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