Wind erosion prevention characteristics and key influencing factors of bryophytic soil crusts

Biological soil crusts (BSCs) are generally considered to reduce wind erosion, however, the extent of reductions is highly dependent on the vegetation type, soil moisture status, and their interactions in the field. The interrelationships between these factors or their combined effects are relatively unknown. The objectives of this study were to evaluate the contributions of the crust coverage (CC), associated with the soil moisture content (SMC), and the vegetation coverage (VC) to reduce wind-erosion and to provide a basis for the effective management of BSCs. We used an orthogonal design and large-scale wind tunnel simulations to determine the erosion-resistance characteristics of BSCs, and the effects of soil moisture content (SMC), vegetation coverage (VC) and crust coverage (CC) on its wind erosion reductions. Our results showed that 1) the medium SMC + low CC + high VC were the most effective contributors in decreasing the wind erosion modulus; 2) the high SMC + medium CC + low VC primarily reduced the sand-transport rate; 3) the medium SMC + high CC + low VC, with the smallest aeolian sand-flow structure index, resulted in the lowest level of aeolian sand-flow saturation; 4) the high SMC + high CC + medium VC exhibited the highest threshold wind velocity; and 5) the VC and CC were found to have significant effects on the surface roughness, but the SMC did not. BSCs should be strongly protected during dry and windy seasons in the spring and winter because of their value in reducing wind erosion. The BSC may be moderately disturbed during wet and weak wind seasons in the summer or autumn to ameliorate soil moisture conditions, especially in the sites with high vegetation coverage, without exacerbating wind erosion. Management that carefully considers the timing and disturbance of BSCs will help to determine the sustainable balance between the "protection" and "destruction" of BSCs and their effective use in reducing wind erosion.