Spiral Grain and Wave Phenomena in Wood Formation

About this book

It is widely recognized that spiral grain in trees severely reduces the value of sawn timber through warping and loss of strength, and that it also causes problems for other wood uses as diverse as transmission poles or plywood. Yet, paradoxically, there are highly valued grain patterns including wavy and interlocked grain, whose origins in the cambium invite direct comparison with those of spiral grain, so that many authorities believe them to be related phenomena. In recent years this concept has prompted extensive research into the anatomy, genetics, and physiology of all such grain patterns in wood. As a result it has become apparent that tree cambia provide excellent systems through which to study the origins of stem polarity and the complex processes of morphogenetic control in plants. Beside these and other pressing topics for research, Spiral Grain and Wave Phenomena in Wood Formation examines methods of measuring grain deviations, and considers their influence on wood properties, on the economics of timber production, and on wood manufacturing.

Contents

1 Defining Spiral Grain
1.1 Patterns of Spirality
1.1.1 The Simple Spiral
1.1.1.1 Direction of the Spiral
1.1.1.2 Degree of Spirality
1.1.1.3 Defect or Normal Growth?
1.1.2 Change in Spiral Angle and Direction
1.1.2.1 Stem Pattern in Softwoods
1.1.2.2 Stem Pattern in Hardwoods
1.1.2.3 A Three-Dimensional View of Spiral Grain
1.1.2.4 Pattern Down an Annual Increment
1.2 Interlocked Grain
1.3 Wavy Grain
1.4 Other Growth Patterns
1.4.1 Spiral Bole and Spiralled Branches
1.4.2 Birdseye and Dimples
1.4.3 Curly Birch
1.4.4 A Collection of Oddities
1.5 Conclusions

2 Measuring Grain Angle
2.1 Detection of Grain Angle
2.1.1 Detection in Trees and Round Produce
2.1.1.1 Evidence from Radial Splits and Scars
2.1.1.2 Evidence from Shape of Stem and Branches
2.1.1.3 Evidence from Bark Patterns
2.1.2 Detection in Seedlings
2.1.3 Detection in Wood
2.1.3.1 Natural Features
2.1.3.2 Ink Test
2.1.3.3 Dye Injection
2.1.3.4 Radioactive Tracers
2.1.3.5 Scribe Test
2.1.3.6 Pick Test
2.1.3.7 Splitting
2.1.3.8 Sonic and Capacitance Properties
2.1.3.9 Microscopic Observation
2.2 Sampling for Grain Angle
2.2.1 Destructive Sampling
2.2.2 Non-Destructive Sampling
2.3 Methods of Measurement and Analysis
2.3.1 Units of Measurement
2.3.2 Precision of Measurement
2.3.2.1 Axis of Reference
2.3.2.2 Techniques of Measurement
2.3.3 Measurements on Trees and Roundwood
2.3.4 Measurements on Sawn Timber
2.3.5 Measurements on Large Wood Samples
2.3.6 Measurements on Increment Cores
2.3.7 Measurements on Veneers
2.3.8 Analysis of Measurements
2.4 Measurement of Interlocked and Wavy Grain
2.5 Conclusions

3 Effects of Grain Angle on Wood Properties and Uses
3.1 Consequences of Anisotropy
3.2 Effects on Shrinkage
3.2.1 Warping in Sawn Timber
3.2.2 Movement in Roundwood
3.2.3 Warping in Plywood and Sliced Wood
3.3 Effects on Wood Strength
3.3.1 Strength of Sawn Timber
3.3.2 Strength of Tree Trunks and Roundwood
3.4 Effect on Other Aspects of Wood Physics
3.5 Effect on Conversion, Use and Economics
3.5.1 Effect on Conversion
3.5.2 Effects on Wood Use
3.6 Effect of Interlocked Grain
3.7 Effect of Wavy Grain
3.8 Conclusions

4 Spiral Grain in Relation to the Environment
4.1 Effect of Environmental Variables
4.1.1 Movement of Earth and Sun
4.1.2 Soil Conditions
4.1.3 Roots
4.1.4 Slope and Aspect
4.1.5 Wind
4.1.6 Altitude
4.1.7 Temperature
4.1.8 Eccentric Growth and Reaction Wood
4.1.9 Structural Breakage and Wounding
4.1.10 The Case for Environmental Influence
4.2 Effect of Growth Rate
4.2.1 Slow Growth, Increased Spirality
4.2.2 Fast Growth, Increased Spirality
4.2.3 Spirality Independent of Growth Rate
4.2.4 Other Consequences of Growth Rate
4.3 Balance of Controls
4.4 Effects of Silviculture
4.5 Advantages for Survival
4.6 Conclusions

5 Anatomy of Changing Grain Angles
5.1 The Role of Cell Structure
5.2 Cambium
5.2.1 Methods of Studying the Cambium
5.2.2 Nature of the Cambium
5.2.3 Cell Division
5.2.3.1 Anticlinal Division
5.2.3.2 Periclinal Division
5.2.4 Cell Survival
5.2.5 Cell Re-arrangement and Elongation
5.2.6 Plasticity of the Cambium
5.3 Morphogenetic Events
5.4 Cambial Domains
5.4.1 Domain Origins and Intensity
5.4.2 Domain Integrity
5.5 Wave Aspects of Domain Structure and Function
5.5.1 Wave Interactions
5.5.2 Complex Wave Interactions
5.6 Anatomy of Slow Changes
5.7 Conclusions

6 Genetics of Spiral Grain
6.1 Basic Requirements
6.1.1 Concept of Heritability
6.1.2 Genetic Gain and Potential for Improvement
6.2 Geographical Variation
6.2.1 Provenance Trials
6.2.1.1 Provenances of Pinus radiata
6.2.1.2 Provenances of Larix kaempferi
6.2.1.3 Provenances of Pinus pinaster
6.2.2 Use of Provenances in Tree Breeding
6.3 Clonal Variation
6.3.1 Clonal Trials
6.3.2 Broad-Sense Heritability
6.4 Sexually Propagated Progeny
6.4.1 Narrow-Sense Heritability
6.5 Modification of Genotypes
6.6 Heritability of Wavy and Interlocked Grain
6.7 Strategies for Tree Improvement
6.8 Conclusions

7 Physiological Aspects of Changing Grain Angles
7.1 Requirements
7.2 Polarity
7.2.1 Manipulating Polarity
7.2.2 Patch Grafting
7.2.3 Implications for Polarity
7.3 The Role of Auxin
7.3.1 Auxin and Cambial Activity
7.3.2 Wave Patterns in Auxin Transport
7.3.3 Auxin and Morphogenesis
7.3.4 Response of Cambial Initials to Auxin Vectors
7.3.5 Orientation of Pseudotransverse Division
7.4 Other Factors
7.4.1 Environmental Causes
7.4.2 Microfibril Angle
7.4.3 Phyllotaxis
7.4.4 Time
7.4.5 Straight Grain and Uncontrolled Grain
7.5 Conclusions
References

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