Abstract: Univariate and partial regressions were used to investigate the influences of predictors. Higher temperate species diversity was mostly observed in the northern parts of the study area, whereas, no any obvious latitudinal trends were observed on tropical species diversity. Higher proportions of tropical species were observed in the southern parts, whereas those of temperate species were observed in the northern parts. Habitat heterogeneity explained higher percentage of the spatial variation of temperate species diversity than for that of tropical species diversity. It may imply that the influence of habitat heterogeneity on plant diversity may be modified by the taxa's biogeographic affinities. Higher percentages of variation in the proportions of tropical and temperate species than those of tropical and temperate species diversities were explained by climate predictors. It suggested that niche conservatism of tropical and temperate plants in the study area was more accurately reflected by the associations between species diversity with tropical and temperate affinities and climatic conditions than those between the proportions of tropical and temperate plants and climatic conditions.