The Influencing Factors of Soil Organic Carbon Density in Lanlingxi Watershed in Three Gorges Reservoir Area

To reveal the influencing factors of soil organic carbon (SOC) density in 0-30 cm soil layer of Lanlingxi watershed in Three Gorges Reservoir Area, build the regression equation for soil organic carbon density and adjust carbon sink strategy in this region, soil samples of top soil profile (0-30 cm) in five land use types were selected by the typical method. The SOC density of top soil profile (0-30 cm) and other environmental factors, such as elevation, slope and aspect and soil properties in five land use types, including grassland, scrubland, woodland, land for tea plantation and farmland in the watershed was investigated. The relationship of SOC density with physical properties of soil was also examined. The SOC density of the above five land use types averaged 7.55, 3.83, 6.04, 10.24, 2.83 kg﹒m-2, respectively. There was a significant difference in the SOC density (p<0.01); SOC density was significantly positively correlated with organic matter content (R=0.942, p<0.01), clay mass percentage (R=0.898, p<0.01), total nitrogen (R= 0.863, p<0.01), elevation (R=0.599, p<0.01); SOC density was significantly negatively correlated with sand content (R= -0.932, p<0.01) and slope (R=-0.407, p<0.05); and the correlation between SOC density and soil pH, total phosphorus or total potassium was not obvious. Multiple correlation coefficient R=0.986 (R>0.8, highly correlated) between SOC density and environmental factors was greater than the correlation coefficient between any one independent variable and dependent variable, which fully proved the combined effect of environmental factors on SOC density.