濒危植物长柄双花木自然种群年龄结构及其生态对策

The age structure and ecological strategy in a wild population of the endangered plant Disanthus cercidifolius var. longipes (Hamamelidaceae)

通过对濒危植物长柄双花木自然种群的年龄结构、图解生命表以及生殖价分析等途径,研究了其种群结构动态及生态对策,结果表明:长柄双花木种群为衰退型种群,虽然种群中也存在一定数量的幼龄个体,但个体死亡率较高。长柄双花木种群表现出r～K对策的混合生态适应策略。该种群数量在下降过程中还存在波动,仍具有一定的实现生殖和恢复的可能,但依靠有性生殖途径实现恢复的能力有限。

Disanthus cercidifolius vat. longipes,a plant species that only occurs in a few counties in Hunan,Jiangxi and Zhejiang Province and with relatively small numbers of individuals,is ranked as a 2^nd class endangered species for conservation in China. The dynamics of age-structure and the ecological strategy in 19. cercidifolius vat. longipes were studied. The results are as follows： the populations of D. cercidifolius var. longipes are withering populations, though there are some young individuals with high death rate in the populations. The ecological strategy is a r-K mix-strategy in D. cercidifolius var. longipes populations. The static life table of populations of D. cercidifolius var. longipes shows that the death rate of the populations with＂1- 5 year-aged class individuals＇is relatively higher than populations with individuals of other age class. The death rate of the populations would reach another peak when they are about 50 years old. The fecundity table indicates that its net reproductive rate（R0 ）,intrinsic rate of increase （rm）and finite ratio fineries（A）were 0. 8337,-0. 0047 and 0. 9953,respectively. These parameters（R0〈1,rm〈0,λ〈 I）indicated that the studied population is a decreasing type, but its declining is relatively slow. We can also refer that the populations of the species can hardly recruit new individuals and make natural regeneration in the current habitats. Using the data from the field investigations,we established the diagrammatize life table in which we can predict that in the coming 20 years,the individuals would most probable decrease from 2 271 to 1 530,i. e. ,only 70% individuals will still remain in the population. The key reasons leading to the endangering of this species are most proba-bly the deforestation and habitat fragmentation.