Search results for "Central Africa"
showing 10 items of 22 documents
Cycles diurnes de rayonnement solaire et forets en Afrique Centrale.
2018
The sunlightconditions prevailing in Central Africa, and their potential impact on forests traits and functioning, have neverbeen fully explored. Using satellite estimates documenting mostly the period 2005-2013, and accounting forscale interactions between the diurnal and annual cycles, we demonstrate that the seasonality of sunlight levelsstrongly vary across Central Africa forests. Gabon stands out with a main dry season strongly light-deficient,cool and moist. An original map of terra firme forest types developed by CIRAD shows that most of theevergreen forests of Central Africa develop in Gabon. We postulate that despite a mean annual precipitationamount below 2000 mm/yr, the Gabonese …
Consequences of the disorders socio-policies on the Central African education system of 1991 to the year 2001: situation of primary education teaching
2006
This work deals about the impacts both on supply and demand of education emerging from socio-political instability and trouble, the Sub Saharan geographical context. The targeted goal is to present a comparative analysis which indicates that countries could attain objective in the development of education if the context for civil peace appear satisfied. Then, by a historical and socio-political step, the study in the evolution of the school since its creation in the Central Africa case shows that multiple factors impacted within time duration the development of education. Lastly, the analysis of the consequences of the disorders encountered in the since the beginning of the Nineties reveals…
Presence of Fusarium emerging mycotoxins in tiger-nuts commercialized in Spain
2012
Abstract Tiger-nuts are tubers from the plant Cyperus esculentus which are commercialized in some regions of West and Central Africa, USA and Spain. These tubers have a high microbial charge such as bacteria, moulds and yeasts which could remain until the finished product. In this study we examined 47 samples of tiger-nut tubers purchased from Spanish supermarkets for contamination with the emerging Fusarium mycotoxins: Enniatins ENs (EN A, EN A1, EN B and EN B1), beauvericin (BEA) and fusaproliferin (FUS). The extraction of the samples was carried out with methanol using an Ultraturrax homogenizer. Mycotoxins were analyzed with a liquid chromatography (LC) coupled to a diode array detector…
Rainfall variability in subequatorial America and Africa and relationships with the main sea-surface temperature modes (1951–1990)
1995
The rainfall variability of subequatorial South America and Africa is poorly documented owing to the scarcity of data. We present a new land-only data set of monthly precipitation from 1951 to 1990, focusing on subequatorial South America and Africa, which improves the knowledge of rainfall variability and allows comparisons with GCM outputs. The results of multivariate analyses are compared with those performed on the best actual global rainfall data set developed by Mike Hulme. The main modes of bimonthly rainfall variability are not located in the major rain-forest basins of Za'ke and Amazonia, but rather on the tropical margins, such as Venezuela or Sudan, and near-coastal equatorial ar…
A new genus for the eastern dwarf galagos (Primates: Galagidae).
2017
13 pages; International audience; The family Galagidae (African galagos or bushbabies) comprises five genera: EuoticusGray, 1872; GalagoGeoffroy Saint-Hilaire, 1796; GalagoidesSmith, 1833; OtolemurCoquerel, 1859; and SciurocheirusGray, 1872, none of which is regarded as monotypic, but some (Euoticus and Otolemur) certainly qualify as oligotypic. We argue for the recognition of a sixth genus, if the taxonomy is to reflect galagid evolution accurately. Genetic evidence has consistently demonstrated that the taxa currently referred to the genus Galagoides are not monophyletic but form two clades (a western and an eastern clade) that do not share an exclusive common ancestor; we review 20 years…
Dyvalocca : un projet pour l'étude des nuages bas de saison sèche sur la façade atlantique de l'Afrique centrale et de leur impact bioclimatique sur …
2020
Low-level clouds are key components of the climate but are not well represented in weather and climate models. Recently it has been shown that an extensive low-level cloud cover develops during the June-September main dry season in western equatorial Africa, from the coastal plains of Gabon and Congo-Brazzaville to the inland plateaus downstream of the low-mountain crests. Such a cloudy main dry season is unique in the moist Tropics and is likely to explain the presence of the densest and evergreen forests of Central Africa as evapotranspiration is low and the quality of light is high. The ANR-DFG funded “DYVALOCCA” project will conduct from 2020 to 2022 a field campaign, raise existing in-…
Paléoenvironnements et caractérisation des roches mères pétrolières des séries pré-salifères du bassin intérieur du Gabon
2003
Resume Le bassin interieur du Gabon, dont l'histoire est liee a la separation des continents Sud-Americain et Africain, comprend des depots continentaux fluvio-lacustres, localement glaciaires, dates du Precambrien superieur a l'Aptien p.p., surmontes par des facies marins aptiens et albiens. L'analyse par pyrolyse Rock–Eval d'echantillons d'affleurements et de forages preleves dans ce bassin met en evidence la presence de facies siliciclastiques riches en matiere organique (jusqu'a 25 % de carbone organique total) de types I et II. Ces niveaux, qui se rencontrent dans le Permien, le Neocomien-Barremien ainsi que dans l'Aptien, constituent d'excellentes roches meres et sont a l'origine des …
État actuel des réseaux de mesures éco-climatiques en Afrique centrale : les ambitions du projet de recherche international FORGREENE.
2016
This work presents an overview of spatio-temporal quality andspatial density of rainfall networks of Cameroon, Gabon, Congo, CAP and DRC, particularly in the recentperiod (1973-2014) through the GSOD international database. Faced with enormous gaps observed, theseresults will help to select metrological and analytical orientations in FORGREENE project (Tropical forestsgreeness and cloudiness in Central Africa: present conditions and future evolution). A comparison with rainfallsatellite estimates (RFE type) also indicates their great potential, provided they are based on in situ validations.
Nothodissotis (Melastomataceae), a new genus from Atlantic Central Africa, including the new species N. alenensis from Equatorial Guinea
2019
Based on morphological and phylogenetic evidence, a new genus of Melastomataceae (Melastomateae), Nothodissotis Veranso-Libalah & G.Kadereit, gen. nov., is described from Atlantic Central Africa. Nothodissotis is distinguished from other African Melastomateae genera by its calyx-lobes that are notched at apex and asymmetrical (vs. entire and symmetrical). Nothodissotis includes two species: the type species N.barteri (Hook.f.) Veranso-Libalah & G.Kadereit, comb. nov. (syn. Dissotisbarteri Hook.f.), and the new species N.alenensis Veranso-Libalah & O. Lachenaud, sp. nov., described and illustrated here. Both species are restricted to open vegetation on rock outcrops w…
Analysis of cloudiness and solar radiation diurnal cycles for a better understanding of the forests greenness mean annual cycle in Central Africa.
2016
To better understand the Central Africa forests sensitivity toclimate variability, we jointly analyse the mean annual cycles of greenness, rainfall, cloudiness and solarradiation for the target region 0-5°N/12-19°E using high resolution satellite data. Our results demonstrate theimportance of the diurnal scale for understanding the mean annual cycles of rainfall, cloudiness and solarradiation and the way they shape those of forest greenness. They also suggest that whereas the March-Mayrainy season appears optimal for greenness especially because of favorable light conditions, water availabilityis the main controlling factor in December-January the main dry season and in February at the star…