GRASSLAND: THREE MAJOR TYPES OF GRASSLANS

 

Grasslands occur mostly in the interiors of continents in areas that are too moist for deserts to form and too dry for forests to grow. Grasslands persist because of a combination of seasonal drought, grazing by large herbivores, and occasional fires—all of which keep shrubs and trees from growing in large numbers. 

The three main types of grassland—tropical, temperate, and cold (arctic tundra)—result from combinations of low average precipitation and varying average temperatures.

1. TROPICAL GRASSLAND:

One type of tropical grassland, called a savanna, contains widely scattered clumps of trees such as acacia, which are covered with thorns that keep some herbivores away. This biome usually has warm temperatures year-round and alternating dry and wet seasons. Tropical savannas in East Africa are home to grazing (mostly grass-eating) and browsing (twig- and leafnibbling) hoofed animals, including wildebeests, gazelles, zebras, giraffes, and antelopes, as well as their predators such as lions, hyenas, and humans. Herds of these grazing and browsing animals migrate to find water and food in response to seasonal and year-to-year variations in rainfall and food availability.

2. TEMPERATE GRASSLAND:

Two types of temperate grasslands are the short-grass prairies and the tall-grass prairies of the mid-western and western areas of the United States and Canada (which get more rain). In all prairies, winds blow almost continuously and evaporation is rapid, often leading to fires in the summer and fall. This combination of winds and fires helps maintain such grasslands by hindering tree growth and adding ash to the soil. Many of the world’s natural temperate grasslands have been converted to farmland, because their fertile soils are useful for growing crops and grazing cattle.

3. COLD GRASSLANDS:

Cold grasslands, or arctic tundra (Russian for “marshy plain”), lie south of the arctic polar ice cap. During most of the year, these treeless plains are bitterly cold, swept by frigid winds, and covered with ice and snow. Winters are long with short days, and scant precipitation falls mostly as snow. Under the snow, this biome is carpeted with a thick, spongy mat of low-growing plants, primarily grasses, mosses, lichens, and dwarf shrubs. Trees or tall plants cannot survive in the cold and windy tundra because they would lose too much of their heat. Most of the annual growth of the tundra’s plants occurs during summer, when the sun shines.