Control of Methane Metabolism in a Forested Northern Wetland, New York State, by Aeration, Substrates, and Peat Size Fractions.

Although many northern peat-forming wetlands (peatlands) are a suitable habitat for anaerobic CH[sub 4]-producing bacteria (methanogens), net CH[sub 4] fluxes are typically low in forested systems. We examined whether soil factors (aeration, substrate availability, peat size fractions) constrained net CH[sub 4] production in peat from a Sphagnum-moss dominated, forested peatland in central New York State. The mean rate of net CH[sub 4] production measured at 24° C was 79 nmol g[sup -1]d[sup -1], and the mean rate of CO[sub 2] production (respiration) was 5.7 μmol g[sup -1]d[sup -1], in surface (0 to 10 cm) and subsurface (30 to 40 cm) peat. Saturated peat (900% water content) exposed to oxic conditions for 2 days or 14 days showed no net CH[sub 4] production when subsequently exposed to anoxic conditions. Rates of CO[sub 2] production, measured concomitantly, were essentially the same under oxic and anoxic conditions, and net CH[sub 4] consumption under oxic conditions was barely affected by short-term exposure to anoxic conditions. Therefore, methanogens were particularly sensitive to aeration. Net CH[sub 4] production in whole peat increased within hours of adding either acetate, glucose, or ethanol, substrates that methanogens can convert directly or indirectly into CH[sub 4], indicating that availability of these substrate might limit net CH[sub 4] production in situ. In longer incubations of 30 days, only ethanol addition stimulated a large increase in net CH[sub 4] production, suggesting growth in the population of methanogens when ethanol was available. We fractionated peat into size fractions and the largest sized fraction (> 1.19 mm), composed mostly of roots, showed the greatest net CH[sub 4] production, although net CH[sub 4] production in smaller fractions showed the largest response to ethanol addition. The circumstantial evidence presented here, that ethanol coming from plant roots supports net CH[sub 4] production in forested sites, merits more research. [ABSTRACT FROM AUTHOR]