A Holocene history of forest vegetation on the northern slopes of a Mediterranean mountain: the Mont Ventoux, Southeast France / Histoire holocène de la végétation forestière du versant nord d’une montagne méditerranéenne : le mont Ventoux (Vaucluse, France)

Abstract

This study aims at reconstructing the late Holocene vegetation dynamics and the maximum altitudinal limit of forest trees on northern slopes of Mont Ventoux before the intense deforestation of the 12th century, in relation to natural environmental changes and anthropogenic disturbances including fire history and sylvo-pastoral practices. Six soil pits were studied out along an altitudinal transect from 925m to 1,860m a. s. l. This transect crosses the beech-fir forests in the lower elevations to open woodlands containing the prostrate hooked pine (Pinus uncinata) near the summit. The study was performed within the framework of the ecological monitoring program ORCHAMP. Pedoanthracological data (identified charcoals and their 14C ages) were further explored by numerical analyses. Charcoal was found in all pits with concentrations significantly decreasing with altitude, as does the proportion of charcoal of deciduous trees over conifers. Some woody species were found at altitudes where they are absent today, notably fir (Abies alba) at high elevations, (up to 1,860m). In contrast to fir, the beech (Fagus sylvatica) charcoals were not found beyond 1,340m, although the species currently reaches elevations as high as 1,700m a. s. l. Radiocarbon dating results suggest that the soils on northern slopes of Mont Ventoux have not been significantly eroded since at least 4,000 years ago. The period covered by the six obtained AMS 14C dates extends from the Bronze Age (oldest 14C age : 3576-3729 cal BP / 1779-1626 BCE) to the Modern Era (youngest 14C age : 346-460 cal BP / 1490-1604 CE), all pre-dating the 1860’ s reforestation projects (RTM, Restoration of Mountain Land). This preliminary pedoanthracological study proved to be promising and complementary to other palaeoecological approaches but is still insufficient to provide a complete picture of the past vegetation history of Mont Ventoux.