XVI International Botanical Congess

Microbiotic soil crusts are a common surface feature of arid and semiarid lands worldwide. In North America, the ecological significance and species composition of these crusts have been studied with some intensity in the Great Basin and Colorado Plateau. The hotter deserts, including the Chihuahuan, Sonoran, and Mojave, have been much less studied. At the conclusion of a three year study of 20 sites within the east Mojave, we have found that algal biomass is considerably lower in the crusts of the Mojave than in the crusts of the Colorado Plateau, Great Basin, and Chihuahuan Desert. The microbiotic crust is less effective at aggregating the surface soil, producing fragile, thin crusts easily disturbed by human activity. The cyanobacterial flora is consistently dominated by Microcoleus vaginatus, Schizothrix calcicola, Nostoc punctiforme, and species of Scytonema and Tolypothrix.