Urban forest community structure and correlation analysis on the plant diversity index in Haikou City, China

In order to have a more comprehensive understanding of the structural change and succession process of plant community in Haikou City, and predict the composition of its future change trend. A total of 235 randomly selected urban forest plots were studied in a built-up area of Haikou City. Structural characteristics and their corresponding plant diversity indexes were determined with a correlation analysis. Results indicated that (1) The presence of 283 species of common plants in the built-up area belonging to 218 genera of 72 families with 114 native species and 169 exotic species. (2) The dominant plants included Cocos nucifera, Pterocarpus indicus, Roystonea regia, and Ficus benjamina. (3) The diameter presented a distribution pattern of small, and the overall tree height was low with an average height of 6.8 m. (4) There was a significant correlation between species diversity and functional diversity indexes (P < 0.05). (5) Also, the phylogenetic diversity index (PD) was significantly correlated (P < 0.05) with species diversity indexes in the tree layer and herb layer. The phylogenetic species variability index (PSV) was not correlated with most species diversity indexes and functional diversity indexes, but the phylogenetic species variability evenness (PSE) index was significantly correlated with most of them (P < 0.05). Haikou City having a large improvement potential in forest development, should avoid the homogeneity phenomenon where native species have been adopted in urban forest development; to ensure comprehensiveness and accuracy, Haikou should consider multi-level and targeted diversity indexes and functional trait parameters when evaluating urban plant diversity.