Leaf out phenology in temperate forests

Monitoring phenology, the study of the timing of natural events, is an ancient practice that has experienced renewed interest in the wake of awareness of climate change. Spring onset has been occurring significantly earlier in temperate regions worldwide. Leaf out phenology is of particular interest because the emergence of leaves in the spring is extremely sensitive to temperature, and leaf out timing controls many essential ecosystem processes. This article reviews the current literature concerning the different methods used to study leaf out phenology, the controls on leaf out in temperate woody plants, and the effects of climate change on leaf out phenology. In addition to the traditional method of on-the-ground leaf out monitoring, new methods using remote sensing and dedicated cameras have been developed which allow scientists to track spring onset at a much larger scale than had previously been possible. Further work is needed on how leaf phenology will respond to future climate change, and the implications of this for interactions among trophic levels.