Tree species diversity and functional traits in forest patches of Benin, West Africa

The conservation of tree communities in forest ecosystems across the world is challenged by various anthropogenic pressures such as deforestation and fragmentation. In many areas in West Africa, fragmentation has reduced the original continuous forest ecosystems to small and isolated forest patches, mostly managed by local communities. While the importance of such small patches in biodiversity conservation is recognized in literature, evidence from tropical forest ecosystems and plant-based studies are still limited. In our study, we (i) assessed the contribution of small, unprotected forest patches to tree species conservation; (ii) determined the variation of seed dispersal syndromes in tree stands between a continuous forest and small forest patches; and (iii) identified the drivers of tree species colonization among forest patches. We sampled 69 plots in the Lama forest reserve (continuous forest) and the surrounding small isolated forest patches within 20-km radius. Trees and natural regenerations were recorded in two vegetation types including the degraded dense forest and old fallow. For each species, the IUCN conservation status and functional traits including dispersal syndrome, seed weight and maximum height were recorded. We used Generalized Linear Models to identify the determinants of immigrant regeneration densities in isolated forest patches. In total, 103 woody species were recorded and the species richness was higher in the forest patches than in the continuous forest for all vegetation types. In the dense vegetation, a similar trend was found and the number of threatened species was higher in the forest patches. Tree assemblages differed between the continuous forest and the forest patches. Tree density was higher in the continuous forest than in small forest patches. Defaunation somewhat affected the regeneration of disturbed forest patches as germination and seedling were dominated by abiotic-dispersed species and local species. Taller or heavier seed species were more likely to colonize forest patches and the density of tree species in a forest patch increased with abundance of immigrant regeneration in the nearest neighbor. We recommend the implementation of sustainable management in form of participative restoration of low-regenerated species in forest remnants  for enhanced biodiversity conservation.

Keywords: Species richness, dispersal syndrome, functional traits, fragmentation, forest patches, continuous forest