Variation in Selected Juvenile Wood Properties in Four Southern Provenances of Loblolly Pine

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Title: Variation in Selected Juvenile Wood Properties in Four Southern Provenances of Loblolly Pine
Author: Belonger, Paul J.
Advisors: Dr. Steven E. McKeand, Chair
Dr. Floyd Bridgwater, Member
Dr. J.B. Jett, Member
Dr. Elisabeth A. Wheeler, Member
Abstract: Gravimetric wood density, x-ray densitometry, and latewood tracheids were used to investigate the relative importance of genetic and environmental effects on various assessments of wood density, tracheid characteristics, and growth traits in loblolly pine (Pinus taeda L.). Breast-height wood samples were taken from four 12-year-old plantings of a genetics trial that included approximately 50 open-pollinated families of loblolly pine from diverse sources. The densitometry and tracheid analysis included wood samples from only two of the test sites and assessed variation in 51 families, and 38 families, respectively. Moderate provenance differences, but strong family and environmental differences were found for wood density and volume, and the pooled genetic correlation between volume and density was -0.30. The Atlantic Coastal and Lower Gulf sources had higher average wood density than the Marion County and Gulf Hammock sources, and the Lower Gulf source had the lowest stem volume. Provenance variation in wood density was not consistent with geographic trends indicating a need for field testing in the area of intended deployment. Location effects were very important and sites which promoted high volume production also appeared to cause low wood density. Strategies are available to combat the unfavorable negative environmental correlation (-0.91, P < 0.01) between stem volume and wood density. Provenance variation was important for disk densities of early ring segments, but diminished with age and was not significant (P > 0.10) beyond the segment consisting of rings 3-6. Pooled narrow-sense heritability estimates for the consecutive-ring group disk densities ranged from 0.142 to 0.225, and all groups were highly correlated with average (tree) disk density (rA > 0.90). Mean latewood density and mean latewood percent both showed a strong positive genetic correlation with average disk density and the disk density of the ring 3-5 segment. Early selection for disk density can be effective.The transition to &quot;mature&quot; wood occurred at ring number 5.9 at the flatwoods location with higher wood density and ring number 8.9 at the upland test site with lower density. The point of transition also showed a strong provenance component (P < 0.05); the higher density Atlantic Coastal and Lower Gulf Coastal Plain sources transitioned sooner than the lower density Gulf Hammock and Marion County sources. Trachied length, total diameter, lumen diameter, and cell wall thickness were measured using outer-ring latewood tracheids. Of the trachied traits, only cell wall thickness showed a marginal location effect (P < 0.10). Measured in the middle-third of the cells, tracheids sampled at the Florida location were about 11% larger in total diameter, lumen diameter, and cell wall thickness, but no difference was detected for tracheid length. Provenance differences were strongest for cell wall thickness (P < 0.01) and marginally important for tracheid length (P < 0.16) and total cell diameter (P < 0.18).Variation among families within provenances was large (P < 0.01 for all tracheid traits) and resulted in relatively high narrow-sense heritability estimates of 0.58 for length, 0.34 for total diameter, 0.22 for lumen diameter, and 0.37 for cell wall thickness. The genetic correlations among these traits were all greater than 0.69 except the correlation between length and lumen diameter which was 0.42. Measurement of tracheid length can be used to assess family differences for cell diameter and cell wall thickness.None of the tracheid traits were strongly correlated with average disk density or the disk density of rings 3-5. Therefore, genetic selection for high average density in 10 to 12 year-old loblolly pines from the provenances studied here will not produce a predictable pattern in the character of outer-ring latewood tracheids.
Date: 1998-10-27
Degree: MS
Discipline: Forestry

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