Regional Landscape Ecosystems of Michigan, Minnesota, and Wisconsin
SUB-SUBSECTION X.6.1. Black Duck Till Plain
DISCUSSION: Sub-subsection X.6.1 is an area of loamy lake-modified till, ground moraine, stagnation moraine, and lake plain, making up the northern part of the subsection. The combination of loamy soils and fire protection results in much less jack pine dominance on the moraines than in Subsection X.5 (Pine Moraines) to the south.
ELEVATION: 1,200 to 1,585 feet (366 to 483 m).
AREA: 2,661 square miles (6,897 sq km).
STATES: Minnesota.
CLIMATE: See subsection.
BEDROCK: Glacial drift thickness over bedrock is generally 200 to 400 feet (Olsen and Mossler 1982). The bedrock beneath the sub-subsection is early Precambrian (middle to late Archean) and middle Precambrian (early Proterozoic) gneiss, amphibolite, undifferentiated granite, and metamorphosed mafic to intermediate volcanic and sedimentary rocks, iron formation, metasedi-ments, quartzose sedimentary rocks, slate, metagraywacke, and quartzite.
LANDFORM: Beginning in the north, the primary landforms include lake-modified till plain, ground moraine, and stagnation moraine. Glacial Lake Aitkin, at the east edge, also includes areas of ground moraine and outwash. Except for the stagnation moraine, the rest of this sub-subsection is flat and poorly drained.
LAKES AND STREAMS: The stagnation moraines contain many small and large kettle lakes. More than 50 kettle lakes larger than 160 acres occur in the sub-subsection; Lake Winnibigoshish is the only large lake.
SOILS: Soils of the Black Duck till plain are clay and silt loams (University of Minnesota et al. 1969, 1980a). These clayey soils are derived from shales and limestones of Manitoba and eastern North Dakota (Hobbs and Goebel 1982). More than 10 percent of the soils are peats.
Fine-textured soils, ranging from loams to silty clays, characterize the sub-subsection. Approximately 70 to 85 percent of the soils are well drained, depending on the landform (University of Minnesota et al. 1980a). The predominant soils are Boralfs (Anderson and Grigal 1984).
PRESETTLEMENT FOREST: Mixed hardwood and pine forests, dominated by a diverse mix of northern hardwood species and white pine, were found in the most fire-protected areas at the northern edge of the subsection (Marschner 1974). On the west part of the Black Duck till plain, where soils were thick, mixed forests of northern hardwoods and white pine occurred. To the east, where the soils of the till plain were thin over bedrock, birch-aspen forest and conifer swamp were more common. The original vegetation on the more steep and irregular stagnation moraines (Erskine and Clearbrook moraines) was largely white pine-red pine forest. Northern hardwoods grew locally on the stagnation moraine just west of Lake Winnibigoshish, possibly as a result of protection from late spring frosts.
NATURAL DISTURBANCE: Fire was probably an important disturbance within the white pine-red pine forests, but it is not clear whether the fires were from the Bemidji outwash plain immediately to the south or from lightning fires originating within the pine stands themselves.
PRESENT VEGETATION AND LAND USE: See subsection.
RARE PLANT COMMUNITIES: See subsection.
RARE PLANTS: See subsection.
RARE ANIMALS: See subsection.
NATURAL AREAS: See subsection.
PUBLIC LAND MANAGERS: See subsection.
CONSERVATION CONCERNS: See subsection.
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