Modern pollen assemblages and their relationships to vegetation and climate in the Lhasa Valley, Tibetan Plateau, China Yan-Jie Zhang a, b, 1 , La Duo c, *, 1 , You-Zhi Pang d , Vivian A. Felde e , Hilary H. Birks e , H. John B. Birks e, f a Lhasa Plateau Ecosystem Research Station, Key Laboratory of Ecosystem Network Observation and Modelling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, PR China b University of Chinese Academy of Sciences, Beijing 100049, PR China c School of Science, Tibet University, Lhasa 850000, PR China d College of Geography and Resources Sciences, Neijiang Normal University, Neijiang 641100, PR China e Department of Biology and Bjerknes Centre for Climate Research, University of Bergen, PO Box 7803, N-5020 Bergen, Norway f Environmental Change Research Centre, University College London, London, UK article info Article history: Received 3 August 2017 Received in revised form 30 January 2018 Accepted 30 January 2018 Available online xxx Keywords: Climatic variables Co-correspondence analysis Multivariate analysis Pollen equivalents Pollen ratios Procrustes analysis abstract Forty-seven surface pollen samples and 141 vegetation quadrats were investigated in the Lhasa Valley in order to assess the relationships between local modern pollen assemblages and vegetation and climate. The regional climatic data for each sample are mean annual precipitation (P ann ), mean annual temper- ature (T ann ), summer temperature (T summer ), actual evapotranspiration (AET), potential evapotranspira- tion (PET), and moisture index (MI), estimated by co-kriging using meteorological data from 16 climate stations in or near the Lhasa Valley. Cluster analysis, principal components analysis (PCA), Procrustes analysis, and co-correspondence analysis (Co-CA) were used to evaluate the relationship between modern pollen assemblages and contemporary vegetation. Linear regression was used to examine the relationships between pollen ratios (Artemisia/Chenopodiaceae (A/C), Artemisia/Cyperaceae (A/Cy), Artemisia þ Chenopodiaceae/Cyperaceae (AC/Cy)), aridity pollen index, total arboreal pollen (AP), and the climatic variables. Cluster analysis and PCA results are generally consistent, and differentiate between pollen assemblages from arid conditions and those from more humid conditions. However, the PCA results distinguish pollen assemblages from shrubland slightly more clearly than the cluster analysis does. The PCA results show a general agreement between the modern pollen assemblages and contemporary vegetation types, but pollen assemblages from coniferous (Juniperus) woodland cannot be distinguished from shrub grassland, meadow, or shrub meadow pollen assemblages in the PCA results. Both Procrustes analysis and associated permutation tests and Co-CA show a strong statistically signif- icant relationship between modern pollen and vegetation composition. Analysis of the relationship between the climatic variables and vegetation types suggests that humidity (P ann and MI) is the main variable related to the vegetation types within the restricted areas of the Lhasa Valley. Neither the A/C ratio nor the aridity pollen index is a reliable aridity indicator in the Lhasa Valley. The AP sum may be a weak precipitation indicator, whereas the A/Cy and AC/Cy ratios appear to be robust indicators of pre- cipitation, aridity, and temperature at the scale of the Lhasa Valley. © 2018 Elsevier Ltd and INQUA. All rights reserved. 1. Introduction Assessing the relationship between modern pollen assemblages and present-day vegetation is an essential step for the interpreta- tion and reconstruction of vegetation history from pollen data due to differential pollen production, dispersal, deposition, and pres- ervation (Birks and Berglund, 2017; Birks and Birks, 1980). These relationships may vary between different areas (Chang et al., 2017). A strong relationship between modern pollen records and climatic variables is also a critical prerequisite for past climate reconstruc- tion from fossil pollen assemblages (Birks et al., 2010). Research on these relationships has been carried out in many regions around * Corresponding author. School of Science, Tibet University, Lhasa 850000, PR China. E-mail addresses: zhangyanjie_zyj@163.com (Y.-J. Zhang), lhaduo@hotmail.com (L. Duo), pangyzh137@126.com (Y.-Z. Pang), Hilary.Birks@uib.no (H.H. Birks), John. Birks@uib.no (H.J.B. Birks). 1 These authors contributed equally to this work. Contents lists available at ScienceDirect Quaternary International journal homepage: www.elsevier.com/locate/quaint https://doi.org/10.1016/j.quaint.2018.01.040 1040-6182/© 2018 Elsevier Ltd and INQUA. All rights reserved. Quaternary International xxx (2018) 1e12 Please cite this article in press as: Zhang, Y.-J., et al., Modern pollen assemblages and their relationships to vegetation and climate in the Lhasa Valley, Tibetan Plateau, China, Quaternary International (2018), https://doi.org/10.1016/j.quaint.2018.01.040