Genetic Variation in Wood Density of Gmelina arborea planted on different sites in Wester Venezuela.

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Title: Genetic Variation in Wood Density of Gmelina arborea planted on different sites in Wester Venezuela.
Author: Espinoza, Jesus Alberto
Advisors: Jose Luis Romero, Committee Member
Gary R. Hodge, Committee Member
Daniel J. Robison, Committee Member
Charles B. Davey, Committee Member
William S. Dvorak, Committee Chair
Abstract: Variation in wood specific gravity from the base to the top of tree and from pith to bark was investigated for Gmelina arborea Roxb. plantations in western Venezuela. Increment cores were taken from 30 trees at five different sections up the stem: 0.1 m, 1.3 m, 1/2 total height, 3/4 total height and at the stem top (10 cm of diameter). These trees were chosen from commercial plantations located at three different sites. Specific gravity was obtained using an X- ray densitometer. The results show that there is an increase in specific gravity from pith to bark. Changes in SG from pith to bark were greater at the top than the bottom of the trees. Slopes of the tendency lines of SG from pith to bark increased from the bottom to the top of tree and they were significantly different at p = 0.012. It was also evident that SG decreased from the base of the tree to 1/2 of the total height, then increased towards the top of the tree. These difference were significantly different at alpha = 0.05. Phenotypic correlations between SG and total height of the tree were very low and ranged from — 0.007 to 0.1 across the three sites. The correlations were non-significant at level alpha = 0.05. In a second study, variation of wood specific gravity among sites and provenances was investigated for Gmelina arborea in four provenance-progeny trials in Venezuela. Eighteen provenances and two controls were evaluated across the sites. Twelve or 5 mm increment cores were extracted from 25 trees in each provenance at every site, with the exception of one trial where 20 samples were taken. Specific gravity was obtained using the gravimetric method. The results indicated that there was high correlation (0.93) among samples taken at 2, 3 and 5 years of age in Gmelina arborea. Variation in wood specific gravity was high among provenances and varied from 0.447 at Muak Lek, (Thailand) to 0.360 at Pawlangyi and Kabaw (Myanmar). A negative correlation between diameter and specific gravity at the provenance level was found, and ranged from - 0.92 to - 0.30 depending on the specific method of calculation.
Date: 2003-06-03
Degree: MS
Discipline: Forestry
URI: http://www.lib.ncsu.edu/resolver/1840.16/1268


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