| Summary: | Height models for juvenile even aged mixed-species stands were developed for locations near
Nelson, British Columbia. Separate models were developed for each conifer species found, as
well as for paper birch (Betula papyrifera). The objectives were to develop models for: 1) the
number of years to reach breast height; 2) height achieved at a given age above breast height
(height yield); 3) separate models for all trees (average height) and the largest diameter dominant
tree free of damage or suppression on a 0.01 ha plot (top height); and, 4) site and stand attributes
incorporated as independent variables.
Numerous biophysical variables were tested as predictors of juvenile height. Statistically
significant models for years to breast height and for height yield were developed for most species;
most using variables other than site index. For modelling height yield, two ad hoc methods for
including independent variables were used. For trees with multiple measurements ad hoc models
were contrasted with a two-stage parameter prediction approach. The best ad hoc models used
functions of site index; however, the parameter prediction approach produced models with equal
or better fit to the best ad hoc models, including those using site index alone.
Few consistent trends in model form were observed for both years to breast height and height
yield, and many models were not biologically tenable and should not be applied operationally.
Because all combinations of independent variables were not equally sampled, the data may have
not been sufficient to capture trends or variables may be acting as analogues for other causal
factors. Regardless, the measured variables were useful predictors of juvenile height, even with
small data sets. This promising result demonstrated the validity of the approach and the potential
for precise height models not based on site index.
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