Effects of Land Use Change of Sloping Farmland on Characteristic of Soil Erosion Resistance in Typical Karst Mountainous Areas of Southwestern China

With the implementation of ecological projects such as the Grain-for-Green Project, rocky desertification control and comprehensive control of soil and water loss for sloping farmland, ecological environment of karst mountainous areas in southwest China has been improved significantly, but soil and water loss of sloping farmland is still an important ecological and environmental problem in this region.In this paper we took a typical karst rocky desertification mountainous area, Jinlan Demonstration Area, as the study area located in Qianxi County, Guizhou Province.On the basis of a previous experimental demonstration of grass planting and afforestation on sloping farmland (planted in 2014), the sample plot method was used to obtain soil samples and soil shearing test piece in 2017, and soil shear strength and soil erodibility factor (K) were measured by direct shear method and hydrometer method in order to study the effect of sloping farmland converted to abandoned land, pastureland and agroforestry on soil erosion resistance.Results showed that the soil sheer strength was no obvious change and soil erodibility was no significant difference (P>0.05) in sloping farmland with the level of rocky desertification becoming more serious; soil sheer strength greatly increased after sloping farmland was abandoned, ultimate shear strength τ 300 was increased by 65.5%, and K was significantly different (P<0.05) after 10 years; in the process of sloping farmland converted to pastureland, the soil ultimate shear strength τ 300 was increased by 34.55% and K decreased significantly (P<0.05), which indicated that the effect of grass planting on improving soil erosion resistance of sloping farmland was obvious; in the process of sloping farmland converted to agroforestry, soil erosion resistance was also enhanced, soil shear strength was increased, and K was decreased (it did not reach the significant level, P>0.05).Based on the preliminary results of this paper, we think both grass (tree) planting and land abandonment could improve soil erosion resistance and reduce soil erosion risk, which