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

•Constructed fen water limits CH4 emissions and pore water concentration.•Carex aquatilis may increase labile carbon root exudates in peat.•Juncus balticus may increase oxygen transport to the root zone (radial oxygen loss).•Higher CH4 concentration and potential production found from C. aquatilis columns. 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.