By David Markham
They may seem like passive entities, but within the leaves, stems, and trunks of trees and other plants, a lot goes on at the chemical and molecular levels. No time of the year illustrates this better than fall.
This is the season when trees we barely notice during the summer burst into bright colors ranging from red to yellow and orange to purple and many shades of rust and brown.
With forested park lands accounting for about 4,300 of acres of its 10,000 total acres, JCPRD offers some great places to observe fall foliage. Several District staff members recently gave their favorite park locations for autumn color:
Central Region Park Manager Kelby Hellwig suggested the view from atop the dam at Shawnee Mission Park looking west.
“Just when you think views of the lake will never be topped, a glance to the west on a splendid fall day makes an argument for the title,” he said. “The glistening sun makes the hillsides of the Mill Creek Valley explode, awash in the reds, yellows, oranges, and golds showcasing all of the season’s splendor.”
Please note that parking on the dam is not allowed, but limited parking is available near the northwest corner of the dam. Be sure to use caution when walking on the roadways.
“Two of my favorite places are watching the native grasses change shades at Kill Creek Park as you drive into the park, and the timber on the south side of the (KCP) lake in some years is breathtaking as you look across the lake,” said Southwest Region Park Manager Dan Haase.
JCPRD Field Biologist Matt Garrett suggested several spots, including the loop trail on the Mill Creek Streamway Park west of the Shawnee Mission Park Dam, the high point of the bluff in the Oakridge Parklands on the south side of SMP, and the Kill Creek Park trail near Shelter #1.
Outdoor Education Manager Bill McGowan suggested the high point on Ernie Miller Park’s Upper Ridge Trail with a variety of yellow leaves from the park’s oak and hickory forest.
Two other well-known spots for viewing fall color in JCPRD parks are maples near the entrance to Antioch Park, and two maples at a traffic triangle located just south of Shawnee Mission Park’s Renner Road entrance near the intersection of John Barkley Drive and West 80th Terrace within the park.
Nature’s fall color show is a complicated recipe, and the leaves of different plants change colors at different times. This makes it especially difficult to predict how things will turn out from year to year
Color changes are due to chemical processes which take place within the tree as the seasons change from summer to winter. It turns out these “passive” organisms can do something we can’t – produce food within their own bodies using the energy of sunlight. In the spring and summer, leaves serve as factories manufacturing food for the tree’s growth. Chlorophyll is the chemical which not only gives leaves their green color, but absorbs from sunlight the energy used to transform carbon dioxide and water into carbohydrates such as sugars and starch, which feed the tree. The chemical reaction involved is called photosynthesis.
Water and nutrients flow from the roots, through the branches and into the leaves. Sugars produced by photosynthesis flow from the leaves to other parts of the tree, where some chemical energy is used for growth and is stored for use during the plant’s dormant seasons of fall and winter.
In addition to green pigment from chlorophyll, leaves also contain orange and yellow pigments called carotenoids. Other chemical changes are occurring in some trees which form additional colors through the development of red anthocyanin pigments. These pigments are within the leaves all year, but are masked during the spring and summer by the green of the active chlorophyll.
It’s the mixture of carotenoids and anthocyanin with the varying amounts of remaining chlorophyll pigments that give rise to the various colors of different species.
It is believed that changes in the length of daylight and temperatures triggers fall changes in leaves. Most importantly, the leaves stop their food-making processes and the chlorophyll breaks down. This essentially “unmasks” the other pigments that have been there all along and provides much of the fall splendor.
It is a common misconception that cold and frost causes trees to change colors, but the changes usually start well before the first killing frost. In reality, a quick frost or freeze tends to shorten the span of a tree’s coloration.
Researchers say a succession of warm, sunny days and cool and crisp, but not freezing, nights bring about the most spectacular color changes. This results in lots of sugars being produced in the leaves, and the cool nights and the gradual closing of leaf veins prevent the sugars from vacating the leaves. These conditions spur the production of brilliant pigments.
Other factors which affect the degree and duration of fall colors include: weather conditions before and during the depletion of chlorophyll in the leaves; temperature; light; and soil moisture. With all these variables, it’s no wonder that no two falls are ever the same in terms of foliage and that colors can vary wildly within the same tree from year to year.
So why do leaves have to fall at all, you might ask. Plants in temperate zones like Kansas have to face winter each year. Dropping leaves in the fall is a protective device plants use to survive freezing temperatures. Because tender leaf tissues would freeze in winter, plants either have to toughen up and protect their leaves or jettison them when temperatures dip.
With modified leaves in the form of needles covered with a heavy wax coating, evergreens take the “toughen up” approach. Broadleafed plants, on the other hand, have tender leaves and fluid in their cells which freezes readily, so these cells cannot survive freezing temperatures. In order to survive winter, they have to be able to seal off and shed these vulnerable tissues.
With high temperatures for the coming weekend projected mostly in the fifties and sixties, considering getting out to explore JCPRD parks and trails.