Regional Landscape Ecosystems of Michigan, Minnesota, and Wisconsin
SUBSECTION X.9. North Shore (Lake Superior) Highlands
DISCUSSION: Major landscapes within Subsection X.9 are the Highland moraine, Highland Flutes, and the Nemadji-Duluth lake plain (University of Minnesota et al. 1981b). Also included is the Brimson outwash plain. The forests were almost completely dominated by conifers; isolated pockets of sugar maple and yellow birch occupied small upland areas within 3 to 4 miles of the Lake Superior shoreline.
SUB-SUBSECTIONS: None. Two potential sub-subsections could be identified on the basis of forest dominance. White pine and red pine originally dominated the clay lake plain and the rocky soils in the southern half of the subsection; aspen-birch forest dominated the northern half of the subsection.
ELEVATION: 602 to 1,900 feet (184 to 579 m).
AREA: 1,753 square miles (4,540 sq km).
STATES: Minnesota.
CLIMATE: Total annual precipitation ranges from 28 to 30 inches, about 40 percent of which occurs during the growing season (Hargrave 1992). Growing season ranges from approximately 121 to 135 days; the longest growing season is along the shore of Lake Superior, where it is about 10 days longer than farther inland at the equivalent latitude (University of Minnesota et al. 1981b). Annual snowfall ranges from 60 to 64 inches (Reinke et al. 1993). The lake effect increases the amount of snowfall by about 10 inches within 5 miles of the Lake Superior shoreline, but a similar trend is not apparent in the annual precipitation data. Extreme minimum temperatures are -30½F to -40½F (Reinke et al. 1993).
The absence of late spring frosts on the ridges within a few miles of Lake Superior may account for the presence of sugar maple-basswood forests; Rosendahl and Butters (1928) noted the importance of large lakes and ridges with free air drainage for occurrence of this forest type in northern Minnesota.
BEDROCK GEOLOGY: Glacial drift is thin over the entire subsection, and bedrock is exposed or near the surface in large areas. The underlying bedrock consists of upper Precambrian (middle Proterozoic) basalt, rhyolite, gabbro, diabase, anorthosite, granite, sandstone, and shale (Morey 1976). The southeastern-dipping Keweenawan basalt and diabase resurface on the Keweenaw Peninsula in the Upper Peninsula of Michigan.
LANDFORMS: Ground moraine and end moraine of the Superior lobe cover much of the subsection (Hobbs and Goebel 1982). Clay lake plain forms a broad band along the Lake Superior shoreline in the southern half of the subsection. The clay plain is flat to rolling, with steep, narrow ravines along many streams. Outwash deposits occur along the western edge. Numerous short streams, 10 to 15 miles long, lead directly from the highland to the shores of Lake Superior; most of the streams have water falls near the shoreline (Wright 1972).
Lakes make up about 2 to 3 percent of the subsection; 20 lakes are larger than 160 acres in size. Of these, 17 are located on the Highland moraine along the western edge of the subsection and 3 are located on the Highland Flutes, near Lake Superior along the eastern edge of the subsection (University of Minnesota et al. 1981b). There are no lakes on the lacustrine clays along Lake Superior.
SOILS: Soils are developed from the rocky, red tills of the Superior lobe; textures range from sand to clay (Hobbs and Goebel 1982). Sands and sandy loams are the predominant soils on the Highland moraine, which occupies much of the western and central parts of the subsection. The Highland Flutes, along the eastern edge of the subsection, have a predominance of thin soils over bedrock and clayey soils (University of Minnesota et al. 1981b). The Nemadji-Duluth lacustrine plain has approximately 95 percent clay soils. Much of the till contains abundant clasts derived from the local igneous and metamorphic bedrock. The most common soils of the subsection are classified as Orthents, Ochrepts, and Boralfs (Anderson and Grigal 1984).
PRESETTLEMENT VEGETATION: Marschner (1974) recorded aspen-birch forest, white pine-red pine forest, mixed hardwood-pine forest, and conifer bogs and swamp. White pine-red pine forest was most common on the clay lake plain and on thin soil over bedrock in the southern half of the subsection. Mixed hardwood-pine forest, with sugar maple, was concentrated on the ridges of the dissected clay lake plain and the Highland Flutes. On the clay plain, these sites were probably some of the best drained; on both the lake plain and the moraines of the Highland Flutes, these sites were probably best protected from late spring frosts (Grigal and Arneman 1970, Flaccus and Ohmann 1964). Aspen-birch forest was less abundant on the clay plain and the thin soils in the southern half of the subsection, but became more common, along with conifer bogs and swamps, farther inland. It is not clear which soils and climatic conditions are responsible for the increase in aspen-birch.
In the northern half of the subsection, aspen-birch became the dominant vegetation, with very little white pine-red pine forest or mixed hardwood-pine forest. Where mixed hardwood-pine forest persists, it is within 6 to 10 miles of the shoreline on ridgetops.
NATURAL DISTURBANCE: Fire and spruce budworm defoliation.
PRESENT VEGETATION AND LAND USE: Almost the entire subsection remains forested; forest management and recreation are the major land uses (Hargrave 1992). Following logging, the extensive white pine-red pine forests have been replaced by forests of trembling aspen-paper birch.
Jahns (1983) mapped the presence of sugar maple within the Tofte subsection of the Superior National Forest. Sugar maple was concentrated within 8 to 10 miles of the Lake Superior shoreline.
High-quality examples of the following plant communities are well represented in this subsection: northern hardwood forest, upland northern white-cedar forest, forested bog.
RARE PLANT COMMUNITIES: None identified to date.
RARE PLANTS: Most of the following rare plants have a northern distribution, and most are found close to the Lake Superior shoreline. Adoxa moschatellina (moschatel), Arnica chionopappa (arnica), Claytonia caroliniana (Carolina spring-beauty), Crataegus douglasii (Douglas thorn-apple), Draba arabisans (Whitlow grass), Eleocharis nitida (neat spike-rush), Empetrum atropurpureum (purple crowberry), Euphrasis hudsoniana (Hudson Bay eyebright), Listera auriculata (auricled twayblade), Luzula parviflora (small-flowered woodrush), Osmorhiza chilensis (Chilean sweet cicely), Pinguicula vulgaris (butterwort), Polygonum viviparum (alpine bistort), Polystichum braunii (Braun's holly fern), Sagina nodosa ssp. borealis (knotty pearlwort), Selaginella selaginoides (northern spikemoss), Tofieldia pusilla (small false asphodel), Vaccinium uliginosum var. alpinum (Alpine bilberry), Woodsia glabella (smooth woodsia).
RARE ANIMALS: Falco peregrinus (peregrine falcon).
NATURAL AREAS: State Natural Areas: Butterwort Cliffs, Lutsen, Moose Mountain, Spring Beauty Northern Hardwoods, Sugar Loaf; Research Natural Areas: Marble Lookout, Schroeder; The Nature Conservancy Preserves: Cathedral Grove, Langley River; Other: Susie Islands, Congdon Park, McNair, Pigeon River #10.
PUBLIC LAND MANAGERS: National Forest: Superior; State Forests: Cloquet Valley, Finland, Grand Portage, Pat Bayle; State Parks: Cascade River, George Crosby-Manitou, Gooseberry Falls, Split Rock Lighthouse, Temperance River, Tettegouche, Judge Magney; State Waysides: Devils Track, Kodonce River, Ray Bergland; Wildlife Management Areas: Canosia.
CONSERVATION CONCERNS: Lake Superior Highlands subsection was identified as critical landscape for biodiversity protection by the Minnesota Heritage Program. The subsection contains significant old-growth northern hardwood and upland northern white-cedar forest. Large populations of deer and sprawling recreational development are concerns near the Lake Superior shoreline.
BOUNDARIES: The inland boundary is located where Superior lobe glacial deposits meet Rainy lobe glacial deposits, as mapped by Hobbs and Goebel (1982).
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| Figure 32.—Subsection X.9: Superior National Forest, Cook County, Minnesota. Upland forests of northern white-cedar grow near Lake Superior. Minnesota Department of Natural Resources photo by K.A. Rusterholz. |
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