EFFECTS OF TEMPERATURE ON METHANE CONSUMPTION IN A FOREST SOIL AND IN PURE CULTURES OF THE METHANOTROPH METHYLOMONAS-RUBRA

Methane oxidation in soil cores from a mixed hardwood-coniferous forest varied relatively little as a function of incubation temperatures from -1 to 30-degrees-C. The increase in oxidation rate was proportional to T2.4 (in kelvins). This relationship was consistent with limitation of methane transport through a soil gas phase to a subsurface zone of consumption by diffusion. The Q10 for CO2 production, 3.4, was substantially higher than that for methane oxidation, 1.1, and indicated that the response of soil respiration to temperature was limited by enzymatic processes and not diffusion of either organic substrates or molecular oxygen. When grown under conditions of phase-transfer limitation, cultures of Methylomonas rubra showed a minimal response to temperature changes between 19 and 38-degrees-C, as indicated by methane oxidation rates; in the absence of phase-transfer limitations, M. rubra oxidized methane at rates strongly dependent on temperature.