Wood—the Internal Optimization of Trees

Mechanical bending stress due to wind exposure has been suggested to be of major importance for induction of resin pockets in gymnosperm trees. In this study, this idea was tested experimentally by applying bending stress to 1-year-old internodes of five-year-old Pinus sylvestris L. seedlings during dormancy and/or growth. The stems were bent manually to 30° from their original upright position at regular intervals. About 30 % of the stems that were bent during growth were wounded in the xylem, whereas no wounding was observed in control stems or stems bent during dormancy. Similarity of these wounds to naturally-occurring resin pockets leads us to conclude that exposure of seedlings to mechanical bending stress due to wind during growth can be a source of formation of resin pockets.

Section: Resultsmentioning

confidence: 99%

Induction of Resin Pockets in Seedlings of Pinus sylvestris L. by Mechanical Bending Stress during Growth

Temnerud¹,

Valinger²,

Sundberg³

1999

“…In optimizing the design of technical components, the morphology of trees has already been successfully introduced as a model (Mattheck and Kubler 1995). The development of new methods to produce synthetic materials with improved properties based on biological materials and principles, often called biomimetics, also draws on wood.…”

Section: Introductionmentioning

confidence: 99%

Wood-Derived Porous Ceramics via Infiltration of SiO2-Sol and Carbothermal Reduction

Klingner¹,

Sell²,

Zimmermann³

et al. 2003

The use of wood as a structure-giving material may be the key to producing temperature-resistant ceramics featuring high and directed porosity combined with necessary strength. The objective of this study was to develop a simple process to convert the evolutionarily optimized material wood into highly porous ceramics. Beech and pine, known to be relatively permeable, were pyrolyzed in a nitrogen atmosphere. The carbon-templates formed were infiltrated with various kinds of silica sol (SiO 2 ). The resulting SiO 2 /C composite was transformed into a SiC-ceramic (silicon carbide) via carbothermal reduction. Through the described process the macroscopic pore-structure of wood was transformed exactly into SiC. The SiC-ceramic produced proved to be thermo-resistant. It remained stable in oxygen atmosphere at 1200°C, after a SiO 2 coating around the SiC had been formed. This study focused on the alteration of the cell wall microstructure during the conversion of wood into SiC. Furthermore, the optimization of the individual process steps, pyrolysis, infiltration and ceramization along the most efficient route was pursued.

“…They are important and necessary for tree growth, especially for the tree form (Wilson and Archer 1979;Yoshida et al 1994Yoshida et al , 1999Fournier et al 1994;Gartner 1997). Growth stresses help trees to reorient themselves to a more favorable position, and by acting as a pre-stressing system against the compressive stress that acts upon the trunk in the direction opposite to that of the wind, they reduce the high risk of fiber buckling (Kubler 1987;Mattheck and Kubler 1995). However, residual stress resulting from the growth stress imposed on the trunk, is one cause of the crooking and checking that occur in lumber (Okuyama and Sasaki 1979;Kubler 1987;Tejada et al 1997).…”

Section: Introductionmentioning

confidence: 99%

Techniques for Measuring Growth Stress on the Xylem Surface Using Strain and Dial Gauges

Yoshida¹,

Okuyama²

2002

Growth stress (growth strain) in trees is usually evaluated using either a strain gauge or a dial gauge to measure the strain release. We summarize the techniques used to assess growth stress and compare the two methods. The dial gauge method measures change in distance between two pin targets when growth stress is released by sawing two grooves; from this the strain released is calculated. The absolute values of the strain released depended on whether the two grooves were sawn inside or outside the pin targets: the values in the first case were approximately twice those in the latter. If the grooves were sawn outside the pin targets, the values for the strain released were about the same as with the strain gauge method, in which the strain released by sawing a groove at each end of a strain gauge is measured. The released strain values were consistent when the strain gauge was glued to the outer surface of the secondary xylem after first fully removing the differentiating xylem. To release most of the surface growth stress and maximize released strain values, the optimal distance between the ends of the strain gauge and the grooves cut to release the growth stress was 3 to 5 mm, and the optimal depth of the groove was 5 to 10 mm. Most of the growth stress was released immediately when the grooves were sawn.