Seasonal patterns in diversity, complexity, and community assembly of soil microorganisms in a subtropical coastal wetland

Soil microbiomes are a significant component of biodiversity, crucial for ecosystem functions, and vital for the health of various organisms. Nevertheless, the impacts of seasons and plant species shifts on microbial diversity and community assembly are still not well understood. In this study, we explore bacterial, fungal, and protistan communities during both summer and winter in a coastal wetland affected by Spartina alterniflora invasion and subsequent Cyperus malaccensis or Kandelia obovata restorations. The results showed that bacterial, fungal, and protistan diversity were 2.63%, 40.3%, and 9.90% higher in winter than in summer, respectively. Plant species had a distinct impact on microbial diversity. Notably, K. obovata restoration significantly increased bacterial diversity, decreased protistan diversity, while having no effect on fungal diversity when compared to S. alterniflora invasion sites. Seasonality and plant species both significantly influenced the community structure of bacteria, fungi, and protists. However, protistan community structure was more sensitive to seasons compared to bacterial and fungal communities. The complexity of co-occurrence networks within or among bacteria, fungi, and protists was higher in winter than in summer. Bacterial and protistan community assembly was primarily driven by stochastic processes, while fungal assembly was dominated by deterministic processes. Bacterial and protistan community assembly exhibited lower stochasticity in winter compared to summer, suggesting a more deterministic assembly of communities during the winter season. Our findings highlight the critical role of seasonality and plant species in regulating microbial communities, revealing higher microbial diversity, network complexity, and determinism in community assembly during winter compared to summer in a subtropical coastal wetland.