Abstract Aims Biocrusts are common in arid ecosystems and perform critical ecosystem services. However, how abiotic (soil stability and aspect) and biotic factors (plant species canopies) interact to influence their community composition remains unclear. This study explores whether different plant species host distinct biocrust communities beneath their canopies, and whether these effects vary with slope aspect and soil stability across gypsum dunes. We hypothesized that (i) early-successional cyanobacteria biocrusts dominate unstable soils, while (ii) shade- and moisture-sensitive types prevail on north-facing slopes; that (iii) moss crusts are more frequent under denser canopies; and that (iv) plant-driven microenvironmental effects are stronger in stable soils but converge across plant species in unstable soils. Methods In White Sands National Park (New Mexico, USA) we assess changes in biocrust community across slope aspect and a soil stability gradient measuring the relative abundance of biocrust types along 27 transects (270 quadrats, 25 cm 2 each). We used linear mixed models and multivariate analyses to compare the changes in relative abundance and composition of different biocrust types amongst these factors and their interactions. Results Plant species significantly influenced biocrust composition. Ephedra trifurca supported more chlorolichen, moss, and cyanolichen crusts, Tiquilia hispidissima more incipient crusts, and Nerisyrena linearifolia light and dark cyanobacteria. Light cyanobacteria dominated unstable soils; mosses increased on north-facing slopes and under large canopies, while dark cyanobacteria prevailed in open spaces, reflecting their UV tolerance. Unexpectedly, plant effects persisted across soil stability gradient. Conclusions Our findings advance predictive understanding of biocrust dynamics.
Collins et al. (Thu,) studied this question.
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