Microhabitat-specific differences on the composition and function of biological soil crust communities

Abstract

Aims: Biological soil crusts (BSC) are key drivers of ecosystem functioning in drylands. Yet understanding their composition/function relationship is still limited due to the poor knowledge about their variability, particularly in terms of small-scale microhabitat differences. Methods: We investigated how changes in BSC community composition (species identity and cover) affect surrogates of soil functions, such as soil erosion resistance, water dynamics and nutrient cycling, in vegetated mound and intermound microhabitats on a semi-arid shrubland of Argentina. We used a correlative approach to evaluate the composition/function relationship, and we compiled information available in the literature about species functional traits to explain the observed patterns. Results: Most BSC species were present in both vegetated mounds and intermounds, and variations in community composition between microhabitat were mainly related to differences in the relative cover of each species. BSC cover improved soil surface stability in both microhabitat, irrespective of the community composition. However, soil functions related to nutrient cycling and water dynamics were correlated to changes in BSC composition, varying in dependence of the cover of species of lichens and mosses characterized by different morphological, anatomical and physiological traits. Most community composition/function relationships did not differ between microhabitat. Conclusion: Our results provide novel evidence that changes in BSC species and functional groups create soil heterogeneity in key soil properties and processes, and those effects are no context-dependent in terms of microhabitat. We identified some functional attributes of the species that may deserve greater attention for improving BSC functional-trait analyses in diverse natural communities.