DEVELOPMENT OF AN IMPROVED MODEL ESTIMATING THE NUTRIENT CONTENT OF THE BOLE FOR 4 BOREAL TREE SPECIES

An improved model for estimating nutrient contents of the commercial p ortion of tree boles was developed for four boreal tree species (Popul us tremuloides Michx., Betula papyrifera Marsh., Picea glauca (Moench) Voss, and Abies balsamea (L.) Mill.). This model considers the spatia l pattern of variation of nutrient concentrations inside the bole and its relationships with tree size. For all species-nutrient combination s, no significant pattern was found for vertical variations in nutrien t concentrations, while two types of nonlinear models, using distance from the tree periphery as the independent variable, fit the pattern o f horizontal (or radial) variations. These patterns of variability wer e used to estimate the global nutrient concentration of the bole by us ing mathematical integration. The values obtained with this method wer e generally lower, especially for large stems, than values obtained wi th traditional methods that do not consider the variability of nutrien t concentrations inside the bole. This improved model would permit bet ter estimates of the amounts of nutrients lost in biomass upon forest harvesting, as well as internal cycling of nutrients within the bole.