Effect of wood properties on within-tree variation in ultrasonic wave velocity in softwood

摘要

The radial variations in the velocity of longitudinal waves propagating through Japanese cedar and Japanese cypress were experimentally investigated. In addition, the tracheid length (T_L), microfibril angle (MFA), air-dried density (AD), and moisture content (MC) were measured in order to determine the effect of wood properties on velocity variations within the wood trunk. For both species, the longitudinal wave velocities measured in the longitudinal direction (V_L) exhibited minimum values near the pith. For Japanese cedar, V_L increased from 3600 m/s toward the bark and soon attained a constant value (=4500 m/s). On the other hand, for Japanese cypress, V _L kept increasing from 4000 m/s near the pith to 4800 m/s at the bark. These radial variations in V_L coincided with those in the tracheid length. V_L exhibited strong correlations with T_L and MFA with a significant level of (p < 0.01). These findings suggest that the T_L and MFA greatly affect the radial variation in the ultrasonic wave velocity in softwood.