Temporal variation in soil erosion resistance of steep slopes restored with different vegetation communities on the Chinese Loess Plateau

Vegetation growth can stimulate the changes in near soil-surface characteristics during a growing season in arid and semi-arid regions, and hence likely induces the temporal variation in soil erosion resistance, reflected by rill erodibility (K-r) and critical shear stress (tau(c)). This study investigated the temporal variations in soil erosion resistance of steep slopes restored with different vegetation communities on the Chinese Loess Plateau. The undisturbed topsoil samples, taken from one control cropland and seven vegetation communities at steep gully slopes, were scoured in a hydraulic flume under six different flow shear stresses. Sampling was conducted for seven times from April 23 to October 10, 2018. Near soil-surface characteristics were simultaneously determined to identify the major influencing factors for the temporal variation in soil erosion resistance. The results showed that the temporal variations in K-r of different vegetation communities differed significantly from that of the control. The relative K-r of vegetation-restored soils decreased exponentially over time. The temporal variations in tau(c) were also significantly different from the control for the vegetated samples. Vegetation restoration was effective to enhance soil erosion resistance, and the grass communities were more effective than shrub communities. Compared to control cropland, the mean K-r of vegetation-restored soils decreased by 72%-96%, while the mean tau(c) increased by 100%-183%. The major factors responsible for the temporal variations in K-r and tau(c) were the seasonal variations in root mass density, soil cohesion, and water stable aggregates. K-r decreased exponentially, while tau(c) increased logarithmically with root mass density, soil cohesion, and water stable aggregates.