Effect of permafrost thaw on CO sub(2) and CH sub(4) exchange in a western Alaska peatland chronosequence

Permafrost soils store over half of global soil carbon (C), and northern frozen peatlands store about 10% of global permafrost C. With thaw, inundation of high latitude lowland peatlands typically increases the surface-atmosphere flux of methane (CH sub(4)), a potent greenhouse gas. To examine the effects of lowland permafrost thaw over millennial timescales, we measured carbon dioxide (CO sub(2)) and CH sub(4) exchange along sites that constitute a ~1000 yr thaw chronosequence of thermokarst collapse bogs and adjacent fen locations at Innoko Flats Wildlife Refuge in western Alaska. Peak CH sub(4) exchange in July (123 + or - 71 mg CH sub(4)-C m super(-2) d super(-1)) was observed in features that have been thawed for 30 to 70 (