Competitive Effects Of Setaria Viridis Beau. (Gramineae) And Lolium Perenne L.(Gramineae), On Invasive Alien Weed, Ageratina Adenophora Spreng. (Asteraceae)

Crofton weed, Ageratina adenphora Spreng. (Asteraceae), is one of the worst worldwide-spread invasive weed. It is perennial with woody rootstock and numerous upright branching stems. Nowadays, it grows commonly in South-western China, including Yunnan, Guizhou, Sichuan, Guangxi, Tibet, and Chongqing, etc. The invasion of crofton weed could cause serious economic loss and environmental disaster in agriculture, forestry and animal husbandry. In order to mitigate its harmful impact on ecosystems, the ecological control method named "replacement control", was suggested in 1951 and has been used for about 30 years in China. Two forages, Ryegrass (Lolium perenne L.) and Bristlegrass (Setaria Viridis (L.) Beau.), which grow fast and have high economic value, were used in this study. And the physiological and biochemical mechanisms of the competition between Ryegrass/Bristlegrass and Crofton weed were studied. The main results were as follows:1. The physiological and biochemical mechanisms and effects of competition between Bristlegrass and Crofton weedA multiple de Wit replacement series was used between Crofton weed and Bristlegrass. Crofton weed and Bristlegrass were grown at a series of density levels in monoculture and also proportion levels in mixture under each of various density levels using potted plants in the greenhouse. The physiological and biochemical mechanisms and effects of competition between Bristlegrass and crofton weed was studied. The result show that, with density levels and proportion levels increased, ramets and biomass of crofton weed reduced notably. Height appeared trend of increase after reducing with increase of density levels and proportion levels at prophase competitive stage, but reduced notably at evening competitive stage. The Bristlegrass is a kind of stronger competitor as to crofton weed and needs the same resources, which can exclude one plant through competition. The relative yield (RY) of crofton weed was significantly less than 1.0 under each of treatment regimes. But...