Microbial Distributions in North American Biological Soil Crusts: Exploring the Great Divide

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Biological soil crusts are topsoil organo-sedimentary assemblages of microorganisms that are prevalent in arid lands, where the lack of water restricts the development of much higher plant cover. This study will build on a previous survey of microbial biodiversity in North American soil crusts by including the Mohave and Chihuahuan desert regions. With the addition of these data the hypothesis that there exists a great biogeographical divide in the distribution of microbes between hot and cold deserts can be tested. Research activities will include attempts to bring into culture a variety of microorganisms that have been detected but not yet studied. In all approaches, a combination of DNA-based methodologies and traditional microbiological and systematic techniques will be used. A sustained effort in inventorying and describing microbial populations of soil crusts is crucial in order to understand the biogeochemical functions of deserts at large, and to safeguard them in the face of ever increasing anthropogenic disturbances. These efforts will likely enhance management and preservation of arid land ecosystems. Because the trial and error approach is not appropriate for ecosystems that are inherently slow-growing, such as soil crusts, explanatory and predictive abilities have to rely on a thorough mechanistic understanding of the environmental constraints and functional properties of these ecosystems, which hinges heavily on available inventories of the microbial diversity that sustains them.