Correlations between substrate availability, dissolved CH 4 , and CH 4 emissions in an arctic wetland subject to warming and plant removal

• Published in: Journal of Geophysical Research: Biogeosciences
• Main Authors: Nielsen, Cecilie Skov, Michelsen, Anders, Strobel, Bjarne W., Wulff, Katrine, Banyasz, Imre, Elberling, Bo
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2017
• Subjects: Arctic; Carex; greenhouse gas; methane; warming; wetland; Greenland; Carex aquatilis
• Online Access: https://curis.ku.dk/portal/da/publications/correlations-between-substrate-availability-dissolved-ch4-and-ch4-emissions-in-an-arctic-wetland-subject-to-warming-and-plant-removal(e2c67524-7167-462a-a3b3-7c261a6efe0d).html; https://doi.org/10.1002/2016JG003511

The Arctic is warming which may potentially affect substrate availability, organic matter decomposition, plant growth, and plant species composition. This may lead to changes in the exchange of methane (CH 4 ) and carbon dioxide (CO 2 ) between the soil system and the atmosphere. Yet the correlations among substrate availability, CH 4 production, and net emissions of CH 4 have been scarcely studied in arctic wetlands. Presently, the impact of increasing temperatures on CH 4 exchange is uncertain as the two existing reports on field warming in arctic wetlands present opposite results. We here report results on how summer warming and shrub removal affect soil water substrate (acetate, formate, oxalate, and dissolved organic carbon) concentrations as well as dissolved CH 4 and CH 4 emissions in a fen at Disko Island (West Greenland). The peak in dissolved CH 4 followed the peak in acetate concentration, and appeared after the peak in CH 4 emissions, which indicates a lack of correlation between CH 4 production and emissions. The peak in CH 4 emissions coincided with maximum gross ecosystem production suggesting that CH 4 emissions are closely linked to photosynthesis. This was supported by an experiment with removal of the sedge Carex aquatilis ssp. stans which contributed with up to 77% of the CH 4 emitted from the ecosystem. By contrast, shrub removal and summer warming did not significantly affect CH 4 emissions, possibly due to the treatments impacting CH 4 production more than emissions. This implies that such wetlands may be less sensitive to moderate warming and changes in shrub cover than previously assumed.