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 tn identify the error structure of the model. A weighting factor of w(i) = 1/(H) over cap(i)(3/2) 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%. (C) 2000 Elsevier Science B.V. All rights reserved.