Spatial-Temporal Variability Of Soil Organic Carbon In Aohan County,Chifeng

Soil carbon pool is the largest carbon pool in terrestrial ecosystem,and its dynamic change and the distribution of reserves not only play an important role in the quality of soil,but also have a great impact on global climate change.A large number of studies have shown that the spatial heterogeneity of soil organic carbon(SOC)exists widely.With the development of precision agriculture and the increasing requirements of scientific land use,the spatial variability of SOC has been widely concerned.Therefore,the accurate estimation of SOC storage,analysis of the spatial-temporal variability and finding out the main factors controlling the spatial distribution of SOC not only could provide scientific reference for the study on the current carbon source and sink,also provide basic data and theoretical basis for regional ecological construction and scientific and rational use of land resources.In this study,Aohan county in Chifeng,Inner Mongolia was collected as the research object,based on soil survey data and remote sensing and GIS tools,classical statistics and geostatistics were used to analyze the spatial variability and distribution patterns of SOC content in 0?100cm depth and find out the dominant factors affecting spatial variability of SOC in different soil depths.The scale effect of spatial variability in surface SOC was studied by multi-scale sampling.Based on the change of land use,spatial-temporal variability of SOC content and reserves in 30 years were analyzed.The main research results were showed as follows:(1)The distribution characteristics of SOC content in 0?100cm depth was basically consistent,generally,the distribution of SOC in the northeast of study area was low and gradually increased to the southwest.A moderate spatial correlation of SOC was found in 0-20cm soil depth,while the strong spatial correlation was found in deeper soil layers(from 20 to 100cm).The obvious differences between the north and the south was found.With the increase of soil depth,the spatial variability caused by random factors gradually decreased,and the structural factors such as topography and soil became the main factors leading to the spatial variability of SOC.The variation range of SOC content was 0.23?20.71g kg-1 in 0?100cm soil depth,SOC content was mainly concentrated in 0?40cm soil depth,SOC content decreased gradually with increasing soil depth and a significant variation was exhibited in different soil types,with the order from high to low:brown soil>cinnamon soil>kastanozems>aeolian sandy soil.SOC content under different land uses was woodland>farmland>grassland.(2)The generalized additive model could well fit the relationship between SOC content and environmental factors.With the increase of soil depth,the SOC content was also different.Vegetation and soil bulk density were the dominant factors affecting SOC content in 0?20cm soil depth;vegetation,altitude and soil bulk density were the dominant factors affecting SOC content in 20?40cm soil depth;slope and elevation were the main factors affecting the SOC content in 40-60cm soil depth;soil moisture was the dominant factor affecting SOC content in 60?100cm soil depth.(3)A moderate spatial correlation of SOC was found in county,medium and small watershed scale.With the reduction of the research scale,the spatial variability caused by random factors decreased gradually,and the spatial autocorrelation distance of SOC decreased gradually.There was a significant difference of the relationship between influential factors and SOC content at different scales,soil and vegetation had the greatest influence on the distribution of SOC content at county scale,vegetation and elevation had the greatest influence on the distribution of SOC content at medium scale,and elevation and slope had the greatest influence on the distribution of SOC content at small watershed scale.(4)A strong spatial correlation of SOC content in 1985 was found.The self-correlation distance of SOC content was shorter than 30 years ago;SOC content in 2014 was higher than that in 1985 in different soil types and land use types.The change of land use was the main driving factors of the spatial-temporal variability of SOC.The SOC density of woodland,farmland and grassland increased by 6.97%,5.39%and 12.12%,respectively.In terms of soil carbon storage,the SOC storage in the forest land was 3.89 times of that in 1985,While the SOC storage decreased by 19.79%and 22.85%,respectively.The total carbon storage reached 16.28 X 106t in Aohan county,which was 3.17%higher than that in 1985.The development of returning farmland to forest and grass,sand control and afforestation allocated appropriately the land use pattern in Aohan county,all the indicators of SOC in each township rose significantly and carbon storage in northern sandy area increased most significantly.