Analysis and experimentation on ecosystems

We present a multidisciplinary approach to document the vegetation and landscape of Upper Guisane Valley around the Lautaret Pass area in the French Southwestern Alps since 7200 calyr BP. We combined pollen analysis in a peat bog (at 2044 m) with a leaf imprint study in two nearby travertine systems (at 2100 and 1950 m). During the last 7200 years, there was an open landscape with scarce trees such asconifers including Larix decidua Mill., Pinus spp., and Abies alba Mill. 2100 m was the highest altitude where fossils of A. alba Mill. have been reported in the Guisane Valley. These results, according to the pollen record of anthropogenic indicators and an increasing biodiversity of grasslands, suggest a human presence in the pass area since ca 6500 years with a preRoman deforestation. This human impact has become maximum from 1100 calyr BP to present, resulting from cereal crop agriculture and deforestation. The comparative study of the different records confirmed the role played by the exposition in the forest dynamics of the alpine valleys during the Holocene.