Grasslands are a distinct environmental habitat, separate from forests in that they are too dry to support trees, but too humid for the more desolate conditions for a desert. Typical grassland weather and climate is that of hot summers, cool winters, and moderate seasonal rainfall, with rainfall usually ranging from 10 - 30 inches annually. Grasslands are usually flat or fairly hilly, and obviously covered by species of grass, presenting lots of wide open areas. For large grassland areas, this large space gives ripe conditions for strong winds, and with enough humidity, the seed for storms to develop. The soil type and composition is fine grained and alkaline, including lots of organic matter from plant decomposition. As implied by seasonal rainfall, grasslands go through periods of rain and perhaps flooding, followed by periods of drought in the dry seasons. All the characteristics of grasslands that have just been mentioned provide the restrictions and requirements needed for species adaptation, and plant and animal survival. In general, plants have the adaptations of strong roots, a low profile and flexible stalks for the insurance of survival.
What can be seen on the surface of prairies makes up for only 15% of the biomass present. For example, the species big bluestem, commonly found in the high grass prairies of the US and Canada, grow up to just below 3 meters tall. But 8 meters is present below ground in the form of massive root systems. Big bluestem is well adapted to prairie conditions, such as alkaline soil, and this makes it a dominant species of grass in North America. They have adapted expendable foliage which dies out during the winter, while the root systems remain alive to start growth come Spring time. The soils are very fertile thanks to the huge amounts of organic matter which decomposes, and makes them highly productive. Big bluestem likes fertile and highly drained soil that is common to grassland, and though it can withstand droughts it prefers wet soil. Reproduction is achieved by the grass dropping its seeds at the end of the rainy season.
Another natural inhabitant of the North American grasslands is the bison. The bison is a strong and large animal, growing to ten feet long, as high as a tall human, and weighing just less than two thousand pounds. The bison has a short tail, and neck hump, long and hard curved horns, and a large head. Its horns are an adaptation to fend off predators, the main predator being wolves. The horns also serve for general defense. Its long thick coat of fur helps to keep it warm in the harsh winters.
The bison has quite an unusual body shape, and like all things in the animal kingdom, this is an adaptation to help the bison forage for food through thick snow in the winter months. While being heavy is not a good adaptation to snow, their body shape and coat helps to compensate, and they are one of the few ungulates that can survive in such conditions. Further adaptations include the large head and strong neck, which acts like a snow plough to drive snow to the side when they travel. Their long spines help to support the muscles which achieve this task, and they are able to survive in snow depths that would render most other hoofed animals helpless.
The bison is a symbol of North American grasslands, but while there were up to 60 million bison existing in the 19th century, today they are almost extinct. It is the job of organizations and national parks to help save this amazing species.
Ricciuti, Edward R. To the Brink of Extinction. 1973. Holt, Rinehart, &Winston. New York, Chicago, San Francisco.
Hall, D. O. and Scurlock, J. M. Climate change and productivity of natural grasslands. 1991. Annals of Botany 67: 49-55.