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Climate of the Past An interactive open-access journal of the European Geosciences Union
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Volume 14, issue 10 | Copyright

Special issue: “Global Challenges for our Common Future: a paleoscience...

Clim. Past, 14, 1543-1563, 2018
https://doi.org/10.5194/cp-14-1543-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 23 Oct 2018

Research article | 23 Oct 2018

Fire, vegetation, and Holocene climate in a southeastern Tibetan lake: a multi-biomarker reconstruction from Paru Co

Alice Callegaro1,2, Dario Battistel1, Natalie M. Kehrwald3, Felipe Matsubara Pereira1, Torben Kirchgeorg1, Maria del Carmen Villoslada Hidalgo1, Broxton W. Bird4, and Carlo Barbante1,2 Alice Callegaro et al.
  • 1Department of Environmental Sciences, Informatics and Statistics, Ca' Foscari University of Venice, 30172, Venice, Italy
  • 2Institute for the Dynamics of Environmental Processes – CNR, 30172, Venice, Italy
  • 3Geosciences and Environmental Change Science Center, U.S. Geological Survey, Denver Federal Center, Denver, CO 80225, USA
  • 4Department of Earth Sciences, Indiana University–Purdue University, Indianapolis, IN 46208, USA

Abstract. The fire history of the Tibetan Plateau over centennial to millennial timescales is not well known. Recent ice core studies reconstruct fire history over the past few decades but do not extend through the Holocene. Lacustrine sedimentary cores, however, can provide continuous records of local environmental change on millennial scales during the Holocene through the accumulation and preservation of specific organic molecular biomarkers. To reconstruct Holocene fire events and vegetation changes occurring on the southeastern Tibetan Plateau and the surrounding areas, we used a multi-proxy approach, investigating multiple biomarkers preserved in core sediment samples retrieved from Paru Co, a small lake located in the Nyainqentanglha Mountains (29°47′45.6′′N, 92°21′07.2′′E; 4845ma.s.l.). Biomarkers include n-alkanes as indicators of vegetation, polycyclic aromatic hydrocarbons (PAHs) as combustion proxies, fecal sterols and stanols (FeSts) as indicators of the presence of humans or grazing animals, and finally monosaccharide anhydrides (MAs) as specific markers of vegetation burning processes. Insolation changes and the associated influence on the Indian summer monsoon (ISM) affect the vegetation distribution and fire types recorded in Paru Co throughout the Holocene. The early Holocene (10.7–7.5calkyrBP) n-alkane ratios demonstrate oscillations between grass and conifer communities, resulting in respective smouldering fires represented by levoglucosan peaks, and high-temperature fires represented by high-molecular-weight PAHs. Forest cover increases with a strengthened ISM, where coincident high levoglucosan to mannosan (LM) ratios are consistent with conifer burning. The decrease in the ISM at 4.2calkyrBP corresponds with the expansion of regional civilizations, although the lack of human FeSts above the method detection limits excludes local anthropogenic influence on fire and vegetation changes. The late Holocene is characterized by a relatively shallow lake surrounded by grassland, where all biomarkers other than PAHs display only minor variations. The sum of PAHs steadily increases throughout the late Holocene, suggesting a net increase in local to regional combustion that is separate from vegetation and climate change.

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Holocene fires and vegetation are reconstructed using different molecular markers with a single analytical method, applied for the first time to lake sediments from Tibet. The early Holocene shows oscillations between grasses and conifers, with smouldering fires represented by levoglucosan peaks, and high-temperature fires represented by PAHs. The lack of human FeSts excludes local human influence on fire and vegetation changes. Late Holocene displays an increase in local to regional combustion.
Holocene fires and vegetation are reconstructed using different molecular markers with a single...
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