The quality of wood in 47-year-old standing trees of Japanese cedar grown in five plantation sites with different spacing (A, 1 X 1 m; B, 2 X 2 m; C, 3 X 3 m; D, 4 X 4 m; E, 5 X 5 m) was evaluated using stress-wave and ultrasonic-wave propagation methods. The magnitude of the velocities of these waves and the calculated dynamic modulus of elasticity (MOE) were used as indexes for assessing wood quality in standing trees. Results indicated that plantation spacings had moderate influence on the stress-wave and ultrasonic-wave velocities, and the degree of influence varied with the wave-propagating direction. Regardless of the testing method used, the velocities of waves propagated parallel to the grain in the standing trees with medium and poor growth conditions were significantly greater than those with superior growth conditions. The dynamic MOE of the trunk of standing trees of Japanese cedar was calculated by adjusting the effective mobility of free water and effective density in the trunk at various moisture contents. Results indicated that the dynamic MOE of wood in the standing trees of Japanese cedar was affected somewhat by the testing methods used. Furthermore, the dynamic MOE of the wood in the standing trees varied with the growth conditions imposed.
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