Green Horizons

Managing Open Forests for Wildlife and Timber

FRANK R. THOMPSON III | U.S. Forest Service Research Wildlife Biologist
JOHN KABRICK | U.S. Forest Service Research Forester

Open forests, also referred to as woodlands and savannas, have more open canopies and lower tree densities than closed canopy forests. These transitional communities were once widespread and common throughout the Midwest, but after European settlement, most were either converted to other land uses or fire suppression resulted in their succession to closed-canopy forests.

Photo courtesy of Rich Guyette

An open woodland demonstrating excellent groundcover for wildlife species and large-crowned trees for mast production.

Open forests require periodic disturbance in the form of mechanical treatments such as tree harvest or fire to maintain their open canopy, suppress invasion of woody vegetation and sustain the herbaceous and shrubby ground cover. There is great interest in managing for open forests in Missouri because they have been greatly reduced in extent from being abundant to becoming rare and because of their floristic and wildlife diversity. Open forests can support a diverse array of wildlife because they are transitional habitat types. They can include species that overlap from forest or grassland habitats, are savanna or woodland specialists or are generalists that occur across most of the habitat gradient. Open forests can provide excellent habitat for game species such as bobwhite quail, turkey and deer. The abundant ground vegetation that develops in open forests provides seeds for adult quail and turkeys, abundant insects for their chicks and browse for deer. Open forests also provide habitat for numerous songbirds, some of which are conservation priorities including the Blue-winged warbler, Prairie warbler, Eastern towhee and Eastern Pewee. How open a forest is will determine what specific species will benefit the most. Species such as bobwhite quail, prairie warbler and blue-winged warbler prefer open woodland and savanna with 10-50% canopy cover, whereas species such as the eastern pewee and summer tanagers prefer closed woodlands and forests with greater than 50% canopy cover. Deer and turkey will use this whole gradient of habitats. Generally, habitat conditions can best be met for these species by a combination of tree harvest and prescribed fire as opposed to using only one of these methods.

How open a condition you manage your forest for and the tools that you use will also depend on non-wildlife objectives such as timber. Where timber is also an important objective, thinning to remove the smallest and least desirable trees in the midstory and understory and leaving only the largest trees with full crowns will create stands with small gaps in the overstory and an open understory. This will provide light to the ground to stimulate the growth of the herbaceous plants and will accelerate the growth rate of the remaining trees much like any other timber stand improvement (TSI) practice. The application of herbicide during the thinning will prevent the production of stump sprouts, keeping the understory open longer. Prescribed fire can be used judiciously to remove leaf litter and to periodically burn off tree seedlings and shrubs in the understory. Care must be taken not to damage the timber with prescribed fire by burning on calm days when fuel moisture and relative humidity are high.

Where open woodland or savanna conditions are desired for wildlife, tree removals can include some of the larger overstory trees that ordinarily would be retained for timber production. Because the open conditions will favor the development of a woody understory, prescribed fire may need to be applied on a regular basis-once every three to five years-to burn off the woody regrowth and maintain an open understory. The combination of prescribed fire and open stand condition will stimulate the growth of a diverse array of forbs and grasses that are beneficial to wildlife species adapted to open forests. For assistance with managing open forests, contact a professional forester.