Abstract:

How plants with different sexual systems grow and distribute in the community? Are they influenced by environmental factors? The answer to these questions is helpful to understand how species diversity is shaped in the plant community. This study summarized the numerical characteristics of sexual systems and the relationship between the distribution of dioecious plants and the topographical factors. Results showed that of the 289 woody seed plants recorded in the 60 ha plot, 176 species are bisexual plants and 113 species are unisexual plants. Of the 113 unisexual species, 51 are monoecious and 62 are dioecious plants. The abundance of unisexual plants accounts for 36.2% of all individuals recorded in the whole plot. The dioecious plants account for 21.5% of all individuals recorded and 59.5% of all individuals of unisexual plants in the plot. At the 20 m × 20 m quadrat spatial scale, 31 dioecious species showed aggregated distribution. Proportion of number of dioecious species of all species showed weak and positive correlation with altitude, convex and slope, but relative abundance of dioecious plants only showed weak and positive correlation with altitude. Furthermore, three diversity indices of plant sexual system did not show significant correlation with altitude, convex and slope. In sum, dioecious plants occupy a large proportion but most species only have relatively small population in the tropical mountain rain forest in Hainan, which are closely correlated with the topographical factors by the changes of numerical characteristics. The existence of dioecious plants has important contribution to the formation of species diversity in the plant community.

Key words: Hainan, tropical rainforest, permanent plot, diversity, dioecious plants, topography