A new method to study simultaneous methane oxidation and methane production in soils

Results of laboratory experiments show that C-14-labeled methane added to soil was consumed faster than atmospheric C-12 methane. This implies a source of methane, presumably through methanogenesis, in a soil that is a net consumer of atmospheric methane. The soil was well-drained forest soil from Ispra, Italy. An undisturbed sample was taken with a steel corer and incubated under oxic conditions in a jar. Headspace samples were taken at time intervals and analyzed for total methane by gas chromatography and analyzed for C-14 methane by liquid scintillation counting. Fluxes calculated from the decreasing headspace mixing ratios were, for example, -6.5 and -7.1 mu mol m(-2) hr(-1) for C-12 methane and C-14 methane, respectively. A simple model is considered which reproduces reasonably well the observed mixing ratios as function of time.