Pollen distribution of sediment core MD96-2048 from the Western Indian Ocean@en

Glacial-interglacial fluctuations in the vegetation of South Africa might elucidate the climate system at the edge of the tropics between the Indian and Atlantic Oceans. However, vegetation records covering a full glacial cycle have only been published from the eastern South Atlantic. We present a pollen record of the marine core MD96-2048 retrieved by the Marion Dufresne from the Indian Ocean ~120 km south of the Limpopo River mouth. The sedimentation at the site is slow and continuous. The upper 6 m (spanning the past 342 Ka) have been analysed for pollen and spores at millennial resolution. The terrestrial pollen assemblages indicate that during interglacials, the vegetation of eastern South Africa and southern Mozambique largely consisted of evergreen and deciduous forests. During glacials open mountainous scrubland dominated. Montane forest with Podocarpus extended during humid periods was favoured by strong local insolation. Correlation with the sea surface temperature record of the same core indicates that the extension of mountainous scrubland primarily depends on sea surface temperatures of the Agulhas Current. Our record corroborates terrestrial evidence of the extension of open mountainous scrubland (including fynbos-like species of the high-altitude Grassland biome) for the last glacial as well as for other glacial periods of the past 300 Ka.南非植被的冰期-间冰期波动，或可阐明印度洋与大西洋之间热带边缘区域的气候系统运作机制。然而，迄今仅南大西洋东部地区发表过覆盖完整冰期旋回的植被记录。本研究报道了由"马里恩·迪弗雷纳"号（Marion Dufresne）科考船于林波波河河口以南约120公里的印度洋海域获取的海洋岩芯（marine core）MD96-2048的孢粉（pollen）与孢子（spores）记录。该站位沉积速率缓慢且沉积序列连续，研究对岩芯上部6米（覆盖过去34.2万年，即342 Ka）的孢粉与孢子开展了千年分辨率（millennial resolution）的分析。陆生孢粉组合显示，间冰期阶段南非东部与莫桑比克南部的植被以常绿林和落叶林为主；冰期则以开阔山地灌丛占据主导。局地强日照加持的湿润期，更利于生长有罗汉松（Podocarpus）的山地森林扩张。通过与该岩芯的海表温度（sea surface temperature）记录对比可知，山地灌丛的扩张主要受控于阿古拉斯海流（Agulhas Current）的海表温度。本研究记录印证了末次冰期以及过去30万年以来其他冰期阶段，开阔山地灌丛（包括高海拔草原生物群系（biome）中类似凡波斯灌丛（fynbos）的物种）扩张的陆生证据。