Characterization of the carbon fluxes of a vegetated drained lake basin chronosequence on the Alaskan Arctic Coastal Plain

摘要

Greenhouse gas fluxes from vegetated drained lake basins have been largely unstudied, although these land features constitute up to 47% of the land cover in the Arctic Coastal Plain in northern Alaska. To describe current and to better predict future sink/source activity of the Arctic tundra, it is important to assess these vegetated drained lake basins with respect to the patterns of and controls on gross primary production (GPP), net ecosystem exchange, and ecosystem respiration (ER). We measured CO2 fluxes and key environmental variables during the 2007 growing season (June through August) in 12 vegetated drained lake basins representing three age classes (young, drained about 50 years ago; medium, drained between 50 and 300 years ago; and old, drained between 300 and 2000 years ago, as determined by Hinkel et al., 2003) in the Arctic Coastal Plain. Young vegetated drained lake basins had both the highest average GPP over the summer (11.4 gCO(2) m-2 day-1) and the highest average summer ER (7.3 gCO(2) m-2 day-1), while medium and old vegetated drained lake basins showed lower and similar GPP (7.9 and 7.2 gCO(2) m-2 day-1, respectively), and ER (5.2 and 4 gCO(2) m-2 day-1, respectively). Productivity decreases with age as nutrients are locked up in living plant material and dead organic matter. However, we showed that old vegetated drained lakes basins maintained relatively high productivity because of the increased development of ice-wedge polygons, the formation of ponds, and the re-establishment of very productive species. Comparison of the seasonal CO2 fluxes and concomitant environmental factors over this chronosequence provides the basis for better understanding the patterns and controls on CO2 flux across the coastal plain of the North Slope of Alaska and for more accurately estimating current and future contribution of the Arctic to the global carbon budget.