Growing season methane emission from a boreal peatland in the 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 CH 4 emission in boreal peatlands are still unclear. In this study, we investigated CH 4 fluxes and abiotic factors (temperature, water table depth, active layer depth, and dissolved CH 4 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 CH 4 fluxes from a boreal peatland. In an Eriophorum-dominated community, mean CH 4 emissions were 1.02 and 0.80 mg m −2 h −1 in 2010 and 2011, respectively. CH 4 fluxes (0.38 mg m −2 h −1) released from the shrub-mosses-dominated community were lower than that from Eriophorum-dominated community. Moreover, in the Eriophorum-dominated community, CH 4 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 CH 4 flux in the shrub-mosses-dominated community. Interestingly, in both Eriophorum- and shrub-sphagnum-dominated communities, CH 4 fluxes did not show close correlation with air or soil temperature and water table depth, whereas CH 4 emissions correlated well to active layer depth and CH 4 concentration in soil pore water, especially in the Eriophorum-dominated community. Our results suggest that CH 4 released from the thawed CH 4-rich permafrost layer may be a key factor controlling CH 4 emissions in boreal peatlands, and highlight that CH 4 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 CH 4 emission.