Kalibrierte, Pollen-basierte Rekonstruktion der ostafrikanischen Vegetations- und Landschaftsveränderungen während der gesamten Existenz von anatomisch modernen Menschen aus den ~ 250.000 Jahre alten Challa-See-Sedimenten
Ökologie und Biodiversität der Pflanzen und Ökosysteme
Zusammenfassung der Projektergebnisse
Lake Chala provides a unique opportunity to study long-term climate and environmental dynamics in a grassland ecosystem. We reconstructed 160,000 years of vegetation dynamics from the upper 121 m of the sediment core, covering a full glacial-interglacial period. The vegetation structure that is recorded in the pollen record of Lake Chala is rather complex, consisting not only of the surrounding wooded grasslands but also the montane vegetation of Mount Kilimanjaro and the dry and wet forests that grow within the rim of the crater itself. The wooded grassland is represented mainly by the overwhelming presence of grass pollen that dominate the record throughout with the wooded taxa fairly underrepresented but showing a response to the changing temperatures. Montane vegetation is also underrepresented, but some patterns can be discerned. During the African Mega Drought from ~115 to 98 ka BP many smaller changes occur in various montane taxa. During the Last Glacial Maximum around ca. 20 ka BP the ericaceous vegetation of the Afroalpine zone increased. The crater vegetation seems less well defined before the Holocene. Many of the important taxa, while present throughout the record, peak in the last 5,000 years. The most pronounced changes in vegetation occurred during the Holocene, with the trees of the wooded grasslands increasing, the Afromontane forest taxa decreasing and the full development of the crater vegetation. Overall, the main driver of vegetation change seems to be temperature, with water balance playing only a minor role. Sediment trap data was collect to examine seasonality of the modern pollen rain. In general, the pollen composition of the sediment traps was similar to that found in the sediment core. Only the very high percentage of Euphorbia pollen present in the uppermost sample of the pollen record was not replicated here. Pollen of the trees of the wooded grassland is found mostly during the two rain seasons. Afromontane taxa on the other hand peak during the dry season in September.
Projektbezogene Publikationen (Auswahl)
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Climate-human-landscape interaction in the eastern foothills of Mt. Kilimanjaro (equatorial East Africa) during the last two millennia. The Holocene, 31(4), 556-569.
van der Plas, Geert W; Rucina, Stephen M; Hemp, Andreas; Marchant, Robert A; Hooghiemstra, Henry; Schüler, Lisa & Verschuren, Dirk
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Modern pollen studies from tropical Africa and their use in palaeoecology. Quaternary Vegetation Dynamics – The African Pollen Database (c(2021, 11, 28)), 317-348. CRC Press.
Julier, Adele C.M.; Manzano, Saúl; Razanatsoa, Estelle; Razafimanantsoa, Andriantsilavo H.I.; Githumbi, Esther; Hawthorne, Donna; Oden, Glory; Schüler, Lisa; Tossou, Monique & Bunting, Jane
