Effects of temperature and water table on the efflux of methane from peatland surface cores

(1) Cylindrical cores, 30 cm diameter by 40 cm deep, were cut from the living surface of a raised bog and installed in buckets of the same diameter. The cores were kept outdoors, and their natural water levels maintained with distilled water, until transfer to constant temperature rooms for experiments. Gas fluxes and concentration profiles were measured by quadrupole mass spectrometry. (2) Concentration profiles show that there is an intense source of CH4 about 15 cm below the watertable, and that peaks in the profile move up and down with the watertable. The source can be turned on and off in a few hours. (3) The efflux of CHL depends exponentially on (Celsius) temperature, and is 20% greater in light than it is in the dark, even when the surface vegetation is Sphagnum moss without any vascular plants. (4) Efflux from hollow, lawn, and hummock microhabitats depends negatively and linearly on the depth of the watertable. The slope of the relation is almost the same in ail three microhabitats. (5) When Menyanthes trifoliata (bogbean) is present in hollows the efflux is greater than when only Sphagnum is present. The movement of argon shows that the roots and shoots of Menyanthes provide a high-conductance route between the peat and the atmosphere. (6) Field temperature, precipitation and watertable were recorded for a hydrological (Oct-Sept) year on a raised bog in southwest Scotland. Expected efflux of CH4 was calculated using the experimentally determined relations and the measured temperature and watertable. The mean of these calculated values agreed with the mean of measured values, though individual points were scattered. (C) 1998 Elsevier Science Ltd. All rights reserved.