Importance Des Produits Forestiers Non Ligneux Medicinaux D’origine Vegetale Et Impacts Des Activites Anthropiques Sur Leur Durabilite Dans Le Sud-Ouest De La Republique Centrafricaine

The forest in the south-west of the Central African Republic has enormous potential for non-timber forest products (NTFPs) of plant origin. The objective of this study is to identify the medicinal value of these NTFPs of plant origin with high health potential and the effects of human activities on their sustainability. The study was carried out in 09 villages in the intervention zone of the Kadéi Forestry Company. From various methodological approaches (ethno botanical survey, participant observation, inventory technique), data were collected, processed and analysed. From the results obtained 91 non-wood medicinal plant species belonging to 29 families and to one large systematic group, the Magnoliophytes were identified. These species represent a means of therapeutic remedies used by 91% of surveyed populations to treat many diseases, symptoms and infections. Tree barks (43.26%) and leaves (39.21%) are the most commonly harvested organs. The variables collected related to the types of uses allowed to identify 19 priority NTFPs medicinal and underline the process of degradation of 7 important NTFPs. This degradation is mainly due to the way in which the natural resource is harvested, causing a large number of non- woody medicinal plant species to become rare. The definition of strategies based on ecological and socioeconomic harvesting techniques of NTFPs are solutions to ensure sustainable management of these products for the benefit of future generations

Biodiversité floristique et phytosociologique des végétations culturale, post-culturale, savanicole et étude du gradient le long du contact forêt-savane dans la région de Ngotto (République Centrafricaine)

LILLE2-BU Santé-Recherche (593502101) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

Analyse phytogéographique comparative des savanes et des forêts de Ngotto (République Centrafricaine)

After several investigations on the savanna and forest of Ngotto (Central African Republic), we propose a phytogeographical interpretation of our data on the systematic (level family), the biological forms, the dispersion of diaspores and phytogeographical elements spectra. These spectra are given regarding both formation type (savanna, forest) to appreciate their originality. Then, a comparaison is driven in order to set up the differences between these two formations.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Abrupt shifts in African savanna tree cover along a climatic gradient

International audienceAim To describe patterns of tree cover in savannas over a climatic gradient and a range of spatial scales and test if there are identifiable climate‐related mean structures, if tree cover always increases with water availability and if there is a continuous trend or a stepwise trend in tree cover.Location Central Tropical Africa.Methods We compared a new analysis of satellite tree cover data with botanical, phytogeographical and environmental data.Results Along the climatic transect, six vegetation structures were distinguished according to their average tree cover, which can co‐occur as mosaics. The resulting abrupt shifts in tree cover were not correlated to any shifts in either environmental variables or in tree species distributions.Main conclusions A strong contrast appears between fine‐scale variability in tree cover and coarse‐scale structural states that are stable over several degrees of latitude. While climate parameters and species pools display a continuous evolution along the climatic gradient, these stable structural states have discontinuous transitions, resulting in regions containing mosaics of alternative stable states. Soils appear to have little effect inside the climatic stable state domains but a strong action on the location of the transitions. This indicates that savannas are patch dynamics systems, prone to feedbacks stabilizing their coarse‐scale structure over wide ranges of environmental conditions

Reconstructing savanna tree cover from pollen, phytoliths and stable carbon isotopes

International audienceAimTo calibrate a model of the relationship between bio‐proxies (pollen, phytoliths and δ13C of soil organic matter) and woody cover, measured as the leaf area index (LAI). This relationship, applied in palaeosequences, enables reconstruction of past savanna tree cover.LocationThe samples are from tropical Africa. Modern soil samples are from the Central African Republic and past samples are from sediments of lakes in Senegal and Congo.MethodsWe analysed the pollen and phytolith content and stable carbon isotope values of 17 soil samples taken from three short transects in the Central African Republic; LAI was measured on the same transects. The indices used were the AP/NAP ratio of arboreal (AP) to non‐arboreal (NAP) pollen, the D/P ratio of ligneous dicotyledons (D) to Poaceae (P) phytoliths, and the δ13C of soil organic matter, i.e. the 13C/12C ratio.ResultsA multi‐proxy model was calibrated. The best model included only a combination of pollen and phytolith as proxies, excluding organic matter δ13C because of its long mean residence time in the soil. The model was then applied to two palaeosequences in Africa, and a time series of relative LAI changes was obtained, providing new information about vegetation changes.ConclusionThis model can be applied in palaeosequences to reconstruct relative time series of LAI in African savannas and can help interpret vegetation changes quantitatively. This approach is complementary to the description of pollen and phytolith assemblages