Annual CO₂ exchange and CH₄ fluxes on a subarctic palsa mire during climatically different years

Carbon dioxide and methane fluxes in a palsa mire characterized by dry (palsa) and wet surfaces in a subarctic zone in Finland were measured using a static chamber technique during two climatically different years, 1998 and 1999. Each of the 24 collars was individually studied for water table level, peat temperature, pH, vegetation, frost depth, CO 2 exchange and CH 4 fluxes. The annual gaseous carbon balance varied from −36.9 g C m −2 to −138.6 g C m −2 (uptake) on wet surfaces. During both years, palsa surfaces with shrub vegetation were sinks for carbon, whereas palsa surfaces with sparse vegetation lost carbon to the atmosphere. In 1999, a wet year, a lower NEE resulted mainly from a decrease in photosynthesis. The annual emissions of CH 4 ranged from 1.0 g CH 4 ‐C m −2 in the palsa to 24.7 g CH 4 ‐C m −2 at the palsa margin. On wet surfaces, photosynthesis, respiration and CH 4 fluxes were tightly linked. Annual NEE and CH 4 fluxes were close to the values reported for boreal peatlands (fens).