Low methane emissions from a boreal wetland constructed on oil sand mine tailings

Abstract. A 58 hectare mixed upland and lowland boreal plains watershed called the Sandhill Fen Watershed was constructed between 2008 and 2012. In the years following wetting in 2013, methane emissions were measured using manual, static, non-steady state chambers. The presence of vegetation with aerenchymous tissues and saturated soils were important factors influencing the spatial variability of methane emissions across the constructed watershed. Nevertheless, median methane emissions were equal to or less than 0.51 mg CH4 m−2 h−1 even from the saturated organic soils in the lowlands. Although overall methane emissions remained low, observations of methane ebullition increased over the three study years. As a ratio to the total number of measurements, the number of ebullition events increased from 10 % in 2013 to 21 % and 27 % in 2014 and 2015, respectively at the plots with saturated soils. Increasing metal ion availability and decreasing sulphur availability was measured using buried ion exchange resins at both seasonal and annual timescales potentially as a result of microbial reduction of these ions. Methane fluxes significantly correlated with the leading Principal Component of ammonium, iron, manganese and sulphur availability (r = 0.31, p