The objective of this study was to develop allometric models for estimating the biomass of Sclerocarya birrea (A.Rich) Hoscht and Boscia senegalensis (Pers.) Lam. ex Poir. The inventory of these ligneous was carried out at Widou Thiengoly (North of Senegal). The sample consists of 43 individuals of Boscia senegalensis and 15 individuals of Sclerocarya birrea. The selected individuals were dendrometrically characterized before being cut, compartmentalized (trunk, branches, and twigs) and weighed entirely. Simple regression tests were performed to examine the most explanatory dendrometric parameter (x) for biomass (y) according to two types of models: the linear model (y = ax + b) and the polynomial model of degrees 2 (y = ax 2 + bx + c).The criteria for selection and validity of the models are based firstly on the tests of normality, nullity, heterogeneity and autocorrelation of the residues. The results showed that the most explanatory dendrometric parameter of the biomass was the crown surface for Boscia senegalensis and the 1.30 m diameter for Sclerocarya birrea of all the tests performed, the second-order Polynomial model is the best predictor of above ground biomass for these two species. Thus, the allometric models established to predict the biomass of these two species are: y = 0.0023x 2 + 0.4851x − 0.0519 for Boscia senegalensis and y = 0.35x 2 + 10.35x − 12.90 for S. birrea; with very significant correlation coefficients (R 2
The general objective of this study is to describe the demographic structure and distribution according to topographic units of two woody species, Boscia senegalensis (Pers.) Lam. Ex Poir and Sclerocarya birrea (A. Rich) Hoscht in Widou Thiengoly (Ferlo) in northern Senegal. Stratified random sampling was used to carry out the study taking into consideration the topographic units (low background, pouring and tray). The ligneous inventory method consisted in carrying out vegetation surveys using a dendrometric approach with a minimum area of 2500 m 2 . The results obtained indicate that in the study area, the population of B. senegalensis is denser (42 ± 7.3 ind/ha) compared to that of S. birrea (6.1 ± 3.4 ind/ha). Topographic variability has a great influence on the life of the species. The study of the structure of individuals in diameter and height classes has shown that the population of B. senegalensis is shrubby and is generally renewed itself well, unlike that of S. birrea, which is more mature and whose lack of regeneration seems to compromise the renewal of the population. Given the total lack of regeneration of the species, this population, therefore requires more effective conservation strategies for its restoration.
Les mares présentent un grand intérêt environnemental en raison des services écosystémiques qu'elles fournissent. Au Ferlo, les activités pastorales sont développées autour des mares. La connaissance des ressources herbacées est importante pour une gestion durable du pâturage autour des mares temporaires. L’objectif de cette étude est de déterminer la répartition spatiale des ressources herbacées autour des mares par une approche phytoécologique. L’échantillonnage sur des transects est réalisé dans les différents faciès morpho-pédologiques de deux mares pâturées et une mare non pâturée. La flore herbacée recensée compte 55 espèces, réparties dans 41 genres dont 22 familles. Les familles des Poacées et des Fabacées sont plus fréquentes quelle que soit l’unité morpho-pédologique et la mare, suivi de la famille des Cypéracées dans les mares et des versants et la famille des Zygophyllacées dont l’espèce Tribulus terrestris sur les dunes. Le recouvrement est globalement élevé (82,6%) dans la mare non pâturée et moyen sur les mares pâturées (55,33% et 46,4%). Au niveau des versants, les espèces sont de grandes tailles, rares et très diversifiées. Les espèces vivaces sont plus fréquentes autour des mares pâturées alors que les espèces rares se retrouvent autour de la mare non pâturée. Ces résultats révèlent ainsi l’influence prédominante des facteurs anthropiques et topographiques sur la répartition spatiale de la végétation herbacée.Mots clés : Transects, pâturée, phytoécologique, morpho-pédologiques.
English Title: Distribution of herbaceous vegetation around temporary ponds: influence of anthropic and topographical factors in Widou Thiengoly (Ferlo, Northern Senegal)At the Ferlo, pastoral activities are developed around the ponds. The knowledge of herbaceous resources is important for sustainable grazing management around the temporary pools. The general objective of this study is to determine the spatial distribution of herbaceous resources around the ponds using a phytoecological approach. Transect sampling was carried out in the different morpho-pedological facies of two grazed ponds and one ungrazed pond. The recorded herbaceous flora includes 55 species, divided into 41 genera including 22 families. The Poaceae and Fabaceae families are more frequent whatever the morpho-pedological unit and the pond, followed by the Cyperaceae family in the ponds and on the slopes and the Zygophyllaceae family including the species Tribulus terrestris on the dunes. The overall coverage is high (82.6%) in the ungrazed pond and medium on the grazed ponds (55.33% and 46.4%). At the level of the slopes, the species are large, rare and much diversified. Perennial species are more frequent around the grazed ponds, while rare species are found around the ungrazed pond. These results thus reveal the predominant influence of anthropogenic and topographical factors on the spatial distribution of herbaceous vegetation.Keywords: Transect, grazed, phytoecological, morpho-pedological.
The objective of this study is to analyze the dendrochronological potential of two Sahelian species (B. senegalensis and S. birrea) and to evaluate the relationships between their growth rings and the climate. The study was conducted in 2016 in the Ferlo area of Senegal. The biological material consists of wood slices, taken from the trunks of these adult woody species at 0.30 m and 1.30 m from the ground after they have been felled. The technique used to examine the slices consists in identifying their rings, establishing their structures, inter-dating them and studying the relationship between the identified rings and climatic factors. The results showed that the species had thin, clear, highly visible and sharp rings. The limit of growth is marked by a line of parenchyma. Intradatation series carried out on the chronologies made it possible to estimate the ages of the individuals, which vary from 10 to 38 years for B. senegalensis and from 29 to 50 years for S. birrea. Their average growth rates are estimated at 0.906 mm/year and 0.89 mm/year respectively. The chronological sequences are 29 years for B. senegalensis and 38 years for S. birrea. The results revealed that there is no signifi-
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