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

Science China Earth Sciences 2021年第3期64卷 425-439页

作者： Feng QIN Key Laboratory of Land surface Pattern and Simulation Institute of Geographic Sciences and Natural Resources ResearchChinese Academy of SciencesBeijing100101China

Modern pollen analysis is the basis for revealing the palaeovegetation and palaeoclimate changes from fossil pollen *** 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 *** 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 *** pollen assemblages from the desert zone contain substantially high relative abundance of Chenopodiaceae while those from the steppe zone are dominated by *** ratios show great potential in terms of separating different vegetation zones and to indicate climate changes on the Tibetan *** Artemisia/Chenopodiaceae ratio and arboreal/non-arboreal pollen ratio could be used as proxies for winter ***/Cyperaceae ratio and the sum of relative abundance of xerophilous elements increase with enhanced warming and *** 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 *** pollen-based vegetation classification models are established using a random forest *** random forest model can effectively separate the modern pollen assemblages of the steppe zone from those of the desert zone on the Tibetan *** model for distinguishing the four vegetation clusters shows a weaker but still valid classifying *** 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

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

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Science China Earth Sciences 2015年第9期58卷 1643-1655页

作者： QIN Feng ZHAO Yan LI Quan CAI MaoTang Key Laboratory of Land surface Pattern and Simulation Institute of Geographic Sciences and Nature Resources ResearchChinese Academy of Sciences

The modern pollen assemblages of surface lake sediments and topsoils in northwestern China were studied to understand the relationship of modem pollen data with contemporary vegetation and climate, and the differences between the pollen assem- blages of surface lake sediments and topsoils. The results show that Chenopodiaceae and Artemisia are dominant elements in the pollen assemblages of northwestern China. Additionally, Ephedra, Cyperaceae, Asteraceae, Poaceae, Picea, Pinus, and Betula are also important pollen taxa. Both pollen assemblages and principal component analysis indicate that pollen data from surface lake sediments and topsoils can be used to differentiate the main vegetation types of this region （desert, steppe, mead- ow and forest）. However, differences exist between modern pollen assemblages of the two types of sediments due to the dif- ferent relevant source areas of pollen and degrees of pollen preservation. For example, the larger relevant source area of sur- face lake sediment results in a higher abundance of Betula in pollen assemblage from surface lake sediment, whereas the ten- dency to disintegrate thin-walled pollen types in topsoil leads to a higher proportion of resistant pollen, such as Asteraceae. Linear regression analysis indicates that the Artemisia/Chenopodiaceae （A/C） ratio in pollen assemblages of surface lake sedi- ments can be used to indicate humidity changes in the study area. However, the A/C ratio in topsoils should be used carefully. Our results suggest that pollen data from surface lake sediments would be better references for interpreting the fossil pollen assemblages of lake cores or lacustrine profiles.

关键词： modern pollen assemblage surface lake sediment topsoil vegetation climate northwestern China

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