Regional Landscape Ecosystems of Michigan, Minnesota, and Wisconsin
SUBSECTION III.2. Big Woods
DISCUSSION: This subsection has been known as the Big Woods (Grimm 1984). Along the western boundary adjacent to the prairie of Section II, water bodies and irregular ice-stagnation topography provide a barrier to allow the forests of the Big Woods to persist. The same features formed the fire barrier to the south and east. The subsection itself has irregular, hilly topography with many lakes and wetlands. It includes portions of the Waconia-Waseca moraine, Minnesota Valley outwash, Lonsdale-Lerdal till section, and the Prior Lake and Emmons-Faribault moraines (University of Minnesota et al. 1973).
SUB-SUBSECTIONS: None.
ELEVATION: 750 to 1,150 feet (229 to 351 m).
AREA: 3,092 square miles (8,008 sq km).
STATES: Minnesota.
CLIMATE: Annual precipitation ranges from 29 inches in the west to 31 inches in the east; growing season precipitation ranges from 12 to 13 inches (Hargrave 1992). Annual average snowfall is 44 to 48 inches (Wendland et al. 1992). Growing season length is approximately 145 to 150 days. Extreme minimum temperature ranges from -35½F to -40½F (Reinke et al. 1993).
BEDROCK GEOLOGY: From 100 to 400 feet of glacial drift cover the bedrock of the subsection (Olsen and Mossler 1982). The underlying bedrocks are Ordovician and Cambrian sandstone, shale, and dolomite to the south and Cretaceous shale, sandstone, and clay to the north (Morey 1976).
LANDFORMS: Ice-stagnation features and end moraines.
LAKES AND STREAMS: Many lakes and bogs on the irregular moraines (University of Minnesota et al. 1979). More than 6 percent of the subsection's surface is occupied by lakes.
SOILS: Loams and clay loams (University of Minnesota et al. 1979). These are classified as both Mollisols (primarily Udolls and Aquolls) and Alfisols (primarily Udalfs and Aqualfs) (Cummins and Grigal 1981).
PRESETTLEMENT VEGETATION: Oak woodland and maple-basswood forest were the most common vegetation types on the irregular ridges of the subsection. Based on his study of the GLO survey notes, Grimm (1984) found that the actual order of dominance in the sugar maple-basswood forest was elm (27 percent), basswood (14 percent), sugar maple (12 percent), bur oak (10 percent), ironwood, red oak, and aspen (7 percent). He also found that along the western margin of the subsection, aspen was most common (53 percent), followed by bur oak (22 percent). On all other margins, the oak woodland was dominated by a mix of aspen, red oak, bur oak, and to the east, white oak.
NATURAL DISTURBANCE: Although fire occurred within the subsection, it was much less common than on the prairies of Section I to the southwest, primarily due to the irregular topography. Windthrow was probably also an important natural disturbance, but no references were encountered in the literature.
PRESENT VEGETATION AND LAND USE: More than 75 percent of the subsection is cropland; an additional 5 to 10 percent is pasture. The remaining 10 to 15 percent of the subsection remains as either upland forest or wetland (University of Minnesota et al. 1979, 1980b, 1981a).
RARE PLANT COMMUNITIES: Dry prairie (sand-gravel subtype), glacial till hill prairie, and mesic prairie. Numerous high-quality areas of maple-basswood forest occur in the subsection, along with flood-plain forests and a few dry oak savannas.
RARE PLANTS: Erythronium propullans (dwarf trout lily) and Trillium nivale (snow trillium), Besseya bullii (kitten-tails), Valeriana edulis ssp. ciliata (valerian).
RARE ANIMALS: Buteo lineatus (red-shouldered hawk), Clemmys insculpta (wood turtle), Emydoidea blandingii (Blanding's turtle).
NATURAL AREAS: State Natural Areas: Black Dog Preserve, Cannon River Trout Lily, Chamberlain Woods, Mary Schmidt Crawford Woods, Savage Fen, Townsend Woods, Kasota Prairie, Mississippi River Islands, Wolsfeld Woods; The Nature Conservancy Preserves: Hardscrabble Point Woods; Other: Nerstrad Big Woods State Park, Lowry Woods, River Bend Nature Center.
PUBLIC LAND MANAGERS: Wildlife Management Areas: Boyd, Cannon River, Dwyer, Esker, Karnitz, Milest, Paulson, Vale; State Parks: Lake Maria, Minnesota Valley Trail, Sakatah Lake; Park Reserves: Carver, Crow-Hassan, Elm Creek, Hyland Lake, Lake Rebecca, Murphy-Hanrehan; Other: McLeod County Park #3, Rice County Wilderness Area, Richter Woods County Park, Carleton College Arboretum, Central Park, Izaak Walton League Park, Morris T. Baker Regional Park, Straight River Wildflower Preserve, Trout Lily Preserve.
CONSERVATION CONCERNS: Loss of remaining woodlots, prairies, and wetlands; heavy selective cutting of red oak from private forest lands.
BOUNDARIES: The southern portion of the Waconia-Waseca moraine is not included in the subsection because it contains fewer lakes and wetlands than the northern portion of the moraine. The subsection is characterized by more southern tree species and greater overall floristic diversity than the Alexandria moraine (Leaf Hills sub-subsection) to the northwest. Soils are generally loamier. To the north is the Anoka Sand Plain, which has sandier soils and flatter topography. To the south and southwest, Section I is flat to rolling ground moraine with prairie soils and vegetation.
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| Figure 12.—Subsection III.2: Maple-basswood forest occupies fire-protected sites in this subsection. Common tree species of this forest type included elm, basswood, sugar maple, bur oak, ironwood, red oak, and aspen. Maple-basswood forest also occupies irregular topography, which provided fire-protection in Sub-subsections III.1.1, III.1.2, and locally in Subsection III.4. Minnesota Department of Natural Resources photo by C.K. Converse. |
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