Fall foliage forecast

September 16, 2003

College Park, MD (September 16, 2003) -- What is fall? Air temperature starts to cool, the daylight hours shrink and nights grow longer. The most beautiful aspect of fall is the spectacular red, orange, and yellow hues of trees preparing for winter.

While the leaves usually start to turn in the northeastern United States within the next few weeks, much of the country won't see the first signs of autumn until mid-October. With cooler weather in the long-term forecast and a little less rain, this year's display has the potential to be perfect.

This week's hurricane Isabel would probably not hurt the autumn leaves' colors, said Bill Hoch, a plant physiologist at the University of Wisconsin at Madison. Strong winds could break off the leaves and heavy rain would remove the drought stress that gives the leaves their color. But since the storm is expected to hit the East coast before the leaves begin changing color, trees probably won't feel the storm's effects very much.

"The weather during senescence is the most important factor in how brilliant the colors will be," Hoch said. The leaves' changing colors are a stress response in trees, as they respond to the normally cooler temperatures and slight drought of approaching winter. "Sunny, cool days are best, but other stresses during this time such as drought also induce more vibrant colors."

Senescence is a seasonal aging period when leaves stop producing chlorophyll and start storing valuable nutrients in the tree for next year before the leaves drop off. Biochemical triggers in the leaves cause trees to stop producing green-colored chlorophyll, their source of energy, and allow molecules that look red or yellow to show through. "The yellow and orange hues are produced by xanthophylls and carotenoids," said Marc Abrams, a forest physiologist at the Pennsylvania State University. "It is the same pigment that makes carrots orange."

Red leaves, on the other hand, are produced by anthocyanins. "Anthocyanins filter light that could otherwise damage the way the plant makes food, which is becoming increasingly vulnerable at this time," said Hoch.

"Anthocyanins act like a sunscreen, an antifreeze, and an antioxidant, qualities that could help leaves deal with an array of environmental stresses," said Paul Schaberg, a plant physiologist with the United States Forest Service. "We are studying stresses on tress such as drought, pollution, acid rain, and cold and we think that the red anthocyanins could be produced by the leaves to help them deal with stress."

The color displayed by the leaf has a lot to do with the species of tree it is, which determines the specific chemicals produced by the leaves during senescence. According to Schaberg, red leaves also seem to have a stronger attachment to the tree than yellow leaves at the same stage of senescence. "The longer the leaves stay on the tree, the more time there is for their nutrients to be sent back into stems for storage for next year," says Schaberg.
-end-
MORE INFORMATION:

William (Bill) Hoch
Plant Physiologist
University of Wisconsin-Madison
608-262-0517
wahoch@wisc.edu

Mark Abrams
Forest Physiologist
Pennsylvania State University
814-865-4901
agl@psu.edu

Paul Schaberg
Plant Physiologist
United States Forest Service
802-951-6772
pschaberg@fs.fed.us

Emilie Lorditch
Science Editor
American Institute of Physics
301-209-3029
elorditc@aip.org

American Institute of Physics

Related Drought Articles from Brightsurf:

Redefining drought in the US corn belt
As the climate trends warmer and drier, global food security increasingly hinges on crops' ability to withstand drought.

The cost of drought in Italy
Drought-induced economic losses ranged in Italy between 0.55 and 1.75 billion euros over the period 2001-2016, and droughts caused significant collateral effects not only on the agricultural sector, but also on food manufacturing industries.

Consequences of the 2018 summer drought
The drought that hit central and northern Europe in summer 2018 had serious effects on crops, forests and grasslands.

Songbirds reduce reproduction to help survive drought
New research from the University of Montana suggests tropical songbirds in both the Old and New Worlds reduce reproduction during severe droughts, and this - somewhat surprisingly -- may actually increase their survival rates.

Predicting drought in the American West just got more difficult
A new, USC-led study of more than 1,000 years of North American droughts and global conditions found that forecasting a lack of precipitation is rarely straightforward.

Where is the water during a drought?
In low precipitation periods - where and how is the limited available water distributed and what possibilities are there for improving retention in the soil and the landscape?

What does drought mean for endangered California salmon?
Droughts threatens California's endangered salmon population -- but pools that serve as drought refuges could make the difference between life and death for these vulnerable fish.

With shrinking snowpack, drought predictability melting away
New research from CU Boulder suggests that during the 21st century, our ability to predict drought using snow will literally melt away.

An evapotranspiration deficit drought index to detect drought impacts on ecosystems
The difference between actual and potential evapotranspiration, technically termed a standardized evapotranspiration deficit drought index (SEDI), can more sensitively capture the biological changes of ecosystems in response to the dynamics of drought intensity, compared with indices based on precipitation and temperature.

Sesame yields stable in drought conditions
Research shows adding sesame to cotton-sorghum crop rotations is possible in west Texas

Read More: Drought News and Drought Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.