INDIRECT SITE PRODUCTIVITY MODELS FOR WHITE SPRUCE IN ALBERTA BOREAL MIXEDWOOD FOREST

Multiple linear regression models are presented for boreal mixed-wood stands that predict white spruce [Picea glauca (Moench) Voss] site pro ductivity as a function of trembling aspen (Populus tremuloides Michx. ) productivity. Site productivity was measured using both age-referenc ed and diameter-referenced site indices. Average tree and stand attrib utes, and environmental parameters that describe topographic and soil conditions were examined for their suitability as additional independe nt variables in the two basic productivity models. The inclusion of ad ditional 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 wh ile the best diameter-referenced model produced an R(2) of 0.908.