The trend in forestry is toward shorter rotations and more complete utiliza­ tion of trees. The reasons are: (1) financial pressures to obtain rapid returns on the forestry investment made possible by an earlier harvest; (2) enforced harvest of young plantations to maintain a continuing supply of cellulose for mills where wood shortages are experienced; (3) thinning young plantations, both because they were planted too densely initially and because thinning is done where long rotation quality trees are the forestry goal; (4) more intensive utilization is being done using tops and small diameter trees; and (5) there is interest in using young (juvenile) wood for special products because of its unique characteristics and the development of new technologies. The largest present-day source of conifer juvenile wood is from thinnings of plantations where millions of hectares of pine were planted too densely. Because of the better growth rate resulting from improved silviculture and good genetic stock, plantations will need to be thinned heavily. As a result of this trend, young wood makes up an increasingly larger proportion of the total conifer wood supply each year. Large amounts of juvenile wood from hard­ woods are also currently available, especially in the tropics and subtropics, because of the fast growth rate of the species used, which results in shorter rotations and ess~ntially all juvenile wood.

Inhalt

1 General Concepts of Juvenile Wood.- 1.1 General Concepts.- 1.2 What Is Juvenile Wood?.- 1.3 The Causes of Juvenile Wood.- 1.4 Importance and Characteristics of Juvenile Wood.- 1.5 Literature on Juvenile Wood.- 1.6 Summary.- 2 Characteristics of Juvenile Wood.- 2.1 General Concepts.- 2.2 Juvenile Compared with Mature Wood.- 2.2.1 Effects upon Wood Uniformity.- 2.3 Characteristics of Conifers.- 2.3.1 Specific Gravity Within and Among Species.- 2.3.2 Variation in Other Wood Properties Within and Among Species.- 2.4 Characteristics of Hardwoods.- 2.4.1 Specific Gravity in Hardwoods.- 2.4.2 Other Wood Properties.- 2.5 Summary.- 3 Occurrence of Juvenile Wood.- 3.1 General Concepts.- 3.2 Where Does Juvenile Wood Occur?.- 3.3 Radial Development in the Conifers.- 3.3.1 Estimation of the Juvenile Wood Zone in Conifers.- 3.3.2 Radial Development of Specific Gravity.- 3.3.3 Radial Development of Other Wood Properties.- 3.4 Radial Development in the Hardwoods.- 3.5 Development with Tree Height.- 3.5.1 In the Conifers.- 3.5.2 In the Hardwoods.- 3.6 Summary.- 4 Characteristics Affecting Juvenile Wood.- 4.1 Relationship to Reaction Wood.- 4.2 Genetics of Juvenile Wood.- 4.3 Relationship to Growth Rate.- 4.4 General Sampling Methods for Different Characteristics.- 4.5 Summary.- 5 Changing Juvenile Wood.- 5.1 General Concepts.- 5.2 Response to Genetic Manipulation.- 5.3 Response to Silvicultural Treatments.- 5.3.1 The Effect of Spacing and Thinning.- 5.3.2 The Effect of Fertilization, Irrigation and Site.- 5.4 Response to Geographic Location, Seed Source and Species.- 5.5 Response to Other Environmental Factors.- 5.6 Summary.- 6 Predictions of Mature and Total Tree Wood Properties From Juvenile Wood.- 6.1 General Concepts.- 6.2 Juvenile to Mature Wood Correlations.- 6.2.1 Predictions Across the Tree Bole.- 6.2.2 Predictions Along the Bole.- 6.2.3 Predictions For the Whole Tree.- 6.3 Summary.- 7 The Importance of Juvenile Wood.- 7.1 General Concepts.- 7.2 In Conifers.- 7.2.1 Utilization in the Hard Pines, Douglas-fir, Larches etc.- 7.2.1.1 Utilization of Top Wood.- 7.2.2 Utilization in the Spruces, Firs, Cypresses etc..- 7.3 In Hardwoods.- 7.3.1 Utilization.- 7.3.1.1 Diffuse-Porous Species.- 7.3.1.2 Ring-Porous Species.- 7.4 Summary.- 8 Use of Juvenile Wood.- 8.1 General Concepts.- 8.2 Juvenile Wood for Pulp and Paper.- 8.3 Juvenile Wood for Solid Wood Products.- 8.4 Future Juvenile Wood Supplies and Utilization.- 8.5 Summary.- 9 Unusual Wood Properties Near the Tree Center.- 9.1 General Concepts.- 9.2 Heartwood.- 9.3 Growth Stresses.- 9.4 Summary.- References.- Species Index.