Potential Geographical Distribution Of Endangered Plant (Gymnocarpos Przewalskii) In Xinjiang

As the main biological germplasm resources in the Gobi and desert areas,desert plants are an important part of the desert ecosystem.Gymnocarpos przewalskii Maxim.is a national first-class key protected plant identified by the State Forestry Administration in 1997 when the National Key Protected Wild Plant Resources Survey was conducted.Central Asia is endangered species and ancient Mediterranean remnants.This paper obtains the actual distribution point data of naked fruit trees in Xinjiang through field surveys and published papers on dissertation,journal articles and conference papers,as well as domestically published specimens.Screening,a total of 97 sample data.With the support of ARCGIS,the spatial distribution characteristics of the sample data were analyzed,and the distribution status of the naked fruit trees of the relict species was clarified,which laid the foundation for the model simulation.Using the two niche models of MAXENT and GARP,19bioclimatic variables were selected to predict the potential distribution of the endangered species naked fruit in Xinjiang,and the contribution of each environmental variable to the distribution pattern of naked fruit trees was analyzed.The optimal model was selected to predict the distribution of human activity disturbance on the distribution of naked fruit trees.Under the future climate model of RCP4.5,the potential distribution pattern of bare fruit trees in 2050(2041-2060)and2070(2061-2080)was predicted.The distribution area is compared with the distribution area and environmental variables under current climatic conditions,and the accuracy of the model is tested.According to the research results,the corresponding protection strategies are proposed.The results show:1.The main distribution area of naked fruit trees in Xinjiang is located in the continuous distribution area of the vast alluvial fan and the alluvial plain on the Gobi south of the Tianshan Mountains.The Hami area in the eastern Tianshan Mountains,the Qitai,Mulei in the northern Tianshan Mountains and the Gobi area in the northern part of the Altun Mountains are bare fruit trees.Three discontinuous distribution areas.The specific natural distribution area is located in Qitai County of Changji Prefecture,north of Hami City in the eastern Tianshan Mountains,and south of Balikun,Yiwu County,Shanshan County,Toksun County,Heshuo County,and Korla City.Counties such as Luntai County,Kuche County,Baicheng County,Wensu County,Akto County,Wushi County,Wuqi County,Shule County,Shufu County and Ruoqiang County.2.Under the current climatic conditions,the MAXENT model was used to calculate the total area of the potential suitable area of bare fruit trees was 43845 km~2,and the total area of potential suitable areas and potential medium-sized areas was20659 km~2.The GARP model predicted the potential area of bare fruit trees.The area is 444,079 km~2.The superior and medium-adapted areas predicted by the GARP model include the area of northern Xinjiang,and the area of the distribution area is significantly different from the actual distribution area of the naked fruit in Xinjiang.At the same time,the MAXENT model training set and test set AUC The values are0.979,0.969,0.981,0.985,0.985,0.982,0.984,and 0.978,respectively,which are close to 1,indicating that the prediction effect is good.Therefore,the MAXENT model was selected for the later simulation calculations.3.Using the MAXENT model to select 19 bioclimatic variables and superimposed human activity disturbance variables,the potential area of the naked fruit trees was calculated to be 19,824 km~2,which was 835 km~2 less than the current potential distribution area,indicating that human activities can distribute the population of the naked fruit trees.The area is reduced.4.Under the future climate model of RCP4.5,the total area of the bare fruit suitable area in the period of 2041-2060 is predicted to be 40,816 km~2,which is 3,029km~2 less than the current potential area,and the total area of the suitable area in the period of 2061-2080 is 38,476 km~2,which is more than the current The potential distribution area decreased by 5369km~2,and the change of the area of the bare fruit trees indicated that the distribution range and population density of the naked fruit trees in the future climate model of RCP4.5 would be reduced.5.Through the correlation analysis of variables,the main variables affecting the potential distribution of bare fruit trees are seasonal changes in precipitation,precipitation in the hottest season,annual precipitation,and seasonal variation coefficient of temperature as dominant environmental variables.The average daily poor,wet season average temperature,and extreme high temperature,annual average temperature and other environmental variables also have a greater impact on the distribution of bare fruit,and the change of rainfall and temperature has the most obvious impact on the potential distribution of naked fruit.The study of naked fruit trees has a high scientific value for the generation and development of deserts in northwestern China,the origin of the components of the cultivar in the northwestern region,and the change of climate.Therefore,the main protective measures proposed by this paper include:naked fruit trees The nature reserves and nature conservation stations will be established in densely populated areas.The existing nature reserves and protection stations will increase the intensity of supervision and protection,minimize the impact of human activities on the protected areas,and attach importance to the introduction and cultivation of naked fruit trees.Strengthen publicity and education,increase law and improve the legal system.