EGU General Assembly 2022  

Forest soils are undeniably recognized to help deliver essential ecosystem services. Nevertheless this provision is facing serious threats at a moment we need forests the most. The increasing frequency of fire-prone weather conditions in the EU such as the ones causing exceptional wildfire scars in 2017 (San-Miguel-Ayanz et al., 2018), combined with extreme climate demands (IPCC, 2021) and an escalation of forest mechanisation driven by a systematic increase in the use of forest products (EUROSTAT, 2021), have been putting  EU forest soils to a new level of pressure. As a result, key ecosystem services such as clean water provision and flood control, habitats for life and biodiversity,  biomass provision and carbon sinks, are at stake.

On the other hand, several positive policy initiatives have been initiated under the umbrella of the European Green deal, such as the EU Forest and Biodiversity strategies for 2030. These aim for more healthy, diverse and resilient EU forests, ensuring we can count on their contribution for the most recent climate and biodiversity ambitions. Such initiatives combined with the new EU Soil Strategy should underpin a new era of ecosystems resilience and halt the latest land degradation trends. But the question remains: what is the current state of the EU forest soils after so many years of coexistence with the Europeans?

This presentations aims to provide an overall perspective on current threats affecting forest soils. Issues such as recurrent wildfires, inappropriate land management, land use and land cover changes are all sides of the same coin. Not surprisingly these will lead to land degradation, triggered most frequently by soil erosion. In addition, this paper will identify several misconceptions driven by remote sensing based assessments, such as the identification of good soil conditions under vigorous leaf area indexes, or the consideration of good soil management practices in all forest terraces.

With this argumentation the author hopes to trigger a healthy discussion on the idea that our EU forest soils are not in their best shape, and they too need to be cared for and managed. 

How to cite: Vieira, D.: Forest soils under threat too., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3542, https://doi.org/10.5194/egusphere-egu22-3542, 2022.

Plant roots and the organisms that surround them are a primary source for stabilized soil organic carbon (SOC). While grassland soils have a large capacity to store organic carbon (C), few field-based studies have quantified the amount of plant-fixed C that moves into soil and persists belowground over multiple years. Yet this characteristic of the soil C cycle is critical to C storage, soil water holding capacity and nutrient provisions, and the management of soil health. We tracked the fate of plant-fixed C following a five-day ¹³CO₂labeling of a Northern California annual grassland, measuring C pools starting at the end of the labeling period, at three days, four weeks, six months, one year, and two years. Soil organic carbon was fractionated using a density-based approach to separate the free-light fraction (FLF), occluded-light fraction (OLF), and heavy fraction (HF). Using isotope ratio mass spectrometry, we measured ¹³C enrichment and total C content for plant shoots, roots, soil, soil dissolved organic carbon (DOC), and the FLF, OLF, and HF. The chemical nature of C in the HF was further analyzed by solid state ¹³C nuclear magnetic resonance (NMR) spectroscopy.
At the end of the labeling period, a substantial portion of the ¹³C (40%) was already found belowground in roots, soil, and soil DOC. By 4 weeks, the highest isotope enrichment and 27% of the total amount of ¹³C remaining in the system was associated with the mineral-rich HF. At the 6-month sampling—after the dry summer period during which plants senesced and died—the amount of label in the FLF increased to an amount similar to that in the HF. The FLF ¹³C then declined substantially by 1 year and further decreased in the 2^ndyear. By the end of the 2-year experiment, 67% of remaining label was in the HF, with 19% in the FLF and 14% in the OLF.
While the ¹³C content in the HF was stable over the final year, the chemical forms associated with the HF evolved with time. The relative proportion of aliphatic/alkyl C functional groups declined in the newly formed SOC over the 2-years in the field; simultaneously, aromatic and carbonyl/carboxylic C functional groups increased and the proportion of carbohydrate (O-alkyl C) groups remained relatively constant.
Our results indicate that plant-fixed C moved into soil within days of its fixation and was associated with the soil mineral fraction within weeks. While most of the annual plant C input in these grasslands cycles rapidly (<2-year timescale), a sizeable proportion (about 23% of the ¹³C present at day 0) persisted in the soil for longer than 2 years. While decadal studies would allow improved assessment of the long-term stabilization of newly fixed plant C, our 2-year field study reveals surprisingly rapid movement of plant C into the HF of soil, followed by subsequent evolution of the chemical forms of organic C in the HF.

How to cite: Firestone, M., Fossum, C., Estera-Molina, K., Yuan, M., Herman, D., Chu-Jacoby, I., Nico, P., Morrison, K., and Pett-Ridge, J.: Belowground allocation and dynamics of recently fixed plant carbon in a California annual grassland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13569, https://doi.org/10.5194/egusphere-egu22-13569, 2022.

The Kigezi highlands, southwestern Uganda, is a mountainous tropical region with a high population density, intense rainfall, alternating wet and dry seasons and high weathering rates. As a result, the region is regularly affected by multiple natural hazards such as landslides, floods, heavy storms, and earthquakes. In addition, deforestation and land use changes are assumed to have an influence on the patterns of natural hazards and their impacts in the region. Landscape characteristics and dynamics controlling the occurrence and the spatio-temporal distribution of natural hazards in the region remain poorly understood. In this study, citizen science has been employed to document and understand the spatial and temporal occurrence of natural hazards that affect the Kigezi highlands in relation to the multi-decadal landscape change of the region. We present the methodological research framework involving three categories of participatory citizen scientists. First, a network of 15 geo-observers (i.e., citizens of local communities distributed across representative landscapes of the study area) was established in December 2019. The geo-observers were trained at using smartphones to collect information (processes and impacts) on eight different natural hazards occurring across their parishes. In a second phase, eight river watchers were selected at watershed level to monitor the stream flow characteristics. These watchers record stream water levels once daily and make flood observations. In both categories, validation and quality checks are done on the collected data for further analysis. Combining with high resolution rainfall monitoring using rain gauges installed in the watersheds, the data are expected to characterize catchment response to flash floods. Lastly, to reconstruct the historical landscape change and natural hazards occurrences in the region, 96 elderly citizens (>70 years of age) were engaged through interviews and focus group discussions to give an account of the evolution of their landscape over the past 60 years. We constructed a historical timeline for the region to complement the participatory mapping and in-depth interviews with the elderly citizens. During the first 24 months of the project, 240 natural hazard events with accurate timing information have been reported by the geo-observers. Conversion from natural tree species to exotic species, increased cultivation of hillslopes, road construction and abandonment of terraces and fallowing practices have accelerated natural hazards especially flash floods and landslides in the region. Complementing with the region’s historical photos of 1954 and satellite images, major landscape dynamics have been detected. The ongoing data collection involving detailed ground-based observations with citizens shows a promising trend in the generation of new knowledge about natural hazards in the region.

How to cite: Kanyiginya, V., Twongyirwe, R., Kagoro, G., Mubiru, D., Kervyn, M., and Dewitte, O.: Understanding natural hazards in a changing landscape: A citizen science approach in Kigezi highlands, southwestern Uganda, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2024, https://doi.org/10.5194/egusphere-egu22-2024, 2022.

Human life in cities is already affected by climate change. The effects will become even more pronounced in the coming years and decades. Next-generation of city climate services is necessary for adapting infrastructures and the management of services of cities to climate change. These services are based on advanced weather forecast models and the access to diverse data. It is essential to keep in mind that each citizen is a unique individual with their own peculiarities, preferences, and behaviors. The base for our approach is the individual specific exposure, which considers that people perceive the same conditions differently in terms of their well-being. Individual specific exposure can be defined as the sum of all environmental conditions that affect humans during a given period of time, in a specific location, and in a specific context. Thereby, measurable abiotic parameters such as temperature, humidity, wind speed, pollution and noise are used to characterize the environmental conditions. Additional information regarding green spaces, trees, parks, kinds of streets and buildings, as well as available infrastructures are included in the context. The recording and forecasting of environmental parameters while taking into account the context, as well as the presentation of this information in easy-to-understand and easy-to-use maps, are critical for influencing human behavior and implementing appropriate climate change adaptation measures.

We will adopt this approach within the frame of the recently started, EU-funded CityCLIM project. We aim to develop and implement approaches which will explore the potential of citizen science in terms of current and historical data collecting, data quality assessment and evaluation of data products.  In addition, our approach will also provide strategies for individual climate data use, and the derivation and evaluation of climate change adaptation actions in cities.

In a first step we need to define and to characterize the different potential stakeholder groups involved in citizen science data collection. Citizen science offers approaches that consider citizens as both  organized target groups (e.g., engaged companies, schools) and individual persons (e.g. hobby scientists). An important point to be investigated is the motivation of citizen science stakehoder groups to sustainably collect data and make it available to science and reward them accordingly. For that purpose, strategic tools, such as value proposition canvas analysis, will be applied to taylor the science-to-business and the science-to-customer communications and offers in terms of the individual needs.

How to cite: Dietrich, P., Ködel, U., Schütze, S., Schmidt, F., Schütze, F., Bonn, A., Herrmann, T., and Schütze, C.: Possible Contributions of Citizen Science in the Development of the Next Generation of City Climate Services, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2929, https://doi.org/10.5194/egusphere-egu22-2929, 2022.

Picture Pile is a flexible web-based and mobile application for ingesting imagery from satellites, orthophotos, unmanned aerial vehicles and/or geotagged photographs for rapid classification by volunteers. Since 2014, there have been 16 different crowdsourcing campaigns run with Picture Pile, which has involved more than 4000 volunteers who have classified around 11.5 million images. Picture Pile is based on a simple mechanic in which users view an image and then answer a question, e.g., do you see oil palm, with a simple yes, no or maybe answer by swiping the image to the right, left or downwards, respectively. More recently, Picture Pile has been modified to classify data into categories (e.g., crop types) as well as continuous variables (e.g., degree of wealth) so that additional types of data can be collected.

The Picture Pile campaigns have covered a range of domains from classification of deforestation to building damage to different types of land cover, with crop type identification as the latest ongoing campaign through the Earth Challenge network. Hence, Picture Pile can be used for many different types of applications that need image classifications, e.g., as reference data for training remote sensing algorithms, validation of remotely sensed products or training data of computer vision algorithms. Picture Pile also has potential for monitoring some of the indicators of the United Nations Sustainable Development Goals (SDGs). The Picture Pile Platform is the next generation of the Picture Pile application, which will allow any user to create their own ‘piles’ of imagery and run their own campaigns using the system. In addition to providing an overview of Picture Pile, including some examples of relevance to SDG monitoring, this presentation will provide an overview of the current status of the Picture Pile Platform along with the data sharing model, the machine learning component and the vision for how the platform will function operationally to aid environmental monitoring.

How to cite: Sturn, T., See, L., Fritz, S., Karanam, S., and McCallum, I.: Extending Rapid Image Classification with the Picture Pile Platform for Citizen Science, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4168, https://doi.org/10.5194/egusphere-egu22-4168, 2022.

Last year, the Institute for Soil Sciences, Centre for Agricultural Research launched Hungary's first citizen science project with the aim to obtain information on the biological activity of soils using a simple estimation procedure. With the help of social media, the reactions on the call for applications were received from nearly 2000 locations. 

In the Hungarian version of the international Soil your Undies programme, standardized cotton underwear was posted to the participants with a step-by-step tutorial, who buried their underwear for about 60 days, from mid of May until July in 2021, at a depth of about 20-25 cm. After the excavation, the participants took one digital image of the underwear and recorded the geographical coordinates, which were  uploaded to a GoogleForms interface together with several basic information related to the location and the user (type of cultivation, demographic data etc.).

By analysing digital photos of the excavated undies made by volunteers, we obtained information on the level to which cotton material had decomposed in certain areas and under different types of cultivation. Around 40% of the participants buried the underwear in garden, 21% in grassland, 15% in orchard, 12% in arable land, 5% in vineyard and 4% in forest (for 3% no landuse data was provided).

The images were first processed using Fococlipping and Photoroom softwares for background removing and then percentage of cotton material remaining was estimated based on the pixels by using R Studio ‘raster package’.

The countrywide collected biological activity data from nearly 1200 sites were statistically evaluated by spatially aggregating the data both for physiographical and administrative units. The results have been published on various platforms (Facebook, Instagram, specific web site etc.), and a feedback is also given directly to the volunteers.

According to the experiments the first citizen science programme proved to be successful. 

Acknowledgment: Our research was supported by the Hungarian National Research, Development and Innovation Office (NKFIH; K-131820)

Keywords: citizen science; soil life; soil health; biological activity; soil properties

How to cite: Árvai, M., László, P., Takáts, T., Kovács, Z. A., Takács, K., Mészaros, J., and Pásztor, L.: Life in undies – Preliminary results of a citizen science data collection targeting soil health assessement in Hungary, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5094, https://doi.org/10.5194/egusphere-egu22-5094, 2022.

Citizen science is often heavily dependent on software tools that allow members of the general population to collect, view and submit environmental data to a common database. While several such software platforms exist, these often require expert knowledge to set up and maintain, and server and data hosting costs can become quite costly in the long term, especially if a project is successful in attracting many users and data submissions. In the context of time-limited project funding, these limitations can pose serious obstacles to the long-term sustainability of citizen science projects as well as their ownership by the community.

One the other hand, distributed database systems (such as Qri and Constellation) dispense with the need for a centralised server and instead rely on the devices (smartphone or computer) of the users themselves to store and transmit community-generated data. This new approach leads to the counterintuitive result that distributed systems, contrarily to centralised ones, become more robust and offer better availability and response times as the size of the user pool grows. In addition, since data is stored by users’ own devices, distributed systems offer interesting potential for strengthening communities’ ownership over their own environmental data (data sovereignty). This presentation will discuss the potential of distributed database systems to address the current technological limitations of centralised systems for open data and citizen science-led data collection efforts and will give examples of use cases with currently available distributed database software platforms.

How to cite: Malard-Adam, J., Harms, J., and Medema, W.: Distributed databases for citizen science, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5147, https://doi.org/10.5194/egusphere-egu22-5147, 2022.

During the last decades, countless seismic sensors have been deployed throughout the planet by different countries and institutions. In recent years, it has been possible to manufacture low-cost MEMS accelerometers thanks to nanotechnology and large-scale development. These devices can be easily configured and accurately synchronized by GPS. Customizable microcontrollers like Arduino or RaspBerryPI can be used to develop low-cost seismic stations capable of local data storage and real-time data transfer. Such stations have a sufficient signal quality to be used for complementing conventional seismic networks.

In recent years Instituto Volcanológico de Canarias (INVOLCAN) has developed a proprietary low-cost seismic station to implement the Canary Islands School Seismic Network (Red Sísmica Escolar Canaria - RESECAN) with multiple objectives:

• supporting the teaching of geosciences.
• promoting the scientific vocation.
• strengthening the resilience of the local communities by improving awareness toward volcanism and the associated hazards.
• Densifying the existing seismic networks.

On Sept. 19^th 2021, a volcanic eruption started on the Cumbre Vieja volcano in La Palma. The eruption was proceeded and accompanied by thousands of earthquakes, many of them felt with intensities up to V MCS. Exploiting the attention drawn by the eruption, INVOLCAN started the deployment of low-cost seismic stations in La Palma in educational centres. In this preliminary phase, we selected five educational centres on the island.

The project's objective is to create and distribute low-cost stations in various educational institutions in La Palma and later on the whole Canary Islands Archipelago, supplementing them with educational material on the topics of seismology and volcanology. Each school will be able to access the data of its station, as well as those collected by other centres, being able to locate some of the recorded earthquakes. The data recorded by RESECAN will also be integrated into the broadband seismic network operated by INVOLCAN (Red Sísmica Canaria, C7). RESECAN will be an instrument of scientific utility capable of contributing effectively to the volcano monitoring of the Canary Islands, reinforcing its resilience with respect to future volcanic emergencies.

How to cite: García-Hernández, R., Barrancos, J., D'Auria, L., Domínguez, V., Montalvo, A., and Pérez, N.: RESECAN: citizen-driven seismology on an active volcano (Cumbre Vieja, La Palma Island, Canaries), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5571, https://doi.org/10.5194/egusphere-egu22-5571, 2022.

Only a few of the increasing number of citizen science projects set out to determine the projects impact on diverse learning outcomes of citizen scientists. However, besides pure completion of project activities and data collection, measurable benefits as individual learning outcomes (ILOs) (Phillips et al. 2014) should reward voluntary work.

Within the citizen science project „TeaTime4Schools“, Austrian students in the range of 13 to 18 years collected data as a group activity in a teacher guided school context; tea bags were buried into soil to investigate litter decomposition. In an online questionnaire a set of selected scales of ILOs (Phillips et al. 2014, Keleman-Finan et al. 2018, Wilde et al. 2009) were applied to test those ILOs of students who participated in TeaTime4Schools. Several indicators (scales for project-related response, interest in science, interest in soil, environmental activism, and self-efficacy) were specifically tailored from these evaluation frameworks to measure four main learning outcomes: interest, motivation, behavior, self-efficacy. In total, 106 valid replies of students were analyzed. In addition, 21 teachers who participated in TeaTime4Schools, answered a separate online questionnaire that directly asked about quality and liking of methods used in the project based on suggested scales about learning tasks of University College for Agricultural and Environmental Education (2015), which were modified for the purpose of this study. Findings of our research will be presented.

How to cite: Wawra, A., Scheuch, M., Stürmer, B., and Sanden, T.: Analysis of individual learning outcomes of students and teachers in the citizen science project TeaTime4Schools, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6970, https://doi.org/10.5194/egusphere-egu22-6970, 2022.

Already sensitive because of its geology (seismic-tsunamic risk) and its interface between arid and temperate ecosystems, the Mediterranean Basin is being transformed by climate change and major urban pressure on resources and spaces. Lebanon concentrates on a small territory the environmental, climatic, health, social and political crises of the Middle East: shortages and degradation of surface and groundwater quality, air pollution, landscape fragmentation, destruction of ecosystems, erosion of biodiversity, telluric risks and very few mechanisms of information, prevention and protection against these vulnerabilities. Further, Lebanon is sorely lacking in environmental data at sufficient temporal and spatial scales to cover the range of key phenomena and to allow the integration of environmental issues for the country's development. This absence was sadly illustrated during the August 4th, 2020, explosion at the port of Beirut, which hindered the effective management of induced threats to protect the inhabitants. In this degraded context combined with a systemic crisis situation in Lebanon, frugal  innovation is more than an option, it is a necessity. Initiated in 2021 within the framework of the O-LIFE lebanese-french research consortium (www.o-life.org), the « Seismic and air monitoring observatory  for greater Beirut » (SMOAG) project aims at setting up a citizen observatory of the urban health of Beirut by deploying innovative, connected, low-cost, energy-efficient and robust environmental and seismological instruments. Through co-constructed web services and mobile applications with various stakeholders (citizens, NGOs, decision makers and scientists), the SMOAG citizen observatory will contribute to the information and mobilization of Lebanese citizens and managers by sharing the monitoring of key indicators associated with air quality, heat islands and building stability, essential issues for a sustainable Beirut.

The first phase of the project was dedicated to the development of a low-cost environmental sensor enabling pollution and urban weather measurements (particle matters, SO2, CO, O3, N02, solar radiation, wind speed, temperature, humidity, rainfall) and to the development of all the software infrastructure, from data acquisition to the synoptic indicators accessible via web and mobile application, while following the standards of the Sensor Web Enablement and Sensor Observation System of the OGC and to the FAIR principles (Easy to find, Accessible, Interoperable, Reusable). A website and Android/IOS applications for the restitution of data and indicators and a dashboard allowing real time access to data have been developed. Environmental and low-cost seismological stations (Raspberry Shake) have been already deployed in Beirut, most of them hosted by Lebanese citizens. These instrumental and open data access efforts were completed by participatory workshops with various stakeholders  to improve the ergonomy of the web and application interfaces and to define roadmap for the implantation of future stations, consistently with  most vulnerable populations identified by NGOs and the current knowledge on the air pollution and heat islands in Beirut.

How to cite: Cornou, C., Drapeau, L., El Bakouny, Y., Lahoud, S., Polikovitch, A., Abdallah, C., Abou Chakra, C., Afif, C., Al Bitar, A., Cartier, S., Fanice, P., Fenianos, J., Guillier, B., Khater, C., and Khoury, G. and the SMOAG Team: Seismic and air monitoring observatory for greater Beirut : a citizen observatory of the "urban health" of Beirut, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7164, https://doi.org/10.5194/egusphere-egu22-7164, 2022.

Water quality in the rivers and tributaries of the Brantas catchment (about 12.000 km²) is deteriorating due to various reasons, including rapid economic development, insufficient domestic water treatment and waste management, and industrial pollution. Various water quality parameters are at least measured on monthly basis by agencies involved in water resource development and management. However, measurements consistently demonstrate exceedance of the local water quality standards. Recent claims presented by the local Environmental Protection Agency indicate that the water quality is much more affected by the domestic sources compared to the others. In an attempt to examine this, we proposed a citizen science campaign by involving people from seven communities living close to the river, a network organisation that works on water quality monitoring, three government agencies, and students from a local university. Beginning in 2022, we kicked off our campaign by measuring with test strips for nitrate, nitrite, and phosphate on weekly basis at twelve different locations from upstream to downstream of the catchment. In the effort to provide education on water stewardship and empower citizens to participate in water quality management, preliminary results – the test strips, strategies, and challenges - will be shown.

How to cite: Pramana, R., Houser, S., Rini, D., and Ertsen, M.: Citizen science for better water quality management in the Brantas catchment, Indonesia? Preliminary results, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7323, https://doi.org/10.5194/egusphere-egu22-7323, 2022.

Available quality-checked institutional meteorological data is often not measured at locations of particular interest for observing specific small-scale and meso-scale atmospheric processes. Similarly, institutional data can be hard to obtain due to data policy restrictions. On the other hand, a lot of people are highly interested in meteorology, and they frequently deploy meteorological instruments at locations where they live. Such citizen data are often shared through public data repositories and websites with sophisticated visualization routines.  As a result, the networks of citizen meteorological stations are, in numerous areas, denser and more easily accessible than are the institutional meteorological networks.  

Several examples of publicly available citizen meteorological networks, including school networks, are explored – and their application to published high-quality scientific papers is discussed. It is shown that for the data-based analysis of specific atmospheric processes of interest, such as mesoscale convective disturbances and mesoscale atmospheric gravity waves, the best qualitative and quantitative results are often obtained using densely populated citizen networks.  

Finally, a “cheap and easy to do” project of constructing a meteorological station with a variable number of atmospheric sensors is presented. Suggestions on how to use such stations in educational and citizen science activities, and even in real-time warning systems, are given.  

How to cite: Sepic, J., Vranic, J., Aviani, I., Milanovic, D., and Burazer, M.: Citizen science - an invaluable tool for obtaining high-resolution spatial and temporal meteorological data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7916, https://doi.org/10.5194/egusphere-egu22-7916, 2022.

Among the greatest constraints to accurately monitoring and understanding climate and climate change in many locations is limited in situ observing capacity and resolution in these places. Climate behaviours along with dependent environmental and societal processes are frequently highly localized, while observing systems in the region may be separated by hundreds of kilometers and may not adequately represent conditions between them. Similarly, generating climate equity in urban regions can be hindered by an inability to resolve urban heat islands at neighborhood scales. In both cases, higher density observations are necessary for accurate condition monitoring, research, and for the calibration and validation of remote sensing products and predictive models. Coincidentally, urban neighborhoods are heavily populated and thousands of individuals visit remote locations each day for recreational purposes. Many of these individuals are concerned about climate change and are keen to contribute to climate solutions. However, there are several challenges to creating a voluntary citizen science climate observing program that addresses these opportunities. The first is that such a program has the potential for limited uptake if participants are required to volunteer their time or incur a significant cost to participate. The second is that researchers and decision-makers may be reluctant to use the collected data owing to concern over observer bias. This paper describes the on-going development and implementation by 2DegreesC.org of a technology-driven citizen science approach in which participants are equipped with low-cost automated sensors that systematically sample and communicate scientifically valid climate observations while they focus on other activities (e.g., recreation, gardening, fitness). Observations are acquired by a cloud-based system that quality controls, anonymizes, and makes them openly available. Simultaneously, individuals of all backgrounds who share a love of the outdoors become engaged in the scientific process via data-driven communication, research, and educational interactions. Because costs and training are minimized as barriers to participation, data collection is opportunistic, and the technology can be used almost anywhere, this approach is dynamically scalable with the potential for millions of participants to collect billions of new, accurate observations that integrate with and enhance existing observational network capacity.

How to cite: Shein, K.: Linking citizen scientists with technology to reduce climate data gaps, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10634, https://doi.org/10.5194/egusphere-egu22-10634, 2022.

The 2019-2020 bushfire season (the Black Summer) in Australia was unprecedented in its breadth and severity as well as the disrupted resources and time dedicated to studying it.  Right after one of the most extreme fire seasons on record had hit Australia, a once-in-a-century global pandemic, COVID-19, occurred. This pandemic caused world-wide lockdowns throughout 2020 and 2021 that prevented travel and field work, thus hindering researchers from assessing damage done by the Black Summer bushfires. Early assessments show that the bushfires on Kangaroo Island, South Australia caused declines in soil nutrients and ground coverage up to 10 months post-fire, indicating higher risk of soil erosion and fire-induced land degradation at this location. In parallel to the direct impacts the Black Summer bushfires had on native vegetation and soil, the New South Wales Nature Conservation Council observed a noticeable increase in demand for fire management workshops in 2020. What was observed of fires and post-fire outcomes on soil and vegetation from the 2019-2020 bushfire season that drove so many citizens into action? In collaboration with the New South Wales Nature Conservation Council and Rural Fire Service through the Hotspots Fire Project, we will be surveying and interviewing landowners across New South Wales to collect their observations and insights regarding the Black Summer. By engaging landowners, this project aims to answer the following: within New South Wales, Australia, what impact did the 2019-2020 fire season have on a) soil health and native vegetation and b) human behaviours and perceptions of fire in the Australian landscape. The quantity of insights gained from NSW citizens will provide a broad assessment of fire impacts across multiple soil and ecosystem types, providing knowledge of the impacts of severe fires, such as those that occurred during the Black Summer, to the scientific community. Furthermore, with knowledge gained from reflections from citizens, the Hotspots Fire Project will be better able to train and support workshop participants, while expanding the coverage of workshops to improve support of landowners across the state. Data regarding fire impacts on soil, ecosystems, and communities has been collected by unknowing citizen scientists all across New South Wales, and to gain access to that data, we need only ask.

How to cite: Ondik, M., Ooi, M., and Muñoz-Rojas, M.: Insights from landowners on Australia's Black Summer bushfires: impacts on soil and vegetation, perceptions, and behaviours, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10776, https://doi.org/10.5194/egusphere-egu22-10776, 2022.

High air pollution concentration levels and increased urban heat island intensity, are amongst the most critical contemporary urban health concerns. This is the reason why various municipalities are starting to invest in extensive direct air quality and microclimate sensing networks. Through the study of these datasets it has become evident that the understanding of inter-urban environmental gradients is imperative to effectively introduce urban land-use strategies to improve the environmental conditions in the neighborhoods that suffer the most, and develop city-scale urban planning solutions for a better urban health.  However, given economic limitations or divergent political views, extensive direct sensing environmental networks have yet not been implemented in most cities. While the validity of citizen science environmental datasets is often questioned given that they rely on low-cost sensing technologies and fail to incorporate sensor calibration protocols, they can offer an alternative to municipal sensing networks if the necessary Quality Assurance / Quality Control (QA/QC) protocols are put in place.

This research has focused on the development of a QA/QC protocol for the study of urban environmental data collected by the citizen science PurpleAir initiative implemented in the Bay Area and the city of Los Angeles where over 700 purple air stations have been implemented in the last years. Following the QA/QC process the PurpleAir data was studied in combination with remote sensing datasets on land surface temperature and normalized difference vegetation index, and geospatial datasets on socio-demographic and urban fabric parameters. Through a footprint-based study, and for all PurpleAir station locations, the featured variables and the buffer sizes with higher correlations have been identified to compute the inter-urban environmental gradient predictions making use of 3 supervised machine learning models: - Regression Tree Ensemble, Support Vector Machine, and a Gaussian Process Regression.

How to cite: Llaguno-Munitxa, M., Bou-Zeid, E., Rueda, P., and Shu, X.: Citizen-science urban environmental monitoring for the development of an inter-urban environmental prediction model for the city of Los Angeles, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11765, https://doi.org/10.5194/egusphere-egu22-11765, 2022.

Routine monitoring of soil chemistry is needed for effective crop management since a poor understanding of nutrient levels affects crop yields and ultimately farmers’ livelihoods.¹ In low- and middle-income countries soil sampling is usually limited, due to required access to analytical services and high costs of portable sampling equipment.² We are developing portable and low-cost sampling and analysis tools which would enable farmers to test their own land and make informed decisions around the need for fertilizers. In this study we aimed to understand attitudes of key stakeholders towards this technology and towards collecting the data gathered on public databases which could inform decisions at government level to better manage agriculture across a country.

In Kenya, we surveyed 549 stakeholders from Murang’a and Kiambu counties, 77% men and 23% women. 17.2% of these respondent smallholder farmers were youthful farmers aged 18-35 years with 81.9% male and 18.1% female-headed farming enterprises. The survey covered current knowledge of soil nutrition, existing soil management practices, desire to sample soil in the future, attitudes towards our developed prototypes, motivation towards democratization of soil data, and willingness to pay for the technology. In Vietnam a smaller mixed methods online survey was distributed via national farming unions to 27 stakeholders, in particular engaging younger farmers with an interest in technology and innovation.

Within the Kenya cohort, only 1.5% of farmers currently test for nutrients and pH. Reasons given for not testing included a lack of knowledge about soil testing (35%), distance to testing centers (34%) and high costs (16%). However, 97% of respondents were interested in soil sampling at least once a year, particularly monitoring nitrates and phosphates. Nearly all participants, 94-99% among the males/females/youths found cost of repeated analysis of soil samples costing around USD 11-12 as affordable for their business. Regarding sharing the collecting data, 88% believed this would be beneficial, for example citing that data shared with intervention agencies and agricultural officers could help them receive relevant advice.

In Vietnam, 87% of famers did not have their soil nutrient levels tested with 62% saying they did not know how and 28% indicating prohibitive costs. Most currently relied on local knowledge and observations to improve their soil quality. 87% thought that the system we were proposing was affordable with only 6% saying they would not be interested in trialing this new technology. Regarding the soil data, respondents felt that it should be open access and available to everyone.

Our surveys confirmed the need and perceived benefit for our proposed simple-to-operate and cost-effective workflow, which would enable farmers to test soil chemistry themselves on their own land. Farmers were also found to be motivated towards sharing their soil data to get advice from government agencies. The survey results will inform our further development of low-cost, portable analytical tools for simple on-site measurements of nutrient levels within soil.

1. Dimkpa, C., et al., Sustainable Agriculture Reviews, 2017, 25, 1-43.

2. Zingore, S., et al., Better Crops, 2015, 99 (1), 24-26.

How to cite: Richardson, S., Kamau, P., Parsons, K. J., Halstead, F., Ndirangu, I., Minh, V. Q., Tri, V. P. D., Le, H., Pamme, N., and Gitaka, J.: Attitudes towards a cafetiere-style filter system and paper-based analysis pad for soil nutrition surveillance in-situ: evidence from Kenya and Vietnam, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11797, https://doi.org/10.5194/egusphere-egu22-11797, 2022.

Keywords: preconcentration, heavy metal, cafetiere, citizen science, paper-based microfluidics

Heavy-metal analysis of water samples using microfluidics paper-based analytical devices (µPAD) with colourimetric readout is of great interest due to its simplicity, affordability and potential for Citizen Science-based data collection [1]. However, this approach is limited by the relatively poor sensitivity of the colourimetric substrates, typically achieving detection within the mg L^-1 range, whereas heavy-metals exist in the environment at <μg L^-1 quantities   [2]. Preconcentration is commonly used when analyte concentration is below the analytical range, but this typically requires laboratory equipment and expert users [3]. Here, we are developing a simple method for pre-concentration of heavy metals, to be integrated with a µPAD workflow that would allow Citizen Scientists to carry out pre-concentration as well as readout on-site.

The filter mesh from an off-the-shelf cafetière (350 mL) was replaced with a custom-made bead carrier basket, laser cut in PMMA sheet featuring >500 evenly spread 100 µm diameter holes. This allowed the water sample to pass through the basket and mix efficiently with the 2.6 g ion-exchange resin beads housed within (Lewatit^® TP207, Ambersep^® M4195, Lewatit^® MonoPlus SP 112). An aqueous Ni²⁺ sample (0.3 mg L^-1, 300 mL) was placed in the cafetiere and the basket containing ion exchange material was moved up and down for 5 min to allow Ni²⁺ adsorption onto the resin. Initial investigations into elution with a safe, non-toxic eluent focused on using NaCl (5 M). These were carried out by placing the elution solution into a shallow dish and into which the the resin containing carrier basket was submerging. UV/vis spectroscopy via a colourimetric reaction with nioxime was used to monitor Ni²⁺ absorption and elution.

After 5 min of mixing it was found that Lewatit^® TP207 and Ambersep^® M4195 resins adsorbed up to 90% of the Ni²⁺ ions present in solution and the Lewatit^® MonoPlus SP 112 adsorbed up to 60%. However, the Lewatit^® MonoPlus SP 112 resin performed better for elution with NaCl. Initial studies showed up to 30% of the Ni²⁺ was eluted within only 1 min of mixing with 10 mL 5 M NaCl.

Using a cafetière as pre-concentration vessel coupled with non-hazardous reagents in the pre-concentration process allows involvement of citizen scientists in more advanced environmental monitoring activities that cannot be achieved with a simple paper-based sensor alone. Future work will investigate the user-friendliness of the design by trialling the system with volunteers and will aim to further improve the trapping and elution efficiencies.

References:

• Almeida, M., et al., Talanta, 2018, 177, 176-190.
• Lace, A., J. Cleary, Chemosens., 2021. 9, 60.
• Alahmad, W., et al.. Biosens. Bioelectron., 2021. 194, 113574.

How to cite: Sari, M., Richardson, S., Mayes, W., Lorch, M., and Pamme, N.: Method development for on-site freshwater analysis with pre-concentration of nickel via ion-exchange resins embedded in a cafetière system and paper-based analytical devices for readout, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11892, https://doi.org/10.5194/egusphere-egu22-11892, 2022.

Hurtigruten Expeditions, a member of the International Association of Antarctica Tour Operators (IAATO) and the Association of Arctic Expedition Cruise Operators (AECO) has been visiting the fragile polar environments for two decades, witnessing the effects of climate change. Tourism and the number of ships in the polar regions has grown significantly. As a stakeholder aware of the need for long-term protection of these regions, we promote safe and environmentally responsible operations, invest in the understanding and conservation of the areas we visit, and focus on the enrichment of our guests.

For the last couple of years, we have supported the scientific community by transporting researchers and their equipment to and from their study areas in polar regions and we have established collaborations with numerous scientific institutions. In parallel we developed our science program with the goal of educating our guests about the natural environments they are in, as well as to further support the scientific community by providing our ships as platforms of opportunity for spatial and temporal data collection. Participation in Citizen Science programs that complement our lecture program provides an additional education opportunity for guests to better understand the challenges the visited environment faces while contributing to filling scientific knowledge gaps in remote areas and providing data for evidence-based decision making.

We aim to continue working alongside the scientific community and developing partnerships. We believe that scientific research and monitoring in the Arctic and Antarctic can hugely benefit from the reoccurring presence of our vessels in these areas, as shown by the many projects we have supported so far. In addition, our partnership with the Polar Citizen Science Collective, a charity that facilitates interaction between scientists running Citizen Science projects and expedition tour operators, will allow the development of programs on an industry level, rather than just an operator level, increasing the availability and choice of platforms of opportunity for the scientific community.

How to cite: Meraldi, V., Morgan, T., Lynnes, A., and Grams, Y.: Collection of valuable polar data and increase in nature awareness among travellers by using Expedition Cruise Ships as platforms of opportunity, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12972, https://doi.org/10.5194/egusphere-egu22-12972, 2022.

Heavy rainfall, floods and debris flow on the Rimac river watershed are recurring events that impact Peruvian people in vulnerable situations.There are few historical records, in terms of hydrometeorological variables, with sufficient temporal and spatial accuracy. As a result, Early Warning Systems (EWS) efficiency, dealing with these hazards, is critically limited.

In order to tackle this challenge, among other objectives, the Participatory Monitoring Network (Red de Monitoreo Participativo or Red MoP, in spanish) was formed: an alternative monitoring system supported by voluntary community collaboration of local population under a citizen science approach. This network collects and communicates data captured with standardized manual rain gauges (< 3USD). So far, it covers districts in the east metropolitan area of the capital city of Lima, on dense peri-urban areas, districts on the upper Rimac watershed on rural towns, and expanding to other upper watersheds as well.

Initially led by Practical Action as part of the Zurich Flood Resilience Alliance, it is now also supported by SENAMHI (National Meteorological and Hydrological Service) and INICTEL-UNI (National Telecommunications Research and Training Institute), as an activity of the National EWS Network (RNAT).

For the 2019-2022 rainfall seasons, the network has been gathering data and information from around 80 volunteers located throughout the Rimac and Chillon river watersheds (community members, local governments officers, among others): precipitation, other meteorological variables, and information regarding the occurrence of events such as floods and debris flow (locally known as huaycos). SENAMHI has provided a focalized 24h forecast for the area covered by the volunteers, experimentally combines official stations data with the network’s for spatial analysis of rainfall, and, with researchers from the University of Bristol, analyses potential uses of events gathered through this network. In order to facilitate and automatize certain processes, INICTEL-UNI developed a web-platform and a mobile application that is being piloted.

We present an analysis of events and trends gathered through this initiative (such as a debris flow occurred in 2019). Specifically, hotspots and potential uses of this sort of refined spatialized rainfall information in the dry & tropical Andes. As well, we present a qualitative analysis of volunteers’ expectations and perceptions. Finally, we also present a meteorological explanation of selected events, supporting the importance of measuring localized precipitation during the occurrence of extreme events in similar complex, physical and social contexts.

How to cite: Arestegui, M., Ordoñez, M., Cisneros, A., Madueño, G., Almeida, C., Aliaga, V., Quispe, N., Millán, C., Lavado, W., Huaman, S., and Phillips, J.: Participatory rainfall monitoring: strengthening hydrometeorological risk management and community resilience in Peru, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13115, https://doi.org/10.5194/egusphere-egu22-13115, 2022.

Soil erosion rates frequently exceed the pace at which new soil is formed. This imbalance can lead to soil thinning (i.e., truncation) whereby subsoil horizons, and the underlying parent material, emerge progressively closer to the land surface. These subsurface horizons may have contrasting physical, chemical, and biological properties from those of the original topsoil. Hence, soil thinning can induce changes in topsoil erodibility – a fact that has been largely overlooked in erosion modelling research and could affect long-term projections of soil erosion rates. Here we present a model-based exploration of the potential feedbacks between water erosion and soil thinning, using measured data from 265 agricultural soil profiles in the United Kingdom. We simulated annual erosion rates on these soil profiles with the Modified Morgan-Morgan-Finey model, assuming time-constant land cover, topographic, and rainfall parameters. As the original topsoil was successively removed, our model gradually mixed the subsurface horizons into a 20 cm ploughing layer. We applied this modelling framework on a yearly time-step over a 500-year period, or until the ploughing layer reached the bottom of the lowermost soil horizon. Soil texture, stone cover, and soil organic carbon content for the ploughing layer were recalculated for each time-step through a mass-balance model. Soil bulk density and soil moisture content at field capacity were estimated for each time-step by pedo-transfer functions developed from our own dataset. In addition, we employed a Monte Carlo simulation with 100 iterations per year to provide a forward error assessment of the modelled soil losses. We found that simulated erosion rates on 42 % of the soil profiles were sensitive to truncation-induced changes in soil properties during the analysed period. Among the profiles sensitive to soil thinning, 68 % displayed a negative trend in modelled erosion rates. This was largely explained by decreasing silt contents on the surface soil due to selective removal of this more erodible particle size fraction and the presence of clayey or sandy substrata. Moreover, an increased residual stone cover shielded the surface soils from detachment by raindrop impact and surface runoff. The soil profiles with a positive trend in erosion rates were characterised by the presence of siltier subsoil horizons, which increased topsoil erodibility as they were mixed into the ploughing layer. Overall, our results demonstrated how modelled erosion rates could be sensitive to truncation-induced changes in soil properties, which in turn may accelerate or slow down soil thinning. These feedbacks are likely to affect how we calculate soil lifespans and make long-term projections of land degradation.

How to cite: Batista, P., Evans, D., Cândido, B., and Fiener, P.: Feedbacks between water erosion and soil thinning, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-37, https://doi.org/10.5194/egusphere-egu22-37, 2022.

Indian is worst affected by soil erosion, especially due to erosion induced by rainfall. A factor of Universal Soil Loss Equation (rainfall erosivity factor) needs to be estimated throughout the country to assess the soil erosion in the country. Indian climate is dominated by monsoons, and their intensity and distribution vary significantly throughout the country. Rainfall erosivity is solely derived from the rainfall intensity, which is a function of climatic properties. In this study, the distribution and variability of the rainfall erosivity factor (R factor) had been analyzed in different regions and sub-divisions of India as classified by India Meteorological Department (IMD). For estimation of rainfall erosivity, the widely adopted principle of kinetic energy and rainfall intensity had been used. A well-known precipitation index, Modified Fournier Index (MFI), was also calculated to check its influence on the R factor. Regression equations in the form of power-law are derived for all regions of the country to establish the relationship between the R factor and MFI. Further, an analysis at the sub-divisional level was also performed to visualize the spatial variability of the R-factor throughout the nation. South peninsula India with the lowest average R factor of 615.61 MJ-mm/ha/h/yr, was recognized as least vulnerable to rainfall erosivity while the East and Northeast India was recognized as most susceptible with a highest R factor of 3312.39 MJ-mm/ha/h/yr. About 36% of the entire subdivisions of the country were spotted with an average rainfall erosivity factor higher than the national average rainfall erosivity factor, and hence they are more prone to erosion induced by rainfall. Estimating rainfall erosivity factors at sub-divisional and regional levels will help policymakers and watershed experts prioritize the watershed management practices to counter soil erosion induced by rainfall erosivity.

Keywords – Rainfall erosivity, IMD, Spatial variability, Climate, Precipitation index

How to cite: Raj, R., Saharia, M., Chakma, S., and Rafieeinasab, A.: Spatial Variability of Rainfall Erosivity over India, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-152, https://doi.org/10.5194/egusphere-egu22-152, 2022.

LANDSLIDES are one of the destructive geological processes that occur throughout the world. At global scale, the landslides are one of the major natural disaster which deteriorate the soil quality at a very large scale. In the Indian Himalayan Region (IHR), the Garhwal Himalayas of Uttarakhand landslides occurred very frequently in rainy season due to the presence of fragile rocks, active tectonic activity and unplanned anthropogenic activities. Landslides causes the loss of soil nutrients and vegetation which in turn deteriorate the soil quality. They can have an enormous effect on biodiversity and significantly alter the soil quality. The rate of soil development in essential for determining the recovering capacity of soil after the losses occurred due to landslides and erosion.

Therefore, the present study analyzed the natural recovery of soil quality in terms of soil characteristics with the passage of time (chronosequence) in 4 disturbed sites of different ages i.e., 6-year-old (L1 site), 16-year-old (L2 site), 21-year-old (L3 site) and 26-year-old (L4 site) including control (undisturbed) site in the Garhwal Himalayas of Uttarakhand. 76 soil samples were collected from all the selected sites at two depths i.e., 0-15cm and 15-30cm. The collected soil samples were analyzed for various physical (bulk density (BD), particle density (PD), total porosity (TP), moisture content (MC) and sand, silt and clay content) and chemical characteristics (pH, electrical conductivity (EC), soil organic carbon (SOC), soil organic matter (SOM), mineralisable nitrogen (MN), available phosphorus (AP) and available potassium (AK). Principal Component Analysis (PCA) was done with all the 14 variables which are significantly different in order to establish minimum data set (MDS). The MDS includes SOC, AP and clay content on the basis of the PCA results. The soil quality index (SQI) was calculated using Integrated Quality Index (IQI) equation. Landslide affected sites L1, L2, L3 and L4 and control site had mean SQI scores of 0.136, 0.279, 0.447, 0.604 and 0.882, respectively.

The results have demonstrated that the control site had much better soil quality in comparison to the landslide affected sites because of its better nutrients content and better physical characteristics. The results have also shown that the soil quality tends to increase with the age of landslide, but the soil quality has not reached to the pre-disturbance level in a period of 26 years. The SQI shows the variations in landslide affected sites which could be used to detect variations in soils of disturbed areas. The results will also provide crucial information for evaluating the consequences, designing, and implementing restoration strategies.

How to cite: goyal, D. and Joshi, V.: Soil quality assessment in a chronosequence of landslides in Garhwal Himalayas, Uttarakhand, India, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-494, https://doi.org/10.5194/egusphere-egu22-494, 2022.

Soil erosion accelerated by climatic variation and human impact has become a severe global environmental concern. It is required to engage policymakers to limit or regulate future soil erosion rates. In the Indian subcontinent, soil erosion in mountainous terrain and ravenous land is the most severely affected. North flowing Cratonic (NFC) Rivers (total catchment area ~ 327570 sq km) in the northern Peninsular region having deeply dissected channels are usually associated with ravenous land and have been proven to be vulnerable to climate change. Due to their climatic and topographic characteristics, NFC rivers basin are expected to exhibit diverse rate of soil erosion. This study focuses on the NFC river basins, namely, Chambal (141578.12 sq km), Sindh (29041.68 sq km), Betwa (43826.4 sq km), Ken (28674.7 sq km), Tons (17172 sq km) and Son (67277.1 sq km), to assess soil erosion and spatial pattern of soil erosion prone areas by employing the widely used RUSLE model. The factors used in the RUSLE model have been derived from different sources. The annual average rainfall derived using the Center for Hydrometeorology and Remote Sensing (CHRS) data shows an increasing trend from west to east, indicating arid climate in the western and humid climate in the eastern section. The Soil erodibility (K) factor has been estimated from soil maps of the National Bureau of Soil Survey and Land Use Planning (NBSS-LUP), Nagpur. Topographic (LS) factor was derived from SRTM 30m DEM and crop management (C), and support practice (P) factors were calculated by assigning appropriate values to LULC classes created by ESRI (Environmental Systems Research Institute) using Sentinel-2 imageries at 10m spatial resolution.

Our findings show that the ravenous land in the Chambal, Sindh, Betwa and Ken river basins account for most of the high soil erosion rate in the study area. The soil loss rate increases from west to east in NFC river basins, ranging from low to extremely high. Although most of the Son river basin is covered by forest, other classes, i.e. bare land and fallow land, exhibit high erosion due to heavy rainfall. The research findings show spatial patterns of soil erosion in the NFC river basins and indicate minimal erosion in the regions of arid climates and significant erosion in the area of humid climates. Further, soil erosion hotspots identified primarily represent ravines and barren area classes. The information may be valuable to policymakers to plan for regulating future soil erosion rates in the region.

Keywords: North flowing cratonic rivers, RUSLE, Chambal River, Ravines, Soil erosion.

How to cite: Kumar, R., Devrani, R., Kumar, R., khiamniungan, S., Chatterjee, S., and Deshmukh, B.: Assessment of soil erosion in the north flowing cratonic river basins, Peninsular India, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-539, https://doi.org/10.5194/egusphere-egu22-539, 2022.

Piping erosion leads to land degradation and causes several environmental and societal problems, although this process is rarely considered in soil erosion studies. So far, there are no systematic studies at regional to global scales aiming to understand the patterns and controlling factors of soil piping. This is mainly due to the methodological challenges related to detecting soil pipes. With this project, we aim to address this gap by identifying piping-affected areas in Europe. For this, we are constructing a database on surface evidences of soil piping, i.e. pipe roof collapses (PCs) for the European Union and the UK. Locations and other details of PCs in this database are collected based on an in-depth literature review in combination with detailed mapping based on Google Earth imagery, ortophotos and LiDAR data (if available). While the work is still ongoing, we have already compiled information on >2000 PCs in 10 different countries. In a next phase, we will use this PC database to construct the very first data-driven piping erosion susceptibility map of Europe.

This research is part of the Twinning project “Building excellence in research of human-environmental systems with geospatial and Earth observation technologies” that has 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., Derii, A., Hałys, J., Nadal-Romero, E., Panagos, P., Piątek, D., Regensburg, T. H., Rodzik, J., Stolarczyk, M., Verachtert, E., Wacławczyk, P., and Zgłobicki, W.: Soil pipe collapses in Europe: towards a continent-wide assessment, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-579, https://doi.org/10.5194/egusphere-egu22-579, 2022.

Reservoir sedimentation constitutes a major issue worldwide and a long-lasting priority for dam managers, especially when hydropower, and hence profit, is involved. Commonly, the problem of excessive sedimentation is attributed to failed prediction of the sediment supply from the upland basin prior to the construction of dams, namely to the underestimation of sediment inflow to the reservoir.

The sediment input in the Rio di Pusteria reservoir (South Tyrol, Italy) between two consecutive sediment flushing operations in June 2014 and May 2019, was determined by obtaining the volumetric difference between very high resolution (0.25 m) reservoir bathymetries conducted after the flushing of 2014 and before the flushing of 2019. The sediment yield in the reservoir during the latter period was found to be 453,783 t.

To calculate the sediment yield in the reservoir, we have applied a gridded seven-factor Universal Soil Loss Equation (USLE) combined with a Sediment Delivery Ratio (SDR) module in a high resolution (2.5 m) GIS environment, which enabled an accurate representation of the rapidly shifting Alpine topography. An additional factor for coarse fragments was added to the conventional six-factor USLE to account for the non-erodible part of the basin. This is of great importance as the USLE-based models are criticized to produce extreme erosion rates in uplands and mountain areas. The topographic factor, LS, was refined by the use of a fine scale DEM and the slope length factor, L, was adjusted to the Alpine terrain by means of a regulating threshold. The proposed SDR module does not rely on one but on several physiographic, topographic and hydrologic characteristics of the basin. Finally, the rainfall erosivity factor, R, was determined in two different ways, one representing the rainfall climatology of the study area and one the specific rainfall conditions of the study period, hence the application of the model in two distinct configurations.

The application of the combined USLE-SDR model resulted in five-year reservoir sedimentation rates of 439,279.2 t and 589,520.5 t, with deviations from the measured sediment yield of 3.3% and -25.5%. Excluding very high altitudes with glaciers and perennial snow, we consider the proposed modeling approach ideal for upper lands and mountainous areas such as the Alps.

How to cite: Kaffas, K., Pisinaras, V., Al Sayah, M., Santopietro, S., and Righetti, M.: A modified USLE-based approach combined with sediment delivery module to estimate soil loss and reservoir sedimentation rates in Alpine basins, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-861, https://doi.org/10.5194/egusphere-egu22-861, 2022.

One of the major issues of the grazing land ecosystem is high sediment yield linked to extensive land clearing and conversion of native vegetation into grazing. It is essential to model hillslope sedimentation for improved prediction of sediment yield in grazed catchments. This study evaluated the performance of Revised Universal Soil Loss Equation (RUSLE) and Modified Universal Soil Loss Equation (MUSLE) models in predicting sediment yield from grazed catchments and analyzed the effects of runoff, peak runoff rate and the RUSLE/MUSLE factor on annual sediment yield. Springvale, Brigalow, and Weany Creek catchments from Fitzroy and Burdekin Basins in Queensland, Australia, were selected as study areas. The MUSLE models performed better as compared to the RUSLE model for all three catchments. Compared to the RUSLE model, the MUSLE1 model with factors runoff and peak runoff rate was able to predict sediment yield for Weany creek and Brigalow catchment and the MUSLE2 with factors rainfall-runoff erosivity (EI₃₀), runoff, and peak runoff rate performed well for Springvale and Brigalow catchment. The study found rainfall and runoff factors in Springvale and Brigalow catchments, and runoff factor and peak runoff rate in Weany catchments contributed to the variation of sediment yield. The estimated soil erodibility factor (K) was found 14%, 24%, and 60% higher for Springvale, Brigalow, and Weany Creek catchments, respectively, compared to K-factor from the Australian Soil Resource Information System (ASRIS). This study recommends using the MUSLE model to improve hillslope sediment yield prediction in grazing lands in Central Queensland.

How to cite: Tiwari, J., Yu, B., Silburn, D. M., Bartley, R., Thornton, C. M., Owens, J., and Brooks, A.: Comparison of the Revised and Modified USLE models for prediction of sediment yield from grazing land in Central Queensland, Australia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-876, https://doi.org/10.5194/egusphere-egu22-876, 2022.

Motivation and aim: Mountain areas with beautiful scenery are attractive to visitors and offer such ecosystem services as recreation and spiritual opportunities. However, the mountain environment is fragile and easily degraded when recreation is not appropriately managed. This degradation limits recreation potential and can also be dangerous to visitors and local communities. Our study presents documentation of landscape degradation in response to a rapid increase in visitors number in an extreme environment of high-altitude (> 4000 m a.s.l) tropical mountains. Rainbow Mountain (Vinicunca) in Peru only recently became a world-renowned tourist destination. Rapid visitors’ influx caused severe landscape degradation and partly uncontrolled infrastructure development. We characterized and mapped different types of impacts related to visitor pressure and evaluated activities aimed to limit degradation and enhance visitor behaviour. 

Method of investigation: Fieldworks in the vicinity of Vinicunca were conducted in 2017, 2018 and 2019. Geomorphological mapping involved a field-based approach combined with the interpretation of orthomosaics generated from UAV imagery and high-resolution satellite data (WorldView-2, 2020). UAV images were processed using the structure-from-motion workflow. The characterization of dominant morphogenetic processes was based on ground-based observations, photographic documentation, and remote sensing data. 

Results and conclusions: We identified seven dominant morphogenetic processes responsible for landscape degradation: Based on field geomorphological mapping, five processes were most important in the degradation of landscape: (1) Vegetation trampling by hikers and animals (mostly horses, but also llamas); (2) Soil erosion concentrated on bare soil surfaces and caused the development of rill erosion and surface flow; (3) Soil compaction lead to soil hardening which in turn facilitate accelerated surface flow from the trail surface and enhancing water erosion further downslope; (4) Freeze-thaw cycles which weakened structure of the material making it more prone to erosion; (5) Dry-wet cycles also preparing the soil for further degradation activity. The abovementioned processes formed characteristic morphogenetic elements of the trails, which included: (1) Severely incised trail surface where the bottom of the trail can be as low as 1 m below the original land surface; (2) Braided trail network consisting of several parallel paths, without incision, or moderately incised with vegetation between individual paths; (3) Single, wide, bare soil trail tread indicating that vegetation was removed, and the surface is prone to soil erosion; (4) Water puddled in flat areas caused the development of muddy section, That in turn lead to increase in trail width, as the visitors tried to bypass muddy segment and trampled vegetation in their vicinity. Based on collected data, trail classification was developed that include a functional model of trails in slope and flat conditions. Our results indicate that in such a fragile environment, a rapid increase in visitors numbers can lead to permanent changes in the environment. Therefore, appropriate managerial actions need to be taken to limit the degradation of the environment. Trails’ maintenance is critical for limiting the degradation of trail vicinity, enhancing visitor perception, and limiting hazardous conditions.

This project was funded by Narodowe Centrum Nauki (National Science Centre, Poland), grant number 2015/19/D/ST10/00251

How to cite: Tomczyk, A. and Ewertowski, M.: Landscape degradation and development as a result of the intensification of tourism activity in a fragile, high-mountain environment: a case study of  Vinicunca (Rainbow Mountain), Peru, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-978, https://doi.org/10.5194/egusphere-egu22-978, 2022.

Abstract:Gully erosion is one of the soil erosion types with the largest sediment yield on the Loess Plateau, and also an important part of soil erosion control on the Loess Plateau. Based on the UAV aerial photography as in 2020, with systematic sampling method in Chabagou watershed and select 32 small watershed as the basic research unit, artificial visual interpretation method is used to draw small watershed, gully ditch, gully and ancient valleys line, gully region of northern Shaanxi loess cutting groove distribution characteristics and influencing factors of medium watershed scale of research and analysis. The results showed that : (1) The intensity of gully erosion in chabagou Basin is middle reaches & GT; Downstream & gt; In the upper reaches of the basin, the length, number and area of ditches per unit area are 9.03 km, 339.04 and 7.29hm², respectively. More than 50% of the ditches are between 10m and 30m in length, and 60% of the ditches are less than 150m²; (2) The ancient gully length density, gully length density, gully strip density and gully area density were the highest in the middle reaches of the basin. (3) The positive and negative terrain area ratio and slope directly affect the gully density, showing a moderate correlation; NDVI and the proportion of cultivated land had an indirect effect on the gully density, and the correlation was strong. The length, density and number of ditches in shady slope were significantly higher than those in sunny slope. This paper can explain the development characteristics of gully at medium watershed scale in loess gully region, clarify its distribution law, and provide theoretical basis for gully erosion control. 

How to cite: zhang, C., wang, C., yang, Q., pang, G., yang, L., wang, L., and long, Y.: Study on distribution characteristics of loess gully at medium watershed scale based on UAV images, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1289, https://doi.org/10.5194/egusphere-egu22-1289, 2022.

Water erosion measurement has been widely studied under different conditions using traditional approaches such as erosion collectors and more innovative ones such as sediment tracers.

La Conchuela is a commercial olive orchard located in Southern Spain. In 2008, six closed runoff plots, where regular machine traffic during farm operations was allowed, were established. Runoff water was channeled from the plots and collected by tipping-bucket gauges with 5-min resolution. This was completed with a sediment trap located upstream of the tipping buckets and a device to collect an integrated sample of the runoff downstream of the tipping buckets (Gómez & Guzmán, 2021). In two of these plots ground cover was controlled with tillage during the whole year while the rest keep a temporary cover crop during fall and winter.

In two of the plots (one with bare soil and other with temporary cover crop), the top 5 cm of the inter tree rows soil were tagged with magnetite. During the following years, three soil sampling campaigns (2008, 2010, 2016) were performed to measure variations of magnetic susceptibility within the soil surface and profile. Seventy locations at both plots were sampled at three depth intervals (0-1, 1-8, 8-12 cm in 2008 and 2010). A third sampling was carried out at 0-2, 2-10, 10-20 cm in 2016 at the same locations. Furthermore, twenty additional samples from 20-30, 30-40, 40-50, 50-60 cm were taken to check if tagged soil went deeper into the soil profile. In all these samplings, tree and inter tree rows were distinguished. Background susceptibility and bulk density at each depth, were characterised at the three sampling campaigns (Guzmán & Gómez, 2017).

During the period 2008-2019 there were not statistically significant differences between managements, bare soil vs temporary cover crops, in runoff or soil losses. Nevertheless, average runoff and soil losses had a trend to lower values for the cover crop treatment (142.9 mm and 16.5 t ha^-1) as compared to bare soil (155.8 mm and 23.8 t ha^-1). With the help of the magnetic tracer, the estimated erosion rates within the plots during 2009-2010 (the rainiest hydrological year within the study period with a precipitation of 1048.5 mm) were 115 t ha^-1 and 58 t ha^-1 in the bare soil plot and 62 t ha^-1 and 44 t·ha^-1 in the cover crop plot, from inter-tree rows and tree rows, respectively. The evolution of susceptibility suggests the potential of magnetite monitoring vertical fluxes at the mid-term also, due to wetting-drying cycles of vertic soils and soil disturbance agricultural practices. In fact, magnetic iron oxide was detected at initially untagged deeper soil layers (20-60 cm) in both inter-tree and tree rows. This highlights the relevance of accounting vertical displacement in any kind of tracer study in vertic soils and its implications at the medium-term (2008-2016) for the determination of erosion rates which will be presented in this communication.

Gómez, J. A., Guzmán, G. 2021. In EGU General Assembly Conference Abstracts (EGU21-606, https://doi.org/10.5194/egusphere-egu21-606).

Guzmán, G., Gómez, J. A. 2017. In EGU General Assembly Conference Abstracts (Vol. 19, EGU2017-4357-2).

How to cite: Guzmán, G., Ramos, A., Montoliu, J., and Gómez, J. A.: How does a vertic soil move? Soil erosion rates and its redistribution in an olive orchard at the medium-term, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1518, https://doi.org/10.5194/egusphere-egu22-1518, 2022.

In France, erosion by water run-off is estimated to 1.5 t ha^-1 yr^-1 and can reach 10 t ha^-1 yr^-1 in the large agricultural area of northern France. The Canche River watershed (1294 km²) in the Hauts-de-France region has been studied since 2016 to better understand its high sensibility to soil erosion. Agricultural soil erosion leads to the gradual disappearance of fertile topsoil, which constitute a non-renewable resource at human time scale. Once the soil is eroded, its pathway through the river may significantly degrade the water quality e.g. in terms of suspended particulate matter and nutrient, fertilizer, pesticide, and heavy metal input. Since almost a decade, efforts are made to reduce soil erosion by installing anti-erosion equipment such as fascines, grass strips, and retention basins. The aim of this study is to understand and characterize erosion process from small to large scale.

This study presents the monitoring of two intercalated sub-catchments from the Canche River watershed. The first elementary catchment (Pommeroye creek; 0.54 km²) disposes of a multiparameter high frequency (10 min) monitoring station (turbidity, liquid yield, conductivity, automatic sampling) completed by monthly field monitoring of the soil surface characteristics. This monitoring aims to understand detailed erosion processes such as hysteresis phenomena or the impact of anti-erosion management at catchment scale. To support these measurements, drone overflights are carried out to calculate the volume of soil moved or stored in ravines and at fascines between two distinct erosion events.

A second monitoring station further downstream in the intermediate-sized catchment (100 km²) of the Planquette River (tributary of the Canche River) follows the transit of suspended particulate matter to understand the transit time from up to downstream and the hysteresis phenomena between liquid and solid fluxes.

Over the last year (2021), more than 30 erosion events have been recorded on the elementary catchment, showing a variability on the amount of exported soil depending on the rain amount but also on seasonality on the soil surface characteristics and finally, the importance of the phenomenon of deposition/remobilization of the eroded material. The drone overflights between two important erosion events will help to estimate the importance of this deposition/remobilization phenomenon. The soil surface monitoring during the last year showed clearly the degradation of the infiltrative characteristics leading to an increased susceptibility to erosion. This degradation rate depends on the culture type and the time passed without plant cover.

How to cite: Delaporte, M., Alary, C., Franke, C., and Billon, G.: Monitoring and understanding soil erosion processes in elementary agricultural catchment and its consequences on the hydro-sedimentary fluxes in river (northern France), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1591, https://doi.org/10.5194/egusphere-egu22-1591, 2022.

 Soil erosion is a serious environmental problem, water erosion and wind erosion pose a greater threat to the sustainable development of Pakistan. In order to provide a scientific basis for the Pakistan’s soil and water conservation, this study used sub-meter resolution sampling survey (totally 475 units) and regional soil erosion factors (R, K, LS, B) as data sources, and calculates soil erosion rate maps (5m resolution) for each sampling unit based on the CSLE model, then uses a machine learning method to quantitatively make a soil erosion rate map in Pakistan that are closer to the real soil erosion characters. Based on climate, soil, topography, vegetation and other datas, the RWEQ model was used to quantitatively estimate the soil wind erosion rate map of Pakistan. Finally, the soil water erosion and wind erosion rate maps of Pakistan were spatially overlaid, taking into account the natural conditions of Pakistan, and according to the soil loss tolerance threshold, the study area is divided into wind erosion area, water erosion area, wind/water erosion interlaced areas. The results showed that : (1) Soil erosion in Pakistan is mainly concentrated in Potohar and its surrounding areas, the desert in the southwest, and the Thar desert in southeast. (2) The Kharan Desert in Balochistan and the Thar Desert in the southeast are dominated by wind erosion, Punjab and Sindh are dominated by water erosion, and wind and water erosion are combined in the northern mountainous areas and around the Suleiman Mountains Range. This study quantitatively estimated the rate of soil water erosion and wind erosion simultaneously in Pakistan, the results can more accurately express the spatial distribution characteristics of soil erosion in the country, provide a scientific basis for policy-making of soil and water conservation.

How to cite: Yang, X., Yang, Q., Zhu, H., and Wang, L.: Quantitative Assessment and Mapping of soil water and wind erosion in Pakistan, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1683, https://doi.org/10.5194/egusphere-egu22-1683, 2022.

Soil erosion is a very complex physical and geographical phenomenon, which is affected by both natural and human activities. Based on theoretical and technical methods such as CSLE model, Classification and Regression Tree (CART) and Google Earth Engine (GEE), on the basis of obtaining medium and high resolution soil erosion factors, this study systematically analyzed the temporal and spatial variation of soil erosion rate on the Loess Plateau in the past 40 years and the changes of the main controlling factors of soil erosion before and after “returning farmland to forest (grass)”. The main conclusions are as follows: (1) The soil erosion rates of the Loess Plateau in 1980, 1990, 2000, 2010, and 2017 were 2207.57, 1725.13, 981.18, 727.79, and 640.00 t/(km²∙a), showing a decreasing trend overall. As the most serious soil erosion area on the Loess Plateau, the Loess Hilly and Gully region has a significant weakening trend in its soil erosion rate, but its five-phase average soil erosion rate is still more than twice the average of the whole region, 4414.77, 3485.19, 1884.37, 1296.21, 1135.04 t/(km²∙a). (2) Before returning farmland to forest (grass) (before 1999), rainfall erosivity (R) was the main controlling factor for soil erosion. After the large-scale implementation of various soil and water conservation measures, the influence of biological measures (B) on soil erosion rate increased; in the sandy region of the Loess Plateau dominated by low-coverage grasslands, soil erosion was significantly affected by rainfall erosivity (R). The main controlling factors of soil erosion in the loess hilly and gully area changed significantly around 2000, from the combined effect of terrain (LS) and vegetation (B) to the combined effect of rainfall erosivity (R), gully erosion factor (g) and vegetation (B). (3) The average soil erosion rate under different land use types on the Loess Plateau is characterized by cultivated land>grassland>forest land. From 1980 to 2017, the soil erosion rate from cultivated land to forest land decreased the most, and the change slope was -74.84 (t/(km²∙a))/a, followed by cultivated land to grassland and grassland to forest land, both of which changed the slope of soil erosion. They are -51.88 (t/(km²∙a))/a and -49.05 (t/(km²∙a))/a, respectively. This research can provide a scientific basis for the needs of future comprehensive management planning and soil and water conservation construction in the basin.

How to cite: Huang, C. and Yang, Q.: Temporal and spatial variation of soil erosion rate in the Loess Plateau and its main controlling factors in the past 40 years, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1966, https://doi.org/10.5194/egusphere-egu22-1966, 2022.

    As one of the important indicators reflecting the regional ecological environment, fractional vegetation coverage is significant for regional eco-environmental protection and sustainable utilization of resources. To understand changes in the ecological environment of the ecologically fragile areas in the Loess Plateau affected by “Grain for Green” Program and its main driving forces in the past two decades, this study taking Yulin City as a typical example of the fragile ecological environment on the Loess Plateau, to analyze spatial-temporal variations of the vegetation coverage in Yulin City during the past two decades based on the pixel dichotomy model with vegetation index, using univariate linear regression methods. The dominant factors and interaction between factors influencing the interannual changes and spatial distribution of vegetation coverage are analyzed using the partial correlation analysis and geographic detector methods during the different period in “Grain for Green” Program. Results showed that: (1) The vegetation coverage in Yulin City significantly increased (S = 0.011, p < 0.01) from 2001 to 2020. The vegetation coverage during the construction periods (2001-2010) increased significantly (S = 0.013, p <0.01); while its increase in the consolidation periods (2011-2020) was relatively slow (S = 0.005, p > 0.05). (2)The spatial distribution of vegetation coverage in Yulin City decreased from east to west from 2001 to 2020. The vegetation coverage of all counties (districts) in Yulin City shows an overall increasing trend, among which the eastern part of Yulin City has a more significant growth trend. However, the proportion of area in the construction periods (82.1%) was larger than that in the consolidation periods (58.0%). (3) The cumulative area of the Grain for Green Program was the dominant factor in the construction periods, while it was rainfall in the consolidation period. (4) Soil texture, rainfall, and land use type mainly affected the spatial distribution of vegetation coverage from 2001 to 2020. Soil texture was closely related to changes in the vegetation coverage both in the construction and consolidation periods. The spatial heterogeneity of vegetation distribution and the interaction between the main influencing factors provides a scientific basis for the precise implementation of ecological restoration measures.

How to cite: Liu, Y., Liu, B., and Zhang, J.: Spatial-Temporal Changes Of Vegetation Coverage In Yulin City And Its Influencing Factors During The Past Two Decades Since The Implementation Of The“Grain For Green” Program, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2091, https://doi.org/10.5194/egusphere-egu22-2091, 2022.

Rainfall erosivity is one of the main inputs for soil erosion modelling. Long high-resolution rainfall time series are needed for the estimation of rainfall erosivity but these are likely to be lacking at many locations around the globe. An alternative approach could be the generation of synthetic rainfall time series using stochastic rainfall models. In this study, four methods for estimating the rainfall erosivity were evaluated at ungauged sites:

i) estimation from regionalised observed 5 minute rainfall time series,

ii) direct regionalisation of the rainfall erosivity estimated from observations,

iii) estimation from 5 minute rainfall time series disaggregated from daily observations,

iv) estimation from rainfall time series generated by a regionalized stochastic rainfall model.

Data from 159 stations from Lower Saxony, Germany, were used to evaluate the performance of different methods. All tests were performed using the leave-one-out cross validation method. Additionally, we also analysed the minimum time series length necessary to adequately estimate the rainfall erosivity.

The results indicated that the direct regionalization of the mean annual rainfall erosivity yielded the best performance in terms of relative bias followed by the regionalization of the 5 minute rainfall data. However, the main advantage of the rainfall generators is that they can generate long synthetic time series and can also provide estimates of other rainfall erosivity characteristics such as number of erosive rainfall events, etc. Applying the alternating renewal model indicated that more than 60 years of data are needed to obtain a stable estimate of rainfall erosivity and that rainfall erosivity estimations using 5 years of data can lead to significant uncertainty. Moreover, it was also found that the rainfall erosivity calculations are sensitive to the resolution of the input data.  

Acknowledgment: The results of the study are part of the bilateral research project between Slovenia and Germany “Stochastic rainfall models for rainfall erosivity evaluation” (BI-DE/18-19-008). 

How to cite: Bezak, N., Pidoto, R., Müller-Thomy, H., Shehu, B., Callau-Beyer, A., Zabret, K., and Haberlandt, U.: Investigation of the applicability of rainfall generators for the estimation of the rainfall erosivity for ungauged locations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2210, https://doi.org/10.5194/egusphere-egu22-2210, 2022.

Temporary cover crops are a well stablished erosion control tool in Mediterranean tree crops such as olives or vines. Short-term (3-4 years) studies have stablished their beneficial effect in term of reducing runoff and soil losses (e.g. Gómez et al. 2009) at hillslope scale. There are few studies which have measured their hydrologic impact in the long-term. Gómez et al. (2021) in a long-term study of runoff and soil losses at hillslope scale in an olive orchard on a vertic soil noted how the reduction of runoff losses using temporary cover crops as compared to a bare soil was less than expected.

Santa Marta is a commercial olive orchard located nearby Seville, Southern Spain, with a mean slope of 11 %, with a sandy-loam textural class, and an average annual precipitation of 534 mm. In 2003, two closed runoff plots (60 long, 480 m²) where regular machine traffic during farm operations was allowed. Four additional plots where stablished in 2005. Since then, runoff and sediment have been collected to determine soil erosion rates, with more details in Gómez et al. (2009). In two of these plots a bare soil management, CT, implemented with regular passes (1 to 3 a year) of chisel has been maintained, while in the other four plots temporary covers controlled by mowing had been used. In 2005 and 2006 two of these plots were seeded with a mix of species, CCm, to enhanced biodiversity, while the other two plots have since the start of the experiment regularly seeded with short-term cycle annual grasses.

During the period 2003-2020 the experiment received an average annual, from 269 to 859 mm, and an average rainfall erosivity of 830 MJ mm ha^-1 h^-1 yr^-1, from 268 to 1750. Average annual runoff and soil losses for the CT treatment were 57.5 mm and 22.9 t ha^-1. For the CCg treatment the average losses were 33.8 mm 2.6 t ha^-1 and for the CCm 33.7 mm 2.6 t ha^-1 without statistically significant differences, at p<0.05 using a Kruskall-Wallis test, in runoff or soil losses between the CCg and CCm treatments. There was a significantly statistical difference in runoff and soil losses between the CT and both CC treatments. The use of temporary cover crops in an olive orchard with moderate machine traffic had a huge effect in reducing erosion, cumulative soil losses were 402.2 t ha^-1 in CT vs. 39.1 t ha^-1 in CC, while moderate in runoff, 57.1 vs. 33.5 mm year^-1. We discuss the temporal evolution of these differences and its implications for soil management, linking them to some soil properties analysed during this time period within the plots.

References:

Gómez, J.A., et al. 2009. The influence of cover crops and tillage on water and sediment yield, and on nutrient, and organic matter losses in an olive orchard on a sandy loam soil. Soil and Tillage Research 106: 137-144

Gómez, J. A., Guzmán, G. 2021. Long-term evaluation of cover crops on soil and runoff losses under trafficked conditions in olive orchards. EGU21-606, https://doi.org/10.5194/egusphere-egu21-606.

How to cite: Gomez, J. A., Montoliu, J., and guzman, G.: Long-term hydrologic effect of temporary cover crops in an olive orchard on a sandy-loamy soil, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2252, https://doi.org/10.5194/egusphere-egu22-2252, 2022.

An extensive erosion plot database measuring soil loss and runoff under natural rainfall in China was compiled to gain new understanding of the overall response of the soil loss and runoff rate to land use, slope gradient, slope length and mean annual precipitation. Our results show that land use dominates the variation of soil loss and runoff: Soil loss and runoff rates on land covered by natural vegetation are one to three orders of magnitude lower in comparison to rates on agricultural land that is strongly disturbed by anthropogenic activities. Slope gradient and slope length affect soil loss and runoff rates on cropland but there is no statistically significant effect on either soil loss or runoff rate on permanent vegetation. This implies that different extrapolating relationships need to be used for cropland in comparison to land with permanent vegetation when erosion plot data are used to assess the erosion risk over large areas. Runoff rates consistently increase with mean annual precipitation. The relationship between soil loss and mean annual precipitation is different and is nonlinear for all land use types, with a clear increase of soil loss with precipitation up to a mean annual precipitation of ca. 700 mm yr^-1, a subsequent decline and a second rise when the mean annual precipitation exceeds ca. 1400 mm yr^-1. This non-linear response can be attributed to the interplay of an increasing rainfall erosivity and an increasing protection due to vegetation cover with increasing mean annual precipitation. It also implies that the effect of climate change on the erosion risk is not straightforward but depends on how both rainfall erosivity and vegetation cover change with changing climate.

How to cite: Zhao, J.: Nonlinear response of soil erosion to mean annual precipitation: evidence from erosion plot data in China, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2546, https://doi.org/10.5194/egusphere-egu22-2546, 2022.

Erosion caused by extreme climate conditions and intense agricultural use is a severe threat to the soil quality of dry steppe ecosystems. The susceptibility of soil to erosion depends mainly on the stability of its structure against mechanical stress, which is directly related to the stability of aggregates. However, there is no generally accepted method to determine soil aggregate stability and most tests cannot be adequately linked to disruptive forces soils experience under field conditions. Thus, our main objective was to explore the aggregate stability of steppe soils against disruptive stresses by wind and water to assess their potential erodibility. We examined 132 topsoil samples from northern Kazakhstan under two land-use types (grassland and cropland), covering a large range of physico-chemical soil properties (texture, organic carbon, inorganic carbon, pH, and electrical conductivity). We combined several methods that capture the soil`s susceptibility against mechanical stresses common in the dry continental climate: An adjusted drop-shatter technique (energy input of 60 Joule) was used to estimate the stability of dry soil against weak mechanical forces, such as wind stroking over bare soil after tillage and before crop emergence. In addition, three wet-aggregate stability tests (fast wetting, slow wetting, and wet mechanical breakdown) were used to estimate the stability of soil aggregates under various stresses caused by precipitation. Results indicate that aggregate stability was generally higher for grassland than cropland soils. Aggregate stability under both land-use types decreased along with increasing sand and decreasing organic carbon contents. The drop-shatter method suggested that only 5% of cropland soils were at high risk of wind erosion (i.e., erodible fraction <60%). In contrast, the fast wetting test revealed that  98% of the samples are unstable after a heavy rain event or snowmelt. Even after a light rain event or the raindrop impact, 54-58% of the samples were unstable and prone to erosion.

We conclude that cropland in the dry steppe of Kazakhstan is much more vulnerable to the disruptive forces caused by water than by wind. Especially the severe breakdown of aggregates during heavy rain events or snowmelts goes well in line with the increasing erosion risk under current and future climate scenarios.

How to cite: Koza, M., Pöhlitz, J., Prays, A., Mikutta, R., Kaiser, K., Conrad, C., Vogel, C., Akshalov, K., Bondarovich, A., and Schmidt, G.: Aggregate stability and potential erodibility of dry steppe soils, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2803, https://doi.org/10.5194/egusphere-egu22-2803, 2022.

One of the strongest challenges for European agriculture is to simultaneously reduce its negative environmental impact and at the same time, remain competitive. A key aspect of the environmental impact is the ongoing soil degradation. Within the Soil Care project, sustainable agricultural practices were investigated that could improve soil quality, termed soil improving cropping systems (SICS); four plausible scenarios were developed with different levels of SICS uptake. In this study we aimed to evaluate how such SICS, through the different scenarios, impact crop yield, soil organic carbon content and land degradation (specifically erosion and soil water dynamics) across Europe, through the application of the PESERA and dyna-QUEFTS models. The Pan-European Soil Erosion Risk Assessment (PESERA) model simulates biophysical processes including above-ground biomass production, soil erosion risk, soil water deficit and soil humus content and was adapted and calibrated for Europe. The dyna-QUEFTS model calculates nutrient limitations and was used to calculate crop yields using PESERA output information. All four scenarios were run from current (2020) until 2050 and for two climate trajectories. Results indicate that the ‘Caring and Sharing’ scenario likely provides the best sustainability impacts (i.e. stable or increased SOC contents and reduced erosion) due to widespread uptake of SICS, compared to the ‘Race to the Bottom’ scenario, in which no SICS were taken up, although regional differences can be seen from the spatially explicit maps that the modelling produces. While, by necessity, the models are a simplification of the reality and assumptions and input data quality affect the results, a comparative analysis of the scenarios and their likely effect can still be made and will be helpful for agricultural policy development across Europe. In addition, the modelling tool provides the opportunity to further analyze which SICS are effective where and to explore the impacts of SICS implementation.

How to cite: Baartman, J., Nunes, J. P., Fleskens, L., Vanhout, R., Gai, L., and Van Delden, H.: The effects of Soil-Improving-Cropping-Systems (SICS) across Europe: a simulation study, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2809, https://doi.org/10.5194/egusphere-egu22-2809, 2022.

Gully erosion is a key driver of soil erosion and land degradation in many regions worldwide, leading to important on- and offsite impacts. While numerous studies have focussed on understanding gully erosion at local scales, we have very little insights into the patterns and controlling factors of this process at a global scale. Overall, gully erosion remains notoriously difficult to simulate and predict. A main reason for this is that the complex and threshold-dependent nature of gully formation leads to very high data requirements when aiming to simulate this process over larger areas.

Here we help bridging this gap by presenting the first data-driven analyses of gully head densities at a global scale.  For this, we developed a grid-based scoring method that allows to quickly assess the range of gully head densities in a given area based on Google Earth imagery. Using this approach, we constructed a global database of mapped gully head densities for around 20,000 sites worldwide. Based on this dataset and globally available data layers on relevant environmental factors (topography, soil characteristics, land use) we explored which factors are dominant in explaining global patterns of gully head densities and propose a first global gully head density map as well as a gully erosion risk map. The latter combines gully density with estimates of the likely expansion rates of gullies. For this we use a combination of machine learning techniques and empirical modelling.

Our results indicate that there might be are around 2 billion gully heads worldwide. This estimate might underestimate the actual numbers of gully heads since ephemeral gullies (in cropland) and gullies under forest remain difficult to map. Our database and analyses further reveal clear regional patterns in the presence of gullies. Around 27% of the terrestrial surface (excluding Antarctica and Greenland) has a density of > 1 gully head/km², while an estimated 14% has a density of > 10 gully heads/km² and 4% has even a density of > 100 gully heads/km². Major hotspots (with > 50 gully heads/km²) include the Chinese loess plateau, but also Iran, large parts of the Sahara Desert, the Andes and Madagascar. In addition, gully erosion also frequently occurs (with typical densities of 1-50 gully heads/km²) in the Mid-West USA, the African Rift, SE-Brazil, India, New-Zealand and Australia.

These regional patterns are mainly explained by topography and climate in interaction with vegetation cover. Overall, the highest gully densities occur in regions with some topography and a (semi-)arid climate. Nonetheless, it is important to point out that not all gully heads are still actively retreating. Building on earlier insights into the magnitude and controlling factors of gully head retreat rates, we hypothesize that hotspots in terms of gully erosion are mostly situated in somewhat more humid and densely cultivated areas. Based on this, we explore what our current results imply for assessing actual gully erosion rates at a global scale.

How to cite: Vanmaercke, M., Chen, Y., De Geeter, S., Poesen, J., Campforts, B., Borrelli, P., and Panagos, P.: Data-driven prediction of gully densities and erosion risk at the global scale, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2921, https://doi.org/10.5194/egusphere-egu22-2921, 2022.

Scale issues in runoff and sediment delivery (SIRSD) is a hot and frontier topic in the fields pertinent to hydrology and soil erosion. This study combined bibliometric analysis and data mining to provide a systematic and holistic review of global SIRSD studies. The bibliometric results indicate that SIRSD is a comprehensive and multidisciplinary issue that has been extensively investigated with a wide variety of methods by scientists from 85 countries since the 1950s. The rapid growth of publications over the last three decades reveals that the discussions on SIRSD are attracting booming attention due to its great potentials for research and practice on various contemporary issues of environment and natural resources. Especially topics about hydrological and sediment connectivity, storm flood, nonpoint pollution, landslide and debris flow are drawing increasing concerns under the context of climate change. Thematic structure analysis indicates that SIRSD field centres the spatial scaling issues in the delivery of suspended sediment, including sediment budget analysis and sediment delivery ratio (SDR) estimation. Compared to studies dealing with erosion and sediment that mainly focus on the spatial scale, studies related to hydrological runoff and climate tend to discuss more temporal scale issues. Regarding the study distribution, most studies cluster on the time scale from an event to 10 years and the spatial scale from plot to meso-watershed (10 m²-1000 km²) and tend to appear in regions that feature free-flowing rivers with rapid agricultural development. Based on the mined 1039 pairs of data on the relationship between SDR and the watershed area, we built a global view of the spatial effect on SDR. The spatial scale effect on SDR is most prominent in Europe, followed by the USA, then the Global average, while most gentle in China due to its high topographic variability. On the contrary, the average SDR is highest in China (0.51), followed by the Global case (0.37), then the USA (0.34), while lowest in Europe (0.28) due to its low mean topographic slope. From this review, we identified several research gaps: 1) lack of multi-scale studies with nested across-scale design and studies on the spatial scale effect on runoff delivery; 2) considerable gaps among the results obtained from different regions, methods, and scales; 3) debatable and unclear questions on the spatio-temporal scale of underground water and soil loss in the karst region. Moreover, we emphasize three areas for future research: 1) scale issues of flood processes regarding extreme rainstorms under climate change; 2) scale transformation methodology and multi-scale modelling of hydrology, erosion, and sediment transport and their integrations with the climate models; 3) comparative study in different regions to bridge the regional gaps.

How to cite: Ke, Q. and Zhang, K.: Scale issues in runoff and sediment delivery: a global review and statistical analysis, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3371, https://doi.org/10.5194/egusphere-egu22-3371, 2022.

Throughfall constitutes the majority of incident precipitation reaching the ground under any type of vegetation canopies. Its characteristics play a crucial role in understanding the sub-canopy hydrologic and erosional processes. The present study examines the drop size distribution (DSD) and erosivity of throughfall beneath the birch tree (Betula pendula Roth.) canopy during its leafed period using a Parsivel¹ optical disdrometer installed in the experimental plot in the city of Ljubljana, Slovenia. The momentum and kinetic energy of throughfall drops were used to express the impact of the tree canopy on the potential erosive power of throughfall on a soil surface which was computed from the measured raindrop size and velocity. The microstructures of open rainfall and throughfall were measured simultaneously by an optical disdrometer during the two separate precipitation events that occurred on August and September 2021 with an accumulated amount of 34.4 mm in 7.3 hours and 87.6 mm in 7.6 hours, respectively. On an event basis, the preliminary results show that the throughfall DSD for both events exhibits two contrasting modes (i.e. bimodal peaks) while open rainfall has only one which is attributed to the influence of canopy interception and storage. The total number of throughfall drops is higher compared to the open field condition but are smaller in size, comprising nearly 89% of the recorded drops are below 1 mm while only 0.23% are greater than 2.4 mm. Additionally, the median-volume drop diameter (D₅₀) of the throughfall is 1.31 mm for an extreme event (September 2021) and 0.98 mm for a medium-magnitude rainfall (August 2021) which is respectively, 70% and 79% lower than those in open precipitation. On the other hand, the raindrops from moderate and heavy precipitation have greater momentum to cause soil particle displacement with a corresponding value of 60.49 and107.83 kg m s^-1 m^-2 than the throughfall drops (40.99 and 87.49 kg m s^-1 m^-2). Similarly, a throughfall kinetic energy of 91.96 and 187.77 J m^-2 is respectively 64% and 82% lower than the energy loads of raindrops in the open environment. Owing to the effects of the birch tree canopy, the distribution of throughfall reduces the erosive potential of raindrops by approximately 36% and 18% for the two selected rainfall events during the leafed period. These results accentuate the importance of understanding the different characteristics of throughfall from the open rainfall which is necessary for the prediction of soil erosion processes in areas where this tree species is abundant in nature.

Acknowledgments: Results are part of the CELSA project entitled “Interception experimentation and modelling for enhanced impact analysis of nature-based solution” and research programme P2-0180 supported by the Slovenian Research Agency (ARRS).

How to cite: Alivio, M. B., Bezak, N., Šraj, M., and Mikoš, M.: Characteristics of the drop size distribution and rainfall erosivity of throughfall beneath a deciduous tree canopy, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3433, https://doi.org/10.5194/egusphere-egu22-3433, 2022.

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. Modelling approaches can deliver indicators on the state of soil erosion impacts and its trends, and scenarios in relation to climate and land use change. This can help define efficient and targeted mitigation strategies. However, to define such strategies, there remains a lack of modelling approaches able to provide with long term baseline information which to measure the success of the mitigation strategies as well as model evaluation approaches robust enough so model results can be trusted by users, including researchers and land managers. The MMF-TWI soil erosion model has demonstrated its ability to simulate soil erosion and the effect of agricultural management practices over centennial scales in humid environments. However, it needs to be revised and evaluated before the model can be applied more widely in other climate areas. In this study, we present a revised version of MMF-TWI incorporating infiltration excess overland flow and a robust and innovative multi-proxy model evaluation approach in an olive orchard catchment in South Spain. The evaluation approach consists of a) the comparison of model simulations with estimations of past soil loss rates obtained from both Pu fallout radionuclide tracers and tree mound measurements and b) the evaluation of the plausibility of the model behaviour by means of global sensitivity analysis.

How to cite: Peñuela, A., Garcia Gamero, V., and Vanwalleghem, T.: A robust evaluation a revised version of the MMF-TWI soil erosion model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3671, https://doi.org/10.5194/egusphere-egu22-3671, 2022.

In order to study the influence of artificial terrain (terraced fields) on topographic factors, this paper, based on the basic principles of soil erosion and soil conservation, uses aerial photogrammetry to obtain high-precision DEM in Zhifanggou watershed, and extracts the slopes of terraced and non-terraced areas , Slope、Length and Slope Length factor, Topographic Wetness Index, Connectivity Index and Relative Path Impact Index, and analyze the changes of these factors to understand the impact of terraces on eroded terrain. The research shows that: (1) The construction of terraces makes the slope slow down, the slope length is cut off, and the LS factor becomes smaller; (2) The construction of terraced fields reduces the connectivity at the field surface and increases the connectivity at the ridge; the IC value of terraced fields is greatly affected by slope, and the IC value of non-terraced fields is greatly affected by slope length. (3) With the increase of slope, the connectivity of sediment increases and soil erosion intensifies; runoff accumulation is likely to occur in local depressions, resulting in increased connectivity of sediment. (4) The relative path impact index is effective for identifying erosion risk areas susceptible to changes in water flow paths. This paper expounds the influence of terraced fields on eroded topographic indicators and hydrogeomorphology, which is of great significance for accurately assessing the impact of terraced fields on soil erosion and for soil erosion control in the Loess Plateau.

How to cite: Qiao, B., Yang, Q., Wang, C., Pang, G., and Li, E.: Influence of terraced fields on eroded terrain indicators：take the second of gullied rolling area on the Loss Plateau as an instance, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3704, https://doi.org/10.5194/egusphere-egu22-3704, 2022.

Gully erosion is an important process of land degradation that threatens soil and water resources worldwide. However, our ability to simulate and predict this process is still very limited, especially on the continental scale. Nevertheless, such models are essential for the development of appropriate land management strategies, but also to better quantify the role of gully erosion in sediment budgets. One of the main challenges is that patterns of gully erosion depend on regional patterns of controlling factors (e.g., rainfall, lithology, soils), but are also strongly determined by local factors (e.g., topography, vegetation cover, land management). This greatly increases the complexity of potential models and their data requirements. We seek to bridge this gap by developing a robust empirical model capable of predicting gully erosion at high resolution on the scale of Africa with feasible data requirements.

More precisely, we are developing a logistic probability model at 30m resolution for the entire African continent that predicts the likelihood of gully head occurrence by using GIS and spatial data sources that are available on the continental scale.  Although empirical in nature, the factors included in this model are consistent with the current process understanding of gully erosion. To calibrate and validate this model, we make use of an extensive database of 44 000 gully heads mapped over 1680 sites, randomly distributed across Africa. The exact location of all gully heads was manually mapped by trained experts, using high resolution optical imagery available in Google Earth. This allows to extract very detailed information at the level of the gully head, such as the local slope and the area draining to the gully.

Our first analyses show that gully occurrences mainly depend on topography (slope and to some extent contributing area), soil characteristics (i.e., mainly silt fraction) and vegetation cover. Combined, these factors already allow for robust and fairly reliable predictions of gully head occurrences (with AUCs of the logistic regression model around 0.7). Better incorporating the role of rainfall and climate will likely result in better predictions which is ongoing work.

Based on these results we present a first gully probability map for Africa at 30m resolution. Besides providing essential information on gully density hotspots, this offers great potential to couple our gully density model to a gully retreat rate model and to make a first assessment of gully erosion rates at the continental scale of Africa.

How to cite: De Geeter, S., Vanmaercke, M., Verstraeten, G., Poesen, J., and Campforts, B.: First gully probability map for Africa at 30m resolution, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4017, https://doi.org/10.5194/egusphere-egu22-4017, 2022.

Soil erosion by water is a severe problem throughout the world that threatens soil security and the health of water bodies. This problem is aggravated by global climate change, leading to more intense rainfall and drought events. Moreover, soil erosion also intensifies the impacts of drought by reducing the soils' capacity to hold water and maintain sustainable crop yields. This project aims to evaluate the current status and future evolution of soil security in the Guadalquivir basin. For this purpose, we use a combination of predictive modelling and estimations of long-term soil erosion-deposition rates based on field observations and measurements of fallout radionuclide (FRN) tracers in representative catchments. We test and apply a novel method for analyzing ^239+240Pu isotopes, that offers a much cheaper way of analysis and hence a potential new standard to estimate long-term soil erosion-deposition rates. Spatially distributed estimations of long-term soil erosion-deposition rates are used to calibrate and evaluate the soil erosion models RUSLE and MMF-TWI which will then be used to assess present and future soil resource status in the catchments of study. Here, we present the preliminary results of this project, particularly the results obtained by the analysis of ^239+240Pu  isotopes in an olive grove catchment and how these results compare against the more established ¹³⁷Cs analysis and estimations of soil truncation based on measurements of the height of olive tree mounds.

How to cite: García-Gamero, V., Peñuela, A., Mas, J. L., Peña, A., Hurtado Bermúdez, S., and Vanwalleghem, T.: Quantifying the impact of soil erosion on soil security by using alternative fallout radionuclides, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4173, https://doi.org/10.5194/egusphere-egu22-4173, 2022.

Soil erosion is high in hillside orchards in Spain. Climate change is causing an increase in the length of dry periods and intensity of rainfall, which exacerbates soil loss from fields. Due to the lack of rain during the summer, orchard farmers, concerned about water competition for tree crops, remove ground cover. However, without raindrop interception the soils are vulnerable to erosion and gullying. While cover crops between tree crops are beneficial in controlling soil erosion, farmers are slow to take up this practice. Both a mesocosm experiment identifying the value of vegetation cover, and survey responses from farmers about erosion management practices are outlined below.

Rainfall simulation was used in a mesocosm experiment to determine the effect of plant cover on sediment loss. Three species native to Spain were used in five treatments consisting of Brachypodium distachyon, Medicago sativa, Silene vulgaris, a mix of the three species, and a bare plot. The plots were raised to a 10^o angle before subsampled runoff and sediment was collected under simulated rainfall. A questionnaire was sent to crop tree farmers in Spain asking about their experiences of soil erosion, techniques used to combat it, if any, and their views on methods of soil and water conservation.

Significantly higher (p < 0.05) rates of sediment loss were measured from the bare plots (34.26 ± 19.85 g min^-1), relative to the vegetated ones (6.13 ± 8.27 g min^-1). This indicates the importance of cover crops to reduce soil erosion. The farmers responding to the questionnaire are aware of this. From a total of 26 respondents, 88% believe that cover crops decrease erosion. However, 58% think that lack of knowledge about effective methods of erosion control is a barrier to implementing techniques.     

This presentation will give an overview of the methods used in carrying out rainfall simulation and the questionnaire, in addition to the results gathered.

How to cite: Ripley, H., Stevens, C., and Quinton, J.: Impact of plant cover on soil erosion, and barriers to cover crop use in Spanish orchards., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4953, https://doi.org/10.5194/egusphere-egu22-4953, 2022.

Gullying is a common soil erosion process in Southern Ethiopia, damaging agricultural landscapes and contributing sediments to water bodies. River catchments extending across the rift escarpment within lakes Abaya and Chamo Basin in the Southern Main Ethiopian Rift are areas experiencing such problems. Impact of gullying depends on the state of activity of gullies, i.e. inactive gullies might have had a role in the landscape formation, but they can now be considered stable and not contributing to sediment delivery to the downstream, unlike the active gullies. In order to reduce the impact of active gullies, understanding the conditions under which gullies initiate, expand and stabilize is vital. In this paper, the location where new gullies initiate and where they stabilize is modelled spatially. To determine factors controlling for the initiation of new gullies, the potential gully initiation points were extracted along more than 4520 active gullies using slope and drainage area thresholds. The susceptibility of gully initiation is then modelled using logistic regression and frequency ratio methods, with a set of 14 predisposing factors. The conditions for gully stabilization are assessed by modeling the location of the head of more than 1080 inactive gullies. Highly susceptible areas for gully initiation are mainly modelled in rejuvenated landscapes downslope of knickpoints, where steep slopes have been recently formed by knickpoint propagation.most susceptible areas for gully initiation are observed in concave slopes with high topographic wetness index, whereas heads of inactive gully stabilized when slopes become convex with a lower topographic wetness index. The area under receiver characteristics curve (AUC) of the validation data ranges from 0.75 to 0.85 for all susceptibility models; prediction rate of gully initiation and stabilization vary from 70 to 93%. Our results indicate that the applied models are reliable and have very good prediction performance of gully initiation and stabilization and that such approach contrasting the gully initiation point and the gully head location enable to better understand the gullying process. The resulting susceptibility maps are a step towards contributing to the decision-making process on the optimized locations of soil and water conservation measures, and thus contributing to landscape sustainability.

How to cite: Belayneh, L., Dewitte, O., Gulie, G., Poesen, J., Stal, C., and Kervyn, M.: Modelling the spatial variation in susceptibility to gully initiation and stabilization in the Southern Main Ethiopian Rift Valley, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5566, https://doi.org/10.5194/egusphere-egu22-5566, 2022.

Quantifying soil erosion is a major research challenge due to erosion's episodic character and spatial variation. Fallout radionuclides as ^239+240Pu and ¹³⁷Cs are powerful tools to assess net soil losses integrated over long periods applicable to most regions of the world. The traditional approach of the FRN method is based on the comparison between an inventory (total radionuclide activity per unit area) at a given sampling site and that of an undisturbed reference site (e.g., located in a flat and well-vegetated area). Compared to reference, a decrease in the FRN inventory indicates erosion and an increase indicating deposition of sediments and associated FRN. So far, FRN based assessment was restricted to a regional/catchment scale as spatially distributed data of reference inventories was missing.

In this study, we aim at upscaling the FRN approach to a central area of Europe covering France, North Italy, South Germany, and Belgium using the Land Use/Cover Area frame Survey – LUCAS soil sample bank. Both fallout sources left a specific radionuclide imprint in European soils. First, plutonium was used to quantify global versus Chernobyl fallout contributions to ¹³⁷Cs found in European soils. Subsequently, spatial prediction models (general additive models) allowed reconstructing the global versus Chernobyl ¹³⁷Cs fallout pattern across national boundaries. The definition of these ¹³⁷Cs and the Pu baseline maps allows assessing soil redistribution rates at n=137 cropland sites with both FRNs across the study area. We selected barley, wheat, maize, and vineyard plots covering different slope angles as cropland sites. For both FRNs, differences between the reference and site-specific FRN inventory show an inventory and associated topsoil (0-20cm) loss of approximately 10% since 1963. Converting these inventory changes with a simple mass balance model to soil redistribution rates results in average soil erosion rates of 8.8 ± 6.3 t/ ha yr, assuming a tillage depth of 20 cm. Although the involved uncertainties are large, these net erosion rates exceed the expected magnitude.

How to cite: Meusburger, K., Evrard, O., Ballabio, C., Borrelli, P., Ketterer, M., van Oost, K., Wilken, F., and Alewell, C.: Fallout radionuclides indicate a 10% loss of European topsoil in 50 years, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6154, https://doi.org/10.5194/egusphere-egu22-6154, 2022.

Soil erosion causes major problems of land degradation in agricultural systems leading to losses of soil fertility. Rubber tree is one of the main tropical perennial crops with about 13 million hectares of plantations worldwide in 2018. In the early stage of a rubber plantation, soil is especially vulnerable to degradations given the low canopy cover and heavy soil surface disturbance related to clear-cutting of the previous plantation. This study aims at assessing runoff and soil losses as well as understanding the main soil factors influencing soil erosion in a young rubber plantation in Côte d’Ivoire. We intensively measured soil runoff, soil detachment, soil structure maintenance and soil macrofauna for 2.5 years under different managements of logging residues and the use or not of a legume cover crop. The results showed that the restitution of logging residues has reduced runoff by 6 and soil losses by 14 compared to plot without logging residues, over the study period. The planting line where soil is kept bare was by far the most critical area in term of soil erosion. The restitution of logging residues significantly improved soil structure maintenance as well as soil macrofauna diversity. We found strong relationships between runoff, soil losses, soil structure and soil macrofauna diversity. These results evidence that the restitution of logging residues and the sowing of cover crop are appropriate agroecological practices in young rubber plantations. Our results suggest that keeping a cover in the planting line could be the most relevant lever to limit soil erosion in the context of the study.

How to cite: Mareschal, L., Janeau, J.-L., Legrand, M., Gay, F., Kouakou, A., Brauman, A., Manizan, A., Laclau, J.-P., and Perron, T.: Logging residues promote positive interactions between soil erosion, soil functioning and soil macrofauna diversity in young rubber plantations in Africa., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7414, https://doi.org/10.5194/egusphere-egu22-7414, 2022.

Soil degradation due to water erosion is one of the greatest problems of agricultural soils worldwide. To be able to map the extent of soil degradation and consequently propose actions for soil improvement, an effective approach is needed. Soil organic carbon (SOC) content and its time fluctuations is one of the key features characterizing the given site and occurring processes. It is widely accepted as the main soil quality indicator and therefore can be used for soil degradation assessment. Traditional laboratory techniques (dry combustion, wet oxidization) of soil organic carbon determination are usually labor intensive and time consuming, which means they are not suitable for large sample collections (e.g., large areas or continual monitoring). Therefore, there is a need for fast, reliable, and cost-effective techniques. Our previous study documented that the VIS-NIR reflectance spectroscopy and magnetic susceptibility can be a very efficient tool for SOC mapping with the Chernozem (a loess region of South Moravia, Czech Republic) areas heavily affected by water erosion. Within this area colluvial soils with up to an about 4 m deep humus enriched horizon were developed. Distribution of soil properties within the colluvial soil profiles at several positions were evaluated using standard and novel methods to distinguishing the different sedimentation phases and understanding colluvial soil formation. The same study was also performed in another two locations (Cambisol and Luvisol areas). Results showed that while both methods could be used for estimation of SOC distribution within the soil profiles in the Chernozem area, in the other two areas the VIS-NIR reflectance spectroscopy method was less accurate and magnetic susceptibility was inaccurate because there was no correlation between SOC and content of ferrimagnetic particles.

Acknowledgement: Study was supported by the Czech Science Foundation, project "Pedogenesis of colluvial soils: a multidisciplinary approach in modeling the dynamics of development in the soil-landscape environment" (No. 21-11879S) and also by the European Structural and Investment Funds, projects NutRisk (No. CZ.02.1.01/0.0/0.0/16_019/0000845).

How to cite: Klement, A., Fér, M., Kodešová, R., Nikodem, A., Zádorová, T., and Penížek, V.: Using VIS-NIR reflectance spectroscopy and magnetic susceptibility to assess soil redistribution due to erosion, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7717, https://doi.org/10.5194/egusphere-egu22-7717, 2022.

The potato is known as a particularly erosion-prone crop due to its late seed development and the unique structure of its seedbed (wide-rows). Therefore, improved tillage practices are needed in order to counteract and mitigate adverse effects of erosion.

This research evaluates the effectiveness of three mitigation measures – furrow greening, micro-dams heaped between furrows, and greened micro-dams – over a three-year study period in Lower Austria. Runoff plots were used to quantify surface runoff and collect each treatment's eroded material during precipitation events. The contents were emptied after each event, dried, weighed, and, if possible, analyzed for grain size distribution and nutrient composition. Additionally, the soil water content of the ridges and furrows and the potato yield was determined for each treatment in the 2021 field campaign to evaluate further effects of each treatment.

Results show that with a furrow greening soil erosion was reduced between 48 – 83% compared to the control treatment. By heaping micro-dams, soil erosion was reduced by 79 – 98%, and with the additional greening of micro-dams sediment yield was lowered by 94 – 99%. Micro-dams increased the water content in the furrows after a precipitation event but not in the ridges. Regarding potato yield, no significant difference was observed between treatments.

The results of this study show the potential of micro-dams to reduce on-site and off-site effects of soil erosion on sloped agricultural land. Depending on the steepness of the slope and the intensity of precipitation events, breaking of micro-dams can occur and therefore lose their mitigation effect. Through the additional greening of micro-dams, further stabilization could be reached, thus withholding precipitation events of higher intensities.

How to cite: Konzett, M., Schmaltz, E., and Strauss, P.: Mitigation of surface runoff and soil erosion in potato farming, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8179, https://doi.org/10.5194/egusphere-egu22-8179, 2022.

Gully erosion represents a core process of land degradation and a serious threat to ecosystems and their services. Loess regions in the northern part of Lower Austria can be considered as particularly susceptible to the development of gullies. However, relatively little attention has been paid to gully erosion in these areas (e.g. neither gully inventories, nor information on gully characteristics are available). Therefore, the aim of this study was to map, document and geomorphometrically analyse gullies and to further delineate gully hot spot areas in the loess regions of Lower Austria.
A Digital Elevation Model (DEM) with a spatial resolution of 1 m has been used to visualise, map and geomorphometrically analyse gully erosion features in the research area in a GIS. Moreover, calculations of gully volumes have been adduced to determine the amount of eroded material in a selected gully hot spot catchment. The main focus throughout the study has been put on sunken lanes and permanent gullies, which have been explicitly identifiable in this region.
The results show strong concentrations of gullying in the loess areas of the eastern Waldviertel and the Weinviertel regions, both being characterised by intensive agricultural use. Sunken lanes are mainly found in the hilly and terraced landscapes of vineyards, while clusters of permanent gullies are usually found in agricultural fields but also forests surrounded by agriculture and used for silviculture. The hot spot areas exhibit a gully density of up to 17 permanent gullies per km² and 5 sunken lanes per km². Permanent gullies are often of remarkable size, showing volumes of up to 100,000 m³, more than 500 m in length and depths reaching 20 m and more. The longest observable sunken lane has a length of 1.6 km and a volume of nearly 70.000 m³.
More detailed results will be presented at the EGU General Assembly 2022.

How to cite: Diem, S. and Pöppl, R.: Mapping and analysing “badass gullies” in the loess regions of Lower Austria, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9179, https://doi.org/10.5194/egusphere-egu22-9179, 2022.

Mapping reservoir siltation is an often-used method for assessing sediment yield and soil erosion from catchments. An advantage of this approach is that measurements can potentially provide mean values that represent timeframes of several decades and thus overcome the bias induced by climate fluctuations, especially in semi-arid and arid regions. Furthermore, reservoir siltation mapping can be performed repeatedly, and thus repeated sediment yield trends over time can be derived. There are several studies that report sediment yield estimates based on reservoir siltation surveys, however, information on the uncertainties involved in these measurements is not frequently reported.

In October 2019 and March 2020, we conducted reservoir siltation surveys of eight mid-size (~ 10 mio m³ water storage capacity), filled and dried-out reservoirs in South Africa. The water-filled reservoirs were surveyed using single beam, single frequency echosounders mounted to a boat. The dried-out reservoirs were surveyed using differential GNSS and a Terrestrial Laser-Scanner (TLS) with a scanning range of up to 1 km deployed at multiple scanning positions.

In this contribution we present survey results, report on the issues encountered during the surveys and the uncertainties observed in the results. For the water-filled reservoirs we derived depth measurement uncertainties from the survey leg intersection points. Here, the mean measurement error is in the order of 0.1 m (p= 0.05). When this uncertainty of the volume estimation is applied to the water storage capacity of the dams, the resulting uncertainties are inthe order of a few percent, only. However, if this volume estimation uncertainty refers to the volume of the sediment at the bottom of the reservoirs, the relative error is can be in the order of a few ten percent. From this we conclude, that depending on the sediment inflow, it may take several decades before a repeated survey can establish a meaningful trend in sediment yield from the catchment beyond the measurement uncertainties involved.

How to cite: Baade, J., Zoller, K., van Zyl, W., and Cawthra, H.: Reservoir siltation mapping uncertainties – experiences from South Africa, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9930, https://doi.org/10.5194/egusphere-egu22-9930, 2022.

Intense gully erosion has sculptured remarkable channels into the Moldavian Plateau of eastern Romania. These permanent gully types are: (1) discontinuous gullies, mostly located on hillslopes and (2) large continuous gullies in valley bottoms.

This study seeks to improve our understanding of the development of 1) continuous gullies over six decades (1961-2020) and 2) discontinuous gullies over variable time-scales (mostly 17-30 years, but also including data collected since 1961) by providing quantitative information on gully evolution and processes. Several methods were used to measure and estimate gully growth. These include intensive field monitoring using the ‘stakes grid method,’ repeated levelling until 2019, analysis of aerial photographs and Caesium-137 analysis.

            As regards the continuous gullies, results indicate that gully erosion rates have significantly decreased since 1981. The mean linear gully head retreat rate (LGHR) of 7.7 m yr^-1 over 60 years was accompanied by a mean areal gully growth rate in plan (AGG) of 213 m² yr-¹.  However, erosion rates between 1961-1980 were 4.0 times larger for LGHR and 5.9 times more for AGG compared to those for 1981-2020. Two regression models indicate that annual precipitation (P) is the primary controlling factor, explaining 57% of the LGHR and 53% of the AGG rate. The contributing area (CA) follows, with ~33%. Only 43% of total change in LGHR and 46% of total change in AGG results from rainfall-induced runoff during the warm season. Accordingly, the cold season (with associated freeze-thaw processes and snowmelt runoff) has more impact on gully development. The runoff pattern, when flow enters the trunk gully head, is largely controlled by the upper approaching discontinuous gully.

The discontinuous gullies occur as single, successive chains or clusters. These are associated with small catchments (usually <100 ha in area) and ephemeral peak runoff discharges are usually ≤2 m³ s^-1. The mean LGHR for 31 gullies was 0.97 m yr^-1, indicative of a relatively small erosion rate. However, their ‘pulsatory’ development was mostly controlled by runoff accommodation when runoff enters and is conveyed through a gully. We further analysed the changing runoff pattern or ‘variable-geometry flow.’ The R² of the relation between LGHR or AGG and  (CA) indicated a weak correlation for discontinuous gullies.

How to cite: Niacsu, L., Ionita, I., Poesen, J., and Fullen, M.: Development of continuous and discontinuous gullies in the Moldavian Plateau of Romania, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10460, https://doi.org/10.5194/egusphere-egu22-10460, 2022.

Soil erosion by water is one of the most widespread forms of soil degradation in Europe, where the relevant annual cost for agricultural productivity loss is estimated to be around 295 million euros. Under climate changes, soil erosion due to rainfall is dramatically increasing, for the most part because of an increasing of the frequency of extreme, localised events.

Here, we present the MSCA-Horizon2020 project, focused on understanding and quantifying extreme rainfall effects on soil erosion, by means of ground-based weather-radar observations and hydrological modelling at regional scale (namely in Tuscany, central Italy).

In critical hydrological phenomena, such as intense surface runoff, flooding and soil erosion, the spatiotemporal extent is crucial in the development of the processes. This feature significantly  affects the impact and the evolution of critical phenomena, especially during extreme events. Therefore, an approach directed to refine as much as possible the knowledge of these dynamics is recommended both at the monitoring and the modelling level.

Using an approach based on statistical analyses of rainfall data from ground-based radar and modelling, this project aims to: 1) Quantify on historical data the spatiotemporal distribution of extreme rainfalls / runoff and soil erosion over the last years, 2) Build a platform to model runoff and soil erosion during extreme events in real-time, 3) Simulate in real-time runoff and soil erosion behaviours related to extreme rainfalls, integrating the current regional-warning-system for the extreme weather events.

How to cite: Ciampalini, R., Moretti, S., Rosi, A., Antonini, A., and Ortolani, A.: Soil erosion under extreme rainfall events: detecting and modelling using a radar-runoff-nowcasting-system, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10994, https://doi.org/10.5194/egusphere-egu22-10994, 2022.

Intensive soil degradation of agricultural lands during the past decades led local authorities in the Harod Catchment, northern Israel, to implement soil and water conservation practices. Herein, for the first time in Israel, we quantified the impact of these practices on water discharge, runoff/rainfall, and sediment yields at the catchment scale. We monitored two neighboring tributaries of the Harod River: Shkedim and Shunem. Both are dominated by intensive agriculture, are similar with respect to soils and rain patterns, but differ in terms of tillage and soil conservation practices - implemented in abundance in the Shkedim catchment. Inner-catchment processes were studied at the plot scale using a structure for motion photogrammetry, utilizing an unmanned aerial vehicle. At the catchment scale, we used airborne LIDAR to provide a better understanding of the extent to which different geomorphometric characteristics might influence flood discharge, suspended sediment concentration, and yield. We monitored the impact of temporal changes in vegetation cover with remote sensing. Intense storms occurring in early winter when the soil was bare and freshly tilled generated much runoff and sediment. During three field seasons, measured mean annual sediment yields were 820 and 2,000 t km⁻² y^-1 for Shkedim and Shunem, respectively. The benefits of soil conservation practices applied in the Shkedim catchment are manifested by lower runoff yields and peak discharges. Conservation practices together with milder topography were identified to limit flow continuity and to promote sinks, while in the Shunem, tillage parallel to contour lines induced higher hydro-geomorphic connectivity. Still, Shkedim soil loss is high due to cultivation of riparian zones, lack of maintenance of engineered structures, and a larger area of bare soil during winter due to rotational cropping. These blur the efficiency of soil conservation practices at the catchment scale.

How to cite: Egozi, R., Bekin, N., Prois, Y., and Laronne, J.: The fuzzy effect of soil conservation practices on runoff and sediment yield from agricultural lands at the catchment scale, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11215, https://doi.org/10.5194/egusphere-egu22-11215, 2022.

Every year 12.5 million tons of plastic are used in agricultural production across the globe with plastic films accounting for 75% of this plastic. Once added to the soil, removing agricultural plastic is challenging as exposure to sunlight and other environmental elements fragment the plastics into macro- and microscopic pieces. In addition to this direct input, agricultural soils accumulate microplastics from several other sources e.g., biosoilds input, runoff from roads and atmospheric deposition. Soils are usually thought of as sinks for plastic waste but growing literature suggests mismanaged agricultural soils could be significant sources of plastics to aquatic and other terrestrial environments. In this study, we investigated the process of microplastic movement in response to rainfall and overland flow. We compared the movement of two types of plastic (linear low-density polyethylene and acrylic) in two size fractions with sand particles in rainfall simulation experiments. We examine the extent to which plastic particles are preferentially eroded compared to fine sand particles, alongside the relative importance of particle size and polymer type for controlling the erosion of plastics from soil.

How to cite: Severe, E., Surridge, B., and Quinton, J.: Processes controlling the transportation of microplastics in agricultural soils, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11484, https://doi.org/10.5194/egusphere-egu22-11484, 2022.

Soil, i.e. the natural outer layer of the lithosphere and an important component of many ecosystems, may be subjected to various degradation processes dependent on different factors. One of the forms of physical degradation is water erosion, where the first stage is the splash phenomenon caused by water drops hitting the soil surface during rainfall. This process results in detachment and ejection of splashed material and transport thereof over different distances. One of the factors that influences the magnitude of soil splash is the incline of the surface (slope). The aim of this study was to check the effect of the slope on the course of the splash phenomenon caused by single-drop impact, with respect to the mass and proportions of the ejected material, taking into account its division into solid and liquid phases i.e. soil and water.

The measurements were conducted on three types of soil differentiated in terms of texture, in moistened conditions (pressure head corresponding to -1.0 kPa). Three slope inclines were investigated: 5°, 15°, and 30°. After a single-drop impact (with a diameter of 4.2 mm), the ejected material was collected using a splash cup. Based on this the following quantities of splashed material were measured: the total ejected mass, the mass of the ejected solid phase and the mass of the ejected liquid phase. Also, the distribution and proportions (soil/water) of the splashed material were analysed in both the upslope and downslope directions. The results showed that: a) the change of slope had a variable influence on the measured quantities for different soils; b) the measured values were mainly influenced by the texture; c) with the increase of slope, the splashed material was mostly ejected in the downslope direction; d) the ejected material consisted mostly of water, this occurred for material ejected both upslope and downslope.

This work was partly financed from the National Science Centre, Poland; project no. 2018/31/N/ST10/01757.

References:

Beczek M., Ryżak M., Mazur R., Sochan A., Polakowski C., Bieganowski A.: Influence of slope incline on the ejection of two-phase soil splashed material. PLOS ONE 17(1): e0262203, 2022

How to cite: Beczek, M., Ryżak, M., Mazur, R., Sochan, A., Polakowski, C., and Bieganowski, A.: Slope incline as a factor influencing the ejection of two-phase soil splashed material, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13030, https://doi.org/10.5194/egusphere-egu22-13030, 2022.

Brazil is seen as a potential world breadbasket in which an increase of around 40% in its current production is expected by the year 2050 to attend food demand imposed by world population growth. The disorderly intensification of agriculture results in erosion, losses and exhaustion of soil nutrients, abandonment of the area, and opening of new agricultural ones. The authors were motivated by the questioning of how significant the changes at surface runoff and soil loss over time are. Thus, this work aimed to investigate the temporal component (10 years) in the surface runoff and soil loss of a typical soil found in the Cerrado biome (Brazilian Savanah), an area that shelters a large part of the national agricultural production. The study area is located in Itirapina municipality, central region of the State of São Paulo, Brazil (22º10'S, 47º52'W, elevation of 790m). The region's mean annual rainfall is about 1486 mm and humid subtropical climate, with hot summers and dry winters. The soil type found is the Orthic Quartzarenic Neosol (RQo), which occupies approximately 15% of the Cerrado biome superficial area. Surface runoff and sediment yield are monitored in rectangular experimental plots (5 meters wide, 20 meters long, and 9% slope). Monitoring takes place in six plots kept under bare soil (three plots constructed in 2011, called P1, and another three plots constructed in 2020, called P2). Runoff flows downhill and is automatically registered through large tipping buckets and then stored in large boxes (360 liters). Runoff samples are collected after each precipitation event to identify the amount of sediment in the liquid sample. To study the pedological characteristics, soil samples were collected at different depths (15, 30, 60, and 90 centimeters) of the experimental plots in 2013 and 2022 and sent to laboratory analyses such as granulometric, porosity, density, and hydraulic conductivity. It was observed that P1 has a runoff volume 10.3% greater than P2 under the same dimensions and slope. Runoff usually starts first and lasts longer at P1 than P2. P1 soil exposure to precipitation and solar radiation over 10 years modified the superficial pedological characteristics, causing: clogging of the pores, loss of superficial soil layer, particle breakdown, and deposition near the outlet plot. Currently, the sediment carried at P1 is rich in soil particles of larger dimensions while P2 has high clay contents. The differences in the hydrological responses of the experimental plots were confirmed through laboratory analyses demonstrating that P1 has lower clay, organic matter, and porosity contents in the plot surface layers compared to P2. Most runoff and soil loss monitoring are limited to campaigns covering isolated events up to 1 year, but records over a long time as given above are scarce, especially in tropical and subtropical areas, demonstrating its relevance to the soil research community.

How to cite: Schwamback, D., Sone, J., Gesualdo, G., Watanabe, A., Zepon, F., Scutti, L., Castro, L., and Wendland, E.: How do runoff and soil loss vary over time in subtropical areas?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13197, https://doi.org/10.5194/egusphere-egu22-13197, 2022.

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 globally available. We present a method for soil carbon stock assessment using satellite data, stratified sampling design, direct soil measurements via mobile soil sensors and machine learning, which fulfills these criteria. 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 and is able to detect variation in soil carbon stock up to a 10 meter resolution. Carbon stocks in the top 30 cm range between 17-55 ton C/hectare. Error propagation analysis showed that the error associated with the soil sensor on the level of farm C stocks is less than 5%. This precision can be achieved with as few as 0.5 field samples per hectare for farms varying from 60 to 250 hectares, ensuring affordability and scalability of the method. The method is globally applicable because it uses covariates which are also globally available. These findings can enable the structural and widespread implementation of carbon farming with a standardized method. In future, as the calibration dataset increases, even less field data will be needed to obtain robust C stock estimates.

How to cite: Verweij, S., van der Voort, T., van Doorn, M., Fujita, Y., and Ros, G.: Enabling carbon farming: presentation of a robust, affordable and scalable method of carbon stock estimates, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2258, https://doi.org/10.5194/egusphere-egu22-2258, 2022.

An increase in the occurrence of drought events potentially aggravate conflicts between agricultural water use and other human and ecological demands for water resources. Increasing the natural soil water retention capacity can help to defuse these conflicts and at the same time strengthen climate mitigation, biodiversity, and food security. Although a variety of measures may be taken to increase soil water retention in agricultural systems, their effects in response to climate extremes are largely unknown. As part of the OPTAIN initiative (OPTimal strategies to retAIN and re-use water and nutrients in small agricultural catchments across different soil-climatic regions in Europe, www.optain.eu), this project aims to evaluate the soil water dynamics affected by these measures and their extent of influence on the cropping system, looking for possibilities to increase the resilience to drought stress under current and future climatic conditions. The steps include (1)  utilizing information from a long-term lysimeter experiment to setup, calibrate and validate a detailed model of soil water dynamics (SWAP) for a typical Swiss cropping system, (2) specifying soil water retention measures through modifications of input parameters based on a literature review (and additional field measurements), and (3) apply the model to conduct a series of simulation experiments with varying combinations of soil water retention measures and future climate scenarios. Study findings will identify soil water retention measures with the largest potential to mitigate drought stress limitations to agricultural productivity, helping to make future arable production systems in Switzerland less dependent on supplement irrigation.

How to cite: Turek, M. E., Prasuhn, V., and Holzkämper, A.: Agro-hydrological modeling of soil water retention measures to increase crop system resilience to extreme events, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2919, https://doi.org/10.5194/egusphere-egu22-2919, 2022.

Carbon sequestration in agricultural soils is an important strategy to mitigate climate change which gained renewed attention in the EU soil strategy for 2030. Stimulation of soil organic carbon (SOC) sequestration can be achieved via soil management strategies. However, these strategies may stimulate greenhouse gas (GHG) emissions such as nitrous oxide (N₂O) and methane (CH₄) and cause nitrogen (N) losses via leaching. While these trade-offs can offset the intended climate change mitigation via SOC sequestration, synergistic (positive) effects of certain soil management strategies may positively affect the mitigation potential as well. Despite the major importance of these trade-offs and synergies for the selection of sustainable and climate-proof soil management strategies, knowledge on the understanding of these effects remains limited.

In the Framework of Horizon 2020 – European Joint Programme SOIL, the ∑OMMIT-project aims to investigate the trade-offs and synergies for the most relevant soil management strategies applied in European agricultural systems. A dedicated literature study was made by eight agricultural research institutes across Europe, summarizing the results of reviews, meta-analyses, reports and original articles. The most important soil management strategies were identified and grouped into four categories: tillage management, cropping systems, water management, and fertilization and organic matter (OM) inputs (crop residues, cover crop, livestock manure, slurry, compost, biochar, liming). Search criteria including literature and land use type, time-period, and geographic origin resulted in a unique selection of 110 references (31 reviews, 46 meta-analyses, and 33 original papers). Meta-data, extracted knowledge gaps, research recommendations and main conclusions were compiled in a knowledge gap review which allows for better insight in existing trade-offs and synergies and provides guidance to future research.

This review highlights that the increase of both SOC stock change and the microbial biomass C and N, as well as the reduction in N leaching are positively affected by conservation tillage, crop rotation, permanent cropping, more efficient water management as well as using fertilization and OM inputs (e.g., cover crops, organic amendments, biochar, and liming). The effects on the N₂O and CH₄ emission mitigation are dependent on the specific soil management strategy (e.g., water management, fertilization and OM inputs) and require more research to allow to define (uniform) conclusions.

In conclusion, more dedicated research is needed for the soil management strategies that simultaneously examines SOC stocks, GHG emissions, and N leaching losses. Furthermore, we identified a lack of information on the impact of pedoclimatic conditions, specifically on the longer-term, on trade-offs and synergies. A more concerted use and installation of new long-term field experiments in different pedo-climatic European regions, seems essential for a comprehensive understanding of the impact of soil management strategies at the European level. Further, since soil management strategies are often combined and their interaction may affect the trade-offs and synergies, the impact of different soil management practices should be assessed simultaneously. Overall, the review provides a unique framework to aid the (re)design of dedicated field experiments and targeted measurements as well as simulations to improve our understanding of the identified knowledge gaps.

How to cite: Maenhout, P., Di Bene, C., Cayuela, M. L., Govednik, A., Keuper, F., Mavsar, S., Mihelic, R., O'Toole, A., Schwarzmann, A., Suhadolc, M., Syp, A., and Valkama, E.: Trade-offs between soil carbon sequestration and greenhouse gas emissions, and nitrogen leaching losses: addressing knowledge gaps, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4712, https://doi.org/10.5194/egusphere-egu22-4712, 2022.

Land abandonment is outstanding as one of the main causes of soil degradation in Mediterranean mid-mountains. This process is closely linked to the rural exodus that took place in the middle of the last century, that led to the activation of natural revegetation mechanisms and massive shrub encroachment. Consequently, several ecosystem disservices have been identified, such as homogenization of landscape, loss of biological and cultural diversity, decrease in water-human-consume resources, reduction of agropastoral resources and higher wildfire risk. However, the effects on soil environment are multiple and controversial. Thus, a case study in the Leza Valley (La Rioja, Spain) has been selected to analyse the effects of post-land abandonment management through shrub clearing practices in soil quality, carbon dynamics and carbon sequestration, in order to give a second chance to these marginalised areas while fighting against Global Change.

For the soil sampling, 5 land uses have been selected: control pasture, 3 shrub clearing sites of different ages; and shrubland after cropland abandonment (6 replicates at different depths, 0-40 cm, have been collected at each study site). Physico-chemical and biological properties of the soil have been analysed in the laboratory, distinguishing between basic and acid soils. Furthermore, a theoretical map of hypothetical future shrub-cleared areas and its potential to sequester carbon has been created.

Preliminary results showed  significant differences between post-land abandonment practices. Time since intervention has resulted a key factor in carbon dynamic evolution, and an increase in carbon storage and concentration with management has been recorded.

To sum up, management through shrub clearing has demonstrated to be an adequate strategy to offset carbon emissions to the atmosphere in soils of abandoned areas in the Mediterranean mid-mountains, offering socio-economic and ecological benefices while becoming an important tool against Global Change.

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

How to cite: Cortijos-López, M., Sánchez-Navarrete, P., Errea, P., Lasanta, T., and Nadal-Romero, E.: Post-land abandonment management through shrub clearing practices as a tool for enhancing soil quality and carbon storage., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4808, https://doi.org/10.5194/egusphere-egu22-4808, 2022.

Temperate forest ecosystems store significant amounts of organic carbon. Site conditions, species composition, and age of stands largely influenced the amount of stored carbon. International and Hungarian studies have shown that nearly half of the carbon stored in the soil in organic matter forms in forest ecosystems. The main goal was to determine the amount of carbon stored in loess soil. Our preliminary studies have shown that climatic conditions (and the forest composition determined) have a huge effect on the carbon stock of soils. To demonstrate this effect, forest stands on loess bedrock under different climatic conditions were selected for the study. Soil drilling was performed in 40 stands and soil samples were taken by 10 cm layers from 0-110 cm depth. In addition to the soil samples, we also determined the litter mass and composition of the forest stand.
Results showed that the loess soil was leached under the forest stands, so its pH was 5.8 on average (min: 3.9; max.: 8.5). Only deeper levels contained 13% CaCO₃ (min: 1.1%; max.: 37%) in the profiles. The texture of the soils was loam or clayey loam with good water holding capacity; therefore, the soil types were Luvisol and Cambisol soils. The average amount of carbon stored in the soils was 1.04 % (min.: 0.02%; max.: 7.3%)  In the future, we will try to clarify the relationship between soil organic carbon stocks and weather conditions.

Project no. 141603 has been implemented with the support provided by the Ministry of Innovation and Technology of Hungary from the National Research, Development and Innovation Fund, financed under the MEC_R_21 funding scheme.

How to cite: Bidló, A., Végh, P., and Horváth, A.: A large-scale study of the carbon stock of Hungarian forest soils, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7762, https://doi.org/10.5194/egusphere-egu22-7762, 2022.

How to cite: Mehmandoost Kotlar, A., Everaer, B., Blanchy, G., Huits, D., and Garré, S.: The potential of adaptive drainage to control salinization in Polder context, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8643, https://doi.org/10.5194/egusphere-egu22-8643, 2022.

Leveraging soil carbon sequestration in croplands can support climate change mitigation; however, it is challenging to develop optimal management practices to maximize both sequestered carbon and crop yield. In intelligent agricultural management systems, large-scale crop models can provide an understanding of the complex soil-water-plant-atmosphere interactions and allow the evaluation of the effects of various management practices on carbon sequestration. This study aims to investigate soil carbon dynamics in maize cropland under different management practices, and discuss their potential to leverage the carbon sink capacity of agricultural soils. The Agricultural Production Systems sIMulator (APSIM) is used to investigate soil carbon dynamics in maize cropland of Baixo Mondego, an agricultural region in central mainland Portugal, under Mediterranean climate. The model was set up using soil properties retrieved from the INFOSOIL national database and run with daily climate data from 2001 to 2020 provided by local weather stations (i.e., solar radiation, maximum and minimum temperature, and rainfall). The maize yields’ records from an agricultural farm were used for model calibration (2017 - 2019) and validation (2020 - 2021). The model was then used to investigate the impact of different scenarios focusing on distinct fertilization management practices (i.e. fertilization rates, timing, and type of fertilizer) on soil carbon and crop yields. This study is part of a larger research project funded by C3.AI Digital Transformation Institute to develop an intelligent agricultural management system using deep reinforcement learning (RL) for agriculture sustainability and climate change mitigation. This project has great potential for impact on climate change and food security, two of the most significant challenges currently facing humanity.

How to cite: S.S. Ferreira, C., Kalantari, Z., Martin, N., Marcillo, G., Zhao, P., Wu, J., and Hovakimyan, N.: Agricultural Management and Soil Carbon Sequestration: the potential of APSIM model to support climate change mitigation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8874, https://doi.org/10.5194/egusphere-egu22-8874, 2022.

Over‑reliance and indiscriminate use of mineral fertilisers have contributed towards declining soil health. Further, mineral fertiliser production contributes close to 1% of UK’s greenhouse gas emissions. Organo-mineral fertilisers (OMFs) are currently being investigated as a more environmentally sustainable alternative to conventional mineral fertilisers as they reduce the amount of mineral fertilisers needed by combining them with organic materials that would otherwise be destined for landfill or incineration, promoting a circular economy by returning recycled nutrients to the soil. Here, we evaluated the efficacy of a novel OMF that incorporates carbon captured from gaseous point sources into their production. This product demonstrates a potential tool for combating both climate change and soil fertility by promoting soil carbon sequestration. To assess the efficacy of these new fertilisers we conducted a field experiment consisting of three batches of OMF (5, 10 and 15%N) and compared them to a conventional mineral fertiliser and an unfertilised control in two soil types with two crops (winter barley and winter wheat).

We found that all fertilisers produced significantly more yield than the control (p < 0.05) but that there was no significant or consistent difference between the fertilisers. There was no significant or consistent differences between the stimulated root growth for any treatments (p = 0.60) and the same for organic matter, microbial biomass, pH, available nutrients (N, P, K), total nutrients (N, C, P), and metals. This leads to the conclusion that organo-mineral fertilisers can perform at least as well as conventional fertiliser. Though more seasons are needed to evaluate the benefits to the soil.

How to cite: Burak, E. and Sakrabani, R.: Evaluating the efficacy of novel green fertilisers derived from combining carbon capture technology and organic waste materials , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9258, https://doi.org/10.5194/egusphere-egu22-9258, 2022.

The Don River Delta is a unique natural structure that performs an important ecological function as a spawning ground for endangered fish species. Shipping is a source of carcinogens of the group of polycyclic aromatic hydrocarbons (PAHs), including benzo(a)pyrene (BaP) - substances of the 1st hazard class. The maximum permissible concentration (MPC) of BaP in the soil is 20 μg / kg. The accumulation of PAHs in the floodplain soils of the delta is especially dangerous since the active washout of pollutants with the soil mass during the flood period (spring) coincides with fish spawning.

The object of the study was saturated alluvial meadow soils. Soil properties vary within the following ranges: pH - 7.3-7.5, organic carbon content - 1.2-2.0%, physical clay - 14.9-19.4%, silt - 4.9-8.9 %. Sampling was carried out to a depth of 0-20 cm. PAHs were extracted from the soil with hexane. Quantitative analysis of PAHs in the extract was carried out using an Agilent 1260 chromatograph. In this work, the content of 16 PAHs included in the list of priority pollutants of the US EPA was determined: naphthalene, anthracene, acenaphthene, acenaphthylene, phenanthrene, fluorene, fluoranthene, pyrene, chrysene, benzo(a)anthracene, BaP, benzo(b)- and benzo(k)fluoranthene, dibenzo(ah)anthracene, benzo(g,h,i)perylene, indeno(1,2,3-cd)pyrene.

This study presents the main patterns of PAHs accumulation in the floodplain soils of the Don River delta used by the shipping channel. The purpose of the study was to establish the influence of the technogenic factor on the accumulation of PAHs in the floodplain soils of the Don River delta. As a result of the study, it was found that, according to the content of PAHs, the soils form the following row: No. 1 - 400 μg / kg> No. 2 - 1729 μg / kg> No. 3 - 9376 μg / kg. A similar series is observed for the amount of BaP in the soil: No. 1 - 22 μg / kg> No. 2 - 201 μg / kg> No. 3 - 2013 μg / kg, which corresponds to an excess of MPC by 1.1, 18 and 100 times.

Thus, the PAHs content in soils increases downstream of the shipping channel. The maximum technogenic load falls on the soil of the monitoring site No. 3, located in the mixing zone of the waters of the Taganrog Bay and the delta of the Don.

The research was financially supported by the Ministry of Science and Higher Education of the Russian Federation project on the development of the Young Scientist Laboratory (no. LabNOTs-21-01AB).

How to cite: Dudnikova, T., Barbashev, A., Sushkova, S., Antonenko, E., Deryabkina, I., Shuvaev, E., Bakoeva, G., Elgendy, H., Johar, J., Bren, D., Yakovlenko, A., and Maltseva, T.: The technogenic factor of PAH accumulation in floodplain soils of the Don River Delta, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9822, https://doi.org/10.5194/egusphere-egu22-9822, 2022.

According to the projections of the Intergovernmental Panel on Climate Change (IPCC) the impact of global warming would be detrimental for ensuring food security in the 21^st century. High temperature stress in different agro-climatic zones uniformly decreases crop yield, primarily due to shortened life cycle and hastened senescence leading to considerable pre- and post-harvest losses. The only available solution for tacking this challenge includes breeding thermal stress tolerant cultivars with equivalent crop yield potential. Though this strategy has many handicaps, the foremost being huge time investments for generating stable cultivars. Hence, exploring all the possible alternatives is a high priority to ensure sustainable crop production. These results demonstrate the role of seed biopriming with a thermotolerant strain of Trichoderma sp. capable of surviving at 47⁰C for the mitigation of thermal stress effects in tomato. Based on these results it was concluded that Trichoderma mediated reprogramming of oxidative stress markers and defense network to enhance thermal tolerance in tomato. The results of the aforementioned biochemical analysis were cross validated through histochemical and HPLC analysis. In addition, the complex route of plant-microbe interaction under both ambient and stressed conditions were also mapped using 2D gel electrophoresis and hydroponics approach. During this presentation, the fascinating journey beginning from the isolation, characterization, and identification of this thermotolerant strain of Trichoderma sp. to its formulation development will be discussed in detail.  

Acknowledgements: The research was financially supported by the Ministry of Science and Higher Education of the Russian Federation project on the development of the Young Scientist Laboratory (no. LabNOTs-21-01AB).

How to cite: Elgendy, H., Krepakova, M., Keswani, C., Voloshina, M., Nefedova, A., Minkina, T., Mandzhieva, S., and Sushkova, S.: Seed Biopriming with Trichoderma sp. as an Effective Strategy for the Mitigation of Thermal Stress Effects in Food Crops, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9850, https://doi.org/10.5194/egusphere-egu22-9850, 2022.

Water regime determines the soil organic matter (SOM) content and dynamics and heavy metals (HM) availability for plants. Uncertainty natural hydrological regime is a consequence of combination of a phase of water supplying to the soil and a phase of water spreading into the soil, which causes biosphere diversity. Current gravitational frontal continually-isotropic irrigation paradigm stipulates huge consumption of the world freshwater reserves. Around 95% of this water uncontrollably spreads in landscape in result of natural hydrological regime simulation. This paradigm causes unsustainable soil organic matter regime and heavy metals uncontrolled penetration of HM into plant roots and then into trophic chains.

Improved biogeochemical cycle, including SOM and HM regime, is possible in the framework of Biogeosystem Technique (BGT*) transcendental methodology. An origin of the developed BGT* soil watering paradigm is an intra-soil pulse continuous-discrete water supply into the soil continuum, fulfilled sequentially. Discrete volume of water is supplied via syringe to the vertical cylinder of soil preliminary watering at a depth of 10 to 30 cm, diameter is of 1–2 cm. Within 5–10 min after injection, the water spreads from this cylinder of preliminary watering into surrounding soil via capillary, film and vapor transfer. Some amount of water is partially transferred gravitationally to a depth of 35–40 cm. The resulting soil watering cylinder is at a depth of 5–50 cm, its diameter is of 3–4 cm. Lateral distance between next injections along the plant raw is about 10–15 cm. The non-watered soil carcass surrounding the wetted cylinder remains relatively dry and mechanically stable. After injection, the structure of soil in the wetted cylinder restores quickly without compression from the stable adjoining volume of soil, and the soil structure memory remain functional. The mean matric potential of the soil solution is 0.2 MPa. At this potential, a leaf stomatal apparatus operates in regulation mode. Relatively high concentration of soil solution provides an increased rate of plant supply with nutrients. Transpiration rate reduced compared to the natural water regime or standard irrigation. Evaporation from soil surface is small as well. Soil solution seepage to vadose zone is excluded. Fresh water saving is up to 20 times.

BGT* soil watering paradigm reduces rate of intra-soil mass transfer, and uncontrolled lateral water redistribution to landscape. In its turn, this reduces SOM leaching from soil and improves conditions for the SOM priority synthesis, providing humic substances function, soil structuring, intra-soil reversible C sequestration, improved plant supply with fresh nutrients, better plant organogenesis, and soil biological productivity. Intra-soil application of plant protection preparation is possible.

Rather low matric potential insures higher ionic strength of soil solution. Corresponding manifestations of ion association and carbonate calcium equilibrium in soil solution provide association of HM with macro-ions PbCO₃⁰, (PbCO₃)₂⁰, PbHCO₃⁺, PbSO₄⁰ PbCl⁺, PbOH⁺, Pb(OH)₂⁰, CdCO₃⁰, CdHCO₃^‒, CdSO₄ CdSO₄⁰, CdCl⁺, CdOH⁺ and other, and consequent irreversible passivation of HM via complexation in soil mineral-organic system.

The research was supported by the Strategic Academic Leadership Program of the Southern Federal University ("Priority 2030").

How to cite: Bakoeva, G., Kalinitchenko, V., Glinushkin, A., Kislov, A., Minkina, T., Sushkova, S., Mandzhieva, S., Budynkov, N., Mukovoz, P., Larin, G., Rykhlik, A., Fedorenko, E., and Grishina, E.: Biogeosystem Technique transcendental intra-soil pulse continuous-discrete watering paradigm for soil organic matter sustainable regime and heavy metal passivation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9941, https://doi.org/10.5194/egusphere-egu22-9941, 2022.

The air pollution with fine particulate matter (PM) of dimension 2.5 µm or less (PM_2.5) causes lung and other diseases. The problem of prevention of water and terrestrial systems pollution with PM dry deposits is multifaceted. The ionized O₂ is capable to intensify the atmosphere turbulence, PM_2.5 сoalescence, and increasing the PM dry deposition velocity. Unfortunately, outdated environmental technologies are incapable to secure this. The quality of air is linked to the pedosphere and plant kingdom. Addressing the problem of environmental quality, including the PM_2.5 content reduction in the atmosphere, the Biogeosystem Technique (BGT*) transcendental (nonstandard and not a direct imitation of Nature) methodology has been developed. The BGT* focus is an enrichment of the Earth's biogeochemical cycle. The heuristic approach to land use and air cleaning is a new niche for development to improve the soil system and ensure a high rate of air cleaning. BGT* ingredients are the intra-soil processing, which provides the soil multilevel architecture; intra-soil pulse continuously discrete watering for optimal soil water regime and freshwater saving up to 10-20 times; intra-soil dispersed environmentally safe recycling of the PM sediments and other pollutants; controlled microbial community and biofilm-mediated interactions in the soil. BGT* enriches the biogeochemical cycle, provides a better function of the humic substances, biological preparation and microbial biofilms as a soil-biological starter, priority plant and trees nutrition. BGT* methodology is capable to increase plant resistance to phytopathogens. BGT* provides the formation of higher underground and aboveground biological products, thus increasing reversible C biological sequestration from the atmosphere in the form of additional aboveground biomass and soil organic matter. BGT* provides a higher rate photosynthetic production of light O₂ ions, a coalescence of PM_2.5, PM_0.1 to the PM₁₀ and larger particles, sedimentation of the PM, and a soil transformation of PM sediments into the nutrients. BGT* allows sustainability of the biosphere, enables a high quality of the atmosphere, stabilizes the climate system of the Earth, and is capable to promote a green circular economy.

The research was supported by the Strategic Academic Leadership Program of the Southern Federal University ("Priority 2030").

How to cite: Fedorenko, E., Glinushkin, A., Kalinitchenko, V., Swidsinski, A., Meshalkin, V., Gudkov, S., Minkina, T., Chernenko, V., Rajput, V., Mandzhieva, S., Sushkova, S., Kashcheev, A., and Aysuvakova, T. P.: New approach to soil health management and air quality: One Earth One Life, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9961, https://doi.org/10.5194/egusphere-egu22-9961, 2022.

As previously foreseen, it seems like climate change effects have begun to take their toll on the environment globally, but especially in the Eastern Mediterranean-Middle East (EMME) region where a hot climate already prevails. Some of these effects include higher temperatures during summer season, greater heat stress, longer summers, lower soil moisture, greater water scarcity, more intense rainstorms, longer duration between rainstorms, reduced air quality due to greater pollution and more. Rainfall temperature is also a variable that potentially will be affected by changes in climate regime.

These alterations in climate regime might play an even greater role in soil erosion which has already become a concern on a global scale due to its impairing effects on human activity. Although, soil erosion variables have been studied extensively on various levels, very little has been researched on the effects of rainfall temperature on the soil. A few years ago, comparative research with a laboratory rainfall simulator was conducted on two soils, a clayey soil and loamy soil from Israel, in dry and wet conditions, under different rainfall temperature regimes. The researchers concluded that rainfall temperature has an impressionable effect on runoff and soil erosion that must not be ignored, and which is more pronounced in the clayey soil. Recently, and in accordance with these findings, follow-up research was conducted on two pre-wetted clayey soils, 43% and 64% clay content, respectively. The Terra Rosa soils were chosen from different locations in Israel and are similar to each other in salt concentration, organic matter content and land use (plots between olive trees in an olive grove), yet are different from one another in clay content, and possibly in clay-mineral type as well. The soils were pre-wetted and allowed to drain to field capacity state, and then were exposed to 21 mm/hr rainfall events at 3 different temperatures: 2, 20 and 35 degrees Celsius, respectively. Runoff and soil samples were collected throughout the experiments. Temperature was monitored at water tank, nozzle, soil surface and soil subsurface with thermocouples and a thermal camera. Each experiment was repeated 4 times on 2 different soils with 3 different temperatures, rendering a total of 24 experiments.

In this presentation, I will demonstrate our theory for the potential of rainfall temperature as an important variable on soil erosion and will present our initial findings based on our recent experiments.

How to cite: Shkedi, D., Sachs, E., and Pariente, S.: Effect of rainfall temperature on the erosion of clayey soils different in clay amount: experiments with a laboratory rainfall simulator, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10427, https://doi.org/10.5194/egusphere-egu22-10427, 2022.

Lately, there has been a lot of discussion on soil terminology, perhaps because policymakers have recognized the need to use soil as an ally tackling future climate demands, but mostly because this recognition will likely be translated from the EU Soil Strategy into a new soil health law for the EU. Such an initiative for soil is tightly connected to the EU Biodiversity Strategy for 2030, the Climate Adaptation Strategy, the UN 15.3 Goal for Land Degradation Neutrality, and other environmentally-related policy initiatives (Figure 1) stemming from the European Green Deal and from the UN Sustainable Development Goals.

Figure 1. Links between EU Soil Strategy and other EU initiatives. Source: European Commission, 2021.

At the end of 2021 the European Commission launched the EU soil strategy for 2030, giving the first step towards a consolidated understanding of what a healthy soil means, “(…) when they are in good chemical, biological and physical condition, and thus able to continuously provide as many of the following ecosystem services as possible (…)”. This definition is therefore expected to be translated into a collection and combination of various soil parameters and associated dynamic thresholds (in time and space). Allowing thus the determination of the spatial extent of healthy - and unhealthy - soils, being likely used to assess the EU progress towards the objectives set.

On top of the importance of such initiatives for our future, this is also a great opportunity for researchers and policymakers to understand i) where we stand in terms of major soil threats, ii) what the major current knowledge gaps for EU soils are, iii) and which are the areas at higher risk for land degradation that then require further restoration actions. The problem seems complex from a diversified European perspective, due to the policy landscape, [the lack of] harmonized data availability, as well as local and regional differences. Nevertheless, the EU needs to start building on the current environmental acquis.

The aim of this work is to present the current status of the EU soils making extensive use of the latest LUCAS soil monitoring campaigns and to identify and discuss with the scientific community the identification of key-thresholds for identified parameters, which will likely determine future land and soil management actions towards a healthy soil.

How to cite: Vieira, D., Muntwyler, A., Marechal, A., Orgiazzi, A., Jones, A., Schillaci, C., Ciupagea, C., Belitrandi, D., de Medici, D., de Rosa, D., Matthews, F., Martin Jimenez, J., Koeninger, J., Liakos, L., Montanarella, L., Labouyrie, M., Van Liedekerke, M., Panagos, P., Wojda, P., and Scarpa, S.: Healthy soils, a fresh start., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11432, https://doi.org/10.5194/egusphere-egu22-11432, 2022.

Soils are by definition important carbon sinks, in particular for non-tropical types of climates, an important part of carbon in ecosystems are located on them. Under climate change, those carbon sinks are placed under stress due to often-subtle changes that modify the conditions for their function and rend them particularly vulnerable to dereliction, reducing the capacity to act as carbon sinks at the long term.

In agricultural soils, the intensification of cropping systems and the reduced addition of organic matter results in a sharp reduction of soils’ organic content, with important impacts on soil functioning, namely in what concerns water and nutrient cycles, which will reduce soil fertility and carbon content on the long run. This will transfer slowly but steadily soil’s organic carbon to the atmosphere, reinforcing climate change.

Forest soils suffer an even more catastrophic impact from climate change, since the regions more vulnerable have a higher frequency and intensity of the big eraser, when the forest systems fail to be in equilibrium with the climate: forest files. They are responsible altogether by the emissions of various compounds to the atmosphere, comparable to the anthropic emissions in a bad forest fire year. The soils derelict by fire lose an important part of environmental services they provide, namely suffer a significant reduction of their capacity to sink carbon. This adds to the instantaneous loss of carbon to the atmosphere during the fire and downstream to aquatic ecosystems thereafter.

We explore methodologies to reduce those losses in wet Mediterranean areas, aiming to increase the carbon sinks to reduce the atmospheric concentrations.

How to cite: Ferreira, A.: Soil and climate interactions in the Mediterranean. Are we heading for disaster?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13285, https://doi.org/10.5194/egusphere-egu22-13285, 2022.

Soil carbon sequestration in croplands has tremendous potential to help mitigate climate change; however, it is challenging to develop the optimal management practices for maximization of the sequestered carbon as well as the crop yield. We aim to develop an intelligent agricultural management system using deep reinforcement learning (RL) and large-scale soil and crop simulations. To achieve this, we build a simulator to model and simulate the complex soil-water-plant-atmosphere interaction, which will run on high-performance computing platforms. Massive simulations using such platforms allow the evaluation of the effects of various management practices under different weather and soil conditions in a timely and cost effective manner. By formulating the management decision as an RL problem, we can leverage the state-of-the-art algorithms to train management policies through extensive interactions with the simulated environment. The trained policies are expected to maximize the stored organic carbon while maximizing the crop yield in the presence of uncertain weather conditions. The whole system is tested using data of soil and crops in both mid-west of the United States and the central region of Portugal. Our study has great potential for impact on climate change and food security, two of the most significant challenges currently facing humanity.

How to cite: Kalantari, Z.: Optimization of Agricultural Management for Soil Carbon Sequestration UsingDeep Reinforcement Learning and Large-Scale Simulations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13307, https://doi.org/10.5194/egusphere-egu22-13307, 2022.

Flooding affects >300 million people each year and causes loss of life, damage to infrastructure, and long-term mental and physical health problems. Across many parts of the globe, climate change is projected to increase the magnitude, frequency, and intensity of rainfall events, thus exacerbating future flood risk and increasing the demand for flood alleviation schemes. Agricultural land covers 39% of Europe, and as such intercepts a significant fraction of precipitation. Agricultural intensification has increased soil compaction and decreased soil porosity and permeability, thus decreasing infiltration, storage and groundwater recharge. Here, we report on experiments that aim to constrain the effects of using cover crops to increase soil porosity and permeability and hence decrease runoff during rainfall events in three arable fields in East Yorkshire, UK.

Half of each field was treated with a cover crop between harvest and winter cultivation, and the organic matter of this crop was incorporated into the soil. The second half of each field was used as a control. A suite of methodologies is being used to assess the long-term influence of this extra organic matter content on soil structure, health and permeability:

• An array of soil moisture loggers (Delta-T PR2/4, DalesLandNet MKII, GroPoint Profile 2625-N-T-4) was deployed in each field to provide long term soil moisture data at high temporal resolution;
• Roaming soil moisture measurements (Campbell Scientific HydroSense II) were used to increase spatial coverage and resolution;
• Laboratory measurements of soil density, ambient soil moisture content, porosity, permeability, and nutrient content (nitrogen, phosphorous and potassium); and
• A 3D MODFLOW model parameterised with collected data was used to assess the long term impact of increased soil porosity and permeability on rainfall transmission in to surface water drainage systems.

Preliminary results suggest that enhanced organic matter – delivered through cover crops – increases soil nutrient and moisture retention and decreases the peak flow stage in adjacent drainage channels after intense rainfall events. These observations suggest soil restoration may provide an important mechanism for attenuating flood peaks under future climate scenarios.

How to cite: Thomas, R., Ahmed, J., and Johnson, J.: Cover crops as a method of enhancing soil moisture and nutrient retention on arable farmland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13528, https://doi.org/10.5194/egusphere-egu22-13528, 2022.

Taiwan has unique geographical characteristics. Located in a subtropical monsoon region, it is plagued annually by exceptional meiyu (East Asian rainy season) in May and June, and numerous typhoons from July to October. This unique climate often brings torrential rains and combined with Taiwan’s steep topography and short rivers, frequently triggers severe floods. Moreover, Taiwan lies at the intersection between the Eurasian Plate and the Philippine Sea Plate and is among the areas with the world’s most frequent felt earthquakes. Natural hazards here can roughly be categorized into four types: earthquake, typhoon, flood, and hillside disasters; manmade disasters include: industrial disasters, residential/commercial fire, road traffic accident, and shipwreck. When disasters strike, they often cause grave impacts and tolls in human lives and properties. In recent years, there has been a rising trend in both their frequency and scale due to rapid urbanization and growing environmental vulnerability.
According to World Bank’s 2005 publication, Natural Disaster Hotspots - A Global Risk Analysis, Taiwan tops the world in the land area simultaneously exposed to three or more natural hazards (73%) and in the population under disasters’ threat (73%). Additionally, there has been an increase in potential hazards such as disease outbreaks and severe public safety accidents. Therefore, when large-scale disasters strike and the impact is beyond what the affected municipalities can or have resources to handle, the key to minimizing death and injuries as well as financial losses becomes how nearby municipalities can offer support, participate rapidly in the emergency response, integrate resources effectively, enhance response effectiveness and prevent the disaster’s spread.
The “Operational Compact for Emergency Management Mutual Aid between Municipality and County Governments” passed in 2005 has now been in effect for four years. Yet, a comprehensive review of recent years’ severe disaster experiences indicates that the chief rescue and relief responsibilities still fall on the central government; the rare implementation of the above Compact by local authorities exposes the inadequacy of the actual system. Thus, this paper examines the literature on relevant ordinances, operating models, and case studies in the American and Japanese regional mutual aid systems to emergency management, in order to offer suggestions for improvement towards a more complete regional mutual aid system, a significant upgrade on municipalities’ disaster response capabilities and effective functional integration and collaboration.

How to cite: Li, Y.-T., Fu, G.-L., and Tsai, C. H.: Study on Establishing the System of Enterprises’ Participation in Flood Disaster Prevention, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-729, https://doi.org/10.5194/egusphere-egu22-729, 2022.

In this study, zone of Gundogdu (Rize) located in the Eastern Black Sea Region were examined in terms of landslide susceptibility and its stability analyzes were conducted. The study area is the region with the highest rainfall in Turkey. Heavy rainfall plays a major role in triggering landslides in this region. In this study, the relationship between precipitation and landslide was investigated. In addition, the effect of precipitation on weathering also determined the geological characteristics of the area. First of all, 1/25.000 scale geological map of Gundogdu and its surrounding was provided, the units are listed as Melyat Formation (Middle Eocene) and alluvium (Quaternary) from older to younger. 1/500 scale cross sections were generated for nineteen different landslides happened at Gundogdu in 2010, 2015, 2018, and 2021 years. Then stability analyzes were done with these data. Angle of internal friction (φ), cohesion (c), saturated unit weight, natural unit weight, dry unit weight and submerged unit weight (ϒ_d, ϒ_n, ϒ_k, ϒ'), specific gravity (Gs), porosity (n), saturation degree (SR), void ratio (e) and grain size distribution were determined with laboratory tests of soil samples which were taken to determine the engineering properties of soils located in places which stability calculations would be held. Following the results of these experiments, stability analyzes were done with 4 different methods (The Zero angle of Shearing Resistance Method, Ordinary Method of Slice, Bishop Method of Slices, and Janbu Method) according to the possible sliding surfaces that were plotted from geological section of landslide. As a result of these data, this region poses a great danger specially after rainfall with the effect of weathering. For this purpose, needs to be done for the prevention of landslides have been introduced.

How to cite: Yalcin, A.: Gundogdu (Ri̇ze) landslides and its surrounding slope susceptibility, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-938, https://doi.org/10.5194/egusphere-egu22-938, 2022.

 Soil erosion seriously damages land resources, which is a global environmental problem. Gully erosion is an important manifestation of soil erosion, in recent years, frequent extreme rainstorms have aggravated the occurrence and development of gully erosion. In order to study the formation and development patterns of newly formed gullies under the condition of climate change, this paper takes the Wangwugou Small Watershed of the Chabagou Watershed on the Loess Plateau in Northern Shaanxi as the research area, and takes the “7·26” extreme rainstorm in Northern Shaanxi Province in 2017 as the main research object based on UAV images, to analyze the occurrence regularity of newly formed gullies, and discuss its development characteristics, its difference with the development of existing gullies before 2017, and its relationship with topographic parameters in the following three years. The results showed that: (1) during the “7·26” extreme rainstorm in Northern Shaanxi, there were 45 newly formed gullies in the Wangwugou Small Watershed, which are about 101 gully/km2, and they could be divided into four categories: slope surface gullies, terraced field gullies, unpaved roadway gullies and bottom gullies. The slope surface gullies were the largest, and the bottom gullies and terraced field gullies were wider and larger in area. Production roads, check dam farmland and sloping farmland are most prone to the occurring of gullies under rainstorm conditions. (2) In the three years after the formation of the new gullies, the development of the new gully heads was faster than that of the original existing gullies, and 34.48% of the heads of newly formed gully was further advanced, which was 1.32 times of the original existing gullies. The average gully head retreat distance of newly formed gullies is 3 times that of the original existing gullies, which is up to 0.58 m/a, and the maximum speed could reach 2.12 m/a. (3) The increase of the drainage area could significantly promote the development of gully heads, which is an important topographic index to simulate the retreat rate of gully heads. Under extreme rainfall conditions, the soil erosion situation is highly serious in the study area, and the source of newly formed gullies could be traced more rapidly within three years after their occurrence. Therefore, special attention and enhanced management should be attached to the prevention and control of such gullies.

How to cite: Yang, L., Wang, C., Zhang, C., Pang, G., Long, Y., Wang, L., Liu, B., and Yang, Q.: Study on the Occurrence and Development of Gullies under extreme Rainstorm Conditions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1241, https://doi.org/10.5194/egusphere-egu22-1241, 2022.

Multivariate logistic regression models are the most popular in estimating landslide susceptibility by assessing various landslide causes—covariates—in mapped landslides or hindcasting landslides by including landslide triggering information such as rainfall. Although the sensitivity of these models to the variety of input data is frequently tested, the influence of data quality on the model accuracy is rarely discussed. For example, accurately representing spatial rainfall variability that triggered landslides may be essential in hindcasting models. Additionally, the properties of the mapped landslides, such as sample size, location, or time, are crucial to set a robust susceptibility model. Using an inventory that predominantly covers larger landslides would hinder a model by broadly covering the diversity of the factors leading to slope instability. Whereas smaller landslides could fail to capture sufficiently the range of values in the covariate space, likely decreasing the model performance. Another aspect is whether the number of mapped landslides is enough to estimate the susceptibility accurately or does more data means a better model. We developed several simple logistic regression models to answer all the above-listed questions relevant to assessing the model sensitivity. The model first demonstrated that global grid rainfall products could not accurately represent spatial rainfall distribution, which has a major influence on a landslide hindcast model. We have further found out that using only part of the individual landslides surprisingly may suffice to make accurate susceptibility estimates. Using smaller landslides in a susceptibility model outperforms a model that relies on larger landslides. Lastly, the model performance marginally varied after progressively adding more landslide data in a pilot study.

How to cite: Ozturk, U.: Role of baseline landslide inventory and grid rainfall precision on the sensitivity of susceptibility or hindcast models, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1284, https://doi.org/10.5194/egusphere-egu22-1284, 2022.

Due to the impact of climate change, the increasing frequency of extreme rainfall events, with concentrated rainfalls, commonly cause landslide hazard in the mountain areas of Taiwan. Although the extraordinary rainfall behavior is critical for the geohazard, it is significantly affected by the factors such as topography, the route of typhoon, etc. Therefore, there are uncertainties for the predicted rainfall as well as the landslide susceptibilities.

This study employs rainfall frequency analysis together with the atmospheric general circulation model (AGCM) downscaling estimation to understand the temporal rainfall trends, distributions, and intensities in the adopted study area in Central Taiwan. The uncertainties within the rainfall prediction was investigated before applied to the landslide susceptibility analysis. The catchments in Taiwan, including Tachia River, Wu River, and Chuoshui River, were adopted as the study area. To assess the hazard of the landslides, logistic regression methods and supporting vector machines method were applied, in which the control factors were analyzed and discussed. The results of predictive analysis with the consideration of uncertainties can be applied for risk prevention and management in the study area.

How to cite: Shou, K.-J.: Impact of Climate Change on Landslide Susceptibility – for the Case in Taiwan, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2299, https://doi.org/10.5194/egusphere-egu22-2299, 2022.

Frequent and extreme meteorological events can lead to an increase in landslide hazard. A multi-temporal inventory plays an essential role in monitoring slope processes over time and forecasting future evolution. In recent years, the province of Belluno (Veneto Region, NE Italy) was affected by two relevant and intense meteorological phenomena that occurred on October 27-30, 2018 (i.e. windstorm Vaia) and on December 4-6, 2020. Both events were characterized by heavy rainfall of up to 600 mm in 72 hours, triggering widespread landslides throughout the area. The analyses conducted on some local rain gauges in the sectors most affected by each storm show very high return periods (over 100 years) for both events, even though they occurred in a two-year time frame. This study aims to evaluate whether these strong meteorological phenomena are characterized by an increase in their frequency in the province of Belluno and to see what influence they have on slope instabilities, which are important for assessing landslide risk. The rainfall data available since 1950 have been investigated through statistical analysis to achieve these goals. The spatial and temporal evolution of slope instabilities has been examined through remote sensing techniques to compare landslides triggered in 2018 and 2020 with past instability phenomena in the same area. The results show the importance of multi-temporal databases for landslide hazard assessment after extreme meteorological events at the regional scale.

How to cite: Puliero, S., Meena, S. R., Catani, F., and Floris, M.: Impact of multi-temporal landslide inventories on landslide hazard assessment: a case study in the province of Belluno (Veneto Region, NE Italy), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2507, https://doi.org/10.5194/egusphere-egu22-2507, 2022.

In this study we assess the influence of changes in the relevant meteorological conditions on the probability for rockfall in German low mountain regions. The study is based on data from a rockfall data base for Germany (Rupp and Damm, 2020) and a data set supplied by the Deutsche Bahn (German railway company) covering the periods 1838-2018 and 2015-2020, respectively. 

In a first approach, a logistic regression model for the probability of rockfall at a given location developed by Nissen et al. 2021 was applied to gridded meteorological station observations (RADOLAN and EOBS) ranging from the year 1950 to 2019. The logistic regression model quantifies the influence of daily precipitation, a proxy for pore water and freeze-thaw cycles on rockfall probability. A probability forecast was made for each day and location. The day-to-day variability in rockfall probability at the individual sites is high. Thus, the sign of the trends is site specific, but the majority of sites is showing a negative trend over the 70-year period investigated. The significance of the trends at most sites is below the 95% level. Sites at which the trend is statistically significant almost all show a negative trend, down to -4% per decade in terms of the annual number of days with a higher than climatological hazard. The mean probability decreased by as much as -2.3% per decade. 

The second approach is based on large-scale weather patterns. An analysis identified 3 weather pattern that occur on average at 9% of all days but include  19% of the days on which a rockfall event occurred. The trend in the number of these patterns was determined for the last 40 years. It suggests a decrease by -2.2% per decade and is not statistically significant. 

How to cite: Nissen, K. M., Ulbrich, U., and Damm, B.: A decrease in rockfall probability associated with changing meteorological conditions in Germany, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2681, https://doi.org/10.5194/egusphere-egu22-2681, 2022.

It is expected that landslide events will occur more frequently, throughout the century, as a direct consequence of climate change. The main triggering factor, over Portugal mainland, is extreme precipitation. Thus, the aim of this study relied on the assessment of the projected future changes in the extreme precipitation over Portugal mainland and quantifying the correlation between extreme rainfall events and landslide events through Rainfall Triggering Thresholds (RTT). This methodology was applied for two specific locations within two Portuguese areas of great geomorphological interest.

To evaluate the possible projected changes in the extreme precipitation, we used the Iberia02 dataset and the EURO-CORDEX models’ runs at a 0.11º spatial resolution. First, it was analyzed the models’ performance to simulate extreme values in the precipitation series. The simulated precipitation relied on RCM-GCM models’ runs, from EURO-CORDEX, and a Multimodel ensemble mean. The extreme precipitation assessment relied on the values associated to the highest percentiles, and to the values associated to the RTTs’ percentiles. To evaluate the possible future changes of the precipitation series, both at the most representative percentiles and RTTs’ percentiles, a comparison was made between the simulated values from EURO-CORDEX historical runs (1971-2000) and the simulated values from EURO-CORDEX future runs (2071-2100), considering two emission scenarios: RCP 4.5 and RCP 8.5. In the models’ performance, the Multimodel ensemble mean appeared to be within the best representing models. As for the projected changes in the extreme precipitation for the end of the century, when following the RCP 4.5 scenario, most models projected an increase in the extreme values, whereas, when following the RCP 8.5 scenario, most models projected a decrease in the extreme values.  

Acknowledgements

This work was financed by national funds through FCT–Portuguese Foundation for Science and Technology, I.P., under the framework of the project BeSafeSlide (PTDC/GES-AMB/30052/2017)

How to cite: Araújo, J., Ramos, A. M., Soares, P. M. M., Melo, R., Oliveira, S. C., and Trigo, R. M.: Landslide events in Portugal under future climate change scenarios, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4314, https://doi.org/10.5194/egusphere-egu22-4314, 2022.

Fast disasters happen slowly. Two of the most notorious “rapid-onset” disasters – earthquakes and landslides – have a common dependency on a single determining parameter known as the Gruntfest number. Deep-seated landslides, seemingly rapid-onset to the naked eye, have historically been monitored with in-situ monitors and borehole sampling to understand conditions within the shear band. These in-situ monitoring techniques, however, are high-cost and labor-intensive. As satellite data and resources expand, remote sensing has become a more cost-effective and realistic option for monitoring gradual ground deformation caused by the creep of a deep-seated landslide. Differential interferometric synthetic aperture radar (InSAR), specifically, can be used to measure displacements on the Earth’s surface with precision to a few centimeters or less. Here we use InSAR and pre-existing borehole data for the Canillo landslide in Andorra to characterize the evolution of temperature and thereby the Gruntfest number from August 2018-December 2021. Our results reinforce the characteristic models for deep-seated landslides in Segui et. al (2020), suggesting that there exists a critical Gruntfest value where the landslide is catastrophically unstable. Given the anticipated increase in extreme climate with climate change, we expect it to become more frequent for landslides to reach this critical Gruntfest value, therefore necessitating a more robust analysis of the evolution of the Gruntfest number and the overall destabilization process for future work.

How to cite: Lau, R., Segui, C., Handwerger, A., Chaney, N., and Veveakis, M.: Forecasting and mitigating natural hazards with remote and in-situ monitoring, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5098, https://doi.org/10.5194/egusphere-egu22-5098, 2022.

Thermo-rock: influence of temperature on rock slope properties

Rock slope stability is closely linked with the mechanical properties of the rock slope mass. These properties are influenced by numerous factors including meteorological, thermal and hydrogeological. Even short-term temperature cycles caused by direct sunlight, together with water saturation cycles can change mechanical properties of rock slope surficial zone. To partially quantify these influences, we have carried out short-term experiments at a former quarry test site. Geotechnical instrumentation of partial blocks with crack meters, surface and microcracks deformation monitoring using strain gauges, geophysical ERT monitoring, subsurface temperature and humidity monitoring, and  IR camera surface temperature sensing were used during 24-hour monitoring campaigns. Additionally, surface hardness was repeatedly measured using Schmidthammer. Before and after monitoring campaigns, rock mass samples from different depths were collected, to perform basic geomechanical tests. Using these complex data, the influence of short-term temperature changes on the rock slope surficial layer properties were estimated.

How to cite: Racek, O. and Blahůt, J.: Thermo-rock: influence of temperature on rock slope properties, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7282, https://doi.org/10.5194/egusphere-egu22-7282, 2022.

Landslides are a major natural hazard, but uncertainties about their occurrence in a warmer climate are substantial. The relative role of rainfall, soil moisture, and land-use changes and the importance of climate change mitigation are not well understood.  Here, we develop and apply a storyline approach to address these issues, considering a severe event from June 2009 in Austria with some 3000 landslides as showcase. The approach leverages on convection permitting simulations that realistically represent the meteorological event while sampling uncertainties.  Depending on the changes of rainfall and soil moisture, the area affected during a 2009-type event could grow by 45% at 4 K global warming, although a slight reduction is also possible. Such growth could be reduced to less than 10% by limiting global warming according to the Paris agreement. Anticipated land-use changes towards a climate resilient forest would fully compensate for such a limited increase in hazard.

How to cite: Maraun, D., Knevels, R., Mishra, A. N., Truhetz, H., Bevacqua, E., Proske, H., Zappa, G., Brenning, A., Petschko, H., Schaffer, A., Leopold, P., and Puxley, B. L.: A severe landslide event in the Alpine foreland under possible future climate and land-use changes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7465, https://doi.org/10.5194/egusphere-egu22-7465, 2022.

Landslide motion can be affected by the thermal effects resulting from the dissipation in heat of the frictional work generated in shearing bands. This problem was initially addressed for simple landslide geometries which have to be defined a priori. In this context, these analyses assume the motion of a rigid block and the thermal-hydro-mechanical phenomena were solved at basal shearing bands and their vicinity.

Later on, in order to generalize the analysis and to face more complex geometries and features, governing equations were implemented in the material point framework. This numerical method (MPM) is able to model large strains and displacements thanks to the double discretization of the domain by means of a Eulerian computational mesh and Lagrangian material points. A new approach was proposed to deal with the pathological dependence of the frictional work generation and the computational mesh element size. The methodology consists in the definition of computational embedded joints whose thickness is defined as a material parameter. 

The presentation will show the formulation of the thermal pressurization phenomena in MPM. First, the methodology will be evaluated under triaxial conditions and simple landslide geometries using different mesh sizes.

Real cases are later analyzed and modelled in MPM. The first case refers to an incipient landslide induced by a drawdown. The potential risk of acceleration induced by thermal pressurization is analyzed. The non-accelerated behavior observed in the field is explained combining the frictional heating induced weakening with non-linear velocity dependent frictional hardening. The results show that increments of a few degrees of the frictional angle with slide velocity can counteract the heating induced acceleration. 

The second case discussed is a coseismic landslide whose acceleration and large run-out cannot be justified by means of simple strength law unless imposing an extremely and probably unrealistic strain softening.

How to cite: Pinyol, N., Alvarado, M., and Lemus, L.: Thermal pressurization effect on landslide motion. Analysis with material point method., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7549, https://doi.org/10.5194/egusphere-egu22-7549, 2022.

Permafrost is perennially frozen ground occurring in about 24% of the exposed land surface in the northern hemisphere. The soil categorized as permafrost is named cryosol (or gelisol). Cryosol is widely spread in the Arctic, where it is continuous in the polar regions while in the sub-arctic it is discontinuous or sporadic. Iceland is located on the edge of the Arctic, and therefore permafrost can be found in many regions of the island. In addition, the frost effect is great, due to the unique climate and weather conditions and the high sensitivity of the Icelandic soil (volcanic soil – andosol). Although the distribution of permafrost is widespread it is in many respects dependent on the weather. As the climate warms, as it does now, the permafrost retreats rapidly, causing major changes in the earth’s surface. These changes can be accompanied by various dangers. In Iceland the retreat of permafrost in high mountains has led the top slopes to become unstable, leading to increased risk of landslides and similar hazards. In this project, permafrost in Iceland will be examined, more specifically the areas where permafrost is considered to be thawing and the dangers that accompany that thawing. The research area is by Strandartindur mountain in Seyðisfjörður. On the slope of Strandartindur is a rock glacier, which is in motion, but it is believed that permafrost is hidden in the ground beneath. The area is a well-known landslide area, where the source of landslides high up in Strandartindur is thick sediments that are partly considered permafrost or rock glaciers. Rock glaciers and thawing of permafrost in the vicinity and/or in the glacier threaten settlements in the area, due to landslides. This will be a threefold multidisciplinary project where aspects of natural hazards and society will be tied together; (i) data from soil thermometers and InSAR data will be examined, (ii) discussed and examined how permafrost can be included in monitoring, (iii) and how information on the dangers associated with permafrost can be disseminated to residents and the general public. The project will be useful for monitoring the hazard area at Strandartindur, while also for monitoring comparable areas in the country. It is hoped that the product of this project will be a monitoring research proposal. The result will show how best to measure permafrost, how best to monitor its thawing and how best to provide information to residents and the general public.

How to cite: A. Bartsch, U. B., Gísladóttir, G., and Grímsdóttir, H.: Permathawing permafrost, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8176, https://doi.org/10.5194/egusphere-egu22-8176, 2022.

The frequency and intensity of heavy precipitation events increased since the mid-20th century and, considering the climate crisis, it is important also to analyze the effects of processes and events that lead to faster snow mantle melting cycles in mountain areas.

Shallow landslides are induced by extreme hydrological events such as the occurrence of short and intense rainfall or by events of medium intensity but prolonged over time. Such slips involve generally reduced portions of land both in area and in thickness, however, they are dangerous due to the absence of warning signals and the lack of knowledge regarding their possible evolution.

This work deals with the experimental study of these landslides through the laboratory simulations on a small-scale slope, reproduced at the LIMAG Lab - Laboratory of mountain hydraulics and applied geology of the Lecco Campus and in situ seasonal processes observation at a mountain closed basin nearby Champoluc village in Aosta Valley region.

The central objective is to study the evolution of shallow landslides in reduced scale caused by external factor as snowmelt and rainfall and to compare the observations done in laboratory with the ones in situ. In order to investigate the behaviour of shallow landslides in these critical conditions, a series of sensors have been installed on the simulator. This technology includes three modified pressure transmitters for the pore water pressure evaluation which have been accompanied by other support instrumentation consisting of GoPro’s cameras, TDR (Time Domain Reflectometry) and georesistivimeter; all of them provide a cross check of phenomena processes.

Throughout the downscaled simulations with snow cover it was possible to observe several processes. The direct interaction between snow and ground does not favor the infiltration of a large amount of water. The protective role of snow lies in keeping the first film of soil at 0 degrees and loading the soil by decreasing its infiltrative capacity; this no longer occurs when the water melted by the snow flows downstream and begins to infiltrate into uncovered and warmer soils. Without thermal or overload barriers, the water pours into the ground. Therefore, a potential susceptible area can be the subject of different filtering and infiltrative contributions from upstream, saturating quickly and collapsing.

These laboratory experiments are the starting point for the in-situ analyses and provide a comparison with the observations made by means of ad hoc instrumentation set up at the Champoluc station. Highly detailed information is obtained concerning the density and thickness of the snowpack during seasonal processes. These contribute to defining the hydrogeological processes within the terrain, already studied in the laboratory, and to establishing the water balance.

How to cite: Longoni, L., Panzeri, L., Mondani, M., and Papini, M.: Experimental analysis of seasonal processes in shallow landslide in a snowy region through downscaled and in situ observation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8247, https://doi.org/10.5194/egusphere-egu22-8247, 2022.

Globally landslides are triggered by a myriad of singular and complex causes however the response of the Irish landscape to predicted climate changes are unknown. Some limited data suggest that there may be an increasing trend observed in the frequency of landslides in Ireland, clustered around specific high magnitude rainfall events. Whether this trend is associated with a changing climate trend is unclear. None of the several peer reviewed compendiums that include regional landslide studies and climate have a dedicated contribution on Irelands landscape. We provide a summary of the climate of Ireland from Holocene to future modelled predictions. We present a qualitative assessment of the role of Irish climate and climate change on landslides by identifying specific climate aspects which are important for slope instabilities including precipitation receipts, intensity and variability; the tracks of storms and other rain bearing weather systems and temperature changes. We examine published case studies and an inventory of known landscape response to past weather to consider, qualitatively, the likely response of landslides to predicted future climate trends. We also present rainfall data for three recent landslides events in Ireland and identify areas that require further landslide research. Our review finds that climatic factors which are predicted for Ireland, are cited in the published literature as contributors to slope failures in the Irish landscape. Analysis of rainfall data for the three recent slope failures further support this. Our review suggests that Ireland may see an increase in the frequency of landslide occurrence in the future. Although the data suggests that the majority of failures occur in peat, we highlight a paucity of data for coastal slope failures.  

How to cite: Cullen, N. and Bourke, M.: The potential impact of predicted climatic change on future slope stability in Ireland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8302, https://doi.org/10.5194/egusphere-egu22-8302, 2022.

Geostatistical models of landslide susceptibility do not usually account for thermal data, although these data are widely available, and experiments demonstrate that temperature does influence the mechanical and hydraulic behaviours of soils and rocks via a variety of thermo-hydro-mechanically coupled processes.

We took the epicentral region of the 2008 Wenchuan earthquake in China as our study area, for which a rich multi-temporal inventory of landslides is available. We built a landslide susceptibility model using a generalised additive model with a slope-unit partitioning of the area (~500 km², comprising 42 sub-catchments), and a minimal set of covariates, including the map of peak ground acceleration of the mainshock and Landsat 7 land surface temperature (LST) data retrieved from Google Earth Engine.

We demonstrated that the LST relates to the decay of post-earthquake landslide activity, and in particular that warmer slopes seems to be comparatively more affected by prolonged landsliding. We also verified that LST data provided different insight from that offered by the normalised difference vegetation index (NDVI), by running our model with NDVI maps instead of LST maps. The two input maps showed little collinearity, and the variable effects of the NDVI in the model output showed less complexity compared to those of the LST. This hints at the presence of thermo-mechanical effects in slopes in addition to the known hydrological effects, the latter being associated with changes in evapotranspiration and thus in principle capturable by the NDVI.

Even though studies in other regions, seismic and non-seismic, are necessary, we suggest that thermal data should be used in landslide susceptibility modelling more systematically because they could potentially improve the model results and suggest physically-based relationships influencing slope stability.

How to cite: Loche, M., Scaringi, G., Yunus, A. P., Catani, F., Tanyaş, H., Frodella, W., Fan, X., and Lombardo, L.: Effect of temperature on post-earthquake landsliding near the epicentre of the 2008 Wenchuan earthquake, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8407, https://doi.org/10.5194/egusphere-egu22-8407, 2022.

The residual shear strength is the sole available strength in regular shear zones of landslides after large displacements. While it does not depend on the stress history, it has been shown to depend on the rate of shearing. Various mechanisms have been proposed to explain the shear-rate strengthening and weakening observed, in particular, in soils containing clay minerals. Frictional heating has been shown to be involved in shear weakening under very large shearing rates. However, changes in temperature (imposed as boundary conditions and propagating into the shear zone) also can affect the residual shear strength, even in drained condition, but evidence in the literature is scarce.

Here, we show results of temperature-controlled ring-shear tests on two pure clays (a commercial bentonite, very active, and a commercial kaolin, inactive), conducted under a wide range of shear displacement rates (0.02–45 mm/min) and normal stresses (50–150 kPa) typical of slow to rapid landslides. After attaining the residual shear strength under the chosen stress and displacement-rate conditions at room temperature (20 °C), we increased the temperature of the cell up to 55 °C and kept it constant over a sufficient shearing distance before gradually decreasing it back to the initial value.

We observed a clear effect of temperature on the residual shear strength of the active clay. We evaluated, in particular, a shear strengthening under slow shearing (up to +1.5 %/°C) which turned into a shear weakening under fast shearing (-0.5 %/°C) under any normal stress. We evaluated that the transition between the two behaviours occurred at a shear displacement rate of 0.1–1 mm/min, which is consistent with the range for the onset of shear rate-dependent behaviours. The effect produced by the increase in temperature was shown to be reversible, although in some cases we noticed a net decrease in strength that could be attributed to an improved alignment of the clay platelets resulting from the thermal cycle. Notably, little thermal effects were seen for the inactive clay, suggesting that such effects should originate from changes in physico-chemical forces of interaction at the microstructural level, which are indeed especially relevant in active clays.

Changes in residual shear strength with temperature could be related to changes in landslide activity (particularly for creeping landslides in clay soils) in terms of seasonal/progressive acceleration or deceleration driven by external hydro-meteorological forcing. Furthermore, these changes could also control the potential for runaway motion if a transition from a strengthening to a weakening behaviour occurs. 

How to cite: Scaringi, G. and Loche, M.: Effects of temperature and shearing rate on the residual shear strength of two pure clays, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8429, https://doi.org/10.5194/egusphere-egu22-8429, 2022.

This presentation is dedicated to a short description of a combined rock slope thermal monitoring system. The newly designed system is affordable and modular, which predisposes it to installation at multiple sites. This system is being used to monitor four different rock slopes in Czechia for a period of up to 3 years. Slopes differ by lithology, structural setting aspect and modes of instability. The monitoring system consists of a climate station, rock mass surface zone thermal monitoring and unstable blocks crackmeter monitoring. Since 2018 we have instrumented 11 blocks, which differ in terms of shape, volume and mode of destabilization. Analyses of crackmeter, thermal and climatic time-series showed influences of weather and temperature cycles on the crackmeter aperture. Consequently, short-term (diurnal) and medium-term (annual) temperature cycles on the rock slope surficial zone were described. Data show high variability linked to the partial blocks geometry and rock slope properties.

How to cite: Racek, O., Blahůt, J., and Hartvich, F.: Multi-site rock slope thermal monitoring: Initial results, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9678, https://doi.org/10.5194/egusphere-egu22-9678, 2022.

The available strength on slip surfaces in landslide after a significant displacement and at motion is the residual strength. The residual strength depends on the soil properties including both solid skeleton (mineralogy, particle shape and size, index properties) and pore fluid (chemical and rheological properties). The available strength also depends, as extensively reported in the literature, on several factors that may not remain constant in time and affect the landslide stability and dynamics: applied stress, accumulated displacement and shear strain rate. With a less extensive literature related to, the effect of temperature on the residual strength have been also observed.

This work reports on the results of a large number of ring shear tests under controlled rate and temperature performed on different types of soils. The results are interpreted in terms of the influence of mineralogy, clay content and plasticity on temperature effects on residual strength.

How to cite: García, L. M., Soncco, E. A., Pinyol, N. M., and Lloret, A.: Temperature effect on the residual shear strength., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10442, https://doi.org/10.5194/egusphere-egu22-10442, 2022.

Shallow landslides (SLs) imply downhill movements of soil, rocks, debris. These typically occur on steep terrains, in mountainous, and hilly areas, representing a major risk for people and infrastructures. Properly mapping of shallow landslides in space and time is fundamental for prediction, forecast, and setting up of countermeasures. However, modelling of shallow landslides is complex, given (very) local nature of the phenomenon. Recently investigation started about the role of snow melt in triggering shallow landslides, displaying increasing evidence of catastrophic events at thaw. Little was done hitherto in modelling snow melt triggered SLs, especially in terms of physically based modeling. Under the umbrella of the recent project MHYCONOS, funded by Fondazione CARIPLO of Italy, we developed a robust, and parameter-wise parsimonious model, able to mimic triggering of SLs accounting for the combined effect of precipitation duration and intensity, and snowmelt at thaw. In our model, when temperature is below 0 °C, precipitation is stored as snowpack on the soil surface, and released later in thaw season. Storage of melting water during springtime increases soil moisture, so creating potential for SLs. The model is demonstratively applied to the Tartano river valley, in the Alps of Lombardia region of Italy. In this region mass movements and flash-floods in the wake of intense storms are common. Currently from our model about 26% of the Tartano valley displays (permanent) unstable conditions, more than 40% of it influenced by soil moisture changes. Conversely, by applying a traditional rainfall-based analysis, only 19% of the basin is predicted as potentially unstable, mainly in fall, when intense rainfall occurs. When including snowmelt as a cause of SLS triggering, one finds anticipation of the (modeled) peak of instability to springtime, during April and May. Forcing the model under 6 different climate change scenarios of IPCC at 2050, and 2100, an increase is expected in temperature (i.e. with rapider snow melt), and extreme precipitation events, further aggravating SLs hazard. Mapping zones prone to instability in space and time under present conditions, and future scenarios, will help to prevent casualties, and damages in the short-term, while providing base for structural mitigation measures in the long term, during periods of potential instability, even at low to medium rainfall rates.

How to cite: Chiarelli, D. D., Bombelli, G. M., Bocchiola, D., Rosso, R., and Rulli, M. C.: Snow melt triggering of shallow landslides under climate change. The case study of Tartano valley, Italian Alps., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11120, https://doi.org/10.5194/egusphere-egu22-11120, 2022.

Landslide risk is one of the most relevant hazard that affects the Emilia-Romagna Region. Almost 80,000 landslides were mapped in the mountainous part, and the percentage of land covered by landslides exceeds in some areas 25%. Although most of the regional landslides are relatively slow, the economic impact is critical: in 2019, 1 million euros was allocated for urgent safety interventions, and it is estimated that at least another 80 would be needed to complete the plan. These numbers place the Emilia-Romagna Region among the areas with the highest landslide risk in the world. The geological characteristics of the Region, combined with the growing exploitation of the territory and the climatic changes underway, are making this problem more and more dramatic. It is now clear that emergency responses are no longer sufficient and that they must be accompanied by prevention actions devoted to mitigate the risk. 

The main objective of this work is to develop Artificial Intelligence models for the prediction of landslides in the Emilia-Romagna Region. The idea is to exploit the data collected by the University of Bologna in the last 15 years, as part of the research activities carried out in collaboration with the Regional Agency for Civil Protection and the Geological Survey of the Emilia-Romagna Region.

Available data consist of time series of rainfall, soil moisture, snow cover and displacement of some active landslides that have occurred in the region in recent years. The displacement data comes from permanent GPS stations, wire strain gauges, and robotic total stations installed in several landslides for emergency purposes. These data show clear relationships between precipitation and rate of movement. However, such relationships are difficult to reproduce using physically-based approaches.

The proposed machine learning approach was applied to the Emilia-Romagna Region of Italy taking advantage of the historical landslide archive, which includes more than 2210 rainfall events  that triggered 2363 landslide, and of the genetic classification algorithm TPOT (Tree-based Pipeline Optimization Tool) with more than 1million combinations of hyperparameters. The results show that landsliding in the study area is strongly related to rainfall event parameters (Precipitation during the event, The day of the event and in which location happened) while antecedent rainfall seems to be less important (Precipitation 30 and 60 days before the rainfall event). The distribution of landslides in the rainfall precipitation - day of the year chart shows that after the dry summer season a rain event of at least 90-100 mm is necessary to trigger a landslide. However, this number decreases as the day of the year increases, and then arrives in spring where many landslides are shown have been triggered with modest rain events (15-30 mm). The algorithm also provided an F1 test result score of 0.825, which means that it can predict a true positive (rainfall event triggers landslide) with a 70% of precision and with 95.5% about true negative (rainfall event do not triggers landslide).

How to cite: Dal Seno, N. and Berti, M.: Development of AI Algorithms for landslides prediction (Emilia-Romagna Region, Italy), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12658, https://doi.org/10.5194/egusphere-egu22-12658, 2022.

In recent years, interest in argillaceous rocks has increased because they are being considered as potential host geological media for underground repositories of high-level radioactive waste (HLW). The host rock around the repository cells, containing the exothermic waste canisters, will be submitted to various coupled mechanical, hydraulic, and thermal phenomena. For a proper understanding and appropriate modelling of the excavation damaged zone around repository cells at elevated temperatures, the combined effects of those phenomena should be considered in an advanced constitutive model. The thermo-hydro-mechanical (THM) model presented herein is dedicated to non-isothermal unsaturated porous media. The model is developed within the framework of elastoplasticity, which includes features that are relevant for the satisfactory prediction of THM behaviour in argillaceous rocks: anisotropy of strength and stiffness, behaviour nonlinearity and occurrence of plastic strains prior to peak strength, significant softening after peak, time-dependent creep deformations, permeability increase due to damage, and shrinking of the elastic domain and the degradation of stiffness and strength parameters with temperature.

The model was applied to the numerical simulation of a full-scale in situ heating test conducted on Callovo-Oxfordian (COx) claystone, in the Meuse / Haute-Marne Underground Research Laboratory, simulating a heat-emitting, high-level radioactive waste disposal concept. The interpretation of the test was assisted by the performance of a numerical analysis based on a coupled formulation incorporating the relevant THM phenomena. Initial and boundary conditions for analysis, as well as material parameters, were determined from a comprehensive field and laboratory experimental programme. Thermal, hydraulic, and mechanical observations in COx claystone were discussed. The numerical analysis was able to accurately reproduce the behaviour of the experiment.

The performance and analysis of the in situ test have significantly enhanced the understanding of a complex THM problem, and have proved the ability of the theoretical formulation to provide adequate modelling capacities.

How to cite: Tourchi, S., Gens, A., Vaunat, J., and Scaringi, G.: Thermo-hydro-mechanical modeling of clayey geological medium: Theoretical framework and numerical study, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13375, https://doi.org/10.5194/egusphere-egu22-13375, 2022.

The study is aimed at verifying the reliability of the ERA5 reanalysis in reproducing histories of soil water fluxes exchanges (in terms of precipitation and evapotranspiration) leading to landslide events that actually occurred in Campania Region (Southern Italy). In the specific, the investigation deals with landslide events affecting pyroclastic covers result of repeated eruptions of Vesuvius and Campi Flegrei over the course of millennia. Indeed, for many events occurred in the last years, it is hard to retrieve continuous and reliable atmospheric data provided by weather stations in the vicinity of the affected slopes. Under such constraints, it could be difficult to identify the weather patterns triggering the events and then how they could vary in a climate change perspective. To deal with these issues, the fifth generation of atmospheric reanalysis made available by European Centre for Medium-Range Weather Forecasts (ECMWF) can represent a valuable support. ERA5 and its downscaling ERA5land return hourly data with an horizontal resolution of respectively 31km and 9 km over the entire globe. The data are available since Fifties and they are continuously updated with a delay of only 5 days for ERA5 and few months for ERA5land. Well-documented test cases over Campania Region for which long datasets of atmospheric data and details about the landslide events are available, are exploited to assess the capabilities of ERA5 reanalysis in reproducing antecedent and triggering soil water fluxes exchanges histories. Then, strengths and potential gaps are identified and thoroughly explained to permit a reliable adoption of the datasets.

How to cite: Rianna, G. and Reder, A.: Interpreting recent landslide events in Campania Region (Southern Italy) by using innovative approaches, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13399, https://doi.org/10.5194/egusphere-egu22-13399, 2022.

Long-life, long linear geotechnical assets such as road, rail and flood embankments provide vital transport and flood defence infrastructure. Slope failures can close transport networks and cause delays, or can reduce the protection provided against flood hazards. This creates huge economic cost and can cause a risk to life for those using affected transport networks or resident on the floodplain. Where emergency repair is needed, the estimated cost of this is 10 times that of scheduled maintenance making effective asset management an industry priority (Glendinning et al., 2009).

However, projected climatic changes pose a threat to the stability of these assets. The most recent IPCC report highlighted projected future changes to temperatures and rainfall. These climatic changes alter the natural cycles of wetting and drying experienced by assets, which results in deterioration of asset performance. Deterioration can occur due to a variety of processes, including crack formation and propagation, downslope plastic strain accumulation and geochemical or mineralogical changes. These ultimately influence the strength, stiffness, permeability and water retention of the soil, which can often mean the construction standard of the asset is not maintained (Stirling et al., 2021).

The ACHILLES project aims to improve understanding of how these processes occur and how they may be affected by projected climatic change. Here, we introduce three large-scale field monitoring sites, including a purpose-built trial embankment, flood embankment and highway cutting. These assets are heavily instrumented to measure soil deformation, soil hydrology and local weather conditions, amongst others. Data from these sites are analysed to further understand deterioration processes and inform future design, construction, monitoring and management of these earthworks. We will discuss key insights from this project, including implications for stakeholders.

References:

Glendinning S, Hall J, Manning L (2009) Asset-management strategies for infrastructure embankments. Proc Inst Civ Eng Eng Sustain 162:111–120

Stirling RA, Toll DG, Glendinning S, Helm PR, Yildiz A, Hughes PN, Asquith JD. Weather-driven deterioration processes affecting the performance of embankment slopes. Géotechnique 2021, 71(11), 957-969.

How to cite: Brooks, H., Stirling, R., Blake, A., Holmes, J., Yu, Z., Watlet, A., Whiteley, J., Briggs, K., Smith, A., Hughes, P., Smethurst, J., Chambers, J., and Dixon, N.: Climate-driven deterioration of long-life, long-linear geotechnical infrastructure, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13409, https://doi.org/10.5194/egusphere-egu22-13409, 2022.

Abstract: Roots play a major role in reinforcing and stabilizing soil. The pullout mechanical characteristics of soil reinforcement and slope protection of the root systems of dominant shrub species (Pyracantha and Geranium) were estimated by in situ pullout tests in a karst area, in which roots were pulled out from soil to reliably test the pulling force. The F-s curves were multipeak curves with a noticeable main peak and main double peaks. The curves showed a linear increasing trend at the initial stage of drawing and decreased rapidly after reaching the peak. The F-s curves of root systems inserted into rock cracks showed secondary fluctuations in the later stage of drawing, and rock cracks stimulated the tensile efficiency of the root system more effectively. The maximum pulling force had a linear relationship with the increase in soil thickness and a disproportionate increasing trend with the increasing number of broken roots. The displacement of the maximum peak was different between the two tree species and was concentrated at 5-15 cm and 5-25 cm for Pyracantha and Geranium, respectively. The maximum pulling force of Geranium was 1.29 times that of Pyracantha, and the root system of Geranium had strong pullout resistance. These findings can enrich the theoretical knowledge of vegetation slope protection and provide a reference for the selection of soil and water conservation tree species.

How to cite: Ruan, S.: The pullout mechanical properties of shrub root systems in a typical karst area, Southwest China, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-745, https://doi.org/10.5194/egusphere-egu22-745, 2022.

How to use a suitable method to accurately measure gully morphology is very important in the study of gully erosion monitoring and development, and the development of Unmanned Aerial Vehicle (UAV) has made it easy to apply UAV photogrammetry techniques to gully erosion studies. The aim of this study is to evaluate the accuracy of data and the efficiency of data processing by analyzing the errors of different schemes, and to provide suitable plan design ideas for the study of gully by UAV. Gully is the object of study and different flight schemes and Ground Control Point (GCP) placement schemes are used to acquire and process the data, and finally the errors are analyzed by Digital Surface Model (DSM) and orthophoto. Among all the schemes, the one with a flight altitude of 30m, 80%/70% photo overlap and 11 GCPs had the highest accuracy (Mean absolute error of 0.0353m and root mean square error of 0.0525m), but this scheme took more data collection and processing time and was less efficient. The number of GCPs and the placement location also have a significant impact on the accuracy，the position closer to the GCPs has a smaller error，and this study proves that the number of GCPs should not be more than 9 and should be evenly distributed in different parts of the gully.. When the flight altitude is 70m, the overlap is not less than 50%/40%, and the number of control points is 6, both accuracy and measurement efficiency can be taken into account at the same time. In addition, the sources of errors and the distribution locations of checkpoints with high errors were analyzed in four aspects: shadow, slope gradient, slope direction and vegetation. The use of UAVs in gully erosion studies is very convenient to get the later products with centimeter-level accuracy, and based on the results of the study we suggest that the flight altitude and photo overlap can be appropriately reduced when designing the scheme, and the number of GCP can be increased in the areas that need to be focused on and the areas with large elevation changes. At the same time, flight safety, UAV battery power, data collection efficiency and processing efficiency should be considered comprehensively.

How to cite: Yang, J., Dong, Y., and Huang, J.: Assessment of the gully morphology measurement method based on UAV photogrammetry, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-828, https://doi.org/10.5194/egusphere-egu22-828, 2022.

Topography is the result of geological tectonic movement and land erosion development, which is min factor for slope processes such as surface runoff and soil erosion. At present, there is insufficient research on the spatial pattern and influencing factors of Slope Length and Steepness (LS) factors in the Qinghai-Tibet Plateau (QTP). Based on the 30m resolution SRTM (Shuttle Radar Topography Mission) digital elevation data, we calculates the Hack profile and area-elevation integral parameters, extracts the slope, slope length and LS factor, and analyze their relationship with the elevation. The results show that: 1) the slope and LS factor are small in the centre area of the plateau, and LS decreases from southeastern to the northwestern. The terrain inside the plateau is flat, surrounded by high mountains, and the slope, slope length and LS value are large in areas with large topographic relief; 2) The Hack profiles of the six main rivers including , etc, in the QTP are convex, and the hypsometric curve  of the rivers is close to convex. The geomorphic evolution of the region is in its youth stage as a whole, indicating that the neotectonics of the Qinghai-Tibet Plateau is active. This geomorphic feature makes the LS value distributed in Hengduan Mountains, Western Sichuan Plateau, Yarlung Zangbo River Grand Canyon, etc; 3) The overall dominent of LS in the QTP is slope steepness, while in the steep areas on the edge of the plateau is slope length, and the gentle areas centre QTP is slope; 4) The distribution characteristics of LS are consistent with soil erosion types. The extremely steep slope areas are mainly affected by glacier erosion, while the steep slope areas such as Southeast Tibet are greatly affected by water erosion, The transition zone between the plateau surface and marginal mountains is mainly water erosion and freeze-thaw erosion, and in the dry Qiangtang plareau has strong wind erosion The geomorphic and erosive topographic characteristics of the QTP discussed in the paper, will be a theorical base for the extraction of topographic factors in soil erosion and hydrology, and also has implications for research of multispherical interactions in Tibetan Plateau's earth system.

How to cite: Li, E., Yang, Q., Pang, G., Wang, C., Yang, L., and Qiao, B.: Spatial pattern and influencing factors of Slope Length and Steepness Factors (LS) in Qinghai Xizang Plateau, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1248, https://doi.org/10.5194/egusphere-egu22-1248, 2022.

Stemflow, as one of the most important elements of forest precipitation redistribution, affects the delivery and spatial distribution of water and nutrient. Although approximately 4% of forests are affected by wildfire worldwide, no study has measured stemflow velocity after forests are affected by wildfire. The aim of this study is to determine (1) whether stemflow velocity changes after wildfire, (2) whether stemflow velocity changes with stem flow rate and height, (3) whether stem surface roughness affects stemflow velocity. In this study, we designed a device to quantify stemflow velocity. Our study revealed that the destructions of bark morphology and biological crust on the stem surface were the main factors affecting the change of stemflow velocity. The wildfire caused an enhanced stemflow velocity by roughly 30% for the burned pine compared to pine that did not affect by the wildfire. The stemflow velocity increased with stemflow rate following a power function. The width of pine bark had a negative linear relationship with stemflow velocity. With the increase in stemflow rate, the difference in stemflow velocity between burnt pine and unburnt pine was not significant. Stemflow velocity did not increase with the height of stemflow starting point increased, probably because increased stemflow energy caused the stemflow to detach from the stem. This study implies stemflow velocity affected the migration rate and spatial distribution of water and nutrient on stems and land surface around the base of tree. The increased stemflow energy is also likely to exacerbate soil erosion. All these can affect the restoration process of forest ecosystems from wildfire.

How to cite: Zhang, Y. and Wang, L.: Effect of wildfire on stemflow velocity of pine, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1257, https://doi.org/10.5194/egusphere-egu22-1257, 2022.

Gully erosion was one of the key processes of soil erosion in Hengduan mountain region, which belonged to the eastern part of Qinghai-Tibet Plateau. This dramatic changes in both horizontal and vertical direction has led to a diversity soil groups within the region. The aims of this study were to investigate the gully distribution and density in different soil zones, and find out the key factors that influenced the susceptibility and intensity of gully erosion of Hengduan mountain area. Totally 2300 investigation quadrats were randomly set with the size of 1 km × 1 km to check whether the occurrence and the density by Google Earth images. The ratio of gully occurrence (GR) was 25.5%, and the average gully density (GD) and gully number (GN) was 2.22 km km^-2 and 20.4 of Hengduan mountain area. The annual temperature, vegetation and slope were the key factors that influences the occurrences of gullies in the alpine (>3700 m a.s.l), middle mountain (2000-3700 m a.s.l) and low mountain (<2000 m a.s.l) soil zones, respectively. The intensity of gully erosion showed exponential decreasing relationships with soil property including soil organic matters and silt content, and the average GD in different soil zones showed the same relationships with the R2 higher than 0.7. These results indicating that the distribution of gully erosion were more related to the external environmental factors, and the intensity of gully erosion were determined by soil properties at the regional scales.

How to cite: Dong, Y.: The distribution and intensity of gully erosion in different soil zones of the Hengduan Mountain area, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1947, https://doi.org/10.5194/egusphere-egu22-1947, 2022.

The plateau-mountain areas around the globe are at risk of food insecurity because of its high intensity of soil erosion, limitied suitability of land for agriculture and increasing population pressure. Although plant breeding, improved plant-protection techniques, new variety, application of fertilizer promote increases of crop yields, more frequent extremes of climatic events, topography related to soil erosion can lead to progressive instability in crop production. However little consideration is given in relationships between climatic, topographical factors and grain yields in the Plateau-mountain region. In this study, we collected county-level data on the actual grain yield and environmental factors of the 119 counties in Yunnan province over the past 28 years (1985–2012) to explore the controls on grain yield and how they affect grain yields. Our findings showed that actual grain yeild(AGY) increased over time with an inter-annual fluctuation. Spatially, our findings revealed AGY were strongly influenced by slope. Regression analysis also showed that slope gradient could explain 26.29% of the spatial distribution variability of AGY. Redundancy analysis revealed that AGY positively correlated with evaporation, TN90p, TK, and pH whereas negative correlations with Apre, RH, R50, C/N, slope, and aspect. However climatic and topographic factors and soil properties exhibited greater impacts on AGY, compared to extreme climate indices. We also found that TK showed a significantly positive effect on AGY, indicating that counties with higher TK content in soils could produce higher actual grain yield. And R50 and aspect also had an indirect effect on AGY through influencing TK. Thus, the application of K fertilizer in northwestern, northeastern, and southeastern Yunnan province where soil TK was relatively low may be the key to improve grain yield.

How to cite: Qin, Y., Rong, L., Duan, X., and Gu, Z.: Slope drivers grain yield in the Yunnan Plateau-Mountain areas, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2620, https://doi.org/10.5194/egusphere-egu22-2620, 2022.

The hydrological conditions near the soil surface influence the soil erosion process, as determined by the soil erodibility and critical shear stress. The soil erodibility and critical shear stress of saturated purple soil slopes were computed and compared with those of unsaturated purple soil slopes. The detachment capacities computed through the numerical method (NM), modified numerical method (MNM) and analytical method (AM), from rill erosion experiments on saturated purple soil slopes at different flow rates (2, 4, and 8 L min⁻¹) and slope gradients (5, 10, 15, and 20°), were used to comparatively compute the soil erodibility and critical shear stress. The computed soil erodibilities and critical shear stresses were also compared with those of unsaturated purple soil slopes. At the different slope gradients ranging from 5° to 20°, there were no significant differences in the soil erodibilities of the saturated purple soil and also in those of the unsaturated purple soil. The critical shear stresses slightly varied with the slope gradients. The saturated purple soil was relatively significantly more susceptible to erosion. The NM overestimated the soil erodibility of both saturated and unsaturated soils by 31% and underestimated the critical shear stress. The MNM yielded the same soil erodibility and critical shear stress values as the AM. The results of this study supply parameters for modeling rill erosion of saturated purple soil slope.

How to cite: Li, D., Chen, X., Han, Z., Gu, X., and Li, Y.: Determination of Rill Erodibility and Critical Shear Stress of Saturated Purple Soil Slopes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3290, https://doi.org/10.5194/egusphere-egu22-3290, 2022.

The soil-covered Pisha stone area is the core source area of coarse sediment in the Yellow River and has become the focal point of ecological control of the Yellow River Basin. It is thus vital to study the spatial distribution of erosion coupling between geomorphology, vegetation, and water in the soil-covered Pisha stone area. Some valuable research results have been obtained already by using high-definition remote sensing aerial photographs and-high precision data from unmanned aerial vehicles. In particular, the image resolution obtained by unmanned remote sensing reveals small watershed topographic features and the characteristics of vegetation structure. Thus, the use of remote sensing is vital for research involving the spatial distribution of soil erosion in the slopes of the Pisha stone area and the dynamics of the geomorphic spatial structure of the slopes. In addition, the negative correlation between the spatial structure of the vegetation community and the energy dissipation impedance of erosion requires further study. Research into soil erosion in the Pisha stone area thus represents an urgent scientific need whose outcome will directly affect the theoretical foundation of a comprehensive model for treating soil erosion in this area.

How to cite: shen, Z.: Research progress of soil erosion in Pisha stone area of Yellow River, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3475, https://doi.org/10.5194/egusphere-egu22-3475, 2022.

Abstract: To explore the adaptable plants soil reinforcement effects in the karst region of southwest China. A horizontal pull friction test was performed on the roots and soil by using a three-year-old shrub Pyracantha, and the friction characteristics of root-soil interface were analyzed by scanning electron microscopy and interference method. The results indicated that :(1) the root system of pyracantha showed two failure modes in the pull-out test: the pull-out friction of root-soil interface increases with the increase of root diameter and vertical load. (2) When gravel content is set at 0, 10%, 30% and 50%, the frictional force between root and soil tends to decrease. (3) There was a positive correlation between root surface roughness and root diameter in diameter range of 1-6mm, with correlation coefficient R =0.995. (4) There is an obvious correlation between root-soil friction and roughness. These results are significant to further explore the mechanical mechanism of plant root-soil interaction, and to strengthen the shallow soil and repair the fragile ecological environment.

Key words: Karst; Pyracantha; Root-soil friction; Roughness

How to cite: Guo, H.: Research on the interaction between roots and soil of adaptable plants pyracantha in the karst region, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4227, https://doi.org/10.5194/egusphere-egu22-4227, 2022.

Terraces are important practice to conserve soil and water in farming systems in mountain areas. Since the mid- 20^th century, marginalization of farmland occurred worldwide in mountainous areas. Farmers reduced investment in terraced fields or even abandoned the fields, and induced negative ecological consequences that are widely concerned. Current studies about marginalization of terraces mainly focus on upland terraces. The understandings of the process of marginalization of paddy terraces and their impacts are limited. Hani Paddy Terraces are one of the Globally Important Agriculture Heritage Systems. However, many of the paddy terraces have changed into upland terraces due to lack of water, labor out-migration ect, which hindered the conservation of the heritage. Taking Amengkong River Basin in Yuanyang County in Southwestern China as the case study area, we explored the changes in terrace structure, productivity of top soil (0~20 cm ) and the water holding capacity soil in 0~70 cm depth in Hani Paddy Terraces since conversion to upland terraces fields by 2~14 years. We found that (1) most ridges disappeared after conversion, the surface of fields were generally maintained in flat conditions, risers of terraces collapsed in varying degrees in more than 70% filed parcels. The degree of damages in terraces structures showed a U-shape curve along with time, as the pattern of drained by 2 years> drained by 3~4 years> drained by 10~14 years > drained by 5~9 years;（2）the soil productivity index increased after converted to upland terraces, and showed a trend of decreasing first and then increasing along with increasing years of conversion. (3) The water holding capacity of 0~70 cm soil dramatically decreased after conversion, and increasingly decreased along with increasing years of conversion. The maximum water holding capacity decreased by 9.16%~21.70% and the capillary volume decreased by 12.09%~24.20%，the decreasing of maximum water holding capacity and capillary volume were most serious in soils of 0~30 cm depth. Our study revealed the impacts of draining on structure of terraces and soil property in Hani Paddy terraces. The findings could enhance the understanding of the biophysical changes in soil during the marginalization in paddy terraces, which would benefit to the conservation and restoration of paddy terraces. 

How to cite: Li, Y., Wang, M., Jiao, Y., Rong, L., and Huang, J.: Changes in Terrace Structures and Soil Properties in Hani Paddy Terraces after Conversion to Upland Terraces, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4391, https://doi.org/10.5194/egusphere-egu22-4391, 2022.

Rocky desertification has become one of the global ecological environmental problems. Karst rocky desertification area of southwest China is suffering from ecosystem degradation, and the combination of water and soil resources determines the stability of their ecosystems. In recent years, soil leakage has attracted attention because it was that under the development of carbonate shallow fissures, the water and soil along the such pipes as shallow fissures leaks underground, resulting in the allocation of soil and water underground, affecting the integrity of the overlying ecosystem. This study aimed to reveal the leakage loss process, characteristic and mechanism of soil in fissures on sloping lands in the karst area, taking fissures on sloping lands in karst plateau of Guizhou province as the research object, combined with the methods of paint marking and soil particle analysis was conducted to study the leakage loss process of soils in fissures. The result showed that rainstorm or downpour is the key factor of soil fissure leakage loss, and its leakage form is mainly soil creep. Soil creep displacements of different fissure at 104.5 mm rainfall event between 1.0 cm and 2.5 cm, accounting for more than 62.5% of the displacement at 332.7 mm rainfall event, while the soil creep displacement of fissures just range from 0.2 cm to 0.3 cm at the larger rainfall of 181.5; the particle content with different particle sizes in rock-soil interfaces and soils of six fissures selected under 3 precipitation events (104.5, 151.2 and 332.7 mm) showed that the fissure soil does not leak down uniformly, but some particles at the soil layers or rock-soil interfaces leak to the lower layer at random in the process of creep leakage loss. In other words, the occurrence of soil layers and particles are accidental, and the soil particles in the rock-soil interfaces and the soil layers of fissures have the possibility to leak down. Facts proved that the soil creep leakage loss in fissures is a complex process which is determined by the internal factors such as fissure structure, fillings characteristics and bottom connectivity, and such external factors as rainfall etc.
Key words: underground leakage loss; soil; karst fissure; sloping land; karst plateau

How to cite: Cen, L., Peng, X., and Dai, Q.: Soil creep and leakage process in shallow fissures on a karst slope based on particle composition analysis, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4557, https://doi.org/10.5194/egusphere-egu22-4557, 2022.

Plant litter incorporation into soil is a widespread phenomenon in the natural environment. Accurate estimation of the soil detachment capacity ( Dc ) driven by overland flow under litter incorporation effects is crucial for improving soil erosion prediction. However, the effects of litter incorporation on soil detachment processes are often ignored, and the temporal variation of Dc under litter incorporation effects remains unclear for the Loess Plateau of China. In this study, we conducted flume tests to determine the temporal variation of Dc for soils incorporating two typical plant litters ( Bothriochloa ischaemum (L.) Keng. litter, and Artemisia sacrorum Ledeb. litter) between May 2017 and October 2018 (a 524-day period). Furthermore, the key factors
affecting Dc were identified. Our results showed that the temporal variation in Dc was consistent across the different soil treatments (two litter incorporation treatments and one bare soil control), showing a rapid decline and then fluctuating at a low level, with Dc ranging from 0.115 to 6.876 kg m⁻² s⁻¹ . Incorporation of litter effectively reduced Dc , with the Dc of soil treatments incorporating litter being 15% to 29% lower than that of bare soil (2.110 kg m⁻² s⁻¹ ). Further analysis showed that the temporal variation in Dc was mainly affected by the development of a physical soil crust. Dc can be successfully estimated using a nonlinear equation incorporating flow shear stress and soil cohesion (R² = 0.77, NSE = 0.65), which represent the erosive force and soil erosion resistance, respectively. Our study reveals the important role of plant litter in the soil detachment process and aids the understanding of soil erosion pathways. Further studies are needed to investigate the effects of a physical soil crust on the soil detachment process driven by overland flow.

How to cite: Liu, J.: Effects of Litter Incorporation on Soil Detachment Processes on the Loess Plateau of China, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4625, https://doi.org/10.5194/egusphere-egu22-4625, 2022.

Soil moisture is a key factor limiting vegetation succession in karst ecosystem. Wildfire changes soil physical and chemical properties, which likely affect evapotranspiration of post-wildfire plant recovery. However, merely studies have been performed to elucidate the evapotranspiration processes and the controlling factors. In this experiment, two typical herbaceous plants (Compositae Artemisia and Gramineae Saccharum) in karst areas were selected for pot experiment. The treatment without plant was used as the control. Combustions were laboratorially carried out with different severity (light, moderate, and high) to simulate different intensities of wildfire disturbance. During the experiments, the mass change in each pot was measured to obtain evapotranspiration under different weather conditions. We also collected meteorological data (total radiation, water vapor pressure, air temperature, relative humidity, atmospheric pressure, soil heat flux, soil temperature, etc.), biomass, and soil properties. Our study showed the impact of wildfire on evapotranspiration. We also compared the differences in evapotranspiration of different herb covers. We detected that weather conditions (e.g., duration of continual drought) also had important influences on the evapotranspiration during post-wildfire restoration. The study provides more insight into characteristics of soil water movement after wildfire in karst areas and evaluating the availability of soil moisture after wildfires. 

How to cite: Liu, K. and Wang, L.: Evapotranspiration process under typical herb cover after wildfire, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4927, https://doi.org/10.5194/egusphere-egu22-4927, 2022.

Despite soil erosion has a strong impact on crop yield, whether soil erosion depth leads to abrupt or gradual crop yield changes is not well understood. To investigate how crop yields respond to soil erosion depth, we conducted a simulated erosion experiment by adopting the cut-and-fill method from 2012 to 2018 in a typical mountain area in the southeastern China. A completely randomized design with five soil erosion depth (5, 10, 20, 30 and 40 cm soil cut) and a control (0 cm soil cut) were used. Each treatment had three replicates. Maize was planted in these simulated erosion plots and maize yields were monitored from 2012 to 2018. Our results showed that the maize yield decreased with erosion depth and with decreasing remaining A_p horizon depth. Inconsistent with earlier studies, maize yield exhibited a quadratic function rather than linear response to increase in soil erosion depth and decrease in remaining A_p horizon depth. Soil erosion depth led to abrupt changes in maize yield. Compared with control, maize yield did not decrease significantly at 5 cm erosion depth or ＞25 cm remaining A horizon depth, but its reduction rate per 1cm of soil loss (3.36%) increased sharply at 10 cm erosion depth or 20 cm remaining A_p horizon. When remaining A_p horizon left 10 cm, maize yield demonstrated the lowest, which may be irreversible via application of chemical fertilization. Considering high heterogeneity of A_p horizon in the mountain area, soil erosion-crop yield relationship could be expressed well by remaining A_p horizon. We also found remaining A_p depth had a significant direct and indirect (via reduced SOM, soil available water, AP and AK contents) negative effect on maize yield. These results could be useful in identifying allowable soil-loss thickness and highlight the importance of soil nutrient monitoring in different soil erosion levels in designing a fertilization scheme aimed at ensuring food security.

How to cite: Rong, L., Duan, X., Liu, T., and Qin, Y.: The effect of soil erosion depth on maize yields, evidence based on a long-term field simulation experiment, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4998, https://doi.org/10.5194/egusphere-egu22-4998, 2022.

Soil erosion in croplands has a strong impact on global carbon (C) cycle. Assessment of erosional effects on soil organic carbon (SOC) dynamics in agricultural soils suffers from the difficulty of distinguishing the erosional effects and complex interaction processes between erosion and C cycling. To simulate the effects of soil erosion, a plots experiment including six erosion levels (0, 5, 10, 20, 30, and 40 cm eroded) was conducted for seven years (2012-2018). The erosion levels were simulated using artificial soil profiles created by mixing soils from different layers in the original soil profile (never eroded) in a certain proportion. Subsequently, based on the field observations during 2012-2018, the SOC dynamics of each experimental plot were simulated by using a process-oriented C cycle model (denitrification-decomposition (DNDC)) to quantify the effects of erosion on SOC dynamics. The measurements at the beginning of the plots experiment showed that simulated erosion resulted in the depletion of SOC with an average reduction rate of 9.7% per 10 cm of soil loss; SOC in eroded soils recovered after seven years of cropping, the declining slope of the SOC measured in 2018 was 3.0% per 10 cm of soil loss, suggesting that dynamic replacement had occurred. Model simulation results indicated that soil erosion could reduce the C inputs from crop residue by lowering soil productivity; soil heterotrophic respiration in eroded soils was restricted due to the lower initial SOC content. As a result, the simulated overall SOC stock in eroded soils was restored after erosion stopped because of the lower C output. These results indicated that SOC loss at eroding sites was caused mainly by lateral transport rather than enhanced decomposition. The fate of the displaced SOC within catchments is key to assess the net impacts of soil erosion on SOC dynamics at a large scale.

How to cite: Lin, H., Duan, X., Li, Y., Zhang, L., Rong, L., and Li, R.: Simulating the effects of erosion on organic carbon dynamics in agricultural soils, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6640, https://doi.org/10.5194/egusphere-egu22-6640, 2022.

How to cite: Li, Y., Duan, X., Li, Y., Li, Y., and Zhang, L.: Interactive effects of land use and soil erosion on soil organic carbon in the dry-hot valley region of southern China, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6676, https://doi.org/10.5194/egusphere-egu22-6676, 2022.

The vegetation cover in China has changed significantly in the past 30 years, however evidence for vegetation cover dynamics in the dry valley region (DVR) is still lacking. This study aimed to detect fractional vegetation cover dynamics in DVR from 2000 to 2020 with MODIS products, and evaluate the effects of precipitation and hydropower construction projects on vegetation cover dynamics. The results showed that: (a) the long-term average annual fractional vegetation cover for the dry valley region, including the dry-hot valleys, dry-warm valleys and dry-temperature valleys were 0.452, 0.426, 0.504 and 0.446, respectively. Significant decreasing trend of annual FVC from 2000 to 2020 was reported for overall dry valley region. Specifically, significant reducing trends were mainly observed in the dry-hot valleys and dry-warm valleys that located in the west-south part of DVR, while significant growing trends in the dry-temperature valleys of the Min and Baishui Rivers; (b) Annual Precipitation and hydropower projects construction are two key factors that contributing to changes in annual FVC for valleys. The present study is probably the first report on vegetation cover dynamics and the effects of influencing factors in DVR of Southwest China, and helpfully for further scientific studies and restoration management practices in DVR, although more detailed studies for the changes of vegetation cover and its mechanism need to be done.

How to cite: Guo, Q., Shan, Z., Zhong, R., and Duan, X.: Fractional Vegetation Cover Dynamics of the dry valleys in Southwest China from 2000 to 2020, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6708, https://doi.org/10.5194/egusphere-egu22-6708, 2022.

    Subsurface water flow above the weakly permeable soil layer commonly occurs on purple soil slopes. However, it remains difficult to quantify the effect of subsurface water flow on the surface flow velocity. Laboratory experiments were performed to measure the rill flow velocity on purple soil slopes containing a subsurface water flow layer with the electrolyte tracer method considering 3 subsurface water flow depths (SWFDs: 5, 10, and 15 cm), 3 flow rates (FRs: 2, 4, and 8 L min^-1), and 4 slope gradients (SGs: 5°, 10°, 15°, and 20°). As a result, the pulse boundary model fit the electrolyte transport processes very well under the different SWFDs. The measured rill flow velocities were 0.202 to 0.610 m s^-1 under the various SWFDs. Stepwise regression results presented the positive dependence of the flow velocity on FR and SG but a negative dependence on SWFD. SWFD had notable effects on the rill flow velocity. Decreasing the SWFD from 15 to 5 cm increased the flow velocity. Moreover, the flow velocities under the 10- and 15-cm SWFDs were 89% and 86%, respectively, of that under the 5-cm SWFD. The flow velocity under the 5-, 10- and 15-cm SWFDs was decreased to 89%, 80%, and 77%, respectively, of that on saturated soil slopes. The results will enhance the understanding of rill flow hydrological processes under SWFD impact.

How to cite: Tao, T., Chen, S., and Chen, X.: Rill flow velocity affected by the subsurface water flow depth of purple soil in Southwest China, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6779, https://doi.org/10.5194/egusphere-egu22-6779, 2022.

A 3-m thick sediment was found in a limestone mine located in the Apulia region (south of Italy), at a depth of 25-30 m from the current ground level. Samples from 5 layers were investigated by X-ray Absorption Near Edge Spectroscopy (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) at the iron (Fe) K-edge, paired with Raman spectroscopy (RS) and thermal analysis.

The pedosediment record under investigation represents a peculiar stratigraphic series showing complex features related to the Fe dynamic.

From a technical point of view, the challenges of phase identification in Fe oxides are many, but the application of multiple techniques provides sufficient evidence for the identification and discrimination of Fe phases. The combination of Fe XANES and EXAFS allowed to get information on the Fe speciation and its local structure. In detail, ferrihydrite is the most abundant Fe species, followed by goethite and minor amounts of hematite. Ferrihydrite content decreases with depth, where goethite and hematite occur. The presence of ferrihydrite, only detected by Linear Combination Fitting (LCF) on the first-derivative XANES spectra and on the EXAFS spectra, suggests that redox cycling of Fe occurred in these sediments. In addition, higher contents in Fe(III) complexed by organic matter is found in the top and deepest layer.

Generally speaking, RS and thermal analysis might present a promising tool to unravel some mineralogical components such as calcite, goethite and some Mn-oxides. Unlike for the identification of some Fe-bearing minerals like ferrihydrite, RS seems to be not well suited and this aspect require further investigations.

Definitely, this study confirms that each layer has preserved the distinct features that relate to its time of deposition. We underline how a multidisciplinary approach is strongly required to obtain reliable records when peculiar environments like karst pedosequences are investigated.

How to cite: Giannetta, B., Cassetta, M., Oliveira de Souza, D., Mariotto, G., Aquilanti, G., and Zaccone, C.: Iron speciation throughout a karst pedosedimentary record in South of Italy, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-218, https://doi.org/10.5194/egusphere-egu22-218, 2022.

The mining region of Upper Silesia has a long tradition with international significance. In 2017, the historic silver mine in Tarnowsky Gory was recognized as a UNESCO World Heritage Site. With the mining of galena (PbS), the region developed into one of the most important industrial centers in Central Europe in the 16th century. In addition to the underground galleries, the historical mining has left thousands of mining shafts as small relief forms, which have not been systematically investigated so far. Partly the mining shafts are associated with Relict Charcoal Hearths (RCH), another small form which is a result of charcoal production. In the Mala Panew River valley, north of Tarnowsky Gory, several tens of thousands of these RCH are found, which could be mapped by LiDAR in recent years. More detailed pedological investigations, which would allow a systematic comparison with other known RCH sites, are missing so far.

Within the framework of a Polish-German cooperation project, we started in 2021 to investigate the mining shafts and the RCH in Tarnowsky Gory and in the Mala Panew River valley from a pedological-sedimentological point of view. At the RCH sites on the Mala Panew River, we focused on the following questions: How was the soil stratigraphy changed by the RCH construction? What are main processes of soil development before and after RCH construction? What was the role of the pits surrounding the RCH? How do the sites differ from the RCHs at Tarnowsky Gory especially with respect to soil properties and soil genesis? In Tarnowsky Gory, where a RCH was excavated directly next to a mining shaft, the following questions were in focus: How did the mining activity change soil distribution and soil properties? What are main processes of soil development on the different parts? What is the origin of the pit infill? What is the origin of the shaft rim deposits?

Our work program included the construction of excavator trenches across the mining remains, construction, description and sampling of soil profiles along the trenches, schematic drawing of the soil stratigraphy, and laboratory analyses for the determination of texture, Munsell color, pH (CaCl2, H20), CaCO3 content, Ctotal & Ntotal and total elements by FPXRF. We present the first results of the ongoing investigations.

How to cite: Raab, T., Bonhage, A., Verschoof-van der Vaart, W., Malik, I., Raab, A., Schneider, A., Chauhan, J. S., and Thekkethala, J. J.: Soils on mining relicts in Upper Silesia, Poland – first results from the Mala Panew River catchment and the UNESCO heritage site Tarnowskie Góry, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-969, https://doi.org/10.5194/egusphere-egu22-969, 2022.

Colluvisols represent an important part of the soil cover, occupying concave slope elements especially in landscapes with undulating relief. Their development reacts to changes in land use or climate, manifested by intense erosion activity or longer resting periods with predominantly in-situ pedogenesis. In climatically, pedologically and historically different regions, diverse colluvial profiles can be encountered. In this study, we investigated deep colluvial profiles in three agricultural plots in Czechia with different soil cover, climatic and geological conditions in order to identify differences in the depositional pattern and erosion history of the areas. In each of the plots, two profiles (depths ranging from 200 to 400 cm) were opened in the toe-slope and side valley areas. Individual layers were investigated by various methods, including optically stimulated luminescence dating, 137Cs activity, concentration of vertically stable geochemical tracers (organochlorine pesticides, nutrients) or micromorphology and clay mineralogy, allowing the layers to be linked to periods of human activity. In all study areas, a significant difference in the colluvial deposition mechanism was found in the toe-slope and side valley areas. While the positions in the side valleys were mainly composed of older material with a minimum concentration of human-bound substances, the profiles in the toe-slopes are characterized by a significant deposition of recently accumulated material. The most pronounced redistribution of material was recorded in the Chernozem area on loess. In the toe-slope area, maxima of 137Cs, DDT (up to 350 µg/kg) and phosphorus were found at 100-140 cm, indicating the very low age of this layer (from the mid-20th century). The mineralogical and chemical composition of this layer and the layer below (140-220 cm) shows considerable similarities to the substrate material, indicating severe truncation of the source soils and accumulation of ploughed parent material. In contrast, in the side valley, this new material was found only in the topsoil, with approximately 3 m of older, humus-rich material beneath. This area is therefore not an area of recent deposition, but rather of material transport. The original buried Chernozem was found in both cases at a depth of about 300-350 cm. In the Cambisol area, the combination of rill and sheet erosion led to the formation of a highly stratified profile with a large variation in texture or humus content. The maximum of human-bound substances (137Cs, HCB, DDT) was found at a depth of 1 m, underlain by older material with signs of post-depositional pedogenesis (weathering and redox processes). The area of side valley was, as in the previous area, almost unaffected by recent sedimentation. In Luvisol area, the concentration on human-bound substances was generally lower and affected only the upper, humus-rich layer (ca 80 cm) of the Colluvisols, both at the toe-slope and the side valley. Below this layer, the profiles are characterised by relatively pronounced pedogenesis in the sedimentary material (clay coatings visible at the thin sections), indicating slower sedimentation and a longer period of sedimentary quiescence.

Study was supported by grant nr. 21-11879S of the Czech science foundation and MEYS CR project nr. CZ.02.1.01/0.0/0.0/16_019/0000845.  

How to cite: Zádorová, T., Penížek, V., Koubová, M., Žížala, D., Kodešová, R., Drábek, O., Tejnecký, V., Fér, M., Klement, A., Nikodem, A., Hrdlička, T., Reyes Rojas, J., Spasic, M., Vokurková, P., Pavlů, L., Němeček, K., Vaněk, A., and Lisá, L.: Identification of the phases and mechanisms of Colluvisols formation in different soil regions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1520, https://doi.org/10.5194/egusphere-egu22-1520, 2022.

Our research on spatially bounded Iron Age enclosure of the Viereckschanze type in southern Bohemia made it possible to distinguish the anthropogenic influence of the Iron Age from modern human activities. We collected over 456 samples from 200 cores to a depth of up to one metre. Samples were measured using pXRF to determine the content of the following elements: Al, Si, P, K, Ca, Ti, Mn, Fe, Cu, Zn, As, Rb, Sr, Zr, Pb, and LE – ‘light elements’). Subsequent isometric log-transformation of ppm elemental contents and PCA allowed to distinguish the prehistoric anthropogenic influence from the current modern one. The result of the analysis is as follows: 1) the P signal typical for archaeological settlements was found mainly outside of the enclosure; 2) the conventional anthropogenic signal from the inside of the enclosure was only represented by Mn; 3) other elements related to possible anthropogenic activities were revealed only after applying statistical analysis (As, Pb, Zn, Cu); 4) the unusual manifestation of Si and Ti was connected to the archaeological contexts. The combination of these results (Cu, Zn, Pb) and magnetic measurements revealed places of metallurgical activity inside Viereckschanze. It is certain that the site was not only a place of residential activity, but also of production activity. Viereckschanze was only occupied for a short period of time.

The presented abstract is adapted from the article published in Catena in 2022.

Acknowledgements:

How to cite: Janovský, M., Danielisová, A., Horák, J., Strouhalová, B., and Bursák, D.: How to determine the anthropogenic signal at less settled spatially bounded archaeological sites?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2222, https://doi.org/10.5194/egusphere-egu22-2222, 2022.

In the North European Lowland, on the sandy deposits of the Weichselian glaciation, soils developed during periods of landscape stability are often conserved under windblown sand. However, small-scale changes of sediments and other soil forming factors can result in high spatial variation of soil properties in these landscapes; and relocation of soil material by geomorphic processes further increases the spatial heterogeneity of the soil landscape. These spatial variations in soil properties and conservation need to be considered in order to correctly decipher and interpret the buried soils as records of past environmental conditions.

In the forefield of the open-cast mine Cottbus-Nord, archaeological excavations in a dune and drift sand area revealed widespread buried soils of different characteristics. The densely spaced excavation trenches give exceptionally good insights into the pedosphere, allow for reconstructing the distribution of fossil and recent soils in a high spatial resolution, and offer good opportunities to improve the understanding of spatial and temporal patterns of soil formation. Remains of postpleistocene hunter-gatherer campsites were documented in archaeological excavations and found to be associated with a buried soil horizon.

We recorded the stratigraphy of soil profiles along more than 15 trenches within an area of about 20 ha, and additionally described the position of buried soils from GPR surveys and microdrone photogrammetry. In a recently opened, 455 m long trench, all characteristic soils and sediments of the study region could be observed and stratigraphically connected. Within this trench, four profiles were identified for further research. Each profile was classified and described according to WRB and German Guidelines for Soil Mapping; and was sampled and investigated through laboratory analyses including determination of organic matter, total carbon and nitrogen contents, soil colour identification, texture analysis, magnetic susceptibility measurement, metal content analysis using X-ray fluorescence analyzer and pH measurement. The compaction and cementation of soil horizons was assessed in situ with a pocket penetrometer.

Results show a small-scale mosaic of soils developed on fluvio-aeolian, limnic and aeolian sediments, high spatial variations in pedogenesis due to varying groundwater influence and intensity of horizontal and vertical leachate transport, and high variations in the erosion or conservation of fossil soils. The soil and sediment stratigraphy reflects several phases of landscape development: i) the formation of a Late Pleistocene soil on fluvio-aeolian deposits, ii) a fossilization by aeolian sands, iii) a stability phase with intensive podsolization and peat formation, and iv) a land use-induced aeolian remobilization of the sands. 

How to cite: Uchino, K., Raab, A., Bonhage, A., Schneider, A., Raab, T., Wechler, K.-P., and Bauriegel, A.: Spatial heterogeneity of buried and recent soils in a drift sand area in North-Eastern Germany, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2354, https://doi.org/10.5194/egusphere-egu22-2354, 2022.

In the Tauer Forest, a woodland area north of the city of Peitz (Brandenburg, Germany), extensive charcoal burning was carried out from the mid-16th century to the mid-19th century resulting in numerous Relict Charcoal Hearths (RCHs). The most prominent feature of the soils on RCHs is the anthropogenically modified 20-30 cm thick RCH substrate that buries the former forest soil. The RCH substrate is a quite heterogenous mixture of mineral and organic compounds which were modified through heat during charring. It is characterized by its black color resulting from charcoal fragments (from fine dust to decimetre size pieces), lower bulk density, and higher porosity.

After their use, the charcoal production sites were abandoned and soon became overgrown. Soil formation could commence in this anthropogenically modified RCH substrate. During recently conducted field work on RCHs in the Tauer Forest we detected features of initial podzolisation (bleaching of quartz grains) within this RCH substrate. To further investigate initial processes of soil formation (acidification, podzolisation, accumulation of soil organic matter) on RCHs, two different RCH sites were selected in the Tauer Forest: one RCH site in the forest district Tannenwald and one RCH site in the forest district Kleinsee.

The Tannenwald site (RCH no. 29958) is situated in the western part of the Tauer Forest. It is an inland dune area with a coniferous forest (Scots pine, Pinus sylvestris L.) plantation. The forest soils are Podzols and the soils on the RCHs are classified as Spolic Technosols.  The dense undergrowth consists of mainly blueberry (Vaccinium L.). Dendrochronological ages (determination by K-U Heußner, DAI Berlin) of charcoal pieces proof, that the charcoal hearth was used after 1655.

The Kleinsee site (RCH no. 29424) is situated in the eastern part of the Tauer Forest. The parent material is sand from glaciofluvial sediments of the Weichselian glaciation. The forest soils are Brunic Arenosols (Protospodic) and the soils on the RCHs are classified as Spolic Technosols (Arenic). The deciduous forest is dominated by sessile oak (Quercus petraea (Matt.) Liebl.). The undergrowth is only scarce with some ferns (sporadic), blueberry (Vaccinium L.), some shoots of rowan (Sorbus aucuparia L.)  and some moss. There is no dendrochronological age available from the RCH, but RCHs nearby were dated from the 18^th to the 19^th centuries.

At both sites, three soil monoliths were sampled on the RCH platform and three monoliths from the natural forest soil as reference soils. The soil monoliths were sampled continuously in 3 cm vertical spacings. Following lab analyses were carried out: pH (CaCl₂), pH (H₂O), total carbon (TC), total nitrogen (TN), CECeff and total concentrations of selected elements. Analyses of pedogenic Fe are in progress. First results of these study will be presented and discussed.

How to cite: Raab, A., Kim, M., Bonhage, A., Schneider, A., Raab, T., and Bauriegel, A.: Initial processes of soil formation on Relict Charcoal Hearths (RCHs) in the Tauer Forest (Brandenburg, Germany), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3563, https://doi.org/10.5194/egusphere-egu22-3563, 2022.

Archaeomalacological analysis is generally undertaken on recovered macro-remains to characterize the overall composition of faunal remains in a deposit. Given the susceptibility of shell middens to a variety of taphonomic processes, it is assumed that the prior presence of shell in deposits may therefore occasionally be missed. Deteriorated micro-remains can mix indistinguishably into surrounding sediments and make their analyses and identification difficult, particularly in older deposits and in environments that experience rapid rates of weathering. This paper explores whether microscopic remains of deteriorated molluscs can be distinguished from other microscopic remains at the coastal rock shelter site of Waterfall Bluff in Mpondoland, South Africa. The methodology uses a multi-scalar approach integrating shell mineralogy and microstructure using the taxonomic distinctiveness of these features. The diagnostic features (e.g. morphology, hinges, spires, and apertures) used for identifying macro-remains are absent in micro-remains, therefore unique methods of identification are needed to identify these microscopic mollusc fragments. Through mineralogical analyses and scanning electron microscope (SEM) imaging, the nacreous remains of mussel shell were identified from previously unidentified degraded shell remains as well as sediment samples from Waterfall Bluff. These highly degraded remains were located under the dripline in the oldest deposits (LBCS) which are sharply comparable to the more well-preserved macro mollusc evidence in the younger (SRCS) deposits. These methods recovered ‘invisible’ evidence of shellfish remains, which led to additional and clearer evidence of continued coastal foraging from Marine Isotope Stage 3 to the early Holocene (40 ka to 10 ka) on the South African coast.

How to cite: Oertle, A., Szabó, K., Gaqa, S., Cawthra, H., Esteban, I., Pargeter, J., and Fisher, E.: Identifying taxa from highly degraded shell micro-fragments in anthropogenic soils from Waterfall Bluff, South Africa, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4341, https://doi.org/10.5194/egusphere-egu22-4341, 2022.

The Chinese loess-paleosol sequences provide valuable records of the Quaternary climate changes. However, the relative contributions of the Quaternary paleoclimate (e.g. precipitation, temperature, evapotranspiration, vegetation and dust addition) on interglacial paleosol development, and which factor plays a key role are inadequately studied in the Chinese Loess Plateau (CLP). Here, we examine the relative contributions of these factors on paleosol development on the CLP by a sensitivity analysis. For this, we simulate paleosol development using the climate-soil model LOVECLIM-SoilGen2.

The sensitivity analysis was done during two interglacials, MIS11 and MIS13, where MIS11 shows quite contrasting climate forcing with MIS-13. Several simulations were run; in each simulation, one parameter is allowed to change at a time (e.g. precipitation), and others are kept constant (as in reference). A reference simulation is included 100-year average values of the end of Holocene simulation mimicking the Pre-Industrial climate. Additionally, combined effects of climatic parameters (e.g. precipitation and evapotranspiration) were investigated, and mean absolute error was calculated between each of the sensitivity simulation and the actual simulation (combination of all soil forming factors).   

Our results show that precipitation has the largest influence on the depth redistribution of soil properties (calcite and clay) in MIS11 and MIS13 and dust addition is the dominant factor affecting the amount of simulated calcite and clay. Our results indicate that potential evapotranspiration has a pronounced impact during MIS13. Unlike the simulated MIS11 paleosol, which is explained by precipitation plus dust addition, the MIS13 paleosol development is better explained when potential evapotranspiration is also taken into account during this extreme interglacial. 

How to cite: Ranathunga, K. N., Finke, P., Yin, Q., and Wu, Z.: Modelling the relative effect of different climate factors, vegetation and dust deposition on the MIS-13 and MIS-11 paleosol development on the Chinese Loess Plateau, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4663, https://doi.org/10.5194/egusphere-egu22-4663, 2022.

A late Chalcolithic period site was discovered in central Tel Aviv during a salvage excavation that was conducted by the Israeli Antiquities Authority. The remains included 113 pits and shafts which were divided according to their shape into four groups:

Group 1: Round pits: a group that includes three types: small (0.5–0.6m diameter); medium (c. 1m); large (c. 2m). Some pits contained brown sediment mixed with ceramic fragments, animal bones, and flint; others had no archaeological finds.

Group 2: Bell shape pits

Group 3: Narrow, deep shafts 1–2m diameter, 3–6m deep. This group includes three types of shafts that differ from each other according to their shape: shafts with uniform width; conical shafts narrowing towards the bottom; shafts with a wide niche in the lower third. In some of the shafts, the fill consisted of brown sediments; some contained archaeological finds and some did not. In some of the shafts, the fill contained fragments of aeolian sandstone, sand, and anthropogenic brown sediment on top that sealed the fill.

Group 4: Shaft that opens into an underground space. Only one shaft like this was exposed.

Many questions arise about the function of these diverse shafts including why were so many of them mined?

Examination using the pOSL (portable luminescence method), showed that some of the shafts were used for a long time, and some were probably used for a short time, or not at all. From this, it can be assumed that the large number of shafts may be the result of trial-and-error style probing.

The pits which contained sand and rock fragments (group 3) had a section with a wide niche in the lower third and a thin clay layer. This suggests that these shafts served as water wells for the site inhabitants, which raises a further question: why was it necessary to dig wells along the Ayalon River? 

This will be discussed in the presentation

How to cite: Ackermann, O., van den Brink, E. C. M., Jakoel, E., Anker, Y., Roskin, J., and Asscher, Y.: The Secret of the Chalcolithic Shafts: Insights from the Portable Luminescence Method (pOSL), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6188, https://doi.org/10.5194/egusphere-egu22-6188, 2022.

Agricultural terraces are a well-known phenomenon in mountainous regions throughout the globe. Those structures are said to have been in the service of agriculture for several hundred or several thousand years. In different places and environments, terraces had different roles. It has been claimed that its primary goal in the sub-humid and semi-arid environments, was to preserve winter precipitation water within the terrace body. Endemic and domesticated vegetation will then flourish utilizing this resource throughout the dry summer season. Agricultural terraces are widely described in the literature as having three main parts, (a) the base, which is normally a naturally inclined bedrock surface, (b) a manmade retaining wall supporting the weight of (c) the terrace body, usually made of soil and gravel. The terrace base is described in all reviewed literature as an impermeable rock layer. However, previously published calculations suggested that in the sub-humid main mountain ridge of Israel, evapotranspiration will prevent retaining water even in a thick terrace body for the entire summer period. Moreover, in many terraces scattered across the given area, a few centimeters thick soil body seems to support decades and centuries old trees. Therefore, water retention mechanism in the agricultural terraces has been examined. Our study indicate that karst substratum is the controlling factor on terrace water retention. We propose that a well-developed, soil filled, karst system at the terrace substratum impedes the conventional evaporation process of a simple homogeneous soil parcel. Under such conditions, thin body terraces are able to support non-irrigated ancient agriculture water demand in sub-humid environment.

How to cite: Inbar, N. and Ackermann, O.: The role of karstic substratum of ancient mountainous agricultural terraces at the semi-arid environment, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6196, https://doi.org/10.5194/egusphere-egu22-6196, 2022.

Common anthropogenic surface features across Scotland and Ireland are raised beds, which are agronomic ridges and furrows created prior to the 20^th century to improve agricultural yield. Creating a raised bed improves yield by providing to the root zone better soil drainage, suitable micro-climatic conditions, and enrichment of organic matter and nutrients. Raised beds are structurally identifiable and can be examined using remote sensing techniques such as LIDAR imagery or aerial photography to analyze different dimensions of raised bed units. We examined the geomorphic parameters (height, length, breadth, ridge shape, furrow depth, unit orientation and block size) of raised beds found in the Fancroft region of County Offlay, Ireland. We developed a model of raised bed structural components and the distribution and change in soil properties including soil drainage, texture, horizon differentiation, soil colour, nutrient distribution, organic matter movement and the carbon influx and outflow have been provided. Our study aims to elucidate the typical geomorphic properties of raised bed landscapes, their basic chemical and physical soil properties and the landform attributes that may influence soil properties. Overall, the conceptual basis of raised bed landscapes have been visualised and presented to formulate an ideal raised bed theoretical model. Such a comprehensive model can be further extended to learn more about ancient agricultural practices, heritage, a causal link between present day and historical farming practices.

How to cite: Sekhri, S., Raab, T., and Drohan, P. J.: A Model Approach Assessing The Soil Properties Of Raised Bed Landscapes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7137, https://doi.org/10.5194/egusphere-egu22-7137, 2022.

Although Pliocene palaeosols can supply palaeoclimate information and help to disentangle stratigraphic reconstructions, soils are sparsely represented in global datasets for Pliocene climate. Pliocene was characterised by global mean annual temperatures 2–4 °C warmer than today, representing an analogue for future climate prevision. We aimed, thus, to investigate palaeosols as suitable archives for reconstructing geomorphic processes, ecosystems and climate patterns in the Pliocene.

We compared the palaeosol record stored in Zanclean and Piacenzian successions locate in central and southern Tuscany, respectively. Palaeosol morphological features observed in the field were used for the sequence-stratigraphic interpretation. To qualitatively evaluate soil development, we considered the time needed to attain various soil properties. Pedogenetic processes and the intensity of weathering were also quantified by applying a range of proxies based on geochemical analyses. Climofunctions based on major element ratios were used to estimate mean annual palaeoprecipitation (MAP). Carbon and oxygen isotopes analysis were performed on carbonate nodules, to verify their pedogenic origin and as a proxy for palaeovegetation and palaeotemperatures.

Though all soils are unconformities in the record, the rank and type of unconformity were defined in detail, to precisely place the soil formation time within the sedimentary sequence and to correlate soil-forming intervals with general environmental changes. Then, soil characteristics were interpreted, considering the geomorphological setting reconstructed by the stratigraphic and sedimentological analysis.

The Zanclean-age soils represent a presumably long-time span, likely a few thousand years, and exhibit strong redoximorphic features such as low-grade plinthite, suggesting that they developed in intervals of humid climate. The mid Piacenzian-age soils represent rhythmic and short intervals of pedogenesis, which correlate to sea level highstands. The main characteristics of palaeosols are due to clay shrink-swell properties (vertic) and carbonate translocation (calcic). Calcic features were interpreted as recording the duration of pedogenesis and thus of the sedimentary hiatuses, suggesting a range of development from 1,000 to 10,000 years. These soil features and the isotopic proxies converge towards indicating a highly seasonal rainfall pattern. This inference matches the sedimentological facies, which point to sediment transport and deposition from highly laden flood flows, recalling the sedimentary dynamics of seasonal fluvial systems. The hypothesis of a very high degree of rainfall seasonality would match well with existing palaeoclimatic records for the Mediterranean Middle Pliocene Warm Period (MPWP), and could shed light on certain unusual features in such records.

Comparing soils developed in the Early and in the Late Pliocene, the MAP estimates confirm the differences in climate condition which likely led to the divergent pedogenesis pathways. Furthermore, the palaeotemperatures estimated from the oxygen isotopic composition of pedogenic carbonates within Piacenzian calcic horizons, point to values matching the modelled temperatures for the MPWP.

How to cite: Andreetta, A., Benvenuti, M., Delgado-Huertas, A., and Carnicelli, S.: Buried palaeosols in Tuscan inland basins provide clues to changing climate conditions across the Pliocene, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7509, https://doi.org/10.5194/egusphere-egu22-7509, 2022.

Soils on relict charcoal hearths (RCHs), i.e. aged charcoal rich Technosols, feature documented legacy effects regarding their physical and chemical soil properties. These forest soils result from the pre-/early-industrial production of charcoal in upright standing hearths. Today, RCHs are found in forested areas as circular microrelief structures with average diameters of about 10 meters that contain technogenic soil horizons of about 20 cm thickness. RCH soils are most distinctly characterized by their large content of pyrogenic soil organic matter and consequently increased total carbon contents. The resulting changes in the soils’ cation exchange capacity, soil acidity, total nitrogen contents and total element stocks are often significant. Furthermore, changes in soil physical properties like a lower bulk density and a higher porosity result in changed soil-water- and temperature regimes. Combined, these effects potentially result in unique soil microhabitats that are restricted to relatively small, clearly defined areas in many forest ecosystems.

Recent studies on RCH soils increasingly focus on potential changes in microbiological and vegetational composition and abundances and report diverse effects. Here, we study the effects of century old charcoal rich Technosols on the drought sensitivity of Scots pine (Pinus sylvestris L.) on three RCH sites located in Lower Lusatia, Saxony (Germany). Through dendrochronologial analysis of increment cores and historical climate data, we study climate-growth relationships for trees on RCH soils and reference forest soils for two periods (AD 1963-1992 & AD 1990-2019). Furthermore, we determine pointer years and components of resilience to quantify the trees’ reaction to extreme weather conditions. This analysis was accompanied by soil sampling and analysis on the RCH sites and adjacent reference forest soils. Here, we present preliminary results and discuss them in the context of findings from other studies on RCH soils.

How to cite: Al Jobayer, M. A., Bloß, K., Porsch, C., van der Maarten, E., van der Maaten-Theunissen, M., Bonhage, A., Raab, A., Schneider, A., and Raab, T.: Drought sensitivity of Pinus sylvestris L. on century old charcoal rich Technosols in the North-German Lowland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7978, https://doi.org/10.5194/egusphere-egu22-7978, 2022.

The Spatiotemporal Variations of Provenance in the Chinese Loess Plateau by the Sensitivity of Quartz Optical Stimulated Luminescence

Jiao Li^1,*

^1,*Department of Geology, Northwest University, Xi’an710069, China

E-mail: ^1,*nwu_lijiao@163.com

Loess contains a lot of quartz, which is stable in nature and is not easy to be weathered and transformed. It can retain the original rock information, and the response of quartz crystals to radiation energy is obvious. Thus, optical stimulated luminescence (OSL) sensitivity can identify provenance. The magnetic susceptibility reflects the strength of the summer monsoon, and the grain size is a proxy for the winter monsoon. The magnetic susceptibility and grain size have been widely used in the study of Chinese loess as proxy indicators of the East Asian monsoon.

By studying the change of quartz optical stimulated luminescence sensitivity of loess-paleosol in the Xifeng section of the Chinese Loess Plateau, combined with the related work from others in the Chinese Loess Plateau, the provenance changes of the Chinese Loess Plateau in the time-space sequence were analyzed. In the time series, the sensitivity of quartz OSL showed a high value in paleosol, and the highest value was about 2700 counts/Gy/mg. Meanwhile, it exhibited a low value in loess, and the lowest value was about 200 counts/Gy/mg, which is different from paleosol. In the spatial sequence, the OSL sensitivity of quartz from west to east in the Chinese Loess Plateau has a large difference (8-10 times) in the interglacial (paleosol), and a small difference (1-2 times) in the glacial (loess). The sensitivity of quartz OSL preliminarily indicates that the provenance of the Chinese Loess Plateau has changed in time series (loess-paleosol). Moreover, in space sequence (among different profiles), the sensitivity of quartz OSL has changed in paleosol during the interglacial, but has a minor difference in the loess during glacial.

At the same time, combined with the study of magnetic susceptibility and grain size, the quartz OSL sensitivity corresponds well to the fluctuation of the climate proxy index, which shows that the quartz OSL sensitivity is positively correlated with the magnetic susceptibility and negatively correlated with the particle size. The OSL sensitivity and magnetic susceptibility of quartz were higher in the paleosol and lower in the loess; the variation of grain size was the opposite.

Keywords: quartz, optically stimulated luminescence sensitivity, loess provenance, glacial-interglacial, Chinese Loess Plateau

How to cite: Li, J.: The Spatiotemporal Variations of Provenance in the Chinese Loess Plateau by the Sensitivity of Quartz Optical Stimulated Luminescence, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9072, https://doi.org/10.5194/egusphere-egu22-9072, 2022.

Quantification of geomorphic processes governing development and long-term stability of vesicular A (Av) horizons in deserts is critical to understanding desert soil genesis and evaluating stability of desert surfaces. Previous attempts to date Av horizons have yielded Holocene ages that are discordant with underlying soil ages, leading some investigators to interpret Av horizons as recently formed features. In contrast, systematic increases in the expression of Av horizon development have been identified from studies that examine trends in soil morphology on Quaternary timescales. This study uses meteoric ¹⁰Be (¹⁰Be_met) as a radiometric tracer in the soil to (1) test the hypothesis that Av horizons are long-lived features in low-relief desert landscapes, and (2) enable improvement of dating techniques applicable to desert soils.

Meteoric ¹⁰Be concentrations were examined for selected soils within a chronosequence from the Mojave Desert, Southern California, USA. The pedons selected for analysis are from an alluvial fan sequence composed of mixed plutonic parent materials sourced from the adjacent Providence Mountains. Samples for ¹⁰Be_met analysis were collected from Av and underlying B horizons of three pedons of varying soil age and from an active alluvial channel to evaluate relationships between ¹⁰Be_met concentrations and soil exposure time. Additionally, two separate peds from the Av horizon of a single pedon were subsampled to evaluate the relative concentrations in four zones within individual Av peds, including the surface, bottom, sides, and interior.

Meteoric ¹⁰Be concentrations from Av horizons range from 6.95x10⁶ at/g (active channel) to 1.09x10⁹ at/g (oldest) and exhibit a systematic increase in ¹⁰Be_met concentration with increasing soil age. Similarly, samples obtained from underlying B horizons in Holocene to Pleistocene soils have ¹⁰Be_met concentrations of 1.34x10⁸ at/g (youngest) to 9.40x10⁸ at/g (oldest). The subsampled Av pedons show apparent physical fractionation of ¹⁰Be_met, primarily towards ped interiors, which contain 1.01x10⁹ to 1.09x10⁹ at/g ¹⁰Be_met. The remainder of the ped exhibits a comparative reduction in ¹⁰Bet_met concentrations by 12-38%. This trend is similar to carbonate and clay-particle trends that also tend to fractionation in Av ped interiors, indicating a greater proportion of moisture content in these zones relative to exterior ped surfaces.

Our preliminary observations strongly support the hypothesis that Av horizons are persistent and stable features in the landscape, contrary to prior studies that attempt to explain universally young Av ages using arguments that favor Av destruction and reformation in response to climate dynamics during and after the Pleistocene-Holocene transition. Our results have several major implications. First, Av horizons strongly influence the flux of water into the soil profile, thereby governing hydrologic, biologic, and pedogenic processes at and below the soil surface. This study will enable detailed investigation of the rates associated with primary moisture and sediment movement in desert soils. Second, our methodologies provide a technique that can be further developed to directly date Av soil horizons independent from the underlying sediment. Finally, our findings have the potential to inform the hydro-pedologic connectivity between Av horizons and underlying soil materials to enable a better understanding of soil genesis in arid environments.

How to cite: Sion, B., McDonald, E., Bustarde, J., and Hidy, A.: Meteoric 10Be analysis from a soil chronosequence in the Mojave Desert, USA reveals the long-term stability of Av horizons and potential avenues for future research, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9963, https://doi.org/10.5194/egusphere-egu22-9963, 2022.

Plot-and-Berm agroecosystems agriculturally utilized marginal lands in a sophisticated fashion, where a high-water table existed within loose, aeolian sand sheets, in semi-arid to Mediterranean climates. The agroecosystems consist of polygonal (~10⁴ m²) agricultural plots sunken between ~5 m high berms. Here we focus on the role of sandy anthrosediments and anthrosols, based on analyzing stratigraphic sections in remains of a Plot-and-Berm agroecosystem, 2 km south of ancient Caesarea (Israel). Geoarchaeological methods included pedological analysis, penetrometer measurements, GIS-based mapping, and portable luminescence (PPSL) and OSL for the analysis of construction and possibly maintenance stages.

Ceramics and glass date the agroecosystem to the 10^th-11^th centuries (Early Islamic period) that are compatible with preliminary published OSL ages. Preliminary finds hint to a sand substrate mixed during Roman times. Anthrosols in the plots have distinct upper and lower boundaries with limited root casts suggesting that the Early Islamic crops were annual and not woody perennial species like vines. The anthrosol is currently only 1 m above the modern groundwater table, which appears to have enabled easy access by hand-dug pits for manual irrigation practices per plot. Their topographic setting probably provided protection of the soil and crops from aeolian erosion.

The anthrosols and anthrosediments have geochemical and textural properties that appear to reflect their role. Anthrosols were enriched to enhance soil productivity. Berm crests and slopes were coated with ~0.3-0.7 m thick and dark anthrosediments that were topped with flat pebble to cobble size artifacts. This coupling remarkably preserved the berm morphology and the whole agroecosystem from aeolian and fluvial erosion until modern times. Light grey anthrosediments comprised the internal berm fill. Additional results will help assess the social-economic effort needed to develop and maintain this agroecosystem, and its relation to ancient Caesarea.

How to cite: Ostrowski, A., Taxel, I., Bookman, R., Robins, L., and Roskin, J.: Role of Anthrosols and Anthrosediments in the Early Islamic Plot-and-Berm Agroecosystem by Ancient Caesarea, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9973, https://doi.org/10.5194/egusphere-egu22-9973, 2022.

Understanding how present-day abrupt change may alter forest ecosystem services is becoming more important due to ever-growing anthropogenic stresses. Forest managers trying the adapt to anthropogenic stress can benefit from the study and quantification of past abrupt changes in forests, especially when the legacy of past disturbance is still evident. Across the United Kingdom, Europe, and recently the northeastern United States, the examination of historic forest change due to charcoal manufacturing for the firing of iron or lime furnaces is yielding new insights relative to landscape stability, anthropogenic vs natural soil genesis, and forest evolution. 

A landscape classification process was used in the Central Appalachians (Pennsylvania) to identify 6,758 RCHs near Greenwood Furnace (Greenwood Furnace State Park) and Pine Grove Furnace (Pine Grove Furnace State Park). Topographic wetness index (TWI), and SAGA wetness index (SWI) were created using ~1m LiDAR data for two study areas to quantify surface hydrology effects and were compared to field soil volumetric water content (VWC) measurements. Modeled TWI and SWI values were different for RCH areas when compared to surrounding non-hearth areas indicating that RCHs were acting as a moisture sink. We also found that RCH platforms have different TWI and SWI values than rim areas. Using field measured volumetric water content, we found that as distance from the center of the RCH increases, the drier the soil becomes. Geomorphic position did not affect wetness.

Surface soil samples were collected at 51 RCHs in the Greenwood Furnace study area. Laboratory analyses revealed that RCH soils have higher C content than surrounding native soils. Furthermore, while the pH of RCH soils is like native soils, the acidity is greater in RCHs. RCH soils at Greenwood Furnace were found to have lower Mehlich 3 P concentrations and lower K potentially effecting plant growth. RCH soils were found to have higher Ca concentration when compared to native soils.

To examine within RCH differences in soil chemistry and morphology more closely, 8 of the 51 RCHs were sampled intensely along a topographic gradient. Control pits were excavated directly upslope from the RCHs. The RCHs were sampled in 5 positions across the hearth from the upslope to down slope position (A upslope rim of the RCH; B halfway point between A and C; C RCH center; D halfway C and E; E downslope rim of the RCH).  Soil profiles were described and sampled at each position. The soil samples were analyzed for trace and rare earth element content (Aqua Regia digestion), soil pH (water) and fertility (Mehlich 3 extraction).  Results indicated that RCHs are potentially a unique location of refugia for forest flora and perhaps fauna due to the unique geochemistry with higher bases and C and some concentrated metals and a higher soil water content hypothesized to be due to an observed restrictive morphology. Future research should more closely investigate whether RCHs support unique species assemblages and how they may play a role in enhancing today’s forest biodiversity.

How to cite: Drohan, P., Bayuzick, S., Guarin, D., Raab, T., Bonhage, A., Diefenbach, D., and McDill, M.: USA Appalachian relict charcoal hearths have complex landscape and pedologic patterns that are unique from surrounding forest ecosystems, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10315, https://doi.org/10.5194/egusphere-egu22-10315, 2022.

In the southwestern coast of Sardinia coastal sediments preserve evidence of geomorphic processes such as slope, colluviation and pedogenesis, as well as human activities. We present the preliminary results of an integrated approach focused on descriptive and analytical soil investigation together with micromorphological data, geoarchaeological investigations and landscape survey as part of a larger project aimed to characterise the geoheritage of the region. We describe palaeosol sequences related to stratal architectures that date back to the Late Pleistocene. Our goal is to gain information on landscape evolution in the area and the effect of human agency on the larger environment, as well as document hydroclimatic change.

At the current coastline level, the last marine transgression exposed marine sequences dated to the MIS5, later covered by fluvial and slope deposits throughout the last portion of the Late Quaternary. Several soil sequences show traces of recent colluvial events of anthropogenic origin. Such deposits contain pottery and other human made materials related to the Iron/roman age. These initial findings seem to suggest a strong control of human activity on environmental change in the area, not related to a single location but widespread in the landscape. This control was such to cover and take precedence over the natural pre-existing surface dynamics, thereby complicating the definition of Anthropocene in Sardinia. Further investigations would bring more light on the ways palaeosols can inform on the shifts in human land use and occupation. How has land use accelerated since the Bronze age? How can these palaeosequences inform us about anthropogenic processes overstepping natural ongoing surface dynamics?

How to cite: Nicoll, K., Mariani, G. S., and Mellis, R. T.: Palaeosol evolution and human disturbance on Mediterranean coastal pedosequences (SW Sardinia, Italy), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11536, https://doi.org/10.5194/egusphere-egu22-11536, 2022.

Charcoal has been produced for centuries, even millenia, in and near forested areas in Europe. The relics are increasingly studied to inform, e.g., on forest composition and woodland exploitation, the effects of biochar on soil properties and plant nutrients, and carbon sequestration. All these studies require a chronological framework, which is most commonly established using radiocarbon (¹⁴C) dating. In NW Europe, however, many relic charcoal kilns have been found to post-date 1650 CE. Owing to limitations imposed by the calibration curve for the last few centuries, ¹⁴C dating results in wide age probability distributions; this implies that the method does not allow resolving the chronology for post-1650 CE features.

In this study, we report on our experiences with optically stimulated luminescence (OSL) dating as a complementary and alternative method to ¹⁴C. The approach uses sand-sized quartz extracted from sediments that were heated during charcoal production. Our study comprises relic charcoal kilns on silty and sandy subsurfaces in Belgium (Sonian and Zoersel forest), The Netherlands (The Veluwe) and France (Grand-Est region). We first demonstrate that OSL dating can yield accurate and precise ages by comparing our results for pre-1650 CE features with independent (¹⁴C) age information. Intricacies, possibilities and limitations are discussed. For most of the features, widely adopted OSL procedures can be applied; for one of the study areas (Zoersel forest, in the northern Belgian sand belt), dedicated analysis using single grains of quartz is the method of choice. We then apply our methodology to post-1650 CE features, for which ¹⁴C dates and or historical information is available. We show that, for the majority of the investigated features, accurate OSL ages can be obtained with a precision that is similar or significantly better compared to independent age information. A considerable added value is the potential of OSL dating to distinguish between multiple features at one or comparable sites with an unprecendented time-resolution of 5 - 40 years (and 95.4% probability).  

 Keywords: OSL dating; radiocarbon dating; relic charcoal kiln; Modern age; natural resources.

How to cite: Karimi Moayed, N., Vandenberghe, D., Buylaert, J.-P., Deforce, K., Debeer, A.-E., Biernacka, P., De Smedt, P., De Clercq, W., and De Grave, J.: Optically stimulated luminescence dating of relic charcoal kilns using sand-sized quartz: a status report, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13221, https://doi.org/10.5194/egusphere-egu22-13221, 2022.

Developing more sustainable agricultural systems represents a challenge and urgent global venture. A sustained collaboration among researchers from diverse fields, policymakers, and the public at large is necessary to deal with this complex global emergency. Landscape archaeology can actively contribute to this movement by exploring the interactions of social and environmental systems over long periods of time and generating insights for potential future applications. Environmental sustainability and historic landscape conservation are typically treated as two separate fields. Still, this research proposes a new way to embrace cultural and natural values as components of the same landscape management plans.
Over the long term, rural activities have given rise to a wide variety of historic landscapes. Historic Landscape Characterisation (HLC) uses a qualitative but formalised method to map historic landscapes' chronological and spatial complexity. Each HLC study uses GIS to map 'historic landscape character types' (HLC types) based on distinctive characteristics which result from known historical processes. Meanwhile, in environmental studies, the diachronic land-use-land cover (LULC) analysis has helped illustrate how different anthropogenic activities have altered the soil erosion rate in specific areas. Modelling can provide a quantitative and consistent approach to estimating soil erosion under a wide range of conditions. GIS integration with the RUSLE (Revisited Universal Soil Loss Equation) model has been applied to estimate soil loss at a regional scale. It has resulted in implementing soil management and conservation practices to reduce soil erosion in fragile ecosystems. In previous HLC studies, LULC has been evaluated from the perspective of cultural heritage. In contrast, RUSLE modellers have used it as a proxy for the LULC of an area (i.e. absence or presence of tree canopy) and its effect on soil erosion. 
This study proposes an innovative methodology that combines both the historical/cultural and the environmental values of LULC to inform the development of a model to evaluate the increasing/decreasing soil erosion rate. From a cultural heritage point of view, the diachronic analysis of historical features (mapped as HLC types) informs understanding of the LULC, which characterised a landscape. At the same time, these features had an impact on local soil erosion rates. In this study, the HLC types have been employed to define the C and P factors, the two most challenging factors to be determined in the RUSLE equation. In literature, the C factor is usually derived from automatic satellite detection (e.g. CORINE), resulting in a low detailed characterisation of the LULC types, especially in the case of local agricultural activities. Conversely, the P factor is often taken equal to 1 because of the lack of geospatial data about the conservative practices adopted regionally (e.g. occurrence of terraced systems, hedgerows or contour ploughing). 
The methodology proposed has been tested in the Tuscan - Emilian Apennines historical landscape (Vetto - Italy) with the aims to assess: i) how the changes in the LULC in the past 70 years impacted the soil erosion rate, and ii) which HLC types perform better in term of soil erosion mitigation.

How to cite: Brandolini, F. and Turner, S.: A landscape archaeological approach to estimate the cover-management and conservation practice factors for RUSLE models., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-83, https://doi.org/10.5194/egusphere-egu22-83, 2022.

Agricultural terraces, which demonstrate an ingenious and sustainable way of transforming hilly slopes into arable land, are widespread in Mediterranean landscapes, stretching from southern Portugal to the Judean Highlands. Despite their ecological and heritage values, there remain significant temporal and spatial gaps in understanding their histories, how they were constructed and what their socio-economic implications were for early populations. This lack of knowledge further restricts understanding the effects of terracing on landscape in terms of mitigating the impacts of past climate change and informing sustainable strategies for the future of land-management. 

To this end, we employed a multidisciplinary approach to a case study in Naxos, Greece. A GIS-based technique which uses a range of cartographic remote sensing data was employed to identify over 20 terrace sites, and trenches were hand-dug and placed in a relative chronological sequence using a portable optically stimulated luminescence (OSL) dating reader and gamma spectrometer. Samples were then collected for absolute OSL dating, micromorphology and x-ray fluorescence (XRF) analyses. Trench profiles were documented using high-resolution image-based modelling for accurate sample location and volumetric reconstruction of soil layers, and historic and modern aerial spaceborne data were used together with sample results to create models of terrace systems for spatiotemporal analyses. 

The results of this multidisciplinary approach adopted here have produced evidence of large-scale land-use in periods for which no other evidence indicative of landscape exploitation survives. A chronological framework based on over 25 OSL ages suggests terrace construction in Naxos between ~400 BC and the 16^th century AD with intensification during the Medieval Greek period. Applications of soil micromorphology and XRF analyses identify key evidence of natural soil development and past land use including irrigation, soil mixing, crop residues and anthropogenic fertilisers. Modelling of terrace system development indicate their value as long-term resilient, adaptable agricultural and environmental features: where terrace systems have been maintained, reused, or abandoned under vegetation landscapes appear to maintain greater stability, retaining valuable soils and habitats compared to areas where terrace systems have been affected by overgrazing or consolidated by mechanical means. We conclude that our multidisciplinary approach has concomitant implications for the future sustainability and biodiversity of Mediterranean landscapes and beyond. 

How to cite: Srivastava, A., Kinnaird, T., Turner, S., Sevara, C., Holcomb, J., Lekakis, S., and Shillito, L.-M.: Agricultural terraces in the Mediterranean: a multidisciplinary approach to understanding human-landscape interactions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-580, https://doi.org/10.5194/egusphere-egu22-580, 2022.

The temple areas in ancient Egypt were most sacred and characterized by a multitude of elements that emphasized their importance and enabled daily cultic activities. Very specific and important features of such temples were sacred water canals or lakes, the so-called Isheru, which provided water for all kinds of purification rites and activities. In addition to textual records, preliminary sedimentological analyses of core drillings and geophysical surveys provided geoarchaeological evidence of a sacred water body at the Temple of Bastet in the ancient city of Bubastis. To further explore the location, shape, or course of the already detected canal and to find evidence on the existence of a second waterway described by Herodotus in the 5th century BCE, 34 drillings and five 2D geoelectrical measurements were carried. Drilling and sediment analyses revealed loamy to clayey deposits with a thickness of up to five meters near the northern and southern enclosures of the Temple of Bastet. 2D electrical surveying confirmed the drilling results, indicating trench-formed layers of low resistivity values. The recovered deposits were interpreted as fluvial sediments, most likely deposited in a very low energy system, e.g. a canal or lake. Evidence of these fluvial sediments in numerous boreholes allows the reconstruction of two separate sacred canals both north and south of the Temple of Bastet. In addition to the course, the width of the canals of about 30 m can also be confirmed according to Herodotus' writings. The presence of numerous artefacts in the fluvial deposits, such as ceramic and limestone fragments, proves the anthropogenic use of the ancient canals. Presumably, these waterways were connected to the Nile via a tributary or canal located west or northwest of Bubastis.

How to cite: Meister, J., Garbe, P., Trappe, J., Ullmann, T., Es-Senussi, A., Baumhauer, R., Lange-Athinodorou, E., and Abd El-Raouf, A.: The Sacred Waterscape of Ancient Egyptian Temples - The Example of the Temple of Bastet at Bubastis, Nile Delta (Egypt), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1436, https://doi.org/10.5194/egusphere-egu22-1436, 2022.

Stone mounds and water conduits dating from the Nabatean, Roman and Byzantine periods (4^th century B.C. to 7^th century A.D.) can be found on hillslopes over large areas in the Negev Desert, as well as in other parts of the Middle East and North Africa.

Based on results from field and laboratory experiments it is suggested that the ancient farmers were very efficient in harvesting water; they took into consideration the size and position of the stones when clearing the hillslope surface in order to increase the overland flow yield.

A comparison of the volume of stones in the mounds to the volume of surface stones from the surrounding areas indicates that the ancient farmers removed only stones that had been rested on top of the soil surface and left the embedded stones untouched. According to the results of simulated rainfall experiments, this selective removal of stones increased the volume of overland flow generation by almost 250%, for small rainfall events, compared to natural untreated soil surfaces. In addition, they realized that installing closely spaced conduits running in parallel along the hillslope would increase the trapping efficiency of overland flow on its way downslope.

This means that the ancient farmers have been well aware of the mechanisms of overland flow generation on stony soils and of overland flow dis-continuity on arid hillslopes.

How to cite: Lavee, H.: Water harvesting by ancient farmers in the Negev desert, Israel: Overland flow generation and continuity considerations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3091, https://doi.org/10.5194/egusphere-egu22-3091, 2022.

It is well-known that floodplain fine-grained alluvial sedimentation rates have been increasing due to human impact. In most catchments, the onset or acceleration of floodplain deposition is dated to medieval times, which has been attributed to increased hillslope soil erosion due to high population densities causing deforestation and slope instability. The also increasing river sediment load has then changed rivers into a single-thread, meandering channel pattern, which is now considered to be the ultima ratio in river restoration. In this presentation, we challenge this view and argue that current channel pattern and shape are related to historic channel engineering, and are hence not the product of fluvial processes associated with a meandering, or avulsing single-thread river system. Here, we present a study from a mountainous region in central Europe (Germany), in which we reconstruct the natural, pre-medieval channel pattern of two low order streams (3rd and 4th Strahler order), and their transition into the current, single-thread channel pattern which is characterised by meanders. This study is based upon a multi-proxy analysis of the chrono-stratigraphy, cross-valley ground penetrating radar, river surveying, analysis of historic maps, and hydrological data for channel pattern prediction. Finally, based on our analysis, we suggest that currently observed channel widening processes and island formation likely represent a tendency of the studied streams to re-create a braided channel pattern, which should be embraced by river management instead of forcing streams into a meandering pattern, as multi-thread, braiding channels are the most natural condition for these streams,  producing a sustainable and resilient river ecosystem.  

How to cite: Larsen, A., Engelmann, C., Fuelling, A., Candel, J., Bork, H.-R., and Larsen, J. R.: Historic river floodplain engineering causes channel pattern shift from multiple to single-thread rivers, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3896, https://doi.org/10.5194/egusphere-egu22-3896, 2022.

Since the Pleistocene, the Mediterranean is a hot spot for climate change and human migrations, thus offering the opportunity to investigate how human populations have responded to environmental changes and sea level variations. This is the main topic of the SPHeritage Project (MUR grant: FIRS2019_00040, P.I.: M. Pappalardo) that proposes an interdisciplinary approach to investigate the human-environment interaction (in particular sea level variations) over the last 400,000 years using a combination of micro-invasive methods. The Project is re-investigating the well-known archaeological area of ​​the Balzi Rossi (Ventimiglia, at the border between Italy and France), which represents a unique assemblage of archaeological sites dating to the Palaeolithic, distributed in a geomorphological setting rich of markers of past sea level changes. As most of the local archaeological sequences have been extensively investigated at the beginning of the last century and large part of the deposits removed, we will combine the analyses of materials preserved in museums (including strips of sediments) and the remnants still preserved inside many rockshelters and caves of the archaeological complex. Moreover, our geomorphological survey identified new sedimentary sequences preserving information on relative sea level changes. This approach will permit to obtain innovative data submitting small samples to state-of-the-art methods for dating and palaeoenvironmental reconstruction, thus offering the opportunity to better constrain the time and steps of climate change, sea level oscillations, and human settlements. Moreover, data will converge into geoheritage analyses aimed at finding the best practices for promoting and protecting the site. Here, we present an overview of the project and preliminary results from some of the major archaeological sites.

How to cite: Zerboni, A., Bollati, I. M., Forti, L., Gazzo, S., Moussous, A., Muttoni, G., Negrino, F., Notter, O., Pelfini, M., Perego, A., Perini, S., Ragaini, L., Regattieri, E., Rossoni-Notter, E., Rovere, A., Ryan, D., Serradimigni, M., Starnini, E., Vacchi, M., and Pappalardo, M.: Upper Pleistocene sea level changes and human peopling at the northern margin of the Mediterranean Sea: the S-P-Heritage Project, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4794, https://doi.org/10.5194/egusphere-egu22-4794, 2022.

The intra-mountain Medjerda Valley is located in North Tunisia and is characterized by its namesake the Oued Medjerda. The Valley has been settled since at least the latest Paleolithic period. Archaeologists from the German Archaeological Institute (DAI) have been studying the region since 1965, concentrating on Roman settlements. Since January 2021 the joint research project “Conquest, Ecology and Economy in Islamic North Africa: The Example of the Central Medjerda Valley” focuses on the subsequent Islamic settlement of the middle Medjerda Valley between Late Antiquity and the Early Medieval Period. The overall project aims to understand the economic and social transformations of the region triggered by the Muslim conquests and subsequent regime changes.

As part of this project, we want to focus on sediment archives in the immediate hinterland of the archaeological sites Chimtou and Bulla Regia, which are located in the central Medjerda Valley. We want to increase our knowledge on local changes in environmental conditions to establish a knowledge base on how economic and social change of the region affects the landscape balance and sediment fluxes.

In this presentation we will present a morphometric analysis of the study area: a GIS-based classification of landforms by applying the algorithm Geomorphons and results from a soil erosion model (USPED). Our results show that combing both methods allows us to derive information on landscape sensitivity, increases our process understanding and supports identify areas of erosion and deposition. Although we currently do not have the opportunity to go into the field, we here introduce a methodological framework, which allows a first geomorphological characterization of a study area – nevertheless, ground checking will be a task for future field work.

How to cite: Pagels, J., Bebermeier, W., and von Rummel, P.: Geomorphometric analysis for the hinterland of the roman sites Chimtou and Bulla Regia (Central Medjerda Valley), North Tunisia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4961, https://doi.org/10.5194/egusphere-egu22-4961, 2022.

       The traditional view on Mesopotamian resources strategies is understood as “resource hunting” in which Mesopotamian empires would have spread to neighbouring regions (Zagros, Taurus, Levant…) to monopolize their resources. Indeed, Mesopotamia lacks some resources/raw materials such as copper, iron, wood, obsidian, and others. Our RessourceCultures approach, developed in SFB 1070, aims to define resources in a wider spectrum, to propose new interpretations on cultures development in this region. By investigating new patterns rules of resources appropriation and uses in peripheral areas, we hope to bring interesting new results. Our survey covered an area of 4.400 km² from the western foothills of the Zagros mountains to the eastern riverbank of the Tigris. 

      To unravel the patterns that define a ResourceCulture we combine both archaeological and geoarchaeological data into a machine learning approach. Many features (topography, water, soil type, resources availability, climate…) influence the founding and location of settlements in different ways and degrees of importance. The trend of these influences can be analyzed through machine learning models in predictive archaeology. Letting the machine run predictive models and underline the relationship between each feature and settlement dynamic will potentially help us to better understand how resources were used in a cultural and economic context through time and space.     

           Our poster will present the first ideas derived from the machine learning approach: Is there any trends appearing and what can we say from them? Can we redefine the ResourceCulture in Northern Mesopotamia through these new interpretations? 

How to cite: Bellat, M., Glissmann, B., Rentschler, T., Schmidt, K., Sconzo, P., Pfälzner, P., and Scholten, T.: Unraveling archaeological settlement, landscape, and resource use patterns with machine learning in Kurdistan (Iraq), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6021, https://doi.org/10.5194/egusphere-egu22-6021, 2022.

Neanderthals are believed to have been adapted to cold climate conditions, nevertheless Neanderthal findings in the north and northeast European region are scares, non-existing or at least speculative. In between periods of arctic and subarctic conditions, warm periods like the Eemian interglacial would have offered mild living conditions in present-day southern Scandinavia and have evidently allowed migration of prey species to the region. We therefore suggest that the apparent absence of Neanderthals in the geological record here is partly steered by poor conditions of conservation, lack of in situ archives and lack of focused investigation, rather than a limit of the Neanderthal habitat per se. In this paper we seek to identify potential hotspots for Neanderthal activity in the geological record. We do this by mapping the paleolandscape from all available data sources and by 3D paleolandscape modelling, to identify potential Neanderthal living sites such as lake beaches, seashores and floodplains, where there would be easy access to water, prey and open habitat. Among the possible candidate sites, we will investigate by means of coring, whether the shores from Eemian lakes offer good conditions for preservation of potential find layers, as they might have a low degree of disturbance and in rare cases can offer in situ burial and conservation of interglacial fossils, archaeological material and sedimentary climate archives.

How to cite: Nielsen, E. S., Nielsen, T. K., and Kristiansen, S. M.: Human-environmental interaction possibilities at the Neanderthals’ northern edge: focus on last interglacial and early last glacial, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7189, https://doi.org/10.5194/egusphere-egu22-7189, 2022.

China’s Yellow River, which gains its name from the extraordinary amount of yellow-brown silt it entrains, was not always so yellow. Current historical and geological evidence suggest that the Yellow River experienced several periods of human-induced transformation that have not only changed the color of the Yellow River’s water, but also fundamentally altered the river’s hydrological properties, specifically by increasing the Yellow River’s propensity for catastrophic floods. In this paper, I argue that the long history of soil erosion and Yellow River floods is a defining characteristic of China’s incipient Anthropocene period and can be understood through the application of geoarchaeological methods and frameworks. Specifically, I focus on how extreme Yellow River flood events at Kaifeng, a former capital of dynastic China, have shaped the city’s urban resilience in the wake of a flood that killed over 300,000 people in AD 1642. Recent geoarchaeological excavations have discovered evidence that reveals the AD 1642 Yellow River flood destroyed Kaifeng’s inner city, entombing the city and its inhabitants within meters of silt and clay. I argue that the geology of the Yellow River floods and the socio-political context of Kaifeng shaped the city’s resilience to extreme flood events. Through this example, the long-term consequences of China’s early Anthropocene are brought out in sharp relief. Flood events like at Kaifeng not only represent significant hydrological shifts in the Yellow River, but also had dramatic social consequences as numerous Yellow River floods have coincided with the collapse major Chinese dynasties. In conclusion, I suggest that a deeper understanding of the origins and long-term development of the Yellow River as a coupled human and natural system is fundamental to designing more sustainable solutions to managing the Yellow River and other large, muddy, rivers around the world.

How to cite: Storozum, M.: The Anthropocene Geoarchaeology of the Yellow River , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7996, https://doi.org/10.5194/egusphere-egu22-7996, 2022.

The role of climatic or human forcing for Holocene silt-clay overbank sedimentation in Central Europe has been debated for decades. To date, former studies were often limited by rather low chronological resolutions of the fluvial stratigraphies, and especially by records of human activity in the studied catchments with rather fragmentary spatial and chronological resolutions.

Within the frame of an interdisciplinary geoarchaeological project carried out in the Weiße Elster catchment in Central Germany, using drill cores, geophysical measurements, sedimentological and micromorphological analyses as well as numerical dating along three transects, we build up a highly resolved record of fine-grained fluvial sedimentation along the middle river reach. Complementarily, based on archaeological data stored in local area files of the State Offices of Archaeology as well as on historical and onomastic data, we build up a catchment-wide record of human activity from the Early Neolithic period until the High Middle Ages with a so far unprecedented high spatial and chronological resolution in Central Europe. Comparing these geomorphologic and archeological/historic datasets with highly resolved paleoclimatic records allows a large step forward in understanding the intricate interplay of the Holocene geomorphodynamics with climate changes and human activity with an exceptional spatial and chronological resolution. So far, first results demonstrate a significant impact of climatic events such as the Little Ice Age on river activity that were linked with fine-grained sedimentation also after the start of intensive human activity in the catchment since the Early Neolithic period ca. 7.5 ka.

How to cite: von Suchodoletz, H., Fütterer, P., Zielhofer, C., Veit, U., Ettel, P., Werther, L., Stäuble, H., Tinapp, C., Schneider, B., Sprafke, T., Werban, U., Ballasus, H., and Miera, J.: Holocene silt-clay overbank sedimentation between climate change and human activitiy within the fragile loess-covered Weiße Elster catchment in Central Germany, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8894, https://doi.org/10.5194/egusphere-egu22-8894, 2022.

The Cerro Colorado Cultural and Natural Reserve is located on the north-eastern slope of the Sierras Pampeanas, Córdoba mountain sector, Argentina (30° 05' S 63° 55' W). This locality is well known for the impressive archaeological legacy recorded in rock art, almost 4200 painted and engraved motifs preserved inside sandstone shelters, made from ca. 400 AD until the arrival of the Spanish conquers in the XVI century. While previous research in the study area has focused mainly on archaeological sites, this work describes the sandstone landforms diversity. In this sense, some of the most geodiversity sceneries on Earth are supported by sandstones, solely or dominating over other rock types, and protected by different institutions as UNESCO. This study aims to characterize the geodiversity of Cerro Colorado by documenting the variety of sandstone morphologies and understanding their possible process origins within a global context. This contribution offers theoretical and applied knowledge that is of interest to different areas of environmental reconstruction and geoarchaeological research. The methodology includes 1) field survey and data collection, 2) sandstone landform inventory, 3) the estimation of the morphological component of geodiversity through the geomorphodiversity index (GmI). ALOS PALSAR DEM at 12.5 m spatial resolution was used as primary data. GmI = S + A + Dv + Ch + Cv + TPI + TWI + TRI; where, S: slope, A: aspect, Dv: deep valley, Ch: horizontal curvature, Cv: vertical curvature, TPI: topographic position index, TWI: topographic wetness index, TRI: topographic roughness index. The GmI was carried out on SAGAGIS through Rao's Q diversity index tool. The landforms are the results of the weathering and erosion processes caused by regional climate changes throughout the geological past (from the Mesozoic to the present day). The GmI considers five classes. The very low and low classes predominate in the study area (55%). The very low diversity refers to plains and eroded short sandstone hills connected with planation surfaces, pavement, and massive domes. The low range is associated with undulating and smooth sandstone shapes. The medium class shows undulating surfaces and the transition to moderately-strong slopes (8-14º). The high diversity is characterized by the middle slopes (14-20º), dominated by cavernous forms as tafoni and caves carved on the cliffs and standing out the presence of tors and rock balance. The very high class comprises steep slopes and deep valleys related to the highest sandstone heights (880 m.a.s.l.). The shelters (high class) contain native rock art paintings which conservation requires geomorphological knowledge to prevent degradation. The sandstone geodiversity of Cerro Colorado is one of the most attractive assets of the central Argentina region. Moreover, taking into account the pre-Hispanic archaeological legacy, this site presents a unique geomorphological and cultural heritage. Hence, the reserve needs special attention for geotourism promotion, scientific and educational uses, world heritage. This contribution allows (i) bridging the relationship between human interaction and sandstone landscapes which research line has not been developed yet for the study area, and (ii) considered an integrated management plan for geocultural conservation.

How to cite: Boretto, G., Cioccale, M., Gordillo, S., Carignano, C., and Recalde, A.: Geodiversity and Geoheritage of sandstone landscape: Cerro Colorado, Córdoba, Argentina, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9325, https://doi.org/10.5194/egusphere-egu22-9325, 2022.

The introduction of vertical mobility for agro-pastoral activities marks an important change in prehistoric society, which has altered the socioeconomic structuring of Alpine areas. It has also had severe consequences for the high Alpine ecosystems, including the destabilisation of soils, sustained vegetation disturbance, and lake eutrophication. With climate change and increasing anthropogenic pressure to Alpine environments, it is critical to better characterise the interaction between natural and anthropogenic factors that have shaped Alpine environments during the last millennia.

We present a Holocene record of domestic and wild animal presence through sediment-DNA analysis from a lake sediment core from the Eastern Swiss Alps and study the effects on soil erosion and vegetation composition. We provide direct evidence for the onset of pastoralism around 5,000 years BP, after which the site became repeatedly abandoned and re-occupied. According to our sediment-DNA reconstructions, several domestic species are present during early occupational periods, while cattle herding has become dominant during the last millennium. The latter period also coincides with a severe change in vegetation composition. Pastoral activities have had marked effects on soil erosion, while catchment deforestation already occurred ~2,000 years prior to the first findings of DNA from domestic animals, suggesting that the onset of Alpine pastoralism did not cause severe vegetation changes in our catchment. Further, sediment-DNA findings indicate that wild animals avoided near-shore territories during periods of human occupation, but returned to the lake shore upon site abandonment.

Our study opens a new perspective on long-term human-environment interactions in Alpine environments by providing direct evidence for animal presence and diversity and linking this information to physical and ecological factors such as soil erosion and vegetation change.

How to cite: Morlock, M. A., Rodriguez-Martinez, S., Huang, D. Y.-T., Glaus, N., Anselmetti, F. S., Vogel, H., Rey, F., Heiri, O., Dwileski, A., and Klaminder, J.: Direct evidence for 5,000 years of Alpine pastoralism: how lake sediments inform about animal diversity, soil erosion and vegetation change, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9339, https://doi.org/10.5194/egusphere-egu22-9339, 2022.

The geological substrate and its landforms, as main providers of natural resources, have a clear influence on landscape management practices The landscape evolution of the island of Sardinia (Italy) during the Holocene has strongly influenced the populations settled there, especially during the Bronze Age. We constructed a map of the land units in the southwestern corner of Sardinia and compared them with the distribution of known Bronze Age megalithic towers called nuraghes. Our aim is to understand which factors represent relevant criteria for settlement and try to infer possible causes.

The vast majority of nuraghes are located in proximity to river networks at low and mid elevations. Most densely settled areas also show the highest landscape diversity with a variety of land units much higher than the rest of the territory. Another potential factor affecting the location choice for nuraghes is the presence of elevated outcrops, which provide the advantage of a raised position and of stable foundations. The interaction of human dispersal patterns with landscape features can provide useful information on the sustenance strategies of past communities. It can therefore be interesting to consider the combined effect of geodiversity and landscape diversity in order to build more accurate dispersal models.

How to cite: Mariani, G. S., Brandolini, F., and Melis, R. T.: Insights into the role of geology in human occupation strategies in Bronze Age Sardinia (Italy), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9549, https://doi.org/10.5194/egusphere-egu22-9549, 2022.

The analysis of steroids (stanols and stanols compounds) preserved within Holocene sediment records represents a novel approach to establish past periods of human and herbivore occupation in the Atlas mountains of Morocco. These organic compounds are faecally produced by omnivorous and ruminant mammals; the concentrations and ratios of the compounds are used in this study as proxies for past dynamics of human presence. In this study, stanol analysis is employed in tandem with multiproxy sedimentological, palaeoecological and geochronological data of a lake-margin sediment core to evaluate Holocene human presence around the high-elevation wetland system of the Yagour Plateau, in the High Atlas mountains (31.31°N, 7.60°W, 2460 m.a.s.l.). The site is a vital resource for modern pastoral communities, providing fodder for livestock during seasonal dry periods. Cultural institutions known as Agdals regulate access to this wetland and have been established since early-historic times at least. The Yagour Plateau is well-known for its remarkable abundance of undated petroglyphs, which may relate to the territorial delineation of these Agdals. However, direct dating of archaeological remains is rare and the timing of human presence on the High Atlas rangelands is not well known. Information gained on the dynamics of human presence of remote, high-elevation sites in the High Atlas may be helpful in improving the understanding of the relationships between Holocene climatic, anthropogenic and ecological signals. Here, we present new data from 25 stanol samples spanning the last 13 kyr, complemented by two multiproxy records that include pollen, charcoal and non-pollen palynomorphs. The temporal context of these proxy records is underpinned by high-resolution age-depth radiocarbon chronology. We observe elevated stanol ratios from 6.2 cal ka BP to modern times, likely indicating intermittent human presence on the plateau since the Mid-Holocene. High coprostanol concentrations between 4.9 to 4.0 cal ka BP are similar to modern levels and indicate peak human presence. Faecal biomarkers match well with pollen-based anthropogenic indicators, particularly Plantago pollen abundance. This study supports a significant human presence on the Yagour Plateau from the Mid-Holocene onwards, contributing to the study of long-term human presence and climate dynamics in a sensitive mountain region at the boundary of the Atlantic and Saharan climate systems.

How to cite: Cornelissen, H., Lupien, R., Fletcher, W., Hughes, P., Bell, B., Rhoujjati, A., Ewague, A., and Fink, D.: Ancient steroids: Human faecal signals and environmental data from a Holocene sediment record of the Yagour Plateau, High Atlas, Morocco, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13327, https://doi.org/10.5194/egusphere-egu22-13327, 2022.

Generalist species vary in resource use with environments. High intraspecific variation in resource use may hamper trophic niche differentiation and coexistence of microarthropod species. To better understand intraspecific niche variation, we quantified stable isotope ratios of carbon (δ¹³C) and nitrogen (δ¹⁵N) within and between populations of 40 Oribatida species (Acari) that co-occur in litter (O_L) and soil (0–5 cm, mainly O_F/H, A_H) of five forest types (native European beech, non-native Douglas fir, range-expanding Norway spruce, two beech–conifer mixed forests). Although stable isotope signature of bulk material differed between litter and soil, δ¹³C and δ¹⁵N values of Oribatida species were remarkably stable irrespective of soil depth. Furthermore, Oribatida were more enriched in ¹³C in European beech than in coniferous forests, but δ¹⁵N values of Oribatida were similar across forest types. We conclude that trophic position (δ¹⁵N values) of Oribatida species is highly consistent across forest type, and that Oribatida species occupy virtually identical trophic niches (δ¹³C and δ¹⁵N values) irrespective of the soil depth they colonize. Despite that stable isotope analysis cannot reveal what animals actually feed on, our results suggest that low intraspecific variability facilitates niche differentiation and coexistence of Oribatida species. Overall, the results indicate that generalist species of soil microarthropods may be highly consistent in their resource use irrespective of environments. 

How to cite: Lu, J. and Scheu, S.: High consistency of trophic niches in soil microarthropod species (Oribatida, Acari) across soil depth and forest type, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-58, https://doi.org/10.5194/egusphere-egu22-58, 2022.

Soil structure is a dynamic property of soils which undergoes continuous changes due to various abiotic and biotic drivers. At the same time, the spatial arrangement of pores, organic matter and minerals influences soil functions, such as storage and filtering of water, nutrient cycling, or habitat for soil organisms and plants. In terms of carbon storage and matter turnover, the rearrangement of soil structure and herewith the change in accessibility of soil carbon for microbial decomposition is highly relevant. However, the turnover of soil structure and its constituents is difficult to quantify. In this study, a new method of structure labelling with inert garnet-particles in combination with X-ray µCT was used to determine the turnover rate of macro-aggregates and their drivers in two field experiments. Trials were conducted in topsoils of a Chernozem and a Luvisol under grassland, both with a silty loam texture but under different climatic conditions (Chernozem = 480 mm precipitation, Luvisol 886 mm). Over the course of 4 years, soil structure was regularly determined by X-ray µCT at two resolutions, 60 µm and 15 µm, to track soil structure development with time and in response to seasons. By excluding roots and soil fauna > 30 µm in half of the samples, it was possible to estimate the contribution of abiotic and biotic drivers. The distribution of garnet particles was determined in order to quantify the rate of soil structure turnover as related to potential biotic drivers. It is shown that soil structure turnover by natural processes is slow and that both abiotic and biotic drivers affect soil structure. Turnover under dry climatic condition was significantly slower due to lower biological activity. When soil is mixed by fauna > 30 µm activity, the distribution of garnet particles originally located at the surfaces of macro-aggregates became increasingly randomised, indicating rearrangement of soil structure and establishment of new pore−soil matrix interfaces.

How to cite: Leuther, F., Mikutta, R., Wolff, M., Kaiser, K., and Schlüter, S.: Soil structure turnover under grassland is mainly driven by biotic drivers, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1063, https://doi.org/10.5194/egusphere-egu22-1063, 2022.

Organic farming aims at improving soil fertility in vineyard soils through a combination of farming practices. We studied the effect of organic management on community traits of free-living nematodes as well as bulk and microstructure properties of soil by comparing them to conventional management, both within vine rows and in interrows. The objectives of this study were to: 1) identify differences between management systems in terms of nematode abundance and molecularly measured community composition, and 2) to scrutinize, whether these changes can be explained by microstructural properties measured with X-ray computed tomography (X-ray CT) of individual soil aggregates. Nematode abundance was mainly  governed by habitat constraints, which was reflected in significant correlations with soil moisture and with porosity in the habitable size range of 20–220 μm obtained with X-ray CT. The lack of bioturbation by fine roots and the absence of irrigation reduced the abundance of water-filled, habitable pores, which resulted in the lowest nematode abundance in conventionally managed interrows without a grass cover. Community composition in terms of diversity and maturity, in turn, was not affected by habitat constraints but mainly governed by resource availability for the soil food web estimated by particulate and dissolved organic matter contents. The permanent grass cover and lack of tillage in interrows of the organic vineyard improved resource availability and promoted the build-up of omnivores and predators that are especially sensitive to disturbance. The organically managed interrows therefore had lower diversity and higher maturity than conventionally managed interrows. Differences between conventional and
organic management were in general greater in interrows than within vine rows.
These findings highlight the added value of pore structure investigations via X-ray CT in understanding trophic interactions of nematodes. At the same time, they stress the importance of exact sampling locations on nematode traits especially for perennial, woody crops.

How to cite: Schlüter, S., Gil, E., Doniger, T., Applebaum, I., and Steinberger, Y.: Abundance and community composition of free-living nematodes as a function of soil structure under different vineyard managements, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1112, https://doi.org/10.5194/egusphere-egu22-1112, 2022.

In-growth mesh bag technique is widely used for assessing production and turnover of the fungal mycelium in soil, but remains poorly standardized. Various filling materials are used mainly quartz sand with particle size range of 0.4–2.0 mm or 0.5–1.5 mm. Substrate particle size plays a crucial role in soil pore formation: larger pore space may increase the growth of mycelium that spreads along cracks and other air-filled pores In contrast, the volume of soil explored by fungi can increase with greater bulk density while mycelium allocation shifts from a few large pores to more evenly distributed small pores. This research was aimed at testing the use of quartz sand of different particle size, as a filling for in-growth mesh bags, in order to obtain a maximum amount of fungal mycelium. Mesh bags were incubated in a Norway spruce forest in Central Russia. Mycelial biomass was higher in sand of coarse (> 0.5 mm) particle size and reached maximum (up to 798 μg of mycelium dry weight g−1 sand).

How to cite: Zuev, A.: Fungal mycelium growth: effects of the sand particle size, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1418, https://doi.org/10.5194/egusphere-egu22-1418, 2022.

Ectomycorrhizae (EcM) are evolved mutualistic associations between soil fungi and plant roots. It has been shown that there can be species-specific differences in the ability to colonise roots. Colo­nised roots have increased longevity, greater resistance to pathogens, toxic elements in the soil and extreme con­ditions of temperature, acidity and moisture.

EcM inocula are an essential resource in forest management. Nevertheless, measures being implemented worldwide to promote forest cover recovery to reduce atmospheric CO₂ levels can cause ecological shifts. Shifts to ecological communities take place as species become more or less abundant, are wiped out or colonise new habitats. However, these changes may not be captured by metrics focusing on species richness alone.

The lack of direct evidence of large-scale EcM temporal change in fungal community structure or function over time - commonly used in animal and plant research - is a basic, structural knowledge gap. Understanding temporal changes in community composition, whether via species losses and gains, or alterations to relative abundance and dominance is therefore essential to fathom the performance of terrestrial ecosystems, in particular the soil environment and its functions.

This study will characterise EcM fungi in woodland sites of varying ages. This study uses a space-for-time approach, benefiting from a collection of sites part of a wider study on the biodiversity responses to woodland planting.

How to cite: Azevedo, O., van der Linde, S., Park, K., Ashwood, F., Fuentes-Montemayor, E., Wilson, C., Watts, K., and Vanguelova, E.: Belowground networking: Biogeography of EcM fungi and species variation at different woodland ages, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2385, https://doi.org/10.5194/egusphere-egu22-2385, 2022.

Soil is a complex habitat that host an important diversity of soil organisms. The latter process soil organic matter along trophic chains that play a key role in soil functioning. While important progress has been made to decipher complex trophic interactions in soils, the role of soil animal mobility within the pore space as a determinant of food accessibility, and thus trophic interactions, remains poorly studied. Collembolans are ubiquitous microarthropods playing a pivotal role in soil food webs. We expected that collembolans colonize soil pores of equivalent dimension to their body size (few hundred microns). In these pores, they may hide from predators and access food resources, notably microbes. However, experimental evidences of the range of soil pores accessible to Collembola, and how it affects their mobility are missing. We used self-designed 3D printed physical pore simulation models with pore cylinders of 0.5, 0.75, 1 and 3 mm diameter (and all 4 mm long) to test how the pore diameter affects the mobility of six collembolan species (Heteromurus nitidus, Sinella curviseta, Folsomia candida, Ceratophysella denticulata, Protaphorura fimata and Mesaphorura macrochaeta). For each species, 10 individuals were placed in the soil pore simulation model at moist and dark conditions, and their ability to pass through pores was assessed after 7.5 minutes of incubation. We observed that collembolan mobility increased with pore diameter (P < 0.001), but this varied among species (P < 0.001). Species with the largest body size, namely H. nitidus (body width 0.58 ± 0.29 mm) and C. denticulata (body width 0.50 ± 0.12 mm) were particularly restricted with less than 1% of the individuals passing through pore necks of 0.4 mm. As the pore neck diameter increased, passage increased more for C. denticulata than for H. nitidus. Only 46 ± 20 % of the individuals of H. nitidus passed through a pore neck of 1 mm, whereas for C. denticulata it was 76 ± 10 %. Across the different pore diameters, P. fimata (body width 0.36 ± 0.08 mm) was the least restricted species, with 76 ± 18 % of individuals passing through pores of 0.4 mm diameter. M. macrochaeta (body width 0.11 ± 0.07 mm), S. curviseta (body width 0.39 ± 0.26 mm) and F. candida (body width 0.31 ± 0.09 mm) showed intermediate restriction in mobility with 54 ± 28 %, 43 ± 19 % and 43 ± 28 % of the individuals passing through pore of 0.4 mm diameter, respectively. At a pore diameter of 1 mm, these proportions raised to 84 ± 20%, 79 ± 10% and 95 ± 5%, respectively. Overall, Collembolan species were able to enter pores 20 ± 37 - 171 ± 33 µm wider than their body width, suggesting different ability to enter narrow pores depending on species. We conclude that the dimension of the pore diameter is a main factor restricting the mobility of collembolans in soil and presumably functions as main determinant of food accessibility.

How to cite: Erktan, A., Winkler, R., Henning-Krogh, P., and Scheu, S.: Effect of pore diameter on the mobility of six collembolan species: an experimental approach using 3D printed soil pore simulation models, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2817, https://doi.org/10.5194/egusphere-egu22-2817, 2022.

Recent studies have identified soil drying as a dominant driver of transpiration reduction at the global scale. Although Arbuscular Mycorrhiza Fungi (AMF) are assumed to play a pivotal role in plant response to soil drying, studies investigating the impact of AMF on plant water status and soil-plant hydraulic conductance are lacking. Thus, the main objective of this study was to investigate the influence of AMF on soil-plant conductance and plant water status of tomato under drought. We hypothesized that AMF limit the drop in matric potential across the rhizosphere, especially in drying soil. The underlying mechanism is that AMF extend the effective root radius and hence reduce the water fluxes at the root-soil interface. The follow-up hypothesis is that AMF enhance soil-plant hydraulic conductance and plant water status during soil drying. To test these hypotheses, we measured the relation between transpiration, soil and leaf water potential of tomato with reduced mycorrhiza colonization (RMC) and the corresponding wild-type (WT). We inoculated the soil of the WT with Rhizophagus irregularis spores to potentially upsurge symbiosis initiation. During soil drying, leaf water potential of the WT did not drop below -0.8 MPa during the first six days after withholding irrigation, while leaf water potential of RMC dropped below -1 MPa already after four days. Furthermore, AMF enhanced the soil-plant hydraulic conductance of the WT during soil drying. In contrast, soil-plant hydraulic conductance of the RMC declined more abruptly as soil dried. We conclude that AMF maintained the hydraulic continuity between root and soil in drying soils, hereby reducing the drop in matric potential at the root-soil interface and enhancing soil-plant hydraulic conductance of tomato under edaphic stress. Future studies will investigate the role of AMF on soil-plant hydraulic conductance and plant water status among diverse plant species growing in contrasting soil textures.

How to cite: Abdalla, M. and Ahmed, M.: Arbuscular mycorrhiza symbiosis improves plant water status and soil-root hydraulic conductance under drought, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3431, https://doi.org/10.5194/egusphere-egu22-3431, 2022.

Linking soil functions to microbial community structure is arguably one of the greatest challenges in soil ecology, presumably due to the structural complexity and heterogeneity of soil across scales and time, as well as the large number of microbial taxa present. To overcome these impediments, we here introduce a model soil ecosystem - the “Synthetic Soil” - which allows soil structure and microbial community composition to be varied separately, to disentangle the complex relationship. The Synthetic Soil consists of a mixture of sterilized primary and secondary soil minerals and organic matter of plant and microbial origin, which together constitute the artificial soil matrix. This abiotic soil matrix is then inoculated with an in-silico designed, minimal microbial community, composed of 12 selected soil bacteria and fungi.

We demonstrate the applicability of the approach, by incubating the Synthetic Soil in a sterile environment for five weeks. During this period, an actively growing soil community established, indicated by stable respiration rates, increasing DNA- and ammonium concentrations, depletion of dissolved organic carbon, and by changes in relative abundances of the community members. Additionally, the minimal community was actively decomposing soil organic matter by the production of extracellular enzymes. In conclusion, the Synthetic Soil approach developed in this study, allows the construction of powerful and modifiable model ecosystems, which will make it possible to link soil functions to microbial community structure and thus to address fundamental questions of soil ecology.  

How to cite: Horak, J., Schmidt, H., Hadziabdic, L., Kits, K. D., and Richter, A.: A synthetic soil approach to link microbial community composition to soil functions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3447, https://doi.org/10.5194/egusphere-egu22-3447, 2022.

Application of farmyard manure (FYM) is common practice to improve physical and chemical properties of arable soil and crop yields. However, studies on effects of FYM application mainly focussed on topsoils, those in subsoils have been rarely been addressed so far. We, therefore, investigated the effects of a 36-year application of different FYM rates (0, 50, 100, 200 Mg ha⁻¹ a⁻¹) on organic carbon (OC) contents of a Chernozem in 0−30 cm (topsoil) and 35−45 cm (subsoil) depth, and its effects on soil structure and hydraulic properties in subsoil. X-ray computer tomography was used to analyse the response of macropore system (≥ 19 µm) and the distribution of particulate organic matter (POM) to different FYM applications. Based on morphological characteristics, POM was subdivided into a fresh and aged fraction. Image-derived POM volumes were related to contents in total OC (TOC) and water-extractable OC (WEOC) in order to differentiate between possible input sources of soil OC below the plough horizon. We show that manure application of up to 50 Mg ha⁻¹ a⁻¹ caused increases in TOC and WEOC contents only in the topsoil, whereas rates of ≥ 100 Mg ha⁻¹ a⁻¹ resulted in TOC enrichment also at deeper depth. In subsoil, the increase in POM (aged and fresh) and WEOC was more marked than that in TOC, indicating that POM and soluble OC may have facilitated the subsoil TOC enrichment. The subdivision of TOC into different OC sources shows that most of the increase was due to fresh POM, likely by roots. The increase in subsoil TOC went along with increases in macroporosity and macropore connectivity, possibly due to the stimulation of bioturbation. We neither observed increases in plant-available water capacity nor in unsaturated hydraulic conductivity. Our study shows that only very high applications of FYM over long periods can increase OC stocks of arable subsoil, but this increase is largely based on fresh, easily degradable POM and accompanied by high C losses.

How to cite: Wolff, M., Leuther, F., Kaiser, K., Schumann, L., Merbach, I., Mikutta, R., and Schlüter, S.: Responses of subsoil organic matter contents and physical properties to long-term application of increasing amounts of manure, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7814, https://doi.org/10.5194/egusphere-egu22-7814, 2022.

It has been established that brown-rot (BR) [1] and some ectomycorrhizal (ECM) [2] fungi use a non-enzymatic Fenton reaction (Fe²⁺ + H₂O₂ à Fe³⁺ + ∙OH) to decompose carbon. This Fenton reaction is driven by secondary metabolites, namely hydroquinones (H₂Q), and to date studies of H₂Q with redox reactive minerals have primarily been conducted under anoxic conditions and in batch setups. This approach introduces two shortcomings: Firstly, oxic iron(III) (oxyhydr)oxide (FeOOH) transformation and vertical translocation in the soil is ignored. Secondly, as the redox potential (E_H) of FeOOH decrease as a function of increasing Fe²⁺ concentration in solution, the reductive dissolution stops when the E_H of Q/H₂Q is higher than E_H of FeOOH/Fe²⁺[3]. It follows that in order to investigate the full potential of H₂Q driven Fe mobilization an experimental setup, in which the solution is removed from the interface of the reaction, is needed. Consequently, this study will investigate the Fe mobilization potential of 2,6-dimethoxhydroquinone (DMHQ, a stable analogue to a common secondary metabolites produced by BR fungi) in a flow setup with continuous application of H₂Q and removal of Fe²⁺ under oxic and natural relevant concentrations. A low-tech column set-up with synthesized ferrihydrite coated sand (1-0.5 mm) were supplied with 100 mL 20 µM DMHQ bi-daily over a three months period (50 times in all) and pH and Fe²⁺ concentration was monitored in the outlet. Before and after DMHQ application the coated ferrihydrite’s crystallinity was investigated with dithionite-citrate-bicarbonate and ammonium oxalate extractions. Results will be presented showing that DMHQ can reduce ferrihydrite and mobilize Fe²⁺ under oxic conditions and further that the ferrihydrite becomes increasingly crystalline, thus less reactive, after exposure to 100 µmol of 2,6-DMHQ. In light of the wide distribution of the Fenton reaction, with BR fungi dominating C sequestration in the boreal forest and ECM fungi being abundant in the boreal forest, eucalyptus forest and heathlands, these findings have interesting implications. Moreover, the results support that podsolization, i.e. the translocation of sesquioxides and soil organic matter associated with the above mentioned ecosystems, is linked to reductive dissolution of FeOOH by fungal secondary metabolites as previously suggested [4].

[1]             E. V Ier, K.E. Hammel, A.N. Kapich, K. a J. Jr, Z.C. Ryan, K. a Jensen, Reactive oxygen species as agents of wood decay by fungi, Enzyme Microb. Technol. 30 (2002) 445–453. doi:10.1016/S0141-0229(02)00011-X.

[2]             L. Qu, K. Makoto, D.S. Choi, A.M. Quoreshi, T. Koike, The Role of Ectomycorrhiza in Boreal Forest Ecosystem BT  - Permafrost Ecosystems: Siberian Larch Forests, in: A. Osawa, O.A. Zyryanova, Y. Matsuura, T. Kajimoto, R.W. Wein (Eds.), Springer Netherlands, Dordrecht, 2010: pp. 413–425. doi:10.1007/978-1-4020-9693-8_21.

[3]             C.A. Gorski, R. Edwards, M. Sander, T.B. Hofstetter, S.M. Stewart, Thermodynamic Characterization of Iron Oxide–Aqueous Fe 2+ Redox Couples, Environ. Sci. Technol. 50 (2016) 8538–8547. doi:10.1021/acs.est.6b02661.

[4]             N. van Breemen, U.S. Lundström, A.G. Jongmans, Do plants drive podzolization via rock-eating mycorrhizal fungi?, Geoderma. 94 (2000) 163–171. doi:10.1016/S0016-7061(99)00050-6.

How to cite: Lyngsie, G.: Oxic transformation and translocation of ferrihydrite by fungal secondary metabolites, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9671, https://doi.org/10.5194/egusphere-egu22-9671, 2022.

A better understanding of soil carbon sequestration is important as the rapid elevation of carbon emission has significantly impacted our climate. The soil carbon dynamic process is strongly associated with trophic interactions in the soil communities. However, direct investigation of microbes and trophic interactions at microscale has been a major challenge due to the opacity of soil and the exceedingly complex pore spaces that limit direct in situ observation of trophic interactions and their variations with soil structure. As such, we decide to use microfluidic technique to create a two dimensional heterogeneous porous microenvironment containing nutrient patches of different quantity and quality to mimic the complex soil pore network and its heterogenous distribution of resources. This allows us to directly visualize and investigate the ability of organisms to access spaces starting from an initial ecophysiological precondition to changes of spatial accessibility mediated by interactions with the microbial community.

Microfluidics is a multidisciplinary platform that integrates micro fabrication, physical chemistry analysis, automation and microscopy. It has been widely used in life science and chemistry as it allows precise liquid manipulation, rapid measurements, real-time visualization at microscale, which is especially of interest and benefit to microbial studies. We created a complex pore network mimicking different soil environments – earlier considered impossible to achieve experimentally. The microfluidic channel contains a random distribution of cylindrical pillars of different sizes so as to mimic the pore space variations found in real soil. The randomness in the design creates various spatial availability for microbes. The nutrient patches within the pore space are achieved via capillary force trapping or UV curing hydrogel. In the former method, the patches are created by trapping nutrients in the predesign pore space due to interfacial tension between air and nutrient liquid. However, displacement instability during air injection makes it hard to control the formation of the patches. The latter enables better and more precise patches size and location manipulation but hydrogel biocompatibility with various fungal species remains a major challenge and hydrogel curing requires special facilities. The microfluidic nutrient patches provide spatial heterogeneities of resource distribution, which allows us to have a better understanding of the influence of spatial accessibility on the microbial community. The chip has five different nutrient distribution levels, ranging from centralized – a single large nutrient patch-  to increasingly dispersed nutrient distributions - sets of up to 49 loosely distributed nutrient patches of equal total volume. The experiments will be carried out using sterile cultures of fluorescent bacteria and fungi, synthetic communities of combinations of these, or a whole soil community inoculum. We will quantify the consumption of organic matter from the different areas via fluorescent substrates, and measure the bio- and necromass produced. We hypothesise that denser distribution will increase the net decomposition of organic matter as a centralized nutrient location increases the interactions within the microbial communities and individuals present in that area, which induces higher competition stress in the different communities.

How to cite: Zou, H., Ohlsson, P., and Hammer, E.: Two-dimensional microfluidic nutrient patches for direct visualization of microbial resource cycling, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9836, https://doi.org/10.5194/egusphere-egu22-9836, 2022.

Abstract

After a Rubber plantation cycle (25 to 40 years), the greatest risk of soil degradation occurred during the replanting period which extends from the clear cutting of an old plantation to the planting of young rubber trees. During this period, the soil is subject to numerous disturbances mainly related to (1) the opening up of the environment following clear cutting (2) the export of organic matter with machines and (3) the practice of deep subsoiling by heavy machinery. These practices may affect directly or indirectly biodiversity and the delivery of soil functions (Missanjo and Kamanga-Thole 2014).

To mitigate soil degradation after one or more plantation cycles, some agricultural practices are commonly used, such as the implementation of a cover crop in the inter-rows at planting (Gao et al. 2017; Liu et al. 2018). Another alternative to restore soil functions is to leave the logging residues (i.e. trunk, branches, leaves and roots of the logged plantation) on the plot, given the high amount of carbon and nutrients accumulated in the tree at the clear-cut stage (Perron et al. 2021). The positive impact of crop residues has been demonstrated on soil fauna resilience (Lassauce et al. 2012; Carron et al. 2015), soil organic carbon and nutrients (Alam et al. 2018). However, so far, this agroecological practice has never been tested in rubber plantations and the effect of the restitution of logging residues on soil functioning has never been addressed.

We set up a field experiment after logging of the previous old RP in two industrial rubber plantations in Ivory Coast with contrasting soil types. In each RP, different type of logging residues and legume were added after clear cutting to determine their respective impact on the resilience of soil biodiversity. We hypothesized that (i) the input of logging residues and legumes after a clear-cutting will promote the resilience of soil biodiversity (microbial, nematode and macrofauna) (ii) soil types will affect the level of resistance and resilience of the soil biodiversity.

In both sites, we observed a significant loss of soil biodiversity, 6 months after clear-cutting and land preparation. The negative impact of mechanical disturbance on the dynamics of soil biodiversity has been revealed by lower abundance, richness, beta diversity, ecological indexes and co-occurrence networks. For example, soil macrofauna density significantly dropped by 36.04 and 93.65% at sandy and clay site respectively. Macrofauna diversity decreased significantly by 60.6% at sandy site and 91.39% at clay site. Practices with logging residues contributed to higher resilience of macrofauna density (~ 360% in clay site and 300% in sandy site) and diversity (134–154% in clay site and 58-73% in sandy site) than practice without residues (75–97% in clay site and 35-38% in sandy site). The application of logging residues and legume was the most efficient practice to promote soil biodiversity and to mitigate the negative impact of clear-cutting in rubber monocultures after a 40 years’ rotation.

Key words: Soil biodiversity, Rubber plantation, Restoration, Logging residues

How to cite: Kouakou, A., Yéo, K., Trap, J., Perron, T., Diakhaté, S., Gay, F., and Brauman, A.: Resistance and resilience of soil biodiversity after tree logging: case studies in rubber plantation in Ivory Coast, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9895, https://doi.org/10.5194/egusphere-egu22-9895, 2022.

∙ To assess how belowground mycorrhizal networks may share resources, we used δ¹³C, δ¹⁵N, and C/N measurements to calculate spatial and temporal dynamics of carbohydrate and amino acid movement through ectomycorrhizal networks of mature trees.

∙ Canopies of 14 deciduous trees were continuously labeled with ¹³C-depleted CO₂ from 2001-2005 (Swiss Forest FACE) and the ¹³C label traced into ectomycorrhizal sporocarps.

∙ Sporocarps derived 69±5%, 30±6%, and 16±7% of their carbon from labeled trees in the elevated (beneath labeled trees), 0-6 m, and 6-12 m distances, respectively. Sporocarp δ¹³C correlated positively with C/N under elevated CO₂ and negatively elsewhere, reflecting that high-δ¹³C carbohydrates from surrounding trees contributed to sporocarps under elevated CO₂ and low-δ¹³C carbohydrates from elevated CO₂ trees contributed to sporocarps elsewhere. Sporocarp δ¹⁵N increased in Cortinarius with decreasing δ¹³C, suggesting that greater hyphal growth with elevated CO₂ sequestered ¹⁵N-depleted N from sporocarp formation. Sporocarp log_e C/N decreased during the 2004 growing season and the contribution of ¹³C-depleted carbon from elevated CO₂ plants decreased at the 0-6 m and 6-12 m distances, suggesting decreased carbohydrate availability and network transport that year. In contrast, sporocarp log_e C/N increased during the 2005 growing season and the contribution of ¹³C-depleted carbon from elevated CO₂ plants increased at the 0-6 m distance, suggesting increased carbohydrate availability and network transport that year. Relative to other taxa, elevated CO₂ reduced C/N by 15% and ambient CO₂ increased C/N by 5% in taxa exclusively associated with deciduous trees, suggesting increased carbohydrate sharing by the deciduous-associated taxa.

∙ These patterns indicated that 1) carbohydrates (high C/N), not amino acids (low C/N), were preferentially transferred between regions differing in source δ¹³C, 2) sporocarp C/N reflected yearly plant productivity, 3) network transport was influenced by climate, and 4) taxonomy influenced transport dynamics belowground.

How to cite: Hobbie, E., Keel, S., Steinmann, K., Wilhelm, M., Saurer, M., Siegwolf, R., and Körner, C.: The Spatial Extent of Carbohydrate Sharing in the Wood-Wide Web Varies with Climate and with Taxonomy of Ectomycorrhizal Fungi : Insights from the Swiss Forest FACE, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10476, https://doi.org/10.5194/egusphere-egu22-10476, 2022.

The production, formulation and use on agricultural soils of biofertiliser or biostimulant mixtures containing several species of microorganisms is becoming increasingly common. The study of the interactions between the biological components of such products is less frequent. Often the marketed mixtures combine a high microbial load, in the form of both spores and propagules of fungi and bacteria whose positive or negative synergies are tested only to a limited extent, mainly because of the costs involved in field trials. The in vitro study of interactions between fungi or between fungi and bacteria is very important for understanding what can be expected in vivo, i.e. once microorganisms are released in large quantities into soils that already have local microbial communities.  The use of innovative techniques such as digital qPCR and phenotype microarrays now makes it possible to rapidly test thousands of interactions between two or more microorganisms. In this work, a method is proposed to evaluate the positive or negative effects of co-inoculums of different microorganisms on some main biological functions, and in particular the use of defined nutritive sources. The proposed protocol combines the application of commercial Biolog^R microplates with the quantification of the biomass of the individual co-inoculated strains by means of molecular tracing techniques and digital qPCR analysis. In vitro analysis of the effects of interactions is crucial because competition or commensalism can give rise to new compounds (i.e. enzymes, antibiotics, allopathic molecules) or behaviours (production of resistant structures, cellular apoptosis, changes in life cycle as perfect state inhibition or stimulation, etc.), which in turn can have definite effects on both the efficacy of the product and the variability of its properties.

How to cite: Mocali, S., Canfora, L., and Pinzari, F.: Qualitative-quantitative protocol for studying the interaction between fungi and between fungi and bacteria to produce bio-fertilising co-inoculants, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13545, https://doi.org/10.5194/egusphere-egu22-13545, 2022.

Litter decomposition in most terrestrial ecosystems is regulated by moisture-dependent microorganism activity, among other things. Decomposition models typically underestimate rates of plant litter decomposition in drylands, suggesting the existence of additional drivers of decomposition. Attempts to reveal these drivers have predominantly focused on abiotic degradation agents, alternative moisture sources, and soil–litter mixing. The role of burrowing animals in promoting decomposition has received less attention despite greatly contributing to plant litter transfer from the harsh desert surface to the moister and nutrient-rich environment belowground. In a previous study in the Negev Desert, we found that macrofauna account for 89% of the litter cleared from the desert surface, and detected elevated nutrient levels near desert isopod (Hemilepistus reaumuri) burrows. Here, our goal was to explore how macro-detritivore burrows affect plant litter mineralization dynamics. We introduced ¹³C-labeled litter belowground into (1) isopod burrows and (2) artificial burrows, and aboveground on top of (3) isopod fecal pellet mounds and (4) bare soil crust. We compared the litter mass loss between the four treatments and used cavity ring-down spectroscopy to reveal the in-situ mineralization dynamics. No litter mineralization was evident during the dry summer months both above- and belowground. Following rain events, mineralization rates spiked in all four micro-environments, quickly diminishing aboveground while slowly waning belowground. Total litter mass loss was twofold higher below than aboveground and was significantly higher in isopod burrows compared to artificial burrows. Our findings demonstrate that burrowing macro-detritivores promote litter decomposition in deserts by transferring organic matter to their burrows where favorable climatic conditions and a nutrient-enriched environment foster microbial activity. Thus, attempts to resolve the dryland decomposition conundrum should not be limited to exploring factors that allow decomposition under harsh desert surface climatic conditions, but focus on the role that animals play in facilitating decomposer-friendly environments to which they translocate plant litter.

How to cite: Sagi, N., Zaguri, M., and Hawlena, D.: Ecosystem engineering by desert macro-detritivores facilitates microbial litter decomposition, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-44, https://doi.org/10.5194/egusphere-egu22-44, 2022.

Abstract

The utilization of termite mounds for the improvement of soil fertility is a worldwide practice and usually explained by the specific properties of this biogenic material. In Cambodia, farmers also use termite mound soils as amendments with the aim to improve the fertility of paddy fields. The first objective of this study was, therefore, to describe the physical and chemical properties of this material and, consequently, to determine its potential for improving soil fertility. A second objective was to consider farmer’s perception and to quantify the diversity of services provided by termite mounds. We confirmed the specific soil properties of termite mounds but showed that their positive influence on soil chemical fertility and water retention are only significant in very sandy soil (>80% sand) while they remain limited in less sandy soil (~40 and 60% of sand). However, termite mounds are considered useful by farmers independently of the soil condition, mostly because this soil material is considered to positively increase soil fertility but also because they host a specific biodiversity which can be used for medicinal purposes or because consumed, then increasing population livelihood. Our work shows the discrepancy between the perception of farmers and the real impact of termite mounds on soil fertility as well as the diversity of services delivered by biodiversity in paddy fields. 

How to cite: Muon, R., Lai, C., Bureau-Point, E., Chassagne, F., Wieringa, F., Berger, J., Sok, K., Audibert, M., Podwojewski, P., Marchand, S., Ann, V., and Jouquet, P.: Termite mounds in Cambodian paddy fields. Are they always kept for improving soil quality?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-55, https://doi.org/10.5194/egusphere-egu22-55, 2022.

Saprophagous macroarthropods are important actors in litter decomposition as they process large amounts of litter and transform it into fecal pellets that differ in  chemical and physical properties compared to ingested litter. When having a choice among several litter types, saprophagous macroarthropods exhibit feeding preferences depending on their nutritional requirements and body size. However, how these preferences affect feces properties is not well known. We compared the feeding preferences, production of fecal pellets and their properties for six widespread saprophagous macroarthropods species feeding on a litter mix of four common tree species from Mediterranean forests. The six animal species showed different feeding preferences that were not correlated to litter nutritional quality. Instead, we suggest that the use as microhabitat of the leaves of one litter species with tubular shape by macroarthropods  induced its higher consumption despite having the lowest nutritional value. Larger species consumed less litter per unit of body mass and had a more diverse diet composition. Furthermore, feces properties could not be linked to the diet composition, but always had higher nutritional value and water holding capacity compared to the leaf litter. The three woodlice species consistently produced feces with higher tannin concentration, higher specific area, and lower water holding capacity than that of the three millipede species. Our study calls for the consideration of other leaf litter properties than the generally studied physical and chemical ones, as well as quantifying the difference between millipede and woodlice faeces properties that may have functional implication for nutrient cycling.

How to cite: Ganault, P., Barantal, S., Coq, S., Hättenschwiler, S., Lucas, S., Decaëns, T., and Nahmani, J.: Leaf litter morphological traits, body mass and phylogenetic affiliation explain the feeding and feces properties of saprophagous macroarthropods., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-98, https://doi.org/10.5194/egusphere-egu22-98, 2022.

Soil fauna is a key control of the decomposition rate of leaf litter, yet its interactions with litter quality and the soil environment remain elusive. We conducted a litter decomposition experiment across different topographic levels within the landscape replicated in two rainforest sites providing natural gradients in soil fertility to test the hypothesis that low nutrient availability in litter and soil increases the strength of fauna control over litter decomposition. We crossed these data with a large dataset of 44 variables characterizing the biotic and abiotic microenvironment of each sampling point and found that microbe-driven Carbon (C) and Nitrogen (N) losses from leaf litter were 10.1 and 17.9 % lower, respectively, in the nutrient-poorest site but this among-site difference was equalized when meso- and macrofauna had access to the litterbags. Further, on average soil fauna enhanced the rate of litter decomposition by 22.6%, and this contribution consistently increased as nutrient availability in the microenvironment declined. Our results indicate that nutrient scarcity increases the importance of soil fauna on C and N cycling in tropical rainforests. Further, soil fauna is able to equalize differences in microbial decomposition potential thus buffering to a remarkable extent nutrient shortages at an ecosystem level.

How to cite: Peguero, G., Sardans, J., Richter, A., Janssens, I., and Peñuelas, J.: Nutrient scarcity strengthens soil fauna control over leaf litter decomposition in tropical rainforests, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-747, https://doi.org/10.5194/egusphere-egu22-747, 2022.

In many terrestrial ecosystems, earthworms operate at the interface between plants and soil. Their incidence and abundance depends on several soil properties, yet simultaneously they also impact soil properties themselves. The existence of a positive feedback loop in which earthworm activity maintains their own niche — by promoting turnover rate in the forest floor, thereby increasing topsoil pH and creating suitable living conditions for themselves — has been suggested before, yet lacks supporting evidence. In our European study we found that in forests where moisture is not limiting, soil acidity is an important factor determining the context of belowground interactions, and we were able to confirm the hypothesized feedback loop for forest ecosystems with soil pH ≤ 5. This indicates that the activity of burrowing earthworms is pivotal in belowground functioning, amplifying external drivers (e.g. tree species effects) on biochemical cycling and triggering potential regime shifts in the abiotic compartment. In acidified soils (e.g. pH ≤ 5), forest management is often focused on counteracting acidification and restoring the soil nutrient status. In that regard, managing soil fauna is a promising avenue to steer belowground functioning and may even be necessary upon restoration.

How to cite: Desie, E., Van Meerbeek, K., De Wandeler, H., Bruelheide, H., Domish, T., Jaroszewicz, B., Joly, F.-X., Vancampenhout, K., Vesterdal, L., and Muys, B.: Positive feedback loop between burrowing earthworms and soil pH reinforces litter effects on belowground functioning, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1423, https://doi.org/10.5194/egusphere-egu22-1423, 2022.

Millipedes, one of the most important detritivores in nature, host a community of microorganisms in their guts that may contribute to their nutrition and overall fitness. However, it remains unclear to what extent do millipedes depend on their microbiome. We evaluated the degree of dependence of methane and non-methane releasing millipedes on their gut microbiome using an experimental approach combining chemical inhibitors, microscopy, stable-isotope probing and meta-omics. First, we used either antibiotics or the methanogenesis inhibitor 2-bromoethanesulphate (BES) on juvenile Epibolus pulchripes (topical; methane releasing) and Glomeris connexa (European; non-methane releasing) to suppress microbial activity. Antibiotics had a large and significant effect on the number of faecal pellets and bacterial plate counts but did not achieve sterilization. It also reduced the weight and CH₄ output in E. pulchripes but did not stop it. BES completely inhibited CH₄ production, but recovery was observed after 14-days of feeding on untreated leaves. BES also reduced the abundance of the functional gene for methanogenesis in the faeces—mcrA—but did not affect their weight or faecal pellet production. While the hindguts of antibiotic-treated E. pulcripes and G. connexa were dominated by Bacteroidota and Proteobacteria, the faeces were dominated by Proteobacteria according to the 16S rRNA amplicon sequencing analysis. Light microscopy and catalysed reporter deposition fluorescence in situ hybridization (CARD-FISH) showed that E. pulchripes harbour a multitude of ciliates with ecto- and endo-symbiotic methanogens belonging to Methanobacteriales and Methanomassilicoccales. Surprisingly, these methanogens were still detectable at similar numbers even when methanogenesis was entirely suppressed. We also used RNA stable isotope probing (RNA-SIP) in conjunction with metagenomics to identify key microbial players in the hindguts and distinguish the microbial metabolic potentials of the two millipede species. RNA-SIP results indicated slow labelling of the bacteria over several weeks, with only a few phyla labelled during the first week of feeding on ¹³C-labelled poplar leaves. We recovered 305 high-quality MAGs (E. pulchripes - 282 and G. connexa - 33) with ≥ 50% completeness using metagenomics, comprising 18 prokaryotic phyla (E. pulchripes - 18 and G. connexa - 5). In addition, the MAGs contained some novel bacteria along with some known members of the termite gut microbiota. The results from reconstructed metabolic pathways indicate that the potential role of hindgut bacteria is carbohydrate metabolism, followed by energy metabolism, lipid metabolism, nucleotide metabolism and amino acid metabolism. Analysis of the metatranscriptome is currently ongoing. Overall, we conclude that while the microbiome is beneficial for the millipede and its composition reflects the prevailing conditions in the gut, it is not essential. Instead, it seems that unlike other methane-releasing animals like termites or ruminants, the millipedes are not dependent on the fermentation products of microorganisms for their nutrition. Together, these results contribute to our understanding of the millipede microbiota and represent the largest genomic resource available to date. 

How to cite: Eyiuche Nweze, J., Gupta, S., Horváthová, T., Šustr, V., and Angel, R.: Do methane and non-methane releasing millipedes depend on their gut microbiome to digest leaf litter?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1603, https://doi.org/10.5194/egusphere-egu22-1603, 2022.

Earthworms have a positive effect on plant growth; this is typically attributed to increased N availability. Earthworms can also increase Si availability; plant Si plays a role in drought tolerance. Finally, earthworms effect microfaunal diversity. We conducted a glasshouse experiment to investigate interactions between these factors. Wheat varieties (Skyfall and four ancient strains) were grown in a greenhouse under presence / absence of adult Allolobophora chlorotica and no-drought / drought watering regimes (39 days watering then a further 17 days of watering or no watering).

Despite earthworm aestivation in drought treatments, plant growth was greater in both the no-drought and drought treatments.

Plant %N was greater in the watered treatments; for the drought treatments, it was greater in the earthworm-present treatments. Plant %C was greater in the earthworm-present treatments. In the earthworm-absent treatments Plant %P and %Si was greater in the watered treatments. In the watered treatments %P and %Si was greater in the absence of earthworms.

Soil pH (c. 8.1) was slightly decreased in the earthworm-present and in the watered treatments. The watered treatments contained more extractable nitrate. Extractable P showed no difference across treatments. The droughted earthworm-present treatments contained more extractable Si than both the earthworm-present watered treatments and earthworm-absent drought treatments.

Different wheat strains behaved similarly with Skyfall showing greater biomass and, sometimes, elemental concentrations.

Bacterial and fungal beta-diversity varied with both watering and earthworm treatments; fungal diversity also varied between wheat strains.

Plants showed significant differences in RNA expression between both watering and earthworm treatments including for genes linked to N uptake.

Earthworms promoted plant growth under both watered and drought conditions. Under drought conditions this does not appear to be related to Si availability or uptake. Similarly we observed no simple relationship between earthworm-presence, N (or P) and plant growth though under drought conditions the presence of earthworms promoted growth and %N in the plants despite lower extractable nitrate. The RNA response of plants suggests a N-related effect perhaps mediated by changes in microbial diversity.

How to cite: Hodson, M., Brailey-Jones, P., Burns, W., Harper, A., Hartley, S., Helgason, T., and Walker, H.: Earthworm-plant-microbiota interactions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2974, https://doi.org/10.5194/egusphere-egu22-2974, 2022.

Summer droughts strongly affect soil organic carbon (SOC) cycling, but net effects on SOC storage are unclear as drought affects both C inputs and outputs from soils. Here, we explored the overlooked role of soil fauna on SOC storage in forests, hypothesizing that soil fauna is particularly drought-sensitive, thereby reducing litter incorporation into the mineral soil and, eventually, long-term SOC storage.

In a drought-prone pine forest (Switzerland), we performed a large-scale irrigation experiment for 17 years and assessed its impact on vertical SOC distribution and composition. We also examined litter decomposition of dominant tree species using litterbags of different mesh sizes and determined soil fauna abundance and community composition.

Long-term irrigation resulted in a C loss in the organic layers (-1.0 kg C m^-2) and a comparable C gain in the mineral soil (+0.8 kg C m^-2) in the first decade of irrigation, and thus did not affect total SOC stocks. Irrigation increased the mass loss of Quercus pubescens and Viburnum lantana leaf litter more strongly when meso- and macrofauna were included (+215%) compared to excluded (+44%). The enhanced faunal-mediated litter decomposition was paralleled by a many-fold increase in the abundance of meso- and macrofauna during irrigation. Moreover, irrigation led to a shift in Acari and Collembola community composition, with irrigation characterized by the presence of drought-sensitive species. In comparison, microbial SOC mineralization was less responsive to lower soil moisture. Our results suggest that the vertical redistribution of SOC with irrigation was mainly driven by litter incorporation through meso- and macrofauna, here accelerated by irrigation and suppressed by naturally occurring summer droughts.

Our study shows that soil fauna is highly sensitive to natural drought reducing the incorporation of C from organic layers to the mineral soil. In the longer term, this potentially affects SOC storage, decreasing the C stored in mineral soil. Therefore, soil fauna plays a key but so far largely overlooked role in shaping SOC responses to drought.

How to cite: Guidi, C., Frey, B., Brunner, I., Meusburger, K., Vogel, M., Chen, X., Stucky, T., Gwiazdowicz, D. J., Skubała, P., Schaub, M., Rigling, A., and Hagedorn, F.: Soil fauna drives vertical redistribution of soil organic carbon by long-term irrigation in a dry pine forest, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4828, https://doi.org/10.5194/egusphere-egu22-4828, 2022.

The role of earthworms on biogeochemical carbon cycling is a major knowledge gap resulting from the difficulty of isolating and exploring the effects provided by the diversity of organisms. In this study, we investigated the effect of six earthworm species belonging to three ecological categories on soil organic carbon (SOC) mineralisation. To this end, we produced casts with the six species using subsoil material with low SOC content and miscanthus litter. Cast were subjected to laboratory ageing for 140 days. During this process, we monitored physicochemical parameters, CO₂ emissions and determined the micro-scale organisation of the casts’ particulate organic matter and pores using X-ray tomography.

Our results showed contrasting properties of fresh casts from the 3 main ecological categories, in accordance with the earthworm species’ morphological or behavioral strategies, indicating that those were maintained in artificial environments. However, species-specific changes in cast properties throughout ageing increased intragroup variability among ecological categories. As a result we observed earthworm species-specific evolution of CO₂ mineralisation rates during casts ageing. We found that at least half of the variability in CO₂ emissions was explained by cast microstructural changes, related to the spatial arrangement between particulate organic matter, porosity, and mineral particles. We conclude that earthworm species-specific traits may play a role in organic carbon protection through their impact on microstructural cast properties.

How to cite: Le Mer, G., Bottinelli, N., Dignac, M.-F., Capowiez, Y., Jouquet, P., Mazurier, A., Baudin, F., Caner, L., and Rumpel, C.: Exploring the control of earthworm cast macro- and micro-scale features on soil organic carbon mineralisation across species and ecological categories, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5216, https://doi.org/10.5194/egusphere-egu22-5216, 2022.

Negative Emission Technologies (NETs) are urgently needed if we want to keep global temperature increase below 1.5 °C. Enhanced Silicate Weathering (ESW) is a NET with as yet unknown potential to mitigate climate change. There are indications that ESW rates can be amplified by biotic activity, including that of earthworms. Earlier studies have suggested various pathways through which earthworms might enhance weathering rates, including the grinding of minerals in their gizzard, the stimulation of microbial communities in their gut, as well as the production of mucus rich in organic acids and digestive enzymes. Within this research, we aim to unravel the mechanisms through which earthworms increase mineral weathering rates, and ultimately to develop a bio-reactor in which these processes are optimized. As a first step, we carried out two experiments to determine the suitability of two earthworm species and to establish the optimal conditions for earthworms and mineral weathering in a small bio-reactor. The first study tested the potential of two endogeic earthworm species, Aporrectodea caliginosa and Allolobophora chlorotica, in a system with two types of rock flours (dunite and basalt) and three organic sources (hay, straw and co-digestate solid). The results showed that both earthworm species can thrive and remain active in the bio-reactor in the presence of basalt mixed with either co-digestate or straw. In the second study we tested the tolerance of the same two earthworm species to two temperatures exceeding earthworms ambient levels (20°C and 25°C) and two flow rates (50 ml/day and 80 ml/day) in a system with basalt and straw. The results showed that both earthworm species can survive and remain active at the highest temperature level and the highest flow rate. Our findings demonstrate that earthworms are suitable for use in a bio-reactor and can tolerate physical conditions which are known to stimulate weathering. Future studies will elucidate to what extent earthworms can enhance weathering.

How to cite: Calogiuri, T., Garamszegi, P., Vidal, A., van Groenigen, J. W., and Hagens, M.: Can earthworms enhance mineral weathering and thereby increase carbon sequestration? , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5706, https://doi.org/10.5194/egusphere-egu22-5706, 2022.

Earthworms are newcomers to South-Eastern Canada, as they were unable to survive the last glaciation period that ended about 11,000 years ago. Since their introduction by Europeans over recent centuries, these exotic earthworm species have substantially affected pedological processes and soil functions. For example, a recent study in the province of Quebec found that earthworms invading native sugar maple (Acer saccharum Marsh.) forests could potentially increase soil nitrous oxide (N₂O) emissions by increasing denitrification rates. However, the underlying microbial mechanisms driving the production of this greenhouse gas via denitrification remain unclear. This led us to conduct field and laboratory studies in order to explore whether earthworms preferentially promote bacterial and/or fungal denitrification pathways. We measured earthworm abundance and collected surface mineral soil samples from 38 sugar maple forests, half of which were earthworm-free. In each soil sample, we measured fungal, bacterial and total microbial biomass by substrate-induced respiration, we measured fungal, bacterial and total denitrification by acetylene inhibition, and we quantified the abundance bacterial (nirK, nirS and nosZ) and fungal (P450nor) denitrifying genes by qPCR. Earthworm abundance correlated positively with bacterial as well as fungal biomass, but did not affect the bacterial-to-fungal biomass ratio. Accordingly, bacterial-mediated and fungal-mediated denitrification rates both increased with the abundance of earthworms. However, earthworm abundance correlated positively with the specific bacterial denitrification rate (SBDR = (bacterial-mediated denitrification rate) ÷ (bacterial biomass)), but not with the specific fungal denitrification rate (SFDR = (fungal-mediated denitrification rate) ÷ (fungal biomass)). Moreover, qPCR analyses showed a positive correlation between earthworm abundance and the proportion of all bacterial denitrifying genes in the microbial population, but no such effect on fungal denitrifying genes. Taken collectively, our results suggest that earthworms may increase N₂O emissions in sugar maple forest soils by preferentially promoting the bacterial-mediated denitrification pathway.

How to cite: Villeneuve, C., Bradley, R., and Beauregard, P. B.: Evidence that invasive earthworms promote bacterial-mediated nitrous oxide emissions in forest ecosystems, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6069, https://doi.org/10.5194/egusphere-egu22-6069, 2022.

The arthropod family Scarabaeidae is estimated to consist of over 30,000 species worldwide, including important pests. Their larvae – commonly known as white grubs – are often part of the soil decomposer community feeding on living plant roots, plant residues as well as faeces. As a result, scarab beetle larvae have the potential to directly and indirectly affect the spatial and temporal variability of soil greenhouse gas (GHG) fluxes, especially through their capability to emit significant amounts of CH₄. However, due to a lack of field data (Görres & Kammann 2020), little is known about their quantitative impact on soil GHG budgets. We conducted a mesocosm experiment with common cockchafer larvae (Melolontha melolontha) with the twofold aim to better understand their effect on soil CO₂, CH₄ and N₂O fluxes as well as the methodological challenges associated with studying this soil fauna group under field conditions. The experiment was conducted in Germany (temperate zone) over an entire vegetation period in mesocosms with three different vegetation types (grassland, grassland + carrots, and carrots, respectively) and three different larval infestation rates (0, 8, and 16 larvae m^-2, respectively). Greenhouse gas flux measurements were conducted with the static chamber method on a monthly basis, including the use of isotopic labels to focus especially on gross soil CH₄ fluxes. In this presentation, we will focus on the methodological difficulties encountered during the experiment and the potential of field-based isotope pool dilution techniques for non-invasive studies of scarab beetle larval CH₄ emissions.

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 703107.

Reference

Görres, C.-M., Kammann, C. (2020). First field estimation of greenhouse gas release from European soil-dwelling Scarabaeidae larvae targeting the genus Melolontha. PLoS ONE 15(8): e0238057, doi 10.1371/journal.pone.0238057.

How to cite: Görres, C.-M. and Kammann, C.: Studying the effect of scarab beetle larvae on soil greenhouse gas fluxes in a mesocosm experiment, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10525, https://doi.org/10.5194/egusphere-egu22-10525, 2022.

Soil fauna can support soil organic matter storage. Important mechanisms facilitation this effect is connected with bioturbation and mixing of organic matter with clay particles which can stimulate accumulation of microbial necromass on mineral surfaces as shown in earthworms. However it has been show that also litter feeding fauna which do not ingest mineral soil may slow down organic matter decomposition and support carbon storage. In this contribution we bring overview of potential mechanisms that may be responsible for this phenomena. Decreased decomposition rate in fauna excrements might result from the removal of easily available polysaccharides, the increase in aliphatic components, an increase in the resistant components of lignin, the accumulation of microbial cell walls (microbial necromass) by increasing of microbial turnover, by binding of nitrogen into complexes with aromatic components, which reduce N availability an finally by higher availability of nitrogen in leachate coming from fauna excrements which may cause negative priming effect and slow down decomposition. These mechanisms will be illustrated on examples and their implication of carbon sequestration will be discussed.

How to cite: Frouz, J.: How litter feeding arthropods can promote carbon sequestration, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11026, https://doi.org/10.5194/egusphere-egu22-11026, 2022.

Soil organisms live and interact in the intricate soil pore space labyrinth, but their natural habitat and natural interactions are difficult to study because of the opaqueness of the soil. We recently developed microfluidic model systems that simulate the spatial microstructure of soil microbial habitats in a transparent material, which we call Soil Chips. They allow us to study the impact of soil physical microstructures on microbes, microbial behavior and realistic microbial interactions, live and at the scale of their cells.

Using soil inocula, we get a large proportion of the natural microbial community into our chips and can study soil bacteria, fungi and smaller protists and nematodes in their food webs and in different spatial habitats. We were especially interested in soil protists that are generally understudied in their diversity and ecosystem functions. We were able to observe a large variety of flagellated, ciliated and amoeboid protists in the chips, predating on the bacterial populations and even on fungal hyphae. Some larger amoebae only entered the chips with their pseudopodia for predation. The colonization succession pattern of the chips showed predator-prey oscillations, with periodically high levels of different protists, followed by retreat or encystation. In chips that were containing initially dry pore spaces, colonization success of protists was strongly increased by the presence of fungal hyphae, which paved the way for protists by wetting pore spaces.

The soil chips enable us to study the influence of trophic interactions such as the presence of predators on bacterial and fungal nutrient cycling. Disturbances that stronger influence protists than bacteria may have a pronounced effect on bacterial population sizes and their organic matter degradation activities. Beyond the scientific potential, the chips can also bring soils closer to people and hopefully increase engagement in soil health conservation.

How to cite: Hammer, E., Mafla Endara, P. M., Klinghammer Nilsson, F., Zou, H., Duljas, J., and Ohlsson, P.: Protists and protist-microbe interactions in soil chips, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12081, https://doi.org/10.5194/egusphere-egu22-12081, 2022.

Earthworm activities in soil generate biogenic aggregates (casts), the mass of which can reach up to 30 - 50t/ha. The dynamics of organic matter (OM) is strongly constrained (accessibility, O₂ content, etc.) within these structures and they tend to have high OM contents. As a result of their large mass and high OM contents, these aggregates can have significant effects on OM dynamics and protection over distinct time scales: (i) over the short term, earthworms increase OM mineralization through their own metabolic processes and by stimulating soil microbial activity, the so-called priming effect; (ii) over longer terms, during cast ageing, a new equilibrium may be reached, leading to the protection of the incorporated OM. However few incubation studies have been conducted for more than three months. Consequently, the net influence of earthworm’s casts on the OM dynamics is still poorly understood and remains to be determined.

Our objective was to estimate whether the incorporation of fresh OM into casts leads to its protection or to an enhanced degradation during the period of cast ageing. To do so, we compared the fate of ¹³C labeled fresh OM added to bulk soil to the fate of fresh OM ingested by earthworms (L. Terrestris) in mesocosms, and monitored OM mineralization during one year. The incorporation of fresh OM into casts was also determined as were the microbial communities involved in the consumption of labelled OM (via ¹³C-phospholipid fatty acid analysis). In addition, the OM stability was estimated as the proportion of mineral associated.

The results showed that fresh OM was largely incorporated into casts, with significant differences in the mineralization rates obtained for the OM incorporated into the soil, compared with that incorporated into the casts. This difference decreased over time, as the casts aged. Fungal activity was lower when OM was incorporated in casts. In conclusion, earthworms influence the fate of fresh OM in soil by delaying its mineralization but do not lead to long-term stabilization.

How to cite: Quenea, K., Nunan, N., Lerch, T., Chenu, C., Aubry, E., Pouteau, V., Plessis, C., and Leloup, J.: Distinct patterns of change of organic matter in bulk soil or in earthworm casts during ageing, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13352, https://doi.org/10.5194/egusphere-egu22-13352, 2022.

In the search for a more sustainable form of agriculture, a better recycling of major nutrients is essential. For phosphorus (P), one of the most limiting factors to better recycling is chemical adsorption to reactive soil particles, which seriously restricts P supply to plants in many soils. It has been known for some time that earthworms can temporarily increase soil P availability in their casts. However, the exact pathways behind this effect are unclear, making it difficult to infer under which conditions earthworms may significantly contribute to P recycling. In two greenhouse experiments, we studied the occurrence of earthworm-induced increased P availability (i) across a range of common earthworm species; and (ii) across four soils with different physico-chemical characteristics. In the first experiment we analyzed casts of eight common Dutch earthworm species for P pools and related soil properties. For all species, pH in casts was higher than in the bulk soil (up to 1.6 pH unit). Dissolved Organic Carbon (DOC) concentrations were an order of magnitude higher in the casts, and directly available P (defined as water-soluble ortho-phosphate) up to two orders of magnitude. Although these effects were significant for all earthworm species, significant changes were found between the species that could not be explained by conventional earthworm feeding guilds. In the second experiment, we tested effects of three different earthworm species across four soils differing in texture, metal oxide composition, P availabilty and pH. We found a significant effect of earthworms on P availability in all soils, but the extent of this effect varied. Using surface complexation modeling we evaluated the relative importance of the various possible mechanisms. We concluded that the effect of pH on P desorption was relatively small. Increased mineralization of organic P did play an important role; as did competitive desorption of DOC to metal oxides. However, our study also showed a new important pathway: a reduction in reactive surface area of soil metal (hydr)oxides during earthworm gut passage. As this decrease was important in iron (hydr)oxide-dominated soils but not in aluminum (hydr)oxide-dominated soils, we suggest that earthworms have the largest potential to affect soil P availability in the former soils.

How to cite: Van Groenigen, J. W., Vos, H. M. J., Hiemstra, T., and Koopsman, G. F.: Through which pathways can earthworms increase soil phosphorus availability?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13417, https://doi.org/10.5194/egusphere-egu22-13417, 2022.

Microbial necromass is regarded as a central pool of soil organic carbon, whose management is critical in efforts to reduce atmospheric CO₂ concentrations and mitigate climate change. However, recent concepts on soil organic matter formation have ignored one of the most important factors for the formation and stabilization of microbial necromass in many soils: earthworms. Based on recent evidence, we conceptualize how the ingestion and mixing of mineral particles and organic matter by earthworms temporarily convert the egested soil to a hotspot of quick and efficient microbial growth and turnover, in which increased amounts of necromass tightly bind to mineral surfaces and stabilize within aggregates. We further stress the low dependence of this process on the quality of pre-existing soil organic matter (in contrast to the assumptions of recent concepts) and its high relevance to the resilience of soil carbon to external disturbances in extensive regions of the soil remote from classical hotspots of microbial necromass formation. We finally provide suggestions on how to close remaining research gaps.

How to cite: Angst, G., Frouz, J., van Groenigen, J. W., Scheu, S., Kögel-Knabner, I., and Eisenhauer, N.: Aligning earthworm activity and microbial necromass formation in mineral soil, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13493, https://doi.org/10.5194/egusphere-egu22-13493, 2022.

In alley cropping sites, parallel tree rows covered with herbaceous vegetation are added into cropped fields. These tree rows provide an additional habitat for many soil organisms in plots that are usually low in biodiversity. Previous studies showed that tree rows present a higher diversity and higher densities of soil fauna compared to the crop alleys. However, it is not sure that the crop alleys really benefit from the presence of additional fauna in the tree rows. A possible benefit could come from a dispersal of soil fauna hosted in the tree rows towards the crop alleys during favorable periods of time, but such movements have never been investigated. Our experiment investigated the movement of earthworms in tree rows vicinity in a Mediterranean alley cropping field planted with walnut trees, in which crop alleys were ploughed and cultivated with pea. Traps, consisting of three joined plastic walls sunk vertically into the soil and delimiting a cubic 25*25 cm wide soil block of 15 cm depth were placed at 30 cm from the tree row border in March 2019. These traps were opened on one side, allowing soil fauna entrance either from the tree row or from the crop alley, and defaunated at trap implementation (5 replications). Traps were removed 2 months after the beginning of the experiment and earthworm density determined by manual sorting. In addition, the plot was sampled at different distances from the tree row (0 m, 0.3 m, 1 m and 6 m i.e. in the middle of the crop alley) for earthworm density determination in 25*25*30 cm soil blocks at trap implementation and removal. Results showed that the distribution of epigeic earthworms (living at the soil surface) vary with the distance from the tree row, with more individuals found in the tree row and in its immediate vicinity than in the middle of the crop alley, while endogeic earthworms (living in the soil) presented no significant variation in their distribution with the distance from the tree row. Traps were mostly recolonized by endogeic earthworms, and significantly more earthworms were found in traps opened towards the crop alley than in traps opened towards the tree row. These results suggest than Spring was not a favorable season for earthworm dispersal from the tree row in this site, and that earthworms more probably used the tree row and its vicinity as a refuge against adverse conditions in the crop alley. This type of experiment should be repeated at other seasons, and with varying management practices of the crop alley, as different conditions could induce different movements.

How to cite: D'Hervilly, C., Bertrand, I., Berlioz, L., Dufour, L., and Marsden, C.: Unexpected movements of earthworms between tree rows and crop alleys in a Mediterranean agroforestry site, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-419, https://doi.org/10.5194/egusphere-egu22-419, 2022.

The objective of this work is to study the effect of microorganisms on carbon sequestration in
different soil landscapes of Ouargla’s basin. Ouargla is part of the arid zones of the Algerian
Sahara, which is characterized by high temperatures, low and irregular precipitation, sparse
vegetation and soils poor in organic matter. However, the soil remains a favorable environment
for macros and microorganisms which tolerates this deficit. The soil provides ecosystem services
to these environments by protecting natural resources. Microbial biomass, which represents on
average 2 to 4% of organic carbon, is involved in renewing organic matter in the soil. For this
study, 7 stations of different pedo- sequences were chosen. After collection, the samples
underwent microbiological analyzes for enumeration of bacteria and fungi, fumigation-extraction
and physicochemical analyzes. The enumeration of the main microbial groups in bacteria and
fungi showed the predominance of bacterial microflora, followed by fungal microflora at higher
values in cultivated soil and those of Sebkhat. The identification of fungal species according to the
determination keys allowed us to identify the following species: Alternaria alternata, Rizopus sp
and Aspergillus niger, as well as yeasts. The microbial carbon values show that this parameter is
higher in Sebkhat N’Goussa, gypsum soil in Frane and in cultivated soil. These are the stations
where high values of organic carbon and organic matter are recorded. We can say that
microorganisms play an important role in carbon sequestration. They mineralize microbial
residues and provide carbon to the stable organic matter fraction of the soil. 

Key words: carbon sequestration, ecosystem service, microbial carbon, organic carbon, Ouargla.

How to cite: Bensayah, M. N. E. H., Karabi, M., Hamdi Aissa, B., and Berkal, I.: Effect of soil microorganisms on organic carbon sequestrationindifferent soil landscapes of the Ouargla’s basin, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1020, https://doi.org/10.5194/egusphere-egu22-1020, 2022.

Reducing chemical fertilizers and agricultural residues substitution is a feasible practice to develop sustainable agriculture. However, there is a lack of evaluation on the ecosystem functioning and services of different reducing chemical fertilizers and agricultural residues substitution practices, as well as the roles of soil micro-food webs in sustainable agriculture. Here, we evaluated changes in crop yields, soil physico-chemical properties, soil micro-food web assembly, and ecosystem multifunctionality, and the contribution of soil micro-food web assembly to ecosystem multifunctionality under six long-term fertilization treatments: no fertilizer control, conventional chemical NPK fertilizers, and the reducing chemical NPK fertilizers and low- (30%) or high- (60%) levels of agricultural residues (i.e., straw or cattle manure) substitution. Our results showed that the reducing chemical fertilizers and agricultural residues substitution practices can maintain crop yields and improve soil fertility compared with chemical fertilizers application alone. The improvement of soil micro-food web was more obvious with the reducing chemical fertilizers and agricultural residues substitution practices, such as increased soil bacterial biomass, maintained soil biodiversity, and mitigated the negative effects of long-term chemical fertilizers application alone on soil micro-food web. More importantly, maintaining soil bacterial biomass, especiallly the beneficial microorganisms (e.g., Proteobacteria and Firmicutes), and bacterivorous nematode abundance is primarily important in  maintaining ecosystem multifunctionality. Overall, the reducing chemical fertilizers and agricultural residues substitution practices improved agroecosystem functioning and services and contributed to sustainable agriculture. 

How to cite: Zhao, J., Li, J., and Wang, K.: Linkages between soil micro-food webs and agroecosystem multifunctionality under organic and/or inorganic fertilization, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1397, https://doi.org/10.5194/egusphere-egu22-1397, 2022.

Soil microbes play a crucial role in terrestrial ecosystem biogeochemical cycling¹ and understanding microbial biogeography has provided fundamental information to predict ecosystem function². In contrast, the biogeography of soil viromes has been largely overlooked, even though viruses are key mediators of the soil microbiome and its function³. Here, we introduce the Global Soil Virome (GSV) dataset, the most comprehensive soil virus dataset to date, and present an overview of global biogeographic patterns and drivers of soil viromes. A total of 345,607 double stranded DNA partial viral genomes, of which 97.2% were unknown viral taxa, were assembled from 1,873 deeply sequenced soil metagenomes across the globe. We observed soil virome endemism across continents and plant biomes which were shaped by dispersal limitation and soil moisture. Unlike the scale-free pattern of most biological co-occurrence networks^4,5, we found that the degree distribution of the global soil virus co-occurrence network has a random pattern. The GSV dataset provides a critical resource for elucidating soil viral diversity and host-virus interactions; it provides in-depth insight into ecological processes that determine soil viral diversity.

How to cite: Ma, B., Wang, Y., and Xu, J.: Biogeographic patterns and drivers of soil virosphere across the globe, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1400, https://doi.org/10.5194/egusphere-egu22-1400, 2022.

Conservation tillage has become the core technology to conquer the degradation of black soil, the ‘giant panda in arable land’. Since soil is a home to a variety of organisms, it is very important to regard soil as a living system to evaluate the impact of conservation tillage on the health of black soil. Therefore, based on the long-term conservation tillage trial established by the Key Laboratory of Mollisols Agroecology of the Chinese Academy of Sciences, the responses of soil biodiversity and its function to conservation tillage were comprehensively elucidated in this study. Compared with conventional tillage, conservation tillage strongly improved the species richness (1-8%), density (25-57%), and biomass (30-50%) of the entire soil assemblages, including microorganisms, nematodes, collembolans, mites and earthworms, as well as the connectance of soil food web (14-32%). Furthermore, conservation tillage promotes the performance of soil biotic function in soil structure formation, soil carbon sequestration and nitrogen efficient utilization and crop yield stability. These results suggest that conservation tillage can effectively utilize the functional potential of soil organisms, which is of great significance to supporting the healthy and sustainable development of agriculture in the black soil region of northeast China.

How to cite: Zhang, S., Chang, L., Chen, X., Zhang, Y., Yang, X., Jia, S., and Liang, A.: Conservation tillage and soil biodiversity in the black soil region of northeast China: results from a long-term tillage trial, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1946, https://doi.org/10.5194/egusphere-egu22-1946, 2022.

Anthropogenic activities have profoundly increased the nutrient inputs into soil through inorganic nitrogen (N) and phosphorus (P) fertilization and atmospheric deposition over recent decades. In grasslands, nutrient enrichment is one of the most important global change factors affecting a range of ecosystem functions and services. Nutrient enrichment promotes some functions such as plant production, but at the cost of other ecosystem functions, which may obscure the net effects on multiple ecosystem functions (i.e., ecosystem multifunctionality). In particular, nutrient enrichment can strongly reduce above- and below-ground biodiversity, which might threaten ecosystem services that delivered by biodiversity. However, our understanding of the importance of soil biota as a component of nutrient-enrichment effects on ecosystem multifunctionality is still limited.

Taking advantages of a long-term field study and a controlled microcosm experiment, we explored whether and how nutrient enrichment affects ecosystem multifunctionality in a Tibetan alpine meadow. The diversity of soil biota across multiple trophic, including bacteria, fungi, protists and nematodes for two consecutive years were investigated from a 13-year field experiment under a gradient of N and P enrichment. A total of 14 ecosystem functions that are influenced by soil biota were measured and were grouped into five categories: (1) nutrient cycling, (2) SOM decomposition, (3) carbon and nutrient cycling drivers, (4) soil structure, and (5) pest control. To generate a comprehensive understanding of the biodiversity-ecosystem-function relationship under nutrient enrichment, a microcosm inoculation experiment using the dilution-to-extinction approach was conducted with soil samples with or without nutrient enrichment.

Our results showed that nutrient enrichment weakened multifunctionality by reducing the multidiversity across soil food webs. Specially, soil biodiversity at higher trophic levels (e.g., microbivorous nematode) supported a greater number of ecosystem functions at high levels of functioning than those of lower trophic levels, such as bacteria and fungi. Microcosm experiment further demonstrated that nutrient enrichment weakened the relationships between soil biodiversity and ecosystem multifunctionality. Together, our results provide insight into the importance of soil biodiversity for maintaining soil multifunctionality under nutrient enrichment, as well as providing strong support for inclusion of multiple aspects of soil biodiversity in conservation and management policies under global change scenarios.

How to cite: Hu, Z., Chen, X., Hu, F., and Liu, M.: Nutrient enrichment reduces soil multidiversity and multifunctionality in an alpine meadow, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2153, https://doi.org/10.5194/egusphere-egu22-2153, 2022.

Soils host approximately 50% of the biomass and a major part of the diversity of animals on land. However, large-scale data that link soil animal diversity with ecosystem functions is limited to few regional studies, hampering our understanding of soil animal contribution to global biogeochemistry. Besides, global abiotic and biotic drivers and assembly processes in soil animal communities and food webs have not been comprehensively assessed. Here we introduce Soil BON Foodweb Team (SBF Team), a novel international voluntary initiative that addresses these gaps by a standardized global assessment of soil animal communities across micro-, meso-, and macrofauna. By sampling Soil BON sites (https://www.globalsoilbiodiversity.org/soilbon), this initiative is the first to link soil animal communities across the size spectrum to a range of soil functions worldwide. At present the initiative includes soil ecologists from 15+ countries covering all continents. We intend to expand the network and conduct the first sampling campaign in 2022 covering a minimum of 200 sampling sites globally. We are welcome for researchers especially from underrepresented countries. Jointly, we will be able to produce unprecedented data to address exciting and challenging questions and establish a global collaboration network for soil animal diversity monitoring and future joint work.

How to cite: Potapov, A. and the Soil BON Foodweb Team: Global monitoring of soil animal communities using a common methodology, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2267, https://doi.org/10.5194/egusphere-egu22-2267, 2022.

Soil microbial properties are highly sensitive to anthropogenic disturbance and a considerable impact of urbanization on soil microbial activity and diversity was reported for various cities and climates. The quantitative parameters of the soils’ microbiome in Arctic cities including the structure of microbial biomass and the number of ribosomal genes remain overlooked. This research aimed to compare quantitative indicators, as well as the functional diversity of soil microbial communities in the Arctic cities of Murmansk and Apatity located on the Kola Peninsula.

Murmansk (68.967 N, 33.083 E) is the biggest Arctic city in the world, located in the natural zone of the forest-tundra. Apatity (67.5°N, 33.4°E) is the fifth largest city in polar zone, located in the northern taiga zone.

Samples were collected from the topsoil horizons according to the standard sampling procedure with possible measures to prevent contamination. Quantitative assessment of the content of ribosomal genes of bacteria, archaea, and fungi was performed by real-time polymerase chain reaction (PCR). The prokaryotes and fungal biomass were determined by luminescence microscopy method. Community level physiological profiling (CLPP) was based on MicroResp^ТМ approach using substrates representing C sources of different quality: amino acids, carbohydrates, carboxylic and phenolic acid.

The number of archaea was an order of magnitude higher in Murmansk (predominantly 10¹⁰ of 16s rRNA genes/g soil) than in Apatity (predominantly 10⁹ of 16s rRNA genes/g soil); the number of 16s rRNA genes copies of bacteria was an order of magnitude lower in Murmansk (10⁹-10¹⁰) compared to Apatity; the number of copies of the ITS rRNA genes of fungi was the same for both locations - 10⁹ on average.

The biomass of prokaryotes was 5 times higher in Murmansk (5-25 μg/g soil) compared to Apatity (1-6 μg/g soil); the fungal biomass was 3.3 times higher in Murmansk (50-1000 μg/g soil) than in Apatity (40-300 μg/g soil). The length of the mycelium of actinomycetes in the soils of Murmansk (1-100 m/g of soil) was an order of magnitude higher than that in Apatity (0-10 m/g of soil); the length of the fungal mycelium was 3.5 times longer in Murmansk (10-600 m/g of soil) than in Apatity (0-170 m/g of soil).

Soil microbial communities in Arctic cities had a similar physiological profile. Groups of microorganisms consuming carbohydrates and carboxylic acids prevailed. The soils of both cities contained microorganisms capable of decomposing complex organic compounds with a benzene ring, such as phenolic acids (vanillic and lilac), which indicates the potential for the destruction of difficult-to-decompose  substances.

Thus, soil microbial communities in Arctic cities differ to a greater extent in quantitative parameters than in qualitative ones (on example of functional diversity). Probably, the quantitative parameters are more influenced by microclimatic conditions, type of vegetation, level of anthropogenic load, etc.

Acknowledgements This research was supported by RFBR #19-29-05187 and RUDN University Strategic Academic Leadership Program.

How to cite: Korneykova, M., Nikitin, D., Vasenev, V., and Dolgikh, A.: Quantitative indicators and functional diversity of soil microbial communities in the Russian Arctic cities, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2756, https://doi.org/10.5194/egusphere-egu22-2756, 2022.

    Grassland ecosystems worldwide are facing habitat degraded due to human activities. Although it is commonly proposed that livestock can have negative repercussions for multiple ecosystem functions in degraded grasslands, this question has yet to receive explicit scientific attention. We used a 3-year field-manipulated grazing experiment, including livestock grazing by sheep across three grasslands with different levels of degradation to evaluate the role of large herbivore in regulating soil nematodes and ecosystem multifunctionality. Our findings reveal the context dependency of this role in grassland degradation. We show that livestock show higher levels of soil nematode biomass and ecosystem multifunctionality than lightly degraded grassland with enclosure, and facilitate soil nematode diversity and maintain ecosystem multifunctionality in moderately and severely degraded grasslands. We propose that moderate herbivore grazing should be considered as nature-based solutions to improve and maintain both soil nematodes and ecosystem multifunctionality in degraded grasslands. The information is fundamental for improving nature’s benefits to people and considering conservation efforts of grassland restoration.

How to cite: Yang, J., Wu, D., and Wang, D.: Proper grazing is nature-based solutions to restore soil nematodes and ecosystem multifunctionality in degraded grasslands, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3485, https://doi.org/10.5194/egusphere-egu22-3485, 2022.

Organic substitution can benefit to enhance soil health and maintain sustainable food production. Soil organisms play important roles in decomposing organic matter, recycling soil nutrients and resisting pests and diseases. However, the effect of soil biodiversity on soil multifunctionality of farmland ecosystem under organic substitution is still unclear. Here, we studied the shifts of soil biotic communities and soil multifunctionality (functions related with C, nutrient cycling and crop yield), and investigated soil biotic diversity-ecosystem function relationship under a 5-year field organic substitution experiment (30% nitrogen fertilizer substitute with straw, cattle manure and biochar, respectively). Our results showed that the highest value of soil multifunctionality was found in straw substitution treatment. Soil nematode community composition significantly associated with soil multifunctionality. We used structural equation modelling to identify the effects of soil biotic diversities and composition on multifunctionality. The SEM model predicted 74% of the variation in soil multifunctionality, and found that nematode community composition directly drove soil multifunctionality, whereas organic substitution and bacterial community composition could indirectly affect soil multifunctionality by changing soil nematode community. Our study has important implications for the contribution of soil biodiversity in driving multifunctionality of farmland ecosystem and for maintaining the sustainable development of agriculture.

How to cite: Du, X. F., Liu, H. W., Li, Y. B., Zhang, X. K., and Liang, W. J.: Effects of soil biodiversity on soil multifunctionality after 5-year organic substitutions in a Maize field, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3500, https://doi.org/10.5194/egusphere-egu22-3500, 2022.

The improvement and protection of ecosystem function are important in the restoration of grassland ecosystem, especially in degraded grasslands. Soil inoculation provides an effective way for the restoration of degraded ecosystems. Here we conducted a field soil inoculation experiment and selected two well-developed soils (meadow steppe and upland meadow) to transplant them into degraded grasslands at three inoculation amounts (0.01 m³, 0.03 m³ and 0.05 m³ per square meter). After three years of soil inoculation, we assessed the ecosystem multifunctionality (including plant productivity, and functions related to nutrient cycling) of different treatments with different identity and amount of soil inoculation. Principal co-ordinates analysis suggested that different identity of soil inoculum resulted in different development of soil fungal and bacterial communities. Ecosystem multifunctionality was significantly improved with the increase of soil inoculation amounts. Spearman’s correlation analysis showed a positive association between ecosystem multifunctionality and soil fungal richness, plant cover, and the amount of soil inoculation. Our results indicate that soil inoculation can enhance ecosystem multifunctionality by affecting the soil biotic and plant communities. Our finding has important implications for better restoration of biodiversity and ecosystem functioning in degraded grassland ecosystems.

How to cite: Li, Y. H., Han, X., Li, Y. B., Li, Q., and Bezemer, M.: Soil inoculation improves ecosystem function in degraded grasslands, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3548, https://doi.org/10.5194/egusphere-egu22-3548, 2022.

The microbiological and agrochemical parameters of the soils of fallow (abandoned), active agroecosystems and background (benchmark) landscapes of the Yamalo-Nenets Autonomous Region were studied. The soils of vegetable gardens (the setllements of Muzhi, Nadym, Tovopogol, Polyarny, Seyakha), the soils of parks, recreational and industrial zones and archaeological monuments (the cities of Nadym, Labytnangi, Salekhard, Novy Urengoy) were studied. The morphological and taxonomic diversity of natural and agro-soils of the key plots of the study has been established. The key chemical and soil-hydrophical differences of agrozems and agro-soils from natural background soils are revealed. The parameters of the alpha and beta diversity of the soil microbial community were studied by new generation sequencing methods. The phylums of microorganisms common to all the studied soils and those phylums that are characteristic of agrogenic soils are revealed. In some cases, there is an increase in the parameters of biodiversity in agrogenic soils in comparison with to natural ones, which indicates the diversification of edaphic ecological niches. The parameters of the metabolic dynamics of the microbial community under the conditions of chemical contamination of cryogenic soils are established. Ecotoxicological studies of soils of urbanized ecosystems of a number of settlements of the Yamalo-Nenets Autonomous Regions were carried out, even in terms of assessing ecosystem services of soils. A structure has been created and a database has been partially filled, including information on the localization, diversity, current state and use of agrogenic soils in the region.

This work was supported by Russian Foundation for Basic Research, project No 19-416-890002

How to cite: Abakumov, E., Nizamutdinov, T., and Morgun, E.: Microbiological and agrochemical characteristics of abandoned agricultural soils of central part of Yamal region, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3795, https://doi.org/10.5194/egusphere-egu22-3795, 2022.

Belowground consumers create complex food webs that regulate functioning, ensure stability and support biodiversity both below and above ground. However, existing soil food-web reconstructions do not match recently accumulated empirical evidence and there is no comprehensive reproducible approach that accounts for the complex resource, size and spatial structure of food webs in soil. I build on generic food-web organization principles and use multifunctional classification of soil protists, invertebrates and vertebrates, to reconstruct “multichannel” food-web across size classes of soil-associated consumers. I then use food-web reconstruction, together with assimilation efficiencies, to calculate energy fluxes assuming a steady-state energetic system. Based on energy fluxes, I describe a number of indicators, related to stability, biodiversity and multiple ecosystem-level functions such as herbivory, top-down control, translocation and transformation of organic matter. The multichannel reconstruction can be used to assess trophic multifunctionality (analogous to ecosystem multifunctionality), i.e. simultaneous support of multiple trophic functions by the food-web, and compare it across communities and ecosystems spanning beyond the soil. With further validation and parametrization, the multichannel reconstruction approach provides an effective tool for understanding and analysing soil food webs. I believe that having this tool will inspire more people to comprehensively describe soil communities and belowground-aboveground interactions. Such studies will provide informative indicators for including consumers as active agents in biogeochemical models, not only locally but also on regional and global scales.

How to cite: Potapov, A.: Multifunctionality of belowground food webs, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3923, https://doi.org/10.5194/egusphere-egu22-3923, 2022.

Climate change´s effect on soil functioning is a major concern in the Mediterranean basin, where rainfall will be likely reduced by 30% by the end of the century. Soil organic matter contributes to water balance by improving soil structure and aggregate stability, increasing water infiltration and holding capacity. Therefore, C-poor soils, as agricultural soils, might be more vulnerable to drought conditions. The addition of organic amendments increases soil organic matter and improves soil properties. The quality of the added substrate may determine soil microbial community structure and activity, which can also influence soil response to drought. The main objective was to evaluate the effect of the application of organic amendments with different quality (as indicated by their C:N ratio) on soil properties, plant development, and the resistance of soil functioning against simulated drought conditions. Hypothetically, the addition of a substrate with a high C:N ratio favours fungal dominance within the soil microbial community, which is usually related to a higher soil resistance.

An experiment was carried out in pot mesocosms under greenhouse conditions. Four organic substrates in a C:N ratio range were selected: 1) leonardite (LE, C:N = 57,8); 2) earthworm humus (HU, C:N = 15,6); 3) biosolid compost (BC, C:N = 8,8); and 4) dry biomass of Vicia faba (VF, C:N = 10,2). Their effect was compared with a non-amended control (NA). After amendment application, seeds of Lolium rigidum and Medicago polymorpha were sown, and a drought treatment was established. Half of the replicates received a 30 % less water supply, belonging to the drought treatment (DR), compared to the control (CT). The factorial experimental design resulted in 10 treatments with 10 replicates per treatment. A base-line soil sampling was done before the establishment of the drought treatment and repeated after 30 days, analysing soil biological properties (microbial biomass, enzyme activities, soil respiration rate). Soil moisture in the upper 5 cm was periodically measured.

Amendment addition improved some of the microbial activity indices in relation to non-amended soils, such as N-acetylglucosaminidase activity (in all the amended soils) and dehydrogenase activity (in HU and VF). Microbial biomass was greatly increased by amendment application (80 % increase). BC was the most efficient in improving soil water availability (32% higher than in NA), showing no significant differences in soil moisture between DR and CT. BC and VF amendments significantly reduced L. rigidum germination rate, and drought conditions significantly reduced plant growth compared to the control. However, by the end of the experiment, L. rigidum biomass in both treatments was higher than in the other treatments. M. polymorpha germination rate was also reduced in BC and VF, but only in LE drought conditions significantly affected plant development. Despite this, the simulated drought conditions did not result in a significant change in any of the soil functioning variables measured. In conclusion, organic amendments enhanced soil microbial activity in a C-poor agricultural soil but did not clearly improve soil response to a simulated drought event.

How to cite: Morales, L., Domínguez, M. T., and Fernández-Boy, E.: Effect of the addition of organic amendments to C-poor agricultural soils on soil resistance against drought, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5532, https://doi.org/10.5194/egusphere-egu22-5532, 2022.

Microbial taxonomic diversity is considered as one of the crucial factors responsible for the sustainable functioning of soil systems. However, it is still unclear to what extent microbial taxonomic diversity reflects its functional diversity. In this study, we compared taxonomic and functional diversity of the soil microbiome in a few natural and agricultural ecosystems.
Soil samples were collected three times (April, July, and October) from grassland, deciduous forest, and three agricultural ecosystems (no fertilizers, NPK, cattle manure). We applied high-throughput sequencing on the Illumina MiSeq platform using a combination of multiple DNA metabarcoding markers and characterized soil prokaryotic (16S rRNA gene: bacteria and archaea) and eukaryotic (ITS2 to target fungi; 18S rRNA gene to target protists) communities. Community-level physiological profiles of the soil microbiomes were analyzed using Biolog Ecoplates to assess functional diversity of heterotrophic microorganisms.
All five soils differed significantly from each other in the taxonomic composition of the bacteriome, the mycobiome, and the protistome. The forest soil microbiome was characterized by the higher relative abundances of Verrucomicrobia, Agaricomycetes, Apicomplexa, and Mesomycetozoa. Proteobacteria, Acidobacteria, Sordariomyces, Cercozoa, and Ochrophyta were the dominant taxa in the agricultural soils. Surprisingly, taxonomic diversity of the bacteriome, the mycobiome, and the protistome in forest soil was significantly lower compared to the agricultural soils (except the NPK treatment). Differences in microbial physiological profiles between distinct ecosystems were much lower than those in taxonomic diversity. The forest soil microbiome was characterized by the highest physiological activity and plasticity, especially for amines and phenolic compounds. Our findings suggest that lower microbial taxonomic diversity does not necessarily result in lower functional diversity of the soil microbiome.

This research was supported by the Russian Science Foundation, Project No 21-76-10025.

How to cite: Semenov, M., Krasnov, G., Ksenofontova, N., and Nikitin, D.: Higher taxonomic diversity of protists, fungi and bacteria, but lower functional diversity in soils of agricultural ecosystems compared to a deciduous forest, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6520, https://doi.org/10.5194/egusphere-egu22-6520, 2022.

The protection of soil biodiversity is essential for ensuring soil functioning and provisioning of related ecosystem services, but also the conservation of species per se. For this purpose, it is essential to know what soil organism is where and how it is influenced by environmental, climate and human activities. 

Numerous studies (there are over 1400 published articles) have been elaborated in Europe regarding soil fauna. A data platform to store data on soil fauna already exists and is currently under further development to become a pan-European data warehouse for soil biodiversity (https://www.eudaphobase.eu/). Though, the data stored in this database until now comprises only a small percent of the available data. Hence, it is evident that a compiled dataset providing an overall understanding of the distribution of several taxa across European biomes and under different land use still is missing.

Attempting to fill this gap, we start a new initiative within the framework of the Cost Action EUdaphobase CA18237: the creation of the first European Atlas of Soil Fauna.  We aim to map, summarize and upscale the current knowledge on soil fauna to help in providing support to the scientific community and directions to stakeholders and policymakers. We seek collaboration (data holders and experts) to identify, collect and analyze data of all groups of micro-, meso- and macrofauna in Europe. 

This presentation will focus on the aims of this initiative and the way we plan to collect data and involve people.

How to cite: Cortet, J., Tsiafouli, M., Krogh, P.-H., and Russel, D.: Towards creating the first European Atlas of Soil Fauna, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6933, https://doi.org/10.5194/egusphere-egu22-6933, 2022.

The resilience of ecological systems is crucially important, particularly in the context of climate change. We present experimental evidence of critical slowing-down arising from perturbation of a key function in a complex ecosystem, exemplified by soil. Different behavioural classes in soil respiratory patterns were detected in response to repeated drying:rewetting cycles. We characterised these as adaptive, resilient, fragile or non-resilient. The latter involved increasing erratic behaviour (i.e. increasing variance), and the propagation of such behaviour (i.e. autocorrelation), interpreted as a critical slowing-down of the observed function. Soil microbial phenotype and land-use were predominantly related to variance and autocorrelation respectively. No relationship was found between biodiversity and resilience, but the ability of a community to be compositionally flexible rather than biodiversity per se appeared to be key to retaining system function. These data were used to map the extent to which soils are close to crossing into alternative stable states at a national scale.

How to cite: fraser, F., Corstanje, R., Todman, L., Bello-Curás, D., Bending, G., Deeks, L., Harris, J., Hilton, S., Pawlett, M., Zawadzka, J., Whitmore, A., and Ritz, K.: Evidence of ecological critical slowing-down in temperate soils, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8252, https://doi.org/10.5194/egusphere-egu22-8252, 2022.

Testate amoebae are a common group of shelled amoeboid protists that are widespread in terrestrial systems. They play a key role in microbial foodwebs and are useful bioindicators of present and past conditions due to their long-lasting shells. However, their diversity and distribution has not yet been investigated and visualised at a global scale. With extensive data collection effort involving the global testate amoebae community, we compiled data on testate amoebae from 10,889 locations worldwide: 9235 terrestrial, 1322 freshwater and 219 marine-interstitial sites. In terrestrial systems, 1187 species were recorded. The highest total number of species was documented on the continent of Asia (699 species) and the lowers in Antarctica (151 species). Preliminary analyses of terrestrial samples showed negative correlation of species number with increasing absolute latitude, peaking at low-mid latitudes. However, longitude also played a significant role in species distribution. The most studied continent is Europe (42 % of all samples) and the least studied is Africa (2 %). The data we have collected are the basis for identifying the fundamental ecological determinants of diversity and species composition of testate amoebae and for understanding patterns in microbial diversity. We will show the recent findings of this ongoing endeavour.

How to cite: Krashevska, V. and the co-authors: Global patterns in testate amoebae diversity, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8672, https://doi.org/10.5194/egusphere-egu22-8672, 2022.

Global biodiversity is being threatened by climate change and human activities. Prior studies have demonstrated the negative concequences of land-use such as conversion of forest into monoculture, while its effects on belowground organisms especially soil invertebrates remain unclear. Earthworms are well-known ecosystem engineers that deliver multiple ecosystem functions including decomposition, carbon sequestration and plant growth. Yet, all of those functions are negatively affected by land-use conversion. Previous studies concerning land-use effects on soil biodiversity were generally conducted at a single site and small spatial scale, how soil biodiversity changes across spatial scales remains poorly understood.

In current study, earthworms were quantitatively sampled from 41 sites in three land-use types (i.e., farmland, orchard and forest at each site, five replicates) in subtropical region of China. Earthworm species were identified using both morphological and molecular methods. Earthworm density, biomass and body size were recorded. Notably, the species were also classified into different functional guilds. Totally, 84 species (or subspecies) were identified. Generally, local diversity (α diversity) was higher in agricultural lands than in forest lands, however, the opposite was true for regional diversity (γ diversity). In addition, the density of earthworm was the lowest in forest, while the biomass and body size were higher in agricultural lands. A higher proportion of endogeic and anecic earthworms were found in farmland and orchard than in forest. The land-use caused changes in soil properties contributed to the difference in earthworm diversity, abundance, biomass and body size.

In conclusion, we suggest that the impacts of human land-use on soil earthworm assemblage are scale-dependent, and the diversity, abundance, biomass and body size respond differently to land-use. Researches on different scales about land-use effects to soil biodiversity are urgently needed.

How to cite: Wang, D., Li, X., Du, Y., Sun, J., Qi, X., Xu, M., Jiao, K., Zhang, Y., Zhang, C., Shi, S., Gong, X., Wu, D., and Liu, M.: Human land-use increases earthworm diversity at local scale but not at the regional scale while improves abundance, biomass, and body size, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8992, https://doi.org/10.5194/egusphere-egu22-8992, 2022.

The issue of exploited soils that become unproductive after extended agriculture use is constantly growing and it is considered of great interest on a global level. Soil degradation induces loss of important ecosystem services and biodiversity, which is aggravated by the on-going climate change. Here, we investigated the chances of reforestation of an exploited soil as a possible nature based solution to this problem. We aimed at identifying a type of forest management capable of requalifying these soils. For that, we investigated a site in Central Italy characterized by a mixed-species plantation represented by tree different associations consisting of particular ancillary species, namely Alnus cordata, Elaeagnus umbellata (both N-fixing species), and Corylus avellana, in association with valuable species, such as Populus alba and Juglans regia planted on a former agricultural land. The criteria for the  improvement of soil quality was an increase in organic matter and biodiversity. We evaluated how the relationship between soil chemical and biological parameters varied among different intercropping systems and in a conventional agricultural field. We tested topsoil (0-10 cm) total organic carbon, total nitrogen, lignin and cellulose, as well as biological parameters such as fluorescein diacetate hydrolase (FDAH) enzyme activity, and fungal biodiversity by using a DNA metabarcoding approach. The comparison with the agricultural field revealed that revegetation led to an increase in both carbon and nitrogen as well as FDAH activity and fungal diversity. In this context, ancillary species could play a key role in restoring degraded soils quality, whereas N-fixing species Alnus cordata increased both soil fertility and biodiversity compared to the agricultural field and to other tree associations.

How to cite: Michele, I., Fioretto, A., Guggenberger, G., De Castro, O., De Luca, D., Di Iorio, E., and Danise, T.: From agriculture to forests: restoring fertility and biodiversity of exploited soils, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9334, https://doi.org/10.5194/egusphere-egu22-9334, 2022.

Soil biota, across multitrophic levels, regulates nutrient cycling and plant performance, and thereby play an important role in delivering multiple ecosystem functions. Soil nematodes occupy diverse positions in the soil food web, such as herbivores, bacterivores, fungivores, omnivores, and predators. Therefore, soil nematodes are usually considered as potential bio-indicators of soil quality or soil health under agricultural managements. However, there is a knowledge gap on how nematode multitrophic biodiversity (here the numbers of nematode trophic groups) affects soil multifunctionality.

This study combined field and laboratory experimental approaches to quantify and disentangle the aforementioned issue. First, we explored the impacts of compost application on nematode assemblages as well as multifunctionality based on a long-term field experiment. Results showed that compost application stimulated multitrophic biodiversity by the increase of microbivore and omnivore-predator abundance, while decreasing the herbivores. Besides, the increase of nematode multitrophic biodiversity was accompanied with the soil multifuctionality. Then a complete factorial design microcosm experiment was conducted with manipulating nematode trophic levels (microbivores, herbivores and omnivore-carnivores) to test the hypothesis that increasing multitrophic biodiversity will lead to higher soil multifuctionality as indicated by plant growth and defense to the pests. Consistent with the hypothesis, we found that integrating different trophic levels, i.e. maximum multitrophic biodiversity, could promote plant growth and notably the resistance to pest infestation through changing plant chemical composition. Particularly, we found microbivores reduced root biomass while omnivore-carnivores increased plant shoot biomass. The presence of omnivore-carnivores could suppress the abundance of insect (brown planthoppers) by regulating soil microbiome. In summary, the increment of soil multitrophic biodiversity have multifunctional consequence.

Overall, we provide direct experimental evidence for the multifunctional roles of soil multitrophic biodiversity. Further, soil organic management practices, regardless of organic amendments, non-tillage or growing cover crops, that improving soil habitat like resource and structure, and consequently promoting soil biodiversity especially higher-level biotic associations or trophic interactions may ultimately contribute to sustaining multiple ecosystem services including both crop productivity and pathogen controls. Such knowledge helps advance the mechanical understanding of biotic drivers of soil ecosystem functioning. It also highlights that organic management could strengthen the carbon-based ecosystem services if considering the extra benefits provided by soil biodiversity. Overall, our study corroborated organic management will be crucial to implement an ecologically multifunctional agriculture.

How to cite: Chen, X., Li, M., Qiu, L., Yang, Q., Zhou, Y., Zhu, B., Wan, B., Liu, T., Hu, Z., and Liu, M.: Consequences of soil multitrophic biodiversity promoted by organic input management for ecosystem multifunctionality, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9338, https://doi.org/10.5194/egusphere-egu22-9338, 2022.

Peatlands are a major carbon (C) sink and represent important habitats for nature conservation because of the occurrence of specifically adapted organisms. Peatlands are typically nutrient-poor environments, and thus extremely sensitive to nitrogen (N) depositions. In fact, increasing N inputs can cause a shift from a Sphagnum moss- to a vascular plant-dominated vegetation as well as an alteration of the mire geochemistry which, in turn, affects the litter composition and decomposition rate. Peatland is an extremely fragile ecosystem: at the European level, >60% of this habitat type has been lost just in the last decades. In Alpine peatlands, in particular, overgrazing has been identified as a main problem for habitat integrity and biodiversity.

In the present study, six Belarus (50-cm deep) cores were collected from several peatlands located in the Adamello-Brenta Nature Park (Trentino, Italy) mirroring a grazing-induced disturbance gradient. All cores were cut frozen into 3-cm sections, and analysed for dry density, water content, pH, EC, and elemental (CHNS) composition. Diatom taphocoenoses were also determined. In particular, diatom frustules were prepared using hot hydrogen peroxide and finally mounted in the Naphrax© resin to produce permanent mounts for identifications and counts. 400 valves were counted and identified to the species level in each slide using a light microscope at x1000 magnification. The whole procedure was kept quantitative to allow the calculation of absolute abundances (n-valves/g-peat-dw).

Physical, chemical and biological parameters generally underlined how the grazing influence was clear mainly in the top 20 cm, and resulted in an increasing of density (up to 2×) and N concentration (up to 3×) as well as in a lower gravimetric water content (up to 50%). No significant differences were observed below 30 cm of depth.  More than 100 diatom species were identified throughout the 6 cores investigated, and several of them are included in threat categories of the Red List for central Europe (e.g., Cymbopleura valaiseana, Eunotia hexaglyphis, E. triodon). Since diatoms can reflect major regional environmental gradients, they can be used as indicators of ecological conditions in peatlands. In fact, some species that are trivial (= frequent and often abundant) in mire environments in spite of being relatively rare at the overall level of European inland waters (e.g., Aulacoseira alpigena, Encyonema perpusillum, Kobayasiella micropunctata) were found in the cores from highly-grazed areas whilst several rare and sensitive species were detected only (or were clearly more frequent) in cores from mildly-grazed areas.

This research can provide useful indications on the harmful effects of grazing in terms of both biogeochemical cycles and nature/habitats conservation.

How to cite: Cid Rodriguez, M., Cantonati, M., Spitale, D., and Zaccone, C.: Impact of cattle grazing on peat properties and diatoms, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9910, https://doi.org/10.5194/egusphere-egu22-9910, 2022.

Soil fauna are now recognized as key components of soil and plant health, but how soil fauna modulates or even dictates plant stress responses remains unknown.Prior studies found the impacts of soil fauna on the plantprioritize either growth or defence depends on the feeding types of herbivores, suggesting that aboveground responses to herbivores and soil fauna are interconnected.However, the molecular and metabolism mechanism underlying this relationship is unclear.Theoretically, soil biotic interactions modified by soil fauna can drive above-ground responses, but there is still shortage of experimental evidence. Here, we aimed to test whether and how the plant survival strategies subjective to different feeding types of herbivores, were affected by rhizosphere microbial interactions exerted by soil fauna. We hypothesized that aboveground stress responses in plants can be orchestrated through coordinating belowground biotic interaction by soil fauna-root commensals.

First, we set out a complete factor design experiment under field condition by manipulating earthworms (Metaphire guillelmi) and the types of above-ground insects (cell-feeding, thrips: Frankliniella occidentalis; phloem-sucking, aphid: Myzus persicae). Soil physicochemical analysis and leaf RNA-seq were used to expound how earthworms dictates the trade-off between plant growth and defence. Second, to further explore the soil biotic-mediate pathway in the presence of earthworms. A microcosm experiment was performed by using a re-inoculated different soil community (obtained from 1000 and 20 μm sieves, respectively) collected from the field, with and without earthworms in the absence of herbivores. We used amplicon sequencing and plant metabolite analysis to elucidate how earthworm function by shaping rhizosphere biotic interactions.

We report here that belowground commensals can orchestrate aboveground stress responses in plants through biotic interaction. Earthworms suppressed thrips number, consistent with a resource-cost model. Contrary, earthworms promoted aphids’ number through the hormone antagonism model. Notably, soil biotic properties affected plant performance rather than soil abiotic properties mediated by earthworm. The microcosm experiment verified that rhizosphere microbial diversity and community structure shaped by earthworms reformed plant performance. In inoculated soil conditioned by earthworms, soil microbiome tended to be bacterial community towards primary metabolic processes, strengthening the interaction between fungi and bacteria in the rhizosphere. Further, the strengthened rhizosphere microbial interactions were increased plant shoot biomass and soluble sugar accumulation but decreased JA content. Taken together, effects of soil fauna on plant growth-defence relationships depend on the feeding types of herbivores, mainly attributing to the shifts in rhizosphere microbial interactions. Phenotypic plasticity and aboveground stress responses in plants can therefore be governed by soil fauna-root commensals.

How to cite: Jin, N., Gong, X., Li, J., Chen, X., Wu, D., Hu, F., and Liu, M.: Soil fauna modify plant growth-defence relationships through coordinating rhizosphere microbial interactions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10834, https://doi.org/10.5194/egusphere-egu22-10834, 2022.

The extreme biophysical and climatic conditions in the trans-Himalayan region of Ladakh limits the plant growth and therefore since, time immemorial, high altitude pastures has been utilized for food and fodder security along with crop farming. The study investigated the changes in the concentration of organic carbon (C), nitrogen (N) and phosphorus (P), potassium (K) and ph in soil of high altitude pastures along the altitudinal gradient (4000 to 5500m amsl) in Leh Ladakh, India. Three sites were chosen for the study: Gya pasture (4500-5500 m), Shang pasture (4200-5000 m) and Igoo pasture (4000 to 4800 m). The results showed that concentration of soil organic carbon C and total nitrogen increased with increasing altitude in all the three sites. The concentration of available phosphorus P and available potassium K slightly decreased and had a non-linear relationship, however in case of Igoo pasture, the P and K value increased with increasing altitude. While the ph remained towards basic (ph= 7-8) irrespective of the site and elevational change. Besides the elevation, the practice of livestock grazing during summer migration could also impact the soil nutrient concentration as higher nitrogen and carbon content is observed near the temporary settlements of the herders in the sites where the practice was still intact.

How to cite: Ladon, P. and Garkoti, S. C.: Soil nutrient concentration with increasing elevational pattern in high altitude pastures in Leh Ladakh, India., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11805, https://doi.org/10.5194/egusphere-egu22-11805, 2022.

The global area of cultivated land has increased considerably over the past five decades. Despite the many ecosystem services provided by soil, at large-scale, it is still poorly understood whether land-use intensification influences soil life and the services that rely upon it. Here we used an extensive soil metabarcoding database, derived from the European Union’s (EU) Land Use/Cover Area frame statistical Survey (LUCAS), to assess how vegetation (land) cover, biogeographic factors (i.e., climate) and soil properties influence the structure and potential functions of bacterial and fungal communities at a continental scale. We selected 715 LUCAS sampling locations, classified according to an increasing land-use intensification: from woodland (less disturbed), to grassland, and cropland (more disturbed). We found that croplands and grasslands had a higher microbial richness than woodlands. We observed that bacteria and fungi were not driven by the same environmental variables. While soil properties (e.g. pH, C:N ratio, potassium, phosphorus and carbonate contents) drove bacterial community composition, vegetation cover was the main driver for the fungal community. We found that vegetation cover, biogeographic factors and soil properties differently determined the distribution of main functional groups; for example, cropland soils with a higher pH and a lower C:N ratio hosted more nitrogen fixing bacteria whereas woodlands were dominated by ectomycorrhizal fungi, especially in non-compacted clay soils, with lower C:N ratio and potassium content. We observed that increasing aridity may inhibit functions beneficial for the plant communities (i.e. bacterial chemoheterotrophy and nitrogen fixation, arbuscular mycorrhizal symbiosis) and favour the spread of fungal pathogens. In addition, a high diversity was not always a positive aspect for ecosystem functioning, as for example, croplands were characterized by a higher presence of fungal pathogens. Maps of microbial functional groups for the EU were also generated. In conclusion, our results represent a step forward to a more comprehensive assessment of soil microbial diversity and associated functions across the European Union. Beside possible ecological implications, our findings can contribute to the development of indicators and implementation of soil management policies.

How to cite: Labouyrie, M., Romero, F., Panagos, P., Jones, A., Tedersoo, L., Ballabio, C., Lugato, E., van der Heijden, M., and Orgiazzi, A.: Soil microbial diversity and ecosystem functioning assessment across Europe, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12360, https://doi.org/10.5194/egusphere-egu22-12360, 2022.

Despite that all above-ground life depends on that below-ground, the knowledge on soil biodiversity is still very limited. Conservation activities have been often postponed due to missing data. For example, this was the case in previous EU Common Agricultural Policy agreements, when environmental indicators for soil biodiversity were meant to be integrated comparable to biodiversity indicators in place. While massive sequencing of soil biodiversity contributes significantly to shredding light on below-ground life, sampling methods are not adequately harmonised, preventing the establishment of reliable quantifiable conservation targets. In addition, broad-scale studies are often biased towards microorganisms and hence, in the majority of the published literature, eukaryotes, and more specifically, animals and protists, are neglected. Therefore, in a first EU-wide study of 885 sites, we investigated the response of environmental factors (i.e., soil properties, biogeographical location and climate) and land cover (cropland, grassland and woodland) on soil eukaryotic diversity. The LUCAS survey and previously published studies provided soil, climate and land cover data. DNA metabarcoding of the 18S genes allowed us to assess the diversity of animals, protists and fungi, but due to their high variability in body size, we grouped them into micro-, meso- and macrofauna. For the bioinformatics analyses, we clustered sequence reads into amplicon sequence variants using DADA2 and thereafter, we assessed alpha and beta diversity and the relationships between eukaryotic diversity and environmental drivers using regression, ordination, and variance partitioning analyses. Our results allowed us to identify potential indicator species for EU soils, representing the effect of different drivers on eukaryotic diversity. These findings will help to understand the links between soil abiotic and biotic patterns at large scale, pathing the way for quantifiable goals to be included in conservation activities and policies.

How to cite: Köninger, J., Panagos, P., Briones, M. J. I., and Orgiazzi, A.: Soil Eukaryotes Diversity in the EU - Environmental drivers in agricultural land, forests and grasslands, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12402, https://doi.org/10.5194/egusphere-egu22-12402, 2022.

The frequency and intensity of environmental fluctuations play an important role in shaping microbial community composition, trait-distribution, and adaptive capacity. We hypothesize here that a communities’ climate history dictates it’s metabolic response to future perturbation under a changing climate. Such a response is significant as changes in microbial metabolism can, in turn, feedback onto metabolite exudation, the chemical structure of necromass, and the formation and stability of soil organic matter. Here we use laboratory and field experiments to examine the metabolic pathways invoked under osmotic and matric stress within semi-arid and tropical soils. For example, using non-destructive, synchrotron-based Fourier-transform infrared spectromicroscopy we profiled the stress response of phylogenetically similar bacteria isolated from soils with contrasting climate histories subjected to both matric and osmotic stress. We note a strong carbohydrate-based, metabolic response of tropical microbes that is entirely absent in semi-arid organisms. At the field scale, we use metagenomic sequencing and metabolite analysis to demonstrate how four different sites established across a 1 m precipitation gradient from the Caribbean coast to the interior of Panama respond to a 50 % reduction in throughfall. The precipitation gradient permits the development of distinct communities at each site that show clearly divergent response to imposed hydrological perturbation. Our contribution here will discuss how communities adapted to different precipitation regimes respond metabolically to drought conditions, and how these change feedback onto the structure and stability of soil organic matter.    

How to cite: Bouskill, N., Karaoz, U., Chacon, S., Khurram, A., Dietrich, L., Holman, H.-Y., and Cusack, D.: Climate history dictates microbial metabolic response to drought stress: from semi-arid soils to tropical forest precipitation gradients, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1233, https://doi.org/10.5194/egusphere-egu22-1233, 2022.

How soil microorganisms respond to global warming is a key question in microbial ecology and eminently relevant for soil ecosystems, the terrestrial carbon cycle, and the climate system. However, physiological responses of soil microorganisms – key to infer future soil-climate feedbacks – are poorly understood.

We here make use of the longest lasting in situ soil warming experiment worldwide, ForHot, in which an Icelandic subarctic grassland site has been exposed to natural geothermal soil warming for more than 50 years. Using a metatranscriptomics approach, allowing the comprehensive study of the entire active soil microbial community and their functions by analysing expressed genes, we revealed key physiological responses of soil Bacteria to medium- (8 years) and long-term (>50 years) soil warming of +6 °C.

Irrespective of the duration of warming, we observed a community-wide upregulation of central (carbohydrate) metabolisms and cell replication and a downregulation of the bacterial protein biosynthesis machinery in the warmed soils. This coincided with a decrease of microbial biomass, a decrease of total and biomass-specific RNA content, and lower soil substrate concentrations in the warmed soils. We conclude that higher biochemical reaction rates, caused by higher temperatures, allow soil Bacteria to reduce their cellular number of ribosomes, the macromolecular complexes carrying out protein biosynthesis. To further test this we revisited the site and conducted a short-term warming experiment (6 weeks, +6 °C), which supported our conclusion.

The downregulation of the protein biosynthesis machinery (i.e., the reduction of ribosomes) liberates energy and matter, leading to a resource re-allocation, and allows soil Bacteria to maintain high metabolic activities and cell division rates even after decades of warming.

How to cite: Söllinger, A., Séneca, J., Dahl, M. B., Motleleng, L. L., Prommer, J., Verbruggen, E., Sigurdsson, B. D., Janssens, I., Peñuelas, J., Urich, T., Richter, A., and Tveit, A. T.: Physiological responses of soil microorganisms to weeks, years, and decades of soil warming, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2657, https://doi.org/10.5194/egusphere-egu22-2657, 2022.

Anthropogenic warming is expected to accelerate global soil organic carbon (SOC) losses via microbial decomposition, yet, there is still no consensus on the loss magnitude. Here we argue that, despite the mechanistic uncertainty underlying these losses, there is confidence that a strong, positive land carbon–climate feedback can be expected. Two major lines of evidence support net global SOC losses with warming via increases in soil microbial metabolic activity: the increase in soil respiration with temperature and the accumulation of SOC in low mean annual temperature regions. Warming- induced SOC losses are likely to be of a magnitude relevant for emission negotiations and necessitate more aggressive emission reduction targets to limit climate change to 1.5 °C by 2100. We suggest that microbial community–temperature interactions, and how they are influenced by substrate availability, are promising research areas to improve the accuracy and precision of the magnitude estimates of projected SOC losses.

How to cite: García-Palacios, P.: Evidence for large microbial-mediated losses of soil carbon under anthropogenic warming, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3539, https://doi.org/10.5194/egusphere-egu22-3539, 2022.

Permafrost soils usually remain frozen in summer, often even for millennia. Due to low temperatures, decomposition rates are low and alone Arctic permafrost is estimated to store 1850 Gt carbon (C). This currently corresponds to about twice the amount of atmospheric CO₂. While microorganisms within their seasonally thawing surface (active) layer are adapted to enormous temperature fluctuations, the intact permafrost microbiome contains spore-formers and extremophiles at low metabolic states. With global warming, seasonal thaw depth increases, not only leading to loss of ancient communities, but also to a growing availability of soil carbon for decomposition. Much of permafrost microbial taxonomic and metabolic diversity is unknown still, but our most urgent gaps of knowledge exist in monitoring this vulnerable microbiome’s ecological and metabolic adaptation in situ during permafrost thaw and erosion. Insights about microbial carbon sequestration in thawing soils is crucial - yet understudied, as permafrost environments are usually remote and modern sequencing techniques require elaborate sample storage and transport.

Here, we present our results of total RNA sequencing of abruptly eroding as well as intact 26200-year-old permafrost soils, from the high Arctic Northeast Greenland. Gene expression of samples describes the community composition (rRNA) and active metabolic pathways (mRNA) in zones of intensely degrading permafrost. The impact of changing physicochemical soil parameters with depth, such as pH, age, soil moisture and organic matter content was compared to determine possible metabolic and community-level responses. We revealed taxonomic composition and diversity, as well as metabolic pathways of microbial organic carbon remineralization especially at the crucial freshly thawed permafrost depths.

How to cite: Scheel, M., Zervas, A., Jacobsen, C. S., and Christensen, T. R.: Should I grow or should I go? - Transcriptomic responses of permafrost soil microbiomes to sudden thaw and erosion, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5516, https://doi.org/10.5194/egusphere-egu22-5516, 2022.

In temperate forests, ectomycorrhizal fungi (EMF) form the dominant mycorrhizal symbiotic association. EMF increase root uptake of nutrients and water in exchange for carbohydrates. The composition, structure and abundance of EMF communities are shaped by abiotic factors such as soil water availability, chemical and physical properties. Biotic factors also play a strong role especially tree species identity and plant physiological activity. Water availability affects both biotic and abiotic factors and thus is a major driver of EMF community structure and function. Under current climate change scenarios, seasonal drought risk is predicted to expand into areas where ecosystems may not be adapted to limited water availability. This is the case of European beech (Fagus sylvatica) forests growing along their southern distribution limit, in the Iberian Peninsula. Here, we characterized the abundance and composition of the EMF community and the patterns of root water uptake, in forests along a precipitation gradient (2500, 1100 and 900 mm/year), in northern Spain. We sampled soil, wood and fine roots in three mature pure beech forests at two times during the growing season, with contrasting soil water availabilities. DNA was extracted from EMF tips for molecular analyses (DNA meta-barcoding) to estimate species richness and diversity for each site and sampling campaign. Root colonization by EMF decreased in the late part of the growing season, when soil water availability was lower and this decline was larger at the rainiest site. We found that EMF species richness and diversity were similar across sites and sampling campaigns, irrespective of soil water availability. Yet, across sites, EMF communities were distinctly separated in the multidimensional space and did not change over the season, suggesting that EMF communities would be adapted to the local climatic and abiotic conditions. Analyses of water isotopic composition showed that root water uptake relied on upper soil moisture at the rainiest site, whereas it relied on deeper water reservoirs at the sites with more limiting water availability. Taken together our results suggest that EMF communities of F. sylvatica forests along their southern distribution limit would be adapted to low seasonal water availability, provided that trees had access to deep soil water. Also, at sites where water availability was more limiting, roots would take up water from deeper soil horizons, whereas nutrients and EMF would still concentrate in the shallower soil layers, which could suggest a spatial decoupling between nutrient and water uptake. Meanwhile, at sites with abundant rainfall, both nutrient and water uptake would be strongly linked to water availability in the upper soil and thus these functions could be potentially more vulnerable to changes in precipitation patterns, mainly increased frequency and duration of rainless periods.

How to cite: Gimeno, T., Moreno-Mateos, D., Matesanz, S., Fanin, N., Wingate, L., Porras, J., and Rodríguez-Uña, A.: Changes in the composition of ectomycorrhizal fungal communities and the water uptake of European beech forests across a natural precipitation gradient, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6050, https://doi.org/10.5194/egusphere-egu22-6050, 2022.

Carbon emissions from soil are large contributors to the global carbon cycle, but depend on processes occurring at a small scale. Carbon cycling in the soils is mediated by plant roots, soil fauna, and microorganisms including fungi and bacteria. Sophisticated molecular analytical techniques have been developed to characterize soil microbial communities, resulting in discovery of new microbial species that are not yet culturable in the laboratory. The unculturable fraction of soil microbial communities make for a large data gap since we are not able to characterize their activity, and even less so their role in the microbial community. As a result, soil carbon models cannot be readily parameterized from the bottom up—essentially, we cannot quantify functions at low taxonomic level and then scale up to the community level. In this numerical study, we aim to explore how soil carbon model predictions are affected by microbial diversity as characterized in silico by distribution of traits.

The resilience of soil microbial communities is related to distance to the surface and diversity. Diverse microbial communities that are closer to the surface, experiencing regular temporal fluctuations in environmental conditions are more resilient to disturbances than microbial communities deeper down in the subsurface. However, forest management practices and extreme climate conditions impose conditions that may be hitherto unforeseen. This makes prediction of response of soil microbial communities to new disturbances and soil carbon respiration thereof to be uncertain. In this contribution, we developed a microbial process network incorporating diverse organic matter compounds, and bacterial and fungal species characterized by distributions of trait values (including co-variations and trade-offs). With this framework, we explore if soil microbial diversity is a good predictor for soil carbon stocks and study diversity effect on community-level responses to disturbance and variations in environmental conditions. These results will assist in the development of a rate expression to capture the contribution of soil microbial community composition to carbon dynamics in soil.

How to cite: Khurana, S. and Manzoni, S.: Linking soil microbial biodiversity to soil carbon dynamics, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6862, https://doi.org/10.5194/egusphere-egu22-6862, 2022.

A diverse range of soil microorganisms accumulate energy to secure their future needs under resource fluctuation or deficiency. Microbial intracellular storage can substantially mediate the stress of resource variability across time, thereby supporting growth and reproduction. Microbial storage is well known in industrial applications and under pure culture conditions, yet few studies address its importance in the soil. To evaluate how widespread microbial energy storage is in soil, we quantified the contents of two intracellular storage compounds, polyhydroxybutyrate (PHB) and triacylglycerides (TAGs), from seven permanent grasslands in Germany differing in field management (grazing/mowing and fertilizing) and soil types. In winter 2021, soil was collected from two depths, 5-10 cm called topsoil, and >30 cm called subsoil, to capture different soil carbon inputs from grass roots. The storage compound contents were determined by gas chromatography–mass spectrometry (GC-MS). We hypothesized that the carbon input controls the storage compound levels. From topsoil to subsoil, as root carbon inputs (estimated from the fresh root weight) drop with depth, microbial storage levels follow suit. Dissolved organic carbon (DOC) was measured to qualify carbon availability to microorganisms, and microbial biomass carbon (MBC) was to assess microbial biomass. The root weight in the topsoil was 20-50 times higher than in the subsoil, while MBC and DOC contents were 3-4 and 1.5-2.5 times higher, respectively. Storage levels and MBC decreased with depth, and showed a positive correlation with DOC. This experiment allowed us to quantify intracellular storage occurrence in soils and to understand how its distribution related to root carbon input. These results point out that microbial intracellular carbon storage might accumulate according to the available carbon level (root carbon inputs) for microorganisms. Thus, this carbon plays a pivotal role for microbial ecology of soils as it prepares the microbial cells to survive throughout the winter when less carbon is provided by plants.

How to cite: Ding, Y., Komainda, M., Mason-Jones, K., Dippold, M., and Banfield, C. C.: Intracellular energy storage mediating soil microbial resource stress, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7699, https://doi.org/10.5194/egusphere-egu22-7699, 2022.

It is projected that the Amazon Forest could act as a carbon (C) sink in future climate change scenarios by efficiently storing extra biomass produced. Under atmospheric dioxide carbon (CO₂) elevation, the forest would experience an effect of C fertilization that could enhance nutrient requirements resulting in increased rates of nutrient cycling, soil enzymes activity, and soil microbial biomass stocks. However, we can expect that the potential effects of elevated CO2 (eCO₂) could be restricted by soil nutrient limitation, especially in the low phosphorus (P) conditions found in central Amazonia. We aimed to estimate the effect of eCO2 belowground, focusing on soil microbial biomass and enzymes activity on bulk soil and rhizosphere in central Amazonia, Brazil. In 2019 we set up the AmazonFACE program a CO₂ fertilization in a central Amazon rainforest in a factorial design experiment with eight Open-Top Chambers (OTC): four controls with ambient CO2 concentration (aCO₂), and four with eCO₂ (200 ppm above the control chambers). We grew six pots with Inga edulis, a native N-fixing species, per OTC; additionally, we added 600 mg/kg of P in three pots per OTC in a total of four treatments: aCO₂, eCO₂, aCO₂+P and, eCO₂+P. In 2021 we harvested the plants and evaluated total soil microbial biomass carbon (MBC) and the potential activity of extracellular enzymes acid phosphatase (AP), β-glucosidase (BG), N-acetyl-β-glucosaminidase (NAG), enzymatic stoichiometry (BG/AP, and BG/NAG), and the microbial biomass specific enzyme rate (the ratio of each enzyme/MCB) in the bulk soil and in the soil attached to the roots, that we considered the rhizosphere. We hypothesized that the effect of eCO₂ and P addition would increase MBC and enzyme activity; higher MBC and enzymes activity would be found in the rhizosphere instead of bulk soil. We found that the effects of eCO₂ were only present with the interaction with P addition: higher MBC, but lower AP and BG/MBC in eCO₂+P compared to controls. We also found an interaction effect of eCO₂ regarding bulk soil and rhizosphere: higher NAG activity on bulk soil, and higher BG/NAG on rhizosphere. We found a difference between bulk soil and rhizosphere in almost all variables, except for MBC and BG/MBC. Enzyme activity and AP/MBC and NAG/MBC were higher for bulk; nevertheless, the enzymatic stoichiometry was greater in the rhizosphere. As we expected, eCO₂+P increased MBC, although we found a higher microbial biomass specific enzyme rate in controls, which can suggest nutrient limitation, such as P. In contrast to our assumption, the bulk soil showed higher enzymes activity and microbial specific enzyme rates than the rhizosphere. However, the higher ratio of BG/AP on the rhizosphere can indicate lower P investment. We also found that the effect of eCO₂ on soil enzymes can be different between bulk soil and rhizosphere (high rhizosphere BG/NAG), potentially decreasing nitrogen investment on soil near the roots. Our results suggest that under eCO₂, the Amazon Forest could increase soil C stock due to MBC and this effect can change nutrients demand especially on the rhizosphere.

How to cite: Bachega, L. and Lugli, L. and the Carlos Quesada1: Soil microbial biomass and enzyme activity under elevated CO2 in Central Amazon: how global changes can affect tropical forests belowground, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8845, https://doi.org/10.5194/egusphere-egu22-8845, 2022.

Atlantic coastal dunes are priority conservation areas highly sensitive to climate change. In the Iberian Peninsula, a large part of the coastal dunes are drylands where the chronic shortage of water acts as a major driver of the ecosystem structure and functioning. The predicted increase in aridity by the end of this century may compromise key ecosystems aspects in drylands, such as biotic cover, vegetation productivity and soil fertility. We know little about how changes in aridity and biotic cover may affect the abundance and diversity of soil microbial communities in coastal dunes, and as such their assembly and ecological interaction networks.

We investigated whether the exposure to different aridity regimes can induce differences in microbial co-occurrence networks as well as alter their spatial heterogeneity. Specifically, we aim to (1) assess whether soil fungal and bacterial networks respond differently  and (2) test the role of the biotic cover driving the bacterial and fungal network relationships, the soil attributes and functions. To that end, we used a climosequence of dune systems with minimal variation in the soil type that covered a wide range of aridity conditions including humid, dry-subhumid and drylands in the coastline of Portugal and Spain (~1500 km).

Our results show that aridity decreased the biotic cover, favoured the formation of shrub vegetation patches and negatively affected microbial diversity, organic matter content and potential nitrogen mineralisation in soils. We also observed that the biotic cover exerts a strong control on soil attributes whose effects depend on the degree of aridity (e.g. formation of fertile islands in arid areas and different control of soil inorganic nitrogen forms in wetter areas). At an ecosystem level, increases in aridity resulted in a strong increase in the coupling of the soil microbial network until a specific threshold (values of aridity index (P/ETP)= 0.5-0.6) beyond which it remained constant. Soil bacterial networks showed lower stability against changes in aridity than fungal networks. Surface microsites strongly drove the interactions among soil bacterial groups, but much less so for fungal groups. Our results suggest that climate change, through increased aridity and associated loss of the biotic cover, will have important implications for microbial communities and soil functioning in these coastal dune systems.

How to cite: Fernández Alonso, M. J., Rodríguez, A., Ochoa-Hueso, R., Maestre, F. T., and Durán, J.: Soil microbial co-occurrence networks and functioning along an aridity gradient in Atlantic coastal dunes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8880, https://doi.org/10.5194/egusphere-egu22-8880, 2022.

After the dry season in a Mediterranean climate grassland, the initial soil rewetting event causes a short period of high microbial activity, growth, and mortality. This wet up leads to microbial succession and community reassembly. Climate change in these semiarid environments is projected to cause reduced precipitation, which may affect the structure and function of the microbial community. However, we know little about how microbial functional traits underlie the rewetting succession, and how previous precipitation regimes affect these traits.

Using ¹⁸O-water stable isotope probing (SIP), we conducted a replicated wet-up experiment in annual grassland soils that had been previously subjected to either average precipitation or 50% of the annual average. We traced microbial succession through 5 time points (0h, 24h, 48h, 72h and 168h) post wet-up. By combining SIP with metagenomics, we identified the actively growing organisms in both precipitation treatments and determined ecophysiological traits that were significantly more represented in growing organisms in each precipitation regime. 

We observed a legacy effect of average vs. reduced precipitation by comparing the differential abundance of genes observed at time 0h in the two soil treatments. However, this legacy effect was surprisingly short-lived, implying that microbial community function rapidly “restarts itself” before the next growing season, regardless of the precipitation conditions experienced in the previous year. While growing organisms were significantly more abundant than non-growing organisms during the wet-up, the most abundant taxa were slow growers. In contrast, fast growing taxa were less abundant throughout the experiment, suggesting mortality plays a large role in the reformation of the microbial community.

We highlight temporal patterns and significant differences based on past precipitation in the abundance of carbohydrate utilization pathways, such as a higher representation of organisms capable of degrading cellulose in the reduced precipitation treatment. There were no temporal patterns in nitrogen cycling pathways; nitrogen acquisition appeared to be based mostly on ammonium assimilation and transport as well as proteases. In conclusion, altering preceding precipitation patterns had a large legacy effect on microbial community assembly and function upon rewetting. However, the functional and compositional changes that resulted from altered precipitation had remarkably short-lived effects after the soils were rewetted.

How to cite: Sieradzki, E., Greenlon, A., Firestone, M., Pett-Ridge, J., Blazewicz, S., and Banfield, J.: Ecophysiological traits underlying microbial succession after rewetting of soil from different precipitation regimes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9015, https://doi.org/10.5194/egusphere-egu22-9015, 2022.

Climate warming can alter microbial activity, potentially altering the composition of the atmosphere and feeding back to climate, as well as health of soils that support production of food and fiber. The vast variation in microbial metabolism, physiology, and traits means that different microorganisms are likely to respond differently to the same forcings. For example, some microorganisms appear to thrive with warming, some are unresponsive, and others decline. Such differences in responses likely result in different contributions by microorganisms to terrestrial feedbacks to climate change, like carbon storage and loss from soils, as well as the release and exchange of the potent greenhouse gases nitrous oxide and methane. Characterizing the magnitude and significance of differential biological responses and feedbacks to environmental forcing is a major focus of ecosystem science and functional ecology. Doing so for microorganisms is challenging, but vitally important given the size and uncertainty of microbial feedbacks to the changing climate. Addressing these issues requires quantitative measurements of microbial responses to warming, responses that can be translated into the material flows in nature that constitute the feedbacks of interest. Further, we need to aim toward quantifying microbial responses under field conditions, under conditions where we can simultaneously characterize the magnitude of the feedback and thus have common context for connecting the two. Examples of efforts to make these connections will be presented, from warming experiments across biomes. Quantitative field-based microbial ecology can push the field by revealing the biology and evolution of the key drivers of important feedbacks to the changing climate and atmosphere, and may help identify organisms that are especially effective in promoting the ecosystem processes that protect the climate.

How to cite: Hungate, B.: The ecology of wild microorganisms in a changing climate, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9064, https://doi.org/10.5194/egusphere-egu22-9064, 2022.

Soil organic carbon (SOC) is the largest terrestrial carbon pool. However, it is still uncertain how it will respond to climate change in the 21^st century. Especially SOC losses due to soil warming are a source of uncertainty. It is generally accepted that microbially driven SOC decomposition will increase with warming, provided that sufficient assimilable substrate is available. Sorption to mineral surfaces or the soil moisture-dependent diffusion of substrates to microbial cells can limit substrate availability. Substrate supply is therefore a potentially rate limiting step for the temperature response of SOC decomposition.

In SOC decomposition models, the combined effects of temperature and soil moisture on the decomposition rate can be represented by the Dual Arrhenius Michaelis-Menten (DAMM) model (Davidson et al. 2012). For any substrate (S), it describes the reaction velocity V = Vmax [S]/(kM_S+ [S]), where [S] is the substrate concentration and kM_S is the half-saturation constant. The maximum reaction velocity, Vmax, is temperature dependent and follows an Arrhenius function. Also, a positive correlation between temperature and kM-values of different enzymes has been empirically shown, with Q₁₀ values ranging from 0.71-2.8 (Allison et al., 2018). As kM_S appears in the denominator of the Michaelis-Menten equation, an increase in kM_S leads to a lower reaction velocity (V) and V would become less temperature sensitive at low substrate concentrations.

Besides temperature, substrate concentration [S] depends on soil moisture content. In a dry soil, substrate diffusion to the microbial surface is limited, whereas in a very wet soil, reduced oxygen availability can lower the reaction velocity (V). Changes in substrate supply in drying/(re)wetting soils coincide with changes in temperature which directly interact with the temperature sensitivities of Vmax and kM_S. These interactions can have consequences for decomposition rates in the topsoil versus the deeper soil, since substrate concentrations and temperature are generally higher in the topsoil, but moisture could be more important for substrate limitation. In contrast, in the deep soil, soil moisture might be more available but substrate concentrations (and potentially soil temperatures) might be lower.

This study focuses on this interaction between climate change and substrate availability by comparing two model experiments: 1) a modelling experiment where only Vmax is temperature sensitive and 2) one where both Vmax and kM_S are temperature sensitive. We also investigate the consequences of the counteracting temperature sensitivities of Vmax and kM_S among a substrate gradient, and at different soil temperatures and soil moisture ranges. Finally, we look at dynamic changes in substrate supply, temperature sensitivities and changes in soil moisture and their effects on SOC decomposition in a microbially explicit dynamic SOC decomposition model which also includes organo-mineral interactions.

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 2022, Vienna, Austria, 23–27 May 2022, EGU22-10050, https://doi.org/10.5194/egusphere-egu22-10050, 2022.

Abiotic factors have long been recognised as important factors in structuring microbial diversity and species associations, among which topography and hydro-geomorphic flows have an impact from plot to large scale. These factors are deeply involved in the dynamics of climate change. However, the actual impact of topography on microbial communities in spatially defined habitats remains unclear and, needing further development, represents a promising branch to investigate microbiological assets in the environment. In this study, we analysed a parcel in continental France which revealed a combined action of hydro-geomorphic fluxes and topography in structuring microbial assemblages. Species-habitat occurrence seems to respond to the effective energy locally displayed by fluxes. Largest richness and microbial variety occurred where fluxes are small such as on limited slope or reduced runoff concentrations. Species dominance was higher in zones with higher fluxes suggesting: 1) an impoverishment of the more sensible species, or 2) a selective adaptation of the most resistant species. This differentiation was evidenced by analysing the potential impact of topography and cumulated fluxes for runoff and sediments (i.e., WTI, LS RUSLE indexes) on microbial richness, dominance, and abondance at Phylum and Class levels.

How to cite: Ciampalini, R., Spor, A., Quiquerez, A., Philippot, L., Bru, D., Mounier, A., and Follain, S.: Topography and hydro-geomorphic fluxes drive the assemblage of microbial communities, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11048, https://doi.org/10.5194/egusphere-egu22-11048, 2022.

Climate change is expected to alter global precipitation patterns, with unknown impacts on biodiversity and ecosystem functioning. Temperate forests are one of the largest terrestrial carbon stocks, acting as sinks for greenhouse gases such as carbon dioxide and methane thus playing a major role in ameliorating global warming. Predicted changes to precipitation intensity, duration and timing under future climates are likely to result in the alteration of soil moisture dynamics in forest soils. This will impact soil microbial functions, with shifts from oxic to hypoxic or anoxic conditions which could affect microbial metabolism and microbially-mediated nutrient cycling. The impacts of these changes on the terrestrial carbon balance under current and future atmospheric carbon dioxide levels is currently not known. Here, we use a novel in situ approach to simulate high rainfall in soil mesocosms within a mature temperate oak-dominated (Quercus robur) forest in Staffordshire, UK (Birmingham Institute of Forest Research Free-Air Carbon Dioxide Enrichment facility) where atmospheric CO₂ levels are elevated 150 ppm above ambient levels. We show that an 8-week period of elevated rainfall and volumetric soil moisture (~ 30% increase in amended mesocosms vs controls) had significant impacts on soil functioning. The forest soil methane sink was significantly reduced in the high rainfall treated soils by ~ 21-67%, resulting in greater methane accumulation in the atmosphere, with no recovery 4 weeks post-event. Using 16S rRNA amplicon sequencing and qPCR approaches, we show how bacterial and archaeal diversity respond to altered precipitation regimes and show significant changes in the abundance of methanotrophic and methanogenic communities. The activities of soil extracellular enzymes, involved in the breakdown of organic carbon, nitrogen, and phosphorus compounds, were reduced during the high rainfall treatment. Our results demonstrate that important climate feedbacks could occur during modest alterations in precipitation which should be considered in climate models and forestry management plans.

How to cite: Faulkner, K., Oakley, S., Hilton, S., Mason, K., Ullah, S., van der Gast, C., McNamara, N., and Bending, G.: High summer precipitation reduces soil methane sink capacity and alters decomposition processes in a mature temperate forest, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11452, https://doi.org/10.5194/egusphere-egu22-11452, 2022.

Climate change is leading to an increased frequency and severity of alternating wet and dry spells. These fluctuations affect soil water availability and other soil properties which are crucial drivers of soil microbial communities. While soil microbial communities have a reasonable capacity to recover once a drought seizes, the expected alternation of strongly opposing regimes can pose a particular challenge in terms of their capacity to adapt. Here, we set up experimental grassland mesocosms where precipitation frequency was adjusted along a gradient while holding total precipitation constant. The gradients varied the duration of wet and dry "spells" from 1 to 60 days during a total of 120 days, where we hypothesized that especially intermediate durations would lead to stochastic community assembly due to frequent alternation of opposing environmental regimes. We examined bacterial and fungal community composition, diversity, co-occurrence patterns and assembly mechanisms across these different precipitation frequencies. Our results show that 1) intermediate frequencies of wet and dry spells increased the stochasticity of microbial community assembly whereas microbial communities at low and high regime persistence were subject to more deterministic assembly, and 2) more persistent precipitation regimes (> 6 days duration) reduced the fungal diversity and network connectivity but had a less strong effect on bacterial communities. Collectively, these findings indicate that recurring wet and dry events lead to a less predictable and connected soil microbial community. This study provides new insight into the likely mechanisms through which precipitation frequencies alter soil microbial communities and their predictability.

How to cite: Li, L., Beemster, G., Reynaert, S., Nijs, I., Laukens, K., Asard, H., Vinduskova, O., and Verbruggen, E.: More frequent dry and wet spells increase stochastic microbial community assembly in grassland soils, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11613, https://doi.org/10.5194/egusphere-egu22-11613, 2022.

Global warming is leading to increased temperatures, accentuated evaporation of terrestrial water and increased the atmosphere moisture content, resulting in frequent droughts and heavy precipitation events. It necessary to assess the sensitivity of soil organic carbon (SOC) under storing practices in response to increasing soil moisture, temperature and frequent dry-wet cycles in order to anticipate future soil carbon losses. We evaluated the impact of these climatic events through an incubation experiment on temperate luvisols from conservation agriculture, organic agriculture, organic waste products applications, i.e. biowaste, residual municipal solid waste and farmyard manure composts compared with conventionally managemed soils. The alternative management options all have led to increased SOC stocks. Soil samples were incubated in the lab under different temperatures (20, 28 and 35°C), different moisture conditions (pF1.5; 2.5 and 4.2) and under dry(pF4.2)-wet (pF1.5) cycles. Dry-wet cycles caused CO2 flushes but overall did not stimulate soil carbon mineralization relative to wet controls (pF1.5 and pF2.5). Overall the additional SOC stored under alternative management options was not more sensitive to climate change (temperature, moisture, dry-wet cycles) than the existing SOC.

How to cite: Chenu, C., Kpemoua, I., Leclerc, S., Barre, P., Houot, S., Pouteau, V., and Plessis, C.: Are carbon-storing soils more sensitive to climate change? A laboratory evaluation for agricultural temperate soils., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12273, https://doi.org/10.5194/egusphere-egu22-12273, 2022.

Exchangeable sodium can have pronounced influences on physicochemical soil properties whereas the combined impact on microbial turnover of organic carbon (OC) remains elusive. In this work, we aimed to differentiate the effects of exchangeable sodium and soil pH on microbially mediated aggregate formation and turnover of cattle slurry. We incubated the soils under controlled laboratory conditions using artificial soil model minerals containing quartz grains, montmorillonite and goethite. The montmorillonite was pre-treated with NaCl solutions of sodium adsorption ratios (SAR) 0, 1 and 5 which resulted in exchangeable sodium percentages (ESP) of 1, 7 and 19 on average. The soil pH was adjusted within two treatments to 7.5 and 8.5 for each ESP at the start of the incubation. We incubated these six treatments with and without cattle slurry ground to < 200 µm after addition of a combined microbial inoculum, extracted from a Cambisol (pH_H2O 7.5, Germany) and a Calcaric Solonchak (pH_H2O 9.3, Spain) added to all samples. The microcosms were incubated with three replicates over a period of 30 days at constant pF of 2.2. The CO₂ emission measurements of the microcosms with exchangeable sodium indicated a delayed respiration. The respiration under ESP 19 increased rapidly within the first days of incubation, whereas it was more delayed under ESP 7 until 15 days of incubation. The delayed CO₂ respiration might be related to inhibited structural formation in treatments with higher exchangeable sodium. To test this, we are investigating the data on water-stable aggregation by wet sieving. The delayed CO₂ respiration was reflected in lower microbial biomass, extracted after the incubation. The microbial biomass under ESP 19 and pH 8.5 was highest whereas the amount of leached C after two rainfall events (at day 7 and 15) was lowest, which could be related to a higher microbially mediated OC sequestration. The composition of exchangeable cations was monitored before and after the whole incubation which might help explaining the processes of microbially mediated aggregate formation and microbial carbon turnover under different levels of exchangeable sodium.

How to cite: Schweizer, S., Fiedler, J., Boehm, A., Dannenmann, M., Garcia-Franco, N., Han, J., Poll, C., Wong, V., and Bucka, F.: How soil sodification and pH restrict microbially mediated organic carbon turnover and aggregate formation: An artificial soil microcosm study, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12833, https://doi.org/10.5194/egusphere-egu22-12833, 2022.

Earth system models project altered precipitation regimes across much of the globe. Soil microorganisms in Mediterranean climates must withstand both direct physiological stress during prolonged periods of low soil moisture and be able to compete for resources when seasonal rains return and plant growth resumes⁵. However, we do not have a mechanistic understanding of how altered soil moisture regimes affect microbial population dynamics and in turn how this will affect soil carbon (C) persistence.

We used quantitative stable isotope probing (qSIP) to compare total and growing soil microbial communities across three California annual grassland ecosystems with Mediterranean climates that span a rainfall gradient and have developed from similar parent material. Sampling was conducted during the wet season, when environmental conditions were most similar across the sites. We assessed multiple edaphic variables, including the radiocarbon (¹⁴C) age of soil C. We hypothesized that the long-term legacy effect of soil water limitation would be reflected in lower community growth capacity at the driest site. We also predicted that actively growing communities would be more compositionally similar across the gradient than the total (active + inactive) microbiome.

Community and phylum mean bacterial growth rates increased from the driest site to the intermediate site, and rates were similar at the intermediate and wettest sites. These differences were persistent across major phyla, including the Actinobacteria, Bacteroidetes, and Proteobacteria. Additionally, soil C at the driest site was younger than the wet or intermediate sites. The microbial families that grew fastest at the driest site include taxa that have been described as having traits that are advantageous for surviving dry spells, such as spore formation, polyhydroxyalkanoate accumulation, carotenoid biosynthesis, extracellular polymeric substances production, and trehalose synthesis. Microbial communities at the driest site displayed phylogenetic clustering, suggesting environmental filtering for slow-growing microbial taxa that can withstand water stress at this site. Taxonomic identity was a strong predictor of growth, such that the growth rates of a taxon at one site predicted its growth rates at the others. We think this finding reflects the influence of genetic and physiological constraints on growth which appear to persist across rainfall gradients, edaphic properties, and biological communities. Lastly, we found that actively growing taxa represented (28-58%) of the taxa comprising total communities and that the composition of growing and total communities were similar. The finding that the growing communities were just a subset of the total microbiome, despite environmental conditions being favorable for growth, raises questions about the mechanisms maintaining soil microbial diversity in ecosystems with Mediterannean-type climates.

How to cite: Foley, M., Blazewicz, S., McFarlane, K., Greenlon, A., Hayer, M., Kimbrel, J., Koch, B., Monsaint-Queeney, V., Morrisson, K., Morrissey, E., Pett-Ridge, J., and Hungate, B.: Historical precipitation regimes structure the growth of soil microorganisms in three California annual grasslands, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13318, https://doi.org/10.5194/egusphere-egu22-13318, 2022.

Intensified land-use management and climate change constitute two major challenges for maintaining the soil functions regulated by microbial communities. It is well known that tillage disturbs the soil structure by changing physical properties such as aggregation and water retention capacity, which both have an impact on microbial carbon cycling. In addition, extreme drought and rainfall events result in a significant release of carbon dioxide, where the amount of carbon respired depends on the legacy of precipitation. Thus, understanding the combined effect of land use and precipitation on microbial processes is important in order to predict the future terrestrial carbon cycle.

In this project, we investigated how both the precipitation history and the disruption of soil structure affect microbial growth and respiration during drying-rewetting. We expected that microorganisms in sites with lower historical precipitation might be used to drier conditions, and then exhibit a faster recovery after rewetting and lower respiration rates than those in wetter sites. We also expected that the disruption of soil aggregates would increase the respiration rates after rewetting. In addition, fungal growth would be more affected than bacterial growth due to a damaged hyphal network.

We selected 11 grasslands sites across an east-west precipitation gradient in Sweden ranging from 380 to 1220 mm mean annual precipitation. Three different experiments were carried out to determine the differences in microbial responses along this gradient, by measuring bacterial growth, fungal growth and respiration at high time resolution during seven days after drying-rewetting. First, we investigated the short-term effect of disturbing aggregates by grinding soils in the laboratory. We compared the results from undisturbed soils with those found after dry or wet crushing. Second, we studied the effect of soil structure disturbance in the field and if results from laboratory experiments could be extended to agricultural practices. For this, we established plots across the precipitation gradient, applied a tillage treatment with a rotary cultivator at the start of the growing season and measured microbial responses at the end of the summer. Third, we explored how the microbial responses to soil structure disturbances developed over time in the field. To do so, we used soil sampled from one site in the gradient after one week, one month and three months after disturbance.

Preliminary results showed that crushing soils in the laboratory accelerated the bacterial recovery after rewetting, but fungal growth and respiration were unaffected compared to undisturbed soil. In the field, the microbial responses over time strengthened up to one month after the tilled treatment. The microbial responses along the precipitation gradient showed the importance of land-use management for carbon cycling under future scenarios of intensified weather events.

How to cite: Winterfeldt, S., Hicks, L., Brangarí, A., and Rousk, J.: Microbial responses to drying and rewetting: The interaction between soil structure and precipitation history, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13369, https://doi.org/10.5194/egusphere-egu22-13369, 2022.

Soil microbial growth, respiration and carbon use efficiency (CUE) are essential parameters to understand, describe and model the soil carbon cycle. While seasonal dynamics of microbial respiration are well studied, little is known about how microbial growth and CUE change over the course of a year, especially outside the plant growing season. In this study we measured soil microbial respiration, growth and biomass in an agricultural field and a deciduous forest 16 times over the course of two years. We sampled plots, at which harvest residues or leaf litter were either incorporated or removed. We observed strong seasonal variations of microbial respiration, growth and biomass. All microbial parameters were significantly higher at the forest site, which contained 3.5% organic C compared to the agricultural site with 0.9% organic C. CUE also varied strongly but was overall significantly higher at the agricultural site ranging from 0.1 to 0.7 compared to the forest site where CUE ranged from 0.1 to 0.6. We found that microbial respiration and to a lesser extent microbial growth followed the seasonal dynamics of soil temperature. Microbial growth was further affected by plant or foliage presence. At low temperatures in winter, both microbial respiration and growth rates were lowest. Due to higher temperature sensitivity of microbial respiration, CUE showed the highest values in the coldest months. Microbial biomass C was also strongly increased in winter. Surprisingly, this winter peak was not connected to high microbial growth or an increase in DNA content. This suggests that microorganisms accumulated osmo- or cryoprotectants but did not divide. This microbial winter bloom and following decline, where C is released and can be stabilized, could constitute the main season for C sequestration in temperate soil systems.  Highly variable CUE, and the fact that CUE is calculated from independently controlled microbial respiration and growth, ask for great caution when CUE is used to describe soil microbial physiology, soil C dynamics or C sequestration. Instead, microbial respiration, microbial growth and biomass should rather be investigated individually to better understand the soil C cycle.

How to cite: Schnecker, J., Baldaszti, L., Gündler, P., Pleitner, M., Richter, A., Sandén, T., Simon, E., Spiegel, F., Spiegel, H., Urbina Malo, C., and Zechmeister-Boltenstern, S.: Seasonal dynamics of soil microbial respiration, growth, biomass, and carbon use efficiency, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1179, https://doi.org/10.5194/egusphere-egu22-1179, 2022.

Soil extracellular enzyme stoichiometry (EES) reflects the biogeochemical balance between microbial metabolic requirements and environmental nutrient availability. Previous studies have focused on the perspective of nutrient acquisition, while soil microbial metabolic limitations (SMML) were minor in the focus of those studies. Therefore, how grassland succession drives SMML has mainly been under explored. Here, we used EES models to identify the response of SMML during grassland restoration while also investigating potential implications of microbial nutritional limitations across the time series (herbaceous succession) and with space (transformation interface soil and underlying topsoil layer) in a grassland restoration series. The results showed that soil microorganisms were generally limited by C, both in the transformation interface soil (TIS) and the underlying topsoil layer (UTS). During herbaceous succession, microbial P-limitation was more substantial than that by N-limitation. Microbial C-limitation displayed a uni-modal direction, peaking in intermediate successional stages. However, microbial P-limitation presented the opposite trend. In the TIS layer, SMML gradually transferred from P- to N- and back to P-limitation at later successional stages. Biotic factors, together with soil basic index, and soil nutrients, explained 92.2% of the variation in microbial C-limitation and 84.4% of the variation in microbial P-limitation. Multi-interaction factors show the most significant relative influences of 65.11% (TIS) and 43% (UTS) of the SMML, respectively. Microbial C-limitation was induced by the imbalance between C supply and microbial C demand, while the changes in microbial P-limitation were due to changes in the competition for P between plants and microorganisms. Therefore, the impacts of long-term grassland succession on SMML resulted from the concerted changes in vegetation composition, soil properties, and the nutritional demands of the soil microorganisms.

How to cite: Xue, Z., Liu, C., and Wolfgang, W.: Extracellular enzyme stoichiometry reflects the C-and P- microbial metabolic limitations along a grassland succession on the Loess Plateau in China., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3020, https://doi.org/10.5194/egusphere-egu22-3020, 2022.

Nitrogen (N) availability is a main constraint to plant productivity, especially when vegetation relies largely on subsoils, which contain considerable N resources but in low availability. Rhizodeposition can promote N cycling by stimulating microbial growth and activity and thus induces the release of mineral-bound nutrients and accelerates decomposition of soil organic matter (SOM). However, many specific processes how root exudates interact with distinct N forms altering their subsoil mobilization still remain unclear. We hypothesize that the lower microbial activity but higher sorption capacity of subsoils induces subsoil-specific N dynamics. To disentangle this, we added four N sources (free NH₄⁺, sorbed NH₄⁺, urea and plant residues with identical total N content) into top-and subsoils. We quantified microbial processes regulating mineral and organic N availability in top-and subsoils by simulating rhizosphere condition via application of collected root exudates in a well-controlled microcosm experiment. Our results showed that neither growth of the total microbial community, nor shift in the community composition occurs based on maize root exudate amendment resembling a daily exudation amount. However, we observed a clear increase in microbial activity and activation of organic nutrient mobilizing mechanisms (e.g. enzyme activation), which was in most cases higher in sub- than in topsoils. This suggests that root exudates may not be of highest relevance for topsoil nutrient mobilization. In contrast, high root exudation is of much higher relevance for crops, which aim to mobilize a significant proportion of their nutrients from subsoils. We could demonstrate that subsoil communities were well capable of using litter-derived N, especially if root exudates accelerate overall activity and N cycling in subsoils. N incorporated from plant litter is successively recycled in microbial bio-and necromass following the initial degradation. Consequently, if breeding for deep-rooting crops with nutrient uptake from subsoils shall be promoted in the future, it is essential to ensure that these crops deep roots have a high root exudation to activate the highly C limited microbial communities of the subsoil.

How to cite: Ai, J., Banfield, C., Shao, G., Zamanian, K., Spielvogel, S., and Dippold, M.: The role of maize root exudates to availability of N source in different forms in top- and subsoils, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4304, https://doi.org/10.5194/egusphere-egu22-4304, 2022.

Arbuscular mycorrhizal fungi (AMF) efficiently take up mineral nutrients such as phosphorus and nitrogen (N) from the soil solution, and trade them for organic carbon with their host plants. Acquisition of nutrients bound in organic forms by the AMF under unsterile soil conditions has previously been reported, assuming an important role of soil prokaryotes, yet mostly without proper mechanistic understanding. Here we present a synthetic approach to study involvement of such inter-kingdom interactions in utilization of organic nitrogen by a mycorrhizal plant. We employ ¹⁵N-labelled chitin (as an organic N source) added to AM fungal (Rhizophagus irregularis) hyphosphere under in vitro conditions, with or without other microorganisms. Upon presence of Paenibacillus sp., the AMF and their associated host plant obtained several-fold larger quantities of N from the chitin than they did with other bacteria, whether chitinolytic or not. Moreover, upon adding a protist Polysphondylium pallidum to the hyphosphere with Paenibacillus sp., the gain of N from the chitin by the AMF and their associated plant further and significantly increased by another 60+%, pointing to soil microbial loop as the underlying mechanism.

This work will appear shortly in the ISME Journal.

Reference: Rozmoš M, Bukovská P, Hršelová H, Kotianová M, Dudáš M, Gančarčíková K, Jansa J (2022) Organic nitrogen utilization by an arbuscular mycorrhizal fungus is mediated by specific soil bacteria and a protist. ISME Journal, in press. doi 10.1038/s41396-021-01112-8 .

How to cite: Jansa, J., Bukovská, P., and Rozmoš, M.: Arbuscular mycorrhizal hyphosphere as a soil nutrient turnover hotspot, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4653, https://doi.org/10.5194/egusphere-egu22-4653, 2022.

The process of transformation of soil organic matter is dependent on functional traits of active microbial decomposers. Microbial functional traits, in turn are selected and driven by the local environmental conditions and can be subdivided into three groups. Microbial traits in the first group are very dynamic, for example, the size of the microbial fraction maintaining activity or alert state (active biomass) and the time required for dormant microorganisms to switch to active growth (i.e., lag time). The second group represents intrinsic functional traits of the microbial population, such as maximal specific growth rate (µ_m), generation time (T_g), and affinity of extracellular enzyme systems (K_m) to soil organic substrates used for microbial growth. The third group refers to phenotypic traits at the level of functional genes, for example, those related to internal microbial metabolism, extracellular resource acquisition, or stress tolerance. Recent developments in molecular approaches have provided potential for microbial trait differentiation based on information regarding genome size, number of ribosomal gene copies per genome, and quantification of functional marker genes or their transcripts by -omics approaches (Li et al., 2019; Malik et al., 2020). This enabled to reconsider the classical concepts of microbial life strategies with the goal of specifying functional groups according to their ecological relevance considering microbial yield, resource acquisition, and stress tolerance (Ho et al. 2017, Krause et al. 2014; Malik et al., 2020). However, it remains challenging to identify proxies for specific traits that can serve as quantitative measures of a category. Based on literature review and own experiments, we compared the specificity of microbial physiological and phenotypic functional traits in contrasting soil environments. We demonstrated that mechanical disturbance of soil structure by tillage rather than chemical properties were responsible for reduction of total biomass and growing microbial fraction, for slower activity of C- and N-acquiring enzymes under conventional versus minimal tillage. High nutrient availability ensured by fertilization generally selected the microbial strategy with low total biomass but high abundance of active microorganisms. Microbial community adapted to resource depletion with soil depth was characterized by low total and growing biomass, retarded activity of enzymes decomposing plant and microbial residues and by accelerated activity and altered affinity of enzyme systems responsible for nutrients acquisition. Thus, environmental selection resulted in the activation of populations with intrinsic functional traits that are mostly suited to the individual soil habitat. This calls for the studies linking genetic and metabolic potential with microbial functions. However, synchronization of experimental design by sampling time is required for correct comparisons of microbial growth rates obtained by different approaches. 

How to cite: Blagodatskaya, E.: Microbial functional traits and life strategies: Bridging physiological and molecular approaches, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5987, https://doi.org/10.5194/egusphere-egu22-5987, 2022.

The rhizosphere is a dynamic region governed by the composition and pattern of root exudates, which in turn impact the beneficial or harmful relationships between the rhizosphere microbiome, which affect their function and plant performance. Successive wheat following wheat shows yield decline, hence, this rhizobox-study aims to illuminate and quantify the effects of subsequent wheat rotations for 3 years (W3) at different growth stages on glucose releasing rate and soil enzyme activity.

We hypothesized that the long-term wheat rotation leads to lower glucose release, which will result in lower microbial activity accompanied by the decline of enzyme production than the first year wheat rotation (W1) using soil samples collected from the experimental farm Hohenschulen, (CAU, Kiel) from 1^st and 3^rd wheat after break crop. Glucose Imaging was utilized for visualizing and localizing glucose exudation rate from wheat roots and β-glucosidase zymography, involved in the degradation of C substances, was applied for rhizoboxes at two growth stages (BBCH 31 (T1), BBCH 59(T2)).

Results showed that crop rotation affected glucose release from roots and β-glucosidase activity and this effect was more pronounced at the second sampling time at BBCH-59. The total hotspot area of enzyme activity declined at W3. Third wheat after break crop had the lowest hotspot percent for glucose release and β-glucosidase activity at BBCH-59 by 1.83 and 4.26 percent of total soil surface area, indicating 68.3 and 47 percent decline compared to W1, respectively. While rhizosphere extends for glucose release increased in W3 compared to W1 at the first sampling date, there was a strong decrease at the second sampling time by 60.2 percent. However, β-glucosidase activity extend around the wheat root at T1 had a decreasing trend from W1 toward W3 and there was a slight decrease at T2. Plants benefit from root exudates by stimulating beneficial microorganisms and improving nutrient acquisition. Decreasing glucose release, as a readily available energy source for microorganisms and declining C availability because of root senescence, leads to competition for C in rhizosphere among beneficial microbes and soil-borne pathogens. Continuous wheat cultivation accelerates root senescence, accompanied by more severe environment for soil microbes and higher abundancy of wheat pathogens which ultimately will affect wheat yield.

How to cite: Rashtbari, M.: Patterns of glucose release and enzyme activity affected by crop rotation and plant senescence, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6074, https://doi.org/10.5194/egusphere-egu22-6074, 2022.

Soil microbiome is an important indicator of soil quality and it is related to various soil functions, including soil carbon cycling. Plant litter decomposition is a key process in carbon cycling, and the use of standardized plant litter for the comparison of decomposition rates between different conditions is a promising method. In this study, we aimed to investigate the difference in microbial community composition in long-term manure amended soils with different crop rotations, and its relationship with litter decomposition by using the Tea Bag Index (TBI) protocol. Green tea and rooibos tea bags were buried pairwise in three long-term experimental sites (LTEs) in Germany, Denmark and Sweden for three months. The TBI, i.e. decomposition rate and stabilization factor, was calculated from the weight loss of tea. The three LTEs have contrasting soil textures and had been manured between 20 and 127 years. The rotation elements in the LTEs include spring barley, winter wheat, winter oat, maize, and grass/clover. The microbial community composition was characterized by biomarkers (phospholipid fatty acids and neutral lipid fatty acids) and 16S and ITS sequencing. Enzyme activity was quantified by fluorescein diacetate hydrolysis analysis. The linkage between TBI and several microbial properties including microbial biomass, enzyme activity, the fungal:bacterial ratio, and the abundance and the diversity of the microbial community, will be discussed. The interactive effect of soil texture and management on the TBI and microbial properties will be addressed, which shall provide implications for soil quality and soil management.

How to cite: Fu, Y., Paradelo, M., Ravnskov, S., de Jonge, L. W., and Arthur, E.: Linking litter decomposition characterized by the Tea Bag Index to soil microbial characteristics under long term manure and crop rotation management, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7721, https://doi.org/10.5194/egusphere-egu22-7721, 2022.

Temperature and soil moisture strongly affect plant root exudates and enzyme activities. Global warming may stimulate root exudation and enzyme activities while drought can drop releasing of root exudates and inhibit enzyme activities. However, how the interaction of warming and drought regulate these processes in the rhizosphere is poorly known. To clarify these interactions, wheat plants were grown for one month at 20 and 30 ^ºC in drought (30% WHC) and optimum (70% WHC) condition. To investigate the pattern of root exudates releasing and enzyme activities, we combined β-glucosidase zymography with glucose imaging and enzyme kinetic.

Drought significantly decreased hotspots of glucose in compare to optimum condition at both temperatures. Releasing of glucose by wheat at 30 ^ºC was 53% lower than at 20 ^ºC in optimum condition. Hotspots of β-glucosidase activity in drought was 52% and 37.7% lower than in optimum at 20 and 30 ^ºC, respectively. β-glucosidase hotspot at 30 ^ºC was 12.2% lower than at 20 ^ºC in optimum condition. The results of enzyme kinetic (V_max and K_m) showed that drought decreased β-glucosidase activity in compare to optimum condition at both temperatures. β-glucosidase activity at 30 ^ºC was 2 times higher that at 20 ^ºC in optimum condition. On the contrary, it was 56% lower than at 20 ^ºC in drought condition. Drought increased K_m at 20 ^ºC while decreased it at 30 ^ºC in compare to optimum condition. The affinity of β-glucosidase for substrates in optimum condition was not affected by temperature. K_m value at 30 ^ºC was lower than at 20 ^ºC in drought condition. According to these results, the warming in optimum condition (high labile carbon availability) decreased enzyme production and substrates release and did not change the affinity of enzyme for substrates. While warming in drought condition (low labile carbon availability) produced an enzyme pool with high efficiencies and did not change enzyme production and substrates release.

How to cite: Hosseini, S. S., Sultan, S. R., Rashtbari, M., Lakzian, A., and Razavi, B. S.: Effect of warming on β-glucosidase activity and root exudates depends on soil moisture: Combining Zymography with glucose imaging and enzyme kinetic, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8437, https://doi.org/10.5194/egusphere-egu22-8437, 2022.

Root morphology and the composition of root exudates shape the spatial organization and various processes in the rhizosphere. For instance, root hairs are essential for plant nutrition, while secondary plant metabolites (i.e. benzoxazinoids) ensure plant defence from herbivore and fungal infection. Nevertheless, it is still unknown to which extent root hairs and benzoxazinoids may change the microbiome and enzymatic activities, as well as formation of rhizosphere hot- and coldspots.

To study the effect of root hairs and benzoxasinoids on the rhizosphere microbiome structure and its enzymatic activities we compared mutants with defective root hairs rth3 or with reduced benzoxazinoids bx1 with the corresponding wild-type (WT) maize.

Root hairs increased acid phosphatase activity by 80 % promoting mineralization of organic phosphorus sources to available forms in the hotspots. In the coldspots, broken root hairs in WT facilitated the intensive microbial hotspots with up to two times higher β-glucosidase and chitinase activities, compared to rth3.

The presence of benzoxazinoids in root exudates strongly supported plant defence against pathogenic fungi (i.e., genus Fusarium and Gibberella) while the total microbial biomass remained unaffected. In response to the presence of pathogenic fungi, bx1 exuded 70 % more chitinase for defence purpose to partly compensate for benzoxazinoids deficiency, which was however, less efficient against pathogens than the presence of benzoxazinoids.

Overall, we conclude that: i) root hairs facilitate better plant nutrition at the shortage of available nutrients (i.e., coldspots), while; ii) the presence of benzoxazinoids in exudates protect plant from pathogenic microorganisms. This two root traits are promising for plant breeding of genotypes suitable for sustainable agriculture and organic farming.

How to cite: Bilyera, N., Waelchli, J., Shi, L., Caggia, V., Zhang, X., Shlaeppi, K., Dippold, M. A., Razavi, B. S., and Spielvogel, S.: Effect of root hairs and benzoxazinoids on maize microbiome and its enzymatic activity in the rhizosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8562, https://doi.org/10.5194/egusphere-egu22-8562, 2022.

Microbial communities are a critical component of the soil carbon (C) cycle as they are responsible for the decomposition of both organic inputs from plants and of soil organic C. However, there is still no consensus about how to explicitly represent their role in terrestrial C cycling. The objective of the study was to determine how the properties of organic matter affect the metabolic response of the resident microbial communities in soils, using a bioenergetics approach. This was achieved by cross-amending six soils with excess water-soluble organic matter (WSOM) extracted from the same six soils and measuring heat dissipated due to the increase in microbial metabolic activity. The conditions of the experiment were chosen in order to replicate conditions in activity hotspots. The metabolic activity was then related to the potential return on investment (ROI) that the microbial communities could derive from the WSOM. The objective of the study was to determine how different energetic profiles in available organic avec the metabolic response of different microbial communities.

The ROI was calculated as the ratio between the total net energy available (ΔE) in the WSOM and the weighted average standard state Gibbs energies of oxidation half reactions of organic C (ΔG°Cox) of the molecules present in the WSOM. The ΔE was measured as the heat of combustion of the WSOM, which was measured using bomb calorimetry. ΔG°Cox was estimated from the average nominal oxidation state of C (NOSC), which itself was determined from the elemental composition of each molecular species in the organic matter amendments analyzed by Fourier transform ion cyclotron resonance mass spectrometry. The soil bacterial community structure was determined by 16S rRNA gene sequencing and using the weighted UniFrac distance of rarefied amplicon sequence variants data.

We found that the potential ROI that microbial communities could obtain from the consumption of the added organic matter was positively related to the overall metabolic response of microbial decomposers. However, the observed temporal differences in metabolism across soils indicate that bacterial communities do not exploit energetic return-on-investment in the same ways. Overall, our results suggest that microbial communities preferentially use organic matter with a high energetic return on investment.

How to cite: Nunan, N., Dufour, L., Herrmann, A., Leloup, J., Przybylski, C., Foti, L., and Abbadie, L.: Potential return on investment that microbial communities can obtain from the consumption of organic matter determines overall soil microbial activity, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9981, https://doi.org/10.5194/egusphere-egu22-9981, 2022.

Interactions between plants, soil, and microbiota makes the rhizosphere of central importance for ecosystem functioning. Although non-pathogenic organism dominate this rhizobiome, plant pathogens have an important functional role for plant performance. In fact, plant pathogens trigger plant defence and alter the metabolism, nutrient flow and survival of the host, leading to changes in overall plant performance which feeds-back to the rhizobiome. However, the links between soil-borne pathogens and the rhizobiome are only starting to be explored. Here we focus on the clubroot pathogen Plasmodiophora brassicae, a pathogen that forces farmers to abandon cultivation of Brassica species for more than a decade, to decipher pathogen impact on the rhizobiome. Furthermore, we aim to identify potentially disease suppressive and disease conducive microbiome members, including bacteria, fungi, protists and animals. We are performing complex plant and soil physicochemical analyses to decipher underlying drivers of taxonomic and functional changes in the rhizobiome to clubroot infection including the impact of the detritusphere. The results of this studies will give an important insight of the ecological role of plasmodiophorid species on the plants and its rhizobiome. Additionally, by identifying pathogen suppressive and conducive soil biota new biocontrol applications can be developed that will also be useful to control other soil-borne pathogens. In this presentation we will provide the framework of the research and initial findings that provide first ideas on the importance of the plant-clubroot-rhizobiome connections.

How to cite: Schwelm, A. and Geisen, S.: Clubroot and soil biology – from ecology to biocontrol?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10214, https://doi.org/10.5194/egusphere-egu22-10214, 2022.

Soil microbiome is the most diverse ecosystem in the world and carries out some of the most important soil functions through nutrient cycling. Agroecosystem health and sustainability are strongly connected to understanding soil microbiome and its composition, yet unknown in many agricultural areas. In this study we compared in a rainfed almond orchard in Spain the long-term effect of intensive tillage (IT), reduced-tillage (RT) and reduced-tillage with alley cropping (RTAC) on soil fungal and bacterial communities and their interrelationship with soil physicochemical properties and almond yield. Fungi and bacteria population were characterized using next-generation sequencing technology. Soil organic C, total N and particulate organic C were were significantly higher in RT and RTAC treatments compared to IT, with no significant differences concerning cation exchange capacity, ammonium or nitrates. RTAC showed the highest proportion of macro-aggregates (>250 µm). Richness and diversity indices showed no significant differences among treatments for fungal and bacterial communities. Within bacterial genera, we observed higher abundance of Sphingomonas, Streptomyces, Blastococcus, and Nocardioides in RT and RTAC treatments. Within fungi genera, Mortierella, Coprinopsis and Chaetomium showed higher abundance in IT. Multivariate analysis showed that soil fungal and bacterial communities were different depending on the treatment, mostly associated to changes in soil organic C. Deep identification of bacterial and fungal taxa may give light to the understanding of soil microbiome and functions in almond orchards, and brings the producers one step closer to make productive areas more sustainable related to soil C sequestration and fertility.

How to cite: Ozbolat, O., Zornoza, R., Sánchez-Navarro, V., Cuartero, J., Ros, M., Canfora, L., Orrù, L., Martínez-Mena, M., Boix-Fayos, C., and Almagro, M.: Composition of Soil Fungal and Bacterial Communities and their Relation with Soil Physicochemical Properties under different Agricultural managements in a Mediterranean Almond Orchard, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12827, https://doi.org/10.5194/egusphere-egu22-12827, 2022.