[Effects of simulated grazing disturbance on soil water infiltration of biocrust slope in the hilly Loess Pla-teau, China].

Water is the key factor for vegetation restoration in the Loess Plateau region. Biological soil crust (biocrust), a widely distributed soil surface cover, significantly affects soil infiltration. Disturbance would affect soil water infiltration of biocrust. The effects of different intensities of disturbance on soil water infiltration of biocrust are still unclear. By simulating the trampling disturbance of sheep, we examined the effects of disturbance intensity (10%, 20%, 30%, and 40%) estimated by the coverage of broken biocrust on the surface cover of biocrust slope in the Hegou catchment of Wuqi County, Shaanxi Province. Soil water infiltration under different intensities were measured by the linear source infiltration method. The influence mechanisms of disturbance on soil water infiltration of biocrust slope were investigated with a structural equation model and correlation analysis. Results showed that compared to that without disturbance, the coverage of cyanobacterial crust was increased by 33.6% at 10% of disturbance intensity, no difference at 20% of disturbance intensity, and decreased by 36.1% and 75.0% at 30% and 40% of disturbance intensities, respectively. Litter coverage was increased by 34.3% under 40% of disturbance intensity, while that of other treatments were not changed. Surface roughness was decreased by 22.3%, 11.1%, and 5.6% at 10%, 20%, and 30% of disturbance intensities, respectively, but increased by 8.2% at the 40% of disturbance intensity. The initial infiltration rate at 40% of disturbance intensity was 77.1% higher than that without disturbance, while other treatments had no significant difference at the initial infiltration rate. Furthermore, distur-bance did not affect the stable and average infiltration rate. Our results confirmed that disturbance mainly promoted the initial infiltration by reducing the coverage of cyanobacterial crust, increasing the coverage of litter, and changing soil roughness. This study would provide scientific basis for the management of biocrust of rehabilitated lands in the Loess Plateau region.