Modern pollen assemblages of the surface lake sediments from the steppe and desert zones of the Tibetan Plateau  

作　　者：Feng QIN 

机构地区：[1]Key Laboratory of Land Surface Pattern and Simulation,Institute of Geographic Sciences and Natural Resources Research,Chinese Academy of Sciences,Beijing,100101,China

出　　处：《Science China Earth Sciences》2021年第3期425-439,共15页中国科学（地球科学英文版）

基　　金：the National Natural Science Foundation of China(Grant Nos.41671202&41690113);the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDA20070101);the National Key Research and Development Program of China(Grant No.2016YFA0600501)。

摘　　要：Modern pollen analysis is the basis for revealing the palaeovegetation and palaeoclimate changes from fossil pollen spectra.Many studies pertaining to the modern pollen assemblages on the Tibetan Plateau have been conducted,but little attention has been paid to pollen assemblages of surface lake sediments.In this study,modern pollen assemblages of surface lake sediments from 34 lakes in the steppe and desert zones of the Tibetan Plateau are investigated and results indicate that the two vegetation zones are dominated by non-arboreal pollen taxa and show distinctive characteristics.The pollen assemblages from the desert zone contain substantially high relative abundance of Chenopodiaceae while those from the steppe zone are dominated by Cyperaceae.Pollen ratios show great potential in terms of separating different vegetation zones and to indicate climate changes on the Tibetan Plateau.The Artemisia/Chenopodiaceae ratio and arboreal/non-arboreal pollen ratio could be used as proxies for winter precipitation.Artemisia/Cyperaceae ratio and the sum of relative abundance of xerophilous elements increase with enhanced warming and aridity.When considering the vegetation coverage around the lakes,hierarchical cluster analysis suggests that the studied sites can be divided into four clusters:meadow,steppe,desert-steppe,and desert.The pollen-based vegetation classification models are established using a random forest algorithm.The random forest model can effectively separate the modern pollen assemblages of the steppe zone from those of the desert zone on the Tibetan Plateau.The model for distinguishing the four vegetation clusters shows a weaker but still valid classifying power.It is expected that the random forest model can provide a powerful tool to reconstruct the palaeovegetation succession on the Tibetan Plateau when more pollen data from surface lake sediments are included.

关 键 词：Modern pollen assemblage Tibetan Plateau Surface lake sediment Pollen-climate relationship Pollen-based vegetation classification model 

分 类 号：P532[天文地球—古生物学与地层学] S812[天文地球—地质学]