Non-destructive monitoring of early stages of white rot by Trametes versicolor in Fraxinus excelsior

Abstract

Abstract• Non-destructive detection of fungal decay in living trees is relevant for forest management of valuable species, hazard tree assessment, and research in forest pathology. A variety of tomographic methods, based on stress wave timing, radioactive radiation, or electrical resistivity have been used to detect decay in standing trees non-destructively. But apart from mobile gamma ray computed tomography (Habermehl and Ridder, 1993) which is virtually unavailable, the detection of incipient stages of decay is still not possible.• Wood moisture and electrolyte content influence the electric resistivity of wood. Both are changed by fungal decay. Therefore electric resistivity tomography (ERT) should detect decay in its early stages. Then it could be used to monitor the spatial and temporal progress of degradation.• We infected four Fraxinus excelsior trees with Trametes versicolor using wooden dowels and measured two-dimensional electric resistivity tomograms 3, 10, 13 and 21 months after infection. Immediately after the last electric resistivity measurement trees were felled for further analyses of stem cross-sections. Wood moisture content and raw density had significantly increased in infected areas, but dry density had not significantly changed after 21 months. Areas of very low electric resistivity around the infected wounds correlated very well with infected wood in the stem cross-sections. Increasing areas of low electric resistivity around the infected wounds during consecutive measurements indicate increasing areas of infected wood.• We conclude that the growth of white rot by Trametes versicolor can be monitored with electric resistivity tomography (ERT) beginning from incipient stages, even before wood density decreases. ERT could therefore be a powerful research tool for decay dynamics as well as a method for diagnosing wood decay in forestry and arboriculture.Mots-clés : développement / ERT / contrôle / tomographie / pourriture fongique du bois Résumé -Contrôle non destructif des premiers stades de la pourriture blanche de Trametes versicolor chez Fraxinus excelsior.• Le contrôle non destructif des champignons de la pourriture du bois dans les arbres vivants est pertinent pour la gestion forestière des essences précieuses, l'évaluation des risques de l'arbre, et la recherche en pathologie forestière. Une variété de méthodes de tomographie, sur la base d'onde de contraintes cadencées, des radiations radioactives, ou de la résistivité électrique ont été utilisés pour détecter la pourriture des arbres sur pied de façon non destructive. Mais, en dehors de la tomographie à rayon gamma mobile (Habermehl et Ridder, 1993) qui est pratiquement indisponible, la détection des débuts de pourriture n'est pas encore possible.• L'humidité du bois et le contenu électrolytique influence la résistivité électrique du bois. Les deux sont modifiés par la pourriture fongique. Par conséquent, la tomographie de résistivité électrique (ERT) devrait détecter la pourriture à ses débuts. Ensuite, elle pourrait être utilisée...

Multiscale geophysical imaging of the critical zone

“…For example, sapwood and hardwood have been imaged using ERT with electrodes in direct contact with the tree trunk to improve transpiration estimates [ Bieker and Rust , ]. ERT has also been used to image tree rot [ Bieker et al ., ], and Jones et al . [] demonstrated the ability to track changes in moisture content of trees with NMR in 2‐D.…”

Electric resistivity tomography shows radial variation of electrolytes in Quercus robur

“…Healthy specimens of other species have patterns of electric resistivity differing from that of oak trees al Hagrey 2006;Bieker et al 2010). Therefore, further investigations should concentrate on the species-specific variation of electric resistivity within the stem cross section.…”

“…They used geophysical instruments and adapted mathematical algorithms to trees. In the following years, ERT was applied to find discolored wood Weihs 2001), decay in trees Nicolotti et al 2003;Rust et al 2007;Martin 2009;Bieker et al 2010), and root detection (Bieker et al 2008). New reconstruction algorithms (Günther et al 2006) have improved the result further by using the exact shape of the measuring level.…”

On the use of X-ray computed tomography for determining wood properties: a review1This article is a contribution to the series The Role of Sensors in the New Forest Products Industry and Bioeconomy.

“…One of these is electric resistivity tomography (ERT), which is originally a geophysical method that is based on the material electric resistivity or its reciprocal, electrical conductivity, both being related to object structure. ERT was applied to identify discoloured wood (Weihs 2001) and decay in trees (e.g., Bieker et al 2010). However, according to Harding et al (2007), the resulting ERT images are rather coarse in the case of logs and reliable results can only be achieved at a maximum depth of six or seven growth rings.…”