干旱区生态环境知识资源中心

Biological soil crusts are found throughout the world. They are generally dominated by cyanobacteria, lichens, and mosses. When moistened, cyanobacteria move through soils, leaving sticky sheaths behind. Sheaths connect loose soil particles, contributing soil resistance to wind and water erosion. Abandoned sheaths are found up to 10 cm down in soils, providing stability at depth. Moistened sheaths absorb ten times their volume of water. Crusted surfaces roughened by frostheaving slow rainfall runoff, thus increasing infiltration.

Crusts can reduce germination of exotic annual grasses. They contribute nitrogen to desert ecosystems, where nitrogen often limits productivity. Plants growing in crusted areas often have higher levels of many nutrients than plants in non-crusted areas.

Many land uses are incompatible with crustal integrity. Cyanobacterial fibers have little resistance to compressional stress. Crushed crusts contribute less nitrogen to soils. Impacted soils are susceptible to both wind and water erosion, leading to soil loss and burial of nearby crusts.

Recovery is generally very slow. Rates depend on climate; size, timing, and intensity of disturbance; and soil type. areas with less stable soils and less rainfall, full recovery may take over 250 years, even with small disturbances. with more inherent stability or areas with greater rainfall will recover more rapidly.