Transcript (7) Juvenile wood - Wood Anatomy and Identification

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Tree growth and juvenile wood formation
1
Mature wood development
Time
mature wood
juvenile wood
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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 heartwoodsapwood distinction
(Josza)
3
Juvenile wood-mature wood vs. heartwood-sapwood
sapwood
juvenile wood
heartwood
mature wood
sapwood/juvenile wood
sapwood/mature wood
heartwood/juvenile wood
heartwood/mature wood
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Physiology of juvenile wood formation
(Josza)
5
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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 ↓
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Juvenile/mature wood ring profiles
(Josza)
7
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Microfibril angle
mw
jw
(Josza)
8
(Mansfield)
9
Longitudinal tracheid length in second growth Douglas-fir
(at breast height)
4.0
Cell length (mm)
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0
5
10
15
20
25
30
35
40
45
50
Rings from pith
(Forintek)
10
Juvenile wood vs. Mature wood
Wood Property
Juvenile
wood
Mature
wood
Density (kg/m3)
Fiber length (mm)
427
2.98
489
4.28
Cell wall thickness (µm)
S2Ɵ (°)
3.88
55
8.04
20
Longitudinal shrinkage (%)
Modulus of Rupture (psi)
Modulus of Elasticity (106 psi)
0.90
7,700
1.12
<0.10
10,660
1.75
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)
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