Effect Of Ambrosia Trifida On Invasion Ecosystem And Feedback Of The Ecosystem

Biological invasion which caused serious damage to social economic development and efected biodiversity attracted the attention of nationwide.This study selected Ambrosia trifida as the object to discuss the invasion feasure of Ambrosia trifida as invasive species and revealed its invasion and diffusion mechanisms.This study had two parts.In the first part,five different habitats were selected to investigate species and number of weeds also the growth condition of Ambrosia trifida and discuss the main environmental factors with mathematics method. In the second part, four invasion areas were selected along with environmental factors to investige cover and number of weeds also the growth of Ambrosia trifida.Meanwhile, Soil nutrients were performed in different invasion areas.The survey results of different habitats showed that the growth of ambrosia trifida was better when the disturbance was stronger. Water, fertilizer and the invasion of Ambrosia trifida had the same important affect on ambrosia trifida itself.Ambrosia trifida had the biggest niche breath in the same habitate.The distribution of the survey samples had a total of 71 kinds of weeds in 28 subjects, of which Asteraceae, Chenopodiaceae, Polygonaceae are the most. Through 34 kind of weed's on first two principal components loads, we can see which principal components factor affects the bitter weeds is the human's interuption level and the soil moisture condition, thus it can be seen that the bitter weed is suitable for interuption and it is suitable live in the habitat which air relative humidity is higher.Three clusters were divided and as the human's interuption level is higher, the bitter weeds'important value elevates higher too.Simultaneously the quadrat species'abundance deqcreases when the bitter weed's important value increases. This explained that in the different habitat, the bitter weeds siring massively can give biodiversity destructive effect.The survey results of different invasion areas showed there were 83 species in studied areas,the most 30 frequent species of which were Artemisia argyi, Echinochloa crusgalli, Polygonum aviculare and so on. Ambrosia trifida invasion had impact on species richness of local plants, but not obvious,while obvious on the impact of species diversity that with the invasion of Ambrosia trifida, simpson values and Shannon-Wiener values decreased significantly. Ambrosia trifida plant height and branch length was significantly increased with the invasion of itself,and biomass partitioning index levels in different invasion areas had no significant differences. The invasion of Ambrosia trifida significantly increased soil total N, total P, total P and available P of soil,and had no significant effect on NH4+-N and available P of soil but reduced NO3+-N of soil significantly. Therefore,it is difficult to restore a habitat invaded heavily by simply cleaning method.It is necessary to restore soil environments and to use the replacement method with suitable plant species to control Ambrosia trifida.