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How are thornbush savannas different from wetter savannas?
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Savanna
A savanna marked with acacia trees in Serengeti National Park, Tanzania. Africa's Serengeti Plain is commonly used as an example of the savanna biome—a hot, seasonally dry ecological region characterized by an open tree canopy (i.e., scattered trees) above an understory of continuous grasses.
Thornbush savannas and wetter savannas are primarily distinguished by the duration of their dry season and the resulting vegetation structure.1
- Dry Season Duration: The length of the dry season is the key factor in categorizing these regions. In wetter savannas, the dry season typically lasts 3 to 5 months, whereas in thornbush savannas, the dry season is significantly longer.1
- Vegetation Characteristics: Wetter savannas support more vigorous plant growth, often featuring taller grasses and a more prominent tree component. For example, in wetter regions, trees such as Brachystegia may grow above a tall understory of elephant grass. In contrast, thornbush savannas are characterized by a higher prevalence of spiny, drought-adapted shrubs and thorny trees, such as Acacia and Mimosa, which are adapted to minimize water loss.123
- Adaptations: Plants in thornbush savannas often exhibit specialized traits to survive prolonged aridity, including small, leathery leaves, deep root systems to access groundwater, and the ability to shed leaves seasonally.3