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UBC Theses and Dissertations

Visualization of the spatial variation of wood density in Western Hemlock Henze, Kim-Jana


Previous studies of the within tree variation in density of western hemlock have constructed 2 dimensional maps of the variation in wood density from pith to bark and longitudinally within the tree, and have concluded that wood from the outer part of the stem is denser than wood found near the centre of the tree, and wood density decreases with tree height. Based on such information it should be possible to segregate wood from the outer, basal, parts of the tree stem following primary conversion and allocate it to end uses requiring hardness and higher strength. This premise assumes that circumferential variation in wood density in hemlock is insignificant, and such information is not available for western hemlock. This study mapped the density of the lower 5 m of four second-growth western hemlock stems in the x, (radial), y, (longitudinal) and circumferential (Θ) directions to determine their relative contributions to the overall pattern of density variation in hemlock stems. Computational and advanced visualization techniques were used to create 3-dimensional models of the spatial distribution of density in the hemlock stems. Circumferential variation in density was not significant, and previously established wood density trends from pith to bark and with height in the stem were confirmed. 3-dimensional images showed higher density wood in the outer part of the stem but the highest density wood did not form a continuous sheath in this part of the stem. Nevertheless, it should still be possible to utilize denser wood from the outer part of the tree for end uses requiring higher strength and hardness. Two novel and previously unreported features were observed. Firstly it appeared that the shape of the lower density juvenile wood core was cylindrical irrespective of the external shape of the stem. Secondly in one tree there was circumferential, helical variation in wood density with increasing height in the tree. It would be desirable to confirm whether these features are commonly found in western hemlock by examining greater numbers of trees.

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