Preserve Profile for Sterne's Woods Fen

General Description and Location

Sterne's Woods Park is an Illinois State Nature Preserve located within the glaciated central region of the United States just north of Crystal Lake, IL, about 90 km northwest of Chicago. 

The wetland complex consists of sedge meadow, wet prairie, and marsh, surrounded on three sides by a large Wisconsinan kamic moraine. We are studying three fens that are underlain by sapric peat soils, saturated with relatively cold, calcareous groundwater under flowing artesian conditions. Fen soils support calciphilic plant communities dominated by prairie grasses and/or sedges. The fens provide habitat for 191 plant species, seven of which are state-listed (three endangered, three threatened).

Surface drainage within the bowl-shaped complex flows through a narrow gap between two kamic glacial landforms. The bedrock, which consists of Silurian-age dolomite, is overlain by Wisconsinan-age loam and clay-loam diamicton (10 to 15 m thick) and sand and gravel outwash (15 to 45 m thick). Peat deposits (3 to 6 m thick) have accumulated within the fens and in other low-lying, poorly-drained areas. The water table is approximately 20 m beneath the upland areas of the study area and at or near ground surface in the low-lying areas. Springs, which are common along the base of the uplands, flow into small ponds and streams within the wetland complex. Springs and/or seeps also occur near the center of each fen. 

Modifications of the natural regime prior to 1990 included construction of ponds, drainage channels 2m deep, and a house and roads within and immediately adjacent to the fen-wetland complex. Changes after 1990 included construction of numerous houses within the watershed of the complex. 

Species of Concern

Seven state-listed species (three threatened and four endangered) have been identified in the fen-wetland complex and include:

• White Ladies Slipper Orchid (Cypripedium candidum)
• Twig Rush (Cladium mariscoides)
• Common Bog Arrow Grass (Triglochin maritima)
• Grass Pink Orchid (Calopogon tuberosus)
• Beaked Spike Rush (Eleocharis rostellata)
• White Beak Rush (Rhynchospora alba)
• Tufted Bulrush (Scirpus cespitosus)

Major Threats

Threats to the fens of the complex include discharge from a private septic system that services the Ranger's house, the infiltration of dissolved road salt, and trenches that were dug in the wetland earlier in the 1900s. Contaminant plumes present in two of the fens are coincident with the occurrence and proliferation of Typha angustifolia, and the absence of Scirpus acutus.

That is, portions of both the two fens contain dense growths of Typha angustifolia coincident with the absence of Scirpus acutus. Both species are emergent aquatics, but Typha angustifolia is a salt-tolerant herb known to invade following salt contamination and physical disturbance of a wetland. It is common in marshes and along expressways and only occurs in fens that have been disturbed.

Because NO3- and PO43- have been found to provide nutrients responsible for rapid growth of cattails in wetlands at the expense of more diverse vegetation, we initially thought that these nutrients might be responsible for the apparent changes in vegetation within the fens. However, the very low concentrations of NO3- and PO43- found in fen ground water during all seasons, strongly suggested that Na+ and Cl- were responsible for the dense growth of Typha angustifolia observed in the study area.

Trenches dug throughout the wetland complex have served to lower the water table, thereby drying out the peat and allowing the invasion of Buckthorn. 

Major Science and Stewardship Activities

We have monitored the site since 1990 and have sampled groundwater every two years to determine if houses constructed within the watershed of the park are affecting the water quality of the fens. The site was last sampled in 1996 and those data are being evaluated.

A program in place at the site is responsible for the removal of a large portion of the Buckthorn forest. Filling of the trenches would allow the water table to recover; however, this has not taken place.

References

• Panno, S.V., Nuzzo, V., Cartwright, K., Hensel, B.R., and Krapac, I.G., 1999. Changes to the chemical composition of groundwater in a fen-wetland complex caused by urban development. Wetlands, March, v. 19, no. 1.
• Panno, S.V., Hackley, K.C., and Nuzzo, V.A., 1998. Teaching of multidisciplinary environmental science in a wetland setting. Journal of Geological Education, v. 46, no. 2, p. 157-163.
• Panno, S.V., Nuzzo, V.A., Hensel, B.R. and Cartwright, K., 1995. Ground-water sampling techniques used in a fen-wetland complex. Natural Areas Journal, v. 15, no. 1, p. 75-76.
• Panno, S.V., Hackley, K.C., Nuzzo, V.A., Krapac, I.G., Casey, M., Garcia, B., Garcia, P., Glatz, J., Greteman, B., Neill, B., Rumpf, R., Roberts, D., Westermann-Clark, E., 1995. Long-term degradation of ground-water quality and vegetation in a fen-wetland complex resulting from development within its watershed. [Abstract] in Program and Abstracts, 40TH Annual Midwest Groundwater Conference, Columbia, MO, p. 7.
• Nuzzo, V.A., Hensel, B.R., Panno, S.V., Cartwright, K. and Krapac, I.G., 1993. Impacts of anthropogenic contaminants on vegetation and groundwater chemistry in a fen complex (IL). [Abstract] in Abstracts with Program, Ecological Society of America, Supplement to v. 74, p. 377.
• Panno, S.V., Hensel, B.R., Cartwright, K., Krapac, I.G. and Nuzzo, V.A., 1992. Ground-water chemistry of a fen-wetland complex in northeastern Illinois. [Abstract] in Abstracts with Program, Geological Society of America, v. 24, no. 7, p. 58A.
• Hensel, B.R., Panno, S.V., Cartwright, K., Miller, M.V., Nuzzo, V.A., 1991. Ecohydrology of a pristine fen. [Abstract] in Abstract with Program, Geological Society of America, v. 23, no. 5, p. A324-A325.

For more information, please contact Sam Panno at panno@isgs,uiuc.edu