Development of ecoregion-based height-diameter models for white spruce in boreal forests.

A large number of height-diameter functions were evaluated using felled tree data for white spruce (Picea glauca (Moench) Voss) grown in Alberta's boreal forests. The logistic-type function was found to produce the most satisfactory fits. Residual analyses were conducted to identify the error structure of the model. A weighting factor of w[sub i] = 1/Ĥ[sup 3/2, sub i] was found appropriate for satisfying the equal error variance assumption. Regional differences in the height-diameter models were examined and tested using the nonlinear extra sum of squares method. It was found that height-diameter models were different among different ecoregions. Incorrectly applying a height-diameter model fitted from one ecoregion to different ecoregions resulted in overestimations between 1.10% and 29.05%, or underestimations between 1.92% and 21.92%. [ABSTRACT FROM AUTHOR]