| Desertification has caused serious social,economic and environmental problems.Sand-control has been conducted in the Mu us Desert in China since 60 years ago and reached remarkable achievement.However,there is no clear rules on how to comprehensively and quantitatively evaluate the effectiveness of the sand-control activities.Therefore,this thesis intends to use multi-temporal satellite remote sensing images(Landsat TM,ETM+and OLI),combined with social and economic data,to monitor the existing desertification progress and evaluate comprehensively the effectiveness of desertification combating in the Mu Us desert and its 15 surrounding counties.Firstly,land classification using multitemporal remote sensing images was carried out based on field survey,and sandy land or desert was accurately classified out.Then,the areas,proportion and biophysical change of sand-control and desertification were quantitatively evaluated by post-classification differencing and indicator differencing on GDVI(Generalized Difference Vegetation Index).The spatial distribution characteristics of sandy land or desert were analyzed by means of geographic concentration degree,spatial trend analysis,Moran’s Index and gravity center migration model.Finally,a set of indicators were selected from climate,social economy,ecological environment and human activities for coupling analysis at county and pixel scales to reveal the driving forces and spatial determinants of desertification by multiple linear regression and logistic regression analyses.The results are presented as follows:(1)Spatial distribution maps of deserts and desertification were produced.We got to know that actually,5106.22 km2 of desert is still existing in Mu Us,6.92%of the study area.These deserts are mainly distributed in the banners of Uxin,Otogqian,Otog and Lingwu City,and the desert distribution showed a pattern of larger in the east and smaller in the west,smaller in the north and south and larger in the middle.(2)The area,proportion and degree of sand-control were quantitatively evaluated.From 1990 to 2020,the area of desert in Mu Us had decreased by 8712.23 km~2,or rather,63.05%of the deserts has been controlled,and the GDVI increased by 0.3518 in the managed area from 1990 to 2020.The effectiveness of sand-control showed a spatial variability,that is,the marginal area of desert is obviously better controlled than the heartland of desert.(3)Based on the two kinds of regression analysis,understanding on the desertification driving force was achieved.The results of model show that:at county-scale,the increase of mean wind speed is an important driving factor of desertification,while at the pixel-scale,the increase of wind speed and the increase of distance from roads are the spatial determinants of desertification.Meanwhile,the driving force model of sand-control shows that the increase in meat(pork,beef and mutton)product,per capita net income of farmers and herdsmen,sheep number and precipitation promotes the sand-control.In conclusion,national and local policies and ecological protection projects on sand-control have achieved good results in Mu Us desert.Meanwhile,reasonable socio-economic activities are extremely important for desertification combating.The quantitative evaluation method based on remote sensing and the multi-scale quantitative model of desertification driving force proposed in this paper can comprehensively evaluate the effectiveness of sand-control in various regions from multiple perspectives and reveal the driving factors and spatial determinants of desertification.It can provide technical and theoretical reference for sand-control and evaluation in local and other areas. |
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