Vorlesung Waldwachstumskunde. Bio-Mechanik am Baum. Zusammenstellung: O.U. Bräker Swiss Federal Research Institute WSL, CH-8903 Birmensdorf

Transkript

1 Vorlesung Waldwachstumskunde Bio-Mechanik am Baum Zusammenstellung: O.U. Bräker Swiss Federal Research Institute WSL, CH-8903 Birmensdorf

2 Übersicht: Übungen Biologie und Mechanik Reaktionsholz 1-3 Ringschäle Zuwachsanpassungen Stützwurzeln Drehwuchs O.U.Bräker, WSL, Vorlesung Waldwachstumskunde

3 Übungen: Was will die Bio-Mechanik aufzeigen? Entdecken Sie selbst mechanistische Funktionen und Prozesse am Baum: Ursache? Ausformung? Betroffene Organe? Vor- / Nachteile? Reaktionsgeschwindigkeiten? O.U.Bräker, WSL, Vorlesung Waldwachstumskunde

4 Biologie und Mechanik: Figure 1: Major tree parts and their mechanical and biological functions. Mattheck, C, 1991, p. 4. Quelle: Mattheck C, Trees. The Mechanical Design. Springer-Verlag Berlin, 121 S O.U.Bräker, WSL, Vorlesung Waldwachstumskunde

5 Reaktionsholz 1: Figure 6: If the whole stem is bent (A), it correctively bows along its length. If the leading shoot breaks, it suffices in most cases to put the replacing side branch upright (B) and rearrange the center of gravity of the crown above the root stock. Mattheck C, 1991, p O.U.Bräker, WSL, Vorlesung Waldwachstumskunde

6 Reaktionsholz 2: Figure 58: The effect of reaction wood in a slanted tree. A: The compression wood of gymnosperms expands in the axial direction and pushes the tree into vertical position. B: The tension wood of angiosperms shrinks in the axial direction and pulls the tree into vertical position. Quelle: Mattheck C, Kubler H, 1995: Wood - The Internal Optimization of Trees. Springer, p O.U.Bräker, WSL, Vorlesung Waldwachstumskunde

7 Reaktionsholz 3: Figure 7: Gymnosperms are pushed upwards into the vertical position by formation of compression wood at their lower sides facing the soil. Angiosperms are pulled into position by forming of tension wood at their upper sides facing away from the soil. Mattheck C, 1991, p O.U.Bräker, WSL, Vorlesung Waldwachstumskunde

8 Ringschäle: Shear stresses between tree rings - a risk and its natural avoidance: Annual tree rings consist of softer, more porous early wood and stiffer and denser late wood. Neighbouring early wood rings are likely to delaminate along their interfaces if exposed to shear stresses. This axicircumferential ring trajectory coincidence avoids the risk of shear stresses and bending and shear are converted into tension or compression. Mattheck C, 1991, p O.U.Bräker, WSL, Vorlesung Waldwachstumskunde

9 Adaptive Growth: Bio-Mechanik am Baum Zuwachsanpassungen: Mechanische Zuwachsanpassungen aufgrund zusätzlicher äusserer Bedingungen. Mattheck C, 1991, p O.U.Bräker, WSL, Vorlesung Waldwachstumskunde

10 Stützwurzeln: Buttress roots - Why they grow: If small roots running vertically (sinker roots) are directly below the stem (A), the main force flow runs down to enter the soil near the stem axis. With wind increase, the lateral end of the horizontal roots are added (B). A rope (C) connecting root tip and stem would be a suitable mechanical aid in transmission of forces. Buttress roots formed by dominant upper-side growth (D) are the natural counterparts. Mattheck C, 1991, p O.U.Bräker, WSL, Vorlesung Waldwachstumskunde

11 Drehwuchs: Spiral Grain - a relief mechanism in response to bending stresses: In pines, beeches and others, significant geotropic corrections and high internal bending stresses are accompanied by twisted growth, spiral grain of the stem. Non-circular beams under bending loads tend to twist or tilt out of plane to increase their flexibility. At bottom side, reaction wood is formed, the angle (A-A ) reveals degree of twisting. Mattheck C, 1991, p O.U.Bräker, WSL, Vorlesung Waldwachstumskunde