Seasonal Dynamics of Methane Pathways Along a Hydrogeomorphic Peatland Gradient

Northern peatlands occupy a very small proportion of the Earth’s surface but contain nearly a third of the world’s soil organic carbon. These wetland systems produce substantial fluxes of CH4, a potent greenhouse gas, and are expected to experience particularly high annual mean temperature increases as global climate change proceeds, which could result in a significant positive feedback. Using radioisotope labeling, we quantified the rates of two pathways of CH4 production in six sites in northern Michigan along a physiochemical and ecological gradient that characterizes northern peatlands. We found that the rates of these two pathways displayed markedly different dynamics in space and time and that the hydrogenotrophic pathway, previously presumed to be less significant in these systems, can increase substantially and become dominant across the landscape when water tables are high. Quantifying these two pathways provides critical insight into understanding dynamics of CH4 production in northern peatlands