Definition

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 Pampas of Argentina, and the steppes of Russia 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 Plains of the United States and Canada. In the U.S., the area is constituted by most or all of the states of North Dakota, South Dakota, Nebraska, Kansas, Oklahoma, Texas, Colorado, Wyoming and Montana, and sizable parts of the states of Indiana, Illinois, Iowa, Wisconsin, Missouri, and Minnesota. The Central Valley of California is also prairie. The Canadian Prairies occupy vast areas of Manitoba, Saskatchewan, and Alberta.

Formation

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 10000 years ago, it deposited this material in the form of till.

These treeless grasslands have an extreme climate: cold in winters and hot in summers.

Fire

Fire is an important part of the prairie ecosystem. Fire does at least two important jobs, removing trees and clearing dead grasses. Forests can overwhelm a prairie grassland, as too many trees create shade, killing the grasses. Fire destroys the trees, but not the grass, as most of the grass is underground and will regrow from its deep roots. As fire clears the dead leaves, the ashes fertilize the soil.

Fertility

In spite of long recurrent droughts and occasional torrential rains, the grasslands of the Great Plains 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 prairie grass, on North America, is usually split into three groups, depending on how much water that area gets. The types are 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.

dry

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