Did the savannah 'flourished' 3000 years ago in the so-called Sangha River Interval of the Guineo-Congolian rainforest ? : a retrospective study using stable isotopes and phytoliths : poster

International audience; We aim to improve our knowledge of the dynamic of the vegetation in Central Africa during the last 5 kyrsand to discuss the main hypothesis described in the literature - humans versus climatic impacts- both suggestedas responsible of the Congo basin rainforest decline observed between 3 and 2.5 kyrs. We use the carbon isotopiccomposition of well-dated Central African soils to reconstruct the dynamic of the vegetation cover.We will discussthe carbon isotopic composition of the soil organic carbon methodology for reconstructing palaeovegetation in thelight of Rayleigh distillation model. We showed that numerous sites exhibit a carbon isotopic ratios reflectingthe Rayleigh distillation but few sites recorded real vegetation changes. Our study suggests that the vegetationof the Guineo-Congolian Region was disturbed between 3000 and 2000 BP (Before Present) without an extremesavannah expansion. We discussed the two hypotheses human versus climate impacts that may conduct to suchnew physiography of the vegetation. We suggest that the climate hypothesis is more likely than the human impactto explain the reduction of the Guineo-Congolian rainforest 3000 years ago.