bio savanna

8/14/2019 Bio Savanna

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Donna Mariel Calimpong

Milcah Ethiel Corona

Jean Tolentino


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Savanna is grassland with scattered individual trees.Savannas of one sort or another cover almost half the surfaceof Africa (about five million square miles, generally central

Africa) and large areas of Australia, South America, and India.

Climate is the most important factor in creating a savanna.Savannas are always found in warm or hot climates where the

annual rainfall is from about 50.8 to 127 cm (20-50 inches) per

year. It is crucial that the rainfall is concentrated in six or eight

months of the year, followed by a long period of drought when

fires can occur. If the rain were well distributed throughout the

year, many such areas would become tropical forest.


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The soil of the savanna is porous, with rapid drainage of

water. It has only a thin layer ofhumus (the organic portion

of the soil created by partial decomposition of plant or animal

matter), which provides vegetation with nutrients.

Savannas receive an average annual rainfall of 76.2-101.6cm (30-40 inches). However, certain savannas can receive

as little as 15.24 cm (6 inches) or as much as 25.4 cm (10

inches) of rain a year.

climatic savannas - Savannas which result from climaticconditions edaphic savannas - Savannas that are caused bysoil conditions and that are not entirely maintained byfire. These can occur on hills or ridges wherethe soil is shallow, or in valleys where clay soils

become waterlogged in wet weather.derived savanna - is the result of people clearing forest landfor cultivation.


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Grasses and deciduous trees dominate the savannahlandscape

The rate at which vegetation grows is known as NetPrimary Production

The NPP for arable land is 650g/m2/yr., and thetropical grasslands are estimated to have a mean NPPof 900g/m2/yr.


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Vegetation Sub Zones;

Savannah parkland -

e.g. baobobs, acacia, and eucalyptus,

twisting, branching deciduous trees

Grasses grow beneath trees, adapted to seedand die back at the start of the dry season.


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less dense, and often draw water from an underlying aquiferthrough a long root system.

Savannah grassland

Grasses tend to be tall and coarse in areas of higherprecipitation, more sparse in areas with lessprecipitation.


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vegetation tends to be a discontinuous layer of bushes,e.g. sagebrush and thorns and sparse, dried up tussocksof grass. This zone has experienced the worst effects ofadvancing desertification.

sagebrush tussocks of grass

Savannah scrub


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Characteristics of Savannah Vegetation;

Trees;

Deciduous

Xerophytic

Sclerophyllous

Roots are long and extended to reach deep underground. Tend to grow to 6-12m in height and contain Y shaped

branches. Trunks are gnarled, and bark is thick to retain moisture.


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Example;

The baobob tree has atrunk of up to 10m indiameter. Its root likebranches hold only aminimum number of tinyleaves in order to restricttranspiration. Some areestimated to be

thousands of years old.Their trunks are resistantto the local fires.


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Shrubs/Grasses; Grasses grow in tufts and tend to haveinward curving blades and silvery spikes.

After the onset of the summer rains,

they grow very quickly to over 3m in height.Elephant grass grows to 5m.


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They become yellow by sun drying.

By early winter, the straw like grass has

died down, leaving seeds dormant on thesurface until next years rains.


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There are many different types ofanimals that can be found in TropicalGrasslands.

Herbivores Ostrich


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Even toed ungulates

Ox


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Carnivores

Lion


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Mammals

Cow


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Invertebrates

Beetle


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The animals that live in tropicalgrasslands have adapted to a great deal ofvariability in the food supply throughout the

year; there are times of plenty (during andafter the wet season) and times of almost nofood or water (during the dry season). Manysavanna animals migrate to deal with this

problem.


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During the rainy season, birds, insects, andmammals thrive in the savannah. During thedry season, surface water from the rain isquickly absorbed into the ground because the

soil is extremely porous. Competition for waterduring the dry season is intense. Consequently,most birds and many of the large mammalsmigrate during the dry season in search ofwater.


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During the dry season, lightningfrequently ignites the brown, dry grassesthat cover the savannah. Many of the

animals have adapted to living with thefires. The ability to fly or to run fastenables most birds and large mammals toescape the flames.


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END ^_^

bio savanna

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