Abstract
Soil stockpiling is a common reclamation practice used in oil sands mining in the boreal forest region of Canada to conserve soil resources; but stockpiling may have detrimental effects on soil quality and plant growth. We examined growth response of trembling aspen (Populus tremuloides Michx.), a fast-growing early successional tree, and green alder (Alnus viridis (Chaix) DC. ssp crispa (Ait.) Turrill), a nitrogen-fixing shrub, to stockpiling and fertilization treatments on two reclamation soils (forest floor mineral mix (FFMM) and peat mineral mix (PMM)). Aspen and alder seeds were planted and their growth monitored for four months in the greenhouse. We found that unfertilized stockpiled FFMM supported significantly higher aspen and alder aboveground biomass than the other fresh and stockpiled soils. Phosphorus and potassium supply rates were highest in stockpiled FFMM and were positively correlated with aboveground plant biomass. There was no significant difference in aspen and alder aboveground biomasses between unfertilized fresh FFMM and PMM soils. Aspen grown in combination with nitrogen-fixing alder did not experience competition or facilitation except on fresh PMM, where aspen height declined. Fertilization increased both aspen and alder growth and eliminated differences in growth between soil types and stockpiling treatments. Our study showed that individual soil properties are more important for revegetation purposes than type of soil or stockpiling treatment.
Highlights
Open-pit mining in the boreal forest region of Canada involves the removal of vegetation, top soils, and overburden in order to access the underlying bitumen [1]
There was no significant difference in aboveground biomass between fresh forest floor mineral mix (FFMM) and fresh peat mineral mix (PMM), but for the stockpiled soils, FFMM supported a higher aboveground biomass than PMM
Growth patterns of unfertilized aspen were generally similar among all the soil and stockpiling treatments except for stockpiled FFMM and fresh PMM (Figure 2a,c)
Summary
Open-pit mining in the boreal forest region of Canada involves the removal of vegetation, top soils, and overburden (i.e., material overlaying a deposit of useful geological material) in order to access the underlying bitumen [1]. This practice is followed by land reclamation to restore the disturbed land to a naturally appearing and self-sustaining state that is integrated with the surrounding habitat [2]. Compaction during mound construction and consolidation during storage increases bulk density, damages soil structure, and impedes plant growth [8,9]. Decomposition and development of anaerobic conditions inside the stockpile can significantly reduce seed viability [10]
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