Keywords: 
• Wuzhishan Mountain /
• Hainan Island /
• slope /
• altitude /
• species diversity

Abstract: In order to study the effects of slope and altitude on species diversity of tropical rain forest communities,two quadrats with 2 500 m² each were set up in lowland rain forest,ravine rainforest and mountain rain forest on the northern and southern slopes,respectively,in Wuzhishan Mountain,totaling 12 quadrats. The dominant species composition and species diversity of tree plant communities on northern and southern slopes were compared. The results showed that on the northern slopes the dominant species were Diospyros hainanensis,Spondias lakonensis and Dysoxylum gotadhora in the lowland rainforest; Schefflera heptaphylla,Spondias lakonensis and Litsea variabilis in the ravine rainforest; and,Castanopsis tonkinensis,Syzygium araiocladum and Syzygium hancei in the mountain rainforest. On the southern slopes the dominant species were Schefflera heptaphylla,Liquidambar formosana and Eurya nitida in the lowland rainforest; Heritiera parvifolia,Diospyros hainanensis and Wrightia laevis in the ravine rainforest; and,Diospyros hainanensis,Dacrycarpus imbricatus var.patulus and Heritiera parvifolia in the mountain rainforest. The species richness,Shannon-Weiner index,Simpson index and Pielou index were higher in the lowland rainforest than in the ravine rainforest and the mountain rain forest on the northern slopes. The species diversity on the southern slope was lower in the lowland rainforest than in the other two plant communities. The species diversity was higher in the ravine rainforests and the mountain rainforests at a relatively high altitude than in the lowland rainforest at a low altitude. The species diversity in the lowland rainforest,the ravine rainforest and the mountain rainforest were lower on the southern than on the northern slopes. The species similarity index in the lowland rainforest and the ravine rainforest was the highest on the southern and northern slopes,while the species similarity was low between the mountain rainforest at a high altitude and the lowland rainforest or the ravine rainforest.