A note on summer CO2 flux, soil organic matter, and microbial biomass fromdifferent high arctic ecosystem types in northwestern Greenland

We measured CO2 flux soil organic matter, and soil microbial biomass carbon in six high arctic tundra communities near Thule, Greenland. in July 1997, including polar desert, polar semidesert, and polar oasis ecosystems. Thre e of the four polar desert sires were in a contiguous toposequence originat ing at the receding margin of the Greenland ice cap and extending away from the ice approximately 400 m. The other sites ranged from 3 to 12 km from t he ice margin. We measured net ecosystem CO2 uptake in the polar desert eco system most distance from the ice sheet (1.2 g CO2 m(-2) d(-1)) and in the polar semidesert ecosystem (0.3 g CO2 m(-2) d(-1)), but net CO2 loss in the polar oasis site and the three polar desert sites in the toposequence. Eco system respiration tended to be greatest in the ecosystems that have appare ntly been ice-free the longest, with efflux rates up to 3.7 g CO2 m(-2) d(- 1). In the toposequence, soil organic matter was greatest adjacent to the i cecap (3.10%) and decreased to 0.93% is the polar desert site 400 m from th e ice. The polar semidesert and polar eases sites had 2.67 and 3.83% soil o rganic matter, respectively. Soil microbial biomass carbon ranged from abou t 1 mg C g(-1) soil in the polar oasis ecosystem to about 0.2 mg C g(-1) so il in one of the polar desert ecosystems but did not follow the patterns we found for soil organic matter Our findings substantiate other recent studi es showing significant CO2 flux between high arctic ecosystems and the atmo sphere, and suggest that carbon exchange in these systems merit considerati on in circumarctic estimates of carbon flux.