The tallgrass prairie is an ecosystem native to central North America. Natural and anthropogenic fire as well as grazing by large mammals (primarily bison) were historically agents of periodic disturbance, which regulates tree encroachment, recycles nutrients back to the soil, and catalyzes some seed dispersal and germination processes. Prior to widespread utilization of the steel plow, which enabled conversion to agricultural land use, tallgrass prairies expanded throughout the American Midwest and smaller portions of southern central Canada, from the transitional ecotones out of eastern North American forests, west to a climatic threshold based on precipitation and soils, to the southern reaches of the Flint Hills in Oklahoma, to a transition into forest in Manitoba. They were characteristically found in the central forest-grasslands transition, the central tall grasslands, the upper Midwest forest-savanna transition, and the northern tall grasslands ecoregions. They flourished in areas with rich loess soils and moderate rainfall of around 760 to 890 mm (30 to 35 in) per year. To the east were the fire-maintained eastern savannas. In the northeast, where fire was infrequent and periodic windthrow represented the main source of disturbance, beech-maple forests dominated. In contrast, shortgrass prairie was typical in the western Great Plains, where rainfall is less frequent and soils are less fertile.
Tallgrass prairie is capable of supporting significant biodiversity. Parts are among the "top ten ecoregions for reptiles, birds, butterflies, and tree species. . [T]allgrass species are found in the understory layer". Oak (blackjack oak (Quercus marilandica) and post oak (Quercus stellata) ) and hickory tree species occur in some areas but generally in moderate densities. Bison (Bison bison) were a dominant species.
The tallgrass prairie biome depends upon prairie fires, a form of wildfire, for its survival and renewal. Tree seedlings and intrusive alien species without fire-tolerance are eliminated by periodic fires. Such fires may either be set by humans (for example, Native Americans used fires to drive bison and improve hunting, travel, and visibility) or started naturally by lightning. Researchers' attempts to re-establish small sections of tallgrass prairie in arboretum fashion were unsuccessful until they began to use controlled burns.
As its name suggests, the most obvious features of the tallgrass prairie are tall grasses, such as indiangrass (Sorghastrum nutans), big bluestem (Andropogon gerardii), little bluestem (Schizachyrium scoparium), and switchgrass (Panicum virgatum), which average between 1.5 and 2 m (4.9 and 6.6 ft) tall, with occasional stalks as high as 2.5 to 3 m (8.2 to 9.8 ft). Prairies also include a large percentage of forbs, such as lead plant (Amorpha spp.), prairie rosinweed (Silphium terebinthinaceum), and coneflowers.
Due to accumulation of loess and organic matter, parts of the North American tallgrass prairie had the deepest topsoil recorded. After the steel plough was invented by John Deere, this fertile soil became one of America's most important resources. Over 99% of the original tallgrass prairie is now farmland.
The tallgrass prairie survives in areas unsuited to ploughing: the rocky hill country of the Flint Hills, which run north to south through east-central Kansas; the eastern fringe of the Red River Valley (Tallgrass Aspen Parkland) in Manitoba and Minnesota; the Coteau des Prairies, which extends from South Dakota through Minnesota and into Iowa; and the far north portion of Oklahoma. In Oklahoma, the tallgrass prairie has been maintained by ranchers, who saw the hat-high grass as prime grazing area for cattle.
The 158 km2 (39,000-acre) Tallgrass Prairie Preserve in Osage County, Oklahoma, and the somewhat smaller 44.1 km2 (10,900-acre) Tallgrass Prairie National Preserve in Kansas, attempt to maintain this ecosystem in its natural form. They have reintroduced Plains Bison to the vast expanses of grass. Other U.S. preserves include Midewin National Tallgrass Prairie in Illinois, Broken Kettle Preserve and Neal Smith National Wildlife Refuge in Iowa, Konza Prairie in Kansas, and Prairie State Park in Missouri. In eastern North Dakota is Sheyenne National Grassland, the only National Grassland on the tallgrass prairie. There are also several small tall grass prairie reservations in Cook County, Illinois, including the National Natural Landmark, Gensburg-Markham Prairie.
The original extent of Tallgrass Prairie in Canada was the 6,000 km2 (2,300 sq mi) plain in the Red River Valley, southwest of Winnipeg in Manitoba (see map). While most of Manitoba's tallgrass prairie has been destroyed through cultivation and urban expansion, relatively small areas persist. One of the largest blocks of remaining tallgrass prairie in Manitoba is protected by several conservation partners in a conservation area called the Tallgrass Aspen Parkland. The Manitoba Tall Grass Prairie Preserve, which occupies small portions of the rural municipalities of Stuartburn and Franklin, forms a part of the Tallgrass Aspen Parkland. This preserve contains about 4,000 ha (9,900 acres) of tallgrass prairie, aspen parkland and wetlands.
There is a small pocket (less than 5 km2/1,200 acres) of tallgrass prairie in the southwest corner of Windsor, Ontario, protected by Ojibway Park, and Spring Garden ANSI (Area of Natural Scientific Interest), along with the inter-connected parks: Black Oak Heritage Park, Ojibway Prairie Provincial Nature Reserve, and the Tallgrass Prairie Heritage Park. Aside from the Provincial Nature Reserve, all are operated by the City of Windsor's Parks and Recreation.
In Minnesota, Glacial Ridge National Wildlife Refuge was established in 2004. The core of the refuge is a preserved 5,000 acres (20 km2) tallgrass prairie remnant, and an additional 30,000 acres (121 km2) are either in the process of restoration or will be soon. According to The Nature Conservancy, so far 100 wetlands have been restored and 8,000 acres (32 km2) of land have been seeded with native plant species.
See also 
- Buffalo Commons
- List of ecoregions in the United States (EPA)
- List of ecoregions in the United States (WWF)
- "Central forest-grasslands transition". Terrestrial Ecoregions. World Wildlife Fund.
- Klinkenborg, Verlyn (April 2007). "Splendor of the Grass: The Prairie's Grip is Unbroken in the Flint Hills of Kansas". National Geographic
- [Chicago Wilderness Magazine, Summer 2000 http://www.chicagowildernessmag.org/issues/summer2000/gensburg.html]
- The Nature Conservancy. Glacial Ridge Project. www.nature.org. Retrieved on: November 14, 2007.
- Manning, Richard. Grassland: The History, Biology, Politics and Promise of the American Prairie
- Cushman, Ruth Carol. Peterson Field Guides: The North American Prairie (Peterson Guides)
- Least Heat-Moon, William. PrairyErth (A Deep Map): An Epic History of the Tallgrass Prairie Country
- Savage, Candace. Prairie: A Natural History
- White, Matt. Prairie Time: A Blackland Portrait
- Chapman, Kim Alan; Mary Kinsella Ziegenhagen and Heidi Fischer (1997). Valley of Grass: Tallgrass Prairie and Parkland of the Red River Valley Region. St. Cloud, Minnesota: North Star Press.
Gruchow, Paul. "Journal of a Prairie Year" University of Minnesota Press.
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