SSS9.3

EDI
Soil organic and inorganic carbon stocks and dynamics in agro-ecosystems: mechanisms, measurements and modelling strategies

Soil is the largest carbon (C) reservoir in terrestrial ecosystems with twice the amount of atmospheric C and three times the amount in terrestrial vegetation. Carbon related ecosystem services include retention of water and nutrients, promoting soil fertility and productivity and soil resistance to erosion. In addition, changes in the soil C can have strong implications for greenhouse gas emissions from soil with implications in environmental health.

Drivers controlling C pools and its dynamics are multiple (e.g. land use/vegetation cover, climate, texture and bedrock, topography, soil microbial community, soil erosion rates, soil and other environment management practices, etc. ) and some of them are mutually interacting. Also, rate of net soil C loss can be high in some environments due to both climatic constrains or management. Thus, investigation of C dynamics should be addressed with regards to the climate change and climatic extreme events to provide a better understanding of carbon stabilization processes and thus support decision making in soil management and climate adaptation strategies.

The present session highlights the importance of soil C changes, and the interaction among the mechanisms affecting C concentration and stocks in soil. Discussion about the proxies to measure and model C stocks, with special emphasis to cropping systems and natural/semi-natural areas, is encouraged. These proxies should be approached at varying the availability of soil and environment information, including, e.g., soil texture, rainfall, temperature, bulk density, land use and land management, or proximal and remote sensing properties. Studies presented in this session can aim to a wealth of aims, including soil fertility, provision of ecosystem services, and their changes, and the implication for economy, policy, and decision making.

Types of contribution appreciated include, but are not limited to, definitive and intermediate results; project outcomes; proposal of methods or sampling and modelling strategies, and the assessment of their effectiveness; projection of previous results at the light of climate change and climatic extremes; literature surveys, reviews, and meta-analysis. These works will be evaluated at the light of the organisation of a special issue in an impacted journal

Co-organized by BG3/GM3
Convener: Sergio Saia | Co-conveners: Jorge Alvaro-Fuentes, Viktoriia Hetmanenko, Laura QuijanoECSECS, Calogero SchillaciECSECS
vPICO presentations
| Fri, 30 Apr, 13:30–15:00 (CEST)

vPICO presentations: Fri, 30 Apr

13:30–13:35
SOIL ORGANIC CARBON
13:35–13:37
|
EGU21-1879
|
solicited
Alina Premrov, Jesko Zimmermann, Marta Dondini, Marie-Laure Decau, Stuart Green, Reamonn Fealy, Rowan Fealy, and Matthew Saunders

ABSTRACT

The work provides insights into soil organic carbon (SOC) modelling procedures associated with different management practices for Irish grassland sites selected from two large soil databases (LUCAS-2009 [1] and Teagasc-SIS [2]) and a single treatment-plot  from France  (paddock of a long- term grassland-experiment) [3]. Modelling of SOC was done at site scale using “Model to Estimate Carbon in Organic Soils -Sequestration and Emissions” (ECOSSE) 6.2b version of the model in site-specific mode [4]. The selection of Irish sites and the Irish model input-parameters followed procedures explained in Premrov et al. (2020) [5]. As explained in Premrov et al. (2020) [5], special attention was given to model SOC-input data because the preliminary findings showed high sensitivity of model predictions to the initial SOC-inputs [5]. Initial SOC-inputs for Irish sites were extracted from the Irish soil NSDB-database [8] because of lack of data at that time. The preliminary SOC modelling results from Irish sites [RMSE >36%; 84 sites (out of total 95 pre-selected LUCAS and SIS sites after excluding 11 potential outliers [7])]indicated that further work is needed on obtaining initial SOC-input data. The new LUCAS-2015 [6] soil-point data in combination with older LUCAS-2009 [1] data provide opportunities to resolve this issue, which is currently work in progress. Considering that Irish sites were selected from large soil-databases that lacked detailed site-specific information (i.e. stocking rates and fertilisation-data could be obtained only in general form), the treatment-plot from France [3] was also simulated to gain further insights into the ECOSSE SOC modelling at site/point-scale. This work confirmed the importance of using appropriate conversion-factor when applying stocking rates as a proxy for the manure-inputs (as an alternative for grazing [7]). Further insights included the importance of assessing the modelled SOC ‘trends’ over time, and its comparison with observed ones [7].

 

Acknowledgements

SOLUM project is funded under the Irish EPA Research programme 2014-2020. Thanks go to Dr Jo Smith (University of Aberdeen, Scotland) for ECOSSE-model and to all who provided data or advice/support, among others, Teagasc-SIS, Ireland;  French national-observatory SOERE ACBB, a part of ANAEE-F French national infrastructure, and Dr Katja Klumpp (INRAe, France).

 

Literature

 

[1] JRC (2018). LUCAS-2009, ESDAC. JRC. EC.

[2] Teagasc, (2018) Irish Soil Information System (SIS). Teagasc, EPA, Ireland.

[3] SOERE ACBB (2020) http://www.soere-acbb.com/

[4] Smith, J., et al. (2010). ECOSSE. User Manual.

[5] Premrov, A., et al. (2020). Insights into modelling of soil organic carbon from Irish grassland sites using ECOSSE model. EGU2020-8090. doi.org/10.5194/egusphere-egu2020-18940; (CC-BY-4).

[6] JRC (2020). LUCAS 2015, ESDAC. JRC. EC.

[7] Saunders, M. et al. (draft-report 2020) SOLUM. EPA Research Report. 2016-CCRP-MS.40.

[8] EPA (2007). National Soils Database (NSDB). Environmental Protection Agency, Ireland.

How to cite: Premrov, A., Zimmermann, J., Dondini, M., Decau, M.-L., Green, S., Fealy, R., Fealy, R., and Saunders, M.: Insights into ECOSSE modelling of soil organic carbon at site scale from Irish grassland sites and a French grazed experimental plot, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1879, https://doi.org/10.5194/egusphere-egu21-1879, 2021.

13:37–13:39
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EGU21-2803
Lena Katharina Öttl, Florian Wilken, Michael Sommer, and Peter Fiener

The young moraine landscape of North-East Germany is highly prone to tillage-dominated soil erosion processes due to highly mechanised farming in a rolling topography. The corresponding soil redistribution pattern highly influences crop biomass production and soil organic carbon (SOC) dynamics. The aims of the study are to understand the effect of soil redistribution processes on SOC dynamics like dynamic replacement and efficient SOC burial. Therefore, an updated version of the spatially explicit soil redistribution and carbon turnover model SPEROS-C was applied for a large-scale (200 km²) simulation of lateral soil and SOC redistribution and vertical SOC turnover (spatial and vertical resolution 5 m x 5 m and 1 m soil depth, respectively). A sensitivity analysis was applied to identify the dominant modulators of SOC in the modelling approach (carbon input by roots, manure, and residues, decomposition of SOC, etc.). Uncertainties in model structure, process parameterisation, and input data are analysed with the GLUE approach (Generalized Likelihood Uncertainty Estimation). This approach is also used to estimate regional model parameters (e.g. SOC turnover rates, crop-specific root length density distribution, C input by aboveground biomass, manure, residues, etc.) to allow landscape-scale estimations of soil redistribution and accompanied C balance and hence, if this leads to a sink or source of CO2.

How to cite: Öttl, L. K., Wilken, F., Sommer, M., and Fiener, P.: Modulators of soil organic carbon (SOC) stocks and dynamics in an intensively used hummocky landscape in North-East Germany, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2803, https://doi.org/10.5194/egusphere-egu21-2803, 2021.

13:39–13:41
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EGU21-3967
|
ECS
Johannes Wilhelmus Maria Pullens, Ji Chen, and Poul Erik Lærke

To meet the growing challenges of food security, sufficient biomass for biorefineries and mitigation of climate change, perennial grass is recommended as an alternative for annual grain crop to increase biomass production while protecting soil C stock. However, the long-term biomass yield production, soil C stock, and ecosystem CO2 flux are rarely simultaneously evaluated in the same study site, limiting the understanding of C flows in different cropping systems. We compared the annual grain crop triticale (Triticosecale) grown every year since 2012 with the productive perennial grass festulolium (Festulolium braunii) both established in 2012 and festulolium renewed in 2018. Annual yield production, five-year changes in soil C stock, and ecosystem CO2 fluxes in 2020 are documented. The first five-year field observations showed that festulolium produced 76% more biomass as compared to triticale (grain and straw). Meanwhile, there was an increasing trend of soil C stock in festulolium but a declining trend of soil C stock in triticale across the first five years, despite both changes were statistically non-significant. By having measurements of the complete carbon balance for 2020, we can investigate the carbon cycling of a cereal and a perennial grass crop. The results improve our knowledge in how we can optimize the biomass, yield and carbon stocks.

 

Keywords: continuous monoculture; perennial grass; biomass production; soil carbon content; ecosystem CO2 flux

How to cite: Pullens, J. W. M., Chen, J., and Lærke, P. E.: Carbon balance of annual versus perennial cropping systems, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3967, https://doi.org/10.5194/egusphere-egu21-3967, 2021.

13:41–13:43
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EGU21-6071
|
ECS
David Bysouth, Merritt Turetsky, and Andrew Spring

Climate change is causing rapid warming at northern high latitudes and disproportionately affecting ecosystem services that northern communities rely upon. In Canada’s Northwest Territories (NWT), climate change is impacting the access and availability of traditional foods that are critical for community health and well-being. With climate change potentially expanding the envelope of suitable agricultural land northward, many communities in the NWT are evaluating including agriculture in their food systems. However, the conversion of boreal forest to agriculture may degrade the carbon rich soils that characterize the region, resulting in large carbon losses to the atmosphere and the depletion of existing ecosystem services associated with the accumulation of soil organic matter. Here, we first summarize the results of 35 publications that address land use change from boreal forest to agriculture, with the goal of understanding the magnitude and drivers of carbon stock changes with time-since-land use change. Results from the literature synthesis show that conversion of boreal forest to agriculture can result in up to ~57% of existing soil carbon stocks being lost 30 years after land use change occurs. In addition, a three-way interaction with soil carbon, pH and time-since-land use change is observed where soils become more basic with increasing time-since-land use change, coinciding with declines in soil carbon stocks. This relationship is important when looking at the types of crops communities are interested in growing and the type of agriculture associated with cultivating these crops. Partnered communities have identified crops such as berry bushes, root vegetables, potatoes and corn as crops they are interested in growing. As berry bushes grow in acidic conditions and the other mentioned crops grow in more neutral conditions, site selection and management practices associated with growing these crops in appropriate pH environments will be important for managing soil carbon in new agricultural systems in the NWT. Secondly, we also present community scale soil data assessing variation in soil carbon stocks in relation to potential soil fertility metrics targeted to community identified crops of interest for two communities in the NWT.  We collected 192 soil cores from two communities to determine carbon stocks along gradients of potential agriculture suitability. Our field soil carbon measurements in collaboration with the partnered NWT communities show that land use conversions associated with agricultural development could translate to carbon losses ranging from 2.7-11.4 kg C/m2 depending on the type of soil, agricultural suitability class, and type of land use change associated with cultivation. These results highlight the importance of managing soil carbon in northern agricultural systems and can be used to emphasize the need for new community scale data relating to agricultural land use change in boreal soils. Through the collection of this data, we hope to provide northern communities with a more robust, community scale product that will allow them to make informed land use decisions relating to the cultivation of crops and the minimization of soil carbon losses while maintaining the culturally important traditional food system.

How to cite: Bysouth, D., Turetsky, M., and Spring, A.: Agriculture in the Boreal Forest: Understanding the Impact of Land Use Change on Soil Carbon for Developing Sustainable Community Food Systems , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6071, https://doi.org/10.5194/egusphere-egu21-6071, 2021.

13:43–13:53
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EGU21-16073
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ECS
|
solicited
Laura Sofie Harbo, Jørgen Eivind Olesen, Zhi Liang, and Lars Elsgaard

Soil organic carbon (SOC) is essential for soil fertility and further represents a global carbon stock with potential to control atmospheric CO2 concentrations. Due to intense agricultural management, SOC is decreasing in many parts of the world, meaning that the soils act as CO2 sources rather than CO2 sinks, which they could have the capacity to be. Therefore, it is important to identify pertinent agricultural management practices that allow for high productivity, but at the same time allow for carbon sequestration and increase in SOC.

In order to document changes in SOC, it is necessary to monitor SOC over decadal time scales, since changes occur slowly and are small as compared with existing stocks. The SOC content in Danish agricultural soils has been monitored at approx. 10-yr intervals (1986, 1997, 2009) since the first systematic national observations in 1986, where soils were sampled from a national 7 km x 7 km grid.

In 2018, a new sampling campaign was conducted from the national 7 km x 7 km grid and soils were analysed for SOC to 1 m depth. The procedures applied in 2018 allowed for more precise relocation of the sampling points from 2009 as compared to precision obtained during the period from 1986-2009. Further, measurements in 2018 included assessment of soil bulk density and stone content in the upper 0-50 cm, which was not measured previously. Thus, one of the aims of the study was to evaluate how more precise point-specific information on bulk density and stone fractions affected the calculated SOC stocks across different soil types and management practices.

The point-specific bulk density measured in 2018 were on average lower than the bulk densities used previously, which were retrieved from a database of texture-based soil classes. The volumetric stone fraction in the upper 0-50 cm was found to be <5% for roughly 90% of the soils, whereas <3% of the soils had stone fractions of >10%. On average, the inclusion of point-specific bulk density and stone fractions lead to approx. 5% lower SOC estimation, with equal approximmately contribution from the two variables.

How to cite: Harbo, L. S., Olesen, J. E., Liang, Z., and Elsgaard, L.: Stocks and changes in organic carbon in Danish agricultural soils – role of bulk density and stone fractions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16073, https://doi.org/10.5194/egusphere-egu21-16073, 2021.

13:53–13:55
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EGU21-8235
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ECS
|
Highlight
Daria Seitz, Lisa Mareen Fischer, Rene Dechow, and Axel Don

Cover crops have been suggested to preserve or even increase the soil organic carbon (SOC) stocks in croplands which can contribute to soil fertility and climate change mitigation. Cover crop cultivation increased in most European countries during the last years. However, it remains unquantified how many additional cover crops can be integrated into existing crop rotations. Moreover, there are no realistic quantitative estimates of the SOC sequestration potential of implementing additional cover crops in Germany.

We analyzed recent German crop rotations obtained from the first German Agricultural Soil Inventory for available cultivation windows (winter fallows) for cover crops, and we simulated the SOC sequestration potential of additional cover crops in the topsoil using a SOC model ensemble consisting of RothC and C-TOOL. In order to estimate a reasonable carbon input via the cover crops’ biomass, we developed a new allometric function which takes the effect of the weather and the seeding date on the development of the biomass into account.

Our study shows that only one third of the cultivation windows are currently used for cultivating cover crops. Thus, the cover crops’ cultivation area could be tripled with additional 2 Mio ha each year. With these additional cover crops, the annual C input could be increased by 12% from 3.68 to 4.13 Mg C ha-1 a-1. Within 50 years, this would result in 35 Tg more SOC in the top 30cm of German croplands which corresponds to 2.6 Tg CO2 equivalents per year. Despite the dry weather conditions, a considerably large increase in SOC can be achieved in the eastern regions of Germany due to a low current cover crop cultivation frequency. However, the limited water availability during the time of cover crop establishment may require undersowing.

We conclude that including cover crops in crop rotations and consequently avoiding bare fallow in winter is a key measure in a climate mitigation strategy for managing cropland soils, and we will discuss the benefits and barriers of growing cover crops in Germany and Europe.

How to cite: Seitz, D., Fischer, L. M., Dechow, R., and Don, A.: Potential soil organic carbon sequestration with cover crops in German croplands, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8235, https://doi.org/10.5194/egusphere-egu21-8235, 2021.

13:55–13:57
|
EGU21-6372
Enrico Balugani, Martina Maines, Denis Zannoni, Alessandro Buscaroli, and Diego Marazza

Soil carbon sequestration (SCS) has been identified by the IPCC as one of the most promising and cheap methodology to reduce atmospheric CO2. Moreover, an increase in soil organic carbon (SOC) levels improves soil quality by increasing soil structure (and, hence, resistance to erosion) and promoting soil ecosystems services like water retention, productivity, and biodiversity. Various agricultural techniques are available to increase SOC; among them, crop rotation can improve SOC through soil coverage, changes in water regimes, increase in both carbon inputs, and increase in soil aggregates formation.

SOC dynamic models, such as RothC, have been suggested by the IPCC as a way to evaluate the SCS potentials of different soils. Such models could also be used to evaluate the sequestration potential of different agricultural practices. Moreover RothC allows to estimate the time within which the SOC variation, due to a certain agronomic management, can be considered significant as measurable above a threshold value.

In this study, we evaluated the SOC changes for different crop rotations through direct measurements and RothC modelling, with the objective of: (a) estimating their SCS potential, and (b) propose a robust monitoring methodology for SCS practices. We performed the study in an agricultural field close to Ravenna (Italy) characterized by Cambisols and humid subtropical climate. Soil carbon content was assessed before the setup of the crop rotation, and after 3 years of rotation. A RothC model was calibrated with field data, and used to estimate SOC dynamics to 50 years, in order to assess long-term SCS. The model results were also used to assess the best methodology to estimate the SOC variation significance.

The measured SOC was similar to the equilibrium SOC predicted by the RothC model, on average, for the crop rotations. The measurements showed that the SOC, already low at the beginning of the experiment, further decreased due to the crop rotation practice. Of those tested, the best for SCS involves the following crops: corn, soybeans, wheat on tilled soil, and soybeans; while the worst is with corn, wheat on tilled soil, and wheat on untilled soil. However, the SOC variations predicted by RothC for the various rotations were too small to be observable in the field during experimentation. This could be due both to the uncertainty associated with SOC sampling and analysis, and to the short duration of the experiment. The moving average computations on the simulation values allowed us to assess the time required to measure the long-term trend of SOC variation as significant with respect to the environmental background, instrumental error, and SOC periodic fluctuations. That time was estimated to range from 8 to 50 years, changing depending on the rotation type. Periodic fluctuations in SOC should be carefully considered in a monitoring protocol to assess SCS.

How to cite: Balugani, E., Maines, M., Zannoni, D., Buscaroli, A., and Marazza, D.: Soil carbon sequestration through crops rotation in a Mediterranean Cambisols: measurement and modelling, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6372, https://doi.org/10.5194/egusphere-egu21-6372, 2021.

13:57–13:59
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EGU21-10562
Margarete Korintenberg, Judith Walter, Katja Märten, and Jutta Zeitz

The Sustainable Development Goals (SDGs) adopetd by the United Nations in 2016 include the SDG 15.3 „Land Degradation Neutrality (LDN)“, which aims to reduce land degradation by national efforts of the member states. Three indicators for land degradation were gloablly identified: landcover, land productivity and soil organic carbon stocks (SOC). In particular, the assessment of SOC is challenging in countries where (a) spatial digital data is largely missing and (b) SOC mapping is difficult due to remotness typical for high mountain regions . Global data provided by the Secretariat of the United Nations Convention to Combat Desertification (UNCCD) may be used for reporting, but experience from various countries indicates inaccuracies due to generalisation. This is especially the case for SOC. Moreover, to report on changes in SOC stocks, a comprehensive baseline is mandatory. In order to approach these challenges, Kirgistan, which has signed the SDG’s but still lacks a baseline for SOC, has been chosen for a case study.

In a multinational project we developed a scientifically based method to map and assess SOC stocks enabling a nationwide upscaling of SOC data (baseline). Using globally available data on landcover, elevation, climate and national soil data, „representative SOC units“ were identified prior to sampling. We assume that mainly these factors determine the spatial variability of SOC and that similar SOC stocks can be expected at comparable site conditions. More than 90% of the surface area, that potentially store SOC, is coverd by only 20 representative units, which were sampled 3-fold in the field. Sampling location within a single unit was determined using a drone to identify a representative location. Using the drone was especially helpful as sampling sites in a high mountain region were often extremely remote. During sampling small-scale variability of SOC was considered in the field. To determine SOC stocks, bulk density of the fine soil, coarse fragments and amount of roots were measured in the laboratory. Furthermore, pH, clay, silt and sand content were analysed to identify further drivers for SOC distribution.

Results show that spatial distribution of SOC in such a high mountain region is mainly controlled by landcover (cropland, grassland, forest), elevation, bulk density and clay content. Within single landcover classes topographic indices, such as aspect, further determine SOC distribution. This is especially the case for grassland, which is the dominant landcover in Kirgistan (53%). For the assessment of SOC stocks different approaches were compared. For instance, precise assessment of stocks using the bulk density of the fine soil corrected for coarse fragments leads to significantly lower SOC stocks when compared to the global data provided by the UNCCD.

How to cite: Korintenberg, M., Walter, J., Märten, K., and Zeitz, J.: An adapted method to assess soil organic carbon stocks in a high mountain region: A LDN case study from Kirgistan, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10562, https://doi.org/10.5194/egusphere-egu21-10562, 2021.

13:59–14:04
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EGU21-12465
|
ECS
|
solicited
|
Highlight
Thomas Guillaume, David Makowski, Zamir Libohova, Luca Bragazza, and Sokrat Sinaj

Increasing soil organic carbon (SOC) in agro-ecosystems enables to address simultaneously food security as well as climate change adaptation and mitigation. Croplands represent a great potential to sequester atmospheric C because they are depleted in SOC. Hence, reliable estimations of SOC deficits in agro-ecosystems are crucial to evaluate the C sequestration potential of agricultural soils and support management practices. Using a 30-year old soil monitoring networks with 250 sites established in western Switzerland, we identified factors driving the long-term SOC dynamics in croplands (CR) and permanent grasslands (PG) and quantified SOC deficit. A new relationship between the silt + clay (SC) soil particles and the C stored in the mineral-associated fraction (MAOMC) was established. We also tested the assumption about whether or not PG can be used as carbon-saturated reference sites. The C-deficit in CR constituted about a third of their potential SOC content and was mainly affected by the proportion of temporary grassland in the crop rotation. SOC accrual or loss were the highest in sites that experienced land-use change. The MAOMC level in PG depended on the C accrual history, indicating that C-saturation level was not coincidental. Accordingly, the relationship between MAOMC and SC to determine soil C-saturation should be estimated by boundary line analysis instead of least squares regressions. In conclusion, PG do provide an additional SOC storage capacity under optimal management, though the storage capacity is greater for CR.

How to cite: Guillaume, T., Makowski, D., Libohova, Z., Bragazza, L., and Sinaj, S.: Soil organic carbon dynamics and sequestration potential in cropland-grassland agro-ecosystems, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12465, https://doi.org/10.5194/egusphere-egu21-12465, 2021.

14:04–14:06
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EGU21-12243
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ECS
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Highlight
Tommaso Tadiello, Marco Acutis, Alessia Perego, Calogero Schillaci, and Elena Valkama

Mediterranean and humid subtropical climate is characterized by hot summer and cold to mild winter with a medium-low soil organic carbon (SOC) content and high risk of land desertification. Recent EU policies pointed out the need to preserve the SOC stock and to enhance its accumulation by promoting the adoption of conservation agriculture (CA) as an efficient action for climate change adaptation and mitigation. The meta-analysis is a powerful data analysis tool, which can be useful to evaluate the effectiveness of CA in increase SOC in comparison with conventional agriculture. In fact, this topic has been addressed by several published articles even though the methodology shortcomings make sometimes difficult to draw reliable conclusions about the contribution of CA. In our work, we applied a robust methodology to comply with the meta-analytic assumptions, such as an independence of effect sizes and weighting, as well as the requirement to use no predictive functions like pedotransfer. Therefore, the present meta-analysis defines a conservative and replicable approach to deal with soil carbon data, explaining the differences between conventional (control) and CA management (treatment) in terms of SOC stock accumulation in the first 0-0.3 m layer. A defined methodology was developed to summarize carbon data within a unique soil layer taking into account the real variance and correlation between different initial soil carbon layers. A final database of 49 studies has been used to summarize the effect and to explain the heterogeneity across studies, including also several pedoclimatic moderators in the analysis. An overall positive effect of about 13 % change in SOC accumulation was found due to CA practices compared to control. To better explain the data variability, we created two different groups of studies ("low carbon in control, LC" and "high carbon in control", HC) base on the amount of SOC in control (with 40 Mg ha-1 as a threshold). This method leads to more reliable conclusions that it is more likely to find a response to CA management in soil with low carbon content rather than in soil that have more than 40 t C stock ha-1 . A positive correlation was also found between clay soils with high carbon content in control and carbon sequestration event though the texture classification did not explain data variability. Agronomic management plays an essential role in inducing C accumulation under CA in both LC and HC groups, especially with high residue retention during long-term experiments (0.21 Mg C ha-1 yr-1 for the whole database). We also found that climatic and geographical moderators can explain the variability among the effect sizes, like the absolute value of latitude or the precipitation during the year, even though the different continent or climate Köppen classification did not give significant results.

How to cite: Tadiello, T., Acutis, M., Perego, A., Schillaci, C., and Valkama, E.: Can Conservation Agriculture Enhance Soil Organic Carbon Sequestration In Mediterranean And Humid Subtropical Climates? A Meta-Analysis, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12243, https://doi.org/10.5194/egusphere-egu21-12243, 2021.

14:06–14:08
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EGU21-10639
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ECS
Calogero Schillaci, Sergio Saia, Aldo Lipani, Alessia Perego, Claudio Zaccone, and Marco Acutis

Legacy data are frequently unique sources of data for the estimation of past soil properties. With the rising concerns about greenhouse gases (GHG) emission and soil degradation due to intensive agriculture and climate change effects, soil organic carbon (SOC) concentration might change heavily over time.

When SOC changes is estimated with legacy data, the use of soil samples collected in different plots (i.e., non-aligned data) may lead to biased results. The sampling schemes adopted to capture SOC variation usually involve the resampling of the original sample using a so called paired-site approach.

In the present work, a regional (Sicily, south of Italy) soil database, consisting of N=302 georeferenced soil samples from arable land collected in 1993 [1], was used to select coinciding sites to test a former temporal variation (1993-2008) obtained by a comparison of models built with data sampled in non-coinciding locations [2]. A specific sampling strategy was developed to spot SOC concentration changes from 1994 to 2017 in the same plots at the 0-30 cm soil depth and tested.

To spot SOC changes the minimum number of samples needed to have a reliable estimate of SOC variation after 23 years has been estimated. By applying an effect size based methodology, 30 out of 302 sites were resampled in 2017 to achieve a power of 80%, and an a=0.05.

After the collection of the 30 samples, SOC concentration in the newly collected samples was determined in lab using the same method

A Wilcoxon test applied to the variation of SOC from 1994 to 2017 suggested that there was not a statistical difference in SOC concentration after 23 years (Z = -0.556; 2-tailed asymptotic significance = 0.578). In particular, only 40% of resampled sites showed a higher (not always significant) SOC concentration than in 2017.

This finding contrasts with a previous SOC concentration increase that was found in 2008 (75.8% increase when estimated as differences of 2 models built with non-aligned data) [2], when compared to 1994 observed data (Z = -9.119; 2-tailed asymptotic significance < 0.001).

Such a result implies that the use of legacy data to estimate SOC concentration changes need soil resampling in the same locations to overcome the stochastic model errors. Further experiment is needed to identify the percentage of the sites to resample in order to align two legacy datasets in the same area.

Bibliography

[1]Schillaci C, et al.,2019. A simple pipeline for the assessment of legacy soil datasets: An example and test with soil organic carbon from a highly variable area. CATENA.

[2]Schillaci C, et al., 2017. Spatio-temporal topsoil organic carbon mapping of a semi-arid Mediterranean region: The role of land use, soil texture, topographic indices and the influence of remote sensing data to modelling. Sci Total Environ. 

How to cite: Schillaci, C., Saia, S., Lipani, A., Perego, A., Zaccone, C., and Acutis, M.: Matching legacy estimation of soil organic carbon changes from non-paired data with measured values in paired soil samples after two decades: a case study, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10639, https://doi.org/10.5194/egusphere-egu21-10639, 2021.

SOIL INORGANIC CARBON
14:08–14:18
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EGU21-11206
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solicited
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Highlight
Laura Turnbull-Lloyd and John Wainwright

Soil carbon content is greatly affected by soil degradation – in particular erosional processes – which cannot be ignored in the context of the global C cycle. Soil degradation, driven largely by wind and water erosion, affects up to 66% of Earth’s terrestrial surface. Understanding how soil degradation affects soil organic carbon (OC) and soil inorganic carbon (IC) stocks is an essential component of understanding global C cycling and global C budgets, and is essential for improved C management and climate-change mitigation policies.

In this study, we quantify the distribution of soil OC and soil IC (using Harmonized World Soil Database v1.2), and estimate the amount of OC and IC that is mobilised by wind- and water-driven erosion.  For water-driven erosion, we estimate spatially variable water-driven erosion rates for different land-use systems (using the Land Use Systems of the World database) and degradation severities (using the GLASOD map of soil degradation), using values obtained from a meta-analysis of soil erosion rates. We account for potential uncertainty in our estimates of soil erosion rates by undertaking stochastic simulations. For wind-driven soil erosion rates we use modelled dust emission rates from AeroCom Phase III model experiments for the 2010 reference year, for 15 participating models. Global surface soil stocks of carbon (in the top 1-m of soil) are 1218 Pg OC and 452 Pg IC, and of this, 651 Pg OC and 306 Pg IC is located in degrading soils. We estimate that global water-driven soil erosion is 217.54 Pg yr-1 which results in the mobilisation of 4.82 Pg OC yr-1. A minimum estimate of soil IC mobilisation by water erosion is 0.45 Pg IC yr-1. AeroCom model ensemble results indicate that 1.58 Pg dust (ensemble mean) is emitted for the 2010 AeroCom reference year, containing 0.0082 Pg OC and 0.0121 Pg IC.  We found that patterns of wind- and water-driven mobilisation of OC and IC are completely different. The total amount of soil OC and soil IC mobilised by water-driven erosion is much greater than wind-driven erosion, and whereas mobilisation of OC dominates carbon mobilisation via water-driven erosion, IC dominates carbon mobilisation in dust emissions. Across all land-use types, water-driven carbon mobilisation is higher than wind. In particular, water-driven SOC mobilisation is highest in cropland (4.30 Pg OC yr-1) where high erosion rates coincide with average SOC content of 68.4 tonnes ha-1. SIC mobilisation follows the same pattern in relation to land use, with highest water-driven mobilisation in cropland (0.33 Pg IC yr-1).  Future land-use change has great potential to affect global soil carbon stocks further, especially with increases in the severity of soil degradation and consequential mobilisation of OC and IC by wind-and water-driven erosion as human pressures on agricultural systems increase.

 

How to cite: Turnbull-Lloyd, L. and Wainwright, J.: Global-scale quantification of organic and inorganic carbon mobilisation via wind- and water-driven erosion , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11206, https://doi.org/10.5194/egusphere-egu21-11206, 2021.

14:18–14:20
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EGU21-8037
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ECS
Anna Bulysheva, Olga Khokhlova, Nikita Bakunovich, Alexey Rusakov, and Tatyana Myakshina

In the forest-steppe and steppe zones of Russia, soils are subject to prolonged agricultural impact which affected their properties and processes. Therefore, the study of soil transformation under different land-use regimes is an urgent task. The aim of the study is to examine the general patterns of changes in the carbonate state and other properties of soils of the steppe and forest-steppe in Russia of land-use changes from arable to abandoned land (fallow).

The objects of research are сhronosequences of fallow Chernozems and Phaeozems. The first сhronosequence is located in the Belgorod region, Russian Federation. It consists of a virgin, arable Phaeozems, and Phaeozems being in the fallow for 40-45 years. The second сhronosequence is located in the Rostov region. It consists of arable Chernozem and abandoned during 14, 20, 30, and 86 years Chernozems. The third сhronosequence is located in the Lipetsk region. It consists of arable Chernozems and abandoned during 15, 25 years Chernozems. The fourth сhronosequence is located in the Kursk region. It consists of a virgin, arable Chernozems and abandoned during 10, 25, and 50 years Chernozems.

It is noted that all soils in the abandoned land tend to restore virgin properties. Restoration of vegetation and water regime plays the main role in the acquisition of natural soil properties. For 25-30 years, the structural state is restored in Chernozems and Phaeozems. Overconsolidation of the subsurface horizon disappears in Chernozems in 10-15 years, and in Phaeozems it persists up to 40 years. The restoration of the organic carbon in Chernozems and Phaeozems proceeds in different ways. If in Сhernozems, in general, there is an increase in the content and reserves of organic carbon, then in Phaeozems, in the opposite, their decrease is observed. In the transition from arable to fallow soils, there is a decrease in the content and reserves of carbonate carbon due to a change in the water regime: the intensity of the ascending water flows decreases and descending - increases.

In fallow soils, the radiocarbon age of pedogenic carbonates decreases. In arable land "ancient" carbonates are pulled up closer to the day surface. And when plowing stops, they are gradually washed out into the depth of a profile. The greatest 14C age of carbonates is observed in fallow soils with large herbaceous vegetation, which sucks the moisture out from the depth with powerful roots.

The recovery time of the natural soil properties depends on the initial state of the soil, the intensity of the agrogenic impact, the use of soil-saving technologies under plowing, and fertilizers use. In general, Chernozems restore faster than Phaeozems. The carbonate state in all сhronosequences acquires the virgin (before plowing) features after about 30 years.

How to cite: Bulysheva, A., Khokhlova, O., Bakunovich, N., Rusakov, A., and Myakshina, T.: Changes in carbonate state and other properties of fallow soils in the forest-steppe and steppe zones of Russia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8037, https://doi.org/10.5194/egusphere-egu21-8037, 2021.

14:20–14:25
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EGU21-8479
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solicited
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Highlight
Isabel Sonsoles De Soto, Iñigo Virto, Alberto Enrique, Rodrigo Antón, Pierre Barré, and Kazem Zamanian

In calcareous Mediterranean soils, pedogenic and lithogenic carbonates can be important constituents of the soil matrix. However, their relative proportion and their relation to soil functioning has been scarcely studied. The interest in determining the proportion of pedogenic carbonates relies on the fact that they can be related to the physical, chemical and biological properties of the soil and, therefore, affect plant growth and soil productivity. Carbonates dynamics can be affected by some farming management practices and land-use changes, such as the adoption of irrigation, due to changes in the soil water regime, the composition of the soil solution, the concentration of CO2 in the soil atmosphere, and the changes related to fertilization.

To gain knowledge on the importance of the effect of the introduction of irrigation on carbonates dynamics in the tilled layer of agricultural soils, we studied the evolution of the proportion of pedogenic carbonates in a Mediterranean calcareous soil after seven years of irrigation. We used the isotopic signature of C in soil carbonates for these estimations. The study was conducted in two plots under contrasting agricultural management on the same soil unit: dryland wheat cropping, and irrigated corn for 7 consecutive years, in Enériz (Navarre, Spain).

Our results showed that the transformation of dryland wheat to irrigated corn, produced a preferential accumulation of pedogenic carbonates (31-56%) in the tilled layer (0-30 cm) of the irrigated soil only over 7 years after the land-use change. Therefore, the processes related to this land use change can alter the soil carbonates dynamics in a very short period of time, and they may have consequences in terms of plant nutrient dynamics and the soil structure. Future research on the origin of the soil carbonates (pedogenic or geogenic) in agricultural soils will help to understand the actual significance of carbonates dynamics in terms of the global C balance in these soils.

How to cite: De Soto, I. S., Virto, I., Enrique, A., Antón, R., Barré, P., and Zamanian, K.: Pedogenic carbonates accumulation in a calcareous Mediterranean soil following introduction of irrigation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8479, https://doi.org/10.5194/egusphere-egu21-8479, 2021.

14:25–14:27
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EGU21-8538
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solicited
Maddalena del Gallo, Amedeo Mignini, Giulio Moretti, Marika Pellegrini, and Paola Cacchio

CO2 emissions triggered by anthropogenic and natural activities contribute to climate change, one of the current environmental threats of public and scientific concern. At present, microbially-induced biomineralization of CO2 by calcium carbonate (CaCO3) is one of the highly topical study subjects as carbon stabilization process. In the present study we focused our attention on the calcifying bacteria of “living rocks”. The origin of these concretions, composed by a silicate skeleton of quartz and feldspars, merged by massive carbonate concrete, has so far been recognized as abiotic. Within this study we investigated the role of calcifying bacteria in their formation of these concretions and we isolated and characterized the species with CaCO3 precipitation abilities. Concretions were sampled in Romania (Trovant) and Italy (Sibari and Rome). Samples were first analyzed for their culturable microflora (i.e. isolation, CaCO3 precipitation capability and molecular characterization). Then, in vitro regeneration tests were carried out to confirm the contribution of bacteria in the formation of these erratic masses. Moreover, natural samples and bioliths regenerated in vitro were (i) observed and analyzed by scanning electron microscopy (SEM-EDS) and (ii) characterized at molecular level by DNA extraction and 16S rRNA analysis (V3-V4 regions). By isolating and characterizing the culturable microflora, we obtained 19 calcifying isolates, with different morphological, bacteriological and mineral precipitation properties. These evidences have given a first relevant contribution for the definition of the biotic role to the formation of these concretions. These evidences were confirmed by the efficient in vitro regeneration and SEM-EDS analysis. The molecular identification of the isolates and the comparison of the data obtained from the Illumina sequencing with those present in the literature, allowed us to hypothesize the genera that most likely contributed to the formation of these concretions. The results obtained provide a good scientific basis for further studies, which should be directed towards the use of isolates in studies of environmental and socio-economic relevance. Several studies demonstrate that microbially mediated biomineralization has the potential to capture and sequester carbon. Calcium carbonate, is a stable pool of carbon and is an effective sealant to prevent CO2 release back into the atmosphere.

How to cite: del Gallo, M., Mignini, A., Moretti, G., Pellegrini, M., and Cacchio, P.: Isolation and characterization of calcifying bacteria from “living rocks”: a possible carbon sink, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8538, https://doi.org/10.5194/egusphere-egu21-8538, 2021.

14:27–14:29
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EGU21-15601
Cécile Gomez, Tiphaine Chevallier, Patricia Moulin, and Bernard G. Barthès

Mid-Infrared reflectance spectroscopy (MIRS, 4000 – 400 cm-1) is being considered to provide accurate estimations of soil inorganic carbon (SIC) contents. Usually, the prediction performances by MIRS are analyzed using figures of merit based on entire test datasets characterized by large SIC ranges, without paying attention to performances at sub-range scales. This work aims to 1) evaluate the performances of MIR regression models for SIC prediction, for a large range of SIC test data (0-100 g/kg) and for several regular sub-ranges of SIC values (0-5, 5-10, 10-15 g/kg, etc.) and 2) adapt the prediction model depending on sub-ranges of test samples, using the absorbance peak at 2510 cm-1 for separating SIC-poor and SIC-rich test samples. This study used a Tunisian MIRS topsoil dataset including 96 soil samples, mostly rich in SIC, to calibrate and validate SIC prediction models; and a French MIRS topsoil dataset including 2178 soil samples, mostly poor in SIC, to test them. Two following regression models were used: a partial least squares regression (PLSR) using the entire spectra and a simple linear regression (SLR) using the height of the carbonate absorbance peak at 2150 cm-1.

First, our results showed that PLSR provided 1) better performances than SLR on the Validation Tunisian dataset (R2test of 0.99 vs. 0.86, respectively), but 2) lower performances than SLR on the Test French dataset (R2test of 0.70 vs. 0.91, respectively). Secondly, our results showed that on the Test French dataset, predicted SIC values were more accurate for SIC-poor samples (< 15 g/kg) with SLR (RMSEtest from 1.5 to 7.1 g/kg, depending on the sub-range) than with PLSR prediction model (RMSEtest from 7.3 to 14.8 g/kg, depending on the sub-range). Conversely, predicted SIC values were more accurate for carbonated samples (> 15 g/kg) with PLSR (RMSEtest from 4.4 to 10.1 g/kg, depending on the sub-range) than with SLR prediction model (RMSEtest from 6.8 to 14 g/kg, depending on the sub-range). Finally, our results showed that the absorbance peak at 2150 cm-1 could be used before prediction to separate SIC-poor and SIC-rich test samples (452 and 1726 samples, respectevely). The SLR and PLSR regression methods applied to these SIC-poor and SIC-rich test samples, respectively, provided better prediction performances (test of 0.95 and RMSEtest of 3.7 g/kg).

Finally, this study demonstrated that the use of the spectral absorbance peak at 2150 cm-1 provided useful information on Test samples and helped the selection of the optimal prediction model depending on SIC level, when using calibration and test sample sets with very different SIC distributions.

How to cite: Gomez, C., Chevallier, T., Moulin, P., and Barthès, B. G.: Using absorbance peak of carbonate to select suitable regression model before predicting soil inorganic carbon concentration by mid-infrared reflectance spectroscopy, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15601, https://doi.org/10.5194/egusphere-egu21-15601, 2021.

DISCUSSION ON SOC ACCUMULATION AND SOC-SIC RELATIONSHIP
14:29–15:00