The focus of this book is the complex impact of environmental stress on the genomes of forest tree species and the genetic structures of populations in the light of globally changing environmental conditions. This book refers to the genetic and phenotypic response to stress, it compiles information on geographically structured genetic variation and its dynamics, it takes into account forest genetic resources, new tools and concepts in forest genetics as well as chances and limitations of tree improvement. It is structured into four parts: (1) Verification of response to stress; (2) Genetic variation under diverse environmental conditions; (3) Genetic resources, reproduction, management; and (4) Tree breeding for uncertain future environments. This book particularly addresses scientists, lecturers and advanced students in the fields of genetics, ecology, conservation biology and various forest sciences. Moreover, it should be useful for decision-makers in the fields of the management of forest genetic resources, of nature conservation, of forest management and tree improvement.