Sampling soil wood charcoals at a high spatial resolution: a new methodology to investigate the origin of grassland plant communities
Résumé
Questions: (i) Can sampling of soil wood charcoals at high spatial resolution produce new evidence concerning the presence of chalk grassland before or during the Neolithic, Bronze and Iron Ages? (ii) Are there correlations between vegetation history and archeological data during these periods at this particular site? Location: The chalk hillsides of Saint-Adrien in the lower Seine Valley, Upper Normandy, northwest France. Methods: The study was carried out at a high spatial resolution in chalk grassland using soil wood charcoal analysis, in which charcoals found in the soil were identified and dated in an area of several hundred square meters. Results: Late-successional woody species (Fagus sylvatica, Quercus sp.) were still present in the study site in an area inconsistent with the existence of large chalk grassland herbaceous plant communities (several hectares) in the Neolithic (6500–3800 BP) and Bronze Age (3800–2700 BP). Conclusions: The presence of late-successional woody species on the studied hillside suggests that fires in the Neolithic were linked to forest clearance for pastoral activities, as already demonstrated for similar ecosystems in eastern France and Germany. Nevertheless, our methodology clearly demonstrates that palaecological studies need to take into account the spatial organisation of plant communities as a complementary element to validate their potential existence in former times.