Upper Holocene vegetation history from the Kalavan Red Lake in Armenia

Résumé En

Vegetation change based on the study of pollen from sediments in the Kalavan Red Lake (1912 m a.s.l.), located on the northern side of the Miapor mountain ridge in Armenia, has been interpreted.This exceptional small lake with red shores coloured by iron oxides is ideally placed in the beech-oak vegetation zone, about three kilometers from archaeological remains. It thus has the potential to cover large gaps in our knowledge of vegetation history, climate and human impact for the Lesser Caucasus. However, this lake was formed as the result of a large landslide, which necessitates investigation of erosion and recolonisation processes in the catchment area.Pollen and XRF analyses have been carried out on a core 5 meters in length which covers the last 3800 years.The basal age of the Kalavan sediment may approximate the age of the landslide, which would indicate a slope without vegetation cover, including the lake catchment area. Erosion and sedimentation processes produced at first coarse, heavy minerogenic elements, then erosion in the catchment area decreased due to the development of grass meadows, which led to a shift in the sedimentation. Throughout the stratigraphy, it is noteworthy that arboreal pollen increases due to the increasing presence of Quercus (oak), Carpinus orientalis (oriental hornbeam) and Fagus (beech), the last two being late invaders having a shade-tolerant ecology.These ecological processes had a major influence on the development of vegetation on Kalavan’s landslide, but this masks other long-term forcing factors such as climate change and human impact. Relating the vegetation and erosion histories of Kalavan to regional climate and archeological data was useful for their identification. The ancient arid phase (2000-1600 cal. BP), the Medieval Warm Period and the Little Ice Age affected the vegetation, while demography variations that occurred during the medieval period are demonstrated by the presence of pastoralism.