Recreating a Functioning Forest Soil in Reclaimed Oil Sands in Northern Alberta: An Approach for Measuring Success in Ecological Restoration

Abstract

During oil-sands mining all vegetation, soil, overburden, and oil sand is removed, leaving pits several kilometers wide and up to 100 m deep. These pits are reclaimed through a variety of treatments using subsoil or a mixed peat-mineral soil cap. Using nonmetric multidimensional scaling and cluster analysis of measurements of ecosystem function, reclamation treatments of several age classes were compared with a range of natural forest ecotypes to discover which treatments had created ecosystems similar to natural forest ecotypes and at what age this occurred. Ecosystem function was estimated from bioavailable nutrients, plant community composition, litter decomposition rate, and development of a surface organic layer. On the reclamation treatments, availability of nitrate, calcium, magnesium, and sulfur were generally higher than in the natural forest ecotypes, while ammonium, P, K, and Mn were generally lower. Reclamation treatments tended to have more bare ground, grasses, and forbs but less moss, lichen, shrubs, trees, or woody debris than natural forests. Rates of litter decomposition were lower on all reclamation treatments. Development of an organic layer appeared to be facilitated by the presence of shrubs. With repeated applications of fertilizers, measured variables for the peat-mineral amendments fell within the range of natural variability at about 20 yr. An intermediate subsoil layer reduced the need for fertilizer and conditions resembling natural forests were reached about 15 yr after a single fertilizer application. Treatments over tailings sand receiving only one application of fertilizer appeared to be on a different trajectory to a novel ecosystem.

Temporal Trends of Ecosystem Development on Different Site Types in Reclaimed Boreal Forests

“…Low shrub cover is common on reclaimed plots [31], but the trajectory of shrub cover in our study is moving towards eventually being similar to natural forests. However, the reclamation sites have very different shrub species composition relative to natural sites.…”

“…Available soil P concentration is greater on dry site types in both reclaimed and natural sites but is much lower in reclaimed plots at year 20 than in mature natural plots [31]. Phosphorus has also been positively related to tree growth [7] indicating that low P availability may be a long-term risk to ecosystem development on reclaimed areas.…”

Comparing soil biogeochemical processes in novel and natural boreal forest ecosystems

“…This equilibrium between soil chemical and biochemical properties may be disrupted following disturbance (Chaer et al, 2009). Prior research in the Athabasca oil sands region demonstrated that organic matter composition, nutrient availability, and microbial communities in these reclaimed soils differed from mature upland forest soils (Turcotte et al, 2009;Rowland et al, 2009;Dimitriu et al, 2010). These past studies looked at each of these variables separately, and did not specifically examine the inherent variability present in the natural landscape.…”

“…Following incubation, the probes were washed with deionized water and returned to Western Ag Innovations, Inc. for elution with 0.5 M HCl and nutrient concentration analysis, including colorimetric ammonium (NH ductively Coupled Plasma (ICP) spectroscopy (PerkinElmer Optima 3000-DV, PerkinElmer, Inc., Shelton, CT, USA). The probe data reported here (mmol per 10 cm −2 of resin area per day) correspond to a total burial period of 95 days (Rowland et al, 2009).…”

Maintaining Ecosystem Function by Restoring Forest Biodiversity – Reviewing Decision-Support Tools that link Biology, Hydrology and Geochemistry

“…First, the soil prescriptions that form the basis for reclamation often lack the historical legacy (propagule bank, organic matter, soil structural and biochemical properties, etc.) common to natural sites [8][9][10][11]. Secondly, forests are growing under climatic conditions that differ from the historical climate regime, particularly in more northerly regions.…”