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  • 1
    In: Global Change Biology, February 2014, Vol.20(2), pp.653-665
    Description: Sequestration of atmospheric carbon (C) in soils through improved management of forest and agricultural land is considered to have high potential for global mitigation. However, the potential of soils to sequester soil organic carbon () in a stable form, which is limited by the stabilization of against microbial mineralization, is largely unknown. In this study, we estimated the C sequestration potential of soils in southeast Germany by calculating the potential saturation of silt and clay particles according to Hassink [ (1997) 77] on the basis of 516 soil profiles. The determination of the current content of silt and clay fractions for major soil units and land uses allowed an estimation of the C saturation deficit corresponding to the long‐term C sequestration potential. The results showed that cropland soils have a low level of C saturation of around 50% and could store considerable amounts of additional . A relatively high C sequestration potential was also determined for grassland soils. In contrast, forest soils had a low C sequestration potential as they were almost C saturated. A high proportion of sites with a high degree of apparent oversaturation revealed that in acidic, coarse‐textured soils the relation to silt and clay is not suitable to estimate the stable C saturation. A strong correlation of the C saturation deficit with temperature and precipitation allowed a spatial estimation of the C sequestration potential for Bavaria. In total, about 395 Mt CO‐equivalents could theoretically be stored in A horizons of cultivated soils – four times the annual emission of greenhouse gases in Bavaria. Although achieving the entire estimated C storage capacity is unrealistic, improved management of cultivated land could contribute significantly to mitigation. Moreover, increasing stocks have additional benefits with respect to enhanced soil fertility and agricultural productivity.
    Keywords: Agricultural Management ; Climate Change ; Mitigation ; Soil Organic Carbon Stocks ; Soil Fractionation ; Stabilization Of Soil Organic Matter
    ISSN: 1354-1013
    E-ISSN: 1365-2486
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  • 2
    Language: English
    In: Science of the Total Environment, 01 December 2015, Vol.536, pp.1045-1051
    Description: To access, purchase, authenticate, or subscribe to the full-text of this article, please visit this link: http://dx.doi.org/10.1016/j.scitotenv.2015.07.064 Byline: Martin Wiesmeier [wiesmeier@wzw.tum.de] (a,*), Rico Hubner (b), Ingrid Kogel-Knabner (a,c) Keywords Soil organic carbon; Climate change; Net primary productivity; Soil C input Highlights * C stocks in agricultural soils may be largely affected by climate change. * It is assumed that C stocks would increase due to an assumed increase of NPP. * However, crop statistics indicate stagnating yields of major crops since the 1990s. * Concurrently stagnating C inputs would lead to C decreases in the long-term. * Indications for declining agricultural C stocks were already found. Abstract The carbon (C) balance of agricultural soils may be largely affected by climate change. Increasing temperatures are discussed to cause a loss of soil organic carbon (SOC) due to enhanced decomposition of soil organic matter, which has a high intrinsic temperature sensitivity. On the other hand, several modeling studies assumed that potential SOC losses would be compensated or even outperformed by an increased C input by crop residues into agricultural soils. This assumption was based on a predicted general increase of net primary productivity (NPP) as a result of the CO.sub.2 fertilization effect and prolonged growing seasons. However, it is questionable if the crop C input into agricultural soils can be derived from NPP predictions of vegetation models. The C input in European croplands is largely controlled by the agricultural management and was strongly related to the development of crop yields in the last decades. Thus, a glance at past yield development will probably be more instructive for future estimations of the C input than previous modeling approaches based on NPP predictions. An analysis of European yield statistics indicated that yields of wheat, barley and maize are stagnating in Central and Northern Europe since the 1990s. The stagnation of crop yields can probably be related to a fundamental change of the agricultural management and to climate change effects. It is assumed that the soil C input is concurrently stagnating which would necessarily lead to a decrease of agricultural SOC stocks in the long-term given a constant temperature increase. Remarkably, for almost all European countries that are faced with yield stagnation indications for agricultural SOC decreases were already found. Potentially adverse effects of yield stagnation on the C balance of croplands call for an interdisciplinary investigation of its causes and a comprehensive monitoring of SOC stocks in agricultural soils of Europe. Author Affiliation: (a) Lehrstuhl fur Bodenkunde, Department fur Okologie und Okosystemmanagement, Wissenschaftszentrum Weihenstephan fur Ernahrung, Landnutzung und Umwelt, Technische Universitat Munchen, 85350 Freising-Weihenstephan, Germany (b) Lehrstuhl fur Strategie und Management der Landschaftsentwicklung, Department fur Okologie und Okosystemmanagement, Wissenschaftszentrum Weihenstephan fur Ernahrung, Landnutzung und Umwelt, Technische Universitat Munchen, 85350 Freising-Weihenstephan, Germany (c) Institute for Advanced Study, Technische Universitat Munchen, Lichtenbergstr. 2a, 85748 Garching, Germany * Corresponding author. Article History: Received 23 April 2015; Revised 12 July 2015; Accepted 13 July 2015 (miscellaneous) Editor: D. Barcelo
    Keywords: Soil Organic Carbon ; Climate Change ; Net Primary Productivity ; Soil C Input ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 3
    In: Global Change Biology, October 2015, Vol.21(10), pp.3836-3845
    Description: Organic carbon () sequestration in degraded semi‐arid environments by improved soil management is assumed to contribute substantially to climate change mitigation. However, information about the soil organic carbon () sequestration potential in steppe soils and their current saturation status remains unknown. In this study, we estimated the storage capacity of semi‐arid grassland soils on the basis of remote, natural steppe fragments in northern China. Based on the maximum saturation of silt and clay particles 〈20 μm, sequestration potentials of degraded steppe soils (grazing land, arable land, eroded areas) were estimated. The analysis of natural grassland soils revealed a strong linear regression between the proportion of the fine fraction and its content, confirming the importance of silt and clay particles for stabilization in steppe soils. This relationship was similar to derived regressions in temperate and tropical soils but on a lower level, probably due to a lower C input and different clay mineralogy. In relation to the estimated storage capacity, degraded steppe soils showed a high saturation of 78–85% despite massive losses due to unsustainable land use. As a result, the potential of degraded grassland soils to sequester additional was generally low. This can be related to a relatively high contribution of labile , which is preferentially lost in the course of soil degradation. Moreover, wind erosion leads to substantial loss of silt and clay particles and consequently results in a direct loss of the ability to stabilize additional . Our findings indicate that the loss in semi‐arid environments induced by intensive land use is largely irreversible. Observed increases after improved land management mainly result in an accumulation of labile prone to land use/climate changes and therefore cannot be regarded as contribution to long‐term sequestration.
    Keywords: Climate Change ; Fine Fraction ; Soil Organic Carbon ; Soil Texture ; Steppe Soils
    ISSN: 1354-1013
    E-ISSN: 1365-2486
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  • 4
    In: Global Change Biology, March 2018, Vol.24(3), pp.987-1000
    Description: Agricultural soils are widely recognized to be capable of carbon sequestration that contributes to mitigating emissions. To better understand soil organic carbon () stock dynamics and its driving and controlling factors corresponding with a period of rapid agronomic evolution from the 1980s to the 2010s in the North China Plain (), we collected data from two region‐wide soil sampling campaigns (in the 1980s and 2010s) and conducted an analysis of the controlling factors using the random forest model. Between the 1980s and 2010s, environmental (i.e. soil salinity/fertility) and societal (i.e. policy/techniques) factors both contributed to adoption of new management practices (i.e. chemical fertilizer application/mechanization). Results of our work indicate that stocks in the croplands increased significantly, which also closely related to soil total nitrogen changes. Samples collected near the surface (0–20 cm) and deeper (20–40 cm) both increased by an average of 9.4 and 5.1 Mg C ha, respectively, which are equivalent to increases of 73% and 56% compared with initial stocks in the 1980s. The annual carbon sequestration amount in surface soils reached 10.9 Tg C year, which contributed an estimated 43% of total carbon sequestration in all of China's cropland on just 27% of its area. Successful desalinization and the subsequent increases in carbon (C) inputs, induced by agricultural projects and policies intended to support crop production (i.e. reconstruction of low yield farmland, and agricultural subsidies), combined with improved cultivation practices (i.e. fertilization and straw return) since the early 1980s were the main drivers for the stock increase. This study suggests that rehabilitation of soils to reduce salinity and increase crop yields have also served as a pathway for substantial soil C sequestration. SOC stocks in the NCP croplands increased significantly; these changes were accompanied by changes in soil total nitrogen (TN). Annual carbon sequestration in surface soils reached 10.9 Tg C yr, which contributed an estimated 43% of total carbon sequestration in all of China’s cropland on just 27% of its area. Successful desalinization and the subsequent increases in carbon (C) inputs, induced by agricultural projects and policies (i.e. agricultural subsidies), combined with improved cultivation practices (i.e. fertilization, and straw return) since the early 1980s were the main drivers for this SOC stock increase.
    Keywords: Agricultural Policies ; Improved Cultivation ; N Stock Change ; Random Forest ; Soil Organic Carbon Stock Change
    ISSN: 1354-1013
    E-ISSN: 1365-2486
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  • 5
    In: Scientific Reports, 2016, Vol.6
    Description: Climate change and stagnating crop yields may cause a decline of SOC stocks in agricultural soils leading to considerable CO2 emissions and reduced agricultural productivity. Regional model-based SOC projections are needed to evaluate these potential risks. In this study, we simulated the future SOC development in cropland and grassland soils of Bavaria in the 21(st) century. Soils from 51 study sites representing the most important soil classes of Central Europe were fractionated and derived SOC pools were used to initialize the RothC soil carbon model. For each site, long-term C inputs were determined using the C allocation method. Model runs were performed for three different C input scenarios as a realistic range of projected yield development. Our modelling approach revealed substantial SOC decreases of 11-16% under an expected mean temperature increase of 3.3 °C assuming unchanged C inputs. For the scenario of 20% reduced C inputs, agricultural SOC stocks are projected to decline by 19-24%. Remarkably, even the optimistic scenario of 20% increased C inputs led to SOC decreases of 3-8%. Projected SOC changes largely differed among investigated soil classes. Our results indicated that C inputs have to increase by 29% to maintain present SOC stocks in agricultural soils.
    Keywords: Biology;
    E-ISSN: 2045-2322
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