Methane flux from northern Alberta fens

Methane flux presented as an average of 6-12 measurements made between May and October of each study year using the closed chamber method. Vegetation cover data, where present, was measured in August. Microform indicates micro topographic position with the site where H is hummock and W is hollow. The sites are: open poor fen (OPF), treed poor fen (TPF), saline fen (SF) and treed rich fen (TRF). Water table (WT) and soil temperature at 5 and 20 cm (T5, T20) are also averages of measurement made coincidentally with the fluxes. Negative values for WT indicate a depth below the soil surface. GEP is gross ecosystem photosynthesis measured on the same days based on net ecosystem exchange measurements with a transparent closed chamber in full sun conditions and respiration measured with a dark chamber (GEP = net ecosystem exchange - respiration). Porewater is the methane concentration in pore water determined using headspace equilibration. Pore water samplers were installed just below the WT in the first year and left in place.