Grasslands

     Grasses first appeared during the Eocene Era, and their success supported the development of the communities of grazers that inhabit the great grassy plains of our planet.

     Grasses grow where there is not enough moisture to support trees, where rainfall is from 10-30 inches a year.  Although coniferous forests get similar amounts of rainfall, they are nearer the poles than the grasslands are. Water evaporates more quickly when it is warmer, so effectively the grasslands get less water for the plants to use.

    There are perhaps 11,000 species of grasses, each one adapted to survive under particular environmental conditions. Some kind of grass can be found almost anywhere on land, and there are even grasses that live in water. About a quarter of the vegetation on our planet consists of grasses, some of them growing under very difficult conditions. Antarctica has only two flowering plants, and one of these is a grass.

     Grasses have developed unique characteristics to help them to survive. Drought can be a problem in the grasslands. During dry periods grasses can become dormant, leaving only dry stems and seed heads standing above the roots. When rain falls, new shoots come up from the roots again. Some grasses are annuals, and survive the winters as seeds: other species are perennials, and sprout again each year from a well-developed network of roots.

 Another adaptive characteristic of grasses is that they grow up from where the stems join the roots. Other plants grow from the tips of shoots, twigs, and branches, but grasses grows from the bottom up. This allows animals to eat grass without slowing its growth, and people to mow lawns without killing the grass.

    Grasses are wind pollinated flowering plants. The tiny flowers form at the top of the stalks where the wind can pick up and deliver the pollen. Later the seed heads form at the top of the stalks. Grasses are monocotyledons, so that when the seeds germinate each one sends up a single leaf.

      There are grasslands in many places in the world. The huge grasslands of this biome are found in the interior of continents, on land that is gently rolling or nearly flat. This type of terrain soaks up the rain from summer thunder showers as it falls, so there are not many rivers.The American prairies, the pampas of Argentina, the steppes of Russia, the Serengeti in Africa -- all are homes to great expanses of grass and distinctive communities of animals.    

     In America we use the buffalo and the prairie dog as symbols of our grasslands. The actual fauna is much more diverse, with antelopes, burrowing mammals, snakes, and ground nesting birds. Predators range from grizzly bears to foxes and include hawks and owls. Each grassland has its own animals, and they tend to live in similar ecological niches.

     Grasslands are subdivided into tall grass, medium grass, and short grass. Grass heights may be 30 inces tall or taller, or less than a foot in height. Shorter grass usually indicates that there is less available moisture, but, in some environments such as mountain tops, short grass may be adapting to a shorter growing season.

     Grasses are an important source of food for people as well as animals. Half of all calories in the human diet come from grasses: wheat, rice and maize (corn). These grains provide carbohydrates, which give us the energy to move, work, and keep our bodies warm

A Grasslands Food Web

Grasslands Energy Pyramid