Mid Holocene vegetation reconstruction from Vanevan peat (south-eastern shore of Lake Sevan, Armenia)

International audienceA sediment core has been retrieved from Vanevan peat (south-eastern shore of Lake Sevan, Armenia), which is today disconnected from Lake Sevan thanks to an artificial shallowing of the lake. Based on 5 radiocarbon dates, Vanevan record covers the Mid Holocene (from ca. 7800 to ca. 5100 cal. BP). The Late Holocene is today absent in the peat stratigraphy due to modern peat exploitation by surface mining. This study focuses on a multi-proxy approach including pollen, charcoals, and pollen-inferred climate reconstruction. An open-land, steppic vegetation is recorded up to ca. 7700 cal. BP, followed by a more forested landscape during the Mid Holocene (up to ca. 5700 cal. BP), and ending again with an open-land vegetation (to the end of record, 5100 cal. BP). This vegetation dynamics responds to general climate changes documented in the Near East. Whether human activities are documented since ca. 7500 cal. BP (Late Neolithic) in Vanevan, they remain marginal and probably did not affect the area. Early Holocene dry climate, which caused the steppic environment to be widespread through the Near East, is strongly related to low late spring precipitation (PMay–Jun = 180 mm). Mid Holocene forested landscape and increasing lake-level seem related to late spring precipitation (+28%), which is the main change in estimated climate parameters. This has to be linked with reinforcement of the Westerlies and less active Siberian High, which are inversely involved in the following, dry phase starting at ca. 5700 cal. B

After landslide forest recolonisation: a 4000 years old case study from Kalavan Red Lake (Armenia).

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Upper Holocene vegetation history from the Kalavan Red Lake in Armenia

International audienceVegetation 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

Post-landslide forest recolonization: a paleoecological view from a 4000 yrs old case-study.

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Impact of climate change on steppe environments around Lake Sevan in Armenia during the Holocene.

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Vegetation dynamics, human impact and climate influences around the Lake Sevan in Armenia.

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Evolution de la végétation et du climat à Vanevan (rive sud-est du lac Sevan, Arménie) durant l'Holocène moyen

Communication à la Journée du "CReAAH", Archéologie, Archéosciences, Histoire, Rennes, 2 avril 201

First pollen record from the Late Holocene forest environment in the Lesser Caucasus

Pollen-based vegetation change has been inferred from sediments in Kalavan Red Lake. This small lake is placed in the beech-oak-hornbeam forest, about three kilometres away from archaeological remains. It has the potential to document the Holocene forest history and climate and human impacts on the Lesser Caucasus, West of the Caspian Sea. However, this lake happens to be formed by a large landslide.Pollen and XRF analysis are provided over the last 3800 years. The basal age of the Kalavan sediment approximates the landslide age. This created a not vegetated slope including the lake catchment. Erosion and sedimentation processes brought coarse and heavy minerogenic elements, declining with the catchment revegetation by tall-grassland. This shift in the sedimentation continues, suggesting less erosion in the catchment when an admixture of Quercus and grasslands settled. Starting from 2000 cal. BP, arboreal pollen increases successively thanks to the step afforestation of Quercus, Carpinus orientalis and Fagus.The comparison with available pollen reconstruction illustrates the uniqueness of the vegetation dynamic recorded at Kalavan. However, the duration of this succession is also questionable. An intermediate hypothesis is proposed: the Kalavan’s dynamic is first initiated by the landslide with the tall-grass development, then paced by the regional vegetation dynamic.Linking vegetation history and erosion with regional climate and archaeological data helps to evidence short-term climate change and human impact on this branch of the Silk Road. Antique arid phase (2000-1600 cal. BP), the Medieval Warm Period and Little Ice Age affect the vegetation, while demography variations during the Medieval period and Modern Age are shown by habitation and pastoral activity

First pollen record from the Late Holocene forest environment in the Lesser Caucasus

Pollen-based vegetation change has been inferred from sediments in Kalavan Red Lake. This small lake is placed in the beech-oak-hornbeam forest, about three kilometres away from archaeological remains. It has the potential to document the Holocene forest history and climate and human impacts on the Lesser Caucasus, West of the Caspian Sea. However, this lake happens to be formed by a large landslide.Pollen and XRF analysis are provided over the last 3800 years. The basal age of the Kalavan sediment approximates the landslide age. This created a not vegetated slope including the lake catchment. Erosion and sedimentation processes brought coarse and heavy minerogenic elements, declining with the catchment revegetation by tall-grassland. This shift in the sedimentation continues, suggesting less erosion in the catchment when an admixture of Quercus and grasslands settled. Starting from 2000 cal. BP, arboreal pollen increases successively thanks to the step afforestation of Quercus, Carpinus orientalis and Fagus.The comparison with available pollen reconstruction illustrates the uniqueness of the vegetation dynamic recorded at Kalavan. However, the duration of this succession is also questionable. An intermediate hypothesis is proposed: the Kalavan’s dynamic is first initiated by the landslide with the tall-grass development, then paced by the regional vegetation dynamic.Linking vegetation history and erosion with regional climate and archaeological data helps to evidence short-term climate change and human impact on this branch of the Silk Road. Antique arid phase (2000-1600 cal. BP), the Medieval Warm Period and Little Ice Age affect the vegetation, while demography variations during the Medieval period and Modern Age are shown by habitation and pastoral activity

First pollen record from the Late Holocene forest environment in the Lesser Caucasus

Pollen-based vegetation change has been inferred from sediments in Kalavan Red Lake. This small lake is placed in the beech-oak-hornbeam forest, about three kilometres away from archaeological remains. It has the potential to document the Holocene forest history and climate and human impacts on the Lesser Caucasus, West of the Caspian Sea. However, this lake happens to be formed by a large landslide.Pollen and XRF analysis are provided over the last 3800 years. The basal age of the Kalavan sediment approximates the landslide age. This created a not vegetated slope including the lake catchment. Erosion and sedimentation processes brought coarse and heavy minerogenic elements, declining with the catchment revegetation by tall-grassland. This shift in the sedimentation continues, suggesting less erosion in the catchment when an admixture of Quercus and grasslands settled. Starting from 2000 cal. BP, arboreal pollen increases successively thanks to the step afforestation of Quercus, Carpinus orientalis and Fagus.The comparison with available pollen reconstruction illustrates the uniqueness of the vegetation dynamic recorded at Kalavan. However, the duration of this succession is also questionable. An intermediate hypothesis is proposed: the Kalavan’s dynamic is first initiated by the landslide with the tall-grass development, then paced by the regional vegetation dynamic.Linking vegetation history and erosion with regional climate and archaeological data helps to evidence short-term climate change and human impact on this branch of the Silk Road. Antique arid phase (2000-1600 cal. BP), the Medieval Warm Period and Little Ice Age affect the vegetation, while demography variations during the Medieval period and Modern Age are shown by habitation and pastoral activity