Savanna , also savannah is a tropical grassland with a scattering of shrubs and small and large trees. Savannas may result from soil conditions, from periodic fires caused by lightning or srt by humans or climatic influences.
Climatically determined savannas, as found in western and southwestern Africa, develop in regions with marked wet and dry seasions where rainful ranges from 100 and400mm a year.These savannas vary from opencanopied forests with a grassy understory to true savannas in which grasses are dominant. When the rainfall is 100to 200mm, generally only grasses can survive the dry seasion.When rainfall reaches 300mm enough water is left to support exceeds 400 mm enough moisture remains during the dry season to allow trees to grow more densely from a canopy shading out the grasses.
Soil determined savannas include the iianos of Venezuela and the campos cerrados of brazil. the latter are characterized by hard crust in the soil formed by feeric oxides.Grasses grow in the soil above the crust trees grow where roots folloing cracks in the crust can reach deeper ground water.
Climatically determined savannas, as found in western and southwestern Africa, develop in regions with marked wet and dry seasions where rainful ranges from 100 and400mm a year.These savannas vary from opencanopied forests with a grassy understory to true savannas in which grasses are dominant. When the rainfall is 100to 200mm, generally only grasses can survive the dry seasion.When rainfall reaches 300mm enough water is left to support exceeds 400 mm enough moisture remains during the dry season to allow trees to grow more densely from a canopy shading out the grasses.
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