Regional Landscape Ecosystems of Michigan, Minnesota, and Wisconsin
SUB-SUBSECTION VI.5.2. Lum Interlobate
DISCUSSION: Sub-subsection VI.5.2 is at the extreme northern end of an interlobate area between three glacial lobes that formed approximately 13,000 to 16,000 years B.P. This section of the interlobate, which has a more northerly climate, is about 30 miles long. This sub-subsection is characterized by relatively steep end-moraine ridges surrounded by pittedm outwash deposits; kettle lakes and wetlands are common within the outwash.
ELEVATION: 750 to 1,041 feet (229 to 317 m).
AREA: 480 square miles (1,245 sq km).
STATES: Michigan.
CLIMATE: Growing season is 130 to 140 days (Eichenlaub et al. 1990). Danger of late spring frosts is great due to numerous lowland depressions (outwash and kettle lakes). Average snowfall is 40 inches, and annual precipitation is 28 to 30 inches. Extreme minimum temperature ranges from -24½F to -28½F.
BEDROCK GEOLOGY: The underlying bedrock is primarily Mississippian- and Pennsylvanian-age sandstone (Dorr and Eschman 1984, Milstein 1987). Bedrock is overlain by 250 to 300 feet of glacial drift (Akers 1938).
LANDFORMS: Sub-subsection contains broad expanses of outwash sands that surround sandy and gravelly end moraines and ground moraines. End and ground moraines remain as islandlike hills surrounded by flat outwash. Large linear segments of end moraine, broken only by narrow outwash channels, are typically located along the margins of the sub-subsection.
LAKES AND STREAMS: Kettle lakes and ponds are numerous on the pitted outwash and end moraines. Extensive wetlands surround many of the lakes and occupy entire ice-block depressions. Both marl and peat deposits were mined in the past. The headwaters of the Flint River originate here.
SOILS: The soils of the moraines are typically well and excessively well drained. Drainage conditions on the outwash are more variable, ranging from excessively well drained to very poorly drained. Thick outwash deposits are usually characterized by excessively well drained conditions. Shallow outwash deposits are underlain in some places by fine-textured till and lacustrine deposits, causing poor or very poor drainage conditions. On ice-contact topography, soils are typically excessively drained on the upland kames and eskers and poorly or very poorly drained in the kettles and outwash channels. Where the topography is steep, organic soils can be 10 to 15 feet deep in narrow outwash channels.
Soil textures range from sand to clay; the most common soil texture is sandy loam on the moraine ridges and sand on the outwash plains. The circumneutral glacial drift that forms the moraines is largely derived from the local limestone bedrock. Illuviation is responsible for the formation of a clayrich (argillic) horizon in many of the soils on moraines, providing better waterholding capacity than many of the outwash soils. In the icecontact areas, soils are sands and gravels. The Soil Conservation Service (1967) classifies the soils of the sub-subsection as Hapludalfs with Argiudolls.
PRESETTLEMENT VEGETATION: Vegetation reflects underlying differences in landform and topography as well as the transition to a more northerly climate. On the sandy moraines at the southern edge, open forests and savannas of black oak and white oak were noted. However, within most of the sub-subsection, forests consisted of a more northerly forest of beech and sugar maple, with large amounts of white pine and often eastern hemlock; white oak commonly occurred with white pine in the southern part of the unit (Comer et al. 1993b).
Kettle lakes and swampy depressions on the outwash typically supported alder swamp or conifer swamp; northern white-cedar and tamarack were common species, along with black ash. White pine and eastern hemlock were also common in the swamps.
NATURAL DISTURBANCE: Windthrown forest was mentioned frequently in the GLO notes, but most of these windthrows appeared to be relatively small, probably because of the steep, irregular topography.
PRESENT VEGETATION AND LAND USE: Many of the uplands have been farmed, except the steepest end moraines and ice-contact ridges, which have been maintained as woodlots or are presently either recreational or wildlife management areas. Many of these steep ridges have been pastured in the past. Both residential development and agricultural land use have resulted in rapid eutrophication of lakes and degradation of many wetlands. Road construction and ditching have also modified the hydrology of many wetlands.
RARE PLANT COMMUNITIES: A few oak savannas were present in the southern part of the sub-subsection, but these have been destroyed by agriculture or degraded by fire exclusion.
RARE PLANTS: Astragalus neglectus (Cooper's milk-vetch), Linum sulcatum (furrowed flax), Panax quinquefolius (ginseng), Polemonium reptans (Jacob's ladder).
RARE ANIMALS: Clemmys guttata (spotted turtle), Carunculina glans (purple lilliput).
NATURAL AREAS: None to date.
PUBLIC LAND MANAGERS: State Game Areas: Lapeer, Murphy Lake, Tuscola, and Deford.
CONSERVATION CONCERNS: Residential development is destroying many of the lakes and wetlands, as well as rapidly fragmenting upland forests.
BOUNDARIES: This sub-subsection has soils and physiography similar to the Jackson Interlobate sub-subsection (VI.1.3) to the southwest, but its climate is cooler. The forest vegetation has a major component of white pine and eastern hemlock, reflecting these cooler, more northerly conditions (Albert et al. 1986).
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