The role of cotton-grass (Eriophorum vaginatum) in the exchange of CO₂ and CH₄ at two restored peatlands, eastern Canada

We measured methane (CH₄) and carbon dioxide (CO₂) exchanges from bare peat and Eriophorum vaginatum ssp. spissum tussocks at recently restored harvested peatlands near Shippagan, New Brunswick and Rivière-du-Loup, Québec over three growing seasons (May to October). Average seasonal CH₄ emission rates ranged from -1 to 65 mg · m^-2 · d^-1, with a generally weak relationship with water table position. A stronger relationship was seen between CH₄ emissions and above-ground plant biomass. CH₄ fluxes from E. vaginatum tussocks were larger than those from bare peat surfaces and increased with increasing above-ground biomass and photosynthetic rate. Clipping fresh leaves from tussocks reduced the CH₄ emission rates by 79%. Photosynthesis rates were large in tussocks, ranging from 0.9 to 3.4 g CO₂-C · m^-2 · h^-1 at high light levels, and respiration rates (autotrophic + heterotrophic) ranged from -0.1 to -1.3 g CO₂-C · m^-2 · h^-1. Some tussocks exhibited net CO₂ loss to the atmosphere, even under high light levels. Although the rapid colonization of restored peat surfaces by E. vaginatum aids the development of other vascular plants and mosses, it increases the flux of CH₄ to the atmosphere and provides little or no net C accumulation on the peat surface.