Wind, occasionally

in the form of tornadoes or severe thunderstorms, knock down trees, returning

a site to an early successional stage. The removal of larger trees in

a forest releases the understory speeding up or slowing down secession.

Wind also disperses seeds over long distances, and when added to the creation

of open space can greatly change the species composition of a forest.

Animals can influence the species makeup of a forest. Large grazing and

browsing animals have a more serious direct impact, while smaller mammals

do not. Insects and diseases can have an even more devastating impact,

from killing just a few trees to wiping out entire forests.

Natural fires

(lightning) usually account for about one percent of all fires in Georgia.

Low intensity, repeated fires create and maintain a thin canopy of fire

resistant trees and fire tolerant vegetation, resulting in a savanna or

woodland situation. Less frequent fires are more intense and have a regenerating

effect on a forest. Without fires to reduce fuel buildups, fires burn

hot and can kill trees. Severe fires can destroy ground litter and humus

and set a forest