Tropical Grasslands (Savanna)


A Savanna is an open grassland with characteristics of few trees in tropical and subtropical regions. Savanna’s are usually found between tropical rain forest and deserts. The cause of the isolation and vastness between trees is the low precipitation. There are two major seasons in a savanna; winter, which is a very long dry season and summer, which is a very wet and humid season. In dry season, only an average of about 4 in. of rain falls. Between December and February there is no rain. Savannas are found on either side of the equator on the edges of tropical rain forest. They cover part of Africa, large areas of Australia where Eucalyptus trees take the place of acacias; regions of South America, countries such as Venezuela, Colombia and Brazil, savannas occupy an area about one-quarter the size of Canada (2.5 million square kilometers).

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Some specific regions with their given organisms are: East African savannas covered with acacia trees; The Serengeti Plains of Tanzania animals like lions, zebras, elephants, and giraffes and many types of ungulates(animals with hooves) graze and hunt; large grass-eating mammals (herbivores) survive in these areas because they can move around and eat plenty of grass. There are also carnivores who eat the herbivores.

Each animal has a specialized eating habit that reduces competition for food.

Organism Adaptations

Thomson’s gazelles (Gazella thomsonii) and other ungulates -- the swiftest of which can barely exceed 40 miles per hour -- must evade cheetahs, which reach 65 miles per hour or more for brief periods.

Lacking trees, birds that live in grasslands must nest on or under the ground. Most grassland bird species try to hide their eggs as much as possible, depositing them in dense vegetation.

Grassland animals have often evolved highly effective camouflage, which allows them to hide while in plain sight. Most gazelles, cattle and antelopes are clad in colors that match the grass and surroundings of their wide-open habitats. Predators like tigers (Panthera tigris) use their orange-and-black pattern to hide in the grass and ambush their prey. Cheetahs have adapted to grasslands somewhat differently, using a spotted pattern to conceal themselves.

Dominant Vegetation

Blue Grama, Buffalo grass, big Bluestem, switchgrass and Little Bluestem are some of the dominant vegetation seen in Grasslands. Tall grasses will grow where rainfall is about 30 inches a year.

Meteorological Elements

The Climate is one of the most crucial abiotic factors that shape the ecosystem and includes rainfall, temperature, wind flow, ground moisture, etc. Natural grasslands have a precipitation of 500 -900 mm per year, except sometimes , the deserts have a rainfall of about 250 mm /year.

Abiotic Factors

The parental material refers to the bedrock on which the soil has been formed. The type of bedrock has influence on the type of soil and therefore, the nutrient value of the soil. Grasslands have a thick layer of humus soil on the top layer of the surface which is a storehouse of different minerals and is the region where the recycling of different elements take place through the waste of food chains. This layer is largely produced due to breakdown of the root structures of plants.

Created by

Jan Franco

Morristown High School student.