Methane efflux from emergent vegetation in peatlands

1 Methane emissions from emergent plants in two peatlands were measured in plant enclosure experiments. During the summer growing season, methane emissions on a plant dry mass basis from Scheuchzeria palustris (130 +/- 14 mu mol g(-1) day(-1)) were higher than from other peatland plants, such as Chamaedaphne calyculata (20 +/- 3 mu mol g(-1) day(-1)) and Carex oligosperma (91 +/- 38 mu mol g(-1) day(-1)), but were lower than from Calla palustris (280 +/- 37 mu mol g(-1) day(-1)). 2 The contribution to net methane efflux from S. palustris, the dominant emergent plant in one peatland, was 15.6 +/- 2.2 mmol m(-2) day(-1), based on the plant enclosure experiments and areal biomass measurements. These results were not significantly different from the difference between measurements of methane efflux using chambers enclosing clipped and unclipped plots (12.0-27.9 mmol m(-2) day(-1)). 3 We determined that methane transport through S. palustris contributed between 64 and 90% of the net methane efflux from the peatland, while the other peatland without plants capable of rapid methane transport had significantly lower methane efflux. The higher annual efflux from peat with aerenchymatous plants appears to be due to several factors, including increased substrate production which enhances methane production, reduction in methane oxidation, as well as easier methane transport from the site of production. 4 Plants capable of transporting methane regulated the methane pool in the saturated zone by depleting both dissolved methane in the pore-waters and the concentration of methane in gas bubbles trapped in the saturated peat. 5 Our experiments indicate that methane transport through S. palustris is due to molecular diffusion, and is not influenced by pressurization or stomatal aperture.