Moisture and temperature sensitivity of CH4 oxidation in boreal soils

We used laboratory experiments to evaluate CH4 uptake kinetics and the influence of soil moisture and temperature on rates of CH4-oxidation by boreal soils at in situ CH4 concentrations. Two upland forest sites (AS2 and BS2) were atmospheric CH4 sinks; a bog site (LB) was an atmospheric CH4 source characterized by distinct depth zonation of CH4 production and consumption. Apparent half-saturation constants (Ks) for CH4-oxidation showed relatively well-adapted communities. The Ks for the high CH4-source soil (LB) was 1.1 μm, about 10-fold higher than values for CH4-sink soils (AS2 and BS2), 37 and 124 nm. Experiments assessing the individual effects of moisture and temperature on CH4-oxidation indicated that moisture was the primary control in CH4-sink soils at AS2 and BS2, while temperature was more important in CH4-source soil at LB. A combination of the highest moisture content and lowest temperature for each soil gave the lowest CH4-oxidation rates in experiments evaluating the interactive effects of these two variables. Conversely, a soil moisture content close to the optimum identified in moisture dependence experiments combined with the highest soil temperature consistently gave the highest CH4-oxidation rate.