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73-459: The Mago National Park was established in 1979, making it the newest of Ethiopia's several National Parks. Its highest point is Mount Mago (2528meters). The major environments in and around the Park are the rivers and riverine forest, the wetlands along the lower Mago and around Lake Dipa, the various grasslands on the more level areas, and scrub on the sides of the hills. Open grassland comprises about 9% of

146-438: A continuous tree canopy which would prevent further grass growth. Prior to European settlement aboriginal land use practices, including fire, influenced vegetation and may have maintained and modified savanna flora. It has been suggested by many authors that aboriginal burning created a structurally more open savanna landscape. Aboriginal burning certainly created a habitat mosaic that probably increased biodiversity and changed

219-458: A diverse local population that relies heavily on the resources of their environment. Until the mid-1960s, agricultural activities in the Cerrado were very limited, since natural cerrado soils are not fertile enough for crop production, directed mainly at the extensive production of beef cattle for subsistence of the local market. After this period, however, the urban and industrial development of

292-491: 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. A number of exotic plants species have been introduced to savannas around

365-797: 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 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, with savanna ranging from 800 to 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 , while Eastern Australian sclerophyll forests have average tree densities of approximately 100 per hectare , comparable to savannas in

438-498: A location in the Southern Nations, Nationalities, and Peoples' Region of Ethiopia is a stub . You can help Misplaced Pages by expanding it . This Africa protected areas related article is a stub . You can help Misplaced Pages by expanding it . Savanna A savanna or savannah is a mixed woodland - grassland (i.e. grassy woodland) biome and ecosystem characterised by the trees being sufficiently widely spaced so that

511-402: A means of clearing land. 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

584-444: 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. 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

657-445: A result of global climate change, particularly at ecotones such as savannas so often represent. A savanna can simply be distinguished by the open savanna, where grass prevails and trees are rare; and the wooded savanna, where the trees are densest, bordering an open woodland or forest. Specific savanna ecoregions of several different types include: Cerrado The Cerrado ( Portuguese pronunciation: [seˈʁadu] )

730-469: 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. Tree clearing in many savanna communities, although causing

803-597: A significant increase in agricultural and cattle production. On the other hand, the urban pressure and the rapid establishment of agricultural activities in the region have been rapidly reducing the biodiversity of the ecosystems, and the population in the Cerrado region more than doubled from 1970 to 2010, going from 35.8 to 76 million. The Cerrado was thought challenging for agriculture until researchers at Brazil's agricultural and livestock research agency, Embrapa , discovered that it could be made fit for industrial crops by appropriate additions of phosphorus and lime. In

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876-455: A simplified yet widespread climatic concept. 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. In different parts of North America, the word "savanna" has been used interchangeably with " barrens ", " prairie ", " glade ", "grassland" and " oak opening ". Different authors have defined

949-399: A temperate crop, and currently, Brazil is the world's main soyabeans exporter due to the boom in animal feed production caused by the global rise in meat demand. Today the Cerrado region provides more than 70% of the beef cattle production in the country, being also a major production center of grains, mainly soya, beans, maize, and rice. Large extensions of the Cerrado are also used for

1022-422: Is a relatively high diversity of snakes in the Cerrado (22–61 species, depending on site) with Colubridae being the richest family. The open nature of the cerrado vegetation most likely contributes to the high diversity of snakes. Information about Cerrado amphibians is extremely limited, although the Cerrado probably has a unique assemblage of species with some endemic to the region. Most birds found in

1095-752: Is a vast ecoregion of tropical savanna in eastern Brazil , being present in the states of Goiás , Mato Grosso do Sul , Mato Grosso , Tocantins , Maranhão , Piauí , Bahia , Minas Gerais , São Paulo , Paraná and the Federal District . The core areas of the Cerrado biome are the Brazilian highlands – the Planalto . The main habitat types of the Cerrado consist of forest savanna, wooded savanna, park savanna and gramineous -woody savanna. The Cerrado also includes savanna wetlands and gallery forests . The second largest of Brazil's major habitat types , after

1168-729: Is composed mainly of the Poaceae , Cyperaceae , Leguminosae , Compositae , Myrtaceae and Rubiaceae . Much of the vegetation in the gallery forests is similar to nearby rainforest; however, there are some endemic species found only in the Cerrado gallery forests. Soil fertility, fire regime and hydrology are thought to be most influential in determining Cerrado vegetation. Cerrado soils are always well-drained and most are oxisols with low pH and low calcium and magnesium. The amount of potassium, nitrogen and phosphorus has been found to be positively correlated with tree trunk basal area in Cerrado habitats. Much as in other grasslands and savannas, fire

1241-410: Is generally thought to be relatively low in the Cerrado compared to other areas like caatinga or lowland rainforest, although one recent study found 57 species in one cerrado area with the high diversity driven by the availability of open habitat. Ameiva ameiva is among the largest lizards found in the Cerrado and is the most important lizard predator where it is found in the Cerrado. There

1314-512: Is heterogeneous in terms of canopy cover. Goodland (1971) divided the Cerrado into four categories ranging from least to most canopy cover: campo sujo ( herbaceous layer with occasional small trees about 3 m tall), campo cerrado (slightly higher density of trees about 4 m tall on average), cerrado sensu stricto (orchard-like vegetation with trees about 6 m high) and cerradão (canopy cover near 50% with general height 9 m). Probably around 800 species of trees are found in

1387-525: Is important in maintaining and shaping the Cerrado's landscape; many plants in the Cerrado are fire-adapted, exhibiting characters like thick corky bark to withstand the heat. Cerrado vegetation is believed to be ancient, stretching back perhaps as far in a prototypic form as the Cretaceous , before Africa and South America separated. A dynamic expansion and contraction between cerrado and Amazonian rainforest has probably occurred historically, with expansion of

1460-429: Is limited to two dominant seasons throughout the year: Wet and dry. Annual temperatures for the Cerrado average between 22 and 27 °C and average precipitation between 80–200 cm for over 90% of the area. This ecoregion has a very strong dry season during the southern winter (approx. April–September). The Cerrado is characterized by unique vegetation types. It is composed of a shifting mosaic of habitats, with

1533-477: Is not prominent but that rivers in savanna landscapes erode more by lateral migration . Flooding and associated sheet wash have been proposed as dominant erosion processes in savanna plains. The savannas of tropical America comprise broadleaved trees such as Curatella , Byrsonima , and Bowdichia , with grasses such as Leersia and Paspalum . Bean relative Prosopis is common in the Argentinian savannas. In

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1606-473: Is possible for there to be multiple stable biomes. The annual rainfall ranges from 500 mm (19.69 in) to 1,270 mm (50.00 in) per year, with the precipitation being more common in six or eight months of the year, followed by a period of drought. Savannas may at times be classified as forests. In climatic geomorphology it has been noted that many savannas occur in areas of pediplains and inselbergs . It has been posited that river incision

1679-419: Is vague and therefore the two can be combined into a single biome as both woodlands and savannas feature open-canopied trees with crowns not usually interlinking (mostly forming 25-60% cover). 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. In some areas, indeed, it

1752-572: The Amazonian rainforest , the Cerrado accounts for a full 21 percent of the country's land area (extending marginally into Paraguay and Bolivia). About 75% of the Cerrado’s 2 million km is privately owned. Vast amounts of research have shown that the Cerrado is one of the richest of all tropical savanna regions and has high levels of endemism . Characterizing it by its enormous ranges of plant and animal biodiversity, World Wide Fund for Nature named

1825-872: The Brazilian Constitution as a National Heritage. It is also home to the Guarani Aquifer , stores the largest fresh water underground reservoirs in South America, and supplies water to a third of the Amazon river and the largest basins in the continent. Brazilian agriculturalists and ministers regard it as having no conservation value, and the government has protected merely 1.5% of the Cerrado biome in Federal Reserves. By 1994, an estimated 695,000 km of cerrado (representing 35% of its area) had been converted to 'anthropic [sic] landscape'. In total, 37.3% of

1898-455: The Mediterranean region were likewise created and maintained by anthropogenic fire. Intentional controlled burns typically create fires confined to the herbaceous layer that do little long term damage to mature trees. This prevents more catastrophic wildfires that could do much more damage. However, these fires either kill or suppress tree seedlings, thus preventing the establishment of

1971-454: The Xingu and Tapajós . During the last four decades, the Cerrado’s river basins have been highly impacted by extreme deforestation, expansion of the agricultural and cattle ranching frontier, construction of dams, and extraction of water for irrigation. The Cerrado is the second largest biome in South America and the most biodiverse savanna in the world. However, it is not currently recognized by

2044-455: 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. Four savanna forms exist; savanna woodland where trees and shrubs form a light canopy, tree savanna with scattered trees and shrubs, shrub savanna with distributed shrubs, and grass savanna where trees and shrubs are mostly nonexistent. Savannas maintain an open canopy despite

2117-476: The greenhouse effect may result in an alteration of the structure and function of savannas. Some authors 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

2190-717: The prairies in North America and steppes in Eurasia , which feature cold winters, savannas are mostly located in areas having warm to hot climates, such as in Africa, Australia, Thailand, South America and India. The word derives from the Spanish sabana , which is itself a loanword from Taíno , which means "treeless grassland" in the West Indies . The letter b in Spanish, when positioned in

2263-544: The Australian savanna, mammals in the family Macropodidae predominate, such as kangaroos and wallabies, though cattle, horses, camels, donkeys and the Asian water buffalo , among others, have been introduced by humans. 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

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2336-622: 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 . Taking advantage of the sprouting of the herbaceous stratum that follows a burning in the Cerrado, the aboriginal inhabitants of these regions learned to use the fire as a tool, to increase the fodder to offer to their domesticated animals. Xavantes , Tapuias  [ pt ] , Karajás , Avá- Canoeiros , Krahôs , Xerentes , Xacriabás were some of

2409-459: The Cerrado and play an important role in consuming and decomposing organic matter, as well as constituting an important food source to many other animal species. The highest diversity of galling insects (insects that build galls ) in the world is also found in the Cerrado, with the most species (46) found at the base of the Serra do Cipó in southeast Brazil. The first detailed European account of

2482-471: The Cerrado are relatively understudied. A yearlong survey of the Cerrado at one reserve in Brazil found that the orders Coleoptera , Hymenoptera , Diptera and Isoptera accounted for 89.5% of all captures. The Cerrado also supports a high density (up to 4000 per hectare) of the nests of leaf cutter ants ( saúvas ), which are also very diverse. Along with termites, leaf cutter ants are the primary herbivores of

2555-495: The Cerrado breed there although there are some Austral migrants (breed in temperate South America and winter in the Amazon basin) and Nearctic migrants (breed in temperate North America and winter in the Neotropics) that pass through. Most breeding birds in the Cerrado are found in more closed canopy areas like gallery forests although 27% of the birds breed only in open habitats and 21% breed in either open or closed habitats. Many of

2628-534: The Cerrado during glacial periods like the Pleistocene . These processes and the resulting fragmentation in multiple refugia have probably contributed to the high species richness both of the Cerrado and of the Amazonian rainforest. The Cerrado has a high diversity of vertebrates, with 150 amphibian species, 120 reptile species, 837 bird species, and 161 mammal species recorded. Lizard diversity

2701-444: The Cerrado has already been totally converted to human use, while an additional 41.4% is used for pasture and charcoal production. The gallery forests in the region have been among the most heavily affected. It is estimated that only about 432,814 km , or 21.3% of the original vegetation, remains intact today. During the last 25 years this biome has been increasingly threatened by industrial monoculture farming, particularly soybeans,

2774-421: The Cerrado 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. The large fraction of private ownership makes protection difficult though. The Cerrado's climate is typical of the wetter savanna regions of the world, with a semi-humid tropical climate . The Cerrado

2847-592: The Cerrado. Among the most diverse families of trees in the Cerrado are the Leguminosae  (153 spp.), Malpighiaceae  (46), Myrtaceae  (43), Melastomataceae  (32), and Rubiaceae  (30). Much of the Cerrado is dominated by the Vochysiaceae (23 species in the Cerrado) due to the abundance of three species in the genus Qualea . The herbaceous layer usually reaches about 60 cm in height and

2920-499: The East African savannas, Acacia , Combretum , baobabs , Borassus , and Euphorbia are a common vegetation genera. Drier savannas there feature spiny shrubs and grasses, such as Andropogon , Hyparrhenia , and Themeda . Wetter savannas include Brachystegia trees and Pennisetum purpureum , and elephant grass type. West African savanna trees include Anogeissus , Combretum , and Strychnos . Indian savannas are mostly cleared, but

2993-513: The Northern Territory, Australia savanna, and 480,000 ha of savanna were being cleared annually in Queensland in the 2000s, primarily to improve pasture production. 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

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3066-534: The Southeast Region has forced agriculture to the Central-West Region. The transfer of the country's capital to Brasília has been another focus of attraction of population to the central region: From 1975 until the beginning of the 1980s, many governmental subsidy programs were launched to promote agriculture, with the intent of stimulating the development of the Cerrado region. As a result, there has been

3139-512: The birds in the Cerrado, especially those found in closed forest, are related to species from the Atlantic rainforest and also the Amazon rainforest. The crowned solitary eagle , hyacinth macaw , toco toucan , buff-necked ibis , dwarf tinamou , and Brazilian merganser are examples of birds found in the Cerrado. Gallery forests serve as primary habitat for most of the mammals in the Cerrado, having more water, being protected from fires that sweep

3212-415: The court of the cacique Carlos in present-day Panama . The accounts are inexact, but this is usually placed in present-day Madugandí or at points on the nearby Guna Yala coast opposite Ustupo or on Point Mosquitos . These areas are now either given over to modern cropland or jungle . Many grassy landscapes and mixed communities of trees, shrubs, and grasses were described as savanna before

3285-494: The diminishing vegetation in the Cerrado, they now are receiving some charcoal from the eucalyptus plantations and these efforts are growing. The Cerrado biome is strategic for the water resources of Brazil. The biome contains the headwaters and the largest portion of South American watersheds (the Paraná-Paraguay, Araguaia-Tocantins, and São Francisco river basins) and the upper catchments of large Amazon tributaries, such as

3358-555: The ecosystem appears to be the result of human use of fire. For example, Native Americans created the Pre-Columbian woodlands of North America by periodically burning where fire-resistant plants were the dominant species. Aboriginal burning appears to have been responsible for the widespread occurrence of savanna in tropical Australia and New Guinea , and savannas in India are a result of human fire use. The maquis shrub savannas of

3431-433: The establishment of a highly mechanized, capital intensive system of agriculture. There is also a strong agribusiness lobby in Brazil and in particular, the production of soybeans in the Cerrado is influenced by large corporations such as ADM, Cargill and Bunge, these latter two directly associated with the mass deforestation of this biome. One issue with expanding this reserve is that research needs to be done to choose

3504-467: The establishment, growth and survival of plant species and in turn can lead to a change in woodland structure and composition. That being said, impact of grazing animals can be reduced. Looking at Elephant impact on Savannas, the overall impact is reduced in the presence of rainfall and fences. Large areas of Australian and South American savannas have been cleared of trees, and this clearing continues today. For example, land clearing and fracking threaten

3577-829: The extremely uncommon Dusky babbler (Turdoides tenebrosus) especially at Lake Dipa, Black-rumped waxbill (Estrilda troglodytes) in the rank grass along streams and swamp edges, Violet wood hoopoe (Phoeniculus damarensis) , Allen's gallinule (Porphyrio alleni) , Striated heron (Butorides striatus) also at Lake Dipa, and in riverine contexts Egyptian plover (Pluvianus aegypticus) , Pel's fishing owl (Scotopelia peli) , and snowy-crowned robin-chat (Cossypha niveicapilla) . Other animals that are interesting to find are Lion , Leopard , Lelwel Hartebeest , Beisa oryx , Hippopotamus , Cape Buffalo , Cheetah , Giraffe , Gerenuk , Hyena , African Wild Dog , Warthog , Nile Crocodile , Zebra , and African Elephant . Different stages of woody plant encroachment were identified at

3650-447: The first indigenous peoples occupying different regions in the Cerrado. Many groups among the indigenous were nomads and explored the Cerrado by hunting and collecting. Others practiced coivara agriculture, an itinerant type of slash-and-burn agriculture . The mixing of indigenous, quilombola maroon communities, extractivists, geraizeiros (living in the drier regions), riverbank dwellers and vazanteiros (living on floodplains) shaped

3723-483: 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. Since stock carrying capacity is strongly correlated with herbage yield, there can be major financial benefits from

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3796-532: The landscape and having a more highly structured habitat. Eleven mammal species are endemic to the Cerrado. Notable species include large herbivores like the Brazilian tapir and Pampas deer and large predators like the maned wolf , cougar , jaguar , giant otter , ocelot and jaguarundi . Although the diversity is much lower than in the adjacent Amazon and Atlantic Forest, several species of monkeys are present, including black-striped capuchin , black howler monkey and black-tufted marmoset . The insects of

3869-400: The late 1990s, between 14 million and 16 million tons of lime were being poured on Brazilian fields each year. The quantity rose to 25 million tons in 2003 and 2004, equaling around five tons of lime per hectare. This manipulation of the soil allowed for industrial agriculture to grow exponentially in the area. Researchers also developed tropical varieties of soybeans , until then

3942-576: The location of these reserves because the Cerrado biome is floristically very heterogeneous and constitutes a biological mosaic. Teams from the University of Brasília , CPAC and the Royal Botanic Garden Edinburgh have been collaborating on this project for a number of years supported by Brazilian, European Community and British funds. The project has recently been expanded into a major Anglo-Brazilian initiative, Conservation and Management of

4015-554: The lower limits of savanna tree coverage as 5–10% and upper limits range as 25–80% of an area. 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 . The distinction between woodland and savanna

4088-461: The middle of a word, is pronounced almost like an English v; hence the change of grapheme when transcribed into English. The word originally entered English as the Zauana in a description of the ilands of the kinges of Spayne from 1555. This was 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,

4161-425: 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 oversimplified assumptions resulted in a tropical savanna classification concept which considered it as a "climatic climax" formation. The common usage to describe vegetation now conflicts with

4234-498: The national park, mainly linked to fire suppression. The park's perhaps best-known attraction is the Mursi people , known for piercing their lips and inserting disks made of clay. Areas along the lower Omo (within the park) are populated with a rich diversity of ethnic groups, including the Aari , Banna , Bongoso , Hamar , Karo , Kwegu , Male and Mursi peoples . This article about

4307-469: The open structure of savannas allows the growth of a herbaceous layer and is commonly used for grazing domestic livestock. 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 plant encroachment . 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

4380-476: The park's area. The largest trees are found in the riverine forest beside the Omo, Mago and Neri. In this park, the main biomes or landforms are Savanna , Acacia trees, Shrubland , and also Woodland . Mago National Park affords protection to 74 species of mammals and 237 species of birds. At least 10 species of reptiles and 14 species of fish are also found within the park's ecosystem. Indigenous bird life includes

4453-438: 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. Other plant species include: white sage, spotted cactus, cotton seed, rosemary. Human induced climate change resulting from

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4526-412: The production of cellulose pulp for the paper industry, with the cultivation of several species of eucalyptus and pines , but as a secondary activity. Coffee produced in the Cerrado is now a major export. Charcoal production for Brazil's steel industry comes in second to agriculture in the Cerrado. They actually are quite intertwined. When land is being cleared to make more land for agriculture,

4599-431: The removal of trees, such as assisting with grazing management: regions of dense tree and shrub cover harbors predators, leading to increased stock losses, for example, while woody plant cover hinders mustering in both sheep and cattle areas. 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

4672-580: The reserved ones feature Acacia, Mimosa , and Zizyphus over a grass cover comprising Sehima and Dichanthium . The Australian savanna is abundant with sclerophyllous evergreen vegetation, which include the eucalyptus , as well as Acacia, Bauhinia , Pandanus with grasses such as Heteropogon and kangaroo grass (Themeda). Animals in the African savanna generally include the giraffe, elephant, buffalo, zebra, gnu, hippopotamus, rhinoceros, and antelope, where they rely on grass and/or tree foliage to survive. In

4745-449: The same region. 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 , though mostly a transition between desert to forest. Savanna covers approximately 20% of the Earth's land area. Unlike

4818-404: The savanna-like cerrado itself on well-drained areas between strips of gallery forest (closed canopy tall forest) which occur along streams. Between the cerrado and the gallery forest is an area of vegetation known as the wet campo with distinct up- and downslope borders where tree growth is inhibited due to wide seasonal fluctuations in the water table. The savanna portion of the Cerrado

4891-515: 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. 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

4964-606: The spread of weeds in savannas by the removal or reduction of the plants which would normally compete with potential weeds and hinder establishment. 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 species). 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

5037-519: The structure of woodlands and geographic range of numerous woodland species. It has been suggested by many authors 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. The introduction of exotic pasture legumes has also led to

5110-463: 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. 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. Grazing also promotes

5183-419: The tree's trunks and roots are often used in the production of charcoal, helping to make money for the clearing. The Brazilian steel industry has traditionally always used the trunks and roots from the Cerrado for charcoal but now that the steel mills in the state of Minas Gerais are among the world's largest, it has taken a much higher toll on the Cerrado. However, recently because of the conservation efforts and

5256-483: The unregulated expansion of industrial agriculture, the burning of vegetation for charcoal and the development of dams to provide irrigation are drawing criticisms and have been identified as potential threats to several Brazilian rivers. This industrial farming of the Cerrado, with the clearing of land for eucalyptus and soy plantations, has grown so much because of various forms of subsidy, including very generous tax incentives and low interest loans. This has resulted in

5329-665: 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

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