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Annual cycle of methane emissions from a subarctic peatland
Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
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2010 (English)In: Journal of Geophysical Research, ISSN 0148-0227, Vol. 115, G02009- p.Article in journal (Refereed) Published
Abstract [en]

Although much attention in recent years has been devoted to methane (CH4) emissions from northern wetlands, measurement based data sets providing full annual budgets are still limited in number. This study was designed to help fill the gap of year-round measurements of CH4 emissions from subarctic mires. We report continuous eddy correlation CH4 flux measurements made during 2006 and 2007 over the Stordalen mire in subarctic Sweden (68 degrees 20'N, 19 degrees 03'E, altitude 351 m) using a cryocooled tunable diode laser. The landscape-scale CH4 fluxes originated mainly from the permafrost free wet parts of the mire dominated by tall graminoid vegetation. The midseason average CH4 emission mean was 6.2 +/- 2.6 mg m(-2) h(-1). A detailed footprint analysis indicates an additional strong influence on the flux by the nearby shallow Lake Villasjon (0.17 km(2), maximum depth 1.3 m). A stable bimodal distribution of wind flow from either the east or the west allowed separating the lake and mire vegetation signals. The midseason lake emission rates were as high as 12.3 +/- 3.3 mg m(-2) h(-1). Documented CH4 fluxes are similar to results obtained by automatic chamber technique and higher than manual chamber measurements made in the wet minerotrophic section dominated by Eriophorum angustifolium. The high fluxes observed from this vegetation type are significant because the areal distribution of this source in the mire is expanding due to ongoing thawing of the permafrost. A simple peat temperature relationship with CH4 emissions was used to fill data gaps to construct a complete annual budget of CH4 fluxes over the studied area. The calculated annual CH4 emissions in 2006 and 2007 equaled 24.5 and 29.5 g CH4 m(-2) yr(-1), respectively. The summer season CH4 emissions dominated (65%) the annual flux, with the shoulder seasons of spring and autumn significant (25%) and a minor flux from the winter (10%).

Place, publisher, year, edition, pages
2010. Vol. 115, G02009- p.
National Category
Natural Sciences
URN: urn:nbn:se:su:diva-25515DOI: 10.1029/2008JG000913ISI: 000277259700001OAI: diva2:199880
authorCount :7Available from: 2008-10-09 Created: 2008-10-01 Last updated: 2011-02-11Bibliographically approved
In thesis
1. Carbon gas biogeochemistry of a northern peatland - in a dynamic permafrost landscape
Open this publication in new window or tab >>Carbon gas biogeochemistry of a northern peatland - in a dynamic permafrost landscape
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is about biogeochemical processes of a northern peatland and their importance as a link between the climate and the terrestrial system. Increased temperatures on a global level, and particularly in the Arctic, have led to melting permafrost and changes in hydrology. In turn, this affect the natural exchange of radiatively important trace gases between land and atmosphere that may reinforce climate change. The aim of this thesis is to increase the understanding about the exchange of carbon dioxide (CO2), methane (CH4) and non-methane volatile organic compounds (NMVOCs) occurring in northern peatlands, to decrease uncertainty about their future carbon (C) balance. In order to pursue this aim, we designed a study that allowed measuring the C exchange at a subarctic peatland, accounting for spatial and temporal analysis at several levels.

The field site was the Stordalen mire, northern Sweden. Exchange rates of CO2, and total hydrocarbons (THCs; CH4 and NMVOCs) were measured using an automatic chamber system for up to six years, at three different types of vegetation communities and permafrost regimes. The gas exchange was found to relate to different environmental and biological variables at different vegetation communities and at different temporal scales. Differences in flux rates and controls between sites could be explained with biological and environmental variables in a better way than the seasonal and interannual variability within a site.

Snow season flux measurements were determined to be of high importance regarding the annual C budget. By excluding the snow season, the potential C source strength of a peatland is likely to be underestimated. The importance of combining the THCs with the CO2 to estimate the annual C balance was demonstrated as THC could be sufficient to shift the mire from a sink to a source of C to the atmosphere. Again, the C source strength may be significantly underestimated if only focusing on CO2 fluxes in wet peatland environments.

Place, publisher, year, edition, pages
Stockholm: Institutionen för geologi och geokemi, 2008. 31 p.
Meddelanden från Stockholms universitets institution för geologi och geokemi, ISSN 1101-1599 ; 333
Carbon balance, Carbon exchange, Peatland, Subarctic, Climate change
National Category
Earth and Related Environmental Sciences
Research subject
urn:nbn:se:su:diva-8241 (URN)978-91-7155-743-8 (ISBN)
Public defence
2008-10-31, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 8 A, Stockholm, 10:00
Available from: 2008-10-09 Created: 2008-10-01Bibliographically approved

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Bäckstrand, KristinaCrill, Patrick, M.
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