1MSHE Ledoux, CNRS – USR3124, Besançon, France
2Laboratoire Chrono-Environnement, Université de Franche-Comté, CNRS – UMR6249, Besançon, France
3LGL TPE, Université Lyon 1, CNRS – UMR5276, Villeurbanne, France
4Quaternary Environments and Geoarchaeology, Geography, School of Environment and Development, University of Manchester, Manchester, M13 9PL, UK
5GEODE, Maison de la Recherche de l'Université du Mirail, CNRS – UMR5602, Toulouse, France
6Institut für Botanik, Universität Innsbruck, Innsbruck, Austria
7Geological Institute, ETH Zurich, Zurich, Switzerland
8ISTO, Université d'Orléans, BRGM, CNRS – UMR7327, Orléans, France
9Institute of Geological Sciences, University of Bern, Bern, Switzerland
10GEHCO, Université de Tours, Tours, France
Received: 08 Nov 2012 – Published in Clim. Past Discuss.: 15 Nov 2012
Abstract. Adding to the on-going debate regarding vegetation recolonisation (more particularly the timing) 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 were 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–middle 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 tree species distribution. 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 the 8.2 kyr cold event suggest a centennial-scale climate forcing in the studied area. Picea (spruce) expansion occurred preferentially around 10 200 and 8200 cal BP in the south-eastern Alps, and therefore reflects the long-lasting cumulative effects of successive boreal and the 8.2 kyr cold event. 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, a weak signal of pollen-based anthropogenic activities suggest 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 middle Holocene (up to ca. 4100 cal BP).
Revised: 14 Mar 2013 – Accepted: 15 Mar 2013 – Published: 09 Apr 2013
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–middle Holocene at Lake Ledro (southern Alps, Italy), Clim. Past, 9, 913-933, doi:10.5194/cp-9-913-2013, 2013.