G. Koch, J. Bauch, J. Puls, E. Schwab
Biological, Chemical and Mechanical Characteristics of "Wulstholz" as a Response to Mechanical Stress in Living Trees of Picea abies [L.] Karst
Summary
In the present study, the biological, chemical and mechanical wood properties of “Wulstholz” as a
response to mechanical stress of spruce trees (Picea abies [L.] Karst.) were investigated. “Wulstholz” is
formed locally on the compression side of overstressed tree trunks after slip planes were initiated. It is
characterized by an increased xylem production leading to bulges. The S2-layers of “Wulstholz”-tracheids
are thicker than the corresponding cell wall layers in normal wood, and the cell lumen diameter
is significantly reduced. The tracheid length decreases gradually from an average of 4 mm to 2.5 mm
compared to normal wood, and the tracheids conspicuously are shifted against each other longitudinally.
“Wulstholz” contains a higher concentration of lignin than normal wood, whereas the concentration
of glucose in the hydrolysates is reduced. The hemicelluloses-concentration, particularly the mannose-content,
is significantly higher compared to normal wood. The compression strength and the modulus of
elasticity, despite a higher density, are significantly reduced in “Wulstholz” in comparison to normal
wood. But due to the specific anatomical and chemical properties, “Wulstholz”-tracheids can be
deformed and compressed considerably without fracturing. The investigations demonstrate that “Wulstholz”
can restabilize wind-exposed trees.
Holzforschung, Walter de Gruyter
Print ISSN: 0018-3830
Volume: 54, 02/2000
Pages: 137 - 143
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