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

Abstract

Trees play a key role in drylands. Monitoring woody communities regeneration and understanding the drivers of its success is crucial to apprehend their long-term persistence. While re, grazing and water availability are key factors for regeneration in drylands, seeds arrival, germination and seedlings recruitment are still poorly studied in natural conditions in the West African Sahel. To promote regeneration, tree planting is a common tool used in West Africa. The cost is great, the success variable and their in uence on spontaneous regeneration is unknown. In this study, we conducted eld inventory to characterize the regeneration ability of woody communities in a Sahelian savanna. We investigated regeneration and adults stands in three land management types (plantations, communal grazing, old enclosures) to determine (i) the proportion of the regeneration modes and the in uence of mature trees; (ii) the in uence of management type and topography on regeneration; and (iii) their temporal dynamics. We rst showed that the regeneration diversity is poor, with half of the adult species not recorded in the regeneration phase. Most of the regeneration came from true seedlings compared to resprout. Second, mature trees have a strong in uence on regeneration density and composition. Third, topography in uences regeneration density whereas we observed little effect of the land management type. Finally, historical data highlighted a steep decline of regeneration density these last decades. These results question the persistence of woody vegetation in Sahelian savannas and highlight the need to protect large trees, in suitable micro-sites such as depressions to favor regeneration.