Recovery of soil organic carbon storage driven by microbial communities during long-term natural restoration in wetland ecosystems

Natural restoration offers a positive strategy for maintaining biodiversity and addressing climate change. Wetland is an important “carbon sink”, yet the dynamic of soil organic carbon (SOC) storage and how it is driven by microbial communities and activities remain unclear during natural restoration. In this work, we investigated the variations of soil organic carbon (SOC) storage, bacterial and fungal communities, as well as microbial activities (including microbial biomass carbon, carbon mineralization rate and extracellular enzymes) in naturally restored wetlands with restoration years of 0 (rice field reclaimed from natural wetland), 15, 20 and 40 in the Poyang Lake wetland. Results showed that SOC storage had been restored to its natural level after 20 years of natural rejuvenation, which was driven by microbial communities via impacting oxidase (peroxidase), microbial biomass and microbial quotient. Fungal diversity and community composition had strong positive effects on SOC storage, while the role of bacteria was limited, emphasizing that fungi exerted a more important control over carbon stock during natural restoration. Fungal taxa Sordariomycetes and Eurotiomycetes were the dominant microbial predictors of SOC storage. Besides, natural restoration significantly shifted bacteria and fungi communities, as well as microbial activities toward a pattern similar to that of natural wetlands. To sum up, our results highlight the significance of natural restoration for recovering carbon storage, and the addition of microbial attributes can potentially improve our capacity to predict changes in SOC storage in wetland ecosystems.