Regional Landscape Ecosystems of Michigan, Minnesota, and Wisconsin
SUBSECTION X.2. Mille Lacs Uplands
DISCUSSION: Subsection X.2 consists primarily of rolling ground moraine with large drumlin fields, but a narrow, steep, clayey band of end moraines occurs along the northern edge of the subsection and along the western and southeastern end of Mille Lacs Lake.
SUB-SUBSECTIONS: None.
ELEVATION: 800 to 1,395 feet (244 to 425 m).
AREA: 6,489 square miles (16,813 sq km).
STATES: Minnesota and Wisconsin.
CLIMATE: Climate here is moderated little by Lake Superior. Total annual precipitation ranges from 27 inches in the west to 30 inches in the east; growing season precipitation ranges from 12 to 13 inches (University of Minnesota et al. 1971, 1977). Snowfall is relatively light, 52 to 60 inches (Wendland 1992); the location, primarily southwest of Lake Superior, is not characterized by lake-effect snows. Growing season length ranges from 97 to 135 days; the longest growing season is in the south and the shortest is on the outwash plains at the northern edge (University of Minnesota et al. 1977, 1980b). Extreme minimum temperature ranges from -40½F to -45½F (Reinke et al. 1993).
BEDROCK GEOLOGY: Glacial drift is typically less than 100 feet thick; bedrock is locally exposed throughout the northern part of the subsection, but not in the southeastern part, where drift thickness is 100 to 300 feet (Olsen and Mossler 1982, Trotta and Cotter 1973). Although bedrock of most of the subsection is Precambrian in age, at the southeastern edge are Cretaceous marine shale, sandstone, and variegated shale (Morey 1976, Morey et al. 1982, Ostrom 1981). In the north there is lower Precambrian (Archean) undivided granite, metavolcanic, and metasedimentary rocks (Morey 1976, Morey et al. 1982). Further south are middle Precambrian (Proterozoic) argillite, siltstone, quartzite, and graywacke, as well as iron formation. Surrounding Mille Lacs Lake are both middle Precambrian undifferentiated granite and lower Precambrian metasedimentary and metaigneous gneiss, schist, and migmatite, as well as amphibolite.
LANDFORMS: Subsection consists primarily of Superior lobe ground moraine and includes the Brainerd-Pierz and Automba drumlin fields and the McGrath till plain (University of Minnesota et al. 1977, 1980b; Hobbs and Goebel 1982). The depressions between drumlin ridges contain peatlands with shallow organic material. Small areas of Des Moines lobe ground moraine are in the southeast part (Hobbs and Goebel 1982). In the northeast, the Sawyer-Cloquet and the Willow River outwash plains occupy more than 100,000 acres (University of Minnesota et al. 1977).
End moraines, concentrated at the northern edge of the subsection and along the western and southern edges of Mille Lacs, are prominent features with rolling to steep, irregular topography (University of Minnesota et al. 1971, 1977).
LAKES AND STREAMS: Few lakes on most of the ground moraine; numerous shallow peat-lands. In contrast, bogs, small wetlands, and kettle lakes are common on the end moraines north and west of Mille Lacs. More than 70 lakes are larger than 160 acres, and lakes cover 7 to 8 percent of the surface area of the end moraines. Kettle lakes and peatlands also occur on the Sawyer-Cloquet and Willow River outwash plains.
SOILS: At the eastern end of the subsection, the end moraines and ground moraines have loamy soils; farther to the west, the soils are stony sands. Soils are described as acidic, stony, reddish sandy loams, silt loams, and loamy sands (Hole 1976, Hobbs and Goebel 1982). The parent material in the Grantsburg (Des Moines lobe) part of the subsection is generally more calcareous and finer textured; but Superior lobe drift underlies the Grantsburg deposits and is locally exposed.
On the end moraines surrounding Mille Lacs, most soils are derived from silt- or clay-rich glacial drift, but there are also sandy and gravelly soils (University of Minnesota et al. 1971, 1977). The glacial drift in the north is calcareous; the drift in the south is typically acidic.
Soils are classified as Psamments on the outwash and both Boralfs and Ochrepts on the ground moraines (Anderson and Grigal 1984). On the end moraines surrounding Mille Lacs, the soils are classified primarily as Boralfs and Hemists, but there are also Aqualfs and Ochrepts (Cummins and Grigal 1981).
PRESETTLEMENT VEGETATION: The original vegetation consisted of a mosaic of forest types on the ground moraine. East of Mille Lacs Lake, on the sandy, stony till of the Mille Lacs moraine, vegetation consisted primarily of white pine-red pine forest and aspen-white birch-white pine forest on the uplands, with equally as much conifer swamp (northern white-cedar, hemlock, larch, and black spruce) on the lowlands (Marschner 1974, Finley 1976). Mixed hardwood-white pine forests were less common than the above mentioned forest types. The Sawyer-Cloquet and the Willow River outwash plains, also located east of Mille Lacs Lake, were dominated by white pine-red pine forests and less commonly by pure stands of white pine. Both of these outwash plains had large areas of jack pine barrens near their northeastern ends.
To the southwest, on the drumlin south of Mille Lacs Lake, the dominant forest types were mixed hardwoods-white pine to the north; areas of pure white pine were concentrated on several narrow outwash channels, which were oriented north-south. In this area, the vegetation changes to forest types containing more oaks. Marschner (1974) called these his Big Woods type, which included bur, white, red, and black oaks, elm, basswood, ash, maple, and many other hardwood species. The Big Woods type continued along the southern edge of the subsection on both the Superior lobe and Des Moines lobe glacial drift. White pine and sugar maple commonly occurred together here. White pine often formed a superstory, with sugar maple as smaller overstory or understory trees.
Both mixed hardwood-pine forests and white pine-red pine forests were well represented on the irregular moraines (Marschner 1974). Aspen-birch forest was also present, and conifer swamps and bogs were common in the kettle depressions of the moraines. Large concentrations of sugar maple grew at the south end of Mille Lacs. White pine-red pine forest was abundant on the moraines north and east of that lake.
NATURAL DISTURBANCE: Both fire and windthrow were important in determining the vegetation of the subsection.
PRESENT VEGETATION AND LAND USE: White pine lumbering was concentrated in this section in Minnesota at the turn of the century (Kratz and Jensen 1983). High-quality examples of the following plant communities are well represented in this subsection: maple-basswood forest, mesic oak forest, northern hardwood forest, white pine-hardwood forest, black ash swamp, forested bog, poor fen, tamarack swamp, wet meadow.
RARE PLANT COMMUNITIES: None identified to date.
RARE PLANTS: Minnesota only: Hydrocotyle americana (American water-pennywort), Poa paludigena (bog bluegrass), Polygonum arifolium var. pubescens (halberd-leaved tearthumb). Minnesota and Wisconsin: Tsuga canadensis (eastern hemlock).
RARE ANIMALS: Minnesota only: Birds: Buteo lineatus (red-shouldered hawk), Haliaeetus leucocephalus (bald eagle), Pandion haliaetus (osprey), Seiurus motacilla (Louisiana waterthrush); Fish: Acipenser fulvescens (lake sturgeon); Reptiles: Clemmys insculpta (wood turtle), Emydoidea blandingii (Blanding's turtle); Mollusks: Quadrula fragosa (winged mapleleaf). Wisconsin only: Alces alces (moose), Canis lupis (gray wolf), great gray owl.
NATURAL AREAS: Wisconsin: State Natural Areas: Bois Brule Conifer Bog, Black Lake Bog.
PUBLIC LAND MANAGERS: Minnesota: State Forests: Nemadji, Chengwatana, St. Croix, Rum River, Snake River; Wildlife Management Areas: Mille Lacs; State Parks: Mille Lacs Kathio, St. Croix Wild River, and St. Croix.
CONSERVATION CONCERNS: The St. Croix River has been identified as a critical landscape for biodiversity protection by the Minnesota Heritage Program. There is some concern over accelerated timber harvest with loss of old-growth and larger blocks of mature forest. Maintaining roadless areas is considered ecologically critical in Wisconsin.
BOUNDARIES: As treated here, the boundaries include most of Kratz and Jensen's (1983) Mille Lacs and Grantsburg Landscape Regions in Minnesota.
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| Figure 30.—Subsection X.2: Black Lake Bog Scientific and Natural Area, Pine County, Minnesota. Bogs occur commonly in depressions on both the rolling ground moraines and the more irregular end moraines of the subsection. Minnesota Department of Natural Resources photo. |
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