The importance of floating peat to methane fluxes from flooded peatlands

The effect of flooding on methane (CH4) fluxes was studied through the cons truction of an experimental reservoir in a boreal forest wetland at the Exp erimental Lakes Area in northwestern Ontario. Prior to flooding, the peatla nd surface was a small source of CH4 to the atmosphere (1.0 +/- SD of 2.3 m g CH4 m(-2) d(-1)). After flooding, CH4 fluxes from the submerged peat surf ace increased to 64 +/- 68 mg CH4 m(-2) d(-1). CH4 bubbles within the subme rged peat caused about 1/3 of the peat to float. Fluxes from these floating peat islands were much higher (440 +/- 350 mg CH4 m(-2) d(-1)) than from b oth the pre-flood (undisturbed) and the post-flood (submerged) peat surface s. The high fluxes of CH4 from the floating peat surfaces may be explained by a number of factors known to affect the production and consumption of CH4 i n peat. In floating peat, however, these factors are particularly enhanced and include decreased oxidation of CH4 due to the loss of aerobic habitat n ormally found above the water table of undisturbed peat and to increased pe at temperatures. The extremely high fluxes associated with newly lifted pea t may decrease as the islands age. However, CH4 flux rates from floating pe at islands that were several years old still far exceeded those from undist urbed peat surfaces and from the water surface of a newly created reservoir .