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Big Woods

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About the Big Woods

The Big Woods are a region in southern Minnesota, located roughly west of Minneapolis. Historically, this region stood out as an island of hardwood forest surrounded by prairie and savanna, although there were numerous regions of wet prairie throughout, along with abundant lakes, so much that in parts of this region there is more open water than land. The Minnesota river also flows northeast through this region.

This region is hilly and irregular, formed of stagnation moraines, with some terminal moraines. There are numerous lakes throughout, most small, but in some places the density of lakes is so high and the different basins are fused to form larger lakes interrupted by isthmuses and peninsulas. In total lakes cover over 6% of this region's surface. Some of the shallower depressions contain bogs and even shallower ones, wet prairies. Glacial drift is thick here, 100-400 feet, deeply burying the bedrock throughout. Soils formed here are mostly loams to clay loams, with a greater portion of clay as one moves north, and tend to be nutrient-rich and often calcium-rich.

Originally this area was mostly covered in hardwood forests, with open prairie only on the wetter sites, and some bogs. The predominate forest cover was oak on the drier sites. Moister sites, as well as sites where topography sheltered plants from fire, supported forest of American elm (Ulmus americana), slippery elm (Ulmus rubra), American basswood (Tilia americana), sugar maple (Acer saccharum), and bur oak (Quercus macrocarpa), with some bur oak (Quercus macrocarpa), northern red oak (Quercus rubra), and quaking aspen (Populus tremuloides). Although this forest is sometimes classified as "Sugar Maple - Basswood", this region probably had more elm than maple or basswood. Drier sites subjected to fire more frequently, supported mostly oak woodland, with dominant species being, northern red oak, bur oak, quaking aspen, and in the east, white oak (Quercus alba), a species that reaches its westernmost range limits in this region. Although fire did occur here, it was much less common than areas to the west and south. Windthrow was probably also an important disturbance.

Nowadays this region has been heavily developed and severely altered from its original state. The dominant land use here is agriculture, with 40% of the region taken up in cropland producing either corn or soybeans. There are small amounts of pastureland but little other agriculture. Especially in the east of this region, near Minneapolis, there is extensive suburban development, and there is also extensive development for recreation and vacation homes around the areas with the highest density of lakes. Only around 15% of the land is still forested, and about 13% is covered in wetlands, much of it along the Minnesota River valley. Forest cover exists mostly as small, isolated woodlots, but there is also a large corridor of contiguous bottomland forests along the Minnesota river, and along some of its larger tributaries. There are significant areas of protected public land here, and some of them include high-quality habitat that has been relatively undisturbed for a long time; such protected areas include both dry oak savannas, maple-basswood forest, and wetlands. Outside protected lands, northern red oak has been reduced in this region by pressure from selective logging on private woodlots, and pressure for higher yields has also led to loss of small woodlots. There are no cities here of appreciable size other than Minneapolis, which lies just outside this region, but there are numerous small towns throughout.

This region is bordered to the southeast by the Eastern Iowa and Minnesota Drift Plains, to the east north of that by the Lower St. Croix and Vermillion Valleys, and to the southwest over most of its length by the Des Moines Lobe; these are all areas of prairie, marking the start of the Great Plains, an area where fire was more common. To the northwest this region borders the McGrath Till Plain and Drumlins, and to the northeast, the Anoka Sand Plain and Mississippi Valley Outwash. There is a small border to the east with the St. Croix Stagnation Moraines, an area with sandier, more acidic soils.

References

1. Albert, Dennis A. "Regional landscape ecosystems of Michigan, Minnesota, and Wisconsin: a working map and classification.", General Technical Report NC-178, U.S. Department of Agriculture, Forest Service, North Central Forest Experiment Station, St. Paul, MN (1995) Web.

2. Denis White "Ecological Regions of Minnesota: Level III and IV maps and descriptions", (2020) Web.