| artemisiifolia is a harmful weed which spread into China from foreign countries in the 1930s.At present,it has invaded over 15 provinces,cities and autonomous regions in China.In Henan province,our research team first collected Ambrosia artemisiifolia in Xinxian County in 2000.In 2009,we found Ambrosia artemisiifolia in Luoshan County.In 2013,Ambrosia artemisiifolia established a large area in Guangshan.Henan is a huge province of China's agriculture.In order to protect grain security,it is necessary to prevent and control Ambrosia artemisiifolia.This experiment mainly focuses on the invasion,spread and prevention of Ambrosia artemisiifolia in Henan.The main results are as follows:1 Studying on genetic diversity and genetic differentiation of Ambrosia artemisiifolia,the main reasons for its invasion in Henan were analyzed.Our study area located in the south of Henan Province which harbours large populations of Ambrosia artemisiifolia.The molecular marker method was used to compare the nuclear gene differences between different Ambrosia artemisiifolia populations.Experimental comparison of Henan Ambrosia artemisiifolia is divided into three branches:Hubei branch,Jiangxi branch,Roshan Xiangnandian branch.Hubei branch contains the Guangshan Ambrosia artemisiifolia(collected in Pohe high speed railway Tuweizi village),the Guangshan huai township,Guangshan Pohe to Yanhe township and Hubei Qiliping Ambrosia artemisiifolia have a good relationship,is likely to spread from Hubei to Henan,and then spread to the Guangshan Pohe and Huaidian town.In the survery,we found that Ambrosia artemisiifolia was distributed in rural roads S219,S339 and Y213 in a relatively concentrated,indicating that highways played a significant role in the diffusion process of Ambrosia artemisiifolia.The greenbelts on both sides of country roads and highways are not well managed,giving Ambrosia artemisiifolia more opportunities to grow.It is difficult to see the distribution of Ambrosia artemisiifolia on the Daguang expressway.There are special green chemicals that are regularly maintained to give Ambrosia artemisiifolia little chance of invasion.The Ambrosia artemisiifolia collected in Y213 township from Pohe town to Yanhe town had a good relationship with the Ambrosia artemisiifolia collected in Hongan county,Hubei province.Ambrosia artemisiifolia spread from Roshan town to Yanhe town.The Jiangxi branch includes the Ambrosia artemisiifolia near Nanchang high-speed railway station in Guangshan,Yanhe township,Hepeng township and Roshan town(collected in Lubang,Roshan).The Ambrosia artemisiifolia relationship in these areas is good,and the Ambrosia artemisiifolia may spread from Jiangxi to Henan.The Luoshan Xiangnandian branch is located on the southwest of Henan Province and is separated separately.The results showed that the origin of Ambrosia artemisiifolia in Henan was not a single.The genetic distance was not related to the geographical distance,the Ambrosia artemisiifolia was brought to Henan in various ways through various transmission channels.2.By studying the influence of Ambrosia artemisiifolia on the species and diversity of native plants in Henan,to analyze the causes of its diffusion.In the Guangshan,Xinxian and Luoshan in the southeastern of Henan Province,37 diverse habitats from diverse regions were selected as plots for surveys.The Shannon Wiener index,Simpson index and PieLou uniformity index of ragweed population were studied.(1)After analysis,it was found that a total of 32 families,62 genera,and 76 species of weeds were mainly composed of Compositae and Gramineae.(2)By comparing the plots,it is found that the number of Ambrosia artemisiifolia near the farmland is less than that of the roadside wasteland,and the intersection of the village entrance is the key area of Ambrosia artemisiifolia distribution.Henan Ambrosia artemisiifolia is mainly distributed on both sides of the road.Traffic is the main factor affecting plant distribution,followed by soil use type.(3)Shannon Wiene index H value range is 0.52-2.09,the change is large;Simpson index D value range is 0.31-0.87,and Pielou evenness index E value range is between 0.25-0.82.The number of Ambrosia artemisiifolia affects the local plant diversity index and evenness index.In areas where the number of is small(less than 80 plants/square meter),the plant diversity index and evenness index are higher;A large number of areas(more than 300 plants/square meter)has a low plant diversity index and uniformity index.When the number of Ambrosia artemisiifolia exceeds a certain amount,it will lead to a decline in the diversity of native plants.Ambrosia artemisiifolia can lead to a decline in the diversity of native plants,helping them to better adapt to the new environment and settle in the invading area.3.Analysis the factors affecting its spread by microbial diversity analysis of Ambrosia artemisiifolia rootsMicrobial diversity of Ambrosia artemisiifolia root soil was investigated in 6 regions of Henan,and the soil without its growth was collected as a blank control.Soil microbial diversity was divided by dilution plate counting method,and the full sequence of 16S rDNA was used for identification.A total of 21 strains,11 genera and 21 species were isolated from the roots of Ambrosia artemisiifolia.Among them,the species and quantity of Bacillus are the most,a total of 9 species,which can produce spores to resist the harsh environment.They have good resistance to insecticides,which can secrete antibiotics,polyaspartic acid,glutamic acid,Cyclic peptides and poly-polysaccharides can make Ambrosia artemisiifolia better adapt to the new environment.Pseudomonas and Streptomyces can promote plant growth,help Ambrosia artemisiifolia root colonization,improve plant resistance.Brevibacterium can repair heavy metal(automobile exhaust)pollution in soil;Klebsiella and Gordonia are resistant to herbicides.The experiment found that the number of soil microbes in the Ambrosia artemisiifolia was higher than other area,and the soil microbes made the ragweed more suitable for the Henan environment and helped to settle.However,the soil rhizosphere microbial species in the areas with different Ambrosia artemisiifolia growth densities are not much different.It is possible that soil microbes are not the main factors affecting the expansion of Ambrosia artemisiifolia.3.MAXENT model and DIVA-CIS were used to predict the potential suitability of Ambrosia artemisiifolia in Henan province,to provide a basis for its prevention and control.Based on the field investigation and consulting published literature and specimen information,data information of the distribution points of 160 Ambrosia artemisiifolia in China was obtained.maxent and DIVA-CIS software was combined to simulate the potential habitat of Ambrosia artemisiifolia.AUC curve analysis was used to verify and the main environmental variables affecting the distribution of Ambrosia artemisiifolia were analyzed by a knife cutting method.From the experimental model,we can see that Ambrosia artemisiifolia with the warmest season average humidity has the highest contribution rate in potential growing areas in Henan,followed by the wettest month humidity,the wettest season humidity and the annual average temperature.We can infer that water and temperature are the main factors affecting the diffusion of Ambrosia artemisiifolia in Henan province.Xinxian,Guangshan and luoshan are located in the south of Henan,in the transition zone from subtropical to warm temperate zone.They have monsoon moist and semi-humid climate in the north of the subtropical zone.The relatively humid and hot environment has become the earliest invasion place of Ambrosia artemisiifolia in Henan,and most areas in Henan are suitable for its.The Funiu Mountain in the southwest of Henan province may affect its diffusion.Ambrosia artemisiifolia will spread to the east and north of Henan,these areas should to be strengthened in prevention and control. |
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