Spatiotemporal Variability of Carbon Dioxide and Methane Fluxes in Six Temperate Wetlands

Abstract Wetlands are important to global carbon cycling, emitting large amounts of the greenhouse gas (GHG) methane (CH 4 ) and acting as sources or sinks of carbon dioxide (CO 2 ). Yet, wetland GHG fluxes are uncertain due to spatiotemporal variability among and within wetlands and multiple environmental factors influencing fluxes. To address these sources of uncertainty, we studied six wetlands representing three wetland types (bog, emergent, and forested) in Central New York (USA) from June to November. We measured CO 2 and CH 4 fluxes and environmental parameters related to porewater, hydrology, temperature, and vegetation. GHG fluxes differed over time across the wetland types, with CO 2 fluxes ranging from -30.31 to 30.85 and CH 4 fluxes from -0.18 to 31.20 mmol m −2 h −1 . For CO 2 , emergent wetlands were sinks in June and emitted the most in July, forested wetlands showed consistent emissions over time, and bogs switched between sources and sinks, with highest emissions in July. For CH 4 , emergent wetlands had the greatest fluxes in July, bogs had similarly variable fluxes over time, and forested wetlands had consistently low fluxes. Within a wetland, spatial variability exceeded temporal variability for CO 2 fluxes but was similar to temporal variability for CH 4 fluxes. Warmer porewater temperatures increased CO 2 and CH 4 fluxes, and CH 4 fluxes positively related to standing water depth. Overall, wetland GHG fluxes varied among wetland types within one region, with idiosyncratic variation across time and space, suggesting that including local vegetation and temporal variability may reduce uncertainty in upscaled models of wetland GHG fluxes.