Canopy processes research.

The forest canopy regulates the exchange of carbon, water and energy between the ecosystem and the atmosphere, and provides a habitat for a wide variety of species. Understanding canopy processes is important for modeling forest production and carbon sequestration, and for predicting the effects of global changes in climate and atmospheric chemistry on the functioning of forest ecosystems. The Canopy Processes Working Group of the International Union of Forest Research Organizations has provided a forum for researchers working on forest canopies for nearly 20 years, principally through international meetings held every 2-3 years. In this paper, I review the history of the Canopy Processes Group, show how the research focus has changed and broadened, and provide a brief overview of some of the problems that remain to be solved. These include the topic of our 2001 meeting (Linking the Complexity of Forest Canopies to Ecosystem and Landscape Function), integration of canopy and respiratory processes, carbon allocation, physiological changes with tree age, predicting the response of forests to global change, understanding the genetic control of canopy structure and function, and scaling ecophysiological processes and modeling. Determining how forests will respond to global change and understanding the physiology of forest production will require increased attention to canopy processes and an increased focus on the interactions of canopy processes with other components of the ecosystem.