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Gewählte Doctoral Thesis:

Michael Grabner (2005): FUNCTIONAL TREE-RING ANALYSIS - Wood as an information source to understand physiological, environmental and technological questions.
Doctoral Thesis, BOKU-Universität für Bodenkultur. UB BOKU obvsg

Data Source: ZID Abstracts
Environmental shifts may lead to physiological responses in tree growth, which also includes adaptations in the wood structure. To study stress responses on wood structure and wood quality dendrochronologically dated tree-ring series have been supplemented with parameters like resin ducts, vessel diameter, appearance of radial cracks, and high contents of extractives in wood. The combination of tree-ring analysis and wood quality research allowed a better understanding of the response-chain environment - physiology - wood formation - wood quality. These insights help improving future utilization of wood according to the demands by end-users. Timber utilization changed over time. On precisely dated wood samples extracted from historical buildings shifts in wood use was found. These findings are important to understand altering wood quality requirements, especially for the species Norway spruce and European larch. An investigation of poplar trees, which have been cut off from groundwater due to a recently erected hydropower plant, showed a clear growth reduction. Alterations were determined in the wood anatomy, i.e. vessel numbers and sizes, by using a novel methodology. A further investigation has shown that physiological processes after long drought periods may lead to a radial cracking in living stems of spruce trees. The formation of such cracks was clearly assigned to climatic extremes, the cracking itself was wood biologically analysed. To comprehend the entire variation within trees a complete stem analysis was performed. The analysis was used to visualize important quality parameters as they alter with stem height and tree age. The strongest annual signal stored in the superficially grown layers on the tree stem was seen with the parameters earlywood-latewood transition, and with intra-annual density fluctuations, respectively. For parameters such as resin duct positions within rings or earlywood-latewood transition the stem analyses were performed for the first time. Finally, the heartwood of larch was another subject of research as the extraordinary high content of extractives directly affects wood density and compression strength. The water-soluble extractives belong chemically to the hemicelluloses and they are deposited in tracheid lumens, filling them almost completely. As these hemicelluloses are non-structural and seen as extractives, proper extraction procedures are needed prior to the radiometric determination of wood density.

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