High-latitude warming has stimulated CO2 and CH4 emissions from permafrost peatland. This study evaluated growing season CH4 and CO2 emissions from a forest floor of a lowland black spruce forest on permafrost in interior Alaska using automated-closed chambers, anaerobic incubation of peat soils and next-generation sequencing. The CH4 emissions from May to October were 723 ± 432 mg C m−2 and 829 ± 628 mg C m−2 from the two Carex wet plots, 124 ± 76 mg C m−2 from the Sphagnum moss plot, and 11 mg C m−2 from the lichen plot (± denotes standard deviation of different years). The CH4 emissions in the peak season showed diurnal variations with a single peak around noon or double peaks depending on the plots. The CH4 emissions were an order of magnitude lower than those for other northern wetlands, possibly because deep, cold peats regulated CH4 production and oxidation at the dry aerobic surface layer. Low water table positions strongly inhibited CH4 emissions in 2018, suggesting the importance of dissolved CH4 pool at the bottom of the active layer. The future trajectory of CH4 emissions could substantially change with water conditions, deep soil temperatures, and sedge compositions.
