克隆植物唐古特白刺不同层次的种群结构与生命表分析

Age Structure and Life Table of Nitraria tangutorum population at the Genet and Ramet Level

以种群生命表及生存分析相关理论为基础,结合乌兰布和沙漠东北部地区唐古特白刺(Nitraria tan-gutorum Bobr.)天然群落基株、分株种群的调查资料,对基株、分株两个层次的唐古特白刺种群年龄结构与生命表进行了分析,以探究其自然条件下克隆繁殖的特性及群落稳定性,为当地唐古特白刺天然群落的保护提供理论依据。研究过程利用空间扩展至时间的思路,以冠幅、径级作为其相对年龄划分的依据。结果表明,唐古特白刺基株、分株种群个体数所占百分比随龄级增加表现出先增加后逐渐减少的变化趋势;二者的存活曲线整体上趋于Deevy-Ⅰ型,种群死亡率呈现波动变化,且均存在两个死亡高峰;在第Ⅲ龄级,唐古特白刺基株种群危险率位于波动变化的谷底,而分株种群危险率位于波峰,与之恰好相反。研究认为:唐古特白刺基株种群生长的关键阶段是第Ⅲ龄级左右,分株种群生长的关键阶段为第Ⅵ、Ⅴ龄级,对唐古特白刺的保育工作的实施应该根据种群水平及龄级的差异而区别进行。

Based on the theories of life table and survival analysis, the age structure and life table of Nitraria tangutorum popula- tion were analyzed at genet and tamer levels by plot investigation and data analysis in northeastern Ulan Buh Desert to in- vestigate its cloning characteristics and community stabilization under natural conditions. Some spatial attributes wele adopted instead of time attributes, for example, relative ages were devided in the light of crown width and basal diameter. The re- suits showed that the percentage of population individual numbers at genet and ramet levels both increased first, but then decreased with age class increasing. The survival curve of two populations trended to the type of Deevy- [ . Moreover, the fluctuation of mortality rate and risk rate were obvious during natural regeneration progress on two levels. And both of the populations had two mortality rate peaks. The risk rate of genet population was in the wave bottom at the third age class. In contrast, the risk rate of ramet population was on the peak at the same age class. In summary, the third age class is the critical period for the growth of genet population, while the fourth and fifth age classes are critical for the growth of ramet population. Theretbre, the conservation of Nitraria tangutorum should be executed differently by the level of population and age class.