Biological soil crusts (biocrusts) are complex communities of photoautotrophic cyanobacteria, algae, lichens, and bryophytes growing together with heterotrophic fungi, bacteria, and archaea within the uppermost millimeters of the soil. They cover about 40 % of the open ground surface in hot, cool, and cold arid and semiarid regions around the world. When active, biocrusts provide significant contributions to ecosystem primary productivity, taking up atmospheric CO₂ and fixing N₂. As result of their physiological activity they secrete some organic compounds that contribute to soil formation rates, modifying key soil surface properties with direct implications for soil fertility, runoff generation, evaporation, and water availability for vascular plants and microorganisms. Moreover, they increase soil cohesion and stability, reducing water and wind erosion and providing stable environments for vascular plants and higher trophic levels. Recent studies also show that they have influenced Earth’s ambient conditions for more than 2 billion years by modifying soil surface albedo and solar radiation budgets, and emitting reactive nitrogen species that affect ozone production and self-cleaning capacity of the atmosphere. However, biocrusts are also recognized as being particularly sensitive to climate change and anthropogenic disturbance, with biocrust destruction causing detrimental effects for habitats and the environment. Natural recovery after disturbance has been shown to depend on a variety of environmental factors and tends to be slow. Thus, there have been several attempts to accelerate biocrust recovery after disturbance by means of artificial inoculation, which presents a promising biotechnological tool for dryland restoration after disturbance events.

In this special issue, we seek to understand the functional roles of biocrusts in biogeochemical cycling processes in a changing environment. We present papers investigating biocrust effects on C and N fluxes, soil formation and stabilization, and restoration methods and success within different areas around the world.