Microphytic crusts: 'Topsoil' of the desert
Permaculture Drylands Journal
Deserts throughout the world are the home of microphytic, or cryptogamic, crusts. These crusts are dominated by cyanobacteria, previously called blue-green algae, and also include lichens, mosses, green algae, microfungi and bacteria. They are critical components of desert ecosystems, significantly modifying the surfaces on which they occur. In the cold deserts of the Colorado Plateau (including parts of Utah, Arizona, Colorado, and New Mexico), these crusts are extraordinarily well-developed, and may represent 70-80% of the living ground cover.
Belnap, J., 1990, Microphytic crusts: 'Topsoil' of the desert: Permaculture Drylands Journal, p. 4, 5, 14.