Bruce J. Zobel – författare

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.

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.

Wood is the usual end product of a forestry operation. Because of its importance, numerous studies have been made relative to wood prop­ erties, the causes of wood variation, and how best to develop wood for desired products. There is voluminous literature related to these subjects, but it is neither well known nor appreciated by foresters because the publications are often not available or are not well understood by the forester or by those who use the wood. Frequently, the literature is confusing and contradictory, making it difficult for the nonspecialist to use what information is available. In order to produce and use wood efficiently, the variation pat­ terns within trees, among trees within species, and among species must be understood. This also requires some knowledge of the causes of variation and the effects of different wood properties upon utiliza­ tion. The information about variation patterns, their causes, and con­ trol and effect upon the product must be known by the tree grower, the tree breeder, and the tree harvester as well as by those who ultimately convert wood into a final, salable product.

Wood is the usual end product of a forestry operation. Because of its importance, numerous studies have been made relative to wood prop­ erties, the causes of wood variation, and how best to develop wood for desired products. There is voluminous literature related to these subjects, but it is neither well known nor appreciated by foresters because the publications are often not available or are not well understood by the forester or by those who use the wood. Frequently, the literature is confusing and contradictory, making it difficult for the nonspecialist to use what information is available. In order to produce and use wood efficiently, the variation pat­ terns within trees, among trees within species, and among species must be understood. This also requires some knowledge of the causes of variation and the effects of different wood properties upon utiliza­ tion. The information about variation patterns, their causes, and con­ trol and effect upon the product must be known by the tree grower, the tree breeder, and the tree harvester as well as by those who ultimately convert wood into a final, salable product.

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.