Regional Landscape Ecosystems of Michigan, Minnesota, and Wisconsin

SUB-SUBSECTION VI.1.2. Ann Arbor Moraines

Loamy end and ground moraines; oak-hickory forest, beech-sugar maple forest, and deciduous swamp forest. 

DISCUSSION: Sub-subsection is a long, narrow band (120 miles long and 20 to 24 miles wide) of fine- and medium-textured end and ground moraine bordered by flat lake plain on the east and by sandy outwash, end moraine, and ice-contact features to the west. The moraines of the sub-subsection continue south into Ohio. Agricultural development has been relatively extensive, but many of the lowlands and steeper upland ridges remain forested.

ELEVATION: 750 to 1,150 feet (230 to 350 m).

AREA: 1,632 square miles (4,225 sq km).

STATES: Michigan.

CLIMATE: Growing season ranges from 150 to 160 days; localized areas near the Maumee Lake Plain (VI.1.1) have a growing season of approximately 170 days (Eichenlaub et al. 1990). Average annual precipitation gradually increases from 30 inches in the north to 36 inches in the south. Annual snowfall shows a similar trend, with 40 inches in the north and 50 inches in the south. Extreme minimum temperature ranges from -22F to -24F.

BEDROCK GEOLOGY: Bedrock is not exposed in the sub-subsection. Glacial deposits are 100 to 250 feet thick over bedrock; the thickest glacial deposits are near the center of the long sub-subsection for much of its length. Underlying bedrock is Mississippian and Devonian (Paleozoic) sandstone and shale (Dorr and Eschman 1984, Milstein 1987). Devonian sandstone and shale are localized along the eastern edge, Mississippian shale underlies the center, and Mississippian sandstone is in the southwest.

LANDFORMS: Narrow parallel bands of both end moraine and till plain (ground moraine). More than 80 percent of the ground moraine is flat, with slopes in the 0 to 6 percent slope class. Ground moraine forms a broad plain. Individual hills of the ground moraine are several miles in area, but are seldom higher than 80 feet.

The topography of the end moraines is more rolling, with slopes in the 7 to 15 percent slope class. Less than 1 percent of the end moraines have slopes greater than 15 percent. End-moraine ridges can be distinct ridges, one to several miles across and several miles long; or they can be broken into several smaller ridges separated by glacial outwash channel and postglacial drainages. Most of the ridges are 30 to 80 feet high; the highest ridges, about 170 feet high, are located in the north.

LAKES AND STREAMS: Few lakes. Major rivers that cross the sub-subsection are the Huron and Raisin.

SOILS: Loam- and sandy loam-textured soils cover most of the sub-subsection. Fine-textured soils, primarily silt loams and clay loams, are more common on the eastern edge. Poorly drained mineral soils are common on lower slopes of the ground moraine. Organic soils are restricted to outwash channels. Soils are classified as gently sloping Hapludalfs with some Argiaquolls and Argiudolls (USDA Soil Conservation Service 1967).

PRESETTLEMENT VEGETATION: The loams and sandy loams originally supported oak and oak-hickory forests. White oak appeared to be the most common species of the oak forest. Black oak was common on the drier ridge tops, and red oak was most common on lower slopes. Oak savannas, dominated by white oak and black oak, probably occurred within the sub-subsection, especially along the western edge, where fires from Sub-subsection VI.1.3 were carried by westerly winds. Beech and sugar maple were restricted to silt loams and clay loams. The distribution of these mesic species was quite restricted; they occurred in some relatively flat and wet areas of ground moraine at the southeastern end of the sub-subsection and on well-drained, irregular end moraine at the northeastern end.

Swamp forest was common in lower slope positions on both ground and end moraine. Common species in the swamps included black ash, red maple, American elm, swamp white oak, bur oak, and basswood. On the flood plain, hackberry, red elm, red ash, and American elm were common.

NATURAL DISTURBANCE: Windthrow probably occurred on the steeper end moraines and within the poorly drained swamp forests. Native American fire management, generally concentrated on the sandier soils of Sub-subsections VI.1.3 and VI.2.1, may have impacted forests at the western margin of Sub-subsection VI.1.2.

PRESENT VEGETATION AND LAND USE: Almost all the ground moraines have been farmed, but the steeper moraines remain forested with oak. Most of the land was cleared for agriculture by the mid 19th century.

RARE PLANT COMMUNITIES: None identified to date.

RARE PLANTS: The flood plains support several rare plant species, including Chelone obliqua (purple turtlehead), Cypripedium arietinum (ram's head lady's slipper), Galearis spectabilis (showy orchid), Gentiana flavida (white gentian), Hybanthus concolor (green violet), Hydrastis canadensis (goldenseal), Morus rubra (red mulberry), Muhlenbergia richardsonis (mat muhly), Panax quinquefolius (ginseng), Spiranthes ovalis (lesser ladies'-tresses).

RARE ANIMALS: Ambystoma texanum (smallmouth salamander), Carunculina glans (purple lilliput), Clinostomus elongatus (redside dace), Clonophis kirtlandii (Kirtland's snake), Cryptotis parva (least shrew), Moxostoma duquesnei (black redhorse), Nerodia erythrogaster neglecta (copperbelly water snake), Phoxinus erythrogaster (southern redbelly dace), Pleurobema clava (clubshell).

NATURAL AREAS: Michigan Nature Association Preserves: Copperbellied Water Snake Nature Sanctuary; The Nature Conservancy Preserves: Ives Road Fen, Sharon Hollow; Other: Horner Woods, Radrick Bog and Forest, Cranbrook Nature Sanctuary, Bicentennial Woods, George Reserve, Saginaw Forest, Osborne Mill Riverland Preserve.

PUBLIC LAND MANAGERS: State Game Areas: Lost Nation; State Recreation Areas: Bald Mountain, Island Lake, Waterloo, Lake Hudson; Metroparks: Dexter-Huron, Stony Creek, Hudson Mills; County Parks: Parker Mill; Research Areas: Mud Lake Bog.

CONSERVATION CONCERNS: Agricultural use of lands in the sub-subsection has been extensive. Few ecologically intact areas are known; these are generally flood-plain forests or small woodlots. 

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Last modified on Wednesday, February 18, 2004
by  Sharon Hobrla