81 research outputs found
Late quaternary palaeoenvironments in the lake Barombi Mbo (West Cameroon) deduced from pollen and carbon isotopes of organic matter
Lithostratigraphy, volcanism, paleomagnetism and palynology of Quaternary lacustrine deposits from Barombi Mbo (West Cameroon) : preliminary results
Asymmetric response of forest and grassy biomes to climate variability across the African Humid Period : influenced by anthropogenic disturbance?
A comprehensive understanding of the relationship between land cover, climate change and disturbance dynamics is needed to inform scenarios of vegetation change on the African continent. Although significant advances have been made, large uncertainties exist in projections of future biodiversity and ecosystem change for the world's largest tropical landmass. To better illustrate the effects of climateâdisturbanceâecosystem interactions on continentalâscale vegetation change, we apply a novel statistical multivariate envelope approach to subfossil pollen data and climate model outputs (TraCEâ21ka). We target paleoenvironmental records across continental Africa, from the African Humid Period (AHP: ca 14 700â5500 yr BP) â an interval of spatially and temporally variable hydroclimatic conditions â until recent times, to improve our understanding of overarching vegetation trends and to compare changes between forest and grassy biomes (savanna and grassland). Our results suggest that although climate variability was the dominant driver of change, forest and grassy biomes responded asymmetrically: 1) the climatic envelope of grassy biomes expanded, or persisted in increasingly diverse climatic conditions, during the second half of the AHP whilst that of forest did not; 2) forest retreat occurred much more slowly during the mid to late Holocene compared to the early AHP forest expansion; and 3) as forest and grassy biomes diverged during the second half of the AHP, their ecological relationship (envelope overlap) fundamentally changed. Based on these asymmetries and associated changes in human land use, we propose and discuss three hypotheses about the influence of anthropogenic disturbance on continentalâscale vegetation change
Vegetation dynamics, palaeoenvironments and climatic changes in the forests of western Cameroon during the last 28,000 years B.P.
Paléo-anthropologie en Afrique centrale : un bilan de l'archéologie au Cameroun
Les rĂ©sultats polliniques majeurs obtenus dans le sud Cameroun, particuliĂšrement au lac Barombi Mbo, permettent de retracer l'histoire de la vĂ©gĂ©tation au cours du Quaternaire rĂ©cent. AprĂšs la derniĂšre grande phase aride, de 20 a 10 000 ans BP, la forĂȘt s'est complĂštement rĂ©installĂ©e dans la rĂ©gion peu aprĂšs le dĂ©but de l'HolocĂšne. Ensuite, l'Ă©vĂšnement est survenu vers 3 000 BP avec une ouverture et un recul brutal du massif forestier au profit des savanes. Cette pĂ©joration climatique a atteint son maximum entre 2500 et 2000 BP et s'est Ă©tendue Ă toute l'Afrique tropicale montrant qu'il s'agit d'un changement de grande ampleur. UltĂ©rieurement, Ă partir d'environ 2000 BP, la forĂȘt a commencĂ© Ă coloniser Ă nouveau les aires perdues. Cette transgression forestiĂšre se poursuit encore au XXe siĂšcle. Les donnĂ©es polliniques montrent aussi que le palmier Ă huile (Elaeis guineensis) a prĂ©sentĂ© une forte extension entre 3000 et 2000 BP, en association avec d'autres arbres pionniers. (RĂ©sumĂ© d'auteur
Late quaternary palaeoenvironments in the lake Barombi Mbo (West Cameroon) deduced from pollen and carbon isotopes of organic matter
Relation entre la composition en acides aminés libres des graines de fenugrec et la qualité aromatique
National audienc
Paléolacs et paléoclimats en Amérique latine et en Afrique (20 000 ans B.P. - Actuel) : résumés des communications présentées au séminaire
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