Some Important Wood Properties & Attributes · 02.05.2014 · John Moore, Dave Cown, Euan Mason...
Transcript of Some Important Wood Properties & Attributes · 02.05.2014 · John Moore, Dave Cown, Euan Mason...
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Use of Tools to Predict Aspects of Wood QualityJohn Moore, Dave Cown, Euan Mason
Some Important Wood Properties & Attributes
Structural Appearance Other
Basic density Colour Tracheid length
Modulus of elasticity Resin features Cell wall thickness
Modulus of rupture Checking Density
Stability Stability Extractives content
Knots Durability Cellulose content
(Microfibril angle) Heartwood
Knots
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Some Major Drivers of Wood Property Variation
• Within-tree variation – biological phenomenon• Site – climate and soil driven• Genetics – contributes to properties and variation• Silviculture – control of growing space + pruning
Timeline for Wood Quality Research in NZ
1960 - 1980 1980 - 2000 2010 +
WQ Site Variation
2000 - 2010
Link WQ Performance
Link WQ to Silviculture
WQI/SWI
FFR
Cambial Modelling
Segregation Tools
Value Recovery
ConversionPlanning
Effect of Silviculture
Genetics of Wood Properties
Sawing Studies
Model Property Patterns
Non-destructive Tools
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Regional Variation in Wood Density
Intra-Stem Variation in Wood Density
(Example from Tarawera stocking trial)
Density = f(RN, RW, Density Index)
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Effect of Genetic Gain on Wood Density
Density Index = 398 + 1.85 GFPlus
350
400
450
500
550
-20 0 20 40 60
De
nsi
ty In
de
x (
kg
/m3)
GF Plus rating
Microfibril Angle
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Source:Walker (1993)
Modulus of Elasticity
• Traditionally measured in bending tests• Can be estimated from:
− portable acoustic tools− density and microfibril angle
MOE = ρV2
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Appearance Characteristics – Resin Features
• Incidence has been recorded across NZ• Range of causal mechanisms suggested
− Wind− Drought− Nutrition (boron deficiency)
(Woollons & Manley 2008– NZ J For. Sci.)
Shrinkage and Distortion
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Growth Stresses
• Not really a problem in radiata pine, but can be a major problem in Eucalypts
Juvenile Wood – A Challenge for Plantation Softwoods
• Juvenile wood refers to the relatively poor properties of the wood formed near the pith
− Often defined as innermost 10 rings
• Characteristics include: − wider growth rings, − lower wood density, − higher spiral grain− higher shrinkage
• Other features such as heartwood, resin content and intra-ring checking are much more prevalent in the juvenile wood
• Main influences on juvenile wood content are:
− Rotation length− Stocking
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Inherent Characteristics of Plantation-grown Softwoods
Levels vary with site, silviculture and genetics
Drivers of Juvenile Wood Content
05
101520253035404550
25 30 35
Juve
nile
Co
rew
oo
d
Co
nte
nt
(%)
Clearfell Age (years)
Clearfell Age
ClearwoodFraming
0102030405060708090
100
0 2 4 6 8 10
Juve
nile
Co
rew
oo
dC
on
ten
t (%
)
Log Position in Stem (5m height classes)
Position of Log in Stem
Clearwood Framing
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Silvicultural Interventions to Improve Wood Quality
• Choice of planting stock• Site preparation (weed control)• Initial planting density• Fertilisation• Timing & intensity of thinning• Pruning• Rotation length
Effect of Growing Space on Wood Properties
1000 1500 2000 2500
0
2
4
6
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Stocking (stems ha−1)
Stif
fne
ss (G
Pa
)
Clone 6Clone 9Others
Lasserre et al (2005) Carson et al (in review)
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Structural volume needs high final stocking and age
< 100m3
>600m3
Source: Brian Rawley
What Can We Model Now?
• Models are available in Forecaster for the following:− Wood density
− MOE (acoustic velocity)
− Heartwood
− Branch size
− Stem form (sweep/forking – probabilistic)
− MfA
− Spiral grain
− Juvenile wood content
• Explicit models do not exist for the following:− Resin blemishes
− Compression wood
− Intra-ring checking
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Linking end product performance back to the forest
Tree Board
Measured and simulated distributions of board
properties are in agreement
MOE Twist
Crook Bow
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Summary
• Variability in wood quality within stems is high for radiata pine anda function of age (juvenile wood – density, fibre length, spiralgrain, etc.)
• Variability between stems within a site is high and can be greaterthan site effects
• Site factors determine average fundamental wood characteristics(wood density, resin features)
• Silviculture (spacing, pruning, fertilisers and rotation) has a majorimpact on stem growth rate, variability and quality (juvenile wood,branching)
• Genetics can potentially alter average wood quality and variability