A primary forest or virgin forest is a forest that is untouched by human influence and is therefore an ecological climax community. The classification as "untouched" depends on the duration of a largely natural development. Traces of human cultivation as terra preta can be found on probably ten percent of the soils in the Amazon, but these are nevertheless considered to be sites of virgin forest.
Primary red beech forest in the Biogradska Gora National Park, Montenegro
A secondary forest or, after massive interventions, initially a secondary vegetation with a varying degree of altered species composition develops after human interventions such as road building, logging, slash-and-burn farming, and multi-story cultivation.
Forests around the world have experienced major changes in terms of their use and characteristics. Depending on the type and intensity of use, replacement communities form within a forest system, which often differ considerably from the naturally cyclical succession of a primary forest.