Distribution Characteristics of Soil Particulate Organic Carbon and Mineral-associated Organic Carbon of Different Land Use in Karst Mountain

The content and distribution characteristics of both soil particulate organic carbon(POC) and mineral-associated organic carbon(MOC) in the soil(0—40 cm) under different land use types were studied in Zhongliang knoll,Chongqing.The results revealed that:(1) the average content of the soil organic carbon(SOC) under different land use were woodlandvegetable landgrasslandgardenabandoned farmland;(2) the contents of soil fine particulate organic carbon(FPOC) were more than soil coarse particulate organic carbon(CPOC) in all land use except garden;(3) the contents of POC were different in the soil layer under different land use.Between 0—20 cm,the average contents of CPOC were gardengrasslandvegetablewoodlandabandoned farmland,and the contents were obviously different in each land with different use.The average contents of FPOC were woodlandgrasslandvegetable landgardenabandoned farmland.Between 20—40 cm,the highest content of CPOC and FPOC appeared in vegetable land,while the lowest occured in abandoned farmland,the distributions of the contends of MOC under different land use types were the same as SOC;(4) the component of soil organic carbon ratio was approximately expressed as: MOC/SOCCPOC/SOCFPOC/SOC except garden;(5) the correlation analysis shows that,under different land use types the SOC and POC were positively correlated,and correlation was not consistent,woodland and grassland correlated significantly(P0.01),abandoned farmland correlated significantly(P0.05),and vegetable and orchard land did not remarkably correlate.So,human interference and tillage would affect contribution POC′s in SOC pool.