Scientific American posted a story this month describing a new study by researchers at Harvard and Macquarie University in Australia on the onset of fall colors in trees. Surprisingly, they linked the onset of fall colors to the onset of spring, showing that when trees experience an earlier spring, the tree also changes color earlier in the fall on average. This is surprising because this is the first time that fall coloration has been linked to the onset of spring. In the past, changes in leaf color have been linked to conditions in the growing season.
This research, which was published in Global Change Biology, provide additional uncertainty for studies of changing climate, since in projections of future climate it was assumed that as the growing season increased, color change in leaves and leaf fall would come later in the season and that trees would grow longer during the summer, trapping excess atmospheric carbon. The scientists now need to study the mechanisms for the early change, but speculate that it may be related to internal dynamics of the trees’ growing cycles or to early reduction in groundwater due to earlier leaf-out and more stress on the trees later in the season. You can read the Scientific American article at http://www.scientificamerican.com/article/may-flowers-bring-leaf-showers/.