Over the years of restoration at our Dixon Waterfowl Refuge in north-central Illinois, you haven’t heard much from us about shrubs and trees. Until now, that is. The 283-acre Hickory Hollow tract on the southeast side of the Refuge, acquired in December 2014, is the first area at the site to require extensive planting of native shrubs and trees as part of its restoration. More than 1,000 have so far been planted in this new upland area of the Refuge.
At the same time we began delving into trees and shrubs at Hickory Hollow, TWI supporters Charlotte Adelman and Bernard Schwartz were completing their most recent book, Midwestern Native Shrubs and Trees: Gardening Alternatives to Nonnative Species (Ohio University Press, 2017). While flowering plants tend to be the attention grabbers, whether in a homeowner’s yard or at a site like the Dixon Refuge, Charlotte and Bernard rightly point out that woody species are the backbone of our gardens and landscapes. Moreover, they are critical reproduction sites and sources of food and shelter for a huge variety of butterflies, birds, and other wildlife. For those of us interested in promoting the return of declining species, native shrubs and trees are an essential part of the ecosystem.
Most of Hickory Hollow is being restored to prairie habitats, though there will be substantial savanna as well. Savannas are characterized by their relatively open canopy allowing sunlight to reach the ground, but those portions of Hickory Hollow had become dense with trees and shrubs, many of them non-natives. Step one was to remove these interlopers along with some of the small or weedy native trees, leaving the large old trees to be the architectural frame for the savanna restoration. Then came the planting of more than 1,000 native saplings and shrubs, most of them intended to attract birds and other wildlife with their smorgasbord of berries and nuts.
Six different oak species dominated the more than 700 saplings planted in the savanna areas. Scattered among them are hickory, pecan, American plum, sand cherry, prairie willow, and other native trees. Along with common shrubs like nannyberry and maple-leaved viburnum are a number of more unusual sand-adapted species such as New Jersey tea, winged sumac, and the endangered dwarf honeysuckle. The very sandy soils of Hickory Hollow are providing the opportunity to bring back some rare habitats including globally imperiled sand oak savanna.
Formal bird surveys at Hickory Hollow have already found a greater diversity of species making use of the reemerging savanna. Species of conservation concern that showed up in the savanna just one year into restoration included the Northern Flicker and Red-headed Woodpecker.
Many other bird species, including neotropical migrants, should also increase at Hickory Hollow along with an increase in the butterfly and moth populations. As discussed in Midwestern Native Shrubs and Trees, native oaks host an astounding 534 Lepidoptera species—valuable sources of food for many birds.
Compared to other habitat restorations at the Dixon Refuge—for example, the marsh, meadow, and prairie areas—the time scale for savanna restoration is really long. In many areas of the Refuge change was dramatic and noticeable after just a few years of restoration. But as TWI Senior Ecologist Dr. Gary Sullivan remarked, “None of us now involved in Hickory Hollow’s restoration will be around to see the mature savanna develop; it could take a hundred years. This one is definitely for future generations.”