Biological and microbial activity in biological soil crusts from the Tabernas desert, a sub-arid zone in SE Spain

► In the crust layers of BSCs, between 5 and 16% of the total C content is Biomass-C. ► From 7 to 12% of TOC was emitted as CO2 by crust layers in a 10 day incubation period. ► Net mineralization rates were very high in all BSCs. ► Ammonification predominated in crust layers and nitrification in middle/deep layers. ► Biochemical properties were higher in crust layers than in A horizons of mesic soils.