The effect of different biocrusts on soil hydraulic properties in the Tengger Desert, China

Water redistribution profoundly affects the dryland ecosystem's function. Biological soil crusts (BSCs or biocrusts), which cover a large part of soil surface in arid land, significantly affect the water redistribution, but the results are conflicting at regional scale. In this study, the effects of different biocrusts on soil hydraulic properties, including soil water retention curve, soil water sorptivity, soil hydrophobicity and unsaturated hydraulic conductivity, were clarified in Tengger Desert. The results showed that the presence of BSCs significantly changed soil hydraulic properties. Compared to sand, BSCs increased water holding capacity and soil hydrophobicity, and decreased soil water sorptivity and unsaturated hydraulic conductivity. The enrichment of fine particles during the change from the less to the more developed BSCs contributed to the enhancement of water holding capacity, but this effect was mainly limited at 3-cm layer of soil underneath the ground surface. Soil hydrophobicity decreased with crust development, which contributed to the increase of soil water sorptivity. Unsaturated hydraulic conductivity decreased during the change from the less to the more developed BSCs, which exerted some negative effect on water infiltration. Our results highlight the important role of BSCs in hydraulic properties, and consideration of biocrusts and its hydrological behavior could help us better understand the distribution, movement and retention of soil water in this area.