Structure and function of biological soil crusts


Jayne Belnap

Document Type


Journal/Book Title/Conference

Proceedings: Sagebrush Steppe Ecosystems Symposium

First Page



Boise State University, Boise, Idaho, Bureau of Land Management

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Publication Date



In arid and semiarid lands throughout the world, the cover of vegetation is generally sparse or absent. Open spaces between the higher plants are not bare of auto- trophic life but usually covered by a community of highly specialized organisms. This soil surface floral community consists of cyanobacteria, green algae, lichens, mosses, microfungi, and other bacteria. Cyanobacterial and microfungal filaments weave throughout the top few millimeters of soil, gluing loose soil particles together to form a biological crust. These crusts occur in all hot, cool, and cold arid and semiarid regions. They may constitute up to 70% of the living cover (Belnap 1994) and have only recently been recognized as having a major influence on terrestrial ecosystems. These communities are also referred to as cryptogamic, cryptobiotic, micro- biotic, or microphytic soil crusts (Harper and Marble 1988).


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