Cover Story: Mount Cameroon spans one of the world's steepest tropical elevational gradients, from hyper-humid coastal rainforest to dry upper montane forest and Afroalpine savanna. Across 160 tree species, we show that leaf traits shift nonlinearly along this gradient as climate, soils, light, disturbance, and phylogenetic history interact to shape plant strategies. Mid-elevation forests support acquisitive leaves with high specific leaf area and nutrient content, whereas lowland and high-elevation communities converge on conservative trait syndromes through different pathways, including nutrient leaching, waterlogging, drought, and fire. Stable isotopes reveal striking shifts in water-use efficiency and nitrogen cycling, highlighting how multiple environmental filters structure tropical forest function under climate change. View the paper.