Abstract:Under natural rainfall conditions, the variations of runoff and sediment yield of typical native plant Rosa roxburghii quantitative studied on karst rocky desertification area of Northwest Guizhou, and the hydrodynamic mechanism of controlling erosion and sediment yield by hedgerow analyzed. The results showed that the interception and diversion of R. roxburghii hedgerow delayed runoff production and confluence time, increased runoff infiltration on karst slopes and reduced erosion power. Under different rainfall intensities, the infiltration rate of karst slope was negatively linearly correlated with runoff and sediment yield. The root system of plants twisted and banded the root soil in series, which changed the infiltration characteristics of the soil and enhanced the erosion resistance and corrosion resistance of the soil. Root density decreased with the increasing of soil depth and sediment reduction effect is also reduced. The soil erosion resistance was significantly positively correlated with the density of fibrous roots less than 1 mm, and linearly correlated with the quantity and length of fibrous roots less than 2 mm and the soil erosion resistance index. When the rainfall intensity of I30 was 2.41 mm, there was almost no runoff erosion in hedgerow plot, but more sediment was produced in the control plot. When I30 was 4.72 mm and 8.35 mm, the erosion and sediment yield of the study plots were all increased, and rills were formed in the control plot, which indicated that the rainfall intensity increased, the productivity of slope surface flow was strengthened, and the sand carrying capacity increased. It showed that hedgerows played an important role in water conservation, soil consolidation and sediment reduction, as well as in regulating the hydrodynamic process of soil erosion. The hydrodynamic forces of runoff erosion and sediment yield on karst slopes were mainly affected by rainfall intensity and kinetic energy of raindrops. The size of raindrop erosion depended on rainfall, rainfall intensity and raindrop size. Erosion sediment yield had a significant power function relationship with rainfall intensity and duration. It is reveals the regulation mechanisms of soil consolidation and sediment reduction by plant roots and the improvement of soil erosion resistance hydrodynamics.