Depth distribution of microbial production and oxidation of methane in northern boreal peatlands

Abstract

The depth distributions of anaerobic microbial methane production and potential aerobic microbial methane oxidation were assessed at several sites in both Sphagnum- and sedge-dominated boreal peatlands in Sweden, and compared with net methane emissions from the same sites. Production and oxidation of methane were measured in peat slurries, and emissions were measured with the closed-chamber technique. Over all eleven sites sampled, production was, on average, highest 12 cm below the depth of the average water table. On the other hand, highest potential oxidation of methane coincided with the depth of the average water table. The integrated production rate in the 0-60 cm interval ranged between 0.05 and 1.7 g CH4 m (-2) day(-) and was negatively correlated with the depth of the average water table (linear regression: r (2) = 0.50, P = 0.015). The depth-integrated potential CH4-oxidation rate ranged between 3.0 and 22.1 g CH4 m(-2) day(-1) and was unrelated to the depth of the average water table. A larger fraction of the methane was oxidized at sites with low average water tables; hence, our results show that low net emission rates in these environments are caused not only by lower methane production rates, but also by conditions more favorable for the development of CH4-oxidizing bacteria in these environments.

Temperature Sensitivity of Methane Production in the Permafrost Active Layer at Stordalen, Sweden: A Comparison with Non-permafrost Northern Wetlands

“…High CH 4 production potentials in surface soil have been reported elsewhere 476 / ARCTIC, ANTARCTIC, AND ALPINE RESEARCH (Segers, 1998;Valentine et al, 1994;Sundh et al, 1994;Yavitt et al, 1987) and reflect the accumulation of above-ground litter inputs, in addition to inputs of fresh organic matter from root turnover and exudation in these layers (Joabsson and Christensen, 2001). The low CH 4 concentrations and production rates in the ombrotrophic bog reflect the unsuitable conditions of this environment for methanogenesis.…”

NifH and NifD phylogenies: an evolutionary basis for understanding nitrogen fixation capabilities of methanotrophic bacteria

“…Thus, it is not surprising that no type I or type II MB strain has ever been isolated using nitrogen-free enrichment conditions, and that growth on nitrogen-free media has never been demonstrated for these organisms. The sensitivity to O 2 of diazotrophic growth of MB might also explain why the maximum population density and activity of these bacteria in nitrogen-depleted environments always corresponds to sites with relatively low pO 2 values, such as the chemocline zone in water reservoirs and the layer below the water table in wetlands (Rudd et al, 1976;Sundh et al, 1994;Krumholz et al, 1995). This pattern of MB distribution is usually explained by the availability of both methane and oxygen.…”

Non-linear response of carbon dioxide and methane emissions to oxygen availability in a drained histosol

“…Increased soil organic C oxidation and associated carbon dioxide (CO 2 2014). Drainage also dramatically decreases Histosol emissions of methane (CH 4 ), a greenhouse 67 gas 34 times more potent than CO 2 over a 100-year timescale (Myhre et al 2013), by facilitating 68 aerobic microbial methanotrophy in drained soil layers (Sundh et al 1994 We used peat soil from 80-100 cm depth that straddles the water table and therefore has only 113 undergone slight oxidation and is classified as a sapric Histosol (mucky peat). Soils at this depth 114 were wet, but not saturated at the time of collection (Table 1); moisture increases seasonally to 115 density by depth are reported in Table 1 (unpublished data) with a Gore-Tex seal at one end that permitted soil-chamber gas exchange (Liptzin et al 2010).…”