Desert Biocrusts

Abstract

Soil biocrusts, also known as biological soil crusts or microbiotic crusts, are composed of different proportions of cyanobacteria, green algae, lichens, mosses, fungi, and bacteria, which commonly occupy the upper 0.1–2 cm of the soil. They are especially abundant between the 100‐ and 300‐mm isohyets, where they may occupy up to 80–90% of the surface. Once covering the surface, they may largely affect the ecosystem. They contribute to surface stability, affect the surface and subsurface hydrology (whether infiltration, runoff, and/or evaporation), the input of organic carbon and nitrogen, increase dust (and subsequently nutrient) entrapment, and affect vascular plant germination and growth. This article will focus on the variable effects of biocrusts on the arid and semiarid ecosystems and the possible factors that determine their establishment and growth. Controversial views regarding their growth and effects as reflected at the current state‐of‐the‐art knowledge will be also discussed.