Abstract: By using an improved wet sieving method, this paper studied the water stability of biological soil crusts with different biological components and biomass in the hilly regions of Loess Plateau. The water stability of the biological soil crusts was related to the crusts’ biological components. Moss-dominated crust had significantly higher water stability than cyanobacteria-dominated crust. After 390 shakings, the thickness- and mass losses of moss-dominated crust were only 47.3% and 40.1% of those of cyanobacteria-dominated crust, respectively. Moss-dominated crust had the highest water stability when the moss coverage was up to 60%, and the thickness- and mass losses were 22.7% and 28.6% of those of cyanobacteria-dominated crust (no moss coverage), respectively. The horizontal stability of the biological soil crusts was significantly higher than the vertical stability. After 390 shakings, the area loss of moss-dominated crust was only 6.4% of thickness loss. The biological soil crusts had a layer structure with strong stability in horizontal direction, which increased the crusts’ resistance against wind- and water erosion.

Key words: biological soil crust, soil structure, water stability, moss-dominated crust, cyanobacteria- dominated crust