Climate Sensitivity of Peatland Methane Emissions Mediated by Seasonal Hydrologic Dynamics

Peatlands are among the largest natural sources of atmospheric methane (CH₄) worldwide. Peatland emissions are projected to increase under climate change, as rising temperatures and shifting precipitation accelerate microbial metabolic pathways favorable for CH₄ production. However, how these changing environmental factors will impact peatland emissions over the long term remains unknown. Here, we investigate a newly developed eddy covariance long-term dataset spanning 11 years from the Marcell Experimental Forest in northern Minnesota, U.S.A., to analyze the influence of soil temperature and water table elevation on peatland CH₄ emissions. We demonstrate the importance of seasonal water availability in controlling the sensitivity of CH₄ emission increase to soil temperature - higher water tables dampen the springtime increases in CH₄ emissions as well as their subsequent decreases during late summer to fall. Importantly, these results imply that any hydro-climatological changes in northern peatlands that shift seasonal water availability from winter to summer will increase annual CH₄ emissions, even if temperature remains unchanged. Therefore, advancing hydrological understanding in peatland watersheds will be crucial for improving predictions of CH₄ emissions.