Savanna Biome

The savanna biome is usually associated with the tropical wet-dry climate of Africa and South America.

Its vegetation ranges from woodland to grassland. In savanna woodland, the trees are widely spaced because there is not enough soil moisture during the dry season to support a full tree cover.

The open spacing lets a dense lower layer develop, which usually consists of grasses. The woodland has an open, park-like appearance. Savanna woodland usually lies in a broad belt adjacent to equatorial rainforest.

In the tropical savanna woodland of Africa, the trees are of medium height. Tree crowns are flattened or umbrella-shaped, and the trunks have thick, rough bark. Some species of trees are xerophytic forms— adapted to the dry environment with small leaves and thorns.

Others are broad-leaved deciduous species that shed their leaves in the dry season. In this respect, savanna woodland resembles monsoon forest.

Fires occur frequently in the savanna woodland during the dry season, but the tree species are particularly resistant to fire.

Many geographers think that periodic burning of the savanna grasses keeps forest from invading the grassland. Fire doesn’t kill the underground parts of grass plants, but it limits tree growth to fire-resistant species.

So, many rainforest tree species that might otherwise grow in the wet-dry climate regime are suppressed by fires. Browsing animals also kill many young trees, helping maintain grassland at the expense of forest.

In Africa, the savanna woodland grades into a belt of thorntree-tall-grass savanna, a formation class transitional to the desert biome.

The trees are largely of thorny species. They are more widely scattered, and the open grassland is more extensive than in the savanna woodland.

One characteristic tree is the flat-topped acacia. Elephant grass is a common species. It can grow to a height of 5 m (16 ft) to form an impenetrable thicket.

Savanna biome vegetation is described as rain-green. That’s because the thorntree-tall-grass savanna is closely identified with the semiarid subtype of the dry tropical and subtropical climates.

In the semiarid climate, soil-water storage is only enough for plants during the brief rainy season. After rains begin, the trees and grasses quickly green up. Vegetation of the monsoon forest is also raingreen.

The African savanna is widely known for the diversity of its large grazing mammals. With these grazers come a large variety of predators—lions, leopards, cheetahs, hyenas, and jackals. Elephants are the largest animals of the savanna and adjacent woodland regions.

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