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  • 1
    Language: English
    In: Plant and Soil, 2011, Vol.340(1), pp.7-24
    Description: Spatial prediction of soil organic matter is a global challenge and of particular importance for regions with intensive land use and where availability of soil data is limited. This study evaluated a Digital Soil Mapping (DSM) approach to model the spatial distribution of stocks of soil organic carbon (SOC), total carbon (C tot ), total nitrogen (N tot ) and total sulphur (S tot ) for a data-sparse, semi-arid catchment in Inner Mongolia, Northern China. Random Forest (RF) was used as a new modeling tool for soil properties and Classification and Regression Trees (CART) as an additional method for the analysis of variable importance. At 120 locations soil profiles to 1 m depth were analyzed for soil texture, SOC, C tot , N tot , S tot , bulk density (BD) and pH. On the basis of a digital elevation model, the catchment was divided into pixels of 90 m × 90 m and for each cell, predictor variables were determined: land use unit, Reference Soil Group (RSG), geological unit and 12 topography-related variables. Prediction maps showed that the highest amounts of SOC, C tot , N tot and S tot stocks are stored under marshland, steppes and mountain meadows. River-like structures of very high elemental stocks in valleys within the steppes are partly responsible for the high amounts of SOC for grasslands (81–84% of total catchment stocks). Analysis of variable importance showed that land use, RSG and geology are the most important variables influencing SOC storage. Prediction accuracy of the RF modeling and the generated maps was acceptable and explained variances of 42 to 62% and 66 to 75%, respectively. A decline of up to 70% in elemental stocks was calculated after conversion of steppe to arable land confirming the risk of rapid soil degradation if steppes are cultivated. Thus their suitability for agricultural use is limited.
    Keywords: Classification and Regression Trees (CART) ; Soil organic carbon (SOC) ; China ; Grassland
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 2
    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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  • 3
    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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  • 4
    Language: English
    In: Plant and Soil, 2010, Vol.331(1), pp.341-359
    Description: In order to identify the effects of land-use/cover types, soil types and soil properties on the soil-atmosphere exchange of greenhouse gases (GHG) in semiarid grasslands as well as provide a reliable estimate of the midsummer GHG budget, nitrous oxide (N 2 O), methane (CH 4 ) and carbon dioxide (CO 2 ) fluxes of soil cores from 30 representative sites were determined in the upper Xilin River catchment in Inner Mongolia. The soil N 2 O emissions across all of the investigated sites ranged from 0.18 to 21.8 μg N m -2  h -1 , with a mean of 3.4 μg N m -2  h -1 and a coefficient of variation (CV, which is given as a percentage ratio of one standard deviation to the mean) as large as 130%. CH 4 fluxes ranged from -88.6 to 2,782.8 μg C m -2  h -1 (with a CV of 849%). Net CH 4 emissions were only observed from cores taken from a marshland site, whereas all of the other 29 investigated sites showed net CH 4 uptake (mean: -33.3 μg C m -2  h -1 ). CO 2 emissions from all sites ranged from 3.6 to 109.3 mg C m -2  h -1 , with a mean value of 37.4 mg C m -2  h -1 and a CV of 66%. Soil moisture primarily and positively regulated the spatial variability in N 2 O and CO 2 emissions (R 2  = 0.15–0.28, P  〈 0.05). The spatial variation of N 2 O emissions was also influenced by soil inorganic N contents ( P  〈 0.05). By simply up-scaling the site measurements by the various land-use/cover types to the entire catchment area (3,900 km 2 ), the fluxes of N 2 O, CH 4 and CO 2 at the time of sampling (mid-summer 2007) were estimated at 29 t CO 2 -C-eq d -1 , -26 t CO 2 -C-eq d -1 and 3,223 t C d -1 , respectively. This suggests that, in terms of assessing the spatial variability of total GHG fluxes from the soils at a semiarid catchment/region, intensive studies may focus on CO 2 exchange, which is dominating the global warming potential of midsummer soil-atmosphere GHG fluxes. In addition, average GHG fluxes in midsummer, weighted by the areal extent of these land-use/cover types in the region, were approximately -30.0 μg C m -2  h -1 for CH 4 , 2.4 μg N m -2  h -1 for N 2 O and 34.5 mg C m -2  h -1 for CO 2 .
    Keywords: GHG fluxes ; Land-use/cover ; Semi-arid grassland ; Xilin River catchment
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 5
    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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  • 6
    Language: English
    In: Plant and Soil, 2011, Vol.340(1), pp.35-58
    Description: Semiarid steppe ecosystems account for large terrestrial areas and are considered as large carbon (C) sinks. However, fundamental information on topsoil sensitivity to grazing is lacking across different spatial scales including the effects of topography. Our interdisciplinary approach considering soil chemical, physical, and vegetation properties included investigations on pit scale (square-metre scale), plot scale (hectare scale), and the scale of a landscape section (several hectares). Five different sites, representing a grazing intensity gradient, ranging from a long-term grazing exclosure to a heavily grazed site were used. On the pit scale, data about aggregate size distribution, quantity of different soil organic carbon (SOC) pools, SOC mineralisation, hydraulic conductivity and shear strength was available for topsoil samples from representative soil profiles. Spatial variability of topographical parameters, topsoil texture, bulk density, SOC, water repellency, and vegetation cover was analysed on the basis of regular, orthogonal grids in differently grazed treatments by using two different grid sizes on the plot scale and landscape section. On the pit scale, intensive grazing clearly decreased soil aggregation and the amount of fresh, litter-like particulate organic matter (POM). The weak aggregation in combination with animal trampling led to an enhanced mineralisation of SOC, higher topsoil bulk densities, lower infiltration rates, and subsequently to a higher risk of soil erosion. On the plot scale, the effects of soil structure disruption due to grazing are enhanced by the degradation of vegetation patches and resulted in a texture-controlled wettability of the soil surface. In contrast, topsoils of grazing exclosures were characterised by advantageous mechanical topsoil characteristics and SOC-controlled wettability due to higher POM contents. A combined geostatistical and General Linear Model approach identified topography as the fundamental factor creating the spatial distribution of texture fractions and related soil parameters on the scale of a landscape section. Grazing strongly interfered with the topography-controlled particle relocation processes in the landscape and showed strongest effects on the aboveground biomass production and biomass-related soil properties like SOC stocks. We conclude that interdisciplinary multi-scale analyses are essential (i) to differentiate between topography- and grazing-controlled spatial patterns of topsoil and vegetation properties, and (ii) to identify the main grazing-sensitive processes on small scales that are interacting with the spatial distribution and relocation processes on larger scales.
    Keywords: Steppe soils ; Soil organic matter fractions ; Organic carbon mineralisation ; Wind erosion ; Texture ; Vegetation cover ; Shear strength ; Hydraulic conductivity ; Water repellency ; Anisotropy
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 7
    In: Land Degradation & Development, April 2018, Vol.29(4), pp.875-883
    Description: Long‐term cultivation of steppe soils in a nonsustainable way caused severe soil degradation and reduced agricultural productivity in Eastern Europe, one of the world's most important areas for cereal production. In order to combat soil erosion and maintain yields, a widespread system of tree windbreaks was introduced in the 1950s, accompanied by improved agricultural practices in recent years. However, information on the effectiveness of such measures to rebuild soil organic carbon (SOC) is scarce. The objective of this study was to estimate the OC storage potential of the fine mineral fraction of degraded arable steppe soils in Moldova and to quantify SOC sequestration rates under (a) windbreaks, (b) cropland with improved crop rotation/manure application, and (c) cropland with cover cropping. Natural grassland relicts served as a reference to estimate the SOC saturation potential. Our results revealed a low SOC saturation of 50% under conventional agricultural use due to high SOC losses, indicating a high potential for SOC sequestration. Relatively high SOC sequestration rates were determined for topsoils (0–30 cm) under windbreaks (0.9 t ha yr), improved crop rotation/manure application (1.3 t ha yr), and cover cropping (1.9 t ha yr). In this regard, sequestration rates derived from OC changes of the fine fraction may be more reliable than total SOC‐based rates, particularly for windbreaks with high proportions of labile SOC. We conclude that implementation of improved agricultural management together with the maintenance of windbreaks is a promising strategy to rebuild SOC, reduce widespread soil erosion and compaction, and secure Moldova's agricultural productivity.
    Keywords: Agroforestry ; Carbon Sequestration ; Cover Crops ; Improved Crop Rotation ; Manure Application
    ISSN: 1085-3278
    E-ISSN: 1099-145X
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  • 8
    Language: English
    In: Forest Ecology and Management, 01 May 2013, Vol.295, pp.162-172
    Description: ► SOC storage and its drivers of different forest types in Bavaria were investigated. ► No SOC differences were found between broadleaf, coniferous and mixed forests. ► Temperature and precipitation controlled total SOC storage in forests. ► No decrease of mineral SOC of broadleaf/mixed forests in regions with high temperatures. ► Incorporation of broadleaf species to prevent future SOC losses of coniferous forests. Temperate forest soils of central Europe are regarded as important pools for soil organic carbon (SOC) and thought to have a high potential for carbon (C) sequestration. However, comprehensive data on total SOC storage, particularly under different forest types, and its drivers is limited. In this study, we analyzed a forest data set of 596 completely sampled soil profiles down to the parent material or to a depth of 1 m within Bavaria in southeast Germany in order to determine representative SOC stocks under different forest types in central Europe and the impact of different environmental parameters. We calculated a total median SOC stock of 9.8 kg m which is considerably lower compared with many other inventories within central Europe that used modelled instead of measured soil properties. Statistical analyses revealed climate as controlling parameter for the storage of SOC with increasing stocks in cool, humid mountainous regions and a strong decrease in areas with higher temperatures. No significant differences of total SOC storage were found between broadleaf, coniferous and mixed forests. However, coniferous forests stored around 35% of total SOC in the labile organic layer that is prone to human disturbance, forest fires and rising temperatures. In contrast, mixed and broadleaf forests stored the major part of SOC in the mineral soil. Moreover, these two forest types showed unchanged or even slightly increased mineral SOC stocks with higher temperatures, whereas SOC stocks in mineral soils under coniferous forest were distinctly lower. We conclude that mixed and broadleaf forests are more advantageous for C sequestration than coniferous forests. An intensified incorporation of broadleaf species in extent coniferous forests of Bavaria would prevent substantial SOC losses as a result of rising temperatures in the course of climate change.
    Keywords: Tree Species Effect ; Soil Organic Matter ; Climate Change ; Forest Management ; Forestry ; Biology
    ISSN: 0378-1127
    E-ISSN: 1872-7042
    Source: ScienceDirect Journals (Elsevier)
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  • 9
    Language: English
    In: Forest ecology and management, 2013, Vol.295, pp.162-172
    Description: Temperate forest soils of central Europe are regarded as important pools for soil organic carbon (SOC) and thought to have a high potential for carbon (C) sequestration. However, comprehensive data on total SOC storage, particularly under different forest types, and its drivers is limited. In this study, we analyzed a forest data set of 596 completely sampled soil profiles down to the parent material or to a depth of 1m within Bavaria in southeast Germany in order to determine representative SOC stocks under different forest types in central Europe and the impact of different environmental parameters. We calculated a total median SOC stock of 9.8kgm⁻² which is considerably lower compared with many other inventories within central Europe that used modelled instead of measured soil properties. Statistical analyses revealed climate as controlling parameter for the storage of SOC with increasing stocks in cool, humid mountainous regions and a strong decrease in areas with higher temperatures. No significant differences of total SOC storage were found between broadleaf, coniferous and mixed forests. However, coniferous forests stored around 35% of total SOC in the labile organic layer that is prone to human disturbance, forest fires and rising temperatures. In contrast, mixed and broadleaf forests stored the major part of SOC in the mineral soil. Moreover, these two forest types showed unchanged or even slightly increased mineral SOC stocks with higher temperatures, whereas SOC stocks in mineral soils under coniferous forest were distinctly lower. We conclude that mixed and broadleaf forests are more advantageous for C sequestration than coniferous forests. An intensified incorporation of broadleaf species in extent coniferous forests of Bavaria would prevent substantial SOC losses as a result of rising temperatures in the course of climate change. ; p. 162-172.
    Keywords: Soil Organic Carbon ; Coniferous Forests ; Parents ; Carbon Sequestration ; Soil Profiles ; Mineral Soils ; Environmental Impact ; Statistical Analysis ; Climate Change ; Temperature ; Temperate Soils ; Inventories ; Soil Properties ; Carbon ; Forest Fires ; Climate
    ISSN: 0378-1127
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
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  • 10
    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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