A savanna is a mixed woodland-grassland ecosystem characterised by the trees being sufficiently widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to support an unbroken herbaceous layer consisting primarily of grasses.

Savannas maintain an open canopy despite a high tree density. It is often believed that savannas feature widely spaced, scattered trees.

However, in many savannas, tree densities are higher and trees are more regularly spaced than in forests.

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