HR: 1340h
AN: B53A-0922    [Abstracts]
TI: Net Productivity and Reduced Carbon Flux at Different Timescales at a Subarctic Mire
AU: * Bäckstrand, K
EM: kristina.backstrand@geo.su.se
AF: Department of Geology and geochemistry, Stockholm University, Svante Arrheniusväg 8C, Stockholm, 10691, Sweden
AU: Crill, P M
EM: patrick.crill@geo.su.se
AF: Department of Geology and geochemistry, Stockholm University, Svante Arrheniusväg 8C, Stockholm, 10691, Sweden
AU: Christensen, T R
EM: torben.christensen@nateko.lu.se
AF: GeoBiosphere Science Centre, Physical Geography and Ecosystem Analysis, Lund University, Sölvegatan 12, Lund, 22362, Sweden
AU: Mastepanov, M
EM: mikhail.mastepanov@nateko.lu.se
AF: GeoBiosphere Science Centre, Physical Geography and Ecosystem Analysis, Lund University, Sölvegatan 12, Lund, 22362, Sweden
AU: Bastviken, D
EM: david.bastviken@geo.su.se
AF: Department of Geology and geochemistry, Stockholm University, Svante Arrheniusväg 8C, Stockholm, 10691, Sweden
AB: While several environmental changes that appear linked to increased temperature and permafrost degradation have been noted in the panarctic, the concern is to what extent positive feedback mechanisms that may accelerate climate change are associated with these environmental and physical changes. Labile organic carbon, currently protected in frozen soils, may mobilize if soils are warmed and thawed and then transferred to the atmosphere as greenhouse gases. Detailed information about carbon cycling in perennially frozen carbon rich soils needs to be incorporated into coupled climate models. In this study, we account for the productivity and reduced carbon flux at the subarctic Stordalen Mire in northern Sweden. Methane (CH₄) and total hydrocarbon (THC; CH₄ and nonmethane hydrocarbons) fluxes were measured at three vegetation communities with different moisture and permafrost regimes; i) a dry palsa site underlain with permafrost, ii) a Sphagnum site with highly variable water table and iii) a wet Eriophorum site. The two latter sites are CH₄ emitting environments. A long-term data record of five sequential growing seasons (2003-2007) acquired with an automatic chamber system allows for analyses at least three levels of temporal variability (diurnal, seasonal and annual). There was a clear relation between seasonal accumulated THC emissions and productivity (measured as NEE of CO₂), when all vegetation communities were compared in the same analysis. At the Sphagnum site, ~2 gC m^-2 was emitted as THC at the same time as ~40 gC m^-2 was taken up as CO₂, (days 173- 235, year 2003-2006). In comparison, a highly productive Eriophorum sp. community emitted ~9 gC m^-2 (THC) while productivity was estimated to ~90 gC m^-2 (CO₂). Productivity differences between sites can be a measure of the THC emission potential, but the seasonal accumulated THC emissions within a site appeared to be largely independent of seasonal productivity at the same site. Short-term (hourly) NEE was related to hydrocarbon emission at the two CH₄ emitting sites. A greater part of the carbon emitted as THC is likely to recently have been sequestered by the plants through photosynthesis and plant mediated CH₄ transport during high CO₂ metabolism will strengthen the short-term correlation between THC and CO₂.
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0428 Carbon cycling (4806)
DE: 0490 Trace gases
DE: 1615 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 4805, 4912)
DE: 1631 Land/atmosphere interactions (1218, 1843, 3322)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting