The influence of Carex aquatilis and Juncus balticus on methane dynamics: A comparison with water sourced from a natural and a constructed fen

As fen peatlands have been heavily disturbed by resource extraction in northeastern Alberta, Canada, fen construction has been completed. In order to optimize biogeochemical function of future constructed fens, it is beneficial to understand methane (CH₄) cycling of newly constructed fens, and how revegetation strategies influence CH₄ dynamics. Here, we investigate the effects of two vascular species used for fen construction on CH₄ dynamics. A factorial greenhouse experiment using peat columns and a laboratory incubation experiment were used to understand differences in CH₄ production, emissions, pore water concentration, and oxidation between Carex aquatilis Wahlenb. and Juncus balticus Willd. The experiment also considered how water sourced from the constructed fen influenced CH₄ dynamics compared to natural rich fen water. Higher pore water CH₄ concentration and potential CH₄ production were found at C. aquatilis columns, possibly associated with higher labile carbon throughout the column. In columns with J. balticus, evidence to support radial oxygen loss reducing CH₄ concentration and production was found. Water sampled from peat columns with constructed fen water had higher Fe (all cation forms), Mn (all cation forms), SO₄²−, and NO₃− compared to columns with rich fen water, which corresponded to lower CH₄ emissions and pore water concentration. Results from this study could be used to inform revegetation designs of future constructed fens that consider greenhouse gas emissions, including CH₄, as a reclamation goal.