Regional Landscape Ecosystems of Michigan, Minnesota, and Wisconsin
SUBSECTION III.1. Hardwood Hills
SUB-SUBSECTIONS: Leaf Hills, Blue Hills. (See figure 3.)
ELEVATION: 1,100 to 1,600 feet (335 to 488 m).
AREA: 7,566 square miles (19,597 sq km).
STATES: Minnesota.
CLIMATE: Continental, with extreme differences between summer and winter temperatures (Hargrave 1992). Total annual precipitation ranges from 24 inches in the west to 27 inches in the east. Growing season precipitation ranges from 10.5 to 11.5 inches. Annual snowfall averages 44 to 48 inches (Wendland et al. 1992). Growing season ranges from approximately 122 days in the north to 140 days in the south. Extreme minimum temperature ranges from -35½F to -40½F (Reinke et al. 1993).
BEDROCK GEOLOGY: From 100 to 500 feet of glacial drift covers the bedrock over most of the subsection, with the thickest drift in the northwestern half (Olsen and Mossler 1982). Middle Precambrian granitic bedrock is locally exposed in the southeast, along the Crow River near the town of Richmond (Morey 1976, 1981). Bedrock underlying the subsection is diverse. In the south are Cretaceous shale, sandstone, and clay; lower Precambrian granite, metasedimentary and metaigneous gneiss, schist, and migmatite; and amphibolite and granulite (Morey 1976). To the north are metasedimentary rocks; iron formation; greenstone; and metavolcanic rocks, including basalt, andesite, pillow lava, tuff, and ultramafic and rhyolitic rocks.
LANDFORMS: Ice-stagnation moraines, end moraines, ground moraines, and outwash.
LAKES AND STREAMS: Kettle lakes are extremely common within the subsection, on both moraine and outwash deposits. There are more than 400 lakes larger than 160 acres and many more small lakes and potholes, covering 8 to 9 percent of the landscape. Few major streams are in the subsection; instead, this is a headwater area where streams originate.
SOILS: Soil textures range from loamy sands and sandy loams on the outwash plains to loams and clay loams on the moraines. Loamy soils are prevalent. Most of the soils are classified as Mollisols (primarily Borolls and Aquolls, with some Udolls), soils developed under grasslands, but there are some Alfisols, developed under forested conditions (Cummins and Grigal 1981).
PRESETTLEMENT VEGETATION: The irregular topography and the many lakes and wetlands provided a partial barrier to fire, resulting in woodland or forest rather than prairie vegetation. The exception to this was in Sub-subsection III.1.2 and the southwest portion of Sub-subsection III.1.1, which supported prairie. Along the prairie boundary to the west was a mosaic of aspen-oak land, and oak openings or savanna (Marschner 1974). Mixed forests of oaks, sugar maple, basswood, and other hardwoods grew in more fire-protected sites farther east. Tallgrass prairie was present on the more level terrain within the subsection.
NATURAL DISTURBANCE: Fire from the tallgrass prairie to the west was important in the oak savanna and to a far lesser extent in the sugar maple-basswood forest, where windthrow was probably more prevalent and provided greater control on the forest composition.
PRESENT VEGETATION AND LAND USE: Although large areas are under cultivation, much of the land supports second-growth forest, especially the steeper portions of the landscape. In agricultural areas, the forests are commonly grazed. Many of the poorly drained potholes remain for either recreational or wildlife use. Tourism is important, especially in areas with concentrations of lakes (Hargrave 1992).
RARE PLANT COMMUNITIES: Subsection contains several remnant dry prairies, mesic prairies, and glaciated till hill prairies. High-quality examples of tamarack swamp, black spruce swamp, and poor fen occur, as do boreal hardwood-conifer forest and aspen-birch forest.
RARE PLANTS: See sub-subsections.
RARE ANIMALS: See sub-subsections.
NATURAL AREAS: State Natural Areas: Agassiz Dunes, Partch Woods, Roscoe Prairie; Other: Glacial Lakes, Moe Woods, Ordway Prairie, Regal Meadow, Rockville Tamarack Bog, Seven Sisters Prairie, Strandness Prairie.
PUBLIC LAND MANAGERS: Wildlife Management Areas: Badger, Barnesville, Dorr, Emerson, Gustafson, Hubbel Pond, Shelley Island; State Parks: Glacial Lakes, Glendalough, Maplewood, Monson Lake, Sibley; State Forests: White Earth; Waterfowl Production Areas: Bjerketvedt, Edwin Lake, Gustafson, Hagen, Haugtvedt, Hintermeister, Julsrud, Kenna, Lager Larson, Larson, McDowell, Nicholson, Pomme de Terre, Underdahl; Other: Tamarac National Wildlife Refuge, Collegeville Game Refuge, Tilsberg Park, West Mill Recreation Area, Inspiration Peak State Wayside.
CONSERVATION CONCERNS: Grazing in woodlands adversely impacts the native flora.
BOUNDARIES: The Alexander moraines are being treated here as a narrower belt than was done previously. This mapping decision is based on the fact that the moraines at the north edge of the subsection become dominated by greater amounts of northern species (e.g., trembling aspen, paper birch, white pine, red pine, and jack pine) as the soils become sandier on some geomorphological units that have been included in the subsection in the past. These sandy units include the Wadena drumlins, the St. Croix moraine, and the Park Rapids-Staples outwash, all of which seem more appropriately lumped with Subsection X.5 to the north.
Previous Section -- Section III. Southeastern Minnesota and West-Central Wisconsin Savanna
Return to Contents
Next Section -- Sub-subsection III.1.1. Leaf Hills
