DETECTION OF DECAY IN TREES WITH STRESS WAVES AND INTERPRETATION OF ACOUSTIC TOMOGRAMS

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Abstract
Summary Cross-sectional maps of stems of beech, Horse chesnut and Norway maple affected by Ganoderma adspersum (Schulz) Donk, Pleurotus ostreatus (Jaquin: Fr.) Kumm and Kretzschmaria deusta (Hoffm.: P. Martin) (=Ustulina deusta (Fr.) Petrak), respectively showing fungal decay were obtained from living trees. Zones of altered fresh- and dry- matter density were constructed, and these compared with Picus® acoustic tomograms of the same cross-sections. The studies shown demonstrate that within a sample cross-section, a zone of decay can be determined accurately for its size and moderately accurately for its position. The shape of the sample cross section influences the accuracy of the acoustic tomograms. Thus the greater the deviation from a circular outline, the poorer the accuracy. Likewise, the number of sensors naturally affects the accuracy. Wood decay caused by Kretzschmaria deusta can be detected by the Picus® acoustic tomograph. The resolution of the tomograms is still worthy of improvement as reaction zones cannot yet be represented, despite their high density. Although capable of improvement in some respects, the Picus® acoustic tomograph currently offers a very good diagnostic support for evaluating the condition of trees and hence their resistance to fracture.

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