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 atmo spheric CH4 source characterized by distinct depth zonation of CH4 pro duction 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 mu M, about 10-fold higher than values for CH4-sink soils (AS2 and BS2), 37 and 124 nM. Experiments as sessing the individual effects of moisture and temperature on CH4-oxid ation indicated that moisture was the primary control in CH4-sink soil s at AS2 and BS2, while temperature was more important in CH4-source s oil at LB. A combination of the highest moisture content and lowest te mperature for each soil gave the lowest CH4-oxidation rates in experim ents evaluating the interactive effects of these two variables. Conver sely, a soil moisture content close to the optimum identified in moist ure dependence experiments combined with the highest soil temperature consistently gave the highest CH4-oxidation rate. Copyright (C) 1996 E lsevier Science Ltd