The Role of Sphagnum Mosses in Methane Oxidation in a Temperate Fen
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Peatlands are a global source of atmospheric methane (CH4); however oxidation of CH4 by methanotrophic microbes residing in the moss layer provides the potential for mitigation of CH4 emissions (Bubier and Moore, 1994). Determining the controls on CH4 oxidation in Sphagnum mosses will increase our understanding of CH4 dynamics in wetlands, and will allow a better understanding of the influence of climate change on these ecosystems. Studies have shown that the primary controls of oxidation are environmental, i.e. water table and temperature; however little is known about the role of moss species in controlling CH4 oxidation (Basiliko et al., 2004; Larmola et al., 2010). A Sphagnum transplantation experiment was conducted at Sallie’s Fen, a temperate peatland in Barrington, New Hampshire, to observe the effect of environmental conditions on CH4 oxidation rates in Sphagnum fallax and Sphagnum magellanicum and to investigate the relative importance of species versus environment in controlling CH4 oxidation. The mosses were sampled four times over a 28 day period. Triplicate control and transplanted samples were incubated in the lab at two concentrations of CH4, 1000 parts per million (ppm; limiting to low affinity methanotrophs) and 10,000 ppm (non-limiting). Averages of the potential CH4 oxidation of all four sampling days show that when CH4 is limiting there is an interaction between Sphagnum species and the environment. The effect of environment on the microbes of S. magellanicum was evident when host rates of potential CH4 oxidation (0.4 μmol g dw-1 d-1 s.e. 0.10) in the hummock increased significantly (p < 0.05) upon transplantation to the hollow (1.8 μmol g dw-1 d-1 s.e. 0.38). The Sphagnum species effect is supported by the response of S. fallax, which, after transplantation, exhibited potential CH4 oxidation rates that were not significantly different (p > 0.05) from the host rates (1.5 μmol g dw-1 d-1 s.e. 0.20) in the hollow. There was no difference between the sites or species when CH4 was not limiting (p > 0.05). These results indicate that there is a joint control of the environment and Sphagnum species on CH4 oxidation; however the particularly dry summer may have confounded the results.