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Effect of aridity and rainfall seasonality on vegetation in the southern tropics of East Africa during the Pleistocene/Holocene transition

Published online by Cambridge University Press:  20 January 2017

Sarah J. Ivory*
Affiliation:
University of Arizona – Department of Geosciences, Tucson, AZ, USA
Anne-Marie Lézine
Affiliation:
Laboratoire des Sciences du Climat et de l'Environnement, UMR 1572 CNRS, CEA UVSQ, Orme des Merisiers, 91191 Gif-sur-Yvette cedex, France
Annie Vincens
Affiliation:
CEREGE, UMR 6635 (CNRS, Université Aix-Marseille, IRD, CdF), BP 80, F-13545 Aix-en-Provence, cedex 04, France
Andrew S. Cohen
Affiliation:
University of Arizona – Department of Geosciences, Tucson, AZ, USA
*
*Corresponding author. Fax: + 1 520 621 2672. E-mail address:ivorysj@email.arizona.edu (S.J. Ivory).

Abstract

Fossil pollen analyses from northern Lake Malawi, southeast Africa, provide a high-resolution record of vegetation change during the Pleistocene/Holocene transition (~ 18–9 ka). Recent studies of local vegetation from lowland sites have reported contrasting rainfall signals during the Younger Dryas (YD). The Lake Malawi record tracks regional vegetation changes and allows comparison with other tropical African records identifying vegetation opening and local forest maintenance during the YD. Our record shows a gradual decline of afromontane vegetation at 18 ka. Around 14.5 ka, tropical seasonal forest and Zambezian miombo woodland became established. At ~ 13 ka, drier, more open formations gradually became prevalent. Although tropical seasonal forest taxa were still present in the watershed during the YD, this drought-intolerant forest type was likely restricted to areas of favorable edaphic conditions along permanent waterways. The establishment of drought-tolerant vegetation followed the reinforcement of southeasterly tradewinds resulting in a more pronounced dry winter season after ~ 11.8 ka. The onset of the driest, most open vegetation type was coincident with a lake low stand at the beginning of the Holocene. This study demonstrates the importance of global climate forcing and local geomorphological conditions in controlling vegetation distribution.

Information

Type
Original Articles
Copyright
University of Washington

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