Holocene paleoecological changes and agro-pastoral impact on the La Narce du Beage mire (Massif Central, France)

A paleoecological study (macrofossils, pollen, cryptogam spores, non-pollen palynomorphs) was performed to investigate environmental changes recorded on the peat deposits of the La Narce du Beage mire (Massif Central, France). We reconstructed the development of a limnogenous mire ecosystem during the Holocene, consequently to the infilling of a small Late Glacial lake. Successions from aquatic flora (Isoetes, Nitella opaca/syncarpa, Botryococcus, Alisma plantago-aquatica, Potamogeton, Sparganium) to mire plant species (Alnus glutinosa, Betula nana, Betula pubescens, Cyperaceae, Ericaceae, Sphagnum) underlined a gradual eutrophication and acidification during the lowering of the water table. We demonstrated a clear link between these local hydro-ecological changes and the early Holocene climatic warming. Also dealing with archeology, we provided key issues for the identification of human-induced environmental changes. Three phases of ecological disturbances with clearings of the mixed-oak forest and agro-pastoral activities were evidenced at 7700-7300, 6800-6420, and 5500-4250 cal. BP. Our results confirmed early Neolithic (Cardial influences), middle Neolithic (Chassean), and late Neolithic (Ferrieres group) frequentations of the Beage Plateau, probably included in large-scale socio-cultural changes (SE France, NW Mediterranean Basin). Later, forest clearings (beech and fir), cultivation, and pastoralism were outlined since the Iron Age (after 2300 cal. BP, that is, 350 BC). Increasing human pressure was especially recorded during the last 1700 years, with rye (Secale cereale) cultivation and extensive livestock grazing around and on the mire, which is nowadays a protected `Natura 2000' area.