Characterising the diversity and functionality of the microbial community within biocrusts associated with different vegetation communities and soil habitats

In arid and semi-arid ecosystems, the biocrust serves as an important biological interface in the topsoil. Although the biocrust and vascular plant and soil are closely related, microbial diversity and functional characteristics in biocrusts of different vegetation communities and soil habitats, especially in watershed conditions, is poorly understood. In this study, biocrust samples were collected from two different soil substrate habitats, the loess and the aeolian sandy soil, as well as three plant communities consisting of Stipa bungeana, Artemisia ordosica, and Populus simonii, with the farmland soil acting as the control at the small watershed scale in the interlaced water and wind eroded area of Northern Shaanxi, China. To characterise the microbial diversity and functionality within biocrusts, a total of 4705 and 219 16S and 18S rDNA OTUs, respectively, were classified using high-throughput sequencing. Proteobacteria, Actinobacteria, and Bacteroidetes were dominant in prokaryotic community, whereas Ascomycota and Basidiomycota were dominant in fungal community in biocrusts. Principal coordinate analysis and hierarchical clustering demonstrated significant differences in prokaryotic and fungal communities between farmland soil and biocrusts, and soil parent materials could be a major factor in shaping the difference in the microbial communities of biocrusts relative to the vegetation types. Soil pH and carbon were dominant environmental factors that affected the prokaryotic and fungal communities in biocrusts. Hence, we demonstrated that the biocrust can significantly improve the topsoil properties in the study region, while their prokaryotic and fungal communities are largely determined by soil properties and environmental parameters.