Abstract
Abstract. A 58 ha 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 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 3 study years. Ebullition events occurred in 10 % of measurements in 2013, increasing to 21 % and 27 % of measurements in 2014 and 2015, respectively, at the plots with saturated soils. Increasing metal ion availability and decreasing sulfur availability was measured using buried ion exchange resins at both seasonal and annual timescales potentially as a result of microbial reduction of these ions. Using principle component analysis, methane fluxes had a significant positive correlation to the leading principle component which was associated with increasing ammonium, iron, and manganese and decreasing sulfur availability (r=0.31, p<0.001). These results suggest that an abundance of alternative inorganic electron acceptors may be limiting methanogenesis at this time.
Highlights
The boreal biome stores large quantities of soil carbon (C) due to the high density of peatlands with some estimates as high as 165 kg C m−2 (Beilman et al, 2008)
To determine the CH4 emissions of a closure watershed in the oil sands mining region of northern Alberta and how these emissions compare to those from the restored peatlands listed above, this paper presents 3 years (2013–2015) of CH4 emission measurements from the Sandhill Fen Watershed (SFW), one of the first wetland complexes constructed in the Athabasca oil sands region (AOSR)
Carbon cycling processes in constructed boreal plains lowlands are not yet well understood as these ecosystems have only existed for a few years
Summary
The boreal biome stores large quantities of soil carbon (C) due to the high density of peatlands with some estimates as high as 165 kg C m−2 (Beilman et al, 2008). A legacy of open pit oil sands mining in northern Alberta, Canada, will be that almost 5000 km of the boreal landscape (Alberta Government, 2017) will require reclamation to restore it to the “equivalent capability” of the pre-mining ecosystems (Environmental Protection and Enhancement Act, 2017) These engineered landscapes will be important in determining the long-term C footprint of the region, potentially helping to offset ecological losses and industrial emissions. Rooney et al (2012) used land cover classification and reclamation plans to estimate a potential net loss of 11.4–47.3 Tg of the stored soil C from the pre-mining landscape and a reduction in CO2 sequestration capacity of the new constructed landscape by 5.7–7.2 Gg C yr−1. Wetland reclamation in the region is still quite novel, and little is known about the surface–atmosphere exchange of C in these newly engineered wetlands (Nwaishi et al, 2015; Clark et al, 2019)
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