Browsing by Author "Dr. Bronson Bullock, Committee Chair"

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    Green Weight, Volume and Taper Equations for Virginia pine (Pinus virginiana) in the Piedmont Region of North Carolina.
    (2005-09-29) Adams, John William; Dr. George Hess, Committee Member; Dr. Robert Abt, Committee Member; Dr. Bronson Bullock, Committee Chair
    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.
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    Modeling the Diameter Distribution in Juvenile Loblolly Pine (Pinus taeda L.) from Diverse Genetic Provenances under Deficient and Optimum Nutrition Regimes.
    (2007-12-07) Smith, Benjamin Christian; Dr. Bronson Bullock, Committee Chair; Dr. Steven McKeand, Committee Member; Dr. Heather Cheshire, Committee Member
    The ability to predict diameter distributions is an important tool for the forest manager. By accurately predicting the diameter distribution, the manager may make better-informed decisions regarding the silvicultural treatments for a stand, such as when and how to conduct a thinning operation. This study compares the suitability of the gamma, lognormal, and two-parameter Weibull distributions for modeling diameter distributions in juvenile loblolly pine from ages 5 to 11. Using the most appropriate distribution as determined by the Anderson-Darling goodness-of-fit statistic, the two-parameter Weibull distribution, the study also determines the most suitable method for estimating distributional parameters from stand level characteristics such as mean basal area, relative spacing, quadratic mean diameter, and age. The methods tested were a parameter prediction method (PPM), a parameter recovery method (PRM), and a percentiles-based method (PCT). Comparisons were made from ages 5 to 10 using a modification of the Reynold's error index, weighted by basal area. Final parameter estimation equations were developed from data from ages 5 to 11. The parameter recovery method of parameter estimation proved to be most appropriate for modeling these data. Although the PPM had a slightly lower Reynold's error index than the PRM, the shape parameter was predicted within a very narrow range about the mean, while the distribution of shape parameters recovered by the PRM was much closer to the empirical distribution. In addition, the PRM required fewer inputs into the model, and as such was more desirable for modeling purposes. An application is presented to demonstrate the construction of stand tables from the output parameters. A second study examined the relationships among the maximum likelihood fitted parameters of the two-parameter Weibull distribution and the treatment effects due to fertilization, genetic provenances, and open-pollinated genetic families. Both the scale and shape parameters differed significantly between the non-fertilized control treatment and the optimally fertilized treatment. Further research utilizing the three-parameter Weibull might lead to significant differences among the location parameter instead of the scale and shape parameters. No significant differences were observed in the shape parameters between genetic provenances, but significant differences did exist in the younger ages between provenances in the scale parameters. Family means tended to increase over time for the scale parameter, and family mean rankings were relatively stable within and across fertilization treatments. The shape parameter family mean rankings were less stable over time, with the means tending to increase in the non-fertilized treatment and decrease in the fertilized treatment, reflecting the differences in stand development. As stand development progressed, year to year rank changes were minor, but less stable family mean rankings over time were observed.