Long-term observations show that leaves on understory woody species emerge slightly ahead of those on overstory species

Phenology, the study of biological events controlled by climate, has received increasing interest recently as a method of measuring some ecological responses to a changing climate. In an ongoing study, Museum Coordinator John O'Keefe began observing the dates of leaf emergence, leaf expansion, leaf coloration and leaf fall of 33 native woody species in 1990. In this chapter from Asko Noormets (ed.) recently published book, Phenology of Ecosystem Processes, recently hired OEB faculty member Andrew Richardson and John use this data set to compare spring leaf development and fall leaf senescence between understory and overstory woody species. In the spring, leaves of understory species generally emerge at least several days ahead of overstory species but this difference disappeared by the time the leaves are 75% developed. No consistent pattern was observed in the fall or among individuals of the same species in different canopy positions.