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

Abstract 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 i =1/ H 3/2 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%.