EFFECTS OF ADDING TREE, STAND, AND SITE VARIABLES TO KOZAKS VARIABLE-EXPONENT TAPER EQUATION

Crown class, site class, and breast-height age were incorporated into Kozak's variable-exponent taper equation (A. Kozak. 1988. Can. J. For. Res. 18: 1363-1368) for three species: Douglas-fir (Pseudotsuga menzi esii (Mirb.) France), western red cedar (Thuja plicata Donn), and aspe n (Populus tremuloides Michx.). For lodgepole pine (Pinus contorta Dou gl.), crown ratio, breast-height age, and quadratic mean diameter were incorporated into Kozak's taper equation. The effects of adding these variables to the exponent part of the taper equation on the predictio n abilities of the taper model were assessed for prediction of diamete r inside bark along the stem, total tree volume, and tree merchantable height. It was found that apart from the use of crown ratio for lodge pole pine, the additional variables resulted in only marginal improvem ents to the published version of Kozak's taper function. Therefore, th e cost of measuring these additional variables is not justifiable.