Abstract:

The monsoon evergreen broad-leaved forest, located in Dinghushan, near the Tropic of Cancer is well protected and has been considered as a climax community in lower subtropical area, with the Castanopsis chinensis-Schima superba-Cryptocarya concinna community as the representative community. The structure, function and dynamics of this community have been well documented in previous studies. Most studies reported that a climax community generally viewed fluctuates spatially and temporally. However, few studies have quantitatively analyzed its changes over time. Therefore, our study aimed to i) monitor the dynamics of the Castanopsis chinensis-Schima superba-Cryptocarya concinna community; ii) examine the fluctuations of plant density and biomass of this community and iii) try to provide information for forest resource managers and policy makers to promote long_term ecosystem sustainability. Based on the plant density and biomass obtained from three consecutive sites (1992 to 1999), a comparative study and paired-samples t-test were conducted. The results demonstrated: 1) plant density generally declined, indicated by 3 979, 3 822 and 3 531 individuals·hm-2 in 1992,1994 and 1999, respectively, with statistical difference between 1994 and 1992 (p<0.05), 1999 and 1992 (p<0.05). Similarly, biomass fluctuated from 293.1 in 1992 to 248.5 t·hm-2 in 1999，with no statistical difference. 2) Plant density and biomass also differed in various DBH (Diameter at Breast Height) classes. Individuals with DBH≤30 cm, including DBH≤10 cm, 10 cm＜DBH≤20 cm and 20 cm＜DBH≤30 cm, differed statistically between 1999 and 1992, 1994 and 1992. Individuals with DBH>90 cm decreased by 50% from 1992 to 1999. The biomass for trees of DBH ≤40 cm and DBH >90 cm did not differ statistically. For middleDBH trees, especially for 40 cm