Ali Mahamane

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

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...

Etudes floristique, phytosociologique et phytogéographique de la végétation du Parc Régional du W du Niger

Cette these a ete realisee en co-tutelle entre IUniversite libre de Bruxelles (Belgique) et IUniversite Abdou Moumouni de Niamey (Niger). Elle a ete soutenue publiquement le 14 avril 2005 a IUniversite libre de Bruxelles sous Ia presidence du Professeur Pierre Meerts, avec le jury suivant : J. Bogaert, J. Lejoly, M. Saadou, G. Mahy, G. Decocq, E. Boudouresque. Elle comporte 536 pages + annexes.

Evaluation of agro-morphological diversity of groundnut (Arachis hypogaea L.) in Niger

This work evaluated a collection of hundred groundnut (Arachis hypogaea L.) varieties from different origin using twenty four (24) agro-morphological traits that can help to enhance selection efficiency in crop improvement. The experiment was carried out at the experimental station of INRAN-Tarna, in the region of Maradi (Niger) during the rainy season of 2010. Analysis of variance showed a large variability among varieties for the agro-morphological traits. Principal Component Analysis (PCA), Agglomerative Hierarchical Clustering (AHC) and Fisher Discriminant Analysis (FDA) revealed that this variability is structured into four distinct groups. Groups I and II consisted of early varieties that have a high emergence rate and high pods and seed weight. These groups included mainly local varieties and those introduced in Niger through seed dissemination. Groups III and IV are composed of late varieties with large pods while group III had mostly varieties with long leaflets. Understanding the genetic control of the most discriminating among the studied traits would bring significant contribution to the genetic improvement of this important crop. n n xa0 n n Key words: Arachis hypogaea L, groundnut, agro-morphological traits, genetic variability, Niger.

Useful near infrared spectroscopy model calibrations on solid wood samples of Pterocarpus erinaceus (Poir.) for physical, mechanical and colour properties

Pterocarpus erinaceus (Poir.) (local name: Toti, Tem) is a species endemic to the Guinea-Sudan and Sudan-Sahel zones. It is over-exploited for its wood, which is sold in international trade to China and Indian markets. The selection of high performance wood based on wood properties and their vegetative reproduction represents the best option for the establishment of plantations with the aim of promoting the restoration of degraded natural resources. However, measurements of these characters are lengthy, time consuming and destructive, and difficult to perform in Togo because of the lack of equipment. An alternative to those methods is near infrared (NIR) spectroscopy. The aim of this study was to assess the efficiency and feasibility of near infrared spectroscopy for predicting the physical and mechanical properties and the colour parameters of P. erinaceus wood from Burkina Faso, Niger and Togo. The properties were determined by conventional method and correlated with near infrared spectra using partial least square regression. The partial least square regression models were tested by cross-validation and by external validation. The results of this study showed the possible use of near infrared spectroscopy to estimate the physical and mechanical properties and the colour parameters of P. erinaceus wood. In fact, when validating prediction models for radial and tangential shrinkage, the fibre saturation point (FSP) showed R2 values of 0.70, 0.71, and 0.92, respectively, with ratio performance deviation values of 1.84, 1.87 and 3.57. For the colour parameters L*, a* and b*, the R2 values were 0.83, 0.74 and 0.67, respectively, with ratio performance deviation values of 2.40, 2 and 1.70. The results showed that the basic density and fibre saturation point models were classed as good to very good, respectively. Near infrared spectroscopy can therefore be used to predict efficiently the properties of P. erinaceus wood for a large number of samples, enabling the incorporation of those traits in breeding criteria.

Floristic Composition, Structural Analysis and Socio-economic Importance of Legume Flora of the Commune of Mayahi, Niger, West Africa

Floristic assessment plays a crucial role in managing and conserving phytodiversity. Thisstudy tried to determine the floristic composition, woody structure and socio-economic importance of the legume flora in the commune of Mayahi. We used plot method based on systematic sampling approach to inventory legume species within the parklands in September 2012. We recorded 55 legume species belonging to 24 genera in 56 releves. Fabaceae is the dominant family among the legume botanical families in the parklands of the commune of Mayahi. The average woody legume density is 62 individuals per hectare in the commune of Mayahi. The woody legume species of highest average density are Faidherbia albida and Piliostigma reticulatum. While the total basal area of legumes of the commune is 1.12m2 / ha in the Mayahi commune. The crown cover varies according to the vegetation types but it is higher in the Goulbi N’kaba forest reserve. Legume flora provides a myriad of benefits to the people of Mayahi. The present study recommends furtherresearch that examines the impact of human activities on the legume flora of the parklands in the commune of Mayahi.

Caractérisation de la structure démographique des ligneux dans les parcs agroforestiers du terroir de Dan Saga (Aguié, Niger)

La regeneration naturelle assistee est une technique de preservation des ligneux dans les parcs agroforestiers pratiquee par les populations du terroir villageois de Dan Saga depuis plus de 20 ans. Cependant, son impact sur les caracteristiques structurales et ecologiques reste a determiner. Cette etude vise a caracteriser les parcs agroforestiers du terroir villageois de Dan Saga et a determiner la structure demographique des peuplements ligneux et des especes ligneuses les plus dominantes et utilisees par les populations. Pour ce faire, un inventaire forestier a ete realise dans 80 placettes de 2500 m² (50 m x 50 m) chacune. La regeneration a ete evaluee dans des placeaux de 25 m². Les structures demographiques construites ont ete ajustees au modele de Weibull a 3 parametres. Les resultats obtenus ont permis d’identifier trois parcs agroforestiers a savoir: le parc a Tamarindus indica et Grewia tenax , le parc a Annona senegalensis et Faidherbia ablida , et le parc a Albizia chevalerie et Cassia singuena . La structure en diametre des peuplements ligneux et des especes dominantes se caracterise par une densite importante d’individus dans les classes de petits diametres. Ces donnees sont utiles pour une gestion durable des parcs agroforestiers. Mots cles : Parc agroforestier, peuplement ligneux, structure demographique, Dan Saga, Niger.

Structure démographique de peuplement naturel et répartition spatiale des plantules de Pterocarpus erinaceus Poir. dans la forê

Pterocarpus erinaceus de la famille des Fabaceae, est un arbrexa0 eminemment utile pour les populations. C’est une espece endemique multi-usage des zones guineo-soudaniennes et soudano-saheliennes. La presente etude analyse les parametres structuraux du peuplement naturel de P. erinaceus, determine la distribution spatiale des plantules et leurs relations spatiales avec leurs geniteurs et les autres especes. Des mesures dendrometriques et la cartographie des peuplements naturels de Pterocarpus erinaceus ont ete effectuees dans la foret de Tiogo en zone soudanienne du Burkina Faso. L’analyse des structures en diametre et enxa0 hauteur montre que le peuplement est domine par des individus âges, les individus jeunes etant absents. La distribution spatiale des jeunes plantules de l’espece montre qu’elles ont une distribution gregaire et ont besoin des milieux plus ou moins ouverts pour germer. L’analyse de la fonction L12 (r) montre que ces plantules sont en competition avec la plupart des especes en presence hormis Acacia macrostachya et Vittelaria paradoxa. Cette germination preferentielle des milieuxxa0 ouverts expose ces plantules a la secheresse pendant la saison seche, aux feux de vegetation et a la dent des herbivores qui parcourent chaque jour les forets en zone soudanienne. Mots cles : Structure, distribution spatiale, regeneration, Pterocarpus erinaceus, Tiogo, Burkina Faso.