Short-term elevated CO _₂ enhances primary productivity and CH _₄ emissions in wet sedge arctic soils

Abstract The Arctic tundra is a significant source of CH 4 generated through anaerobic methanogenesis, and vegetation explains much of the heterogeneity in CH 4 fluxes across the Arctic landscape. Wet sedge-dominated tundra exhibits particularly high rates of CH 4 flux due to the presence of aerenchyma and therefore, plant-mediated transport of CH 4 . However, the response of CH 4 to future CO 2 concentrations remains largely uncertain. Model predictions assumed that elevated CO 2 (eCO 2 ) will increase primary production and, as a result, CH 4 emissions, but this has been poorly tested given the challenges of conducting eCO 2 experiments in the Arctic. To address this knowledge gap, we tested the response of CH 4 fluxes in soil and vegetation cores from a wet-sedge tundra ecosystem in Alaska to eCO 2 . The eCO 2 stimulated plant productivity and increased CH 4 emissions in a short-term treatment. The instantaneous response suggests a direct contribution of plant-derived labile carbon input in stimulating methanogenesis despite the large soil carbon store in these tundra ecosystems.