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International audience; In a context of climate change characterized by rising temperatures, increased greenhouse gases and frequent droughts, the Sahel is presented as one of the most vulnerable areas to the adverse effects of climate change. The Sahel is presented as one of the most vulnerable areas to the adverse effects of climate change. The objective of this study is to assess the above-ground biomass and carbon stock of three Sahelian species: Acacia raddiana tortilis (Forsk.) hayne ssp. raddiana (savi) Brenan, Acacia senegal (L.) Willd and Balanites aegyptiaca (L.). The study was carried out in northern Senegal commonly known as Ferlo. Biomasses of the populations of the three target species were first assessed by harvesting the entire epigenetic part of the species and then modelled by correlation using dendrometric parameters measured on each individual of the sample. Two models, mono-specific and multi-species, were used. The results obtained showed that the diameter at breast height (x) and the parameter best correlated to the epigeal biomass (y). The dry biomass of woody plants was 31.4 ± 15.2 kg/tree for B. aegyptiaca, 30.6 ± 13.2 kg/tree for A. senegal and 26.2 ± 11.1 kg/tree for A. raddiana; i.e. carbon equivalents of 14.75 - 14.38 - 12.31 kg/tree respectively. The amount of carbon contained in the above-ground woody biomass is estimated at 4.48 t/ha. The carbon equivalent, atmospheric CO2 is estimated at 16.44 tons of CO2/ha and based on the actual density of Ferlo (108.08 ± 49.79 ind/ha) the sequestered carbon of the area is estimated at 1777.008 tons of CO2. The comparison between the models developed in this study and the multispecific or mono-specific models from the literature showed substantial differences. This study contributes to a better understanding of the contribution of Sahelian woody species to carbon sequestration and the results could be used in the framework of adaptation to climate change.

International audience; 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 (1987-2016) for B. senegalensis and 38 years (1964-2012) for S. birrea. The results revealed that there is no significant correlation between the growth chronologies of B. senegalensis and the climatic regressors (temperature and precipitation). In contrast, the ring-climate relationship shows that in S. birrea winter precipitation positively influences ring growth while temperature has no effect on ring growth in this species. This study provides a better understanding of the response of forest ecosystems to possible climate change, particularly in the current context of sustainable forest management.

International audience

International audience; 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 = ax2 + 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 = 0.0023x2 + 0.4851x - 0.0519 for Boscia senegalensis and y = 0.35x2 + 10.35x - 12.90 for S. birrea; with very significant correlation coefficients (R2) of 0.85 and 0.94 respectively. These results can be used for a sequestered carbon assessment study and will play a role in monitoring the carbon market in Africa.

International audience; Aim : This study focuses on the spatio-temporal dynamics of the ecosystems between 1965 to 2017.Location : sylvopastoral reserve of the six Ferlo boreholes in SenegalMethods : The methodological approach consists in delineating and mapping land cover in the reserve, in 1965 and 2017 and, analyzing changes during this period using remote sensing techniques and Geographic Information Systems (GIS).Results : The results obtained show the identification of 10 land-use patterns in the reserve for the year 2017: savannah woodland, shrub savannah with tree, shrub savannah, shrub steppe with tree, shrub steppe, vegetable crop rainfall, village, pond, bare soil, tree plantation. In addition to savannah with tree, all these classes are present in 1965, except for the "tree plantation" class. The zones of shrub savannah and shrub steppe and shrub steppe with tree gradually changed between these dates, while the zones of shrub savannah with tree decreased. The areas occupied by savannah with tree disappeared completely. Analysis of changes between 1965 and 2017 showed that 19.71% of the reserve area remained in its original state, 70.58% was modified and 9.71% was converted.Main conclusion : This study has been widened to the whole “sylvopastoral reserve” protected area, which will make possible to evaluate the effectiveness of the management plans for protected areas in the Ferlo.

International audience

International audience; In the last several decades, the Sahel has undergone desertification due to a combination of climatic and anthropogenic factors. In order to identify the most appropriate native tree species for reforestation activities, woody species inventories were performed and coupled to ethnobotanical surveys in the vicinity of four villages (Tessékéré-Forage, Widou-Thiengoly, Labgar, and Lougré-Thiolly) in the Ferlo region of the Senegalese Sahel. In general, the region is characterized by a low degree of biodiversity with only 20 tree and shrub species represented by 13 different families. Questionnaires and semi-structured interviews with local populations identified seventeen tree species that are commonly used for food, construction, energy, health, commerce, and handicrafts. The most highly cited tree species was Balanites aegyptiaca which was also the most abundant in the study region. In contrast, other species including Grewia bicolor, Ziziphus mauritiana, Adansonia digitata, and Sclerocarya birrea came under the categories of most highly cited for their various uses but have become rare in nature, making them ideal candidates for reforestation trials. This study is particularly timely in that the Ferlo region is currently undergoing major ecological restoration efforts in the framework of the Great Green Wall for the Sahara and the Sahel Initiative.