5.10. SR 12-20-2004 - Laserfiche WebLink

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frequently and sUPPol1ed oak woodland communities, while wetlands were found in depressions and valleys with denser, hydric soils. After the glaciers Immediately after the glaciers melted, spruce trees and tundra colonized the periglacial environment. This was later followed by pine barrens and mixed boreal forests with a bracken fern-dominated ground layer. As the climate of the region warmed dramatically about 9,000 years ago, pines began to decline, and prairie expanded into the region, along with elm and oak forests. The climate remained in this warm period until about 7,000 years ago, when midgrass prairie reached its maximum extent in Minnesota, and covered the southwest half of the state. Prairie, oak woodlands and brush lands, and oak savanna, consisting of scattered trees with a prairie-like ground cover, dominated the Region until about 4,000 years ago, when the climate gradually became cooler and moister. Oak thickets spread, and oak woodlands came to dominate some upland areas, interspersed with tall grass and wet prairies. White pines also migrated to just northeast of Sherburne County as the climate cooled. About 300 years ago, the climate became especially moist and cool, and fires became less frequent. As a result, extensive forests of elm, sugar maple, and basswood (known as the Big Woods) developed in eastern Minnesota. After this, the major patterns of vegetation in the area at the time of European settlement were then in place. Influence of Landform and Climate on Vegetation Types Plant communities that exist in any given area are the result of numerous biological and physical factors. These work in concert to influence plant communities in often subtle ways, and sometimes dramatic and immediate ways such as drought, or a tornado Biological factors can include such varied things as the presence or absence of pollinators, burrowing activities, herbivory, or over utilization of an area by a single species or number of species. Of the physical factors, two have a consistently strong influence in the shaping of plant communities. These are climate and landform. The climate in east-central Minnesota is considered to be continental and subhumid, with long, cold winters and relatively brief, warm summers. Wide fluctuations in temperature and precipitation strongly influence the plant communities present in the region and causes plants to be adapted to extremes, rather than averages. City of Elk River. MN - Natural Resouce Inventory Bonestroo Natural Resources. September 2004 4