Seasonal methane emission from a boreal peatland in continuous permafrost zone of Northeast China: effects of active layer depth and vegetation.

Boreal peatlands are significant natural sources of methane and especially vulnerable to abrupt climate change. However, the controlling factors of CH₄ emission in boreal peatlands are still unclear. In this study, we investigated CH₄ fluxes and abiotic factors (temperature, water table depth, active layer depth, and dissolved CH₄ concentrations in pore water) during the growing seasons in 2010 and 2011 both in shrub-sphagnum-and sedge-dominated plant communities in continuous permafrost zone of Northeast China. The objective of our study was to examine the effects of vegetation types and abiotic factors on CH₄ fluxes from a boreal peatland. In Eriophorum-dominated community, mean CH₄emissions were 1.015 and 0.801 mg m^-2 h^-1 in 2010 and 2011, respectively. CH₄ fluxes (0.384 mg m^-2h^-1) released from the shrub-mosses-dominated community were lower than that from Eriophorum-dominated community. Moreover, in Eriophoru m-dominated community, CH₄ fluxes showed a significant temporal pattern with a peak value in late August both in 2010 and 2011. However, no distinct seasonal s variation was observed in the CH₄ flux in the shrub-mosses-dominated community. Interestingly, both in Eriophorum- and shrub-sphagnum-dominated communities, CH₄ fluxes did not show close correlation with air or soil temperature and water table depth, whereas CH₄ emissions correlated well to active layer depth and CH₄ concentration in soil pore water, especially in Eriophorum-dominated community. Our results suggest that CH₄ released from the thawed CH₄-rich permafrost layer may be a key factor controlling CH₄ emissions in boreal peatlands, and highlight that CH₄ fluxes vary with vegetation type in boreal peatlands. [ABSTRACT FROM AUTHOR]