A POLYNOMIAL TAPER CURVE FUNCTION FOR ZAMBIAN EXOTIC TREE PLANTATIONS

Abstract

Defining tree taper gives advantages in deriving the utilisable portions of trees. A high degree polynomial is used to estimate average relative taper. Some of the parameters of the polynomial should be functions of diameter at breast height and total height of the tree, and the remaining parameters can be held constant within a tree species. The study describes a somewhat simplified version of the polynomial taper curve model developed by Laasasenaho and presents a simple method for transforming the overbark taper curve models to underbark ones. Taper curve functions for the main exotic tree species Pinus kesiya, Pinus oocarpa, Pinus merkusii, Pinus michoacana, Eucalyptus grandis and Eucalyptus cloeziana in Zambia are derived. The polynomial appears to fit equally well with differently tapering tree species and gives good estimates for both over- and underbark diameters. Regression functions for bark thickness are also given.