, Volume 41, Issue 3, pp 215-235

Response of tundra CH4 and CO2 flux tomanipulation of temperature and vegetation

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Abstract

We conducted plant species removals, air temperaturemanipulations, and vegetation and soil transplants inAlaskan wet-meadow and tussock tundra communities todetermine the relative importance of vegetation typeand environmental variables in controlling ecosystemmethane (CH4) and carbon dioxide (CO2) flux. Plastic greenhouses placed over wet-meadow tundraincreased air temperature, soil temperature, and soilmoisture, but did not affect CH4 or CO2 flux(measured in the dark). By contrast, removal ofsedges in the wet meadow significantly decreased fluxof CH4, while moss removal tended to increaseCH4 emissions. At 15 cm depth, pore-waterCH4 concentrations were higher in sedge-removalthan in control plots, suggesting that sedgescontribute to CH4 emissions by transportingCH4 from anaerobic soil to the atmosphere, ratherthan by promoting methanogenesis. Inreciprocal-ecosystem transplants between thewet-meadow and tussock tundra communities, CH4and CO2 emissions were higher overall in thewet-meadow site, but were unrelated to transplantorigin. Methane flux was correlated with localvariation in soil temperature, thaw depth, andwater-table depth, but the relative importance ofthese factors varied through the season. Our resultssuggest that future changes in CH4 and CO2flux in response to climatic change will be morestrongly mediated by large-scale changes in vegetationand soil parameters than by direct temperature effects.