The Water Economy, The Faunas Of The Savannas
A savanna is a plant community characterized by a continuous grassy layer, often with scattered trees or shrubs, that is subject to regular, severe drought and occasional bush fires. A savanna is also the flat, open landscape in which such plant communities thrive. The word savanna comes from the Taino word zabana, which was used to describe a grassy, treeless plain. (Taino was the language of a now extinct Native American group that lived in the Greater Antilles and Bahamas.) The word entered the English, French, and Spanish languages almost simultaneously, between 1529 and 1555, as a result of Spanish exploration of the Caribbean.
Savannas occur in a broad band around the globe, occupying much of the land in the tropics and semitropics that is not a rain forest or a desert. Savanna grasslands occur predominantly in South America, Africa, Madagascar, the Indian subcontinent, and northern Australia. Over time, the original meaning of savanna as a treeless, grassy plain has been lost, and the scientific definition has becoming increasingly broad. Thus, the term now encompasses the treeless grasslands of Florida; the grasslands with palm trees in the Orinoco basin in Venezuela; the open pampas, semi-enclosed cerrados, and thorny, brushy caatingas of Brazil; the woodlands (miombo) and park like grasslands (veldt) of southern Africa; and various grasslands in Asia that resulted from cutting of forests over the centuries. Overall, savanna accounts for 20% of the land cover on Earth, and some savanna is to be found on every continent.
Savannas still defy adequate classification, although several complex schemes have been developed that take into account soil types, distance between plants, average height of the woody layer in relation to the herbaceous (grassy) layer, and similar quantifiable factors. A useful four-part descriptive classification divides savannas according to the increasing proportion of trees and shrubs: grassy savannas, open savannas, closed savannas, and woodland. Even in the most heavily wooded savannas, however, where trees may reach 40% of the cover, the primary flow of energy and nutrients is still through the grassy layer.
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