Validation of ecoregion-based taper equations for white spruce in Alberta

Ecoregion-based variable-exponent taper equations for white spruce (Picea glauca (Moench) Voss) were validated on independent tree sectioning data sets. Criteria used for model validation were briefly reviewed, along with applicable interpretations. Examination of the validation plots and statistics indicated that the mean prediction biases were small and very close to zero (−0.0058 ≤ ē ≤ 0.0247; −0.03% ≤ ē% ≤ 0.20%), and the mean squared error of prediction was low. The agreement between observed and predicted values from the taper equations was strong and obvious, and was consistent across the size classes of the predicted values. Approximately 99% of the total variation in both the diameter inside bark predictions and volume predictions were explained by the application of the fitted taper equations. Key words: model validation, accuracy and precision, taper function, Picea glauca