Modeling the diameter distribution in juvenile loblolly pine (pinus taeda l.) from diverse genetic provenances under deficient and optimum nutrition regimes.

by 1978- Smith, Benjamin Christian

Abstract (Summary)
SMITH, BENJAMIN CHRISTIAN. Modeling the Diameter Distribution in Juvenile Loblolly Pine (Pinus taeda L.) from Diverse Genetic Provenances Under Deficient and Optimum Nutrition Regimes. (Under the direction of Dr. Bronson P. Bullock.) The ability to predict diameter distributions is an important tool for the forest manager; by accurately predicting the diameter distribution, the manager may make betterinformed decisions regarding the silvicultural treatments for a stand. 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. The twoparameter Weibull distribution was found to be the most appropriate distribution as determined by the Anderson-Darling goodness-of-fit statistic. The study also determined the most suitable method for estimating distributional parameters from stand level characteristics (e.g. mean basal area, relative spacing, quadratic mean diameter, and age). 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 Reynolds error index, weighted by basal area. Final parameter estimation equations were developed for juvenile loblolly pine over 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 Reynolds 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 of the PRM was presented to demonstrate the construction of stand tables from the estimated parameters. The relationships among the maximum likelihood fitted parameters of the twoparameter Weibull distribution and the treatment effects due to fertilization, genetic provenances, and open-pollinated genetic families were also examined. Both the scale and shape parameters differed significantly between the non-fertilized control treatment and the optimally fertilized treatment. 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 than the scale parameter ranks, with the means tending to increase in the non-fertilized treatment and decrease in the fertilized treatment, reflecting the differences in stand development. Year to year rank changes were more minor than long-term family mean rankings. Modeling the Diameter Distribution in Juvenile Loblolly Pine (Pinus taeda L.) from Diverse Genetic Provenances Under Deficient and Optimum Nutrition Regimes by Benjamin Christian Smith A thesis submitted to the Graduate Faculty of North Carolina State University in partial fulfillment of the requirements for the Degree of Master of Science Forestry Raleigh, North Carolina 2007
Bibliographical Information:


School:North Carolina State University

School Location:USA - North Carolina

Source Type:Master's Thesis

Keywords:north carolina state university


Date of Publication:

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