Botanical Inventory of Prairie Ridge State Natural Area, Jasper County, Illinois

Gordon Tucker¹, Sean A. Jones¹, Bob Edgin² and John E. Ebinger¹

¹Dept. of Biological Sciences, Eastern Illinois University
²Illinois Nature Preserves Commission, 9940 E 500th Ave., Newton, IL 62448
 

Introduction
 

Although Illinois is known as the “Prairie State,” grassland habitats come at a premium in Illinois, and so do many grassland birds. Prairie Ridge is rated as one of the five most significant grassland habitat complexes in Illinois and is well known for supporting the only population of Greater Prairie Chickens in the state. Besides the Prairie Chickens, the site also has the largest wintering and breeding populations of Northern Harriers and Short-eared Owls in Illinois (Simpson & Esker 1997). Also breeding on the site are King Rails, American Bitterns, Upland Sandpipers, and a growing population of Henslow’s Sparrows, all endangered in Illinois. While the grasslands and wetlands of Prairie Ridge are the most unique feature of this area, a wide variety of habitats is nearby, including forested areas and Newton Lake.

Prairie Ridge State Natural Area comprises about 1100 ha in the Southern Till Plain Natural Division (Figure 1). The preserve, which was established in 1960, now includes 15 separate tracts, and is located ca. 10 km S of Newton, Illinois (Figure 2). Government Land Office Survey notes of 1820 indicate that 87% of the site was prairie, with the balance forest. Following extensive settlement of Jasper County, these prairie areas were converted to agriculture.

There is abundant information on the site’s fauna, especially breeding birds (Simpson, 1998). However, only two studies have focused on the plant life. A natural prairie restoration was studied by Edgin & Ebinger (2000), and the five tracts of man-made prairie restorations were surveyed by Kessler, Tucker & Ebinger (2001). In total, these two studies dealt with only about 20% of the preserve.

Methods

Our study had two goals: complete inventory of species and quantitative study of plant communities. In addition to occasional visits by the authors since 1998, the site was visited by the authors 25 times during the growing seasons of 2004 through 2006, to observe and collect plant specimens. Field work covered the growing season from April through October. Specimens were identified, labeled, and accessioned into the Stover-Ebinger Herbarium of Eastern Illinois University. Vegetation sampling of the community was carried out using standard methods (Mueller-Dombois & Ellenberg 1974). Quantitative abundance of herbaceous and woody species was determined using standard methods (Bailey & Poulton 1968). We sampled 12 grassland areas using 50 m transects.

Results

We found a total of 508 vascular plant species. Of these, 411 were native. We found two new state records (Penstemon tubaeflorus, Figure 3, and Schoenoplectus americanus; Tucker 2002). No other state listed rare species were found. However, we did document a total of 40 new county records for Jasper County. A number of interesting species was seen, including two orchids, Platanthera peramoena and Liparis lilifolia. Some genera are especially well represented. We are not aware of any other site in the state that has so many species (8) of Asclepias (milkweed) as does Prairie Ridge (Figure 4). The percentage of exotic species (19%) is substantially less than that of Illinois as a whole (31%); cf. Mohlenbrock (2002). The average coefficient of conservatism, following the method of Taft et al. (1997) for Illinois, was 3.1 for all species and 3.75 for native species only (cf. Figure 5). The average number of species per transect was 12.75 (range: 9 to 18).

Discussion

Grassland communities fell into two types (Table 2): cool season grasslands, managed by mowing and co-dominated by Festuca arundinacea and Agrostis gigantea and warm season grasslands, managed by fire or mowing, and co-dominated by Andropogon gerardii and Sorghastrum nutans. However, Solidago canadensis was typically the most abundant species in most sites. The number of exotics that are genuinely plentiful and widespread at the preserve is small.

There was no direct correlation between age of the restored site and quality of the site. Many variables existed between the sites, such as seed source, number of burns, and other maintenance practices. For example, Lew’s Prairie, the oldest of the sites, ranked second to Galbreath Sanctuary, the third oldest of the sites. Lew’s Prairie had a FQI of 21.57, compared to an FQI of 25.20 for Galbreath Sanctuary. Based on the results of this study, Galbreath proved to be the best quality of restored prairie at Prairie Ridge State Natural Area. Techniques applied in this area should serve as a starting point for future restoration projects.

Exotic Species are sometimes a problem in grassland, forest, and wetlands, and in site management plans. The number of exotics that are genuinely plentiful and widespread at the preserve is few. Phragmites australis occurs at one tract in a localized patch that could be removed. Woody exotics are few in the grassland areas, apparently effectively controlled by mowing and burning practices.
Future Research Plans: Because the 2005 season included several weeks of drought, we are making regular visits to Prairie Ridge during the 2006 growing season, to search for species that may not have been evident last year. Also, we plan to monitor the wetlands for additional species. A series of vernal pool wetlands was created last year for amphibian breeding habitat; these sites may well be a source of additional species.

References

Bailey, A.W. & C.E. Poulton. 1968. Plant communities and environmental relationships in a portion of the Tillamook Burn, northwestern Oregon. Ecology 49: 1-13.
Edgin, B., & J.E. Ebinger. 2000. Vegetation of a successional prairie at Prairie Ridge State Natural Area, Jasper County, Illinois. Castanea 65: 139-146.
Kessler, A., G.C. Tucker, & J.E. Ebinger. 2001. Prairie Restorations at Prairie Ridge State Natural Area, Jasper County, Illinois. Transactions of the Illinois State Academy of Science 94: 127-138.
Mohlenbrock, R. 2002. Vascular Flora of Illinois. SIU Press, Carbondale & Edwardsville.
Mueller-Dombois, D., & H. Ellenberg. 1974. Aims and methods of vegetation ecology. John Wiley and Sons, New York, New York.
Simpson, S. A. 1998. Prairie Ridge State Natural Area: a grassland bird success story involving 40 years of cooperation among public agencies, private conservation organizations and dedicated individuals. Illinois Audubon 266:4-9.
_____ & T.L. Esker. 1997. Prairie Ridge State Natural Area Habitat Plan. Illinois Dept. of Natural Resources: Division of Natural Heritage. vii + 80 pp.
Taft, J.B., G.S. Wilhelm, D.M. Ladd, & L.A. Masters. 1997. Floristic quality assessment for vegetation in Illinois, a method for assessing vegetation integrity. Erigenia 15: 1-95.
Tucker, G.C. 2001. Scirpus sensu lato (Cyperaceae) in Illinois: an update. Transactions of the Illinois State Academy of Science 94: 53.

Acknowledgements

IDNR site managers Scott Simpson and Terry Esker (IDNR)

Brent Wachholder, Jason Cunningham, April McDonnell, Matt Zmich, Zhi Wei Liu, Vicky Tucker, Daniel Tucker, and Sarah Tucker for help with field work

Illinois Dept. of Natural Resources (Non-game Wildlife Fund) for major funding

Eastern Illinois Dept. of Biological Sciences for vehicle use and equipment

Illinois Audubon Society, Illinois Nature Preserves Commission and Illinois Department of Natural Resources for allowing this study to be conducted on properties under their care.