Wednesday, August 8, 2007 - 2:30 PMCOS 91-4: Origin of open landscapes in Western Europe revisited by soil wood charcoal analyses
Thierry Dutoit1, Michel Thinon2, Elise Buisson1, and Didier Alard3. (1) IMEP UMR-CNRS 6116 & IUT Avignon, (2) Université Paul Cézanne, (3) Université de Bordeaux,
Open landscapes, such as chalk grasslands in Western Europe, are considered to be the result either of land clearing in the Neolithic or of the grazing impact of wild herbivores in the Mesolithic. However, the origin of open habitats such as chalk grasslands, a species-rich ecosystem, is still debated. They are generally believed to have been formed under such processes but they may have existed since the Late-Glacial and persisted during the forested eras of the PreBoreal and Boreal. Evidences for the origin and persistence of chalk grasslands have been found in land clearing for hunting in the Mesolithic, in the grazing impact of wild herbivores but also in particular soil conditions, unsuitable for the establishment of woody species. Despite these arguments, the long-term history of chalk grasslands and the age of their formation remain particularly controversial because pollen records suffer from a lack of spatial resolution and because it is difficult to assess grazing history and grazing impacts of herbivores on the vegetation of specific sites. For the first time, a study was carried out at a high spatial resolution in a chalk grassland by using soil wood charcoal analysis, a technique in which charcoals found in the soil are identified and dated. Here we show that late-successional woody species (Fagus sylvatica, Quercus sp.) were present in the Neolithic and at the Bronze Age on a chalk grassland of Upper-Normandy. Consequently, these fires were linked to forest clearance for pastoral activities from which these grasslands have clearly originated.