Competition Effects And Mechanisms Between The Replacing Herbaceous Plants And Invasive Weed Eupatorium Adenophorum Sprengel

Eupatorium adenophorum Sprengel is one of major invasive weeds in China and has caused great ecological disaster and economic losses, such as the decrease in biodiversity and the change in structure and function of ecosystem. Many methods of controlling Crofton weed have been conducted, including the prevailing method of replacement control. Theories predicted that such a success should be related to the competitive ability for limiting resource, mainly to below-ground resources. However, the role of competition for light has rarely been tested. We proposed the hypothesis that the light played an important role for Crofton weed in constructing communities. In this research, the competition effects and their mechanisms between three non-invasive plants and Crofton weed were comparatively studied. The main results are as follows:(1) In this study, the effects of aqueous leaf extract of Crofton weed on germination rate (GR) and germination time (GT) of Lolium perenne L., Dactlis gloerata L., and Festuca arundinacea Schreb, were determined with different concentrations of the extract by using the modified filter paper-Petri dish method, as well as the changes in seedling growth and the activities of anti-oxidative enzymes in early growth stages of D. gloerata. Besides, the effects of the extract on the Ureae activity, Phosphatase activity, and the Catalase activity in soils were measured. The results showed that the GT of all the three plants were significantly affected by the extract. High concentration of the extract could affect the GR of D. gloerata and F. arundinacea. There was no significant difference in seedling height, biomass and the SOD in the late stages. Low concentration of the extract decreased the Ureae activity. The high concentration of the extract had no distinct effect on Ureae activity, but increased the Catalase activity. All these showed that the Crofton weed had the allelopathical effect on native plants.(2) Based on the seed germination experiment above, the L. perenne and D. gloerata, were chosed as the replacement plants in this study. There were two time treatments-A:the replacement plants were planted one month ahead the Crofton weed; B:replacement plants and Crofton weed were planted at the same time. The changes of height, as well as the leaf number, biomass and the number of Crofton weed seedlings with the time were measured as well as the biomass and the height of the replacement plants. The results showed that in treatment A, no Crofton weed seedlings were found. In treatment B, the leaf number, height, biomass, and the number of Crofton weed seedlings were much lower that those in control. And the competition apparently decreased the biomass and height of L. perenne.(3) In this study, by comparing the competition effects of Crofton weed seedlings planted with three other non-invasive plants, L. perenne, D. gloerata, F. arundinacea, as well as the shaded ration of photosynthetically active radiation (rPAR) blocked and the Ureae activity, Phosphatase activity and the Catalase activity in soil at field. The result showed that there were no Crofton weed seedling in both of L. perenne and D. gloerata communities. The tiller number and the number of Crofton weed seedlings in the F. arundinacea community were significantly less than those in control. But there was no significant difference between them. The biomass and the height of L. perenne were remarkably decreased at the late stages in rainy season. The D. gloerata kept high biomass all the stages. There was no distinctive difference in soil enzyme and the available nutrients except the K in treatments and control, while the light resources measured as the rPAR were significantly different.