Regional Landscape Ecosystems of Michigan, Minnesota, and Wisconsin
SUBSECTION X.8. Nashwauk Uplands
DISCUSSION: Subsection X.8 is characterized by diverse landforms and soils, which provide the basis for further subdivision into several sub-subsections or landtype associations. Most of the subsection consists of noncalcareous, loamy glacial drift of the Rainy lobe (Hobbs and Goebel 1982). Probably the most distinctive feature of the subsection is the Giants Range, a narrow ridge of thin till over bedrock, which is part of the Mesabi Range. The subsection contains several outwash plains and sandy end moraines along its northern and eastern edge, including the Prairie River and Big Rice outwash plains and the Big Rice and Vermilion moraines. Loamy moraines include the Nashwauk-Warba moraines, and parts of the Highland moraine.
SUB-SUBSECTIONS: None.
ELEVATION: 1,300 to 1,850 feet (396 to 564 m).
AREA: 2,120 square miles (5,494 sq km).
STATES: Minnesota.
CLIMATE: Average annual precipitation ranges from 24 to 27 inches; the lowest amounts are at the western edge (University of Minnesota et al. 1971). About half of the precipitation arrives during the summer. Annual snowfall is 56 to 64 inches; heaviest amounts are in the east, closer to Lake Superior (Wendland et al. 1992). Growing season ranges from 106 to 121 days. Extreme minimum temperatures are -40½F to 45½F or colder (Reinke et al. 1993).
The narrow upland ridge of the Giants Range, rising 400 to 450 feet above the adjacent plain, is probably less prone to late spring frost. Lack of late spring frosts may be responsible for increased dominance of northern hardwood forest.
BEDROCK GEOLOGY: Glacial drift thickness is quite variable. The Mesabi Range has thin, sandy glacial drift overlying bedrock (Olsen and Mossler 1982), as does the Prairie River and Big Rice outwash and associated sandy moraines. The Nashwauk-Warba moraine, between the outwash plains and the Mesabi Range, has glacial drift less than 100 feet thick, but few areas of bedrock outcrop.
Along the northern edge of the Mesabi Range is a 200- to 400-foot highland of lower Precambrian granite known as the Giants Range (Wright 1972). Immediately to the south of the Giants Range is quartzite and the iron formation of the Mesabi Range (Sims et al. 1970, Southwick et al. 1988). The iron formation, a major source for iron ore, has been heavily mined, first for "soft" iron ore and later for taconite (Wright 1972). The Precambrian (late Archean and early Proterozoic) bedrock includes gneiss, undifferentiated granite, and metamorphosed mafic to intermediate volcanic and sedimentary rocks. Metasediments, quartzose sedimentary rocks, slate and meta-graywacke and quartzite are also present, as are middle Proterozoic basalt, rhyolite, gabbro, diabase, anorthosite, granite, sandstone, and shale (Morey 1976).
LANDFORMS: Ground moraines, stagnation moraines, end moraines, and outwash plains (Hobbs and Goebel 1982). Outwash covers much of the northern part of the subsection. The outwash plains are flat to rolling; outwash deposits are thicker at the west end. Within and adjacent to the outwash plains, there are also narrow, steep end moraines with sandy to gravelly soils. These include the Vermilion and Big Rice moraines. Bedrock is locally exposed both in the end moraines and on outwash plains.
The Nashwauk moraine, which occupies the western part of the subsection, consists of rolling moraines with some steeper moraines. The Giants Range, a ridge of bedrock with a thin veneer of sandy till, has some of the highest relief in the State. South of the Giants Range is rolling ground moraine of clayey till (University of Minnesota et al. 1971).
LAKES AND STREAMS: Lakes on the outwash plains are concentrated at both the northeast and northwest edges of the subsection; Big Rice plain contains six lakes larger than 160 acres, and the Prairie River plain contains 27 lakes in that size range (University of Minnesota et al. 1971). On the Nashwauk moraine, small bogs and potholes are common, and 27 lakes are larger than 160 acres (University of Minnesota et al. 1971). Kettle lakes are also common on the Vermilion moraine. The headwaters of the St. Louis River are located within the subsection. Other rivers are the Prairie, Little Fork, and Bear (Hargrave 1992).
SOILS: Soils of the outwash plains are sands and loamy sands developed from thick sandy and gravelly glaciofluvial deposits (University of Minnesota et al. 1971). Soils of the Vermilion and Big Rice moraines are also sands and gravelly sands, with some sandy loams. Stones and cobbles are locally abundant. The till is variable in depth, and there are localized bedrock outcrops. Soils are classified as Orthents, Orthods, Ochrepts, Psamments, and Boralfs (Cummins and Grigal 1981).
Soils of the Nashwauk moraine are calcareous clay loams, but there are also shallow, sandy soils over loamy till (University of Minnesota et al. 1971). Small areas of rock outcrop occur northwest of Chisholm. Soils of the Giants Range are cobbly loamy sands and sandy loams; these soils are well to excessively drained (University of Minnesota et al. 1971). Soils of the ground moraine to the south of the Giants Range are silty or clayey. Most of these fine-textured tills are well drained, but poorly drained soils are included. Soils are classified as Boralfs, Aqualfs, and Hemists on the ground moraine and as Ochrepts and Boralfs on the thin soils of the Giants Range (Cummins and Grigal 1981).
PRESETTLEMENT VEGETATION: Forest types represented within the subsection included white pine-red pine forest, aspen-birch forest, mixed hardwood-pine forest, and jack pine barrens on the uplands (Marschner 1974). The original vegetation of the outwash included jack pine barrens, aspen-birch forest, white pine-red pine forest, and conifer swamps and bogs. Jack pine was most common in areas of outwash not dissected by streams, kettle lakes, or kettle wetlands. Aspen-birch was common in the west; white pine-red pine was more common in the east, where there were more lakes and narrow moraines to provide partial fire protection. The conifer swamps were concentrated in kettle depressions and drainages within the outwash.
On the Nashwauk moraine, aspen-birch forest was most common in the west; further to the east, white pine-red pine forest was much more prevalent (Marschner 1974). The aspen-birch forest appeared to be concentrated where the topography was flattest and where there were many small streams. White pine-red pine forest was on more rolling to steep topography. Jack pine barrens were much less extensive, restricted to small fire-prone outwash deposits at the western edge of the moraines. Conifer swamps and bogs were also found in depressions and along drainageways throughout.
The Giants Range supported a forest of mixed hardwood-pine, and the adjacent ground moraine to the south supported primarily white pine-red pine forest, along with aspen-birch forest and conifer swamps and bogs (Marschner 1974). Dominance by northern hardwoods (mixed hardwood-pine) may be the result of protection from both fire and late spring frosts on the large ridge.
Wetland vegetation includes conifer bogs and swamps and open muskeg. The largest area of wetlands was at the southeastern edge of the subsection, just north of the drumlin fields of the Laurentian Highland (Toumi drumlins).
NATURAL DISTURBANCE: Fire was important on the outwash plains and probably, to a lesser degree, on the moraines. Windthrow had the strongest impact on the moraines, especially on the exposed ridges of the Giants Range.
PRESENT VEGETATION AND LAND USE: Forestry, mining, and tourism are important land uses (Hargrave 1992). Aspen, the most common tree species, is used for paper and waferboard. Tourism is important, especially where lakes are numerous. Historically, iron mining was an important industry, but it has decreased significantly in recent years.
Inventory work is insufficient to determine which plant communities are well represented in this subsection.
RARE PLANT COMMUNITIES: None identified to date.
RARE PLANTS: Geocaulon lividum (northern comandra), Viola novae-angliae (New England violet).
RARE ANIMALS: Clemmys insculpta (wood turtle).
NATURAL AREAS: State Natural Areas: Sand Lake Peatland; The Nature Conservancy Preserves: Wabu Woods.
PUBLIC LAND MANAGERS: State Forests: Bear Island, Finland, George Washington, Pat Bayle, Sturgeon River.
CONSERVATION CONCERNS: Accelerated timber harvest with resulting fragmentation, loss of mature forest, and simplification of forest communities.
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