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The Holocene history of low altitude Mediterranean Fagus sylvatica forests in southern France

Azuara, Julien, Lebreton, Vincent, Peyron, Odile, Mazier, Florence, Combourieu‐Nebout, Nathalie
Journal of vegetation science 2018 v.29 no.3 pp. 438-449
Fagus sylvatica, altitude, anthropogenic activities, charcoal, climate change, deforestation, dry environmental conditions, ecosystem engineers, forests, humans, pollen, trees, France, Mediterranean region
QUESTIONS: As the dominant tree in many European forests, Fagus sylvatica functions as an ecosystem engineer, yet its istory remains little understood. Here we ask: (a) are there indications for its presence in southeast France during the last Glacial period; (b) what was the timing of the expansion and decline of F. sylvatica dominated forests; (c) which factors influenced their dynamics and in particular to what extent did past precipitation changes impact upon them; and (d) at which altitudes did these beech forests occur within the region? LOCATION: Languedoc, the French Mediterranean area. METHOD: This article presents a well dated and high‐resolution pollen sequence covering the last 7,800 years from the Palavas Lagoon in the Languedoc together with a review of Fagus charcoal occurrences in the Languedoc and the lower Rhône Valley, and a review of pollen data from a compilation of 69 sites in southeast France. RESULTS: The Palavas pollen sequence provides a regional summary of F. sylvatica abundance changes near the Mediterranean coast. Around 6,000 years cal BP, an abrupt transition from small beech populations to well‐developed forests is recorded. The maximum development of beech forests occurred between 4,000 and 3,000 years cal BP, while F. sylvatica started to regress after 3,000 years cal BP. CONCLUSION: Scattered F. sylvatica populations probably survived throughout southern France during the last Glacial period. F. sylvatica started to spread around 8,000 years cal BP while beech forests never expanded before 6,000 years cal BP. The complex patterns of F. sylvatica expansion in southern France after 6,000 years cal BP suggests that a combination of global (climate change) and local (human impact) factors were responsible for this major change. Recurrent abrupt climate changes, the aridity trend and human deforestation caused beech forests to decline after 3,000 years cal BP.