Abstract:

It has been 〖HT5〗worldwidely trying to increase soil carbon sequestration to mitigate carbon emission pressures. The spatial distribution of soil organic carbon (SOC) pools, and the dynamics in storage and loss of SOC are internationally frontier research fields. Soil organic carbon pool is an important component of terrestrial ecosystem, and soil organic carbon plays a key role in the carbon cycle dynamics. Because of the varied study scales and methods, there exists a huge difference in various results for the current estimates of our country’s soil organic carbon pool. Research on soil organic carbon storage and its spatial pattern characteristics under typical county scale could provide a reference for regional carbon sequestration, and provide a basic data supporting for the study of regional soil organic carbon storage in China. Based on the latest data in 2012, combined with GIS and GPS techniques, the soil organic carbon density and soil organic carbon stock were estimated and its spatial distribution pattern was analyzed, in the typical hilly area of the central Sichuan Basin. The results showed that the soil organic carbon densities of these major soil types ranged from 1.11 kg m2 to 4.26 kg m2 and the average soil organic carbon density in hilly areas of central Sichuan Basin was 266 kg m2. The soil organic carbon density of paddy soil and dry land were 3.45 kg m2 and 2.34 kg m2, respectively, which were both lower than that of national level. The total soil organic carbon stock of the Yanting was 2.50×109kg C in the depth of 20 cm. The maximum SOC stock was in purple soil group with 1.53 ×109kg C, followed by paddy soil with 0.93×109kg C, accounting for about 98% of the total SOC stock in Yanting County altogether. The soil carbon storage richness index (RI) of each soil type was low, indicating that the SOC storage capacity of each soil type was in the lower level. Soil erosion is prone to happen in the purple soil area due to its natural property and the shallow topsoil as well as the steep slope gradient of upland. Furthermore, the soil erosion is seriously affected by the rain in summer. Therefore, contour plough, crossslope planting, straw and residues returned to cropland will effectively prevent the loss of soil organic carbon. There was a large spatial difference of cropland SOC between north and south in Yanting County, and with increase of slope gradient, soil erosion exacerbated and soil organic carbon density showed a decreasing trend. In the county scale, the climate difference and the types of vegetation have little effects on the spatial pattern of cropland SOC, the spatial difference of soil type and topography are the main reason for the formation of the SOC spatial pattern.