Permanent Forest Openings Provide Early Successional Habitats
All wildlife species have the same four basic habitat requirements – food, water, shelter, and space. However, each species requires different kinds and combinations of food or shelter. Successful wildlife management requires an understanding of how specific land management treatments affect individual species. In most cases, habitat management should emphasize the community occupied by a species rather than focus only on a single target species. A healthy community benefits multiple species – both game and nongame.
Permanent forest opening comprised of young trees.
If left undisturbed, non-forested lands (in areas that were previously comprised of forests) typically undergo a predictable series of vegetation growth stages, eventually becoming mature forests again. Each stage, from annual grasses and forbs, to brush, to mature forest, benefits certain types of wildlife. In forests, wildlife habitat conditions shift in response to changes in age, structure, size, and species composition. As a result, the assemblage of wildlife species inhabiting the area typically shifts as the land moves through each successional stage.
Openings in the forest canopy occur naturally due to overstory tree loss from insects, fire, storms, age and disease. As succession begins, these openings will become occupied by a mixture of tree seedlings, shrubs, grasses, and/or forbs that contribute to the diversity of the forest. These early successional forest stages are rich in insects, berries and seeds. They also provide cover making them valuable habitat for many species of wildlife including deer, turkeys, ruffed grouse, rabbits, mourning dove, songbirds and American woodcock.
Studies have shown that early successional grassland and forest habitats have declined throughout most of eastern North America due to changes in land use practices. In southern Indiana, forests have matured and fire disturbances have lessened. Nearly 60 percent of forestland in our region is 40 to 80 years old, but only eight percent of forestland is 20 years or younger. Predictably, the species that depend on these habitats for food, cover and nesting have declined as well. For example, since 1983 Indiana has lost over ninety-five percent of its ruffed grouse population and their hunting season has been suspended since 2015.
During their first 4-6 weeks of life, ruffed grouse chicks feed exclusively on insects found in early successional areas.
To help reverse these trends, the Hoosier National Forest (NF) in south central Indiana has an active early successional habitat management program that maintains about 4,250 acres as 718 permanent forest openings. The sizes of the openings varies from one quarter acres to 110 acres. The average size is 6 acres. Some openings are maintained as warm-season grasslands, some as shrublands, and others as wildflowers for pollinators. They are maintained by methods such as mowing and burning to prevent the re-establishment of trees. This differs from clearcuts where trees are expected to grow back. Clearcuts provide temporary early successional habitat lasting perhaps 10 years.
In areas managed as grasslands, Forest Service staff encourages or establishes native warm season grasses that actively grow during the hotter months when most cool season grasses are dormant. Because they grow in erect clumps, open space at ground level is provided when bunches are not too dense, allowing mobility for small wildlife. The structure of native warm season grass stands allows a diverse community of forbs such as legumes and wildflowers to exist between grass clumps, which create an ideal environment for grouse, quail, and turkey to forage and raise young. During winter, fields of native warm season grasses are magnets for rabbits, over-wintering songbirds, and deer. This can be especially critical for small wildlife at a time when quality cover is at a premium.
In 2018, 2,760 acres of permanent forest openings were treated through mowing or prescribed fire, and 20 acres were seeded with native herbaceous plants. Ideally, treatments of individual openings occur at three to four year intervals to set back woody plant growth.
The Central Hardwoods Joint Venture (CHJV), a partnership of state, federal, and non-profit wildlife conservation agencies and organizations, works to insure the long-term viability of native bird populations across the Central Hardwoods Bird Conservation Region. The region includes southern Indiana along with parts of Alabama, Arkansas, Illinois, Kentucky, Missouri, Oklahoma, and Tennessee. They have classified 21 grassland and shrubland birds as priority species due to regional conservation concerns. Fifteen of these are likely to occur year round or during summer breeding season in the vicinity of the Hoosier NF. Two species may be migrants in our area.
Early successional plant communities provide habitat for pollinators such as native bees and butterflies. Areas having a large grassland component like the one in this photo also support Henslow’s sparrows during the summer breeding season.
Purdue University has a multi-year agreement to conduct breeding bird surveys on the Hoosier NF. During May and June 2016, the first efforts to specifically survey birds in early successional habitat areas were done. Birds were counted at 311 points within 11 distinct areas. Surveyors recorded a total of 3,802 observations and documented the occurrence of 88 species of birds, including all but one of the CHJV priority species. Priority species field sparrow, yellow-breasted chat, prairie warbler, and Henslow’s sparrow accounted for 30% of the total observations. All of these species, except Henslow’s sparrow, were present at all 11 survey areas. Because of Henslow’s sparrow’s habitat requirements, they were only present at seven survey areas that contain a large grassland component. This sparrow is a state endangered species.
As one of the largest public land holders in Indiana, the Hoosier NF plays a major role in providing forest ecosystems that enhance biological diversity on a regional scale. Since the majority of land in Indiana is privately owned, individual landowners play an important role in providing habitat diversity too. If your woodland management goals include hunting, wildlife viewing, photography, or increasing habitat and wildlife diversity, consider implementing and maintaining permanent forest openings.
Large grassland forest opening.
The Hoosier NF acknowledges our many partners - Ducks Unlimited, Indiana Department of Natural Resources, National Wild Turkey Federation, and Quail Unlimited, without whom we could not develop and maintain wildlife habitats on the forest.
Richard Winstead is the supervisory wildlife biologist, and Marion Mason is the public affairs specialist for the Hoosier National Forest.