Spatial correlation analysis on soil organic carbon and the influencing factors in the Xiangxi River Basin

Base on the information of national soil survey for the second time and the date come out of field collection and lab. test, this paper firstly studies organic carbon density and pool of different soil types in the Xiangxi River Basin， then chooses information statistics method which is based on information entropy principle to study the spatial relationship quantitatively between soil organic carbon density and its influencing factors, including soil types, topography and geomorphology, soil parent material, vegetation coverage, soil thickness, slope and diversity of the land use types in basin. The results show that the total organic carbon pool of the basin is 75.18 Tg, and soil organic carbon density mainly ranges from 6.00 to 16.00 kg/m2, the soil organic carbon density is high in the northern part of basin and main stream area, and the soil organic carbon density in the other areas of the basin is distributed alternately with high and low. The spatial distribution of soil organic carbon density is affected by the distribution of soil types and topography and geomorphology conditions. The differences of information entropy values for soil organic carbon density at various levels by different soil types are significant, which are broadly consistent with the analysis and compute results of SOC density and carbon storage in the Xiangxi River Basin. In the alpine zone, forest land, farmland and bush land are benefit for storage of soil organic carbon with high density. The soil organic carbon density is highly correlated with soil thickness, but the relevance between the slope and organic carbon density is not obvious. The results of information entropy method used in quantitative calculation and analysis on soil organic carbon density and each impact factors are more reasonable and reliable.