Succession of Cyanobacterial Community Contributes to Bacterial and Fungal Community Assembly in Dryland Biocrusts.

Biological soil crusts (Biocrusts), which are widely distributed across arid and semi-arid surfaces, play important ecological roles. Cyanobacteria are considered key intrinsic drivers of biocrust persistence and functioning, exerting a profound influence on their ecological roles. Although the distribution patterns and environmental drivers of cyanobacteria have been extensively studied in biocrusts, their role in microbial community assembly remains insufficiently understood. This study investigated the dynamics of cyanobacterial communities during biocrust succession and their relationships with bacterial and fungal community variations. The results revealed pronounced shifts in the cyanobacterial community, explained by ASV (amplicon sequence variants) turnover and changes in dominant taxa such as Microcoleaceae, unclassified Cyanobacteriales, and Chroococcidiopsidaceae. Total phosphorus, nitrogen, and pH were identified as key environmental factors associated with changes in cyanobacterial community. The bacterial community was primarily governed by homogeneous selection within deterministic processes, whereas the fungal community appeared to be shaped by stochastic processes and variable selection within deterministic processes. Together with abiotic factors such as phosphorus, nitrogen, soil organic carbon, and pH, the cyanobacterial community significantly contributed to bacterial and fungal community structure, as supported by multiple analytical approaches. A few cyanobacterial species from Chroococcidiopsidaceae, Microcoleaceae, and Nostocaceae were identified as keystone taxa in the microbial co-occurrence network, enhancing its stability during early biocrust development. These keystone cyanobacteria also underwent succession and exhibited strong co-occurrence with specific microorganisms, including