Twenty years of methane and carbon dioxide flux measurements from a temperate peatland

We have measured ecosystem respiration, net ecosystem CO2 exchange (NEE), CH4 flux, water table height, and meteorological data on a semi-continuous basis at Sallie's Fen, NH, USA, a nutrient poor fen located at the southern limit of boreal peatlands in North America, for nearly 20 years. Our major findings include: 1. Instantaneously measured CH4 fluxes show high interannual variability and reveal clear relationships between CH4 fluxes and environmental variables. 2. However, seasonally averaged CH4fluxes show low interannual and spatial variability. 3. Species composition and environmental variables (air temperature, peat temperature, water table level) affect relationships between CH4 fluxes and measures of plant productivity (NEEmax, photosynthesismax, respiration. 4. Each year rates of photosynthesis and respiration increase throughout the season with increasing temperature. 5. Interannual variability is driven by changes in weather in a climate-determined landscape. 6. Measured dark chamber respiration rates have increased over the 20-year period. 7. Plant species composition in the peatland is transitioning to a more shrub-dominated ecosystem which may be driving increased respiration rates observed at this site. 8. Regional O3events appear to impact respiration rates in autochamber measured CO2 exchange. Long-term datasets of trace gas exchange from peatlands like those presented here are essential in the development and validation of process based models for prediction of future climate impacts on these sensitive ecosystems.