Tropical Savanna ≠ Lush Forest: Grassland with Scattered Trees

Defining the Savanna Biome

No. Lush, closed-canopy forests are not characteristic of tropical savannas.

Savanna Structure

• Continuous grass layer (C4 grasses: 2–4 m tall)
• Scattered trees/shrubs (10–30% canopy cover)
• Tree adaptations: Thick bark, deep roots, deciduous in dry season (acacia, baobab, Terminalia)

Why Not Forest?

• Fire: Annual dry-season fires kill tree seedlings, maintain grass dominance
• Herbivory: Grazers/browsers suppress woody regeneration
• Seasonal drought: 4–8 months without rain favors grasses' deep roots
• Soil: Often lateritic, nutrient-poor, hardpan layers limit rooting

Forest Patches Exist

Gallery forests along rivers, termite mounds, fire refugia—but these are azonal (site-specific), not the savanna matrix.

Contrast

• Tropical rainforest: Closed canopy, multi-story, no fire, evergreen
• Savanna: Open canopy, grass-fueled fire, deciduous, seasonal

The savanna-forest boundary is dynamic—fire suppression or CO₂ fertilization can shift it toward woodland.