Relations of fiber length to within-tree variation of ultrasonic wave velocity in fast-growing trees

The within-tree variation of longitudinal wave velocities in Acacia auriculiformis (AA), Eucalyptus dunnii (ED), and Melia azedarach (MA) was experimentally investigated. The velocities in the longitudinal direction (VL) exhibited a minimum value near the pith. The minimum values in AA, ED, and MA were measured to be 4000, 4600 and 3600 m/s, respectively. VL increased from the pith to the bark. On the other hand, the velocities in the radial and tangential directions exhibited constant values. The radial variation patterns of the VL coincided with those of fiber length (FL). VL exhibited a strong correlation with the FL at a 1% significant level. These findings revealed that wood properties such as FL greatly influence the velocity in the longitudinal direction.