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Prairies are considered part of the temperate grasslands, savannas, and shrublands biome by ecologists, based on similar temperate climates, moderate rainfall, and grasses, herbs, and shrubs, rather than trees, as the dominant vegetation type. Temperate grassland regions include the Pampasmarker of Argentinamarker, and the steppes of Russiamarker and Central Asia.

Lands typically referred to as "prairie" tend to be in North America. The term encompasses much of the area referred to as the Great Plainsmarker of the United Statesmarker and Canadamarker. In the U.S., the area is constituted by most or all of the states of North Dakotamarker, South Dakotamarker, Nebraskamarker, Kansasmarker, Oklahomamarker, Texasmarker, Coloradomarker, Wyomingmarker and Montanamarker, and sizable parts of the states of Indianamarker, Illinoismarker, Iowamarker, Wisconsinmarker, Missourimarker, and Minnesotamarker. The Central Valleymarker of Californiamarker is also prairie. The Canadian Prairies occupy vast areas of Manitobamarker, Saskatchewanmarker, and Albertamarker.

Formation

Prairie grasses
The formation of the North American Prairies started with the upwelling of the Rocky Mountains. The mountains created a rainshadow that killed most of the trees.

Most prairie soil was deposited during the last glacial advance that began about 110,000 years ago. The glaciers expanding southward scraped the soil, picking up material and leveling the terrain. As the glaciers retreated about 10,000 years ago, it deposited this material in the form of till.

Tallgrass Prairie evolved over tens of thousands of years with the disturbances of grazing and fire. Native ungulates such as bison, elk, and white-tailed deer, roamed the expansive, diverse, plentiful grassland before European colonization of the Americas. For 10,000-20,000 years native people used fire annually as a tool to assist in hunting, transportation, safety, and probably entertainment. Evidence of ignition sources of fire in the tallgrass prairie are overwhelmingly human as opposed to lightning. Humans, and grazing animals, were active participants in the process of prairie formation and the establishment of the diversity of graminoid and forbs species. Fire has the effect on prairies of removing trees, clearing dead plant matter, and changing the availability of certain nutrients in the soil from the ash produced. Fire kills the vascular tissue of trees, but not prairie, as up to 75% (depending on the species) of the total plant biomass is below the soil surface and will re-grow from its deep (up to 6 feet) roots. Without disturbance, trees will encroach on a grassland, cast shade, which suppresses the understory. Prairie and widely spaced Quercus trees evolved to coexist in the oak savanna ecosystem.

Fertility

In spite of long recurrent droughts and occasional torrential rain, the grasslands of the Great Plainsmarker are not subject to great soil erosion. The deep, interconnected root systems of prairie grasses firmly hold the soil in place and prevent run-off of soil. When a plant dies, the fungi, bacteria and the other decomposers slowly eat the roots and leaves, returning nutrients to the soil.

These deep roots also help prairie plants to reach water in even the driest conditions. The grass suffers much less damage from dry conditions than the farm crops that have replaced many former prairies.

Types

The types of prairies in North America are usually split into three groups: wet, mesic, and dry.

Wet

In this type of prairie, the soil is usually very moist most of the growing season, and has poor water drainage. This can possibly contain a bog or fen, since it often has plentiful stagnant water.

Mesic

Mesic prairies have good drainage, but have good soil moisture during the growing season. This type of prairie is the one most often converted for agricultural usage, consequently it is one of the more endangered types of prairie.

Dry

Dry Prairie is a prairie which has somewhat wet to very dry soil during the growing season because of good drainage. Often, this prairie can be found on uplands or slopes.

Farming

The very dense soil plagued the first settlers who were using wooden plows, which were perfectly good for loose forest soil. On the prairie the plows bounced around and the soil stuck to them. This problem was solved in 1837 by an Illinoismarker blacksmith named John Deere who developed a steel moldboard plough that was stronger and cut the roots, making the fertile soils ready for farming.

The tallgrass prairie has been converted into one of the most intensive crop producing areas in North America. Less than one tenth of one percent (<0.09%) of="" the="" original="" landcover="" tallgrass="" prairie="" biome="" remains.="" States="" formerly="" with="" in="" native="" such="" as="" Iowa,="" Illinois,="" Minnesota,="" Wisconsin,="" Nebraska,="" and="" Missouri="" have="" became="" valued="" for="" their="" highly="" productive="" soils="" are="" included="" Corn Belt. As an example of this land use intensity, Illinois and Iowa for the United Statesmarker, rank 49th and 50th out of 50 states in total uncultivated land remaining.

Biofuels

Research, by David Tilman, ecologist at the University of Minnesotamarker, suggests that "biofuels made from high-diversity mixtures of prairie plants can reduce global warming by removing carbon dioxide from the atmosphere. Even when grown on infertile soils, they can provide a substantial portion of global energy needs, and leave fertile land for food production." Unlike corn and soybeans which are major food crops, prairie grasses are not used for human consumption. Prairie grasses can be grown in infertile soil, eliminating the cost of adding nutrients to the soil. Tilman and his colleagues estimate that prairie grass biofuels fuel would yield 51 percent more energy per acre than ethanol from corn grown on fertile land. Some grasses commonly used are lupine, turkey foot, blazing star, switchgrass, and prairie clover.

Preservation

Only 1% of tallgrass prairie remains in the U.S. today.

Significant preserved areas of prairie include:

Virgin prairies

Virgin prairie refers to prairie land that has never been plowed. Small virgin prairies exist in the American Midwestern states and in Canada. Restored prairie refers to a prairie that has been reseeded after plowing or other disturbance.

Prairie garden

A prairie garden is a garden primarily consisting of plants from a prairie.

See also



References

External links




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