Abstract
Internal decay and cavities in wood are known to reduce the structural functionality of trees. Such damage may lead to detrimental effects not only on the wood, but also on humans. This is especially the case with old, large trees that are more vulnerable to heavy snow and strong wind. Thus, preventative management (e.g., detecting internal wood defects) is essential. The present study investigated the reliability of noninvasive measurements using sonic tomography (SoT) to detect internal defects in Abies holophylla Maxim. trees and compared the results with measurements using the invasive method of resistance microdrilling (RM). The tomograms were visually compared with tree cross-section images. The results of SoT and RM showed no significant differences, while the explanatory power, as determined by a regression analysis, were considerably high at 67% with a positive correlation between the two methods. In comparison to the cross-section images, the tomograms were found to reflect the size and position of internal decay, although the detected size tended to be larger than the actual decay area. Our findings indicate SoT as a promising noninvasive technique for detecting internal defects in A. holophylla trees.
Highlights
The loss of structural functionality in trees due to internal wood decay or cavities may decrease the value of the trees and may even cause severe damage to humans or property upon heavy snow and strong wind
The defective section on the tomogram of each of the 54 measuring points (MPs) and the defect lengths measured by resistance microdrilling (RM) showed a deviation of approximately 5.6 cm on average
There was no significant difference in the average defect length in wood between the results obtained by RM and sonic tomography (SoT), and the regression analysis showed a high explanatory power of 67%, leading to the conclusion that the two measurement results were consistent with each other
Summary
The loss of structural functionality in trees due to internal wood decay or cavities may decrease the value of the trees and may even cause severe damage to humans or property upon heavy snow and strong wind. Trees that are deemed to have heritage value are important to the general public. It is, important to prevent physical damage through preventive management based on the detection of internal defects. In the past two decades, studies have actively investigated the use of noninvasive techniques to detect internal wood decay or cavities. These techniques include X-ray computerized tomography [1], stress waves [2], and ultrasound [3,4]. SoT should first be verified for reliability in relation to different tree species, as the measurement accuracy may vary according to species-specific wood characteristics
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