Diversity and relationship with succession of naturally regenerated southern subtropical forests in Shenzhen, China and its comparison with the zonal climax of Hong Kong

We studied composition, structure, and species diversity of the five principal naturally-regenerated forest communities in Shenzhen and compared these communities with the zonal climax in Hong Kong, China. We have elaborated upon the successional stages and the relationship between species diversity and succession in these communities. We speculated that these five communities were at various stages in a six-stage succession mode: Sinosideroxylon wightianum community was at the third stage; Itea chinensis + Acronychia pedunculata community at fourth; and Schefflera octophylla, Sterculia lanceolata and Cleistocalyx operculatus communities at the fifth stage. All these communities had not reached the sixth stage—the zonal climax. Based on the succession stages and importance value (IV) of heliophytes and mesophytes, we hypothesized that the Shenzhen subtropical naturally-regenerated forest communities have evolved in the following succession: from S. wightianum community to I. chinensis and A. pedunculata community, to S. octophylla community, to S. lanceolata community and finally to C. operculatus community. With this succession path species diversity (α-diversity) in the communities increased and reached their peaks when the heliophytes and mesophytes in the communities had similar dominance, and then declined gradually. The species diversity of a community increased again and reached a higher peak than the original one after it developed to its zonal climax. β-Diversity (or the species replacement rate) between different styles of communities, i.e., the mixed conifer and evergreen broad-leaved forest at the third stage and the evergreen broad-leaved forest at the fourth stage, was larger than that between the evergreen broad-leaved forests. β-Diversity between the communities at close successional stages was smaller than that between the communities at farther successional stages. This study also showed that due to human disturbance the structure and species diversity in the five communities of Shenzhen were significantly simpler than the Endospermum chinense community in Hong Kong.