Fall Color Change Reflects Healthy Forest Diversity As Different Species Start To Turn
September 15, 2015
Wisconsin's fall color show is just beginning in northern Wisconsin and the changing colors help highlight the state's healthy forest diversity, Wisconsin Department of Natural Resources forestry experts say.
Weather during the growing season is critical for the abundant quantity of leaves needed to provide the potential for an excellent fall color display, according to Carmen Hardin, DNR forestry sciences section chief.
"The 2015 growing season has been excellent across much of Wisconsin and the fall color season is anticipated to be spectacular," Hardin said.
So far this year, color change is starting to occur in certain species - especially the birch, basswood and red maple in spots across northern Wisconsin. With Wisconsin state forests, parks and natural areas conveniently accessible throughout the state, it's possible to follow the progression of fall colors from hundreds of locations.
Hardin said peak fall color varies slightly from year to year depending on the weather conditions, but the shortened day length is the primary trigger for trees to begin changing color.
Kirsten Held, DNR forestry outreach specialist, said peak fall color usually occurs in far northern Wisconsin during the last week of September and first week of October. However, significant color typically appears earlier in isolated, lower lying areas by mid-September.
"Peak color generally occurs in central Wisconsin during mid-October and in southern Wisconsin during the latter half of October," Held said. "While we are beginning to see the showy maple trees turning red and the birch trees taking on a golden hue, it will take the oak trees a bit longer to yield their yellow, red and russet hues. Fall provides a great opportunity to pick out a variety of tree species on a hillside and understand just how diverse our forests are."
Wisconsin's state parks and forests and state natural areas, offer prime locations for enjoying nature's annual fall color show, starting with the forests in northern and central Wisconsin. The Flambeau River State Forest, in Sayer, Price and Rusk counties, can be one of the state's top destinations to check out the fall colors, said Jim Halvorson, forest superintendent.
"You can view the colors from the road, by walking trails or by canoeing down the river," he said. "Historically the peak comes early to the Flambeau River State Forest due to the strong mix of maple that we have. Peak comes during the last week of September to the first week of October. Call ahead to 715-332-5271 ext. 101 prior to your visit to check on how colors are progressing."
Peter Bakken, Superintendent of the Black River State Forest, said red maple is often the first to turn on there, with good color typically evident by mid to later September. Among the best viewing sites are along Campground Road, north of Highway 54 or North Settlement Road, south off of Highway 54. Peak colors typically arrive in the first part of October.
Find other state forests, parks, trails and recreation areas for fall coloring viewing on the DNR website.
"The intensity of the fall color season is really dependent on the weather that Wisconsin receives during September and October," Hardin said. "To have the most brilliant and vibrant fall color display, a series of fall days filled with bright sunshine and cool, but frost free, evenings are required. These weather conditions cause anthocyanins to be produced by certain species of trees (e.g. maples) which protect the leaves of the trees from the light as they are storing nutrients and sugars for the winter. This ultimately leads to the intense red, orange and purple coloration in the leaves."
The duration of the fall color season is related to the intensity of wind and rain during late-September and October. High winds and driving rains cause significant numbers of the leaves to fall from the trees, which can prematurely shorten the fall color season.
For current information on the current best fall color viewing areas in Wisconsin contact the Department of Tourism's Fall Color Hotline at 1-800-432-TRIP or online at the Fall Color Report (exit DNR) on the Travel Wisconsin website.
What causes trees to turn color?
The timing of fall color in Wisconsin's forests is determined more by the shortening daylight hours than it is by temperature, but temperature and other weather conditions play a big role in the intensity and duration of fall colors, said Held.
There are three types of pigments that are directly involved in producing colorful leaf displays: chlorophyll, carotenoids and anthocyanins. Here's how they work:
Chlorophyll is present in the leaves during the growing season and gives the leaves their green color. In the process called photosynthesis, chlorophyll utilizes the sun's energy to produce simple sugars - the tree's food - from water and carbon dioxide.
Carotenoids are present in the leaf chloroplasts also, but because the green coloration of the chlorophylls predominate, they aren't seen through the growing season. The carotenoid pigments are responsible for the yellow colorations of fall leaves.
Anthocyanins produce the brilliant reds and purples that everyone associates with a spectacular fall color season. This color pigment develops in the early autumn within the leaf cells to protect the leaves from bright light as biological processes transition from food production to storage. During this period, called senescence, the leaves' photosynthetic components are broken down and the nutrients, mainly nitrogen and phosphorus, are moved within the tree for storage and use the following year.
Certain tree and shrub species commonly are associated with differing colors during the fall: green ash, white birch and aspen turn golden yellow; red maple a brilliant red; oak and hickory become a reddish-brown color; white ash a deep purple; and sumac a scarlet red. Even tamarack turns a beautiful deep golden yellow and loses its needles in the fall, the only conifer (evergreen) tree in Wisconsin to shed its needles.
Learn more about why state forests change colors throughout the year by searching the DNR website, dnr.wi.gov, for "science of fall leaf colors."