Savannas are characterized as areas connecting the equator forests and tropical deserts, with a wide range of vegetation in grassland, deserts and woodlands. The biggest savannas are in South Africa, occupying 46 percent of the land in that area. Savanna soil types are determined by the climate they occupy, but are typically porous with rapid drainage of water.
Climatic Savanna Soil
As their name suggests, climatic savannas are conditioned by the climate they exist in. Annual rainfall in these areas are 20 to 50 inches and concentrated into six months of the year. As a result, the soil is generally very dry and porous most of the year, contributing to natural fires, which burn the grass and vegetation in the area. Ash from these fires reintegrate nutrients into the soil and make them more fertile for new plant growth. It is through this process that new plant life thrives. Savannas in Africa, Brazil and Australia have areas with this soil type.
Edaphic Savanna Soil
Edaphic savanna conditions are determined by their soil, rather than climatic conditions. The soil is not as dependent on wild fires to restore the nutrient content. This soil type is quite shallow and made up of clay, usually occurring on ridges or in valleys. The clay that characterizes this soil type is capable of becoming water logged in wet conditions, which sustains plant grow. The soil is only capable of sustaining grasses, small shrubs and few trees, becoming more barren during the drier months. Parts of the Australian savanna possess this type of soil.
Derived Savanna Soil
The soil in this savanna type results from human intervention on the land. When people clear fertile land for cattle grazing or crops, derived savannas are formed. Derived savannas are unable to keep up the soil nutrient content because all the vegetation that previously renewed the soil is removed. The soil never truly regains the plant life that existed before it was cleared, only giving life to small grasses. The characteristics of this type of soil are dry, clay-like and eventually becoming sandy. Without root systems, wind displaces the soil within these savannas quickly, leading way to dust storms. Savannas of this type often occur around farming areas in Africa.