Stem volume equations for native tree species in southern New South Wales and Victoria

SUMMARY

Equations for predicting total stem volume underbark from ground to tip were developed for 25 native forest species in southern New South Wales and Victoria using the best available data from State Forests of New South Wales and the Department of Natural Resources and Environment of Victoria. The equation form for each species was selected from 18 modified versions of the combined variable volume equation (Spurr 1952) which took into account changes in stem form with tree size in order to minimize bias within any specified diameter class in volume prediction. A weight function was used to obtain confidence curves for prediction error over the entire range of diameter in the data for each species. This method overcomes the shortcomings of the commonly used segmented approach of dividing data into diameter classes when evaluating prediction accuracy. In practice, the confidence curves can be used to derive confidence limits for stand volume or any product category when they are estimated from individual trees.