鄂西北濒危植物红椿天然种群动态分析

Analysis on natural population dynamics of endangered species Toona ciliata in northwestern Hubei

采用相邻格子法对分布于鄂西北的3个红椿(Toona ciliata Roem.)天然种群(竹山、谷城T1和谷城T2)进行统计;采用立木径级结构代替种群年龄结构的方法,分析了各种群不同龄级的个体数量动态指数(Vn)、静态生命表及存活曲线,并对3个种群进行谱分析。结果表明:3个红椿种群均属于增长型种群,自然状态下竹山、谷城T1和谷城T2种群个体数量动态指数分别为46.27%、53.46%和37.71%,标准化存活曲线分别为DeeveyⅢ型、DeeveyⅡ型和DeeveyⅡ型。3个种群第2龄级〔2.5 cm≤胸径(DBH)<7.5 cm〕幼树的死亡率均较高,竹山种群第3龄级(7.5 cm≤DBH<12.5 cm)幼树的死亡率最高,谷城T1种群第7龄级(27.5 cm≤DBH<32.5 cm)大树的死亡率最高,谷城T2种群第6龄级(22.5 cm≤DBH<27.5cm)中树的死亡率最高;3个种群第1龄级(DBH<2.5 cm)和第2龄级个体的平均期望寿命均较高。竹山、谷城T1和谷城T2种群的基波振幅分别为1.061 6、1.097 1和0.788 2,明显的小周期分别出现在第4、第2和第4波序,表明分布于鄂西北的红椿天然种群更新存在着周期性,且存在小周期的多谐波叠加,种群波动与龄级的Vn值相吻合。种群动态分析结果表明:由于红椿的强阳性生理特征,其天然种群受环境筛抑制和环境干扰,造成幼树个体损失和中龄级个体不足,这是造成红椿濒危的主要因素,因此,建议加强人为正向"干扰"以制造林窗、增强种群天然更新能力、引种造林,以保护和利用红椿这一濒危植物资源。

Statistics on three natural populations （ Zhushan, Gucheng T1 and Gucheng T2） of Toona ciliata Roem. in northwestern Hubei were carried out by contiguous grid quadrate method, individual quantity dynamic index （ Vn ） in different age classes, static life table and survival curve of different populations were analyzed by method of diameter class structure of tree replacing age structure of population,and spectrum analysis of three populations was also conducted. The results show that all of three populations of T. ciliata belong to growth population, individual quantity dynamic index of Zhushan,Gucheng T1 and Gucheng T2 populations in natural state is 46. 2 7 %,53.46% and 37.71%, respectively. And standardized survival curve of three populations is conformed to be Deevey Ⅲ type, Deevey Ⅱtype and Deevey Ⅱ type, respectively. Mortality of sapling in the 2nd age class 〔2. 5 cm ≤ DBH （diameter at breast height） 〈7. 5 cm〕of three populations is comparatively high, that of sapling in the 3rd age class （7.5 cm≤DBH〈12.5 cm） of Zhushan population is the highest, that of big tree in the 7th age class （27.5 cm≤DBH〈32.5 cm） of Gucheng T1 population is the highest, and that of middle-aged tree in the 6th age class （22.5 cm ≤ DBH〈27.5 cm） of Gucheng T2 population is the highest. Average life expectancy of individuals in the 1st age class （ DBH〈2. 5 cm） and the 2nd age class of three populations is relatively high. Amplitude of fundamental wave of Zhushan, Gucheng T1 and Gucheng T2 populations is 1.061 6 , 1.097 1 and 0.788 2, respectively, and their obvious minor cycles appear in the 4th , 2nd and 4th harmonic waves accordingly, which is indicated that there is periodicity in regeneration of natural population of T. ciliata in northwestern Hubei with multi-harmonic wave superposition of minor cycle, and fluctuation of population is in accordance with Vn value of age class. The analysis result of population dynamics shows that due to strong light-demanding physiological feature, natural population of T. ciliata is under restriction of environmental sieve and experiences environmental disturbance, resulting in loss of sapling and deficiency of middle-aged plants, which is the principal extinctive factor of T. ciliata. Therefore, some suggestions for T. ciliata are proposed, including intensification of artificial positive “ disturbance” to make forest gap, increase of natural regeneration capacity of population, and species introduction and afforestation, to preserve and develop this endangered plant resource.