Controls on Plot-Scale Evapotranspiration from a Constructed Fen in a Post-Mined Oil Sands Landscape, Fort McMurray, Alberta

English Abstract:

In the oil sands development region of the Western Boreal Plains (WBP) mining companies now recognize the importance of peatland ecosystems, as they cover >60% of the regional pre-mined landscape. To date, reclamation efforts have been focused on uplands and open water marsh wetlands. However, these wetland systems are not abundant in the sub-humid climate of the WBP due to high evaporative demand, where evapotranspiration (ET) is the dominant hydrologic flux from wetlands in this region. Suncor’s pilot constructed fen was completed in 2013, engineered with the intent to support natural fen vegetation and hydrologic processes. The purpose of this study is to evaluate the influences of vegetation and treatment types on evapotranspiration demands from the constructed fen. Multiple study sites (31) were monitored across the fen during the 2014 field season, located in vegetation plots (control/moss/vascular) with varying treatments (mulched/unmulched). Plot-scale actual ET was quantified with weighing lysimeters and chamber measurements. These measurements were used to adjust equilibrium ET, calculated using Priestly-Taylor for control and moss plots and Penman-Monteith for seedling plots, where values of stomatal resistance and leaf area index were available. A roaming meteorological station was used to quantify available energy over individual plot types. ET rates were, on average, lower in moss plots than control and vascular. Mulch further reduced ET, with lowest rates in mulched moss plots. These trends were likely caused by different thermal regimes and lower available energy in mulched plots, where ground temperatures were ~3°C lower. Mulch further provided a favorable microclimate for moss establishment by elevating near-surface relative humidity. Currently, these reclamation practices have not yet been well tested in this region and have relied on knowledge from other study areas where climate is dissimilar. The results of this study will provide insight into effective reclamation practices for reducing evaporative stress and ensuring successful establishment of functioning peatland ecosystems in the WBP.