Sahelian woody communities are endangered by regeneration impoverishment in three land management types

International audience

English. Monitoring regeneration in woody communities and understanding the drivers of its success is crucial for gaining insight into the long-term persistence of trees in African dry-lands, where they play key socio-ecological roles. While fire, grazing and water availability are key factors for regeneration in these ecosystems, seed arrival, germination andseedling recruitment are still poorly documented under natural conditions in the West African Sahel. Tree planting is commonly carried out in West Africa to promote regeneration. The cost is considerable, the success is variable and its influence on spontaneous regeneration is unknown. We conducted a field inventory to ascertain the regeneration ability of woody communities in a Sahelian savanna in three land management types (plantations, communal grazing, old enclosures) to determine (i) the proportion of the different regeneration mechanisms; (ii) the influence of adult trees; (iii) the influence of management type and topography and (iv) their temporal dynamics. We first showed that regeneration diversity was poor, with half of the adult species not recorded in the regeneration phase. Secondly, regeneration mostly came from true seedlings compared to resprouting. Thirdly, adult communities were found to greatly influence regeneration density and composition. Fourthly, topography proved to influence regeneration density, whereas we observed little effect of the land management type. Lastly, historical data highlighted a steep decline in regeneration density over recent decades. These results raise questions about the persistence of woody vegetation in Sahelian savannas and highlight the need to protect large trees in suitable microsites, such as topographic depressions, to promote regeneration.