Abstract:

Aims Parashorea chinensis, an endangered plant listed as the first class protected in China, now survives in local fragmented forests in Mengla, Hekou in Yunnan and Bama, Tianyang, Longzhou, Napo in Guangxi. We developed regression models for individual growth, age structure and biomass and analyzed population density, age structure, biomass dynamics and survivorship curves for local populations and the entire population in Mengla, Xishuangbanna, Yunnan Province, SW China. Our objective was to understand the population dynamics to aid protection of this endangered plant.
Methods We established different numbers and sizes of plots (50 m × 20 m or 100 m × 20 m ) in five local patches according to patch size, and each plot was divided into 10 m × 10 m subplots to measure the height, diameter at breast height (DBH) or basal diameter and crown of each individual >0.5 m height. We also measured height, basal diameter and crown of each individual <0.5 m height in 2 m × 2 m quadrats in each subplot.
Important findings There were large differences in population density and age structure as well as mortality rate for different age stages of local populations in different patches. The local population density of the patch in which some trees were cut was 3-4 times as much as the patch which was protected and 16 -18 times as much as the patch which was planted with Amomum villosum. Moreover, the local population of the smallest patch had no mature individuals and lacked individuals in some age stages. Although the biomass of local populations showed logistic increase with stand age, maximum biomass and biomass dynamics with time were different for local populations. The survivorship curve of the entire population was approximately a straight line, indicating that the age structure of entire population was stable and increasing. The mortality of 1-60 year-old individuals declined, mortality of 60-150 year-old individuals increased with age, and peak mortality occurred after 180 years. The biomass of the entire population was consistent with logistic growth before 180 years and was at a maximum at about 180 years. However, some patches had been so badly disturbed that the local populations were on the edge of extinction. Effective steps must be taken to protect this endangered plant population.

Key words: Parashorea chinensis, population density, age structure, survivorship curves, biomass