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In order to implement the spirit of General Secretary Xi Jinping's important speech on strengthening the comprehensive control of desertification and promoting key ecological engineering projects such as the "Three-North Shelterbelt Program", this study is designated to make concrete efforts to win the battle against desertification on the edge of Hexi Corridor--Taklimakan Desert. The study deeply explores the situation of wind-blown sand flux and prevention tasks in the area. Based on the characteristics of desertified land and wind-blown sand activities on the edge of Hexi Corridor--Taklimakan Desert, the goal is set to effectively prevent the spread of sand and control dust sources. The core focus is on wind prevention, sand resistance, and dust control. The strategic thinking has been formulated for the counterattack battle on the edge of Hexi Corridor--Taklimakan Desert. By systematically analyzing the source areas and paths of "wind, sand, and dust" and targeting the key zones of the desert edge and areas requiring prevention, the key areas and tasks are proposed for desertification control on the edge of the Hexi Corridor--Taklimakan Desert, so as to provide scientific and technological support for winning the battle against desertification on the edge of Hexi Corridor--Taklimakan Desert. [ABSTRACT FROM AUTHOR]

The Belt and Road region crosses different geographic areas and ecological zones. Ecologic problems and hazards risks are complicated in these zones and they threat seriously the green development and economic corridors security along the Belt and Road region. Based on multiple data sources platform installation and experiment-demonstration researches and observations, the regional ecologic-environmental regulations of the Belt and Road region are well and scientifically recognized, key areas/zones and the ecologic-environmental security and risk response programmes of major projects are systematically integrated. The findings of the key advanced research project on the environment change and construction of the Green Silk Road of the Pan-Third Pole provide scientific and technical supports to the further promotion of the Green Belt and Road development, and they also serve the world successful cases for global environmental governance. [ABSTRACT FROM AUTHOR]

China has made remarkable achievements in combating desertification over the past 70 years. At present, China has entered a new stage of combating desertification while facing many problems such as large desertification land base and high difficulty in combating desertification, and it is more important to meet the national strategic needs of ecological construction, rural revitalization, and the development and utilization of renewable energy in desert, Gobi, and wasteland areas. The strategic choice of combating desertification in China in the new era is overall improvement and key breakthroughs. The core of the strategy is whole-area governance, innovation-driven, and technology integration. The institutional arrangement of preferential policies is to fully implement the "one desert, four mechanisms" (cultivation, prevention, combating, and utilization), make every effort to win the "three iconic battles" of the "Three-North" battle, give priority to the implementation of key demonstration projects, and accelerate the update of policy. A new engine of science and technology will be built to improve the quality and efficiency for combating desertification, draw a bright vision of Chinese-style modernization featuring integration of production, life, and ecology and harmonization between human being and desert, and promote the "Chinese solution" of combating desertification to benefit the whole world. [ABSTRACT FROM AUTHOR]

Microclimates play important roles in controlling water budgets and water vapor transportation, as well as vegetation growth characteristics. In order to understand the differences in meteorological parameters under different vegetation cover (VC) and terrain conditions, wind velocity, air temperature, relative humidity (RH), photosynthetically active radiation (PAR), and solar radiation were simultaneously monitored on shifting, semi-fixed and fixed sandy lands, and an oasis. The air temperature and RH differences among the four landscape types were obvious in the period from May to October. It was found that the higher elevations of semi-fixed sandy land can influence PAR and solar radiation during sand-blowing weather. The differences of air temperature and RH among the four sites during the dust-storm and rainy days were not obvious, but their differences during sand-blowing weather were greater than during rainy weather and less than during floating-dust and sunny weather. The differences of PAR and solar radiation among the four landscape types were most obvious during the dust-storm event. During most of the weather types studied, significant positive correlations were found between wind velocity and temperature, PAR, and solar radiation, as well as between temperature and PAR, and solar radiation. Meanwhile, significant negative correlations were found between RH and wind velocity, temperature, PAR, and solar radiation. VC and topography were found to be the main factors influencing the changes in meteorological parameters between desert–oasis ecotone and oasis. [ABSTRACT FROM AUTHOR]

Dust emission is a common catastrophic weather phenomenon in Northern China. This phenomenon not only causes environmental problems, such as air pollution, but also has an important impact on the global dust cycle and climate change. On the basis of the dust weather observation data of 44 surface meteorological stations in the Tarim Basin from 1989 to 2021, combined with the dust aerosol optical depth (DAOD), dust surface mass concentration (DUSMASS) and wind speed data, this paper analyses the spatial and temporal dust weather characteristics in the Tarim Basin over the past 33 years. Results show that the frequency of dust weather in the Tarim Basin has declined in the past 33 years. Dust weather mainly consisted of floating dust, followed by blowing dust and dust storm. This weather had a significant seasonal change, with more dust in spring and summer and less in autumn and winter. The dust weather was mainly distributed along the south edge of the Tarim Basin and the desert hinterland of Tazhong. The spatial distribution of the dust intensity (DI) index was basically consistent with the dust weather days. Moreover, the DAOD was obviously affected by dust weather and had a significant positive correlation with the number of dust weather days and the DI, suggesting the vertical concentration of dust particles to a certain extent. Wind is also one of the most important factors affecting the release of dust. The frequency of strong wind weather decreases from the northeast to the southwest, which corresponds to the distribution of the DUSMASS. [ABSTRACT FROM AUTHOR]

Water scarcity is a world-wide problem, especially in desert ecosystems. To overcome this shortage, saline groundwater is increasingly being used, although it has risks of increasing soil salinity and causing plant salt toxicity. In this study, we investigated the effects of saline water irrigation on soil properties and plant growth along the Taklimakan Desert Highway shelterbelt. The results showed that soil salts (about 8 mS cm −1 ) and nutrients significantly accumulated at the soil surface (crust and 0–10 cm soil layers) with saline irrigation, but the soil salinization did not increase (<1.0 mS cm −1 ) within the 40–60 cm soil depth where abundant lateral roots also germinated and extended horizontally. While the deepest main root system was 200 cm for Tamarix , it extended to about 150 cm for other two species studied ( Haloxylon and Calligonum ). More than 87% of the biomass of the lateral roots was present in the 20–80 cm soil depths for the three species; although no active absorbing roots were found within the 0–10 cm soil depths where the salts had accumulated. These findings indicated that saline water irrigation within artificial shelterbelts may be beneficial for soil nutrient accumulation and accentuates the potential uses of these sandy soils. After 7-yrs irrigation with nutrient accumulation, structured soil under shelterbelt has progressively formed, as indicated by increased soil aggregate size and stability. Saline water irrigation did not influence the normal growth of adaptive plants, which may be attributed to the plant adaptability to salt stress through root morphology adjustment. In summary, saline groundwater irrigation offers potential advantages and opportunities for plant growth on sandy soils evolution in a desert environment where saline groundwater is the sole water resource for plants. [ABSTRACT FROM AUTHOR]

The oasis-desert ecotone is a fragile ecological zone that is affected both by oasis and desert conditions. To understand the impact of the differences in wind power, and the influence of wind erosion and deposition on the ecotone, meteorological data and contemporaneous wind erosion and deposition data were collected on the southern margin of Tarim Basin with serious sand-blown hazards. The wind velocity, average wind velocity, sand drift potential (DP), resultant sand drift potential (RDP), and sand transportation rate decrease significantly and successively across four landscape types with increasing vegetation coverage (VC). Flat surfaces and areas of shifting sandy ground experience intense wind erosion with fast movement of mobile sand dunes; semi-fixed sand areas experience extensive wind deposition but only slight wind erosion; and fixed sand areas experience only slight wind erosion and deposition. Volume of wind erosion on bare newly reclaimed farmland is up to 6.96 times that of bare shifting sandy ground. Wind erosion volume per unit area and VC follow an exponential function relationship in natural conditions, while wind deposition volume per unit area does not conform to any functions which has close relationship with vary topography and arrangement patterns of vegetation besides for VC. The results indicate that the volume of wind erosion has a close correlation with VC, and different types and distribution patterns of topography and vegetation also profoundly influence the wind deposition volume in the field, and underground water tables in different landscape types control the plant community distribution. [ABSTRACT FROM AUTHOR]

Accurate estimation of vegetation Net Primary Productivity (NPP) has important theoretical and practical significance for ecological environment governance, carbon cycle research, and the rational development and utilization of natural resources. In this study, the spatial characteristics, temporal changes, and driving factors of NPP in the Conventional Lake Chad Basin (CLCB) were based on MODIS data by constructing a Carnegie Ames Stanford Approach (CASA) model and using a combination of Residual trends (RESTREND) and correlation analysis. The results showed that from 2001 to 2020, the NPP of the CLCB decreased annually (1.14 g C/m2), mainly because of overgrazing, deforestation, and large-scale irrigation. We conducted a driving factor analysis and found that the main influencing factor of the NPP of the CLCB is high-intensity human activities, including farmland reclamation and animal husbandry. Although the impact of climate change on NPP is not obvious in the short term, climate change may help recover NPP in the long term. The continued reduction in NPP has greatly increased the difficulty of regreening the Sahel; the increase in population density and rapid urbanization have led are major contributing factors to this. Our findings have important implications for the continued implementation of stringent revegetation policies. However, owing to limited data and methods, only the overall change trend of NPP was obtained, and comprehensive follow-up studies are needed. [ABSTRACT FROM AUTHOR]

Abstract: Soil particle-size distribution (PSD) is one of the most fundamental physical attributes of soil due to its strong influence on other soil properties related to water movement, productivity, and soil erosion. Characterizing variation of PSD in soils is an important issue in environmental research. Using ordination methods to characterize particle size distributions (PSDs) on a small-scale is very limited. In this paper, we selected the Cele River Basin on the north slope of the Middle Kunlun Mountains as a study area and investigated vegetation and soil conditions from 1960 to 4070m a.s.l. Soil particle-size distributions obtained by laser diffractometry were used as a source data matrix. The Canonical Correspondence Analysis (CCA) ordination was applied to analyse the variation characteristics of PSDs and the relationships between PSDs and environmental factors. Moreover, single fractal dimensions were calculated to support the interpretation of the ordination results. Our results indicate that a differentiation of 16 particle fractions can sufficiently characterize the PSDs in CCA biplots. Elevation has the greatest effect on PSDs: the soil fine fractions increase gradually with increasing elevation. In addition, soil pH, water and total salt content are significantly correlated with PSDs. CCA ordination biplots show that soil and vegetation patterns correspond with one another, indicating a tight link between soil PSDs and plant communities on a small scale in arid regions. The results of fractal dimensions analysis were rather similar to CCA ordination results, but they yielded less detailed information about PSDs. Our study shows that ordination methods can be beneficially used in research into PSDs and, combined with fractal measures, can provide comprehensive information about PSDs. [ABSTRACT FROM AUTHOR]

Abstract: Characterizing soil particle size distributions (PSD) and their variation is an important issue in environmental research. In this study, fractal theory was used to analyse the soil PSD and its variations in the Cele Oasis, which is located at the southern margin of the Tarim Basin. The characteristics of the soil PSD were then evaluated to identify the primary factors that influence soil PSD. The results showed that the fractal dimension () values ranged from 2.11 to 2.27, and that there were significant differences among groups. Furthermore, the values showed a significant positive correlation with fine particles (<50 μm) and soil organic matter contents. According to a comparative analysis of values, the utilization years of farmlands had a significant influence on PSD, while the difference in the spatial distribution of farmlands did not. These results indicated that long-term and effective tillage management of the farmlands will be beneficial to keeping and improving the states of the soil PSD and other soil properties. [Copyright &y& Elsevier]

In this work, we report a comprehensive study about the eco-environmental effects of the shelter forest along the Tarim Desert Highway, including the effects on aeolian environment, soil, micro-climate, biodiversity, and groundwater. The results show that: (1) The movement of windblown sand near the ground surface was affected by the shelter forest. The wind speed and sediment transport rate in the shelter forest decreased by 64%?80% and 87.45%?99.02%, respectively. In addition, there were also significant changes in the sand flux structure, the sand grain size, and the deflation and deposition on the ground surface. (2) Compared to the natural mobile sand, the soil bulk density in the forest area decreased while the total salt content, the total porosity, and the water content increased. In addition, the soil fertility was significantly improved in the forest area, and showed the "first rapid, then slow" variation pattern. (3) The shelter forest showed positive effects on the micro-climate. Within the 6 m height above the ground, the air temperature in the shelter forest at different heights was lower than that in the mobile sand, while the air humidity was higher, while, the soil temperature was also lower in the shelter forest than mobile sand. (4) The number of soil microbial species increased significantly with the improvement of habitat in the shelterbelt. However, the population of different species was not distributed evenly across the surveyed area. (5) Currently, no significant effects of groundwater- pumping and forest-irrigation water have been found on the groundwater level and its salinity. The variation amplitude of both groundwater level and salinity was at the level of centimeters and 1g/L, respectively. No obvious variation trend has been observed. [ABSTRACT FROM AUTHOR]

Through analysis of satellite images from Google Earth, this article expounds the characteristics of large-scale geomorphic patterns of the complex longitudinal sand ridge zone in the Taklimakan Desert, and reduces the large-scale geomorphic patterns to six types: parallel pattern, "..." character-shaped and "..." character-shaped pattern, comb-shaped pattern, fork-shaped pattern, toe-shaped pattern and miscellaneous pattern. And according to the large-scale geomorphic pattern type (or composition of pattern types) as well as some other factors, the article divides the complex longitudinal sand ridge zone into 55 subzones. Lastly, aiming at the genetic problems of the large-scale geomorphic patterns, the article suggests three connective types of the sand ridges in the complex longitudinal sand ridge zone, i.e., connecting or intersecting after natural elongation, connecting in a narrow place and connecting with the aid of intermediary. [ABSTRACT FROM AUTHOR]

Through the systematic field survey and observations, the factor quantification as well as setting the criteria, the sand disaster-forming environment along the Tarim Desert Highway can be divided into four grades by the classification and regionalization based on fuzzy mathematics. The length of the regions with significant sand disaster accounted for 37.1% of the total highway length. Particularly, the area along the Tarim Desert Highway, based on the sand disaster-forming environment classification as well as the difference in the five basic landform units along the highway, combined with the difference of wind regime, can be divided into five regions, in which the length of the regions suffering severe sand damage occupied 64.3% of the total highway length. In addition, the index of disaster formation grade along the highway decreased from north to south, showing a repeated spatial pattern in small length scales. [ABSTRACT FROM AUTHOR]

Phreatic evaporation is a great lose for shallow groundwater in the Taklimakan Desert. Given soil type and groundwater table, the limiting rate of phreatic evaporation is defined as the maximum of water transferred from groundwater to soil surface per unit time, which is a key parameter and control condition for phreatic evaporation model developing. The soil water characteristic curve for the aeolian sandy soil in the Taklimakan Desert was fitted with the least square method based on the formula of soil moisture characteristics curve proposed by Van Genuchten, using observed soil moisture and soil water suction data. The unsaturated hydraulic conductivity was determined by the instantaneous profile method in situ and the calculation formula for unsaturated hydraulic conductivity was established. According to the steady flow theory, the quasi-analytical solution of limiting rate of phreatic evaporation was derived on the basis of generalization of the formula of unsaturated hydraulic conductivity. The results show that the soil moisture characteristics in the Taklimakan Desert can be well described by Van Genuchten's formula, and the limiting rate of phreatic evaporation declines by power function with the descending of groundwater table. [ABSTRACT FROM AUTHOR]

To study the changes of soil fertility of the shelter-forest land along the Tarim Desert Highway, soils from the forest land were collected at the layers of 0?10 cm, 10?20 cm, 20?30 cm. Different soil fertility parameters were measured, and quantitative evaluation of soil fertility was performed by the soil integrated fertility index (IFI). The main results show that the construction of the shelter forest along the Tarim Desert Highway improved the soil physical structure, increased soil porosity and enhanced water- holding capacity. With the increase of plantation time of the shelter forest, soil microbial biomass C, N, P and the activities of six types of enzyme were enhanced, which promoted the accumulation and transformation of soil nutrients of the forest land. Consequently, the soil nutrients in 12-year-old forest land were much higher than in the newer ones and drifting sand. However, soil salt content of the older forest land was higher owing to the drip-irrigation with salt water. Through the comprehensive evaluation, we found that soil fertility index in the forest land was enhanced with the forest age, and it had close correlations with the growth indices of the forest trees. In summary, construction of the shelter-forest along the Tarim Desert Highway accelerated the improvement of aeolian soil in the forest land, and the soil fertility improved year by year. We conclude that the forest trees grow normally under the stress of the present drip-irrigation with salt water. [ABSTRACT FROM AUTHOR]

To study the effects of sand protection project on modern aeolian landform, the types, distribution, and intensity of topographical changes of the ground surface affected by the shelterbelt along the Tarim Desert Highway were determined by measuring the deflation and deposition of sand surface in the Tazhong area located in the hinterland of the Taklimakan Desert. The results showed that (1) the newly-formed landform in sand protection systems is dominated by aeolian deposition including the small-scale Nabkha Dunes, the medium-scale sheet-like sand deposition and the large-scale ridge-like sand deposition. To some degree, aeolian deflation landform can also be formed in the open space in the shelterbelt. Furthermore, it is difficult for aeolian deflation landform to develop in a large scale in the interdunes. However, aeolian deflation landform can be developed in a large-scale on the windward slope of secondary dunes in longitudinal complex sand ridges; (2) on the windward side of the sand protection systems, both the morphology and strike of dwarf mobile dunes in the interdunes are changed by the sand-obstructing forest belts and the ridge-like sand deposition around it. The windward slope of the ridge-like deposition around the sand-obstructing forest belt forms a stable ground surface. After being damaged by forward-moving dunes in a short period, the ground surface is recovered gradually; (3) on the leeward side of the sand protection systems, aeolian deflations are formed widely. Particularly, the deflation depression is formed in the interdunes. In addition, the dunes in the region with highly topographic relief are cut flat by aeolian deflations; thereafter its relief of topography is reduced. The above analysis indicates that shelterbelts have obvious effects on the windward wind-sand flux in terms of dissipating energy and intercepting sand. With the recovery of wind velocity on the leeward side of the sand protection systems, the wind-sand flux gradually tends to be unsaturated; therefore the sand surface deflation is formed. [ABSTRACT FROM AUTHOR]

The temperature and humidity of the shelterbelt micro-climate on both horizontal and vertical scales in the extremely drought area were measured with multiple HOBO temperature and humidity automatic observation equipments in the hinterland of the Taklimakan Desert. The results show that the shelterbelt ecosystem of the desert highway plays typical micro-climate adjustment rolesin stabilizing surface air temperature and increasing air humidity, and so on. Solar radiation significantly affects both temperature and humidity of surface layers, and it has a positive correlation with the temperature but a negative correlation with the air humidity. When it is cloudy, the weather has a great impact on keeping temperature and humidity in the shelterbelt. The shelterbelt also significantly influences the environment, and the micro-climate in the belt has an obvious characteristic of cooling and humidification: compared with the original sand area, the temperature in the shelterbelt is always lower and the humidity is always higher. Moreover, the temperature range at the shelterbelt edge is greater than that in the sand area, but the humidity is always higher. Our conclusion is that the vertical-effect range of temperature of the shelterbelts is 4 -10 m, and the humidity range is 6 to 8 m; the horizontal-effect range of temperature is 16 m and the humidity range is about 24 m. [ABSTRACT FROM AUTHOR]

• Asian desertification land significantly changed in 30 years, mainly increasing. • Soil moisture shifts dominated Asia's desertification process. • Post-2009, desertification land reversed, highlighting intervention success. • Sustainable land management is key to combating Asia's desertification. Owing to the combined effects of climate change and human activities, the type of desertification in the arid regions of Asia has undergone profound changes, and the problem of desertification has become increasingly prominent. To help address this problem, this study clarifies the transformation trends and characteristics of desertification types across Asia and discusses key areas for desertification prevention and control. Based on a series of Landsat satellite images, combined with the classification method of the desertification degree and a machine learning model, the desertification types, trends, and conversion degrees in the arid regions of Asia were systematically evaluated. In addition, the impact mechanism of climate change on the conversion between desertification types was evaluated. The primary results were as follows: (1) Various desertification types in the arid areas of Asia from 1990 to 2022 exhibited evident time series characteristics. Extremely severe desertification expanded from 1990 to 2009 and subsequently shrunk; (2) The degree of desertification in the arid regions of Asia exhibited different change characteristics in different periods, and the converted area of the same conversion type was different in different periods; (3) Different desertification conversion types in different periods have different drivers; however, overall, soil moisture has the greatest contribution to desertification conversion type. These results provide a scientific reference for the formulation of reasonable desertification prevention and control policies. [ABSTRACT FROM AUTHOR]

The dust originating from the extinct lake of the Aral Sea poses a considerable threat to the surrounding communities and ecosystems. The accurate location of these wind erosion areas is an essential prerequisite for controlling sand and dust activity. However, few relevant indicators reported in this current study can accurately describe and measure wind erosion intensity. A novel wind erosion intensity (WEI) of a pixel resolution unit was defined in this paper based on deformation due to the wind erosion in this pixel resolution unit. We also derived the relationship between WEI and soil InSAR temporal decorrelation (ITD). ITD is usually caused by the surface change over time, which is very suitable for describing wind erosion. However, within a pixel resolution unit, the ITD signal usually includes soil and vegetation contributions, and extant studies concerning this issue are considerably limited. Therefore, we proposed an ITD decomposition model (ITDDM) to decompose the ITD signal of a pixel resolution unit. The least-square method (LSM) based on singular value decomposition (SVD) is used to estimate the ITD of soil (SITD) within a pixel resolution unit. We verified the results qualitatively by the landscape photos, which can reflect the actual conditions of the soil. At last, the WEI of the Aral Sea from 23 June 2020, to 5 July 2020 was mapped. The results confirmed that (1) based on the ITDDM model, the SITD can be accurately estimated by the LSM; (2) the Aral Sea is experiencing severe wind erosion; and (3) the middle, northeast, and southeast bare areas of the South Aral Sea are where salt dust storms may occur. [ABSTRACT FROM AUTHOR]

The geographical detector model (GDM) is based on the spatial variance analysis of geographical strata of variables to assess the association between the independent variables ( X) and dependent variables ( Y). The independent variables of the GDM must be discretized into classes. However, current discretization methods employ univariate analysis, which may lead to inaccurate results. The aim of this study was to develop a novel bivariate optimal discretization approach, known as the multiscale discretization (MSD) method. The objective of the MSD method is to determine an appropriate set of thresholds for X , thereby minimizing the variance of Y within the spatial partitions determined by the discrete X. We successfully applied the MSD method to assess the relationship between the precipitation and enhanced vegetation index on the African continent, as well as the habitat range of pandas in Ya'an County, Sichuan Province, China. The results demonstrate that the MSD is a feasible, robust, and rapid method for converting continuous data into discrete data, with globally optimal discretization results. Furthermore, the MSD method can evaluate the degree of association between X and Y more accurately, and can optimize the results of the GDM. [ABSTRACT FROM AUTHOR]

The landscape in desert margin regions is simultaneously shaped by both wind and water forces, resulting in a particular spatial distribution of dunes. It has been suggested previously that aeolian and fluvial systems should be integrated in investigations of the development of regional landforms. We carried out a comprehensive study of landforms on the southern margin of the Taklimakan Desert, China based on remote sensing images, meteorological data and morphodynamic theories of dune formation. Our results indicate that the major characteristic of dunes in this region is the coexistence of dunes with different orientations in a small geographical area. As the development of dunes is mainly determined by the wind regime and the availability of sand, the coexistence of dunes with different orientations might be caused by differences in the availability of sand. The topographic relief and fluvial systems both affect the grain size distribution and the amount of sediment in different regions, resulting in variations in the availability of sand. A comprehensive analysis of the spatial distribution of dunes and the regional environment can help our understanding of the regional variations of sediment in aeolian–fluvial interaction systems and help to model the development of landforms in these environments. [ABSTRACT FROM AUTHOR]

Despite paleochannels play a key role in the evolution of aeolian dune patterns, little attention has been paid on the interactions between paleochannels and aeolian processes. The objective of this article is to analyze the interactions between paleochannels and aeolian processes and their implications on the aeolian dune patterns. One site in the Kuruk Tagh Desert in eastern margin of the Tarim Basin, northwestern China is selected as the case study area. We analyze the sedimentary environment of the aeolian dunes around paleochannels based on the grain-size parameters. Furthermore, we present spatial and temporal dynamics of the vegetation and aeolian dunes around the paleochannels. The results indicate that: (1) ground water determines the spatial distribution of the vegetation and controls the evolution of aeolian dune patterns indirectly; (2) aeolian dunes around the paleochannels are initially controlled by fluvial and aeolian processes collectively. Then, the aeolian processes always play a dominant role after the drying up of these paleochannels; (3) the paleochannels in aeolian processes dominated areas ultimately evolve into a belt sand source due to the deposition of aeolian sediments and the encroachment of aeolian dunes. The timescale of the paleochannels'vanishment depends not only on the depth and width of the channels, but also on the angle between bedform orientation and prevailing sand flux direction. [ABSTRACT FROM AUTHOR]

Oasification is a complex oasis expansion and ecological processes caused by climate changes and human activities under available water supply in arid and semiarid regions. The process can effectively improve soil productivity, vegetation cover, and biomass production in fighting against land degradation, such as desertification and soil erosion. However, the significance of oasification has not yet reached the general cognition compared to desertification, which is regarded as one of the most severe global eco-environmental issues. This paper identifies desertification and oasification processes and their perspectives in cognition. The implication of oasification in combating desertification and controlling land degradation is emphasized by the justification between desertification and oasification processes. As opposite process of desertification, the oasification is an unable evasive process that can provide positive environmental effects in the control of desertification, ecological restoration, and land rehabilitation. According to the interaction of climatic variations and human activities, the oasification processes is classified into six main forms: natural oasis evolution process, engineering forest construction, conversion of natural landforms into farmlands, urban encroachment, constructed environments, and coupled ecosystems. These processes gradually modify the productive capacity of soils, increase vegetation cover for restoring degraded lands, and improve the living environment for human settlement and sustainability of an oasis ecosystem. Moreover, an overview of oasification research is detailed, and Northwest China as an example is used to illustrate the progress of the oasification research in recent decades. Currently, the oasification process and its mechanistic research still remain less concern in the arid and semiarid regions. A new science framework of the oasification research is proposed to effectively deal with ecological and environmental issues in the arid and semiarid regions. • Desertification and oasification and their perspectives are identified. • Implication of oasification is emphasized in comparison with desertification. • Oasification processes are classified into six main forms. • Overview of oasification research is detailed and illustrated in Northwest China. • A new science framework of the oasification research is proposed. [ABSTRACT FROM AUTHOR]

The vegetation of desert oasis regulates the regional microclimate in arid or hyper-arid regions. A wide range of studies on the oasis microclimate effects have been conducted under sunny conditions. However, less concern has been focused on microclimatic variations of oasis effects caused by the influences of different types and coverage of vegetation in oasis during other different weather events, especially during catastrophic weather conditions. Based on the measurements from 1 August, 2010 to 30 December, 2014 in the Qira oasis, a hyper arid zone of southern Taklimakan desert, Northwest China, this paper investigates the existences and variabilities of the oasis microclimate effects during dust storm, blown sand, floating dust, and rain events and analyzes the impacts of different types of vegetation (bare desert, sparse desert grassland, desert oasis dense shrub grassland and forests, and oasis crops and fruit trees) on desert oasis microclimates. Moreover, the importance of maintaining the oasis sustainability mirrored by the oasis microclimate effects is highlighted and discussed. Results show that the oasis with abundant vegetation exerts cooling and humidifying effects under four weather events relative to bare desert land. As a result of high wind velocities, the oasis microclimatic effects are weakened during catastrophic weather conditions such as dust storm or blown sand events. The type and coverage of vegetation and the topography as well as weather events jointly impact on the oasis microclimate effects. The findings of this work provide an implication for the conservation and restoration of oasis vegetation to maintain both the oasis microclimate environment and the sustainability of desert oasis. [ABSTRACT FROM AUTHOR]

Agriculture and the eco-environment are increasingly competing for water. The extension of intensive farmland for ensuring food security has resulted in excessive water exploitation by agriculture. Consequently, this has led to a lack of water supply in natural ecosystems. This paper proposes a trade-off framework to coordinate the water-use conflict between agriculture and the eco-environment, based on economic compensation for irrigation stakeholders. A hybrid Bayesian network (HBN) is developed to implement the framework, including: (a) agricultural water shortage assessments after meeting environmental flows; (b) water-use tradeoff analysis between agricultural irrigation and environmental flows using the HBN; and (c) quantification of the agricultural economic compensation for different irrigation stakeholders. The constructed HBN is computed by dynamic discretization, which is a more robust and accurate propagation algorithm than general static discretization. A case study of the Qira oasis area in Northwest China demonstrates that the water trade-off based on economic compensation depends on the available water supply and environmental flows at different levels. Agricultural irrigation water extracted for grain crops should be preferentially guaranteed to ensure food security, in spite of higher economic compensation in other cash crops’ irrigation for water coordination. Updating water-saving engineering and adopting drip irrigation technology in agricultural facilities after satisfying environmental flows would greatly relieve agricultural water shortage and save the economic compensation for different irrigation stakeholders. The approach in this study can be easily applied in water-stressed areas worldwide for dealing with water competition. [ABSTRACT FROM AUTHOR]

There is an increasing consensus on the importance of coupling ecosystem services (ES) into integrated water resource management (IWRM), due to a wide range of benefits to human from the ES. This paper proposes an ES–based IWRM framework within which a participatory Bayesian network (BN) model is developed to assist with the coupling between ES and IWRM. The framework includes three steps: identifying water-related services of ecosystems; analysis of the tradeoff and synergy among users of water; and ES-based IWRM implementation using the participatory BN model. We present the development, evaluation and application of the participatory BN model with the involvement of four participant groups (stakeholders, water manager, water management experts, and research team) in Qira oasis area, Northwest China. As a typical catchment-scale region, the Qira oasis area is facing severe water competition between the demands of human activities and natural ecosystems. Results demonstrate that the BN model developed provides effective integration of ES into a quantitative IWMR framework via public negotiation and feedback. The network results, sensitivity evaluation, and management scenarios are broadly accepted by the participant groups. The intervention scenarios from the model conclude that any water management measure remains unable to sustain the ecosystem health in water-related ES. Greater cooperation among the stakeholders is highly necessary for dealing with such water conflicts. In particular, a proportion of the agricultural water saved through improving water-use efficiency should be transferred to natural ecosystems via water trade. The BN model developed is appropriate for areas throughout the world in which there is intense competition for water between human activities and ecosystems. [ABSTRACT FROM AUTHOR]

In hydrological time series prediction, singular spectrum analysis (SSA) and discrete wavelet transform (DWT) are widely used as preprocessing techniques for artificial neural network (ANN) and support vector machine (SVM) predictors. These hybrid or ensemble models seem to largely reduce the prediction error. In current literature researchers apply these techniques to the whole observed time series and then obtain a set of reconstructed or decomposed time series as inputs to ANN or SVM. However, through two comparative experiments and mathematical deduction we found the usage of SSA and DWT in building hybrid models is incorrect. Since SSA and DWT adopt ‘future’ values to perform the calculation, the series generated by SSA reconstruction or DWT decomposition contain information of ‘future’ values. These hybrid models caused incorrect ‘high’ prediction performance and may cause large errors in practice. [ABSTRACT FROM AUTHOR]

The existence and development of oases in arid plain areas depends mainly on the runoff generated from alpine regions. Quantifying the uncertainties of runoff simulation under climatic change is crucial for better utilization of water resources and management of oases in arid areas. In the present study, based on the ungauged Qira River Basin in Xinjiang, China, a modified version of the Delta statistical downscaling method was applied to reconstruct the monthly mean temperature (MMT), monthly accumulated precipitation (MAP), and monthly accumulated evaporation (MAE) of two target stations. Then, the uncertainty in runoff simulation, implemented using the Three-Layered Feedforward Neural Network model with the Back-Propagation learning algorithm, was quantified. The modified Delta method reproduced the MMT, MAP, and MAE time series of the two target stations very well during the calibrated periods, and the reconstructed uncertainty ranges were small among reconstructed datasets using data from 12 observation stations. The monthly accumulated runoff simulated by the reconstructed MMT, MAP, and MAE as input variables of the model possessed unpredictable uncertainty. Although the use of multi-data ensembles in model inputs are considered an effective way to minimize uncertainties, it could be concluded that, in this case, the efficiency of such an approach was limited because of errors in the meteorological data and the deficiency of the model's structure. The uncertainty range in the runoff peak was unable to capture the actual monthly runoff. Nevertheless, this study represents a significant attempt to reproduce historical meteorological data and to evaluate the uncertainties in runoff simulation through multiple input ensembles in an ungauged basin. It can be used as reference meteorological data for researching long-term climate change and producing runoff forecasts for assessing the risk of droughts and/or floods, as well as the existence and management of plain oases in the Qira River Basin. [ABSTRACT FROM AUTHOR]

• Dust sources in the Aral Sea region cover an area of more than 27,000 km2. • The multi-year average potential dust emission of 80.5 Tg from 2010 to 2020. • The eastern basin of the Aral Sea was found to be the main dust source. • The potential diffusion range of the Aral Sea dust could exceed 38.5 × 106 km2. The rapid drying of the Aral Sea has led to a series of complex environmental changes and a large amount of aeolian dust have been swept up from the exposed bottom. This study used a wind erosion model and the Hysplit model to investigate emission and transport characteristics of the Aral Sea dust. The spatial pattern of dust emission was determined by quantifying the surface conditions. The total source area in the Aral Sea region exceeds 27,000 km2, with annual average dust emission of up to 87.6 Tg from 2010 to 2020. The main source of dust was found to be in the eastern Aral Sea basin. The spatial pattern of dust emission in a year was seasonal and the highest value and the widest spatial range occurred in spring. Modeling of a dust event on March 22, 2020 showed that PM 10 dust emitted from the Aral Sea region can be transported over 4,000 km, and the area of land surface affected was more than 6.21 × 106 km2. The potential impact area of the Aral Sea dust was mapped by the numerical simulations for the past 24 severe dust storms, which indicates that the Aral Sea dust can reach the Arctic Ocean, Iran, the Atlantic Ocean through France, and the Pacific Ocean through Japan, covering a land area of more than 38.5 × 106 km2. [ABSTRACT FROM AUTHOR]

An oasis is a unique landscape that fuels human subsistence and socioeconomic development in the desert ecosystem. However, the overexpansion of oases, especially farmlands, poses severe threats to available land and water resources. This study aims to assess the expansion levels, carrying capacity dynamics, and planting structure optimization to maximize economic returns in northwest China's five Typical Oasis Groups (5TOGs) using uniform data sources, time scales, and methods. Satellite products and a water-heat balance model were used to evaluate the changes in the area and carrying capacity dynamics of the 5TOGs. A linear programming approach was used to optimize each oasis's cropping structure for the carrying level scenario. The results showed that the area of 5TOGs has expanded from 1980–2020, and the increment of oasis farmland is the main driver of oasis expansion. The most dramatic expansion of oases and their farmlands occurred during 2010–2020. As a consequence, the carrying capacity of each oasis is deteriorating with this expansion. The additional water resources to support this expansion of the oases and their farmlands come from groundwater, which is declining rapidly. Based on the optimized planting structure, cotton remains the main crop in Xinjiang oases with more than 60% area, the cotton area should be reduced in the Hotan River Oases, and the planting structure of the Heihe River Oasis will remain unchanged. The findings of this study have provided a quantitative analysis of oasis expansion and planting structure optimization, which have practical implications for water resource management and sustainable development of agriculture to maintain the stability of the oasis ecosystem. [ABSTRACT FROM AUTHOR]

• The sand flow channel provides sand sources between deserts. • Sand flow channels promote the development of modern desert systems. • The sand flow channels connected independent deserts to an entire desert system. Based on the interactions between mountains, we identified three sand flow channels in the Badain Jaran, Tengger, and Ulan Buh Deserts, northern China. We found that the height difference of the terrain in these areas provided favorable conditions for the transportation of sand. Owing to the venturi effect of their geomorphologies, airflow was compressed in these channels, and their wind regimes were strong and unimodal. Compared with the interior of the desert, the sand transport potential was relatively large in these areas, and westerly and northwest winds prevailed. We found that the wind accelerated in the sand flow channels, resulting in faster-moving dunes. The dune types that developed in these channels were relatively simple owing to the unimodal wind regimes; they mainly comprised barchan and transverse dunes. We also identified a transition landscape from barchan dunes to transverse, or complex dunes. Based on their sediment characteristics and the prevailing wind directions, we found that the sand flow channels provided a direct sand supply between the three deserts. The sand flow channels connected these independent deserts to an entire desert system. Similar sand flow channels can also be found in other deserts globally. Collectively, these sand flow channels reflect interactions between deserts. [ABSTRACT FROM AUTHOR]

• The albedo-MSAVI point-to-point model is the most suitable feature space model for desertification monitoring in the Sahel. • The level of desertification has reduced from 2000 to 2020 in the Sahel. • Light, moderate desertification lands undergoing greater change intensity. • Precipitation is the dominant factor of desertified land area change. The transitional characteristics of desert grasslands in the Sahel determine the ecosystem's fragility, which is extremely susceptible to the expansion and reversal of land desertification under the influence of climate change and anthropogenic activities. Accordingly, monitoring desertification dynamics is essential to combat this process. Based on Moderate Resolution Imaging Spectroradiometer (MODIS) data, this study analysed the applicability of different feature space models to monitor desertification levels in the Sahel from 2000 to 2020, revealing the optimal monitoring model, analysing the spatiotemporal changes and primary driving factors. The results were as follows: In the Sahel, the albedo-modified soil adjusted vegetation index (MSAVI) based on the point-to-point model is the best for desertification monitoring, with an overall accuracy of 86.78%. Generally, the level of desertification was reduced from 2000 to 2020, the area of extremely severe desertification decreased by retreating northward; and the areas of light, moderate, and severe desertification increased slowly by expanding northward. Light, moderate, and severe desertification lands were more sensitive to climate change and anthropogenic activities, undergoing greater change intensity. Precipitation was the most influential factor determining the spatial distribution of desertification in the Sahel, with anthropogenic activities also having a significant effect on the desertification level. This study comprehensively analysed desertification patterns in the Sahel and identified the primary driving factors, which are essential to inform Sahelian desertification control mechanisms in the future. [ABSTRACT FROM AUTHOR]

Aerosols are an important component of the atmospheric system. Long time-series observations for aerosols are essential for examining global climate change and the ecological environment. Based on Google Earth Engine and MODIS MCD19A2 data, we monitored the spatio-temporal dynamic characteristics of the aerosol optical depth (AOD) in Central Asia from 2001 to 2020. The effects of six environmental factors on the AOD distribution were explored using a geographic detector model and analysed in combination with the land-use/land-cover change (LUCC) and desertification in different periods. The results showed that the average multi-year AOD in Central Asia was 0.1442, with insignificant interannual variations. The high-value areas were mainly distributed in the Aral Sea and surrounding areas of the Tarim Basin in Xinjiang, with notable seasonal variations. The evaluation results for the influencing factors showed that the relative humidity and precipitation had a large effect on the spatial distribution of the AOD. The LUCC directly affected contributions to the AOD. Desertification of land provides rich dust sources, which are the main aerosol sources in Central Asia, thus exacerbating dust aerosol pollution. This study investigated the temporal and spatial characteristics and influencing factors of the AOD in Central Asia, providing a theoretical basis for the prevention and control of air pollution. [ABSTRACT FROM AUTHOR]

Although the western Sahara Desert is dominated by aeolian dunes, research on the geomorphology of aeolian dunes throughout this region as a unit has been limited compared with other large deserts. In the present study, comprehensive research is conducted on the geomorphology of dunes in the western Sahara Desert based on aeolian parameters and dune growth mechanisms. We identified the controlling factors on the dune morphology and formation of superimposed dunes. The results suggest that the spatial patterns of dune morphology are closely correlated with the drift potential (DP) and dune orientation. A well-defined gradient of declining DP, resultant drift potential (RDP), and directional wind variability from north to south was found, indicating a gradual weakening trend in the DP along the sand flow path. Linear and transverse dunes are distributed on the central part of the desert. Barchan dunes are distributed on the western coastal areas and desert margins. Lastly, star dunes are distributed in the upwind on the northern desert margin. We concluded that the wind regime and sand availability directly impact the dune morphology in the western Sahara Desert by considering the growth mechanisms. This study provides valuable reference data on regional aeolian activities that can be used by subsequent regional aeolian geomorphology studies in the western Sahara Desert. • Controlled by wind regime and sand availability, a variety of aeolian dune types was found in the western Sahara Desert. • The spatial patterns of dune morphology are closely correlated to the drift potential and dune orientation. • Superimposed dunes grow in the bed instability mode and modify the preexisting dunes which are growing in the fingering mode. [ABSTRACT FROM AUTHOR]

[Display omitted] • SBAS-InSAR is used to monitoring the wind erosion of lake basin. • Subsidence of up to 100 mm was observed during the period from 2015 to 2018. • Wind speed and soil moisture content are the primary factors driving the seasonal variations in wind erosion. • Water bodies and vegetation play a significant inhibitory role in wind erosion. In arid regions, terminal lakes play a crucial role in maintaining the local ecological environment. However, due to the impact of climate change and human activities, terminal lakes are prone to shrinkage and drying up. The exposed lakebeds became new sources of sand and dust, leading to severe land degradation. This study extracted the water surface area of the Chaiwopu Lake in Urumqi and calculated the fractional vegetation cover (FVC) in the surrounding areas based on Landsat images from 2000 to 2022. The changes in FVC and lake area before and after the implementation of the policies on fallow and groundwater extraction restriction in 2014 were analyzed. Using the SBAS-InSAR method, the surface deformation during the period of minimum lake area from 2014 to 2018 was estimated, and the process of wind erosion and accumulation in the dried lake basin was analyzed. The results showed that from 2011 to 2014, Chaiwopu Lake experienced rapid shrinkage, and the lake almost disappeared. After 2014, the lake rapidly recovered, reaching 70% of its original area by 2021. With the recovery of the lake, the vegetation coverage in the surrounding area has changed from decreasing to increasing. During the period of lake shrinkage, the dried lake basin experienced severe wind erosion, with the maximum erosion rate exceeding 40 mm/year. The sand and dust from the dried lake basin accumulated around the lake under the influence of wind, further accelerating land degradation in the surrounding areas. After 2021, the restored lake and wetland surface covered the once-dry lake basin again, and the largest dust source in the region nearly disappeared. The study results indicated that the restoration of the lake and surrounding vegetation can eliminate the sources of sand and dust and prevent their transportation, effectively preventing land desertification. [ABSTRACT FROM AUTHOR]

We studied the variation of soil moisture as well as its regularity over the irrigation cycle at shelterbelts along the Tarim Desert Highway at different site types and different planting years. The results show that: (1) There is an obvious temporal variation of soil moisture within a typical irrigation period in shelterbelts along the Tarim Desert Highway, and the soil water storage varied linearly with the number of days after irrigation. Along the direction perpendicular to the soil top, the soil profile can be divided into four layers and each shows different dynamics of soil moisture variation, including the quickly changing layer (0-20 cm), the active layer (20-60 cm), the weakly layer (60-100 cm), and the regulated layer (under 100 cm). (2) Both the soil moisture and soil water content decreased gradually with the number of planting year, while the soil water deficit increased. It indicates that shelterbelts along the Tarim Desert Highway can retain the water accumulated from previous years. (3) The soil water storage of harden sand is the maximum among all types of sites. Specifically, it is about 1.58 times higher than that of longitudinal dune, 1.15 times higher than clay, and 1.43 times higher than flat sand. Its soil water deficit was over 900 mm. [ABSTRACT FROM AUTHOR]

The EC analysis and water serial sampling was performed in the Tarim Desert Highway shelterbelt to explore the water and salt dynamics of the shallow aeolian sandy soil ( 0-30cm) under high salinity groundwater drip irrigation. It was found that in one irrigation cycle, the EC of the shallow shifting aeolian sandy soil ( 0-30cm) increased while the water content decreased. The EC of the surface aeolian sandy soil at the wetting front was far greater than that of the wetting area or the outside of the wetting area. During the irrigation cycle, the EC of the wetting front and the wetting area changed at a significant magnitude, whereas the EC of the outside of the wetting area remained largely steady. The horizontal influence distance of drip irrigation on the salt accumulation at the soil surface was about 100 cm, and the vertical influence depth was 5 cm. The three most abundant ions in the accumulated salt at the aeolian sandy soil surface were Na+, Cl- and SO42-. The salt accumulation at the soil surface was influenced by air temperature, wind speed, mineralization of irrigation water, sand burial thickness, soil texture, and litter content. [ABSTRACT FROM AUTHOR]

Site types of the afforestation region of the shelter-forest ecological project along the Tarim Desert Highway were classified based on the natural conditions and windblown sand damages. The extremely severe environment, the irrigation with saline water, and large-scale linear project makes this classification of site types most unique and significant. It adopted a three-level classification system integrating the dominant factors and restrictive factors in regard to their impacts on plant survival and growth as well as on the protective property. Six site type districts were classified based on the medium- scale geomorphic unit, the windblown sand damages, and the major production facilities; 21 site type groups were obtained according to the small-scale geomorphic type, terrain, and wind regime; 36 site types were further classified based on the salt contents of the underground water and soil types. Especially, in this study, spatial distribution of the six site type districts along the desert highway is continuous, which is unique and different from that of most other classifications. In addition, the salt-stress tolerance threshold of the main afforestation plant species to underground water have been set to 8 g/L and 15 g/L according to selective breeding tests and the salinity spatial distribution of the underground water. Thus, the underground water with salinity lower than 8 g/L is defined as light saline water in this area. [ABSTRACT FROM AUTHOR]

The Tarim Desert Highway shelterbelt, located in hinterland of Taklimakan Desert, is irrigated by underground saline water, with three to thirty gram per litter mineral degrees. The sustainability and stability are affected by multifarious stress. The structural and functional characteristics of shelterbelt are studied to probe into correlation between environment and shelterbelt. On basis, decision analysis is applied to study ecological stability of the Tarim Desert Highway shelterbelt, to screen out limited factors, to establish general index system, and to evaluate the stability of the shelterbelt nowadays. Finally, the concept of ecological stability is utilized to manage the artificial ecosystem. The results show that the artificial ecosystem is relatively flimsy, whose stability can be increased by adjusting stand structure and improving the nutrient cycle. [ABSTRACT FROM AUTHOR]

This paper examines turbulent flow structures over a nebkha. We use high-frequency 3D ultrasonic anemometers to sample the wind velocity and turbulent flow across the longitudinal axis (center-line) of the nebkha. Results determined using quadrant analysis of wind velocity show that although the ejection and sweep events are dominant in the toe region of the nebkha, making a positive contribution to the Reynolds shear stress, the reversed wind flow can occur near the toe region when the stoss slope is sufficiently steep. The reversing flow causes an increase of the frequency of occurrence of inward and outward events in the lower stoss region, which suppresses the generation of Reynolds shear stress. Computational fluid dynamic (CFD) modelling demonstrates that when the stoss slope is lower than 20∘, flow reversing can not occur at the toe region, suggesting that 20∘ can be considered as the threshold stoss slope for the generation of reversing flow near the toe region of the nebkha, which is confirmed by the field observations. When the instantaneous Reynolds shear stress − u ′ w ′ ¯ is one order of magnitude larger than the mean Reynolds shear stress, it contributes approximately 40% to the mean Reynolds shear stress with < 5% of the time share rate, suggesting that the instantaneous Reynolds shear stress might be the controlling factor for the entrainment of sand particles. As a consequence, when monthly, daily or hourly wind data are used to estimate the sand flux, some important instantaneous information (i.e., storm events) may be smoothed out by the averaging process. [ABSTRACT FROM AUTHOR]

Land degradation and desertification are the serious ecological problems and challenges to achieve global sustainable development goals. The Chinese government proposes to integrate the construction of the Silk Road Economic Belt with the environmental improvement of the Central Asia, to build an intimate community of shared destiny between China and the Central Asia countries, and to promote the green and sustainable development of the Silk Road Economic Belt. However, the ecological crisis in the Aral Sea causes a significant shrinking in water body, loss of biodiversity, salinization, desertification, and salt dust storm, which have become major environmental problems encountered in the construction of the Silk Road Economic Belt in the Central Asia. On the basis of sorting out the problems of land degradation and desertification caused by the ecological crisis in the Aral Sea, this study scientifically analyzed the development trend and causes of desertification and salinization land in the Aral Sea region in the past 30 years, discussed the spatial differences of vegetation stability and its carrying capacity in the Amu Darya Basin and the Aral Sea region, and put forward the directions, strategies, key technologies and innovative modes of ecological restoration for the desertification and salinized land. Solving the ecological crisis and desertification in the Aral Sea is one of the key points in the construction of the Green Silk Road, and also an important embodiment of building a community of shared future for mankind and practicing the global values of ecological civilization. [ABSTRACT FROM AUTHOR]

The ecological system of the desert/grassland biome transition zone is fragile and extremely sensitive to climate change and human activities. Analyzing the relationships between vegetation, climate factors (precipitation and temperature), and human activities in this zone can inform us about vegetation succession rules and driving mechanisms. Here, we used Landsat series images to study changes in the normalized difference vegetation index (NDVI) over this zone in the Sahel region of Africa. We selected 6315 sampling points for machine-learning training, across four types: desert, desert/grassland biome transition zone, grassland, and water bodies. We then extracted the range of the desert/grassland biome transition zone using the random forest method. We used Global Inventory Monitoring and Modelling Studies (GIMMS) data and the fifth-generation atmospheric reanalysis of the European Centre for Medium-Range Weather Forecasts (ERA5) meteorological assimilation data to explore the spatiotemporal characteristics of NDVI and climatic factors (temperature and precipitation). We used the multiple regression residual method to analyze the contributions of human activities and climate change to NDVI. The cellular automation (CA)-Markov model was used to predict the spatial position of the desert/grassland biome transition zone. From 1982 to 2015, the NDVI and temperature increased; no distinct trend was found for precipitation. The climate change and NDVI change trends both showed spatial stratified heterogeneity. Temperature and precipitation had a significant impact on NDVI in the desert/grassland biome transition zone; precipitation and NDVI were positively correlated, and temperature and NDVI were negatively correlated. Both human activities and climate factors influenced vegetation changes. The contribution rates of human activities and climate factors to the increase in vegetation were 97.7% and 48.1%, respectively. Human activities and climate factors together contributed 47.5% to this increase. The CA-Markov model predicted that the area of the desert/grassland biome transition zone in the Sahel region will expand northward and southward in the next 30 years. [ABSTRACT FROM AUTHOR]

Compared with longer-crested linear dunes formed in the bimodal wind regime, little is known about the driving forces of linear dunes that elongate in the lee side of obstacles under a unimodal wind regime. Here, we present the flow dynamics and sand deposition patterns around the aligned nebkhas with different spacing distances (∆) based on computational fluid dynamics (CFD) simulation, wind tunnel experiment and field measurement. In terms of the relationships between the width of horseshoe vortex around two laterally aligned nebkhas (T 1 and T 2 , respectively) and ∆, four wake flow patterns were identified: distinctly merged wake flow when ∆ → 0, merging flow when 0 < ∆ < T 1 + T 2 , two isolated and weakly interfered flows when 0 ≪ ∆ < T 1 + T 2 , and two independent wake flows when ∆ ≫ T 1 + T 2. Considered two aligned nebkhas with the same dimension of diameter D , ∆ < 1.5 D commonly contributes to the merging and elongation of shadow dunes. We suggest that wake flow interference has been reported to produce a region of enhanced deposition with the minimum wind speed and shear stress, i.e., secondary deposition zone, which is determined by sediment supply and ∆ of nebkha alignments. Spatial distance ∆ between tandem aligned nebkhas strongly controls the morphology of bead-like shadow dunes. It is found that the elongation of shadow dunes in the unimodal winds can be well explained by the deflection flow around sand ridges, thus demonstrating the driving forces for the elongation of unimodal-wind-subjected shadow dunes. • Four types of wake flow patterns are discerned at the wake region of laterally aligned nebkhas. • Flow interference between laterally aligned nebkhas is crucial for convergence and elongation of neighboring shadow dunes. • The spacing distance between tandem aligned nebkhas plays a key role in the bead-like shadow dune elongation. • The flow deflection around sand ridges drives shadow dune elongation in a unimodal wind. [ABSTRACT FROM AUTHOR]

Central Asia (CA) occupies the hinterland of the Eurasian continent, containing the countries of Uzbekistan, Kyrgyzstan, Turkmenistan, Tajikistan, and Kazakhstan [[1]]. Therefore, the climate of CA is comprised of both an alpine climate (including snow and ice) with extremely low temperatures and a desert climate with extremely high temperatures. Both the maximum and minimum temperatures exhibited significant increasing trends from southwestern CA to eastern CA. The temperature rise in CA is significantly higher than the global average; thus, the impact of climate change on water-cycle processes is likely to be magnified in CA compared with other regions of the world. [Extracted from the article]

Calculating the ecological footprint at the regional scale is a complicated topic for researchers in quantifying ecosystem services, but as well a crucial step for local decisionmakers to formulate pertinent and feasible polices in guiding the region's sustainable development, particularly in such a severe dryland region as Xinjiang Uygur Autonomous Region (Xinjiang Region), China, with vastly extensive drylands covered by deserts up to more than million square kilometers. Aiming at improving the effectiveness of ecological footprint calculation (EFC) for dryland areas, this study has modified the methodology of EFC for drylands by incorporating both ecological and productive contributions from desert areas into the EFC process, including the net primary production, emissions from energy consumption, and contaminant discharge, as well as water resources use. The modified method of EFC for drylands involved some recalibrated equivalence factors for desert areas in the calculating process to determine the yield factors for each local administrative unit at prefecture level based on its net primary production (NPP). The results from this study revealed the following: (1) From 2009 to 2020, the average ecological deficit in Xinjiang Region was 16.172 global hectares per capita (gha/cap), with average human use of the desert at 0.22 gha/cap, representing approximately 1.41% of the total ecological footprint. The average biocapacity of desert was 0.12 gha/cap, accounting for approximately 6.73% of the total biocapacity. (2) During the same period, the ecological footprint exhibited an initial increasing trend followed by a subsequent decrease. The ecological biocapacity demonstrated a significant decreasing trend (p < 0.05). All prefectural administrative units within Xinjiang Region exhibited an ecological deficit from 2009 to 2020, whereas a desert ecological surplus occurred only in the Kyzylsu, Kashgar, and Hotan prefectures. (3) As the ecological deficit in Xinjiang was on an increasing trend, it is recommended that in these regions, replacing thermal power with wind and/or photovoltaic power might be a way out to alleviate much of the deficit, since it could reduce the ecological footprint by 8.44%, and would decrease the ecological deficit by benefiting from deserts' carbon reduction. Based on this study, we would like to advocate for optimizing the energy structure in regions with significant desert coverage and enhancing desert production through implementing ecological farming practices. [Display omitted] • Desert ecosystems were included in the ecological footprint accounting for drylands. • The equivalence factors of desert quantified by NPP was 4.4% of that of grassland. • Xinjiang showed ecological deficits but Kizi, Kash, Hota were in surplus in deserts. • Renewable energy development in the desert may reduce ecological footprint by 8.44%. [ABSTRACT FROM AUTHOR]

The detailed precipitation characteristics is required for the investigation of regional hydrological processes, precipitation related disasters, and water resources management. Quantifying and understanding the precipitation change in arid area are crucial for prediction of its future and avoiding disasters. In this study, it was investigated the precipitation concentration, and its variability along with the linkage of global large-scale circulation anomalies in Xinjiang between 1960 and 2016. Using meteorological data from 54 weather stations coupling with atmospheric circulation indices, several precipitation indices were used as standard measures for determining the basic characteristics of floods and droughts. Results showed that the characteristics of the precipitation concentration feature were identified by two precipitation indices: precipitation concentration degree (PCD) and precipitation concentration period (PCP). The PCD value has decreased in recent years, which illustrates the characteristics of drought. The values of the precipitation concentration index (PCI) that indicated extreme precipitation ranged from 9 to 20 in 57 years and exhibited a significant decreasing trend in 1960–2016. However, an increasing precipitation condition can be observed through the monthly standardized precipitation index (SPI), which indicates that drought–flood abrupt alternation will be more frequent and the abrupt change should be noticed in recent years. It is found to be suitable to use the long-cycle drought–flood abrupt alternation index (LDFAI) to investigate the characteristics of drought–flood abrupt alternation during summers. Further investigations on the linkage between drought–flood abrupt alternation and atmospheric circulation indices showed that the time delay of LDFAI after an atmospheric anomaly will be 1–4 months. The results of this study will help mitigate and regulate the precipitation related problems in arid area, as well as in other regions. [ABSTRACT FROM AUTHOR]

Wind erosion models are important tools for assessing soil erodibility and identifying management practices to control erosion. The Agricultural Policy/Environmental eXtender (APEX) model and Revised Wind Erosion Equation (RWEQ) were tested using data collected from the Tarim Basin of China and Columbia Plateau of the United States of America. Adequate performance in simulating soil loss was achieved using the original APEX model and RWEQ in respectively a cotton field and desert-oasis ecotone in the Tarim Basin and winter wheat - summer fallow (WW-SF) field in the Columbia Plateau. We calibrated the APEX model and RWEQ to improve performance because both models have many empirical parameters. After calibration, both models adequately simulated soil loss from all land use types except the RWEQ from the red date orchard in the Tarim Basin. Inadequate performance of the calibrated RWEQ in the red date orchard was likely due to underestimating maximum mass transport. [ABSTRACT FROM AUTHOR]

The competition for water resources between agricultural and natural oasis ecosystems has become an increasingly serious problem in oasis areas worldwide. Recently, the intensive extension of oasis farmland has led to excessive exploitation of water discharge, and consequently has resulted in a lack of water supply in natural oasis. To coordinate the conflicts, this paper provides a decision-making framework for modeling environmental flows in oasis areas using Bayesian networks (BNs). Three components are included in the framework: (1) assessment of agricultural economic loss due to meeting environmental flow requirements; (2) decision-making analysis using BNs; and (3) environmental flow decision-making under different water management scenarios. The decision-making criterion is determined based on intersection point analysis between the probability of large-level total agro-economic loss and the ratio of total to maximum agro-economic output by satisfying environmental flows. An application in the Qira oasis area of the Tarim Basin, Northwest China indicates that BNs can model environmental flow decision-making associated with agricultural economic loss effectively, as a powerful tool to coordinate water-use conflicts. In the case study, the environmental flow requirement is determined as 50.24%, 49.71% and 48.73% of the natural river flow in wet, normal and dry years, respectively. Without further agricultural economic loss, 1.93%, 0.66% and 0.43% of more river discharge can be allocated to eco-environmental water demands under the combined strategy in wet, normal and dry years, respectively. This work provides a valuable reference for environmental flow decision-making in any oasis area worldwide. [ABSTRACT FROM AUTHOR]

The terminal branch orders of plant root systems have been proposed as short-lived 'ephemeral' modules specialized for resource absorption. The occurrence of ephemeral root modules has so far only been reported for a temperate tree species and it is unclear if the concept also applies to other woody (shrub, tree) and herb species., Fine roots of 12 perennial dicotyledonous herb, shrub and tree species were monitored for two growing seasons using a branch-order classification, sequential sampling and rhizotrons in the Taklamakan desert., Two root modules existed in all three plant functional groups. Among the first five branch orders, the first two (perennial herbs, shrubs) or three (trees) root orders were ephemeral and had a primary anatomical structure, high nitrogen (N) concentrations, high respiration rates and very short life spans of 1-4 months, whereas the last two branch orders in all functional groups were perennial, with thicker diameters, no or collapsed cortex, distinct secondary growth, low N concentrations, low respiration rates, but much longer life spans., Ephemeral, short-lived root modules and long-lived, persistent root modules seem to be a general feature across many plant functional groups and could represent a basic root system design. [ABSTRACT FROM AUTHOR]