METHANE METABOLISM IN RAISED BOGS OF NORTHERN WETLANDS

Laboratory columns wider continuous flow were packed with peat from th e catotelm of an ombrotrophic bog to simulate the natural environment. Methane concentration increased from 1.4 to 47.8 mumol ml-1 due to an aerobic microbial degradation of the peat, while at the same time the water flow rate decreased from log -1.39 to -3.03 cm3 s-1 and the mois ture content decreased from 85.7 to 56.6%. A control column sterilized by irradiation produced carbon dioxide, but, as the flow of water was hed this soluble gas out of the column, the hydraulic conductivity and moisture content increased These two results suggest that it is the v olume of the gas (in the gas phase within the bog) that controls the h ydraulic conductivity of peat bogs. Volume accounting at the end of th e experiment showed no gas in rhe sterilized column but 17% gas by vol ume in the microbially active column. We suggest that as gas bubbles o cclude the interstitial pores of the peat the water flow is impeded, r educing both the hydraulic conductivity and the water saturation. The difficulty experienced in draining peat bogs is due to this occlusion, which is also responsible for the heightened water table found in rai sed bogs. Although methane is produced in bogs, only very low levels o f methane emission have been reported Thus the methane released from n orthern areas will only significantly contribute to increasing radiati ve gases in the atmosphere if the bogs themselves are disturbed, for e xample by mining, when the entrapped methane is released, the water ta ble falls, and the bog dries out.