The problem of land desertification in northwest region of China is serious and the ecological environment is severe. It is of great significance to clarify the spatio-temporal variation characteristics and driving factors of vegetation cover in this area for ecological environment protection. In this study， MOD13A3 products in this area were used as the data source to obtain the NDVI sequence set from 2000 to 2019 through the maximum value synthesis method. Trend analysis， anomaly analysis， Hurst index， geographic detector， correlation analysis and residue analysis were used to analyze the spatiotemporal variation characteristics and impact factors of vegetation cover in the study area. The results showed that ：（1） In recent 20 years， the vegetation coverage in the study area showed an overall growth trend， with an increase rate of 0.0027·a^-1 and an average NDVI of 0.252. However， the growth rate of the Yellow River basin area （0.0062·a^-1） is higher than that of the semi-arid grassland area （0.0026·a^-1） and inland arid area （0.0018·a^-1）. （2） The vegetation coverage in the study area is on the rise， accounting for 55.77% of the total area， while the degraded area accounts for 3.76% of the total area. The increased land use types were mainly tillage， forest and grassland. The area with sustainable change trend of vegetation cover accounted for 31.87% of the total area， the sustainable improvement （17.04%） was greater than the sustainable degradation （1.27%）， and the growth and sustainable growth of the Yellow River basin area were the best. （3） The main contributing factors that affect the spatial distribution of vegetation cover are precipitation， temperature， sunshine and relative humidity in order of influence， but the influence degree of each sub-region is slightly different. The spatial distribution of arid areas in the Yellow River basin and inland is most affected by precipitation， and the semi-arid grassland is most affected by sunshine. （4） Vegetation cover changes is mainly driven by natural factors and human activities， and natural factors on the growth of vegetation role in promoting are greater than human activity， and natural factors on vegetation cover change in the rate of contribution are higher. The results of this study can provide reference for assessing the ecological environment change under the background of climate change in northwest China.

The operational agricultural drought monitoring system is a powerful tool for monitoring and predicting agricultural drought， as well as agricultural risk assessment and prevention. In order to better promote the development of the operationalization of agricultural drought monitoring， we systematically reviewed four types of commonly used drought indices based on meteorological variables， soil moisture， vegetation status and multivariate， and analyzed the characteristics of operational agricultural drought monitoring systems in the United States， China， Europe and the United Nations Food and Agriculture Organization， etc. in detail， and discussed the problems existing in operational agricultural drought monitoring systems. For example， the quality and fusion of data are unstable， the construction of the comprehensive drought index is uncertain， the temporal resolution of monitoring needs to be improved， and the hydrological conditions and the growth process of crops are not considered. Looking forward to the future， the operational agricultural drought monitoring system should develop further from using multi-source data to monitor drought， considering regional spatial and temporal differences and the accumulation and lag between different indicators when constructing comprehensive indicators， strengthening the role of machine and deep learning in the construction of comprehensive indices， developing daily time-scale monitoring of drought to deal with the occurrence of flash drought events， strengthening the role of crop growth process models and advanced technical means in drought monitoring.

This study focuses on wind-blown sand problems along highways， reviews the development history， current situation and characteristics of highways in sand region， and systematically summarizes wind-blown sand damage and achievements of sand control in China's sandy highways， according to wind-dynamical environments along highways， sand damage characteristics， disaster-causing mechanisms， wind-blown sand prevention and control measures along highway， structural composition and benefits of sand-control system. Considering that the drifting sands environments on both sides of the highway， gobi surface and the regional differences in natural environments， while taking into account the sand controlling， green corridor construction and landscape efficacy， and ensuring the continuous stability and functional perfection of road protection systems in sandy areas， three representative sand-control mode have been systematically sorted out to ensure the continued stability and functional perfection of the protection system for highways in sandy areas. Based on the practical needs of the increasing improvement of highway network skeleton system and the challenges of safe operation of highways in sandy areas， the focus is on strengthening the engineering and technical foundation of highway wind-blown sand control and improving the capacity of blown sand hazards control， and condensing and proposing the future research focus and development trend of sandy roads.

According to the requirement from the First National Conference on Combating Desert in November， 1958， the Chinese Academy of Sciences organized rapidly the Scientific Investigation Team for Combating Deserts （SITCD， CAS） in the January， 1959 and carried out fieldwork soon， which was the maximal national desert comprehensive survey up to now with the widest areas， the most complete majors， the most diverse team members， and the most concentrated campaigns. This paper， as the pioneering part （1） of the practice on prevention and control of aeolian desertification and the development of desert science in China for 70 years， briefly retrospect the results and experience from a smaller scale desert survey in 1957 and 1958， which was cooperative implemented by Chinese Academy of Sciences and Academy of Sciences of the USSR， and talk over the achievement and positive impacts from the desert comprehensive survey of the Scientific Investigation Team for Combating Deserts， Chinese Academy of Sciences in 1959. Based on the references and available data， every Investigation Team Branch for different desert and Gobi in Northern China had reported the progression of field-survey and the analysis and research mostly focused on the distribution of deserts/Gobi， different genetic types， sand material source area， hazards of sand blown， desert control measures， socioeconomic status， agriculture， forestry， and animal husbandry production. We also specially discus and praise highly the followings milestone events such as （1） the pioneering and development of desert science is the practiced paragon of “task promoting subject development”， （2） “national demand is our first choice” radiated the scientist’s enthusiasm and dedication spirit during 1950s， （3） professional selection and prominent contribution of 8 distinguished scientists， and （4） the international cooperation assisted development of desert science in China.

Desert is one of the important terrestrial ecosystems in Northern China and covers 1/5 of the land of China. Plant community is an important part of the desert ecosystem， which has important implications for the enhancement of Northern Ecological Shelter Zone， and for the implementation of state key ecological projects， as well as for the Belt and the Road Initiative and economic-social development. The surveying zone includes Tarim-Jungar basin deserts， Qinghai-Tibet Plateau desert， Alax-Hexi Corridor desert， West Edos and North-to-Yinshan desert， and semi-arid desert-like sandy lands in the middle and eastern Inner-Mongolia. A total of 2 300 sample sites were set up systematically to investigate vegetation types， species composition， spatial distribution， and habitat attributes of desert plant communities across northern China. There were 8 300 plant specimens， 50 000 habitat parameters， and 2 300 DNA bar-codes obtained in the present study. On this base， a report on the desert plant community types， characteristics and status， and the atlas of distribution of desert plant communities will be compiled， as well as a monitoring system will be built for future long-term surveying. The data supporting the above report， atlas， and monitoring system will be pooled into a data bank of the major desert plant communities in China， being shared through the National Cryosphere Desert Data Center （NCDC）. This project and the output will provide solid support for combating desertification， plant conservation and sustainable development in the northern part of China.

On the basis of field survey， Ground-penetrating radar （GPR） was used to detect the internal structure of vegetation linear dunes in the southeastern Gurbantunggut Desert， and radar facies image information was obtained. Combined with regional natural geography and morphological characteristics， the evolution model of vegetation linear dunes internal structure was preliminarily discussed. The results indicate that： （1） GPR reveals the shallow （3-5 m） structure information below the dune surface， which can identify high-angle dipping， convex and wedge cross-bedding in the middle-upper part of dunes and crest， and sub-horizontal to low-angle dipping bedding in interdunes and the middle-lower part of dunes， which reflects the strong wind erosion and deposition activity in the upper part of dune， and the accretion in the middle-lower parts of dune wings and interdunes. （2） From desert edge to the center， the shallow sedimentary structure assemblage of dune slope changes from asymmetrical to symmetrical， the dune cross-section morphology showed the same variation， but no evidence of lateral dune migration have been found. （3） According to different scale dune structure sequence， the evolution mode could be divided into four stages： shrub dunes， shadow shrub dunes， longitudinal dune chains and vegetation linear dunes. With the continuous merging and integration of overlapping shrub dunes， the width and height of linear dunes increase， frequent wind activity at the dune crest， and the types of high-angle dipping， convex and wedge cross-bedding increase. （4） The causes of massive bedding （below 3-5 m， not hit the bottom） and GPR signal attenuation should be further verified. Besides， to systematic clarify the evolution process of vegetation linear dunes in study area， it is necessary to supplement more GPR data and chronology study.

The global environment has undergone profound changes since the industrial revolution. Due to the poor stability， anti-interference and self-recovery abilities of ecosystems， global change has led to the decline of natural resource supply capacity， land degradation， biodiversity reduction， frequent disasters， and increased ecosystem risks in ecologically vulnerable regions. Therefore， it is urgent to implement researches on global change risk in ecologically vulnerable regions. This study mainly summarized the researches on the risk sources and the impact of global change on ecologically vulnerable areas of China， as well as the response to global change. The study then put forward the future strategies for global change to promote the in-depth understanding of the response of ecosystem to global change and improve the ability to cope with global change in typically and ecologically vulnerable regions of China. The risk of global change in ecologically vulnerable regions comes from the impact of environmental change on complex systems of natural， social， and economic. Global change has a great impact on the ecosystem of ecologically vulnerable regions， with climate change as the main symbol and human activities as the main driving force. Global change causes extreme climate events， frequent disasters， land degradation， the reduction of vegetation productivity and biodiversity， the melting of glaciers and frozen soil， and the change of water resources pattern， which may intensify under the continuous impact of global change in the future. However， the implementation of ecological construction project has significantly improved the ecological environment. In the future， we should strengthen the researches on the coupling of natural， social， and economic systems， the monitoring of resources and environmental factors， and the risk assessment and early warning of global change.

Desert inverted channel is a special river-liked positive landform in arid land， which contains information of significant environmental change that results in riverbed revising. Following the geomorphology law， this study investigated desert inverted channels around the world based on the published literature and our field observation. We summarized its spatial distribution， morphological characteristics， material composition， sedimentary structure and formation mechanism. Generally， inverted channels developed in the main sand seas around world. Its surface is composed of debris or cemented materials， subsurface consist of sandy-clay materials with a relatively soft texture. Due to the differential erosion of the sediments in the riverbed and riverbank， the riverbed is relatively elevated. Although some progress has been made in the study of deserts inverted channels on Earth， further research needs to be carried out in terms of their formation age and climatic significance. Meanwhile， more studies should be carried out to compare with the different types of inverted channels on Mars. This will provide important basis for revealing the hydrological activities and environmental changes on Mars.

The arid and semi-arid regions cover more than half of China's land area， which are sensitive to global climate change and human activities with fragile ecological environment. Extreme climate events are frequent and strong in those regions， where the climate anomalies are not only modulated by the internal atmospheric variability， but also affected by the underlying surfaces such as sea surface temperature， sea ice and snow cover. These physical factors play a key role in the climate anomalies in arid and semi-arid regions. This article systematically reviews and sorts out the effects of these physical factors on climate anomalies in arid and semi-arid regions of China. Studies have shown that atmospheric teleconnection is an internal influencing factor of climate anomalies， and the circulation anomalies caused by its phase transition will cause climate anomalies in arid and semi-arid regions by regulating the position of jet stream， planetary wave activity， blocking intensity， and the location of trough-ridge. Sea surface temperature affects the climate anomalies in arid and semi-arid regions by influencing the intensity of monsoon and Walker circulation and the location of western Pacific subtropical high， in the meantime stimulating the response of atmospheric Rossby waves. Moreover， snow cover changes the thermal conditions of the underlying surfaces such as surface radiation and soil temperature and humidity through the albedo effect and hydrological effect， and then has a significant effect on the temperature and precipitation in arid and semi-arid regions by diabatic heating or changing atmospheric baroclinicity. On the basis of summarizing the existing research progresses and achievements， the paper points out that the synergistic mechanism among different factors and the contribution of each factor to the climate anomalies in the arid and semi-arid regions of China still need further research.

Based on the analysis of the morphology， grain-size characteristics and wind regimes among three different dunes （barchan， parabolic dune and reversing dune） in Mu Us Sandy Land， we investigated the response of dune forms and their surface grain-size parameters to the change of external conditions （i.e.， wind regimes and vegetation cover）. The results show that the mean grain-size （ M_{\mathrm{Z}} ） of barchan decreases gradually from the bottom to the top of the stoss face， and the sorting becomes better， but the fine grain-size and poor sorting appear in the middle of the stoss face. With the increase of vegetation cover， barchan gradually transforms into the parabolic dune， and the near-surface sand transport and incoming sand supply are also limited. As a result， the mean grain size of the parabolic dune becomes coarser from the bottom to the top of the stoss face， and the sorting gradually becomes better. Seasonal wind regimes in Mu Us Sandy Land promoted the development of reversing dunes and reorganized sand grain-size characteristics. Under the influence of wind erosion in summer， eroded sand deposited on the upper of the stoss face and dune crestline flip. Thus， the mean grain-size and sorting are getting coarser and better in the dune crestal area， respectively.

The characteristics of regional sandstorms in Northwest of China from 2000 to 2020 were analyzed using ground observation data， and based on climatic dynamic factors， temperature， precipitation and NDVI data to analyse the causes of regional sandstorms changes in Northwest of China. The study results show that from 2000 to 2020， the annual total number of days of regional sandstorms in Northwest of China showed a fluctuating downward trend， and there were two high （low） frequency periods. Spring is the season of high incidence of regional sandstorms， of which the total number of days in April is the highest， reaching 47 days. Compared with the first ten days and the middle ten days of the month， regional sandstorms are more likely to occur in the last ten days of each spring months. The Tarim Basin in southern Xinjiang and central-western Inner Mongolia and the Hexi in Gansu are frequent areas of regional sandstorms in Northwest of China with total number of days more than 10 days， and the total number of days in most other places of Northwest of China is less than 8 days. The area index and intensity index of the polar vortex in the northern hemisphere and the polar vortex intensity index in Asia have a significant positive correlation with the number of days of regional sandstorms. The transition of the northern hemisphere polar vortex from an expansion period to a contraction period and the weakening of its intensity are important climatic dynamic factors for the reduction of regional sandstorms in Northwest of China. The annual （spring） precipitation and average NDVI in Northwest of China are significantly negatively correlated with the number of days of regional sandstorms. In the past 21 years， the climate in most parts of the northwest region has tended to be warm and humid， and the vegetation cover has improved as the main trend. The transformation is conducive to the shrinkage of the desertified area and reduces the occurrence of non-imported sandstorms.

Populus euphratica with heteromorphic leaves plays an irreplaceable role in maintaining the ecological balance in the arid desert area of Northwest China. It is of great significance to study the relationship between branch and leaf morphology and biomass and to explore the strategy of resource allocation for P. euphratica. By measuring the morphological characters and biomass of annual branches and leaves of male and female P. euphratica at different diameter classes， we studied the relationship between male and female branches and leaves of P. euphratica， at different development stages and canopy. The results showed that the number of leaves of male and female plants decreased， and the diameter of branches， petiole length， diameter of the petiole， leaf area， the number of leaves， branch dry weight， and dry weight increased with the increase of diameter class. Further analysis showed that there was an allometric relationship between the branch and leaf morphology of male and female P. euphratica with different diameter classes. The morphological transformation speed between branches and leaves was faster in males， while the biomass conversion efficiency between the branches and leaves was higher in females. Also， there was an allometric growth relationship between the branches and leaf morphology of male and female P. euphratica at different canopy heights. With the change in canopy height， the transformation speed between the branches and leaves of female plants was faster， while the biomass transformation efficiency of male plants was higher. There was an allometric growth relationship between male and female branches， leaf morphology， branch dry weight， leaf dry weight， and leaf morphology of P. euphratica in different diameter classes or different canopy layers. In the high canopy and mature development stages， P. euphratica may efficiently provide water and mineral elements for the leaves with large petiole length， the diameter of the petiole， and leaf area through shorter and thicker annual branches. It provides a theoretical basis for further understanding of the differences in environmental adaptability between male and female P. euphratica and the distribution of male and female in the future planting.

The arid and semi-arid areas in China are the important agricultural development regions. There are serious wind-erosion and dust emission in these regions， which threaten the sustainable development of agriculture and the balance of ecosystem. At present， dust emission schemes in weather and climate models only consider wind erosion over desert， and those occurred in farmland are seriously ignored or underestimated. It leads to large uncertainty for estimating dust physical processes and its climate impacts. This review summarizes scientific findings that have been published regarding the characteristics and parameterization of wind erosion in arid and semi-arid areas of China since the 1950s. The research progress and existing problems of wind erosion observation and numerical simulation in arid and semi-arid areas of China are discussed. It is of great significance for preventing and controlling wind-erosion， land desertification and understanding the impact of land use change on air pollution in arid and semi-arid areas of China in future.

Taking 66 cities in the Yellow River Basin as the research object， and selecting 34 indicators from new development philosophy to construct a high-quality development index system， the entropy method was used to calculate the high-quality development level of the Yellow River Basin， and the high-quality development level and the average growth volume and average growth rate of the high-quality development level are used as variables to analyze spatial correlation and pattern evolution characteristics of high-quality development in the Yellow River Basin from 2000 to 2020 by ways of ESDA. The result shows that：（1）Similar high-quality development levels cities in the Yellow River Basin had spatial correlation during the study period， and the high-quality development levels increased amid fluctuations， and the development tended to be balanced. （2） From 2000 to 2015， the average growth volume and average growth rate of high-quality development in the Yellow River Basin had significant spatial correlations， the evolution characteristics tended to shift from strong agglomerations to weak ones and to strong ones， cities with similar growth were close to each other； but in 2015-2020， cities with similar growth were randomly distributed and spatially uncorrelated. （3） The spatial pattern of high-quality development average growth volume and average growth rate changed greatly， with high-value regions migration from the east to middle and then to the west. The number of high-value regions was greater than the number of low-value regions， and the overall high-quality development speed of the Yellow River Basin was relatively fast. Average growth volume hot and cold areas changed from a relative dispersion to a centralized distribution one and then to a decentralized layout one， and the average growth rate of similar cities evolved from relatively scattered to concentrated and contiguous one， and different levels of hot and cold spots were distributed in layers.（4）Regions with relatively weaker development foundations displayed a higher growth rate， and urban agglomerations were still key areas to drive high-quality development in the Yellow River Basin. In the future， we should adhere to the new development philosophy， innovate the urban agglomeration cooperation model， and promote the high-quality integrated development of the Yellow River Basin.

The Second National Conference on Combating Desert had been held in September， 1959 in Urumqi， which further to demonstrate the attention and expectation from the state's responsibility for prevention and control of aeolian desertification. In the years that followed， the Scientific Investigation Team for Combating Deserts， CAS and relevant provincial （autonomous region） departments carried out a more systematic investigation， experiment， research and practice. This paper focus on following three parts： （1） Based on the experimental investigations in the filed fixed station and semi-fixed station to comprehensive control of the desert， the author discusses some progress and function in the selection and introduction of plant species for moving dune fixing and optimal allocation， the mechanical sand fixation， the moving dune's moisture state and its stabilization and afforestation， the transpiration intensity of the major psammophytes， the process of soil formation in the fixed quicksand area and the dune soil microorganisms， etc. （2） Based on the research results of several major scientific and technological issues in prevention and control of aeolian desertification， the author discusses some main progress and function in the cause of the desert， the relationship between moving regular pattern of sand dune and wind prevention and sand-fixation， the assessment of aircraft seeding， the vegetation types and their evolution law in desert， the psammophytes characteristics， rational use of grassland in desert， the classification of the Gobi Desert and its transformation and utilization， water resources and their utilization， etc. （3） The author expounds briefly the process and the achievements of prevention and control of aeolian desertification during the establishment of the People's Republic of China （PRC） from 1949 to 1965，which affirmed the research objectives， formed the spirit of pioneering dedication and effective research method， and formed preliminarily in theory， practice， team and platform of the desert science. Thus laid the foundation and conditions for the start-up and pioneering of China Desert Science， so that let it enter the development period smoothly.

The soil erosion in China was characterized by various types and complicated processes. It is of great significance to accurately quantify the temporal variation and spatial patterns of soil wind erosion and water erosion intensity in watersheds， to identify regional dominant erosion types for reasonable arrangement of soil and water conservation measures. This study quantified the temporal and spatial patterns and evolution of soil wind erosion and water erosion intensity in the Yellow River Basin from 2000 to 2020 combined remote sensing monitoring， field survey， and model simulation， revealed soil erosion type area， and its significance to zoning control of soil erosion. The results showed that： （1） The intensity of soil wind erosion and water erosion in the region showed a downward trend as a whole， while the wind erosion and water erosion showed a fluctuation and continuous decrease， respectively. In the past 20 years， the modulus of soil wind erosion and soil water erosion have respectively decreased at a rate of 18.88 t·km^-2·a^-1 and 34.98 t·km^-2·a^-1. （2） The type zones dominated by soil wind erosion and soil water erosion accounted for 16.35% and 83.65% of the total land area of the region， respectively， and the overall performance of soil erosion type zoning from north to south was the transition from soil wind erosion to water erosion. The areas dominated by soil wind erosion were distributed in the upper reaches of the main stream of the Yellow River and the Ordos inland flow area， accounting for 41.53% and 28.57% of the area of soil wind erosion area， respectively. Moderate erosion intensity of soil wind erosion accounted for the largest proportion， 24.72%. The areas dominated by soil water erosion were distributed in the middle reaches of the Yellow River （25.04%）， the Wei River-Yiluo River system （22.06%）， the source water system of the Yellow River （18.60%）， the upper reaches of the Yellow River （15.49%）， Huangshui-Taohe River System （13.35%）. Soil water erosion was mainly micro-erosion intensity， accounting for 49.30% of the soil water erosion area， and light （17.28%）， moderate （14.98%） and strong erosion intensity （11.95%） were widely staggered. （3） Desertification control project and soil and water conservation engineering made soil erosion modulus and erosion intensity decrease significantly in areas with strong wind and water erosion. According to the zoning characteristics of soil erosion types， the measures of vegetation restoration and agricultural oases in the soil wind erosion area were discussed. Agricultural cultivation measures， forest and grass measures and engineering measures are used to protect and control soil water erosion areas， in order to provide scientific guidance for the high-quality development of the ecosystem in the Yellow River Basin.

Although the important role of dew in arid system has been widely recognized， its characteristics of temporal and spatial variation under sand-fixing shrubs has been paid less attention. To better understand the influence of surface dew under sand-fixing shrubs， three typical artificial sand-fixing shrubs （Salix psammophila，Caragana korshinskii and Artemisia ordosica） on the southern edge of the Mu Us Sandy Land， Northern China were selected and the bare sand without the effect of sand-fixing shrubs was used as the control in this study. The deposition and evaporation characteristics of surface dew in different positions （root， 1/2 crown width and periphery crown width） and directions （east， south， west and north） under sand-fixing shrubs were measured by micro-lysimeter. The results showed：（1） compared with the control， the presence of sand-fixing shrubs significantly reduced the amount of surface dew， and the amount of dew under Salix psammophila， Artemisia ordosica and Caragana korshinskii decreased by 29%， 32% and 33% respectively. （2） The amount of surface dew under different types of sand-fixing shrubs showed a significant increasing trend from the inside to the outside， but the difference in the amount of surface dew in different directions was not significant. （3） The existence of sand-fixing shrubs slowed down the deposition and evaporation of surface dew， that was， the formation of dew started at 19:00 at night， ended at 08:00 the next day， and evaporated from 13:00-15:00. The deposition process of dew showed an overall trend of increasing， fluctuating and increasing. The surface dew under Caragana korshinskii and Artemisia ordosica even evaporated a little from 03:00 to 05:00， and the evaporation process showed a steady downward trend. （4） The formation process of dew had a significant positive correlation with relative humidity， and a significant negative correlation with atmospheric temperature and surface temperature. Sand-fixing shrubs buffered surface temperature changes by intercepting solar radiation to slow down the deposition and evaporation processes of dew.

Revealing the dynamic evolution of the sandy ecosystem service value and its stability network pattern has important practical guiding significance for the regional management of degraded desert and the adjustment of the agricultural， forestry and animal husbandry industry structure. Based on the land use change data since 1986， this paper statistically analyzes the temporal and spatial differentiation of the ecosystem service value （ESV） of the Mu Us Sandy Land. It takes the maximization of ecological service value as the goal and strategy， and uses the least resistance model （MCR） to discussing the evolution law of the ecological network pattern in the Mu Us Sandy Land. The results show that： （1） In the past 34 years， with the progress of the Mu Us Sandy Land oasis process， woodland has replaced desert to become the dominant land type in the Mu Us Sandy Land， and the forest and grass coverage rate reach 71.38% in 2020. （2） From 1986 to 2020， the overall ecological service value of the Mu Us Sandy Land has increased by 19.876 billion yuan. During the process of oasis， the growth rate of desert ecological service value from 1986 to 2006 and 2006 to 2020 was 251 million yuan·yr^-1 and 1.062 billion yuan·yr^-1 respectively； from a spatial point of view， extremely high ecological service value areas were concentrated in Henan Township and Maugaitu Sumu， and has gradually expanded to Sumitusum， Gartu Town and other areas since 2016. （3） The ecological network pattern is obviously different， namely the northwest area where the ecological network is sparse， mainly sand reclamation land， mobile sand dunes and semi-mobile sand dunes； and the southeast area with dense ecological network is covered by forests and grasses. High fixed desert and areas with rich water resources in rivers and lakes are the main areas， and with the migration of high value points of ecological service value， the stability network structure shifts to the northeast direction year by year.

Microorganisms are an important part of the desert ecosystem and are of great significance to the function and stability of the ecosystem. The current research on desert microorganisms in our country basically covers the main desert areas. This paper summarizes the progress of microbiology research methods， the composition and diversity of desert microbial communities， the distribution characteristics and influencing factors of desert microbial communities， functional diversity of desert microbial communities， and microbial resources based on the existing research results of sandy areas in our country. It is expected to provide an important basis for the development and utilization of microbial resources in sandy areas.

The restoration and reconstruction of reasonable vegetation coverage and soil habitat， and the maintenance of ecosystem stability and sustainable development are important objectives of desertification land govern in arid and semi-arid regions. As an effective and economical environmental protection material for water conservation， soil improvement and plant growth， eco-mat has been widely used in desertification control. The study on the influence of eco-mat laying on sand fixation and soil temperature and humidity can provide theoretical basis for wind prevention， sand fixation and vegetation construction in sandy area. This paper takes sand dunes covered by different eco-mats and mobile sand dunes （control area） in the southeast edge of Tengger Desert as the research object， to analyze the influence rule of eco-mat laying on wind-sand flow， soil temperature and soil moisture. The results indicated that eco-mats significantly increased the soil surface roughness of quicksand and decreased the sediment transport. The surface roughness of eco-mats experimental plots for pin shape laying with grass seed， pin shape laying without grass seed， strip shape laying with grass seed， strip shape laying without grass seed was 45， 22， 29 and 15 times as much as that of the surface layer of quicksand， the surface sediment transport for 0 to 20 cm was reduced by 90.57%， 87.14%， 88.14%， and 86.71% compared to quicksand， respectively. When the temperature was low， the soil temperature of 0-20 cm layer under eco-mats coverage was lower than that of quicksand， the result was opposite when the soil temperature wad high. Eco-mats laying increased the soil moisture content of 0-100 cm layer， only the value of 0-20 cm layer was lower than the quicksand， the soil moisture content of 40-60 cm， 60-80 cm and 80-100 cm was 1.61， 1.28 and 1.83 times of that of quicksand， respectively. Eco-mats coverage plays an important role in increasing surface roughness， reducing sediment transport， heat preservation， reducing evaporation， and maintaining soil moisture， which provides favorable conditions for the survival and growth of vegetation in sandy areas.

In the context of the realization of the task of poverty alleviation in the new era， improving the coordinated development level of new urbanization and rural revitalization is conducive to consolidating and expanding the achievements of poverty alleviation in Northwest China， continuously enhancing the endogenous development power， and accelerating its integration into the new pattern of western development. In view of this， the improved coupling coordination degree model is used to quantify the coordinated development degree of new urbanization and rural revitalization in Gansu Province， and the influencing factors of their coupling coordination degree are studied combined with panel Tobit model. The results show that： （1） The spatial distribution of new urbanization and rural revitalization is basically the same， which generally presents the spatial development pattern of Hexi region > central Gansu region > southeast Gansu region > southern ethnic minority region. （2） During 2013-2018， the coordinated development effect of new urbanization and rural revitalization in the whole province， Hexi region， central Gansu region and southern ethnic areas has gradually increased. The coupling and coordinated development shows the spatial differentiation characteristics of strong northwest and weak southeast. The coupling and coordination level of Hexi and central Gansu region is significantly higher than that of southeast and southern ethnic areas. （3） There are fewer cities and prefectures with the synchronous development of new urbanization and rural revitalization， and the cities and prefectures with lagging rural revitalization have increased significantly， which are concentrated in central Gansu and southeast Gansu region. （4） Government capacity， industrialization and transportation infrastructure level play a positive role in promoting the coupling and coordination level of the two， while fixed asset investment and urban-rural income gap are not conducive to the coordinated development of new urbanization and rural revitalization. The factors affecting the coupling coordination degree of the two have obvious regional heterogeneity.

Sediment grain size parameters are of great significance for studying material sources and measuring the energy size. The grain size characteristics of 45 surface sand samples from the top of the dunes in the Tengger Desert were measured， and the Drift Potential of four weather stations in the past 30 years was calculated. The results show that： （1） Samples are mainly composed of fine （71%） and medium sands （20%）， with main grain size of 2.38 Φ and sorting of 0.40 Φ. There are good linear relationships between grain size and sorting， grain size and skewness. （2） The very well and well-sorted samples are entirely distributed in the middle and southwest of the desert， the former tends to be nearly symmetrical and medium-kurtosis， and the probability cumulative curve is composed of two-distinctive populations， while the latter tends to be positive skewness， medium or leptokurtosis， and the probability cumulative curve is composed of three-distinctive populations. However， the sorting of desert edge is inconsistent， and the probability cumulative curve is composed of multi-different populations. （3） The direction of prevailing sand-driving wind in the study area is northwest wind. The northwest and northeast parts of the desert were characterized by intermediate wind energy environment， with the unimodal and complex wind direction. The southern and southeastern parts of the desert belong to low and intermediate wind energy environment respectively， both of which are bimodal wind direction. The main sources of dunes in this area should be local detritus act of the underlying fluvial and lacustrine sediments. The fluvial and lacustrine sediments at the edge of the desert provide sources for the dune sands in the central region， the dune sands in the southwestern part may have originated from alluvial-lacustrine deposits in the lower reaches of Shiyang River， and the wind sorting effect is long， while the dune sands at the edge of the desert should be derived from local detritus act of the alluvial and lacustrine sediments， and the wind sorting effect is insufficient. There is a certain relationship between the spatial distribution characteristics of grain size parameters and dune type and size.

Soil salinization is an important environmental problem that threatens lands in arid regions. Using remote sensing technology to dynamically monitor soil salinity and analyze the level and spatial distribution of soil salinity is conducive to grasping the current situation of soil salinization， and providing a theoretical basis for the sustainable utilization of land resources. However， most of the existing studies focus on the field scale， with the increasing scale of soil environmental problems， the extraction of regional patch information cannot macroscopically simulate and display the spatial distribution of the overall soil environment. To solve this problem， taking the Alxa area as an example， combined with remote sensing spectral index and measured soil salt data， this paper built soil salinization inversion model at regional scale by using the partial least squares regression （PLSR） method to realize the accurate simulation and quantitative monitoring of soil salinity in a large area. The results show that the verification accuracy of the model reaches 0.8788， reaching a very significant level， and the prediction results are more consistent with the actual situation， which can accurately simulate the soil salinization in the study area. Due to the comprehensive influence of terrain， climate， landscape type， agricultural activities， and land management， about 20% of the regional soil in Alxa shows varying degrees of salinization， and the most serious soil salinization areas are the riparian zone of the lower reaches of Heihe River， the west side of Yabulai Mountain， and the alluvial fan on the west side of Helan Mountain. This study can provide a feasible method for the rapid monitoring and remote sensing quantitative inversion of soil salinity in a large area， and provide a basis for the treatment of different degrees of salinized soil and land use management in this area.

Based on tree-ring width index （RWI）， normalized differential vegetation index （NDVI） and climate data in the arid areas of inland Asia， spatial statistical and correlation analysis methods are used to analyze the consistency of NDVI and RWI changes， discuss the climatic response of NDVI and RWI， and reveal the related factors affecting the climate response of NDVI and RWI. The results showed that the growth of trees and vegetation in the arid areas of inland Asia showed an increasing trend in 1982-2000. Most of the NDVI and RWI in the growing season had the characteristics of synchronous changes. In most regions， NDVI in May and June was affected by the temperature of the same period， while the NDVI in April and May was mainly affected by the precipitation of the same period； RWI is mainly affected by temperature in June and July and precipitation or Palmer Drought Severity Index （PDSI） in April， June and July. The responses of NDVI and RWI to temperature are consistent in most regions， but there are great differences in their responses to precipitation or PDSI. The climatic responses of NDVI and RWI were significantly affected by altitude and hydrothermal conditions in different regions. This study has certain scientific significance for understanding the climate response and influencing factors of vegetation and tree growth in the arid areas of inland Asia.

Dusty weather is an extreme weather phenomenon that occurs frequently in the northern China. It leads to a turbidity of the air and a sharp decline in visibility， causing adverse effects on various aspects of human society. Dust aerosols transported into the atmosphere by strong winds also have a significant impact on weather and climate by modulating atmospheric radiation budget and cloud microphysics. Accurate identification and forecasting of dusty weather are of great significance in ecological protection and climate change mitigation. This paper provides a comprehensive review of recent research on methods for identifying and forecasting dust events. Important methods are described in detail， and their advantages and disadvantages are analyzed and compared. Finally， this paper summarizes the research achievements related to the identification and forecasting of dusty weather and proposes valuable future research directions.

China has achieved remarkable prevention and control effects of aeolian desertification in northern China， and has shown an overall reversal trend since 2000. The Yellow River Basin is an important barrier to national ecological security， and its aeolian desertification prevention and control is a key link in consolidating the foundation for high-quality development of the basin. Based on the background of the overall reversal of aeolian desertification in northern China since 2000. The aeolian desertification process in the Yellow River Basin from 2000 to 2020 was discussed in this study， and the dominant factor which driving the dynamics of aeolian desertification in the basin and their relative contributions were analyzed using the quantitative method. The results showed that： （1） The aeolian desertification land in the Yellow River Basin mainly consisted of moderate and severe aeolian desertification lands， and was concentrated in the middle and upper reaches of the Yellow River Basin. From 2000 to 2020， the total aeolian desertification land decreased by 7 529 km² （5.6%） in the Yellow River Basin. In detail， the serious aeolian desertification land continued to decrease by 47.1%， while the increasing trend of the slight， moderate， and severe aeolian desertification lands slowed down significantly after 2010. （2） In space， the aeolian desertification land was mainly distributed in the middle and upper reaches of the Yellow River Basin， and the total aeolian desertification land further shrank to the upper reaches of the Yellow River Basin from 2000 to 2020. The reversed aeolian desertification land with a large distribution area of 2020， 35 542 km² （26.5%）， and the developed aeolian desertification with a scattered distribution area of 2 823 km² （2.1%） was mainly concentrated in the Hobq Desert， Mu Us Sandy Land， and the source area of the Yellow River. The reversal or development of aeolian desertification was dominated by the transfer to the aeolian desertification land with a lighter or a higher desertification degree， and the transfer has also slowed down significantly after 2010. （3） The area jointly driven by climate change and human activities accounted for 89.67% of the aeolian desertification dynamic area of the Yellow River Basin from 2000 to 2020， and that driven by individual climate change or individual human activities only accounted for 7.30% and 3.03%， respectively. The relative contribution of human activities （54.91%） was generally higher than that of climate change （45.09%）， but this relative contribution of human activities decreased with the increase of the relative contribution of climate change in different periods. This work can provide a decision-making basis and reference for the key desertification control in the ecological protection and high-quality development strategy of the Yellow River Basin， and can also provide significant theoretical support for realizing the high-quality development of the Yellow River basin.

Water is the backbone of hydraulic connection and water cycle process between different landscape in arid area， which further maintains the structure and function of wetland ecosystem in arid area. In order to quantify water source and its contribution to plant water， this paper takes riparian shrub wetland and salt-marsh grassland wetland as research objects， by measuring the δD and δ¹⁸O composition of precipitation， runoff， groundwater， soil water and plant water， to analyze the contribution rate of water sources to water use of desert plants with the linear mixed model. The results showed that： （1） annual rainfall average 104.6 mm， accounting for about 17.03% of the evapotranspiration （604.47 mm） in desert oasis wetlands in which has obvious seasonal distribution characteristics. The fluctuation of groundwater and soil water content depends on the distance from the river. The depth of groundwater and soil water content of riparian shrub wetlands near the river vary little with the seasons， while vary greatly in salt marsh grass wetlands far away from the river channel. （2） The precipitation line of local atmospheric is δD=6.33δ¹⁸O+4.04 （R²=0.931）， and the slope and intercept are slightly smaller than the precipitation line of global atmospheric， which is consistent with the characteristics of less precipitation and large evapotranspiration in the wetlands of the Heihe River Basin. The mean values of δD and δ¹⁸O of Heihe River groundwater， runoff， soil waterand and plant water were -50.98‰±13.18‰ and -9.74‰±25.49‰， -43.80‰±12.09‰ and -8.65‰±23.33‰， -42.07‰±6.89‰ and -7.22‰±2.49‰， -51.84‰±14.46‰ and -8.50‰±24.13‰， respectively. （3） Surface evaporation is the main cause of soil hydrogen and oxygen isotope enrichment in desert oasis wetland. Runoff and groundwater were the main water sources of desert oasis wetlands，and the contribution rate of runoff to plant water use was about 50% in riparian shrub wetland， while the contribution rate of groundwater was about 61% in salt marsh grass wetland. However， precipitation infiltration contributed little to the water use of riparian shrub wetlands and salt marsh grass wetlands， with values of 4% and 13%， respectively. （4） Depth of root and distribution of capillary root were important determinants of plant water use strategy in desert oasis wetland.

Atmospheric drought is an important factor affecting vegetation construction， ecological restoration and social-economically sustainable development in the semi-arid sand areas. To understand the spatiotemporal characteristics of drought events in the Mu Us Sandy Land during the past 40 years， this paper estimated the standardized precipitation evapotvanspiration index （SPEI） at monthly， seasonal and annual scales， based on the monthly meteorological data from 1981 to 2020. The results showed that： （1） The average annual precipitation （351.61 mm） and the temperature （8.49 ℃） in nearly 40a both showed a significant upward trend （P<0.05）. Seasonal precipitation increased throughout the four seasons， of which precipitation showed a significant upward trend in autumn and winter （P<0.05）. The average temperature in all four seasons showed a significant upward trend （P<0.05）. （2） Based on the SPEI index， it generally showed an insignificant wetting trend in the Mu Us Sandy Land （P>0.05） and a significant wetting trend in autumn （P<0.05）. Meanwhile， it showed a trend of wetting both in the central and western regions， while it showed a drying trend in the eastern region of the Mu Us Sandy Land. （3） In the past 40 years， the total drought frequency in Mu Us Sandy Land reached 31.9%. The order of the drought frequency was following as： light drought>moderate drought>severe drought>very severe drought； and the drought frequency had an order of winter>summer， autumn>spring. The light drought mainly occurred in the north， central， southeast and southwest regions； the middle drought occurred mainly in the eastern， northern and western edges regions； the severe drought mainly occurred in the eastern， central and southern regions； while the very severe drought events mainly occurred in the northwest， south and southeast regions of Mu Us Sandy Land. These results will contribute to the water resources planning， ecological restoration， disaster prevention and mitigation in the Mu Us Sandy Land.

China， especially the arid and semi-arid regions of northern China， is one of the leading contributors in global greening， and ecological projects has been thought as the main causal factors. As a key desertification-combating actions， the impacts of desertification control on vegetation temporal dynamics have not been fully clarified. This study analyzed the differences of temporal dynamics of normalized difference vegetation index （NDVI） and its influencing factors between desertification vegetation and its adjacent zonal vegetation in arid regions of northern China. The results showed that： （1） Desertification in the study region initially expanded， peaked in 2000， and then reversed， implying desertification control worked after 2000. （2） During 1982-2021， NDVI in 44.5% of the study area significantly increased， while 5.8% of the study area experienced a notable reduction， suggesting a generally greening. The greening primarily occurred in the Hetao Plains， Horqin Sandy Land， Kubuqi， Mu Us Sandy Land， Southern Xinjiang， Junggar Basin and the Tianshan Mountains. More area in desertified areas （45.7%） showed remarkable increase than their adjacent zonal vegetation （41.7%）. （3） Notably， the increasing rate after 2000 （0.0055 a^-1） markedly greater than that of pre-2000 （0.0036 a^-1）. Moreover， larger increasing rate was found in desertified areas after 2000 but in adjacent zonal vegetation before 2000. （4） Precipitation and specific humidity were the dominant factors in both the desertification and their adjacent zonal vegetation， with wind speed exerting a more significant influence in some natural units. The correlation coefficient of NDVI with moisture was lower in desertified areas compared with their adjacent zonal vegetation， whereas wind speed exhibited a stronger correlation. Our results will provide a scientific foundation to evaluate desertification control effectiveness in the past and improve related measures in the future.

The northern agro-pastoral interlaced zone is one of the most sensitive areas to cliamte change and human activity. The study of water resource change therefore in the interlaced zone under the background of climate change and land use/cover change（LUCC） provides an important scientific and practical significance for scientifically responding to the effective use and management of water resource in ecologically fragile aeras in a changing environment.Through the research on the characteristics of the climate and LUCC evolution in the northern agro-pastoral interlaced zone and their impact on water resources. The conclusions are as follows： （1） in the past 70 years， the climate in the northern agriculture-pastoral zone has shown a warming and drying trend， and the rate of temperature increase and precipitation decrease are higher than that of the global average. （2） LUCC is mainly based on the mutual transformation of agriculture and animal husbandry， and the land use structure has not changed significantly. （3） The watershed runoff and groundwater level in the region are positively correlated with temperature， negatively correlated with precipitation， and the effect of precipitation is more obvious； in recent decades， LUCC has become the dominant factor affecting the ecological and hydrological processes in the region， and the contribution rate of the impact on water resources has increased. Considering the problems and weakness in studies，we proposed the development trends of future research and key problems to be solved in the study.

The sandy land around the Poyang Lake is a typical sandy land in subtropical humid region. The problem of land desertification is serious， and has always been a research hotspot. However， there is little significance for the study of sandy land around the Poyang Lake because it is concentrated in a small area. Hence， it is extremely important to study the grain size comparison based onf a lot of sampling points around the Poyang Lake. In this paper， 57 sand samples were selected from Lushan City， Duchang County， Yongxiu County and Xinjian District， etc， and their grain size characteristics were analyzed. The results showed that： （1） The sandy land around the Poyang Lake is mainly composed of medium sand， fine sand and coarse sand， and the content of the three sand is more than 90%.The mean value of M_z is 1.79 Φ， and the sorting is poor with positive deviation and sharp distribution. （2） The grain size characteristics of sediment surface layer and 20-40cm depth were different in different sandy land types around the Poyang Lake. The surface layer of fixed dune， semifixed dune， active sand dune， wetland grass beach and benchland were coarser grain size than those of 20-40 cm depth， but the surface layers of active sand dune and wetland grass beach were better sorting than those of 20-40 cm depth. The dominant grain size content and grain size parameters of wetland grass beach and benchland are different from those of dune. （3） The fixed dune， semifixed dune and active sand dune are eolian deposits around the Poyang Lake. The benchland is dominated by fluvial action and supplemented by wind erosion.The wetland grass beach is formed under the combined wind force and hydrodynamic force. The S_d， SK and K_g of sandy land decreased from south to north along the prevailing wind direction. The aeolian sand movement of the Poyang Lake is mainly two jumps and one suspension style， and the main source of aeolian sand is on the spot， supplemented by river beach and lake beach.

In recent years， with the rapid expansion of highway construction area in China， some problems about wind force disasters on highway have appeared under special environmental conditions， which seriously threaten the safety of highway traffic. The compound disaster of snow drift and blown sand on Kete Highway in Altay Prefecture of Xinjiang just is a special seasonal wind-driven disaster. It is found that the occurrence of this kind of disaster is related to the regional disaster-pregnant environment with the reginonal east gale and abundant sand & snow sources in winter， as well as the layout of sand control system， the configuration of subgrade section and the artificial disturbance such as sand or snow stacking. In accordance with the principle of adapting measures to local conditions， fortifing against harm， complying with nature and addressing both symptoms and root causes， strengthening protection ability， and linking mechanical control with plant control have been formed in order to comprehensively control the blown sand disaster in spring and sand-snow compound disaster in winter. A comprehensive treatment scheme of road side terrain leveling， resistance-solid-transport structure protection system construction and later scientific management and protection has been formulated. This research results can provide a scientific plan for the disaster prevetion of Kete Highway， and also provide a reference for similar disaster control in other areas.

As an important synoptic and climate index， diurnal temperature range （DTR） reflects the extreme temperature difference between day and night. Compared with average temperature， DTR is more sensitive to changes in surface radiation budget and has important reference value for environmental changes and climate anomalies. The physical process of dust aerosol and its climatic effect are important factors affecting the lithosphere-atmosphere-ocean system， but the influence of dust climate effects on DTR has not been studied. The study reveals the climatic impact of dust aerosol on DTR over East Asia during 2002-2005 based on the WRF-Chem model （Weather Research and Forecasting coupled with Chemistry）. The results show that the WRF-Chem model can well reproduce the spatial-temporal distributions of meteorological field and dust aerosol over East Asia. The dust climate effect dominated by direct radiative forcing leads to the decrease of DTR in most parts of East Asia continent. During daytime， the direct radiative effect induced by dust heats the atmosphere and cools the surface， contributing to net surface radiation-cutting， thus further the decrease of the maximum Temperature and DTR. In contrast， an opposite variation tendency of DTR， primarily regulated by dust indirect effect， occurred over the Tibet Plateau and the northeast of China due to reduction of snow cover and liquid water path， respectively.

Grassland is the dominant ecosystem in arid and semi-arid areas. It is the main way to evaluate the ecosystem service value on time scale to judge whether the region ecosystem is in improvement or degradation. Based on the field survey， remote sensing classification and interpretation method， and the desertification grassland area data of different types and different degrees in Hexi Corridor， this paper established the evaluation standard system of ecosystem service value of different types and different degrees of desertification grassland in Hexi Corridor to evaluate the dynamic changes of ecosystem service value and service structure of desertification grassland in Hexi Corridor during the third （2004）， fourth （2009） and fifth （2014） desertification monitoring. The results showed that： （1） The desertification of grassland in Hexi Corridor showed a slight reversal trend from 2004 to 2014， and the area of desertification grassland decreased from 5.197×10⁶ hm² to 3.577×10⁶ hm². （2） The total value of desertification grassland ecosystem services in Hexi Corridor was mainly lost， which was up to 20.9 billion yuan. （3） The total value of ecosystem services of desertification grassland in Hexi Corridor was significantly different in terms of spatial and temporal distribution of desertification types and degrees. （4） The ecosystem service functions of desertification grassland ecosystem in Hexi Corridor tended to be climate regulation， environment purification and hydrological regulation.

Chemical measures， engineering measures and biological measures are called the three major sand control measures. The application and development of chemical sand fixation measures are strictly constrained by materials， and there is a trough period in the development of sand control technology. In recent years， with the development of materials science， inorganic， organic and inorganic organic composite chemical new materials have been widely used in the field of sand control， and chemical sand fixation measures have become a research hotspot. Sand fixation materials with low cost， high efficiency and good biocompatibility have become the key of chemical sand fixation technology， and environmental protection is the primary restrictive factor in the selection of materials. This paper summarizes the research progress of environmentally friendly sand fixation materials processed from natural materials， classifies environmentally friendly sand fixation materials， and analyzes the problems existing in the development of chemical sand fixation and the necessity of environmentally friendly sand fixation materials. This study will provide a theoretical basis for the development of high-performance environmental friendly chemical sand fixation materials.

The effect of dust storm on human living and production do not speak for themselves. Dust storm occurrence days decreased in recently 70 years， but it had been obviously increased since 2021， and attracted a lot of attentions. However， all the published papers were based on simulation or dust geochemistry， and almost no field data. We used field measurement of sand transport， PM₁₀ concentration and transported aeolian sediment grain size to explain the dust hazard in the dust sources during a strong dust storm. Our results indicated that： （1） Wind velocity was much larger in the dust sources than national weather station data. （2） PM₁₀ concentration can reach to 100 mg·m^-3， and is also larger than national measured data. （3） Sand transport reached to 10 kg·m^-1·h^-1， and dust can be transported longer distance. （4） The mean grain size of transported aeolian material was 0.07 mm， and coarse sand frequency can reach to 9%， and PM₁₀ frequency can reach to 8%. Coarse sand impacted on erodible land surface and caused more dust come into air and supplemented dust concentration in the sources. （5） Sand transport rate increased about 2 times， PM₁₀ concentration increased 2.90 time， and PM₁₀ frequency increased 1.29 time on disturbed land surface than undisturbed land surface， which means that protected gobi land surface can greatly decreased dust material during dust storm.

In order to promote the research on climbing dunes in Lhasa River Basin， this paper takes the climbing dune in Lhasa River Valley in the south of Qinghai Tibet Plateau as the research object， and analyzes the characteristics of grain size and geochemical elements of dune sediments on the surface and at the depth of 0-60 cm. The results show that： （1） Fine sand is the dominant particle size of surface sediments of climbing dune in Lhasa River Valley， followed by medium sand and very fine sand， with less silt content and very few coarse sand and clay. All samples do not contain very coarse sand， with an average particle size of 2.51 Φ （fine sand）， medium sorting， positive skewness and narrow kurtosis. With the increase of altitude， the particle size of surface sediment gradually becomes smaller， and with the deepening of depth， the particle size of sediment gradually becomes thicker， with the maximum change in the range of 0-10 cm. （2） The SiO₂ content of major elements is the highest， the variation coefficient of CaO is the largest， the Ba content of trace elements is the highest， and the variation coefficient of Co is the largest. Except SiO₂ and K₂O， the content of major elements decreases gradually from surface to deep layer， and the content change of trace elements from surface to deep layer can be divided into stable type， decreasing type， increasing type. The content of both major and trace elements changes most strongly at 0-10 cm. Compared with the average chemical composition of the upper continental crust， except that Na₂O， MnO， Cr， Co and Mo are partially enriched， and the SiO₂ content is equivalent to that of the upper continental crust， the rest are in a loss state. In terms of weathering degree， the chemical weathering degree of climbing dunes in Lhasa River Valley is higher than that of other deserts. They have experienced moderate chemical weathering. They are the products of the first cyclic deposition in arid and cold environment. Their composition characteristics are mostly similar to the upper continental crust and are in the early stage of continental weathering.

Land desertification is one of the most serious environmental problems in the Shule River Basin， and its assessment is of great importance to effectively control desertification. This paper aims to calculate environmental sensitivity index based on MEDALUS model by integrating multi-source GIS and remote sensing data. MEDALUS model takes into account four quantitative evaluation indexes of soil， vegetation， climate and management to identify desertification sensitive areas. Upon which， the causes of desertification sensitivity are analyzed. The main influencing factors of desertification sensitivity are determined by coefficient of variation method. The results show that the desertification situation in the middle and lower reaches of the Shule River Basin is severe， 17.70% of the total study area belongs to the extreme sensitivity zone， 54.34% belongs to the high sensitivity zone. The desertification sensitivity is higher in the central parts of study area， lower in the north， which is mainly controlled by management quality index related to human activities. The desertification sensitivity is gradually increased from the inside to the outside of the oasis， and the distribution is roughly layered， indicating that human activities have a significant impact on desertification. It is necessary to strengthen and consolidate the construction of the oasis edge protection system.

Fractional vegetation coverage is a key parameter for monitoring ecosystems and its functions. How to improve the retrieval accuracy of fractional vegetation coverage in large areas is very important for the sustainable development of the environment in ecologically fragile areas. Based on machine learning methods such as back propagation neural network （BP-ANN）， support vector regression （SVR） and random forest （RF）， this study uses UAV， Worldview-2 and Landsat 8 OLI remote sensing data to carry out multi-scale inversion of fractional vegetation coverage in Horqin Sandy Land. The results show that： （1） The RF model performs better than the BP-ANN and SVR model. It can invert the vegetation coverage of sandy land with higher accuracy on the scale of unit （experimental area） and regional （research area）. There was a significant correlation between the inversion value and the measured value of UAV at the linear level （P is less than 0.01）. （2） On the unit and regional scales， the test set of the constructed vegetation coverage inversion model are R² of 0.84 and 0.80， MSE of 0.0145 and 0.0370， and the consistency index d of 0.9576 and 0.8991 respectively. The method of gradually realizing the large area fractional vegetation coverage inversion of low spatial resolution remote sensing images by using multi-source remote sensing data and machine learning method， which can not only effectively improve the inversion accuracy of fraction vegetation coverage in sandy land （R²=0.78， less than 0.63）， but also provide support for regional ecological environment monitoring and ecosystem health assessment.

Grassland desertification is the main ecological problem in Hexi Corridor. Therefore， exploring the status and changes of grassland desertification in the Hexi Corridor is the key to maintain regional ecological security and ensure healthy and stable economic and social development. Based on the three national desertification monitoring data in 2009， 2014 and 2019， and combined with the meteorological and yearbook data of the same period， our study analyzed the rule of dynamic changes of grassland desertification in the Hexi Corridor by applying trend analysis， grey correlation and structural equation modeling， and on this basis， the factors driving grassland desertification were quantified. The results show that： （1） The threat of grassland desertification persists in the Hexi Corridor region. In 2019， the desertified grassland area was 3.7193 million hm²， accounting for 43.7% of the total grassland area in the Hexi Corridor， and the degree of desertification was mainly moderate， accounting for 65.58% of the total desertification grassland. （2） From 2009 to 2019， the area of desertified grassland decreased by 1.3468 million hm²， and the grassland desertification tended to be reversed. The comprehensive evaluation index of grassland desertification degree showed that， except for Jinchang City， the grassland desertification in Jiuquan City， Jiayuguan City， Zhangye City and Wuwei City showed reversing trend. （3） Among the driving factors that cause the dynamic changes of grassland desertification， the increase of precipitation is helpful for the reversal of desertification. Among them， temperature， crop sown area， number of large livestock， and permanent population are positively correlated with grassland desertification， and the permanent population indirectly promote the exacerbation of grassland desertification by affecting the sown area of crops.