ABSTRACT
In arid lands of many diverse climates of the world, where vegetation is sparse or absent, the open ground is not bare but generally covered by a community of small, highly specialized organisms. Together with crustose, foliose, and fruticose, lichenized fungi (i.e., lichens), cyanobacteria, algae, microfungi, and bryophytes aggregate soil particles to form a coherent skin — the biological soil crust (see Chapter 6). Biological soil crusts play an important ecological role worldwide and are a substantial force in shaping the structure and function of many ecosystems. They increase the stability and fertility of soils and influence local hydrological cycles.
