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Trace gas exchange in a high‐Arctic valley: 1. Variationsin CO 2 and CH 4 Flux between tundra vegetation types

Ecosystem exchanges of CO 2 and CH 4 were studied by chamber techniques in five different vegetation types in a high arctic valley at Zackenberg, NE Greenland. The vegetation types were categorized as Cassiope heath, hummocky fen, continuous fen, grassland and Salix arctica snowbed. Integrated dayti...

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Published in:Global biogeochemical cycles 2000-09, Vol.14 (3), p.701-713
Main Authors: Christensen, T. R., Friborg, T., Sommerkorn, M., Kaplan, J., Illeris, L., Soegaard, H., Nordstroem, C., Jonasson, S.
Format: Article
Language:English
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Summary:Ecosystem exchanges of CO 2 and CH 4 were studied by chamber techniques in five different vegetation types in a high arctic valley at Zackenberg, NE Greenland. The vegetation types were categorized as Cassiope heath, hummocky fen, continuous fen, grassland and Salix arctica snowbed. Integrated daytime fluxes for the different vegetation types of the valley showed that the fen areas and the grassland, were significant sources of CH 4 with a mean efflux of 6.3 mg CH 4 m −2 hr −1 and sinks for CO 2 , with almost ‐170 mg CO 2 m −2 hr −1 . The heath and snowbed areas had much lower carbon sequestration rates of about −25 mg CO 2 m −2 hr −1 and were also sinks for CH 4 . Methane emissions from the valley dominated in the hummocky fens. Computation of area integrated mean daytime flux values across all vegetation types of the entire valley bottom revealed that it was a sink of CO 2 in the order of −96 ± 33 mg CO 2 m −2 hr −1 and a source of 1.9 ± 0.7 mg CH 4 m −2 hr −1 . These values were in accordance with eddy correlation measurements reported elsewhere in this issue and reflect a high‐carbon exchange despite the high arctic location. In the fens, where the water table was at or above the soil surface, methane emissions increased with net ecosystem CO 2 flux. In places with the water table below the soil surface, such as particularly in the hummocky parts of the fen, oxidation tended to become the dominant controlling factor on methane efflux.
ISSN:0886-6236
1944-9224
DOI:10.1029/1999GB001134