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Grassland Praries

Grassland Prarie

About one-fourth of the land surface on Earth is covered by grassland biomes.  Grasslands generally exist on flat or rolling terrain, underlain by a variety of rock types.  All occur in similar soils that are rich in organic matter, slightly alkaline and very fertile.  American grasslands exist in areas where the annual precipitation averages between ten and thirty-nine inches, anymore and they would be classified as a forest, any less and they would be classified as a desert.  There are rarely firm borders separating  them, although there is some overlapping.  Wind is an important factor in the climate.  The wind seems to blow constantly and in the process evaporates water.

The vegetation differs in size, color, and general aspect from area to area.  Boundaries between types are rarely precise but importance between them does not exist across the country.

 Caplin Volcano National Monument Caplin Volcano National Monument Grass

Because of the fertile soil, grasslands are highly productive when converted into agricultural uses.  The organic materials which make the soil so productive come from hundreds of thousands of years of decomposition.  The grasslands are the richest regions in the world.  Almost all of our food comes directly or indirectly from these areas.

There are three types of grassland in North America.  There are tall grass, mixed, and short grass. These three types are not absolutely restricted to separate geographic zones.  Soil moisture is the controlling factor.  They are still distinct enough to be mapped as three separate zones.

As the prairies, move west to east, precipitation levels increase and the plants show a corresponding pattern of increased height. Map of North American Prairies:

Tall grass prairies, which are called true prairies, lie mainly in the eastern portion of the Midwest.  The western parts of the tall grass prairies support grasses over five feet tall.  Tall grass prairies are characterized by sod grasses such as Big Blue Stem and Indian Grass. The tall grass prairie lives up to its name because of these tall grasses.  There are a multitude of wild flowers flowering in the late summer.  It is a beautiful sight to behold.

Among the few mammals that are restricted to the tall grass prairie are the Pocket Gopher and Franklin's Ground Squirrel.  Also, the magnificent American Elk inhabit this region.

The most important crop plants are grasses such as wheat, rice, corn, oats, sorghum, millet, barley, rye, and sugar cane.  Because of the abundance of these crops, this region is known as "America's Breadbasket".

 Prickly Poppy
Prickly Poppy

 Butterfly Weed
Butterfly Weed


The mixed prairie or  mid grass prairie lies mainly in the middle portion of the Midwest and may shift according to weather cycles.  The areas may represent a transition zone between tall grass and short grass prairies.  Some areas support enough rainfall to support tall grass species.  In some areas there is very little rainfall to support the growth of short grass species.  The grasses here often grow to be two or three feet tall.  Precipitation ranges between fifteen and twenty-five inches per year.  Most of the precipitation falls in the summer and is subject to great yearly fluctuations.  The great drought of the 1930's affected the mixed grass prairies dramatically.  Parts of the region became known as the Dust Bowl.

If the mixed grass prairie could be characterized by a single plant species, it will be the Little Blue Stem.  Big Blue Stem is also present.

The mixed prairie is an important faunal boundary.  It is the range for many grassland animals.  Prairie dogs, Pronghorn, Swift fox, Black-tailed Jack Rabbit, and Desert Cottontail.  The true Bison habitat occurs here in the mixed prairie.  The story of the Bison emphasizes that the prairie has been a constantly changing ecosystem.  Plant and animal communities change, sometimes gradually, sometimes suddenly with changes in weather, topography, and soils.  This is where the buffalo once roamed.

The short grass prairie, also known as the Great Plains, and the High Plains lies mainly in the western portion of the Midwest.  The most significant feature is the small amount of precipitation it receives.  In some places the annual average is as low as ten inches.  Most precipitation comes during the growing season, May through July.  The moisture is soon used up and the plants go into a state of dormancy during the summer.  Low precipitation, high velocity winds, and hailstorms, which average about four per year, makes life difficult for plants.

The plant species are constantly battling for dominance within a community.  The dominant grasses are Blue Grama and Buffalo Grass.  Blue Grama is easily recognizable by its delicate, arched flower stalks with flowers lined up along one side; wiry often curled tufts of blue-green arched flower stalks with flowers lined up along one side; wiry often curled tufts of blue-green basal leaves. Stalks may grow between six and twenty inches and the tufted leaves grow three to five inches.  Buffalo Grass, a shorter plant, has above ground stems.  They can grow an inch or two a day and may extend as much as two and half feet.  Buffalo grass can colonize a bare site easily.  The male and female flowers are located on separate plants.  Seeds easily trailed in the Bison's fur.  Bison reseeded its range as it went along.

The short grass prairie is the domain for prairie dogs and the pronghorn.  These animals rely on their ability to see a predators from long distances or to detect a hawk or an eagle by its shadow.  The Burrowing owl, which is the only species of owl that does not nest in trees, hatches and raises its young in prairie dog towns in the burrows.  They eat young prairie dogs and the prairie dogs eat owl eggs, allowing both species to survive.   Rattlesnakes are frequent visitor to prairie dog towns, often eating the young prairie dogs.  Last but certainly not least Bison prefer the sites for feeding and wallowing.  When the Bison disappeared, the prairie dogs followed the cattle.  This did not please the ranchers.

Short grass prairie was never considered attractive for agriculture, but the cattle industry started growing.  However the cattle boom of the 1881 - 1882 ended with drought disaster and the short grass prairie was devastated.  Most of it still supports uncultivated vegetation.  The short grass prairie continues to survive even if it is no longer the domain of the Bison and the prairie dog.

Prairies need disturbances such as drought, fire, and grazing to survive. They rely on these things to keep woody plants from invading the prairie and turning it into a forest.  In pre-settlement times, enormous herds of grazers, such as bison, roamed the Plains, and their impacts helped to create the diversity that is essential to the prairie's health.  Grazers, through their browsing, wallowing, and fertilizing, help to create a patchy landscape that promotes the growth of different kinds of plants.  Drought is also important because prairie plants are much better adapted to survive dry conditions than trees, so droughts give the grasses and forbs a competitive advantage.  Fire is extremely important in maintaining the health and diversity of the prairie while keeping wood plants from establishing themselves.

 Windmill Cattle Windmill

The grassland, prairies, seems as an endless ocean of grasses waving in the wind.  The wind blowing the grasses is like the ripples across the ocean. There are still fires deliberately set by man or when nature's lightning strikes.  Afterwards you can see the grasses grown back lush and beautifully green.

We can see many birds, pronghorns and prairie dogs, which is just a few of the many animals that inhabitant the prairie.  Look how animals have adapted to the environment and how animals have affected the growth of plants.  We can see the differences between the various types of grasslands (prairies), which are a result of climate and the geology across the country.  In spite of all the changes the grasslands (prairies) can still be seen today.




What Is a Biome? 
Crabtree Publishing Company  1998 New York, NY

MacMahon, James A.
Audubon Society Nature Guide
Chanticleer Press, Inc. 1997 New York, NY


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