Reconstructing Holocene vegetation and climate history of Nam Co area (Tibet), using pollen and other palynomorphs Mark Herrmann a, * , Xinmiao Lu b , Jonas Berking c , Brigitta Schu ¨ tt c , Tandong Yao b , Volker Mosbrugger a a Senckenberg Research Institute and Natural History Museum, Susenckenberganlage 25, D-60325 Frankfurt/Main, Germany b Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Shuangqing Road NO.18, Haidian District, Beijing 100085, China c Freie Universita ¨t Berlin, Institut fu ¨r Geographische Wissenschaften, Malteserstrasse 74-100, D-12249 Berlin, Germany article info Article history: Available online 31 May 2009 abstract A drill core (1.8 m; 34 samples) was taken out of a swamp near Nam Co (Tibet, China) for palynological analysis. C 14 -Dating of the cores sediment at 3 different layers led to an numerical core age of about 8000 BP and the palynomorph content of prepared samples enabled reconstruction of the vegetation and climatic history of Nam Co Area. Pollen of Alpine Steppe elements together with Cyperaceae dominates the palynoflora reflecting the existing vegetation units around the lake throughout the investigated time span. Due to availability of water/precipitation, the different vegetation units extended or had to retreat, and hence the amount of their pollen increased or decreased. The presence of arboreal plants, verified by charcoal particles, suggest the existence of woodlands in the lake’s surrounding area until possibly human made fires changed the environment over time. Holocene climate history around Nam Co shows several phases of a strengthening/weakening or even an interruption of monsoonal activity. Changing conditions between dry and humid evolved from 8017 BP until 4800 BP. A mostly humid and relative stable system occurred from 4800 until 700 BP whereas the last 700 years are characterized by drier conditions according to fluctuating monsoonal activity. Humid or arid periods have been different in duration and intensity. The interaction of both parts of the monsoonal system, the South Asian Monsoon and the East Asian Monsoon, influenced the climatic conditions around Nam Co. Ó 2009 Elsevier Ltd and INQUA. All rights reserved. 1. Introduction The South Asian Monsoon and its fluctuations in intensity and dimension plays an important role for the Asian water balance in general as well as on the Tibetan Plateau in particular (e.g. Overpeck et al., 1996; Thompson et al., 2000; Anderson et al., 2002; Gupta et al., 2003; Duan et al., 2006). Its fundamental driving force is the land-sea heating contrast between the Indian Ocean and the Indian Subcontinent. In spring the air masses above the Indian Subconti- nent heat in a much shorter time than the air masses above the Indian Ocean, resulting in a South-West wind current transporting huge amounts of precipitation into Asia (Hodges, 2007). Many previous studies suggest that the Asian monsoon responds to changes in other parts of the climatic system, including the El Nino Southern Oscillation and the North Atlantic Thermohaline Circu- lation (see Hong et al., 2003, 2005; Morill et al., 2003). This paper examines the variability of the South Asian Monsoon using paly- nological data recovered from a drill core out of a swamp at Nam Co (South Central Tibet, China). Analysing the palynomorph content of those per maximum 8000 years old core samples provided the opportunity to reconstruct past vegetation changes due to fluctu- ations in precipitation. Hence, it has been possible to reconstruct monsoonal intensity around Nam Co in South Central Tibet and times in which monsoonal precipitation reached Nam Co. Human presence in Southern Tibet is documented by several scientists (see Miehe et al., 2008) from Last Glacial Maximum (Zhang and Li, 2002) through upper Palaeolithic sites, and a number of Neolithic sites (Chayet, 1994; Fu et al., 2000; Alden- dorfer and Zhang, 2004). Brantigham et al. (2007) suggest a more permanent occupation of the Tibetan Plateau not before 8200 BP. Miehe et al. (2006, 2008) have evidence for human induced envi- ronmental changes which have occurred at least over the past 4600 years around Lhasa. Did humans affect vegetation changes around Nam Co during Holocene times? The palynological results address this question for the last 8000 years. * Corresponding author: Tel.: þ49 69 97075 1185; fax: þ49 69 97075 1137. E-mail addresses: mark.herrmann@senckenberg.de (M. Herrmann), lvxm@itp- cas.ac.cn (X. Lu), Jonas.Berking@Fu-Berlin.de (J. Berking), schuett@geog.fu-berlin.de (B. Schu ¨ tt), tdyao@itpcas.ac.cn (T. Yao), volker.mosbrugger@senckenberg.de (V. Mosbrugger). Contents lists available at ScienceDirect Quaternary International journal homepage: www.elsevier.com/locate/quaint 1040-6182/$ – see front matter Ó 2009 Elsevier Ltd and INQUA. All rights reserved. doi:10.1016/j.quaint.2009.05.007 Quaternary International 218 (2010) 45–57