A conceptual framework for tree improvement programs

Forest tree improvement programs have become quite complex and program strategies and intensities vary dramatically around the world. It is often necessary to examine the reasons for each activity separately in order to ascertain how all steps fit together in a strategy aimed at achieving genetic gain. This paper establishes a conceptual framework that explains the purposes of the various activities of tree improvement and allows complicated program strategies to be easily conveyed. This conceptual model, called the breeding cycle, stresses why, not how, each activity is conducted. The breeding cycle turns around one time for each generation of breeding and is composed of various types of plant populations. Each plant population serves a role in the tree improvement program and is created form a preceding population in the cycle by an activity of the breeder.Tree improvement concepts are explained and the roles of genetic test plantations are described in the context of the breeding cycle. This conceptual model is useful for foresters responsible for implementing tree improvement programs, for students and breeders trying to understand and compare divergent program strategies and for managers responsible for making investment decisions.