Stem taper equations, which predict the change in form from ground to tip, have become the primary means for estimating volume. They can provide predictions with similar levels of accuracy as volume equations, but with greater flexibility, a wider range of potential uses, and consistency between taper and volume. This review is a synthesis of current knowledge and an assessment of challenges for future refinement. It primarily focuses on the history and evolution of stem taper model forms. Additional focal areas covered are: (1) the use of additional covariates beyond diameter at breast height and total height; (2) alternative statistical parameterization methods like parametric, semi-parametric, and non-parametric; (3) key considerations for proper development, application, and use of these equations such as sample size requirements, local calibration, and evaluation; and (4) a synthesis of key findings, future opportunities, and ongoing challenges. Emerging technologies, such as terrestrial laser scanning (TLS) offer an unprecedented opportunity to measure stem form in much greater detail at significantly lower costs and time requirements than traditional methods. Overall, continued development, refinement, and application of stem taper equations will remain important given the critical nature of tree volume for science, accurate inventories, and ultimately, sustainable forest management.
EVALUATION OF NON-LINEAR TAPER EQUATIONS FOR PREDICTING THE DIAMETER OF EUCALYPTUS TREES
