The importance of ebullition as a mechanism of methane (CH4) loss to the atmosphere in a northern peatland

Abstract

We measured the escape of methane-containing gas bubbles to the water table in two microhabitats (muddy hollows and Sphagnum-plus-sedge lawns) in a raised bog in West Wales, typical of many northern peatlands. Our study was unusual in its degree of replication (14 gas traps in each microhabitat). Seasonally integrated bubble loss of CH4 to the water table did not differ significantly between microhabitats. After applying an oxidation correction to give CH4 fluxes to the atmosphere, the microhabitats still did not differ. Our results suggest that ebullition is an important mechanism of CH 4 loss to the atmosphere, with mean summer rates of 11.7 mg CH 4 m-2 d-1 (muddy hollows) and 6.8 mg CH 4 m-2 d-1 (Sphagnum-plus-sedge lawns). Our data show that the process is spatially and temporally very variable, and that the small sample sizes of many studies (e.g., n = 5) may lead to considerable errors in flux estimation. © 2013 American Geophysical Union. All Rights Reserved.