Early to late Holocene vegetation and fire dynamics at the treeline in the Maritime Alps
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ORIGINAL ARTICLE
Early to late Holocene vegetation and fire dynamics at the treeline in the Maritime Alps Walter Finsinger1 · Quentin Vanel2 · Adriano Ribolini3 · Willy Tinner4 Received: 18 April 2020 / Accepted: 8 July 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract We used pollen, plant macrofossil, and charcoal records to investigate local long-term timberline shifts and changes in vegetation composition in relation to fire activity at the modern upper forest limit (ca. 2,000 m a.s.l.) in the Mont Bégo area, Maritime Alps of France and Italy. The area is an important place for Alpine archaeology because it has thousands rock-art carvings whose age cannot be directly assessed. Our new record confirms the occurrence of distinct land use phases (7,450– 7,150, 6,200–4,900, and 4,250–3,700 cal bp), as suggested by earlier studies of rock art typology. Moreover, the vegetation reconstruction from macrofossils, with co-dominance of Pinus and Betula, suggests that early Holocene conditions were moister than in drier inner Alpine valleys, where Larix decidua played a more important role, both in the past as well as in modern timberline forests. After 8,000 cal bp, the timberline shifted upwards and mixed Abies alba and Pinus cembra stands established around the study site. These fire sensitive trees were finally replaced during the Bronze Age (around 4,000 cal bp) by L. decidua, which still dominates the subalpine woodlands in the area today. Our study supports the notion that while the range of A. alba has been reduced at the colder end of its natural distribution, that of L. decidua has been widened by land use changes and fire disturbances to create high alpine wood pastures. Keywords Vegetation dynamics · Mountain ecosystems · Treeline ecotone · Land use phases · Wood pasture · Fires
Introduction In mountain landscapes, the altitudinal treeline ecotone marks a prominent ecosystem boundary (Arno and Hammerly 1984) between the upper limit of subalpine closed Communicated by T. Giesecke. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00334-020-00795-x) contains supplementary material, which is available to authorized users. * Walter Finsinger [email protected] 1
ISEM, University of Montpellier, CNRS, EPHE, IRD, Montpellier, France
2
Ecosphère, Agence Nord-Ouest, 28 rue du Moulin, 60490 Cuvilly, France
3
Dipartimento di Scienze della Terra, Universitá di Pisa, 56126 Pisa, Italy
4
Oeschger Centre for Climate Change Research and Institute of Plant Sciences, University of Bern, Altenbergrain 21, 3013 Bern, Switzerland
forest (the timberline or forest line) and open alpine meadows above stands of stunted trees (Krummholz) and tree seedlings (tree species line) (Körner 2003). While the species composition of the treeline ecotone and of subalpine forests is mainly influenced by water availability, rainfall, soils and disturbances (Henne et al. 2011; Schwörer et al. 2014a), the upper limit of tree growth is prima
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