1. Tree growth and juvenile wood formation*
Tree growth and juvenile wood formation

2. Mature wood development
Time
mature wood
juvenile 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/juvenile wood
sapwood/mature wood
heartwood/mature wood

5. Physiology of juvenile wood formation
(Josza)

6. Juvenile wood – characteristics and properties*
Juvenile wood – characteristics and properties
Anatomy
Wider growth rings
Thinner cell walls
Less latewood
Shorter longitudinal tracheids
More spiral grain
Ultrastructure
Larger S2Ө
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 mw jw
(Josza)

9. (Mansfield)

10. Longitudinal tracheid length in second growth Douglas-fir (at breast height)
(Forintek)

11. Juvenile wood vs. Mature wood
Wood Property
Juvenile wood
Mature wood
Density (kg/m3)
427
489
Fiber length (mm)
2.98
4.28
Cell wall thickness (µm)
3.88
8.04
S2Ɵ (°) 55 20
Longitudinal shrinkage (%)
0.90
<0.10
Modulus of Rupture (psi)
7,700
10,660
Modulus of Elasticity (106 psi)
1.12
1.75

12. 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)

13. Juvenile wood (first 20 years of growth) marked on 50 year-old Douglas-fir log ends and visible on lumber ends.
(Forintek)