Secondary forest

Secondary forest is a woodland area which has re-grown after a major disturbance such as fire, insect infestation, timber harvest or wind throw. Secondary forest tends to have trees closer spaced than primary forest and contain more undergrowth. Secondary Forests typically have with less biodiversity than old growth forests. Usually, secondary forests have only one canopy layer, whereas old growth forests have several.

Secondary forestation is common in areas where forests have been lost by the slash-and-burn method, a component of some shifting cultivation systems of agriculture. Secondary forests may also arise from forest that has been harvested heavily or over a long period of time, forest that is naturally regenerating from fire and from abandoned pastures or areas of agriculture. It takes a secondary forest typically forty to 100 years to begin to resemble the original old-growth forest; however, in some cases a secondary forest will not succeed, due to erosion or soil nutrient loss in certain tropical forests.

Secondary forests re-establish by the process of sucession. Openings created in the forest canopy allow sunlight to reach the forest floor. An area that has been cleared will first be colonized by pioneer species. Even though some species loss may occur with primary forest removal, a secondary forest can protect the watershed from further erosion and provides habitat. Secondary forests may also buffer edge effects around mature forest fragments and increase connectivity between them. They may also be a source of wood and other forest products.

Today most of the forest of the United States, the eastern part of North America and Europe consist of secondary forest.