极小种群野生植物峨眉含笑的种群结构与数量动态

Population Structure and Quantitative Dynamics of an Extremely Small Population, Michelia wilsonii

该研究以极小种群野生植物——峨眉含笑(Micheliawilsonii)为对象,采用样地调查法对雅安市周公山峨眉含笑野生种群进行群落调查,依据空间代替时间理论及匀滑技术,将种群动态变化情况量化,编制种群静态生命表,绘制存活曲线、死亡率曲线、消失率曲线和生存函数曲线分析其年龄结构现状,并用时间序列预测模型对其未来的数量动态进行预测,以揭示峨眉含笑的生存潜力和濒危机制,为该种群的恢复与重建提供依据。结果表明:(1)研究区内峨眉含笑种群的数量变化动态指数Vpi和Vpi′均大于0,年龄结构呈倒J型,存活曲线趋于Deevey-Ⅱ型,种群结构属于增长型,但种群的演替过程存在波动性,幼苗的数量丰富但向幼树的发展受阻,幼树向中、壮树阶段的补充也有所减少,种群存在衰退风险。(2)峨眉含笑野生种群的死亡率和消失率均在第Ⅰ龄级、第Ⅶ~Ⅷ龄级和第Ⅹ龄级出现高峰,而在第Ⅱ~Ⅵ龄级阶段比较稳定。(3)随龄级增加,峨眉含笑种群的生存率持续下降,累积死亡率持续上升,危险率在第Ⅰ龄级时最高(1.308),死亡密度在第Ⅶ~Ⅷ龄级降至最低,在整个龄级阶段中对应龄级的危险率均高于生存率,种群存在断代衰退的风险。(4)时间序列预测分析表明,经历未来2、4、6、8个龄级时间后,中、壮树阶段个体数量有减少的趋势。研究认为,峨眉含笑野生种群具有前期锐减、中期稳定、后期衰退的特点。

The study focused on the extremely small population of wild plants-- Michelia wilsonii . The plot investigation method was used to investigate the community of the wild population of M. wilsonii in Zhougong Mountain, Ya an City. According to the theory of space replacement time and smooth out method, we compiled the static life table and plotted the survival curve, mortality curve, disappearance rate curve and survival function curve to analyze its current population structure. The forecasting model of time sequence analysis were used to predict its future quantitative dynamics. in order to reveal the survival potential and endangered mechanism, provide a basis for the restoration and reconstruction of the population. The results showed that:(1) at the study area, the age structure dynamic index V pi and V pi ′ both are greater than 0. The age structure of M. wilsonii population showed an inverted J-shaped, survival curve tends to Deevey-Ⅱ type, which showed that the M. wilsonii population was the growing type, but the population structure also has volatility. The number of seedlings is abundant, the development of saplings is hindered, the supplement of saplings to the middle and strong trees was reduced, which means there was a risk of decline.(2) The trends of mortality, disappearance rate of the M. wilsonii wild population were similar, they all peaked at age class Ⅰ,Ⅶ-Ⅷ and Ⅹ, and more stable at age class Ⅱ-Ⅵ.(3) With the increase of the age class, the survival rate of the M. wilsonii population continue to fall, the cumulative mortality continue to rise. The highest hazard rate was showed in the first I age class, reached 1.308, in the Ⅶ-Ⅷ age class, death density lowered to a minimum, and in the stage of the whole age class corresponding to the hazard rate are higher than the survival rate, the population was at risk of decline.(4) The forecasting model of time sequence analysis indicated that after 2, 4, 6, 8 years of age class in the future, there is a decreasing trend in the number of individuals in the middle and strong tree stage. Based on this study, the M. wilsonii wild population had the characteristics of sharp reduction in the early age period, stable in the middle age period and decline in the late age period.