Indirect site productivity models for white spruce in Alberta's boreal mixedwood forest

Multiple linear regression models are presented for boreal mixed-wood stands that predict white spruce [Picea glauca (Moench) Voss] site productivity as a function of trembling aspen (Populus tremuloides Michx.) productivity. Site productivity was measured using both age-referenced and diameter-referenced site indices. Average tree and stand attributes, and environmental parameters that describe topographic and soil conditions were examined for their suitability as additional independent variables in the two basic productivity models. The inclusion of additional regressors provided substantial increases in the explanation of variance over the models which used the site productivity measures alone. The best age-referenced model yielded an R(2) value of 0.794 while the best diameter-referenced model produced an R(2) of 0.908.