Insights into the desert living skin microbiome: geography, soil depth, and crust type affect biocrust microbial communities and networks in Mojave Desert, USA

Abstract

Biocrusts are the living skin of drylands, comprising diverse microbial communities that are essential to desert ecosystems. Although we have extensive knowledge on biocrust ecosystem function and what drives biodiversity in lichen and moss dominated biocrusts, much less is understood about the impacts of diversity among microbial communities. Moreover, most biocrust microbial composition studies have primarily focused on bacteria. We used amplicon-based metabarcode sequencing to explore composition of both fungal and bacterial communities in biocrusts. Specifically we tested how geography, soil depth, and crust type structured biocrust microbial communities or fungal-bacterial networks. Microbial communities were surveyed from biocrust surface and subsurface soils collected from Joshua Tree National Park, Granite Mountain, Kelso Dunes, and Cima volcanic flows located within the Mojave Desert, USA. Five biocrust types were examined: Light-algal, Cyano-lichen, Green-algal lichen, Smooth moss, and Rough moss crust types. We found the primary characteristics structuring biocrust microbial diversity were 1) geography, as central and southern Mojave sites displayed different community signatures, 2) presence of plant associated fungi (plant pathogens and wood saprotrophs), indicator, and endemic species were identified at each site, 3) soil depth patterns, as surface and subsurface microbial communities were distinctly structured, and 4) the crust type, which predicted distinct microbial compositions. Network analysis showed that Cyanobacteria and Dothideomycetes (Pleosporales) were the major hubs of overall biocrust microbial community. Such hierarchical spatial organization of biocrust communities and their associated biotic networks can have pronounced impacts to ecosystem functions. Our findings provide crucial insights for dryland restoration and sustainable management.