Clim. Past Discuss., 8, 5583-5632, 2012
© Author(s) 2012. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Climate of the Past (CP). Please refer to the corresponding final paper in CP.
Climate and vegetation changes during the Lateglacial and Early-Mid Holocene at Lake Ledro (southern Alps, Italy)
S. Joannin1,2,3, B. Vannière2, D. Galop4, O. Peyron2, J.-N. Haas5, A. Gilli6, E. Chapron7, S. B. Wirth6, F. Anselmetti8, M. Desmet9, and M. Magny1,2
1MSHE Ledoux, USR3124, CNRS, Besançon, France
2Laboratoire Chrono-Environnement, UMR6249, CNRS – Université de Franche-Comté, Besançon, France
3Laboratoire de géologie de Lyon: Terre, planètes et environnement (TPE), UMR5276, CNRS – Université Lyon 1, Villeurbanne, France
4GEODE, UMR5602, CNRS – Maison de la Recherche de l'Université du Mirail, Toulouse, France
5Institut für Botanik, Universität Innsbruck, Austria
6Geological Institute, ETH Zurich, Switzerland
7ISTO, UMR7327, CNRS – Université d'Orléans, BRGM, Orléans, France
8Institute of Geological Sciences, University of Bern, Bern, Switzerland
9GEHCO, Université de Tours, France

Abstract. Adding to the on-going debate regarding vegetation recolonisation in Europe and climate change since the Lateglacial, this study investigates a long sediment core (LL081) from Lake Ledro (652 m a.s.l., southern Alps, Italy). Environmental changes that where reconstructed using multiproxy analysis (pollen-based vegetation and climate reconstruction, lake-levels, magnetic susceptibility and X-ray fluorescence (XRF) measurements) recorded climate and land-use changes during the Lateglacial and Early-Mid Holocene. The well-dated and high-resolution pollen record of Lake Ledro is compared with vegetation records from the southern and northern Alps to trace the history of distribution tree species. An altitude-dependent progressive time-delay of the first continuous occurrence of Abies (fir) and of the Larix (larch) development has been observed since the Lateglacial in the southern Alps. This pattern suggests that the mid-altitude Lake Ledro area was not a refuge and that trees originated from lowlands or hilly areas (e.g. Euganean Hills) in northern Italy. Preboreal oscillations (ca. 11 000 cal. BP), Boreal oscillations (ca. 10 200, 9300 cal. BP) and n.e. 8.2 kyr cold event suggest a centennial-scale short-lasting climate forcing in the studied area. Picea (spruce) expansion occurred preferentially around 10 200 cal. BP and 8200 cal. BP in the south-eastern Alps and, therefore, reflects the long-lasting cumulative effects of successive boreal and 8.2 kyr cold events. The extension of Abies is contemporaneous with the 8.2 kyr event, but its development in the southern Alps benefits from the wettest interval 8200–7300 cal. BP evidenced in high lake-levels, flood activity and pollen-based climate reconstructions. Since ca. 7500 cal. BP, low signal of pollen-based anthropogenic activities suggest a weak human impact. The period between ca. 5700 and ca. 4100 cal. BP is considered as a transition period to colder and wetter conditions (particularly during summers) that favoured a dense beech (Fagus) forest development which in return caused a distinctive yew (Taxus) decline. We conclude that climate was the dominant factor controlling vegetation changes and erosion processes during the Early and Mid Holocene (up to ca. 4100 cal. BP).

Citation: Joannin, S., Vannière, B., Galop, D., Peyron, O., Haas, J.-N., Gilli, A., Chapron, E., Wirth, S. B., Anselmetti, F., Desmet, M., and Magny, M.: Climate and vegetation changes during the Lateglacial and Early-Mid Holocene at Lake Ledro (southern Alps, Italy), Clim. Past Discuss., 8, 5583-5632, doi:10.5194/cpd-8-5583-2012, 2012.
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