Compatibility, Development, and Estimation of Taper and Volume Equation Systems

Abstract

The meaning of compatibility in systems of taper and volume equations has been extended. It is desirable and possible to develop completely compatible taper and volume equation systems that have algebraic compatibility and numeric consistency among all the component equations. Two such taper and volume systems were developed for slash pine in the southeastern United States. One was derived from a recently developed merchantable volume equation (Zhao and Kane 2017), and the other was derived from the well-known Max and Burkhart segmented polynomial taper equation (1976). Three fitting methods were used to obtain numerically consistent estimates of parameters in these two systems. The performance of the systems associated with fitting methods were evaluated with taper, merchantable volume and total volume predictions, and bias trends over different dbh classes, total height classes, and different relative height intervals. The new system outperformed the Max-Burkhart taper-based system for merchantable and total volume predictions and was competitive in diameter prediction. Optimization of parameters of the system for both taper and cumulative volume simultaneously is preferable to separate optimization for taper or volume only.