Southern Niger Research Articles

Powers, Problems, and Paradoxes of Twinship in Niger

Among Hausaphone Mawri communities of Niger, twins are powerful yet dangerous beings endowed from birth with extraordinary abilities. While they are welcomed by parents who interpret multiple births as lucky, twins are feared because they kill offenders and perceive things which normal people cannot see. Twins are also fiercely jealous of each other. Defusing this rivalry entails treating both children identically, lest they hurt each other. This essay explores how the Mawri deal with the paradox of double births through practices that emphasize the magical powers of twins or, conversely, stress their vulnerability. It also discusses how, with the emergence of reformist Islam, the meanings and implications of twin births are being reassessed through debates over morality. (Twinship, West Africa, Islam, reformist movements) Soon after my arrival in the Hausa-speaking town of Dogondoutchi in Arewa (southern Niger) to conduct fieldwork, my neighbor Houre took me to the house of Salamatou and Abarshi, who were celebrating the birth of their twin girls. Outside the walled family compound, the men who early that morning had come to share the joy of the new father and to receive kola nuts were now gone. The two rams slaughtered in celebration of the twins' birth had already been cut up and their meat apportioned between different family members and patrons. The courtyard's messiness betrayed the unusual degree of activity that had taken place in the last few days. In one corner, two women were engaged in the careful division of cooked millet balls into communal portions that, with sauce, would be later served to guests. Upon entering the room where the new mother sat surrounded by the female friends and neighbors who had come to attend the naming ceremony, Houre and I deposited our monetary contributions into the mother's hands before sitting on a mat next to the barber who would soon shave the infants' hair. In a corner, a young schoolgirl was busily tallying the gifts of money in a rumpled notebook, the Carnet de Sante (immunization record) of Salamatou's first-born (a girl who had died in infancy), that would help the young mother keep track of each visitor's contribution.(1) Meanwhile, we were each handed a small plastic bag filled with fried cakes covered with powdered sugar, the usual counter-gift whose lengthy preparation had absorbed the neighbors and co-wives of the parturient for most of the morning. As is customary for a biki (birth celebration), the walls of the crowded and stuffy room were decorated with the colorful handwoven blankets Salamatou had received as wedding gifts. A couple of griots (praise singers) standing in the doorway were singing the praises of the newly named babies, Hassana and Housse, each of whom lay in a pair of arms, unaware of the turmoil generated by their recent arrival. One of the babies is so much bigger than her sister, I remarked to the woman sitting next to me. Shhh! she exclaimed before I had a chance to finish. You must never say this! Let's hope they haven't heard you. Puzzled, I asked her why I should hope that the babies had not heard what I assumed to be an inoffensive comment. If she feels jealous, she will try to kill her twin, the woman answered softly before she was asked to trade places with the midwife, who, following conventions, would hold one of the babies while her pagan hair was shaved away. I soon became too immersed in the aski (shaving) performance to pursue inquiring about twinship, but later found ample confirmation that in Mawri society twins are powerful beings endowed from birth with special capacities that make them at once, more than and less than human (Turner 1969:47). These special capacities, the practices that have traditionally surrounded the treatment of twins, and the emergence of a new moral framework for dealing with the problem of twinship are discussed here. This article explores how the experience and interpretation of twinship have recently become the focus of local debates over the meaning of Islamic identity, marriage, and morality. …

Rainfall Estimation in the Sahel: What Is the Ground Truth?

Areal rainfall estimation from ground sensors is essential as a direct input to various hydrometeorological models or as a validation of remote sensing estimates. More critical than the estimation itself is the assessment of the uncertainty associated with it. In tropical regions knowledge on this topic is especially scarce due to a lack of appropriate data. It is proposed here to assess standard estimation errors of the areal rainfall in the Sahel, a tropical region of notoriously unreliable rainfall, and to validate those errors using the data of the EPSAT–Niger experiment. A geostatistical framework is considered to compute theoretical variances of estimation errors for the event-cumulative rainfall, and rain gauge networks of decreasing density are used for the validation. As a result of this procedure, charts giving the standard estimation error as a function of the network density, the area, and the rainfall depth are proposed for the Sahelian region. An extension is proposed for larger timescales (decade, month, and season). The seasonal error is estimated as a product of the error at the event scale by a reduction coefficient, which is a function of the number K of recorded events and the probability distribution function of the point storm rain depth. For a typical network of 10 stations regularly dispatched over a 1° × 1° square, the relative estimation error decreases from 14% for an average storm rain depth of 16 mm to 5% for an average August rainfall of 160 mm. For a density comparable to that of the operational rain gauge network of southern Niger and similar Sahelian regions, the standard errors are, respectively, 26% at the event scale and 10%–15% at the monthly scale, depending on the number of events recorded during the month. The areas considered here are 1° × 1° and smaller, which makes a comparison with results obtained in previous studies for other regions of the world difficult since the reference area most often used in these studies is either 2.5° × 2.5° or 5° × 5°. Further work is thus needed to extend the results presented here to larger spatial scales.

Use of the trolox assay to estimate the antioxidant content of seventeen edible wild plants of niger

Although wild edible plants of the western Sahel and other parts of sub-Saharan Africa are consumed to some extent at all times of the year, greater amounts are consumed when cereal harvests are insufficient to support the populations living in these areas. The purpose of this study was to use a recently reported Trolox-based assay to measure the total antioxidant capacity of aqueous extracts of 17 plants that we gathered from southern Niger. The antioxidant contents of the aqueous extracts were compared to those of spinach and potato. Of the 17 plants, 11 had a greater antioxidant content than spinach and 14 had a greater antioxidant content than potato. The leaves of Tapinanthus globiferus had the greatest antioxidant content, and the fruit of Parinari macrophylla had the lowest. In general, leaves contained more antioxidants than either fruits or seeds. The total antioxidant capacity of the aqueous extracts was relatively high, indicating that the wild plants of the western Sahel may contain substantial amounts of water-soluble flavonoid glycosides, which are potent antioxidants and have been shown to have anticancer properties.

Farmers' knowledge of wind erosion processes and control methods in Niger

Field research on wind erosion processes in Sahelian Africa has revealed that wind-blown particle transport forms a constraint for local crop production systems. This paper describes the results of an on-farm survey on wind-erosion processes and soil conservation practices. Interviews were held with 138 farmers from seven villages in southern Niger. Of the interviewed farmers, 63 per cent consider wind-blown particle transport as damaging to their cropping systems. Nearly all farmers reported to observe differences between fields with respect to wind erosion. Fields that are mainly eroded were said to lose fertility and produce less, whereas deposition of material results in a better fertility and production. These differences occur also on a smaller scale, with erosion and deposition spots in the same field. Most farmers (96 per cent) are familiar with techniques to reduce wind erosion, and 92 per cent applied one or more of these techniques in the field. The indigenous soil conservation techniques are application of manure and mulching with crop residues or tree branches. New techniques are tree planting, natural regeneration of woody vegetation, and application of zai, a method of soil preparation from Burkina Faso, using pits filled with compost for sowing crops. The farmers who have applied these new techniques reported to have less wind-erosion problems in their fields. © 1998 John Wiley & Sons, Ltd.

Clothing and Difference: Embodied Identities in Colonial and Post-Colonial Africa

Clothing and Difference: Embodied Identities in Colonial and Post-Colonial Africa. Edited by HII.DI HENDRICKSON. Durham NC: Duke University Press, 1996; 261 pp. (paper). Clothing and difference brings together an engaging and useful set of case studies that detail how clothing, toilette, and related body practices become ways to constitute, challenge, signal, and inculcate social identities and differences. Drawn from a range of African settings, they illustrate the changing nature of such practice and identities and the subtle distinctions of meaning encoded in variations of style. Most relate their concerns to recent work in cultural theory and cultural studies. A few go further to demonstrate how careful ethnographic analysis and cultural history provide a firm and fertile grounding for critical engagement with contemporary theory as well as an avenue for its creative reformulation. Hendrickson's brief introduction emphasizes the socially constructed, historically particular, and semiotic nature of clothing practice and the body surface. She defines the book in relation to three literatures: recent studies on fashion and dress, particularly feminist and cultural studies; social science analyses of dress; and Africanist scholarship. These are treated more like isolated traditions than theoretically and historically entwined endeavors, but the short discussions highlight basic questions that show the importance of comparative work stretching beyond Europe and North America. Hendrickson emphasizes their eclectic mix of material and methods in the papers and the counterpoint of perspectives that this often allows. The eight case studies are divided into three sections. The first groups three papers under a very general rubric, Creating Social Identities. Elishe Renne considers changing meanings of virginity, as represented by special white cloths and as a bodily state, for Ekiti Yoruba in Nigeria. She shows how enlightened behavior became defined this century in relation to education, elite status, and alternative kinds of sociality, reversing other Ekiti understandings of marriage arrangement and young women's physical states and status. Deborah James' fascinating paper about northern Sotho-speaking communities in South Africa describes the dynamics of setswana and sekgowa (Sotho ways and White ways). By tracing the history of women's dress over three generations, James explains how the former incorporated aspects of the latter and how gendered shifts in the political economy of labor, financial obligation, education, and marriage have been intimately related through clothing. She also examines how women in a local dance group forge temporary economic solidarity and community through performance and dress. Adeline Masquelier closes the section with a paper on Bori spirits and their mediums in southern Niger. She outlines not only how different costumes identify deities, but how mediums build, display, and break their relations with deities and others by means of cloth. Misty Bastian's marvelous account of fashion history and the daring stylistic maneuvers of youth in Onitsha, Nigeria, begins the second section, Challenging Authority. Bastian explores the way young women and young men alike adapted particular senior male styles in the late 1980s, questioning notions of power, wealth, and morality in the process. Her creative use of diverse sources, close attention to particular cases of stylistic choice and innovation, and perceptive commentary on consumption-based theories of fashion and identity make this a particularly compelling essay. One other paper is included in this section, though its relevance to challenging authority is less than clear. Bradd Weiss' fragmentary account of Haya death shrouds and funeral dressing in Tanzania touches some classic anthropological themes but is rather disengaged from Haya social experience. …

Protopterus nigeriensis nov. sp., l'un des plusanciens protoptères — DIPNOI — (In Beceten, Sénonien du Niger)

The In Beceten locality (Early Senonian) in the southern Niger has yielded two dipnoans Neoceratodusafricanus and Protopterus nigeriensis nov. sp., this near species is probably closely related to Lavocatodus protopteroides.

Vectors of Witchcraft: Object Transactions and the Materialization of Memory in Niger

Among Mawri communities of southern Niger, deaths are occasionally blamed on bloodsucking spirits whose deadly appetite is unleashed by human greed Identifying the agency behind the crime involves focusing on certain objects the circulation of which once wove link between victims and culprits. This article examines how gift-giving figures in local experiences of time and remembrance and discusses the mnemonic functions some objects come to have in the course of social practices involving witchcraft and its inscription as memory. [Niger, witchcraft, memory, gift-giving, object transactions] Intrduction: Objects, Tune and Memory Although the capacity of objects to bind people together has long been noted (Mauss 1954), more recent studies have built on Mauss' insight to focus on the various ways in which objects serve to create or emphasize continuities and discontinuities (Battaglia 1992; Munn 1986). Much attention has thus been paid to cloth, the very structure of which already evokes notions of connectedness and tying (Schneider and Weiner 1989). Describing how, in sixteenth century India, robes worn by the king could transmit his authority, Cohn notes that clothes are a medium through which substances can be transferred (1989: 312). Focusing on the relation between objects and memory, some studies (Feeley-Harnik 1989; Darish 1989) have highlighted the capacity of things to mediate between the dead and the living, and the past and the present, while others (Weiss 1996) have drawn attention to the ways in which remembering and forgetting are dynamically interrelated in the uses clothing are sometimes put to. If cloth can be said to absorb time, as Weiner (1989: 62) puts it, we must nevertheless not lose sight of the fact that even if absorbency is in itself an intrinsic quality of textiles, the capacity of clothing-and other objects-to transcend-or to stresstime, death, and the succession of generations only derives from how these things are used, manipulated, and circulated (Appadurai 1986). The ability of objects to serve as mnemonic forms is not inherently vested in these objects but rather emerges in the context of their engagement in human transactions and relations. Among Mawri communities of southern Niger, where people continuously and repeatedly engage in gift exchange of all kinds to create and secure social ties, the act of giving often serves to inscribe continuities, establish social connections, reciprocate prior contribution, or simply make concrete friendship or good-will. The incessant exchange of kola nuts in greeting procedures, the sprinkling of coins onto the sweaty foreheads of dancers during public celebrations, the food contributions brought to spirit possession rituals, the gifts of soap and perfume received by new mothers at their infants' naming ceremonies all exemplify the deeply rooted transactionalism of Mawri society. While cloth once figured prominently in marriage ceremonies-to reassert symbolically the creation of marital ties between the newlyweds-and other transactions, cash has now become the preferred means of strengthening bonds and generating social capital. Whether one is attending the installment of village chief or simply visiting sick friend, these occasions inevitably call for gifts of money. Currency may be progressively displacing goods in kind as the standard gift, but some objects nonetheless remain an important medium for weaving the intricate fabric of social relations. For instance, no wedding transactions are complete without the complex exchange and distribution of ka,van daki (things for the room; wedding gifts) that celebrate bride's worthiness, her social ties to women's networks, and her productive ability to generate dowry-since the bride has usually worked throughout her childhood to help generate the income that would purchase some of the furniture, pots, and hand-woven blankets that will fill her new home. …

Energy budgets of windbreak canopies in the Sahel

Windbreaks are openly exposed to turbulent motions in the atmosphere because they are taller than adjacent crops and usually only one or two trees in width. Transpiration by trees in windbreaks, consequently, can be expected to deviate substantially from the equilibrium rate as a result of advection and vertical entrainment, which may therefore influence water budgets for windbreak systems and competitive interactions between trees and crops. To quantify the effects of advection and entrainment on transpiration by windbreak trees, the energy budgets of canopies of Azadirachta indica A. Juss. windbreaks at a site in southern Niger were measured at four different times of year. Each component of the energy budget was determined independently and expressed per unit of windbreak length: net radiation ( R n) was measured using an array of eight linear net radiometers enclosing the windbreak foliage; latent heat fluxes ( λAE) were determined by scaling sap flow, measured using the heat-pulse technique, from tree to windbreak length on the basis of leaf area; sensible heat fluxes ( H) were determined from measurements of the difference in temperature between the crown of a windbreak tree and ambient air, using aerodynamic conductances estimated by scaling-up in situ measurements of leaf boundary layer conductances; the change in heat storage by the canopy ( ΔS) was estimated from changes in wood temperature over time. ΔS was found to be a negligible component of the energy budget of windbreak canopies and comparison of λE + H with R n showed good agreement. R n was mostly dissipated as λE during the rainy season and early dry season but as H during the driest period of the year. Examination of exchange fluxes for the windbreaks showed that partitioning of energy by windbreak canopies was strongly affected at all times of year by exchanges of energy between sensible and latent heat at canopy surfaces as a result of advection and entrainment. During moist periods of the year, advection and entrainment enhanced λE relative to λE eq the latent heat flux at equilibrium, by up to 60%, but depressed λE during the driest time of year, so that λE was as low as 40% of ΛE eq Depression of ] glE relative to λE eq by advection and entrainment occurred when surface conductances of the windbreaks were reduced by lack of moisture, whereas λE was enhanced when surface conductances were high. The effects of advection and entrainment on water use by windbreak trees must be accounted for when assessing the wager budgets of windbreak systems, because any reductions in evapotranspiration by crops resulting from shelter may be offset by enhancement of tree transpiration.

Estimation of rainfall inputs and direct recharge to the deep unsaturated zone of southern Niger using the chloride profile method

An estimate of direct groundwater recharge below a region of natural woodland (tiger bush) has been made in south-west Niger using the solute profile technique. Data has been collected from a 77 m deep well drug within the study area covered by HAPEX-Sahel (Hydrological and Atmospheric Pilot Experiment), an international large-scale energy, water and carbon balance experiment carried out during the summer of 1992. During well construction samples were taken from the unsaturated zone at the following intervals: every 25 cm from 0–10 m, every 50 cm from 10–62.5 m, then every metre to the bottom of the well. Pore water was extracted from each sample either by centrifugation or elutriation and analysed for chloride; moisture contents of samples were obtained gravimetrically. These data have been used to produce depth profiles of pore water chloride concentration and moisture content throughout the unsaturated zone. From these profiles it has been possible to derive an estimate of historic direct recharge at the site. The chloride concentration of rainfall, which is required to make the estimate, was determined from the analysis of 123 rainfall samples collected from five EPSAT (vers une Estimation des Précipitation par Satellite au sahel) rain gauges in 1992. A mean recharge rate of 13 mm year −1 (range 10–19 mm) is estimated for the upper 70m of the profile, with a total residence time of 790 years (range 520–990 years). This is considered to be a representative estimate of the magnitude of direct recharge taking place below tiger bush areas.

Variation and geographical distribution of ploidy levels inPennisetum sectionBrevivalvula (Poaceae) in Burkina Faso, Benin and southern Niger

Pennisetum sect.Brevivalvula is a species complex characterized by polyploidy and apomixis. Ploidy level was assessed by DAPI-flow cytometry for 304 plants of the section, originating from Burkina Faso, Benin and southern Niger. The results were confirmed for 54 plants based on chromosome counts. The samples show four euploidy levels (with x = 9) distributed among five species:P. hordeoides (2n = 36, 54),P. pedicellatum (2n = 36, 45, 54),P. polystachion (2n = 18, 36, 45, 54),P. setosum (2n = 54), andP. subangustum (2n = 18, 36, 54). The geographical distribution of these ploidy levels seems related to major vegetation zones present in Africa. Diploid populations ofP. polystachion andP. subangustum were found in the Banfora area, in Burkina Faso.

Mineralogy of salt efflorescences in paddy field soils of Kollo, southern Niger

This study examines the mineralogy of salt crusts developed on the irrigated paddy soils in the Soudano-Sahelian region of Niger. It involved field observations supplemented by laboratory determinations: powder XRD, SEM-EDAX, IR spectral analyses. The salt crusts were found in the concave zones near to the dike along the Niger River. They consisted of white mamillated konyaite crystals supported by a continuous hexahydrite crust. Upslope, konyaite disappeared progressively and the discontinuous crust was constituted by hexahydrite only. At a few centimeters below the soil surface, epsomite crystallized in the cracks and voids. In the subsoil, gypsum and calcite were deposited. The salt minerals were distributed vertically and laterally in the soil horizons according to the chemical composition of shallow groundwater, in particular the NaMg ion ratio, the water table depth and the extent of surface runoff. Human activity, particularly superfluous irrigation, constitutes the most pertinent explanation of the salinization processes at Kollo.

Biostratigraphy of some Maastrichtian and Paleocene formations in the lullemmeden Basin (southern Niger)

Biostratigraphy of some Maastrichtian and Paleocene formations in the lullemmeden Basin (southern Niger)

A two year pollen calendar for traditionally produced honey types from Gaya, southern Niger

Abstract A pollen calendar of traditionally produced honeys in Gaya/southern Niger was established for a two year period. The region is situated in the transition zone from the sahelian to the sudanian savannas. In this area honey represents an appreciated source for further income for the cultivators. Palynological investigations of the honey samples showed that the bees regularly exploit a restricted number of trees and bushes, such as Combretum, Terminalia or Guiera throughout the whole year or Lannaea, Parkia and Bombax during the winter and spring. Other Sudanian trees and bushes are only occasionally visited in addition. During the dry season Gramineae are also exploited because of the sap provided by the Aphids. In their pollen spectra the honeys reflect both the vegetation types and the agrarian systems of the region as for as can be traced from their collection time and from observations on the flowering period of the trees and bushes visited. Ein zweijähriger Pollenkalender konnte für die Region Gaya/Südniger mit Hilfe traditionell produzierter Honige aufgestellt werden. Die Region liegt im Übergang von den sahelischen zu den sudanischen Savannen. In dieser Region ist Honig eine willkommene zusätzliche Einkommensquelle für die Bauer. Die pollenanalytischen Untersuchungen zeigen, daß nur eine begrenzte Zahl von Bäumen und Stäuchern regelmäßig von den Bienen besucht wird, Combretum, Terminalia und Guiera über das ganze Jahr und Parkia, Lannaea und Bombax innerhalb der Wintersaison. Eine größere Zahl sudanischer Elemente wird nur zufällig genutzt. Während der Trockenzeit werden auch Gräser abgesammelt, hauptsächlich wegen des Honigsaftes, der von Aphiden produziert wird. Die Honige spiegeln die Vegetationstypen der Region und deren Agrarsysteme in ihren Pollenspektrum und können auch durch den Vergleich mit den Blühperioden der entsprechenden Bäume und Sträucher in ihrer Produktionszeit bestimmt werden. Les études de mélissopalynologie présentées portent sur la région de Gaya au Sud du Niger. A partir des spectres polliniques obtenus par l'analyse des miels de production traditionelle il a été possible d'établir un calendrier pollinique. La région de Gaya est située dans une zone de transition entre les savanes sahéliennes et soudaniennes. C'est dans cette partie du Niger que la production de miel est la plus élevée et fournit un surplus économique notable pour les cultivateurs. Les investigations palynologiques ont montré que les abeilles visitent régulièrement un nombre restreint d'arbres et d'arbustres tels Combretum, Terminalia et Guiera pendant toute l'anné, ainsi Parkia, Lannaea et Bombax durant la période hivernale. A la saison sèche, les graminées sont également exploitées pour Ieurs exsudats dus aux Aphides. Les spectres polliniques reflètent parfaitement les principaux types de végétation et des systèmes agaires de la région durant la période de production mellifère, par comparaison avec la saison de floraison des arbres et des arbustres butinés.

Estimating sensible heat flux from radiometric temperature over sparse millet

A two-layer model was developed and used to estimate sensible heat flux over a sparse millet crop from surface radiometric temperature. The millet crop was grown in farming conditions on the central site of the HAPEX-Sahel experiment in southern Niger. Surface temperature was measured with a nadir-looking radiometer. Measurements of the convective fluxes of sensible and latent heat were made simultaneously by means of the energy balance-Bowen ratio method. It is assumed that infra-red surface temperature can be represented by a weighted sum of foliage and soil surface temperatures, the weighting factors being the fractional areas of foliage and soil surface. With this assumption, the basic equations of two-layer models lead to an expression of sensible heat flux H close in form to the Ohm's law type formulation obtained from a one-layer approach, but in which the temperature difference between the surface and the air T r − T a has to be corrected by a factor proportional to the temperature difference δT between the foliage and the substrate. δT being not available in our experiment, it was assumed that a statistical relationship linking δT to T r − T a of the type δT = a( T r − T a) m could be used. Using one part of the data set, m and a were statistically determined by adjusting H estimated by the model to H observed by the Bowen ratio method. The best adjustment gave m = 2 and a = 0.10. For the other part of the data set (different from the one employed to calibrate this relationship) it was found that H estimated using the two-layer model with this empirical relationship compared fairly well with the values of H observed.

Soil Tillage and Windbreak Effects on Millet and Cowpea: II. Dry Matter and Grain Yield

AbstractIn the West Africa Sahel, sand storms occurring early in the growing season may severely damage emerging crops. This study was conducted to determine the Influence of ridges and windbreaks on growth, water use and grain yield of millet, Pennisetum glaucum (L.), and cowpea, Vigna unguiculata (L.) Walp. A field trial was carried out from 1985 to 1987 on a Psammentic Paleustalf in southern Niger using 12 ha of land fallowed over the previous 5 yr. Treatments for millet and cowpea were flat and ridged soil preparation and windbreaks spaced at 6, 20, 40, and 90 m. Total annual rainfall was 558, 641, and 363 mm in the 3 yr of the experiment; onset and distribution of the rains varied. Millet total dry matter (TDM) increased as total water use Increased from 250 to 400 mm. Ridging did not change total dry matter or grain yield in millet but increased cowpea grain yield by 90 and 300 kg ha−1 in 2 of the 3 yr. Protection by windbreaks spaced 6 and 20 m apart resulted in a 48 to 90% Increase in early millet TDM and a 74 to 89% improvement of cowpea ground cover. However, these early effects were not sustained throughout the growing period. Average TDM at maturity and grain yields were similar in all windbreak spacings for millet and cowpea. Although windbreaks may not increase yields of two important Sahelian crops, they may help to stabilize longterm crop production by conserving the soil and providing additional marketable commodities if an appropriate selection is made of type of windbreak and species planted.

Soil Tillage and Windbreak Effects on Millet and Cowpea: I. Wind Speed, Evaporation, and Wind Erosion

AbstractDeforestation, overgrazing, and declining soil regeneration periods have resulted in increased wind erosion problems in dry areas of the West African Sahel, but little is known about the bio‐physical factors involved. This research was conducted to determine the effects of ridging and four different windbreak spacings on wind erosion, potential evaporation, and soil water reserves. A field trial was conducted from 1985 to 1987 on 12 ha of a Psammentic Paleustalf in Southern Niger. Millet, Pennisetum glaucum (L.), and cowpea, Vigna unguiculata (L.) Walp., were seeded in strips on flat and ridged soil. Windbreaks of savannah vegetation were spaced at 6, 20, 40, and 90 m. The effects of ridging on wind speed, evaporation, and wind erosion were small and mostly non‐significant. However, average wind speed at 0.3 m above ground in the center of cowpea and millet strips was significantly reduced from 2.8 to 2.1 m s—1 as windbreak distances narrowed from 90 to 6 m. As a consequence, potential evaporation declined by 15% and the amount of wind blown soil particles by 50% in ridged and by 70% in flat treatments. Despite reduced potential evaporation, average subsoil water reserves were 14 mm smaller in the 6‐ than in the 20‐m windbreak spacing indicating excessive water extraction by the windbreak vegetation. Thus, establishing windbreaks with natural savannah vegetation may require a careful consideration of the agronomic benefits and costs to competing crops.

Les ammonites du Niger (Afrique occidentale) et la transgression transsaharienne au cours du Cénomanien-Turonien

Our study is a paleontological revision of the ammonite faunas connected with the Sahara Cenomanian-Turonian transgression. It is also a refinement of the biostratigraphical framework in the sedimentary Iullemeden basin (Western and Southern Niger: Mt Iguelela and Damergou). About 700 well preserved ammonites have been collected from 8 outcrops (Berere, Tanout Aviation, Birgimari, Dan Dordo, Bakatchiraba in the Damergou and towards West Abalak, Korahane and Iguelela Mountains). It is possible to recognize, locally, nine horizons permitting the description of three new taxa. The Metoicoceras geslinianum (d’ Orbigny) Nigericeras gadeni ( Chudeau) association in particular allows an improved correlation with the N. gadeni ( Chudeau) levels with North-Western Europe and also with the Western Interior and Texas - New Mexico (USA). In addition the presence of such ammonites as Cibolaites (?) africaensis nov. sp. or Coilopoceras inflatum Cobban & Hook also allows acute correlations with USA. However authors admit that the ammonite faunas from Niger essentially have their affinities with the Tethyan realm and even some taxa such as Nigericeras gadeni ( Chudeau) and Thomasites nigeriensis ( Woods) are endemic in the Saharan countries of the Sahel (Algeria, Niger, Northeast Nigeria). Although the connection between the Tethys and the South Atlantic via the Benue trough is at the moment disputed by some authors for the Cenomanian - Turonian, the ammonite distributions lead to the conclusion of their livinghence sea-connection there. This connection began during the upper part of the Gadeni zone (Upper Cenomanian) and ended about the upper limit of the Nigeriensis zone (Uppermost Lower Turonian). This study also deals with ontogenetic and evolutionary analysis. On the one hand Nigericeras gadeni ( Chudeau) - N. jacqueti Schneegans - N. jacqueti involutes nov. subsp. tend to lose their juvenile ornamentation by peramorphosis during their evolution and on the other hand, in Vascoceras (Paravascoceras) cauvini ( Chudeau)- V. (P.) proprium ( Reyment), the strong adult ornamentation seems to disapear by virtue of an opposite tendency: paedomorphosis. The general tendency shown by the Niger ammonite faunas, is to become smoother and to adopt simplified suture lines. It is probably a response to the extrinsic constraints (synergy of climatic, ecological and physiographical constraints) by development of quite different and perhaps more efficied morphologies for the group (channelling of morphological tendency) as a function of their intrinsic constraints (ontogenetic potential).

PALHYDAF (Palaeohydrology in Africa) program: objectives, methods, major results

The PALHYDAF program aims to reconstruct the Late Quaternary (130 ka B.P. to Present) environmental and hydrological changes of northwest Africa, and to interpret them in terms of palaeoclimate for testing coupled atmospheric/ocean circulation models. Lacustrine sequences were obtained from closed basins which lie along two meridional transects: southern Tunisia-southern Niger, and Algeria-Mali. Particular attention is given to groundwater storage and periods of recharge of the aquifers. The chronological framework is based on 14C dates (conventional and AMS methods) and/or the Th/U disequilibrium method. In favourable cases (e.g. Mali), correlations can be made between the chronology of surface palaeohydrology and that of aquifer recharge. Various environmental markers (mineralogy, elemental chemistry, stable isotopes, biological remains) are used for palaeoenvironmental purposes. Quantitative estimates of palaeoclimatic variables (e.g. air humidity) may be attempted through the combination of geochemical and palaeobiological data. The major results already obtained are summarized for the following individual sectors: 1 — southern Tunisia. 1′ — northern Algeria. 2 — southern Algeria. 3 — northern Niger. 3′ — Mali. 4 — southern Niger. At the present stage of investigation, the following new inferences can be drown. • - One, or several humid episode(s) occurred in the northern Sahara between ≈ 150 and ≈ 75 ka B.P. Several factors suggest that these humid conditions also affected lower latitudes, although their southern extent cannot be given precisely at present. • - The previously postulated existence of large lakes at ≈20–35 ka B.P. is not confirmed. This time interval seems to coincide with raised water-tables, but not to a major humid phase. In all cases, the 14C chronologies obtained for the Late Pleistocene have to be checked by comparison with other dating methods (e.g. Th/U disequilibrium). • - After the arid period of the Last Glacial Maximum, the return of humid conditions occurred in two major steps, at ≥12 and ≈9.5-9 ka B.P. for both the southern and the northern Sahara.

Socioeconomic impact of oil in Nigeria

Taxes and royalties from the oil industry in Nigeria have made possible massive infrastructural and social development throughout the country; this single industry continues to be the most important contributor to the national treasury. Along with oil, however, have come environmental and social problems, some severe and, in the social sector, possibly of long duration. Questionnaires were employed to solicit environmental and socioeconomic information from residents in the oil-impacted area as well as to ascertain the views of the oil companies with respect to their Nigerian operations, in particular to their socio-economic responsibilities to the local residents. Responses point to serious discontent on the part of the impacted population, especially in the most important southern (Niger Delta) oil producing region. These negative attitudes in part are based upon the impacted population’s inability to secure for itself a sufficiently large number of oil industry jobs and in part to the presence in the local community of ethnic strangers who do have such employment. There is evidence of serious environmental damage, but its biological dimension has been overshadowed by claims for monetary compensation at the local level. Data derived from these investigations might well be applicable in the wider field of trans-national mining and petroleum extraction operations in developing countries, especially to the unwritten social obligations of the expatriate firm to local residents.

Plant Density and Nitrogen Fertilizer Effects on Pearl Millet Production in Niger

AbstractPearl millet (Pennisetum glaucum [L.] R. Br) is an important crop in many developing countries in West Africa and provides 80 to 90% of the food requirement for Niger. Farmers plant at a wide range of densities which may affect crop response to fertilizer. Studies were conducted for 3 yrs in a sandy soil in southern Niger to assess the effects of N fertilization (0–60 kg N ha−1) and plant density (5000–40 000 pockets ha−1, three plants per pocket) on millet yield and yield components. The effects of N and density on yield were influenced by midseason rainfall. With low midseason rainfall, highdensity planting reduced yield slightly and N had no effect. With average or above rainfall, N application and high plant density increased millet grain yield four‐ to fivefold. Nitrogen increased stover production 33% in a dry year and 100% in the wetter year. Plant density significantly affected stover yield only in 1983, a year with high early season rainfall. Increasing plant density tended to increase stover production in all years. Grain weight in 1983 decreased 14% when plant density exceeded 20 000 pockets ha−1. Nitrogen fertilizer doubled the number of heads per pocket at low plant densities when rainfall was normal or above. A plant density of 15 000 to 20 000 pockets ha−1 and N application of 30 kg N ha−1 in two splits achieved good yields in average and wet years, with only a small yield reduction in the drought year.