| Summary: | This renewal represents a continuation request for the third year of our current research program. While this renewal follows the original research proposed, it is modified to reflect information gained in the first two years of the project. Important findings of the last 12 months include the fact that carbon is being lost as CO{sub 2} from most sites measured along a latitudinal transect from Toolik Lake to Prudhoe Bay, Alaska. All locations measured but one showed a net loss of carbon as CO{sub 2} to the atmosphere. The drier sites tended to show greater rates of carbon loss. The only site showing net carbon accumulation was the wettest tussock tundra site measured. The average rate of loss for all sites was about 180 g C m{sup {minus}2} y{sup {minus}2}, or about 0.2 GtC y{sup {minus}1} for the circumpolar wet sedge tundra and tussock tundra combined. This observation fits well with the conclusion of Tans et al. (1990) that there is currently a high latitude terrestrial source of CO{sub 2} to the atmosphere. These high rates of carbon loss, combined with the very large store of carbon in northern ecosystems (about 500 GtC) suggested that the current rates of carbon loss from arctic tundra to the atmosphere should be further examined. This includes analysis of the temporal and spatial pattern of carbon flux, the pattern of carbon flux for different vegetation types and micro-habitats, and the moisture and temperature controls on ecosystem carbon loss to the atmosphere.
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