| Yellow-poplar (Liriodendron tulipifera L.) is an important source of raw material for the forest products industry in West Virginia. Accurate taper and volume functions are an important component of most inventory systems for use in estimating upper stem diameter, form, and tree volume. Compatible taper and volume functions can be derived through the mathematical integration of taper functions. Non-linear regression techniques were employed to estimate the parameters in both the taper and volume functions while accounting for correlated error structures. This technique was used to simultaneously minimize the error in both the taper and volume functions. The data included 44 sample trees equally distributed in both the Central Appalachian Broadleaf Forest and Eastern Broadleaf Forest provinces. Six systems were evaluated to determine the best equation forms for predicting upper stem diameter and stem volume: Kozak et al. (1969), Demaerschalk (1972), Max and Burkhart (1976), Clark et al. (1991), and two alternate forms of Clark's equation. The alternate forms of the original Clark et al. (1991) provided the lowest mean squared error for both volume and taper. |
