Adaptive features that permit the species to survive in grasslands

Grasslands are the areas that are too dry to support forests, but too humid to be deserts. Hot summers, cold winters, and seasonal rainfall are typical for grasslands, with precipitation ranging from 10 to 30 inches per year.  As the name implies, grasslands are flat or gently hilly areas covered by grasses.

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Having few or no trees, grasslands create a sense of “wide open spaces.” This provides perfect conditions for strong wind gusts which often lead to powerful storms. Grasslands have alkaline, fine-grained soil that contains much organic matter. In grassland areas, periods of rain are followed by periods of drought. The set of such characteristics of grasslands presents certain requirement for the inhabitants which need to develop special adaptation. Thus to survive grassland conditions, plants must have: flexible stalks, strong roots and a low profile.

The grass above the surface is only 15 percent of the prairie’s total biomass. For example, big bluestem, found in the tall-grass prairies of North America, grows up to 9 feet (2.75 m) tall – but the roots penetrate 26 feet (7.9 m) into the soil. Big bluestem (Andropogon gerardii) is one of the dominant grass species in this eco-region. It is well adapted to alkaline conditions. It is perennial and has flexible stalks and an extensively developed root system.

These roots survive underground during the winter months when the grasses die out. When these grasses die and decompose, immense amounts of organic matter are added to the soil, which makes the soil in grasslands very productive. Big bluestem is best suited to fertile, well-drained soils found in grasslands. It will withstand drought stress but is better suited to moderately wet soils. At the end of the rainy season, grass drops its seeds onto hard earth.

The grasslands are native habitat for the bison of North America. It is a very large animal. The bull grows to be ten feet long, six feet high, and weighs almost two thousand pounds. The bison has a large head, hump behind the neck, long cured horns and a short tail. The long horns of the bison are used for protection against predators. Wolves are the main predators of northern bison. Another adaptation of the bison is its long curved horns, which are also used for defense. The bison has a long shaggy coat of fur, which keeps it warm in winter.

The bison’s unusual body shape is partly an adaptation to the need to forage through snow, which is a usual feature of their grasslands environment in winter. The bison’s chest height and the weight load on their feet make them poorly adapted to snow, but they can survive where few other ungulates can.

The bison’s wintering adaptations include the unique head-swinging action it uses to clear away deep snow; they have spines on their upper vertebrae up to 50 cm long in adult bulls. These spines support large muscles that bison use to swing their neck and head from side to side and clear snow away from their food. Although bison feed almost entirely on grasses and sedges that easily get covered by snow, they can exist in areas where snow cover is too deep for most other hoofed mammals.

In the 1800’s there were 50 to 60 million bison in he world, but after the 1850’s they were almost extinct. There are many parks and organizations trying to save the bison.

Bibliography

Books

Ricciuti, Edward R. To the Brink of Extinction. 1973. Holt, Rinehart, ;Winston. New York, Chicago, San Francisco.

Articles

Hall, D. O. and Scurlock, J. M. Climate change and productivity of natural grasslands. 1991. Annals of Botany 67: 49-55.

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