The southern boundary is Leech Lake and the moraines south of the lake. The northern boundary is the southern shore of Glacial Lake Agassiz. On the east side, the boundary of the subsection is a series of end moraines (Rainy Lobe in origin, but later covered by the St. Louis Sublobe). The west side is framed by the Alexandria Moraine Complex.
Level to gently rolling lake plains and till plains characterize this subsection. Three large, heavily used lakes are found here. These include Leech Lake, Lake Winnibigoshish, and Cass Lake. Conifers dominated the sandier portions of the subsection before settlement. Aspen-birch, sugar maple, basswood, northern red oak, and bur oak were common components on more productive sites. Present day land use is recreation and forestry.
The primary landforms are ground moraines, a lake plain, stagnation moraines, and an outwash plain. All are associated with the Des Moines lobe or the Wadena lobe (middle to late Wisconsin glaciation period). The ground moraines are characterized by gently rolling topography and have calcareous loamy parent material. The lake plain (Glacial Lake Aitkin) is level to gently rolling and has variable parent material, ranging from fine sands to clays. The stagnation moraines have gently rolling to hilly topography and have calcareous, loamy parent materials. The outwash plain has level to gently rolling topography and has fine to medium sandy parent material.
Thick glacial drift covers bedrock over most of the subsection. Drift thicknesses range from 200 to over 600 feet. The underlying bedrock consists of a diversity of Precambrian rock, including Early Precambrian (Late Archean) and Middle Precambrian (Early Proterozoic) gneiss, undifferentiated granite, and meta-morphosed mafic to intermediate volcanic and sedimentary rocks (Morey 1976; Morey et al. 1981)
Soils range from sandy to clayey, depending on parent material. Most fall in the Alfisol, Entisol, or Histosol orders. On moraines, most soils are loamy well to moderately well drained and are classified as Boralfs. Soils on the outwash plain are dominantly sandy and excessively well drained. They are classified as Psamments (young, undeveloped sandy soils).
Total annual precipitation ranges from 23 inches in the northwest to 27 inches in the east, with about 40% occurring during the growing season. Only 12 to 16% of the annual precipitation falls during winter months (based on Midwest Climate Center 1992). Growing season length varies from 111 to 131 days.
The major river running through this subsection is the Mississippi River. The headwaters is just to the south in the Pine Moraines and Outwash Plains Subsection. Two large bodies of water are present, Lake Winnibigoshish (a reservoir) and Cass Lake. The drainage network throughout the subsection is poorly developed due to the age and characteristics of the landforms.
Presettlement vegetation was a mixture of deciduous and conifer forests. White pine and red pine were present on the moraines. Jack pine was the dominant cover type on outwash plains and sandy lake plains. Hardwoods (northern red oak, sugar maple and basswood) grew in sheltered areas of the moraines, generally close to large lakes. Forested lowlands were occupied by black spruce, tamarack, white cedar, and black ash. Non-forested wetlands were dominated by sedge meadow communities.
Present vegetation and land use
Much of this subsection is presently forested and forestry is one of the most important land uses. Aspen is the most common tree species. It is found in both pure stands and mixed stands with birch, maple, oak, white spruce, jack pine, and red pine. Tourism and recreation is the other important land use. There are many lakes present and most are developed with summer homes. Agriculture is important locally, particularly in the western part.
Fire was an important disturbance within the white pine-red pine forests and jack pine forests/woodlands. However, 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.