Monitoring global change with phenology: The case of the spring green wave

The centuries-old practice of recording plant and animal events that take place at specific times each year (phenology) should play an important role in monitoring mid-latitude global changes. At least three problems related to the detection of biosphere changes could be investigated using this information. Firstly, the technique can be generalized from the local to global scale. Secondly, an integrated approach could be developed to represent biome diversity effectively. Lastly, physical mechanisms responsible for the events can be deduced in order to incorporate the phenological information into global-scale models, and detect changes in related environmental factors. With these goals in mind, regional phenological data collection networks were initiated in eastern North America during the early 1960s, using cloned lilacs and several species of honeysuckle. This paper reviews research projects which address the problems outlined above, using first leaf data (associated with spring green-up or green wave in mid-latitudes) gathered from these networks. The results of such studies in North America have demonstrated the potential of phenology as an efficient monitor of global change throughout mid-latitude regions. Future research efforts will concentrate on the development of a coordinated strategy to link phenological information from satellites, indicator plants (such as the lilac), and representative species from each biome.