Rainfall replenishment threshold and efficiency of soil water in vegetated slopes: an experimental study

Abstract Vegetation cover has a significant impact on the processes of rainfall utilization and soil water replenishment (SWR). Exploring the characteristics of SWR under different vegetation covers is crucial to clarify the hydrological processes of slopes and to optimize ecological restoration strategies. In this study, the threshold and efficiency of rainfall replenishment to soil water in vegetated slopes were investigated. First, four large-scale model slopes were established to constantly monitor soil water dynamics. The variations of soil water distributions in bare, grass, shrub, and grass-shrub slopes were analyzed. The responses of soil water associated with four slopes to different individual rainfall events were discussed. The threshold and efficiency of SWR in ecologically restored slopes were revealed. The results showed that SWR and rainfall were closely related. Heavy rainfall and rainstorms sufficed to affect soil water deep to 60–100 cm. Vegetated slopes reduced the fluctuation of soil water compared with bare slope. Comparably, SWR was more susceptible to Cynodon dactylon (grass) than Magnolia multiflora (shrub). Shrub slope earned the highest threshold of SWR. Grass-shrub slope gained the greatest efficiency, which was more conducive to effective recharge soil water content (SWC).