Changes of bacterial community structure,monosaccharide composition and CO2 exchange along the successional stages ofbiological soil crusts.

Abstract

Biological soil crusts (BSCs) are a dominantecological landscape of drylands, which have asignificant impact on global biogeochemical flux. However, it is unclear how bacterial community and physiological characteristics vary along the BSCssuccessional stages. In this study, bacterial community composition, physiological characteristics, and monosaccharide composition of extracellular polysaccharides (EPSs)were compared among different successional stages. Our findings demonstrated that besidesthe dominant bacterial species, the bacterial communities also showed considerable differences between these two stages. Cyanobacteria were keystone taxain the early stage, while heterotrophic bacteria (Proteobacteria, Actinobacteria and Acidobacteria) were keystone taxa in the later stages. According to the results ofCO2 exchange, cyanobacterial crusts accumulated net carbon faster than moss crusts, whilemoss crusts had a significantly higher respiration rate. The monosaccharide analysis indicated that the EPSs components also varied depending on BSCs' successional stages. Specifically, the contents of rhamnose and arabinose were higher in thecyanobacterial cruststhan other types of crusts, while the contents of fucose, xylose, mannose and glucose were the highest in cyanobacterial-lichen crusts, andgalactose contentwas highest inthe moss crusts. Altogether, our results stress the heterogeneous variation of BSCs along with succession, andthis work offered a fresh viewpoint for a deeper comprehension of the interactions between the monosaccharide components of EPS and the networks of bacterial communities in BSCs.