Reserves Estimation And Spatial Distribution Of Soil Organic Carbon In Small Watershed Scale

The spatial distribution of SOC at different depths was studied at two typical watershed---Langling watershed and Shamu watershed. Langling watershed was an important science demonstration of Zigui County’s returning farmland to forest. It is also an important area to ecological restoration and reconstruction of Three Gorges. Shamu River includes large area of natural forest, while Shamu watershed had a large area of natural forest. This study could not only contribute to the regional carbon cycle research, and could provide the basis for China’s Three Gorges reservoir were a of ecological and environmental protection and sustainable use of resources studies.This study took Langling watershed and Shamu watershed for example,322soil surface (0-20cm)samples and73profile(0-100cm) samples were collected to investigate. Geostatistics were used for the analysis of spatial variability of SOC by GIS. And the effect of land coverage and terrain on SOC spatial distribution was discussed. Conclusion were as followed:(1) The mean SOC density of Langling watershed and Shamu watershed were10.32kg/m2and9.79kg/m2.100cm SOC density of Langling watershed in different Land coverage types were12.41kg/m2of tea,11.55kg/m2of farmland,12.45kg/m2of economic forest,13.23kg/m2of coniferous forests,14.49kg/m2of Broad-leaved forest,9.02kg/m2of mixed forest. While100cm SOC density of Shamu watershed in different Land coverage types were8.26kg/m2of tea,10.14kg/m2of farmland,8.74kg/m2of economic forest,9.81kg/m2of coniferous forests,13.94kg/m2of Broad-leaved forest,7.87kg/m2of mixed forest. The surface (0-20cm) SOC density of Langling watershed were between4.27kg/m2to5.28kg/m2, while Shamu watershed’s were between2.95kg/m2to5.75kg/m2. Surface soil carbon reserves accounted for33.07%and47.32%of the whole soil, which further demonstrates the accumulation of the role of soil organic carbon in surface soil.(2)10years of implementation of the Grain measures Lanling watershed layers of SOC, as opposed to five years ago, has significantly improved, Farmland afforestation on organic carbon accumulation on the one hand may play a favorable role in the other hand, fertilization, irrigation and other human factors. The Lanling watershed surface soil organic carbon content was significantly higher than the Shamu watershed topsoil organic carbon content, with the deepening of the soil, the difference decreases gradually.(3)Study on57of Langling watershed and22of Shamu watershed profile(0-100cm) samples, we find that SOC decreases with increasing soil depth, and there is a extremely significant between0-40cm depth, but there is A more gentle decline in soil organic carbon content, even some of rebound phenomenon between40-100cm.(4)The content difference of soil organic carbon of different land coverage type was: Broad-leaved forests>Coniferous forests>Mixed forests>tea>Farmland>Economic Forest. All in all, SOC of man-made Forest was obviously lower than nature forests. Broad-leaved forests was obviously higher than Coniferous forests and Mixed forests. Soil organic carbon in such a change was made up of different land cover, different types and extent human interference, which cause the difference of SOC.(5)Different landscape position analysis showed that the soil active organic carbon and soil organic carbon content were:Lower slope> middle slope> uphill. The content of soil active organic carbon and soil organic carbon on0-15was highest, and on15-25was lowest. This characteristics was correlate to the slope of the migration, different land-use characteristics of landscape and slope. Soil organic carbon and altitude performance is a significant positive correlation.(6)The semi-variance function under sisotropic showed that both soil organic carbon’s space relation was moderate. The relevant range were802.2m and1283.1m.The the relevant range of0-10cm SOC were shorter than the relevant range of10-20cm SOC, Spatial variation structure and spatial interpolation results show basin soil organic carbon content by the slope, slope location and altitude, and other structural factors and land coverage and other human random factors.