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

摘要

Boreal peatlands are significant natural sources of methane and especiallyvulnerable to abrupt climate change. However, the controlling factors ofCH₄ emission in boreal peatlands are still unclear. In this study, weinvestigated CH₄ fluxes and abiotic factors (temperature, water tabledepth, active layer depth, and dissolved CH₄ concentrations in porewater) during the growing seasons in 2010 and 2011 in both shrub-sphagnum-and sedge-dominated plant communities in the continuous permafrost zone ofNortheast China. The objective of our study was to examine the effects ofvegetation types and abiotic factors on CH₄ fluxes from a borealpeatland. In an Eriophorum-dominated community, mean CH₄ emissions were 1.02 and0.80 mg m?2 h?1 in 2010 and 2011, respectively. CH₄ fluxes(0.38 mg m?2 h?1) released from the shrub-mosses-dominatedcommunity were lower than that from Eriophorum-dominated community. Moreover,in theEriophorum-dominated community, CH₄ fluxes showed a significant temporal patternwith a peak value in late August in both 2010 and 2011. However, no distinctseasonal variation was observed in the CH₄ flux in theshrub-mosses-dominated community. Interestingly, in both Eriophorum- andshrub-sphagnum-dominated communities, CH₄ fluxes did not show closecorrelation with air or soil temperature and water table depth, whereasCH₄ emissions correlated well to active layer depth and CH₄concentration in soil pore water, especially in the Eriophorum-dominated community. Ourresults suggest that CH₄ released from the thawed CH₄-richpermafrost layer may be a key factor controlling CH₄ emissions inboreal peatlands, and highlight that CH₄ fluxes vary with vegetationtype in boreal peatlands. With increasing temperature in future climatepatterns, increasing active layer depth and shifting plant functional groupsin this region may have a significant effect on CH₄ emission.