Study On Changes Of Soil And Water Resources And Ecological Recovery In The Main Stream Of Tarim River

The main stream of Tarim River is the lifeline of the ecological environment and an ecological barrier of the Taklamakan Desert in southern Xinjiang.However,its ecological service functionis greatly weakened due to climate change and irrational utilization of natural resources.To analyze and study the changes of water and soil resources and their ecological restoration in the main stream of the Tarim River,this paper took the soil and vegetation along the main stream of the Tarim River as the research object,and used statistical methods to analyze the characteristics of soil water and salt under different condition of Populus euphratica in the main stream of the Tarim River.The characteristics of age class structure and spatial distribution pattern of Populus euphratica population were analyzed from the aspects of diameter class structure,static life table and distribution pattern,and the dynamic characteristics and development trend of Populus euphratica population were pointed out.At the same time,combined with the MODIS satellite image data from 2010 to 2019and field investigation,with the support of geographic information technology,the remote sensing monitoring of soil moisture in the main stream of the Tarim River was realized from a macro perspective,wihich has a certain reference value for the ecological restoration of the main stream of Tarim River.The main research findings and innovations are as follows:(1)Through the study of soil water and salt of Populus euphratica forest samples in ten different habitats in the main stream of the Tarim River,it can be concluded that the soil water content shows an increasing trend with the increase of soil depth,and the results of variance analysis indicates that there are no significant differences in water content and salt content among different soil depths.From the lateral distance to the main stream of the Tarim River,the closer to the river,the higher the soil water content of each soil layer,and the increasing trend of soil salt content.The suitable conditions for the growth of Populus euphratica seedlings are soil water content of 16.75%～18.76%,the soil salt content is 0.08%～0.47%,the soil salt content is 4.55%～16.75%,the soil salt content is 0.%～1.36%When Populus euphratica is aging,the soil water content is less than 4.55%and the total salt content is more than 1.36%.(2)The population of young Populus euphratica in the main stream of Tarim River accounts for a relatively high proportion(33.47%of Class Ⅰ and Ⅱ),which belongs to the growth type population.In the static life table,the mortality of Class Ⅰ and Class Ⅱ of Populus euphratica are 39%and 50%respectively,and the life expectancy of Class Ⅲ of Populus euphratica is the highest,which is 10.04.The distribution pattern of Populus euphratica population is cluster distribution,and the aggregation intensity of Populus euphratica population in the main stream was in the main stream is upstream<midstream<downstream(3)MODIS image data can be used to monitor soil moisture in the main stream of Tarim River.Correlation analysis shows that the reflectivity of MODIS Band 7 is negatively correlated with soil moisture,which can reflect the change of soil moisture.Soil moisture and Band 7 reflectivity is fitted by one-dimensional linear regression,and the fitting formula is y=-0.45x+0.19,R2=0.47,F=60.38(4)The soil moisture in the upper,middle and lower reaches of the main stream of Tarim River varies greatly in space and time during the year.Comparative analysis of different river sections in the same period:soil moisture in the upper reaches of the main stream of Tarim River>soil moisture in the middle reaches>soil moisture in the lower reaches.The comparative analysis of the same river section in different periods:soil moisture increment in the upper reaches of Tarim River>soil moisture increment in the middle reaches of Tarim River>soil moisture increment in the lower reaches of Tarim River;The soil moisture(0⒍10 cm)in the main stream of Tarim River has a great seasonal variation,and reached the maximum soil moisture(6.29%)in June of 2019.The lowest soil moisture for the whole year was February,which was only about 4.16%.In the past ten years,the data of soil moisture in February of each year has changed greatly,the coefficient of variation was over 15%,and the data of soil moisture in the lower reaches changed greatly,the coefficient of variation was over 15%(5)The growth and regeneration of Populus euphratica forest is closely related to the depth of groundwater.The self-designed groundwater level monitoring device and the ecological water demand prediction and early warning method of Populus euphratica forest were used to monitor the ecological water demand of Populus euphratica in the main stream of Tarim River.The monitoring data can provide a reference for the improvement of ecological water supply of Populus euphratica and the regulation of water resources and groundwater level in the region,and provide scientific basis for the hydrological ecological research of the main stream of Tarim River.