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A savanna, or savannah, is a grassland ecosystem characterized by the trees being sufficiently widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to support an unbroken herbaceous layer consisting primarily of grasses. Some classification systems also recognize a grassland savanna from which trees are absent. This article deals only with savanna under the common definition of a grassy woodland with a significant woody plant component.

It is often believed that savannas feature widely spaced, scattered trees. However, in many savannas, tree densities are higher and trees are more regularly spaced than in forest. Savannas are also characterized by seasonal water availability, with the majority of rainfall confined to one season. Savannas are associated with several types of biomes. Savannas are frequently in a transitional zone between forest and desert or grassland. Savanna covers approximately 20% of the Earth's land area.

Etymology

Although the term savanna is believed to have originally come from an Arawak word

Distribution

Many grassy landscapesare rainfall variations from year to year, and dry season [[

Threats

=== savannas are being replaced by forest and shrub thickets with little herbaceous layer.

The consumption of herbage

Savanna ecoregions

Savanna ecoregions are of several different types:

• Tropical and subtropical savannas are classified with tropical and subtropical grasslands and shrublands as the tropical and subtropical grasslands, savannas, and shrublands biome. The savannas of Africa, including the Serengeti, famous for its wildlife, are typical of this type.
• Temperate savannas are mid-latitude savannas with wetter summers and drier winters. They are classified with temperate savannas and shrublands as the temperate grasslands, savannas, and shrublands biome, that for example cover much of the Great Plains of the United States. (See areas such as the Central forest-grasslands transition).
• Mediterranean savannas are mid-latitude savannas in Mediterranean climate regions, with mild, rainy winters and hot, dry summers, part of the Mediterranean forests, woodlands, and scrub biome. The oak tree savannas of California, part of the California chaparral and woodlands ecoregion, fall into this category.
• Flooded savannas are savannas that are flooded seasonally or year-round. They are classified with flooded savannas as the flooded grasslands and savannas biome, which occurs mostly in the tropics and subtropics.
• Montane savannas are high-altitude savannas, located in a few spots around the world's high mountain regions, part of the montane grasslands and shrublands biome. The lowland savannas of the Angolan Scarp savanna and woodlands ecoregion are an example.

See also

• Cerrado
• Coastal plain
• Coastal prairie
• Field
• Flood-meadow
• Flooded grasslands and savannas
• Grassland
• Meadow
• Oak savanna
• Pampas
• Pasture
• Plain
• Prairie
• Rangeland
• Steppe
• Veld
• Water-meadow
• Wet meadow

References

1. Anderson, Roger A., Fralish, James S. and Baskin, Jerry M. editors.1999. Savannas, Barrens, and Rock Outcrop Plant Communities of North America. Cambridge University Press.
2. McPherson, G. R. (1997). Ecology and management of North American Savannas. Tucson, AZ: University of Arizona Press.
3. Werner, Patricia A. (1991). "Introduction". In Patricia A. Werner (ed.). Savanna Ecology and Management: Australian Perspectives and Intercontinental Comparisons. Oxford: Blackwell Publishing. ISBN 978-0-632-03199-3. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
4. grass savanna, Encyclopædia Britannica Online

External links

• The Savanna

• Ecosystems
• Grasslands
• Temperate grasslands, savannas, and shrublands
• Tropical and subtropical grasslands, savannas, and shrublands