Regional Landscape Ecosystems of Michigan, Minnesota, and Wisconsin
SUBSECTION X.5. Pine Moraines and Outwash Plains
DISCUSSION: Subsection X.5 consists of a number of steep, end-moraine ridges surrounded by large expanses of outwash. The subsection has been subdivided into two sub-subsections on the basis of landform and soil texture.
SUB-SUBSECTIONS: The Itasca, Alexandria, and St. Croix Moraines sub-subsection (X.5.1) consists of sandy end moraines, and the Park Rapids-Staples and Crow Wing Outwash Plains sub-subsection (X.5.2) consists of several outwash plains. (See figure 3.)
ELEVATION: 1,100 to 1,850 feet (335 to 564 m).
AREA: 5,602 square miles (14,497 sq km).
STATES: Minnesota.
CLIMATE: Total annual precipitation ranges from 24 inches in the northwest to 27 inches in the east; about 40 percent occurs during the growing season (University of Minnesota et al. 1969, 1980a). Only 12 to 16 percent of the annual precipitation falls during winter (based on Wendland et al. 1992). Annual snowfall is 44 to 52 inches, heaviest in the east (Wendland et al. 1992). Growing season ranges from 111 to 131 days. Extreme minimum temperature ranges from -40½F to -45½F (Reinke et al. 1993).
BEDROCK GEOLOGY: Thick glacial drift covers bedrock over most of the subsection. Drift thicknesses range from 200 to more than 600 feet; the greatest thicknesses are in the southwest (Olsen and Mossler 1982). At the southeastern edge, drift is thin, with very localized bedrock exposures just south of the Crow Wing River and west of the Mississippi River.
The underlying bedrock consists of diverse Precambrian rock, including early Precambrian (late Archean) and middle Precambrian (early Proterozoic) gneiss, undifferentiated granite, and metamorphosed mafic to intermediate volcanic and sedimentary rocks (Morey 1976, Morey et al. 1981). There is also iron formation at the southeastern edge of the subsection, along with argillite, siltstone, quartzite, and graywacke. Cretaceous marine shale, sandstone, and variegated shale are localized in the southwest.
LANDFORMS: Large outwash plains, narrow outwash channels, and end moraines (Hobbs and Goebel 1982). Subsection X.5 is divided into sub-subsections because of the diversity of these landforms. The relatively large moraines of the subsection were formed from parts of several glacial lobes; most of the glacial drift was sandy.
LAKES AND STREAMS: Kettle lakes are common within most of the larger outwash plains and within the stagnation moraines; thousands of lakes are within the subsection. Leech Lake forms the northeastern boundary. Large rivers flowing through the outwash plains include the Mississippi, Pine, and Crow Wing.
SOILS: Soils of the moraines are predominantly sands and sandy loams (University of Minnesota et al. 1969, 1980a). Soils of the outwash plains are primarily excessively or well drained sands, but there are also numerous wetlands with very poorly drained soils. More than 10 percent of the soils are peats.
Soils are classified as Psamments and Aquents on the outwash plains (Anderson and Grigal 1984). Boralfs are the predominant soils on the moraines.
PRESETTLEMENT VEGETATION: Jack pine, with northern pin oak, dominated the excessively drained parts of the broad outwash plains, but trembling aspen-paper birch forest dominated large expanses and conifers dominated the very poorly drained portions of the outwash (Marschner 1974). Red pine-white pine forests, along with trembling aspen-paper birch forests, occupied the rolling to irregularly sloped end moraines. Mixed hardwood and pine forests, dominated by a diverse mix of northern hardwoods and white pine, were found in the most fire-protected areas at the eastern edge of the subsection. Fire protection was provided by irregular topography, broad wetlands, and relatively large lakes. Some of the hardwood-pine forests mapped by Marschner (1974) may have been dominated by red oak and basswood, without sugar maple.
Sugar maple may have always been an understory or minor overstory component in some of the white pine and white pine-red pine forests; drought broke the water column in the sugar maple, and it remained a lower canopy species. On the Chippewa National Forest in the east, sugar maple was a significant component of several upland ecosystems (Grigal and Kernik 1980).
A common original forest type mapped by Marschner (1974) within the subsection was aspen-birch. This designation was probably used for several very different vegetation types found on very different soils and landforms. The floristic analysis of Grigal and Kernik (1980) on the Chippewa National Forest describes paper birch and trembling aspen as a major component on both excessively drained outwash plains and moist ground moraine. Trembling aspen, with little or no associated paper birch, was also common on sandy moraines and poorly drained lake plain. Bigtooth aspen was also present, sometimes in combination with trembling aspen, on moist outwash plains, and sometimes with red oak and sugar maple on drier moraines. It thus appears that this vegetation type, as delineated by Marschner, actually represents several vegetation types found on several ecosystems, and it is less useful for characterizing ecological relationships than jack pine barrens, white pine-red pine forest, white pine forest, or mixed hardwood-pine forest.
Approximately 6,000 years ago, this subsection was the eastern extent of prairie. A strong prairie component remains in the groundcover. Balsam fir occurs commonly as an understory species, but it is an overstory dominant only at upland/wetland edges.
NATURAL DISTURBANCE: Fire occurred on a 10- to 40-year rotation within much of the subsection, accounting for the dominance by upland conifers and trembling aspen-birch forests (Frissel 1973).
PRESENT VEGETATION AND LAND USE: After logging of white and red pines, paper birch and trembling aspen became more common dominants within much of the subsection (Frissel 1973).
High-quality examples of the following plant communities are well represented in this subsection: dry oak savanna, jack pine barrens, mixed pine-hardwood forest, mesic oak forest, red pine forest, white pine forest, black ash swamp, black spruce swamp, tamarack swamp, wet meadow, and poor fen.
RARE PLANT COMMUNITIES: None identified to date.
RARE PLANTS: Malaxis paludosa (bog adder's-mouth).
RARE ANIMALS: Buteo lineatus (red-shouldered hawk), Haliaeetus leucocephalus (bald eagle), Pandion haliaetus (osprey), Emydoidea blandingii (Blanding's turtle).
NATURAL AREAS: State Natural Areas: Iron Springs Bog, Itasca Wilderness Sanctuary (National Natural Landmark); Research Natural Areas: Height of Land, Pine Point (NNL), Sugar-bush; The Nature Conservancy Preserves: Paul Bunyan Savanna; Other: Lake Alexander Preserve, Spearhead Lake.
PUBLIC LAND MANAGERS: National Forests: Chippewa; State Forests: Badoura, Crow Wing, Foot Hills, Huntersville, Land O'Lakes, Mississippi Headwaters, Paul Bunyan, Pillsbury, Smokey Hills, Two Inlets; State Parks: Itasca, Big Island; Wildlife Management Areas: Birch-dale, Bull Moose, Crow Wing Chain, Dry Sand Lake, Huntersville, Kabekona, Lowell, Upper Rice; Other: Camp Ripley Military Reservation, Belle Prairie Park, Paul Bunyan Arboretum, Smith Memorial Forest.
CONSERVATION CONCERNS: The Minnesota Department of Natural Resources planning team has recommended (1) maintaining a certain percentage of each forest community in old- growth conditions, (2) increasing the amount of oak, northern white-cedar, and white pine within the subsection, (3) maintaining large areas of contiguous forest for forest-interior dwelling species, (4) maintaining semi-primitive conditions (few or no roads), (5) providing habitat for endangered, threatened, and special concern biota, and (6) protecting cultural resources.
Itasca State Park Pines was identified as a critical landscape for biodiversity protection by the Minnesota Heritage Program. Accelerated timber harvest is a concern throughout the subsection. Fragmentation, loss of conifers, simplification of forest stand structure and communities, and a reduction in the extent of mature forests are special concerns. The only remaining large areas of old-growth red pine and white pine forest, in Itasca State Park, exhibit little pine regeneration due to high deer populations and lack of fire.
BOUNDARIES: The Park Rapids-Staples plain, along the southern edge of the subsection, has been treated by others as part of Sub-subsection III.1.1. I have included it within this subsection, along with parts of the Wadena drumlins and the St. Cloud moraine, because northern species, such as jack pine, white pine, and red pine, are the dominant vegetation. Along the eastern boundary, the finer textured Sugar Hills have been excluded; instead, they have been joined with other fine-textured moraines into Subsection X.6. These moraines also support white pine-red pine forest and northern hardwood-pine forests, but almost no jack pine.
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| Figure 31.—Subsection X.5: Stumphages Rapids Natural Heritage Registry, Hubbard County, Minnesota. Outwash plains of the subsection support extensive forests of jack pine. Minnesota Department of Natural Resources photo by K.A. Rusterholz. |
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