Biological soil crusts: effects of global change on ecosystem roles and restoration

Abstract

Biological soil crusts (BSC) are a dominant feature in arid and semi-arid ecosystems. BSC stabilize soils, contribute nitrogen and carbon, enhance vascular plant nutrition, and influence local hydrologic cycles. However, these ecological roles are determined by the species composition, morphology, and physiological functioning of the BSC. These factors, in turn, can be strongly affected by land use, invasive plants, and climate change. Soil surface disturbance and/or dominance by invasive plants both result in loss of lichens and mosses, leaving cyanobacteria dominating the soil surface. This loss reduces soil stability, carbon and nitrogen contributions, surface temperatures, and soil water retention times. Climate change will differentially affect species and thus change the crusts' species composition (as currently observed in crust composition in different desert with various climate regimes). These changes will alter nutrient cycles, soil moisture, and soil temperatures and reverberate throughout the soil food webs and attendant nutrient cycles. Estimates of recovery times and restoration goals for soil crust communities need to account for global change. We will discuss which of these factors are most likely to influence recovery and restoration, as well as what additional research is needed to best inform restoration efforts.