Fall Leaves
College of Science and Mathematics

Fall Colors

Biologist explains nature’s secret

Summer will soon be a distant memory and winter will be just around the corner, but in between we will get to enjoy fall. And the cooler, drier temperatures of shorter days and longer nights mean the potential for lots of fall color in most deciduous trees.

So, what’s the science behind the color change in the leaves of these hardwood trees?

Kennesaw State assistant professor of biology Joel McNeal says it’s the cooler temperatures that are ultimately behind the color change when “chlorophyll which reflects green light breaks down in the leaves, allowing the carotenoid pigments – the yellows and oranges that were previously masked by the chlorophyll – to show through.

“The red anthocyanins usually aren’t produced until fall,” says McNeal. “These are more prevalent in species like sugar maples, sourwood and black gum trees.”

But why?

“In some cases, the colors are useful for attracting birds for seed dispersal, or they may act as a sunscreen while the leaves are reabsorbing nutrients.”

Joel McNeal, assistant professor of biology at Kennesaw State University

The biologist notes that European maples usually produce fewer anthocyanins than sugar and red maples do in the United States.

Bird on Branch of Tree with Colorful Leaves

“Some of the most common maple trees in Europe like the sycamore maple and Norway maple don’t make the red/orange anthocyanins that sugar maples and red maples, the dominant colorful species in New England, do,” McNeal says.

The falling leaves are a reminder to look up at the beautiful colors of the leaves on the trees this time of year. While both campuses offer plenty of vantage points from which to enjoy the turning of the leaves, the Arboretum next to the College of Science and Mathematics on the Kennesaw Campus contains more than two dozen varieties of deciduous trees. Created in 1976, this 6-acre site is typical of a small urban forest in the Southern Appalachian region.

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