The Community Characters Of Invasive Plant Conyza Canadensis And The Potential Distribution In Xinjiang

Conyza canadensis--a species of the genus Conyza(Compositae),is widely distributed in majority province in China,native to North America and being considered a first order invasive species.Situating in the arid and semi-arid area with fragile relatively eco-environment,Xinjiang may be more vulnerable to invasive species than any other part of China and has become an area with a host of alien invasive plants.Investigation on Conyza canadensis communities in Xinjiang between 2019 and 2020,collecting data,calculating the abundance,frequency,important value and diversity index,to study on potential distributions and community characteristics.The MaxEnt(maximum entropy)and GARP(Genetic Algorithem for Rule-Set Prediction)models were used to predict Conyza canadensis's potential distribution.Potential distribution of invasive species in Xinjiang under climate change scenarios from a number of angles such as suitable habitat,the change of the distribution,distribution center of mass centroid movement path,analysis of primary variable.The main conclusions are as follows:(1)A total of 45 species of herbs were investigated and collected,belonging to41genera and 18 families mainly for angiosperms,among which 38 dicotyledons belong to 34 genera and 16 families,occupying for 88.89%.7 monocotyledonous belong to 7 genera and 2 families,occupying for 11.11%.The characteristic of family and genus composition is that there are more Compositae,Chenopodiaceae and Gramineae family,among which there were 2 species of alien herbs.Analying the weighted average important value of species that under different habitats and areas,top three were Conyza canadensis,Polygonum aviculare and Polygonum aviculare.The top important value is Conyza canadensis in various habitats.The important value of Conyza canadensis in the habitat that human activity frequently,such as roadside or the weed-grown field are higher than other habitat.It indicated that human activities were affecting the distribution.The main reason is moderate man-made disturbance of the weed-grown field and good soil conditions.(2)By comparing ROC and omission we found that the comprehensive prediction ability is the MaxEnt model.The potential distribution of Conyza canadensis was in the north,west,and east part of Xinjiang,including parts of west and southeast of Altay,Tacheng,Boertala,the central region of Changji,the north and central of Ili Kazakh autonomous prefecture,Urumqi,parts of Aksu,Kirghiz autonomous prefecture and parts of Kashgar.The potential distributions predicted by GARP were wider than MaxEnt,it's conforms to the researches of the predecessors.In the future climate scenarios,suitable habitats of Conyza canadensis have not undergone significant migration,and the distribution pattern has generally stabilized,but the potential distribution increased was located within Hami under the RCP8.5 scenarios to 2070s.With the warming of the climate,the expansion of suitable habitats of Conyza canadensis senticosus has a positive correlation with the CO₂ emissions of typical concentration paths.Overall,the present distributions of Conyza canadensis is far did not achieve the level of saturation,there is a trend that invasive species Conyza canadensis spread from Tacheng to the south of Xinjiang but the basins.(3)The omission rating of the MaxEnt model were 3.969,but the GARP model's were 3.969 in current climate pattern.The AUC test value of MaxEnt model were0.858.In terms of analysis result,the MaxEnt model was better than GARP model in this study.Under the RCP4.5 scoscenario,the area expanded in 2050s is 1.6 times than in 2070s.(4)Jackknife test indicated that the four environmental variables with a large contribution to the potential distributions of Conyza canadensis model were variation coefficient of precipitation(bio15),variation coefficient of precipitation(bio14),mean temperature of the coldest quarter(bio11)and precipitation of the wettest month(bio13).It's existence probability value has reached 50%when the variation coefficient of precipitation(bio14)being 4 mm only.It indicated that Conyza canadensis were extremely adaptable in arid environment.(5)Under the background of climate change,Hejing County,located in Bayingolin Mongol Autonomous Prefeccture,is the central area of the spread of Conyza canadensis.With the continumous increase of temperature and the passage of time,the risk of invasion to the south and southwest will continue to increase.Comprehensive evaluation identified Conyza canadensis retroflexus as a high-risk invasive plant in Xinjiang under the background of climate change.This species has great potential for spreading to southern and eastern Xinjiang based on the existing region.This invasive plant Conyza canadensis in Xinjiang region may show explosive growth in the latter half of this century.Early warning should be given to high-risk areas where the fitness of Conyza canadensis has been significantly enhanced under the background of climate change,and the existing distribution areas should be eradicated in a timely manner,and diffusion restrained.Prevention and control work should be considered in a unified manner,comprehensively consider its owmn application value,and reduce costs and difficulty with minimal environmental and resources costs.When using the ecology niche model,you should choose according to your own data conditions and research needs.It is recommended to use multiple models for comprehensive cross-analysis and prediction to break the limitations of a single model.