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

Abstract

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 in both shrub-sphagnum- and sedge-dominated plant communities in the 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 an <i>Eriophorum</i>-dominated community, mean CH₄ emissions were 1.02 and 0.80 mg m⁻² h⁻¹ in 2010 and 2011, respectively. CH₄ fluxes (0.38 mg m⁻² h⁻¹) released from the shrub-mosses-dominated community were lower than that from <i>Eriophorum</i>-dominated community. Moreover, in the <i>Eriophorum</i>-dominated community, CH₄ fluxes showed a significant temporal pattern with a peak value in late August in both 2010 and 2011. However, no distinct seasonal variation was observed in the CH₄ flux in the shrub-mosses-dominated community. Interestingly, in both <i>Eriophorum</i>- 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 the <i>Eriophorum</i>-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. With increasing temperature in future climate patterns, increasing active layer depth and shifting plant functional groups in this region may have a significant effect on CH₄ emission.