干旱区生态环境知识资源中心

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. Three of the four polar desert sires were in a contiguous toposequence originating 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 the ice margin. We measured net ecosystem CO2 uptake in the polar desert ecosystem 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. Ecosystem respiration tended to be greatest in the ecosystems that have apparently 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 icecap (3.10%) and decreased to 0.93% is the polar desert site 400 m from the ice. The polar semidesert and polar eases sites had 2.67 and 3.83% soil organic matter, respectively. Soil microbial biomass carbon ranged from about 1 mg C g(-1) soil in the polar oasis ecosystem to about 0.2 mg C g(-1) soil in one of the polar desert ecosystems but did not follow the patterns we found for soil organic matter Our findings substantiate other recent studies showing significant CO2 flux between high arctic ecosystems and the atmosphere, and suggest that carbon exchange in these systems merit consideration in circumarctic estimates of carbon flux.