Regional Landscape Ecosystems of Michigan, Minnesota, and Wisconsin
SUB-SUBSECTION VIII.1.4. Green Bay Till Plain and Lake Plain
DISCUSSION: Sub-subsection VIII.1.4 has been separated from adjacent mapping units (Sub-subsections VIII.1.3 and VIII.3.1) on the basis of its clay soils; the prevalent soil textures in those sub-subsections are loams and sandy loams.
ELEVATION: 580 to 935 feet (177 to 285 m).
AREA: 1,855 square miles (4,808 sq km).
STATES: Wisconsin.
CLIMATE: Growing season is approximately 120 days farthest from Lake Michigan and as long as 180 days near the lake (Hole and Germain 1993). Average minimum temperature is 6 to 10½F (Wendland et al. 1992). Extreme minimum temperature is approximately -30½F along the Lake Michigan shoreline and closer to -35½F inland. Annual precipitation is 30 to 32 inches, with 44 to 52 inches of snowfall. Snowfall increases with latitude, but does not appear to be greatly affected by Lake Michigan.
BEDROCK GEOLOGY: The entire sub-subsection is underlain by Silurian- and Ordovician-age sedimentary bedrock, principally limestone and dolomite, but also including less resistant shale and gypsum (Dorr and Eschman 1984, Morey et al. 1982). The resistant Niagaran series dolomite and limestone of Silurian age form the Niagaran Escarpment, which underlies this sub-subsection as a broad, flat cuesta from the east side of Green Bay on the Door Peninsula to the eastern shore of Lake Winnebago. The west edge of the sub-subsection is underlain by Ordovician limestone and dolomite. Green Bay occupies a depression where soft gypsum and shales were eroded, probably by both glacial and lacustrine processes (Sinclair 1960).
LANDFORMS: A relatively flat plain. The western edge consists of lacustrine clays, and the remainder is primarily clayey ground and end moraines (Farrand et al. 1984).
LAKES AND STREAMS: Major rivers include the Fox and Manitowac. No large inland lakes. Many drainage ditches have been constructed on the flat lake plain and ground moraine to facilitate farming.
SOILS: The soils are somewhat leached (but not podsolized), red calcareous clays. The primary soils are silty clay loam to clay loam in texture, classified as Typic Hapludalfs (Hole 1976). Slopes range from level to rolling. Gullying, from geological and agricultural erosion, occurs on some of these clay soils. Carbonate materials make up about 30 percent of the soils.
PRESETTLEMENT VEGETATION: The dominant vegetation was northern hardwood forest, dominated by beech and sugar maple, with basswood and some oaks, including red, white, and black. Hemlock was present, but much less prevalent than in Sub-subsections VIII.3.1 to the west and VIII.1.3 to the east. There were several areas of wetland, primarily dominated by northern conifers. Northern white-cedar was common on the lake plain. There was a large area of marsh and wet meadow where the Fox River meets Green Bay as well as extensive areas of conifer swamp along the Green Bay shoreline.
NATURAL DISTURBANCE: Windthrows, noted by the GLO surveyors, were most common near the Lake Michigan shoreline; many were probably the result of storm winds off the lake.
PRESENT VEGETATION AND LAND USE: Approximately 60 percent of the landscape is cropland, 15 percent pasture, and 25 percent woodland and wetland (Hole 1976).
RARE PLANT COMMUNITIES: Sand dunes are found at two locations. There were very localized tallgrass prairie and oak savanna near the Fox River; both have been destroyed by agriculture. Dolomite glade is in northeastern Brown County, and interdunal wetlands are along the Lake Michigan shoreline.
RARE PLANTS: Cirsium pitcheri (Pitcher's thistle), Iris lacustris (dwarf lake iris).
RARE ANIMALS: None identified to date.
NATURAL AREAS: Cedarburg Bog, Cedar Grove Hawk Research Station, Wilderness Ridge, Maribel Caves, Two Creeks Buried Forest, Fairy Chasm, Kohler Park Dunes, Point Beach Ridges.
PUBLIC LAND MANAGERS: Point Beach State Forest, Kohler-Andrae State Park.
CONSERVATION CONCERNS: Sub-subsection VIII.1.4 is part of a major migratory bird corridor, especially for raptors and waterfowl.
BOUNDARIES: This sub-subsection can be further subdivided into an eastern unit of till plain and a western unit of lake plain.
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