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grassland with scattered trees,
Savanna is grassland with scattered individual trees. Savannas of one sort or another cover almost half the surface of Africa (about five million square miles, generally central Africa) and large areas of Australia, South America, and India. 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 50.8 to 127 cm (20-50 inches) per year. It is crucial that the rainfall is concentrated in six or eight months of the year, followed by a long period of drought when fires can occur. If the rain were well distributed throughout the year, many such areas would become tropical forest. Savannas which result from climatic conditions are called climatic savannas. Savannas that are caused by soil conditions and that are not entirely maintained by fire are called edaphic savannas.
These can occur on hills or ridges where the soil is shallow, or in valleys where clay soils become waterlogged in wet weather. A third type of savanna, known as derived savanna, is the result of people clearing forest land for cultivation. Farmers fell a tract of forest, burn the dead trees, and plant crops in the ashes for as long as the soil remains fertile. Then, the field is abandoned and, although forest trees may recolonize, grass takes over on the bare ground (succession), becoming luxuriant enough to burn within a year or so.
In Africa, a heavy concentration of elephants in protected parkland have created a savanna by eating leaves and twigs and breaking off the branches, smashing the trunks and stripping the bark of trees. Elephants can convert a dense woodland into an open grassland in a short period of time. Annual fires then maintain the area as a savanna.
The soil of the savanna is porous, with rapid drainage of water. It has only a thin layer of humus (the organic portion of the soil created by partial decomposition of plant or animal matter), which provides vegetation with nutrients. Savannas are sometimes classified as forests. The predominant vegetation consists of grasses and forbs (small broad-leaved plants that grow with grasses).
Different savannas support different grasses due to disparities in rainfall and soil conditions. Because the savanna supports such a large number of species competing for living space, usually only one or a few kinds of grass are more successful than the others in a particular area. For example, in drier savannas such as those on the Serengeti plains or Kenya’s Laikipia plateau, the dominant grasses on well-drained soils are Rhodes grass and red oat grass; throughout the East African savannas, star grasses are dominant; the lemon grasses are common in many western Uganda savannas. Deciduous trees and shrubs are scattered across the open landscape.
One type of savanna common in southwestern Kenya, Tanzania, and Uganda, known as grouped-tree grassland, has trees growing only on termite mounds — the intervening soil being too thin or poorly drained to support the growth of trees at all. Frequent fires and large grazing mammals kill seedlings, thus keeping the density of trees and shrubs low. Savannas receive an average annual rainfall of 76.2-101.6 cm (30-40 inches).
Are tropical grasslands and savannas the same?
What is another name for a grassland?
What does a grassland look like?
Which biome has trees and very tall grasses scattered throughout?
The biome with trees and tall grasses is known as the savanna, or sometimes simply the grassland.
What kind of vegetation is found in a savanna?
A savanna is a rolling grassland scattered with shrubs and isolated trees, which can be found between a tropical rainforest and desert biome. Not enough rain falls on a savanna to support forests. Savannas are also known as tropical grasslands.
Characteristics of the Savanna
Warm – The savanna stays pretty warm all year. It cools down some during the dry season, but stays warm and humid during the rainy season.
Animals in the Savanna
Plants in the Savanna
The majority of the savanna is covered in different types of grasses including lemon grass, Rhodes grass, star grass, and Bermuda grass. There are also lots of trees scattered about the savanna. Some of these trees include the acacia tree, the baobab tree, and the jackalberry tree. The plants need to be able to survive the dry season and drought in the savanna. moreover Some store water and energy in their roots, bulbs, or trunks. Others have roots that go deep into the ground to reach the low water table.
Savannas arose as rainfall progressively lessened in the edges of the tropics during the Cenozoic Era (66 million years ago to the present)—in particular, during the past 25 million years. Grasses,
the dominant plants of savannas, appeared only about 50 million years ago, although it is possible that some savanna-like vegetation lacking grasses occurred earlier. The South American fossil record provides evidence of a well-developed vegetation,
rich in grass and thought to be equivalent to modern savanna, being established by the early Miocene Epoch, about 20 million years ago.
Climates across the world became steadily cooler during that period. Lower ocean surface temperatures reduced water evaporation, which slowed the whole hydrologic cycle, with less cloud formation and precipitation.
The main regions in which savannas emerged in response to that long-term climatic change—tropical America, Africa, South Asia, and Australia—were already separated from each other by ocean barriers by that time. moreover Plant migration across those barriers was inhibited, and the details of the emergence of savannas on each continent varied. In each region different plant and animal species evolved to occupy the new seasonally dry habitats.
in temperate regions, savannas became much more widespread, at the expense of forests, during the long, cool, dry intervals—contemporaneous with the ice ages, or glacial intervals, of the Pleistocene Epoch (2.6 million to 11,700 years ago). Studies of fossilized pollen in sediments from sites in South America, Africa, and Australia provide strong support for this view.
When human beings (Homo sapiens) first appeared, in Africa, they initially occupied the savanna. Later, as they became more adept at modifying the environment to suit their needs,
they spread to Asia, Australia, and the Americas. There their impact on the nature and development of savanna vegetation was superimposed on the natural pattern,
adding to the variation seen among savanna types. The savannas of the world currently are undergoing another
phase of change as modern expansion of the human population impinges on the vegetation and fauna.