Community features of two types of typical tropical monsoon forests in Bawangling Nature Reserve,Hainan Island

The tropical monsoon forest is an azonal vegetation type in Hainan Island and mainly distributes in the similar elevational ranges as the tropical lowland rainforest but in locations where environmental conditions are stressful,especially in the dry season.Most species and individual trees in the monsoon forest defoliate in the dry season.Bawangling Nature Reserve in Hainan Island contains well-preserved natural and typical tropical monsoon forests which can be classified into Terminalia hainanensis community type(TC) and Liquidambar formosana community type(LC) according to the dominant species.In this present study,species composition,structure,and diversity were investigated on three plots(50m×50m) for each of the two community types.On each plot,species name,height,and DBH(diameter at breast height) of all individuals≥1cm DBH were recorded.The community features of the two community types were compared and analyzed in terms of species richness,abundance,size class distribution,and deciduousness and presence of thorns.The results showed that only a few species(mainly T.hainanensis and L.formosana) apparently dominated in the tropical monsoon forests of Hainan Island.The species richness and abundance for shrubs were higher in the TC than in the LC whereas the species richness,abundance and Shannon-Wiener index for trees were lower in the TC than in the LC.The two community types had no significant difference in species richness and abundance for all but the smallest size class,in which the TC had greater plant density and lower species richness than the LC.The species richness and abundance for trees,shrubs and woody plants with thorns were higher in the TC than in the LC except for lianas,which showed no apparent difference between the two community types.Judging by the community features,the TC is more of typical tropical monsoon forest than the LC in Hainan Island.