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Spatial variation in landscape‐level CO 2 and CH 4 fluxes from arctic coastal tundra: influence from vegetation, wetness, and the thaw lake cycle
Author(s) -
Sturtevant Cove S.,
Oechel Walter C.
Publication year - 2013
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1111/gcb.12247
Subject(s) - tundra , chronosequence , environmental science , arctic , ecosystem , sink (geography) , arctic vegetation , spatial variability , carbon cycle , physical geography , growing season , flux (metallurgy) , biogeochemical cycle , carbon sink , atmospheric sciences , ecology , oceanography , geography , geology , soil water , soil science , chemistry , statistics , organic chemistry , biology , mathematics , cartography
Abstract 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.