The justification for development of elite loblolly pine (Pinus taeda L.) genotypes includes potential increases in stand uniformity and reduction in planting densities and corresponding establishment costs. However, some genotypes produce less desirable characteristics than others. The ability to realize full potential genetic gains is dependent on selecting appropriate combinations of genetic material and silvicultural management. In 2008, a study was established in the upper coastal plain of Mississippi to examine the performance of two varietal loblolly pine genotypes, a “crop tree” ideotype (CROP) and a “competitor” ideotype (COMP), at two levels of management intensity and three different initial tree spacings. After nine growing seasons, differences in crown morphology, top dieback frequency, and growth and yield variables are apparent between genetics and silvicultural intensity. The COMP ideotype had, on average, greater crown volume, less acute branch angles, and LAI than the CROP ideotype. Increasing management intensity had greater impact on crown characteristics than genotype. Current annual increment growth of stem wood was statistically higher in the COMP ideotype under intensive management and lowest stocking level. The interaction of ideotype, management intensity and spacing level significantly impacted growth and yield. The COMP ideotype is projected to produce greater volume than the CROP ideotype on this site. There was no significant difference between ideotypes with respect to specific gravity for any combination of cultural treatments. Instances of top dieback were significantly higher in the CROP ideotype across management and spacing levels. Nutrient sufficiency levels for fast growing loblolly pine and foliar levels in the current study were statistically significant. Differences due to management intensity were related to reduced competition and lower incidence of damage. The results of this study provide a reference point for elite loblolly pine under different silvicultural regimes for landowners interested in performance potential in Mississippi’s upper coastal plain.

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Ph. D. / incomplete_metadata

Ovariole development and termination of diapause in the white pine weevil were studied by dissecting weevils at various intervals throughout the winter. Old-generation adults brought into the laboratory November produced viable eggs within 5 days. New generation adults brought into the laboratory on November 4 produced viable eggs during November. Viable eggs were deposited by other new-generation adults after 10 to 15 day. at room temperature in winter. On each of the 3 collection date studied, new generation adult produced viable eggs without copulating after collection from hibernation indicating that capulation occurs in the fall. There was no evidence of progressive ovariole development throughout the winter. New generation adults which were isolated as soon as they emerged from the shoots and maintained at constant room temperature had poorly developed ovarioles by November 20 and produced no eggs. Weevil flight and dispersal through a white pine plantation was studied by releasing 409 marked weevils at a central point within a l431-tree plantation and checking every tree at 5-day intervals. Weevils flew readily at the time of re1ease. Marked weevils were recorded throughout the plantation. which extended as far as 330 feet from the release point. A few weevils were observed on scattered white pines 200-300 yards from the release point beyond a hardwood barrier. Total numbers of weevils present on the leaders increased from April 26 to May 5, after which numbers steadily decreased. By June 15, only 20 weevils were observed on the leaders. / Ph. D.

The hypothesis that stressed loblolly pine (Pinus taeda L.) could be distinguished from non-stressed loblolly pine by increased foliage temperatures was tested. The foliage temperatures of seedlings and trees were measured with an AGA Thermovision 680 system, imported by the AGA Corporation, Secaucus, New Jersey. The AGA Thermovision 680 system is a simple, easily transported remote sensing system for detecting relative apparent temperatures of plant foliage without direct contact with the leaves. This system is sensitive to infrared wavelengths in the 2-5.6 micron region of the electro-magnetic spectrum. Foliage temperatures in loblolly pine seedlings increased within one week of stress induced by drought, flooding, or severing. Increased temperatures of stressed seedlings were associated with reduced needle moisture content prior to visual symptoms of stress. Foliage temperatures of loblolly pine trees stressed by severing the bole were warmer relative to neighboring control trees. Increased temperatures were detected within one week after severing. Previsual detection of stress can be achieved by measuring foliage temperatures of loblolly pine. The AGA Thermovision should prove to be a useful tool for non-destructive sampling of plant stress, for locating stressed trees, and potential bark beetle infestations. / Ph. D.

Loblolly pine (<i>Pinus taeda</i>) productivity on wet flats of the lower coastal plain of Virginia is largely affected by the presence of high water tables and infertile soil. Site preparation by bedding and ditching can alleviate high water tables and increase aerated soil rooting volume, enhancing pine productivity. Fertilizing and liming may improve soil fertility by increasing available nutrients and soil pH. The purpose of this study was to evaluate two widely used site preparation methods, bedding and ditching, and to study the effects of fertilizer added at plantation age 9 years. Three site preparation treatments, on jurisdictional wetlands near Franklin, VA, were evaluated for their effects on water table depths and rotation-aged loblolly pine growth and yield. The study consisted of three blocks of three 4-ha plots each; all blocks had been harvested and chopped and burned in 1969. The treatments were none (control), bedded and ditched. In 1978, fertilizer treatments were applied to four-O.l0 ha subplots in the center of the 4-ha plots. Treatments were none (control); P; N and P; and N, P, and lime. Water table levels were measured biweekly during the growing season and monthly, thereafter, for the first three years and at age 23 years. A 12.5-percent inventory of overstory diameters with a subsample of total heights was completed for all species on each plot. / Master of Science

The influence of thinning at age eight on the photosynthetic rate, needle conductance, xylem water potential, water use efficiency and growth of loblolly pine trees was studied during their ninth and tenth growing seasons. Litterfall dynamics were monitored throughout the study period as well. At the end of the second post-thinning growing season, trees in thinned plots had greater stem diameters, greater live crown ratios, greater live crown diameters and greater average volumes and basal areas than did trees in control plots. Significant physiological changes due to thinning were observed only in the lower crowns where needles were found to adapt to the sudden increase in available light by adjusting their physiology to resemble that of sun needles. Lower crown photosynthesis and needle conductance in thinned plots were more similar to upper crown values for these parameters than to lower crown, control plot values. Foliage produced during the current year and measured after full elongation had a higher average photosynthetic rate, needle conductance and lower average water potential than did foliage in its second growing season during both 1988 and 1989. Additionally, the water use efficiency of current-year foliage was significantly greater than that of the second-year foliage. In both thinned and control plots, significant diameter growth and photosynthesis continued throughout the dormant season although at a slower rate than during the growing season. Litterfall timing did not differ between thinned and control plots, nor did the amount of litterfall per unit basal area during the first year following thinning. Partial second-year data suggest that subsequent litterfall amounts will mirror the greater average crown size in thinned plots. / Master of Science

Master of Science

Although there remains some controversy as to the benefits of individual tree growth and yield prediction models over stand-level models, individual tree models still have wide acceptance. A generalized thinning response variable which can account for the intensity of thinning, as well as the age of the stand at the time of thinning and the time elapsed since thinning, was applied to two existing models for loblolly pine (Pinus taeda) in cutover site-prepared plantations. A site index equation for predicting mean total height of dominant and co-dominant trees and a diameter increment model were developed to incorporate the thinning response variable. New fits of height increment and mortality functions to the available data were also completed. Separate mortality functions were fit to data from unthinned and thinned stands. The base models for this analysis were from the individual tree growth simulation model PTAEDA2. Evaluations for predictive ability of these models were done in a reduced version of the growth simulator which was modified to accept external data. The mean total height model had improved predictive ability over the original PTAEDA2 model for this variable. The diameter increment model produced no significant improvement in simulation comparisons. Fitting the two mortality functions to the multiple observation data resulted in the reduced predictive ability of the simulator compared to the original mortality model from PTAEDA2 which was fit to data from unthinned stands only. / Master of Science