Land use and climate control the spatial distribution of soil types in the grasslands of Inner Mongolia |
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| Institution: | 1. Department of Soil Science, College of Agriculture, University of Jiroft, Kerman, Iran;2. Department of Soil Science, College of Agriculture, Isfahan University of Technology, Isfahan 84156-83111, Iran;3. Department of Soil Science, College of Agriculture, Shahid Bahonar University of Kerman, Kerman 76169-14111, Iran;1. University College London, London, Greater London WC1E 6BT, United Kingdom;2. Cranfield University, Cranfield, Bedfordshire MK43 0AL, United Kingdom;3. University of Leicester, Leicester, Leicestershire LE1 7RH, United Kingdom;4. Teagasc, Johnstown Castle, Wexford, Co. Wexford, Ireland;1. State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China;2. Alterra, Wageningen University and Research Centre, PO Box 32, 6700 AA Wageningen, The Netherlands;1. Office of Environment and Heritage, PO Box 644, Parramatta, New South Wales 2124, Australia;2. Faculty of Agriculture and Environment, Biomedical Building C81, University of Sydney, New South Wales 2006, Australia;3. Geoscience Australia, GPO Box 378, Canberra, ACT 2601, Australia |
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| Abstract: | The spatial distribution of soil types is controlled by a set of environmental factors such as climate, organisms, parent material and topography as well as time and space. A change of these factors will lead to a change in the spatial distribution of soil types. In this study, we use a digital soil mapping approach to improve our knowledge about major soil type distributing factors in the steppe regions of Inner Mongolia (China) which currently undergo tremendous environmental change, e.g. climate and land use change. We use Random Forests in an effort to map Reference Soil Groups according to the World Reference Base for Soil Resources (WRB) in the Xilin River catchment. We benefit from the superior prediction capabilities of RF and additional interpretive results in order to identify the major environmental factors that control spatial patterns of soil types. The nine WRB soil groups that were identified and spatially predicted for the study area are Arenosol, Calcisol, Cambisol, Chernozem, Cryosol, Gleysol, Kastanozem, Phaeozem and Regosol.Model and prediction performances of the RF model are high with an Out-of-Bag error of 51.6% for the model and a misclassification error for the predicted map of 28.9%. The main controlling factors of soil type distribution are land use, a set of topographic variables, geology and climate. However, land use and climate are of major importance and topography and geology are of minor importance. The visualizations of the predictions, the variable importance measures as result of RF and the comparisons of these with the spatial distribution of the environmental factors delivered additional, quantitative information of these controlling factors and revealed that intensively grazed areas are subjected to soil degradation. However, most of the area is still governed by natural soil forming processes which are driven by climate, topography and geology. Most importantly though, our study revealed that a shift towards warmer temperatures and lower precipitation regimes will lead to a change of the spatial distribution of RSGs towards steppe soils that store less carbon, i.e. a decrease of spatial extent of Phaeozems and an increase of spatial extent of Chernozems and Kastanozems. |
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