Regional patterns of biological soil crust lichen species composition related to vegetation, soils, and climate in Oregon, USA

Biological soil crusts are ecosystem engineers in arid and semi-arid habitats; they affect soil chemistry, stability, and vegetation. Little is known about regional variation in biotic crust communities of North America. We explored how biotic crust lichen community composition and richness are related to vascular plant, soil and climate characteristics in Oregon. In 59 0.4-ha plots, we found 99 biotic crust lichen species, one-third of which were observed only once. Biotic crust lichen communities rich in cyanolichens characterized Juniperus stands whereas warm grasslands were home to regionally uncommon species including Texosporium sancti-jacobi and Rhizocarpon diploschistidina. We discerned biotic crust communities in sandy Artemisia tridentata ssp. wyomingensis sites from those loamy A. arbuscula sites. Hotspots of biotic crust lichen species richness were geographically scattered, weakly negatively associated with abundance of shrubs of disturbed sites, Gutierrezia and Chrysothamnus. The sites with lowest biotic crust lichen richness were heavily grazed, burned plots with Gutierrezia in the grassy north; unstable steep talus slopes at the center of the study area; and sandy, grazed sites with Chrysothamnus in the southern portion of our region. Overall, regional patterns in biotic crust lichen communities were strongly associated with vegetation, soils, and climate. Published by Elsevier Ltd.