[Ancientness and maturity: two complementary qualities of forest ecosystems]. / Ancienneté et maturité: deux qualités complémentaires d'un écosystème forestier.

Ancientness and maturity are two major qualities of forest ecosystems. They are components of naturalness and are affected by human impact. These qualities and the associated terms are often mixed up and incorrectly used. We have carried out a synthesis in order to propose an adapted French terminology based on international literature. The topics of ancientness and maturity for biodiversity and soil characteristics are explained. This review leads us to submit different potential thresholds for ancientness and maturity. An analysis on ancientness and maturity on forest data for France leads to the conclusion that about 29% of all forests can be considered "ancient woodland", and less than 3% of the even-age forest is older than the harvesting age.