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Wednesday, Dec 6, 2023

Science fuels magic of fall foliage

When it becomes too cold for chlorophyll, tourists  flock to Vermont. According to the Vermont Department of Tourism and Marketing, tourists spend over $370 million in the fall.

“We’re on track for another spectacular fall season,” said Ginger Anderson, Chief of Forest Management for the Vermont Department of Forests, Parks and Recreation. “Most parts of the state had good summer moisture, and early color can already be seen in some places.”

Behind all that breathtaking beauty, however, lies an interesting science. With the onset of autumn come longer nights. Leaves are able to sense this change, and as a result, a layer of cells called an abcission layer forms near the stem of the leaf, blocking transport of vital nutrients like carbohydrates. The production of chorophyll, the pigment responsible for giving leaves their green color, stops relatively quickly. Other pigments such as xanthophylls and carotenoids (which provide the leaves with yellow and orange color, respectively) now show, giving leaves beautiful bursts of color. When these pigments eventually freeze, tannins are left. These pigments are responsible for the brown color of leaves after the great foliage season has ended.

If this phenomenon occurs in deciduous trees all over the world, why is Vermont such a destination location?

“If you look at the map of the United States and figure out where the places are that have a foliage tourist industry, it’s very closely related to where there are maples,” said Andrea Lloyd, Professor of Biology. “It makes a very big difference to have a landscape that’s got red in it… As the leaves turn those conifers really pop out, and you get this amazing moment when the reds and oranges are at their peak and those conifers just look so dark green in contrast.”

The Green Mountains in particular showcase this well because trees in higher elevations change earlier than lower elevations, making the turning of colors gradual. From many places on campus you can look at a mountainside and see most of Vermont’s trees in a single collage. It can look as if someone is sprinkling color directly on the summit, and it gradually trickles down until it is replaced by snow.

Tree diversity is key to the beauty of Vermont’s foliage, and New England’s climate gives the state a broad mix of trees.  As described by Lloyd, brown-turning oaks are more prevalent as you go south, and red-turning maples disappear as you go north into Canada.  Vermont has the best of both worlds.

Middlebury College students take note, says Kristen DeGraff ’13.5 who has been living in Middlebury for her entire life.

“I love the smell of fall, and I love the colors of fall, but I kind of take it for granted,” said DeGraff. “I really have to stop and remember that this is beautiful, and when I do, it blows me away.”

Thanks to Tim Parsons, the Middlebury College Horticulturalist, trees from outside Vermont also enhance the tree diversity on campus.

“In Middlebury, there’s a broader pallet of colors that you don’t see up in the hills,” said Parsons. “[Here on campus] there’s a greater variety of oaks. There are certainly ornamental trees that you don’t see out in the woods, and there are a handful of trees that aren’t even supposed to live this far north. There’s even a pecan tree.” It’s on the left as you walk up the sidewalk from McCullough to Hepburn.

When Mother Nature strokes her brush across the tops of the Green Mountains, the campus peaks with beauty, with temperatures perfect for outdoor trips and activities. Autumn traditions such as apple picking, cider donuts and corn mazes are popular.  Outdoor enthusiasts also enjoy hiking and boating especially.

“As soon as the leaves change, they’re not taking up water anymore,” said Christian Woodard ’10.5, resident extreme kayaker. “All the water that falls can go straight into the rivers. It’s higher water. It’s better boating.”

Other students enjoy the changing of seasons regardless of their preferred activities.

“Everyone appreciates the landscape around here,” said Anoushka Sinha ’13. “It’s not so cold that everyone wants to huddle up and hibernate. I feel much more active and lively in the fall.” Gabriela Juncosa ’13 compared the fall in Middlebury to where she grew up in Ecuador.

“Some of the trees lose their leaves, but it’s not an event,” said Juncosa.

The event, however, doesn’t simply end when the leaves drop. What happens to the foliage when it gives this season its name?

Usually, Parsons and his team pick up fallen leaves and combine them with food waste from the dining hall to produce compost.  This year, they will try a new program. Instead of raking and removing the leaves, Parsons and his team plan to mow them and leave them on the ground.

“It chops them up real fine, and we just leave them right where they are and over the winter they will either break down, or the earth worms will come and drag them down,” said Parsons.

The fruits of this program will be healthier trees next spring and even more beautiful foliage in fall 2011.