Effect Of Flaveria Bidentis(L) Kuntze On Soil Physical And Chemical Properties And Biological Activity

Top Huang[Flaveria bidentis(L) Kuntze]is a typical vicious invasion of weeds.It has resulted in serious economic and ecological losses in many countries and regions. This research based on the interaction between Top Huang and soil.Through the field sampling and greenhouse experiments,we study the soil mechanism of the invasion of Top Huang,different from the effects of Top Huang root's allelopathy on different habitat soil's physical,chemical properties and biological activity,the effects of the extracts of stems and leaves on the number of soil microbes and the activity of soil enzyme.The main results are summarized as follows:1.The exudates of Top Huang root changes the physical and chemical properties of soil partly.In flowering period,it significantly improved the soil salinity content. The soil salinity content respectively improved 298.8%,435.3%,40.0%,175.7%,226.9%on 5 tested soil.In flowering period,it improved the nitrogen content.The nitrogen content respectively improved 20.7%,18.7%,5.1%,57.0%,60.0%on 5 tested soil.In flowering period,it reduced the available K content.The available K content all reduced 50%on each tested soil.The soil pH all improved on each tested soil except Hengshui corn soil.In short,comparing with the physical and chemical properties of soil in different period after the invasion of Top Huang,we found that, the exudates of Top Huang root significantly improved the soil salinity content, improved the soil pH,nitrogen,reducing the soil available Potassium content,half of it to the original.2.Comparing with the number of soil microbes community in different periods after the invasion of Top Huang,we found that the exudates of Top Huang root changed in soil microorganisms dynamics.The change of bacteria,fungi, actinomycete's number is accordant.The number of microbes surged in the seedling stage.Along with the growth period,the number dropped,maintain to the level of contrast.But different soil has different seedling growth rate.Soil bacteria in Xianxian jujube soil are up to contrast 21.0 times and that in Xianxian corn soil are only 1.3 times to contrast.The number of soil fungi in tested soil is 1.5-2.9 times to contrast. The number of actinomycosis in Xianxian jujube soil is up to contrast 28.8 times and in Hengshui cotton soil is 3.1 times to the contrast.The number of actinomycosis in the other three soils is more than one times to contrast.Spraying corn with the extracts of Top Huang's stems and leaves,total number of microbes in the rhizosphere soil significantly reduced,while non-rhizosphere soil increased;the actinomycosis proportion in the total number of microbes of rhizosphere soil increased.It showed that the extracts of Top Huang stems and leaves changed the microbial community structure and composition.The number of the non-rhizosphere soil bacteria,fungi,actinomycetes decreased with the increasing of the concentration of the extracts,and along with the rhizosphere.The largest R / S is fungi,fungi is most affected by the rhizosphere.3.Comparing with the soil enzyme activity in different periods after the invasion of Top Huang,we found that the exudates of Top Huang root changed the activity of soil enzyme.In flowering period,the exudates of Top Huang root increased soil urease activity,catalase activity,decreased the soil alkaline phosphatase activity.The soil protease activity is different in different nutritious condition.It increased in poor nutritious condition,decreased in well nutritious condition.In the beginning stage after spraying the extracts of Top Huang's stems and leaves, the higher concentration of extracts,the inhibited effect to soil urease activity and soil alkaline phosphatase activity is stronger.But the extracts improved the soil catalase activity.After a time,the extracts to the soil catalase activity still had promoter action. The extracts to the soil urease activity still had inhibited effect in high concentration: had promoter action in low concentration.The extracts performed to promote soil alkaline phosphatase activity.4.Through the relevant analysis,we obtained root exudates of Top Huang to different soil has close correlation among the number of soil microorganisms,soil enzyme activity and soil nutrient content.We can use the number of soil microorganisms,soil enzyme activity as soil indicators of Top Huang invasion.It can offer reference of Top Huang invasion for the environmental impact. Through the cluster analysis,Top Huang invasion was main due to physical and chemical properties of the soil,it did not have great relationship with vegetation and region.Through the principal component analysis,we can use soil urease activity for the overall response of soil biological activity level.After adding the extracts,the soil urease activity with concentration dropped significantly.Soil Urease activity and soil organic matter content was positively correlated.In the experiment of Top Huang invasion,the exudates of Top Huang root stimulated soil urease activity.Top Huang's invasion to soil environmental is belong to self-reinforcing.