Bacterial community in two successional crusts. BSCs

Biological soil crusts (BSCs) are ubiquitous in arid and semiarid regions, bacterial communities in BSCs have been widely investigated, however, most studies have focused on a specific BSCs or at a single study site. Comparative studies on different successional crusts across a precipitation gradient helps to comprehensively understand inconsistent ecological roles BSCs participated among studies. We investigated bacterial communities at the early (cyanobacterial-lichen crusts) late (moss crusts) successional stage of BSCs in five arid and semiarid regions with a precipitation gradient from 224 to 559 mm. Bacterial community structure was separated by two successional-stage crusts rather than by precipitation, soil clay and silt content, organic carbon content and total nitrogen were significantly correlated with bacterial community structure, precipitation was associated with bacterial community at the marginal significant level. The relative abundance of Proteobacteria, Bacteroidetes and Cyanobacteria contributed to the difference in bacterial community between crusts. Proteobacteria were higher in moss crusts while Bacteroidetes and Cyanobacteria were higher in cyanobacterial-lichen crusts. Similar to bacterial community structure, bacterial abundance and diversity were significantly higher in late successional stage crusts, and were similar among five regions. This study demonstrates the formation and development of BSCs profoundly impacts soil bacterial community, improved soil properties by BSCs succession is more vital to shape bacterial communities and influence biogeochemical cycles in arid and semiarid regions.