Analyses chimiques des eaux du fleuve Niger à Niamey : premiers résultats d'une campagne annuelle de mesures

Nous avons déterminé, d'août 1984 à février 1986, les concentrations des silicates, chlorures, nitrites, phosphates, potassium, sodium, calcium, magnésium, ammonium et fer ferrique ainsi que le pH, la conductivité, la turbidité, l'oxygène dissous, l'alcalinité et la D.B.O. dans l'eau du fleuve Niger à hauteur de la ville de Niamey. L'exploitation statistique de ces résultats fait apparaître l'existence de deux périodes stables et d'une période instable au cours de l'année. (Résumé d'auteur

Proliferation de Sida cordifoloia L. sure les parcours Saheliens, cas du Niger

RESUMECette étude vise à caractériser la prolifération de Sida cordifolia L. sur les parcours naturels au Niger. Les données, collectées au moyen de relevés phytosociologiques, ont permis de caractériser par zone bioclimatique, l’abondance et la dominance des espèces herbacées en mettant en exergue Sida cordifolia L. Une typologie des pâturages faite en fonction de leur degré de colonisation par cette espèce a permis de distinguer trois types de pâturage : les pâturages colonisés (fortement ou moyennement, faiblement), tous situés au sud et ou au centre de la région en zone agricole ouagropastorale, soumis à une très forte pression pastorale et les pâturages non colonisés par cette espèce, essentiellement situés au nord de la région en zone pastorale, soumis à une faible pression animale. La pression pastorale serait la cause principale de la prolifération de Sida cordifolia L. sur ces parcours. Ainsi, les pâturages non ou faiblement colonisés seraient fortement colonisés si la pression de pâture ne diminue pas. Il est donc nécessaire d’adapter la charge animale aux capacités de charge de ces pâturages afin de renverser cette tendance à la dégradation de ces écosystèmes pastoraux et améliorer leur valeur pastorale. ABSTRACTPROLIFERATION OF SIDA CORDIFOLIA L. ON SAHELIAN RANGELANDS, CASE OF NIGERThis study aims to characterize the proliferation of Sida cordifolia L. on natural rangelands in Niger. The data, collected by phytosociological surveys, made it possible to characterize by abundance and dominance of herbaceous species by bioclimatic zone, highlighting Sida cordifolia L. A typology of pastures made according to their degree of colonization by this species made it possible to distinguish three types of pasture: colonized pastures (strongly or moderately, weakly), all located in the south and or in the center of the region in agricultural or agro-pastoral zones, subjected to very strong pastoral pressure and pastures not colonized by this species, mainly located in the north of the region in pastoral areas, subject to low animal pressure. Pastoral pressure is the main cause of the proliferation of Sida cordifolia L. on these rangelands. Thus, non-colonized or poorly colonized pastures would be strongly colonized if the pasture pressure does not decrease. It is therefore necessary to adapt the animal load to the carrying capacity of these pastures in order to reverse this deteriorating tendency of these pastoral ecosystems and improve their pastoral value

Germination et croissance initiale de Neocarya macrophylla (Sabine) Prance, une espèce oléagineuse du Niger

Germination and Initial Growth of Neocarya macrophylla (Sabine) Prance, a oleaginous Species of Niger. The study conducted in parallel in the real environment, nursery and laboratory to better understand the characteristics of germination and seedling development Neocarya macrophylla, a species of oleaginous Niger. The treatments applied to seed have a waiting time shorter than the untreated seeds. The control has a staggered germination (30 days) and shelling of nuts influenced seed germination bundled (16 days). Unprocessed nuts are the best germination rate (89.53%). Soaking nuts during 72 h and 120 h is fatal for germination. The shelf life has significant effects on the germination of walnuts and almonds. The observation shows a germinating seed cryptogeal. The low germination rates nuts without water shows that water is a limiting factor to the spread of this tree species. The seedlings are very sensitive to dampingoff and tolerant enough to transplantation with a survival rate of 79%

Vegetation and plant diversity pattern study of Central Eastern Niger grasslands

Vegetation and plant diversity patterns of Central Eastern Niger grasslands were investigated following phytosociological methods. Vegetation data collected on 76 plots by using the Braun-Blanquet’s (1932) coverabundance scale were analyzed through five multivariate analyses (TWINSPAN, NMS, DCA, ISA and MRPP) in order to distinguish and to describe plant communities. Alpha diversity (H’, E and R) was also used to describe these communities. A total of 162 species belonging to 37 families and 104 genera were identified. Dominant families were the Poaceae (18%), Leguminosae-Papilionoideae (8%), Convolvulaceae (7%) and Leguminosae-Caesalpinioideae (4%). Life forms were dominated by Therophytes (59%) and Phanerophytes (27%), whereas the most prominent geoelements were of the Soudano-zambesians-saharo-sindians (33%), Soudano-zambesians (25%) and Guineo-congolian-soudano-zambesians (25%) types. In total, five plant communities were identified on the basis of environmental gradients and species composition. The environmental parameters that favorably influence these plant distributions are topography, moisture, texture and land use (fallow, pasture). Importantly, each of these communities seems to correspond to a particular wildlife habitat. These habitats shelter their own species that may be seen as a keystone species.Keywords: Multivariate analysis, vegetation communities, characteristic species, Central East grassland, Nige

Utilisation de Prosopis africana (G. et Perr.) Taub dans le sud du département d’Aguié au Niger : Les différentes formes et leur importance

La présente étude menée dans la région de Maradi (Niger), plus  précisément dans le sud du département d’Aguié, vise à recenser et à classer les différents usages de Prosopis africana. La méthode de collecte des informations s’est appuyée sur une enquête ethnobotanique au niveau des ménages. Les résultats de ces investigations révèlent que les principaux usages faits de Prosopis africana dans cette zone sont  l’alimentation humaine, le fourrage, le bois énergie, la pharmacopée  traditionnelle, le bois d’artisanat et de service. Parmi ceux-ci, les deux (2) derniers sont les plus importants et portent sérieusement atteinte à l’état sanitaire des individus végétaux. La cueillette, bien que moins pratiquée que ces deux (2), n’est pas moins importante à cause de son impact sur la régénération en diminuant le stock des semences.Mots clés : Prosopis africana, fourrage, bois, pharmacopée traditionnelle, Niger

Socio-Economic Impact of Corn Fielding in The Iffou Region of Eastern Central Ivory Coast

In the present paper, the socioeconomic impact of weed control (manual and chemical + manual) of maize field technologies is assessed using indicators such as cropland, weed control, yield, total cost, gross margin (production value), net margin and net income. The article shows that in the Iffou region of Ivory Coast, where grass cover is a major problem, the use of herbicide reduces weed control time, contributes to solving the problem of scarcity and high cost of labor, and the positive effects on these indicators compared to manual weeding. However, the incidence of the use of herbicide remains low in relation to the number of farmers

Field evaluation of two rapid diagnostic tests for Neisseria meningitidis serogroup A during the 2006 outbreak in Niger.

The Pastorex((R)) (BioRad) rapid agglutination test is one of the main rapid diagnostic tests (RDTs) for meningococcal disease currently in use in the "meningitis belt". Earlier evaluations, performed after heating and centrifugation of cerebrospinal fluid (CSF) samples, under good laboratory conditions, showed high sensitivity and specificity. However, during an epidemic, the test may be used without prior sample preparation. Recently a new, easy-to-use dipstick RDT for meningococcal disease detection on CSF was developed by the Centre de Recherche Médicale et Sanitaire in Niger and the Pasteur Institute in France. We estimate diagnostic accuracy in the field during the 2006 outbreak of Neisseria meningitidis serogroup A in Maradi, Niger, for the dipstick RDT and Pastorex((R)) on unprepared CSF, (a) by comparing each test's sensitivity and specificity with previously reported values; and (b) by comparing results for each test on paired samples, using McNemar's test. We also (c) estimate diagnostic accuracy of the dipstick RDT on diluted whole blood. We tested unprepared CSF and diluted whole blood from 126 patients with suspected meningococcal disease presenting at four health posts. (a) Pastorex((R)) sensitivity (69%; 95%CI 57-79) was significantly lower than found previously for prepared CSF samples [87% (81-91); or 88% (85-91)], as was specificity [81% (95%CI 68-91) vs 93% (90-95); or 93% (87-96)]. Sensitivity of the dipstick RDT [89% (95%CI 80-95)] was similar to previously reported values for ideal laboratory conditions [89% (84-93) and 94% (90-96)]. Specificity, at 62% (95%CI 48-75), was significantly lower than found previously [94% (92-96) and 97% (94-99)]. (b) McNemar's test for the dipstick RDT vs Pastorex((R)) was statistically significant (p<0.001). (c) The dipstick RDT did not perform satisfactorily on diluted whole blood (sensitivity 73%; specificity 57%).Sensitivity and specificity of Pastorex((R)) without prior CSF preparation were poorer than previously reported results from prepared samples; therefore we caution against using this test during an epidemic if sample preparation is not possible. For the dipstick RDT, sensitivity was similar to, while specificity was not as high as previously reported during a more stable context. Further studies are needed to evaluate its field performance, especially for different populations and other serogroups