Impacts of Vegetation on CO2 exchange, permafrost thaw depth, and NDVI in Alaskan tundra.

Changes in terrestrial carbon cycling in response to a warming climate in the Arctic will, in large part, be driven by current and future composition of the plant community. To better understand the variation in plant community structure and impacts on carbon cycling, we examined relationships between vegetation composition, NDVI, CO2 exchange, and permafrost thaw depth in the Yukon Kuskokwim Delta (YKD) in southwest Alaska. Our study sites included lichen-dominated peat plateaus, tussock tundra, fens, and drained lakes. We found a significant and positive relationship between NDVI and net ecosystem exchange across sites. Dominant functional groups across sites included lichen, moss, and graminoid vegetation, but variability in vegetation cover was high both within and across sites. Tussock-dominated tundra, peat plateaus, and drained lakes shared many of the same species, while the fen site had several unique species. Areas with higher lichen cover were associated with low NDVI, low gross primary productivity (GPP), and low net ecosystem exchange (NEE) in comparison with areas with little or no lichen cover. Because lichen comprises a large portion of this region's biomass, it is an important variable to consider in the context of CO2 exchange in the arctic tundra.