紫茎泽兰种群年龄结构动态及对控制的指示意义

 外来入侵植物紫茎泽兰（Eupatorium adenophorum）给我国西南地区的经济、社会和环境造成了严重的危害。为了阐明紫茎泽兰种群的年龄结构和未来发展趋势，为今后的防治工作提供科学依据，在攀枝花地区设置了20个样地（10 m×10 m），对4种不同生境种群的年龄结构、静态生命表和时间序列预测进行了分析。这4个种群是该地区有代表性类型中紫茎泽兰的种群：路旁荒地、云南松(Pinus yunnanensis)林、阔叶林和阔叶林的林缘。种群年龄结构分析表明，目前 (几个类型总和)个体数量比重分别为：幼年期占92.32%，青年期占6.40%，成熟期占2.20%，衰老期占0.18%,个体数量主要集中于幼年期。紫茎泽兰不同种群生命表和存活曲线的分析显示，紫茎泽兰对4个种群的入侵过程是路旁荒地→阔叶林林缘→阔叶林→云南松林，尽管所处的生境差异较大，但基本属于DeeveyⅢ型,一年生幼苗死亡率高达97.30%，种群偏离典型曲线的程度与群落受干扰程度强弱有关，一般由幼年期到青年期和由成熟期到衰老期死亡率较高(分别为93.07%和92.00%)。时间序列分析表明，在未来的3～5年中，紫茎泽兰种群仍然是以青年期和成熟期个体占绝对优势。

AGE STRUCTURE DYNAMICS OF EUPATORIUM ADENOPHORUM POPULATIONS AND ITS IMPLICATIONS FOR CONTROL

The invasion of Eupatorium adenophorum has caused serious damage to natural ecosystems by suppressing native species populations in disturbed forests and pastures in southwest China. In this study, the age structure dynamics of E. adenophorum populations were examined in 20 plots (10 m × 10 m) using the Greig-Smith grid method, in Panzhihua Prefecture, Sichuan Province of China. There is no standard method for identifying the age of an E. adenophorum plants, but through careful observations of the growth characteristics of E. adenophorum over several years in Panzhihua, we found a reliable method for aging individual plants. During the coldest season of every year, the apical half of branches grown in the current year wither and die, and a pair of opposite branches expand out from the lignified half that is below the wilted top. Although it can turn out clone genet alone once the branch touches the ground. At the same time sexual propagation and vegetative reproduction of radicicolous branches carry through from year to year. That is to say, the most number of branching ranks of the same branch is likely to indicate the real age of the plant. We dug out the entire plant in each grid and counted the grade rank of each branch to determine the age of each individual plant. The results showed that the age structure of the 4 populations were similar with most individuals in the infancy (92.3%) and youth (6.4%) periods. The analysis of life tables and survival curves showed that chronological sequence of an E. adenophorum invasion was as follows: first, invasion occurred along roadside fields, followed by invasion into the margins of broad-leaved forest, then deep into broad-leaved forest, and finally into Pinus yunnanensis forest. Even under different environmental conditions, survival curves of all E. adenophorum populations belonged to the Deevey type Ⅲ pattern, and mortality of all populations showed a peak in 1-2 years old with mortality rates of 97.3%. The degree to which a population deviated from a typical curve related to the intensity of human disturbance. In general, mortality during infancy period and mature period were high (93.1% and 92.0%). The invasion time-sequence model predicts that young and mature individuals will dominate the populations at 3 and 5 years from the present. Therefore, in the Panzhihua Prefecture, we predict that E. adenophorum will become a serious problem in 3 to 5 years. Compared with populations of other invasive plants, the population of E. adenophorum has a similar break out pattern among populations. Traits promoting weediness included the ability to reproduce sexually and asexually, rapid growth from seedling to sexual maturity, and, most importantly, adaptation to environmental stress (phenotypic plasticity) and high tolerance to environmental heterogeneity.