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Article Dans Une Revue The Holocene Année : 2009

Vegetation history and human impact at subalpine belt in the French North-Western Alps (Upper-Arve Valley)

Résumé

Pollen analyses were undertaken on three small peatbogs, located on the Anterne mountain (Upper-Arve Valley, French north-western Alps) at different altitudes - 1855, 2060 and 2235 m asl, respectively. Their comparative study allowed for the detremination of the role played by human activity in Holocene vegetation dynamics of the nowadays treeless subalpine belt. Sixteen AMS 14 C ages support the chronology. At 2235m asl, first organic sediment have been deposited over basal clay at 10,050 cal. Years BP (+/- 150). First trees (Salix and Betula) grew at around 9000cal. Years BP. Abies pollen grains are recorded at the end of Corylus pptimum at 8890 cal. Years BP (+/-122).Picea percentages have increased after 3900cal. BP at 1850m and after 3600 cal. Years BP at 2235m, but spruce has never constituted large stands in the study area. Pinus cembra grew in the vicinity of three sites as early as 8890 cal. Years BP (+/- 122). Three main phases of anthropisation seem outsand from our results: the final Neolithics ( - 4.6 cal. BP), the Mid-Bronze (3,6 ka cal. BP and after), and the Roman Period ( - 2ka cal. BP). At 2235m trees have retreated after 4600 cal. BP and completely disappeared around 3600 cal. Years BP. As a consequence above 2000m deforested areas became more sensitive to climate events that caused intense erosion processes and detrital inputs. At 1850m the onset of human perturbation caused a retreat of Abies stands and an expansion of Alnus viridis which consequentlydominated the landscape from 3700 up to 1965 cal. Years BP the lowest-altitude site was invaded by grasslands without any ligneous species.
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Dates et versions

hal-00444367 , version 1 (06-01-2010)

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  • HAL Id : hal-00444367 , version 1

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Fernand David, Fabien Arnaud, Claire Delhon, Pierre-Jérôme Rey, Charline Giguet-Covex. Vegetation history and human impact at subalpine belt in the French North-Western Alps (Upper-Arve Valley). The Holocene, 2009, 26pp. ⟨hal-00444367⟩
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