High-resolution vegetation history of West Africa during the last 145 ka Auteur(s) : Dalibard, Mathieu Popescu, Speranta-maria Maley, Jean Baudin, Francois Melinte-dobrinescu, Mihaela-carmen Pittet, Bernard Marsset, Tania Dennielou, Bernard Éditeur(s) : Elsevier France-editions Scientifiques Medicales Elsevier Résumé : The essential characteristics of the vegetation dynamics of tropical Africa remain only partially known. This study assesses the succession of vegetation-types over Central Africa during the last two glacial/interglacial cycles. Analysis of core KZai 02, which contains pollen from the Zaire River watershed (latitudes 9°N-13°S), allows the investigation of long-term patterns of plant ecosystem development and their climatic causes. Core KZai 02 (18.20 m long) was recovered from 6°24.20′S/9°54.10′E in the uppermost axial edifice of the Zaire deep sea fan. The chronology of this sedimentary archive was established using nannofossils and correlations of pollen and total organic carbon signals with the nearby core GeoB1008. The pollen record indicates that: (i) glacials (MIS 6, 4, 2) are marked by the development of afromontane (Podocarpus) forest at high altitudes when central basin lowlands were occupied by Cyperaceae marshes and savannah; (ii) during interglacials (MIS 1, 5) lowland forests were developed, marked by the successive expansion of pioneer, warm-temperate, rain forests, and mangrove indicating sea-level rise; (iii) glacial-interglacial transitions (MIS 6/5, 2/1) display similar vegetation dynamics. The strong evidence of afromontane forest and the opening of the vegetation during glacials suggest a reduced latitudinal distribution of rainfall by the strengthening of the trade wind system. West African monsoon systems were enhanced during interglacials, allowing the progressive development of lowland forests. The development of rain and pioneer forests during glacial Heinrich stadials suggests an enhancement of water availability in tropical Africa associated with these high latitude events. However, no augmentation of wind activity, described by previous studies, is evidenced by our pollen record. Similar vegetation successions during glacial/interglacial transitions suggest the diachronous and stepped intervention of CO2 (emphasizing the influence of temperature on plant ecosystems) and water availability. Geobios (0016-6995) (Elsevier France-editions Scientifiques Medicales Elsevier), 2014-07 , Vol. 47 , N. 4 , P. 183-198 Droits : 2014 Elsevier Masson SAS. All rights reserved. http://archimer.ifremer.fr/doc/00199/31031/29436.pdf DOI:10.1016/j.geobios.2014.06.002 http://archimer.ifremer.fr/doc/00199/31031/ | Partager Voir aussi Central Africa Climate Environmental parameters Late Pleistocene Pollen Vegetation dynamics Télécharger |
30 ans de biotechnologies à l’Ifremer Auteur(s) : Chatry, Gilles Éditeur(s) : Elsevier France-editions Scientifiques Medicales Elsevier Résumé : La France a initié les premières études de biotechnologies en rapport avec l’aquaculture, les produits et sous-produits de la pêche et l’environnement, il y a plus de 30 ans. Mais le tournant s’opère réellement en 1990 lorsque le spectre des molécules étudiées s’élargit. Grâce aux apports de la génomique et des souchothèques, les perspectives pour l’environnement et la santé s’annoncent très prometteuses pour l’Ifremer. Biofutur (0294-3506) (Elsevier France-editions Scientifiques Medicales Elsevier), 2014-12 , N. 360 , P. 26-27 Droits : 2014 Lavoisier SAS tous droits réservés http://archimer.ifremer.fr/doc/00252/36320/34867.pdf http://archimer.ifremer.fr/doc/00252/36320/ | Partager |
Microalgues: de petits végétaux aux grandes promesses ! Auteur(s) : Bougaran, Gael Saint-jean, Bruno Éditeur(s) : Elsevier France-editions Scientifiques Medicales Elsevier Résumé : Pour nos sociétés modernes, en quête de nouveaux procédés et de molécules actives innovantes, les microalgues représentent un formidable potentiel. Leurs nombreuses espèces et leur biodiversité constituent un réservoir de métabolites et de propriétés biochimiques quasi-inexploré, pour le développement de nouvelles applications biotechnologiques. Biofutur (0294-3506) (Elsevier France-editions Scientifiques Medicales Elsevier), 2014-12 , N. 360 , P. 28-31 Droits : 2015 LAVOISIER S.A.S. http://archimer.ifremer.fr/doc/00252/36321/34885.pdf http://archimer.ifremer.fr/doc/00252/36321/ | Partager |