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You can email the site owner to let them know you were blocked. Please include what you were doing when this page came up and the Cloudflare Ray ID found at the bottom of this page. Your IP: Click to reveal 46. On this Wikipedia the language links are at the top of the page across from the article title. For the city in the U. Savannas maintain an open canopy despite a high tree density. 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 forests. The word derives from the Spanish sabana, which is itself a loanword from Taíno, which means “treeless grassland” in the West Indies. The word originally entered English as the Zauana in a description of the ilands of the kinges of Spayne from 1555. A savanna woodland in Northern Australia demonstrating the regular tree spacing characteristic of some savannas. Many grassy landscapes and mixed communities of trees, shrubs, and grasses were described as savanna before the middle of the 19th century, when the concept of a tropical savanna climate became established.
In different parts of North America, the word “savanna” has been used interchangeably with “barrens”, “prairie”, “glade”, “grassland” and “oak opening”. In some areas, indeed, it is possible for there to be multiple stable biomes. In climatic geomorphology it has been noted that many savannas occur in areas of pediplains and inselbergs. The savannas of tropical America comprises broadleaved trees such as Curatella, Byrsonima, and Bowdichia, with grasses such as Leersia and Paspalum. Bean relative Prosopis is common in the Argentinian savannahs. It is estimated that less than three percent of savanna ecosystems can be classified as highly intact. Reasons for savanna degradation are manifold, as outlined below.
Savannas are subject to regular wildfires and the ecosystem appears to be the result of human use of fire. These fires are usually confined to the herbaceous layer and do little long term damage to mature trees. However, these fires either kill or suppress tree seedlings, thus preventing the establishment of a continuous tree canopy which would prevent further grass growth. The consumption of herbage by introduced grazers in savanna woodlands has led to a reduction in the amount of fuel available for burning and resulted in fewer and cooler fires.
The closed forest types such as broadleaf forests and rainforests are usually not grazed owing to the closed structure precluding grass growth, and hence offering little opportunity for grazing. In contrast the open structure of savannas allows the growth of a herbaceous layer and is commonly used for grazing domestic livestock. The removal of grass by grazing affects the woody plant component of woodland systems in two major ways. Grasses compete with woody plants for water in the topsoil and removal by grazing reduces this competitive effect, potentially boosting tree growth. In addition to this effect, the removal of fuel reduces both the intensity and the frequency of fires which may control woody plant species.
Introduced grazing animals can also affect soil condition through physical compaction and break-up of the soil caused by the hooves of animals and through the erosion effects caused by the removal of protective plant cover. Such effects are most likely to occur on land subjected to repeated and heavy grazing. Large areas of Australian and South American savannas have been cleared of trees, and this clearing is continuing today. For example, until recently 480,000 ha of savanna were cleared annually in Australia alone primarily to improve pasture production.
Clearing is carried out by the grazing industry in an attempt to increase the quality and quantity of feed available for stock and to improve the management of livestock. The removal of trees from savanna land removes the competition for water from the grasses present, and can lead to a two to fourfold increase in pasture production, as well as improving the quality of the feed available. A number of techniques have been employed to clear or kill woody plants in savannas. Early pastoralists used felling and girdling, the removal of a ring of bark and sapwood, as a means of clearing land.
In many ways “artificial” clearing, particularly pulling, mimics the effects of fire and, in savannas adapted to regeneration after fire as most Queensland savannas are, there is a similar response to that after fire. Acacia savanna, Taita Hills Wildlife Sanctuary, Kenya. A number of exotic plants species have been introduced to the savannas around the world. Human induced climate change resulting from the greenhouse effect may result in an alteration of the structure and function of savannas. Temperate savanna in New South Wales. Mediterranean savanna in the Alentejo region, Portugal.
A montane savanna in the Colombian Andes. Tropical 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. Subtropical and 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 plains of southeastern Australia, northern India, Southern Africa, southeastern Argentina and Uruguay. 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. 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 mid- to high-altitude savannas, located in a few spots around the world’s high mountain regions, part of the montane grasslands and shrublands biome. Savannas, Barrens, and Rock Outcrop Plant Communities of North America. Ecology and management of North American Savannas. Tucson, AZ: University of Arizona Press.