Tree abundance, richness, and phylogenetic diversity were studied along an elevation gradient in the tropical forest of Diaoluo Mountain in Hainan, China. The researchers found that as elevation increased, tree diversity initially rose, peaked at intermediate elevations, and then decreased at the highest elevations. The composition of tree species was mainly influenced by elevation, with intermediate elevations providing optimal conditions for plant growth due to high temperature and humidity. This suggests that protecting plant species and habitats at these intermediate elevations is crucial for maintaining biodiversity in the area.