A 1-year greenhouse gas budget of a peatland exposed to long-term nutrient infiltration and altered hydrology: high carbon uptake and methane emission.

Long-term increased nutrient influx into normally nutrient-limited peatlands in combination with altered hydrological conditions may threaten a peatland's carbon storage function and affect its greenhouse gas (GHG) budget. However, in situ studies on the effects of long-term altered conditions on peatland functioning and GHG budgets are scarce. We thus quantified GHG fluxes in a peatland exposed to enhanced water level fluctuations and long-term nutrient infiltration in Ontario, Canada, via eddy-covariance and flux chamber measurements. The peatland was a prominent sink of - 680 ± 202 g carbon dioxide (CO) and a source of 22 ± 8 g methane (CH) m year, resulting in a negative radiative forcing of - 80 g CO eq. m y. During the growing season CH fluxes were constantly high (0.1 g m s). Further, on three dates, we measured nitrous oxide (NO) fluxes and observed a small flux of 2.2 mg m day occurring during the thawing period. Taking the studied ecosystem as a model system for other peatlands exposed to long-term increased nutrient infiltration and enhanced water level fluctuations, our data suggest that such peatlands can maintain their carbon storage function and CO sequestration may outweigh emissions of CH.