Savannas can form in areas with a five to eight month wet season, but they more commonly have a longer wet season. | Soil stress caused by drought, extreme moisture, or low nutrient levels favors the formation of savannas. | Studies conducted in various regions indicate that an upper layer of white, sandy, soil is present in most permanent savannas. | Drought stress affects trees and shrubs in savannas far less than it affects savanna grasses. | Frequent fire is a major factor contributing to the formation and maintenance of savannas. | In some areas, human cutting and burning is associated with savanna formation, and increase in pastureland had led to savanna expansion. |
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