| Summary: | 碩士 === 國立宜蘭大學 === 森林暨自然資源學系碩士班 === 100 === The wood quality and variations of Taiwan acacia (Acacia confusa), camphor wood (Cinnamomum camphora), and mahogany (Swietenia macrophylla) plantation hardwoods grown in Taiwan were investigated in this study. The mean green moisture content (MC) of heartwood in Taiwan acacia and camphor wood planted in Ilan, Taiwan were significantly higher than those of sapwood. Average MC values of the sapwood and heartwood in mahogany planted in Tainan, Taiwan were almost the same, but both were lower than those of the other two species. The mean values of growth ring width obtained from ring charateristics were respectively 3.76mm, 3.39mm, and 5.44mm for Taiwan acacia (TA), camphor wood (CW), and mahogany (MA). It indicate the growth rate in diameter of mahogany was faster than the other two species. The mean values of ring density were respectively 759 kg/m3, 605kg/m3, and 522kg/m3. The latewood percentage for TA, CW, and MA were 45.8%, 54.7%, and 37.1%, respectively. The growth history and variations of growth ring in radial direction of tree could be accurately determined through the tree ring analysis. The diameter growth increment curve shows a second order equation at different height positions of three test species. Significantly negative correlation in ring width and ring density of MA was observed, while both the relationships for TA and CW were not significant. It reveals the wood quality of mahogany could be affected by growth rate. The variations of crushing strength parallel to grain obtained form fractometer in the radial direction at breast height of test species did not show any specific distribution pattern. Juvenile wood zone judged by wood fiber length were found to be present from the pith to ring number 8, 10, and 15 at 1.3m height of three mahogany trees, respectively. Wider diameter at breast hegith of mahogany tree was associated with higher juvenile wood portion. The distribution patterns of modulus of rupture in the lower height of trunk showed lower bending strength near the pith, then increased toward the bark, and slightly near the bark of three test species. The values of MOR near the pith for the middle height of trunk were the highest, and decrcased toward the bark. However, there was no specific distribution pattern for crushing strength variations in radial direction or along the tree height.
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