4 research outputs found
Une légumineuse alimentaire, le niébé
Le niĂ©bĂ©, Vigna unguiculata (L.) Walp., fait partie des principales lĂ©gumineuses alimentaires mondiales. Il est aujourdâhui cultivĂ© dans toutes les zones intertropicales et mĂȘme au-delĂ Â : bassin mĂ©diterranĂ©en, Iran, Chine, sud des Ătats-Unis... Le niĂ©bĂ© est, comme le voandzou (Vigna subterranea (L.) Verdc.), une espĂšce africaine. Les formes spontanĂ©es du niĂ©bĂ© se rencontrent uniquement en Afrique (elles sont dâailleurs assez communes dans le nord du Cameroun) oĂč il a Ă©tĂ© domestiquĂ©, il y a qu..
Atlas de la province ExtrĂȘme-Nord Cameroun
RĂ©alisĂ© par lâIRD et lâINC (Institut national de cartographie, YaoundĂ©), lâAtlas de la province ExtrĂȘme-Nord Cameroun a Ă©tĂ© publiĂ© en avril 2000 en grand format. Lâensemble rĂ©unit et synthĂ©tise une somme considĂ©rable de rĂ©sultats de recherche collectĂ©s, trois dĂ©cennies durant, par une vingtaine de chercheurs. Trente-neuf cartes, accompagnĂ©es de notices trĂšs Ă©toffĂ©es et dâun grand nombre de graphiques, diagrammes, tableaux et dessins, rendent compte de lâenvironnement physique, des Ă©lĂ©ments dĂ©mographiques, ethniques, archĂ©ologiques et linguistiques, et de toute la diversitĂ© des ressources agraires. Trois cartes traitent en outre de questions trĂšs spĂ©cifiques au nord du pays : parcs et vĂ©gĂ©tation anthropique ; aliments de famine ; stratĂ©gies de conservation du grain. La prĂ©sente rĂ©Ă©dition amĂ©liore beaucoup les possibilitĂ©s de visualisation dĂ©taillĂ©e sur PC par rapport Ă la premiĂšre version cĂ©dĂ©rom qui accompagnait lâatlas papier. Elle fait partie dâun ensemble de trois cĂ©dĂ©roms qui offrent, sous une forme nettement plus compacte, lâensemble des atlas rĂ©alisĂ©s par lâOrstom/IRD au Cameroun, dont la plupart sont maintenant introuvables
Distance decay 2.0 â A global synthesis of taxonomic and functional turnover in ecological communities
Aim
Understanding the variation in community composition and species abundances (i.e., ÎČ-diversity) is at the heart of community ecology. A common approach to examine ÎČ-diversity is to evaluate directional variation in community composition by measuring the decay in the similarity among pairs of communities along spatial or environmental distance. We provide the first global synthesis of taxonomic and functional distance decay along spatial and environmental distance by analysing 148 datasets comprising different types of organisms and environments.
Location
Global.
Time period
1990 to present.
Major taxa studied
From diatoms to mammals.
Method
We measured the strength of the decay using ranked Mantel tests (Mantel r) and the rate of distance decay as the slope of an exponential fit using generalized linear models. We used null models to test whether functional similarity decays faster or slower than expected given the taxonomic decay along the spatial and environmental distance. We also unveiled the factors driving the rate of decay across the datasets, including latitude, spatial extent, realm and organismal features.
Results
Taxonomic distance decay was stronger than functional distance decay along both spatial and environmental distance. Functional distance decay was random given the taxonomic distance decay. The rate of taxonomic and functional spatial distance decay was fastest in the datasets from mid-latitudes. Overall, datasets covering larger spatial extents showed a lower rate of decay along spatial distance but a higher rate of decay along environmental distance. Marine ecosystems had the slowest rate of decay along environmental distances.
Main conclusions
In general, taxonomic distance decay is a useful tool for biogeographical research because it reflects dispersal-related factors in addition to species responses to climatic and environmental variables. Moreover, functional distance decay might be a cost-effective option for investigating community changes in heterogeneous environments