503 335w9 02 wood quality

Wood quality: resource to end-use "You can't make a Silk Purse out of a Sow's Ear.“ Jonathan Swift 1667 - 1745 Content • Definition • The link between resource quality and end use

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Wood quality: resource to end-use

"You can't make a Silk Purse

out of a Sow's Ear.“

Jonathan Swift (1667 - 1745)

Content

•  Definition

•  The link between resource quality and end use

•  Growth manipulation and wood quality

•  Genetic improvement and wood quality

•  Measuring wood quality

Art work, MONA

www.csaw.utas.edu.au

KDA503/335 Timber, its origin and characteristics

Definition of wood quality

•  Wood quality is the combination of

characteristics of the log and

properties of its wood that affect:

–  the recovery of useful products and

–  their value and serviceability in

intended applications (Hillis 2000)

•  The characteristics are not consistent

For any log, they vary with:

–  the species of the source tree,

–  its growing conditions and age at

harvest,

–  the section of the tree that the log

comes from, and

–  the part of the log sampled

•  While generally applied to the log, the

term can be applied at other stages

during production and use

Veneer at DEEDI, Qld

The link between resource quality and

end use

Resource to end-use market: sawn wood

Patterns like this demonstrate that differences exist in the value and serviceability

in the applications of sawn material drawn from different resources

Limits on the function of timber products

•  Timber product functionality is limited by:

–  The form of the log

•  Its shape, length and diameter

•  Its primary wood properties

–  Size constraints on recovered pieces –  The directionality of its key properties –  Its structural consistency

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Table of resultant primary wood elements

Long grain

elements Poles Timber Scantling Veneer <2.4mm thick

Veneer

>2.4mm thick

Veneer Strips

Short grain

elements

Chips or

flakes Strands Splinters Shavings Sawdust

Wood flour

Fiberal

Elements Fibre bundles Whole fibers Macerated fibers Fibrils

Chemical

Decreasing width and/or thickness

Increasing formability, decreasing strength/weight ratio, reducing dependence on log quality, increasing homogeneity and isotropy

From Marra, 1972, Wood products into the future

Log resources obviously differ

What are desirable log and wood characteristics?

Desirable wood properties

•  Different wood properties can be loosely

grouped under four headings, namely:

– Visual character;

– Wood properties - Usage;

– Wood properties - Processing; and

– Log Characteristic - Form

•  The groupings are not exclusive and

assessment of their importance varies at

the production stage and point of sale

Visual Character

Clear wood - present 2.3 4.1 2.4 Grain - even 2.0 4.2 2.3 Colour consistency

Colour - pale - present 2.0 2.9 2.2 Gum Vein -kino -present 2.3 1.2 2.0

Insect feature- present 1.8 1.4 1.8 Knots - present 1.5 1.2 1.7

Source: Nolan et al 2005 Eucalypt Plantations for Solid Wood Products in Australia FWPRDC project PN04.3002

Wood Properties -Usage

Wood Properties -Usage Rounds Appearance Structural

Wood Properties-Processing

Tension wood - low 3.8 4.7 4.5

Growth strain - low 3.8 4.4 3.9

Internal checking - low 2.5 4.7 3.4

Surface checking - low 3.0 4.6 2.9

Collapse - low 2.3 4.4 3.6

Shrinkage - low 2.5 4.0 3.5

Shrinkage ratio -tangential/radial 2.5 3.1 2.4

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Log characteristic - Form

branch frequency - low 4.0 4.7 3.9

End split - low 4.3 4.0 4.0

Knotty core diameter -small 3.0 4.9 4.2

Log form - taper - low 3.3 4.0 3.8

Heartwood content - high 3.0 3.6 3.3

Sapwood thickness - low 2.8 3.5 3.2

Heart / corewood diameter - low 3.0 3.1 2.9

Log diameter and value recovery

0 10 20 30 40 50 60

Log small end diameter (cm)

r = 0.68

Plot of log diameter and recovery for pruned eucalypts processed

with standard industry practice (Washusen and Clark, in prep)

Log quality and value recovery

Growth manipulation and wood

quality

Silviculture is day-to-day forestry techniques used to modify growth

and wood quality

Forestry for wood quality

•  Wood quality correlates

strongly with:

–  The genetic characteristics

of the resource and

–  Growth manipulation

through silvicultural

practice

Limits on manipulation

•  Forest management objectives limit silvicultural options and the potential for manipulation

•  Manipulation is constrained with native forestry:

–  wood production is only one

objective in broad multi-use forestry

•  Manipulation is encouraged with plantation forestry:

–  wood production for a given

target market is a primary objective

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Variables for manipulation

•  Trees for harvest may differ

through being:

–  Different genetic background

(between or within species),

–  Grown to different ages

–  Grown in different environments

–  Managed differently over their

growing life

•  Even with all these factors

being constant, grown trees

still differ from tree to tree

Different genetic background

•  For native forests, trees from a site generally provide the seeds used

to regenerate a site

–  Genetic selection is generally not an option

•  For plantation forestry, trees with desirable characteristics are selected from growth trials, and propagated in seed orchards

Genetic assessment and selection

Selecting preferred genetic material

Managed differently: silvicultural approaches

For a given site and species, the major silvicultural options for plantations are:

•  Thinning

–  Reducing the stocking levels of trees to give each tree more space and resources

–  The result is bigger trees and larger logs

•  Pruning

–  Removing branches to encourage the growth of clear wood

–  The result is more consistent, high value wood in the logs

Managed differently: unthinned, unpruned

Landscape view

Managed differently: unthinned, unpruned

Close up view

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Managed differently: thinned

Relation between crown width and dbh in E globulus grown in Galicia, Spain.

Source: Nutto and Touza (2004), Figure 2

Managed differently: thinned

heavier thinning = higher basic density

Basic density versus final stocking in 33-year-old E grandis in South Africa

(Malan and Hoon 1992) – All treatments established at 6,850 stems per

hectare, multiple thinning operations

0.500 0.520 0.540 0.560 0.580 0.600 0.620 0.640 0.660 0.680 0.700

final stocking (sph)

Managed differently: prune

(a) The stem cross-section highlighting the defect knotty core The knotty core is a product

of the diameter over-pruned branch stubs (DOS); plus the additional growth before clear

wood is produced to give the DOO, and (b) the tapering characteristic of the knotty core

within the tree Source: Montagu et al (2003a), Figure 2

While the branches are still green

Managed differently: thin, prune, wait

10 year old unthinned, unpruned E.nitens 28 year old thinned, pruned E nitens

Measuring and sorting for wood

quality

Grading for forest products

Harvested trees yield logs of different quality and characteristics up the stem

These are graded (and separated) at the harvesting site, and checked in the log yard

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Log grade definitions

Sweep

Grain

tight kino <3mm width : length % of diameter 25 200

tight kino >3mm width : length% of diameter 25 100

loose kino/kino pockets/shakes : length % of diameter 100

stain

allowable defective quarters

GRADE

<20% of diameter over 2.4 m length

<1:8 ul

<1:10

ul 200 dark 25

light

Grades 1, 2, 3 and 4 are equivalent to Victorian A, B, C and D grades

Grades 5 & 6 are research grades devised for plantations

Source: Innes et al 2008 Determining the Economics of Processing Plantation Eucalypts for Solid Timber Products, FWPRDC project PN04.3007

Defective quarters

Logs to be graded Defective quarter of the log

Log grade and value recovery

$0

$50

$100

$150

$200

$250

$300

$350

$400

log grade 1 log grade 2 log grade 3 log grade 4 log grade 5 log grade 6

sawlog grade

E nitens 26yo - thinned, pruned butt log - ITC Newood

E nitens 26yo - thinned, pruned upper log (unpruned) - ITC Newood

E nitens 26yo - fibre - ITC Newood

,E globulus 19yo - thinned pruned butt log - ITC Newood

Total product value per cubic metre of sawlog, by log-grade and log

type - logs processed by ITC Newood

Source: Innes et al 2008 Determining the Economics of Processing Plantation Eucalypts for Solid Timber Products, FWPRDC project PN04.3007

Log grades

Log grades & merchandising

Modern harvesting heads measure and can access other properties

using NDE tools, such as near infrared spectroscopy (NIR)

Grades are confirmed in the log yard

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Non-destructive evaluation (NDE) AWV

Summary

•  There is a link between resource quality,

production value and end use

•  Wood quality can be manipulated by

– Genetic improvement

– Silvicultural action

•  Forestry objectives limit the potential for

manipulation

•  Logs are generally visually graded for

quality NDE processes are being

introduced

Thanks to Patrick Cook

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