A modern pollen–climate calibration set based on lake sediments from the Tibetan Plateau and its application to a Late Quaternary pollen record from the Qilian Mountains

Abstract

Aim Fossil pollen spectra from lake sediments on the Tibetan Plateau have been used for qualitative climate reconstruction, but no modern pollen–climate calibration set based on lake sediments is available to infer past climate quantitatively. This study aims to develop such a dataset and apply it to fossil data. Location The Tibetan Plateau, between 30 and 40° N and 87 and 103° E. Methods We collected surface sediments from 112 lakes and analysed them palynologically. The lakes span a wide range of mean annual precipitation (Pann; 31–1022 mm), mean annual temperature (Tann; −6.5 to 1 °C), and mean July temperature (TJuly; 2.6–19.7 °C). Redundancy analysis showed that the modern pollen spectra are characteristic of their respective vegetation types and local climate. Transfer functions for Pann, Tann and TJuly were developed with weighted averaging partial least squares. Model performance was assessed by leave‐one‐out cross‐validation. Results The root mean square errors of prediction (RMSEP) were 104 mm (Pann), 1.18 °C (Tann) and 1.17 °C (TJuly). The RMSEPs, when expressed as percentages of the gradient sampled, were 10.6% (Pann), 15.7% (Tann) and 11.9% (TJuly). These low values indicate the good performance of our models. An application of the models to fossil pollen spectra covering the last c. 50 kyr yielded realistic results for Luanhaizi Lake in the Qilian Mountains on the north‐eastern Tibetan Plateau (modern Pann 480 mm; Tann−1 °C). Tann and Pann values similar to present ones were reconstructed for late Marine Isotope Stage 3, with minimum values for the Last Glacial Maximum (c. 300 mm and 2 °C below present), and maximum values for the early Holocene (c. 70 mm and 0.5 °C greater than present). Main conclusions The modern pollen–climate calibration set will potentially be useful for quantitative climate reconstructions from lake‐sediment pollen spectra from the Tibetan Plateau, an area of considerable climatic and biogeographical importance.

Strengths and Weaknesses of Quantitative Climate Reconstructions Based on Late-Quaternary Biological Proxies

“…Besides having consistent taxonomy and nomenclature and being of comparable quality, the modern biological data should be from the same sedimentary environment (e.g. lakes of similar size) as the fossil data-sets used for reconstruction purposes (Herzschuh et al 2010a). Recent developments in modelling pollen-source areas (e.g.…”

Lagged response of summer precipitation to insolation forcing on the northeastern Tibetan Plateau during the Holocene

“…However, significant discrepancies exist among different proxy records; in particular, pollen and ostracod oxygen isotope (δ 18 O) records indicate different periods for the climatic optimum during the Holocene (Lu et al 2010;. Pollen records from Qinghai Lake and the surrounding lakes of the northeastern Tibetan Plateau suggest a relatively dry early Holocene, with the wettest period spanning the middle Holocene, and then another dry period in the late Holocene Herzschuh et al 2010;Cheng et al 2013;Wang et al 2014a). Pollen-based moisture changes lag the Northern Hemisphere June insolation maxima by ~3 ka.…”

Modern pollen assemblages from surface lake sediments in northwestern China and their importance as indicators of vegetation and climate

“…The deciphering of fossil pollen data must be performed on the basis of the investigation of modern pollen assemblages. Numerous studies (e.g., Wright et al, 1967;Gaillard et al, 1992;Sugita, 1994;Cour et al, 1999;Davis, 2000;Shen et al, 2006;Ma et al, 2008;Zhao and Herzschuh, 2009;Herzschuh et al, 2010;Lu et al, 2011;Fall, 2012;Zheng et al, 2013;Tian et al, 2014) have been conducted to understand the relationship of modern pollen assemblages with contemporary vegetation and climate. Modern pollen assemblages are mainly collected from airborne pollen collectors (e.g., Cour et al, 1999;Giesecke et al, 2010), moss polsters (e.g., Hicks and Birks, 1996;Mazier et al, 2006), topsoils (e.g., Xu et al, 2009;Zhang et al, 2010) and surface lake sediments (e.g., Herzschuh, 2007;Seppa et al, 2004).…”

“…Herzschuh (2007) investigated the modern pollen assemblages of 113 lakes, and established a surface lake sediment pollen database in the northeastern Tibetan Plateau. Based on this database, Herzschuh and her colleagues (Herzschuh et al, , 2010 developed pollen-climate transfer functions for the northeastern Tibetan Plateau, and used the transfer functions to quantitatively reconstruct the Holocene climatic changes in Lakes Koucha , Luanhaizi (Herzschuh et al, 2010) and Ximencuo . Tian et al (2014) reported the pollen assemblages from surface lake sediments of 90 lakes in central-western Mongolia.…”