Tree growth and juvenile wood formation

1
Tree growth and juvenile wood formation

2
Mature wood development
Time
juvenile wood
mature wood
3
Juvenile wood Wood formed by the vascular cambium
under the prolonged influence of the apical
meristem in the live crown. Also know as core
wood and crown wood. Juvenile wood is formed
throughout the life of the tree not just in young
trees. Mature wood is formed by the vascular
cambium lower down the stem where the influence
of the live crown is much less. Juvenile-mature
wood distinction is completely different from
heartwood-sapwood distinction
(Josza)
4
Juvenile wood-mature wood vs. heartwood-sapwood
sapwood
juvenile wood
heartwood
mature wood
sapwood/juvenile wood
heartwood/juvenile wood
sapwood/mature wood
heartwood/mature wood
5
Physiology of juvenile wood formation
(Josza)
6
Juvenile wood characteristics and properties

• Anatomy
• Wider growth rings
• Thinner cell walls
• Less latewood
• Shorter longitudinal tracheids
• More spiral grain
• Ultrastructure
• Larger S2?
• Chemistry
• More lignin
• Less cellulose
• Hemicelluloses differ

• Properties
• Lower wood density
• Lower strengths
• Greater longitudinal shrinkage
• Paper strengths
• burst, tensile ?
• tear ?

7
Juvenile/mature wood ring profiles
(Josza)
8

Microfibril angle
(Josza)
9
(Mansfield)
10
Longitudinal tracheid length in second growth
Douglas-fir(at breast height)
(Forintek)
11
The transition from juvenile wood to mature wood
is not sudden as might be interpreted from some
graphical representations. The transition is
gradual as the right stem profile illustrates.
(Josza)
(Haygreen Bowyer)
12
Juvenile wood (first 20 years of growth) marked
on 50 year-old Douglas-fir log ends and visible
on lumber ends. (Forintek)