濒危树种五莲杨种群结构与动态特征

Abstract

五莲杨（Populus wulianensis）为山东特有种，属于极小种群野生植物。以昆嵛山国家级自然保护区内的五莲杨种群为研究对象，旨在通过建立静态生命表，绘制种群存活曲线来描述其种群的结构特征，使用4个生存函数进行种群的生存分析，运用数量动态指数定量描述种群的数量动态特征，并采用谱分析方法揭示种群年龄结构更替过程的周期性和结构的波动性。结果表明：（1）五莲杨种群龄级结构呈基部极宽顶部狭窄的金字塔形，种群存活曲线趋近于Deevey-Ⅲ型，幼龄个体数量丰富但存活率极低，种群增长性低；（2）死亡率和消失率曲线呈现"降低-增长-降低-增长"的复杂动态变化，种群在Ⅰ龄级死亡率最高；（3）生存分析表明该种群生存力低，具有前期锐减，中期和后期衰退的特点，呈现衰退特征；（4）种群数量动态指数显示种群呈增长趋势，但种群稳定性差且抗干扰能力弱；（5）谱分析表明该种群除受到基波影响外还受到个别小周期波动的显著影响。繁殖策略、有限的空间和资源是限制五莲杨种群增长的主要因素。建议对五莲杨种群进行原地保护的同时，通过输入实生苗防止种群在多个世代后因无性繁殖而导致抗性和遗传多样性降低。;Populus wulianensis, a wild plant species with extremely small population, is endangered and endemic in Shandong Province, China. In this study, the structural characteristics of P. wulianensis population distributed in Kunyu Mountain National Nature Reserve was investigated by establishing a static life table and drawing population survival curves. Four survival functions, number dynamic index, and the spectral analysis were used to describe survival status, population dynamics and the periodicity and structural volatility of the population-age-structure replacement process of P. wulianensis, respectively. The results are as follows. Firstly, the age-class structure of P. wulianensis population was a pyramid type with a very wide base and a narrow top. Its population survival curve appeared as Deevey-Ⅲ type. The number of young individuals was abundant but the survival rate was at an extremely low level. The population growth rate was very low. Secondly, the tendency of mortality and vanish curves was decrease-increase-decrease-increase, which showed the mortality rate of P. wulianensis population was the highest at age class Ⅰ. Thirdly, its survival analysis revealed that P. wulianensis population was at an extremely low viability level in the whole life cycle with the characteristics of a sharp decrease in the early stage and decline in the middle and late stages. Fourthly, although population dynamic index suggested that the population was increasing, its population stability was poor and the anti-interference ability was weak. Fifthly, spectral analysis demonstrated that the population was not only affected by the fundamental wave but also significantly affected by some separated small periodic fluctuations. Reproduction strategy, limited space and resource conditions are the major factors limited the growth of P. wulianensis population. Given these, in situ conservation should be introduced and seedlings importation is also recommended so as to avoid the population from decreasing resistance and genetic diversity due to asexual reproduction after multiple generations.