Abstract
We analyzed the floristic composition and woody species diversity along the vertical profile of a subtropical evergreen broadleaf forest (a 1225 m(2) plot in Dinghushan Nature Reserve, South China). Five vertical strata were discerned. Cryptocarya concinna showed the highest importance value in the entire stand and was the most abundant in the lowest two strata. Based on the cluster analysis of similarities in species composition, the lowermost two strata were very similar; the bottom, fourth and third strata clustered together as one group, which was very dissimilar from the other group (second + top). Among strata, the lowermost two strata were most similar in generic composition, whereas the fourth and the third stratum were most similar in family composition. Shannon's and Pielou's indices based on numbers of individuals (H'(n) and J'(n), respectively) and those based on basal area (H'(a) and J'(a), respectively) tended to increase from the bottom strntum upward, except for H'(n) and H'(a) calculated for the upper two strata. Values of H'(n) and H'(a) (and of J'(n) and J'(a)) were similar within vegetation strata and within the small trees (< 1.3 m tall), because the basal area was proportional to the number of individuals among species. For the entire stand, values of H'(a) (3.51 bit) and J'(a) (0.56) were much higher than those of H'(n) (3.01 bit) and J'(n) (0.48), respectively. For the large trees (>= 1.3 m tall), the values of H'(a) (3.36 bit) and J'(a) (0.60) were lower than those of H'(n) (4.15 bit) and J'(n) (0.74), respectively. The number of species decreased from the bottom to the top stratum. Hence, the stratum closest to the forest floor contributed to maintaining woody species richness in this forest.