A savanna, or savannah,'s a tropical grassland ecosystem characterized by the trees being sufficiently small or widely spaced so that the canopy doesn't close. The open canopy allows sufficient light to reach the ground to support an unbroken herbaceous layer consisting primarily of C4 grasses. Some classification systems also recognize a grassland savanna from which trees are absent. This article deals only with savanna under common definition of a grassy woodland with a significant woody pl… (More on Savanna)