Soil Water Erosion and Its Hydrodynamic Characteristics in Degraded Bald Patches of Alpine Meadows in the Yellow River Source Area, Western China

Abstract

Degraded bald patches have been active influencing factors in recent years, leading to meadow degradation and soil erosion in the Yellow River source area. In this study, we aimed to quantify the soil water erosion patterns and the hydrodynamic characteristics of degraded bald patches under different vegetation coverage (10%, 30%, 50%, 70% and 90%) and slope (10°, 20° and 30°) combination treatments through simulated rainfall experiments, and to investigate the influence of rodent activities on meadow degradation and soil erosion using zokor mound bare ground as a control. The results show that rodent activity exacerbates erosion problems and that soil erosion rates are negatively correlated with the degree of meadow degradation as an exponential function (p < 0.01). All slope flows are laminar; Reynolds and Froude numbers decrease as a function of vegetation coverage exponentially and linearly (p < 0.01), respectively, and are positively correlated with slope. Flow resistance increases with increasing vegetation coverage and decreasing slope, and vegetation coverage and slope are significant factors affecting flow resistance (p < 0.05). Runoff shear stress was found to range from 1.71 to 5.27 N m−2 in the study area and is positively correlated with vegetation coverage and slope, with a much greater influence of slope than vegetation coverage (p < 0.05). Based on the Pearson correlation and grey correlation method analysis, we concluded that runoff rate, flow velocity, Reynolds number and the Froude number can all describe the hydraulic erosion state under the action of soil erosion on slopes. The Reynolds number was tentatively judged to be the best hydrodynamic parameter to describe the soil erosion process. We conclude that developing degraded bald patches reduces flow resistance and increases surface runoff capacity and soil erodibility by reducing vegetation coverage. The reasonable control of rodent activity can effectively combat erosion on degraded bald patches.