Development of a new variable-form taper equation to investigate differences in stem from following release in eastern white pine ( Pinus strobus L.)

A new, variable-form stem taper equation was developed using data from 87 eastern white pine (Pinus strobus L.) trees. The new model (Model I) was compared to two, well-tested variable-form taper models that were fitted to the same data set. The results show that the new model can perform as well as, and, for some criteria, better than the existing two taper equations in both predicting upper stem diameters and estimating total tree volume.; A linear mixed model was used to account for the correlation between the longitudinal measurements taken along the stem. Different covariance structures were tested to identify the most suitable one. It was determined that a first-order, autoregressive covariance structure is best for the data used in this study.; The effect of tree canopy position and partial cutting treatments on stem form was assessed by incorporating dummy variables in the taper model (Model II). Results showed that the inclusion of canopy dominance class and release treatment improved the estimation of inside bark diameter and total tree volume for white pine.