Late Pliocene vegetation turnover on the NE Tibetan Plateau (Central Asia) triggered by early Northern Hemisphere glaciation
Late Pliocene vegetation turnover on the NE Tibetan Plateau (Central Asia) triggered by early Northern Hemisphere glaciation
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DOI：
10.1016/j.gloplacha.2019.06.001
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发表时间：
2019-09
影响因子：
3.9
通讯作者：
A. Koutsodendris;Frederik J. Allstädt;Oliver A. Kern;Ilias Kousis;F. Schwarz;Martina Vannacci;Amber Wou
中科院分区：
文献类型：
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作者：
A. Koutsodendris;Frederik J. Allstädt;Oliver A. Kern;Ilias Kousis;F. Schwarz;Martina Vannacci;Amber Wou
结果表明，柴达木盆地主要的草原/半荒漠生物群落在~3.6和3.3 Ma时发生了明显的更替。最值得注意的是，这些更替事件中较年轻的特征是蒿属植物以牺牲其他草原/半沙漠分类群为代价扩大了2至3倍。这一更替事件导致柴达木盆地古近纪以麻黄科/ chenopodiaceae为主，中新世丰富的麻黄科/ chenopodiaceae为主的草原/半荒漠被蒿科/ chenopodiaceae为主的草原/半荒漠所取代。在中国黄土高原和北太平洋中部的气候记录中，植被更替事件与中亚向干旱条件的转变是同步的。在全球范围内，它们可以与北半球上新世早期的冰川事件相关联。虽然与更新世相比，这些冰期相对较小，但向更干燥/更冷条件的过渡使以前存在的植物群落超出了它们的容忍极限，从而导致干旱生态系统的根本重组。这一重组导致的~3.3 Ma以来蒿属植物的优势标志着蒿/藜科花粉比可以作为中亚地区水分有效性的可靠指标。
To reconstruct the timing and underlying forcing of major shifts in the composition of terrestrial ecosystems in arid Central Asia during the late Cenozoic (past ~7 Ma), we carry out palynological analysis of lake sediments from the Qaidam Basin (NE Tibetan Plateau, China). Our results show that the steppe/semi-desert biomes dominating the Qaidam Basin experienced marked turnovers at ~3.6 and 3.3 Ma. Most notably, the younger of these turnover events is characterized by a two- to three-fold expansion ofArtemisiaat the expense of other steppe/semi-desert taxa. This turnover event led to the replacement of the Ephedraceae/Chenopodiaceae-dominated andNitraria-rich steppe/semi-deserts that were dominant in the Qaidam Basin during the Paleogene and abundant during the Miocene byArtemisia/Chenopodiaceae-dominated steppe/semi-deserts as they exist until today. The vegetation turnover events are synchronous with shifts towards drier conditions in Central Asia as documented in climate records from the Chinese Loess Plateau and the Central North Pacific Ocean. On a global scale, they can be correlated to early glaciation events in the Northern Hemisphere during the Pliocene. Integration of our palynological data from the Qaidam Basin with Northern Hemisphere climate-proxy and regional-scale tectonic information suggests that the uplift of the Tibetan Plateau posed ecological pressure on Central Asian plant communities, which made them susceptible to the effects of early Northern Hemisphere glaciations during the late Pliocene. Although these glaciations were relatively small in comparison to their Pleistocene counterparts, the transition towards drier/colder conditions pushed previously existing plant communities beyond their tolerance limits, thereby causing a fundamental reorganization of arid ecosystems. TheArtemisiadominance since ~3.3 Ma resulting from this reorganization marks a point in time after which theArtemisia/Chenopodiaceae pollen ratio can serve as a reliable indicator for moisture availability in Central Asia.