Ecosystems Historically in the Watershed

--Lake Michigan Basin Prairies

Lakeplain System: Lakeplain Prairies

Lakeplain prairies consist of rich and deep soils on which a variety of tall grasses and flowers grow. The grasses may reach 12 feet in height. The roots of some of the prairie plants reach as far below the ground as the plant above ground. The lakeplains on which the tall grass prairies grow were formed from sediments deposited as the Wisconsin glacier receded more than 10,000 years ago. Prior to European settlement, the tall grass prairie peninsula extended from the southern Lake Michigan area in northeastern Illinois and Northwest Indiana through southern Michigan to Ontario. Since the mid-1800s, lakeplain prairies have been converted to agriculture. Only tiny parcels remain–less than 0.01 percent of the original. The best remaining fragments in the Lake Michigan basin are found at Chiwaukee Prairie in Southeastern Wisconsin, Markham Prairie in Northeast Illinois, Hoosier Prairie in Northwest Indiana, and Allegan State Game Area in Southwest Michigan (Albert 1996). Lakeplain prairies depend on the water-level fluctuation of the lake. Their deep root systems enable these prairies to hold water, acting much as marshes do. Periodic fires and fluctuating water levels help prairies maintain their open, treeless condition. Organic material such as leaf litter is eliminated, allowing new growth.

Wet lakeplain prairies are found at the shoreline or growing contiguously with coastal marshes. Vegetation includes grasses such as blue joint grass (Calamagrostis canadensis) and prairie cordgrass (Spartina pectinata), sedges such as Carex stricta and Carec aquatilus, red osier dogwood (Cornus stolonifera), and shrubby cinquefoil (Potentilla fruticosa) (Reid and Holland 1997). Dry or mesic lakeplain prairies lie at the edges of the wet prairies. Plant species include big bluestem grass (Anropogon gerardii), little bluestem grass (Andropogon scoparius), Indian grass (Sorgastrum nutans), switch grass (Panicum virgatum), tall coreopsis (Coreopsos tripteris), blazing star (Liatris spicata), and Ohio goldenrod (Solidago ohioensis) (Reid and Holland 1997). The Prairie white fringed orchid (Platanathera leucophaea) is a federally threatened lakeplain prairie plant (Reid and Holland 1997).

Formerly, the foremost lakeplain prairie animals were bison and elk. Both species are gone, along with other large mammals, from present lakeplain prairies. Today, muskrats are found in wet prairie areas. Prairie ant mounds and crayfish chimneys lie inconspicuously among tallgrasses. The king rail is sometimes spotted at wetter sites. Insects, including grasshoppers, true bugs, leafhoppers, spittlebugs, planthoppers, and treehoppers. Papaipema sciata, a moth borer dependent on Culver's root (Veronicastrum viginicum), is also a notable lakeplain prairie forb (Reid and Holland 1997).

Lakeplain prairie fragments retain insect populations and many plant species. However, few of these prairies remain. The tiny sites that have been preserved are disconnected from the large lakeplain system and are still at risk from being impacted by stressors from outside the preserves, such as water level changes due to nearby development. In addition, lack of prescribed fire and exotic species are major challenges for preserve managers. Since many sites are located in urban areas, conducting prescribed burns must be done with extreme caution. Exotic species are numerous and require laborious efforts to control.

Lakeplain System: Oak Savannas

Oak savannas are areas that lie between the prairies of the west and the deciduous forests of the east. In pre-European settlement times, they were a transition zone, maintained by frequent fires and probably by bison, elk, and deer. A variety of oaks dominate the canopy. The understory and ground layer vegetation is characterized by few shrubs and a rich variety of grasses and forbs. Plant species vary in relation to shade and sun tolerance. Savanna plant species found in preserves today include Indiana plantain, yellow pimpernel, downy wild rye, elm-leaved goldenrod, and New Jersey tea (Wisconsin Department of Natural Resources 1995).

Savannas formerly were habitat for the timber wolf, bison and elk, now extirpated from this landscape. Long-tailed weasels, red fox, woodchuck, rabbits, and white-tailed deer, however, are doing well today. Except for the ill-fated passenger pigeon, many savanna birds species, such as the American robin, indigo bunting, blue jay, and American goldfinch are still doing well. This is due to the many wood lots still found on many home sites. A number of species have begun to decline in recent years, including the red-headed woodpecker and the warbling vireo. One butterfly, the Karner blue butterfly (Lycaeides melissa samuelis), is currently designated as a federally endangered species, but remains in healthy populations in the savannas of Northwest Indiana and central Wisconsin, as well as in oak barrens (Wisconsin Department of Natural Resources 1995).

Of the many amphibians and reptiles associated with oak savannas, many seem to be surviving well. These include gray tree frog, five-lined skink, and smooth green snake; however, the western slender glass lizard and the eastern Massasauga rattlesnake are now threatened. The Blanding's turtle is also considered rare and threatened (Wisconsin Department of Natural Resources 1995). Although they were probably relatively dynamic, not much is known about the original savannas. Since they were attractive to early settlers, they were first settled and cleared for agriculture or used for cattle grazing. Fires were controlled, and invasive exotic species, such as honeysuckle and buckthorn, moved in to replace the diverse ground cover. It is estimated that of the original 5.5 million acres of oak savanna in Wisconsin at the time of European settlement, less that 0.01 percent remains, most in degraded condition.

Threats to the oak savanna ecosystem continue due to increasing development, invasion by exotics, a resistance or lack of understanding about the role of prescribed burning in maintaining the ecosystem, and the acceleration of forest succession and lack of recruitment (Wisconsin Department of Natural Resources 1995).

Text excerpted from the Lake Michigan Lakewide Management Plan, U.S. Environmental Protection Agency Great Lakes National Program Office, 2000.

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