This book provides an overview of how boreal and temperate tree species have adapted their annual development cycle to the seasonally varying climatic conditions. Therefore, the frost hardy dormant phase, and the susceptible growth phase, are synchronized with the seasonality of the climate. The volume discusses the annual cycle, including various attributes such as timing of bud burst and other phenological events, seasonality of photosynthetic capacity or the frost hardiness of the trees. During the last few decades dynamic ecophysiological models have been used increasingly in studies of the annual cycle, particularly when projecting the ecological effects of climate change. The main emphasis of this volume is on combining modelling with experimental studies, and on the importance of the biological realism of the models.