UC Irvine

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 site (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 (K(s)) for CH4-oxidation showed relatively well-adapted communities. The K(s) 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.