Plant invasion reconstructs soil microbial assembly and functionality in coastal salt marshes

Microbiologically driven ecosystem processes can be profoundly altered by alien plant invasions. There is limited understanding of the ecological mechanisms orchestrating different microbial constituents and their roles in emerging functional properties under plant invasions. Here, we investigated soil microbial communities and functions using high-throughput amplicon sequencing and GeoChip technology, respectively, along a chronological gradient of smooth cordgrass invasion in salt marshes located in the Yellow River Estuary, China. We found a positive correlation between microbial diversity and the duration age of invasion, and both bacterial and fungal communities showed consistent changes with invasion. Soil microbial metabolic potential, as indicated by the abundance of microbial functional genes involved in biogeochemical cycling, decreased in response to invasion. As a consequence, declining soil microbial metabolisms as a result of plant invasion facilitated carbon accumulation in invaded salt marshes. Bacteria and fungi exhibited distinct contributions to assembly processes along the invasion gradient: bacterial communities were mainly driven by selection and dispersal limitation, while fungi were dramatically shaped by stochastic processes. Soil microbial-mediated functions were taxon-specific, as indicated by community-function relationships. This study demonstrates the distinct contributions of microbial constituents to microbial community assembly and functions and sheds light on the implications of plant invasion on microbiologically driven ecosystem processes in coastal wetlands.