Spatial distribution of biological soil crusts along an aridity gradient in the central-west of Argentina

Biocrusts presented their highest expression in the inter-patches. However, an increase in the level of aridity along the landscape could lead to vascular plants to make a notable influence on the spatial distribution of biocrusts. Our objective was to determine the spatial variation of the vascular plant interactions with biocrusts, and the individual variations of biocrusts and each of its components along a gradient of aridity in Argentina. We worked on three sites following a semiarid-arid-hyperarid environmental aridity gradient. We established 15 plots along the stress gradient. In each plot, we evaluated the spatial distribution of cyanobacteria, mosses, and lichens and the interaction with the dominant shrubs using a distance index analysis. The hyperarid site showed an aggregate distribution pattern for each biological group (biocrusts, mosses, lichens, and cyanobacteria). The semiarid site showed an aggregate distribution for mosses and cyanobacteria. Respect to the interaction with the shrubs, only the hyperarid site showed a positive interaction between shrubs and the components of biocrusts. We found positive interactions of lichens on the semiarid site, but the arid studied site did not show interactions. Reductions in vegetation cover could directly influence in the biocrust coverage, generating impacts on ecosystems.