Savannas are grasslands covered with perennial plants including grasses and shrubs and are identified by the amount of tree cover they have. An area is designated a savanna if less than half of it is covered by trees. There are several types of savannas including grass; tree, such as an oak savanna, and shrub, and savannas are further classified into how they were formed, such as tropical, which occur in warm, humid climates; edaphic, which occur when the soil is thin and derived or man-made. Vegetation in savannas is determined by climate and region, so tree savannas found in different parts of the world will contain plants native to that region.
Grass savannas are found in eastern Africa, Australia and the Llanos in Venezuela and Colombia and both are considered tropical savannas, according to the University of California Museum of Paleontology. The shrubs found in Africa include forbs, small, flowering, broad-leafed plants that grow with the grass. Shrubs found in the Llanos savanna include melastomataceae, which are small flowering shrubs.
Examples of tree savannas include the cerrado savanna in Brazil, pine savannas in the Ozarks and oak savannas in the Midwestern United States. Shrubs found in the cerrado include several small flowering plants such as leguminosae, malpiphiaceae, myrtaceae, melastomaceae, rubiaceae and qualea grandiflora, which is used in folk remedies, according to "The Cerrado Biome in Central Brazil--Natural Ecology and Threats to its Diversity," by Nadja Schmidt.
In the pine savannas of the American south, native shrubs such as titi thicket, buckwheat tree, gallberries and bayberries thrive.
Shrubs found in the oak savannas of the Midwest include native plants such as wild plum, sand cherry, black cherry, smooth sumac and gray dogwood, according to OakSavannas.org.
An example of a shrub savanna is found in Namibia, which is covered in thornbush, and several places in the United States including the Rio Grande Plains and the Balcones escarpment in Texas. Native shrubs on the Rio Grande plains include Mexican trixis, skeletonbush, Mexican caesalpinia, desert yaupon, low croton and yellow sophora, according to the NativePlantProject.com.
In the Balcones, native shrubs such as sedges, bundleflowers, prairie clover, laurels and creepers, are prevalent, according to "Plants of the Balcones Preserve," by the Balcones Canyonlands Partners.