Methane emissions from natural peatlands in the northern boreal zone in Finland, Fennoscandia

Methane (CH4) emissions were measured over two snow-free seasons from ten natural minerotrophic peatlands in the northern boreal zone of Finland using a static chamber technique. The daily CH4 fluxes at the sites ranged from −2.9 to 790 mg m−2 d−1. At nine wet fens, representing three ecological peatland classes, the seasonal mean CH4 emissions were 8.1–250 mg m−2 d−1 during a dry summer, and 15–330 mg m−2 d−1 during a wet summer. At these sites, the mean CH4 emission correlated positively with the mean water table level (r2=0.64). The driest site (herb-grass spruce mire) showed the lowest CH4 emissions, with the seasonal averages being below 1 mg m−2 d−1. The CH4 emissions from these natural northern boreal peatlands in the main aapa-mire zone were similar or higher than those reported from other boreal peatlands in Finland and elsewhere, probably attributable to the high fertility and moisture of the northern boreal sites, characteristics typical of peatlands in the aapa-mire zone. Thus, the aapa mires in the boreal zone in Fennoscandia, Canada and Russia should be a larger natural source for atmospheric CH4 than estimated in the global inventories for wetland CH4 emissions.