Effects of land reclamation practices on the productivity of young trembling aspen and white spruce on a reclaimed oil sands mining site in northern Alberta

Abstract

Identifying the main drivers of tree height growth on reclaimed oil sands sites of northern Alberta can provide useful information on what can be done to shorten the recovery time of these disturbed sites. The effect of water availability, foliar nutrient concentrations, competition, and soil chemical properties on young trembling aspen and white spruce height across two soil types (peat-mineral mix and forest floor-mineral mix) and two fertilizer levels (200 kg NPK ha−1 and no fertilizer) was examined. For comparison, we also studied a natural site that burned the same year the reclaimed site was established. On the reclaimed site, peat-mineral soil had the greatest tree height for both species, though not by a significant margin in the case of white spruce. The fertilizer treatment had no apparent effect on tree height on the forest floor-mineral soil and a negative effect on the peat-mineral soil. Fertilization increased vegetation cover on both soil types, which, when combined with the negative or lack of durable effect of fertilization on tree height, suggest that the increase in competition for resources could have had a stronger effect on tree height than the increase in immediately available nutrients following fertilization. The majority of tree height growth drivers found were related to nutrient availability and, as far as we can tell, did not significantly differ between reclamation soil types. Aspen sucker height on the burned site was not strongly correlated to the measured variables, suggesting that suckers do not yet fully rely on their environment for height growth.