江苏南通古银杏的种群结构与动态

Population structure and dynamics of old Ginkgo biloba in Nantong,Jiangsu Province

古银杏(≥100年)是苏中地区大型古树的主要组分之一,能够为人类提供重要的生态系统服务功能。对一个地区古银杏的调查分析有助于揭示其种群的数量特征。以种群生命表和生存分析理论为基础,采用空间代替时间法和匀滑技术,编制江苏南通古银杏(DBH≥50 cm)种群特定时间生命表,绘制其死亡率曲线、消失率曲线、存活曲线和生存函数曲线,分析其种群数量动态变化。结果表明:该区古银杏有282株,雌雄比为1.37,总体上偏雌性;它们主要分布于南通的西南部。古银杏的种群结构呈倒"J"形,种群的存活曲线趋于Deevey-Ⅱ型。古银杏种群的生命期望在不同龄级间存在波动,第Ⅱ龄级的生命期望较低。古银杏种群的死亡率曲线与消失率曲线变化趋势一致,均在第Ⅱ、Ⅳ龄级出现小的峰值。由于古银杏寿命长,呈片段化分布,因此建议对该区分布相对集中的区域,尤其是Ⅴ龄级以后的个体,改善其生境并加强保护。

Old ginkgoes with age≥100 years are main components of large old trees in central Jiangsu,providing vital ecosystem services.It is significant to understand quantitative population characteristics of such old ginkgo trees by population inventory within a certain area.The static life table of old ginkgo population in Nantong of Jiangsu Province was compiled by applying age class structure represented by diameter at breast height(DBH)classes and smoothing technique.There were 282 individuals of old ginkgo trees,with the sex ratio of female to male being 1.37.Most of the old trees were distributed in the southwest of Nantong.The population of old ginkgo trees showed inverse-J size distribution,and its survival curve trended to the type of Deevey-Ⅱ.There was a fluctuation of life expectancy for the whole population.The life expectancy of the second age classes was relatively low.The mortality rate curve and disappearance rate curve in the lifespan had similar variation trend,with the peaks in the 2 nd and 4 th age classes.Due to long life span with severe fragmentation in the distribution of those old trees,it is suggested to improve their habitat quality and strengthen protection in concentrated areas of Nantong,especially for the individuals after the 5 th age classes.