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How do fires help maintain the balance of grasses and trees in a savanna?
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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.
Fire is a fundamental driver in maintaining the balance between grasses and trees in savanna ecosystems by preventing the encroachment of woody plants. Because savannas are characterized by a continuous grass cover, dry-season fires—fueled by dead grasses and leaf litter—frequently occur.123
These fires help regulate vegetation structure in several ways:
- Selective Pressure: Frequent burning kills fire-sensitive trees and young saplings, which prevents the landscape from reverting to deciduous forest.23
- Adaptation: Many savanna trees have evolved to survive these fires once they reach a certain size, often by developing thick, corky bark that protects their trunks from heat.12
- Regeneration: Fire promotes the growth of grasses and certain plants that can quickly regenerate from underground buds, seeds, or shielded structures after the surface vegetation is scorched.12
Without the regular disturbance of fire, many savanna areas would transition into denser forests, as seen in protected plots where trees and shrubs quickly dominate the landscape.2