Biological soil crusts [Chapter 3.4]

Biological soil crusts (BSCs) develop when various combinations of a vast array of bacteria, cyanobacteria, fungi, lichens, terrestrial algae, and mosses occupy the surface and upper few millimeters of the soil (Warren et al. 2019b). Historically, BSCs have been referred to as cryptobiotic, cryptogamic, microbiotic, microfloral, microphytic, and organogenic crusts. They can be present in a wide range of ecological, successional, and climatic conditions when and where disturbance and/ or aridity have resulted in opportunities for colonization of exposed bare soil surfaces. BSCs are most prevalent, however, in arid and semiarid ecosystems, such as those of Northeastern California, where vascular plant cover and diversity are perennially low, leaving large areas available for colonization by some combination of the organismal groups mentioned above.