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

## TL;DR

Cyanobacteria in dryland soil crusts change over time and influence the structure of bacterial and fungal communities through environmental and interaction effects.

## Contribution

This study reveals how cyanobacterial succession shapes microbial community assembly in biocrusts through deterministic and stochastic processes.

## Key findings

- Cyanobacterial communities shift during biocrust succession, driven by ASV turnover and changes in dominant taxa.
- Cyanobacteria influence bacterial and fungal community structures through abiotic factors and microbial interactions.
- Keystone cyanobacteria from specific families enhance biocrust stability and co-occur with distinct microorganisms.

## Abstract

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 Craurococcus caldovatus, Rubellimicrobium, Rubrobacter, and Microvirga. Overall, these findings elucidate how cyanobacteria are involved in structuring microbial communities during biocrust succession and provide a theoretical basis for improving biocrust restoration in dryland ecosystems.

Cyanobacteria are key components driving the formation and development of biological soil crusts in dryland ecosystems. Their community distribution differs significantly across stages of biocrust development. The presence of cyanobacteria influences variations in bacterial and fungal communities within biological soil crusts by regulating the physicochemical properties and potential interspecific microbial interactions.