Green Weight, Volume and Taper Equations for Virginia pine (Pinus virginiana) in the Piedmont Region of North Carolina.

Abstract

Virginia pine (Pinus virginiana) is a prolific pioneer tree species in the Piedmont region of North Carolina that has the potential to be a commercially important tree species. Reliable estimates of weight, stem volume and taper are needed for proper management of approximately 405,000 acres of Virginia pine presently located in the North Carolina Piedmont region. A study was conducted to derive merchantable green weight and merchantable volume equations to any upper stem diameter or height for Virginia pine (Pinus virginiana) across the Piedmont region of North Carolina. Models were derived from data collected at the North Carolina State University?s Hill Demonstration Forest. For total and merchantable green weight models, 100 Virginia pine trees were destructively sampled and weighed. Fixed and mixed effects models were fit and prediction equations were developed for total green weight, green weight to any merchantable outside bark or inside bark diameters, and green weight to any upper merchantable height. Combined variable equations, nonlinear ratio equations and nonlinear exponential ratio equations were fit to these data. Using AIC and minus two log likelihood as the criterion for model fit, the mixed effects ratio model proved superior for predicting green weight to any upper merchantable height, while the mixed effects exponential ratio model was superior for predicting green weight to any upper diameter (outside or inside bark).

For merchantable volume, 105 Virginia pine trees were sampled to obtain outside and inside bark diameters to estimate stem volume. A combined variable equation was used to determine both inside and outside bark total volume. Fixed and mixed effects models were fit and prediction equations were developed for merchantable volume outside bark to any upper merchantable diameter outside bark and inside bark volume to any upper merchantable diameter inside bark. Equations to predict merchantable outside and inside bark volume to any upper merchantable stem height were also derived. Nonlinear ratio equations and nonlinear exponential ratio equations were fit to these data. Using AIC and minus two log likelihood as the criterion for model fit, the mixed effects ratio model proved superior for predicting merchantable outside bark volume and merchantable inside bark volume to any upper stem height, while the mixed effects exponential ratio model was superior for predicting merchantable outside bark volume to any upper stem diameter outside bark. A mixed effects exponential ratio model was also superior for predicting merchantable inside bark volume to any upper stem diameter inside bark. Taper equations were derived for the fixed effects models to predict diameter at any given height and to predict height at any given diameter for Virginia pine trees. The results of this research should be of interest to forest managers and private landowners in the Piedmont physiographic province of North Carolina and will enable foresters to develop more accurate estimates of weight or volume to any specified merchantable diameter or height limit for Virginia pine trees.