Spatial variation in landscape-level CO 2 and CH 4 fluxes from arctic coastal tundra: influence from vegetation, wetness, and the thaw lake cycle

• Published in: Global Change Biology
• Main Authors: Sturtevant, Cove S., Oechel, Walter C.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: 2013
• Subjects: Arctic; Barrow; Tundra; Alaska
• Online Access: https://oro.open.ac.uk/38751/; https://doi.org/10.1111/gcb.12247

Regional quantification of arctic CO 2 and CH 4 fluxes remains difficult due to high landscape heterogeneity coupled with a sparse measurement network. Most of the arctic coastal tundra near Barrow, Alaska is part of the thaw lake cycle, which includes current thaw lakes and a 5500-year chronosequence of vegetated thaw lake basins. However, spatial variability in carbon fluxes from these features remains grossly understudied. Here, we present an analysis of whole-ecosystem CO 2 and CH 4 fluxes from 20 thaw lake cycle features during the 2011 growing season. We found that the thaw lake cycle was largely responsible for spatial variation in CO 2 flux, mostly due to its control on gross primary productivity (GPP). Current lakes were significant CO 2 sources that varied little. Vegetated basins showed declining GPP and CO 2 sink with age (R 2 = 67% and 57%, respectively). CH 4 fluxes measured from a subset of 12 vegetated basins showed no relationship with age or CO 2 flux components. Instead, higher CH 4 fluxes were related to greater landscape wetness (R 2 = 57%) and thaw depth (additional R 2 = 28%). Spatial variation in CO 2 and CH 4 fluxes had good satellite remote sensing indicators, and we estimated the region to be a small CO 2 sink of -4.9 ± 2.4 (SE) g C m -2 between 11 June and 25 August, which was countered by a CH 4 source of 2.1 ± 0.2 (SE) g C m -2 . Results from our scaling exercise showed that developing or validating regional estimates based on single tower sites can result in significant bias, on average by a factor 4 for CO 2 flux and 30% for CH 4 flux. Although our results are specific to the Arctic Coastal Plain of Alaska, the degree of landscape-scale variability, large-scale controls on carbon exchange, and implications for regional estimation seen here likely have wide relevance to other arctic landscapes.