濒危植物猪血木(Euryodendron excelsum H.T.Chang)自然种群结构及动态

The structure and dynamics of natural population of the endangered plant Euryodendron excelsum H.T.Chang

猪血木(Euryodendron excelsum H.T.Chang)是中国特有的山茶科单型属猪血木属的珍稀濒危植物,目前只在广东省阳春县八甲镇有分布且种群数量不足200株。通过样地调查和数据统计,绘制了猪血木种群的高度结构和径级结构图,在此基础上编制了种群的特定时间生命表,分析了存活曲线、死亡率曲线和寿命期望等重要参数,并运用时间序列模型预测种群数量动态。结果表明:猪血木种群幼年个体丰富,中老年个体相对较少,受环境因素和人为干扰的影响,种群在第Ⅱ级出现死亡高峰,且只有少量幼年个体能进入成年阶段生长,个体平均生存能力的期望在第Ⅳ级最大,种群存活曲线属于Deevey-Ⅲ型,猪血木种群目前仍表现为稳定型种群。时间序列预测分析表明,猪血木种群具备一定的恢复潜能,故现有植株和生境斑块的保护是保持猪血木种群自然更新和进行种群恢复的关键因素。

Euryodendron excelsum H. T. Chang is an endangered species from the family Theaceae endemic to China. It is listed as a Grade Two endangered plant for state protection in the Red Data Book of plants in P. R. C. The species is restricted to one remnant population with less than 200 individuals in Bajia region of Yangchun County, Guangdong Province. This study was conducted to determine the status of the population, analyze the past population structure and forecast the future population dynamics of E. excelsum. The size structure and height structure of the population of E. excelsum were tabulated and analyzed. Based on these data, we estimated the values of parameters such as survival curve, mortality curve and life expectancy. Population dynamics were predicted by a time-sequence model. The size distribution of the whole population generally fit a reverse ＂J＂ type curve, suggesting a stable population. The number of young individuals was larger than that of middle-aged and old individuals. The analysis of life table and survival curves showed that under environmental screening and human disturbance, the population had one peak of mortality in size class Ⅱ and only 11.43% individuals could survive from size class Ⅱ to size class Ⅲ. The life expectancy of E. excelsum was highest in size class Ⅳ. The survival curve of the population belongs to Deevey-Ⅲ type. Time-sequence models for E. excelsum population predict that the number of different size classes will increase after 2 and 5 years. As a result, the crucial factors for the natural regeneration and restoration of E. excelsum are the protection of living individuals and their habitat.