Carbon exchange and primary production in a High-Arctic peatland in Svalbard

Moss tundra with a thick peat layer dominated by bryophytes is one of the most important ecosystems in the High Arctic of Svalbard, but little is known about the carbon dynamics of moss tundra. Here, we estimated the net primary production (NPP) and net ecosystem production (NEP) of moss tundra on Broggerhalvoya (Brogger Peninsula) of north-western Svalbard (79 & DEG;N). The net photosynthetic and respiration rates of the two dominant moss species, Calliergon richardsonii and Tomenthypnum nitens, were measured under laboratory conditions. On the basis of the photosynthetic and respiration characteristics and climatic data, we estimated the cumulative NPP of the dominant moss species during the growing season to be 143-207 gC m-2. Net CO2 exchange, which was determined by subtracting the respiration of the brown moss layer from NPP, was similar to that estimated using field gas flux measurements. The field measurements indicated that methane emissions contributed little to car-bon flow. The NEP estimated in this study was much larger than the long-term carbon accumulation rate reported in a previous study. These data suggest that a significant amount of fixed carbon was lost from the peat layer or that carbon accumulation has recently increased. The NPP and NEP values of the moss tun-dra are larger than those reported for other vegetation types in this area, sug-gesting that moss tundra is an active site with high rates of carbon fixation.