History of the Pinus sylvestris and Pinus nigra ssp. salzmanni forest in the Sub-Mediterranean mountains (Grands Causses, Saint-Guilhem-le-Désert, southern Massif Central, France) based on charcoal from limestone and dolomitic deposits

Abstract

Charcoal, the remains of Holocene fires recorded in natural sediments, allows a new approach to the study of forest evolution in the mountains of the Mediterranean region. The area of the Grands Causses and St Guilhem, southern Massif Central (France) played an important role in the preservation of steppic and pre-steppic ecosystems up to the middle Holocene. The present biodiversity developed recently (between 5000–3000 b.p.), which explains the persistence of typical alpine and steppic flora characteristic of these areas. From the middle Holocene on, both fire events in the Eastern areas of the Causse Mejean and grazing have contributed to creating the bald landscape characteristic of this region. Further south the present day forest of Pinus nigra ssp. salzmanni is a recent phenomenon. It was during the Middle Ages that the initial forest of Pinus sylvestris and Pinus nigra ssp. salzmanni, a heritage from the last glaciation, started to change. δ13C measurements were carried out and the results compared with reference material. These show that fire events are closely related to dry periods, implying climatic changes of increasing dryness after the middle Holocene climatic optimum.