Sensitivity of predictions of merchantable tree height, log production, and lumber recovery to tree taper

Tree taper models characterize the change in diameter from the bottom to the top of a tree, thereby contributing to the estimation of tree volume. This paper examines the sensitivity of predictions of merchantable height defined as the tree height at a given top diameter inside bark (DIB) determined by the utilization standard, log production, and lumber recovery to the eight parameters in Kozak's (1988) tree taper model. We found that predictions of merchantable height and log production were sensitive to two parameters, whereas predictions of the percentage of lumber recovery were sensitive to one parameter. Because the three measures examined in this study are not very sensitive to tree taper, especially the percentage of lumber recovery that is of most concern to the forest industry, together with the relatively small variations in tree taper parameters across Canada and the limited contribution of tree taper to characterizing the value of lumber recovery at the stand scale, one could infer that it may be possible to develop a single Canadian national softwood tree taper model for predicting forest product variables such as log production and percentage of lumber recovery from forest inventory.