this thesis synthesizes two related papers investigating competitive interactions of second growth white spruce (picea glauca [moench] voss) and trembling aspen (populus tremuloides michx.) at the fallingsnow ecosystem project sites near thunder bay, ontario. in the first paper, biweekly white spruce foliar concentrations and ratios of n, p, k, ca, mg and micronutrients were analyzed for 12 trees of varying mixture proportion, throughout the 2010 growing season. results were analyzed with repeated measures design to determine patterns in foliar nutrient concentrations, including seasonal stability and the effect of mixture proportion on the timing of these relationships. seasonal trends were evident in concentrations of n, p, k and ca, as well as in many nutrient ratios (ca/n, mg/n, mn/n and zn/n). significantly lower foliar p, k and p/n and higher ca, ca/n, mn/n and zn/n were observed in foliage from spruce trees in spruce dominated stands. the presence of aspen appeared to influence the amount and duration of nutrient uptake. these results suggest that it is important to differentiate between mixed- and mono-cultures for foliar nutrient research in plantation white spruce.