Late Holocene vegetation changes in relation with climate fluctuations and human activity in Languedoc (southern France)

摘要

Holocene climate fluctuations and human activity since the Neolithic haveshaped present-day Mediterranean environments. Separating anthropogeniceffects from climatic impacts to better understand Mediterraneanpaleoenvironmental changes over the last millennia remains a challengingissue. High-resolution pollen analyses were undertaken on two cores from thePalavasian lagoon system (Hérault, southern France). These records allowreconstruction of vegetation dynamics over the last 4500 years. Results arecompared with climatic, historical and archeological archives. A long-termaridification trend is highlighted during the late Holocene, and threesuperimposed arid events are recorded at 4600–4300, 2800–2400 and1300–1100 cal BP. These periods of high-frequency climate variabilitycoincide in time with the rapid climatic events observed in the AtlanticOcean (Bond et al., 2001). From the Bronze Age (4000 cal BP) to the end ofthe Iron Age (around 2000 cal BP), the spread of sclerophyllous taxa andloss of forest cover result from anthropogenic impact. Classical Antiquity ischaracterized by a major reforestation event related to the concentration ofrural activity and populations in coastal plains leading to forest recoveryin the mountains. A major regional deforestation occurred at the beginning ofthe High Middle Ages. Around 1000 cal BP, forest cover is minimal while the cover of olive, chestnut and walnut expands in relation to increasing humaninfluence. The present-day vegetation dominated by Mediterranean shrublandand pines has been in existence since the beginning of the 20th century.