Sm. Huang et Sj. Titus, AN AGE-INDEPENDENT INDIVIDUAL TREE HEIGHT PREDICTION MODEL FOR BOREALSPRUCE ASPEN STANDS IN ALBERTA, Canadian journal of forest research, 24(7), 1994, pp. 1295-1301
This study presents an individual tree height prediction model for whi
te spruce (Picea glauca (Moench) Voss) and trembling aspen (Populus tr
emuloides Michx.) grown in boreal mixed-species stands in Alberta. The
model is based on a three-parameter Chapman-Richards function fitted
to data from 164 permanent sample plots using the parameter prediction
method. It is age independent and expresses tree height as a function
of tree diameter, tree basal area, stand density, species composition
, site productivity, and stand average diameter. This height-predictio
n model was fitted by weighted nonlinear regression for spruce and unw
eighted nonlinear regression for aspen. Almost all estimates of parame
ters were significant at alpha = 0.05 and model R2-values were high (0
.9192 for white spruce and 0.9087 for aspen). No consistent underestim
ate or overestimate of tree heights was evident in plots of studentize
d residuals against predicted heights. The model was also tested on an
independent data set representing the population on which the model w
as to be used. Results showed that the average prediction biases were
not significant at alpha = 0.05 for either species, indicating that th
e model appropriately described the data and performed well when predi
ctions were made.