Reconstruction of Holocene vegetation dynamics at Lac de Bretaye, a high-mountain lake in the Swiss Alps

Thöle, Lena; Schwörer, Christoph; Colombaroli, Daniele; Gobet, Erika; Boltshauser-Kaltenrieder, Petra; van Leeuwen, Jacqueline; Tinner, Willy (2016). Reconstruction of Holocene vegetation dynamics at Lac de Bretaye, a high-mountain lake in the Swiss Alps. Holocene, 26(3), pp. 380-396. Sage 10.1177/0959683615609746

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A deeper understanding of past vegetation dynamics is required to better assess future vegetation responses to global warming in the Alps. Lake sediments from Lac de Bretaye, a small subalpine lake in the Northern Swiss Alps (1780 m a.s.l.), were analysed to reconstruct past vegetation dynamics for the entire Holocene, using pollen, macrofossil and charcoal analyses as main proxies. The results show that timberline reached the lake’s catchment area at around 10,300 cal. BP, supporting the hypothesis of a delayed postglacial afforestation in the Northern Alps. At the same time, thermophilous trees such as Ulmus, Tilia and Acer established in the lowlands and expanded to the altitude of the lake, forming distinctive boreo-nemoral forests with Betula, Pinus cembra and Larix decidua. From about 5000 to 3500 cal. BP, thermophilous trees declined because of increasing human land use, mainly driven by the mass expansion of Picea abies and severe anthropogenic fire activity. From the Bronze Age onwards (c. 4200–2800 cal. BP), grazing indicators and high values for charcoal concentration and influx attest an intensifying human impact, fostering the expansion of Alnus viridis and Picea abies. Hence, biodiversity in alpine meadows increased, whereas forest diversity declined, as can be seen in other regional records. We argue that the anticipated climate change and decreasing human impact in the Alps today will not only lead to an upward movement of timberline with consequent loss of area for grasslands, but also to a disruption of Picea abies forests, which may allow the re-expansion of thermophilous tree species.

Item Type:

Journal Article (Original Article)

Division/Institute:

10 Strategic Research Centers > Oeschger Centre for Climate Change Research (OCCR)
08 Faculty of Science > Institute of Geological Sciences
08 Faculty of Science > Department of Biology > Institute of Plant Sciences (IPS) > Palaeoecology
08 Faculty of Science > Department of Biology > Institute of Plant Sciences (IPS)

Graduate School:

Graduate School of Climate Sciences

UniBE Contributor:

Thöle, Lena; Schwörer, Christoph; Colombaroli, Daniele; Gobet, Erika; Boltshauser-Kaltenrieder, Petra; van Leeuwen, Jacqueline and Tinner, Willy

Subjects:

500 Science > 580 Plants (Botany)
500 Science > 550 Earth sciences & geology

ISSN:

0959-6836

Publisher:

Sage

Language:

English

Submitter:

Peter Alfred von Ballmoos-Haas

Date Deposited:

04 Apr 2016 15:06

Last Modified:

09 Sep 2017 18:56

Publisher DOI:

10.1177/0959683615609746

Uncontrolled Keywords:

afforestation, forest diversity, human impact, mountain vegetation, palynology, Ulmus

BORIS DOI:

10.7892/boris.80014

URI:

https://boris.unibe.ch/id/eprint/80014

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