九宫山红椿种群数量动态及预测

摘要

通过对九宫山惟一红椿(Toona ciliata Roem.)种群进行调查和数据统计分析,绘制了红椿自然种群的龄级结构图,量化分析了种群各龄级间个体数量、变化动态,编制了种群的特定时间生命表,分析了存活曲线、种群生存函数;运用时间序列模型预测红椿种群数量动态.结果表明,(1)Ⅰ龄级存活植株占总存活植株的45.64%,Ⅱ~Ⅳ龄级占28.20%,V~Ⅵ龄级占13.33%,Ⅶ~Ⅶ龄级占12.82%;个体数量变化动态指数VⅠ最高,为62.92%,除VⅣ和V V 2个龄级间波动外,V pi=45.96%,V pi'=3.83%>0.(2)种群存活曲线:Nx=8.448 e-0.09x,R2=0.956,符合DeeveyⅡ型存活曲线,说明种群在生活史各个阶段具有较为稳定的死亡率.(3)生存率函数S(i)单调下降,积累死亡率F(i)呈单调上升,两者下降和上升的幅度前5个龄级高于后期,F(i)到Ⅵ龄级达0.881.死亡密度函数f(ti)随龄级逐渐下降,到Ⅷ龄级后稳定在0.003.危险率函数λ(ti)出现V、Ⅶ、Ⅺ龄级的3个峰值,均为0.250,龄级结构和动态分析的趋势一致.(4)对Ⅱ、Ⅳ、Ⅵ、Ⅷ龄级动态预测表明,种群各龄级个体数量呈增加-下降-平稳变化,种群趋于老龄化.总之,九宫山红椿种群受特定环境影响,改善了红椿林下幼苗在生长过程中的光照条件,光照环境筛和竞争成为中间龄级植株的抑制条件,因此该种群为增长型种群,但趋于老龄化.在管理上应针对不同阶段种群生长发育特征,采取适当措施,使种群健康发展.%By field survey and statistic data analyses of Toona ciliata Roem. population in Jiugong Mountain Nature Reserve in Hubei province, the age-class structure figure was drawn; and the quantitative analyses of plant individuals and change dynamics in different age class were conducted; the life table in specific time spectrum of the population was made, and the survival curve, survivorship function and life-expectation figures were analyzed. The result indicated that firstly, the survival number of age-class Ⅰ accounted for 45.64% of the total number, while age class Ⅱ to Ⅳ accounted for 28.20%; V toⅥ accounted for 13.33%, Ⅶ to Ⅶ accounted for 12.82%. The dynamic change index of the age structure of the population V pi=45.96%>0 and V pi'=3.83%>0,with V 1 surging to the highest 62.92%,indicating the population was in growth form. Second, the survival curve of the population was in accordance with the curve of Deevey Ⅱ,with Nx=8.448 e-0.09x,R2=0.956, revealing a comparatively stable mortality rate in the life history of the T. ciliata population. Third, livability function S(i) were in mono-tonic decrease while accumulative mortality rate in monotonic increase, and the changing extent of the former 5 age-classes was sharper than that of the latter, with F(i) reaching 0.881 only on age-class Ⅵ;the mortality density function f(ti) descended gradually with the age-class and stabilized at 0.003 on the Ⅷ age class;the hazard rate function λ(ti) had 3 same peak val-ues, 0.250 on the V,Ⅶ and Ⅺ age-classes, showing the same tendency with the previous quantitative analyses. Fourth, the time-dynamic expectation of the population to Ⅱ,Ⅳ,Ⅵ and Ⅷ age classes showed a approximate trend of increaseing, de-creaseing and then stabilizing, developing an aging tendency. The research demonstrate that the T. ciliata population of Jiu-gong Mountain was regulated with a specific environment, which assisted to enhance the light condition of the saplings, and environmental sieves of light and competition between both intraspecific and interspecific plants became restriction factors to the middle age-classes,but the population was still in growth form with an aging tendency. Therefore, targeting at growth and developing characteristics, appropriate measures are supposed to take to maximize the ecological benefits of the population.