Adaptive growth

• Taper of the stem: adaption to mechanical load situation

• Säbelwuchs, Fold away from wind

• Adaption of the tree form (e.g. interaction with the environment)

• Local stress situation determines how much the tree grows

• Adaption of the tree form

• Adaption by assymetric growth e.g. because of wind loading from one direction

• Wind loading from one direction can result in compression wood formation

• not neccessarily reaction wood if eccentric growth

• Optimization of root form

• Adaption at materials level: Cell wall thickness, MFA cellulose orientation

• Bening loads predominantely in one direction —> Ovalization

• Wind

• Own weight

• Direct deflection

• Changing response to wind loads as function of tree age

• old tree: Small MFA makes the stem stiffer, can not escape anymore, makking more material on one side

• small tree: verbiegt sich (possible because of MFA and entire form of tree)

• Juvenile wood: High MFA, low stiffness

• Adult wood: Low MFA, high stiffness

• MFA stable after 10 years

• Density differences

• needs to stay upright

• tree makes stiff band to keep it upright

Main difference in earlywood density (lower in normal wood)

Heartwood formation and/or defence reaction

Closure of bordered pits in SW

Closure of transport channels in HW (simple perforations, perforation plates)

Efficient mechanism to clog vessels

Axial parenchyma cells surrounding vessels

• sapwood trees: No heartwood formation e.g. birch, maple, beech ash (may form false heartwood)

• Reifholzbäume: Trees with heartwood formation, but no colour difference (spruce, fir)

  • cracks in the inner part because they are dryer in the inner part

• Heartwood trees: Trees with coloured heartwood , increase in durability (oak, black locust, pine, larch)

Genetically determined

Physiological changes also without colour changes

Parechyma cells die off: beforehand enhanced parenchyma cell activity in a transition zone between sapwod and heartwood

Starch is converted into extractives

Many hardwood trees form tylosis

Water content is reduced

Not following the growth rings

loss of branches can cause that

Only lumina impregnated with extractives —> no increase in durability