Modern pollen distributions in Qinghai-Tibetan Plateau and the development of transfer functions for reconstructing Holocene environmental changes Houyuan Lu a, * , Naiqin Wu a , Kam-biu Liu b , Liping Zhu c , Xiangdong Yang d , Tandong Yao c , Luo Wang a , Quan Li a , Xingqi Liu d , Caiming Shen e , Xiaoqiang Li f , Guobang Tong g , Hui Jiang h a Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China b Department of Oceanography and Coastal Sciences, Louisiana State University, Baton Rouge, LA 70803, USA c Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100085, China d State Key Laboratory of Lake Science and Environment, Nanjing Institute of Limnology and Geography, Chinese Academy of Sciences, Nanjing 210008, China e Atmospheric Sciences Research Center, State University of New York, Albany, NY 12203, USA f Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China g Institute of Hydrology and Geology, Chinese Academy of Geological Sciences, Zhengding 050803, China h State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200062, China article info Article history: Received 23 March 2010 Received in revised form 23 December 2010 Accepted 18 January 2011 Available online 9 February 2011 Keywords: Qinghai-Tibetan plateau Vegetation Pollen Transfer functions Holocene Climatic changes abstract This study investigates the distribution of modern pollen assemblages in the Qinghai-Tibetan Plateau, China, based on surface soil samples collected at 1202 sites along an altitudinal gradient of 10 e5500 m asl, where mean annual precipitation (MAP) ranges from 12 to 1840 mm and mean annual temperature (MAT) from 7 to 21.5  C. A total of 153 pollen taxa were found with relative abundances greater than 1% in at least two samples. Canonical correspondence analysis (CCA) was used to determine the main environmental variables influencing pollen distributions. The results reveal that MAP is the most significant dominant variable. However, MAT, altitude (ALT), July temperature (MT7), and relative humidity (HHH) are also significant variables that clearly follow the gradients in the CCA ordination, suggesting that pollen assemblages probably not only reflect a single climatic parameter, but also a variety of other climatic inter-related parameters. Transfer functions, based on locally weighted weighted averaging (LWWA), were developed for MAP (R 2 -boot ¼ 0.89, RMSEP ¼ 109 mm), MAT (R 2 -boot ¼ 0.78, RMSEP ¼ 2.3  C), ALT (R 2 -boot ¼ 0.73, RMSEP ¼ 597 m), HHH (R 2 -boot ¼ 0.82, RMSEP ¼ 4.5%), and July mean precipitation (MP7) (R 2 - boot ¼ 0.87, RMSEP ¼ 23 mm). Overall, our results confirm that pollen can provide reliable estimates of the primary climatic parameters. The application of the LWWA model to the fossil records of Chen Co Lake allowed quantitative inferences to be made about Holocene climatic changes in the southern Tibetan Plateau, suggesting that LWWA is a robust calibration method for quantitative palaeo-environ- mental reconstruction based on pollen data in the regions. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Accurate quantitative reconstructions of regional environmental patterns are needed to understand the global and regional changes in climate and environment and to assess global circulation models on a regional scale (COHMAP Members, 1988; Holmgren and Tjus, 1996; Nakagawa et al., 2002; Seppä et al., 2004; Lu et al., 2007). The Qinghai-Tibetan Plateau, with an area of over 2.3 million km 2 at an average elevation of over 4000 m asl, is the largest and highest mountain plateau on Earth (Liu and Chen, 2000). Its global signif- icance does not lie simply in its physical parameters, but more importantly in influencing the atmospheric circulation of the Northern Hemisphere, and in constituting a significant forcing factor on the intensity of the Asian monsoons (Kutzbach et al., 1989; An et al., 2001). However, there are only a few quantitative envi- ronmental records available for the Qinghai-Tibetan Plateau region (Shen, 2006,2008; Herzschuh et al., 2009a,b,2010). These are generally limited to tree ring studies (Shao et al., 2005; Gou et al., 2007), ice core records (Yao et al., 2008), and meteorological records (the latter spanning less than 40 years). Recent advances in quantitative environmental reconstruction techniques have led to rapid expansion of fossil-based long-term * Corresponding author. Tel.: þ86 10 82998259; fax: þ86 10 8299 8122. E-mail address: Houyuanlu@mail.iggcas.ac.cn (H. Lu). Contents lists available at ScienceDirect Quaternary Science Reviews journal homepage: www.elsevier.com/locate/quascirev 0277-3791/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.quascirev.2011.01.008 Quaternary Science Reviews 30 (2011) 947e966