Holocene climate and vegetation change in the Main Ethiopian Rift Valley, inferred from the composition (C/N and δ13C) of lacustrine organic matter

Angela L. Lamb*, Melanie J. Leng, Mohammed Umer Mohammed, Henry F. Lamb

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

89 Citations (SciVal)

Abstract

In order to track changes in the relative abundance of C3 and C4 plants in savanna vegetation, C/N and δ13C values were measured on bulk organic material in an 8840 14C-year record from Lake Tilo, Ethiopia. Between 8840 and 2500 BP, high C/N ratios suggest that input to the lake was predominantly from terrestrial plants. The corresponding δ13C values thus provide a proxy for changes in catchment vegetation that are supported by pollen data. δ13C values in the early Holocene are relatively low, reflecting the dominance of C3 vegetation (woody plants) and a more humid climate. δ 13C shows no response to a known regional arid interval at 7800yr BP, suggesting that woody vegetation was able to survive relatively prolonged dry periods. A gradual, rather than sharp, δ13C response to the end of the early Holocene humid interval at ∼4500yr BP further supports this. Higher δ13C values at ∼2800-2300 and ∼1000yr BP correspond to increases in sedge pollen, thought to be growing in freshwater springs, exposed as lake-level fell. The C/N and δ13C composition of bulk organic material complements the pollen evidence and may be useful in other lakes in savanna regions as indicators of terrestrial vegetation change.

Original languageEnglish
Pages (from-to)881-891
Number of pages11
JournalQuaternary Science Reviews
Volume23
Issue number7-8
Early online date27 Feb 2004
DOIs
Publication statusPublished - 01 Apr 2004

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