川中丘陵紫色土区农田土壤有机碳储量及空间分布特征

土壤有机碳在陆地生态系统碳循环中起着举足轻重的作用。针对农田区域内典型县域尺度有机碳储量及其空间格局特征的研究，可以为区域农田土壤固碳提供参考，为研究我国土壤有机碳储量提供基础数据支持。基于2012年农田土壤有机碳分析调查数据，结合GIS和GPS技术对川中丘陵区盐亭县土壤有机碳密度和储量及空间格局进行了估算和分析。结果表明:其主要土壤类型的0~20 cm耕层土壤有机碳密度为111~426 kg/m2，平均值为266 kg/m2，水田和旱地耕层土壤有机碳密度分别为345和234 kg/m2，均低于全国平均值；全县20 cm深度土壤有机碳总储量250×109 kg C，紫色土类土壤有机碳储量最大，为153×109kg C，水稻土次之，有机碳储量0.93×109kg C，两者占据了农田土壤有机碳储量约98%，冲积土和黄壤土类由于面积小，有机碳储量也最低。各土壤类型有机碳储量丰度指数(RI)值都较低，碳存储能力处于中下水平。在县域农田尺度，有机碳空间格局与气候差异、植被类型关系不大，土壤类型空间差异和地形差异是有机碳空间格局形成的主要原因。

STOCKS AND SPATIAL CHARACTERISTICS OF TOPSOIL ORGANIC CARBON OF CROPLAND IN THE TYPICAL PURPLE SOIL AREA OF HILLY AREAS IN CENTRAL SICHUAN

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.