Microbiota-induced asymmetry in coastal methane emission potential under experimental precipitation gradients

Climate models predict that the frequency and intensity of extreme precipitation events will increase globally. Despite carbon budget in coastal wetlands is known to be sensitive to precipitation variability, in where CH₄ productions and potential mechanisms remain poorly understood. We investigated CH₄ emission potential and its drivers after 7-year of field experiments with five precipitation gradients (-60%, -40%, ambient condition, +40%, +60%) in Yellow River Delta, China. The response of CH₄ emission potential to precipitation gradients exhibited significant asymmetry, with the highest emission potential occurring under +40% precipitation. ¹³C-isotope tracing experiment discovered the primary contribution of acetoclastic methanogenic pathway. +40% precipitation significantly improved the accumulation of aboveground biomass, soil organic carbon and total nitrogen. Microbial community abundance, but not composition, referring to metagenome-assembled genomes also actively responded to precipitation changes. For example, +40% precipitation increased the relative abundance of Methanosarcinia and Methanobacteria. Furthermore, CH₄ emission potential was also promoted by higher microbial enzyme activity. Collectively, CH₄ emission potential in response to 7-year experimental precipitations was regulated by microbiota-driven, showing obvious asymmetry.