Savanna Biome

The Savanna biome is part of a larger grassland biome and is mainly made up of flat grassland vegetation. With the exception of Antarctica, the grassland biome is present in all continents and spans over 20% of the earth’s surface. From this biome comes the Savanna biome, also called tropical grassland and the temperate grassland.

Despite these different features, the two biomes have a common thing, which is grass that sustains the ecosystem, thus the name ‘grassland.’ The Savanna biome is characterized by dominant ground cover by grass species and scattered trees and shrubs.

Savanna-biome

Location

The Savanna biome is Tropical grassland. It is located between the two topics, the Tropic of Cancer to the north and the Tropic of Capricorn to the south. The area between the tropics is what is known as the tropical grasslands. The biome covers over half of Africa, most of South America and portions of Asia such as India. For instance, in Africa, the biome has its presence mostly in the Eastern part, which includes Kenya and Tanzania.

Acacia savannas are mostly spread in the region. These biomes have provided habitat for various wild animals leading to the establishment of animal game parks and reserves. Notable ones are the Maasai Mara in Kenya and the Serengeti in Tanzania. These two are home to one of the most unique animal migrations of the world.

Climate

The climate of this biome varies with the pre-existing season. There are two distinct seasons consisting of a wet and a dry season. The wet season comes during the summer period while the dry season comes during the winter. The climate during the dry season is disastrous to animal and plant life since most plants wither and dry up, leading to no food for the animals.

Most of the rain in the Savanna biome is from the wet season. With the warmth of the Savanna, there is more rainfall. Also, there is the sprouting of healthy plants owing to the presence of adequate water. Rivers flow, and ponds of water fill with water.

The two seasons of the biome are the key in determining precipitation in the ecosystem. There are two major rainy seasons per annum. The dry season experiences lower rainfall of about 4 inches per annum for a period of 4 months spanning from October to January. On the other hand, the wet season with an average height of 25 inches provides a lot of rainfall for the biome.

This results in the presence of constant precipitation regardless of the intensity means and, consequently, adequate water for plant life and animal life all year long. Despite the presence of two dominant seasons, there are other predisposing factors preventing equal rainfall all over the Tropical grasslands. The distance from the Equator contributes a lot to precipitation fluctuations.

The area that lies around the Equator is characterized by equal days and nights. This means that for areas far away from this latitude, there are either longer nights and shorter days or longer days and shorter nights. Again, due to the long spells of months without enough rainfall, there are occurrences of drought in the biome.

The climate of the Savanna is gradually changing for the worst. Human interference of the original grasslands has led to a lot of destruction of the ecosystem as well as the reduction of forest cover due to deforestation. In some areas, it has led to desertification, thus changing the climate of the place.

Overgrazing and artificial fires have also contributed to a lot of harm to the Savanna biome. Nonetheless, these fires do not always negate the soil or plant life. For sure, they destroy habitats and scorch both animal and plant life, but they also help in the regeneration of grass every year. Also, they regulate plant life and animal population to ensure balance in the ecosystem.

Temperature

The Savanna biome has an average temperature of 25oC. It goes as high as 30oC during the summer and as low as 20oC during the winter, annually. Because of the slight temperature changes within the ranges of just between 20oC and 30oC in the Savanna biome, it is easy for the animals and plants to adapt.

Though there are only two seasons in the biome, the dry season can be further divided into two due to the range in temperatures. The first one is the cold, dry season characterized by high mid-day temperatures of about 29oC but experiences lower temperatures of about 21oC during the night. The second dry season is the warm, dry season, which experiences day temperatures of 32oC to 38oC. This is caused by the nature of the rays of the sun, which are close to vertical, thus the high temperatures.

Soil

The soil in the savannah is not very fertile and only has a thin layer of humus, which is made up of decomposed plant and animal matter. It is porous, which means the water drains away very quickly. Soils tend to be red in color due to their high iron content.

The humus gives the plants nutrients. The nutrients in the soil are found near the surface as they come from decayed organic matter (vegetation) from the previous growing season. This organic matter decays rapidly due to the high temperatures. There are four layers of soil in savanna grassland. The first layer is of humus. Second is the hardpan of laterite, the third is red clays, and re-deposited silica and the fourth is bedrock. Plant roots cannot penetrate the hard ‘pan’ layer in or subsoil. This restricts vegetation growth.

There are generally 6 types of soils in the savannahs around the world.

  • Lithosols – these are not very fertile and consist of mostly stones and gravel.
  • Lateritic – these soils have an iron content, which makes the soil look reddish. It is also not very fertile.
  • Cracking clays – this soil can hold a lot of water but dries out and cracks easily. It is difficult to cultivate because heavy machinery is needed to dig the soil.
  • Red yellow earths – red earth is dry and yellow earth is not very fertile.
  • Saline and alluvial – this is the soil found near waterways and estuaries. It is the most fertile of the soil types in the savannah.
  • Deep sands – this is very sandy soil and hardly fertile at all. They are nearer to the desert biome

Plants

Plantlife in the Savanna is vastly adapted to cope with the climate. There are a variety of plant species in this biome, both tree and grass species. Trees and grasses grow in the biome. These grasses grow to heights of as low as 80cm to as high as 350cm. There are also serious environmental weeds amongst the woody plant species.

Plants

  • Acacia
  • Baobab
  • Pine
  • Palm

Weed

  • Prickly Acacia (Acacia nilotica)
  • Rubbervine (Cryptostegiagrandiflora)
  • Mesquite (Prosopis spp.)
  • Lantana (Lantana camara and L. montevidensis)
  • Prickly Pear (Opuntia spp.)

Grass

  • Rhodes grass
  • Red oat grass
  • Lemongrass
  • Star
  • Buffel grass (Cenchrusciliaris)
  • Giant rat’s tail grass (Sporoboluspyramidalis)
  • Parthenium (Partheniumhysterophorus)
  • Stylos (Stylosanthes spp.)
  • other legumes

Other

  • White sage
  • Spotted cactus
  • Cottonseed
  • Rosemary

In as much as the Savanna biome is grassland, there are areas in the biome with open patches devoid of grass. During the dry season, the grasses take on a brown desert-like color, probably due to low photosynthesis. All the same, when seasons change, and it is humid again, they turn green. Plus, there are a few vast spaces that favor the scattered growth of shrubs. The trees grow to an average height of 6m.

Plants in this biome have developed long taproots constituting a hydrophilic root system that is able to extend deeper in the soil in search of water. They have large tree trunks for storage of excess water when there is adequate water in the biome to prepare for the dry seasons. Their barks are hardened and thick and are prone to wildfires in the forests. Wildfires easily spread in the Savanna biome due to the vast presence of grass.

The leaves of the plants are deciduous and fall during the winter season. Since leafy plants are at risk of losing a lot of water to the atmosphere through transpiration, they shed their leaves once in a season in an effort to conserve water.

girraffe-zebra-savanna-biome

Animals

Savanna biome is one of the most diverse biomes in terms of animals. It’s not only aided by the vastness of the tropical grassland but also the varying change in the climate. This biome supports one of the world’s most renowned species of animals.

Herbivores

  • zebras
  • gazelles
  • warthogs
  • elephants
  • kangaroo
  • rhinoceroses
  • hippos
  • buffalo
  • baboons
  • antelopes
  • crocodiles
  • meerkats
  • snakes

Carnivores

  • lions
  • cheetahs
  • hyenas
  • leopards

Birds

  • parrots
  • parakeets
  • kingfishers
  • finches
  • ostriches

Insects

  • ants
  • termites

Most of these animals are found in the African Savanna. The South American Savanna has fewer mammals but has more bird species. Also, it is only in the Australian Savanna that hosts mammals such as the kangaroos. Overall, the Savanna biome is home to thousands of insect species that attract birds for feeding and nesting.

The carnivore population grows exponentially during the rainy season. The reason being, the rainy season leads to more grass growth in the Savanna leading to more reproduction of the herbivores. As keystone species, carnivores such as lions and cheetahs have to be present in the ecosystem in order to strike a balance in the biome.

They prevent incidences of overgrazing that can arise due to the overpopulation of prey species like the gazelles and zebras. In spite of a large number of animals in the biome, there is always enough food for all, especially for the herbivores. Each of these animals has developed uniquely different feeding habits that reduce competition for food.

For instance, giraffes feed on the top vegetation on trees that other animals such as the zebra cannot reach. Elephants feed on leaves from shorter trees. Zebras feed on shrubs and tall grasses, while wildebeests and gazelles feed on medium and short grasses, respectively. It is for this reason that these groups of animal species can be found in the same area, feeding without competing for food.

The dry season leads to loss of water through evaporation and transpiration. Consequently, there is inadequate drinking water for animals, and the soils are dry and cracked due to extensive loss of water. With no means of plant growth, herbivores start reducing in number. Carnivores may increase slightly due to abundant food.

Due to the fluctuation in climatic levels, animals migrate in search of food. They may migrate to very far places to search for water and pasture. The migration varies among animals. There are some that migrate only to come later when the rainy season is back while others migrate never to return. Again, there are those that move during the rainy season.

References:
Blueplanetbiomes , Sciencing

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