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savannah(both: səvăn`ə), tropical or subtropical grassland lying on the margin of the trade windtrade winds,
movement of air toward the equator, from the NE in the Northern Hemisphere and from the SE in the Southern Hemisphere. The trade winds originate on the equatorial sides of the horse latitudes, which are two belts of high air pressure, one lying between 25° and
..... Click the link for more information. belts. The climate of a savanna is characterized by a rainy period during the summer when the area is covered by grasses, and by a dry winter when the grasses wither. Savannas near the equatorial belt, e.g., in Nigeria, support clumps of trees. The most extensive savannas—all important pasture lands—are in Africa; others include the llanos and the campos of South America.
The term savanna was originally used to describe a tropical grassland with more or less scattered dense tree areas. This vegetation type is very abundant in tropical and subtropical areas, primarily because of climatic factors. The modern definition of savanna includes a variety of physiognomically or environmentally similar vegetation types in tropical and extratropical regions. The physiognomically savannalike extratropical vegetation types (forest tundra, forest steppe, and everglades) differ greatly in environment and species composition.
In the widest sense savanna includes a range of vegetation zones from tropical savannas with vegetation types such as the savanna woodlands to tropical grassland and thornbush. In the extratropical regions it includes the “temperate” and “cold savanna” vegetation types known under such names as taiga, forest tundra, or glades. See Grassland ecosystem, Taiga, Tundra
a type of tropical and subtropical grassland with individual trees, groups of trees, and shrubbery. The plants are able to withstand long periods of drought. Their stiff leaves are heavily pubescent or reduced to thorns. Gramineous herbs predominate, sometimes growing to a height of 3–5 m. The trees are mostly low and have knotty trunks, thick bark, and, frequently, an umbrella-shaped crown. The trunks of some trees, such as the baobab and Brachychiton, contain large reserves of water.