Understanding species distributions and coexistence has been a major focus in the study of ecology. Tree species distributions and diversity maintenance is a function of multiple mechanisms, which continue to receive considerable attention. One of the more widely studied mechanisms is conspecific negative density dependence where seedlings have reduced growth and survival when establishing in close proximity to adult conspecifics. Variations in seed dispersal and abiotic factors are also important drivers of forest structure. A large body of work exists that tests hypotheses around these factors and mechanism in tropical forests but the majority of these studies are concentrated in the Neotropics and Asian tropics. There is a shortage of studies on plant recruitment and community dynamics from the Afrotropics especially in Afromontane forest ecosystems, which are small areas that are increasingly threatened by anthropogenic activities. This thesis investigates the diversity and coexistence patterns in a woody plant community of an Afromontane forest in West Africa using a combination of field observation and experimental studies. The first two studies examined woody plant composition and distribution at different life stages, providing the base for the subsequent three chapters that examine negative density dependence as a major force shaping the composition and distribution of woody plants in this community.

Firstly, trees having ≥ 1 cm diameter at breast height were sampled, mapped and identified from a 20.28-hectare forest plot in Ngel Nyaki Forest Reserve, southeast Nigeria to determine their composition, diversity and habitat preference. Next, seed arrival and seedling recruitment and establishment in the regeneration layer were examined and seed arrival patterns were compared to seedling recruitment. Diversity in the seeds and seedlings was lower than that observed for adult trees. The role of negative density dependence in shaping diversity patterns was assessed by estimating individual seedling survival as a function of conspecific and heterospecific adult and seedling densities and exploring how it varied across

different functional groups. There was evidence for non species-specific positive and negative density dependence (i.e. general effects of crowding). In another study, the effect of density dependence and abiotic factors on the survival of newly recruited seedlings was examined. Lastly, using two sets of experiments and 10 species, I tested for plant-soil feedback and intraspecific competition. I tested for plant-soil feedback in six tree species and tested for intraspecific competition in the other four species. There was evidence for plant- soil feedback in only one out of the six species tested and only a marginally significant effect of density on plant growth.

Forty percent of all tree species identified showed a clear preference for either the edge/grassland habitat or the forest core, which was not explained by variation in seed sizes or dispersal modes. There was evidence for strong dispersal and establishment limitation in Ngel Nyaki forest, which may be consequences of the loss of animal dispersers and high seed predation rates.

In conclusion, I have provided in my thesis a picture of the woody species composition of an Afromontane forest and show the role (or lack thereof) of negative density dependence in driving the woody plant seedling diversity. Overall, the results from my thesis contribute to the knowledge on plant interactions in Afromontane forest systems and variations in biotic interactions among species functional groups. Detailed species-specific and trait-based studies will aid our understanding of the mechanisms that shape diversity and drive community patterns. This is critical for conservation management purposes especially for making predictions on the consequences that anthropogenic pressures could have on plant communities.