Spatial Differentiation And Regulation Of Soil Organic Carbon Driven By Land Use Practices In The Dongting Lake Watershed

As the most important carbon pool in terrestrial ecosystems,the soil carbon pool is more than the sum of carbon in terrestrial vegetation and the atmosphere.Land use and management will largely influence whether soil becomes a source or sink of atmospheric carbon.In general,soil organic carbon accumulation is favored when land management practices are less disturbed,and it is mineralized and lost when land use practices are more influenced by external sources.Therefore,studying the characteristics of soil organic carbon changes driven by land use is crucial for implementing land use management to increase carbon content and reduce carbon emissions.The implementation of ecological restoration projects such as "returning fields to lakes","returning farmland to forests" and the Three Gorges Project has had a significant impact on the land use patterns in the Dongting Lake basin,and its carbon content and carbon cycle status are changing.Therefore,this study takes the forest land,paddy field,garden land and sloping land of Dongting Lake as the research object,and combines traditional statistical methods,semi-variance function and Kriging interpolation method to analyze the spatial variation characteristics of organic carbon driven by land use patterns in the study area,and mainly achieves the following results:(1)The order of the magnitude of soil p H and powder content under different land use practices is basically the same,in the order of paddy field > garden land >sloping cultivated land > forest land.The order of size of total nitrogen,cation exchange and sand content is similar,which is forest land > paddy field > garden land >sloping cultivated land.The order of clay content was garden land > forest land >sloping cultivated land > paddy land.The soil p H of forest land and sloping cultivated land was acidic,while the soil p H of garden land and paddy field was slightly acidic.The total nitrogen in forest land,paddy field,garden land and sloping cultivated land reached the national level,level 1,level 2 and level 3,respectively;the cation exchange amount was all at the national level 2.The results of the coefficient of variation showed that each soil physical and chemical property parameter was of medium variability.The correlations showed that soil p H was highly significantly positively and negatively correlated with sand and clay grains,respectively;total nitrogen and cation exchange were highly significantly positively correlated,and sand and powder and clay grains were highly significantly positively correlated.(2)Using the semi-variance function method to study the spatial differentiation of soil physical and chemical properties,it was found that soil p H,total nitrogen,cation exchange and sand grains had strong,strong,strong and moderate spatial autocorrelation in forest land,paddy field,garden land and sloping cultivated land.Soil powder particles had moderate,strong,moderate and medium spatial autocorrelation in forest,paddy field,garden and sloping cultivated land,respectively.Soil clay particles have weak,strong,weak and weak spatial autocorrelation in forest,paddy field,garden and sloping cultivation,respectively.(3)Soil organic carbon was normally distributed in forest,paddy field,garden and sloping cultivated land,and its content was different,showing that forest > paddy field > garden > sloping cultivated land,which reflected that the land use pattern significantly affected soil organic carbon.(4)Using semi-variance function and kriging interpolation to study the spatial differentiation characteristics of soil organic carbon,it was found that soil organic carbon had medium,strong,medium and medium spatial autocorrelation in forest land,paddy field,garden land and sloping cultivated land,respectively.In addition,the interpolation results of organic carbon within each watershed under different land use practices can better show the characteristics of spatial land use practices driving soil organic carbon differences.(5)The results of principal component analysis showed that the contribution of soil total nitrogen and cation exchange to organic carbon was larger under the four land use practices,while the contribution of the remaining indicators to organic carbon was weak.The results of correlation analysis showed that soil organic carbon was highly significantly and positively correlated with total nitrogen and cation exchange under the land use patterns of Dongting Lake Basin,indicating that the relationship between soil organic carbon content and total nitrogen and cation exchange in forest land,paddy field,garden land and sloping cultivated land was strong.(6)In the light of the above findings,it is recommended that the forest cover should be increased by adhering to the measures of returning farmland to forest;that the combination of chemical and organic fertilizers should be applied to farming activities to accelerate the accumulation of carbon;and that shade trees should be added to the ecosystem to improve the carbon sequestration potential of the garden to promote the sustainable development of the study area.