Autumn has always been my favorite season. Oaks are my favorite trees. So, it seems fitting in "Oaktober" to write about oaks and oak woodlands
At Nachusa Grasslands and other places in the Midwest, we are trying to restore the health of our oak woodlands. And really, our region is defined by the oaks. The Nature Conservancy calls our eco-region “The Prairie-Forest Border” between the grand prairie to the south and the mixed woodlands in neighboring states to the north. The area was historically maintained as prairie intermixed with oak savanna and woodlands by Native American nations.
Natural plant and animal communities of the region were a direct result of Native Peoples’ use of fire on the land. Without fire, in “The Prairie-Forest Border,” the amount of rain we receive would have yielded dense forests.
Many botanists have defined the various intergrades between savanna, open woodland, and closed woodland by the level of sunlight and density and species of trees. (See https://oaksavannas.org/)
Today, much of our Illinois woodlands have become too shady to allow sun-loving oaks to grow. Shade is the enemy of oaks. Acorns in shade will not thrive after germination and the limbs of oaks will also die if shaded.
How can we tell if the “woods” we are looking at was historically savanna or naturally shady? The presence of large, old oaks with limbs that stick straight out (or used to, but are dead now) indicate the area was likely savanna. An oak growing in full sun without other trees close by will grow limbs horizontally. Oaks that grow close together grow their limbs vertically to reach the sun.
To give the oaks a fighting chance modern prairie restorers make use of controlled burns, as well as actual removal of invasive trees growing under and up into the limbs of the old sentinel oaks. We also remove the non-native bush honeysuckle (and other non-native shrubs) from the understory.
Our region’s historic mixture of prairie interspersed with woodland types — from dry to wet, from open to somewhat shady — had an enormous species diversity of understory flowers, grasses, and native shrubs.
If action is not taken by restorers, the result is a mud forest floor, impenetrable understory with honeysuckle bushes, and an overstory of dead oaks. Elms, maples, and other shade-loving fire intolerant trees move in to take the place of oaks and hickories.
This combination of a solid thicket of invasive honeysuckle and loss of oaks gives hardly any habitat for animals. For example, deer and turkey dislike maple and elm, but they love acorns!
Native oak-hickory savannas and woodlands in the region are disappearing along with bird species that depend on the open structure: red-headed woodpeckers, great crested flycatchers, and eastern bluebirds. Native wildflowers such as kitten tails, wild hyacinth, prairie lily, and starry campion along with grasses such as bottle brush rye, woodland brome, and long-awned wood grass will not grow in heavy shade. And there are the native shrubs: hazelnut, American plum, hawthorn, and Iowa crabapple! None of these tolerate shade either.
I encourage you to read up on oak woodlands, then take a hike. Explore the Stone Barn Savanna and see how we are doing. It’s a work in progress and sometimes messy, but we see the native oak savanna dependent plants and animals are thriving.
Here are some great websites that discuss oak savannas:
Pleasant Valley Conservancy—Oak Savannas
Last of the Oak Savannas Survive in Minnesota
What is an Oak Savanna?
Written by Susan Kleiman, a Nachusa volunteer.
It is easy to spot and identify in late autumn. The tall deciduous trees, the oaks, the hickories and others, have but a few brown leaves still clinging to their skeleton frames. Below, on shorter plants, abundant leaves remain green. A drive in the country reveals this late season green plant growing at the edge of a woodlot, deep in a forest or in abandoned fields. It is in the fall that its abundance becomes most visible. It is exotic and invasive bush Honeysuckle.
Nonnative Honeysuckles such as Amur Honeysuckle, Showy Fly Honeysuckle, Common Fly Honeysuckle and others were introduced into the United States from Eurasia more than 100 years ago. They were brought into new habitats for ornamental reasons, for erosion control and for wildlife cover. In the absence of repeated fires and in grazed and disturbed wooded areas the exotic Honeysuckles have reproduced rapidly and spread widely.
There are woodland and savanna areas now in Nachusa Grasslands where the Honeysuckle has become abundant over many decades and is disruptive to the native ecosystems. These multi-stemmed bushes can grow up to twelve feet tall and form very thick shrub layers that prevent the growth of native species by decreasing the amount of light reaching the forest floor and by using up nutrients and water in the soil. Honeysuckles are considered an allelopathic species as they release chemicals into the soil that inhibit the growth of native species. Birds that may build nests in Honeysuckle are more susceptible to predation because the Honeysuckle branches are nearer the ground than native bushes. The abundant berries, while high in carbohydrates, do not produce the fats and nutrients needed by migrating birds in the fall.
I have been a steward of the East Tellabs Unit at Nachusa Grasslands since 2011. With the help of many volunteers, other stewards and the Nachusa crew, we have cut and treated thousands of Honeysuckle plants of all sizes. It is rewarding to use a pair of loppers or a saw to cut a plant near its base and treat the stump with a chemical to kill the Honeysuckle and prevent resprouting. The forest floor is exposed and sunlight may reach it for the first time in years. Other methods of attacking this invasive plant include chemically spraying the leaves, applying chemicals to the base of the plant and seasonal fires.
The work to decrease the Honeysuckles continues. A few hours working among the Honeysuckle can leave one tired, sweaty, sore, scratched and covered in burrs. Yet the tired and sore will go home feeling proud for doing a necessary task that makes a difference in the diversity and ecology of the woodlands and savannas. Each Saturday a Nachusa steward leads a volunteer workday. You might collect seeds, you might pull weeds, you might pile deadfall, or you might cut, treat, stack and burn Honeysuckle.
Text and Photography by Tellabs Steward Mark Jordan
I have been a high school French teacher, registered piano technician, and librarian. In retirement I am a volunteer historian at Lee County Historical and Genealogical Society.