Presentation type:
SSS – Soil System Sciences

EGU23-2801 | ECS | Orals | MAL10 | SSS Division Outstanding Early Career Scientist Award Lecture

Sustainable management of agricultural soils: Balancing multiple perspectives and tradeoffs 

Gina Garland

As the global population expands, the demand for food, fuel and fiber rises steadily. Meeting these needs in a sustainable manner, without depleting natural resources or polluting the environment remains one of the greatest challenges of our time. What is more, anticipating changes in these systems as a result of climate change, and across a multitude of environmental and socioeconomic contexts adds yet even further complexity to this already convoluted issue. 

At the heart of this matter lies agricultural soils, and how management practices are used to modify and adapt their capacity to sequester carbon and provide nutrients and water to growing plants. While soils are notoriously heterogenous on their own, this is further enhanced by their role as an important environmental reservoir linking plants and residues to soil microbial communities and soil fauna, the atmosphere, and water. Understanding how management practices influence these interactive aspects of the soil environment is key to developing agricultural management systems in a sustainable, effective and site-specific manner.

In this presentation I will highlight how it is vital for future studies to consider a) how management practices will simultaneously impact a variety of different soil functions or services, not just one or two, in order to assess environmental tradeoffs within a given system, b) how these are impacted across different spatial scales, and c) the importance of developing management practices that are adapted to local, site-specific conditions. It is clear that the complexity of modifying agricultural systems to survive in a rapidly changing climate demands interdisciplinary approaches. It is thus my hope that this presentation will foster open discussion and meaningful collaborations to address such challenging societal questions.

How to cite: Garland, G.: Sustainable management of agricultural soils: Balancing multiple perspectives and tradeoffs, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2801, https://doi.org/10.5194/egusphere-egu23-2801, 2023.

EGU23-17578 | Orals | MAL10 | Alina Kabata-Pendias Medal Lecture

Can we clean up the earth? 

Ravi Naidu

Introduction: Contamination causes undue risks to society, ecosystems, water and soil resources, and threatens the viability of many industries1,2. As well as affecting soil, surface water and groundwater, air pollution has been recognised as one of the planet’s most challenging problems. This contamination of the living environment has been linked to 13.7 million deaths a year by the World Health Organisation, almost a quarter of all human fatalities https://www.who.int/data/gho/data/themes/public-health-and-environment). Even more concerning are the nonlethal side effects of global contamination, e.g. the decline in human IQ, the collapse of male fertility, the increase in child developmental and mental disorders etc. which, on a daily basis, adds millions of dollars to medical costs and indeed impacts the quality of human life. Describing contamination’s impact by deaths alone understates the problem. It is the lifelong disabilities and suffering of a growing percentage of the population which is also a core issue. There are hardly any measures in place to minimise these impacts other than some regulatory measures that rarely include all toxins in circulation around the planet.

The extent and severity of air pollution depends on many factors – including population, industrial activities, and measures in place to minimise contamination – and thus varies considerably among and within countries. Although more than $US$2 billion is spent annually to manage or remediate contaminated land and water bodies in Australia, limited funds have been allocated towards the management or remediation of air. Globally, environmental management costs exceed $US750 billion per annum with US $65 to $85 billion of this used for clean-up costs. However, these costs do not include the medical costs linked to many debilitating human health issues confronted in most if not all countries globally.

Globally, it is estimated that there are more than 10 million potentially contaminated sites. Despite growing awareness of the risks of exposure to contaminants, activities that contribute to contamination of our environment are on the increase in many countries as populations grow and industrialisation increases. One reason for this is a lack of adherence to regulatory policies, especially in developing countries, many of which are chronically under-resourced. What is needed are global protocols for restricting the use of toxic chemicals and a global 'contamination IPCC' to oversee and reduce universal contamination. Take a metaphor of IPCC that the climate talk and action has been much visible as a result of forming Intergovernmental Panel on Climate Change (IPCC) in 1988.

The proportion of contaminated sites that are successfully remediated is disconcertingly small. Uncertainties about the nature and extent of contamination can be a major constraint to sustainable development in both urban and rural areas, thereby increasing pressure on the use of limited uncontaminated land. Moreover, many techniques available for in situ or ex situ remediation are prohibitively expensive and thus poorly adopted.1

Unlike point source contamination associated with industrial activities, diffuse pollution, such as that encountered in broadacre or agricultural farmlands, poses a different challenge. Although the risk of direct exposure from soil to person is low, the bioaccumulation of contaminants into crops and subsequent exposure via food consumption poses a major risk to humans and also damages local and international trade. Added to these are the inherent dangers of chemical mixtures, even from innocuous substances. The dangers of chemical mixtures are rarely considered by regulatory jurisdictions and indeed industries linked to contaminants. Also, the absence of information about the toxicity of new and existing chemicals further constrains management of environmental contamination.

Although generally present in low concentrations, diffuse contamination is often difficult and expensive to remediate because it can be spread over very large areas.

Exposure risks: The risks associated with exposure to contaminants vary considerably depending on the source and pollutant matrix. While 4 million deaths per year are linked to soil, water or food contamination, a recent World Health Organization report estimates air pollution poses a much higher risk than other forms of pollution, killing an estimated 6 million people every year. UK estimates suggest that air pollution will make 2.4 million people ill in England between now and 2035 and the healthcare and social costs of air pollution could reach US $23 billion by 2035.3 Air pollution is now seen as the invisible killer. Air pollution is caused almost entirely due to the use of fossil fuels and is expected to decline as they are phased out. Furthermore, environmental management is constrained by the highly leachable nature of soils in countries with sub-humid to humid tropical conditions (compared to soils in USA and Europe), and this limits application of technologies developed elsewhere. To make sound risk and remediation decisions, we need to refine the way we assess risks from contaminants. We need improved data and protocols that provide reliable prediction of exposures and the associated human/eco-impacts. We also need improved monitoring and assessment procedures and instrumentation for contaminants to deliver reliable, accurate data on contaminant presence and fate.

Clean up: The cost of clean-up continues to rise given the challenges of remediating both surface and subsurface contamination. Soil is now seen as a complex heterogeneous system that, once contaminated (especially when coupled with groundwater), is not easily remediated. Furthermore, drastic risk control (e.g. cleaning up sites to background concentrations or to the levels suitable for sensitive land use) is rarely technically or economically feasible. It is thus desirable to apply remedial approaches that reduce the risk of contamination while allowing the soil to remain on site. This approach to site remediation, which is gaining increasing acceptance, is commonly known as risk-based land management.

While clean-up is desirable it does not address and will never solve the overall contamination problem. It treats only one of the symptoms. What is needed is a global treaty to reduce Earth system contamination at source – i.e. to prevent pollution occurring in the first place by not releasing any more untested chemicals, maintaining a global inventory of what is released, and pinpointing major sources of toxicity (e.g. plastics in the home).

While the act of contaminating the environment may itself expend low energy and cost, the complex nature of contaminants – coupled with the heterogeneity of media in which contamination resides, risks and multiple receptors – means that the act of cleaning up is complex and cost- and energy-intensive. Given our planet’s large number of contaminated sites, the fragmented approach along national lines and the slow pace of remediation, it will take many generations to clean up the Earth, and we will never achieve the pristine conditions that existed prior to human civilisation.

Can we clean up the earth? This paper has provided an overview of the extent of global contamination, its risks and impacts, the challenges to remediation, and why a clean Earth is humanity’s next great challenge. The paper has also proposed that an international ‘contamination IPCC’ is necessary to meet this challenge. An international body of this type could champion a coordinated approach to the following issues.

Global issues that need to be considered:
(a)    The development of a comprehensive database and international chemical inventory and improved exposure pathway models that would assist with risk assessment of contaminated sites and air pollution.
(b)    The prioritisation of action for target contaminants/circumstances, especially for recalcitrant contaminants and mixtures in complex environments or where high risks are posed.
(c)    The development of specific remediation techniques relevant to region- or country-specific conditions, and demonstration of those techniques at national scale to encourage uptake.
(d)    The development of a database that provides the basis for a decision-support system on techniques for remediation or management of contaminated sites.
(e)    The availability of highly qualified environmental management and risk assessment graduates.
(f)    Environmental legislators with expertise in assessment and management of site contamination.
(g)    Trained professionals who can assist with the social implications of contaminants.
(h)    A global industry training program to raise industry awareness of the effects of global poisoning (which they ignore) and build a culture of stewardship for dangerous products.

Capacity building: Addressing the issues outlined above will also require a significant effort to build sufficient skilled capacity around the globe. There is strong demand for trained graduates with expertise in not only environmental management but also legal and social issues relating to contaminated soils.

Conclusion: The large number of contaminated sites together with increasing evidence of health effects from the consumption of foods grown on contaminated sites or farms with low level of contamination suggests that there would be considerable benefit in assembling a focussed group of international leaders in the field – through mechanisms such as the globalCARE™ initiative – to tackle these problems on a global scale. Members of this group should have skills to develop technology for (a) assessment of risks, and (b) management or remediation of degraded environments contaminated from both point and dispersed sources. A well-resourced international group such as this, together with a global treaty to reduce contamination at its source, may be able to reverse the trend and in time may well be able clean up the earth.

References

1.    Naidu, R. (2013). Recent Advances in Contaminated Site Remediation. Water, Air, and Soil Pollution. 224(12), 1705.
2.    Naidu, R. et al. (2021). Chemical pollution: A growing peril and potential catastrophic risk to humanity. Environment International. 156, 106616.
3.    Kass, D. (2018). Air pollution kills six million people every year: it's time for us to wake up to this grave threat. The Telegraph, 27 September 2018. www.telegraph.co.uk/news/2018/09/27/air-pollution-kills-six-million-people-every-year-time-us-wake/ 

 

 

 

 

 

 

 

 

How to cite: Naidu, R.: Can we clean up the earth?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17578, https://doi.org/10.5194/egusphere-egu23-17578, 2023.

Growth and death of microorganisms is central to the understanding of almost all global element cycles. To grow, heterotrophic microorganisms need to assimilate organic carbon, and to sustain a flux of readily available organic carbon, they need to depolymerize and deconstruct soil organic matter. When soil organisms die, their remnants become part of the soil organic matter. Thus, the processes that lead to both the decomposition and the accumulation of organic matter in terrestrial environments, are driven by the growth, activity and turnover of heterotrophic microbial communities in soil. Yet, little is known about how microbial growth, turnover, and activity is controlled in the current and in a future climate. In this lecture, I will share insights from a range of experiments that aimed at understanding the effects of soil warming, elevated CO2, and drought, alone or in combination on microbial growth, turnover, and carbon use efficiency. I will draw on examples not only from my own work, but those of others, covering different levels of resolution, from the growth of microbial communities to that of individual bacterial taxa. I will argue that activity, growth, and turnover of microorganisms are the fundamental units of biogeochemical functioning in soils and that we need to move beyond the commonly reported metrices in soil ecology, and even beyond measuring rates of decomposition and mineralization themselves, if we are to understand the effects of climate changes on soil processes.

How to cite: Richter, A.: What controls carbon and nutrient cycling in soil? Microbial growth as the fundamental driver of soil biogeochemistry., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10907, https://doi.org/10.5194/egusphere-egu23-10907, 2023.

SSS0 – Inter- and Transdisciplinary Sessions

High urbanization rate and climate change are the main drivers of urban floods in developing countries. The increase in urban flooding incidents has become a significant threat to cities, which also result into considerable losses of life and the economy. Adapting to the risks of a changing climate and ill-effects of urbanization is imperative for national and local governments. This calls for a functionally and structurally resilient urban drainage infrastructure. Functional resilience is the coping capacity of system against external threats such as urbanization and climate change, whereas structural resilience is the resilience against internal failures such as blockage of inlets or sewers, structural damage of a pipe, bed load sediment deposition, asset aging/decay, and sewer collapse. This work aims to understand the impact of nature-based solutions on urban drainage resilience. Various researchers have identified Low Impact development (LID) practices as a potential solution to enhance drainage systems' resilience. LID can be defined as a land development and retrofit strategy that emphasizes the protection and use of distributed interventions to reduce the volume and rate of stormwater runoff from a developed landscape. In the present study, the green roofs and rain gardens are simulated in a part of Gurugram city of India using the Storm Water Management Model (SWMM) 5.2. Sensitivity analysis is conducted to overcome the problem of a lack of in-depth data to perform model calibration and validation. The simulations were carried out by developing various scenarios for functional and structural resilience assessment. The results indicate that if 25% of potential subcatchments are deployed with LIDs, functional resiliency of the system enhances by 25%, and structural resilience of vulnerable nodes decreases by 17%.  The study reveals that introduction of LIDs aids into enhancing the functional resilience of the system rather than structural resilience. This research provides evidence of LIDs' positive influence on the resilience performance of drainage systems. Overall, the study can help urban planners and drainage management engineers to develop understanding on LIDs role vis-à-vis city's resilience to urban flood problems.

How to cite: Mehta, O., Kansal, M. L., and Bisht, D. S.: Integrating Green and Grey Infrastructure for Resilience Enhancement of Conventional Urban Drainage System and its Evaluation through Modeling, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-137, https://doi.org/10.5194/egusphere-egu23-137, 2023.

EGU23-569 | ECS | Posters on site | ITS3.4/SSS0.1

The positive effect of Nature-based Solutions for achieving the Sustainable Development Goals in Mediterranean agroecosystems: a meta-analysis  

Miguel Rodrigues, Luís Filipe Antunes Dias, and João Pedro Carvalho Nunes

The increasingly frequent impacts of climate change in the Mediterranean region challenge the resilience and sustainability of the region's agroecosystems. In this context, Nature-based Solutions (NbS) emerge as a sustainable strategy to address climate change adaptation and mitigation. Extensive literature focuses on the analysis of NbS to address this problem, although no analysis discriminates against the individual and combined effect of NbS in agroecosystems. In this work, we capitalize on state-of-the-art results and present a random-effects meta-analysis of NbS. Our analysis focuses on a cohort of 80 NbS for agricultural land management, such as conservation tillage practices, soil-improving cropping systems, organic amendments and fertilizers, and landscape solutions. We used response ratios as effect sizes to determine the most suitable NbS for improving soil health. We built a database with field-scale data from 70 published case studies comparing NbS and conventional agricultural management practices in agroecosystems in 12 countries with a Mediterranean climate. Our analysis results from a literature selection of 988 scientific articles published from 2019 to 2022. We have analyzed the combined effect that NbS have on soil's ability to retain water, organic matter, and carbon and to reduce soil loss. To further understand the influence of abiotic factors, we also analyze the impact of precipitation, soil texture, and irrigation systems on the effects of NbS. These results shall contribute to leveraging climate change adaptation in Mediterranean agroecosystems, addressing land and water-related Sustainable Development Goals (SDGs).

How to cite: Rodrigues, M., Antunes Dias, L. F., and Carvalho Nunes, J. P.: The positive effect of Nature-based Solutions for achieving the Sustainable Development Goals in Mediterranean agroecosystems: a meta-analysis , EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-569, https://doi.org/10.5194/egusphere-egu23-569, 2023.

EGU23-934 | Posters on site | ITS3.4/SSS0.1 | Highlight

Towards implementation of hybrid solutions for flood risk management under climate change 

Nejc Bezak, Mojca Šraj, Pavel Raška, Lenka Slavikova, and Jiri Jakubínský

Climate change is expected to affect the frequency, magnitude, and seasonality of several rainfall-related hazards, including flooding as one of the costliest hazards in Europe. Recent studies have shown that flood risk in Europe is both increasing and decreasing, with increases in most eastern and southern European countries, including Slovenia and Czechia. In addition, significant changes in the seasonal occurrence of floods have also been observed in Europe, thus challenging conventional approaches to flood risk management.

As natural hazards have major impacts on infrastructure, human lives, and habitats, and cause large social and economic damages, it is clear that adaptation measures aimed at both prevention and mitigation of impacts must be considered to cope with climate change. To deal with the changing occurrence and characteristics of floods, different types of measures need to be adopted, including green, blue, and grey measures or combinations of these. Although their application is currently emphasized, purely green or blue-green measures in some cases may not be insufficient to cope with predicted future climate hazards. Additionally, implementation of such measures often encounter resistance in planning departments and among decision makers due to institutional path dependency related to the history of utilizing grey infrastructure measures. This is especially the case for some Central-Eastern European countries. An alternative are hybrid solutions that combine parts of grey and green infrastructure, since these kinds of measures can reflect the variety of environmental conditions. However, not much attention has been given to the documentation and evaluation of hybrid infrastructure in comparison to purely green measures. Hence, there are still several open questions related to the implementation and functioning of solutions combining elements of green and grey measures, so called hybrid solutions.

The main objective of this contribution is to present the theoretical framework, research design and initial research steps of a newly launched international project focusing on: (i) enhancement of documentation and standardization related to hybrid solutions, (ii) development and testing of applicability and social acceptability of specific hybrid infrastructure in different environments and climate change scenarios, and (iii) environmental modelling and evaluation of effectiveness of different measures from the perspective of the flood risk management. Within the project, the effects of hybrid solutions on flood hazard and hydrological regime of the landscape will be modelled for selected small catchments in Slovenia and Czechia, but the standardization of hybrid solutions will enable to extrapolate our results beyond Central and Eastern Europe.  

Acknowledgment: The research was conducted within the project [Evaluation of hazard-mitigating hybrid infrastructure under climate change scenarios] co-granted by Slovenian Research Agency (J6-4628) and Czech Science Foundation (22-04520L). 

How to cite: Bezak, N., Šraj, M., Raška, P., Slavikova, L., and Jakubínský, J.: Towards implementation of hybrid solutions for flood risk management under climate change, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-934, https://doi.org/10.5194/egusphere-egu23-934, 2023.

Recent disasters have demonstrated the challenges faced by our global society because of the increasing complexity of disasters caused by natural hazards. For example, a community hit by a natural hazard while still recovering from the impacts of an earlier hazard faces many different challenges than when it is hit by a single hazard that occurs in isolation. With growing awareness of this complexity and its impact on disaster risk, there has been a push, from scientists as well as international organizations such as the UNDRR, for disaster risk research to account for these complexities. This research has aimed to take an increasingly integrated approach, often bridging across individual hazard types to accomplish a more comprehensive understanding of overall risk.

 

Incorporating spatiotemporal dynamics of all risk components (i.e., hazards, exposure, and vulnerability) is key to accurately modelling compound and multi-hazard risk events. There is great potential to better capturedynamics between and within risk components by learning from common approaches and methods used in different research communities. For example, recent years have seen a growing attention for research into compound hazards and hazard drivers using methods such as storylines, agent-based models, and system dynamics, all novelties for this field of research. An important, less studied aspect is that of the dynamics of vulnerability. Many of these once-novel methods now applied in compound hazard research have the potential to improve modelling capabilities of other compound risk aspects, such as vulnerability dynamics. This talk will highlight recent developments in assessing the complexities of disaster risk and discuss potential opportunities to further advance our modelling capabilities through multidisciplinary exchanges.

How to cite: de Ruiter, M.: The challenges of risk dynamics and how to assess them, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1243, https://doi.org/10.5194/egusphere-egu23-1243, 2023.

In Mediterranean areas, rainfall is one of the main variables affecting the control of eco-geomorphological processes. Water erosion processes, sealing and degradation of soils, reduction of the amount of water available for vegetation, modification of hydrological regimes can be cited among the most remarkable. Thus, the modifications in climatic variables resulting from Global Change are having an impact on the Mediterranean eco-geomorphological system, especially issues associated with water risks. Specifically, a dual pattern can be observed: on the one hand, a notable increase in the recurrence of the number of torrential events and an increase in the risk of water erosion, and on the other hand, an increase in the intensity or frequency of droughts, determining productivity and ecological and economic values due to the reduction in the availability of water in the soil. In this context, the research has focused on a traditionally agricultural territory that is highly fragile to these processes, namely GIAHS (Globally Important Agricultural Heritage Systems) dedicated to the raisin production in the Axarquia (Malaga, Spain). The main objective has been to (i) assess the impact of the most important water risks and (ii) identify the main Nature-based Solutions (NbS) implemented as adaptive mechanisms that have been implemented to ensure food security and the sustainability of these areas. To achieve these objectives, the rainfall dynamics have been statistically analysed with the data downloaded from nine meteorological stations of the SAIH Hidrosur Network located in the region (1997-2021). In addition, a total of 60 soil samples have been collected and analysed for the estimation of soil water erosion rates, based on the RUSLE model, and for the evaluation of its hydrological dynamics in recent decades. Finally, the NbS identified in the study area have been qualitatively assessed and analysed from an ecosystemic and agricultural approach. The results show an increased water stress in this GIAHS area according to the projections published by the latest IPCC report for the Mediterranean region. A slight tendency to concentration and increased rainfall erosivity is detected, as well as a lower water availability in soil for crop phenology. Similarly, soil erosion rates show very high values, with slopes exceeding 250 t ha-1 year-1) However, agricultural practices and the different structures identified have been determinant in the control of these natural risks, being considered as sustainable adaptation strategies and conforming as NbS.

How to cite: Sillero-Medina, J. A. and Ruiz-Sinoga, J. D.: Nature-based solutions to address water threats in the Mediterranean region. A characterisation of the GIAHS area of Axarquia (Málaga, Spain), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1521, https://doi.org/10.5194/egusphere-egu23-1521, 2023.

EGU23-1871 | ECS | Orals | ITS3.4/SSS0.1

Seaweed as a resilient food solution in nuclear winter 

Florian Ulrich Jehn, Farrah Jasmine Dingal, Aron Mill, Ekaterina Ilin, Cheryl Harrison, Michael Y. Roleda, and David Denkenberger

Abrupt sunlight reduction scenarios such as a nuclear winter, an asteroid impact or an eruption of a supervolcano would decimate agriculture as it is practised today. We therefore need resilient food sources for such an event. One promising candidate is seaweed, as it can grow quickly in a wide range of environmental conditions. To explore the feasibility of seaweed in a nuclear winter, we simulate the growth of seaweed on a global scale using an empirical model based on Gracilaria tikvahiae forced by nuclear winter climate simulations. We assess how quickly global seaweed production could be scaled to provide a significant fraction of global food demand. We find seaweed can be grown in tropical oceans, even in nuclear winter. The simulated growth is high enough to allow a scale up to an equivalent of 70 % of the global human caloric demand, while only using a small fraction of the global ocean area. The results also show that the growth of seaweed increases with the severity of the nuclear war, as more nutrients become available due to upwelling. This means that seaweed has the potential to be a viable resilient food source for abrupt sunlight reduction scenarios. 

How to cite: Jehn, F. U., Dingal, F. J., Mill, A., Ilin, E., Harrison, C., Roleda, M. Y., and Denkenberger, D.: Seaweed as a resilient food solution in nuclear winter, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1871, https://doi.org/10.5194/egusphere-egu23-1871, 2023.

EGU23-2659 | Posters on site | ITS3.4/SSS0.1

Sustainability of Pastoralism: Climate Change Risk to Rangelands in Eurasia 

Banzragch Nandintsetseg, Jinfeng Chang, and Omer L. Sen

Climate change is projected to increase the aridity of semi-arid ecosystems, including Eurasian rangelands (EAR), which provide ecosystem services that support food supply and pastoralist lifestyles. Climate hazards are expected to become more frequent and intense, leading to the most significant risk to pastoralists and impacting their future sustainability. There is an urgent need for research-based interventions that can help herder communities adapt to future risks. However, rigorous impact assessments of climate change on pastoralism-based livelihoods considering region-specific socioeconomic changes in the Eurasian Drylands are relatively neglected research areas with limited knowledge. Thus, we assess the climate change risk to rangelands in Eurasia under regional grazing patterns and intensity across EAR spatial domain (34−56◦ N, 20−130◦ E: West Asia, Central Asia and East Asia) during 1971–2100. We conducted a grid-scale (0.5 °× 0.5°) probabilistic risk assessment of EAR in the context of climate change based on probability theory. Risk is quantified as the product of the probability of a hazardous drought and vulnerability of the ecosystem. The probability of hazardous drought is defined by the Standardized Precipitation–Evapotranspiration Index. Vulnerability is defined as the expected difference in key ecosystem variables between years with and without hazardous conditions. The ecosystem variables were productivity (aboveground biomass, net primary productivity, soil carbon, and leaf area index) and plant-available soil moisture in the root zone, simulated with a process-based ecosystem model ORCHIDEE-GM (Organizing Carbon and Hydrology in Dynamic Ecosystems-Grassland Management) validated with field observations of biomass and soil moisture. Climate data were based on gridded observations and projections of CMIP6 the Coupled Model Intercomparison Project Phase 6) using scenarios ssp1-2.6, ssp3-7.0, and ssp5-8.5. Historical land-use data were based on the number of province-based livestock during 1971–2019. The constant value of 2019 is used to simulate the future impact of grazing on EAR. The results revealed that EAR experienced more frequent hazardous droughts with rapid warming and slight drying during 1971−2020, aggravated by increasing grazing intensity, which resulted in a reduction in soil water availability and grassland productivity, particularly in northeastern areas. In the future, climate change will lead to increased droughts in the EAR under these three scenarios. These great drought hazards increase the risk of rangeland productivity in the EAR, particularly in the western and southern parts of Central and Eastern Asia.

How to cite: Nandintsetseg, B., Chang, J., and Sen, O. L.: Sustainability of Pastoralism: Climate Change Risk to Rangelands in Eurasia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2659, https://doi.org/10.5194/egusphere-egu23-2659, 2023.

As a vital element of public spaces, trees in urban settings are acclaimed to offer numerous social and environmental benefits, making them a quintessential nature-based solution for a more sustainable city. While carbon sequestration, air quality, and urban heat island mitigation benefits have long been acknowledged, less emphasis is directed to utilizing the hydrologic function of trees in terms of stormwater runoff reduction in the urban environment and this benefit is often underutilized. For urban areas with high proportions of impervious surfaces, increasing the percentage of tree canopy cover and green spaces is crucial in restoring the natural functioning of the ecosystem and water cycle. Within the framework of our ongoing research, we are investigating the positive impacts of trees (i.e., single tree elements, forests) as nature-based solutions on the urban water cycle using field measurements of rainfall partitioning, runoff, soil moisture, and infiltration from experimental catchments in the city of Ljubljana, Slovenia which started on August of 2021. Preliminary results revealed that open-grown birch (deciduous) and pine (coniferous) tree canopies intercepted a relative amount of gross rainfall with pine trees having a greater interception capacity. The following trees also modified the drop size distribution (e.g., drop number, diameter, fall velocity) of below-canopy rainfall before reaching the ground, thus attenuating the mean and maximum 10-minute rainfall intensities by 42-50% and 40-44%, respectively, depending on canopy phenoseasons. Such reduction in the intensity of rainfall has a significant effect on the peak water level of event runoff which could provide important information for understanding the runoff generation process. Moreover, this benefit with the root system of trees has a positive impact on the condition and structure of soils in urban areas promoting infiltration, preferential flow, and soil water recharge. In addition to this, tree canopies also dampen the average kinetic energies of rainfall to cause soil erosion by 34%. These initial findings suggest that the hydrological benefits of trees in the urban environment are adequate to warrant a further investigation into their potential to regulate the flow mechanisms of stormwater runoff and reduce urban pluvial flooding. Thus, it is also imperative to explore how the integration of trees interacts with other stormwater control measures and how this interaction could leverage their functions. This will deliver invaluable information to urban planners, landscape designers, stormwater management experts, and decision-makers on the need to expand the efforts of urban greening to address the associated adverse impacts of rapid urbanization and various environmental challenges.

 

Acknowledgments: Results are part of the CELSA project entitled “Interception experimentation and modelling for enhanced impact analysis of nature-based solution” and research programmes and projects P2-0180, J6-4629, and N2-0313 financed by the Slovenian Research Agency (ARRS).

How to cite: Alivio, M. B. and Bezak, N.: Role of trees as part of the nature-based solutions in cities and their effects on stormwater runoff generation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3140, https://doi.org/10.5194/egusphere-egu23-3140, 2023.

EGU23-3378 | ECS | Orals | ITS3.4/SSS0.1

Negative year-to-year agricultural yield extremes projected to occur more frequently under global warming 

Leonard Borchert, Anton Orlov, Jonas Jägermeyer, Christoph Müller, and Jana Sillmann

Studies on projected agricultural yields focus on end-of-century scenarios. Simulations from the Global Gridded Crop Model Intercomparison (GGCMI) Project phase 3b show conflicting results for global and regional changes of different crops by the end of the century. Here, we interrogate the same simulations, focusing on year-to-year variations of agricultural yields in the important staple crops maize, rice, soybean and wheat.

An ensemble of GGCMI models shows a larger agreement on the variations of crop yields than for the long-term trend. Year-to-year variations of projected crop yields become more pronounced over time, especially so for negative crop yield anomalies. As a result, the frequency of negative global crop yield extremes increases with global warming. We show that these negative yield extremes may occur for individual or multiple crops at the same time, and may originate from individual or multiple regions. North America dominates global maize and soybean yield extremes (57% and 44% of all significant global extremes, respectively), and South East Asia and South Asia are important for rice extremes (24% and 22%, respectively), while regional results are inconclusive for wheat. Multi-crop extremes occur most commonly for the combination of maize and soybean, and are dominated by the North America region. Based on these findings, we show that depending on the region and crop, persistent spring or summer drought, cold or heat can be associated with years of global and regional negative agricultural yield extremes.

Our results show how specific climatic boundary conditions can lead to year-to-year extremes in important staple crops, highlighting the potential to anticipate such events in the future.

How to cite: Borchert, L., Orlov, A., Jägermeyer, J., Müller, C., and Sillmann, J.: Negative year-to-year agricultural yield extremes projected to occur more frequently under global warming, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3378, https://doi.org/10.5194/egusphere-egu23-3378, 2023.

In light of the hysteresis and acceleration of the climate crisis, climate overshoot has only recently been acknowledged as inevitable. As the IPCC belatedly reports, current pledges are not even remotely on track to limit global warming to 1.5°C above pre-industrial levels (Anderson 2015, IPCC 2018). Further, no amount of future emissions reductions can suffice to avert climate overshoot. Hence, this presentation critically analyses the proposition that a climate change technofix – namely Negative Emission Technologies (NETs) – is the only potentially efficacious means to avert runaway climate change (Carton 2020, Reynolds 2015).

However, not only is the efficacy of NETs to reduce sufficient greenhouse gas concentrations highly dubious, but any such technofix requires gambling on a host of unknown unknowns – namely, the inexorable complexity of the Earth System, coupled with planetary-scale interventions in the crisis. Therein, this presentation explores the linkages between extreme climate and societal dynamics surrounding risk, offering a theoretical study from the fields of social sciences and humanities as to the non-linearity of cascades and feedbacks between the biosphere and society.

To do so, I put forth a critique of how normative ethics remains anchored in rigid positions of anachronistic risk aversion, given how any attempted climate technofix entails unprecedented realms of risk and uncertainty. Using the frameworks of the Environmental Humanities, and Science & Technology Studies, I critically engage with the risk ethics of imminent climate overshoot, in relation to the interventionist gambles proposed by NETs through Synthetic Biology and Climate Engineering. Given the scale of the unknown unknowns unleashed by the Anthropocene, I present gambling as the most apt analogy for both the absurdity (and denied imminence) of the existential predicament, as well as the sheer improbability that any technofix can be invented in a sufficiently short time and implemented on a sufficiently large scale.

Given the profound social, cultural and ethical dimensions that this entails, discussion will include an overview of outreach activities I have undertaken as a Chief Investigator at the Australian Research Council Centre for Excellence in Synthetic Biology, including the At Risk in the Climate Crisis symposium and podcast series that I co-produced in 2021-22. Overall, in the context of the rapidly diminishing prospect for any efficacious environmental action, the presentation contemplates the unthinkable questions that our current situation demands we ask, and perhaps even try to answer.

How to cite: Wodak, J.: The Non-Linearity of Cascades and Feedbacks Between The Biosphere and Society: Risk Ethics for a Climate Change Technofix, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3746, https://doi.org/10.5194/egusphere-egu23-3746, 2023.

EGU23-4088 | ECS | Posters on site | ITS3.4/SSS0.1

Analysing Trade-Offs between Safety from Tsunamis Risk and Views of Ocean Water Using an Optimal Residential Area Model 

Fuko Nakai, Tatsuya Uchiuzo, Kazuaki Okubo, and Eizo Hideshima

Disaster risk reduction has become an increasingly prominent concern in urban planning due to recent catastrophic disasters such as the Great East Japan Earthquake in 2011. Building levees or relocating to higher ground are measures used to reduce the risk of tsunamis. However, if those measures are implemented too extensively, they may obstruct views of coastal water that benefit residents. Environments where residents can visually access the waterfront are crucial for promoting awareness of river and disaster risk reduction and repairing the way we interact with nature. However, in Japan, safety has frequently been prioritized by ignoring the views of coastal water that may be lost.

This study developed an optimal residential area model for analysing the trade-offs between safety from tsunamis and views of coastal water (hereafter, ocean views), which will be able to support detailed urban planning. The model comprises weighted multicriteria, that is, the total tsunami risk and ocean views with controlling optimal allocations of population. Here we optimized “Improved Potential Achievement (IPA).” This indicated the extent to which the respective optimal value achieved has been achieved against the value (improved potential) of the two objectives being optimized alone as a baseline. 

We used the viewshed analysis to quantify ocean views. The analysis used the elevation value of each cell of the digital elevation model (DEM) to determine the visibility of a particular point of the ocean from a specific residential mesh. Using the visibility between specific locations, we conceptualized the index of “the ocean view presence” and “the width of the ocean view”. The ocean view presence expresses how many locations in a particular residential mesh have an ocean view. Meanwhile, the width of the ocean view expresses whether people have a panoramic view of the open ocean or whether they can only see a small area of ocean. We quantified ocean views using these indices.

We applied the model to Kuroshio, a tsunami-prone area along the Nankai Trough in Japan and the optimal residential area is calculated for each 500-meter mesh. The results of the sensitivity analysis that changed the weight β (0<β<1) of the safety from tsunami criteria showed trade-offs in which the more safety from tsunami risk is weighted, the more the view of ocean water in the target area is reduced. If weight β is larger than 0.7, ocean views decreases steadily. This is a case study of a specific area and such results are not spatially consistent in all areas. However, similar trade-offs are likely to be obtained in areas with the ocean and mountains in close proximity. This analytical technique is likely to be useful in pre-disaster recovery planning that explores induction-encouraged residential areas that benefit safety from tsunamis and ocean views.

How to cite: Nakai, F., Uchiuzo, T., Okubo, K., and Hideshima, E.: Analysing Trade-Offs between Safety from Tsunamis Risk and Views of Ocean Water Using an Optimal Residential Area Model, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4088, https://doi.org/10.5194/egusphere-egu23-4088, 2023.

EGU23-4262 | Posters virtual | ITS3.4/SSS0.1

Governance Innovations for Nature-based Solutions from Translocal Networks 

Rui Shi and Haozhi Pan

Environmental governance innovation, especially nature-based solutions (NbS), is gaining scholarly attention over the past years due to issues including urban expansion and climate change. Most existing studies of such innovation focus on national, provincial or single city level, while few explore the translocal interactions among urban agglomeration levels. This paper illustrates the process of emergence and adoption of environmental governance innovations in the context of NbS. Furthermore, this paper analyzes the contributing factors of the innovation processes with particular focus on the role of translocal governance networks that involves the center and local governments, urban agglomeration networks and non-governmental actors.

Event history analysis is used to understand the sources and processes of environmental innovation generation and adoption. Environmental innovation event history is established via obtaining policy documents published on government portals across the country and case reports published by mainstream media from 2011 to 2021. Then, we use the pooled regression model to explain the probability of innovation being generated or adopted to analyze the contributing factors of environmental governance innovation in urban agglomeration. Vertical, horizontal, internal and external interactions are measured and used to explain the processes with other explanatory variables including political factors, economic factors, and other socioeconomic covariates. The following results are expected. First, environmental governance innovations mostly originate from external factors, such as breakthrough of environmental technology and global environmental alliances, and are generated from both central and provincial government. Second, the probability of innovation adoption is positively correlated with interactions across and within urban agglomeration, and the frequencies of vertical, internal and external interactions, and significantly negatively correlated with horizontal interaction factors. Third, economic and educational factors are expected to have the most significant influence on the probability of innovation generation; among social factors, population density could be negatively correlated with the probability of innovation generation. The findings of this study can further optimize relationship between local actors and governance structure to promote environmental governance innovation.

How to cite: Shi, R. and Pan, H.: Governance Innovations for Nature-based Solutions from Translocal Networks, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4262, https://doi.org/10.5194/egusphere-egu23-4262, 2023.

EGU23-4599 | ECS | Orals | ITS3.4/SSS0.1

A multiple-benefit framework for implementing nature-based solutions using conservation finance 

Tessa Maurer, Kimberly Seipp, Micah Elias, and Phil Saksa

Sitting at the intersection of knowledge production and project implementation, our work as conservation finance project developers leverages economic and other benefits of environmental restoration to attract new and diverse funding sources for nature-based solutions (NBS). Our work supports project activities ranging from variable density thinning and prescribed burning to low-tech and process-based riparian restoration. In our experience, NBS presents a powerful, cost-effective opportunity to create scaled improvements in ecosystem function. However, funding NBS projects can be challenging, as some NBS outcomes are only achieved through large-scale landscape restoration, which is expensive, or are realized gradually over a period of time following restoration activities. Conservation finance is one tool that can catalyze meaningful NBS work at scale by providing the necessary upfront capital for projects while contracting funding commitments based on outcomes over time. Using several examples of successful NBS projects, we present a process-based, multiple-benefit framework to demonstrate how NBS can be leveraged to increase funds and enable financing. This framework is grounded in western U.S. forest management to address catastrophic wildfire, but can be applied in other regions and for other types of restoration activities. This approach addresses the logistical, governance, and sociocultural challenges we have encountered to leveraging NBS within a conservation finance framework. We also propose future avenues of research to help increase investment based on NBS. These include formalizing metrics for measuring and monitoring of different NBS activities, managing the uncertainty and expectations around outcomes of NBS projects, and incorporating the future impacts of climate change into NBS models and planning. By describing this work in a U.S. context, we hope to catalyze a discussion about how the needs and opportunities identified in our projects can inform work in Europe and vice versa.

How to cite: Maurer, T., Seipp, K., Elias, M., and Saksa, P.: A multiple-benefit framework for implementing nature-based solutions using conservation finance, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4599, https://doi.org/10.5194/egusphere-egu23-4599, 2023.

EGU23-4835 | Orals | ITS3.4/SSS0.1

Extreme rainfall reduces one-twelfth of China’s rice yield 

Yiwei Jian, Jin Fu, Xuhui Wang, and Feng Zhou

Extreme climate events constitute a major risk to global food production. Among these, the extreme rainfall is often dismissed from historical analyses and future projections, whose impacts and mechanisms remain poorly understood. Here, we find that rice yield reductions due to extreme rainfall in China were comparable to those induced by extreme heat over the last two decades, reaching 7.6 ± 0.9% (one standard error) according to nationwide observations and 8.1 ± 1.1% according to the crop model incorporating the mechanisms revealed from manipulative experiments. Extreme rainfall reduces rice yield mainly by limiting nitrogen availability for tillering that lowers per-area effective panicles and by exerting physical disturbance on pollination that declines per-panicle filled grains. Considering these mechanisms, we projected ~8% additional yield reduction due to extreme rainfall under warmer climate by the end of the century. These findings demonstrate the critical importance to account for extreme rainfall in food security assessments, posing greater challenges to climate change adaptation.

How to cite: Jian, Y., Fu, J., Wang, X., and Zhou, F.: Extreme rainfall reduces one-twelfth of China’s rice yield, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4835, https://doi.org/10.5194/egusphere-egu23-4835, 2023.

Given observed and predicted increases in the frequency and intensity of many climate extremes, researchers have shown an increased interest in the climate extremes and their impacts on ecosystems because of the profound effects. However, most previous studies on the responses of ecosystems to climate extremes focus on droughts and summer heatwaves, and relatively little is known about the effects of other kinds of extremes, such as winter heatwaves, extreme wet periods, and cold waves.

In this study, we identify four types of extremes (two temperature (heatwaves and cold waves) and two precipitation ones (droughts and extreme wet periods)) and present 4 alternatives to identify compound extreme events. We demonstrate the relevance of the different types of year-round (compound) events for ecological studies by demonstrating their impact on the abundance of 34 UK butterfly species across each species' life stages (hibernation, egg, larval, pupal, and adult) over a 45-year period. We chose this example as these species are expected to respond rapidly to climates due to their ectothermic nature and short life cycles.

The results show that considering different types of year-round (compound) extreme events is relevant from an ecological point of view as at different stages, other extremes have more impact on the survival of individuals. For instance, statistics show that heatwaves and droughts during the pupal and adult stages appear beneficial for butterflies in England, with around 30% of univoltine species showing significant positive influences, whereas extreme wet periods during the pupal life stage cause negative population change for 26% of univoltine species. Our study demonstrates that considering different forms of extremes during all seasons of a year may bring interesting new insights for ecologists. However, we did not seek any eco(fysio)logical explanations of the obtained results.

How to cite: Shan, B., De Baets, B., and E.C. Verhoest, N.: Four alternative ways to identify compound climate extremes and their relevance to ecological impacts: a case study of UK butterflies, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5001, https://doi.org/10.5194/egusphere-egu23-5001, 2023.

EGU23-5017 | Orals | ITS3.4/SSS0.1

Accounting for systemic complexity in the assessment of climate risk 

Jakob Zscheischler and Seth Westra

Widespread changes to climate-sensitive systems are placing increased demands on risk assessments as a key for managing climate risk, enabling adaptive responses and enhancing system resilience. Although the complex, uncertain and ambiguous nature of climate-sensitive systems has been long recognised, recent attention on concepts such as compounding and cascading risks, deep uncertainty and ‘bottom-up’ risk assessment frameworks have stressed the need to more explicitly confront the overarching theme of systemic complexity. Drawing on insights from the field of systems thinking, we provide a theoretical foundation for addressing systemic complexity when assessing climate risks. We first describe the sources of systemic complexity as they pertain to climate risk, and highlight the role of climate risk assessment as a formal sense-making device that enables learning and the organisation of knowledge of the interplay between the climate-sensitive system and its (climatological) environment. We then highlight boundary judgements as one of the core concerns of risk assessment, acting as a filter of both information and value judgements, and thereby creating islands of analytical and cognitive tractability in a complex, uncertain and ambiguous world. Yet boundary judgements necessarily result in partiality, leading to the need for boundary critique, which emphasises the need of multi-methodologies and second-order learning processes as part of standard risk assessment practice. We build these concepts into a framework that divides climate risk assessments into five distinct but interrelated concerns or ‘problematics’ that collectively can be used as a starting point for managing systemic complexity in the assessment of climate risk. 

How to cite: Zscheischler, J. and Westra, S.: Accounting for systemic complexity in the assessment of climate risk, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5017, https://doi.org/10.5194/egusphere-egu23-5017, 2023.

EGU23-5754 | Orals | ITS3.4/SSS0.1

NBS implemented in the Pyrenees during the PHUSICOS project 

Anders Solheim, Didier Vergès, Santiago Fabregas, Laurent Lespine, Carles Räimät, Eva Garcia, Amy Oen, Bjørn Kalsnes, and Vittoria Capobianco

The H2020 project PHUSICOS designs and implements NBS for DRR at demonstrator case sites in rural areas of Norway, Italy, and in the French and Spanish Pyrenees. This presentation covers four locations in the Pyrenees, where NBS to reduce risk from snow avalanches, rockfall and debris flows are implemented. Snow avalanches from the steep slopes of the Capet Forest threaten the French village of Barèges. The NBS here consist of afforestation in the release areas. 5000 trees have been planted in groups of 30-50, protected behind wooden tripods, which also act as protection structures until the trees are large enough to stabilize the snowpack. Rockfall poses a severe hazard at two locations along the important road A-136 / RD-934 between France and Spain. At St. Elena, Spain, the rocks are released by erosion of a slope in a thick till deposit. The implemented NBS consists of vegetated terraces, built up by a dry masonry wall and gabions constructed from wood and filled with the local till. At the location in Artouste, France, rockfalls in the steep slope are released from exposed ledges and from loose blocks in the till surface. The measures here consist of wooden stabilising and retaining structures for each individual ledge or block. These solutions are also tested at newly established laboratory and full-scale test facilities in Spain and France, respectively. The fourth location is near the Spanish village Erill-la-Vall, where debris flows from a >50m thick till deposit pose the threat. Several gullies feed the main debris flow path towards the village during periods of extreme precipitation. The implemented solution is a series of terraces, built up by local rocks and whole-log gabions in the lower parts of the gullies. These will prevent deepening of the erosional base and form increased rugosity in the debris flow paths. The site has been monitored during the last 15 years. In-situ borehole (piezometer) data shows two processes: a deep-seated (15-20 m) failure level, which reacts up to two weeks after a period of heavy rain, and shallow erosion, which reacts almost immediately as a direct response to heavy precipitation. The implemented NBS are primarily to mitigate against the latter process.

The NBS described here all have large upscaling potential, as there are numerous locations in the Pyrenees and elsewhere with similar problems. Terracing and afforestation for slope stabilization is not a new concept but is here re-vitalized in cooperation with stakeholders through Living-Lab processes. These processes have also helped overcoming challenges related to land ownership issues and permissions to operate, e.g., in national parks, which have caused implementation delays. Monitoring of the implemented measures, focused on both the resilience aspect and, not the least, the NBS' co-benefits will be important for building up an evidence-base for the functionality of NBS for DRR.

How to cite: Solheim, A., Vergès, D., Fabregas, S., Lespine, L., Räimät, C., Garcia, E., Oen, A., Kalsnes, B., and Capobianco, V.: NBS implemented in the Pyrenees during the PHUSICOS project, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5754, https://doi.org/10.5194/egusphere-egu23-5754, 2023.

EGU23-6712 | ECS | Orals | ITS3.4/SSS0.1

Deriving targeted intervention packages for ecosystem-based adaptation: A geospatial multi-criteria approach for building climate resilience in the Puna region, Peru. 

Oscar Higuera Roa, Davide Cotti, Natalia Aste, Alicia Bustillos-Ardaya, Stefan Schneiderbauer, Ignacio Tourino-Soto, Francisco Roman-Dañobeytia, and Yvonne Walz

Emergent dynamic climate risks challenge conventional approaches for climate adaptation and disaster risk reduction. This situation demands new ways of addressing climate risks with integrated solutions. However, little attention has been paid to exploring methodological approaches for combining adaptation measures to reduce climate risks. Still, selecting the appropriate and effective combination of adaptation measures is a challenging task. This research results in a geospatial multi-criteria approach for developing ecosystem-based adaptation packages to face climate change effects and applies this innovative methodology to a case study area in the Puna region in Peru. We started with an in-depth literature analysis combined with a participatory process with local experts to identify and select locally valid adaptation measures for the specific context of the case study area. Building upon that, we developed the overall multi-criteria approach consisting of a matrix-based procedure to evaluate the applicability of relevant adaptation measures and their feasibility of being combined in adaptation packages. We then integrated the multi-criteria analysis into a Geographic Information System using a spatial analysis model to map suitable intervention areas. Next to the methodological innovation, we applied this multi-criteria approach in the case study area to generate a place-based adaptation package for addressing the risk of reduced water provision, with its respective potential intervention sites differentiated by adaptation measure. This methodological approach is novel and considered an affordable support tool that helps practitioners design more robust and effective adaptative interventions. Furthermore, this methodological approach involves shifting the perspective from activities focused on "single adaptations" to "multi-solution" strategic interventions that address climate risks more comprehensively, recognizing the dynamics and complexities of the social-ecological systems. We encourage researchers and practitioners to transfer the methodological approach to other contexts and, with that, accelerate the efficient and targeted implementation of nature-based solutions for climate resilience.

How to cite: Higuera Roa, O., Cotti, D., Aste, N., Bustillos-Ardaya, A., Schneiderbauer, S., Tourino-Soto, I., Roman-Dañobeytia, F., and Walz, Y.: Deriving targeted intervention packages for ecosystem-based adaptation: A geospatial multi-criteria approach for building climate resilience in the Puna region, Peru., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6712, https://doi.org/10.5194/egusphere-egu23-6712, 2023.

EGU23-7906 | ECS | Orals | ITS3.4/SSS0.1

Connected urban green spaces for pluvial flood risk reduction in the Metropolitan area of Milan 

Andrea Staccione, Arthur Hrast Essenfelder, Stefano Bagli, and Jaroslav Mysiak

Rethinking cities in a more sustainable and integrated way is a key opportunity for successful climate change adaptation and mitigation. Nature-based solutions and green infrastructures can help to safeguard urban nature and biodiversity while providing multiple benefits to reduce climate risks and improving human well-being. Nature-based solutions help to mitigate flood risk by regulating storm-water runoff and peak-flow. This paper investigates the effects of nature-based solutions and green infrastructure networks on pluvial flood risk in Milan metropolitan area in terms of direct economic damage to buildings and population exposed. Results show that extended urban green networks can reduce pluvial flood damages (by up to 60%) and the population exposed (up to 50%). For all analysed rainfall intensities, damages to buildings and share of population exposed decrease as green area coverage increases, with slightly higher risk reduction for lower-intensity events. 25% of additional urban green coverage can halve the expected annual damage and reduce by 40% the expected annual population exposed. The applied methodological framework makes it possible to identify priority-action urban areas and hence inform decision-making processes as for where green solutions are most efficient.

How to cite: Staccione, A., Hrast Essenfelder, A., Bagli, S., and Mysiak, J.: Connected urban green spaces for pluvial flood risk reduction in the Metropolitan area of Milan, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7906, https://doi.org/10.5194/egusphere-egu23-7906, 2023.

EGU23-8181 | ECS | Orals | ITS3.4/SSS0.1

Impact of global change on the protective effect of forests in mountain areas 

Christine Moos, Alessandra Bottero, Ana Stritih, and Michaela Teich

Forests in mountain regions provide an indispensable ecosystem service by protecting people and infrastructure against natural hazards. Thanks to this Nature-based Solution (NbS), costs of engineered technical protection measures can be reduced or even avoided. Numerous studies have proven the high effectiveness of forests in mitigating the negative impacts of natural hazards. However, open questions remain about the long-term and sustainable provision of protective service by mountain forests, which are expected to be increasingly affected by global change. Natural forest dynamics and disturbances can result in temporary or irreversible loss of protective effects of forests, potentially accelerated by climate change. At the same time, rising temperatures and more frequent and severe droughts will lead to shifts in tree species distribution and forest composition, which may in turn impact their protective effect depending on the type of natural hazard. Furthermore, socio-economic changes, such as land-use change or the expansion of settlements, may affect the protective function of forests. The uncertainties related to these changes pose great challenges for the quantification and sustainable management of this key ecosystem service in mountain areas. To improve our understanding of the various effects global change has on protective forests, we summarized current knowledge based on a quantitative review. We conducted a systematic literature search using predefined terms in different databases. We focused on forests in mountain regions protecting against gravitational hazards (i.e., snow avalanches, landslides, rockfall, torrential floods and debris flow). This resulted in 70 peer-reviewed articles, books or book chapters that we systematically assessed. Most studies focused on anthropogenic forest change (i.e., management, de-/afforestation), followed by natural disturbances, whereas climatically induced changes (e.g., clearly linked to drought or rising temperatures) were less often addressed in the literature. The analyzed studies mainly examined the protection against floods, followed by avalanches, landslides and rockfall. Preliminary results indicate that global change had a predominantly negative impact on the protective effect of forests in mountain areas. In a next step, the types of impacts and potential interacting and compound effects will be analyzed in more detail.

How to cite: Moos, C., Bottero, A., Stritih, A., and Teich, M.: Impact of global change on the protective effect of forests in mountain areas, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8181, https://doi.org/10.5194/egusphere-egu23-8181, 2023.

EGU23-9392 | Orals | ITS3.4/SSS0.1

Nature-based solutions for wildfire risk management: the role of insurance 

JoAnne Bayer, Valentina Bacciu, Eduard Plana, Luis Sousa, Swenja Surminski, and teresa Deubelli-Hwang

A consensus is emerging that restoring the fire-adapted forest ecology through nature-based solutions (NBS), such as prioritizing fire-resistant vegetation, promoting less fire-prone forests, enabling grazing by herbivores in areas facing land abandonment, prescribed burns, and restricted or risk-adapted development in wildlands, can reduce the risk of extreme wildfires. This paradigm shift away from fire suppression towards a fire loss-prevention strategy is urgently needed. The question is whether risk financing strategies, especially insurance, can untap the potential for promoting NBS, for example, by providing protection in case of damages from livestock grazing or prescribed burns, or by giving discounts to forest owners and homeowners that pursue ecological fire-prevention measures. Additionally, insurers can provide (parametric) policies that repair ecological damage, for example, for coral reefs after extreme storms, or policies that transfer the construction or liability risk of NBS. Since wildfire mitigation is to a large extent collective, another potential policy option to support NBS is community-based insurance strategies. This presentation will explore the opportunities and constraints for public and private insurers to support NBS for wildfire risk management. It reflects on-going research in three recently funded Horizon Europe projects: (Cross sector dialogue for wildfire risk management (FireLogue), Building a safe haven for climate extremes (The HuT), and Nature for insurance and insurance for nature (NATURANCE).

How to cite: Bayer, J., Bacciu, V., Plana, E., Sousa, L., Surminski, S., and Deubelli-Hwang, T.: Nature-based solutions for wildfire risk management: the role of insurance, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9392, https://doi.org/10.5194/egusphere-egu23-9392, 2023.

EGU23-9646 | Orals | ITS3.4/SSS0.1

Economic benefits of ecosystem-based disaster risk reduction and ecosystem-based climate change adaptation: a global review 

Marta Vicarelli, Karen Sudmeier-Rieux, Ali Alsadadi, Michael Kang, Madeline Leue, Simon Schütze, Aryen Shrestha, Ella Steciuk, David Wasielewski, Jaroslav Mysiak, Shannon McAndrew, Michael Marr, and Miranda Vance

Ecosystems and ecosystem services may contribute to reduction in disaster risk, sustainable development and climate change adaptation. The potential of Nature-based Solutions (NbS) is now recognized by major national policies and international framework agreements. However, to date there is limited scientific evidence about their economic viability and equity impacts. In this study we developed a global database of 406 observations from 87 peer-reviewed studies published between 2000 and 2020, completing economic evaluations of NbS for Ecosystem-based Climate Adaptation (EbA) and Ecosystem-based Disaster Risk Reduction (Eco-DRR). We examine available scientific knowledge on the economic viability and performance of NbS for Eco-DRR and EbA, both in terms of efficiency and equity. More than 40% of the studies analyze the role of coastal ecosystems, coral reefs, wetlands, and mangroves in attenuating disaster risk, with a special focus on floods, storms and erosion. Abundant are also studies examining forest ecosystems (30%), followed by urban (25%) and riparian ecosystems (23%). A smaller number of studies analyzes agro-ecosystems. The number of studies per region suggests that Europe, Asia, and North America are the regions where most Eco-DRR research was undertaken. Based on our results, 71% of studies found that the ecosystems studied were effective NbS in mitigating hazards. 24% of studies found that the ecosystems were occasionally effective in mitigating hazards. None of the studies found NbS ineffective in mitigating hazards. The ecosystems most frequently effective in mitigating hazards included mangroves (80%), forests (77%), and coastal ecosystems (73%). A subset of studies compared the efficacy and cost-effectiveness of NbS and engineering-based solutions in mitigating certain hazards (39%). Among these studies, 65% found that NbS are always more effective in attenuating hazards compared to engineering-based solutions, and 26% found that NbS are partially more effective. No study found that NbS are less effective than engineering-based solutions. 

How to cite: Vicarelli, M., Sudmeier-Rieux, K., Alsadadi, A., Kang, M., Leue, M., Schütze, S., Shrestha, A., Steciuk, E., Wasielewski, D., Mysiak, J., McAndrew, S., Marr, M., and Vance, M.: Economic benefits of ecosystem-based disaster risk reduction and ecosystem-based climate change adaptation: a global review, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9646, https://doi.org/10.5194/egusphere-egu23-9646, 2023.

EGU23-12053 | ECS | Posters on site | ITS3.4/SSS0.1

Nice weather or burning heat? Sentiment analysis of temperature-related media reports. 

Ekaterina Bogdanovich, Alexander Brenning, Lars Guenther, Markus Reichstein, Dorothea Frank, Mike S. Schäfer, Georg Ruhrmann, and René Orth

The frequency, duration, and intensity of heat waves are expected to increase in the coming decades. This could lead to elevated heat stress and consequently an increase in excess mortality, caused by hyperthermia, dehydration, respiratory disease, cerebrovascular disease, or heat stroke. Public awareness of such impacts is key to mitigate heat-related consequences of hot temperatures. For example, the sentiment of heat-related media coverage can affect the perceived risk and the motivation of people to implement risk mitigation such as avoiding outside activities and ensuring sufficient water intake.  

In this study, we analyze the sentiment of temperature-related newspaper reports from multiple countries in an automated way. In particular, we investigate (i) how newspapers in different countries respond to hot temperatures in terms of the number of on-topic articles and their sentiment, and (ii) to what extent socioeconomic and climatic characteristics can explain differences between countries.
For this purpose, we employ data on minimum, mean, maximum, and apparent temperature from the ERA5 reanalysis. We obtain country-specific relationships between the sentiment of temperature-related newspaper articles and the respective temperatures. We hypothesize that these relationships differ, for example, between cold and warm countries, and that heat waves are generally perceived more positively in cold regions.

In summary, this work reveals the links between the sentiment of newspaper articles and hot temperatures across countries. Linking these results with observed heat-related health impacts can guide public health agencies, newspapers, and journalists in particular to ensure public awareness of the detrimental impacts of heat waves, which are expected to further aggravate in a warming world.

How to cite: Bogdanovich, E., Brenning, A., Guenther, L., Reichstein, M., Frank, D., Schäfer, M. S., Ruhrmann, G., and Orth, R.: Nice weather or burning heat? Sentiment analysis of temperature-related media reports., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12053, https://doi.org/10.5194/egusphere-egu23-12053, 2023.

EGU23-12929 | ECS | Orals | ITS3.4/SSS0.1

Global societal vulnerability to volcanic eruptions 

Lara Mani, Mike Cassidy, Asaf Tzachor, and Paul Cole

The climatic cooling effects associated with large magnitude volcanic eruptions – the so-called ‘volcanic winter’ scenario – have long been identified as an extreme risk that may impact the continued flourishing of humanity. Such eruptions are relatively rare, but perhaps not as rare as we might think. A greater understanding of this mechanism and increased resolution of our geological records through the study of ice core records demonstrate that the recurrence of an eruption capable of this impact may be as frequent as 1 in 6 per century. These large magnitude volcanic eruptions (VEI 7 and above), could cause a global cooling event for up to a decade, if not longer, with more severe effects felt in the northern hemisphere, presenting a unique challenge for global food security.

Further, viewed through the lens of vulnerability, human society now closely intersects with regions of volcanic activity, potentially forging new pathways for volcanic eruptions to cause global disruption. Our research identified regions of intersection, or ‘pinch points’, where a compounding of global critical systems and infrastructure, such as submarine cables, global shipping lanes, and transportation networks, are proximal to regions of volcanic activity. These pinch points present locations in our interconnected world where volcanic eruptions may disrupt our systems, cascading us toward global catastrophe. With climate change increasing the frequency and intensity of volcanic eruptions globally and enhancing their impacts, more must be done to accelerate our preparedness for such events.

How to cite: Mani, L., Cassidy, M., Tzachor, A., and Cole, P.: Global societal vulnerability to volcanic eruptions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12929, https://doi.org/10.5194/egusphere-egu23-12929, 2023.

Extreme weather and climate events (EWCEs) have jeopardized crop yields globally. The evidenced increasing trends of EWCEs would amplify their impacts if they co-occurred. This would bring additional shocks to global food markets, and result in severe risks to food security. A systemical analysis of the risk of crop yield failure under EWCEs and their changes in a warming future is essential to guide adaptations adequately and ensure food security. In this study, we compared the relations between maize yield anomalies and 14 climatic indices over the growing season in the breadbasket (10 provinces) in China during 1981-2018 to identify the main EWCEs determining maize yield anomalies. We then compared the probabilities of crop yield failure under current climatic conditions and its projected changes under 1.5 and 2.0 oC global warming using 28 climate models from CMIP6. The result shows that the maize yield anomalies can be mainly explained by extreme temperate-related indices, despite the various indices for individual provinces. The probability of synchronous yield failure in 1981-2018 was below 7.5% when we randomly summed up seven maize provinces among ten. The probability may reach 2.45% and 7.73% on average under 1.5 and 2.0 oC global warming conditions for all ten provinces, respectively. The transferred risk of crop yield failure revealed that more current maize land would be outstripping its climate-safe space under warmer conditions. Our results highlighted the benefits of limiting global temperature rise within 1.5 oC. Furthermore, enhancing crop resistance to adverse climate situations through appropriate adaptations would be a promising solution to stabilize crop productivity.

How to cite: Liu, S. and Xiao, L.: Limit global warming to 1.5 oC will alleviate the synchronous failure of maize yield in China, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13890, https://doi.org/10.5194/egusphere-egu23-13890, 2023.

EGU23-15116 | ECS | Orals | ITS3.4/SSS0.1

The WOODPDLAKE project. Lakes, wood and sediment: Natural and Cultural Heritage affected by climate changes 

Swati Tamantini, Giancarlo Sidoti, Federica Antonelli, Giulia Galotta, Maria Cristina Moscatelli, Davor Kržišnik, Vittorio Vinciguerra, Rosita Marabottini, Natalia Macro, and Manuela Romagnoli

Wooden pile dwellings (WPD) are an inexhaustible and precious source of information on landscape evolution and contingent cultural activities. There have been significant investigations on WPD submerged in Alpine areas, but important knowledge gaps are evident regarding Mediterranean volcanic and karstic lakes. The conservation of the latter archaeological remnants is endangered by the climatic change impacts and anthropogenic pressure, further exacerbated by the sensitive and circumscribed lake environments. Wood from pile dwellings is waterlogged, and its conservation mostly depends on the surrounding environment i.e. sediments and water quality. This project aims to study all the aspects of WPD in volcanic and karstic lakes through studies ranging from their potential exploitation, the investigation into their conservation and restoration, monitoring lake environment and forecasting scenarios through an aquarium reproducing the most significant abiotic conditions occurring in the lake. This last study will be achieved by means of an aquarium model. Three case studies have been selected in which agricultural practices influence climatic stress and pollution impact: Lake Banyoles in Spain and Lakes Bolsena and Mezzano in Italy. The foreseen investigations will employ an extraordinarily wide spectrum of skills and disciplines (palynology, dendrochronology, micromorphology, soil science and innovative tools like isotopic analysis). The characterization of wooden materials will involve gravimetric measurements, Fourier-transform infrared spectroscopy (FTIR), pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and thermogravimetry. Samples will derive from different sources to include immersed, reburied finds and restored wood, lake water and lake sediment samples. The main activities will be devoted to fields campaigns and unmanned aerial vehicle (UAV), high-resolution methods for monitoring environmental conditions (for example the installed probe will measure water lake temperature, pH and so on), capitalization of results (network of big data about lake sites), involvement of local actors and population on the historical, cultural and environmental value of WPDs to establish decision-making processes and to foster high-quality tourism.

How to cite: Tamantini, S., Sidoti, G., Antonelli, F., Galotta, G., Moscatelli, M. C., Kržišnik, D., Vinciguerra, V., Marabottini, R., Macro, N., and Romagnoli, M.: The WOODPDLAKE project. Lakes, wood and sediment: Natural and Cultural Heritage affected by climate changes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15116, https://doi.org/10.5194/egusphere-egu23-15116, 2023.

EGU23-16961 | ECS | Orals | ITS3.4/SSS0.1

Effect of weather extremes on climate change media coverage - Evidence from 57 000 newspaper articles 

Jakob H. Lochner, Annika Stechemesser, and Leonie Wenz

Climate change media coverage shapes climate-related societal and political debates and decisions [1, 2]. Yet it is unclear what drives media attention for climate change. More frequent and more intense weather extremes are a clear consequence of climate change and have a large impact on society. Extreme weather events might hence be an important factor for climate coverage. Here, we investigate whether weather extremes lead to more climate change coverage in the media. Further, we analyse how this changes over time and whether it differs between different types of extreme weather events such as heat waves or floods. Finally, we examine how the influence on climate coverage varies between weather extremes and other climate-related events such as climate protests, IPCC report publications and world climate summits.

To this end, we analyse approximately nine million articles from nine German newspapers over the last three decades (1991 - 2021). The selection of newspapers is diverse and includes regional and national media, daily and weekly publication rhythms, as well as various political leanings. Currently, the nine newspapers have a cumulative readership of more than 12 million people. Within all nine million articles, we identify approximately 57 000 climate-related articles, using a bag-of-word machine learning approach. Changes in the share of climate-related articles are evaluated against the background of the occurrence of weather extremes and other climate-related events, while controlling for potential confounders using fixed effects panel regressions. Information about extreme weather events are derived from the meteorological ERA5 reanalysis data as well as from the international disasters' database EM-DAT. In addition, we use data on activists’ protest, scientific publications and political climate-related conferences, derived from press releases of the corresponding organizations. 

Our study provides evidence that weather extremes increase climate change coverage. Separate analyses for the three decades (1991 - 2000, 2001 - 2010, 2011 - 2021) show that the influence of weather extremes on climate coverage increases over time. Differences in the influence on climate coverage are found for different weather extreme types. The influence of floods in Germany on climate coverage is about twice as large as that of heat waves. Comparing the effect of weather extremes with that of other climate-related events shows that the influence of social events on climate coverage is much stronger than the influence of weather extremes. We find evidence that protests exceed the influence of heat waves by a factor of four, and world climate summits even exceed the influence of heat waves by a factor of ten. These trends apply to all newspapers studied and are preserved under different controls and alternative climate coverage measures.

[1] Brulle, R. J., Carmichael, J. & Jenkins, J. C. Shifting public opinion on climate change: An empirical assessment of factors influencing concern over climate change in the U.S., 2002-2010. Climatic Change 114, 169–188 (2012).

[2] Sampei, Y. & Aoyagi-Usui, M. Mass-media coverage, its influence on public awareness of climate-change issues, and implications for Japan’s national campaign to reduce greenhouse gas emissions. Global Environmental Change 19, 203–212 (2009).

How to cite: Lochner, J. H., Stechemesser, A., and Wenz, L.: Effect of weather extremes on climate change media coverage - Evidence from 57 000 newspaper articles, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16961, https://doi.org/10.5194/egusphere-egu23-16961, 2023.

EGU23-17016 | ECS | Orals | ITS3.4/SSS0.1

Constructing multi-functional Technosols for storm-water management: mixing high-carbon organic amendments, a microcosm experiment 

Lauren Porter, Franziska Bucka, Maha Deeb, Natalie Paez-Curtidor, Monika Egerer, and Ingrid Kögel-Knabner

As the global water cycle intensifies – with it’s increased variability projected to cause greater storm-events, more extensive flooding and more severe droughts – the obsolescence of current urban infrastructure is made clear, particularly in the face of an ever increasing urban population. To combat these challenges, concepts have been developed across the globe in order to better manage and utilize stormwater run-off; many leaning on the larger concept of green infrastructure, implementing solutions replicative of a more natural water cycle. The simplistic design, low capital costs and flexible application and incorporation into urban spaces has made bio-infiltration swales an excellent choice for urban planners and a center point of recent research. As the base of these systems, the soil substrate lends significantly to a swale’s services of dewatering, pollutant processing, biodiversity promotion and carbon accumulation. By combining urban mineral and organic wastes, we attempt to optimize the synergies between these services. In a microcosm incubation experiment, an extracted deep soil horizon was mixed with green waste compost to form a fertile constructed Technosol. Subsequently, biochars of varying feedstock and pyrolysis processing temperatures were added individually and in combination to determine their impact on water processing properties and nutrient availability. We hypothesized the combinations of biochars will create a structure that maximizes water-substrate interactions while also retaining a larger variety of pollutants due to their differences in chemical composition. The addition of biochar will also minimize run-off of nutrients introduced by the green waste compost, increasing their availability to potential vegetation.

How to cite: Porter, L., Bucka, F., Deeb, M., Paez-Curtidor, N., Egerer, M., and Kögel-Knabner, I.: Constructing multi-functional Technosols for storm-water management: mixing high-carbon organic amendments, a microcosm experiment, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17016, https://doi.org/10.5194/egusphere-egu23-17016, 2023.

EGU23-17315 | Posters on site | ITS3.4/SSS0.1

Connecting COVID-19 and climate change in the anthropocene: evidence from urban vulnerability in São Paulo 

Alexandre Pereira Santos, Miguel Rodriguez Lopez, and Jürgen Scheffran

Global crises such as climate change and the COVID-19 pandemic do not affect cities uniformly. These crises converge in urban areas and often interact through their primary and secondary impacts with the vulnerability of urban populations. This paper investigates urban development dynamics and socio-environmental vulnerability in a megalopolis in the Global South, São Paulo (Brasil). Our goal is to assess the connections between urbanisation and risk exposure, a gap in vulnerability research when considering climate and health hazards. We implement an innovative mixed methods research design using thematic, hot spots, and survival analysis techniques. Two focus groups at the central and peripheral regions of the city provide qualitative data, while open data sets and COVID-19 case microdata (n= 1,948,601) support the quantitative methods. We find a complex system of relationships between urbanisation and risk exposure. Socioeconomic vulnerability characteristics of the population do not explain exposure entirely but significantly contribute to risk-prone location choices. Additionally, social vulnerability factors such as low income and social segregation are highly concentrated in São Paulo, coinciding with substantial COVID-19 fatality rates during 25 months of the pandemic. Finally, qualitative analysis helps us overcome the limitations of quantitative methods on the intraurban scale, indicating contrasting experiences of resilience and resistance during the health crisis. While the low-income group faced mental health and food security issues, the upper-middle-income sample took advantage of opportunities arising during the pandemic to improve work and well-being. We argue that these results demonstrate potential synergies for climate adaptation and health policies in combating socio-environmental vulnerability at the community scale. Environmental justice is thus paramount for global development agendas such as the Sustainable Development Goals, Sendai Framework, and the Paris Agreement.

How to cite: Pereira Santos, A., Lopez, M. R., and Scheffran, J.: Connecting COVID-19 and climate change in the anthropocene: evidence from urban vulnerability in São Paulo, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17315, https://doi.org/10.5194/egusphere-egu23-17315, 2023.

Small island states and jurisdictions face enormous sustainability challenges such as isolation from global markets, tenuous resource availability, heavy reliance on imports to meet basic needs, coastal squeeze, and reduced waste absorption capacity. At the same time, the adverse effects of global environmental change such as global warming, extreme events, and outbreaks of pandemics significantly hinder island economies’ progress towards sustainability, and consistently rank them high on various vulnerability indices. This talk introduces the concept of socio-metabolic risk, defined as systemic risk associated with the availability of critical resources, the integrity of material circulation, and the (in)equitable distribution of derived products and societal services in a socio-ecological system. Drawing on years of socio-metabolic research on islands, I will argue that specific configurations and combinations of material stocks and flows and their ‘resistance to change’ contribute to the system’s proliferation of socio-metabolic risk (SMR). For better or for worse, these influence the system’s ability to consistently and effectively deliver societal services necessary for human survival. Governing SMR would mean governing socio-metabolic flows, and easing resource requirements through green(-blue) infrastructure and nature-based solutions (NBS) to provide crucial societal services. Such interventions will need strategies to reconfigure resource-use patterns and associated services that are sustainable as well as socially equitable.

How to cite: Singh, S.: Socio-metabolic Risks and Tipping Points on Islands, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17529, https://doi.org/10.5194/egusphere-egu23-17529, 2023.

EGU23-172 * | ECS | Posters on site | ITS4.1/SSS0.2 | Highlight

Open Science as the new normal, Citizen Science as the new component of research infrastructure 

Kaori Otsu and Joan Masó

The increasing involvement of citizens in scientific projects over the last decade is another critical factor that has encouraged Open and FAIR data. Citizen science is in fact one of the eight priorities of the European Open Science Agenda (2018), along with the establishment of the European Open Science Cloud (EOSC) enabling a federation of multidisciplinary research infrastructures.

Until now, citizen science projects and platforms, also known as Citizen Observatories (COs) in Europe, are yet to be considered among the research sector in the EOSC ecosystem. With the ambition of overcoming this challenge, the Cos4Cloud (Co-designed Citizen Observatories Services for the EOS-Cloud) project was the first ‘Enabling an operational, open and FAIR EOSC ecosystem (INFRAEOSC)’ project to include citizen science as a core part of research infrastructure.

Specifically, the Cos4Cloud aimed to integrate citizen science in the EOSC through co-designing innovative services to support widely used COs in biodiversity and environmental monitoring. To make COs interoperable, the services adopted internationally recognized standards such as SensorThings API and Darwin Core. As a result, over 30 interoperability experiments have been reported in various combinations among the new services and existing COs during the project period; some of which are now offered in the EOSC Marketplace following open and FAIR principles. The Cos4Colud has also demonstrated that the services combined with AI technologies and robust algorithms could improve COs by leveraging the data quality to the research grade.

We thus expect more resources and services derived from COs to be reused in the EOSC ecosystem, eventually enabling to establish its own thematic cluster for citizen science in the research infrastructure as well as facilitate the reuse of data by other researchers. We conclude with the key role of such diverse scientific communities enriched in the EOSC that may create a bridge among researchers, citizens and decision-makers.

 (This work has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement no 863463.)

How to cite: Otsu, K. and Masó, J.: Open Science as the new normal, Citizen Science as the new component of research infrastructure, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-172, https://doi.org/10.5194/egusphere-egu23-172, 2023.

Motivation. Recent research shows promising results in gridding methods that aim to fuse official and citizen weather observations to produce high-resolution weather maps. These high-resolution weather maps are essential to verify weather models at finer spatial resolutions and are crucial for Early Warning Centres to provide measures of risk at neighborhood scale. In this way, citizen weather observations may be the key to better inform communities and decision makers about the local weather and important for future generation’s climate adaptation research. Citizen science weather collections like WOW-NL (http://wow.knmi.nl) offer dense monitoring networks, potentially providing sheer volumes of observations. Continuous growth is a desired characteristic of these alternative networks overall. However, a “guided growth” could prove a more robust strategy in the long term. For this purpose, in this research we focus on quantifying the insights of some questions: How important is it to keep increasing the volume of observations? When should we do so? And at which locations in a region should these stations be located? 

Approach. In this work we apply multi-fidelity adaptative sampling (MF-AS) to daily interpolations of WOW-NL air temperature and wind speed observations. MF-AS is a method developed in the discipline of simulation-based engineering, where it is used to efficiently optimise the design of vehicles. The questions that we try to answer are: what would be the best locations for a sequence of new stations? Should they be official stations or (clusters of) citizen stations? And how much improvement by the network can we expect? We apply and develop MF-AS for the Netherlands: 

We identify typical weather patterns and define some important focus areas for gridded weather products. In this example, we focus on three user areas for the accuracy for our weather products: accuracy over the entire country, accuracy in populated areas and accuracy for road traffic. We then develop and apply MF-AS. The performance for the different user areas, evaluated for different candidate station locations, defines the cost function for our MF-AS strategy. Then, during this MF-AS approach – again borrowing heavily from vehicle design optimisation – in each iteration we do not only quantify the expected improvement in accuracy, but we also determine whether the next station should be an official station or a cluster of citizen stations, as well as where in the country it should ideally be located. In this way, we aim to develop a strategy for efficient growth of the combined official / citizen station network. 

Results. This study acts a proof-of-concept for the use of quantitative methods to optimally design future multi-fidelity weather observation networks. The results will illustrate why, when and where, ideally, we should attract people to engage in citizen weather observation. We are convinced that these quantitative results can contribute to the broader effort to engage people in citizen weather science. 

How to cite: de Baar, J. and Garcia-Marti, I.: Towards quantifying why, when and where to engage citizens to participate in weather observation networks, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2655, https://doi.org/10.5194/egusphere-egu23-2655, 2023.

EGU23-2698 | Orals | ITS4.1/SSS0.2

UndercoverEisAgenten - Monitoring Permafrost Thaw in the Arctic using Local Knowledge and UAVs 

Marlin M. Mueller, Christian Thiel, Soraya Kaiser, Josefine Lenz, Moritz Langer, Hugues Lantuit, Sabrina Marx, Oliver Fritz, and Alexander Zipf

The Arctic is experiencing severe changes to its landscapes due to the thawing of permafrost influenced by the twofold increase of temperature across the Arctic due to global warming compared to the global average. This process, which affects the livelihoods of indigenous people, is also associated with the further release of greenhouse gases and also connected to ecological impacts on the arctic flora and fauna. These small-scale changes and disturbances to the land surface caused by permafrost thaw have been inadequately documented.

To better understand and monitor land surface changes, the project "UndercoverEisAgenten" is using a combination of local knowledge, satellite remote sensing, and data from unmanned aerial vehicles (UAVs) to study permafrost thaw impacts in Northwest Canada. The high-resolution UAV data will serve as a baseline for further analysis of optical and radar remote sensing time series data. The project aims to achieve two main goals: 1) to demonstrate the value of using unmanned aerial vehicle (UAV) data in remote regions of the global north, and 2) to involve young citizen scientists from schools in Canada and Germany in the process. By involving students in the project, the project aims to not only expand the use of remote sensing in these regions, but also provides educational opportunities for the participating students. By using UAVs and satellite imagery, the project aims to develop a comprehensive archive of observable surface features that indicate the degree of permafrost degradation. This will be accomplished through the use of automatic image enhancement techniques, as well as classical image processing approaches and machine learning-based classification methods. The data is being prepared to be shared and analyzed through a web-based crowd mapping application. The project aims to involve the students in independently acquiring data and developing their own scientific questions through the use of this application.

In September 2022, a first expedition was conducted in the Northwest Territories, Canada and UAV data was collected with the assistance of students from Moose Kerr School in Aklavik. The data consists of approximately 30,000 individual photos taken over an area of around 13 km². The expedition also provided an opportunity for the students to learn about the basics of data collection and the goals of the collaborative permafrost survey, which included the incorporation of local knowledge to address the questions of the local community.

By involving school students in the data acquisition, classification and evaluation process, the project also seeks to transfer knowledge and raise awareness about global warming, permafrost, and related regional and global challenges. Additionally, a connection through the shared research experience between students in Germany and Canada is established to enable the exchange of knowledge. The resulting scientific data will provide new insights into biophysical processes in Arctic regions and contribute to a better understanding of the state and change of permafrost in the Arctic. This project is funded by the German Federal Ministry of Education and Research and was initiated in 2021.

How to cite: Mueller, M. M., Thiel, C., Kaiser, S., Lenz, J., Langer, M., Lantuit, H., Marx, S., Fritz, O., and Zipf, A.: UndercoverEisAgenten - Monitoring Permafrost Thaw in the Arctic using Local Knowledge and UAVs, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2698, https://doi.org/10.5194/egusphere-egu23-2698, 2023.

EGU23-4538 | Orals | ITS4.1/SSS0.2

How do roots restructure water and carbon dynamics in the critical zone? 

Pamela L. Sullivan and the SitS, FRES, and CZCN teams

Roots are physical and chemical engineers of the subsurface that are sensitive to changes in climate, and whose power to reshape the subsurface differs with land cover. Roots create and destroy porosity through enmeshment of particles, lateral and vertical boring through regolith, and cleaving of rocks from parent material. Their ability to translocate water, exude sugars and acids, and take up solutes influences hydrologic connectivity, water residence times, carbon transport and transformation, microbial access to resources, and chemical equilibrium conditions. Analysis of land-cover datasets suggest that root depth distributions are changing globally, shallowing in agricultural environments and deepening with woody encroachment. Yet where, when, and how changes in root distributions alter water and carbon dynamics in the critical zone is not well known. Using data generated at environmental observatories across the U.S. Long-Term Ecological Research program, the Critical Zone Collaborative Network, National Ecological Observatory Network, and the Department of Energy Watershed Focus Areas in combination with the Pedogenic and Environmental Dataset (PEDS), we ask: How do roots shape regolith hydrology and carbon dynamics? 


A clear signal is emerging from grassland, forest, and agricultural sites across the U.S. that indicates changes in rooting dynamics have measurable and meaningful impacts on critical zone functions. Evidence shows that changes from forest to crop and back to forest impacts soil structure deep beneath the plow line in systematic ways. Losses of rooting abundance upon conversion of grasslands to agriculture affects the propensity of organic carbon to form and protect aggregates throughout the subsoil. Reduced fire frequency at tallgrass prairie sites in the Midwest have led to rapid woody expansion in recent decades. Where woody encroachment persists, coarse roots, smaller mean soil aggregate diameters, and more readily destabilized carbon pools proliferate. Encroachment of woody plants increases the infiltration of soil water rich in  CO2 into deep rocks and enhances carbonate weathering as predicted by models. These woody plants rely on deeper water sources, draw soil moisture down to a greater degree at depth, and are likely responsible for reducing streamflow and changing the timing of groundwater contributions to the stream. At Rocky Mountains sites dominated by conifers and aspen, coarse- and fine-root abundances are elevated under aspen in the upper 75 cm of the soil profile compared to conifer sites. Elevated soil organic carbon, lower extractable organic carbon, lower C:N values and elevated enzyme activity indicate soil carbon under aspen is likely more stable as a result of more microbial processing. Finally, in a predominantly Douglas-fir forest in the Pacific Northwest, second-growth forests exhibit substantially fewer fine roots at depths <50 cm, which appears to exert control on nitrogen availability in this nutrient-limited system and thus potentially limits carbon stability as more extractable organic carbon is generated from second-growth forests at depth. Data from these sites demonstrate how alterations to rooting distributions change the physical structure and moisture status of soil, and may be linked to carbon stability as the proportion of fine and coarse roots dictate overall access to carbon pools.     

How to cite: Sullivan, P. L. and the SitS, FRES, and CZCN teams: How do roots restructure water and carbon dynamics in the critical zone?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4538, https://doi.org/10.5194/egusphere-egu23-4538, 2023.

EGU23-7238 | Posters on site | ITS4.1/SSS0.2

Improving efficiency of citizen science projects by targeted activation of selected stakeholder groups 

Christine Liang, Claudia Schütze, Uta Ködel, Thora Herrmann, Felix Schmidt, Fabian Schütze, Sophia Schütze, and Peter Dietrich

As citizen science is becoming a widely accepted research approach across multiple disciplines, it is essential to explore methods for effective recruitment, involvement, and retention of participants for these programs. An effective recruitment strategy results in motivated and engaged contributors, longer-term participation, and better communication exchange.

In this research, we present two marketing approaches adapted from best practice in customer-facing fields in order to identify appropriate stakeholder groups for citizen science and keep motivation and retention of the participants high. Firstly, stakeholder analysis is a major tool within the frame of stakeholder management and includes the systematic identification of stakeholders and their relevance and influence on a project. Thus, efficiency of citizen science projects can be improved significantly by targeted identification and selection of participants and groups through stakeholder analysis, which are suited to generate the data needed to reach the project and research goals. Secondly, the value proposition canvas approach is based on business strategies to match products and services to the market or customer. The value proposition canvas can be adapted to scientific processes and the data generated can help citizen science groups to build a communication strategy that can clearly communicate the value of their message and shared goals to the participants.

The application of stakeholder analysis and value proposition canvas is demonstrated using the case study of the project "Next Generation City Climate Services Using Advanced Weather Models and Emerging Data Sources" (CityCLIM, a European Union Horizon 2020 funded project), where the focus is to develop next-generation City Climate Services based on advanced weather forecast models enhanced with data from emerging data sources such as Citizen Science approaches for urban climate monitoring. Before meetings with citizens in pilot cities, stakeholder groups involved in the CityCLIM project were examined and their profiles were analysed using the value proposition canvas. Lessons learned from the use of these tools for engagement with citizens in pilot cities will be presented. Findings also provide an approach that can be used by citizen science groups in environmental observation to strategically target participants and tailor key communication messages, towards the goal of a focused and sustained monitoring of environmental processes.

How to cite: Liang, C., Schütze, C., Ködel, U., Herrmann, T., Schmidt, F., Schütze, F., Schütze, S., and Dietrich, P.: Improving efficiency of citizen science projects by targeted activation of selected stakeholder groups, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7238, https://doi.org/10.5194/egusphere-egu23-7238, 2023.

EGU23-7615 | ECS | Posters on site | ITS4.1/SSS0.2

PrESENCE : a participative citizen seismic network. 

Mathieu Turlure, Marc Grunberg, Hélène Jund, Fabien Engels, Antoine Schlupp, Philippe Chavot, and Jean Schmittbuhl

The SeismoCitizen (SismoCitoyen) project presents and tests a new paradigm of collaborative monitoring of geohazards in urban and peri-urban environments. Seismological observations are obtained using a large number of low cost internet-connected equipment (Raspberry Shake seismic sensors and associated open access data). The breakthrough strategy of the project relies on the deployment of the sensors in residences or administrative buildings of non-seismologist voluntary citizens or authorities. The aim is to use those stations to densify the french permanent seismic network, and to improve the detection and location of seismic events, in particularly small ones. The volunteers take part in a sociological survey to estimate the impact of that participative project on their perception of science. Candidates are primarily chosen according to the seismic interest of their location and for some of them to represent the social variability of the population. 

 

Since the “Sismocitoyen” project was launched in 2018 by BCSF-Rénass and EOST (CNRS and Strasbourg University), sixty sensors have been deployed and are currently hosted by voluntary citizens in the region of the Upper Rhine Graben, in the area of Strasbourg, Mulhouse and alongside Vosges mountains. They were able to strongly improve our monitoring of the seismic events induced by a deep geothermal project close to Strasbourg where several events have been largely felt (2019-2022). The topic is becoming a major issue in the development of renewable energies that involve the subsurface as seismic hazards are of significant public concern and can have major socio-economic impacts. 

 

With the new PrESENCE ANR project (2022-2025) we focus on seismic hazards induced by deep geothermal operations in northern Alsace and their associated societal perception.  Seventy Raspberry Shake seismic stations are being deployed since the end of 2022 and installations will continue in 2023. We will use our previous experience to improve, refine and develop all aspects such as site selection, protection of privacy and confidentiality of volunteers data and information, station calibration before deployment, data transmission and protocol to minimize data losses, stations monitoring and data analysis.

 

During the project, interactions with the station hosts will be reinforced, in particular with convivial meetings (Stammtisch) to answer questions, present the use of the data and the results obtained.

How to cite: Turlure, M., Grunberg, M., Jund, H., Engels, F., Schlupp, A., Chavot, P., and Schmittbuhl, J.: PrESENCE : a participative citizen seismic network., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7615, https://doi.org/10.5194/egusphere-egu23-7615, 2023.

EGU23-7816 | ECS | Orals | ITS4.1/SSS0.2

Darwinian approaches for the Urban Critical Zone — A case study in the city of Braunschweig, Lower Saxony, Germany 

Mikael Gillefalk, Franziska Neumann, Matthias Bücker, and Ilhan Özgen-Xian

The ecohydrology of the Urban Critical Zone is characterised by strong heterogeneity and the entangling of hydrological and human time scales (Sivapalan & Blöschl, 2015). This not only poses a challenge to field measurements and the transfer of insights to other urban systems, but consequently limits the development of universal theoretical approaches for urban systems. In this contribution, we propose an interdisciplinary methodology to approach this challenge. Following the school of Darwinian hydrology (Harman & Troch, 2014), we hypothesise that analog to the co-evolution of natural systems, the history of a city and its neighbourhoods is a strong control on current ecohydrological patterns and processes. Thus, we argue that field measurements must be complemented by research into the historical evolution of the urban area to provide a full description and explanation of any observations made. While we need to be careful to avoid a too deterministic or simplistic view of history, research into the historical evolution of an urban area can strengthen explanation of current urban ecohydrological behaviour and potentially enable knowledge transfer and prediction capabilities in “ungauged” cities with similar historical development, as well as to help guide measurement campaigns. Hence, we search for historical and environmental patterns that correlate to provide a testable explanation of current ecohydrological function of urban space. Similar to the "uniqueness of place" in hydrology, every society and city has a unique history that is shaped by the complex interaction among culture, environment, and political events (Berking & Löw, 2008). Thus, we want to formulate a framework for determining similarities in historical development at relevant temporal scales. This requires a strictly interdisciplinary approach, because the application of historical sciences and the interpretation of results is non-trivial and should not be attempted separately. 
 
We discuss our current progress in developing such an interdisciplinary framework in a case study of the city of Braunschweig, Germany. Braunschweig has 250,000 inhabitants, a medieval city centre with Gründerzeit–era neighbourhoods surrounding it. The former fortifications of the city have been converted into urban green spaces during the 18th century. The Oker river that surrounds the medieval city centre has been heavily modified. The built areas of the city centre show very little green space with few trees, especially compared to the surrounding neighbourhoods, where we find a multitude of street trees, smaller green spaces scattered throughout, and large parks adjacent to the built-up area. This works as an example of how the policy regarding green spaces has changed over time. In this heterogeneous environment, we hunt for urban ecohydrological units. In particular, we are interested in whether similar historical development is an indicator of similar ecohydrological function in an urban context.

References
Berking, H. & Löw, M. (2008). Die Eigenlogik der Städte, Campus Verlag, Frankfurt, Germany.
Harman, C. & Troch, P. (2014), Hydrology & Earth System Science, 18, 417–433.
Sivapalan, M. & Blöschl, G. (2015), Water Resources Research, 51, 6988–7022.

How to cite: Gillefalk, M., Neumann, F., Bücker, M., and Özgen-Xian, I.: Darwinian approaches for the Urban Critical Zone — A case study in the city of Braunschweig, Lower Saxony, Germany, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7816, https://doi.org/10.5194/egusphere-egu23-7816, 2023.

EGU23-8059 | Posters on site | ITS4.1/SSS0.2

Evaluation and correction of precipitation data obtained with different measurement methods using data from precision lysimeter network 

Thomas Puetz, Tobias Schnepper, Horst H. Gerke, Barbara Reichert, and Jannis Groh

Accurate precipitation measurements are essential for various applications such as determining the water balance of ecosystems and modelling soil-water fluxes in the earth critical zone. Gauge based point precipitation measurements are affected by wind, gauge design, and maintenance of the device. Ground-level gauges, like high precision weighing lysimeters, are less affected by environmental factors and thus provide more accurate data if well managed and the data are post-processed with filters. However, studies evaluating precipitation measuring methods with lysimeter references at multiple sites with high temporal resolution and detailed weather data are rare.

In the present study, high-precision weighing lysimeter precipitation data from four years of measurement with an hourly resolution were used as references to evaluate data from four different precipitation measurement methods at three sites under different climatic conditions. The methods were tipping bucket gauges (TB), weighing gauges (WG), acoustic sensors (AS), and laser disdrometers (LD). Different sites and climatic conditions were chosen to be able to draw conclusions as to whether deviations between the measurement and comparison data were environment-dependent or unit-specific. Methodically, the evaluation included correlation analyses, comparison of catch ratios, x-y scatter plots, and the application of correction schemes.

For the total period, all measurement methods recorded less precipitation than the lysimeters, with catch ratios between 33 to 92 % depending on the measuring method. Non-rainfall water inputs, like dew and fog, have been excluded for this study, therefore the measuring differences are attributed to the precipitation gauges. The bias of the hourly measurements varied between -0.69 to -0.01 mm h-1 based on the measuring method and no site-specific influence on the data was detected. Correction algorithms reduced the bias and improved the catching ratios of hourly precipitation data with similar improvements at all sites for the same gauge models, thus one adequate correction scheme may be sufficient to be used for the same model under different climatic conditions and environments. The findings suggest that a correction of the data by empirical or mathematical models appears to be necessary to ensure the quality of the precipitation data and to reduce over- and underestimations, which is the prerequisite for environmental studies in the critical zone.

How to cite: Puetz, T., Schnepper, T., Gerke, H. H., Reichert, B., and Groh, J.: Evaluation and correction of precipitation data obtained with different measurement methods using data from precision lysimeter network, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8059, https://doi.org/10.5194/egusphere-egu23-8059, 2023.

EGU23-8411 | ECS | Posters on site | ITS4.1/SSS0.2 | Highlight

What does it mean to be a data researcher and platform facilitator of crowdsourced weather observations? 

Irene Garcia-Marti and Jan Willem Noteboom

In 2011 the UK Met Office established the Weather Observations Website (WOW) initiative, a global-coverage project in which users of personal weather stations (PWS) can contribute their weather observations to a central repository. In this decade, more than 10,000 PWS around the world have contributed 2 billion measurements to this project, with a remarkable presence of WOW users in Europe. The Dutch Met Office (KNMI) joined this initiative as partner in 2015. In the past 8 years, 1,000+ PWS located in the Netherlands have collected 250+ million observations of the most relevant weather variables, and the interest of the Dutch public in this network continues growing. 

In this context, the KNMI has two main roles with respect to WOW-NL observations: Platform Facilitator and Data Researcher. The KNMI facilitates WOW-NL to the public via the portal http://wow.knmi.nl, which enables visualizing the latest observations in a map, allows querying to inspect the historical data contributed by each station, and provides a space for news. As platform facilitator, the KNMI aims for a measurement system of PWS that provides optimal added value to our science and services. The Data Research teams at KNMI have dedicated continuous efforts to develop quality controls (QC) enabling a full quality assessment of the WOW-NL observations. The latest results show that the application of QC methods yields promising results for air temperature, rainfall, and wind speed measurements. This means that WOW-NL observations may have sufficient quality to be incorporated into successive research or operational workflows and become part of the ‘daily business’ of the organization. 

These two roles are designed to work independently, but we believe that bringing them together would positively and effectively impact quality of data for the organization’s science and services. Hence, how can we interlace them most optimally in a feedback loop and take them to the next level? How can we expand the Platform Facilitator role, to stimulate and provide guidance for citizens to obtain quality of crowd sourced data most optimal for our science and services? How to enable the Data Researcher role to deliver peer-reviewed scientific content to a broader audience and in a real-world set up? Last but not least, how to establish a dialogue with the users to create a community ensuring long-term data provision for national meteorological services?

In this work we investigate the relationship between the Platform Facilitator and the Data Researcher roles to balance investment in actions “upstream” (e.g. network design, PWS location) vs “downstream” (e.g. metadata, statistical QC procedures). We also elaborate on how the inclusion of WOW-NL in operational workflows might require revisiting or creating new policies for crowdsourced data or assessing the readiness of the digital infrastructure of the organization.

How to cite: Garcia-Marti, I. and Noteboom, J. W.: What does it mean to be a data researcher and platform facilitator of crowdsourced weather observations?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8411, https://doi.org/10.5194/egusphere-egu23-8411, 2023.

In the context of a double democratic and environmental crisis, participatory/collaborative action-research has multiplied in recent years with increased attention from institutions. Over the last ten years, many participatory research projects have taken up the democratic and environmental crises by proposing an emancipatory normative scheme to improve public participation and the effectiveness of environmental action.

Our paper presents the first results of a participatory science project, BREATHE, funded by the ANR. It aims to articulate two components : (1) a participatory measurement of fine particulate matter (PM) concentration (PM 10 - PM 2.5 - PM 1 - PM 0.1) and an identification of pollution sources) from passive filters (plants and sensors) and micro-sensors subject to standardization (2) a component of accompaniment and support of public policies based.

The project is based on a participatory science protocol (Chevalier and Buckles, 2009) based on participation engineering (Dosias-Perla et al., 2020). Our fieldwork covers three targets: (a) the incinerator (waste recovery center) - (b) a highways around a small town; (c) a street canyon, city of Montpellier, south of France. On the metrological level, the project aims at analyzing the implication and the effects of the Citizen Science device aiming at "co-constructing" at micro-scales a fine cartography of fine particles concentrations while discriminating the source and modeling the dispersion phenomena. On the political level, the project aims on the one hand to analyze the institutionalization process of the device and on the other hand to analyze its effects on the "co-production" of public policies and strategies through different regulatory frameworks (EPZ, PCAET, Mobility Plan, etc.).

We will also discuss the limits and contributions of this type of interdisciplinary and participatory approach aiming at acting on pollution with and for society. We will present current results and first analyses concerning the complex intertwining of technical and political issues related to air quality metrology, the importance and difficulties of standardizing measurement and of truly developing metrology at relevant scale levels when it comes to supporting public action and addressing health issues

How to cite: Dosias-Perla, D., Lefevre, M., and Camps, P.: Observing, measuring and tackling air pollution with citizens and elected officials: the case of public policy and technical democracy about particulates matter issue in Montpellier, France., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9605, https://doi.org/10.5194/egusphere-egu23-9605, 2023.

EGU23-9749 | Posters virtual | ITS4.1/SSS0.2 | Highlight

A synthesis of the use of citizen science on soils and agroecosystems across Europe 

Chantal Gascuel-Odoux, Ulrike Aldrian, Sophia Goetzinger, Eloise Masson, Julia Miloczki, and Taru Sandén

Along with the development of citizen science, more and more citizen science initiatives on soils are emerging. Soils are key components of ecosystems and from where 95% of our food originates. Because soils integrate multiple impacts of human activities, they are increasingly taken into account in public policies (agroecology, biodiversity, food, climate). This presentation will share the results of an online survey on agricultural soil citizen science across Europe. Most reported citizen science projects were at the national level (56%, n=40), limited in time (64.9%, n=40) because of funding (82.6%, n=23), with a budget less than 50.000 € (41.7%, n=36) and funded by a national research funding agency (47.2%, n=36). Regarding agricultural soil systems, half of citizen science projects studied urban or urban-countering gardening and 39% studied cropping systems, 29% fruit-vegetables and grassland systems, 18% arboriculture and vineyards. Over 57% of the reported projects have generated soil biodiversity data, 46% and 35% vegetation cover and soil organic carbon data, respectively. According to citizen science coordinators (n=33), the benefits for the scientists taking part in citizen science were ranging from publication of research outputs (69.7%) and learning opportunities (63.6%) to the potential to influence policy (45.5%). The reported benefits for the citizen scientists (n=33) ranged from learning opportunities (81.8%) and satisfaction through contributing to scientific evidence (72.7%) to publication of research outputs (24.2%). ‘Project very time consuming’ and ‘funding temporary’ were identified as the main research challenges for citizen science projects (n=31). ‘More staff resources’ was reported as the most important prerequisites for citizen science work followed by ‘more financial resources’ and ‘more recognition from academia for citizen science’ (n=28). This synthesis shows the state of the art in agricultural soil citizen science, but also the main lockers for citizen science development on soils.

How to cite: Gascuel-Odoux, C., Aldrian, U., Goetzinger, S., Masson, E., Miloczki, J., and Sandén, T.: A synthesis of the use of citizen science on soils and agroecosystems across Europe, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9749, https://doi.org/10.5194/egusphere-egu23-9749, 2023.

EGU23-11150 | Posters on site | ITS4.1/SSS0.2

Marsh migration in the coastal critical zone: Drivers and impacts of hydrological, biogeochemical, and ecological change 

Holly Michael, Dannielle Pratt, Yu-Ping Chin, Sergio Fagherazzi, Keryn Gedan, Matthew Kirwan, Angelia Seyfferth, Lee Slater, Stotts Stephanie, and Katherine Tully

Ghost forests and abandoned farms are stark indicators of ecological change along world coastlines, caused by sea level rise (SLR). These changes adversely affect terrestrial ecosystems and economies, but expanding coastal marshes resulting from SLR also provide crucial ecosystem services such as carbon sequestration and mediate material fluxes to the ocean. We introduce a US-NSF Critical Zone Network project designed to untangle the hydrological, ecological, geomorphological, and biogeochemical processes that are altering the functioning of the marsh-upland transition in the coastal critical zone. We have instrumented six sites in the mid-Atlantic region of the US, along the coastlines of the Atlantic Ocean, Delaware Bay, and Chesapeake Bay where marshes are rapidly encroaching into forests and farmland. We have installed field sensors to observe the effects of slow hydrologic change (i.e. SLR) and fast episodic events such as high tides and storm surges on water levels, land surface elevation, salinity, redox conditions, and sap flow. We are coupling these measurements to laboratory experiments and analyses, as well as modeling to elucidate drivers and feedbacks in these complex and highly transient critical zone systems.

How to cite: Michael, H., Pratt, D., Chin, Y.-P., Fagherazzi, S., Gedan, K., Kirwan, M., Seyfferth, A., Slater, L., Stephanie, S., and Tully, K.: Marsh migration in the coastal critical zone: Drivers and impacts of hydrological, biogeochemical, and ecological change, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11150, https://doi.org/10.5194/egusphere-egu23-11150, 2023.

EGU23-11691 | Orals | ITS4.1/SSS0.2

Environmental and social drivers behind spatial variability of soil carbon in urban green infrastructures of Wageningen 

Slava Vasenev, Mirabel Vlaming, Josca Breeman, Olga Romzaykina, and Jetse Stoorvogel

Recent IPCC reports claim carbon neutrality as the key strategy for climate mitigation, therefore compensating greenhouse gases’ emissions by carbon (С) sequestration become the core of climate mitigation measures taken by cities. Developing urban green infrastructures is considered an efficient measure for C sequestration and climate mitigation in cities. However, most of these solutions consider C sequestration in aboveground biomass and ignore the role of urban soil-C stocks. Urban soils’ contribution to C balance in urban ecosystems remains overlooked so far, but gets increasingly important with ongoing climate change. Urban soils are exposed to direct and indirect anthropogenic influences, they are very heterogeneous and dynamic. This variability is driven by both environmental (e.g., vegetation, geomorphology, and parent material) and social (e.g., decisions on maintenance and management) factors. Traditional soil surveys focus on the environmental factor and barely ignore the social drivers, that might be appropriate for natural or agricultural areas, but can hardly be implemented to study soil C stocks in cities.  In the Netherlands, urban areas cover at least 15% of the territory and are projected to expand with more than 1000 km2 by 2040, however urban soils remain overlooked and sustainable urban development strategies are not supported by soil data. this study we aimed to explore the effect of natural and social factors on the spatial variability in soil C on Wageningen – a middle-size university town in the Netherlands.

Wageningen is a perfect case study to investigate factors influencing spatial variability of urban soil C. A long history and unique landscape diversity create conditions for high spatial variation in soil-forming factors. Based on the parent materials, the residential blocks outside the center can be subdivided into strata dominated by sandy and clayey soils. Urban expansion and building up new residential blocks, public and private green areas coincided with development and management of urban soils. A random stratified soil survey (n=56) allowed capturing the effect of parent materials, land cover and land-use history. The effect of the social factor was studied by expert interviews with the owners of the green areas (key plots, n=10), where detailed soil survey was done. Expert interviews included information on soil management as well as personal questions. In result, typical ‘portraits’ of landowners/ green-keepers were developed and related to soil C-stocks assessment. It was concluded that land-cover and land-use history/ historical zoning distinguished spatial patterns in soil C at the city level, whereas at the local scale social factors dominated. Moreover, local spatial variability distinguished by differences in maintenance/ management practices (e.g., minimal management in a student house in comparison to an intensive maintenance with irrigation and adding composts in a high-price cottage) was comparable or even higher than total variance at the city level.  This is an important message for urban planners and landscape designers, claiming that the social factors and personal decisions shall not be ignored in climate-resilient strategies and practices to develop and maintain urban green infrastructures.

How to cite: Vasenev, S., Vlaming, M., Breeman, J., Romzaykina, O., and Stoorvogel, J.: Environmental and social drivers behind spatial variability of soil carbon in urban green infrastructures of Wageningen, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11691, https://doi.org/10.5194/egusphere-egu23-11691, 2023.

EGU23-12067 | Orals | ITS4.1/SSS0.2

Groundwater flow patterns and subsurface heterogeneity drive critical zone geochemical reactions 

Camille Bouchez, Ivan Osorio, Charlotte Le Traon, and Tanguy Le Borgne

In continental subsurface environments, biogeochemical reactions drive nutrient delivery, deep microbial life and mineral weathering, with crucial importance in the critical zone. Current models often simplify groundwater transport, using the residence time approach or hillslope models. However, increasing observations suggest that the nature, location and efficiency of reactions are strongly affected by groundwater 3D flow patterns, chemical gradients and subsurface heterogeneity. Here, we investigate how hydrological and geological structures control where and when biogeochemical reactions occur in the deep critical zone. For this purpose, our approach integrates long-term and widespread local observations in a catchment-scale framework and is based on data from two critical zone observatories of the French OZCAR national network. The first study took place in Guadeloupe (Obsera), where we integrated geophysical, hydrological and geochemical data in a reactive-hydrogeological model to simulate the 3D structure of groundwater flow paths and weathering. We found that the downstream evolution of the river chemistry is controlled by the pattern of hydrogeological circulations and by the depth of the weathering front. Furthermore, the calibrated 3D model allowed the delimitation of areas where weathering occurs and we showed that active weathering is restricted to catchment-areas where downward groundwater flows are deep. The second study focused on the dynamics of dissolved oxygen (DO) in a fractured aquifer at the Ploemeur catchment (Bretagne, France). Deep and intermittent inputs of DO in groundwater were observed, enabling the reaction of DO with dissolved Fe2+, in turn sustaining the development of deep microbial communities. In this study, we designed a simple model to simulate jointly the depth-distribution of DO and Fe2+ and to investigate the hydrological and geological factors controlling the DO depth-distribution. We found that the reducing capacity of the bedrock and the mean fluid transit time are the main parameters to explain and predict the depth of the oxic-anoxic transition in crystalline environments. In this presentation, we will provide new perspectives to observe and understand the origin of subsurface biogeochemical reactions and we will illustrate key processes that breakdown classical assumptions of reactive groundwater models.

How to cite: Bouchez, C., Osorio, I., Le Traon, C., and Le Borgne, T.: Groundwater flow patterns and subsurface heterogeneity drive critical zone geochemical reactions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12067, https://doi.org/10.5194/egusphere-egu23-12067, 2023.

EGU23-12542 | Orals | ITS4.1/SSS0.2

Comparison of Mobile Environmental Sensors for Citizen Science Based Climate Monitoring 

Felix Schmidt, Claudia Schütze, Uta Ködel, Fabian Schütze, Christine Liang, David Schäfer, and Peter Dietrich

The possibilities of citizen science-based approaches to environmental research and especially climate monitoring have recently expanded. This is among other things due to the availability of diverse measuring equipment at low costs, so that citizen science-based measuring missions can be implemented with a large number of participants. The advantages of high data density and spatial coverage are obvious. These advantages have been exploited for years by platforms such as www.awekas.at or www.weatherunderground.com and many others. With the help of mobile monitoring systems, the spatial coverage can now be extended even further. This means that the variability of climate values such as air temperature and relative humidity in cities can be investigated and more accurate forecasting models can be used.

A crucial aspect here is the reliability and comparability of the data collected with different devices. Therefore, we tested and compared within the EU project CityCLIM (www.cityclim.eu) different measurement equipment. Important characteristics of these devices are their low cost, ease of use and data access, data security and protection and the reliability of the measurement data. In the experiments presented here, 4 mobile systems were used: Meteotracker, senseBox, CHEAL5, PAM-AS520. All of these devices can determine air temperature, relative humidity, GPS-location and time and partly also particulate matter. In order to compare these systems, several measurement trips were made in the city of Leipzig in Saxony/Germany at different times of the year.

Surprisingly, there are considerable deviations between the devices in all measured values. This starts with the time and the GPS position. Here, there are sometimes shifts of several minutes and several metres. These errors could certainly be corrected with the help of calibration. However, this must also be practicable for the citizen scientist. In general, this example shows that quality control and backup of the data is necessary. In this sense, it is advantageous if there is a possibility to check the data live from the measurement operator or citizen. For this purpose, a direct upload of the data into the online portal/dashboard is very helpful. This direct data transfer also allows a simple and automated evaluation and storage of the large amounts of data.

Also the measurements of the air parameters show larger differences. Here, air flow at the sensor during the journey, protection from direct sunlight and the sensors used influence the measurement results. In any case, it is necessary to provide the users with detailed guidelines for the use of the sensors in order to increase the data quality. In summary, it turned out that the mobile measuring systems are suitable for citizen science-based climate observation with some limitations. Through the experiments, clear requirements for the devices could be worked out, which is helpful for the planning of future projects. The investigation of further devices and especially of quality control tools for the data are important next steps.

How to cite: Schmidt, F., Schütze, C., Ködel, U., Schütze, F., Liang, C., Schäfer, D., and Dietrich, P.: Comparison of Mobile Environmental Sensors for Citizen Science Based Climate Monitoring, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12542, https://doi.org/10.5194/egusphere-egu23-12542, 2023.

EGU23-12615 | ECS | Posters on site | ITS4.1/SSS0.2 | Highlight

Exploring practical citizen science in China 

Xudong Zhou, Luwen Wan, Jingyu Lin, Manqing Shao, Sifang Feng, Beichen Zhang, Yuanhao Xu, Yuxin Li, Yuan Liu, Ming Liu, Libo Wang, and Xingyan Tan

The development of citizen science is still at a very early stage in China. There are three primary reasons: 1. The government has strict data collection and sharing regulations. 2. There are very limited official leading groups, guidelines, and financial support on citizen science. 3. The public still lacks enthusiasm and basic training in citizen science. However, given the large population, increasing educational level of the society, and the help of new technologies, we can see a bright future for citizen science in China. We need to be prepared for that.

Hydro90 is a bottom-to-top established scientific community within the field of hydrology and earth science. It shares the latest academic research, broadcasts latest news, and organizes lectures, webinars, and workshops. It aims to enhance the communication among scholars, and between scholars and the public, especially among the young ages. It has been run for almost three years, with around 20,000 followers on the social media platform. However, we are still exploring how to promote citizen science in China. We want to share our recent experiences and efforts to overcome the current barriers in citizen science in the EGU. We are also looking forward to the great suggestions from European communities.

How to cite: Zhou, X., Wan, L., Lin, J., Shao, M., Feng, S., Zhang, B., Xu, Y., Li, Y., Liu, Y., Liu, M., Wang, L., and Tan, X.: Exploring practical citizen science in China, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12615, https://doi.org/10.5194/egusphere-egu23-12615, 2023.

EGU23-12709 | Posters virtual | ITS4.1/SSS0.2

The influence of deep groundwater flow systems on the Earth’s critical zone  

Brigitta Czauner, Szilvia Szkolnikovics-Simon, and Judit Mádl-Szőnyi

The depth of the Earth’s critical zone can be questionable especially in thousands meter deep sedimentary basins. Therefore, extension of the critical zone’s usually studied 10s of meters depth considering groundwater flow systems has critical importance. Growing demand for groundwater resources (water, geothermal energy), economic services of the groundwater flow related surface and subsurface processes and phenomena (e.g., groundwater dependent ecosystems, surface salinization), and the potential role of groundwater in the adaptation to and mitigation of the effects of human activities and climate change represent the significance and functions of groundwater flow systems in the critical zone.

Regarding the complexity of these flow systems, the primary goal could be the determination of their relative significance in the shallower parts of the critical zone. To this end, the present study proposes a methodology based on the hydrodynamic analysis of measured data to separate flow systems with different driving forces (topography, vertical compaction) and pore pressure regimes (normal or  close to hydrostatic, overpressured, underpressured). These characteristics define the renewability of groundwater resources, the near-surface conditions (e.g., distribution of nutrients, salts and heat, type of vegetation and soils, slope stability, etc.), and the exposure of flow systems to the effects of global and climate change.

As a case study, groundwater flow systems of the Great Hungarian Plain (Pannonian Basin, Hungary) were evaluated and characterized by analyzing about 5,800 measured hydraulic data (pre-production static water levels and static formation pressures) in hydraulic head vs. elevation and pressure vs. elevation profiles, tomographic maps, and hydraulic cross sections in combination with the geologic build-up and some surface phenomena (distribution of saline soils and vegetation). As a result, spatial extension and distinct functions in the critical zone were defined for three flow regimes, namely i) the near-surface topography-driven groundwater flow systems, ii) an underlying overpressured regime, and iii) the transition zone of i) and ii). For instance, outstanding significance of the upward flows of saline water from the transition zone was revealed in the generation of saline soils and vegetation.

The research was funded by the National Multidisciplinary Laboratory for Climate Change, RRF-2.3.1-21-2022-00014 project.

How to cite: Czauner, B., Szkolnikovics-Simon, S., and Mádl-Szőnyi, J.: The influence of deep groundwater flow systems on the Earth’s critical zone , EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12709, https://doi.org/10.5194/egusphere-egu23-12709, 2023.

Academia is more and more under the demand to create both scientific and societally relevant research with beneficial effects for society. There is a strong consensus that the engagement of non-academic actors in research activities is associated with greater societal relevance and usability of science for society. Involving non-academic actors within natural hazards and disaster risk research has seen a rise in popularity with the advent of participatory and transdisciplinary research approaches. Particularly in countries of the Global South, the participation, engagement, or involvement of non-academic actors in research on natural hazards and disaster risk is seen as promising strategy for solving data issues, raising awareness and generating knowledge. However, besides beneficial consequences, the participation, engagement, or involvement in scientific research may also have negative side-effects for non-academic actors (e.g., causing mistrust, anxiety, or research-fatigue). Against this background, the aim of the ImSE-R project is to assess how the participation, engagement, or involvement in scientific research on natural hazards and disaster risk may have consequences – ranging from intended impacts to unintended implications and negative side-effects for non-academic actors. This contribution presents the results of a systematic review of studies on hazards and disaster risk in the Himalayan region (2000-2022) to better understand how academic actors negotiate and manage research relationships with non-academic actors in the context of natural hazards and disaster risk research. The contribution derives insights on how non-academic actors were involved in natural hazard and disaster risk research activities (actively, passively); underlying motivations and goals of academic actors for involving non-academic actors in natural hazard and disaster risk research; and perceived impacts and implications of involving non-academic actors in research. The results of the review feed into the development of a conceptual framework on research impacts and implications in the context of natural hazard and disaster risk research.

How to cite: Posch, E.: Side-effects of doing research? Potential consequences of involving non-academic actors in natural hazard research, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14528, https://doi.org/10.5194/egusphere-egu23-14528, 2023.

EGU23-14567 | ECS | Posters on site | ITS4.1/SSS0.2

The impact of landscape and land use changes on the critical zone and society: the Belmont Forum ABRESO project 

Chiara Richiardi, Maria Adamo, Andrea Scartazza, Lisa Sella, Ilaria Baneschi, Serena Botteghi, Enrico Brugnoli, Silvana Fuina, Olga Gavrichkova, Michael Maerker, Michele Mattioni, Elena Ragazzi, Valentina Rossi, Francesca Silvia Rota, Matteo Salvadori, Cristina Tarantino, Saverio Vicario, Alberto Zanetti, and Maddalena Pennisi

The stable presence of humans in the Alps dates back to the Bronze Age and peaked in the mid-19th century, deeply shaping the landscape and allowing the co-evolution of numerous plant and animal species. Since the 1950s, socio-economic changes have led to the gradual depopulation of mountain areas, and the consequent abandonment of traditional agro-pastoral activities. The rupture of the long-established balance between man and nature has triggered a process of transition, further exacerbated and accelerated by climate change. The Belmont Forum project ABRESO (Abandonment and rebound: Societal views on landscape and land-use change and their impacts on water and soils) started in 2021 and aims at advancing the understanding of mitigation and adaptation strategies to environmental change, through an international partnership involving five countries (the United States, France, Italy, Japan and Taiwan). Italy contributes to the project with three case studies: Gran Paradiso National Park, Val Grande National Park and the Tesino highlands are investigated in the Italian Alps. Using an interdisciplinary approach, the project aims to study the impact of the abandonment of traditional activities on ecosystem services provisioning, such as biodiversity conservation and soil sustainability, as well as the actual perception of the ongoing environmental changes by different stakeholders and its subsequent integration into local land management practices and policies. The land use and land cover change occurring due to land abandonment can have profound implications in the critical zone (CZ), inducing changes in soil, vegetation, carbon fluxes and water resources. This project integrates the natural and social sciences approaches to study the evolution of ecosystems in response to these factors. More specifically, advanced techniques that integrate Earth Observation, biogeochemical analyses and socio-economic investigation are used in the Italian sites to understand in which extent geo-biophysical and social landscapes reciprocally interact. The environmental variables collected for ecosystem monitoring and to study and upscale the ongoing dynamics in the CZ include snow cover and phenology parameters, soil organic carbon, and land use change maps extracted from time series of satellite imagery, validated via in situ measurements. Then, the observed processes will be compared to the perception of different stakeholders (local population, policy makers, tourists, business keepers, etc.) to unveil new insights into the way land use change in the mountain areas influence and is influenced by the local land management practices and policies.

How to cite: Richiardi, C., Adamo, M., Scartazza, A., Sella, L., Baneschi, I., Botteghi, S., Brugnoli, E., Fuina, S., Gavrichkova, O., Maerker, M., Mattioni, M., Ragazzi, E., Rossi, V., Rota, F. S., Salvadori, M., Tarantino, C., Vicario, S., Zanetti, A., and Pennisi, M.: The impact of landscape and land use changes on the critical zone and society: the Belmont Forum ABRESO project, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14567, https://doi.org/10.5194/egusphere-egu23-14567, 2023.

EGU23-15940 | ECS | Orals | ITS4.1/SSS0.2

Tracking natural hazard disasters in non-surveyed regions: the “citizen” observer network of the Kivu in DR Congo 

Caroline Michellier, Théo Mana Ngotuly, Jean-Claude Maki Mateso, Joseph Kambale Makundi, Jean-Marie Bwishe, Olivier Dewitte, and François Kervyn

In the Tropics, disasters associated with natural hazards (intense convective rainfalls, floods, landslides) occur regularly. However, the general scarcity of reliable and accurate data collected on these events does not allow for a complete picture of their frequency and magnitude, thus hindering effective Disaster Risk Reduction (DRR). Such situation is observed in the Kivu region, in the eastern part of the DR Congo. Recurrent insecurity, long distances to travel, poor communication networks and the lack of financial resources to reach the affected areas are the main challenges faced by the Congolese Civil Protection in building a database that would allow for a better knowledge of these phenomena, in view of an appropriate disaster response and, in the long term, efficient DRR.

Based on this observation, a group of 20 citizen observers was set up to collect data on six different types of natural hazard disasters (floods, landslides, wind storms, hail storms, lightning, and earthquakes) using smartphone technology connected to an online platform. This new approach, based on citizen science, makes it possible to significantly improve the documenting and understanding of the spatial and temporal occurrence of these disasters that affect the provinces of North and South Kivu. Since the establishment of this network in December 2019, more than 700 events have been recorded.

If the data collected by this network of citizen observers constitute above all an unprecedented amount of information on the disasters occurring in such a tropical environment, they also allow for the compilation of a WebGIS and quarterly reports illustrated with maps and graphs, disseminated by Civil Protection to key DRR stakeholders active in the region, for a more tailored response, its planification, and, to some extent, the anticipation of such events. Scientists from universities and research centers in Bukavu and Goma are associated to that data collection and analysis. Moreover, citizen observers position themselves within their communities as key actors in raising awareness about disaster risks. However, although this type of approach has proven to be effective in the short term, the motivation on the long term of citizen observers, as volunteers, has been identified as a weakness to be addressed.

How to cite: Michellier, C., Mana Ngotuly, T., Maki Mateso, J.-C., Kambale Makundi, J., Bwishe, J.-M., Dewitte, O., and Kervyn, F.: Tracking natural hazard disasters in non-surveyed regions: the “citizen” observer network of the Kivu in DR Congo, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15940, https://doi.org/10.5194/egusphere-egu23-15940, 2023.

Processes linking lower and upper parts of the Critical Zone (CZ) are crucial for sustaining life on continents and ecosystem services provided by eco- or agro-systems. Rock weathering at depth is expected to be an essential source of nutrients and deep-rooted trees are believed to induce water and nutrient ‘lift’, benefiting the whole community. However, quantifying this nutrient lift remains a challenge linked on the one hand to the hidden nature of the roots and on the other hand to the complexity of the rhizosphere dynamics. The Nutrilift project aims at quantifying the role of deep critical zone in the supply of nutrients to eco- and agrosystems, based on the hypothesis that while in natural forests, deep-rooted species can derive part of their nutrient resources from increased mineral weathering at depth, the relative importance of this process in shallow-rooted agrosystems is much less - and agroforestry systems represent an intermediate situation. Conducted within the framework of the Indo-French Cell for Water Sciences (IRD - CNRS - INRAE - UPS - Indian Institute of Science, Bangalore, India), the project is based on long-term monitoring in the Mule Hole (diversified forest) and Berambadi (irrigated agriculture and agroforestry) watersheds of the M-TROPICS Observatory in Peninsular India. For this purpose, we study the vertical evolution of soil properties and associated pedological processes as a function of plant cover/land-use. Weathering processes and/or plant uptake will be studied in the vicinity of the roots using micro-characterization techniques, which will allow to calibrate combined hydro-geochemical models. The deep contribution to the nutrient budgets of each site will be quantified by intra-plant isotopic balances as well as by the identification of specific geochemical signatures to the deep contribution of the critical zone. An originality of the project is the observation of the deep critical zone (up to 10m) via instrumented pits with continuous pCO2 and moisture measurements, scanners (root dynamics) imaging and pore water collection. The effects of future changes -associated with climate and land uses- on the dynamics of the deep critical zone will be explored from scenarios co-constructed with local stakeholders.

How to cite: Riotte, J. and the Nutrilift team: Deep roots versus pumps: comparison of deep nutrient removal in dry tropical eco- and agrosystems (ANR project Nutrilift), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17441, https://doi.org/10.5194/egusphere-egu23-17441, 2023.

While developed nations are assumed to provide high groundwater quality security, populations reliant on (typically rural, unregulated) private domestic groundwater wells are often uniquely vulnerable to supply contamination. The potential health ramifications of exposure to contaminated groundwater may be especially grave for immunosuppressed populations residing in service-deprived and climate-vulnerable areas, necessitating concerted government (educational) and household-level (behavioural) action. In response, a growing number of studies (spanning quantitative contamination risk assessments, policy strategies, communicative interventions and householder surveys) have emerged within the last several decades. To date, few investigations have sought to synthesise this literature and ascertain the potential generality of drivers of both private groundwater contamination and preventive responses in high-income countries.

 

The developed regions of the Republic of Ireland (ROI) and Ontario represent an appropriate point of comparison to establish research transferability. Both regions are characterised by high private groundwater reliance (> 10% of their respective populations), pervasive microbial groundwater contamination and significant associations between acute gastrointestinal illness (AGI) and private well use. Consumption of private well water contributes to approximately 4,800 annual cases of AGI in Ontario and as many as 80% of annual cases of verotoxigenic E.coli (VTEC) in the ROI. However, despite similarities, regional discrepancies exist with respect to policy landscapes (e.g., monetary requirements for private water quality testing) and contamination risk profiles (e.g., frequency of extreme weather event concurrence). In efforts to elucidate the potential implications of these phenomena, a scoping review of literature (1990-2022) in the ROI and Ontario outlining risk management measures to prevent private groundwater contamination in the was undertaken. The SPICE (Setting, Population/Phenomenon, Intervention, Setting, Perspective) methodology was utilised to inform literature search terms, with Scopus and Web of Science selected as primary databases for article searches. Following removal of duplicate studies and article screening, 92 articles (Canada = 70, ROI = 22) were retained for analysis.

 

Articles were predominantly comprised of quantitative contamination risk assessment studies (n = 68), with qualitative and quantitative questionnaire investigations (n = 16), interventions (n = 2) and policy studies (n = 6) noticeably less frequent. Quantitative risk assessments published after the year 2000 demonstrated an overwhelming focus on microbial supply contamination, identifying well type and proximity of agricultural activity as significant determinants of supply contamination. Survey studies in both regions also consistently highlighted gender, perceived confidence in maintaining supply and economic and convenience barriers as significant determinants of well user knowledge and behaviour. However, well users in Ontario demonstrated markedly higher rates of prior well testing (irrespective of adherence to regional guidelines), suggesting that incentivised (or free) well testing may lead to significant increases in uptake of well water quality testing. The paucity of identified intervention studies suggests that increased research investigating methods of well user outreach and groundwater risk communication will be necessary in the future to determine the broad efficacy of risk communication in developed nations.

How to cite: Mooney, S., O’Neill, E., and Hynds, P.: Top-down and bottom-up management of private groundwater contamination risk: A comparative scoping review of similarities, drivers and challenges in two developed regions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17513, https://doi.org/10.5194/egusphere-egu23-17513, 2023.

SSS2 – Soil Erosion and Conservation

EGU23-149 | ECS | Orals | SSS2.1

Predicting badland occurrence in Catalonia by applying random forest techniques and a multi-scale approach 

Ona Torra, Marcel Hürlimann, Càrol Puig-Polo, and Mariano Moreno-de las Heras

Badlands are highly erosive landforms of dissected morphology, which can be found on soft rocks and unconsolidated sediments, with little or no vegetation, that are useless for agriculture. The erosion rates of these areas are high, causing important environmental and economic problems. For that reason, detecting the main conditioning factors that control badland occurrence and identifying susceptible areas is higly important to prevent soil erosion phenomena and their negative consequences.
This work attempts to assess badland susceptibility and their governing factors at a multi-scale level, using a random forest (RF) modelling approach. Previous RF-based research have demonstrated that RF modelling is a powerful tool for making predictions in the same spatial context and scale where the model has been trained. However, upscaling RF-modelling results to obtain accurate predictions in other, more extensive spatial contexts than that used for model training, remains an important challenge.
For that, the Upper Llobregat River Basin (ULRB, 504.8 km2) and Catalonia region (CAT, 32000 km2) have been selected as study areas. We have evaluated the viability of training a RF model for the analysis of badland suceptibility in the small spatial context of the ULRB, and further testing it to the more extensive spatial context of CAT. Revealing the most important factors that control badland distribution in the territory has been another goal in the present study. Eleven governing factors and two badland inventories developed for these study areas have been used for model training and testing. Model performance has been analyzed through validation tests and three different evaluation metrics: AUC, Kappa coefficient and accuracy. The outcomes of this work manifest that the two variables that have the most important relevance for badland occurrence are lithology and NDVI. In addition, our results showed that upscaling RF model results defined in the ULRB to the more extensive spatial context of CAT in order to predict badland occurrence, it’s possible but not ideal. Last, badland susceptibility maps of ULRB and Catalonia have been obtained with a very high accuracy (96% and 97% respectively), confirming the feasibility and uselfuness of RF approach for badland susceptibility assessment.

 

How to cite: Torra, O., Hürlimann, M., Puig-Polo, C., and Moreno-de las Heras, M.: Predicting badland occurrence in Catalonia by applying random forest techniques and a multi-scale approach, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-149, https://doi.org/10.5194/egusphere-egu23-149, 2023.

EGU23-261 | Orals | SSS2.1

Testing simple approaches to map sediment mobilization hotspots after wildfires 

Joana Parente, João Nunes, Jantiene Baartman, and Dante Föllmi

The models currently used to predict post-fire soil erosion risks are limited by high data demands and long computation times. An alternative is to map the potential hydrological and sediment connectivity using indices to express the general properties of the landscape under evaluation and map the possible connectivity between the different parts of a catchment.

In this study, we aim to answer the question: Do these alternative approaches identify post-fire sediment mobilization hotspots?  To achieve this, we assess the spatial variability distribution of the location of soil erosion hotspots using the Index of Connectivity (IC), Revised Universal Soil Loss Equation (RUSLE model) and the Sediment Export (SE) and compare it to the simulation results of a more complex Landscape Evolution Model (LAPSUS model). Additionally, we evaluate statistical measures of association between the four tools. Furthermore, IC, RUSLE model and SE are used due to their simplistic representation of erosion and ease of application, and the LAPSUS model is used as the best representation of erosion and sediment transport in the study area.

Our results show that the three tools (IC, RUSLE model and SE) tested in this study are suitable for identifying sediment mobilization hotspots, i.e., areas where the erosion rates are above the 90th percentile, in recently burnt areas, and differences between their performance are minor. These findings can be considered for post-fire and water contamination risk management, especially for fast prioritization of areas needing emergency post-fire intervention.

How to cite: Parente, J., Nunes, J., Baartman, J., and Föllmi, D.: Testing simple approaches to map sediment mobilization hotspots after wildfires, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-261, https://doi.org/10.5194/egusphere-egu23-261, 2023.

EGU23-477 | ECS | Orals | SSS2.1

Trapping efficiency of vegetative barriers in agricultural landscapes. An operational model from a review of available information 

Jose Antonio Muñoz, Gema Guzmán, María Auxiliadora Soriano, and Jose Alfonso Gómez

Vegetative barriers have proven their effectiveness in controlling erosion and promoting other ecosystem services in agricultural areas. This has led to their conservation and promotion as landscape elements by the Common Agricultural Policy and other policy initiatives. However, predicting their efficiency in reducing hydrologic connectivity presents a large uncertainty (Gumiere et al., 2011).

This communication presents an analysis of trapping efficiency of sediment, runoff, and nutrients (P and N) by vegetative barriers aimed to provide a statistical approach to efficiency, based on a review of available studies, considering two climates: humid and arid/semi-arid (Muñoz et al, 2022). For this, different independent variables were grouped and identified to explore its influence: i) those defining the vegetative barrier dimension (width, slope of the plot, and area ratio buffer/plot) and ii) those related to experimental conditions (type of vegetation, soil protection of the non-buffered area, type of climate, type of experimental measurement and origin of the rainfall). A more detailed analysis was performed with the studies which reproduce similar situations to the ones occurring naturally (natural rainfall and paired plots).

In general, average trapping efficiencies for runoff and sediment are 40.1 and 62.6% and ranging between -81.0 to 99.9% and -109 to 100%, respectively. For nutrients, values of trapping efficiencies had an average of 44.9 and 38.4% for phosphorus and nitrogen, respectively. The lack of data and the large variability among and within the measurements from the studies considered in our review only allowed to detect slight trends and statistically significant differences in some cases for the different variables analysed.

In order to provide guidelines to farmers and technicians, a probabilistic model was developed for sediment trapping efficiency regarding the width of the vegetative barrier and the climatic region. The model showed that in 92% of the cases, a vegetative barrier will reduce erosion in humid climates while this trapping efficiency will be 100% in semi-arid/arid conditions. Grouping the vegetative barriers’ width in different intervals, it was observed that the maximum trapping efficiency is ~80 % for a width of 2.75 to 3-m in arid/semi-arid climate and 5 to 6-m in humid regions.

 

Acknowledgement: This work supported by the project PID2019-105793RB-I00 financed by the Spanish Ministry of Science and Innovation, and project TUdi, GA 101000224, of the European Union’s Horizon 2020 research and innovation programme

References

Gumiere, S. J., Le Bissonnais, Y., Raclot, D., & Cheviron, B. (2011). Vegetated filter effects on sedimentological connectivity of agricultural catchments in erosion modelling: A review. Earth Surface Processes and Landforms, 36(1), 3–19. https://doi.org/10.1002/esp.2042.

Muñoz, J. A., Guzmán G., Soriano M.A., & Gómez J. A. (2022). Trapping efficiency of vegetative barriers in agricultural landscapes. An operational model from a review of available information. Manuscript submitted for publication.

How to cite: Muñoz, J. A., Guzmán, G., Soriano, M. A., and Gómez, J. A.: Trapping efficiency of vegetative barriers in agricultural landscapes. An operational model from a review of available information, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-477, https://doi.org/10.5194/egusphere-egu23-477, 2023.

EGU23-646 | ECS | Orals | SSS2.1

Topographic signature of badlands landscapes 

Aydogan Avcioglu, Wolfgang Schwanghart, Tolga Görüm, Ömer Yetemen, Mariano Moreno-de las Heras, and Ci Jian Yang

 

As part of the earth's dynamic systems, badland landscapes are chiefly generated by the interaction between bedrock weathering, climate seasonality, and the controversial contribution of the hillslope and fluvial erosion processes. Although contemporary definitions clearly point out that badland initiation is a function of overland-flow-dominated gully channels, gravitational processes-dominated mass movements, and subsurface processes-driven piping, the following related questions remain to be tackled regarding their topographic position in the landscape: (1) Are the badland landforms signature of hillslope or fluvial erosion domain? (2) How do climate and regional settings (i.e., macro landforms, homogenous or heterogenous lithologies, etc.) influence the topographic position of badlands? To address these questions, we have selected climatically distinct badlands from different continents where; digital elevation models are available: Utah and South Dakota (USA), Upper Llobregat and Murcia (Spain), Northern Apennines and Basilicata (Italy), Mediterranean and Plateau – Margin Transition Badlands (Turkey), and Southern Taiwan. The badland boundaries were visually inspected and manually digitized based on diagnostic morphologic indicators. We have utilized the slope and drainage area relationship by using a 5m digital terrain model to identify topographic thresholds at TopoToolbox, a MATLAB-based software for topographic analysis. Preliminary results show that most badland areas occupy a maximum of 104 to 105 m2 contribution area in the landscapes. Although contribution areas relatively represent uniform thresholds in the sites, the local gradient (S), which is proportional to the contribution area, tends to be higher in the sub-humid mountainous badlands (Upper Llobregat, Northern Apennines) and wet tropical SW Taiwan than in semi-arid badlands (Basilicata, Murcia). We conclude that the topographic signature of badlands in the context of the sub-catchment scale may depict an appropriate instance of a transitional domain from a diffusive erosional process to a fluvial erosion process. Our findings may serve as a foundation for a better understanding of the classification and automatic detection of badland landscapes, also known as erosional hot spots.

This study has been produced benefiting from the 2232 International Fellowship for Outstanding Researchers Program of the Scientific and Technological Research Council of Turkey (TUBITAK) through grant 118C329 and TUBITAK 2214-A International Research Fellowship Programme.

 

 

How to cite: Avcioglu, A., Schwanghart, W., Görüm, T., Yetemen, Ö., Moreno-de las Heras, M., and Yang, C. J.: Topographic signature of badlands landscapes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-646, https://doi.org/10.5194/egusphere-egu23-646, 2023.

EGU23-883 | ECS | Orals | SSS2.1

National Scale Soil Erosion and Sediment Yield Assessment over India 

Ravi Raj, Manabendra Saharia, and Sumedha Chakma

Soil erosion has always been a threat to the environment and agricultural practices throughout the world. For a country like India, where agriculture contributes primarily to its economy, it becomes a major problem. Identifying these vulnerable regions and planning for mitigation is crucial for sustainable soil resource management. For this, mapping or modeling soil erosion at a national scale is required to understand the variability of soil losses throughout the country. Performing field-based experiments to estimate soil losses over a large country is always expensive and tedious. Revised Soil Loss Equation (RUSLE), an empirical model, has been more prominent worldwide due to its simplicity and less forcing data requirements. In this study, average annual Potential Soil Erosion (PSE) was estimated over India using IRED (Indian Rainfall Erosivity Dataset), ISED (Indian Soil Erodibility Dataset), SRTM (Shuttle Radar Topographic Mission), DEM (Digital Elevation Model), and LULC (Land-use/Land-cover) obtained from NRSC (National Remote Sensing Institute) India. PSE was further analyzed using LULC categories and soil types to visualize the impact of soil erosion in each class. As erosion significantly affected agricultural activities, financial losses over the nation were also estimated, considering the severity of soil erosion. Further, Sediment Delivery Ratio (SDR) and Specific Sediment Yield (SSY) were also mapped over the national boundary to visualize the actual soil displacement at a grid scale of 250 m. Using the SSY map, the incoming sediment load to reservoirs/dams/lakes was also estimated considering its watershed areas. This study will be helpful for the experts in the field of sustainable soil resources management for planning mitigation measurements against soil losses in India.

Keywords: Soil Erosion, Sediment Yield, Sediment Delivery Ratio, India, RUSLE, LULC

How to cite: Raj, R., Saharia, M., and Chakma, S.: National Scale Soil Erosion and Sediment Yield Assessment over India, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-883, https://doi.org/10.5194/egusphere-egu23-883, 2023.

EGU23-1467 | ECS | Orals | SSS2.1

A European database of soil piping-related features: a major step towards producing 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, Panos Panagos, Dawid Piątek, Taco H. Regensburg, Jan Rodzik, Estela Nadal-Romero, Mateusz Stolarczyk, Patryk Wacławczyk, and Wojciech Zgłobicki

A better understanding of soil erosion is not possible without including subsurface erosion. Soil piping may significantly contribute to the overall erosion problem in a given area and may therefore change the conditions and methods for controlling soil degradation. Therefore, there is an urgent need to identify regionally and globally sites where soil piping occurs which then may require a change of the strategies to control soil erosion. In this project, we are constructing the very first data-driven piping erosion susceptibility map of Europe. The crucial point is to identify piping-affected areas by mapping the soil piping-related features, i.e. pipe roof collapses (PCs) and pipe outlets in the European Union and the UK. Mapping is based on an in-depth literature review in combination with detailed mapping using Google Earth imagery, and LiDAR data (if available). The database currently consists of 6841 piping-related features (6171 PCs, and 670 outlets), among which the location of 88% features is certain (within a resolution of 25 m). Almost 28% (1889 features) were located based on detailed fieldwork, 25% (1726) were extracted from published papers, and 47% based on a detailed analysis of Google Earth imagery and LiDAR data (19% and 28%, respectively). This database is currently used to construct the very first data-driven piping erosion susceptibility map of Europe.

 

This research is part of the project “Building excellence in research of human-environmental systems with geospatial and Earth observation technologies” that received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 952327.

How to cite: Bernatek-Jakiel, A., Vanmaercke, M., Poesen, J., Biernacka, A., Borrelli, P., Derii, A., Hałys, J., Holden, J., Jakab, G., Panagos, P., Piątek, D., Regensburg, T. H., Rodzik, J., Nadal-Romero, E., Stolarczyk, M., Wacławczyk, P., and Zgłobicki, W.: A European database of soil piping-related features: a major step towards producing a piping erosion susceptibility map of Europe, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1467, https://doi.org/10.5194/egusphere-egu23-1467, 2023.

EGU23-1468 | ECS | Posters on site | SSS2.1

Gully and cliff erosion feature detection in the Wairoa catchment in Hawke’s Bay, New Zealand 

Lorena Abad, Daniel Hölbling, Hugh Smith, Andrew Neverman, Harley Betts, and Raphael Spiekermann

Gullies and cliff erosion are significant indicators of land degradation. Knowledge of the spatial distribution and dimensions of these erosion features is needed to effectively quantify sediment budgets and to implement erosion mitigation measures. Expert delineation can help identify features at a local sale, however, mapping larger extents becomes time consuming. Object detection techniques based on aerial photographs and LiDAR elevation data can improve the automated delineation of such features. In this study, we tested a region-based convolutional neural network (Mask-RCNN) deep learning approach to identify gully and cliff features. 

An expert-based delineation of gully and cliff features was performed in the Wairoa catchment in Hawke’s Bay, New Zealand based on aerial photographs obtained between 2017 and 2020. These delineations served as reference data to create labelled chips for training deep learning models. Several terrain derivatives from the LiDAR digital elevation model (DEM), including slope, hillshade, slope length and steepness (LS) factor, and terrain ruggedness index, were computed. The terrain derivatives and spectral bands (R-G-B-NIR) from the aerial photographs were used to train deep learning models based on different band combinations. 

Despite achieving high accuracy (average precision score above 85%) during training, transferring the models to validation areas resulted in low detection rates, with a large number of false negatives. However, the correctly detected erosion features correspond very well to the reference data delineations, even achieving good results for the differentiation between gullies and cliffs. A closer inspection of the false positive features suggests that the reference data could be incomplete. Our study shows that deep learning has a high potential for automated gully and cliff mapping, but further improvement of the model transferability is needed. A combination of automated and expert-based delineation would potentially result in reliable and efficient erosion feature detection.

How to cite: Abad, L., Hölbling, D., Smith, H., Neverman, A., Betts, H., and Spiekermann, R.: Gully and cliff erosion feature detection in the Wairoa catchment in Hawke’s Bay, New Zealand, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1468, https://doi.org/10.5194/egusphere-egu23-1468, 2023.

EGU23-1523 | ECS | Posters on site | SSS2.1

Soil erosion susceptibility assessment in Mediterranean areas by means of soil quality. A test in the Guadalmedina watershed (Málaga,Spain) 

Javier González-Pérez, José Antonio Sillero-Medina, Julia Espinosa-Muñoz, and José Damián Ruiz-Sinoga

Soil erosion is one of the most relevant environmental problems facing society today. Climate change has a direct impact on these processes through a feedback loop, especially in the Mediterranean region, where the situation is conceived as one of extreme fragility. The increase in extreme rainfall and temperature events, together with differential human land use, are leading to an intense degradation of Mediterranean soils. Therefore, it is essential to determine the levels of susceptibility of the landscape to erosion processes to create new strategies to improve the management of the land and reduce the potential risks that may exist. Specifically, this work has focused on the Guadalmedina watershed, in Malaga (Spain), which is characteristic of the current dynamics of the Mediterranean landscape. For this purpose, a soil quality index based on a multi-criteria analysis of different soil indicators (water, physical and organic) has been applied in this study, using a total of 132 soil samples measured in the laboratory. In addition, the results of this analysis have been contrasted with soil erosion values derived from the application of RUSLE model. From this process, those slopes and fields with the highest water erosion risk values have been identified at the most detailed scale. In general, the lowest soil erosion rates are found in those areas where soil quality indicators show optimal values. Furthermore, the results obtained indicate that organic soil indicators are decisive in the processes of water erosion in the Mediterranean area.

How to cite: González-Pérez, J., Sillero-Medina, J. A., Espinosa-Muñoz, J., and Ruiz-Sinoga, J. D.: Soil erosion susceptibility assessment in Mediterranean areas by means of soil quality. A test in the Guadalmedina watershed (Málaga,Spain), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1523, https://doi.org/10.5194/egusphere-egu23-1523, 2023.

EGU23-1892 | ECS | Orals | SSS2.1

Modified global soil risk map using soil erosion and saturated hydraulic conductivity maps 

Surya Gupta, Pasquale Borrelli, Panos Panagos, and Christine Alewell

Soil erosion (SE) and saturated hydraulic conductivity (Ksat) are the essential indicators for land degradation and soil nutrient loss. Both processes are linked with each other as one can enhance the other resulting in positive feedback loops. The increase in soil erosion might block the macropores and reduce Ksat. In contrast, the reduction in Ksat triggers the runoff and increases soil erosion. However, modelling and predicting soil erosion, hydraulic properties are usually not adequately considered. We tried to link soil erosion directly with Ksat on a global scale. For this, we used global soil erosion and saturated hydraulic conductivity maps to yield combined soil risk classes. SE and Ksat maps were obtained from Borrelli et al. (2017) and Gupta et al. (2021), respectively. Each map was classified into six classes based on the previous studies. Moreover, both maps' classes were combined by creating six merged classes to develop the modified soil risk map. The modified soil risk map highlights regions with low Ksat and high SE. Furthermore, the final map was validated using continental and/or national sediment yield (SY) datasets. SY classes were compared with final risk classes to validate the accuracy of the map. The modified soil risk map showed higher accuracy compared to the SE map when compared with SY classes. This study demonstrates the first attempt to link soil erosion to soil hydraulic properties on large scales.

How to cite: Gupta, S., Borrelli, P., Panagos, P., and Alewell, C.: Modified global soil risk map using soil erosion and saturated hydraulic conductivity maps, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1892, https://doi.org/10.5194/egusphere-egu23-1892, 2023.

EGU23-2355 | ECS | Posters on site | SSS2.1

airSUM - Structure from Motion supported Stock Unearthing Method: Erosion modeling in Viennese vineyards 

Robert Kanta and Sabine Kraushaar

Soil mobilization is particularly high in viticulture. In Austria and especially in Vienna, soil protection measures are frequently implemented, without the vintners knowing about the extent of erosion rates and where they can take additional measures in particular. However, new methods for erosion estimation with high accuracy and cost efficiency are expected to improve this situation. Of which one application will be presented in this study.

A relatively fast and low-cost possibility is the stock unearthing method (SUM), which provides a rough estimation of erosion, based on biomarkers but neglects the inter-row area. The improved ISUM is using additional measurement points in this area and therefore delivering more accurate erosion volumes. Additionally, the use of structure from motion (SfM) DEMs provided respectable results on small plots in vineyards. The combination of SUM and SfM allows the new airSUM approach to provide a significantly more precise estimation of annual erosion rates, making rendering interpolation techniques unnecessary. The resulting model represents the present relief and is able to reproduce visible runoff patterns. The use of airSUM enabled the detection of 32.7 m3 (avg. of ~83.9 t ha-1 yr-1) soil erosion on an area of 700 m2 in a period of 8 years. Erosion hotspots could be modeled mainly in the wheel tracks with depths of up to 20.5 cm parallel to the slope and correspond excellently with field observations. This is partly due to the compaction of the surface, but mainly due to the preferential runoff and erosion. The identification of the erosion hot spots, runoff breaches and consequently runoff concentration allows the precise allocation of mitigation funds to reduce overland flow and erosion.

How to cite: Kanta, R. and Kraushaar, S.: airSUM - Structure from Motion supported Stock Unearthing Method: Erosion modeling in Viennese vineyards, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2355, https://doi.org/10.5194/egusphere-egu23-2355, 2023.

EGU23-2588 | ECS | Posters on site | SSS2.1

Erosive rainfall clustering across Austria's agricultural areas 

Cristina Vasquez, Andreas Klik, Christine Stumpp, Peter Strauß, Gregor Laaha, Nur Banu Özcelik, Pistotnik Georg, Tomas Dostal, Shuiqing Yin, and Stefan Strohmeier

A few low-frequent but extreme rainfall events generate substantial erosion amounts and, as a result, land degradation negatively affects soil health and agricultural productivity. Determining rainfall erosivity (from small to extreme events) that drive soil erosion will improve our knowledge and understanding of extreme erosion processes and our ability to develop and adapt adequate soil protection strategies. This study aims to analyze rainfall erosivity characteristics across Austria‘s main agricultural production zones using long-term (from 27 to 82 years) with high-resolution (5-minutes) rainfall data from 27 rain gauges. Erosive rainfall characteristics such as rainfall amount, event duration, and the maximum 30-minute intensity were investigated, and typical rainfall types were assessed through a clustering approach based on the k-means algorithm. Results identified three dominant types (clusters) of erosive rainfalls across Austria's agricultural areas. Seasonal distribution analysis showed that the predominant erosive events, characterized by short duration and high intensities, occur during the summer months from June to August. In contrast, the long-duration and low rainfall-intensity events are evenly distributed throughout the year. The spatial distribution of rainfalls related to the largest rainfall erosivities showed a pronounced occurrence in the southeastern pre-alpine areas. Knowledge of the occurrence of erosive rainfall events in space and time eventually supports the implementation of locally adapted Soil Conservation (SC) practices in Austria.

How to cite: Vasquez, C., Klik, A., Stumpp, C., Strauß, P., Laaha, G., Özcelik, N. B., Georg, P., Dostal, T., Yin, S., and Strohmeier, S.: Erosive rainfall clustering across Austria's agricultural areas, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2588, https://doi.org/10.5194/egusphere-egu23-2588, 2023.

EGU23-3436 | ECS | Posters on site | SSS2.1

The potential to reconstruct 20th century soil carbon erosion in rangelands from small reservoir sediments 

Lu Li, Juliane Krenz, and Nikolaus J Kuhn

Land degradation affects the productivity of the land, but is also associated with a flux of greenhouse gases (GHGs) from soil and vegetation into the atmosphere. The large area of rangelands (35 million km2, cover about 40% of earth’s surface) can contribute significantly to changes of atmospheric CO2 concentrations following even a minor alteration of the rangeland soil C pool (Wang et al. 2002). Degradation of South African rangelands has been a concern for more than 100 years (Rowntree, 2013). The Karoo drylands, covering 30% of the land surface of South Africa, have experienced particular intense soil erosion and thus loss of topsoil C. To sustain the large number of animals, many small farm dams have been constructed mainly in the first half of the twentieth century. As a consequence of the soil erosion, they are now often silted-up and have breached (Boardman, 2014). The sediment deposited behind such small dams offers the possibility to reconstruct the loss soil C for the time peirod between construction and breaching of dams. Five dams were chosen to explore the possibility to use their sediment as an environmental archive for 20th century rangeland soil Carbon loss. The specific aims of our study are to 1) find out whether distinct C profiles can be discerned in dam sediments; 2) identify whether these changes potentially reflect erosion and soil C loss in the dam catchments; and 3) to discuss whether the dam sediments can serve as an environmental archive to reconstruct soil-atmosphere interaction during recent decades. The initial survey of the dams involved the sampling of individual sediment strata and the analysis of their organic and nitrogen content, as well as the 137Cs activity of selected samples to gain an insight into the time of deposition. Two dams showed a profile that indicates a loss of soil C during the first decreased after their construction, while the other dams showed no clear signal or even an increase of sediment C in the younger sediment. One dam showed no 137Cs activity, indicating that it was filled with sediment very quickly after construction. These results illustrate that soil degradation and associated loss of soil C stocks can potentially be reconstructed based on the small dam sediments. However, the source of the sediment C has to be tested, as well as the individual land use and erosion history of each dam catchment. 

How to cite: Li, L., Krenz, J., and Kuhn, N. J.: The potential to reconstruct 20th century soil carbon erosion in rangelands from small reservoir sediments, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3436, https://doi.org/10.5194/egusphere-egu23-3436, 2023.

EGU23-3537 | Posters on site | SSS2.1

Impact of rapid deforestation and conversion of traditional agricultural practices into food crop production on land and water degradation: a case study from Mayotte Island, Indian Ocean, France (2011-2022) 

Anthony Foucher, Olivier Evrard, Laura Rabiet, Olivier Cerdan, Valentin Landemaine, Maxime Vitter, and Jean-François Desprats

During the last twenty years, Mayotte island (France, Comoros archipelago) has experienced an explosion of population (+80% between 2002 and 2021, taking the official population into account only) leading to a deforestation and a decline in traditional agricultural practices (mahorais garden) in favor of intensive food crop monocultures (e.g. banana, manioc…). These changes in land use are at the origin of an acceleration of erosion dynamics and an excessive transfer of sediments to water bodies downstream. In addition to land degradation, sediment transfers contribute to the filling of reservoirs devoted to supplying drinking water, to the deterioration of the lagoon and to a general loss of biodiversity.

The inertia, trajectory and the sources of this erosion remain poorly documented despite the acceleration of this land use evolution during the last 10 years. In this study, we propose a retro-observation of sedimentary fluxes and sources of sediment based on the analysis of sedimentary archives collected in one of the main reservoirs of the island (Dzoumogné reservoir, 22 ha) along with the development of a sediment tracing approach (associating radionuclide measurements, elemental geochemistry, organic matter and color analyses) in order to reconstruct the evolution of erosion rates and sources of since 2011.

The first results reveal the occurrence of two periods of erosion acceleration between 2013 and 2015, and then after 2019. The first increase (+140% of erosion rates, from 3.5 to 8.5 t ha-1 yr-1) occurred during a period of deforestation, which induced an opening of the landscape (e.g. creation of unpaved roads). The second acceleration phase took place during the most recent period of agriculture expansion associated with an intensification of agricultural practices (+115% of erosion rates, from 3 t ha-1 yr-1 in 2017 to 6.5 t ha-1 yr-1 in 2020). The sediment accumulated in the reservoir between 2011 and 2021mostly originated from subsurface sources (bank erosion, unpaved roads, gullied soils) and intensive cultivation (e.g., in 2021, 35% of sediment originated from unpaved roads, channel banks, landslides and 27% from intensive cultivation) while forests that are less exposed to erosion only supplied a limited contribution to sediment (<18%). As land use changes are expected to continue in the coming years, understanding the factors controlling the erosion dynamics and the supply of sediment sources are of prime importance in order to implement effective conservation measures and to protect the land and water resources.

How to cite: Foucher, A., Evrard, O., Rabiet, L., Cerdan, O., Landemaine, V., Vitter, M., and Desprats, J.-F.: Impact of rapid deforestation and conversion of traditional agricultural practices into food crop production on land and water degradation: a case study from Mayotte Island, Indian Ocean, France (2011-2022), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3537, https://doi.org/10.5194/egusphere-egu23-3537, 2023.

EGU23-3578 | Orals | SSS2.1

Soil loss by water erosion assessment uncertainties – experiences from South Africa 

Jussi Baade, Kevin Zoller, and Jay Le Roux

The Universal Soil Loss Equation (USLE) was initially developed to support the implementation of conservation measures to minimize soil loss by water erosion, i.e. sheet and rill erosion, on a local scale and in the context of agricultural land use. The approach was refined over decades and became the Revised Universal Soil Loss Equation (RUSLE).  At the same time the scope of applications has grown considerably. Due to its rather simple structure and relatively low demand for input data, it has been used for the assessment of soil loss from water erosion for ever growing spatial entities, i.e. regional scale catchments or whole countries. Recently this has been applied on a global scale in order to identify global hotspots of soil erosion. This coherent approach for a global comparison is most welcome against the background of the large number of country-specific assessments which are rather difficult to compare.

However, there are two issues of concern. First, one needs to remember that RUSLE-derived soil loss assessments do not account for gully erosion, which might not be linearly scaled with sheet and rill erosion. Furthermore, information on the uncertainties of RUSLE based erosion assessments are not frequently reported. This especially concerns the impact of specific combinations of varying unique input data on the results.

In this contribution we compare in high spatial resolution the results of two RUSLE-based soil loss by water erosion assessments conducted for six 100 by 100 km large study sites in South Africa. The first assessment was conducted about two decades ago and was based on the then available data covering the whole of South Africa. The second assessment is a revision, which includes the latest input data for rainfall erosivity, soil erodibility, the topographic factor as well as land cover and management. When compared, the results of the current soil loss estimates are an order of magnitude lower than the previous estimates. Does this difference represent a temporal trend or just the inherent uncertainties reflecting different input data and slightly different data processing? This is the question discussed in this contribution.

How to cite: Baade, J., Zoller, K., and Le Roux, J.: Soil loss by water erosion assessment uncertainties – experiences from South Africa, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3578, https://doi.org/10.5194/egusphere-egu23-3578, 2023.

Global efforts to restore the world’s degraded croplands require knowledge on the degree and extent of accelerated soil organic carbon (SOC) loss induced by soil erosion. However, methods for assessing where and to what extent erosion takes place is still inadequate for precise detection of erosion hotspots at high spatial resolution.

 

In this study, we attempted to develop a spectra-based soil erosion mapping approach to pinpoint eroded hotspots in a typical catchment located in the black soil region of Northeast China as characterized by undulating landscapes. We built a ground-truth dataset consisting of three classes of soils representing Severe, Moderate, and Low erosion intensity because of their inter-class contrasts in estimated erosion rates from 137Cs tracing. The spectral separability of different erosion classes was first tested by a combined principal component and linear discriminant analysis (PCA-LDA) against laboratory hyperspectral data and then validated against Sentinel-2 derived broadband spectra.

 

We will present results on the performance of the PCA-LDA model to classify soil erosion intensity classes based on laboratory and satellite-based soil spectra. We further identified distinctive spectral features representative of shifting soil albedo and biochemical composition due to erosion-induced SOC mobilization. A classification scheme comprising the spectral features was applied to the Sentinel-2 bare soil composite for pixel-wise soil erosion mapping, from which 15.9% of the catchment area was detected as erosion hotspots while the Moderate class occupied 65.4%.Our study highlights the potential of the spectral-based remote sensing approach for  better targeted cropland management to combat soil degradation.

How to cite: Qi, L. and Shi, P.: Detection of soil erosion hotspots with accelerated carbon losses in the black soil region of Northeast China as driven by Sentinel-2 multispectral remote sensing, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4089, https://doi.org/10.5194/egusphere-egu23-4089, 2023.

EGU23-5030 | ECS | Posters on site | SSS2.1

Eco-geomorphological repercussions of recent climate dynamics on soil quality from Cabo de Gata-Níjar Natural Park (Almería, Spain) 

Julia Espinosa-Muñoz, José Antonio Sillero-Medina, and José Damián Ruiz-Sinoga

In the Mediterranean area of southern Spain, a well-defined rainfall gradient is identified, ranging from 1.000-1.500 mm annual rainfall in the western sector to less than 150 mm in the extreme east. This fact implies a related impoverishment of ecosystem services, intensified by the impacts of current climate dynamics and leading to a degradation of soil-water-plant relationships and reflected in different indicator properties. In this respect, protected natural environments have a fundamental role to preserve and protect ecosystem services. Thus, the mitigation of the effects of climate change on them is a crucial challenge.  For this reason, this study has focused on the Cabo de Gata-Níjar Natural Park (UNESCO Global Geopark), located at the eastern end of the above-mentioned gradient, with territorial characteristics related to arid and semi-arid climatic conditions where the consequences of the current pluviometric pattern are emphasising the vulnerabilities of these areas. This research aims to (i) analyse the eco-geomorphological dynamics in last decades from a climatic and vegetation cover perspective and (ii) contrast this evolution with the soil quality situation, with emphasis on soil organic properties as determinants of the main degradation processes in the Mediterranean area. Methods used combine the statistical analysis of climatic variables based on data from the SAIH Hidrosur Network (1997-2022) with the use of spatial remote sensing techniques by applying vegetation indices in Sentinel-2 images. In addition, a total of 276 soil samples were collected and analysed to determine their physical, hydrological, and organic properties. On a preliminary way, the results show large differences between different landscape units. On the one hand, areas where abiotic factors control the current eco-geomorphological dynamics and where the aggressiveness of rainfall is causing important degradation processes, a reduction in the organic content of soils and, in general, a dynamic associated with rhexistasy, and on the other hand, areas where biotic factors are improving environmental conservation and the prevalence of biostasy processes.

How to cite: Espinosa-Muñoz, J., Sillero-Medina, J. A., and Ruiz-Sinoga, J. D.: Eco-geomorphological repercussions of recent climate dynamics on soil quality from Cabo de Gata-Níjar Natural Park (Almería, Spain), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5030, https://doi.org/10.5194/egusphere-egu23-5030, 2023.

EGU23-5160 | ECS | Posters on site | SSS2.1

Short- and long-term changes in soil physical properties following biochar addition to soils with different textures 

Martin Zanutel, Sarah Garré, and Charles Bielders

In the context of global soil degradation, biochar is being promoted as a potential solution to improve soil quality in addition to its carbon sequestration potential. Burying biochar in soils has been shown to affect soil physical properties, but the intensity of this effect depends, among others, on soil properties and application rates. Moreover, the long-term effects of biochar remain largely undocumented yet they are important to quantify given biochar’s persistency in soils. The objective of this study was therefore to determine the short-term and long-term effects of biochar on soil physical properties in function of soil texture and biochar application rates. For this purpose, experiments were conducted in Wallonia (southern Belgium) at two sites with different soil texture (silt loam and sandy loam). Both sites are characterized by the presence of former kiln sites that were used for studying the long-term (> 150 years) effect of hardwood biochar. In addition, fresh biochar produced from Picea abies at 500°C by GreenPoch SA was buried in subplots at both sites at rates of 1% and 2% in mass in the top 10 cm just before the spring sowing in 2021. Samples were collected on September 2021 in kiln sites, in fresh biochar (1 & 2%) subplots and in biochar-free reference plots, in triplicate. The measured soil physical properties were the bulk density, the water retention curve and the hydraulic conductivity curve.

Reference subplots were characterized by higher bulk density and lower saturated water content than biochar subplots. The presence of biochar increased the water content for pF < 1.5. These biochar effects were higher for the sandy loam compared to the silt loam and in the short-term compared to the long-term. The plant available water capacity increased with the presence of biochar on the sandy loam, but was unaffected on the silt loam. The hydraulic conductivity was slightly higher for pF < 1.5 in the biochar subplots compared to the reference subplots. On the silt loam, this effect was more visible for fresh biochar whereas on the sandy loam, this effect was higher in the kiln sites. Therefore, the study highlighted a positive effect of biochar in the short-term and in the long-term on soil physical properties for the range of soils and biochar application rates investigated here. Further research may be needed to confirm the observed trends over a wider range of soil types, biochar types and biochar application rates as well as to better understand the underlying mechanisms.

How to cite: Zanutel, M., Garré, S., and Bielders, C.: Short- and long-term changes in soil physical properties following biochar addition to soils with different textures, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5160, https://doi.org/10.5194/egusphere-egu23-5160, 2023.

EGU23-5433 | ECS | Orals | SSS2.1

Non-contact methods for measuring craters formed on soil after a drop impact 

Rafał Mazur, Michał Beczek, Magdalena Ryżak, Agata Sochan, Cezary Polakowski, Karolina Gibała, and Andrzej Bieganowski

The splash phenomenon is one of the stages of water erosion, i.e. a process that causes soil degradation. The crux of splash is the detachment and displacement of soil particles due to the impact of raindrops. Another important aspect of the phenomenon is that a deformation called a crater is formed at the point of the impact. Research on craters helps to expand the knowledge of the splash phenomenon and may contribute to understanding its relationship with successive stages of water erosion. The quantities used to describe the deformation include static dimensions (e.g. depth or diameter of the crater) and dynamic quantities to describe the course of the deformation (e.g. the time for the crater to reach a stable shape). The small size of the craters and the high dynamics of their formation induce the use of accurate and advanced measurement methods.

The aim of the work is to present selected non-contact methods for measuring craters formed on soil after a drop impact.

The study was focused on photography, high-speed imaging, 3D surface modelling, and computed tomography (CT). The discussion of the methods includes a brief description of the measurements, the range of quantities that can be determined with the methods, and indication of their strengths and weaknesses. Knowledge of these issues allows making an informed choice of measurement methods when planning new experiments or projects, which may significantly affect the results that can be obtained.

 

References

Mazur, R.; Ryżak, M.; Sochan, A.; Beczek, M.; Polakowski, C.; Bieganowski, A. Soil Deformation after Water Drop Impact—A Review of the Measurement Methods. Sensors 2023, 23, 121. https://doi.org/10.3390/s23010121

This work was partially supported by the National Science Centre, Poland within the framework of project no. 2020/37/N/ST10/03363.

How to cite: Mazur, R., Beczek, M., Ryżak, M., Sochan, A., Polakowski, C., Gibała, K., and Bieganowski, A.: Non-contact methods for measuring craters formed on soil after a drop impact, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5433, https://doi.org/10.5194/egusphere-egu23-5433, 2023.

EGU23-5853 | ECS | Posters on site | SSS2.1

Land use changes and spatial susceptibility in small Mediterranean basins 

Ana Triano-Cornejo, María Eugenia Pérez-González, and José Damián Ruiz-Sinoga

Soil erosion is one of the most recurrent environmental problems of public interest today. The western Mediterranean is an area sensitive to the effects of Climate Change, according to the latest IPCC Sixth Assessment Report, due to the proven increase in extreme events such as heat waves, extreme rainfall and droughts. Within this, the importance of competition in the territory between tourism and agriculture will be the result of radical changes in land use that are affecting the ecomorphological system to the point of making it even more susceptible due to the emergence and increase of high risks in the Mediterranean basins. Therefore, it will be essential to determine the levels of susceptibility of the basins under study with respect to erosive processes in order to create new mitigation measures to improve soil management and reduce these risks. Through this study we intend to analyze changes in land use and territorial susceptibility in several basins in southern Spain, in Malaga. The main objective is to determine the incidence and susceptibility of these basins and to analyse how they have been affected by land use changes through an observation of land use changes and the application of the RUSLE model. This project will look at the differences between two contrasting basins. One basin with steep slopes and the emergence of more sensitive crops, such as vineyards, which will increase the fragility of Mediterranean basins after torrential events, causing the appearance of a higher risk of erosion, while the other basin will be differentiated with the appearance of clearings that decrease the steep slopes together with changes to more competitive crops, such as subtropical crops. The results demonstrate the correlation between land use and torrential events in Mediterranean basins with respect to their susceptibility in their ecogeomorphological system.

How to cite: Triano-Cornejo, A., Pérez-González, M. E., and Ruiz-Sinoga, J. D.: Land use changes and spatial susceptibility in small Mediterranean basins, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5853, https://doi.org/10.5194/egusphere-egu23-5853, 2023.

EGU23-6421 | ECS | Orals | SSS2.1

Modelling Switzerland’s actual erosion risk on arable land 

Anina Gilgen, Silvio Blaser, Jérôme Schneuwly, Catherine Hutchings, and Volker Prasuhn

In Switzerland, soil erosion by water is a challenge due to the complex topography. It is stipulated by law that a soil removal rate of 2 t/ha/yr (for soil depth < 70 cm) or 4 t/ha/yr (for soil depth > 70 cm) on arable land must not be exceeded as a long-term average. Furthermore, an impairment of soil fertility and of water bodies and near-natural habitats due to erosion should be avoided by all means.

In this study, we calculated the actual erosion risk on arable land of Switzerland for 2021 using newly available data sources on crops and tillage practices. The erosion risk was calculated with the Revised Universal Soil Loss Equation:

A = R∗K∗L∗S∗C∗P

With R = rainfall and surface runoff factor, K = soil erodibility factor, L = slope length factor,  S = slope gradient factor,  C = soil cover and cultivation factor, and P = erosion control factor.

The product of the factors R∗K∗L∗S represents the potential erosion risk. For the calculation, we used the available potential erosion risk map by Bircher et al. (2019).

To derive realistic C factors adapted to Swiss climate conditions, the following procedure was applied: average crop-specific C  factors for two geographical regions (valley, mountain) and three distinct tillage types (plough mulch, direct seeding) were deduced from data of the Swiss agri-environmental monitoring programme (SAEDN; Gilgen et al. 2023), which provides detailed management data on the field level of approximately 300 farms since 2009. The categorised C  factors were allocated to individual parcels using geo-referenced crop area polygons of the Swiss cantons as well as direct payment data from the Federal Office for Agriculture on crop-specific tillage types.

Since no data on the P factor was available, it was estimated using expert knowledge. Calculation was carried out on a 2x2m grid and summarised at municipality level.

Our calculations represent the best yet for Switzerland's actual erosion risk. However, a comparison with the erosion that has actually occurred, as carried out by Bircher et al. (2022), is still pending. The described method can be used in the future for monitoring that focuses on the environmental impact of farmers' management changes. A prerequisite for this is that sufficiently detailed data on farm management continues to be available.

 

References:

Bircher, P., Liniger, H.P., and Prasuhn, V. (2019): Aktualisierung und Optimierung der Erosionsrisikokarte (ERK2): Die neue ERK2 (2019) für das Ackerland der Schweiz: Schlussbericht. Bundesamt für Landwirtschaft, Bern 

Bircher, P., Liniger, H.P., and Prasuhn, V. (2022): Comparison of long-term field-measured and RUSLE-based modelled soil loss in Switzerland. Geoderma Regional, 31, e00595, https://doi.org/10.1016/j.geodrs.2022.e00595

Gilgen, A., Blaser, S., Schneuwly, J., Liebisch, F., and Merbold, L. (2023): The Swiss agri-environmental data network (SAEDN): Description and critical review of the dataset. Agricultural Systems, 205, 103576, https://doi.org/10.1016/j.agsy.2022.103576

How to cite: Gilgen, A., Blaser, S., Schneuwly, J., Hutchings, C., and Prasuhn, V.: Modelling Switzerland’s actual erosion risk on arable land, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6421, https://doi.org/10.5194/egusphere-egu23-6421, 2023.

EGU23-8245 | ECS | Orals | SSS2.1

Effect of wind-driven rain on runoff, infiltration and soil erosion 

Sophia Bahddou, Wilfred Otten, Richard Whalley, Ho-Chul Shin, Mohamed El Gharous, and Jane Rickson

Soil erosion is a result of detachment and transport of particles or small aggregates from the soil surface. Previous research has predominantly focused on studying the effects of either rainfall or wind on soil erosion processes as separate erosive agents. To date, there have been only few studies into the simultaneous effect of both agents operating at the same time on soil erosion and hydrological processes. In this research, the effect of wind velocities on the erosivity of rainfall was studied, comparing windless rain (WLR) and wind-driven rain (WDR) events when applied to a sandy loam soil. A moderate slope gradient of 11%, a simulated rainfall intensity of 90 mm hr-1, a rainfall duration of 30 minutes and wind velocities up to 9 m s-1 were used. The runoff, infiltrate and soil loss (including splash erosion measured at different heights) were compared between the different events and treatments. The soil surface roughness was measured before and after the rainfall event, using a hand-held laser scanner, to evaluate the effect of WLR and WDR on the surface morphology. The outcome of this study shows that, for the smooth surface under WDR, infiltrate volumes were less than under WLR and decreased with increasing wind velocity, while the runoff volumes increased under WDR compared with WLR. The rate of rainsplash erosion increased under the WDR event compared to the WLR event at all heights. The amount of splash-eroded particles decreased with height above the soil surface. We conclude that wind has an effect on the erosivity of rainfall; therefore, it should be considered in erosion studies.

Acknowledgments: This work was funded by OCP group, Morocco

How to cite: Bahddou, S., Otten, W., Whalley, R., Shin, H.-C., El Gharous, M., and Rickson, J.: Effect of wind-driven rain on runoff, infiltration and soil erosion, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8245, https://doi.org/10.5194/egusphere-egu23-8245, 2023.

EGU23-8611 | Orals | SSS2.1

Historical evolution and future storylines of degradation drivers in Mediterranean arid and semiarid agro-ecosystems 

Aristeidis Koutroulis, Manolis Grillakis, and Athanasios Tsilimigkras

Mediterranean ecosystems are already under pressure from the combined impacts of direct human activities and anthropogenic climate change. In this highly human-managed region, land degradation and accelerated dryland expansion threaten the biological systems and the natural resources that sustain agriculture and forests [1]. The question of "what is the driving force of the changes," and specifically whether anthropogenic climate change or direct human management is to blame, is crucial. The attribution of these changes plays a key role in better managing the arid and semiarid Mediterranean agro-ecosystems, especially considering a different future climate. Here we examine the net effect of anthropogenic climate change-induced changes in the state of two significant land degradation factors, aridity and rainfall erosivity, across the Mediterranean.

We rely on a state-of-the-art counterfactual stationary climate dataset, a hypothetical climate in a world without climate change [2], to estimate impact indicators since the onset of industrial revolution (1900-2019). We compare results against aridity and rainfall erosivity calculated from observational (factual) climate data to examine historical imposed long-term changes attributed to human induced climate change. The difference between past impacts and counterfactual impacts is a proxy for a broad-scale concept facilitating a top down approach to define degradation and physical vulnerabilities of Mediterranean agro-ecosystems, in the frame of REACT4MED project. We further analyze scenarios of future climate change to unravel future trends. The information is further downscaled at pilot area level to support the co-development and analysis of local-scale indicators. Results will serve as a basis for the detection of potential future degradation trends used in the identification of potentially suitable areas in the Mediterranean for up or out-scaling of restoration measures beyond REACT4MED pilot areas.

 

[1] Daliakopoulos, N., et al. "Yield response of Mediterranean rangelands under a changing climate." Land Degradation & Development 28.7 (2017): 1962-1972.

[2] Mengel, M., et al. “ATTRICI v1.1 – counterfactual climate for impact attribution.” Geosci. Model Dev., 14, 5269–5284.

Acknowledgements: This work has received support from REACT4MED (GA 2122) PRIMA funded project, supported by Horizon 2020.

How to cite: Koutroulis, A., Grillakis, M., and Tsilimigkras, A.: Historical evolution and future storylines of degradation drivers in Mediterranean arid and semiarid agro-ecosystems, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8611, https://doi.org/10.5194/egusphere-egu23-8611, 2023.

EGU23-8889 | ECS | Orals | SSS2.1

A crop phenology-based approach to quantify the C-factor at the field-parcel scale in Europe 

Francis Matthews, Panos Panagos, Pasquale Borrelli, and Gert Verstraeten

The crop cover-management (C-) factor in arable landscapes describes the soil erosion susceptibility associated with seasonally cultivated crops. Previous informatic and computational limitations have led many modelling studies to prescribe C-factor values and assume spatial and temporal stationarity. However, the multiple influencing factors ranging from parcel-scale crop cultivation and management to regional-scale rainfall regimes motivate new methods to capture this variation when identifying at-risk areas. Modern data systems (in this case: field parcel vector data, Sentinel-2 time series, rainfall erosivity time series networks, EU-scale land survey (LUCAS) and European regional statistical data) provide spatially and/or temporally dense information sources on which scalable model parametrisation frameworks can be built and updated. Here, we define a multi-component method to derive the C-factor by associating time series of canopy and residue surface cover from Sentinel-2 and climate-specific rainfall erosivity with Integrated Administration and Control System (IACS) field parcel data from European Union Member States. A standardised approach is emphasised to increase the future interoperability and inter-comparability of soil erosion modelling studies deploying the C-factor. Additionally, field parcel simulation units with associated crop declarations provide a new reference scale to link predictions of soil erosion risk with specific management decisions and declarations by farmers. After implementing the method on a homogenised subsample of 8600 field parcels covering available IACS data regions, several key findings are outlined: 1) time series information provides new opportunities to predict the time-criticality of erosion in specific crop cultivations, 2) the varying (a-)synchronicity between seasonal crop canopy cover and heavy rainstorms means that spatial variability is inherent within the C-factor across Europe, and 3) the addition of agricultural management practices (e.g. tillage practice descriptions) to open-access IACS repositories can facilitate more comprehensive evaluations of the C-factor and soil erosion risk in the future.

How to cite: Matthews, F., Panagos, P., Borrelli, P., and Verstraeten, G.: A crop phenology-based approach to quantify the C-factor at the field-parcel scale in Europe, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8889, https://doi.org/10.5194/egusphere-egu23-8889, 2023.

Soil erosion by water is considered as one of the most serious processes degrading the soil functionality of arable soils around the globe. To assess the risk of water erosion at larger scales, the universal soil loss equation (USLE) and its derivates are commonly used for the implementation of policy instruments.

An important factor needed within (R)USLE model exercises is the K-factor, which reflects the natural erodibility of the topsoil. The spatial explicit determination of the K-factor is crucial to create reliable soil loss estimate maps. However, the accurate estimation of the K-factor at the regional level is challenging due to different existing calculation methods and as a variety of spatial data (e.g. soil texture fractions, rock fragments, soil organic matter) is needed. The latter severely limits the choice of available data, which differ in spatial resolution and information content of the required parameters. This leads to a high potential of uncertainty in the regional estimation of K-factors, but also of the soil erosion estimates at regional level.

Therefore, the aim of the study presented is to determine the spatial and quantitative accuracy of different soil data sets and calculation methods for estimating the K-factor for Germany. Furthermore, the influence of possible uncertainties on the estimation of soil erosion risk by combining all factors of the (R)USLE should be evaluated. Based on the aim of this study we modelled K-factors for three available harmonized German-wide datasets: I) LUCAS soil dataset of Europe), II) BÜK1000 and III) BÜK200 (soil overview maps for Germany) using the existing equations of A) Wischmeier and Smith (1978) and its extension of B) Auerswald et al. (2014) representing the original K-factor nomograph. For the validation of the three datasets, K-factors based on 2234 arable soil profiles across Germany from the Agricultural Soil Inventory (BZE_LW) with most detailed soil information were calculated.

The results reveal significant differences between calculation methods and data sets for the German-wide assessment of K-Factors. The LUCAS soil dataset overestimates average K-Factors of the BZE-LW by ~ +21 % (RMSE = 0.015, R² = 0.30), while BÜK200 underestimates K-Factors by ~ -30 % (RMSE = 0.016; R² = 0.34). In contrast the calculation method has a low impact on the average K-Factor estimation (~ 5 %) while the RMSE is comparable high with 0.012 (R² = 0.57).

The results imply that the choice of the calculation method and dataset at regional level is important and that detailed information on soil texture (e.g. very fine sand fraction) are crucial and strongly needed in order to improve the estimation of reliable K-Factors and soil erosion risk on regional-scales. 

 

How to cite: Saggau, P. and Steinhoff-Knopp, B.: Uncertainties in the regional estimation of Soil Erodibility. A German wide evaluation of the K-Factor comparing current datasets and calculation methods., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9045, https://doi.org/10.5194/egusphere-egu23-9045, 2023.

EGU23-9334 | Orals | SSS2.1

The impact of new detailed (R)USLE-C-factor maps for Germany on soil loss estimates 

Bastian Steinhoff-Knopp and Philipp Saggau

The (R)USLE and its many derivates are the most used models to estimate soil loss by water at regional scale. Within the (R)USLE the C-factor is used to assess the impact of crop and soil management on erosion. The exact, temporal and spatial explicit determination of the C-factor is crucial to create reliable maps on soil loss estimates, monitoring the impact of agricultural practices on soil erosion and evaluating the efficiency of policy instruments.

The derivation of accurate high-resolution C-factor data for larger regions remains a challenge, as a variety of spatio-temporal data (crops/crop rotation, tillage management, interannual variation of rainfall erosivity) is needed. Based on recent improvements in calculation methods and the availability of earth observation data, the C-factor can be estimated using agricultural statistics and parcel-based information on crop cultivation. Consequently, we developed two types of spatially explicit and regional C-factor datasets for Germany, mapping the impact of agricultural practice on soil erosion in a more reliable and spatially detailed way: i) harmonized mean C-factors for municipalities for 1999, 2003, 2007, 2010, 2016 and 2020, and ii) parcel-based C-factors for the period 2017-2020 based on crop type maps from satellite data.

In this contribution, we will present the implemented methods and will discuss the impact of the new detailed C-factor maps on soil loss estimates in a spatial resolution of 10 x 10 m for German cropland. The results show an increase in the C-factors for municipalities during the last two decades by 17 %. The parcel-based data reveals the C-factor ranges within the municipalities: While the mean C-factor for all parcels across Germany is 0.107 (conventional cropping; 2017-2020), the standard deviation within the municipalities ranges from 0 to 0.141 at a mean standard deviation of 0.045. This results in differences in erosion rates of up to 7 t / (ha • a), highlighting the importance of spatially explicit C-factor estimates.

How to cite: Steinhoff-Knopp, B. and Saggau, P.: The impact of new detailed (R)USLE-C-factor maps for Germany on soil loss estimates, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9334, https://doi.org/10.5194/egusphere-egu23-9334, 2023.

EGU23-9800 | ECS | Orals | SSS2.1

Statistical analysis of a systematic review on soil water erosion assessment in Morocco 

Houda Lamane, Latifa Mouhir, Rachid Moussadek, Bouamar Baghdad, Hamza Briak, Abdelmjid Zouahri, and Ali El Bilali

A large effort has been devoted over the past century to assessing soil erosion using a variety of methods under a wide range of climatic conditions, soil types, land uses, topography, and others. Thus, we attempt to provide an analysis of national data of several soil erosion modeling and fingerprinting. The methodology adopted for this research is a review of scientific articles, conference papers and thesis on soil erosion, focusing more on categorization of the different soil erosion models and methods applied. Based on the statistical analysis provided by this review, the results are as follows: (i) Even though the threat of soil erosion is grave, the number of studies conducted to characterize and evaluate soil erosion in Morocco is limited. (ii) Studies on water erosion modeling are concentrated in the north of the country (Rif 32.89%, High Atlas 32.89%, Occidental Meseta 18.43% and Middle Atlas 10.53%). (iii) Water erosion models have been steadily developed and interfaced with GIS based approaches in recent decades. (iv) Although Morocco is geomorphologically and geologically varied (Rif, Middle and High Atlas, Mesetian and Saharan domain), several authors use soil erosion assessment models that ignore the unique characteristics of each study area and fail to adapt them to local conditions. (v) USLE (R) models have been widely used and modified over the past two decades and remain the most commonly used modeling tool today. (vi) The largest proportion of the erosion rate is concentrated in the Atlas and Rif mountains. (vii) Demonstration of a strong relationship between soil erosion rates with environmental factors and modeling conditions, and the lack of correlation with study area size and erosion rate. While the overall results show a relatively high variance, which cannot be explained by this combination of factors, it is partly related to the experimental conditions. This review is intended to support future soil erosion assessment and to facilitate the identification of priorities for soil erosion research in Morocco by supplying a state of the art for future targeted and comprehensive analyses to deal with the issue of soil erosion in Morocco.

Keywords: Soil water erosion models, Fingerprinting methods, Literature review, Morocco.

How to cite: Lamane, H., Mouhir, L., Moussadek, R., Baghdad, B., Briak, H., Zouahri, A., and El Bilali, A.: Statistical analysis of a systematic review on soil water erosion assessment in Morocco, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9800, https://doi.org/10.5194/egusphere-egu23-9800, 2023.

Soil erosion and associated land degradation, accelerated by anthropogenic activities, are serious worldwide environmental problems that can reduce crop productivity and cause on- and off-site damages resulting from sediment transport and deposition. A common feature of the agriculture-dominated landscape of the Prairie Pothole Region in western Canada is depressional wetlands (typically 10 to 20, small seasonal to permanent waterbodies per square kilometer).  These wetlandscapes are fragile agro-ecosystems that have been disturbed and impacted through human-induced soil erosion, receiving influxes of sediment and associated constituents (e.g., phosphorus, organic carbon and pesticides) from the surrounding local and regional sources (e.g., cultivated fields). The general objective of this study was to estimate the severity of soil loss and sedimentation rates, and sediment flux from surrounding cultivated fields into wetlands. The study area included two sub-watersheds in the Prairie Provinces of Manitoba and Alberta, within the Canadian portion of the Prairie Pothole Region. Soil and sediment cores were collected along multiple transects from the uppermost portion of each catchment to the central area of the wetland.  Transects were distributed within catchments to capture the variability resulting from the topographic complexity. The results of this study demonstrated high rates of soil loss in the upper slope and middle slope positions, and high rates of deposition in lower slope and foot slope positions of wetlandscapes. Furthermore, the areal average of transect data provided sediment delivery ratio estimates of 57% for Manitoba and 35% for Alberta, which indicates that a relatively high amount of the mobilized sediment was exported beyond the cultivated fields towards the wetlands, mostly deposited in riparian areas.

How to cite: Zarrinabadi, E. and Lobb, D. A.: Assessing soil erosion and sediment flux using 137Cs within topographically complex landscapes of Prairie Pothole Region of Canada, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9841, https://doi.org/10.5194/egusphere-egu23-9841, 2023.

EGU23-10002 | ECS | Orals | SSS2.1

Historical evolution of gullies: Impact of climate 

George Olivier, Marco J. Van De Wiel, and Willem P. De Clercq

Gully erosion is regarded as one of the worst land degradation processes in the world. It is a complex geomorphic process resulting in on-site land degradation due to the removal of soil, and off-site land degradation, due to mobilised soil, pollutants, and pesticides adversely affecting soil and water resources. Climate change predictions show that the frequency of high-magnitude rainfall events will increase, thereby exacerbating the degradation impacts of gullying. By assessing long-term datasets (>30 years), the relationship between gully evolution and climate variability can be observed, providing potential insight into gully evolution under climate change. We aim to isolate climate as a driving factor by investigating three sites under similar land-use, environments transformed into conservation areas but exhibiting contrasting climates. The sites are in South Africa (SA), located in the arid Karoo, a Lowveld area with Savanna land cover and a humid Grassland region. A triangulation of methods was implemented, including i) digitising gully change from remotely sensed imagery spanning up to 78 years, ii) conducting field measurements, and iii) interviewing land managers. In the arid Karoo, gullies were discontinuous, forming successive chains waning into deposition zones, only to be reactivated again with an abrupt headcut downstream of the depositional area. Continuous gullies were found in the Grassland and Savanna regions. Remotely sensed image analysis shows a mean annual linear expansion along the main drainage line was the largest in the Savanna, 2.8 m, compared to 0.5 m and 0.4 m recorded in the Grassland and Karoo. However, the mean planimetric area changes of gullied extent were 6 and 8.4 times larger in the Grasslands compared to the Karoo and Savanna. Fieldwork confirmed active gully processes at all three sites, identifying active sub-surface processes, only found in the Grassland, as the leading cause for the morphological difference between the extensive Grassland gullies and the narrower linear gully features in the Savanna and Karoo. However, certain gully headcuts in the Karoo present as bulbous transforming into narrower downstream channels, most likely a result of being artificially enlarged from failed gabion installations at the headcut. During interviews with land managers, concerns about contemporary gully erosion were noted at all three sites, with the implementation of mitigation measures ongoing. There is consensus among the three methodologies, identifying that gully erosion remains stubbornly active, even after transforming to a conservation-orientated land-use. In the Karoo and Savanna, human influence and rainfall variability were attributed as causal factors of gullying, inherited from ill-placed farm roads and overgrazing, respectively. In the Grasslands, soil type is deemed the dominant driver of gullying, although animal tracks (specifically those from antelope) forming pathways for water after rainfall was contentious. Our analysis shows that gully erosion severity follows the climate gradient of SA. However, it remains difficult to completely isolate climate as a driver due to different inherent soil properties, geology, and slope. We expect an increase in gully erosion for all three sites under climate change predictions, although more pronounced in the Grassland region.

How to cite: Olivier, G., Van De Wiel, M. J., and De Clercq, W. P.: Historical evolution of gullies: Impact of climate, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10002, https://doi.org/10.5194/egusphere-egu23-10002, 2023.

EGU23-11081 | ECS | Posters on site | SSS2.1

Effects of vegetation root on erosion degree under different arrangements of river banks. 

Yen-Ching Chiang, Jin-Fu Li, and Su-Chin Chen

With environmental protection becoming more and more important in recent years, the suitability of traditional regulation methods in rivers such as bank protection and river cutoff begins to be challenged. The regulation methods combined with ecology have become an important goal in natural rivers nowadays. In this research, a series of flume experiments were conducted to discuss the effect of bank erosion on vegetation roots between bare and vegetated banks.

The experimental parameters of flow discharge, water depth,  and channel slope are 0.014 , 9.5 cm, and 0.001, respectively. A kind of vegetation, Vigna radiate, is planted in cultivation boxes for 1 – 2 weeks and then moves into the channel as the vegetated banks. A laser scanner is set up on the flume channel to record the variation of initial and final topography. The results show that the erosion ratios of bare and vegetated banks are 40.24 % and 24.34 %, respectively. The root system of vegetation has a function of anti-erosion on river banks. In addition, we observe the exposed roots formed a protective layer along the flow direction on the bank over a period of time after beginning the experiment. The protective layer by roots helps the river bank resist water erosion and reduce the amount of erosion in the covered area.

How to cite: Chiang, Y.-C., Li, J.-F., and Chen, S.-C.: Effects of vegetation root on erosion degree under different arrangements of river banks., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11081, https://doi.org/10.5194/egusphere-egu23-11081, 2023.

EGU23-11902 | Orals | SSS2.1

Modelling gully head formation in badlands 

Mauro Rossi, Dino Torri, Sofie De Geeter, Cati Cremer, and Jean Poesen

Gully erosion is a damaging process not yet sufficiently understood and parameterized. Gully head topographic thresholds are empirical models used to predict the gully head formation. Such model have been used to investigate gully processes mostly in cropland, rangeland and forest. This study extends such modelling approach to badlands. Different badlands (eight sites) have been studied in the Mediterranean environment in Italy and Spain, characterized  by diversified climatic, lithological, and geological settings under different anthropogenic conditioning. Badlands have been characterized by their specific human history in addition to their geomorphological properties. Land use, as part of the human history, strongly affected many badland formation and development, through  extremely impacting land exploitation (usually overgrazing). The effect of geological and geo-morphological processes are usually particularly well visible. While the weakening effect of joints is confirmed, the different geological layer bedding orientation with respect to the slope aspect generates a different development of badland morphologies and different values of gully head thresholds values (as shown in two badlands sites on the same geological material and climate). The selection of Curve Number values, at the base of the introduction of land use into the gully head thresholds, has been more objectively defined in order to reduce arbitrariness in threshold application. The study additionally revises some of the physical basics behind the gully head threshold concept, requiring a description of the soil resistance in terms of frictional and cohesive components. This implies the explicit inclusion of rock fragment into the grain size distribution, which cannot be limited to fine grains. It results into an enriched threshold formulation that allows to describe the condition for gully head initiation and retreat as the result of the tradeoff between the frictional and cohesive components of the soil resistance forces. Eventually, the gully head threshold concept is confirmed and extended to include badlands.

How to cite: Rossi, M., Torri, D., De Geeter, S., Cremer, C., and Poesen, J.: Modelling gully head formation in badlands, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11902, https://doi.org/10.5194/egusphere-egu23-11902, 2023.

EGU23-12400 | Posters virtual | SSS2.1

Land degradation estimation by SDG 15.3.1 computed at the local scale: the case of the six Mediterranean study sites of the NewLife4Drylands project 

Cristina Tarantino, Saverio Vicario, Maria Adamo, Rocco Labadessa, Francesca Assennato, Nicola Alessi, Nicola Riitano, Marcello Vitale, Martina Perez, Cristina Domingo-Marimon, Pau Montero, and Vicenc Carabassa

In 2015, during the 12th Conference of the Parties (COP) a new overall vision objective of the United Nations Convention to Combat Desertification (UNCCD) and the Sustainable Development Goals (SDGs) for 2030 called “Achieving Land Degradation Neutrality (LDN)” was incorporated. NewLife4Drylands (NL4DL; https://www.newlife4drylands.eu/), the LIFE Preparatory project, focuses on the use of remote sensing for the identification of a framework for the monitoring of land degradation and results of nature-based restoration interventions for achieving LDN. With this aim, Indicators and/or their proxies have been extracted from satellite data as essential variables for land degradation status assessment. Six Mediterranean Natura 2000 study sites located in Italy, Greece and Spain were considered as case studies and pressures and threats affecting each of them were analysed as land cover mappings, burn severity mappings, time series of climatic and phenology spectral indices, precipitation indices, soil organic carbon mappings.  Freely available satellite data from Landsat and Sentinel-2 programs were considered: in the case of sites less than 50 hectares in size, commercial satellite data at very high spatial resolution were used for evaluation. The indices analyzed will be integrated for the computation of SDG 15.3.1 indicator “proportion of land that is degraded over the total land area” according to the 2030 Agenda for Sustainable Development and UNCCD guidelines. SDG 15.3.1 standard formula considers sub-indicators to be integrated: trends in land cover, primary productivity and soil organic carbon. The novelty in the project outcomes is two-fold: 1) the estimation of drivers/disturbance (drought, fire, etc.) of LDN together with sub-indicators will allow to give practical indication to land manager; 2) sub-indicators have been computed at the local scale. For each study site, short-term and long-term analyses will be approached. Results will be part of a protocol for the assessment of land degradation and monitoring restoration interventions of degraded land.

How to cite: Tarantino, C., Vicario, S., Adamo, M., Labadessa, R., Assennato, F., Alessi, N., Riitano, N., Vitale, M., Perez, M., Domingo-Marimon, C., Montero, P., and Carabassa, V.: Land degradation estimation by SDG 15.3.1 computed at the local scale: the case of the six Mediterranean study sites of the NewLife4Drylands project, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12400, https://doi.org/10.5194/egusphere-egu23-12400, 2023.

EGU23-13380 | ECS | Posters on site | SSS2.1

Future soil erosion of shifting cultivation on hillslopes – modeling interactions between slope steepness, fallow periods, and climate change 

Lea Sophia Schröder, Livia Rasche, Kerstin Jantke, Gaurav Mishra, Stefan Lange, and Uwe A. Schneider

Shifting cultivation, also known as slash-and-burn agriculture, on steep terrain has been criticized for causing high rates of soil erosion thus promoting land degradation in South and Southeast Asia. Particularly, short fallow periods resulting from increasing land pressure are suspected of accelerating degradation processes. In addition, the rising frequency of high-intensity precipitation events associated with climate change can be expected to further increase the pressure on shifting cultivation. However, abandonment of shifting cultivation has turned out to be hardly feasible or desirable, particularly, where it provides food security and cultural identity to the tribal population, as is the case in Northeast India. This raises the question how increasing pressure from reduced fallow periods and climate change will affect future soil erosion of uphill shifting cultivation systems. As measured data on these interactions are not available, we applied a modeling approach to identify trends in soil erosion for different slope inclinations, fallow periods, and climate change scenarios. We used the Environmental Policy Integrated Climate (EPIC) Model to simulate daily soil loss for three different climate scenarios (SSP126, SSP370, SSP585) derived from five climate models for the near (2021-2050) and far (2071-2100) future. Simulations were carried out for six collected soil profiles, short, medium, and long fallow periods, and slope inclinations up to 70 %. Our results indicate a negative, non-linear relationship between the length of the fallow period and erosion, with soil loss being more than twice as high for systems with a 10-year compared to a one-year fallow regime. Further, our research demonstrates that long fallow periods can compensate, to a limited extent, for steep slopes. However, climate change, particularly under the medium-high (SSP370) and high-end (SSP585) emission scenarios, will lead to substantial increases in erosion by a factor of 2.2 and 3.1, respectively, towards the end of the century, thus reducing the possibility space for sustainable shifting cultivation.

How to cite: Schröder, L. S., Rasche, L., Jantke, K., Mishra, G., Lange, S., and Schneider, U. A.: Future soil erosion of shifting cultivation on hillslopes – modeling interactions between slope steepness, fallow periods, and climate change, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13380, https://doi.org/10.5194/egusphere-egu23-13380, 2023.

Soil erosion represents a serious challenge for agricultural production and for the environment. Soil erosion impacts, such as reduction of fertile soil, alteration of the carbon cycle and pollution and eutrophication of water bodies, represent a significant management concern for the European Union. Modelling can help define efficient and targeted mitigation strategies by identifying the long-term controlling factors and the areas where, and periods during which, soil is at high risk of erosion. However, to define such strategies, there remains a lack of modelling approaches a) able to provide with longer term baseline information which to measure the success or otherwise of mitigation strategies at the catchment scale and b) accessible and robust enough to be used, understood and trusted by users with more or less expertise, including researchers, land managers and policy makers. In response, this project will improve the robustness and accessibility of quantitative methods for supporting agricultural land management. The objectives of this project are: (i) to develop an accessible soil erosion model, iMPACt-erosion, based on interactive Jupyter Notebooks, to support agricultural land management at the catchment scale, (ii) to apply a robust model evaluation based on the use of both long-term soil loss observations and global sensitivity analysis to achieve greater confidence in model predictions and (iii) to identify the soil erosion controlling processes and vulnerable areas and periods to define targeted and effective mitigation strategies until 2100. We present the model and the first model evaluation results, which show that simulations are consistent with observed soil loss rates (estimated from both fallout radionuclides and tree mound measurements) in the last 60 years in olive orchard catchments in South Spain.

How to cite: Peñuela, A. and Vanwalleghem, T.: iMPACt-erosion: A robust and accessible model for a long-term effective management of agricultural soil erosion, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13611, https://doi.org/10.5194/egusphere-egu23-13611, 2023.

EGU23-13709 | Posters on site | SSS2.1

Soil loss due to crop harvesting – a spotlight on research gaps and the need of further research activities at the global scale 

Fritjof Busche, Michael Kuhwald, Philipp Saggau, and Rainer Duttmann

Worldwide, soil erosion is one of the main causes of soil degradation and the loss of important soil functions. Wind, water and tillage erosion and their environmental, economic and social impacts have been researched for decades. Soil erosion by root and tuber crop harvesting (SLCH), however, is rarely focused in research, although erosion rates can reach up to 22 Mg ha-1 harvest-1 (Parlak et al. 2016).
The aim of this study is to raise awareness of SLCH and to advance research on this topic. To achieve this aim, all available peer-reviewed studies on this topic are used to provide an overview of investigated soil erosion rates worldwide and to identify the environmental impact of SLCH. In addition, the differences between SLCH and other forms of erosion are highlighted. Furthermore, important future research aspects for an enhanced understanding of SLCH are identified.
Comparing soil loss due to crop harvesting with other forms of erosion, it can be stated that (i) erosion rates of SLCH are as high as for water erosion and wind erosion, (ii) SLCH always and only occurs during the harvest of tuber and root crops, which affected 8.4 % of the world’s arable land in 2019 (1.1 million km²), (iii) SLCH can occur at any relief position and any parent material, thus it can be the only erosion process of an affected field without the appearance of wind or water erosion and (iv) SLCH always affects entire fields that are harvested multiple times over several years, depending on the crop rotation.
Based on the reviewed studies, the following further research activities are necessary for a better understanding of the processes of SLCH: (i) global data collection of crops whose erosion rates have not been studied yet, (ii) conduct studies on continents such as North America, South America and Oceania, where data on SLCH erosion rates are currently missing, (iii) development of models to predict SLCH erosion rates and (iv) monitoring the distribution of the adhering soil to evaluate the environmental effects of SLCH.
This review shows that further studies on the topic of SLCH are necessary to quantify actual data on erosion rates for different crops in different regions and provide more awareness of this topic in erosion research.

How to cite: Busche, F., Kuhwald, M., Saggau, P., and Duttmann, R.: Soil loss due to crop harvesting – a spotlight on research gaps and the need of further research activities at the global scale, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13709, https://doi.org/10.5194/egusphere-egu23-13709, 2023.

EGU23-13925 | ECS | Orals | SSS2.1

Challenges and progress in the detailed estimation of sediment export in agricultural watersheds in Navarra (Spain) after two decades of experience 

Iñigo Barberena, Eduardo Luquin, Miguel Ángel Campo-Bescós, Javier Eslava, Rafael Gimenez, and Javier Casalí

In 1993, the Government of Navarre (northern Spain) began the installation and operation of a network of experimental watersheds in order to assess, among other aspects, soil erosion in representative agricultural areas of the territory. Initially, sediment sampling at the outlet of each of the five basins was performed on a daily basis, despite which it was possible to get a highly fruitful and novel knowledge on sediment export (Merchán et al., 2019). However, in the last 16 years, with the aim of studying sediment export in more detail, the sampling frequency was increased so that the behavior of the sedimentogram at the event level could be known. In these cases, when the amount of sediment was large enough, the sediment texture was also determined. In addition, from the beginning of the observations, a turbidimeter was used to record turbidity data every 10 minutes. The aim of this work is to deepen the knowledge of sediment export dynamics in representative agricultural watersheds of Navarre by analyzing the database described above and focusing in specific events. To do this, first, the entire database was represented in graphs that include variables such as sediment texture, samples taken per event, daily mean precipitation, turbidity, flow rate, etc. Next, events with a minimum of six samples were selected and the linear relationship between turbidity and sediment concentration was analyzed using simple linear regressions, as this is the method used in similar works. Subsequently, these same event data were added to set up monthly samples where again linear regressions were performed. Apart from the simple linear analysis, where the linear relationship with turbidity was analyzed as the only predictor variable, different artificial intelligence methods have been explored, such as the generalized linear model (GLM), support vector machine (SVM), multivariate adaptive regression splines (MARS) and random forest (RF), adding additional variables such as accumulated precipitation, and season or water level in the analysis. The results from all these statistical studies have been disappointing, since no pattern or generalization has been found to predict sediment concentration from the variables considered. These results suggest that the sediment export behavior of small agricultural watersheds is particularly complex and controlled by spatially and temporally varying variables. It is evident that at least some of these variables have not been taken into account in the study. The high variability found in sediment textures supports the hypothesis that the erosive behavior of watersheds is of great complexity. We believe that the consideration of variables such as vegetation on slopes and channels and its evolution can be helpful in the analysis.

 

Merchán, D., Luquin, E., Hernández-García, I., Campo-Bescós, M. A., Giménez, R., Casalí, J., & Del Valle de Lersundi, J. (2019). Dissolved solids and suspended sediment dynamics from five small agricultural watersheds in Navarre, Spain: A 10-year study. CATENA, 173, 114–130. https://doi.org/10.1016/J.CATENA.2018.10.013

How to cite: Barberena, I., Luquin, E., Campo-Bescós, M. Á., Eslava, J., Gimenez, R., and Casalí, J.: Challenges and progress in the detailed estimation of sediment export in agricultural watersheds in Navarra (Spain) after two decades of experience, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13925, https://doi.org/10.5194/egusphere-egu23-13925, 2023.

EGU23-14413 | Orals | SSS2.1

Field monitoring of cyclic freezing process: effect of air temperature on frozen layer thickness 

Kateřina Bočková, José Moya, Andrés Macías, and Jean Vaunat

Freezing is an important factor in soil degradation. In order to predict soil erosion in mountainous areas, the freezing process and the frequency and extent of freezing must be understood. This study aims to identify a relationship between air temperature and a depth of freezing, taking into account soil water content. The soil is considered to be frozen when all the free water within the pores freezes which, according to our numerical model, mainly occurs at temperatures slightly below 0°C. On the other hand, the temperature is not homogeneous in the soil as it is driven by the process of heat diffusion from the soil-atmosphere interface to depth, controlled by soil thermal conductivity and heat capacity, which depend on ice and water contents. As a consequence, the relationship between air temperature and the thickness of the frozen layer is not direct, and the relevance of using air temperature as a measure of frozen depth is to be evaluated.

A small N-S-oriented claystone ridge in an Eastern Pyrenees badland is being monitored. A series of thermometers, water content sensors, and specific heat sensors are collecting data in 5-minute intervals on both sides of the ridge. The data show an attenuation of temperature oscillation with an increasing depth and a time delay of the surface temperature propagation. The differences in the soil temperatures on the north and south side are moreover showing the importance of solar radiation in the process. These observations are further integrated into a procedure allowing for the analysis of possible ad-hoc relationships between current and past air temperature and depth of the frozen layer.

How to cite: Bočková, K., Moya, J., Macías, A., and Vaunat, J.: Field monitoring of cyclic freezing process: effect of air temperature on frozen layer thickness, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14413, https://doi.org/10.5194/egusphere-egu23-14413, 2023.

EGU23-14553 | ECS | Orals | SSS2.1

Assess land degradation status based on Earth Observation driven proxy indicator 

Nikiforos Samarinas, Nikolaos Tziolas, and George Zalidis

Land degradation is a global topic in climate change debates resulted from different types of human activities as well as from physical processes. Resilient, healthy soils are important to help reduce the ecological and economic impact of environmental change and extreme conditions. The development of adequate and broadly applicable indicators and thresholds is challenged by the great diversity of European soils and climate, as well as different political, economic, and social conditions which lead to different priority settings for targets and indicators. This work built upon current environmental awareness (e.g CAP, SDGs, etc.) to design a methodological framework for environmental performance metrics related to land degradation. The framework was oriented towards a data-driven environmental metric approach leveraging Copernicus Sentinel-2, existing open-access databases such as LUCAS (Land Use/Cover Area frame statistical Survey) and GEOSS (e.g., Soil Grids) vast dataset archives to provide metrics for environmental actors. Based both on the international literature and European commission documentations this work is focused on the combination of vital importance indicators of soil degradation and soil health. A novel deep learning architecture was implemented to support the final knowledge extraction with a pixel-based spatial resolution of 10m for the determination of Soil Organic Carbon (SOC) and Clay content. The above indicators are used as enhanced geospatial inputs to a soil erosion modelling approach providing improved predictions. A proper approach was followed for the SOC:clay ratio generation and with the soil erosion product combination to provide an ambitious land degradation index. An agricultural area in Northern Greece was used as a demonstration test site area for the proposed methodology.

How to cite: Samarinas, N., Tziolas, N., and Zalidis, G.: Assess land degradation status based on Earth Observation driven proxy indicator, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14553, https://doi.org/10.5194/egusphere-egu23-14553, 2023.

EGU23-15335 | ECS | Orals | SSS2.1

Towards a more sustainable global soil health monitoring through soil spectroscopy 

Zampela Pittaki, Tor-Gunnar Vagen, Valentine Karari, Elvis Weullow, Dickens Alubaka Ateku, and Leigh Ann Winowiecki

Healthy soil can be defined as a dynamic ecosystem that performs a variety of essential functions such as controlling plant disease, nutrient cycling, improving soil function with positive effects for filtering and storing water, and nutrient capacity, and contributing to improving crop production. Healthy soil also contributes to mitigating climate change by maintaining or increasing its carbon content. Therefore, information on spatial variability of key soil properties is essential for prioritizing and tracking land management interventions, from the small-scale farm level to the global landscape level. In addition, healthy soil is critical for achieving several SDGs such as #2, 3, 6, 13, 15 and 17. However, the determination of soil properties through wet chemistry measurements is often expensive and time-consuming process, and consequently, soil analyses are restricted to a limited number of soil samples. A method that predicts the soil properties fast, inexpensively, and accurately is soil spectroscopy, which can provide immense opportunities for monitoring important soil health indexes. In this study, the evaluation of three algorithms for predicting three key soil properties, soil organic carbon (SOC), pH and Magnesium (Mg) using mid-infrared spectral data were studied using a dataset of more than 3400 samples. The soil samples were collected across Sub-Saharan Africa (SSA) region using the well-established Land Degradation Surveillance Framework (LDSF) method developed from World Agroforestry (ICRAF). The developed trained calibration models were based on the widely used in the soil spectroscopy research Partial Least Squares (PLS) and Random Forest (RF), and the not applied so far Bayesian Regularization for Feed-Forward Neural Networks (BRNN). The dataset was split into calibration (70%) and validation (30%) sets. Furthermore, the threshold of 5% was applied and thus, only the data with value that lie between 5% and 95% of each soil property were included. In this way, the extreme values that will bias the model and the predictions were excluded. Results has shown that the calibration model developed based on the BRNN algorithm yielded the more robust predictions among the three studied soil properties (R2 of val 0.90, 0.92, 0.87 for pH, Mg, SOC, respectively). The predictions utilizing soil spectroscopy for determining soil properties in this study are showing its extremely potential to be beneficial in the support of soil health.

How to cite: Pittaki, Z., Vagen, T.-G., Karari, V., Weullow, E., Ateku, D. A., and Winowiecki, L. A.: Towards a more sustainable global soil health monitoring through soil spectroscopy, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15335, https://doi.org/10.5194/egusphere-egu23-15335, 2023.

EGU23-16219 | Posters on site | SSS2.1

Simulation of spatial and temporal dynamics of soil organic carbon reserve in Romania 

Cristian Valeriu Patriche, Ionuț Vasiliniuc, Bogdan Roșca, and Radu Gabriel Pîrnău

The present study performs a simulation of soil organic carbon (SOC) dynamics in Romania by coupling an evolution model of organic carbon with an erosional model. The simulation starts from the current SOC reserve, computed for the first 20 cm of soil, based on organic carbon content and bulk density, the latter being estimated through a pedotransfer function. The evolution model of SOC takes into account the annual accumulation of organic residues, the active and stable organic carbon contents, the humification and mineralization rates. The annual accumulation of organic residues is estimated from crop type for the arable land and from Corine Land Cover land use / cover types for the rest of the territory. The humification rate of organic residues is expressed through the izohumic coefficient, which depends on the land use/cover type. The mineralization rate of the active organic carbon content depends on climate factors (temperature) and granulometry (clay content). The application of the SOC evolution model produces an estimation of SOC accumulation under automorphic conditions. On the other hand, erosional processes determine soil loss and implicitly soil carbon loss. To account for this impact, we used an erosion model based on the universal soil loss equation, which was adapted and validated for the Romanian territory. Assuming the annual erosion rates are constant, our 50 years simulation show that important areas of the country, situated in the plateau and hilly regions, are experiencing a regressive dynamic of SOC. Under climate change scenarios, the temperature increase may enhance the mineralization of active SOC, leading to a more intense depletion of soil fertility.

How to cite: Patriche, C. V., Vasiliniuc, I., Roșca, B., and Pîrnău, R. G.: Simulation of spatial and temporal dynamics of soil organic carbon reserve in Romania, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16219, https://doi.org/10.5194/egusphere-egu23-16219, 2023.

EGU23-16736 | Orals | SSS2.1

Conservation Agriculture to Rebuilt Soil Fertility in Northern Tunisia 

Mohamed Annabi, Haithem Bahri, Hatem Cheikh M'hamed, Meriem Barbouchi, and Wael Toukebri

Tunisia is an agriculture country. Such as many other Mediterranean countries precipitations  remains a decisive factor not only for the different agricultural uses of lands (rainfed or irrigated system) but also for the soils erosion. The latter  is accentuated by agricultural practices (tillage, pesticide inputs, low crop residue restitution…) which are often productive but do not protect natural resources. All these factors have led to the development of conservation agriculture based on no-tillage as a mean to combat soil erosion. In fact, in Tunisia, no-tillage areas increased from 52 ha in 1999 to 17000 ha in 2020. Based a set of 20 plots covering 6 soils types and located in the semi-arid area of the country, a periodic monotoing of a set of soil parameters were done during three years, which include soil sensitivity to erosion according Le Bissonnais method, soil organic matter content and soil microbial respiration. For each plot, a half  of the surface was no-tilled and the other half was conducted according the conventional method based on soil returning. The results show a rapid effect of no-tillage on soil erosion, since an improvement of 18%, 42% and 39% of soil resistance to erosion, respectively after the first, second and third year of switching to no-tillage system. The soil microbial activity response was also significative, whit a progressive increase of soil respiration in the no-tilled treatments compared to tilled treatments. The microbial respiration was higher in non-hydromorphic soils and particularity in the red Mediterranean soils, calcic-magnesic soils and isohumic soils were moisture conditions was the most favorable for a development of soil microorganisms. For soil organic matter content, the evolution trend was not detectable in relation to the slow evolution of this soil parameter. However, the evolution of particulate organic matter content (a part visible of soil organic matter, with a size larger than 2mm) shown an increase in no-tilled treatments comparative to the tilled treatments. The increase of the particulate organic matter content was more important in vertisols, podzol, calcic-magnesic soils and isohumic soils in relation with their higher wheat production compared to other studier soil types.

 

How to cite: Annabi, M., Bahri, H., Cheikh M'hamed, H., Barbouchi, M., and Toukebri, W.: Conservation Agriculture to Rebuilt Soil Fertility in Northern Tunisia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16736, https://doi.org/10.5194/egusphere-egu23-16736, 2023.

EGU23-16894 | ECS | Orals | SSS2.1

Influence of anthropogenic climate change on soil erosion occurrence: Gully Nacala, Mozambique 

Ingrid Ferreira Lima, Chiaki Kobayashi, Benedito da Silva, Yumi So, and Yasui Hitomi

Gully is an issue of the climate crisis in most coastal areas of the world. More than 70% of the world's sandy coastlines would be eroded in recent decades. Anthropogenic climate change is one of key factors controlling soil erosion occurrence. Soil erosion control is extremely important for soil conservation work and territorial planning. The municipality of Nacala, province of Nampula, Mozambique, has gully susceptibility as a known problem. The Japan International Cooperation Agency (JICA), concerned about the intense urban erosion in the Nacala region, which causes problems not only for the population living in critical areas but also for the proper functioning of the Nacala Port, has been making efforts to identify the causes and mechanisms of the phenomenon and suggest corrective and preventive measures covering the area of the Mocone basin, Nacala. Thus, we obtained information on the causes and mechanisms of evolution of these phenomena to allow the joint search for the features that determine the natural susceptibility to erosion of the municipal territory. We also identified that the soil type in the Mocone basin is sandy-clayey, with an infiltration capacity of 50mm/hour, erodible, with a drainage network mainly characterized by rills and gullies, with periodic surface runoff, only during heavy rains. Our studies indicated a catchment with a significant area upstream of the erosion process (2.34 km2). The maximum project flows obtained in the our preliminary hydro-meteorological studies, considering intense rains with a return period of 100 years, and with duration equal to the time of concentration of the catchment basin (90 min), also proved to be quite significant, with values above of 25 m³/s. Accelerated erosion in this location seems to occur, preferentially, in sectors where those natural factors have been exacerbated by anthropic factors due to inadequate occupation of the physical environment. This urbanization resulted in waterproofing, an increase in surface runoff volumes and a reduction in the concentration time of this basin. In addition, the rainwater drainage of some streets was released directly into the natural terrain, without the proper hydraulic works to reduce energy. The rapid development of the erosion branch towards the Nacala Port proves this close relationship between inadequate urban drainage and the evolution of the analyzed erosion process. The results obtained also prove, once again, the importance of analysis and mitigation approaches for large scale erosion processes that contemplate the catchment basin in its entirety, where erosion control practices or changes in soil cover are necessary.

How to cite: Ferreira Lima, I., Kobayashi, C., da Silva, B., So, Y., and Hitomi, Y.: Influence of anthropogenic climate change on soil erosion occurrence: Gully Nacala, Mozambique, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16894, https://doi.org/10.5194/egusphere-egu23-16894, 2023.

EGU23-277 | ECS | Orals | SSS2.3

Local assessment of technical forestry awareness on soil erosion after wildfire – the case study of Central Portugal region 

Ana R. Lopes, Sandra Valente, Jacob Keizer, and Diana Vieira

Wildfires consist in an environmental problem with a global dimension, but also with future demands as fire prone regions will likely increase, driven by new climate constrains but also socioeconomic drivers. Similarly to other land degradation pressures, despite the large scale of its occurrence, wildfires impacts require assessment and mitigation actions at local scale. Therefore, there is an urgent need to identify local agent’s perspectives regarding wildfires impacts in the ecosystems, and incorporate their local knowledge into post-fire land management decision making. Can a local analysis contribute to political decision-making, streamlining and simplifying processes established at national level?

In an attempt to assess the local perception that technical forest managers have on soil erosion after wildfire, an investigation was conducted, having the central region of Portugal as case study. In this project, we assessed the relevance that technical forest managers give to post-fire soil erosion, by identifying the priority of their activities, established procedures, and their perception of present and future risk following wildfires. Thus, a survey was structured and provided to 108 entities (100 municipalities and 8 inter-municipal communities), being active for reply between 14 September and 14 October 2022. The survey was structured in three main sections: i) general characterization of the entity, ii) description of its global relationship with forest land management and actions after wildfire, and iii) identification of procedures and technical tools used for post-fire land management.

From the 108 requests, 78 answers were obtained, and 52 were considered valid for analysis. The results identified a general concern with soil erosion after wildfire. However, the focus of individual local concerns with wildfires impacts is mostly targeted to loss of biodiversity, the abandonment and degradation of affected areas, followed only then by the soil losses by erosion. Respondents also identified that they have implemented, or are aware of the implementation, of erosion mitigation measures in their actuation area, being these measures mainly represented by the construction of organic barriers and interventions in water bodies, for soil stabilization and overflow redirection. Technical tools are generally used for forest management planning, but not with the main intention to control soil erosion neither to promote its rehabilitation. Respondents also refer that an open source, and updated, technical tools on this scope would allow them to design an emergency strategy on time. This would also enable the support of the local decision-making process, and contribute to a standardized and streamlined response from diverse municipalities affected by the same wildfire.

According to the results obtained, two main strategies can be inferred in order to promote the local conservation of forest soils after an wildfire: i) local empowerment to act and contribute with technical support to private local forest owners and managers, and ii) the reinforce of the awareness-raising process, by adapting campaigns (information/language) to the different, affected and interested, stakeholders.

How to cite: R. Lopes, A., Valente, S., Keizer, J., and Vieira, D.: Local assessment of technical forestry awareness on soil erosion after wildfire – the case study of Central Portugal region, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-277, https://doi.org/10.5194/egusphere-egu23-277, 2023.

EGU23-1570 | ECS | Orals | SSS2.3

How acidic or alkaline soils affect SOC stock in a post-abandonment secondary succession process: a case study in th Mediterranean mid-mountains. 

Melani Cortijos-López, Pedro Sánchez-Navarrete, Teodoro Lasanta, and Estela Nadal-Romero

Mediterranean mountains have been affected by an intense process of cropland abandonment since the middle of the last century, as a result of the rural exodus. This has led to the activation of natural revegetation processes in marginal areas that have not been managed. Literature has recorded different soil responses to secondary succession depending on factors such as climate, altitude, soil depth and type, but still very little is known about the influence of soil pH. Thus, the main objective of this work is to identify how soil quality and carbon sequestration are affected by secondary succession after abandonment for two types of soil lithologies (acidic and alkaline). For this purpose, the Leza Valley (La Rioja, Spain) was selected as the representative study area. Soil samples were collected for each lithology, at different depths (0-40 cm), for 5 stages of succession (cropland (CRL); shrubland (SH); bushland (BS); young forest (YF); and old forest (OF)), and their physicochemical properties were analysed in the laboratory. Data analysis was carried out and these are the most relevant results: i) there are significant differences between acidic and alkaline organic carbon stocks; ii) the alkaline soils increase their SOC stock with the advance of succession, and significant differences were observed between the first stages of abandonment and BS, YF and OF; iii) while in the acidic soils no significant differences were observed, and the highest values were recorded in YF; iv) these results may be the combination of interactions between pH, soil properties and plant and microbiological communities that establish in these areas. Our work has shown the relevance of considering the lithology of our soils in order to determine which post-abandonment management practices may be the most appropriate for our study area. Therefore, it is necessary that policies and management strategies include this type of analysis to achieve the best results of soil carbon sequestration.

Acknowledgement: This research project was supported by the MANMOUNT (PID2019-105983RB-100/AEI/ 10.13039/501100011033) project funded by the MICINN-FEDER. Melani Cortijos-López is working with an FPI contract (PRE2020-094509) from the Spanish Ministry of Economy and Competitiveness associated to the MANMOUNT project

Keywords: abandoned croplands, natural revegetation, carbon sequestration, soil pH, Iberian System (Spain)

How to cite: Cortijos-López, M., Sánchez-Navarrete, P., Lasanta, T., and Nadal-Romero, E.: How acidic or alkaline soils affect SOC stock in a post-abandonment secondary succession process: a case study in th Mediterranean mid-mountains., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1570, https://doi.org/10.5194/egusphere-egu23-1570, 2023.

EGU23-3504 | Orals | SSS2.3

New approach to evaluate the intensity of ancient human activities, based on organic matter characteristics using Rock-Eval® thermal analysis. 

Marie-Liesse Aubertin, Oscar Pascal Malou, Manuel Arroyo-Kalin, Umberto Lombardo, Tiphaine Chevallier, Priscia Oliva, Frédéric Delarue, Julien Thiesson, Katell Quenea, David Sebag, and Geoffroy de Saulieu

Archaeological anthrosols constitute a heritage of long-term carbon storage and soil fertility. Their anthropogenic features are affected by the type and intensity of ancient human activities. Human activities can follow a gradation of disturbance intensity, with lower intensity related to a weak human pollution of natural soil, and stronger intensity related to anthropogenic materials inputs (e.g. refuse pits). Soil properties are indeed deeply modified by the addition of objects (e.g. bones, ceramic) and of organic matter with distinct chemical composition and biological stability (e.g. charcoal). The aim of the study was to establish a new analytical approach to distinguish intensities of human activities, based on organic matter characteristics. To this end, we studied intertropical soil profiles (0-120 cm) from Cameroon, Brazil and Bolivia, with spatial or temporal intensity variations of human activities. We used standard compositional parameters (hydrogen index, HI, and oxygen index, OI) and advanced thermal parameters (I-index and R-index) from Rock-Eval® pyrolysis, as well as magnetic susceptibility, to characterize anthrosols.

Results demonstrated the potential of Rock-Eval® pyrolysis parameters to identify human activities changes. First, the deviation of I-index (delta-I) between our samples and a reference value from natural sites informed about the intensity of human impacts, allowing for the distinction between artificial infilling of refuse pits and soil profiles with no or few human impacts. Second, positive HI:OI correlation established the importance of charcoal as main organic C source. The magnetic susceptibility informed about the presence of burnt soils in a Brazilian and one of the Bolivian sites. The combination of all these parameters, when represented with soil depth, allowed for the estimation of temporal changes in Brazilian and Bolivian sites. The topsoils were similar for all sites, relative to a low intensity of human activities or to the resumption of natural pedogenesis, thereby alleviating the effects of ancient human activities on organic matter characteristics. In contrast, the subsoils exhibited higher intensities of ancient human activities, with even higher values of intensities in Bolivian sites, thereby evidencing the long-term conservation of their effects on organic matter characteristics.

To conclude, anthropogenic activities may durably affect organic matter characteristics in tropical sites, even after several centuries. Beyond being of interest for archaeological research, this new approach raises questions about the long-term consequences of our current human activities.

How to cite: Aubertin, M.-L., Malou, O. P., Arroyo-Kalin, M., Lombardo, U., Chevallier, T., Oliva, P., Delarue, F., Thiesson, J., Quenea, K., Sebag, D., and de Saulieu, G.: New approach to evaluate the intensity of ancient human activities, based on organic matter characteristics using Rock-Eval® thermal analysis., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3504, https://doi.org/10.5194/egusphere-egu23-3504, 2023.

EGU23-5949 | ECS | Posters on site | SSS2.3 | Highlight

Sustainable increase of SOC stocks and nutrients in sandy subsoils by ameliorative fractional deep tillage (aFDT) 

Marisa Gerriets, Martin Leue, Sylvia Koszinski, and Michael Sommer

The sandy soils of Eastern Germany show a high gradient in soil organic carbon (SOC) between topsoil and subsoil. This is reflected in the low nutrient supply, water storage capacity and increased compaction susceptibility of the subsoil. In view of these productivity limitations, ameliorative fractional deep tillage (aFDT) was developed in the late 1950s.

The aim of this subsoil melioration measure is to create shafts enriched with organic-rich topsoil material in the subsoil to remediate root restricting layers and promote accessibility of subsoil resources. At the same time, organic C sequestration is induced by mixing of subsoil material low in organic matter into the topsoil. The 50 cm deep and 7-15 cm wide shafts are created at 35-80 cm intervals by a special plough or modified loosener. Thereby, solid zones remain between the shafts to ensure stability and reduce the risk of re-compaction of the strip wise deep tillage.

We studied three 37- to 43-year-old historical field trials representing a soil quality gradient near Müncheberg to investigate the long-term effects of aFDT on SOC accumulation as well as nutrient stocks in the subsoil and organic carbon sequestration in the topsoil. Besides the shaft, the topsoil, the area next to the shaft, the subsoil material below the shaft and reference topsoil without aFDT outside the trial plot were sampled. In total, 43 shafts were sampled.

We found that the 50-75% of the original SOC was still preserved in the shafts. The shafts had significantly higher SOC contents (+286%) and nutrient contents (P+75%, K +33%, Mg +50%) compared to surrounding subsoils (E/Bw horizons). These results indicate that aFDT is an effective melioration method to increase the SOC and nutrient stocks.

How to cite: Gerriets, M., Leue, M., Koszinski, S., and Sommer, M.: Sustainable increase of SOC stocks and nutrients in sandy subsoils by ameliorative fractional deep tillage (aFDT), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5949, https://doi.org/10.5194/egusphere-egu23-5949, 2023.

The development of the balance of carbon stocks is at the EU level as well as nationally a key issue related to climate change and the state of the environment, and nowadays it is also strongly linked to the economic perspective through common agreements related to taxonomy. This places the need to produce new researched information as a basis for decision-making.

In Finland, the lack of soil information is becoming a limitation of climate-resilient agriculture and forestry policy measures. Because of this, Geological Survey of Finland (GTK) and its partners have launched several projects to improve the situation. In the new projects, remote sensing methods, digital tools and the use of artificial intelligence have been developed in particular to expand the regional coverage of soil data and to enable the assessment of the national carbon stock. By developing the production of information and making the use of databases more efficient, land use measures can be directed and targeted in such a way that they maintain and strengthen carbon sinks and stores.

GTK's partners in the projects have been the Natural Resources Institute Finland, the Universities of Helsinki and Turku, the Finnish Food Authority, the National Land Survey of Finland and RADAI, and the work would not be possible without interdisciplinary cooperation.

How to cite: Pihlaja, J.: Development of soil research supporting climate resilience and decision-making in Finland, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6129, https://doi.org/10.5194/egusphere-egu23-6129, 2023.

EGU23-6290 | Posters virtual | SSS2.3

Adapting irrigated maize cropping to a changing climate 

Carla S.S. Ferreira, Matthew T. Harrison, Nicolas F. Martin, Guillermo S. Marcillo, Pan Zhao, Ran Tao, Naira Hovakimyan, and Zahra Kalantari

The European Mediterranean region is heralded globally for both its high vulnerability to soil degradation and realization of the climate crisis, with ambient temperatures increasing at rates 20% faster than the global average. Maize crops in this region experience moderate to severe water stress during late spring and summer, although such trends are being exacerbated by lack of agricultural irrigation, which has exhausted ~70% of freshwater reserves to date. Future water scarcity is expected to increase as evaporative demand ramps in line with global warming, with rainfall intensity and distribution becoming more variable, and with intensification of weather extremes including drought. Agricultural droughts occur when soil moisture for a prolonged period is below the wilting point threshold, leading not only to yield reduction or failure, but also impaired soil biogeochemical processes, enhanced losses of terrestrial carbon and soil biodiversity. Thus, agricultural water management is key not only in terms of global food security but also in terms of natural capital and environmental stewardship, namely planning for net-zero greenhouse gas emissions. Here, our aim was to identify adaptations for maize crops that improve water-use efficiency, resulting in greater production for lower water requirement. Using the Agricultural Production Systems sIMulator (APSIM) crop model, we simulated maize growth in 14 regions across the European Mediterranean region under historical (1984-2021) and future (2064-2100) climate horizons, assuming a 22% decrease in precipitation and a 5.6ºC increase in temperature following the Six Assessment Report of the IPCC (IPCC, 2022). Treatments included a range of irrigation quanta per season (0 mm, 200 mm, 400 mm, 560 mm, 920 mm, 1400 mm, 1600 mm and 2000 mm) and several representative irrigation infrastructures. Irrigated water was applied with furrow, sprinkler and drip-irrigation systems. Under future climates, we reveal that penalties in rainfed maize yields range from between 30% to complete catastrophic collapse. Increasing irrigation applied helped alleviate negative impacts of the climate emergency. However, even under optimal irrigation, maize yields decreased by 6-44% (except for modest increases in Villamanan [north Spain] and Montelier [south France]). For the same amount of water applied over the season, drip and sprinkler systems were conducive to greater yields than furrow irrigation (1-63% and 1-52%, respectively), with the rotating sprinkler (pivot) irrigation providing the highest average water use efficiency (10-17 kg grain/mm water). Drip irrigation – characterised by smaller amounts of water applied more frequently for a longer duration - was conducive to higher evaporation losses than pivot and furrow. Understanding the impacts of climate variability under future climates will be critically important for developing productive, profitable, efficient irrigation strategies that improve security of carbon, water and food.

Keywords: Climate change, irrigation management, crop yield, water use efficiency, Mediterranean region

 

How to cite: S.S. Ferreira, C., T. Harrison, M., F. Martin, N., S. Marcillo, G., Zhao, P., Tao, R., Hovakimyan, N., and Kalantari, Z.: Adapting irrigated maize cropping to a changing climate, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6290, https://doi.org/10.5194/egusphere-egu23-6290, 2023.

Soils are often underestimated and overlooked in reviewing national economic structures. Soils and groundwater are the essential basics for food production. Beyond securing nourishment, quantity and quality of soils are pivotal factors in farming, forestry and further land use. The potential of soils governs the availability and variety of its products for national food security and trading. In most industrial European countries, farming has only a share of about 1% of the national gross domestic product but secures vital needs. In the Sub-Saharan region, the same share varies between 16% and 20%, largely depending on regional weather, water availabilty and soil quality. The largest threats are climate change and depletion of soils. Whereas European countries aim for steadily increasing sustainability, countries in Southern Africa are often struggling between short term profits, preservation of soils and necessary climate adaptions. The study sheds some light on the different roles of soils in European and Southern African economies, their inter-dependencies, the necessity to map quantities and qualities of soils for managemant measures and growing needs with a still fastly rising population in Southern-Africa. 

How to cite: Meyer, U.: Soils and Economy - Snapshots on Europe and Southern Africa, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6715, https://doi.org/10.5194/egusphere-egu23-6715, 2023.

EGU23-7463 | Posters on site | SSS2.3

Options for reducing agricultural ammonia emissions on different soil types 

Kitti Balog, Sándor Koós, Béla Pirkó, Nóra Szűcs-Vásárhelyi, Marianna Magyar, János Mészáros, Mátyás Árvai, Anita Szabó, Zsófia Adrienn Kovács, Tünde Takáts, and Péter László

A governance perspective of the European Union, that increasing efforts are dedicated towards reducing emissions of air pollutants, including ammonia. To reach this goal, Directive 2016/2284 (NEC) has been adopted, which sets a total annual emission limit value for all EU countries to be achieved by 2030. To contribute to the ambitions of sustainable agriculture, Hungary needs to reduce ammonia emissions by 32% compared to 2005 levels. Since 90% of ammonia emissions are related to agriculture, change in agrotechnical practices is needed to reach the target.

Our goal is to find optimal land use management practices in order to minimize ammonia emission, thus creating interactions between land degradation reduction and climate neutrality. A small-scale plot field trial was set up to demonstrate the possibilities of reducing ammonia emissions from urea fertilizer (46.6% active N ingredient), due to agrotechnical treatment combinations [split dose (60-40%) fertilizer application and incorporation] taking into account different test crops (wheat, triticale, grain sorghum, maize, sunflower), soil properties, climatic factors and vintage effect. In the experiment, urease inhibitor (Limus  Yellow) was tested, which was designed to inhibit the urease enzymes catalyzing the hydrolysis of urea, thus reducing and slowing the formation of ammonium, and reducing the loss of ammonia. Treatment combinations were set up in 4 replicates in a randomized design, with a total of 32 plots and 4 controls on four different soil types (Arenosol in Őrbottyán, Chernozem in Nagyhörcsök, Luvisol in Keszthely and Gleyic Chernozem in Karcag – according to WRB) with sand, loam, clayey loam and clayey loam texture, respectively. The volatilized ammonia was investigated using a passive  chamber method (phosphoric - acid  and glycerol mixture as trap to NH3) for 6 weeks in the case of hoe culture and for 12 weeks in the case of cereals, during which the ammonia release was determined at 2-week intervals.

The inhibitor delayed the rate of ammonification in all soil types, thus reducing ammonia emissions in the weeks following application, but at a decreasing rate. The order of the soils from high to low ammonia reduction due to the inhibitor (2-year averages) was Arenosol (52%) > Chernozem (50%) > Luvisol (46%) > Gleyic Chernozem (20%), which shows a correlation with soil texture (from low to high clay content).

Split fertilizer application reduced ammonia emissions by 48% (3-year average) compared to treatments where 100% of the N dose was applied at the start (2020, 85%; 2021, 24%; 2022, 35%).

Incorporation has an ammonia emission reduction effect of 57% (3-year average) (2019, 53%; 2021, 70%; 2022, 49%). On Gleyic Chernozem, ammonia emission reduction was 68%, while on Luvisol it was 71% (2021) and 49% (2022) compared to leaving it on the surface.

Considering the test crops, incorporation was the most effective in reducing ammonia emissions in maize (62%), sunflower (67%) and grain sorghum (68%), against inhibitor effect (49, 54 and 3 %, respectively). In contrast, the inhibitor effect was the strongest in winter wheat (46 %) and triticale (52 %), against split dose application (28 and 31%, respectively).

How to cite: Balog, K., Koós, S., Pirkó, B., Szűcs-Vásárhelyi, N., Magyar, M., Mészáros, J., Árvai, M., Szabó, A., Kovács, Z. A., Takáts, T., and László, P.: Options for reducing agricultural ammonia emissions on different soil types, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7463, https://doi.org/10.5194/egusphere-egu23-7463, 2023.

EGU23-8708 | Orals | SSS2.3

Trading water for carbon in agricultural systems 

Erik Schwarz, Anna Johansson, Cristina Lerda, John Livsey, Anna Scaini, Daniel Said-Pullicino, and Stefano Manzoni

Climate change and agricultural intensification are placing enormous pressure on soil to provide essential services, from water storage and nutrient provision to carbon sequestration. Indeed, storing carbon in agricultural systems is proposed as an effective climate mitigation approach. Yet, storing carbon comes often at a cost in terms of water consumed—water used either to increase productivity and carbon inputs to soil, or to create conditions in the soil that promote carbon storage. These linkages are perhaps most evident in rice paddy systems.

Rice – a staple food for 3 billion people – consumes more water than any other crop, leading to unsustainable water withdrawals. However, this large water consumption allows paddy soils to store more carbon than under other land uses, because flooding of the fields keeps soils saturated and inhibits organic matter decomposition. Therefore, changing water saving approaches such as alternate wetting and drying has the potential to reduce carbon storage and alter the provision of other ecosystem services. But how much can soil organic carbon change across land uses and when water management is altered?

In this contribution, we discuss the mechanisms of carbon storage in paddy fields, using data from a meta-analysis of soil carbon budgets in tropical rice paddies and from a detailed investigation of carbon storage along a gradient of a land use and soil age in a temperate rice system. The meta-analysis shows that, as expected, reducing the time of flooding decreases soil organic carbon, but also results in a net decrease of greenhouse gas emissions. The more detailed study shows that in temperate conditions with relative short flooding time, rice paddies can store as much organic carbon as forest sites, despite the higher carbon inputs of forests compared to rice systems. This higher carbon storage is achieved thanks to decreased soil respiration in anaerobic conditions and increased mineral associations of organic carbon. These results show that water management strongly affects soil carbon storage, and that trade-offs emerge between sustainable water use and long-term provision of soil-related ecosystem services.

How to cite: Schwarz, E., Johansson, A., Lerda, C., Livsey, J., Scaini, A., Said-Pullicino, D., and Manzoni, S.: Trading water for carbon in agricultural systems, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8708, https://doi.org/10.5194/egusphere-egu23-8708, 2023.

EGU23-11518 | Orals | SSS2.3

Mapping spatial and vertical repartitions of soil carbon stocks, additional storage potential and storage dynamics at the regional scale 

Delphine Derrien, Clémentine Chirol, Laurent Saint-André, and Geoffroy Séré

Soils constitute a carbon reservoir that can help to mitigate climate change, or conversely accelerate greenhouse gas emissions if not managed properly. Soils are heterogenous and dynamic systems, which physico-chemical properties impact their current soil organic carbon (SOC) stocks and their capacity to store more carbon. Land-use planning aiming to preserve and increase SOC stocks should therefore be aware of the spatial repartition of various soil types and of the SOC dynamics therein.

This project aims to map the effect of soil typology on the spatial and vertical repartition of soil carbon stocks, additional storage potential and storage dynamics at a regional scale to improve guidance of SOC storage strategies. The study site is a 320 km2 temperate rural region in NE France. Eight dominant soil types are defined, notably Calcaric cambisols in the agricultural valleys, deep silty and acidic soils in the forested plateaus, shallow rocky calcaric soils on the hillslopes, and deep clay-rich hydromorphic soils in the alluvial valleys.  

Based on logarithmic fits of soil carbon data extracted from 197 full-depth soil profiles, mean soil organic carbon stocks are obtained as a function of depth for each represented soil type and land cover. The additional storage potential corresponds to the difference between the current stock and the maximum stock, as estimated by the fit of the upper 25% of the soil carbon content data.  Finally, a depth-dependent SOC dynamic model using multilayer soil modules is used to simulate SOC stock evolution. Results are mapped by combining the spatial information given by a pedological map and a map of land covers.

Median soil carbon stocks over the full soil profile range from 78 to 333 tC ha-1, of which 59 to 148 tC ha-1 are in the topsoil (0-30 cm). The lower stocks are found in the shallow, rocky cultivated soils, and the highest stocks in the gleysols under grasslands. The additional storage potential varies from 19 tC ha-1 for shallow, rocky forest soils to 197 tC ha-1 for cultivated gleysols. SOC build-up is heterogenous and depends on the mean residence time of carbon in the represented soil types.

Maps of carbon stocks show the areas to preserve to avoid C losses, and maps of additional storage capacity for different time horizons show areas in which to implement carbon storage practices. Going forward, the association of carbon stock mapping and modelling should allow us to estimate at which depths and over which timescales.

How to cite: Derrien, D., Chirol, C., Saint-André, L., and Séré, G.: Mapping spatial and vertical repartitions of soil carbon stocks, additional storage potential and storage dynamics at the regional scale, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11518, https://doi.org/10.5194/egusphere-egu23-11518, 2023.

EGU23-12830 | Posters virtual | SSS2.3

Quantifying the potential of agricultural soils to store carbon. A data-driven approach illustrated for the Netherlands.  

Yuki Fuijta, Sven Verweij, Tessa van der Voort, and Gerard Ros

Improved soil and cropland management changes the soil carbon stocks and thereby mitigate climate change. However, spatially explicit insights on management impacts as well as critical thresholds for optimum SOC levels are lacking, which is crucial for actionable changes in farming practices. In this study we unravelled the contribution of soil texture, geohydrology and soil quality to changes in SOC in the Netherlands using a data-driven approach (using XGBoost) using 21.123 soil analyses done by agricultural laboratories. The current C stock of the 0-30cm soil layer is 119 ton C ha-1 and could be increased by 21 to 59 ton C ha-1 depending on soil type, land use and the agronomic measures taken. The SOC saturation capacity, expressed as the ratio between the actual and potential SOC stock varied from 85 to 93% in grassland soils, from 55 to 83% in arable soils and from 69 to 91% in other land uses. On average, the actual C saturation degree was 75%. The key factors controlling the potential of soils to sequester additional carbon within environmental limits for N and P included the crop sequence in the last decade, soil texture (i.e. oxide extractable aluminium, iron and phosphorus), the acidity, and groundwater depth. The data driven approach shows that spatially explicit recommendations for carbon farming are possible up to the farm and field scale, facilitating the implementation of carbon farming and the mitigation of climate change. When all agricultural fields are saturated with C, an equivalent of 257 Mton of CO2 can be stored.  

How to cite: Fuijta, Y., Verweij, S., van der Voort, T., and Ros, G.: Quantifying the potential of agricultural soils to store carbon. A data-driven approach illustrated for the Netherlands. , EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12830, https://doi.org/10.5194/egusphere-egu23-12830, 2023.

EGU23-13552 | Orals | SSS2.3

Enabling carbon farming: a robust, affordable and scalable approach leveraging remote and proximal sensing 

Sven Verweij, Maarten van Doort, Yuki Fuijta, Tessa van der Voort, and Gerard Ros

The main hurdle in instrumentalizing agricultural soils to sequester atmospheric carbon is a development of methods to measure soil carbon stocks on farm level which are robust, scalable and widely applicable. Specifically, it is necessary that socio-economic barriers related to cost, usability and accessibility are overcome. We present the Wageningen Soil Carbon Stock pRotocol (SoilCASTOR), a method for soil carbon stock assessment using satellite data, direct soil measurements via mobile soil sensors and machine learning which can help overcome these socio-economic hurdles. The method has a low cost per hectare and uses plug-and play tools (soil scanner), which lower the threshold users need to overcome. The method has been tested and applied for multiple farms in Europe and the United states on agricultural fields with variable crop rotations, soil types and management history. Results show that the estimates are precise, repeatable and that the approach is rapidly scalable. Carbon stocks in the top 30 cm range between 1.8-6.1 kg C/hectare and resolution is up to 10x 10 meters. The precision of farm C stocks is below 5% enabling detection of SOC changes desired for the 4 per 1000 initiative. The assessment can be done robustly with as few as 0.5 samples (or 2-3 minutes) per hectare over a range of scales, for farms varying from 20 to 200 hectares.These findings can enable the structural and widespread implementation of carbon farming. This approach has recently been awareded the Bayer Grants4Tech innovation prize.

How to cite: Verweij, S., van Doort, M., Fuijta, Y., van der Voort, T., and Ros, G.: Enabling carbon farming: a robust, affordable and scalable approach leveraging remote and proximal sensing, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13552, https://doi.org/10.5194/egusphere-egu23-13552, 2023.

EGU23-14111 | ECS | Orals | SSS2.3

Investigation of soil carbon sequestration and storage in Hungarian forest sites under different climatic conditions 

Péter Végh, Pál Balázs, András Bidló, and Adrienn Horváth

A szén-elnyelő erdők és talajok előtérbe kerülnek a szénsemlegesség mielőbbi elérése érdekében. A folyamatosan növekvő kibocsátás felborítja a légkör egyensúlyát, és a folyamatok eltolódásával klímaváltozásban vagy időjárási szélsőségekben nyilvánul meg. Kutatásunk célja az erdei ökoszisztémákban különböző éghajlati és erdészeti viszonyok között tárolt szerves széntartalom felmérése volt. A talajelemzésre helyeztük a hangsúlyt, mert a talaj szén mennyisége közel azonos a föld feletti biomasszában tárolt szén mennyiségével. Mintegy 40 kijelölt erdőállományból vettünk mintát, hogy meghatározzuk az egyes erdőállományok talajában tárolt szerves szén mennyiségét. A talajmintákat 40 cm mélységű fúrással gyűjtöttük. A talajmintavétellel egyidejűleg a mintavételi pont közelében lévő egyes állományok élőfaállományát is felmértük. A 40 kijelölt erdőállományban eddig végzett vizsgálatok alapján a területek Cambisols, Luvisols és Arenosols talajosztályokba sorolhatók (WRB 2020). A talajminták pH-értéke többnyire savas (átlag = 5,9), az állaga vályogként határozható meg. A 0-40 cm-es termőtalajok talaj szervesanyag-tartalma (SOM) 1,45%, ami ~14 t széntartalmat jelent hektáronként. A környéken még mindig van elegendő csapadék a növényzethez zavartalanul; így a szénmérleg a térségben jelenleg stabil annak ellenére, hogy az alommennyiség csökkenése miatt a készletek már most is csökkennek. 9) és a textúra vályogként határozható meg. A 0-40 cm-es termőtalajok talaj szervesanyag-tartalma (SOM) 1,45%, ami ~14 t széntartalmat jelent hektáronként. A környéken még mindig van elegendő csapadék a növényzethez zavartalanul; így a szénmérleg a térségben jelenleg stabil annak ellenére, hogy az alommennyiség csökkenése miatt a készletek már most is csökkennek. 9) és a textúra vályogként határozható meg. A 0-40 cm-es termőtalajok talaj szervesanyag-tartalma (SOM) 1,45%, ami ~14 t széntartalmat jelent hektáronként. A környéken még mindig van elegendő csapadék a növényzethez zavartalanul; így a szénmérleg a térségben jelenleg stabil annak ellenére, hogy az alommennyiség csökkenése miatt a készletek már most is csökkennek.

Ez a cikk a TKP2021-NKTA-43 projekt keretében készült, amely a Magyar Innovációs és Technológiai Minisztérium (jogutód: Kulturális és Innovációs Minisztérium) a Nemzeti Kutatási, Fejlesztési és Innovációs Minisztérium támogatásával valósult meg. Alap, a TKP2021-NKTA támogatási konstrukció keretében finanszírozott. A Kulturális és Innovációs Minisztérium ÚNKP-22-3-I-SOE-99 Új Nemzeti Kiválósági Programja pedig a Nemzeti Kutatási, Fejlesztési és Innovációs Alapból támogatott.

How to cite: Végh, P., Balázs, P., Bidló, A., and Horváth, A.: Investigation of soil carbon sequestration and storage in Hungarian forest sites under different climatic conditions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14111, https://doi.org/10.5194/egusphere-egu23-14111, 2023.

EGU23-14616 | Posters virtual | SSS2.3

Effect of afforestation on the organic carbon stock of soils 

András Bidló, Mátyás Csorba, Pál Balázs, Péter Végh, and Adrienn Horváth

Since 1922, the territorial proportion of forests has increased from 12% to 22% due to large-scale afforestation in Hungary. These planted forests bind huge amounts of carbon dioxide from the atmosphere. The sequestered carbon is partly stored in the above-ground biomass of forests in the form of organic matter. At the same time, a similar amount of carbon can be found underground. The research aims to assess the effect of afforestation on the amount of organic carbon stored in the soil (SOC).

During our investigations, we collected samples from 3 study areas from the Hungarian Great Plain. We compared the soil of the poplar and acacia forests in the sample areas with the grassland soils located directly next to these plantations. By the natural conditions, the pH of forest (7.75 and 8.29 pH(H2O)) and grassland (8.01 and 8.45 pH(H2O)) samples was weakly alkaline/alkaline. We measured a lower pH value in case of forests, which clearly shows the leaching effect in the forest soils. The average humus content of the tested soil samples was 0.94%. The lowest measured value was 0.09%, while the highest was 4.21% which clearly showed that dry sandy soils have a low organic matter content.

The soil and the litter cover contain 7 to 37 tons SOC/ha. The differences between the studied areas were very large. The carbon stock of the soils was higher in forest stands in every case. This shows that in long term the afforestation increases the amount of carbon stored in soils compared to grasslands.

This article was made in frame of the project TKP2021-NKTA-43 which has been implemented with the support provided by the Ministry of Innovation and Technology of Hungary (successor: Ministry of Culture and Innovation of Hungary) from the National Research, Development and Innovation Fund, financed under the TKP2021-NKTA funding scheme.

 

How to cite: Bidló, A., Csorba, M., Balázs, P., Végh, P., and Horváth, A.: Effect of afforestation on the organic carbon stock of soils, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14616, https://doi.org/10.5194/egusphere-egu23-14616, 2023.

Cropland soils show large potential to sequester carbon to achieve climate neutrality. Changes in management can affect an increase of carbon sequestration or reducing carbon losses in form of emissions or leaching. However, the impact of management changes on the sequestration and other processes needs to be quantified to provide advice to farmers. Experiments to analyse impacts of management changes are costly and labour intensive. Additionally, these experiments take time and cover only a small range of environmental conditions. Therefore, modelling is widely used to over-come these limitations. Model results allow the estimation of all relevant fluxes for the overall greenhouse gas emission balance or, depending on the model, for some parts. This is a fast and efficient method to quantify soil organic carbon (SOC) changes due to modifications in agricultural management. Even though, models proved their quality of simulating SOC changes, there are some restrictions in the use of models for actual advice based on model results. In the here presented study, three key points will be analysed: First, the additional impacts beside the SOC changes. Carbon sequestration can be offset by emission of other greenhouse gases or management changes affect yield, which needs to be included in the analysis. While these two variables are well covered by usual model approaches, other aspects like food quality are more difficult to include. Second, how does the complexity of the model affect the result. The simple assumption that more complex models are potentially more accurate, but also require more input data is in most cases realistic (this is a generic assumption which is not always true). More input data and more complexity are also associated with potentially increased uncertainty. Third, who is running the model. While research-based advice using more complex models might be potentially more accurate, models used by farmers might be more specific and direct in providing key information. Additionally, the impact of the increased data demand and required data can affect an increased error. These points are analysed on examples and case studies. This includes an analysis beyond the carbon sequestration and how to include these aspects in the analysis. Further, results of a tool developed for stakeholders/farmers is compared with results of a biogeochemical model for selected sites. Finally, an analysis of the limitations of the models due to data demand and data availability. The analysis of wheat yields shows mainly positive impacts on the SOC change, but mainly reduced yield. The comparison of the two models indicates the impracticability of the more complex option, as the data demand is not orientated on the data availability. The decision based on model results requires a careful use of models and a good understanding of the results.

How to cite: Kuhnert, M.: Using modelling and tools for advice on improved agricultural management to achieve climate neutrality in croplands, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14833, https://doi.org/10.5194/egusphere-egu23-14833, 2023.

EGU23-15333 | ECS | Orals | SSS2.3

The effects of olivine fertilization on growth and elemental composition of barley and wheat differ with olivine grain size and rain regimes. 

Jet Rijnders, Sara Vicca, Eric Struyf, Thorben Amann, Jens Hartmann, Patrick Meire, Ivan Janssens, and Jonas Schoelynck

With rising population growth, there is a need for increased food production. With rising temperatures and more frequent droughts due to climate change, it becomes more challenging to keep up with this increased demand for food. Therefore, a change in land use and management is needed in which enhanced silicate weathering (ESW) can play an important role. Weathering of silicate rocks has been regulating the atmospheric CO2 concentrations for over decades, but with the rise in atmospheric CO2, the natural weathering is too slow. Grinding the silicate rocks into a fine powder and spread it over for example agricultural fields will increase the reactive surface area and hence, the amount of CO2 that is stored in soils. The application of silicate minerals to soils can enhance plant growth by multiple processes, for example by counteracting soil acidification and by the release of plant nutrients. In this way, ESW can be used on agricultural fields without competing for land like other carbon capture techniques (e.g. Bio-Energy with carbon capture and storage). This study investigates the use of olivine (a fast-weathering Mg-rich silicate mineral) as a fertilizer in agriculture using a full-factorial mesocosm experiment. Barley and wheat were grown under two different rain regimes (daily rain vs weekly rain) and with application of two different grain sizes of olivine (p80 = 1020 µm and p80 = 43.5 µm). Our results showed increased plant growth and biomass with olivine addition, albeit only for fine olivine. However, this was not translated in an increase in yield of wheat and barley. Besides changes in biomass, we found significant differences in plant nutrient concentrations. As expected, Mg concentration increased significantly. However, BSi and Ca concentrations decreased with fine olivine application. Nitrogen in grains was also increased in the fine olivine treatment. In contrast to fine olivine, coarse olivine addition had almost no influence on nutrients. Ca, Mg and Si concentrations in plant samples followed the same trend as in the soil pore water, in contrast to metal concentrations. Olivine addition increased Ni and Cr availability in the soil pore water, but the concentrations of these elements in plant tissue did not increase and were even below detection limit for the majority of samples. While the influence of olivine on metal concentrations in plant samples was not affected by rain treatment, the influence of olivine on nutrients in the plants and plant growth was. Fine olivine addition enhanced the plants resistance to drought as it reduced the decrease in biomass with weekly rain treatment compared to daily rain treatment. This positive effect of olivine addition can be due to the increased weathering rate in combination with enhancement of soil properties like increased soil water retention. In this way, the use of olivine as a fertilizer on agricultural fields can mitigate climate change while it can also contribute to the solution for increased food demand.

How to cite: Rijnders, J., Vicca, S., Struyf, E., Amann, T., Hartmann, J., Meire, P., Janssens, I., and Schoelynck, J.: The effects of olivine fertilization on growth and elemental composition of barley and wheat differ with olivine grain size and rain regimes., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15333, https://doi.org/10.5194/egusphere-egu23-15333, 2023.

EGU23-15465 | Posters on site | SSS2.3

Climate change impacts on crop production and soil carbon stock in a continuous wheat cropping system in southeast England 

Shuo Liang, Nan Sun, Jeroen Meersmans, Bernard Longdoz, Gilles Colinet, Minggang Xu, and Lianhai Wu

Understanding dynamics of soil organic carbon (SOC) stock in agroecosystems under climate change is imperative for maintaining soil productivity and offsetting greenhouse gas emissions. Simulations with the SPACSYS model were conducted to assess the effects of future climate scenarios (Representative Concentration Pathway (RCP) 2.6, 4.5 and 8.5) and fertilization practices on crop yield and SOC stock by 2100 for a continuous winter wheat cropping system in southeast England. Weather data between 1921 and 2000 was considered as a baseline. SPACSYS was first calibrated and validated with the data of the Broadbalk continuous winter wheat experiment for over a century. Six treatments were used: no fertiliser (control), a combination of chemical nitrogen, phosphorus and potassium with three N application rates (N1PK, N3PK and N5PK), manure only (FYM) and a combination of manure and chemical nitrogen application (FYMN). SPACSYS simulated grain yields and the dynamics of SOC and TN stocks well compared with the observations. Future climatescould significantly increase wheat yield by an average of 8.3% as compared to the baseline. FYMN was characterized by the highest grain yield. Moreover, when considering NPK practices, the relative increase in SOC stock under the RCP8.5 (+3.3%) was higher than those under the RCP4.5 (+1.4%), whereas the RCP2.6 indicated a negative effect (-0.6%) on SOC stocks. When considering manure amendments, the SOC stock decreased (-1.2%) under all RCP scenarios. However, continuous manure amendments can still be considered as a sustainable strategy for SOC sequestration with C stock increases between 34-106 kg C ha-1 yr-1. Future climates generally had positive effects on C sequestration in continuous wheat system with an annual C sink of 43-425 kg C ha-1 yr-1. Mineral fertiliser plus manure could be recommended as a good practice for simultaneously increasing crop productivity and having a rather high C sink under future climate change.

 

How to cite: Liang, S., Sun, N., Meersmans, J., Longdoz, B., Colinet, G., Xu, M., and Wu, L.: Climate change impacts on crop production and soil carbon stock in a continuous wheat cropping system in southeast England, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15465, https://doi.org/10.5194/egusphere-egu23-15465, 2023.

SSS3 – Soils as Records in Time and Space

EGU23-828 | ECS | Posters virtual | SSS3.1

"Paleopedology of Siwalik Paleosols of Kangra Sub-Basin, NW Himalaya: Implication for Weathering and Climate change 11 Ma to 6 Ma" 

Pooja Yadav, Abdul Hameed, Rohit Kumar, and Pankaj Srivastava

The Himalayan Mountain range is the most prominent and active intracontinental range in the world. The outer part of this range is marked by the Himalayan foreland basin (HFB) in south that resulted due to the thrust loading and subsidence with synorogenic sedimentation from the hinterland. The lowermost part of the HFB is marked by the molassic sediments of “Siwalik” which thins out to the south. The time frame between 11Ma to 6 Ma (mid to late Miocene) is critical to understand the changes related to monsoon and vegetation as there is no detailed record or systematic study of late Cenozoic weathering and paleopedogenesis in fluvial sediments of the HFB. In the present study, we present a high-resolution paleopedological record of the paleosols along a traverse of ~ 1.8 km in the Kotla-Brail section of the Kangra sub-basin of the HFB. In the field, the paleosols are characterized by 1-2 m thick Bw, Bt, Bk, Bss, Bk horizons, rhizocretions, pedogenic carbonates (PC), and Fe/Mn mottles and concretions. The paleosols in the Lower Siwaliks show a dominance of 2.5 Y and 5 YR hue, whereas in the Middle Siwaliks they are defined by 5 YR and 7.5 YR hue. Micromorphology of these paleosols confirmed varying degrees of weathering, and paleopedogenesis showing a blocky structure, clay coatings, biogenic activity, and diffused impure micritic nodules as PC in the Bw and Bt, Btk horizons. These pedofeatures are more strongly developed in paleosols of the Lower Siwaliks than in comparison to weakly-moderately paleosols of the Middle Siwaliks.

Clay mineralogy determined based on XRD study of the total (<2 µm) fine clay (<0.2 µm) fractions of these paleosols is characterized by the dominance of smectite, vermiculite, and mixed-layer minerals in paleosols of the Lower Siwalik. The clay mineral assemblage shows a  decrease in the abundance of smectite and increase of kaolinite towards the transitions to Middle Siwalik at ~10 Ma. This also shows transformation of the smectite and vermiculite to interstratified clays at about ~8 Ma. After ~8.5 – 8.0 Ma, the paleosols are again marked an increase of the amount of smectite, vermiculite, and mixed-layer minerals in paleosols of the Middle Siwalik towards their transitions to Upper Siwalik. The varying intensity of weathering, paleopedogenesis, and clay mineral assemblage of the paleosols in the Lower and Middle Siwalik suggest fluctuating climatic conditions that evolved from initial semi-arid to sub-humid at ~11 Ma that to higher precipitation at ~8.5 to 8 Ma then again to semi-arid to arid conditions at ~6.5 Ma.

 

Keywords: Himalayan Foreland Basin (HFB), Siwalik, Paleosols, Micromorphology, Clay Minerals

How to cite: Yadav, P., Hameed, A., Kumar, R., and Srivastava, P.: "Paleopedology of Siwalik Paleosols of Kangra Sub-Basin, NW Himalaya: Implication for Weathering and Climate change 11 Ma to 6 Ma", EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-828, https://doi.org/10.5194/egusphere-egu23-828, 2023.

In the present study we report paleopedology of the fluvial sequences of the Siwalik Group in the Himalayan Foreland Basin, NW Himalaya that formed during ~12 Ma -5.5 Ma. The paleosols formed during this time period are critical to understand weathering and paleopedogenic processes during the evolution of foreland basin over the entire Himalayan range. This work highlights field-characteristics, micromorphology, clay mineralogy, and geochemistry of the ~0.5 km thick Lower Siwalik and ~1.7 km thick Middle Siwalik successions along the Katilu Khad, Kangra sub-basin. In the field, the paleosols are characterized by 1-2 m thick Bw, Bt, Bk, Bss, and BC horizons, blocky and wedge-shaped pedogenic structures, root traces, color mottling, Fe-Mn oxide concretions, slickensides, pedogenic CaCO3 (PC), and bioturbation features. 

Micromorphological observations show the dominance of moderate to well-developed paleopedofeatures in paleosols of the Lower Siwalik in contrast to the moderately to weakly-developed paleopedofeatures in paleosols of the Middle Siwalik. The comparative analysis of various pedogenic features i.e., PC, illuvial clay, mottles, Fe-Mn concretions, microstructures, and bioturbation features confirmed varying degree of the paleopedogenic maturity in the paleosols at different intervals of the Siwalik successions.

Clay mineralogy of the total clay (<2 μm) and fine clay fraction (< 0.2 μm) of the Lower and Middle Siwalik paleosols suggests varying chemical weathering of silicates and change of paleoclimatic conditions during paleopedogenic processes during this time period. The clay mineral assemblage of the total clay and fine clay fraction show the varying distribution of illite, chlorite, kaolinite, smectite, vermiculite and interstratified clay minerals in these paleosols. Large amounts of smectite together with pedogenic carbonates in part of the Lower Siwalik at 12.0 Ma, and at 10.9 Ma and in Middle Siwalik at 9.2 Ma, and at 5.5 Ma suggest arid to semiarid dry climatic conditions Whereas, dominance of kaolin, illuvial features, and dissolution of pedogenic carbonates suggests sub-humid to humid climatic condition at 11.6 Ma, 8.5 Ma, 7.1 Ma, and at 6.5 Ma.

The bulk geochemistry of the paleosols also confirmed varying degree of pedogenic weathering showing high CIA and CIA-K (CIW) values and ~ 800 mm to 1400 mm MAP for paleosols of the Lower and Middle Siwalik. The high MAP (~ 1200 mm to 1400 mm) at ~11.6 Ma, ~8.5 to 8.0 Ma, and 7.1 to 6.5 Ma in paleosols of the Lower Siwalik and Middle Siwalik correspond to increased chemical weathering and paleopedogenesis. While the intervening periods correspond to less MAP (~800 mm to 1100 mm) with large amount PC and less chemical weathering. Based on micromorphology, clay mineralogy, and geochemical characteristics of the paleosols it is interpreted that climate change during ~12 Ma to 5.5 Ma is characterized by humid (11.6 Ma) to semiarid (11.0 Ma to 8.5 Ma), and humid-subhumid (8.5 Ma to 6.5 Ma) in response to Himalayan orogeny and its linkage to regional and global atmospheric conditions.

Keywords: Himalayan Foreland Basin, Paleosols, Siwalik, Micromorphology, Clay mineralogy, Geochemistry

How to cite: Hameed, A., Yadav, P., Kumar, R., and Srivastava, P.: Paleopedological evolution of Siwalik succession from Kangra sub-Basin, NW Himalayan: Implications for climate change and weathering conditions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-838, https://doi.org/10.5194/egusphere-egu23-838, 2023.

EGU23-2241 | Posters on site | SSS3.1

Post-sedimentary pedogenesis in colluvial soils in the context of the landscape sedimentary history (Czechia) 

Tereza Zádorová, Vít Penížek, Magdalena Koubová, Lenka Lisá, Daniel Žížala, Lenka Pavlů, Václav Tejnecký, and Ondřej Drábek

Colluvisols, representing a significant part of the erosional catena in undulating landscapes, often changed by long-term agricultural management, undergo a complex development with alternating phases of material deposition and slope stability, with subsequent initiation of soil formation processes. The presented study focuses on the detailed description of the post-depositional evolution of four up to 4m-deep colluvial profiles, formed in different colluvial positions in two environmentally and historically distinct areas of Czechia, situated in the loess region of South Moravia and Central Bohemian Upland, built on plutonic rocks. A multi-proxy approach consisting of analyses of clay mineralogy, micromorphology, humic acids and geochemical parameters was applied to distinguish the inherited and in-situ developed pedogenetic features and link them with the sedimentary history of the studied soils, assessed using optically stimulated luminescence dating and 137Cs activity. Marked differences in the type and maturity of pedogenetic features were identified not only in individual plots but also in different colluvial positions within the same plot. While signs of bioturbation, mainly related to root activity and soil fauna, were observed even in recent colluvial layers after a short period of stabilization, more advanced processes of weathering, organic matter stabilisation and clay illuviation are typical only for early-sedimented layers with long post-depositional development. Redoximorphic features were more pronounced in the side valleys compared to the toe-slope colluvial positions; similarly marked differences between colluvial positions were observed for humus quality, with significantly more stable organic matter concentrated within side valleys. In both sites, distinct and largely contradictory trends in the transformation of clay minerals, reflected in the proportions of different phyllosilicate layers, were observed, corresponding to the specific conditions of soil development. 

Study was supported by grant nr. 21-11879S of the Czech Science Foundation.

How to cite: Zádorová, T., Penížek, V., Koubová, M., Lisá, L., Žížala, D., Pavlů, L., Tejnecký, V., and Drábek, O.: Post-sedimentary pedogenesis in colluvial soils in the context of the landscape sedimentary history (Czechia), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2241, https://doi.org/10.5194/egusphere-egu23-2241, 2023.

As one of the soil types, peat is an important soil carbon storage and archive of past environmental changes. Here we used multi-core and multi-proxy records from a peatland near Da’erbin Lake in the Arxan region of Northeast China to reconstruct peatland development and carbon accumulation history and to understand their responses to past climate changes during the last 2500 years. Our macrofossil results show that the peatland was characterized by a sedge-dominated fen from 490 BCE to 1450 CE, changed to a Sphagnum-dominated poor fen or bog with abundant shrubs (mostly Ericaceae) during the period of 1450–1960 CE, and finally became predominated by Sphagnum after 1960 CE. The time-weighted mean apparent carbon accumulation rate (aCAR) from three cores range from 19.5 to 53.0 g C m-2 yr-1 with a mean value of 32.4 g C m-2 yr-1, but increase rapidly to 139.2 g C m-2 yr-1 during last several decades. During the early stage of the past 2500 years, three coring sites that are only 50 m apart were all in the fen phase but they had highly variable peat properties. The fen-bog transition occurred at different times at these sites due to local influences of autogenic process, permafrost dynamics, or fire disturbance. These observations suggest that fens are highly heterogeneous, not only in peat properties but also in ecosystem dynamics. The dramatic increase in aCAR during the late stage of bog phase after 1960 CE cannot be explained entirely by limited decomposition of recently-accumulated peat. Instead, this was likely due to increasing Sphagnum dominance and resultant low decomposition of Sphagnum-derived organic matter, suggesting the important role of vegetation change in controlling carbon accumulation rates. Around the 1990s CE, an increase in allogenic CAR—after removing the age-related long-term autogenic effect—seems to correspond with a period of increase in regional summer precipitation, revealing a sensitive response of ombrotrophic bog ecosystem to climate change at decadal timescale.

How to cite: Xia, Y., Yang, Z., and Yu, Z.: Responses of peatland development and carbon accumulation to climate change over the past 2500 years in the Arxan region, Northeast China, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2515, https://doi.org/10.5194/egusphere-egu23-2515, 2023.

EGU23-2822 | Posters on site | SSS3.1 | Highlight

Neolithic Agronomists shaped Chernozem in South-Eastern Bavaria 

Jörg Völkel, Prof. Dr., Anna Sophia Holmer, Ildikó Bösze, and Günther Moosbauer, Prof. Dr.

Up to today, the reason for the genesis of chernic horizons in Germany is a matter of discussion. Recent literature is strongly suggesting a purposeful anthropogenic soil management from neolithic times as an origin of these soils. Here we provide another example of neolithic activities meliorating the soil from a calcic Luvisol to a Chernozem with a dimension of several hectares. This is striking, since it is the first finding of a chernic horizon of this extensiveness in Bavaria, Germany.

The Chernozem has been discovered close to the city of Straubing (48°53′N, 12°34′O, MAP 757 mm, MAT 8,6°C), which is situated in the highly arable Danubian Gäuboden and part of the so called Altsiedelland. It has been home to human settlers ever since the first settlers belonging to the Linearbandkeramik (LBK) culture immigrated, among other things like the optimal climatic conditions due to its very favorable soil characteristics (luvisols) developed on Loess. The neolithic Chernozem is located directly next to a graveyard with graves dating in early neolithic times and later as well as neolithic settlements 500 m away. Collected 14C and OSL-data strongly suggest that part of the Chernozem was covered by a roman colluvium probably eroded from the former graveyard hill by roman ploughing activities. Our obtained 14C data places the chernic horizon itself into the early LBK and onwards. Nowadays the chernic horizon is mostly overprinted by the ongoing soil genesis as an argic horizon. Small charcoal flakes (< 0.5 mm) make the chernic horizon appear greyish-black up to today, with carbon-contents of around 1%. The colour intensifies in the center of the Chernozem area closely by the settlements and graveyard and fades out to a distinct grey shadow in the argic horizon of the calcic luvisol above around 2 km away.

These findings leave no room for doubt: The Chernozem has an anthropogenic origin and was created by the neolithic settlers, following a purpose in managing and meliorating the soil.

How to cite: Völkel, Prof. Dr., J., Holmer, A. S., Bösze, I., and Moosbauer, Prof. Dr., G.: Neolithic Agronomists shaped Chernozem in South-Eastern Bavaria, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2822, https://doi.org/10.5194/egusphere-egu23-2822, 2023.

The Volyn’ Upland is a “loess island” in the middle of the European loess belt. In the previously studied sections of this region, the Pleistocene palaeosols are mainly polygenetic; therefore, the pedocomplexes comprise no more than two soils. The study of the sections located both on the slopes of the river valleys and in the buried gullies, contributed to detailed stratigraphy of the pedocomplexes.  

Three pedocomplexes have been distinguished in the sections, which, according to palaeopedological and palynological data, were tentatively correlated with MIS 5, 7 and 9, respectively. The lower pedocomplex (S3, MIS 9) comprises two soils. The lower soil (S3-II) is a Luvisol with multi-phased clay coatings in the Bt horizon. However, micromorphology detects a clear primary A horizon with abundant coprolites. The upper soil (S3-I) has a well-developed A horizon and Ag horizon in the depression. However, clay coatings in the Bt horizon testify to the clay translocation.

The middle pedocomplex (S2, MIS 7) comprises two welded soils separated by a thin loess bed. The lower soil (S2-II) is a Luvisol, in places marked by a pronounced A horizon, in which clay coatings occur, whereas in the E horizon secondary carbonate nodules appear.  In places, the upper soil (S2-I) turns into two separate soils: the lower Haplic Chernozem and the upper Cambisol, both densely dissected by soil veins. These soils are dark, leached of carbonates, with crumby and granular microstructure. Many krotovinas occur in the subsoil.

The upper pedocomplex (S1, MIS 5) is subdivided into three sub-pedocomplexes, interbedded with sandy facies in depressions and thin loess-like deposits at the topographically higher positions. The lower sub-pedocomplex (S1-III, MIS 5e) is represented, depending on the parent material, by Luvisol, Retisol or Podzol with abundant clay coatings in the Bt horizon. In places, the forest soil is overlain by Entic Podzol with a more pronounced A horizon and is underlain by a Gleysol in depression. The middle sub-pedocomplex (S1-II, MIS 5c) comprises three soils: the lower Entic or Albic Podzol, the middle Chernozem and the upper Cambisol. A distinguished feature of these soils is the rapid increase in sand content in almost all studied sections. The upper sub-pedocomplex (S1-I, MIS 5a) is interpreted as a Cambisol, in places with a well-developed A horizon. In the upper soils of S1, pale brown spots occur.

Three Gleysols have been distinguished in the upper thick loess unit (L1, MIS 2-4). The lower Gleysol (MIS 3) is better developed and mostly polygenetic; in places the soil turns into a pedocomplex consisting of two or three soils: the lower Gleysol, the middle Gleyic Cambisol and the upper Calcaric Cambisol. The middle Gleysol appears to be polygenetic, as evidenced by palynology and micromorphology. Large ice-wedge pseudomorphs are associated with the upper Gleysol, which makes it possible to interpret soil as tundra-gley.

The study was supported by the National Research Foundation of Ukraine, grant number 2020.02/0406.

How to cite: Bonchkovskyi, O.: A detailed palaeosol record of Middle and Upper Pleistocene from the central part of the Volyn’ Upland (the NW Ukraine), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3857, https://doi.org/10.5194/egusphere-egu23-3857, 2023.

EGU23-5502 | ECS | Posters on site | SSS3.1

Using advanced geophysical data processing to improve low detection data in archaeological sites 

Rui Jorge Oliveira, Bento Caldeira, José Fernando Borges, and Mourad Bezzeghoud

Geophysical data with noise issues are quite common, resulting in low detection conditions. This prevents the ground content from being evaluated to determine the existence of structures buried in the ground in an archaeological site. Standard processing on ground-penetrating radar and magnetic data does not effectively eliminate or mitigate this effect. The use of advanced and customized data processing is a viable solution to the problem. This processing can be applied using mathematical transforms in conjunction with data decomposition techniques, allowing for easier and less computationally intensive data manipulation. The circular symmetry of the data is enabled by the 2D Fourier transform, making operations like filtering easier to implement. In the transformed domain, factoring techniques such as singular value decomposition can be used (SVD). After analyzing the decomposed signal, the components can be matched to the signal and noise. The 2D wavelet transform allows for data decomposition, with operations such as multiresolution SVD and multidirectional gradient calculation applied to each channel to select the most informative content from a dataset. The chain application of these operations allows for the improvement of geophysical data despite an apparent lack of information. Testing on field data obtained at Villa Romana de Pisões (Beja, Portugal) is an example of successful application. Advanced geophysical data processing operations can improve the data and should be used in conjunction with standard operations.

Acknowledgment: The work was supported by the Portuguese Foundation for Science and Technology (FCT) project UIDB/04683/2020 - ICT (Institute of Earth Sciences).

How to cite: Oliveira, R. J., Caldeira, B., Borges, J. F., and Bezzeghoud, M.: Using advanced geophysical data processing to improve low detection data in archaeological sites, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5502, https://doi.org/10.5194/egusphere-egu23-5502, 2023.

As sea levels rose since the end of Last Glacial Maximum (LGM) ancient coastal communities were often forced to abandon their settlements and move inland. Today, many of these abandoned sites are covered by sand or lay in shallow water. Examining these can shed light on past coastal communities as well as settlement patterns in ancient times. Archaeological excavation along the coast is particularly tricky and often sporadic in nature. Thus, high‐resolution shallow geophysical methods, which have become a standard in archaeological studies since they provide a noninvasive way of imaging the subsurface before an excavation, would seem like a perfect solution. However, most methods are limited in their ability to work near the shoreline – the transitional zone between classical land-based methods and standard marine ones. Ground penetrating radar (GPR), for example, is greatly affected by moisture and salinity and is therefore limited in its ability to work in areas saturated with seawater. Seismic reflection is time consuming to overcome issues of poor vertical and spatial resolution and sensitive to urban noise, while magnetics would provide poor results for sand covered sandstone. Other techniques, such as electrical resistivity tomography (ERT) have been shown to work in coastal areas and in shallow water. However, this method can be slow, as it involves setting up complex arrays for each cross section measured. This study will present the frequency domain electromagnetic (FDEM) method, which has the potential to overcome these problems and can bridge the gap in knowledge by measuring in the nearshore environment. The ease of use and quick scanning capability means that large areas can be covered in a relatively short time. There are no electrodes or loops to set up. Since it measures swaths, results are obtained in map-view and not cross-section, with little interpolation. Different frequencies penetrate to different depths (lower frequencies corresponding to deeper penetration). Therefore, the result is a series of frequency maps corresponding to the integration of all subsurface data in a specific sampled volume (i.e. down to the frequency-related depths), providing important information on shallow subsurface properties. The use of multiple frequencies allows for the resolving of internal structures within the depth range. Overall, the FDEM method has proven to be a valuable tool for studying coastal archaeology, and it is likely to continue to play an important role in the field in the coming years. Its ability to detect buried objects and structures and to study the geomorphology of submerged landscapes makes it an essential tool for researchers working in this field.

How to cite: Lazar, M. and Basson, U.: Frequency domain electromagnetic methods for coastal archaeology – a new(ish) approach for the detection of ancient settlements, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5919, https://doi.org/10.5194/egusphere-egu23-5919, 2023.

EGU23-8737 | ECS | Orals | SSS3.1 | Highlight

Geophysical characterization of the shallow subsoil at a heavily urbanized archaeological site: the Roman Amphitheater and the Scrovegni Chapel in Padua. 

Giorgio Cassiani, Ilaria Barone, Mirko Pavoni, Jacopo Boaga, and Rita Deiana

The characterization of the shallow subsoil at complex archaeological sites requires sufficient spatial coverage and resolution as to provide the necessary information. This is all but trivial, particularly where historical superposition of layers requires also sufficient depth investigation and resolution. The Scrovegni Chapel in Padua, with its Giotto's fourteen century frescoes, and recently added to the list of UNESCO World Heritage Sites, stands on the remains of the local Roman amphitheater. The hypogeum located under the chapel shares its western wall with a part of the wall of the amphitheater. To date, no information is available about the soil below the apse of the chapel. Over the past decade, several ERT and GPR measurements have been conducted outside the chapel, straddling the amphitheater structure for archaeological and geomorphological characterization of the area. In 2021, a first 3D active and passive seismic survey was conducted using about 1500 wireless sensors, aiming at using surface waves to provide a 3D image of the subsurface in terms of shear wave velocity. In 2022 three 20 m deep boreholes were drilled around the chapel and equipped with fiber optics, ground deformation sensors, and electrodes for cross-hole ERT, and about 200 1-C and 3-C wireless seismic sensors were placed around the drilling area. During the drilling, additional 3D seismic data were acquired from the surface, which completed the datasets acquired in 2021. The geophysical data thus acquired and the time-lapse monitoring that will be possible around the area of the Scrovegni Chapel in Padua will allow reconstructing the geomorphology of the subsurface on which the chapel rests, but also to better study and analyze the possible interactions between the structure of the chapel and the buried structure of the Roman amphitheater from the mechanical point of view as well as from the perspective of the seismic response of this specific site.

How to cite: Cassiani, G., Barone, I., Pavoni, M., Boaga, J., and Deiana, R.: Geophysical characterization of the shallow subsoil at a heavily urbanized archaeological site: the Roman Amphitheater and the Scrovegni Chapel in Padua., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8737, https://doi.org/10.5194/egusphere-egu23-8737, 2023.

EGU23-9663 | Posters on site | SSS3.1

Khalat al-Saharij - An Iron Age Small Site and Long Anthropogenic Effect on the Soil 

Oren Ackermann, Jenny Marcus, Jan Fišer, Gilad Itach, Martin Janovský, and Nimrod Wieler

Ancient anthropogenic long-term effects on soil chemical composition is a well-known phenomenon in large archaeological sites. In the current presentation, this effect will be shown in Khalat al-Saharij, a small site located in central Israel, in the footslope of the main highlands of the country. The site served as a farmhouse during the Neo Assyrian rule and was dated to the second half of the 8th century BCE.

Archaeological excavations of the site revealed a building that included two strips of rooms built around a square courtyard, a rock-hewn water reservoir, and agricultural facilities scattered in the area east and west of the building, including agricultural terraces.

The main aim of the current research was to find an anthropogenic signature in the sediments of the site, and in the sediments of the surrounding fields. 

POSL, PXRF and XRF methods were applied in order to achieve this aim.

The results showed that a significant anthropogenic signature was recorded on the sediments of the building and its square courtyard. This is reflected in the chemical composition that was enriched by phosphorus (P) and calcium (Ca), and by the mixed pOSL signal values. In the anthropogenic fields, the chemical signature is typical of natural soil with a high amount of Iron (Fe) and Manganese(Mn) which reflect high water availability.  

It is interesting that although the site is small in size and was inhabited for a short period of time, the human imprint has remained hundreds of years after its abandonment.

How to cite: Ackermann, O., Marcus, J., Fišer, J., Itach, G., Janovský, M., and Wieler, N.: Khalat al-Saharij - An Iron Age Small Site and Long Anthropogenic Effect on the Soil, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9663, https://doi.org/10.5194/egusphere-egu23-9663, 2023.

EGU23-10838 | ECS | Orals | SSS3.1

Geophysical investigation of kurgans in Uzun Rama steppe, Goranboy region, Azerbaijan 

Kamal Bayramov, Clara Jodry, Gunel Alizada, Sarvar Mammadov, Vusal Azimov, and Malik Abdullayev

Kurgans are funeral chambers, evidence of burial tradition dating back to the first thousand years BCE, of nomadic populations that covered a vast area in-between Europe and Asia. In Azerbaijan, past archaeological explorations revealed numerous large kurgans from the Early Bronze, which correspond to Kura-Arexed period (ca. 3500-3000 BCE), and relatively smaller burials of Late Bronze/Early Iron Ages. To improve the efficiency of the excavation process, geophysical methods have been widely and effectively applied for many years to provide clear and useful images of archeological targets hidden underground such as kurgans.

In this work, we introduce a multi-method archaeo-geophysical survey done in May 2022 to investigate Early Bronze Age kurgans located in Uzun Rama Steppe of Goranboy region in Azerbaijan. Applied method cover different depth of investigation and resolution to provide a wealth of information on the structure of three kurgans aligned in a North-South direction. It comprises coincidental DC-resistivity and seismic refraction tomographies of 70.5 m with a 1.5 m spacing going over all kurgans, a Ground Penetrating Radar (GPR) 40 m long profile using a 500 MHz antenna on the northern kurgans going from East to West and a magnetic map 24 x 25 m on the southern one.

The DC-resistivity profile shows two layers, a medium resistivity layer (500 to 600 W.m) from the surface to 6 m depth and a very conductive layer (> 10 W.m) under it. The first layer contains three areas of lower resistivity (~ 60 W.m) that are limited in thickness and length. As these three spots are marked by higher height on-site, we interpret them as the three kurgans. The coincidental seismic profile is a lot less detailed (due to physical properties and higher spacing between receiver) and define only three homogeneous layers, a first layer from the surface to 1 m depth with a P-wave velocity of 300 m/s, a second layer of higher velocity (1000 m/s) from 1 m depth to approximately 6 m depth and a final third layer of 2000 m/s velocity. Even though, the resolution is lower, we interpret the first layer as an attempt of the model to represent the kurgans. The GPR profile give a high attenuate image due to low resistive layer. However multiple diffractions can be seen in the first meter of the subsurface that can indicate the presence of ancient artefact related to the kurgans. Finally, the magnetic map defines the limit of the kurgan as a positive-negative anomaly probably due to the burning ritual that ended the implementation of a kurgan.

This geophysical campaign allowed us to accurately locate the kurgans as well as provide information on the environment. DC-resistivity and magnetic mapping seem to get the best results in our case. A future archaeological investigation will be put in place based on these results.

How to cite: Bayramov, K., Jodry, C., Alizada, G., Mammadov, S., Azimov, V., and Abdullayev, M.: Geophysical investigation of kurgans in Uzun Rama steppe, Goranboy region, Azerbaijan, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10838, https://doi.org/10.5194/egusphere-egu23-10838, 2023.

EGU23-10982 | Orals | SSS3.1 | Highlight

Construction and Agriculture in Sand at the Early Islamic Plot-and-Berm Groundwater Harvesting Agroecosystem South of Ancient Caesarea 

Lotem Robins, Joel Roskin, Elle Grono, Revital Bookman, and Itamar Taxel

Based on surveys and three excavation seasons, we report details on one of the first major utilizations of loose aeolian sand for construction and (hypothesized) vegetable agriculture at the Early Islamic Plot-and-Berm (P&B) agroecosystem south of Caesarea Maritima, along the Mediterranean coast of Israel. P&B agroecosystems are an innovative initiative to reconstruct sand bodies and dunefields into agricultural plots sunken between sand berms. These agroecosystems are sporadically found between Iran and Iberia and some are still in use. The plots, usually ~1 m above the groundwater table allowed easy access to the water via shallow wells for irrigation.

Research methods included pedological and sedimentological analyses, micromorphology and compositional analyses such as Fourier Transform Infrared Spectroscopy to detect heating of cultural additives (e.g., fired clays, pyrogenic lime); plant ashes (e.g., deliberate enrichment of fuel and/or recycling of former crop cycles as part of plot maintenance); and pollen and phytolith analysis to detect micro-botanical proxies of crops. Relative chronologies were obtained from portable luminescence profiling (pOSL). OSL ages along with artifacts analysis indicate that the agroecosystem was established during the late 9th or 10th century and functioning until the early decades of the 12th.

Refuse, including ash, carbonate, trace elements and artifacts, extracted from the dumps of Caesarea was combined with local sand to stabilize the berm surface but also partly altered the physical and chemical properties of the sand and increased its fertility, mainly in the plots, to form grey sandy to sandy loam anthrosols. This refuse was combined in different mixtures along the ~5 m thick berm fill and upon its slope and crest surface to stabilize the earthwork and comprise an anti-erosive agent. Similar mixtures were used to support berms and foundations of structures that served for lime production, agroecosystem management and local farming utilities. A 5 m high mound constructed out of interchanging anthrosediments was also piled up within a plot to support a presumable guarding structure. 

Plot anthrosols appear to include a basal, dark grey 20-40 m thick unit, ~ 1 m above the groundwater table that was enrichened with carbonate overlaid by a ~1 m thick grey sand anthrosol. The lower unit probably served for preserving infiltrating irrigation water that was applied to the crops grown atop the light grey anthrosol.

The agroecosystem remained well-preserved and untouched until the mid-20th century. Its pristine preservation is evidence of the ingenious and widespread utilization of refuse for construction and agriculture in sand. The untouched shape of this agrotechnological earthwork in the last millennia is intriguing and may be due to either lack of knowledge, or resources per revenue for similar endeavors.

How to cite: Robins, L., Roskin, J., Grono, E., Bookman, R., and Taxel, I.: Construction and Agriculture in Sand at the Early Islamic Plot-and-Berm Groundwater Harvesting Agroecosystem South of Ancient Caesarea, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10982, https://doi.org/10.5194/egusphere-egu23-10982, 2023.

Soil marks are detectable by airborne images due to the difference in soil colour between the archaeological feature and the surrounding background soil. Colour of the soil only represents the visible part of the soil spectrum which contains physical and chemical information of the soil. This study will present a spectral analysis method to prospect soil mark features and buried archaeological remains using airborne image data. This method statistically calculates the difference between the targeted spectrum and the background (non-archaeological) soil spectrum. The difference is quantified by an R-value. If the R value is larger than 1, then the spectral behaviour of the targeted spectrum is different from the spectrum of the background soil and, thus, likely to be an archaeological soil spectrum (soil mark). In this study, the spectral analysis method will be applied to APEX imaging spectroscopy data collected from an archaeological site in Sárvíz Valley, Hungary. Previously, the method was successfully applied to the same archaeological site using soil spectra gathered by a portable hand-held VIS-NIR spectrometer. Here, the results showed clear spectral difference between soil mark features and background soil. This study will 1) compare the results of the method from hyperspectral image and ground-based spectral data, and 2) investigate the most effective waveband for identifying archaeological spectral signatures to verify the effectiveness of the method.

How to cite: Choi, Y. J.: Detection of archaeological soil marks using airborne hyperspectral images, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11168, https://doi.org/10.5194/egusphere-egu23-11168, 2023.

EGU23-12360 | Posters on site | SSS3.1

Intense pedogenic development and large carbon contents in soils above the Pleistocene trimline (NW Italian Alps) 

Michele D'Amico, Emanuele Pintaldi, Dario Melacarne, Andrea Benech, Nicola Colombo, and Michele Freppaz

Most of the Alpine range was influenced by glacier movement or by intense erosive processes during Pleistocene glacial periods, which erased previously existing soils and landforms. Thus, most of the soils in the Alps began developing since at least the end of the Last Glacial Maximum (LGM). However, some surfaces located above the trimline (the upper limit reached by valley and cirque glaciers) still retain “old” morphologies and can be considered paleosurfaces, often covered by fossil or active periglacial features.

After having found very well developed Umbrisols hidden inside blockfields at 3030 m a.s.l. on the Stolenberg Plateau, Monte Rosa Massif – NW Italian Alps (Pintaldi et al. 2021a, 2021b, 2022), we explored other relict cryogenic landforms located above the Pleistocene trimline, such as blockfields and blockstreams, observing the soils hidden below the surface stone layers.

In most cases, we found extremely well-developed soils, such as Podzols with extremely thick E horizons or Umbrisols with A-Bh horizons up to more than 1-m thick. One of the most important properties was the large organic carbon content, up to 10-13% in soils located inside barren blockstreams and blockfields presently devoid of vegetation, at elevations between 1000 and 2950 m a.s.l..

The age of this organic matter is likely very old. For instance, inside the blockfield on the Stolenberg Plateau (3030 m a.s.l.), the organic matter was up to 22 ka old, corresponding to the early retreat glacial phase after the LGM. The age and nature of the organic matter in the other soils is still being analyzed, and it will be able to give important information on past environmental condition in understudied high-elevation areas in the Alps.

 

References

Pintaldi E., D’Amico M.E., Colombo N., Colombero C., Sambuelli L., De Regibus C., Franco D., Perotti L., Paro L., Freppaz M. (2021a). Catena. https://doi.org/10.1016/j.catena.2020.105044

Pintaldi E., D’Amico M.E., Colombo N., Martinetto E., Said-Pullicino D., Giardino M., Freppaz M. (2021b). https://doi.org/10.1016/j.gloplacha.2021.103676

Pintaldi E., Santoro V., D’Amico M.E., Colombo N., Celi L., Freppaz M. (2022). European Journal of Soil Science. https://doi.org/10.1111/ejss.13328

How to cite: D'Amico, M., Pintaldi, E., Melacarne, D., Benech, A., Colombo, N., and Freppaz, M.: Intense pedogenic development and large carbon contents in soils above the Pleistocene trimline (NW Italian Alps), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12360, https://doi.org/10.5194/egusphere-egu23-12360, 2023.

EGU23-14081 | ECS | Orals | SSS3.1

Morphology, distribution and origin of soil biogenic carbonates “queras” presents in Loess-palaeosols of Ebro Valley 

Daniela Alvarez, Carlos A. Torres-Guerrero, Rosa M. Poch, and Frank Preusser

Several types of secondary carbonate accumulations have been reported, but some of them are not completely well defined in the field due to unclear nomenclature. This is the case of the “queras”, reported in several Loess-palaeosol sequences of the Ebro Valley, which have often been described as pseudomycelia. Micromorphologically, they are complex pedofeatures (including calcified root cells, infillings and hypocoatings of carbonates and a decarbonated zone), resulting from calcification/decalcification processess at a microscale. They are composed of a central channel (1-2 mm wide and 2-3 cm long) filled with biosparite crystals (Herrero et al., 1992). The study of these secondary carbonate bioaccumulations are important archives for climatic reconstructions in terrestrial environments and can be used for paleoenvironmental reconstructions. The aims of this research are the characterization (morphological, optical and isotopically) of the biocalcifications present in Loess-palaeosols sequences, OSL-dated, to determine the main factors that originate them and their possible use as a palaeoenvironmental proxy. We collected soil samples from seven profile of Loess-palaeosols where the presence of these biocalcifications was recorded. We isolated and manually cleaned complete fragments of queras to describe them and to determine their isotopic composition. For that purpose, we used the queras fraction (sieved fraction of bulk soil between 100-250 µm) removing the residues of micrite with a buffer solution and manually separating the quera fragments with the help of a stereoscope. Thin sections were made to analyse the micromorphology in a petrographic microscope and cathodoluminescence techniques to determine the origin of the calcite. The micromorphology of these biocalcifications is similar in most cases: they present the same number of rows around the central channel (4 to 5), and a decarbonated hypocoating around it, supporting the hypothesis that their origin is derived from the calcification of cells of the root tips as a strategy to acidify the soil surrounding to absorb nutrients. Under cathodoluminescence biosparite has a different behaviour than non-biological calcite crystals. The age of the queras was similar in most horizons and their formation is independent of the age of the loess deposit. The isotopic composition of δ13C correspond mainly to CAM plants and the temperatures of precipitation calculated correspond to a Mediterranean template climate (Cerling and Quade, 1993), implying that the biocalcifications developed in warm environments. Finally, we hope to gain some more certainty of their origin and formation processes from the ongoing analyses of DNA sequencing and pollen recording.

How to cite: Alvarez, D., Torres-Guerrero, C. A., Poch, R. M., and Preusser, F.: Morphology, distribution and origin of soil biogenic carbonates “queras” presents in Loess-palaeosols of Ebro Valley, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14081, https://doi.org/10.5194/egusphere-egu23-14081, 2023.

EGU23-14576 | ECS | Orals | SSS3.1

Geochemical analysis in the area of a medieval Cistercian manorial farm 

Martin Janovský, Jan Horák, Tomáš Klír, and Laszlo Ferenczi

A multi-element and multivariate geochemical analysis has been carried out at a medieval farm site and village settlement, which belonged to the Cistercian monastery of Plasy (in W Bohemia). The results of our geochemical survey have been evaluated in context of the LiDAR survey covering the same area and the available historic maps (Habsburg Military surveys), which helped to locate relict landscape features and land-use changes. Approximately 300 samples were taken in a grid point pattern within the courtyard of the farm, as well as randomly, in the surrounding areas, in order to identify geochemical signals related to the observable surface phenomena. We have applied different analytical techniques, including PCA, log-transformation and isometrical log-transformation, and through spatial interpolation (IDW) it was possible to link  signals of both anthropogenic and geogenic character to archaeological, cultural and land-use phenomena. The results illuminated more intensive anthropogenic impact in connection to the courtyard area, and the intravillain area of the village, and additionally helped to locate different land-use activities in the  surrounding area (agricultural and possibly industrial). In that regard, this methodology was successfully applied to trace anthropogenic impact beyond narrowly defined archaeological sites. This abstract has been reformulated on the basis of our recently published paper (Horák et al 2023).

Horák, J., Janovský, M.P., Klír, T., Malina, O., Ferenczi, L., 2023. Multivariate analysis reveals spatial variability of soil geochemical signals in the area of a medieval manorial farm. Catena 220. https://doi.org/10.1016/j.catena.2022.106726

This abstract is part of the research project: “Monastic manors and the landscape impact of Cistercian estate management: A landscape archaeological and historical ecological study on Plasy Abbey“ financed by the GAČR - Czech Science Foundation, grant No. 21-25061S.

How to cite: Janovský, M., Horák, J., Klír, T., and Ferenczi, L.: Geochemical analysis in the area of a medieval Cistercian manorial farm, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14576, https://doi.org/10.5194/egusphere-egu23-14576, 2023.

EGU23-15478 | Posters on site | SSS3.1

Elemental and isotopic composition of silver in selected peat profiles of the Czech Republic 

Martin Mihaljevič, Aleš Vaněk, Mária Vaňková, and Vojtěch Ettler

Silver content and isotopic composition were studied in 3 selected 210Pb-dated profiles of ombrotrophic peat bogs in the Jizera Mountains, Ore Mountains and Sumava. The individual peat bogs differ in the rate of peat accumulation and intensity of immission load.

All peat bogs show a peak in the 1970s, which is related to the peak of industrial production in Europe and the associated coal burning. This peak is found at a depth of 7-12 cm in the peatlands studied.

In peat bogs in the Jizera and Ore Mountains, a smaller peak at a depth of 22-25 cm is followed by a peak in Pb concentration, probably related to Ag metallurgy in the 17th century.  This peak is not evident in the Šumava profile, where it is suppressed by elevated Ag concentrations in the underlying rocks.

The individual sources of silver are documented by isotopic composition that appears in the studied geochemical archives.

How to cite: Mihaljevič, M., Vaněk, A., Vaňková, M., and Ettler, V.: Elemental and isotopic composition of silver in selected peat profiles of the Czech Republic, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15478, https://doi.org/10.5194/egusphere-egu23-15478, 2023.

Paleosol horizons preserved in loess-palaeosol sections (LPS) provide valuable archives of Quaternary palaeoenvironmental changes over time and spatial palaeoenvironmental gradients during the same period. Here, we present the characteristics of paleosol horizons in two LPS near the western edge of the Rhône Rift Valley in southeastern France: (1) the LPS “Baix” (total thickness: 14 m), located about 17 km north of Montélimar (44°42’36”N, 4°43’21”E), thus, in the transition zone between the presently temperate and the Mediterranean region of Europe; (2) the LPS “Collias” (total thickness: 9 m), located in the Uzès Basin, about 15 km northeast of Nîmes (43°57’11.94”N, 4°27’56.71”E), thus, in presently fully Mediterranean climate. Investigation of the paleosol horizons in the main profile at Collias was complemented by those of three smaller nearby LPS, “Collias-North_D112” (43°57’12.55”N, 4°27’55.83”E), “Collias-South_D112” (43°57’12.44”N, 4°27’53.36”E), and “Collias-North” (43°57’21.67”N, 4°28’6.99”E), in order to capture the spatial variability of the characteristics of some key horizons.

To our knowledge, no LPS have been analysed yet in such a transitional position between the presently temperate and Mediterranean climate. Primarily the LPS Baix may provide a crucial link between the rigorously analysed LPS in the presently temperate regions further north (e.g., in northern France, the Alsace region and Germany) and the LPS in the Mediterranean region (e.g., in southern France, Catalonia, Italy and Croatia), including the LPS Collias. Therefore, we aimed to decipher the paleoenvironmental record of the LPS Baix and Collias, and to identify similarities and differences between them. Optically stimulated luminescence (OSL) dating provided a chronological frame for both LPS.

The basal part of the LPS Baix starts with reddish Bt(g) horizons of a Stagnic Luvisol, representing the remains of an Eemian to Early Würmian (MIS 5) pedocomplex formed under warm and - at least temporarily - relatively moist conditions. The corresponding pedocomplex in the profile Collias-North_D112 displays an intensive red (chromic) Bt horizon overlain by several Bw horizons formed in reworked soil sediment and underlain by a massive calcrete. In the main profile at Collias, this red horizon has been entirely reworked by slope processes and has regained an angular blocky structure afterwards. Thus, it appears as a dark orange-red Bw horizon. Both, the LPS Baix and Collias include a prominent brown Bw horizon of a truncated Cambisol that developed in middle Pleniglacial (MIS 3) deposits. It is associated with large, elongated, vertically oriented calcium carbonate nodules, indicating that considerable amounts of calcium carbonate must have been leached from the former middle Pleniglacial Cambisol and accumulated in the underlying loess unit. No distinct palaeosols were observed in the Late-Pleniglacial deposits of the LPS Baix and Collias; a slightly brownish colour indicates very weak weathering (several BCk horizons) in the Late-Pleniglacial sediments of both LPS.

How to cite: Sauer, D., Pfaffner, N., Kadereit, A., Kreutzer, S., Karius, V., Kolb, T., Bertran, P., and Bosq, M.: Palaeosols in the loess section of Baix (Rhône Rift Valley, SE-France), compared to those of Collias: a unique Late-Pleistocene record of the transition zone between the presently temperate and the Mediterranean region of Europe, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15899, https://doi.org/10.5194/egusphere-egu23-15899, 2023.

EGU23-16684 | Posters on site | SSS3.1

Using biomarker lipids to reconstruct soil fertility through time 

Cindy De Jonge, Jingjing Guo, Petter Hallberg, Marco Griepentrog, Rienk Smittenberg, Francien Peterse, Pascal Boeckx, and Gerd Dercon

Glycerol dialkyl glycerol tetraethers (GDGTs) are ubiquitous membrane-spanning lipids with a wide environmental distribution. In soils, branched GDGTs are produced by a possibly large diversity of bacteria. The relative abundance of methyl groups attached to the central alkyl chains is at the basis of the paleotemperature proxy MBT’5ME. However, MBT’5ME values in soils can also be directly influenced by pH (De Jonge et al., 2021). A second group of compounds, the isoprenoid GDGTs, are produced by archaea. They have been used only sparsely as environmental proxies in soils, although they are at the base of the marine paleotemperature proxy TEX86. In soils, a recent compilation by Yang et al. (2016) illustrates that the temperature dependency of TEX86 is sometimes present, but potentially influenced by other soil (chemistry) parameters.

In addition to temperature, other soil parameters are expected to vary with time, even on a Holocene timescale. For instance, soil mineral fertility (specifically, the concentration of exchangeable cations) will vary following climate or land use changes. As soil mineral fertility will impact the soil nutrient status for vegetation, and impact the soil capacity to store organic carbon (von Fromm et al., 2021), it is a relevant parameter to reconstruct over time. However, as soil fertility of surface soils will decrease during eroision or burial, this parameter can currently not be reconstructed quantitatively.

To investigate the potential of GDGTs as soil fertility proxies, branched and isoprenoid GDGTs were measured in soils from 5 elevation transects (Austria, Bolivia, China, Indonesia and Tanzania, n=74) that cover a large gradient in mean annual temperature (0-28 ℃), seasonality, and soil chemical parameters. Supplemented with climate (temperature and precipitation) data, we evaluate both changes in absolute concentration and relative distribution of the GDGTs. Of the chemical parameters, exchangeable calcium and exchangeable iron are shown to correlate with the absolute abundance of several branched (6 methyl brGDGTs) and isoprenoid (crenarchaeol isomer) GDGT compounds. Based on these relations we have developed ratios to quantify calcium (and summed bases) and iron (and summed metals) [r2=0.61-0.68, p<0.001] using GDGTs in soils. As GDGTs are stable on geological timescales, their presence in paleosoil sequences will thus allow us to reconstruct changes in surface soil fertility (specifically, calcium and iron) through time, even after the mineralogy of the original topsoil has changed.

Based our promising preliminary data we propose that GDGT ratios to reconstruct soil mineral fertility should be developed further using well-characterized modern soils. In addition, we look forward to testing our proxies on paleosoils by starting new collaborations.

 

De Jonge, C. et al. The influence of soil chemistry on branched tetraether lipids in mid- and high latitude soils: implications for brGDGT- based paleothermometry. Geochimica et Cosmochimica Acta (2021).

von Fromm, S.F., et al. Continental-scale controls on soil organic carbon across sub-Saharan Africa. SOIL 7, 305–332 (2021).

Yang, H., et al. The Response of Archaeal Tetraether Membrane Lipids in Surface Soils to Temperature: A Potential Paleothermometer in Paleosols. Geomicrobiology Journal 33, 98–109 (2016).

How to cite: De Jonge, C., Guo, J., Hallberg, P., Griepentrog, M., Smittenberg, R., Peterse, F., Boeckx, P., and Dercon, G.: Using biomarker lipids to reconstruct soil fertility through time, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16684, https://doi.org/10.5194/egusphere-egu23-16684, 2023.

EGU23-17056 | ECS | Posters on site | SSS3.1

Studying the water supply system of the Roman villa of Pisões (Beja, Portugal) using ground-penetrating radar and geospatial methods 

Pedro Trapero, Rui Oliveira, Bento Caldeira, Jose Fernando Borges, and André Carneiro

The Roman villa of Pisões (Beja, Portugal), was part of the Lusitanian colony of Pax Iulia. This place stands out for the predominance of the water element in several structures of the villa, highlighting the balneum and the large natatio, one of the largest known in Roman Hispania. The records of the initial excavations that took place since 1967 do not allow the establishment of clear functionalities of the villa. The University of Évora, owner of the site, conceived an action plan for the requalification and enhancement of the archaeological site. One of the tasks aims to investigate using Applied Geophysics. This work analyses the landscape directly related to the villa, given that it is in the flooded area of a river, with a Roman containment dam. It is uncertain whether the water supply comes from this structure or other nearby springs. The use of ground-penetrating radar, combined with unnamed aerial vehicles, all integrated in a geographic information system, allows us to know the location of underground water connections and create a topographic model with high resolution. Considering all the information, we propose a model for the water transport inside the villa and estimate the location of the water supply.

Acknowledgment: The work was supported by the Portuguese Foundation for Science and Technology (FCT) project UIDB/04683/2020 - ICT (Institute of Earth Sciences).

How to cite: Trapero, P., Oliveira, R., Caldeira, B., Borges, J. F., and Carneiro, A.: Studying the water supply system of the Roman villa of Pisões (Beja, Portugal) using ground-penetrating radar and geospatial methods, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17056, https://doi.org/10.5194/egusphere-egu23-17056, 2023.

EGU23-171 | ECS | PICO | GM11.4

The infancy of Chinese geoarchaeology: dilemmas from the Quaternary to the Anthropocene 

Yajing Zhao, Zhicai Zhu, Michael J. Benton, and Hao Lu

The study of some classic cases in archeology could provide key information to track where geoarchaeology came from. Joseph Anderson made great contributions to Chinese archaeology and geoarchaeology from the 1920s to 1940s. Previous academic historical studies reflected particularly on pure archaeological methodology; however, in rare cases there has been a focus on the decisive transition from geology to archaeology. Anderson was one of the pioneers who used his knowledge from field work in Europe and America to inform his geoarchaeological work in China. His earliest geoarchaeological study addressed earlier human-environmental interactions by deploying basic concepts and tools. Anderson combined methods from geology with archaeology in three case studies from the 1920s to the 1940s. He came across three dilemmas: i) Analogy dilemma: homological fossils or multiregional origin of artifacts; ii) Principle dilemma: cross-cutting relationships in stratigraphy or archaeology; iii) Time dilemma: synchronic or diachronic systems. At the time, his conclusions drew massive criticism from some archaeologists, especially because of confusion in terminology or principles arising from immature archaeological methodology and neglect of premises in different disciplines. After the development of stratigraphy in the work of classical archaeology before the 1900s and studies on Quaternary human-environmental interactions during the 1900s to 1920s, Anderson found a means to approach the Anthropocene. In summary, here we review the initial geoarchaeological exploration of China during the 1920s to1940s, which is crucial to better understand archaeological academic history and the early history of the Anthropocene as an independent stratigraphic geological unit.

How to cite: Zhao, Y., Zhu, Z., Benton, M. J., and Lu, H.: The infancy of Chinese geoarchaeology: dilemmas from the Quaternary to the Anthropocene, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-171, https://doi.org/10.5194/egusphere-egu23-171, 2023.

The settlement of Chimtou located in the Medjerda valley is known for its marble quarry, where yellow marble was mined for the entire roman empire. During the Roman period Chimtou has been a major roman city but little is known about the changes during the transition to the Arab period. The interdisciplinary project ISLAMAFR aims to understand the cultural, economic and landscape transformations of the western Medjerda Valley from late antiquity to the early medieval period (600 to 1000 AD).

Earlier studies in the region by Christoph Zielhofer and Dominik Faust have shown that the landscape evolution of the Medjerda Valley derived from alluvial records indicates short-term changes in fluvial dynamics in the Holocene. During the upheaval from Roman to Arab period they reconstructed great flooding events for the Western Medjerda Valley with a brief slow-down in fluvial activity during the Arab conquest. On the basis of their work we will densify the landscape history using two fluvial and alluvial archives from the hinterland of Chimtou for the period from 600 to 1000 AD. We analyzed sediment cores in the laboratory from an infilled oxbow lake of the Oued Medjerda and a flood channel, which regularly overflows. The successive phases of channel infill of the archives allow us to reconstruct the fluvial activity and landscape changes in their surroundings. A multi-proxy approach was applied, integrating the analysis of the dated high-resolution sediment records with geomorphological mapping, archaeological records, and geological and topographical data. Coupling the long-term landscape changes with high resolved short-term landscape changes identifies the human-environmental interactions in the hinterland of Chimtou from late antiquity to early medieval period.  

How to cite: Pagels, J., von Rummel, P., Chaouali, M., and Bebermeier, W.: Meso-scale landscape changes reconstructed from fluvial and alluvial sedimentological archives around the roman town Chimtou (Medjerda Valley), North Tunisia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-809, https://doi.org/10.5194/egusphere-egu23-809, 2023.

EGU23-1479 | PICO | GM11.4

Holocene human-environmental interactions and seismic activity in a Late Bronze to Early Iron Age settlement center in the southeastern Caucasus 

Hans von Suchodoletz, Giorgi Kirkitadze, Tiiu Koff, Markus L. Fischer, Rosa M. Poch, Azra Khosravichenar, Birgit Schneider, Bruno Glaser, Susanne Lindauer, Silvan Hoth, Anna Skokan, Levan Navrozashvili, Mikheil Lobjanidze, Mate Akhalaia, Levan Losaberidze, and Mikheil Elashvili

Long-term human-environmental interactions in naturally fragile drylands are an actual topic of geomorphological and geoarchaeological research. Furthermore, many prehistoric societies in drylands were also affected by seismic activity. The semi-arid Shiraki Plain in the tectonically active southeastern Caucasus is currently covered by steppes and largely devoid of settlements. However, numerous Late Bronze to Early Iron Age city-type fortified settlements suggest early state formation between ca. 3.2 – 2.5 ka that abruptly ended after that time. A paleolake was suggested for the lowest plain, and nearby pollen records suggest forest clearcutting of the upper altitudes under a more humid climate during the Late Bronze/Early Iron Ages. Furthermore, also an impact of earthquakes on regional Early Iron Age settlements was suggested. However, regional paleoenvironmental changes and paleoseismicity were not systematically studied so far. We combined geomorphological, sedimentological, chronological, paleoecological and hydrological modelling data to reconstruct regional Holocene paleoenvironmental changes in the Shiraki Plain, and identify possible natural and anthropogenic causes as well as possible seismic events during the Late Bronze/Early Iron Ages. Our results show a balanced to negative Early to Mid-Holocene water balance probably caused by forested upper slopes. Hence, no lake but an incipient Chernozem developed in the lowest plain. Following, Late Bronze/Early Iron Age forest clear-cutting obviously caused lake formation and the deposition of lacustrine sediments derived from intensive soil erosion. Subsequently, regional aridification obviously caused slow lake desiccation. Remains of freshwater fishes indicate that the lake potentially offered valuable ecosystem services for regional prehistoric societies even during the desiccation period. Finally, colluvial coverage of the lake sediments during the last centuries could have been linked with hydrological extremes during the Little Ice Age. Our study demonstrates that the Holocene hydrological balance of the Shiraki Plain was and is situated near a major hydrological threshold, making the landscape very sensitive to also small-scale human or natural influences with serious consequences for local societies. Furthermore, seismites in the studied sediments do not indicate an influence of earthquakes on the main and late phases of Late Bronze/Early Iron Age settlement. Altogether, our study underlines the high value of multi-disciplinary approaches to investigate long-term human-environmental interactions and paleoseismicity in drylands on millennial to centennial time scales.

How to cite: von Suchodoletz, H., Kirkitadze, G., Koff, T., Fischer, M. L., Poch, R. M., Khosravichenar, A., Schneider, B., Glaser, B., Lindauer, S., Hoth, S., Skokan, A., Navrozashvili, L., Lobjanidze, M., Akhalaia, M., Losaberidze, L., and Elashvili, M.: Holocene human-environmental interactions and seismic activity in a Late Bronze to Early Iron Age settlement center in the southeastern Caucasus, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1479, https://doi.org/10.5194/egusphere-egu23-1479, 2023.

When looking into land use and human agency in the modification of the landscape, the concepts of socio-economic opportunities vs. natural constraints is one of the key issues. In comparison with the modern world, past human communities relied much more upon local resources and a tight societal structure to better adapt to the conditions and changes in the surrounding environment. Therefore, in the study of prehistorical cultures land use is both a strong source of information about sustenance strategies and community behaviours and a subject potentially easier to model within a set of natural and social parameters. To this purpose, we investigated the settlement distribution patterns of Bronze Age structures of the Nuragic culture on the island of Sardinia (Italy) using spatial point pattern analysis. We investigated different covariates divided into natural (topography, water and geological resources) and cultural (type of structure, settlement hierarchy), alone and in combination, and looked at how each could explain the distribution of Nuragic sites.

Several covariates from both natural and cultural groups show significant values, with the best representing models of pattern distribution coming from the combination of covariates from both groups. Aside from topographic parameters, distance from known ore deposits seems to have an impact on structure density. Among cultural covariates, there is a clear association between simple and complex megalithic structures (nuraghes). This pattern suggests the collation of smaller structures around larger settlements, either by the former emerging from the presence of the latter or vice versa. These findings offer new insight on the development and ways of life of the Nuragic society in their geographical context, and highlight how the relationship between the physical and the social aspects of human-landscape interactions is fundamentally interdependent. This approach could also represent a potential tool to compare to other Bronze Age and prehistorical communities.

How to cite: Mariani, G. S., Brandolini, F., and Melis, R.: Natural and social patterns in the distribution of Bronze Age Nuragic sites (Sardinia, Italy): using the Widom-Rowlinson penetrable sphere model to understand past human occupation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5051, https://doi.org/10.5194/egusphere-egu23-5051, 2023.

The transition from roaming/mobile hunters-gatherers to sedentary settlements in the southern Levant during the Late Epipaleolithic (Natufian) is considered a decisive point of no return in the history of mankind. While the first sedentary settlements are known predominantly from the Mediterranean area of the Levant, the reasons for this fundamental change in subsistence are deeply rooted in socio-economic adaptations of the last mobile hunters-gatherers in the region at large, and in particular, the Sinai-Negev desert. Here diverse nomadic Epipaleolithic groups left behind numerous small open-air sites along the fringe of the northwestern Negev desert dunefield (Israel). Geoarchaeological and palaeoenvironmental analysis of newly discovered Epipaleolithic sites allow better understandings of the unique socio-economic adaptations of these humans.    

The studied middle Epipaleolithic (Ramonian) open-air Ashalim-west site is situated in a unique geomorphic setting atop a slightly deflated surface upon a 3-5 m thick falling dune at the southeastern edge of the Negev dunefield. The dune is comprised of very fine sand that differs from the common vegetated linear dunes (VLD) of the Negev dunefield, dominated by fine sand. The falling dune mantles a 2nd-order wadi slope of a ~40 m high plateau of Eocene chalk, interbedded with chert beds that probably served for lithic production. The small wadi drains into the Besor basin, the largest ephemeral stream in the northwestern Negev, and the only one that currently transverses the dunefield. Therefore, opposed to smaller basins, it was prone to damming by a wide band of encroaching dunes that may have led to extensive water bodies upstream dune dams and possibly beyond drainage divides.

Four OSL ages in the range of 16.5±0.8 – 15.5±0.8 ka from the upper ~2 m of two sections at the Ashalim-west site correlate with raw portable OSL signals, and reflect rapid aeolian deposition. This deposition, synchronous with the main sand incursion episode into the Negev dunefield during the Heinrich 1 cold event (Roskin et al., 2011), closely fits the age associated with the Ramonian character of the overlaying lithics.

The Heinrich 1 massive aeolian episode may have led to major damming of the Besor basin and widespread expansion of dune-dammed water-bodies upon the Besor floodplains. 1.5 km northeast to Ashalim-west site, remains of slightly later Middle Epipaleolithic (Geometric Kebaran) and Late Epipaleolithic (Natufian and Harifian) are sited on top of fossilized aeolian sand between synchronous seasonal dune-dammed water bodies (Goring-Morris, 1997; Vardi et al., 2018). Here OSL ages of aeolian and fluvial sand beneath the sites also date to the Heinrich 1 period. Later and less intense episodes of dune-damming in these parts of the Besor basin may have allowed for short-term camping upon dune crests and flanks adjacent to water bodies. The perched setting of Ashalim-west, overlooking the largest Besor basin, along with two other Middle Epipaleolithic (Ramonian and Mushabian) sites (Rosen, 1990; Rosen and Kolska-Horwitz, 2005) therefor differs from the abundant Epipalaeolithic open-air sites along the dunefield fringe and may indicate a local choice of high grounds during times of intense dune-damming and water body expansion.

 

How to cite: Roskin, J., Robins, L., Greenbaum, N., Porat, N., and Yaroshevich, A.: Reconstructing palaeoenvironments of the last mobile hunters-gatherers in the southern Levant during the middle Epipaleolithic period, northwestern Negev dunefield, Israel, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9267, https://doi.org/10.5194/egusphere-egu23-9267, 2023.

EGU23-11087 | PICO | GM11.4

Documenting the diversity of human responses to Quaternary environmental changes when the stratigraphic record is gone. The experience of the SPHeritage Project 

Andrea Zerboni, Alessandro Perego, Deirdre Ryan, Elisabetta Starnini, and Marta Pappalardo

Archaeological sequences and landscapes preserve evidence of the complex relationship between human communities and climatic/environmental changes occurred in the Quaternary. In this perspective, archaeological sediments and landscapes are proxy data for past ecosystems evolution, as much as for changes in land use, exploitation of natural resources, and human behavior. Most of the latter can be detected and explored with a geoarchaeological approach, using the tools and methods offered by Earth Sciences. For that reason, accurate sampling during the excavation of archaeological sites allows to increase the number and quality information useful to reconstruct the formation of an archaeological sequence, its preservation, and human activities. What can we do when archaeological excavations were carried out before the application of methods from the Earth Sciences? How can we gather information from residual strips or archaeological sediments? The SPHeritage Project (MUR grant: FIRS2019_00040, P.I.: M. Pappalardo) is coping with this challenging task reinvestigating the Balzi Rossi archaeological area (Western Liguria, Northern Italy). This area represents a key site for the reconstruction of how human populations have responded to Pleistocene environmental changes and sea-level variations since the Middle Pleistocene. Local anthropogenic cave sequences have been excavated since the half of the XIX century; unfortunately, the geological processes in charge of the formation of such deposits have been only occasionally considered. As most of the local archaeological sequences were removed, we are combining the analyses of the remnants of strips of anthropogenic sediments still preserved inside local rock shelters as much as sediment samples preserved in museums. Moreover, our geomorphological survey identified new sedimentary sequences preserving information on relative sea level changes, better constraining the time and steps of climate change, sea-level oscillations, and human settlements. Our results confirm that this approach is an effective tool to reconstruct the formative processes of anthropogenic sequences excavated in the past, thus expanding our possibility of understanding the climate-environment-human nexus.

How to cite: Zerboni, A., Perego, A., Ryan, D., Starnini, E., and Pappalardo, M.: Documenting the diversity of human responses to Quaternary environmental changes when the stratigraphic record is gone. The experience of the SPHeritage Project, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11087, https://doi.org/10.5194/egusphere-egu23-11087, 2023.

EGU23-12609 | ECS | PICO | GM11.4

Human impact on the environment as derived from colluvial deposits – example from the La Tène Period until the Middle Ages in the Siegerland (Germany) 

Kristina Reetz, Jonas Kirch, Jago Jonathan Birk, Astrid Stobbe, and Sabine Fiedler

Human impact on the environment as derived from colluvial deposits – example from the La Tène Period until the Middle Ages in the Siegerland (Germany)

Reetz, K1., J. Kirch1, J.J. Birk1,2, A. Stobbe3 and S. Fiedler1

1 Johannes Gutenberg-University Mainz

2 recent adress Georg - August - University Göttingen

3 Goethe - University Frankfurt am Main

The Siegerland is one of the most cohesive mining regions in the Iron Age in Central Europe. While the number of settlement and smelting sites has been increasingly better researched over the last few years, it was basically unknown which impacts by the La Tène iron production on the primary forests have to be considered, and how are such correlated with other activities and soil erosion. Below a smelting site in the southwestern part of the Siegerland, we made a rare find of colluvial deposits in the valley of the Obersdorfbach. It tells about the human impact between the Earlier Iron Age and the heyday of iron production during the La Tène period and the Middle Ages. In addition to pollen and NPP analysis, we used element contents, and molecular markers (n-alkanes, steroids).

The small stream has cut in sections in meanders up to 180 cm deep into the relatively narrow floodplain. There, they lie on a gravel bed with embedded peat (Obersd 1, 170 – 153 cm, calibrated age 700/500 – 350 BC). In the uppermost 10 cm of the fen peat, the proportion of mineral components increases and pebbles are intercalated (Obersd 2, 153 – 145 cm, 350 – 200 BC).  On top are multi-textured sandy-clayey colluvial/floodplain loams with charcoal bands (Obersd 3, 145 – 125 cm, 200 BC – unknown). It is followed by a sandy colluvium from the Middle Ages (Obersd 4, 125 – 110 cm).

In the 7th to the middle of the 4th century BC the forests near Obersdorf consisted mainly of beech and linden trees. Nevertheless, non-arboreal pollen provides evidence of anthropogenic impact (Obersd 1). According to the mountain-archaeological picture, at first iron was produced only on a small scale and the interventions in the vegetation were still small. Although the area should have been sparsely populated at the time, fecal markers suggesting human presence can be found. However, human influence on the landscape increased significantly from about 350 cal. BC (zone Obersd 2). Pollen and n-alkanes show a distinct impact into the vegetation. Forest clearing led to erosion and the accumulation of thick colluvial deposits. Pollen from ruderal places increase significantly, cereals and coprophilous spores occur. The strong anthropogenic influence in zone Obersd. 2 can be correlated with the archaeologically known smelting site. In addition to wood for firing the furnaces, large quantities of clay were needed for their construction. During the transformation of the landscape, erosion increasingly occurred on the slopes. The result is clayey silt sediments with intercalated charcoal bands (Obersd 3). The following sandy colluvium (Obersd 4) from the early Middle Ages shows a dominance of beech, hornbeam, and rye. Steroids show the presence of humans and livestock here.

How to cite: Reetz, K., Kirch, J., Birk, J. J., Stobbe, A., and Fiedler, S.: Human impact on the environment as derived from colluvial deposits – example from the La Tène Period until the Middle Ages in the Siegerland (Germany), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12609, https://doi.org/10.5194/egusphere-egu23-12609, 2023.

EGU23-12871 | PICO | GM11.4

From Romans to the Anthropocene: Geoarchaeological Investigations in the Central Vienna Basin (Austria) 

Michael Weissl, Diana Hatzenbühler, Christian Baumgartner, and Michael Wagreich

The project »From Romans to the Anthropocene, from Carnuntum to Vienna: An Urban Anthropocene Field Lab« (WWTF ESR20-027) focuses on the urban transformation from the Roman legionary camps of Carnuntum and Vindobona to Vienna's periurban areas. Combining historical and geoarchaeological methods, we investigate the diverging development of the two sites and their manifold relations over time.

The Danube river crosses the mountain ranges of the Wienerwald and Malé Karpaty, forming the eastern and western limits of the central Vienna Basin. For many centuries, the river was both a barrier and a transportation route. The floodplains and river terraces along the Danube served as concentration areas and battlegrounds during countless conflicts between central Europe and its enemies.

The legionary camps of Carnuntum and Vindobona were built during the first century AD at the rim of glacial river terraces, next to the shortest passages across the Danube. During late antiquity, the former provincial capital Carnuntum lost importance. However, Vindobona became first a local center and later the capital of the Austrian rulers. After a sudden Turkish siege in 1529, the fortifications of Vienna were strengthened and maintained until the middle of the 19th century.

Urban development of the region over the centuries was limited not only by permanent military threats. North of the Danube, agriculture was always restricted climatically by aridity and sand drift. Most settlements on the riverbanks of the Danube and its tributaries were affected frequently by floods and erosion. Many villages vanished completely as a consequence of such natural hazards. Since some decades, natural river dynamics have been restricted technically, and many areas under cultivation are now irrigated artificially. The analysis of the sedimentary record downstream of Vienna clearly shows the anthropogenic impact on sedimentation processes.

Contrary to Carnuntum, Vienna could evolve from a legionary camp step by step into a capital and a strong fortress. The demolition of the city walls after the middle of the 19th century, the following long period of peace, and, in particular, the consequent river engineering, were preconditions for the development into a modern metropolis.

How to cite: Weissl, M., Hatzenbühler, D., Baumgartner, C., and Wagreich, M.: From Romans to the Anthropocene: Geoarchaeological Investigations in the Central Vienna Basin (Austria), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12871, https://doi.org/10.5194/egusphere-egu23-12871, 2023.

The catchment basin of the Sarandopotamos on Evia Island (Greece) has been an environment of habitation and worship since the early Neolithic. Many settlements from different periods have been found in this area. It is also in this catchment, close to the Sarandopotamos delta, that the Swiss School of Archaeology in Greece discovered in 2007, the sanctuary of Artemis Amarysia after centuries of investigation. This discovery aside, we still do not understand if, and the extent to which, the human history of occupation and abandonment in this region is related to its environmental history. Thus, the aim of this research is to use a suite of paleoenvironmental reconstruction methods to recreate ancient landscapes, their environments and their evolution to understand the society-environment relation. The sanctuary and its eventual abandonment could potentially be impacted by synergistic reactions between changes in sediment supply, changes in basin hydrology and sea-level all of which may have impacted both the magnitude and frequency of local flooding via changes in river bed level, lateral shifting of the river and water table rises and falls. Thus, the aim of this project is to undertake an integrated, multi-method reconstruction of the local water-sediment environment and to relate this to the history of the sanctuary and wider human settlement. This will then test whether an environmental influence needs to be retained as a hypothesis for wider societal changes in this area. In order to do this, a model of the sedimentary dynamics of the catchment is being carried out using LAPSUS software, and sedimentary cores are being obtained in order to understand the relationship between environmental and human-driven (e.g. land use) change in the catchment, the geomorphic response of the delta and the history of human occupation. The relationship between the delta and eustatic and isostatic history also has to be understood. A single beam eco sounder survey is been conducted in order to investigate the different delta created by the shift in the Sarandopotamos bed. Moreover, in order to better understand the local context and the landscapes observed today, this project is also interested in the geomorphological history of periods prior to human occupation. These different aspects emphasize the complexity of the project but through developing a multi-disciplinary and multi-scale appraisal of environmental history and how it links to human history we may get a better understanding of the extent to which the two are connected. This poster will present preliminary modelling results that demonstrate the sensitivity of the land-ocean interaction to sea-level rise and delta dynamics from the late Pleistocene through the Holocene to the present.

How to cite: Talas, T.: Society-environment links in the area of the sanctuary of Artemis Amarysia (Evia Island, Greece) based upon paleoenvironmental reconstruction, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13095, https://doi.org/10.5194/egusphere-egu23-13095, 2023.

Twelve potsherds from the 3rd millennium BCE pottery in southeastern Lithuania were analyzed using X-ray fluorescence (XRF), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) to obtain the bulk geochemical and mineralogical characteristics of the ceramic paste. Microstructures and geochemical variability of the clay matrix and temper were studied by Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS). The purpose of this study was to characterize the pottery attributed to the foreign Corded Ware Culture and local Hunter-Gatherers, to imply possible sources of raw material and to evaluate technology choices.

The main clusters of major and trace elements in the bulk compositions (XRF; Šatavičė et al., 2022) reflect the five technological styles identified by the manipulation, shaping, and firing conditions of the ceramic raw material. The XRD and FTIR analysis (Šatavičė et al., 2022) indicated a predominance of iron-rich illite clay, quartz, and alkali feldspar minerals. The early coarse pottery was fired at low to medium temperatures, accompanied by a decrease in the firing temperature of both the cord-decorated and hunter-gatherer pottery. The FTIR and XRD results are not indicative of firing in a reducing atmosphere.

The SEM-EDS with SE and BSE imaging and point analysis allowed to determine the detail mineral chemical composition of the ceramic pastes and tempers. The SEM SE and BSE images showed textural differences in the clay matrix, some of which may be explained by intentionally mixing the clay or a specific pottery surface treatment. The other may be attributed to internal differences in glacial till formation. No grog temper characteristic for the classic Corded Ware was detected, only clay pellets, ferruginous nodules and weathered minerals, which may look like grog to the naked eye. The SEM-EDS point analysis allowed us to investigate the gradual changes in the chemical composition of the clay matrix and to evaluate weathering process. To sum up, both the Corded Ware and the local Hunter-Gatherer pottery were made from the same hydro-micaceous variegated clay from the local Quaternary glacial sediments, which contain weathered granitoid fragments, but display different technological choices for the clay paste preparation, surface treatment, and firing strategies.

The study provided a lot of hitherto unknown information on glacial till, glacial lacustrine and post-glacial lacustrine sediments in SE Lithuania. Their composition, textural properties, susceptibility to weathering were evaluated for the first time in this region.

Šatavičė, E. et al., 2022. Minerals 12, 1006. https://doi.org/10.3390/min12081006.

How to cite: Skridlaite, G., Šatavičė, E., Zaludiene, G., and Selskiene, A.: Linking geology and archeology: investigations of Corded Ware and contemporary Hunter-Gatherer pottery from SE Lithuania by micro-invasive spectroscopic methods, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14840, https://doi.org/10.5194/egusphere-egu23-14840, 2023.

In order to investigate the interaction between different human societies and their effect on the natural environment, we focus on three main questions. 1: Where were historical settlements located? 2: Where have the routes connected these settlements passed? 3: How have both these settlements and routes interacted with local pedological and geomorphological processes? The northern Ethiopian Highlands (Tigray) have a documented settlement history spanning at least the last three millennia. Some sites have a centuries- or even millennia-long settlement continuity and the reconstruction of their entanglement can help to learn about the interaction between past societies. Pathways, be it over long- or short distances, provide the potential to investigate past and present decision-making processes in route planning. Furthermore, pathways are an impressive example of human-environment interactions. These pedogeomorphological expressions of human trampling on the same piece of land over a certain period of time have different soil characteristics (soil compaction, pedogenic iron contents) than adjacent land areas and can influence the surface hydrology. Under certain conditions in hilly terrain, pathways can either stabilize or destabilize the landscape, depending on their orientation with regard to the local hydrological network, and their degree of incision into the surface (holloways). As such, we analyzed geomorphic and pedogenic properties of pathways as well as feedback mechanisms between pathways and gully erosion, and how these may influence route planning. The reconstruction of historical routes in northern Ethiopia using a combined approach of geolocating historical travel reports and historical maps dating back to the 15th century as input data for least-cost-path analyses, have the potential to reveal points of interest for further archaeological research.

How to cite: Busch, R., Hardt, J., Nir, N., and Pfeiffer, K.: Routes of Interaction – Research on pre-modern route-setting, pedogenic and geomorphic effects of trampling, and feedback mechanisms between pathways and gully erosion in the Northern Ethiopian Highlands (Tigray), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14877, https://doi.org/10.5194/egusphere-egu23-14877, 2023.

EGU23-16741 | PICO | GM11.4

O’Estrucan Ports, Where Are Thou ? Multiproxy sedimentological investigation of the Orbetello Lagoon 

Cécile Vittori, Guillaume Jouve, Gilles Brocard, Jean-Philippe Goiran, Quentin Vitale, Lionel Darras, Laurent Mattio, Alessandro Conforti, Christine Oberlin, Frank Preusser, Pierre Sabatier, Edwige Pons-Branchu, Camille Gonçalves, Brahimsamba Bomou, Anne-Lise Develle, Amber Goyon, Stoil Chapkanski, Kevin Jacq, and Maxime Debret

Technical improvements at the end of the Bronze Age led to the rise of a 1rst generation of major sea powers around the Mediterranean Sea, such as Etruria in modern Italy. The Etruscan coast was the fringed by a series of large lagoons. Only one survives today: the lagoon of Orbetello. The lagoon is preserved by two subparallel sand spits that connect former Argentario island to mainland Italy, as situation that today protects it from rapid infilling. A third sand spit, in the middle of the lagoon, hosts the Etruscan city of Orbetello. Today, three canals connect the lagoon to the sea. A massive phase of eutrophication driven by the ingress of fertilizers has plagued the lagoon in late 20th Century. Eutrophication at times has spurred fish and bird kills, and the release of mercury in the water column. Major contingency plans have been implemented to fight off eutrophication, with various success. 

              However little is known of the lagoon management and the evolution of Orbetello before the 17th century CE. Nonetheless, the wealth of the city and the health of its lagoon have been tightly related during the past three millennia. To track this coevolution, a large team of researcher has been assembled to conduct an analysis of the lagoon sediments using XRF scanning of cored sediments, SMIR, Rock Eval, hyperspectral imaging of chromatic pigments, analysis of mercury and phosphorus content, ostracods and pollen assemblages, to document the links between sediment facies, eutrophication and salinity crises, as a result of successive phases of rise and demise of lagoon management over the past three millennia. Here, we focus on the sub-bottom imaging conducted in the very shallow (< 1.5m) waters of this extensive (30 km2) lagoon. The Exail Echoes 10 000 sub-bottom profiler reveals individual layers that can be traced across the lagoon, allowing stratigraphic correlations between cores, and highlighting the environmental significance of the sedimentary facies. Acoustic imaging using a 3.5 kHz Chirp systems from Exail (Haliotis R/V) was conducted offshore to document the architecture of the sand spits protecting the lagoon. The architecture of the deposits, 14C, OSL, and U-Th dating reveal that the lagoon results from the drowning of strandplains that started forming on both side of the older, central sand spit, at the end of the postglacial transgression. Drowning accompanied the final rise in sea level over the past 6.5 ka, forming two lagoons on both sides of the central spit. These initial lagoons eventually coalesced after drowning the central sand spit. Continuation of the lagoon level rise since Antiquity led to the flooding of Bronze Age, Etruscan and Roman settlements. Sub-bottom imaging in the lagoon reveals buried structures possibly used for navigation and salinity control. Sedimentation is marked by an alternation of black, shelly organic silty clays and decimeter-thick layers of broken shells. Radiocarbon dating indicates that the cores capture up to five millennia of sedimentation, with a sharp decrease in sedimentation rates four millennia ago.

How to cite: Vittori, C., Jouve, G., Brocard, G., Goiran, J.-P., Vitale, Q., Darras, L., Mattio, L., Conforti, A., Oberlin, C., Preusser, F., Sabatier, P., Pons-Branchu, E., Gonçalves, C., Bomou, B., Develle, A.-L., Goyon, A., Chapkanski, S., Jacq, K., and Debret, M.: O’Estrucan Ports, Where Are Thou ? Multiproxy sedimentological investigation of the Orbetello Lagoon, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16741, https://doi.org/10.5194/egusphere-egu23-16741, 2023.

SSS4 – Soil Biology, Microbiology and Biodiversity

EGU23-148 | ECS | Posters on site | SSS4.3

Higher earthworm abundance in conventionally managed agricultural fields than ecologically managed fields 

Sachin Bhattarai, Stephen Asabere, Daniela Sauer, and Jürgen Friedel

Agricultural activities affect soil fauna and may thus impede biological soil functions. In the field of soil biology, uncertainty remains about which specific activity adversely affects biological soil functions.  This study aimed: (i) to quantify the effect of ploughing activity on earthworm abundance in an experimental farm of the University of Göttingen, Reinshof, and (ii) to compare the earthworm abundance between an ecologically managed field vs. a conventionally managed field. Earthworm sampling, using the mustard method, was done between the 22nd of April and 3rd of May 2021. Three differently managed fields were sampled: ecologically managed with ploughing, conventionally managed with ploughing and conventionally managed without ploughing. Earthworms were collected in 30 locations per field. Soil organic matter contents, penetrometer resistance, and soil moisture were also measured. The conventionally managed ploughed field exhibited a mean earthworm abundance of 98.9 individual per square metre, which was more earthworms than the ecologically managed field that showed a mean earthworm abundance of only 7.86 individuals per square metre. The highest mean earthworm abundance of 160.8 individual per square metre was observed in the conventionally managed non-ploughed field. Species richness of earthworms was also higher in the conventionally managed fields compared to the ecologically managed field. The conventionally managed non-ploughed field had the highest soil organic matter content, moisture status, nitrogen content, and penetrometer resistance, in contrast to the ecological ploughed field, which showed the lowest values for all these parameters. The findings of this study are consistent with previous studies that the non-ploughed fields provide a suitable environment for earthworm communities, as perturbation of earthworms is avoided and soil organic matter levels are maintained, which is a key requirement for earthworms’ survival, therefore increasing their abundance. The very low earthworm abundance of the ecologically managed field was unexpected, but might be explained by the frequent ploughing, used for weed control instead of herbicides. We concluded that ploughing is an important activity that impacts the abundance of earthworms.

Keywords: soil, earthworms, conventional farming, ecological farming, ploughing

How to cite: Bhattarai, S., Asabere, S., Sauer, D., and Friedel, J.: Higher earthworm abundance in conventionally managed agricultural fields than ecologically managed fields, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-148, https://doi.org/10.5194/egusphere-egu23-148, 2023.

EGU23-524 | ECS | Orals | SSS4.3

Crop diversification and seed inoculation strategies effects on soil microbial community in soybean cropping systems 

Aghata Cristie Rewa Charnobay, Carl Lalonde-Haman, Luisa Caroline Ferraz Helene, Thiago Gumiere, Mariangela Hungria, and Marco Antonio Nogueira

Crop diversification has gained importance in Brazilian soybean (Glycine max L.) cropping systems, usually cultivated in soybean/2nd season maize (Zea mays L.) successions. Brachiaria grass (Urochloa spp.), a forage highly grown in Brazilian livestock systems, can be a suitable option for the soybean systems diversification. Brachiarias are well adapted to tropical conditions, produce high amounts of above and belowground biomass, have high nutrient cycling capacity, and release exudates known as biological nitrification inhibitors (BNI). All these traits might increase soybean yield and nutrient use efficiency in the agroecosystem.

Brazilian cropping systems rely on plant growth-promoting bacteria (PGPB), like seed inoculation of soybean with the nitrogen-fixing bacteria Bradyrhizobium, alone or in combination with Azospirillum, to replace mineral N fertilizers.

In this study, we aimed to investigate the soil bacterial community (activity and diversity) response to the diversification of soybean/maize cropping systems with Urochloa ruziziensis and inoculation with different combinations of PGPB. We hypothesize that inoculation with PGPB and diversification of the system with maize intercropped with Brachiaria will enhance microbial community activity and diversity.

A 5-year experiment has been conducted in Londrina (Paraná State, Southern Brazil) in a randomized complete block design with a split-plot arrangement and six replicates. Main plots consisted of soybean during the cash crop season (S: soybean without inoculation; Si: soybean inoculated with Bradyrhizobium; Sc: soybean co-inoculated with Bradyrhizobium + Azospirillum). Sub-plots consisted of different diversification systems after the cash crop season (M: succession with maize; M+U: maize intercropped with U. ruziziensis; Mi+Ui: maize intercropped with U. ruziziensis, both inoculated with Azospirillum). After the soybean harvest in the 2021/2022 cropping season, soil samples were taken at the 0-10 cm soil layer. We analyzed soil enzymes (arylsulfatase, β-glucosidase, and acid phosphatase), environmental factors (soil pH and nutrients), and the 16S gene sequence.

Preliminary results suggest an increase in the relative abundance of some bacterial phyla with Brachiaria. The phylum Proteobacteria, which harbors numerous PGPB, showed higher relative abundance in the cropping systems with Brachiaria, independently of the inoculation strategy in the summer soybeans. On the other hand, for the Nitrospirota phylum, which contains nitrite-oxidizing bacteria, higher relative abundance was observed in S/MiBi and Si/MiBi, compared with Sc/MiBi. Additional results on bacterial community diversity and composition and their relationship with microbial activity and environmental indicators will be discussed.

This study provides novel insights into how crop diversification combined with PGPB affects the soil microbial community and nitrogen dynamics, supporting agricultural and soil management practices to achieve more sustainable production systems.

How to cite: Rewa Charnobay, A. C., Lalonde-Haman, C., Ferraz Helene, L. C., Gumiere, T., Hungria, M., and Nogueira, M. A.: Crop diversification and seed inoculation strategies effects on soil microbial community in soybean cropping systems, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-524, https://doi.org/10.5194/egusphere-egu23-524, 2023.

EGU23-1050 | ECS | Posters on site | SSS4.3

Extracellular polymeric substances from soil-grown bacteria delay evaporative drying 

Pascal Benard, Samuel Bickel, Anders Kaestner, Peter Lehmann, and Andrea Carminati

When soils dry, water flow and nutrient diffusion cease as the liquid phase vital for soil life becomes fragmented. To delay soil drying locally and related adverse effects, bacteria and plants modify their surroundings by releasing extracellular polymeric substances (EPS). As a result, the physical properties of hotspots like biological soil crusts or the rhizosphere differ from those of the surrounding bulk soil. Specifically, EPS-induced modifications delay evaporative soil drying. Despite the evidence of reduced evaporation from EPS-amended soils, the mechanisms controlling soil water content dynamics remain elusive. Thus, our study aimed to elucidate the potential of bacteria to modify their environment when exposed to oscillations in soil water content. We incubated sand microcosms with two contrasting strains of Bacillus subtilis for one week in a flow cabinet. At the end of the incubation period, local water loss was quantified and spatially resolved using time-series neutron radiography. Strain NCIB 3610, a complex biofilm producer steadily modified soil evaporation dynamics during the incubation period resulting in substantially delayed soil drying due to hydraulic decoupling of the evaporation front from the soil surface. Evaporation dynamics remained largely unaltered in the microcosms inoculated with the domesticated EPS-deficient strain 168 trp+ compared to the control treatment. The mechanism of hydraulic decoupling induced by NCIB 3610 was verified by estimates of diffusive fluxes and the position of the evaporation plane in the microcosm. Additionally, the role of polymeric substances in hydraulic decoupling was confirmed by an evaporation experiment using xanthan as an EPS analogue.

How to cite: Benard, P., Bickel, S., Kaestner, A., Lehmann, P., and Carminati, A.: Extracellular polymeric substances from soil-grown bacteria delay evaporative drying, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1050, https://doi.org/10.5194/egusphere-egu23-1050, 2023.

EGU23-2907 | ECS | Posters on site | SSS4.3

Soil microbial responses to rewetting depend on rewetting intensity and soil properties 

Xiankun Li, Ainara Leizeaga, Johannes Rousk, Gustaf Hugelius, and Stefano Manzoni

Soil drying and rewetting (DRW) events are perceived differently by the soil microbes depending on their adaptation to the previous soil moisture history. Microbes adapted to intense cycles of DRW can experience an experimental DRW event as less harsh than microbes adapted to stable and moist conditions. The perceived harshness in turn can affect the carbon balance after DRW because it can determine the responses of microbial growth (eventually leading to SOC gains) and respiration (SOC loss) after rewetting. These responses have been categorized as “type 1” with immediate fast recovery, or “type 2” with a time lag before fast recovery, due to low and high levels of perceived harshness, respectively. However, we lack a quantitative definition of perceived harshness and how it varies depending on pedoclimatic conditions. Moreover, microbial response types could vary continuously along a continuum from prototypical type 1 to type 2. Therefore, if the shapes of the response curves could be synthesized by using a single function, then the fitted parameters could be used to reflect the harshness levels perceived by the microbes. In turn, these parameters might be combined into an index of harshness with biological interpretation. Relating this index to climatic and edaphic factors would then help to understand the drivers of harshness and microbial recovery after rewetting. To these aims, we described microbial growth with a single logistic function G(t)=Gmax/(1+eb(t-τ)) and respiration with a rescaled gamma distribution R(t)=Ckntn-1e-kt/Γ[n] using data from 15 papers (in total 97 datasets). These functions described well the rates of fungal and bacterial growth, and whole community respiration after rewetting, resulting in a range of shapes consistent with the idea that soil microbial responses form a continuum between types 1 and 2. The product of growth parameters τ (delay time) and b (growth rate at time τ) allowed separating type 1 and 2 responses better than τ or b alone or than any other parameter describing the growth or respiration response. Thus, the product τ×b could be regarded as an effective index to quantify harshness. This index varied depending on soil and experimental conditions: τ×b increased with rewetting intensity (the difference in soil moisture between dry and wet conditions) and declined with higher pH; moreover, bacteria in carbon-rich soils had lower τ×b and thus perceived lower harshness. These results suggest that both fungi and bacteria facing the challenges of acidic soils are also worse adapted to respond to DRW compared to microbes from near-neutral soils. Carbon-rich soils might instead promote bacterial resilience thanks to the more available resources compared to carbon-poor soils. In conclusion, this study places soil microbial responses to DRW along a continuous gradient from fast to slow recovery as quantified by perceived harshness (which in turn is quantifiable by fitting growth and respiration curves to data). Our results help to predict the microbial carbon allocation to growth and respiration at rewetting across ecosystems and environmental conditions.

Keywords: soil drying and rewetting, microbial resilience, microbial resistance, growth, respiration

How to cite: Li, X., Leizeaga, A., Rousk, J., Hugelius, G., and Manzoni, S.: Soil microbial responses to rewetting depend on rewetting intensity and soil properties, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2907, https://doi.org/10.5194/egusphere-egu23-2907, 2023.

EGU23-3959 | ECS | Posters on site | SSS4.3

Temperature fluctuation promotes the thermal adaptation of soil microbial respiration 

Yan Zhang and Ming Nie

Microbial respiration is the main process contributing to soil carbon (C) loss and is simultaneously regulated by changes in mean temperature and temperature fluctuation. The magnitude of the feedback between soil microbial respiration and increased mean temperature may decrease (i.e., thermal adaptation) or increase over time, and accurately representing this feedback within models improves predictions of soil C loss rates. However, climate change entails changes not only in mean thermal conditions but also in the patterns of temperature fluctuation, and whether temperature fluctuation could also cause thermal adaptation has never been addressed. Here, we collected soil samples from 6 sites along a 2,000-km-long west-east transect extending across subtropical forests in China and used them in an incubation experiment involving various temperature regimes to explore how temperature fluctuation influences the thermal response of soil microbial respiration and the underlying mechanisms of this process. We revealed that soil biomass-specific microbial respiration (Rmass) was significantly lower with increasing temperature fluctuation during incubation regardless of the assay temperature, while a positive relationship between Rmass and temperature was observed under increased constant incubation temperature. Structural equation modelling further indicated that increased bacterial species turnover and reduced substrate affinity (Km) promoted the decrease in Rmass associated with greater temperature variation. Our results demonstrate that if such an adaptive response of soil microbial respiration occurs under greater temperature variation, the stimulatory effect of climate warming may be less than that predicted and thus may not increase atmospheric CO2 concentrations as much as anticipated.

How to cite: Zhang, Y. and Nie, M.: Temperature fluctuation promotes the thermal adaptation of soil microbial respiration, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3959, https://doi.org/10.5194/egusphere-egu23-3959, 2023.

EGU23-4609 | ECS | Orals | SSS4.3

Quantifying soil microbial thermal adaptation 

Charlotte Alster, Allycia van de Laar, Jordan Goodrich, Vickery Arcus, Julie Deslippe, Alexis Marshall, and Louis Schipper

Thermal adaptation of soil microbial respiration has the potential to greatly alter carbon cycle-climate feedbacks through acceleration or reduction of soil microbial respiration as the climate warms. However despite its importance, the relationship between warming and soil microbial activity remains poorly constrained. Part of this uncertainty stems from persistent methodological issues and difficulties isolating the interacting effects of changes in microbial community responses from changes in soil carbon availability. To address these challenges, we sampled nearly 50 soils from around New Zealand, including from a long-term geothermal gradient, with mean annual temperatures ranging from 11-35°C. For each of these soils we constructed temperature response curves of microbial respiration given unlimited substrate and estimated a temperature optima (Topt) and inflection point (Tinf). We found that thermal adaptation of microbial respiration occurred at a rate of 0.29°C ± 0.04 1SE for Topt and 0.27°C ± 0.05 1SE for Tinf per degree of warming, demonstrating that thermal adaptation is considerably offset from warming. These relatively small changes occurred despite large structural shifts in microbial community composition and diversity. We also quantitatively assessed how thermal adaptation may alter potential respiration rates under future warming scenarios by consolidating all of the temperature response curves. Depending on the specific mean and instantaneous soil temperatures, we found that thermal adaptation of microbial respiration could both limit and accelerate soil carbon losses. This work highlights the importance of considering the entire temperature response curve when making predictions about how thermal adaptation of soil microbial respiration will influence soil carbon losses.

How to cite: Alster, C., van de Laar, A., Goodrich, J., Arcus, V., Deslippe, J., Marshall, A., and Schipper, L.: Quantifying soil microbial thermal adaptation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4609, https://doi.org/10.5194/egusphere-egu23-4609, 2023.

EGU23-8185 | ECS | Posters on site | SSS4.3

Vegetation changes following forest disturbance affect soil carbon and nitrogen cycles through microbial communities 

Mathias Mayer, Florian Hechenblaikner, Christoph Rosinger, Beat Stierli, Beat Frey, and Frank Hagedorn

Increasing forest disturbance is among the most profound impacts of climate change on terrestrial ecosystems. Insect outbreaks, storms, or wildfires can destroy the whole tree layer, with serious consequences for biogeochemical cycles until succession returns the ecosystem back to a forested state. However, tree regeneration is often inhibited by ungulate herbivory and herbaceous competition, and disturbed ecosystems remain in non-forested states for decades. The impact of such vegetation changes on soil carbon (C) and nitrogen (N) cycles is highly unknown, because a multitude of plant-soil feedbacks are involved, and underlying processes have hardly been investigated. Here, we studied soil microbial community structure, gene abundance of bacteria, fungi, and N cycling microorganisms, soil enzymes, and C-N dynamics across a disturbed forest landscape in Central Europe, covering a range of successional stages after storm damage and bark-beetle attacks. We used a chronosequence-approach including disturbed sites regrown with Picea abies stands, and disturbed sites dominated by herbaceous pioneer plants, particularly Calamagrostis grasses. Soil C and N stocks increased under a prolonged herbaceous cover. Three decades after disturbance the stocks were ca. 45% higher than those of regrown forest stands. Beside C inputs from herbaceous fine roots, we link this increase to changes in the structure and functioning of the microbial community, which reduces the decomposition of organic matter. With a prolonged herbaceous cover, decreasing fungal abundances coincided with declining activities of phenol oxidase and of hydrolytic enzymes used to acquire nutrients. Since ectomycorrhizal fungi were almost absent compared to regrowing forest stands, this may be linked to reduced ectomycorrhizal mining for organic N. Moreover, ammonia-oxidising (amoA) gene abundances increased along with ammonium and nitrate concentrations, pointing towards an accelerated inorganic N cycle under a prolonged herbaceous cover. A surplus of inorganic N and grass-rhizodeposits renders it also likely that saprotrophs are less dependent on organic matter-bound C and N. Taken together, we found strong evidence for a linkage between above- and belowground communities following forest disturbance. We suggest a prolonged cover of herbaceous pioneer plants opens the nitrogen cycle through microbial communities which reduces mining for organic N and thus, increases soil C storage.

How to cite: Mayer, M., Hechenblaikner, F., Rosinger, C., Stierli, B., Frey, B., and Hagedorn, F.: Vegetation changes following forest disturbance affect soil carbon and nitrogen cycles through microbial communities, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8185, https://doi.org/10.5194/egusphere-egu23-8185, 2023.

EGU23-9543 | ECS | Orals | SSS4.3

Microbial metabolic response to throughfall exclusion and feedback on soil carbon dynamics along a tropical forest precipitation gradient 

Stephany S. Chacon, Ulas Karaoz, Katherine Louie, Ben Bowen, Trent Northen, Lee H. Dietterich, Daniela F. Cusack, and Nick Bouskill

Tropical forest soils represent some of Earth's largest stores of soil carbon. Humid and warm conditions promote high primary productivity offsetting high ecosystem respiration rates, and this balance has resulted in significant carbon accumulation in plant biomass and soils. These vast carbon stocks can be destabilized under a changing climate, and model projections predict tropical and subtropical regions will experience disturbance to the hydrological cycle, with an increased likelihood of more frequent and prolonged droughts interspersed with periods of intense precipitation. Herein, we examine the functional response of belowground communities to a reduction in throughfall across a 1 m precipitation gradient (2350 to 3400 mm) spanning three sites from the Caribbean coast to the interior of Panama. At each site, 4 throughfall exclusion plots (10 x 10 m) were established to reduce precipitation, and exacerbate the natural variability in seasonal hydrological cycles. In January 2020, approximately 18 months since the inception of throughfall exclusion, each plot was sampled at six locations and two depths (0-10 and 10-20 cm). To identify the traits and mechanisms involved in responding to drought perturbation, we sequenced the microbiomes of the soil samples from the throughfall exclusion and corresponding controls at each site, and measured metabolite accumulation within the soils. Here we report on the accumulation of distinct metabolites along the precipitation gradient and under throughfall exclusion. We note that constitutive production of compatible solutes increases from the wettest to the driest site, indicative of trait selection due to climate history. However, under throughfall exclusion the gradient end members show a more muted metabolic response than the intermediate site. We discuss these responses with respect specific pathways invoked under drying stress, and soil carbon dynamics.  

How to cite: Chacon, S. S., Karaoz, U., Louie, K., Bowen, B., Northen, T., Dietterich, L. H., Cusack, D. F., and Bouskill, N.: Microbial metabolic response to throughfall exclusion and feedback on soil carbon dynamics along a tropical forest precipitation gradient, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9543, https://doi.org/10.5194/egusphere-egu23-9543, 2023.

EGU23-10184 | ECS | Posters on site | SSS4.3

What’s brewing? Impacts of cultivation management on the Coffea arabica soil microbiome 

Steve Kutos, Ruth Bennett, and Carly Muletz Wolz

Coffea arabica (coffee) is cultivated on ~28-million acres and is essential to local economies in the tropics. Coffee cultivation, however, is threatened by ongoing climate change as its optimal growth occurs in narrow temperature and precipitation ranges. Areas currently growing coffee might become unsuitable leading to increased deforestation and negative effects on coffee quality. These impacts may be especially strong in coffee cultivated in sun-grown monocultures (~75% of all production) versus shade-grown agroforestry systems given relatively higher temperatures in deforested landscapes. As such, shade-grown coffee systems might be one management strategy used to buffer from future climatic shifts. While shade-grown systems provide many ecosystem benefits, the impact of the cultivation system on soil microbiomes is poorly understood. Soil microorganisms perform vital ecosystem functions including aiding plants in nutrient acquisition, buffering against stress, as well as improving nutrient cycling. This is particularly true in shade-grown coffee systems where soil carbon could be increased through increased microbial biomass and soil nitrogen could be increased through increased plant-association with N-fixing bacteria. Therefore, further understanding of the effects of coffee cultivation methods on soil microbial communities may be key to future coffee productivity and local soil biogeochemical function. To explore these themes, we sampled the soil microbial communities at 30 coffee farms in Colombia, Peru, and El Salvador. These farms varied in cultivation system (sun vs. shade) and flavor profiles that separate specialty grade from conventional quality. Our aim was to explore if soil microbiome diversity and composition differ among the three countries, cultivation systems, and coffee quality. We sequenced the DNA of bacterial (16S) and fungal (ITS) communities in coffee soil on an Illumina MiSeq with analysis completed in QIIME2 to identify microbial taxa and composition. Coffee soil microbiomes had similar relative abundance of phyla and similar number of bacterial and fungal taxa, regardless of country of origin or cultivation system. However, coffee soil microbiomes showed pronounced differences in the microbial community composition among the different countries and cultivation systems. We show that biogeography is an important determinant of coffee soil microbiomes and location-specific impacts need to be considered in future coffee management. Further, our data suggests that sun-grown systems can alter microbial community composition compared to more-sustainable shade-grown systems potentially changing soil functionality. As an example, there were increases in taxa punitively classified as mycorrhizal fungi and N-fixing bacteria in shade-grown coffee systems. Our next steps are to link this microbial data to coffee quality and soil characteristics to uncover potential factors influencing the community structure as well as nutrient cycling rates.

How to cite: Kutos, S., Bennett, R., and Muletz Wolz, C.: What’s brewing? Impacts of cultivation management on the Coffea arabica soil microbiome, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10184, https://doi.org/10.5194/egusphere-egu23-10184, 2023.

EGU23-10271 | Orals | SSS4.3

Response of soil fauna to land use intensification in a global meta-analysis 

Bibiana Betancur-Corredor and David Russell

Land use intensification, particularly a shift from extensively to intensively managed agroecosystems is often seen as one of the main drivers of global biodiversity decline and is considered the main factor applying pressure on soil biodiversity. When confronted with future land use change, understanding the responses of soil biodiversity to different land use regimes is decisive for adequate land management. However, there is still substantial uncertainty about how consistently different taxonomic groups respond to land use intensification. Oftentimes, different taxa show divergent responses to more intense land use regimes, and the community composition is rarely correlated with land use intensity, which may suggest that the drivers of community composition may not be the same as drivers of diversity. The mechanisms that determine the response of different taxa to land use intensification may be regulated by changes in the plant community and abiotic environmental drivers. We systematically assessed and quantified through meta-analysis the effects of land use intensification on soil organisms in global agroecosystems 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.

How to cite: Betancur-Corredor, B. and Russell, D.: Response of soil fauna to land use intensification in a global meta-analysis, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10271, https://doi.org/10.5194/egusphere-egu23-10271, 2023.

EGU23-11850 | ECS | Posters virtual | SSS4.3

Composition of extracellular polymeric substances (EPS) produced by a range of soil bacteria and fungi 

Rebeca Leme Oliva, Umesh Bahadur Khadka, Jens Dyckmans, Marc Redmile-Gordon, and Rainer Georg Jörgensen

Microorganisms are known to form a matrix of extracellular polymeric substances (EPS) on several solid surfaces such as soils. The formation of this matrix provides various benefits not only to the microbial community, but also to the surface it is attached. In soils, for instance, it promotes protection and adherence of microorganisms to soil aggregates and benefits the soil increasing aggregate stability. Even in spite of this knowledge, the contribution of EPS to soil organic matter (SOM) and to SOM turnover is yet unclear, mainly due to methodological limitations. Furthermore, it has also not been determined how the EPS composition affects soil structure, fertility and organic matter dynamics. It is therefore of uttermost importance to study the composition of the EPS matrix and how different microbial functional groups produce EPS in face of varying environmental conditions. To this end, 10 bacterial and 10 fungal species commonly found in soils were grown under different treatments in order to stimulate EPS production. Microorganisms were grown in either glycerol or starch medium with or without the presence of sterile quartz. EPS was extracted using a cation-exchange resin (CER) and its composition was subsequently determined with the quantification of proteins, carbohydrates, amino sugars and DNA. We hypothesized firstly, that EPS production would be higher in cultures with quartz. Secondly, we also expected bacterial EPS production to be higher in cultures with glycerol whereas fungal cultures would produce more EPS in starch medium, reflecting contrasting substrate effects on bacterial and fungal EPS formation. Lastly, we hypothesized that considerable amounts of galactosamine would be found in all extracted EPS, similarly to mucins excreted in the intestines of vertebrates, protecting enzymes. Mucins are a family of proteins with high GalN contents, consequently, GalN might be an indicator to EPS production in soils.

How to cite: Leme Oliva, R., Bahadur Khadka, U., Dyckmans, J., Redmile-Gordon, M., and Georg Jörgensen, R.: Composition of extracellular polymeric substances (EPS) produced by a range of soil bacteria and fungi, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11850, https://doi.org/10.5194/egusphere-egu23-11850, 2023.

EGU23-12303 | Orals | SSS4.3

Warming may cause substantial nitrogen losses from subarctic grasslands 

Sara Marañón Jiménez, Xi Luo, Andreas Richter, Phillipp Gündler, Lucia Fuchslueger, Bjarni D. Sigurdsson, Ivan Janssens, and Josep Peñuelas

High-latitude soils are particularly vulnerable to temperature-driven C losses and may contribute substantially to the increasing atmospheric CO2 concentrations. The magnitude of their contribution is, however, uncertain, and largely dependent on the interactions between C and nitrogen (N) biogeochemical cycles, soil microbial activities and the feedbacks between plants and soil microbes. Warming may cause a particularly pronounced acceleration of soil N transformation in N-poor cold regions. The consequent alleviation of plant N limitations in cold ecosystems may increase plant productivity and C inputs to the soil, compensating the expected soil C loss, at least partially. Alternatively, warming may desynchronize or unbalance the intimate coupling between microbial N mineralization and vegetation N uptake, leading to potential soil N loss, but also higher soil C losses. We aimed to elucidate potential mechanisms of ecosystem N losses in subarctic grasslands by determining the effects of soil warming on the seasonal patterns of plant N acquisition and microbial net N immobilization. For this, we performed a seasonal isotope tracing experiment using a mix of 15N-labelled amino-acids along soil temperature gradients in geothermal systems in Iceland.

Soil microbial biomass acted as a temporal reservoir of N by increasing N immobilization particularly during unfavorable winter periods for vegetation, likely due to the alleviated microbial C limitation. However, soil warming exacerbated microbial C limitation and decreased the N storage capacity of soil microbes during snowmelt periods. As a result, a higher proportion of N remained in the extractable soil fraction susceptible to leaching losses.  , however, this increased plant N uptake did not compensate for the lower microbial biomass N storage, leading to ecosystem N losses. Our results highlight the relevant role of soil microbes to safely store and immobilize N when plants do not need it and to release N when plants require it. Warming can weaken this particularly important soil microbial function in cold regions, leading to substantial ecosystem N and fertility losses, which may also promote irreversible soil C losses in these ecosystems.

How to cite: Marañón Jiménez, S., Luo, X., Richter, A., Gündler, P., Fuchslueger, L., Sigurdsson, B. D., Janssens, I., and Peñuelas, J.: Warming may cause substantial nitrogen losses from subarctic grasslands, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12303, https://doi.org/10.5194/egusphere-egu23-12303, 2023.

EGU23-13475 | ECS | Orals | SSS4.3

Distribution and drivers of soil bacterial communities across different soil management practices and soil diagnostic units in agricultural ecosystems 

Benjamin Bukombe, Sándor Csenki, Dora Szlatenyi, Ivan Czako, and Vince Láng

Soil bacterial communities play an important role in soil health, carbon (C), and nutrient cycling, as well as in soil-plant relationships in agroecosystems. However, our understanding of the drivers and distribution of soil bacterial communities across landscapes is limited. For example, it is not clear how changes in soil management practices (i.e. Till vs No-till vs cover crop), soil diagnostic units, and their associated physical-chemical properties interact to influence the composition and abundance of soil bacterial communities at a larger scale. Here, using samples collected in a countrywide soil survey in Hungary, we combined soil metagenomic sequencing, soil management practices, and soil geochemical data to develop a mechanistic understanding of the drivers of bacterial communities in contrasting agroecosystems. We found that bacterial community composition and distribution significantly differed between soil management practices. Furthermore, we found that soil geochemical properties influenced soil bacterial composition and abundance under similar soil diagnostic units, suggesting that the effects of soil management practices on bacterial communities outweighed the ones of pedogenic processes. Together, these results suggest that soil management practices influence soil geochemical properties that drive the composition and spatial distribution of soil bacterial communities. Consequently, effects and types of soil management should be taken into account when developing soil health indicators for agroecosystems.

How to cite: Bukombe, B., Csenki, S., Szlatenyi, D., Czako, I., and Láng, V.: Distribution and drivers of soil bacterial communities across different soil management practices and soil diagnostic units in agricultural ecosystems, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13475, https://doi.org/10.5194/egusphere-egu23-13475, 2023.

Forest soils store large amounts of organic matter from aboveground litter. Consequently, practices that affect plant development and soil properties may have crucial impacts on forest ecosystem functions and C feedbacks. In Europe, thinning of forests is a commonly used management practice to promote natural trees regeneration through increasing the temperatures, microbial activity, nutrient availability and irradiance of soil. Forest management influences the occurrence of tree species, the maximum stand density, the organic matter input to the soil decomposer system and hence the availability and quality of microbial resources. Thus, forest management can alter soil microbial community and key ecosystem functions they perform affecting the related ecosystem services, although the functional redundancy of soil microbial communities may minimize these impacts.
Due to the importance of forest soils as both sink and potential source of carbon and their predicted sensitivity to climate change, they became in the last years, one of the key targets of microbial ecologists.
In the present study, we assess the effects of forest management (coppice and high forest) on soil properties and microbial community functions in two Italian forests (turkey oak and beech), in two different seasons, summer and autumn. We investigated functional diversity of microbial communities based on the carbon consumption patterns (by community-level physiological profile, CLPP, and derived average well color development AWCD) and several enzyme activities linked to biogeochemical cycles of C, N and P.
The soil microbial community showed higher metabolic activity in both beech and turkey oak under coppice management (1.32 and 1.54 AWCD, respectively) respect to high forest regime (1.09 and 1.32 AWCD, respectively), only in summer. Significant differences in AWCD values between seasons were found only in forests under high forest management.
Among the investigated soil enzyme activities, only hydrolase showed in summer higher value in beech under coppice respect to high forest management (0.41 vs 0.25 mg FDA g-1soil d.w. h-1). This enzyme activity, however, showed higher values in summer than autumn in both forest soils, regardless the management. Hydrolase activity measures the total microbial activity in soil and is a good general index of organic matter turnover in natural ecosystems.
The results will provide useful data for: improving the sustainability of ecosystems in a scenario of climate change; identifying new biological indicators of soil health and fertility to predict the effects of forest practices.

How to cite: Picariello, E. and De Nicola, F.: The impact of forest management on soil microbial community functions in two forests of South Apennines (Italy), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13840, https://doi.org/10.5194/egusphere-egu23-13840, 2023.

EGU23-14006 | Orals | SSS4.3

Drought legacy effects on microbial community structure in a managed grassland 

Hannes Schmidt, Joana Séneca, Alberto Canarini, Eva Simon, Marlies Dietrich, Judith Prommer, Ivana Bogdanovic, Victoria Martin, Moritz Mohrlok, Bela Hausmann, Erich Pötsch, Andreas Schaumberger, Wolfgang Wanek, Michael Bahn, and Andreas Richter

The last decades were characterized by rising temperatures, enhanced atmospheric CO2 concentrations, and by an increasing frequency of extreme events such as drought. Soil microorganisms are major drivers of biogeochemical processes, yet the effects of climate change in shaping microbial communities remain poorly understood.

To address this knowledge gap, we examined how future climate conditions (combined +300 ppm CO2 and +3 °C warming, relative to ambient) and drought, alone and in combination, affect microbial community composition throughout the vegetation period in a sub-montane managed grassland (‘ClimGrass’ experiment; Styria, Austria). We combined amplicon sequencing of bacteria, archaea, and fungi with droplet digital PCR to perform quantitative microbiome profiling of seasonal and drought-legacy effects on soil microbial communities.

Drought strongly shaped the bacterial/archaeal and the fungal community structure during peak drought conditions, and this effect could still be detected two and fourteen months after ending drought by rewetting and removing rain-out shelters. In comparison, future climate conditions were observed to exert less pressure on the structure of bacterial/archaeal and fungal communities. Interestingly, abundances of members of Actinobacteria and Bacteroidota for bacteria, as well as Cladosporiaceae and Phaeosphaeriacea for fungi (amongst others) significantly increased during peak drought. Our findings suggest that drought can have immediate and lasting effects on the soil microbial community structure by contributing to the establishment of drought-tolerant microbial communities.

How to cite: Schmidt, H., Séneca, J., Canarini, A., Simon, E., Dietrich, M., Prommer, J., Bogdanovic, I., Martin, V., Mohrlok, M., Hausmann, B., Pötsch, E., Schaumberger, A., Wanek, W., Bahn, M., and Richter, A.: Drought legacy effects on microbial community structure in a managed grassland, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14006, https://doi.org/10.5194/egusphere-egu23-14006, 2023.

EGU23-15148 | Posters on site | SSS4.3

Bacterial cell-mineral associations and their stability under varying moisture conditions 

Marc-Oliver Goebel, Mariam Karagulyan, Anja Miltner, Abd Alaziz Abu Quba, Dörte Diehl, Gabriele E. Schaumann, Matthias Kästner, and Jörg Bachmann

Soil particle wettability controls the water dynamics of dry and unsaturated soil and has an impact on many processes where water is involved. Pure soil minerals are usually wettable, but under environmental conditions they are easily covered by organic compounds, changing their surface properties and potentially making them water repellent. Besides organic compounds such as alkanes, fatty acids, free lipids and waxes, research also indicates a direct influence of bacterial cells on the development of soil water repellency. In a series of stress experiments with different Gram-negative and Gram-positive strains of bacteria we could show that cell surface wettability measured in terms of contact angle is affected by cell stress response caused by hypertonic or drought environmental conditions. The changes in wettability were found to be accompanied by changes in physicochemical surface properties and surface elemental composition of the cells, as indicated by X-ray photoelectron spectroscopy. Furthermore, coverage of minerals by cells caused significant changes in particle wettability, rendering originally wettable minerals water repellent, with the effect being more pronounced for cell-mineral associations (CMA) formed with stressed cells. To investigate the physical stability of these CMA, we conducted an incubation experiment with CMA formed by quartz particles and Bacillus subtilis cells either grown under physiological or hypertonic conditions. The CMA were incubated at different water potentials (pF 2.5 and 4.2) and part of them subjected to wetting-drying cycles. The results showed that the quartz–B. subtilis CMA formed with stressed cells remained significantly more water repellent than those formed with unstressed cells during the whole incubation time of 80 days and independent of the incubation conditions. Furthermore, we observed a slight tendency of increasing contact angle with increasing incubation time. Besides the generally lower wettability of the stressed cells, the lower wettability of the CMA formed with stressed cells can be related to a higher degree of microbial coverage, as indicated by higher surface C content and lower surface O/C and Si/C ratios compared to the CMA formed with unstressed cells. The higher microbial coverage can probably be explained by attachment conditions being more favorable in case of the stressed cells, as suggested by interaction free energies calculated using the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory. In summary, the results indicate that the hydrophobizing effect of hypertonic stress on B. subtilis was stable over time and support the assumption that stress-related changes in cell surface properties remained also in necromass and their effect on surface properties of CMA can persist.

How to cite: Goebel, M.-O., Karagulyan, M., Miltner, A., Abu Quba, A. A., Diehl, D., Schaumann, G. E., Kästner, M., and Bachmann, J.: Bacterial cell-mineral associations and their stability under varying moisture conditions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15148, https://doi.org/10.5194/egusphere-egu23-15148, 2023.

EGU23-15955 | ECS | Orals | SSS4.3

Restoration of soil microbial functional stability in the face of climate extremes 

Shangshi Liu, Adam Bilton, and Richard Bardgett

Ecosystem restoration is known to enhance the functioning and stability of plant communities in the face of climate extremes. However, the effects of ecosystem restoration on soil microbial communities and their functional stability remain poorly understood. Here, we used a long-term (33 years) multiple factorial grassland restoration experiment to assess how different restoration approaches, including farmyard manure (FYM) addition, low amounts of inorganic fertiliser, mixed seed addition, and promotion of red clover, affect multiple dimensions of soil microbial functional stability in response to drought. We found that specific restoration approaches (e.g., FYM addition) not only increased the stability of plant biomass production, but also enhanced drought resistance of soil microbial multifunctionality. Moreover, we identified key factors that drive the multi-dimensional stability of plant and soil microbial communities, which provide mechanistic insights into how grassland restoration impacts above- and below-ground stability in the face of drought.

How to cite: Liu, S., Bilton, A., and Bardgett, R.: Restoration of soil microbial functional stability in the face of climate extremes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15955, https://doi.org/10.5194/egusphere-egu23-15955, 2023.

EGU23-16057 | Orals | SSS4.3

Effects of intensified freezing-thawing cycles on arctic soil microbiota investigated via soil chips 

Edith Hammer, Julia Duljas, Fredrik Klingenhammer, Hanbang Zou, Bo Elberling, and Louise C. Andresen

Arctic ecosystems are experiencing a strong and fast warming in the realms of climate change, and understanding the involved processes are important to predict impacts and feedbacks on their C cycling. Winter warming leads to frequent and reoccurring snow melts and as a consequence exposed bare ground. This leads to accelerated freeze-thaw cycles, since the snow cover that was insulating the soil below to temperature variations around a few degrees minus now can be exposed to much harsher freezes. We experimentally exposed soil crusts from Greenland to freezing-thawing cycles of different intensities and frequencies and measured the abundance of the three soil microbial groups bacteria, fungi and protists with help of microfluidic soil chips. The soil chips are brought into tight contact with the soil sample, and the microbial community colonizes their transparent pore spaces which enable us to image-based analysis of microbial abundance and interactions. We found that increased freezing frequency (daily versus bi-weekly) strikingly reduced bacterial populations, stronger than increased freezing intensity (-5°C vs -18°C). We also exposed the soil chips to live-freezing under the microscope to analyze direct effects of the approaching ice front on the microbial community. At intermediate freezing temperatures, dead-end pockets in the pore space remained liquid-filled and could act as refugia for the organisms. Fast approaching ice fronts caught fleeing organisms and in some cases led to detrimental outcomes, especially for protists. Disturbances in the trophic network differently affecting predators and pray may thus also contribute to changes in the bacterial carbon cycling.

 

How to cite: Hammer, E., Duljas, J., Klingenhammer, F., Zou, H., Elberling, B., and Andresen, L. C.: Effects of intensified freezing-thawing cycles on arctic soil microbiota investigated via soil chips, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16057, https://doi.org/10.5194/egusphere-egu23-16057, 2023.

EGU23-16820 | Posters on site | SSS4.3

Soil properties, habitat structure, climate, and topography as drivers of soil biodiversity 

Xavier Domene, Rubén Olmo-Gilabert, Marcos Fernández-Martínez, and Lluís Comas

The Catalonia Plot System for Terrestrial Biodiversity Monitoring (SISEBIO) is a long-term project aiming to monitor above- and below-ground biodiversity changes due to global change in permanent experimental sites. The project aims: a) to catalogue the existing biodiversity using metabarcoding, b) to describe the environmental drivers explaining such, and c) to identify habitats acting as biodiversity hotspots.

For this purpose, 109 permanent plots were set up in natural areas to covering all the main habitats and climates of Catalonia (NE Spain). Plant, microbial (bacteria and fungi), protists, and microarthropods richness and diversity were assessed between 2018-2021, together with a variety of environmental drivers (soil physicochemical properties, habitat structure, climate, and topography). While plant diversity was assessed through traditional morphological identification, that of soil organisms was assessed by metabarcoding and using operational taxonomic units (OTUs) for this purpose.

Concerning soil biodiversity, 42077 unique OTUs were identified, with around 40% of them only found in once. The highest biodiversity values corresponded to sites located in the Pyrenees, and the environmental factors driving biodiversity were clearly different depending on the taxa studied. However, we failed to find habitat-specific hotspots except for microarthropods, with higher richness values in conifer forests when compared to deciduous forests, shrublands and grasslands.

The existence of biological interactions and historical factors may hinder the emergence of strong environmental trends to describe soil biodiversity patterns. Our results might may guide stakeholders with the implementation of management policies in the most vulnerable habitats to protect their biodiversity, but are also of interest for modelling the impact of global change on soil biodiversity and their ecosystem services.

How to cite: Domene, X., Olmo-Gilabert, R., Fernández-Martínez, M., and Comas, L.: Soil properties, habitat structure, climate, and topography as drivers of soil biodiversity, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16820, https://doi.org/10.5194/egusphere-egu23-16820, 2023.

EGU23-73 | ECS | Posters on site | SSS4.4

Preceding crop history modulates the early growth of winter wheat by influencing root growth dynamics and rhizosphere processes 

Nikolaos Kaloterakis, Mehdi Rashtbari, Bahar S. Razavi, Andrea Braun-Kiewnick, Adriana Giongo, Doreen Babin, Kornelia Smalla, Charlotte Kummer, Sirgit Kummer, and Nicolas Brüggemann

Self-succession of winter wheat (WW) in crop rotations results in substantial yield decline. This decline has been mostly attributed to the soil-borne fungus Gaeumannomyces graminis var. tritici (Ggt; take-all) causing earlier root senescence. A broad shift in the soil microbial community has also recently been proposed to confound this effect even in years without significant Ggt infestation in the field. We aimed to establish a mechanistic basis for the relationship between rotational position of WW and yield decline at an early wheat growth stage. To this end, an outdoor experiment with 1 m deep rhizotrons was set up using a sandy loam soil. WW was grown in soil after oilseed rape (KW1), soil after one season of WW (KW2) and soil after three successive seasons of WW (KW4). The plants were grown until the beginning of stem elongation (BBCH 30). At harvest, both shoot and root dry weight were markedly affected by the preceding crop, with a pronounced reduction of plant biomass of KW2 (-43%) and KW4 (-45%) compared to KW1. At BBCH 30, KW1 soil had much lower mineral N compared to KW2 (-49%) and KW4 (-39%). Non-purgeable organic C, a readily available energy source for soil microorganisms, was further reduced in successive WW rotations compared to KW1. Increased NH4+ and NPOC concentrations were found in root-affected soil compared to root-free bulk soil, indicating a strong hotspot for organic N mineralization in the rhizosphere. At the same time, the markedly higher shoot N concentration led to a lower C:N ratio of 31 for KW1 compared to KW2 and KW4, which had a C:N ratio of 46 and 44, respectively, suggesting a better exploitation of soil mineral N sources by KW1. In contrast, microbial biomass C and N were higher in KW2 and KW4 compared to KW1, pointing to enhanced microbial N immobilization in KW2 and KW4. The higher C:N ratio of WW straw compared to oilseed rape residues that are returned to the soil following harvest, obviously stimulated immobilization of soil N in microbial biomass, thereby limiting the availability of N for WW growth in KW2 and KW4. Root growth traits exhibited a strong response to WW rotational position, with higher root tissue density, root mean diameter and lower specific root length for KW1 compared to KW2 and KW4. Root length density (RLD) was overall higher in KW1 compared to KW2 (-29%) and KW4 (-31%), especially at 0-30 cm soil depth. Interestingly, higher RLD values for KW1 were also observed at the lowest depth of 60-100 cm compared to KW4, suggesting a strong effect of rotational position on nutrient accessibility in the subsoil. Successive WW invested more in acquisitive root traits that did not compensate for the reduction of biomass production. Our results highlight the effect of rotational position of WW on soil and plant properties and provide guidance for management-based adaptations at field level to improve WW productivity.

How to cite: Kaloterakis, N., Rashtbari, M., S. Razavi, B., Braun-Kiewnick, A., Giongo, A., Babin, D., Smalla, K., Kummer, C., Kummer, S., and Brüggemann, N.: Preceding crop history modulates the early growth of winter wheat by influencing root growth dynamics and rhizosphere processes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-73, https://doi.org/10.5194/egusphere-egu23-73, 2023.

EGU23-1389 | Orals | SSS4.4 | Highlight

Complete thermodynamic characterization of the soil organic matter from forest ecosystems. 

Nieves Barros, Marko Popovic, and César Pérez-Cruzado

Thermodynamic characterization of soils is a developing field that involves the calculation of the enthalpies, Gibbs energy, and entropy of the soil organic matter, SOM. Its achievement would contribute to the development of the bioenergetics of soil systems beyond the existing theoretical models.

This work shows different experimental procedures and theoretical models for the complete thermodynamic characterization of SOM. It was applied to a total of 31 samples representing different soil horizons from different locations.

Thermodynamic characterization of SOM was achieved through the calculation of empirical formulae for SOM from the SOM elemental composition, application of Patel-Erickson, Sandler-Orbey, and Battley methods, as well as direct measurements of the energy content by simultaneous TG-DSC.

The used computational methods belong to a group of approaches modeling thermodynamic properties of SOM as a sum of contributions from its constituent elements. The first computational approaches were those from the Patel-Erickson and Battley equations. Patel-Erickson equation was used to find the standard enthalpy of combustion, ΔCH⁰PE, of SOM based on its elemental composition:

ΔCH⁰PE(SOM) = –111.14 kJ/mol ∙ (4nC + nH – 2nO – 0nN + 5nP + 6nS)

where nJ is the number of atoms of element J in the empirical formula of SOM. The Battley equation gives the standard molar entropy, S⁰m, of SOM:

S⁰m(SOM) = 0.187 ∑J [ S⁰m(J) / aJ ] nJ

where S⁰m(J) and aJ are standard molar entropy and the number of atoms of element J in its standard state elemental form. The enthalpy from the Patel-Erickson equation is combined with entropy from the Battley equation, to find the Gibbs energy of SOM.

The second computational approach handled equations proposed by Sandler and Orbey that allow finding standard enthalpy of combustion ΔCH⁰SO and standard Gibbs energy of combustion, ΔCG⁰, of SOM:

ΔCH⁰SO(SOM) = –109.04 kJ/C-mol ∙ (4nC + nH – 2nO – 0nN + 5nP + 6nS)

ΔCG⁰(SOM) = –110.23 kJ/C-mol ∙ (4nC + nH – 2nO – 0nN + 5nP + 6nS)

The enthalpy and Gibbs energy obtained using the Sandler-Orbey method were combined to find entropy.  

Results obtained by the application of Patel-Erickson and Sandler-Orbey methods to calculate the enthalpy of SOM combustion did not significantly differ when comparing data given by the TG-DSC with those obtained from the SOM empirical formulation. The same results were obtained when comparing the Gibbs energy. These results enabled the calculation of the entropy of SOM and the comparison of those values among different soil layers and sampling sites.

How to cite: Barros, N., Popovic, M., and Pérez-Cruzado, C.: Complete thermodynamic characterization of the soil organic matter from forest ecosystems., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1389, https://doi.org/10.5194/egusphere-egu23-1389, 2023.

EGU23-1397 | ECS | Orals | SSS4.4

Linking mass balances and thermodynamic energy balances in simplified model systems with artificial soils 

Shiyue Yang, Alina Rupp, Matthias Kästner, Anja Miltner, and Thomas Maskow

Soils represent the largest terrestrial carbon (C) sink and understanding its dynamics is crucial. The metabolic degradation and stabilization of soil organic matter (SOM) follow the rules of thermodynamics. In the catabolic reaction, SOM is oxidized to CO2 and the part of the energy delivered by this reaction is used in anabolism, during which biomass formation and, thereby, energy and C conservation take place. C and energy fluxes are thus linked and contribute to the C transformation and stabilization in natural soil systems. These processes are among others largely influenced by environmental conditions (e.g. temperature, soil moisture, C/N ratio).

Due to the complexity and heterogeneity of soil, thermodynamic models and experimental approaches to study the linkage of C and energy fluxes in soil systems are rare and still in their infancy. To establish it, we use calorimetric and carbon mass balancing methods to study both C and energy fluxes in artificial soil systems in incubation experiments over 64 days with cellulose and over 16 days with glucose as substrates. This simplified system allows reliable measurement and interpretation of energy input, accumulation and output and their interaction with SOM turnover processes. Carbon and Energy Use Efficiency (CUE and EUE) are studied under varying environmental conditions. The heat production rate and the reaction enthalpy of metabolism in artificial soil systems are monitored with isothermal microcalorimeters. C mass balances consist of mineralization (measured using gas chromatography coupled with thermal conductivity detector), changes in total carbon (quantified by elemental analysis - isotope ratio mass spectrometry), and carbohydrates (recorded via a phenol sulphuric acid assay). In addition, biomass and necromass contents are quantified by phospholipid fatty acid and amino sugar analysis.

EUE will be calculated from calorimetric data and further we will build an energy balance model. Furthermore, evolution of carbon input and output measurements will be further utilized for carbon balance model. Calorimetric and respirometric data provide the calorespirometric (CR) ratio of the soil system, which is closely related CUE (Chakrawal et al., 2020; Hansen et al., 2004). Experimentally determined CUE will be compared to that derived theoretically from CR ratio through calorimetric data and biomass yield modelling (Brock et al., 2017). Preliminary results on the linkage between carbon and energy balance in soil systems will be presented.

Brock, A. L., Kästner, M., & Trapp, S. (2017). Microbial growth yield estimates from thermodynamics and its importance for degradation of pesticides and formation of biogenic non-extractable residues. SAR and QSAR in Environmental Research, 28 (8), 629–650. https://doi.org/10.1080/1062936X.2017.1365762

Chakrawal, A., Herrmann, A. M., Šantrůčková, H., & Manzoni, S. (2020). Quantifying microbial metabolism in soils using calorespirometry — A bioenergetics perspective. Soil Biology and Biochemistry, 148 (May), 107945. https://doi.org/10.1016/j.soilbio.2020.107945

Hansen, L. D., MacFarlane, C., McKinnon, N., Smith, B. N., & Criddle, R. S. (2004). Use of calorespirometric ratios, heat per CO2 and heat per O2, to quantify metabolic paths and energetics of growing cells. Thermochimica Acta, 422 (1–2), 55–61. https://doi.org/10.1016/J.TCA.2004.05.033

How to cite: Yang, S., Rupp, A., Kästner, M., Miltner, A., and Maskow, T.: Linking mass balances and thermodynamic energy balances in simplified model systems with artificial soils, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1397, https://doi.org/10.5194/egusphere-egu23-1397, 2023.

EGU23-2713 | ECS | Posters on site | SSS4.4

Combining the time-lapse amino-mapping and zymography to co-localize spatial distribution of organic N with enzymatic activity in the rhizosphere 

Guoting Shen, Andrey Guber, Sajedeh Khosrozadeh, Negar Ghaderi, and Evgenia Blagodatskaya

As N limitation strongly influences ecosystem functioning, numerous studies explored the transformation process of mineral nitrogen. In contrast, the importance of organic nitrogen, which can short-circuit the mineralization step, for plant nutrition in different ecosystems often overlooked. A spatial link between the sources of organic N and N-acquiring enzymatic activity in soil is still missing due to the lack of suitable techniques. Here we developed a novel approach: in situ amino-mapping and coupled it with time-lapse zymography to quantify distribution of organic nitrogen in the rhizosphere of Zea mays L and tested spatial association of enzymatic activity with organic nitrogen abundance at the root-soil interface. Coupling the two approaches enabled identification the hotspots of amino-N, and revealed their co-occurrence with N-related enzymatic activity in seminal roots and root tips: intensive enzymatic activity was accompanied by large amino-N content, especially in the rhizosphere of seminal root tips. This work was conducted within the framework of the Priority program 2089 “Rhizosphere spatiotemporal organization – a key to rhizosphere functions”, funded by German Research Foundation (DFG – Project number: 403664478). Seeds of the maize were provided by Caroline Marcon and Frank Hochholdinger (University of Bonn).

How to cite: Shen, G., Guber, A., Khosrozadeh, S., Ghaderi, N., and Blagodatskaya, E.: Combining the time-lapse amino-mapping and zymography to co-localize spatial distribution of organic N with enzymatic activity in the rhizosphere, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2713, https://doi.org/10.5194/egusphere-egu23-2713, 2023.

EGU23-3113 | ECS | Orals | SSS4.4

Development of ultrahigh resolution mass spectrometry techniques to extend the molecular view of soil organic matter in solution and on mineral particles 

Carsten Simon, Paul Pietsch, Konstantin Stumpf, Klaus Kaiser, and Oliver Lechtenfeld

Soil organic matter plays important roles in soil reactivity and fertility as well as soil physics. Nevertheless, we know relatively little about the individual molecules that make up soil organic matter but ultimately determine its properties. Ultrahigh-resolution mass spectrometry like FT-ICR-MS has revealed an enormous molecular diversity yet it often remains limited to the water-soluble fractions (i.e., dissolved organic matter) analyzed with electrospray ionization (ESI) that represent only a small fraction of the total organic matter contained in soils. To extend the analytical window and leverage the value of non-targeted mass spectrometry, parallel analyses of soluble (via ESI) and particle-associated organic matter (PAOM) via laser-desorption ionization (LDI) and FT-ICR-MS detection is a promising approach, that has yet to prove its full potential. Here, we studied the sensitivity and robustness of the LDI technique based on a combination of dried arable soils, their aqueous DOM extracts, reference DOM samples (Suwannee River Fulvic Acid, SRFA), model compounds (syringic acid, sinapic acid, syringaldehyde, vanillic acid and tannic acid) and model mineral phases (goethite, illite). DOM samples were used to study the effects of a mineral matrix and dilution, while model compounds and SRFA were used to test the effects of laser strength and presence of an organic matrix on intact ionization of analytes. Lastly, non-extracted and extracted soil samples were used to assess if DOM composition trends observed in solution are reproduced in PAOM composition. In general, ESI ionized a very different fraction of the DOM mixture, being more polar and more saturated, while LDI ionized rather small, low-to-mid polar, and less saturated ions. Besides clear differences in PAOM and DOM analytical windows, molecular trends such as aromaticity or nominal oxidation state were well-aligned. Although most insight was gained by combining both types of analyses, our results therefore suggest that direct analysis of soil particles is a fast, reproducible, sensitive and less invasive alternative to routine protocols employing FT-ICR-MS detection, and avoids additional extraction or purification steps.

How to cite: Simon, C., Pietsch, P., Stumpf, K., Kaiser, K., and Lechtenfeld, O.: Development of ultrahigh resolution mass spectrometry techniques to extend the molecular view of soil organic matter in solution and on mineral particles, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3113, https://doi.org/10.5194/egusphere-egu23-3113, 2023.

Vegetation patchiness is hypothesized to affect the spatial heterogeneity of resources and soil nutrient distribution in drylands. Nutrient accumulation under perennial vegetative patches leads to faster nitrogen (N) cycling in times of water availability. Compared to perennials, annual plant patches have a shorter life cycle, and labile nutrient buildup can occur more quickly in these patches due to faster nutrient turnover rates of litterfall and root death. The buildup of these labile nutrient pools, in surface soils under annual plant patches over time, may indirectly facilitate succession by other plants, thus aiding in the establishment of fertility islands. To understand how the establishment of annual plant patches affects soil nutrient dynamics, we planted replicated patches of a widespread local summer annual plant, saltwort (Salsola inermis Forssk.), and assessed how these patches influence the soil N cycle and soil N oxides (N2O and NO) emissions. We also assessed rates of surface litter decomposition of the saltwort plant. We found that rates of soil N transformations and soil N oxides emissions were highest under the plant patch, while they decreased across the patch-to-bare-soil gradient. Water extractable organic carbon (WEOC) accumulation increased in the surface soil beneath the plants and was associated with a large burst in soil N oxides emissions within the patch, following dry soil wetting by the first winter rains. Soil N2O emission pulse increased by 5.2 folds, whiles NO increased by 95.8 folds. Each N-oxide gas, however, had a different post-wetting pattern, with N2O peaking a few hours after wetting and NO after one day. We measured a second pulse in soil N oxide emissions after the third rain event. This pulse occurred only with the plant patch and not outside the patch and was reduced by 54% and 31% for N2O and NO respectively. However, the temporal (peaking) pattern of the second N-oxides pulse was similar to that of the first pulse. Suggesting a reduction in substrate availability as a cause of the reduced pulse. We also found 43% mass loss from the plant litter after 12 months of decomposition. Together, these results suggest that the establishment of saltwort plants affects soil nutrient dynamics and accumulation, thus creating nutrient-rich microsites for potential succession by other annuals and perennials, leading to fertility island establishment in the Negev Desert ecosystem.

How to cite: Yagle, I., Segoli, M., and Gelfand, I.: Patch establishment of the summer annual saltwort plant (Salsola inermis Forssk.) increases N cycling rates and soil N-oxide emissions in Israel’s Negev Desert, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3645, https://doi.org/10.5194/egusphere-egu23-3645, 2023.

The role of biochar-microbe interaction in plant rhizosphere mediating soil-borne disease suppression has been poorly understood for plant health in field conditions. Chinese ginseng (Panax ginseng C. A. Meyer) is widely cultivated in Alfisols across Northeast China, being often stressed severely by pathogenic diseases. In this study, topsoil of a continuously cropped ginseng farm was amended at 20 t ha-1 respectively with manure biochar (PB), wood biochar (WB) and maize residue biochar (MB) in comparison to conventional manure compost (MC). Post-amendment changes in edaphic properties of bulk topsoil and the rhizosphere, in root growth and quality and in disease incidence were examined with field observations and physicochemical, molecular and biochemical assays. Three years following amendment, increases over MC in root biomass was parallel to the overall fertility improvement, being greater with MB and WB than with PB. Differently, survival rate of ginseng plants increased insignificantly with PB but significantly with WB (14%) and MB (21%) while ginseng root quality unchanged with WB but improved with PB (32%) and MB (56%). For the rhizosphere at harvest following three years growing, total content of phenolic acids from root exudate decreased by 56%, 35% and 45% with PB, WB and MB respectively over MC. For rhizosphere microbiome, total fungal and bacterial abundance was both unchanged under WB but significantly increased under MB (by 200% and 38%), respectively over MC. At phyla level, abundances of arbuscular mycorrhizal and Bryobacter as potentially beneficial microbes was elevated while those of Fusarium and Ilyonectria as potentially pathogenic microbes reduced, with WB and MB over MC. Moreover, rhizosphere fungal network complexity was enhanced insignificantly under PB but significantly under WB moderately and MB greatly, over MC. Overall, maize biochar exerted great impact rather on rhizosphere microbial community composition and networking of functional groups, particularly of fungi, and thus plant defense than on soil fertility and root growth.

How to cite: Liu, C. and Pan, G.: More microbial manipulation and plant defense than soil fertility for biochar in food production: A field experiment of replanted ginseng with different biochars, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4105, https://doi.org/10.5194/egusphere-egu23-4105, 2023.

EGU23-4926 | Orals | SSS4.4 | Highlight

Biogeochemical consequences of agricultural soil contamination with Sulfamethoxazole (SMX) 

Oleg Menyailo, Heleen Deroo, Corinna Eichinger, and Gerd Dercon

Agricultural soils are increasingly polluted by antibiotics, and this makes them a source of antimicrobial resistance (AMR). However, antibiotics may also change microbial communities in soils, and so alter microbiological processes. Given the knowledge gap on how antibiotics affect soil functioning, in particular soil organic carbon (C) cycling, we conducted an experiment to investigate how different concentrations of the model antibiotic sulfamethoxazole (SMX) alter soil heterotrophic respiration (C mineralization) and priming of soil C.

  We collected Austrian soils rich and poor in soil organic C from Seibersdorf and Grabenegg, respectively. After the samples were sieved at 2 mm, we incubated 80 g of soil in 100 mL jars at room temperature for 30 days. SMX was added at day 1, at six rates (0; 0.01; 0.1; 1; 10 and 100 mg.kg-1) in water solution. Soil moisture was kept constant at 45% of the soil water-filled pore space throughout the incubation experiment. The flux of CO2 and isotopic composition of C in respired CO2 were determined with a Picarro 2201-i laser isotope analyzer using Keeling plots.

In general, SMX negatively affected the CO2 production rate. The negative effect was larger with a higher SMX concentration. The inhibitory effect of SMX followed a logarithmic function, after excluding outliers. The fitted equations may be used to predict how much the microbial activity is inhibited if the concentration of SMX in soil is known. However, it was also observed in our study that when the antibiotic concentration increases, the marginal toxic effect declines at some specific concentrations, and even a stimulation of CO2 production could be found. This observed increase can be related to the following processes: it may be concentration-dependent AMR, or SMX may act as a C source, but the most likely explanation is that bacterial growth is inhibited. This last suggested process may then reduce competition, so that other microbial groups may proliferate and actively decompose soil organic matter.    

The estimated priming of soil C was positively related to SMX concentration. When readily available C source (glucose) was added, mineralization of soil C increased and this effect was accelerated with an increase in SMX concentration. Overall, the incubation experiment with different concentrations of SMX provided important insights on the toxicological effects of SMX on soil microbial life and the soil C cycle in agricultural soils. The SMX was shown to inhibit soil heterotrophic activity, but would increase losses of soil C in the presence of readily available C.

 

How to cite: Menyailo, O., Deroo, H., Eichinger, C., and Dercon, G.: Biogeochemical consequences of agricultural soil contamination with Sulfamethoxazole (SMX), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4926, https://doi.org/10.5194/egusphere-egu23-4926, 2023.

EGU23-5193 | Orals | SSS4.4 | Highlight

Bioenergetic control of soil carbon dynamics across depth 

Ludovic Henneron, Jerôme Balesdent, Gaël Alvarez, Pierre Barré, François Baudin, Isabelle Basile-Doelsch, Lauric Cécillon, Alejandro Fernandez-Martinez, Christine Hatté, and Sébastien Fontaine

Soil carbon dynamics is strongly controlled by depth globally, with increasingly slow dynamics found at depth. The mechanistic basis remains however controversial, limiting our ability to predict carbon cycle-climate feedbacks. Combining radiocarbon and thermal analyses with long-term incubations in absence/presence of continuously 13C/14C-labelled plants, we show here that bioenergetic constraints of decomposers consistently drive the depth-dependency of soil carbon dynamics over a range of mineral reactivity contexts. The slow dynamics of subsoil carbon was tightly related to both its low energy density and high activation energy of decomposition, leading to an unfavorable ‘return-on-energy-investment’ for decomposers. We also observed strong acceleration of millennia-old subsoil carbon decomposition induced by roots (‘rhizosphere priming’), showing that sufficient supply of energy by roots is able to alleviate the strong energy limitation of decomposition. These findings demonstrate that subsoil carbon persistence results from its poor energy quality together with the lack of energy supply by roots due to their low density at depth. These findings provide insights into the bioenergetic control of SOC persistence and indicate that an increase in plant rooting depth induced by global change could threaten the storage of millennia-old SOC in deep layers.

How to cite: Henneron, L., Balesdent, J., Alvarez, G., Barré, P., Baudin, F., Basile-Doelsch, I., Cécillon, L., Fernandez-Martinez, A., Hatté, C., and Fontaine, S.: Bioenergetic control of soil carbon dynamics across depth, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5193, https://doi.org/10.5194/egusphere-egu23-5193, 2023.

EGU23-6404 | Orals | SSS4.4

Microbiome of rhizosphere: from structure and functions 

Yakov Kuzyakov, Ning Ling, and Tingting Wang

Microbial composition and functions in the rhizosphere – an important microbial hotspot – are among the most fascinating yet elusive topics in microbial ecology. Based on the similarity of rhizosphere properties with respect to carbon availability and nutrient depletion, we hypothesized that (i) rhizobacterial populations are recruited from the bulk soil, but are preselected by excess released root carbon, so that bacterial diversity is lower in the rhizosphere and bacterial networks are less stable, (ii) the rhizosphere is home to more abundant copiotrophic bacteria than the bulk soil, and iii) the functional capacity involved in the carbon and nitrogen transformation would be greater in the rhizosphere.

We used 557 pairs of published 16S rDNA amplicon sequences from the bulk soils and rhizosphere in natural and agricultural ecosystems (forests, grasslands, croplands) around the world to generalize bacterial characteristics with respect to community diversity, composition, and functions.

The rhizosphere selects microorganisms from bulk soil to function as a seed bank, reducing microbial diversity. The rhizosphere is enriched in Bacteroidetes, Proteobacteria, and other copiotrophs. Highly modular but unstable bacterial networks in the rhizosphere (common for r-strategists) reflect the interactions and adaptations of microorganisms to dynamic conditions. Dormancy strategies in the rhizosphere are dominated by toxin–antitoxin systems, while sporulation is common in bulk soils. Functional predictions showed that genes involved in organic compound conversion, nitrogen fixation, and denitrification were strongly enriched in the rhizosphere (11–182%), while genes involved in nitrification were strongly depleted. Thus, rhizosphere is the most powerful factor shaping the composition, structure and functions of the soil microbiome and of biogenic element’s cycling.

Reference

Ling N, Wang T, Kuzyakov Y 2022. Rhizosphere bacteriome structure and functions. Nature Communications 13, 836. https://doi.org/10.1038/s41467-022-28448-9

How to cite: Kuzyakov, Y., Ling, N., and Wang, T.: Microbiome of rhizosphere: from structure and functions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6404, https://doi.org/10.5194/egusphere-egu23-6404, 2023.

EGU23-6542 | ECS | Orals | SSS4.4 | Highlight

Energy content of soil organic matter in soil profiles investigated by bomb calorimetry and DSC-TG 

Marcel Lorenz, Dörte Diehl, Thomas Maskow, and Sören Thiele-Bruhn

Soil organic matter (SOM) represents a continuum of progressively decomposing organic compounds mainly provided by primary producers and predominantly metabolized by adapted dynamic microbial communities. The carbon (C) in SOM flows through the microbial biomass, which needs – beside C and nutrients – Gibbs energy for growth and maintenance. The microbial metabolism and thus the degradation and stabilization of SOM follow thermodynamic laws. The thermodynamic perspective on soil systems is increasingly becoming the focus of research and has the potential to take us a substantial step towards a mechanistic understanding of SOM turnover and stabilization. An integral part of new bioenergetic concepts and models is the energy content of SOM, but the number of empirical studies dealing with soil C cycling or storage in relation to energy contents and flux is small.

In this study, topsoil profiles (comprising organic forest floor horizons OL, OF, OH and the mineral soil layer 0-5 cm) at an afforested post-mining site were investigated to evaluate the influence of (i) soil depth – representing different stages of organic matter (OM) turnover – and (ii) litter quantity and quality (litterfall and fine root tissues) provided by different tree species (Douglas fir – Pseudotsuga menziesii, black pine – Pinus nigra, European beech – Fagus sylvatica, red oak – Quercus rubra) on the energy contents of SOM. The total energy content stored in soils and plant litter was determined using two calorimetric approaches: bomb calorimetry and differential scanning calorimetry combined with thermogravimetry (DSC-TG).

The results of the litter inputs obtained with both methods showed the same trends: the C cycle in the soil was fueled by aboveground and belowground litter inputs, with energy-richer litterfall tissues (needles > leaves) compared to fine root tissues. However, with bomb calorimetry higher energy contents were generally observed in plant litter but also in the upper two forest floor horizons (OL, OF) of the soil profiles. The energy content per unit C (calorific value) changed with increasing depth due to the progressive turnover and stabilization of organic compounds but surprisingly, we identified opposite depth trends with both methods: bomb calorimetry revealed decreasing calorific values, while with DSC-TG increasing calorific values were determined. The few existing studies reported either the one trend or the other with ongoing decomposition, leading to different interpretations of the energetic driven microbial modulated formation and turnover of SOM.

It is mandatory to overcome this fundamental challenge to achieve a reliable integration of the promising bioenergetic approaches into conceptual and modelling frameworks to assess SOC turnover and persistence based on robust empirical data.

How to cite: Lorenz, M., Diehl, D., Maskow, T., and Thiele-Bruhn, S.: Energy content of soil organic matter in soil profiles investigated by bomb calorimetry and DSC-TG, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6542, https://doi.org/10.5194/egusphere-egu23-6542, 2023.

EGU23-7293 | ECS | Orals | SSS4.4

Designing of novel hydroxyapatite nanoparticles from fish by-products to be coupled with highly efficient phosphate solubilising bacteria 

Piera Quattrocelli, Elisa Pellegrino, Clara Piccirillo, Robert C. Pullar, and Laura Ercoli

Hydroxyapatite nanoparticles (nHAs) deriving from by-products have gained increasing interest as novel phosphorus (P)-based fertilisers, since they can provide a slow P release, minimising P losses and adverse environmental side-effects, and reducing the dependency of agriculture on mineral fertiliser inputs. Phosphate solubilising bacteria (PSB) have proven to release P available for crop uptake from different inorganic sources (e.g. tricalcium phosphate, TCP, hydroxyapatite, HA). In the present study, nHAs were prepared from salmon (S-nHAs) and tuna (T-nHAs) bones by a calcination process, followed by a high energy ball milling. The obtained fine powders were characterised by scanning electron microscopy (SEM) for size and shape and by X-ray diffraction (XRD) for crystal phase composition. The phosphate solubilisation activity of seven selected PSB strains belonging to Pseudomonas and Paraburkholderia genera was in vitro investigated under acidic (pH = 5.5) and alkaline (pH = 7.5) conditions by a quantitative assessment of the solubilised PO43- from TCP, S-nHAs and T-nHAs over time. Moreover, time trend of pH and organic acids in the liquid media were investigated. Characterization of S-nHAs by XRD and SEM revealed a biphasic composition of the material consisting of TCP and HA – about 50 wt% of each phase - and a heterogeneous rounded-shape (Ø < 50 nm) material. By contrast, XRD pattern of T-nHAs showed a single-phase composition mainly made of pure HA (> 95 wt%) and SEM micrographs exhibiting an elongated shape uniform in size (200 x 30 nm). At day seven, Pseudomonas graminis PG0319 solubilised the highest proportion of the total PO43- in the TCP substrate under acidic pH (83%), followed by Pseudomonas rhodesiae PR0393 and P. graminis PG1211 (79% and 72%, respectively). In S-nHAs under alkaline pH, Paraburkholderia terricola PT0405, PR0393, PG0319 and PG1211 solubilised from 53% to 57% of the total PO43-, whereas in T-nHAs under acidic pH the maximum solubilisation efficiency was 27% by PT0405 at day seven. The difference in the solubilisation of S-nHAs and T-nHAs is due to the lower solubility of HA in comparison with TCP. Values of pH in in the liquid media decreased over the time along with an increasing PO43- solubilisation activity, suggesting an extracellular secretion of organic acids by PSB. Accordingly, differential patterns of organic acids were detected among strains with TCP as well as S-nHAs and T-nHAs. Notably, gluconic, propionic, fumaric and acetic acids played key roles during P solubilisation with all the tested strains, substrates, and pH conditions. Our results indicate that the use of microbial inocula together with P-based nanofertilisers is a promising option for a sustainable agricultural transition.

How to cite: Quattrocelli, P., Pellegrino, E., Piccirillo, C., Pullar, R. C., and Ercoli, L.: Designing of novel hydroxyapatite nanoparticles from fish by-products to be coupled with highly efficient phosphate solubilising bacteria, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7293, https://doi.org/10.5194/egusphere-egu23-7293, 2023.

EGU23-8157 | ECS | Orals | SSS4.4

Evaluating soil structure and biological activity in soil cores under different management systems 

Frederic Leuther, Dorte Fischer, Naoise Nunan, and Anke Herrmann

Soil structure is a key feature in controlling microbial access to organic matter in soils. The spatial arrangement of solids and pores in agricultural soils is shaped by the used tillage and crop system. However, spatial heterogeneities make it difficult to determine relationships between soil biology and soil structure, and often homogenized, sieved soils are used to evaluate organic matter turnover in soils. In this study, we used heat dissipation as an indicator for biological activity in soils taken from two different tillage systems (conventional vs. reduced tillage) and two different cropping systems (crop rotations with either maize or winter wheat as main crop) running for 12 years. In order to evaluate the impact of soil structure, we investigated the response of both repacked and undisturbed soil cores (3 cm in height, 2.7 cm in diameter) to water and glucose addition. Pore structure indicators and particulate organic matter content were quantified by X-ray computer tomography at a resolution of 15 µm.

We will show that calorimetry is a suitable tool to monitor the biodegradation of C sources in undisturbed soil cores and that both tillage system and crop rotation effect biological activity in soil. In summary, soil under maize cultivation dissipated more heat compared to the wheat crop rotation. In both, repacked and undisturbed samples, conventional tillage promoted heat dissipation in response to water addition, likely due to the annual incorporation of labile organic matter. However, structural and organic matter indicators could only explain the variance in heat dissipation to some extent. Thus, the usage of undisturbed soil cores provides new challenges to evaluate the link between soil structure and microbial activity due to increased variability.

How to cite: Leuther, F., Fischer, D., Nunan, N., and Herrmann, A.: Evaluating soil structure and biological activity in soil cores under different management systems, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8157, https://doi.org/10.5194/egusphere-egu23-8157, 2023.

EGU23-8238 | ECS | Orals | SSS4.4

Functional traits of Zea mays L. varieties determine drought effects on soil structure and carbon allocation in the rhizosheath 

Franziska Steiner, Andreas J. Wild, Nicolas Tyborski, Shu-Yin Tung, Tina Köhler, Franz Buegger, Andrea Carminati, Barbara Eder, Jennifer Groth, Benjamin D. Hesse, Johanna Pausch, Tillmann Lüders, Wouter Vahl, Sebastian Wolfrum, Carsten W. Mueller, and Alix Vidal

The spatial arrangement of the soil surrounding the root can improve plant resource acquisition under drought and is closely related to the fate of soil organic carbon (SOC). Thus, the formation of soil structure and the establishment of a stable rhizosheath can potentially improve plant drought resistance and contribute to maintained crop yields during drought events. Yet, soil structure formation is a complex process determined by the interaction between various functional plant and soil properties, such as the soil (micro)biome, root exudation, or root morphological characteristics. To date, it is not understood how water scarcity affects soil aggregation in the vicinity of roots, by which functional traits these drought effects can be modified, and how this feedbacks on the cycling of SOC. 

Thus, we investigated drought effects on rhizosheath properties and their link with functional plant traits. We conducted a greenhouse experiment with 38 maize varieties where half of the plants were grown under optimum moisture, while the second half of replicates were subjected to drought stress after an initial establishment phase. For each plant, the rhizosheath soil was sampled and its aggregate size distribution, carbon (C) and nitrogen (N) content, and the proportion of newly maize-derived C were analysed via natural abundance 13C. In addition, we recorded functional plant and rhizosphere traits, such as morphological and chemical root properties, microbial enzyme activities, and plant biomass.

Drought-stressed plants formed lower amounts of rhizosheath, with a decreased physical aggregate stability and increased concentrations of SOC, N, and newly maize-derived C. Furthermore, under drought larger proportions of the elements were allocated into the microaggregate fractions. In particular, maize-derived C, along with N, accumulated under drought stress in the smaller aggregate size classes of the rhizosheath. Maize varieties forming larger amounts of roots under drought stress tended to maintain higher macroaggregate stability in the rhizosheath. In contrast, cultivars that invested little in root growth but promoted higher microbial enzyme activities in the rhizosheath and maintained root N contents under drought were associated with a strong accumulation of maize-C and N in the smaller aggregate size classes. 

Trait-based experimental approaches, such as the one presented here, are deepening our mechanistic understanding of drought effects in the crop rhizosheath and can thus help to guide future crop selection for improved drought resistance.

How to cite: Steiner, F., Wild, A. J., Tyborski, N., Tung, S.-Y., Köhler, T., Buegger, F., Carminati, A., Eder, B., Groth, J., Hesse, B. D., Pausch, J., Lüders, T., Vahl, W., Wolfrum, S., Mueller, C. W., and Vidal, A.: Functional traits of Zea mays L. varieties determine drought effects on soil structure and carbon allocation in the rhizosheath, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8238, https://doi.org/10.5194/egusphere-egu23-8238, 2023.

EGU23-8627 | ECS | Posters on site | SSS4.4

How do soil mechanical properties and mucilage affect the root penetration resistance to root growth? 

Ravi Kumar Mysore Janakiram, Jan Vanderborght, and Johan Alexander Huisman

Root elongation is affected by biological, physical, and chemical soil properties. Key soil physical properties determining soil strength are water content and bulk density. Highly compacted soils provide strong resistance to root growth. Therefore, it is vital to understand the effects of water content and density on the ability of roots to penetrate soil. Plant roots release a polymeric gel consisting of polysaccharides and lipids called mucilage. Mucilage also affects the physical, chemical, and biological properties of the soil, and thus is expected to have a significant effect on the penetration forces associated with root growth. In this study, penetration resistance is investigated for two soil types (sand and loam) treated with two types of mucilage obtained from flax and chia seeds. To determine penetration forces, a rheometer (MCR 102e, Anton Paar, Germany) equipped with a stainless steel needle with a shaft diameter 1 mm and an apex angle of 60° was used to mimic a root. In all measurements, the needle penetrated the soil with a velocity of 40 µm/s. Soil samples were prepared with various water content (6%, 9%, 12%, and 15%) while keeping the dry density of the soil constant following standard procedures of a mini-compaction test.  To investigate the effect of mucilage concentration, penetration tests were carried out for different concentrations (control, 0.1%, and 0.5%). Results suggest that an increase in water content significantly reduced the penetration forces. A clear effect of the type and the concentration of root exudate on the penetration resistance was also observed. It is concluded that root penetration forces are significantly affected by soil type, water content, and the type and concentration of mucilage in the rhizosphere. 

How to cite: Mysore Janakiram, R. K., Vanderborght, J., and Huisman, J. A.: How do soil mechanical properties and mucilage affect the root penetration resistance to root growth?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8627, https://doi.org/10.5194/egusphere-egu23-8627, 2023.

Flavonoids are known to perform complex physiological functions in the plant organism. The synthesis of flavonoids, their quantitative and qualitative composition depends on the genotype, age and habitat of the plant. Flavonoids are predominantly synthesized in assimilating organs and then distributed throughout the plant organism. Part of the flavonoids is released through the roots into the rhizosphere. Depending on the chemical structure, flavonoids in the soil can be ionized, oxidized or form covalent adducts with thiol compounds, complexes with metals or ammonium forms of nitrogen.

Rutin (quercetin-3-O-rutinoside), when excreted by plant roots in a slightly alkaline environment, like most flavonols, is partially ionized, acquiring greater mobility in soil solutions. In combination with ammonium nitrogen, rutin actively spreads in the rhizosphere and is recognized by rhizospheric bacteria. Thus, PGPR (plant growth-promoting rhizobacteria) isolated from the seed coat of soybean (Glycine max (L.) Merr.) reveal high sensitivity to rutin-ammonium complexes. Pseudomonas putida strain PPEP2-SEGM-0220 (GenBank: MW255059.1) stimulated the growth of main and lateral roots in soybean seedlings. The sensitivity of this strain to the rutin-ammonium complex on nutrient medium (King's B) was found at a solution concentration of 5 µg/ml. This indicates that the ionized form of rutin is biologically active and performs the function of a selective attractant for symbiotic microorganisms in the rhizosphere. Obviously, isolated PGPRs have molecular mechanisms for recognition of the rutin-ammonium complex. The presence of positive chemotaxis increases the probability of colonization of the plant with the PGPR strains it needs. Thus, the processes of transformation of quercetin-3-O-rutinoside in the soil are extremely important in the formation of plant-microbial systems.

How to cite: Likhanov, A.: Positive chemotaxis of plant growth-promoting rhizobacteria to the ionized form of rutin, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8644, https://doi.org/10.5194/egusphere-egu23-8644, 2023.

EGU23-9096 | ECS | Orals | SSS4.4

Isothermal Macrocalorespirometry – Novel Instrument Design to Analysis Microbial Metabolism in Soil Systems 

Eliana Di Lodovico, Maximilian Meyer, Thomas Maskow, Gabriele Schaumann, and Christian Fricke

Isothermal microcalorespirometry is a non-destructive technique widely used to study terrestrial activity in ecosystems by measuring the heat and the carbon dioxide (CO2) released by metabolic reactions of soil organisms. Therefore, microbial communities naturally present in the soil play a key role in the C and N cycle thereby releasing heat and CO2 which are quantitatively related to the matter fluxes via the law of Hess. In order to measure both quantities simultaneously, current methods follow mainly a purely calorimetric approach (absorbent method or GC analysis) [1]. In the absorbent method, CO2 is measured indirectly via the heat released during the absorption reaction in a NaOH-solution (CO2-trap), which is placed in the sample vessel together with the soil sample. This approach presents a few disadvantages, e.g. indirect CO2 measurement, small sample size, low sample throughput, low CO2 partial pressure and oxygen limitation. 

To overcome the drawbacks of the current calorespirometric approach, a newly designed isothermal macrocalorespirometer (IMCR) was developed by combining a classic respirometer and the proven concept of isothermal microcalorimetry. The IMCR is composed of 10 mobile channels placed in a thermally isolated box, water-thermostated at 20°C. Each channel is composed of a heat sink and a heat sensor directly in contact with the sample vessel (calorimetric unit), plus a vessel with a KOH-solution (CO2-trap) in which a pair of electrodes is immersed (respirometric unit) connected to the channel’s lid. The spatial separation between the two units, the use of electrodes and the size of the channel, make it possible to overcome the disadvantages of the absorbent method (NaOH-solution) mentioned above. The new approach has been successfully tested with glucose-induced microbial metabolic activity in soil samples, allowing the quantification of the calorespirometric ratio . Additionally, TGA-DSC-MS and GC-MS analysis will be performed, necessary to close balances of mass and energy fluxes.

This newly designed IMCR will be applied in the wider frame of calorimetric environmental soil studies, aiming at understanding the carbon dynamics in soil, the latter being known as the biggest carbon pool among the natural matrix. New knowledge in this area support potential solutions for climate change, intimately connected to the global carbon fluxes.

[1] Wadsö L., A method for time-resolved calorespirometry of terrestrial samples, Methods 76 (2015) 20–26

How to cite: Di Lodovico, E., Meyer, M., Maskow, T., Schaumann, G., and Fricke, C.: Isothermal Macrocalorespirometry – Novel Instrument Design to Analysis Microbial Metabolism in Soil Systems, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9096, https://doi.org/10.5194/egusphere-egu23-9096, 2023.

EGU23-9613 | ECS | Orals | SSS4.4 | Highlight

Soil Microorganisms Involved in Glucose Assimilation in Small and Large Pore Micro-habitats of Different Plant Systems 

Zheng Li, Alison Cupples, Andrey Guber, and Alexandra Kravchenko

Background. High plant diversity is known to increase carbon inputs to soils, impact soil microbial community composition and promote soil microbial activity. Large pores are likely to hold more roots residues, provide more efficient oxygen supply, and have more dissolved nutrients and carbon carried by water fluxes. Soil pore structure also impacts the activities of soil microbial communities. The aim of this study was to investigate the effects of 1) plant systems, representing a 9-year gradient of plant diversity (no plants, monoculture switchgrass (Panicum virgatum L.), and high diversity prairie), 2) soil pore size (small (4-10 µm Ø) and large (30-150 µm Ø)), and 3) incubation time (24 hr (short-term) and 30 days (long-term)) on the microbial communities involved in the utilization of a newly added carbon (glucose). This is the first work to explore the influence of soil micro-habitat, as presented by pores of different sizes ranges, on the microbial communities’ responses to new carbon inputs.

Methods. The intact soil cores (5 cm Ø) from the three systems were supplied with either 50 μM C g-1 soil of 13C labeled glucose, unlabeled glucose, or no glucose. Glucose was added to small or large pores based on matrix potential approach. After 24 hr or 30 day incubations stable isotope probing (SIP) was used to identify the phylotypes actively responsible for glucose assimilation in the small and large pore micro-habitats. Both extracted DNA and the fractions separated by SIP were subject to 16S rRNA gene sequencing. PICRUST2 was used to predict the microbial functions of the sequencing data from KEGG orthologs.

Results. The overall microbial communities were affected by multiple years of contrasting vegetation, but not by pore sizes or incubation times. Pseudomonas (Proteobacteria) played an important role in carbon uptake from glucose in all short-term incubations and in the long-term incubations within large pores. In the long-term incubations of both switchgrass and prairie systems’ soils, the community compositions of carbon consumers acting within the small and large pore micro-habitats differed and could be linked to disparate carbon assimilation strategies (r- vs. K-strategists) and to disparate carbon acquisition ecological strategies (plant polymer decomposers, microbial necromass decomposers, predators, and passive consumers). The predicted enriched functional genes indicated the dominance of glucokinase in the soil of the prairie, but not switchgrass system, suggesting a competitive advantage for consuming glucose.

How to cite: Li, Z., Cupples, A., Guber, A., and Kravchenko, A.: Soil Microorganisms Involved in Glucose Assimilation in Small and Large Pore Micro-habitats of Different Plant Systems, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9613, https://doi.org/10.5194/egusphere-egu23-9613, 2023.

EGU23-9746 | Orals | SSS4.4

Exploring Real-time Oxygen Dynamics in the Rhizosphere of Sorghum with High Spatial and Temporal Resolution 

Joanne Shorter, Joseph R. Roscioli, Elizabeth Lunny, William Eddy, and Wendy Yang

The presence of oxygen in soil controls the occurrence and rates of biogeochemical processes underlying soil nutrient transformations and greenhouse gas dynamics.  Oxygen (O2) levels within the rhizosphere are heavily modulated by both root and microbial respiration.  Thus, a microscopic environment near the root may be a microbial hotspot and not well represented by broader, non-rhizosphere soil.  Here we examine the millimeter-scale oxygen consumption or loss processes in the rhizosphere of sorghum, how they are influenced by irrigation practices, and the relationship between oxygen dynamics and nitrification in the rhizosphere.

In a field study at a research farm at the University of Illinois Urbana-Champaign, sorghum was grown under a rainout shelter with plants undergoing one of 2 irrigation treatments.  Soil O2 concentration and isotopic ratios, nitrous oxide (N2O), and carbon dioxide (CO2) were measured in the rhizosphere of the sorghum via an array of novel microvolume probes coupled to an Aerodyne TILDAS (Tunable Infrared Laser Direct Absorption Spectrometer).  Probes were placed within the rhizosphere or outside the root zone with the aid of root windows installed at the site.

We collected continuous, real-time, in situ measurements of O2, O2 isotopes, CO2 and N2O over the 2022 sorghum growing season.  The high spatial and temporal resolution of the measurements allowed us to observe spatiotemporal heterogeneity of biogeochemical activity in the rhizosphere as a function of agricultural activity.  

We will also report on controlled laboratory incubations to quantify the impact of soil microbial oxygen consumption on 18O enrichment as compared to water displacement in the soil; and controlled greenhouse experiments to measure fine scale gradients of oxygen concentrations and isotopic composition near roots.

The novel microvolume sampling system coupled with the O2 detection method can provide insights into fine scale gradients driven by higher microbial activity in microbial hotspots within the rhizosphere.  Measurements on this mm-scale have further applications for monitoring other trace soil gases and their spatial and temporal heterogeneity in soil systems. 

How to cite: Shorter, J., Roscioli, J. R., Lunny, E., Eddy, W., and Yang, W.: Exploring Real-time Oxygen Dynamics in the Rhizosphere of Sorghum with High Spatial and Temporal Resolution, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9746, https://doi.org/10.5194/egusphere-egu23-9746, 2023.

The growth-stimulating bacteria (PGPB-group) in the increasing of the plant-microbial interaction potential in the winter wheat agrocenosis

 

Boroday V.V.1, 2,

Doctor of Agriculture Science,

Yakovenko D.O.1,

1 Institute of Agroecology and Environmental Management, Metrologichna str., 12, Kyiv, 03143, Ukraine

2National University of Life and Environmental Sciences of Ukraine, Heroiv

Oborony str.15, building 3, of. 207, Kyiv, 03041, Ukraine

 

The use of microorganisms of the PGPB group will contribute to the activation of nitrogen fixation and phosphate mobilization in the soil, and increase the potential of plant-microbial interaction. The purpose of our research was to find out the effect of biological preparations Groundfix® and Azotofit-r® (“BTU-Center”) on the main physiological groups of soil microorganisms during the cultivation of wheat plants of the Bohdana variety in the conditions of the Western Forest-Steppe of Ukraine. The biological preparation Groundfix® includes Bacillus subtilis, B. megaterium var. phosphaticum, Azotobacter chroococcum, Enterobacter spp., Paenibacillus polymyxa. Azotofit-r® contains nitrogen-fixing bacteria A. chroococcum and its biologically active products.

It is established that in the agrocenosis of winter wheat, biological preparations Groundfix® and Azotofit-r® affect the ratio of ecological and trophic groups of microorganisms, in particular nitrogen-fixing, oligotrophic and microorganisms involved in the mineralization of humic substances, and the direction of mobilization processes in the soil. The complex application of biological preparations in different phases of plant development contributed to the slowing down of mineralization processes, the preservation of soil nitrogen in a more accessible form to plants during the period of active growth.

The coefficient of oligotrophicity for the soil with the use of biological preparations in the spring weeding phase was low (<1). This indicates a high supply of soil microbiota with easily digestible organic substances and the formation of optimal conditions for the functioning of the soil microbial complex.

The use of Azotofit and Groundfix (3 l/ha) for pre-sowing cultivation contributed to the abundance of saprotrophic species in these variants within 88.9-90.0% of the total abundance of micromycetes.

Thus, the use of biological preparations Azotofit and Groundfix contributed to reducing the infectious potential of the soil and  increasing its microbiological activity in the agrocenosis of winter wheat.

 

How to cite: Boroday, V. and Yakovenko, D.: The growth-stimulating bacteria (PGPB-group) in the increasing of the plant-microbial interaction potential in the winter wheat agrocenosis , EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10067, https://doi.org/10.5194/egusphere-egu23-10067, 2023.

EGU23-12829 | ECS | Orals | SSS4.4

Traitbased modeling of microbial distribution and carbon turnover in the rhizosphere 

Ahmet Sırcan, Thilo Streck, Andrea Schnepf, and Holger Pagel

Microorganisms possess the ability to adapt to different environmental conditions through the use of various strategies. This diversity in strategies allows us to categorize them based on their functions in the ecosystem. Copiotrophs have a fast growth rate but a low carbon use efficiency (CUE), while oligotrophs have a slow growth rate but a high CUE. In the rhizosphere, the effect of root exudation on different functional microbial groups is not well understood. Process-based modeling is a useful tool to analyze the complex feedback between roots and soil in the rhizosphere. Here, we present a rhizosphere model that explicitly considers two different microbial groups (oligotrophs and copiotrophs) classified based on their microbial traits that correlates each other due to physiological trade-offs and organic carbon accessibility (dissolved organic carbon, mucilage and sorbed carbon). The model is one-dimensional axisymmetric, simulating a soil cylinder around individual root segments. The model was conditioned using a novel constraint-based Markov chain Monte Carlo parameter sampling method. Applying this approach enabled the identification of parameter sets that led to plausible model results in agreement with experimental findings from a comprehensive literature review. The conditioned model predicts organic matter concentration curves from the root surface into the soil driven by root exudation. Our simulations show a decreasing pattern of dissolved organic carbon, which is utilized by oligotrophs and copiotrophs, away from the root surface. Furthermore, we observe a slightly higher proportion of copiotrophs than oligotrophs near the root surface and dominance of copiotrophic biomass at very high nutrient availability conditions as expected from ecological theory and experimental evidence. However, the model predictions are still highly uncertain. Thus, further experimental data and observations are required for model conditioning.

How to cite: Sırcan, A., Streck, T., Schnepf, A., and Pagel, H.: Traitbased modeling of microbial distribution and carbon turnover in the rhizosphere, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12829, https://doi.org/10.5194/egusphere-egu23-12829, 2023.

EGU23-14382 | ECS | Orals | SSS4.4

Drought increases the relative contribution of mycorrhiza-mediated mineral N uptake of Sorghum bicolor 

Rosepiah Munene, Osman Mustafa, Sara Loftus, Mutez Ahmed, and Michaela Dippold

Climate change scenarios forecast increasing droughts in large areas globally with significant effects on food production. Nutrient availability is an imperative factor for plant growth and it is greatly modulated by water availability. Nitrogen (N) availability extensively constrains plant growth in most terrestrial ecosystems especially in sub-Saharan Africa, where soils are unfertile and often degraded. How rhizosphere traits at the plant soil-interface affect N uptake in response to drought in N poor tropical soils remains elusive. We used 15N, and 13C pulse labelling to trace and quantify N transport from a root-restricted compartment by AMF across an air gap to the host plants coupled with quantifying the allocation of carbon to below-ground pools. Three sorghum genotypes were grown under optimal and water deficit conditions. By tracer analysis in the plant tissues, we assessed that drought enlarged uptake and delivery 15N by arbuscular mycorrhizal fungi (AMF) from the root restricted compartment across the air gap to the host plant. In addition, drought induced enhanced below-ground incorporation of recently assimilated carbon (C) into the microbial biomass pool both in rhizo-hyphosphere and hyphosphere. Enzyme assays revealed that whereas potential enzymatic reaction (Vmax) of chitinase was reduced under drought, that of leucine amino peptidase (LAP) was upregulated by water scarcity suggesting that N input from protein mineralization was relatively enhanced to that of chitin following moisture limitation. Michaelis-Menten constant (Km) of LAP strongly increased by drought compared to that of chitinase which displayed genotype-specific shifts in rhizosphere enzyme systems. We conclude that in addition to AMF symbiosis, enzyme regulation and enhanced belowground C allocation are key strategies to enhance nitrogen uptake under adverse conditions of resource limitations.

How to cite: Munene, R., Mustafa, O., Loftus, S., Ahmed, M., and Dippold, M.: Drought increases the relative contribution of mycorrhiza-mediated mineral N uptake of Sorghum bicolor, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14382, https://doi.org/10.5194/egusphere-egu23-14382, 2023.

EGU23-15250 | ECS | Posters on site | SSS4.4

Short-term drought effect on biochemical processes and microbial growth in the rhizosphere of two maize genotypes. 

María Martín Roldán, Roman Hartwig, Monika Wimmer, and Evgenia Blagodatskaya

The rhizosphere is a highly dynamic biological interface where most decomposition processes of soil organics are performed by actively growing microorganisms producing extracellular enzymes. As the rate of enzymatic reactions and affinity of enzymes to the substrate are influenced by plant genotype and water content in soil, we hypothesized to boost genotype effect of wild and root hair deficient maize plants after a short-term drought due to resources limitation. We further hypothesized that (1) maximum enzymatic rates (Vmax) for ß-glucosidase, leucine-aminopeptidase, acid phosphatase, and N-acetylglucosaminidase will decrease due to low accessibility to substrates; and (2) microbial growth will be retarded due to limited nutrients availability. We tested these hypotheses on the Zea mays L. (WT) and a root hair deficient mutant (rth3) grown in soil columns. Drought effect was compared between the brushed soil from roots called root-affected soil, and the rhizosphere soil obtained after the subsequent washing of roots. Microbial growth induced by glucose and nutrients application was determined by microcalorimetry.

Only two of four enzymes tested were sensitive to drought: ß-glucosidase and phosphatase. Maximum enzymatic rates of ß-glucosidase and phosphatase in the rhizosphere were, respectively, 73 and 47 % slower under drought treatment, compared to the well-watered plants. In the rhizosphere of rth3, only ß-glucosidase activity was reduced by 32 % under drought treatment compared to well-watered plants In root-affected soil, drought decreased ß-glucosidase activity by 72 and 57% for WT and rth3 plants, respectively. In the rhizosphere of WT plants, higher affinity for substrates was revealed for ß-glucosidase and phosphatase, respectively, as 31 and 42% lower Michaelis-Menten affinity constant (Km) under drought versus optimal watering. In the root-affected soil of rth3 mutant, only ß-glucosidase showed a 39 % lower Km under drought compared to well-watered plants. Higher enzymatic affinity under drought versus optimal moisture indicated a different set of enzymes either of microbial or plant origin. On the other hand, plant genotype effect was visible under drought for ß-glucosidase activity in rhizosphere soil, when maximum rate was 54 % lower for WT plants compared to rth3, suggesting that ß-glucosidase activity hotspots were not associated to root-hairs.

Glucose-induced microbial growth was retarded for 12 to 14 hours under drought compared to well-watered treatment. A prolonged lag phase could be due to the smaller fraction of active microorganisms, which is driven by a non-optimal moisture of the soil. Moisture appeared to be a more determinant factor for microbial growth and enzymatic activity compared to plant genotype, whose effect was reinforced under drought.

How to cite: Martín Roldán, M., Hartwig, R., Wimmer, M., and Blagodatskaya, E.: Short-term drought effect on biochemical processes and microbial growth in the rhizosphere of two maize genotypes., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15250, https://doi.org/10.5194/egusphere-egu23-15250, 2023.

EGU23-15947 | ECS | Posters on site | SSS4.4

Role of root hairs in rhizosheath aggregation and in the carbon flow into the soil 

Pedro Paulo de C. Teixeira, Svenja Trautmann, Franz Buegger, Vincent J.M.N.L. Felde, Johanna Pausch, Carsten W. Müller, and Ingrid Kögel-Knabner

Plants' roots promote changes in soil structure, forming a strongly-bound soil layer in the surroundings of the root, which is named as rhizosheath. Rhizosheath formation is attributed mainly to the root hairs' presence, that favors the enmeshment of the soil particles around the roots, and the release of mucilage and exudates, which acts as gluing agents of those soil particles. In the present work, we studied the rhizosheath aggregate formation of two Zea mays L. genotypes with contrasting root hair development: a mutant with root hair defective elongation (rth3) and a corresponding wild type (WT). We also tracked the fate of recently-deposited C in the rhizosheath aggregates using two 13CO2 pulse labeling approaches (single vs. multiple pulse labeling). The sampled rhizosheath aggregates were further separated using dry-sieving fractionation into three aggregate size classes: primary small particles and smaller microaggregates (<53 µm), larger microaggregates (53-250 µm) and macroaggregates (>250 µm). We observed that the aggregate size distribution followed the same pattern in both genotypes. This result reinforces the assumption that other soil properties are more important for rhizosheath aggregation than root hair elongation. We observed that the higher potion of the recently-deposited root-derived C (57%) was accumulated in the macroaggregates. Moreover, the multiple pulse labeling approach proportioned a higher 13C enrichment of the rhizosheath aggregates fractions than applying a single pulse. Despite both single and multiple labeling approaches have resulted in a similar distribution of 13C in the rhizosheath aggregates, multiple pulse labeling provided a higher enrichment in the rhizosheath aggregates, which allowed a better separation of significant differences between the genotypes.

How to cite: de C. Teixeira, P. P., Trautmann, S., Buegger, F., J.M.N.L. Felde, V., Pausch, J., W. Müller, C., and Kögel-Knabner, I.: Role of root hairs in rhizosheath aggregation and in the carbon flow into the soil, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15947, https://doi.org/10.5194/egusphere-egu23-15947, 2023.

EGU23-16129 | ECS | Orals | SSS4.4

Influence of organic amendments, moisture content and temperature on carbon mineralization of forest soils 

Ina Krahl, Karsten Kalbitz, and Christian Siewert

Predicting soil organic carbon (SOC) mineralization under changing climatic conditions is complicated by the diversity of SOC composition. We combined incubation experiments with continuous respiration measurements and thermal analysis to investigate the informativeness of SOC thermal stability. Thermogravimetry is used in studies to determine soil properties such as total organic C, nitrogen, and clay content and to investigate the relationships between thermally labile and stable SOC and biodegradability. Soil respiration (SR) was measured in forest soils with added organic materials (wood, litter, and weeds with C contents of 49, 10, and 35%, respectively, and N contents of 0.1, 0.6, and 3%, respectively) at 20°C and 10°C and different soil moisture contents (5, 10, 20, 40, and 75% of field capacity). Wood amendments were further subdivided into pine (Pinus sylvestris) and beech (Fagus sylvatica) with three different particle sizes. We used topsoil samples from a pine forest, a beech forest, and a long-term agricultural experiment with different properties (C in %: 1.5, 2, and 4; clay in %: 5, 9, and 25, respectively). Basal respiration increased with soil C content, while Q10 levels decreased with field capacity 10 > 40 > 75% in forest and agricultural soils. This order changed depending on the sampling location when organic material was added. Decreasing wood particle size significantly increased SR. Weed additions caused the highest increase in soil respiration. After 10 weeks of incubation at different moisture and temperature conditions, organic amendments were mineralized faster in beech forest soils than in soils under pine forests. A multifactorial analysis of variance showed a significant influence (p < 0.01) of the interactions between temperature, moisture, site, and wood particle size on SR. Preliminary results from analysis of changes in thermal mass loss (TML) between 200 and 550 °C (reflecting SOC thermal stability) due to added organic material and incubation will be presented. Approaches to determine relationships between TML and carbon mineralization will be discussed.

How to cite: Krahl, I., Kalbitz, K., and Siewert, C.: Influence of organic amendments, moisture content and temperature on carbon mineralization of forest soils, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16129, https://doi.org/10.5194/egusphere-egu23-16129, 2023.

EGU23-16135 | Orals | SSS4.4

The role of water management technologies in regulating iron-phosphorus interaction in rice rhizosphere 

Luisella Celi, Sara Martinengo, Michela Schiavon, Marco Romani, Daniel Said-Pullicino, Angelia Seyfferth, and Maria Martin

Phosphorus (P) availability to rice plants is influenced by its strong interaction with iron (Fe). In the rhizosphere microenvironment, the soil-plant interactions cause the formation of Fe-plaques that can retain porewater components, such as P. The Fe-P processes have been extensively described in paddy soils managed under continuous flooding, although, due to the increasing water scarcity, new water-saving techniques have been adopted. However, their effects on P retention/release mechanisms are largely unknown.  

 

In order to assess the impacts of water-saving techniques on the rhizosphere Fe-P dynamics and P availability to rice, a macrocosm experiment was conducted to compare the effects of three different water management practices: continuous water flooding (WFL), alternated wet and dry (AWD), and delayed flooding (DFL). Three P fertilization levels were tested for each water management strategy. The concentrations of Fe and P in porewater were monitored until rice harvesting. The plant tissues were analyzed for P concentration, and the content of amorphous and crystalline Fe (hydr)oxides in root plaque was estimated via oxalate and dithionite extractions at mid-tillering, stem elongation, heading and harvesting.

 

The molar P/Fe ratio in porewater and the formation of Fe plaques differed as a result of the combined effect of water management and P fertilization.  The WFL and DFL treatments led to a higher Fe plaque formation with respect to AWD, while in all water management treatments, Fe plaque formation was higher without P fertilization. The early rice development stages were characterized by a greater amount of amorphous Fe (hydr)oxides in root plaques. The proportion of crystalline Fe (hydr)oxides increased with plant development, despite the lower amount of total Fe plaques, suggesting a reduction of the poorly ordered fraction, especially when no P was supplied. Rice plants could be supposed to respond to P-limited conditions, exuding protons and/or organic acid anions that increase P availability through Fe plaque dissolution. This was confirmed by the negative correlation between porewater P concentration and the content of crystalline Fe in the plaques. These results indicate the complex spatio-temporal interconnection between P and Fe cycling at the root-soil interface. The amount of Fe plaques formed on the root surface and their crystallinity degree can explain the mechanisms that regulate their potential in P retention/release and the consequent effects on plant uptake.

 

This study was funded by the PSR Lombardia 2014-2020 (“P-rice Fosforo in risaia: equilibrio tra produttività e ambiente nell'ottica delle nuove pratiche agronomiche”)

 

How to cite: Celi, L., Martinengo, S., Schiavon, M., Romani, M., Said-Pullicino, D., Seyfferth, A., and Martin, M.: The role of water management technologies in regulating iron-phosphorus interaction in rice rhizosphere, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16135, https://doi.org/10.5194/egusphere-egu23-16135, 2023.

EGU23-16304 | Posters on site | SSS4.4 | Highlight

SoilSystems, a research program on systems ecology of soils – energy discharge modulated by microbiome and boundary conditions 

Sören Thiele-Bruhn, Matthias Kästner, Anja Miltner, Thomas Maskow, and Marcel Lorenz

Large fluxes of solar energy conserved in organic matter pass through soil as conduit from primary production to mineralisation. Soil organisms are channelling the flux, are fuelled by the energy, and contribute by their bio- and necromass. Previous research targeted either biogeochemical turnover processes or the microbiome but rarely linked both. Microbial biomass and its necromass were identified as major constituents of soil organic matter (SOM) and highly counterintuitive results were found on the relation of the microbiome to the systems boundary conditions provided by water, oxygen, nutrients, and minerals etc. A major deficit is that soils are currently not considered as energy driven open systems. Energy is the `fuel´ of all animate systems including soils in which microbial biomass consume the organic matter and energy input. With the necromass plus other SOM it constitutes carbon and energy containing intermediates.

The general aim of SoilSystems is to link energy and matter turnover and fluxes in soils to functional and structural biodiversity. SoilSystems proposes a systems ecology concept for linking balances of changes of Gibbs energy and heat production to organic matter turnover and the microbiome. This concept will be applied in model experiments with various bulk soils and isotope labelled substrates with defined energy supply and molecular structures in order to evaluate losses, efficiencies, and the modes of energy and matter retention.

This presentation gives an overview on the recently started research priority program SoilSystems, funded by the German Research Foundation. The planned research will be outlined that is aimed to elucidate microbial processes driving organic matter along energy use channels, thereby converting easily degradable detritus molecules to microbial biomass and finally long-term stabilised necromass. Thermodynamic principles are generally valid for the Earth system and thus also for soils; however, only few studies exist regarding energy use and maintenance (energy budgets) of microbiomes related to carbon use and ecosystems in soil.

SoilSystems aims to answer the key-question: What drives the interrelated energy and matter fluxes in soil systems exemplified by carbon turnover and storage? The microbiome, energy input, mineral and boundary conditions, and how do they interact?

How to cite: Thiele-Bruhn, S., Kästner, M., Miltner, A., Maskow, T., and Lorenz, M.: SoilSystems, a research program on systems ecology of soils – energy discharge modulated by microbiome and boundary conditions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16304, https://doi.org/10.5194/egusphere-egu23-16304, 2023.

EGU23-16674 | Posters on site | SSS4.4

Enzymatic kinetics and microbial growth in the rhizosphere of maize: visualization and quantification of the functions 

Evgenia Blagodatskaya, Maria Martin Roldan, and Guoting Shen

Biochemical processes in the rhizosphere are distributed heterogeneously and depend on biotic and abiotic factors such as root morphology and physiology which affect the allocation of substrates, nutrients and water availability. In the frame of Priority Program ‘Rhizosphere Spatiotemporal Organisation – a Key to Rhizosphere Functions ’ we aim to visualize and quantify enzymatic activity related to C, N and P turnover in order to link them with microbial functional traits in space and time. To do that, we apply a time-lapse zymography of hydrolytic and oxidative enzymes coupled to micro-sampling of rhizosphere hotspots for enzymatic kinetics determination at the early vegetation stage of maize. Kinetic parameters of microbial growth will be estimated by micro-calorimetry. Traditional approaches of rhizosphere sampling will be compared with novel methodology at the level of individual soil aggregates. Specific strategies of two plant genotypes (wild type and root hair deficient mutant) in response to limiting conditions of water and nutrients content will be tested on two soil substrates of contrasting texture (loam and sand). Field experiments in a long-term maize monoculture will help disclose the interactions between rhizosphere and detritusphere from decaying roots of previous years.

How to cite: Blagodatskaya, E., Martin Roldan, M., and Shen, G.: Enzymatic kinetics and microbial growth in the rhizosphere of maize: visualization and quantification of the functions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16674, https://doi.org/10.5194/egusphere-egu23-16674, 2023.

Soil saprophagous fauna strongly impacts litter decomposition through its modification of microbial communities and activity. However, soil fauna is very diverse, with different feeding strategies. For example, arthropods such as woodlice and millipedes and epigeic earthworms (litter-feeders) are known to feed on the litter layer, while endogeic earthworms feed on organic particles mixed with the soil mineral layer. Distinct fauna may have a very different impact on the final forms of the soil organic matter. They could act synergistically as endogeic earthworms may require the fragmentation and incorporation of litter into the soil by litter-feeders to access their food. We performed a three-months microcosm experiment in which we tested the effect of litter fragmentation and presence of litter-feeders (isopods or epigeic earthworms of Dendrodrilus rubidus species) on the survival and change in biomass of endogeic earthworms (of Aporrectodea caliginosa species). We also tested whether different combinations of fauna and litter fragmentation affect microbial biomass and respiration, and the forms of the soil organic matter. We used a recent post mining soil, to create a stressful environment with poor food resources for the endogeic species. The hypotheses were that endogeic earthworms would be positively affected by the fragmentation and mixing of litter with the soil, whether it would be done manually or by epigeic earthworms or isopods, and that this would impact soil properties. First results showed no decrease in the biomass of A. caliginosa in any of the treatments. A. caliginosa was able to consume the alder litter added at the soil surface at a similar rate than the epigeic D. rubidus, even without previous fragmentation and in the absence of litter-feeders. A loss of carbon through respiration and an increase of dissolved organic carbon content in the soil were associated with the presence of epigeic earthworms, while an increase in soil microbial biomass carbon was induced only by endogeic earthworms when litter was added at the soil surface. Nitrates content was increased when both types of earthworms were present. Interestingly, endogeic earthworms had an opposite impact on microbial biomass and dissolved organic carbon content when litter was mixed in small pieces with the soil or added at the soil surface. First conclusions are that though the endogeic earthworm A. caliginosa do not seem to require a first fragmentation of the litter to access it, the final effect on decomposition differ according to the other fauna present and to the fragmentation of the litter. Analyses of the forms of the organic matter in the different treatments will allow to determine how this impacted the incorporation of organic matter into the soil.

How to cite: D'Hervilly, C. and Frouz, J.: Do interactions between litter-feeders and endogeic earthworms impact soil organic matter content and its forms? Results of a microcosm experiment, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-837, https://doi.org/10.5194/egusphere-egu23-837, 2023.

Globally soil fauna can consume about half of litter fall. Important question is how this activity affect mineralization and stabilization of soil organic matter. Here we explore how much fauna effect litter decomposition and organic matter stabilization in soils of various ages supplied by litter of various quality.   Laboratory mesocosm consist from litter and mineral layer mineral soil originated either from spruce and alder stand which were growing either on post mining soils (young soil) or from soil in close vicinity of post mining sites (mature soil), mineral soils were supplied by matching litter, mesocosms were either without fauna or supplied by two individuals of earthworm Aporectodea rosea. Results show significant effect of tree, soil age and earthworm; alder respire more than spruce, young soil respire more than old soil, and mesocosms with earthworms respire more than without earthworms.  Earthworm effect show statistically significant interaction with tree and soil age, earthworms always increase respiration in alder soil, but in spruce only in mature soil while opposite was true for young soil.  In general earthworms promote removal of litter from soil surface and its accumulation in mineral soil. Earthworms promote C storage in MAOM  namely in young spruce soil. Results indicate that in young soils which are far from saturation (spruce on post mining soil) earthworm activity promote soil C storage most likely by promoting C storage in MAOM, in the contrary in mature,  C saturated soils, earthworms rather promote soil respiration.

How to cite: Frouz, J. and Irshad, S.: How the effect of earthworms on soil organic matter mineralization and stabilization is affected, by litter quality and stage of soil development., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1118, https://doi.org/10.5194/egusphere-egu23-1118, 2023.

EGU23-1282 | Orals | SSS4.5

Fungal pairwise interactions shift from positive to negative under warming stress 

Francois Rineau, Wouter Reyns, Camille Carpentier, Fons Van Der Plas, Richard Bardgett, Natalie Beenaerts, and Frederik De Laender

The impact of climate change on soil processes depends on how abiotic stressors (drought, flood, heatwave…) affect soil species physiology directly, but also indirectly through their interactions. A number of different theoretical frameworks have been designed to conceptualize the latter. The most widely used is the stress gradient hypothesis, which states that facilitation should be more common in stressful environments. However, these interactions are notoriously difficult to investigate in soils, because of the difficulty to isolate low competitor species and of the sheer number of species in soil, and therefore of interactions to test experimentally. Consequently, this topic has been traditionally approached through network analyses, that are based on frequency of co-occurrences, but has its own flaws.

In this paper, we used a combination of isolation methods to recover the widest possible range of soil fungi with randomized co-cultivation tests to cover as many interactions as possible. This way, we investigated how multiple pairwise competitive interactions were affected by abiotic stress (high temperature, low water availability).

In absence of abiotic stress, the presence of another species mostly affected growth positively, demonstrating facilitation among soil fungal species under benign conditions. In presence of temperature stress, either alone or combined with water stress, these positive effects became negative, contradicting the stress gradient hypothesis. We did not find the interaction outcomes to be predictable by some of the trait data we investigated, such as abiotic stress tolerance or intrinsic growth rate.

Overall, our results demonstrate that in a very simplified but controlled system, climate change shifts the interaction types from mostly facilitative to mostly negative. We discuss further potential implications in the presentation.

How to cite: Rineau, F., Reyns, W., Carpentier, C., Van Der Plas, F., Bardgett, R., Beenaerts, N., and De Laender, F.: Fungal pairwise interactions shift from positive to negative under warming stress, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1282, https://doi.org/10.5194/egusphere-egu23-1282, 2023.

EGU23-2092 | Posters on site | SSS4.5

Microscopis fungi of Technosols in cities of different climatic zones 

Maria Korneykova, Dmitriy Nikitin, Maria Vasilieva, and Viacheslav Vasenev

Among the high diversity of urban soils, of particular interest are soil constructures (Technosols) created by man to solve certain problems: landscaping and recultivation. Microorganisms quickly respond to external influences and are indicators of changes occurring in ecosystems. Microfungi determine the soil health, and the activity of saprotrophic microscopic fungi can lead to improved soil properties associated with soil fertility.

The aim of the study was to evaluate the quantitative indicators of soil fungal communities of 2-years-old Technosols, created on the basis of peat, sand and loam, in different climatic zones in comparison with background soils.

The studies were carried out in cities located in different climatic zones: subarctic (Apatity), temperate continental with a humid climate (Moscow), and temperate continental with a dry climate (Rostov-on-Don). Soil sampling was carried out at stations with soil constructures of a composition universal for all regions: peat/sand/loam in the ratio 1/1/1.

Quantitative assessment of the content of ribosomal genes of fungi was performed by real-time polymerase chain reaction (PCR). The fungal biomass was determined by luminescence microscopy method.

The predominance of fungal biomass over that of prokaryotes was revealed in all climatic zones, both in background soils and in Technosols. The fungal biomass in Technosols of different climatic zones varied from 0.073 to 0.790 mg/g of soil. In Apatity and Moscow, its values 2 years after the creation of Technosols were lower than in the background soil; in Rostov, the values were close. In the Technosols of Apatity and Moscow, microfungi were mainly in the form of mycelium, while in Rostov-on-Don, spores prevailed over mycelium. However, small spores prevailed in all zones, both in background soils and in Technosols. Over the 2-years period of Technosols development in the subarctic and the temperate zone, similar trends in the state of the fungal community were noted, while in the area with a warmer climate, other patterns were revealed.

The number of the fungal ITS rRNA ribosomal genes copies in the soils varied from 5.95×108 in the Technosols of Apatity to 3.39×109 gene copies/g soil in the background soil of the Moscow region. According to the quantitative content of fungal genes copies over a two-year period, the Technosols of Rostov-on-Don correspond to the background soils and slightly exceed the values of the latter. In the subarctic, the values of this indicator are also comparable for Technosols and background soils, while in Moscow, the number of copies of Technosols genes is 2.5 times less.

Thus, the change in the quantitative indicators of soil fungal communities over time makes it possible to judge the dynamics of the development of Technosols in different climatic zones. However, for such a short period (2 years), the state of fungal communities does not reach the state of the background ecosystems in any of the regions. We can only talk about trends in the parameters of the fungal community in the direction of background ecosystems.

How to cite: Korneykova, M., Nikitin, D., Vasilieva, M., and Vasenev, V.: Microscopis fungi of Technosols in cities of different climatic zones, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2092, https://doi.org/10.5194/egusphere-egu23-2092, 2023.

EGU23-3352 | ECS | Posters on site | SSS4.5

Can earthworms increase inorganic carbon sequestration in an artificial environment? 

Tullia Calogiuri, Mathilde Hagens, Jan Willem van Groenigen, and Alix Vidal

Enhanced Silicate Weathering (ESW) has emerged as a promising Carbon Dioxide Removal (CDR) technology. However, it is still not clear which factors could maximize ESW rates. Previous studies have shown the potential of soil biota to amplify mineral weathering rates. Among the relevant soil biota are earthworms, which have been found to enhance nutrient release from soil minerals. This is indicative of their ability to increase weathering rates and further inorganic carbon (C) sequestration. Here we aim to accelerate ESW rates in a bio-reactor through earthworm activity. First, we identified the optimal conditions for earthworm survival and activity in an environment exclusively composed of ground silicate rocks and organic substrate. Second, we determined to what extent earthworms can enhance inorganic C sequestration in such a system. We carried out 5 rounds of 2-month experiments in a climate chamber at 25°C. The set-up of the experiments consisted of 200 columns, each topped by a sprinkler connected to an irrigation system, which allowed for different water irrigation rates and watering frequencies. The leachate of each column was collected in a jerrycan kept at 4˚C. Within this set-up, we used two endogeic earthworm species (Aporrectodea Caliginosa and Allobophora Chlorotica) at different densities (10, 20, and 30 earthworms kg-1 soil), three types of rock flours (Basalt, Lava and Dunite) of two grain sizes (0.063 and 1.5 mm), one organic source (straw) and two water irrigation rates (125 and 250 ml day-1 kg-1 soil) at three watering frequencies (1, 2 and 5 times/day). Rock flours were used not only as single type or single size, but also as mixtures of types and/or sizes. At the end of each experiment, we measured earthworm survival and activity, and inorganic C sequestration rates by summing cumulative dissolved inorganic C in the leachate and the newly formed solid inorganic C content. We found no differences in survival and activity between the two earthworm species, but we did find an optimum for both parameters at a density of 10 earthworms kg-1 soil. Earthworms showed a clear preference for a mixture of grain sizes compared to single size, and for single mineral type compared to a mixture of mineral types. The response of earthworm survival and activity to the two water irrigation rates was similar, but at a water irrigation rate of 250 ml day-1 kg-1 soil a frequency of 5 times/day resulted in higher activity. Preliminary results indicate that earthworms increase mineral weathering rates and thereby sequester inorganic C. We demonstrate that earthworms can thrive in a fully artificial environment designed to ESW rates, removing one hurdle for designing a bio-reactor aimed at optimizing carbon sequestration.

How to cite: Calogiuri, T., Hagens, M., van Groenigen, J. W., and Vidal, A.: Can earthworms increase inorganic carbon sequestration in an artificial environment?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3352, https://doi.org/10.5194/egusphere-egu23-3352, 2023.

EGU23-6338 | ECS | Posters on site | SSS4.5

Nutrient Dynamics in Soil and Soil Water impact Arbuscular Mycorrhizal Fungi (AMF) Colonization and Abundance on Grassland Slopes in Eastern Bavaria, Germany 

Anna Sophia Holmer, Kaiyu Lei, Sigrid van Grinsven, and Jörg Völkel

It is widely known that natural soils under different land use provide a heterogenous environment regarding nutrient availability. This affects plants as well as microorganisms such as arbuscular mycorrhizal fungi (AMF).  It can have an impact on the abundance and amount of root colonization by AMF. These complex systems are often studied in experimental setups, while the wider scope of natural systems shaping entire landscapes so far received less attention.

To unravel the impact of land use and the soil parent material (including the typical periglacial layering along slopes in the area) on nutrient availability and thus AMF root colonization and total abundance, two forest-grassland-creek catenae were selected in the low mountain region of the eastern Bavarian Forest (Germany). This landscape is characterized by the uniformity of the bedrock and its weathering product (saprolite), which decisively shapes the landscape. One of the two catenae was extensively used for feed production with 2-3 cuts per year. It received slurry twice a year as well as carbonic magnesium lime. The other catena had always been used as part of a deer browsing area with low stocking density. It has never been fertilized (apart from deer excretions) or limed and is mulched once per year. Soil profiles along both catenae were sampled and suction cups placed according to the periglacial layering, to investigate the nutrients in percolation- and interflow water coming downslope. Moreover, samples were taken for the investigation of AMF colonization and abundance according to the catena-profiles.

We will present our results on the nutrient dynamics observation along the two catenae. These consist of nutrient concentrations in slope water from the suction cups as well as carbon, nitrogen and phosphorus contents along the catenae. Moreover, we will show the corresponding AMF root colonization and AMF abundance data. We expect these data to show a correlation of nutrient dynamics along the slope with AMF colonization and abundance as well as a difference between the two sites in nutrient dynamics and resulting AMF occurrence, according to the divergent land use.

To summarize, we will provide a field-based observation of the impact of land use regimes and landscape-shaping geological disposition on nutrient dynamics along grassland slopes in the Bavarian Forest, which influence AMF colonization and abundance.

How to cite: Holmer, A. S., Lei, K., van Grinsven, S., and Völkel, J.: Nutrient Dynamics in Soil and Soil Water impact Arbuscular Mycorrhizal Fungi (AMF) Colonization and Abundance on Grassland Slopes in Eastern Bavaria, Germany, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6338, https://doi.org/10.5194/egusphere-egu23-6338, 2023.

EGU23-6714 | ECS | Orals | SSS4.5 | Highlight

Interactions among earthworms species affect soil functioning 

Thomas Z. Lerch, José H.R. Araujo, Yvan Capowiez, Anne Pando, Christian Hartmann, and Lise Dupont

Earthworms are involved in the regulation of many soil ecosystem services. Their communities are often composed of several species but the role of each species and the potential interactions among these species on soil functioning is still poorly understood. The aim of this study was to test the hypothesis that the higher the earthworm diversity, the stronger the effect on soil processes and plant growth. A second assumption relied on the fact that earthworm effects depend on soil texture. To test our hypotheses, a laboratory controlled experiment was conducted on 5L mesocosms filled with 3 grassland soils with different textures (from sandy to loamy), covered by a layer of green waste compost. In each soil, 8 combinations of 3 different species of earthworms (Lumbricus terrestris, Lumbricus castaneus, and Allolobophora chlorotica) were tested. The experiment lasted about 14 months during which the CO2 and the water holding capacity were recorded. Then, Lolium perenne were grown during 6 months. At the end of the experiment, analyses of soil porosity and aggregation were performed by X-ray-tomography followed by dry sieving. Results obtained shows that the assembly of the 3 species had the strongest effects on compost mineralization and hydric properties, depending on the soil texture. The analyses of the soil physical structure revealed that interactions between earthworm species lead to significant changes in the soil porosity and aggregation profiles. The ongoing analyses of plant biomass will determine whether the demonstrated changes in soil properties will result in changes in plant growth and physiology.

How to cite: Lerch, T. Z., Araujo, J. H. R., Capowiez, Y., Pando, A., Hartmann, C., and Dupont, L.: Interactions among earthworms species affect soil functioning, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6714, https://doi.org/10.5194/egusphere-egu23-6714, 2023.

EGU23-8071 | Posters on site | SSS4.5

An endohyphal bacterium impacts growth and metabolism of carbohydrates associated with storage and hemicellulose degradation of its fungal host 

Monika Schmoll, Miriam Schalamun, Sabrina Beier, Ida Scalmani, Stephane Compant, and Wolfgang Hinterdobler

In nature, complex organismic communities have evolved for optimal colonization of habitats. Interkingdom interactions between fungi and bacteria can be mutualistic, but also parasitic. Ongoing research reveals an increasing number of fungi inhabited by bacteria, which results in diverse phenotypic alterations in fungi. Therefore, we were interested, how widespread the presence of endofungal bacteria is in strains of the genus Trichoderma, which fulfil a variety of ecological functions – from beneficial plant interaction and mycoparasitism on pathogenic fungi to degradation of cellulosic litter.

We found evidence for the presence of endohyphal bacteria of different species in the majority of Trichoderma strains tested. Interestingly, we did not detect a preference of specific bacterial species for a fungal species or vice versa. In the saprophyte Trichoderma reesei, we detected endohyphal bacteria by confocal microscopy and specific staining. We could confirm the presence of a Methylobacterium species in the hyphae by sequencing of 16S rRNA. After curing T. reesei QM6a from the bacteria using antibiotics, re-sequencing of the 16S rRNA and whole genome sequencing of the isolated bacterium confirmed its identity. Again, the association with Methylobacterium turned out to be strain specific with strains from different tropic habitats than species specific. Isolation of the bacterium from T. reesei QM6a showed that it is not obligate biotroph and both the bacterium and the fungus are viable individually.

In order to evaluate the interrelationship of Methylobacterium and T. reesei, we applied phenotype microarrays to assess metabolic contributions of the bacterium and performed functional assays. Antagonism against pathogenic fungi on plates was not perturbed in the absence of Methylobacterium from T. reesei on no general growth defect was obvious. However, BIOLOG analysis clearly showed a light dependent alteration of growth in the cured strain especially on xylitol, an intermediate of hemicellulose degradation and D-mannitol, a carbohydrate with important roles in stress response and carbon storage.

Accordingly, comparative transcriptome analysis between wild-type and cured fungal strains indicates an influence of the endohyphal Methylobacterium of T. reesei QM6a on diverse metabolic pathways, with different patterns upon growth in light or in darkness. The hypothesis, that the endohyphal bacterium of T. reesei QM6a supports the metabolic adaptation of the fungus to growth in light is corroborated by sequencing the genome of Methylobacterium, which comprises multiple genes with light-response associated protein domains.

In summary, we discovered an intriguing new physiological aspect of T. reesei, which opens up a new field of research with high potential for gaining an in depth understanding of interkingdom interaction of fungi with their prokaryotic inhabitants. On a broader scale, our findings highlight the abundance and important interaction of soil fungi with their endohyphal bacteria for ecosystem functions like carbon degradation, which is currently hardly considered in microbiome research and warrants further studies into the role of such interkingdom interactions in microbial communities.

How to cite: Schmoll, M., Schalamun, M., Beier, S., Scalmani, I., Compant, S., and Hinterdobler, W.: An endohyphal bacterium impacts growth and metabolism of carbohydrates associated with storage and hemicellulose degradation of its fungal host, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8071, https://doi.org/10.5194/egusphere-egu23-8071, 2023.

EGU23-8993 | ECS | Orals | SSS4.5

Mycorrhizal guild interactions, rather than the Gadgil effect, slow decomposition of mor-layer humus 

Louis Mielke, Julien Klein, Alf Ekblad, Roger Finlay, Björn Lindahl, and Karina Clemmensen

Boreal forest soils are dominated by three fungal guilds; ectomycorrhizal fungi associated with canopy-forming trees, ericoid mycorrhizal fungi associated with understory shrubs and free-living saprotrophic fungi. We followed decomposition of pine needle litter and mor-layer humus in a factorial pine root exclusion and shrub removal experiment in a mature pine forest over three years to evaluate fungal guild effects on mass loss. Litter mass loss was 10% faster when ectomycorrhizal fungi were excluded, however this ‘Gadgil effect’ was only found in one of two litter sets, and it was independent of shrub presence. In contrast, humus mass loss was hampered by shrub presence and promoted by ectomycorrhizal fungi, although presence of both guilds resulted in the largest humus mass remaining. This suggests that saprotrophic-ectomycorrhizal interactions are of little significance for early-stage litter decomposition, while ericoid and ectomycorrhizal guilds interact to determine late-stage organic matter balance in boreal forest soils.

How to cite: Mielke, L., Klein, J., Ekblad, A., Finlay, R., Lindahl, B., and Clemmensen, K.: Mycorrhizal guild interactions, rather than the Gadgil effect, slow decomposition of mor-layer humus, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8993, https://doi.org/10.5194/egusphere-egu23-8993, 2023.

EGU23-9220 | ECS | Posters on site | SSS4.5

Arbuscular mycorrhizal fungi and their associated plant communities jointly respond to long-term nutrient deficiencies in a managed grassland 

Kian Jenab, Lauren Alteio, Stefan Gorka, Ksenia Guseva, Sean Darcy, Lucia Fuchslueger, Alberto Canarini, Victoria Martin, Julia Wiesenbauer, Felix Spiegel, Bruna Imai, Hannes Schmidt, Karin Hage-Ahmed, Erich M. Pötsch, Andreas Richter, Jan Jansa, and Christina Kaiser

Arbuscular mycorrhizal fungi (AMF) form mutualistic associations with roughly 70% of vascular plant species, supporting the nutrient acquisition of their host plants and deriving carbon in return. AMF and plant communities are linked to each other by host-specificity and the ecological selection of favorable nutrient and carbon trading strategies. Changing soil nutrient availabilities can affect both plant and AMF communities directly and also indirectly via the response of their partners.  We aimed to elucidate the combined response of AMF (belowground) and plant (aboveground) community compositions to changing soil nutrient availabilities.

We sampled soil and roots from a long-term nutrient deficiency experimental grassland in Admont (Styria, Austria). The grassland plots have been fertilized with different combinations of nitrogen (N), phosphorus (P), and potassium (K) over 70 years. Aboveground biomass cuts were removed three times each year, leading to long-term deficiencies of nutrients not replaced by fertilizers. Soil and root AMF community compositions were measured by DNA and RNA amplicon sequencing of the 18S rRNA gene. In addition, we assessed the plant community composition of the sampled roots by amplicon sequencing of the chloroplast rbcL (RuBisCo large subunit) gene region, and visually recorded the plant community composition on each investigated plot.

Our results demonstrate that N and P deficiencies influenced soil AMF community composition, whereas K deficiency had a major impact on root AMF community composition. Interestingly, the plant community composition was affected by N and P, similar to the soil AMF community composition. Both, soil and root AMF community compositions were significantly correlated to plant community composition across all treatments, the correlation was however stronger for soil AMF communities (R2 = 0.55, p< 0.001). By using bipartite network analysis, we identified several fungus-plant pairs that responded consistently to treatments.

Our results indicate that the response of grasslands to nutrient deficiencies is potentially driven by strong feedbacks between plant and belowground AMF community compositions. We here demonstrate that the known interactions between grassland plants and AMF - which are often investigated from a single plant or monoculture perspective - are major drivers of how diverse plant community compositions will respond to environmental change, such as fertilization. In conclusion, considering the ecology of the subsurface AMF communities may strongly benefit our understanding of plant communities in a future environment.

How to cite: Jenab, K., Alteio, L., Gorka, S., Guseva, K., Darcy, S., Fuchslueger, L., Canarini, A., Martin, V., Wiesenbauer, J., Spiegel, F., Imai, B., Schmidt, H., Hage-Ahmed, K., Pötsch, E. M., Richter, A., Jansa, J., and Kaiser, C.: Arbuscular mycorrhizal fungi and their associated plant communities jointly respond to long-term nutrient deficiencies in a managed grassland, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9220, https://doi.org/10.5194/egusphere-egu23-9220, 2023.

EGU23-10025 | ECS | Orals | SSS4.5

Differential climate dependence of microbial, mesofaunal and macrofaunal litter decomposition across a Mediterranean to hyper-arid aridity gradient 

Nevo Sagi, Viraj Torsekar, J Alfred Daniel, Efrat Gavish-Regev, and Dror Hawlena

Litter decomposition in most terrestrial ecosystems is regulated by moisture-dependent biological activity, leading to a positive association between precipitation and decomposition rates. In drylands, decomposition is often higher than predicted by climate conditions and weakly associated with annual precipitation, a discrepancy known as the dryland decomposition conundrum. One possible resolution may be that low microbial decomposition is compensated by litter consuming macro-arthropods that are better adapted for activity under arid conditions. In this study we quantified the contribution of organisms of different sizes to litter decomposition across an aridity/precipitation gradient from Mediterranean (mean annual precipitation (MAP) of 526 mm) to hyper-arid climate (MAP = 22 mm). We performed a litter box experiment in seven sites along the gradient during two different seasons – a dry summer and a wetter winter. We manipulated access to litter by organism size and monitored the activity of macro-detritivorous fauna in each site during both periods. We found that microbial decomposition rate increased with MAP. However, litter mass loss induced by mesofauna and macrofauna followed a unimodal pattern, with mesofaunal and macrofaunal decomposition peaking under semi-arid (MAP = 367 mm) and arid (84-148 mm) climate conditions, respectively. This result corresponded to macro-detritivore abundance, species richness and biomass that similarly peaked in the arid sites. These patterns were consistent across seasons, but macrofaunal decomposition rates in the arid sites were 2.5- to 7-fold higher in summer than in winter. Whole-community decomposition was dictated by microbial decomposition in winter and by macrofaunal decomposition in summer. Whole community decomposition rates in arid sites during summer were as high as in the semi-arid and Mediterranean sites in winter, eliminating total differences across these climates at the annual scale. Our findings highlight the importance of macro-detritivores for litter decomposition under arid conditions, which compensates for low microbial and mesofaunal activity, advocating a possible resolution for the dryland decomposition conundrum. This is not the case under hyper-arid climate conditions, where macrofaunal activity is severely limited and cannot compensate for low microbial decomposition. We conclude that the relationship between climate conditions and decomposition is mediated by organism size. Moreover, differential adaptation of microorganisms, mesofauna and macrofauna to aridity may alleviate the dependence of decomposition on moisture availability. This new mechanistic understanding is essential for integrating faunal effects into biogeochemical models in the face of the global aridification trend.

How to cite: Sagi, N., Torsekar, V., Daniel, J. A., Gavish-Regev, E., and Hawlena, D.: Differential climate dependence of microbial, mesofaunal and macrofaunal litter decomposition across a Mediterranean to hyper-arid aridity gradient, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10025, https://doi.org/10.5194/egusphere-egu23-10025, 2023.

EGU23-10742 | Posters on site | SSS4.5

Nematode hitchhiking in soil bacteriophage dispersal 

Kyle Mason-Jones, Cassidy Dietz, Mark Zwart, Johannes Helder, and Lisa van Sluijs

Lytic bacteriophages are major drivers of bacterial mortality and biogeochemical cycles in several ecosystems, roles that have also been hypothesized in soil. Phage particles have no metabolism of their own, yet to achieve sustainable replication they must travel from one host to the next through the surrounding environment. Evidence from soil physics and phage biology suggests that this is a hazardous journey for unprotected phages, especially under the prevailing assumption that dispersal occurs by diffusion. However, many other viruses overcome dispersal challenges by taking advantage of vectors – third-party organisms that carry the virus from one host to the next. We hypothesized that bacterivorous nematodes play this role in soil, picking up phages while feeding on bacteria and transferring them to uninfected bacteria while foraging. We postulated that nematodes would provide active and directed transport of phages between bacterial patches via two possible mechanisms. First, nematode intestines could temporarily harbour infected bacteria during nematode movement. Second, nematodes could carry phages through external attachment to the nematode cuticle. Using experiments with model nematodes (C. elegans) and bacteria (E. coli, P. putida) along with phages (T7, Phi Ppu-W11) we confirmed that transfer occurs at high frequency when facilitated by nematodes, and does not occur without nematodes. Resource availability was found to influence the transfer by modulating nematode behaviour in agar, but this effect was not found in structured compost habitats. Based on these results we propose that vectors are crucial for soil phage dispersal, suggesting that phage roles in soil function are mediated by interactions with local fauna.

How to cite: Mason-Jones, K., Dietz, C., Zwart, M., Helder, J., and van Sluijs, L.: Nematode hitchhiking in soil bacteriophage dispersal, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10742, https://doi.org/10.5194/egusphere-egu23-10742, 2023.

Podsolization is influenced by soil forming factors such as precipitation, parent material, variation in e.g., snowpack melt, groundwater table, water flow velocity, and pH. However, in a thorough meta-analysis of 48 publications, containing 259 dated profiles, Zwanzig and co-authors used the formation of an E-horizon and its increase in thickness over time as an indicator of progressive podsolization1 and showed that progressive podsolization was linked to “Coniferous” and “Ericaceae-Coniferous-Mix” vegetation. Both vegetation types are affiliated with mycorrhizal fungi, which obtains energy from the host plant and in return deliver nutrients to the plant. Specifically, Coniferous and Ericaceae vegetation hosts ectomycorrhizal (ECM) and ericoid mycorrhiza (ERM) fungi, respectively. Linking ECM fungi to the podsolization process was done more than two decades ago by Van Breemen and co-authors2. They observed extensive tunnel weathering of primary minerals by ECM fungi in the top horizons which was almost absent in the underlying B-horizon, thus indicating that some ECM fungi accelerate mineral weathering in the top part of the soil and increase Al mobilization. Furthermore, within the last two decades it has been discovered that ECM fungi with diverse evolutionary origins have a large capacity to reductively dissolve iron minerals as a part of their decaying mechanism driven by Fenton chemistry3. Furthermore, genomic analyses suggest that ERM species might have the ability to initiate a Fenton reaction4 albeit this has only been experimentally verified for one species5. Here it is suggested that the ability to generate tunnel weathering and reductively dissolve iron minerals are not driven by the same mechanism, nor by the same metabolites, but can be done by (at least) two taxonomically distinct yet functionally similar groups of fungi affiliated nutrient pore soils.  Thus, it is suggested that podsolization, or at least Fe translocation in podzol, is driven by mycorrhiza fungi and is an artifact of the fungi decaying mechanism.

Zwanzig, L., Zwanzig, M. & Sauer, D. Outcomes of a quantitative analysis of 48 soil chronosequence studies in humid mid and high latitudes: Importance of vegetation in driving podzolization. CATENA 196, 104821 (2021).

van Breemen, N., Lundström, U. S. & Jongmans, A. G. Do plants drive podzolization via rock-eating mycorrhizal fungi? Geoderma 94, 163–171 (2000).

Tunlid, A., Floudas, D., Op De Beeck, M., Wang, T. & Persson, P. Decomposition of soil organic matter by ectomycorrhizal fungi: Mechanisms and consequences for organic nitrogen uptake and soil carbon stabilization. Front. For. Glob. Chang. 5, (2022).

Martino, E. et al. Comparative genomics and transcriptomics depict ericoid mycorrhizal fungi as versatile saprotrophs and plant mutualists. New Phytol. 217, 1213–1229 (2018).

Burke, R. M. & Cairney, J. W. G. Carbohydrate oxidases in ericoid and ectomycorrhizal fungi: a possible source of Fenton radicals during the degradation of lignocellulose. New Phytol. 139, 637–645 (1998).

How to cite: Lyngsie, G.: Fungal triggered iron translocation in the oxic environment - Advances in understanding podsolization, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11550, https://doi.org/10.5194/egusphere-egu23-11550, 2023.

EGU23-11680 | ECS | Posters on site | SSS4.5

Interplay between aboveground plant biodiversity, soil organic matter, and soil microbial functional diversity in a grazed Danish island ecosystem 

Joanne O'Keeffe, Jeppe Aagaard Kristensen, Camilla Fløjgaard, and Carsten W. Müller

Animal grazing is known to affect both, soil carbon storage and above and belowground biodiversity. However, we lack a more detailed understanding how specific soil properties might determine biodiversity and soil carbon storage as affected by grazing. Thus, in the present work we aim to connect the geo- and biodiversity with organic matter decomposition functionalities of the soil community, and thus identify how this regulates soil carbon and nitrogen storage. Therefore, we analysed aboveground plant biodiversity, soil microbial functional diversity, and soil organic matter (SOM) characteristics on a summer grazed island (Eskilsø) in a Danish fjord. Specifically, plant biodiversity analyses were conducted and topsoils sampled at thirty plots (4 replicated soil samples per plot) on the ca. 140 ha island. The plots cover the island’s main habitats: salt meadows, meadows, and developing dry grasslands. Soils were analysed for organic carbon (OC), total nitrogen (TN), organic phosphorus (OP), inorganic phosphorus (IP), and pH. Additionally, community level physiological profiles (CLPP) were analysed using the Microresp technique to make inferences about soil microbial functional diversity and activities. 
We are able to demonstrate that plant biodiverse plots contained greater contents and stocks of SOM. This also correlates with an increased soil microbial functional diversity. The findings are in line with the often observed positive interaction between aboveground diversity and belowground functionality of the soil biome in grassland ecosystems, partly due to increased amounts and diversity of rhizodeposits. As microbial activity is important for mediating the turnover of plant derived organic matter into more stable soil OM pools, this reflects the correlation with higher soil OC stocks and thus links to soil carbon persistence. For the studied island ecosystem we are able to demonstrate how the fate of soil organic matter is functionally linked to the interactions between above- and below-ground components of the ecosystem. 

How to cite: O'Keeffe, J., Aagaard Kristensen, J., Fløjgaard, C., and Müller, C. W.: Interplay between aboveground plant biodiversity, soil organic matter, and soil microbial functional diversity in a grazed Danish island ecosystem, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11680, https://doi.org/10.5194/egusphere-egu23-11680, 2023.

EGU23-11986 | ECS | Orals | SSS4.5

Revealing the contributions of the belowground plant root associated microbiome to soil aggregation in agricultural soils 

Marta Gil Martinez, Eve Isobel Galen, Simon Andersen, Eva Faurholdt Jørgensen, Lea Ellegaard-Jensen, Thanassis Zervas, Carsten Suhr Jacobsen, Flemming Ekelund, Kristian Holst Laursen, and Rasmus Kjøller

Soil aggregation is an important physical indicator of soil health. Aggregation result from biological and physicochemical processes in which primary soil particles and organic matter are bound. Biotic-mediated soil aggregation is mainly assisted by fungal hyphae facilitating macroaggregate formation through mechanical union and exudation of binding agents. In agricultural soils, many crops establish a symbiosis root- arbuscular mycorrhizal (AM) fungi where the extensive mycelium directly connects roots and soil aggregates. However, the relative importance and specific contributions of the belowground plant root associated microbiome to soil aggregation is still not known.

We set up a pot experiment under controlled conditions to investigate the aggregate stability of different crop species in an organic agricultural sandy soil. We manipulated the soil microbiome by planting 10 common crop species with different mycorrhizal status, 5 species with AM fungal symbiosis (barley, clover, maize, oat and wheat) and 5 non-mycorrhizal species (buckwheat, lupine, quinoa, rapeseed and spinach). We filled each pot with sandy soil sieved to 2 mm and added two sealed mesh bags, with mesh size of 40 µm to avoid roots but promoting hyphal entrance. Mesh bags were filled with the same sandy soil further sieved to 1 mm and 0.25 mm, respectively. All pots were harvested in the 10th week and biomass, roots and soil samples were processed.

Soil aggregate stability, measured by wet sieving method, showed that soils with AM fungal symbiosis became more aggregated as these soils presented a higher % in soil fractions > 500 µm and > 250 µm. Moreover, non-mycorrhizal crops soils showed a significantly higher free mineral fraction (< 63 µm), i.e. a loss of soil aggregation. Still, our results showed that no crop species, independently their mycorrhizal status, were able to form aggregates above the sieving size and not all crop species conferred the same soil aggregation. Among mycorrhizal crop species, barley and wheat showed a higher soil aggregation compared to oat and maize. Curiously, barley and wheat were the crop species with the highest AM root colonization, 74 and 69 %, respectively, as well as the soils with the highest microbial biomass C, N and their ratio. Our results showed that exists a positive correlation between microbial biomass, root colonization and soil aggregation. Further analysis will provide data on soil mycelial length as well as fungal and bacterial community profiles.

In conclusion, the mycorrhizal status of different crop species revealed the key role of AM fungi in soil aggregation and its relationship with microbial biomass; however, not surprisingly, the effects are species dependent. Our forthcoming data of the soil microbial communities and their functionality will further reveal which groups have a direct effect on soil aggregation.

How to cite: Gil Martinez, M., Galen, E. I., Andersen, S., Faurholdt Jørgensen, E., Ellegaard-Jensen, L., Zervas, T., Jacobsen, C. S., Ekelund, F., Laursen, K. H., and Kjøller, R.: Revealing the contributions of the belowground plant root associated microbiome to soil aggregation in agricultural soils, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11986, https://doi.org/10.5194/egusphere-egu23-11986, 2023.

EGU23-12246 | ECS | Posters on site | SSS4.5

Fungal root endophytes and their role in carbon to nitrogen exchange with plants 

Alberto Canarini, Jinsen Zheng, Keisuke Koba, Joana Séneca, Kazumichi Fujii, Saori Furukawa, Mie Honjo, Hiroshi Kudoh, Takanori Nishino, Yoshihiro Kobae, Kei Hiruma, Kazuhiko Narisawa, Katie Field, Yin-Tse Huang, Toby Kiers, and Hirokazu Toju

Root fungal endophytes are present in most plants and co-occur with other mycorrhizal fungi. Their intraradical colonization suggests a special, differentiated relationship with host plants and increases opportunities for close interactions between hosts and fungal symbionts (e.g., carbon to nutrient exchange or hormone signalling). During the symbiosis between plant and arbuscular mycorrhizal fungi (AMF), specific trading features are established. These features have been incorporated into the biological market hypothesis, where dynamics of carbon to nutrient trading in the plant‐mycorrhizal fungal mutualism are compared to trades in a market economy. Multiple examples of similar dynamics have been shown for root endophytic fungi: soil nutrients are transported to the plant in exchange for carbon. However, plants have been shown to be able to reward AMF that exchange larger amount of nutrients (and vice versa), while at least some root fungal endophytes have been described as “by-product mutualists”, where the fungal symbiont enhances the performance and fitness of their host plant by providing benefits, but not requiring major investments from the host. Whereas AMF have received large attention, the role of fungal endophytes in carbon to nutrient exchange with plants remains largely uninvestigated.

In this study we aimed at developing a controlled system to evaluate effects of multiple fungal endophytes (Colletotrichum tofieldiae and Cladophialophora chaetospira) on a model plant species (Lotus japonicus) and their role in the carbon to nitrogen exchange in the presence of different nitrogen sources (organic and inorganic). We further developed this controlled system to include plants colonized by AMF. Two-compartment petri dishes were used to achieve plant root colonization in a nutrient limited compartment and allow separation of nutrient sources only accessible by the fungal endophytes. We performed dual 15N and 13CO2 pulse-labelling experiments to trace the fate of plant carbon into fungal biomass and of different nitrogen sources into plant aboveground tissues. We analysed root for RNA sequencing to gain insights into the genetic controls over the observed dynamics.

We successfully established a controlled system and found that C. tofieldiae can elicit positive effects on plant growth and nitrogen acquisition. These effects are dependent on the nutrient source to which the fungus has access to, with positive effects displayed in the presence of organic nitrogen. Plants exchange relatively less carbon to C. tofieldiae accessing organic nitrogen. Root transcriptome shows specific changes in response to root fungal colonization which are dependent on the nitrogen source available to the fungal endophyte. Furthermore, the presence of AMF did not modify the observed carbon to nitrogen exchange dynamics.

In conclusion we show that the root fungal endophyte C. tofieldiae can play an important role for plant nutrient acquisition in the presence of organic nitrogen. The trade of nitrogen for plant carbon displays different features from the AMF symbiosis (i.e., higher amount of nitrogen is not rewarded with plant carbon investment) and different gene regulations are involved. Our results indicate complementarity between C. tofieldiae and AMF during root colonization, offering mechanistic explanations for the concomitant presence of AMF and fungal endophytes in terrestrial ecosystems.

How to cite: Canarini, A., Zheng, J., Koba, K., Séneca, J., Fujii, K., Furukawa, S., Honjo, M., Kudoh, H., Nishino, T., Kobae, Y., Hiruma, K., Narisawa, K., Field, K., Huang, Y.-T., Kiers, T., and Toju, H.: Fungal root endophytes and their role in carbon to nitrogen exchange with plants, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12246, https://doi.org/10.5194/egusphere-egu23-12246, 2023.

Earthworms may act as double-edged swords for soil organic matter (SOM). While they can enhance organic matter (OM) mineralization via increased microbial activity they can also elevate OM stabilization in aggregates as particulate or mineral-associated OM. In this study, we will test this potentially opposing impact in beech (Fagus sylvatica L.) forests on limestone, a forest ecosystem with particularly high earthworm activity. A specific focus will be on OM transformation along the continuum from the forest floor (O horizons) to mineral soil (A horizons). The forest floor can represent a substantial OM-pool which is an important source for SOM formation via bioturbation or leaching but can be vulnerable to alterations due to climate change. In an extended lab mesocosm experiment, we will incubate local earthworm species in soil columns consisting of O and A horizons from four beech forest sites along an elevation gradient from 550 to 1250 m in the Swiss Jura Mountain range. Along this gradient, the dominating forest floor type is mull with its thickness increasing with altitude. We will establish the following three treatments (1) control with soil and unlabeled litter, (2) with soil and labeled litter and (3) with soil, labeled litter, and earthworms. For this setup, the Ol horizon will be replaced with beech litter highly enriched with 13C, 15N, and 2H. Soil respiration (CO2) and leaching (C, N, and H in dissolved OM) will be repeatedly measured. Our setup will allow for a separation of fluxes from the O horizons and the A Horizon. After approximately 4, 7, and 10 months each, a subset of mesocosms will be harvested to investigate isotope enrichment in earthworm biomass, earthworm casts, physical soil fractions, PLFAs, and microbial necromass. This will allow us to establish a mass balance of beech litter turnover as affected by earthworms for a time scale representative of one vegetation period. Fluxes of unlabeled OM will inform on the fate of inherent SOM. We expect that (1) following an initial colonization phase, earthworms will stimulate labeled litter mineralization and enhance litter transfer to aggregate fractions while not affecting the total SOM stock. (2) In the long term, less of the labeled material will be mineralized and more SOM stabilized in aggregate fractions will be recycled.

How to cite: de Jong, P., Schleppi, P., and Hagedorn, F.: Earthworms as double-edged swords for organic matter turnover from forest floor to mineral soil – a mesocosm experiment with labeled beech litter, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12586, https://doi.org/10.5194/egusphere-egu23-12586, 2023.

EGU23-13605 | Posters on site | SSS4.5

Long-term manuring enhances glomalin-soil-carbon sequestration by increasing its recalcitrance and macro-aggregation 

Hongbo Yang, Jeroen Meersmans, Gilles Colinet, Wenju Zhang, and Qiong Xiao

It’s well known that agroecosystems have a great carbon sequestration potential. Within this process plays Arbuscular mycorrhizal fungi (AMF) an important role. Glomalin is a recalcitrant carbon fraction processed from AMF, its accumulation in response to fertilization is unclear. Here, we used a 30-year various fertilization experiment, including CK, NPK, NPKM, NPKS, M, NPKMR, and Fallow treatments, to observe the temporal trend of GRSP in bulk soil as well as across different aggregates. Meanwhile, we combined soil abiotic (pH, nutrients, MWD, GRSP chemical composition) and biotic (AMF biomass and diversity) properties to distinguish the mechanisms of long-term different fertilization on GRSP accumulation. Our results showed that GRSP content increased with time under both the fertilization and fallow treatment, but remained unchanged under the CK treatment. Manuring (M, NPKM, NPKMR) significantly increased GRSP content by increasing recalcitrance (aromatic) C in GRSP and mass percentage of macroaggregates (>0.25mm) compared with no (CK) and mineral fertilization (NPK) treatments. Manuring increased mean weight diameter (MWD) and GRSP content in macroaggregates (>0.25mm), relative to CK and NPK. There was a significant positive correlation between MWD and GRSP content in macroaggregates (>0.25 mm). Organic fertilizer also increased the proportion of aromatic C in GRSP, AMF biomass and diversity in cropland. Random forest and variance partitioning analysis showed that chemical composition of GRSP and aggregate stability together controlled the accumulation of GRSP. The structural equation model indicated that AMF properties regulate soil aggregate stability and composition of GRSP, which mediates the effects of fertilization on GRSP accumulation. In summary, long-term manuring promotes the GRSP accumulation, mainly be ascribed to the increased of AMF biomass, diversity, corresponding GRSP recalcitrance and aggregate stability. This study contributes to the understanding of the fertilization impacts on GRSP accumulation, and provides a feasible way forward for long-term soil carbon sequestration in sustainable agriculture.

 

How to cite: Yang, H., Meersmans, J., Colinet, G., Zhang, W., and Xiao, Q.: Long-term manuring enhances glomalin-soil-carbon sequestration by increasing its recalcitrance and macro-aggregation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13605, https://doi.org/10.5194/egusphere-egu23-13605, 2023.

EGU23-14905 | ECS | Posters on site | SSS4.5

Increased tundra root biomass offset invasive earthworm effects on SOC decomposition 

Hanna Jonsson, Gesche Blume-Werry, Adrian Wackett, Emeli Arvidsson, Oscar Lundgren, and Jonatan Klaminder

Arctic soils store nearly half of the global soil organic carbon, but what will happen with this large carbon pool if soil macrofauna, able to ingest organic matter accumulated at depths in the soil, establish in the Arctic? The question is justified as emerging evidence suggests that low soil organic carbon (SOC) turnover rates in high latitude ecosystems could, in addition to abiotic factors, partly be due to the current lack of larger detritivores that can stimulate the breakdown of organic matter. Earthworms are large detritivores increasing their distribution into arctic ecosystems. With potential to both increase stabilisation and decomposition of SOC, but also enhance plant productivity, it has been difficult to determine what net effect earthworms have on ecosystem C storage. The scientific debate around this ‘earthworm dilemma’ has however primarily focused on the fate of SOC in response to earthworms, leaving cascading effects on plant productivity largely undiscussed.

Here, we use a four-year outdoor experiment to study the effects of introducing earthworms to tundra vegetation types on both plant biomass (above and belowground) and SOC. We found that earthworms invasive to the Arctic: i) reduced the SOC pool beneath herb dominated tundra while they increased the SOC pool under dwarf-shrub dominated tundra; ii) increased the below ground biomass in both vegetation types; and iii) increased the total plant biomass C to the degree that it offset the SOC losses from the herb dominated soil. In the dwarf-shrub vegetation, earthworms increased both the plant C pool and the SOC pool resulting in a net increase of the ecosystem C stock. We highlight that the effect on root growth seems of great importance when predicting how ecosystem C sequestering responds to invasive earthworms. Both through increased plant biomass C but also through increased deposition of persistent root-derived organic matter.

How to cite: Jonsson, H., Blume-Werry, G., Wackett, A., Arvidsson, E., Lundgren, O., and Klaminder, J.: Increased tundra root biomass offset invasive earthworm effects on SOC decomposition, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14905, https://doi.org/10.5194/egusphere-egu23-14905, 2023.

EGU23-16494 | ECS | Posters on site | SSS4.5

Characterization of cellulose decomposed by saprotrophic fungi using Raman spectroscopy 

Ashish Ahlawat and Dimitrios Floudas

Wood decomposition has been studied extensively due to its importance in wood deterioration and carbon cycling processes. Wood decaying fungi are categorised into white rot, soft rot and brown rot. White rot fungi have an enzymatic mechanism by which they can digest lignin and crystalline cellulose. Instead, brown rot fungi lack the enzymes to digest lignin and crystalline cellulose. Several hypotheses have been made on the mechanism by which brown rot fungi mine carbon out without the required enzymes mainly focussing on extracellular metabolites and metal ions. Here, we investigate chemical and structural modifications on cellulose produced by saprotrophic fungi using Raman specrtroscopy under different conditions. In additions, known modifications introduced by chemicals on cellulose will also be compared to fungal changes on cellulose.

How to cite: Ahlawat, A. and Floudas, D.: Characterization of cellulose decomposed by saprotrophic fungi using Raman spectroscopy, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16494, https://doi.org/10.5194/egusphere-egu23-16494, 2023.

EGU23-16863 | Orals | SSS4.5

Effect of agricultural soil conservation practices on arbuscular mycorrhizal fungal and bacterial communities and crop productivity in two agro-ecological zones in Italy and Zambia 

Elisa Pellegrino, Gaia Piazza, Blessing Mhlanga, Myriam Arcidiacono, Christian Thierfelder, Marco Nuti, and Laura Ercoli

Agricultural production in regions such as sub-Saharan Africa (SSA) is very low as compared to other regions such as the Mediterranean area (MED). Differences are mainly due to agricultural input use which is generally lower in SSA. Indeed, in both regions, where unsustainable agricultural practices are largely applied although varying in intensification, soil organic carbon degradation and soil biodiversity decline are widespread issues. However, whether changes of soil microbial diversity have consequences on agroecosystem services, like crop productivity, in such agro-ecological zones is still scarcely investigated at field level. This long-term field study aimed to understand how different agricultural practices, such as conservation agriculture (CA)-based systems, affect soil microbiome (i.e., arbuscular mycorrhizal fungi (AMF) and bacteria) and their implications on crop productivity. We selected two contrasting soils and agro-ecological zones, in Italy (Centre of Agro-Environmental Research “Enrico Avanzi” – CiRAA – in Pisa) and in Zambia (Msekera Research Station – MRS – in Chipata), to investigate the responses of AMF and bacterial community to CA practices. The experiment at CiRAA was started in 1993 on a silt loam soil and was set up as a split plot design to test tillage regime as the main plot factor and nitrogen (N) fertilization rate as the sub-plot factor. Tillage regimes were conventional tillage (CT) and minimum tillage (MT), while the N fertilization rates were no fertilization (N0) and fertilized with 200 kg N ha-1 split into three applications (N200). For all treatments, wheat (Triticum aestivum L.) was rotated with soybean (Glycine max L.) in one-year rotations. The experiment at MRS was started in 2012 on a sandy clay loam soil and tested three treatments: CT and maize (Zea mays L.) as sole crop, no-tillage plus mulch (NT+M), and no-tillage plus mulch and rotation (NT+M+R) with maize in rotation with soybean. The climate is cold humid Mediterranean (Csa) at CiRAA and warm temperate with dry winters and hot summers (Cwa) at MRS. DNA was extracted from soil: for AMF PCRs were carried out amplifying part of the SSU, ITS1, 5.8S, ITS2 and part of the LSU of the 18S rRNA region, while for bacteria PCRs were carried out amplifying the V3 and V4 regions of the 16S rRNA region. AMF were characterized by a cloning and Sanger sequencing approach (ca. 1700 bp), whereas bacteria by an Illumina sequencing approach (ca. 630 bp). In both zones, AMF and bacterial composition was similar among CA systems, whereas the long-term implementation of the CA systems resulted in more diverse microbial communities across the agro-ecological zones. CA systems led to positive interactions between AMF and bacterial communities and more complex soil microbial networks. This ultimately led to an improved crop yield. At MRS, soybean as a rotational crop enriched bacterial diversity and within the AMF communities, members of the family Gigasporaceae were more dominant. We finally identified the microbial taxa highly related to crop productivity, providing cause-effect relationships for the involvement of microbes in crop productivity.

How to cite: Pellegrino, E., Piazza, G., Mhlanga, B., Arcidiacono, M., Thierfelder, C., Nuti, M., and Ercoli, L.: Effect of agricultural soil conservation practices on arbuscular mycorrhizal fungal and bacterial communities and crop productivity in two agro-ecological zones in Italy and Zambia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16863, https://doi.org/10.5194/egusphere-egu23-16863, 2023.

EGU23-16888 | Posters on site | SSS4.5

Armored mesh bags: collecting mycelium of mycorrhizal fungi in a tropical rainforest 

Andrey Zuev, Ina Schaefer, Nguyen Van Thinh, and Anna Zueva

Mycorrhizal fungi play a vital role in soil processes and form a large part of belowground biodiversity in tropic ecosystems. Unlike temperate forests, many tree species in tropical stands are dominated by arbuscular mycorrhizal fungi (AMF), which form high amount of extraradical mycelium and even rhizomorphs, penetrating both soil and leaf litter. The quantification of mycelium biomass in natural systems often being conducted with the use of sand filled in-growth mesh bags made of nylon mesh [1]. The use of plastic polymer for mesh bags in temperate systems is justified by low bioavailability of the material that can be hardly decomposed by soil bacteria and fungi or penetrated by roots or soil invertebrates. In a number of tropical forests, the activity of invertebrates is more aggressive, mostly due to the termites foraging, resulting in the disruption of the integrity of the mesh bags and consequent samples loss.

Here we introduce the use of dual-walled in-growth mesh bags made of nylon and stainless steel. Its relevance was attested in Dong Nai (Cat Tien) National Park in Southern Vietnam. The harvested biomass of extraradical EMF mycelium and taxonomic composition of EMF and AMF fungi was compared in regular and dual-walled in-growth mesh bags across two tropical rainforests, dominated by both EMF and AMF associated tree species. The biomass was accessed with PLFA analysis for fungal biomarkers 18:2ω6,9, 18:1ω9 [2] and 18:0 [3]. The taxonomic composition of extraradical mycelium from harvested in-growth mesh bags was studied with new-generation sequencing, including specific primer pair WANDA/AML2 for the SSU ribosomal RNA gene of AMF fungi and ITS fragment (primer pair ITS3/ITS4) for ectomycorrhizal fungi.

Double-walled mesh bags remained completely intact, while about 40% of regular mesh bags were damaged by termite activity after 180 days of exposure. The biomass of extraradical mycelium of ectomycorrhizal fungi was comparable between forests dominated by EMF and AMF associated trees and reached 114.5 and 122.1 µg of «fungal» carbon g-1 of substrate respectively. The total amount of the three measured PLFA biomarkers did not differ between both variants of in-growth mesh bags and surrounding soil, while the median values were slightly higher for mesh bags compared to soil (1.9 and 1.6 µg g-1 of substrate respectively). Application of ITS fragment was 100% positive among harvested mycelium samples from both forests, while AMF fungi were detected in 62% of samples from the forest dominated by AMF-associated trees and 70% samples from the forest dominated by EMF-associated trees.

This study was supported by Alexander von Humboldt Foundation (project 3.4-1071297-RUS-IP).

References:

[1] Wallander H, Nilsson LO, Hagerberg D, Bååth E (2001) Estimation of the biomass and seasonal growth of external mycelium of ectomycorrhizal fungi in the field. New Phytol 151:753–760. https://doi.org/10.1046/j.0028-646x.2001.00199.x

[2] Ruess L, Chamberlain PM (2010) The fat that matters: Soil food web analysis using fatty acids and their carbon stable isotope signature. Soil Biol Biochem 42:1898–1910. https://doi.org/10.1016/j.soilbio.2010.07.020

[3] Chen J, Ferris H, Scow KM, Graham KJ (2001) Fatty acid composition and dynamics of selected fungal-feeding nematodes and fungi. Comp Biochem Physiol B Biochem Mol Biol 130:135–144. https://doi.org/10.1016/S1096-4959(01)00414-6

How to cite: Zuev, A., Schaefer, I., Van Thinh, N., and Zueva, A.: Armored mesh bags: collecting mycelium of mycorrhizal fungi in a tropical rainforest, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16888, https://doi.org/10.5194/egusphere-egu23-16888, 2023.

EGU23-802 | ECS | Orals | SSS4.7

Adaptation dampens the response of microbial community respiration to temperature 

Rebecca Millington, Francisca C. García, and Gabriel Yvon-Durocher

Microbial respiration in soils controls a key flux in the global carbon cycle, yet its sensitivity to warming remains uncertain. Respiration rates increase exponentially with rapid warming, but the response is dampened over time. Several possible mechanisms have been suggested to explain the response: taxon-level adaptation, changes to community composition and changes to community biomass. However, the role played by each mechanism has not been resolved. Here, we separate the relative importance of these mechanisms, finding that taxon-level adaptation has a larger role in controlling the dampening of the temperature sensitivity of community respiration rather than changes to community composition. We used a novel dataset of five taxa incubated simultaneously in monoculture and as a community across a range of temperatures in a controlled laboratory environment, which showed the expected dampening of community respiration. Taxon-level adaptation, changes to community composition and changes to community biomass were all observed, with a new mathematical model of taxon-level adaptation revealing that the dampening of taxon-level respiration was due to changes in maintenance respiration and cell mass. The importance of taxon-level adaptation in the dampening of community respiration response to temperature reconciles disagreement from previous studies and provides evidence for a robust representation of microbial processes in carbon cycle models.

How to cite: Millington, R., García, F. C., and Yvon-Durocher, G.: Adaptation dampens the response of microbial community respiration to temperature, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-802, https://doi.org/10.5194/egusphere-egu23-802, 2023.

Microorganisms catalyze almost all transformation processes of organic carbon in soil and are largely responsible for changes in soil carbon cycle feedback to climate change. To account for the microbial role in regulation of carbon-climate feedback, several dozens of microbial models have been developed in the past decades, mostly based on an idea that microbial biomass or microbial extracellular enzymes control decomposition of soil organic carbon (SOC). However, these idea-based models may or may not be well supported by empirical evidence. This presentation will show how data have been used to develop and test microbial models with three case studies. The first case study is to infer microbial mechanisms from observed patterns of lignin decomposition. Our study indicates that time-dependent growth and mortality of the microbial community, instead Michaelis-Menten kinetics, control microbial decomposition of lignin. The second case is to incorporate observed mechanisms into a carbon cycle model. Our meta-analysis indicates that changes in SOC under experimental warming and nitrogen addition are closely related to changes in microbial oxidative enzyme activities but not in hydrolytic enzyme activities. We directly incorporated this observed mechanism into a terrestrial ecosystem model to predict SOC changes. The third case study is to confront microbial models with nearly 58,000 vertical profiles of SOC over the globe to identify mechanisms underlying global SOC storage. Overall, scientists have developed different microbial models to explore all kind of possibilities while data offer reality. The data-model integration helps identify the most probable mechanisms under a Bayesian inference framework.

How to cite: Luo, Y.: Data-driven approaches to soil microbial modeling, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1751, https://doi.org/10.5194/egusphere-egu23-1751, 2023.

EGU23-2882 | Orals | SSS4.7

Response of soil organic matter turnover to soil salinization and climate warming 

Shang Wang, Bahar Razavi, Sandra Spielvogel, and Evgenia Blagodatskaya

Climate change is turning soil salinization into a global problem due to the increasing frequency and severity of coastal salt and brackish water ingress. How increasing salinity affects microbial metabolic activity and its consequences for matter and energy turnover under climate warming remain unclear. Thus, we conducted a lab incubation experiment to explore the interactive effects of salinization and warming on microbial and enzymatic functional traits related to the CO2 (matter) and heat (energy) losses in the course of glucose metabolism.

Soil from coastal grassland was artificially salinized to, middle (2.06 mS cm-1) and high (3.45 mS cm-1) levels by gradually adding salt solution, while the soil with ambient salinity (0.49 mS cm-1) was defined as control. Effect of realistic warming (+2 ℃) on CO2 emission and heat release from soil amended with glucose was estimated by the respirometer Respicond V and microcalorimeter TAM Air, respectively. Energy and carbon use efficiency, calorespirometric ratio, microbial growth parameters and enzyme kinetics were determined in the salinity gradient.

Despite cumulative CO2 emission and heat release were not affected by soil salinity, we observed gradual delay in glucose induced respiration (GIR) and heat release with the increasing salinity level. In contrast, warming facilitated both GIR and heat release, and increased the cumulative CO2 by 8-14%, but had no effect on the cumulative heat.

Before glucose addition, high salinity greatly reduced the C-acquiring enzyme activities (β-D-glucosidase, cellobiohydrolase) by 17-39% compared with control, while an activity of the P-acquiring enzyme (acid phosphomonoesterase) notably increased by 24 and 82% under middle and high salinity, respectively. In soil activated with glucose, high salinity greatly increased the activities of both C- and P-acquiring enzymes up to 74 and 30%, respectively, compared with control. Surprisingly, irrespectively of microbial activation by glucose, the N-acquiring enzyme activity (leucine aminopeptidase) was not affected by salinity.

The interactive effect of soil salinity and climate warming on the fate of soil organic matter, energy and carbon use efficiency, calorespirometric ratio and microbial community will be discussed in our presentation.

How to cite: Wang, S., Razavi, B., Spielvogel, S., and Blagodatskaya, E.: Response of soil organic matter turnover to soil salinization and climate warming, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2882, https://doi.org/10.5194/egusphere-egu23-2882, 2023.

EGU23-2918 | Orals | SSS4.7

Decomposition kinetics as an optimal control problem 

Stefano Manzoni, Arjun Chakrawal, and Glenn Ledder

Microbial explicit models are constructed by linking decomposition (the process of organic matter break-down) and substrate uptake to microbial growth, respiration, and mortality. Therefore, the specific choice of the decomposition and/or uptake kinetics affects how in the model microbes grow and die, with consequences for carbon stabilization. There are well-established theories for extracellular enzymatic reactions and for substrate transport and uptake by cells, which allow deriving formulas for the decomposition and uptake kinetics, respectively. These laws account for microbial growth (e.g., in the Monod equation), but implicitly assume that microbial traits encoded in model parameters are static. Yet, microbes adapt to the environmental conditions they experience, resulting in temporally dynamic traits at both population and community levels. Adaptation is a result of natural selection for the fittest organisms. Therefore, we can describe adapted microbes by assuming they maximize their growth for given environmental conditions (e.g., limiting the amount of available resources) and given metabolic tradeoffs (e.g., decreasing efficiency of substrate to biomass conversion at high growth rates). In this contribution, we translate this assumption into a formulation of decomposition as an optimal control problem, where the objective is the maximization of cumulative growth, the constraint is imposed via a substrate mass balance, and the control parameter is the realized substrate uptake rate, assumed to be the outcome of optimally adapted production of extracellular enzymes and cellular uptake capacity. This optimal control problem is solved analytically for a simple case study (one substrate, homogeneous microbial community), leading to optimal decomposition kinetics that scale with the square root of substrate carbon content (different from Monod or Michaelis-Menten equations) and with a strong effect of maintenance respiration. If maintenance respiration is high, the kinetics flattens, and the optimal decomposition rate remains larger than zero even as the substrate is depleted. This means that the optimal decomposition rate approaches zero-order kinetics and exhibits increasingly high values as maintenance costs are increased. Interestingly, a tradeoff emerges between the rate of substrate consumption at the beginning of decomposition and microbial carbon use efficiency (ratio of growth over uptake). At high resource availability, efficient but slow-growing microbes are selected, whereas at low resource availability inefficient but fast-growing microbes are favored because they can more effectively compete for the limited resources. These results suggest that optimization methods offer an alternative way to define decomposition kinetics laws that account for microbial adaptation.

How to cite: Manzoni, S., Chakrawal, A., and Ledder, G.: Decomposition kinetics as an optimal control problem, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2918, https://doi.org/10.5194/egusphere-egu23-2918, 2023.

EGU23-3290 | ECS | Orals | SSS4.7

Particulate organic matter as electron acceptor for microbial respiration in peatlands 

Rob A. Schmitz, Nikola Obradović, Martin H. Schroth, and Michael Sander

Northern peatlands store approximately 500 Pg carbon in the form of peat particulate organic matter (POM). Ombrotrophic bogs are peatlands that only receive water and nutrients through precipitation, creating anoxic, water-logged soils deprived of inorganic terminal electron acceptors (TEAs). In the absence of suitable TEAs for anaerobic respiration, methanogenesis prevails as final step in the degradation of organic matter and is expected to result in equimolar CO2:CH4 production ratios. However, field and laboratory studies revealed higher CO2:CH4 production ratios than expected based on low concentrations of canonical inorganic TEAs, suggesting the presence of a previously unrecognized TEA used in anaerobic microbial respiration. It has been hypothesized that oxidized particulate organic matter (POMox) functions as TEA, explaining elevated CO2:CH4 production ratios. Through seasonal water table fluctuations, POM gets re-oxidized abiotically, creating a microbial hotspot at the oxic-anoxic interface. To investigate these processes, incubation studies linking CO2 and CH4 production to the reduction of POMox are indispensable. Here, we present data strongly indicating that POM collected from ombrotrophic bogs in Sweden functions as TEA in anaerobic respiration, suppressing methanogenesis. We ran anoxic incubations with various initial ratios of oxidized and reduced POM and hence a range of starting electron accepting capacities, which we quantified using a novel spectrophotometric assay. Increasing contributions of POMox resulted in higher CO2:CH4 production ratios and prolonged transition times from anaerobic respiration to methanogenesis. These findings strongly support the use of POM as TEA, suppressing methanogenesis until POMox was depleted through respiration. Additionally, we developed an incubation system that allowed amending incubations with 13C-labeled substrates to selectively track their conversion to 13CO2 and 13CH4. Using 13C-glucose we successfully linked 13CO2 and 13CH4 formation ratios to POM redox state. Our results advance our understanding of microbial carbon turnover in peatlands in the present and future climate.

How to cite: Schmitz, R. A., Obradović, N., Schroth, M. H., and Sander, M.: Particulate organic matter as electron acceptor for microbial respiration in peatlands, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3290, https://doi.org/10.5194/egusphere-egu23-3290, 2023.

Soil imaging visualizes and quantifies processes in soil hotspots across space and time involving microorganisms, roots and carbon and nutrient sources, thereby helping to elucidate mechanisms. A wide range of individual approaches exists to determine spatial distributions of soil pH (optodes), root exudation and pesticides (14C phosphor imaging), fertilizers (33P phosphor imaging), nutrient fluxes (DGT), etc.

Since processes and mechanisms are clearly multi-factorial, combining individual approaches is key for any real understanding of soil processes. Multi-imaging comes with a set of challenges as firstly, scales need to be bridged as imaging methods operate at different spatial scales from cm to nm. Secondly, their time scales vary from minutes to days. Thirdly, the sequence of method application needs careful consideration as some methods leave behind chemicals, which may interfere with other measurements.

Imaging methods were initially developed for laboratory-controlled conditions, and only several were already adapted for field conditions. We will present the challenges for application soil imaging techniques in the field and problems related to sequential application. We will suggest a workflow for multi-imaging, which includes suggestions on coupling methods to study defined soil process, the sequence of the methods application, image alignment, hotspot thresholding and analysis, co-localization of images and quantitative image analysis. The perspectives, advantages and challenges of multi-imaging approaches will be comprehensively discussed.

How to cite: Bilyera, N., Banfield, C. C., and Dippold, M. A.: Perspectives and methodological challenges of imaging soil hotspots and coupling soil images of different origin in multi-imaging approach, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4445, https://doi.org/10.5194/egusphere-egu23-4445, 2023.

Peatlands are a globally important carbon sink, storing up to 455 Pg C as soil organic carbon. One of the drivers of this immense storage relates to the extremely low rate of peat decomposition, which is ultimately regulated by the bacterial community of these peat soils. Previous studies note that vegetation type (e.g., bog vs. fen), depth of peat, water level and pH may determine bacterial composition in peatlands. However, in terms of global patterns, the key controlling variables remain elusive due to a lack of data synthesis and direct experimental evidence. To identify bacterial community composition in global peatlands and key controlling variables, we conducted a field survey of 7 peatland sites in Korea, a meta-analysis of published data from over 95 peatland sites, and pH-manipulation experiments in the UK, by employing NGS analysis targeting 16sRNA.

Although immense variabilities in bacterial composition among sites were observed, pH appears to be a dominant controlling variable shaping bacterial community structure. For example, high pH is associated with higher relative abundance of Proteobacteria, while low pH appears to be related to the abundance of Acidobacteria. Variations of bacterial composition at different depths or vegetation types in a single site are smaller than those among different locations, suggesting that environmental changes in local conditions such as water level fluctuation and carbon availability may be less critical than the mean temperature or overall pH of a given site. Our study further suggests that the long-term changes in pH may have much greater implications than previously assumed, with peat decomposition likely to accelerate during the current recovery from acidification being experienced by peatlands across the world.

 

How to cite: Kang, H. and Freeman, C.: Patterns of bacterial composition in global peatlands and their controlling variables, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4559, https://doi.org/10.5194/egusphere-egu23-4559, 2023.

EGU23-5249 | Orals | SSS4.7

Stoichiometrically constrained soil microbial community adaptation modeled with SESAM 

Thomas Wutzler, Bernhard Ahrens, and Marion Schrumpf

Describing the coupling of nitrogen (N), phosphorus (P), and carbon (C) cycles of land ecosystems requires understanding microbial element use efficiencies of soil organic matter (SOM) decomposition. These efficiencies are studied by the soil enzyme steady allocation model (SESAM) at decadal scale. The model assumes that the soil microbial community and their element use efficiencies develop in a way that maximizes the growth of the entire community. Specifically, SESAM approximated this growth optimization by allocating resources to several SOM degrading enzymes proportional to the revenue of these enzymes, called the Relative approach. However, a rigorous mathematical treatment of this approximation has been lacking so far. 

Therefore, this study derives explicit formulas of enzyme allocation that maximize total return from enzyme reactions, called the Optimal approach. When comparing predictions across these approaches, we find that the Relative approach is a special case of the Optimal approach valid at sufficiently high microbial biomass. However, at low microbial biomass, it overestimates  allocation to the enzymes having lower revenues.

The model finding that a smaller set of enzyme types is expressed at low microbial biomass provides another hypothesis for why some substrates in soil are preserved over decades although being decomposed within a few years in incubation experiments. This study is another step in integrating a simple representation of an adaptive microbial community into coupled stoichiometric CNP SOM dynamic models. 

How to cite: Wutzler, T., Ahrens, B., and Schrumpf, M.: Stoichiometrically constrained soil microbial community adaptation modeled with SESAM, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5249, https://doi.org/10.5194/egusphere-egu23-5249, 2023.

EGU23-5268 | ECS | Orals | SSS4.7

Using the Calorespirometric Ratio to investigate the metabolism of a growing microbial community dominated by Firmicutes in glucose-amended soil 

Martin-Georg Endress, Ruirui Chen, Evgenia Blagodatskaya, and Sergey Blagodatsky

Soil microorganisms rely on coupled fluxes of carbon and energy from the decomposition of organic substrates to fuel their maintenance and growth requirements. This complex coupling depends on environmental conditions as well as the specific metabolic reactions carried out by the microbial community, but our understanding of the principles governing these dynamics is still limited. The joint analysis of both matter and energy fluxes and in particular the linkage of the microbial carbon and energy use efficiencies (CUE and EUE) during substrate turnover have the potential to elucidate the underlying metabolic pathways. However, such evaluations remain rare.

In this study, we present measurements of heat and CO2 release from soil after batch input of glucose along with estimates of microbial biomass and community composition. The results reveal a temporal variation in the ratio of heat to CO2 release (Calorespirometric Ratio, CR) that is inconsistent with simple aerobic decomposition of the substrate. In addition, we find that the dynamics are dominated by the growth of Firmicutes, whose relative abundance increases from 2 percent of initial biomass to almost 50 percent over the course of the incubation.

To interpret these findings, we developed a dynamic model of carbon and energy fluxes during growth on glucose. The model simulates aerobic respiration as well as anaerobic fermentation to lactate and acetate depending on the time-varying availability of O2 and accounts for activation of the microbial population after initial dormancy. Model simulations capture the complex experimental CR pattern and suggest a gradual depletion of available O2 and a concurrent shift to anaerobic pathways as the main driver of the dynamics. Given the widespread adaptation to anaerobic conditions found in prevalent members of the Firmicutes, this interpretation is consistent with the observed dominance of the phylum. Notably, model variants of lower complexity that do not include fermentation or increasing microbial activity fail to appropriately reproduce the measured CR and biomass.

These results highlight the potential of the joint analysis of matter and energy fluxes in a combined experimental and modeling approach. The evolution of CR over time revealed the presence of complex dynamics even in the simple case of glucose-amended soil samples and provided constraints on the metabolic processes behind those dynamics that align with the available biomass and community composition estimates. By considering the balance of multiple metabolic pathways as well as the concept of microbial activity, our findings offer a more detailed description of temporal microbial carbon and energy use that goes beyond the assumption of constant CUE and EUE. Such an approach will be essential for the investigation of more complicated transformations of organic matter in soil.

How to cite: Endress, M.-G., Chen, R., Blagodatskaya, E., and Blagodatsky, S.: Using the Calorespirometric Ratio to investigate the metabolism of a growing microbial community dominated by Firmicutes in glucose-amended soil, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5268, https://doi.org/10.5194/egusphere-egu23-5268, 2023.

EGU23-5847 | ECS | Orals | SSS4.7

Disentangling the effects of microbial functional diversity and carbon availability on soil organic carbon decomposition 

Swamini Khurana, Rose Abramoff, Elisa Bruni, Bertrand Guenet, Boris Tupek, and Stefano Manzoni

The factors governing stability of soil organic carbon vary from chemical characteristics to physical occlusion from either biotic (such as plant roots, soil fauna and microorganisms) or abiotic agents (such as water). By mediating the decomposition potential, microbial community diversity and structure may play an important role in the fate of soil organic carbon. In this theoretical study, we aim to understand the role of the microbial community diversity and composition in soil organic carbon storage and decomposition. 

We constructed a model describing a microbial process network incorporating diverse organic matter compounds and microbial groups. The microbial groups varied from each other with respect to their affinity to depolymerise, take-up, metabolise and assimilate organic compounds. We allowed for adaptation of microbial communities to available carbon, and competition among microbial groups.  We tested this process network with functionally diverse microbial communities which were subjected to varying carbon availability. This framework allowed us to explore organic carbon decomposition rates and their temporal evolution under different conditions of microbial diversity and carbon availability, as well as the tendency of a soil microbial system to store carbon. 

We found that the microbial community functional diversity is a good predictor of organic carbon decomposition rates. This result suggests that an  organic carbon decomposition rate modifier could be defined based on functional diversity and then included in soil carbon models. Furthermore, we observed that organic carbon decomposition by functionally similar communities in carbon poor conditions slowed down after approximately half of the initial carbon was consumed. In the same conditions, functionally diverse communities with a higher number of biotic agents allowed a more complete decomposition. However, with increasing initial carbon availability, the functional diversity of the microbial community ceased to play a role in soil carbon storage. These results link microbial community diversity and carbon availability to decomposition potential and thus organic carbon stability in soils.

How to cite: Khurana, S., Abramoff, R., Bruni, E., Guenet, B., Tupek, B., and Manzoni, S.: Disentangling the effects of microbial functional diversity and carbon availability on soil organic carbon decomposition, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5847, https://doi.org/10.5194/egusphere-egu23-5847, 2023.

EGU23-6112 | ECS | Orals | SSS4.7

Modelling climate-substrate interactions in microbial SOC decomposition 

Marleen Pallandt, Bernhard Ahrens, Marion Schrumpf, Holger Lange, Sönke Zaehle, and Markus Reichstein

Soil organic carbon (SOC) is the largest terrestrial carbon pool, but it is still uncertain how it will respond to climate change. Especially the fate of SOC due to concurrent changes in soil temperature and moisture is uncertain. It is generally accepted that microbially driven SOC decomposition will increase with warming, provided that sufficient soil moisture, and hence enough C substrate, is available for microbial decomposition. We use a mechanistic, microbially explicit SOC decomposition model, the Jena Soil Model (JSM), and focus on the depolymerization of litter and microbial residues by microbes. These model processes are sensitive to temperature and soil moisture content and follow reverse Michaelis-Menten kinetics. Microbial decomposition rate V of the substrate [S] is limited by the microbial biomass [B]: V = Vmax * [S] *  [B]/(kMB + [B]). The maximum reaction velocity, Vmax, is temperature sensitive and follows an Arrhenius function. Also, a positive correlation between temperature and kMB-values of different enzymes has been empirically shown, with Q10 values ranging from 0.71-2.80 (Allison et al., 2018). Q10 kMB-values for microbial depolymerization of microbial residues would be low compared to those of a (lignified) litter pool. An increase in kMB leads to a lower reaction velocity (V) and V becomes less temperature sensitive at low substrate concentrations. In this work we focus on the following questions: “how do temperature and soil moisture changes affect modelled heterotrophic respiration through the Michaelis-Menten term? Is there a temperature compensation effect on modelled decomposition rate because of the counteracting temperature sensitivities of Vmax and kMB?” We model these interactions under a mean warming experiment (+3.5 °K) as well as three soil moisture experiments: constant soil moisture, a drought, and a wetting scenario.

How to cite: Pallandt, M., Ahrens, B., Schrumpf, M., Lange, H., Zaehle, S., and Reichstein, M.: Modelling climate-substrate interactions in microbial SOC decomposition, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6112, https://doi.org/10.5194/egusphere-egu23-6112, 2023.

EGU23-6453 | ECS | Posters on site | SSS4.7

Numerical comparison of five soil microbial models, in relation to measurable soil organic matter fractions 

Enrico Balugani, Simone Pesce, Celeste Zuliani, and Diego Marazza

The last decade has seen an increase of innovative soil carbon models that takes explicitly into account the microbial community interaction with the soil organic matter, and various state of protection of the soil organic matter itself. This proliferation is fuelled by (a) the recognition that microbial ecology is the main determinant of soil organic carbon mineralization, and (b) that soil organic matter can be protected from microbial degradation in various ways. Of particular interest is the interaction of the organic matter with the mineral fraction of the soil, which can lead to mineral adsorbtion and the formation of soil aggregates. However, the uncertainties about soil microbial ecology and organic matter – mineral fraction have led to the formulation of various soil microbial models, each one modelling some of the aspects of the complex net of interacting processes, but not other. These models often use different assumptions, model structures, and pool definitions. The lack of comparability among models, and the low comparability of models with measurable data, makes it hard to discriminate among them and to use them to assess the driving processes relevant for soil carbon dynamics depending on climatic, soil and vegetation conditions.

A first attempt to compare some of these models has been presented in Sulman et al. (2018); however, the lack of a harmonization framework for the models, and the use of lumped model pools/flows such as soil respiration and bulk soil organic carbon, have led to the conclusion that the uncertainties are too elevated to discriminate among the models.

Here, we propose a framework to harmonize five different soil microbial models among them (MEND, CORPSE, MIMIC, DEMENT, RESOM), and harmonize them with measurable soil organic matter fraction widely recognized as related to processes of interaction with the soil mineral fraction (aggregates, mineral associated organic matter, dissolve organic matter, and particulate organic matter). We reformulated the five models based on this framework, and analysed them on the same parameter space to understand in which regions of said space the models gave results that were substantially different.

The results show that: (a) the model can be clearly distinguished in most regions of the parameters space, (b) it is possible to calculate an index of robustness of the models. This information can help in design specific experiments to test the models and, this way, get insights about the driving processes in certain conditions (different climates, soils, vegetations); moreover, the robustness index can give indication about their applicability to different conditions, which is of utmost importance if they are to inform Earth System Models.

How to cite: Balugani, E., Pesce, S., Zuliani, C., and Marazza, D.: Numerical comparison of five soil microbial models, in relation to measurable soil organic matter fractions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6453, https://doi.org/10.5194/egusphere-egu23-6453, 2023.

EGU23-7231 | ECS | Posters on site | SSS4.7

Microbial enzyme activities and use channels during microbial turnover of organic carbon substrates in soil  

Denise Vonhoegen, Ubaida Yousaf, and Sören Thiele-Bruhn

Recent studies of soil organic matter formation focus on energy and matter fluxes and their linkage to broaden the understanding of the processes and drivers underlying microbial turnover of organic carbon substrates in soil. In this study, which is part of the DriverPool project in the SoilSystems priority program, the energy and mass balances of organic matter turnover are investigated with special reference to the soil microbial community by testing selected hydrocarbon substrates with different properties.

In a first incubation experiment the effect of substrate size was investigated by comparing the turnover of glucose (180 Da) and α-1,4-maltoteraose (666.6 Da). We hypothesize that exoenzymatic activity is required for substrates exceeding a size of 600 Da; thus, resulting in a different process type (adaptation-oriented process) compared to the intracellular turnover of  glucose (growth-oriented process). From a batch microcosm experiment, subsamples were collected after different incubation periods to determine microbial pools (biomass, necromass) and the incorporation of the C13-labeled substrates. Enzymatic activity of exoenzymes (α- and β-glucosidase, N-acetyl-glucosaminidase, sulfatase, phosphatase, fungal peroxidase) and endoenzymatic activity (dehydrogenase) were assessed to elaborate the understanding of metabolic pathways. To analyze shifts in the microbial community and to identify a bacterial- or fungal-dominated use channel for each substrate, substrate induced alteration in phospholipid fatty acid (PLFA) patterns of the harvested samples will be studied as well. First results show differences in enzyme activity pattern for glucose and maltotetraose.

How to cite: Vonhoegen, D., Yousaf, U., and Thiele-Bruhn, S.: Microbial enzyme activities and use channels during microbial turnover of organic carbon substrates in soil , EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7231, https://doi.org/10.5194/egusphere-egu23-7231, 2023.

EGU23-7245 | ECS | Orals | SSS4.7

Implications of optimal resource allocation in soil microorganisms 

Erik Schwarz, Salim Belyazid, and Stefano Manzoni

Soil microbes are key players in the cycling of soil organic carbon. In the complex soil system, microbes are faced with multiple stresses and trade-offs. In order to build biomass and proliferate, microbes have to mine accessible substrate and simultaneously have to survive abiotic stresses such as dry conditions. How they allocate carbon to the production of microbial biomass, extracellular enzymes, or biomolecules that help resist abiotic stresses is an important control of soil organic carbon fate. High carbon use efficiency fuels the build-up of microbial necromass, while increased production of exoenzymes might accelerate the breakdown of particulate organic matter. Production of additional biopolymers needed to sustain metabolic activity under stress – e.g., the production of osmolytes for maintaining turgor pressure in drying soils – poses an additional carbon cost that trades-off with the production of biomass and extracellular enzymes. Here we propose a conceptual model of soil carbon cycling with an explicit representation of these microbial allocation trade-offs. The model resolves physical processes such as saturation dependent substrate diffusion and is formulated at steady-state. It is based on the premise that microbes are optimally adapted to the environment they inhabit – meaning that the allocation trade-offs between the production of biomass, extracellular enzymes, and biomolecular stress response are adapted to maximize the microbial growth rate under these conditions. Using this conceptual model, we investigate how microbial allocation traits (fraction of carbon taken up and allocated to new biomass, extracellular enzymes, or osmolytes) might vary over a range of environmental conditions. Optimal allocation of carbon leads to increased investment in extracellular enzymes when carbon is scarce, and to progressively higher investment in osmolytes in drier conditions. While these trends are somewhat expected, the model predicts (rather than prescribing) the sensitivity of these allocation traits to changes in soil moisture and available carbon as a consequence of the optimality assumption. We conclude by exploring what implications these results might have for soil organic carbon fate.

How to cite: Schwarz, E., Belyazid, S., and Manzoni, S.: Implications of optimal resource allocation in soil microorganisms, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7245, https://doi.org/10.5194/egusphere-egu23-7245, 2023.

EGU23-7550 | ECS | Orals | SSS4.7

Beyond growth? The significance of microbial maintenance for carbon-use efficiency in the light of soil carbon storage 

Tobias Bölscher, Melanie Brunn, Tino Colombi, Luiz A. Domeignoz-Horta, Anke M. Herrmann, Katharina H.E. Meurer, Folasade K. Olagoke, and Cordula Vogel

During decomposition of organic matter, soil microbes determine the fate of C. They partition C between anabolic biosynthesis of various new microbial metabolites (i.e. C reuse) and catabolic C emissions (i.e. C waste, mainly through respiration). This partitioning is commonly referred to as microbial carbon-use efficiency (CUE). The reuse of C during biosynthesis provides a potential for the accumulation of microbial metabolic residues in soil. The microbial metabolic performance is a key factor in soil C dynamics, because the vast majority of C inputs to soil will – sooner or later – be processed by soil microorganisms. Soil C inputs will thus be subjected to microbial allocation of C towards reuse or emitted waste, with the former leading to C remaining in soil. Recognized as a crucial control in C cycling, microbial CUE is implemented – implicitly or explicitly – in soil C models, which react highly sensitive to even small changes in CUE. Due to the models’ high sensitivity, reliable soil C projections demand accurate CUE quantifications, capturing unambiguously all metabolic C fluxes.

The current concept of microbial CUE neglects microbial maintenance which could make up considerable parts of the microbially processed C. Commonly, CUE is quantified from C incorporated into biomass or used for growth and C released as CO2. Extracellular metabolites, such as polymeric substances (EPS), exoenzymes or nutrient mobilizing compounds, as well as intracellular maintenance metabolites, such as storage compounds or endoenzymes, are ignored although they represent microbial metabolic C reuse and thus C remaining in soil.

Based on theoretical considerations and a case study for EPS production, we will demonstrate that neglecting microbial maintenance can have severe impact on estimation of terrestrial C storage. For instance, ignoring measured EPS production (of a quantity of C which equals 37 % of the C used for growth) causes a substantial underestimation of CUE. Here, current approaches of CUE provide an apparent CUE of 0.20 while disregard an actual CUE of 0.25 (i.e. CUE is 25 % higher when maintenance metabolism is considered). Based on our findings, we suggest an adjustment of how we conceptualize and calculate microbial CUE in soils.

How to cite: Bölscher, T., Brunn, M., Colombi, T., Domeignoz-Horta, L. A., Herrmann, A. M., Meurer, K. H. E., Olagoke, F. K., and Vogel, C.: Beyond growth? The significance of microbial maintenance for carbon-use efficiency in the light of soil carbon storage, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7550, https://doi.org/10.5194/egusphere-egu23-7550, 2023.

EGU23-7901 | ECS | Orals | SSS4.7

General drivers of microbial carbon use efficiency in soils 

Julia Schroeder, Florian Schneider, Christoph C. Tebbe, and Christopher Poeplau

The efficiency by which soil microbes direct metabolised carbon to their growth, i.e. the microbial carbon use efficiency (CUE), is hypothesised to be driven by soil pH, nutrient stoichiometry and the microbial community composition (e.g. Fungi-to-Bacteria ratio). Despite extensive research it remains difficult to identify general trends in how these drivers affect CUE and results of individual studies often point in different directions. To unravel general trends, we aggregated a unique data set of samples analysed using the 18O-labelling technique - all derived from the same laboratory - to gain deeper insights into the relationship between CUE and pH, CN ratio and the relative abundance of domains (based on 16S and ITS gene copy numbers by qPCR). To date, the growing data set comprises 685 observations of 18O-CUE, including samples from 41 individual sites under three different land use types (forest, managed grassland, cropland) from tropical to subarctic climate. A Random Forest model and a linear mixed-effects model approach were used to analyse the data. Preliminary results on a filtered and aggregated subset (n= 221; aggregated to reduce the heterogeneity of the data set structure) suggest that the CUE is strongly dependent on soil pH, following a U-shaped curve. The relationship between CUE and pH was found negative for pH < 5.5 and positive for pH ≥ 6.5, while overall the CUE was found to be negatively correlated to soil C:N ratio. Additional data on climate (MAT, MAP), soil texture, and soil microbial community will complement the analysis.

How to cite: Schroeder, J., Schneider, F., Tebbe, C. C., and Poeplau, C.: General drivers of microbial carbon use efficiency in soils, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7901, https://doi.org/10.5194/egusphere-egu23-7901, 2023.

EGU23-8678 | Orals | SSS4.7

A spatial microbial competition mechanism of soil carbon persistence 

Oskar Franklin, Mark T.L. Bonner, Shun Hasegawa, and Torgny Näsholm

Here we present a novel model supplementing existing theories of soil organic matter (SOM) decomposition, based on evolutionary-ecological principles rather than chemical or physical limitations to decomposition. We argue that decomposition of some substrates, in particular nitrogen-rich non-hydrolyzable matter (NHLS), may be constrained by spatial competition from opportunists (Bonner et al., 2022). Our model is based on two linked hypotheses: (1) From an evolutionary point of view, microbes should optimise their enzyme production to maximise the net fitness gain (F), and they should only decompose NHLS if the uptake of decomposition products (S) brings a net fitness gain (F > 0) in terms of growth minus costs of enzyme production. (2) F strongly depends on the fraction of decomposition products absorbed by the decomposer, i.e. the return on enzyme investment, which depends on the distance to the substrate and the competition from opportunistic bacteria. A minimum ‘safe’ distance for oxidative decomposition is included, based on the idea that cost of oxidative stress to the decomposer will surpass potential gain from decomposition when the activity is too close. Although the model predictions have not been tested directly against observations, they provide proof-of-concept that substrate can be spared decomposition and accumulate even when it is physically and chemically accessible. Due to the spatial competition effect, it is not profitable for either bacteria or decomposer fungi to decompose NHLS under certain conditions.  Our framework can help explain a variety of SOM dynamics, including priming and the suppression of decomposition by nitrogen addition.

 

Reference

Bonner MTL, Franklin O, Hasegawa S, Näsholm T. 2022. Those who can don't want to, and those who want to can't: An eco-evolutionary mechanism of soil carbon persistence. Soil Biology and Biochemistry 174: 108813.

How to cite: Franklin, O., T.L. Bonner, M., Hasegawa, S., and Näsholm, T.: A spatial microbial competition mechanism of soil carbon persistence, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8678, https://doi.org/10.5194/egusphere-egu23-8678, 2023.

Soil microbes govern biogeochemical processes such as carbon and nutrient cycling, but the microbial controls on soil nutrient stoichiometry vary under different environmental contexts. Recent evidence suggests that microbial genomic traits such as GC content and genome size correlate with soil pH and soil C: N ratios, but how this pattern relates to the fate of soil organic carbon (SOC) and in which microbial groups this occurs is inconclusive. The rapid generation of environmental metagenomic datasets presents a unique and relatively untapped resource that can be used to examine microbial niche breadth, or soil resource use and reuse, and how specific groups of microbes respond to environmental gradients. Metagenome assembled genomes (MAGs) for soil microbes can describe the functional potential of populations, serving as valuable descriptors of niche breadth for soil microbial communities.  Here, we aimed to identify the ecological factors structuring microbiological nutrient cycling functions, and how they vary with microbial traits and functional groups by harmonizing soil metagenome datasets with soil nutrient measurements across space and time. We applied the Hutchinsonian niche hypervolume concept to examine relationships between microbial functional niche and environmental resource space. We expect that comparative analysis of MAGs across diverse environments varying in soil organic C and N can identify specific functional and/or taxonomic groups of microbes contributing to SOC dynamics, such as fungal saprotrophs. Biotic and abiotic controls such as climate and vegetation that influence these groups of microbes can then be identified using large-scale amplicon sequence datasets that represent broad spatiotemporal scales.

How to cite: Shek, K. and Wymore, A.: Microbial niche breadth as a tool to identify controls on carbon and nutrient cycling across environmental gradients, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9060, https://doi.org/10.5194/egusphere-egu23-9060, 2023.

EGU23-9238 | ECS | Posters on site | SSS4.7

Investigation of the growth rate and antibiotic production of Marine Actinobacteria in the International Space Station 

Marialina Tsinidis and Manolis Simigdalas

The present experiment investigates the behavior of marine actinobacteria in the International Space Station (ISS). More specifically, the aim of the experiment is to examine the growth rate and antibiotic production of the actinobacteria and as a result the correlation between the growth rate and the viscosity of the liquid (mix of actinobacteria and nutrient agar). The experiment is performed in cooperation with Nanoracks and launched via Falcon 9, Space – X and remained in the ISS for a 90-day time period under constant temperature (4 degree Celsius), being stirred by the astronauts on a weekly basis. There is a medical and pharmacological interest since marine actinobacteria are a source of bioactive natural and antibiotic products, beneficial for the human organism, producing a variety of secondary metabolites. The experiment in the ISS indicates growth similar to the experiment on Earth, with slightly higher values showing that the bacteria survived the microgravity conditions. The viscosity is slightly greater in the ISS, potentially due to the change in the density of the liquid, following the growth of the bacteria.

 

How to cite: Tsinidis, M. and Simigdalas, M.: Investigation of the growth rate and antibiotic production of Marine Actinobacteria in the International Space Station, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9238, https://doi.org/10.5194/egusphere-egu23-9238, 2023.

EGU23-9585 | ECS | Posters on site | SSS4.7

Linking soil microbial carbon sequestration to cover crop diversification in agricultural soil systems across Europe 

Alexander König, Christoph Rosinger, Katharina Keiblinger, Sophie Zechmeister-Boltenstern, Anke Herrmann, and Erich Inselsbacher

Sequestering atmospheric CO2 into soil organic matter through changes in agricultural practices is an appealing idea to improve soil ecosystem services and to improve global change mitigations. The old view of carbon (C) stability in soil, based on the intrinsic properties of the organic matter inputs (e.g. lignin content), would lead policy towards greater percentages of recalcitrant organic matter content in crops. Recent research suggests otherwise and that managing how the soil microbiome process C inputs is a more fruitful approach (Sokol et al., 2019, Poeplau et al., 2019). It is therefore to decipher and evaluate the link between the aboveground plant community and the complex belowground diversity of the microbiome and their metabolic processes that mediate C sequestration. Lehmann et al. (2020) proposed a theoretical framework in which the persistence of C in soil can be understood as the outcome of interactions between the molecular variability of organic matter input and spatio-temporal microbial heterogeneities of the soil system.

Within the EnergyLink framework we therefore investigate various microbial markers to illuminate possible physiological changes across several European agricultural field sites with different cover crop management types. Specifically, for detecting shifts in microbial necromass composition and quantity we target amino-sugars (galactosamin, gluctosamine, mannosamine and muramic acid), for evaluating effects on growth rates we measure 14C incorporation into ergosterol for fungi and 14C-leucine incorporation for bacteria and to grasp changes in uptake strategies we test extra cellular enzyme activities for different nutrient classes. Additionally, we determine C:N:P ratio for bulk soil, microbial biomass and above ground plant biomass to estimate stoichiometric imbalances. Here we present results from our first sampling campaign and discuss implications of diversified cover crops on soil carbon properties on a European scale.

How to cite: König, A., Rosinger, C., Keiblinger, K., Zechmeister-Boltenstern, S., Herrmann, A., and Inselsbacher, E.: Linking soil microbial carbon sequestration to cover crop diversification in agricultural soil systems across Europe, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9585, https://doi.org/10.5194/egusphere-egu23-9585, 2023.

EGU23-9924 | Orals | SSS4.7

Long-term plant-microbe interactions weaken the rhizosphere priming effect in tundra systems 

Nicholas Bouskill, Bill Riley, Zhen Li, and Zelalem Mekonnen

Ecosystem priming is a critical process contributing to the carbon balance of tundra soils. On one hand, plant exudation of labile organic compounds can stimulate microbial activity inducing the decomposition of more complex organic matter, resulting in soil carbon loss. On the other hand, the efficient processing of plant exudates, and stabilization of microbial necromass in soils, can increase soil carbon stocks, reducing CO2 emissions to the atmosphere. The divergence between positive and negative priming depends on ecosystem stoichiometry, microbial trait distribution, climate, and non-linear interactions between plants and microbial activity. Here we employ a mechanistic model, ecosys, to examine the role of microbial trait distribution and plant-microbe interactions in determining priming effects on tundra soil carbon stocks. The ecosys model represents distinct functional guilds of bacteria (e.g., heterotrophic decomposers, nitrifiers) and fungi (e.g., mycorrhizae and saprotrophs), and the diversity within, as a function of their traits, including carbon use efficiency (CUE). We examine the role of priming in short- and long-term experiments. We initially benchmarked the ecosys model to well-studied sites in the North American Arctic and explore how diversity in microbial CUE regulates soil carbon stocks under different priming conditions (e.g., a single application of labile carbon vs. semi-continuous exudation conditions) over the course of one year. We then scale up these simulations to the whole of Alaska and examine how plant-microbe interactions alter the priming effect over centennial time scales, with and without warming. We generally observed the attenuation of the priming effect contingent upon elevated nutrient concentrations under warming, which reduced plant exudation to soils. We will discuss these results, and how microbial traits influence the long-term balance of soil carbon in tundra ecosystems. 

 

How to cite: Bouskill, N., Riley, B., Li, Z., and Mekonnen, Z.: Long-term plant-microbe interactions weaken the rhizosphere priming effect in tundra systems, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9924, https://doi.org/10.5194/egusphere-egu23-9924, 2023.

EGU23-10879 | ECS | Orals | SSS4.7

Global links between soil microbes and biogeochemical functions 

Gabriel Reuben Smith, Johan van den Hoogen, Kabir Peay, Manuel Delgado-Baquerizo, Robert Jackson, Kailiang Yu, and Thomas Crowther and the Soil Organisms Team

Soil contains immense stocks of carbon, which may accelerate climate change if released. Soil microbes affect these carbon stocks by producing decomposition-catalyzing enzymes, a capacity varying across different microbial groups. Consequently, establishing links between global variation in microbial communities and functions should substantially enhance future projections of soil carbon. To this end, we here reveal global patterns in soil microbial community function using nearly 13,000 observations of microbial biomass, community structure, and enzyme activities (>100,000 measurements). We find total biomass and fungal and Gram-negative bacterial dominance increase with latitude, whereas Gram-positive bacteria predominate near the equator. Enzyme stoichiometry correspondingly suggests greater nitrogen and carbon limitation at higher latitudes. Comparing microbial and enzyme patterns, fungal biomass indicates nitrogen limitation, whereas Gram-negative bacterial biomass indicates carbon limitation. Together, microbial community structure explains significant variation in enzyme profile uncaptured by climate, soil properties, or landcover. Soil microbial communities dominated by fungi and Gram-negative bacteria exhibit less enzyme activity per unit biomass, with two- to four-fold variation in temperature- and biomass-normalized activity rate observed across the Earth. Significant functional differences thus arise with global turnover in microbial communities, indicating that community structure merits a central position in process-based soil models.

How to cite: Smith, G. R., van den Hoogen, J., Peay, K., Delgado-Baquerizo, M., Jackson, R., Yu, K., and Crowther, T. and the Soil Organisms Team: Global links between soil microbes and biogeochemical functions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10879, https://doi.org/10.5194/egusphere-egu23-10879, 2023.

EGU23-10998 | ECS | Orals | SSS4.7

Modeling population-level controls on soil microbial turnover across scales 

Katerina Georgiou, Ksenia Guseva, Jennifer Pett-Ridge, and Christina Kaiser

Soil is organizationally complex and spatially heterogeneous with exceptional microbial diversity that varies in time and space. Hotspots of microbial activity are prevalent, yet they are patchy and periodic and it remains intractable to represent this level of detail in macro-scale soil microbial models. Most macro-scale microbial models have, therefore, been focused on exploring theory and capturing select processes in a simplified way. However, effective equations that account for population- and community-level controls may be needed to suitably capture emergent feedbacks at macro-scales. In this study, we explore the effective relationships that emerge between spatially aggregated carbon pools in a micro-scale soil model with competition and space constraints. Specifically, we use an individual-based, spatially explicit model to simulate the response of soil microbes to a range of scenarios with increasing carbon inputs, including spatially-uniform (homogeneous) and spatially-clumped (heterogeneous) increases, where the input flux integrated over the total area is the same in both scenarios. The latter is meant to mimic hotspots of carbon inputs, for example, in the rhizosphere or near preferential flow paths. We find that competition between microbes and the probability of invasion from neighboring microsites plays a critical role in emergent density-dependent dynamics of microbial growth and turnover. Our study elucidates the role of population-level controls on microbial turnover at macro-scales, and motivates careful consideration of scale-dependent model representations. 

How to cite: Georgiou, K., Guseva, K., Pett-Ridge, J., and Kaiser, C.: Modeling population-level controls on soil microbial turnover across scales, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10998, https://doi.org/10.5194/egusphere-egu23-10998, 2023.

EGU23-11025 | ECS | Orals | SSS4.7

Tracking transcription in soil microbial communities during the Birch Effect 

Peter Chuckran, Mary Firestone, Alexa M. Nicolas, Ella T. Sieradzki, Jennifer Pett-Ridge, and Stephen Blazewicz

In drought affected ecosystems, a large portion of the annually respired CO2 from soil may occur in the short period following the first rain event after drought. This process, where the rewetting of dry soil results in a pulse of CO­2, is commonly known as the Birch Effect. This pulse of activity influences the stability and persistence of soil carbon which, considering the large and growing extent of dryland and drought-impacted ecosystems, may have far reaching implications. It’s been shown that the consumption of the compounds driving the Birch Effect varies temporally and that different taxa grow over the course of wet-up; however, the transcriptional response of specific taxa during wet-up, and their associated characteristics, has not been fully explored.  In this study we map metatranscriptomes against metagenome-assembled genomes (MAGs) in order to assess the transcriptional response of taxa to wet-up at 0, 3, 24, 48, 72, and 168 h post rewetting. We found distinct temporal response patterns that were often conserved on the family-level. Based on response patterns, we grouped genomes into early, mid, and late responders. The average transcriptional profile of MAGs within these different response types did not vary substantially from each other. Instead, for a majority of MAGs, we found shifts in the transcriptional profile of functional genes over time. Together, these findings suggest that much of the temporal dynamics of microbial transcription during the Birch Effect are controlled by differences in within-taxa response time as opposed to stark differences in functional gene transcription between response groups.

How to cite: Chuckran, P., Firestone, M., Nicolas, A. M., Sieradzki, E. T., Pett-Ridge, J., and Blazewicz, S.: Tracking transcription in soil microbial communities during the Birch Effect, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11025, https://doi.org/10.5194/egusphere-egu23-11025, 2023.

EGU23-11477 | ECS | Orals | SSS4.7

Linking heat and matter turnover over microbial successional stages in the soil to substrate quality and quantity 

Fatemeh Dehghani Mohammad Abadi, Thomas Reitz, Steffen Schlüter, and Evgenia Blagodatskaya

One of the major research foci of modern environmental sciences is the mechanism of carbon sequestration in the course of microbial decomposition of organic compounds in soil. Microorganisms decompose soil organic matter as a source of carbon, energy, and nutrients for their metabolism. The transformation process of various organic compounds in the soil is driven by competition between diverse microorganisms during several successional stages. The number, duration, and amplitude of which are dependent on substrate quality and quantity by regulating the tradeoff between fast but less efficient and slow but more efficient microbial taxa. In the frame of the Priority Program “Soil Systems”, funded by the German Research Foundation (DFG), we aim to study the relationships between substrate turnover rate, CO2 release, heat production, and efficiency of microbial metabolism at various stages of microbial succession in the course of cellulose decomposition in a fertilized Haplic Cambisol soil. To link metabolism efficiency with microbial functional traits, the kinetic parameter of microbial enzymes and growth parameters are determined at different stages of microbial succession. This research will thus contribute to the elucidation of regulatory mechanisms of energy and matter turnover in soil.

How to cite: Dehghani Mohammad Abadi, F., Reitz, T., Schlüter, S., and Blagodatskaya, E.: Linking heat and matter turnover over microbial successional stages in the soil to substrate quality and quantity, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11477, https://doi.org/10.5194/egusphere-egu23-11477, 2023.

EGU23-11989 | ECS | Posters on site | SSS4.7

Chemical and microbial mass balances in microbial turnover of two easily degradable carbon substrates 

Ubaida Yousaf, Denise Vonhoegen, and Sören Thiele-Bruhn

Recent research indicates that soil microbes play a significant role in the formation and turnover of soil organic matter (SOM). Thus, OM is metabolized by microorganisms through intracellular and extracellular enzymatic activity, with one portion of it being converted into biomass and another being respired for energy. This causes an energy and matter flux that is adjusted and slowed down by ongoing recycling of the matter and residual energy. Matter and energy are conserved as much as possible throughout repeating microbial growth cycles, resulting in an "energy use channel," and/or storage as necromass. Soil fertility and several other soil functions depend on the activity of diverse soil microbial populations and, consequently, on continual energy and carbon flows within the soil system. Fluxes and stoichiometry concerns must be considered for the maintenance of microbial diversity and ecosystem activities in soil, including C storage. To comprehend C turnover and sequestration in terrestrial ecosystems, further knowledge of the relationship between element cycling and energy fluxes is required. In this project, we present a conceptual overview of microorganisms as mediators of SOM production, we do that by investigating seven carbon substrates with varying complexity with the same model soil (fertilized Dikopshof) in five different incubation experiments.

In the first experiment, we study the effect of substrate size (Glucose — 180 Da, α — 1,4-maltotetraose — 666,6 Da). We hypothesize that exoenzymes would be required to degrade any substrate greater in size than 600 Da, meaning different CUE/EUE due to a change in the process type from growth-oriented processes — high energy flux for glucose degradation to the adaption-oriented processes for the larger substrate, i.e., maltotetraose in this case. The substrates were labelled with 13C to determine various carbon pools in the samples. Destructive sampling was used to obtain subsamples from 6 different time points. Aminosugars and acids were used as markers of microbial biomass/necromass. Chloroform fumigation extraction was performed to determine microbial biomass of carbon and nitrogen. In combination with further data to calculate the microbial quotient (Cmic/OC), the respiratory quotient (qCO2= resp./Cmic), and CUE. Gas flux sampling and isotope selective CO2 analysis to determine the differences in the turnover of the substrates (Energy consumption respiration) The energy accumulation includes the formation of additional biomass, necromass, and metabolites. Analysis of C, H, N, S, O, and P to calculate the stoichiometry of OM. 

 

How to cite: Yousaf, U., Vonhoegen, D., and Thiele-Bruhn, S.: Chemical and microbial mass balances in microbial turnover of two easily degradable carbon substrates, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11989, https://doi.org/10.5194/egusphere-egu23-11989, 2023.

EGU23-12021 | ECS | Posters on site | SSS4.7

Effect of pore network architecture on the efficiency of microbial soil organic matter decomposition 

Magdalena Rath, Ksenia Guseva, and Christina Kaiser

Microbial decomposition of soil organic matter is one of the major drivers of nutrient and carbon cycling in terrestrial ecosystems. Soils are spatially heterogeneous habitats built up hierarchically from µm- to mm-sized aggregates that provide a complex pore system. An enormous diversity of microbes occupies this physically and chemically heterogeneous pore space. Although, in recent decades the consensus has largely been established, that microbial processes are strongly affected by the architecture of the soil pore space and the patchiness of the substrate distribution within it, still, the integration of pore network characteristics in models of microbial activity is scarce. 

We use an individual-based modelling approach to address the following questions:

  • How does pore network architecture affect the efficiency of microbial organic matter decomposition?
  • How do pore network properties like average node degree, shortest path length, and clustering coefficient affect the efficiency of organic matter decomposition?
  • What is the effect of additional heterogeneity in pore sizes or distribution of substrate between pores on microbial efficiency?

To incorporate the spatial structure the soil pore space that forms microhabitats is modelled as nodes of a network. Specific attributes are assigned to the nodes to describe their physical and biochemical conditions. Microbes inhabit a certain fraction of microhabitats (nodes) of the network and degrade organic matter that is available to them. Depending on microbial growth neighboring pores can be invaded  through the connecting links.
 We were able to identify a number of network properties that affect the spread of microorganisms trough the network and the subsequent decomposition efficiency of the total substrate available in the system. While high clustering of nodes enables nearly complete decomposition of substrate, the presence of highly connected nodes (hubs) can decrease the efficiency of decomposition and lead to higher amount of substrate that remains undegraded. Regarding microbial growth parameters, the system shows a threshold behaviour. If microbial growth stays below a certain threshold value, microbes live only in the initially occupied pores and are not able to invade new pores. When the substrate concentration or the growth rate reaches the threshold value, there is a jump to large-scale invasion of all reachable pores in the network and much higher efficiency in the decomposition. In addition, high heterogeneity in substrate concentration or pore sizes lead to lower invasion efficiency, lower decomposition rate and a higher amount of substrate that is left at the end. Overall, we found that the spatial structure of the pore network had a more pronounced effect on microbial decomposition efficiencies than microbial physiological parameters, such as maximum microbial growth rates or extracellular enzyme kinetics.
 Our findings allow for better understanding of the impact of soil pore network architecture on microbial processes. This is of high relevance when modelling the response of soil microbial communities to climate change.

How to cite: Rath, M., Guseva, K., and Kaiser, C.: Effect of pore network architecture on the efficiency of microbial soil organic matter decomposition, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12021, https://doi.org/10.5194/egusphere-egu23-12021, 2023.

EGU23-12332 | ECS | Orals | SSS4.7

Labile substrate availability shapes interactions in a synthetic chitin-degrading soil bacterial community 

Moritz Mohrlok, Lauren Alteio, Ksenia Guseva, Julia Mor Galvez, Erika Salas Hernández, and Christina Kaiser

Chitin decomposition involves different extracellular enzymes and intermediate products, giving rise to complex social dynamics within chitin-degrading communities. These communities are therefore an ideal model system to investigate how complex organic matter is decomposed in soil, and what effect microbial interactions have on the decomposition process. We used a synthetic consortium consisting of three unrelated, potentially chitin-degrading soil bacterial strains (Paenibacillus alginolyticus, Paraburkholderia xenovorans and Solirubrobacter soli) to investigate how their interactions affect the decomposition of chitin, and how the availability of labile carbon influences these interactions.

The strains were grown in monoculture and in all possible combinations on three different substrates (2% chitin, 2% n-acetylglucosamine (NAG, the monomer of chitin) and a mixture of 1% chitin and 1% NAG). Cumulative respiration as a community performance metric was measured over the course of two weeks using the MicroResptm system. We measured the concentration of chitin oligomers (chitobiose and chitotriose) at the endpoint using PMP-derivatisation and UPLC-Orbitrap MS. The final microbial community composition was assessed via 16s Amplicon sequencing and the 16s gene copy number was measured with droplet-digital PCR.

Depending on the substrate, each strain showed distinct respiration patterns in monoculture, indicating different functionalities. We found both competitive and synergistic interactions in the strain combinations, depending on the involved species and available substrate. P. xenovorans dominated the other strains whenever the labile substrate (NAG) was added. The relative abundance of the less competitive strains (P. alginolyticus and S. soli) was however increased in the treatment containing only chitin compared to the NAG-treatments. Chitin was degraded a lot more when all three strains were included, as shown by both the maximum respiration and chitobiose concentration. All three strains were still detectable in this treatment, which was not the case when NAG was present from the beginning.

Based on these results we assume that energy limitation forces synergistic interactions in this model community, increasing the chitin decomposition efficiency. Adding labile substrate alters these interactions, leading to the exclusion of less competitive strains. Our results emphasize how interacting bacteria of different functional groups can result in increased decomposition of complex soil organic matter and how the relationships between different species in a microbial community at a soil microsite might change based on the available substrate.

How to cite: Mohrlok, M., Alteio, L., Guseva, K., Mor Galvez, J., Salas Hernández, E., and Kaiser, C.: Labile substrate availability shapes interactions in a synthetic chitin-degrading soil bacterial community, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12332, https://doi.org/10.5194/egusphere-egu23-12332, 2023.

EGU23-13193 | Orals | SSS4.7

Heterogeneity and C dynamics in soil 

Naoise Nunan, Hannes Schmidt, Claire Chenu, Valerie Pouteau, and Xavier Raynaud

Heterogeneity (spatial, temporal chemical and biological) is a fundamental property of soils. Although it is rarely explicitly accounted for in models of soil microbial functioning, it is a determinant of microbial access to substrate and therefore of microbial activity. Microbial adaptation to heterogeneity is also likely to play a significant role in determining microbial activity and therefore C persistence in soil. A more developed understanding of heterogeneity and how microbial communities interact with their heterogenous environment can help us better understand the mechanisms that regulate microbial activity and soil C dynamics, as well as offer potential avenues for upscaling. In this presentation I will show how microbial communities have adapted to spatial and molecular heterogeneity at the microbial scale and, through the use of a spatial explicit model, how spatial and molecular heterogeneity interact to reduce decomposition. Pore scale heterogeneity affects the distribution of both decomposers and organic matter. Using a stable isotope approach, I will show that, although there does not appear to be a clear relationship between microbial decomposer composition and pore size, a simple relationship emerges between pore size and microbial decomposition of organic substrate. As the pore size distribution of soils can be deduced from pedo-transfer functions, this relationship may provide a more mechanistic basis for the representation of moisture effects on C dynamics in larger scale models.

How to cite: Nunan, N., Schmidt, H., Chenu, C., Pouteau, V., and Raynaud, X.: Heterogeneity and C dynamics in soil, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13193, https://doi.org/10.5194/egusphere-egu23-13193, 2023.

EGU23-13715 | ECS | Orals | SSS4.7

Organic fertilizer amendment affect soil aggregates during crop growth: a hotspot for microbial phosphorus turnover? 

Nelly Sophie Raymond, Federica Tamburini, Astrid Oberson, Jakob Magid, and Carsten Müller

Farming practices affect soil structure and aggregate formation. The addition of organic fertilizers, such as cow manure, is a practice that can affect soil aggregation and can foster the formation of macroaggregates, which resemble high contents of rather labile soil organic carbon (SOC). Soil aggregates, known to be hotspots for microbial activity, can also be assumed to be hotspots for microbial nutrient cycling. Within the soil system, microorganisms play an active key role in the cycling of phosphorus (P) by: 1) storing P within their biomass, 2) mineralizing non-plant available organic P, and 3) solubilizing inorganic P forms. Microorganisms are thus a key driver in the cycling of P in soil. However, P cycling through the microbial biomass is often limited by SOC availability. The use of organic fertilizers may provide the OC required for microorganisms to cycle P, especially in SOC rich maccroaggregates. The main objective of the present work is to better understand how soil microorganisms’ habitat and P-cycling is affected by the addition of cow manure and how it affect the P cycling through microbial biomass. We collected soils from a long term field trial consisting of different organic soil amendments (Taastrup, Denmark), namely a soil amended with cow manure and a soil amended with mineral fertilizer (nitrogen, potassium and P). We determined soil aggregate size distribution as well as macroaggregate stability, soil C, N and P contents and microbial biomass C, N and P within aggregate size fractions We are able to demonstrate that the application of organic fertilizer has clearly affected soil macroaggregation and stability, as well as the nutrient distribution and content within the aggregates. As large macroaggregates between 2 and 8 mm dominated the sampled soils (49-79 % of the soil mass), we selected these macroaggregates as a functional unit to evaluate the effect of the organic fertilizer on microbial P cycling. We suggest that the addition of cow manure alleviates microorganisms’ OC limitation and thus stimulate P cycling through microbial biomass. The better understanding of soil microorganisms activity and organic fertilizer interaction at the aggregate scale is providing a better understanding of plant-P availability which will benefit the development of future sustainable cropping systems.

How to cite: Raymond, N. S., Tamburini, F., Oberson, A., Magid, J., and Müller, C.: Organic fertilizer amendment affect soil aggregates during crop growth: a hotspot for microbial phosphorus turnover?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13715, https://doi.org/10.5194/egusphere-egu23-13715, 2023.

EGU23-14428 | Orals | SSS4.7

The importance of bacterial metabolism contribution to soil organic carbon revealed by Monte Carlo simulations 

Annette Dathe, Laurel Lynch, Dominic Woolf, and Johannes Lehmann

Soil is the largest terrestrial carbon reservoir and processes leading to carbon sequestration play a crucial role in quantifying size as well as changes of this important pool. Microorganisms transform plant residues to smaller organic compounds, and often necromass is assumed to be the main stable end product. The turnover of microbial biomass at end of life, however, is only one pathway by which microorganisms contribute to soil organic matter. As a proof-of-concept, we use a mechanistic modeling approach with Monte Carlo simulation of 10,000 iterations, where input parameters vary according to values derived from literature. Bacterial growth follows a Monod kinetic, and biomass is further transformed to exudates, waste, and exo-enzymes, which vary in their C:N ratios. Assuming abundant N-resources, bacterial necromass contributes with 23.2% (median) of organic carbon only a minor portion to microbially-derived soil organic matter at the end of the simulation of 72 days. Most of the microbially derived organic carbon originates as part of metabolism by a combination of exudation (median 39.0%), wastes such as for osmotic regulation (median 22.4%), and exoenzyme production (median 10.3%). The organic product yields vary by about 300% between anabolic stages six days after substrate additions compared to catabolic stages at the end of the simulation. Predictions and management of soil organic carbon sequestration should therefore be based on carbon input through microbial metabolism rather than assumptions of carbon input solely at end of life.

How to cite: Dathe, A., Lynch, L., Woolf, D., and Lehmann, J.: The importance of bacterial metabolism contribution to soil organic carbon revealed by Monte Carlo simulations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14428, https://doi.org/10.5194/egusphere-egu23-14428, 2023.

EGU23-14657 | ECS | Orals | SSS4.7

Investigating the effect of temperature on growth and microbial biomass accumulation during winter 

Christoph Gall, Lucia Fuchslueger, Hannes Schmidt, Andrea Söllinger, Mathilde Borg Dahl, Alexander Tveit, Bjarni Sigurdsson, Stephanie Eichorst, Ben Roller, and Andreas Richter

It is well documented that microbial biomass increases during winter in cold mountain or tundra ecosystems, but the cause and mechanism of such accumulation is unclear. Results from a grassland in Iceland demonstrated that the microbial biomass carbon (MBC, measured by the fumigation-extraction method) increased in winter, while microbial DNA content remained constant. We thus hypothesized that this accumulation of microbial biomass during the cold season is driven by the decrease in temperature, that increases the carbon storage of individual cells, but not by an increase in microbial cell numbers.

To test this hypothesis, we conducted a laboratory incubation experiment with soils from a grassland in Iceland sampled before the onset of winter in early October (around 9 °C). We then exposed the soils to decreasing temperatures (0.5 °C, 3 °C, 6 °C and 9 °C) over five months. We analyzed microbial biomass carbon (MBC) and quantified the DNA content. Over the course of five months, we found higher MBC values at cool temperatures compared to warm conditions. As expected, cooling did not affect the DNA content, leading to a significantly higher MBC to DNA ratio when soils were incubated at 0.5 °C compared to 9 °C. This indicates that numbers of microbial cells did not change across temperatures, but that microbes at lower temperatures stored more carbon. We also found similar patterns in soils collected at different time points in the field. Furthermore, we estimated microbial DNA production, i.e., growth rates, by measuring the incorporation of 18O from labelled water into DNA. We observed lower microbial growth rates under field conditions in winter, indicating that increasing biomass carbon was not due to increased growth and that growth and turnover was balanced at all temperatures. Instead, we suggest that carbon uptake (which was decreased at lower temperatures) was less affected by cold temperatures than growth, so that microbial carbon could accumulate. We also verified this pattern in growth and carbon uptake rates with decreasing temperatures in the laboratory incubation experiment.

Decreasing growth (cell division) and turnover rates with decreasing temperatures, at a lower but sustained carbon uptake rate, suggest that the cell size of soil microorganisms may increase when exposed to cooling. We will show and discuss first results from measurements with a suspended microchannel resonator (SMR), that, together with microscopic imaging allows to assess the mass (size) of individual cells of microorganisms at different temperatures. 

How to cite: Gall, C., Fuchslueger, L., Schmidt, H., Söllinger, A., Borg Dahl, M., Tveit, A., Sigurdsson, B., Eichorst, S., Roller, B., and Richter, A.: Investigating the effect of temperature on growth and microbial biomass accumulation during winter, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14657, https://doi.org/10.5194/egusphere-egu23-14657, 2023.

EGU23-14803 | ECS | Orals | SSS4.7

Uniting microbial modelling with microfluidic soil chips 

Edith Hammer, Pelle Ohlsson, and Hanbang Zou

Empirical soil models reproducing soil characteristics can help to reduce the inherent complexity of soils in experiments. Microengineered or microfluidic soil chips can simulate the soil pore space at microscale in a transparent material that enables direct visual investigation of soil- and soil microbial processes including monitoring of single cells and their interactions in communities. Through the chips it is possible to control and closely monitor microhabitat conditions including oxygen levels and pH, and to single out factors such as spatial relations, pore space structure or resource patch size. They can be designed either close to realistic conditions such as based on µCT measurements, or using simple geometrical patterns that can be frequently replicated and modified within the chip design. They can thus be tailored to fit scenarios of spatially explicit soil computer models and used for iterative in-silico – in-situ experiments. We found amongst others that the geometric shape of a pore space and its connectivity influences bacterial and fungal growth, their interactions and enzymatic activity. We can measure those factors spatially resolved at cellular scale.  We want to initiate a discussion for future collaborations between soil chip experimentalists and computer modelers.

How to cite: Hammer, E., Ohlsson, P., and Zou, H.: Uniting microbial modelling with microfluidic soil chips, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14803, https://doi.org/10.5194/egusphere-egu23-14803, 2023.

EGU23-16018 | ECS | Posters on site | SSS4.7

Successful characterisation of on-site wastewater treatment system biomats using the Microbes of Activated Sludge and Anaerobic Digesters (MiDAS) taxonomic database 

Alejandro Javier Criado Monleon, Jan Knappe, Celia Somlai, Carolina Ospina Betancourth, Muhammad Ali, Thomas P. Curtis, and Laurence William Gill

There has been a large output of genomic data in ecological studies of centralised wastewater treatment plants over the past number of years. One significant collaboration of Danish and Swedish research institutions lead to the development of the Microbes of Activated Sludge and Anaerobic Digesters (MiDAS 4) global taxonomic database. The database has been an effective tool in understanding centralised systems, however, there has been no known application of this tool in understanding the ecology of organisms in the on-site wastewater treatment systems. The growth of microbial mats or "biomats" has been identified as an essential component in the attenuation of pollutants within the soil treatment unit (STU) of conventional on-site wastewater treatment systems (OWTSs). Two research sites were employed to determine the influence of the pre-treatment of raw-domestic wastewater on these communities. The STUs at each of the two sites were split, whereby half received effluent directly from septic tanks, and half received more highly treated effluents from packaged aerobic treatment systems [a coconut husk media filter on one site, and a rotating biodisc contactor (RBC) on the other site]. Effluents from the RBC had a higher level of pre-treatment [~90% Total Organic Carbon (TOC) removal], compared to the media filter (~60% TOC removal).  These sites' biomat were sampled two-dimensionally in respect of distance and depth, to configure ecological data with changes in the volumetric water content values which had been used successfully as an indicator of the location of the biomat. A total of 92 samples were obtained from both STU locations and characterized by MiDAS taxonomic database. Our study has shown that the biomats receiving primary or untreated effluent have less pronounced increases in denitrifiers compared to the biomats receiving treated or partially treated effluent. but biomats receiving primary effluents have been found to be capable of removing six times the amount of total nitrogen. This suggests that the increases in functional richness within the STU are secondary to bioclogging, as metabolic rates could be limited by hydraulic conductivity.

How to cite: Criado Monleon, A. J., Knappe, J., Somlai, C., Ospina Betancourth, C., Ali, M., Curtis, T. P., and Gill, L. W.: Successful characterisation of on-site wastewater treatment system biomats using the Microbes of Activated Sludge and Anaerobic Digesters (MiDAS) taxonomic database, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16018, https://doi.org/10.5194/egusphere-egu23-16018, 2023.

EGU23-16359 | Orals | SSS4.7

Use of PGPR (GROUNDFIX®) to Improve Soil Health 

Dmytro Yakovenko and Svitlana Korsun

Nowadays, the integral indicators of soil health in agrocenoses are the crop yield and the quality of raw material. In order to achieve efficient use of soil in the field, it is necessary to understand its physical, chemical and biological properties. It is essential to consider the possibilities of improving of the soil health and plant nutrition using different types of biofertilizers, especially of microbial origin. The standard indicators included in the agrochemical certificate describe various physical and chemical properties: humus content, granulometric composition, soil density, productive moisture, acidity, salinity degree, content of mobile or hydrolyzed nutrients – N, P, K, and microelements as well as different contaminants - mobile forms of cadmium, lead, pesticide residues, etc. For the microbial analysis, it is suggested to evaluate biological indicators by the number of microorganisms and the ratio of certain physiological groups. Principle of soil condition assessment according to the research conducted includes main groups of microorganisms: oligotrophs, pedotrophs, microorganisms that use different nitrogen compounds (mineral – organic), nitrogen-fixing bacteria; different groups of fungi: saprotrophs or pathogens.

The results of conducted experiments showed that before and after application of a complex of PGPR (Groundfix®) at a rate 1 l/ha, the soil indicators had a tendency to improve. The content of mobile phosphorus compounds increased by 49.3% and potassium increased by 55.8% respectively. This efficiency was achieved due to the microorganisms that contribute to the release of phosphorus and potassium from hard-to-reach compounds. Statistical data analysis showed that humus content and hydrolyzed nitrogen dependent were high during both the first soil sampling in May and the next one in August (204.4 mg/kg and 207.2 mg/kg). This stability was provided by the high number of microorganisms that transform organic compounds contributing to both the destruction of light organic matter of plant residues and the synthesis of humus substances. According to the results of the soil analysis, the bacteria could affect the acidity of the soil. Another important fact to discover was increase in the diversity of saprophytic fungi from two to five genera, including fungi genus Trichoderma, counting 15% from the total number of fungi. These changes could be explained by the activation of the indigenous agronomically valuable microbiota in the soil. Therefore, application of the product Groundfix affected the number of microorganisms of certain physiological groups. The ratio between these groups showed that in the soil there is a predominance of synthesis over destruction processes. The number of Azotobacter bacteria increased by 2.4 times, which confirms the high level of soil fertility.

Contrary to what has often been assumed, the efficacy of PGPR bacteria usage in soil health improvement has confirmed by multiple analyses and statistical data. Our finding indicate that this complex of bacteria not only activate other beneficial groups of organisms but also make P and K more available for plants uptake. As a result, farmers get more rich harvest on their fertile soil.

How to cite: Yakovenko, D. and Korsun, S.: Use of PGPR (GROUNDFIX®) to Improve Soil Health, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16359, https://doi.org/10.5194/egusphere-egu23-16359, 2023.

EGU23-16479 | ECS | Posters on site | SSS4.7

Deep learning-based object detection for soil bacterial community analysis in microfluidics 

Hanbang Zou, Pelle Ohlsson, and Edith Hammer

Microfluidics is a multidisciplinary platform that integrates microfabrication, physical chemistry analysis, automation, and microscopy. It has the advantages of precise liquid manipulation, rapid measurements, and real-time visualization at the microscale, which is especially of interest and benefit to microbial studies. Soil Chips are microfabricated microfluidic devices typically made of glass and polydimethylsiloxane (PDMS), designed to mimic the real soil network and allow real-time visualization and characterization of microbial activity at the micro-scale. They have so far been used to investigate microbial activities, interactions, community composition, and distribution under different conditions in soil analog systems. Challenge comes when working with natural soil samples. Due to mineral aggregates and debris, valuable information such as the abundance of individuals, cell morphology, and the relationship between bacteria and their geochemical and physical environment are difficult to extract via a simple thresholding method. Since microorganisms and microfluidic structures have distinct features from the noisy background that can be easily picked up by our eyes, a biologically inspired convolutional neural network model for object detection is the most suitable tool for this task.
We used a small part of data from three different experiments to train a well-developed object detection and segmentation algorithm Mask RCNN and implemented further analysis of bacteria abundance, spatial distribution, and morphological characterization. We are able to plot the distribution of all the detected bacteria including clusters in terms of abundance, size, shape, and index of aggregation. A distinct difference in bacteria characteristics can be observed in the samples acquired from three locations (Greenland, Sweden, and Kenya). We are now planning to extend the classification library to include other microbial groups including fungi, protists, invertebrates, and micro arthropods.

How to cite: Zou, H., Ohlsson, P., and Hammer, E.: Deep learning-based object detection for soil bacterial community analysis in microfluidics, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16479, https://doi.org/10.5194/egusphere-egu23-16479, 2023.

EGU23-16487 | Orals | SSS4.7

Microbial necromass ≠ microbial biomass: Microbial death pathways affect soil organic carbon sequestration 

Tessa Camenzind, Kyle Mason-Jones, India Mansour, Matthias C. Rillig, and Johannes Lehmann

The last two decades soil organic matter research developed rapidly, uncovering a central role of soil microorganisms in the sequestration and storage of soil organic carbon (C), especially through accumulation of their necromass. However, despite strong evidence that the so-called soil microbial carbon pump is an important process, the direct characterization of microbial necromass in soil is difficult to achieve, leaving the actual chemical composition and formation of necromass unresolved. To fill this knowledge gap, we compiled evidence from microbiological literature on the processes of microbial dying, here referred to as microbial death pathways (MDPs). We discuss how fungi and bacteria die in soil, regarding the causes of death but also the consequences for chemical composition of microbial necromass. Evidence from existing literature clearly shows that MDPs in soil microorganisms represent relevant processes that affect necromass composition and its subsequent fate. Depending on environmental conditions and the relative significance of different MDPs, cell wall : cytoplasm ratios increase, while nutrient contents and easily degradable compounds are depleted. Thus, microbial necromass does not equal microbial biomass. These insights on microbial necromass are relevant for our understanding of mechanisms underpinning biogeochemical processes: (i) the quantity and persistence of microbial necromass is also governed by MDPs, not only the initial  biomass composition; (ii) efficient recycling of nutrients in microbial biomass during MDPs may minimize nitrogen losses during the process of C sequestration; (iii) human-induced disturbances do not only affect microbial activity, but also necromass quantity and composition. We present evidence for this novel concept of MDP, showing that not only microbial growth, but also death drive the soil microbial carbon pump. Additionally, we show some first data on actual experiments with “real” microbial necromass based on these principles, and discuss possibilities to explore this topic in future research studies.

How to cite: Camenzind, T., Mason-Jones, K., Mansour, I., Rillig, M. C., and Lehmann, J.: Microbial necromass ≠ microbial biomass: Microbial death pathways affect soil organic carbon sequestration, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16487, https://doi.org/10.5194/egusphere-egu23-16487, 2023.

SSS5 – Soil Chemistry and Organic Matter Dynamics

Hummock-hollow microtopography is common in the northern peatlands of the world, but its effects on soil organic carbon (SOC) components are still poorly understood. In this study, we investigated effects of microtopography on SOC stocks and soil labile organic carbon (LOC) fractions in a sedge peatland in Changbai Mountain in northeast China. We found that SOC and soil LOC fractions had much heterogeneity in microtopography. SOC concentration in hummocks was significantly higher than under hummocks and in hollows. On average, the total SOC stock to a depth of 0.3 m below the ground surface was 19.00 kg C/m2. 56% of the total SOC stock was stored in soils in and under hummocks, despite the hummock only covering 30% of the total area. Light fraction organic carbon (LFOC), easily oxidizable organic carbon (EOC), microbial biomass carbon (MBC) and dissolved organic carbon (DOC) in hummocks were significantly higher than under hummocks and in hollows. In addition, the cumulative soil CO2 emissions in hummocks were 2.0 and 4.5 times higher than those under hummocks and in hollows. The temperature sensitivity of soil CO2 fluxes (Q10) were 1.55, 1.67, and 1.52 in hummock, under hummock and in hollow, respectively. Redundancy analysis (RDA) identified that SOC explained most variations in soil LOC fractions (59.6%), followed by soil total phosphorus (7.4%) and soil water content (6.6%). Our findings indicate that the hummocks are important carbon pool in the sedge peatland, but they are vulnerable to global warming and human disturbance. Hummock-hollow microtopography creates heterogeneity in hydrological conditions and soil physicochemical properties, and thus influences SOC stocks and soil LOC fractions at a small scale. This study highlights the importance of microtopography in carbon storage and cycling and has direct implications for the assessment of the carbon sequestration function in northern peatlands.

How to cite: Wang, M.: Heterogeneity of soil organic carbon dynamic regulated by microtopography in boreal peatlands, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1207, https://doi.org/10.5194/egusphere-egu23-1207, 2023.

EGU23-4845 | ECS | Posters on site | SSS5.1

Assessment of thermal analysis techniques for determining organic, black, and inorganic carbon contents in urban soils 

Junge Hyun, Jeehwan Bae, and Gayoung Yoo

Although urban greenery is an important area for soil carbon (C) sequestration in national and international policies, there is a lack of studies on its unique soil C status. Especially the contribution of black carbon (BC) and inorganic carbon (IC), which originated from anthropogenic activities, need to be separated from ecosystem-driven organic carbon (OCeco) to accurately quantify the soil C sequestration in urban ecosystems. However, there is currently no standardized, widely used method to separate various forms of C in this soil. In this study, we suggested a robust and reliable method to discriminate the OCeco, BC, and IC contents and understand the anthropogenic effects on C in urban soils. To achieve this objective, we tested the accuracy of the “EGA with peak deconvolution approach” that derives a CO2 thermogram from an evolved CO2 gas analyzer (EGA) connected to a thermal analyzer and conducts sample-by-sample peak deconvolution. Since we used the model mixtures that had known OCeco, BC, and IC contents, the absolute accuracy of this approach could be tested. As a result, EGA with peak deconvolution approach showed high accuracy (R2 > 0.90), and the regression lines between the known and measured values were close to the 1:1 line.

Using the EGA with peak deconvolution approach, we further investigated the soils in urban greeneries. EGA with peak deconvolution approach was helpful in understanding the impacts of human intervention on the soil C cycle. Surrounding land use significantly altered the soil OCeco/TC and BC/TC but was not soil IC/TC; the OCeco/TC tended to increase with green area, while the BC/TC had a positive relationship with impervious area. The suggested method can be used to evaluate the C sequestration rate of SSM practices in the urban area. Without the information on OCeco and BC, the impacts of human intervention on soil C can be misinterpreted, which overestimates the C sequestration rate.

How to cite: Hyun, J., Bae, J., and Yoo, G.: Assessment of thermal analysis techniques for determining organic, black, and inorganic carbon contents in urban soils, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4845, https://doi.org/10.5194/egusphere-egu23-4845, 2023.

EGU23-5864 | Posters on site | SSS5.1

New opportunities to unravel the microarchitecture of soil organo-mineral associations by NanoSIMS using the upgraded Oxygen source 

Carmen Höschen, Steffen Schweizer, and Ingrid Kögel-Knabner

Organic matter (OM) and soil mineral constituents interact closely at the submicron scale forming structural units and providing biogeochemical interfaces. Soil structure itself plays a key role for carbon storage, microbial activity and soil fertility and pollutant mitigation. A better understanding to which extent biogeochemical processes and interactions in the soil are driven by the spatial arrangement of OM and mineral constituents requires advanced efforts to apply novel microspectroscopy approaches.

NanoSIMS, allowing unique elemental and isotopic analyses at nanometer spatial resolution, provide valuable insights into the architecture of soil organo-mineral constituents and crucial processes taking place at the microscale.

The instrument is equipped with two ion sources: the Cesium source (Cs+) convenient to detect ions related to organic matter distribution and the Oxygen source (O-) favourable to provide information on mineral phases or metals in samples. With a spatial resolution similar to the Cesium source and high stability, the upgraded radio frequency (RF) plasma Oxygen source  recently installed at the TUM is now best suited for novel analytical approaches to probe elemental and isotopic composition of soil organo-mineral constituents in soils at the microscale.

We will show examples of how the two primary ion sources, single or correlatively applied, enable novel experimental designs in soil biogeochemistry. Novel combinations of the OM distribution (12C, 13C and 14N, 15N) detected by the Cs+ source with the distribution of e.g. Si, Al, Fe, Ca, Mg, K, and Na of minerals as revealed by the O- source are now possible.

Post-processing tools for unsupervised clustering and supervised segmentation facilitate the comparison and quantitative analysis of the spatial architecture within intact soil structures. These ongoing developed tools can contribute to the extent of our understanding of biogeochemical processes taking place at organo-mineral and mineral-mineral interfaces in soil systems at the microscale.

How to cite: Höschen, C., Schweizer, S., and Kögel-Knabner, I.: New opportunities to unravel the microarchitecture of soil organo-mineral associations by NanoSIMS using the upgraded Oxygen source, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5864, https://doi.org/10.5194/egusphere-egu23-5864, 2023.

EGU23-6871 | ECS | Orals | SSS5.1

Detecting the Disintegration: Insights into soil structure decay following OC depletion 

Franziska B. Bucka, Vincent J.M.N.L. Felde, Stephan Peth, and Ingrid Kögel-Knabner

Aggregate forming and stabilizing processes have been intensively studied as they are closely linked to organic carbon (OC) sequestration. However, soils are no static systems and consequently, their structure is subject to constant breakup and turnover processes.

In order to study soil structure turnover with respect to the loss of OC, we designed an incubation experiment with soil microcosms, allowing OC-loss by leaching and microbial respiration, while preventing any mechanical disturbance.

We incubated intact soil cores of an arable Luvisol derived from Loess-deposits in south-east Germany for 300 days at constant water-tension and 25 °C to promote microbial activity. During the incubation, CO2-release and OC leaching from the microcosms were monitored. A subset of microcosms was sampled each month to assess the effect of progressing OC depletion on the size distribution, OC content and stability of the aggregates.

The incubation led to a reduction of the initial OC (11.2 mg g-1) by 2.2 mg per g soil and a more narrow C:N ratio, which corresponded 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 both by wet- and dry-sieving) did not change significantly, although there was a trend towards a reduced aggregate mean weight diameter (higher reduction after wet-sieving). The aggregates’ mechanical stability (as determined by dry-crushing), even slightly increased with a lower OC-content in the bulk soil.

Those observations highlight that OC depletion, without additional mechanical influence, does not immediately lead to the decay of soil structure. This suggests the existence of OC-storage sites that are not prone to OC-loss by leaching or microbial degradation. In contrast, the sites of initial OC-loss might not contribute to the structural stability of a soil.

How to cite: Bucka, F. B., Felde, V. J. M. N. L., Peth, S., and Kögel-Knabner, I.: Detecting the Disintegration: Insights into soil structure decay following OC depletion, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6871, https://doi.org/10.5194/egusphere-egu23-6871, 2023.

EGU23-7089 | ECS | Posters on site | SSS5.1

Effects of pedon-scale soil heterogeneity on soil temperature and surface energy fluxes - Does it matter? 

Melanie A. Thurner, Xavier Rodriguez-Lloveras, and Christian Beer

Soil texture, i.e. its composition of clay, silt and sand, as well as organic material, is often very heterogeneous within small distances. State-of the-art land-surface models usually cannot capture this due to their coarse grid. However, neglecting small-scale soil heterogeneity may affect the estimated exchange of energy, water, and carbon between land and atmosphere strongly.

This discrepancy is especially problematic when modelling permafrost soils, where the heterogeneity-induced mismatch can make the difference between frozen and unfrozen soil, as well as waterlogged and unsaturated soil, as soil texture determines physical properties such as heat and water-storage capacity. By that, soil heterogeneity affects the build of soil ice and resulting frost heave, determines pond locations, and ultimately influences soil genesis, e.g. by inducing cryoturbation. The determination of soil geophysics also propagates into biogeochemical dynamics, affecting the arctic carbon cycle by providing the environment for either carbon stabilization or degradation.

 

To assess the effect of soil heterogeneity in detail, and quantify the potential mismatch, we develop a two-dimensional geophysical soil model with a spatial resolution of less than 10 cm at the region of interest. We apply our model at permafrost sites, because our ultimate aim is to understand cryoturbation as a permafrost-specific soil process and its relevance for the arctic carbon cycle, which will finally allow us to improve predictions of the Arctic carbon budget.

Here we present our first results, where we study the effect of fine-scale soil heterogeneity on soil temperature, water, and implications for the simulated sensible and latent heat fluxes between soil and atmosphere. By comparing simulations with and without soil texture heterogeneity, as well as with and without lateral fluxes of heat, we are able to quantify the effect of soil heterogeneity at small scale and discuss the effect on larger scales.

How to cite: Thurner, M. A., Rodriguez-Lloveras, X., and Beer, C.: Effects of pedon-scale soil heterogeneity on soil temperature and surface energy fluxes - Does it matter?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7089, https://doi.org/10.5194/egusphere-egu23-7089, 2023.

EGU23-8300 | Posters on site | SSS5.1

Going with the flow: Initial soil structure development by percolating dissolved organic matter 

Ingrid Kögel-Knabner, Franziska B. Bucka, Vincent J.M.N.L. Felde, and Stephan Peth

Percolating dissolved organic matter (DOM) from the topsoil is considered the main source of subsoil organic carbon (OC) in temperate soils. Although DOM adsorption to minerals has been extensively studied, comprehensive knowledge about its influence on subsoil OC storage and structure development is limited.

We conducted a short-term incubation experiment using artificial model soils without pre-existing aggregates to study the effects of percolating DOM within varying soil textural conditions on OC turnover and initial structure development.

The model soils were designed with contrasting texture (clay loam, loam, sandy loam), but identical mineral composition (quartz, illite, montmorillonite, goethite), mimicking subsoil conditions, where mineral surfaces free of OM come into contact with percolating DOM. The regular application of DOM under a constant suction head (-15 kPa) enabled the DOM to percolate freely through the soil matrix over the course of the experiment.

A higher sand content caused a lower porosity, which was accompanied by a lower moisture content. In contrast, the OC retention (21% of the OC input), and the microbial abundance and activity were unaffected by the soil texture. The percolating DOM created patches of OM covers on 10% of the mineral surfaces (N2-BET) within an otherwise OC-free mineral matrix.

The biochemical processing of the percolating DOM solution induced the formation of large, water-stable aggregates (wet-sieving) in all textures without requiring the presence of physical organic nuclei. Aggregate formation was pronounced in the clay-rich soils (58% mass contribution), which also exhibited a higher mechanical stability of the aggregates.

The results highlight that retention and microbial mineralization of dissolved OM are decoupled from pore sizes and soil solution exchange, but are instead driven by the mineral composition and OC input.

The biochemical processing of percolating DOM can induce large soil aggregates. Here, the presence of fine mineral particles enhances the formation and mechanical stability of the aggregates, irrespective of their surface charge or sorption properties.

How to cite: Kögel-Knabner, I., Bucka, F. B., Felde, V. J. M. N. L., and Peth, S.: Going with the flow: Initial soil structure development by percolating dissolved organic matter, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8300, https://doi.org/10.5194/egusphere-egu23-8300, 2023.

EGU23-9140 | ECS | Orals | SSS5.1

Small scale soil heterogeneity shows stable subsoil preferential flow paths of water and DOC over a 5 year period in a Dystric Cambisol 

Sebastian Socianu, Hanna Böhme, Timo Leinemann, Patrick Liebmann, Karsten Kalbitz, Robert Mikutta, and Georg Guggenberger

Preferential flow paths (PFPs) are intertwined soil regions that link top and subsoil and through which water and consequently nutrients flow across the soil profile. PFPs enable newly available carbon sources to reach deeper soil layers, enabling soil microorganisms to flourish in an otherwise substrate-poor subsoil. A reliable assessment of organic carbon (OC) translocation into the subsurface requires an understanding of the small scale variability of dissolved organic carbon (DOC) concentrations and fluxes into the subsoil.

Using segmented suction plates over a 5-year period, we measured DOC and water fluxes, and subsequently OC translocation, at three depths in three soil profiles down to 1.5 m in a sandy Dystric Cambisol in Lower Saxony (Germany). DOC fluxes and water fluxes were correlated and decreased with depth. Overall fluxes were dependent on seasonal fluctuations of precipitation, with the winter and spring months bearing the highest water fluxes. We found significant flux variability between suction plates and soil depths. Rank analysis showed stable regions of high and low water and DOC fluxes, suggesting stable subsoil PFPs over these five years. Furthermore, the significance of small scale spatial heterogeneity as estimated by intraclass correlation was higher than the seasonal variability in each hydrological year, strengthening the idea that PFPs in a soil profile persist over years. In addition, SUVA analysis showed a decrease in OM aromaticity with depth in all three profiles and it was moderately correlated with water fluxes, indicating selective retention of complex organic matter along the soil profile.

These findings highlight the potential for long-term stability of PFPs in subsoils and their significance for the development and maintenance of biogeochemical subsoil C hotspots, and that small scale soil heterogeneity plays a major role in controlling water and nutrient movements across the soil profile.

How to cite: Socianu, S., Böhme, H., Leinemann, T., Liebmann, P., Kalbitz, K., Mikutta, R., and Guggenberger, G.: Small scale soil heterogeneity shows stable subsoil preferential flow paths of water and DOC over a 5 year period in a Dystric Cambisol, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9140, https://doi.org/10.5194/egusphere-egu23-9140, 2023.

Abstract :[Background] The black soil area in northeast China is an important grain production base in China, and soil erosion is serious. Soil aggregate stability has a profound influence on soil erosion process. The purpose of this study was to clarify the fragmentation characteristics of surface and bottom soil aggregates in sloping farmland under different damage mechanisms, and to evaluate the stability characteristics of aggregates under different damage mechanisms, so as to provide theoretical basis for the prevention and control of soil erosion in sloping farmland in rainy season. [Methods] The typical long straight sloping farmland in northeast Black soil region was selected as the study area. Samples were taken every 30 m along the longitudinal section of the slope length, with a sampling depth of 30 cm and a sampling length of 1020 m. The particle size distribution and stability parameters of soil aggregates were determined by Le Bissonnais (LB) method (including fast wetting (FW), slow wetting (SW) and runoff disturbance (WS) treatments. [Results] 1) Under the three treatments of LB method, FW treatment (rainstorm) had the largest damage to soil aggregate structure, SW treatment (light rain) had the least damage to soil aggregate structure, and WS treatment (disturbance) was in the middle. On the whole, the aggregate stability showed MWDSW>MWDWS>MWDFW. 2) Analysis of soil aggregates in the topsoil (0-10 cm) showed that SW treatment (light rain) caused the soil aggregates to break into aggregates of >0.2 mm. WS treatment (disturbance) caused the fragmentation of soil aggregates mainly concentrated in 2-0.2 mm grain size, indicating that the >2 mm grain size aggregates were mainly destroyed by raindrop splashing, which made them split into microaggregates. After FW treatment (rainstorm), the aggregates were broken in <1 mm size, which provided abundant loose aggregates for raindrop splash erosion and runoff erosion process, and became the main source of erosion materials in soil erosion process. 3) The aggregate fragmentation of surface layer (0-30 cm) was more sensitive to 0-10 cm soil layer after light rain. The aggregate fragmentation effect under rainstorm and irrigation was more obvious in 0-20 cm soil layer. The effects of raindrop splashing and runoff disturbance on aggregate fragmentation in 0-30 cm soil layer are similar. MWD0-10cm < MWD10-20cm < MWD20-30cm in different soil layers under the three failure mechanisms. 4) In the three treatments of LB method, 1 mm grain size was taken as the critical, and 1 mm grain size was used as the index to distinguish soil stability. Soil aggregate size >1 mm had a strong resistance to soil dissipation, clay expansion and mechanical oscillation. This result could characterize the factors affecting soil stability structure.

How to cite: Liu, H. and Jia, Y.: Study on the structure and stability characteristics of typical black soil aggregates in Northeast China based on Le Bissonnais method, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10424, https://doi.org/10.5194/egusphere-egu23-10424, 2023.

EGU23-10958 | ECS | Posters on site | SSS5.1 | Highlight

The thermodynamics of aggregate development, structure, and size 

Thomas Ritschel and Kai Totsche

Soil's aggregated structure is fundamental for the functioning of soil, and aggregation is a crucial process within pedogenesis. While aggregates are often considered stable entities, bonds between aggregate forming materials can form, consolidate, and break over time. Consequently, individual aggregates are subject to permanent restructuring and do not show a final spatial configuration that remains stable. Instead, only the temporal average of aggregate features converges to a constant value and –in case the system comprises a large ensemble of aggregates– a situation of thermodynamic equilibrium will establish over time. The dynamics of disaggregation and restructuring might be equally important for the establishment of aggregate structure as the aggregation mechanisms themselves and should therefore be considered when modeling structure formation. We conducted a comprehensive numerical analysis to reveal the interplay of aggregation mechanisms and the breaking of aggregate bonds in a physicochemical framework that combines three-dimensional transport with DLVO-type surface interactions. The attractive and repulsive energies between aggregate forming materials were used to model the temporal dynamics and stability of bonds in a heuristic manner. Despite the ongoing formation and breaking of bonds, we show that aggregation approaches a thermodynamic equilibrium depending on the physicochemical environment. Specifically, an ensemble of aggregates of sufficient size to provide robust statistical averages converges to a state of constant mean properties, e.g., aggregate size and aggregate morphology. Aggregates and their structure should therefore be considered dynamic entities, where an ensemble might reach a steady-state equilibrium, but each individual aggregate does not.

How to cite: Ritschel, T. and Totsche, K.: The thermodynamics of aggregate development, structure, and size, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10958, https://doi.org/10.5194/egusphere-egu23-10958, 2023.

EGU23-11593 | Orals | SSS5.1

Elucidating cm-scale heterogeneity in soil biogeochemistry with a 13C pulse-chase assay 

Lukas Kohl, Petri Kiuru, Marjo Palviainen, Maari Raivonen, Markku Koskinen, Laura Matala, Mari Pihlatie, and Annamari Laurén

Spatial heterogeneity in the soil pore network is commonly understood to lead to spatially distinct biogeochemical transformations like the production of methane in anaerobic pockets in unsaturated soils. Yet, demonstrations of this heterogeneity and its linkage to soil structure (e.g., the spatial position in the soil pore network architecture) remains elusive.

We therefore developed an assay to elucidate centimeter-scale differences in biogeochemical reactions within and between peat soil cores. For this, we injects a isotope-labeled substrate (sodium 13C2-acetate) at different locations in intact peat samples (10 cm diameter x 10 cm height) and followed its conversion to 13CO2 and 13CH4 over 5 days time in an automated measurement system using a Picarro G2201-i trace gas analyser. We analyse the ratio of 13CH4 and 13CO2 produced from the amended substrate, the fraction of substrate converted to 13CH4/13CO2, and the time course of 13CH4/13CO2 release. 

To test this approach, we collected seven pairs of peat core samples (15-25cm depths, 10 cm diameter, >30m between apart) at a drained forested peatland in Southern Finland. As one of the goals was to evaluate the effects of water retention hysteresis, half of the samples were set to -15 hPa water potential after draining to -30 hPa water potential, while the other half was set to same water potential after water-saturating the samples. In three experiments per core, we injected 10 nmol sodium acetate in 1mL water at 2, 5, and 8cm depth. We find both fixed effects (of core, injection depth, water treatment) and random effects that might be governed by the position of the injection with the peat core. 

We find, for example, that while a subset of the peat cores emitted (natural abundance) CH4, these cores showed highly heterogeneous conversions of the injected label into CH4 and CO2 that could not be explained by the fixed effects, demonstrating the spatial heterogeneity of methanogenesis and heterotrophic respiration within the peat core.

In our future work, we will explore if pore networks models extracted from microtomographic images can explain these contrasting results. 

How to cite: Kohl, L., Kiuru, P., Palviainen, M., Raivonen, M., Koskinen, M., Matala, L., Pihlatie, M., and Laurén, A.: Elucidating cm-scale heterogeneity in soil biogeochemistry with a 13C pulse-chase assay, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11593, https://doi.org/10.5194/egusphere-egu23-11593, 2023.

EGU23-11663 | Posters on site | SSS5.1

Spatial variability of Carbon turnover in soil microaggregates and the challenge of combining multi-scale approaches 

Nele Meyer, Jacqueline Kaldun, Andrey Rodionov, Wulf Amelung, and Eva Lehndorff

The long-term stability of soil organic carbon (SOC) is controlled by stabilization mechanisms, among which physical stabilization through microaggregate (<250µm) formation is considered to be critically important. Yet, the turnover of Carbon in aggregates is not well understood. Here, we aimed at unravelling the importance of microaggregates for long-term C storage in a soil subjected to a C3-C4 vegetation change 36 years before sampling. We hypothesized that Carbon in microaggregates is characterized by a longer mean residence time (MRT) than that of bulk soil and that SOC turnover appears predominantly at the outside of aggregates. Free and occluded size fractions (250-53 µm) were obtained by wet sieving and ultrasound. True aggregates were manually isolated from size fractions and analyzed for quantity, C content, and bulk δ13C. Additionally, we used laser ablation isotope ratio mass spectrometry (LA-IRMS) with a resolution of 20 µm to study small-scale patterns of δ13C within aggregates and on their surfaces. The calculated MRT of Carbon in occluded and free aggregates was with 62 and 105 years only slightly longer than that of bulk soil (58 years). Also the low quantity of true aggregates (<5% aggregates in size fraction) questions their importance for soil C storage. The spatial variability of δ13C within individual aggregates was considerable, both in C3 (-18.8±6.4) and C4 (-19.6 ±5.5) soil, but without difference between inside and surface locations. No aggregates being clearly older than 36 years, i.e. with only C3-derived SOC isotope signatures were found, suggesting that on the micro-scale microbial turnover processes control δ13C more than expected. In summary, aggregates seemed to be subjected to high rates of formation and decay. Altogether, it is therefore questionable whether aggregates considerably contribute to overall long-term SOC storage. Yet, results need to be treated with caution and we will present evidence that the concept of source mixing between C3 and C4-derived Carbon is not valid in small-scale approaches where differences in δ13C are dominated by C turnover processes rather than source.

How to cite: Meyer, N., Kaldun, J., Rodionov, A., Amelung, W., and Lehndorff, E.: Spatial variability of Carbon turnover in soil microaggregates and the challenge of combining multi-scale approaches, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11663, https://doi.org/10.5194/egusphere-egu23-11663, 2023.

EGU23-12421 | ECS | Orals | SSS5.1

Quantifying the impact of 3D pore space morphology on diffusive mass transport in loam and sand 

Matthias Weber, Benedikt Prifling, Nadja Ray, Alexander Prechtel, Maxime Phalempin, Steffen Schlüter, Doris Vetterlein, and Volker Schmidt

Effective diffusion is an important macroscopic property for assessing mass transport in porous media. Numerical computations on segmented 3D CT images yield precise estimates for diffusive properties. On the other hand, geometrical characteristics of pore space like, e.g., porosity, specific surface area and further transport-related descriptors can be easily computed from 3D CT images and are closely linked to diffusion processes. In the present contribution, we consider six different soil samples of loam and sand, whose 3D microstructure is quantitatively investigated using univariate as well as bivariate distributions of geometrical descriptors of pore space. This information is used for investigating microstructure-property relationships by means of empirically derived regression formulas, where a particular focus is put on the differences between loam and sand samples. In this way, it is possible to obtain a deeper understanding for the relationship between the 3D microstructure of the pore space and the resulting diffusive properties due to the analytical nature of the prediction formulas. In particular, it is shown that formulas existing so far in the literature for predicting soil gas diffusion can be significantly improved by incorporating further geometrical descriptors such as geodesic tortuosity, chord length distribution or constrictivity. The robustness of these formulas is investigated by fitting the regression parameters on different data sets as well as by applying the empirically derived formulas to certain data that is not used for fitting. Among others, it turns out that a prediction formula based on porosity as well as mean and standard deviation of geodesic tortuosity performs best with regard to the coefficient of determination and the mean absolute percentage error. Moreover, it is shown that with regard to the prediction of diffusive properties the concept of geodesic tortuosity is superior to geometric tortuosity, where the latter is based on the skeleton of the pore space. 

How to cite: Weber, M., Prifling, B., Ray, N., Prechtel, A., Phalempin, M., Schlüter, S., Vetterlein, D., and Schmidt, V.: Quantifying the impact of 3D pore space morphology on diffusive mass transport in loam and sand, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12421, https://doi.org/10.5194/egusphere-egu23-12421, 2023.

EGU23-13591 | Posters on site | SSS5.1

Seven years of research on process-based, mechanistic modeling of aggregation and its drivers 

Alexander Prechtel, Simon Zech, and Nadja Ray

Advanced imaging techniques now allow to take snapshots of soils even down to the nanoscale. Nevertheless, assessing the temporal evolution of elemental distributions, distinguishing different liquid phases and identifying dynamic microbial processes is experimentally still challenging. Consequently mechanistic models operating at the pore scale facilitate the study and understanding of phenomena shaping soil structures as, e.g., carbon turnover, and vice versa.

We present an overview of a versatile hybrid discrete continuum modeling approach combining cellular automata and partial differential equations, which integrates the complex coupling of biological, chemical, and physical processes. Dynamic liquid and gaseous phases, diffusive processes for solutes, mobile bacteria transforming into immobile biomass, and ions are prescribed by means of partial differential equations. Furthermore the solid phase is dynamic, e.g. through aggregation of soil particles, the addition and decomposition of particulate organic matter, or the mechanical influence of roots and their exudates. The virtual soil structures rely on micro-CT images or particle libraries derived from dynamic image analysis of water-stable aggregates.

Applications include structure formation of clay minerals, the interplay between soil structural dynamics and organic matter turnover, or the impact/importance of liquid phase connectivity and substrate supply. Finally the mathematical homogenization technique is used to show a way how to incorporate information from the pore scale to macroscale models, e.g. by coupling microscale carbon turnover to profile-scale CO2 transport.

How to cite: Prechtel, A., Zech, S., and Ray, N.: Seven years of research on process-based, mechanistic modeling of aggregation and its drivers, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13591, https://doi.org/10.5194/egusphere-egu23-13591, 2023.

EGU23-14821 | ECS | Orals | SSS5.1

The functional roles of mucus during aggregation 

Tom Guhra, Arnold Wonneberger, Katharina Stolze, Thomas Ritschel, and Kai Uwe Totsche

Soil organisms influence pedogenesis on a molecular level through the production of biopolymers which potentially interact with soil minerals depending on their molecular properties. Specifically, biopolymers can inhibit aggregation as separation agent or promote aggregation as bridging agent (Guhra et al. 2022). Mucus, a biopolymer excreted by earthworms consisting mainly of proteins, polysaccharides, and, to a lesser extent, lipids, has often been neglected so far, despite earthworm's fundamental contribution to soil quality and structuring via bioturbation. In our study, we investigate the role of cutaneous earthworm mucus (CEM) of L. terrestris during the formation of organo-mineral associations and aggregates. For this purpose, batch experiments were carried out with goethite and CEM at different pH values and increasing CEM concentrations resulting in the formation of mucus-goethite associations. Afterwards, the (homo/hetero) aggregation of these newly formed mucus-goethite associations with quartz particles was investigated in response to mucus-C loadings on mineral surfaces and CEM concentration in solution.

Our experiments showed a pH dependent CEM structure and an adsorption to goethite controlled by concentration and pH. Polysaccharides from CEM adsorb preferentially under acidic conditions (pH 3) and low CEM concentration (6 mg mucus-C/l). In contrast, a stronger adsorption of proteins was observed at higher CEM concentrations (30 mg mucus-C /l). In subsequent aggregation experiments, the hetero-aggregation rate of organo-mineral associations and quartz was decreased at low C-loadings and increased at high loadings in comparison to the CEM-free reference. Furthermore, the aggregation between goethite particles was inhibited by electrostatic/steric repulsion (separation agent) when high CEM concentrations were present in solution (mineral:mucus ratio of 17), while CEM functions as bridging agent at low relative CEM supply (mineral:mucus ratio of > 83).

The formation and the aggregation behavior of mucus-mineral associations contribute to nutrient/carbon storage as well as structure formation in soil. The composition, function, and (im-)mobilization of CEM and corresponding organo-mineral associations in earthworm-influenced soil structures is shaped by CEM availability and the structure/reactivity of CEM affected by environmental parameters.

 

 

References:

Guhra, T., Stolze, K. and Totsche, K.U. 2022. Pathways of biogenically excreted organic matter into soil aggregates. Soil Biology and Biochemistry, 164, 108483.

How to cite: Guhra, T., Wonneberger, A., Stolze, K., Ritschel, T., and Totsche, K. U.: The functional roles of mucus during aggregation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14821, https://doi.org/10.5194/egusphere-egu23-14821, 2023.

EGU23-15383 | Posters on site | SSS5.1

X-ray imaging demonstrates that air-filled porosity and its connectivity controls carbon mineralisation near saturation in intact soil cores. 

Elsa Coucheney, Emilien Casali, Nicholas Jarvis, and Johannes Koestel

One source of uncertainty in the prediction of soil carbon (C) dynamics is the regulation of microbial activity by soil moisture. This important factor regulates both the survival and the activity of the microbial community through the availability of water, air and substrates. The role of soil structure in the response of C mineralisation to soil moisture is not taken into account in models. We need to better understand how the heterogeneity of the soil pore space and changes in soil structure affect C mineralisation through the regulation of soil water retention and thus the distribution of air and water in the pore system. We hypothesized that soil structure has a predominant effect on the response curve close to saturation by affecting the amount and distribution of the air phase in soil, in which the diffusion of gases takes place: transport of air (O2) to microbes and transport of the mineralisation product (CO2) back to the atmosphere.

To obtain soils of contrasting structure, we sampled 8 intact cores (at a depth of 10-15 cm) from four blocks of an agricultural field experiment located in northern France a under conventional or no-till management. Each core (5 x 6.5 cm) was consecutively incubated over a period of one week after equilibration at water potentials of -2.5, -10, -20 and -30 cm and C mineralisation rates were estimated at day 1, 3 and 7. Air distributions in the soil pore networks were quantified by X-ray tomography between each equilibration/incubation period. Water retention curves, soil dry bulk density and porosity were estimated from water contents (weights) measured at each potential.

The estimated porosity varied from 0.40 to 0.52 and the Van Genuchten parameter alpha (estimated from water retention curves) varied from 0.05 to 0.09 cm-1 and both were slightly smaller under no till compared to conventional management. Air contents varied from zero to 0.09 m3 m-3 and were positively correlated to the C mineralisation rates, which varied from 18 μg CO2 g-1C h-1 near saturation to 65 μg CO2 g-1C h-1 at water potentials of -20 to -30 cm. X-ray analyses carried out at the four different water potentials further showed that C mineralisation rates were positively correlated to the volume fraction of the air-filled porosity connected to the upper surface of the cores.

These results confirm that soil structure is important in the C mineralisation response to soil moisture close to saturation by regulating the air content and its distribution in soil at water potentials ranging from 0 to -30 cm.

How to cite: Coucheney, E., Casali, E., Jarvis, N., and Koestel, J.: X-ray imaging demonstrates that air-filled porosity and its connectivity controls carbon mineralisation near saturation in intact soil cores., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15383, https://doi.org/10.5194/egusphere-egu23-15383, 2023.

EGU23-15453 | ECS | Orals | SSS5.1

Changes in soil organic matter quality during long-term bare fallow do not affect microaggregate stability 

Alexander Fechner, Robert Mikutta, Klaus Kaiser, Tobias Bromm, Cordula Vogel, Jeroen Zethof, Michaela Aehnelt, Georg Guggenberger, and Stefan Dultz

Organic substances of diverse origins are known to promote the formation of microaggregates in soils. However, their contribution to the resistance of microaggregates against mechanical stress remains unclear. This study tests for possible effects of plant- and microbial-derived organic matter on the stability of microaggregates against ultrasonic dispersion, taking advantage of a 14-year field experiment with either continuous (cropland) or minimum (bare fallow) organic inputs. The idea was that minimum input will result in the depletion of organic matter and, consequently, in decreased microaggregate stability. Microaggregates were separated into three size fractions (<20, 20-53, 53-250 µm) by wet sieving and subjected to ultrasonic disturbance at various energies. The contents of organic C, total N and neutral and amino sugars in microaggregates were determined by thermal combustion and biomarker analyses, and X-ray photoelectron spectroscopy of intact and crushed microaggregates was used to analyse the spatial distribution and oxidative alteration of organic matter. The results show that most microaggregate samples under bare fallow showed little to no decline in organic C concentrations, while bulk soil C decreased from 1.2 to 0.9 %. Amino and neutral sugars, however, decreased significantly, indicating decreased contribution of microbial products. This finding is in conflict with the missing plant C input, which should have promoted microbial processing of organic matter, resulting in declining contents of organic C with increased contributions of microbially derived compounds. Microaggregate surfaces were significantly enriched in C, with no decrease under bare fallow, which might indicate that microaggregates are not built around organic cores but are structural units collecting organic matter from their surroundings. This agrees with the finding that more oxidised and microbially processed material is stored within microaggregates, while organic matter on the outer surfaces is less oxidised, i.e. less strongly processed and thus fresher. This may explain why microaggregates lost very little organic C during fallow, as degrading plant material could have provided organic matter, substituting the loss of mineralized microbial organic matter. All microaggregate size fractions showed little and rather similar resistance against mechanical stress, achieving near complete dispersion after the application of 25 J/ml. Microaggregate stability was, in agreement with organic C contents, similar for both treatments but showed no indication that the varying contribution of amino and neutral sugars was of relevance to microaggregate stability. We conclude that, despite the clear effect of bare fallow on the organic matter composition, it had little effect on microaggregate organic C contents and their resistance to mechanical stress. This indicates that the composition of organic matter may not be the primary factor for the mechanical stability of microaggregates.

How to cite: Fechner, A., Mikutta, R., Kaiser, K., Bromm, T., Vogel, C., Zethof, J., Aehnelt, M., Guggenberger, G., and Dultz, S.: Changes in soil organic matter quality during long-term bare fallow do not affect microaggregate stability, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15453, https://doi.org/10.5194/egusphere-egu23-15453, 2023.

Soil structure is a dynamic property of soils, which refers to temporal changes in the spatial arrangement of pores, organic matter, and minerals. As for many chemical reactions, also soil structure can be at a state of dynamic equilibrium, in which bulk properties, such as macroporosity, average pore size, and others apparently remain constant even though pores are formed and destroyed continuously. On the long term, the creation and destruction of structural properties are in balance as long environmental conditions, such as climate or cover crops, do not change or no external disturbances, such as tillage, become effective.

The irreversible redistribution of soil constituents, i.e. soil structure turnover, itself determines essential soil functions. For example, the creation and disruption of a pore network affects water flow, water storage, and aeration. Microsites of higher densities limit the accessibility of plant residues and organic amendments for microbiology through pores, and in consequence, increase the capacity of soil to store organic carbon. However, so far there are only few experiments trying to capture these dynamic processes and quantify the contribution of different drivers. Using examples describing the relationship between soil structure and soil functions at different sites, I will show that there is a need for new long-term monitoring experiments to capture these dynamics at temporal resolution.

How to cite: Leuther, F.: Soil structure – a dynamic soil property which effects multiple soil functions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15721, https://doi.org/10.5194/egusphere-egu23-15721, 2023.

EGU23-16345 | Orals | SSS5.1

Soil heterogeneity and how it controls ecosystem functions and soil development 

Stephan Peth, Daniel Uteau, Vincent John Martin Noah Linus Felde, and Svenja Roosch

Soil structure is complex and dynamic on various scales. Soil heterogeneity as an expression of soil structural complexity develops over time and is controlled by biological, physical and geochemical processes and their interactions. Biotic and abiotic mechanisms shape the soil (micro)environment by forming interconnected pore spaces and solid particle arrangements. Commonly soil development begins with a more or less homogeneous initial structure which evolves towards an increasingly heterogeneously shaped soil architecture serving as a habitat of living organisms and in turn controlling matter, energy and gas fluxes. The relationship between soil structure and function seems to result in a self-organized system of pores and biogeochemical interfaces that is in equilibrium with its boundary conditions. 

In this presentation, we will demonstrate the interaction between soil heterogeneity and function using imaging approaches. Examples will include (i) root – soil interactions and rhizosphere oxygen distribution, (ii) spatial distribution and mineralization of organic matter in soil aggregates with contrasting architecture, (iii) the effect of initial soil heterogeneity on soil structural evolution and (iv) in-situ deformation patterns upon mechanical stresses. These examples provide an insight into the internal dynamics of soil architectures and their related physical, biological and geochemical processes which are important to understand ecosystem-relevant soil functions.

How to cite: Peth, S., Uteau, D., Felde, V. J. M. N. L., and Roosch, S.: Soil heterogeneity and how it controls ecosystem functions and soil development, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16345, https://doi.org/10.5194/egusphere-egu23-16345, 2023.

EGU23-17493 | Posters on site | SSS5.1

Are pseudo-sands internal soil biophysical reactors? 

Hermann F. Jungkunst, Simone Kilian Salas, Paul A. Schroeder, Jens Boy, and Georg Guggenberger

Most biogeochemical models commonly obtain their soil input from pedotransfer functions based on soil texture and other crude but widely available soil data. However, soil texture based on single grain size distribution neglects the impact of actual soil structures in the field. Consequently, scientific efforts are being made to correct for this systematic bias in predicting soil functioning. Pronounced discrepancies between field measurements and model predictions occur for tropical soils: overestimated N2O emissions is a prominent example of this mismatch. A well-known characteristic of tropical soils, potentially responsible for the systematic error, are stable aggregates called pseudo-sands. In the field they are perceived as sand, but in the lab measured as clay and silt. The simple assumption that pseudo-sands act just like sands in the field seems to work satisfactorily for certain hydrological predictions, so models were easily adjusted to it. However, here we pursue the hypothesis that, biogeochemically, pseudo-sands do not act like sands. Due to their high internal surface and rough structure, pseudo-sands, unlike sands, provide a wide variety of ecological niches for a diverse community of microorganisms to establish. We will present first evidence for pseudo-sands to act more like a biophysical reactor than just another grain of sand. The long-term goal is to develop a transfer function related to the properties of pseudo-sands that will lead to improved models for tropical soils.

How to cite: Jungkunst, H. F., Kilian Salas, S., Schroeder, P. A., Boy, J., and Guggenberger, G.: Are pseudo-sands internal soil biophysical reactors?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17493, https://doi.org/10.5194/egusphere-egu23-17493, 2023.

EGU23-303 | ECS | Orals | SSS5.2

Do published field experiments inform the longevity of biochar in soil? 

Chenzhe Xu, Saran Sohi, Jonathan Hillier, and Elizabeth Baggs

The efficiency of biochar application in soil carbon sequestration (SCS) is highly sensitive to biochar longevity. To predict biochar longevity at extended timescales, modelling is essential. It is often expressed that data from field experiments can support this understanding, especially long-term field experiments (LTEs). Our work tests this assertion, using the existing evidence base. A literature search for LTEs of greater than 3-year duration and other criteria was conducted, with the null assumption that biochar C is inert in soil. Observations of soil organic carbon (SOC) after biochar additions from selected LTEs were made against predictions from the Roth C model, assuming no biochar decay.

At the end of July 2022, we found 982 articles describing field experiments that concerned biochar longevity and SCS and initiated within the last two decades. Among them, only 17 reported LTEs matching our screening criteria and providing long-term data suitable for modelling. In these LTEs, a range of SOC dynamics were observed where an acceptable level of fit could not be achieved using a plausible range in parameters. A range of potential reasons for the deviation between measured observations and model predictions were considered, including priming effects on native SOC, migration of biochar particles, sampling and measurement issues, etc. Such factors could not be isolated with sufficient confidence to adjust observational data or model parameters, confounded by the inability to distinguish the dynamics of biochar C and non-biochar C.

Current field data do not enable us to reject the null hypothesis. Reliable parameterization for biochar longevity solely based on field experiments may not be possible on timescales relevant to mitigation of climate change. Instead, alternative strategies for assessing biochar longevity are required, that can be verified in real-time alongside a set of permanent benchmark sites, across different agro-ecological zones with uniform experimental standards, not least in sampling strategy and biochar C and non-biochar C distinction. That will support the incremental adoption of biochar, while providing a robust method for post-hoc adjustment of mitigation benefit.

How to cite: Xu, C., Sohi, S., Hillier, J., and Baggs, E.: Do published field experiments inform the longevity of biochar in soil?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-303, https://doi.org/10.5194/egusphere-egu23-303, 2023.

EGU23-700 | ECS | Posters on site | SSS5.2

Effect of Organic Fertilization and Deficit Irrigation Management on Processing Tomato 

Jenny Shrestha, Silvia Locatelli, Carlo Nicoletto, Francesco Morbidini, Giampaolo Zanin, Dorcas Franklin, Paolo Sambo, and Carmelo Maucieri

An experiment was carried out to determine if organic fertilizer and deficit irrigation combination could replace the traditional management of processing tomato crop (mineral fertilizer and irrigation of 100% crop evapotranspiration, ETc), without affecting yield and quality of production. The study was conducted from June 2022 to September 2022 at the experimental farm of the University of Padova, adopting a split-plot experimental design. The experiment was conducted under a plastic tunnel greenhouse where only the roof was covered to avoid the rainfall influence and at the same time to permit air circulation. Four fertilizer treatments, control (no fertilization), mineral fertilizer, unseived compost, and sieved compost (< 2mm) were applied in factorial combination with two irrigation treatments, 100% ETc and 75% ETc. Data on the vegetative, physiological, yield, and quality parameters were collected. The maximum plant height (75.3 cm) and stem diameter (17.0 mm) were recorded on plants fertilized with unseived compost; both of these parameters did not show significant differences in response to the irrigation level. For physiological parameters, significant differences were found among irrigation treatments. During the daytime, the 25% reduction of optimal irrigation water volume determined a reduction of 4.6% for stomal conductance (0.372 mol m-2 s-1 at 100% ETc) and of 14.2% for transpiration (4.56 mmol m-2 s-1 at 100% ETc). Regarding fluorescence, the highest value (0.769) was recorded for 75% ETc and mineral fertilization, while the lowest (0.733) was for 100% ETc and mineral fertilization. The number of ripe fruits per plant was significantly higher in the treatments with compost (60 fruits plant-1) than in the unfertilized control (39 fruits plant-1). The yield was neither influenced by fertilization nor by irrigation level showing an average value of 2 kg plant-1. Similarly, the qualitative analysis of the tomato fruits showed significantly higher soluble solid content (+5.8%) and pH (+1.4%) at 100% ETc than 75% ETc which showed an average value of 4.11 ˚Brix and 4.20, respectively. The fruits' dry matter content was not significantly influenced by the studied treatments. The results were derived from one year experiment, and they have to be confirmed in future experiments. However, they indicate that compost, whether sieved or not can be a valuable solution for the processing tomato fertilization and that deficit irrigation can be a valuable solution to reduce agricultural water use with only a few effects on plant production and quality parameters.

How to cite: Shrestha, J., Locatelli, S., Nicoletto, C., Morbidini, F., Zanin, G., Franklin, D., Sambo, P., and Maucieri, C.: Effect of Organic Fertilization and Deficit Irrigation Management on Processing Tomato, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-700, https://doi.org/10.5194/egusphere-egu23-700, 2023.

EGU23-2694 | Posters on site | SSS5.2

Revisiting a short rotation coppice plot trial 10 years after biochar application: can we expect long-term effects on soil organic carbon content? 

Stefan Pätzold, Ester Bellantone, Alexandra Sandhage-Hofmann, and Felix von Glisczynski

Biochar and related commercial products have been intensively studied in the past years with respect to their potential benefit for soil fertility and carbon sequestration. Yet, little is known about long-term effects of modern biochar application to soil organic carbon (SOC) content at plot scale and in temperate climate.

To evaluate potential effects of biochar application on soil organic carbon (SOC) and total nitrogen (Ntot) content, the soils of a field trial at Campus Klein-Altendorf, an experimental site of the University of Bonn (Germany), were re-sampled in 2022. The short rotation coppice plot experiment with four tree species had been established in 2012 on a Luvic Stagnosol formed from loess. Four treatments in threefold replication were realised: untreated control, compost, and two biochar–compost substrates with 15% (BCS15) and 30 % biochar (BCS30), respectively (in total 48 plots). All amendments were applied at 30 Mg dry matter ha–1 and incorporated to 0.15 m depth before the trees were planted.

Prior to application of the amendments in 2012, the mean SOC and Ntot content were typical for arable loess soils in the region. In the first three years, no significant effects on soil fertility parameters and plant growth were observed, but C stocks were enhanced in the biochar treatments (von Glisczynski et al., 2016).

During the re-sampling campaign after ten years, soil samples were taken from 0-0.1, and 0.1-0.2 m depth, corresponding to the sampling design at the beginning of the trial. The samples were conventionally analysed for SOC and Ntot (elemental analysis). Priority was given to the control and the 30% biochar treatment to estimate the maximum effects. The first and preliminary results point to a significant increase of the SOC content in the BCS30 treatment, but also in the untreated control when compared to the initial contents published by von Glisczynski et al. (2016). The mean SOC content in 0-0.2 m depth over all tree species raised from 12.5 g kg-1 to 13.8 g kg-1 (control) and 16.9 g kg-1 (BCS30) SOC, respectively. Total N also increased to 1.3 (control) and 1.4 g kg-1 (BCS30), respectively. Resolving more in detail the depth distribution clearly showed that the SOC increase occurred predominantly in the uppermost 0-0.1 m (BCS30: 21.5 g kg-1, control: 16.5 g kg-1); here, the BCS30 treatment showed a significantly larger C:N ratio than the control. In contrast, little difference was observed in 0.1-0.2 m depth (BCS30: 12.2 g kg-1, control: 11.2 g kg-1). The increase of SOC and Ntot also in the untreated control as well as their depth profiles point to an effect not only of biochar application, but also of abandonment of soil cultivation for 10 years in the short rotation coppice. However, further in-depth investigations are necessary to confirm these presumed long-term effects.

How to cite: Pätzold, S., Bellantone, E., Sandhage-Hofmann, A., and von Glisczynski, F.: Revisiting a short rotation coppice plot trial 10 years after biochar application: can we expect long-term effects on soil organic carbon content?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2694, https://doi.org/10.5194/egusphere-egu23-2694, 2023.

EGU23-2978 | ECS | Orals | SSS5.2

Co-composted biochar enhances soil fertility more than individual additives 

Irina Mikajlo, Brice Louvel, Jaroslav Záhora, Thomas Z. Lerch, and Bertrand Pourrut

Biochar is considered a promising amendment to store carbon and improve degraded soil properties. However, this additive could have disadvantageous effects on plants and soil organisms due to its charring process toxic by-products and its ability to retain nutrients. To mitigate these negative effects, co-amendments with an organic additive such as compost have been proposed, but comparative studies are scarce. In this study, we investigated the influence of biochars applied (i) solely, (ii) mixed with matured compost or (iii) co-composted biochar on soil properties and plant growth. To this aim, three different types of biochar derived from various feedstocks were tested in two soil with different agronomic properties (Luvisol and Fluvisol). After three months of greenhouse experiment with grown lettuce (Lactuca sativa var. capitata L.), the shoot and root biomasses were quantified and the soil physicochemical properties were measured (pH, CEC, total N, organic C and soil available P). Solely applied biochar did not influence plant yield and maintained alkaline soil pH. Contrariwise, biochar mixed with matured compost maintained an average increase of lettuce growth by three times with risen soil nutrient content and kept alkaline pH. Whereas treatments with co-composted biochar and solely added compost promoted plant growth by almost six times, kept pH on neutral levels and nutrients on an average level with CEC equally enhanced, regardless of the biochar origin or the soil type. These results suggest that co-composted biochar addition to the soil is a convincing way to maintain soil fertility in a long term.

How to cite: Mikajlo, I., Louvel, B., Záhora, J., Lerch, T. Z., and Pourrut, B.: Co-composted biochar enhances soil fertility more than individual additives, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2978, https://doi.org/10.5194/egusphere-egu23-2978, 2023.

EGU23-3104 | ECS | Posters on site | SSS5.2

The effect of new leonardite-based soil amendments on soil organic carbon and carbon dioxide emissions from black soil 

Viktoriia Hetmanenko, Olesia Volosheniuk, Ievhen Skrylnyk, and Angela Kutova

The current declining soil fertility along with the need for intensification of crop production and greenhouse gas (GHG) emissions reduction is a great challenge, which may be mitigated by sound soil organic carbon (SOC) management. Organic soil amendments have long been known to increase the organic matter content of the soil. Locally available organic soil amendments are an essential source of carbon and nutrients. The significance of the production of new soil amendments has become even clearer considering the escalating prices of chemical fertilizers. Leonardite (oxidized lignite) has a high content of carbon (48.3%) and can be an efficient raw material for soil amendment production. To increase the degree of humification of leonardite and to improve its fertilization value mechano-activation with different materials was used. Iron as a variable-valent metal played the role of a catalyst for the synthesis of the humic substance while bentonite was used as matrice to their synthesis. Molasses was used as the binder during the granulation of soil amendments. For the production of organo-mineral amendment to organic granules obtained a mineral fertilizer layer was added to achieve an N:P:K ratio of 1:0.86:0.95. Correct dose and method of soil amendment application play an important role in its efficient use. We have tested two methods of application of new soil amendments (band incorporation and broadcasting) at two rates of total nitrogen fertilization (30 and 60 kg N ha-1) in a field trial for two years. The sum of positive temperatures on the experimental field is 2400-2900 С. The average annual precipitation is 465-680 mm. The soil - Chernozem Podzolic with organic carbon content by the Tyurin method is 2.37 %. Application of organo-mineral amendment (N60) led to an increase of total organic carbon content in the topsoil by 10% compared to the no treatment and mineral fertilization. The integral indicator of the complex dielectric permeability revealed a decrease of polarity of the humic supramolecular structure due to organo-mineral amendment application. This change led to the formation of a more complex, polydisperse, and heterogeneous molecular aggregate organization with high hydrophobicity and stability. The data obtained during the growing period of maize showed that the intensity and the dynamics of carbon dioxide (CO2) emissions from soil depend on the hydrothermal conditions and the type of soil amendments. Cumulative CO2 flux increased with an increasing application rate of soil amendments. The highest mean value of CO2 emissions (0.77 kg CO2/ha/hour) during the growing season was observed under broadcasting of organic soil amendment (N60). Further long-term measurements of soil organic carbon dynamics on different soil types across a variety of technological operations of new soil amendments application are important to reliably quantify rates of SOC accumulation and GHG emissions.

How to cite: Hetmanenko, V., Volosheniuk, O., Skrylnyk, I., and Kutova, A.: The effect of new leonardite-based soil amendments on soil organic carbon and carbon dioxide emissions from black soil, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3104, https://doi.org/10.5194/egusphere-egu23-3104, 2023.

EGU23-5371 | ECS | Orals | SSS5.2

Inclusion of biochar hydrological properties in a C dynamic model with field data 

Maria Caterina Vaccari, Simone Pesce, Enrico Balugani, and Antonio Volta

Biochar is considered one of the most promising tools to increase soil organic carbon (SOC) sequestration to achieve IPCC climate change targets. Research on the effect of biochar on soil carbon dynamics and its indirect effect on soil moisture through models that need to be extended, tested and validated with long term experiments.

Our work aimed at providing a starting point through the integration of two models: Criteria 1D and RothC to account the indirect effect of biochar on SOC due to changes in soil hydrological properties. 

In order to account the indirect effect of biochar on soil moisture, we modified the RothC-Biochar (Pulcher et al 2022), a modified version of RothC that account the biochar priming effect and biochar recalcitrance properties, modifying the calculation of Total Soil Moisture Deficit (TSMD), a parameter related to soil moisture in RothC, through the relation between TSMD and θ (soil water content) suggested in Farina et al 2013.

Thus, we ran the CRITERIA 1D agrometeorological model to estimate the Van Genuchten water retention curve parameter from a multi-year field experiment (2017-2022) in a vineyard in Tebano (Ravenna, Italy), to estimate θ from field.

Since 2017 in Tebano we applied biochar produced from vine clippings and pruning residues. We installed sensors for weather and soil moisture between plots in 2019, with 5TE probes we monitored soil moisture, temperature and conductivity and with MPS1 probes soil matrix potential.

We applied a correction on the parameters that regulate the Van Genuchthen water retention curve function in CRITERIA 1D to account the effect of biochar on soil hydraulic properties. Then we compared the data obtained from the field probes with Criteria outputs to verify that the applied correction was accurate; finally, we use the Criteria results as input for RothC-Biochar.

The simulation with the modified RothC-Biochar models suggests that applying biochar on agricultural field would result in an increase of 2 tC ha-1of native SOC after 4 years compared to a bare soil due to indirect effect of biochar on soil moisture.

 

How to cite: Vaccari, M. C., Pesce, S., Balugani, E., and Volta, A.: Inclusion of biochar hydrological properties in a C dynamic model with field data, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5371, https://doi.org/10.5194/egusphere-egu23-5371, 2023.

Accurately predicting the stability of a biochar sample placed in the environment is important for guiding climate policies and the emerging voluntary market for carbon removal. The stability of biochar in soils varies with feedstock type, pyrolysis parameters, and environmental conditions. Previous assessments have correlated biochar stability estimates to single features – like pyrolysis temperature, elemental molar ratios, or incubation duration – but these assessments used different datasets and methodologies and reached different conclusions. Therefore, our aim was to develop an open dataset of biochar decomposition experiments, and to develop a transparent data preparation and processing toolchain, enabling reproducibility of scientific results. We first made an inventory of all published biochar incubation experiments, and then collected the incubation data and an extensive set of associated metadata (i.e., biomass and biochar properties, pyrolysis and incubation conditions). In a second step, we developed a data analysis toolchain, including functions for extrapolation of the incubation data to longer times and models for correlation between metadata and estimated biochar stability. In the extrapolation step, the incubation data was fitted to decay functions. Care was taken to explore the effect of using different fitting algorithms and constraints, and to apply a recalibration of the incubation temperature. For the correlation step, several strategies were applied, including both single-feature linear regressions to reproduce previous results and multi-feature regressions based on decision trees. So far, a dataset of 135 observations with more than 8000 data elements was collected making it one of the largest biochar stability datasets available. For the first time, raw biochar decomposition data is also compiled for 111 observations (mostly laboratory incubations). The initial data exploration revealed that although pyrolysis temperatures in the range 350 to 700°C are well represented, there is a data gap at higher temperatures with only a few data points at 1200°C. Likewise, only two observations are available with a molar H/C ratio below 0.2. These gaps can guide design of future incubation studies, as these parameters are often seen as indicators of stability. During curve fitting with single, double, or triple exponential models, we noted that the choice of initial conditions was important for finding a good fit, but we also noted that in many cases fitting uncertainties were high, residuals were not necessarily randomly distributed, and that some observations did not fit well to any type of exponential model (likely due to experimental conditions). Nevertheless, we were able to approximately reproduce the fitting results reported in Woolf et al. (2021). Finally, linear correlations were established between predicted stability and pyrolysis temperature, molar H/C ratio, but also other features available in the dataset, yielding similar correlation coefficients as previously reported (0.1 to 0.4). Attempts to understand the variability in predicted stability (using principal component analysis) and to develop multi-variate and non-linear models have so far not significantly improved model performance without overfitting. Opportunities remain to use the compiled data for other types of modelling, e.g. in soil carbon models.

How to cite: Azzi, E. and Sundberg, C.: Revisiting biochar decomposition data and long-term stability estimates: a transparent and reproducible analysis, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5625, https://doi.org/10.5194/egusphere-egu23-5625, 2023.

Soil fertility refers to the capacity of soil to support plant growth and development. Cation exchange capacity (CEC) is a fundamental measure of soil fertility quantifying soil's ability to retain essential cation nutrients such as potassium, ammonium, calcium, and magnesium, serving as a reservoir for soil native cations and artificially applied ones. However, soils are a finite resource and therefore subjected to unprecedented pressure due to rapid human population growth, agricultural activity, and food consumption, resulting in unsustainable soil degradation. For this reason, the application of exogenous organic matters (EOMs) such as biosolid, compost, manure, and biochar, is regarded as one of the most sustainable approaches for enhancing soil fertility, plant growth, and yield, soil carbon content, microbial biomass, and activity as well as preventing desertification by improving soil structure stability. Given the diverse origins of organic amendments from agriculture, forestry, industry, or wastewater-derived biosolids, their physical and chemical properties are different and may differently affect the adsorption and affinity of nutrient cations such as NH4+ and K+. Understanding the intrinsic properties of these EOMs in conjunction with the K-NH4 cation exchange behavior would improve our understanding of K-NH4 fertility management in organic matter-amended soil. The motivation for this study is the recognized knowledge gaps regarding cations exchange in organic materials, in particular, exchange reversibility. The main objective of this study is to quantify the cation exchange reversibility of K-NH4 in EOMs and to assess the hysteretic desorption behavior. Binary exchange experiments were conducted in which soils or organic materials were pre-saturated with NH4+. The results were analyzed based on the Gapon equation and the Freundlich model. The results demonstrated significant differences between soil and organic materials in adsorption capacity and selectivity of K+ and NH4+. In the desorption phase, the hysteretic desorption of K+ and NH4+ was observed and found to be concentration dependent. In our presentation, the results of exchange isotherm and adsorption-desorption will be presented and discussed.    

Keywords: soil organic matter, cation exchange, selectivity coefficient, adsorption, desorption, potassium, ammonium.

How to cite: Nguyen, B.-T. and Arye, G.: Cation exchange reversibility of potassium-ammonium binary solution: effect of organic matter, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5668, https://doi.org/10.5194/egusphere-egu23-5668, 2023.

EGU23-5811 | ECS | Orals | SSS5.2

Long-term action of biochar in paddy soils: effect on organic carbon and functioning of microbial communities 

Qianqian Zhang, Tida Ge, Michaela Dippold, and Anna Gunina

Increasing soil carbon (C) sequestration in paddy fields is significant for ensuring food security and achieving C neutrality in China. Biochar has been widely used as a soil amendment; still, long-term effects on the mechanisms of biochar's effect on soil C accumulation and the mediating role of microorganisms are poorly understood. To address this issue, three field experiments on paddies were chosen (Changsha, Nanjing, and Jiaxing), where biochar was applied for 7 to 8 years. The treatments included control (no addition), N (N fertilizer, 120 kg ha-1), N+B1 (N and low amount of biochar, 15-24 t ha-1), and NB2 (N and high amount of biochar, 22.5-48 t ha-1), effects on soil organic C (SOC) mineralization, dissolved organic C (DOC), activities of enzymes, microbial biomass C (MBC) and community composition (based on phospholipid fatty acids (PLFAs), and C utilization efficiency (CUE) were studied. Biochar reduced cumulative CO2 emissions in Changsha (by 32-34 %), Jiaxing (3.0-27 %) (p<0.05), and in Nanjing with under NB2 treatment (by 36 %) compared to N treatment. Biochar increased soil pH (0.03-0.38 units) in Changsha and Nanjing but did not affect Jiaxing plots. Biochar increased SOC, total N, chitinase activity, MBC (by 18-28 %,) and CUE (by 24-65 %, except in Jiaxing) but decreased DOC content (by 3-14 %) and peroxidase activity. Biochar addition increased the total and bacterial PLFA contents and decreased the bacteria:fungi ratio at the three sites (except for total PLFA in Nanjing) compared to the N treatment. The correlation analysis revealed that cumulative CO2 emission was reduced under the increase of pH, MBC, SOC, and CUE, bacterial PLFA, and stimulated by DOC content and the rise of bacterial:fungi ratio. These indicated that long-term biochar amendments mainly increased the amount of C that bacteria can assimilate; the increase of MBC content and CUE could point to the stimulation of microbial C sequestration.

How to cite: Zhang, Q., Ge, T., Dippold, M., and Gunina, A.: Long-term action of biochar in paddy soils: effect on organic carbon and functioning of microbial communities, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5811, https://doi.org/10.5194/egusphere-egu23-5811, 2023.

EGU23-6280 | Posters on site | SSS5.2

Varying soil organic matter composition differences between pools in acidic and calcareous soils 

Gergely Jakab, Balázs Madarász, Zoltán Dévény, Dóra Zacháry, Tibor Filep, and Zoltán Szalai

Intensive inversion tillage operations triggered a considerable organic carbon release from cultivated topsoils. Decreasing tillage intensity or land use change are reported to increase the soil organic matter (SOM) content of the degraded topsoil even within a decade. However, the chemical composition, storage mechanisms, and fate of the SOM surplus are not fully understood. Among the environmental and soil conditions, the role of carbonates is considered essential. The present study compares the SOM surpluses due to tillage intensity drop under acidic forest soils and Chernozems. The topsoils (0-10cm) of three long-term (~20 years) field trials were investigated in Hungary. SOM composition was estimated using Fourier transform infrared spectroscopy. Tillage intensity drop and pasture construction significantly increased the SOM content in all sites’ topsoils. At two locations, both organic matter pools increased, whereas only the mobile SOM pool has grown due to pasture construction. This suggests that a considerable amount of additional carbon can be stored in the soil, even in crop fields, using conservation technics. The SOM surplus did not change the original SOM composition trends of the labile and stable OM pools; consequently, the OM composition of the pools is rather the functions of soil and environmental conditions than sequestration mechanisms. In the acidic soil and the Chernozem under pasture, the mineral phase associated OM (stable pool) was ruled by aliphatic components, whereas the mobile, aggregation occluded OM was more aromatic. In agreement with the mainstream literature, we found the opposite trend on the other Chernozem site. Therefore the role of carbonates solely does not explain the differences. For more general trends, additional case studies must be involved. This research was funded by the National Research, Development, and Innovation Office (NKFIH), grant number: K-123953, and supported by the Eötvös Loránd Research Network SA41/2021, and EJP Sic-Soc-Dyn.

How to cite: Jakab, G., Madarász, B., Dévény, Z., Zacháry, D., Filep, T., and Szalai, Z.: Varying soil organic matter composition differences between pools in acidic and calcareous soils, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6280, https://doi.org/10.5194/egusphere-egu23-6280, 2023.

The interest in biochar, the persistent product of pyrolysis as a soil amendment, began in the first decade of the 2000s and rooted in research on fertile, anthropogenic Terra preta soils in the Amazon region. Research paper numbers started to rise exponentially from 2007/2008 onwards, resulting in more than 27,434 published papers with the keyword “biochar” to date (January 2022) according to Easy Web of Science. Its persistence [1] makes properly produced biochar an interesting approach for carbon dioxide removal (CDR) with added benefits for soil fertility [2]. For the overall soil C sequestration that comes with biochar use, three points are crucial: (1) the persistence of biochar itself with depends largely on the pyrolysis temperature and duration, the soil and climatic conditions; (2) the effect that biochar application may have on the already existing soil organic carbon, where an initial short-lived positive priming seems to switch towards a negative priming after 0,5 – 2 years when soil-biochar only mixtures are investigated [3]. However, the least well-known item regarding the overall CDR potential of biochar use in soils is the question (3) if and under what circumstances biochar may cause an additional soil organic carbon build-up, above that observed in a control soil/agricultural ecosystem without biochar application when soils receive permanently new C, e.g. via a green cover, crops plus intercropping and other practices. For example Blanco-Canqui et al. [4] observed a significantly higher SOC build-up over 6 years after biochar application on average in three field experiments in the mid-west US of about 7 vs. 2 tons per ha in the biochar versus control plots. Weng et al. [5] demonstrated that, indeed, the maximum soil C concentration ceiling could be lifted by (repeated) biochar applications to a subtropical grassland in Australia. In this contribution, I examine the available experimental evidence and mechanistical understanding with regard to such “humus-return of biochar investment” effects, if and under what conditions they can be obtained and what methods are available to investigate this effect in long-term field experiments. The contribution aims to stimulate discussion on a joint methodical framework to investigate such a potentially free “SOC interest return” effect of biochar use in agriculture which may be as important as the C sink generated by biochar application itself.

  • Lehmann, J., et al., Biochar in climate change mitigation. Nature Geoscience, 2021. 14(12): p. 883-892.
  • Schmidt, H.P., et al., Biochar in agriculture - A systematic review of 26 global meta-analyses. Global Change Biology Bioenergy, 2021. 13(11): p. 1708-1730.
  • Wang, J., Z. Xiong, and Y. Kuzyakov, Biochar stability in soil: meta-analysis of decomposition and priming effects. GCB Bioenergy, 2016. 8(3): p. 512-523.
  • Blanco-Canqui, H., et al., Soil carbon increased by twice the amount of biochar carbon applied after 6 years: Field evidence of negative priming. GCB Bioenergy, 2020. 12(4): p. 240-251.
  • Weng, Z., et al., Microspectroscopic visualization of how biochar lifts the soil organic carbon ceiling. Nature Communications, 2022. 13(1): p. 5177.

How to cite: Kammann, C.: Evidence and research needs to identify potential SOC stock increases after biochar application: A literature study and roadmap to understand long-term effects, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6678, https://doi.org/10.5194/egusphere-egu23-6678, 2023.

EGU23-6867 | ECS | Posters on site | SSS5.2

Strengthening the bioeconomy in tropical countries while preserving soil organic carbon stocks by recycling recalcitrant coproducts: A case study for Ecuador. 

Christhel Andrade Diaz, Enrico Baluganic, Ezequiel Zamora-Ledezma, and Lorie Hamelin

Crop residues are a key supply of renewable carbon for the bioeconomy. However, the mobilization of crop residues from agricultural fields to the bioeconomy is commonly limited to 15-60% [1] of their technical potential to avoid depleting soil organic carbon (SOC) stocks [2]. Nevertheless, the coproducts remaining from several bioeconomy pathways are rich in recalcitrant carbon that could be returned to soils to maintain the SOC levels. In tropical countries, the great diversity of pedoclimatic conditions promotes the production of a vast variety of crops, which produce large amounts of residues that are commonly left unharvested or burned on the fields. This study investigates, for the specific context of tropical countries, the interaction between crop residue harvesting and long-term SOC dynamics when coproducts obtained from pyrolysis (biochar), gasification (char), hydrothermal liquefaction (hydrochar), and anaerobic digestion (digestate) are returned to soils. Besides the focus on tropical conditions, important novelties are that the soil carbon model RothC [3] was adapted to include extra pools representing the labile and recalcitrant (%CL and %CR) fractions of each coproduct, as well as their mineralization rates (kL and kR). In addition, the potential effect of coproducts in SOC mineralization, commonly referred to as priming effect (PE) was also included in the adapted model. The model was applied to the entire croplands in mainland Ecuador, used as a representative of tropical context given the availability of high spatial resolution data. Ecuador’s croplands were clustered in >105,000 simulation units, including 10 crops representing 95% of the total national production (i.e., banana, plantain, cocoa, coffee, oil palm, sugarcane, rice, maize, wheat, and barley). Simulations were carried out with our adapted RothC-bioeconomy model to compare, over 100 y (2020-2120), the four bioeconomy pathways studied herein to a reference scenario where crop residues are not supplied to the bioeconomy (unharvested). The climate variables used followed the RCP4.5 trajectory [4]. The spatially-explicit results, which are still being processed, describe the conditions and amount of crop residues that can be harvested for bioeconomy in order to maintain or increase long-term SOC stocks.

 

[1] C. Andrade Díaz, et al., 2022. doi: 10.1016/j.apenergy.2022.120192. [2] H. Blanco-Canqui and R. Lal, 2009. doi: 10.1080/07352680902776507. [3] K. Coleman and D. S. Jenkinson, 1996. doi: 10.1007/978-3-642-61094-3_17. [4] IPCC, 2018.

How to cite: Andrade Diaz, C., Baluganic, E., Zamora-Ledezma, E., and Hamelin, L.: Strengthening the bioeconomy in tropical countries while preserving soil organic carbon stocks by recycling recalcitrant coproducts: A case study for Ecuador., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6867, https://doi.org/10.5194/egusphere-egu23-6867, 2023.

EGU23-7294 | ECS | Orals | SSS5.2

Impact of organic amendments from date palm residues on water retention properties of two coarse texture soils 

Elie Le Guyader, Xavier Morvan, Maxime Gommeaux, Vincent Miconnet, Béatrice Marin, Mohamed Moussa, Nissaf Karbout, Rahma Inès Zoghlami, María José Delgado-Iniesta, and Diego S. Intrigliolo

The cultivated dryland soils of North Africa present low fertility and productivity due to low organic matter content (Brahim et al., 2021). Date palm residues are an abundant resource in these regions and only a minor part is recovered in oasian agroecosystems. The ISFERALDA project – Improving Soil FERtility in Arid and semi-arid lands using Local organic DAte palm residues – aims at developing the use of organic amendments based on traditional production (composting and slow pyrolysis) as a key tool to improve soil fertility and soil properties.
The objective of this study was to quantify the effects of compost and biochar based on date palm residues on soil water retention. Two soils with properties similar to North Africa soils (sandy loam texture, alkaline pH, low organic matter content) were collected in a semi-arid Mediterranean area of southeast Spain. In addition, and in order to test further the influence of soil texture, soil sand content was artificially increased by supplementing the natural soils with washed quartz sand. The different types of organic amendments were tested at a dose of 60 t/ha (Edeh et al., 2020): compost alone, biochar alone and mixture of compost and biochar (50:50 in weight). Water content was measured using pressure membrane apparatus at nine different matric potential (pF), ranging from the saturation to the permanent wilting point.
The results showed that water retention was higher in soil with organic amendments regardless of the pF and the soil type. For a specific soil, the addition of biochar alone or in combination with compost to the soil resulted in higher values than compost alone. The improvement in water retention properties was more pronounced for soils amended with sand. Thus, composting and/or pyrolysis of date palm residues is a viable alternative to improve the water retention properties of sandy and loamy soils. 

Keywords:
Date palm – arid and semi-arid lands – organic amendments – soil water retention

References :

Brahim, N., Karbout, N., Latifa, D., & Bouajila, A. (2021). Global Landscape of Organic Carbon and Total Nitrogen in the Soils of Oasis Ecosystems in Southern Tunisia. Agronomy, 11, 1‑17.

Edeh, I. G., Mašek, O., & Buss, W. (2020). A meta-analysis on biochar’s effects on soil water properties—New insights and future research challenges. The Science of the Total Environment, 714, 136857. https://doi.org/10.1016/j.scitotenv.2020.136857

How to cite: Le Guyader, E., Morvan, X., Gommeaux, M., Miconnet, V., Marin, B., Moussa, M., Karbout, N., Zoghlami, R. I., Delgado-Iniesta, M. J., and Intrigliolo, D. S.: Impact of organic amendments from date palm residues on water retention properties of two coarse texture soils, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7294, https://doi.org/10.5194/egusphere-egu23-7294, 2023.

EGU23-7996 | ECS | Posters virtual | SSS5.2

Influence of solid vs. liquid digestate application on soil organic matter accrual and stabilization, and microbial communities evolution 

Martina Sinatra, Beatrice Giannetta, Giorgio Galluzzi, Alessandra Tondello, Piergiorgio Stevanato, Andrea Squartini, and Claudio Zaccone

The decline of soil organic matter (SOM) as well as the depletion of micro and macronutrients are among the most serious threats facing many agricultural soils of the world. Consequently, in many countries, soil amendments are increasingly originating from a wide range of organic wastes, as a win-win strategy to mitigate global warming while increasing soil fertility. Digestate, a by-product of the anaerobic digestion generally characterized by both high biological stability and content of nutrients (including nitrogen – N –), is often used as a fertilizer and/or organic amendment. However, a safe and functional application of digestate in agriculture requires an in-depth understanding of its possible impacts on the native SOM, on carbon sequestration mechanisms, as well as on soil microbial communities.

The aim of this work was to test the influence of solid vs. liquid digestates on both SOM accrual and the distribution of SOM in particulate organic matter (POM) and mineral associated organic matter (MAOM) pools.

The experiment was set up as a randomized complete block design with two factors, namely solid and liquid digestate, with 3 replicates. A control treatment (no digestate), two depths (0-15 and 15-30 cm) and a digestate application at a rate of 340 kg of potentially available N ha-1 yr-1 were considered. Soil samples were collected few days following the amendment (t0), and after 3 (t3) and 6 (t6) months. All samples (54) were characterized for pH, EC, bulk density, total organic C (TOC), total N (TN), texture and major and trace elements. Moreover, the abundance of key genes related to the N cycle was assessed by quantitative polymerase chain reaction (PCR). Finally, POM and MAOM fractions were isolated and characterized by elemental analysis (CHNS).

Preliminary data suggest that, after 6 months from the amendment, soil organic C (SOC) stock in the first 15 cm of depth was not affected by digestate application, whereas a significant influence was observed for TN, especially when liquid digestate was added. On the opposite, the application of digestate had a significant influence on both SOC and TN stock at 15-30 cm of depth. Moreover, while the distribution of SOC between MAOM and POM was exclusively affected by the application of digestate, independently of depth, the distribution of TN between SOM pools was influenced by both the treatment and the time. In particular, the time factor seems to play an important role on TN concentration in the MAOM. As regards the abundance of bacterial genes, the solid digestate conferred an increase to those for nitrification (amoA), denitrification (nirK, nosZ) and total bacteria (16S), particularly at 15-30 cm of depth. The effect reached its maximum after three months from the application and decreased near control levels after six months.

 

Acknowledgements

SM and CZ thank Cattolica Agricola soc. agr. a r.l. and Iniziative Biometano s.p.a. for allowing the experimental activity.

How to cite: Sinatra, M., Giannetta, B., Galluzzi, G., Tondello, A., Stevanato, P., Squartini, A., and Zaccone, C.: Influence of solid vs. liquid digestate application on soil organic matter accrual and stabilization, and microbial communities evolution, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7996, https://doi.org/10.5194/egusphere-egu23-7996, 2023.

EGU23-8354 | Orals | SSS5.2

Response of soil organic matter fractions to biochar and organic fertilizers – Results from a nine-year field experiment 

Beatrice Giannetta, César Plaza, Giorgio Galluzzi, Iria Benavente-Ferraces, Juan Carlos García-Gil, Marco Panettieri, Gabriel Gascó, and Claudio Zaccone

We investigated the effects of biochar (BC) at 0 and 20 t ha-1, combined with two organic fertilizers (municipal solid waste compost, MC, and sewage sludge, SS), on soil organic matter (SOM) in a 9-year field experiment. To capture the protection by soil minerals and iron (Fe) against microbial decomposition, we fractionated SOM into particulate (POM) and mineral-associated organic matter (MAOM), and analyzed the fractions by iron (Fe) K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy.

BC and the two organic amendments increased soil organic carbon (OC) content, but only the organic fertilizers significantly increased total nitrogen (N) content. BC increased particulate OC and total N contents, while the organic fertilizers only increased particulate total N content. BC significantly increased mineral-associated OC content, while the organic fertilizers increased both mineral-associated OC and total N contents. We found no interaction between BC and organic fertilizers on mineral-associated OC and total N contents. The Fe EXAFS data fitting showed that the Fe(III)-SOM content of the Fe phases in POM and MAOM in unamended soils were noticeably different. Hematite represented the main Fe oxide phase in the POM fractions from all the amended soils, and Fe(III)-SOM averaged around 15%. In the amended soils, besides hematite (also present in the unamended soil), ferrihydrite occurred in all MAOM fractions, although at a different proportion.

How to cite: Giannetta, B., Plaza, C., Galluzzi, G., Benavente-Ferraces, I., García-Gil, J. C., Panettieri, M., Gascó, G., and Zaccone, C.: Response of soil organic matter fractions to biochar and organic fertilizers – Results from a nine-year field experiment, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8354, https://doi.org/10.5194/egusphere-egu23-8354, 2023.

Biochar is an aspirational strategy for long-term carbon sequestration in soil, emergent in guidelines by the Intergovernmental Panel on Climate Change (IPCC). Yet, the rate and pathways of biochar mineralization remain uncertain, and information is scarce on the role of soil temperature. Recent studies predicting the 100-yr stability of biochar in soil use a profile of temperature sensitivity (Q10) for biochar mineralization that deviates markedly from common biochemical temperature relationships, especially at mean annual temperatures of 0-10°C, which prevail in many temperate soils. Here, we compared estimates of biochar stability using (i) empirical Q10 data and (ii) Arrhenius activation energies for biochar mineralization similar to those for other recalcitrant biomolecules. The results indicate that empirical Q10 data used so far overestimate the long-term stability of biochar in soils at 0-10°C, but underestimate the stability at >10°C. The size of these effects increases with higher molar ratio of hydrogen to organic carbon (H/Corg) in the biochar, meaning that predictions for labile biochars are more uncertain. We conclude that care should be taken when normalizing biochar stability data to prevailing soil temperatures and call for further studies to document the temperature sensitivity of biochar mineralization

How to cite: Elsgaard, L. and Eriksen, R. L.: Temperature control on biochar decomposition in soil - implications for long-term carbon sequestration, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9326, https://doi.org/10.5194/egusphere-egu23-9326, 2023.

Biochars have notable potential in sequestering atmospheric carbon over long terms and offer various agricultural and environmental co-benefits. However, there is limited information about the long-term effects of added biochars, as there are only handful of continuously monitored biochar field experiments expanding over a decade, and especially poorly have been studied the long-term effects from boreal regions. The soils in northern colder boreal regions typically have higher carbon content and undergo continuous freeze-thaw cycles. Therefore, effects of biochars in these regions may differ from those observed in warmer climates.

We studied the effects of a single application of softwood biochars on two contrasting boreal agricultural soils (nutrient-poor, coarse textured Umbrisol and fertile, fine-textured Stagnosol), both with high initial soil organic carbon contents, over 13 years following the application in 2010 or 2011. We focused on plant yield formation as well as nutrient uptake dynamics of all major Finnish field crops, as well as on soil physical properties and greenhouse gas emissions.

We found that the ability of biochar to enhance the supply of nutrients to plants and hence to improve the crop biomass yield exists in boreal conditions, although these effects were minimal and not consistent over the years. Biochar notably increased plant K content, and reduced the plant content and uptake of Al and Na in several years in Stagnosol. The relative plant contents of Cd and Ni in Umbrisol, and P, K, Mg, S, Al, Cu, Fe and Ni in Stagnosol increased over the years. Despite these increased plant contents, no significant improvement was observed in crop biomass yield by added biochar over the first eight years.

The enhanced plant available water and reduced bulk density previously reported during the initial years were faded in long-term, likely due to dilution of biochar concentration in topsoil. However, the potential of biochar to affect N2O emission persisted, even seven years after the application, this contributed to reduced yield-normalized non-CO2 GHG emissions. In the presentation, we will share also the preliminary results for the latest growing seasons 2019–2022.

How to cite: Tammeorg, P., Kalu, S., Karhu, K., and Simojoki, A.: Long-term effects of softwood biochars on boreal soils: results from two experiments through 13 years on soils, nutrient cycling and crops, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9707, https://doi.org/10.5194/egusphere-egu23-9707, 2023.

Fusain is a macroscopic component, or lithotype, of coal. Microscopic fragments of fusain are referred to as “inertinite” maceral, which is commonly found in all carbonaceous and most sedimentary rocks. Fusain/inertinite is formed by carbonization of biomass in oxygen deficient paleo-wildfires and subsequent transportation into peatbogs and sedimentary basins. Substantial quantity of fusain/inertinite is commonly found in most post-Devonian coal and sedimentary rocks. Inertinite fragments are often microscopically characterized by their intricate vacuole structures inherited from the original cell lumens, which attests to their remarkable high preservability during geological processes.

Fusain/Inertinite is generally believed by geologists to be chemically highly inert due to its intense degree of aromatization and ordering of carbon molecular structure and cannot be degraded by shallow surface processes including oxidation and biodegradation. The “selective diagenesis” processes continue to preferentially degrade the more labile organic carbon fractions while preserving the most refractory fractions that are thermodynamically least favored to breakdown. The long-term, geological evolution of organic carbon in the Earth’s crust through three main stages of diagenesis, catagenesis, and metagenesis, is studied by organic petrology and organic geochemistry methods. This presentation provides results of these methods for a set of 20 synthetic biochars produced from different feedstocks to compare their geochemistry and optical characteristics with the commonly preserved geological fusain/inertinite in coal and other carbonaceous rocks.

The results show that biochars that have been produced at maximum pyrolysis temperature of over 600°C, resemble properties of the most refractory fusain/inertinite in the Earth’s crust and would not be degraded as long as other more thermodynamically labile organic carbon compounds are in existence. Any degradation of these biochars can only be perceived under intense geological burial heat in the Earth’s mantle or contact metamorphism by igneous intrusions and hydrothermal processes. The claim of short-term carbon permanence for biochars contradicts co-existence of fusain/inertinite with labile organic carbon commonly observed in carbonaceous rocks. Degradation of refractory fusain/inertinite would not be thermodynamically favored while large quantity of labile organic carbon is readily and commonly available in carbonaceous rocks. The results of this study highlight the need for re-thinking carbon permanence of biochars within the context of the deep geological carbon cycle.

How to cite: Sanei, H. and Petersen, H. I.: Carbon permanence of biochar; a lesson learned from the geologically preserved charcoal in carbonaceous rocks, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10913, https://doi.org/10.5194/egusphere-egu23-10913, 2023.

EGU23-11054 | ECS | Orals | SSS5.2

Permanence of soil applied biochar: Conclusions from the natural pyrogenic carbon cycle validate carbon sink accounting. 

Johannes Meyer zu Drewer, Samuel Abiven, Nikolas Hagemann, and Hans-Peter Schmidt

Biomass pyrolysis and a non-oxidative use of the produced biochar is widely acknowledged as a negative emission technology and part of Pyrogenic Carbon Capture and Storage (PyCCS). Biochar with a molar H/C ratio < 0.4, which is usually achieved by pyrolysis at 550°C or above, is highly persistent when applied to the soil. Still, the exact residence time remains subject to debate. Practical assessment tools and reliable models for carbon accounting are needed. Persistence of soil applied biochar is often assessed using soil incubation trials of rather short time horizons, lasting several month or years, with consecutive extrapolation of the observed degradation rate. Within such experiments, the decomposition rate of the biochar continues to decrease over time indicating that biochar consists of a broad range of carbonaceous compounds of different recalcitrance. Hydrogen pyrolysis, an analytical method used to determine the degree of aromatisation, suggests that 75% of the carbon in biochar with an overall H/C ratio <0.4 consists of persistent aromatic carbon (PAC), which will persist after soil application for > 1000 years, (Bowring et al., 2022; Howell et al., 2022), independent of the soil type and climate. The remaining 25% of the biochar carbon (heteroaromatic, aliphatic, etc) are considered semi-persistent carbon (SPC), presenting a mean residence time (MRT) in soil of 50 to 100 years, depending on soil type and climate. Based on this, up to 99% of the PyC loss quantified in an incubation trial may be attributed to the spectrum of SPC compounds, while the occurring PAC decay is very small and a neglectable loss in the context of carbon sink accounting. To validate the PAC residence time, data on long-term dynamics of the global, natural PyC cycle provides new insights. Natural PyC is produced from incomplete combustion in e.g. forest fires and is introduced to ecosystems globally at a scale of 0.114-0.383 Gt year-1. Given the global deposits of natural PyC of 550-1,650 Gt a MRT of 1,440 to 14,500 years can be calculated (Bird et al., 2015; Santín et al., 2016; Bowring et al., 2022 ). Natural PyC is produced in an uncontrolled manner, thus achieving a lower degree of aromatisation, a smaller PAC pool and lower MRT compared to optimized PyC produced by controlled pyrolysis. Therefore, observations from the natural PyC cycle render the assumed PAC residence time conservative. Further research is necessary to enable empirical quantification of the PAC content of biochar across a broad range of feedstock material and pyrolysis conditions. Hydrogen pyrolysis is an elaborate, yet expensive tool not suitable for routine analysis e.g. in biochar and biochar C-sink certification. Thus, further methods for PAC quantification must be developed and standardized.

  • Bird et al. (2015). Annual Review of Earth and Planetary Sciences, 43(1), 273–298. https://doi.org/10.1146/annurev-earth-060614-105038
  • Bowring et al. (2022). Nature Geoscience 15:2, 15(2), 135–142. https://doi.org/10.1038/S41561-021-00892-0
  • Howell et al. (2022). Science of The Total Environment, 849, 157610. https://doi.org/10.1016/J.SCITOTENV.2022.157610
  • Santín et al. (2016). Global Change Biology, 22(1), 76–91. https://doi.org/10.1111/gcb.12985

How to cite: Meyer zu Drewer, J., Abiven, S., Hagemann, N., and Schmidt, H.-P.: Permanence of soil applied biochar: Conclusions from the natural pyrogenic carbon cycle validate carbon sink accounting., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11054, https://doi.org/10.5194/egusphere-egu23-11054, 2023.

EGU23-11195 | Orals | SSS5.2

Sorption and desorption controls on alanine bioavailability in volcanic soils 

Natsuko Kitagawa, Tetsuhiro Watanabe, Kozue Sawada, Takashi Kunito, and Shinya Funakawa

Recent studies have shown that mineral-associated organic N is an important source of bioavailable N, and organic N sorption to/desorption from clay minerals may be a key factor of N dynamics in soils. This study aims to elucidate the importance of sorption/desorption to the mineralization of amino acids in volcanic soils. We hypothesized that in volcanic soils, sorption of amino acid to minerals reduces its mineralization and that desorption of amino acid differs reflecting soil properties.

Soils sampled from the O, A, and B horizons of three volcanic soils were used. Incubation experiments using the tracer method were carried out to assess the mineralization of alanine, which was used as a representative amino acid in the soil. Soils were placed in glass jars and were amended with 13C labeled alanine at a rate of 1% of total N to investigate the effects of alanine sorption on its mineralization. Similarly, separate soils were amended with 13C labeled alanine sorbed to iron oxides to examine the desorption of alanine. The percentage of mineralization of the added alanine over 7 days of incubation was determined. Acid oxalate extractable Al and Fe (Alo and Feo) of soil were measured as representative clay mineral components contributing to sorption. Sorption isotherm experiments were carried out to understand each soil’s sorption characteristics, and the results were fitted to Freundlich’s sorption equation.

The percentage of mineralization of free alanine was the highest in O horizon soils at 40% and showed a decreasing trend going down the soil profile. The mineralization of alanine sorbed to iron oxides was approximately 56% of that of free alanine, regardless of the soil properties. Our results suggest that approximately 44% of the sorbed alanine was strongly sorbed to the iron oxides, but the remaining alanine was easily desorbed and mineralized similarly to free alanine. Freundlich-k constants were correlated with both Alo and Feo content and mineralization of alanine (r = 0. 70, P < 0.05, r = −0.63, P < 0.05, respectively). Furthermore, based on the fitted Freundlich’s equation, the amount of alanine that was sorbed of the added alanine in the incubation experiment was calculated, and the results indicated that alanine mineralization was strongly correlated with the ratio of sorbed to added alanine (r = −0.95, P < 0.001).

We conclude that the desorption of sorbed alanine was constant regardless of soil properties and that sorption reduced alanine mineralization rather than delaying it.

How to cite: Kitagawa, N., Watanabe, T., Sawada, K., Kunito, T., and Funakawa, S.: Sorption and desorption controls on alanine bioavailability in volcanic soils, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11195, https://doi.org/10.5194/egusphere-egu23-11195, 2023.

Average soil temperatures in winter in Germany are frequently between 0 and +10℃, usually at high soil moisture levels. Therefore, the decomposition of soil organic matter and soil nitrogen (N) cycling are still active and could be substantial under these conditions, potentially leading to high N losses both in the form of nitrate to the groundwater and nitrous oxide to the atmosphere. High carbon soil amendments (HCA) have the potential to immobilize excess mineral N in the soil due to stimulation of microbial biomass growth. However, to date, it is not sufficiently known how well this N immobilization works at lower temperatures, and how long the effect will last over winter. In order to elucidate how the application of different HCA affects N immobilization in soil under winter conditions, we conducted a 7-month laboratory incubation experiment with silty clay soil low in soil organic carbon from a recultivation area after open-cast lignite mining near Jülich, Germany. Each soil column contained about 500 g of recultivation soil sieved at 2 mm. A scenario of a typical mineral N content after harvest was created by adding 50 kg NH4+-N ha-1 to the soil before application of the different HCA, which were then added at a rate of 4 t C ha-1. Eight different treatments were implemented: application of NH4+ only (B), and then NH4+ applied with wheat straw (WS), biochar (BIO), spruce sawdust (SS), lignite (LIG), cellulose (CEL), a combination of wheat straw (2 t C ha-1) and spruce sawdust (2 t C ha-1) (CWS), and a combination of wheat straw (2 t C ha-1) and biochar (2 t C ha-1) (CWB), respectively. In the three straw treatments, carbon dioxide (CO2) emissions peaked 14 days after the start of the experiment. In all treatments, CO2 emissions decreased with time. In the end, the CEL treatment had the highest cumulative CO2 emission during the entire incubation period. In contrast, the CEL treatment had a significantly lower soil nitrate content than all other treatments over the whole duration of 7 months, indicating that cellulose was most effective and long-lasting in stimulating microbial N immobilization under temperate winter conditions in silty clay soil.

How to cite: Zhao, K., Reichel, R., Wissel, H., and Brüggemann, N.: The effect of different high carbon soil amendments on N retention capacity under winter conditions in silty clay soil with low organic carbon content: An incubation study, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12342, https://doi.org/10.5194/egusphere-egu23-12342, 2023.

EGU23-12758 | Posters on site | SSS5.2

Effect of land management on incorporation of prickly pear crop residues in different soil organic matter fractions of a Sicilian soil under desertification risk 

Eleonora Grilli, Iseult Malrieu, Hafiz Khuzama Ishaq, Rosaria D’Ascoli, Elio Coppola, Giovanna Battipaglia, Simona Altieri, and Simona Castaldi

The return of organic amendments and plants residues to the soil is a fundamental measure for carbon (C) accrual in soil, in particular in agroecosystems of Southern Mediterranean areas, where aridity limits plant growth and litter inputs as well as soil organic matter (SOM) decomposition, often resulting in land degradation and desertification risk. The allocation of this residual C in SOM fractions which are more prone to fast mineralization, at the onset of the rainy season, might significantly vary with the quality of the residues and the type of land management. The extent of residues incorporation is also relevant as it increase the SOM-microbial interactions responsible of SOM processing, mineralization and stabilization. We investigated the effect of two types of land management, no tillage and minimum tillage, on the incorporation of C from a list studied soil amendment, pruned prickly pear cladode residues, in the SOM of the same crop site, and its distribution in the particulate organic and mineral associated organic matter fractions. The characteristics 13C signature of the Opuntia ficus-indica (L.) Mill, which is an obligate CAM plant, was used to identify which of the two soil management practices was more effective in storing more C and of a more stable form along the soil profile (0-30 cm). Two adjacent cactus plantation located in southern Sicily, were used, where the different land management was maintained in the last 10 years. The analysis was part of the measures of adaptation investigated by the project Desert-Adapt (LIFE16 CCA/IT/000011) in areas under desertification risk.

How to cite: Grilli, E., Malrieu, I., Ishaq, H. K., D’Ascoli, R., Coppola, E., Battipaglia, G., Altieri, S., and Castaldi, S.: Effect of land management on incorporation of prickly pear crop residues in different soil organic matter fractions of a Sicilian soil under desertification risk, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12758, https://doi.org/10.5194/egusphere-egu23-12758, 2023.

EGU23-15258 | ECS | Orals | SSS5.2

Studying Soil Organic Matter Composition in Arable land: Can Soil Management Impact Carbon Pools? 

Thulfiqar Al-Graiti, Gergely Jakab, Noémi Ujházy, Károly Márialigeti, Tamás Árendás, Máté Karlik, and Zoltán Szalai

Soil organic matter (SOM) is an essential fraction of soil and contributes to its fertility. Land use and cultivation may affect SOM. This study investigates whether SOM concentration and composition differ in soil pools or are changed by soil management (tillage, fertilisations, and crop covers). Soil samples were collected in April 2019 from cropland and nearby grassland. The study sites were part of a long-term experiment in Martonvasar (Hungary), established in 1958 and characterised by Chernozem soils. Total organic carbon (TOC) contents and compounds were studied in three soil pools (bulk soil, fast pool, and slow pool). Both TOC and total N concentrations were high in the slow pool, with higher stored C contents in grassland than in cropland. Tillage effects reduced aggregate stability in cropland, which explains a lower aliphatic content than grassland. Insufficient physical protection due to the tillage practice may enhance OM loss in cropland even under fertiliser inputs. Neither fertiliser nor crop covers affected SOM compositions, while they were different in soil pools. More complex OM in the slow pool than in the fast pool. It indicates that the slow pool is the main protecting path for SOM, possibly referred to older or decayed organic compounds. To understand the bottom-up process, microorganisms’ community role in SOM stabilisation needs to be studied.

How to cite: Al-Graiti, T., Jakab, G., Ujházy, N., Márialigeti, K., Árendás, T., Karlik, M., and Szalai, Z.: Studying Soil Organic Matter Composition in Arable land: Can Soil Management Impact Carbon Pools?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15258, https://doi.org/10.5194/egusphere-egu23-15258, 2023.

EGU23-15356 | Orals | SSS5.2

Subsoil management in agriculture and changes in organic matter stocks 

Julien Guigue, Sara L Bauke, Sabine J Seidel, Miriam Athmann, Oliver Schmittmann, Ingrid Kögel-Knabner, and Wulf Amelung

Global environmental changes are threatening the productivity of agroecosystems. Floods or droughts, together with long-term decline in soil organic matter stocks are pointing to the necessity of finding solutions for sustainable performance of agroecosystems.

Deep soil horizons store significant amounts of water, soil organic carbon and nutrients, and thus subsoil management is being increasingly considered as an option to sustain crop productivity under unfavorable conditions.

We used samples from several field experiments in Germany designed to investigate the potential benefits of deep ploughing together with deep placement of organic fertilizers on soil organic matter stocks. We recorded hyperspectral images of 1-metre soil cores in the Vis-NIR range and modelled the C distribution at a very high spatial resolution (53×53 μm²). Using approaches for GIS analyses, we quantified the changes in C and N stocks and we will present their spatial distribution resulting from the incorporation of different types of organic fertilizer (compost vs green manure) in subsoils. The organic matter stocks and C:N stoichiometry are both impacted by the agricultural management and the imaging technique allows us to distinguish between increased amount of organic matter in hotspots or in soil mineral matrice and to discuss the mechanisms controlling the observed changes.

How to cite: Guigue, J., Bauke, S. L., Seidel, S. J., Athmann, M., Schmittmann, O., Kögel-Knabner, I., and Amelung, W.: Subsoil management in agriculture and changes in organic matter stocks, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15356, https://doi.org/10.5194/egusphere-egu23-15356, 2023.

EGU23-17040 | Orals | SSS5.2

Impact of biomass ash content on biochar carbon speciation and stability 

Nikolas Hagemann, Pellegrino Conte, Jens Leifeld, Robin Giger, Thomas D. Bucheli, Hans-Peter Schmidt, and Jannis Grafmüller

Amending biomass with wood ash (2-10%) is a novel strategy in biochar production to increase the amount of biomass carbon retained in the solid phase (biomass to biochar) during pyrolysis by up to 35%. Thereby, the carbon sink potential of industrial biochar production could be substantially increased, when such ash-amendments would be used on large scale. Also, this research enables insight on the impact of ash-derived minerals on the resulting carbonaceous compounds during pyrolysis. In addition to pyrolysis conditions and initial biomass carbon speciation, the content of alkali and alkaline earth metals (AAEM) in the biomass ash phase may be another important factor determining the speciation of the resulting pyrogenic carbon. Here, we will present data on the thermal stability analyzed with differential scanning calorimetry and the carbon speciation of ash-amended biochars investigated with 13C and 1H Nuclear Magnetic Resonance spectroscopy.

Differential scanning calorimetry revealed a lower thermal stability of these ash-amended biochars compared to biochars without an ash amendment, which may indicate the formation of carbon species of lower persistence during pyrolysis induced by the added minerals. While the persistent carbon pool of biochar is made of numbers of fused aromatic carbon rings, the semi-persistent carbon pool is including aliphatic, small aromatic and heteroaromatic carbon frameworks. Therefore, analyzing the differences in carbon speciation of ash-amended biochars compared to non-amended biochar gives a closer insight on the impact of AAEM and other ash components on pyrogenic carbon speciation and how resulting biochars may persist in soil.

How to cite: Hagemann, N., Conte, P., Leifeld, J., Giger, R., Bucheli, T. D., Schmidt, H.-P., and Grafmüller, J.: Impact of biomass ash content on biochar carbon speciation and stability, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17040, https://doi.org/10.5194/egusphere-egu23-17040, 2023.

EGU23-17065 | ECS | Orals | SSS5.2

Quantification of the persistent aromatic carbon content in biochar 

Silvio Voßwinkel, Axel Ulbricht, Nikolas Hagemann, Hans-Peter Schmidt, Volker Herdegen, and Andreas Siegfried Braeuer

Quantification of the time-dependent carbon sequestration by biochar remains a challenge. Recently, hydrogen pyrolysis was suggested to identify the content of stable polycyclic aromatic carbon (SPAC) or persistent aromatic carbon (PAC), which would not degrade to a relevant extent for centennial timescales due to their high degree of aromaticity and condensation (>7 rings). However, hydrogen pyrolysis is too expensive and laborious for broad application or even use in routine analysis.

Here, we test a suite of analytical methods in order to identify alternatives to hydrogen pyrolysis for the quantification of SPAC/PAC in routine analysis of biochar or other pyrogenic carbons. We use 34 experimental biochars out of two precursors, wood and straw, produced at different highest treatment temperatures (HTT = 400-800 °C) and eight industrial biochars obtained from different feedstocks and different pyrolysis technology with HTT of 550-1200 °C. The methods include elemental analysis to obtain molar ratios of H/C and O/C, electrical conductivity of the solid as a proxy for the degree of condensation, thermogravimetric analysis coupled to differential scanning calorimetry (TG-DSC) to assess thermal stability (R50) and Raman spectroscopy. Raman spectra of the D- & G band provide information on the nanostructural development and should allow relative quantification of the semi-persistent and persistent carbon fractions. An incubation experiment (biochar + sand + compost microbial consortium) under laboratory conditions will provide direct data on biochar mineralization to quantify the semi-persistent fraction (SPC).

Using a broad range of HTT and two different precursors as well as industrial biochars out of existing commercial pyrolysis reactors, we aim to cover a relevant parameter space to identify the possible range of SPAC/PAC and SPC content in industrial biochars. In an ideal case, this work will enable the use of low-cost technology such as Raman and/or electrical conductivity of the solid to quantify or estimate SPAC/PAC with a sufficient accuracy and precision.

How to cite: Voßwinkel, S., Ulbricht, A., Hagemann, N., Schmidt, H.-P., Herdegen, V., and Braeuer, A. S.: Quantification of the persistent aromatic carbon content in biochar, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17065, https://doi.org/10.5194/egusphere-egu23-17065, 2023.

EGU23-17470 | Posters on site | SSS5.2

Long Term Experiment Platform : proposition for a global site network and experience coordination for the study of agronomical and environmental effects of biochar 

Diego Marazza, Simone Pesce, Enrico Balugani, Alessandro Buscaroli, and Nicolas Greggio

After a long debate spanning 20 years, biochar has emerged as a promising land management technique for addressing climate change and improving soil fertility. Biochar is an effective long-term carbon store due to its resistance to decomposition compared to fresh organic matter or compost, and it has the potential to stabilize soil organic matter when added to the soil. 

However, there is a lack of long-term data and knowledge about Soil Organic Carbon (SOC) stocks due to a lack of historical databases. Studies have shown that few experiments have lasted over 3 and focused on estimating SOC increase from biochar application. Additionally, few of these studies have measured biochar decay rate.  

In line with the lack of a consistent number of historical databases we developed the LTEP-BIOCHAR (https://site.unibo.it/environmental-management-research-group/en/activities/long-term-platform): a specific platform for experimenting with biochar application to soil with the agronomic and environmental purposes such as carbon sequestration, soil erosion, and soil biodiversity in real conditions and over a significant timeframe. The LTEP-BIOCHAR is community-driven resource dedicated to biochar and includes around 22 long-term experiments from Europe, the Middle East, and Africa. The platform aims to list active field experiments, identify methodological gaps in current experiments, suggest new hypotheses, establish a minimum standard of analysis, create a network of expert researchers, support the design of coordinated experiments, and promote the platform at a wider international level. 

Next steps in research will include collaboration with experts in the domain of pyrogenic carbon from vegetation fires and finding agreement among practitioners on the mean residence time of C-biochar and related measurements (e.g. isotopic signature, loss of ignition, near-infrared spectroscopy).  

How to cite: Marazza, D., Pesce, S., Balugani, E., Buscaroli, A., and Greggio, N.: Long Term Experiment Platform : proposition for a global site network and experience coordination for the study of agronomical and environmental effects of biochar, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17470, https://doi.org/10.5194/egusphere-egu23-17470, 2023.

EGU23-1525 | ECS | Orals | SSS5.3 | Highlight

Carbon preservation in soils: The role of carbon chemistry in soil aggregate formation 

Alba Otero-Fariña, Helena Brown, Ke-Qing Xiao, Juan Antelo, Sarah Fiol, Pippa Chapman, Joseph Holden, Steven Banwart, and Caroline Peacock

To mitigate climate change, it is of vital importance to increase the stocks of global soil organic carbon (SOC), which also improves soil resilience, soil fertility and thus food security. 

The preservation of SOC heavily depends on its vulnerability to microbial degradation. Two processes and their interplay strongly influence carbon protection: the formation of primary organo-mineral (O-M) complexes via the sorption of dissolved organic carbon (DOC) to fine-grained soil minerals, and the aggregation of these to form micro and macroaggregates. To date, research suggests that the chemistry of the SOC and the mineralogy of the soil matrix play a key role in the formation of O-M complexes and their stability against microbial degradation, but whether and to what extent these factors help control micro and macroaggregation are unknown. 

We focus our investigation on how the chemistry of the SOC source affects the stability and aggregation of iron (oxyhydr)oxide O-M complexes. Thus, we determine the sorption behaviour of different SOC sources chosen to represent different functional group chemistries, using sorption isotherm experiments and electrophoretic techniques. We also conduct long-term aggregation experiments to track aggregate particle size using a novel Particle Size and Shape Analyzer technique.  

Our findings suggest that the stability and aggregation modes of O-M complexes are a function of SOC chemistry, and that aggregation patterns are strongly influenced by the presence of microbial exudates and communities. 

How to cite: Otero-Fariña, A., Brown, H., Xiao, K.-Q., Antelo, J., Fiol, S., Chapman, P., Holden, J., Banwart, S., and Peacock, C.: Carbon preservation in soils: The role of carbon chemistry in soil aggregate formation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1525, https://doi.org/10.5194/egusphere-egu23-1525, 2023.

EGU23-2051 | ECS | Orals | SSS5.3

Long-term fertilization and PFM changed the accumulation of stalk-derived POM in soil aggregates under field conditions 

Xinxin Jin, Roland Bol, Tingting An, Lihong Zheng, Shuangyi Li, Jiubo Pei, and Jingkuan Wang

Plastic film mulching (PFM) is critical for agricultural planting and production in semi-arid and arid areas. Particulate organic matter (POM) is assumed to be a sensitive indicator of evaluating the effects of different agricultural practices on soil fertility and soil organic carbon (SOC) pool. Soil aggregates are the main storage sites for POM. However, there is limited information regarding how PFM and fertilization influences the dynamic changes of newly added stalk-derived POM in Brown earth. Consequently, a depth-study of the fate of carbon (C) and nitrogen (N) derived from maize stalk residues as the POC and PON fractions in soil aggregates will help in predicting the active organic matter component sequestration in the soil. The dynamics and contribution of the newly added maize stalk C and N as POC and PON in different soil aggregates (using dry sieving method divided to > 2, 1-2, 0.25-1and < 0.25 mm) was analyzed by an in-situ 13C15N-tracing technique under 27-year long term PFM and different fertilization treatments. Over the 360 d cultivation, the POC and PON contents were significantly (P < 0.05) higher in the nitrogen (N) and organic manure (M) treatments than other fertilizer addition treatments. Compared with no PFM, PFM accelerated the decomposition of maize stalk C in the N fertilizer treatment, exhibiting an increase of 64% in stalk-derived POC in the initial cultivation time. In addition, stalk-derived POC tended to accumulate in 1-2 mm aggregates in the summer and fall as a result of long-term PFM coupled with fertilization. However, the stalk-derived PON was decreased with the cultivation time in different four aggregates. Stalk-derived POM was tended to accumulate in the macroaggregate size fraction (> 0.25 mm) over 360 days of cultivation in the field conditions. Accordingly, PFM application and fertilization practices had important effects on accumulation of newly added stalk-derived POM in soil aggregates.

How to cite: Jin, X., Bol, R., An, T., Zheng, L., Li, S., Pei, J., and Wang, J.: Long-term fertilization and PFM changed the accumulation of stalk-derived POM in soil aggregates under field conditions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2051, https://doi.org/10.5194/egusphere-egu23-2051, 2023.

EGU23-2255 | ECS | Posters on site | SSS5.3

Molecular characterisation of fire-affected soil organic matter by a 5th generation wildfire in SW-Portugal 

Nicasio T. Jiménez-Morillo, Nuno Guiomar, Ana Z. Miller, José M. De la Rosa, and José A. González-Pérez

Forest fires are a recurrent ecological phenomenon in the Mediterranean basin. They induce molecular changes in soil organic matter (SOM) leading to immediate and long-term environmental consequences [1]. The SOM is of paramount importance as indicator of soil health [2]. Fire-induced changes in SOM include the alteration of biogenic chemical structures and the accumulation of newly formed ones, enhancing dynamics in the complex balance between the different C-types [2,3]. Therefore, understanding SOM molecular composition, before and after fire, is fundamental to monitor changes in soil health, as well as its natural or man-mediated recovery [3,4]. Our aim was to assess the molecular composition of organic matter in fire-affected leptosols, at two depths (0–2 and 2–5 cm) under different vegetation types located in the southwestern of Portugal (Aljezur, Algarve). The SOM characterization was conducted by analytical pyrolysis (Py-GC/MS), a technique based on the thermochemical breakdown of organic compounds in the absence of oxygen at elevated temperatures [5]. The Py-GC/MS has been found suitable for the structural characterization of complex organic matrices [4], providing detailed structural information of individual compounds considered fingerprinting of SOM. However, due to the relative high number of molecular compounds released by analytical pyrolysis, the use of graphical-statistical methods, such as van Krevelen diagrams, are usually applied to help monitoring SOM molecular changes produced by fire [3,4]. This work represents the first attempt to evaluate the fire effects in SOM using a detailed molecular characterisation of SOM under different vegetation canopies, recently affected by wildfire, in southern Portugal.

 

References:

[1] Naveh, Z., 1990. Fire in the Mediterranean – a landscape ecological perspective. In: Goldammer, J.G., Jenkins, M.J. (Eds.), Fire in Ecosystems Dynamics: Mediterranean and Northern Perspective. SPB Academic Publishing, The Hague.

[2] González-Pérez, J.A., González-Vila, F.J., Almendros, G., Knicker, H., 2004. The effect of fire on soil organic matter—a review. Environ. Int. 30, 855–870.

[3] Jiménez-Morillo, N.T., De la Rosa, J.M., Waggoner, D., et al., 2016. Fire effects in the molecular structure of soil organic matter fractions under Quercus suber cover. Catena 145, 266–273.

[4] Jiménez-Morillo, N.T.; Almendros, G.; De la Rosa, J.M.; et al., 2020. Effect of a wildfire and of post-fire restoration actions in the organic matter structure in soil fractions. Sci. Total Environ. 728, 138715.

[5] Irwin, W.J., 1982. Analytical pyrolysis—a comprehensive guide. In: Cazes, J. (Ed.), Chromatographic Science Series, 22: Chapter 6. Marcel Dekker, New York.

 

Acknowledgments: This work was funded by national funds through FCT–Fundação para a Ciência e a Tecnologia (EROFIRE project, ref. PCIF-RPG-0079-2018) and by the EU-FEDER co-funded project MARKFIRE (ref. P20_01073) from Junta de Andalucía. This research was also funded by the European Union through the European Regional Development Funds in the framework of the Interreg V A Spain-Portugal program (POCTEP) through the CILIFO (Ref.: 0753_CILIFO_5_E) and FIREPOCTEP (Ref.: 0756_FIREPOCTEP_6_E) projects. A.Z.M. and N.T.J.M. thank the FCT for contracts CEECIND/01147/2017 and 2021/00711/CEECIND, respectively. N.T.J.M. and A.Z.M. were also supported by MCIN “Ramón y Cajal” contracts (RYC2021-031253-I and RYC2019-026885-I, respectively).

How to cite: Jiménez-Morillo, N. T., Guiomar, N., Miller, A. Z., De la Rosa, J. M., and González-Pérez, J. A.: Molecular characterisation of fire-affected soil organic matter by a 5th generation wildfire in SW-Portugal, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2255, https://doi.org/10.5194/egusphere-egu23-2255, 2023.

EGU23-2423 | Orals | SSS5.3

The subsoil horizons are the preferential location for organic carbon stabilization in chestnut forests 

Mauro De Feudis, Gloria Falsone, William Trenti, Gilmo Vianello, and Livia Vittori Antisari

Forest soils are recognized to be important organic carbon storage, but the role of surface and subsurface soil horizons on such function and its drivers are still field of debate. In this context, we examined the dynamics of soil organic carbon (SOC) for a chestnut forestry system in a temperate area of northern part of Apennine mountain range in Italy. Specifically, we questioned: what are the main i) SOC forms both in mineral surface and subsurface soil horizons? ii) factors affecting SOC stabilization?. Soil samples were collected by horizon and SOC was separated into organic C of the particulate organic matter (POM_C), sand–size aggregates (sand_C) and the mineral–associated organic C (MAOM_C). The easily oxidizable C (EOC), water–soluble organic C (WSOC), the microbial biomass–C and its respiration, and the total and easily extractable glomalin–related soil protein (T–GRSP and E–GRSP, respectively) were also estimated. Then, the E–GRSP–to–T–GRSP and E-GRSP–to–SOC ratios, the metabolic (qCO2) and microbial (qMIC) quotients were calculated. The POM_C, sand_C and MAOM_C showed the highest concentrations in A horizon (26.5, 14.6 and 13.9 g kg–1, respectively) highlighting the importance of the litter floor on the organic matter pools quantity in the topsoil. Further, the A horizon was enriched of the most labile organic C forms (i.e., EOC and WSOC) indicating the key role of A horizon for the development and growth of chestnut forest ecosystems. In fact, the labile organic C forms provide several ecosystem services, such as plant growth and yield. Unlike A horizon, the subsurface horizons preserved SOC mostly in the most stable form (63.8 %, on average). Because of the role of fungal biomass and its exudates to increase SOC capture and stabilization, the great potential of the subsurface horizons to store MAOM_C can be attributed both to the higher release of exogenous GRSP (higher E–GRSP–to–T–GRSP ratio) by mycorrhizal fungi and fungal mycelium expansion (higher E-GRSP–to–SOC ratio) within such horizons (0.504  and 0.061, respectively) compared to the A horizon (0.244 and 0.034, respectively). Therefore, the subsurface soil horizons seemed to have more favourable conditions for microorganisms compared to surface one as shown by the lower qCO2 and the higher qMIC values found in the former than in the latter. Overall, the present investigation highlighted the importance of subsurface soil horizons of chestnut forests on C stabilization processes compared to the A horizon likely due to the better edaphic conditions for the microbial communities. Thus, our results pointed out the key role that the subsurface soil horizons of chestnut forests could have for mitigating the current climate change.

How to cite: De Feudis, M., Falsone, G., Trenti, W., Vianello, G., and Vittori Antisari, L.: The subsoil horizons are the preferential location for organic carbon stabilization in chestnut forests, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2423, https://doi.org/10.5194/egusphere-egu23-2423, 2023.

Lipids from the wax layers of plant leaves and plant roots as preserved in soils and sediments have been used for decades as proxies for environmental reconstructions. In particular the n-alkanes of higher chain-lengths (ca. C25-C37) are used to this end. The past decade has seen an increased research attention for the use of plant lipids as molecular proxies. This includes an emerging interest in applications aimed at unravelling the dynamics of soil organic matter (SOM) rather than answering purely palaeo-ecological questions[1] as well as in reconstructing multiple environmental factors at once. Here I highlight these developments via two examples of recent work by our group. In the first example we applied analysis of n-alkanes and n-alcohols preserved in plaggic Anthrosols to reconstruct the origin of the plant material that was used as the stable fillings that were applied to fertilize the soils in this unique agricultural system. In the second example we examined plant derived n-alkanes preserved in soils along an altitudinal transect in the Ecuadorian Andes as part of a coupled reconstruction of palaeo-vegetation and palaeo-climate. I discuss both the exciting new insights gained as well as the challenges that still remain.

References

[1] J.M. van Mourik, T.V., Wagner, J.G. de Boer, B. Jansen, (2016). The added value of biomarker analysis to the genesis of plaggic Anthrosols; the identification of stable fillings used for the production of plaggic manure. SOIL, 2, 299-310

[2] B. Jansen, H. Hooghiemstra, S.P.C. de Goede, J.M. van Mourik, (2019). Chapter 5 - Biomarker analysis of soil archives, Eds. J.M. van Mourik, J.J.M. Van der Meer, Developments in Quaternary Sciences, 18: 163-222

[3] M.L. Teunissen van Manen, B. Jansen, F. Cuesta, S. León-Yánez, S., W.D. Gosling, (2020). From leaf to soil: n-alkane signal preservation, despite degradation along an environmental gradient in the tropical Andes. Biogeosciences, 17, 5465-5487

How to cite: Jansen, B.: Plant lipids as proxies to trace the origin and dynamics of soil organic carbon, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2772, https://doi.org/10.5194/egusphere-egu23-2772, 2023.

ABSTRACT: Global nitrogen (N) deposition has impacted the structure and functioning of soil microbial communities, translating into important changes to the cycling of soil organic matter (SOM). Recent frameworks have proposed that portioning the particulate and mineral-associated organic matter (POM and MAOM) fractions can help us better understand SOM cycling. However, how N deposition affect the fractionation of SOM into MAOM and POM forms, and how soil microbes process these across soil profile all remain unclear. Here we examined the microbial phospholipid fatty acids and determined N and soil organic carbon (SOC) content in POM and MAOM at depths of 0–10, 30–40 and 70–100 cm after 10-year N addition at rates of 0, 2, 10 and 50 g m-2 yr-1 in a temperate steppe. We found that N addition remarkably shifted microbial communities by increasing the relative abundances of bacteria and gram-positive (GP) bacteria, and decreasing gram-negative bacterial across the three soil layers. These effects of N addition tended to increase with the N addition rate but diminished with soil depth probably as pH decreased with the N addition rate but increased with soil depth. Both N addition and soil depth may cause similar microbial community shifts, through which fungi and GP bacteria become dominant, but may through different mechanisms. More than 60% of total SOC and N are stored as MAOM in this grassland. The share of SOC and total N in the MAOM was slightly decreased by N addition in 0-10 cm but significantly increased in deeper soils. The ratios of POM-C/MAOM-C and POM-N/MAOM-N significantly decreased with soil depth regardless of N addition treatments. Moreover, N addition increased the two ratios in 0-10 cm soil, but decreased them in deeper soil layers. N addition increased the stocks of SOC (MAOM: +11 %; POM: +23 %) and total N (MAOM: +10 %; POM: +27 %) in 0–10 cm soil, but increased only in MAOM in 30–40 cm (SOC: +24 %; total N: +24 %) and 70–100 cm (SOC: +15 %; total N: +13 %) soils. Soil physicochemical features exerted stronger controls than microbial properties in the distribution of SOC and total N in the two fractions regardless of soil depth because of eight soil features explaining more of the total variation than eight microbial properties. Our findings imply that increase in N deposition may make more SOC stabilized as MAOM fraction in grassland soils.

Keywords: Nitrogen deposition, Soil microbiome, Mineral-associated organic matter, Subsoil

How to cite: Niu, G., Huang, J., Lu, X., and Rousk, J.: Decadal nitrogen addition enhanced soil C and N storage in mineral-associated organic matter by altering soil abiotic and microbial properties in a temperate grassland, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3272, https://doi.org/10.5194/egusphere-egu23-3272, 2023.

Subsoils have gained increasing attention due its slower soil organic carbon (SOC) turnover than in topsoil. Thus, subsoil with low content of mineral associated organic matter but a large number of exchange sites on mineral surfaces represents the potential to accumulate and sequester carbon (C). Generally, it has been assumed that the carbon turnover mechanism in topsoil and subsoil is influenced by similar environmental factors, with the difference of a lower C content in subsoil. In contrast, diverse abiotic variables prevalent in subsoils, like low temperature, high moisture, nutrient availability, etc., have been shown to imply different processes influencing C turnover in subsoils. Therefore, differences in processes and factors affecting SOC turnover in topsoil and subsoil are incompletely identified and understood.

Our objective is to investigate whether C decomposition and stabilisation mechanisms in topsoil and subsoil differ given the same added substrate content, as well as how it responds to increasing substrate C content. To assess these questions, a long-term (total duration 20-year) field incubation experiment was conducted at three different locations with varied soil textures in which soil was mixed and labelled with isotopically (13C) enriched beech litter substrate with different C contents of 8, 16, 32, and 64 g substrate kg-1 in topsoil (10 cm) and 2, 4, 8, and 16 g substrate kg-1 in subsoil (60 cm), filled in mesocosms, and buried. Soil samples were collected after one, two, and four years. Soil was fractionated into particulate organic matter (>20µm) and mineral-associated organic matter (<20µm) to find out how carbon is stabilised in these fractions, and stable C isotopes were measured. Our results indicate that the decomposition of the identical litter substrate strongly depends on the soil depth. The results of four years of buried field-microcosms will be presented, which will shed more light on differences in mechanisms responsible for SOC dynamics and the fate of litter substrate into different SOC pools of topsoil and subsoil.

 

How to cite: Begill, N., Don, A., and Poeplau, C.: Investigating soil organic matter dynamics in topsoil and subsoil by burying isotopically labelled litter substrate for four years, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3538, https://doi.org/10.5194/egusphere-egu23-3538, 2023.

EGU23-3581 | ECS | Posters on site | SSS5.3

Plastic film mulching combined with manure fertilizer application promotes microbial necromass carbon accumulation within soil macroaggregates 

Xu Liu, Roland Bol, Tingting An, Yaocen Liu, Hongbo Wang, Chang Peng, Shuangyi Li, and Jingkuan Wang

Plastic film mulching is a common agricultural management to increase crop yield in the dry and cold regions. The improved soil hydrothermal environment under mulching conditions could change soil microbial activities and soil aggregation, thereby affecting soil organic carbon (C) sequestration. However, it remains not clear that how mulching regulates microbial necromass C accumulation and distribution within soil aggregates, especially under different fertilizer applications. We analyzed the contents of fungal and bacterial necromass C (taking amino sugar as biomarkers) and their contributions to organic C within soil aggregates under mulching combined with different fertilization treatments (no fertilization, CK; inorganic fertilizer application, IF; and manure fertilizer application, MF) in a 900-day in-situ field experiment. On day 360, the contents of fungal and bacterial necromass C within macroaggregates were 25% and 12% higher in the mulching combined with IF treatment, and were 20% and 32% higher in the mulching combined with MF treatment relative to the corresponding no-mulching treatments, respectively. On day 900, the mulching combined with CK and IF treatments decreased microbial necromass C content within soil aggregates, while the mulching combined with MF treatment promoted microbial and fungal necromass C accumulation within macroaggregates (>0.25 mm), compared with the corresponding no-mulching treatments. Mulching increased the fungal/bacterial necromass C ratio within macroaggregates on day 900, but decreased this ratio within microaggregates during the whole incubation period compared with the corresponding no-mulching treatments. Moreover, microbial necromass C occupied 28%–43% and 40%–56% of organic C within macroaggregates and microaggregates on day 900, respectively. Overall, mulching combined with the application of manure fertilizer greatly promoted microbial necromass C accumulation, and thus increased organic C sequestration within macroaggregates.

How to cite: Liu, X., Bol, R., An, T., Liu, Y., Wang, H., Peng, C., Li, S., and Wang, J.: Plastic film mulching combined with manure fertilizer application promotes microbial necromass carbon accumulation within soil macroaggregates, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3581, https://doi.org/10.5194/egusphere-egu23-3581, 2023.

EGU23-3868 | ECS | Posters on site | SSS5.3

Alterations of soil organic matter following 130 years of afforestation assessed by molecular markers 

Tatjana Carina Speckert and Guido Lars Bruno Wiesenberg

In alpine areas of the European Alps, many of the pastures are no longer economically profitable and are converted into forests (Bolli et al., 2007). Afforestation on former pastures affects soil organic matter (SOM) dynamics through alteration of quality and quantity of root and aboveground biomass litter input. Compared with pasture OM, forest OM is less decomposable and characterized by increased C:N ratio as well as increased lignin concentration (Hiltbrunner et al., 2013). Therefore, it could be expected that long-term afforestation on a centennial scale may have a severe impact on SOM dynamics, an aspect that remains so far unknown as most of the earlier studies focused on successions between 30 and 50 years (Vesterdal et al., 2002).

In the current study, we aimed to identify the major sources of SOM in a subalpine afforestation sequence (40-130 years) with Norway spruce (Picea abies L.) on a former pasture in Jaun, Switzerland. Therefore, we combined plant- and microorganism-derived molecular proxies from several compound classes such as free-extractable fatty acids and phospholipid fatty acids.

We observed a decline in soil organic carbon (SOC) stock (9.6 ± 1.1 kg m-2) after 55 years and a recovering of the SOC stock 130 years (12.7 ± 0.9 kg m-2) after afforestation. Overall, there is no alteration of the SOC stock in the mineral soil following afforestation of former pasture (13.3 ± 0.9kg m-2) after 130 years. But if we consider the additional SOC stock accumulated in the organic horizons (between 0.8 and 2 kg m-2), the total SOC stock slightly increased, although OM in organic horizons is less stabilized than mineral-bound OM. An increase of the C:N ratio in the Oi-horizon with increasing forest age (40yr: 36.9 ± 2.6; 55yr: 40.9 ± 4.1; 130yr: 42.4 ± 6.6) reflects the alteration in litter quality towards poorly decomposable compounds in older forests. In addition, preliminary results show an increase in the abundance of Gram+ (+3%) and Gram- bacteria (+6%), especially in the young (40yr) forest. Thus, the bacterial community seems to proliferate in the early succession before the fungal-dominated community takes over. Thus, the change in SOM source and quality following afforestation may not result in considerable stock changes, but results in better stability of SOM in the mineral soil.

References

Bolli, J. C., Rigling, A., Bugmann, H. (2007). The influence of changes in climate and land-use on regeneration dynamics of Norway spruce at the treeline in the Swiss Alps. Silva Fennica, 41, 55.

Hiltbrunner, D., Zimmermann, S., Hagedorn, F. (2013). Afforestation with Norway spruce on a subalpine pasture alters carbon dynamics but only moderately affects soil carbon storage. Biogeochemistry, 115, 251-266.

Vesterdal, L., Ritter, E., Gundersen, P. (2002). Change in soil organic carbon following afforestation of former arable land. Forest Ecology and Management, 169, 137-147.

How to cite: Speckert, T. C. and Wiesenberg, G. L. B.: Alterations of soil organic matter following 130 years of afforestation assessed by molecular markers, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3868, https://doi.org/10.5194/egusphere-egu23-3868, 2023.

Soil organic matter (SOM) is a key player in soil functioning and services in forest lands, which had been subject to accelerated land degradation particularly in karst terrain in Southwest China. So far, there had been poor knowledge of pool and molecular composition of SOM associated with soil aggregates across lithologic origins of karst soil. In this study, undisturbed topsoil (0-10 cm) samples were collected in forest lands on sandstone (SS), dolomite (DS) and limestone (LS) sedimentary rocks in a karst terrain from Guizhou, Southwest China. Changes in SOM pool distribution and molecular composition of water-stable aggregates were explored using size and density fractionation and GC/MS detection of extracted biomarkers. The OC content ranged from 41.05 g kg-1 on SS to 50.94 g kg-1 while the mean weight diameter of sand-free soil water-stable aggregates ranged from 420.9 μm on SS to 544.4 μm on DS, across the lithologic sequence. With biomarker molecular assay, the higher SOC storage was relevant to the higher abundance of plant-derived organics (lignin, cutin, suberin, wax and phytosterols) in macro- and micro- aggregates. Whereas, the higher OC in silt & clay fraction of topsoil on DS and LS could be explained by the higher abundance of microbial lipids plus cutin and suberin. Also, the higher ratio of (Ad/Al)v to (Ad/Al)s of silt-clay fraction pointed to a stronger degradation of lignin thereby. Thus, the forest soil of dolomite and limestone origin preserved a relatively high level of SOC storage in topsoil, mainly with accumulation of POC physically protected in macro- and micro- aggregates. Moreover, the high SOC of topsoil on dolomite could also be attributed to enrichment of SOC in the clay silt fraction, mainly with mineral association of microbially degraded OCs.

How to cite: Lin, Q., Chen, S., Feng, X., and Pan, G.: Pool distribution and molecular composition of organic matter among water-stable aggregate size fractions of karst topsoil across a lithologic sequence from Guizhou, Southwest China, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3957, https://doi.org/10.5194/egusphere-egu23-3957, 2023.

EGU23-5557 | Orals | SSS5.3

Tracing sources and turnover of soil organic matter in a long-term irrigated dry forest - a non-exchangeable hydrogen isotope approach 

Claudia Guidi, Marco Lehmann, Katrin Meusburger, Matthias Saurer, Valentina Vitali, Martina Peter, Ivano Brunner, and Frank Hagedorn

Soil organic matter (SOM) originates from various sources such as foliar litter, roots and microbial (e.g. fungal) components. The relative sources contribution represents one of the key unknowns in SOM dynamics. Our study aimed to explore whether stable isotope ratios of non-exchangeable hydrogen (Hn) bound to organic matter can be used to differentiate SOM sources, since natural 2Hn abundance can strongly differ between root and foliar tissues. We also investigated if long-term irrigation with 2H-depleted water in a pine forest can be used to track Hn incorporation into organic matter inputs and eventually in the soil pools.

In a 17-year-long irrigation experiment in a dry pine forest, we assessed variations in natural abundance of 2Hn, 13C, and 15N in SOM sources (foliar litter, fine roots, fungal mycelia), decomposing litter, soil (organic layers and uppermost 5 cm-mineral soil) and particle-size fractions. We then applied a Bayesian mixing model (including δ2Hn,δ13C, and δ15N) to estimate the relative sources contribution to SOM.

Natural 2Hn abundance was significantly higher in roots vs. foliar litter (up to +39‰), and in fungal mycelia vs. roots (up to +41‰). Results from Bayesian mixing model suggest that foliar litter contributed to approximately 68 ± 10% of SOM in organic layers and in coarse particulate organic matter (POM). Foliar litter and roots contributed similarly to upper 2 cm of mineral soil (46 ± 11%), while 2-5 cm of mineral soil were largely derived from roots (61 ± 13%). Fungal mycelia contributed to 18 ± 8% of mineral-associated organic matter (MOM), while only to 1-2% of coarse and fine POM. Bayesian mixing models provided only a general indication of the sources contribution to SOM, also considering that isotopic signatures shifted during decomposition. Measurements of isotope signatures in microbial necromass might allow a more accurate assessment of the different SOM sources contribution.

The δ2Hn depletion of soil water under irrigation was paralleled by a comparable decrease in δ2Hn of roots (~12‰). In comparison, the natural 2Hn abundance in fresh needles and foliar litter decreased less strongly (~ 7‰ and 4‰, respectively), likely due to photosynthetic adjustments that may have counterbalanced the irrigation water 2H-depletion. Similar to soil water 2H-depletion, δ2Hn values in coarse POM were 11‰ lower in irrigated vs. dry plots, suggesting that nearly all organic Hn turned over or exchanged with soil water in less than two decades. In contrast, δ2Hn values in fine POM and MOM decreased only by 3‰ under irrigation, which indicate that these fractions comprise slower cycling Hn pools.

Our study showed that the natural 2Hn abundance represents a promising tool to differentiate among SOM sources. While 13C and 15N did not clearly separate between roots and foliar litter, Hn isotopic signatures allowed a good discrimination between SOM sources. In addition, long-term irrigation can provide a potential in situ 2H-labelling of SOM, which may help to examine organic Hn turnover rates across SOM pools.

How to cite: Guidi, C., Lehmann, M., Meusburger, K., Saurer, M., Vitali, V., Peter, M., Brunner, I., and Hagedorn, F.: Tracing sources and turnover of soil organic matter in a long-term irrigated dry forest - a non-exchangeable hydrogen isotope approach, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5557, https://doi.org/10.5194/egusphere-egu23-5557, 2023.

The sequestration of carbon in the form of organic compounds in the soil is considered one of the main strategies for mitigating climate change. Mountain ecosystems have a great potential to store soil organic carbon (SOC) due to relatively lower temperatures and higher precipitation, which slow down the rate of organic matter decomposition. However, mountains are also regions particularly vulnerable to changes caused by direct and indirect human activity, in particular climate change and land cover change. All these changes have an impact on soil properties and thus on SOC stocks and their stability. One of the changes that has been particularly evident in mountainous regions in recent decades is the rapid succession of forests over grasslands, due to the land abandonment and the effects of global warming. In addition, the soil cover of mountainous regions is characterized by a large natural diversity of soil-forming processes, which is reflected in differences in the SOC sequestration potential. Thus, the aim of this research was to determine the effect of different soil-forming processes compared to different land cover on SOC stock and SOC stability. 
The SOC stock was measured in soils subjected to various soil-forming processes (podzolization, brunification, peat accumulation) and with different land cover (ancient forests, succession forests, meadows) in three similar study areas in the Carpathians (S Poland). The highest SOC stocks in the first 30 cm of soil were found in ancient forests (between 4.2 kg m-1 and 8.8 kg m-1) and the lowest in meadows dominated by tall-grass communities (1.3–2.0 kg m-1). The SOC stock was significantly higher in Podzols than in Cambisols and Histosols; however, most of the soils subjected to podzolization were found in forests. In addition, in mineral soils with contrasting pedogenic pathways (Podzols and Cambisols) soil organic matter fractionation was carried out. The preliminary results indicate that Podzols are characterized by much higher SOC content outside water-stable aggregates and in light fractions (particulate organic matter), which suggests relatively a weaker stability of organic matter in this type of soils than in Cambisols.
This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 952327 (HES-GEO) and has been supported by a grant from the Priority Research Area Antropocene (Young Labs) under the Strategic Programme Excellence Initiative at Jagiellonian University.

How to cite: Musielok, Ł., Stolarczyk, M., Rudnik, A., and Buczek, K.: The role of soil-forming processes and changes in land cover in the storage and stabilization of soil organic carbon - preliminary results from the Carpathians (Southern Poland), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6229, https://doi.org/10.5194/egusphere-egu23-6229, 2023.

EGU23-6849 | ECS | Posters on site | SSS5.3

Complementarity and drivers of thermal and physical soil organic carbon fractions at the scale of mainland France 

Amicie Delahaie, Lauric Cécillon, Claire Chenu, Dominique Arrouays, Line Boulonne, Claudy Jolivet, Céline Ratié, Nicolas Saby, Marija Stojanova, Antonio Bispo, Manuel Martin, Pierre Arbelet, Jussi Heinonsalo, Christopher Poeplau, Kristiina Karhu, Pierre Roudier, Samuel Abiven, Lorenza Pacini, and Pierre Barré

Assessing soil organic carbon biogeochemical stability is critical for estimating future changes in soil carbon stocks. Several methods for the assessment of soil organic carbon (SOC) biogeochemical stability have been proposed but very few can be implemented on large sample sets. Indeed, to date, only simple physical fractionation protocols (e.g. Lavallee et al., 2020) and Rock-Eval® thermal analysis techniques (Delahaie et al., 2022, SOIL discussion) have been implemented on data sets larger than a few hundred samples. Simple fractionation techniques allow separating a particulate organic carbon fraction (POC; considered labile) and an organic fraction associated with minerals (MaOC; considered more stable). Regarding thermal analyses, Rock-Eval® results associated to the PARTYsoc machine-learning model (Cécillon et al., 2021) provide a measure of the active (mean residence time of ca. 30 years) and centennially stable SOC fractions.

In this study, we present the results of physical fractionations performed on ca. 1000 samples and thermal analyses performed on ca. 2000 samples from French mainland topsoils (RMQS program). We compare the amount and the drivers of each fraction. Our results show that most of the MaOC fraction is not stable at a centennial timescale. However, we show using a Random Forest model that the MaOC content and the centennially stable SOC content are similarly influenced by a common set of drivers: clay, pH and climatic conditions (mean annual temperature and mean annual precipitation). Finally, we discuss the complementarity of these two types of relatively high-throughput fractionation protocols.

 

References

  • Cécillon, L., Baudin, F., Chenu, C., Christensen, B. T., Franko, U., Houot, S., Kanari, E., Kätterer, T., Merbach, I., van Oort, F., Poeplau, C., Quezada, J. C., Savignac, F., Soucémarianadin, L. N., & Barré, P. (2021). Partitioning soil organic carbon into its centennially stable and active fractions with machine-learning models based on Rock-Eval® thermal analysis (PARTY SOC v2. 0 and PARTY SOC v2. 0 EU). Geoscientific Model Development14(6), 3879-3898.
  • Delahaie, A. A., Barré, P., Baudin, F., Arrouays, D., Bispo, A., Boulonne, L., Chenu, C., Jolivet, C., Martin, M. P., Ratié, C., Saby, N. P. A., Savignac, F., & Cécillon, L. (2022). Elemental stoichiometry and Rock-Eval® thermal stability of organic matter in French topsoils. EGUsphere, 1-31.
  • Lavallee, J. M., Soong, J. L., & Cotrufo, M. F. (2020). Conceptualizing soil organic matter into particulate and mineral‐associated forms to address global change in the 21st century. Global Change Biology26(1), 261-273.

How to cite: Delahaie, A., Cécillon, L., Chenu, C., Arrouays, D., Boulonne, L., Jolivet, C., Ratié, C., Saby, N., Stojanova, M., Bispo, A., Martin, M., Arbelet, P., Heinonsalo, J., Poeplau, C., Karhu, K., Roudier, P., Abiven, S., Pacini, L., and Barré, P.: Complementarity and drivers of thermal and physical soil organic carbon fractions at the scale of mainland France, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6849, https://doi.org/10.5194/egusphere-egu23-6849, 2023.

EGU23-7186 | ECS | Posters on site | SSS5.3

Soil organic matter as a mediator of energy fluxes - a new perspective 

Anna Gunina and Yakov Kuzyakov

The transformation of “energy to (soil organic) matter’’ has long been the focus of scientific attention, but a definitive conceptual framework does not yet exist. Following the classical definition of energy given by Odum and Odum (1977) and the principles and laws of energy, we have developed an experiment-based review of the complex process of microbial conversion of energy and carbon (C) from litter to soil organic matter (SOM). Based on the transformation rate of plant residues, the amount of plant-derived energy persisting in soil (after one year) ranges from 7 to 20 % of total energy input depending on the plant community (for example, spruce and broadleaf forests and grasslands were taken). This represents 0.8-10 % of the energy already stored in SOM but only adds 0.4-5 % C to the existing SOM pool. We have introduced two new parameters - energy quality representing primarily substance, and energy availability representing the ability of microorganisms to utilize that substance (or pool of substances) under actual soil conditions. According to these parameters, we have assigned the main classes of organic substances to one of the three groups that show the availability of energy stored in microorganisms. When the energy availability is >1, microorganisms gain more energy than invest by the decomposition of organic substances; when energy availability is <1, then energy investment is required for the co-mining of nutrients, and some compounds are unsuitable for energy mining due to low efficiency, and in this case, they will be partially decomposed by co-metabolism (no energy gain). We have estimated the energy investment of soil microorganisms for exoenzyme production and concluded that the disadvantage of enzymatic degradation could explain the ‘stability’ of the SOM because the energy input (investment) required for degradation exceeds the energy gain. Following the linear decrease in energy density (by 106 kJ mol-1 C) of a broad range of organic substances per nominal oxidation state of C (NOSC) unit upon oxidation and experimental data on litter decomposition, we have developed the concept showing changes in the NOSC and the energy content of plant residues during decomposition and formation of SOM. Mineralization, recycling, and accumulation processes control energy and NOSC changes in organic pools. Mineralization processes lead to energy losses and an increase in NOSC, while SOM accumulation increases energy content and decreases NOSC. Recycling can shift both the energy content and NOSC values depending on the environmental conditions of the soil and the quality/quantity of litter input. As a result, the SOM pool is different from the initial litter in the energy content and NOSC. The SOM has a more diverse molecular composition but a narrower range of NOSC values than plant residues, consists of microbial necromass and substances recycled by microorganisms, and contains, on average, substances with a higher energy content than the initial plant residues. Based on the developed concept, we have concluded that plant-derived C and energy that persist in the form of SOM ensure energy fluxes in the soil system.

How to cite: Gunina, A. and Kuzyakov, Y.: Soil organic matter as a mediator of energy fluxes - a new perspective, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7186, https://doi.org/10.5194/egusphere-egu23-7186, 2023.

EGU23-7318 | ECS | Orals | SSS5.3

Soil organic matter stability decreases with increasing urbanization in highly weathered rainfed tropical arable soils 

Stephen Boahen Asabere, Axel Don, Tino Peplau, and Daniela Sauer

Urbanization is a major land use change factor affecting soils. There is little understanding of how expansions of tropical West African cities have affected soil organic matter (SOM) composition and dynamics. In such cities, urban agriculture is common, playing an essential role in food security and urban sustainability. However, tropical soils tend to have low nutrient contents and cation exchange capacity. Thus, management strategies that enhance soil fertility and carbon (C) sequestration are needed. Developing such strategies requires a thorough understanding of how SOM dynamics alter in response to urban growth. Here, our objective was to assess how urbanization has affected the relatively stable mineral-associated-SOM (MAOM) and the labile particulate-SOM (POM) fractions in rainfed urban arable maize fields of Kumasi, a typical expanding city in Ghana (West Africa).

Using a grid-based satellite approach, and keeping other factors constant (including climate, topography, parent material and soil type), we took topsoil samples (0–10 cm) along an urban-intensity (UI) gradient, distinguishing: (i) low UI, located >400 m away from any primary road and having been under urbanization for <30 years, (ii) mid-low UI, located ≤400 m from a primary road and having been under urbanization for <30 years, (iii) mid-high UI, located >400 m from primary road and having been under urbanization for ≥30 years, (iv) high UI, located within ≤400 m from a primary road and having been under urbanization for ≥30 years. SOM fractions were isolated from the soils using a size separation approach, whereby the sand-sized fraction (0.063 - 2 mm) was regarded as POM and the clay- and silt-sized fraction (<0.063 mm) as MAOM. Prepared samples were ultimately analyzed for SOC using a Leco temperature ramp C analyzer, where a temperature threshold of 600 ºC was used to separate organic from inorganic C.

We found that mean SOC contents of the POM fraction increased markedly from 7.7 g kg-1 in the low UI topsoils to 13 g kg-1 in their high UI counterparts, suggesting an increase in POM with increasing urbanization. This trend was not observed for the MAOM that showed SOC contents of 4.5, 4.1, 4.9, and 4.1 g kg-1 for the low, mid-low, mid-high, and high UI topsoils, respectively. Moreover, the share of SOC contents of POM in the bulk SOC increased from 51% in the low UI topsoils to 64% in the high UI topsoils, whereas that of MOAM decreased by 6% from 31% to 25%, respectively. These findings suggest that while there is evidence of strong anthropogenic contributions of SOM to urban arable soils, urbanization does not seem to promote SOC storage in the relatively stable MAOM fraction. Consequently, rainfed urban arable soils in Kumasi will need management interventions for keeping appropriate long-term SOM levels to maintain soil functions.       

How to cite: Asabere, S. B., Don, A., Peplau, T., and Sauer, D.: Soil organic matter stability decreases with increasing urbanization in highly weathered rainfed tropical arable soils, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7318, https://doi.org/10.5194/egusphere-egu23-7318, 2023.

EGU23-7982 | ECS | Posters on site | SSS5.3

Formation of organo-Fe (oxyhydr)oxide interactions during the first stages of Martian regolith simulant terraforming 

Beatrice Giannetta, Antonio G. Caporale, Danilo Oliveira De Souza, Paola Adamo, and Claudio Zaccone

Future long-term space missions beyond Low Earth Orbit (e.g., to Mars) depend on the development of bioregenerative life support systems able to produce food crops based on in situ resource utilization. Mars regolith potentially contains most of the essential nutrients for plant growth, except for organic matter (OM). Several strategies and treatments can be applied to improve nutrient deficiency of simulants and enhance their performance as plant growth substrates. Although Mars regolith simulants have been characterized by mineralogical, physico-chemical and hydraulic properties, no data are available to date in the scientific literature about the stabilization of exogeneous OM by minerals, including iron (Fe) oxides, over time.

This study aims at understanding the mineral transformation and OM turnover in the early stages of terraforming. The Mojave Mars Simulant MMS-1, alone (R100) and with a commercial compost 70:30 v:v (R70C30), was compared to a fluvial sand, alone and with compost (S100 and S70C30). Potato was grown on these substrates for 99 days in greenhouse. Samples were fractionated, obtaining particulate OM (POM) and mineral associated OM (MAOM), andcharacterized for total nitrogen and organic carbon (OC), total element concentration (ICP-OES) and by Fe K-edge X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS).

In the whole medium, OC increased in S70C30 (10×) and R70C30 (25×). As expected, most of the OC accumulated in the POM fraction of both growing media (10× in S70C30 and 20× in R70C30), while OC in the MAOM was 3-times higher in R70C30 than in S70C30. Chlorite, smectite and goethite were the main Fe species in S100, according to XANES, while Fe(III)-OM was found in both fractions of S70C30. Moreover, according to EXAFS, hematite occurred in POM, whereas goethite in MAOM. XANES revealed the occurrence of smectite, maghemite and ferrihydrite in R100, and of nontronite and hematite in the MAOM and POM, respectively.

Revealing Fe species involved in the formation of organo-mineral interactions will help to identify the main critical aspects and future challenges related to sustainable space farming improving the in-situ use of Martian resources.

How to cite: Giannetta, B., Caporale, A. G., Oliveira De Souza, D., Adamo, P., and Zaccone, C.: Formation of organo-Fe (oxyhydr)oxide interactions during the first stages of Martian regolith simulant terraforming, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7982, https://doi.org/10.5194/egusphere-egu23-7982, 2023.

EGU23-8025 | ECS | Orals | SSS5.3

Is the additional organic carbon stored thanks to alternative cropping systems and organic waste products application predominantly stable at a decadal timescale? 

Tchodjowiè Israel Kpemoua, Pierre Barré, Sabine Houot, François Baudin, Cédric Plessis, and Claire Chenu

The implementation of agroecological practices can lead to an additional soil organic carbon (SOC) storage. The carbon sink effect will be more effective, even in the short and medium term, if the additional storage is realized in the form of persistent organic carbon (OC) and not in labile OC. The objective of this study was to evaluate the biogeochemical stability of additionally C stored by agroecological practices. Biogeochemical stability was assessed using particles size and density fractionation and Rock-Eval (RE) thermal analyses with PARTYsoc machine learning model. Samples were collected from the QualiAgro experiment, where organic wastes products (OWPs) including biowaste compost (BIOW), residual municipal solid waste compost (MSW) and farmyard manure (FYM) were applied, and from the La Cage experiment, where conservation (CA) and organic (ORG) agriculture had been established for 20 years. The plots that received the OWPs showed that 60-66% of the additional C was stored in mineral-associated organic matter (MAOM-C) and 29 - 39% in particulate organic matter (POM-C), whereas in CA and ORG, 77 - 84% of the additional C was stored in MAOM-C versus 15 - 23% in POM-C. While leading to additional C stocks of similar sizes, MSW and FYM exhibited higher proportions of the additionally stored C as POM-C (39 and 29% respectively) compared to CA (15%). This suggests a recalcitrance of POM under OWPs management compared to CA. The PARTYSOC model using RE thermal analysis parameters allows to predict the active (30 - 40 years) and stable (>100 years) carbon pools as defined in the AMG model. The results revealed that most, if not all, of the additional C belonged to the active C pool. These findings suggest that although additional SOC is mainly associated with MAOM-C, it is probably not stored in a form with a mean residence time exceeding ~30 years. The agroecological practices implemented in both long-term field experiments have resulted in substantial short-term additional C storage, but this storage will only be maintained at a high level if these storing practices are continued.

How to cite: Kpemoua, T. I., Barré, P., Houot, S., Baudin, F., Plessis, C., and Chenu, C.: Is the additional organic carbon stored thanks to alternative cropping systems and organic waste products application predominantly stable at a decadal timescale?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8025, https://doi.org/10.5194/egusphere-egu23-8025, 2023.

EGU23-8035 | ECS | Posters on site | SSS5.3

13C natural abundance for analysis of steps of organic carbon transformation in soil: application for various ecosystems 

Ying Wang, Anna Gunina, and Yakov Kuzyakov

Following the developed concept of carbon (C) flows during soil organic matter (SOM) formation, from which the probable C pathways between the aggregates and SOM fractions can be suggested based on the natural changes of the 13C/12C ratios, we have prepared the review based on 42 publications. The data were collected from the existing databases using the following keywords: “soil organic matter fractions and 13C”, “density fractionation and 13C”, and “soil aggregates and 13C”; publications contained the data from forest, shrubland, grassland, and cropland ecosystems that were located in the Temperate, Mediterranean, subtropical and tropical climatic zones were chosen; only the top 20 cm were considered. Besides the δ13C data, the main soil properties, including pH, total C and nitrogen contents, texture, and the dominant type of soil minerals, were collected. All data for the isotopic composition of aggregates (>2000, 250-2000, 52-250, and <53 µm) and density fractions (<1.4, 1.4-1.6, 1.8-2.0, and >2.2 g cm-3) were normalized to the δ13C values of bulk soils. The preliminary analyses have shown that the isotopic composition of density fractions separated from the soils allocated in temperate and Mediterranean climates followed the previously established order, namely was getting heavier with the increase of particle densities. In contrast, density fractions separated from the soils of subtropical and tropical zones did not show prominent trends, or isotopic composition showed the enrichment in 12C with increased particle density. The isotopic composition of fractions separated from forest soils was also found with more minor variations compared to cropland and grassland. The data related to the probability of C flow between the density fractions and aggregates during SOM formation were also calculated and will be presented, as well as the concept explaining the effect of land use and climatic variables on the changes of the isotopic composition of density fractions and aggregates.

How to cite: Wang, Y., Gunina, A., and Kuzyakov, Y.: 13C natural abundance for analysis of steps of organic carbon transformation in soil: application for various ecosystems, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8035, https://doi.org/10.5194/egusphere-egu23-8035, 2023.

EGU23-8543 | ECS | Orals | SSS5.3

Organic carbon stabilisation mechanisms in estuarine marsh soils: Effect of salinity and flooding frequency 

Friederike Neiske, Joscha N. Becker, Maria Seedtke, Daniel Schwarze, and Annette Eschenbach

The capability of coastal wetland soils to store large amounts of organic carbon (OC) has been increasingly recognised. Stabilisation mechanisms (e.g. aggregation or mineral association) and stability of organic matter (OM) (recalcitrant vs. labile) are important features for the long-term storage of soil organic carbon (SOC). In estuarine marshes, SOC storage is dominated by a complex and dynamic interaction of abiotic conditions such as tidal inundation or changes in salinity. However, little is known on OC stabilisation and stability in these transitional ecosystems and how they are affected by system-specific characteristics. Therefore, our aim was to assess the effect of flooding and salinity on (i) OC stabilisation by aggregation and mineral association and (ii) the stability of the OC pool in estuarine marsh soils.

We analysed topsoil (0 – 10 cm) and subsoil (10 – 30 cm) samples from 9 marsh zones along the salinity gradient (salt, brackish and freshwater) and flooding gradient (pioneer zone, low and high marsh) of the Elbe Estuary for their SOC contents, OC stabilisation mechanisms (density fractionation), OC stability (incubation with one- and two-compartment model fits) and dissolved organic carbon (DOC) concentrations.

Total SOC contents were highest in the freshwater marsh and decreased towards topsoils with higher salinity. Flooding frequency had no uniform effect on SOC contents: While there was a positive tendency with decreasing flooding frequency, subsoils of the freshwater marsh showed the opposite trend. Total SOC contents were positively correlated with mineral-associated OC (CMAOM) and pedogenically unprotected particulate OM (CfPOM). The highest proportion of CMAOM was found in topsoils of freshwater marshes and it decreased towards higher salinities in topsoils of high marshes and pioneer zones. The OM protection by aggregation (CoPOM) increased in topsoils of high marshes. The proportion of CfPOM was less directly affected by salinity and flooding than by the CN ratio of the aboveground biomass (CNlitter). Furthermore, CfPOM correlated positively with the potential mineralisable C (Cpot) and labile C (Clabile) and negatively with the recalcitrant C pool (Crecalcitrant) that were derived from the one- and two-compartment models. Labile C, Cpot and Crecalcitrant were also strongly influenced by CNlitter. Moreover, Crecalcitrant was linked to the proportion of CMAOM. Concentrations of DOC increased with total SOC and Cpot but decreased with CoPOM.

We conclude that SOC stabilisation in the Elbe Estuary is mainly related to mineral association of OM. With increasing terrestrial influence, physical protection in aggregates becomes more important. Besides these pedogenic stabilisation mechanisms, recalcitrance is strongly determined by vegetation characteristics.

How to cite: Neiske, F., Becker, J. N., Seedtke, M., Schwarze, D., and Eschenbach, A.: Organic carbon stabilisation mechanisms in estuarine marsh soils: Effect of salinity and flooding frequency, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8543, https://doi.org/10.5194/egusphere-egu23-8543, 2023.

EGU23-10208 | ECS | Orals | SSS5.3

Assessing soil carbon cycling as a function of intercropped maize-forage systems and nitrogen rates using 13C natural abundance 

Laudelino Vieira da Mota Neto, Marcelo Valadares Galdos, Vladimir Eliodoro Costa, and Ciro Antonio Rosolem

Intercropping maize along with forages fertilized with N can potentially increase soil carbon sequestration, contributing to climate change mitigation. However, there is a lack of knowledge if the input of new C sources in this production system impacts the cycling of the original soil C and SOM fractions, especially in tropical soils. To investigate this, soil samples were taken up to 80 cm depth from a 7-year experiment where ruzigrass (Urochloa ruziziensis), palisadegrass (Urochloa brizantha) and Guinea grass (Megathyrsus maximus) were intercropped with maize fertilized with (270 kg N ha-1) or without N. In these samples, SOM was fractionated by size into particulate (POM) and mineral-associated (MAOM) organic matter and submitted to 13C natural abundance measurements. Intercropping with Guinea grass reduced the δ13C values in comparison to ruzigrass and palisadegrass, especially under N fertilization. Forage grasses reduced the δ13C values up to 40cm, indicating the contribution of the grasses for the cycling of the original carbon of the soil. Nitrogen supply increased the contribution of C from the grasses to the POM fraction if compared to the no N application. Further, 13C  in POM at 0-10 and 10-20 cm differed from deeper layers, probably due the above- and belowground C inputs on the uppermost soil layers. Under N supply, Guinea grass lowered the δ13C value, which did not occur in the palisade and ruzigrass treatments. In contrast to POM, the δ13C values of MAOM decreased in all depths, with the highest change at the uppermost soil layer. Our findings showed that intercropping influenced the cycling of total C and SOM fractions , with differences in the soil profile. However, only Guinea grass changed δ13C values under N supply.

How to cite: Vieira da Mota Neto, L., Valadares Galdos, M., Eliodoro Costa, V., and Antonio Rosolem, C.: Assessing soil carbon cycling as a function of intercropped maize-forage systems and nitrogen rates using 13C natural abundance, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10208, https://doi.org/10.5194/egusphere-egu23-10208, 2023.

EGU23-10362 | ECS | Orals | SSS5.3

Divergent controls on particulate and mineral-associated organic carbon formation and persistence 

Paige Hansen, Alison King, Jocelyn Lavallee, Meagan Schipanski, and M. Francesca Cotrufo

Identifying global controls on soil carbon (C) storage, as well as where soil C is most vulnerable to loss, are essential to realizing the potential of soils to mitigate climate change via C sequestration. However, we currently lack a comprehensive understanding of the global drivers of soil C storage, especially with regards to particulate (POC) and mineral-associated organic carbon (MAOC). To better understand global controls on these two C fractions, we synthesized climate, and net primary production (NPP), and soils data from 73 published studies and databases. This large dataset is representative of multiple land cover types, including broadleaved and coniferous forests, grasslands, shrublands, wetlands, tundra, and wetlands. We then applied structural equation modeling (SEM) to assess hierarchical, interactive controls on global POC and MAOC pools (i.e., g POC or MAOC per kg soil) in topsoils. Our SEM tested relationships between NPP and climate (i.e., mean annual temperature (MAT) and effective moisture, assessed as mean annual precipitation minus potential evapotranspiration), as well as the extent to which climate and NPP, along with soil texture and pH, govern POC and MAOC storage. We found that NPP is positively related to MAT and effective moisture. Additionally, POC storage is negatively related to both MAT and pH, while MAOC storage is positively related to NPP and effective moisture, but negatively related to soil % sand. Given that temperature and pH impose constraints on microbial decomposition, these results indicate that POC storage is primarily controlled by C output limitations. In contrast, strong relationships with variables related to plant productivity constraints and to mineral surfaces available for sorption indicate that MAOC storage is primarily controlled by climate-driven C input limitations and C stabilization mechanisms. Together, we demonstrate that divergent controls govern C storage in POC and MAOC, and that these controls are consistent across multiple ecosystem types.

How to cite: Hansen, P., King, A., Lavallee, J., Schipanski, M., and Cotrufo, M. F.: Divergent controls on particulate and mineral-associated organic carbon formation and persistence, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10362, https://doi.org/10.5194/egusphere-egu23-10362, 2023.

A wide range of image-based techniques revealed mounting evidence of a heterogeneous arrangement of mineral-associated organic matter (OM) in soils at the microscale and nanoscale. Spectromicroscopic approaches using such as NanoSIMS, STXM-NEXAFS, AFM, STEM-EELS, and others have provided insights about a patchy and piled-up arrangement of OM. This arrangement is determined by different local OM properties and mineral composition as well as OM-OM interactions. The emerging conceptual framework of the microscale arrangement of OM affects our understanding of soil functions: By compartmentalizing and decoupling local carbon sequestration in the mineral soil matrix, by localizing the mechanical stabilization of soil structure, by altering surface properties and re-distributing ion exchange sites, and by shaping distinct biotic microenvironments. After an overview on the spectromicroscopic evidence, this contribution will illustrate the emerging conceptual framework of localized soil functions, and highlight opportunities for research approaches based on the patchy and piled-up arrangement of OM at the microscale and nanoscale.

How to cite: Schweizer, S.: Taking a closer look: How spectromicroscopic imaging of organo-mineral associations leads to a novel perspective on interrelated soil functions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11969, https://doi.org/10.5194/egusphere-egu23-11969, 2023.

EGU23-12085 | ECS | Orals | SSS5.3

Mineral type, land use, and management intensity drive the formation of mineral-associated organic matter in temperate soils 

Susanne Ulrich, De Shorn Bramble, Ingo Schöning, Robert Mikutta, Klaus Kaiser, and Marion Schrumpf

Formation of mineral-associated organic matter (MAOM) supports accumulation and stabilization of carbon in soil, and thus, is a key factor in the global carbon cycle. Little is known about the interplay of mineral type, land use, and management intensity on the extent of MAOM formation. We addressed this research question by exposing mineral containers with pristine minerals (goethite, as a representative of oxide-type mineral phases, and illite, representing layered aluminosilicate minerals) for five years to ambient soil conditions at 5 cm depth in 150 grassland and 150 forest plots in three regions across Germany. After recovery, the content of organic carbon (OC) of the minerals was determined by dry combustion. Results show that irrespective of land use and management intensity, more OC accumulated on goethite than illite (on average 0.23 and 0.06 mg m-2 mineral surface, respectively), demonstrating that mineral type was the most crucial factor for MAOM formation. Carbon accumulation was consistently greater in coniferous forests than in deciduous forests and grasslands. Structural equation models revealed that in grasslands, fertilization had contradictory effects on carbon accumulation, with the positive effect being mediated by enhanced plant productivity and the negative effect by reduced plant species richness. Overall, our results suggest that OC stabilization in soil is primarily driven by mineral type, in particular iron and other metal oxides. The mineral-driven MAOM formation is further modified by land use and management intensity.

How to cite: Ulrich, S., Bramble, D. S., Schöning, I., Mikutta, R., Kaiser, K., and Schrumpf, M.: Mineral type, land use, and management intensity drive the formation of mineral-associated organic matter in temperate soils, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12085, https://doi.org/10.5194/egusphere-egu23-12085, 2023.

EGU23-12386 | Posters on site | SSS5.3

Hair-ice, fungal guttation droplets, ice ribbons and needle ice from a chemical perspective 

Diana Hofmann, Gisela Preuss, Pietro Fontana, and Christian Mätzler

As a result of global warming, now evident also in temperate latitudes, longer periods of snow-free winters, instead with plenty of precipitation are becoming increasingly common. If the temperatures then fall below freezing point, one can, with a little luck, discover hair ice - hair-like, flexible structures reaching up to 10 cm in length without any ramifications.

This natural phenomenon, already described in 1918 by Alfred Wegener, was a mystery for a long time. Only in the 21st century a fungus (Exidiopsis effusa) was discovered as the causative agent [1].

Hair ice develops exclusively on rotten hardwoods on/in which this fungus is present, at high humidity, preferably windless, and temperatures slightly below freezing. Once infected, corresponding branches can be repeatedly elicited hair-rise growth under optimal conditions (field & climate chamber). Hair ice, unlike frost needles, arises from the base. At the onset of hair-ice melt a very thin fibre becomes apparent, which carries brownish water drops. Melting water samples show complex mass spectra similar to dissolved organic carbon e.g. from terrestrial/ marine waters, soil extracts or aerosols.

Hair ice samples of various tree species were desalted, concentrated by solid phase extraction and subsequently analyzed by flow injection analysis in a Fourier Transform Ion Cyclotron Resonance Mass Spectrometer, equipped with an ESI source and a 7 T supra-conducting magnet (LTQ-FT Ultra, ThermoFisher Scientific) - the key technique for the analysis of complex samples, simultaneously providing molecular level details of thousands of compounds. As main result, complex, but almost identical spectra were found. For their chemical characterization van Krevelen diagrams, typical to classify samples regarding polarity and aromaticity were plotted. By comparison with references biopolymer substance classes were derived. As result, lignin and tannin could be detected as the main hair-ice substance classes, supposed to act as freezing catalyst as well as recrystallization inhibitor.

For the question, if and what happens in summer, we sampled in several years guttation droplets, too – of this fungus and for comparison from a fungus of another family. Both samples were carbon riche, but only the samples from Exidiopsis effusa show such a complex DOC-spectrum, but in contrast to hair ice peak depleted with mainly tannin assignment.

Popular scientific publications have led to an increasing interest in hair ice and related phenomena in recent years. We have received spectacular photos of various ice structures, followed by first samples of needle ice and ice ribbons. After initial measurements for their C content, HPLC-MS investigations still with a triple quadrupole mass spectrometer have been performed. For final analyses a cooperation with a FTICRMS working group is now sought.

[1] D. Hofmann, G. Preuss and C. Mätzler (2015) Biogeosciences 12: 4261–4273

How to cite: Hofmann, D., Preuss, G., Fontana, P., and Mätzler, C.: Hair-ice, fungal guttation droplets, ice ribbons and needle ice from a chemical perspective, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12386, https://doi.org/10.5194/egusphere-egu23-12386, 2023.

EGU23-12839 | ECS | Orals | SSS5.3

Dynamics and stability of soil organic matter: climate vs. time 

Giorgio Galluzzi, César Plaza, Simone Priori, Beatrice Giannetta, and Claudio Zaccone

This study aims to investigate the mechanisms of soil organic carbon (SOC) sequestration with depth as a function of time and climate. Two chronosequences located along a climate gradient were investigated. The first chronosequence (ADI) consisted of fluvial terraces, whereas the second (LED) of fluvio-glacial terraces. Four sites (Q2, Q3, Q4 and Q5) located in 3 terraces (T1, T2, and T3), with age ranging from about 125,000 to 2,000 yr, were investigated for ADI, while 3 sites (Q1, Q2, and Q3) in 3 terraces (T1, T2, and T3, respectively), with age range from about 16,000 to 10,000 yr, were selected for LED. All sites were grasslands. Soil samples were collected (1 profile and 2 cores per site) by horizon, and each horizon sub-sampled by depth (each 5 cm). The sub-samples were characterized for pH, EC, total organic C, total N, texture, mineralogy, total and extractable elements, and for soil respiration. Particulate organic matter (POM) and mineral-associated organic matter (MAOM) were isolated and characterized by elemental and thermal analyses.

In ADI, the oldest site (ADIQ2) stocks 2 times more C in the topsoil (15 cm) than the youngest site (ADIQ5) (60 and 27 MgC/ha, respectively). Furthermore, in ADIQ3, 38% of the total SOC accumulated between 30 and 80 cm (48 MgC/ha). In LED, the youngest site (LEDQ3) shows the highest SOC stock to both 15 and 30 cm (86 and 138 MgC/ha, respectively). In LEDQ1, 46% of the total SOC accumulated between 30 and 90 cm (94 MgC/ha). Among sites having same age but different climate, LEDQ3 (the wettest and coldest site) stocks ~2 times more carbon than ADIQ3 (the driest and warmest site) to the first 30 cm of depth.

In LED, the ratio between the organic C in MAOM/POM in the topsoil ranges between 0.6 and 1.8, while in ADI between 1.1 and 3.9. Thermal indices (e.g., WL400-550/200-300, TG-T50) show that the stability of bulk SOM and pools generally increased with depth in ADI sites, whereas remained constant in LED. ADI soils had similar cumulative respiration (RHCUM), whereas LEDQ3 exhibited the highest RHCUM along the first 30 cm. Indeed, LEDQ3 had a 3× higher RHCUM than ADIQ3 in topsoil.

Our data show that significant amounts of organic C were accumulated in deeper soils (>30cm). Moreover, soil organic matter (SOM) stability, and especially that of MAOM, in ADI increased with depth. The relative contribution of POM to C storage was more important in LED than in ADI, especially in the topsoil. Overall, our data suggest that climate has a greater influence on the size of SOC stocks than age, which in turn exerts a major influence on the stability of SOM.

How to cite: Galluzzi, G., Plaza, C., Priori, S., Giannetta, B., and Zaccone, C.: Dynamics and stability of soil organic matter: climate vs. time, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12839, https://doi.org/10.5194/egusphere-egu23-12839, 2023.

EGU23-13410 | ECS | Posters on site | SSS5.3

Turnover of soil organic matter and microbial biomass under C3-C4 vegetation change: implications for carbon sequestration in Mediterranean agricultural soils. 

Layla M. San-Emeterio, José Antonio González-Pérez, Rafael López-Núñez, Lorena M. Zavala, Yakov Kuzyakov, and Anna Gunina

 Carbon isotopic composition of soils subjected to C3–C4 vegetation change can be used to estimate C turnover in bulk soil, but more specifically in soil organic matter (SOM) pools with fast and intermediate turnover rates. Analysis of phospholipid fatty acids (PLFA) has been widely used to evaluate rapid changes in soil microbial populations. In this study we investigated the effect a C3–C4 vegetation change experiment, along with a sustainable practice versus tillage soil microbial community composition as well as their isotopic C composition by compound-specific PLFA 13C analysis.

Soils (Calcaric Cambisol) from an agricultural trial located in Southern Spain were sampled, which are characterized by high carbonate content (~27%) low fertility and low organic matter contents. The experimental trial consisted in replacing former C3 vegetation by maize crop (C4 plant) since February 2017, comprising two different treatments: A) after harvesting, maize surpluses were chopped and applied to surface soil, hereafter known as aboveground biomass “A” treatment; B) the total part of maize plant was left out after harvesting, including the roots, known as belowground biomass “B” treatment. Moreover, untreated soil was taken as control plots, “C”, where soil was tillaged and kept the same isotopic signature as the former land use. Composite soil samples (0-5 cm) were taken.

PLFA profiles revealed a great abundance of bacterial activity, comprising gram-positive and gram-negative, along with branched (i-14:0, i-&a- 15:0, i:16:0, i-&a- 17:0) and mono- and polyunsaturated groups (16:1n7, 18:2n6, 18:1w9c and 18:1w7c). Significant increase of fungal abundance in “B” treatment may indicate decrease of litter decomposability, which facilitates fungal development. The “A” treatment also indicated a greater microbial activity, though intermediate in most of the groups compared to control. Lastly, in control plots, it is observed a significant decrease of G- bacteria, which correlates well with lower C content. indicates the low amount of easily available root exudates (Gütlein et al., 2017), which are the preferred C source for this microbial group. On the other hand, significant 13C enrichment of PLFAs varied across microbial groups. “B” plots showed greater 13C contribution for fungi, whereas the application of aboveground biomass contributes greatly to the gram-positive and gram-negative bacteria. PLFA 13C mean residence times were much longer for bacteria compared to the rest of microbial groups.

Our results indicate that the addition of biomass in SOM-depleted agricultural soils resulted an increase of microbial biomass, denoting a predominant bacterial activity. Over 5 years of C3-C4 vegetation change, fungi and actinobacteria showed the fastest turnover rates compared to bacteria, which appeared to play a major role in the rapid acquisition of C into the soil microbial community. Fungi and actinobacteria appeared to have a delayed utilization of C or to prefer other C sources upon application of grounded biomass. Further discussion will be made on the implications of sustainable practices for enhancing C sequestration under Mediterranean climate.

How to cite: M. San-Emeterio, L., González-Pérez, J. A., López-Núñez, R., M. Zavala, L., Kuzyakov, Y., and Gunina, A.: Turnover of soil organic matter and microbial biomass under C3-C4 vegetation change: implications for carbon sequestration in Mediterranean agricultural soils., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13410, https://doi.org/10.5194/egusphere-egu23-13410, 2023.

EGU23-13825 | Posters on site | SSS5.3 | Highlight

How does edaphic context affect soil organic matter persistence? 

Karen Vancampenhout, Judith Schellekens, Sascha Nijdam, Keunbae Kim, Maria I.J. Briones, Bart Muys, Ellen Desie, and Boris Jansen

European and Flemish climate-change policies aim to enhance carbon (C) storage in soils of conservation areas, including natural areas such as forests, grasslands and wetlands. Soil capability and condition however may impact C persistence and material cycles in soils, and therefore the sustainability of this policy effort, by making soil C stocks more vulnerable to climatic anomalies, shocks and disturbances. Edaphic limitations in terms of nutrients, acidity, temperature or moisture availability have been shown to affect soil C persistence, but processes behind this effect remain elusive and poorly quantified.

In this contribution, we therefore present several case studies in western European forests and wetlands, where we assess how the molecular composition of several soil organic matter fractions varies along gradients of soil cover, edaphic conditions and perturbation intensity. Furthermore, by comparing different fractions and markers, we evaluate the suitability of different methods to evaluate changes in soil carbon dynamics, as a tool to predict the potential impact of anthropogenic stresses and management interventions on soil carbon persistence.

How to cite: Vancampenhout, K., Schellekens, J., Nijdam, S., Kim, K., Briones, M. I. J., Muys, B., Desie, E., and Jansen, B.: How does edaphic context affect soil organic matter persistence?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13825, https://doi.org/10.5194/egusphere-egu23-13825, 2023.

EGU23-13926 | ECS | Orals | SSS5.3

The role of lignin in the saprotrophic degradation of plant biomass in boreal forest soil. 

Aswin Thirunavukkarasu, Mats Öquist, Jurgen Schleucher, Tobias Sparrman, Mattias Hedenstrom, Mats Nilsson, and Stefan Bertilsson

The amount of carbon stored in boreal forests soil as Soil organic matter (SOM) is significant. Carbohydrate polymers such as cellulose and hemicellulose constitute 40-50% of the SOM mass in the surface mor layer, even in SOM that has been decomposed for decades to centuries. This is in contrast to conceptual decomposition models assuming aromatic and aliphatic polymers to constitute the fraction of recalcitrant SOM. One prevailing view for support is that lignin manifest itself as a factor in the stabilization of carbohydrate polymers as SOM. However, detailed elucidation of how the complex array of molecular moieties making up SOM decompose over time is lacking. Here we investigated the effect of lignin content and composition during the progressive degradation of polymeric carbohydrates, lignin, and lipids in the lab during a year-long soil decomposition study using Aspen (Populus tremula) wood as a model substrate. To specifically address lignin decomposition we used a range of Aspen clones that varied naturally in their lignin content (high lignin 30% - low lignin 25%) with boreal coniferous forest soil obtained from the surface moor layer (O-horizon). The decomposition of the different molecular moieties of the model substrate was evaluated by Two-dimensional (2D) liquid state 1H–13C nuclear magnetic resonance (NMR) spectroscopy. In addition, the CO2 production during decomposition was monitored continuously and assays for exo-enzymatic activity was carried out at selected time points.

The NMR spectroscopy revealed that for different periods of decomposition, saprotrophic microorganisms preferred different monomers of polymeric lignin, carbohydrates, and lipids. The relative degradation of resinol, spirodienone, and cinnamyl alcohol were higher among lignin interlinkages and the relative degradation of p-hydroxybenzoate and syringyl were higher among lignin subunits. For carbohydrates, the relative degradation of mannose and glucose were higher than that of e.g. xylose. The relative degradation of unsaturated fatty acids was higher among lipids. The lignin: carbohydrates ratio decreased linearly over the period of decomposition. This showed that the initial degradation of lignin compounds was greater compared to the decomposition of carbohydrate compounds. The significant difference in the relative degradation of mannose among model substrate with different lignin content showed that lignin had no effect on cellulose degradation but may have had an effect on the preferential degradation of hemicelluloses. The high-resolution decomposition patterns we observe are crucial for obtaining a detailed mechanistic understanding of plant polymer decomposition by soil microorganisms during the initial stages of SOM genesis.

 

Keywords: Soil organic matter (SOM), Lignin, Carbohydrates, 2D NMR, Decomposition

How to cite: Thirunavukkarasu, A., Öquist, M., Schleucher, J., Sparrman, T., Hedenstrom, M., Nilsson, M., and Bertilsson, S.: The role of lignin in the saprotrophic degradation of plant biomass in boreal forest soil., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13926, https://doi.org/10.5194/egusphere-egu23-13926, 2023.

EGU23-15659 | ECS | Posters on site | SSS5.3

SOC sequestration affected by fertilization in rice-based cropping systems over the last four decades 

Shuhui Wang, Nan Sun, Shuo Liang, Shuxiang Zhang, Jeroen Meersmans, Gilles Colinet, Minggang Xu, and Lianhai Wu

Enhancing soil organic carbon (SOC) stocks through fertilization and crop rotation will contribute to sustaining crop productivity and mitigating global warming. Although it is known that cropping systems may affect SOC stocks by influencing the balance between C input and C decomposition, only few studies focused on the impact of different rice cropping systems on SOC stock changes in paddy soils. In this study, we analyzed the differences in SOC stocks and their driving factors in the topsoil (0–20 cm) with various fertilization measures in two rice-based cropping systems (i.e. rice-wheat rotation and double rice rotation systems) over the last four decades from seven long-term experiments in the Yangtze River catchment. The treatments include no fertilizer application (CK), application of chemical nitrogen, phosphorus and potassium fertilizers (NPK) and a combination of NPK and manure (NPKM). Results showed that during the last four decades, the topsoil SOC stock significantly increased by 8.6 t ha-1 on average under NPKM treatment in rice-wheat system and by 2.5–6.4 t ha-1 on average under NPK and NPKM treatments in double rice system as compared with CK. A higher SOC sequestration rate and a longer SOC sequestration duration were found in NPKM treatment than that in NPK treatment in both cropping systems. The highest relative SOC stock percentage (SOC stock in fertilized treatments to CK) was observed under the NPKM treatment in both cropping systems, though no significant difference was found between these two cropping systems. However, the fertilization-induced relative increase of the SOC stock was 109.5% and 45.8% under the NPK and NPKM treatments, respectively in the rice-wheat system than that in the double rice system. This indicates that the rice-wheat system is more conducive for SOC sequestration. RF and SEM analyses revealed that the magnitude and influencing factors driving SOC sequestration varied between two systems. In the double rice system, continuous flooding weakens the influence of precipitation on SOC sequestration and highlights the importance of soil properties and C input. In contrast, soil properties, C input and climate factors all have important impacts on SOC sequestration in rice-wheat system. This study reveals that the rice-wheat system is more favorable for SOC sequestration despite its lower C input compared to the double rice system in China’s paddies.

How to cite: Wang, S., Sun, N., Liang, S., Zhang, S., Meersmans, J., Colinet, G., Xu, M., and Wu, L.: SOC sequestration affected by fertilization in rice-based cropping systems over the last four decades, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15659, https://doi.org/10.5194/egusphere-egu23-15659, 2023.

EGU23-15729 | ECS | Orals | SSS5.3

Managed pastures enhance soil carbon stocks from degraded pasture in Ferralsol of Brazilian Cerrado 

Lucas Raimundo Bento, Steffen A. Schweizer, Patrícia P. A. Oliveira, José R. M. Pezzopane, Alberto C. de C. Bernardi, Ingrid Kögel-Knabner, and Ladislau Martin-Neto

The conversion of native vegetation into agricultural lands is often associated with a decrease in soil C. The soils from the Brazilian savannah (named Cerrado), with 200 million hectares, are rich in Fe and Al (hydr)oxides, which could result in more organo-mineral associations and lead to particularly high C storage. The changes in the C stocks from the conversion of native forest into degraded pasture (DP), and the adoption of proper management to recover DP and increase C stocks in such Ferralsols are not well understood. To provide insights into the drivers of C storage, this study compared the C stocks across depth in the top 1m and the distribution of C in the soil fractions 24 years after the adoption of different management systems in degraded pastures in the Brazilian Cerrado.

A DP area located in São Carlos, São Paulo, Brazil was converted into different management systems: (i) RMS: rainfed pasture with moderate animal stocking rate, (ii) RHS: rainfed pasture with higher animal stocking rate, and (iii) IHS:  irrigated pasture with higher stocking rate. As a control, the adjacent native vegetation (FO) was also evaluated. The adoption of management started in 1996 with RMS and in 2002 for RHS and IHS. Except for the DP, all areas were limed and N-fertilized. RMS with 200 kg N ha, RHS 400 kg N ha, and IHS with 600 kg N ha. Soil sampling was carried out in 2020 and the C stocks were evaluated up to 1 m deep. To state vegetation change from C3 (native forest) to C4 (introduced pasture) the isotopic natural abundance of 13C was analyzed. To evaluate the contribution of mineral-associated and particulate organic matter forms to C storage, we performed a physical fractionation by size and density with SPT 1.8 g cm-3, respectively.

Our results showed that the conversion of FO into DP decreased soil C stocks.  Otherwise, the adoption of management in DP with RMS and RHS increased C stocks achieving levels similar to FO. RMS showed the highest C stocks with the lower dosage of N-fertilizer and animal stocking rate. IHS area did not increase their C stocks compared to DP, which may be related to limited root growth after irrigation decreasing the C input. Around 50% of the C stocks in RHS and RMS systems are pasture-derived (C4 plants) according to the 13C abundance. This shows that half of C stocks from rainfed pastures is of preserved organic matter from previous FO. While in the IHS and DP systems, the organic matter composition is mainly pasture-derived. Our preliminary data showed that the RMS topsoil contained more free particulate organic matter than the FO, suggesting that the C stocks were enhanced mainly by pasture-derived biomass input. The contribution of mineral-associated organic matter still will be evaluated.

Our study shows that the recovery of degraded pasture soils by management leads to increased OC stocks derived from fertilized pasture but also higher maintenance of OC from FO.

How to cite: Bento, L. R., Schweizer, S. A., Oliveira, P. P. A., Pezzopane, J. R. M., Bernardi, A. C. D. C., Kögel-Knabner, I., and Martin-Neto, L.: Managed pastures enhance soil carbon stocks from degraded pasture in Ferralsol of Brazilian Cerrado, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15729, https://doi.org/10.5194/egusphere-egu23-15729, 2023.

Under conservation agriculture (CA), soil aggregates physically protect soil organic C, creating microhabitats with heterogeneities in nutrient availability. These may become rich in microbial taxa with structured interconnections, and thus maintain the equilibrium between C sources and sinks. A long-term experiment on tillage and N fertilization located in the Mediterranean was used to investigate the microbiota within small macroaggregates (sM), and occluded microaggregates (mM). At surface layer N fertilization was the main driver of diversity of prokaryotes and fungi in soil aggregates, whereas at subsurface layer tillage intensity was the primary driver. Moreover, although along the soil profile a conserved core microbial community was found across managements in soil aggregates, some taxa were unique to certain managements. At surface layer, N fertilization significantly modified the prokaryotic community structure in sM and mM under conventional tillage, whereas in the subsurface layer, tillage modified the community structure of prokaryotes in both soil aggregates, and of fungi in mM. The fungal community structure in sM was strongly modified by the interaction between tillage and N fertilization at both soil layers and in mM only at surface layer. Overall sM had a higher diversity of prokaryotes and a lower diversity of fungi than mM. Small macroaggregates and mM had distinctive microbial community structures. Prokaryotic taxa, such as Actinobacteria, Chloroflexi and Thermomicrobia, and fungi, such as Agaricomycetes, Dydimellaceae, and Mortierellaceae, characterized sM, whereas others prokaryotes (Betaproteobacteria, Sphingobacteriia, Blastocatellia) and fungi (Sordariales, Lasiosphaeriaceae and Glomeraceae) characterized mM. Within- and cross-domain network were more complex in mM than sM at surface layer, and the opposite occurred at subsurface. Some prokaryotic and fungal taxa (Chloroflexi and Sordariomycetes), found abundant in hubs within soil aggregate networks, were consistently positively related to C cycling and soil structuring. We can therefore conclude that soil aggregation should be included in a more complete ‘multifunctional’ perspective of soil ecology, and that a full understanding of soil processes requires analyses emphasizing feedbacks between soil structure and soil microbiota, rather than a unidirectional approach simply addressing single members in bulk soil. As CA systems and soil structure were strongly connected to soil microbiome and function, the application of CA practices should be supported for the restoration of disturbed soils, the prevention of soil erosion and the enhancement of SOC storage. Overall, the higher diversity and differentiated soil microbial structures observed in minimum and fertilized tillage systems may offer biological buffering capacity and maintain agriculturally relevant soil functions. This study allows to improve the knowledge on taxa resistant and sensitive to modifications induced by tillage and N fertilization, according to soil aggregation size. We also demonstrate that linking taxonomy to function is a priority for explaining the ecological interactions that promote SOC accumulation in soil aggregates.

How to cite: Ercoli, L., Piazza, G., Helgason, T., and Pellegrino, E.: Microbiome structure and interconnection in soil aggregates across conservation and conventional agricultural practices allow to identify taxa related to soil functioning, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16928, https://doi.org/10.5194/egusphere-egu23-16928, 2023.

EGU23-17105 | ECS | Orals | SSS5.3

Evidence for the diagenetic formation of fused aromatic ring structures in an organic soil 

Jeewan Gamage, James Longstaffe, Adam Gillespie, Andy Lo, Sameer Al-Abdul-Wahid, and Paul Voroney

Understanding the molecular make-up of recalcitrant organic matter (rSOM) is important to postulate the capability of soil organic matter (SOM) to sequester carbon and mitigate climate change. Humic acid (HA) extracted from the river bed sediment (RS) from the West Holland river was analyzed, aiming to characterize and quantify the fused ring aromatic structures (FRA) portion. FARs can be formed through condensation and polymerization reactions and act as an important skeletal structure of the rSOM which has a mean residence time >1000 years. We conducted a series of nuclear magnetic resonance (NMR) experiments, 13C Direct Polarization Magic Angle Spinning (DP-MAS) NMR spectroscopy, and Dipolar dephased (dd) DPMAS NMR, chemical shift anisotropy (CSA) cross-polarization (CP) total sideband suppression (TOSS) NMR experiment and a dd-CSA filtered CPTOSS to accurately quantify the proportion of FRAs in the sediment HA sample. We compared the proportions of the functional groups of the RS with the surface (0-20 cm, TS) and deep (>90 cm, CS) soil HAs of the nearby Holland Marsh, Muck Crops Research Station to understand the linkages and the transformations of SOM happened while transportation (wind erosion and horizontal seepage) to the muck river sediment. We found that 90% of the aromatic C in the RS is non-protonated, and 32% of the aliphatic region was non-protonated. The DPMAS spectral comparison between RS, TS and CS clearly showed that RS contains characteristic peaks of both TS and CS. Moreover, the proportion of non-protonated aliphatics in RS (32%) is high compared to TS (18%) and CS (29%). Our results indicate that in muck river sediment soil HA, non-protonated aliphatics (CRAM-like structures) contribute to the rSOM more than FRAs, while in TS and CS, FRAs' contribution is higher than the non-protonated aliphatics. Collectively our results show the link between terrestrial organic matter transportation to the river sediment and the transformation that occur in the rSOM fraction in the river sediment SOM. This new knowledge allows us to understand the structural changes that happen in the sequestered carbon in different soil environments.

How to cite: Gamage, J., Longstaffe, J., Gillespie, A., Lo, A., Al-Abdul-Wahid, S., and Voroney, P.: Evidence for the diagenetic formation of fused aromatic ring structures in an organic soil, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17105, https://doi.org/10.5194/egusphere-egu23-17105, 2023.

EGU23-1101 | Orals | SSS5.5

Soil management effects on soil organic matter properties and carbon sequestration (SOMPACS) 

Jerzy Weber, Peter Leinweber, Yakov Kuzyakov, Edyta Hewelke, Magdalena Frąc, Michael Hayes, Vaclovas Boguzas, Lilla Mielnik, James J. Leahy, Urszula Norton, Andy Gregory, Maria Jerzykiewicz, Riccardo Spaccini, Wojciech Stępień, and Vincenzo Di Meo

Purpose

SOMPACS is a project recommended by EJP SOIL for funding under the 1st External Call "Towards Healthy, Resilient and Sustainable Agricultural Soils". The purpose of SOMPACS is to disclose management practices enriching soils with the organic matter pools that are most resistant to microbial decomposition. The project started in 2022 and will be implemented by a consortium of 12 research institutions from Poland, Germany, Ireland, Lithuania, UK, Italy and the USA until 2025.

Methods

Soil samples from eight long-term field experiments with different soil management and cultivation systems (conventional tillage vs. no-tillage; mineral vs. organic fertilization; management with and without catch crop; arable land vs. grassland; and cultivated vs. non-cultivated soils) will be investigated. Field experiments will include trials of increasing duration: 22-year (Lithuania); 26-year (Italy); 30-year (Poland, Ireland); 46-year (Poland); 54-year (Lithuania); 100-year (Poland), and 178-year Broadbalk experiment (UK). Experiments will also be carried out in production fields, where additives that stimulate root growth and provide very stable C (commercial humic products, biochar, and biogas digestate) will be applied. The effects of these additives on the content and properties of SOM will be investigated also in experimental plots accompanied by the incubation studies on the microbial decomposition of SOM and these additives. In parallel with soil sampling, plant productivity will be measured in all field experiments. Basic soil properties will be supplemented by the following investigations based on state-of-the-art approaches: SOM composition and stability by Py-GC-MS; aggregate size classes and C pools of increasing physicochemical protection; analysis of δ13C and δ15N of the separated SOM pools; microbiological properties (community-level physiological profiling, selected functional genes involved in C and N cycles, microbiome and mycobiome analyzes by next-generation sequencing, genetic diversity using terminal restriction fragment length polymorphism);  enzymatic activity; soil water retention and soil water repellency; mineral composition of clay fraction; soil structure stability. The most resistant SOM pool (humin) will be isolated by different methods (isolation vs. extraction) and examined for chemical composition and structure, using spectrometric and spectroscopic techniques (mass spectrometry, NMR, FTIR, EPR, UV-Vis-NIR, fluorescence). The C stocks in the soil profile will be evaluated and the extractable C in cold water will be determined to assess the potential leaching and microbial availability of C. Additionally, CO2 emissions from the soil of chosen experiments will be measured directly under field conditions.

Results

In the first stage of the research, soil samples were collected from a depth up to 100 cm and the humin fraction from surface horizons was isolated for spectroscopic studies. Meantime, the impact of various types of cultivation on the yield was determined. 

Conclusions

A closer understanding of the persistence of SOC in top- and subsoil, as well as identifying management practices that contribute to minimizing greenhouse gas emissions, will show the possibilities of increasing the stable SOM pools, thus improving the potential of C sequestration. Understanding the impact of soil management on sustainable agricultural production and the environment, and in particular on climate change mitigation, should be widely promoted and put into practice.

Project partly financed by NBCR (project EJPSOIL/I/78/SOMPACS/2022).

How to cite: Weber, J., Leinweber, P., Kuzyakov, Y., Hewelke, E., Frąc, M., Hayes, M., Boguzas, V., Mielnik, L., Leahy, J. J., Norton, U., Gregory, A., Jerzykiewicz, M., Spaccini, R., Stępień, W., and Di Meo, V.: Soil management effects on soil organic matter properties and carbon sequestration (SOMPACS), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1101, https://doi.org/10.5194/egusphere-egu23-1101, 2023.

In June of 2009, a long-term field experiment was conducted in the Shang-zhuang Experimental Station of China Agricultural University (CAU) at Haidian District, Beijing (N 40° 08′ 21″, E116°10′ 52″). The soil is calcareous fluvisol and the field located on an alluvial plain at an altitude of 51 m and a shallow groundwater level of 1-1.5 m. The region has a typical continental monsoon climate with an annual average air temperature of 11.6 °C and an annual average precipitation of 400 mm. The typical cropping system is winter wheat (from October each year to June of the following year) and summer maize (from June to September each year).

There are 6 treatments in the experiment: chemical fertilization with returned-straws both of wheat and maize was as experiment control (CK, or B0); 30, 60, and 90 t/ha Biochar were applied on the base of CK, coding as B30, B60, and B90; meanwhile, returning straw of wheat and maize but no chemical fertilizer (WM) and only wheat straw returning (W) were also as a treatment. After application of Biochar in June of 2009, all other agronomic practices were same as local real production way.

Although the field experiment is going on, we have got important conclusions till now, that are, (1) About 40% biochar lost from the 0-20 cm soil layer during the first 5 years after Biochar application; (2) No more than 25% biochar located in the aggregates >53 um in the 5th year after Biochar application; (3) Biochar decreased the turnover of C in the returned-straw to SOC by 11% to 31% during the first 5 years after Biochar application, and the main decrease occurred from the wheat straw; (4) Biochar decreased soil labile organic carbon pool about 50%; (5) Priming effect caused by Biochar was positive during the first 3 years but negative during the 3 to 5 years after Biochar application; (6) Biochar decreased wheat-straw-derived SOC in larger aggregates, but accumulated more in smaller aggregates; (7) Biochar increased soil pedogenic carbonate content in the 0-20 cm soil layer during the 8 years after Biochar application; (8) Biochar amendment significantly increased subsoil pH (0.3−0.5 units) during the 10 years after biochar application; (9) The transported Biochar in subsoil acted as nuclei to precipitate pedogenic carbonate; (10) Biochar amendment enhanced soil inorganic carbon pool by up to 80% in the 2m soil profile. All these results have been published on international journals such as Science of the Total Environment, Soil Tillage Research, CATENA, Journal of Soils and Sediments, Journal of Integrative Agriculture, Agricultural Ecosystems & Environment, Soil Use Management, and Environmental Science & Technology.

How to cite: Li, G.: Long-term field experiment for exploring effects of Biochar on soil processes in winter wheat-summer maize cropping system in Northern China, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2157, https://doi.org/10.5194/egusphere-egu23-2157, 2023.

EGU23-2191 | ECS | Orals | SSS5.5

Microbial growth kinetics under deeply- vs. shallow-rooted plants with soil depth profiles 

Kyungjin Min, Eric Slessarev, Megan Kan, Jennifer Pett-Ridge, Karis McFarlane, Erik Oerter, and Erin Nuccio

Climate-smart land management practices that replace shallow-rooted annual crop systems with deeply-rooted perennial plants can contribute to soil carbon sequestration. However, deep soil carbon accrual may be influenced by active microbial biomass and their capacity to assimilate fresh carbon at depth. Incorporating active microbial biomass, dormancy, and growth in microbially-explicit models can improve our ability to predict soil’s capacity to store carbon. But, so far, the microbial parameters that are needed for such modeling are poorly constrained, especially in deep soil layers. Here, we used a lab incubation experiment and growth kinetics model to estimate how microbial parameters vary along 240 cm of soil depth in profiles under shallow- (soy) and deeply-rooted (switchgrass) plants 11 years after plant cover conversion. We also assessed resource origin and availability (total organic carbon, 14C, extractable organic carbon, specific UV absorbance of K2SO4 extractable organic C, total nitrogen, total dissolved nitrogen) along the soil profiles to examine associations between soil chemical and biological parameters. Even though root biomass was greater and rooting depth was deeper under switchgrass than soy, resource availability and microbial growth parameters were generally similar between vegetation types. Instead, depth significantly influenced soil chemical and biological parameters. For example, resource availability and total and relative active microbial biomass decreased with soil depth. Decreases in the relative active microbial biomass coincided with increased lag time (response time to external carbon inputs) along the soil profiles. Even at a depth of 210–240 cm, microbial communities were activated to grow by added resources within a day. Maximum specific growth rate decreased to a depth of 90 cm and then remained consistent in deeper layers. Our findings show that >10 years of vegetation and rooting depth changes may not be long enough to alter microbial growth parameters, and suggest that at least a portion of the microbial community in deep soils can grow rapidly in response to added resources. Our study determined microbial growth parameters that can be used in microbially-explicit models to simulate carbon dynamics in deep soil layers.

How to cite: Min, K., Slessarev, E., Kan, M., Pett-Ridge, J., McFarlane, K., Oerter, E., and Nuccio, E.: Microbial growth kinetics under deeply- vs. shallow-rooted plants with soil depth profiles, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2191, https://doi.org/10.5194/egusphere-egu23-2191, 2023.

EGU23-2338 | ECS | Posters on site | SSS5.5

Evaluating the Impact of Blanket Peatland Restoration on Carbon Dynamics using 3D X-ray Micro-Computed Tomography 

Jack Brennand, Simon Carr, and Elizabeth Evans

Peatlands are the second largest global store of carbon and represent the most efficient terrestrial carbon store on the planet. ~13% of the world’s blanket peatlands are located in the UK, and they play a potentially crucial role in regulating climate. It is estimated that they store ~3.12 billion tonnes and sequester ~5.5 million tonnes of carbon per year, equivalent to ~1% of the UK’s total annual greenhouse gas emissions. However, unsustainable anthropogenic exploitation of blanket peatlands has resulted in ~90% of the known extent in the UK categorised as being in poor condition under the Joint Nature Conservation Committee standards. This is a consequence of these peatlands experiencing cutting, overgrazing, burning, drainage, and erosion. Due to these anthropogenic disturbances, UK blanket peatlands are suggested to emit ~10 million tonnes of carbon per year, representative of ~2% of the UK’s total annual greenhouse gas emissions. In response, the UK Government has incorporated peatlands in national level policy through the setting of restoration targets under climate change commitments. However, restoration targets are not being met and there are no ‘hard’ policies for blanket peatland restoration specifically. This is partly due to a lack of primary research into the effectiveness of peatland restoration.

This study explores the interactions between peat structure and peat function, which is indicative of carbon sequestration and storage (carbon dynamics), in restored blanket peatlands under different treatments and timescales in Cumbria, England. 3D X-ray Micro-Computed Tomography (µCT) is applied to peat core samples from natural, degraded, and restored blanket peatlands to visualise and quantify the internal structure of peat soils at a 0.51µm resolution. Structures include; 1) air filled and water filled pore networks; 2) air filled and water filled root networks; 3) peat matrix density; and 4) other organic matter developments which regulate the carbon dynamic function of peat soils. For the first time, this study will identify and evaluate the impact of blanket peatland restoration on peat structure and function. The investigation is also reinforced with bulk chemical and field monitoring datasets. These are integrated with the µCT outputs to understand the response of carbon dioxide and methane dynamics to blanket peatland restoration.

How to cite: Brennand, J., Carr, S., and Evans, E.: Evaluating the Impact of Blanket Peatland Restoration on Carbon Dynamics using 3D X-ray Micro-Computed Tomography, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2338, https://doi.org/10.5194/egusphere-egu23-2338, 2023.

EGU23-2591 | Orals | SSS5.5

Data science approaches for soil carbon mapping – a call for greater transparency 

Victoria Janes-Bassett, Richard Bassett, Jordan Phillipson, Ross Towe, Peter Henrys, and Gordon Blair

Soils are the largest terrestrial store of carbon, storing more carbon than the atmosphere and the biosphere combined. Soil carbon plays a key role in the delivery of a wide range of ecosystem services including climate regulation, food production, water quality and regulation and as such is often used as a proxy for ‘soil health’. International initiatives such as ‘Carbon 4 per mille’ highlight the potential for carbon sequestration in soils as a mechanism for climate mitigation, and the UK’s NetZero target depends on significant land-based carbon sequestration. Therefore, a need exists to quantify present-day soil carbon stocks at both regional and national scales to guide policy decisions and provide a baseline to enable estimates of carbon sequestration potential. 

To meet this need Digital Soil Maps (DSMs) have gained significant provenance, providing high-resolution maps through spatial extrapolation of observed data to regional, national and global scales. These maps are created by applying data-science methods to observational point data and associated covariates to create a predictive model. The model is used to extrapolate the prediction over the area for which covariate information is available. The predictive models often indicate impressively high levels of accuracy based on test/validation data. However, due to differences in both the range of data, methods and covariates used to drive predictive models, multiple DSMs created for the same areas are unlikely to be identical, which is indicative of the uncertainty associated with these mapped products. Much like with process-based models, there is a need to understand which data-science methodology is most suitable for a given research question and provide clarity on the magnitude of uncertainty associated with predictions. 

In this study, we quantify uncertainty in DSMs as a result of methodological choice; we apply several approaches (Random forest, Gaussian Process, Generalised Additive Model, Neural Network and Linear Regression) to create multiple predictive models of SOC concentration across the UK. By allowing the models to select from identical input data we provide a fair comparison of each approach through isolating uncertainty in DSMs as a result of methodological choice. In addition to accuracy assessment of each of the generated DSMs, we evaluate the suitability of each of these methods for DSM application. Most crucially, we highlight the need for caution in relation to the assumed levels of accuracy of generated DSMs when considering only standard validation statistics, and the limitations of these approaches when data has bi-modal distribution, a common feature of data that encompasses both mineral and organic soils. Whilst standard statistics evaluating the overall accuracy of the DSMs are highly significant, levels of accuracy across land use classifications vary considerably. Our study highlights the need for increased transparency in communication of uncertainty and limitations of derived map products. 

How to cite: Janes-Bassett, V., Bassett, R., Phillipson, J., Towe, R., Henrys, P., and Blair, G.: Data science approaches for soil carbon mapping – a call for greater transparency, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2591, https://doi.org/10.5194/egusphere-egu23-2591, 2023.

EGU23-2817 | ECS | Orals | SSS5.5

The role of zero-tillage in mitigating climate change in tropical soils 

Hannah Cooper, Murray Lark, Sofie Sjogersten, and Sacha Mooney

Soils are a significant store of organic carbon, globally storing an estimated 1550 Gt C to a depth of 1 metre. They are also substantial sources of greenhouse gas (GHG) emissions, contributing one-fifth of global CO2 emissions, one-third of CH4 emissions and two-thirds of N2O emissions. Soil carbon in agricultural lands can represent a net sink or source of CO2 depending on microclimate, cropping history and land management. Zero-tillage is an increasingly popular strategy to minimise soil erosion, increase biological activity and promote soil health. However, the extent to which zero-tillage reduces GHG emissions whilst increasing soil carbon, compared to other management strategies, is extensively debated, and represents a crucial knowledge gap in the context of climate change mitigation. Contrasting tillage strategies not only affect the stability and formation of soil aggregates but also modify the concentration and thermostability of soil organic matter (SOC) associated within them. Understanding the thermostability and carbon retention ability of aggregates under different tillage systems is essential to ascertain potential terrestrial carbon storage and greenhouse gas release.

 

Across Brazil, zero-tillage accounts for c. 45% of agricultural management, thereby making it a critical agricultural management practice throughout South America. This has been a popular management strategy since the 1940s and provides long-term field sites for which to understand and elucidate the key mechanisms which govern carbon retention/mineralization across different tillage managements. We measured GHG release and characterized the concentration and thermostability of SOC within various aggregate size classes under both zero and conventional tillage using Rock-Eval pyrolysis. The geometry of the pore systems was quantified by X-ray Computed Tomography and used to link soil structural characteristics to organic carbon preservation, thermostability and GHG release. Soil samples were collected from experimental fields across Brazil, which had been under zero-tillage for as little as one year up to 31 years, and from adjacent fields under conventional tillage.

 

Soils under zero-tillage had significantly increased pore connectivity whilst simultaneously decreasing interaggregate porosity, providing a potential physical mechanism for protection of SOC in the 0–20-cm soil layer. Changes in the soil physical characteristics associated with the adoption of zero-tillage resulted in improved aggregate formation compared to conventionally tilled soils, especially when implemented for at least 15 years. In addition, we identified a chemical change in composition of organic carbon to a more recalcitrant fraction following conversion to zero-tillage, suggesting aggregates were accumulating rather than mineralizing SOC. This study also revealed that, when combining all three GHG fluxes, potential global warming potential from zero-tilled soils was 50% smaller than that of conventionally tilled soils. These data reveal profound effects of different tillage systems upon soil structural modification, with important implications for the potential of zero-tillage to simultaneously increase carbon sequestration and decrease GHG release compared to conventional tillage, contributing to mitigating against climate change in these soils.

How to cite: Cooper, H., Lark, M., Sjogersten, S., and Mooney, S.: The role of zero-tillage in mitigating climate change in tropical soils, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2817, https://doi.org/10.5194/egusphere-egu23-2817, 2023.

EGU23-3089 | Posters on site | SSS5.5

Long-term SOC stabilization in sandy subsoils – evidence from historical tillage experiments 

Michael Sommer, Marisa Gerriets, Dymphie Burger, Sara Bauke, and Wulf Amelung

Large SOC sequestration rates can be achieved by admixing C undersaturated subsoil into topsoil (e.g. by deep tillage), hence creating a strong disequilibrium in the C cycle of the local soil-plant-microbiome system. The magnitude of C sequestration (sum of SOC changes in top- and subsoil) strongly depends on the fate of SOC translocated into the subsoil. Here we present evidence for a strong preservation of subsoil SOC even after 40-60 years by re-analyses of historical field trials on sandy soils (Albic Luvisols, Arenic, Neocambic) in E Germany. Compared to Ap horizons (retain samples),  which were translocated into subsoil decades ago, 50-70% of former SOC is still detectable after 40-60years. From one field experiment (V210) a non-linear decline of SOC contents can be concluded (levelling off after 20y).

How to cite: Sommer, M., Gerriets, M., Burger, D., Bauke, S., and Amelung, W.: Long-term SOC stabilization in sandy subsoils – evidence from historical tillage experiments, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3089, https://doi.org/10.5194/egusphere-egu23-3089, 2023.

The combination of biochar and nitrogen (N) addition has been proposed as a potential strategy to mitigate climate change by sequestering carbon (C), while simultaneously boosting crop yields. However, our current knowledge about how biochar and N addition alter mineralization of native soil organic C, which is referred to priming effects (PEs), is largely limited. To address these uncertainties, three C3 biochar (pyrolyzing rice straw at 300, 550, and 800 ℃) and its combination with N fertilizer (urea) were incubated in a C4-derived soils at 25 ℃ in the laboratory. Our results showed that all these 3 types of biochar with different addition rate caused positive priming of native soil organic C decomposition (up to +58.4%), but negative or no priming occurred in biochar bound N treatments. The maximum negative PEs (-14.5%) were observed in 300 ℃ biochar with 1% addition rate bound N (B1300N) treatment. We find a negative correlation between the priming intensity and soil inorganic N content across all treatments. Furthermore, the biochar-induced PEs regulated by microbial biomass, fungi/bacteria ratio, and microbial metabolic efficiency. These findings indicated that eligible biochar used for blending traditional mineral fertilizer has a larger climate-change mitigation potential than biochar and fertilizer alone, while sustain relatively high crop yields.

How to cite: He, Y. and Zhou, X.: Nitrogen input alleviates the priming effect of biochar addition on soil organic carbon decomposition, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4092, https://doi.org/10.5194/egusphere-egu23-4092, 2023.

EGU23-4814 | ECS | Posters on site | SSS5.5

In situ 13C isotope labelling of maize to determine root carbon inputs to the soil. 

Celia Fernández Balado, Elisabeth Ziss, Ferdinand Hartmann, and Rebecca Hood-Nowotny

Soil organic carbon (SOC) depletion mainly affects croplands, and it reduces the function of soil to control erosion, to hold water and to store carbon. Hence, arable production needs adaptation of restorative practices to increase C sequestration. Roots are key for sustainable agriculture because they are the main precursors of SOC. Increased and deeper roots are a viable option to maximize carbon input to the soil to enhance SOC. However, there is a lack of data on the extent and distribution of roots for different crop types under different management conditions. This study aimed to quantify root carbon inputs and sequestration potential of maize as well as to determine root biomass and architecture under different organic amendment applications. Maize was labelled with 13C-CO2 in the field at the beginning of the growing period. Leaf, root, and soil subsamples from labelled and unlabelled plants were taken during the three weeks after labelling. The carbon distribution and turnover in the investigated pools was assessed by analysing 13C by Elemental Analyzer Isotope Ratio Mass Spectrometer (EA-IRMS). Furthermore, to test the effect of the organic amendments on root growth, maize was grown in an adjacent field with identical conditions with the following treatments: (i) control, (ii) biochar (iii) compost and (iv) NPK. At the end of the growing period, roots were excavated to 30 cm depth and prepared for biomass and root architecture determination. The data collected will allow us to determine carbon distribution and turnover in the investigated pools and assess total C inputs to the soil. Moreover, it will allow us to assess whether the management practices investigated can be used to enhance root C input.

How to cite: Fernández Balado, C., Ziss, E., Hartmann, F., and Hood-Nowotny, R.: In situ 13C isotope labelling of maize to determine root carbon inputs to the soil., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4814, https://doi.org/10.5194/egusphere-egu23-4814, 2023.

EGU23-5647 | Orals | SSS5.5

Additions of ochre to soil increase the retention of organic carbon 

Mark E Hodson, Mahmuda Islam, Matty Metcalf, and Amy Wright

Fe oxyhydroxides are known to adsorb organic carbon in soil, protecting it from degradation. In this presentation we will report the results of experiments in which we added waste ochre (Fe oxy-hydroxide) precipitated by waters draining former UK coal mines to soils and observed decreases in carbon lability and thus increased carbon storage.

 

In batch experiments in which ochre was added to soil at rates of 5 wt % and 10 wt % by mass and shaken in 20 mL 0.01 M CaCl2, organic carbon release into solution was significantly reduced suggesting that the ochre had adsorbed organic carbon. In an initial set of plant growth experiments soil was amended with 5 wt% ochre and wheat plants grown for 6 weeks. The concentration of organic carbon leached from the soil over the course of the experiment and the hot water extractable organic carbon at the end of the experiment were significantly reduced by c. 43 % and 16 % respectively indicating a reduction in carbon lability. However, plant growth was reduced by c. 50 % by the ochre amendments. As Olsen P was reduced by the ochre amendments we ascribe this growth reduction to reduced P availability due to adsorption of P to the ochres. In a follow up set of experiments we added both ochre and KH2PO4 to soils. The KH2PO4 was added at a rate equivalent to levels of recommended P fertiliser application in the UK. In this second plant experiment, there was no difference in plant biomass between the study control and the ochre-treated soils and carbon lability was still significantly reduced by the ochre treatments. In addition to this the ochre amended soils leached less phosphate over the course of the experiment.

 

These results suggest that Fe oxide amendments to soil may be a practical way of changing soil chemistry in order to increase the amount of carbon retained in soils but that care must be taken to ensure that phosphorus availability is not negatively affected.

 

However, rough calculations indicate that the global supply of Fe-rich waste may be insufficient for Fe-oxide waste amendments to generate significant increases in soil carbon at a global scale. So addition of Fe-oxide wastes may represent a local means of waste-generating industries to offset their carbon footprint.

How to cite: Hodson, M. E., Islam, M., Metcalf, M., and Wright, A.: Additions of ochre to soil increase the retention of organic carbon, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5647, https://doi.org/10.5194/egusphere-egu23-5647, 2023.

EGU23-5814 | ECS | Posters on site | SSS5.5

Soil carbon storage as affected by the conversion from croplands to pastures with holistic grazing in Eastern Denmark 

Klara Sørensen, Joanne A. O’Keeffe, Kari Bækgaard Eriksson, and Carsten W. Müller

Agricultural management is strongly affecting soil organic carbon (SOC) stocks and cycling in half the world’s habitable land areas. Regular cropping with annual crops is known to considerably reduce soil carbon stocks, with detrimental effects to soils’ fertility and heightening atmospheric greenhouse gas concentrations. Compared to croplands, grasslands and pastures generally store more SOC. Thus, the conversion of croplands into pastures and grassland can be beneficial for soil carbon storage. The objective of the present study was to elucidate how the conversion of a cropland into holistically grazed pastures affect SOC storage. To test differences in soil OC we used a space for time approach and sampled a chronosequence consisting of a 4-year-old pasture, 10-year-old pasture and a nearby crop-field near Ringsted, Denmark. Mean annual temperature is 8.9°C and annual precipitation 695 mm, all three sites classified as a sandy loam according to Danish soil texture maps. Sampling was done in late September and early October, where 10 soil cores to 40 cm depth were taken from each field and split into samples of 0-10, 10-25 and 25-40 cm. SOC, total N, pH and bulk density (BD) was determined for each sample. SOC concentrations and stocks were calculated by equivalent soil mass approach, and comparisons of SOC and BD between managements done through linear mixed modelling, to account for spatial autocorrelation between samples from one soil core. Results show that both pastures have significantly higher SOC concentrations and lower bulk densities than the crop field. The 10-year-old pasture showed slightly higher SOC concentrations and stocks in the top 10 cm, but this difference was not statistically significant. No other significant differences were found between the two pastures. This suggests that SOC and BD changes happen rapidly after conversion from croplands to pastures, and a steady low build up of additional soil OC occurs after a certain threshold of SOC stocks is reached. However, as we used a space for time approach, one can not fully rule out differences in historic land-use and thus certain similarities between the pastures before the conversion compared to the sampled cropland. 

How to cite: Sørensen, K., A. O’Keeffe, J., Bækgaard Eriksson, K., and W. Müller, C.: Soil carbon storage as affected by the conversion from croplands to pastures with holistic grazing in Eastern Denmark, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5814, https://doi.org/10.5194/egusphere-egu23-5814, 2023.

EGU23-7401 | Orals | SSS5.5

Impacts on surface and sub soil physical properties under minimum tillage through long-term compost application 

Kenneth Loades, Anna Barclay, David Boldrin, Sandra Caul, Madeline Giles, and Mark Hanlon

Background: The application of composts to agricultural soil is a well-established practice with evidence showing multiple benefits within the field and beyond through changes in a number of soil functions. With soil health and function becoming increasingly important it is critical to understand the impact of soil management on function and changes in soil carbon, both within the root growth zone and, more importantly, within soil below the plough pan, an area of increasing interest.

Methods: A long-term compost application trial was established in 2004 under continuous spring barley with 3 differing compost application rates and a unamended control treatment. Following establishment in 2004 all treatments, except the control, received 50 t ha-1 of municipal green compost, no amendments in 2005, low (35 t ha-1), medium (100 t ha-1), and high (200 t ha-1), applications in 2006 and 2007 before continuous 35 t ha-1 annual applications from 2008 to 2022. Plot structure is a randomised block design with soil being a sandy silt loam cultivated under minimum tillage practices. Intact soil cores were collected from both surface soils (~20mm) and subsoils (~300mm) for each plot in spring 2022 prior to compost application, cultivation, and sowing. Full water release data was collected including characterisation of the least limiting water range (LLWR), the available water beyond which mechanical impedance restricts root elongation (2.0 MPa). Additionally, soil resilience tests were performed to simulate trafficking with impacts on soil bulk density quantified and data on wet aggregate stability, visual evaluation of soil structure, and hydraulic conductivity were also collected.

Results: Within surface soils, medium and high compost application rates increased hydraulic conductivity when compared to control plots, the low compost application rate decreased hydraulic conductivity when compared to unamended plots. Surprisingly, within subsoil, compost application was found to significantly impact hydraulic conductivity (P<0.04) with hydraulic conductivity shown to be higher within the medium rate compost application treatment. A significant difference in water stable aggregates (WSA) within surface soils was observed between treatments (P<0.01) and a significant difference in soil bulk density (BD) between treatments (P<0.01) with BD decreasing with increasing compost levels. No significant differences in sub soil bulk density were observed between treatments (P=0.131) however WSA was found to be significantly different in sub soils between treatments (P<0.01). Data on carbon, soil water release characteristics, and nutrient status will also be presented highlighting the long-term benefits of compost application.

Conclusions: Results show that the surface application of compost under minimum tillage practice and the production of continuous spring barley can influence subsoil functions with wider ecosystem benefits.

How to cite: Loades, K., Barclay, A., Boldrin, D., Caul, S., Giles, M., and Hanlon, M.: Impacts on surface and sub soil physical properties under minimum tillage through long-term compost application, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7401, https://doi.org/10.5194/egusphere-egu23-7401, 2023.

EGU23-8248 | ECS | Orals | SSS5.5

Adjustments of the Rock-Eval® thermal analysis for Soil Organic and Inorganic Carbon (SOC and SIC) quantifications 

Joséphine Hazera, David Sebag, Isabelle Kowalewski, Herman Ravelojaona, Eric Verrecchia, and Tiphaine Chevallier

Quantifying Soil Organic and Inorganic Carbon (SOC & SIC) separately in carbonate soils involves successive pretreatments and/or measurements to separate the two carbon forms. The Rock-Eval® (RE) thermal analysis has been developed in the 70’s by IFPEN to study oil bearing rocks with a ramped heating pyrolysis and oxidation. The RE has been increasingly used over the past 20 years to quantify and characterize SOC without pretreatments and with a single analysis in any kind of soils. To improve the SOC and SIC quantifications by RE, Disnar & al. (2003) and Sebag & al. (2022a; 2022b) suggested statistical corrections of the TOC and MinC standard parameters, which are SOC and SIC content estimators respectively. However, few applications have focused on SIC quantification and no adjustments of the RE standard analysis cycle have been investigated. This study aims at adjusting the RE standard analysis protocol to quantify SOC and SIC. For this, a panel of carbonate soils with a wide range of SOC and SIC contents was analyzed by RE. The SOC and SIC quantifications by RE were compared to those obtained by elemental analysis (EA, standard method to quantify soil carbon). A too high SIC amount in the RE crucible (> 4 mg) led to an underestimation of the SIC content, even after correcting the MinC parameter. The higher the SIC amount in the RE crucible, the more the SIC content was underestimated. The standard analysis cycle was too short to achieve a complete thermal decomposition of the SIC amount in the crucible leading to an underestimation of the SIC content. Thus, we propose to extend the last oxidation isotherm from 3 min to 5 or 7 min to achieve the complete SIC thermal decomposition. Moreover, the temperature limit used during the pyrolysis to distinguish the CO and CO2 emitted by organic matter thermal cracking and carbonate thermal decomposition phase is often inappropriate as the thermoresistant part of SOC and the main part of SIC decompose simultaneously after 550°C. Thus, we suggest to stop the pyrolysis phase at the onset of SIC decomposition to drag all SIC signal during the oxidation phase only. This modification of the standard analysis protocol for carbonate soils allows us to avoid some of the statistical corrections suggested by Disnar & al. (2003) and Sebag & al. (2022a; 2022b). Finally, we propose a new RE analysis protocol to simplify the calculations and improve the accuracy of SOC and SIC quantifications in carbonate soils.   

Disnar, J.R., B. Guillet, D. Keravis, C. Di-Giovanni & D. Sebag, 2003. Soil organic matter (SOM) characterization by Rock-Eval pyrolysis: scope and limitations. Organic Geochemistry 10.1016/S0146-6380(02)00239-5

Sebag, D., V. Lamoureux-Var, I. Kowalewski, D. Pillot & H. Ravelojoana, 2022a. Procédé pour la quantification et la caractérisation du carbone dans les sols. IFP Energies Nouvelles Patent No. 3121225. France.

Sebag, David; Lamoureux-Var, Violaine; Kowalewski, Isabelle; Ravelojoana, Herman; Lefrançois, Noémie, 2022b. Improved quantification of SOC and SIC in Rock-Eval® thermal analysis. SOM (8th International Symposium on Soil Organic Matter), Seoul, Korea.

How to cite: Hazera, J., Sebag, D., Kowalewski, I., Ravelojaona, H., Verrecchia, E., and Chevallier, T.: Adjustments of the Rock-Eval® thermal analysis for Soil Organic and Inorganic Carbon (SOC and SIC) quantifications, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8248, https://doi.org/10.5194/egusphere-egu23-8248, 2023.

EGU23-9063 | ECS | Orals | SSS5.5

Predicting Spatiotemporal Soil Organic Carbon Responses to Management Using EPIC-IIASA Meta-Models 

Tara Ippolito, Juraj Balkovič, Rastislav Skalsky, Christian Folberth, and Jason Neff

The management of Soil Organic Carbon (SOC) is a critical component of both nature-based solutions for climate change mitigation and global food security. Agriculture has contributed substantially to a reduction in global SOC through cultivation, thus there has been renewed focus on management practices which minimize SOC losses and increase SOC gain as pathways towards maintaining healthy soils and reducing net greenhouse gas emissions. Mechanistic models are frequently used to aid in identifying these pathways due to their scalability and cost-effectiveness. Yet, they are often computationally costly and rely on input data that are often only available at coarse spatial resolutions. Herein, we build statistical meta-models of a multifactorial crop model in order to both (a) obtain a simplified model response and (b) explore the biophysical determinants of SOC responses to management and the geospatial heterogeneity of SOC dynamics across Europe. Using 35 years of multifactorial, spatially-explicit simulation data from the gridded Environmental Policy Integrated Climate-based Gridded Agricultural Model (EPIC-IIASA GAM), we build multiple polynomial regression ensemble meta-models for unique combinations of climate and soils across Europe in order to predict SOC responses to varying management intensities. We find that our biophysically-determined meta-models are highly accurate (R² = .97) representations of the full mechanistic model and can be used in lieu of the full EPIC-IIASA GAM model for the estimation of SOC responses to cropland management. Model stratification by means of climate and soil clustering improved the meta-model’s performance compared to the full EU-scale model. In regional and local validations of the meta-model predictions, we find that the meta-model accurately predicts broad SOC dynamics while it often  underestimates  the measured SOC responses to management.  Furthermore, we find notable differences between the results from the biophysically-specific models throughout Europe, which point to spatially-distinct SOC responses to management choices such as nitrogen fertilizer application rates and residue retention that illustrate the potential for these models to be used for future management applications.While more accurate input data, calibration, and validation will l be needed to accurately predict SOC change, we demonstrate the use of our meta-models for biophysical cluster and field study scale analyses of broad SOC dynamics with basically zero fine-tuning of the models needed. This work provides a framework for simplifying large-scale agricultural models and identifies the opportunities for using these meta-models for assessing SOC responses to management at a variety of scales.

How to cite: Ippolito, T., Balkovič, J., Skalsky, R., Folberth, C., and Neff, J.: Predicting Spatiotemporal Soil Organic Carbon Responses to Management Using EPIC-IIASA Meta-Models, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9063, https://doi.org/10.5194/egusphere-egu23-9063, 2023.

EGU23-9460 | Posters virtual | SSS5.5

Integrating manure management with winter rye for sustainable intensification of no-till corn silage systems for sequestering soil carbon. 

Gabriella Burkett, Oladapo Adeyemi, Casey Kula, and Amir Sadghpour

Dairy producers often apply manure to meet the nitrogen (N) needs of a corn (Zea mays L.) crop (N-based management). This can increase soil carbon (C) but leads to overapplication of phosphorus (P) and potassium (K) which could result in increased soil test P (STP) and K (STK) over time. One stategy used in manure management to achieve N requirement of a corn crop while reducing STP and STK buildup and increasing soil C is to move from a N‐based applications of manure to a P‐based (crop‐removal) management with integrating winter cereal rye (Secale cereale L.; WCR) as double crop with corn silage and supplementing N need with inorganic fertilizer. A four-year trial was initiated in Breese, IL in 2019. The experimental design was a randomized complete block design with four replicates. Treatments were (1) corn silage with liquid UAN fertilizer; (2) P-based manure with no WRC; (3) N-based manure (liberal N credit) with no WCR; (4) N-based manure (conservative N credit) with no WCR; (5) P-based manure with WRC; (6) N-based manure (liberal N credit) with WCR; (7) N-based manure (conservative N credit) with WCR. We measured corn and rye yield, the N and P concentrations in the biomass, N and P removal and balances for the system, and soil test P. We also evaluated phospholipid fatty acids (PLFA), soil aggregate size distribution and stability, soil bulk density, soil β-glucosidase (BG) enzyme, soil organic C and labile C (POXC) over a 90 cm soil profile. Our results indicated that integrating WCR with P-based manure rates maintains STP over time. High rate of manure (conservative N credit) and WCR resulted in increased soil C which was supported by higher fungi:bacteria ratio in the soil.

How to cite: Burkett, G., Adeyemi, O., Kula, C., and Sadghpour, A.: Integrating manure management with winter rye for sustainable intensification of no-till corn silage systems for sequestering soil carbon., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9460, https://doi.org/10.5194/egusphere-egu23-9460, 2023.

EGU23-10555 | ECS | Posters virtual | SSS5.5

Impact of Agroecological Methods on Aggregate Associated Carbon Fractions 

Casey Kula, Amir Sadeghpour, and Reza Keshavarz Afshar

Using agroecological methods such as biochar amendments, manure-based fertilizer, and leaving crop residue on field is known to add organic matter and carbon to the soil which in turn can lead to soil health improvement as well as changes in soil physical properties. The previously stated methods were used as treatments as well as a combination of each in a Colorado farm field. Post analysis soil physical tests were run to evaluate the aggregate fractionation, organic matter, water-stability, permanganate oxidizable carbon, and the carbon to nitrogen ratio of each aggregate fraction as well as range of macro- (2mm-6.3mm), meso- (.25mm-2mm), and micro-aggregates (<.25mm).

How to cite: Kula, C., Sadeghpour, A., and Keshavarz Afshar, R.: Impact of Agroecological Methods on Aggregate Associated Carbon Fractions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10555, https://doi.org/10.5194/egusphere-egu23-10555, 2023.

EGU23-12579 | ECS | Orals | SSS5.5

Soil carbon-sequestration and climate mitigation – definitions and their implications 

Felix Seidel, Axel Don, Claire Chenu, Daria Seitz, Thomas Kätterer, and Jens Leifeld

Carbon sequestration has become a buzz word and generates large expectations on ecosystems to take up carbon (C) from the atmosphere. These so-called negative emissions could compensate greenhouse gas emissions and help to stabilise the global climate.  However, the term C sequestration is often misleadingly used fostering biased conclusions and exaggerated expectations. C sequestration is defined as net uptake of C from the atmosphere. Soils have a particularly large potential to take up C yet many soils currently continuously loose C. Measures to build up soil C may only reduce soil C losses (C loss mitigation) but will not result in a net C sequestration. While checking 100 recent papers we found only 5% correctly using the term C sequestration. Even worse, 13% of the papers used C sequestration equivalent to soil C stocks. Here we call for a rigorous and concise use of the term C sequestration and discuss implications of misleading applications.

How to cite: Seidel, F., Don, A., Chenu, C., Seitz, D., Kätterer, T., and Leifeld, J.: Soil carbon-sequestration and climate mitigation – definitions and their implications, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12579, https://doi.org/10.5194/egusphere-egu23-12579, 2023.

EGU23-12794 | ECS | Posters on site | SSS5.5

Physical protection of soil organic carbon in Swedish arable soils in relation to oxalate-extractable aluminum. 

Miyanda Chilipamushi, Tino Colombi, Thomas Kätterer, Claudia von Brömssen, and Mats Larsbo

Stabilizing soil organic carbon (SOC) is essential for maintaining soil structure and carbon sequestration. Soil aggregation through organic-mineral associations helps to protect SOC from microbial decomposition physically. Recent research has shown that the chemical interactions between SOC and reactive aluminum (Al) phases may be central for this aggregation in acidic soils and, hence, for the protection of SOC. However, the role of reactive Al phases in protecting SOC on a national level in Sweden is unclear. We analyzed 100 topsoil samples from the Swedish national monitoring program ‘Swedish soil and crop monitoring inventory’ taken between 2001 and 2017 in a grid covering all major agricultural areas in Sweden and determined the Al and iron content after chemical extraction using ammonium oxalate acid. We also estimated silt-sized aggregation from the differences in particle size distributions measured with a laser diffraction analyzer (Partica LA-950 V2, Horiba) between mechanically and chemically dispersed samples. Preliminary results show that SOC is indeed positively correlated with oxalate extractable Al on a national scale in Sweden, while correlations with clay and oxalate extractable iron are much weaker. The results derived from this study can help to determine the relationship between reactive Al phases, soil aggregation, structure, and the potential for carbon sequestration in Swedish arable soils.

How to cite: Chilipamushi, M., Colombi, T., Kätterer, T., von Brömssen, C., and Larsbo, M.: Physical protection of soil organic carbon in Swedish arable soils in relation to oxalate-extractable aluminum., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12794, https://doi.org/10.5194/egusphere-egu23-12794, 2023.

EGU23-13898 | Orals | SSS5.5

What limits carbon sequestration in soils? 

Axel Don, Florian Schneider, Henrike Heinemann, Daria Seitz, Neha Begill, and Christopher Poeplau

Carbon (C) sequestration in soils has been discussed as important climate mitigation option with the potential to generate negative emissions. Agriculture requires such negative emissions since some of their greenhouse gas emissions are unavoidable and require compensation to achieve net zero. Expectation of soils contribution to climate mitigation need to come down from theoretical assumptions to realistic estimates. In order to do so the limitations for soil C sequestration need to be analysed and discussed. Here we present a framework with case studies looking at limitations that are i) intrinsic due to the soils´ ability to stabilize SOC on mineral surfaces (C saturation) and the current state of high SOC stocks ii) constraints by net primary productivity and biomass availability, and iii) restrictions due to limited land area and increasing global demand for food, feed and fibre from agricultural production. For the start of this analysis we used data of the first German Agricultural Soil Inventory comprising more than 3000 sites. In total 34% of agricultural topsoils (0-10 cm depth) in Germany contain high SOC stocks with more than 4% soil organic matter. In particular soils with ground water influence and grassland land-use contain high SOC stocks, which need to be maintained first before further SOC accumulation can be achieved. C saturation was frequently discussed as reason for preventing further built up of stabilised SOC in C-rich soils. However, based on data from long-term field experiments and the national soil inventory we challenge the perception that C saturation is a limiting factor for soil C sequestration in our soils.

Biomass is required to maintain and enhance SOC. However, the quality and form of biomass influences the effectiveness for SOC formation. Roots are more important than above ground biomass. This shifts the view of C-management to below ground. Above ground biomass, such as straw, maybe harvested without harms to SOC stocks and used in industrial processes or converted to biochar. Strongly limited is the land area on which measures for SOC built-up can be implemented without compromising other ecosystem services. Avoiding leakage of greenhouse gas emissions due to measures for SOC sequestration are a major challenge. With the example of cover crops as agricultural management option we illustrate these limitations and discuss how some of the limitations for SOC sequestration could be removed.

How to cite: Don, A., Schneider, F., Heinemann, H., Seitz, D., Begill, N., and Poeplau, C.: What limits carbon sequestration in soils?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13898, https://doi.org/10.5194/egusphere-egu23-13898, 2023.

EGU23-14004 | Orals | SSS5.5

The effect of land management on soil organic carbon dynamics along the soil profile in a tropical region (southern Kenya) 

Marijn Van de Broek, Claude Müller, Bernard Vanlauwe, and Johan Six

While the importance of soil organic carbon (SOC) in the global carbon cycle is well-established, many knowledge gaps remain related to how land management affects changes in SOC stocks, and protection mechanism of SOC. This is particularly the case for the tropics, as is clear from multiple recent meta-analyses on data related to soil biogeochemistry. In addition, while current knowledge on SOC dynamics is derived from the topsoil, studies on how land management affects subsoil OC properties are scarce.

Therefore, we studied how two types of land management affect SOC characteristics down to 1 m depth in two locations in southern Kenya. At one location (Embu), the effect of nutrient management on protection mechanisms of SOC is assessed, while at the second location (Mau Forest region) we study the effect of land use changes on soil biogeochemistry. The focus of this study is on assessing how land management affects SOC protection mechanisms (using carbon fractionation) and the contribution of microbial necromass to total SOC (using amino sugar analysis). In addition, multiple other soil properties, including microbial ecology, have been quantified to improve our understanding of the effect of land management on subsoil OC dynamics.

Using our results, we aim (i) to improve understanding of these processes and (ii) to use this knowledge to improve a mechanistic model simulating soil C and N dynamics along the soil profile.

How to cite: Van de Broek, M., Müller, C., Vanlauwe, B., and Six, J.: The effect of land management on soil organic carbon dynamics along the soil profile in a tropical region (southern Kenya), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14004, https://doi.org/10.5194/egusphere-egu23-14004, 2023.

EGU23-14590 | ECS | Posters on site | SSS5.5

Priming effects decrease with quantity of cover crop residues – implications for net soil carbon sequestration 

Zhi Liang, Jim Rasmussen, Christopher Poeplau, and Lars Elsgaard

Recent meta-analyses suggest a global potential of cover crops to increase soil organic carbon (SOC), thus contributing to climate change mitigation. However, some studies also found that cover cropping did not affect or even reduced SOC, thus it is uncertain how this effect is controlled. Here we aimed at comprehensively evaluating the potential and mechanisms of carbon (C) sequestration from cover crops in a Danish long-term crop rotation field experiment (LTE) initiated in 1997. We quantified SOC to 1-m depth, and also operationally divided soil organic matter into fractions of particulate organic matter (POM) and mineral associated organic matter (MAOM) to investigate the C saturation status of soils. Moreover, we performed a mescosm study with topsoils where the fate of varying doses (0.1-1.6 mg C g-1 soil) of 14C-labeled cover crop residues (fodder radish, FR; Raphanus sativus L.) and SOC priming were traced in two texturally similar soils having the same long-term management, but different SOC contents (2.0 vs. 2.6% SOC). Our LTE results showed that cover cropping for up two decades had negligible effect on SOC contents in POM and MAOM fractions in the topsoil and in the subsoil. However, the mesocosm study showed considerable net C increases (20-25% of added) when the cover crop C input exceeded 0.3 and 0.6 mg C g-1 in soils with 2.0 and 2.6% SOC, respectively. This was due a combination of new SOC formation and priming effects shifting from positive to negative. Collectively the LTE and mesocosm study suggests that buildup of SOC stock was not essentially constrained by soil C saturation, but rather by the low productivity and C input from cover crops. Our study suggests that agricultural management practices should be adopted (e.g., species choice and sowing time) to achieve a cover crop C input that exceeds a certain threshold to ensure effective C sequestration.

How to cite: Liang, Z., Rasmussen, J., Poeplau, C., and Elsgaard, L.: Priming effects decrease with quantity of cover crop residues – implications for net soil carbon sequestration, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14590, https://doi.org/10.5194/egusphere-egu23-14590, 2023.

EGU23-14924 | ECS | Orals | SSS5.5

Influence of enhanced silicate weathering on microbial processes and soil carbon formation in agricultural soil 

Jaeeun Sohng, Iris Holzer, Heath Goertzen, Radomir Schmidt, and Kate Scow

Enhanced silicate weathering (ESW) is an innovative technique to leverage natural processes which usually operate over millions of years to potentially replenish nutrients and carbon (C) in soil. ESW involves applying pulverized silicates to increase reactive mineral surfaces which in turn may speed-up the weathering and scale to aid in global CO2 removal. However, current studies supporting ESW has been relying on theoretical estimates and short-term laboratory experiments whose results are difficult to extrapolate to the field. Also, many studies have focused on inorganic C chemistry while soil is a rich medium that mediates a multitude of chemical and biological processes, many of which are not well studied but may play an important role in controlling ESW. To address this gap, the Working Lands Innovation Center (WLIC) Project was launched in 2019 for a field scale test, and three commercial amendments (compost, biochar, and silicate powder—meta-basalt) have been applied yearly with a full factorial design in a 2.07 ha corn field at the Campbell Tract research facility located on the UC Davis campus. My project within WLIC evaluates the impact of ESW on soil surface C pools related to microbial processes and its potential synergies with traditional organic amendments. We hypothesized that co-applying organic amendments plus pulverized silicate minerals will: 1) increase microbial biomass with distinct microbial community composition; and 2) increase the formation of stable carbon pools (e.g., mineral associated organic matter) relative to only silicate applied soil. To test this, we sampled soils from all possible amendment combinations at pre-, and post-harvesting seasons in 2021 and 2022. We completed a suite of analyses to monitor temporal changes of soil chemistry, multiple C pool sizes, and microbial parameters. Here, we will examine the causal mechanisms that explain how adding extra C with silicates may change microbial environments and carbon pool dynamics over a two-year period. Our findings will provide critical information whether natural soil processes, such as rock weathering and soil organic C stabilization, can be engineered (and accelerated) for management purposes at agricultural field scale.

How to cite: Sohng, J., Holzer, I., Goertzen, H., Schmidt, R., and Scow, K.: Influence of enhanced silicate weathering on microbial processes and soil carbon formation in agricultural soil, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14924, https://doi.org/10.5194/egusphere-egu23-14924, 2023.

EGU23-15783 | ECS | Orals | SSS5.5

Alteration of the Black Carbon pool shortly after a fire under dry conditions at the boreal southern border 

Oliver Donnerhack, Patrick Liebmann, Philipp Maurischat, and Georg Guggenberger

Fires belong to the most intensive disturbances in ecosystems, but do have different effects on the soil depending on their intensity and fuel materials. Taiga ecosystems contain significant reserves of potentially fire-prone materials, and as temperatures rise in the circumpolar region and precipitation patterns change, an increase in the frequency and intensity of fires is observed. In these fires, incomplete combustion processes result in the formation of black carbon (BC), which is known as a long-term carbon sink due to its chemical properties. As the majority of forest fires are ground fires burning at a rather low intensity in terms of duration and temperature, it is discussed that the BC species formed under these circumstances are chemically less stable than those formed at high temperatures and should therefore only be considered as temporary carbon sinks.

Here we studied the effects of low intensity ground fire shortly after the event and tracked changes in BC within the first four years after the fire event at the southern edge of the boreal forest. We analysed a fire transect running through the two main forest types of this region, focusing on the BC species that we could quantify using the BPCA method. Our results indicate a decline in BC after the fire within the four years of observations, which mainly mainly occurred for the low condensed BPCAs. This finding is independent of the forest typ. Since the precipitation within the experimental period was also negligible and only occurred in very small amounts, we exclude leaching as well as a possible significant aeolian losses, since the trees remained unaffected by the fire and covered the soil against strong wind. We therefore deduce that in situ degradation of the BC must have occurred.
Concluding, the general assumption that BC is a stable, long-term carbon sink needs to be questioned more critically. Together with other studies, our results show a quite fast decrease in the concentration of low-condensed BC species in soil over time, indicating a potential for degradation.

How to cite: Donnerhack, O., Liebmann, P., Maurischat, P., and Guggenberger, G.: Alteration of the Black Carbon pool shortly after a fire under dry conditions at the boreal southern border, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15783, https://doi.org/10.5194/egusphere-egu23-15783, 2023.

Soils play a major role in mitigating climate change, as they sequester vast stocks of organic carbon and thereby buffer atmospheric CO2 concentrations. Inorganic nitrogen has been shown to have varying effects on soil C, sometimes promoting soil C buildup yet enhancing C loss in other cases. This contradiction may be a function of how soil C is stored, with C in particulate organic matter (POM) being much more susceptible to microbial decomposition than C in mineral-associated organic matter (MAOM). We have compiled a global dataset of over 200 papers which used a rigorous density fractionation methodology for quantifying stocks of C in POM and MAOM. Preliminary results suggest that inorganic N addition via deposition decreases organic C storage in MAOM, while not affected POM. Further, soil C storage in both pools increased with lower pH, countering our hypothesized negative effect of acidification on microbial activity.

How to cite: Willard, S. and Waring, B.: Quantifying the global impact of nitrogen deposition on persistent and vulnerable soil C pools, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16023, https://doi.org/10.5194/egusphere-egu23-16023, 2023.

Soil organic matter consists of components that differ in their specific stabilization/decomposition dynamics, and turnovers. From a simplified viewpoint, two fractions in particular can be distinguished from one another. Particulate organic matter (POM) is predominantly unbound in the soil matrix. The POM decomposition rate is defined by its inherent chemical recalcitrance and occlusion within aggregates. Mineral-associated organic matter (MAOM) is significantly smaller and is protected from decomposition by its adsorption to mineral surfaces. MAOM-C has therefore significantly longer mean residence times in soil than POM-C. Since the soil organic carbon (SOC) stocks are determined by C input/output balances, it is important to decrease C output quantities by increasing the long-term stabilization of OC within the MAOM-C stocks. However, MAOM-C cannot be enriched indefinitely. It is limited by the amount of clay and fine silt particle surfaces it can adsorb to and to the general land-use management. We investigated the validity of a POM-C/MAOM-C ratio indicator on 25 long-term field experiments in Central Europe to evaluate the sustainability of SOC management measures. We found that the POM-C/MAOM-C ratio might be used to assess the sustainability of agricultural management in before/after management change comparisons. Accordingly, a sharply increasing ratio indicates that the change in management does not adequately affect the long-term MAOM-C storage of soil. Moreover, we found a dependence between the POM-C/MAOM-C ratio and the MAOM-C sequestration deficits in soils, where arable soils with a POM-C/MAOM-C ratio indicator > 0.35 are close to MAOM-C saturation. If these observations are repeatable on further arable soils, the POM-C to MAOM-C ratio of 0.35 could be used as a management target to avoid organic over-fertilization and N loss, especially in coarse-textured soils. Thereby, the indicator might help to optimize SOC management and sequestration on arable soils and support climate change mitigation strategies.

How to cite: Just, C., Kögel-Knabner, I., and Wiesmeier, M.: The POM-C / MAOM-C ratio as a compliance indicator for sustainable soil organic carbon management of arable soils in Central Europe, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16476, https://doi.org/10.5194/egusphere-egu23-16476, 2023.

EGU23-16807 | ECS | Posters on site | SSS5.5

Carbon storage in soil parent materials - a source, a sink, or both? 

Daniel Evans and Thomas Blattmann
 

Soils are an important component of the global carbon cycle. Ensuring and maintaining the ability of soils to sequester and store carbon is crucial for mitigating climate change. A large proportion of research to date has focused on carbon storage in the uppermost horizons of a soil profile. Meanwhile, the sequestration and storage of carbon in subsoils and underlying soil parent materials is an area that is only recently being studied. This presentation will evaluate the role of soil parent materials as long-term sinks for organic carbon, using recent empirical research across a range of ecosystems and lithologies. However, some soil parent materials could also represent important sources of petrogenic (i.e., rock-derived) organic carbon. Research currently being carried out on carbon-rich bedrock exposed by retreating glaciers in Switzerland will be used to highlight how petrogenic organic carbon, once mobilized into the soil profile during soil formation, could threaten net zero carbon targets. The presentation will conclude with a synthesis of the research gaps that require further attention by a multidisciplinary geoscience community.

How to cite: Evans, D. and Blattmann, T.: Carbon storage in soil parent materials - a source, a sink, or both?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16807, https://doi.org/10.5194/egusphere-egu23-16807, 2023.

EGU23-16809 | Orals | SSS5.5

Biochar amendment on greenhouse gases emissions and soil carbon sequestration in subtropical paddy fields: a ten-year study 

Jianlin Shen, Yanyan Li, Zongming Li, Juan Wang, and Jinshui Wu

Paddy field is one of the important sources for CH4 emissions, and can also be the carbon sink by soil carbon sequestration. In this study, a ten-year study was conducted to evaluate the long-term effects of biochar amendment on greenhouse gas emissions and soil carbon sequestration. Straw-derived biochar was applied once in 2012 at 24 and 48 t ha-1. The results showed that the annual CH4 emissions decreased by 20-50% as compared with no biochar amendment in the first four years after biochar addition. There were consistent CH4 emission reduction in the 10th year after biochar addition, with a reduction rate of 18-27%. The reduction of CH4 emission from paddy field was mainly related the improve of aeration, and the redution of the abundance ratio of methanogen/ methanotrophy. Biochar only increased N2O emissions in the first year after biochar addition due to additional nitrogen input caused by biochar addition. Biochar addition increased soil total organic content (TOC) in the first year after biochar addition, and the TOC contents showed no decrease after 10 years. Biochar addtion did not increase or decrease rice yield in a ten-year average. This indicated that biochar can be a useful measure for decreasing greenhouse gases emissions from subtropical paddy fields, and for increasing soil carbon sequestration in a long-term period. 

How to cite: Shen, J., Li, Y., Li, Z., Wang, J., and Wu, J.: Biochar amendment on greenhouse gases emissions and soil carbon sequestration in subtropical paddy fields: a ten-year study, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16809, https://doi.org/10.5194/egusphere-egu23-16809, 2023.

EGU23-16926 | Posters on site | SSS5.5

Changes in carbon stock in agricultural soils over 20 years in South Korea 

Jung-Hwan Yoon, Hyuck Soo Kim, and Jae E. Yang

In the carbon neutral era, soil carbon became more important. Soil carbon pools (2400 Gt) are about three times larger than atmospheric pools, and soil carbon sequestration can store large amounts of organic carbon. Soil carbon storage has been reported as an effective tool to mitigate climate change in various studies, including the IPCC. Among them, it is known that agricultural soil can sequester carbon every year through sustainable soil management. In this study, we investigated changes in soil carbon storage (excluding volcanic soils) using the results of the Monitoring Project on Agri-Environmental Quality in South Korea from 1999 to 2018. Land use was categorized into paddy, upland, orchards and greenhouses. The soil organic carbon content of cultivated land has increased steadily over the past two decades, with annual organic carbon increases of 0.16 g kg-1 in paddy, 0.26 g kg-1 in upland and 0.33 g kg-1 in orchard, and 0.21 g kg-1 in greenhouse. In the 2000s, the use of chemical fertilizers decreased and the amount of livestock manure compost increased, which seems to have increased soil organic carbon. As a result of calculating the total annual increase in soil organic carbon in the entire cultivated land, it was found that 770,000 tons of C were stored in the soil (0-20 cm) per year. This corresponds to about 11% (2.8 million tons CO2-eq) of the 24.7 million tons CO2-eq of Korea's agricultural and livestock greenhouse gas emissions in 2018. South Korea also presented a scenario to achieve carbon neutrality by 2050, but currently does not include a method for using carbon sequestration. Looking at changes in soil carbon over the past 20 years, we found that soil can make a significant contribution to carbon neutrality if we introduce soil management that increases soil carbon and quantify the carbon sequestration. Therefore, it is judged necessary to introduce a soil management method that can maximize the carbon sequestration of the soil.

How to cite: Yoon, J.-H., Kim, H. S., and Yang, J. E.: Changes in carbon stock in agricultural soils over 20 years in South Korea, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16926, https://doi.org/10.5194/egusphere-egu23-16926, 2023.

Purpose To meet the Paris Agreement targets the Government of the Netherlands aims to sequester 0.14 Mt C per year in clay and sandy soils from 2030 onwards through alternative management practices. Multiple international meta-analyses and modelling studies have been carried out to quantify the soil carbon sequestration potential of alternative management practices. However, the specific impact of such practices for Dutch field conditions have not yet been assessed. In this study, we quantified the potential of a broad range of alternative management practices to sequester carbon in Dutch agricultural clay and sandy soils.  MethodsAlternative management practices included altered crop rotations, non-inversion tillage, use of compost and use of animal manure for arable farming and extending pasture age, maize-grass rotation replacing continuous maize cropping, and non-inversion tillage in maize cultivation for livestock farming. Measurements were performed in existing long-term field experiments (LTE’s) comparing treatments of the alternative practices to the standard practices. For some practices like altered rotations and extending pasture age no LTE’s were available. In those cases the comparison between practices was designed by comparing field plots on farmers’ fields based on history of the field and comparable soil conditions. Soil sampling was carried out at the 0-30 cm and 30-60 cm depth layers between 2018-2020 using a standardized protocol including soil density sampling.  ResultsThe variation in carbon sequestration rates appeared to be higher on sandy soil as compared to clay soil. The most promising management practices on clay soil were compost additions (0.4 t C ha-1 year-1), extending pasture age (1.3 t C ha-1 year-1) and non-inversion tillage in maize cultivation (0.7 t C ha-1 year-1). On sandy soils maize-grass rotation significantly increased soil carbon levels (1.8 t C ha-1 year-1) together with liquid manure applications (0.6 t C ha-1 year-1).ConclusionOur study shows that the potential of alternative management practices under Dutch field conditions to sequester carbon in agricultural soil is largely determined by soil type. In addition, our results show that, based on the investigated management practices, livestock farming has more options to sequester carbon in agricultural soil than arable farming.
 

 

How to cite: Schepens, J. and Koopmans, C.: Evaluating carbon sequestration of different alternatieve management practices in the Netherlands, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16990, https://doi.org/10.5194/egusphere-egu23-16990, 2023.

EGU23-1544 | ECS | Posters on site | SSS5.11

Changes in soil carbon, nitrogen, phosphorus along two temperate slope-floodplain-creek catenas under different land use - A case study in Southeast Germany 

Kaiyu Lei, Franziska Bucka, Sigrid van Grinsven, Jörg Völkel, and Ingrid Kögel-Knabner

The impacts of land use on organic carbon (OC) and nitrogen (N) in different ecosystems have been widely studied. However, less attention has been paid to its influence on the change of total phosphorus (Pt) and its two fractions, inorganic P (Pi) and organic P (Po), along slopes. In addition, since N and P are the main factors causing the eutrophication of aquatic ecosystems, it is essential to link the terrestrial and aquatic ecosystems.

Two slope-floodplain-creek catenas were chosen in the low mountain region of the eastern Bavarian Forest. The slopes of the two catenas have been extensively managed for grassland and cropland use, respectively. The floodplain was under grassland use. They were fertilized with sludge, occasionally with farmyard manure, under the same regime. Additional carbonic magnesium lime was applied annually at the cropland. Soil profiles at the top, middle and bottom slope, as well as the floodplain area, were sampled according to their horizons and replicated with three soil cores in each catena. Liquid-nitrogen freeze-cores of the aquatic sediments were sampled to extend each catena into the below-slope creek.

We found the grassland slope had higher OC and N content in the topsoil (0-10 cm) and higher Pt and Po content in both the topsoil (0-40 cm) and subsoil (40-60 cm). The P content in the topsoil (0-40cm) of the grassland slope was dominated by Po, while the cropland slope was Pi -dominated. The OC and N stocks on the grassland slope were significantly higher than at the corresponding position on the cropland slope. Except for the lowest P stock found on the top slope of grassland, the Pt stock in topsoil (0-20 cm) was not land-use affected while the Po stock was significantly higher on the grassland slope. An accumulation of OC, N and Po in topsoil (0-20 cm) from top to bottom of the slope was observed. In the floodplain, upslope cropland use decreased the OC, N, Pt content and stocks, but reversely for Po. The upslope land use effect on OC, N and P content in the creek sediment was limited.

In conclusion, this study provides a field-based observation on the change of OC, N and P (Pt and Po) under different land use upslope from terrestrial to aquatic systems through two slope-floodplain-creek catenas.

How to cite: Lei, K., Bucka, F., van Grinsven, S., Völkel, J., and Kögel-Knabner, I.: Changes in soil carbon, nitrogen, phosphorus along two temperate slope-floodplain-creek catenas under different land use - A case study in Southeast Germany, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1544, https://doi.org/10.5194/egusphere-egu23-1544, 2023.

EGU23-2731 | ECS | Posters on site | SSS5.11

Effects of nitrogen and phosphorus inputs on the diversity of carbon-, nitrogen-, and phosphorus- mineralization microbial communities in subtropical Chinese fir plantations 

Shuang Liu, Xinyu Zhang, Huimin Wang, Junxiao Pan, Yuqian Tang, and Fusheng Chen

The regulation of N and P input on microbial communities is related to the bottom-up effects of soil resources (i.e., nutrients), and the top-down effects of predators (i.e., protists). However, it is not clear how exogenous N, P, and NP inputs effect on the bottom-up (pH, soil nutrients, and eco-stoichiometry ratio of C: N: P), and top-down (abundance and diversity of protist community) factors to estimate soil microbial community involved in C-, N-, and P- mineralization. In this study, we explored the effects of a 7-years N, P, and NP inputs on the bottom-up and top-down controls on the abundance and diversity of functional microbial communities in the subtropical Chinese fir plantations using metagenomic sequencing. The results showed that N and NP inputs decreased soil pH and soil acidifying cause a reduction in the alpha diversity of microbial function. Exacerbated soil microbial C limitation under N, P, and NP inputs was negatively correlated with the alpha diversity of metagenomic function. The alpha diversity of bacteria was negatively correlated with the ratios of soil total and available N: P, due to increasing available P content. Regarding top-down effects of protists on the abundance and diversity of microbial C-, N-, and P- mineralization community, P and NP inputs increased alpha diversity of protist, thus, selectively increased the relative abundances of Calditrichaeota involved in C-mineralization, and decreased the relative abundances of Elusimicrobia and Marinimicrobia involved in N-mineralization. Although protozoa feed on both bacteria and fungi, changes in protists under N, P, and NP inputs mainly affected bacterial diversity and abundance, with no significant changes in fungi. Overall, the present results provide important knowledge on bottom-up (pH, soil nutrients, and eco-stoichiometry ratio of C: N: P), and top-down (abundance and diversity of protist community) factors of the abundance and diversity of the microbial community involved in C, N and P mineralization in the context of elevated N and P input.

How to cite: Liu, S., Zhang, X., Wang, H., Pan, J., Tang, Y., and Chen, F.: Effects of nitrogen and phosphorus inputs on the diversity of carbon-, nitrogen-, and phosphorus- mineralization microbial communities in subtropical Chinese fir plantations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2731, https://doi.org/10.5194/egusphere-egu23-2731, 2023.

Conventional overfertilization combined with flooding irrigation is common practice in solar greenhouse vegetable production systems in Eastern China. However, how these practices may affect soil nutrient concentrations remains understudied. Here we report on a regional soil sampling study in Shouguang county, which is the major and pioneer area of greenhouse vegetable production in China. In our study, we measured soil nutrient concentrations (mineral N, Olsen-P, and available K) as well as soil physico-chemical parameters (e.g. pH, SOC) down to 3 m soil depth in 60 greenhouses differing in years since establishment (5, 10, and 20 years) and compared those to nutrient concentrations in 20 adjacent arable fields. We found that in greenhouse soils compared to soils of adjacent arable fields: (1) soil nutrients were significantly elevated in the topsoil (0-30 cm), while nutrient concentrations in the subsoil were much lower and differences between greenhouse and arable soils diminished; (2) N:P:K ratios were imbalanced towards P and K as these elements are not easily leached as N; (3) the soil pH is decreased. After about 20 years of continuous greenhouse vegetable production, the topsoil pH was lowered by 0.92 ± 0.07 units. Our study shows that overfertilization combined with flooding irrigation has serious impacts on soil chemistry and soil nutrient concentrations. The observed nutrient imbalances are dramatic and indicate that e.g. P and K fertilization may not be needed for years to come. Also the observed decline of the significant decrease in the soil pH of calcareous soil indicates, that the soil pH carbonate buffer system is at the edge to break down, with unknown consequences for soil fertility. These facts strongly suggest that unnecessary excessive fertilizer and irrigation water applications for producing vegetables in solar greenhouse systems should be stopped and replaced with more sustainable production methods, e.g. drip fertigation with reduced fertilizer application.

How to cite: Wan, L., Lv, H., Xia, L., Lin, S., and Butterbach-Bahl, K.: Overfertilization combined with flooding irrigation contributes to soil nutrient accumulation and pH decline in greenhouse vegetable production systems, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3156, https://doi.org/10.5194/egusphere-egu23-3156, 2023.

EGU23-3208 | Posters on site | SSS5.11

Soil nitrogen pool and its fractions in German apple orchards under organic vs conventional management 

Magdalena Sut-Lohmann, Mark Grimm, Martina Heinrich, Sawdha Baig, and Thomas Raab

Agriculture is a massive production with intensive practices, like large variety of agro-chemicals, heavy machinery etc., that support food security. However, recently more and more attention is given to food safety in relation to human, environment and soil health. An alternative strategy is organic agriculture that avoids the use of synthetic chemicals and maintain the sustainable food production. But organic farming cannot completely support the worlds foods demand, so adaptation is needed to reach a sustainable productivity while protecting the environment.

Soil nitrogen (N) pool consists of inorganic and organic fractions. Inorganic and a part of labile organic N is a primary nutrient source for plants and microbes. Different nitrogen fractions play various roles in soil ecosystems and can be strongly influenced by the site management. Soil nitrogen transformations are directly relatable to plant health, thus strongly influence healthy functioning of soil ecosystem. Knowledge about the soil nitrogen pools is necessary to assess the proper and sustainable fertilization approaches under various management practices. To evaluate various N fractions, fresh soil samples were sampled (20 cm depth, row and near tree) at 8 conventional and 8 organic apple farms (Germany: states of Brandenburg, Saxsony and Saxony-Anhalt), with various age, locations and management practices. Soil samples were analyzed using CNS, Kjeldhal digestion, spectrophotometer and chloroform fumigation. The aim of this study is to compare the total and labile (particulate organic, microbial biomass and water extractable organic) N fractions in soil samples considering various site management approaches, topography and climate.

 

How to cite: Sut-Lohmann, M., Grimm, M., Heinrich, M., Baig, S., and Raab, T.: Soil nitrogen pool and its fractions in German apple orchards under organic vs conventional management, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3208, https://doi.org/10.5194/egusphere-egu23-3208, 2023.

Nitrogen (N) availability is one of the critical limiting factors regulating plant growth, microbial activity, and the interactions between plants and soil microorganisms. The competition between plants and microorganisms, represented by the ratio of microbial N immobilization and plant N uptake (measured as Nim: PNU ratio), generally reflects the degree of N limitation in a terrestrial ecosystem. However, the key factors driving the pattern of Nim: PNU ratio across global ecosystems remain little understood. Here, using a global data set of 1022 observations from 184 studies, we examined the relative importance of mycorrhizal associations, N availability, climate, plant, and soil properties on the Nim: PNU ratio. Our results show that mycorrhizal fungi type (arbuscular mycorrhizal (AM) vs. ectomycorrhizal (EM) fungi) in combination with soil N availability explain the variation in the Nim: PNU across terrestrial ecosystems. In AM fungi-associated ecosystems, the relation between Nim and PNU displayed a weaker negative correlation (r =-0.06, p < 0.001), whereas there was a stronger positive correlation (r = 0.25, p < 0.001) in EM fungi-associated ecosystems. Those results indicated that the AM-associated plants display a weak interaction with soil microorganisms for N absorption, while EM-associated plants cooperate with soil microorganisms. Further, we found that the Nim: PNU ratio for both AM- and EM-associated ecosystems gradually converge at a stable value (14.7 vs. 13.5, p > 0.05) with greater N availability. Our study thus highlights that plant-microbial interaction for N absorption both equalize and stabilize at increased N supply, and both these mechanisms primarily depend on the mycorrhizal association of plants in terrestrial ecosystems.

How to cite: Du, Z. and Zhou, X.: Plant-microbial interactions for nitrogen absorption converge between arbuscular- and ectomycorrhizal-dominated ecosystems at high nitrogen availability, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4095, https://doi.org/10.5194/egusphere-egu23-4095, 2023.

EGU23-4261 | ECS | Orals | SSS5.11

Effects of spatial variations on soil nitrogen transformations in Chamaecyparis obtusa forest through in situ 15N tracing method 

Zixiao Wang, Makoto Shibata, Jinsen Zheng, Keitaro Fukushima, Jiajie Du, and Shinya Funakawa

Soil inorganic nitrogen (N), i.e., NH4+ and NO3-, are essential resources for tree growth in forest ecosystems. Input of these inorganic resources are regulated by ammonification and nitrification and output are consumed either by abiotic or biotic (soil microbes, tree fine roots) processes. To the best of our knowledge, although previous studies have discussed net uptake rates of fine roots among different soil groups or vegetation types, variations within a local scale (same soil group and vegetation) remain an enigma. Moreover, since widely-used experiment set-ups in soil N transformation studies exclude live fine roots, uptake strategy of trees and their competition for inorganic nutrients with microbes are unknown. Therefore, this study aims to clarify 1) net uptake rates of fine roots; and 2) uptake strategy of the same tree species and the ratio of microbial/plant assimilation along a hillslope.

An in situ incubation combining 15N tracing method with virtual soil cores was performed in Chamaecyparis obtusa (Japanese cypress) forests at up and down sites of a hillslope. 15N-labeled moieties (2.2 mg 15NH4NO3 g-1 soil and 0.2 mg NH415NO3g-1 soil, both are 98+ atom% 15N) were injected evenly through the cores located around the trees with five replicates. A-horizon soil was sampled after 0.25 h and 24 h. Soil and fine roots were sent for further analyses after sieving. The soil-environmental factors were determined.

Differences in the soil-environmental variables were observed at up and down slopes, including soil pH, NH4+, NO3-, total dissolved N, microbial biomass carbon (C) and N, total C and C/N ratio. Fine root biomass was higher at up slope (1.5 kg m-3) than down slope (0.8 kg m-3) while net uptake rates of fine roots in both 15NH4NO3 (11 and 20 μg 15N g-1 roots d.w. d-1) and NH415NO3 (4.7 and 8.3 μg 15N g-1 roots d.w. d-1 at up and down slope, respectively) were higher at down slope. Ammonification and nitrification rates were also higher at down slope (0.6 and 3.2 mg N kg-1 d-1 for ammonification and 0.1 and 1.1 mg N kg-1 d-1 for nitrification at up and down slope, respectively), where soil pH was higher and C/N ratio was lower. However, net uptake amount per core did not demonstrate any trend at both slopes. Such results suggest that fine roots may try to ensure the supply of nutrients to trees by increasing their biomass when less soil inorganic N can be produced. Soil pH and C/N ratio could play a key role in determining uptake strategy of trees through affecting soil N transformation rates.

In addition, the ratio of microbial/plant assimilation of N was higher at up slope for 15NH4+ and for 15NO3- to a lesser extent. Since soil moisture content was higher at down slope, such results might suggest a higher mass transfer of N nutrients induced by a higher mass flow of water. Therefore, higher N concentration could be maintained onto root surfaces at down slope, decreasing acquisition rates by microbes and increasing net uptake rates by fine roots.

 

How to cite: Wang, Z., Shibata, M., Zheng, J., Fukushima, K., Du, J., and Funakawa, S.: Effects of spatial variations on soil nitrogen transformations in Chamaecyparis obtusa forest through in situ 15N tracing method, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4261, https://doi.org/10.5194/egusphere-egu23-4261, 2023.

Dissolved organic matter (DOM), the most active functional component of soil organic matter (SOM), plays a vital role in regulating soil biogeochemical processes and accumulation and decomposition of SOM and their responses to global change. Although the quantity and fluxes of soil DOM has been inventoried across diverse spatio-temporal scales, the underlying mechanisms accounting for the variability in DOM dynamics remain unclear especially in upland ecosystems.

Mollisols is famous for its high fertility and is vital for global crop production. Northeast China is one of the three Mollisols regions in the world, contributing to 1/4 of Chinese grain production. However, a loss of SOM has occurred in this area over the past decades, both in its content and activity. Understanding the processes involved in DOM transformations is of critical importance for SOM management. Here, a gradient of SOM storage across twelve Mollisols uplands with various cultivation years in northeast China were used to understand links between DOM dynamics, microbial metabolism, and abiotic conditions. We assessed the composition, biodegradability and key biodegradable components of DOM. In addition, SOM and mineral-associated organic matter (MAOM) composition, soil enzyme activities, oxygen availability, soil texture, and iron (Fe), Fe-bound organic matter and nutrient concentrations were quantified to clarify the drivers of DOM quality.

Changes in concentrations of DOM and SOM were tightly coupled across various croplands. The proportion of biodegradable DOM increased exponentially with decreasing DOM concentration. Spectral analyses showed that larger fractions of small-molecular phenols and proteinaceous components mainly contributed to the greater biodegradability of DOM. Unexpectedly, the composition of DOM was decoupled from that of SOM or MAOM, but significantly related to enzymatic properties. Further analyses indicated that soil oxygen availability exhibited a dominant role in DOM generation. As DOM concentration declined, increased soil oxygen availability regulated DOM composition and enhanced its biodegradability mainly through three ways: 1) stimulated oxidase-catalyzed depolymerization of humic substances into small aromatic molecules; 2) promoted production of protein-like DOM components due to lower enzymatic C/N acquisition ratio; and 3) oxygen-induced oxidation of Fe(II) to Fe(III) removed complex DOM compounds with large molecular weight. Therefore, along with aggregates fragmentation during the decline of SOM in Mollisols with longer cultivation history, the increased oxygen availability improved the biodegradability of DOM and accelerated the turnover and loss of active SOM pool.

Overall, this study demonstrated the cascading effects of oxygen on soil Fe oxidation-reduction, microbial metabolism and the dynamics of DOM, which would help understand the processes of labile SOM transformations and interactions among various drivers and improve the SOM managements in upland ecosystems and the predictions of responses of soil carbon to climate change.

How to cite: Chen, Z., Li, Y., and Ding, W.: Oxygen availability regulates the persistence of soil dissolved organic matter by mediating microbial metabolism and iron oxidation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4294, https://doi.org/10.5194/egusphere-egu23-4294, 2023.

EGU23-4568 | Posters on site | SSS5.11

Soil phosphorus content determined by Mehlich 3 and modified Mehlich 3 methods 

Tonu Tonutare, Tõnis Tõnutare, Raimo Kõlli, Kadri Krebstein, and Kersti Vennik

During the last century multiple methods have been developed for the determination of the amount of plant available nutrient elements in the soil. One of the critical nutrient elements in soil is phosphorus. Most of the phosphorus exists in soil in the form of insoluble inorganic and organic compounds. Therefore the amount of plant available P is limited as soluble P. The goal in the development of methods is to find an extraction solution, which can extract the nutrients from soil in a similar amount as plant roots. Due to large variations in soil properties and plants abilities it is a very complicated task. 
Several methods for determination of plant available P in soils are P specific (Bray P1, Olsen, CAL). Many methods are developed using the same extractant for two (DL, Joret-Hebert) and three (AL, AAC-EDTA) element extraction simultaneously. To minimize the time of analysis and laboratory costs the focus of the research is directed to the development of multielement methods, which is usable for macro and micro nutrients analysis from the same extract.
One widely used multielement method is Mehlich 3, developed in 1983. This method is useful for determination of macro elements (P, K, Ca, Mg) and microelements (Zn, Fe, Cu, Mn, B) in soil. As used extractant (0,2M CH3COOH, 0,25M NH4NO3, 0,015M NH4F, 0,013M HNO3, 0,001M EDTA) consists of nitrate (NO3-) ions, this method can not be  used to determine nitrate in soil. The modified multielement method was proposed by Yanai et al. in 2000, where the composition of the extraction solution is: 0,2M CH3COOH, 0,25M NH4Cl, 0,005M citric acid, and 0,05M HCl. As there are no nitrate ions in the composition of the solution, it could be used beside macro and micro nutrient elements also for nitrate content determination in soils. 
In our research soil sample sets with different pH, texture and carbon content were analyzed by Mehlich 3 and modified Mehlich 3 method. Correlations of analyzed P contents between methods and impact of soil properties to the correlations were investigated. 

How to cite: Tonutare, T., Tõnutare, T., Kõlli, R., Krebstein, K., and Vennik, K.: Soil phosphorus content determined by Mehlich 3 and modified Mehlich 3 methods, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4568, https://doi.org/10.5194/egusphere-egu23-4568, 2023.

EGU23-4899 | ECS | Orals | SSS5.11

Estimation of N and N₂O cycling processes using the information of bacterial functional genes in the East Sea 

Hyo-Ryeon Kim, Jae-Hyun Lim, Hae-Kun Jung, Seo-Young Kim, and Il-Nam Kim

Marine nitrogen (N) cycle plays important roles in controlling marine ecosystem and biogeochemistry, as it is well known as a limiting element for marine productivity and significantly influences on the carbon and phosphorus cycles in the marine environment. Also, nitrous oxide (N₂O) production via marine N cycling is regarding as climate interaction with a big concern owing to its significant warming potential in the atmosphere. The East Sea (ES) is a semi-enclosed marginal sea, but frequently referred to as a miniature ocean as it shows multiple ocean dynamic processes. Recently, a number of studies reported that the ES is rapidly changing due to anthropogenic perturbations. Given that understanding of the ES’s biogeochemical cycles under such a condition is apparently urgent, we have little knowledge about particularly N cycling and N₂O production mechanisms to date. At present, the application of metagenomics approaches is widely used for understanding marine N cycle as an important means. Here, using the information of bacterial functional genes, we for the first time investigate (1) N cycling processes and (2) N2O production pathways during June and October 2021 at three different depths (0m, 150m, and 750m) of the ES.

How to cite: Kim, H.-R., Lim, J.-H., Jung, H.-K., Kim, S.-Y., and Kim, I.-N.: Estimation of N and N₂O cycling processes using the information of bacterial functional genes in the East Sea, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4899, https://doi.org/10.5194/egusphere-egu23-4899, 2023.

EGU23-5437 | Posters on site | SSS5.11

Investigation of the decay of DOM fraction in soils with different vegetation types by fluorescence and 2D-correlation spectroscopy 

Tibor Filep, Dóra Zacháry, Marianna Ringer, Gergely Jakab, and Zoltán Szalai

Dissolved organic matter (DOM) fraction of four soils with different vegetation types (grassland, spruce, oak, agricultural) were incubated at 15 °C and the chemical changes of organic matter were monitored by synchronous fluorescence and 2D-correlation spectroscopy. Fluorescence spectroscopy revealed that at the beginning of incubation, on day 3, the proportion of low molecular weight readily biodegradable compounds increases, and from day 8 onwards, the initiated microbial degradation generates a large number of medium molecular weight molecules. At further samplings (days 21, 35 and 60), the proportion of compounds of microbial origin decreases systematically, due to a decrease in microbial activity caused by the lack of substrate. In 2D correlation measurements, we found that the temporal change in spectral ranges was as follows: 250 → 290 → 360 nm. This provides spectroscopic evidence that microorganisms start to consume low molecular weight peptide or sugar-like substances and then release organic matter into the environment through their death and metabolism. At a later stage of incubation, they start to break down the higher molecular weight fulvic acid-like molecules.

We concluded that (i) similar patterns emerged in the spectral features of degradation for the four different soils: the dynamics of organic molecules with different size ranges were the same, (ii) a general scheme was found during the decomposition: microorganisms begin to break down the low-molecular-weight organic substances, and then, through their death and metabolism, release organic substances into their environment; finally, in the later stages of mineralization, the higher molecular weight, fulvic acid-like molecules are degraded and (iii) 2D-correlation spectroscopy has proven to be an effective tool for monitoring chemical changes in dissolved organic matter, revealing both simultaneous and sequential chemical events.

This work was supported by the Development and Innovation Fund of Hungary [grant No. NKFIH 132191].

How to cite: Filep, T., Zacháry, D., Ringer, M., Jakab, G., and Szalai, Z.: Investigation of the decay of DOM fraction in soils with different vegetation types by fluorescence and 2D-correlation spectroscopy, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5437, https://doi.org/10.5194/egusphere-egu23-5437, 2023.

Microbial transformation of organic compounds is a key process in soil. Microorganisms are responsible for important soil functions such as degradation of organic pollutants, but also for the formation and transformation of soil organic matter (SOM). Research on both processes suffers from missing knowledge on the process details, but also on the controlling factors and transformation products formed. In case of organic pollutants, most studies relied on the use of radiolabelled compounds, as such studies are required for market approval of chemicals, e.g. for pesticides. Such studies regularly show formation of non-extractable residues (NER), even under optimal conditions for microbial activity. The characterization of NER is difficult, preventing adequate risk assessment. In contrast, SOM studies usually comprise general C balances, without focus on detailed microbial processes. We are now using considerations on general principles of microbial metabolism and a combination of knowledge on the degradation of natural organic compounds as well as organic pollutants to get more detailed insight into both processes. This includes better characterization of NER for improved environmental risk assessment, an improved framework describing SOM transformation and stabilization as well as the identification of controlling factors for both types of metabolic processes.

For heterotrophic organisms, each growth substrate is both a C- and an energy source. The allocation depends on the actual requirements of the organisms as well as on the chemical structure of the substrate. Therefore, each substrate will only partially be mineralized (catabolism), the other part will be used as C source for biomass synthesis (anabolism). As a consequence, microbial biomass will be formed, and its residues will contribute to SOM after cell death. We already showed in earlier studies on pesticide degradation in soils that biomass residues of the degraders (biogenic NER = bioNER) account for a substantial part of the NER found by isotope mass balances. The close link between mineralization and biomass formation suggests a relation between mineralization and formation of biomass and bioNER, which represents the carbon use efficiency (CUE). CUE may vary and controls the allocation of natural organic substrates to respiration vs. microbial biomass formation, which is a key prerequisite for necromass accumulation. However, CUE is strongly affected by microbial metabolism, which adapts to environmental conditions.

Mass balances for a number of pesticides including bioNER formation were performed under different conditions, by manipulating pH and TOC concentrations of a study soil and incubating at different temperatures or in different soils. In particular, incubation temperature had a strong effect on the total degradation efficiency, but also on CUE during pollutant degradation and therefore on the contribution of bioNER to total NER. We can expect similar effects for the turnover of natural organic compounds and thus SOM formation. If supported by modelling of microbial biomass formation, this information can significantly improve the risk assessment in the framework of market approval of chemicals and advance our knowledge on factors controlling organic compound turnover and SOM formation under climate change.

How to cite: Miltner, A., Nowak, K. M., Muskus, A., Zheng, T., and Kästner, M.: Combining results on organic pollutant degradation and on soil organic matter turnover gives indications for the control of key microbial transformation processes in soils under global change, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5550, https://doi.org/10.5194/egusphere-egu23-5550, 2023.

EGU23-6965 | ECS | Posters on site | SSS5.11

Origin and chemical composition of DOM fractions from topsoil and subsoil layers of a silty and a sandy forest soil using FT-IR and fluorescence spectroscopy 

Dóra Zacháry, Tibor Filep, Áron Sziklai, Csilla Király, Gergely Jakab, Marianna Ringer, and Zoltán Szalai

The different environmental conditions (temperature, oxygen and water availabilities), microbial composition, availability of fresh organic inputs and textural and mineralogical properties of soil layers with the depth result differences between the origin, composition, C/N ratio and stability of the dissolved organic matter (DOM) of topsoils and subsoils.

This research examines the content and chemical composition of the DOM of topsoil and subsoil layers of a silty Luvisol and a sandy Arenosol. Both soils are derived from oak forests from Hungary. The soils were collected as composite samples (10 random subsamples within a 20 m × 20 m area) from the 0–20 and 30–50 cm layers.

The DOM was extracted with ultrapure water for 12 h at room temperature with a tumbling shaker. The sample was centrifuged for 35 min (1400 × g) and the supernatant was decanted and passed through a 250 µm-sieve. The fraction that passed through the sieve was filtrated through a 0.45 μm membrane filter to obtain the DOM samples. The filtered samples were acidified to pH 2 with HCl, passed through a solid phase extraction cartridge using a styrene divinyl benzene polymer sorbent (Agilent Mega Bond Elut PPL), eluted with methanol and dried.

The dried DOM samples were analyzed with a Bruker Vertex 70 FT-IR spectrometer. For each sample a spectral range of 4000–400 cm1, a resolution of 4 cm1, 128 scans, and three replicates were recorded. Relative absorbances were calculated for six peaks (2920, 2850, 1730, 1640, 1515, or 1420 cm1) representing characteristic organic matter compounds.

The dried DOM samples were dissolved in 0.05 M NaHCO3 solution in order to determine the C and N content and the fluorescence and UV-VIS-NIR spectroscopical properties. The total organic carbon and nitrogen content of the DOM samples were analysed using a TOC/TN analyser (Shimadzu TOC-L). The chemical composition of the DOM samples was determined using fluorescence (Shimadzu RF6000) and UV-VIS-NIR (Shimadzu UV3600) spectrometry. Excitation-emission matrices were obtained by measuring fluorescence intensity excitation wavelengths ranging from 230–450 nm and emission wavelengths ranging from 260–600 nm with 2 nm increments. Fluorescence, humification and biological indices were determined from the fluorescence spectra in order to determine the sources, structural complexity and humification degree of the DOM samples. Synchronous fluorescence spectra were recorded with a fixed wavelength difference (Δλ=18) to separate SOM components with different molecular weights. Specific UV absorption (SUVA254 and SUVA280, L mg-1 m-1) was calculated by dividing the absorption at 254 and 280 nm by the DOC concentration.

The study aimed to assess the differences between the sources and the structural and chemical variability of the DOM samples from varying soil depths with different textural properties.

This work was supported by the Development and Innovation Fund of Hungary [grant No. NKFIH 142936] and the Eötvös Loránd Research Network [grant No. SA41/2021].

How to cite: Zacháry, D., Filep, T., Sziklai, Á., Király, C., Jakab, G., Ringer, M., and Szalai, Z.: Origin and chemical composition of DOM fractions from topsoil and subsoil layers of a silty and a sandy forest soil using FT-IR and fluorescence spectroscopy, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6965, https://doi.org/10.5194/egusphere-egu23-6965, 2023.

EGU23-7993 | Orals | SSS5.11 | Highlight

Microbial carbon use efficiency in soil under N deposition: Meta-analysis of 13C and 18O approaches 

Yakov Kuzyakov, Junxi Hu, Congde Huang, and Shixing Zhou

The carbon use efficiency (CUE) of soil microorganisms is a critical parameter for the first step of organic carbon (C) transformation by and incorporation into microbial biomass and shapes C cycling in terrestrial ecosystems. As C and nitrogen (N) cycles interact closely and N availability affects microbial metabolism, N addition to soil may shift the microbial CUE. We conducted a meta-analysis (100 data pairs) to generalize information about the microbial CUE response to N addition in soil based on the two most common CUE estimation approaches: (i) 13C-labelled substrate addition (13C-substrate) and (ii) 18O-labelled water addition (18O-H2O).

The mean microbial CUE in soils across all biomes and approaches was 0.37. The effects of N addition on CUE, however, were depended on the approach: CUE decreased by 12% if measured by the 13C-substrate approach, while CUE increased by 11% if measured by the 18O-H2O approach. These differences in the microbial CUE response depending on the estimation approach are explained by the divergent reactions of microbial growth to N addition: N addition decreases the 13C incorporation into microbial biomass (this parameter is in the numerator by CUE calculation based on the 13C-substrate approach). In contrast, N addition slightly increases (although statistically insignificant) the microbial growth rate (in the numerator of the CUE calculation when assessed by the 18O-H2O approach), significantly raising the CUE. We explained these N addition effects based on CUE regulation mechanisms at the metabolic, cell, community, and ecosystem levels. Consequently, the differences in the microbial responses (microbial growth, respiration, C incorporation, community composition, and dormant or active states) between the 13C-substrate and 18O-H2O approaches need to be considered. Thus, these two CUE estimation approaches should be compared to understand microbially mediated C and nutrient dynamics under increasing anthropogenic N input and other global change effects.

Reference

Hu J, Huang C, Zhou S, Kuzyakov Y 2022. Nitrogen deposition affects microbial carbon use efficiency: Meta-analysis of similarities and differences in 18O and 13C approaches. Global Change Biology 28 (16), 4977-4988. http://doi.org/10.1111/gcb.16226

How to cite: Kuzyakov, Y., Hu, J., Huang, C., and Zhou, S.: Microbial carbon use efficiency in soil under N deposition: Meta-analysis of 13C and 18O approaches, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7993, https://doi.org/10.5194/egusphere-egu23-7993, 2023.

EGU23-9903 | ECS | Posters on site | SSS5.11

Effects of Lactobacilli inoculum on tomato plants, soil nitrogen transformations and greenhouse gass emissions. 

Aikaterina (Katerina) Bouzaki, Lars Elsgaard, George Menexes, George Zanakis, and Georgios Giannopoulos

In the framework of the EU Green Deal, the reduction of chemical fertilization is promoted to enhance sustainable agriculture. An ecological option is to utilize the potential of soil microorganisms to improve plant growth and secure crop production. Past studies focused mainly on Rhizobia and their specific plant-growth promoting effects on target plant hosts (N-fixing). Recently, Lactobacilli (Firmicutes) gained increasing appreciation as soil nutrient regulators, besides their known plant protecting properties, for a broad range of plant hosts.

In this pot experiment, we studied the short-term effects of a Lactobacillus soil inoculant (LB) on tomato plants (Solanum lycopersicum L. var. extasi) and nitrogen kinetics, in two different soils (sandy (S), loamy (L)), with chemical (U; urea; 460 N mg/kg) and organic (DC; digestate compost; 22 g/kg) treatment. An unfertilized control (C) treatment for each soil was also included. The experiment lasted 115 days and two experimental setups run in parallel; soil containers a) without and b) with plants. During the experiment soil concentrations of NH4+, NO3-, NO2-, CO2 and N2O were measured. At the end of the experiment, additional agronomic traits (total biomass, total N) and soil N mineralization potential (AMN) were measured. 

The addition of LB in C and DC treatments increased soil NH4+ that ranged 1.5 – 28% relative to the treatments without LB, for both soils. When LB was added in the U treatment we observed a negative effect, -3% and -54% for L and S soil, respectively. A contradicting pattern was observed for soil NO3-, when LB was added in all treatments, soil NO3- increased and decreased in L and S soil, respectively. Soil NO2-, CO2 and N2O emissions increased in DC and U treatments for both soils, relative to C. Interestingly, when LB was added we observed a consistent decrease in soil NO2- and N2O emissions but a consistent increase in CO2 emissions for both soils was observed, relative to those treatments without LB. The addition of LB had a positive effect on plant biomass and total plant N for all treatments and for both soils, except U+LB treatment in S soil. As for AMN rates, there was not a consistent pattern.

In conclusion, our preliminary results indicate a positive effect of non-N-fixing lactobacilli inoculant on plant attributes for soils amended with compost. Furthermore, we documented a microbial approach to mitigate potential N2O emissions from organic amendments for the first time.

The BSc research work by Katerina Bouzaki was partly supported by the Hellenic Foundation for Research and Innovation (H.F.R.I.) under the 2nd Call for H.F.R.I. Postdoctoral Research Projects (#1053) awarded to Principal Investigator Dr. Georgios Giannopoulos.

This project was co-implemented with industrial partner Corteva Agriscience Hellas SA.     

How to cite: Bouzaki, A. (., Elsgaard, L., Menexes, G., Zanakis, G., and Giannopoulos, G.: Effects of Lactobacilli inoculum on tomato plants, soil nitrogen transformations and greenhouse gass emissions., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9903, https://doi.org/10.5194/egusphere-egu23-9903, 2023.

EGU23-10043 | ECS | Posters on site | SSS5.11

Organic P in soil and its extraction by Mehlich 3 method. 

Tõnis Tõnutare, Tõnu Tõnutare, Raimo Kõlli, Kadri Krebstein, and Kersti Vennik

Phosphorus (P) is limiting plant nutrient in natural and agriculturally used soils. P is presented in soil composition of various inorganic (mineral) and organic compounds.  Organic P compounds are very strongly adsorbed on the mineral surfaces and are therefore not available to the plants. Desorption of P from mineral surfaces into soil solution would be more limited for organic P compounds compared to inorganic P compounds. It is suggested that organic P availability is limited mainly by the solubility of organic P compounds. Due to very few works on soil organic P there is not enough information about potential contribution to P availability in the soil–plant system.
The goal of this research was to investigate the correlation between soil organic phosphorus and fraction of organic phosphorus extracted by Mehlich 3 method. Also the impact of soil pH, organic carbon content and texture to this correlation is under interest. 

How to cite: Tõnutare, T., Tõnutare, T., Kõlli, R., Krebstein, K., and Vennik, K.: Organic P in soil and its extraction by Mehlich 3 method., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10043, https://doi.org/10.5194/egusphere-egu23-10043, 2023.

Forest ecosystems in central Europe are currently experiencing various environmental changes like ongoing nitrogen deposition, rising CO2 levels and more frequent summer droughts, with potential impacts on biogeochemical processes in soils. Monitoring of soil properties, especially sensitive indicators like the activities of extracellular enzymes, enables studying the net effect of different simultaneously ongoing global changes on soil processes. Therefore, we measured the potential activities of four extracellular enzymes related to the C, N, P and S cycle (beta-glucosidase, N-actetyl-glucosaminidase, acid phosphatase and sulfatase)  of topsoils (0-10 cm of the mineral soil) from 150 forest plots under different management in three German regions as part of the Biodiversity Exploratories (https://www.biodiversity-exploratories.de/en/) project (Swabian Alb in the South, Hainich-Dün in the center and Schorfheide Chorin in the North of Germany) in May of 2011, 2014, 2017 and 2021. Analyzed soil samples were mixed samples composed of 14 soil cores (5 cm diameter) per plot, taken along two 40 m transects, sieved to < 2mm, and stored frozen before analyses.  Additional information on soil C, N and pH was obtained for the same samples.
Results revealed that the interannual variation of enzyme activities was about twice as high as that of soil organic carbon contents. Organic carbon, total nitrogen contents or soil pH showed no consistent trend over time across the regions. The same was true for the enzymes beta-glucosidase, N-acetyl-glucosaminidase and sulfates while acid phosphatase activity increased in all regions from 2011 to 2021 with the smallest absolute increase from on average 1290 to 2753 nmol MUF g−1 dw h−1 in the sandy and most acidic region Schorfheide Chorin, and the largest one in the loess-dominated silt-clay soils of the Hainich-Dün region (from 3474 to 5570 nmol MUF g−1 dw h−1).  Accordingly, the ratio of carbon-to-phosphorus acquiring enzymes declined with time. Plots following Moorhead et al. (2016, http://dx.doi.org/10.1016/j.soilbio.2015.10.01) indicated a consistent shift from N- to P-limitation across regions, independent of their total P contents and for both, coniferous and deciduous forests. Forest ecosystems seem to need to acquire more P from organic sources but given that both, plants and microorganisms can produce acid phosphatase, we are currently not able to say, if the increased phosphatase activity was a direct plant response or one (potentially mediated) by microorganisms. However, elevated CO2 and N-deposition can both potentially lead to nutrient imbalances and thus increasing forest P requirements, and also summer droughts might reduce plant nutrient uptake, so that the observed trend might be an additive effect of all, rather than being attributable to one alone. As next steps we will test if changes in enzyme activities go along with changes in soil microbial communities and with leaf litter P contents.

How to cite: Schrumpf, M. and Schöning, I.: Soil enzyme monitoring reveals increasing forest phosphorus demand in central Europe over the last decade, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11858, https://doi.org/10.5194/egusphere-egu23-11858, 2023.

EGU23-11961 | Posters on site | SSS5.11

Cover crop C inputs; Multiple aerial and isotope insights from a long-term field trial. 

Rebecca Hood-Nowotny, Celia Fernández-Balado, Katharina Schott, Anna Wawra, Matthias Konzett, Maria Heiling, and Gerd Dercon

Use of cover crops, mulches and other soil management practices have been widely promoted within the EU, as measures to draw down carbon dioxide and increase soil organic carbon in the fight against climate change. These approaches are being investigated in a number of programs and projects EU-wide, for example the EJP-SOIL program.

We used a long-term fully replicated maize based field trial with different crop and soil management practices, namely residue incorporation and/or inclusion of a cover crop, to explore carbon sequestration potential. We used natural abundance stable isotope approaches to follow the fate and residence time of mulched residues and to determine the most stable organic matter pools in these systems. We measured isotope signatures in particulate organic matter (POM), mineral associated organic matter (MOAM), stable aggregate bound organic matter (IA-POM) and soil microbial biomass (Mi-BIO) to characterize the impact of the soil fraction, on the fate and stability of the carbon pool and to test a number of emerging paradigms in soil science. We hypothesized that the residence time of the POM fraction and MOAM fractions would be lower under higher nitrogen inputs and that it would be possibly to detect these shifts using a stable isotope approach. Moreover, we used handheld and unmanned aerial vehicle UAV-captured multispectral data to investigate impacts of management on a plot scale.

Preliminary results show that even at low mulch rates (<3 t plant material ha-1) mulching significantly increased soil carbon storage in the long term, albeit at lower rates than predicted. This increase was due to increases in SOM in the top-soil. As hypothesized mulch with lower C:N ratios contributed less to overall soil carbon storage, but whether this was due to differences in carbon accumulation in the short-term POM pool or long-term MOAM pool remains to be revealed by on-going isotope analysis. The high replication and detailed investigation of this long term field trial should allow us to tease out a number of processes in the carbon and nitrogen cycle and allow us recommend suitable management practices for increasing soil organic carbon stocks. 

How to cite: Hood-Nowotny, R., Fernández-Balado, C., Schott, K., Wawra, A., Konzett, M., Heiling, M., and Dercon, G.: Cover crop C inputs; Multiple aerial and isotope insights from a long-term field trial., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11961, https://doi.org/10.5194/egusphere-egu23-11961, 2023.

EGU23-13173 | Posters virtual | SSS5.11

Drivers of spatial variability of soil respiration along altitudinal gradient in Northwest Caucasus Mountains 

Olga Gavrichkova, Sofia Sushko, Lilit Ovsepyan, Ilya Yevdokimov, Alexandra Komarova, Anna Zhuravleva, Sergey Blagodatsky, and Kristina Ivashchenko

Mountains occupy almost a quarter of the land area and store significant pools of soil organic matter (SOM), which is a potential source of atmospheric CO2 under warming climate. However, carbon fluxes in mountain areas with high environmental heterogeneity remain poorly understood, in particular regarding the spatial variability of soil respiration (RS). The study was conducted on the northeastern slope of the Northwest Caucasus Mountains (1260-2480 m a.s.l.; Russia) that crossed five vegetation belts (i.e., mixed, fir and deciduous forests, subalpine and alpine meadows). RS was measured simultaneously (at 10 a.m. on 11 August 2018) across five vegetation belts (at 12 randomly distributed points per belt; totally n = 60) using the closed static chamber technique. As potential drivers of RS spatial variability, soil physico-chemical (temperature, moisture, total and dissolved C and N contents, C:N ratio, pH), soil microbial (microbial biomass C content, basal respiration, enzymatic activities: β-glucosidase, chitinase and leucine aminopeptidase) and vegetation properties (grasses projective cover, its species richness, Shannon-Wiener diversity index, abundance of graminoids and forbs) were assessed. The RS rate ranged from 1.3-12.7 µmol CO2 m-1 s-1, with average values of 3.7 and 7.3 µmol CO2 m-1 s-1 for forests and grasslands respectively. Stepwise regression and subsequent path analysis showed that key driver of RS spatial variability in forests was temperature-sensitive soil chitinase activity (explained variance 50%), while in grasslands it was graminoid abundance (explained variance 27%). The forest soils are mostly limited in N, therefore RS variability depends largely on SOM-derived CO2 sources, i.e. activity of the N-acquiring enzyme. In the grasslands, extensive network of fine roots and the associated considerable contribution of root-derived respiration to Rs, makes the flux more sensitive to vegetation composition and associated phenology and C allocation patterns. Thus, soil N availability and differences in plant cover play a crucial role in regulation of RS spatial patterns in mountains ecosystems.

This study was financially supported by Russian Science Foundation, No 22-74-10124.

How to cite: Gavrichkova, O., Sushko, S., Ovsepyan, L., Yevdokimov, I., Komarova, A., Zhuravleva, A., Blagodatsky, S., and Ivashchenko, K.: Drivers of spatial variability of soil respiration along altitudinal gradient in Northwest Caucasus Mountains, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13173, https://doi.org/10.5194/egusphere-egu23-13173, 2023.

EGU23-16629 | ECS | Orals | SSS5.11 | Highlight

Modelling the phosphorus cycle in European agricultural soils under current and different management scenarios 

Anna Muntwyler, Panos Panagos, Stephan Pfister, and Emanuele Lugato

Phosphorous (P) is an essential nutrient for all crops, yet excess P leads to the pollution of the environment. Additionally, the mineral P fertilizer production uses rock P, a non-renewable resource that is on the critical raw materials list of the European Commission. This context calls for action to find ways to increase P use efficiency and reduce the loss of P to the environment. To come up with effective solutions, process-based models, such as DayCent, can help depict and investigate the effects of scenarios on the P cycle. On top of the calibrated Nitrogen and Carbon submodels, the P submodel of the biogeochemical model DayCent has recently been calibrated and tested using European long-term experiments. DayCent has a detailed representation of soil biogeochemistry and can reproduce the major effects of climate and agricultural management on crop production. We exemplify the possibility of the model to represent the current European agricultural soil P budget, including changes in the P pools in space and time. For this task, the model is run with data-derived soil characteristics and complemented with state-of-the-art input data sets. Additionally, the model is used to project the influence of various agricultural management scenarios from 2019 until 2030 and 2050 compared with a baseline of current agricultural practices targeted at different European biogeochemical hotspot areas. Finally, the detailed model and scenario results showcase a promising tool for assessing biogeochemical cycles in agricultural soils, including their interconnections.

How to cite: Muntwyler, A., Panagos, P., Pfister, S., and Lugato, E.: Modelling the phosphorus cycle in European agricultural soils under current and different management scenarios, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16629, https://doi.org/10.5194/egusphere-egu23-16629, 2023.

EGU23-17165 | Posters virtual | SSS5.11

Interaction between water, crop residue and fertilization management on the source-differentiated nitrogen uptake by rice 

Andrea Vitali, Federica Russo, Francesco Vidotto, Eleonora Francesca Miniotti, Luisella Celi, Marco Romani, and Daniel Said Pullicino

Alternate wetting and drying (AWD) is considered as an effective water-saving practice for rice cultivation widely applied across the world. Although AWD can reduce global warming potential compared to continuous flooding (CF), it may have negative effects on N availability for crop by promoting N losses (nitrification-denitrification, leaching) and immobilization, due to the frequent soil redox cycling. By means of a growth chamber pot experiment and a 15N stable isotope approach we investigated the interactions between water, crop residue and fertilizer N management on the contribution of different N sources (i.e. fertilizer, rice straw, soil) to rice plant N uptake. We hypothesized that with respect to CF, AWD will decrease plant uptake of fertilizer (FDN), straw (StDN), and soil (SDN) derived N due to greater losses, greater microbial N immobilization during residue turnover under oxic conditions, and less N supply from soil organic matter (OM) desorbed under reducing conditions. Moreover, we hypothesized that the underlying processes will be influence by the timing of straw addition with respect to flooding and the temporal distribution of mineral N application.

Rice was grown for 60 d in a factorial setup including: (i) two water regimes: CF for 60 d vs. AWD (30 d of flooding followed by 30 d of alternating conditions involving 3 drain-flood cycles), and (ii) three straw and fertilizer managements that involved a combination of straw addition (10 Mg ha-1) 30 or 60 d before seeding (S30 and S60, respectively), and N fertilization (ammonium sulfate) split between pre-seeding and tillering in 60+60 or 80+40 kg N ha-1, such that treatments compared were S30-N60-N60, S30-N80-N40 and S60-N60‑N60. 15N-enriched fertilizer and straw were used in separate replicated setups to quantify the relative contribution of FDN, StDN and SDN to plant N uptake, as well as fertilizer use efficiency (FUE).

Plant N was mainly soil and fertilizer-derived (≈ 58 and 40%, respectively), while straw only contribute a minor amount (< 3%). Although AWD reduced total N uptake by about 10-13% with respect to CF, FDN and FUE were only slightly affected by water management, suggesting that differences in N nutrition did not depend exclusively on fertilizer N losses. SDN contributed more to plant nutrition in CF than in AWD, particularly when straw was incorporated in proximity to flooding. The combination of a fresh OM supply and reducing conditions under CF favoured the reductive dissolution of Fe oxides and desorption of soil OM that increase soil N supply via mineralization. StDN contributed less to plant nutrition in AWD than in CF albeit the higher mineralization rates we expected with more frequent oxic conditions. We attributed this to a higher microbial N demand under aerobic conditions that leads to a greater immobilization SDN during decomposition. The higher SDN and StDn for N60-N60 treatment with respect to N80-N40 suggested that an equilibrated splitting of N fertilizer between pre‑seeding and tillering stages could favor microbial activity under AWD improving straw degradation and soil N release.

This research was funded by the Lombardy Region through the project RISWAGEST

How to cite: Vitali, A., Russo, F., Vidotto, F., Miniotti, E. F., Celi, L., Romani, M., and Pullicino, D. S.: Interaction between water, crop residue and fertilization management on the source-differentiated nitrogen uptake by rice, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17165, https://doi.org/10.5194/egusphere-egu23-17165, 2023.

SSS6 – Soil Physics

EGU23-2544 | ECS | Orals | SSS6.1

Bacterial growth and decomposition are regulated by soil pore network characteristics, while fungi are independent: insights from computed tomography 

Diego Soto Gómez, José Eugenio López Periago, David Fernández Calviño, Johannes Rousk, and Paula Rodríguez Pérez

The characteristics of the soil pore network condition the flow of nutrients, liquids, gases, and temperature through this medium. We hypothesized that soil structure properties will also control soil microbial processes. To test this, we selected soil samples where land use generated differences in soil structure. Unaltered soil samples from three adjacent plots were analysed: a potato field soil, ploughed after harvesting, two weeks before sampling (Control); another ploughed potato plot, in which bioaugmentators (plant growth promoting bacteria) had been applied to increase soil biodiversity (Bio); and a third soil, dedicated to melon cultivation, without bioaugmentation, followed by six months of fallow (Melon). In each soil, three different depths were analysed (between 0/-3.33 cm; -3.33/-6.67 cm; and -6.67/-10 cm), and, at each depth, we separated aggregates into three size categories: >0.8 cm, 0.8-0.2 cm, and <0.2 cm. The structure of each core was analysed by computed tomography, while the leucine incorporation method (bacterial growth) and the acetate incorporation into ergosterol method (fungal growth) were used to estimate rates of microbial growth, and respiration was measured to estimate soil decomposer functioning.

The land uses affected soil structural variables. Bio pores had a significantly higher number of branches than Control and Melon. Regarding the aggregate fraction, most of the parameters considered (physical and biological) showed significant differences: the matrix fraction pores (aggregates < 0.2 cm) had a higher connectivity, were more tortuous, but presented a lower number of branches and junctions. On the other hand, there were also lower rates of bacterial growth, fungal growth and respiration in larger aggregates. No significant differences were found considering depth.

We detected links between rates of microbial growth, decomposer functioning and the porous network characteristic differences between samples. The fractal dimension was generally correlated with bacterial growth (r = 0.43, p-value = 0.04), also within Control (r = 0.86, p-value = 0.03) and Melon (r = 0.88, p-value = 0.02) land uses but not for Bio (r = 0.51, p-value = 0.30). Bacterial growth also increased in higher pore tortuosity (r = 0.49, p-value = 0.02), but was inversely correlated with the proportion of pores that end in the matrix (r = -0.41, p-value = 0.05). In the Bio treatment, microbial growth and decomposer were more independent of the pore architecture, and less correlated than in Control and Melon treatments. There, bacterial growth was favoured by higher connectivity (r > 0.86) and optical density (r > 0.69), while respiration increased with the number of pores (r > 0.75) and pore length (r > 0.71). The respiration rate within small aggregates (0.2 to 0.8 cm) increased with the length and number of pores (r > 0.84).

In conclusion, aggregation seems to have a greater effect on the physical and biological properties of the soil than differences between land uses studied and the depths considered. On the other hand, characteristics such as connectivity, tortuosity, and the length and number of pores seem to regulate both bacterial growth and respiration, while fungal growth appears independent.

How to cite: Soto Gómez, D., López Periago, J. E., Fernández Calviño, D., Rousk, J., and Rodríguez Pérez, P.: Bacterial growth and decomposition are regulated by soil pore network characteristics, while fungi are independent: insights from computed tomography, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2544, https://doi.org/10.5194/egusphere-egu23-2544, 2023.

EGU23-3366 | ECS | Orals | SSS6.1 | Highlight

Diversity of soil biopores and their influence on soil water infiltration under various pedoclimatic conditions 

Charlotte Védère, Hanane Aroui Boukbida, Yvan Capowiez, Sougueh Cheik, Guillaume Coulouma, Rinh Pham Dinh, Séraphine Grellier, Claude Hammecker, Thierry Henry des Tureaux, Ajay Harit, Jean-Louis Janeau, Pascal Jouquet, Jean-Luc Maeght, Cornelia Rumpel, Stéphane Sammartino, Norbert Silvera, Siwaporn Siltecho, Lotfi Smaili, Bounsamay Soulileuth, and Nicolas Bottinelli

Despite the large contribution of macropores made by soil engineers to the soil macroporosity and water infiltration, few studies have addressed the specific contribution of soil engineer groups, dynamics of biopores and their efficiency in conducting water. Thus, we aimed to investigate the link between soil macrofauna, soil biopores and water infiltration under different pedoclimatic conditions. To do so, we conducted an experimentation in twelve study sites with a large longitudinal gradient from France to Vietnam.  The experiment consisted in the field incubation of repacked soil in cores (15 cm in height and 15 cm in diameter) and controlling the activity of soil engineers in the manner of litter bag. For each site, soil columns were: (i) covered with a mesh (200µm) or not and (ii) with or without addition of organic residues to the soil surface. After 12 months, we measured (i) the 3D organization of biopores by X-ray computed tomography and (ii) the saturated hydraulic conductivity by Beerkan method. In addition, soil macrofauna communities and the 3D organization of biopores was measured in each study field. 

Addition of organic residues increased up to 2-fold the volume percentage of biopores which reached similar values than those observed for each study field. The co-inertia analysis between the data matrix characterizing the shape of biopores and the data matrix of the macrofauna communities showed no statistically significant correlation. Saturated hydraulic conductivity increased with the presence of biopores by 2 to 50-fold with the lowest increased in soils presenting largest saturated hydraulic conductivity. In conclusion, these results demonstrated that biopores are rapidly regenerated regardless the pedoclimatic conditions while the efficiency of biopores in conducting water is related to soil properties.

How to cite: Védère, C., Aroui Boukbida, H., Capowiez, Y., Cheik, S., Coulouma, G., Pham Dinh, R., Grellier, S., Hammecker, C., Henry des Tureaux, T., Harit, A., Janeau, J.-L., Jouquet, P., Maeght, J.-L., Rumpel, C., Sammartino, S., Silvera, N., Siltecho, S., Smaili, L., Soulileuth, B., and Bottinelli, N.: Diversity of soil biopores and their influence on soil water infiltration under various pedoclimatic conditions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3366, https://doi.org/10.5194/egusphere-egu23-3366, 2023.

EGU23-5106 | Posters on site | SSS6.1

Soil structure dynamics matters: Modelling the impact of land management on soil functions using BODIUM 

Sara König, Ulrich Weller, Bibiana Betancur-Corredor, Andrey Zaytsev, Ute Wollschläger, and Hans-Jörg Vogel

BODIUM is a systemic soil model that integrates the most important processes and components in soil and at the soil-plant interface in order to predict land management impact on soil functions.

A central role plays soil structure dynamics. Different land use and tillage regimes alter the pore space in a characteristic way. Biological processes such as root growth and earthworm activity contribute to the changes in soil pore structure.

We show model scenarios where different structure dynamics are evaluated in their effect on plant growth, water percolation including fast breakthrough due to macropore flow, and nutrient efficiency.

Parts of the soil structure modeling are supported by the open access soil structure library (https://structurelib.ufz.de/; Weller et al., 2022), where characteristic macro- and mesopore architectures obtained from Xray-CT imaging are available for different soil types and soil managements.

The model also allows exploration of climate change scenarios and evaluation of mitigation strategies.

Reference:

Weller, U., Albrecht, L., Schlüter, S., and Vogel, H.-J.: An open Soil Structure Library based on X-ray CT data, SOIL, 8, 507–515, https://doi.org/10.5194/soil-8-507-2022, 2022.

How to cite: König, S., Weller, U., Betancur-Corredor, B., Zaytsev, A., Wollschläger, U., and Vogel, H.-J.: Soil structure dynamics matters: Modelling the impact of land management on soil functions using BODIUM, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5106, https://doi.org/10.5194/egusphere-egu23-5106, 2023.

EGU23-5679 | ECS | Posters on site | SSS6.1

Monitoring the temporal evolution of soil structure of three innovative production systems in the field 

Clémence Pirlot, Anne-Catherine Renard, and Aurore Degré

Alternative agricultural practices emerge to provide more sustainable productions systems and to meet
tomorrow's diets. These practices and varying climatic conditions will have impacts on soil structure and
thus, on soil hydraulic properties. However, most models do not consider the temporal variability of soil
hydraulic properties, which can lead to poor decision making. Thus, quantifying the temporal evolution of
hydraulic properties is essential to better understand the impact of emerging agricultural practices on soil
structure (Chandrasekhar et al., 2018).


In most studies, temporal variation of soil hydraulic properties is investigated using punctual
measurements in the field or in the laboratory (Alskaf et al., 2021; Geris et al., 2021). Results are often
inconsistent between studies due to the timing and type of measurement performed (Chandrasekhar et
al., 2018; Strudley et al., 2008). In addition, most research focuses on the topsoil layers and does not
consider the longer term effects on the deeper layers of the soil (Wahren et al., 2009).


In this research, temporal evolution of the hydraulic properties of three innovative production systems is
continuously monitored up to 90 cm depth. The three systems are designed to disrupt current agronomic
trials and aim to produce the ingredients of tomorrow’s diets. They are pesticide-free and have long-term
rotations of 8 years with intercrops. These systems are implemented on 8 parcels of the University of
Gembloux Agro-Bio Tech on a typical loamy soil in Belgium.


The innovative systems were instrumented with 24 Teros 12 water content and 24 Teros 21 water
potential sensors from MeterGroup. Both types of sensor are robust and highly accurate. The Teros 12
probes also measure soil temperature and salinity. Potential probes can measure potential over a wide
range of values from -9 to -2000 kPa. All probes are connected to MeterGroup's ZL6 data loggers which
allow real-time data collection. The water content and potential probes are placed in parallel in the first
three soil layers at 30, 60 and 90 cm depth in 8 plots. Intact soil cores are also taken every two months to
determine bulk density and total soil porosity.


The simultaneous determination of both water content and water potential over time under natural
conditions allows the temporal evolution of the hydrodynamic properties to be captured at the level of
the first three horizons. This monitoring will make it possible to quantify the temporal evolution of the
structure of a loamy soil under the effect of alternative agricultural practices and varying climate
conditions. The first two years were contrasted in climatic conditions with a wet and a dry year. In addition,
a diverse range of agricultural practices with different crops such as beet, camelina, corn, rapeseed and
winter wheat were grown in both years. The results of these first two years of monitoring will be presented
at the EGU 2023 General Assembly and compared to theoretical properties that would be obtained using
classical PTF.

How to cite: Pirlot, C., Renard, A.-C., and Degré, A.: Monitoring the temporal evolution of soil structure of three innovative production systems in the field, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5679, https://doi.org/10.5194/egusphere-egu23-5679, 2023.

Freeze-thaw (FT) cycles have shown to affect the evolution of the pore space of agricultural soils, thereby affecting their hydraulic properties. In the temperate-boreal zones, FT patterns are projected to shift from relatively long and uniform freezing periods to more frequent fluctuations around 0°C as a result of climate change. To better anticipate potential consequences for water storage and flows in agricultural soils, a thorough evaluation of the importance of FT cycles in this context is required.

Here we summarize the findings of studies investigating the effects of FT cycles on various pore-space characteristics (e.g. macroporosity, pore connectivity, percolating pore space) and hydraulic properties (e.g. infiltration capacity, hydraulic conductivity, water retention) of agricultural soils. This includes the results of a laboratory experiment where we simulated different FT scenarios representative for current and future winter conditions in the temperate-boreal zones.

Our findings suggest that a shift in FT patterns with climate change indeed has the potential to alter, at least temporarily, water retention properties and (near-)saturated hydraulic conductivities of agricultural soils. We highlight that this is despite most changes in pore-space characteristics seem to occur in pores with a diameter smaller than 50 µm. The persisting increase in pore connectivity of specific soils with an increasing number of FT cycles appears to be decisive in this respect. However, to assess fully the magnitude of changes in soil water functions at the field scale may require modelling. We finally stress that the sensitivity of hydraulic properties to FT patterns questions the transferability of results of some previous studies to the natural environment, applying unrealistic temperatures and rates of freezing and thawing.

How to cite: Klöffel, T., Larsbo, M., Jarvis, N., and Barron, J.: Freeze-thaw effects on pore space and hydraulic properties of agricultural soils – a summary of studies and implications for the temperate-boreal zones in a changing climate, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6054, https://doi.org/10.5194/egusphere-egu23-6054, 2023.

Heterogeneous soil-landscapes with varying land uses and land covers are common in the hilly areas of the lower Yangtze valley of China. Variations of soil quality, mainly driven by soil organic matter and soil aggregation, across these soil-landscapes impacts the development of agro-industries in rural areas. How the development of macroaggregates (MAC) and their pore structure in relation to soil organic matter and microbial community varies with soil-landscapes (disturbed and undisturbed) remained unclear. Both bulk samples and undisturbed cores were collected from topsoil (0-15 cm) respectively on forestland (FL) under vegetation conservation on the hill slope, orchard (OR) and upland cropland (UL) on the slope and paddy fields (PF) in the basin in a small watershed from suburb Nanjing of China. Soil organic carbon (SOC) pools and microbial phospholipid fatty acids (PLFAs) as well as basic physico-chemical properties were measured while size fractionation of water-stable aggregates were performed. Further, the pore structure of the macroaggregate samples were analyzed with X-ray micro-computed tomography (X-ray μCT). Compared to FL, topsoil SOC was lower by 54%-70%, soil aggregate stability by 41-67% and total PLFAs by 14%-42% under the disturbed agricultural soil-landscapes. The mass fraction of macroaggregates was lower in OR, UL and PF, by over 44%. The total porosity of the macroaggregates, estimated by the μCT images, was lower by 17% and 33% under UL and OR though unchanged under PF. A similar trend was found for the connected porosity and total throat area. To note, both SOC and microbial PLFAs of the macroaggregate samples were significantly positively correlated to total porosity, connected porosity and total throat area, across the landscapes. Overall, soil quality was seen profoundly reduced in the disturbed soil-landscapes under agricultural activities although PF was shown most close to FL in the context of organic carbon stabilization and microbial biomass conservation. Thus, improving rice paddy management through soil organic matter conservation and macroaggregation could contribute to sustaining local soil quality for better agricultural development in the hilly rural area.

How to cite: Zheng, Z. and Genxing, P.: Changes in microbial community and soil organic matter mediated by macroaggregate pore structure across soil-landscapes in a hilly watershed, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6755, https://doi.org/10.5194/egusphere-egu23-6755, 2023.

EGU23-9069 | ECS | Orals | SSS6.1

Grazing livestock move by Lévy walks: Implications for soil structure dynamics 

Alejandro Romero-Ruiz, Paulo De-Meo-Filho, Simon Pulley, Carmen Segura, Jordana Rivero-Viera, Kevin Coleman, Laura Cardenas, Alice Milne, and Andy P. Whitmore

Animal behavior is a complex trait known to have strong feedbacks with environmental conditions across all ecosystems. Understanding how animals interact with their environment is therefore a key element for gaining new insights on how ecosystem landscapes develop and what is the potential environmental degradation caused by different species of animals. Within animal behavioral traits, characterizing animal movement has received attention because it is relatively easy to monitor. Despite the widely differing conditions in which different species of animals exist, it has been demonstrated that statistical models of animal movement based on random walks (e.g., Brownian and Lévy walks) often offer a consistent and accurate representation of animal movement in diverse ecosystems. Grazing livestock systems are particularly interesting to explore as they play an important role in the context of climate change and agricultural sustainability. Movement of grazing livestock has not been fully explored nor described, and knowledge on the way they impact the environment temporally and spatially is often empirical and remains largely unknown. To fill these gaps and to provide new insights on spatio-temporal impacts of grazing animals on soil structure, we characterized daily and seasonal patterns of grazing livestock using GPS (Global Positioning System) data from conventionally grazed and cell-grazed paddocks. In addition, we used a soil compaction model to predict changes in bulk density due to grazing. We found that the way grazing livestock move is consistent with a Lévy walk and that Lévy properties depend on the dimensions of the grazing cells (constraints and attractors). The combination of an animal movement model and a soil compaction model allowed us to obtain treatment-specific spatially explicit maps of soil properties affected by grazing that are consistent with observations.

How to cite: Romero-Ruiz, A., De-Meo-Filho, P., Pulley, S., Segura, C., Rivero-Viera, J., Coleman, K., Cardenas, L., Milne, A., and Whitmore, A. P.: Grazing livestock move by Lévy walks: Implications for soil structure dynamics, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9069, https://doi.org/10.5194/egusphere-egu23-9069, 2023.

EGU23-9129 | ECS | Posters virtual | SSS6.1

Influence of soil pore structure on the rate of microbial oxygen consumption 

Poulamee Chakraborty, Andrey Guber, and Alexandra Kravchenko

O2 availability is one of the main factors influencing microbial processing of soil carbon and nitrogen and their cycling, and soil pore structure is what drives micro-scale patterns of O2 availability. The diffusivity of O2 is known to be a function of soil porosity and moisture content. However, the actual distribution of O2 in the soil is a product of dynamic interactions between physical (O2 diffusion) and microbial (O2 consumption) processes and is influenced by the soil pore structure. Measurements of gas diffusivity can be achieved via several laboratory techniques, while the determination of O2 consumption by microorganisms is challenging. The objectives of this study are, first, to propose a method for measurement of microbial O2 consumption under steady-state conditions in saturated soil and near saturated soil, and, second, to quantify the rate of O2 consumption in soil materials with contrasting pore structures but similar microbial compositions. The proposed method is based on Fick’s second law of diffusion, given as , where R(z) is an O2 consumption term, C is the concentration of O2, and Ds is the effective molecular diffusion coefficient of O2. The equation was solved for R(z) under steady-state conditions (near saturated soil) where the flux (J)=0. Two soil materials with contrasting pore structures, namely dominated by > 30 μm Ø pores (i.e., large-pore soil) and by < 10 μm Ø pores (i.e., small-pore soil), were prepared. The O2 profile was measured to the depth of 1 cm in the two materials under saturated and near-saturated conditions using O2 microsensor (Unisense, Aarhus, Denmark). As expected, the O2 diffusion was higher in large-pore soil as compared to the small-pore soil, however, the estimated rate of volumetric O2 consumption was also higher in the large-pore soil as compared to the small-pore soil. This finding supports the notion that large pores provide a better micro-environment for soil microorganisms stimulating their activity with subsequent increases in O2 consumption. Our ongoing work builds on these findings and explores the rate and spatial distribution patterns of O2 diffusion and microbial O2 consumption in soils with contrasting pore structures in the presence of plant residues.

How to cite: Chakraborty, P., Guber, A., and Kravchenko, A.: Influence of soil pore structure on the rate of microbial oxygen consumption, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9129, https://doi.org/10.5194/egusphere-egu23-9129, 2023.

EGU23-10771 | Orals | SSS6.1

Long-term contrasting land uses influence on soil pore structure and organic carbon 

Maoz Dor, Lichao Fan, Kazem Zamanian, and Alexandra Kravchenko

The advancements of agriculture practices and technologies in harnessing natural resources has been a major component of humanity's development to produce and maintain food safety. As the bed for agricultural crops, soils are a major natural resource, and soil structure plays a crucial role in agricultural productivity. Long term differences in land use and agronomic management result in differences in soil physical structure, which also translates into variations in pore networks. Decomposition of organic matter and, hence, soil carbon storage capacity are closely related to the pore domain, which is the main environment where chemical and biological processes leading to carbon protection or decomposition take place. In this study, we explored pore structure, carbon characteristics, and their relationships in contrasting ecological systems from a long-term (> 30 years) experiment located at Kellogg Biological Station (Michigan, USA). The studied systems are (i) an agricultural intensively managed system of corn-soybean-wheat rotation (CT), (ii) a native early successional community abandoned from agriculture in 1989 (ES), (iii) a mowed grassland that has never been tilled or in agriculture (NTG), and (iv) late-successional deciduous forest that has never been cleared for agriculture (DF). An x-ray tomography analysis of intact soil cores was used to investigate pore size distributions, connectivity, and morphology to assess soil pore structure. We also measured total soil carbon and nitrogen contents, mineral associated organic carbon (MAOM), and particulate organic carbon (POM), short- and long-term soil respiration, and microbial biomass carbon. Preliminary results showed that the volumes of the soil pores with 30-180 mm Ø, the size range considered as the optimal microbial habitat, followed the trend of DF>NTG »ES>CT. The nitrogen and carbon content of these systems are also in agreement with this trend. Interestingly, MAOM fraction, considered to be a more recalcitrant form of carbon, followed the same trend, while the ratio of MAOM to total organic carbon did not change notably among the systems.

How to cite: Dor, M., Fan, L., Zamanian, K., and Kravchenko, A.: Long-term contrasting land uses influence on soil pore structure and organic carbon, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10771, https://doi.org/10.5194/egusphere-egu23-10771, 2023.

EGU23-11103 | Posters on site | SSS6.1

Impacts of soil management on the pore structure of boreal arable clay soils 

Jari Hyväluoma, Petri Niemi, Kofi Brobbey, Sami Kinnunen, Arttu Miettinen, Riikka Keskinen, and Helena Soinne

Soil management is known to have significant effects on soil structure. Especially, grassland renovation and associated ploughing may have destructive influence on structure, but on the other hand conversion of arable land to grassland can improve pore structure and soil functions. In crop rotations including perennial grasses, soil structure is affected by these counteracting processes. The purpose of this work was to study and quantify the impacts of varying soil management practices on the structure of boreal arable heavy clay soils. We studied intact topsoil samples collected from two sites by X-ray computed microtomography, image analysis, image-based pore-scale flow simulations, and water retention measurements. At both sites, one area under long-term (at least 30-year-old) grassland was compared with adjacent field area with contrasting managements:

  • Site 1: Cereal production under no-till management for 13 years prior to sampling.
  • Site 2: Crop rotation of a livestock farm with cereals and perennial grasses, tillage by ploughing. At the sampling time this field area had been two years under grass after preceding 3-year cereal period.

Both imaging and water retention showed statistically and practically significant differences in the soil macropore structure at site 1 such that porosity of the long-term grassland was clearly higher that that under cereal production. On the contrary, at site 2, only minor differences between managements were observed. Our results show that the soil management practices affect the macropore structure of boreal arable clay soil and that no-till and crop-rotation managements had clearly different effects on soil structure as compared to long-term grasslands.

How to cite: Hyväluoma, J., Niemi, P., Brobbey, K., Kinnunen, S., Miettinen, A., Keskinen, R., and Soinne, H.: Impacts of soil management on the pore structure of boreal arable clay soils, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11103, https://doi.org/10.5194/egusphere-egu23-11103, 2023.

EGU23-11624 | ECS | Posters on site | SSS6.1

Soil structure changes of constructed soil in bioretention cell during three years 

Petra Heckova, Michal Snehota, John Koestel, Ales Klement, and Radka Kodesova

Constructed soils play an important role in urban hydrology e.g. in the functioning of green roofs and stormwater bioretention cells. Water infiltration, colloid transport, and heat transport are affected by changes in pore system geometry particularly due to the development of macropores and clogging by particles. The aim is to elucidate changes in bioretention cell performance by studying the structural changes of soils at the microscale by invasive and noninvasive methods. Noninvasive visualization methods such as computed microtomography (CT), are an effective mean of soil structure assessment. X-ray CT is capable to investigate soil in terms of structure development, pore-clogging and pore geometry deformations.

Two identical bioretention cells were established in December 2017. The first bioretention cell (BC1) collects the stormwater from the roof of the nearby experimental building (roof area 38 m2). The second bioretention cell BC2 is supplied from a tank using a controlled pump system for simulating artificial rainfall. Each BC is 2.4 m wide and 4.0 m long. The 30 cm thick biofilter soil mixture is composed of 50% sand, 30% compost, and 20% topsoil. Bioretention cells are isolated from the surrounding soil by a waterproof membrane. The regular soil sampling program was initiated in 2018 in order to visualize and quantify the soil structure and internal pore geometry of samples. Undistributed samples were collected from the surface of the filter layer twice a year from each BC. The aluminum sampling cylinders had an internal diameter and height of 29 mm. Three batches of samples were taken during three years. The first set of 24 undisturbed samples was collected upon planting in June 2018, while the second set of 24 samples was taken after the end of the first vegetation period in November 2018. The second batch of 48 samples, were taken in the same period as in the previous year.  The last batch of 24 samples was taken in June 2020. Those collected samples were scanned by CT imaging.

Analyses of pore network morphologies were performed on the scanned samples. Macroporosity, pore thickness, pore connection probability, critical diameter and Euler-Poincare density were determined to understand pore space in the biofilter. Macroporosity in BC1 shows a decreasing trend in the first three periods, it can be a result of soil consolidation. In subsequent periods, macroporosity remains constant in BC1. The characteristic pore connection probability in BC1 also shows a decreasing trend in the first three periods, but compared to the macroporosity, the connectivity increases in the last two periods in BC1. This may be due to plants growth, which was most pronounced in 2019. The samples' most frequently represented pore thickness ranges from 80 to 330 µm in all periods in both BCs. The percentage of these pores was higher than 50% in both BCs.

How to cite: Heckova, P., Snehota, M., Koestel, J., Klement, A., and Kodesova, R.: Soil structure changes of constructed soil in bioretention cell during three years, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11624, https://doi.org/10.5194/egusphere-egu23-11624, 2023.

EGU23-12086 | ECS | Posters on site | SSS6.1

Use of Anionic Polyacrylamide to improve soil properties and challenge slope instabilities: preliminary data 

Giulia Frutaz, Claudia Meisina, Massimiliano Bordoni, and Rinaldo Sorgenti

Nowadays, changing climate is continuously posing new challenges to land management and conservation, also in built areas and agricultural fields. Polymers such as polyacrylamide (PAM) offer a suitable tool to stem soil degradation, as well as having a wide range of applications. We performed a detailed investigation about this polymer applications with particular attention to the field of slope instabilities through a systematic literature review to assess the extent and the specifics of the research done on Polyacrylamide as an improver of soil features, browsing between more than 800 articles published from 1990 to 2022. Research on polyacrylamide application increased since the 2000s, its main use being the prevention of irrigation-connected erosion, even if in more recent years its ability as a soil stabilizer became more and more newsworthy. We then proceeded to reconstruct soil samples in laboratory to observe the effects of application of anionic polyacrylamide (PAM) on their physical, volumetric, mechanical, and hydrological properties. First, two sets of samples were reconstructed using kaolin and sandy loam soil, respectively, with three different dry densities (varying between 1.2 and 1.6 g/cm3), three different initial water contents (varying between 10% and 40%) and five different polymer application rates (0%, 0.003%, 0.03%, 0.3%, and 1%by weight). The polymer, a granular anionic polyacrylamide, provided by Micronizzazione Innovativa Srl, has been manually applied and mixed with the samples, constituted by pvc cylinders with a diameter of 9.5 cm and 15 cm high. Preliminary results showed that the increase of PAM percentage in samples generally coincided with increase of liquid limit and plasticity index, causing at the same time a more gradual and regular release of samples water compared to untreated samples. These preliminary results can stress on the possible application of PAM to improve other soil features which could impact on slope instabilities occurrence, in a frame of sustainable solutions for reduction of landslides susceptibility, hazard and risk.

 

 

Keywords

 

Polyacrylamide

Landslides

Soil conservation

Land degradation

How to cite: Frutaz, G., Meisina, C., Bordoni, M., and Sorgenti, R.: Use of Anionic Polyacrylamide to improve soil properties and challenge slope instabilities: preliminary data, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12086, https://doi.org/10.5194/egusphere-egu23-12086, 2023.

EGU23-12345 | Posters on site | SSS6.1

Integrating MRI and modeling for Understanding Freeze-Thaw Processes in Saturated Soil and Sand 

Michal Snehota, Martina Sobotkova, Tomas Princ, Jan Sklenar, Martin Jex, Michal Benes, and Andreas J Pohlmeier

In this study, magnetic resonance imaging (MRI) was used to investigate the freezing and thawing process of a series of repacked samples of sand, soil, and sand-soil mixture. The samples were placed in a thermally insulated container inside a vertical bore MRI scanner and cooled by flowing cold gaseous nitrogen through a porous material at the top of the container. Temperatures were monitored in several points above the sample and at the sample surface, and a marker placed on the sample surface was used to measure sample deformation. A 4.7 T magnet was used for MRI and the Multiple-Slice Spin-Echo (MSME) and Zero Echo Time (ZTE) pulse sequences were employed to obtain the images. The contrast between the frozen and unfrozen water in the samples was given by the substantial difference in T1 and T2 relaxation times between the two states. The hydrogen in the frozen water does not produce any signal for both pulse sequences, thus all the signal represent the liquid/unfrozen water. The time-lapse three-dimensional (3D) imaging was performed during the entire course of the experiment with alternating use of the MSME and ZTE imaging techniques. Once the freezing front reached near the bottom of the sample, the thawing process was initiated by switching the inflow of cooling gas to the inflow of nitrogen at room temperature. The small changes in sand structure as a consequence of volumetric ice-water changes were studied using spatiotemporal analysis of the freezing front advancement and frozen water volume. The study detected interesting patterns of preferential thawing on the onset of thawing process in the case of sand. The MSME pulse sequence was successfully used to image the process in the sand, whereas the ZTE was capable of detecting water in the finer soil material. The data obtained in the study were used to develop two-phase ice-water simulation models to interpret the experimental results and better understand the freezing and thawing phenomena.

How to cite: Snehota, M., Sobotkova, M., Princ, T., Sklenar, J., Jex, M., Benes, M., and Pohlmeier, A. J.: Integrating MRI and modeling for Understanding Freeze-Thaw Processes in Saturated Soil and Sand, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12345, https://doi.org/10.5194/egusphere-egu23-12345, 2023.

EGU23-12630 | Posters on site | SSS6.1

Quantifying earthworm bioturbation from changes in vertical bulk density profiles 

Mats Larsbo, Johannes Koestel, Eveline Krab, and Jonatan Klaminder

The rate at which soil becomes physically mixed due to earthworm actions (bioturbation) has relevance for the fate of nutrients and pollutants and for the soil’s ability to sequester carbon. Nevertheless, methods to quantify bioturbation under field-like conditions are largely lacking. The soils of the Fennoscandian tundra offer a special possibility to quantify bioturbation, because they have developed in the absence of soil burrowing macrofauna. They commonly exhibit a thick organic layer on top of the mineral soil with a sharp layer boundary. The bulk density of the two soil layers differs markedly. Since bioturbation mixes both soil layers, the temporal changes in the bulk density profile of such soils may be exploited to estimate bioturbation rates in the field. In this study, we applied a model for earthworm bioturbation to observed changes in soil densities occurring in a mesocosm experiment with intact soil carried out in the arctic during four summers. We show that changes in soil density profiles can indeed be used to infer realistic earthworm bioturbation rates. Although uncertainties in parameter values were sometimes large, the results from this study suggest that soil turnover rates and endogeic earthworm soil ingestion rates in tundra soils may be as high as those reported for temperate conditions. Such large bioturbation rates can explain observed large morphological changes in nearby soils where dispersing earthworms have resulted in complete inmixing of the organic layer into the mineral soil. Our model is applicable to soil profiles with marked vertical differences in bulk density such as the soils of the Fennoscandian tundra where earthworms are currently dispersing into new areas and to layered repacked soil samples that are incubated in the field.

How to cite: Larsbo, M., Koestel, J., Krab, E., and Klaminder, J.: Quantifying earthworm bioturbation from changes in vertical bulk density profiles, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12630, https://doi.org/10.5194/egusphere-egu23-12630, 2023.

EGU23-12683 | Posters on site | SSS6.1 | Highlight

Coupled modelling of soil structure dynamics, carbon cycling, hydrological processes and crop production 

Nicholas Jarvis, Elsa Coucheney, Mats Larsbo, Elisabet Lewan, and Katharina Meurer

Soil-crop models are potentially useful tools to support analyses of the effects of climate and crop and soil management practices on crop production and the environment (e.g. carbon sequestration and greenhouse gas emissions or the leaching of agro-chemicals). However, it is not clear whether current generation models can be used to simulate long-term trends in crop production and the environmental impacts induced by changes in climate or land use because they do not consider the effects of soil structure dynamics at seasonal to decadal  (e.g. root growth, activity of macro-fauna) and centennial time scales (e.g. changes in organic matter content) on soil hydraulic functions, hydrological processes, crop growth and carbon cycling.

Here, we present a new soil-crop model that accounts for the interactions between soil structure dynamics, carbon cycling, soil physical and hydraulic properties, soil water balance and crop growth. The importance of soil structure dynamics is illustrated by long-term simulations of soil organic matter storage, soil water balance components and crop yields for a field site in central Sweden under climate change and contrasting management practices (organic amendments and crop varieties with an enhanced allocation of carbon to roots).

How to cite: Jarvis, N., Coucheney, E., Larsbo, M., Lewan, E., and Meurer, K.: Coupled modelling of soil structure dynamics, carbon cycling, hydrological processes and crop production, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12683, https://doi.org/10.5194/egusphere-egu23-12683, 2023.

EGU23-12922 | Orals | SSS6.1

Towards a quantification of the interactions between soil architecture and microbial dynamics under a dynamical soil architecture 

Valérie Pot, Claire Chenu, Patricia Garnier, and Xavier Portell

Over the last decade, the joint development of soil imaging tools and microscale models has made possible to start quantifying the role of soil architecture on soil functions and in particular on soil microbial activity. Microscale heterogeneity of soils have been considered to explain the microbial response, developing the concept of ‘hot-spots'. A major result highlighted from these studies is that spatial accessibility between the trophic resource and soil microorganisms is a key factor (Dungait et al., 2012). Under conditions of limited access, the decomposition of soil organic matter can be drastically reduced, whereas under conditions of optimal access the physiological traits of the microorganisms control the decomposition rate (Vogel et al., 2018). Interactions between soil architecture and microbial dynamics can also be indirect through the degree of soil pore aeration. For instance, the spatial accessibility between particulate organic matter and aerated soil pores can be related to the N2O production of soil samples (Ortega et al., 2023). New indicators quantifying the spatial accessibility are now emerging (Mbé et al., 2021 ; Rohe et al., 2021). Such spatial indicators of soil heterogeneity could feed the pedotransfer functions used to modulate organic matter decomposition rate in macroscale models of soil carbon dynamics. However the relevance and the robustness of these indicators to explain microbial activity remain to be evaluated (Schlüter et al., 2022). They have been established for static environmental conditions while soil architecture is highly dynamical, continuously changing under biotic and abiotic factors. Due to the complexity of obtaining sequential imaging datasets, few studies have imaged the 3D dynamics of soil architecture (Bottinelli et al., 2016). Mathematical models simulating the deformation of the 3D arrangement of solid particles using geomechanics laws for granular media (Duriez & Galusinski, 2021) or using fractal approaches for simplified soils (Perrier, 1995) have been developed. Other microscale modelling studies have attempted to simulate soil architecture dynamics through the action of microbes or physico-chemical processes using simplified rules (Crawford et al., 2012 ; Rupp et al., 2019). These incentive models have yet to be used to simulate microbial soil functions. We discuss these approaches and how they could be used to investigate to what extent the dynamics of soil architecture modifies the spatial accessibility between organic matter and microorganisms and in fine the soil organic matter decomposition rate.

 

References:

Bottinelli et al., 2016. Geoderma 65, 78-86.

Crawford et al., 2012. J R Soc Interface 9, 1302-1310.

Dungait et al., 2012. Global Change Biology 18, 1781-1796.

Duriez & Galusinski, 2021. Computers & Geosciences 15, 104936.

Mbé et al., 2021. Eur J Soil Sci., 13144

Ortega et al., 2023. Geoderma, 116224.

Perrier , 1995. PhD Thesis.

Rupp et al., 2019. Front Environ Sci. 7, 170.

Schlüter et al., 2022. Soil, 8, 253–267.

Vogel et al., 2018. Ecological Modelling 383, 10-22.

How to cite: Pot, V., Chenu, C., Garnier, P., and Portell, X.: Towards a quantification of the interactions between soil architecture and microbial dynamics under a dynamical soil architecture, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12922, https://doi.org/10.5194/egusphere-egu23-12922, 2023.

EGU23-13683 | Orals | SSS6.1

Mechanistic understanding of the effect of soil carbonates and organic amendments on soil structure and biological activity. 

Xavier Portell, Isabel S. de Soto, Wilfred Otten, Paul D. Hallett, and Iñigo Virto

Calcareous soils are common in arid and semi-arid regions and account for around half of the earth surface. In addition to the more widely studied soil organic carbon (SOC) pools, these soils also hold a large stock of soil inorganic carbon (SIC) surpassing SOC stocks. Nonetheless, despite their relevance, the effect of the interplay between SOC and SIC in calcareous soils is still poorly understood.

Soil carbonates can dissolve and re-precipitate in soil pores in short periods of time, dynamically changing the soil pore space, causing direct and indirect impacts on the SOC cycle that increase organic matter turnover rates (Fernández-Ugalde et al., 2011) than in soils of similar characteristics (climate, clay content, etc) without carbonates. This can be partially caused by the fact that carbonates dynamics (dissolution-precipitation) contributes somehow to a slower mineralization of organic matter. Several hypotheses exist to explain this positive effect for the stabilisation of SOC. One is the abundance of Ca that would favour mineral-mineral and organo-mineral interactions and associations. Another is that carbonates can protect SOC from further degradation by cementation. This can be related to carbonate crystals interfering with SOC mineralization by microorganisms.

We use a combination of 3D X-ray Computed Tomography and new mechanistic modelling to determine the relationship between the presence of carbonates in soil (and their dynamics) on the SOC mineralization rates (modelled). Preliminary results will be presented in this contribution.

Soil samples subject to different treatments were obtained from two soil sites: Arazuri (Navarra, Spain) and Rodezno (Rioja, Spain). The Arazuri soil supports a long-term experiment assessing the effect of the continuous application of sewage sludge on agricultural soil quality and productivity. Two contrasting fertilisation treatments corresponding to a baseline (mineral fertilization) and a high organic fertilisation treatment (80 t ha-1 of sewage sludge) were selected. Rodezno samples were obtained in an agricultural field subject to identical historical agricultural management for decades but naturally presenting two types of soils, differing in their carbonate content in their upper horizon (none and 20% equivalent calcium carbonate) due to their position on the landscape. Air-dried soil aggregates were scanned using a Nikon XT H 225ST X-ray CT system at two voxel resolutions 5 µm (2-5 mm aggregate size) and 25 µm (> 5 mm aggregate size). In parallel, a spatially-explicit mechanistic model of the SOC dynamics (Portell et al. 2018) considering explicitly the role of soil bacteria was expanded to take into account the modifications of the soil architecture due to the presence of soil carbonates as observed in the scanned samples.

Image-analysis of the X-ray CT data allowed to quantify the effect of calcium and organic fertilisation in the pore space distribution and connectivity. In addition, the combination of imaging data and the mechanistic model allowed to estimate mineralisation rates and link them to the calcium carbonate content and fertilisation treatment. Overall, our research provides a deeper understanding of the soil carbon organic and inorganic cycles.

References: Fernández-Ugalde et al. (2011). Geoderma,164: 203-214; Portell et al. (2018) Front. Microbiol. 9:1583.

How to cite: Portell, X., de Soto, I. S., Otten, W., Hallett, P. D., and Virto, I.: Mechanistic understanding of the effect of soil carbonates and organic amendments on soil structure and biological activity., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13683, https://doi.org/10.5194/egusphere-egu23-13683, 2023.

EGU23-13930 | Posters on site | SSS6.1

Freezing-Thawing Cycles of Saturated Sand Sample 

Martina Sobotkova, Alexandr Zak, Michal Snehota, and Michal Benes

Freezing and thawing cycles in laboratory were studied. Freezing-thawing cycles were carried out in the laboratory on fully saturated packed sand sample (15 cm in diameter and 20 cm in height). Series of freezing-thawing cycles were conducted with newly designed experimental setup. The setup consisted of inner plastic tube covered on its sides and outer plastic tube. The column sample was placed into the precisely controlled freezer chamber. The top of the sample was covered by an aluminum lid. Initially the sample was equilibrated at +10 °C then the temperature inside the chamber was changed to -10 °C. The inner temperature of the sample was monitored in three depths by thin temperature sensors (109 SS, Campbell Scientific, USA) horizontally inserted into the sample. The experiment aims to provide information on freezing dynamics and thermo-mechanical changes during the freezing and thawing cycles. Horizontal gradient within freezing cycle was monitored. The data were compared with simulations obtained by a numerical model (Žák et al., 2013). The model is based on the heat balance within the sample assembly and a modified heat equation for the porous medium temperature allowing for the phase transition below the freezing point depression. 

How to cite: Sobotkova, M., Zak, A., Snehota, M., and Benes, M.: Freezing-Thawing Cycles of Saturated Sand Sample, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13930, https://doi.org/10.5194/egusphere-egu23-13930, 2023.

EGU23-15651 | ECS | Orals | SSS6.1

Soil N2O emissions: how much does soil structure matter? 

Emile Maillet, Isabelle Cousin, Marine Lacoste, and Agnes Grossel

Nitrous oxide (N2O) is a greenhouse gas almost 300 times more powerful than CO2 in terms of global warming potential, and it is also the first ozone-depleting substance emitted in the 21st century. Approximately 43% of N2O emissions are estimated to be due to anthropogenic activities worldwide, and 52% of this anthropogenic part come from cultivated soils. The main cause of anthropogenic emissions is nitrogen fertilization.

The production, transfer and emission of N2O from soils are complex multifactorial processes, with a high spatial and temporal variability. Although N2O production in soils has multiple origins, the main source remains denitrification reactions during microbial respiration under anaerobic conditions. Thus, one of the major soil control factors is the availability of oxygen to soil organisms, which partly depends on the soil structure. The spatiotemporal variability of N2O emissions is explored by deterministic studies that focus either on the soil microstructure scale, i.e. the scale of N2O production and microorganism habitat, or on the macrostructure scale, to focus on fluids transfers. However, the influence of soil micro- and macrostructure studied together on N2O emissions is still poorly known, and represents the objective of this work.

A multi-scale approach was adopted to better understand the determinism of N2O emissions. The spatial variability of N2O emissions at the field scale was estimated during a snap-shot campaign on the same soil type with contrasted structural states, induced by different agricultural practices (4 soil modalities crossing strip-till and tillage with compacted or uncompacted areas). 24 soil cylinders were collected in low and high N2O emission zones and were then scanned by using both X-ray macro- and micro-tomography. Quantitative morphological tools were used to describe soil structure at the macro and micro scales while simultaneously studying other soil properties influencing N2O emissions (air permeability, gas diffusivity, nitrogen, pH, soil texture, etc.). The 4 soil modalities studied showed contrasted N2O emissions along with contrasting macrostructural and gas transfer indices. The ongoing work is aimed at clarifying the relationships between multiscale soil structure, gas transfer and other soil factors on N2O emissions.

How to cite: Maillet, E., Cousin, I., Lacoste, M., and Grossel, A.: Soil N2O emissions: how much does soil structure matter?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15651, https://doi.org/10.5194/egusphere-egu23-15651, 2023.

Deep burrowing earthworms produce exudates that coat the biopore wall with compacted finer-textured and organic matter-rich. The coating exhibit high spatial heterogeneity that, although connected to the inter- and intra-aggregate pore network in structured soils, can limit the flow exchange between the macropore and the soil matrix during preferential flow. Such flow exchange can be dynamically quantified if known the complex hydro-mechanical interrelations between biopore structure and soil matrix affecting the stress-strain behaviour at macroscopic scale. Our hypothesis was that the hydro-mechanical interrelations may be described with the discrete element method (DEM) coupled with the pore finite volume (PFV) approach if the model reproduces the pore network between coating and soil aggregates. Therefore, the objective was to develop a coupled DEM-PFV model together with a parameterization procedure based on machine learning algorithm to find the dependency between macroscopic mechanical and hydraulic soil properties obtained from drainage experiments of biopore samples to calibrate micro parameters of the model. The solid phase of the soil matrix was created using DEM inside a cube of about 5 cm edge, randomly filled with two aggregate sizes of 1 mm diameter (constituted by particles of 0.052 mm in diameter) and 0.4 mm diameter (constituted by particles of 0.03 mm in diameter). The pack of aggregates was compressed until the porosity reached the experimental value. The coating surface was created with a thickness of 0.25 mm and particles of 0.015 mm in diameter and compressed to reproduce the experimental porosity. The DEM models were coupled with a two-phase PFV model (2PFV) to simulate hydro mechanical effects during drainage. A total of 500 drainage simulations were performed for matrix and coated sample by randomly varying particle Young's modulus and bond strength. Saturation and strain along with the pressure head were measured to train the machine learning algorithm. The drainage experiments were designed to promote the movement of water from the soil matrix across the coated burrow surface. Thus, the samples were placed in the sandbox with the coated burrow in contact with the sand layer. An optical-laser sensor together with a tensiometer were used to quantify the pressure-head and sample shrinkage while the pressure was reduced at a rate of approximately 50 Pa s-1. In total, 40 samples of each treatment were used in these measurements. The poly-dispersed DEM-2PFV model was able to reproduce the pore network of coating material and the inter- and intra-aggregate pore network of the matrix that changed dynamically with the increment of pressure head. The machine learning model revealed that the bond strength among particles within aggregates governed the shrinkage of soil matrix, while the particle stiffness of the coating material reduced the susceptibility of aggregate breakage producing a more stable inter-aggregated pore network during the drainage process. This study confirmed that coating material present in biopore surface increases the horizontal soil hydro structural stability. The microscale hydro-mechanic modelling can be useful for finding flow exchange parameters inputs for upscaled models and correlating pore-scale parameters to experimentally determined stress-strain macro parameters.

How to cite: Barbosa, L. A. and Gerke, H. H.: A discrete element model for describing coupled hydro-mechanical processes during drying of soils with coated worm burrows, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16408, https://doi.org/10.5194/egusphere-egu23-16408, 2023.

EGU23-16637 | ECS | Orals | SSS6.1

Compared physical properties of repacked and undisturbed soil samples as assessed by shrinkage analysis: method, interest and limitations 

Cédric Deluz, Pascal Boivin, Thomas Keller, and Sebastian Dötterl

Field scale is a key scale for soil quality management in cropland, particularly for organic carbon and nutrient contents. To cope with within field variability, composite samples are collected which allows determining inexpensive average analytical properties for purposes such as soil quality monitoring. This is not feasible for most soil physical properties which require the collection of undisturbed soil samples for their determination. Unfortunately, most physical properties show large and unpredictable variability, thus leading to heavy soil sampling, laboratory costs and physical data processing to determine field properties and their time trend. Shrinkage analysis (ShA) provides a characterization of the soil pores, their air and water equilibrium and the soil structure stability, on the full soil water content range. It is usually performed on undisturbed soil samples; however, it was also performed on repacked soil samples from 2 mm size hand-fractioned aggregates. Moreover, it characterizes the physical properties of the two pore systems, namely the structural pores and the plasma pores. The later can be assumed to remain unchanged upon fractionation. Oppositely, the coarser structural pores are obviously destroyed. However, the intra aggregate structure and, therefore, the smaller size structural pores, might be conserved. In the frame of a large scale on-farm diagnosis of soil quality, we hypothesized that a part of the soil physical properties quantified with ShA could be characterized on repacked composite soil samples collected at field scale. This was tested by comparing (i) the physical properties of undisturbed soil samples and repacked soil samples on a wide range of soil types and quality and (ii) the relationships between soil organic carbon content, soil clay content, and the physical properties of undisturbed and repacked soil samples, respectively. 

How to cite: Deluz, C., Boivin, P., Keller, T., and Dötterl, S.: Compared physical properties of repacked and undisturbed soil samples as assessed by shrinkage analysis: method, interest and limitations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16637, https://doi.org/10.5194/egusphere-egu23-16637, 2023.

EGU23-1164 | ECS | Orals | SSS6.3

Development of a probability approach to determine water and colloidal pollutant flow behavior in urban heterogeneous soils 

Gersende Fernandes, Simone Di Prima, Gislain Lipeme Kouyi, Rafael Angulo-Jaramillo, Matteo Martini, and Laurent Lassabatere

Nature-based systems are being employed to allow stormwater to infiltrate directly in the soil, which is supposed to capture pollutants. To better track the evolution of such systems performances, in particular the infiltration and filtration performances, and to be able to optimize their management, these systems need to be better known. Currently, there is a lack of knowledge and methods regarding the characterization of the macropores and matrix contributions in infiltration and filtration of urban soils, whereas the quality of groundwater and the capacities of these systems are at stake. 

To tackle these limits, a large infiltrometer of 50 cm in diameter with two water-supply reservoirs of approximately 40 L each, was developed to characterize both hydrodynamic and nanotracers transfer parameters. Cumulative water infiltration was carried out at a constant hydraulic pressure head of 10 cm. Superparamagnetic iron oxide nanoparticles (SPIONs), which mimic both colloidal pollutants and bacteria flow behaviors in soils, were designed to be detectable by ground-penetrating radar (GPR). Fifty volumes of SPIONs solution (i.e., 50 x 5 mL at 3.35g/L) were injected into the ring and the GPR was passed along different survey lines around the ring several times during the infiltration experiment. GPR data was treated with ReflexW (Sandmeier Scientific Software, Karlsruhe, Germany) and Rockware (RockWare, Inc, 2015) to define a 3D block diagram of the infiltration bulb. The probability of presence of the nanoparticles was obtained from comparing the radargrams, before and after nanoparticle injection, by using two methods (Allroggen and Tronicke, 2015; Di Prima et al., 2020) on a R software (https://www.R-project.org/).

The large infiltrometer device, compared with a smaller one (Di Prima et al., 2015), is proved effective for estimating water and transfer parameters. The dispersion of SPIONs gave an idea of the relative importance of the transfer through the soil macropores as compared to the soil matrix. The probability of SPIONs presence gave information on the filtration function of soils. The whole device application will be illustrated and discussed with regard to its use for the assessment of the infiltration and filtration functions of bio-infiltration systems. 

 

Allroggen, N., Tronicke, J., 2015. Attribute-based analysis of time-lapse ground-penetrating radar data. Geophysics 81, H1–H8. https://doi.org/10.1190/geo2015-0171.1

Di Prima, S., Lassabatere, L., Bagarello, V., Iovino, M., Angulo-Jaramillo, R., 2015. Testing a new automated single ring infiltrometer for Beerkan infiltration experiments. Geoderma 262, 20–34. https://doi.org/10.1016/j.geoderma.2015.08.006

Di Prima, S., Winiarski, T., Angulo-Jaramillo, R., Stewart, R.D., Castellini, M., Abou Najm, M.R., Ventrella, D., Pirastru, M., Giadrossich, F., Capello, G., Biddoccu, M., Lassabatere, L., 2020. Detecting infiltrated water and preferential flow pathways through time-lapse ground-penetrating radar surveys. Sci. Total Environ. 726, 138511. https://doi.org/10.1016/j.scitotenv.2020.138511

How to cite: Fernandes, G., Di Prima, S., Lipeme Kouyi, G., Angulo-Jaramillo, R., Martini, M., and Lassabatere, L.: Development of a probability approach to determine water and colloidal pollutant flow behavior in urban heterogeneous soils, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1164, https://doi.org/10.5194/egusphere-egu23-1164, 2023.

EGU23-2830 | ECS | Orals | SSS6.3

Evidence of hillslope connectivity on Aleppo pine plantation by artificial stemflow experiments and preferential flow pathways detection using time-lapse ground penetrating radar surveys 

Elisa Marras, Gersende Fernandes, Filippo Giadrossich, Ryan D. Stewart, Majdi R. Abou Najm, Thierry Winiarski, Brice Mourier, Rafael Angulo-Jaramillo, Alessandro Comegna, Antonio del Campo, Laurent Lassabatere, and Simone Di Prima

The hydrological response of steep slopes catchments is strongly conditioned by the connectivity of subsurface preferential flows. The objective of this research is to investigate the role played by stemflow infiltration in subsurface water flow dynamics, focusing on a forested hillslope located in an Aleppo pine Mediterranean forest (Pinus halepensis, Mill.) located at Sierra Calderona, Valencia province, Spain. We combined stemflow artificial experiments with ground-penetrating radar (GPR) techniques as a non-invasive method to investigate stemflow-induced preferential flow paths activated by different trees and the related hydrological connectivity at the hillslope scale. Our observations allowed us to identify different dynamics associated with the initiation of stemflow and then lateral preferential flow, including the activation of connected preferential flow paths in soils that received stemflow water from different trees. These observations provided empirical evidence of the role of stemflow in the formation of lateral preferential flow networks. Our measurements allow estimations of flow velocities and  new insight on the magnitude of stem-induced lateral preferential flow paths. The applied protocol offers a simple, repeatable and non-invasive way to conceptualize hillslope responses to rainstorms.

How to cite: Marras, E., Fernandes, G., Giadrossich, F., Stewart, R. D., Abou Najm, M. R., Winiarski, T., Mourier, B., Angulo-Jaramillo, R., Comegna, A., del Campo, A., Lassabatere, L., and Di Prima, S.: Evidence of hillslope connectivity on Aleppo pine plantation by artificial stemflow experiments and preferential flow pathways detection using time-lapse ground penetrating radar surveys, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2830, https://doi.org/10.5194/egusphere-egu23-2830, 2023.

EGU23-2879 | ECS | Orals | SSS6.3

Spatio-temporal variation of surface soil hydraulic properties under different tillage and maize-based crop sequences in a Mediterranean area 

Rasendra Talukder, Daniel Plaza-Bonilla, Carlos Cantero-Martínez, Simone Di Prima, and Jorge Lampurlanés

In arid and semi-arid regions, high intensity rainfall and/or irrigation water drop leads to development of surface crust, and it has the potential to alter surface soil hydraulic properties while also accelerating runoff and erosion. However, the temporal variation of soil hydraulic properties under irrigated conditions due to surface crust under different soil management practices has rarely been studied. On a long-term tillage field experiment (26 years), in Agramunt, NE Spain, a study was carried out using Beerkan infiltration tests in conjunction with the inverse optimization algorithms of  the BEST method (Beerkan Estimation of Soil Transfer parameters) to investigate the effects of surface crusting on the spatio-temporal variation of saturated soil hydraulic conductivity (Ks, mm s-1), sorptivity (S, mm s-0.5), mean pore size (r, mm) and number of hydraulically active pores per unit area (N, m-2). Three tillage systems (intensive tillage, IT, reduced tillage, RT; and no-tillage, NT), two crop sequences (short fallow-maize, FM; and legume-maize, LM) and two positions (within the row of crops, W-row, and between the rows of crops, B-row) were assessed to evaluate the crusting effect on the above-mentioned soil hydro-physical properties. In response to autumn tillage, IT increased Ks and S due to higher r and N, but both declined after 60 days. RT, on the other hand, exhibited resilient to crust formation and despite having a lower N value, maintained comparable Ks and S values. After the spring tillage, its effect was immediately lost because of high-frequency water application, and both IT and RT developed crusted layers, resulting in decreased Ks, S and N. Long-term NT was resilient to form crust and an increasing trend of Ks and S was observed over time, except for the last sampling. Spatial variation (i.e., B-row vs. W-row) of Ks and S was found because of crusting, and independently of crop sequence, non-crusted soils (W-row) had consistently higher Ks (0.021 vs. 0.009 mm s-1)and S (0.65 vs. 0.38 mm s-0.5) than crusted soils (B-row) due to their lower bulk density and N. According to the findings of this study, conservation agriculture practices such as RT and NT improve the stability of surface soil structure and steadily reduce the risk of crust development. Further, surface cover by crops may help to prevent crust formation within the row of crops, improving soil hydraulic conductivity. This enhanced water flow path must not be neglected when measuring infiltration.

How to cite: Talukder, R., Plaza-Bonilla, D., Cantero-Martínez, C., Di Prima, S., and Lampurlanés, J.: Spatio-temporal variation of surface soil hydraulic properties under different tillage and maize-based crop sequences in a Mediterranean area, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2879, https://doi.org/10.5194/egusphere-egu23-2879, 2023.

Homogeneous soil and related darcean approaches are sometimes insufficient to describe flow processes in porous media. For this purpose, the double permeability (DP) approach was proposed by Gerke and van Genuchten (1993) and was then adapted by Lassabatere et al. (2014) to the quasi-exact implicit infiltration model of Haverkamp et al. (1994). The separation into two compartments called fast-flow and matrix regions with related volumetric fractions allows the modeling of preferential flow in soils. The inverting procedure from multiple-tension disc infiltration experiments proposed by Lassabatere et al. (2014) allows the estimation of DP hydraulic soil properties, i.e., the quantification of the volumetric fractions occupied by the two regions and their related hydraulic properties. This approach was applied to the studied experimental green roofs. Green roofs are structures known to play the role of buffer medium by absorbing the peak loads in the stormwater networks (thus reducing the risk of floods) and contributing to the attenuation of the urban heat island. The quantified hydrological contribution of these structures at the urban scale can be approached with the help of numerical modeling. In this study, we investigated the numerical modeling of the flow in vegetated roofs, which remain a challenging topic. In this study, multiple-tension infiltrometry tests were applied to experimental lysimeters simulating a vegetated roof (Yilmaz et al., 2016). These experimental infiltration data were inverted using the DP approach to estimate the properties of the material constitutive of the studied green roofs. Then Hydrus 1-D software was used to model the runoff produced by the experimental roof for several rainfall events. For this purpose, a summer period with three successive rain events was chosen, and the ability of DP to simulate the observed runoff was investigated. The results allow the validation of the proposed characterization and modeling method and provide material for understanding the hydraulic behavior of green roofs and the permanence of preferential flow in these structures. 

Gerke, H.H., van Genuchten, M.T., 1993. A dual‐porosity model for simulating the preferential movement of water and solutes in structured porous media. Water Resources Research 29, 305–319. https://doi.org/10.1029/92WR02339

Haverkamp, R., Ross, P.J., Smettem, K.R.J., Parlange, J.Y., 1994. 3-Dimensional analysis of infiltration from the disc infiltrometer .2. Physically-based infiltration equation. Water Resources Research 30, 2931–2935.

Lassabatere, L., Yilmaz, D., Peyrard, X., Peyneau, P.E., Lenoir, T., Šimůnek, J., Angulo-Jaramillo, R., 2014. New analytical model for cumulative infiltration into dual-permeability soils. Vadose Zone Journal 13, vzj2013.10.0181. https://doi.org/10.2136/vzj2013.10.0181

Yilmaz, D., Sabre, M., Lassabatère, L., Dal, M., Rodriguez, F., 2016. Storm water retention and actual evapotranspiration performances of experimental green roofs in French oceanic climate. European Journal of Environmental and Civil Engineering 20, 344–362. https://doi.org/10.1080/19648189.2015.1036128

How to cite: Yilmaz, D. and Lassabatere, L.: Estimation of dual permeability hydraulic properties and modeling the hydrological response of an experimental green roof, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2926, https://doi.org/10.5194/egusphere-egu23-2926, 2023.

EGU23-3409 | Posters on site | SSS6.3

Infiltrometer ring-size effects on infiltration and macropore hydraulic activation 

Saint-Martin Saint-Louis, Anthony Traullé, Gersende Fernandes, Simone Di Prima, Rafael Angulo-Jaramillo, and Laurent Lassabatere

Climate and global changes will force cities to adapt to new drastic meteorological and hydrological conditions. Within this context, urban planning has pointed to the need to restore the natural water cycle in urban cities. Restoring the natural water cycle means promoting water infiltration in urban areas to facilitate groundwater recharge and minimize runoff at the soil surface. Several techniques were developed with this goal, including those aimed at infiltrating water in specific drainage works like sustainable urban drainage systems (SUDS). However, the management of SUDS requires monitoring their capability to infiltrate water and its permanence with time. Indeed, several processes may impact the hydraulic characteristics of soils and, consequently, the infiltration capacity of bio-retention. Among others, clogging may reduce the soil's hydraulic conductivity and decrease infiltration. Conversely, plant growth and related development of root systems may promote macropore networks and increase the bulk hydraulic conductivity of soil, resulting in an increase in infiltration.

Infiltration techniques, including single-ring water infiltration experiments, were developed to monitor the soil's hydraulic properties and investigate their evolution with time. Infiltration techniques are based on infiltration tests with rings with radii in the order of 5-10 cm. If the question of the type of condition imposed at the soil surface was already posed (e.g., the question of the value of the water pressure head to impose, the presence of a sand layer for tension infiltrometers, etc.), the question of the ring size has not been investigated in depth.

In this study, we investigate the impact of the ring size on the results of water infiltration experiments, particularly regarding the activation of the soil macropore network and the hydraulic characterization of soils. We then performed infiltration experiments with rings of two contrasting sizes (7.5 cm versus 25 cm for the radius). Water infiltrations were carried out, involving the same total cumulative infiltration depth of 300 mm. BEST methods were then applied to derive the soil hydraulic parameters (Angulo-Jaramillo et al., 2019). The results were then compared between the large and the regular (small) rings. Differences in estimate means and standard deviations were discussed for each hydraulic parameter. Numerical modeling was also performed using HYDRUS (Radcliffe and Simunek, 2018) with synthetic soils to explain the difference in results between ring sizes with the concept of partial activation of the macropore network depending on the ring size. Our results constitute the first step toward understanding the ring effect on soil hydraulic characterization and its optimization with regard to the activation of all types of porosities.

References

Angulo-Jaramillo, R., Bagarello, V., Di Prima, S., Gosset, A., Iovino, M., Lassabatere, L., 2019. Beerkan Estimation of Soil Transfer parameters (BEST) across soils and scales. J. Hydrol. 576, 239–261. https://doi.org/10.1016/j.jhydrol.2019.06.007

Radcliffe, D.E., Simunek, J., 2018. Soil physics with HYDRUS: Modeling and applications. CRC press.

How to cite: Saint-Louis, S.-M., Traullé, A., Fernandes, G., Di Prima, S., Angulo-Jaramillo, R., and Lassabatere, L.: Infiltrometer ring-size effects on infiltration and macropore hydraulic activation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3409, https://doi.org/10.5194/egusphere-egu23-3409, 2023.

EGU23-3810 | Posters on site | SSS6.3

Modeling cumulative infiltration into dual-permeability soils 

Laurent Lassabatere, Deniz Yilmaz, Pierre-Emmanuel Peyneau, Simone Di Prima, Majdi Abou Najm, Ryan D. Stewart, Jesús Fernández-Gálvez, Joseph Pollacco, and Rafael Angulo-Jaramillo

Preferential flow is the rule rather than the exception, which questions the applicability of homogeneous models to simulate flows accurately. Gerke and van Genuchten (1993) developed the dual-permeability (DP) approach to account for preferential flow. This approach describes the soil as a combination of the fast-flow and the matrix regions. It defines a set of partial differential equations based on the application of Richards' equation to each region, in combination with an additional equation to govern water exchange between the two regions. In this study, we propose a strategy to model cumulative infiltration into DP soils considering the magnitude of the water exchange between the two regions.

In the absence of water exchange, infiltration can be considered independently in each region (Lassabatere et al., 2014). Consequently, the bulk infiltration at the soil surface equals the sum of the infiltration into the two independent regions weighted by their volumetric fractions. For this reason, the quasi-exact implicit (QEI) analytical model developed by Haverkamp et al. (1994) for single permeability (SP) Darcian soils can be applied to each region, and the two separate infiltrations can be summed to compute the bulk infiltration. The resulting QEI-Σ model was already detailed in Lassabatere et al. (2014). In the case of instantaneous water exchange, the water pressure head equilibrates instantaneously between the two regions. At any water pressure head, the bulk soil water retention and unsaturated hydraulic conductivity equal the combination of these hydraulic functions for the two regions. On a physical basis, the soil behaves as a Darcian soil with bimodal hydraulic functions, and water infiltration can be quantified by solving Richards’ equation considering bimodal hydraulic functions. Consequently, the QEI model can be used with the "bimodal" sorptivity computed from the bimodal hydraulic functions to depict the QEI-S2K model. Between these two limiting scenarios (i.e., zero versus instantaneous water exchange between the two regions), the problem must be solved numerically.

In this study, we modeled water infiltration into DP soils for various scenarios between the two extreme cases of zero and instantaneous water exchange. We used the two limiting models, QEI-Σ and QEI-S2K, to compare the cumulative infiltration for zero versus instantaneous water exchange. We used numerical simulation with HYDRUS-1D to solve the same scenario and compared it with the analytical models. Then, we modeled the cases with intermediate magnitudes of water exchange to characterize the progression from one extreme to the other. We then varied the value of the hydraulic conductivity of the interface between the two regions, with null values corresponding to zero water exchange, and quasi-infinite values corresponding to instantaneous water exchange. Our findings participate in the optimization of direct and inverse modeling procedures for preferential flow and their contributions to water infiltration into soils.

Gerke, H.H., van Genuchten, M.T., 1993. Water Resources Research 29, 305–319.

Haverkamp, R., Ross, P.J., Smettem, K.R.J., Parlange, J.Y., 1994. Water Resources Research 30, 2931–2935.

Lassabatere, L., Yilmaz, D., Peyrard, X., Peyneau, P.E., Lenoir, T., Šimůnek, J., Angulo-Jaramillo, R., 2014. Vadose Zone Journal 13.

How to cite: Lassabatere, L., Yilmaz, D., Peyneau, P.-E., Di Prima, S., Abou Najm, M., Stewart, R. D., Fernández-Gálvez, J., Pollacco, J., and Angulo-Jaramillo, R.: Modeling cumulative infiltration into dual-permeability soils, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3810, https://doi.org/10.5194/egusphere-egu23-3810, 2023.

EGU23-3977 | ECS | Orals | SSS6.3

The linkage between near-saturated hydraulic conductivity and tritium leaching 

Ping Xin, Charles Pesch, Trine Norgaard, Goswin Heckrath, Kai Zhang, Lis W.de Jonge, and Bo V.Iversen

Macropore flow in structured soils is an important process in relation to the transport of water, contaminants and nutrients in the soil. A close relation exists between hydraulic conductivity K(h) near saturation and the potential of macropore flow. At the same time, tracer breakthrough experiments in the laboratory can determine the degree of macropore flow. In this study, we aim to investigate a direct link between tracer breakthrough characteristics and soil hydraulic properties (SHPs) of structured soils, which may explain spatial variation of solute transport in soils. We used SHPs and tracer breakthrough characteristics for 71 undisturbed topsoil columns (19 cm height, 20 cm diameter) from Denmark. We defined K10 (near-saturated hydraulic conductivity) as K(h) at a matric potential (h) of −10 cm and used logarithmic transformation, logK10. On the same soil columns, we calculated the 5%, 25%, and 50 % arrival times (AT) as the percentage of the cumulative relative mass of tracer percolating through the bottom of the soil column. The regression analyses proved significant positive relation between logK10 and 5% AT, 25% AT, and 50 % AT. The saturated hydraulic conductivity appeared to be less critical for the shape of the tracer breakthrough curves. In addition, the 5% AT, 25% AT, and 5 0%AT correlated with soil pF values at 1.7, 2.0, and 2.5 (volumetric water content at h equal to −100 cm, −300 cm, and −500 cm, respectively) showing significant negative correlations.  Linking SHPs with tracer breakthrough characteristics on large intact columns thus proves highly useful for characterizing soil macropore functions.

How to cite: Xin, P., Pesch, C., Norgaard, T., Heckrath, G., Zhang, K., W.de Jonge, L., and V.Iversen, B.: The linkage between near-saturated hydraulic conductivity and tritium leaching, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3977, https://doi.org/10.5194/egusphere-egu23-3977, 2023.

EGU23-4078 | Orals | SSS6.3

Assessment of the BEST-WR three-term formulation to estimate water repellent soil hydraulic properties 

Deniz Yilmaz, Simone Di Prima, and Laurent Lassabatere

It’s known that certain soils surfaces may be subjected to water repellence, which prevents immediate water infiltration. With time, the water repellence vanishes and the water infiltration initiates. In such situation, the infiltration models developed for regular soils are not able to describe this early infiltration process. Recently, Abou Najm et al. (2021) proposed a simple corrector factor to deal with this problem and to account for water repellence at the beginning of the infiltration process in water-repellent soils. These authors applied their correction factor to the Philip two-term approximate transient expression. Recently, Di Prima et al. (2021) used this approach to adapt the BEST-slope algorithm (Lassabatere et al., 2006), based on the two terms transient expansion of the quasi-exact implicit (QEI) model for modelling water infiltration into regular soils for the estimation of the initial soil sorptivity (S) and the saturated hydraulic conductivity (Ks) of water repellent soils. The new model for the hydraulic characterization of soils regardless the degree of water-repellence, was named BEST-WR. It was validated using analytically generated data, involving soils with different textures and a dataset that included data from 60 single-ring infiltration tests. However, some points of the BEST-WR method deserved further investigations, especially concerning the validity time of the two-term approximate expansion used to fit the data. Indeed, if this validity time is defined for the BEST-Slope method, this is not the case for the BEST-WR method. To alleviate the issue of the limitation in time, Yilmaz et al. (2022) proposed an extension of the BEST-WR model by increasing the number of terms considered for the approximate expansions of the QEI model. They applied the correction factor to the three-term approximate expansion which is known to have a much wider validity time interval. This new formulation called BEST-WR-3T has the advantage of being valid on a very large time interval, allowing the modelling of the whole experimental datasets, without worrying about time limitations, for most practical applications. In this study, this new more robust formulation is evaluated on several examples using both analytical and field infiltration obtained with different approaches: the regular manual Beerkan method or using the automated infiltrometers developed by Di Prima et al. (2016). The robustness of the new method is observed when the BEST-WR method encounters difficulties in estimating soils parameters.  

References:

Abou Najm et al. (2021). A Simple Correction Term to Model Infiltration in Water‐Repellent Soils. Water Resources Research, 57(2), e2020WR028539.

Di Prima et al. (2016). Testing a new automated single ring infiltrometer for Beerkan infiltration experiments. Geoderma, 262, 20-34.

Di Prima, et al. (2021). BEST-WR: An adapted algorithm for the hydraulic characterization of hydrophilic and water-repellent soils. Journal of Hydrology, 603, 126936.

Lassabatère et al. (2006). Beerkan estimation of soil transfer parameters through infiltration experiments—BEST. Soil Science Society of America Journal, 70(2), 521-532.

Yilmaz et al. (2022). Three-term formulation to describe infiltration in water-repellent soils. Geoderma, 427, 116127.

How to cite: Yilmaz, D., Di Prima, S., and Lassabatere, L.: Assessment of the BEST-WR three-term formulation to estimate water repellent soil hydraulic properties, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4078, https://doi.org/10.5194/egusphere-egu23-4078, 2023.

EGU23-4174 | ECS | Orals | SSS6.3

Does soil structure affect water infiltration? Global results from a meta-data systematic review 

Christelle Basset, Majdi Abou Najm, Xiaoxiao Hao, and Andre Daccache

Soil structure is a crucial component of soil health and quality that significantly impacts water infiltration. Natural or anthropogenic drivers, such as soil management practices, can drastically alter soil structure, which in turn can affect water infiltration. These changes in soil structure have opposing effects on water infiltration into soils and are often difficult to quantify. Here, we present a narrative systematic review (SR) of the impacts of soil structure on water infiltration. Based on inclusion and exclusion criteria, as well as defined methods for literature search and data extraction, our systematic review led to a total of 153 papers divided into two sets: experimental (131) and theoretical (22) papers. That implied a sizable number of in-situ and field experiments that were conducted to evaluate the effects of soil structure on water infiltration under the influence of different land uses and soil practices. Significant effects of soil structure on water infiltration were inferred from analyzing the metadata extracted from the collected articles. These effects were further linked to land use and management, where we demonstrated the influence of three distinct categories: tillage, crop management, and soil amendments. Additionally, significant correlations between infiltration rate and soil structural characteristics were established, with R2 values ranging from 0.51 to 0.80, as well as between saturated hydraulic conductivity and soil structural characteristics, with R2 values varying from 0.21 to 0.78. Finally, our review emphasized the significant absence of and the need for theoretical frameworks studying the impacts of soil structure on water infiltration.

How to cite: Basset, C., Abou Najm, M., Hao, X., and Daccache, A.: Does soil structure affect water infiltration? Global results from a meta-data systematic review, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4174, https://doi.org/10.5194/egusphere-egu23-4174, 2023.

EGU23-4362 | Posters on site | SSS6.3

Capturing SUbsurface PREferential transport processes in agricultural HILLslope soils: SUPREHILL CZO 

Lana Filipović, Vedran Krevh, Jasmina Defterdarović, Zoran Kovač, Igor Bogunović, Ivan Mustać, Steffen Beck-Broichsitter, Horst H. Gerke, Jannis Groh, Radka Kodešová, Aleš Klement, Jaromir Dusek, Hailong He, Giuseppe Brunetti, Thomas Baumgartl, and Vilim Filipović

Agricultural hillslopes present particular challenges for estimating vadose zone dynamics due to a variety of processes, such as surface runoff, vertical flow, erosion, subsurface preferential flow affected by soil structure and layering, non-linear chemical behaviour, evapotranspiration, etc. To investigate these processes and complexity, the SUPREHILL critical zone observatory (CZO) was started in 2020, at vineyard hillslope site in Croatia. The observatory is extensively equipped for the soil-water regime and agrochemical fluxes monitoring, and includes an extensive sensor network, lysimeters (weighing and passive wick), suction probes, surface and subsurface flow and precipitation collection instruments. The main objective of the SUPREHILL observatory is to quantify subsurface lateral and local scale preferential flow processes. Local-scale nonlinear processes in eroded agricultural hillslope sites have large significance on water and solute behaviour within the critical zone and thus need to be researched in depth using combined methods and various approaches. First results from the sensor and lysimeter network, soil-water regime monitoring, isotope analysis, and agrochemical concentrations in 2021 supported the hypothesis of the observatory, that the subsurface flow plays a relevant part in the hillslope soil-water dynamics. In the wick lysimeter network, although the highest cumulative outflow values were found at the hilltop, the highest individual measurements were found at the footslope. During high-intensity rainfall events, there were differences in weighing lysimeters, possibly related to subsurface lateral flow. Based on the isotope analysis, wick lysimeters exhibit a greater variation of d-excess values than suction probes. Agrochemical fluxes confirmed the sloping effect on their transport in soil and demonstrated the favourability of Cu transport by subsurface flow. Using the comprehensive database presented herein, future analyses of this hypothesis will be carried out in more detail using model-based analyses.  

How to cite: Filipović, L., Krevh, V., Defterdarović, J., Kovač, Z., Bogunović, I., Mustać, I., Beck-Broichsitter, S., Gerke, H. H., Groh, J., Kodešová, R., Klement, A., Dusek, J., He, H., Brunetti, G., Baumgartl, T., and Filipović, V.: Capturing SUbsurface PREferential transport processes in agricultural HILLslope soils: SUPREHILL CZO, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4362, https://doi.org/10.5194/egusphere-egu23-4362, 2023.

Treated wastewater (TWW) has gained recognition as an alternative source for freshwater irrigation and is steadily expanding worldwide, particularly under the current climate change. Beyond its many advantages, it has been found that prolonged use of TWW renders the soil water-repellent to certain degrees. The flow in these soils has been known to take place in preferential flow pathways (unstable flow). This lecture presents the results of a study performed in a commercial citrus orchard grown on sandy-loam soil in central Israel that has been irrigated with TWW. Electrical resistivity tomography (ERT) surveys revealed that water flow in the soil profile is occurring along preferential flow paths, leaving behind a considerably nonuniform water-content distribution. The preferential flow in the soil profile led to uneven distribution of salts and nutrients, with substantially high concentrations in the drier spots and lower concentrations in the wetter spots along the preferential flow paths. The chemical's pore concentration, which depends on the local soil water content, is higher than paste-measured concentrations and may even reach toxic values. This could partially explain the negative effect that prolonged TWW irrigation has on soil and trees. The relationship between water-repellent soils and the spatially nonuniform distribution of nutrients and salts in the root zone was verified in a consecutive in-situ study where soil water repellency was eliminated by surfactant application to the soil. Repeated ERT surveys and chemical concentration measurements in disturbed soil samples along transects revealed that the surfactant application diminished the preferential flow pathways and rendered the soil water and dissolved chemicals uniformly distributed. The preferential flow elimination and increased chemical distribution uniformity result in a yield increase compared to the surfactant-untreated soil. The different aspects of the results will be further presented and discussed. 

How to cite: Wallach, R.: The effect of water-repellent soil-induced preferential flow on the spatial distribution of nutrients and salts in the soil profile of a commercial orchard, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4692, https://doi.org/10.5194/egusphere-egu23-4692, 2023.

The soil water retention curves(SWRCs) were acquired by experiments based on the evaporation method and compared with the result of volumetric pressure plate and chilled mirror tests for five samples in Korean residual soils. Under 100kPa suction, the SWRCs by the evaporation test agreed with those of volumetric pressure plate tests in the axis of effective saturation for five samples. In two samples, initial values of water content have shown 6% of difference, which doesn’t affect the fit of SWRCs. In the higher suction, the SWRCs were measured rapidly by chilled mirror tests. The SWRCs were fit efficiently  from low to high suction by both the evaporation and the chilled mirror tests. It is found that the fit only by low suction data couldn’t the actual SWRC accurately. Using the result of the current SWRCs and other data, the DB has been constructed and the parameters of the van Genuchten fit were interpreted. It was found that Korean residual soils are classified by three soils based on the range of void ratios.

Acknowledgements This research is supported by grant from Korean NRF (2019003604), which are greatly appreciated.

How to cite: Oh, S., Park, G., and Seo, Y.: A comparative study of soil water retention curves by the evaporation test with other experiments for Korean residual soil, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4893, https://doi.org/10.5194/egusphere-egu23-4893, 2023.

EGU23-5271 | ECS | Orals | SSS6.3

Evaluating stemflow infiltration through time-lapse ground-penetrating radar surveys on a Faidherbia albida tree in Senegal's Sahel 

Saidou Talla, Waly Faye, Gersande Fernandez, Laurent Lassabatere, Rafael Angulo-Jaramillo, Olivier Roupsard, Simone Di Prima, and Frederic C. Do

In the Sahel region, agroforestry is a land-use system widely adopted as a more sustainable agricultural production system. In this type of system, woody perennials that are grown in association with agricultural crops and pastures, constitute spatially disconnected zones where microclimate and soil’s infiltrability, physical, chemical, and biological conditions are assumed locally improved. Particularly the stemflow concentrates a part of the intercepted rainfall from the canopies to the stems. Hence stemflow can induce preferential infiltration around the stem base and promote groundwater recharge.

In the West African Sahel, Faidherbia albida (Delile) A.Chev. is commonly adopted as multi-purpose woody perennial in agroforestry systems. It is a deciduous tree with an inverse phenology as it loses the leaves during the rainy season. Although, the absence of leaves during the rainy season is expected to decrease the interception and to consequently decrease stemflow, evidence of stemflow at the base of F. albida trees were reported in the literature when the stems were partially covered with green leaves (Chinen, 2007).

In this study, we carried out timelapse ground penetrating radar (GPR) surveys in conjunction with a simulated stemflow event to investigate stemflow-induced infiltration by an F. albida tree trunk and root system. We established a survey grid (2.1 m × 2.1 m) around an F. albida, consisting of twelve horizontal and ten vertical parallel survey lines with 0.3 m intervals between them. Two stemflow pulses, each of 20 L, were poured on the tree trunk using a PVC pipe with a 1-mm-diameter hole every 50 mm. The pipe was connected to a plastic funnel and positioned around the tree trunk at 0.4 m from the soil surface. One grid GPR survey was carried out before the stemflow simulation experiment. A total of 40 L of water was used during the experiment. A second survey was carried out after the injection of the first 20 L, while the last survey was carried out after the second stemflow pulse. We collected a total of 66 (3 GPR surveys × 22 survey lines) radargrams using a GSSI (Geophysical Survey System Inc., Salem, NH) SIR 3000 system with a 900-MHz antenna. We therefore obtained for each survey line a pre-wetting and two post-wetting radargrams. Next, we created other forty-four matrixes based on absolute differences between pre- and post-wetting amplitude values. Higher differenced values occurred because of amplitude changes and time shifts related to wave propagation.

The analysis of the differentiated radargrams provided evidence of deep infiltration along the tap roots. The wetted zone extended mainly in-depth providing evidence of the potential role played by the F. albida trees in groundwater recharge processes due to their deep rooting, preferably reaching the groundwater table. Put all together, this study shows a first signal of the importance of accounting for stemflow infiltration in the water balance of agroforestry systems with F. albida trees.

References

Chinen, T., 2007. An observation of surface runoff and erosion caused by acacia albida stemflow in dry savanna, in the south-western republic of Niger 10.

How to cite: Talla, S., Faye, W., Fernandez, G., Lassabatere, L., Angulo-Jaramillo, R., Roupsard, O., Di Prima, S., and Do, F. C.: Evaluating stemflow infiltration through time-lapse ground-penetrating radar surveys on a Faidherbia albida tree in Senegal's Sahel, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5271, https://doi.org/10.5194/egusphere-egu23-5271, 2023.

EGU23-5608 | ECS | Orals | SSS6.3

INFILTRON-mod, a simplified preferential infiltration model for modeling bioretention systems 

Asra Asry, Gislain Lipeme Kouyi, Jérémie Bonneau, Tim D. Fletcher, and Laurent Lassabatere

The preferential flow and transport through unsaturated zones have received considerable attention in the soil and agricultural fields, particularly in increasing discharge rates and amounts and the subsequent transportation of pollutants to groundwater. Over the past century, traditional stormwater control has been replaced by a new low-impact development (LID) approach called " on-site alternative design strategy", which aims to restore or maintain the hydrological functions of urban watersheds by using the capacity of soil and vegetation to retain and filter wastewater pollution, such as bioretention facilities. Therefore, obtaining an accurate estimation of water Infiltration within Bioretention basins is crucial. The Bioretention modeling usually refers to the implicit reservoir base model, which is based on the mass balance and interaction between all the components of the hydrologic cycle (evapotranspiration, overflow, exfiltration to surrounding soils, infiltration through filter media or non-saturated zone, and underdrain discharge) during the time. Among the existing bioretention models, the unsaturated zone or filter medium is considered a homogeneous medium, and the flow is calculated with conceptual infiltration models, such as the Green-Ampt model, the Horton model, etc. Despite our knowledge that the soil reservoir medium is heterogeneous (e.g., coarse materials, plant root systems), it is, therefore, necessary to use a physics-based infiltration model that considers the impact of non-equilibrium and preferential flow on the hydrological and hydrogeochemical performance of bioretention facilities. The INFILTRON-mod, a generic physics-based package, has been proposed for this aim.

This package consists of infiltration models, including the Green-Ampt model and three other specific custom-made models, for uniform and non-uniform flows in soils based on the Darcian approach and mass balance. Uniform and non-uniform flows are modeled using the single and double permeability approaches, respectively. The dual permeability concept assumes that the soil consists of two reservoirs, i.e., the general matrix and fast flow regions, each obeying the Darcian approach. We assumed instantaneous exchange between the two regions. Consequently, we assumed that the wetting fronts in the two reservoirs advance at the same rate. Then the different sets combined with the single or double permeability approaches were tested against numerically generated data using HYDRUS and real experimental data obtained with INFILTRON-exp, "a specific large ring infiltrometer" deployed at several experimental sites.

The results show that the custom-made models lead to different results, with some being better. In addition, considering the dual permeability models improved the fits of the experimental data acquired with the infiltrometer. Then, the improved model was used to model the observations from the Wicks Reservoir bioretention basin (Melbourne, Australia), including the water head in the filter layer and outflow rates, and this led to satisfactory results. The results obtained from this study will be used to develop the INFILTRON-mod package that can be easily integrated into the LID modeling performance for calculating the infiltration element in the unsaturated filter medium.

How to cite: Asry, A., Lipeme Kouyi, G., Bonneau, J., Fletcher, T. D., and Lassabatere, L.: INFILTRON-mod, a simplified preferential infiltration model for modeling bioretention systems, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5608, https://doi.org/10.5194/egusphere-egu23-5608, 2023.

EGU23-6752 | ECS | Orals | SSS6.3

Impact of the use of woodchips as drainage material on infiltration in secondary wastewater effluents infiltration trenches 

Pauline Louis, Laura Delgado-Gonzalez, Vivien Dubois, Laurent Lassabatère, 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. If there is no woodchip-filled soil infiltration surfaces downstream wastewater treatment plant in France, woodchips are however used for decentralized wastewater treatment, even though no study has quantified precisely their efficiency. The understanding of the flow processes and the risk of preferential flows in the woodchip-filled infiltration trenches is a prerequisite for a proper management of these works.

Our study aims at investigating flow regimes in woodchip-filled infiltration trenches. Several woodchip-filled infiltration trenches were studied and analyzed with regards to their infiltration capacity in four decentralized wastewater treatment sites, located in South-West of France on silty-clay soil. Measurements of infiltration capacity of the soil below the woodchips-filled trenches were conducted with infiltration tests according to the Beerkan method (Braud et al., 2005). On each site, two tests were conducted on the bottom of the infiltration trenches after extracting woodchips and two others in the soil at a lateral distance of 1 m from the infiltration trench at the same soil depth, in order to sample the same type of soil. The soil hydraulic functions, i.e., water retention and hydraulic conductivity curves, below the woodchips and in the natural soil profiles were then calculated using the BEST method (Angulo-Jaramillo et al., 2019) and compared. Our findings showed that the use of woodchips locally maintains or even enhances the infiltration rate in the soil below. Moreover, the hydraulic conductivity was 5 to 14 times higher (up to 8600 mm.d-1) in soils under woodchip-filled infiltration trenches than in the reference soils. To explain such positive effects, several hypothesis were formulated and discussed against physical, biogeochemical and ecological factors (woodchips organic amendment, suitable moisture conditions, earthworm communities’ activity). Dye tracer experiment, soil pit, and soil samples (chemical tracings and analyses) revealed the presence of preferential pathways induced by macro fauna and roots plants. An earthworm count showed that the majority of earthworms in the woodchips were 10 times higher than in the natural soil profile. Experiments also showed an organic carbon enrichment in woodchip-filled infiltration trenches soils that could lead to an improvement and stabilization of soils structure.

How to cite: Louis, P., Delgado-Gonzalez, L., Dubois, V., Lassabatère, L., and Clément, R.: Impact of the use of woodchips as drainage material on infiltration in secondary wastewater effluents infiltration trenches, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6752, https://doi.org/10.5194/egusphere-egu23-6752, 2023.

EGU23-7099 | ECS | Orals | SSS6.3

Assessment of long-time series of soil water content through an innovative robust statistical model 

Giada Sannino, Mirko Anello, Marco Riani, Fabrizio Laurini, Marco Bittelli, Massimiliano Bordoni, Claudia Meisina, and Roberto Valentino

The aim of this research is testing a new statistical model able to describe the interaction between soil and atmosphere. The model is based on a robust parametric LTS (Least Trimmed Squares) method and harmonic functions. It has been developed taking into account field measurements of quantities involved in both infiltration and evapo-transpiration phenomena, such as volumetric water content, soil-water potential, air temperature, rainfall amounts and solar radiation. The proposed statistical model allows assessing the volumetric water content at different sites using only time series of daily rainfall amount as input data. The model was applied in different test sites, whose data were assumed by the International Soil Moisture Network (ISMN). In fact, ISMN allows getting free time series of soil and meteorological data from monitoring stations all over the world. This note shows how the proposed model is accurate with respect to field data in estimating the volumetric water content in different soils, climates and depths. Future implications of this research will regard water content predictions, especially in areas where field data are scarce. Since the proposed LTS algorithm is very efficient and the computational workload is rather low, the possibility of coupling it with a slope stability analysis over large areas will be investigated, in order to get a distributed real-time model for shallow landslides susceptibility.

How to cite: Sannino, G., Anello, M., Riani, M., Laurini, F., Bittelli, M., Bordoni, M., Meisina, C., and Valentino, R.: Assessment of long-time series of soil water content through an innovative robust statistical model, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7099, https://doi.org/10.5194/egusphere-egu23-7099, 2023.

In recent years, scientists & physicists faced a question about the macroscope boundary condition interacting with the capillary pressure related to fluid topology. How to integrate the relationship of mechanics between thermal physical quantities (e.g free energy, entropy, & pressure) and fluid topology variables (e.g surface area, mean curvature, & Euler-Characteristic) play a main role in Continuum Mechanics research on low Reynold number flow in porous media in the future. As well, developing the theory approach is our research purpose. The perspective of Newton's Mechanics can not fit the demand of dealing with multiphase porous media flow with a lot of complex and unknown constraints and cross-scoping variables. To build up the dynamic model containing the topology states for multiphase flow in porous media, we introduced two concepts to cross the barricade of Newton mechanics applying to multiphase porous media flow, the generalized coordination and Lagrangian mechanics based on Hamilton’s Principle (The Least Action Principle). The principle shows that any physical quantity changing path making the “Action” as a function(Lagrangian integration) of generalized coordination is holding the minimum. Lagrangian mechanics is widely used in many other frontal research regions depending on the Lagrangian quantity design and generalized coordination setting, including dynamical Structure Analysis, Automatic control theory, electrodynamic and Standard Models in Particle Physics.

We provide the approach from Lagrangian mechanics to describe the thermodynamic and topology changing path during the multiphase flow process. This study recognized the topology state variable as generalized coordination. Furthermore, the Lagrangian quantity and dissipation terms were designed in this research with the kinetic energy, Landau potential, and Rayleigh dissipation function. We combined Steiner’s formula as fluid geometric constraint, dissipation system, and Lagrangian Mechanics to develop the evolution dynamic equations for fluid topology properties. Then we derive the geometrical conservation equations for the topology state variables during the whole dynamics process. Also, the derivation of Darcy’s law finished from Lagrangian mechanics under saturated and steady conditions.

 

How to cite: Liu, C. Y. and Hsu, S. Y.: Thermodynamic and Topology path equations, Multiphase flow in porous media with Steiner’s Formula & Lagrangian Mechanics, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7331, https://doi.org/10.5194/egusphere-egu23-7331, 2023.

EGU23-8089 | ECS | Orals | SSS6.3

Dynamic neutron and X-ray three-dimensional imaging of fluid flow and mixing during mineral precipitation in porous rocks 

Paiman Shafabakhsh, Tanguy Le Borgne, Joachim Mathiesen, Gaute Linga, Benoît Cordonnier, Anne Pluymakers, Anders Kaestner, and François Renard

Flow and mixing processes in porous media control many natural and industrial systems, such as microbial clogging, oil extraction, and effluent disposal. In many systems, the porosity may evolve during mineral precipitation, such as in rocks, and control fluid mixing and fluid transport properties. Here, we use three-dimensional in situ dynamic neutron and X-ray micro-tomography imaging to explore fluid transport into Berea sandstone core samples during in-situ carbonate precipitation. Neutron imaging can track fluid flow inside the rock, whereas X-ray imaging illuminates the regions where mineral precipitation occurs. We control the precipitation of calcium carbonate in the rock through reactive-mixing between solutions containing CaCl2 and Na2CO3. By solving the advection-diffusion equation using the contrast in neutron attenuation from time-lapse images, we derive the 3D velocity field of the injected fluids and characterize the evolution of the permeability field into the rock during mineral precipitation. We also investigate the mixing between heavy water and a cadmium solution under the influence of mineral precipitation. Results show that, under the effect of mineral precipitation, a wide range of local flow velocities develop in the sample, under the same fluid injection rate, and we quantify the distribution of flow velocities in the sample. Moreover, we observe more efficient mixing between heavy water and a cadmium solution after mineral precipitation. The finding of this experimental study is useful in progressing the knowledge in the domain of reactive solute and contaminant transport in the subsurface.

How to cite: Shafabakhsh, P., Le Borgne, T., Mathiesen, J., Linga, G., Cordonnier, B., Pluymakers, A., Kaestner, A., and Renard, F.: Dynamic neutron and X-ray three-dimensional imaging of fluid flow and mixing during mineral precipitation in porous rocks, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8089, https://doi.org/10.5194/egusphere-egu23-8089, 2023.

EGU23-8263 | Posters on site | SSS6.3

Preferential flow in a long-term no-tillage experiment on a silt loam soil in Mediterranean conditions 

Jorge Lampurlanes, Rasendra Talukder, Daniel Plaza-Bonilla, Carlos Cantero-Martínez, and Ole Wendroth

Water flow throughout the soil allows and regulates life on the Earth's surface. Knowing where this flow mainly takes place (preferential flow) is critical i) to measure it appropriately, ii) to take advantage of it for a more efficient use of water. Soil management has great impact on soil hydrological properties and can have an effect at catchment scale, while knowing within plot variability can improve flow estimations at plot level. On a 22-year-old experiment comparing intensive (IT) and no-tillage (NT), soil hydrological properties were determined within (W-row) and between (B-row) crop rows several times along two cropping years (2018-19 and 2019-20) on undisturbed soil cores. Tillage significantly influenced soil water retention being higher under IT than NT in the wet range above -10 cm soil matric potential. The cause was a larger volume of mesopores (1000 to 300 µm in diameter) in IT. Despite that, hydraulic conductivity was significantly higher in NT in this range, especially because mesopores in NT revealed greater pore continuity than in IT. No differences in soil hydraulic conductivity were found at lower soil matric potentials. These results suggest that, although IT increases soil porosity creating new pores regularly, these pores are less interconnected than the long-standing pores created in NT by the roots and fauna activity. The lower hydraulic conductivity in IT can reduce infiltration and increase runoff losses resulting in less water available for crops.  The position with respect to the crop row (W-row or B-row), did not have an impact on soil water retention but on soil hydraulic conductivity, that was significantly higher under W-row than B-row above -10 cm H2O soil water potential. Although the volume of pores of different size classes did not differ between both row positions, continuity of macropores (>1000 µm) was significantly higher under W-row than B-row and tended to be higher W-row also for the other pore classes. The effect of the sowing slot, the growth of the plant roots, and the protective effect of the plant cover itself can explain the preferential flow pathway found W-row. The differences between flow regimes under different tillage systems found at the small scale highlight the importance of considering the site-specific management impacts on soil structure and pore geometry, as these will affect hydrological flow processes at the catchment scale. Differences between positions with respect to the plant row need to be considered to properly characterize hydrological flow phenomena in soils, even under the same management practices.

How to cite: Lampurlanes, J., Talukder, R., Plaza-Bonilla, D., Cantero-Martínez, C., and Wendroth, O.: Preferential flow in a long-term no-tillage experiment on a silt loam soil in Mediterranean conditions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8263, https://doi.org/10.5194/egusphere-egu23-8263, 2023.

The macropore-matrix mass transfer of water and solutes is an important aspect of non-equilibrium-type of preferential flow in structured soils. For a representative soil volume, effective mass transfer parameters depend on heterogeneous local properties of the soil macropore structure, its geometry and shape, and on properties at macropore walls that can differ from those of the matrix with respect to texture, organic matter, bulk density, and porosity. These affect the soil pore system locally with respect to hydraulic, mechanic, bio-geo-chemical, and other processes. Clayey aggregate skins, for example, may be more due to plastic deformation but can restrict water exchange; solutes may become adsorbed along macropore surfaces and released under changing condition. Still relatively little is known about formation of such local biological hotspots in soil, on how to determine the local mass transfer parameters, and how to upscale to the scale of the soil volume, and on the interrelations between all the individual local properties and the combined effect on relevant bulk soil transport processes. The present contribution reviews recent experimental and modeling work including field and lab percolation experiments using the movement of bromide, Brilliant Blue, iodide, and Na-Fluorescein to identify the flow paths and parameter optimization approaches for determining such parameters. It seems that preferential transport of reactive solutes depends even more strongly on the geometry and properties at flow paths surface than the water flow itself or the movement of conservative solutes. The identification and determination of effective mass transfer parameters in two-domain models remains a challenge when considering that local changes in the soil structure are highly dynamic during the vegetation, the seasons, and due to soil management.

How to cite: Gerke, H. H.: Characterization of macropore-matrix mass transfer parameters in two-domain preferential flow models, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8635, https://doi.org/10.5194/egusphere-egu23-8635, 2023.

EGU23-13041 | ECS | Posters on site | SSS6.3

Coupled surface and subsurface flows for earthen embankments using finite-volume methods 

Nathan Delpierre, Hadrien Rattez, and Sandra Soares-Frazao

The majority of breaching of earthen embankments is triggered by overtopping flows or waves. These phenomena are usually simulated using the shallow-water equations complemented by the Exner equation to reproduce the progressive erosion of the embankment and the growth of the breached area. Such an approach neglects the degree of water saturation in the embankment as well as the flow through the embankment that can alter the stability of this structure by reducing the soil’s mechanical strength. This is enhanced in case of severe droughts, as observed during the summer 2022, when desiccation cracks were observed in several embankments, leading to preferential paths for the water to infiltrate the soil during subsequent rainfalls.

In this paper, we present a combined approach in which the degree of saturation and the flow through the embankment are solved using the Richards equation that is coupled to the system of shallow-water equations for the flow over the embankment. The groundwater flow is simulated by solving the 2D Richards’s equation on an unstructured triangular mesh with an implicit finite volume scheme, based on a direct gradient evaluation. The shallow-water equations are solved in one dimension on a structured mesh using an explicit scheme with Roe’s formulation for the fluxes.

Several tests were performed to demonstrate the capacity of the proposed Richards’s solver to reproduce transient groundwater flows and compared to results from the literature obtained with different numerical approaches. In the same way, the shallow-water’s equation solver was validated by comparison with previous experimental results from the literature.

Then, by coupling both models using a source term, a mass-conservative coupled model was obtained. It became possible to simulate the evolution of the pore water content inside a dike subjected to overtopping for different initial conditions. Further work will focus on the interaction of dike’s related flows with erosion and mechanical failure processes, and on the validation of the model by comparisons with experimental data that will be obtained with medium-scale tests.

How to cite: Delpierre, N., Rattez, H., and Soares-Frazao, S.: Coupled surface and subsurface flows for earthen embankments using finite-volume methods, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13041, https://doi.org/10.5194/egusphere-egu23-13041, 2023.

EGU23-14883 | ECS | Orals | SSS6.3

Could hydraulic parameters variation affect the vegetation development in treatment wetlands? 

Liviana Sciuto, Alessandro Sacco, Giuseppe L. Cirelli, Antonio C. Barbera, and Feliciana Licciardello

Abstract: Treatment wetlands (TWs) are complex ecosystems due to variable conditions of hydrology, soil hydraulics, plants and microbiological species diversity and mutual interactions. On the one hand, hydraulics plays a vital role on the treatment performance and on the life cycle of TWs, on the other hand, the vegetation substantially contributes to remove and to retain pollutants. As well known, the unavoidable and progressive clogging phenomenon in TWs affects their hydraulics. A lack of knowledge still remains to what extend hydraulic parameters variation can affect the vegetation developments in TWs. To answer to this question, the Phragmites australis development in comparison with hydraulic characteristics was monitored in a 8 years old - horizontal flow (HF) TW located in Mediterranean area (Eastern Sicily, Italy). Data were collected in nine observation points equally distributed along three transects established at 8.5 m (T1), at 17 m (T2) and at 25.5 m (T3) from the inlet. The falling head (FH) test was conducted to assess the hydraulic conductivity (Ks) variation in the HF-unit. Residence time distribution (RTD) analysis was performed to evaluate the real hydraulic retention time (HRT) and the hydraulic efficiency parameter (λ). Finally, the saturation method was applied for substrates porosity (φ) determination. In the HF-TW a morphological and chemical characterization of Phragmites australis above-ground biomass was carried out in 2022. In particular, plants density (in terms of culms number) and height (m) were measured at the end of the growing season (July). In each transect of the HF-TW, fresh weight (g), dry matter (DM, %), ash (%), volatile solids (VS, %), pH, Total Kjeldahl Nitrogen (TKN, % of DM) and fiber content (cellulose, hemicellulose and lignin) were estimated. Preliminary results showed a strong positive regression between DM and both Ks (R2 = 0.78) and porosity values (R2 = 0.97) observed in the HF-TW. This study could contribute to help plant operators to understand hydraulic characteristics effects on the biomass, to improve TWs treatment efficiency, system management and lifespan.

Keywords: Wastewater treatment, Phragmites australis, plants growth, hydraulic characteristics, substrate.

Acknowledgments: This research was funded by the University of Catania-PIAno di inCEntivi per la RIcerca di Ateneo 2020/2022—Linea di Intervento 3 “Starting Grant” and the PhD Course in Agricultural, Food and Environmental Science (Di3A, University of Catania).

How to cite: Sciuto, L., Sacco, A., Cirelli, G. L., Barbera, A. C., and Licciardello, F.: Could hydraulic parameters variation affect the vegetation development in treatment wetlands?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14883, https://doi.org/10.5194/egusphere-egu23-14883, 2023.

EGU23-16621 | ECS | Orals | SSS6.3

Spatio-temporal analysis of soil surface hydraulic properties in a semi-arid agroforestry system of the Senegalese groundnut basin 

Waly Faye, Didier Orange, Seydou Talla, Frederic Do, Christophe Jourdan, Olivier Roupsard, Abdoulaye Faty, Awa Niang, Alioune Kane, Simone Di prima, Raphael Angulo-Jaramillo, and Laurent Lassabatere

In Senegal, the groundnut basin is the main agricultural region under a semi-arid climate, heavily cultivated in an agrarian system combining agricultural rotation and agroforestry dominated by Faidherbia albida trees. The soils of the groundnut basin, essentially sandy, have a low water retention capacity. In this area, water is a limiting factor, and the climate variability represents an additional constraint on an already precarious agricultural production system. It is therefore essential to improve knowledge on water saving practices and soil humidity dynamics. The management of water resources in agricultural fields requires reliable information about soil hydraulic properties, which control the partition of rainfall into infiltration and runoff, and their spatio-temporal variability.

To investigate the variability of soil hydraulic parameters we have carried out infiltration measurement in open space without tree and below tree canopies. A total of 24 infiltration measurements were carried out using an automatic single-ring infiltrometer in the nearby of each plot (4 measurements × 6 plots), and after removing the first 10 cm of uncompacted sand. The infiltration tests were carried out in June, October and December, respectively before, during and after the crop season. We used the Beerkan Estimation of Soil Transfer Parameters (BEST) method to retrieve the soil hydraulic parameters from infiltrometer data and field measurements of soil porosity, initial and saturated soil water contents and soil bulk density.

The statistical analysis of the data showed a high variability during the cultivating period, both in time and space, especially of the saturated soil hydraulic conductivity Ks. However, the Ks seems higher under tree cover, around 0.186 mm/s, for 0.167mm/s without any tree canopy influence.  Despite the expected homogeneity of the investigated sandy soil, the presence of the perennials triggered a patchy distribution of soil hydraulic conditions. These preliminary results evidenced the importance of taking into account parameters variability and landscape structure when simulating soil water dynamics in the Senegalese groundnut basin.

How to cite: Faye, W., Orange, D., Talla, S., Do, F., Jourdan, C., Roupsard, O., Faty, A., Niang, A., Kane, A., Di prima, S., Angulo-Jaramillo, R., and Lassabatere, L.: Spatio-temporal analysis of soil surface hydraulic properties in a semi-arid agroforestry system of the Senegalese groundnut basin, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16621, https://doi.org/10.5194/egusphere-egu23-16621, 2023.

EGU23-16729 | Orals | SSS6.3

Swell ways to measure how plant roots, biological exudates and temporal weathering impact soil structure and infiltration characteristics 

Paul Hallett, Maria Marin, Hannah Balacky, Md Dhin Islam, Annette Raffan, Erika Salas Hernández, and Utibe Utin

Time results in large changes to soil infiltration characteristics due to weather, mechanical stability and the action of biology.  Even as the water status changes in a wetting soil, swelling may alter infiltration characteristics. Our laboratory has developed several novel approaches to measure how soil water infiltration characteristics vary over time and are influenced by biological processes or weathering stresses.  The measurements are often combined with an assessment of mechanical properties and pore structure so that underlying processes driving soil structure dynamics can be disentangled. An overview and a discussion of the benefits and challenges of the approaches will be provided.

A small-scale infiltrometer (sub-mm size) was adapted to allow for measurements of water infiltration and repellency at aggregate or rhizosphere scale.  It has been applied in numerous studies exploring the impacts of biological exudates, plant roots and weathering.  More recent research has compared results from this infiltrometer with X-Ray CT imaging to determine the impacts of soil pore structure on infiltration characteristics.  A challenge with a small-scale infiltrometer is experimental error caused by tip contact with the soil and the shape of the wetting front.  This has been demonstrated from repeated tests on repacked sands and sieved soils.

If soil aggregates, spatial variability or hot spots like the rhizosphere are not of interest, conventional infiltration measurements with flow across the entire surface of a soil core offer less laboratory experimental error.  We used this approach to explore the dynamics of soil wetting and swelling as affected by a range of biological exudates.  Repacked soil discs were wetted by a sintered disc attached to a weighed water reservoir, with swelling measured dynamically in horizontal and vertical directions using infra-red sensors.  Whereas polygalacturonic acid (PGA) had no affect on sorptivity, increasing concentrations of lecithin and actigum decreased sorptivity, likely due to different mechanisms of surface tension and viscosity respectively.  Total swelling was positively correlated with water sorptivity for both lecithin and actigum, suggesting that an expanding pore structure in the unconfined soil discs may enhance water uptake rates.  Biological exudates therefore have dual impacts on decreasing wetting and swelling rates, which will affect soil structural stability.

Current research is exploring soil structural stability impacts on soil hydrological properties over time.  This includes field studies exploring the impacts of soil amendments and management practices, and laboratory studies with controlled structural changes from wetting/drying and mechanical stresses.  In this work, changes in water infiltration due to stresses are explained from pore structure analysis with X-Ray CT imaging and mechanical stability tests.

How to cite: Hallett, P., Marin, M., Balacky, H., Islam, M. D., Raffan, A., Salas Hernández, E., and Utin, U.: Swell ways to measure how plant roots, biological exudates and temporal weathering impact soil structure and infiltration characteristics, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16729, https://doi.org/10.5194/egusphere-egu23-16729, 2023.

EGU23-17539 | Posters on site | SSS6.3

Subsurface preferential flow occurrence and relevance in agricultural hillslopes: experimental evidence 

Vilim Filipović, Annelie Ehrhardt, and Horst H. Gerke

Preferential flow (PF) has long been discussed as potential cause for unintended contamination of ground and surface waters with agrochemicals. In agricultural soil landscapes, especially along hillslopes, the mostly vertically-directed preferential flow (VPF) of infiltrating water in unsaturated topsoil horizons fosters the formation of water saturated pore regions at less permeable subsoil horizons that can trigger laterally-oriented preferential flow (LPF) along subsurface preferred flow paths. The occurrence of LPF processes depends on complex interrelations between soil properties and subsurface structures, climatic conditions, crop development, and agro-management, among other factors. Field observations in hillslope agricultural soil landscapes to quantify the relevance of LPF are rare. Here we present studies on LSF processes at two contrasting sites. One is the CarboZALF-D, located in northeastern Germany in hummocky arable soil landscape (Luvisol and Regosol soil types). The second (SUPREHILL) is an agricultural vineyard hillslope with Stagnosol soils located in central Croatia. Both sites show erosion and tillage effects in the soils along slopes. An extensive network of soil moisture sensors, suction cups, and lysimeters are installed at both sites. Relevant soil physical, hydraulic, and chemical properties have been determined for running simulation models. The SUPREHILL site has been equipped also with self-constructed subsurface runoff collection system, while at CarboZALF-D site, LPF was captured by a field tracer experiment; and in the laboratory, LSF along a soil horizon boundary was studied on undisturbed soil monoliths. Different subsurface flow processes were identified and captured at the two sites, for SUPREHILL shortly below the topsoil along the lower permeable Btg horizon and for CarboZALF-D at buried topsoil under colluvium and along coarser-textured bands within compact glacial till C-horizon. The collected experimental results revealed the qualitative importance of LPF and transport in the subsurface; the presented experimental data will be used for the model-based quantitative analysis of the LPF related processes.

How to cite: Filipović, V., Ehrhardt, A., and Gerke, H. H.: Subsurface preferential flow occurrence and relevance in agricultural hillslopes: experimental evidence, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17539, https://doi.org/10.5194/egusphere-egu23-17539, 2023.

EGU23-2141 | ECS | Posters on site | HS8.2.1

Estimating hydraulic conductivity using extended leak-off test conducted during drilling large-diameter borehole 

Yeonguk Jo, Yoonho Song, and Sehyeok Park

Extended leak-off test (XLOT) is one of the in-situ tests, routinely conducted to evaluate integrity of the cased and cemented wellbores during deep borehole drilling, as well as in situ hydraulic properties at a casing shoe depth.

We introduce results of the XLOT conducted in a large diameter borehole, which is drilled for installation of deep borehole based geophysical monitoring system to monitor micro-earthquakes and fault behavior of major linearments in the subsurface. The borehole was planned to secure a final diameter of 200 mm (or more) at a depth of ~1 km deep, with 12" diameter wellbore to intermediate depths, and 7-7/8" (~200 mm) to the bottom hole depths.

We drilled first the 12" diameter borehole to approximately 504 m deep and installed API standard 8-5/8" casing, then cemented the annulus between the casing and bedrock. Then we carried out the XLOT, for several purposes such as confirming casing and cementing integrity, as well as estimating in-situ stress and hydraulic conductivity at the casing shoe depth. To that end, we drilled 4 m length interval to directly inject water and pressurize into the rock mass using the upper API casings. During the XLOT, we recorded flow rates and interval pressures in real time. Based on the logs, we tried to analyze hydraulic conductivity of the test interval, and compare the results with previously reported hydraulic properties measured in other ways.

How to cite: Jo, Y., Song, Y., and Park, S.: Estimating hydraulic conductivity using extended leak-off test conducted during drilling large-diameter borehole, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2141, https://doi.org/10.5194/egusphere-egu23-2141, 2023.

EGU23-2274 | ECS | Orals | HS8.2.1

Evaluating solute-Trapping Induced Non-Fickian Transport in Partially Saturated Porous Media 

Ilan Ben-Noah, Juan J. Hidalgo, Joaquin Jimenez-Martinez, and Marco Dentz

We study the upscaling of pore-scale solute transport in partially saturated porous media at different saturation degrees. The interaction between structural heterogeneity, phases distribution and small-scale flow dynamics induces complex flow patterns and broad probability distributions of flow. In turn, this spatial distribution of flow velocities, at the pore scale, induces irregular (non-Fickian) transport of dissolved substances (e.g., contaminants), causing an earlier arrival and longer tailing, which may have grave consequences in underestimating risk assessments and prolonged cleanup times of contaminated sites.

Here, we suggest an integrated continuous time random walk (CTRW) modeling framework, which accounts for also the entrapping of particles in zones of low flow velocities, to estimate the resident times of solutes in the media. Furthermore, comparing the results of the CTRW model to a well-established numerical simulation method allows a phenomenological evaluation of the model's physical parameters for different conditions (i.e., volume of entrapped air, mean water flow rate, or solute molecular diffusion coefficient).   

In this study we show that entrapped air promotes preferential solute transport and solute trapping in low flow regions. Moreover, we demonstrate that the trapping frequency and trapping time depend on the interaction between advection and diffusion (i.e., the Péclet number). An integrative CTRW model captures the effects of trapping in stagnant regions and preferential transport on non-Fickian dispersion of solutes.

How to cite: Ben-Noah, I., Hidalgo, J. J., Jimenez-Martinez, J., and Dentz, M.: Evaluating solute-Trapping Induced Non-Fickian Transport in Partially Saturated Porous Media, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2274, https://doi.org/10.5194/egusphere-egu23-2274, 2023.

EGU23-3033 | ECS | Posters on site | HS8.2.1

Land subsidence induced by groundwater withdrawal: from conceptual model to Hydromechanical model in Chousui River Alluvial Fan, Taiwan 

Gumilar Utamas Nugraha, Chuen-Fa Ni, and Thai Vinh Truong Nguyen

The Choushui River Alluvial Fan (CRAF) is facing serious land subsidence problems. In recent years, the main subsidence areas have gradually moved inland, causing security issues for the Taiwan High-Speed Rail (THSR) in the Yunlin county. Although pumping groundwater along the high-speed railway is forbidden, the problem of sinking land has remained. The causes of land subsidence can be multiple and complex. There are discussions about the causes of land subsidence in the Chousui River Alluvial Fan. This study aimed to develop a hydromechanical land subsidence model in this groundwater basin. The modeling process is divided into two broad parts: the groundwater flow model and the hydromechanical/land subsidence model. The development of the model was focused on the severe area of land subsidence in this basin; for this situation, the so-called “site specific model” was developed. Another reason this study used the site-specific model is that the Taiwan government has installed an integrated land subsidence monitoring system in the severe area, including Multilevel Compacting Well (MLCW), GNSS, and Groundwater observation well. This abundant data can be used when calibrating the groundwater flow and mechanical model. The modeling process starts with the construction of site-specific conceptual modeling derived from the basin scale conceptual modeling. This process revealed that the site consists of four aquifers and four aquitard layers with various thicknesses. The next process was creating a numerical groundwater model that began with creating a grid of the model domain. The model consists of fifty rows and fifty columns with ten by-ten meter grid cells and eight layers representing four aquifers and four aquitards. For perimeter boundary conditions, the model has specified head boundary conditions on the east and west part and no-flow boundary conditions on the north, south, and bottom of the model. the hydraulic and mechanical for the initial input of the model were generated using the previous study in this basin. Groundwater flow calibration processes were done using the PEST package. The model was evaluated using a multi-criteria performance meter: R-squared, root mean squared error (RMSE), mean absolute error (MAE), and Nash Sutcliffe Error (NSE). The calibration process for the groundwater flow model shows an excellent result for both mechanical and groundwater flow. The next step is modeling simulated subsidence using scheduling pumping using a different pumping rate scenario. This simulation aimed to reduce subsidence using calibrated pumping rate value but the difference in time of pumping. The result shows a significant subsidence reduction with scheduling pumping in a certain well. Any stakeholder can consider this result to reduce subsidence in the Chousui River Alluvial Fan.

How to cite: Utamas Nugraha, G., Ni, C.-F., and Vinh Truong Nguyen, T.: Land subsidence induced by groundwater withdrawal: from conceptual model to Hydromechanical model in Chousui River Alluvial Fan, Taiwan, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3033, https://doi.org/10.5194/egusphere-egu23-3033, 2023.

Experimental observation and measurement are essential to fundamentally understanding the processes that govern fluid flow and mass transport in rough-walled fractures. The micro-PIV (micro-Particle Image Velocimetry) technique has been introduced for flow visualization inside microscale rough-walled fractures. However, the methodology for mass transport visualization has yet to be established, which is crucial for the analysis/quantification of mass transport and dispersion in rough-walled fractures. This study presented the improved micro-PIV technique to visualize mass transport and measure solute concentration in rough-walled rock fractures. Calibration processes for determining the solute concentration from the measured fluorescence intensity were presented, and measured concentrations were applied to the solute transport and dispersion analyses to validate the measurement technique. The microscopic imaging and analysis demonstrated the transition from macrodispersion to Taylor dispersion-dominant transport. As the fluid velocity increased, higher concentration gradients occurred across the fracture aperture, enabling the solute to break through rapidly along the main flow channel in the middle of the fracture aperture. We successfully visualized channelized solute transport associated with eddies that accounts for Taylor dispersion and non-Fickian transport. This technique enables phenomenon-based experimental research on fluid flow and solute transport in microscale rock fractures, which used to remain in the realm of numerical simulations. Our improved visualization technique will contribute to experimentally elucidating mass transport processes in rough-walled rock fractures.

How to cite: Kim, D. and Yeo, I. W.: Microscopic imaging technique for solute transport in rough-walled rock fractures using micro-PIV, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3285, https://doi.org/10.5194/egusphere-egu23-3285, 2023.

EGU23-4020 | ECS | Orals | HS8.2.1

Thin film flow: fluid transport via thin liquid films in slow porous media flows 

Marcel Moura, Paula Reis, Gerhard Schäfer, Renaud Toussaint, Eirik Grude Flekkøy, Per Arne Rikvold, and Knut Jørgen Måløy

The standard liquid transport processes in porous media happens through a network of interconnected pore bodies and pore throats (here called the primary network). When a non-wetting phase displaces a wetting phase from a porous sample (drainage), thin films of the wetting phase are bound to be left on the surface of the constituting grains (for example when air displaces water from a porous rock, thin films of water are left behind, covering the rock grains). Under certain conditions, isolated liquid films can eventually merge, forming a secondary network of interconnected films and capillary bridges (see red arrows in the figure) that can effectively enhance the overall connectivity of the medium and act as a new pathway for fluid transport. We have performed experiments using transparent networks with the objective of studying transport processes that are enhanced by film flow. Our setup allow us to directly visualize the secondary network in the sample and we have shown how fluid bodies that are not linked via the primary network can actually be connected via the secondary network. This connection has important consequences for processes such as the dispersion of pollutants in soils and the transport of nutrients to plants in arid regions.

 

 

References

Moura, E. G. Flekkøy, K. J. Måløy, G. Schäfer and R. Toussaint, “Connectivity enhancement due to film flow in porous media,” Phys. Rev. Fluids 4, 094102 (2019).

Moura, K. J. Måløy, E. G. Flekkøy, and R. Toussaint, “Intermittent dynamics of slow drainage experiments in porous media: Characterization under different boundary conditions,” Front. Phys. 7, 217 (2020).

How to cite: Moura, M., Reis, P., Schäfer, G., Toussaint, R., Flekkøy, E. G., Rikvold, P. A., and Måløy, K. J.: Thin film flow: fluid transport via thin liquid films in slow porous media flows, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4020, https://doi.org/10.5194/egusphere-egu23-4020, 2023.

EGU23-4701 | Posters on site | HS8.2.1

Evaluating groundwater responses to earthquakes using hydrological and environmental tracer data 

Dugin Kaown, Dong-Chan Koh, Jaemin Lee, Jaeyoun Kim, and Kang-Kun Lee

Environmental tracer data were applied to assess chemical signatures of deep fluid in the fault zones in the southeastern part of South Korea. After MW 5.5 Pohang Earthquake in November 2017, hydrogeochemical and environmental tracer data from groundwater samples around epicenter were monitored from 2017 to 2021. Monitoring wells significantly responded to the earthquakes were selected to evaluate temporal variations of environmental tracer data in the groundwater system. The southeastern part of South Korea shows a distinctive NNE-directed geomorphological feature with several strike-slip fault systems and two wells are closely located to this fault. One monitoring station, KW5, is closely located to the Ulsan Fault, which is a reverse. 3He/4He was slightly increased in most of groundwater samples from monitoring wells after MW 5.5 Pohang Earthquake, while 3He/4He decreased in some groundwater samples from wells around reverse fault (Ulsan fault). Especially, 3He/4He in the wells of KW5 station closely located to the Ulsan Fault considerably decreased after the earthquake. However, the concentrations of Na, Ca, SO4 and HCO3 increased around wells in Ulsan Fault after the earthquake. In this study, the response of aquifer system after earthquakes was compared to assess the differences in chemical changes of fluid around strike-slip and reverse faults using hydrogeochemical and environmental tracer data.

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. 2022R1A5A1085103).

How to cite: Kaown, D., Koh, D.-C., Lee, J., Kim, J., and Lee, K.-K.: Evaluating groundwater responses to earthquakes using hydrological and environmental tracer data, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4701, https://doi.org/10.5194/egusphere-egu23-4701, 2023.

The fracture density of rock could create the applying shock waves phase difference at the laboratory scale. For using this technology in determining the stress status along the wave propagating path, removing unnecessary noise is the most crucial task. In this study, a machine learning method with Long short-term memory (LSTM) algorithm to retreat the signals from sophisticated seismograms is proposed. The primary analyzing target is data across the 2022 Taitung, Eastern Taiwan seismic event and another micro-seismic data set associated with a surface crack on a hill of Ping-Tong, southern Taiwan. It is found that there is no phase difference among vertical and horizontal components from the same record, when comparing the difference between two various records then the result is distinct. The detecting sub-surface crack density via phase difference has increased in some seismic data pairs of eastern Taiwan after the rupture of the 2022 Taitung earthquake. The machine learning method with LSTM helps to elevate the data retrieval accuracy which cannot be done by conventional Fast Fourier Transformation (FFT). Records from stations adjacent to the hypocenter offer better agreement in phase difference measurement, the higher signal possibly causes it to noise ratio (SNR) in the such neighborhood.

 

Keywords: phase difference, machine learning, LSTM, crack density, stress field

How to cite: Yu, T.-T. and Peng, W. F.: Inverting the Subsurface Fracture Density by Detecting the Phase Difference of Various Seismic wave with Machine Learning, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4868, https://doi.org/10.5194/egusphere-egu23-4868, 2023.

EGU23-6531 | Posters on site | HS8.2.1

About the possibility of monitoring groundwater fluxes variations through active-DTS measurements 

Olivier Bour, Nataline Simon, Nicolas Lavenant, Gilles Porel, Benoît Nauleau, and Maria Klepikova

The monitoring of temporal variabilities of groundwater flows is a critical point in many hydrogeological contexts, especially for the characterization of coastal aquifers, sub-surface heterogeneities or else groundwater/stream interactions. Considering the lack of available methods, we investigate the possibility of monitoring and quantifying groundwater fluxes variations over time through active-Distributed Temperature Sensing (DTS) measurements. Active-DTS, consisting in heating a fiber optic cable, performs very well for investigating the spatial distribution of groundwater fluxes but the method has never been tested to continuously monitor groundwater fluxes changes. In this context, both numerical simulations and sandbox experiments were performed in order to assess the sensitivity of temperature elevation to variable flow conditions. Results first demonstrate that when a flow change is followed by a long-enough steady-state flow stage the temperature elevation stabilizes independently of previous fluxes conditions. Thus, the stabilization temperature can easily be interpreted to estimate groundwater fluxes using the analytical model commonly used under steady flow conditions to interpret active-DTS measurements. Under certain flow conditions, depending on the nature of flow variations, the approach also allows the continuous monitoring of fluxes variations over time. If instantaneous flow changes occur, the superposition principle can even be used to reproduce the temperature signal over time. In summary, we demonstrated through these preliminary results the possibility of for monitoring and/or quantifying the temporal dynamic of groundwater fluxes at different temporal scales including diurnal and periodic fluxes variations, which open very interesting perspectives for the quantification of subsurface processes.

How to cite: Bour, O., Simon, N., Lavenant, N., Porel, G., Nauleau, B., and Klepikova, M.: About the possibility of monitoring groundwater fluxes variations through active-DTS measurements, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6531, https://doi.org/10.5194/egusphere-egu23-6531, 2023.

EGU23-6663 | ECS | Posters on site | HS8.2.1

3D characterisation of the Yorkshire Wolds chalk aquifer, UK 

Laura Burrel, Rowan Vernon, Jon Ford, Richard Haslam, Tom Randles, Helen Burke, Mark Woods, Jonathan Lee, and Katie Whitbread

The Yorkshire Wolds Chalk aquifer, provides the main source of water supply in East Yorkshire and the city of Hull, which have a population over 900.000. Its structural configuration, including the effects of faulting, influence groundwater flow across the region. However, stratigraphic and structural characterisation is challenging due to limited bedrock being exposed at surface, with most of its extension covered by Quaternary glacial deposits and arable fields and pastures. While the coastal sections have been well characterised through the years, inland areas of the Yorkshire Wolds Chalk aquifer have not been systematically mapped since the late 19th century. The available maps do not reflect present-day stratigraphic divisions or current tectonic understanding, leading to an underestimation of the structural complexity of the aquifer.

A multi-faceted approach to geological mapping is being undertaken in the region by the British Geological Survey, in collaboration with the Environment Agency and Yorkshire Water, integrating remote sensing, targeted field mapping, palaeontological analysis, 2D onshore seismic interpretation and borehole records. The objective of the project is to deliver an up-to-date geological map and structural model of the Chalk bedrock and Quaternary deposits which will impact on the groundwater resources management.

The recent mapping campaigns have led to identifying and characterising numerous new faults in different structural trends, which were not present on previous maps. It has also led to a significant shifting of stratigraphic contacts and formation thicknesses, which have more lateral variability than previously thought. We present some of the most recent updates on the Yorkshire Wolds Chalk aquifer map, which highlight the importance of revising old cartography using modern tectonic and stratigraphic concepts and a multidisciplinary approach to field data collection and compilation. We are also interested in discussing with the hydrogeologist community how to better capture and represent structural complexity around fault zones, so it has an impact on hydrogeological modelling.

How to cite: Burrel, L., Vernon, R., Ford, J., Haslam, R., Randles, T., Burke, H., Woods, M., Lee, J., and Whitbread, K.: 3D characterisation of the Yorkshire Wolds chalk aquifer, UK, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6663, https://doi.org/10.5194/egusphere-egu23-6663, 2023.

EGU23-6813 | Posters on site | HS8.2.1

An interactive map platform for groundwater data visualization and real-time numerical modeling 

Chuen-Fa Ni, I-Hsien Lee, Gumilar Utamas Nugraha, and Thai Vinh Truong Nguyen

Accurate assessment of groundwater resources relies on sufficient measurements and efficient analysis tools. The integrated technologies and multidisciplinary knowledge of groundwater have enhanced the understanding of dynamics in groundwater systems. Taking advantage of wide developments in computer sciences and web services, the web platform provides an excellent open environment for groundwater investigations. Most groundwater-relevant web platforms are mainly focusing on data visualization. The data, such as points, polylines, polygons, and pre-analysis results (i.e., the figures) overlap a street map to indicate the locations of interest and quantify the influenced regions of groundwater hazards. Such a one-way interaction framework has significantly limited the implementations of measurement data and groundwater-relevant applications. The study aims to develop an online web-based platform for groundwater data visualization, temporal and spatial data analysis, mesh generation and flow modeling. The study integrates multiple program languages to bridge the data flow and online visualization. The interactive real-time web environment enables users to screen temporal and spatial measurements on the web map, conduct online data analyses, and develop numerical groundwater models. With a well-designed database and numerous modules for data analyses and modeling, the platform allows users to share data and develop collaborative activities. The built-in analysis tools can also improve the efficiency of groundwater management and decision-making processes.

How to cite: Ni, C.-F., Lee, I.-H., Nugraha, G. U., and Nguyen, T. V. T.: An interactive map platform for groundwater data visualization and real-time numerical modeling, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6813, https://doi.org/10.5194/egusphere-egu23-6813, 2023.

EGU23-6983 | Orals | HS8.2.1

Surface and subsurface mapping of the Flamborough Head Fault Zone to inform groundwater management in the Yorkshire Wolds, UK. 

Rowan Vernon, Laura Burrel, Jon Ford, Richard Haslam, Tom Randles, Dave McCarthy, Mark Woods, and Helen Burke

The Flamborough Head Fault Zone (FHFZ) is a regionally-significant structural zone in northeast England which dissects the Upper Cretaceous Chalk Group, a 500 m thick limestone succession which is a principle aquifer and main source of water supply in the region. The geometry and physical characteristics of the Chalk succession, including the effects of faulting, influence groundwater flow across the region. Consequently, understanding the architecture of the FHFZ is vital to sustainably managing water resources in this area.

The FHFZ marks the southern extent of the Cleveland Basin and the northern margin of the Market Weighton Block and has a complex history of Mesozoic-Cenozoic extension and compression. It is predominantly comprised of east-west trending faults which form a graben that is dissected by north-south trending faults, including the southern extension to the Peak Trough, the Hunmanby Fault. To the west, FHFZ links with the Howardian Fault System and offshore, in the east, it is truncated by the north-south trending Dowsing Fault. The FHFZ is well exposed and described in coastal cliff sections at Flamborough Head but the inland architecture of the faults has hitherto been poorly explored predominantly due to limited inland-exposure.

To address this a multi-faceted approach to geological mapping has been undertaken in the region by the British Geological Survey, in collaboration with the Environment Agency and Yorkshire Water Limited. Remote sensing, targeted field mapping, palaeontological analysis, passive seismic and 2D onshore seismic interpretation have been integrated to understand the inland architecture of the FHFZ in unprecedented detail. Combining these techniques has enabled us to bridge the gap between the surface geology and deeper subsurface structure, increase our understanding of the geology of the region and produce an improved conceptual model at a range of depths which will be used to better manage water resources.

How to cite: Vernon, R., Burrel, L., Ford, J., Haslam, R., Randles, T., McCarthy, D., Woods, M., and Burke, H.: Surface and subsurface mapping of the Flamborough Head Fault Zone to inform groundwater management in the Yorkshire Wolds, UK., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6983, https://doi.org/10.5194/egusphere-egu23-6983, 2023.

EGU23-7325 | Orals | HS8.2.1

Groundwater flow changes in response to extensional earthquakes: a case study from the 2016-17 seismic sequence in Central Italy 

Costanza Cambi, Francesco Mirabella, Marco Petitta, Francesca Banzato, Giulio Beddini, Carlo Cardellini, Davide Fronzi, Lucia Mastrorillo, Alberto Tazioli, and Daniela Valigi

Changes in groundwater flow in response to strong earthquakes are widely described in many tectonic environments. For example, a post-seismic discharge variation is often attributed to an increase of bulk permeability due to co-seismic fracturing and/or to a change in the role of faults in acting as conduits/barrier to groundwater flow.

We take as an example the fractured aquifer of the Mts. Sibillini carbonate massif, in Central Italy, which were affected by a strong and prolonged extensional seismic sequence in 2016-17. The sequence was characterized by an M=6.5 event (mainshock), an M=6 event, an M=5.9 event, up to 60 M>4 events and several M>5 earthquakes. The strongest events caused rupturing of the topographic surface for a cumulative length in the order of 30 km and an important portion of aftershocks occurred at depths where groundwater is stored.

As a response to the seismic sequence, the main NNW-directed groundwater flow was diverted to the west and a discharge deficit was observed at the foot-wall of the activated fault system with a relevant discharge increase, accompanied by geochemical variations, at the fault system hanging-wall.

By integrating geo-structural reconstructions, seismological and ground deformation data, artificial tracer tests results and a 4-years discharge and geochemical monitoring campaign data, we show that the observed groundwater variations are due to a combination of permeability increase along the activated fault systems and hydraulic conductivity increase of the hanging-wall block due to fracturing, extension and subsidence, which determined a fast aquifers emptying. Seismicity temporarily triggered a change of the pre-existing predominant along-faults-strike NNW-SSE oriented regional flow to a west-directed flow, perpendicular to faults strike. We discuss the position of the aquifer with respect to the activated faults and how this affected the observed phenomena.

 

REFERENCE

Cambi, C., Mirabella, F., Petitta, M., Banzato, F., Beddini, G., Cardellini, C., ... & Valigi, D. (2022). Reaction of the carbonate Sibillini Mountains Basal aquifer (Central Italy) to the extensional 2016–2017 seismic sequence. Scientific Reports, 12(1), 1-13. DOI: 10.1038/s41598-022-26681-2

How to cite: Cambi, C., Mirabella, F., Petitta, M., Banzato, F., Beddini, G., Cardellini, C., Fronzi, D., Mastrorillo, L., Tazioli, A., and Valigi, D.: Groundwater flow changes in response to extensional earthquakes: a case study from the 2016-17 seismic sequence in Central Italy, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7325, https://doi.org/10.5194/egusphere-egu23-7325, 2023.

EGU23-7646 | Posters on site | HS8.2.1

Experimental and simulation study of quasistatic capillary rise resulting in pressure-saturation (p-s) hysteresis 

Animesh Nepal, Marco Dentz, Juan J Hidalgo, Jordi Ortin, and Ivan Lunati

During imbibition, fluid-fluid interface at the inlet of a constriction experiences an increase in capillary force that results in rapid fluid invasion known as Haines jump. During drainage, the interface gets pinned at the end of the constriction, which causes p-s trajectories to follow different paths during imbibition and drainage resulting in p-s hysteresis. In this work, we performed quasistatic two-phase flow experiments and simulations of cyclic imbibition and drainage to have a quantitative understanding of pore-scale processes resulting in pressure-saturation (p-s) hysteresis. We considered two different 2D Hele-Shaw cell setups: a capillary tube with a horizontal constriction (ink-bottle) and a heterogeneous porous media randomly populated by cylindrical obstacles. In both setups, drainage and imbibition were driven by quasitatically changing the pressure gradient between the inlet and the outlet of the domain. The experimental results were compared with the results from numerical model in OpenFOAM, which solves the Navier-Stokes equations employing volume of fluid method to calculate the position of the interface and the continuum surface force model to describe surface tension. For the ink-bottle setup, we observed that multiphase flow through a single constriction displayed the signature trait of p-s hysteresis, which depends innately on the cross-section gradient. The steeper the cross-section gradient, the more pronounced the p-s hysteresis, moreover, p-s hysteresis did not occur below a critical gradient. We derived an analytical solution to calculate the critical gradient and compared it with the critical gradient obtained from experiments and simulations. In heterogeneous porous media setup, we observed rapid fluid invasion and retention patterns in small pores during imbibition-drainage cycles, which give rise to hysteretic p-s trajectories. This comparative study will allow us to quantitatively link the pore-scale capillary physics to large-scale p-s hysteresis.

How to cite: Nepal, A., Dentz, M., Hidalgo, J. J., Ortin, J., and Lunati, I.: Experimental and simulation study of quasistatic capillary rise resulting in pressure-saturation (p-s) hysteresis, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7646, https://doi.org/10.5194/egusphere-egu23-7646, 2023.

Nanoparticles (NPs), especially nanoscale zero-valent iron (nZVI) particles, have been extensively used to directly treat contaminated zones in aquifers because of their desirable properties, i.e., high specific surface area and potential mobility. Understanding the transport of nZVI particles, through water-saturated porous media has important implications for many natural and engineered systems. For the first time, we used spin-echo single point imaging (SE-SPI) of low-field Nuclear Magnetic Resonance (LF-NMR) to monitor nanoparticle transport through a heterogeneous porous medium. The ability of this method to provide information of nano- to micro-scale pore structure and to monitor transient processes is verified by a transport experiment using modified nZVI particles. Experimental observations, including (i) the more rapid migration of the front relative to bulk transport of the injected solution of NPs and (ii) the retention of NPs, with 27% of the iron retained at the conclusion of deionized water flushing, highlight the important controls of complex pore structure on the resulting retardation, attenuation and efflux of NPs. Complementary numerical simulations evaluate sample heterogeneity and its effects on local transport properties. In general, the model considering four regions of distinct porosities shows improved performance, as highlighted by the low overall residual sum of squares (0.041 to 0.138), compared to another model assuming a homogeneous pore structure (0.044 to 0.328). Overall, SE-SPI imaging is shown to be an important tool in refining transport processes of NPs in heterogeneous porous media with application to constrain complex natural systems. 



How to cite: Zhang, Q. and Dong, Y.: High-resolution characterization of nanoparticle transport in heterogeneous porous media via low-field nuclear magnetic resonance, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7850, https://doi.org/10.5194/egusphere-egu23-7850, 2023.

EGU23-9396 | ECS | Orals | HS8.2.1

Characteristics of saltwater wedge under the chalk cliffs of Sainte-Marguerite-sur-Mer (Normandy, France) using optical and geophysical methods. 

Thomas Junique, Raphael Antoine, Stéphane Costa, Bruno Beaucamp, Vincent Guilbert, Cyril Ledun, Olivier Maquaire, Faycal Rejiba, and Cyrille Fauchard

Saltwater wedge is a natural phenomenon defined as the displacement and retention of saltwater in a freshwater aquifer. This saline intrusion can modify the content of dissolved elements in coastal freshwater aquifers, which can have consequences for water use (drinking or agricultural), on the ecology, the environment, the erosion of coasts, and the stability of coastal structures.

This study focuses on the integration and coupled interpretation of various geophysical and optical data obtained on the ground and by drone to evaluate the intrusion of seawater in a coastal chalk cliff in Sainte-Marguerite-sur-Mer in Normandy, France. The objective is to characterize the freshwater-saltwater interface and describe the internal structure of the formation. To do so, the combination of geophysical (Electrical Resistivity Imaging, ERI), aerial (visible and thermal infrared photogrammetry, IRT), and geotechnical (piezometers) methods was adopted.

The ten ERI profiles (transverse and longitudinal to the cliff) allowed for the mapping of the electrical resistivity distribution. The novel contribution of this study was the highlighting of a marine intrusion under the chalk cliffs visualized using transverse ERI profiles implanted directly on the steep dip of the cliff. The use of a 30m deep piezometer positioned on the plateau of the cliff and intersecting the ERI profiles made it possible to constrain the resistivity values to the measured salinity values. The presence of this saltwater wedge was characterized by low resistivity values. The top of the cliff and the parts close to the outcrop showed significant resistivities, indicating a high level of potential damage (cracks in the outcrop, underground cavities). This allowed for the identification of a zone (about 10m before the main scarp) vulnerable to the risk of collapse.

It has been shown that the difference in groundwater density leads to unstable conditions. We propose that the denser saline water covering the less dense freshwater creates a haline convection of the brackish waters at the base of the cliff and at the level of the rocky shore platform. The IRT was used to identify the wet areas of the cliff and the resurgences of the water table on the platform. Finally, all the data were grouped to propose a conceptual model of saline intrusion under the coastal cliffs.

How to cite: Junique, T., Antoine, R., Costa, S., Beaucamp, B., Guilbert, V., Ledun, C., Maquaire, O., Rejiba, F., and Fauchard, C.: Characteristics of saltwater wedge under the chalk cliffs of Sainte-Marguerite-sur-Mer (Normandy, France) using optical and geophysical methods., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9396, https://doi.org/10.5194/egusphere-egu23-9396, 2023.

EGU23-9766 | ECS | Orals | HS8.2.1

Investigating sediment transport in karst using hydrograph unmixing, sediment transport modeling and multi-source hysteresis 

Leonie Bettel, James Fox, Admin Husic, Tyler Mahoney, Arlex Marin, Junfeng Zhu, Ben Tobin, and Nabil Al Aamery

Karst characterizes almost 15% of the worlds terrain, however the mechanics of sediment transport and its prediction in karst river and cave systems remains underdeveloped. Hysteresis analysis has recently been used more to investigate the behaviors of sediments during storm events in surface systems and to some extent in karst systems. Historically, clockwise and counter-clockwise hysteresis typically refer to proximal and distal sourcing for streams. For karst systems, clockwise and counter-clockwise hysteresis has been identified to refer to an saturated and unsaturated aquifer prior to the event.

However, most interpretation of hysteresis assumes a single dominant water source, for example runoff, and assumes that baseflow is not contributing to the sediment load. One aspect of sediment hysteresis and its interpretation that has received less attention is the occurrence of several, significant water sources, eroding and delivering sediment to the watershed outlet. It is common for both surface stream systems  and karst subsurface systems to have multiple water sources contributing to the total sediment load. Each of the sources carries their own sediment time distribution, and often lead to complex hysteresis looping behavior after mixing. The primary goals of this work are to (1) study how the complex source water-sediment mixing processes impact hysteresis results and (2) to carry out solutions to the water-sediment mixing processes for karst streams, caves, and springs and show the utility and uncertainty of the method.

Several high-resolution sensors have collected data at a karst spring in central Kentucky, USA, for a 2.5 year period. Water unmixing was performed using electrical conductivity as a tracer to separate the groundwater from the surface water and infer sediment sources. Theoretical analyses have shown that not only timing and magnitude of sedigraphs influence the result of the hysteresis loops, but also timing and magnitude of each of the multiple water sources have a strong effect on the resulting hysteresis loop. The groundwater flow shows to have dominant counter-clockwise hysteresis loop, surface water shows to have clockwise loops dominating. Depending on the timing and magnitude of the water sources, the hysteresis loop at the karst spring varies from strictly counterclockwise, to a figure-8 loop, to a complex pattern.

How to cite: Bettel, L., Fox, J., Husic, A., Mahoney, T., Marin, A., Zhu, J., Tobin, B., and Al Aamery, N.: Investigating sediment transport in karst using hydrograph unmixing, sediment transport modeling and multi-source hysteresis, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9766, https://doi.org/10.5194/egusphere-egu23-9766, 2023.

EGU23-10078 | Orals | HS8.2.1

Large-scale physics of hydrodynamic transport in random fracture networks 

Marco Dentz and Jeffrey D. Hyman

We study flow and hydrodynamic transport in spatially random fracture networks.
The flow and transport behavior is characterized by first passage
times and displacement statistics, which show heavy tails
and anomalous dispersion with a strong dependence on the injection
condition. The origin of these behaviors is investigated
in terms of Lagrangian velocities sampled equidistantly along particle
trajectories, unlike classical sampling strategies at a constant rate. The
fluctuating velocity series is analyzed by its copula density, the
joint distribution of the velocity unit scores, which reveals a simple correlation
structure that can be described by a Gaussian copula. This insight
leads to the formulation of stochastic particle motion in terms of a
Klein-Kramers equation for the joint density of particle position and
velocity. The upscaled model captures the heavy-tailed first passage
time distribution and anomalous dispersion, and their dependence on the
injection conditions in terms of the velocity point statistics and
average fracture length. The first passage times and displacement
moments are dominated by extremes occurring at the first step.
The developed approach integrates the complex interaction of flow and structure
into a predictive model for large scale transport in random fracture networks.    

How to cite: Dentz, M. and Hyman, J. D.: Large-scale physics of hydrodynamic transport in random fracture networks, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10078, https://doi.org/10.5194/egusphere-egu23-10078, 2023.

EGU23-10693 | ECS | Orals | HS8.2.1

Data acquisition and processing of multi-frequency oscillatory hydraulic tomography in a granular aquifer 

Aymen Nefzi, Daniel Paradis, René Lefebvre, and Olivier Bour

Transport of solutes in aquifers is controlled by the heterogeneous spatial distribution of hydraulic properties, but the characterization of aquifer heterogeneity is quite challenging with conventional methods. Hydraulic tomography (HT) was developed to define the heterogeneous distribution of hydraulic conductivity (K) and specific storage (Ss). HT involves the emission of a series of hydraulic head perturbations in a stressed well and the recording of this signal at several levels in the stressed and observation wells. All recorded hydraulic head responses are simultaneously analyzed through numerical inversion, which provides the spatial distribution of hydraulic properties at a scale relevant for local site investigations.

This communication reports on a tomographic experiment carried out in a heterogeneous and highly anisotropic granular aquifer at the Saint-Lambert research site near Quebec City, Canada. This site has already been the object of detailed characterizations with multiple hydraulic methods: pumping tests, packer slug tests, flowmeter profiles, vertical interference tests, and slug test tomography. A relatively new approach named oscillatory hydraulic tomography (OHT) was tested, in which multi-frequency oscillatory head perturbations are induced in an interval isolated by packers of the stressed well by a submerged rod that is electronically controlled by a winch system. Hydraulic responses are measured in the stressed intervals and in multiple intervals of an observation well.

This study was primarily aimed at testing, first on an operational level, if the OHT signal could be generated in the stressed well and propagated to the observation well in a highly anisotropic granular aquifer. Second, the study developed a rigorous workflow for the treatment of the measured hydraulic heads. Third, in terms of characterization efficacy, the study aimed to determine if multiple controlled frequencies would allow the assessment of K spatial distribution.

Results show that the field experiment provided clear measured hydraulic responses that could be used to obtain the 2D distribution of hydraulic properties from the inversion of OHT measurements. Comparison was made of inversion results using a single oscillatory frequency and multiple frequencies. Under conditions of realistic field measurement noise and uncertainty, it will be valuable in future work to compare the imaging capabilities of oscillatory hydraulic tomography against other tomographic methods. Further investigation is also needed to examine the information content of oscillatory hydraulic tomographic data for characterizing K and Ss heterogeneities through a sensitivity and resolution analysis. This study demonstrates the practical potential for the implementation of OHT experiments in relatively low permeability and highly anisotropic granular aquifers.

How to cite: Nefzi, A., Paradis, D., Lefebvre, R., and Bour, O.: Data acquisition and processing of multi-frequency oscillatory hydraulic tomography in a granular aquifer, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10693, https://doi.org/10.5194/egusphere-egu23-10693, 2023.

EGU23-11028 | ECS | Posters on site | HS8.2.1

Impact of structural heterogeneity on solute transport and mixing in unsaturated porous media: An experimental study 

Oshri Borgman, Francesco Gomez, Tanguy Le Borgne, and Yves Méheust

Solute transport in unsaturated porous media plays a crucial role in soil nutrient dynamics, pesticide leaching, and contaminant migration to aquifers through the vadose zone. Natural porous media are characterized by a strong structural heterogeneity, which impacts solute spreading and mixing and the resulting chemical reaction rates. In addition, incomplete pore-scale solute mixing requires high-resolution experimental measurements to understand the system’s mixing dynamics. Our goals are to 1) study the impact of structural heterogeneity on the spatial distribution of fluid phases and 2) establish how fluid phase arrangement impacts solute spreading and mixing during unsaturated flow. We use two-dimensional porous media consisting of circular posts in a Hele-Shaw-type flow cell. The positioning of the posts is random, but we control the medium’s heterogeneity by varying the disorder in the posts’ diameters and their spatial distribution’s correlation length; increasing this length introduces more structure in the porous medium.

In our experiments, we first establish an unsaturated flow pattern with a connected liquid phase and then introduce a fluorescent solute pulse transported by the moving liquid phase. We track the solute concentration and gradients’ evolution by taking periodic images of the flow cell and analyzing the fluorescence intensity field. Our results suggest that, as previously shown, decreasing the saturation degree enhances and sustains mixing rates in a disordered porous media due to the emergence of several preferential flow pathways during unsaturated flow. Moreover, increasing the solid posts’ spatial correlation reduces the number of air clusters and their interface roughness, and increases their mean size. This leads to fewer preferential flow paths during unsaturated flow for the higher correlated, more structured, porous media, compared to the less structured ones. This reduction in preferential flow paths’ number suppresses mixing rate enhancement in the more structured porous media, compared with the less structured porous media, during unsaturated flow. Our experiments show the non-trivial effect of structural heterogeneity and saturation degree on solute mixing in porous media flows. The effects demonstrated by these results are likely to affect reactive solute transport processes such as dissolution and precipitation and adsorption-controlled solute migration.

How to cite: Borgman, O., Gomez, F., Le Borgne, T., and Méheust, Y.: Impact of structural heterogeneity on solute transport and mixing in unsaturated porous media: An experimental study, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11028, https://doi.org/10.5194/egusphere-egu23-11028, 2023.

EGU23-12405 | ECS | Orals | HS8.2.1

Quantifying aquifer interaction using numerical groundwater flow model evaluated by environmental water tracers data: Application in Bandung groundwater basin, Indonesia 

Steven Reinaldo Rusli, Albrecht Weerts, Syed Mustafa, Dasapta Erwin Irawan, and Victor Bense

Anthropogenic impact on groundwater storage depletion has been detected in many places from catchment to global scales, including in our study area, the Bandung groundwater basin, Indonesia. Groundwater abstraction of various magnitudes, pumped out from numerous depths of aquifers, stimulates different changes in hydraulic heads among vertical subsurface stratifications. Such circumstances generate groundwater movement, where it flows from the upper layer storage to underlying aquifers, referred to as aquifer interaction in this study. Meanwhile, remote-sensing products such as GRACE measure the integrated water storage changes over depth and space, making it difficult to capture and derive the storage internal vertical groundwater fluxes from such signals. As an alternative, environmental water tracers (EWT) have been used to investigate subsurface water movement and to gain a conceptual understanding of groundwater flow dynamics. However, quantitative measurement of the rates of fluxes is not often possible, despite being essential to ensure sustainable groundwater resources management.

In this study, we utilize (a) groundwater flow modeling in conjunction with (b) EWT data to quantify the aquifer interaction driven by multi-layer groundwater abstraction in the Bandung groundwater basin, Indonesia. The available environmental water tracers data include major ion elements (Na+/K+, Ca2+, Mg2+, Cl-, So24-, HCO3-), stable isotope data (d2H and d18O), and groundwater age estimates (radiocarbon/14C content). These measurements are used to qualitatively evaluate the numerical groundwater flow model. The model, forced by recharge calculated using the hydrological model of wflow_sbm, is calibrated by minimizing the difference between the dynamic steady-state simulated and the observed groundwater levels.

We evaluate the groundwater flow model and the EWT-driven analysis from multiple perspectives. The results suggest that the groundwater recharge is uniformly distributed spatially, the groundwater is flowing regionally from the basin periphery inward to the basin’s center following the topographical distribution, and vertical groundwater fluxes are identified. All three deductions, in a qualitative sense, are agreed upon by both the EWT observations and the groundwater flow model. From the groundwater flow model, we quantify that the aquifer interaction is equivalent to, on average, 0.110 m/year, which is highly significant compared to the other groundwater budgets. We also determine the unconfined aquifer storage volume decrease, calculated from the change in the groundwater table, that results in an average declining rate of 51 Mm3/year. This number shows that the upper aquifer storage is dwindling at a rate that is disproportionate to its groundwater abstraction, hugely influenced by the aquifer interaction. The storage lost from only this partition contributes up to 60.3% of the total groundwater storage lost, despite contributing to only 32.3% of the groundwater abstraction. Additionally, we also investigate and examine the correlation between the groundwater level changes and the groundwater abstraction zones. The results of our study confirm that quantification of the aquifer interaction and groundwater level change dynamics driven by multi-layer groundwater abstraction in multi-layer hydrogeological settings is possible by our proposed methods. Applying such methods will assist in deriving basin-scale groundwater policies and management strategies under the changing anthropogenic and climatic factors, thereby ensuring sustainable groundwater management.

How to cite: Rusli, S. R., Weerts, A., Mustafa, S., Irawan, D. E., and Bense, V.: Quantifying aquifer interaction using numerical groundwater flow model evaluated by environmental water tracers data: Application in Bandung groundwater basin, Indonesia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12405, https://doi.org/10.5194/egusphere-egu23-12405, 2023.

EGU23-12447 | Orals | HS8.2.1

Estimating Fracture Network Damage After a Subsurface Detonation Using Geogenic Noble Gases. 

W. Payton Gardner and Stephen J. Bauer

Noble gas release can be used to investigate the timing, location and magnitude of fracture creation.  Here, a numerical model of gas release and transport, resulting from fracturing events, is used to estimate first-order fracture network characteristics after subsurface detonation.  Released radiogenic noble gases after detonation of three different subsurface explosions of varying source characteristics were interpreted.  A broad suite of gases was sampled from 62 discrete sampling intervals in a 3-D array surrounding the explosion location using an automated field sampling system and a capillary inlet quadrupole mass spectrometer.  Gases analyzed include: 4He, 36,40Ar, 20Ne, N2, O2, NO and CO2/N2O.  Geogenic gas arrivals were observed in a subset of sampling locations.  All geogenic gas arrivals were observed in ports with explosive-derived gas arrivals.  Helium amount and arrival time were used to estimate fracture network damage using a numerical model which allows dynamic changes in fracture aperture, matrix porosity and permeability.  The amount of fracture damage was significantly different between the three different explosions and consistent with other observations of damage.  These results illustrate how geogenic noble gases can be used to understand damage, transport, and fracture creation in fracture networks, with implications for a variety of subsurface topics including hydraulic fracking, mine failure, earthquake and volcanic monitoring.

How to cite: Gardner, W. P. and Bauer, S. J.: Estimating Fracture Network Damage After a Subsurface Detonation Using Geogenic Noble Gases., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12447, https://doi.org/10.5194/egusphere-egu23-12447, 2023.

EGU23-13617 | Orals | HS8.2.1

Stochastic modeling of bacterial transport and retention during aquifer artificial recharge 

Juan J. Hidalgo, Benjamín Piña, Cristina Valhondo, Claudia Sanz, and Marta Casado

Managed aquifer recharge (MAR) sytems based on water filtration allow to improve recharged water quality and quantity by retaining suspended particles and microorganisms. However, the periodic detection in groundwater of pathogens and other microorganisms that represent a significant risk for human health makes it necessary to study the mechanisms affecting the propagation and fate of microbial populations during the process.

In this work a series of column experiments were performed to characterize bacteria transport in porous media. Two type of columns were built. One using only sand and another using a combination of sand, compost and wood chips. In each column a punctual injection of tracers (rhodamine and amino-G acid) and bacteria consortium collected from the effluent of a wastewater treatment plant were injected. Samples of column outflows were collected to obtain breakthrough curves of the tracers and the different amplicon sequence variants (ASVs) of bacteria to determine the material influence on the retention of bacteria. Bacteria displayed a strong anomalous behavior with late arrival peaks and longer tails than those obtained with the tracers.

A continuous time random walk (CTRW) transport model was developed to interpret the experimental results. The model characterizes transport in terms of mobile-immobile domains. Bacteria are transported with the mean flow and experience transitions from and to low mobility zones with a certain frequency. Transport is described in terms of four parameters, namely, the mean flow velocity, the dispersion coefficient, the trapping rate, and the mean residence time in the immobile zones. The model was able to reproduce satisfactorily the observed breakthrough curves of over 470 measured ASVs. The analysis of the breakthrough curved determined that bacteria form two clusters. The breakthrough curve of one cluster has heavy tails and it is formed by small, motile, gram-negative bacteria. The other cluster displays strong peaks and a relatively weaker tailing. CTRW parameters are able to predict the cluster in which a certain bacteria belongs.

How to cite: Hidalgo, J. J., Piña, B., Valhondo, C., Sanz, C., and Casado, M.: Stochastic modeling of bacterial transport and retention during aquifer artificial recharge, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13617, https://doi.org/10.5194/egusphere-egu23-13617, 2023.

Knowledge of the saturated hydraulic conductivities of aquitards in provisional groundwater abstraction sites is essential to assess the sustainability of future water production. The subsurface of the site in the southwest of The Netherlands has a simple layer cake stratigraphy. Temperature-depth profiles in 12 boreholes were measured and analysed to infer vertical fluxes across an aquitard at a depth (~100 m) below where the impact of recent surface warming could be detected. Hence, the analytical mathematical solution for coupled groundwater-heat flow described by Bredehoeft & Papadopulos in 1965 could be be employed for this purpose. The selection of the depth interval for the aquitard for which the solution is applied, is guided by scanning through the TDP to find depth-intervals for which both a low RMSE between observed temperature and solution is obtained as well as a high Peclet number indicative of significant vertical groundwater flow. Through comparison of the depth intervals with lithological data, temperature-depth profiling is shown to have the capacity to detect aquitards, provided that the approximate depth of the aquitard is known, as well as the flux direction and magnitude across the aquitard. In combination with observed hydraulic gradients, the spatial variability of hydraulic conductivity of the aquitard could be evaluated. These values range from 10 to 100 mm/d, where earlier estimated values using more traditional methods suggested a range of  5 to 10 mm/d.

How to cite: Bense, V., Nie, L., and Oosterwijk, J.: Thermal profiling to quantify the spatial variability of ambient groundwater flow at a provisional groundwater abstraction site, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13937, https://doi.org/10.5194/egusphere-egu23-13937, 2023.

EGU23-14697 | Orals | HS8.2.1

Quantitative three-dimensional imaging of macropore flow in undisturbed soil under different irrigation intensities 

John Koestel, Anna Schwenk, Nick Jarvis, and Mats Larsbo

Macropores have important beneficial impacts on the hydrological cycle, since they reduce risks of waterlogging, surface runoff, soil erosion and flooding. On the other hand, macropore flow is also associated with significant ecosystem disservices, since it can dramatically accelerate the leaching of contaminants to surface water and groundwater. Several approaches to model preferential macropore flow have been developed. One approach is to use the kinematic wave equation, in which the kinematic exponent should depend on the exponent in a power law relationship between wetted macropore surface area and macropore saturation. Most model applications have relied on calibration of model parameters against measured data on water flow. This makes critical testing of the underlying model concepts difficult and raises the question of whether the model is matching the data for the right reasons or not. In this study, we used X-ray tomography to quantify water and air distributions in macropores at varying steady-state flow rates in two topsoil and two subsoil columns (diameter 9 cm) sampled from a clay soil. We collected sufficient data to derive the kinematic wave exponent from the image data for the two topsoil samples. We found that the wetted macropore surface area and macropore saturation were indeed related by a power law for the first three irrigation intensities, corresponding to kinematic exponents of 1.22 and 1.26, respectively. These promising results need to be verified in future experiments that should be conducted on soil samples with smaller diameters to achieve better image resolutions and signal-to-noise ratios.

How to cite: Koestel, J., Schwenk, A., Jarvis, N., and Larsbo, M.: Quantitative three-dimensional imaging of macropore flow in undisturbed soil under different irrigation intensities, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14697, https://doi.org/10.5194/egusphere-egu23-14697, 2023.

EGU23-15371 | ECS | Posters on site | HS8.2.1

Connecting the dots: Fracture mapping for landfill sites in fractured bedrock” 

Bilal Tariq, Helen Kristine French, Stéphane Polteau, Helgard Anschütz, and Sean Salazar

A landfill constructed in fractured bedrock can pose a potential risk of contaminant leachate to the surroundings through fractures and/or fracture networks. Therefore, adequate understanding of factures and fracture networks is a key element for constructing environmentally safe, sustainable and long-term landfills in fractured bedrocks. Mapping of geological features especially fracture networks provides essential data to establish a fundamental understanding of the local geology and hydrogeology of such landfill sites.

The objective of this study to develop  a 3D model of fractures and fracture networks, surrounding a quarry in southwestern Norway, Rekefjord. The test site, selected as a potential landfill site, consists of  moderately fractured crystalline monzonorite near the shoreline. Eight previously drilled and logged observation boreholes (NGI) on the crest surrounding the open pit were analysed. Results of subsurface fracture mapping from well logs show that orientations of natural fractures are scattered and mostly appear to be open. The Terzaghi correction shows there could be more steeply dipping fractures, these are not well captured through vertical borehole logging. Additional field work consisted of drone scanning of the interior of the whole quarry and specific locations to generate a virtual 3D model. This 3D model is used to conduct fracture measurements using the LIME software. The fracture data extracted from the 3D model will be used to assess the correlation and consistency in fracture orientation between the internal rock face and borehole measurements. The geometry of fracture networks and individual fractures can have significant impact on flow through fractured rock. 

Results will also be used to constrain a numerical groundwater flow model to improve understanding of potential pathways of contaminants from the landfill to the surroundings. The results of this research will improve assessment methodology and criteria for new landfill sites in fractured bedrock.

How to cite: Tariq, B., French, H. K., Polteau, S., Anschütz, H., and Salazar, S.: Connecting the dots: Fracture mapping for landfill sites in fractured bedrock”, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15371, https://doi.org/10.5194/egusphere-egu23-15371, 2023.

EGU23-15397 | Orals | HS8.2.1

Forchheimer gravity currents in porous media 

Vittorio Di Federico, Alessandro Lenci, and Sepideh Majdabadi Farahani

The displacement of one fluid by another in porous media is of interest in reservoir engineering, groundwater remediation, and subsurface heat recovery. In several instances, i.e. in coarse or macro porous media, or in heavily fractured rocks, the threshold Reynolds number is exceeded and inertial effects cannot be neglected. Consequently, the Forchheimer extension of Darcy’s law describes the motion, and a novel quantity, the Forchheimer or inertial coefficient, enters the picture, entailing implications on several coupled phenomena. We study plane gravity currents propagating in a homogeneous porous medium of given permeability saturated with a lighter fluid, but results are also valid for the displacement of a heavier ambient fluid (brine) by a lighter one advancing below the roof of a porous layer such as in CO2 injection. The injected fluid volume is given by a global conservation of mass and varies as a power-law function of time. Under the lubrication approximation, the pressure gradient is hydrostatic and the one-dimensional transient problem governing the current depth, when expressed in dimensionless form, depends uniquely by a pure number equal to the combination of a Reynolds number multiplied by a Forchheimer number and divided by the square of a densimetric Froude number. We explore the two limit cases of dominating inertial effects or prevailing viscous effects and demonstrate that in both cases the governing equations are amenable to a semi-analytic similarity solution governed by the aforementioned pure number. For a current with constant volume, the solution takes a closed form. 

How to cite: Di Federico, V., Lenci, A., and Majdabadi Farahani, S.: Forchheimer gravity currents in porous media, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15397, https://doi.org/10.5194/egusphere-egu23-15397, 2023.

EGU23-15772 | Orals | HS8.2.1

Theory of drying of polymer solutions in porous media 

Andrea Carminati, Pascal Benard, and Peter Lehmann

Plant roots and bacteria release in soils polymeric blends of substances which alter the physics of soil water flow and support life in soils. They adsorb water, decrease the surface tension of the soil solution and increase its viscosity, and, more generally, they change the soil solution into a non-Newtonian liquid with viscoelastic properties. A theory of drying of polymer solutions in porous media is missing and it is needed to understand the feedback between physics of porous media and life in soils. It was observed that during drying polymer solutions are deposited as thin surfaces spanning multiple pores and that these depositions are associated with a decrease in evaporation rate. Here, we provide a physical explanation of surface formation. The modeling framework includes Darcian flow across the polymeric network driven by a gradient in water potential. As the polymer dries and air invades the pore space the polymer network is stretched. The stretching causes a stress in the polymer network that alters the relation between water potential and polymer concentration: the more stretched is the polymer network the smaller is the spacing between the polymers at a given water potential, and the lower is the permeability of the network. The model predicts that at a critical point during evaporation there is an asymptotic increase in polymer concentration at the gas-gel interface corresponding to the deposition of solid-brittle interfaces. The onset of this glass transition depends on flow rate and pore size, with earlier deposition for fast high evaporative fluxes and small pores. The model explains why evaporation is suppressed much earlier and more significantly when the polymer solution dries into a porous medium, in comparison to the case when the polymer solution is free to dry outside a porous medium.

How to cite: Carminati, A., Benard, P., and Lehmann, P.: Theory of drying of polymer solutions in porous media, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15772, https://doi.org/10.5194/egusphere-egu23-15772, 2023.

Fate and transport of colloids and bio colloids in structurally heterogeneous porous media are known to exhibit anomalous behaviours such as non-Gaussian breakthrough curves. Classical approaches, like Colloid Filtration Theory, relies on spatial averaged quantities, neglecting flow topology heterogeneity brought about by both local pore scale surface irregularities and broad pores size distribution: two potential triggers for super diffusive effects and broad trapping time distributions. Recent theoretical work has tried to address these deficiencies by modeling deposition and flow variations as stochastic processes (Miele et al., Phys. Rev. Fluids 2019; Bordoloi et al., Nat. Commun. 2022). However, experimental evidence to demonstrate its validity for 3D geologic structures is still lacking. We thus design a novel experimental set-up to assess colloid fate transport under realistic structural heterogeneity with controlled laboratory conditions. Heterogeneous pore structures are first obtained from X-ray tomography of field samples and are subsequently 3D-printed at high resolution. Column transport experiments with gold (Au) nanoparticles are then conducted at different flow regimes, from which effluent concentration (at the macro scale) and colloid deposition (at the pore scale) are collected. These empirical data are complemented with pore network analysis that parametrizes the co-presence of preferential channels and stagnant cavities and, further, validates the stochastic model of interest. The findings shed light on the main drivers and structural hotspot for colloid filtration in realistic porous media.

How to cite: Miele, F., Patino, J., and Morales, V.: Surface Induced Anomalous Transport of Nanoparticle in 3D Printed Structurally Heterogeneous Soils: coupling experiments and stochastic models, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16451, https://doi.org/10.5194/egusphere-egu23-16451, 2023.

EGU23-16609 | ECS | Posters on site | HS8.2.1

Effect of spatially correlated disorder on solute dispersion and mixing in partially saturated porous media 

Ali Saeibehrouzi, Petr Denissenko, Soroush Abolfathi, and Ran Holtzman

The transport of solute particles is common in many natural and engineering processes, such as nutrition/contamination transport in subsurface systems or underground carbon dioxide sequestration.  While most of the available investigations concentrate on single-phase scenarios, more often, multiple fluids coexist, denoted frequently as unsaturated conditions. Here, and by means of direct numerical simulation, the effect of spatially correlated disorder in pore size is examined for two-phase displacement in viscous fingering regime. Following the stabilisation of fluids interface (steady-state condition), the solute solution is introduced into the invading phase with lower viscosity. Simulation results indicate that the spatial disorder impacts solute migration through the invading phase saturation and tortuosity of velocity streamlines. A bimodal variation can be seen from the histogram of probability of pore-scale Peclet number with zones being mostly dominated by either advection or diffusion. In addition, there exists a transition region with an interplay between both advective and diffusive mechanisms. The creation of trapped regions focuses the flow into preferential pathways, resulting in a higher dispersion coefficient. This, on the other side, forms a concentration gradient transverse to the direction of flow, directing solute solution through diffusivity from preferential pathways to low-velocity zones.

How to cite: Saeibehrouzi, A., Denissenko, P., Abolfathi, S., and Holtzman, R.: Effect of spatially correlated disorder on solute dispersion and mixing in partially saturated porous media, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16609, https://doi.org/10.5194/egusphere-egu23-16609, 2023.

The Pharmaceuticals and Personal Care Products, PPCPs, a category of Emerging Contaminants are omnipresent in the environment. These PPCPs have allured significant importance globally over two decades. Because of the lack of efficient treatment systems concerning to their varying Spatio-temporal effects, they impose chronic toxicity on the environment. Therefore, understanding the fate and transport behavior of PPCPs is of prime importance for the successful accomplishment of remediation operations.  In the study, three different PPCPs viz. Metformin, Triclosan and Erythromycin were modeled using numerical techniques in the silty saturated porous media using the software- COMSOL Multiphysics. A fate and transport model considering advection, dispersion, degradation, and adsorption is conceptualized as imitating the real soil column scenario. The column was fed with continuous injection of the contaminants in consideration. Further, sensitivity analysis is carried out by varying flow and transport parameters (longitudinal dispersivity, Darcy’s velocity, adsorption coefficient (Kd), and degradation coefficient) by three orders of magnitude. The degradation and adsorption delayed the process of transport of the three ECs, thereby taking more time to travel through the column. Erythromycin having comparatively less Kd is detected in the column outlet before metformin and triclosan. The results depicted a denoting effect of adsorption, Darcy’s velocity, and degradation co-efficient, thereby highlighting the importance of adsorption, advection and degradation being important factors in the transportation of PPCPs via saturated silty soil. Moreover, the longitudinal dispersivity tends to have a negligible effect on the concentration modeled, thus proving to be a less significant parameter influencing the transport of PPCPs in the environment. The results of the simulation may serve as a foreboding tool for prior identification of the ever-increasing ECs in the environment. Furthermore, the results may prove to be useful in policymaking and risk assessment due to the PPCPs. 

How to cite: Ashraf, M., Chakma, S., and Ahammad, Z.: Apprehending the complex transport and fate behavior of Pharmaceuticals and Personal Care Products in Silty Saturated Porous media - A Numerical Study, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16896, https://doi.org/10.5194/egusphere-egu23-16896, 2023.

EGU23-17037 | Orals | HS8.2.1

Early Time Effective Reactivity of Reactive Transport in Cylindrically-Advected Reaction Fronts is enhanced by Hydrodynamic Dispersion 

Pratyaksh Karan, Uddipta Ghosh, Yves Méheust, and Tanguy Le Borgne

Reaction fronts are widespread in nature and are encountered frequently in the geological context. Examples include contaminant spread, neutralization-based reservoir decontamination, biogeochemical phenomena, and many more. The complex porous structures of subsurface formations renders the flow geometry incredibly complex, which in turn can, and often does, lead to interesting and peculiar reactive transport. For instance, the stretching and folding of the reaction front due to flow shear can enhance the effective reactivity, and flow stagnation spots can serve as sites for accummulation of reactants.

At the Darcy scale, the spreading of the front is controlled by hydrodynamic dispersion, which is a continuum scale manifestation of the pore scale interaction between heterogeneous advection and molecular diffusion. When the flow field is uniform, the consequence of dispersion is only a quantitative enhancement of diffusion. However, if the flow field varies in space, as may occur for example during aquifer remediation by injection of a neutralizing agent, the effect of hydrodynamic dispersion will lead to qualitative modifications in reactive transport dynamics as compared to hypothetic scenarios where the only diffusive mechanism is molecular diffusion. Yet, despite the ubiquity of dispersion, its impact on reactive fronts in porous media has not been addressed for flows with an axisymmetrical geometry, which are typical of well injection scenarios.

Therefore, we study the impact of hydrodynamic dispersion on reactive transport in cylindrically-advected bimolecular reaction fronts. We show that, in the reaction-limited regime at early times, mechanical dispersion is the dominant transport process and augments the reaction front’s advancement (which scales as t1/3, t being the time), the reaction rate (which scales as t2/3) and the product mass (which scales as t5/3), in comparison to a dispersion-free scenario (for which, the reaction front advancement, the reaction rate and the product mass scale as t1/2, t1 and t2 respectively). On the other hand, depending on the strength of hydrodynamic dispersion, we may encounter a dispersion-dominated, mixing-limited, regime of the reactive front at large times, which exhibits a declining reaction rate. This bevahior is significantly different from the dispersion-free scenario where a declining reaction rate is never encountered. Lastly, at sufficiently long times (longer for stronger dispersion), the reaction front transitions to a behavior akin to that seen in the dispersion-free scenario, wherein the differences between the dispersive and the dispersion-free scenarios become negligible.

How to cite: Karan, P., Ghosh, U., Méheust, Y., and Le Borgne, T.: Early Time Effective Reactivity of Reactive Transport in Cylindrically-Advected Reaction Fronts is enhanced by Hydrodynamic Dispersion, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17037, https://doi.org/10.5194/egusphere-egu23-17037, 2023.

EGU23-17055 | ECS | Orals | HS8.2.1

Convective dissolution of carbon dioxide in 2D water-saturated porous media: an experimental study in two-dimensional micromodels 

Niloy De, Naval Singh, Remy Fulcrand, Yves Méheust, Patrice Meunier, and François Nadal

Convective dissolution is a perennial trapping mechanism of carbon dioxide in geological formations saturated with an aqueous phase. This process, which couples dissolution of supercritical CO2, convection of the liquid containing the dissolvedCO2, and mixing of the latter within the liquid, has so far not been studied in two-dimensional porous media. In order to do so, two-dimensional (2D) porous micromodels (patterned Hele-Shaw cells) have been fabricated from UV-curable NOA63 glue. NOA63 is used instead of PDMS, which is permeable to CO2 and does not allow for a controlled no flux boundary condition at the walls. The novel fabrication protocol proposed here, based on the bonding of a patterned photo-lithographed NOA63 layer on a flat NOA63 base, shows good reproducibility regardless of the pattern’s typical size, and allows for easy filling of the cell despite the small value of the gap. A pressure chamber allows pressurizing the CO2 and outside of the flow cell up to 10 bars. Experiments were performed in 11 different porous media geometries. As expected, a gravitational fingering instability is observed upon injection of gaseous carbon dioxide in the cell, resulting in the downwards migration of dissolved CO2 plumes through the 2D porous structure. The initial wavelength of the fingers is larger in the presence of a hexagonal lattice of pillars. This effect can be correctly predicted from the theory for the gravitational instability in a Hele-Shaw cell devoid of pillars, provided that the permeability of the hexagonal porous medium is considered in the theory instead of that of the Hele-Shaw cell. Fluctuations around the theoretical prediction observed in the data are mostly attributed to a hitherto unknown weak locking of the wavelength on the distance between closest pillars.

How to cite: De, N., Singh, N., Fulcrand, R., Méheust, Y., Meunier, P., and Nadal, F.: Convective dissolution of carbon dioxide in 2D water-saturated porous media: an experimental study in two-dimensional micromodels, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17055, https://doi.org/10.5194/egusphere-egu23-17055, 2023.

EGU23-17293 | Orals | HS8.2.1

Controlling colloid transport through porous media via local gradients of solute concentration 

Mamta Jotkar, Ilan Ben-Noah, Juan J. Hidalgo, Marco Dentz, and Luis Cueto-Felgueroso

Diffusiophoresis referring to the colloidal particle migration triggered by gradients of local salt concentration, has been established in the recent years as an efficient particle manipulation tool in relatively simple microfluidic setups such as plane channels, dead-end pores, Y-shaped channels, vertical diverging pores, etc. Owing to the fact that the particle velocities depend logarithmically on the solute concentration gradients, small variations in the concentration fields can result in significantly large diffusiophoretic particle motion. However, despite the recent investigations hardly anything is known about its effects in the field of flow and transport in porous media. Spatial heterogeneities and complex fluid-phase distributions are quite ubiquitously found across spatial scales ranging from pore-scale to field-scale. These have a strong impact on the flow and transport of dissolved solutes through porous media giving rise to rich heterogeneous solute landscapes that provide local gradients of solute concentration, a prerequisite for diffusiophoretic motion. Following this motivation, we perform pore-scale simulations to understand the effects of diffusiophoresis at pore-scale in partially saturated media for varying degrees of fluid saturation and quantify their impact on the macroscopic particle transport. We envision that by exploiting the heterogeneous solute landscapes, particle motion can be controlled in an efficient manner. Depending on the sign of the diffusiophoretic mobility, determined by the size and surface charge of the colloidal particle, localized particle entrapment or removal can be achieved systematically. Our results that are pioneer in the field of diffusiophoretic transport through porous media, will pave the way to attaining controlled particle manipulation through porous media. 

How to cite: Jotkar, M., Ben-Noah, I., Hidalgo, J. J., Dentz, M., and Cueto-Felgueroso, L.: Controlling colloid transport through porous media via local gradients of solute concentration, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17293, https://doi.org/10.5194/egusphere-egu23-17293, 2023.

EGU23-17488 | Posters on site | HS8.2.1

Optical thermometry to characterize heat transport in permeable porous media 

Arwa Rashed, Maria Klepikova, Gauthier Rousseau, Francesco Gomez, Joris Heyman, Benoît Fond, and Yves Méheust

The study of heat transport in porous media has recently attracted a lot of attention due to the wide range of industrial and geological applications, yet the impact of the structural heterogeneity of naturally occurring aquifers on their hydraulic and thermal properties is often disregarded. In that regard, a novel application of phosphor thermometry to porous media is proposed with the aim of examining under which conditions the validity of existing thermal transfer models in complex natural saturated porous media can be questioned. This experimental technique relies on monitoring the temperature-dependent luminescence properties of solid phosphor particles seeded into the fluid as tracers, using light sources and cameras. It offers the possibility of characterizing quantitatively the interaction between flow and heat transport processes at the pore scale in transparent analog porous media, with minimal interference and from spatially-resolved measurements, hereby overcoming the technical limitations of current experimental techniques, which are constrained to point temperature measurements.

Here, as proof of concept, we present a demonstration experiment performed on a slow-moving flow in a synthetic porous medium with a heterogenous size distribution, and using YAG:Cr3+, a thermographic phosphor with a temperature sensitivity exceeding 0.3%/K [1]. The measurements are performed using a modulated light source and are recorded at a sampling rate of 1 kHz during continuous injection of an aqueous solution which is initially at a constant temperature, different from that of the resident solution. The results show the dynamics of the spatial temperature distribution in the porous medium with a precision of ±0.3°C.

[1] J. L. Bonilla and B. Fond, "Phosphor thermometry using the phase-shift method: optimization and comparison with decay time method," 2022.

How to cite: Rashed, A., Klepikova, M., Rousseau, G., Gomez, F., Heyman, J., Fond, B., and Méheust, Y.: Optical thermometry to characterize heat transport in permeable porous media, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17488, https://doi.org/10.5194/egusphere-egu23-17488, 2023.

EGU23-17523 | ECS | Orals | HS8.2.1

Experimental characterization of Rayleigh-Taylor convection in granular media for CO2 sequestration by dissolution trapping 

Shabina Ashraf, Jayabrata Dhar, François Nadal, Patrice Meunier, and Yves Méheust

A large fraction of greenhouse gases (about 60%) released into the atmosphere are due to CO2 emissions from industrial processes and the burning of fossil fuels [1]. One of the strategies employed to reduce the emissions is rapping them securely in the subsurface [2-4]. Dissolution trapping, in particular, involves injection of CO2 into the subsurface where the supercritical CO2 (sCO2) dissolves in the aquifer brine and forms a CO2 enriched layer within solution. The interface between the high density CO2 rich brine on the top and the ambient low density aquifer water below results in destabilization of the aforementioned layer [2-4]. This leads to a gravitational instability which then causes a natural convection of CO2 rich brine to lower layers, thereby accelerating further dissolution of the sCO2 into the fresh brine.

The study of Brouzet et al. shows that traditional continuume scale, Darcy law-governed, models underestimate the timescales of the convective dissolution’s dynamics, owing to local heterogeneity in the pore-scale flow, and that it may thus be necessary to take pore-scale fluctuations into account [5]. We present here a 2D experimental study using miscible analog fluids with a contrast in densities to understand the convective transport of the dissolved sCO2. The fluids and the granular media are refractive index matched, which renders the medium transparent and helps in accurate quantification of experimental findings at various Rayleigh (Ra) and Darcy numbers (Da). Darcy scale simulations are used to complement the two-dimensional experimental measurements and it was found that Darcy scale simulations underpredict the experimental findings by several orders of magnitude, which is consistent with the findings by Brouzet et al. We investigate convective dynamics for various values of the number by changing the density of fluids, the properties of the granular medium (permeability, size of the granular medium) which determines the size of the instability with respect to pore size. When that number is much smaller than 1, obvious causes for the failure of the continuum scale description can be excluded, yet discrepancies remain between the experimental results and the simulations.

References:

[1] Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, IPCC 2014.

[2] Emami-Meybodi, H., Hassanzadeh, H., Green, C. P., & Ennis-King, J. (2015). Convective dissolution of CO2 in saline aquifers: Progress in modeling and experiments. International Journal of Greenhouse Gas Control, 40, 238-266.

[3] Pau, G. S., Bell, J. B., Pruess, K., Almgren, A. S., Lijewski, M. J., & Zhang, K. (2010). High-resolution simulation and characterization of density-driven flow in CO2 storage in saline aquifers. Advances in Water Resources, 33(4), 443-455.

[4] Meunier, P., & Nadal, F. (2018). From a steady plume to periodic puffs during confined carbon dioxide dissolution. Journal of Fluid Mechanics, 855, 1-27.

[5] Brouzet, C., Méheust, Y., & Meunier, P. (2022). CO2 convective dissolution in a three-dimensional granular porous medium: An experimental study. Physical Review Fluids, 7(3), 033802.

How to cite: Ashraf, S., Dhar, J., Nadal, F., Meunier, P., and Méheust, Y.: Experimental characterization of Rayleigh-Taylor convection in granular media for CO2 sequestration by dissolution trapping, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17523, https://doi.org/10.5194/egusphere-egu23-17523, 2023.

SSS7 – Soil Pollution and Reclamation

EGU23-1876 | ECS | Posters on site | SSS7.1

Methodological proposal for the reconstruction of paleofire and fire history from sedimentological analysis 

Carlos Sánchez-García, Marcos Francos, and Manuel Esteban Lucas-Borja

Fire is a transcendental natural element in ecosystems. At the level of anthropic use, it plays a fundamental role when it comes to managing forest areas, and at the environmental level, it is a key factor in the evolution of ecosystems. Anthropogenic fires began to be detected in the Mesolithic-Neolithic transition, and in recent centuries they have become a constant in the Mediterranean regions. One of the post-fire effects is the loss of soil due to erosion, and in turn, the restoration measures are aimed at stabilizing the soil. Levees are one of the measures that has been used historically, these places act as sediment traps and, therefore, from the analysis of sediment and the analysis of sedimentary coals, the forest history of an affected area by fire, could be reconstructed. This presentation aims to provide a methodological proposal for the study and analysis of historical and prehistoric fires based on sedimentary analysis. The area that has been chosen for the proposal is dissociated between the southeast and the center-west of the Iberian Peninsula, Province of Albacete and Provinces of Salamanca, respectively. The sampling of sediment containment dikes and the analysis of the different soil layers (clay, sand or ash) are part of erosion and transport after fire. In this case, the ash layers serve as dating and the accumulation of sediments in upper layers allows us to know the loss of soil that occurred after the fire event. The different restoration measures that have been taken after the fire will cause the sedimentary aggradation in the dike to be different. Finally, in areas where the dry-stone walls have been built with the same intention as the dikes, it is possible to reconstruct the history of the fires from the sedimentary carbon; this technique is widely used in paleoenvironmental studies and, in this case, would provide information about the forest response at different climatic moments during the Holocene.

How to cite: Sánchez-García, C., Francos, M., and Lucas-Borja, M. E.: Methodological proposal for the reconstruction of paleofire and fire history from sedimentological analysis, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1876, https://doi.org/10.5194/egusphere-egu23-1876, 2023.

EGU23-2606 | Posters on site | SSS7.1

Effects of prescribed fire on soil hydrology on a global scale: a systematic review and a meta-analysis 

Demetrio Antonio Zema and Manuel Esteban Lucas-Borja

Wildfires are becoming more intense and threatening increasingly larger areas, with loss of biodiversity and increased hydrogeological risks. Prescribed fires are one of the most effective tools to control and limit the risk of catastrophic wildfires, preserving the natural state of forests. However, indications about the correct use of prescribed fire are needed by forest managers, and the analysis of published data reported in the relevant literature may be essential. This paper presents a review of 41 papers published in international scientific journals in the last 20 years about the hydrological and erosive effects of prescribed fire on forest soils. A quantitative database of observations about water infiltration, soil water repellency, surface runoff and soil erosion has been set up, based on measurements in 85 case studies reported in those articles. The effects of annual precipitation, soil slope, burn severity, fire application season, post-fire ground cover, and vegetation type on post-fire hydrology have been statistically explored using meta-analysis techniques. The bibliographic research has revealed that the case studies are not homogeneously distributed on the global scale but concentrated in few countries. The meta-analysis has shown that water infiltration decreases and soil water repellency appears in the short-term after prescribed fire. Noticeable increases in surface runoff (up to 20-fold the values measured in the unburned soils) and mainly in soil erosion (with peaks of 700-fold the pre-fire conditions) are common in the few months after the prescribed fire. Water infiltration is significantly influenced by precipitation, soil slope, soil burn severity, and vegetation type. All these variables together with burn season and ground cover after fire application are significant factors of variability of surface runoff, while only soil slope, vegetation type and burn season are significant drivers of soil erosion. The period of soil disturbance due to fire on soils commonly last few months, but some studies show that the pre-fire hydrological and erosive response to prescribed fire does not restore after two years. The post-fire increase in soil erosion is higher compared to surface runoff, and the highest soil loss is observed when fire is applied in summer in forest covered by trees, at soil slopes higher than 40%, moderate to high severities. On a practical approach, indications about the control and mitigation of the hydrogeological hazard after prescribed fire are given to land managers as follows: (i) need for post-fire management actions and control of soil burn severity and level of post-fire ground cover burning; (ii) temporal and spatial extensions of experimental activities to multi-year monitoring, catchment-scale investigations and observations also in case of repeated applications of prescribed fire; (iii) integration of the experimental observations with measurements of soil properties, vegetation characteristics and water quality; (vii) guidelines for standardized and appropriate measurement and analytical methods in experimental activities, in order to ensure the comparability of data and consistent interpretation of results.

How to cite: Zema, D. A. and Lucas-Borja, M. E.: Effects of prescribed fire on soil hydrology on a global scale: a systematic review and a meta-analysis, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2606, https://doi.org/10.5194/egusphere-egu23-2606, 2023.

EGU23-3221 | Orals | SSS7.1

Growing perennial grasses on contaminated soils for phytoremediation and renewable energy: a nature-based solution to maximise energy and eco-system service provision? 

Richard Lord, Ben Nunn, Ben Wright, Andrea Colantoni, Leonardo Bianchini, Riccardo Alemanno, Oleksandra Tryboi, Maico Severino, and Wilson Leandro

Available data indicates 2.8 million potentially contaminated sites, just across the EU-28. While 650,000 sites have been registered, only 1 in 10 have so far been remediated[1]. The management cost of European contaminated sites is estimated at €6 billion annually[2]. The main types of contaminants are potentially toxic elements (including heavy metals). Similarly, a 2014 Government study in China found 16.1% of all soil and 19.4% of arable land showed contamination, with Cd, Ni and As being the main pollutants[3]. Meanwhile, the global challenge of feeding growing populations while still reducing greenhouse gas emissions leaves less agricultural for dedicated bioenergy crops[4]. Therefore, there is a pressing need to successfully combine nature-based decontamination through phytoremediation with bioenergy production.

 

Given the wide variety of non-agricultural marginal lands[5], species selection must combine significant biomass production with acceptable levels of contamination for subsequent use or energy conversion.  Whereas specialist hyperaccumulator plants may achieve higher levels of contaminants and greater bioconcentration and translocation factors, their inherently lower productivity means that biomass, energy yield and mass of contaminants removed per unit area will be relatively small.  In contrast, high yielding, low contaminant uptake characteristics, such as for conventional energy crop species, could result in greater energy production, economic viability and biomass utilisation potential.

 

Here we report on field scale trials to implement this strategy, part of the CERESiS (ContaminatEd land Remediation through Energy crops for Soil improvement to liquid biofuels Strategies) H2020 Project (GA 101006717). We have evaluated the performance of Phalaris, Miscanthus, Saccharum and Pennisetum species for combined phyto-remediation and phyto-management of contaminated land during energy crop production in Brazil and Europe.  Reed canarygrass (Phalaris arundinacea) is a native perennial rhizomatous C3 species suitable for non-agricultural or marginal lands and climatic zones such as Scotland (where Miscanthus x giganteous cannot grow).  Our phytoremediation trials using Phalaris in Italy and Ukraine are the first we are aware of.  In the UK the CERESiS project has utilised field trials originally established during the BioReGen (Biomass, Remediation, re-Generation: Reusing Brownfield Sites for renewable energy crops) EU Life demonstration Project (LIFE05 ENV/UK/000128) in 2007.  These allowed direct comparison of the actual contaminant removal rates of three crop species:  Although the biomass of Miscanthus and short-rotation coppice Salix contained higher concentrations of certain elements, Phalaris far out-performed these in terms of biomass, ease and economy of production[6].  Surprisingly, despite lower contaminant concentrations in Phalaris, such was the increased biomass that the total mass removed was still greater than for Miscanthus or Salix.  This suggests that low-uptake phyto-excluding plants which can tolerate contaminated soils and grow productively may still represent the best and most economically viable option for clean-up of contaminated sites. Meanwhile this nature-based solution can simultaneously deliver a variety of wider societal and environmental benefits, such as greening-up derelict land or the enhanced storage of carbon in soils[7].


[1] Pérez & Eugenio (2018).

[2] Panagos et al. (2013).

[3] https://www.bbc.com/news/world-asia-china-27076645

[4] Searchinger et al. (2018).

[5] Mellor et al. (2021).

[6] Lord (2015).

[7] Lord & Sakrabani (2019).

How to cite: Lord, R., Nunn, B., Wright, B., Colantoni, A., Bianchini, L., Alemanno, R., Tryboi, O., Severino, M., and Leandro, W.: Growing perennial grasses on contaminated soils for phytoremediation and renewable energy: a nature-based solution to maximise energy and eco-system service provision?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3221, https://doi.org/10.5194/egusphere-egu23-3221, 2023.

EGU23-4373 | ECS | Orals | SSS7.1 | Highlight

Engineered soils for recultivation of degraded sites 

Anja Gantar, Vesna Zupanc, Helena Grčman, and Marko Zupan

The total area of agricultural land in Europe and Slovenia is constantly decreasing, causing the loss of a potential for food production and self-sufficiency capacity. In addition to limiting soil sealing, one of the main objectives of the EU Soil Strategy for 2030 involves recultivating degraded sites, which requires appropriate materials, in particular for fertile, top layers.

Due to the complexity of the restoration process of agricultural land, the ability of the restored areas to provide full or any scope of ecosystem services as expected depends on several factors. What the opencast mines have in common is the removal of the top, fertile part of the soil in the exercising of mining rights. The availability of fertile soils with suitable properties is often one of the main limitations for appropriate recultivation. Whilst less fertile soil or even inert construction or industry residuals may be used to recultivate the lower layers, the top layers require using engineered soils with appropriate physical, biological and chemical properties. These properties depend on the purpose of the final use of sites. Apart from making sure that the engineered soils have appropriate physical, chemical and biological properties, it is also necessary that they do not contain excessive concentrations of potentially hazardous substances when it comes to agricultural use.

The primary aim and objective is to develop technologies for producing fertile soils from inorganic and organic waste resulting from construction work or opencast mines and other industrial processes. The main categories of waste where the Slovenian recycling rate is lower than the EU rate are sewage sludge and non-hazardous construction and demolition waste. In this contribution, we are studying how to improve non-fertile soils with various additives of secondary origin to prepare fertile soil mixtures that enable a safe space greening or even food production.

Acknowledgements: Project LIFE20 IPE/SI/000021 je co-financed by European Union.

Keywords: agricultural landscape, land rehabilitation, recultivation, top soil

How to cite: Gantar, A., Zupanc, V., Grčman, H., and Zupan, M.: Engineered soils for recultivation of degraded sites, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4373, https://doi.org/10.5194/egusphere-egu23-4373, 2023.

EGU23-4533 | Posters on site | SSS7.1

How do mine rehabilitation strategies affects soil heterogeneity and structure in the long term? 

Thomas Baumgartl, Franziska Bucka, Evelin Pihlap, and Vilim Filipovic

Open-cast or surface mining present a site-specific and a temporary use of land that unavoidably involves the displacement of the fertile topsoil layer and overall environmental change. Following mine closure, rehabilitation of mining areas is essential to build sustainable and stable landforms. Reclamation of soils is particularly challenging as their construction needs to take into account broader land reclamation analysis including soils, water, vegetation, stability and biodiversity effects. The objective of this study was to assess development in soil properties of rehabilitated soils since construction (1980, 1998, 2009, 2016, 2017) focusing on hydraulic and mechanical soil properties. The study was performed at an open-cast lignite coal mine site in south-east Australia (Victoria) in 2021. Soil hydraulic properties (SHP) were determined using the extended evaporation method while the mechanical properties were assessed using in-situ vane shear tests. The study indicated the relevance of a consistent soil cover design and construction. The soil hydraulic properties results showed a shift in soil water retention curve characteristic (1980 vs 2017 site), together with a decrease in saturated hydraulic conductivity (Ks), which can certainly influence soil water dynamics and increase surface runoff. The vane shear test showed large heterogeneity among the sites with rehabilitated sites indicating large internal variation compared to the reference site and generally higher shear resistance. Differences in soil hydraulic conductivity and higher SOC storage over time revealed developments in soil recovery, but the improvement in soil mechanical strength did not show any relation to soil properties affecting soil structural stability. Rather, the change was driven by the large variability in texturally affected pore size distribution among the sites. The observed small-scale heterogeneity of the rehabilitated soils is most likely explained by disturbance due to excavation activities and used rehabilitation methods as well as availability of the soil material. Closer monitoring of rehabilitated areas temporally and spatially as well as in improvement in topsoil cover design is recommended, as such heterogeneity leads to uncertainty in long-term sustainable landscape formation.

How to cite: Baumgartl, T., Bucka, F., Pihlap, E., and Filipovic, V.: How do mine rehabilitation strategies affects soil heterogeneity and structure in the long term?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4533, https://doi.org/10.5194/egusphere-egu23-4533, 2023.

EGU23-4561 | Posters on site | SSS7.1

How a Short Prescribed Fire Affects Soil Physical and Hydraulic Properties, Soil Water Balance, and Emergent Vegetation in a Grassland 

David Zumr, Tailin Li, Jakub Jeřábek, Jan Winkler, and Magdalena Vaverková

A controlled burn was conducted on a grassland in Řisuty, Czech Republic, to study the effects of a short prescribed fire on soil physical and hydraulic properties, soil water balance and emergent vegetation. The grassland was newly established on arable soil three years prior to the study. The experimental site contained a weather station and sensors to measure soil temperature and soil moisture at three different depths. The soil, a loamy Cambisol, was not water repellent. A 5 x 5 m plot covered with sun-dried grass was burnt. The fire reached a temperature of about 700 °C over a period of 15 minutes. The subsequent hydrological regime of the soil was compared with that of a nearby unburned reference plot. Immediately after the fire and at weekly to monthly intervals thereafter, soil samples were taken to determine organic carbon content, soil structure stability, hydraulic conductivity, bulk density and soil texture. The results showed that temporary burning improved the hydraulic properties of the topsoil, with the infiltration capacity and water content of the soil in the burnt plot increasing throughout the year compared to the control plot. This provided a suitable habitat for the colonising vegetation. The findings suggest that small-scale controlled biomass burning can have a positive impact on the soil ecosystem and a temporary improvement in the hydraulic properties of the upper soil layer. The contribution is a result of a INTER‐COST project of the Ministry of Education, Youth and Sports of the Czech republic, grant no. LTC20001.

How to cite: Zumr, D., Li, T., Jeřábek, J., Winkler, J., and Vaverková, M.: How a Short Prescribed Fire Affects Soil Physical and Hydraulic Properties, Soil Water Balance, and Emergent Vegetation in a Grassland, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4561, https://doi.org/10.5194/egusphere-egu23-4561, 2023.

EGU23-4613 | ECS | Posters on site | SSS7.1

Changes in soil chemical properties along afforestation chronosequence in the dried Aral Sea bed, Kazakhstan, from 1990-2019 

Gaeun Kim, Jieun Ahn, Hanna Chang, Jiae An, and Yowhan Son

Desiccation of the Aral Sea left a vast area of unstable, saline, and barren seafloor. In response, afforestation using indigenous trees, mainly Haloxylon species, has been performed to ameliorate the soil. This study examined 1) changes in topsoil chemical properties after vegetation establishment based on 30-year chronosequence of afforested sites and 2) dynamics in the topsoil properties in two cases of naturally vegetated versus afforested areas. In August 2019, soils were sampled from the northeastern Aral Sea bed, Kazakhstan, where the shoreline retreated during the 1970s. We selected a non-saline area without any vegetation, a visibly salinized area without any natural vegetation, and 12 paired sites with predominantly sandy soil texture that were naturally vegetated or afforested during 1990, 2000, 2005, 2008, 2013, and 2017. In the 0‒10 cm soil layer, 3 points were sampled in each site and we analyzed soil pH, electrical conductivity (EC), total dissolved solids (TDS), exchangeable sodium percentage (ESP), total nitrogen (TN) and carbon (TC), total organic carbon (TOC), available phosphorus concentration (P2O5), exchangeable cation concentrations (K+, Mg2+, Ca2+, and Na+), and cation exchange capacity (CEC). The soil samples in chronosequence sites showed a wide range of EC, without any significant temporal trend. The pH ranged between 8.5 and 10.0, characterized soil as alkaline. CEC ranged from 9 to 45 cmolc kg-1. Soil pH, EC, and TDS variations among the chronosequence sites (natural or afforested) were not statistically significant. In contrast, we observed marginal increases in K+ and P2O5 after the vegetation establishment. Also, TN and TOC concentrations increased over time, significantly faster in afforested than in naturally vegetated sites. However, TC contents showed a sudden decrease in the oldest natural vegetation. This result may be partly attributed to the spatial variability in sampling locations used for the chronosequence analysis. Lastly, there were strong positive correlations among TOC, TN, K+, and P2O5; which imply an increase in soil organic materials’ contribution to nutrient accumulation and overall soil quality. In conclusion, afforestation contributed to soil amelioration but this effect was also observed in naturally vegetated sites.

How to cite: Kim, G., Ahn, J., Chang, H., An, J., and Son, Y.: Changes in soil chemical properties along afforestation chronosequence in the dried Aral Sea bed, Kazakhstan, from 1990-2019, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4613, https://doi.org/10.5194/egusphere-egu23-4613, 2023.

Irrigation with secondary treated waste water (TWW) may harm soils, especially clayey ones, through increasing soil salinity and sodicity that subsequently impair its physical and hydraulic properties. We compared the effects of TWW-irrigated  compost and tuff trenches placed in an almond orchard of Kibutz Lavee, Israel, on  properties of a clayey soil to those of TWW or fresh water (FW) irrigation.  Both types of trenches did not reduce soil sodicity (expressed in terms of sodium adsorption ratio, SAR). Compost trenches had no effect on soil salinity while the Tuff ones reduced salinity.  Compost trenches increased soil water content and oxygen concentration, whereas Tuff increased aeration but not soil water content. All treatments irrigated with TWW did not improve aggregate stability relative to irrigation with FW. We conclude that compost and tuff trenches could be considered as solutions for enhancing aeration in the root zone and thus potentially improve crop performance.

How to cite: Levy, G., Zireeni, Y., and Bar-Tal, A.: Effects of Trenches Filled with Compost or Tuff on some Properties of a Clayey Soil Irrigated  with Secondary Treated Waste Water., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4888, https://doi.org/10.5194/egusphere-egu23-4888, 2023.

EGU23-5920 | Posters virtual | SSS7.1

The response of soil in a semi-arid landscape with SE orientation after early prescribed burning. 

Álvaro Fajardo-Cantos, Esther Peña-Molina, Javier González-Romero, Daniel Moya, Asunción Díaz, Raúl Botella, Manuel-Esteban Lucas-Borja, and Jorge Antonio De las Heras

The current forest fire regimes are increasing due to high temperatures, global warming and frequency of wildfires in dry ecosystems like in the Mediterranean Basin. These issues are decreasing ecosystem’s resistance and resilience, worsening desertification, for this reason, it is of great importance to analyze the effects on the soil. However, it is now possible to apply some preventive tools to avoid wildfire effects or reduce their impacts on ecosystems. Fire is used as preventive tool, prescribed burning (PB) change both the fuel loads in forest ecosystems and vegetation strata. However, fire can produce changes in soil characteristics and physico-chemical parameters.

The studied PB was carried out in spring 2021 (early burn) in SE Spain. The mainly vegetation is shrub (i.e., Macrochloa tenacissima (L.) Kunth, Cistus Clusii Dunal, Salvia rosmarinus (L.) Schleid) with poor dry soils formed mainly by cambisols. For improve the knowledge at short/medium-term PB effects on soil, this study attempted to analyze the ecological early PB effects on semi-arid land soils by CO2 flow soil respiration (SR) automatic chamber (CFLUX-1 Soil CO2 Flux System), minidisk infiltrometers for soil hydraulic conductivity (SHC) by infiltration rate and Water Drop Penetration Time (WDPT) methodology for measuring soil water repellency (SWR). It also analyzed soil physico-chemical properties. In addition, this study tries to generate a protocol or guide of good practices for PB. There were no significant differences in any studied variables after the 1-year period according to our formulated hypotheses. However, effects were observed on some parameters on the first days after the PB, such as SOM and nutrients.

How to cite: Fajardo-Cantos, Á., Peña-Molina, E., González-Romero, J., Moya, D., Díaz, A., Botella, R., Lucas-Borja, M.-E., and De las Heras, J. A.: The response of soil in a semi-arid landscape with SE orientation after early prescribed burning., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5920, https://doi.org/10.5194/egusphere-egu23-5920, 2023.

EGU23-7858 | Orals | SSS7.1

The potential of plantations to restore ecosystem services, a case study from Ghana 

Frank Berninger, Hugh Brown, and Mark Appiah

The role of plantations for restoring humid forest ecosystems is subject to intense debate. Some studies suggest that plantations are inferior to secondary forests in most ecosystem services. In contrast, other studies emphasise the role of planted trees that could catalyse an accelerated development towards late-successional forests. Our study analyses a unique dataset of old (>40 years) unmanaged timber plantations. Planted species were Aucoumea klaineana, Cedrela odorata, Tarrietia utilis, and Terminalia ivorensis. We compare these to secondary forests, and pristine primary stands. Our results indicate that in the unmanaged plantations, species-rich stands with high biomass evolved. The carbon stocks of the unmanaged plantations exceeded the secondary forest and had similar levels to the primary stands. The biomass of the naturally regenerated trees in the plantations was similar to secondary forests. Not surprisingly, timber value of the plantations surpassed both primary forests and secondary forests. Results were more mixed for biodiversity attributes. Plantations of Aucoumea klaineana had lower diversity values than the primary and secondary forests. However, other species, especially plantations of Cedrela odorata, had similar diversity to primary and secondary forests. Species with high conservation value were present in all three ecosystem types. Above-ground carbon stocks in plantations were highest, and there were no statistical differences in below-ground carbon stocks. Our results indicate that plantations could play a role in rapidly accruing carbon in tropical landscapes. 

How to cite: Berninger, F., Brown, H., and Appiah, M.: The potential of plantations to restore ecosystem services, a case study from Ghana, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7858, https://doi.org/10.5194/egusphere-egu23-7858, 2023.

EGU23-8228 | ECS | Posters on site | SSS7.1

Adaptive land management to fight land degradation in Mediterranean agroforestry pastoral areas 

Hafiz Khuzama Ishaq, Eleonora Grilli, Iseult Malrieu, Micol Mastrocicco, Rosaria D’Ascoli, Gianluigi Busico, Flora Angela Rutigliano, Rossana Marzaioli, Elio Coppola, Fernando Pulido, Filipe Silva, Marco Bijl, Joao Madeira, and Simona Castaldi

Healthy soils are fundamental to support ecosystem functions and productivity and represent an adaptive fundamental condition to face climatic change extremes, like in Southern Mediterranean often characterized by land degradation, soil erosion and desertification risk. As part of the project LIFE16 CCA/IT/000011 Desert Adapt, since 2018 we have been working on agroforestry pastoral areas of Portugal to test more adaptive strategies, including changes in grazing cycles which can allow a better regeneration of the grass cover, higher protection of the soil and improvement of the overall soil functions that support pasture productivity. We present the first data set of soil monitoring from spring 2022 and we combine the evaluation of soil amelioration with a full integrated management view of the improved grazed system to underline the multiple beneficial environmental effects of soil protection within and beyond the soil system.

How to cite: Ishaq, H. K., Grilli, E., Malrieu, I., Mastrocicco, M., D’Ascoli, R., Busico, G., Rutigliano, F. A., Marzaioli, R., Coppola, E., Pulido, F., Silva, F., Bijl, M., Madeira, J., and Castaldi, S.: Adaptive land management to fight land degradation in Mediterranean agroforestry pastoral areas, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8228, https://doi.org/10.5194/egusphere-egu23-8228, 2023.

EGU23-8507 | ECS | Orals | SSS7.1

Optimising soil profiles to support calcareous grassland habitat creation 

Chris McCloskey, R. Jane Rickson, Wilfred Otten, Rebecca Butler, Chris Cantle, Matt Hobbs, and Ceri Spears

Calcareous grasslands are some of Europe’s most species-rich plant communities and important biodiversity sites. These habitats are, however, threatened; many in the UK were lost to changing land use during the 20th century and pressure continues on the remaining (often scarce and fragmented) sites. Habitat restoration and rewilding are increasingly important both in the public consciousness and in governmental policy, and the ecological value and threatened nature of calcareous grasslands make them a prime target for restoration efforts. A growing number of projects are therefore working to restore or re-create chalk grassland ecosystems. An under-explored aspect of this, however, is how by-products from land development projects might be re-purposed to create the specialised soil environment needed to support calcareous grassland communities. This has the potential to combine sustainable re-use of construction materials with novel ways to create or restore calcareous grassland habitats and thus ensure infrastructure projects contribute to net biodiversity gain.

 

In this study we investigate how to optimise the design of soil profiles to support calcareous grassland ecosystems. The study site is located in within the Central 1 section of the HS2 (High Speed 2) Phase One rail development in the Colne Valley (England) being delivered by the Align joint venture. The aim is to create a large area of calcareous grassland as part of a broader (127 hectare) mosaic habitat creation including calcareous grassland, wood pasture and wetland in land that is currently used for construction but was previously arable land. The ‘Colne Valley Western Slopes’ will, when complete, be the largest single area of habitat creation along the HS2 route and will significantly contribute to the project’s commitment to deliver ‘No Net Loss’ in biodiversity.

 

The properties of underlying soils are critical for the establishment, development and health of this internationally important chalk grassland ecosystem. Physical, chemical and biological properties such as soil structure, drainage and restricted nutrient availability are essential for supporting the diverse plant assemblages found in calcareous grasslands. In this project, we are testing through a combination of controlled environment studies and field trials four constructed soil profiles using different configurations of site-derived materials/construction by-products, using both controlled environment studies and field trials. The site-won materials include: 2.6 M m3 of excavated chalk from 16 km of tunnel construction, crushed limestone and concrete from decommissioned compounds/haul roads, and subsoils (stripped during site clearance) that contain highly variable percentages of CaCO3. Here we present results from a large-scale mesocosm trial alongside initial field trial data to assess how these constructed soil profiles affect key factors for habitat creation, including soil hydrology, soil microbial dynamics, nutrient cycling, and vegetation establishment and diversity. The findings for this project will inform and effectively complete the earthworks design for the creation of 88 hectares of calcareous grassland in the Colne Valley, as well as providing insights for other chalk grassland restoration projects elsewhere.

How to cite: McCloskey, C., Rickson, R. J., Otten, W., Butler, R., Cantle, C., Hobbs, M., and Spears, C.: Optimising soil profiles to support calcareous grassland habitat creation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8507, https://doi.org/10.5194/egusphere-egu23-8507, 2023.

EGU23-10170 | ECS | Orals | SSS7.1

Seed microbial community characterisation and isolation from three species common to fire-prone Australia. 

Nathali Maria Machado de Lima, Ryan Tangney, Miriam Muñoz Rojas, and Mark Ooi

Microorganisms called endophytes are passed from parent plants to their offspring and play significant roles in plant growth and development. In recent years, endophytes have gained attention for their ability to help plants withstand stress and have been used in revegetation efforts. However, there is still a lack of understanding about seed endophytes in ecosystems prone to fire, where the dormancy and germination of seeds are affected by various factors that can impact the persistence of plant populations. This gap in knowledge hinders the ability to predict how plant populations will respond to selective pressures and stress caused by climate change. To address this, the present study focused on characterizing seed-borne endophytes in order to understand their potential to enhance germination and growth under stress. Mixed and pure cultures of endophytes were isolated from the fire-prone species Anigozanthos manglesii, Haemodorum planifolium and Haemodorum spicatum, all of which are native to Banksia woodlands in Western Australia and belong to the Haemodoraceae family. The bacterial community composition and diversity of each species were also analyzed using next-generation sequencing targeting the 16S rRNA. This study is unique in examining seed endophytes in fire-prone species and provides a foundation for future research on the relationship between seed microbiome composition, germination success, and seedling vigour.

How to cite: Machado de Lima, N. M., Tangney, R., Muñoz Rojas, M., and Ooi, M.: Seed microbial community characterisation and isolation from three species common to fire-prone Australia., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10170, https://doi.org/10.5194/egusphere-egu23-10170, 2023.

EGU23-12372 | ECS | Posters virtual | SSS7.1 | Highlight

Dry grassland restoration in Mediterranean degraded lands: the NewLife4Drylands pilot case in Alta Murgia 

Rocco Labadessa, Luigi Forte, Serena D’Ambrogi, Paolo Mazzetti, Laura Tomassetti, and Cristina Tarantino

The need of adopting practices to restore degraded land has been stressed by the new Soil Strategy, with regard to dry ecosystems showing greater risk of desertification. To assess the effectiveness, feasibility and replicability of restoration techniques applied to Mediterranean dry ecosystems, a set of different restoration techniques has been tested in Alta Murgia National Park (Southern Italy), one of the NewLife4Drylands project (NL4D; https://www.newlife4drylands.eu) pilot sites. This area is particularly subjected to land degradation processes as a result of recent and widespread activities of rock shattering for the conversion of calcareous pastures to croplands, which had caused an extensive loss of semi-natural vegetation and ecosystem functions. Experimental efforts were aimed at testing sustainable techniques for the restoration of protected dry grassland types that naturally occur in the study area. Within an overall surface of 9000 m2, 42 experimental plots of 20x10m areas (14 treatments with 3 replicates) were selected in either recently ploughed or unploughed surfaces. For each soil type, a set of restoration techniques was tested, including different combinations of soil processing (i.e. harrowing, topsoil inversion, sod cutting, soil compression), transfer of plant material (i.e. dry hay, seed-enriched hay, shrub seeds) and so