Biological Soil Crusts: How Will a Changing World Affect Their Ecological Roles?.

Biological soil crusts (biocrusts) are central to dryland ecosystem functioning. They contribute carbon and nitrogen to soils and nearby vascular plants via the newly discovered fungal loop. They are crucial to soil stability in these regions, as sparse plant cover offers little protection. This biocrust-enhanced stability is critical, as soil formation in drylands is very slow, soils are already low in nutrients and carbon, and dust production a major issue with impacts to human health and regional hydrologic cycles. Biocrusts also have a profound influence on soil temperature and albedo, thus affecting local plants and possibly global climate cycles. The extent to which biocrusts influence dryland ecosystems increases with their biomass and biodiversity, and both of these variables are highly susceptible to global change. Increased frequency of small precipitation events or an increase in temperature reduces both biomass and biodiversity. Compressional disturbances (e.g., trampling, vehicles) and fire have similar effects. The reduction in biomass and simplification of the community results in greatly compromised soil stability and reduced ability to fix C or N. In addition, future higher temperatures will slow recovery of the biocrusts, resulting in slower recovery of ecosystem functions as well..