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SUB-SUBSECTIONS: None.

ELEVATION: 1,250 to 1,350 feet (381 to 412 m).

AREA: 2,794 square miles (7,237 sq km).

STATES: Minnesota.

CLIMATE: Total annual precipitation ranges from 26 inches in the west to 28 inches in the east; about 40 percent falls during the growing season (University of Minnesota et al. 1971). Annual snowfall ranges from 52 inches in the west to 64 inches in the northeast (Wendland et al. 1992). The growing season is short, from 92 to 115 days, because the low-lying subsection forms a frost pocket with late spring frosts and early fall frosts. Extreme minimum temperature ranges from 40½F to -45½F (Reinke et al. 1993) and probably colder in local areas.

BEDROCK GEOLOGY: Glacial drift within the lake bed ranges from 100 to 300 feet thick; some of the thickest sediments are at the northern edge of Glacial Lake Upham, where it meets the Mesabi Range (Olsen and Mossler 1982). The bedrock beneath Lake Upham is middle Precambrian (early Proterozoic) argillite, siltstone, quartzite, or graywacke, weakly metamorphosed (Morey 1976, Morey et al. 1982). There is also Cretaceous shale, sandstone, and clay near the southwest end of the basin and along the border with the Mesabi Range.

LANDFORMS: Glacial lacustrine deposits occupy much of the subsection. There are beach ridges, but most are not well defined. There is ground moraine along the borders of Glacial Lake Upham, including low drumlin ridges.

LAKES AND STREAMS: The St. Louis and Whiteface Rivers and several creeks meander across the flat lake plain. No lakes.

SOILS: Extensive areas of Histosols (peats) over both fine-textured (both silt- and clay-rich) and sandy lacustrine deposits. Soils are classified by Anderson and Grigal (1984) as primarily Ochrepts, Hemists, Aquents, and Boralfs.

PRESETTLEMENT VEGETATION: A large part of the lowlands was dominated by sedge meadow, black spruce-sphagnum bog, and northern white-cedar and black ash swamp (Marschner 1974). Uplands supported aspen-birch and spruce-fir forest, and locally, northern hardwood forests. White pine-red pine forests were located on the ground moraine at the edges of the lake plain, but were not extensive.

NATURAL DISTURBANCE: Fire was probably important, on both the hardwood-conifer-dominated uplands and wetlands. Windthrow was probably important in the conifer swamps. In this type of flat, lacustrine setting, natural water level fluctuations and flooding behind beaver dams often cause extensive tree mortality.

PRESENT VEGETATION AND LAND USE: Present land use is estimated to be 35 to 45 percent forest, 40 to 50 percent cultivated land, and 10 to 20 percent pasture (University of Minnesota et al. 1971). Most of the agriculture is on silt-loam soils. The vegetation of the uplands is presently more heavily dominated by trembling aspen and birch than originally. Much of the remaining old-growth northern hardwood forests in the State are found in this subsection. The conifer- and sedge-dominated peatlands remain largely dominated by the original vegetation.

Insufficient biological survey has been done to determine which plant communities have good examples here.

RARE PLANT COMMUNITIES: None identified to date.

RARE PLANTS: Caltha natans (floating marsh-marigold), Tsuga canadensis (eastern hemlock).

RARE ANIMALS: Clemmys insculpta (wood turtle).

NATURAL AREAS: State Parks: Savanna Portage; State Natural Areas: McGregor Marsh.

PUBLIC LAND MANAGERS: State Forests: Savanna, Solana, Cloquet Valley, Golden Anniversary; State Parks: Savanna Portage; Wildlife Management Areas: Aitkin, Grayling, Great Scott, Kimberly, Roberts-Wickstrom; Other: Rice Lake National Wildlife Refuge.

CONSERVATION CONCERNS: Concern about accelerated timber harvest; need to protect remaining old-growth northern hardwood and hardwood swamp forests.

BOUNDARIES: The boundaries of this subsection have been modified to include the Aurora till plain, located along the southeastern and northern edges of Glacial Lake Upham. This ground moraine has clayey soils, large parts of which are poorly drained; it also forms a relatively flat plain ecologically similar to the adjacent lacustrine plain.