Northern fens: methane flux and climatic change

Methane flux from northern peatlands is believed to be an important contribution to the global methane budget. High latitude regions are predicted to experience significant changes in surface temperature and precipitation associated with the 2 × CO₂ climate scenarios, but the effects of these changes on methane emission are poorly understood. A peatland hydrologic model predicted June - August decreases in water storage of between 82 and 144 mm, using as inputs increases in temperatures of 3 °C and rainfall of 1 mm d^-1. These changes translate into a water table drop, relative to the peat surface, of between 14 and 22 cm, depending on whether the fen has a floating or non-floating surface. The 3 °C air temperature increase was predicted to raise peat temperature at 10 cm depth by 0.8 °C. These changes were then applied to relationships derived at a subarctic fen for water table: methane flux: temperature at 10 cm depth. Increased temperatures raise the methane flux by between 5 and 40%, but the lowered water table decreases methane flux by 74 and 81%, at the floating and nonfloating fen sites, respectively. These results suggest that methane emissions from northern peatlands are more sensitive to changes in moisture regime than temperature within the range of changes predicted for 2 × CO₂ scenarios.