Methane flux dynamics in an Irish lowland blanket bog

Pristine peatlands are a significant source of atmospheric methane (CH4). Large spatio-temporal variation has been observed in flux rates within and between peatlands. Variation is commonly associated with water level, vegetation structure, soil chemistry and climatic variability. We measured spatial and temporal variation in CH4 fluxes in a blanket bog during the period 2003-2005. The surface of the bog was composed of different vegetation communities (hummocks, lawns and hollows) along a water level gradient. CH4 fluxes were measured in each community using a chamber method. Regression modelling was used to relate the fluxes with environmental variables and to integrate fluxes over the study period. Water level was the strongest controller of spatial variation; the average flux rate was lowest in hummocks and highest in hollows, ranging from 3 to 53 mg CH4 m(-2) day(-1). In vegetation communities with a permanently high water level, the amount and species composition of vegetation was also a good indicator of flux rate. We observed a clear seasonal variation in flux that was chiefly controlled by temperature. The annual average flux (6.2 g CH4 m(-2) year(-1)) was similar to previous estimates from blanket bogs and continental raised bogs. No interannual variation was observed.