Over the past years, a great deal has been learned about variation in wood prop­ erties. Genetic control is a major source of variation in most wood properties. Wood is controlled genetically both directly in the developmental or internal pro­ cesses of wood formation and indirectly by the control of tree form and growth patterns. Emphasis in this book will be on the internal control of wood production by genetics although there will be two chapters dealing with the indirect genetic control of wood, which was covered in detail in the previous book by Zobel and van Buijtenen (1989). The literature on the genetics of wood is very variable, SO'lle quite superficial, on which little reliance can be placed, and some from well-designed and correctly executed research. When suitable, near the end of each chapter, there will be a summary with the authors' interpretation of the most important information in the chapter. The literature on the genetics of wood can be quite controversial. This is to be expected, since both the environment and its interaction with the genotype of the tree can have a major effect on wood properties, especially when trees of similar genotypes are grown under widely divergent conditions. Adding to the confusion, studies frequently have been designed and analyzed quite differently, resulting in conflicting assessments of results.

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1 The Role of Genetics in Wood Production-General Concepts.- 1.1 Background Information.- 1.2 Categorization of Wood and Trees.- 1.3 Wood Properties of Importance.- 1.3.1 Wood Density (Specific Gravity).- 1.3.1.1 The Genetics of Wood Density in Conifers - General Introduction.- 1.3.1.2 The Genetics of Wood Density in Hardwoods - General Introduction.- 1.3.2 Other Wood Properties.- 1.4 The Causes and Types of Wood Variation.- 1.4.1 Importance and Magnitude of Wood Variation.- 1.4.2 Assessing Genetic Improvements.- 1.4.2.1 Strength of Inheritance - General.- 1.5 Environmental vs. Genetic Influence on Wood.- 1.6 Literature on the Inheritance of Wood.- 1.7 Summary.- 2 Genetic Controls in Wood Formation.- 2.1 Controls Influencing Wood Development.- 2.1.1 The Kinds and Strength of Genetic Control in Wood.- 2.1.1.1 The Measurement of Genetic Control.- 2.1.1.2 The Change of Genetic Control with Tree Age - Juvenile and Mature Wood.- 2.1.1.3 The Environmental Control.- 2.1.1.4 Reaction with the Environment - Genotype × Environment Interaction.- 2.2 The Value of Genetic Differences in Wood.- 2.3 Summary.- 3 Sampling and Analysis in Genetic Studies on Wood.- 3.1 Making Wood Studies - Sampling Methods.- 3.2 Size of Sample.- 3.3 Location and Age of Sample.- 3.3.1 Estimating Whole Tree Specific Gravity Values from a Single Sampling Point.- 3.3.1.1 Age of Wood-Juvenile to Mature Wood Correlations.- 3.3.1.2 Removing Extractives.- 3.4 Obtaining Wood Samples.- 3.5 Methods of Determining Wood Density.- 3.6 Methods of Determining Other Wood Properties.- 3.6.1 Spiral Grain.- 3.6.2 Tracheids and Fibers.- 3.6.3 Moisture Content.- 3.6.4 Pulp Yield.- 3.7 Indirect Selection for Wood and Pulp Properties.- Appendix Table 3.1 Some methods used to determine wood density in trees.- Appendix Table 3.2 Some methods that have been used to determine spiral grain.- 4 The Importance of Wood Density (Specific Gravity) and Its Component Parts.- 4.1 General Concepts and the Importance of Wood Density.- 4.1.1 Earlywood and Latewood.- 4.1.1.1 The Ratio of Latewood to Earlywood and Its Value.- 4.1.1.2 Inheritance in Earlywood and Latewood.- 4.1.1.3 Wall Thickness.- 4.2 The Effect of Genetic Manipulation of Wood Density on the Final Product - General.- 4.2.1 The Effect of Wood Density on the Final Product for Conifers.- 4.2.2 The Effect of Wood Density on the Final Product for Hardwoods.- 4.2.2.1 Wood Density in the Diffuse-Porous Hardwoods.- 4.2.2.2 Wood Density in the Ring-Porous Hardwoods.- 4.2.2.3 The Effect of Rays and Vessels.- 4.3 Summary.- 5 The Genetics of Wood Density.- 5.1 General.- 5.2 The Genetic Control of Wood. Density in ·the Conifers.- 5.2.1 Hard Pines.- 5.2.2 Soft Pines.- 5.2.3 Other Conifers of Major Importance.- 5.2.3.1 The Spruces and Firs.- 5.2.3.2 Douglas-Fir and Larch.- 5.2.4 Other Conifers of Minor Importance.- 5.3 The Genetic Control of Wood Density in Hardwoods.- 5.4 Genetic Gains in Wood Density Using Vegetative Propagation and Coppice.- 5.5 Inheritance of Within-Tree Variation in Wood Density.- 5.6 Summary.- 6 Inheritance of the Cellular Components of Wood, Cellulose Yield and Pulp and Paper Products.- 6.1 General Concepts.- 6.1.1 Variability and its Causes.- 6.2 Cells of the Hardwoods.- 6.2.1 Fiber Length.- 6.2.2 Fiber Diameter, Wall Thickness, and Percentage of Cell Types.- 6.2.3 Vessels and Rays.- 6.3 Cells of the Conifers.- 6.3.1 Tracheid Length.- 6.3.2 Other Tracheid Characteristics.- 6.4 Cellulose Yield and Pulp and Paper Products.- 6.5 Summary.- 7 Grain, Fibril Patterns, and Internal Defects.- 7.1 General.- 7.2 Spiral Grain.- 7.2.1 Interlocked Grain.- 7.3 Microfibrillar Angle.- 7.4 Miscellaneous Wood Grain Patterns, Figured Wood.- 7.5 Reaction Wood.- 7.6 Cracks, Shake, and Other Internal Defects.- 7.7 Summary.- 8 Tree Form and Internal Tree Characteristics.- 8.1 Introductory Comments.- 8.2 Stem. Form and Branching.- 8.2.1 Stem Straightness and Sinuosity.- 8.2.2 Stem Taper.- 8.2.3 Branching Characteristics.- 8.3 Juvenile Wood and Genetics.- 8.3.1 Juvenile to Mature Wood Transition.- 8.3.2 Changing the Properties of Juvenile Wood.- 8.4 Chemistry of Wood.- 8.4.1 Cellulose and Lignin.- 8.4.2 Extractives and Gum Yields.- 8.4.3 Heartwood.- 8.4.4 Other Chemicals.- 8.5 Miscellaneous Traits.- 8.5.1 Moisture Content.- 8.5.2 Bark Characteristics.- 8.5.3 Wood Color.- 8.6 Summary.- 9 Wood Genetics Related to Provenance and Seed Source.- 9.1 The Meaning of Provenance and Seed Source.- 9.1.1 Provenance, Geographic Source, or Geographic Race.- 9.1.2 Confusion and Complexity of Terms.- 9.1.3 Assessment of the Wood of Provenances.- 9.2 The Overall Effect of Provenance.- 9.2.1 Genetic Differences in Wood Properties Among Provenances of the Hard Pines.- 9.2.2 Genetic Differences in Wood Properties Among Provenances in Conifers Other Than the Hard Pines.- 9.2.3 The Importance of Provenance in Determining the Wood Properties of Hardwoods.- 9.3 S Summary.- 10 Correlations Among Wood Properties and with Growth Rate.- 10.1 General Concepts.- 10.2 Growth Rate and Wood Properties.- 10.2.1 Growth Rate and Wood Density.- 10.2.2 Growth Rate and Other Wood Properties.- 10.3 Wood Property Relationships in the Conifers.- 10.4 Relationships Among Wood Properties in Hardwoods.- 10.5 Relationship of the Wood Properties of Coppice, Rooted Cuttings, and Grafts to Donor Trees.- 10.6 Wood Property Relationships Between Chemical Composition and Pulp Properties.- 10.7 Summary.- 11 The Genetics of Miscellaneous Factors That Affect Wood.- 11.1 What Are Miscellaneous Factors?.- 11.2 Diseases and Insects.- 11.2.1 Diseases.- 11.2.1.1 Wood Decay and Discoloration.- 11.2.1.2 Other Effects of Disease.- 11.2.2 Insects.- 11.3. Wood Uniformity.- 11.4 Hybridization to Change Wood Properties.- 11.5 Effects of Polyploidy on Wood.- 11.6 The Effect of Tissue Culture and Biotechnology.- 11.7 Wood for Energy.- 11.8 Summary.- 12 Determination of Wood Properties to Be Used in a Tree Improvement Program.- 12.1 Using Genetic Information.- 12.2 Selection of Trees for a Genetics Program.- 12.2.1 Considerations for Selection.- 12.2.2 Opportunity for Early Selection.- 12.3 Choice of Wood Properties - What Should Be Included?.- 12.4 Summary.- 13 Improvement in Wood by Using Genetics.- 13.1 Current and Future Usage of Genetics to Change Wood.- 13.1.1 When to Employ Genetics.- 13.2 Examples of Changes in Wood by the Use of Genetics.- 13.2.1 The Hard Pines.- 13.2.2 Other Conifers.- 13.2.3 Temperate Hardwoods.- 13.2.4 Tropical Hardwoods.- 13.2.4.1 Eucalypts.- 13.3 Improving Wood When There Is a Negative Correlation with Growth Rate.- 13.4 Summary.- References.- Sp…