Research On Shear Strength Of Root-soil Composite And Effect Evaluation Of Soil-fixing For Plant Communities On Steep Slope Ridge Of Loess Plateau

The Loess Plateau is the most serious soil erosion area in China,the Fixing Gulley and Protecting Tableland is very important for local ecological,agricultural and economic development.Vegetation roots can increase soil shear strength through reinforced anchorage,so that the soil can be stabilized.To support the Fixing Gulley and Protecting Tableland,different community types in Wangdonggou watershed were chosen as the object in this paper,the difference of soil shear strength and the effects of vegetation roots characteristics and soil characteristics on soil shear strength were studied,and soil fixation vegetation were selected.The result are as follows:（1）The root density characteristics of the 6 communities were all significantly different,The root weight density,root length density and root surface area density of Sophora davidii-Artemisia sacrorum community were all the highest,which were2757.07g/m³、17886.22 m/m³and 16.96m^2/m³.The specific root length of Lespedeza floribunda-Agropyron cristatum community was the highest,which was 14.00m/g,the specific root surface area of Hippophae rhamnoides-Artemisia giraldii community was the highest,which was 10.89×10^-3m²/g.（2）There was a linear relationship between the shear strength and the vertical stress.There were significant differences in the shear strength among the 6 communities and pure soil,the shear strength of Sophora davidii-Artemisia sacrorum community was the highest.Compare to pure soil,the cohesive force increasing value of Sophora davidii-Artemisia sacrorum community were the highest,the internal fiction angle increasing value of Periploca sepium-Poa sphondylodes community was the highest.（3）The largest influence on soil cohesive force increasing value was root surface area density and the largest influence on soil internal fiction angle increasing value was soil moisture,and shear strength was negatively correlated with soil moisture and soil bulk density,and positively correlated with root density characteristics.（4）Chose three indicators of hydrological effect,mechanical effect and living ability to select soil-fixing vegetation,and the best soil-fixing vegetation was Sophora davidii-Artemisia sacrorum community,followed by Hippophae rhamnoides-Artemisia giraldii community.