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Aim Previous studies have failed to reconstruct the regional post-glacial migration pattern of Abies alba in southern France. Based on the first exhaustive compilation of palaeoecological data in this region, we present the state-of-the-art and attempt to synthesize the available information concerning glacial refugia and post-glacial migration, and analyse the information with regard to climate and orography. Location South-western Alps and adjacent areas, southern France. Methods The work compiles the available palaeoecological data in the south-western Alps (52 sites, 290 radiocarbon dates). The post-glacial migration pattern of Abies alba is reconstructed based on 22 selected palynological analyses (11 well-dated reference sites and 11 supplementary ones). Results The geographical patterns of approaching area limit, immigration and expansion are reconstructed at the scale of the southern French Alps. Main conclusions Despite previous assertions, the evidence of refugia in southern France is non-existent. The late-glacial records of fir pollen, previously interpreted in French Mediterranean regions and on adjacent foot-hills as possibly reflecting regional refugia, most probably correspond to reworking phenomena or long-distance pollen transport. Fir migration, originating in the Apennine refugia and through the south-western extremity of the Alps, was extremely rapid in the southern French Alps, only spanning a few centuries between 10,100 and 9800 cal. yr BP. The subsequent spread of fir populations was controlled by local parameters, such as the aridity of the inner valleys, which resulted in a delayed expansion in comparison to other regions. Abies almost disappeared from the south-western Alps during the Roman era, around 2000 cal. yr BP.

We quantify the Holocene Rhone delta evolution by the assessment of sediment vertical accumulation, horizontal progradation of the delta plain, and volumes of the sedimentary sequences. We use for this purpose a 3D reconstruction with a GIS program and as input data a géomorphologie map with high chronological resolution, many high resolution seismic profiles located in the internal platform, and some cores. The calculation of the volumes we obtain underestimates strongly the sedimentary storage if we refer to the usual quoted values. This is probably linked to the lack of cores onshore and in the shelf to calibrate the seismic fades, and also to the difficulty in assessing the porosity of sediments in the column. However the period 2800/2525 cal BP seems clearly identified as a period of fast sediment storage and deltaic progradation which could correspond to the climatic deterioration of the first Iron Age known upstream in the Rhone catchment area. The same trend appears also during the second Iron Age but with a lower impact. The antitetic apparent functioning of the Durancian upstream watershed with the contributions on the delta of the Rhône is to be noted, but the not exhaustive character of the quantification of the sedimentary accumulation on the internal continental shelf does not allow to confirm this hypothesis., Les datations radiocarbone d'une vingtaine de coupes naturelles dans les petits organismes torrentiels des Alpes du Sud mettent clairement en évidence une bi-partition dans l 'évolution de la morphogenèse de la période 14500 cal BP à aujourd'hui. De 14500 à 7000 cal BP une sédimentation importante caractérise les zones de piémont. Les taux de sédimentation, assez faibles de 14500 à 11 700 cal BP deviennent plus élevés de 11 700 à 9000 cal BP et très forts de 9000 à 7500 cal BP. Ces processus géomorphologiques, comme d'autres proxies paléoenvironnementales, témoignent d'une d'humidité importante. Un arrêt de la sédimentation alluviale dans les secteurs d'amont a lieu vers 7000 cal BP. Peu de données documentent la période suivante. Une phase d'incision majeure a lieu antérieurement au dépôt d'une basse terrasse caillouteuse attribuée au Petit Age Glaciaire. Globalement la période postérieure à 7000 cal BP est caractérisée par des flux hydrologiques qui permettent un transit sédimentaire vers les zones d 'aval., Miramont Cécile, Boutterin Clément, Sivan Olivier, Bruneton Hélène, Mantran Murielle. Grandes séquences et principales ruptures morphogéniques en Haute Provence : les complexes sédimentaires des petits organismes torrentiels de Moyenne Durance. In: Collection EDYTEM. Cahiers de géographie, numéro 6, 2008. Du climat à l’homme, dynamique holocène de l’environnement dans le Jura et les Alpes. pp. 145-154.

International audience; Dans les Alpes, le débat sur la dégradation de la forêt par les sociétés montagnardes remonte au moins au 17è siècle. Alors, plusieurs pistes sont évoquées. Puis au début du 20ème siècle, des scientifiques prennent le contre-pied de la pensée dominante qui attribuait à l'impéritie des sociétés montagnardes la déforestation et la cascade de ses conséquences catastrophiques.