Height prediction equations using diameter and stand density measures

Height equations for western hemlock (Tsuga heterophylla (Raf.) Sarg.), western red cedar (Thuja plicata Donn), Douglas-fir (Pseudotsuga menziesii (Mirb.) France), and alder (Alnus rubra Bong. and Alnus tenuifolia Nutt.) were fitted using dbh as the predictor variable. A simple, non-linear equation gave very similar results to the Weibull distribution, except for hemlock, which was better modelled using the more flexible Weibull distribution function. Introducing stand density variables into the base equations resulted in increased accuracy for predicting heights of alder. Smaller improvements were found for Douglas-fir, cedar, and hemlock.