TY - JOUR
T1 - Holocene climate and vegetation change in the Main Ethiopian Rift Valley, inferred from the composition (C/N and δ13C) of lacustrine organic matter
AU - Lamb, Angela L.
AU - Leng, Melanie J.
AU - Mohammed, Mohammed Umer
AU - Lamb, Henry F.
N1 - Funding Information:
The authors would like to thank Dr. Solomon Tadesse and Professor Getaneh Assefa from the Department of Geology and Geophysics, University of Addis Ababa for help with many aspects of fieldwork in Ethiopia. Dr. Elias Dadebo and Dr. Zinabu Gebre-Mariam from the Awassa College of Agriculture also kindly arranged fieldwork permits and assisted with fieldwork. Special thanks are also due to Richard Telford for useful discussions and to Seifu Kedebe, Wolde Selassie, Geoff Duller and Nick Pearce for help in the field. Hilary Sloane and Carol Arrowsmith (NERC Isotope Geosciences Laboratory) provided technical assistance with isotope analysis. Finally the authors would like to thank Françoise Gasse and Matthew Wooller for their useful reviews of the manuscript. This research was supported by a NERC case studentship with the NERC Isotope Geosciences Laboratory and a NERC research grant (GR3/10767). NIGL publication number 568.
PY - 2004/4/1
Y1 - 2004/4/1
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=1642326864&partnerID=8YFLogxK
U2 - 10.1016/j.quascirev.2003.06.010
DO - 10.1016/j.quascirev.2003.06.010
M3 - Article
AN - SCOPUS:1642326864
SN - 0277-3791
VL - 23
SP - 881
EP - 891
JO - Quaternary Science Reviews
JF - Quaternary Science Reviews
IS - 7-8
ER -