ENVIRONMENTAL CONTROLS ON SOIL RESPIRATION IN THE EURASIAN AND GREENLANDIC ARCTIC

Arctic regions contain large amounts of stored soil carbon and compris e huge areas of discontinuous vegetation. The potential for feedback e ffects on possible changing climatic conditions through altered source /sink action for atmospheric CO2 is therefore an important issue in tu ndra regions. In this, study we investigate environmental controls on CO2 evolution rates in Arctic soils through observations along a Euras ian transect of tundra sites and comparative experiments in northern S weden and northeast Greenland. Among factors potentially controlling d ecomposition rates in Eurasian wet and mesic tundra temperature and de pth of the water table significantly influenced the CO2 efflux, while thaw depth, soil nitrogen, and organic matter concentrations explained very little of the variation in fluxes. The minor importance of the s oil N status in controlling decomposition rates was confirmed in exper iments in which N and P was added in a factorial manner at a subarctic heath and a high-Arctic drained fen. Phosphorus decreased the CO2 emi ssions, while the combined N and P treatment increased the emissions i n the subarctic. These effects were not reproduced in the high Arctic. The results support most assumptions in current decomposition models on the soil climatic controls on decomposition rates in the Arctic.