Too Much Sugar!

By Gus Raeker and Mike Stambaugh | March 2, 2004
From Missouri Conservationist: Mar 2004

In the fall, the hills adjacent to the Missouri and Mississippi rivers seem ablaze with brilliant orange sugar maples. Few trees are as attractive as a sugar maple in autumn, but there is something haunting in all that orange.

Not long ago, these same hills contained a lot more of the reds, purples and yellows of oak and hickory. Slowly but surely, the oranges are taking over, indicating that the river hill forests are changing, and not for the better.

We have long had some sugar maple in our woods. In the last 50 years, however, the amount of sugar maple has increased dramatically. This is especially true in counties adjacent to the Missouri and Mississippi rivers, where land is especially productive because of loess, or wind blown silt. Loess is blown from the river bottoms and deposited on nearby slopes. In some areas, loess is more than 100 feet deep. In areas like these, sugar maples are overtaking most other forest vegetation.

The primary reason for the maple takeover is that over the last 50 or so years, we have stopped fires from burning our woods. Native Americans commonly used fire as a tool in Missouri. They burned the landscape to aid in hunting and fighting wars. They also used fire to improve wildlife habitat, which helped ensure an abundance of game. The first European settlers also used fire, primarily to create and improve pasture lands.

Fire played a huge role in shaping the composition of our woods. Oaks and hickories are relatively tolerant of fire. Their thick bark helps protect them from intense heat. Smaller seedlings and trees may be "top-killed," but their deep root crown allows them to resprout quickly and vigorously.

Maples have thinner bark at all ages and are much more vulnerable to fire. Until the widescale suppression of wildfire, maple growth was limited to protected sites that did not burn often. Now, maples grow uncontrolled in many places.

Where there is no fire, maples have an advantage over many oaks and hickories. Maples thrive in shaded conditions. They grow quite well in the understory of an oakhickory forest. They'll persist for decades, and have a good, growing head start when a large oak or hickory tree dies or falls. Generally, the competition in a forest is for sunlight, and maples usually shade out young oaks or hickories.

Although maple trees are beautiful, allowing them to continue to take over our river hill forests will reduce plant and wildlife diversity.

The typical river hill forest overstory contains many different kinds of trees, including oak, hickory, ash, basswood, cherry and walnut. Beneath the canopy, you'll often find a rich carpet of wildflowers, native grasses, sedges, shrubs, understory trees and some seedlings.

When sugar maple dominates, very few of these plants can survive. The densely leafed canopies of sugar maples allow very little light to reach the ground. Most types of vegetation cannot tolerate such heavy shade, so very little grows on the forest floor, except other maples.

Oaks, on the other hand, have fairly open canopies. Even in a dense oak forest, a considerable amount of light still reaches the ground.

Maple colonization also means fewer acorns for wildlife. Acorns last for several months, and without them, many animals could not survive through winter. Most of our river hill forests still contain many oaks in the overstory. However, as these old oak trees mature and die, or are harvested, they will be replaced by maple instead of oak, and there will be few acorns for wildlife.

Maple does not provide much food value to wildlife. Deer and squirrels may eat maple buds in the spring, and birds might get some insects from the bark, but when a sugar maple seed drops in the fall, it either rots or sprouts quickly.

A lack of wildflowers, native grasses and shrubs in the understory of maple dominated stands means less vegetation for deer to browse, fewer insects for turkeys and other birds to eat, and less nectar for butterflies. It also means fewer places for animals to hide from predators.

Many landowners can improve their forests by controlling sugar maple. Many forests, including those in the southern Ozarks, have little or no problem with maple competition. In the river hills, however, maple control can improve wildlife habitat, promote diverse forest vegetation and increase the long-term value of the timber.

The River Hills region is one of the world's most important producers of oak veneer lumber. In some parts of Missouri, sugar maple can produce quality saw timber, too. However, on many of our soils, sugar maple wood becomes mineral-stained. Although structurally sound, such wood is not aesthetically suitable for furniture, flooring or similar uses.

Under the right conditions, a carefully controlled, prescribed burn can kill maple trees while doing little or no damage to your desirable trees. Prescribed burns mimic historical disturbances and stimulate growth of herbaceous vegetation.

Prescribed burns usually won't kill maples larger than a couple of inches in diameter. Herbicide is a better method of controlling larger maples, and is a good alternative in areas where prescribed burns aren't practical or desirable. Herbicide also helps ensure that treated trees won't sprout back. Killing maples with herbicide is easier than it sounds. Depending on the chemical used and method chosen, it can be as simple as making a couple of hatchet marks in the bark and spraying the marks with herbicide. Don't cut or girdle maples without treating them with herbicide. They will just sprout back, and your efforts will be wasted.

If you cut trees down just as they are starting to leaf out, they may not sprout back. However, you only have a short window of time to try this.

Unless there are no maples present, a timber sale will only serve to accelerate maple growth and domination. If there is maple present in the understory, you need to treat it before cutting the overstory trees to ensure that future trees will be oak.

After treating the maple, it is important to wait until oak regeneration is established before cutting the overstory trees. After you are confident that enough oak regeneration is present, you can harvest trees.

The Conservation Department offers assistance to landowners who wish to control maples on their property. If you don't have the time or equipment, you can hire a contractor. Cost-share money may be available to help cover costs. If you are interested in conducting a prescribed burn on your property, you can learn a lot from attending a burn workshop sponsored by the Conservation Department.

Conservation Department foresters and private lands conservationists are available to offer guidance on how to best meet any conservation objectives. Call your local office to get more information or set up an appointment. Working together, we can ensure that there will be some reds, purples, and yellows in our River Hills for future generations to enjoy.

This Issue's Staff

Editor - Tom Cwynar
Managing Editor - Bryan Hendricks
Art Director - Ara Clark
Artist - Dave Besenger
Artist - Mark Raithel
Photographer - Jim Rathert
Photographer - Cliff White
Staff Writer - Jim Low
Staff Writer - Joan McKee
Circulation - Laura Scheuler