COLUMBUS, OH -- Every fall, Ohio's wooded landscapes turn hues of red, orange and yellow. And with the annual autumn change comes the question: How exactly does this happen?
We expect a great Fall Color season here in Ohio, says Bill Schultz, forestry expert with the Ohio Department of Natural Resources (ODNR). We need plenty of moisture, as well as cool nights and sunny days in the late summer, to bring on the state's annual forest fireworks. And this year we've had it all. Cool nights and sunny days kick off a series of chemical reactions within tree leaves, Schultz explained. During summer months, a leaf is green thanks to an abundance of pigments in the chlorophyll family. These green pigments capture energy from the sun, using it to manufacture simple sugars that are necessary for the tree's growth. This is the process many learned about in sixth-grade science class as photosynthesis.
Photosynthesis steadily consumes the leaf's supply of chlorophylls, which trees replenish at a steady rate through summer months. But when days grow short and nights are cool, trees slow their chlorophyll pigment production. As demand outstrips supply, the leafy green begins to fade. That allows other pigments, which have been present in the leaf all along, to show through the fading green. These are the carotenoids, producing hues of yellow, brown, and orange.
Other colors, including reds, purples and their blends, are created by anthocyanin pigments. Unlike the carotenoids, these pigments are not present in a leaf all year and develop in sap cells by late summer.
According to Schultz, large quantities of sugar are produced in leaves during ideal weather conditions. When complemented by cool nights, the leaf's veins begin to close, preventing the sugars from being released. These conditions stimulate the production of the red and purple anthocyanin pigments, particularly in sugar-rich tree varieties such as maple, oak, sweetgum, dogwood and blackgum. When high levels of both anthocyanin and carotenoid pigments are present, leaves display the deeper oranges, fiery reds and bronzes that can light up a fall landscape.
Ohioans and out-of-state visitors who enjoy viewing the state's fall color in a variety of locations can call the 1-800-BUCKEYE tourist information line for updates on fall color conditions around the state. Internet users can find the Fall Color Report on ODNR's web site at www.dnr.state.oh.us. This year's web site also offers an opportunity to e-mail Schultz for answers to fall nature questions and free "wallpaper" and other seasonal treats for personal computer users. The web site also gives suggested fall color driving and hiking routes and photographs highlighting the progress of Fall Color Season across Ohio.