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Natural Features Inventory
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Ecosystems Historically in the Watershed --Lake Michigan Basin Forests Inland Terrestrial System The inland terrestrial system or upland areas of the Lake Michigan basin include numerous forest types, barrens, and prairies. The oak and pine barrens of northern Wisconsin and Michigan are globally significant ecological communities due to their rarity. The Kirtland's warbler (Denroica kirtlandii) is an endemic species found only in the barrens of Michigan. The inland terrestrial system is the result of a glaciated landscape and of the climatic effects, such as temperature and humidity, of the Great Lakes themselves. It is the collector of precipitation that feeds the other systems. Large forested areas, for example, influence the rate and quality of that precipitation. The system filters the water going to groundwater and to the lakes and rivers. A healthy inland system provides for erosion control, as well as habitat and migration corridors for many species (The Nature Conservancy 1994). Inland Terrestrial System: Forests In general, the inland terrestrial system of the Lake Michigan basin is forest interspersed with numerous lakes and streams. The southern forests are generally dominated by oak species and the northern forests are dominated by conifers. Southern Forests In the southern part of the basin, the forests are characterized by red, white, black, bur, northern pin and swamp white oaks trees, and by shagbark hickory, hackberry, boxelder, and black walnut. Conifers are generally absent except for remnant jack and white pines in sandy areas of preserves close to the lake. Although dominated by oak communities, these southern forests also have an eastern hardwood component. Sugar maple, basswood, American beech, ironwood, American elm, and white ash are found, particularly in southwest Michigan (Wisconsin Department of Natural Resources 1995). In addition to the general absence of conifers in the southern forests, the ground layer of southern forests is known from surveyors' notes to have differed from northern forests in that it was in general more open due to lack of small trees and shrubs. This was a result of frequent fires that were a part of the landscape for thousands of years prior to human settlement (Wisconsin Department of Natural Resources 1995). All of the large mammals, including buffalo, bison, elk, cougar, bobcat, and black bear, have been extirpated from Lake Michigan southern forests. Generalist species and those that adapt well to human inhabitants remain, sometimes in large numbers. Racoons, skunks, red fox, and coyote have been particularly adaptive to changed landscapes. White-tailed deer are present in populations considered unsustainable by many wildlife biologists. Deer have increased greatly and are browsing on native vegetation causing great damage. Browsing is hampering the reproduction of trees and certain rare plants, such as orchids (Wisconsin Department of Natural Resources 1995). Fragmentation or elimination of southern forests has resulted in a change in the composition of bird species. The understory or ground layer has changed from a rich assemblage of forbs and grasses to an over-grazed or mowed simplified structure and therefore does not support a variety of bird species. Songbird species, therefore, have decreased and are undergoing further declines. Even cavity nesting and insect-foraging birds have declined due to logging and wood gathering (Wisconsin Department of Natural Resources 1995). Forests in the southern part of the basin are extremely fragmented. In some southeastern Wisconsin counties, for example, there are probably no true remaining forests. In Michigan, the percentage of forests remaining compared to pre-European settlement is not known. Current predictions are that these forests, now wood lot size for the most part, will continue to be lost due to harvest and fragmentation; forest composition will continue to shift from commercially valuable oak species to less desirable species; and the long-term economic value of the southern forests will diminish (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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