Land Degradation And Soil Organic Carbon Density Change In The Liusha Basin

According to the data of field investigation about plant identification and soil chemical analysis of 57 samplings in 2005 in the Liusha Basin,Hanyuan County,Sichuan Province.Land degradation of the Liusha Basin were assessed by main component analysis method,discriminant analysis and K-means cluster.This paper studied on the soil organic carbon density characteristics under different land degradation degrees by statistic methods and variance analysis,discussing the influence of soil type,orographic factor, plant type,parent material,land using type on land degradation and soil organic carbon density.The main results were as follows.The results showed that the average of TOCD in Basin declined with the degree of land degeneration were 5.42±1.21 kg m^-2,3.61±0.94 kg m^-2,1.78±0.30 kg m^-2,0.77±0.16 kg m^-2,respectively.Variance analysis indicated that TOCD highly significantly decreased, F=13.55^**(P＜0.01).WSOC took an important part in soil organic carbon,TOeD and WSOCD had singnificant positive relationship(R²=0.91).WSOCD in the topsoil declined with the degree of soil degeneration were 43.79±7.63 g m^-2,38.21±9.31 g m^-2,18.34±2.82 g m^-2, 9.56±2.17 g m^-2,respectively.The results of variance analysis showed that the different land degradation degree had the extremely difference with WSOCD,F=12.83^**(P＜0.01).The main influential factors of land degradation in Liusha Basin were parent material(rock),soil type,altitude,the types of vegetation and land use types.Under different types of parent material(rock),the results of variance analysis showed that the different land degradation degree had both the extremely difference with TOeD F= 5.35^**(P＜0.01) and WSOCD,F=3.58^**(P＜0.05).Different soil type,the variance analysis showed that TOeD and WSOCD both were the extremely significant differences F=5.20^**(P＜0.01) and F=5.25^**(P＜0.01) in different soils.The orographic factor analyses from slope,slope aspect and altitude.The results of variance analysis showed that both TOCD and WSOCD had no singnificant difference under different slope,F=0.12 and F=0.44(P＞0.05).Analysis of variance showed that there were no significant differences of WSOCD and TOeD in different slopes,F=0.83 and F=1.57(P＞0.05),respectively.Under different altitudes,the analysis of variance showed that there wre extremely significant differences of WSOCD,F=4.60^**(P＜0.01) and significant differences of TOeD F= 3.33^*(P＜0.01).The types of vegetation can be analyzed in terms of vegetation community and biomass.The retrograde succession like Joe-irrigation-grasslands existed in vegetation community in investigative area,with the aggravation of land degradation,the density of soil organic carbon gradually decreases,and the plant evolves gradually from arbors and shrub into herbage as the main type,and the structure of community gradually become simpler,which also noted the range of the density of soil organic carbon.There was a trend that the surface biomass decreases with the aggravation of land degradation.Analysis of variance showed that there were extremely significant differences between different extents of land degradation and the biomass with the value of F=59.79^**(P＜0.01).The value of TOCD was positively correlated to surface biomass.So the area of low biomass was the focus of regions under land degradation governance.Different soil type,the variance analysis showed that TOCD and WSOCD both were the extremely significant differences F=5.20^**(P＜0.01) and F=5.25^**(P＜0.01) in different soils.Different types of land use,the variance analysis showed that TOeD and WSOCD both were the extremely significant differences F=9.55^**(P＜0.01) and F=9.70^**(P＜0.01) in different types of land use.