Both arid and moist savannas include structural forms ranging from open treeless grasslands to closed-canopy stratified woodlands. Fires sweep most of the central African miombo annually in June or July, often preceding leaf fall and being followed, before the onset of the rains, by the appearance of deeply colored red or purple foliar buds. The presence of high levels of anthocyanins in foliar buds is described from the physiognomically and ecologically similar Brazilian cerrado but is absent in African arid savannas. Trees and shrubs in arid savannas tend to more distinctly deciduous than those of moist savannas, often losing their leaves as early as May and not producing new leaves until September or October. The appearance of both foliar and floral buds usually precedes the onset of rains.
Arid savannas have a high incidence of spinescence, a feature almost absent in moist savannas.
Although spinescence has been related to water economy there is little physiological evidence in support of the suggestion. The absence of strongly spinescent savannas, and past or present high densities of indigenous herbivores in Australia adds to the evidence favoring herbivores browsers as being the causal factor in the evolution of spinescent savannas. It is of interest that heavily overgrazed base rich savannas in Queensland soon become dominated by Maytenus, Canthium, Carissa and other spinescent taxa. The low nutrient value of moist savanna herbagem and hence low herbivore biomass, accounts for the absence or rairity of spinescent forms in this system - such as the cerrado of Brazil, the miombo of Africa and the tropical moist savannas of Northern Territory, Australia. Succulents are common in arid savanna but rare or absent in moist savannas.