Methane emissions dynamics from a constructed fen and reference sites in the Athabasca Oil Sands Region, Alberta

Recently, fen construction projects on surface mines in northeastern Alberta have been attempted as a reclamation strategy to reintroduce peatlands into the region where industry disturbs a substantial amount of wetland ecosystems. Knowledge of carbon cycling and greenhouse gas (GHG) dynamics, including methane (CH₄), is one way to understand the biogeochemical function of newly constructed fen ecosystems. In this study we monitored CH₄ emissions and CH₄ pore water concentration, as well as ecological and soil chemistry controls on CH₄ emissions and pore water concentration, from a constructed fen. The same variables were also monitored at two natural reference fens that had similar vascular vegetation to the constructed fen. Methane emissions were lower at the constructed fen compared to the reference poor fen, but similar to the reference saline fen. However, CH₄ concentration in pore water at 0.2m and 0.7m depth was lower at the constructed fen than either of the natural reference sites. The supply rate of sulfur (all mobile forms) was the most dominant control on CH₄ emission and CH₄ pore water concentration. While low CH₄ emissions may be beneficial for constructed fens from a GHG perspective, this condition indicates that peat and carbon accumulation at these reclaimed sites may ensue slowly. Therefore, a clear statement of goals is required to determine how CH₄ dynamics from constructed fen ecosystems relate to the reclamation outcome.