Invasion Biology Of Solidago Canadensis

More and more studies show that invasion of alien plants has caused severe impacts on native biodiversity. However, not all of the alien plants are able to become invasive, only a small part of them may successfully invade native ecosystems. Therefore, it is very important to study mechanisms underlying successful invasion of alien plants. Biological invasion depends on both of the high invasiveness of the invader (such as rapid growth from seedling to sexual maturity, high competitive ability, rapid evolutionary changes, adaptation to environmental stress and high tolerance to environmental heterogeneity) and high invisibility of ecosystems (such as empty niches, high level of disturbance, without natural enemy, similar environmental conditions with native distribution area of the invader). Studies on compensationary growth of invasive plants, which are subjected to different intensities of leaf-eating, in different levels of soil fertility are very important for us to determine the suitable density of its natural enemy population. Studies of genetic diversity of invasive plants would be useful for understanding their genetic differentiation in novel habitats, and the genetic mechanisms underlying their high adaptation to novel habitats. Furthermore, it can provide genetic proofs for management practices of the invaders. Studies on capacity of asexual reproduction of invasive species under disturbed conditions can help us to understand their establishment potential. Studies on allelopathic activity of invasive plants on native plants grown in the habitats they invade should be valuable for understanding the mechanisms in chemical ecology that alien plants can successfully invade a novel ecosystem. Canadian goldenrod (Solidago canadensis) is a perennial rhizomatic plant native to North America; it was introduced into China as ornamental plant in 1935, and has become one of the detrimental weeds in Shanghai. The purpose of the present study is to investigate the mechanisms underling its successful invasion, and try to find some effective ways for its control. This work included the following four aspects: effects of soil fertility and artificial defoliation on the growth of S. Canadensis; establishment; allelopathic potential; genetic diversity of S. canadebsis. The experiments are summarized as following: 1. Study on effects of simulated herbivory feeding on growth of S. canadensis is favorable to the practice in its control. Our field investigation showed that growth of the goldenrod seemed flourish although its leaves were eaten with different patterns and different intensities by insects. To understand the effects of feeding intensities, feeding patterns, and soil fertility levels on compensationary growth of the goldenrod, 4 we simulated the intensities and patterns of herbivore feeding (apex clipping with intensities of 25%, 50%, and 100%; and 25% of defoliation with apex, edge, small and large perforation removal). The artificial defoilation experiments showed that 25% of defoliation significantly increased its photosynthesis and its growth; especially at hig...