Microbial mechanism of soil organic carbon content under waterlogging and water table fluctuation in drained peat soils

Abstract

Peatlands serve as crucial reservoirs within the global carbon cycle; however, widespread degradation has led to significant reductions in soil organic carbon (SOC) contents. The effects of rewetting on the active SOC and the underlying microbial mechanisms in degraded peatlands are still not fully elucidated. This study examined changes in bulk and active SOC contents, as well as microbial community composition and enzyme activities via controlled water table (WT) manipulation in intact peat columns sourced from drained sites in the Changbai Mountains. The results demonstrated that variations in WT significantly influenced microbial biomass and enzymatic activities within the surface soil layer. Waterlogging resulted in decreased total bacterial and actinomycete biomass, accompanied by a marked increase in fungal biomass, especially under WT fluctuation. Soil oxidase and hydrolase activities only increased significantly under WT fluctuation treatments. SOC contents rose under waterlogged conditions but declined with WT fluctuation. Both dissolved organic carbon (DOC) and microbial biomass carbon were elevated in surface soils subjected to waterlogged and WT fluctuation compared to those in drained peat. However, the easily oxidizable carbon contents were only elevated in surface soils subjected to waterlogged treatments compared to those in drained peat. Soil moisture content had the greatest positive influence, while pH had the greatest negative influence on SOC contents. Actinomycete and DOC had negative impacts on SOC contents under varied WT conditions. This study clarifies the regulatory influence of WT on microbial community dynamics and enzyme activities relevant to SOC storage in degraded peatlands, highlighting the importance of WT management for effective peatland restoration.