Dynamic Monitoring And Risk Assessment Of Soil Salinization In Manasi River Basin,Xinjiang

Soil salinization is one of the main forms of soil degradation in arid and semi-arid areas.The aggravation of salinization makes the crop yield decrease and the abandoned ploughing increases,which seriously threatens the sustainable development of agriculture,forest and animal husbandry.As an important reserve resource area of cultivated land in China,Xinjiang is affected by topography,climate,natural conditions of soil and water as well as irrational exploitation and utilization.The ecological environment is very fragile,and the soil salinization is serious(Qiao M,2012).It is of great significance to prevent the further deterioration of soil salinization and the sustainable development of ecological environment by the real-time and accurate information of soil salinization and the scientific and rational evaluation of Soil Salinization Risk.In this study,the Manasi River Basin in the typical agricultural development zone of Xinjiang was selected as the research area,and the 3 phase Landsat multispectral remote sensing images were used as the basic data sources.Remote sensing technology,geographic information technology and field survey data were used to systematically study the dynamic change process of soil salinization in the Manasi River Basin in the last 27 years.The temporal and spatial variation of soil salinization in different degrees in the region was changed,and the risk of soil salinization was evaluated and dynamic analyzed by selecting land use type,salt index,elevation and vegetation cover as evaluation factors.The following conclusions are obtained:(1)Through the pre processing of different period images of the study area,the classification map of soil salinization in the study area is drawn by the combination of supervised classification and expert decision tree,which is verified by the obfuscation matrix method,Overall Accuracy=94.01% and Kappa Coefficient=0.84.The classification method combining the supervised classification and decision tree can provide the technical theory support for the high precision extraction of salinized soil and the dynamic monitoring of soil salinization.(2)The temporal and spatial dynamic changes of salinization in the last 27 years were analyzed with the transfer matrix.In space,the overall trend of soil salinization in the oasis area was alleviated,and the severe salinization in the northern part of the region was aggravated.In time,the total body of soil salinization was reduced,especially from 2000 to 20.The 16 year process has become a significant downward trend.For the severe soil salinization,the most dramatic region is around Manasi Lake in the north,which is due to the changes in the water of Manasi Lake in different years to cause soil salinization,and in the oasis region,the soil salinization degree of this region is improved by the continuous action of human activities.(3)Soil salinization is caused by natural factors and human activities.The natural factors are long-term and relatively stable process,and the influence of human activities on the formation of soil salinization is obvious.In the process of human social development,how to organize human activities in an orderly way,make rational use of land and reasonable irrigation and drainage ratio,is of great significance to regulating the hydrological process of the Manasi River Basin and ensuring the balance of water and salt in the soil.To a certain extent,it can maximize the control of the soil salinization in the hydrological process.It ensures the coordination of material,energy and information in the study area.(4)The temporal and spatial distribution and change of soil salinization ecological risk in the last 27 years were analyzed by transfer matrix.It was found that the soil salinization of the spring overflow zone on the edge of the Manasi River Basin and alluvial fan was higher,while the risk of soil salinization in the surrounding and part of the irrigation area of Manasi Lake reached a very high level.In the last 27 years,the medium and high risk of soil salinization in the research area have been changed sharply,the land area of moderate risk is increasing,the land area of high risk is decreasing,and the area of high risk of salinization in the study is reduced first and then increased.Therefore,the soil salinization in the research area has been known in recent years.The change of fan margin in alluvial alluvial fan of Manasi river is more obvious.For the area of high risk of salinization in the Manasi River Basin,for example,the alluvial fan margin area in the study area and the surrounding area around the reservoir,on the one hand,the management of water resources should be strengthened.On the other hand,the rational prevention and control and control of salinization should be strengthened.