Tree Improvement Program

Forest tree improvement has mainly been implemented to enhance the productivity of artificial forests. However, given the drastically changing global environment, improvement of various traits related to environmental adaptability is more essential than ever. This book focuses on genetic information, including trait heritability and the physiological mechanisms thereof, which facilitate tree improvement. Nineteen papers are included, reporting genetic approaches to improving various species, including conifers, broad-leaf trees, and bamboo. All of the papers in this book provide cutting-edge genetic information on tree genetics and suggest research directions for future tree improvement.

Three tree improvement programs were analyzed by break-even, cost-benefit technique: one for ponderosa pine in the Pacific Northwest, and two for Douglas-fir in the Pacific Northwest-one of low intensity and the other of high intensity. A return of 8 percent on investment appears feasible by using short rotations or by accompanying tree improvement with thinning. Interest rates, length of rotation, the inclusion of thinnings, and site index had greater effects on profitability than program design. Large breeding zones improved profitability, although they incur the biological risks of nonadaptation to local conditions and loss of local genetic resources. Increasing orchard seed yield affected the results only slightly unless the planting program could be expanded, which is equivalent to increasing the size of the breeding zone. If the increase in seed yield merely reduced the required acreage of seed orchard and associated costs, the financial results improved only slightly.

General Concepts of Tree Improvement. Variation and Its Use. Provenance, Seed Source, and Exotics. Quantitative Aspects of Forest Tree Improvement. Selection in Natural Stands and Unimproved Plantations. Seed Production and Seed Orchards. Use of Tree Improvemente in Natural Forests and in Stand Improvement. Selection and Breeding for Resistance to Diseases, Insects, and Adverse Environments. Vegetative Propagation. Hybrids in Tree Improvement. Wood and Tree Improvement. Advanced Generations and Continued Improvement. Gain and Economics of Tree Improvement. The Genetic Base and Gene Conservation. Developing Tree Improvement Programs.

Review of current literature establishes that most authors believe that tree improvement expands production, although some point out drawbacks and alternatives. Both softwood and hardwood improvement programs have been analyzed. The authors used various models, economic assumptions, and standards of measurement, but available data were limited. Future models shouId attempt to be more eclectic.