Shrub encroachment modulates soil microbial assembly, stability, and functional dynamics in temperate marshes: Emphasizes the key role of bacterial two-component systems

The physical and chemical changes that accompany shifts in plant community composition directly impact marsh soil microbial communities. This leads to uncertainty in microbial communities and plant feedback, which limits our ability to predict marsh biogeochemical cycling and microorganism responses to changes in plant community composition. Therefore, this study employed high-throughput sequencing to elucidate the mechanisms regulating marsh soil microbial community assembly, stability, and functional profiles in response to varying levels of shrub encroachment. The results showed that shrub encroachment significantly altered the composition of soil microorganisms, leading to increased phylogenetic conservation within bacterial and fungal communities. Following shrub encroachment, bacteria sensed, responded, and adapted to environmental changes through the two-component system, shifting community assembly from deterministic (variable selection) to stochastic (homogenizing dispersal) processes. However, fungal community assembly was weakly responsive to shrub encroachment remained primarily stochastic, with the dominant mode transitioning from undominated processes to homogenizing dispersal, largely due to the differential expression of metabolic pathways and interactions (exchange of material, energy, and signaling) with bacterial two-component systems. Additionally, shrub encroachment enhances the networks scale and complexity of soil microorganism, promotes competitive behaviour, and increases community stability while reshaping functional profiles. Further investigation into these issues will contribute to our understanding of microbial ecology theory, thereby providing more effective strategies and methods for the management and conservation of marsh ecosystems.