Effects and use of fire in southern African Savannahs

Fire is the most widespread ecological disturbance in the world second to human activities related to urban living and agricultural production. Therefore it cannot, and should not, be ignored when considering the management of rangeland for both wildlife and domestic livestock systems. This is particularly pertinent to African savannahs where fire can have a very significant effect on the botanical composition and structure of savannah vegetation, particularly when combined with the impact of herbivores. The ability of African savannahs to support fire is because they are highly prone to lightning storms and have an ideal fire climate comprising a distinct wet season when plant materials can grow and accumulate, and a dry season when they become highly flammable plant fuels. the effect of fire on savannah vegetation depends upon the type and intensity of fire, and the season and frequency of burning i.e.e fire regime. The most common types of fire are surface fires, burning either as head or backfires. Head fires have the least depressive effect on the recovery of grass sward, but cause the highest top-kill of stems and branches of trees and shrubs as compared to back-fires. Fire intensity has no significant effect on the recovery of the grass sward and the mortality of trees and shrubs. Generally, the main effect of fire on woody vegetation is to cause a top-kill of stems and branches forcing the plants to coppice from the collar region of the stem. this effect is positively correlated with fire intensity. The effect of seasonal burning is that fire causes the least damage to the grass sward if applied when the plants are domant, while trees and shrubs are apparently insensitive as to when fires are applied. The frequency of burning has a marked effect of the botanical composition of the grass sward and on the physiognomic structure of trees and shrubs. Conversely, it generally has minimal effect on the density of woody vegetation.