grassland

Temperate
Temperate grasslands (veldts, pampas, steppes, plains and prairies) have grasses as the dominant vegetation. Trees and large shrubs are absent.

Summers are hot and winters are cold. Summer temperatures can be well over 38° C or 100° F, while winter temperatures can be as low as -40° C or -40°F.

Rainfall is moderate, usually occurring in the late spring and early summer. The annual average is 20-35 inches. The amount of annual rainfall influences the height of grassland vegetation.

Seasonal drought and occasional fires are important to biodiversity. However, their effects aren’t as dramatic in temperate grasslands as they are in the tropical grasslands (savannas).

The soil is deep and dark, with fertile upper layers. It is nutrient-rich from the growth and decay of deep, branched grass roots. The rotted roots hold the soil together and provide a food source for living plants. Each different species of grass grows best in a particular grassland environment (determined by temperature, rainfall, and soil conditions). The seasonal drought, occasional fires, and grazing by large mammals all prevent shrubs and trees from growing. However, a few trees, such as cottonwoods, oaks, and willows grow in river valleys, and a few hundred species of flowers grow among the grasses. The various species of grasses include purple needlegrass, blue grama, buffalo grass, and galleta. Flowers include asters, blazing stars, coneflowers, goldenrods, sunflowers, clovers, psoraleas, and wild indigos.

The fauna (which do not all occur in the same temperate grassland) include gazelles, zebras, rhinoceroses, wild horses, lions, wolves, prairie dogs, jack rabbits, deer, mice,coyotes, foxes, skunks, badgers, blackbirds, grouses, meadowlarks, quails, sparrows, hawks, owls, snakes, grasshoppers, leafhoppers, and spiders.

Few natural prairie regions remain because most have been turned into farms or grazing land.This is because they are flat, treeless, covered with grass, and have rich soil. Overgrazing, plowing, and excess salts left behind by irrigation waters have harmed some steppes. Strong winds blow loose soil from the ground after plowing, especially during droughts. This causes the dust storms of the Great Plains of the U.S.

Tropical
Savanna is grassland with scattered individual trees. Savannas of one sort or another cover almost half the surface of Africa and large areas of Australia, South America, and India.

The soil of the savanna is porous, with rapid drainage of water. It has only a thin layer of humus (organic material), which provides vegetation with nutrients.The vegetation consists of grasses and forbs (small broad-leaved plants that grow with grasses). The savanna supports a large number of species competing for living space and usually only one or a few kinds of grass are successful in a particular area.

Climate is the most important factor in creating a savanna. Savannas are always found in warm or hot climates where the annual rainfall is from about 20-50 inches per year. The rainfall is concentrated during six or eight months of the year (rainy season), followed by a long period of drought (dry season) when fires can occur.