A segmented stem profile model for Pinus sylvestris

A stem-profile model describing diameter above stump height was developed f or Scots pine. The segmented model is intended to predict stem diameters in side the bark for standing trees. For an efficient parameter estimation alo ng the stem, stem diameter inside the bark was transformed for each sub-fun ction. The transformed, dependent variables were constructed by subtracting the diameter obtained along the stem using a segment-dependent form of a c one or a cone frustum from the observed stem diameter inside the bark. In all, data from 467 sample trees were used. The predictive properties of the base model constructed were similar to those of the variable-form taper model developed by Newnham [Newnham, R.M., Can. J. For. Res., 22 (1992) 21 0-223]. The base model was improved by introducing auxiliary variables such as terms constructed using the variables crown height, age at breast heigh t, and site index. The auxiliary variables improved the base model the maxi mum near the butt. (C) 1999 Elsevier Science B.V. All rights reserved.