The bed sheets They are ecosystems with a tropical to subtropical climate, in which grasses abound and there are few trees and shrubs. They are part of the so-called grasslands next to the meadows, differing from these by climate and species composition. The rainfall, fertility and permeability of soils is what determines the presence of savanna instead of tropical forest.
Savannas are distributed throughout much of tropical and subtropical America, from southern North America to South America. We find them in large areas of sub-Saharan Africa, from the Atlantic Ocean to the Indian Ocean..
Similarly, there are savannas in the foothills of the Himalayas, in northern and eastern Australia, and in Hawaii. These plant formations have a simple structure with a herbaceous cover dominated by grasses and some scattered trees..
Savannas develop in variable soil conditions from sandy loam to clay. Among the factors that affect the ecology of these ecosystems are fires (natural and man-made) and herbivory.
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The geographical delimitation of the savannas is framed in the intertropical zone, conditioned by climatic and edaphic factors (soils). Savannas develop in low tropical areas, with high average temperatures and low total rainfall.
Savannas have a simple structure, where trees only appear sparsely and are even absent in large areas. The dominant stratum is the herbaceous cover, mainly composed of grasses, with some subshrubs and shrubs.
The grass cover can have a height from 0.20 to 3 m. while in the wooded savannas the trees have heights between 5 and 15 m.
Although in the savannas soils are variable, in most cases they are loamy-sandy, clay-sandy to clayey. In well-drained savannas, entisol and oxisol soils predominate; while in poorly drained savannas there are mainly vertisols and alfisols.
There are also regional peculiarities such as the volcanic ash soils of the Serengeti in Tanzania.
Fires are a characteristic component of the savannas, being both natural and human-caused. The grasses that dominate the savanna have developed adaptations that allow them to survive burning.
These periodic burns allow the renewal of biomass to the extent that it promotes the emergence of new grass shoots.
Savannas, like all herbaceous biomes in the world, have developed a process of coevolution between herbivores and herbs. Herbivores have specialized to reduce competition and some consume mainly grass while others browse the leaves of scattered trees.
The human being has caused great negative impacts on the savannas, especially with agriculture, farming and hunting. In some cases, it has expanded the limits of the ecosystem by deforesting bordering forests that are transformed into secondary savannas..
In others, the limits of the natural savanna are reduced by dedicating extensions to the cultivation of cereals or the raising of cattle.
Hunting has been the main cause of the decline in large herbivore populations in the savannas. For example, the intensification of hunting with the arrival of Europeans in Africa, substantially reduced the fauna in the Guinean and Sahelian savannas..
Savannas exist in different regions of the Earth:
We find savannas in America from southern North America to northern South America in Colombia and Venezuela. The most representative being the Colombian-Venezuelan plains and the Guayanese savannas that limit the Amazon and the Guiana jungle to the south..
Then there is the Cerrado, stretching through central Brazil, northeastern Paraguay, and eastern Bolivia. There is also an extensive savanna from Rio Grande do Sul (Brazil), all of Uruguay and even part of Entre Ríos (Argentina).
In Africa the savannah extends in a wide strip below the Sahara desert, from the Atlantic to the Indian Ocean, in what is known as the Sahel. To the south are savannas up to the edge of the Congo jungles and another area that includes the wooded savannas of Zimbabwe.
In the Indomalaya region are the Terai-Duar savannas, in the foothills of the Himalayas. This tall grass savanna spans Bhutan, India and Nepal.
In this region of the world there are savannas in the north and east of Australia as well as shrubby savannas in Hawaii.
The types of savanna can be classified in different ways:
The World Wildlife Foundation o World Wildlife Fund (WWF), identifies up to 50 savanna ecoregions worldwide. Each ecoregion represents a type of savanna defined by some combination of species composition, climate, and soils..
The biotype is the general morphological expression of the plant, of which four basic forms are recognized: grass, subshrub, shrub and tree. In the savanna the predominant biotype is grass, although there are savannas with scattered trees or with shrubs and subshrubs.
In this sense, we speak of non-wooded savannas, shrubby savannas and wooded savannas. For example, the non-wooded savannas of the Gran Sabana in Venezuelan Guiana.
On the other hand, the bush savannas of northwestern Tanzania or the wooded miombo savannas of the central Zambezi from Tanzania to Angola.
Another criterion for classifying savannas is the water regime; thus there are floodable and non-floodable savannas. For example, in the Colombian-Venezuelan plains there are savannas associated with the course of large rivers that flood in the rainy season..
In this case we speak of seasonal savannas, hyperstational savannas and semi-seasonal savannas given by the duration of the dry and rainy seasons. The seasonal savannas alternate a rainy season of 6-8 months with a dry season of 4-6 months, have well-drained soils and do not flood.
Hyperstational savannas have poorly drained soils and are periodically flooded; with a dry season of 3 to 4 months. These savannas actually have four seasons which are the dry season, the rainy season, the flooding season and the rainy season..
On the other hand, semi-seasonal savannas are similar to hyperstational ones, but with a dry season that lasts only a few weeks..
A criterion that is also used to define the types of savannas is the presence of characteristic species due to their abundance or representativeness. Thus, for example, in the Colombian-Venezuelan region they speak of savannas of Trachipogon (not floodable) and sheets of Paspalum fasciculatum (floodable).
Savannas develop in warm tropical and subtropical climates with variable rainfall. In the savannas there are two seasons: a dry period and a rainy or humid one; the duration of one and the other being variable.
In northern South America the dry period lasts from 3 to 5 months and the rainy one from 7 to 9 months. However, in the Australian savannas the relationship is reversed, with 5 months of rainfall and 7 months of drought..
During the dry period, sporadic rainfall does not contribute more than 100 mm. While in the rainy period the rains are intense and long-lasting. The amount of water supplied varies depending on the region, even locally, and can range from 600 to 3,000 mm.
The average annual temperature is around 27 ºC although it is variable in the extension of the biome.
In the Australian savannas, temperatures are high throughout the year with maximums of 25 to 35 ºC. In the Serengeti (Africa) the average maximum temperatures vary from 24 to 27 ºC, and the minimum from 15 to 21 ºC.
The dominant family in the savannas is Poaceae, with an enormous diversity of genera and species. Among the few subshrubs, shrubs and trees, legumes (Leguminosae or Fabaceae) abound.
Species such as Tridens texanus, Tridens muticus, Trichachne hitchcockii, Aristida roemeriana Y Bouteloua radicosa.
On the other hand, in the savannas of the Colombian-Venezuelan plains, species of the genera Trachypogon Y Paspalum. Other genres represented are Axonopus, Andropogon, Leptocoryphium, Sporobolus Y Aristida.
Further south, the Cerrado is the largest savanna region in South America and one of the most biologically rich in the world. Here are species such as Gymnopogon foliosus, Country panicum, Saccharum asperum, and many others.
A representative tree of the American savanna is the chaparro (Byrsonima crassifolia Y Byrsonima coccolobifolia). There are also savannas where the “arboreal” element is palms, for example the plains palm savannas (Copernicia tectorum) In Venezuela.
In the plains, the formation of tree islands in the middle of the savannah is common, associated with conditions of the water table and fertility. These islands are called "matas" and are made up of species of trees and shrubs.
Among the common species in the plain "bushes" are oil (Copaifera officinalis), the carob tree (Hymenaea courbaril) and cane fistula (Cassia grandis).
In the African savannas, short and medium grasslands predominate with species of grasses of the genera Sporobolus, Chloris, Digitaria, Eragrostis, Cynodon, Panicum, Pennisetum, among others. Although there are also taller species such as Hyparrhenia rufa up to 3 m.
In the savannas near the Sahara desert there are typical species of this desert such as Panicum turgidum Y Aristida sieberana. Wooded savannas of tall grasses also develop where the dominant species is elephant grass (Pennisetum purpureum).
Among the trees of the savannas of Africa, the most characteristic species are those of the genus Acacia (legumes). Legumes are rich in protein, being highly desired by species that browse (consume tree leaves), such as giraffes.
One of Africa's savanna ecoregions is the Sahelian acacia savannas, which form a continuous band from the Atlantic Ocean to the Red Sea. Also this ecoregion includes the Sahara desert to the north.
Common tree species in this ecoregion include Acacia tortilis, Acacia laeta, Commiphora africana, Balanites aegyptiaca Y Boscia senegalensis. While to the south of the sahel there are shrubby savannas with a predominance of shrubs of Combretum Y Terminalia.
Likewise, you can find the teak wooded savannas (Baikiaea plurijuga) Zambezi (Zimbabwe).
In the Indo-Malay savannas there are tall grasses with grass species Saccharum spontaneum, Saccharum benghalensis, Arundo donax, Narenga porphyracoma, among other. Low grass savannas are also found with species such as Imperata cylindrica, Andropogon spp. Y Aristida ascensionis.
In the Australian savannas there are grasses of the genera Sorghum, Chrysopogon, Aristida, among others. There are also low grass savannas such as those dominated by the species of Dichanthium spp.
In the case of the Australian savannas, legumes are abundant (Acacia spp., Bauhinia spp., Albizia spp.) and myrtaceae (Eucalyptus spp.). There are also species of the genera Macropteranthes Y Terminalia of the family Combretaceae.
Savannas are home to a large number of animal species, in some cases such as those in Africa with large populations. The abundance of grasses allows the development of large herds of herbivores that attract large predators.
In the savannas of the Colombian-Venezuelan plains the most prominent animal is the capybara or chigüire (Hydrochoerus hydrochaeris). This mammal is considered the largest rodent in the world and lives in the lagoons of the savannas.
Another inhabitant of the savannas is the plains deer or caramerudo deer (Odocoileus virginianus apurensis).
The savannas of America are very rich in birds, including the jabirú (Jabiru mycteria) and the red corocora or scarlet ibis (Eudocimus ruber). Among the birds of prey are the chimachimá or caricare (Milvago chimachima) and the red busardo or red hawk (Busarellus nigricollis).
Among the predators of the capybara are large carnivores that inhabit the savannah. Among them is the jaguar or yaguar (Panthera onca), the largest feline in America.
In the water the green anaconda (Eunectes murinus) and the Orinoco caiman (Crocodylus intermedius). The latter was abundant in the past, but hunting for their skin and meat brought them to the brink of extinction..
The Orinoco caiman is one of the largest crocodiles in the world, reaching up to 7 m in length. For its part, the anaconda is the largest snake in the world, reaching up to 10 m long.
In the rivers and lagoons of the plains there is an abundance of the spectacled caiman or baba (Caiman crocodilus) relatively small in size (1-2.5 m). Also inhabits an ant predator, known giant anteater or palm bear (Myrmecophaga tridactyla).
Among the herbivores of the African savannas, the wildebeest (Connochaetes gnou Y C. taurinus) and zebras (Equus quagga, E. zebra Y E. grevyi). Other grass eaters are gazelles (Gazella spp.) and the savanna elephant (Loxodonta africana).
There are browsers like the giraffe (Giraffa camelopardalis), which consume the leaves of the Acacia. Among the omnivores is the wild pig or string (Hylochoerus meinertzhageni) that consumes herbs, roots, but can also be a scavenger.
The emblematic animal of the savannas of Africa is the lion (Panthera leo). Likewise, there are other felines such as the leopard (Panthera pardus pardus) and cheetah (Acinonyx jubatus).
Other carnivores are hyenas (Crocuta crocuta) and spotted wild dogs (Lycaon pictus), which hunt in packs. Additionally there is the Nile crocodile (Crocodylus niloticus), which stalks herds of wildebeest and zebra on their migrations.
The savannas at the foot of the Himalayas are home to the largest number of tigers, rhinos and ungulates in Asia.
These plant formations constitute the habitat of the Asian elephant (Elephas maximus).
Among the ungulates are the nilgó or blue bull (Boselaphus tragocamelus) and the water buffalo (Bubalus arnee).
The hispid hare (Caprolagus hispidus) is threatened while the dwarf wild boar (Porcula salvania) is critically endangered.
In these savannas lives the one-horned rhinoceros (Rhinoceros unicornis) and the Asian tiger (Panthera tigris) which is the second largest feline in the world.
The fauna of the Australian savannas is not very diverse compared to the other regions of the biome. There is an important diversity of reptiles, including the Ctenotus rimacola.
Similarly, there are small marsupials such as the kangaroo hare (Lagorchestes conspicillatus), the fluted kangaroo (Onychogalea unguifera) and the bronze quat (Dasyurus spartacus).
In the savannas there can be several economic activities:
The soils of the savannas are variable in fertility and water availability, with wide areas useful for agriculture. Sorghum and millet are grown in parts of Africa, while soy, corn, sunflower and sesame are grown in America..
Savannas are ecosystems linked to grazing, which is why they are ideal for extensive livestock rearing. A large part of the savannas of the Colombian-Venezuelan plains have traditionally been dedicated to this activity..
Likewise, dual-purpose cattle and sheep farming mainly for wool in the savannas of Uruguay.
There are protected savannahs such as national parks or fauna reserves and in these areas the main activity is tourism. For example, the national parks of Africa where the famous photographic safaris take place.
A historical activity in the savannas has been hunting, leading to the extinction of many species. In the acacia savannas of the Sahel the huge herds of ungulates were drastically reduced by the hunting of European settlers.
Today, even in protected areas hunting continues. For example, an estimated 200,000 animals are killed within the Serengeti National Park annually in poaching..
Its 13,000 km² extend through the volcanic savannas of the Serengeti in northern Tanzania, near the border with Kenya. It was created in 1951 and shelters acacia wooded savannas in flat plains and rolling areas..
The dominant tree species is acacia (Acacia spp.) of mimosoid legumes. For its part, the predominant plant group is the short and intermediate grasslands of grasses.
Among the dominant species are Sporobolus spp., Pennisetum mezianum, Eragrostis tenuifolia, Andropogon greenwayi Y Panicum coloratum. Are also found Cynodon dactylon, Chloris gayana Y Digitaria macroblephara.
It is home to a huge amount of fauna, both in species diversity and population size. Elephants, wildebeest, giraffes, lions, hyenas, gazelles, rhinos, among others live here.
It is also inhabited by the black rhinoceros (Diceros bicornis) and the kaffir buffalo (Syncerus caffer).
This region is famous for the migrations of huge herds such as the blue wildebeest (Connochaetes taurinus) that reach up to 1.3 million. For their part, Thomson's gazelles (Gazella thomsoni) displace up to 400,000 individuals and Burchell's zebras (Equus burchelli) 200,000.
These animals make a long journey between this area and the ecoregion of the forests of Acacia-Commiphora from the South every year.
It is the land of the Masai, an ethnic group that traditionally practices livestock and agriculture. However, as part of the creation of the park, these natives were transferred to the Ngorongoro Highlands..
For the rest, tourism is a highly developed activity that generates high income for the country. However, there are also illegal activities such as poaching that seriously affects the ecosystem.
Its 5,844 km² extend between the Cinaruco and Capanaparo rivers until the confluence of both with the Orinoco river. It was created in 1988 and is located in the Apure state in southern Venezuela, close to the border with Colombia..
It is a representative area of the flooded savannas of the Colombian-Venezuelan plains, with flat relief, except for some granite elevations.
Grass Paspalum fasciculatum (Chigüirera straw) is the most abundant in these savannas. Other species of the shallows (lower parts) are Imperata contracts (viper) and Leersia hexandra (licking straw).
Then in the highest parts (benches) you will find Andropogon sealanus, Sporobolus indicus (tupuquén), Paspalum plicatulum (gamelotillo), among others. There are some bushes (Ex .: Cassia tetraphylla) and trees (Ex .: Bowdichia virgilioides, the American cork oak).
In these lands live the capybara or chigüire, the jaguar and the caramerudo deer. In the rivers are the Orinoco caiman, the anaconda and the piranhas. As well as the giant otter (Pteronura brasiliensis), the arrau turtle (Podocnemis expansa) and the pink or boto dolphin (Inia geoffrensis).
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