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A 90,000-year record of Afromontane forest responses to climate change

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Science  11 Jan 2019:
Vol. 363, Issue 6423, pp. 177-181
DOI: 10.1126/science.aav6821

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Ancient changes in the African tropics

Long-term records of past vegetation change are key to understanding how climate change affects ecosystems, but data are scarce—especially in highly biodiverse regions in the tropics. Lezine et al. present a detailed 90,000-year pollen core from an upland crater-lake site in the west African tropical montane forest, which is important from conservation and biogeographic standpoints. The upper treeline moved in response to climate change during the Pleistocene glacial and interglacial periods, whereas the lower limit of the Afromontane forest was stable. The constituent species of the forest also changed. This record resolves debates concerning the biogeographic history of Afromontane vegetation.

Science, this issue p. 177

Abstract

Pollen records from African highlands are scarce; hence, the paleoecology of the Afromontane forest and its responses to glacial cycles are poorly known. Lake Bambili (Cameroon) provides a record of vegetation changes in the tropical mountains of Africa over the past 90,000 years, with high temporal resolution. Pollen data and biome reconstructions show a diverging response of forests to climate changes; the upper tree line was extremely unstable, shifting substantially in response to glacial-interglacial climate alternation, whereas the transition between the montane and lowland forests remained remarkably stable. Such ecological instability may have had a critical influence on species richness in the Afromontane forests.

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