Biocrust microbiomes influence ecosystem structure and function in the Mu Us Sandland, northwest China

Biocrusts (biological soil crusts) are a living consortium of microbes that form a protective cover on many dryland soil and rock surfaces and provide important ecological functions in ecosystems. Characterising biocrust microbial communities is an important step in understanding their functional traits. Our aims were to explore the composition, diversity, and ecological function of the microbial community in two types of biocrusts in the Mu Us Sandland, China. High-throughput sequencing (Illumina MiSeq) and Functional Annotation of Prokaryotic Taxa (FAPROTAX) were used to analyze the soil bacterial and fungal communities in two types of biocrusts and their potential functions. In our study we showed that the richness and diversity of bacterial and fungal communities was significantly different between the lichen and moss biocrusts based on high-throughput sequencing. Dominant bacteria in lichen biocrusts (68.0%) were Actinomycetes, Cyanobacteria, and Proteobacteria, with 59.9% in moss biocrusts. In lichen crusts the dominant phylum of fungi was mainly Ascomycota. Microcoleus (11.1%) and Exophiala (7.4%) lichen crusts, while the dominant genus in moss crusts was RB41 (5.2%). The top three factors that were correlated with both bacterial and fungal community structures were pH, soil dissolved organic carbon, and soil organic carbon. Further analysis by FAPROTAX corroborated that the function of the bacterial community in two types of biocrusts was quite different. The relative abundances of metabolic functions in moss crusts, such as chemoheterotrophy, ureolysis, aromatic compound degradation, and nitrate reduction, were significantly higher than those in lichen crusts, however, the relative abundances of cyanobacteria, oxygenic photoautotrophy, photoautotrophy, and phototrophy were significantly lower ( P < 0.05). Together, our results showed that the taxonomic and metabolic diversity, including specific species, have significant effects on the biocrusts types and their functional traits. This study provides a theoretical basis for elements of the soil microbiome restoration that may influence the establishment of plant communities. • The species composition, richness and microbial metabolic function varied among the three cover types in the Mu Us Sandland. • Diverse microbial communities exist in a landscape with multiple edaphic conditions and these may alter the biodiversity and function of biocrusts. • Compared with lichen crusts, moss crusts had an clear carbon sink effect. • Carbon had a greater influence on microbial community distribution than nitrogen.