Environmental Controls on CO₂ Exchange along a Salinity Gradient in a Saline Boreal Fen in the Athabasca Oil Sands Region

Understanding the controls on carbon dioxide (CO₂) exchange within saline boreal fens, appropriate natural analogs for landscape reclamation in areas affected by salinization in the Athabasca Oil Sands Region, can provide insights into the biogeochemical and carbon sink functioning of constructed wetlands under saline conditions. Hence, this study aims to assess net ecosystem exchange (NEE), ecosystem respiration (R), and gross ecosystem productivity (GEP) of peatland and open-water areas within a saline boreal fen near Fort McMurray (Alberta, Canada) to determine environmental controls on CO₂ fluxes using community-scale CO₂ measurements along a salinity gradient. Strong positive correlations between NEE, GEP, leaf area index within peatland, and between GEP and vegetation density within open-water areas (ponds) were observed, demonstrating the importance of vegetation properties for carbon uptake. Strong negative correlations were found between NEE, GEP, R and water table depth and electrical conductivity within peatland. In contrast, GEP and R were positively correlated with phosphate concentrations in ponds, and electrical conductivity had no effect on CO₂ fluxes within ponds. In peatlands, links between CO₂ exchange and environmental factors were influenced by microtopography, and complex relationships between NEE, GEP, R and environmental variables were observed within depressions.