Methane and carbon dioxide production in, transport through, and efflux from a peatland

The top 5-50 cm of a peat deposit above the water table are predominantly oxic while below that the peat is anoxic. The concentrations of CH4 and CO2 in the peat below 50 cm do not change with the seasons. The concentrations are greatest at or near the base of the peat and decrease quadratically upwards, consistent with a gas production rate (CH4 + CO2) of 0.03 μ mol cm-3 a-1 and movement by diffusion. The upward efflux of CH4, calculated from the concentration profile in deep peat, is 1, and of CO2 is 17 μ mol m-2 h-1. Just below the water table there is a small peak in CH4 concentration. The peak concentrations are greater in summer than in winter. This indicates a second, seasonal and local, but not yet quantified source of CH4. Effluxes of CH4 from the peatland surface range from ordinary summer maxima of about 200 down to winter values less than 10 μ mol m-2 h-1, and at times negative values. The efflux from hummocks is usually about a third of that from hollows. These results indicate that methane oxidation may be important in hummocks.