太行山特有珍稀濒危植物槭叶铁线莲种群年龄结构与数量动态

Population age structure and quantitative dynamics of Clematis acerifolia,a rare and endangered species endemic to Taihang Mountains

珍稀濒危植物槭叶铁线莲(Clematis acerifolia)为国家二级重点保护野生植物,仅零星分布于太行山北部的石灰崖壁之上。在居群调查基础上,本研究测量了来自11个分布点的458丛植株,以最长枝条的芽鳞痕数作为龄级划分依据,对该种群进行了年龄结构及数量动态研究。结果表明:(1)种群年龄结构总体表现为非典型的金字塔型结构,1龄级的幼年个体数量明显偏少;(2)种群数量在第1~2、6~7龄级间呈现衰退,但总体上仍具有更新和维持的能力;(3)种群存活曲线为N_(x)=259e^(-0.4)^(x),接近于DeeveyⅡ型。种群在第5龄级出现死亡率和消失率的第一个峰值,随后死亡率保持稳定,而消失率快速上升;(4)种群的生存率和累积死亡率均在前6个龄级升降幅度较大,从第7龄级后两条曲线升降都趋于平缓。危险率的第一个峰值出现在6龄级,死亡密度则整体偏低,在第3龄级出现最大值;(5)时间序列模型预测,在未来2、5、8龄级时间后,中、老龄级个体数量均有所增加。研究认为,槭叶铁线莲种群具有前期淘汰率高、中期稳定、后期衰退的特点,虽然当前其种群年龄结构相对稳定,但已有衰退的早期迹象,幼龄个体缺乏是其种群更新的主要瓶颈。

Clematis acerifolia is an endangered national key protected wild plant species in China(Class II),which is distributed only on the limestone cliffs in northern Taihang Mountains.Based on field investigation,the shoot age data of 458 individuals were obtained from 11 sites.Ages of the individuals were estimated based on the number of bud scale scars on the longest shoot.Accordingly,the age structure and dynamics of the populations were quantitatively analyzed.The results showed that:(1) The population age structure was a typical pyramid pattern,with few young individuals at age class 1;(2) The population declined between age class 1-2 and 6-7,but had the ability to renew and maintain;(3) The population survival curve was N_(x)=259e^(-0.4x),which was close to Deevey Ⅱ.The first peak of mortality rate(q_x) and disappearance rate(K_x) curve emerged at the age class 5.After that q_(x) remained stable and K_(x) rose rapidly;(4) The greatest increase or decrease of survival rate and cumulative mortality rate happened to the first six age classes,and such changes tended to be gentle after age class 7.The first peak of risk function λ_((ti)) curve appeared in the age class 6.The death density f_((ti)) was generally low,with the maximum value at the age class 3;(5) The prediction analysis of time sequence model suggested an increase in the number of middle-aged and old-aged individuals after the time of age class 2,5,and 8.The population showed a high elimination rate in young age class,stable in middle age class,and depressed in old age class.The age structure was relatively stable at present,but with early signs of depression that lack of young age class individuals was the main cause limiting the population growth of Clematis acerifolia.