Forest water use in the initial stages of reclamation in the Athabasca Oil Sands Region

Abstract

Following large‐scale surface oil sands mining, large tracts of the boreal forest in the Athabasca Oil Sands Region of Western Canada are legally required to be reclaimed. A greater understanding of how these novel ecosystems function and develop with regard to water use is crucial to aid in the development of regulatory practices and protocols based on information from ecosystem recovery. In this paper, a 12‐year (2003–2014) eddy covariance measurement record of latent and sensible heat fluxes and gross ecosystem productivity of carbon dioxide is analysed to evaluate how a reclaimed boreal forest has developed during its initial growth period. The study site is a reclaimed oil sands saline‐sodic clay shale overburden deposit that was topped with 100 cm of glacial till and 20 cm of peat mineral mix. The site was seeded with barley (Hordeum spp.) in 2001 to reduce erosion of the soil cover whereas aspen (Populus tremuloides Michx.) and spruce (Picea glauca [Moench] Voss) boreal tree species were planted in 2004. Changes in structure and function corresponded to the transition of dominant vegetation cover from early successional species to forest. Leaf area index increased from a growing season peak of 0.9 in 2003 to 4.0 in 2014 and was associated with an increased growing season gross ecosystem productivity (4.9 to 8.9 g C m−2 day−1), an increased evapotranspiration (1.6 to 3.4 mm day−1), and a decreased partitioning of energy to sensible heat (Bowen's ratio decreased from 1.1 to 0.4). Although canopy conductance increased throughout the 12 years, the shift from early successional species to trees with more conservative water use resulted in a decrease in conductance normalized by leaf area. Water use efficiency has increased slightly since 2008 with an average of 10.0 g CO2 kg−1 H2O for the last 6 years. No prolonged dry periods were observed during the study period. The functioning of this novel ecosystem is evolving as expected on the basis of the trends observed for other natural and disturbed boreal forests.

Water table dynamics in a constructed wetland, Fort McMurray, Alberta

“…Furthermore, the middle and eastern regions of the lowland (B2 and B3) are surrounded by upland/hummock areas (Figure ), suggesting some influence of the upland and hummock zone in sustaining wetness in adjacent lowland areas within SFW. Water loss via evapotranspiration (ET) is a potential threat to wetland sustainability by lowering WTs as upland vegetation develops with time (Carey, ; Strilesky et al, ). This is especially important in constructed wetlands in the AOSR because, in the absence of water level management and pumping, evapotranspiration was the largest loss of water in both SFW (Nicholls et al, ) and the constructed Nikanotee Fen (Ketcheson et al, ; Scarlett et al, ).…”

“…This enhanced drying resulted in a hydrologic disconnection between the western region of the lowland (B1) and the middle and eastern regions of the lowland (B2 and B3) due to the loss of the zone of standing water that had previously connected these zones (Figure 7). (Carey, 2008;Strilesky et al, 2017). This is especially important in constructed wetlands in the AOSR because, in the absence of water level management and pumping, evapotranspiration was the largest loss of water in both SFW (Nicholls et al, 2016) and the constructed Nikanotee Fen Scarlett et al, 2017).…”

“…Under the Government of Alberta Environmental Protection and Enhancement Act, industry is required to reclaim disturbed landscapes to a state of “equivalent land capability” (Daly et al, ; OSWWG, ). Until recently, upland areas have been the focus of reclamation efforts (Brown et al, ; Carey, ; Huang, Barbour, & Carey, ; Kelln, Barbour, & Qualizza, ; Lilles, Purdy, Chang, & Macdonald, ; Rowland et al, ; Sorenson, Quideau, MacKenzie, Landhausser, & Oh, ; Strilesky, Humphreys, & Carey, ). However, considering approximately 90% of wetlands in this region are fen peatlands (Vitt, Halsey, Thormann, & Martin, ) and oil sands extraction activities are removing large portions of these ecosystems from the landscape (Daly et al, ), research has now shifted towards constructing wetlands within reclaimed areas (Daly et al, ; Ketcheson et al, ; Ketcheson et al, ; Nicholls, Carey, Humphreys, Clark, & Drewitt, ; Price et al, ).…”

Functioning of reclaimed oil sands ecosystems and the implications for reclamation certification

“…For example, if more water is consistently used by vegetation than is available, this indicates a potential for drought conditions accompanied by water stress on the vegetation and the subsequent decline of an ecosystem (Aber et al, 2001;Nelson et al, 2018). There is an established body of literature on the application of the EC technique to assess the water use of ecosystems (Mkhabela et al, 2009;Ewers et al, 2011;Brümmer et al, 2012;Cammalleri et al, 2013), but there are few studies of reclaimed landscapes within the AOSR (Carey, 2008;Nicholls et al, 2016;Ketcheson et al, 2017;Strilesky et al, 2017).…”

“…have not yet included AOSR reclamation sites (Amiro, 2001;Law et al, 2002;Coursolle et al, 2006;Humphreys et al, 2006;Goulden et al, 2011;Brümmer et al, 2012). A recent study focusing on a single reclaimed oil sands ecosystem suggests that water use at that site was within the range of natural variability after approximately a decade (Strilesky et al, 2017).…”