Summer soil CH₄ emission and uptake in taiga forest near Yakutsk, Eastern Siberia

摘要

Summer CH₄ emission and uptake was measured in three contrasting environments (eutrophic lake bank, hummocky mesotrophic fen, forest floor) in taiga forest near the Spasskaya Pad field station (north of Yakutsk, Eastern Siberia). Wet eutrophic lake bank sites showed locally high emission rates (up to 49 mg CH₄ m-2 h-1, average 11.9 mg m-2 h-1). By contrast, fen emissions were an order of magnitude lower despite high water tables. Emission did not exceed 4.2 mg m-2 h-1 (average 1.3 mg m-2 h-1). The emission was highly dependent on water table, slight differences in water table could turn a soil from a source into a sink of CH₄. The dry forest sites show uptake of CH₄ (average 0.4 mg m-2 h-1), even at sites where the water table was situated a few centimeters below the soil surface. A clear relation with water temperature or soil temperature appears to be absent. Also in the wet year of 2006, with higher water table in the forest during the measurement period, CH₄ uptake remained stable. Spatial variation of the uptake fluxes within the site is minimal, but on a larger scale spatial differences are caused by soil texture differences. Our data indicate that the Siberian taiga forest floor is a small sink for CH₄ in the boreal summer.