Methane ebullition from two lowland floodplain fens

Fieldwork measurements were made following the protocols developed by Defra project SP1210 'Lowland Peatland Systems in England and Wales'. Methane ebullition fluxes were measured using twelve inverted glass funnels at each site. Chamber methane fluxes were measured using six tall, static chambers at each site to capture diffusion, plant-mediated transport and steady ebullition. Measurements were taken within a 0.04 km2 area at each site in vegetation dominated by Phragmites australis. At each site an automatic weather station (MiniMet, Skye Instruments, UK) was used to measure meteorological variables. Six pressure transducers (Levelogger Gold, Solinst, Canada) were installed in dipwells adjacent to each static chamber collar to measure water level. Manual dips taken on a monthly basis were used to calibrate the pressure transducer data. Vascular Green Area was monitored non-destructively within each chamber collar. Measurements of methane concentration in funnels and static chambers were made by gas chromatography coupled with flame ionization detector. The analytical instrument was calibrated each run and certified gases were used to ensure accuracy.