Influence of the Plateau Pika Mound Numbers on Soil Water Erosion Properties in Alpine Meadows of the Yellow River Source Zone, Western China

Abstract

The plateau pika (Ochotona curzoniae) actively contributes to soil erosion and meadow degradation in western China’s Yellow River source zone. This study aimed to elucidate the effects of the pika mound numbers on the hydrodynamic characteristics and soil water erosion through simulated rainfall experiments. The inhibition effects of restored vegetation growth on meadow degradation and soil erosion were explored using a revegetated pika mound as a control. The results showed that at a rainfall intensity of 30 mm/h, the soil loss per unit time increased and then decreased with rainfall time and that 15–20 min of rainfall duration was the sensitive period for soil loss in different pika mound patch lands. The degradation of meadows due to the activities of plateau pika is an essential factor influencing soil erosion, and the soil erosion rate is positively correlated with both the pika mound numbers and slope. The mean flow velocity can better describe the process of the soil erosion, and its value increased with the number of pika mounds and slope. The Reynolds number ranged from 57.85 to 153.63 (Re <500), and it was preliminarily determined that all slope runoff was laminar flow. The Froude number increased linear function with pika mound numbers (p < 0.01), and both the pika mound numbers and slope were significant factors affecting it (p < 0.05). The Darcy–Weisbach resistance coefficient instead decreased with the pika mound numbers and slope, and the inhibitory effect of vegetation on soil erosion was probably limited when the mound numbers reached a certain level. According to the results of the grey correlation and Pearson correlation analysis, changes in the number of pika mounds led to variability in the soil water erosion properties by altering the landscape scale effect. The number of pika mound patches (NP), edge length index (TE), area index (AREA), and volume index (V) were the key influencing factors on the soil erosion rate and hydrodynamic parameters. We conclude that plateau pika activities intensify meadow degradation, and the continuous increase in pika mounds decreases the vegetation cover and flow resistance and increases soil erodibility. Controlling the intensity of plateau pika activities will effectively prevent soil erosion in degraded areas.