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.
"The mean annual precipitation is 418 mm, with 283 mm occurring as rainfall during the growing season (Environment Canada, 2014). Details about reconstruction of soil profiles following oil sand mining can be found in Rowland et al. (2009) and Sorenson et al. (2011b). Briefly, soil profiles were reconstructed with surface salvaged organic and geologic materials removed during oil sands mining, and placed as a 10 cm cap of peat and 40 cm of mineral soil as a clean top layer (peat mineral mix; PMM). "
[Show abstract][Hide abstract] ABSTRACT: Examining the spatial interactions between above and belowground components of terrestrial ecosystems can give meaningful insight into the ecological processes happening at different scales. Understanding spatial dependence in these processes may help to evaluate reclamation success which is crucial for future management of such areas. The aim of this study was to measure the spatial patterns of soil biogeochemical properties in a young aspen stand reclaimed after oil sands extraction and to evaluate how the patterns were related to nutrient availability. Samples were collected from a 14-year old reclaimed site using a spatially explicit protocol with a minimum resolution of 0.5 m. Field-measured variables included forest floor depth and mass, tree cluster (canopy overlap), distance to nearest tree, and resin available nutrients. Soil microbial properties including microbial biomass C and N, basal respiration, and extracellular enzyme activity were measured during an eight-week laboratory incubation experiment. Geo-statistics were applied to examine the spatial patterns and model the space effect. A fine scale (< 10 m) spatial pattern was found for the majority of stand variables, soil microbial properties, and available macronutrients (N, P, S and base cations). Macronutrients such as N, P and S availability had a fine scale cyclic spatial association with soil microbial properties, with an 8–10 m oscillation, which indicated belowground control on these nutrients. Spatial regression models also suggested a stronger microbial influence on the availability of these nutrients when compared to stand characteristics. However, stand characteristics exhibited significant control on base cations and micronutrient availability through the effect of forest floor depth and tree clustering. Although nutrient availability showed strong spatial relationships with belowground processes in the studied reclaimed site, similar relationships with aboveground properties appeared to be weak, and might require further time to develop.
"Coarse-textured TS is generally a poor plant growth medium because of its low water and nutrient holding capacities, which would often cause trees to be under water stress, especially in dry years. In the AOSR, oil companies used different capping depths depending on the substrate placed (Rowland et al., 2009) because there was no standard prescription for soil reconstruction. Placing thick cover soil layers with fine materials over coarse-textured TS layers could increase water holding capacity due to the high organic matter content in the peat material used as a cover soil and decreased infiltration induced by the capillary barrier between layers (Moskal, 1999; Barbour et al., 2007; Li et al., 2014). "
"Oil sands companies are legally bound to reclaim the disturbed land according to the Alberta Environmental Protection and Enhancement Act (Powter et al. 2012). Current oil sands reclamation practices predominantly involve the use of peat mineral soil mix (PMM) as an organic capping material over tailings sand or overburden substrates (Rowland et al. 2009). Inherent properties of these materials , such as the slow decomposition rate of PMM, means that it releases nutrients (e.g., nitrogen) slowly due to a wide carbon to nitrogen ratio (Jamro et al. 2014; Kwak et al. 2015). "
[Show abstract][Hide abstract] ABSTRACT: Open-pit mining activities in the oil sands region of Alberta, Canada, create disturbed lands that, by law, must be reclaimed to a land capability equivalent to that existed before the disturbance. Re-establishment of forest cover will be affected by the production and turnover rate of fine roots. However, the relationship between fine root dynamics and tree growth has not been studied in reclaimed oil sands sites. Fine root properties (root length density, mean surface area, total root biomass, and rates of root production, turnover, and decomposition) were assessed from May to October 2011 and 2012 using sequential coring and ingrowth core methods in lodgepole pine (Pinus contorta Dougl.) and white spruce (Picea glauca (Moench.) Voss) stands. The pine and spruce stands were planted on peat mineral soil mix placed over tailings sand and overburden substrates, respectively, in reclaimed oil sands sites in Alberta. We selected stands that form a productivity gradient (low, medium, and high productivities) of each tree species based on differences in tree height and diameter at breast height (DBH) increments. In lodgepole pine stands, fine root length density and fine root production, and turnover rates were in the order of high > medium > low productivity sites and were positively correlated with tree height and DBH and negatively correlated with soil salinity (P < 0.05). In white spruce stands, fine root surface area was the only parameter that increased along the productivity gradient and was negatively correlated with soil compaction. In conclusion, fine root dynamics along the stand productivity gradients were closely linked to stand productivity and were affected by limiting soil properties related to the specific substrate used for reconstructing the reclaimed soil. Understanding the impact of soil properties on fine root dynamics and overall stand productivity will help improve land reclamation outcomes.
Ecology and Evolution 09/2015; DOI:10.1002/ece3.1742 · 2.32 Impact Factor
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