Savanna

A savanna or savannah is a mixed woodland grassland ecosystem characterised 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.[1][2][3]

Savannas maintain an open canopy despite a high tree density.[4] 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.[5][6][7][8] The South American savanna types cerrado sensu stricto and cerrado dense typically have densities of trees similar to or higher than that found in South American tropical forests,[5][7][8] with savanna ranging from 800–3300 trees per hectare (trees/ha) and adjacent forests with 800–2000 trees/ha. Similarly Guinean savanna has 129 trees/ha, compared to 103 for riparian forest,[6] while Eastern Australian sclerophyll forests have average tree densities of approximately 100 per hectare, comparable to savannas in the same region.[9]

Savannas are also characterised by seasonal water availability, with the majority of rainfall confined to one season; they are associated with several types of biomes, and are frequently in a transitional zone between forest and desert or grassland. Savanna covers approximately 20% of the Earth's land area.[10]

Australian savanna
Typical tropical savanna in Northern Australia demonstrating the high tree density and regular spacing characteristic of many savannas

Etymology

The word originally entered English in 1555[11] as the Latin Zauana,[13] equivalent in the orthography of the times to zavana (see history of V). Peter Martyr reported it as the local name for the plain around Comagre, the court of the cacique Carlos in present-day Panama. The accounts are inexact,[15] but this is usually placed in present-day Madugandí[16] or at points on the nearby Guna Yala coast opposite Ustupo[17] or on Point Mosquitos.[18] These areas are now either given over to modern cropland or jungle.[19]

Distribution

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. The Köppen climate classification system was strongly influenced by effects of temperature and precipitation upon tree growth, and his oversimplified assumptions resulted in a tropical savanna classification concept which resulted in it being considered as a "climatic climax" formation. The common usage meaning to describe vegetation now conflicts with a simplified yet widespread climatic concept meaning. The divergence has sometimes caused areas such as extensive savannas north and south of the Congo and Amazon Rivers to be excluded from mapped savanna categories.[20]

"Barrens" has been used almost interchangeably with savanna in different parts of North America. Sometimes midwestern savanna were described as "grassland with trees". Different authors have defined the lower limits of savanna tree coverage as 5–10% and upper limits range as 25–80% of an area.[21]

Two factors common to all savanna environments are rainfall variations from year to year, and dry season wildfires. In the Americas, e.g. in Belize, Central America, savanna vegetation is similar from Mexico to South America and to the Caribbean.[22]

Over many large tropical areas, the dominant biome (forest, savanna or grassland) can not be predicted only by the climate, as historical events plays also a key role, for example, fire activity.[23] In some areas, indeed, it is possible the occurrence of multiple stable biomes.[24]

Threats

Changes in fire management

Savannas are subject to regular wildfires and the ecosystem appears to be the result of human use of fire. For example, Native Americans created the Pre-Columbian savannas of North America by periodically burning where fire-resistant plants were the dominant species.[25] Pine barrens in scattered locations from New Jersey to coastal New England are remnants of these savannas. Aboriginal burning appears to have been responsible for the widespread occurrence of savanna in tropical Australia and New Guinea,[26] and savannas in India are a result of human fire use.[27] The maquis shrub savannas of the Mediterranean region were likewise created and maintained by anthropogenic fire.[28]

Fire-sav-S-slope-3720
Prescribed burn; Wisconsin bur oak savanna

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. Prior to European settlement aboriginal land use practices, including fire, influenced vegetation[29] and may have maintained and modified savanna flora.[3][26] It has been suggested by many authors[29][30] that aboriginal burning created a structurally more open savanna landscape. Aboriginal burning certainly created a habitat mosaic that probably increased biodiversity and changed the structure of woodlands and geographic range of numerous woodland species.[26][29] It has been suggested by many authors[30][31] that with the removal or alteration of traditional burning regimes many savannas are being replaced by forest and shrub thickets with little herbaceous layer.

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.[32] The introduction of exotic pasture legumes has also led to a reduction in the need to burn to produce a flush of green growth because legumes retain high nutrient levels throughout the year, and because fires can have a negative impact on legume populations which causes a reluctance to burn.[33]

Grazing and browsing animals

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.[34] In contrast the open structure of savannas allows the growth of a herbaceous layer and are commonly used for grazing domestic livestock.[35] As a result, much of the world's savannas have undergone change as a result of grazing by sheep, goats and cattle, ranging from changes in pasture composition to woody weed encroachment.[36]

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.[37] In addition to this effect, the removal of fuel reduces both the intensity and the frequency of fires which may control woody plant species.[38] Grazing animals can have a more direct effect on woody plants by the browsing of palatable woody species. There is evidence that unpalatable woody plants have increased under grazing in savannas.[39] Grazing also promotes the spread of weeds in savannas by the removal or reduction of the plants which would normally compete with potential weeds and hinder establishment.[29] In addition to this, cattle and horses are implicated in the spread of the seeds of weed species such as Prickly Acacia (Acacia nilotica) and Stylo (Stylosanthes spp.).[32] Alterations in savanna species composition brought about by grazing can alter ecosystem function, and are exacerbated by overgrazing and poor land management practices.

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.[40] The effects of overstocking are often worst on soils of low fertility and in low rainfall areas below 500 mm, as most soil nutrients in these areas tend to be concentrated in the surface so any movement of soils can lead to severe degradation. Alteration in soil structure and nutrient levels affects the establishment, growth and survival of plant species and in turn can lead to a change in woodland structure and composition.

Tree clearing

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.[29] Substantial savanna areas have been cleared of woody vegetation and much of the area that remains today is vegetation that has been disturbed by either clearing or thinning at some point in the past.

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.[41] Since stock carrying capacity is strongly correlated with herbage yield, there can be major financial benefits from the removal of trees,[42] such as assisting with grazing management: regions of dense tree and shrub cover harbors predators, leading to increased stock losses, for example,[43] while woody plant cover hinders mustering in both sheep and cattle areas.[44]

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.[45] In the 1950s arboricides suitable for stem injection were developed. War-surplus heavy machinery was made available, and these were used for either pushing timber, or for pulling using a chain and ball strung between two machines. These two new methods of timber control, along with the introduction and widespread adoption of several new pasture grasses and legumes promoted a resurgence in tree clearing. The 1980s also saw the release of soil-applied arboricides, notably tebuthiuron, that could be utilised without cutting and injecting each individual tree.

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.[46] Tree clearing in many savanna communities, although causing a dramatic reduction in basal area and canopy cover, often leaves a high percentage of woody plants alive either as seedlings too small to be affected or as plants capable of re-sprouting from lignotubers and broken stumps. A population of woody plants equal to half or more of the original number often remains following pulling of eucalypt communities, even if all the trees over 5 metres are uprooted completely.

Exotic plant species

A number of exotic plants species have been introduced to the savannas around the world. Amongst the woody plant species are serious environmental weeds such as Prickly Acacia (Acacia nilotica), Rubbervine (Cryptostegia grandiflora), Mesquite (Prosopis spp.), Lantana (Lantana camara and L. montevidensis) and Prickly Pear (Opuntia spp.) A range of herbaceous species have also been introduced to these woodlands, either deliberately or accidentally including Rhodes grass and other Chloris species, Buffel grass (Cenchrus ciliaris), Giant rat's tail grass (Sporobolus pyramidalis) parthenium (Parthenium hysterophorus) and stylos (Stylosanthes spp.) and other legumes. These introductions have the potential to significantly alter the structure and composition of savannas worldwide, and have already done so in many areas through a number of processes including altering the fire regime, increasing grazing pressure, competing with native vegetation and occupying previously vacant ecological niches.[46][47] Other plant species include: white sage, spotted cactus, cotton seed, rosemary.

Climate change

Human induced climate change resulting from the greenhouse effect may result in an alteration of the structure and function of savannas. Some authors[48] have suggested that savannas and grasslands may become even more susceptible to woody plant encroachment as a result of greenhouse induced climate change. However, a recent case described a savanna increasing its range at the expense of forest in response to climate variation, and potential exists for similar rapid, dramatic shifts in vegetation distribution as a result of global climate change, particularly at ecotones such as savannas so often represent.[49]

Savanna ecoregions

Quercus suber.Alentejo04
Mediterranean savanna in Alentejo region, Portugal

Savanna ecoregions are of several different types:

See also

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. ^ a b Werner, Patricia A.; B. H. Walker; P. A Stott (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.
  4. ^ Alexandro Solórzano, Jeanine Maria Felfili 2008”Comparative analysis of the international terminaoolgy for cerrado” IX Symposio Nacional Cerrado 13 a 17 de outubro de 2008 Parlamundi Barsilia, DF
  5. ^ a b Manoel Cláudio da Silva Jánior, Christopher William Fagg, Maria Cristina Felfili, Paulo Ernane Nogueira, Alba Valéria Rezende, and Jeanine Maria Felfili 2006 “Chapter 4. Phytogeography of Cerrado Sensu Stricto and Land System Zoning in Central Brazil” in “Neotropical Savannas and Seasonally Dry Forests: Plant Diversity, Biogeography, and Conservation” R. Toby Pennington, James A. Ratter (eds) 2006 CRC Press
  6. ^ a b Abdullahi Jibrin 2013 “A Study of Variation in Physiognomic Characteristics of Guinea Savanna Vegetation” Environment and Natural Resources Research 3:2
  7. ^ a b Erika L. Geiger, Sybil G. Gotsch, Gabriel Damasco, M. Haridasan, Augusto C. Franco & William A. Hoffmann 2011 “Distinct roles of savanna and forest tree species in regeneration under fire suppression in a Brazilian savanna” Journal of Vegetation Science 22
  8. ^ a b Scholz, Fabian G.; Bucci, Sandra J.; Goldstein, Guillermo; Meinzer, Frederick C.; Franco, Augusto C.; Salazar, Ana. 2008 “Plant- and stand-level variation in biophysical and physiological traits along tree density gradients in the Cerrado”, Brazilian Journal of Plant Physiology
  9. ^ Tait, L 2010, Structure and dynamics of grazed woodlands in North-eastern Australia, Master of Applied Science Thesis, Central Queensland University, Faculty of Science, Engineering and Health, Rockhampton.
  10. ^ Sankaran, Mahesh; Hanan, Niall P.; Scholes, Robert J.; Ratnam, Jayashree; Augustine, David J.; Cade, Brian S.; Gignoux, Jacques; Higgins, Steven I.; Le Roux, Xavier (December 2005). "Determinants of woody cover in African savannas". Nature. 438 (7069): 846–849. doi:10.1038/nature04070. ISSN 0028-0836. PMID 16341012.
  11. ^ Oxford English Dictionary, 3rd ed. "savannah", n. Oxford University Press (Oxford), 2012.
  12. ^ a b D'Anghiera, Peter Martyr. De Orbe Novo Decades. Cum Ejusdem Legatione Babylonica. [The Decades of the New World. With the Babylonian Legation.] Arnao Guillén de Brocar (Alcala), 1516 (in Latin). Trans. Richard Eden as The decades of the newe worlde or west India conteynyng the nauigations and conquestes of the Spanyardes with the particular description of the moste ryche and large landes and Ilands lately founde in the west Ocean perteynyng to the inheritaunce of the kinges of Spayne, Book III, §3. William Powell (London), 1555.
  13. ^ Richard Eden: "The palace of this Comogrus, is ſituate at the foote of a ſtiepe hyll well cultured. Hauynge towarde the ſouthe a playne of twelue leages in breadth and veary frutefull. This playne, they caule Zauana."[12]
  14. ^ Eden (1555), Book III, §6.
  15. ^ The account of Peter Martyr itself differs in places, variously placing Comagre 25 leagues west of and accessible by ship from Dariena[14] or 70 leagues (roughly 290 kilometers or 180 miles) west of Dariena and beside a river flowing into the southern ocean.[12]
  16. ^ Bancroft, Hubert H. (1882). "History of Central America. 1501–1530". San Francisco: A.L. Bancroft & Co. p. LXXIV.
  17. ^ Bancroft (1882), p. 362.
  18. ^ Bancroft (1882), p. 347.
  19. ^ NASA. "[earthobservatory.nasa.gov/Experiments/ICE/panama/Images/igbp_panama2000289_lg.gif Land Cover Classification]" from Earth Observatory. The Image Composite Explorer. Exercise 4: Vegetation Vital Signs. Accessed 1 August 2014.
  20. ^ David R. Harris, ed. (1980). Human Ecology in Savanna Environments. London: Academic Press. pp. 3, 5–9, 12, 271–278, 297–298. ISBN 978-0-12-326550-0.
  21. ^ Roger C. Anderson; James S. Fralish; Jerry M. Baskin, eds. (1999). Savannas, Barrens, and Rock Outcrop Plant Communities of North America. Cambridge University Press. pp. 2–3. ISBN 978-0-521-57322-1.
  22. ^ David L. Lentz, ed. (2000). Imperfect balance: landscape transformations in the Precolumbian Americas. New York City: Columbia University Press. pp. 73–74. ISBN 978-0-231-11157-7.
  23. ^ Moncrieff, G. R., Scheiter, S., Langan, L., Trabucco, A., Higgins, S. I. (2016). The future distribution of the savannah biome: model-based and biogeographic contingency, Philos. T. R. Soc. B, 371, 2015.0311, 2016. link.
  24. ^ Staver, A.C., Archibald, S., Levin, S.A. (2011). The global extent and determinants of savanna and forest as alternative biome states. Science 334, 230–232. link.
  25. ^ "Use of Fire by Native Americans". The Southern Forest Resource Assessment Summary Report. Southern Research Station, USDA Forest Service. Retrieved 2008-07-21.
  26. ^ a b c Flannery, Timothy Fridtjof (1994). The Future Eaters: An Ecological History of the Australasian Lands and People. Frenchs Forest, New South Wales: Reed New Holland. ISBN 978-0-8076-1403-7.
  27. ^ Saha, S. (2003). "Patterns in woody species diversity, richness and partitioning of diversity in forest communities of tropical deciduous forest biomes". Ecography. 26 (1): 80–86. doi:10.1034/j.1600-0587.2003.03411.x.
  28. ^ Pyne, Stephen J. (1997). Vestal Fire: An Environmental History, Told through Fire, of Europe and Europe's Encounter with the World. Seattle: University of Washington Press. ISBN 978-0-295-97596-2.
  29. ^ a b c d e Wilson, B., S. Boulter, et al. (2000). Queensland's resources. Native Vegetation Management in Queensland. S. L. Boulter, B. A. Wilson, J. Westrupet eds. Brisbane, Department of Natural Resources ISBN 0-7345-1701-7.
  30. ^ a b Lunt, I. D.; N. Jones (2006). "Effects of European colonisation on indigenous ecosystems: post-settlement changes in tree stand structures in EucalyptusCallitris woodlands in central New South Wales, Australia". Journal of Biogeography. 33 (6): 1102–1115. doi:10.1111/j.1365-2699.2006.01484.x.
  31. ^ Archer S, (1994.) "Woody plant encroachment into southwestern grasslands and savannas: Rates, patterns and proximate causes." pp. 13–68 in Vavra, Laycock and Pieper (eds.) Ecological Implications of Livestock Herbivory in the West. Society For Range Management, Denver ISBN 1-884930-00-X.
  32. ^ a b Pressland, A. J., J. R. Mills, et al. (1988). Landscape degradation in native pasture. Native pastures in Queensland their resources and management. W. H. Burrows, J. C. Scanlan and M. T. Rutherford. Queensland, Queensland Government Press ISBN 0-7242-2443-2.
  33. ^ Dyer, R., A. Craig, et al. (1997). Fire in northern pastoral lands. Fire in the management of northern Australian pastoral lands. T. C. Grice and S. M. Slatter. St. Lucia, Australia, Tropical Grassland Society of Australia ISBN 0-9590948-9-X.
  34. ^ Lodge, G. M. and R. D. B. Whalley (1984). Temperate rangelands. Management of Australia’s Rangelands. G. N. Harrington and A. D. Wilson. Melbourne, CSIRO Publishing.
  35. ^ Mott, J. J., Groves, R.H. (1994). Natural and derived grasslands. Australian Vegetation. R. H. Groves. Cambridge, Cambridge University Press.
  36. ^ Winter, W. H. (1991). "Australia's northern savannas: a time for change in management philosophy". In Patricia A. Werner (ed.). Savanna Ecology and Management: Australian Perspectives and Intercontinental Comparisons. Oxford: Blackwell Publishing. pp. 181–186. ISBN 978-0-632-03199-3.
  37. ^ Burrows, W. H., J. C. Scanlan, et al. (1988). Plant ecological relations in open forests, woodlands and shrublands. Native pastures in Queensland their resources and management. W. H. Burrows, J. C. Scanlan and M. T. Rutherford eds. Brisbane, Department of Primary Industries ISBN 0-7242-2443-2.
  38. ^ Smith, G., A. Franks, et al. (2000). Impacts of domestic grazing within remnant vegetation. Native Vegetation Management in Queensland. S. L. Boulter, B. A. Wilson, J. Westrupet al. Brisbane, Department of Natural Resources ISBN 0-7345-1701-7.
  39. ^ Florence, R. G. (1996). Ecology and silviculture of eucalypt forests. Collingwood, CSIRO Publishing ISBN 0-643-10252-3.
  40. ^ Foran, B. D. (1984). Central arid woodlands. Management of Australia’s Rangelands. G. N. Harrington and A. D. Wilson. Melbourne, CSIRO Publishing ISBN 0-643-03615-6.
  41. ^ Scanlan, J. and C. Chilcott (2000). Management and production aspects. Native Vegetation Management in Queensland. S. L. Boulter, B. A. Wilson, J. Westrupet al. Brisbane, Department of Natural Resources.
  42. ^ Harrington, G. N., M. H. Friedel, et al. (1984). Vegetation ecology and management. Management of Australia's Rangelands. G. N. Harrington and A. D. Wilson. Melbourne, CSIRO Publishing ISBN 0-643-03615-6.
  43. ^ Harrington, G. N., D. M. D. Mills, et al. (1984). Semi-arid woodlands. Management of Australia's Rangelands. G. N. Harrington and A. D. Wilson. Melbourne, CSIRO Publishing ISBN 0-643-03615-6.
  44. ^ Harrington, G. N., D. M. D. Mills, et al. (1984). Management of Rangeland Ecosystems. Management of Australia's Rangelands. G. N. Harrington and A. D. Wilson. Melbourne, CSIRO Publishing ISBN 0-643-03615-6.
  45. ^ Partridge, I. (1999). Managing grazing in northern Australia. Brisbane, Department of Primary Industries ISBN 0-7345-0035-1.
  46. ^ a b Scanlan, J. C. (1988). Managing tree and shrub populations. Native pastures in Queensland their resources and management. W. H. Burrows, J. C. Scanlan and M. T. Rutherford. Queensland, Queensland Government Press ISBN 0-7242-2443-2.
  47. ^ Tothill, J. C. and C. Gillies (1992). The pasture lands of northern Australia. Brisbane, Tropical Grassland Society of Australia ISBN 0-9590948-4-9.
  48. ^ Archer, S. (1991). "Development and stability of grass/woody mosaics in a subtropical savanna parkland, Texas, USA". In Patricia A. Werner (ed.). Savanna Ecology and Management: Australian Perspectives and Intercontinental Comparisons. Oxford: Blackwell Publishing. pp. 109–118. ISBN 978-0-632-03199-3.
  49. ^ Allen, C. D. & D. D. Breshears (1998). "Drought-induced shift of a forest–woodland ecotone: Rapid landscape response to climate variation". Proceedings of the National Academy of Sciences. 95 (25): 14839–14842. doi:10.1073/pnas.95.25.14839. PMC 24536. PMID 9843976.
  50. ^ Calvachi Zambrano, Byron (2002). "La biodiversidad bogotana" (PDF). Revista la Tadeo (in Spanish). Universidad Jorge Tadeo Lozano. 67: 89–98. Retrieved 2017-03-04.
  51. ^ Pérez Preciado, Alfonso (2000). La estructura ecológica principal de la Sabana de Bogotá (PDF) (in Spanish). Sociedad Geográfica de Colombia. pp. 1–37. Retrieved 2017-03-04.
  52. ^ Angolan Scarp savanna and woodlands

External links

African bush elephant

The African bush elephant (Loxodonta africana), also known as the African savanna elephant, is the larger of the two species of African elephants, and the largest living terrestrial animal. These elephants were previously regarded as the same species, but the African forest elephant has been reclassified as L. cyclotis.

The bush elephant is much larger in height and weight than the forest elephant, while the forest elephant has rounder ears and a trunk that tends to be more hairy. The adult bush elephant has no predators other than humans. While the most numerous of the three extant elephant species, its population continues to decline due to poaching for ivory and destruction of habitat. Elephants are social animals, traveling in herds of females and adolescents, while adult males usually live alone. The desert elephant or desert-adapted elephant is not a distinct species of elephant, but there are African bush elephants that live in the Namib and Sahara deserts.

Bogotá savanna

The Bogotá savanna is a montane savanna, located in the southwestern part of the Altiplano Cundiboyacense in the center of Colombia. The Bogotá savanna has an extent of 4,251.6 square kilometres (1,641.6 sq mi) and an average altitude of 2,550 metres (8,370 ft). The savanna is situated in the Eastern Ranges of the Colombian Andes.

The Bogotá savanna is crossed from northeast to southwest by the 375 kilometres (233 mi) long Bogotá River, which at the southwestern edge of the plateau forms the Tequendama Falls (Salto del Tequendama). Other rivers, such as the Subachoque, Bojacá, Fucha, Soacha and Tunjuelo Rivers, tributaries of the Bogotá River, form smaller valleys with very fertile soils dedicated to agriculture and cattle-breeding.

Before the Spanish conquest of the Bogotá savanna, the area was inhabited by the indigenous Muisca, who formed a loose confederation of various caciques, named the Muisca Confederation. The Bogotá savanna, known as Bacatá, was ruled by the zipa. The people specialised in agriculture, the mining of emeralds, trade and especially the extraction of rock salt from rocks in Zipaquirá, Nemocón, Tausa and other areas on the Bogotá savanna. The salt extraction, a task exclusively of the Muisca women, gave the Muisca the name "The Salt People".

In April 1536, a group of around 800 conquistadors left the relative safety of the Caribbean coastal city of Santa Marta to start a strenuous expedition up the Magdalena River, the main fluvial artery of Colombia. Word got around among the Spanish colonisers that deep in the unknown Andes, a rich area with an advanced civilisation must exist. These tales bore the -not so much- legend of El Dorado; the city or man of gold. The Muisca, skilled goldworkers, held a ritual in Lake Guatavita where the new zipa would cover himself in gold dust and jump from a raft into the cold waters of the 3,000 metres (9,800 ft) high lake to the northeast of the Bogotá savanna.

After a journey of almost a year, where the Spanish lost over 80% of their soldiers, the conquistadors following the Suárez River, reached the Bogotá savanna in March 1537. The zipa who ruled the Bogotá savanna at the arrival of the Spanish was Tisquesusa. The Muisca posed little resistance to the Spanish strangers and Tisquesusa was defeated in April 1537 in Funza, in the centre of the savanna. He fled towards the western hills and died of his wounds in Facatativá, on the southwestern edge of the Bogotá savanna. The Spanish conquistador Gonzalo Jiménez de Quesada established the New Kingdom of Granada with capital Santa Fe de Bogotá on August 6, 1538. This started a process of colonisation, evangelisation and submittance of the Muisca to the new rule. Between 65 and 80% of the indigenous people perished due to European diseases as smallpox and typhus. The Spanish introduced new crops, replacing many of the New World crops that the Muisca cultivated.

Over the course of the 16th to early 20th century, the Bogotá savanna was sparsely populated and industrialised. The rise in population during the twentieth century and the expansion of agriculture and urbanisation reduced the biodiversity and natural habitat of the Bogotá savanna severely. Today, the Metropolitan Area of Bogotá on the Bogotá savanna hosts more than ten million people. Bogotá is the biggest city worldwide at altitudes above 2,500 metres (8,200 ft). The many rivers on the savanna are highly contaminated and efforts to solve the environmental problems are conducted in the 21st century.

Cerrado

The Cerrado (Portuguese pronunciation: [seˈʁadu], [sɛˈʁadu]) is a vast tropical savanna ecoregion of Brazil, particularly in the states of Goiás, Mato Grosso do Sul, Mato Grosso, Tocantins and Minas Gerais. The Cerrado biome core areas are the plateaus in the center of Brazil. The main habitat types of the Cerrado include: forest savanna, wooded savanna, park savanna and gramineous-woody savanna. Savanna wetlands and gallery forests are also included. The second largest of Brazil's major habitat types, after the Amazonian rainforest, the Cerrado accounts for a full 21 percent of the country's land area (extending marginally into Paraguay and Bolivia).The first detailed account of the Brazilian cerrados was provided by Danish botanist Eugenius Warming (1892) in the book Lagoa Santa, in which he describes the main features of the cerrado vegetation in the state of Minas Gerais.Since then vast amounts of research have proved that the Cerrado is one of the richest of all tropical savanna regions and has high levels of endemism. Characterized by enormous ranges of plant and animal biodiversity, World Wide Fund for Nature named it the biologically richest savanna in the world, with about 10,000 plant species and 10 endemic bird species. There are nearly 200 species of mammal in the Cerrado, though only 14 are endemic.

Edwards Plateau

The Edwards Plateau is a region of west-central Texas which is bounded by the Balcones Fault to the south and east, the Llano Uplift and the Llano Estacado to the north, and the Pecos River and Chihuahuan Desert to the west. San Angelo, Austin, San Antonio and Del Rio roughly outline the area. The eastern portion of the plateau is known as the Texas Hill Country.

Grassland

Grasslands are areas where the vegetation is dominated by grasses (Poaceae); however, sedge (Cyperaceae) and rush (Juncaceae) families can also be found along with variable proportions of legumes, like clover, and other herbs. Grasslands occur naturally on all continents except Antarctica. Grasslands are found in most ecoregions of the Earth. For example, there are five terrestrial ecoregion classifications (subdivisions) of the temperate grasslands, savannas, and shrublands biome (ecosystem), which is one of eight terrestrial ecozones of the Earth's surface.

Kalahari Desert

The Kalahari Desert is a large semi-arid sandy savanna in Southern Africa extending for 900,000 square kilometres (350,000 sq mi), covering much of Botswana, parts of Namibia and regions of South Africa.

It is not to be confused with the Angolan, Namibian and S. African Namib coastal desert, whose name is of Khoekhoegowab origin and means "vast place".

Sahel

The Sahel () is the ecoclimatic and biogeographic zone of transition in Africa between the Sahara to the north and the Sudanian Savanna to the south. Having a semi-arid climate, it stretches across the south-central latitudes of Northern Africa between the Atlantic Ocean and the Red Sea. The name is derived from the Arabic word sāḥil (ساحل, Arabic pronunciation: [ˈsaːħil]) meaning "coast" or "shore" in a figurative sense (in reference to the southern edge of the vast Sahara), while the name in Swahili means "coastal [dweller]" in a literal sense.

The Sahel part of Africa includes (from west to east) parts of northern Senegal, southern Mauritania, central Mali, northern Burkina Faso, the extreme south of Algeria, Niger, the extreme north of Nigeria, central Chad, central and southern Sudan, the extreme north of South Sudan, Eritrea, Cameroon, Central African Republic and the extreme north of Ethiopia.Historically, the western part of the Sahel was sometimes known as the Sudan region. This belt was roughly located between the Sahara and the coastal areas of West Africa.

Savanna-la-Mar

Savanna-la-Mar (commonly known as Sav-la-Mar, or simply Sav) is the chief town and capital of Westmoreland Parish, Jamaica. A coastal town, it contains an 18th-century fort constructed for colonial defence against pirates in the Caribbean.

Savanna dwarf shrew

The savanna dwarf shrew (Crocidura nanilla) is a species of mammal in the family Soricidae. It is found in Guinea, Kenya, Mauritania, Senegal, Tanzania, and Uganda. Its natural habitats are dry savanna and moist savanna.

Savanna path shrew

The savanna path shrew (Crocidura viaria) is a species of mammal in the family Soricidae. It is found in Benin, Burkina Faso, Cameroon, Chad, Eritrea, Ethiopia, Ghana, Kenya, Mali, Mauritania, Morocco, Niger, Nigeria, Senegal, Somalia, Sudan, and Uganda. Its natural habitats are subtropical or tropical moist lowland forest, dry savanna, and heavily degraded former forest.

Savanna shrew

The savanna shrew (Crocidura fulvastra) is a species of mammal in the family Soricidae. It is found in Benin, Burkina Faso, Cameroon, Central African Republic, Chad, Democratic Republic of the Congo, Djibouti, Eritrea, Ethiopia, Kenya, Mali, Mauritania, Niger, Nigeria, Sudan, and Uganda. Its natural habitat is dry savanna.

Savanna swamp shrew

The Savanna swamp shrew (Crocidura longipes) is a species of mammal in the family Soricidae. It is endemic to Nigeria. Its natural habitat is swamps. It is threatened by habitat loss.

Savannah, California

Savannah (also, Savanna) is a former settlement in Los Angeles County, California. The rail depot of that name was located on the line of the Southern Pacific Railroad between San Gabriel and El Monte, at an elevation of 276 feet (84 m).Savannah was promoted with considerable dignity in 1887-88 but vanished, nevertheless; the neighborhood of the depot has been absorbed by Rosemead. The name survives in Savanna High School and Savanna School District of Orange County, which seceded from Los Angeles County in 1889.

Savannah was the location of Camp Monte, a Rebel base where State militias trained openly for participation in the Civil War until Federal troops suppressed it by establishing Camp Carleton in 1862. Camp Monte is recalled today in "Johnny Rebel," the mascot of Savanna High School and name for a statue of a Civil-War era soldier in the quad.

Steppe

In physical geography, a steppe (Russian: степь, IPA: [stʲepʲ]) is an ecoregion, in the montane grasslands and shrublands and temperate grasslands, savannas and shrublands biomes, characterized by grassland plains without trees apart from those near rivers and lakes. In South Africa, they are referred to as veld. The prairie of North America (especially the shortgrass and mixed prairie) is an example of a steppe, though it is not usually called such. A steppe may be semi-arid or covered with grass or shrubs or both, depending on the season and latitude. The term is also used to denote the climate encountered in regions too dry to support a forest but not dry enough to be a desert. The soil is typically of chernozem type.

Steppes are usually characterized by a semi-arid or continental climate. Extremes can be recorded in the summer of up to 45 °C (113 °F) and in winter, −55 °C (−67 °F). Besides this huge difference between summer and winter, the differences between day and night are also very great. In both the highlands of Mongolia and northern Nevada, 30 °C (86 °F) can be reached during the day with sub-zero °C (sub 32 °F) readings at night.

The mid-latitude steppes can be summarized by hot summers and cold winters, averaging 250–510 mm (10–20 in) of precipitation per year. Precipitation level alone is not what defines a steppe climate; potential evapotranspiration must also be taken into account.

Sudanian Savanna

The Sudanian Savanna is a broad belt of tropical savanna that runs east and west across the African continent, from the Atlantic Ocean in the west to the western lowlands in the east. The Sahel, a belt of drier grasslands and acacia savannas, lies to the north, between the Sudanian Savanna and the Sahara Desert. To the south the forest-savanna mosaic is a transition zone between the Sudanian Savanna and the Guinean moist forests and Congolian forests that lie nearer the equator.

Tropical and subtropical grasslands, savannas, and shrublands

Tropical and subtropical grasslands, savannas, and shrublands is a terrestrial habitat type defined by the World Wide Fund for Nature.. The biome is dominated by grass and/or shrubs located in semi-arid to semi-humid climate regions of subtropical and tropical latitudes.

Tropical climate

A tropical climate in the Köppen climate classification is a non-arid climate in which all twelve months have mean temperatures of warmer than 18 °C (64 °F). In tropical climates there are often only two seasons: a wet season and a dry season. Tropical climates are frost-free, and changes in the solar angle are small. In tropical climates temperature remains relatively constant (hot) throughout the year. Sunlight is intense.

Tropical monsoon climate

An area of tropical monsoon climate (occasionally known as a tropical wet climate or a tropical monsoon and trade-wind littoral climate) is a type of climate that corresponds to the Köppen climate classification category "Am". Tropical monsoon climates have monthly mean temperatures above 18 °C (64.4 °F) in every month of the year. Tropical monsoon climates is the intermediate climate between the wet Af (or tropical rainforest climate) and Aw (or tropical savanna climate).

A tropical monsoon climate, however, has its driest month seeing on average less than 60 mm, but more than 100 – [total annual precipitation {mm}/25] of average monthly precipitation. This latter fact is in direct contrast to a tropical savanna climate, whose driest month sees less than 60 mm of precipitation and also less than 100 – [total annual precipitation {mm}/25] of average monthly precipitation. In essence, a tropical monsoon climate tends to either see more rainfall than a tropical savanna climate or have less pronounced dry seasons. Additionally, a tropical monsoon climate tends to see less variance in temperatures during the course of the year than a tropical savanna climate. This climate has a driest month which nearly always occurs at or soon after the "winter" solstice for that side of the equator.

Tropical savanna climate

Tropical savanna climate or tropical wet and dry climate is a type of climate that corresponds to the Köppen climate classification categories "Aw" and "As".

Tropical savanna climates have monthly mean temperatures above 18 °C (64 °F) in every month of the year and typically a pronounced dry season, with the driest month having less than 60 mm (2.36 inches) of precipitation and also less than 100 – [total annual precipitation {mm}/25] of precipitation. This latter fact is in direct contrast to a tropical monsoon climate, whose driest month sees less than 60 mm of precipitation but has more than 100 – [total annual precipitation {mm}/25] of precipitation. In essence, a tropical savanna climate tends to either see less rainfall than a tropical monsoon climate or have more pronounced dry season(s).

In tropical savanna climates, the dry season can become severe, and often drought conditions prevail during the course of the year. Tropical savanna climates often feature tree-studded grasslands, rather than thick jungle. It is this widespread occurrence of tall, coarse grass (called savanna) which has led to Aw and As climates often being referred to as tropical savanna. However, there is some doubt whether tropical grasslands are climatically induced. Additionally, pure savannas, without trees, are the exception rather than the rule.

Biomes
Biogeographic
realms
See also
Physiognomy
Latitude
Climatic
regime
Altitude
Leaves
Substrate
See also

This page is based on a Wikipedia article written by authors (here).
Text is available under the CC BY-SA 3.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.