Light grazing promotes soil water infiltration of the rehabilitated grassland in the hilly region of the Loess Plateau

Water infiltration plays an important role in water hydrological processes, especially in precipitation-limited drylands. Biocrusts are ubiquitous in drylands which had significant influence on soil water infiltration in most cases, while grazing may affect water infiltration by the disturbance of biocrusts. Toward this end, the effects of grazing on surface land cover characteristics, soil physical attributes, and water infiltration rates were measured at non-grazed area (NG) and five intensities grazing slope grasslands (G1, 2.2 goat·hm⁻²; G2, 3.0 goat·hm⁻²; G3, 4.2 goat·hm⁻²; G4, 6.7 goat·hm⁻²; G5, 16.7 goat·hm⁻²) by conducting a fenced grazing experiment. Results showed that surface cover characteristics and soil physical properties changed significantly after grazing, especially at the G5 grazing intensity. Grazing decreased the vegetation coverage and biocrust thickness, while it increased biocrust coverage, bare soil coverage, surface roughness, and splitting index (SPLIT) of biocrust, and the influence was related to grazing intensities. Consequently, there was an increase in the water infiltration rate of 24%–47% after G1-G2 grazing, and the stable infiltration rate and average infiltration rate increased about 56% and 33% at G1, respectively when compared with non-grazed area. The infiltration rate decreased sharply when the grazing intensity was below G3, and infiltration rates remained stable when the grazing intensity was over G3. Improvement of soil infiltration under light grazing after one year was due to the changes of soil surface characteristics and biocrusts characteristics. Among them, disturbance, biocrusts thickness, soil surface roughness together explained the increase of initial infiltration rate, and 0–5 cm soil bulk density, biocrust coverage and its thickness together affected the stable infiltration rate. This link points to the possible use of grazing on the slope grassland with widespread biocrusts and their potential use for the management of soil water in drylands ecosystems.