Stem profile equations for young trembling aspen in northern Ontario

Stem profile equations were developed for young trembling aspen (Populus tremuloides Michx.) growing on 6 different sites in northern Ontario. The objective was to develop a model using stem diameter at any height to predict stem diameter at other heights and then compare the model among sites. The 262 sample trees were split into calibration (180) and validation (82) sets. Four stem profile models having from 1 to 3 parameters were tested for parameter significance for each site, and then compared among sites. Data analysis was performed using bootstrap methods. One of the 4 models was not significantly different (P > 0.278) among sites. Validation of this model produced mean prediction errors and mean :relative prediction errors of less than 0.001 cm and 0.09%, respectively; standard deviations of these errors were 0.15 cm and 4.09%, respectively. The presented method can be used to develop stem profile equations that are applicable to a broad range of growing conditions.