AbstractThe 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 (CH4) and carbon dioxide (CO2) between the soil system and the atmosphere. Yet the correlations among substrate availability, CH4 production, and net emissions of CH4 have been scarcely studied in arctic wetlands. Presently, the impact of increasing temperatures on CH4 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 CH4 and CH4 emissions in a fen at Disko Island (West Greenland). The peak in dissolved CH4 followed the peak in acetate concentration, and appeared after the peak in CH4 emissions, which indicates a lack of correlation between CH4 production and emissions. The peak in CH4 emissions coincided with maximum gross ecosystem production suggesting that CH4 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 CH4 emitted from the ecosystem. By contrast, shrub removal and summer warming did not significantly affect CH4 emissions, possibly due to the treatments impacting CH4 production more than emissions. This implies that such wetlands may be less sensitive to moderate warming and changes in shrub cover than previously assumed.