Abstract:

Aims Lower subtropical evergreen broadleaved forest in Dinghushan is one of typical vegetations in Southern China. Its vegetation is protected very well. Because of its geographical location, the composition of its flora is transitional between the subtropical and tropical. A 20 hm² permanent plot of 400 m × 500 m was established in 2005 for long-term monitoring of the biodiversity in the forest.
Methods The plot was established following the field protocol of the 50 hm² plot in Barro Colorado Island (BCI) in Panama. All free-standing trees with diameter at breast height (DBH) at least one centimeter were mapped and identified to species.
Important findings There are 71 617 individuals, belonging to 210 species, 119 genera and 56 families. Its floristic composition is transitional between the subtropical and tropical. The vertical structure of the forest is clear. There are five layers from the top of the canopy to the ground floor, three tree layers (upper, middle and low), one shrub layer and one herb layer, respectively. Based on important value, Castanopsis chinensis, Schima superba and Engelhardtia roxburghiana are the three most dominant species in the upper layer. There are many shade-tolerant and intermediate light-demanding species, such as Cryptocarya chinensis, Xanthophyllum hainanense, Machilus chinensis in mid-layer. Species in low layer are rich and complex, which composition varies a lot. The species-area curve indicates that there is high diversity in the forest and the number of species is close to BCI. There is high proportion of rare species represented by <20 individuals which account for 52.38% of the total number of species. Among these rare species 45% of them lead to be rare by species characteristics, 20% by the floristic transitional nature of the plot, while the rest by disturbances.Size distribution of all individuals shows an invert J-shape, which indicates that the community is in a stable and normal growth status. Size distributions of the dominant species are classified into four types based on their size-class frequencies, unimodal in the top layer, inverse J-shape in middle layer, close to inverse J-shape in middle and low layer, and L-shape in low and shrub layer. Dominant species in different layers are aggregated by the spatial pattern analysis and the spatial patterns of these species in different layers vary with size-classes. However, spatial patterns of them also show complementary within the same size classes, especially in 10-40 cm DBH. The individuals with DBH>40 cm are randomly distributed.

Key words: Dinghushan plot, forest biodiversity monitoring, lower subtropical evergreen broadleaved forest, spatial pattern, species composition