Pinus cembra L. (arolla pine), a common tree in the inner French Alps since the early Holocene and above the present tree line: a synthesis based on charcoal data from soils and travertines

Authors

  • Adam A. Ali,

    Corresponding author
    1. Centre de Bio-Archéologie et d'Ecologie (UMR 5059 CNRS/U. Montpellier 2/EPHE), Institut de Botanique, Montpellier, France
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  • Christopher Carcaillet,

    1. Centre de Bio-Archéologie et d'Ecologie (UMR 5059 CNRS/U. Montpellier 2/EPHE), Institut de Botanique, Montpellier, France
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  • Brigitte Talon,

    1. Institut Méditerranéen d'Ecologie et de Paléoécologie (UMR 6116 CNRS), Université de Aix-Marseille 3, Faculté des Sciences et Techniques de St-Jérôme, Marseille Cedex, France
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  • Paul Roiron,

    1. Centre de Bio-Archéologie et d'Ecologie (UMR 5059 CNRS/U. Montpellier 2/EPHE), Institut de Botanique, Montpellier, France
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  • Jean-Frédéric Terral

    1. Centre de Bio-Archéologie et d'Ecologie (UMR 5059 CNRS/U. Montpellier 2/EPHE), Institut de Botanique, Montpellier, France
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Adam A. Ali, Centre de Bio-Archéologie et d'Ecologie (UMR 5059 CNRS/U. Montpellier 2/EPHE), Institut de Botanique, 163 rue Auguste Broussonet, F-34090 Montpellier, France.
E-mail: ali@univ-montp2.fr

Abstract

Aim  In this study, charcoal-based data for Pinus cembra L. (arolla pine) were gathered from soil and travertine sequences in order to reconstruct its historical biogeography at the landscape level in the inner western Alps during the Holocene.

Location  The study sites are located between 1700 and 2990 m a.s.l., in the southern (Queyras Massif and Ubaye Valley) and the northern (Maurienne Valley) parts of the inner French Alps.

Methods  Charcoal fragments were extracted from sediments by water sieving, using meshes of 5, 2, 0.8 and 0.4 mm. The charcoal mass of P. cembra was determined in each charcoal assemblage. Accelerator mass spectrometry and conventional 14C measurements were used to date the fragments.

Results  Supported by 40 14C datings, the fragments show that, over 2000 m a.s.l., P. cembra accounts for around 40% (mean value) of identified fragments. Data reveal that arolla pine once extended between 260 and 375 m above the present-day local tree lines. It was established in the southern and the northern French Alps from at least c. 9000 and 6000 cal yr bp, respectively.

Main conclusions  While present-day populations of P. cembra are very fragmented in the inner French Alps, charcoal records indicate large past occurrences of this tree since the early Holocene. Human disturbance since the Neolithic seems to be the main reason for the regression of the arolla pine woodlands. On the south-facing slopes of the study sites, currently deforested, this species extended up to 2800 m a.s.l. In the northern areas, charcoal records of the P. cembra expansion are consistent with the regional pollen archives, but in the southern massifs charcoal records indicate its presence c. 2600 years earlier than other palaeobotanical studies suggest. This discrepancy highlights the necessity to crosscheck data using several different proxies in order to assess the validity of conclusions regarding tree development in space and time.

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