Last winter’s cold legacy: Fall colors slower to peak

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FallColors

Satellite image shows fall colors across Michigan’s Upper Peninsula and Canada on Sept. 30. Image: NASA

By Juliana Moxley

Fall colors are not exploding as uniformly in the Great Lakes region as they have in the past.

Experts say this is because of last winter’s extreme cold.

The NASA recently posted two satellite images displaying the fall colors beginning to appear in Michigan’s Upper Peninsula in late September.

Fall color tours are a tourist attraction promoted by the state’s Pure Michigan advertising campaign. About 2 million people traveled throughout Michigan for fall color tours last year, according to Michelle Grinnell, travel public relations manager for Pure Michigan.

Those colors have an economic impact, Grinnell said. Of the $13.8 billion made in leisure and travel spending in the state last year, $2.4 billion was made during the fall season. About $294 million of that was contributed by fall color tours.

Grinnell said Michigan is seeing peak colors come in a little later this year.

The harsh 2014 winter is partly to blame, said Bert Cregg, a professor in the department of horticulture at Michigan State University.

We are still having a good fall color season in Michigan, but we are likely to see some trees in full color while others are just beginning to turn, he said.

“As you’ll recall, last winter was extremely cold — one of the coldest winters on record,” Cregg said. “The winter stress delayed leaf-out for many trees, and then the tree’s timing was further delayed by a cold rather than normal spring.”

A warming climate can also affect fall color, said Howard Neufeld, a professor in the department of biology at Appalachian State University in North Carolina. Higher temperatures, altered timing and/or amounts of precipitation, changes in humidity, changes in cloud cover, increases in the length of the growing season and higher levels of nitrogen inputs in the ecosystem can all affect fall color variance.

“Increased precipitation means that light levels are most likely lower, and trees will do less photosynthesis,” Neufeld said. “With less photosynthesis, there are fewer sugars in the leaves. Warmer temperatures mean higher respiration rates, and more sugars will be metabolized.”

Sugars stimulate the production of anthocyanins, the pigments that are responsible for red leaves, Neufeld said. High precipitation also means trees can take up more nutrients, such as nitrogen. If trees are deprived of nutrients, such as nitrogen, the leaves will become more red because of the anthocyanins.

Here’s what makes leaves turn color:

Dry, sunny days, followed by cool, dry nights are essential for autumn displays, according to NASA. Throughout the growing season, leaves produce chlorophyll, the green pigment in plants that turns light into energy. When nights become longer and cooler, chlorophyll production slows and eventually stops.

That lets other chemical compounds, such as anthocyanins, carotenoids and flavonoids, to appear in the leaves. They bring out the yellow, orange, red and purple hues.

“Overall, the biggest factor in how intense fall color is for a given location is the type of trees present,” Cregg said.

For the trees that are prominent in the Great Lakes region, Cregg said sugar maple and red maple give off the most vibrant reds and yellows; oaks add deeper reds and purples; hickories add yellow; and sassafras adds orange and yellow.

Although Michigan is experiencing fall colors at different rates this year, it is not unusual that fall colors began to emerge near Michigan’s Upper Peninsula.

Grinnell said Michigan’s Upper Peninsula tends to peak with its fall colors the earliest, which usually starts in mid-September.

“Further down state you get its peak colors in October,” Grinnell said. “Lakeshore areas peak a little later.”

According to NASA, since temperatures drop sooner and sunlight fades faster at higher altitudes, fall color changes tend to move from north to south across North America.

To put Michigan’s climate into perspective, Neufeld said the cold winter in North Carolina, where he lives, did not have any obvious effects on this fall’s color change. He said it looks as if North Carolina’s trees are right on schedule to peak at their normal time, which is about now.

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