A Comparison of Soil Nitrogen Availability Between a Post Mined Reclaimed Wetland and Two Natural Wetlands in Fort McMurray, Alberta.

English Abstract:

In situ measurement of soil nitrogen dynamics is a potential method for evaluating the health of constructed wetlands following oil sands mining. The objective of this study is to measure and compare the soil nitrogen availability of a reclaimed fen (Sandhill fen) with a nutrient-rich reference fen (Poplar fen) and a nutrient-poor reference fen (Pauciflora fen) in the Athabasca oil sands region of Northern Alberta. TIN, NO₃^-, and NH₄⁺ supply rates were determined along hillslope-wetland transects using Western Ag Innovations Plant Root Simulator (PRS) probes at all three sites in 2014. Net N mineralization was determined simultaneously using the buried polyethylene bag approach. Overall, TIN supply rates were greatest at the poor fen and least at the constructed Sandhill fen. In contrast, net mineralization was greatest at the rich fen but again least at the Sandhill fen. Relatively low N supply rates and net mineralization at the Sandhill fen were likely due to lower soil organic matter content and limiting soil moisture in these newly constructed substrates. Spatial differences along the hillslopes also varied among sites. The Sandhill fen had higher TIN supply rates upslope but no differences in net N mineralization rates. The rich fen also had higher TIN supply rates upslope but greatest net mineralization rates downslope. Furthermore, the nutrient rich site exhibited a strong negative correlation between NO₃^- supply and net N mineralization, which contrast the measurement approaches. These results highlight the importance of N storage and transport processes and offer insight into the N processes of a constructed fen.