Effects Of Four Exotic Compositae Plants On Soil Arbuscular Mycorrhizal Fungi In Invaded Habitats

Compositae is main group of exotic invasive plants. Arbuscular mycorrhizal fungi playimportant role in the regulation of ecosystem nutrient and energy cycling is pivot to maintainecosystem stability and community succession. The symbiosis of compositae and AM fungi and itsrole of in the invasion of exotic compositae plants need to be studied. In this study, combining fieldsampling and laboratory studies, a comparative study about the influences to soil physicochemicalproperties and AM fungi diversity of four exotic invasive compositae: Mikania micrantha,Eupatorium adenophorum, Eupatorium odoratum, Flaveria bindentis. Clarify the relevance of soilAM fungi structural changes and the soil physicochemical properties, trace elements, enzymeactivities. Discuss the ecological significance of symbiotic interaction between invasion compositaeplants and AM fungi. Provide the theoretical basis of comprehensive defense and control of alienplant invasion mechanism. The main results as following:1. Four exotic invasive compositae plants changes the rhizosphere soil nutrient contentsrespectively. Compared with the non-invasion (control) group, Eupatorium adenophorum,Eupatorium odoratum and Flaveria bindentis show the invasion plants rhizosphere soil pH decreased,total nitrogen and available nitrogen content in rhizosphere soil has increased, total phosphorus inrhizosphere soil has declined. The rhizosphere soil available phosphorus content of Eupatoriumadenophorum, Eupatorium odoratum and Flaveria bindentis decreased81.16%and59.41%,84.83%respectively. In contrast, Mikania micrantha increased pH in invasion rhizosphere soil, soil organicdeclined, total nitrogen content NH4+-N increased, total phosphorus, available phosphorus contentwere not show significant changes.2. Trace elements have changed in four exotic invasive compositae plants rhizosphere soilrespectively. Total manganese content was increased in Eupatorium adenophorum, Mikaniamicrantha rhizosphere soil significantly.Total copper, total zinc, total cadmium content in rhizospheresoil increased significantly in Eupatorium adenophorum. In Eupatorium odoratum group, total zincin rhizosphere soil decreased, total cadmium level was increased significantly. Total and availablecopper, zinc, cadmium were increased in Eupatorium adenophorum rhizosphere soil significantly.Available manganese, available cadmium in rhizosphere soil were significantly increased inEupatorium odoratum group; available copper were increased in rhizosphere soil of Flaveriabindentis significantly.3. Urease, phosphatase and catalase activities in rhizosphere soil have changed by four invasivecompositae plants respectively. Enzyme activities in rhizosphere soil have improved in Eupatoriumodoratum, Mikania micrantha, Flaveria bindentis.. Acid phosphatase activities were increased inrhizosphere soil0f Flaveria bindentis and E. adenophorum significantly. Catalase activities in rhizosphere soil were increased in the Flaveria bindentis and Mikania micrantha significantly.4. AM fungal diversity were changed in rhizosphere soil by four invasive compositae respectively.Similarity of AM fungal community in rhizosphere soil of Eupatorium, odoratum, Mikania, bidentiscompared to control group were56%,63%,64%,60%, respectively. The diversity index of AMfungal community in rhizosphere soil in Mikania micrantha, Eupatorium odoratum, Flaveriabindentis. were improved. AM fungal abundance index in rhizosphere soil were increased ofEupatorium adenophorum significantly. Diversity and abundance index of AM fungi in rhizospheresoil level were increased of Eupatorium adenophorum, Flaveria bindentis significantly. AM fungirichness, Shannon-Wiener and evenness index in rhizosphere soil have no significant difference inMikania micrantha,.5. The soil enzyme activities, soil physicochemical properties and AM fungal diversity of fourinvasive compositae plants were significantly relevant. Urease activity showed a significant positivecorrelation with soil organic, total nitrogen, available nitrogen content. Phosphatase activity and soilpH, total phosphorus content was significantly negatively correlated. Urease, phosphatase, catalaseactivity and total phosphorus content correlation coefficient and significantly, the correlationcoefficient were-0.882,-0.801and0.852, respectively. AM fungal community rich index wasshowed a highly significant positive correlation with total phosphorus, urease, catalase. AM fungaldiversity index and soil available phosphorus content have a very significant negative related andsignificantly positive related with phosphatase, the correlation coefficient of-0.709;. AM fungievenness index and pH, total phosphorus content was negative correlated significantly. AM fungievenness index have positive correlation with phosphatase activity significant AM fungal communitydiversity and trace element contents also showed correlation.