Studies On Biological Invasion By Eupatorium Adenophorum

Biological invasion has brought about serious loss to social and economic development and exerted heavy impacts on biodiversity, which received great concern in international community. The mechanism for the invasion is the key scientific issue among others. In the paper, we examined the biological, ecological traits and changing in allelopathy of croften weed (Eupatorium adenophorum), and alteration of the soil properties in different habitats to describe the special properties of invasive plants and seek the mechanisms of invader success.Our results suggested that the dominating traits and ecological strategy of E. adenophorum population were different between habitats. In stressing habitat, the population exhibited r- strategy for its survival. In optimum habitat, the adult individuals of E. adenophorum could inhibit the growth of their seedlings, decreasing the survival rate of seedlings, to restrain the seed regeneration rate and command them preferred K- strategy to realize the steady development and colonize the natural habitat.In stressing habitats, small numbers of weak adult individuals of the invader played a minor role on the seedling banks; and the populations made good use of the heterogeneous resources by using their abundant seed source. In contrast, in optimum habitat densely and boomingly growing individuals greatly influenced the seedlingsresulting in low survival rate of seedlings, the population competed effectively for resources by its abundant clonal seedlings with high growth and competitive features. These two ecological strategies could transform to each other at space and time and facilitate E. adenophorum to establish in extensive habitats.Allelopathy explained a part of the invasiveness of E. adenophorum. The allelopathy of roots and stems of E. adenophorum were significant difference between habitats. This allelopathy of roots or stems was strong in optimum habitat, however that was weak in stressing habitat; the result was significantly related to the abundances of native plants in habitats, showing that the difference of allelopathy in E. adenophorum results in different invasiveness of E. adenophorum between habitats. In optimum habitat, E. adenophorum grown strongly and abundantly thus they could produce much more allelopathicsubstance in unit area than those grown in stress habitats, which might compel the native plants into more competition pressure in the habitat.The properties of soil from E. adenophorum heavily invaded habitat were significantly altered; the content of available N, P, K in heavily invaded habitat were all greatly enhanced than in lightly invaded; and the functional structure of soil microbe community was altered too, the catabolic activity of the soil microbe community at acids was significantly greater, and that at glucide or hydroxyketone was significantly low in heavily invaded habitat than those in lightly invaded.The invasive species might destroy the closely coupled soil-plant communities that developed over time by changing the soil microbial community, and successfully invaded the habitat by inhibiting the growth and regeneration of native plant species. The restoration of the soil microbial community in invaded habitats might be long-term and difficult process. This may be a formidable obstacle to overcome for controlling invasive plants and restoring the vegetation in agricultural and natural ecosystems. Thus, single reason, such as physiological or chemical characteristics of invasive plant, is limited and failed to provide adequate explanations of invadersuccess. A holistic perspective that considers the whole system and the interactions among the components will be a more fruitful approach to understanding invasive ecology. A knowledge of how the invading species replaces the native species is probably the key to the effective management and soil restoration strategies.