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1994 Proceedings
North American Conference on Savannas and Barrens


Victor Guarino
and Jean Guarino
Thatcher Woods Savanna Restoration Project
1004 North Oak Park Avenue
Oak Park, IL 60302
Tel: (708) 848-7175

Living in the Edge: 1994 Midwest Oak Savanna Conferences

In River Forest, Illinois, a Chicago suburb ten miles west of the city, are two parcels of Cook County Forest Preserves District (CCFPD) property: The Grand Army of the Republic (GAR) and Thomas Jefferson (TJ) Woods. This land is part of the Thatcher Woods corridor along the DesPlaines River, and represents a cross section of the DesPlaines River valley within the Chicago Lake Plain Section of the Northeastern Morainal Natural Division of Illinois. The restoration site encompasses approximately 85 acres on the west side of the river. This area is comprised of flood plain forest and upland savanna above 625' elevation.

The upland savanna is being managed for pre-European settlement conditions by the Thatcher Woods Savanna Restoration Project (TWSRP), a local community organization operating within the Volunteer Stewardship Network. This area, besides being geologically unique, is ecologically unique in the Chicago region because it has never been plowed, grazed, or logged, and thus has retained much of its natural ecological character. Qualitatively, the preservation value of this area lies in the human experience of its natural character in the middle of a major metropolis.

Practices used to gradually restore the savanna consist primarily of clearing the understory of woody plants, both native and non-native, by cutting, girdling, and burning. The primary invasive woods are: basswood, maple, ash, and buckthorn. Removal was done to gradually introduce sunlight to the herbaceous ground cover.

After four years of monthly three-hour work days, results of clearing are readily observable. These results are expressed in qualitative terms as affirmative answers to four questions relating to the authors' subjective observations as stewards of the site.

Management practices of the Thatcher Woods Savanna Restoration Project (TWSRP) during the period June, 1990 to June, 1994, and results to date are described.


The subject restoration site is a mesic oak savanna of approximately 45 acres of upland area occurring above 625 feet elevation. This area is within two preserves owned by the Cook County Forest Preserves District (CCFPD), the Grand Army of the Republic (GAR) to the north of Washington Boulevard in River Forest, Illinois, and the Thomas Jefferson (TJ) Woods to the south. Along the western side of the site is approximately 40 acres of bottomland wet mesic forest that drops to an elevation of 610 feet to the DesPlaines River. The site is geologically unique in that it is a portion of the only section of the DesPlaines river valley in which the river flows over the sediment of the ancient lake plain formed by the Glenwood Stage of Glacial Lake Chicago. The site is ecologically unique in that it has never been plowed, grazed, or logged since its purchased from the federal government in 1887 by Ashbel Steele, the first permanent settler of River Forest. The site's history, natural character, topographical diversity, and plant life and the formation of the TWSRP are described in recent papers (Bowels and Radke 1992; Donahue et al.1993). Our poster identifies the site in three different perspectives as follows:

  1. On the Illinois State Geological Survey plat of the Surficial Geology of the Chicago Region, 1970.
  2. On the pre-European settlement survey of township T39N,R12E, March, 20, 1821.
  3. On the Northeastern Illinois Planning Commission aerial photograph of township T39N,R12E, Proviso, Cook County, 1990

The TWSRP site was first identified as a remnant oak savanna by local naturalist Jim Hodapp who observed that an existing small oak opening located approximately in the center of the GAR area had an unusually dense and diverse herbaceous ground cover of native plants under a white and red oak canopy. It was speculated that this opening existed due to occasional fires that were spread from a fireplace in a trailside concrete shelter constructed adjacent to the opening by the CCFPD in the 1930s. The shelter had deteriorated over the years, and had become a gathering place for teen-agers to light a fire and drink beer, and subsequently leaving their empty bottles and hot embers.

Fire suppression on the other hand, is accountable for the dense understory of basswood, maples, and ash in most of the upland savanna. A plant inventory conducted of the entire 85 acre site which revealed a natural area of over still rich with 150 native species, including many specifically common to the savanna landscape. A complete species list (1992 inventory) is provided in Bowels and Radke (1992) and the savanna species are identified in Donahue et al. (1993). Based on the total number of native species, the Wilhelm Natural Area Rating Index (NARI) was calculated to be 66.3, indicating that the TWSRP site is an extremely rare area in the Chicago region.


The TWSRP was fortunate to have the previously described existing oak-opening as a benchmark for future restorations. The management objective for the site was to gradually open the 45 acre upland savanna under an existing canopy of red, white, and bur oaks. This objective also is supported by the prevalent tree species on the site, the surveyor's notes of the pre-European survey of 1821 and the present native species inventory. To this end, starting in June, 1990, the following management practices, not necessarily in chronological order, were put in place and continue today.

  1. Starting in the existing oak-opening and immediate vicinity, we began to selectively remove by cutting and girdling the prevalent basswood understory.
  2. At the north end of TJ and at a central section of GAR, maples were the prevalent understory. We selectively removed these primarily by cutting, careful not to cut or girdle any trees existing along the boarder with the surrounding residential area.
  3. At the north end of GAR, we began to selectively remove the ash understory by girdling.
  4. On the entire upland area, all the common buckthorn and bush honeysuckle were removed by cutting, and shoots are continually cut when sighted.
  5. At the south end of GAR, several non-native large polars in the overstory were girdled.
  6. Over the entire upland area each spring all flowering garlic mustard and dame's rocket plants were removed by pulling them out at the roots
  7. Prescribed burns were introduced in small sections of the upland savanna. As burn experience accumulated larger areas were burned, until all portions of the entire site were burned at least once in the past four years. Annual burns are planned as the basic management tool.
  8. The aforementioned dilapidated concrete shelter was removed by the CCFPD, and the disturbed area cleared of debris and seeded using seed from near-by savanna grasses and forbs.
  9. Foot-trail management was introduced to remove any sections of fallen trees that blocked the trail, and caused the encroachment of paths into natural areas.
  10. We began the restoration of a 0.2 acre area at the southeast end of TJ that was severely damaged by the Metropolitan Water Reclamation District construction project. The site was covered with top soil supplied by the CCFPD, manually graded and planted to native grasses and forbs in the summer of 1993. The CCFPD planted several small diameter oaks in the spring of 1994. We will continue to weed and seed until a native landscape is completed.

These management practices were carried out in monthly three-hour work-day activities during past four years. It must be emphasized that the objective is to gradually introduce more sunlight to the herbaceous ground cover. We can quantify richness of the TWSRP site using the NARI computation.


In this project, restoration efforts are viewed in purely subjective terms. Four questions were developed from the authors' experience working at the TWSRP site. The affirmative answers we give to these questions are the basis on which we assert that restoration is taking effect, but it is a long continuing process. The questions are:

  1. Has the original oak-opening expanded significantly in size? That is, is there now a much larger opening similar in native herbaceous ground cover density and diversity? The answer is a definite yes. A panoramic photograph of the site is presented in our poster.

  2. Has a reduction in the woody understory had a significant increase in sunlight penetration resulting in a readily observable enhancement of the savanna? The answer is a definite yes. The once dense understory has been significantly cleared in TJ so that now the native ground cover is clearly visible. Plants that were small and did not flower in previous years, such as the Solomon seals, are now tall and flowering. Also, referring to the entire site, several savanna plants such as wild coffee and purple Joe-pye weed and savanna grasses are present in greater abundance.

  3. Have any new species been sighted that can be attributed to the restoration effort? The answer is yes. In the past year (1993-1994), two species have been sighted. They are: nodding Trillium flexipes, and Hydrastis canadensis which have a coefficients of conservation value of 6 and 8, respectively. A photograph of the trillium is shown in our poster.

  4. Is there an awareness and support of the restoration effort within the local community? The answer is yes. Numerous articles have been written in the local papers calling attention to this "jewel" that exists in the community. The CCFPD erected a prominent sign at the entrance to the site with the name Thatcher Woods Savanna and a description of the restoration effort. The Village of River Forest, in February, 1994, unanimously passed a resolution supporting a proposal for dedication of the site as an Illinois Nature Preserve.


Bowels, M. and T. Radke. 1992. Proposal for Dedication of Thatcher, Gar, and Jefferson Woods in Cook County Illinois as an Illinois Nature Preserve. The Morton Arboretum, Lisle, IL 60532.

Donahue, K., Guarino, J. and Guarino, V. 1993. Restoration of an oak savanna within an urban Area. Proceedings of the Midwest Oak Savanna Conference, Northeastern Illinois University, Chicago, IL. In press.


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