Habitat restoration has been heralded as an important tool to ameliorate the tremendous impact that humans have had on natural ecosystems. Restoration refers to the purposeful assembly of plant and animal communities in order to reconstruct a stable ecosystem that is compositionally and functionally similar to that which originally existed.
Among the first attempts at habitat reconstruction have involved the tallgrass prairie, and the first of these prairie restorations was started at the University of Wisconsin-Madison Arboretum. Aldo Leopold and John Curtis provided the early leadership, and the early stages of work utilized crews from the Civilian Conservation Corps between 1935 and 1941. The two prairie restorations at the Arboretum, Curtis and Greene, now total more than 110 acres (46 hectares) making them among the largest prairies now occurring in that state. More than 300 species of native vascular plants have been recorded from the restorations, and they provide excellent habitat for numerous prairie insects, small mammals, and birds.
Within Illinois, several prairie restorations have been successful in establishing high biological, or at least botanical, diversity on formerly agricultural or degraded land. A good example is the Schulenberg Prairie at the Morton Arboretum in Lisle, which covers over 100 acres (40 hectares). Initially, volunteers were used extensively to grow plants from seed in a greenhouse, hand-plant the material on the site, and control non-native species. Some direct seeding has been done on additional parts of the site, and there has been considerable species enrichment through transplanting, and this is one of few prairie restorations with a complete phenology of plants, from early spring through late fall. Another diverse restoration is the Doris L. Westfall Prairie in Forest Glen Preserve. Over 120 species of prairie plants native to Vermilion County are found in this site, and most have been introduced through repeated seeding.
A large prairie restoration project is at Fermilab in Bativia, Illinois. The goal is to convert the entire area enclosed by the nuclear accelerator ring into prairie; the ring is 1.2 miles (2 km) in diameter, 3.9 miles (6.3 km) in circumference, and encloses 776 acres (314 hectares), with an area of 455 acres (184 hectares) available for restoration; additional restorations have been planted outside the ring.
A very excting development in prairie restoration is the conversion of the former U.S. Joliet Army Ammunition Plant into the Midewin National Tallgrass Prairie. Created when President Clinton signed the Illinois Land Conservation Act of 1995 on February 10, 1996, Midewin is the nation's first federally-designated tallgrass prairie. The legislation designated the transfer of a 19,165 acre parcel of land in Illinois from the U.S. Army to the U.S. Department of Agriculture Forest Service. Much of the land will be the subject to a massive prairie restoration project, which is far beyond the scale of previous prairie projects.
However, most prairie restorations are much smaller, often just a few acres, and many are simplistic and contain at most one-fourth to one-half of the plant species that would be found in a natural prairie remnant of comparable size. Several factors are responsible. Because of cost and labor limitations, most prairie restorations are planted with a one-time seeding. Relatively few species (mostly warm season grasses and rather aggressive forbs) are included in the seeding mixes, a complete phenology of species is not attempted, a number of species included in the mixes rarely succeed from seed, and follow-up species enrichment does not take place.
The following steps are often used with prairie restorations:
1) Site Preparation - The mode of site preparation depends on the vegetation present on the site before restoration. For a spring planting, soil can be turned over in the fall to kill the roots of perennial weeds by exposing them to winter temperatures. Annual weeds are controlled by working the ground at a shallow depth at least twice during early spring. A dense sod of non-prairie cool-season grass may require the application of a short-lived, non-selective herbicide.
2) Seed Selection and Storage - Prairie seed should be of high quality and should originate within 200 miles of the planting site. Most prairie seed needs to be stratified (cold, damp storage) before they will break dormancy. This fact is useful in counteracting the problem of prairie grass outcompeting forbs. Forbs can be stratified for an appropriate time (this varies depending on the species) while grasses are planted without a stratification period. This differential stratification will give prairie forbs an advantage over grasses in the initial phase of establishment.
3) Planting Methods - Depending on the species/site conditions, prairie plants can be established by broadcasting seed, by drilling seed into the soil, or by transplanting plants from the greenhouse to the field. A good way to prevent prairie grasses from outcompeting forbs is to plant in a mosaic and create areas where forbs are disproportionally represented.
4) Fire - Restored areas should be burned regularly, often yearly. Opinions differ (often heatedly) on the advantages and disadvantages of "spring" versus "fall" season burns. In my view, the primary emphasis should be on whether burns are conducted during the growing season or when the plants are dormant. There are situation where burning is not practical or legal, and yearly mowing may be used, although this does not have the same effect.
The success of prairie restorations seems to depend largely upon the techniques used to restore the prairie. While there are a great many prairie restoration that have been planted in the past 20 years or so, few long-term detailed monitoring studies have been undertaken quantifying different techinques. Restorations can be conducted through a process of seeding, planting seedlings, or transferring sod from intact prairie. It appears that transplanting sod increases the likelihood of success in establishing soil microorganisms and a fuller complement of vascular flora. The lack of a full diversity of prairie plants, however, should not discourage the use of restoration techniques to increase the total area of prairie within the Midwest. At present, we do not yet know whether these restored sites will eventually become more diverse. Also, over the short term these restoration sites provide habitat for species that are becoming increasingly rare in the state. The application of ecological theory (Burton et al. 1988a, b), such as niche quantification, mechanisms of succession and community stability, and spatial heterogeneity and landscape ecology, may improve the success of prairie restorations.
The restoration of ecosystems is a practical science and generally not based on rigidly controlled and monitored experimental plantings. Rather, increases in knowledge are acquired by the arduous process of trial and error. One example is the paper by Peter Schramm entitled "Prairie restoration: a twenty-five year perspective on establishment and management," which was published in the Proceedings of the Twelfth North American Prairie Conference. The reference given below by Scott Weber (1999) have a very good discussion on the issue of seed mixes and suggestions for improvements that will result in prairie restorations and plantings that contain more species diversity, including "conservative" species.
Common ecological problems associated with natural prairies, but which also need to be addressed with prairie restorations, include fragmentation, the suppression of fire, exotic species invasions, and habitat destruction and degradation. Small, isolated fragments tend to support many species at low population levels (thus prone to local extinction) too distant to be enhanced through natural mechanisms of species dispersal. Isolated prairies may also be lacking appropriate pollinator species for successful sexual reproduction of many outcrossing species. The greater edge-to-volume ratios of small sites offer greater opportunities for exotic species invasions since the matrix areas typically are dominated by non-native vegetation. Highly fragmented and developed landscapes also lead to altered fire regimes often eliminating fire from prairie remnants until restoration efforts commence. Fire absence results in ecological changes such as encroachment of woody plants that can eliminate many prairie species. Fire absence can also lead to a severe invasion of exotic cool-season grasses like the ubiquitous species meadow fescue, smooth brome, and Kentucky bluegrass. Over-grazing by domestic stock typically degrades prairie remnants by eliminating many species and promoting the increase of several weedy native and non-native taxa. Soil disturbances such as past efforts at cultivation result in loss of prairie species and opportunities for the establishment of weedy taxa. All of these factors, and combinations of factors, tend to result in loss of species diversity and ecological integrity for all prairie community types. The water regimes of mesic, wet-mesic, and wet prairies have often been altered by the installation, sometimes long ago, of drainage tile and/or drainage ditches in adjacent areas.
While new restorations are an important way to increase prairie acreage in Illinois, they are no substitute for the preservation/restoration of the remnants of original prairie. Even the best prairie restorations do not approach the species diversity of the original systems. Some new restorations are successful at recreating the prairie plant community but, most fall short of replicating the insect, small mammal and soil invertebrate communities. Some restorationists feel we will never reach that point.
For more information on prairie restoration, the following sources may be consulted.
The Tallgrass Restoration Handbook: For Prairies, Savannas, and Woodlands, by Stephen Packard and Cornelia F. Mutel, editors. 1997. Society for Ecological Restoration by Island Press, 1718 Connecticut Avenue NW, Suite 300, Washington, D.C. 2009-1148. xxxii + 463 pages
Restoring the Tallgrass Prairie: An Illustrated Manual for Iowa and the Upper Midwest by Shirley Shirley. 1994. University of Iowa Press, Iowa City. xiii + 330 pages.
Prairies, Forests, and Wetlands: The Restoration of Natural Landscape Communities in Iowa by Janette R. Thompson. 1992. University of Iowa Press, Iowa City. viii + 139 pages.
Prairie Establishment and Landscaping by William E. McClain. Illinois Department of Natural Resources, Division of Natural Heritage, 524 South Second Street, Springfield, Illinois 62701-1787. vi + 62 pages. [Available from the Illinois Department of Natural Resources, Division of Natural Heritage, 524 South Second Street, Springfield, IL 62706. Also available on the www at: http://dnr.state.il.us/flora/prairie/table.htm
Designing seed mixes for prairie restorations: Revisiting the formula. Ecological Restoration by Scott Weber. 1999. Volume 17, number 4, pages 196 - 201.
Prairie restoration: A 25-year perspective on establishment and management by Peter Schramm. 1992. Pages 169 - 177 in Proceedings of the Twelth North American Prairie Conference, edited by Daryl D. Smith and Carol A. Jacobs. University of Northern Iowa, Cedar Falls.
Also see the bibliography section of this web site http://www.inhs.uiuc.edu/~kenr/prairiebiblio.html.
Below are links to mailorder sources for prairie plants and seeds*
*Disclaimer: The listing of companies or individuals in this web site does not represent an endorsement of these organizations or their products by the author or the Illinois Natural History Survey.
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