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1993 Proceedings of the Midwest Oak Savanna Conferences1993 Proceedings of the Midwest Oak Savanna Conferences



Martha A. Maxon, Ph.D. 
RUST Environmental & Infrastructure
501 Sycamore Street, Suite 222
Waterloo, IA 50703
Tel: (319) 232-6531


The restoration and management of natural plant communities and animal habitat of the Mallard Ridge Recycling and Disposal Facility (RDF) in Walworth County, Wisconsin, will create open space, protect and enhance the ecological integrity of the site, establish stable upland and wetland plant communities, restore native species while removing exotic competitors, and provide for nesting sites and migration areas for the Blanding's turtle. Waste Management of Wisconsin, Inc., with the Wisconsin Department of Natural Resources, will coordinate the implementation of the plan.


Waste Management of Wisconsin, Inc., (WMWI) has initiated plans for the restoration and management of natural plant communities and animal habitat at the Mallard Ridge Recycling and Disposal Facility (RDF) in Walworth County, Wisconsin. Coordination with Wisconsin Department of Natural Resources (WDNR) was maintained while developing this plan. The goals of WMWI for the restoration management activities for this site are:

  • Creation of natural open space.
  • Protection and enhancement of long-term ecological integrity of site, and linkage to Turtle Creek.
  • Establishment of diverse and stable upland and wetland plant communities.
  • Restoration of native species and elimination of exotic, non-native competitors.
  • Provision for open upland nesting sites and migration areas for the Blanding's turtle.

The plant communities that would be established, restored, or enhanced on this site include:

  • Enhancement of 150 acres of existing oak openings (savanna) in wooded areas that are now overgrown with woody underbrush. 
  • Establishment of 89 acres of dry-mesic prairie on borrow/stockpile areas, cropland, former quarry, hayfield, entrance corridor.
  • Establishment of 92 acres of native grasses/forbs on 3 closed landfills.
  • Enhancement of 6 small wetland areas within these woods (about 10 acres total).
  • Establishment of 37 acres of wet prairie/southern sedge meadow in cropland along Turtle Creek.
  • Enhancement of 3 acres of existing calcareous fen/southern sedge meadow that currently is disturbed.

The total amount of the site that will be vegetated with native plant communities with this plan will be about 381 acres. The plan would be conducted in phases between 1993 and 2003. 

The plan also includes measures to protect and improve habitat for three state protected reptiles: Blanding's turtle (Emydoidea blandingii), queen snake (Regina septemvittata), and eastern massasauga snake (Sistrurus).

This plan is designed to be a flexible one that will evolve over the years of implementation. This flexibility is necessary because the state-of-the-art of restoration and management of natural systems is constantly changing as new information, techniques and seed sources become available. Also, information on the micro-environmental conditions and monitoring results of these restorations at Mallard Ridge RDF will become available over the years. 

This plan is presented in detail in Appendix R - Ecological Restoration and Management Plan, in Volume 4 of Plan of Operation, Mallard Ridge Recycling and Disposal Facility Northern Expansion, Walworth County, Wisconsin, submitted by WMWI to WDNR, October, 1992.

This paper will focus on the planned oak savanna enhancement part of the plan that was the subject of our poster presentation at the Midwest Oak Savanna Conference on February 20, 1993, in Chicago. 


Physical Setting

Waste Management of Wisconsin, Inc., (WMWI) currently owns and operates the 600-acre Mallard Ridge RDF site located immediately north of STH 11, four miles west of Delavan, Wisconsin (Figure 1). The facility accepts non-hazardous municipal, commercial and industrial waste from Walworth and several adjacent counties. Besides the active landfill, the area also includes the closed Greidanus Landfill. 

The area outside these landfills contains native woods, wetlands, row crop areas and hayfields. The woods are actually degraded oak openings (savannas) that through past grazing and fire suppression, have been taken over by a weedy shrub understory. Likewise, the wetlands have been degraded by grazing and sedimentation from adjacent cropland areas. The southeastern area of the property abuts Turtle Creek, a high quality stream. This general area of Turtle Creek has been identified as a primary environmental corridor by the Southeast Wisconsin Regional Planning Commission. 


Elevations range from 980 feet MSL on the west side to 865 feet MSL near Turtle Creek. The eastern area is lowland with a very shallow water table, discharging groundwater to Turtle Creek. The rest of the site is upland, with from 50 to 80 feet between the ground surface and the water table.

The site is underlain at 150 to 200 feet by Ordovician Age dolomite and shaley dolomite. The bedrock is overlain unconformably by 150 to 200 feet of unconsolidated glacial and glacial-fluvial material of three Wisconsinan age formations. Two units of the Walworth Formation consisting of a lacustrine fine-grained unit and a silty sand till were encountered beneath the site. Dolomite and igneous gravel and cobbles are common throughout this formation. The uppermost formation, exposed at the surface over most of the Mallard Ridge RDF property, is the New Berlin Formation. This formation ranges from 80 to 150 feet thick and includes three undifferentiated members: calcareous deposits of till, outwash, and lacustrine silts and clays.


Soils of the glacial moraine deposits that cover most of the site include well-drained loams and silt loams of the Miami, McHenry and Dodge series. Poorly drained silt loam soils of the Pella series occur in depressions. The Miami, McHenry and Dodge soil series are classified as Typic Hapludalfs of the Alfisol order. Soil formation probably occurred under a tree canopy ranging from oak-hickory woods to oak openings with prairie (USDA Soil Conservation Service, 1971).

Prolonged soil saturation has led to the formation of Houghton muck soils of the Histosol order (organic soils) on much of this southeast part of the site (Soil Conservation Service, 1971). Snails use calcium to make their shells and the abundance of shell fragments on the soil surface in this area indicates a calcareous variant of the Houghton muck saturated by mineral rich groundwater. The muck soils are surrounded by shallow, poorly drained silt loam soils of the Drummer series. Zones of wet prairie, southern sedge meadow and calcareous fen plant communities were probably the original vegetation of this 40 acres. 

Plant Communities

The plant communities on the site were surveyed by RUST botanist, Mark Leoschke, and Dr. Gerould Wilhelm in 1992 and 1993. The community types used here generally follow the classification system of the WDNR's Natural Heritage program. These communities on the site are: calcareous fen, southern sedge meadow, oak opening, old field, and deep and shallow marshes. The existing vegetation is briefly described in the following paragraphs. The oak openings are described in detail in the next section. The calcareous fen is on the southeast portion of Mallard Ridge RDF and is rather small (less than 0.5 acre). It is found along either side of a small stream that drains east into Turtle Creek. The soil here is a shallow muck, too shallow to be a Houghton muck. The presence of Houghton muck adjacent to the fen (in the abandoned cropland) indicates that the fen may have been larger at one time. Four fen indicators were found on the fen: sterile sedge (Carex sterilis), fewflowered spikerush (Eleocharis pauciflora), grass of Parnassus (Parnassia glauca), and slender bog arrow grass (Triglochin palustris).

The adjacent abandoned cropland probably was (and still is) a source of siltation, with soil deposited on the fen. This soil deposition has probably smothered portions of the fen remnant, making it possible for reed canary grass and purple loosestrife (Lythrum salicaria) to invade the outer portions of this plant community. 

The southern sedge meadow at the Mallard Ridge RDF, about 2.5 acres in size, is adjacent to (and in places blends in with) the calcareous fen. Like the fen, the southern sedge meadow may have once occurred on thenearby cropland of Houghton muck. Much of the southern sedge meadow was probably destroyed by draining and plowing. It has been degraded by siltation, plus Eurasian weed, tree and shrub invasion.

One deep marsh exists on the site and is a mix of open water and vegetation such as cattail (Typha sp.), sedges (Carex spp.), bulrushes (Scirpus spp.), spikerushes (Eleocharis spp.), rushes (Juncus sp.), arrowhead (Sagittaria spp.), bur reed (Sparganium spp.) and pondweeds (Potamogeton spp.). A portion of this wetland is dominated by the invasive reed canary grass. 

Shallow marshes on the site are dominated by emergent plants such as sedges (Carex spp. and Dulichium arundinaceum), rushes (Juncus spp.), manna grass (Glyceria spp.), horsetail (Equisetum fluviatile) and knotweeds (Polygonum spp.). Sedimentation has partially filled in these shallow marshes on Mallard Ridge RDF. This has resulted in their becoming dominated in part or entirely by reed canary grass. 


Plant Species

No endangered or threatened plant species were found in the field surveys conducted by RUST botanist Mark Leoschke in July, August and September, 1992, and May, 1993, on this site. The Bureau of Endangered Species, WDNR, has reviewed the project site and provided records for an area within two miles of the project location. These records show that two plant species have been reported from this 2-mile area:

  • Asclepias purpurascens - purple milkweed - State Endangered
  • Cirsium hillii - prairie thistle - State Threatened and under federal review for listing as federally threatened by the U.S. Fish and Wildlife Service.

This survey found four species that are county records but that are more common in other areas of Wisconsin. Hairy-fruited sedge, (Carex trichocarpa) and few flowered spikerush, (Eleocharis pauciflora), were found in the calcareous fen/southern sedge meadow. Crawford's sedge, (Carex crawfordii), was found in a cleared corridor in the west oak opening. It previously was only known in Wisconsin from the northwest part of the state. Water fern, (Azolla caroliniana), was found floating in the deep marsh.


Existing Plant Community

An oak opening (a type of savanna) is a terrestrial community dominated by bur oak (Quercus macrocarpa), black oak (Quercus velutina), Hill's oak (Quercus ellipsoidalis) or white oak (Quercus alba). The canopy ranges from fairly open (with individual tree canopies not overlapping) to fairly closed, with tree canopies overlapping. Canopy cover ranges from 1080% (Curtis, 1959; Nelson, 1985). The primary branches are held in a position at or below horizontal to raised at an angle above the horizontal. The understory of an oak opening has some shrubs (American hazelnut, Corylus americana, etc.). The herb layer has herbaceous plants found in prairies and oak woods. Fire is an important factor in maintaining an oak opening. It kills small trees, shrubs, and some herbaceous plants (those that are not fire adapted), helping to keep the understory relatively open. It also trims the lower tree branches to variable heights, which was also historically done by large herbivores (Nelson, 1985), probably bison and elk.

Several hundred acres of oak opening remnants occur in four areas on the site, referred to as East, West, North and South Woods. These currently appear as closed canopy woods, but indicators of their former nature were present, such as open-grown oaks and herbaceous species. 

Lack of fire and overgrazing have altered these oak openings. Fire suppression has meant a serious decrease in oak recruitment, plus the growth of shrubs and trees intolerant of fire. Fire favors oak opening oaks over trees and shrubs intolerant of fire. Some species of trees intolerant of fire are also tolerant of shade, while the oaks are intolerant of shade. This has resulted in increased shading of the ground, reducing or eliminating plant species that grew in partial shade or open sun. Much of the groundcover layer has been shaded away. 

Grazing and fire suppression has also encouraged the growth and survival of dense, prickly thickets of gooseberry (Ribes sp.), blackberry (Rubus sp.), multiflora rosa (Rosa multiflora) and prickly ash (Xanthoxylum americanum). Other shrubs also have done well under these conditions including common buckthorn (Rhamuscathartica) and honeysuckle (Lonicera spp.).

These woods contain several oak species, including white, bur, black and Hill's oak, as well as shagbark hickory, black maple and black walnut. A few old, open-grown oaks are scattered throughout the woods. 

Plant surveys were conducted in the West, East and South Woods in July, August and September, 1992, and May, 1993, to characterize the subcanopy and herbaceous layers by RUST botanist Mark Leoschke and Dr. Gerould Wilhelm. The species list from these surveys appears in Tables 1, 2 and 3. Several of these species are those reported by Curtis (1959) or Bray (1960) as being characteristic of the shrub layer or groundcover in Wisconsin savannas, as indicated on these tables. 

Although disturbance to the oak opening community by past grazing, logging and lack of fire has been significant, it is possible that state protected species may be found. Some rare species may be easier to locate after active management has taken place. Apfelbaum and Haney (1988) report that wild hyacinth, Camassia scilloides (endangered in Wisconsin) became more abundant after a managed burning. They also report that 16 species of plants were present after an oak opening burn that were not apparent before fire management was applied. Packard (1988) reports that yellowish gentian, (Gentiana flavida, threatened in Wisconsin) was not apparent before applied burning in an Illinois oak opening fire, but appeared and increased in number after initiation of fire management.

The South Woods has received the same abuse as the other woods but has been constantly perturbed by regular mowing and perhaps by more recent grazing. The groundcover, rather than being sparsely vegetated, as in the other woods, is dominated by Eurasian pasture grasses, although in the northern part of these woods a west slope of the southernmost knoll has an unusually dense turf of the native graminoid sedge, Carex pensylvanica. A species list was not developed for the North Woods, but it appeared to be similar to the other woods on the site.

Enhancement Plan

The enhancement of these wooded areas will involve a combination of annual controlled burns and clearing of underbrush. Experience has shown that when annual fire is restored, and 10-15 percent of available light can penetrate to ground, there is a surprising floristic response from the latent seed bed. 

An example of this response was found on the site in a remnant oak opening located where the proposed northern expansion area is planned, and referred to as West Woods. An approximately 50-foot corridor had been cleared of trees and brush through this area in 1988-1989 to establish monitoring wells. This allowed sunlight to penetrate and the groundcover to respond. Observations on plant species and cover in this area in July and August, 1992, found some of the fuel species associated with oak openings, such as tufted wood sedge (Carex convoluta), to be abundant and more obvious than in the adjacent closed canopy areas. Likewise, several of the forb species associated with oak openings, such as shooting star (Dodecatheon media), were apparent in this open area. 

These observations led to the opinion that there was high rehabilitation potential for the oak openings on the site, with proper management. Our early impression, from examining this area, is that supplemental plantings may not be needed in the early years. There appears to be enough remnant diversity to indicate that response might be fairly pronounced after 5 years of management. In any event, it would make no sense to do any seeding until the system is open to light and most of the weedy trees have been removed, since little germination can occur in the shade. 

Based on this assessment of rehabilitation potential, Waste Management of Wisconsin, Inc., determined that the following wooded areas on the site will be rehabilitated:

  • West Woods - 8 Acres
  • East Woods - 60 Acres
  • North Woods - 66 Acres
  • South Woods - 16 Acres

The rehabilitation procedure for these areas will be:

  • Clear woody understory.
  • Remove selected trees, leaving only oaks, hickories, walnuts and old maples.
  • Begin prescribed burning on an annual basis during the rehabilitation stage (protocol for first 5 years and then re-evaluate).
  • Monitor the development of species composition in groundcover and follow demography of canopy.
  • Use broad-leaved herbicide (applied with a wick applicator) and/or continue cutting on sprouts of remaining undesirable shrubs, as necessary.
  • Plant supplemental species, only if needed and using only species native to Walworth or Rock Counties and seeds that originate from this area.

Evaluations should be made at the end of each management year to determine what actions may be indicated for succeeding years. It is probable that ad hoc decisions on the need for brushhogging and/or herbiciding will be necessary for the first 4 or 5 years. Because this area is adjacent to a residential neighborhood to the east, public education regarding this plan will be conducted by WMWI. This is especially important in the area of prescribed burning. 


It will be important to the success of this plan to assess the extent to which the natural groundcover vegetation is re-establishing in the South, North, West and East Woods. A baseline transect, or suite of sampling transects will be established in these areas before restoration efforts begin. The transects will include 1/4 m2 quadrats in these woods. The quadrats will be deployed randomly along a permanent transect.

A complete inventory of the vascular plant species will be recorded from each quadrat, and each species evaluated as to its cover/abundance and the number of native taxa per quadrat. The mean coefficient of conservatism and the mean floristic quality index will be calculated (Swink and Wilhelm, 1979). The same factors will be calculated for the aggregate suite of native species encountered along the transect as a whole. In this way, the extent to which conservative native species are coalescing on the site can be determined. As conservative native species coalesce into a natural community, the mean coefficients of conservatism and floristic quality indices rise (Swink and Wilhelm, 1979). Should the system begin to degrade, the occurrence of such species would become more diffuse and the indices would drop.


This enhancement plan was developed in association with Dr. Gerould Wilhelm, Morton Arboretum, Lisle, Illinois, and was based on his field review of the site. Others who participated in the development of this plan include Mike Ettner, Dan LeClaire and Bob Vallis, Waste Management of Wisconsin; Jane Shuttleworth, Mark Leoschke and Joan Underwood, RUST Environment & Infrastructure; and Gary Casper, Casper Consulting, Milwaukee, Wisconsin.


Apfelbaum, S. I. and A. W. Haney. 1991. Management of degraded oak savannah remnants in the upper midwest: preliminary results from Three years of study. In: 

G. V. Burger, J. E. Ebinger and G. S. Wilhelm, eds. Proceedings of the oak woods management workshop. Eastern Illinois University, Charleston, Illinois.

Bray, J. R. 1960. The composition of savanna vegetation in Wisconsin. Ecology, 41:721-732.

Bray, J. R. 1955. The savanna vegetation of Wisconsin and an application of the concepts order and complexity to the field of ecology. Ph.D. Thesis, University of Wisconsin. 

Curtis, John T. 1959. The vegetation of Wisconsin. An Ordination of Plant Communities. The University of Wisconsin Press, Madison, Wisconsin.

Natural Heritage Program. 1992. Wisconsin natural community working list. Wisconsin Department of Natural Resources, Madison, Wisconsin.

Nelson, P. W. 1985. The terrestrial natural communities of Missouri. Missouri Natural Areas Committee. Missouri Department of Conservation and the Department of Natural Resources, Jefferson City, Missouri. 197p.

Nuzzo, V. A. 1986. Extent and status of midwest oak savanna: Presettlement. 1985. Natural Areas Journal, 6(2):6-36.

Packard, S. 1988. Rediscovering the tallgrass savanna of Illinois. In: A. Davis and G. Stanford, eds. Proceedings of the tenth North American prairie conference. Texas Woman's University, Denton, Texas. 

Swink, F. and G. Wilhelm. 1979. Plants of the Chicago region. Revised and Expanded Edition With Keys. The Morton Arboretum, Lisle, Illinois. 

USDA Soil Conservation Service. 1971. Soil survey of Walworth County, Wisconsin. Government Printing Office, Washington, D.C.


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