Biological Soil Crusts of North America

Abstract

Biological soil crusts in North America are diverse and found in many different habitats. On a broad scale, there are several different vegetation zones or ecoregions in western North America that contain biological soil crusts as major components (Fig. 2.1, Table 2.1). These include hot deserts (Mojave, Chihuahuan, Sonoran; see Chap. 1, Photos 34, 35), cool deserts (Great Basin, Colorado Plateau; also often denoted as semideserts, Photos 29–33), the coastal woodlands, chaparral and islands of California; and the subhumid grasslands of the Great Plains. These habitats span a large range of annual precipitation (75–740 mm) and annual mean temperatures (4–24°C). Soil crusts are also found on a smaller scale in shallow lithic sites, infertile forest soils, alpine habitats, and more mesic ecosystems as an early successional vegetation type. Fig. 2.1. Arid and semiarid ecoregions of western North America.Areas shaded in black are cool deserts,while grayshaded areas are hot deserts Table. 2.1. Soil, climatic and vegetative characteristics for low and mid-elevations in North Amrican arid, semaiarid, and subhumid ecoregions. (After Bailey 1994, MacMahon 1987)