VARIATION OF STRESS WAVE VELOCITY, WOOD DENSITY AND STATIC BENDING STRENGTH OF 22-YEAR-OLD PLANTED <em>TECTONA</em> <em>GRANDIS</em> TREES IN NORTHWEST VIETNAM

Abstract

We studied stress wave velocity and wood properties at different radial and axial levels of 22-year-old planted Tectona grandis trees growing in Northwest Vietnam. We measured stress wave velocity of logs (SWV_L) and small clear specimens (SWV_S) obtained from the logs. In addition, we measured air-dry density (AD), modulus of rupture (MOR), and modulus of elasticity (MOE) at 12% moisture content. Within tree, radial position was not a source of variation of stress wave and wood properties, except for MOR. In contrast, the longitudinal variation was highly significant and the most important of variation in SWV_S and MOE. There was statistically significant (0.1% level) but weak correlation (r = 0.36) between AD and MOE, while strong correlation was found between AD and MOR (r = 0.67). The increase of SWV_L and SWV_S may result in significant increase in dynamic modulus elasticity of log (E_L) and MOE, respectively. These results suggest that the stress wave technique could be applied for grading or segregation of the stiffness of timber in teak.