Analyse der Auswirkungen von Rücke- und Fällschäden bei Rotbuche (Fagus sylvatica L.) auf Basis computertomografischer Bilder : Impact of extraction and felling wounds on European beech (Fagus sylvatica L.) analyzed in computertomographically generated imagery

Alfeld

2016

S. 43-53

Artikel aus einer ZeitschriftUnselbständiges Werk

200199421

In einem Experiment wurden in einem Buchenbestand (Fagus sylvatica L.) im Jahr 2006 durch künstlich angelegte Rindenverletzungen am selben Stamm "Rückeschäden" am Stammfuss (Fläche 442 cm²; 34cm hoch, 13cm hoch, 13 cm breit) und "Fällschäden" in fünf Metern Höhe (Fläche 442 cm²; 68 cm hoch; 6,5 cm breit) simuliert. 2009 wurden die Bäume eingeschlagen und die Stammabschnitte mit den Rindenverletzungen mittels Computertomographie (CT) untersucht. In den CT-Aufnahmen zeigten sich deutliche Störzonen mit veränderten Durchstrahlungseigenschaften im wundnahen Gewebe. In der überwiegenden Zahl der Fälle fanden sich Störzonen mit erhöhter Strahlungstransmission (Typ 1), welche höchswahrscheinlich auf reduzierte Feuchtegehalte im Zusammenhang mit verletzungsinduzierten Austrocknungsvorgängen zurückzuführen sind. Häufig waren aber auch wundparallel ausgerichtete, linienförmige Störzonen mit verringeter Durchstrahlung (Typ 2) zu beobachten.
Schlüsselwörter: Rotbuche, Rindenverletzung, Computertomographie, Störzone, Holzfeuchte
In an experiment with beech (Fagus sylvatica L.), two types of bark lesions were created artificially in 2006 at the same time on each tree to simulate an “extraction wound” (surface area 442 cm²; 34 cm in height, 13 cm in width) at the stem base, and a “felling wound” (442 cm²; 68 cm in height, 6,5 cm in width) at five meters height. In 2009, the trees were felled and the stem sections including the respective bark wounds were subjected to compute tomographic analysis (CT). The CT-generated imagery revealed distinct disturbance zones with diverse X-ray-transmission in the tissue adjacent to the wound surface. The majority of the disturbance zones were caused by increased X-ray transmission (type 1). Most probably, formation of this type of disturbance zone was with reduced moisture content in the wood as a consequence of wound induced dehydration and tylosis close to the wound surface. Furthermore, a large number of CT-images also showed disturbance zones with reduced X-ray transmission (type 2) parallel to the wound surface and linearly oriented aligned with the type 1 disturbance zones. Obviously, these type 2 disturbance zones were associated with increased water content in the course of the compartmentalization process. In comparison, the two types of bark wounds showed significant differences with respect to the frequency and the extent of the developed disturbance zones. Our results indicate, that disturbance zones adjacent to the felling wounds involved a more intense impact compared to the extraction wounds. This affected both the radial expansion of the disturbance zones into the stem tissue adjacent to the respective bark wound as well as the extension along the stem axis beyond the upper and lower margins of the wounds’ surface. However, due to the experimental design we were not able to determine conclusively whether this difference between the two wound types is based on either the wounds’ position along the stem and/or the shape of the respective wound type.
European beech, bark injuries, computer tomography, disturbance zone, water content