The distribution of the surface soil organic carbon storage and density in western Chongqing

Based on the soil data obtained by multi-purpose regional geochemical survey,the authors estimated the surface soil organic carbon storage and organic carbon density in western Chongqing. The results show that the surface soil organic carbon storage is 41 038589 t,with organic carbon average density of 2 929 t·km-2. As for geomorphological types,the soils of low maintains( 2 984 t·km-2) and middle maintains( 2 986 t·km-2) have higher organic carbon density,the density of hills soil is the lowest,and the maintainous soil has most abundant organic carbon storage. In different soil types,the organic carbon density of limestone soil is the highest( 5 043 t·km-2),followed by yellow soil( 3 756 t·km-2),the organic carbon density of purple soil is the lowest( 2 329 t·km-2),and the organic carbon storage of purple soil is the highest. Regarding the land use,the organic carbon density of forest land is the highest( 4 071 t·km-2),the cultivated land is at the middle level( 2 752 t·km-2),the resident and building soil is the lowest( 2416 t·km-2),and the organic carbon storage of the cultivated land is the highest. A comparison with the data of the Second Soil General Survey shows that the surface soil organic carbon storage and organic carbon density have been reduced and,as‘carbon source',the surface soil has released organic carbon to the air. Especially the soil in Nanchuan and Jiangjin has decreased by 56.7% and 45.1%respectively.