Upper pleistocene and holocene vegetation in the south of France and Andorra: adaptations and first ruptures: new charcoal analysis data

(ENG) Our knowledge of prehistoric vegetations depends on the development of methodology. The application to charcoal analysis of new rules concerning sampling and study gives greater accuracy to the present biochronological model in the northwestern Mediterranean, especially in the south of France. As regards palaeoecology we emphasize the Tardi/Postglacial period, especially the Mesolithic-Neolithic transition. Synchronic phases, based on results of charcoal analysis, are obtained from Margineda ( Andorra, 960 m) and Abeurador (France, Hérault, 560 m) except those concerning altitude displacements. The vegetation dynamics allows a better understanding of man-environment relationships in this important cultural period. During Epipaleolithic times, hunter-gatherer groups lived at first in an open landscape (phase 1a) and later in a pre-forest environment (phase 1b). During the Late Mesolithic, an enlarged spectrum of angiosperms follows a climatic optimum and emphasizes the progressive evolution towards a more closed vegetal habitat (phase 2). This propitious context favours the beginning of the Neolithic. A most trenchant observation is made at Margineda: ecological changes precede cultural changes. At both sites no regressive evolution of forest is observed which proves that the natural vegetation was exploited wisely. Climatic factors are the basis of vegetal evolution. A synchronous site-catchment study was made in the middle Rhone valley with the aim of obtaining a synthetic image of a particular cultural period the Mid Neolithic, "Chasséen". Three contemporaneous sites, lying at different altitude levels (mesomediterranean, supramediterranean and mountain levels), are studied. During the Mid Neolithic, human activity is noted in lowlands, slopes and mountains.