福建省明溪县极小种群野生植物喜树种群结构与动态特征

Population Structure and Dynamic Characteristics of Wild Plant Species with Extremely Small Populations of Camptotheca acuminata in Mingxi,Fujian Province,China

喜树(Camptotheca acuminata)为中国特有种,也是中国120种极小种群野生植物之一。在第二次全国重点保护野生植物资源调查中,发现福建省明溪县角溪区域有喜树种群野生分布点。为了探讨该区域喜树种群的生存状况,基于样地调查数据,以径级代替龄级,编制种群静态生命表并引入4个生存分析函数,分析种群数量特征;利用种群动态变化指数和时间序列模型对种群动态和未来发展趋势进行分析和预测。结果表明,(1)喜树种群龄级结构呈倒“J”型,各龄级均有个体分布,其中小树个体数量最多,幼苗、幼树存储量不足;种群动态指数在相邻龄级间存在一定的波动,Vpi和Vpi′的值均大于零,表明该种群当前属于增长型,但种群对外界干扰比较敏感,抗干扰能力较差。(2)静态生命表显示,喜树种群存活数量和个体生命期望值都随着龄级的增加逐渐下降;种群存活曲线趋近于Deevey-Ⅱ型,前期死亡率下降较为迅速,而后期死亡率下降趋于平缓;死亡率和消失率曲线的变化趋势基本一致,均在第Ⅱ、Ⅷ龄级出现峰值。(3)生存分析表明,该种群具有前期迅速下降、中期小幅波动、后期逐渐衰退的变化特点。(4)时间序列分析预测,在经历未来2个龄级时间后,Ⅱ龄级和Ⅴ龄级个体数量均出现不同程度的减少;而经历未来4、6、8个龄级时间后,所有龄级个体数量均呈增长趋势。人为干扰、自然干扰、种子成苗率低是影响该地区喜树种群增长的主要因素。在今后的保护工作中,建议采取就地保护、近地保护和加强宣传等拯救措施,保护和改善生境,促进喜树种群的更新和发展。

Camptotheca acuminata,one of 120 species of wild plant species with extremely small populations,is endemic to China.It was found that there were wild distribution points of C.acuminata population in Jiaoxi region of Mingxi,Fujian Province,during the second national key conversation wild plant resources survey.In order to investigate the survival status of C.acuminata population in this region,a static life table and four survival analysis function curves were worked out based on quadrat survey data with diameter class instead of age class,for analyzing the quantitative characteristics of the population.Moreover,population dynamics and future development trend were analyzed and predicted by using population dynamics index and time sequence model.The results showed that:(1)The age structure of the C.acuminata population appeared roughly inverted J-shape.Individuals were distributed in each age classes,among which the number of small trees was the highest,and the number of seedlings and young trees was insufficient.The dynamic index of population fluctuates between adjacent age classes,and the values of Vpi and Vpi′were greater than zero,indicating that the population tended to a stable growth type at present,but the population was sensitive to external disturbances and had poor anti-interference ability.(2)The static life table showed that the survival number and individual life expectancy of the C.acuminata population decreased with the increase of age class.The survival curve tended to the Deevey-Ⅱtype,and the mortality rate decreased rapidly in the early period,while it decreased gradually in the later period.The change trends of mortality and vanishing rate curves were nearly similar,both reaching the peak values at the second and eighth age classes.(3)The four survival functional curves showed that the C.acuminata population was characterized by decline in the early stage,small fluctuation in the middle stage,and gradual decline in the later stage.(4)The time series prediction analysis indicated that the number of individuals at the second and fifth age classes decreased at different ranges after the next 2 age classes while the number of individuals in all age classes increased after the next 4,6,and 8 age classes.Human disturbance,natural disturbance and low seed seedling rate were the primary factors affecting the growth of the population in the future.We suggested that,in the future conversation effects,it should be introduced to take measures such as in situ protection,near situ conservation and strengthening publicity to protect and improve the habitat and promote the regeneration and development of C.acuminata population.