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Functional type contributions to production, biomass and carbon flux along a structural gradient from tundra to forest at treeline in Council, Alaska .
Copass, Catharine1, Beringer, Jason1,2, Chapin, F. Stuart1, McGuire, A. David1, Walker, Donald1, 1 2
ABSTRACT- Climate change has the potential to influence vegetation dynamics in high latitude ecosystems, which may in turn feedback to the climate system through alterations in water, energy, and carbon dynamics. Our research focuses on improving our understanding of the role of species, or groupings of species (plant functional types) in the carbon exchange of ecosystems located near Council on the Seward Peninsula, Alaska. The Council sites represent a structural transition from lichen dominated moist acidic tundra through low shrub, shrub and woodland tundras to forest, analogous to transitions that might be expected in arctic ecosystems in response to warming. During the summers of 1999 and 2000 we evaluated CO2 fluxes using eddy covariance techniques, in combination with sampling of biogeochemical and biophysical parameters, including production, biomass and leaf area by functional type. Along the gradient, biomass increased by a factor of 10, from 748gm-2 (tundra) to 8037 gm-2 (forest). Leaf area index increased fourfold, from 0.5 in the tundra to 2.2 in the forest. CO2 uptake followed similar trends with biomass and leaf area. All sites showed net uptake of CO2, with greatest uptake in the woodland and shrub sites (5 and 6 gCm-2d-1), followed by the forest and low shrub tundra (3 and 2 gCm-2d-1). These results are being used to develop a dynamic vegetation model which will be used to evaluate carbon fluxes in high latitude regions.
KEY WORDS: arctic, carbon, biomass, production