Title page for ETD etd-04142011-115420

Type of Document Dissertation
Author Sabatia, Charles Obuya
Author's Email Address csabatia@vt.edu
URN etd-04142011-115420
Title Stand dynamics, growth, and yield of genetically enhanced loblolly pine (Pinus taeda L.)
Degree PhD
Department Forestry
Advisory Committee
Advisor Name Title
Burkhart, Harold E. Committee Chair
Fox, Thomas R. Committee Member
Radtke, Philip J. Committee Member
Reynolds, Marion R. Jr. Committee Member
Zedaker, Shepard M. Committee Member
  • intraspecific competition
  • diameter distribution
  • height distribution
  • height-age relationship
  • height-diameter relationship
  • genetic uniformity
Date of Defense 2011-03-31
Availability unrestricted
Genetic improvement has been an integral part of loblolly pine plantation forestry in southern United States for about 60 years with focus on improving timber yield, wood quality, and pest and disease resistance. Advances in techniques of genetic selection, breeding, and propagation of planting material have made it possible to achieve genetic gains that are likely to result in significant changes in loblolly pine stand dynamics. Height-age relationships, height and diameter relationships and distributions, and intraspecific competition were investigated in second generation open-pollinated, controlled-pollinated, and clonal loblolly pine with an objective of characterizing the nature and magnitude of changes in these characteristics due to genetic improvement and clonal forestry. Genetic improvement and/or clonal forestry had no practical effect on parameters of the height-age and height-diameter relationships beyond the effect on the asymptote parameter of the Chapman-Richards and Korf equations that were used to model these relationships. Genetic improvement resulted in an increase in the mean of height distribution without a corresponding increase in the mean of the diameter distribution, but had no effect the variance and skewness of the distributions. Thus, growth and yield models in which basal area is a function of height at a specific age (site index) are likely to over predict genetic gains in basal area growth and volume yield. Increase in stand density resulted in an increase in variance of the diameter distribution of non-clonal stands but had no effect on the variance of the diameter distribution of clonal stands. Thus, diameter distribution of clonal stands may differ from that of non-clonal stands after crown closure despite the distributions not being different before and during early stages of crown closure.

This study also evaluated methods that may be used to predict height growth of new genetic varieties and those that may be used to asses intraspecific competition in forest stands. Mixed-model approach of calibrating a height-age relationship to a new loblolly pine clone gave biased estimates for clones that were at the extremes of the distribution of the groups. The use of maximum likelihood with simulated annealing (MLSA) to evaluate competitive interactions among trees in loblolly pine stands gave non-unique estimates of optimum competitor selection radius. A simpler technique that uses Pearson correlations was proposed and was found to work better than MLSA.

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