Holocene vegetation, landscape, and reconstruction of human activity from Prehistory to Roman times based on new pollen data performed in "the plateau de Millevaches" (Limousin, Massif central, France).
Résumé
New pollen analyses from four peat bogs and fens located on the plateau de Millevaches (Limousin, French Massif Central) are compared with one peat sequence situated at lower altitude in the northern Limousin (Mont d'Ambazac). This study, which is supported by eleven accepted AMS radiocarbon data, was undertaken to consider changes in regional vegetation from the beginning of the Holocene and to provide a first reconstruction of land-use history. A singular vegetation history characterizes the "plateau de Millevaches" from the center of the French Massif Central such as the simultaneous start of Corylus and Quercus dated from ca. 10560-10150 cal. BP (ca. 8550-8200 cal. BC). The composition of the forest cover remained largely unchanged with a large supremacy of Corylus in the regional vegetation until ca. 8050-7650 cal. BP (ca. 6100-5700 cal. BC) when the decline of Corylus was synchronous with the expansion of Quercus. The diversified oak woodlands were rapidly filled by Tilia, and pollen data indicate early Neolithic farming around 6600-6500 cal. BP (ca. 4600-4500 cal. BC). The installation of Fagus, which is dated about 5660-5300 cal. BP (ca. 3700-3400 cal. BC), occurs nearly 700 years later than in neighbouring Auvergne. The first oak and beech forests spread after ca. 4800-4400 cal. BP (ca. 2850-2450 cal. BC), and Fagus constitutes the dominant arboreal taxa in the regional vegetation only since ca. 3900-3550 cal. BP (ca. 1930-1530 cal. BC). While climatic factors may have played a major role in its delayed installation, these new pollen analyses provide the first pollen evidence of an anthropogenic factor particularly for the late Neolithic - early Bronze Age transition when increased human pressure (woodland clearances and presence of agricultural and grazing indicators) is evidenced. Different stages related to human activities are shown for the following periods. According to the pollen data, between ca. 2350-2100 cal. BP (ca. 400-150 cal. BC), the second Iron Age, and more particularly, the 4th-2nd centuries BC, represents an important threshold in the shaping of this medium mountain cultural landscape. Large beech-oak forest clearances are related to an important agropastoral extension which continues to increase during the beginning of the Roman period.