Regional Landscape Ecosystems of Michigan, Minnesota, and Wisconsin
SUB-SUBSECTION VIII.1.1. St. Ignace
DISCUSSION: Sub-subsection VIII.1.1 is typified by sandy lake plain and limestone bedrock at or near the surface. Limestone bedrock is exposed along the Lake Huron shoreline in the east, especially on Drummond Island. Lacustrine features include sand dunes, embayments with complexes of parallel beach ridges and swales, and extensive conifer-dominated wetlands on sand or bedrock.
ELEVATION: 580 to 1,040 feet (177 to 317 m).
AREA: 1,578 square miles (4,088 sq km).
CLIMATE: Growing season ranges from 130 to 140 days, longest along the Lake Michigan and Lake Huron shorelines (Eichenlaub et al. 1990). Extreme minimum temperatures are coldest inland, where they can be as low as -46½F, and warmest along the Lake Michigan shoreline, where they are as high as -30½F. Average annual precipitation is 30 to 32 inches across the entire sub-subsection. Annual snowfall averages 60 to 80 inches, uniform across the sub-subsection.
BEDROCK GEOLOGY: The entire sub-subsection is underlain by Silurian- and Ordovician-age sedimentary bedrocks, principally limestone and dolomite, but also including less resistant shale and gypsum (Dorr and Eschman 1984). The resistant Niagaran series dolomite and limestone of Silurian age form the Niagaran Escarpment, which is locally exposed as cliffs and limestone pavement along the Lake Michigan shoreline from the Stonington Peninsula in the west to Drummond Island at the far eastern edge of the Upper Peninsula of Michigan, and eastward to Cockburn Island, Manitoulan Island, and the Bruce Peninsula of Ontario. The underlying bedrock is typically less than 50 feet below the surface of the glacial drift (Vanlier and Deutsch 1958; Sinclair 1959, 1960). Limestone is mined in several places within the sub-subsection; large limestone quarries are located on Drummond Island and at Cedarville.
LANDFORMS: Various landforms of glacial lacustrine origin characterize the sub-subsection, including flat lake bed, deltaic deposits of sand, parabolic dune fields, and shallow embayments containing transverse dunes.
Large areas consist of lacustrine sand deposits that have flat to gently undulating surfaces. On this topography, only a few inches of elevation change can greatly alter drainage conditions. Drainage conditions also depend on depth to underlying bedrock or fine-textured substrate.
Ground moraine is locally present. Exposed limestone and dolomite bedrock forms flat, pavement-like areas, and breccia chimneys are locally exposed.
LAKES AND STREAMS: Several large lakes. The largest are on ground moraine, including Manistique and South Manistique Lakes. On the sandy lake plain, there are two large lakes, Millecoquins and Brevoort, and several smaller lakes. On bedrock, or where limestone and dolomite bedrock is near the surface, there are numerous lakes, including Merwin, Gulliver, McDonald, Caribou, and East. Several other small, highly calcareous lakes are located on the dolomite of Drummond Island.
Rivers are not numerous. Two of the larger are the Pine and Carp, which originate in other sub-subsections farther to the north.
SOILS: Soils are diverse. Lacustrine soils are primarily sands, but there are small, local areas of lacustrine clays. The clays are primarily poorly drained. The sands are generally either excessively drained or poorly drained. Excessively drained sands are on beach ridges or dunes. Poorly drained sands are more common, occupying much of the flat lake plain or depressions between dunes and beach ridges. Soils of the ground moraine range from loamy sands to loams; they are often stony. Where bedrock is near the surface, soils are often calcareous and poorly drained. The most common soil orders here are Alfisols (Boralfs), Histosols, and Entisols (Aquepts), with some Orthods and Aquods (USDA Soil Conservation Service 1967).
PRESETTLEMENT VEGETATION: Along the Lake Huron and Lake Michigan shorelines, there were many broad coastal marshes in protected coves and embayments. These were most numerous on Lake Huron where there was more protection from wave action. They were especially common in and around the Les Cheneaux Islands. The substrate in these marshes was often clay or marl (Albert et al. 1989).
The forests of the flat lake plain were generally dominated by conifers, especially on the poorly drained or excessively drained portions (Comer et al. 1993a). The most common swamp conifers were northern white-cedar, tamarack, balsam fir, and black spruce. The most common upland conifers were white pine and hemlock, with increased red pine on dry sand ridges and localized areas of jack pine on droughtiest sites.
Extensive complexes of beach ridges and swales were in large embayments; these supported forests of white pine, red pine, red oak, and other hardwoods on the driest ridges and conifer swamp and shrub swamp in the drier swales. Emergent vegetation grew in the swales near the present Great Lakes shoreline. The largest area of beach ridges and swales is at Pointe Aux Chenes, west of St. Ignace.
In some of the embayments, there were extensive fens, dominated by stunted white pine, northern white-cedar, tamarack, and black spruce. GLO surveyors noted marly pools in these fens. Much of the coastal zone along northern Lake Huron and Lake Michigan, where soils were thin overlay bedrock, was dominated by balsam fir-spruce-cedar forests and northern hardwoods.
The flat, sandy lake plain supported diverse swamp forest types, including extensive cedar swamps, tamarack swamps, and mixed conifer swamps. Hemlock and northern hardwood forest also dominated many uplands on sandy lake plain.
On the low parabolic dunes along the sandy lake plain of Lake Michigan, the moist air and presumably higher precipitation and soil moisture caused most of the dunes to be dominated by northern hardwood forests of sugar maple, beech, hemlock, red oak, yellow birch, paper birch, and basswood. The Brevoort Lake dunes, located near the Lake Michigan shore, are a good example of this forest type. In contrast, the dunes located near Round Lake, several miles inland from Lake Michigan, support forests dominated by red and jack pines; this possibly indicates the lack of local microclimatic influence bringing moisture from Lake Michigan.
Ground-moraine ridges were dominated by northern hardwoods, hemlock-beech, and hemlock-white pine forests.
NATURAL DISTURBANCE: GLO surveyors recorded many occurrences of fire in upland and swamp forests on both sand and bedrock. There were both wildfires and windthrows on Little St. Martin Island and the beach ridges near the mouth of the Crow River were burned off at the time of the surveys.
Many windthrows were noted by surveyors on both the uplands and wetlands along the shorelines of both Lake Michigan and Lake Huron, especially on the islands. Thin soils over bedrock and poorly drained soils, common along the shoreline, combined with the strong lake winds to produce extensive windthrow areas. White pine appears to be especially susceptible to coastal wind storms.
PRESENT VEGETATION AND LAND USE: European settlements were well established at St. Ignace, Bois Blanc Island, and at Gros Cap at the time of the GLO surveys in the 1840's. The 1829 survey of Mackinac Island showed only small second-growth timber over the entire island, probably as a result of firewood cutting. A British military outpost was established at the southwest end of Drummond Island. Fishing camps were based at various locations along the shoreline from Epoufette west to Seul Choix Point. Native American settlements were also located on Bois Blanc Island and St. Martins Island. Native American sugar camps were also located throughout the area where northern hardwoods dominated. Limestone has been quarried at several locations within this sub-subsection, including Drummond Island, inland areas northeast of Hessel, Millecoquins Lake, and Seul Choix Bay. Upland areas dominated by pines and northern hardwoods were cut, and often burned, by the early 20th century. Roads and highways have probably had the most enduring negative impact on coastal wetlands, by disrupting wetland hydrology and facilitating shoreline development. Several emergent marshes along northern Lake Huron have been degraded by coastal highway construction. Residential development is increasing along Lake Huron. Residential development is quite dense on many of the Les Cheneaux Islands, which are connected to the mainland by roads. Ground moraine has been cleared for agriculture and pasture use.
RARE PLANT COMMUNITIES: Some of the more resistant dolomites and shales, when exposed at the surface, proved to be too droughty for successful forest establishment; instead, they support alvar communities. As a result of severe droughtiness, alvar contains grasses, herbs, and occasional shrubs as well as stunted clones of trembling aspen on thin soil. Thin organic soils develop, but they appear to be subject to destruction by fire. Some of the best remaining alvar, globally, is found today on the northern Maxton Plains of Drummond Island and south of Gulliver Lake in Schoolcraft County.
RARE PLANTS: Amerorchis rotundifolia (round-leaved orchid), Asplenium rhizophyllus (walking fern), Asplenium scolopendrium var. americana (Hart's-tongue fern), Asplenium viride (green spleenwort), Calypso bulbosa (Calypso orchid), Carex richardsonii (Richardson's sedge), Carex scirpoidea (bulrush sedge), Cirsium pitcheri (Pitcher's thistle), Cypripedium arietinum (ram's-head lady's-slipper), Eleocharis compressa (flattened spike-rush), Empetrum nigrum (black crowberry), Erigeron hyssopifolius (hyssop-leaved fleabane), Iris lacustris (dwarf lake iris), Juncus stygius (moor rush), Mimulus glabratus var. Michiganense (Michigan monkey-flower), Muhlenbergia richardsonis (mat muhly), Piperia unalascensis (Alaska orchid), Ranunculus lapponicus (Lapland buttercup), Scutellaria parvula (small skullcap), Solidago houghtonii (Houghton's goldenrod), Sporobolus heterolepis (prairie dropseed), Stellaria longipes (stitchwort), Sterna forsteri (Forster's tern), Sterna hirundo (common tern), Tanacetum huronense (Lake Huron tansy).
RARE ANIMALS: Alces alces (moose), Canis lupus (gray wolf), Charadrius melodus (piping plover), Chlidonias niger (black tern), Haliaeetus leucocephalus (bald eagle), Pandion haliaetus (osprey), Sterna caspia (Caspian tern), Trimerotropis huroniana (Lake Huron locust).
NATURAL AREAS: The Nature Conservancy Preserves: Bois Blanc Island, Maxton Plains, Voight Bay, Dudley Bay-Trout Lake, Poe Point, Little LaSalle Island, Northern Lake Huron Bioreserve; Michigan Nature Association Preserves: Purple Coneflower, Michigan Monkey-Flower, Green Spleenwort, Rare Fern, Beaver Dam, Beavertail Point, Three Wilderness Islands, Carlton Lake Wetlands, Lake Huron Sand Dunes, Drummond Island, Harvey's Rocks; Proposed Research Natural Areas (Hiawatha National Forest): Summerby Swamp, Pointe aux Chenes Marsh; Wilderness Areas (Hiawatha NF): Horseshoe Bay, Round Island, Government Island; State Natural Areas: Maxton Plains, Snake Island, Mixed Forest Nature Study Area, North Shore, Northern Lake Michigan (proposed), Seiners Point (proposed), Little Brevoort Lake Scenic Area.
PUBLIC LAND MANAGERS: Michigan: National Forests: Hiawatha; National Wildlife Refuges: Seney; State Forests: Lake Superior, Mackinac; State Parks: Detour, Mackinac Island; State Forest Campgrounds (Lake Superior State Forest): Big Knob, DeTour; Environmental Areas: Little St. Martin Island, Voight Bay, Goose Island, Pointe Aux Chenes Bay, Mismer Bay, Carp River, St. Helena, Crow River, Scammon, Epoufette, Crow Island, Cedar Island, Paw Point, Search Bay, Lone Susan, Pontchartrain, Seiners Point, Naubinway Island, Scotty Bay, Seymour Bay, Duck Bay, Gravel Island.
CONSERVATION CONCERNS: Low sand dunes and beach ridges along the shoreline support healthy populations of Pitcher's thistle (federally threatened), a Great Lakes endemic, as well as Lake Huron tansy. Three other Great Lakes endemics are found near the shoreline: dwarf lake iris (federally threatened) is found on calcareous till or sand deposits near the shoreline, Houghton's goldenrod (federally threatened) grows in moist interdunal swales along the shore, and Michigan monkey-flower (federally threatened) grows in cold, spring fed streams near the Great Lakes shoreline.