δC Characteristics of Soil Organic Carbon in Hilly Karst Area

To understand the effects of geomorphology and environment on the C character of soil organic carbon (SOC) in a hilly karst area, 26 soil samples were collected in 2008 in Nanchuan, Chongqing, SW China. The results showed that the δC-SOC values were between -18.66‰~-27.41‰, with the mean value of -23.3‰. The data firmly indicated that the modern soil organic carbon was the mixture of C3 and C4 plants and mainly originated from C3 plants rather than C4 plants. According to the sequence of δC-SOC along the geomorphological change at this hilly karst area, it can be seen that the δC-SOC values was the crest > brae > foot. Based on the results of correlation analysis, the positive correlation between the δC-SOC values and their altitude is 0.432 (p=0.028), which reflects the land/soil degradation effects caused by the hilly geomorphology, especially in the water and soil erosion process.