, BVOC uptake of peat-derived compounds was observed in the living moss layer, as well as in the oxic and anoxic peat layers. The most important layer for BVOC release and uptake varied between the peatland habitats. For example, the number of released compounds and the total BVOC emissions were largest for anoxic peat in the fen, while it was the living mosses in the bog hollow. Anoxic bog peat had the largest BVOC uptake of all of the habitats and layers. BVOC uptake varied between the studied compounds; while ethanol was taken up by all layers in every habitat, we observed no uptake of acetic acid. Acetone was mostly consumed in the peat layers, while acetaldehyde uptake occurred in bog hummock and fen habitats, regardless of the layer. According to our results, BVOC emissions from boreal peatland soil into the atmosphere are a net outcome of production and consumption both in the peat and moss layers. As these patterns vary even within habitats of the same site, changes in vegetation have the potential to modify BVOC fluxes in boreal peatlands.

How to cite: Korrensalo, A., Davie-Martin, C., Männistö, E., Blande, J., and Rinnan, R.: Differences in the uptake of biogenic volatile organic compounds (BVOCs) between habitat types and peat layers in boreal peatlands, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17493, https://doi.org/10.5194/egusphere-egu24-17493, 2024.

EGU24-18734 | ECS | Orals | BG3.23

Numerical investigation of methanotrophs in a biofilter for methane emission mitigation 

Morgane Bellec, Cristian Picioreanu, Muhammad Ali, and Laurence Gill

Methane is the second highest contributor to human greenhouse gas emissions. In Ireland, it represented 29% of the total CO2 equivalent emissions in 2022. A drastic reduction methane emissions is thus crucial to meet the Paris Agreement commitment of 30% reduction of emissions between 2005 and 2030. It is, however, challenging as more than half of anthropogenic methane emissions are produced at concentrations below 5%. At such low concentrations, methane cannot be efficiently recovered or even flared as it is lower than its flammability level in air. In Ireland, this concerns mainly the agriculture and the waste sector. In terms of wastewater treatment, on-site domestic wastewater treatment systems serve approximately one third of the households in Ireland and so represent a significant source of methane coming from the anaerobic processes (mainly septic tanks).

A promising alternative way to treat methane is microbial oxidation by methanotrophs grown on a suitable porous media. Such a passive biofilter could be easily placed on top of septic tank gas vents, capturing the emitted methane before it is released into the atmosphere. The methane-oxidizing bacteria will then convert it into carbon dioxide, which is approximately thirty times less potent greenhouse gas in terms of global warming potential.

 

Multiple questions must be addressed to confirm the practical feasibility of this methane biofilter concept. The environmental conditions in the filter must allow the methanotrophs to thrive and outcompete other bacteria, thus ensuring an efficient methane oxidation, without obstructing the airflow. In addition to methane, an adequate supply of oxygen is necessary. This requires complex simulations of both the fluid dynamics involved as well as microbial growth and other kinetic dynamics. To investigate these different physical and biological aspects, a numerical study has been conducted combining computational fluid dynamics (CFD) modelling and multispecies biofilm modelling.

The CFD approach is carried on at the system level, producing velocity fields in the septic tank and the different pipes and vents. Knowledge of the gas flow in the full wastewater treatment system is essential to estimate the inlet flow conditions the biofilter will be subjected to depending on the wind weather. The information obtained on the gas phase, especially oxygen and methane levels, is then fed into a multispecies biofilm model. At this local level, we model the methanotrophs as well as the other bacteria expected to grow, compete for space and oxygen, and decay in the biofilter environment: heterotrophs, nitrifiers and Sulphate Reducing Bacteria. The results show that the methanotrophs should not be outcompeted. Moreover, the model enables the height of the filter to be estimated such that it should reach the target of 90% of methane consumption. Finally, transient simulations give insight into the expected time of usage of the filter before it needs to be regenerated.  

How to cite: Bellec, M., Picioreanu, C., Ali, M., and Gill, L.: Numerical investigation of methanotrophs in a biofilter for methane emission mitigation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18734, https://doi.org/10.5194/egusphere-egu24-18734, 2024.

EGU24-19680 | Orals | BG3.23

Bioelectrochemical biosensors for in-situ monitoring microbial activity in outdoor soil mesocosms from postharvest rice field 

Marc Viñas, Maite Martínez-Eixarch, Abraham Esteve-Núñez, Antonio Berna, Belén Fernández, Yolanda Lucas, Cristy Medina-Armijo, Miriam Guivernau, Lluis Jornet, Joan Noguerol, and Carles Alcaraz

The decomposition of buried straw in rice fields during post-harvest generates volatile fatty acids (VFA), thus activating methanogenesis (1). In this study, bioelectrochemical biosensors were used to measure the in-situ electrical current produced by electroactive microorganisms, related to the biodegradation of buired straw,  in outdoor mesocosms containing rice paddy soil from the Ebro Delta (Spain) .

Three  biosensors (BS1-BS3), based on bioelectrochemical cells buried in the water saturated soil (at a -10 cm), were used in 3 rice paddy soil mesocosms, with a poised working electrode (graphite) potential at +0.2V vs Ag/AgCl, by using a potentiostat. During 5 months (November 2022-March 2023), the production of electrical current (I) in the soil mesocosms was monitored using chronoamperometry. The presence of electroactive microbial biofilms on the electrodes was assessed by cyclic voltammetry (CV). Simultaneously, soil chemical parameters were monitored (total and soluble COD, VFA and CH4 emission), and microbial diversity (bacteria and archaea) in  the soil and the electrodes biofilms was assessed by 16S rRNA-metabarcoding.

Chronoamperometry data in BS1-BS3 showed a marked current production curve from the day 3 to 5 after straw addition, with an I max of 110-180µA (4.26-6.91 µA cm-2) at day 10, remaining higher than the baseline for 30-45 days, and concomitant with VFA accumulation  (69-28 mg-eq Acetic kg-1 soil , 7-40 days) and a high emission rate of CH4 (198.1±101.0 mg C-CH4· m-2 soil · h-1 7 days after straw addition. The CV revealed electroactive profiles in the 3 biosensors, similar in BS1-BS2 (oxidation peak -0.16/-0.22 V vs Ag/AgCl, similar to Geobacter), and different in BS3 (oxidation peak +0.26 V vs Ag/AgCl), revealing different electroactive microbial communities. 16S-based metataxonomy revealed an enrichment of well known electroactive bacteria on the three anode biofilm but with different relative predominances, encompassing mainly Desulfobulbus in BS1-BS3,  Geobacter mainly in BS1, but in less predominance in BS2 and BS3, Proteiniclasticum solely in BS3, and Clostridium in BS2 and BS3.  Methanogenic archaea such as Methanosarcina and Methanobacterium were also depicted on the anode, but at lower relative abundance than observed in the soil, where ammonium oxidizing archaea (Nitrososphaera and candidatus Nitrosocaldus) were also predominant.

The results showed the capacity of the bioelectrochemical-based biosensors for real time detection of microbial in-situ degradation processes of buried edible organic carbon (straw) in the soil of rice  paddy fields, also linked to methane emissions.

Aknowledgements
This research was funded by Agencia Estatal de Investigación (PID2019-111572RB-I00/AEI/10.13039/501100011033 ) from Spain.

References
1. Martínez-Eixarch, M., Alcaraz, C., Viñas, M., Noguerol, J., Aranda, X., Prenafeta-Boldú, F. X., Saldaña-De la Vega, J.A., Català, M.M. & Ibáñez, C. (2018). Neglecting the fallow season can significantly underestimate annual methane emissions in Mediterranean rice fields. PLoS One, 13(5), e0198081. DOI: 10.1371/journal.pone.0202159

How to cite: Viñas, M., Martínez-Eixarch, M., Esteve-Núñez, A., Berna, A., Fernández, B., Lucas, Y., Medina-Armijo, C., Guivernau, M., Jornet, L., Noguerol, J., and Alcaraz, C.: Bioelectrochemical biosensors for in-situ monitoring microbial activity in outdoor soil mesocosms from postharvest rice field, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19680, https://doi.org/10.5194/egusphere-egu24-19680, 2024.

EGU24-20187 | Orals | BG3.23

Soil microbial functional diversity changes under contrasting N2O emission events 

Stefania Mattana, Cinta Sabaté, Tiphaine Tallec, Francois Boland, Tanguy Manise, Bernard Heinesch, Iris Feigenwinter, Fabio Turco, Helena Rautakoski, Annalea Lohila, Rossella Guerrieri, Ivan Janssens, Marilyn Roland, Sílvia Poblador, Enzo Magliulo, Luca Vitale, Liyou Wu, Jizhong Zhou, Josep Peñuelas, and Angela Ribas

Denitrification, the reduction of nitrogen oxides (NO3-and NO2-) to NO, N2O and, ultimately, to N2 gas in soils, is classified as a microbiologically ‘broad process’ which can be conducted by a wide array of microbes belonging to remote phylogenetic groups. Further, understanding how environmental and management factors drive denitrification is challenging because they are scale-dependent, with large scale drivers affecting denitrification fluxes both directly and through drivers working at detailed small scales. 

Despite of this, we hypothesized that denitrification processes, although highly complexes due to the multiple processes and environmental conditions involved, they could present a functional convergence at the microbial community level explained by a short list of microbial groups or functions.  

On the other hand, different methodological approaches to assess soil microbial diversity are currently used; among them are multiple substrate-induced respiration by MicroResp™, enzymes activities and functional genes abundance and structure by GeoChip 5S microarray. We applied all those methods to study functional diversity in 5 different soils from 5 countries: Finland, Belgium; France, Switzerland and Italy. Studied soils have a wide range of soil pH, organic Carbon and Nitrogen content, and texture. Soils were sampled at Hot Moment and Low flux emission of N2O.   

The main objective of this study was to explore possible convergences in terms of functional microbial diversity in contrasting N2O emission events (low emission versus hot moments).  

Result showed that MicroResp™ , enzyme activities and GeoChip 5S microarray were reliable ecological indicator to evaluate soil microbial functionality diversity. Results stressed the importance to study soil microbiome at different magnitude of N2O emission with the aim to gain a deeper knowledge of nitrifiers community. Reciprocal relationship of those methodologies, soil proprieties and magnitude of flux emission of N2O are discussed.   

How to cite: Mattana, S., Sabaté, C., Tallec, T., Boland, F., Manise, T., Heinesch, B., Feigenwinter, I., Turco, F., Rautakoski, H., Lohila, A., Guerrieri, R., Janssens, I., Roland, M., Poblador, S., Magliulo, E., Vitale, L., Wu, L., Zhou, J., Peñuelas, J., and Ribas, A.: Soil microbial functional diversity changes under contrasting N2O emission events, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20187, https://doi.org/10.5194/egusphere-egu24-20187, 2024.

EGU24-20747 | ECS | Orals | BG3.23

Dynamics of soil N2O fluxes and hot-moments typification: How are they related to environmental characteristics? 

Maria Cinta Sabaté Gil, Josep Peñuelas, Marcos Fernandez-Martinez, Stephania Mattana, Tiphaine Tallec, François Boland, Bernard Heinesch, Iris Freigenwinter, Helena Rautakoski, Annaela Lohila, Enzo Magliulo, Ivan Jansens, Marilyn Roland, Sílvia Poblador, and Àngela Ribas

To date, extensive field measurements of nitrogen oxide (N2O) exchanges in soils across diverse terrestrial ecosystems, complemented by controlled laboratory incubation studies, have unveiled considerable variability in N2O soil fluxes. This variability arises from the intricate interplay of various factors. Notably, soil N2O emissions display significant spatiotemporal fluctuations, including extreme events. The primary objective of this study is to enhance our understanding of the environmental factors influencing soil N2O fluxes and to characterize instances of pronounced N2O emissions, hereafter termed "hot-moments."

Our investigation encompassed six distinct sites of the Integrated Carbon Observation System (ICOS) network including agricultural systems, sylvicultural systems, and unmanaged forests spanning the northern hemisphere. To identify and categorize hot-moments events, we standardized N2O values and considered events greater than or equal to 4, or -4-fold standard deviations from the mean of each site.

We then conducted wavelet coherence analyses to delve into the patterns of N2O fluxes. In the biwavelet plots, our variable of interest was juxtaposed with each soil environmental variable, illustrating the distribution of correlations in the time-frequency domain of our signals. Employing this advanced approach, we explored N2O patterns and their variability in relation to specific environmental characteristics (soil water content, soil temperature, and CO2 flux) within the six temporal series (different soil types).

Our analyses revealed a recurring pattern across all time series, with a frequency of approximately 24 hours for the N2O vs. CO2 plots, indicating a daily correlation between the emissions of both gases. This correlation may be linked to seasonality in certain sites. Soil temperature emerged as a leading factor in shaping the daily patterns of N2O fluxes in most sites, exhibiting also a 24-hour pattern. Although the periodicities related to soil water content were less clear, a discernible pattern persisted with variations within sites. However, we will deepen into the discussion of these results and their implications in our EGU presentation.

 

Key words: N2O fluxes, hot-moments, soil environmental variables, temporal series, wavelet coherence analysis

How to cite: Sabaté Gil, M. C., Peñuelas, J., Fernandez-Martinez, M., Mattana, S., Tallec, T., Boland, F., Heinesch, B., Freigenwinter, I., Rautakoski, H., Lohila, A., Magliulo, E., Jansens, I., Roland, M., Poblador, S., and Ribas, À.: Dynamics of soil N2O fluxes and hot-moments typification: How are they related to environmental characteristics?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20747, https://doi.org/10.5194/egusphere-egu24-20747, 2024.

EGU24-20969 | ECS | Posters on site | BG3.23

Methanotrophy Potential in Tropical Peatland under Different Land Use in Sarawak, Malaysia 

Claudia Jenai Yeong, Herman Umbau Lindang, Adrian Ho, Sharon Yu Ling Lau, Samuel Lihan, Marcus Andreas Horn, and Lulie Melling

Tropical peatlands hold immense global significance, serving as critical ecosystems that provide a wide range of services including carbon storage. The conversion of a large fraction of tropical peatlands into primarily agricultural lands in Malaysia has raised concern over the dynamics of carbon cycle including methane (CH4) in tropical peat soil. As CH4 is a potent greenhouse gas mainly produced under anoxic conditions, it is widely assumed that the waterlogged nature of peatlands emit a significant amount of CH4, though CH4 emission in tropical peatlands are comparatively lower than boreal peatlands. Methane oxidation (methanotrophy) by methanotrophic bacteria is the only known biological oxidation of CH4. However, there is a limited understanding of the methanotrophy in tropical peat soil of different land use. This study aims to study the methanotrophy potential in both tropical peat swamp forest and oil palm plantations. Soil sampling was carried out in July 2023 (dry season) from peat swamp forest of Maludam National Park and an oil palm plantation (OPP), encompassing both matured and young OPP. All sites are historically from Mixed Peat Swamp (MPS) forest type. Peat sample was collected from the topsoil (0-10 cm depth). Methanotrophy potential was assessed by incubation in 100 mL vial bottle supplemented with 2-3% v/v CH4. Soil pH, moisture content, total C and N, and electrical conductivity were determined. The total N differs significantly (p<0.05) with 1.93%, 1.72%, and 1.53% in the peat swamp forest, matured OPP, and young OPP, respectively. Total N has been associated with methanotroph community composition and its oxidation activity. Soil methanotrophy ranged from 0.35 to 0.60 µmol g dw soil-1 day-1 during the microcosm study. Results from this incubation demonstrated methanotrophy potential rate across three sites showed no significant difference, suggesting methanotrophy of topsoil may not be affected by different land use. In addition, the methanotrophy rate showed no correlation with the total N in this study. Nevertheless, validation of pmoA gene abundance across different land uses using quantitative polymerase chain reaction analysis will be conducted to further confirm if methanotrophy is affected by different land use on tropical peat soil.

How to cite: Yeong, C. J., Lindang, H. U., Ho, A., Lau, S. Y. L., Lihan, S., Horn, M. A., and Melling, L.: Methanotrophy Potential in Tropical Peatland under Different Land Use in Sarawak, Malaysia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20969, https://doi.org/10.5194/egusphere-egu24-20969, 2024.

EGU24-21985 | Posters on site | BG3.23

Dynamics of Microbial Communities and Greenhouse Gas Flux Responses to Short-Term Flooding in Riparian Forest Soil 

Kristel Reiss, Ülo Mander, Maarja Öpik, Kärt Kanger, Thomas Schindler, Kaido Soosaar, and Mikk Espenberg

The growing interest in the impact of short-term floods on various ecosystems is driven by climate change and the increasing occurrence of extreme rainfall events. The control of nutrient quantity and distribution relies on complicated biogeochemical processes. Yet, our understanding of the microbial processes governing carbon and nitrogen cycling needs improvement, hindering our ability to estimate the effects of climate change on forests.

This study aimed to evaluate the influence of short-term flooding on bacterial, archaeal, and fungal communities and microbial processes with greenhouse gas (GHG) emissions in riparian alder forests. Topsoil peat samples were collected from riparian alder forests and analyzed with quantitative polymerase chain reaction (qPCR), and sequencing techniques were employed to assess processes and communities, while physicochemical parameters and in-situ GHG emissions were concurrently measured.

Floods exert a substantial influence on the intricate biogeochemical cycles within soil ecosystems. The flooding event led to a change in bacterial 16S rRNA abundances and a noticeable expansion in the size of Bryobacter and Candidatus Solibacter communities associated with the breakdown of organic carbon. Several aerobic genera like Arthrobacter, Ferruginibacter, Lacunisphaera, and Novosphingobium, which were identifiable before short-term flooding, became undetectable. Many of these organisms were known for their role in breaking down carbon compounds, highlighting the transformative impact of short-term flooding on the composition and functions of soil microbial communities and GHG emissions.

In the examined sites, a diverse array of arbuscular mycorrhizal (AM) fungal genera were identified, including Acaulospora, Archaeospora, Claroideoglomus, Diversispora, and Paraglomus. One pivotal aspect of these fungal communities is their role in establishing arbuscular mycorrhiza, a beneficial symbiotic association between plant roots and fungi. AM fungi contribute significantly to enhancing plant nutrition, stress resistance, and shaping soil structure and fertility.

Nitrifiers, particularly those associated with archaeal amoA, experienced notable shifts. Denitrifiers, identified through the nosZII gene, were also significantly impacted. Moreover, microorganisms engaged in the n-damo process displayed alterations. The flooding event was observed to augment the community size of denitrifying and nitrogen-fixing genera such as Rhodanobacter, Pseudolabrys, and RB41. In contrast, a decrease was noted in the abundance of nitrifiers, exemplified by the decline of Nitrospira. Furthermore, several associations were observed between marker genes of the nitrogen cycle and N2O emissions.

How to cite: Reiss, K., Mander, Ü., Öpik, M., Kanger, K., Schindler, T., Soosaar, K., and Espenberg, M.: Dynamics of Microbial Communities and Greenhouse Gas Flux Responses to Short-Term Flooding in Riparian Forest Soil, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21985, https://doi.org/10.5194/egusphere-egu24-21985, 2024.

SSS5 – Soil Chemistry and Organic Matter Dynamics

EGU24-221 | ECS | Orals | SSS5.2

Effects of Contrasting Organic Amendments on Carbon Stability and Soil Carbon Dynamics in Acidic and Alkaline Soils  

Sara M. Pérez-Dalí, Águeda Sánchez-Martín, Jorge Márquez-Moreno, Jose A. González-Pérez, Layla M. San-Emeterio, and José María de la Rosa

The application of organic amendments, both traditionally utilized (e.g., compost) and more recent innovations (e.g., biochar), to degraded agricultural soils is being driven by international initiatives in the current context of global change, such as the "4 per mil initiative". The main goal is to achieve sustainable soil quality restoration, contributing to carbon (C) sequestration, while also providing a practical use and value addition to agro waste products. Despite the generally recognized benefits of such applications on soil productivity and physical properties [1,2], their effects on soil C cycling and sequestration are not as comprehensively understood. Results exhibit considerable variability depending on the type of amendment and the specific soil, emphasizing the need for a more in-depth investigation in this area [3]. Therefore, the aim of this study was to analyze the effects of contrasting organic amendments on soil carbon stability.

To accomplish this, two soils commonly employed in humid grasslands of the northern region and rainfed agriculture in the southern region of the Iberian Peninsula, respectively, were amended in triplicate at 10% (w/w) with wastewater sludge biochar, olive pomace biochar , white poplar wood biochar, rice husk biochar, cow manure digestate, a mixture of cattle manure and straw digestate (CM&SD), green compost (GC), and a mix of GC and OPB. A control was also established for each type of soil. After inoculating all the vessels with 1 mL of a standard microbial solution, respiration rates (CO2 emissions) were measured every 6 h over 100 days using an automated respirometer (Nordgren Innovations, Sweden) under controlled conditions (25°C; 60% water holding capacity). The data obtained were plotted against the incubation time by an exponential curve to discern the C stability through fast and slow C pools.

Our findings revealed significantly enhanced stability of recalcitrant carbon (slow C pool) in both soils treated with biochars, particularly in the case of RHB and WB. These amendments substantially extended the mean residence time of the slow C pool (MRT2) by a factor of six to nine. The overall trend observed for the studied amendments was as follows: biochar >> green compost >> digestates > native soil carbon. In contrast, the alkaline rainfed soil exhibited a faster carbon turnover rate compared to the grassland soil, resulting in a lower C MRT2.

Acknowledgements:  The Spanish Ministry of Science and Innovation (MCIN) and AEI are thanked for funding the project RES2SOIL (PID2021-126349OB-C22). The European Joint programme EJP SOIL from the EU Horizon 2020 R&I programme is thanked for funding the subproject EOM4SOIL (Grant agreement Nº 862695).

References:
[1] De la Rosa, J.M., Pérez-Dalí, S.M., Campos, P., Sánchez-Martín, Á., González-Pérez, J.A., Miller, A.Z., 2023. Agronomy, 13, 1097.
[2] Doblas-Rodrigo, A., Gallejones, P, Artetxe, A., Merino, P., 2023. Sci. Total Environ., 901, 165931.
[3] De la Rosa, J.M., Rosado, M., Paneque, M., Miller, A.Z., Knicker, H., 2018. Sci. Total Environ., 613-614, 969-976.

How to cite: Pérez-Dalí, S. M., Sánchez-Martín, Á., Márquez-Moreno, J., González-Pérez, J. A., San-Emeterio, L. M., and de la Rosa, J. M.: Effects of Contrasting Organic Amendments on Carbon Stability and Soil Carbon Dynamics in Acidic and Alkaline Soils , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-221, https://doi.org/10.5194/egusphere-egu24-221, 2024.

ABSTRACT

Nowadays, due to high population pressure more fragile lands are put into farming which then leads to low crop yield, loss of biodiversity and above all contributing to increased greenhouse gas emissions. This two year study (2020-2021) evaluated the potential of legume green manure (GM) species in improving soil fertility and barley yield, and their ability to effectively sequester soil organic carbon (SOC) towards reducing greenhouse gas emissions. The GM crops; lupine and vetch were planted during the main rainy season on the land that previous barley crop was harvested and left bare and fallow. The green manures crops were chopped and ploughed under at their 50% flowering stage and the main test crop, barley was introduced during the next cropping season. The treatments included (i) vetch GM, (ii) vetch GM + 23N + 20P, (iii) lupine GM, (iv) lupine GM + 23N + 20P, (v) fallow, (vi) fallow + 46N + 20P laid down in RCBD design with three replications. The N rate used was half when integrated with the GM species but full dose with the fallow system, whereas P was full dose. Results showed that barley grain & biomass yields were increased by 3.7 to 39.8% and 10.66 to 38.58%, respectively due to the application of the GM crops. The highest grain yield (4.1 t ha-1) and biomass yield (10.1 t ha-1) were recorded from vetch + NP application while the least grain yield (2.94 t ha-1) & biomass yield (7.24 t ha-1) were registered from the traditional fallow system. Green manure addition has brought 25 to 95.41% SOC relative change in the top 0-20cm soil depth compared with the traditional fallow system. Since both GM species are legumes, they added more N to the soil alongside with storing more C in the soil so that C: N ratio was also not affected. The highest carbon sequestered was from sole application of vetch GM (26.18 t C ha-1 yr-1) followed by vetch + NP applications (22.82 t C ha-1 yr-1). Lupine GM alone sequestered 9.24 t C ha-1 yr-1 and lupine + NP sequestered 6.86 t C ha-1 yr-1. The carbon balance in the fallow and fallow + NP combinations were negative (-0.98 and -1.40 t C ha-1 yr-1, respectively) indicating that there was C loss to the atmosphere. Therefore, application of vetch and lupine GMs with and/or without inorganic fertilizer integration had positively contributed towards improving the yield of barley and sequestering more C as compared to the local fallow practice.

How to cite: Debele, G. G., Kassie, K., and Getachew, T.: Improving Carbon Sequestration and Yield of Barley (Hordeum vulgare) through Combined Application of Green Manure and Mineral Fertilizers under Cambisols in Ethiopian Highlands, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-802, https://doi.org/10.5194/egusphere-egu24-802, 2024.

EGU24-1004 | Posters on site | SSS5.2

Comparative effect of incorporated and surface spread crop residues, poultry manure and their biochars on soil health indicators along a soil profile  

Tanvir Shahzad, Rummana Basit Mir, Umme Aiman Fiaz, Huma Shahid, Fiza Arshad, and Muhammad Sanaullah

Biochar is being touted as a wonderful amendment for improving soil health. However, its effectiveness for alkaline soils that are poor in organic matter has rarely been evaluated, particularly in long term field experiments. We laid down a field experiment based on wheat-maize crop rotation where we either incorporate or spread on surface the residues of the previous crop (wheat or maize), poultry manure or biochar(s) derived from these organic amendments. They are applied at the rate of 2 tons ha-1 before sowing each crop. It was hypothesized that the organic amendments applied in their feedstock or biochar form will considerably differ in space and time vis-à-vis soil health indicators. Moreover, tillage (incorporation i.e., conventional tillage vs surface spreading i.e., no tillage) would significantly alter the effect of these organic amendments. Over two years and four cropping seasons, the CO2-C emissions from the field were significantly higher (12-17%) when residues or biochar were incorporated. However, the feedstocks (residues/manure) induced significantly higher CO2-C emissions than their respective biochars across the tillage treatments (13-23%). Furthermore, the ammonia emissions were significantly reduced when biochars were added (5-11%) where surface spreading, or incorporation didn’t induce any difference. First soil sampling was done till 75 cm in depth increments of 15 cm, after two years of the experiment (Nb: the experiment is running). Microbial biomass (MBC) was significantly higher in upper layers (0-15 cm, 15-30 cm) in the plots incorporated with residues while all other amendments or tillage treatments showed similar MBC. No change in MBC was observed below 30 cm in any treatment. The soil organic carbon content (& stocks) were slightly but significantly higher (by 5-14%) in upper layers where biochars were incorporated, whereas incorporating residues increased soil organic carbon compared to biochar surface spreading. The extracellular enzymatic activity particularly of β-glucosidase, was significantly altered to 60 cm in some treatments with residue addition (incorporation or spreading) inducing higher activity. The leucine aminopeptidase activity remained unchanged throughout the soil profile in most of the treatments. However, chitinase activity was significantly higher in some biochar amended soils. These preliminary results indicate that residues/manure as well as their biochar significantly improve soil health indicators and that their method of application (incorporation vs spreading) significantly alter their effects. However, it must be noted that both types of amendments have improved different soil health indicators at this stage of the experiment.  

How to cite: Shahzad, T., Mir, R. B., Fiaz, U. A., Shahid, H., Arshad, F., and Sanaullah, M.: Comparative effect of incorporated and surface spread crop residues, poultry manure and their biochars on soil health indicators along a soil profile , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1004, https://doi.org/10.5194/egusphere-egu24-1004, 2024.

EGU24-1152 | ECS | Orals | SSS5.2

Soil moisture determines dead wood effects on soil organic matter in temperate beech forests 

Robin Schäfferling, Lilli Zeh, Patrick Wordell-Dietrich, Alina Azekenova, Alexandra Koller, Kenton Stutz, Karl-Heinz Feger, Stefan Julich, Goddert von Oheimb, and Karsten Kalbitz

Dead wood has important functions in forest ecosystems. It is a biodiversity hot spot, serves as a storage of water and stores 8% (73 +- 6 Pg) of the world’s forest carbon (Pan et al., 2011). The fate of this carbon (C) is still highly debated particularly concerning its influence on soil organic matter (SOM) and its contribution to the forest soil’s C sink. The aim of this research is to investigate how downed beech dead wood affects the stable soil C pool of temperate beech forests, and how this depends on soil moisture.

The research was conducted in a near natural beech forest near Leipzig, Germany (Dübener Heide) and is part of the BENEATH-Project. We sampled three sites representing a soil moisture gradient, i.e. dry, intermediate (i.e. moist) and wet conditions. Undisturbed soil cores were taken from these sites in three depth (0-10 cm, 10-20 cm and 20-30 cm) beneath dead wood at an advanced stage of decay. Reference soils were sampled at a distance of about 2 m. Soil moisture and soil temperature are constantly monitored. We applied a physical fractionation scheme to identify the effects of dead wood on differently stable SOM fractions. The samples were separated in the free light fraction (F-LF), the occluded light fraction (O-LF) and the heavy fraction (HF) via density fractionation using sodium polytungstate solution (ρ =1,6 g cm-³). For each fraction, the organic C and N contents were determined.

Our results indicate a positive influence of dead wood on SOC stocks in the dry and wet regions of our soil moisture gradient. In the intermediate region of the soil moisture gradient, dead wood has no or even a negative effect on SOC stocks. Changes in the SOC content under dead wood compared to the reference soil occurred manly in the F-LF and HF fraction at 0 cm and 10 cm depth. The observed pattern of dead woods effect on SOC along the moisture gradient is suggested to be a result of the relationship between soil moisture and microbial activity. According to the literature, we assume that the microbial activity should be highest in the intermediate moist soil and to some extent inhibited under either wet or dry conditions. In this case, it is not the input but the rate of decomposition that changes with soil moisture, resulting in a different net increase in SOC. To test our hypothesis, we attempt to estimate the theoretical time of effective microbial decomposition per year based on soil moisture and soil temperature data for our three sites. Correlation analysis will be used to test this indicator of microbial activity for the effect of dead wood on SOC.

Our results should sharpen the picture of the dead wood’s role for long-term C stabilization in forest soils and how this process is affected by differences in the soil moisture status. They will give implications for climate mitigating forest management.

How to cite: Schäfferling, R., Zeh, L., Wordell-Dietrich, P., Azekenova, A., Koller, A., Stutz, K., Feger, K.-H., Julich, S., von Oheimb, G., and Kalbitz, K.: Soil moisture determines dead wood effects on soil organic matter in temperate beech forests, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1152, https://doi.org/10.5194/egusphere-egu24-1152, 2024.

EGU24-1321 | ECS | Posters on site | SSS5.2

A demonstration of the compositional stability of saline-hosted sedimentary carbon in a coastal wetland 

Mollie Lowrie, Mark Schuerch, Jack Lacey, and Daniel Magnone

Tidal wetlands sequester around ~4.8-87.2 Tg of carbon per year1 and represent approximately 25% of the global carbon sink, as a result of high inputs of organic matter and slow below-ground decomposition. The rate of carbon storage is hypothesised to be linked to the composition, particularly the relative oxidation, of soil organic carbon and the relationship with the sediment mineral matrix. The complex and dynamic biogeochemical processes governing tidal wetland carbon are not yet fully understood and therefore, the aim of this research was to understand how the composition of organic material varies across a tidal wetland and how this in turn is related to source, mineralogy and salinity.

Topsoil (0-20cm) and subsoil (20-40 cm) samples were collected from three marshes along a transect representing a salinity, inundation and elevation gradient and were analysed to assess the variations of SOC source, prevalence and composition, as well as the influence of salinity and sediment mineral composition on SOC stabilization.

SOC in the saline environments was highly oxidised with a low oxidation potential and thus had a particularly stable composition. In contrast, the carbon in the freshwater marsh was significantly less oxidised and thus demonstrated a greater potential for CH4 and CO2 emission. Carbon isotope (δ13C) and C:N analysis revealed that the SOC in all sites was produced in-situ by C3 plants, but highlighted differences between the photosynthetic pathway of the vegetation in each marsh. The freshwater marsh carbon was also more δ13C depleted, indicative of methane-consuming organisms and we hypothesise this variation in production pathway links to oxidation state.  

The compositional stability of SOC affected overall concentrations with the highest concentration of SOC in the first 20 cm of sediment in the high saltmarsh (between 0.35% and 5.34% w/w) and the lowest concentration of SOC in the lower 20-40 cm of sediment of the freshwater marsh (0.4% - 2.7% w/w). SOC prevalence is also positively associated with Fe-Al clay minerals, which was the dominant sediment type in the saltmarshes, whereas the freshwater marsh was predominantly siliceous sediment.

We conclude that the relative stability and concentration of SOC is greatest in the saltmarshes compared to the freshwater marsh. This aligns with emerging theory that mineral association is an important pathway of SOC stabilisation, and that salinity may exhibit a positive effect on cation bridging between organic material and mineral surfaces.

Acknowledgements: This project received funding from the National Environmental Isotope Facility (# 2656.0424).

References: Mcleod, E., Chmura, G. L., Bouillon, S., Salm, R., Björk, M., Duarte, C. M., Lovelock, C. E., Schlesinger, W. H., and Silliman, B. R.: A blueprint for blue carbon: toward an improved understanding of the role of vegetated coastal habitats in sequestering CO2, Frontiers in Ecology and the Environment, 9, 552–560, https://doi.org/10.1890/110004, 2011. 

How to cite: Lowrie, M., Schuerch, M., Lacey, J., and Magnone, D.: A demonstration of the compositional stability of saline-hosted sedimentary carbon in a coastal wetland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1321, https://doi.org/10.5194/egusphere-egu24-1321, 2024.

EGU24-1635 | ECS | Posters on site | SSS5.2

The impact of land use change on soil organic carbon pools: A multi-method assessment 

Marcus Schiedung, Pierre Barré, and Christopher Poeplau

Soil organic carbon (SOC) is significantly affected by land use change (LUC), which can lead to either SOC losses or gains. In consequence, LUC is a major controlling factor of total SOC contents and its dynamics. In general, LUC from forest or grassland to permanent cropland results in losses of SOC, while the reverse can result in long-term gains. Several methods have been developed to assess distinct SOC pools. This includes particle size separation, thermal analysis and soil reflectance spectroscopy. The responses of such defined SOC pools to LUC have rarely been studied comprehensively, while doing so is a straightforward way to reveal their biogeochemical relevance. Here we used 23 sites covering six different LUC (i.e. forest-cropland, grassland-cropland, grassland-forest, cropland-grassland, cropland-forest and cropland-perennial Miscanthus) to assess SOC pool changes. We used particle size fractionation to obtain coarse (>50µm) and fine (<50µm) fractions and Rock-Eval 6 analysis to estimate active and stable SOC pools. Additionally, we used mid-infrared spectroscopy (Diffusive Reflectance Infrared Fourier Transformed Spectroscopy (DRIFT)) on bulk soils and particle size fractions to determine the relative SOC composition.

All methods identified kinetically different SOC pools across all LUC. The fine particle size fraction, representing a stabilized and slow cycling SOC pool, was more responsive to LUC compared to the stable pool estimated using Rock-Eval. Assessing the relative changes of total SOC and organic carbon contents of the fractions across all LUC, showed that the fine particle fraction follows closely the total SOC changes (R2=0.91 with slope of 0.77). In comparison, the stable pool extracted by Rock-Eval was less dynamic (R2=0.72 with a slope of 0.43). Absolute changes in bulk SOC were well described by the absolute organic carbon change of extracted Rock-Eval pools (active: R2=0.99 and stable: R2=0.91), while organic carbon changes of the particle size fractions were less sufficient to describe bulk SOC changes (coarse: R2=0.77 and fine: R2=0.33). The SOC composition, determined by DRIFT, revealed that changes in the relative composition of fast cycling aliphatic to slow cycling aromatic compounds can well explain relative total SOC changes (R2=0.81). This shows that three conceptually different methods (physical, thermal and spectroscopic) are suitable to determine SOC pool changes for a large diversity of LUC, but the sensitivity of the individual pools can differ strongly, depending on the method.

How to cite: Schiedung, M., Barré, P., and Poeplau, C.: The impact of land use change on soil organic carbon pools: A multi-method assessment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1635, https://doi.org/10.5194/egusphere-egu24-1635, 2024.

Given that microbial mediated input of crop residues and their humification products may be more conducive to the transformation and sequestration of soil organic matter. The study aims to use 13C15N double labeling tracing technology in incubation experiments to quantify the differences in the fate and distribution contribution of the C and N of crop residues and their decomposition products under the mediation of different exogenous microorganisms with different life strategies in soil organic matter (SOM) and dissolved organic matter (DOM). The study utilized exogenous microorganisms, such as Trichoderma reesei, Trichoderma harzianum, and Phanerochaete chrysosporium (K-strategists), as well as Bacillus subtilis (r-strategist). Additionally, a combination microbial treatment comprised of Trichoderma harzianum, Phanerochaete chrysosporium, and Bacillus subtilis was also employed. The study also aims to reveal the variation patterns of soil active organic carbon and humic carbon components in response to different exogenous microorganisms. The main conclusions of the study are as follows:

  • The addition of exogenous k-strategy microorganisms was more favorable than r-strategy microorganisms in mediating the increase in soil SOM contribution of crop residues derived C and N.Trichoderma treatments were more adept at mediating crop residues derived dissolvd organic carbon, and k-strategy microorganisms were more likely to stimulate soil production of dissolved nitrogen. Although the combination microbial treatment was the most effective at translational immobilization of crop residues in SOM, the Trichoderma reesei treatment had the best ability to increase soil organic carbon content by mediating crop residues translational immobilization with the lowest depletion of SOM. In addition, the addition of K-strategy microorganisms was more effective than r-strategy microorganisms in increasing the content of labile organic carbon and humic carbon fractions in the soil.
  • Fungimediated humification products was significantly better than bacterial and no microbe mediated for translational immobilization in soil, and the fungal treatments contributed more to DOM and stimulated soil deriving dissolved nitrogen. The Trichoderma reesei treatment was the most effective in immobilizing the carbon and nitrogen dereived from humification products. Fungi mediated humification products was superior to bacteria in boosting labile organic carbon and humic acid fractions. The Trichoderma reesei treatment was the most effective in boosting contents of easily oxidizable organic carbon, microbial biomass carbon and humic acid carbon, whereas the combination microbial treatments significantly increased fvlic acid carbon and substantially reduced PQ values in the early part of the experiment, and the three fungal treatments were effective in increasing fvlic acid carbon in the later part of the experiment.

In summary, these conclusions provide a theoretical basis for seeking suitable microbial regulation of farmland management measures to improve SOM transformation and humification effects and provide practical reference for scientifically guiding agricultural production and soil carbon sequestration and fertilization.

How to cite: Zhang, Y.: The impact of microbial-mediated crop residues and their humification products on transformation of soil organic matter, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2329, https://doi.org/10.5194/egusphere-egu24-2329, 2024.

Soil contains three times more carbon (C) than the atmosphere and biosphere combined. It therefore represents an important tool for removal of carbon dioxide (CO2) from the atmosphere and its long term sequestration. However, in the current climate crisis, C that is already stored in soil reservoir represents a potential threat because different fractions of C in soil have different stability against the rising global temperatures. C is stored in soil in the form of soil organic matter (SOM) which is a mixture of many different organic components. Based on different properties we can divide SOM into two pools. The first pool is represented by small fragments of dead biomass referred to as free particulate organic matter (FPOM). The other pool is comprised of organic matter, usually chemically transformed or converted to microbial necromass, which is in various ways associated with soil mineral matrix. This pool is referred to as mineral associated organic matter (MAOM). It is assumed that MAOM becomes C saturated during soil development because it is limited by the amount of available mineral surfaces. FPOM, on the other hand, does not saturate and can therefore play an important role in later stages of soil development. Beside this some OM is stored in organic horizons in forest floor (Oe layer), which we expect will have similar pattern as FPOM. However, there is scarcity of studies that examine this assumption. In this work we studied the hypothesis that soils in different stages of development will differ in the amount of C stored in FPOM and MAOM fractions. On top of that, we assumed that this difference will be affected by the dominant tree species growing on the soil and the effect of tree species and soil age will not always be additive. We tested this hypothesis by analyzing C storage in soil and amount of C in FPOM and MAOM using two types of soils - recultivated spoil heap (immature soil) and forest soil in the surrounding area (mature soil). Plots with only one type of tree species (spruce or alder) in 3 replications were present on each of these soil types. Our results show that different tree species have different effects on the amount of C stored in mineral soil and Oe layer in immature and mature soils. In mineral soil more, C was sequestered under alder on recultivated heap, while in the surrounding area no difference between tree species was found. In Oe layer more C was sequestered under spruce in both types of soils. Soils did not differ in the amounts of FPOM and MAOM present in soil, but they did differ in the amount of C stored in these fractions. In young soil, MAOM fraction stored more C under alder than spruce. For mature soil the opposite was true. For FPOM fraction no significant effect of tree species or soil age was found but in young soil higher C storage in FPOM was found under alder compared to spruce.

How to cite: Hüblová, L. and Frouz, J.: Sequestration of soil organic matter in broadleaf and coniferous forests in soil at various stages of pedogenesis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2696, https://doi.org/10.5194/egusphere-egu24-2696, 2024.

EGU24-3039 | Posters on site | SSS5.2

Effect of topsoil dilution on stabilization of plant derived carbon 

Maire Holz, Bryan Salzmann, Rainer Remus, Valerie Pusch, Eva Mundschenk, Mathias Hoffmann, and Jürgen Augustin

Soil tillage often results in tillage erosion in hilly croplands, i.e. to subsoil incorporation into topsoil. However, up to now effect of tillage erosion on the turnover and stabilization of freshly added plant material remains poorly understood. We therefore conducted an incubation experiment comparing topsoil, diluted topsoil and subsoil from an erosion effected field site in north-east Germany. (14)CO2 respiration was traced over a period of 33 days after addition of 14C labelled plant residues and (14)C incorporation into several C fractions was studied. The topsoil showed increased C turnover compared to subsoil, however, topsoil dilution resulted in slightly higher C fluxes than in the topsoil, indicative of a more diverse microbial community. The addition of plant residues induced increased decomposition of native soil organic matter, resulting in a priming effect of similar magnitudes in all treatments ranging around 20%. This indicated that C might not be preferentially stabilized in the studied diluted topsoils or in the subsoil. In terms of carbon fractionation, topsoil dilution primarily affected the POM and MAOM (< 20 µm) fractions, with a decline in the order of topsoil > diluted > subsoil. Freshly assimilated carbon was preferentially stabilized in the MAOM fraction (<20µm), especially in subsoils, indicating potential for carbon stabilization in these soils. Overall we observed small effects of topsoil dilution on soil C storage, however, it's important to note that this study used shoot material, which is less intensively retained in soil compared to root material. Topsoil dilution seems to be a promising way to enhance C sequestration but further research is needed to assess its effectiveness for long-term soil carbon sequestration and to evaluate the role of root-derived carbon in these processes.

How to cite: Holz, M., Salzmann, B., Remus, R., Pusch, V., Mundschenk, E., Hoffmann, M., and Augustin, J.: Effect of topsoil dilution on stabilization of plant derived carbon, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3039, https://doi.org/10.5194/egusphere-egu24-3039, 2024.

EGU24-3492 | Orals | SSS5.2

Microbial and mineral interactions decouple litter quality from soil organic matter formation  

Jeanette Whitaker, Kelly Mason, Ashley Taylor, Pengzhi Zhao, Tim Goodall, Rob Griffiths, Niall McNamara, and Dafydd Elias

Mineral-associated organic matter (MAOM) forms from plant or microbial-derived compounds and comprises the largest reservoir of soil organic carbon (SOC) globally.  Most SOC is associated with soil minerals and mineralogy is considered a primary control on SOC persistence due to variations in mineral reactivity. However, most mineral-associated SOC is microbial in origin thus microbial residue formation, through the processing of plant inputs, may also control SOC dynamics. Current understanding suggests that litter quality controls the formation of MAOM with high-quality litter producing more microbial residues which are then stabilised on mineral surfaces. We hypothesized that inputs of high-quality litter would lead to a net increase in MAOM stocks, relative to low-quality litter, through more efficient formation of MAOM and less priming of existing SOC.  We also hypothesised that soil mineralogy would act as the primary control on the formation of MAOM relative to litter quality. To test our hypotheses, we amended an agricultural soil with common soil minerals (Kaolinite, Montmorillonite and unamended control) and incubated these amended soils in the laboratory with two surface-applied 13C labelled litters of contrasting qualities (high quality - White Clover and low quality - Winter Wheat). During the incubation, litter decomposition and priming were quantified by δ13CO2 analysis. After 4 months, mineral stabilisation of litter-C, the amounts of particulate organic matter (POM) remaining and litter-C assimilated into microbial biomass were all quantified, along with characterisation of the soil microbial communities. Soil mineralogy strongly influenced the efficiency of MAOM formation, with Montmorillonite-amended soils respiring less litter-C and stabilising more as MAOM. High quality litter led to less (not more) efficient production of MAOM due to soil microbial community shifts associated with lower carbon-use efficiency. Low-quality litter enhanced priming of pre-existing SOC, counterbalancing the effect of litter quality on MAOM stocks.  Taken together, our findings demonstrate that soil mineralogy was the primary control on MAOM formation and that litter-microbial interactions determine the effect of litter quality on MAOM.  These findings refute the hypothesis that high-quality plant litters form MAOM most efficiently and demonstrate that mineral and microbial interactions regulate the formation of stable SOC.

How to cite: Whitaker, J., Mason, K., Taylor, A., Zhao, P., Goodall, T., Griffiths, R., McNamara, N., and Elias, D.: Microbial and mineral interactions decouple litter quality from soil organic matter formation , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3492, https://doi.org/10.5194/egusphere-egu24-3492, 2024.

Most of the organic carbon (C) in soil is linked to various degrees with the mineral matrix, which includes the formation of aggregates and the association of organic C with clay minerals and Fe and Al hydro(oxides). Both mechanisms ensure the physical stabilization of organics against microbial decomposition and the stability of the soil system. The present work analyzed the processes of C stabilization, and C flows between the aggregate size classes of macro- and macroaggregates and density fractions (free and occluded light (FL, OL), occluded dense (OD) and mineral (MF)) based on the 13C natural abundance approach using 73 published works and looked at the two groups of factors: i) internal (edaphic soil properties) and ii) external (type of land use and climate).

The global pattern showed the relative enrichment of 13C in silt + clay fraction for 0.4‰ and MF for 0.25-0.6‰ compared to bulk soil. In contrast, organics in micro- and macroaggregates and FL and OL fractions were 13C depleted, reflecting the fast decomposition of these pools and input of fresh plant-derived organics. The difference in 13C enrichment between the OL and MF fractions was 1.3‰, whereas between macroaggregates and silt+clay fraction 0.6‰, showing that density fractionation could more accurately reflect the intensity of organic C processing by microorganisms and fractions are more homogeneous in composition than aggregates.

The 13C enrichment in silt + clay and MF increased with the clay content; the difference between the 13C enrichment for OL and both dense fractions and macroaggregates and silt + clay fractions rose. Forests, grasslands, and croplands showed the same trend of increasing 13C enrichment with decreasing aggregate size classes; grasslands and croplands showed higher enrichment of silt+clay associated C (~0.3‰ relative to bulk soil) than forests. Under grasslands and forests, 13C enrichment in OD and MF was higher than in agriculture, showing deep microbial processing of organic matter without structure disturbance. The differences in 13C enrichment of organic matter between the aggregate size classes (0.6-0.9‰) and density fractions (2.5-3‰) were higher under subtropical and tropical climates, compared to temperate and Mediterranean, reflecting more intensive recycling of organic matter by microorganisms.

C flows between the aggregates followed the trend from macroaggregates to silt+clay fraction and from large macro- to microaggregates, reflecting the well-known sequential formation of soil structure and macro aggregates' role in stabilizing plant residues. More intensive C flows were found from FL to MF, compared to the C flow from OD to MF, pointing to the importance of plant-derived organics and microbial metabolites for the formation of MF. Thus, the global pattern of organic C transformation identified that the 13C natural abundance approach could be used for a broad range of automorphic soil types and can open a new perspective for the estimation of processes of C recycling and reveal the intensity of microbial processes depending on the land use, soil edaphic factors and climate.

How to cite: Gunina, A., Wang, Y., and Kuzyakov, Y.: 13C natural abundance approach for analysis of steps of organic carbon transformation in soil: application for various ecosystems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4695, https://doi.org/10.5194/egusphere-egu24-4695, 2024.

EGU24-5359 | ECS | Orals | SSS5.2

Cover Crops Affect Pool Specific Soil Organic Carbon in Cropland – a Meta-analysis 

Julia Fohrafellner, Katharina Keiblinger, Sophie Zechmeister-Boltenstern, Rajasekaran Murugan, Heide Spiegel, and Elena Valkama

Cover crops (CC) offer numerous benefits to agroecosystems, particularly in the realm of soil organic carbon (SOC) accrual and loss mitigation. However, uncertainties persist regarding the extent to which CCs, in co-occurrence with environmental factors, influence SOC responses and associated C pools. We therefore performed a weighted meta-analysis on the effects of CCs on the mineral associated organic carbon (MAOC), the particulate organic carbon (POC) and the microbial biomass carbon (MBC) pool in arable cropland. Our study summarized global research of comparable management, with a focus on climatic zones representative of Europe, such as arid, temperate and boreal climates. 
    In this meta-analysis, we included 71 independent studies from 61 articles published between 1990 and June 2023 in several scientific and grey literature databases. Sensitivity analysis was conducted and did not identify any significant publication bias. The results revealed that CCs had an overall statistically significant positive effect on SOC pools, increasing MAOC by 4.8% (CI: 0.6% - 9.4%, n = 16), POC by 23.2% (CI: 13.9% - 34.4%, n = 39) and MBC by 20.2% (CI: 11.7% - 30.7%, n = 30) in the top soil, compared to no CC cultivation. Thereby, CCs feed into the stable as well as the more labile C pools. The effect of CCs on MAOC was dependent on soil clay content and initial SOC concentration, whereas POC was influenced by moderators such as CC peak biomass and experiment duration. For MBC, e.g., clay content, crop rotation duration and tillage depth were identified as important drivers. 
    Based on our results on the effects of CCs on SOC pools and significant moderators, we identified several research needs. A pressing need for additional experiments exploring the effects on CCs on SOC pools was found, with a particular focus on MAOC and POC. Further, we emphasize the necessity for conducting European studies spanning the north-south gradient. 
    In conclusion, our results show that CC cultivation is a key strategy to promote C accrual in different SOC pools. Additionally, this meta-analysis provides new insights on the state of knowledge regarding SOC pool changes influenced by CCs, offering quantitative summary results and shedding light on the sources of heterogeneity affecting these findings.

How to cite: Fohrafellner, J., Keiblinger, K., Zechmeister-Boltenstern, S., Murugan, R., Spiegel, H., and Valkama, E.: Cover Crops Affect Pool Specific Soil Organic Carbon in Cropland – a Meta-analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5359, https://doi.org/10.5194/egusphere-egu24-5359, 2024.

EGU24-6188 | ECS | Posters on site | SSS5.2 | Highlight

Transformation and backfilling of peatland soils and effect on CO2 emissions 

Ciriaco McMackin, Luisa Minich, Wiesenberg Guido, Burgos Stéphane, and Egli Markus

Peatlands are the Earth's largest natural terrestrial carbon reservoir, storing more than 40% of all soil organic carbon. Despite their significance, damaged peatlands emerge as a major source of greenhouse gas emissions, contributing to nearly 5% of global anthropogenic CO2 emissions.

Peatlands have been drained in the Three Lakes region (Switzerland). These drainage efforts were initiated to develop agricultural land use and enhance the overall quality of life in the region. While the drainage improved living conditions, it also accelerated peat decomposition. This accelerated decomposition gave rise to a loss of soil, reaching up to 4 meters at specific locations, and drastically increased CO2 emissions.

Various strategies have been developed to reduce CO2 emissions from degraded peatland. Backfilling—the deposition of a mineral layer on the soil— is one promising method to mitigate CO2 emissions. Backfilling disconnects the peat from the surface soil by a mineral layer. CO2 emissions from the peat are diminished, while the surface soil can still be used for agricultural purposes.

Peatlands contain very old carbon preserved by water-logged conditions that limited carbon decomposition. We measured rates and radiocarbon (C14) signals of the CO2 emissions at three locations in the Three Lakes Region to compare the amount and age of carbon emitted from drained and drained-backfilled peatland soils. First results show that the backfilled peatland soils emit less and younger CO2 than peatland soils having no backfilling. The covered peatland still continues to degrade, however at a slower pace. The overed peat contributes to about 50% of the measured CO2 emissions from the transformed sites. Further investigation will be needed to identify the spatio-temporal variability and the influence of other factors such as the groundwater table level.

How to cite: McMackin, C., Minich, L., Guido, W., Stéphane, B., and Markus, E.: Transformation and backfilling of peatland soils and effect on CO2 emissions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6188, https://doi.org/10.5194/egusphere-egu24-6188, 2024.

EGU24-7874 | ECS | Posters on site | SSS5.2

Rapid analysis using Diffuse Reflectance Spectroscopy can enhance Soil Carbon Monitoring 

Sean Adam and Conrad Jackisch

To gain a better understanding of changes in soil carbon stocks and composition it is essential to have data on relevant soil properties with high temporal and spatial resolution. However, traditional laboratory analysis can be both time-consuming and expensive, ultimately limiting data availability. Mid-DRIFTS (Diffuse Reflectance Infrared Fourier Transformed Spectroscopy in the mid-IR range) is a cost-effective alternative to conventional analytical methods. It enables the simultaneous inference of multiple soil properties, such as soil organic carbon, nitrogen and phosphorus content, soil texture, and cation exchange capacity, from measured spectra. This makes it a valuable analytical tool for soil monitoring.

To successfully integrate mid-DRIFTS into a soil monitoring concept, a spectral library representative of the target is required as the basis for multivariate or machine-learning-based calibration models. Here, we want to present the initial results obtained using the BDF-SSL, a soil spectral library we created as the foundation for integrating mid-DRIFTS in agricultural soil monitoring in Saxony, Germany. The library's core consists of nearly 300 spectra obtained from retention samples from agricultural soil monitoring sites in Saxony, which were collected over the past 20 years.
We focused on the inference of soil carbon content, including three thermally derived carbon fractions (TOC400, ROC, TIC900) we measured according to DIN19539 by combustion. Additionally, we calibrated models for a wide range of other soil properties, such as soil texture, nitrogen and phosphorus content, elemental concentrations and cation exchange capacity. We used both Partial Least Squares Regression (PLSR), Cubist, and the Memory Based Learner (MBL) to calibrate the models.

Both Cubist and MBL consistently outperformed PLSR. Our models show high predictive accuracy for the carbon fractions, total nitrogen and phosphorous contents, cation exchange capacity and texture. In addition, we are also able to predict several elemental concentrations, such as Fe, Al, or Ni contents with high accuracy. Our results show that mid-DRIFT can be used to enhance spatial and temporal coverage of soil monitoring, allowing not only for more accurate estimations of soil carbon stocks and sequestration rates, but also for the rapid estimation of several other soil properties.

How to cite: Adam, S. and Jackisch, C.: Rapid analysis using Diffuse Reflectance Spectroscopy can enhance Soil Carbon Monitoring, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7874, https://doi.org/10.5194/egusphere-egu24-7874, 2024.

EGU24-8770 | ECS | Orals | SSS5.2

Influence of initial soil carbon content on the stabilization of new carbon: a 2-year lab incubation study 

Neha Begill, Axel Don, and Christopher Poeplau

The hotly debated concept of carbon (C) saturation in mineral soils not only affects our understanding of soil organic matter (SOC) dynamics but also holds critical implications for negative emissions strategies. Many recent studies have indicated that soil’s capacity to store and stabilize C in mineral form depends on the initial SOC content, i.e., the soil C saturation deficit. According to these studies, low-C soils are suggested to have a higher potential for SOC storage compared to high-C soils. In light of these considerations, our hypothesis presents a different viewpoint, suggesting that initial C content in soils mainly affects the absolute loss of old carbon (following first-order kinetics), while it will not significantly impact the soil’s ability to stabilize new C. To investigate this experimentally, we selected soils from the first German Agricultural Soil Inventory with varying C contents (0.7–14.5%) and three different soil textures (light to heavy). These soils were then incubated in air-tight glass jars, where the same amount of 13C labeled litter was added, along with an unamended control of each sample. After two years, soils were dried and physically fractionated into mineral-associated organic carbon (MAOC) and particulate organic carbon (POC) using a size-cutoff of 20µm to find and δ13C as well as total SOC was measured. Here, we will present the first results from this lab incubation experiment, providing further systematic insights into whether the amount of initial carbon content or the ‘saturation C’ deficit truly affects the SOC dynamics with varying amounts of C contents in it.

How to cite: Begill, N., Don, A., and Poeplau, C.: Influence of initial soil carbon content on the stabilization of new carbon: a 2-year lab incubation study, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8770, https://doi.org/10.5194/egusphere-egu24-8770, 2024.

EGU24-8970 | Orals | SSS5.2

Coupling scales in process-based soil organic carbon modeling including dynamic aggregation 

Alexander Prechtel, Simon Zech, and Nadja Ray

Background: Carbon storage and turnover in soils depend on the interplay of soil architecture, microbial activities and soil organic matter dynamics. For a fundamental understanding of the mechanisms that drive these processes, not only the exploitation of advanced experimental techniques down to the nanoscale is necessary, but also spatially explicit and dynamic image-based modeling at the pore scale.
We present a modeling approach which is capable of transferring microscale information into macroscale simulations at the profile scale. This enables the prediction of future developments of carbon fluxes and the impact of changes in the environmental conditions linking scales.
We consider a mathematical model for CO2 transport across soil profiles (macroscale) which is informed by a pore-scale (microscale) model for C turnover. It allows for the dynamic, self-organized re-arrangement of solid building units, aggregates and particulate organic matter (POM) based on surface interactions, realized by a cellular automaton method, and explicitly takes spatial effects on POM turnover such as occlusion into account. We further include the macroscopic environmental conditions water saturation, POM content, and oxygen concentration.

The coupled simulations of macroscopic transport and pore scale carbon and aggregate turnover reveal the complex, nonlinear interplay of the underlying processes. Limitations by diffusive transport, oxygen availability, texture dependent occlusion and turnover of OM drive CO2 production and carbon storage.

Zech, Prechtel, Ray (2024): Coupling scales in process-based soil organic carbon modeling including dynamic aggregation. J. Plant Nutr. Soil Sci.

How to cite: Prechtel, A., Zech, S., and Ray, N.: Coupling scales in process-based soil organic carbon modeling including dynamic aggregation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8970, https://doi.org/10.5194/egusphere-egu24-8970, 2024.

EGU24-9176 | Posters on site | SSS5.2

Carbon Sequestration and Mitigation of Agricultural Greenhouse Gas Emissions through management: Insight from an incubation experiment 

Sobia Bibi, Hassan Ahmad, Wolfgang Wanek, Mohammad Zaman, Magdeline Vlasimsky, Maria Heiling, Reinhard Pucher, and Gerd Dercon

Climate change poses a significant threat to soil quality and global food security, with projections indicating potential crop yield declines of 17% by 2050. Simultaneously, agriculture contributes to an estimated 24% of all greenhouse gas (GHG) emissions. The dynamics of carbon (C) and nitrogen (N) play a pivotal role in GHG emissions and soil C sequestration, yet further research is needed on how management practices influence these dynamics.

 

To address these challenges and provide data can facilitate efficient resource utilization in agricultural production, an incubation experiment was conducted to provide data on the impact of management options on C sequestration and GHG emissions from agricultural soils. The experiment took place in 850 mL glass jars under controlled conditions at 60% water-filled pore space and a temperature of 25°C. Composite soil samples, derived from a moderately fertile soil (2-3% SOC) from Grabenegg, Austria, at a depth of 0-15 cm, were subjected to five treatments: 1) control, 2) labeled urea, 3) inhibitor and labeled urea, 4) biochar + 15N labeled urea, and 5) inhibitor and biochar and labeled urea.

 

The 15N-labeled urea (5% atom excess) was applied at a rate of 150 kg N ha-1, while biochar was applied at 2% of the soil by dry mass basis. A neon inhibitor which includes NBPT to limit nitrogen loss into the atmosphere as ammonia and DCD to reduce leaching, were applied at a rate of 4 mL per 100g urea as instructed by the manufacturer. All treatments were replicated four times. Soil and gas samples were collected on days 1, 3, 8, 15, 24, 31, 38, 45, 52, and 59 after treatment application. Gas samples were collected over a two hour period each day. Soil samples were analyzed for pH, soluble organic C, and mineral-N (NH4+, NO3-), while gas samples were analyzed using a gas chromatograph (GC) for NO2, CO2, and CH4.

 

Preliminary results indicate that the addition of biochar increased soil C content, aligning with expectations from prior studies and that the addition of the inhibitor had a discernible impact on the pathways of nitrogen in the study samples. The use of isotopic methods and GHG measurements can furnish critical data supporting the most efficient use of resources for both climate mitigation and adaptation.

 

How to cite: Bibi, S., Ahmad, H., Wanek, W., Zaman, M., Vlasimsky, M., Heiling, M., Pucher, R., and Dercon, G.: Carbon Sequestration and Mitigation of Agricultural Greenhouse Gas Emissions through management: Insight from an incubation experiment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9176, https://doi.org/10.5194/egusphere-egu24-9176, 2024.

EGU24-9202 | ECS | Posters on site | SSS5.2

Assessing inert pool models for estimating long-term biochar stability in soil 

Haichao Li, Elias S. Azzi, Cecilia Sundberg, Erik Karltun, and Harald Cederlund

Estimating the long-term stability of biochar in soil often relies on extrapolating mineralization data from short-term laboratory incubations. Various models such as single first-order (SFO), double first-order (DFO), triple first-order (TFO) and the power model have been employed for this purpose, all of which have an inherent assumption that biochar is completely biodegradable. However, recent insights challenge this assumption by highlighting that biochar consist largely of highly condensed aromatic structures, which have been proposed to be essentially inert. If biochar were resistant to microbial degradation it would make sense if this was reflected in the choice of model used. Therefore, our aim was to assess whether the proposed inert pool models (SFO+I and DFO+I) fit the data better compared to existing models (SFO, DFO, TFO and power model) using a recently compiled extensive dataset. We hypothesized that models incorporating an inert pool would fit better (or at least comparably well) to incubation data compared to the existing models and give more reliable long-term predictions. As a way of assessing the model’s predictive ability, we fitted them to progressively shortened incubation times derived from the longest biochar incubation data sets available, and then evaluated how well they extrapolated to the full measured range. Our results indicated that the proposed DFO+I model did indeed fit better than the both DFO and TFO models. Moreover, predictions of BC100 (% of carbon remaining after 100 years) by the inert pool models and by the power model displayed stronger correlations with the biochar stability indicator (H/C ratio) than both SFO and DFO models, which aligns with our initial hypothesis. However, the power model in general outperformed all other models, including the inert pool models, with the highest number of best fits. From our extrapolation exercise, it is clear the DFO model, which has been most widely used to date, substantially underestimated biochar stability in the longer term while the inert pool models tended to overestimate it. This uncertainty appears to be quite severe when fitting inert pool models to incubation data from non-pyrolysed materials. By comparison, the power model appeared to be more robust when estimating biochar persistence in soils. From these results we cannot conclusively confirm nor reject the idea of inert pool models. It is possible that an inert-pool model is the more suitable choice for extrapolating biochar decomposition data. However, it is clear from their tendency to overestimate stability of biodegradable materials. Our current understanding is hampered by the fact that the incubation data set available contains a high proportion of biochars produced at relatively modest temperatures and by a lack of chemical/structural characterization of the incubated biochars. Future research could remedy this by providing better information on the degree of aromatic condensation/proportion of inertinite in incubated biochars samples. For now, we recommend the power model as the most robust option.

How to cite: Li, H., Azzi, E. S., Sundberg, C., Karltun, E., and Cederlund, H.: Assessing inert pool models for estimating long-term biochar stability in soil, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9202, https://doi.org/10.5194/egusphere-egu24-9202, 2024.

EGU24-9216 | Orals | SSS5.2 | Highlight

Net primary production rather than saturation of mineral surfaces limits soil carbon sequestration  

Christopher Poeplau, Rene Dechow, Neha Begill, and Axel Don

Accrual of soil organic carbon (SOC), and especially the formation of mineral associated organic carbon (MAOC), has a large theoretical potential to act as sink for atmospheric CO2. For reliable estimates of this potential and efficient policy advice, the major limiting factors need to be understood. The positive correlation between the content of fine mineral particles (silt + clay) and the content of MAOC is widely used to estimate a general maximum MAOC storage capacity of soils, based on the notion that mineral surfaces get C saturated. However, recent literature raised doubts about the concept of C saturation and it remains unclear, if and to what extent the mineral capacity of soils to stabilise C limits SOC accrual. Here, using large scale soil datasets and the model RothC, we provide two independent lines of evidence, that the upper boundary line of the correlation between MAOC and silt and clay does not resemble a maximum mineralogical SOC stabilisation capacity. 1. In coarse-textured soils, the C loading of the silt and clay fraction was found to strongly overshoot the mentioned upper boundary line and thus exceed previous C saturation estimates. 2. A global modelling exercise revealed that only for 28.8 % of all soils, local net primary production (NPP) would be sufficient to reach a C loading of 80 g C kg-1 silt and clay, which is currently assumed to be the maximum capacity of soils to stabilise C. This proportion decreased strongly with increasing silt and clay content, which revealed that high C loadings can hardly be reached in more fine-textured soils. We conclude that SOC accrual is mainly limited by C inputs and strongly modulated by texture, mineralogy and climatic conditions. Taken together, those factors could be used to be formulate an ecosystem capacity to stabilise SOC. However, a potential C saturation point of MAOC appears still unknown and of no relevance for strategies of climate mitigation via SOC sequestration.

How to cite: Poeplau, C., Dechow, R., Begill, N., and Don, A.: Net primary production rather than saturation of mineral surfaces limits soil carbon sequestration , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9216, https://doi.org/10.5194/egusphere-egu24-9216, 2024.

EGU24-9335 | ECS | Posters on site | SSS5.2

Andosol genesis: Transition from silandic to aluandic properties and the related changes in organic carbon storage 

Antonia Zieger, Klaus Kaiser, and Martin Kaupenjohann

Andosols are commonly subdivided according to silandic and aluandic features. Both subgroups are considered to be end members of the Andosol genesis. Silandic Andosols are characterized by organic matter (OM) strongly bound to imogolite-type material (ITM), while Aluandic Andosols mainly consist of aluminium-OM complexes (Al-OM complexes). According to current theory, silandic and aluandic properties are direct results of primary weathering, assuming two separate lines of genesis.

Our previous results, however, suggest that silandic horizons can transform into aluandic over time, resulting in additional carbon accumulation. This is likely caused by dissolved organic matter (DOM) entering the subsoil with the percolating soil solution, masking dissolved aluminium as soluble Al-OM complexes. This promotes the dissolution of ITM, releasing aluminium. The latter reacts with DOM, inducing the formation of insoluble, Al-OM complexes, which then precipitate.

To test this hypothesis, we conducted a long-term percolation experiment with material of an Ecuadorian Andosol formed in a homogeneously tephra deposit. This soil exhibits aluandic properties in the topsoil and silandic properties in the subsoil. Ions, pH, and DOC in the feed and eluate solution were monitored over a period of 18 months. The convection-dispersion-equation as implemented in HYDRUS-1D was used to model the percolation experiment as a one-dimensional standard reactive solute transport.

Our results revealed a strong carbon accumulation of 14 g·kg-1 in the silandic material after 18 months, with the vertical transport of Al-OM complexes only explaining up to 33 % of the carbon accumulation. The HYDRUS-1D model revealed that sorption of DOM dominates at the beginning of the experiment and explains up to 40 % of carbon accumulation (including vertically transported Al-OM complexes). For the silandic material, the results indicate that up to 91% of the carbon accumulation are due to ITM dissolution and subsequent formation of insoluble Al-OM complexes.

In summary, our findings support the hypothesis, that ITM dissolution and the subsequent formation of Al-OM precipitates significantly contribute to the increase in carbon concentration in the silandic material, while the above aluandic material did not change.

How to cite: Zieger, A., Kaiser, K., and Kaupenjohann, M.: Andosol genesis: Transition from silandic to aluandic properties and the related changes in organic carbon storage, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9335, https://doi.org/10.5194/egusphere-egu24-9335, 2024.

EGU24-9389 | ECS | Orals | SSS5.2 | Highlight

Cover crop´s carbon inputs to soils via aboveground and root biomass as affected by species, mixtures and sowing date 

Laura Reinelt, Nicole Christin Maack, Henrike Heinemann, and Axel Don

An increased use and optimised management of cover crops is a promising way to promote soil organic carbon accrual in agricultural soils. However, data is lacking on aboveground and especially root biomass of important cover crop species depending on the length of their cultivation window and on climatic conditions. We sampled aboveground and root biomass in a German field trial covering twelve common cover crop species and eight commercially available seed mixtures in 2021, a year with a rather wet summer, and 2022, a year with a rather dry summer. Each species and mixture were sown at three different dates and were sampled in early November, after having grown for 8 to 14 weeks.

Root and shoot biomass differed significantly between species, years and sowing dates. Oil radish, Phacelia, Bristle oat and Italian rye-grass had the highest root biomass. Cover crop mixtures did not have significantly higher aboveground or root biomass than single species. Aboveground biomass was 60% lower in 2022 compared to 2021 and root biomass on average 52% lower. Biomass generally decreased substantially with later sowing dates, by up to 80%. In 2021, the root to shoot ratio decreased by on average 41% from the earliest to the latest sowing date.

Based on the results of our study, management recommendations can be given regarding the selection and management of cover crop species for soil carbon accrual. Our data is also useful for more accurate mechanistic modelling of the soil carbon dynamics under different agricultural management scenarios. We conclude that there is a large optimisation potential for cover crop cultivation in Europa that could reveal a significant soil carbon sequestration potential.

How to cite: Reinelt, L., Maack, N. C., Heinemann, H., and Don, A.: Cover crop´s carbon inputs to soils via aboveground and root biomass as affected by species, mixtures and sowing date, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9389, https://doi.org/10.5194/egusphere-egu24-9389, 2024.

EGU24-10155 | ECS | Posters on site | SSS5.2

Impact of cover crops and conventional and reduced tillage on plant productivity in a bicultural maize-oat cropping system 

Giulia De Luca, Eszter Sugar, Nándor Fodor, Tamás Árendás, Péter Bónis, and Renáta Sándor

Agricultural crop production plays a key role in satisfying the increasing food demand of our ever-growing population. However, continuous production and certain land use practices often result in the depletion of soil quality. This revelation developed a need to improve soil fertility by enhancing carbon sequestration and storage in our cultivated fields using different methods.

Even though the application of green manure crops can significantly increase the amount of carbon stored in the soil while improving its water storage capacity and protecting the surface from erosion, it is still not a widespread method in Hungary due to usual water shortage during their sowing and germination periods. Furthermore, different soil management techniques can also alter the quality and carbon sequestration potential of our soils. The objective of our study is to determine how soil management and the usage of catch crop cover may affect crop productivity.

A maize-oat bicultural field trial with two different soil management techniques (conventional ploughing and reduced tillage) combined with four types of cover crops (fallow, trefoils-buckwheat mixture, phacelia and oilseed radish) was established in 2020. Changes in soil water content and temperature were continuously monitored at three depths (5, 25 and 45 cm), while leaf area index (LAI) and chlorophyll content (SPAD) were measured periodically. At the end of the vegetation periods measurements regarding crop quality and quantity were executed as well. Furthermore, soil respiration and additional (soil penetration resistance, SWC, VIgreen index) measurements were carried out during the study period, these results will be presented in a separate poster (Effect of cover cropping and soil tillage on soil CO2 emissions).

Our results showed that differences between treatments regarding management techniques and cover crops are more characterized in maize than in oat.

How to cite: De Luca, G., Sugar, E., Fodor, N., Árendás, T., Bónis, P., and Sándor, R.: Impact of cover crops and conventional and reduced tillage on plant productivity in a bicultural maize-oat cropping system, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10155, https://doi.org/10.5194/egusphere-egu24-10155, 2024.

EGU24-10379 | Orals | SSS5.2

Climate conditions control the SOC sequestration potential of agricultural terraces 

Pengzhi Zhao, Daniel Fallu, Sara Cucchiaro, Ben Pears, Andreas Lang, Paolo Tarolli, Sebastian Doetterl, Jeanette Whitaker, Tony Brown, and Kristof Van Oost

Agricultural terraces, being among the volumetrically largest and most common man-made landforms, have been widely implemented to support essential soil ecosystem services, e.g., erosion control, soil nutrient, and water retention, and have had an essential impact on soil organic carbon (SOC) stock and its exchange with the atmospheric C. However, the direction and magnitude of this impact remain highly uncertain. By integrating the broad-scale field observations of 14 terrace sites across the EU with a global data synthesis, we demonstrate that the effectiveness of terracing-driven SOC sequestration potential is intricately controlled by climate conditions that govern in-return soil properties.

Our findings reveal that the terracing practices represent a promising land management strategy for enhancing SOC sequestration, but also that risks of SOC loss exist when building terraces under arid climate, where they could be potentially very beneficial to crop productivity and SOC storage. We recommend that future terrace construction should integrate water and nutrient recycling techniques to ensure soil moisture and nutrient availability, enhancing land productivity and maximizing SOC sequestration potential. Our data suggest that promoting the recovery of the lost topsoil C during terrace construction through increasing C inputs and C use efficiency, i.e., straw return and nutrient amendment is an efficient way to counteract initial SOC losses.

How to cite: Zhao, P., Fallu, D., Cucchiaro, S., Pears, B., Lang, A., Tarolli, P., Doetterl, S., Whitaker, J., Brown, T., and Van Oost, K.: Climate conditions control the SOC sequestration potential of agricultural terraces, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10379, https://doi.org/10.5194/egusphere-egu24-10379, 2024.

EGU24-10695 | Posters on site | SSS5.2

Effect of cover cropping and soil tillage on soil CO2 emissions 

Györgyi Gelybó, Giulia De Luca, János Balogh, Nándor Fodor, Szilvia Fóti, Eszter Sugár, and Renáta Sándor

It has long been in the focus of research interest how cover cropping affect water regime of the soil. However, its simultaneous effect on CO2 emission, i.e. soil respiration is not so widely reported. We examined an agricultural experiment set up as a maize-oat rotation under conventional and reduced tillage tillage and four different cover-cropping treatments (fallow, oilseed radish, mixture, phacelia) in Martonvásár (Hungary). Soil respiration measurements were carried out using infrared gas analyzer in 5 replicates per treatment plot (tillage-main-crop-cover crop combinations). Measurements covered two years in the different main crops and also in cover crops. A total of 10 measurement campaigns were organized in 2021 and 2022, which covered both main crops and cover crops. Meteorological parameters were measured in a nearby automatic meteorological station.

Besides soil respiration measurements ancillary measurements have been carried out to better characterize soil status. Using a penetrologger soil penetration resistance, using handheld sensors, soil water content measurements and soil temperature was recorded. Also, point scale continuous soil water content profile measurements were carried out. At each plot, vegetation was characterized using the VI green index derived from RGB imagery and periodically chlorophyll content (SPAD) and leaf area index was recorded. Here we analyze soil respiration, VI green soil temperature and soil water content measurements. The results showed differences between tillage treatments and between main crops. For further results please see abstract “Impact of cover crops and conventional and reduced tillage on plant productivity in a bicultural maize-oat cropping system”.

How to cite: Gelybó, G., De Luca, G., Balogh, J., Fodor, N., Fóti, S., Sugár, E., and Sándor, R.: Effect of cover cropping and soil tillage on soil CO2 emissions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10695, https://doi.org/10.5194/egusphere-egu24-10695, 2024.

EGU24-11164 | ECS | Orals | SSS5.2 | Highlight

Areas available for potential carbon sequestration in European agricultural soils 

Florian Schneider, Daria Seitz, Felix Seidel, and Axel Don

In order to estimate a feasible carbon (C) sequestration potential in European agricultural soils, we need to know the area where additional measures that increase soil organic carbon (SOC) can be implemented and the corresponding SOC accrual rates. In this study, we focus on the former and identify areas where promising SOC increasing practices can be implemented on European agricultural soils.

The practices considered include a higher share of agroforestry, cover crops replacing bare winter fallows, reduced tillage instead of ploughing and the integration of perennial legumes and leys into crop rotations. Open-access data of European Farm Structure Surveys as provided by EUROSTAT at NUTS2 level serve as a reference for the intensities at which the measures are already implemented in Europe. It was assumed that only the further spread of these measures could potentially sequester additional C in soils.

We argue that the adoption of reduced tillage is the practice that covers by far the largest area relevant for potential C sequestration in soils under current food, feed, and fibre demands. The replacement of bare winter fallow with cover crops is restricted to regions with sufficient growing degree days to allow a second crop after harvest. The introduction of more woody features like hedgerows and alley cropping to agro-ecosystems, as well as the integration of more perennial legumes or leys in present crop rotations creates the need for land reallocation and likely compromises agricultural productivity.

Overall, we conclude that reduced tillage may emerge as the most promising practice for atmospheric C sequestration in European agriculture despite its reported relatively low SOC accrual rate per hectare. Trade-offs between C sequestration in soils, agricultural production and agricultural demand warrant further inter-disciplinary attention.

How to cite: Schneider, F., Seitz, D., Seidel, F., and Don, A.: Areas available for potential carbon sequestration in European agricultural soils, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11164, https://doi.org/10.5194/egusphere-egu24-11164, 2024.

EGU24-11742 | ECS | Orals | SSS5.2 | Arne Richter Awards for Outstanding ECS Lecture

Digging into the Future: The transition between bedrock and soil as an underexplored frontier zone in geoscience 

Daniel Evans

Terrestrial environments and their ecosystems demand healthy, sustainable, and resilient soils. Over the past couple of decades, significant efforts have been made to safeguard global soils, yet the materials and resources responsible for soil formation have been widely overlooked.  The transition from bedrock to soil – a zone often described as ‘soil parent material’ – holds an exciting yet untapped potential for helping us address some of the largest environmental challenges, including climate change and the biodiversity crisis. In this award lecture, I will present a strand of my research programme ‘Building Tomorrow’s Soils’ which seeks to establish how soil parent materials enhance the sustainability, health, and resilience of soil systems. First, with a focus on carbon sequestration, I will highlight how the bedrock–soil transition zone has the potential to be a long-term store of organic carbon. I will then present research which shows that some soil parent materials release petrogenic (i.e. rock-derived) organic carbon into soils. These understudied inputs of organic carbon to soils are currently absent from most, if not all, soil carbon models, which threatens our ability to optimize soil carbon management in the long-term. Finally, I will argue that developing a mechanistic understanding about this transition zone – this underexplored material which is neither rock nor soil in structure and function, but a blend of both – requires a similarly cross-disciplinary approach.

How to cite: Evans, D.: Digging into the Future: The transition between bedrock and soil as an underexplored frontier zone in geoscience, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11742, https://doi.org/10.5194/egusphere-egu24-11742, 2024.

EGU24-12025 | ECS | Posters on site | SSS5.2 | Highlight

Enhancing soil carbon sequestration in the parks of the city of Barcelona  

Sílvia Poblador, Lucía Álvarez, Bárbara Díaz, Marc Felip, Francesc Sabater, Arthur Vienne, and Sara Vicca

Climate change is progressing at an alarming pace. In order to limit global warming to the agreed-upon 2°C in the United Nations Paris Agreement, we require both rapid decarbonization and the implementation of negative emissions technologies (NETs), that actively remove carbon dioxide (CO2) from the atmosphere and ensure stable long-term carbon storage. In this context, enhanced silicate weathering (ESW) has been proposed as a NET based on a nature solution. ESW aims to accelerate the natural uptake of atmospheric CO2 during the weathering of silicate rocks by grinding them, increasing their reactive surface and speeding up the process. This NET is particularly interesting as it does not compete for space with other economical activities. For instance, in agroecosystems, ESW is already considered a promising NET, offering multiple co-benefits for crop production when spreading silicate minerals on arable soils (i.e. increase in crop yields, restoration of soil base cations and micro- and macronutrient stocks). Besides agricultural land, urban soils can also be suitable for ESW. The application of ESW in city parcs and gardens presents an opportunity to increase the capture of atmospheric CO2, while also favoring vegetation growth (lawn, shrubs and flowers) and potentially enhancing resistance to drought and pests.

EMBARCARB is a pilot project that aims to increase soil carbon sequestration and improve the vegetation status in two parcs of the city of Barcelona (SE Iberian Peninsula), during an extremely dry year. Moreover, the project also aims to compare the carbon sequestration capacity of soils with weathering of silicate rocks and concrete demolition fines, thus reusing construction debris and strengthening the circular economy of the region. Here, we explore the preliminary results of the project and give a first estimation of the weathering rates and the capacity of such NETs to enhance soil carbon sequestration in the green areas of the cities.

How to cite: Poblador, S., Álvarez, L., Díaz, B., Felip, M., Sabater, F., Vienne, A., and Vicca, S.: Enhancing soil carbon sequestration in the parks of the city of Barcelona , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12025, https://doi.org/10.5194/egusphere-egu24-12025, 2024.

EGU24-12698 | ECS | Orals | SSS5.2 | Highlight

The centennial legacy of land-use change on organic carbon stocks of temperate agricultural soils 

David Emde, Christopher Poeplau, Axel Don, Stefan Heilek, and Florian Schneider

Land-use change (LUC) in agricultural settings is common both historically and under more recent climate-smart agriculture guidelines aimed at reducing the impact of agriculture on the climate. Recognising that conversion of perennial grasslands to annual cropland results in a large, but potentially reversible, loss of soil organic carbon (SOC) such guidelines often call for increasing the overall area under grassland. To date, the magnitude and direction of SOC change following LUC has been fairly well accounted for, but the time it takes to reach a new SOC equilibrium is not well understood. While broad scale emission reporting best practices (e.g. IPCC) suggest that SOC equilibrium is reached approximately 20 years after LUC, there is a growing body of knowledge that supports a centennial timescale in temperate or boreal climates. With data from the first German Agricultural Soil Inventory alongside extensive per-site land-use histories, we established SOC change timelines that show that not only does SOC take much longer than 20 years to reach equilibrium but it reaches equilibrium at vastly different rates depending on the direction of LUC. Sites converted from cropland to grassland took 83 years (95 % CI: 79 to 90 years) to reach SOC equilibrium whereas sites converted from grassland to cropland took 180 years (95 % CI: 151 to 223 years). In order to map the effects of historic LUC on SOC stocks in temperate agroecosystems with similar grassland and cropland SOC stocks to Germany, we applied these timeline models to comparable sites from the HILDA+ global LUC database (Winkler et al., 2020); a global reconstruction of annual land use and land cover at a 1 km spatial resolution from 1899 to 2019. Compiled from a range of open data sources (remote sensing, reconstructions, and census data) the HILDA+ dataset offers insights into relatively fine scale LUC dynamics that follow known socioeconomic drivers over the past 120 years. Using this dataset, we determined that 112 Million ha, or 3.5 % of the total agricultural area worldwide, was comparable to German agriculture in terms of SOC and growing conditions, and 11 % of that land (12.6 Million ha) had undergone LUC from cropland to grassland or vice versa since 1899. After accounting for duration on a per-cell basis, areas having undergone LUC from cropland to grassland (7.5 million ha) accounted for a 86.2 million Mg C increase over the past 120 years. Conversely, areas having undergone LUC from grassland to cropland (5.1 million ha) accounted for a -55.0 million Mg C decrease in SOC. The overall net increase of 31.2 million Mg C corresponds to about 5‰ of total SOC stocks across all agricultural land with pronounced regional differences. We conclude that land-use change histories of at least one century should be considered when interpreting present-day, and predicting future, SOC dynamics.


Winkler, K., Fuchs, R., Rounsevell, M. D. A., & Herold, M. (2020). HILDA+ Global Land Use Change between 1960 and 2019 [dataset]. PANGAEA. https://doi.org/10.1594/PANGAEA.921846

How to cite: Emde, D., Poeplau, C., Don, A., Heilek, S., and Schneider, F.: The centennial legacy of land-use change on organic carbon stocks of temperate agricultural soils, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12698, https://doi.org/10.5194/egusphere-egu24-12698, 2024.

EGU24-13751 | ECS | Posters on site | SSS5.2

Assessing the environmental benefits of biochar application in agriculture: Insights from lifecycle assessment 

Sirjana Adhikari, M A Parvez Mahmud, Ellen Moon, and Wendy Timms

Organic waste-derived biochar has been proven to have a significant potential for soil improvement, with recent results from this group showing evidence for improved water holding capacity, carbon stability and exchangeable cations. However, to contextualise these benefits it is important to consider environmental impacts during each stage of life cycle for the product.

In this study, a cradle-to-gate life cycle assessment (LCA) was performed, comparing a common use for garden organics (composting) to two alternative scenarios. One involved converting over-sized compost screenings (otherwise considered waste) to biochar as a supplementary product from the process, and the other involved converting garden organics directly to biochar as an alternative product.

LCA was conducted using ReCiPe2016 impact assessment method in OpenLCA software. Data for assessment were collected from the participating industries and Ecoinvent database. Sensitivity analysis considering different transport distances was carried out and finally an optimum transport distance with the lowest environmental impacts was recommended. Additionally, physico-chemical characterisation and carbon stability assessment were conducted to provide a comprehensive idea about the overall benefits of organic waste-derived biochar for soil and climate.

Our results revealed that global warming was increased from 675 kgCO2eq during composting of garden waste to 1017 kgCO2eq where over-sized screenings of compost is converted to biochar as a value-added product. Direct conversion of organic waste to biochar showed reduced global warming impact of 428 kgCO2eq compared to the previous two scenarios. Among 16 environmental impact indicators studied, the magnitude of 10 impact indicators increased with transport distance, while the remaining six indicators were not influenced by transport distance.

Soil application of biochar from organic waste has multiple co-benefits, that can be short and/or long term. Nevertheless, this study emphasises that research focused on agricultural application of biochar needs to be coupled with LCA or other holistic assessments for a comprehensive evaluation of net environmental impacts and benefits that consider the processes involved in sourcing of feedstock, biochar production, transport, and application.

How to cite: Adhikari, S., Mahmud, M. A. P., Moon, E., and Timms, W.: Assessing the environmental benefits of biochar application in agriculture: Insights from lifecycle assessment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13751, https://doi.org/10.5194/egusphere-egu24-13751, 2024.

The process of organic horizon formation is reflected in the quantity and quality of the mineral materials contained. In the highland of mountains in northern Japan, thick organic horizons develop due to heavy snowfall. The organic horizons are rich in 2:1 clay minerals from Asian dust originating from the Eurasian Continent and active Al and Fe derived from volcanic ash. Organic matter in the organic horizons is present in separation or associations with these clay minerals or active Al and Fe. These organo-mineral associations make different biogeochemical properties between relatively free and mineral-associated organic matter in its dynamics, even in the organic horizons, because minerals can protect organic matter from microbial decomposition. Evaluating the biogeochemical arrangements of organic matter and minerals is valuable to understanding organic matter dynamics in the organic horizons containing rich minerals. The objective of this research is to evaluate the organo-mineral associations in the organic horizons in the snowy mountains of northern Japan using density fractionation.

The organic horizon samples were collected from three mountains. Two selected mountains (Mt. Chokai and Mt. Kurikoma) are volcanoes, and the other is a non-volcanic mountain (Mt. Makihata). Samples in Mt. Chokai were taken from each soil horizon from two soil profiles of snow meadow soils and one of dwarf bamboo and dwarf pine soil. In Mt. Kurikoma, one soil profile of a snow meadow was selected. One soil profile and two surface soils (5-15 cm) of snow meadow were collected in Mt. Makihata. Freeze-dried organic horizon samples were shaken with 1.6 g cm-3 SPT and grass beads at 16 h and 120 rpm. Recovered floating materials were sieved at 0.5 mm to remove coarse, fresh plant roots. The fraction larger than 0.5 mm was termed course light fraction (cLF), and the smaller fraction was termed small light fraction (sLF). The residue heavier than 1.6 g cm-3 was  heavy fraction (HF). Isolated fractions were freeze-dried and observed by SEM. Organic carbon and total nitrogen of isolated fractions were measured by an elemental analyzer.

The mass recovery ranged from 91.5 to 97.0%. A lower recovery rate was observed in the upper horizons, presumably due to losses attributable to higher dissolved organic carbon contents. Each isolated fraction separated by density and size showed different physicochemical properties. cLF mainly consisted of fresh roots. Decomposed plant residue was found in sLF. In HF, structures of highly decomposed plant residues combined with minerals were observed. Lower C/N of HF compared to cLF and sLF in Mt. Chokai indicated more decomposed organic matter associated with minerals. These results showed that even in organic horizons, organic matter had different physicochemical properties depending on their associations with minerals. This study highlights the importance of focusing on minerals in evaluating organic matter dynamics in organic horizons affected by aeolian dust. The stability of organic matter bound to minerals in organic horizons needs further evaluation.

How to cite: Kobayashi, K., Asano, M., and Tamura, K.: Organic matter characteristics in density fractionation of organic horizons with Asian dust and volcanic ash in snowy mountains of northern Japan, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13777, https://doi.org/10.5194/egusphere-egu24-13777, 2024.

EGU24-14590 | ECS | Posters on site | SSS5.2

Improving Biochar Suitability for Arid-Land Use: Impact of Elemental Sulfur and Compost on Acidification and Biological Activation 

Ahmed Al Rabaiai, Daniel Menezes-Blackburna, Said Al-Ismailya, Rhonda Janke, Ahmed Al-Alawi, Mohamed Al-Kindi, and Roland Bol

This study aimed to enhance the quality of biochar for applications in arid lands by employing elemental sulfur (S, 0.013%) as an acidifying agent and compost (10%) as a biological activator. The addition of elemental sulfur significantly reduced the biochar pH, with the most substantial decrease from 8.1 to 7.2 observed when co-amended with vermicompost was used. Elemental sulfur markedly increased the water-soluble concentrations of calcium (Ca) by 147% and 105%, as well as magnesium (Mg) by 929% and 447% in compost and vermicompost, respectively. This suggests a decline in biochar basicity due to acid mineral dissolution and desorption. Sulfate (SO42-) levels showed the greatest increase when compost was co-applied with sulfur, indicating more efficient oxidation in this treatment. FT-IR analysis revealed increased carbonyl groups (C=O) and decreased alkyne (C≡C) groups in compost and vermicompost-treated samples, while sulfur treatment resulted in the decrease of hydroxyl groups, but only in the presence of vermicompost. SEM-EDX analysis demonstrated changes in the elemental composition and microscale pore structure of biochar samples after incubation with sulfur. Sulfur amendments stimulated substrate-induced respiration, particularly in biochar amended with sulfur (BS, 0.011 ug CO2- C/g/h) and biochar with vermicompost (BV, 0.18 ug CO2- C/g/h) treatments. Microbial diversity (Shannon H) significantly increased in compost treatments with sulfur amendment from 3.08 to 4.52, while it decreased in vermicompost from 4.25 to 4.02. Vermicompost treatments (BV, BVS) exhibited higher microbial evenness (0.27 and 0.28) and equitability (0.67) diversity indices. The bacterial community structure was significantly influenced by all treatments, with sulfur reducing the abundance of Proteobacteria by 30% in the presence of compost and 8% with vermicompost, while increasing the abundance of Actinobacteria by 18% and 4% for compost and vermicompost treatments, respectively.Multivariate principal component analysis (PCA) indicated that soluble sulfate was associated with specific sulfur-oxidizing bacterial clusters, which were differentially expressed under different compost treatments. Integrating biochar with sulfur and compost emerges as a promising sustainable technology for managing alkalinity, enhancing soil fertility, and improving agricultural productivity in arid regions.

 

How to cite: Al Rabaiai, A., Menezes-Blackburna, D., Al-Ismailya, S., Janke, R., Al-Alawi, A., Al-Kindi, M., and Bol, R.: Improving Biochar Suitability for Arid-Land Use: Impact of Elemental Sulfur and Compost on Acidification and Biological Activation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14590, https://doi.org/10.5194/egusphere-egu24-14590, 2024.

Crop residues play a key role in supplying renewable carbon for the envisioned future greenhouse gas-neutral economy. However, their harvest is often limited below their technical potential to avoid soil organic carbon (SOC) stock losses. Nevertheless, the use of crop residues in the bioeconomy often involves the generation of a coproduct rich in recalcitrant carbon that can be reintegrated into soils to maintain SOC stocks. Yet, the environmental implications of such a strategy beyond those on climate change remain uncertain and contingent on specific contexts. Here, we present a novel framework that integrates a recalcitrance-adapted SOC model with a consequential life cycle assessment (LCA) to comprehensively evaluate the spatially explicit long-term SOC evolution and environmental impacts associated with returning various bioeconomy coproducts to croplands. The study spans diverse contexts, including temperate (France) and tropical (Ecuador) regions and five environmental impact categories, assessing the conversion of crop residues into maritime fuels, here hydrodeoxigenated pyrolysis oil (HPO) and cryogenic liquefied biomethane (bio-LNG), generating biochar and digestate as coproducts, respectively. The simulations were performed for >60,000 and >15,000 simulation units in France and Ecuador, employing adapted versions of AMG and RothC, respectively, under the RCP4.5 climate pathway in both regions. Results revealed that after 100 years, compared to a reference scenario where crop residues are directly incorporated into soils, biochar allows harvesting 100% of crop residues without any SOC losses in both French and Ecuadorian contexts. In contrast, digestate demonstrates a more limited potential, reaching 50% in France and 0% in Ecuador. This is referred to as the C-neutral harvest rate, which allows a surplus potential of 71-125 PJ in France and 113 PJ in Ecuador. The LCA revealed environmental benefits for all five impact categories for HPO and three categories for bio-LNG, per tonne of crop residues. Despite bio-LNG representing higher net avoided emissions (946 MgCO2e) than HPO (563 MgCO2e) per tonne of crop residues, the scaled results for the national C-neutral harvest rate showed the opposite trend with net avoided emissions of 11,912 MgCO2e for HPO and 10,707 MgCO2e for bio-LNG. Further, the scaled results revealed increased eutrophication impacts in marine water in the bio-LNG case, reflecting the nitrogen emissions associated with digestate, which is responsible for N2O, NH3, and nitrate losses to water. Yet, these can be mitigated with simple solutions such as treating digestate with nitrification inhibitors, microbial enrichment, or acidification at spreading. Moreover, biochar could be applied in tandem with digestate to create synergies from the nutrient-fertilizer effect of digestate and reduced C and N mineralization properties of biochar. In conclusion, defining a C-neutral harvest rate emerges as a pivotal strategy, ensuring a harmonious balance between SOC maintenance and net environmental impacts across diverse scenarios, emphasizing the potential of integrating bioeconomy practices with soil carbon management.

 

How to cite: Andrade Diaz, C. and Hamelin, L.: Tradeoffs between long-term SOC storage and overall environmental impacts of supplying crop residues to the bioeconomy: where, when, how and what does it depend on? , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17426, https://doi.org/10.5194/egusphere-egu24-17426, 2024.

Examining soil carbon losses across various time scales is essential for understanding the potential of soil carbon stabilization. It allows for considering these losses in estimating the net changes in carbon stocks. The soil's intrinsic physical and chemical properties, particularly those associated with the mineral phase, have been suggested to regulate soil organic carbon (SOC) losses. However, the relationship between these properties and SOC losses remains to be determined in long-term experiments. A 600-day incubation experiment was conducted on sieved soil samples (<2 mm) and intact cores (volume=~200 cm3) collected from an arable field in Bjertorp in southwest Sweden with large variations in soil texture and SOC to determine the respiration rate through chamber alkali trap respirometry using a Portable conductivity meter. After the incubation experiment, soil properties (carbon, nitrogen, and pH) were also measured. In addition, previously determined soil texture, oxalate extractable aluminum (Alox), and iron measurements were used to explain the results of the incubation experiment. The ratios between Alox and SOC and Alox and clay content were used as proxies for the protection of SOC. Preliminary results from the sieved soil samples indicate that the respiration rate (µg C-CO2 g-1 SOC h-1) was positively correlated to the Alox:SOC  and clay:SOC ratio. These findings can be interpreted as the absence of SOC protection by Alox and/or clay complexes or interactions. The conclusions drawn from this study suggest the need for additional exploration into the intricate dynamics that influence the fate of soil organic carbon (SOC) associated with mineral phases when assessing carbon stocks.

How to cite: Chilipamushi, M., von Brömssen, C., Colombi, T., Kätterer, T., and Larsbo, M.: The role of oxalate-extractable aluminum in regulating soil organic carbon decomposition in agricultural topsoil in humid continental climates: Insights from a long-term incubation field-scale study., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17497, https://doi.org/10.5194/egusphere-egu24-17497, 2024.

EGU24-17654 | ECS | Orals | SSS5.2

Distribution of soil organic carbon across contrasting fractionation techniques - results from a long-term field trial with increasing shares of leguminous cover crops 

Ferdinando Binacchi, Murilo Veloso, Cimélio Bayer, Christopher Poeplau, Carsten Mueller, Franz Buegger, and Andreas Gattinger

Diversification of no-till cropping systems through the inclusion of leguminous crops can be a sustainable means for enhancing both the bioavailability as well as the persistence of soil organic carbon (SOC). Therefore a comprehensive assessment of long-term soil organic matter (SOM) dynamics is crucial to realize the potential of sequestering atmospheric carbon dioxide, while concomitantly restoring the productivity and functionality of degraded soils. In the current study, soil samples were taken from a 39 years old subtropical trial at seven soil increments until one meter depth. Treatments included five maize-based cropping systems, with increasing shares of leguminous cover crops, with or without nitrogen (N) fertilizer applications to the maize plants. Varying degrees of labile and recalcitrant SOC were distinguished by means of thermal analysis as well as through physio-chemical fractionation, yielding contrasting results in shares of carbon accumulation across conceptual pools. While thermally recalcitrant SOC (combusted at temperatures between 400˚C and 800 ˚C) represented a small percentage of total C accrual, chemically recalcitrant SOC (silt and clay fraction resisting sodium hypochlorite oxidation) reported both a large share of total C content, as well as a high C accumulation. Although limited overlap among C pools from the two fractionations was found, irrespective of C detection method, systems with higher shares of leguminous cover crops reported highest SOC stocks. Interestingly, including additional leguminous cover crops contributed in storing as much SOC as systems with N fertilization, but the depth at which SOC sequestration occurred varied between fertilized and non-fertilized systems. While SOC stocks in the 0-30 cm depth correlated positively to total C inputs from crop residues in both fertilized and unfertilized systems, SOC stocks in the subsoil (30-100 cm depth) only correlated (p<0.05) to inputs from leguminous cover crops in non-fertilized systems.

Moreover, shifts in δ¹³C signatures across the five physically separated C fractions (silt+clay, recalcitrant SOC , stable aggregates + sand, dissolved organic carbon and particulate organic matter), were used to calculate contributions of C₃ leguminous C inputs in mixed C₃/C₄ cropping systems and study pathways of SOC dynamics.  

Overall, the study reports high potential of leguminous cover crops to contribute to SOC build-up in subtropical Oxisols, especially through the association of labile organic matter to soil minerals.

How to cite: Binacchi, F., Veloso, M., Bayer, C., Poeplau, C., Mueller, C., Buegger, F., and Gattinger, A.: Distribution of soil organic carbon across contrasting fractionation techniques - results from a long-term field trial with increasing shares of leguminous cover crops, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17654, https://doi.org/10.5194/egusphere-egu24-17654, 2024.

EGU24-18070 | ECS | Posters virtual | SSS5.2

Stability of microbial necromass in soil is controlled by necromass chemical composition 

Sam Walrond, Jeanette Whitaker, Caroline Peacock, and Nick Ostle

Reversing the trend of decreasing soil carbon stocks is important to help mitigate current environmental challenges. Improving knowledge on the mechanisms that control the stabilisation and persistence of soil organic carbon will provide a foundation to tackle the issue. This includes the mechanisms controlling the stability of organomineral associations, considered to be the most persistent pool of soil carbon. Uncertainties remain in how the composition of carbon involved in mineral associations can control the persistence of this soil organic carbon (SOC) pool.

With the mineral associated pool being dominated by soil carbon derived from microbial necromass, composition of microbes and their cell components will have a significant impact on organomineral stability. This study aims to investigate whether differences in cell wall composition between fungi, gram-positive and gram-negative bacteria, contribute to contrasting stability of the organominerals synthesised using necromass of these microbial groups.

Organominerals composed of ferrihydrite and montmorillonite minerals and three types of necromass were synthesised and tested for their stability. This was done using chemical washes that bring about desorption (NaOH) and oxidation (NaOCl) of the necromass C. Solid fraction C and N were measured before and after chemical wash treatments to determine the extent of organic carbon (OC) destabilisation, and Fourier transform infrared (FTIR) spectroscopy was used to semi-quantitatively assess changes in OC functional groups before and after destabilisation.

Results indicate that organominerals containing fungal necromass have greater stability compared to organominerals containing gram-positive and gram-negative bacterial necromass. The most stable fraction within organominerals was C rich and did not comprise N-containing necromass components. The results imply that necromass derived from soil fungi could enhance the persistence of the mineral-associated pool of SOC.

How to cite: Walrond, S., Whitaker, J., Peacock, C., and Ostle, N.: Stability of microbial necromass in soil is controlled by necromass chemical composition, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18070, https://doi.org/10.5194/egusphere-egu24-18070, 2024.

EGU24-18494 | ECS | Posters on site | SSS5.2

Modelling priming effect to explain the effect of DOC input quality on soil C turnover 

Olga Vindušková, Gaby Deckmyn, Kateřina Jandová, and Veronika Jílková

Even though priming effects (PE) could reduce soil organic C gains from enhanced ecosystem productivity under global change, the PE has been introduced to few models only recently. Both particulate organic matter (POM) and mineral-associated organic matter (MAOM) decomposition may be increased by DOC (dissolved organic carbon) inputs via the priming effect (PE) which is stronger in less-protected fractions (i.e., POM) and is also influenced by the DOC input quality. In our previous study, we showed that spruce litter leachates induced a higher PE than root exudates and could track their utilization by fungi and bacteria using isotope labelling, 13C-PLFA and 13C in respired CO2 and soil C fractions (Jílková et al. 2022)

Here we use components from the KEYLINK model to develop a model that can be optimized using data from the experiment of Jílková et al. (2022) and used to predict outcomes of ongoing follow up incubation experiments using 13C-labelled spruce and beech litter leachates and root exudates on soils and fractions alone. We use this approach to test our understanding of the mechanisms of the microbially-driven soil C turnover under contrasting quality of DOM inputs.

How to cite: Vindušková, O., Deckmyn, G., Jandová, K., and Jílková, V.: Modelling priming effect to explain the effect of DOC input quality on soil C turnover, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18494, https://doi.org/10.5194/egusphere-egu24-18494, 2024.

EGU24-18626 | ECS | Posters on site | SSS5.2 | Highlight

Combining remote sensing products with crop and soil models to estimate changes in soil organic carbon on cropland 

Gaétan Pique, Basile Goussard, and Andréa Géraud

Agricultural land is a major contributor to human greenhouse gas emissions, but it is also affected by climate change. At the same time, the recent 4p1000 initiative has identified cropland as having important the potential to sequester atmospheric carbon in the soil.
However, there is currently a lack of robust and accurate tools to assess the carbon budget of cropland at plot level and over large areas. This lack is due to the heterogeneity of the landscape, characterised by a wide range of soil and climatic conditions and many agricultural practices. However, these tools are needed to better understand the contribution of cropland to greenhouse gas emissions and to properly identify the most efficient levers for sequestrating carbon in the soil.
In this study we propose a modelling framework to estimate carbon budgets at plot scale and over large areas. This approach assimilates optical remote sensing products with high spatial and temporal resolution into a crop model (SAFYE-CO2). This model allows the estimation of CO2 fluxes as well as crop productions (biomass and yield) of the main crops and the cover crops. This information is then used as input to a soil model (RothC) to estimate the carbon storage following the introduction of the cover crops into the soil.
This framework is validated using CO2 flux measurements from the ICOS network and cover crop in situ biomass data.
This approach is in line with the search for the 'monitoring, reporting and verification' tools that is needed today to drive the agricultural transition, to enable sustainable agriculture that provides sufficient production in a changing climate, while identifying the best practices to use agricultural land as a way of achieving net zero carbon targets.

How to cite: Pique, G., Goussard, B., and Géraud, A.: Combining remote sensing products with crop and soil models to estimate changes in soil organic carbon on cropland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18626, https://doi.org/10.5194/egusphere-egu24-18626, 2024.

EGU24-19022 | Orals | SSS5.2

Enhanced rock weathering application on sub-tropical agroecosystems for carbon sequestration and sustainable crop production 

Shinya Iwasaki, Kosuke Hamada, Kazutoshi Kinjo, Yudai Yamaura, Yoshifumi Terajima, and Toshihiko Anzai

Achieving increased or sustained crop yields while minimizing environmental impact is a pressing challenge in agricultural science. Enhanced Rock Weathering (ERW) has emerged as a novel negative emission technology that accelerates natural geological processes of carbon (C) sequestration by applying crushed silicate rocks, specifically basalt, to croplands. However, field-scale evaluations to demonstrate carbon sequestration potential and agricultural co-benefits have been limited. This study quantitatively assessed the carbon and nitrogen (N) flow resulting from basaltic rock application in sugarcane and upland rice cultivation in a sub-tropical agroecosystem.

Two types of experiments were conducted on Ishigaki Island, located in the subtropical zone of Japan, where the annual rainfall and annual temperature were 2,500 mm and 24.0 ℃, respectively. Firstly, an outdoor field experiment on sugarcane cultivation was conducted. The following six treatments were applied with four replicates using a completely randomized block design: bare soil (no sugarcane), control without any amendment, lime application, manure application (10 Mg C ha−1), basaltic rock application (10% by weight), and a combination of manure and basaltic rock. Soil water at the 0.6 m depth, which we defined as leaching water, was collected from all plots using the porous cup method and subjected to dissolved C and N analysis. Secondly, an indoor lysimeter experiment was conducted on upland rice cultivation to understand the comprehensive flow of C and N, including greenhouse gas emissions. The following four treatments were assigned with three replicates to 12 concrete lysimeters with 2 m2 and 1 m depth: control without any amendment, torrefied plant residue (1% by weight), basaltic rock application (10% by weight), and a combination of torrefied plant residue and basaltic rock.

In the outdoor field experiment, continuous monitoring of soil volumetric water content and electric conductivity showed that the weathering of basaltic rock was enhanced by solid-liquid contact. Soil pH increased by the basaltic rock application the same as lime application. Similarly, the acidification of leaching water was buffered in the basaltic rock application treatments. Consequently, the inorganic carbon concentration in leaching water was higher in the basaltic rock application treatments than in the control and lime application treatments. Although there were no significant differences in the plant height of sugarcane, the number of leaves and Single Photon Avalanche Diode (SPAD) increased by basaltic rock application. Similarly, the indoor lysimeter experiment observed higher pH and dissolved inorganic C concentrations in leaching water. Although carbon dioxide flux increased by basaltic rock application in the first month, it was decreased in the crop growing period. These results indicated that the ERW application has a C sequestration potential and co-benefit on crop production. The annual C and N budget and further discussion will be presented in the session.

How to cite: Iwasaki, S., Hamada, K., Kinjo, K., Yamaura, Y., Terajima, Y., and Anzai, T.: Enhanced rock weathering application on sub-tropical agroecosystems for carbon sequestration and sustainable crop production, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19022, https://doi.org/10.5194/egusphere-egu24-19022, 2024.

EGU24-19605 | ECS | Posters virtual | SSS5.2

Soil carbon storage and greenhouse gas fluxes in forested and grassland ecosystems of Gujarat undergoing anthropogenic and climatic disturbances 

Niharika Sharma, Mohammad Atif Khan, Priyamvada Dubey, Chhavi Nath Pandey, Sanjeev Kumar, and Vikrant Jain

Carbon storage in soils is a significant nature-based solution for adaptation and mitigation of climate change. However, soil carbon storage varies with the change in land cover and the association of organic matter with differently sized soil aggregates. To compare the effects of these parameters on the carbon cycling of soils, we have analyzed the soil carbon content and greenhouse gas emissions from soils under different land cover in Gujarat, India. We sampled forest soils from regions covered with dry deciduous trees, moist trees, forest fires, and forest conversion to agriculture. We further sampled grassland soils in the areas showing matured grasses, harvested grasses, salinity-affected grasses, grazing-affected grasses, and the grassland region impacted by the invasion by Prosopis juliflora species. We classified some of these land features as a result of climatic disturbances (increase in salinity, invasion by Prosopis, forest fire) and others as anthropogenic disturbances (cattle grazing, harvesting, agriculture). Physico-chemical properties and greenhouse gases emitted from soils were measured using handheld probes and chamber methods, respectively. Laboratory analysis of soil carbon and its isotopes was performed for bulk soils and the soil density-size fractions (particulate fractions, sand-sized fractions, clay and silt size fractions, and recalcitrant organic matter fractions). Our analysis reveals the change in carbon emissions and carbon storage in soils of arid-moist stretch in Gujarat is caused by different land cover and management practices. The presence of aboveground biomass has a significant control on the carbon storage capacity of soils highlighting the importance of afforestation and ecosystem restoration in building up the soil carbon stock. Carbon emissions were also higher in soils with large aboveground vegetation; however, this mainly represents soil microbial respiration and thus indicates healthy soil and rich pedo-biodiversity. Most of the carbon in grassland soils was associated with silt and clay-sized particles whereas the carbon content in forested soils is higher within sand-sized particles. Soils from both grasslands and forests acted as a sink for atmospheric methane except for soils from grazed grasslands, indicating the importance of grazing management in grassland ecosystems. Climatic stressors like an increase in salinity and Prosopis invasion showed no significant impact on soil carbon stock and greenhouse gas emissions and behaved similarly to harvested grasslands or dry-deciduous forests. Forest fire, on the other hand, can change the texture and carbon and nitrogen association in the soils. Conversion of forests to croplands has the most detrimental impact on soil carbon storage and can lead to loss of stored carbon in the form of high greenhouse gas emissions. Forest land conversions should, therefore, also consider this aspect of forest conversion in its management plan.

How to cite: Sharma, N., Khan, M. A., Dubey, P., Pandey, C. N., Kumar, S., and Jain, V.: Soil carbon storage and greenhouse gas fluxes in forested and grassland ecosystems of Gujarat undergoing anthropogenic and climatic disturbances, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19605, https://doi.org/10.5194/egusphere-egu24-19605, 2024.

Improving carbon storage in soils and the biosphere is a promising nature-based solution to combat climate change and is receiving more and more attention with little understanding how this can be achieved globally and in a sustainable way.

Many of our expectations in finding nature-based solutions rely on vast, less developed–but nevertheless populated and rapidly changing– regions of the Global South. At the same time, concepts and assumptions about which solutions work for increasing long-term carbon capture in soil systems are based on knowledge gathered largely from the Global North in often fundamentally different environmental settings and development history. 

In my talk I will illustrate with examples from the socio-ecological context of the African Tropics how these knowledge gaps and our lack of understanding of tropical carbon cycling mislead us into thinking that we can find easy solutions in the Tropics to mitigate climate change. I will highlight how the interactions of weathering and erosional disturbance can influence and dominate biogeochemical cycles in soils and discuss some directions where geochemical proxies that are available at the global scale can be useful for improving the spatial and temporal representation of tropical carbon storage and turnover.

How to cite: Doetterl, S.: Soil carbon sequestration in sub-Saharan Africa – Great expectations, limited potentials?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22139, https://doi.org/10.5194/egusphere-egu24-22139, 2024.

EGU24-3409 | ECS | Orals | SSS5.3

Microbial iron(III) reduction of iron-organic carbon phases across a permafrost thaw gradient and its impact on methane emissions 

Eva Voggenreiter, Daniel Straub, Laurel Thomas Arrigo, Andreas Kappler, and Prachi Joshi

Wetlands account for roughly 20-30% of global methane (CH4) emissions, in part due to (permanently) anoxic conditions that promote methanogenesis. Low-lying permafrost peatlands are expected to be an increasing source of CH4 due to permafrost thaw in the future, due to waterlogging, anoxia and organic carbon (OC) mobilization. These processes can force an increase of the extent of wetlands and higher total CH4 emissions. Net release of CH4 depends on the availability of more energetically favorable electron acceptors in soil, such as ferric iron (Fe(III)). Fe(III) may be present as Fe(III) oxyhydroxides or Fe(III)-OC phases in peatlands. Since Fe(III)-reducing microbes and methanogens compete for the same substrates (e.g., small organic molecules such as acetate), CH4 production is often suppressed as long as there is bioavailable Fe(III) present. However, the dissolution of Fe(III)-OC phases during Fe(III) reduction would release the previously bound OC and make it more bioavailable to fermenting microorganisms. This would produce more substrates for methanogens and could therefore increase CH4 production. It is currently unknown to what extent microbial reduction of Fe(III)-OC phases and the coupled OC release effects CH4 emissions across permafrost thaw.

In this study, we therefore aim to elucidate the extent of reduction of Fe(III)-OC phases upon permafrost thaw and the corresponding effect on CH4 emissions across three distinct thaw stages: (i) recently collapsed palsa hills, (ii) partly thawed bog and (iii) fully thawed fen habitats. We simulated permafrost thaw by a series of incubation experiments with soils from each thaw stage from a permafrost peatland (Stordalen Mire, Abisko, Sweden). Soils were incubated under anoxic, flooded conditions for 30 days, after which synthesized 57Fe-labelled Fe(III)-OC coprecipitates were added as representative Fe-OC phases. Over the course of the incubations (42 days), we followed Fe speciation and 57Fe fractions in the dissolved and solid phases using geochemical and synchrotron-based spectroscopy techniques in addition to quantification of greenhouse gas production. Results show that added coprecipitates were completely reduced (within 1 day) in palsa and bog soils, leading to increases in dissolved Fe2+, OC concentrations and CO2 emissions. CH4 production was not detected in palsa soils over the course of the incubation and CH4 suppression in bog soils due to Fe(III) reduction was only short-term. In contrast, added coprecipitates in fen soils were only reduced by 10% after 42 days, likely due to low dissolved OC concentrations. However, this led to a significantly higher inhibition of methanogenesis than in the palsa and bog soils. We also studied the microbial community by 16S rRNA amplicon (gene) sequencing and quantified mcrA gene copy numbers to assess the potential activity of methanogens. Overall, these results help to understand the influence of Fe-OC coprecipitates on methane emissions in thawing permafrost peatlands.

How to cite: Voggenreiter, E., Straub, D., Thomas Arrigo, L., Kappler, A., and Joshi, P.: Microbial iron(III) reduction of iron-organic carbon phases across a permafrost thaw gradient and its impact on methane emissions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3409, https://doi.org/10.5194/egusphere-egu24-3409, 2024.

Diffusion is acknowledged as the principal mechanism for the soil solution transport of limiting nutrients in terrestrial ecosystems. This process is influenced by the interplay among the chemical, biological, and physical properties of soil, where alterations in these properties can variably impact other factors, thereby influencing diffusive fluxes. This study, based on theoretical analysis and the review of existing literature, explores how soil biological properties such as microbial activity and soil enzyme activity, as well as abiotic soil properties like soil pH, soil texture, soil cation and anion exchange capacity, and moisture, influence the diffusion and availability of nutrients in soils. We first formalize the drivers of diffusive solute fluxes into three contributors according to Fick’s first law of diffusion (the diffusion coefficient controlled by soil physicochemistry, the path length by pore size distribution and soil water content and the concentration gradient related to source-sink relationships) and then discuss and study the effects of soil biological and abiotic properties on these three principal drivers and on nutrient diffusion. Microbial activity plays a crucial intermediary role in the diffusion of nutrients in soils, significantly influencing their availability and distribution. Soil microorganisms, by decomposing soil organic matter, alter the form and availability of soil nutrients, thereby impacting the concentration gradient for nutrient diffusion. Additionally, the competitive relationship between plants and soil microorganisms affects the forms and quantities of available nutrients. Abiotic soil factors also significantly influence the migration and diffusion of nutrients. Soil chemical properties, such as soil pH and surface charge which vary among different forms of nitrogen, including inorganic forms such as nitrate and ammonium as well as organic forms such as amino acids. These forms exhibit considerable differences in net charge, hydrophobicity, and molecular weight, affecting their interaction with the soil matrix. Through processes like ion exchange, adsorption, and hydrophobic interactions, these interactions consequently alter their individual diffusion coefficients based on soil properties. Additionally, the physical structure of soil, such as the porosity, pore size distribution and aggregate structure, determines the mobility of water and nutrients within the soil through affecting the diffusive path length, together with soil water content, thereby affecting nutrient diffusion. In conclusion, this study underscores the importance of understanding and evaluating the interplay between soil biotic and abiotic properties when conducting nutrient diffusion research using soil microdialysis techniques. This comprehensive analytical approach is crucial for enhancing the effectiveness of soil nutrient management, as well as for its long-term implications on agricultural production and environmental conservation. The conceptual/analytical approach will be applied to a wide range of soils differing in texture, mineralogy, pH, chemistry, management and microbial activity, and diffusive fluxes of multiple elements and solute forms determined simultaneously at similar soil moisture and temperature, and then be linked - using machine learning approaches - to those key soil properties potentially controlling nutrient diffusive fluxes to develop a generalized model of controls of soil diffusive fluxes of elements.

How to cite: Wen, M. and Wanek, W.: Biotic and Abiotic Controls on Soil Nutrient Diffusion Fluxes Based on Microdialysis Measurerments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5844, https://doi.org/10.5194/egusphere-egu24-5844, 2024.

EGU24-5967 | ECS | Posters on site | SSS5.3

Gross Nitrogen Transformation: Insights from 15N Tracing in a Gas Sampling Incubation Experiment 

Barira Shoukat Hafiza, Wolfgang Wanek, Magdeline Vlasimsky, Mohammad Zaman, Gerd Dercon, Maria Heiling, and Christian Resch

Nitrous oxide (N2O) stands out among greenhouse gases due to its global warming potential, surpassing carbon dioxide by 310 times and methane by 16 times over a 100-year period. Its primary source lies in the application of fertilizers to agricultural soil. Despite its significance, traditional methods for understanding the intricate relationships within gross nitrogen (N) transformation processes are limited in their analytical depth.

Current research increasingly centers on the N2O/(N2O+N2) product ratio, offering valuable insights into the efficiency of nitrogen transformations and the potential for N2O emissions. Quantifying both gases, however, poses challenges that demand specialized techniques. Leveraging isotopic methods, such as the introduction of enriched NO3− and monitoring 15N labelled denitrification products, proves instrumental in unravelling N2O sources and facilitating emission mitigation strategies.

This study aims to contribute to this knowledge by measuring N2O and N2 and identifying their sources using a 15N tracer. Soil samples were collected from a 0-15cm depth at Grabenegg, an agricultural site in Austria. Two treatments were applied, with 15NH414NO3  for treatment one and 14NH415NO3 for treatment two, both at a rate of 100 kg N/ha (equivalent to 150 kg N/ha when expressed as 100 mg N/kg soil). The incubation experiment spanned 10 days in 850ml glass jars at 60% WFPS, involving seven sampling days. Soil analyses included ammonium and nitrate content through colorimetric methods, pH determination, and 15N analysis using an Isotope Ratio Mass Spectrometer (IRMS) following an adjusted Brooks microdiffusion.

Gas samples extracted from the jars over a two-hour period underwent analysis for CO2, CH4, and N2O content using a Picarro G5102-i isotopic and gas concentration analyzer. Integration with N tracing models yielded crucial insights into the connections between substrates and N transformation products, shedding light on the impacts of synthetic fertilizer and enabling the quantification of transformation rates.

How to cite: Hafiza, B. S., Wanek, W., Vlasimsky, M., Zaman, M., Dercon, G., Heiling, M., and Resch, C.: Gross Nitrogen Transformation: Insights from 15N Tracing in a Gas Sampling Incubation Experiment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5967, https://doi.org/10.5194/egusphere-egu24-5967, 2024.

EGU24-6628 | ECS | Orals | SSS5.3

Time to Anoxia: Oxygen Consumption in Soils Varies Across a Coastal Gradient 

Kaizad Patel, Kenton Rod, Jianqiu Zheng, Peter Regier, Fausto Machado-Silva, Matthew Kaufman, Kenneth Kemner, J. Patrick Megonigal, Nicholas Ward, Michael Weintraub, and Vanessa Bailey and the COMPASS-FME Team

The coastal terrestrial-aquatic interface (TAI) is a highly dynamic system characterized by strong physical, chemical, and biological gradients. In particular, shifting soil redox conditions, due in part to dynamic water conditions, is a strong driver of carbon availability and transformations across TAIs. However, one of the important unknowns across TAIs is how soils with different characteristics and inundation regimes respond quantitatively to water saturation and resulting shifts between oxic and anoxic subsurface conditions. We used field measurements, laboratory incubations, and model simulations to investigate oxygen consumption and redox transformations following short-lived oxygenation events under different environmental conditions. Soils were collected along a coastal gradient (upland to wetland) from the Western Lake Erie region (freshwater TAI) and the Chesapeake Bay (estuarine TAI) and incubated in microcosms for two weeks. When inundated in MilliQ water, the upland A horizon soils went anoxic in 24 hours, whereas the wetland and transitional soils went anoxic in 0.5 - 10 hours. In contrast, the upland B horizon soils did not go anoxic during the 2-week incubation. Model simulations suggested stronger abiotic controls of oxygen consumption in the wetlands vs. biotic controls in the upland soils. These simulations also suggested nutrient limitation in the subsurface soils. Subsequent incubations with glucose and acetate additions showed increased rates of oxygen consumption in the B horizon soils, suggesting that these soils were indeed carbon limited. These experiments provide insight on shifting redox conditions during flooding events, especially relevant in coastal systems that experience rapidly shifting hydrological conditions and are becoming increasingly vulnerable to sea level rise and episodic disturbances (e.g., storm surges, king tides).

How to cite: Patel, K., Rod, K., Zheng, J., Regier, P., Machado-Silva, F., Kaufman, M., Kemner, K., Megonigal, J. P., Ward, N., Weintraub, M., and Bailey, V. and the COMPASS-FME Team: Time to Anoxia: Oxygen Consumption in Soils Varies Across a Coastal Gradient, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6628, https://doi.org/10.5194/egusphere-egu24-6628, 2024.

 The repetitive wetting and drying cycles, driven by intense rainfall and drought, intricately alter subsurface conditions, affecting redox states and pH levels. Consequently, these alterations may prompt the dissolution or transformation of ferrihydrite (Fh), an amorphous iron oxide used as a stabilizing agent in soil, thereby influencing the leaching behavior of heavy metals. This study investigates the impact of wetting and drying cycles on Fh crystallinity, and the leaching behavior of immobilized heavy metals, specifically focusing on cadmium (Cd) and zinc (Zn) at Fe/heavy metals molar ratios of 1 and 10. Fh synthesis was induced by neutralizing pH to 7.0 with 1 M NaOH, simultaneously fostering the coprecipitation of Fh-heavy metals. The experimental design entailed 12 cycles, each involving 8 hours of wetting at room temperature, followed by 16 hours of drying at 40 °C. The Synthesis Precipitation Leaching Procedure (SPLP) was then used to confirm the variations in leaching quantities observed throughout the cycles, following the guidelines of EPA METHOD 1312. Analyses using X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) revealed distinct variations in morphology and crystallinity based on the type and ratio of heavy metals. Pure ferrihydrite remained stable after 12 cycles; however, heightened crystallinity emerged after 3 cycles in high heavy metal concentrations, forming otavite (CdCO3) in Cd samples and petalline-shaped ferrihydrite in Zn samples. In contrast, low heavy metal concentrations displayed no such changes, indicating variable effects of wetting-drying cycles depending on the iron-to-heavy-metals ratio. The supernatant concentration decreased by 11-37% during wetting in all samples, yet SPLP leaching tests exhibited consistent heavy metal concentrations between wetting and drying, suggesting a minimal impact on heavy metal stability. These findings underscore the environmental factors influencing the stability of iron oxide-based immobilized heavy metals and raise the need for long-term stability assessments to consider variables that can cause more complex changes in the field. 

How to cite: Kim, C. and Nam, K.: Effect of Wetting and Drying Cycles on the Stability of Cadmium and Zinc Immobilized with Ferrihydrite , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7067, https://doi.org/10.5194/egusphere-egu24-7067, 2024.

EGU24-7518 | ECS | Posters on site | SSS5.3

Faster P cycling upon permafrost collapse 

Ziliang Li and Yuanhe Yang

Permafrost collapse is expected to accelerate carbon (C) release and induce a positive C-climate feedback. As the frequently limiting key element in permafrost ecosystems, phosphorus (P) could mediate ecosystem C balance by modulating microbial decomposition and primary production. However, little is known about the changes in P cycling upon permafrost collapse. By combining sequential extraction, 31P NMR spectroscopy and metagenomic sequencing, we explored whether and how different soil P pools and microbial P transformation genes responded to permafrost thaw based on six thermokarst (abrupt collapse of ice-rich permafrost)-influenced sites on the Tibetan Plateau. We observed a significant decrease in soil labile P, NaOH-Po and residual P after permafrost collapse. The negative relationship between aboveground biomass P content and the soil labile P as well as NaOH-Po indicated that the reduction in these P pools were associated with the plant P uptake. Moreover, the increased relative abundance of the genes involved in inorganic P-solubilization and organic P-mineralization upon permafrost collapse reflected the potential increase in microbial P mobilization. These findings highlight a faster P cycling through plant P uptake and microbial P mobilization after permafrost collapse, which could impact the ecosystem C cycle and its feedback to climate warming.

 

How to cite: Li, Z. and Yang, Y.: Faster P cycling upon permafrost collapse, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7518, https://doi.org/10.5194/egusphere-egu24-7518, 2024.

EGU24-9618 | Posters on site | SSS5.3

Exchangeable soil and sediment fractions compared 

Manfred Sager

Soil to plant transfer depends on availability, plant needs and plant excretion. Readily soluble and exchangeable ions represent the minimum available fraction. Traditionally, different extracts have been standardized to monitor just one or two nutrients resp. trace elements. Whereas customers expect a “true value”, leachings with neutral salts lead to slightly different results. Some of the uncertainties are due to the low concentration levels, others due to resorption of reagent blanks at the solid matrix. Thus, the interpretation is of relevance, and not the numeric level.

From the point of view of blanks and ICP-compatibility, ammonium salts or weak organic acids should be preferable extractants.

Data from a ring test of 5 soils and 12 participants show widely overlapping data ranges of extracts obtained with ammonium acetate and ammonium nitrate, but a trend to lower release of Cd, Cu, Pb and Zn into nitrate versus acetate, contrary to Cr and Ni. This is expectable due to complexation capabilities of acetate.

Also from sediments of the River Danube, 1M ammonium acetate released much more Pb, Zn, P, Ca, and Mn than 1M ammonium chloride at the same pH = 7. For Cr, Al, and As, however, this effect was rather reverse. The proportion of acetate versus chloride release did not significantly correlate with loss of ignition, nor with pedogenic of these samples. (The pedogenic oxides were calculated as the sum of Al+Fe+Mn released into oxalate buffer pH 3, and turned into their oxides).

Is it possible, to substitute the fraction exchangeable with LiCl by much cleaner dilute acetic acid? The released amount into LiCl is quite low, and in non-contaminated samples, As, Be, Cd, Cr, Mn, Mo, Pb and V were below detection limits. There is resorption of Cr, Ni, Pb, Zn reagent blanks at the solid, and Li blanks at the ICP for subsequent determinations get reduced. In case of K, Mn, Ba, and B, a good correlation and for S and P a moderate one, had been achieved between concentrations extracted into LiCl and dilute acetic acid, but not for others.

In order to optimum use of ICP-OES as a multi-element instrument, and to cope with decreasing manpower in the labs, the number of extractions should be minimized. Thus, it was tried to simulate the concentration of K and P by CAL extract, B by Baron-extract, and Mg by CaCl2-extract, by a simple (BCR-like) sequence of 0,16M acetic acid, with subsequent 0,1M oxalate buffer pH 3. This would widen the scope for acid exchangeable trace elements and S also. K, P and B could be very well simulated, and fitted to equal numeric values by partial correlation analysis with other parameters obtained, but for Ca-exchangeable Mg, this was difficult.

How to cite: Sager, M.: Exchangeable soil and sediment fractions compared, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9618, https://doi.org/10.5194/egusphere-egu24-9618, 2024.

EGU24-11857 | Orals | SSS5.3

Soil organic matter turnover: global implications from δ13C and δ15N signatures 

Yakov Kuzyakov and Evgeniya Soldatova

The residence time of carbon (C) and nitrogen (N) in soil is a fundamental parameter reflecting the rates of soil organic matter (SOM) transformation and the contribution of soils to greenhouse gases fluxes. Based on the global database of the stable isotope composition of C (δ13C) and N (δ15N) depending on soil depth (171 profiles), we assessed С and N turnover and related them to climate, biome types and soil properties. The 13C and 15N discrimination between the litter horizon and mineral soil was evaluated to explain the key litter transformation processes. The 13C and 15N discrimination by microbial utilization of litter and SOM, as well as the continuous increase of δ13C and δ15N with depth, enabled to assess C and N turnover within SOM. N turnover was two times faster than that of C, which reflects i) repeated N recycling by microorganisms accelerating the N turnover, ii) C loss as CO2 and input of new C atoms to cycling, which reduces the C turnover, and iii) generally slower turnover of N free persistent organic compounds (e.g. lignin, suberin, cellulose) compared to the N containing compounds (e.g. amino acids, ribonucleic acids). An increase in temperature and precipitation accelerated C and N turnover because: i) higher microbial activity and SOM decomposition rate, ii) larger soil moisture and fast diffusion of dissolved organics towards exoenzymes, iii) downward transport of 13C-enriched organic matter (e.g. sugars, amino acids), and iii) leaching of 15N-depleted nitrates from the topsoil and losses from the whole soil profile. Temperature accelerates SOM turnover stronger than precipitation. The temperature increase by 10 °C accelerates the C and N turnover for 40%. SOM turnover is boosted by decreasing C/N ratio because: i) SOM with a high C/N ratio originated from litter is converted to microbially-derived SOM in mineral soil characterized by a low C/N ratio; ii) litter with a low C/N ratio is decomposed faster than litter with a high C/N; iii) microbial carbon-use efficiency increases with N availability. The biome type affects SOM decomposition by i) climate: slower turnover under wetter and colder conditions, and ii) by litter quality: faster utilization of leaves than needles. Thus, the fastest C turnover is common under evergreen forests and the lowest under mixed and coniferous ones, whereas temperature and C/N ratio are the main factors controlling SOM turnover. Concluding, the assessment of SOM turnover by δ13C and δ15N approach showed two times faster N turnover compared to C, and specifics of SOM turnover depending on the biomes as well as climate conditions.

Soldatova E, Krasilnikov S, Kuzyakov Y 2024. Soil organic matter turnover: global implications from δ13C and δ15N signatures. Science of the Total Environment 912, 169423. https://doi.org/10.1016/j.scitotenv.2023.169423

How to cite: Kuzyakov, Y. and Soldatova, E.: Soil organic matter turnover: global implications from δ13C and δ15N signatures, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11857, https://doi.org/10.5194/egusphere-egu24-11857, 2024.

EGU24-12106 | Orals | SSS5.3

Divergent patterns of Carbon, Nitrogen and Sulfur storage in grassland soils 

Sara L. Bauke, Jospehine Iser, Heike Schimmel, Dymphie Burger, and Wulf Amelung

Sulfur (S) in soils mainly occurs in organic forms, and its cycling should be primarily controlled by the same factors as those for carbon (C) and nitrogen (N), two other main constituents of soil organic matter. Here, we aim to test this assumption based on a global meta-analysis of soil organic C, N and S contents in grassland soils. We reviewed existing literature with a focus on grassland soils as one of the major global ecosystems, including both native grasslands and managed grasslands with additional fertilization. Element concentrations and supplementary parameters (mean annual temperature and precipitation, texture, pH, soil group, management) were retrieved from the studies, while C:S and N:S element ratios were either directly obtained from the studies or calculated. Additionally, we analyze isotope ratios of the respective elements (δ13C, δ15N and δ34S) in soil samples collected from native and managed grassland sites along climatic transects across Europe and North America.

In literature data concentrations of OC and N, but not S, were significantly higher in pastures compared to native grassland. As a consequence, C:S and N:S ratios were significantly lower in cultivated grassland than in native sites. Further, climatic conditions and soil group significantly affected C:S and N:S ratios, with significantly lower ratios in arid climate and in soil groups typically occurring there (e.g. Kastanozems) compared to more humid conditions and respective soil groups (e.g. Luvisols). However, the variation of C:S and N:S ratios was considerably higher than for C:N ratios. This was also evident in the isotope data obtained from the soil samples along the continental transects. Here, compared to δ13C and δ15N, δ34S values showed strong variation that was only partially explained by climate and land use, and was additionally affected by the specific parent material at each site. We therefore suggest that the availability and turnover of S in organic matter of grassland soils is not strictly analogous to C and N cycling. 

How to cite: Bauke, S. L., Iser, J., Schimmel, H., Burger, D., and Amelung, W.: Divergent patterns of Carbon, Nitrogen and Sulfur storage in grassland soils, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12106, https://doi.org/10.5194/egusphere-egu24-12106, 2024.

EGU24-13254 | ECS | Posters on site | SSS5.3

P dynamics in rainfed forage maize crop soils under different maize-grassland rotation cycles 

Begoña Maroñas, Ángeles Prieto-Fernández, Beatriz Rodriguez-Garrido, Serafín González-Prieto, M. Carmen Monterroso-Martínez, and Carmen Trasar-Cepeda

In a context of environmental sustainability, fertiliser application to agricultural soils must be optimised through sustainable cultivation practices. Over-fertilisation, the use of soluble mineral forms and/or their application at inappropriate stages of crop growth, has generated serious problems associated with the alteration of biogeochemical cycles (mainly C, N and P), eutrophication of waters, emission of greenhouse gases and depletion of natural resources. For this reason, our research team is conducting a project aimed at developing and evaluating sustainable agricultural soil management practices that reduce dependence on inorganic fertilisers and pesticides, prevent SOM loss and erosion, and contribute to the restoration of soil biodiversity. As part of this project, this study focuses on assessing P dynamics in rainfed forage maize crop soils subjected to different management practices, aiming to evaluate the influence of these practices on the bioavailability of P and its potential leaching into drainage waters.

We selected several maize plots subjected to two distinct management types, each under conventional inorganic/organic fertilisation regime. The first management type follows a typical rotation for maize crops in the area - after maize harvest (September-October) the plot is maintained as grassland for 2-3 years before being cultivated with maize again (3-year rotation). The second management type focuses on analising P dynamics in soils during the early stages of conversion to cultivation. In this case, we choose a site where soil that had been under grassland for at least 100 years was converted to maize; however, in this case the maize-grassland rotation is annual, with the two crops alternating each year (1-year rotation).

Over three consecutive years, samples were taken from the top 10 cm of the soil under the triennial grassland-maize rotation, while for the annual rotation, samples were taken from the top two soil layers (0-10 and 10-20 cm). Soil sampling occurred at various times when the soil was under maize and grassland. P forms were analysed following the sequential fractionation of Hedley et al. (1982). Residual inorganic and total P were analysed through extraction with 0.5 N sulfuric acid before and after calcination (550 ºC, 2 h) of the fractionation residue, estimating the residual organic phosphorus by difference between both. The pseudo-total P content of the soils was determined by ICP-OES after acid digestion with HNO3 +HCl in a microwave oven (MILESTONE, Italy).

The results were analysed in relation to the type of rotation and the time elapsed since the transformation from grassland to maize cropland. The P content, especially inorganic P, in the soil subjected to the 3-year rotation was significantly higher compared to the soil under the 1-year rotation. This discrepancy reflects the historical overfertilization experienced by the former over an extended period. Moreover, the transition from grassland to maize cultivation resulted in the loss of the typical stratification observed in grassland soils. This was evidenced through the homogenization of P contents across all organic and inorganic forms in the two soil layers investigated.

Hedley M.J., J. Stewart J.W.B., Chauhan B.S. 1982. Soil Sci. Soc. Am. J. 46, 970-976.

How to cite: Maroñas, B., Prieto-Fernández, Á., Rodriguez-Garrido, B., González-Prieto, S., Monterroso-Martínez, M. C., and Trasar-Cepeda, C.: P dynamics in rainfed forage maize crop soils under different maize-grassland rotation cycles, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13254, https://doi.org/10.5194/egusphere-egu24-13254, 2024.

EGU24-13568 | ECS | Orals | SSS5.3

Effect of biochar application depths on leaching of nitrate and crop growth 

Kosuke Hamada and Satoshi Nakamura

Abundant use of chemical fertilizer causes reactive nitrogen load to the environment. Leaching of reactive nitrogen occurs mainly in nitrate (NO3−N) form, which moves into groundwater and other water bodies causing human health hazard and harming ecosystems, especially in tropical islands. Biochar application, which is known as a measure of carbon sequestration, can mitigate the leaching of NO3−N. We have accumulated knowledge regarding the effective application rate of biochar. However, the information on the effect of biochar application depth remains unclear, although it would affect the leaching of NO3−N and crop growth. The objective of this study was to evaluate the effect of biochar application depth on the leaching of NO3−N and crop growth. Using biochar made from bagasse, which is a major organic waste in tropical islands, we conducted a pipe experiment with upland rice (NERICA). We set four treatments: control (no biochar application); surface application (0−5 cm); plow layer application (0−30 cm); subsurface application (25−30 cm). Regarding leaching of NO3−N, the result under surface application showed a 12% decrease, while that under plow layer application showed an 11% increase against that under the control. Whereas the leaching of NO3−N was the same under subsurface application as that under the control. Total nitrogen uptake by crop was the highest under surface application, whereas those under plow layer and subsurface applications were smaller than those under the control. By comparing the leaching of NO3−N with the total nitrogen in the root, we obtained a clear relationship that the higher the total nitrogen in the root was, the lesser the leaching became. The result of the matric potential head in each pipe revealed that soil water condition was stressless for crops under the surface application. On the other hand, dry stress occurred more frequently under plow layer and subsurface applications. These results indicated that, depending on biochar application depth, soil water stress conditions differed and affected root growth positively/negatively. Consequently, crop growth and the leaching of NO3−N were changed. The surface application can be considered as an effective application, which mitigates the leaching and promotes crop growth simultaneously. We believe the finding of this study encourages the establishment of sustainable agriculture.

How to cite: Hamada, K. and Nakamura, S.: Effect of biochar application depths on leaching of nitrate and crop growth, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13568, https://doi.org/10.5194/egusphere-egu24-13568, 2024.

EGU24-15009 | ECS | Orals | SSS5.3

Trace metal transport during managed aquifer recharge with monovalent-partial desalinated water: The role of divalent ions and organic matter 

Laura Braeunig, Jack Longman, Frederik Gäng, and Gudrun Massmann

Global fresh groundwater resources are threatened due to increasing withdrawal and salinization. Managed Aquifer Recharge (MAR) is an effective approach to augment overexploited aquifers and can also be applied to improve the groundwater quality by infiltration of desalinated water. But MAR can also bear risks when the soil passage or aquifer contains trace metals (e.g. As, V, Co, Cd) with their mobilization and subsequent human uptake. Understanding of metal mobilization (especially As) due to mineral dissolution at MAR sites with desalinated water was subject of investigation in many studies. Ionic strength and divalent ions concentration of the infiltrating water are known to influence the transport behaviour of trace metals by controlling dissolution and stabilization. As a new approach for water desalination, the aim of the cooperative project “innovatION” is the development of a monovalent-selective membrane capacitive deionization method to remove monovalent ions from brackish water. Other than fully desalinated water, the product water is still enriched in divalent ions. Here, we present first insights on how trace metal transport during MAR depends on the chemistry of the infiltrating water. Trace elements, as for example As, were found in sands of the East Frisian Island Langeoog, Northern Germany, and could be mobilized during potential MAR. We conducted column experiments with infiltration of a fresh groundwater (fGW), monovalent partial desalinated water (mPDW) and pure water (PW) into grey dune sand from Langeoog.

Our results show As mobilization due to shifting redox conditions and iron mineral dissolution up to a maximum of 16 µg/l in the outflow. Notably, the infiltration of mPDW, with a higher ionic strength than fGW and PW, lead to a temporary retention of As with a concentration decline to 2 µg/l and subsequently a slow increase. Whereas As is further mobilized with a very slow decrease with infiltration of fGW and PW. Arsenic concentrations were positively connected to dissolved organic carbon concentrations of the outflow, an indication that organic complexation of As takes place after dissolution of Fe-minerals. Clearly, the infiltration of mPDW can mitigate potentially harmful colloidal trace element transport. These results help to understand the mechanisms of sorption, desorption and transport of trace metals in environments with changing pore water chemistry during MAR. Our research also aids to better assess the functionality of this novel desalination technique that has high potential to improve groundwater quality.

How to cite: Braeunig, L., Longman, J., Gäng, F., and Massmann, G.: Trace metal transport during managed aquifer recharge with monovalent-partial desalinated water: The role of divalent ions and organic matter, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15009, https://doi.org/10.5194/egusphere-egu24-15009, 2024.

EGU24-15729 | ECS | Posters on site | SSS5.3

The influence of liming with oil-shale ash on the soluble P fraction in soil 

Tonu Tonutare, Raimo Kõlli, Tõnis Tõnutare, and Kadri Krebstein

The acidification of agriculturally used soils is a widely known phenomenon. Acidification may be caused by various factors. One part of the acidification results from natural processes, including acid plant root exudates and the oxidation of flora and fauna residues in the soil. Another contributing factor is acidic rain, which may have a natural origin or be caused by human activities such as burning coal, sulfur-containing materials, and emissions from metallurgy and chemical factories.

For sustainable agriculture, it is essential to maintain the optimum soil pH to ensure high yields. Typically, liming is employed to establish the suitable pH for plant growth, using carbonaceous materials. Commonly used materials include milled limestone or dolomite, and sometimes ashes from biomaterial. In Estonia, for over 60 years, fly ash from the burning of oil shale in power plants has been used for liming agriculturally used fields. However, the bottom ash from power plants remains unused and is stored in ash hills, accumulating to more than 600 million tons. This ash is an alkaline material with a high content of calcium, potassium, and magnesium. In 2025, the company RagnSells plans to start an experimental factory producing high-quality CaCO3 from this ash. The residue of this process will be a white solid alkaline material with an increased content of magnesium, making it suitable for liming agriculturally used fields. As liming can lock some phosphorus in the soil into an insoluble phase, there may be a decrease in soluble (plant-available) phosphorus. Therefore, we conducted an incubation experiment with this experimental liming agent on three different soils and used two fertilizer norms.  Our research aimed to monitor changes in water-extractable and plant-available P (by the AL method) content in different soils during a 24-week incubation period.

How to cite: Tonutare, T., Kõlli, R., Tõnutare, T., and Krebstein, K.: The influence of liming with oil-shale ash on the soluble P fraction in soil, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15729, https://doi.org/10.5194/egusphere-egu24-15729, 2024.

Planting trees on non-forested land has the potential to sequester atmospheric CO2 in biomass and soil. While afforestation on former agricultural land often results in an increased soil organic carbon sequestration, the outcomes of afforestation on pastures vary from carbon sink to source. Alpine soils are characterized by a higher proportion of labile carbon compounds compared to soils in temperate ecosystems, which makes alpine ecosystems more sensitive to environmental changes. The conversion of subalpine pasture to forests thereby might have a substantial effect on the SOC dynamics and  on soil organic matter (SOM) stabilization. In addition, the alteration in the proportion of aboveground biomass- and root-derived organic matter and the associated alterations in the soil microbial community following afforestation on subalpine pastures are not yet fully understood.

In this study, the alteration in SOC stocks as well as in the SOM composition following  afforestation (0 to 130 years) with Norway spruce (Picea abies) on a subalpine pasture is investigated in the Swiss Alps. To determine the alteration of potential sources and decomposition of SOM, a multi-proxy molecular marker approach was applied. Specifically, the combination of n-fatty acids, n-alkanes, and n-alcohols was applied to identify possible sources of plant-derived SOM. For the identification of microorganism-derived SOM, a combination of phospholipid fatty acids and glycerol dialkyl glycerol tetraethers was used.

Afforestation with Norway spruce on a subalpine pasture did not result in any significant change in SOC stocks (Pasture: 11.5 ± 0.5 kg m-2; 130-year-old forest 11.0 ± 0.3 kg m-2) after 130-years. The organic matter input, however, changed from grass leaves to spruce needles with increasing forest stand age. Surprisingly, root-derived organic matter seems to play a minor role in the pasture soil as well as in forest soils of all stand ages as one of the predominant sources of SOM. With increasing forest age an increased abundance of Gram+ bacteria as well as arbuscular mycorrhizal fungi was observed. In the pasture soil, a clearly higher abundance of archaea was observed compared with the forest. This shift in the soil microbial community shows its adaptation to the changes in the vegetation cover.  Furthermore, the difference in the soil microbial community structure implies a use of different carbon substrates of the microorganisms between the pasture and forests, which can have substantial effects on soil organic matter stabilization. Conclusively SOC stocks did not change after 130 years of afforestation on a subalpine pasture, but the SOM dynamics has changed due to the changes in the vegetation cover. For a better understanding of the connection between organic matter input and its decomposition, the analysis of plant polymers such as cutin and suberin polymers can help to unravel the difference in shoot- vs. root-derived organic matter and their contribution to the stable SOM pool in subalpine ecosystems.

How to cite: Speckert, T. C. and Wiesenberg, G. L. B.: Afforestation on a subalpine pasture does not result in an increase in carbon sequestration but in a change in the soil organic matter (de)composition  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18440, https://doi.org/10.5194/egusphere-egu24-18440, 2024.

EGU24-18712 | ECS | Orals | SSS5.3

Drought induces changes to redox chemistry and C exports from boreal riparian soils 

Martin Škerlep, Melissa Reidy, Hjalmar Laudon, and Ryan Sponseller

Extreme summer droughts can drastically lower water tables and lead to oxygenation of normally anoxic soils in boreal ecosystems. In organic rich riparian soils, this creates a dynamic redox environment, driving changes in soil organic matter stability and the export of redox sensitive elements (e.g., C, N, S, Fe, etc.) to surface waters.  We hypothesized that the destabilization of redox cycles and the activation of oxidative soil enzymes during drought periods can lead to prolonged periods of altered soil biogeochemical processes that drive element export from terrestrial to surface water systems upon rewetting. Here we simulated a soil core drying-rewetting event, to ask how riparian soil solution biogeochemistry changes during two months post drought. To three drought treatments (dry, semi-dry, wet), we also added a root exudate treatment (exudates or no exudates) to simulate the effects of riparian vegetation on microbial organic matter decomposition. We found that following drought, dissolved organic carbon (DOC) concentrations initially decreased, due to the increased acidity caused by the oxidation of reduced S to SO42-. As other preferred electron acceptors (O2, NO32-, Fe3+) were gradually reduced, reduction of SO42- lead to increases in DOC concentrations, which after 2 weeks surpassed concentrations in the control (wet) treatment, and continued increasing until the end of the experiment. Once SO42- was depleted and CO2 became the preferred electron acceptor, methane (CH4) in solution also increased to concentrations higher than those in control treatments. Peroxidase activity was increased post drought and remained elevated throughout the experiment, suggesting that microbial organic matter breakdown was enhanced, and could explain why DOC concentrations in drying treatments eventually surpassed those in wet controls. While the root exudate treatments produced mixed results, an increase of labile C supply appeared to increase extracellular enzymatic activity and serve as an alternative electron acceptor, thereby suppressing methanogenesis. Our results show that drought drastically changes the biogeochemistry of boreal riparian soils and that upon rewetting this can eventually lead to increased lateral exports of both organic and inorganic C. Changes in C biogeochemistry are seemingly caused by shifts in redox chemistry and by changes in microbial decomposition of soil organic matter induced by the oxygenation of riparian soils. Since this has implications for surface water chemistry, further study is needed on the length of drought effects to establish the duration of this influence of stream and riparian biogeochemistry.

How to cite: Škerlep, M., Reidy, M., Laudon, H., and Sponseller, R.: Drought induces changes to redox chemistry and C exports from boreal riparian soils, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18712, https://doi.org/10.5194/egusphere-egu24-18712, 2024.

EGU24-18833 | ECS | Posters on site | SSS5.3

Changes in soil organic matter forms after the conversion of a meadow into a rainfed forage maize-ley grassland rotation cropland 

Ana María Martínez-Solino, Carmen Trasar-Cepeda, Carmela Monterroso, Beatriz Rodríguez-Garrido, Serafín González-Prieto, and Ángeles Prieto-Fernández

Agricultural management deeply affects soil properties, with soil organic matter (SOM) being among those most impacted. Nowadays, the importance of adopting agricultural management systems and practices that enhance the storage and stabilization of organic matter in the soil is widely accepted. In this context, the analysis of different SOM fractions is essential for evaluating its stability and obtaining valuable information about its potential long-term persistence.

In the present study 0-10 cm and 10-20 cm soil samples were collected 2 months and 2 years after the conversion of an old meadow into a rainfed forage maize-ley grassland rotation system. Similar reference soil samples were taken from an undisturbed area of the meadow. The SOM in samples collected was analysed using different chemical extractants and particulate organic matter (POM) and mineral associated organic matter (MAOM) were studied using a physical fractionation method (Lopez-Sangil and Rovira, 2013 with unpublished modifications suggested by P. Rovira).

The conversion of the meadow into the rotation cropland induced a reduction of soil organic C content and modifications of SOM fractions. Generally, the changes were detected in the first sampling and persisted two years after the implementation of the rotation system. The modification induced by the agricultural management were more pronounced in the 0-10 cm layer than in the 10-20 cm layer.

Lopez-Sangil L., Rovira P. 2013. Soil Biol. Biochem. 62, 57–67

How to cite: Martínez-Solino, A. M., Trasar-Cepeda, C., Monterroso, C., Rodríguez-Garrido, B., González-Prieto, S., and Prieto-Fernández, Á.: Changes in soil organic matter forms after the conversion of a meadow into a rainfed forage maize-ley grassland rotation cropland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18833, https://doi.org/10.5194/egusphere-egu24-18833, 2024.

EGU24-20796 | Orals | SSS5.3 | Highlight

Predicting Soil Nitrogen Mineralization Potential using Pyrolysis-coupled FTIR 

Sevendeep Kaur and Adam Gillespie

Soil nitrogen (N) is a key component of plant nutrition but our ability to predict organic N mineralization potential remains incomplete.  Several methods are commonly used to characterize and measure mineralizable N; however, they are generally lacking because of required lab resources and poor predictive power. Pyrolysis is an emerging technology used to characterize soil organic matter and the thermal stability of soils. However, the idea of using Pyrolysis technology to characterize soil N and measure soil N release is novel. We adopted a novel online pyrolysis coupled with FTIR (Fourier-transform infrared spectroscopy) technology to investigate soil N. The soil samples used were collected from a long-term field trial involving different crop rotations and fertilization to include a wide array of samples. Samples were pyrolyzed from 25 to 850 °C with a heating rate of 10 K min-1. The temperature at which 50% of the material underwent pyrolysis, referred to as T50, was determined to quantify the thermal stability. The focus was to look at mass loss characteristics, identify volatile matter released, T50, and the correlation of TG-FTIR data with a 12-week lab mineralization study. We found a negative correlation (R2= -0.67) between the T50 and mineralized N at week 12. In conclusion, this study elucidates the intricate interplay between temperature kinetics and nitrogen mineralization. The negative correlation between T50 and mineralizable N underscores the potential of the material to release N over time. This research offers a valuable foundation for optimizing Pyrolysis application in the context of soil nitrogen. 

How to cite: Kaur, S. and Gillespie, A.: Predicting Soil Nitrogen Mineralization Potential using Pyrolysis-coupled FTIR, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20796, https://doi.org/10.5194/egusphere-egu24-20796, 2024.

EGU24-416 | ECS | Posters on site | BG1.10

The dissolution pattern of the flattened otolith of Pacific cod using the stepwise acid dissolution method 

Keito Aonuma, Yusuke Yokoyama, Yosuke Miyairi, Masayuki Chimura, Tomonori Hamatsu, Osamu Sakai, and Guido Plaza

The inner ear of fish contains calcium carbonate (CaCO3)-based crystals called otoliths, which play an essential role in hearing and balance. During otolith formation, new calcium carbonate is deposited in layers on the surface of the existing part and the part is no longer affected by metabolism. This feature means that each layer of the otolith retains the trace element ratios and isotope ratios it had at the time of formation. By analysing this preserved information, it is possible to make estimates about the environment and habitat at that time.

The stepwise acid dissolution method has been used in several studies as a technique for analysing the radiocarbon isotope ratios preserved in otoliths. In this method, phosphoric acid is used to dissolves the otolith from the outermost to the innermost layers. It has the advantage that a large amount of carbon can be collected from a single otolith, compared to the mechanical methods for the calcium carbonate sampling from each layer of the otolith.

However, this method involves dissolving the otolith in acid and the pattern of dissolution cannot be controlled minutely by the experimenter. Pacific cod (Gadus macrocephalus) otolith used by us is flattened and the dissolution pattern of such otoliths is not yet known. Furthermore, no direct observation of the otolith dissolution process has been made in relation to previous studies.

In this study, we dissolved three Pacific cod otoliths in phosphoric acid to directly confirm the process of otolith dissolution in the stepwise acid dissolution method. We removed each otolith from the acid one or more times during the dissolution process, weighed it and observed the change in the shape of the otolith and the layer structure exposed on the otolith surface. As the dissolution progressed and the otoliths became smaller, we polished them to check that the internal layered structure had not been destroyed by acid penetration.

As a result, we found that the serrated structures present on the outer edges of the otoliths are maintained when they are dissolved from the outside by acid. We also confirmed that acid dissolution from the outside does not destroy the inner layer structure, even microstructures such as daily rings. The validity of the stepwise acid dissolution method would be strengthened by these results. On the other hand, the otoliths were thinner as a result of acid dissolution, exposing the more inner layers on the flat surface. This is due to the thin vertical thickness of the flattened otoliths. This observation suggests that the collected carbon may be mixed with the carbon collected from more inner layer. This carbon mixing is able to be taken into account with future work. In addition, care should be taken when using this method near the nucleus, as the final stage of dissolution results in multiple holes in the otolith.

How to cite: Aonuma, K., Yokoyama, Y., Miyairi, Y., Chimura, M., Hamatsu, T., Sakai, O., and Plaza, G.: The dissolution pattern of the flattened otolith of Pacific cod using the stepwise acid dissolution method, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-416, https://doi.org/10.5194/egusphere-egu24-416, 2024.

EGU24-815 | ECS | Orals | BG1.10

From sediments to the atmosphere: a mass spectrometry approach revealing structural dissimilarities of common NOM components 

Alexander Zherebker, Oliver Babcock, Roman Vasilevich, and Chiara Giorio

Natural organic matter (NOM) is a complex mixture of thousands of organic molecules that reflects environmental conditions and chemical transformations occurring nowadays or in the past. Fourier transform mass spectrometry (FTMS) resolves isobaric constituents and it is widely applied to obtain aquatic, terrigenous and aerosol NOM fingerprints. Traditionally, comparison of mass peak intensities is used to make a distinctive conclusion about samples behavior, but it has the limitation of omitting structural information on the corresponding ions. Due to the stochastic character of NOM synthesis, drastically different samples may appear as resembling, which hampers mechanistic study of NOM dynamics and its attribution to the source. Here we present how implementation of chemical and isotopic tagging in combination with FTMS helps to overcome this issue. The developed approach provides an upper boundary for the presence of specific structural features, e.g. functional groups, in individual NOM components. This facilitates a clear distinction between different NOM samples, which would share isobaric ions, and provides insights on isomeric complexity of these ions. The advantages of the method were demonstrated on two sets of samples. Firstly, we collected permafrost peat cores from different depths in the European Arctic region, which varied in corresponding botanical conditions, peat degradation and oxidation states. Selective deuteromethylation and bromination coupled to FTMS enabled to capture structural differences between shared ions, which differed in carboxylic functionality and aromaticity. Surprisingly, structural differences were found for ions, which abundance positively correlated with peat characteristics and geo-temporal conditions. The second set included aerosol particles collected in marine, rural and urban areas. Application of in-source H/D exchange for FTMS analysis of extracted NOM enabled to enumerate functional groups in shared ions and point molecular constituents with similar and distinct structural features. The observed trends serve to better understand aerosol formation processes and accompanied conventional formula-based statistical analysis including better understanding of Kendrick mass defect series.

How to cite: Zherebker, A., Babcock, O., Vasilevich, R., and Giorio, C.: From sediments to the atmosphere: a mass spectrometry approach revealing structural dissimilarities of common NOM components, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-815, https://doi.org/10.5194/egusphere-egu24-815, 2024.

EGU24-1109 | ECS | Orals | BG1.10

Post fire Black Carbon alteration: Rapid changes in a supposedly inert pool 

Oliver Donnerhack, Patrick Liebmann, Philipp Maurischat, and Georg Guggenberger

Forest fires are among the most influential disturbances in ecosystems and have varying effects on the soil depending on fire intensity and biomass consumption. The significant decline in biodiversity in European forests due to centuries of non-sustainable forest management, combined with worsening drought from climate change, has greatly increased vulnerability to wildfires. Incomplete combustion during fires leads to the formation of black carbon (BC), a group of substances known for their persistence in soil. However, studies suggest that medium-condensed BC species may have lower chemical and spatial stability and are therefore potentially more mobile and consequently only serve as temporary carbon sinks.

In order to assess the mobilization of BC, we investigate short-term changes in BC under field conditions, particularly of the low-condensed BC, and call into question the established concept of the general stability of BC pools. We investigated the dynamics of BC alterations during the post-fire period within one winter, following a late summer forest fire. We selected two comparable sites featuring spruce-dominated forest stands with different geologic parent material and weather conditions, particularly with respect to the amount of precipitation during the observation period. We sampled soil profiles down to 40 cm depth shortly after the fire event in late summer and after a 6-month period in late spring. After performing density fractionation to separate the mineral associated organic matter (MAOM) from particulate organic matter (POM), we analysed the BC content in the MAOM fraction using benzene polycarboxylic acids (BPCA) analysis.

The results show a high content of low to medium condensed BPCAs directly after fire, which decreased, especially the medium condensed BPCA marker, during the observation period. Taking into account the fast change in medium BPCA values in the MAOM fraction, we conclude that the general assumption that BC is in principle a stable, long-term carbon sink needs to be addressed more carefully.

How to cite: Donnerhack, O., Liebmann, P., Maurischat, P., and Guggenberger, G.: Post fire Black Carbon alteration: Rapid changes in a supposedly inert pool, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1109, https://doi.org/10.5194/egusphere-egu24-1109, 2024.

EGU24-1180 | ECS | Orals | BG1.10

Net CO2 release during chemical weathering in the north-western Himalaya: A dominant role of pyrite oxidation 

Rakesh Kumar Rout, Gyana Ranjan Tripathy, Satyabrata Das, and Santosh K. Rai

Oxidation of pyrites plays a key role in global chemical and climatic cycles. In particular, interaction of sulfuric acid produced through this process with carbonates releases CO2 to the atmosphere. This CO2 source counterbalances the CO2 consumed during silicate weathering in river basins, and hence, may influence earlier-suggested linkage between silicate weathering and global cooling events. In this study, we have investigated the dissolved major ions and sulfur isotopes of Indus headwaters to quantify the net effect of sulfide oxidation on the CO2 budget. This research is an attempt to evaluate the coupling between global Cenozoic cooling event and Himalaya weathering - ­a hypothesis which overlooked the CO2 supply via sulfide and organic oxidation. Towards this, we have employed sulfur isotopes (δ34S) as a proxy for riverine sulfate sources, mainly due to its distinct composition for the two major end-members [pyrite (~ -12 ‰) and gypsum (~ 17 ‰); [1]]. The average sulfate concentrations for the Indus headwaters are found to be higher than the regional rainfall, global average for rivers, and other major Himalayan rivers (e.g., Ganga and the Brahmaputra). Consistently, the mean δ34S for the Indus headwaters is also depleted with respect to that reported for the Ganga (~ 2 ‰) and Brahmaputra (~ 4 ‰) outflows [1-5]. Also, the sulfur isotopic values for the Indus headwaters are systematically depleted by 3 to 4 ‰ than that reported earlier for Indus mainstream [3]. These lighter δ34S values for the headwaters hint at relatively higher sulfide oxidation in the northwestern (NW) Himalaya compared to central and eastern Himalayas. Also, these processes are found to be more intense in the mountainous regions than in the floodplains. These observations are consistent with the basin lithology dominated by Paleozoic carbonates and organic-rich shales, and higher glacial coverage. Estimation of sulfide-derived cations from carbonate weathering and silicate-derived cations indicate that the chemical weathering in the Indus headwaters serve as a net source of CO2 to the atmosphere. This finding is in contrast with previous suggestion of significant CO2 removal during the Himalaya weathering and hence, challenges the role of land surface processes in the NW Himalaya in regulating the Cenozoic cooling event.

 

 

References

[1] Burke et al., (2018), Earth Planet. Sci. Lett., 496, 168-177.

[2] Chakrapani et al., (2009), J. Asian Earth Sci., 34, 347-362.

[3] Karim and Veizer, (2000), Chem. Geol., 170, 153-177.

[4] Kemeny et al., (2021), Geochim. Cosmochim. Acta, 294, 43-69.

[5] Turchyn et al., (2013), Earth Planet. Sci. Lett., 374, 36-46.

How to cite: Rout, R. K., Tripathy, G. R., Das, S., and Rai, S. K.: Net CO2 release during chemical weathering in the north-western Himalaya: A dominant role of pyrite oxidation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1180, https://doi.org/10.5194/egusphere-egu24-1180, 2024.

EGU24-1546 | Posters on site | BG1.10

Soil chemistry and hydrophobicity caused by four 2021-22 western U.S. megafires. 

Vera Samburova, Eric Schneider, Christopher Rüger, Brad Sion, Lukas Friederici, Yasaman Raeofy, Markus Berli, Palina Bahdanovich, Hans Moosmüller, and Ralf Zimmermann

In the past decade, the size, frequency, and severity of wildfires have increased around the world, especially in forests of the western United States, where ecosystems are dominated by dry conifer forests. It is known that fires can greatly affect not only air quality, climate, forest, and fauna, but also soil. The heat from fires can alter soil chemistry and change soil water repellency (SWR). SWR can reduce soil infiltration, which can increase surface runoff, erosion, and the potential for flooding and mud and debris slides. The increased frequency and intensity of western U.S. wildfires due to the rapidly changing climate poses an important question: What are the short- and long-term effects of wildfires on soil’s hydrologic responses, including SWR, and what is the role of fire-induced chemistry in SWR?

In the summer and fall of 2021 and 2022, there were four mega-wildfires (Caldor, Dixie, Beckwourth Complex, and Mosquito) in the Eastern Sierra Nevada mountains (California, USA). These wildfires provided us an opportunity to collect post-fire soil and ash samples and study the effects of fires on the physical and chemical properties of soils. We collected over 80 samples and performed multiple water-droplet penetration time (WDPT) tests in the field and, in the laboratory, apparent contact angle (ACA) measurements with the goniometer technique. For all four fires, a significant increase in SWR was observed between unburned and burned soils, with WDPT increasing from <1 s to 600 s (maximum measured value) and ACA values increasing between 1.1 and 9 times (p-value < 0.001). Our WDPT and ACA measurements of the samples collected 6 months and 1 year after the 2021 megafires (Dixie, Caldor, and Beckwourth Complex megafires) showed no significant changes in SWR for unburned and burned soils. The chemical analysis of organic constituents of unburned and burned soils with ultra-high-resolution mass spectrometry (thermogravimetry atmospheric pressure photoionization in combination with Fourier transform ion cyclotron resonance mass spectrometry or TG APPI FT-ICR MS) suggests that burned soils became water-repellent due to the formation and/or deposition of aromatic organic species (e.g., polycyclic aromatic hydrocarbons or PAHs) on the soil surface during fires. We found a positive correlation (R2 = 0.813) between the ACA values of analyzed fire-affected samples and aromaticity derived from the TG APPI FT-ICR MS spectra.

These results of our research highlight the importance of future research on the chemical composition of post-fire soils and the need to study the long-term effects of fires on soil properties.

How to cite: Samburova, V., Schneider, E., Rüger, C., Sion, B., Friederici, L., Raeofy, Y., Berli, M., Bahdanovich, P., Moosmüller, H., and Zimmermann, R.: Soil chemistry and hydrophobicity caused by four 2021-22 western U.S. megafires., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1546, https://doi.org/10.5194/egusphere-egu24-1546, 2024.

EGU24-1595 | ECS | Posters virtual | BG1.10

Hyperspectral Reflectance of Pre- and Post-Fire Soils: Toward Remote Sensing of Fire-Induced Soil Hydrophobicity 

Yasaman Raeofy, Vera Samburova, Markus Berli, Brad Sion, and Hans Moosmüller

Recently, wildfire activity and intensity in the western U.S. have greatly increased, mainly due to a warming climate, population growth, land use changes, and fuel accumulation. Disastrous effects during fires include loss of human lives and infrastructure, ecosystem disturbances, and emissions of carbon dioxide and air pollutants. In addition, wildfires modify physical and chemical soil properties and can cause Fire-Induced Soil Hydrophobicity (FISH), which reduces water infiltration into the soil and accelerates runoff during precipitation events. This may induce cascading disasters including flooding, landslides, and deterioration of water quality. To predict and mitigate such disasters, FISH is generally quantified at a few fire-affected locations using a manual infiltration test. However, this limited spatial coverage poorly represents FISH on a watershed scale as needed for prediction and mitigation purposes.

Watershed-wide, high-resolution monitoring of FISH is only practical using airborne or satellite-based remote sensing, for example utilizing solar reflectance spectra to characterize and monitor physical and chemical properties of fire-affected soils. Such spectra depend on light scattering and absorption at the soil surface. For this study, we have sampled ash, burned, and unburned soils, fresh (0 month), 1 year, and 2 years after three recent California (US) megafires: the Dixie (2021, 3,890 km2), Caldor (2021, 897 km2), and Beckwourth Complex (2021, 428 km2) fires. We studied the optical, chemical, and physical properties of all our samples. Optical hyperspectral reflectance spectra (350–2,500 nm) were obtained using natural solar (blue sky) illumination and a spectroradiometer (ASD FieldSpec3), operated in reflectance mode.  For all three fires, the results show that 700 nm wavelength reflectance of ash samples collected 1 and 1.5 years after the fire decreased between 36% and 76% compared to that of samples collected right after the fires. Additionally, significantly higher visible reflectance has been found for unburned compared to burned soil samples in each fire region that was studied. Fourier-transform infrared (FTIR) measurements were used to characterize the carbonate content of soil and ash samples demonstrating a positive relationship between carbonate content and visible reflectance, indicating a possible contribution of carbonate to the reflectance of soil/ash samples.

How to cite: Raeofy, Y., Samburova, V., Berli, M., Sion, B., and Moosmüller, H.: Hyperspectral Reflectance of Pre- and Post-Fire Soils: Toward Remote Sensing of Fire-Induced Soil Hydrophobicity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1595, https://doi.org/10.5194/egusphere-egu24-1595, 2024.

EGU24-1957 | ECS | Orals | BG1.10

Bacterial decomposition of dissolved organic matter: including the colloidal perspective 

Erika Andersson, Lars Tranvik, Marloes Groeneveld, Anders Tunlid, Per Persson, and Ulf Olsson

Dissolved organic matter (DOM) is a major carbon pool and considered the most bioavailable and most mobile fraction of organic matter. DOM is generally defined as the organic matter passing a filter pore size of 0.2 or 0.45 µm, and this size cut off means that DOM not only contains dissolved molecules but also colloidal objects and aggregates up to a few hundred nanometres. The properties of this colloidal DOM fraction, such as for example size, shape, and surface charge, will affect its actual bioavailability and mobility in the environment. Although previously not well studied, there has recently been a growing interest in this colloidal fraction of DOM.

We have studied DOM extracted by water from a boreal spruce forest soil, filtered through a 0.2 µm pore size. By using a combination of spectroscopy techniques, such as NMR, and light (SLS, DLS), X-ray (SAXS) and neutron (SANS) scattering techniques, we can access chemical and physical information on both the molecular and colloidal fractions of DOM.

Our results show that the colloidal DOM has a homogenous chemical composition, and that carbohydrates is the dominating chemical component in both the colloidal and molecular DOM. The colloids have a mass fractal structure which does not change upon dilution and they are electrostatically stabilised against aggregation. In a lab scale study, we investigated the bacterial decomposition of this DOM during a two-month incubation. The molecular fraction of DOM was quickly decomposed. However, no change was observed for the colloidal DOM, constituting ca. 50% of the carbon, indicating that it persisted bacterial decomposition.

Our results suggest that colloidal properties could be an important but hitherto overlooked aspect to the central question of what dictates organic matter reactivity and persistency in different environments and across different time scales. Our current work extends from soil solution to aquatic ecosystems, to assess the ubiquity of the colloidal fraction of DOM.

How to cite: Andersson, E., Tranvik, L., Groeneveld, M., Tunlid, A., Persson, P., and Olsson, U.: Bacterial decomposition of dissolved organic matter: including the colloidal perspective, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1957, https://doi.org/10.5194/egusphere-egu24-1957, 2024.

EGU24-2117 | Orals | BG1.10

Biochar enhanced microbial carbon use efficiency, while reducing mineralization of added and native soil organic carbon 

Kristiina Karhu, Subin Kalu, Aino Seppänen, Kevin Mganga, Outi-Maaria Sietiö, and Bruno Glaser

Biochar can increase long-term soil organic carbon (SOC) storage due to its polyaromatic structure. In addition to the recalcitrant carbon (C) contained in the biochar itself, biochar can also increase SOC storage by adsorption or organic matter on its surfaces, and reduced decomposition rate of native SOC (negative priming). Limited number of studies have looked at how biochar affects decomposition and stabilization of fresh C inputs, and native SOC decomposition. To fill this knowledge gap, we conducted a laboratory incubation study, where we followed the fate of added 13C-labeled glucose in a fine-textured agriculturally used soil (Stagnosol) amended with two different biochar levels corresponding to 15 and 30 Mg ha-1 in field conditions. Biochar addition reduced mineralization of SOC and added 13C glucose, while increasing microbial biomass and microbial carbon use efficiency (CUE). Most of the added biochar, as well as remaining 13C were found in the free particulate organic matter (POM) fraction after 6 months, indicating that added 13C glucose was preserved within the biochar particles. Our closer study of 13C amino sugar fraction extracted from the biochar particles revealed that the microbes that had efficiently grown on the added 13C glucose in the presence of biochar, were retained as dead microbial residues inside the biochar pores. This microbial route could provide a way for additional formation of rather recalcitrant C in the form of microbial residues in the presence of biochar, which could with time contribute to building SOC stock in biochar amended soils beyond the C present in biochar itself. We found that biochar also increased the portion of occluded POM in the treatments without 13C glucose addition, demonstrating that increased soil occlusion following biochar addition reduced SOC mineralization. The effects were found to be dose-dependent, i.e. higher biochar application rate resulted in lower mineralization rate of native SOC and of added 13C-glucose.

How to cite: Karhu, K., Kalu, S., Seppänen, A., Mganga, K., Sietiö, O.-M., and Glaser, B.: Biochar enhanced microbial carbon use efficiency, while reducing mineralization of added and native soil organic carbon, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2117, https://doi.org/10.5194/egusphere-egu24-2117, 2024.

Elevated concentration levels of geogenic ammonium in groundwater arise from the mineralization of nitrogen-containing natural organic matter in various geological settings worldwide, especially in alluvial-lacustrine and coastal environments. However, the difference in enrichment mechanisms of geogenic ammonium between these two types of aquifers remains poorly understood. To address this knowledge gap, we investigated two representative aquifer systems in central Yangtze (Dongting Lake Plain, DTP) and southern China (Pearl River Delta, PRD) with contrasting geogenic ammonium contents. The use of optical and molecular characterization of DOM combined with hydrochemistry and stable carbon isotopes has revealed differences in DOM between the two types of aquifer systems and revealed contrasting controls of DOM on ammonium enrichment. The results indicated higher humification and degradation of DOM in DTP groundwater, characterized by abundant highly unsaturated compounds. The degradation of DOM and nitrogen-containing DOM was dominated by highly unsaturated compounds and CHO+N molecular formulas in highly unsaturated compounds, respectively. In contrast, the DOM in PRD groundwater was more biogenic, less degraded, and contained more aliphatic compounds in addition to highly unsaturated compounds. The degradation of DOM and nitrogen-containing DOM was dominated by aliphatic compounds and polyphenols and CHO+N molecular formulas in highly unsaturated compounds and polyphenols, respectively. As DOM degraded, the ammonium production efficiency of DOM decreased, contributing to lower ammonium concentrations in DTP groundwater. In addition, the CHO+N(SP) molecular formulas were mainly of microbial-derived and gradually accumulated with DOM degradation. In this study, we conducted the first comprehensive investigation into the patterns of groundwater ammonium enrichment based on DOM differences in various geological settings.

How to cite: Xiong, Y.: Characteristics of Dissolved Organic Matter Contribute to Geogenic Ammonium Enrichment in Coastal versus Alluvial-lacustrine Aquifers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3292, https://doi.org/10.5194/egusphere-egu24-3292, 2024.

EGU24-3355 | Posters on site | BG1.10

NOM quality differences in sediments of land based aquacultures – insights by liquid chromatography-high resolution mass spectrometry 

Peter Herzsprung, Carolin Waldemer, Matthias Koschorreck, and Oliver Lechtenfeld

Natural organic matter (NOM) was widely investigated in natural waters, sea water, river water, lake water, groundwater. The highest molecular resolution of NOM can be achieved by Fourier-transform ion cyclotron resonance mass spectroscopy (FT-ICR-MS). This analytical tool generates molecular formulas (MF) for thousands of NOM components. By coupling liquid chromatography to FT-ICR-MS insights into the polarity (hydrophilic versus hydrophobic) of NOM compounds can be achieved.

Anthropogenic inputs have an imprint on NOM and it changes its overall composition. Aquaculture is one of the fastest growing sectors of food production by covering over 8 Mio ha. The consequences of fish farming for the organic matter quality in fish pond waters and sediments are poorly understood. Here we investigated the stages of pollution by comparison the water extractable organic matter (WEOM) in the sediment at the main site of fish feed application and open water sediments at different distances (transect) to the feeding site.

Full profile HPLC-FTICR-MS chromatograms were segmented into approx. one-minute wide segments between 10 and 15 Min (five segments), the main eluting region of WEOM. MF were calculated for the mass range 150 - 1000 Da with an error threshold of 1 ppm using in-house software considering the following carbon (C), hydrogen (H), oxygen (O), nitrogen (N) and sulphur (S) elements: 12C0–60, 13C0–1, 1H0–122, 16O0–40, 14N0–8, 32S0–3, and 34S0–1.

For all retention times, N3, N4, N5, N6, N7 (CHNO) MF with 0.2 < O/C < 0.5 and 1.5 < H/C < 2.0 showed relative higher intensities in the feeding center compared to the distant sites. For some MF like C20H37N5O7, C22H39N5O7, C24H42N6O10 the intensity was more than five times higher in the center compared to open water site. Such components can be suggested to be oligopeptides (Leu-Asn-Thr-Ile, Glu-Pro-Lys-Ile, Leu-Leu-Asp-Ser-Gln as possible isomeric solutions). The sediment in the feeding center exhibited a prevalence of CHNOS and CHOS2 MF, whereas N1, N2, CHOS1, and CHO displayed relatively uniform intensities along the transect, with some instances of slightly higher intensities observed away from the feeding site. The number and abundance of CHNOS MF decreased with increasing retention time (decreasing polarity). Notably, these compounds appear to be inherently hydrophilic, characterized by predominantly low molecular weights (< 400 Da).

The results obtained suggest the following biogeochemical processes: Initially, the protein-rich fish feed undergoes hydrolysis, leading to the formation of oligopeptides. Subsequent partial desamination of these molecules facilitates their interaction with inorganic sulphides, resulting in the formation of CHNOS MF. Notably, the component C8H13N1O3S1, exhibiting a five-fold intensity at the feeding site, appears to correspond to one of the possible metabolites (Sulfanylpropanoyl-proline).

The results indicate a potential overfertilization with easily biodegradable protein-rich substances. The WEOM quality seems highly affected by additional input of CHNO, CHNOS and CHOS.

How to cite: Herzsprung, P., Waldemer, C., Koschorreck, M., and Lechtenfeld, O.: NOM quality differences in sediments of land based aquacultures – insights by liquid chromatography-high resolution mass spectrometry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3355, https://doi.org/10.5194/egusphere-egu24-3355, 2024.

EGU24-3667 | ECS | Orals | BG1.10

Rapid lateral transport of fresh dissolved organic matter to the deep ocean in the NE Atlantic 

Bingbing Wei, Michael Seidel, Gesine Mollenhauer, Hendrik Grotheer, Jenny Wendt, Thorsten Dittmar, and Moritz Holtappels

Deepwater formation in the North Atlantic Ocean is a major gateway for dissolved organic matter (DOM) transport into the deep ocean. Despite focusing on vertical mixing, lateral transport of DOM from productive shelf regions is underexplored. Previous research suggested substantial offshore DOM transport on the Irish and Hebrides Margin via the bottom Ekman Drain. Our in-depth bottom water DOM analyses of carbon isotopes in combination with ultrahigh-resolution mass spectrometry (FT-ICR-MS) indicated that downwelling in this region leads to higher DOM concentrations (by 7–11 μM) and younger radiocarbon ages (by 190–330 yrs) compared to DOM of the central Northeast Atlantic at similar depths. During downslope transport, conservative mixing shapes the molecular composition of recalcitrant DOM, while minor particulate organic matter degradation contributes to producing less-refractory DOM with terrigenous signals. Consequently, the bottom Ekman transport emerges as a rapid and efficient channel for transporting fresh DOM into the deep North Atlantic Ocean, acting as a crucial carbon sink for atmospheric CO2.

How to cite: Wei, B., Seidel, M., Mollenhauer, G., Grotheer, H., Wendt, J., Dittmar, T., and Holtappels, M.: Rapid lateral transport of fresh dissolved organic matter to the deep ocean in the NE Atlantic, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3667, https://doi.org/10.5194/egusphere-egu24-3667, 2024.

EGU24-3890 | ECS | Posters on site | BG1.10

Carbon cycling in coexisting marine ecosystems: Cold seeps and coral reefs in Northern Norway 

Muhammed Fatih Sert, Knut Ola Dølven, Sebastian Petters, Timo Kekäläinen, Janne Jänis, Jorge Corrales-Guerrero, and Bénédicte Ferré

Cold seeps and cold water corals (CWCs) coexist on Northern Norway's continental shelf at the Hola trough between Lofoten and Vesterålen. Here, cold seeps release methane from the seabed, yet only a limited amount reaches the atmosphere. The remaining methane dissolves and disperses in nearby seeps. Methane is unreactive for most microorganisms in the water column, yet it is a unique energy and carbon source for methane-oxidizing bacteria (MOB). MOBs metabolize methane and release carbon dioxide as the end product of oxidation. Increasing carbon dioxide may constrain pH-sensitive CWCs in the region. We investigated the biogeochemistry of carbon, carbon isotopes, nutrients, dissolved organic matter (DOM) compositions and microbial diversity through water column profiles and water samples collected in June 2022. Preliminary results indicated that elevated methane increases dissolved inorganic carbon concentrations and modifies carbon isotopic compositions. Additionally, DOM compositions implied a positive correlation between prokaryotic diversity and protein-like DOM components at cold seeps and the entire water column near CWCs, suggesting analogous microbial modifications. Our preliminary conclusion suggests cold seeps and CWCs symbiotically coexist in Northern Norway continental shelves; however, enhanced water temperatures and consequent increase in methane release at cold seeps may mitigate the functioning of CWCs in future.

This study is supported by the Research Council of Norway, project number 320100, through the project EMAN7 (Environmental impact of Methane seepage and sub-seabed characterization at LoVe-Node 7).

How to cite: Sert, M. F., Dølven, K. O., Petters, S., Kekäläinen, T., Jänis, J., Corrales-Guerrero, J., and Ferré, B.: Carbon cycling in coexisting marine ecosystems: Cold seeps and coral reefs in Northern Norway, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3890, https://doi.org/10.5194/egusphere-egu24-3890, 2024.

EGU24-5444 | ECS | Orals | BG1.10

Efficiency of Biological Carbon Pump: Insights from Compound-Specific Amino Acid δ15N 

Chen Li, Zhimin Jian, and Haowen Dang

As a vital component of the global carbon cycle, the ocean’s biological carbon pump determines the amount of carbon fixed by primary production in the surface waters. The efficiency of this biological pump is closely interconnected with the nitrogen cycle, which regulates nutrient inventory and primary productivity rates. Additionally, the structure of the upper ocean ecosystem influences the efficiency of the biological pump by determining how much fixed carbon is exported to the deep ocean. Compound-specific nitrogen isotope (δ15NAA) is a novel proxy that could provide valuable insights into both aspects of these questions. The δ15NAA could unravel isotopic information of source nitrogen and show δ15N changes associated with trophic processes. This study generates sedimentary δ15NAA, as well as bulk sediment δ15N and organic δ15N records from a western equatorial Pacific site (MD10-3340) covering the last 140 kyr. Our results demonstrate an overall agreement among three proxies, all indicating distinct precessional variations in source nitrate δ15N and potential changes in nutrient inventory. More importantly, the δ15NAA signatures suggest an inverse relationship between animal trophic activity in the surface water and the degradation of organic matter precipitating through the water column. Higher ecosystem trophic position is found during glacial periods, accompanied by inactive organic matter recycling, which implies a greater potential for carbon burial in deep reservoirs. Together, we suggest that the δ15NAAsignatures can provide a detailed picture of carbon cycle coupled with nitrogen cycle.

How to cite: Li, C., Jian, Z., and Dang, H.: Efficiency of Biological Carbon Pump: Insights from Compound-Specific Amino Acid δ15N, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5444, https://doi.org/10.5194/egusphere-egu24-5444, 2024.

EGU24-5586 | Orals | BG1.10

Temporal and spatial changes in DOM revealed by FT-ICR MS 

Catherine Moody, Nicholle Bell, Logan Mackay, and Ezra Kitson

DOM from peatlands is a collection of complex molecules, but also a significant source of carbon to aquatic pathways. It has a wide impact on aquatic ecosystems, providing an energy source for microbes and buffering capacity for water chemistry changes. The composition of DOM in drinking water reservoirs also impacts on chemical and energy demands of treatment processes, and is an area of growing concern for UK drinking water providers.

DOM was extracted from water collected from peatland headwater streams and reservoirs in the UK. The DOM was analysed with elemental analysis and FT-ICR MS to determine how the composition changes as water moves through the catchment. A combination of spatial and temporal sampling strategies allowed seasonal and catchment characteristics to be investigated (from 2018-2021, and 53-61°N).

There were significant trends in DOM composition metrics across a north/south gradient, with higher lipid content, and lower carbohydrate and peptide content in northern sites than southern sites. Samples collected in 2021 had several significant composition differences to other years. Monthly sampling showed the largest changes in DOM composition coincided with the end of the growing season (September in the UK).

These results show variable DOM in headwaters can be, and how reservoirs act to buffer the most extreme changes, resulting in more stable DOM compositions in reservoirs. Understanding how DOM composition is impacted by season, climate and catchment characteristics will have important ramifications for drinking water providers, and will help catchment managers plan land use changes and timing of water draw-off from peatland reservoirs.

How to cite: Moody, C., Bell, N., Mackay, L., and Kitson, E.: Temporal and spatial changes in DOM revealed by FT-ICR MS, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5586, https://doi.org/10.5194/egusphere-egu24-5586, 2024.

EGU24-6501 | Orals | BG1.10

Variations in binding properties of dissolved organic matter along river-ocean continuum 

Pablo Lodeiro, Joao C. A. Macedo, Calin David, Carlos Rey-Castro, Jaume Puy, María Martínez-Cabanas, Roberto Herrero, Manuel E. Sastre de Vicente, and José L. Barriada

The binding properties of dissolved organic matter (DOM) play a crucial role in the biogeochemical cycles of trace metals and carbon. The composition of DOM is anticipated to exert influence over the magnitude and distribution of the intrinsic ion binding affinities that occur over a continuum of values, referred to as the affinity spectra. These spectra encompass many different organic acid groups that contribute to the nuanced binding characteristics of DOM. The total proton binding capacity represents the maximum sites available for other chemical species that may compete with protons for the same DOM binding sites, particularly in the case of metals. Consequently, the study of proton binding by DOM becomes the initial step to investigate deeper into metal binding mechanisms. Here, we research the variability in proton binding exhibited by DOM extracted from the Ebro and Mero Rivers (NNE and NW of Spain), and at the Atlantic Ocean and Mediterranean Sea. Our approach combines the non-ideal competitive adsorption (NICA) isotherm, offering insights into chemical binding on heterogeneous ligands, with the Donnan electrostatic model, which accounts for polyelectrolytic effects, i.e., the non-specific binding. This methodology enables us to pinpoint potential shifts in DOM binding affinities and derive a comprehensive set of intrinsic binding parameters for DOM. Importantly, these parameters are thermodynamically consistent and remain independent of the specific conditions of the samples, enhancing the extrapolation to future environmental changes.

 

Acknowledgements: Authors thank Agencia Española de Investigación for the financial support through the research projects PID2020-117910GB-C21 and -C22/AEI/10.13039/501100011033. P.L. acknowledges current support from the Ministerio de Ciencia, Innovación y Universidades of Spain and University of Lleida (Beatriz Galindo Senior award number BG20/00104)

References:

[1] Lodeiro, P., Rey-Castro, C., David, C., Humphreys, M. H., Gledhill, M., 2023. Proton Binding Characteristics of Dissolved Organic Matter Extracted from the North Atlantic. Environmental Science & Technology 57, 21136–21144.

[2] Waska, H., Brumsack, H.-J., Massmann, G., Koschinsky, A., Schnetger, B., Simon, H., Dittmar, T., 2019. Inorganic and organic iron and copper species of the subterranean estuary: Origins and fate. Geochimica et Cosmochimica Acta 259, 211–232.

[3] Heerah, K. M.,  Reade, H. E., 2023. Towards the identification of humic ligands associated with iron transport through a salinity gradient. Scientific Reports 12:15545.

How to cite: Lodeiro, P., Macedo, J. C. A., David, C., Rey-Castro, C., Puy, J., Martínez-Cabanas, M., Herrero, R., Sastre de Vicente, M. E., and Barriada, J. L.: Variations in binding properties of dissolved organic matter along river-ocean continuum, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6501, https://doi.org/10.5194/egusphere-egu24-6501, 2024.

EGU24-6516 | ECS | Posters on site | BG1.10

Spatio-temporal dimensions of organic carbon-mineral interactions in a source-to-sink system 

Nora Gallarotti, Bernhard Peucker-Ehrenbrink, Sophia Johannessen, Lisa Bröder, Reto Wijker, Britta Voss, Negar Haghipour, and Timothy Eglinton

Rivers play a key role in the global carbon cycle by transferring organic carbon (OC) from the terrestrial biosphere to marine sediments, which act as an important long-term carbon sink. Associations between biospheric OC and mineral phases can alter OC stability and hydrodynamic properties, thereby influencing its transport and storage patterns within a river basin and dictating the fate of terrestrial biospheric OC discharged to the ocean. While research has mainly investigated the formation of these associations within soils, open questions remain on how these interactions evolve over space and time.

The Fraser River Basin in British Columbia, Canada drains regions with distinctive lithological and climatic gradients allowing the simultaneous study of leaf-wax-specific isotopic compositions (δ2H, δ13C) and inorganic geochemical signatures (εNd) of sediments as tracers of the provenance of biospheric OC and detrital mineral phases, respectively. In addition, bulk radiocarbon (D14C) serves as a tool to constrain biospheric OC residence times. Here, to investigate seasonal variations in the geochemical signatures of OC and its mineral host in sediments exported by the Fraser River to the Strait of Georgia using samples from a time-series sediment trap deployed cover the course of a year adjacent to the river mouth.

Both εNd and D14C follow a seasonal pattern by which aged OC (-176 to -140‰) is mostly transported during high discharge events such as the freshet in June and heavy rainstorms occurring in the upper basin in fall. During the former event, the geochemical signature (εNd: -9.2 to -7.2) points towards the Coastal Range affecting the detrital mineral composition more strongly, which shifts towards a greater proportion of Rocky Mountains-sourced sediment (εNd: -11.7 to -9.1) during the second high discharge event. Biomarker specific δ2H will further elucidate the extent to which the provenance of biospheric OC coincides with the mineral detrital load. Further, comparison with geochemical signatures of fluvial sediments within the Fraser basin, together with corresponding signatures in river-proximal sediments deposited in the Strait of Georgia allow for OC-mineral interactions to be assessed from a source-to-sink perspective.

This coupled investigation of organic and inorganic tracers provides new insights into terrestrial organic carbon export and the role of organo-mineral interactions on riverine organic carbon dynamics. These findings also have important ramifications for the interpretation of sedimentary archives.

How to cite: Gallarotti, N., Peucker-Ehrenbrink, B., Johannessen, S., Bröder, L., Wijker, R., Voss, B., Haghipour, N., and Eglinton, T.: Spatio-temporal dimensions of organic carbon-mineral interactions in a source-to-sink system, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6516, https://doi.org/10.5194/egusphere-egu24-6516, 2024.

EGU24-6629 | ECS | Orals | BG1.10

Different dissolved organic matter (DOM) sources sustain microbial life in beach subterranean estuary 

Grace Abarike, Simone Brick, Bert Engelen, and Jutta Niggemann

Dissolved organic matter (DOM) is diverse in composition and serves as substrate for microbial metabolism. Within subterranean estuaries (STEs), DOM is introduced from different sources along the groundwater flow paths. These different DOM sources make it challenging to disentangle degradation pathways, especially in high-energy beaches with dynamic porewater advection and changing redox conditions. We performed sediment incubations in flow-through reactors (FTRs) to investigate how DOM from different sources is transformed by STE microbial communities. We used sediment and groundwater from the STE of a high-energy beach on Spiekeroog Island (Germany). Intertidal beach sediments were incubated for 13 days in FTRs with groundwater of low (~1.6) and high salinity (~29.1) as marine and terrestrial endmember, respectively, in triplicate setups, and additional control FTRs with artificial seawater of respective salinities. The FTRs ran under oxic conditions with recirculating advective flow. Porewater samples were taken daily for quantification of dissolved organic carbon (DOC) and nutrient concentrations, and samples from the start and the end of the incubation were taken for the analysis of microbial community composition, microbial cell numbers, and DOM composition. DOM samples were isolated through solid phase extraction and molecularly characterized via ultrahigh-resolution Fourier-transform ion cyclotron resonance mass spectrometry. Over the course of the incubation, DOC concentrations increased, presumably from sediment leaching and potentially also by primary production in light-exposed parts of the setup, as oxygen concentrations also increased. The DOM composition of the porewater samples at start and end of the incubation was highly diverse, with a total of up to 2900 different molecular formulae detected in each sample. As expected, the low salinity porewater had a more terrestrial DOM signature with a higher proportion of aromatic compounds compared to the DOM in the high salinity porewater. In all setups, the DOM composition changed significantly from start to end. We observed an increase in DOM lability in both endmember setups indicating the mobilization of fresh DOM from sediments and/or microbial activity, including primary production. Interestingly, the changes observed were similar for both DOM endmembers. Our results indicate that the microbial communities of the high-energy beach STE thrive on a similar fraction of DOM, independent of its source.

How to cite: Abarike, G., Brick, S., Engelen, B., and Niggemann, J.: Different dissolved organic matter (DOM) sources sustain microbial life in beach subterranean estuary, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6629, https://doi.org/10.5194/egusphere-egu24-6629, 2024.

EGU24-7088 | ECS | Posters on site | BG1.10

Using a novel N-15 natural abundance approach to quantify soil nitrogen transformations in biochar-treated vineyard soils. 

Kate Kingston, Zhihong Xu, Chris Pratt, Brendan Mackey, Paul Petrie, and Yihan Li

The increased frequency and intensity of climate extremes challenges vineyards to adapt and mitigate to ensure the survival of grape vines (Vitis vinifera) to meet the growing demand for quality wine.  Regenerative Viticulture (RV) is a novel approach with a strong focus on increasing soil carbon (C) stocks to regenerate vineyard soil that is largely degraded and in poor health.  When soil health and fertility is low, this impacts vine health and reduces its ability to fight disease and pests and withstand extreme climatic events. We hypothesised that biochar would increase nitrogen (N) cycling and retention and that these would differ in relation to the distinct physiochemical properties of the two vineyard soils.   Conscious of contributing to a sustainable circular economy, we utilised viticulture industry waste to produce biochar’s to compare with standard pine biochar.  Biochar was produced with three feedstocks at different pyrolysis temperatures, grape marc (475°C), vine pruning (450°C) and pine (600°C).  Soil (0 - 10 cm depth) was collected from under vines from vineyards at the South Burnett (heavy texture) and Granite Belt (sandy texture) regions in Queensland, Australia. We used a novel 15N natural abundance approach in a laboratory incubation experiment to investigate the potential of using biochar, a C-dense material produced by high temperature pyrolysis of organic materials in limited oxygen conditions as a suitable climate smart RV method for vineyard soils.  A short three-day laboratory incubation followed by microdiffusion was conducted to quantify the impacts of the three biochars on N transformations in the two soils.  Soil moisture was controlled at 60% and 90% water holding capacity (WHC) and biochar applied at 0% and 10% (w/w), with samples harvested on incubation days 0 and 3. Preliminary results indicate that in the short term for both experimental soils, biochar stimulated microbial activity, increased N availability and water use efficiency and reduced N loss through denitrification.  The results indicate that fungicides use in vineyards impacted the underlying soil health and microbial communities and influencing N cycling.  For the long term impact, the potential to use biochar for increase biodiversity and ecosystem recovery as a climate smart RV method in vineyards needs to be trialled in the field.  This is to establish the long-term effects of C accumulation and improved N cycling on soil health, biodiversity, vine resilience under extreme natural weather events, and on wine grape quality and quantity.

How to cite: Kingston, K., Xu, Z., Pratt, C., Mackey, B., Petrie, P., and Li, Y.: Using a novel N-15 natural abundance approach to quantify soil nitrogen transformations in biochar-treated vineyard soils., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7088, https://doi.org/10.5194/egusphere-egu24-7088, 2024.

EGU24-7317 | ECS | Orals | BG1.10

Reactivity of hydrogen sulfide toward organic compounds with sulfur-sulfur bonds 

Irina Zweig and Alexey Kamyshny

The presence of organic molecules containing sulfur-sulfur bonds was identified in both water columns and sediments of natural aquatic systems. While processes leading to formation of these compounds were intensively studied during recent decades, the kinetics and mechanisms of reactions responsible for their decomposition remain poorly understood. This study focuses on the kinetics and products of the reactions of dimethyl disulfide, dimethyl trisulfide, and cyclic polysulfide lenthionine (1,2,3,5,6-pentathiepane) with hydrogen sulfide at the pH and temperature ranges typical of environmental conditions. The findings reveal that under environmental conditions (pH≥5), the overall reaction rates are primarily controlled by the reaction of bisulfide anion (HS-) rather than hydrogen sulfide. The activation energy and the order of the reaction with respect to bisulfide anion is dimethyl disulfide < dimethyl trisulfide < lenthionine, while the order of the reaction with respect to organosulfur compounds is lenthionine < dimethyl trisulfide < dimethyl disulfide. The rates of the reactions between linear dimethyl polysulfides with bisulfide anion were found to be higher than the rates of their reactions with cyanide and hydroxyl anions, but lower than the rates of their photodecomposition. These results suggest that rapid decomposition of organosulfur compounds in sulfidic aphotic natural aquatic systems should be controlled by HS- decomposition pathway. Products of the decomposition of dimethyl disulfide and dimethyl trisulfide include methanethiol, higher dimethyl polysulfides, and inorganic polysulfides. The cyclic polysulfides were shown to be more stable than their linear analogs, resulting in their preferential preservation during the maturation process.

How to cite: Zweig, I. and Kamyshny, A.: Reactivity of hydrogen sulfide toward organic compounds with sulfur-sulfur bonds, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7317, https://doi.org/10.5194/egusphere-egu24-7317, 2024.

EGU24-7593 | Posters on site | BG1.10

Towards an online ramped oxidation approach for thermal dissection and serial radiocarbon measurement of complex organic matter 

Marco A. Bolandini, Daniele De Maria, Negar Haghipour, Lukas Wacker, Jordon D. Hemingway, Timothy I. Eglinton, and Lisa Bröder

Radiocarbon (14C) measurements provide a powerful tool to deconvolute sources and dynamics of organic matter in the environment. However, interpretation of conventional bulk-level 14C data is challenging due to the myriad components comprising organic matter in soils and sediments. Thermally ramped oxidation provides one approach for overcoming this limitation, and involves subjecting a sample to gradually increasing temperatures, serially oxidizing the OC to CO2. Collected over prescribed temperature ranges ('thermal fractions'), this CO2 is then analyzed for 14C content using accelerator mass spectrometry (AMS). While effective, current ramped oxidation methods are mostly 'offline', involving manual collection and subsequent AMS analysis of evolved CO2, hindering sample throughput and reproducibility.

Here, we introduce a compact, online ramped oxidation (ORO) setup in which CO2 from discrete thermal fractions is directly collected and measured for 14C by AMS equipped with a gas ion source. The setup comprises two modules: (i) an ORO unit with two sequential furnaces - the first, ramped from room temperature to 900 °C, holds the sample; the second, maintained at 900 °C, includes a catalyst ensuring complete oxidation to CO2; and (ii) a dual-trap interface (DTI) collection unit with two parallel molecular sieve traps alternately collecting and releasing CO2 from a given fraction for direct injection into the AMS.

Preliminary results indicate reproducible data, evident in both thermograms and F14C results. Analysis of natural reference samples reveals that measured 14C values and their associated uncertainties align with those reported in the literature using conventional “off-line” ramped oxidation methods, affirming the utility of the new ORO-DTI-AMS setup.

Our goal is to apply this new method for comprehensive investigation of a range of natural samples, with a particular focus on the improved understanding of the fate of OC held in permafrost soils in the context of on-going climate and carbon cycle change in high latitude ecosystems.

How to cite: Bolandini, M. A., De Maria, D., Haghipour, N., Wacker, L., Hemingway, J. D., Eglinton, T. I., and Bröder, L.: Towards an online ramped oxidation approach for thermal dissection and serial radiocarbon measurement of complex organic matter, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7593, https://doi.org/10.5194/egusphere-egu24-7593, 2024.

Subterranean estuaries underlying high-energy beaches are efficient turnover sites for dissolved organic matter (DOM) and nutrients from marine and terrestrial waters. In addition, leaching of beach wrack during tidal inundation and precipitation can contribute to DOM and nutrient loads. However, the combined impact of diverse environmental settings on the release of DOM and nutrients from beach wrack has so far not been studied, although e.g., salinity oscillations and temporary exposure to sunlight are common in high-energy beach subterranean estuaries. Here, we present the results of an extensive beach wrack leaching experiment taking beach wrack type, age, sunlight exposure, and leaching matrix into consideration. A combination of UVA irradiation, advanced wrack age, and leaching by low-salinity artificial rainwater resulted in high dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) releases of mmoles- to moles per kg dry weight in the macroalga Fucus sp. Furthermore, jellyfish wrack released millimoles of TDN in artificial seawater incubations. Ultra-high-resolution analyses of DOM revealed a prevalence of molecular formulae resembling biochemical building blocks such as sugars, amino acids, and vitamins, indicating that the released DOM could be of substantial nutritional value for the heterotrophic microbial communities on and near beach wrack. An interesting finding was the high abundance of aromatic and humic-like DOM released from macroalgal beach wrack, which may impact typically used marine and terrestrial source- and sink proxies. As such, beach wrack DOM and nutrients could further complicate biogeochemical distribution patterns in the subterranean estuary.

How to cite: Waska, H. and Banko-Kubis, H.: Experimental comparison of dissolved organic matter and nutrients leached from beach wrack by sea- and rainwater: A nutritional boost for the sandy beach subterranean estuary, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8750, https://doi.org/10.5194/egusphere-egu24-8750, 2024.

EGU24-10047 | Orals | BG1.10

Carbonate-associated organic matter: A form of “dissolvable” organic matter? 

Mary Zeller, Bryce Van Dam, Amy McKenna, Christian Lopes, Christopher Osburn, James Fourqurean, Kominoski John, and Michael Böttcher

Carbonate-associated organic matter (CAOM) is the organic matter associated with carbonate minerals, and a survey of carbonate-rich surface sediments suggests that it is incorporated at a consistent amount scaling with the internal surface area of the carbonate grains. As the carbonate sediment is sensitive to changes in saturation state due to benthic biogeochemical processing, we predicted that CAOM could exhibit interesting biogeochemical cycling, based on its potential to bridge particulate and dissolved pools of organic matter. Here, we report on a study in a seagrass meadow in central Florida Bay, USA. We utilize a combination of inorganic stable isotope (C, S, O) and high resolution mass spectrometry (21T FT ICR-MS) techniques to explore the carbon and sulfur cycles here, with a particular emphasis on dissolved organic matter (DOM) characterization. CAOM is examined similar to standard solid phase extraction (SPE-DOM) methods, after first washing carbonate sediment and dissolving it incompletely under a mild hydrochloric acid treatment. The δ34S and δ18O of sulfate, as well as the δ13C of dissolved inorganic carbon (DIC), suggest that the promotion of sulfide oxidation in the seagrass rhizosphere drives rapid carbonate dissolution and re-precipitation cycles. Sulfide oxidation, as well as elevated sulfide concentration, promotes sulfurization of CAOM, which is more sulfurized than porewater and surface water, as 42% of CAOM formulas vs 28% of surface water are sulfurized. Furthermore, a substantial quantity of molecular formulas present in the overlaying surface waters (90% of formulas, 97% by relative abundance) are also present in CAOM. Despite the CAOM sample containing nearly twice the number of formulas compared to surface water, due in part to its higher dissolved organic carbon concentration, these shared formulas make up 75% of the abundance of CAOM formulas. We argue that repeated coupled sulfur and inorganic carbon cycles, intensified by seagrasses, leads to increased sulfurization and release of CAOM, affecting DOM quality in the broader aquatic system. We estimate that approximately 9% of the particulate organic carbon (POC) stored in the sediments of this site are CAOM. Our results suggest that CAOM here is a form of “dissolvable” organic carbon which cycles much more rapidly than POC more broadly.

How to cite: Zeller, M., Van Dam, B., McKenna, A., Lopes, C., Osburn, C., Fourqurean, J., John, K., and Böttcher, M.: Carbonate-associated organic matter: A form of “dissolvable” organic matter?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10047, https://doi.org/10.5194/egusphere-egu24-10047, 2024.

EGU24-10209 | ECS | Posters on site | BG1.10

Apparent Aging and Rejuvenation of Terrestrial Organic Carbon Along the River-Estuary-Coastal Ocean Continuum 

Meng Yu, Timothy Eglinton, Pengfei Hou, Negar Haghipour, Hailong Zhang, Zicheng Wang, and Meixun Zhao

The balance between remineralization and sedimentary burial of terrestrial organic carbon (OCterr) in large river-dominated marginal seas influences atmospheric CO2 inventory on a range of timescales. Here we systematically investigate the evolution of OCterr along the river-estuary-coastal ocean continuum for three fluvial systems discharging to the Chinese marginal seas. The 14C-depleted characteristics of bulk OC and molecular components of riverine suspended sediments and marine sediments suggest that the Chinese marginal seas are a significant sink of pre-aged OCterr. Lower plant-wax fatty acid 14C contents suggest selective degradation of labile OC within estuaries, resulting in apparent aging of OCterr, followed by an apparent rejuvenation in OCterr in shelf sediments, the latter likely reflecting inputs from proximal sources that contribute younger OCterr. This selective degradation, aging and rejuvenation of OCterr along the continuum confounds the use of plant wax lipid 14C to constrain lateral transport times, and sheds light on more complex OCterr dynamics in marginal seas.

How to cite: Yu, M., Eglinton, T., Hou, P., Haghipour, N., Zhang, H., Wang, Z., and Zhao, M.: Apparent Aging and Rejuvenation of Terrestrial Organic Carbon Along the River-Estuary-Coastal Ocean Continuum, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10209, https://doi.org/10.5194/egusphere-egu24-10209, 2024.

EGU24-11112 | ECS | Orals | BG1.10

Exploring CO2 Cycling in Karst Critical Zones: Lessons from Milandre Cave 

Sarah Rowan, Marc Leutscher, Sönke Szidat, and Franziska Lechleitner

We know that the concentrations of CO2 and DIC in the subsurface are often magnitudes higher than in the soil zone, and therefore we need to understand this reservoir and its vulnerability to change. Understanding the critical zone in the context of CO2 input, cycling dynamics, and export is essential as this carbon is particularly vulnerable to changes in water table rise which may result in rapid release of CO2 into the atmosphere. Cave environments provide an accessible natural window into the critical zone as they connect meteoric water, soils, the unsaturated vadose zone, and saturated zone. We conducted a two year monitoring campaign at Milandre cave in northern Switzerland, analyzing pCO2, d13CO2, and 14CO2 at various environmental interfaces, including the soil zone, within the epikarst, and in the cave itself. Forest soils maintained stable, modern 14C signatures and low d13C indicating year-round contribution of CO2 from C3 tree and plant root respiration. Conversely, meadow soils exhibited notable seasonality in F14C, suggesting a dominance of respiration from older soil pools in the winter months. Distinct variations in CO2 concentrations were observed within the cave, influenced by temperature driven ventilation dynamics. Keeling plot analysis revealed a consistent contributing endmember of C3 vegetation. However, similarities between the F14C of the meadow soils and cave CO2 suggests a significant contribution of meadow soil CO2 into the cave. These findings offer vital insights into the nuanced dynamics of CO2 sources and cycling processes within the critical zone of Milandre Cave, shedding light on the influences of seasonal variation and ecological influences of critical zone carbon and the export of carbon from terrestrial ecosystems.

How to cite: Rowan, S., Leutscher, M., Szidat, S., and Lechleitner, F.: Exploring CO2 Cycling in Karst Critical Zones: Lessons from Milandre Cave, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11112, https://doi.org/10.5194/egusphere-egu24-11112, 2024.

EGU24-11285 | Orals | BG1.10

Global expression of bomb radiocarbon in Earth's surface carbon reservoirs 

Timothy Eglinton and the Bomb-spike team

The Earth’s carbon cycle encompasses myriad processes that connect different reservoirs containing diverse forms of carbon that turnover and exchange on a wide range of spatial and temporal scales. Increased atmospheric CO2 from anthropogenic perturbation of the carbon cycle associated with fossil fuel combustion and land-use change reflects the release of carbon from stable, slow-cycling reservoirs.  Much current research seeks to quantify carbon transfer from slow to fast cycling reservoirs, as well as the ability of different carbon reservoirs, particularly the terrestrial biosphere and the oceans, to compensate for these increased CO2 emissions through carbon uptake and storage. Determination of the turnover time and rate of transfer of carbon between reservoirs is crucial in this regard. Radiocarbon, 14C, represents a powerful tool to address this question by virtue of its ~ 5700-year half-life that allows processes occurring on centennial to millennial timescales to be resolved. Superimposed on natural abundance 14C variations, above-ground nuclear weapons testing during the mid-20th Century created an abrupt spike in atmospheric radiocarbon (“bomb spike”) that has subsequently permeated into and moved through various Earth surface carbon reservoirs, serving as a useful tracer of carbon cycle processes occurring on annual to decadal timescales. Numerous studies have exploited this signal for assessment of turnover or transit times within and through carbon pools, atmospheric and oceanic circulation, ecosystem functioning and source attribution. However, much 14C data currently tends to be compartmentalized, with a focus on specific reservoirs or geographic locations.

In this study, we evaluate the global expression of the radiocarbon bomb spike across the different Earth surface active carbon reservoirs (terrestrial biosphere, soils, freshwater aquatic systems, and marine carbon reservoirs). We compile 14C data from existing and nascent databases as well as new measurements, including direct observations and records from natural archives spanning the pre-bomb period to the present, to develop an overview of the general features of 14C (timing, amplitude and character of the bomb peak) within each reservoir over this time interval.  In addition to using this information to refine our understanding of the interactions between different reservoirs, this study seeks to (i) identify gaps and biases in data with a view to motivating further 14C studies, (ii) underline the value of systematic data reporting, as well as careful archiving of samples for future 14C analysis, (iii) inform isotope-enabled carbon cycle and earth system models, and (iv) serve as benchmark against which to gauge future carbon cycle changes.

How to cite: Eglinton, T. and the Bomb-spike team: Global expression of bomb radiocarbon in Earth's surface carbon reservoirs, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11285, https://doi.org/10.5194/egusphere-egu24-11285, 2024.

EGU24-11446 | ECS | Orals | BG1.10

Pyrogenic Carbon production in eucalypt forests: implications for the carbon cycle in fire-prone ecosystems 

Minerva García-Carmona, Cristina Santín, and Stefan Doerr

Wildfires play an important role in the carbon cycle, influencing both atmospheric carbon concentrations and terrestrial carbon storage. Pyrogenic carbon (PyC) derived from incomplete biomass combustion during wildfires is currently considered a relevant carbon sink at the global level. In order to assess the quantitative importance of PyC production, accurate data on PyC generation in different ecosystems and under a range of fire conditions are needed. In this study, we focus on the fire-prone continent of Australia, specifically on eucalypt forests, which are the most common type of native forests. Eucalypt forests, subjected frequently to both wildfires and human-prescribed fires, provide an important context for understanding PyC dynamics.
We conducted comprehensive pre-fire and postfire fuel inventories and quantified all pyrogenic materials generated in three representative eucalypt forests in Sydney, Melbourne, and Perth. Experimental fires, simulating low to medium-severity wildfires, were used to quantify PyC conversion rates in the main fuel components: forest floor, understory, down wood, and overstory (comprising only tree bark as these fires did not affect the crowns).
Our results show an average pyrogenic carbon conversion rate of 24% for eucalypt forests. This translates to 9 t C ha-1 of the carbon affected by the fire being emitted to the atmosphere, while 3 t C ha-1 is transformed into PyC, underscoring the relevance of PyC in carbon budgets from eucalypt forest fires. The conversion rates varied substantially among fuel components, with the bark component exhibiting the highest conversion rate, at approximately 40%, and the down wood component displaying the lowest rate at around 15%. Intermediate conversion values were reported for forest floor and understory components. 
Given the recurrent nature of fires in eucalypt forests in Australia, both naturally and under human-prescribed conditions, our findings suggest that PyC production plays a significant role in the carbon cycle, of sufficient magnitude to be considered in global carbon budget estimations.

How to cite: García-Carmona, M., Santín, C., and Doerr, S.: Pyrogenic Carbon production in eucalypt forests: implications for the carbon cycle in fire-prone ecosystems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11446, https://doi.org/10.5194/egusphere-egu24-11446, 2024.

EGU24-11885 | Orals | BG1.10

Radiocarbon measurements of archived fish scales reconstruct past carbon cycle changes in a peri-alpine lake 

Margot White, Benedict Mittelbach, Timo Rhyner, Negar Haghipour, Thomas Blattmann, Martin Wessels, Nathalie Dubois, and Timothy Eglinton

Climate change and other anthropogenic impacts such as nutrient pollution result in perturbations to freshwater systems that alter aquatic carbon cycling. In the alpine Rhine basin, for example, long-term monitoring over the past four decades has documented increasing water temperatures that cause a decrease in the solubility of CO2. However, this same dataset records a small increase in the concentration of dissolved inorganic carbon (DIC) over the same period. This requires increasing inputs of DIC to aquatic systems and an acceleration of the carbon cycle, but the source of this additional carbon is not clear. Possible explanations include increased weathering of bedrock or increased soil organic matter respiration, with sharply contrasting implications for carbon storage and turnover. Radiocarbon (14C) is an ideal tool to distinguish between these different scenarios, as bedrock weathering will contribute 14C-depleted (fossil) DIC whereas increased soil respiration will contribute DIC that is more 14C-enriched (younger). Furthermore, large changes in the atmospheric radiocarbon content over the past century resulting from the testing of nuclear weapons provide a strong signal with which to track the exchange between aquatic and atmospheric carbon pools by examining how lake water DI14C changes through time. Here we focus on Lake Constance, a large peri-alpine lake fed mostly by the alpine Rhine River. We measured natural abundance radiocarbon in archived fish scales collected from Lake Constance over the past 100 years to reconstruct changes in lake water DI14C. These fish scales come from young fish caught in the lake who feed primarily on phytoplankton and thus reflect the 14C of the lake DIC pool. Preliminary measurements of fish scales from the pre-bomb period were 0.78 to 0.79 Fm, reflecting the addition of 14C dead rock-derived carbon from the dissolution of carbonate rocks within the catchment. These values are 14C-depleted compared to present day water column DIC values of 0.82 to 0.84 Fm, where the bomb spike signal persists. Results from fish scales will ultimately be compared with other archives of water column DI14C currently in development, including 14C of chlorophyll degradation products and zooplankton exoskeletons isolated from varved lake sediments. These records permit us to investigate how carbon cycling in the lake and its catchment has responded to anthropogenic perturbations such as warming and nutrient pollution over the past century, with the eventual goal of calibrating isotope enabled carbon cycle models.

How to cite: White, M., Mittelbach, B., Rhyner, T., Haghipour, N., Blattmann, T., Wessels, M., Dubois, N., and Eglinton, T.: Radiocarbon measurements of archived fish scales reconstruct past carbon cycle changes in a peri-alpine lake, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11885, https://doi.org/10.5194/egusphere-egu24-11885, 2024.

EGU24-11886 | Posters on site | BG1.10

Direct radiocarbon measurements of dissolved inorganic carbon from environmental water using a gas ion source  

Negar Haghipour, Charlotte Schnepper, Thomas Blattmann, Kayley Kundig, Maxi Castrillejo, Nuria Casacuberta, Timothy I. Eglinton, and Margot E. White

An increasing demand for radiocarbon analysis of small samples has led to the development of various methods to further improve and simplify the CO2 extraction needed for accelerator mass spectrometer (AMS) measurements. Here, the performance of a direct feeding system of CO2 from dissolved inorganic carbon (DIC) from small water samples (<6 ml) and direct AMS measurement via a gas ion source coupled to a gas interface system (GIS) is presented and compared to the conventional preparation by graphitization that demands significantly larger samples (> 60 ml).

Seawater samples collected from Sargasso Sea, southeast of and lake water samples collected from Lake Constance have been prepared by both methods. The extraction of CO2 gas from samples for GIS measurement is performed using a carbonate handling system (CHS-Ionplus AG) through purging the headspace, acidifying the water, and sparging out the CO2. The preparation time is greatly reduced compared to conventional analysis that requires the labor-intensive graphitization step. The yielded 14C results from the direct CO2 measurements are in good agreement with values obtained from graphite measurements. The observed deviation between the two methods is below the uncertainty of radiocarbon gas measurement (~7‰).

This new approach will facilitate understanding of carbon cycle dynamics in many different environments and applications where a high throughput (up to 80 sample/day) is required. The new method is suitable for groundwater, pore water, seawater, freshwaters from lakes, rivers and glacial settings. Furthermore, it enables the analysis of small milliliter-scale samples and those containing low DIC concentrations.

How to cite: Haghipour, N., Schnepper, C., Blattmann, T., Kundig, K., Castrillejo, M., Casacuberta, N., Eglinton, T. I., and White, M. E.: Direct radiocarbon measurements of dissolved inorganic carbon from environmental water using a gas ion source , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11886, https://doi.org/10.5194/egusphere-egu24-11886, 2024.

EGU24-12192 | Posters on site | BG1.10

There to remain? Pyrogenic carbon production of savanna fires 

Cristina Santin, Carmen Sánchez-García, Minerva García-Carmona, Tercia Strydom, Philippa Ascough, and Stefan H. Doerr

Southern African savanna fires account for ~30% of the annual global carbon (C) emissions from vegetation fires, but their impact on the global C cycle extends beyond direct emissions During fire, part of the C burnt is converted to pyrogenic carbon (PyC), which is more resistant to degradation than original biomass and acts as a buffer to global fire C emissions when stored in soils or sediments. Despite its recognized importance for the C cycle, how much PyC is produced and how much of it stays in savanna ecosystems is still not well known, with no information yet for Southern African savannas. To address this research gap, we quantified how much PyC was produced during four fires in Kruger National Park (South Africa) and how much PyC was stored in surface soils. We also characterized the chemical and thermal recalcitrance of this PyC. Our results will be discussed in the broader context of C emissions from savanna fires as well as the role PyC plays as a C sequestration mechanism through its accumulation in soils, redistribution and ex-situ transport.

How to cite: Santin, C., Sánchez-García, C., García-Carmona, M., Strydom, T., Ascough, P., and Doerr, S. H.: There to remain? Pyrogenic carbon production of savanna fires, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12192, https://doi.org/10.5194/egusphere-egu24-12192, 2024.

EGU24-12381 | ECS | Posters on site | BG1.10

Assessing the biodegradability of dissolved organic carbon in freshwater systems: A method evaluation study 

Danielle Green, Fereidoun Rezanezhad, Scott Smith, Stephanie Slowinski, and Philippe Van Cappellen

Dissolved organic carbon (DOC) is an important contributor to both carbon cycling and other biogeochemical processes in aquatic ecosystems. The biodegradable fraction of DOC can be microbially degraded over time, producing carbon dioxide (CO2), a greenhouse gas. In addition, microbial degradation-resistant DOC can accumulate in water bodies, causing chemical and physical changes to aquatic systems. Although biodegradable DOC (BDOC) is widely studied, there is no agreed-upon standard method for assessing its biodegradability. Here, we aimed to develop and evaluate a new method for determining BDOC in freshwater samples. Our method includes filtering water samples to below 0.22 µm, to remove existing microbial cells, prior to inoculating the samples with a concentrated microbial inoculum produced by stepwise isolation of microbial cells from a peat sample. In addition, we added solutions containing nitrogen and phosphorus (in the forms of NH4NO3 and K2HPO4, respectively) to ensure that the microbes were not nutrient-limited. The samples were then capped with foam stoppers and incubated in the dark at 25⁰C on a shaker for 28 days to allow constant aeration during BDOC degradation. When applied to five freshwater samples collected from rivers, stormwater ponds, and a lake, and a glucose control, we observed that the amount of BDOC in the natural samples ranged from 15% to 53% and was 90% in the glucose control. Rates of BDOC degradation were calculated from DOC measurements at six sampling time points between days 0 and 28. We found that the DOC trends with time were best explained by two successive phases for BDOC degradation in all of the samples: an initial, fast, phase of BDOC degradation followed by a second, slower, phase of BDOC degradation where the rate constant for the second phase was between 5.57 and 565 times slower than for the initial phase. Changes in chemical characteristics of DOC measured using absorbance and fluorescence parameters including specific ultraviolet absorbance at 254 nm (SUVA254), humification index (HIX), and parallel factor analysis (PARAFAC) at each sampling time revealed that the initial, fast, phase of BDOC degradation often represents the utilization of small, non-aromatic compounds while the later, slower, phase of BDOC degradation often represents the utilization of more complex, aromatic compounds. The presented method provides a new approach to measure and characterize BDOC degradability and degradation kinetics that can be applied to future studies on biogeochemical processes in aquatic ecosystems.

How to cite: Green, D., Rezanezhad, F., Smith, S., Slowinski, S., and Van Cappellen, P.: Assessing the biodegradability of dissolved organic carbon in freshwater systems: A method evaluation study, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12381, https://doi.org/10.5194/egusphere-egu24-12381, 2024.

EGU24-12504 | ECS | Posters on site | BG1.10

Burning poop: carbon dynamics in herbivore dung during southern-African savanna fires 

Carmen Sánchez-García, Cristina Santín, Tercia Strydom, and Stefan Doerr

Herbivores play a vital role in the functioning of savanna ecosystems. They ingest plants, modifying the vegetation cover, and disperse nutrients across the landscape in the form of dung. Fire in savanna is also a key nutrient recycling pathway, making elements readily available through the resultant ash and smoke. Wildfire ash, known for its susceptibility to be transported by wind and water, plays a key role in redistributing pyrogenic organic matter and nutrients across the landscape. However, our level of understanding of ash characteristics from burnt dung is very low. In addition, and due to its high carbon content, dung also adds to the wildland fuels for fires, alongside vegetation. Given that savannas are the dominant source of global Cemissions from fires, assessing the role of burnt dung in C dynamics is, therefore, also crucial for more accurate estimations of the overall C released during savanna fires.

We quantified C losses from dung combustion during fire in four savanna sites burnt by experimental fires in Kruger National Park (South Africa). We also analysed chemical properties, including major nutrients and metals, of dung and dung-derived ash. The studied dung came from large herbivores (zebra, elephant, giraffe, buffalo and wildebeest). The concentration of carbon and nitrogen in burnt dung was significantly lower than unburnt dung (carbon: 41 and 4.1%, nitrogen: 1.1 and 0.3% in unburnt and burnt dung, respectively). The carbon released from dung burning accounted for up to 6% of the carbon released from vegetation burning, emphasizing the substantial role of dung in carbon emissions during savanna fires. Our results also highlight burnt dung as a hotspot for minerals and nutrients with chemical characteristics different to those found in vegetation ash (e.g., phosphorus: 9,195 and 6,158 mg kg-1, copper: 55.8 and 28.1 mg kg-1 in dung-derived and vegetation ash respectively). This is likely to affect local soil physical and chemical properties and hence enhance ecosystem diversity.

How to cite: Sánchez-García, C., Santín, C., Strydom, T., and Doerr, S.: Burning poop: carbon dynamics in herbivore dung during southern-African savanna fires, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12504, https://doi.org/10.5194/egusphere-egu24-12504, 2024.

EGU24-13692 | ECS | Posters on site | BG1.10

Unveiling the role of soil water: Identifying primary sources of dissolved organic matter in surface waters 

Livia Vieira Carlini Charamba, Tobias Houska, Klaus Kaiser, Klaus-Holger Knorr, Stephan Krüger, Tobias Krause, Huan Chen, Pavel Krám, Jakub Hruška, and Karsten Kalbitz

Dissolved organic matter (DOM) is crucial for various ecological processes, playing essential roles in carbon and nutrient cycling. In forested catchments, litter input contributes to soil organic matter, influencing DOM composition in surface waters. The transition of DOM from soil organic matter to the dissolved state significantly impacts ecological balance and highlights the role of specific soil horizons in the catchment for stream water. DOM fingerprints, reflecting variations and similarities, act as valuable indicators for identifying primary DOM sources. The increasing trend in dissolved organic carbon (DOC) concentrations in surface waters underscores the urgency to understand contributing sources comprehensively. This study aims to characterize DOM along the terrestrial-aquatic continuum, identifying sources in stream water.

Soil, soil water, and stream water samples were collected biweekly for approximately two years at various depths in the Sosa drinking water reservoir catchment (Ore Mountains, Saxony, Germany). Two sub-catchments (one with a significant peatland component and one with predominantly mineral soils) were considered, each with two streams. The soil and soil water samples included four different soil types that characterize the entire catchment, i.e., intact and degraded peatland, cambisol, podzol. Pyrolysis gas chromatography-mass spectrometry (Py-GC-MS) was employed to characterize DOM in both solid and aqueous samples. Rstudio was used as a semiautomatic data processing aiming to achieve consistent compound identification. A principal component analysis (PCA) and cluster analysis were used to identify DOM sources in stream water.

PCA results showed a clear distinction between solid and aqueous samples. Overlaps were observed among soil water and stream water samples, revealing shared organic compound sources and potential transfer pathways. Fluctuations and degradation patterns were noted across seasons, especially for soil water samples. Cluster analysis revealed that soil water DOM from peat horizons predominantly influenced upstream stream water DOM in peatland-dominated areas. Downstream, the DOM composition changed and was influenced by soil water from the cambisol and the podzol (mineral soils). Concerning the sub-catchment composed mainly of mineral soils, stream water reflected DOM of deep mineral horizons of cambisols and podzols. Forest floor soil water from cambisol had no to very little effect in both sub-catchments, however, soil water of the podzol forest floor slightly contributed to the streams located in the mineral soil-dominated sub-catchment. Thus, the results show that the primary source of DOM in the Sosa catchment came from soil water of deep mineral soil horizons and that stream proximity was a primary factor influencing the influx of allochthonous DOM into stream water.

The research emphasized that DOM composition in the four streams closely resembled soil water DOM and analyzing the composition of the solid organic soil horizons did not help to identify the potential DOM source of the streams. Therefore, although recognizing intrinsic stream processes is important, successful source identification requires analysis of DOM in soil water from major catchment soil types. Proximity to stream water played a critical role as the predominant factor contributing to the introduction of allochthonous DOM into stream water.

How to cite: Vieira Carlini Charamba, L., Houska, T., Kaiser, K., Knorr, K.-H., Krüger, S., Krause, T., Chen, H., Krám, P., Hruška, J., and Kalbitz, K.: Unveiling the role of soil water: Identifying primary sources of dissolved organic matter in surface waters, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13692, https://doi.org/10.5194/egusphere-egu24-13692, 2024.

EGU24-14728 | Orals | BG1.10

Transformations of soil organic matter induced by volatile organic compounds 

Laura Meredith, Juliana Gil Loaiza, Adrian Castro, Antonette DiGuiseppe, Gemma Purser, Zhaoxin Zhang, Qunli Shen, Kolby Jardine, Romy Chakraborty, Eoin Brodie, and Malak Tfaily

Volatile organic compounds (VOCs) are diverse and prevalent metabolites exchanged in microbial systems but are often overlooked as vectors of soil organic matter (SOM) transformations. Roots, litter, aboveground vegetation, and microbial metabolism are all sources of VOCs to soil; however, little is known about how they can contribute to soil carbon (C) cycling. VOCs have been shown to contribute to key soil C pools including microbial biomass, dissolved organic matter, particulate organic matter, and mineral-associated organic matter (MAOM), suggesting that they can participate in critical soil C stabilization pathways such as the microbial necromass conduits to MAOM. Yet, we still lack an understanding of the specific VOC-induced transformations in SOC, hindering the characterization of this process across soil and volatile compounds.

 

To address this research gap, we conducted a soil incubation study to evaluate the contributions of VOCs to SOM composition. We hypothesized that VOCs would impact SOM composition and soil carbon pool magnitudes. We evaluated whether the diversity and quality of soil metabolites change in response to weekly additions of five individual VOCs over a 3-month period: methanol, acetone, acetaldehyde, isoprene, and alpha-pinene. In our study, we utilized soil matrices from a semi-arid agroecosystem, alongside sterile (irradiated) soil controls and silica controls, enabling us to distinguish between biotic and abiotic interactions. We monitored CO2 concentrations regularly as a proxy for microbial activity. Destructive triplicate samples were harvested each month for metabolite extraction and high-resolution SOM analysis by Fourier-transform ion cyclotron resonance mass spectrometry (FTICRMS). We found that VOCs stimulated SOM transformations and generally increased the number of lipids and amino sugars—markers of microbial biomass. VOCs a-pinene, acetaldehyde, and methanol had the most unique compounds, suggesting that these VOCs may support biomass production and its transformation, while isoprene and acetone had no unique compounds and may have predominantly been used for catabolic, CO2-producing processes. With this study, we aim to grow understanding of the role of VOCs in soil C cycling and their contribution to soil ecological and metabolic interactions related to carbon stabilization.

How to cite: Meredith, L., Gil Loaiza, J., Castro, A., DiGuiseppe, A., Purser, G., Zhang, Z., Shen, Q., Jardine, K., Chakraborty, R., Brodie, E., and Tfaily, M.: Transformations of soil organic matter induced by volatile organic compounds, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14728, https://doi.org/10.5194/egusphere-egu24-14728, 2024.

EGU24-15386 | ECS | Posters on site | BG1.10

Dissolved Organic Matter from Coastal Vegetated Ecosystems Through the Lens of Carbon Sequestration 

Dariya Baiko, Thorsten Dittmar, Philipp Böning, and Michael Seidel

Coastal vegetated ecosystems (CVEs) are highly productive habitats whose role in coastal biogeochemical cycles cannot be understated. The high productivity of salt marshes, seagrass meadows, and mangrove forests is channeled into the sediments and into the sea in form of particulate and dissolved organic matter (DOM). While labile DOM is degraded within a short time frame, recalcitrant DOM compounds can remain in the oceanic water column for hundreds to thousands of years. However, so far, DOM has received little consideration in carbon sequestration approaches. In sulfidic porewater of CVEs, DOM can undergo abiotic sulfurization, producing dissolved organic sulfur (DOS), which may render it resistant to biodegradation. Thus, the formation of DOS in CVEs can act as a link between labile and recalcitrant pools of DOM and provide the means of carbon transport across and beyond ecosystem boundaries. We analyzed DOM as well as inorganic nutrients in samples from temperate (German) and tropical (Malaysian) mesotidal CVEs. Unprecedentedly high porewater DOC concentrations were found in both temperate salt marshes as well as in tropical mangroves. High proportions of DOS in the DOM pool demonstrated accumulation of sulfurized compounds in the porewater. Molecular DOM patterns deduced from ultrahigh-resolution mass spectrometry (FT-ICR-MS) analysis indicated that up to 50% of the several thousand molecular formulas identified were characteristic of the analyzed CVEs. Adjacent habitats shared a substantial proportion of DOM molecular formulas indicating lateral transfer of organic material. This emphasizes that the potential for carbon dioxide removal of CVEs extends beyond the areas with above-ground biomass.

How to cite: Baiko, D., Dittmar, T., Böning, P., and Seidel, M.: Dissolved Organic Matter from Coastal Vegetated Ecosystems Through the Lens of Carbon Sequestration, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15386, https://doi.org/10.5194/egusphere-egu24-15386, 2024.

EGU24-15535 | ECS | Orals | BG1.10

The climate control of soil organic carbon dynamics inferred from speleothem radiocarbon ages 

Gang Xue, Yanjun Cai, Peng Cheng, Franziska Lechleitner, Haiwei Zhang, Yanhong Zheng, Yingying Wei, Shouyi Huang, Ling Yang, Xing Cheng, Yanbin Lu, Jie Zhou, Le Ma, Hai Cheng, and Lawrence Edwards

The complexity of processes affecting soil organic carbon (SOC) turnover on spatio-temporal scales often hinders the extrapolation of results from specific sites to larger scales. This study presents Holocene speleothem U-Th ages paired with 14C ages of carbonate and dissolved organic carbon (DOC) through three caves located on a north-south transect through China. The deviations of speleothem 14CDOCages from the U-Th ages show clearly spatial variability, and they are positively correlated with mean ages of modern SOC and soil turnover time, suggesting that deviations can be used to infer the SOC turnover. We further demonstrate that slow SOC turnover (large deviation) was associated with weak monsoon (low temperature/less precipitation) on temporal scales. Our findings reveal that climate dominates the speleothem 14CDOCages and SOC turnover. As global warming likely will intensify, the accelerated turnover of SOC, particularly at higher latitude areas, may partially offset the existing soil carbon stock. 

How to cite: Xue, G., Cai, Y., Cheng, P., Lechleitner, F., Zhang, H., Zheng, Y., Wei, Y., Huang, S., Yang, L., Cheng, X., Lu, Y., Zhou, J., Ma, L., Cheng, H., and Edwards, L.: The climate control of soil organic carbon dynamics inferred from speleothem radiocarbon ages, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15535, https://doi.org/10.5194/egusphere-egu24-15535, 2024.

EGU24-15782 | ECS | Posters on site | BG1.10

Lambda-Miner: Enhancing Reproducible Natural Organic Matter Data Processing with a Semi-Automatic Web Application  

Johann Wurz, Anika Groß, Kai Franze, and Oliver Lechtenfeld

As the volume and complexity of data in environmental sciences continue to grow, the need for data management and reproducible processing methods becomes increasingly crucial. In the specific research domain of natural organic matter (NOM), there is currently no standardized tool for data processing, particularly for the management of data and its respective metadata. We developed and present the Lambda-Miner - a semi-automatic web application for data processing of ultrahigh-resolution mass spectrometry data of NOM. The platform provides an end-to-end data processing pipeline and supersedes manual steps via standardized data and metadata management. It empowers users to execute interactive workflows for mass spectra calibration, assignment of molecular formulas by specific rules to peak masses, and validation of these formulas according to specific sets of rules. Peak data as well as sample and measurement metadata are stored in a relational database management system (RDBMS). The Lambda-Miner thus facilitates reproducible, standardized data processing which builds a common repository for mass data, metadata (such as sample type and geolocation), intermediate, and final results in a format suitable for subsequent analyses. The combination of this information in one place enables meta-analyses such as long-term quality control studies and software optimization assays. The Lambda-Miner supports domain-specific requirements for research data management and contributes to achieving FAIR data principles in the domain of NOM analytics. The Lambda-Miner allows researchers to process their ultrahigh-resolution mass spectrometry data of NOM within minutes and linking it to features such as extraction efficiency, accumulation time, and relation of total assigned current to total ion current. Processed data can be downloaded in an interoperable format, facilitating individual data processing or visualization. The current implementation of the Lambda-Miner is designed for studying NOM with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) allowing formula assignments with widely used elemental compositions of NOM in the mass range from 0 to 1000 Da. But its modular structure makes it easy to adjust and extend the implementation for other kind of analyses or instrumentations. With its adaptability and focus on reproducibility, the Lambda-Miner introduces a valuable tool for advancing standardized data storage, processing, and analysis in the study of Natural Organic Matter.

How to cite: Wurz, J., Groß, A., Franze, K., and Lechtenfeld, O.: Lambda-Miner: Enhancing Reproducible Natural Organic Matter Data Processing with a Semi-Automatic Web Application , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15782, https://doi.org/10.5194/egusphere-egu24-15782, 2024.

EGU24-16215 | ECS | Orals | BG1.10

Detection and exclusion of false molecular formula assignments via mass error distributions in ultrahigh resolution mass spectra from natural organic matter. 

Shuxian Gao, Elaine Jennings, Limei Han, Boris Koch, Peter Herzsprung, and Oliver Lechtenfeld

Ultrahigh resolution mass spectrometry (UHRMS) routinely detects and identifies thousands of molecular formulas (MFs) in natural organic matter (NOM). However, multiple assignments (MultiAs) occur when the several chemically plausible MFs are assigned to one single mass peak. MultiAs for a mass peak consist of one common core MF but different “formula residuals”, or replacement pairs, and increase as more heteroatoms and isotopes are being considered during the assignment process. This poses a major problem for the reliable interpretation of NOM composition in a biogeochemical context. A number of approaches have been proposed to rule out false assignments based on structural constraints or isotopologue detection and intensity ratios. But this becomes increasingly challenging for low abundance mass peaks or when stable isotope labeling (e.g. with 15N, 2H) is employed. Here, we present a new approach based on mass error distributions for the identification of true and false-assignments among MultiAs. An automatic workflow was developed for the detection and exclusion of false assignments in MultiAs based on their recurring replacement pairs and Kendrick mass defect values. The workflow can validate MFs for mass peaks that are close to detection limit or where naturally occurring isotopes are rare (e.g. 15N) or absent (e.g. P, F), substantially increasing the reliability of MFs assignments and broadening the applicability of UHRMS in characterization of NOM, e.g. for organic nitrogen and organic phosphorus in different environmental compartments, which are key components for global elemental cycles.  

How to cite: Gao, S., Jennings, E., Han, L., Koch, B., Herzsprung, P., and Lechtenfeld, O.: Detection and exclusion of false molecular formula assignments via mass error distributions in ultrahigh resolution mass spectra from natural organic matter., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16215, https://doi.org/10.5194/egusphere-egu24-16215, 2024.

EGU24-16483 | ECS | Orals | BG1.10

Radiocarbon signatures of dissolved black carbon in early winter water masses from the Beaufort Sea 

Linn Speidel, Negar Haghipour, Thomas Blattmann, Lisa Bröder, Julie Lattaud, Alysha I. Coppola, and Timothy I. Eglinton

Black carbon (BC) is a fraction of organic carbon resulting from the incomplete combustion of biomass and fossil fuels. The production and fate of BC is a topic of great interest in the context of ongoing climate change, as the intensity and severity of fires is increasing. The recalcitrant nature enables BC to buffer these changes by removing biomass-derived carbon into longer cycling pools. BC is mainly produced on land and a portion is transported in both particulate and dissolved form by the rivers to the oceans. Dissolved BC (DBC) cycles on millennial timescales, thereby storing BC as fraction of Dissolved Organic Carbon (DOC) in the marine DOC pool before deposition to sediments or complete degradation. However, there is currently limited information on the cycling, transport and evolution of modern riverine DBC, and how it contributes to the deep ocean DOC pool.
The arctic and boreal regions are well recognized as a nexus for climate change, given amplified rates of change in average temperatures and summer precipitation, which exacerbate carbon cycle feedbacks, including enhanced BC production by intensified wildfire seasons. The Beaufort Sea in the Arctic Ocean is composed of different water masses, with Pacific water masses entering from the Chukchi Sea, and arctic rivers - in particular the Mackenzie River - being the major source of freshwater that delivers both terrestrial DOC and DBC. Presently, information on the sources and fate of BC in the Arctic Ocean remains sparse.
Here, we report DBC concentrations and Δ14C values in the Beaufort Sea during early winter conditions. Distinct water masses were sampled, including the outflow of the Mackenzie River and the Pacific water jet on the shelf break, during two cruises in 2021 and 2022 that spanned the coast of north Alaska to the Amundsen Gulf. Preliminary radiocarbon results show that DBC on the shelf break is up to five millennia old. We discuss our findings in the context of regional hydrography and carbon cycle processes.

How to cite: Speidel, L., Haghipour, N., Blattmann, T., Bröder, L., Lattaud, J., Coppola, A. I., and Eglinton, T. I.: Radiocarbon signatures of dissolved black carbon in early winter water masses from the Beaufort Sea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16483, https://doi.org/10.5194/egusphere-egu24-16483, 2024.

EGU24-16551 | ECS | Orals | BG1.10

Prediction of soil pyrogenic carbon contents from Rock-Eval® thermal analysis: a machine-learning based model 

Johanne Lebrun Thauront, Severin Luca Bellè, Marcus Schiedung, Amicie Delahaie, Marija Stojanova, François Baudin, Pierre Barré, and Samuel Abiven

Pyrogenic carbon (PyC) is a continuum of aromatic and condensed organic molecules. It represents about 15 % of organic carbon in soils and sediments1. However, there is a discrepancy in the literature regarding quantification of PyC: different methods that are currently considered as reference differ largely in their results1,2. Indeed, most methods used to quantify PyC are based on different operational principles (e.g. chemical, thermal or physical stability of PyC, molecular markers) and consequently, they do not cover the same range of the PyC continuum2. In addition, most of them are expensive and/or time consuming. Here, we propose a new PyC quantification method based on Rock-Eval® thermal analysis, thought to be rapid, inexpensive and comparable to the previous methods toolbox. Rock-Eval® thermal analysis has been successfully introduced to the field of soil carbon analysis in the last two decades and allowed to distinguish between various pools of soil carbon (inorganic carbon, stable and active organic carbon) using a single analysis of combined pyrolysis and thermal oxidation3,4. In this study, we formulate the hypothesis that Rock-Eval® thermal analysis in combination with predictive modelling is suitable to quantify PyC in soil matrices.

To build and validate such a model, we chose soil samples originating from contrasting climate zones and parent material and with varying properties including clay content and mineralogy, iron oxide speciation and content, pH, cation-exchange capacity and organic carbon content. We measured PyC using a set of established methods (i.e. CTO-375, BPCA and HyPy) and acquired Rock-Eval® thermograms. Then, we identified the relevant features for PyC quantification in the thermograms by applying several machine-learning approaches. This work adds a new soil carbon pool to the ones already accessible from Rock-Eval® thermal analysis and allows an efficient and rapid quantification of PyC in soils, which is needed for large-scale studies of soil carbon pools.

(1) Reisser, M.; Purves, R. S.; Schmidt, M. W. I.; Abiven, S. Pyrogenic Carbon in Soils: A Literature-Based Inventory and a Global Estimation of Its Content in Soil Organic Carbon and Stocks. Front. Earth Sci. 2016, 4 (August), 1–14. https://doi.org/10.3389/feart.2016.00080.

(2) Hammes, K.; Smernik, R. J.; Skjemstad, J. O.; Schmidt, M. W. I. Characterisation and Evaluation of Reference Materials for Black Carbon Analysis Using Elemental Composition, Colour, BET Surface Area and 13C NMR Spectroscopy. Appl. Geochemistry 2008, 23 (8), 2113–2122. https://doi.org/10.1016/j.apgeochem.2008.04.023.

(3) Disnar, J. R.; Guillet, B.; Keravis, D.; Di-Giovanni, C.; Sebag, D. Soil Organic Matter (SOM) Characterization by Rock-Eval Pyrolysis: Scope and Limitations. Org. Geochem. 2003, 34 (3), 327–343. https://doi.org/10.1016/S0146-6380(02)00239-5.

(4) Cécillon, L.; Baudin, F.; Chenu, C.; Houot, S.; Jolivet, R.; Kätterer, T.; Lutfalla, S.; Macdonald, A.; Van Oort, F.; Plante, A. F.; Savignac, F.; Soucémarianadin, L. N.; Barré, P. A Model Based on Rock-Eval Thermal Analysis to Quantify the Size of the Centennially Persistent Organic Carbon Pool in Temperate Soils. Biogeosciences 2018, 15 (9), 2835–2849. https://doi.org/10.5194/bg-15-2835-2018.

How to cite: Lebrun Thauront, J., Luca Bellè, S., Schiedung, M., Delahaie, A., Stojanova, M., Baudin, F., Barré, P., and Abiven, S.: Prediction of soil pyrogenic carbon contents from Rock-Eval® thermal analysis: a machine-learning based model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16551, https://doi.org/10.5194/egusphere-egu24-16551, 2024.

EGU24-16627 | Posters on site | BG1.10

Direct analysis of marine dissolved organic matter using LC-FT-ICR MS 

Oliver Lechtenfeld, Jan Kaesler, Elaine Jennings, and Boris Koch

Marine dissolved organic matter (DOM) is an important component of the global carbon cycle, yet its intricate composition and the sea salt matrix pose major challenges for chemical analysis. The current view on marine DOM as assessed with ultrahigh resolution mass spectrometry (UHR-MS) is largely based on SPE-extracts known for its consistent underestimation of e.g. the mean nominal oxidation state of carbon (NOSC) and molecular weight as compared to bulk measurements. We introduce a direct injection, reversed-phase liquid chromatography Fourier-transform ion cyclotron resonance (FT-ICR) MS approach to analyze marine DOM without the need for solid-phase extraction. Effective separation of salt and DOM is achieved with a large chromatographic column and an extended isocratic aqueous step. Post-column dilution of the sample flow with buffer-free solvents and implementing a counter gradient reduced salt buildup in the ion source and resulted in excellent repeatability. With this method over 5,500 unique molecular formulas were detected from just 5.5 nmol of carbon in 100 µL filtered Arctic Ocean seawater. We observed highly linear detector response for variable sample carbon concentrations and a high robustness against the salt matrix. We could demonstrate the bias of SPE in marine DOM on a molecular level leading to a predominant detection of less polar DOM, while neglecting a large fraction of polar, heteroatom-rich DOM. In addition, a substantial fraction of terrestrial-derived DOM was previously overlooked in solid-phase extracted marine DOM. Overall, the direct analysis of seawater offers fast and simple sample preparation and avoids fractionation introduced by extraction. The method facilitates studies in environments, where only minimal sample volume is available e.g. in marine sediment pore water, ice cores, or permafrost soil solution. The small volume requirement also supports higher spatial (e.g. in soils) or temporal sample resolution (e.g. in culture experiments). Chromatographic separation adds further chemical information to molecular formulas, enhancing our understanding of marine biogeochemistry, chemodiversity, and ecological processes.

How to cite: Lechtenfeld, O., Kaesler, J., Jennings, E., and Koch, B.: Direct analysis of marine dissolved organic matter using LC-FT-ICR MS, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16627, https://doi.org/10.5194/egusphere-egu24-16627, 2024.

EGU24-17503 | ECS | Orals | BG1.10

Sediment source and transport along the Iberian Margin 

Sara Campderrós, Leopoldo D. Pena, Jaime Frigola, Ester Garcia-Solsona, Eduardo Paredes, Negar Haghipour, Heather M. Stoll, and Isabel Cacho

The Iberian Margin is a dynamic margin, affected by complex sedimentary and oceanographic processes. The Mediterranean Outflow Water (MOW) is a prominent water mass that flows along the Iberian margin and interacts with the sediment on the slope. However, more information about how MOW interacts with sediment delivery, distribution, deposition along the margin is needed. In this study we combine Nd, Sr and Pb isotopes on fine-grained detrital sediments (< 63 μm) and 14C measurements in planktonic foraminifera (G. bulloides) in 25 coretop sediment samples collected along the entire Iberian Margin (from the Gulf of Cadiz to the “Cachucho” mount in the Cantabrian Sea). Nd, Sr and Pb isotopes were used to (i) identify the main source areas of terrigenous sediments coming from the Iberian Peninsula and (ii) trace the distribution of these sediments along the Iberian Margin. Additionally, 14C data in planktonic foraminifera were used to obtain radiocarbon ages, that allowed us to date the coretop sediments. Results from Nd, Sr and Pb isotopes allow us to identify three main terrigenous sediment source provinces in the Iberian margin, depicting a prominent south to north gradient. Moreover, large age discrepancies in coretop sediments are strongly associated with the main pathway of MOW, thus suggesting erosion and lateral transport of sediments along the main path of the MOW.

How to cite: Campderrós, S., Pena, L. D., Frigola, J., Garcia-Solsona, E., Paredes, E., Haghipour, N., Stoll, H. M., and Cacho, I.: Sediment source and transport along the Iberian Margin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17503, https://doi.org/10.5194/egusphere-egu24-17503, 2024.

EGU24-17520 | ECS | Posters on site | BG1.10

A multi-method approach to characterise and quantify pyrogenic carbon in tropical urban agroecosystems.  

Stephen Boahen Asabere, Ankit Ankit, Tino Peplau, Simon Drollinger, Christopher Poeplau, Daniela Sauer, and Axel Don

Pyrogenic carbon (PyC) is produced by the incomplete combustion of biomass. It is chemically inert and nutrient-deficient, making it relatively stable in soils. PyC can thus form an important pool of total soil organic carbon (TOC) for C preservation in soils. Despite its significance, data on the nature, level, and relative contribution of PyC to TOC in tropical urban agroecosystems is largely non-existent. In this study, we aim to determine the content and chemical composition of PyC in urban arable soils of Kumasi, a rapidly expanding city in Ghana, West Africa. PyC is likely enriched in these soils, mainly due to soot deposition from traffic, combined with widespread burning of household waste and use of charcoal for cooking.

We sampled topsoils (0–10 cm) from arable fields under four levels of urbanisation intensity (UI), from low to high UI. We employed a range of analytical techniques including visual, chemothermal, thermogravimetric, and biomarker analysis, as well as fourier transformed infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy. Visual assessment indicated that ≥80% of all bulk soil samples contained charred macro particles, pointing to PyC enrichment in the urban arable soils. Separating TOC into particulate organic C (POC, ≥63 µm particle size) and mineral-associated organic C (MAOC, <63 µm), chemothermal assessment revealed that PyC contributed less than 0.1% to each fraction under all urban intensity conditions. These PyC levels increased notably along with increasing UI in both TOC fractions. Thereby, median PyC levels in the MAOC fraction (7.8–20.4 mg kg-1) were markedly higher compared to those of the POC fraction (0.1–0.3 mg kg-1). This finding highlight a noticeable PyC contribution to TOC preservations in Kumasi’s tropical urban arable soils, although overall contribution is low. Ongoing thermogravimetric, FTIR spectroscopy, NMR spectroscopy, and biomarker analysis will further detail the amount and chemical composition of PyC in these soils. For instance, we will integrate diagnostic ratios of polycyclic aromatic hydrocarbons with masoccharide anhydrides in order to decouple the relative amount of PyC from biomass and that of fossil fuel.

By characterising the chemical nature of PyC with this wide range of analytical techniques, insights into the source and transformation of PyC in a tropical urban agricultural context can be provided. This will lead to better understanding of the role of PyC in the urban soil carbon cycle and its implications for urban sustainability and global C sequestration efforts.

How to cite: Asabere, S. B., Ankit, A., Peplau, T., Drollinger, S., Poeplau, C., Sauer, D., and Don, A.: A multi-method approach to characterise and quantify pyrogenic carbon in tropical urban agroecosystems. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17520, https://doi.org/10.5194/egusphere-egu24-17520, 2024.

EGU24-18669 | Orals | BG1.10

Pyrogenic carbon: Is it a sink in the global carbon cycle? And why we can’t be sure. 

Matthew Jones, Alysha Coppola, and Cristina Santín

Fires play a critical role in modulating the quantity and quality of carbon (C) stored in the terrestrial biosphere, including in aboveground vegetation and soils. Via riverine transport routes, fires also affect the quantity and quality of C delivered to the global oceans.

The mission of this talk is to set the scene on the multifaceted ways in which fire impacts the global C cycle, with a special focus on the widely-overlooked role of pyrogenic C.

We will begin by summarising how fires impact on terrestrial stores of C, starting with natural cycles of disturbance and recovery that influence total stocks of C on the terrestrial landscape. We will then demonstrate how shifting fire regimes, related to climate change and changes in land use, are perturbing the cycle of C and influencing the quantity of C stored on the landscape. Increased fire frequency and intensity generally promotes a loss of C from landscapes, especially in cases where vegetation cannot recover completely in the shortening time available between disturbance events.

Set within the broader cycle of biogenic C is a sub-cycle of highly recalcitrant ‘pyrogenic’ C – a by-product of incomplete combustion during fires. We will highlight how the special properties of this pyrogenic C promote its longevity in terrestrial stores in a manner that can offset (or ‘buffer’) losses of total C. The process of pyrogenic C storage has been widely overlooked in models of the global C cycle leading to C accounting errors, however we will highlight some recent examples of its implementation in land surface models and the lessons learned from doing so.

Due to its exceptional longevity in terrestrial pools, pyrogenic C has enhanced odds of reaching the global oceans via rivers. We will discuss the disproportionate export of pyrogenic C to the global oceans (relative to biogenic C) and how this leads to an unusual potential for long-term C sequestration.

Finally, we will provide an overview of the current understanding of the global budget of pyrogenic C, integrating best estimates for the fluxes of C to and from terrestrial stores and to and from marine stores. We will also highlight how uncertainties in the magnitude of fluxes in the C cycle lead to poor understanding of whether pyrogenic C currently acts as a sink or source of C to the atmosphere. We will underscore the particular need to constrain the decomposition rates and residence times of pyrogenic C in soils and marine stores if we are to build a complete picture of its role in the global C cycle.

How to cite: Jones, M., Coppola, A., and Santín, C.: Pyrogenic carbon: Is it a sink in the global carbon cycle? And why we can’t be sure., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18669, https://doi.org/10.5194/egusphere-egu24-18669, 2024.

EGU24-19168 | Orals | BG1.10

Molecules and microbes: monitoring peatland health below the surface 

Nicholle Bell, Ezra Kitson, Gianluca Trifiro, and Richard York

Peatlands are organic matter rich (with over 60% organic matter) ecosystems that act as ‘carbon sinks’, storing many times the carbon stored by Earth’s forests. Peatlands act as sponges storing excess water from rain events and releasing it slowly, a mechanism that not only mitigates floods but also filters drinking waters. However, peatlands can only conduct these vital services when healthy and functioning, with a near surface water table and anoxic acidic conditions below the surface. Unfortunately, 80% of UK peatlands have been assessed as damaged mainly via drainage for repurposing the land for other uses. Rewetting peatlands by installing dams is one of the most common methods to restore these damaged bogs. While there is a large amount of evidence that rewetting restores the water table, questions remain whether rewetting successfully restores peatlands to their full health. To answer this question, we need to know what is happening below the surface and examine the roles of key players in peat formation and carbon cycling, namely the microbes and the carbon-containing molecules. It is not clear which of these players is more important, or how they depend on each other. To address this question, we are using the latest technologies (DNA/RNA sequencing, NMR spectroscopy and FT-ICR mass spectrometry) to uncover who they are, how they interact and how they are impacted by drainage and rewetting. The task is not easy as peat is an uncharacterised complex mixture on a molecular and microbial level and the key players could be found in different phases (solid or liquid). In this presentation, I will provide a brief overview of what insights the technologies we are using provide for below the surface characterisation of UK peatlands.

How to cite: Bell, N., Kitson, E., Trifiro, G., and York, R.: Molecules and microbes: monitoring peatland health below the surface, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19168, https://doi.org/10.5194/egusphere-egu24-19168, 2024.

EGU24-19501 | ECS | Posters on site | BG1.10

Inorganic biogenic carbon redistribution and transport in marine sediments 

Prabodha Lakrani Hewage, Luz María Mejía, Negar Haghipour, Mariem Saavedra-Pellitero, Ben Trundley, Timothy Eglinton, David Hodell, and Blanca Ausín

Coccolithophores are calcifying marine phytoplankton whose blooms can be seen from space and play an important, yet complex, role in the global carbon cycle. On one hand, coccolithophores sequester atmospheric CO2 to the deep ocean via photosynthesis contributing to the biological pump. On the other hand, coccolithophores increase aqueous CO2 via precipitation of tiny calcite scales named coccoliths (i.e., carbonate counter pump), which are a major component of marine sediments. Coccoliths are generally in the 2-20 µm size range, and thus they can be winnowed by strong currents and transported to distal locations. Here, we show the first coccoliths radiocarbon (14C) ages and explore the influence of size-dependent coccolith sorting and transport, redistribution, and fate in marine sediments. Because the coccolith depends on the species, we have separated and 14C dated four coccolith size fractions: 8-11 µm, 5-8 µm, 3-5 µm, and 2-3 µm, in  five depth intervals on a sediment core recovered from SHAK06-5K site, off the Iberian Margin. Coccolith separation was achieved by a combination of dry sieving, microfiltration, centrifugation, and settling experiments. Energy Dispersive Spectroscopy (EDS) images of selected size fractions were used to estimate the relative contribution of coccolith and non-coccolith carbonate. A relationship between coccolith 14C age and grain size is apparent in all samples, with the smallest size class recording the youngest ages and the largest coccoliths being the oldest. The latter suggests that hydrodynamic sorting largely influences coccolith redistribution in marine sediments, where larger coccoliths result in increased mobility, as they are prone to resuspension than coccoliths in 2-3 µm size fraction that tend to show cohesive behaviour. The 14C ages of coccoliths are older than those of co-deposited planktic foraminifera, bulk organic carbon (OC), long-chain fatty acids (LCFA), and alkenones. Coccoliths within the 2-3 µm size class show 14C ages comparable to those of OC in all samples. Such a pattern indicates similar transport mechanisms for both the smallest coccoliths and OC, and that the majority of carbonate in the 2-3 µm size fraction, including the non-coccolith particles, is predominantly derived from marine primary production and thus, of biogenic origin. Our study has implications for palaeoceanographic studies using coccoliths as paleo-productivity and geochemical proxies.

How to cite: Hewage, P. L., Mejía, L. M., Haghipour, N., Saavedra-Pellitero, M., Trundley, B., Eglinton, T., Hodell, D., and Ausín, B.: Inorganic biogenic carbon redistribution and transport in marine sediments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19501, https://doi.org/10.5194/egusphere-egu24-19501, 2024.

EGU24-19642 | Orals | BG1.10

Insight in high alpine soil carbon dynamics from compound-specific and soil fraction radiocarbon analysis on a glacier forefield chronosequence  

Rienk Smittenberg, Valerie Schwab, Hans Sanden, Iso Christl, Frank Hagedorn, Irka Hajdas, Lukas Wacker, Negar Haghipour, Susan Trumbore, Xiaomei Xu, and Stefano Bernasconi

The ecosystem carbon balance of high latitude and high altitude ecosystems is particularly sensitive to climate change, where increasing temperatures generally lead to a rise of the ecosystem carbon storage, but also increasing carbon turnover times. In this study, we investigated the carbon dynamics of the 150-year long Damma Glacier forefield chronosequence, Switzerland. Specifically, we performed radiocarbon analysis of a range of organic matter fractions, sampled in 2007, 2017 and 2022 from soils developing on areas having been exposed for 20-150 years due to the retreat of the glacier. To characterize the age spectrum of material making up the bulk soil carbon, we isolated a range of different fractions, from supposedly 'stable' carbon pools (fine mineral-bound, and peroxide-resistant carbon), microbially ‘labile’ respired CO2, dissolved soil organic carbon (DOC), hydrophobic leaf wax-derived alkanes, and microbial-derived fatty acids. Comparison of our results with the penetration of the radiocarbon bomb spike and the increase of soil and ecosystem carbon over the both the chronosequence (space-for-time) and over the sampling period (time-for-time) allowed us to make the following inferences: (i) A small but persistent contribution of ancient carbon is present in the forefield area exposed by the glacier, which is particularly visible in the hydrophobic leaf wax 14C data. From this we conclude that this old carbon pool is at least in part a remnant of ancient soil carbon from a previous warm and glacier-free period, potentially adding to contributions of fossil-fuel derived black carbon deposition. (ii) There is a significant portion of soil carbon with a decadal-scale carbon turnover rate, and (iii) mineral-bound carbon clearly has a slower turnover time. (iv) Microbial lipids, soil CO2 and DOC 14C content reflect different carbon sources: in younger soils, relatively low 14C contents indicate a higher relative contribution of ancient carbon decomposition, while in older soils this signal is swamped by decomposition of freshly photosynthesized organic matter.

How to cite: Smittenberg, R., Schwab, V., Sanden, H., Christl, I., Hagedorn, F., Hajdas, I., Wacker, L., Haghipour, N., Trumbore, S., Xu, X., and Bernasconi, S.: Insight in high alpine soil carbon dynamics from compound-specific and soil fraction radiocarbon analysis on a glacier forefield chronosequence , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19642, https://doi.org/10.5194/egusphere-egu24-19642, 2024.

EGU24-21439 | ECS | Orals | BG1.10

Modeling microbial functional trait-environment interactions at the continental scale 

Katherine Shek, James Stegen, Alan Roebuck, Amy Goldman, Mikayla Borton, Kelly Wrighton, and Adam Wymore

Inferring linkages between microbial metabolism and dissolved organic matter (DOM) across environmental gradients is a promising avenue to improve biogeochemical predictions at large spatial scales. Despite decades of metagenomic studies identifying microbial functional trait-environment patterns at small spatial scales, general patterns at continental or global scales that may improve large-scale models remain unresolved. Recent influx of multi-omics datasets that represent diverse environmental conditions has enabled scalable analyses linking microbial metabolic niche breadths with key environmental processes, such as carbon and nutrient transformations.

Here, we leveraged publicly available microbial metagenome assembled genomes (MAGs) derived from the Worldwide Hydrobiogeochemistry Observation Network for Dynamic River Systems (WHONDRS) data paired with metabolomic (FTICR-MS) and sediment chemistry data to link microbial metabolic potential with organic chemistry. We annotated 1,384 MAGs representing 65 sites using the R tool microTrait, which categorizes functional traits under the YAS (growth yield-resource acquisition-stress tolerance) framework. Following Hutchinsonian niche theory, we modeled microbial trait combinations as n-dimensional hypervolumes and observed trait-DOM patterns at the continental scale, showing microbial functional tradeoffs along gradients of organic carbon. We expect that at the continental scale, microbial trait profiles will be distinct across climatic regions, and that niche breadth (i.e. the size of individual hypervolumes in trait space) will correlate with DOM/metabolite diversity. The results of this work will distill generalizable patterns of microbe-DOM availability and diversity at large spatial scales, thus identifying information to improve current biogeochemical models.

How to cite: Shek, K., Stegen, J., Roebuck, A., Goldman, A., Borton, M., Wrighton, K., and Wymore, A.: Modeling microbial functional trait-environment interactions at the continental scale, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21439, https://doi.org/10.5194/egusphere-egu24-21439, 2024.

Soil pore structure, dictated by factors such as porosity, size distribution, and geometry, is crucial for various soil processes and is significantly influenced by soil organic carbon (SOC). As the primary architect of pore geometry within soil aggregates, SOC plays a vital role in determining soil functionality and ecosystem services, yet traditional in-situ analysis methods have fallen short in accurately depicting its intricate distribution. The study employed a two-fold approach to analyze soil structure: a hydrogen peroxide fogging system was used to selectively remove organic carbon from soil aggregates, followed by synchrotron radiation micro-computed tomography (SR-μCT) for in-depth three-dimensional imaging. The results revealed that hydrogen peroxide treatment variably reduced organic carbon in soil aggregates, with Cambisol showing a higher removal efficiency (68-79%) compared to Ultisol (42-47%). The data highlighted the transformation of smaller pores and an increase in larger pore spaces following organic carbon removal, with Cambisol aggregates experiencing the most substantial alterations in pore structures. The impact of organic carbon on the shaping of pore structure within soil aggregates was profound and varied distinctly between the two studied soils—Ultisol and Cambisol. In Ultisol, the organic carbon, initially minimal, played a subtle role in pore structure formation, leading to limited changes post-removal, which suggested a structural resilience possibly due to its inherent mineralogy and physicochemical characteristics. In contrast, Cambisol, with higher initial organic carbon content, showed dramatic alterations in pore structure upon organic carbon removal. This indicated a more critical role of organic carbon in maintaining pore space configurations, with significant increases in larger pore spaces and a decrease in smaller, disconnected pores. These changes highlighted the organic carbon’s crucial function in not only sustaining pore integrity but also in facilitating the complex soil functions such as water retention and root penetration.

How to cite: Liu, J., Tian, Y., and Lu, S.: Investigating the influence of soil organic carbon on pore structure within aggregates a comparative study of Ultisols and Cambisols in China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-139, https://doi.org/10.5194/egusphere-egu24-139, 2024.

EGU24-627 | ECS | Posters on site | SSS5.5

The effect of slope on soil organic matter and on microbial communities under different soil management practices. 

Laura Gismero Rodríguez, Inés Aguilar-Romero, José Alfonso Gómez, Ángel Valverde, and Heike Knicker

In Mediterranean regions, olive plantations are commonly located on steep 
slopes, leading to significant erosion. To mitigate soil loss, sustainable management 
practices often involve allowing natural vegetation cover to grow in the inter-tree 
spaces. 

To provide insights into the impact of different management forms on soil quality, we 
collected topsoil samples (0-15 cm) from an olive orchard with an 11% slope located in 
Southern Spain (Benacazón, Seville). Samples were taken along the slope of plots
managed with conventional tillage (CT) and with natural cover (NC). Additionally, soils
from the tree line, treated with herbicide (TL-Herb.), were included. To account for 
seasonality effects, sampling campaigns were conducted in autumn 2022 (following the 
dry season) and spring 2023 (after the rainy season). 

Soil organic matter content will be correlated with the management practices, slope 
location and microorganism abundance, determined through phospholipid fatty acid 
analysis (PLFA). Microbial respiration analysis will be also performed, using MicroResp
to assess microbial activity. The main hypothesis is that plots with vegetation cover will 
have higher SOM and total microbial biomass contents. We also expect an impact of 
slope location not only on the size of the microbial pool but also on the microbial 
biodiversity.

How to cite: Gismero Rodríguez, L., Aguilar-Romero, I., Gómez, J. A., Valverde, Á., and Knicker, H.: The effect of slope on soil organic matter and on microbial communities under different soil management practices., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-627, https://doi.org/10.5194/egusphere-egu24-627, 2024.

Landsliding creates new substrates upon which ecosystems develop. From a recovery perspective, these substrates may limit plant growth due their harsh conditions. Yet, from a soil formation perspective, these substrates may enhance weathering rates due to a combination of abiotic and biotic factors. Central to both is the role that mycorrhiza may play in ecosystem development, including biogeochemical cycles. Given that at mountainscape scales landslide populations are diverse due to variation in underlying climatic and edaphic conditions, we hypothesize that plant-mycorrhizal associations and their functions will mirror this diversity. To test this hypothesis, we focus on the Sierra de Las Minas in Guatemala (SLM), a mountain range that offers contrasting climatic characteristics associated with aspect (south aspect is dry to mesic and north aspect wet) and steep elevation gradients (400 – 2600 m a.s.l.). Leveraging plant and soil inventories conducted in forest and landslide habitats in the SLM we ask 1) How do plant-mycorrhizal associations vary with aspect, elevation, and habitat? 2) What is the contribution of soil chemistry to the observed variation in plant-mycorrhizal associations? And 3) How do plant-mycorrhizal associations and environmental conditions explain variation in weathering rates? To answer these questions, we integrated our plant inventories with a global database on plant-mycorrhizal associations. The former contains species composition and soil elemental analyses that we used to estimate a variety of weathering indices. The latter was used to assign plants from our field inventories to one or more mycorrhizal type.

Plant-mycorrhizal associations were diverse and greatly contributed to the separation of plant communities in multivariate space. Aspect followed by habitat explained a large fraction of the observed variability. Subsets of soil variables correlated with different dimensions derived from principal component analyses suggesting that plant-mycorrhizal associations contribute diverse functions. In general, weathering indexes differed with aspect and habitat. For example, Vogt Residual Index and Chemical Index of Alteration, were higher in landslide than forest and this difference was more pronounced in the wet than dry to mesic aspects. Further analyses will allow us to examine the contribution of plant-mycorrhizal associations to ecosystem development and soil formation in tropical mountainscapes influenced by landslide activity.

How to cite: Restrepo, C. and Ortiz, Y.: Plant-mycorrhizal associations vary with climate and soil in tropical mountainscapes influenced by landslides: Implications for ecosystem development and soil formation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4322, https://doi.org/10.5194/egusphere-egu24-4322, 2024.

EGU24-4570 | ECS | Posters on site | SSS5.5

Seasonal floodplain dynamics control Fe-rich colloid characteristics 

Maya Engel, Vincent Noel, Samuel Pierce, Tristan Babey, Libor Kovarik, Ravi Kukkadapu, Qian Zhao, Rosalie Chu, Kristin Boye, and John Bargar

High concentrations of Fe-rich colloids have been detected in the anoxic zones of our Slate River floodplain field site (CO, USA) since 2018. We speculated that the composition and abundance of the colloids is controlled by the seasonal dynamics and spatial heterogeneities of the subsurface. Therefore, our goals were to 1) decipher the structure and chemical composition of Fe-rich colloids, 2) identify mechanisms of colloid transformation and 3) understand their biogeochemical function.

TEM analysis revealed nano-spheres and nano-assemblages that consist mainly of Fe, O, Si, and C, with lower contributions from Al, S and Ca. Based on this elemental distribution, we hypothesized that the colloids are composed of Fe minerals that are associated with organic matter and Si. This was further confirmed through Mössbauer spectroscopy and Fe-EXAFS that indicated the colloids consist ferrihydrite associated with organic matter and Si. NanoSIMS imaging detected co-localities of Fe, S, Si, and O, as well as C and N, which demonstrate once more that these are ferrihydrite-based colloids that are embedded in an organic matter-Si matrix.

 These findings are intriguing as they demonstrate high abundance of ferrihydrite-based colloids in anoxic depths of our field site. The stability of the colloids is likely attributed to the coating of organic matter and Si that serves as a protective layer against the reducing conditions. Nevertheless, our data also showed that colloids collected during snowmelt (Spring 2021) contained a higher proportion of Fe(II) than colloids collected during baseflow conditions (Summer 2021). XPS analysis measured higher atomic percentages of C and Si compared to Fe and O in baseflow versus snowmelt colloids, indicating a decrease in the organic-Si protective layer under baseflow conditions, allowing for Fe(II) oxidation and an increase in Fe(III)/ferrihydrite content. The fact that there is an occurrence of S species only in the more reduced snowmelt colloids illustrates the dynamic and delicate composition of these environmental colloids during seasonal changes in hydrology and porewater chemistry.

We are also in the process of interpreting our seasonal data that will shed light on the controls over the seasonal dynamics of the colloids. We have already linked Fe(II) colloid abundance to lower vertical porewater velocities and higher organic matter levels, and are working on additional analyses including data acquired from FT-ICR-MS analysis of the organic composition of the colloids.

How to cite: Engel, M., Noel, V., Pierce, S., Babey, T., Kovarik, L., Kukkadapu, R., Zhao, Q., Chu, R., Boye, K., and Bargar, J.: Seasonal floodplain dynamics control Fe-rich colloid characteristics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4570, https://doi.org/10.5194/egusphere-egu24-4570, 2024.

Soil particle size distribution determines the soil water and nutrient availability, but the spatial variance of the soil texture is often unknown in agricultural fields. This knowledge gap limits demand-oriented and ecological nutrient and water management of crops. It also hampers our understanding of the crop resource use in the field as mediated by soil microbes such as the arbuscular mycorrhizal symbioses. To better understand to which soil conditions maize-mycorrhiza associations respond, we used proximal sensing of soil texture to map within-field variation soil particle size in high spatial resolution and related soil texture to the mycorrhization of organic maize.

To obtain the soil texture maps, we used the mobile sensor platform Geophilus electricus [1]. This proximal soil sensing system deploys a multi-sensor approach to discriminate soil properties by simultaneously measuring the electrical resistivity (up to 1.5m depth) via rolling electrodes and the natural gamma activity, whilst a DGPS guarantees the required precision in geo-referencing during mapping [2]. After calibration of the sensor data with soil samples of the selected fields, the final output is a high-resolution map of the mean soil particle diameter (MPD), which was then used as the independent variable in correlations with the mycorrhization of maize.

The soil texture mapping took place for three investigated fields in 2020 at an organic farm in Lower Saxony, Germany, which is dominated by sandy soils and on which a crop rotation with maize was deployed. The plant and soil sampling took place in 2017, 2020 and 2021 at the respective sites with maize. For each field, the sampling of soils and plants occurred equidistantly in 12 parallel transects along the moving lane direction. We analyzed plant and soil C/N, P, K, Mg, soil pH and organic matter and root colonization by native mycorrhizal fungi during the maize culture.

According to our expectations, we found that the MPD and the clay fraction are accurate describers of the soil P, N, Mg and Corg concentrations for the three years and fields in the crop rotation, while soil K was not responding to the soil texture. Interestingly, we also found a conserved correlation between root colonization by arbuscular mycorrhizal fungi and the MPD of the soil surrounding the roots of the sampled plants. Lower MPD (i.e. higher clay contents) gave rise to stronger maize-mycorrhiza root associations. This response pattern was conserved in years markedly different in mean annual temperature and precipitation. However, the lowest rates of root colonization by mycorrhizas were observed in the dry year of 2020.

We discuss that precision farming technologies may have the potential to guide the management of crops for improved and microbe-assisted resource use. 

 

 

[1] Lück, E., & Rühlmann, J. (2013). Resistivity mapping with GEOPHILUS ELECTRICUS—information about lateral and vertical soil heterogeneity. Geoderma, 199, 2–11. [2] Meyer, S. et al. (2019). Creating soil texture maps for precision liming using electrical resistivity and gamma ray mapping. In Stafford, J. V. (Ed.) Precision Agriculture’19 Proceedings of the 12th European Conference on Precision Agriculture Wageningen (pp. 92). Wageningen, The Netherlands: Wageningen Academic Publishers.

How to cite: Bitterlich, M., bönecke, E., and Rühlmann, J.: Mycorrhiza likes clay - High resolution soil texture maps reveal a conserved correlation of maize mycorrhization to soil particle size across years and fields, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4761, https://doi.org/10.5194/egusphere-egu24-4761, 2024.

EGU24-5851 | Posters on site | SSS5.5

Synergistic relationships between the age of soil organic matter, Fe speciation, and aggregate stability 

Nina Siebers, Eva Voggenreiter, Prachi Joshi, Janet Rethemeyer, and Liming Wang

Understanding the formation and stability of soil aggregates is crucial for sustaining soil functions. This study investigates the impact of organic matter (OM), pedogenic Fe (oxyhydr)oxides, and aggregate size on aggregate stability in an arable soil. Samples were collected from the Ap and Bt horizons of a Luvisol after 14 years of bare fallow, and results were compared with a control field under permanent cropping. In the Ap horizon, bare fallow led to a 26% reduction in the median diameter of the 53-250 µm size fraction, indicating decreased stability of larger microaggregates. Simultaneously, the mass of the 20-53 µm size fraction increased by 65%, suggesting reduced stability, particularly of larger soil microaggregates, due to the absence of fresh OM input. The 14carbon (14C) fraction of modern C (F14C) under bare fallow ranged from 0.50 to 0.90, lower than the cropped site (F14C between 0.75 and 1.01). This difference was most pronounced in the smallest size fraction, indicating the presence of older C. Higher stability and reduced C turnover in <20 µm aggregates were attributed to their elevated content of poorly crystalline Fe (oxy)hydroxides, acting as cementing agents. Colloid transport from the Ap to the Bt horizon was observed under bare fallow treatment, highlighting the release of mobile colloids. This transport may initiate elemental fluxes with potential unknown environmental consequences. In conclusion, the absence of OM input decreased microaggregate stability, releasing mobile colloids and initiating colloid transport.

How to cite: Siebers, N., Voggenreiter, E., Joshi, P., Rethemeyer, J., and Wang, L.: Synergistic relationships between the age of soil organic matter, Fe speciation, and aggregate stability, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5851, https://doi.org/10.5194/egusphere-egu24-5851, 2024.

EGU24-6272 | Posters on site | SSS5.5

Long-Term Effects of Silphium perfoliatum on Soil Pore Dynamics and Organic Carbon Accumulation 

Maik Lucas, Lina Rohlmann, and Kathrin Deiglmayr

Perennial bioenergy crops like Silphium perfoliatum (cup plant) are a promising alternative to currently used energy crops such as maize because of their positive feedbacks on various soil properties including carbon sequestration, edaphon activity and erosion control. This study investigates the long-term impact (over 10 years) of the cup plant on soil organic carbon and soil structural parameters in comparisons to a to a nearby ploughed reference site.

We employed tension infiltrometers to measure water infiltration rates at two soil depths (5 and 45 cm). Following this, 100 cm³ aluminum soil cores were extracted for X-ray computed tomography at a resolution of 35 µm. The image analysis, enhanced by machine learning, classified structures including roots, particulate organic matter (POM), biopores, and two types of soil matrix: dense and loose, the latter indicating higher carbon content or more pores slightly below image resolution. The dataset was complimented by the determination of total carbon content and the root length distribution with RhizoVisionExplorer.

The results indicate significant differences in pore structure, primarily in the topsoil, where the cup plant site showed a greater volume of biopores than the reference site. In contrast, the subsoil differences were less marked. Organic carbon content analysis demonstrated a notable increase in the upper soil layer (10-15 cm) at the cup plant site, contributing to a higher soil organic carbon stock than the reference site. However, this effect diminished with depth, becoming negligible at 50-55 cm. In the topsoil, extensive bioturbation/biomixing was observed, as indicated by the darker, more loosely structured soil matrix, which often had the shape of biopores. This bioturbation, which mixed particulate organic matter (POM) into the soil, significantly enhanced soil organic carbon, as evidenced by linear regression analysis.

These findings underscore the substantial impact of the perennial cup plant in enhancing soil structure and carbon content, particularly in the topsoil.

How to cite: Lucas, M., Rohlmann, L., and Deiglmayr, K.: Long-Term Effects of Silphium perfoliatum on Soil Pore Dynamics and Organic Carbon Accumulation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6272, https://doi.org/10.5194/egusphere-egu24-6272, 2024.

EGU24-7710 | Orals | SSS5.5

Probing microbe-mineral-organic matter interactions in soils with photothermal infrared spectromicroscopy 

Floriane Jamoteau, Mustafa Kansiz, and Marco Keiluweit

Interactions among microbes, minerals, and organic matter are key controls on carbon, nutrient, and contaminant dynamics in soil and sediments. However, probing these interactions at relevant scales and through time remains an analytical challenge due to both their complex nature and the lack of tools permitting non-destructive time-step analysis. The recent development of optical photothermal infrared (O-PTIR) microscopy has opened the way for non-invasive analysis of these interactions at submicron resolution through time. Here we demonstrate the ability of O-PTIR microscopy to analyze mineral-organic microstructures down to 400 nm, without contact, allowing the time-resolved, non-destructive characterization of both mineral and organic components. Results showed that, while all these mineral-organic microstructures can be analyzed without measurable beam damage using the appropriate laser power, poorly crystalline minerals, and high-molecular-weight compounds are more sensitive to damage than crystalline minerals and low-molecular-weight compounds, respectively. Despite these differences in beam damage sensitivity, we found analytical conditions under which all materials were analyzed without damage and could therefore be analyzed repeatedly over time. With synthetic mineral-organic microstructures, we localized mineral-bound and unbound organic compounds, down to the sub-micron scale. Our results highlight the potential of and provides analytical recommendation for the application of O-PTIR microscopy to resolve microbe-mineral-organic matter interactions in soil and sediments.

How to cite: Jamoteau, F., Kansiz, M., and Keiluweit, M.: Probing microbe-mineral-organic matter interactions in soils with photothermal infrared spectromicroscopy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7710, https://doi.org/10.5194/egusphere-egu24-7710, 2024.

EGU24-8956 | ECS | Posters on site | SSS5.5

Seasonal greenhouse gas flux and microbial community dynamics along a landslide soil chronosequence at the west side of New Zealand's Southern Alps 

Olivia Rasigraf, Anne Riedel, Alexander Bartholomäus, Timothy Clough, Thomas Friedl, and Dirk Wagner

Landslides are an important erosion mechanism in mountainous terrain. They strip large quantities of organic material from ecosystems and expose bedrock to weathering. At the west side of New Zealand’s Southern Alps, super-humid climate and slope instabilities create ideal conditions for frequent landslides, allowing studies of soil formation processes in short-term chronosequences. Here, we investigated soils from three landslides that occurred in 2019 (“young”), 1997 (“intermediate”), and 1965±5y (“old”), respectively. Additionally, reference forest soils located outside of landslide areas were sampled at each location. Closed PVC chambers were installed at different positions on landslide surfaces and reference soils, and gas samples were collected for flux analysis. Soil samples were collected at the same positions from the surface and 20 cm depth and investigated for physico-chemical parameters and microbial community composition.

Net CO2 emissions reached 830 mg h-1m-2 at the “old” site in summer and remained below 356 mg h-1m-2 in winter. Net N2O emissions showed a patchy spatial pattern, reaching rates of 0.2 mg h-1m-2 at the “old” site in summer. At most locations, N2O flux was below the detection limit during winter.

Soils were dominated by bacterial phyla Acidobacteria, Bacteroidota, Chloroflexi, Gemmatimonadota, Planctomycetota, Proteobacteria and Verrucomicrobiota. Dominant archaeal phyla comprised Thermoplasmatota and Crenarchaeota. Beta diversity analysis revealed distinct community composition patterns with the “young” site forming a separate cluster from the older landslides and reference soils. Surface- and depth-associated microbial communities showed high similarity at the “young” site, but they became increasingly distinct at the “intermediate”, “old” and reference soil sites. Community composition at the “old” site showed the least difference to reference sites, indicating that ecosystem development rapidly reached a state similar to older mature forests.

In general, the three landslide sites showed a gradient in the development of soil chemical parameters, microbial community composition and soil respiration rates, with the “old” site being closest to reference sites. Soil respiration rates showed strong seasonal dependence and soil temperature sensitivity.

Our results indicate that respiration rates and microbial community composition of landslide soils reach those of older mature forest soils within a few decades after mass wasting events, if no reactivation occurs and soil development can proceed without disturbance.

How to cite: Rasigraf, O., Riedel, A., Bartholomäus, A., Clough, T., Friedl, T., and Wagner, D.: Seasonal greenhouse gas flux and microbial community dynamics along a landslide soil chronosequence at the west side of New Zealand's Southern Alps, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8956, https://doi.org/10.5194/egusphere-egu24-8956, 2024.

EGU24-9465 | Posters on site | SSS5.5

Mapping redox conditions in a tar-oil contaminated technosol by S K-edge XANES at the micrometer scale 

Karin Eusterhues, Jürgen Thieme, Thomas Ritschel, Pavel Ivanov, and Kai Uwe Totsche

At numerous open pits worldwide, carcinogenic and geno‐toxic tar oil is still exposed to the environment. To understand ongoing tar degradation under different environmental conditions we studied soil structure, water retention, tar composition, and microbial biomass of a technosol under a small tar-oil spill at a former brown coal processing site. We observed that microbial biomass increased with pore volume on our study site: Generally, contaminated layers of the technosol were more porous than uncontaminated control soils and accommodated more microbes. However, the relationship was not linear. We therefore wondered whether the redox regimes within the aggregates of the different layers provide comparable conditions for microbial degradation.

We used the chemical state of S as a proxy for the prevailing redox-conditions and µXANES on thin sections (5 µm spatial resolution) to analyze the S speciation in relation to soil structure. First results show that the tar is not homogeneously composed and that the proportion of reduced S compounds increases with soil depth: Particularly S-rich domains within the tar are often roundish, up to 200 µm in size and composed of varying proportions of inorganic sulfide-S, organic monosulfide-S or thiol-S, sulfoxide-S, and sulfonate-S. The topmost layer (0-5 cm) of the technosol is very porous. Here, the tar matrix is dominated by sulfonate-S. At more than 5 cm depth, the soil also has a high porosity due to large pores > 50 µm but at the same time includes mm-sized, compact aggregates with only few small pores (1-10 µm and 10-50 µm). The tar matrix within these aggregates contains sulfidic S in addition to the sulfonate-rich component. However, adjacent to pore surfaces we observe 5-15 µm thick (oxidized) rims with only sulfonate-S.

Our data show that the tar is not only chemically complex, but also heterogeneous in composition at the µm scale. Below a soil depth of 5 cm, we can assume that microbial tar degradation is slowed down because of the anoxic conditions within the aggregates, although pores > 50 µm are abundant and bacterial cell counts are high.

How to cite: Eusterhues, K., Thieme, J., Ritschel, T., Ivanov, P., and Totsche, K. U.: Mapping redox conditions in a tar-oil contaminated technosol by S K-edge XANES at the micrometer scale, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9465, https://doi.org/10.5194/egusphere-egu24-9465, 2024.

EGU24-11128 | Orals | SSS5.5

The influence of structural complexity of microbial habitats on soil organic matter decomposition: a theoretical analysis 

Ksenia Guseva, Carlos Arellano, Magdalena Rath, Paul Prinz, Moritz Mohrlok, and Christina Kaiser

The soil pore space constitutes a highly heterogeneous habitat that harbors a rich microbial diversity. Microbial processes within soils are intricately linked to the physical and chemical characteristics of micro-environments of pores where they reside. The dynamics of decomposition of organic matter therefore is shaped by the dispersion dynamics or spatial constraints imposed on microorganisms and their enzymes. Therefore, incorporating the complex soil architecture into computational models at the microscale is a crucial step to improve our predictions of the dynamics of soil organic matter (SOM) turnover.

In this work, we employ theoretical models to elucidate the impact of soil structural complexity and heterogeneity on organic matter decomposition dynamics, and characterize mechanisms that enhance or constrain it. In the first part, we show the impact of compartmentalization of the substrate on enzyme activity, considering a scenario where microbes have no direct physical access to the substrate and only smaller freely diffusing enzymes can reach it. Our findings reveal that, in this context, enzyme lifetime imposes limitations on the turnover rate of the reaction, subsequently affecting the uptake and growth rates of microorganisms. In the second part, we examine the effect of soil architecture on microbial decomposition dynamics. Our results highlight two contrasting aspects necessary for rapid decomposition: on one hand there is a need for refuges/shelters where microbial activity is boosted trough accumulation of enzymes, and on the other there is a need for high connectivity (accessibility) of the pore space for the microbial population to spread. Through our examination, we unveil the intricate interplay between these apparently conflicting conditions and their profound effects on population growth and substrate decomposition rates.

How to cite: Guseva, K., Arellano, C., Rath, M., Prinz, P., Mohrlok, M., and Kaiser, C.: The influence of structural complexity of microbial habitats on soil organic matter decomposition: a theoretical analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11128, https://doi.org/10.5194/egusphere-egu24-11128, 2024.

EGU24-11265 | ECS | Posters on site | SSS5.5

Aged carbon mineralisation from headwater peatland floodplains in the Peak District, UK 

Danielle Alderson, Martin Evans, Mark Garnett, and Fred Worrall

Floodplains are dynamic ecosystems that cycle carbon, which is both delivered from upstream catchment sources and produced in-situ by pedogenesis. These landforms are being progressively acknowledged as important environments of carbon processing, with the capacity for both substantial carbon sequestration in addition to acting as hotspots of carbon mineralisation. The balance between storage and release is dependent on a number of controls including landscape position, environmental conditions and soil characteristics. This study focuses on three headwater floodplains in a single catchment (approximately 10km in length), downstream of a highly eroded blanket bog peatland in the Peak District, UK. Aged organic carbon of peatland origin has been found in floodplains in this area based on prior research, and therefore we aimed to understand whether the allochthonous carbon was being mineralised in this context. We examined sediment cores and analysed the radiocarbon (14C) content of CO2 respired from the floodplain soils using a partitioning approach to scrutinise the depth and age relations of respiration in the individual floodplains and patterns of age distributions downstream. As such, we examined whether soil heterogeneity as a function of distance downstream and within individual floodplain profiles had an impact on age of respired CO2.

Aged organic carbon was released from the upper and mid floodplain sites (14C ages of 682 and 232 years BP, respectively), whereas only modern dates were recorded at the lower site. The sedimentology was in accordance with the radiocarbon dates, suggesting primarily allochthonous deposition at the upper sites, but a dominance of in-situ soil development at the lower site. There was no age-depth relationship within individual floodplains, suggesting that the floodplain sediments were well-mixed and that aged organic matter was being processed both at the surface and at depth in the uppermost sites. An isotope mass balance mixing model indicated the control of two sources of CO2; recently fixed C3 organic matter and CO2 produced by methanogenesis. The results indicate that floodplains in a relatively narrow halo around eroding headwater peatlands could be important sites of aged carbon turnover originally derived from upstream sources, with those further downstream playing a different role. Reworked carbon does not transfer passively through the system and experiences periods of deposition where it can be subject to microbial action. In areas where organic carbon has previously been ‘locked up’ (e.g., permafrost regions) but is now under the threat of release due to climate change, this is an important consideration.

How to cite: Alderson, D., Evans, M., Garnett, M., and Worrall, F.: Aged carbon mineralisation from headwater peatland floodplains in the Peak District, UK, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11265, https://doi.org/10.5194/egusphere-egu24-11265, 2024.

EGU24-11474 | ECS | Posters on site | SSS5.5

Spatiotemporal variations of manganese-mediated litter decompositions across oxic-anoxic transitions in deciduous forest soils 

Nathan Chin, Egon Van Der Loo, Kristen DeAngelis, and Marco Keiluweit

Manganese (Mn) has been demonstrated to be a significant driver of litter decomposition in forest soils, regulating nutrient cycling, CO2 production, and ultimately soil carbon storage across forest systems globally. Recent evidence suggests that Mn-driven litter decomposition is dependent on ubiquitous oxic-anoxic interfaces in soils, which act as potential hotspots for the formation of reactive Mn(III) oxidants. Here we will show how oxic-anoxic interfaces in forest soils, arising from spatiotemporal variations in moisture, affect Mn(III)-driven litter decomposition. To do this, we tested the effect of in-field Mn additions on litter decomposition along a deciduous forest upland-to-wetland transect exhibiting dynamics in oxic-anoxic transitions. Within Mn-amended litterbags incubated across the transect, we monitored spatiotemporal variations in Mn(III) formation and litter decomposition. Over the course of the experiment, increased Mn amendments in litter correlated with both enhanced CO2 production as greater mass loss compared to untreated litter, particularly during periods of greater Mn(II) oxidation. Wet-chemical extractions revealed increasing Mn(II) oxidation over the growing season in elevated Mn treatments, resulting in enhanced Mn(III) formation. Additionally, the greater abundance of Mn(III) phases in Mn treated litter compared to untreated litter was significantly correlated to a greater degree of oxidation in the litter and greater water extractability of litter carbon, demonstrating enhanced litter decomposition in Mn amended litter. Across the forest transect, Mn oxidation and Mn(III) formation were greatest at sites with greater presence of oxic-anoxic transitions, which coincided with the sites exhibiting higher litter decomposition. Therefore, our results show that Mn(III)-mediated litter decomposition occur in hotspots present at oxic-anoxic interfaces across spatiotemporal gradients in forest soils. These findings provide first insights into the spatiotemporal links between Mn and carbon coupled redox cycling in forest ecosystems.

How to cite: Chin, N., Van Der Loo, E., DeAngelis, K., and Keiluweit, M.: Spatiotemporal variations of manganese-mediated litter decompositions across oxic-anoxic transitions in deciduous forest soils, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11474, https://doi.org/10.5194/egusphere-egu24-11474, 2024.

EGU24-13293 | Orals | SSS5.5

Laboratory for Observing Anoxic Microsites in Soils (LOAMS) 

Vincent Noël, Samuel Webb, and Kristin Boye

Redox reactions essentially underlie several biogeochemical processes and are typically spatiotemporally heterogeneous in soils and sediments. However, redox heterogeneity has yet to be incorporated into mainstream conceptualizations and modeling of soil biogeochemistry. Anoxic microsites, a defining feature of soil redox heterogeneity, are non-majority oxygen depleted zones in otherwise oxic environments. Neglecting to account for anoxic microsites can generate major uncertainties in quantitative assessments of greenhouse gas emissions, C sequestration, as well as nutrient and contaminant cycling at the ecosystem to global scales. However, only a few studies have observed/characterized anoxic microsites in undisturbed soils, primarily, because soil is opaque and microsites require µm-cm scale resolution over cm-m scales. Consequently, our current understanding of microsite characteristics does not support model parameterization.

To resolve this knowledge gap, we simultaneously (i) study impact from anoxic microsites on biogeochemical cycles at the soil scale and (ii) detect, quantify, and characterize anoxic microsites directly from natural cores.

We have examined the influence of anoxic microsites on biogeochemical cycles of nutrients (C, S, and Fe) and contaminants (Zn, Ni, As, U), combining results from experimental columns and natural cm-scale anoxic microsites of floodplain sediments at the upper Colorado River Basin scale. In parallel, we have demonstrated through a proof-of-concept study that X-ray fluorescence (XRF) 2D mapping can reliably detect, quantify, and provide basic redox characterization of anoxic microsites using solid phase “forensic” evidence. Rapid screening of large cores at high spatial and energy resolution, i.e. 1-100 µm resolution over cm-m areas, followed by systematic algorithm-driven data processing, allows for relatively quick identification, quantification, and characterization of actual anoxic microsites. To date, these investigations have revealed direct evidence of anoxic microsites in predominantly oxic soils such as from an oak savanna and toeslope soil of a mountainous watershed, where anaerobicity would typically not be expected. We also revealed preferential spatial distribution of redox microsites inside aggregates from oak savanna soils. We anticipate that this approach will advance our understanding of soil biogeochemistry and help resolve “anomalous” occurrences of reduced products in nominally oxic soils.

How to cite: Noël, V., Webb, S., and Boye, K.: Laboratory for Observing Anoxic Microsites in Soils (LOAMS), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13293, https://doi.org/10.5194/egusphere-egu24-13293, 2024.

EGU24-13732 | Orals | SSS5.5

Exploring subsurface heterogeneity of nitrogen and carbon cycling under a southeastern U.S. cattle grazing pasture  

Joseph Roscioli, Joanne Shorter, Elizabeth Lunny, Scott Herndon, Nuria Gomez-Casanovas, and Peter Byck

Subsurface cycling of nitrogen and carbon is central to our understanding of biosphere-atmosphere exchange and can strongly impact the ability of soil to be a greenhouse gas source or sink.  The underlying processes exhibit strong environmental dependence that can lead to substantial spatiotemporal heterogeneity across scales.  Here we present a study that explores how that variability manifests in subsurface greenhouse gases and their isotopes under a cattle grazing pasture in the southeastern U.S.  We used an automated array of 24 diffusive soil gas probes connected to a tunable infrared laser direct absorption spectrometer (TILDAS) to produce real-time maps of nitrous oxide isotopes, carbon dioxide, and oxygen with high spatial (meters) and temporal (hours) resolution.  We discuss ways to visualize and process the heterogeneity data, including using Lorenz plots and two-dimensional correlation, to reveal the magnitude and persistence of spatial heterogeneity of these gases.  CO2 is found to be much more spatially homogeneous than N2O, indicating a stronger dependence of N processing upon the local environment.  Analysis of N2O isotopic signatures shows that the last step in subsurface N-cycling, N2O reduction, is spatially heterogeneous and related to the magnitude of “hot spots” of N2O production.   

How to cite: Roscioli, J., Shorter, J., Lunny, E., Herndon, S., Gomez-Casanovas, N., and Byck, P.: Exploring subsurface heterogeneity of nitrogen and carbon cycling under a southeastern U.S. cattle grazing pasture , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13732, https://doi.org/10.5194/egusphere-egu24-13732, 2024.

EGU24-14399 | Orals | SSS5.5

The interplay of soil spatial heterogeneity and water in stabilizing and destabilizing soil organic matter 

Claire Chenu, Charlotte Védère, Israel Kpemoua, Naoise Nunan, Valérie Pot, Patricia Garnier, Clémentine Chirol, and Laure Vieublé-Gonod

Soil moisture is a main driver of soil organic matter dynamics of soil organic matter and is an important environmental variable in all models predicting changes in soil carbon stocks from site to global scales. Despite this, the mechanisms determining the response of heterotrophic soil respiration to soil moisture remain poorly quantified, being represented in most current carbon cycle models as simple empirical functions. Soils are extremely complex and heterogeneous environments and many properties observed at the profile or at the plot the scale are, in fact, determined by microscale conditions and processes.

The spatial heterogeneity of soil constituents and assemblages defines a myriad of contrasted micro-habitats, hosting diverse microorganisms, with contrasted moisture related characteristics and presumably contrasted levels of microbial activity. In addition, the respective spatial distributions of organic resources and microbial decomposers and the transfer rates between them, that depend on soil moisture, explain that similar organic compounds may have contrasted residence times in soil, being stabilized or not.

We consider how do soil moisture and soil spatial heterogeneity may explain the stabilisation of organic matter. Different pore size classes exhibit different rates of microbial decomposition, when considering different soils, across published studies and in a single laboratory experiment. Soil moisture affects the dynamics of biogeochemical hotspots, such as the detritusphere.

Regarding destabilization of soil organic matter, priming effect was revealed to be soil moisture dependent, that can be explained by varying access of newly produced enzymes to native soil organic matter. The Birch effect, a well-described flush of mineralization observed after rewetting dry soils, may also be partly explained at the microscale by changes in the local architecture of soils.

Overall, considering the interplay between soil spatial heterogeneity, soil moisture and the activity of microbial decomposers offers insights in understanding the stabilisation and de-stabilisation of soil organic matter. Incorporating this process level understanding into soil organic matter dynamics models is a challenge, as it requires the identification of relevant soil structure descriptors of these processes, at different time scales.

How to cite: Chenu, C., Védère, C., Kpemoua, I., Nunan, N., Pot, V., Garnier, P., Chirol, C., and Vieublé-Gonod, L.: The interplay of soil spatial heterogeneity and water in stabilizing and destabilizing soil organic matter, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14399, https://doi.org/10.5194/egusphere-egu24-14399, 2024.

EGU24-14407 | ECS | Posters on site | SSS5.5

The effect of habitat complexity on bacterial competition 

Carlos Arellano-Caicedo, Ara Fadhel, Pelle Ohlsson, and Edith C. Hammer

The way microbes interact in nature can vary widely depending on the spatial characteristics they are located in. This aspect of the microbial environment can determine whether processes such as organic matter turnover, community dynamics, or microbial speciation, among others, occur and their impact on soil functions. Investigating how the geometry of microhabitats influences microbes has been traditionally challenging due to methodological limitations. A major challenge in soil microbial ecology is to reveal the mechanisms that allow a wide diversity of microorganisms to co-exist. This study is directed towards answering the question of how spatial complexity affects bacterial competition, and how this can lead to organic matter turnover.

Using microfluidic chips that mimic the inner soil pore physical geometry, and fluorescence microscopy, we followed the effect of an increasing complexity in the growth and substrate degradation of two soil bacterial strains. The parameters used to define complexity were two: the turning angle and order of pore channels, and the fractal order of pore mazes. When we tested the effect of an increasing in turning angle sharpness on microbial growth, we found that in sharper angles, both species coexisted, but only until certain sharpness where both populations decreased. We also found that substrate degradation was highest in the same sharp angles that permitted the coexistence of both strains. Our next series of experiments, testing the effect of maze fractal complexity showed that both strains could coexist and degrade the most substrate in complex mazes that had dead ends as opposed to mazes that were highly connected. Our results demonstrate the relevance of microhabitat complexity in bacterial competition and substrate degradation, showing that complex habitats allow bacterial strains to coexist and perform functions with higher efficiency than in less complex ones.

How to cite: Arellano-Caicedo, C., Fadhel, A., Ohlsson, P., and Hammer, E. C.: The effect of habitat complexity on bacterial competition, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14407, https://doi.org/10.5194/egusphere-egu24-14407, 2024.

EGU24-15015 | ECS | Orals | SSS5.5 | Highlight

On the Microgeography of Soil Bacterial Communities 

Samuel Bickel and Dani Or

The highly fragmented soil physical environment and the dynamic aqueous phase jointly constrain bacterial life by limiting cell dispersion and modulating diffusion and access to patchy nutrients. A modeling framework that integrates soil hydration conditions with soil organic carbon inputs provides systematic estimates of size distributions and interaction distances among soil bacterial populations. The patterns of bacterial community microgeography provide an important building block for interpreting soil ecological functioning. Experiments and mechanistic modelling show that soil bacterial cluster sizes (measured by counting cell numbers within a community) follow an exponentially truncated power law with parameters (e.g., largest community size) that vary with mean soil water content and carbon inputs across biomes. Theory predicts that similar to human settlement size distributions, tree sizes and other systems in which growth rates are defined by the environment independent of the object size, the resulting bacterial community size distributions is likely to obey the so-called Gibrat’s law. Our results support a potential for generalization using positively skewed distributions of soil bacterial community sizes (e.g., log normal and Gamma). We show that soil bacteria reside in many small communities (with over 90% of soil bacterial communities having less than 100 cells), supported by theoretical predictions of log-normal distribution for non-interacting soil bacterial community sizes with scaling parameters that vary with biome characteristics. We will use estimates of the fraction of the largest bacterial communities where anoxic conditions may develop under prevailing conditions to constrain the number of anoxic hotspots per soil volume.

How to cite: Bickel, S. and Or, D.: On the Microgeography of Soil Bacterial Communities, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15015, https://doi.org/10.5194/egusphere-egu24-15015, 2024.

A large fraction of organic matter in soils is associated with mineral phases. This association is mediated by manifold processes (reactive transport, drying-rewetting cycles, biofilm formation, digestion of mineral particles, etc.) and ultimately leads to a stabilization of organic matter in soil [1]. Adsorption describes the mechanism for this association at the molecular level. Ultrahigh resolution mass spectrometry like FT-ICR-MS has gained interest in the study of adsorption processes because of its high sensitivity, resolving power and mass accuracy which allow to study the complex organic mixtures present in soils, and therefore provides molecular insight [2]. For that, supernatant composition can be compared before and after adsorption, but this indirect approach is often not sensitive enough to detect the sorption of small amounts of organic matter, i.e., during initial adsorption to pristine mineral surfaces. An alternative approach is to use laser desorption ionization (LDI) to directly analyze the adsorbed molecules on the mineral surfaces. The method theoretically allows laser spot size of ~ 20-50 µm and even allows imaging of thin sections; methodological advances could therefore improve our understanding of soil organic matter and its spatial heterogeneity [3].

We applied LDI-FT-ICR-MS to study the ionization of individual molecules with and without the presence of DOM (SRFA and pine/ beech litter extracts), and measured adsorption isotherms of individual molecular formulas in dissolved organic matter on quartz, illite and goethite after 24h of contact. Analog to organic matrices used in matrix-assisted LDI, detectability of model compounds improved by factor 2.5 – 40 when spiked into a DOM matrix. In case of sinapic acid, presence of DOM shifted the ionization towards the monomer ion [M-H]- as compared to a mixture of mono-, di- [2M-H]- and trimer [3M-H]- species when analyzed in pure form. These results suggest that soil organic matter and its soluble analogs act as suitable matrices in LDI experiments that ensure proper ionization of the mixture as a whole. In a next step, ion abundance data from sorption experiments was used to model the adsorption process of individual molecular formulas by a Langmuir isotherm approach. We derived estimates of sorption capacity and sorption affinity for each molecular formula, and identified the molecular properties explaining differences in both estimates, as well as their differences between mineral phases. Our data highlight the benefits of LDI-FT-ICR-MS for the study of sorption phenomena in soils, and opens perspectives for resolution of spatial heterogeneity in soils.

References

[1] Kleber, M., Bourg, I. C., ... & Nunan, N. (2021): Dynamic interactions at the mineral–organic matter interface. Nature Reviews Earth & Environment 2: 402-421.

[2] Bahureksa, W., Tfaily, M. M., ... & Borch, T. (2021): Soil organic matter characterization by Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS): A critical review of sample preparation, analysis, and data interpretation. Environmental Science & Technology 55: 9637-9656.

[3] Lohse, M., Haag, R., ... & Lechtenfeld, O. J. (2021). Direct imaging of plant metabolites in the rhizosphere using laser desorption ionization ultra-high resolution mass spectrometry. Frontiers in Plant Science 12: 753812.

How to cite: Simon, C. and Lechtenfeld, O.: Adsorption of dissolved organic matter to mineral phases studied by laser desorption ionization mass spectrometry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15127, https://doi.org/10.5194/egusphere-egu24-15127, 2024.

EGU24-15762 | ECS | Orals | SSS5.5

Continuum and particle scale analysis of nutrient gradients in the rhizosphere  

Eva Lippold, Magdalena Landl, Eric Braatz, Steffen Schlüter, Rüdiger Kilian, Carmen Höschen, Gertraud Harrington, Carsten W. Mueller, Andrea Schnepf, Robert Mikutta, Martina I. Gocke, Eva Lehndorff, and Doris Vetterlein

Plant roots create chemical gradients within the soil rhizosphere but little information exists on the effect of root types and ages on the distribution of chemical gradients. Research aim was to develop an imaging workflow and to analyze and model the effects of radial root geometry, root hairs, and ages on nutrient gradients around roots.

The presented correlative imaging workflow is suitable for targeted sampling of roots in their 3D context and assessing the imprint of roots on chemical properties of the root-soil contact zone at µm to mm scale. Maize (Zea mays) was grown in 15N-labelled soil columns and pulse-labelled with 13CO2 to visualize the spatial distribution of carbon inputs and nitrogen uptake together with the redistribution of other elements. Soil columns were scanned by X-ray computed tomography (X-ray CT) at low resolution (45 µm) to enable image-guided subsampling of specific root segments. Resin embedded subsamples were then analysed by X-ray CT at high resolution (10 µm) for their 3D structure and chemical gradients around roots using micro X-ray fluorescence spectroscopy (µXRF), nanoscale secondary ion mass spectrometry (NanoSIMS), and laser-ablation isotope ratio mass spectrometry (LA-IRMS). NanoSIMS and LA-IRMS detected the release of 13C into soil up to a distance of 100 µm from the root surface, whereas 15N accumulated preferentially in the root cells.

Concentration gradients with different spatial extents could be identified by µXRF. The observed concentration gradients were compared to simulated gradients generated by a process-based, radially symmetric 1D rhizosphere model. An accumulation of calcium and sulfur was observed, particularly around old root segments. Our model simulations indicated that this phenomenon originates from the radial structure of the root, leading to enhanced nutrient transport towards the root surface. Gradients of calcium and sulfur could be accurately predicted by the model around a single growing root, when they were mainly caused by sorption.

However, at the pore-scale, phenomena like local precipitation, which could be visualized using our methodology, were inadequately accounted for by the classic model approach. Nonetheless, the observed extension of the gradients was well described by the model. The presented approach combining targeted sampling of the soil-root system and correlative microscopy opens new avenues for unravelling rhizosphere processes in situ.  

 

 

How to cite: Lippold, E., Landl, M., Braatz, E., Schlüter, S., Kilian, R., Höschen, C., Harrington, G., Mueller, C. W., Schnepf, A., Mikutta, R., Gocke, M. I., Lehndorff, E., and Vetterlein, D.: Continuum and particle scale analysis of nutrient gradients in the rhizosphere , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15762, https://doi.org/10.5194/egusphere-egu24-15762, 2024.

EGU24-16443 | Orals | SSS5.5

Embracing the structural framework of soil in microbiological and ecological research 

Hannes Schmidt, Naoise Nunan, Xavier Raynaud, Steffen Schlueter, Vincent Felde, Berit Zeller-Plumhoff, Gaëlle Marmasse, Alberto Canarini, Lucia Fuchslueger, and Andreas Richter

Soil is a complex system with a high degree of physical, chemical, and biological heterogeneity. Soil structure is organized into entangled pore networks that provide an immense surface area and are partially filled with gases and aqueous solutions. This heterogeneous landscape houses a multitude of active and inactive organisms of which soil bacteria and fungi are considered the driving forces of nutrient cycling and biogeochemical processes. Standard analyses such as soil respiration are meaningful measures to estimate processes on a meso- and macroscale while the biological agents whose actions we measure are mainly to be found on the microscale. Yet, our understanding of microbial living conditions in soil and their consequences for activity, growth, and turnover is severely limited. In this presentation I will focus on a microbial perspective and present data from various experiments where soil microbial identity and/or activity were investigated while acknowledging spatial aspects of their microenvironments. I will provide an updated view on spatial distribution of microbial communities within soils, including evidence that suggests that the density of bacteria in soils has likely been underestimated by orders of magnitudes for decades. Microbial density arguably is a major determinant of cell-to-cell interactions, and thus many processes involved in microbial nutrient cycling that we measure on a larger scale. I will further argue to embrace soil heterogeneity rather than minimizing it, for example by using intact soil cores instead of sieved soils for stable isotope labelling experiments. I will present data on in situ bacterial and fungal growth which suggests that preserving soil physical architecture while investigating microbial parameters could bring experimental measurements significantly closer to field conditions, while also opening new avenues to improve our understanding of spatial aspects of soil microbiology.

How to cite: Schmidt, H., Nunan, N., Raynaud, X., Schlueter, S., Felde, V., Zeller-Plumhoff, B., Marmasse, G., Canarini, A., Fuchslueger, L., and Richter, A.: Embracing the structural framework of soil in microbiological and ecological research, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16443, https://doi.org/10.5194/egusphere-egu24-16443, 2024.

EGU24-16904 | ECS | Posters on site | SSS5.5

Two-step unsupervised clustering method on soil nanoscale secondary ion mass spectrometry (NanoSIMS) images to determine the spatial arrangement of minerals and organic matter 

Yahan Hu, Johann Zollner, Martin Werner, Steffen Schweizer, and Carmen Höschen

In the soil, mineral particles, organic matter, and soil organisms are arranged in a complex architecture which can influence organic matter dynamics. Nanoscale secondary ion mass spectrometry (NanoSIMS) provides insights into the microscale arrangement of soil minerals and organic compounds at a resolution of approximately 50 nm. However, current NanoSIMS image processing lacks methods to analyze large datasets automatically and requires manual intervention. We developed a two-step unsupervised clustering method for batch analyses of NanoSIMS images. Our two-step method consists of K-Means clustering as the first step generating around 100 clusters, followed by hierarchical agglomerative clustering (HAC) re-grouping the K clusters into less than 10 cluster groups. The elbow method, HAC linkage method and gap statistics are used to automatically select the optimal clustering numbers. Subsequently, soil minerals and organic matter can be spatially segmented and identified as different species. Further, this method could apply to the spatial arrangement of mineral-dominated and organic matter-dominated parts or different mineral types. Moreover, this method enables the analyses of larger datasets with >100 NanoSIMS images providing insights of organo-mineral interactive hotspots or even micro function domains involved in soil organic matter dynamics.

How to cite: Hu, Y., Zollner, J., Werner, M., Schweizer, S., and Höschen, C.: Two-step unsupervised clustering method on soil nanoscale secondary ion mass spectrometry (NanoSIMS) images to determine the spatial arrangement of minerals and organic matter, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16904, https://doi.org/10.5194/egusphere-egu24-16904, 2024.

EGU24-17573 | ECS | Posters on site | SSS5.5

Plant-derived organic exudates in soil: Mobility and aggregation 

Tom Guhra, Jona Schönherr, and Kai Uwe Totsche

Plant derived photosynthates are a component of the biotic organic matter involved in carbon cycling and storage due their mobility and formation of organo-mineral associations and (micro-)aggregates. Such photosynthates are typically found as components of mucilage or generate during the germination of seeds in the soil environments. While the effect of, e.g., mucilage, on soil physical properties has been intensively investigated, their role for carbon transport, adsorption, and aggregation process is rather unclear. Most of the knowledge available originates from studies that used single compounds, e.g., oxalic acid, glucose, polygalacturonic acid or mixtures of those in aqueous solutions. In our study, we utilized hydrogel-freed plant exuded photosynthates (PDE) extracted from four different seed types (Linum usitatissimum, Plantago ovata, Ocimum basilicum and Salvia hispanica) to investigate their interactions with minerals typically for temperate soil. In batch experiments, PDE adsorbed to both illite and goethite minerals with a preference of polysaccharide-rich PDE to goethite. During the adsorption, organo-mineral associations were formed leaving behind a less mineral-affine fraction of PDE prone to transport or degradation. Hence, PDE transport was also studied in column experiments using quartz functionalized with reactive minerals where we measured the breakthrough of PDE exploiting their distinct fluorescence. Furthermore, we followed the gravity-constrained aggregation dynamics of PDE-mineral associations using tensiometric measurements. We showed that low PDE concentrations facilitate aggregation via polymer bridges leading to a rapid sedimentation of aggregates while PDE available in excess prevents aggregation via steric repulsion and thus decelerates sedimentation. These results showed that PDE extracted from seeds might serve as better surrogates of natural plant exudates to study their role for the formation and transport of organo-mineral associations and aggregates in soils.

How to cite: Guhra, T., Schönherr, J., and Totsche, K. U.: Plant-derived organic exudates in soil: Mobility and aggregation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17573, https://doi.org/10.5194/egusphere-egu24-17573, 2024.

EGU24-18568 | Posters on site | SSS5.5

Intrinsic potential and activity of nitrate turnover examined for different hydrogeological aquifer settings 

John Lester Pide, Johann Holdt, Vitor Patricio Cantarella, Adrian Mellage, Olaf Cirpka, Carsten Leven-Pfister, Jan-Peter Duda, Daniel Buchner, and Christian Griebler

Nitrate (NO3-) is one of the most serious contaminants in groundwater, frequently deteriorating water quality and groundwater use as drinking water. Nitrate can, at specific environmental conditions, be removed within the subsurface environment via natural biogeochemical processes, such as denitrification and dissimilatory nitrate reduction to ammonium (DNRA). Traditionally, research has concentrated on the NO3- attenuation potential and microbial activity in groundwater, largely overlooking an aquifers’ sediment matrix as a reaction contributor. We hypothesize that the sedimentary deposits host the major potential for NO3- reduction, carrying the majority of microorganisms as well as different sources of electron donors. Moreover, diverse hydrogeological settings harbor different sources and varying amounts of electron donors such as reduced iron minerals and organic matter. Therefore, subsurface physicochemical heterogeneity, determined by sedimentology, controls the potential of an aquifer to reduce nitrate. We hypothesize that locations where physicochemical conditions favor NO3- reduction, we may expect microbes involved in these processes to be more abundant and highly active, leading to a fast NO3- removal from groundwater.

Here, we present results from temperature-controlled (12°C) batch incubations and flow-through experiments conducted over several months using fresh sediments from an alluvial, tufaceous unconfined aquifer, with embedded peat layers, in an agricultural landscape in southwest Germany. Batch experiments received an addition of NO3- of 50 mg L–1. Sediment columns were supplied with nitrate-spiked groundwater collected from the site at a maximum inlet concentration of 150 mg L and run in continuous injection mode. Batch experiments showed a gradual decrease in the initially high hydrogen sulfide (H2S) concentration, becoming undetectable after Day 7, compared to an untreated control, which revealed a slow conversion of HS-. These preliminary findings indicate a strong autotrophic denitrification with NO3- reduction coupled to aqueous HS- oxidation. In contrast to nitrate, NH4+ concentrations remained stable in all experiments. In the column experiments, the sediment exhibited a substantial NO3- reduction capacity in the early phase but rapidly declined with time. We hypothesize that a dual contribution to denitrification via easily bioavailable electron donors in the groundwater followed by slower denitrification coupled to organic matter in the sediment matrix is responsible for the observed dynamics. Our ongoing experiments, including groundwater and sediments from other, hydrogeologically different aquifers, will dissect the individual redox processes and key microorganisms involved in turnover of prominent nitrate and carbon species in the context of different hydrogeological settings. 

How to cite: Pide, J. L., Holdt, J., Cantarella, V. P., Mellage, A., Cirpka, O., Leven-Pfister, C., Duda, J.-P., Buchner, D., and Griebler, C.: Intrinsic potential and activity of nitrate turnover examined for different hydrogeological aquifer settings, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18568, https://doi.org/10.5194/egusphere-egu24-18568, 2024.

EGU24-18644 | ECS | Posters on site | SSS5.5

Investigating the distribution and residence time of carbon in the rhizosphere by image-based modelling at the pore-scale 

Maximilian Rötzer, Alexander Prechtel, Eva Lehndorff, and Nadja Ray

Mathematical models serve as valuable tools for unraveling the spatial heterogeneity and evolution of soil particles and carbon, particularly on the pore scale, that might be challenging to measure directly. The model we provide facilitates the exploration of interactions in the rhizosphere by the manipulation of different drivers and their parametrization. 

The focus of our study is on the residence time and spatial distribution of carbon originating from particulate organic matter and rhizodeposits. This process of turnover and distribution is influenced by a number of drivers. We provide insights into the role of some of these drivers across different stages of root growth, including carbon occlusion due to aggregation, chemical composition of rhizodeposits, and root morphology. We employ a spatially and temporally explicit mathematical model in which different components such as soil particles, carbon and a dynamic root interact. It is realized within a cellular automaton framework combined with an organic matter turnover model. Through numerical simulations, we track the temporal evolution of mineral soil particles bound by gluing agents. Spatially resolved datasets of soil texture and organic matter distribution are used to implement different soil types comparable with field experiments. Realistic parametrizations are derived from a laboratory experiment conducted in a rhizobox, measuring the carbon-to-nitrogen ratio at distinct temporal states of root growth and varying spatial distances from the biopore.

We compare and quantify the individual impact that soil, root and rhizodeposit characteristics have on the residence time and dispersal of carbon. Using an image-based modeling approach, we gain insight into spatiotemporal patterns and analyze the properties of regions with low turnover, so-called cold spots. 

How to cite: Rötzer, M., Prechtel, A., Lehndorff, E., and Ray, N.: Investigating the distribution and residence time of carbon in the rhizosphere by image-based modelling at the pore-scale, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18644, https://doi.org/10.5194/egusphere-egu24-18644, 2024.

EGU24-54 | ECS | Orals | SSS5.6

Effects of conservation tillage on soil organic carbon storage, fractions and stability in Black soil 

Yan Zhang, Aizhen Liang, Xiaoping Zhang, Xiujun Li, Edward Gregorich, and Neil McLaughlin

In Northeast China, conventional tillage practices involve removal of crop residue after harvest and prior to moldboard plowing; this has been shown to cause a decline of soil organic carbon (SOC) and degradation of Black soils (Mollisols). Conservation tillage, particularly no tillage (NT), has been suggested to be an effective practice to control soil erosion and increase the SOC content. Hence, we established an experiment (since 2001) to evaluate how a combination of different tillage and cropping systems could improve SOC in black soils. The total SOC storage, SOC fractions (physical and chemical), SOC stability were assessed to evaluate the effects of tillage and cropping system. Our results shows that: 1) different tillage and cropping system combinations had different effects on SOC storage; NT combined with continuous maize had the highest SOC storage among all treatments; 2) The effects of tillage on aggregate size and OC concentration mainly occurred in the surface layer (0–5 cm) while the effect of cropping system on aggregate size and OC concentration mainly occurred at deeper depths; 3) NT increased the recalcitrant carbon pool in surface layer showing the critical need for returning crop residues to maintain long-term SOC storage; 4) SOC mineralization (biological stability) appears to be related to the SOC proportion in the light fraction; 5) More than half of the increase in SOC storage due to NT existed as microbial necromass carbon storage under continuous maize which was higher than maize-soybean rotation. Our study shows that in black soils (Northeast China), NT and appropriate cropping systems can not only halt soil degradation caused by poor management but can induce substantial increases in SOC which is beneficial for SOC long-term sequestration.

How to cite: Zhang, Y., Liang, A., Zhang, X., Li, X., Gregorich, E., and McLaughlin, N.: Effects of conservation tillage on soil organic carbon storage, fractions and stability in Black soil, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-54, https://doi.org/10.5194/egusphere-egu24-54, 2024.

EGU24-1063 | ECS | Orals | SSS5.6

Investigating the complementarity of thermal and physical soil organic carbon fractions 

Amicie Delahaie and the Freacs team

Evaluating SOC biogeochemical stability is key to better predict the impact of SOC on both climate mitigation and soil health. This evaluation can be conducted using SOC partition schemes that allow us to quantify SOC fractions with different biogeochemical stability. However, most of these schemes are costly or time consuming and cannot be implemented on large sample sets. Two exceptions are  the widely used physical fractionation protocol allowing to separate particulate organic carbon (POC) and mineral-associated organic carbon (MAOC) and the emerging thermal fractionation protocol distinguishing active SOC (Ca; MRT ~30 years) from stable SOC (Cs; stable at a centennial timescale).

Here, we use analyzes conducted on samples from the French soil monitoring network (RMQS) to compare the results of thermal fractionations (Ca/Cs) performed on ca. 2000 samples, and physical fractionations (POC/MAOC) performed on ca. 1000 samples. Our results show that MAOC and Cs from one side and POC and Ca from the other side have different sizes. The most biogeochemically stable fractions (Cs and MAOC) are mostly influenced by soil characteristics whereas land cover and climate influence more substantially POC and Ca. However, the more stable fractions provided by both fractionation schemes (respectively the more labile fractions) do not have the exact same environmental drivers. Our results therefore suggest that both fractionation scheme gives complementary results. The relative contribution of these fractionation schemes to the evaluation of soil functions and OC stock evolution remains to be evaluated on soil monitoring networks and constitutes a promising research avenue.

How to cite: Delahaie, A. and the Freacs team: Investigating the complementarity of thermal and physical soil organic carbon fractions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1063, https://doi.org/10.5194/egusphere-egu24-1063, 2024.

EGU24-1422 | ECS | Orals | SSS5.6 | Highlight

Long-Term Phosphorus Fertilisation: Effects on Nitrogen and Carbon Cycle Dynamics and Greenhouse Gas Fluxes in European Agricultural Soils  

Lea Dannenberg, Christian Eckhardt, Christoph Müller, and Kristina Kleineidam

Phosphorus (P) is a crucial nutrient for plant growth, its limitation reduces plant and microbial biomass, affecting soil organic carbon (SOC) sequestration. Changes in soil P content may influence microbial composition, shaping pathways in the carbon (C) and nitrogen (N) cycles and impacting greenhouse gas emissions. In this lab incubation experiment we investigate the impact of different P fertilisation levels in three European long-term experiments (LTE) on N and C transformation processes and greenhouse gas fluxes in agricultural soils using stable isotope techniques (15N and 13C). The study is part of the EJP SOIL project “ICONICA” (Impact of long-term P additions on C sequestration and N cycling in agricultural soils).

The soil samples derived from Johnstown Castle, JC (grassland soil, Ireland), Lanna Skara, LS (arable soil, Sweden) and Jyndevad, JY (arable soil, Denmark). Two P levels were examined from each LTE: low P (0 kg P/ha and year) and high P additions (different P application rates among LTEs). The soils were mixed with 13C- and 13C15N- labelled maize biomass, respectively, and received ammonium nitrate (NH4NO3) in the 13C treatment as 15NH4NO3 and NH415NO3, respectively, and unlabelled NH4NO3 in the 13C15N treatment. Soil and gas samples were taken 0, 1, 3, 7 and 10 days after addition of NH4NO3 and were analysed for (15)NH4+-N, (15)NO3--N, organic (15)N, organic (13)C contents as well as for nitrous oxide ((15)N2O), carbon dioxide ((13)CO2), and methane (CH4) fluxes.

Preliminary findings display clear differences among the three LTEs as well as the two P levels. Regarding the impact of P fertilisation history: JC soil exhibited elevated CO2 emissions at high P compared to low P level. Significantly, high P levels showed higher CH4 uptake rates in JC and JY soils compared to the respective low P levels. JY had the highest N2O emissions, while JC had the lowest. JC had higher NH4-N values than LS. The highest NO3-N values were measured in JC, and the lowest in JY. In JC, higher NO3-N values were measured in high P compared to low P.

The results so far underscore the complex interactions within the carbon-nitrogen-phosphorus cycles under varying P inputs. Further analyses and interpretations are in progress.

How to cite: Dannenberg, L., Eckhardt, C., Müller, C., and Kleineidam, K.: Long-Term Phosphorus Fertilisation: Effects on Nitrogen and Carbon Cycle Dynamics and Greenhouse Gas Fluxes in European Agricultural Soils , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1422, https://doi.org/10.5194/egusphere-egu24-1422, 2024.

EGU24-1464 | ECS | Posters on site | SSS5.6

Less than 4% of dryland areas will desertify due to climate change.   

Xinyue zhang, Jason Evans, and Arden Burrell

Drylands with low biological productivity are more fragile compared with non-drylands, making many human activities within them sensitive to long-term trends. Any negative trend in dryland condition is considered desertification. The Aridity Index, widely used to define drylands, indicates increasing aridity in the drylands over several decades, which has been linked to increasing occurrence of desertification. Future projections show continued increases in aridity due to climate change, suggesting that drylands will expand. However, satellite observations show a general greening of the drylands. Given the past inconsistency between the Aridity Index changes and observed vegetation changes, future evolution of vegetation productivity within the drylands remains an open question. Here we use a data driven approach to estimate the state of vegetation in the drylands and project their future changes. Results shows most of the global drylands are projected to see an increase in vegetation productivity due to climate change through 2050. The general increases are in-part due to CO2 fertilization effects and are in-line with recent trends and continue the past inconsistency with changes in the Aridity Index. Climate change negates the changes in at most 4% of global drylands to produce desertification. These regions include parts of north-east Brazil, Namibia, western Sahel, Horn of Africa and central Asia.

How to cite: zhang, X., Evans, J., and Burrell, A.: Less than 4% of dryland areas will desertify due to climate change.  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1464, https://doi.org/10.5194/egusphere-egu24-1464, 2024.

EGU24-2093 | ECS | Orals | SSS5.6

Development CNtrace tool 

Anne Jansen-Willems, Kristina Kleineidam, Tim Clough, Lea Dannenberg, and Christoph Müller

The Ntrace tool was developed as a flexible 15N analysis tool to determine gross nitrogen (N) transformations. Since the development of the tool, it has been applied to many ecosystems world-wide as documented in more than 190 peer-reviewed publications. Over time, the tool has evolved to become much more flexible including different pools and determining more transformation rates. Up until now, the focus has been on the N cycle. However, the N and carbon (C) cycle are closely connected. Considering both cycles concomitantly provides a more comprehensive understanding of how elements move through the system. Thus, the next step in the development of the Ntrace tool includes connecting the N and C pools (CNtrace) in order to simultaneously quantify gross N and C transformations based on the observed 15N and 13C dynamics. Data from specifically designed experiments, using either labelled organic matter or C4 plants in a C3 soil, with the addition of differentially 15N labelled mineral fertilizer will be used for the development of the CNtrace tool. The theoretical background and the various development steps will be presented.

How to cite: Jansen-Willems, A., Kleineidam, K., Clough, T., Dannenberg, L., and Müller, C.: Development CNtrace tool, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2093, https://doi.org/10.5194/egusphere-egu24-2093, 2024.

EGU24-2759 | ECS | Orals | SSS5.6

Effects of aridification on soil total carbon pools in China's drylands 

Zhuobing Ren, Changjia Li, Bojie Fu, Shuai Wang, and Lindsay C. Stringer

Drylands are important carbon pools and are highly vulnerable to climate change, particularly in the context of increasing aridity. However, there has been limited research on the effects of aridification on soil total carbon including soil organic carbon and soil inorganic carbon, which hinders comprehensive understanding and projection of soil carbon dynamics in drylands. To determine the response of soil total carbon to aridification, and to understand how aridification drives soil total carbon variation along the aridity gradient through different ecosystem attributes, we measured soil organic carbon, inorganic carbon and total carbon across a ~4000 km aridity gradient in the drylands of northern China. Distribution patterns of organic carbon, inorganic carbon, and total carbon at different sites along the aridity gradient were analyzed. Results showed that soil organic carbon and inorganic carbon had a complementary relationship, that is, an increase in soil inorganic carbon positively compensated for the decrease in organic carbon in semiarid to hyperarid regions. Soil total carbon exhibited a nonlinear change with increasing aridity, and the effect of aridity on total carbon shifted from negative to positive at an aridity level of 0.71. In less arid regions, aridification leads to a decrease in total carbon, mainly through a decrease in organic carbon, whereas in more arid regions, aridification promotes an increase in inorganic carbon and thus an increase in total carbon. Our study highlights the importance of soil inorganic carbon to total carbon and the different effects of aridity on soil carbon pools in drylands. Soil total carbon needs to be considered when developing measures to conserve the terrestrial carbon sink.

How to cite: Ren, Z., Li, C., Fu, B., Wang, S., and Stringer, L. C.: Effects of aridification on soil total carbon pools in China's drylands, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2759, https://doi.org/10.5194/egusphere-egu24-2759, 2024.

EGU24-2926 | ECS | Orals | SSS5.6

Inorganic carbon: an overlooked pool in global soil carbon research   

Sajjad Raza, Annie Irshad, Andrew Margenot, Kazem Zamanian, Sami Ullah, Irina Kurganova, Xiaoning Zhao, and Yakov Kuzyakov

Soils are one of the major players in the global carbon (C) cycle and climate change by functioning as a sink or a source of atmospheric carbon dioxide (CO2). The largest terrestrial C reservoir in soils comprises two main pools: organic (SOC) and inorganic C (SIC), each having distinct fates and functions but with a large disparity in global research attention. This study quantified global soil C research trends and the proportional focus on SOC and SIC pools based on a bibliometric analysis. Research on soil C pools started in 1905 and has produced over 42,000 publications (> 1.6 million citations). Although the global C stocks down to 2 m depth are nearly the same for SOC and SIC, the research has dominantly examined SOC (> 96% of publications and citations) with a minimal share on SIC (< 4%). Approximately 39% of the soil C research was focused on climate change. Despite poor coverage and publications, the climate change-related research impact (citations per document) of SIC studies was higher than that of SOC. Machine learning, biochar, soil properties, and climate change were the recent top trend topics for SOC research (2018-2022), whereas soil acidification, organic C, climate change, and Holocene were recent trends for SIC. SOC research was contributed by 150 countries compared to 85 for SIC. As assessed by publications, soil C research was mainly concentrated in a few countries, with only 10 countries accounting for 75% of the research. China and the USA were the major producers (44%), collaborators (36%), and funders of soil C research. SIC is a long-lived soil C pool with a turnover rate of more than 1000 years in natural ecosystems but intensive agricultural practices have accelerated SIC losses, making SIC an important player in global C cycle and climate change. The lack of attention and investment towards SIC research could jeopardize the ongoing efforts to mitigate climate change impacts to meet the 1.5-2.0 oC targets under the Paris Climate Agreement of 2015. This study calls for expanding the research focus on SIC and including SIC fluxes in C budgets and models, without which the representation of the global C cycle is incomplete.

How to cite: Raza, S., Irshad, A., Margenot, A., Zamanian, K., Ullah, S., Kurganova, I., Zhao, X., and Kuzyakov, Y.: Inorganic carbon: an overlooked pool in global soil carbon research  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2926, https://doi.org/10.5194/egusphere-egu24-2926, 2024.

Post mining ecosystems are severally degraded.  This is particularly true for soils which are either excavated or buried and replace by overburden which differ remarkably, from normal soils. Despite these severe degradation, post mining soils of numerals opportunities: they are valuable secondary habitat for rare and endangered species, and soils developing in these areas are able to sequester carbon in much higher rate than soils in surrounding landscape.. Here we compare effect of reclaimed and unreclaimed sites on provisioning ecosystem services in Sokolov (Czech Republic) and on climatic gradient across USA. In suitable substrates, the succession is driven mainly by site topography. In sites which were leveled grassy vegetation develops. In sites where original wave like topography was preserved the ecosystem develops towards shrubs and forest. Reclaimed and unrecaimed forest sites have similar development of canopy cover,   stems number gradually decreased with age in reclaimed sites and increased in succession, in 20 year both reaching the same density.  Tree biomass was higher in young reclaimed sites, in sites 30 years old or older tree biomass in succession sites was comparable or higher than in reclaimed sites.  Initial rate of soil carbon storage in reclaimed sites namely those planted by alder was faster than in succession sites but it decrease with plot age.  In unclaimed sites, the rate of C storage increase and peaked in site 20-30 years old. Amount of C stored in unreclaimed sites c 50 years old is comparable to alder plantations of the same age.  Alder plantation of intermediate age store more water than unreclaimed sites but water budget is similar due to higher water demand of alder.  In leveled sites where grassland establish, reclaimed sites are slightly higher in all studied parameters. In conclusion, development of key ecosystem process is fasted in reclaimed sites but latter on difference disappear. The reasons are, soil   leveling, promote soil compaction, which slows root growth. Focus on achieving a close cannopy often lead to dense three stand which limit a light availability for trees. This is even supported by leveling and homogenous pattern of planting which lead to one layer cannopy, compare to multi-layer cannopy in unreclaimed sites. Also planting N fixers, my contribute, to this slow down, as nitrogen fixing plant often fixed nitrogen even in conditions when nitrogen is already plentiful in soil. This cause additional energy expense for the trees.

Comparison of benefits of reclamation and spontaneous ecosystem development vary depending on climatic conditions and target ecosystem. For example, in dry cold conditions when target is grassy vegetation such as short grass prairie in Wyoming (USA), to reclamation practices show often much better results than unassisted ecosystem development. In contrary in wet warm climate, when broadleaf forest is a target (e.g. in Eastern USA), unassisted ecosystem development often shows better results in many parameters namely in long run.  These results show that we should try to better understood naturel processes of ecosystem development so we can implement them in improvement of reclamation technologies.

 

 

How to cite: Bartuška, M. and Frouz, J.: Natural regeneration as restoration strategy to restore functional soils and ecosystems in post mining sites, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3229, https://doi.org/10.5194/egusphere-egu24-3229, 2024.

Simple conceptual overview how peculiarities of food production and food supply chain affect land degradation.

Most of the land suitable for agriculture is located in the temperate zone, while the yields of comparable crops in tropical countries (countries of the global south) are almost half compared to developed countries in the temperate zone. In addition to greater soil fertility, the more advanced technological base of economically developed countries. Developed counties the increase their production mainly through its intensification, i.e. greater production on the same area and greater meat, milk or egg production per one livestock specimen. This leads to the concentration of production in suitable conditions, the homogenization of the landscape, reduction of grazing and other extensive form of land use and other negative effects of agricultural intensification on ecosystems. On the other hand, in the countries of the global south, agricultural production is increasing mainly through increasing the production areas, which results in endangering the remnants of the original ecosystems. Number of farmers is decreasing yet they feed larger amount of food consumers. This increasing the efficiency of human work is connected with the transfer of part of the work to the work of animals and later machines which allow one farmer to cultivate larger area of land, and further to the intensification of agricultural production, the use of fertilizers, pesticides, and other substances, so-called additional energy is needed to obtain them. As the intensity of agriculture and the ability of one farmer to feed more people increases, the total amount of energy required to achieve production also increases, not only because total output increases, but also because the amount of additional energy required per unit of output increases. As the amount of additional energy increase recycling of biomass (and energy) inside agriculture system decrease. Along with this, the negative impacts of agricultural production on ecosystems are increasing. These negative impacts are usually greater in the less fertile soils of the global south than in the more fertile soils of developed countries.  Pressure of consumers increase not only due to population increase, but also due to detachment of people from food production, which cause that consumers perceive food mainly by its cost. Food supply chain become driven by retailers, which increase pressure on price, and thus pressure on farmers to optimize production cost often on expense of more intensive soil and land use which may lead to land degradation. Many retailers now use environmental standards which are well suited to control for extensification (such as zero deforestation) but tackling of agriculture intensification is rare.

How to cite: Frouzova, J. and Frouz, J.: Simple conceptual overview how peculiarities of food production and food supply chain affect land degradation., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3233, https://doi.org/10.5194/egusphere-egu24-3233, 2024.

Improved tillage practice plays a positive role in restoring degraded cropland, maintaining crop productivity, and mitigating climate change, which has been proposed as a sustainable agricultural technology. Based on a long-term experiment in black soil area of Northeast China, effects of different tillage practices on soil organic carbon (SOC) and nutrient content were explored, and ecological and economic benefits were also evaluated. Three tillage practices were included: conventional tillage with complete removal of residue (CT), moldboard plowing with residue return (MP) and no-tillage with residue return (NT). As the trial period increased, the SOC content of the CK decreased in the 0-20 cm soil layer, while the total nitrogen (TN) content remained. Residue return treatments (MP and NT) increased SOC and TN content. The SOC and TN were uniformly distributed in the 0-20 cm soil layer of MP, whereas the SOC and TN increased significantly in the 0-5 cm soil layer of NT, especially during the 5-8 years of the experiment. The total phosphorus (TP) and total potassium (TK) contents of all treatments slowly increased over time, and there was no significant difference among treatments. Compared with CT, NT could reduce N2O emissions and absorb more CH4, whereas MP significantly increased CO2 emissions from soil. Moreover, NT led to both the lowest GHG emissions from soil (GWPGHG) and agricultural inputs (AIGHG), thus reduced approximately 40% carbon footprint (CF) compared to CT. However, no significant difference in maize yield and net ecosystem ecological benefit (NEEB) were observed among three tillage practices, although MP and NT showed lower investments during maize production than CK. In conclusion, NT could not only enhance the SOC and nutrient content but also minimize CF while ensuring economic benefit from a long-term perspective. Long-term NT can be implemented in Northeast China and similar agro-eco-regions around the world.

How to cite: Zhang, Y. and Liang, A.: Effects of long-term residue return on nutrient content, ecological and economic benefits of black soil in Northeast China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6534, https://doi.org/10.5194/egusphere-egu24-6534, 2024.

EGU24-6933 | Posters on site | SSS5.6

Application of the Ntrace tool to investigate long-term P fertilizer effects on gross N transformations in a pasture soil 

Tim Clough, Anne Jansen-Willems, Kristina Kleineidam, Lea Dannenberg, and Christoph Müller

The Ntrace tool uses soil 15N analysis of soil N pool dynamics to establish soil gross nitrogen (N) transformations. An understanding of what initiates and controls soil N transformation dynamics is critical when considering the environmental impacts (e.g. nitrate leaching and nitrous oxide emissions) and fate of N in pasture soils. Phosphorus (P) is an essential nutrient required by soil microbes that facilitate both soil N and soil organic matter transformations. A laboratory mesocosm study was performed to examine the effect of long-term superphosphate use on soil gross N and soil organic matter transformations. Sheep grazed pasture soils, undisturbed for 71 years, receiving either nil fertilizer (control) or 188 kg ha-1 year-1 of single superphosphate (17 kg P ha-1 yr-1) were collected at a depth of 0 – 7.5 cm. Soils were sieved (4 mm) and placed in kilner jars, whereupon they received treatments that consisted of: 15NH414NO3 + natural abundance 13C perennial ryegrass (Lolium perenne) root material; 14NH415NO3 + natural abundance 13C perennial ryegrass root material; or 14NH414NO3 + 13C enriched ground perennial ryegrass root material. Over 7 days measurements included soil inorganic-N concentration and 15N enrichments, nitrous oxide emissions, microbial biomass, and soil organic C concentrations. Data and initial conclusions from this experiment will be presented with respect to the long-term P fertilizer effects on soil gross N and soil organic matter transformations.

How to cite: Clough, T., Jansen-Willems, A., Kleineidam, K., Dannenberg, L., and Müller, C.: Application of the Ntrace tool to investigate long-term P fertilizer effects on gross N transformations in a pasture soil, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6933, https://doi.org/10.5194/egusphere-egu24-6933, 2024.

EGU24-7661 | ECS | Orals | SSS5.6

Soil organic carbon dynamics after land-use change – combining process-based modelling with machine learning 

Daria Seitz, Rene Dechow, David Emde, Florian Schneider, and Axel Don

Land-use changes affect soil organic carbon (SOC) stocks over decades. However, IPCC default for greenhouse gas emissions reporting suggests a simple linear SOC stock change over 20 years only. Using process-based modelling approaches such as RothC to describe SOC dynamics after land-use change requires model validation. However, there are only few long-term field experiments where SOC stocks have been observed long enough to get sufficient data for such a model validation. This lack of data makes validating models for large-scale use challenging.

Based on empirical data from over 3000 sites from the German Agricultural Soil Inventory we selected 204 sites with land-use change history within the last 60 years and created an artificial data-set using a reciprocal modeling approach. This approach utilizes machine learning models trained on sites under permanent land use to predict SOC stocks for similar sites where the land use had been changed. In addition, we extracted further empirical data from over 30 sites with land-use change in the temperate zone from a comprehensive meta-analysis.

These two datasets were used to test the ability of the well-known SOC model RothC to simulate land-use change effects on SOC stocks. In these tests, we use the observed or predicted SOC stocks assumed at equilibrium to model the carbon input under permanent land use and corresponding SOC dynamics after land-use change. These modelled SOC dynamics are then compared with observed SOC stocks after land-use change.

We will discuss opportunities and challenges of using process-based models to describe SOC dynamics after land-use change on regional to national scale.

 

How to cite: Seitz, D., Dechow, R., Emde, D., Schneider, F., and Don, A.: Soil organic carbon dynamics after land-use change – combining process-based modelling with machine learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7661, https://doi.org/10.5194/egusphere-egu24-7661, 2024.

EGU24-7763 | Orals | SSS5.6

Possible interactions of hazardous elements with pharmaceuticals in soils of a Mediterranean wetland (L’Albufera, Valencia, Spain) 

Vicente Andreu, Eugenia Gimeno-Garcia, Danielle Sadutto, and Yolanda Picó

There is scarce information about toxic effects, environmental dynamics and even toxic levels or regulations, mainly in soils, of several elements widely used in agriculture and industry. These so called elements “of emerging concern” have not been studied, mainly regarding their environmental effects or relationships. By the other hand, tons of pharmaceuticals are liberated by effluents of the wastewater treatment plants to the environment and agricultural fields daily. As study case, we have selected an important area in Spain that is affected by high anthropogenic pressures.

The target area of study the alluvial plain between the rivers Turia and Jucar (Valencia, SPAIN), with an extension of 486 km2, which is characterized by its dense network of channels and ravines for irrigation one of the most productive agricultural areas of Spain. This area includes a wide zone of rice farming and a Natural Park (L’Albufera). In this study area, 33 sampling zones were selected covering the different water sources and agricultural types, to monitor the distribution of the levels of 15 hazardous metals.

Total concentrations of the selected metals (Al, As, B, Be, Bi, Co, Fe, Li, Mo, Se, Rb, Sr, Ti, Tl and V) were determined. Standard analytical methods were used to measure soil physical and chemical properties. Total content of the twelve heavy metals, in soil samples, were extracted by microwave acid digestion and determined by ICP-OES. In the same zones, 32 pharmaceuticals were also studied. soil samples were extracted by pressurized liquid extraction (SPE). and determined by liquid-chromatography tandem mass spectrometry (LC-MS/MS).

Maximum average values were determined for Ti, Sr and Rb with 466.36, 263.16 and 63.62 mg/kg, respectively. Highest values for B, Li and Tl were 76.05, 70.91 and 56.37 mg/kg, respectively. The Northern part of the Albufera lake, devoted to rice farming, concentrated the highest values of almost all the selected elements. From the 32 studied pharmaceuticals, 29 were detected being the most frequents Bisphenol A, Caffeine and Tramadol. Maximum values were observed for Alprazolam (67.28 ng/g), Ibuprofen (76.11 ng/g) and Lorazepam (62.02 ng/g).

The interactions between metals and pharmaceuticals, and from both with soil characteristics and the influence of environmental factors were also studied.

More research is needed to stablish their toxic levels and effects, or even their average concentrations in soils of these elements, very scarcely studied in the majority of them.

Acknowledgements

This work has been supported by the Generalitat Valenciana (Regional Autonomous Government) through the project CIPROM/2021/032.

How to cite: Andreu, V., Gimeno-Garcia, E., Sadutto, D., and Picó, Y.: Possible interactions of hazardous elements with pharmaceuticals in soils of a Mediterranean wetland (L’Albufera, Valencia, Spain), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7763, https://doi.org/10.5194/egusphere-egu24-7763, 2024.

EGU24-7793 | Orals | SSS5.6

Nutrients and carbon losses due to wind erosion in Sahelian Senegal 

Caroline Pierre, Jean Louis Rajot, Pierre-Marie Bonneval, Paul-Alain Raynal, Abdourahmane Tall, Issa Faye, Dioumacor Fall, and Alfred Tine

Land degradation appears today as a major issue for feeding humans, whose population on Earth is still increasing. Such issues are particularly acute in semi-arid regions like the Sahel, where, in addition, soils are already poor in nutrients and carbon. Wind erosion is one of the processes likely to cause soil depletion of nutrients and carbon in this region, thus potentially leading to land degradation. However, there is little scientific literature providing quantitative estimates of soil losses of nutrients and carbon through the windblown sediments, particularly for the Sahel.

We monitored the horizontal flux of windblown sediments (collected every 2 weeks in MWAC sand-traps) for the main land use types of Western Sahel in the Peanut Basin of Senegal: a field (bare, then cropped with groundnut) (2020-2021), 4 fallows (2022/2023), and 4 millet fields (2023/2024) to characterize differences in windblown sediment fluxes due to land management (e.g. management of crop residues, grazing pressure, …). Each plot was about 1 ha, and had 5 masts of 5 MWAC each, from 5 cm to 80 cm above ground level. During these experiments, we also monitored vegetation characteristics (every week) and meteorological variables (at 5-minutes resolution).

We then carried out analyses on the windblown sediments collected in the sand traps for the bare/groundnut field (the amounts of sediments collected in the fallows were too low to perform such analyses, and the erosive period, which extends from January to April in Western Senegal, just started in early 2024 for the millet fields experiment).

Our first results show that the horizontal flux of windblown sediments is much larger for a bare/groundnut field (around 40 t/ha/year) than for fallows (0.03 to 0.80 t/ha/year). The results also suggest that differences in land management among fallows (e.g. age, woody cover) may have an impact on this horizontal flux.

Additionally, the orders of magnitude of the organic C, total N and available (Olsen) P concentrations of the horizontal (saltation) flux from the bare/groundnut field are respectively approximately 0.22%, 0.02%, and 8 ppm, thus larger than the concentrations of the topsoil, that are respectively 0.15 %, 0.01 % and 7 ppm. These values compare well with those existing in the literature (e.g. for Niger), and confirm an enrichment of the horizontal flux (by a factor of 1.1 to 1.8) in soil carbon and nutrients compared to the topsoil. A rough estimate of organic C losses from the monitored field of 1 ha would be about 80 kg/year, and 8 kg/ha and 0.32 kg/ha for N and available P, respectively.

To better characterize the composition of windblown sediments, we also plan to carry out microbiological analyzes to determine the composition of the microbial communities (bacteria and fungi) they contain. Indeed, these microbial communities play a role in the biogeochemical cycle of nutrients and in the storage of carbon in the soil, thus potentially impacting their fertility.

We thank the IMAGO/LAMA analytical laboratory of Dakar for the analyses of the composition of the sediment samples.

How to cite: Pierre, C., Rajot, J. L., Bonneval, P.-M., Raynal, P.-A., Tall, A., Faye, I., Fall, D., and Tine, A.: Nutrients and carbon losses due to wind erosion in Sahelian Senegal, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7793, https://doi.org/10.5194/egusphere-egu24-7793, 2024.

We studied the effect of grazing on carbon sequestration in semi-natural grasslands.  The study was conducted on three farms with known history of land use in W Iceland. On each farm, we located an intensively (IG) and an extensively (EG) grazed site, which both had been constantly grazed for centuries, and a parallel site were grazing had been excluded (NG) for over 50 years. We measured net ecosystem exchange (NEE), ecosystem respiration and normalized difference vegetation index (NDVI) on a regular basis over the growing season. Samples were taken from 60 cm deep soil profiles for analysis of soil organic carbon (SOC). The grazed sites showed significantly more negative NEE than the NG sites, indicating more carbon dioxide uptake on the grazed sites compared to the NG sites. NDVI was also significantly higher on the grazed sites. On all farms, the total SOC content was higher in the grazed sites than in the parallel NG sites. The study indicates that cessation of grazing decreases productivity and carbon dioxide uptake in a semi-natural grassland in Iceland, as well as SOC content in the soil. Historically, all the NG sites in the study had the same grazing history as the continuously grazed sites until grazing exclusion. The measured lower SOC on the NG sites seems to indicate that, without grazing, SOC is lost with time and/or grazing is needed to maintain SOC in these grasslands.

How to cite: Thorhallsdottir, A. G. and Gudmundsson, J.: Carbon dioxide fluxes and soil carbon storage in relation to long-term grazing and grazing exclusion in Icelandic semi-natural grasslands, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8473, https://doi.org/10.5194/egusphere-egu24-8473, 2024.

EGU24-9123 | Posters on site | SSS5.6

The role of (in)organic carbon removal as a pretreatment in the 13C isotope composition of various soils 

Gergely Jakab, Tibor Filep, Tiphaine Chevallier, Zoltán Szalai, and Dóra Zachary

Soil carbon content is a crucial property in fertility and soil health. Carbon occurs in the soil in organic and inorganic forms. Soil organic carbon enters the soil mainly as plant residues and root extracts from the biosphere, whereas the primary source of inorganic carbon is the parent material. Both organic and inorganic carbon forms are affected by the current environmental and artificial conditions and, consequently, change in space and time. In this dynamic system, biogen or pedogen effects can reform carbonates and change organic matter composition. Both carbon forms are the focus of research in the soil however, the interaction between them is less understood. Inorganic carbon forms play an essential role in soil organic matter stabilization and, therefore, in maintaining soil functions. The present study aimed to investigate the organic-inorganic carbon interaction processes in various soil horizons. As a proxy, the stable isotope δ13C values were measured separately in the organic and inorganic pools and the bulk soil. Altogether, 55 soil samples were taken from top and subsoils under various land uses and texture classes. Beyond the measurement of the bulk soils, one aliquot was heated to 550°C for six hours to eliminate the organic carbon content, whereas another one was treated with HCl to remove the carbonates. All samples were measured using a Thermo Scientific FLASH 2000 HT elemental analyzer mass spectrometer, identifying δ13C composition. The sum of organic and inorganic carbon was higher than the total carbon content (R2=0.94), suggesting that at least one carbon removal pretreatment was incomplete. Some low inorganic carbon content (<0.5%) revealed a deficient δ13C value (-15 – -30 ‰), indicating organic carbon residue presence. However, other slightly carbonated samples parallel with higher inorganic carbon content ones are in the range of pedogenic carbonates (0 – -10 ‰). The reason for the incomplete organic carbon removal is probably related to the organic-mineral complexes; however, further investigations are needed for a more convincing result. This work was supported by the National Research, Development and Innovation Fund of Hungary [project no. 2019-2.14-ERA-NET-2022-00037 and FK 142936]. Project no. 2019-2.14-ERA-NET-2022-00037 has been implemented with the support provided by the Ministry of Culture and Innovation of Hungary from the National Research, Development and Innovation Fund, financed under the ERA-NET COFUND/EJP COFUND funding scheme with co-funding from the European Union Horizon 2020 research and innovation programme.

How to cite: Jakab, G., Filep, T., Chevallier, T., Szalai, Z., and Zachary, D.: The role of (in)organic carbon removal as a pretreatment in the 13C isotope composition of various soils, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9123, https://doi.org/10.5194/egusphere-egu24-9123, 2024.

EGU24-11107 | ECS | Posters on site | SSS5.6

A new machine-learning model to partition soil organic carbon into its centennially stable and active fractions based on Rock-Eval(r) thermal analysis 

Marija Stojanova, Pierre Barré, Hugues Clivot, Lauric Cécillon, François Baudin, Thomas Kätterer, Bent T. Christensen, Claire Chenu, Ines Merbach, Adrián Andriulo, Sabine Houot, and Fabien Ferchaud

The quantification of soil organic carbon (SOC) biogeochemical stability is important for assessing soil health and its capacity to store carbon. Models simulating SOC stock evolution divide SOC into different kinetic pools with contrasting residence times. The initialization of compartment sizes is a major source of uncertainty for SOC simulations. In a previous study, Cécillon et al. (2021) developed a machine-learning model (PARTYsoc v2) that uses Rock-Eval(r) thermal analysis results as input variables to quantify the proportion of centennially stable and active SOC fractions using samples from long term bare fallow sites. The outputs of PARTYsoc v2 have been shown to be particularly effective for initializing the AMG model, enabling very accurate simulations of SOC stock evolutions for a dozen French sites (Kanari et al., 2022). The objective of the present work is to build a new version of PARTYsoc, validated on a larger sample set, and extend the usefulness of the AMG model initialized with PARTYsoc to different parts of the world.

To do so, we have first identified sites with known crop yields and SOC stock evolutions and archived samples available for Rock-Eval(r) characterization. We then determined, for each site, the stable SOC stock value leading to the best simulation accuracy of SOC stock evolution with the AMG model. This optimal stable SOC stock allowed us to quantify the stable SOC proportion for all samples from the selected sites. Finally, we developed PARTYsoc v3 using Rock-Eval(r) measurements as input variables to predict stable SOC proportions sensu AMG model.

PARTYsoc v3 is significantly different from PARTYsoc v2. In the v3, the target variable, i.e., the centennially stable SOC proportion, is determined to be optimal for the AMG model whereas in the v2 it was calculated from SOC declines at bare fallow sites. Moreover, the current v3 model uses Support Vector Machine (SVM) regression coupled with a Beta Regression instead of Random Forest. This combination of machine-learning models allows for a non-linear relationship between the target and the features, and predictions are always bounded in the [0, 1] interval. The data set has also been extended to use a larger number of sites (6 sites in the v2, and 12 sites in the v3), including both bare fallows and other types of long-term experiments.

The features (Rock-Eval(r) features) are selected by first removing highly-correlated features (Spearman correlation > 0.9) and then ranking them based on their predictive importance when randomly permuted. This procedure allows us to decrease the effects of overfitting the training data. The final model uses 7 Rock-Eval(r) features (18 for the v2). We obtain satisfactory performance in both internal validation (R2=0.82, RMSE=0.07), as well as Leave-One-Site-Out (LOSO) validation (R2=0.76, RMSE=0.09).

The proposed model builds upon and significantly improves the work laid out by PARTYsoc v2. Currently, we are working on further extending the data set as well as stabilizing the processes of feature selection and model parameters.

How to cite: Stojanova, M., Barré, P., Clivot, H., Cécillon, L., Baudin, F., Kätterer, T., T. Christensen, B., Chenu, C., Merbach, I., Andriulo, A., Houot, S., and Ferchaud, F.: A new machine-learning model to partition soil organic carbon into its centennially stable and active fractions based on Rock-Eval(r) thermal analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11107, https://doi.org/10.5194/egusphere-egu24-11107, 2024.

EGU24-12395 | Posters on site | SSS5.6 | Highlight

Long-term P fertilizer effects on pasture soil nitrous oxide and carbon dioxide emissions 

Tim Clough, Naomi Wells, Parag Bhople, Karl Richards, and Giulia Bondi

Grazed pasture ecosystems are key contributors to anthropogenic nitrous oxide (N2O) emissions. Within the grazed pasture, it is the deposition of ruminant urine, from the grazing animal, that creates the hot-spot for N2O emissions. Grazed pastures also receive phosphorus (P) fertilizer to sustain plant nutrient needs. This in turn increases the soil microbial biomass pool and promotes dry matter production: this affects soil moisture dynamics and plant N uptake. How long-term P fertilizer affects N2O emissions from pasture soils in situ is poorly understood. To address this an in situ study was performed on the Winchmore long-term fertilizer trial, in New Zealand. This has run for 71 years and the pasture has not been disturbed over this time. The trial consists of replicated (n = 4) field plots (0.09 ha) receiving either 0, 17, 23, or 34 kg P ha-1 yr-1 as single superphosphate. These field plots are rotationally grazed by sheep, with stocking rate adjusted according to feed on offer. Headspace chamber bases were installed in each field plot and synthetic ruminant urine or distilled water (control) were applied. Static chambers were placed on the chamber bases during gas flux measurement. Gas measurements were taken over a 76-day period to determine N2O and CO2 fluxes. Soil inorganic-N concentrations (0 – 7.5 cm) were also followed over time, along with soil sampling for determining soil chemical characteristics. Data from this study and their interpretation will be presented to assess the effect of long-term P fertilizer on grazed pasture N2O and CO2 fluxes.

How to cite: Clough, T., Wells, N., Bhople, P., Richards, K., and Bondi, G.: Long-term P fertilizer effects on pasture soil nitrous oxide and carbon dioxide emissions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12395, https://doi.org/10.5194/egusphere-egu24-12395, 2024.

EGU24-13467 | Posters on site | SSS5.6

Organic Vineyard Fertilization: Soil Carbon and Nitrogen in Southern Brazil 

Tadeu L. Tiecher, Allan Augusto Kokkonen, Daniéle Gonçalves Papalia, Luana Paula Garlet, Vanessa Ferraz Costa, Samuel Bolívar de Mello Schemer, Arthur Gonçalves Gulartt, Barbara Clasen, and Gustavo Brunetto

In recent years, vineyard areas in organic production system have been increasing significatively, in both develop and developing nations. This trend aligns with the growing concerns of people and governments. They are increasingly worried about health issues and the environmental impact of conventional agriculture and horticulture. In contrast, agroecology and organic fertilization have the potential to offer safe products and promote carbon (C) sequestration in the soil. The latter benefit is also a crucial strategy to mitigate the climate effects of greenhouse gas emissions. This aligns with the UN's guidelines for carbon-neutral production systems However, in vineyard agroecosystems, there is limited technical information about the impact of organic fertilizers and plant CO2 fixation on carbon levels. This is especially true in subtropical climates. Therefore, this research aimed to evaluate how different fertilization systems affect soil organic carbon (SOC) and soil organic nitrogen (SON). An experiment was set up in a commercial organic vineyard with two different cultivars: ‘Isabella’ (Vitis labrusca x V. vinifera) and ‘Chardonnay’ (V. vinifera), in Veranópolis (Cfa climate), in Southern Brazil. The soil in the experiment was classified as Cambisol (WRB). Since 2020, the following fertilization systems have been applied yearly: no fertilization (T), grape pomace vermicompost (GPV), grape pomace compost (GPC), GPV plus mineral fertilizers (GPV+MF), GPC plus mineral fertilizers (GPC+MF), and mineral fertilizers only (MF). The organic fertilizers were applied in the dose of 40 kg of N ha-1, on the surface beneath grapevine canopies. The mineral fertilizers consisted of natural phosphate and potassium sulphate, in the doses of 160 and 100 kg ha-1 of P2O5 and K2O, respectively. In 2023, soil samples were collected from 0 to 5, 5 to 10, 10 to 20 and 20 to 40 cm layers, at bud burst (August), and analyzed for SOC and SON, via combustion followed by gas chromatography. No fertilization system increased SOC or SON in layers up until 20 cm deep after three years of treatment. In 20 to 40 cm layer, there was variability among treatments; however, that is probably main to natural variation. Mean C:N ratio of soil organic matter was 12,0. In light of this, we suggest the evaluation of SOC and SON after a longer period of treatment application, since their low increase in humid subtropical regions, which presents hot and wet summers.

How to cite: Tiecher, T. L., Kokkonen, A. A., Papalia, D. G., Garlet, L. P., Ferraz Costa, V., Bolívar de Mello Schemer, S., Gonçalves Gulartt, A., Clasen, B., and Brunetto, G.: Organic Vineyard Fertilization: Soil Carbon and Nitrogen in Southern Brazil, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13467, https://doi.org/10.5194/egusphere-egu24-13467, 2024.

EGU24-15383 | ECS | Orals | SSS5.6

On-farm soil management distinctly influences the stabilization of dissolved organic carbon within soil aggregates 

Orracha Sae-Tun, Christoph Rosinger, Gernot Bodner, Axel Mentler, Herwig Mayer, Sabine Huber, and Katharina Keiblinger

Dissolved organic carbon (DOC) is a highly active carbon pool which can easily be utilized by soil microbes and is thereby a crucial fraction of the soil carbon cycle. Occlusion within soil aggregates is one important stabilization mechanism of DOC in the soil and is affected by various factors including soil management and site-specific conditions. However, details about this mechanism and its regulating factors are still largely unclear. Thus, this study aims to investigate the stabilization mechanism of DOC in soil aggregates under different soil managements across varying soil textures (fine, medium, and coarse). In the study, the soil managements were categorized into three different systems depending on the degree of conservation measures implemented on the farms: state-of-the-art system (standard), conservation systems (pioneer) which were primarily characterized by intensive use of cover cropping together with crop diversification and rotation, and semi-natural grassland (reference). We employed a combination of ultrasonication and online UV-visible spectroscopy to examine the concentration of DOC released from soil aggregates decayed. The experimental setup followed the theory that the duration of low-amplitude ultrasonication energy correlates with higher aggregate stability (resistant to decay), which in return affects the stability of DOC. Influential factors were assessed from relationships with soil physico-chemical and biological characteristics. Based on the observed release pattern, the study deduced that DOC was stabilized within soil aggregates across three different stability levels: low, moderate, and high. 

The results revealed that soil management systems exerted a significant effect on DOC in moderately and highly stable aggregates. Standard systems exhibited the lowest DOC concentration, while reference systems demonstrated the highest concentration. A significant effect of soil texture was found only at the moderate aggregate stability level where coarse soil displayed the lowest DOC concentration. Contrastingly, neither soil management systems nor soil texture had a significant effect on DOC concentration at the low aggregate stability level. The stabilized DOC within moderately stable aggregates, as evidenced by DOC concentration at the moderate level of aggregate stability, exhibited more pronounced correlations with soil microbial variables (i.e., microbial biomass C and ergosterol) than with soil texture as identified through particle size distribution. Therefore, our results suggest that changes induced by soil management, particularly in microbiological attributes, have a more crucial role on the stabilization of DOC in highly stable aggregates than site-specific conditions such as soil texture. Furthermore, the application of low-energy ultrasonication in this study enables the differentiation of soil managements, even within arable systems, in an on-farm setting.

How to cite: Sae-Tun, O., Rosinger, C., Bodner, G., Mentler, A., Mayer, H., Huber, S., and Keiblinger, K.: On-farm soil management distinctly influences the stabilization of dissolved organic carbon within soil aggregates, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15383, https://doi.org/10.5194/egusphere-egu24-15383, 2024.

EGU24-17574 | ECS | Posters on site | SSS5.6

Determining factors of soil organic carbon in the sclerophyll ecosystem of central Chile 

Nancy Daniela Mallitasig, Marcelo Miranda, and Eduardo Arellano

The sclerophyllous forest of Central Chile, a Mediterranean-type ecosystem, is facing increasing vulnerability, exacerbated by anthropogenic pressures and drought conditions that have intensified over the past decade.

The objective of this study was to determine, at both regional and local scales, the factors influencing soil organic carbon (SOC), considering the integrated soil-vegetation system. Biophysical conditions such as primary productivity (PP), soil properties (SP), terrain physiography, and climate were considered.

At the regional scale, predictive variables for PP were selected using remote sensing techniques, including the Enhanced Vegetation Index (EVI) and the Normalized Difference Water Index (NDWI) in the spring period. Additionally, climatic variables (maximum, mean, and minimum temperature in spring and annual precipitation between 2001 and 2021) and physiographic variables such as exposure, slope, elevation, and topographic position index (TPI) were included. Statistical analysis was analyzed using a Random Forest model.

At the local scale, a forest inventory has been made, and soil samples were taken at a depth of 20 cm in 45 field plots of 400 m2, located in multi-species shrub vegetation (>4m in height). Concentrations and stocks of SOC were quantified, along with physical properties (texture, field capacity, and macroaggregates), chemical properties (pH, organic matter content, total nitrogen, and C/N ratio), and microbial activity estimated through basal respiration. Biomass, nitrogen content, and C/N ratio of leaf litter also measured. Statistical analysis was performed using a stepwise regression.

Preliminary results indicate that the most significant variables in predicting SOC were EVI, slope, elevation, total nitrogen, DA, LAI, coverage of the tree stratum, and vegetation height at the corresponding spatial scale.

How to cite: Mallitasig, N. D., Miranda, M., and Arellano, E.: Determining factors of soil organic carbon in the sclerophyll ecosystem of central Chile, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17574, https://doi.org/10.5194/egusphere-egu24-17574, 2024.

EGU24-17771 | Posters on site | SSS5.6 | Highlight

Modelling of C stock development for assessing the feasibility and implications of humus build-up in humus-oriented farming  

Susanne Stadler, Lisa Bahlmann, Ursula Noell, Florian Stange, Silke Mollenhauer, Alice Woelk, Andrea Rode, and Christina Aue

Soil and groundwater resources in the North Sea region are under increasing pressure due to climate change and human activities, calling for the need of sound strategies for their sustainable protection. The EU Interreg North Sea Project "Blue Transition" targets at a systemic change that balances activities in urban, agricultural or natural areas. It considers a transition in land-use and fosters political structures and governance, investigating 16 pilot sites in Denmark, The Netherlands, Sweden, Belgium, France and Germany to exchange and develop transnational solutions for water boards, farmers, authorities and society.

Within the project, we conduct scenario-based simulations (some based on strip experiments) regarding humus build-up under climate-induced rising temperatures and leaching from humus decomposition in arable soils in Lower Saxony, comparing conventional and organic farming. The aim of our study is an improvement of soil management in conventional and organic farming – especially regarding humus build-up and N loss reduction from soil. The results will serve as a base for elaborating best practices in management strategies for humus-oriented farming, and for investigating implications on soil water. We show first approaches of the numerical simulations.

How to cite: Stadler, S., Bahlmann, L., Noell, U., Stange, F., Mollenhauer, S., Woelk, A., Rode, A., and Aue, C.: Modelling of C stock development for assessing the feasibility and implications of humus build-up in humus-oriented farming , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17771, https://doi.org/10.5194/egusphere-egu24-17771, 2024.

EGU24-18519 | ECS | Posters on site | SSS5.6

Impacts of long term P availability on Soil Organic Carbon stocks and cycling – insights from the EJP ICONICA project 

Parag Bhople, David Wall, Karl Richards, Fiona Brennan, Gary Lanigan, and Giulia Bondi

The management of agro-ecosystems enhancing soil and subsoil organic carbon (SOC) sequestration could be a potential strategy to mitigate climate change. However, soil quality and organic matter (SOM) transformation is highly regulated by the cycle and interactions with other nutrients such as carbon (C), nitrogen (N) and phosphorus (P). In agricultural management, the addition of P fertilizers and its effect on C and N cycling (CNP stoichiometry) is still largely unknown. Therefore, the ICONICA project intends to provide context-based information on soil nutrients (C & N) and their stocks and cycling in P fertilizer scenarios. To determine the influence that P fertilization has on SOC stabilizations and greenhouse gas (GHG) emissions in agricultural systems, ICONICA employed a unique set of long-term P fertilizer experiments (LTEs) across Europe, including a range of P treatments to establish relationship between long-term P availability and interaction with C and N. In this project soils up to 50 cm depth were collected from six LTEs distributed across Europe. The LTEs feature different soil type/textural classes and land uses. The objective was to quantify C stocks and provide initial reference value of soil C storage for soil depths and link that to the soil stoichiometric ratios (C:N:P) in different management systems. Overall, in grassland sites the average SOC stocks ranged from 54.76±6.65 (tC/ha) in The Netherlands, followed by 43.07±5.71 (tC/ha) in Ireland. The average SOC stocks in arable sites in Sweden were 21.22±1.19 (tC/ha) and the least SOC stocks (18.60±2.35 (tC/ha) occurred in arable site in Denmark. Grassland sites showed a higher SOC stock within the topsoil (0-10 cm) while arable sites contributes most of the C in the subsoil especially at 10-30 cm. The mean soil C/N ratio was higher in the topsoil (0-10 cm) in the arable with respect to the grasslands and ranged from 13.74 to 10.28 with similar trend at soil depth gradients. The variations in C flow and in stocks through the sampled profile of different land uses such as grassland to arable is highly complex and driven by multiple factors indicating the need for further assessment. Nevertheless, the observations indicated the indispensable nature of long-term field experiments to quantify the optimum C:N:P stoichiometry that may enable efficient SOC sequestration as opposed to production in the managed agricultural systems.

How to cite: Bhople, P., Wall, D., Richards, K., Brennan, F., Lanigan, G., and Bondi, G.: Impacts of long term P availability on Soil Organic Carbon stocks and cycling – insights from the EJP ICONICA project, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18519, https://doi.org/10.5194/egusphere-egu24-18519, 2024.

EGU24-18694 | ECS | Orals | SSS5.6

Greenhouse gas emissions and nitrate leaching as a result of grassland renovation practices 

Mart Ros, Jordy van 't Hull, and Gerard Velthof

Grasslands are a major sink of organic carbon and for that reason are interesting as a means to achieve national and international climate goals. Grassland renovation (reseeding or conversion to arable land) is a common measure to counteract yield declines in intensively managed agricultural grasslands. The destruction of the sod that accompanies this practice induces a strong increase in mineralization of soil organic carbon and can therefore be a major source of nitrate (NO3) leaching and emissions of carbon dioxide (CO2) and nitrous oxide (N2O).

 

Most farmers prefer reseeding in autumn instead of spring because of better establishment of the sward and low weed infestation. However, limited crop nitrogen (N) demand during autumn increases the risk of NO3 leaching and N2O emissions. Potentially, such N losses could be mitigated by measures such as reducing tillage intensity, reducing fertilizer N application, or applying nitrification inhibitors. In 7 different experiments, we studied the effect of various grassland renovation practices on soil N cycling, greenhouse gas emissions, and nitrate leaching. We hypothesized (i) that conversion to arable land leads to greater CO2 and N2O losses than the reseeding of grassland; (ii) that reseeding in autumn causes enhanced risk of NO3 leaching during winter; and (iii) that these losses can be mitigated by reducing tillage and/or N application rates.

 

Results show that NO3 concentrations in groundwater after harvest were higher for observed after autumn reseeding combined with mitigation strategies than for reseeding in spring. This implies that confining the renewal of grassland to spring season could be a viable strategy to mitigate NO3 leaching. Emissions of N2O varied between experiments and could generally be linked to precipitation events and agricultural management (fertilization and renovation). Grassland renovation led to higher N2O (and CO2) emissions, but the effects of mitigation practices were inconsistent. The results from these experiments will be discussed in more detail. Mitigation strategies for N2O are less straightforward than those for nitrate leaching.

How to cite: Ros, M., van 't Hull, J., and Velthof, G.: Greenhouse gas emissions and nitrate leaching as a result of grassland renovation practices, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18694, https://doi.org/10.5194/egusphere-egu24-18694, 2024.

EGU24-19029 | ECS | Posters on site | SSS5.6 | Highlight

Phosphorus modelling on agricultural fields – trade-offs between applicability and complexity 

Julius Diel, Sara König, Ulrich Weller, and Hans-Jörg Vogel

Besides nitrogen, phosphorus is the second most important nutrient for plants, but has only little natural inputs. If it is not added regularly by fertilizers, be it mineral or organic, the soil gets depleted after a few years. As a consequence, crop growth is impeded as well as the microbial turnover of soil organic matter.  However, many crop growth models do not account for phosphorus dynamics, although it might be a limiting factor.

In a mechanistic soil process model such as BODIUM, crops are growing dynamically adapting to their boundary conditions and affect many other soil functions due to water and nutrient uptake, root exudation and biomass input to the soil. Moreover, microbial metabolism depends on the stoichiometry of soil organic matter and available nutrients, i.e. C/N/P ratios. A phosphorus component shall therefore enhance the nutrient cycle and improve the crop growth prediction, both in regard to yields as well as to feedbacks with other soil processes.

Here, we want to present an extended BODIUM version including the representation of the P cycle and present first simulations with data from the Static Fertilization Experiment in Bad Lauchstädt. Beside stoichiometric considerations for all organic pools, the mineral dynamics are represented with only ‘total’ and ‘available’ P. These can easily be measured by standard procedures and are now mandatory in some countries, although with varying protocols. This is especially relevant for farmers, who are a declared target group of the model.

How to cite: Diel, J., König, S., Weller, U., and Vogel, H.-J.: Phosphorus modelling on agricultural fields – trade-offs between applicability and complexity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19029, https://doi.org/10.5194/egusphere-egu24-19029, 2024.

EGU24-19722 | ECS | Posters on site | SSS5.6 | Highlight

Quantifying baseline soil organic carbon (SOC) stocks to allow establishment of robust carbon accounting framework for sustainable agriculture in Ireland  

Alex Martin Castellon Meyrat, Lilian O'Sullivan, David Wall, Paul Holloway, and Giulia Bondi

The soil organic carbon (SOC) and stocks mediate pivotal ecosystem services such as carbon sequestration, climate regulation by mitigating greenhouse gas emissions, nutrient cycling, provisioning habitats for organisms, water supply, and production of food, fiber and fuel. In agricultural systems, multiple factors including climate, soil types, vegetation, and land management affect the SOC dynamics. However, the coupled impacts among these factors on SOC stocks at farm and regional scale are still unknown. Therefore, it is crucial to expand our understanding of carbon cycle under different scenarios to develop more sustainable agro-ecosystems at national level. To achieve this, Teagasc is leading the Signpost Program a multiannual sampling campaign aiming to build an accurate baseline of SOC stocks across different soil types, land uses and management regimes in Ireland. This will help to understand the carbon dynamics in Irish agricultural soils, revealing the composition and stability of SOC in depth. To build the baseline for longtime soil carbon observatory, SOC data and soil health indicators for 148 soil profiles have been collected to date within 37 farms across the country. The method for site selection was based on combination of geographic information system (GIS) techniques and the catena approach, covering different climatic regions, soil types, and farming systems along the dominant hillslope within each farm. The soil samples were taken at each 15 cm increment up to 60 cm soil depth. The baseline data includes estimation of chemical properties such as potassium (K) and phosphorus (P) obtained by Morgan’s extraction; pH, total nitrogen (N), total carbon (C), and organic carbon (SOC); aluminum (Al), calcium (Ca), Magnesium (Mg), and phosphorus (P). It also includes physical properties such as bulk density based on three replicates per each range of sampling depth and finally clay, silt, and sand content to be assessed by spectroscopy measurements. Finally, SOC stocks across P scenarios, C/N ratio, and C:N:P ratios are estimated to understand the capacity of soils to sequester carbon and the nutrients dynamics under different management regimes and soil types. The Signpost initiative emphasizes soil management practices with long-term benefits for the environment and expand knowledge to contribute to sequestering carbon, improving overall soil health to support progression of sustainable agricultural systems.

How to cite: Castellon Meyrat, A. M., O'Sullivan, L., Wall, D., Holloway, P., and Bondi, G.: Quantifying baseline soil organic carbon (SOC) stocks to allow establishment of robust carbon accounting framework for sustainable agriculture in Ireland , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19722, https://doi.org/10.5194/egusphere-egu24-19722, 2024.

EGU24-20186 | Posters on site | SSS5.6

Trace metals in the soils of the Sanjiang Plain in the Northeast Asia: Land use influence 

Jing Wang, Hongguang Cheng, Kai Yang, and Chunye Lin

The Sanjiang Plain is located in the Northeast Asia, where the large areas of farmland and wetland are distributed. The soil cores of 40 to 100 cm depth were collected at 48 sites in the Sanjiang Plain and sectioned into 3-, 5- or 10-cm slices. In total, 451 soil samples were got and were analyzed for trace, minor, and major elements. The concentration ranges of trace and minor metals (mg kg-1) in the soil were 1.08-65.7 for As, 0.03-0.36 for Cd, 5.26-103.8 for Co, 42.6-102.9 for Cr, 12.4-64.4 for Cu, 0.01 to 0.14 for Hg, 139.3-4184.5 for Mn, 13.4 to 58.2 for Ni, 15.3-106.2 for Pb, 0.25-1.67 for Sb, 7.87-23.6 for Sc, 2525-6265 for Ti, 51.7-283.4 for V, and 42.8-184.6 for Zn. The average contents of Al2O3, Fe2O3, MgO, CaO, Na2O, and K2O in the soil were 9.72%, 5.34%, 1.00%, 0.98%, 1.63, and 2.28%, respectively. The soil pH ranged from 5.03 to 6.97, with an average of 5.84. Land uses had important effects on trace metal concentrations in the soil. The average concentrations of As, Co, Mn, and Pb the soil decreased from forest land, to dry farmland, to paddy field, and to wetland. On the other hand, the average concentrations of Cr, Cu, Ni, Sc, and Ti in the soil of wetland and paddy field were higher than those of dry farmland and forest land. However, the average concentrations of Hg and V in the soil of wetland and forest land were higher than those of paddy field and dry farmland. The difference in the concentrations of trace and minor elements among the four types of land use originate from anthropogenic activity, hydrologic conditions, and pristine soil properties. Atmospheric deposition of V and Hg led to higher Hg and V concentrations in the soil of natural wetland and forest land than in the agricultural land (paddy field and dry farmland). Higher leaching of redox sensitive elements such as As, Co, Mn, and Pb led to lower concentrations of As, Co, Mn, and Pb in wetland and paddy field than in forest land and dry farmland. The difference in the concentrations of Cr, Cu, Ni, Sc, and Ti in the soil among the four kinds of land use should be ascribed to the difference in the pristine soil properties.  

This study was funded by the National Natural Science Foundation of China (42276233). 

How to cite: Wang, J., Cheng, H., Yang, K., and Lin, C.: Trace metals in the soils of the Sanjiang Plain in the Northeast Asia: Land use influence, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20186, https://doi.org/10.5194/egusphere-egu24-20186, 2024.

It has been advocated that nitrogen (N) availability plays an essential role in mediating plant and microbial growth in cold environment, and could thus regulate the direction and magnitude of permafrost carbon (C)-climate feedback. However, compared to widely concerned N, little is known about soil phosphorous (P) availability and its biological acquisition strategies in permafrost environment. Here we explored soil microbial P acquisition strategies using shotgun metagenomics across the Tibetan permafrost area, encompassing a large scale survey spanning 1,000 km. In contrast to the traditional opinion that microorganisms in cold area usually obtain P mainly through mineralization process, our results revealed that the P cycling genes responsible for solubilization, mineralization and transportation were widespread, illustrating multiple microbial strategies for acquiring P in permafrost regions. Moreover, the higher gene abundance related to solubilization and mineralization as well as an increased ration of MAGs carrying these genes were detected in the active layer, while the greater abundance of low affinity transporter gene (pit) and proportions of MAGs harbouring pit gene were observed in permafrost deposits, reflecting a stronger potential for P activation in active layer but an enhanced P transportation potential in permafrost deposits. Taken together, these results highlight that besides microbial P mineralization, multiple P-related acquisition strategies and their differences among various soil layers should be considered simultaneously to improve model prediction for the responses of biogeochemical cycles in permafrost ecosystems to climate change.

How to cite: Wang, L. and Yang, Y.: Divergent microbial phosphorous acquisition strategies between active layer and permafrost deposits, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2973, https://doi.org/10.5194/egusphere-egu24-2973, 2024.

EGU24-3208 | ECS | Orals | BG1.4 | Highlight

Seagrasses' role as a reverse sedimentary phosphate pump 

Neta Soto, Gilad Antler, and Avner Gross

Seagrasses are marine-flowing plants that form an important coastal ecosystem. Although occupying less than 0.2% of the ocean’s surface, seagrasses store over 15% of the accumulated global carbon storage in the ocean’s sediments. Thus, Seagrass meadows play a pivotal role in mitigating climate change by carbon sequestration. Seagrasses are widely distributed in oligotrophic tropical waters despite the low nutrient levels in the water column due to their ability to absorb nutrients from the sediment porewater. Moreover, seagrasses can actively mobilize unavailable nutrients e.g., iron and phosphorus in the rhizosphere via multiple biogeochemical interactions. This provides them with an important advantage over pelagic photoautotrophs, which are limited by the availability of nutrients in the water column. Despite their ability to transport nutrients from sinks e.g., sediments to the water column where they can be recycled trough grazing or decomposition, the potential role of seagrass as a revers sedimentary phosphate pump remains unclear. The aim of this study is to examine the effect of seagrass disappearance on phosphate flux in marine coastal environments. In a series of incubation experiments, the change in the phosphate release was examined in different tissues of seagrass Halophila stipulacea. The results showed that the while the highest decomposition rate of the rhizomes was the fastest, the highest phosphate release rate was measured in the leaves, despite having similar phosphate content. Since the leaves mostly decompose in the water column, the released phosphate is made available to planktonic photoautotrophs and further enhances more carbon fixation. Overall, we suggest that in oligotrophic environments seagrasses act as a reverse phosphate pump by accessing phosphate in the sediment and later translocating it to the aboveground parts and releasing in the water column, thus fertilizing planktonic photoautotrophs and enhancing further carbon sequestration.

How to cite: Soto, N., Antler, G., and Gross, A.: Seagrasses' role as a reverse sedimentary phosphate pump, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3208, https://doi.org/10.5194/egusphere-egu24-3208, 2024.

EGU24-3472 | Orals | BG1.4

Elevated atmospheric CO2 increased soil plant available and soil organic phosphorus in a mature temperate oak (Quercus robur L.) forest 

Amin Soltangheisi, Adam Pinder, Keegan Blazey, Robert T. Grzesik, Miles Marshall, Angeliki Kourmouli, Carolina Mayoral, Kris M. Hart, Sami Ullah, Iain P. Hartley, A. Robert MacKenzie, and Andy R. Smith

Enhanced productivity of forest ecosystems in response to rising levels of anthropogenically generated atmospheric carbon dioxide (CO2) has the potential to mitigate against climate change by sequestering carbon in woody biomass and soils. However, the physiological response of trees to elevated atmospheric CO2 may be constrained by the availability of soil nutrients, predominantly nitrogen and phosphorus (P). Here, we assess the impact of elevated atmospheric CO2 on P cycling in a temperate 180-year-old oak (Quercus robur L.) forest exposed to free-air CO2 enrichment (ambient + 150 ppm) for six years. Soil cores were collected to a depth of 1 m in July 2023 and separated into three horizons and three layers (O, A, B, 30-50, 50-70, 70-100 cm) before analysis using the Hedley1 sequential P fractionation and the DeLuca2biological based P extraction techniques. Plant available P in soil pore water and total organic P from the O horizon increased by 84 and 128%, respectively, whilst organic P extracted with phosphatase increased by 62% under elevated CO2. Total organic P in soil horizons beyond the B horizon (> 15 cm) decreased under elevated CO2 in comparison with ambient CO2. As soil organic P is derived from the turnover of both vegetation and microbial biomass, increased soil organic P in the O horizon may be due to the faster turnover of organic matter or an increase in the net primary productivity of the forest. Soil P cycling in this forest ecosystem appears to be predominantly influenced by biological rather than chemical processes, since elevated CO2 only affected the organic P and not inorganic P fractions. Forest productivity may be constrained by P limitation in future elevated CO2 environments, if there is faster organic matter turnover which is probably the case in our study.

1Hedley, M. J., Stewart, J. W. B., & Chauhan, B. (1982). Changes in inorganic and organic soil phosphorus fractions induced by cultivation practices and by laboratory incubations. Soil Science Society of America Journal, 46(5), 970-976.

2DeLuca, T. H., Glanville, H. C., Harris, M., Emmett, B. A., Pingree, M. R., de Sosa, L. L., Cerdá-Moreno, C. & Jones, D. L. (2015). A novel biologically-based approach to evaluating soil phosphorus availability across complex landscapes. Soil Biology and Biochemistry, 88, 110-119.

How to cite: Soltangheisi, A., Pinder, A., Blazey, K., Grzesik, R. T., Marshall, M., Kourmouli, A., Mayoral, C., Hart, K. M., Ullah, S., Hartley, I. P., MacKenzie, A. R., and Smith, A. R.: Elevated atmospheric CO2 increased soil plant available and soil organic phosphorus in a mature temperate oak (Quercus robur L.) forest, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3472, https://doi.org/10.5194/egusphere-egu24-3472, 2024.

EGU24-4491 | Posters on site | BG1.4

Silicone availability and NaCl water type enhances the phosphorus release from sediments in coastal forest catchments in Akita, Japan 

Atsushi Hayakawa, Yuka Kuroe, Ayumi Kawata, Kazuya Nishina, Yuichi Ishikawa, and Tadashi Takahashi

[Background] Phosphorus (P) availability in soils and sediments is a critical parameter influencing primary production in terrestrial and aquatic ecosystems, controlled by both P chemical fractions in solid phase and solution composition. A recent study using Arctic soils reported that the addition of Si to the soil released P bound to Fe(II) compounds, but reports on other soils and sediments are limited. In our previous study, we detected higher P concentrations in stream water and iron-bound P content in river sediments in the marine sedimentary rock catchments of the Akita coastal area compared to catchments in the adjacent igneous rock area. Furthermore, high-P stream waters were NaCl water type with relatively lower Ca2+ and higher SiO2 concentrations. In this study, we evaluated the effects of different solution compositions and amorphous Si addition on P solubilization in sediments using river sediments from marine sedimentary and igneous rock regions. [Method] We tested each five river sediments (<2 mm) in the headwaters of western Akita Prefecture, Japan, where the surface geology is composed of marine sedimentary rocks and igneous rocks. Available Si (easily water-soluble Si) was measured by a long-term flooded incubation in distilled water at 30°C for 30 days. In the P dissolution incubation, four types of treatment solutions (distilled water, 1 mM NaCl and NaHCO3 solutions, and 0.5 mM CaCl2 solution) were added to 0.5 g sediment and in the Si addition treatment, amorphous Si (hydrophilic fumed silica, AEROSIL300) was also added. SRP, DOC and pH in the solution were measured after shaking for 48 hours. A statistical analysis was performed using a linear mixed model (LMM) with SRP, DOC and pH in the liquid phase as objective variables. The surface geology, four types of solutions, and the Si addition as explanatory variables. Additionally, each five sediment was treated as a random effect. [Results and discussion] Easily water-soluble Si content in sediments was significantly higher in marine sedimentary rock areas (p < 0.001), indicating that the easily soluble Si causes higher SiO2 concentration in stream water. The incubation results showed Si addition significantly increased P concentration in the liquid phase (p < 0.001), and combined Si addition with NaHCO3 treatment further increased P concentration. Conversely, CaCl2 treatment significantly decreased the liquid-phase P concentration. The influence of surface geology on extracted P concentration was not significant. Si addition did not affect pH (p = 0.58) and DOC (p = 0.90), while the effects of solution composition on pH and DOC were also significant; NaHCO3 solution increased pH and DOC while CaCl2 solution decreased pH and DOC. In conclusion, in marine sedimentary rock areas in coastal Akita with NaCl water type where Ca2+ concentration is relatively low and sediments have higher easily soluble Si, P release from sediments easily occurs and a high P concentration keeps in the liquid phase.

How to cite: Hayakawa, A., Kuroe, Y., Kawata, A., Nishina, K., Ishikawa, Y., and Takahashi, T.: Silicone availability and NaCl water type enhances the phosphorus release from sediments in coastal forest catchments in Akita, Japan, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4491, https://doi.org/10.5194/egusphere-egu24-4491, 2024.

EGU24-6352 | ECS | Posters on site | BG1.4

Phosphorous in the seabed sediments of the Gulf of Riga, Baltic Sea: Fe-Mn concretions as main carriers of mobile phosphorous  

Markus Ausmeel, Martin Liira, Päärn Paiste, Aivo Lepland, and Sten Suuroja

Baltic Sea is a geologically young semi-enclosed brakish-water body which water exchange with the ocean has been gradually declining. Approximately 85 million people live in the Baltic Sea's catchment area, resulting in significant human impact on the basin's ecosystem. Eutrophication due to anthropogenic discharge of nutrients is considered to be the most serious environmental problem which leads to a greater growth of phytoplankton and algae, deterioration of water quality, and lack of oxygen in near-bottom water masses. As a result of recent large-scale input of nutrients, phosphorus has accumulated in the seabed sediments from where it can be remobilized and released into the water column under favorable conditions (hypoxic or anoxic). Marine sediments contain phosphorus in various components i.e. fractions, but not all of them are affected by remobilization. Therefore, knowing how phosphorus fractions are distributed in seabed sediments is important.

One part of the Baltic Sea that has received little attention, but will significantly affect the entire Baltic Sea in the future, is the Gulf of Riga. The Gulf of Riga accounts for less than 5% of the total area of the Baltic Sea and less than 2% of the total water volume. Due to its shallowness and limited connection with the open Baltic Sea, the Gulf of Riga is strongly influenced by riverine input. Intense agriculture, rapid development of industry, and urbanization have resulted in high loads of nutrients into the Gulf of Riga already since the 1960s.

Phosphorus fractions and their vertical distribution were studied from the sea-bottom sediments from the Gulf of Riga and other coastal areas of western Estonia. The amount of potentially mobile phosphorus stored in the surface sediments of the Gulf of Riga is several times higher than in other accumulation areas of the Baltic Sea, with concentrations as high as 980 mg/kg(dw). A strong correlation between Mn and mobile phosphorus concentration suggests that Fe-Mn concretions control the amount of phosphorus in the sediments of the Gulf of Riga. Although the bottom waters of the Gulf of Riga are currently predominantly oxic, a decreasing trend of deep-layer oxygen concentrations and more frequent hypoxia in the Gulf of Riga during previous decades have been documented. Considering the large amount of potentially mobile phosphorus in the sediments of the Gulf of Riga, surpassing the annual total phosphorus input to the Baltic Sea, a substantial release of phosphorus could be inevitable, possibly impacting the entire Baltic Sea ecosystem.

How to cite: Ausmeel, M., Liira, M., Paiste, P., Lepland, A., and Suuroja, S.: Phosphorous in the seabed sediments of the Gulf of Riga, Baltic Sea: Fe-Mn concretions as main carriers of mobile phosphorous , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6352, https://doi.org/10.5194/egusphere-egu24-6352, 2024.

EGU24-7212 | ECS | Orals | BG1.4

Vivianite verified in early Cambrian strata in northwestern China: Implications for phosphorus recycling in ancient anoxic oceans 

Xuyang Cao, Pengcheng Ju, Yigui Han, Lihui Lu, and Dong Shao

In modern low sulfate and anoxic (euxinic) waters, the precipitation of mineral vivianite (an easily oxidized hydrated ferrous-iron phosphate) has played a crucial role in restraining the limiting nutrient element phosphorus (P) recycling back to the water column and consequently decreasing primary productivity. Although such low sulfate and anoxic conditions were widespread in ancient coastal oceans, vivianite has not been directly discovered in the paleo-sediments, which hampers the understanding of P cycling in ancient anoxic environments. Here, we combined techniques of scanning electron microscopy-energy dispersive X-ray spectroscopy, focused ion beam-transmission electron microscopy and P K-edge X-ray absorption near edge structure spectroscopy to analyze samples of P-bearing siliceous rocks and shales from the early Cambrian Yurtus Formation in the Tarim Craton, northwest China. Our results have demonstrated that micron- to nano-scale vivianite crystals are well preserved in the rocks and the vivianite dominates the P phase in some samples. The cherty matrix of the rocks most likely increased the chances of preservation of the oxidation-sensitive vivianite. In light of recent advances, we suggest that vivianite was a crucial P phase in ancient continental margin sediments, spanning most time from the Neoarchean to the early Cambrian. During this interval, the precipitation of vivianite was likely aided by the prevalent dynamic ocean euxinic conditions linked with the seawater sulfate reservoir and the flux of organic matter settling. We propose a negative feedback mechanism in which vivianite precipitation from ancient euxinic waters restricted P availability for biota, reduced marine primary productivity, and possibly abated the rate of Earth's oxygenation and associated evolution of life. This work was financially supported by NSFC projects (grants 42072264, 41730213) and Hong Kong RGC GRF (17307918).

How to cite: Cao, X., Ju, P., Han, Y., Lu, L., and Shao, D.: Vivianite verified in early Cambrian strata in northwestern China: Implications for phosphorus recycling in ancient anoxic oceans, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7212, https://doi.org/10.5194/egusphere-egu24-7212, 2024.

EGU24-9578 | ECS | Posters on site | BG1.4

Lithology-constrained phosphorus (P) releasement 

Shenghui Ouyang

Phosphorus (P), as an indispensable nutrient element in Earth’s biological system, exerts a pivotal role on the burial of organic carbon over million-year time scales. By producing oxygen and consuming carbon dioxide, organic carbon burial may have paved the path for multicellular organisms by reforming the anoxic atmosphere to an oxic one. Organic carbon burial, on long time scales, is ultimately limited by continental P influx released by chemical weathering of P-bearing minerals. As crystalline rocks characterized by prominent discrepancy in P-bearing mineral composition undergoing various dominant weathering forces on surficial environment, P availability for organic carbon burial could be controlled by lithology. To decipher the conundrum of P releasement, a catchment scale case study was conducted, encompassing a series of lithologies following the crystalline rock order. Preliminary data suggests that the P release efficiency is lithology-constrained, indicating an enhanced P releasement in felsic catchment. The result gives us a hint that felsic crust would export more P to the ocean and promote the organic carbon burial, the lithology-constrained P releasement also enlightens us a new perspective to understand the coevolution among crust, atmosphere and life.

How to cite: Ouyang, S.: Lithology-constrained phosphorus (P) releasement, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9578, https://doi.org/10.5194/egusphere-egu24-9578, 2024.

EGU24-9674 | ECS | Orals | BG1.4

Linking phosphorus research to impact: advances and challenges in mapping soil phosphorus pools 

Julian Helfenstein, Bruno Ringeval, Federica Tamburini, Daniel S. Goll, Xianjin He, Vera Mulder, Yingping Wang, Edwin Alblas, and Emmanuel Frossard

Improved management of phosphorus (P) is essential for achieving a range of Sustainable Development Goals (SDGs), including maintaining food security, preserving water quality, and mitigating climate change. This requires an integration of comprehensive mechanistic understanding with accurate spatial data. In this interdisciplinary review, we combine insights from empirical P research, digital soil mapping, biogeochemical modeling, and environmental law to critically examine the current state, pinpoint challenges and propose novel pathways for desperately needed P maps. We first elucidate the relevance of spatial data on P for different SDGs. Subsequently, we summarize the current efforts in mapping P pools at regional to global scales, and discuss the challenges of mapping “available P” due to substantial local scale variability and poor correlation with predictors relative to other soil properties. The practical applicability of these recently published maps is tested by evaluating them with independent measurement data. Finally, we outline ways forward to enhance the accuracy and reliability of P maps, as a basis for science-informed management of P resources.

How to cite: Helfenstein, J., Ringeval, B., Tamburini, F., Goll, D. S., He, X., Mulder, V., Wang, Y., Alblas, E., and Frossard, E.: Linking phosphorus research to impact: advances and challenges in mapping soil phosphorus pools, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9674, https://doi.org/10.5194/egusphere-egu24-9674, 2024.

EGU24-14368 | Orals | BG1.4

Phosphorus Cycling and Transport in Phosphorus Saturated Soils of the Chesapeake Bay Watershed, USA 

Gurpal Toor, Jesse Radolinski, Emileigh Lucas, Charles Burgis, Bradley Kennedy, Fajun Sun, and Patricia Steinhilber

Long-term application of organic products (manure, biosolids, other wastes) and inorganic phosphatic fertilizers have created hot spots of phosphorus (P) saturated soils in intensive animal production regions worldwide. In such regions, P losses from P-saturated (i.e., legacy P) soils continue to plague efforts to improve water quality. Understanding the P cycling and fluxes from these P-saturated soils is critical to advancing our knowledge and developing strategies to manage P in soils and curb P losses. This presentation will discuss P cycling and transport in agricultural catchments (with Maize-Soybean rotation) from the lenses of P chemistry in soils and hydrologic responses from soils to further advancements in managing the P cycle in the soil-plant-water continuum for agricultural sustainability and environmental protection.

How to cite: Toor, G., Radolinski, J., Lucas, E., Burgis, C., Kennedy, B., Sun, F., and Steinhilber, P.: Phosphorus Cycling and Transport in Phosphorus Saturated Soils of the Chesapeake Bay Watershed, USA, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14368, https://doi.org/10.5194/egusphere-egu24-14368, 2024.

EGU24-14436 | ECS | Orals | BG1.4

Balancing crop production, water quality and the use of finite P reserves by using the soil P sorption capacity in revised fertilizer recommendations 

Maarten van Doorn, Debby van Rotterdam-Los, Gerard H. Ros, and Wim de Vries

Phosphorus (P) is an essential nutrient for plant growth and is applied to agricultural soils in the form of organic manure or inorganic fertilizer. To guide farmers in achieving optimal crop yields, P fertilizer recommendations are in place with the rationale to bring soils to a “target soil P status” following the classic build-up and maintenance approach. The target soil P status where crop yield is not limited by P deficiencies is generally operationalized as the soil P status at which 90-99% of the potential crop yield is found in long-term fertilization field experiments. Though these fertilizer recommendations allow for an economic optimization of crop yield versus P inputs, environmental objectives are barely considered. In our research, we revised the classic build-up and maintenance approach to balance crop production, water quality and the use of finite P reserves. This revision requires insights into the P sorption capacity of soils (PSC) and its saturation with P. We identify the oxalate extraction method as a key component of this approach since it quantifies the PSC from the combined measurement of amorphous iron- and aluminium-(hydr)oxides and the total pool of reversibly bound P. For the Netherlands, we show the implications of the approach for P fertilizer use. We quantified soil amorphous iron- and aluminium(hydr)oxides contents at a 25m resolution across the soil depth profile using a Digital Soil Mapping approach and used these predictions to translate agronomic soil P data to new insights to optimize P fertilizer use. We finally argue that agronomic P target levels should be lowered in soils with a low PSC to decrease the risk of P leaching and in soils with a high PSC to ensure judicious use of finite P reserves.

How to cite: van Doorn, M., van Rotterdam-Los, D., Ros, G. H., and de Vries, W.: Balancing crop production, water quality and the use of finite P reserves by using the soil P sorption capacity in revised fertilizer recommendations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14436, https://doi.org/10.5194/egusphere-egu24-14436, 2024.

EGU24-16417 | ECS | Orals | BG1.4

31P NMR Reveals Predominance of Small Molecules in Organic Phosphorus within NaOH-EDTA Soil Extracts 

Lenny Haddad, Andrea Vincent, Reiner Giesler, and Jürgen Schleucher

Organic phosphorus (P) plays a crucial role in maintaining the health and productivity of soils. Understanding the composition of organic phosphorus in soils is thus relevant to a range of disciplines, spanning from agricultural sciences to ecology. Over the past few decades, efforts have been directed towards characterizing and quantifying various soil organic P compounds and determining their turnover rates. Despite these efforts, the precise nature of soil organic P remains unclear, particularly that of orthophosphate monoesters, which dominate 31P NMR spectra of NaOH-EDTA extracts globally.

Typically, the monoester region of 1D 31P NMR spectra appears as a series of sharp signals "sitting" on a broad background where the broad background can account for a substantial part of the monoester region. This is prompting questions about how to integrate and identify these signals and to what extent this fraction may be ecologically important. To investigate this monoester background, we employed 1D 31P NMR and 2D 1H-31P NMR1, along with 31P transverse relaxation (T2)2 measurements to calculate intrinsic linewidths. We related this linewidth to molecular weight to unveil the nature of the observed background. Analysing seven soils from different ecosystems, we observed linewidths ranging from 0.5 to 3 Hz for both resolved monoester signals and the background. This suggests that the background comprises numerous, possibly exceeding 100, sharp signals associated with small (<1.5 kDa) organic P molecules.

Organic P in the form of nucleic acids, phospholipids, P-containing metabolites, and phosphorylated proteins dominate the P content of live leaves, leaf litter and microbial tissues. Furthermore, P-containing metabolites are exuded by roots and are present in a vast array of organisms. Evidence that the background potentially can contain a large number of small metabolites is thus not surprising and may account for an important part of the organic P pool given that the background accounts for about 55% of the monoester region. Our findings warrant further research specifically addressing to what extent this pool may play for plant and microbial P nutrition.

We provide recommendations for treating 31P NMR spectra to accurately quantify phosphomonoester species, representing a crucial step in linking observed P speciation to its bioavailability. Our findings align with previous 31P NMR studies detecting background signals in soil-free samples and new evidence suggesting that alkali-soluble soil organic matter consists of self-assemblies of small organic compounds mimicking large molecules.

1Vestergren, J.; Vincent, A. G.; Jansson, M.; Persson, P.; Ilstedt, U.; Gröbner, G.; Giesler, R.; Schleucher, J. High-Resolution Characterization of Organic Phosphorus in Soil Extracts Using 2D 1H–31P NMR Correlation Spectroscopy. Environmental Science & Technology 2012, 46 (7), 3950–3956. https://doi.org/10.1021/es204016h.

2Vincent, A. G.; Schleucher, J.; Gröbner, G.; Vestergren, J.; Persson, P.; Jansson, M.; Giesler, R. Changes in Organic Phosphorus Composition in Boreal Forest Humus Soils: The Role of Iron and Aluminium. Biogeochemistry 2012, 108 (1), 485–499. https://doi.org/10.1007/s10533-011-9612-0.

How to cite: Haddad, L., Vincent, A., Giesler, R., and Schleucher, J.: 31P NMR Reveals Predominance of Small Molecules in Organic Phosphorus within NaOH-EDTA Soil Extracts, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16417, https://doi.org/10.5194/egusphere-egu24-16417, 2024.

EGU24-16549 | ECS | Posters on site | BG1.4

A meta-analysis of global soybean plant growth and yield improvement in response to phosphorus addition 

Hannah Walling, Mariana Rufino, Jose Rotundo, Lucas Borras, Shane Rothwell, John Quinton, and Phil Haygarth

Application of phosphorus (P) fertiliser to soybean accounts for a large proportion of the global consumption of P as an agricultural fertiliser. Despite this key a knowledge gap exists surrounding the mechanisms of P fertiliser uptake and how it interacts with nitrogen fixation processes and yield improvements.

This paper aims to improve the understanding of P cycling in global cropping systems and will present a global meta-analysis of published data quantifying the effect of P fertiliser application on soybean above- and below-ground plant response variables. 790 paired observations (P fertiliser treatment and control treatment) were synthesised from 81 peer-reviewed articles that reported soybean response, including seed yield and nodulation, to P addition under a range of different environmental conditions.

We tested the hypothesise that:

  • soybean productivity will increase following P addition, with this response being driven by below-ground processes;
  • environmental conditions, particularly soil chemical properties would explain the variance in the observed response.

Analysis of these observations showed an overarching increase in soybean plant response following P addition. We found that several environmental and experimental conditions, particularly soil phosphorus status and phosphorus fertiliser rate influence the response of soybean to phosphorus addition, highlighting the complexities of sustaining P use across such a globally cultivated crop.

We recommend further experimental work needs to be conducted, which controls for such factors and allows for the improved mechanistic understanding of below-ground processes, to inform better use of finite P resources.

How to cite: Walling, H., Rufino, M., Rotundo, J., Borras, L., Rothwell, S., Quinton, J., and Haygarth, P.: A meta-analysis of global soybean plant growth and yield improvement in response to phosphorus addition, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16549, https://doi.org/10.5194/egusphere-egu24-16549, 2024.

EGU24-17700 | ECS | Posters on site | BG1.4

Vivianite as a phosphorus sink in estuarine systems: The case study of the Brillantes mudflat, Loire, France 

Mohammed Barhdadi, Aurélia Mouret, Christine Barras, Guillaume Morin, Grégoire Maillet, Matthieu Durand, Meryem Mojtahid, Eric Bénéteau, Nicolas Dubosq, and Edouard Metzger

Phosphorus (P) is a key nutrient controlling primary production in aquatic systems. In coastal systems, the P cycle involves dynamic interactions between terrestrial, aquatic and sedimentary compartments. Over the last century, human activities such as deforestation, intensive agricultural practices and the disposal of municipal and industrial wastes have increased P inputs to coastal ecosystems. As a result, this increase in P inputs has led to an increase in the occurrence of algal blooms and higher oxygen demand in estuaries. In the Loire estuary, dissolved oxygen deficits have been a recurrent and worrying issue for several decades despite the improvement of water quality over the last 30 years due to reduced wastewater discharge and better effluent treatment. In this context, the burial of bioavailable P may influence the recovery of waters from eutrophication. The major P burial phases are apatite, organic P and iron-bound P. The results of sequential chemical extraction and pore water analysis carried out over a 5m-long sediment core from the intertidal Brillantes mudflat in the Loire estuary indicated a greater abundance of the iron-bound P compared to other phases. Iron-bound P occurs in two different forms: phosphorus bound to iron oxides and in the iron phosphate mineral known as vivianite. Vivianite is a ferrous iron phosphate mineral formed under reducing and low sulphate conditions in sediments where organic matter serve as electron donor for ferric iron reduction. Results of sequential chemical extraction of freeze-dried sediment samples combined with pore water data and scanning electron microscope–energy dispersive x-ray spectroscopy (SEM-EDXS) on resin-embedded sediment samples indicated that vivianite-type minerals may act as an important sink for P at the studied site. Authigenic vivianite crystals were found below the shallow sulphate/methane transition zone (SMTZ) at 94 cm depth and contain significant amounts of manganese, as observed in freshwater sediments. We therefore hypothesise that anthropogenic over-fertilization of coastal regions in the last century may have increased the importance of vivianite authigenesis in surface sediments. Consequently, vivianite is likely to be an important sink for P in estuarine systems worldwide.

This study is part of a PhD financed by the European Project Life REVERS’EAU.

How to cite: Barhdadi, M., Mouret, A., Barras, C., Morin, G., Maillet, G., Durand, M., Mojtahid, M., Bénéteau, E., Dubosq, N., and Metzger, E.: Vivianite as a phosphorus sink in estuarine systems: The case study of the Brillantes mudflat, Loire, France, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17700, https://doi.org/10.5194/egusphere-egu24-17700, 2024.

EGU24-19011 | Orals | BG1.4

Microbial phosphorus limitiation with soil age along a chronosequence on the Galapagos Islands 

Katharina Maria Keiblinger, Sebastian Socianu, Maria Rechberger, Martin Gerzabek, and Franz Zehetner

The Galápagos archipelago, a volcanic island chain, is comprised of a series of progressively older islands with increasingly weathered soils away from the volcanic hotspot. Volcanic soils are known for their high phosphate sorption capacity. In this study, we explore differences in soil microbial abundance and activity across a soil age gradient (1.5 to 1070 ka) to understand how soil microorganisms are affected by soil development, shifting soil characteristics and P sorption over extensive periods.

Basal respiration, substrate-induced respiration and microbial biomass P decreased with soil development, suggesting increasing nutrient limitation for soil microbes. Also, soil enzymatic stoichiometry revealed a limitation driven mainly by P and not by N or C. C- and N-acquiring exoenzyme activities peaked at 26 ka with lower activities in younger and older soils. Phosphatase activity increased with soil age, indicating microbial P limitation in the older soils. This is only partly in line with  P sorption-desorption characteristics along the studied weathering sequence. Phosphate sorption capacity was high in the 4.3 ka soils likely due to amorphous soil constituents. A change towards 2:1-type crystalline clays after 26 ka of soil weathering led to weaker P sorption and stronger desorption, and acidification and increased P occlusion in Al and Fe (hydr)oxides became an important factor for microbial P limitation in the older soils.

Our results reveal striking differences in soil properties on the Galápagos Islands, suggesting relatively little nutrient constraints for soil microbes, despite strong P sorption, in the younger volcanic soils but growing P limitation in the older, highly weathered soils. These observations have important bearings on nutrient cycling and may therefore also affect the evolution of plant and animal species on this unique archipelago.

How to cite: Keiblinger, K. M., Socianu, S., Rechberger, M., Gerzabek, M., and Zehetner, F.: Microbial phosphorus limitiation with soil age along a chronosequence on the Galapagos Islands, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19011, https://doi.org/10.5194/egusphere-egu24-19011, 2024.

EGU24-20517 | Posters on site | BG1.4

A spatial perspective on internal phosphorus cycling in morphologically complex eutrophic lakes: the importance of stratification 

Tom Jilbert, Siqi Zhao, Jussi Vesterinen, and Juha Niemistö

Many eutrophic lakes suffer from long term accumulation of legacy phosphorus (P) in sediments. Repeated cycling of P between sediments and water column leads to delayed recovery from eutrophication even after abatement of external loading. Moreover, in complex multi-basin lake systems, legacy P can be internally redistributed over time, leading to spatial heterogeneity in regeneration and burial of P and consequent impacts on water quality. Few studies have attempted to map such internal variability in individual lakes in the context of understanding long term recovery from eutrophication. Here we use a combination of sediment trap deployments through one full stratification cycle (May-October 2021), sediment core biogeochemical analyses, and mass balance calculations, to quantify P cycling in Lake Hiidenvesi, a dimictic lake with 5 sub-basins in southern Finland. We show that exchange of P between sediments and water column is more intense in shallow (approximately 0-10 m depth) non-stratified sub-basins, due to both sediment resuspension and diffusive fluxes across the sediment-water interface. In contrast, deeper stratified sub-basins serve as P sinks by promoting sedimentation in relatively quiescent conditions. Due to lateral exchange of water and suspended materials between sub-basins, P is shuttled towards long term burial in deeper, downstream sub-basins. Budget calculations show that net sediment P burial exceeds external loading on the whole-lake scale, indicating a long-term trend towards recovery from eutrophication. However, temporary retention and repeated recycling of legacy P in the shallower upstream sub-basins continues to impact negatively on water quality, despite external loading reductions. The results have implications for understanding the timescales of recovery and for targeting restoration actions aimed at modifying internal P cycling to improve water quality.

How to cite: Jilbert, T., Zhao, S., Vesterinen, J., and Niemistö, J.: A spatial perspective on internal phosphorus cycling in morphologically complex eutrophic lakes: the importance of stratification, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20517, https://doi.org/10.5194/egusphere-egu24-20517, 2024.

EGU24-20917 | Posters on site | BG1.4

Controls on global patterns of dissolved organic phosphorus utilisation in the surface ocean 

Bei Su, Xianrui Song, Solange Duhamel, Claire Mahaffey, Clare Davis, Ingrid Ivančić, Shuo Zhou, and Jihua Liu

          Utilisation of dissolved organic phosphorus (DOP) by marine microbes as an alternative phosphorus (P) source when phosphate is scarce can help sustain non-Redfieldian carbon:nitrogen:phosphorus ratios and efficient ocean carbon export. Alkaline phosphatase (AP) is an important enzyme group that facilitates the remineralisation of DOP to phosphate and thus its activity is a promising proxy for DOP-utilisation, particularly in P-stressed regions. In order tounderstand the global spatial patterns and rates of microbial DOP utilization and their environmental controls, we compiled a Global Alkaline Phosphatase Activity Dataset (GAPAD) with 4083 measurements collected from 79 published manuscripts and one database and further investigated the possible mechanisms controlling global ocean APA. We find that DOP concentration, salinity, excess phosphate (P*), and chlorophyll a concentrations are critical factors in predicting global patterns of APA, which together explain as much as 39% of the variance in the observed APA dataset. Among all environmental factors, DOP concentration explains the most variance in the observed APA data and is negatively correlated with APA. P* is negatively correlated with APAwhile chlorophyll a concentration is positively correlated.  Moreover, wind speed, dust iron deposition rate, and zinc concentration are also possible important environmental factors controlling APA. Using structural equation modeling, DOP and P* concentrations have a total negative effect on APA of -0.36. and -0.2 respectively, while chlorophyll a concentration and salinity have a total positive effect of 0.16 and 0.24. Via a set of numerical competition experiments between an AP-producing phytoplankton and a non AP-producing competitor, AP-producing phytoplankton are found to have an advantage in regions with low P*, but only alongside sufficiently high DOP and DIN concentrations. This trend arises due to the trade-off between P acquisition and N allocation to AP synthesis and is not affected by varying the model assumptions regarding nutrient supplies, N-demand, and key physiological traits.  Extending our results to the global ocean using DIN, DIP, and DOP datasets enables us to pinpoint key regions where optimal conditions for DOP-utilisation are prevalent. These findings align closely with the patterns illuminated by our APA dataset. Our results show that on a global scale, when phosphate limitation is severe, plankton utilize DOP through producing AP, and this will help understand the biogeographical shift of different microbial groups in response to future climate change. Further work is needed to include the parallel role of the trace metal co-factors iron and zinc in driving AP synthesis and its spatial distribution in our modelling experiments.

How to cite: Su, B., Song, X., Duhamel, S., Mahaffey, C., Davis, C., Ivančić, I., Zhou, S., and Liu, J.: Controls on global patterns of dissolved organic phosphorus utilisation in the surface ocean, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20917, https://doi.org/10.5194/egusphere-egu24-20917, 2024.