Mineral Nutrient Elements Dynamics And Secondday Metabolism Of Eupatorium Adenophorum Spreng And Its Invasion On The Soil Nutrient Contents

Eupatorium adenophorum Spreng.,with the English common name Crofton weed or Pamakani, is a kind of perennial weed belonging to eupatorium category of composite.Originally foaled in South America,it has been introduced to Europe as ornamental plant,and then to Australia and Asia. Now this weed has been widely spreaded and distributed in more than 30 countries and areas in tropic and subtropical zones.After introduced to China in the 40s,E.adenophorum has distributed in most areas in Southwestern China and caused serious damage.It is an exotic alien species,the reason for its successful invasion may lie in its extremely unyielding acclimatization and competitiveness.The invasion of E.adenophorum has not only influenced the local plants' growth, changed or even deteriorated the construction and function of ecosystem,accelerated the bereavement of biodiversity and extinction of species,but also has a strong impact on the development of local economy.Thus,this research starts with the influence to soil nutrient,which caused by the invasion of E.adenophorum,and makes further study on E.adenophorurn to deepen our knowledge of the invasion rules and establish the foundation of preventing its spreading and further deracinating.Through three years study,main results are summarized as follows.(1)The variation and correlations of seven mineral nutrient elements(N,P,K,Ca,Mg,Al, and Mn)in E.adenophorum leaves during its reproductive growth stages are analyzed.The results shows that the.content of elements N,Mg,and Al decreases during its flower bud differentiation stage,while the content of elements K and Mn incrases,with the content of elements P and Ca remains stable;the content of elements N and K decreases during its bud and florescence period, while the content of elements Mg,Al,and Mn increases with the content of elements P and Ca remains stable;the content of elements N,P,Mg,and Mn decreases during its seed stage,while the content of elements AI increases with the content of elements K and Ca remainsstable.The significant correlation exists between Ca and P,while the correlations among the others are not significant.(2)In this study,five different micro-habitats as abandoned land,woodland,farm and wood interleaving land,bank field and trench edge land are selected and the content of flavonoids(the secondary mctabolite substance)in different organs of E.adenophorum are measured during its vegetative growth and reproductive growth stages,and meanwhile the correlation between soil nutrients and the content of flavonoids in different organs of E.adenophorum are analyzed, respectively.The results show that the leaf is the major organ to synthesize flavonoids;after being synthesized in the leaf,flavonoids are transferred into the stem and root.The reproductive growth stage is the critical period for the synthesizing and accumulation of flavonoids;The accumulation content of flavonoids is closely related with its specific micro-habitats.The more environmental stress,the higher content of flavonoids Eupatorium adenophorum Spreng accumulates,and vice versa.The correlation between the content of flavonoids and soil nutrient gene is not significant.The content of soil available nitrogen is the major factor that affect the overall content of flavonoids,and other soil nutrients have little influence to the overall content of flavonoids.(3)By monitoring the dynamic of soil pH value in five micro-habitats,the influences of the growth of E.adenophorum on soil pH values are analyzed.The results show that the growth of E. adenophorum has stronger regulatory ability to soil pH values,and the growth of E.adenophorum could adjust wide range of pH values,this might be the major reason why this weed has compotition advantages.Based on the soil pH values between invaded and non-invaded micro-habitats,it is found that the dynamics of soil pH values are different at various micro-habitats(4)Based on the systematically monitoring the content of soil available nitrogen,phosphorus, and potassium,exchangeable calcium and magnesium,and active aluminum in E.adenophorum invaded and non-invaded abandoned lands,the invasion of E.adenophorum on soil nutrients are analyzed.The results show that the invasion E.adenophorum could remarkably regulate(up or down)the content of available soil nitrogen,phosphorus,and potassium,exchangeable calcium and magnesium,and active aluminum,and it has different regulating ability in different developmental stages.During the expeditious trophophase(July to September),the growth of E.adenophorum remarkably increases the contents of soil available nitrogen,phosphorus,and potassium, exchangeable calcium and magnesium,while decreases the content of active aluminum,and accordingly accelerates its own growth and development.It is also one of the reasons for the successfully invasion of E.adenophorum.