Abstract
Quantifying the palaeoclimates of Qinghai–Tibetan Plateau is vital for understanding the uplift history of plateau and the evolution of Asian monsoon since Cenozoic. Recently, the Coexistence Approach (CA) has been employed to reconstruct the palaeoelevation and palaeoclimate of the plateau by several studies. However, the application of CA in mountainous areas and the realism of climate reconstructions via this method are seldom discussed, although the complexity of reconstructions is speculated. Here we reevaluated the realism of climate reconstruction using the CA with modern pollen samples from the Qinghai–Tibetan Plateau, and try to explore the possible factors influencing the precipitation and temperature reconstructions by CA. We suggest that the long-distance transport pollen as a result of the Asian summer monsoon potentially significantly affects the reconstructions both for precipitation and temperature. The precipitation complexly interacting with snowmelt and permafrost thaw leads to the discrepancy between the reconstructed precipitation and the real value. The response temperature for blossoming of dwarfed plants on the plateau is mostly likely higher than the air temperature (usually measured at 1.5 m above ground) due to energy flux or morphological adaptation of inflorescences during the growing season, causing the distortion of temperature reconstructions. Precipitation reconstruction is notoriously difficult as the establishers of CA have already suggested, but reconstructing the low temperatures may be even more challenging on Qinghai–Tibetan Plateau. Though all of the explorations in current paper are in a qualitative way, it offers an inspiration of how appropriately interpret the disagreements between CA results and the observations, and of how to obtain a reasonable reconstruction of palaeoclimate of the plateau.
Highlights
1 Introduction The Coexistence Approach (CA) is a plant-based method to reconstruct palaeoclimates, in which the climatic envelopes for each species found in a fossil assemblage are superimposed and the climate interval common to all species is assumed to represent the climate of the sampling site (Mosbrugger and Utescher 1997; Utescher et al 2014; Zhang 2016)
The Coexistence Approach is a quantitative method of palaeoclimate reconstruction that is frequently employed by many scientists to retrace the palaeoclimates of Eurasian continents (e.g. Mosbrugger and Utescher 1997; Bruch et al 2006; Erdei et al 2007; Yang et al 2007; Xia et al 2009; Yao et al 2009; Jacques et al 2011; Qin et al Table 1 Comparisons among weighted reconstructions (WR), non-trees reconstructions (NTR) and observed climates from Zhang et al 2015
3.1 Influence of long-distance transported pollen on climate reconstructions Pollen transportation with long distance on Qinghai–Tibetan Plateau has already been found in several studies (e.g. Cour et al 1999; Yu et al 2001; Jiang and Ding 2009; Lu et al 2010; Zhang et al 2018)
Summary
The Coexistence Approach (CA) is a plant-based method to reconstruct palaeoclimates, in which the climatic envelopes for each species found in a fossil assemblage are superimposed and the climate interval common to all species is assumed to represent the climate of the sampling site (Mosbrugger and Utescher 1997; Utescher et al 2014; Zhang 2016). Zhang et al (2015) is the first study to evaluate the realism of climate reconstructions using the method of CA with modern pollen samples from the Qinghai– Tibetan Plateau.
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