Throughout the world natural forest ecosystems have been, and are being massively disrupted or destroyed. The boreal forests of Canada are no more immune to man's intervention than the tropical rain forests of Africa, and the day is rapidly approaching when natural forest ecosystems, undisturbed by man, will be found only as remnants in national parks and other protected areas. Yet where they continue to exist these ecosystems are an extraordinarily rich, though relatively neglected source of data that illuminate many aspects of the classic theory of evolution. The subject matter of this book is not, however, confined to natural forest ecosystems. Forest ecosystems under varying degrees of management, and manΒ made forests are also a rich source of information on ecological genetics. In general, however, it can be said that the published evidence of this fact has not yet significantly penetrated the botanical literature. All too frequently it is confined to what might be termed forestry journals. It is hoped that this book will to some extent redress the balance, and draw attention to a body of published work which not only provides a basis for the rational management and conservation of forest ecosystems, but also complements the literature of ecological genetics and evolution. The first draft of Chapters I to V was written in German by the senior author and translated by E. K. MORGENSTERN of the Canadian Forestry Service.