Regional Landscape Ecosystems of Michigan, Minnesota, and Wisconsin
SUB-SUBSECTION VI.5.1. Sandusky Lake Plain
DISCUSSION: Sub-subsection VI.5.1 is a flat lake plain that slopes gradually to Lake Huron; a narrow moraine that parallels the shore of Saginaw Bay and Lake Huron occupies the center of the narrow sub-subsection. Agricultural development has been intensive as a result of a lake-modified climate and productive loamy soils.
ELEVATION: 572 to 870 feet (175 to 265 m).
AREA: 3,210 square miles (8,319 sq km).
STATES: Michigan.
CLIMATE: See subsection.
BEDROCK GEOLOGY: See subsection.
LANDFORMS: Sub-subsection consists of broad expanses of level lake plain along its margins, but it also includes long, narrow till plains and ridges of end moraine that are parallel with Saginaw Bay or Lake Huron. At the inland margin of the clay lake plain there is a broad sand channel, which is largely poorly drained. The till plain is quite flat and difficult to distinguish from the lake plain. The end moraine is several miles wide and forms a low ridge, which has better drainage conditions than the surrounding lake plain.
SOILS: On the lake plain, slopes are typically in the 0 to 2 percent slope class. Approximately one-third of the soils are poorly drained or very poorly drained; most of the remaining soils are moderately well drained. In the past, the soils of the sandy channels on the lake plain were often poorly drained or very poorly drained. Low dunes within these channels had excessively drained soils. Most of the lacustrine soils were drained to allow agricultural development of the land. Peat soils were also burned. On the end moraines, slopes are gentle to moderate, generally in the 2 to 6 percent slope class, and soils are moderately well and well drained. Soils on the end moraines are classified as Hapludalfs, with some Argiaquolls; those of the lake plain are classified as Haplaquents, with some Haplaquods (USDA Soil Conservation Service 1967).
LAKES AND STREAMS: No lakes. Most of the streams are small, beginning on the moraines and forming relatively straight, shallow trenches across the lake plain before entering Saginaw Bay or Lake Huron. The exceptions are the Cass River and Black River; both flow several miles between parallel moraines before crossing the lake plain.
PRESETTLEMENT VEGETATION: The presettlement vegetation often differed greatly among the clay lake plain, sand lake plain, and end moraine (Comer et al. 1993a, b). Almost the entire clay plain was forested. Most of the clay lake plain was dominated by upland conifer forests of eastern hemlock. Topography was flat, with slopes of less than 2 percent. These forests were not generally considered swamps, but the soils were probably wet. Hemlock often made up 40 percent or more of the overstory; other common species were beech, northern white-cedar, sugar maple, [American] elm, balsam fir, paper birch, white pine, white ash, black ash, basswood, [red] maple, and [trembling] aspen. In the wettest parts of the lake plain, lowland hardwoods were prevalent; the common dominants were black ash and American elm. In closed depressions, lowland hardwoods dominated by black ash were common.
On slightly steeper portions of the clay plain, where slopes were generally greater than 2 percent, northern hardwoods forests of beech-sugar maple were numerous, sometimes making up more than 50 percent of the overstory; hemlock was much less common.
The low dunes and relatively flat sand plain supported conifer forests of hemlock and white pine. Small areas of forests dominated by white oak and black oak were also common near the shoreline, both on low beach ridges and sand dunes.
Wetlands within the forested sand plain contained abundant black ash. Along the border with clay lake plain, lowland conifers dominated by tamarack, and occasionally northern white-cedar, were dominant, often forming a dense linear band. Locally, there were extensive emergent marshes one-fourth to one-half mile wide, which occupied depressions within the lake plain, often between beach ridges formed along long-abandoned shorelines of Saginaw Bay.
Extensive Great Lakes marshes occurred along the entire coast of Saginaw Bay and locally along the shore of Lake Huron southeast of Saginaw Bay (Albert et al. 1988). The marshes, which extended into water 4 to 5 feet deep, were 1 to 2 miles wide in places. Upland of the marshes there was typically a broad zone of swamp forest; but on large expanses of Saginaw Bay, 1- to 3-mile-wide expanses of wet prairie occurred. Wet prairie was concentrated at the far northwestern edge of the sub-subsection along Saginaw Bay in Tuscola and Huron Counties. The plant composition of the wet prairie changed along with the water level of Lake Huron. Within the coastal marshes and wet prairies were low beach ridges and sand spits that supported scattered white oak and black oak.
Expansive bands of parallel beach ridges and swales occupy some of the embayments along Saginaw Bay. White pine dominated the beach ridges, along with some white oak, black oak, trembling aspen, and paper birch. The wettest swales near Saginaw Bay were dominated by floating and emergent aquatic plants; swales further inland typically supported swamp forests of northern white-cedar, tamarack, and occasionally black ash.
Forests of beech-sugar maple, with lesser quantities of hemlock, basswood, white ash, and red maple, grew on much of the moraines, which generally have better drainage conditions than the lake plain. Black ash dominated many of the wetland depressions within the moraines. Conifer swamps, dominated by northern white-cedar, occupied broad wetlands in footslope positions. These cedar swamps also contained tamarack, balsam fir, hemlock, and some white pine, along with birch, [trembling] aspen, and other hardwoods.
NATURAL DISTURBANCE: Extensive areas of windthrown forest were recorded in the GLO notes. These extensive windthrows are the result of a combination of strong winds off Lake Huron and poorly drained soils. Windthrow appears to have been more common within the wetlands and on the flattest parts of the lake plain. Water level fluctuations of 2 to 3 feet are common along the Great Lakes shorelines, causing tree mortality, shoreline erosion, and major alteration in species composition of marshes and wet prairies. The surveyors noted such water-level fluctuations near the west edge of the subsection.
PRESENT VEGETATION AND LAND USE: Before European settlement, Native American settlements were common along the shorelines of the Great Lakes, primarily upon beach ridges. Indian fires were probably responsible for maintaining oak savannas on the beach ridges near Saginaw Bay.
Most of the clay plain has been ditched and tiled, and these lands are among the most valued for agriculture in the State. Parts of the sand plain were also ditched for agriculture; but the wettest areas remain, either as swamp forest, wet prairie, or marsh. Diking and pumping have allowed vast expanses of wet prairie and some areas of marsh to be farmed, especially along Saginaw Bay. Organic soils were burned to improve their suitability for agriculture (Deeter and Matthews 1931).
The better drained soils on the moraines have also been intensively converted to agriculture. The extensive drainage networks created on the lake plain were not necessary on the end moraines.
Almost no forests remain within the sub-subsection, and the composition of those that do remain has changed considerably. Conifer-dominated forests have been eliminated on both upland and wetland sites. Conifer swamps have converted to lowland hardwoods or brush.
RARE PLANT COMMUNITIES: Wet and wet-mesic prairie were originally extensive, along with oak savannas or "openings," but these now remain as only small remnants, primarily on State-owned lands. Prairies and savannas on the lake plain are called lakeplain prairie or oak opening because of the distinctive flora and fauna. Some of the most extensive upland conifer forests of the lake plain, dominated by either white pine or hemlock, have been virtually eliminated.
RARE PLANTS: Most of the species in this sub-subsection are associated with either Great Lakes marshes or lakeplain prairies. Agalinis gattingeri (Gattinger's gerardia), Agalinis skinneriana (Skinner's gerardia), Aristida longespica (three-awned grass), Asclepias hirtella (tall green milkweed), Asclepias sullivantii (Sullivant's milkweed), Astragalus neglectus (Cooper's milk-vetch), Astragalus canadensis (Canadian milk-vetch), Cacalia plantaginea (prairie Indian-plantain), Juncus brachycarpus (short-fruited rush), Juncus biflorus (two-flowered rush), Platanthera leucophaea (prairie fringed orchid), Scirpus clintonii (Clinton's bulrush), Trillium undulatum (painted trillium).
RARE ANIMALS: Chlidonias niger (black tern), Dysnomia torulosa rangiana (northern riffleshell), Elaphe vulpina gloydi (eastern fox snake), Lanius ludovicians (loggerhead shrike), Sterna caspia (Caspian tern), Sterna forsteri (Forster's tern), Sterna hirundo (common tern).
NATURAL AREAS: Michigan Nature Association Preserves: Jasper Woods Memorial and Red Wing Nature Sanctuaries, Ray Memorial Plant Preserve.
PUBLIC LAND MANAGERS: State Game Areas: Fish Point, Deford, Rush Lake, Sanilac, Vassar, Port Huron, Minden City, Cass City, Murphy Lake, Tuscola, Verona; State Wildlife Areas: Fish Point, Quanicassee, Wildfowl Bay; State Parks: Lakeport, Port Crescent, Sanilac Petroglyphs, Albert E. Sleeper; Environmental Areas: Fish Point, McKinley, Rose Island, Sebewaing, Thomas, Weale, Bay Port.
CONSERVATION CONCERNS: The GLO surveyors commented on the importance of the wet prairies for waterfowl.
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