L’abri du Pas de l’Échelle (Rovon, Isère) : évolution du couvert végétal d’après les analyses polliniques et anthracologiques

The Pas de l’Échelle (980 m a. s. l.) is a natural passage from the Isère valley to the Hauts-Plateaux of the Vercors massif. At this place a rock shelter has yielded an important Mesolithic and Neolithic sequence, well dated by artefacts and by a series of 14C datings. Pollen analysis was mainly performed on this sequence, and on the gravels at the base of the excavation (Dryas III), as well as on Neolithic layers. As for charcoal analysis it covers a larger chronological range, from Mesolithic to Early Middle Ages. It enables to describe the dynamics of the vegetation through several thousands of years under human influence. Therefore, these two botanical approaches are chronologically complementary. The vegetation dynamics is divided in three steps characterized for the first by pine and broadleaved oak forest, then by yew during the Neolithic, next by ash tree and by the fir-beech forest from Bronze Age onwards.