It has been widely reported that sacred forests are not just socio-cultural creations emanating from traditional societies as a privileged setting for ritual ceremonies, but that they also represent important local forms of biodiversity conservation. In recent decades, it is this latter role that has attracted the attention of international institutions, states and scientists. Although such forests have been widely studied in Asia and other parts of Africa, our understanding of Guinea’s sacred forests remains poor because local communities, not the state, manage them. In effect, because of the sacred status of these forests, the state favours local management strategies by individual communities. In this thesis, four representative case studies of the sacred forests of Upper Guinea, located near Kankan, are studied. The region’s ecosystems have been profoundly affected by human impacts, notably agriculture and mining. The villages of Diankana, Tintioulenkoro and Dossori, where these forests are amongst the few areas to conserve sacred forests. The aim of this thesis is to probe the socio-cultural and ecological values of the forests, in a local context of strong human pressures, with a view to their documentation and the elaboration of sustainable management strategies. Several methodological approaches have been used: sociological and ethno biological surveys, ecological and botanical inventories. The study elucidates a mode of management of these sacred forests by an ethnic group, the Malinkés, which is based on both "mythical codes" and laws defined by traditional legislation. The rigor of this management system, and the socio-cultural importance of these forests for local populations, favours their conservation in the wider context of profound human pressures on the environment. However, social changes in recent years appear, agriculture and urbanisation to have weakened this management system and exposed the area’s sacred forests to factors that preclude their effective conservation. The diachronic analysis shows that over the last three decades, the forest cover of all sacred sites studied has decreased by just over 40% of their initial area by agriculture and urbanization. The results also identified twelve plant groups, five of which were forested and seven of which are characteristic of degraded vegetation around these sacred forests. The groupings of the peripheral zones of the forests correspond to agrosystems and ruderal vegetation. The study of the flora of the different plant groups highlights the dominance of Afro-tropical species, Guinean-Congolese and Sudanese. This finding underlines the major influence of the entire Sudano-Guinean zone. Geomorphology, texture, soil moisture, light, and human impacts are more significant in explaining the distribution of plant communities at the local scale. Overall, the analysis shows that the stands studied are characterized by a decreasing heterogeneous structure indicating good natural regeneration. The highest density of trees is found in the dry land forest of Dossori (325 ± 153.3 trees/ha) and the highest basal area in the Kolonbatou forest (53.9 ± 32.5 m2/ha). The average diameter of the forests varies between 21.48 ± 10.12 and 48.58 ± 30.21 cm. Among the species of high ecological value are: Carapa procera, Cola cordifolia, Erythrophleum suaveolens, Isoberlinia doka, Anthonotha crassifolia and Garcinia ovalifolia. This study also shows that the stands of Tintioulenkoro are more mature (67 and 57 years) than those of Diankana and Dossori, respectively 39 and 33 years old. 242 species, 187 genera and 64 families represent the total floristic diversity of the sacred forests studied. The important conservation role of these forests is confirmed by the presence of 16 species threatened, 30 species previously unknown, in this part of Guinea, and 4 species not reported in the country according to the Flora of Guinea. These sacred forests are among the richest in Africa.