As the sun begins to set, it highlights a farm and some of the fall floiage in Vermont File/UPI/Sandy Macys | License Photo
PRINCETON, N.J., Sept. 18 (UPI) -- Those burnt oranges, amber yellows, and deep siennas that send flannel-clad city dwellers into the countryside in search of hot cider and pumpkin patches may be showing up bit later than usual. But don't worry, the colors of fall are expected to stick around a bit longer, too.
That's according to a new study by researchers at Princeton University who predict a warming planet could push the peak of fall foliage back a few weeks by the end of the century.
In addition to shorter days, cooler temperatures are also necessary to suppress the chloroplasts that produce the green pigments in leaves and plants. It's not the addition of new chemical compounds that creates fall's collage of color, but the absence of chlorophyll. The longer it takes for trees to shut down their chlorophyll faucets, the longer lovers of pumpkin lattes will have to wait for perfect hay ride backdrop.
The logic sounds simple enough, but previous attempts to understand why some fall colors have been emerging later or why some trees might be keeping their leaves longer had left many scientists stumped. Existing models used to analyze the patterns of fall were largely limited to localized data, but researchers at Princeton wanted to understand how climate and land-based biological processes (like fall foliage) interact over a broad scale.
So David Medvigy, an assistant professor of geosciences, and Su-Jong Jeong, a former postdoctoral student now working for NASA, developed a model that organized local tree data on a macro scale. The model categorized different tree species based on the amount of shade needed, and it also focused on both daily temperatures and amount of daylight -- previous studies had focused on only one or the other.
"We now have a much better understanding of how temperature, day-length and leaf color are related," Medvigy said. "This understanding will help us make better forecasts for climate, as well as for the basic dynamics of forests."
And while the forecasts suggests fall will generally start later and last longer, not all forests will be affected equally -- trees in New England, for example, are likely to respond more dramatically to changes in climate than trees in Alaska.
"We're really interested in understanding how these systems will change as we experience global warming or climate change," Medvigy said. "What these results are suggesting is that different locations will change in different ways, and that these differences are actually going to be quite interesting."
Medvigy and his colleagues say their method of research can do more than just predict when leaves will turn red, yellow, brown and orange, but can help researchers better understand all sorts of dynamic ecological and biological systems.
"When you get at the growing season you can relate this to a huge number of things. In order to understand how it might change in the future we have to understand how it functions now," explained Mark D. Schwartz, a professor of geography from the University of Wisconsin-Milwaukee who assisted the new study. "This research is a useful addition to what we're trying to do in terms of improving the way that we model plants. A lot of models that we use in terms of global change are fairly simplistic."
The study was published this week in the journal Global Ecology and Biogeography.