Regional Landscape Ecosystems of Michigan, Minnesota, and Wisconsin
SUBSECTION IV.3. Maple-Basswood Forested River Ravines
DISCUSSION: This subsection is designated on the basis of extensive sugar maple-basswood-dominated forests, concentrated in the steepest, most fire-protected topography within the section. Three areas where maple-basswood forest dominated within the section have been designated as distinct sub-subsections because they are spatially disjunct from each other, separated by other units of Section IV.
SUB-SUBSECTIONS: Kickapoo-Wisconsin River Ravines, a protected 1,300-square-miles block between the Kickapoo River and the Wisconsin River in Wisconsin (IV.3.1); Chippewa River Ravines, the northern edge of the subsection (IV.3.2) in St. Croix and Pierce Counties, Wisconsin, where fire protection is provided by several north-south-oriented ravines; and Mississippi River Ravines, the steep ravines of the Mississippi River and its major tributaries in Minnesota (IV.3.3). (See figure 3.)
ELEVATION: 625 to 1,450 feet (190 to 442 m).
AREA: 3,859 square miles (10,001 sq km).
STATES: Minnesota and Wisconsin.
CLIMATE: See section.
BEDROCK GEOLOGY: Large exposures of bedrock occur in the steep ravines, primarily Ordovician dolomite, limestone, and sandstone in Minnesota, with Cambrian sandstone, shale, and dolomite exposed along the valley walls of the Mississippi River (Morey 1981, Sims et al. 1966).
LANDFORMS: See section.
LAKES AND STREAMS: No natural lakes. Both the Kickapoo and Wisconsin Rivers form boundaries of Sub-subsection IV.3.1, and the Chippewa River flows through Sub-subsection IV.3.2.
SOILS: Silt loam over acid till in the north; silt loam over cherty red clay (residuum), dolomite, and sandstone in the south (Hole 1968, 1976; Hole and Germain 1994; Cummins and Grigal 1981). Soils are classified as Udalfs on the ridges and Orthents on the flood plain (Anderson and Grigal 1984).
PRESETTLEMENT VEGETATION: Maple-basswood forest on highly dissected topography with fire protection. It occurred primarily on north-facing slopes, especially in lower slope positions. Maple-basswood forest was concentrated in three areas within Section IV, as represented by Sub-subsections IV.3.1, IV.3.2, and IV.3.3).
NATURAL DISTURBANCE: Fire was presumably less prevalent within the maple-basswood forest than in adjacent oak savanna or prairie.
PRESENT VEGETATION AND LAND USE: Most of the forest has been cleared for agriculture except on the steep valley walls.
RARE PLANT COMMUNITIES: See sub-subsections.
RARE PLANTS: See sub-subsections.
RARE ANIMALS: See sub-subsections.
NATURAL AREAS: See sub-subsections.
PUBLIC LAND MANAGERS: See sub-subsections.
CONSERVATION CONCERNS: See sub-subsections.
BOUNDARIES: Boundaries are based on interpretations by Hole and Germain (1994) and my interpretations of Marschner (1974).
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