the effect of competitve species upon crop tree regeneration and growth continues to receive attention from researchers due to the importance of the outcomes. this study stakes a new approach, by examining the combined effects of varied levels of trembling aspen (populus tremuloides michx.) and red raspberry (rubus idaeus l.) upon microclimate and 68-83 cm high white spruce (picea glauca [moench.] voss) seedling growth and rates of photosynthesis. regression, curve estimation and response surface methodology were used to examine the interactions between the two competitive species and the crop species, to ascertain the importance of each competitor and in what aspect it competes.