Study On The Geographical Distribution Patterns And Potential Suitable Areas Of Four Nitraria Species

Global climate change is a major environmental problem facing mankind at present.The geographical distribution of plants is greatly affected by climate and soil.The vegetation in the environment with serious desertification is more sensitive to climate change.Due to the increasing desertification in most areas of our country,the coverage of most of the vegetation is reduced.For the desertification environment,Nitraria belongs to the most suitable type of ideal plant species,which can improve the ecosystem of desertification.The selected research areas in this paper are Xinjiang Uygur Autonomous region,Qinghai Province,Gansu Province,Inner Mongolia Autonomous region and Ningxia Hui Autonomous region.The climate type is temperate continental climate,and most of them are classified as arid and semi-arid areas.In view of the geographical distribution and possible suitable areas of Nitraria,by collecting the geographical distribution of four Nitraria species in China,analyzing the characteristics of resource distribution in the whole country,and coupling the influence of climatic factors on the distribution of four Nitraria species,the geographical distribution pattern of four Nitraria species was analyzed.The purpose of this paper is to provide some theoretical basis and reference materials for the protection of the above-mentioned plants and the rational utilization of resources as well as the large-scale cultivation of this kind of plants.In this paper,the data of Nitraria tangutorum,Nitraria sphaerocarpa,Nitraria roborowskii and Nitraria sibirica in Nitraria were collated and their distribution was obtained.the distribution data and environmental variables were used for correlation analysis,and the potential suitable growth areas of N.tangutorum,N.sphaerocarpa,N.roborowskii and N.sibirica were measured by MaxEnt model software,and the corresponding cross distribution areas of the above four species were obtained by superposition analysis with the application of Arc GIS software.The main environmental factors were measured by knife-cutting method,the contribution value was obtained by discussing the response curve under different environmental factors,and the distribution of Nitraria was obtained by superimposing the land type map and the high suitable area of Nitraria.To provide scientific basis for the utilization and protection of Nitraria resources.The main results are as follows:(1)The prediction results of MaxEnt model showed that the AUC values of four Nitraria species under different climate scenarios were all greater than 0.8,indicating that the MaxEnt model had a good prediction accuracy for the four Nitraria species.The highest and lowest AUC of N.tangutorum was 0.947 and 0.835.The highest and lowest value of AUC were 0.960 and 0.878 of N.sphaerocarpa.The values of N.roborowskii 0.967 and 0.848,respectively.The values of N.sibirica were 0.947 and 0.843 respectively.(2)Through the analysis of the predicted data from the MaxEnt model,it is found that the niche parameters that affect the main environmental variables in the middle and high suitable areas of Nitraria plants under different climatic scenario are basically the same,so this paper only statistics the variation range of niche parameters under the benchmark climate scenarios,in which Bio11(mean temperature in the coldest season)and Bio18(precipitation in the hottest season)are the four main environmental variables that affect the distribution of Nitraria.(3)The analysis of environmental factors affecting the potential distribution of four Nitraria species showed that the main environmental factors affecting the distribution of N.tangutorum were temperature,soil porosity and available phosphorus.Temperature was the main environmental factor of N.sphaerocarpa,followed by precipitation,soil organic matter and available phosphorus.Rainfall,soil organic matter,temperature and altitude were the main environmental factors affecting the distribution of N.roborowskii.Temperature,rainfall,soil organic matter,altitude and available phosphorus were the most important environmental factors affecting the distribution of N.sibirica.(4)The results show that the distribution range of four Nitraria species in different periods has changed under different climate scenarios.As a whole,the range from the base period to the cross region is the smallest.In the future,the range of RCP4.5 is relatively small compared with the other two climate scenarios in 2050 and 2070,while it increases from the base period to the future period in turn in some areas.the floating volume is not very large,and it will basically change in a small area in the future.(5)The analysis of land use status in the distribution areas of four Nitraria species showed that the unused land area of four Nitraria species showed a decreasing trend with time,while the construction land and cultivated land showed an increasing trend.In terms of land use types,the proportion of grassland in different periods is higher,while the area change of unused land in different periods is not obvious.