Invasion Mechanisms Of Alien Species, Eupatorium Adenophorum Spreng.

Eupatorium adenophorum Spreng, crofton weed or pamakani in English, belonging to Composite, is a perennial weed species. This weed occurred originally from Mexico to Costa Rica in the South America, and it was taken to Europe as ornamental plant firstly, then to Australia and Asia. Up to now, E. adenophorum Spreng has spread to more than 30 countries and regions in the tropic and sub-tropic areas. In 1940s, Eupatorium adenophorum Spreng invaded Lincang area of Yunan province, the border of China and Burma. At present, it is widely distributed in southwest of China, including Yunan, Guizhou, Guangxi, Sichuan, and Tibet, and endangers the local ecology deeply after about 50 years' spread. Moreover, it has spread at a speed of 60 km per year in the directions of east and north along with southwest wind. The better understanding on the biological and ecological properties and the deeper clarification of the invasion mechanisms of E. adenophorum Spreng is essential to establish some base for preventing the extension of this weed in the future. This work was supported by the National Basic Research Program (2002CB111400), after 3 years' study, the main results were as follows:1. Study on population dynamics of E. adenophorum Spreng seedThe dynamics of seed population of E. adenophorum was observed on the levels of seed rain and seed bank in three different habitats of waste land, farm filed and forest. The results showed that the appearance of the seed was at the first ten days of March, and reached the peak at the end of April. The total seed rainfall of the waste land where E. adenophorum was the unique dominant species was over 240 thousands individuals per m2 per year, and most seeds were distributed in 5 cm soil layer upwards. To the first ten days of July, the density of vigorous seed in the seed banks ranged from 52 to 107 individuals per m~2. Among the three different habitats, the activity and weight of seeds was the highest in the waste land. The seed weight in the forest was heavier than that in the farm filed, but the activity of seeds was lowest among the three habitats, and it was 1/3 lower than that in the waster land.2. Characters of seed germination of E. adenophorum Spreng...