Validation on the accuracy of non-destructive diagnosis devices for the detection of internal wood defects in an urban tree

Abstract

A rise in tree damage caused by internal decay, including breakage and uprooting, especially for trees planted as a street tree in an urban area is of concern specifically for safety issues to human life and property. Although, to predict and proactively respond to such events, structural stability assessment against urban and street trees is being monitored through visual inspection, its difficulty in determining the extent of damage inside trees based solely on such evaluation method requires alternatives that enable to accurately detect and estimate internal structural defects, including cavities and decay. In this regard, non-destructive diagnostic devices, including sonic tomography (SoT) are widely used for estimating internal structural defects of the trees, the accuracy of these techniques varies depending on the tree species, requiring prior reliability analysis of measurement results before field application. Thus, this study aimed to verify whether internal defects in actual wood specimens are accurately reflected by measurements generated by three non-destructive diagnostic devices, including resistance micro-drilling (RESI), SoT and electric resistance tomography (ERT). This was achieved using Prunus × yedoensis that are widely distributed and planted with its popularities in the urban areas of the country. The results showed that the internal structural defects assessed by the wood section inspections were, in general, inappropriately reflected the location and size of the defects with a tendency to under-estimate when compared to those from SoT and ERT, while the RESI was relatively effective for detecting the internal wood decay and cavity the internal structural defects. The findings of this study offer valuable insights as to how measurements obtained from the non-destructive diagnostic techniques should be accurately interpreted for the widespread field application to street trees across the country and further provide a solid foundation for future tree structure evaluations and preventive management practices.