A Study On The Temporal And Spatial Evolution Of Desertification In The Mu Us Sandy Land Combined With Multi-source Remote Sensing Technology

There is a vast desertification area in northern my country,which seriously threatens the environmental quality and social stability of the surrounding areas.Therefore,since the 1970 s and 1980 s,my country has launched a series of ecological projects and desertification prevention and control norms,which have greatly alleviated the erosion of sandstorm disasters in the north.Among them,the management of the Mu Us Sandy Land is the most successful.However,few current studies have combined optical and In SAR technology and other remote sensing products to analyze and explain the desertification reversal process in the Mu Us Sandy Land.Therefore,this paper systematically researches and analyzes the Mu Us Sandy Land by combining optical matching technology,In SAR-Stacking technology,SAR multi-temporal coherence analysis technology,NDVI time series,ERA5-Land meteorological data and the planting range of the Three-North Shelterbelt.The main research contents are as follows:(1)A quantitative method for obtaining the spatiotemporal parameters of sand dune migration is proposed.Based on the COSI-Corr software and the Landsat-5/8 image data of the Mu Us Sandy Land,this paper proposes a quantitative acquisition method for the temporal and spatial parameters of sand dune migration.The method is modularized and divided into 4 modules.In module 1,this paper proposes a baseline network construction strategy for Landsat-5 images,which reduces the systematic error of the initial offset field by limiting the baseline variables of 3 image pairs,and controls the number of image pairs within The number of images is between 2 and 3 times to balance the computational efficiency and the accuracy requirements of time series inversion.And in module 3,the main error source,elimination method and elimination effect of Landsat-5/8 initial offset field are analyzed statistically.Finally,this method was used to quantify the sand dune migration pattern in Mu Us from 1986 to 2020,and the results were consistent with the wind conditions.And based on the results,the accuracy of the offset field after each processing step of the method is quantitatively evaluated,which verifies the effectiveness and feasibility of the method in this paper.The quantitative monitoring results complemented the monitoring gap of the temporal and spatial parameters of dune migration in the Mu Us Sandy Land from 1986 to 2020.(2)For the first time,the In SAR-Stacking technology and the multi-temporal coherence analysis technology of SAR were used to monitor the surface deformation and dune stability of the Mu Us Sandy Land.The law of surface deformation and the characteristics of dune stability.There are many subsidence areas in the northeastern part of the Mu Us Sandy Land from 2017 to 2020,and the subsidence rate is between 0.06 m/year and 0.15 m/year.The subsidence may be due to the excessive extraction of groundwater from large-scale afforestation and agricultural and animal husbandry irrigation.cause.The weighted average coherence MSTCW and the weighted time stability index TSIW calculated by SAR multi-temporal coherence analysis technology can detect unstable ground objects such as water bodies and active sand dunes in the Mu Us Sandy Land,but TSIW has better distinguishability and is more conducive to long-term Identification of unstable ground objects.(3)Combined with multi-source remote sensing technology and products,the desertification process of the Mu Us Sandy Land from 1986 to 2020 was analyzed from multiple perspectives,and the response mechanism of its dune-vegetation-climate-policy over the past few decades was revealed.The successful management of desertification in the Mu Us Sandy Land is closely related to climate change,vegetation growth and policy promotion,which benefits from a benign response mechanism.Among them,vegetation coverage and climate,vegetation coverage and sand dune migration have interactive effects,while policies have unidirectional effects on vegetation coverage,local climate on sand dune migration,and the Three-North Shelterbelt on sand dune migration.The results show that the Three-North Shelterbelt Project,which was implemented in 1978,played a key role in the reversal of desertification in the Mu Us Sandy Land,while previous studies may have overestimated the driving role of climatic factors.However,the excessive extraction of groundwater caused by large-scale afforestation and irrigation of agriculture and animal husbandry may aggravate the imbalance of water storage in Mu Us and lead to surface deformation.