Disturbance Patterns

What is it? "Disturbance" refers to environmental changes brought on by fires, floods, volcanic eruptions, storms, winds, insect invasions, and invasions from non-native or exotic species.

Many disturbances are natural such as many fires, storms, and drought. Others are human caused, such as timber harvesting and land development, recreational use, applications of chemical such as pesticides, herbicides, and fertilizers.

At Coweeta LTER scientists study the role of fire in the southern Appalachian Mountains. Forests in this region (and indeed in many parts of the world) depend on this natural disturbance for their health. Fire helps the ecosystem by returning nutrients to the soil, clearing vegetation to allow more light into the forest, and aiding the germination of many plant species.

Scientists at CWT LTER study the impacts of fire as a tool to restore ecosystems, to reduce fuel loads, and to study the recovery of vegetation (tree, shrub, and herb layer). Fire has been suppressed in most of these areas approximately since the 1920s.

	A scientists measures moisture of the downed branches or "fuel" before starting the fire. Studying how the fuel relates to the intensity of the fire and the effect on the biology is an important part of understanding how fire affects the ecosystem.
A prescribed (or human-initiated) burn is started after fuel moisture and fuel loads are measured. Fires are a natural disturbance and are necessary for maintaining the health of the mixed pine-hardwood forest of the southern Appalachian mountains.
After the prescribed burn, the site looks desolate and lifeless.
	A tool called a ‘duff pin’ is inserted into the ground to study how deeply the soil was affected by the fire.
Two years after the prescribed burn, the plant regrowth is green and vigorous. The nutrients released and increased light availability will benefit the ecosystem as plants and animals reclaim the land. Scientists study succession - or the changes in the plant and animal community following a disturbance such as a burn.

4 years after the burn.

In another controlled burn project at Coweeta LTER, scientists are trying to reconstruct he fire regime as it was while Cherokee Indians lived here. The Cherokee burned frequently (every 1 to 5 years) to maintain meadows and an open under storey for game hunting and chestnut gathering.