Nondestructive Evaluation of Crushing Strength of Young Taiwania Trees Grown Under Different Thinning and Pruning Treatments Using a Fractometer

The effects of different thinning and pruning methods on the crushing strength of young Taiwania trees (Taiwania cryptomerioides Hay) using a fractormeter were investigated. The method of study was to explore the crushing strength of incremental cores as an alternate nondestructive testing method. The average crushing strength in the thinning treatments revealed the trend of no thinning > medium thinning > heavy thinning, indicating that thinning reduced the average compressive strength. The average compressive strength in the pruning treatments showed the following trend: medium pruning > no pruning > heavy pruning. A better average compressive strength of trees was obtained from wood subjected to no thinning and medium pruning treatments. However, most results showed no statistically significant differences among thinning and pruning treatments. Transverse variations in the average crushing strength decreased from the pith outwards to 3.6 cm, and then gradually increased to 12.6 cm. Finally, strength showed a gradual decrease toward the bark. Generally speaking, the average crushing strength increased linearly with increasing distance from pith by linear regression. Observations of testing incremental core specimens and its validity are discussed in this study.