Regional Landscape Ecosystems of Michigan, Minnesota, and Wisconsin
SUBSECTION VI.1. Washtenaw
DISCUSSION: This subsection, located in extreme southeastern Michigan, is characterized by the longest growing season in the State.
Sub-subsections: the Maumee Lake Plain (VI.1.1), Ann Arbor Moraines (VI.1.2), and the Jackson Interlobate (VI.1.3). (See figure 5.)
ELEVATION: 572 to 1,280 feet (175 to 390 m).
AREA: 5,995 square miles (15,530 sq km).
STATES: Michigan.
CLIMATE: Subsection VI.1 has the longest growing season in the section and in Michigan, ranging from approximately 130 days inland to 180 days along Lake Erie and Lake St. Clair in the east (Eichenlaub et al. 1990). Extreme minimum temperature ranges from -26½F inland to -16½F in the south along Lake St. Clair and Lake Erie. Total annual precipitation averages between 28 and 36 inches, and total snowfall averages 30 to 50 inches.
BEDROCK GEOLOGY: Surface glacial deposits, which are as thick as 300 feet near the inland margin of the subsection and locally less than 5 feet near the Lake Erie shoreline, are underlain by Pennsylvanian, Mississippian, Devonian, and Silurian marine and nearshore bedrock, including sandstone, shale, coal, marine limestone and dolomite, and gypsum and other evaporites (Dorr and Eschman 1984, Milstein 1987). Bedrock is only locally exposed in stream banks and near the shorelines of Lake Erie. The oldest Silurian bedrock is near the surface and locally exposed to the south. Mississippian and Pennsylvanian sandstone and shale are locally exposed in the west, in Sub-subsection VI.1.3.
LANDFORMS: Glacial lake plain characterizes Sub-subsection VI.1.1; ground moraine, end moraine, and outwash cover the remainder of the subsection. See sub-subsections.
LAKES AND STREAMS: See sub-subsections.
SOILS: Soils are classified as Alfisols (Aqualfs) by the Soil Conservation Service (1967). See sub-subsections.
PRESETTLEMENT VEGETATION: See sub-subsections.
NATURAL DISTURBANCE: See sub-subsections.
PRESENT VEGETATION AND LAND USE: This subsection has some of the most intensive urban, industrial, and agricultural land use in the State. It supports closed-canopy oak forests due to fire suppression. The oak ecosystems of this and adjacent subsections were classified and described by Archambault et al. (1990), and the ecological species groups of their groundflora were described and classified (Archambault et al. 1989). Coastal marshes are described in Albert et al. 1988. See sub-subsections.
RARE PLANT COMMUNITIES: See sub-subsections.
RARE PLANTS: See sub-subsections.
RARE ANIMALS: Subsection VI.1 supports several rare species, most of which occupy the prairies, marshes, or shorelines of the Great Lakes. See sub-subsections.
NATURAL AREAS: See sub-subsections.
PUBLIC LAND MANAGERS: See sub-subsections.
CONSERVATION CONCERNS: See sub-subsections.
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