Showing papers by "Abdou Moumouni University published in 2010"

Long term measurements of sulfur dioxide, nitrogen dioxide, ammonia, nitric acid and ozone in Africa using passive samplers

Abstract: In this paper we present the long term monitoring of ambient gaseous concentrations within the framework of the IDAF (IGAC-DEBITS-AFRICA) program. This study proposes for the first time an analysis of long-term inorganic gas concentrations (1998 to 2007) of SO2, NO2, HNO3, NH3 and O3, determined using passive samplers at seven remote sites in West and Central Africa. Sites are representative of several African ecosystems and are located along a transect from dry savannas-wet savannas-forests with sites at Banizoumbou (Niger), Katibougou and Agoufou (Mali), Djougou (Benin), Lamto (Cote d'Ivoire), Zoetele (Cameroon) and Bomassa (Congo). The strict control of measurement techniques as well as the validation and inter-comparison studies conducted with the IDAF passive samplers assure the quality and accuracy of the measurements. For each type of African ecosystem, the long term data series have been studied to document the levels of surface gaseous concentrations. The seasonal and interannual variability have also been analyzed as a function of emission source variations. We compared the measured West and Central African gas concentrations to results obtained in other parts of the world. Results show that the annual mean concentrations of NO2, NH3, HNO3 measured in dry savannas are higher than those measured in wet savannas and forests that have quite similar concentrations. Annual mean NO2 concentrations vary from 0.9±0.2 in forests to 2.4±0.4 ppb in the dry savannas, NH3 from 3.9±1.4 to 7.4±0.8 ppb and HNO3 from 0.2±0.1 to 0.5±0.2 ppb. Annual mean O3 and SO2 concentrations are lower for all ecosystems and range from 4.0±0.4 to 14.0±2.8 and from 0.3±0.1 to 1.0±0.2 ppb, respectively. A focus on the processes involved in gas emissions from dry savannas is presented in this work, providing explanations for the high concentrations of all gases measured at the three dry savannas sites. At these sites, seasonal concentrations of all gases are higher in the wet season. Conversely, concentrations are higher in the dry season in the wet savannas. In forested regions, we measure no significant difference between wet and dry seasons. This unique database of long term gases concentrations monitoring is available at: http://medias.obs-mip.fr/idaf/.

The WAMME regional model intercomparison study

Abstract: Results from five regional climate models (RCMs) participating in the West African Monsoon Modeling and Evaluation (WAMME) initiative are analyzed. The RCMs were driven by boundary conditions from National Center for Environmental Prediction reanalysis II data sets and observed sea-surface temperatures (SST) over four May–October seasons, (2000 and 2003–2005). In addition, the simulations were repeated with two of the RCMs, except that lateral boundary conditions were derived from a continuous global climate model (GCM) simulation forced with observed SST data. RCM and GCM simulations of precipitation, surface air temperature and circulation are compared to each other and to observational evidence. Results demonstrate a range of RCM skill in representing the mean summer climate and the timing of monsoon onset. Four of the five models generate positive precipitation biases and all simulate negative surface air temperature biases over broad areas. RCM spatial patterns of June–September mean precipitation over the Sahel achieve spatial correlations with observational analyses of about 0.90, but within two areas south of 10°N the correlations average only about 0.44. The mean spatial correlation coefficient between RCM and observed surface air temperature over West Africa is 0.88. RCMs show a range of skill in simulating seasonal mean zonal wind and meridional moisture advection and two RCMs overestimate moisture convergence over West Africa. The 0.5° computing grid enables three RCMs to detect local minima related to high topography in seasonal mean meridional moisture advection. Sensitivity to lateral boundary conditions differs between the two RCMs for which this was assessed. The benefits of dynamic downscaling the GCM seasonal climate prediction are analyzed and discussed.

Subglacial deformation and water-pressure cycles as a key for understanding ice stream dynamics: evidence from the Late Ordovician succession of the Djado Basin (Niger)

Abstract: Subglacial deformation is crucial to reconstructing glacier dynamics. Sediments associated with the Late Ordovician ice sheet in the Djado Basin, Niger, exhibit detailed structures of the subglacial shear zone. Three main types of subglacial shear zones (SSZ) are discriminated. The lowermost SSZ, developed on sandstones, displays Riedel macrostructures and cataclastic microstructures. These resulted from brittle deformation associated with strong glacier/bed coupling and low pore-water pressure. Where they developed on a clay-rich bed, the overlying SSZ display S–C to S–C′ fabrics, sheath folds, and dewatering structures. These features indicate high ductile shear strain and water overpressure. On fine-grained sand beds, the SSZ exhibit homogenized sand units with sand stringers, interpreted as fluidized sliding beds. The succession of subglacial deformation processes depends on fluid-pressure behavior in relation to subglacial sediment permeability. Fluid overpressure allows subglacial sediment shear strength and ice/bed coupling to be lowered, leading to ice streaming.

Evaluating rapid participatory rural appraisal as an assessment of ethnoecological knowledge and local biodiversity patterns.

Abstract: : There is a pressing need to find both locally and globally relevant tools to measure and compare biodiversity patterns Traditional ecological knowledge (TEK) is important to biodiversity monitoring, but has a contested role in preliminary biodiversity assessments We examined rapid participatory rural appraisal (rPRA) (a tool commonly used for local needs assessments) as an alternative to surveys of vascular plants conducted by people with local knowledge We used rPRA to determine the local-knowledge consensus on the average richness, diversity, and height of local grasses and trees in three habitats surrounding Boumba, Niger, bordering Park-W We then conducted our own vascular plant surveys to collect information on plant richness, abundance, and structure Using a qualitative ranking, we compared TEK-based assessments of diversity patterns with our survey-based assessments The TEK-based assessments matched survey-based assessments on measures of height and density for grasses and trees and tree richness The two assessments correlated poorly on herb richness and Simpson's D value for both trees and grasses Plant life form and gender of the participant affected the way diversity patterns were described, which highlights the usefulness of TEK in explaining local realities and indicates limitations of using TEK as a large-scale assessment tool Our results demonstrate that rPRA can serve to combine local-knowledge inquiry with scientific study at a cost lower than vascular plant surveys and demonstrates a useful blunt tool for preliminary biodiversity assessment Resumen: Existe una necesidad apremiante para encontrar herramientas local y globalmente relevantes para medir y comparar patrones de biodiversidad El conocimiento ecologico tradicional (CET) es importante para el monitoreo de biodiversidad, pero su papel en evaluaciones preliminares de biodiversidad ha sido cuestionado Examinamos el diagnostico rural participativo rapido (DRPr) (una herramienta comunmente utilizada para evaluaciones de necesidades locales) como una alternativa a muestreos de plantas vasculares realizados por personas con conocimiento local Utilizamos DPRr para determinar el consenso de conocimiento local sobre la riqueza promedio, diversidad y altura de pastos y arboles locales en tres habitats alrededor de Boumba, Niger, en los limites del Parque-W Posteriormente realizamos nuestros propios muestreos de plantas vasculares para recolectar informacion sobre la riqueza, abundancia y estructura de plantas Mediante la clasificacion cualitativa, comparamos las estimaciones de patrones de diversidad basadas en CET con nuestras estimaciones basadas en muestreos Las estimaciones basadas en CET fueron equivalentes a las estimaciones de la altura y densidad de pastos y arboles y la riqueza de arboles Las dos estimaciones se correlacionaron debilmente con la riqueza de hierbas y con el valor D de Simpson para arboles y pastos La forma de vida de plantas y el genero del participante afecto la manera en que se describieron los patrones de diversidad, lo cual resalta la utilidad de CET para explicar las realidades locales e indica las limitaciones de la utilizacion de CET como una herramienta de evaluacion a gran escala Nuestros resultados demuestran que el DRPr puede servir para combinar encuestas sobre conocimiento local con estudios cientificos con un costo menor que los muestreos de plantas vasculares y muestran una util herramienta contundente para la evaluacion preliminar de biodiversidad

Géométrie classique de certains feuilletages de degré deux

Abstract: L’ensemble ℱ(2; 2) des feuilletages de degre deux du plan projectif complexe s’identifie a un ouvert de Zariski dans un espace projectif de dimension 14 sur lequel agit le groupe Aut(ℙ2(ℂ)). Nous classifions, a automorphisme de ℙ2(ℂ) pres, les feuilletages de degre deux ayant une unique singularite. a automorphisme pres il y a 4 feuilletages ayant cette propriete; alors que trois ont une dynamique que l’on peut decrire facilement, celle du quatrieme reste mysterieuse. Cette classification intervient dans la description de l’action de Aut(ℙ2(ℂ)) sur ℱ(2; 2). Nous montrons d’une part que la dimension des orbites est superieure ou egale a 6 et qu’il y a exactement deux orbites de dimension 6 dont l’une correspond a un feuilletage ne presentant qu’un seul point singulier; d’autre part nous obtenons que l’adherence de l’orbite d’un element generique de ℱ(2; 2) contient au moins sept orbites de dimension 7 et une seule orbite de dimension 6.

Illness in French Travelers to Senegal: Prospective Cohort Follow‐up and Sentinel Surveillance Data

Abstract: Objective. To investigate travel-associated illnesses in French travelers to Senegal. Methods. A prospective cohort follow-up was conducted in 358 travelers recruited at a pre-travel visit in Marseille and compared to data from ill travelers collected from the GeoSentinel data platform in two clinics in Marseille. Results. In the cohort survey, 87% of travelers experienced health complaints during travel, which most frequently included arthropod bites (75%), diarrhea (46%), and sunburns (36%). Severe febrile illness cases, notably malaria and salmonella, were detected only through the surveillance system, not in the cohort follow-up. Food hygiene was inefficient in preventing diarrhea. Arthropod bites were more frequent in younger patients and in patients with pale phototypes. Sunburns were also more frequent in younger patients. Finally, we demonstrate that mild travel-related gastrointestinal symptoms and the lack of arthropod bites are significantly associated with poor observance of antimalarial prophylaxis. Conclusions. In this study, we suggest the complementary nature of using cohort surveys and sentinel surveillance data. Effective protection of skin from arthropod bites and sun exposure should result in significantly reduced travel-associated diseases in Senegal. Travelers to Senegal should be informed that diarrhea is extremely common despite preventive measures, but it is mild and transitory and should not lead to the disruption of malaria chemoprophylaxis.

Coping with Rainfall Variability: Dry Spell Mitigation and Implication on Landscape Water Balances in Small-scale Farming Systems in Semi-arid Niger

Abstract: Rainfall variability and inherent dry spells are a reality with severe implications for smallholder agro-ecosystems in semi-arid Sahel. To increase both on- and off-farm biomass production and productivity is challenging with these climate-induced temporal and spatial variations of water. This paper tests the idea that increased vegetation through tree cover may impact water balance in a water-stressed landscape: South-east Niger. Local rainfall data, farming systems data and a landscape water-modelling tool (ArcSWAT) are used. Four production domains (conventional or fertilized combined with millet crop or millet crop plus trees) were assessed for long-term yield and landscape water balance impacts. The dry-spell analysis shows a frequency of dry spells less than 14 days is in the order of one to two dry-spell events per season in 7 years out of 10 years. The occurrence has increased between 1960 and 2004, despite a slight recovery of total annual rainfall amounts since the severe droughts of the 1980s. ...

Caractérisation de la structure spatiale des individus ligneux dans une « brousse tachetée » au sud-ouest du Niger

Abstract: La structure spatiale des vegetations periodiques en zones arides est liee, selon des modeles d’auto-organisation, a des processus locaux (facilitation ou competition). La presente etude visait a v...

Roselle (Hibiscus sabdariffa L.) yield and yield components in response to nitrogen fertilization in Niger.

Abstract: Although nitrogen application could improve growth and yield of roselle, fertilizer recommendations for Niger are lacking. The objective of this study was to evaluate the effects of two treatments of nitrogen (N1=50 kg N,ha−1 and N2=100 kg N.ha−1) on yields and yield components in three ecotypes of Roselle (A3, A7 and A9). An increase in nitrogen was associated with an increase in leaf yield in every ecotype. However, there was no significant difference in yields between N1 and N2. Compared with the control plants (N0), the increase was about 181% for A3, 70% for A7 and 95% for A9 at N2. This level of nitrogen significantly decreased seed yield by 30% for A3 and 48%, respectively for A7 and A9. Nitrogen treatment had no effect on calyx yield which was approximately identical for the three ecotype (420 kg ha−1). With the exception of the number of branches/plant, yield components were not affected by nitrogen application. Therefore, N1 could be considered as the optimum fertilization for leaf yield.

Multiscale comparison of spatial patterns using two-dimensional cross-spectral analysis: application to a semi-arid (gapped) landscape

Abstract: Spectral analysis allows the characterization of temporal (1D) or spatial (2D) patterns in terms of their scale (frequency) distribution. Cross-spectral analysis can also be used to conduct independent correlation analyses at different scales between two variables, even in the presence of a complex superposition of structures, such as structures that are shifted, have different scales or have different levels of anisotropy. These well-grounded approaches have rarely been applied to two-dimensional ecological datasets. In this contribution, we illustrate the potential of the method. We start by providing a basic methodological introduction, and we clarify some technical points concerning the computation of two-dimensional coherency and phase spectra and associated confidence intervals. First, we illustrate the method using a simple theoretical model. Next, we present a real world application: the case of patterned (gapped) vegetation in SW Niger. In this example, we investigate the functional relationships between topography and the spatial distribution of two shrub species, Combretum micranthum G. Don. and Guiera senegalensis J.F. Gmel. We show that both the global vegetation pattern and the distribution of C. micranthum are independent at all analyzable scales (i.e., from 10 to 50 m) from possible relief-induced determinisms. Additionally, the two dominant shrub species form distinct patches, thus suggesting separate niches.

Performance of Acacia senegal (L.) Willd Provenances in Dryland Savannah of Niger

Abstract: Abstract A study was conducted to evaluate the performance of 11 Acacia senegal provenances in Niger, West Africa, grown on 2 different soil types. Among the provenances, 6 are from Niger, 4 from Mali and 1 from Sudan. The assessment was carried out with measurements of growth parameters (survival rate, height, diameter and basal area) as well as gum and fruit production at age 15. The results showed significant differences in growth parameters between soil types and provenances. The provenances from Mali perform best, followed by the local Niger provenances. There were no significant differences in gum and fruit production between provenances, but it cannot be excluded that this was a result of limited power in the test of provenance variation in these traits. Survival of the provenances was correlated to the precipitation and the latitude of the origin, whereas basal area was correlated to latitude, and height was correlated to longitude/altitude at the origin. Recommendations could be made for genetic selection of two Mali provenances if growth is a desired character. We conclude that recommendations in terms of gum and fruit production must be based on a relative high number of sample trees as tree to tree variation within provenances may be large.

Essais préliminaires d’inséminations artificielles en station chez les femelles zébus Azaouak au Niger

Abstract: Artificial inseminations of estrus-induced and natural estrus were carried out in 138 Azawak zebu females at the Sahelian Experimental Station of Toukounous. Estrous was induced with a Crestar implant, a progesterone releasing intra-vaginal device, and prostaglandin and gonadotropin-releasing hormone (GnRH) injections. Two inseminations were performed: the first one at estrus observation and the second one 12 hours later. The influence of zootechnical parameters was tested. The achieved non cumulative pregnancy rates were 24.5% at first insemination, 33.72% at second, and 29.48% at third and beyond. The use of fresh semen and of cows instead of heifers was among the zootechnical parameters that significantly and positively influenced inseminations. The 60-day postpartum period usually observed before insemination had no significant effect on the results. As the season of insemination did not influence the results, calvings were observed throughout the year. The nutritional status was also an essential factor of successful inseminations. The results highlighted the ability of Azawak zebus to make optimum use of fodder in all seasons, with ovarian activity resuming soon after parturition.

Une Politique D’adaptation Climatique Inachevée Mais Persistante: Le Cas de la Zone Pastorale du CEZIET de Samorogouan (Burkina Faso)

Abstract: In Samorogouan (Burkina Faso), pastoral migration has been planned by the World Bank through a project titled « Projet d’Elevage Ouest Volta (PEOV) ». With the agreement of the local authorities, the project defines a large territory (125.000 hectares) dedicated to ranching and to the settlement of the pastoralists who had fled the region during the droughts of the 70s. The project was cancelled in 1984, during the Sankarist revolution. Nowadays, the pastoral zone is threatened by clearance and by various conflicts between settled pastoralists, Justice, the local administration and farmers.

Météorologie de l'Espace en Afrique (II) le programme ISWI - International Space Weather Initiative

Abstract: The project ‘International Space Weather Initiative’ (2010-2012), is in the continuity of the program International Heliophysical Year IHY (2007-2009). These two projects are followed by the United Nations Committee for the peaceful applications of the Science to Space (http://www.oosa.unvienna.org). In this presentation, we will focus on the objectives of ISWI project, which pursue the deployment of networks of scientific tools over Africa, started in the framework of the International Heliophysical Year. We develop the following topics: existing networks and more particularly the networks of GPS stations and magnetometers; scientific teams using the distributed scientific tools; training schools organized by ICTP (International Centre for Theoritical Physics) and IGRGEA (International Research Group in Geophysics Europe Africa); the scientific results in Africa during the last years. It is particularly important to have ground networks of scientific tools to complete satellite measurements. Journées scientifiques 'PROPAGATION ET PLASMAS'