By using FY-4A satellite data and artificial observation data of recent (2018-2020) severe precipitation cases in Ningxia, four different FY-4A satellite product types are examined in terms of their availability. Results show that: (1) The data transmission rate and physical preservation of FY-4A are sufficient to support real-time monitoring and early warning services; (2) The five kinds of products i.e., Cloud Type (CLT), Cloud Phase (CLP), Cloud Top Height (CTH), Quantitative Rainfall-Rate Estimation (QPE), and Tropopause Folding Depth (TFTP_Z_depth), have different performances in the case of severe convective weathers in Ningxia. Among them, CLT and CLP have good availability, making it possible to determine the type of cloud more accurately. However, both CTH and QPE have large errors and tend to be smaller, so they need to be revised in conjunction with other means. The relationship between CTT or TFTP_Z_depth products and recent severe precipitation is obvious. The high value of CTH is conducive to the occurrence of heavy precipitation but is not a necessary condition. Overall, the FY-4A satellite has certain usability and reference in severe convective weather in Ningxia, which can provide better data support for convective weather discrimination and artificial influence on weather operation.

The vapor pressure deficit can reflect the ability of the atmosphere to obtain water from the surface,which is one of the main driving factors of evapotranspiration. Clarifying the spatial and temporal variation of vapor pressure deficit (VPD) can help to investigate the response of air dryness to climate change in Tibetan Plateau. Mann-Kendall test, multiple linear regression were used to analyze temporal and spatial variation characteristics and the influencing factors of VPD before and after the breakpoint from 1961 to 2020 in Qinghai Province. The results showed that VPD had an increasing trend in Qinghai Province from 1961 to 2020 and a mutation in 1998. The seasonal averages and corresponding climatic trend rates of VPD were the same as summer>spring>autumn>winter. In different functional areas, average VPDs showed as Qaidam Basin>Eastern Agricultural Area>Qinghai Lake Area>Qingnan Pastoral Area, the corresponding climatic trend rates were the Eastern Agricultural Area>Qaidam Basin>Qingnan Pastoral Area>Qinghai Lake Area. The multi-year average VPD showed a “saddle field” distribution in space, and had an increasing trend except the Guinan Station in the northeastern of Qingnan pastoral area, which had a decreasing trend. The predominant meteorological factors of VPD were different before and after mutation in Qinghai Province. However, the highest temperature and relative humidity in general were the main factors. During the variation of VPD in the spring, summer, autumn and multi-year, the contribution rate of altitude was the highest, followed by longitude; while in winter, the contribution rate of altitude is still the highest, followed by latitude.

For maintaining crop yield in salt-affected dry agricultural settings, monitoring and analyzing spatio-temporal dynamics of soil salinity over broad areas is crucial yet challenging due to its high variability. The most popular techniques for evaluating spatial distribution patterns and temporal trends are classical statistical analysis and traditional geostatistical analysis, but they are not suitable for accurately capturing spatio-temporal trends of soil salinity due to irregular sampling time and inconsistent spatial position during sampling time. Spatio-temporal Kriging is an extension of spatial geostatistics to space-time geostatistics and may overcome this problem effectively because its model covariance/variance is a function of both space and time. However, its application in spatio-temporal modeling and prediction of regional soil salinity is still unclear. Based on 4582 soil salinity data of 0-1.8 m soil profiles from 68 monitoring locations in the Longsheng study area of Hetao Irrigation District, Inner Mongolia, spatio-temporal variation characteristics of regional soil salinity using a spatio-temporal geostatistical method, and spatio-temporal Kriging interpolation accuracy was compared with traditional spatial Kriging interpolation. Furthermore, the ability of spatio-temporal Kriging to obtain regional soil salinity dynamics was verified using less than half of the original monitoring locations. The results showed that the spatial variation coefficient of soil salt in the study area ranged from 0.43 to 1.14, which was categorized as medium to strong variability. Regional averaged soil salinity dynamics had obvious seasonal variation characteristics, and the root zone (0-0.6 m) soil salinity accumulated in the crop growing season and desalted in the fallow season, while the deep soil salinity (0.6-1.8 m) was the opposite. The sum-metric model can fit the temporal and spatial experience semi-variance of soil salinity well, and the root mean square error (RMSE) between the predicted value and observed value of soil salinity in each layer was less than 0.21 dS·m^-1, which was 0.02-0.09 dS·m^-1 less than that of traditional spatial Kriging. The areas of different soil salinity determined by 32 sparse monitoring locations were in good agreement with those determined by all sampling sites, and the mean relative error between areas of different soil salinity for 0-0.6 m and 0.6-1.2 m were -13.20% and -8.35%, respectively. Similarly, the respective RMSE were 466.67 hm² and 494.43 hm² and the determination coefficient (R²) were 0.79 and 0.72, indicating that spatial distribution of soil salinity obtained by sparse monitoring locations is consistent with the results of all sampling locations. Spatio-temporal Kriging significantly improves the prediction accuracy of soil salinity compared with ordinary Kriging, since it uses more information on soil salinity in time and space. The accurate estimation of spatio-temporal dynamics of soil salinity in the data set of sparse monitoring points was realized, which can greatly improve the monitoring efficiency of the spatio-temporal pattern of soil salinity in the region.

A grazing and enclosed Pinus sylvestris var. mongolica forests in sandy land was selected to explore the effects of grazing on soil nutrients and microbial communities. The microbial community composition and diversity between grazing and enclosed soil was determined using high-throughput sequencing technology. Soil chemical indexes were determined for estimating variation in the nutrients. The results showed that total phosphorus content decreased significantly after grazing (P < 0.05). Soil organic carbon and total nitrogen content also decreased, while ammonium nitrogen, nitrate nitrogen, and available phosphorus increased, but the change was not significant (P > 0.05). The grazing and enclosed plots showed 17.1%-24.6% similarity in the soil microbial community composition and the OTUs of fungi and bacteria were lower in grazing than enclosed plots. At each classification level, the number of fungi and bacteria in grazing plots was less than that in enclosed plots. Results showed grazing significantly reduced the number of bacteria at the genus level(P < 0.05). The proportion of basidiomycetes in grazing was significantly lower than that in enclosure (P < 0.05). No significant indigenous effect on bacterial phylum level (P > 0.05) was observed. In terms of soil microbial diversity, grazing significantly reduced the Chao1 index and Shannon index of bacteria (P < 0.01), and had no significant effect on fungal community diversity (P > 0.05). The effect of grazing on soil bacterial diversity index was greater than that of fungi. In summary, grazing in the Pinus sylvestris var. mongolica forest in sandy land has different degrees of negative impacts on soil nutrients and soil microorganisms. Therefore, the grazing should be moderately reduced in this region to alleviate land pressure and ensure the sustainable utilization of the Pinus sylvestris var. mongolica plantation.

Carrying out the optimal allocation of land use is aimed at promoting the scientific use of regional land resources and achieving carbon emission reduction targets. In this paper, the Fenhe River Basin is taken as the research area. Based on the data on land use and resistance factors in 2015 and 2020, the FLUS-MCR model and the carbon budget coefficient method are used to verify the accuracy of the model. Five simulation scenarios, such as low-carbon development priority, economic development priority, cultivated land protection priority, ecological protection priority, and natural development in 2030, are set up to compare the layout characteristics of land use types under different scenarios in the future, and an optimized layout scheme is proposed. The results showed that: (1) In 2020, the areas of four land use functional zoning of the prohibited, restricted, key, and optimized development zones in Fenhe River Basin were 2491.76 km², 6445.99 km², 16325 km², and 14477 km², respectively. The net carbon emission of the basin is 2002.46 × 10⁴ t. The prohibited development zone is the carbon sink area of the basin, and the total carbon absorption is 0.76×10⁴ t. The remaining three areas are carbon source areas, and the total carbon emission is 2003.22 × 10⁴ t. (2) In 2030, the carbon balance of land use in each scenario from high to low is low-carbon development priority, ecological protection priority, cultivated land protection priority, natural development priority, and economic development priority. (3) In 2030, under different scenarios, in addition to the relatively reasonable land use structure of the prohibited development zone, the restricted development zone still needs to appropriately reduce the proportion of cultivated land and construction land in the area. To support the coordinated development of land use, production, living conditions, and ecological functions and to accomplish low-carbon land use goals, the key and optimal development zones should take arable grassland development into consideration.

The contradiction between supply and demand of congenital water shortage and acquired water supply in southern Xinjiang stems from the natural accumulation over time and the effects of human long-term production activities on the ecological environment, including its destruction. It is necessary to formulate a scientific and perfect water use plan to improve the contradiction between supply and demand. In order to assess the current state of water supply and demand in southern Xinjiang, a water resource carrying capacity evaluation index system based on the three aspects of water resources, social economy, and ecological environment was constructed using 24 indicators. The spatio-temporal evolution of water resource carrying capacity and coupling coordination between subsystems in southern Xinjiang from 2005 to 2020 was quantitatively evaluated based on the entropy weight-TOPSIS method and coupling coordination model. The results show that: (1) The overall carrying capacity of water resources in southern Xinjiang is low, and the carrying capacity of water resources in Bayingol Mongolian Autonomous Prefecture is good, however, the variation range is wide and the trend is unsteady. The overall carrying capacity of water resources in the Aksu and Kashgar regions showed a fluctuating upward trend, with similar growth rates. Compared with 2005, the comprehensive evaluation value of water carrying capacity in the two regions increased by more than 40% in 2020. The overall water carrying capacity of Kyzylsukol Autonomous Prefecture and the Hotan area showed a fluctuating and decreasing trend first and then slowly rising. The water carrying capacity of resources in the Hotan area fluctuated greatly. (2) From 2005 to 2020, the water-socio-economic-ecological environment in southern Xinjiang was in a low-level coupling stage, indicating that the degree of correlation between various subsystems was poor, and in 2020, the coupling coordination degree transitioned from serious uncoordinated to the basic uncoordinated stage, showing an overall upward trend and large upward space. Among them, Bayingol Mongolian Autonomous Prefecture has the best level of coupling and coordination between subsystems, and the type of mild dysregulation recession has increased from the mild dysregulated recession type to the endangered dysregulated recession type. The coupling coordination level in the other four states increased from the level of moderate imbalance recession to the level of mild imbalance recession. Combined with the comprehensive evaluation values of water resources, socio-economic and ecological environment subsystems, Bayingol Mongol Autonomous Prefecture, Aksu region, and Kashgar region belong to the water resources lagging type. Kyzylsukol Autonomous Prefecture belongs to the socio-economic and ecological environment interaction lag type, and Hotan area belongs to the socio-economic lag type. (3) From the perspective of space, based on geographical differences, the coupling and coordination degree of the five prefectures in southern Xinjiang has a strong correspondence with it. The coupling coordination degree of water resources-socio-economic-ecological environment is better in the east than in the central and western regions. Bayingol Mongolian Autonomous Prefecture has the best level of coupling and coordination, and among the other four regions, Kyzylsukol Autonomous Prefecture has a slow increase in coupling and coordination due to its western border and complex geographical environment, while Aksu, Kashgar, and Hotan regions have similar change rates and stable growth trends.

A thorough investigation of the distribution of natural Populus euphratica, tree growth, regeneration characteristics, soil types, and factors in the Hexi Corridor was conducted. The distribution and regeneration status of natural P. euphratica in the Hexi Corridor, as well as its relationship with soil factors, were then examined. The results showed that: (1) Natural P. euphratica forests in the Hexi Corridor were mainly distributed in riparian terraces, ancient river terraces and the edge of oasis cultivated land in the lower reaches of Shule River, Black River, and Shiyang River. There are four main types of forest land: abandoned land, the land around cultivated fields and irrigation canals, land along the current river course, and land among ancient river course and Gobi low-lying land. (2) The growth status, age structure, and seedling regeneration of P. euphratica in the land around cultivated fields and irrigation canal, land along the current river course are better than those of the abandoned land, and among ancient river course and Gobi low-lying land. In terms of the number of renewed seedlings per unit area, the land around the cultivated field and irrigation canal was the largest, with an average value of 22.13, followed by abandoned cultivated land (20.92), land along the current river course (10.50), and among ancient river course and Gobi low-lying land (1.33). (3) Different types of P. euphratica forests have different soil factor contents: (i) Available P: In the 0-20 cm soil layer, the soil available phosphorus showed the trend as; land along the current river course < land among ancient river course and Gobi low-lying land < abandoned land, land around cultivated field and irrigation canal cultivated land; in the 20-40 cm soil layer, land along the current river course had significant less available phosphorus than the other three types of forest land (all P < 0.05); (ii) Moisture content was higher in the land around cultivated fields and irrigation canals, and land along the current river course than in abandoned land, land among ancient river course and Gobi low-lying land (all P < 0.05); (iii) In comparison to the other three types of forest land, abandoned land has significantly lower soil conductivity between the 0-20 cm and 20-40 cm soil layers (P < 0.05). There was no significant difference in the contents of total N and organic matter among different types of forest land (P > 0.05) and in the 40-60 cm soil layer, land among the ancient river course and Gobi low-lying land was significantly higher (P < 0.05). Except for the coarse sand in the 0-20 cm soil layer, the soil clay particles, silt particles, and coarse particles in the land around the cultivated field and irrigation canal performed significantly higher than those in the other three types of forest land (P < 0.05). (4) The contents of soil moisture and available P were positively correlated with the middle and young age of P. euphratica and the number of seedlings (P < 0.05). (5) To encourage the sustainable development of P. euphratica forest, improve forest management and protection, timely thinning, removal of branches and dieback, thinning, and irrigation.

We analyzed the tensile properties and its influencing factors of a single root of the pioneer herbaceous plant alfalfa (Medicago sativa Linn.). Alfalfa roots with different root diameters and lengths were selected for indoor single-root tensile tests under different loading rates. The tensile force and tensile strength of a single root were estimated quantitatively for different root diameters, root lengths, and loading rates. The results showed loading rate had a significant effect on the tensile force and tensile strength of alfalfa roots (P<0.05). For a root diameter less than 3 mm, the tensile force and tensile strength reached their maximum at the loading rate of 500 mm·min^-1. However, when the root diameter was relatively thick, the tensile force and tensile strength of alfalfa roots reached their maximum at the loading rate of 100 mm·min^-1. No significant difference between root length, tensile force, and tensile strength of alfalfa root was observed (P<0.05). The root diameter of alfalfa showed a significant influence on root tensile force and tensile strength (P<0.001). The root diameter was positively correlated with root tensile strength by a power function (R²=0.380, P<0.001) and negatively correlated with root tensile strength by a power function (R²=0.363, P<0.001). The regression model about the impact of various factors on the alfalfa root tensile force and tensile strength showed that root diameter was the main factor affecting the tensile properties.

Populus euphratica Oliv. is an indicator species of eco-environmental changes in arid areas and it plays an irreplaceable role in maintaining the stability of a regional fragile ecosystem. At present, relevant research on the hollow tree of P. euphratica is still lacking. In this paper, we investigated the hollow ratio, architecture trait differences in living trees with hollow and without hollow, and its variation among the different aged forests in the Tarim River National Positioning Observation Station of P. euphratica Forest Ecosystem. The results showed that the hollow ratio of P. euphratica living standing trees in the study area was 17% (about 78 trees·hm^-2) and the hollow rate increased with the increasing forest age. The hollow rate was related to maturity as the hollow occurrence rate of mature trees was 4.3 times higher than that of immature trees. The degree of hollowing of living trees was significantly positively correlated with the diameter at breast height, tree height, crown width, and ulcer area (P < 0.05), while it negatively correlated with height-to-diameter ratio. No significant correlation of the degree of hollowing was observed with the crown loss and crown length. The hollow phenomenon did not cause an obvious disadvantage in tree growth. The architectural traits of the living standing trees of P. euphratica showed resource-conserving adaptation characteristics with the increase in standing age. and their hollowing was likely to be the adaptation strategy of P. euphratica to the extremely arid environment.

Leaves and roots respond to drought stress through morphological, physiological, and biomass accumulation changes. Alhagi sparsifolia is the dominant plant in the desert-oasis transition zone of Cele. We analyzed the characteristics of growth and physiological changes in leaves and roots of 1-year-old A. sparsifolia seedlings through a pot experiment. Results revealed the adaptive strategy of A. sparsifolia to drought stress. We simulated three water conditions (CK is well-watered: 70%-75% field capacity (FC); W₁ is mild stress: 50%-55% FC; W₂ is severe stress: 25%-30% FC). The results show the following: (1) Drought significantly inhibited the growth of the aboveground and underground tissues of A. sparsifolia. The main manifestations are: leaf area, root length, root surface area, root tissue density, and soluble sugar content of leaves and roots decreased significantly under stress (P < 0.05). The leaf tissue density, leaf dry matter content, specific root length, proline and malondialdehyde contents of leaf and root increased. (2) In the early growth stage, the aboveground biomass of A. sparsifolia under all treatments was relatively high (root-shoot ratios under CK, W₁, and W₂ were 0.43 ± 0.14, 0.59 ± 0.1, and 0.83 ± 0.83), while in the late growth stage, the below-ground biomass under all treatments was relatively high. The root-shoot ratio was the highest under severe stress (3.12 ± 0.32). The results indicate that A. sparsifolia enhanced the investment of resources underground in the late growth stage, and the resource allocation characteristic is more obvious under severe drought stress. (3) Pearson-correlation analysis showed that there was a significant tradeoff between core traits related to leaf morphology and root physiology in A. sparsifolia (P < 0.05). Meanwhile, the leaf and root had synergistic changes in physiological metabolism. The results preliminary indicate the adaptive characteristics and A. sparsifolia seedlings under drought exhibit high dry matter storage, defense capacity, and low water consumption. A. sparsifolia can coordinate the resource allocation relationship between leaves and roots. At the same time, with drought stress time increased, the adaptive strategy of slow investment and conservative growth of A. sparsifolia was gradually formed. The results provide a reference for the restoration and management of desert vegetation in this region.

The benefits of wind and sand control under the combined measures of sand-fixing plant species with regenerative sand barriers of Salix mongolica, polylactic acid (PLA) sandbags, and straw rope sand barriers in the Mu Us sandy land was studied. The wind speed, near-surface sand transport, and erosion pattern inside the barrier were measured at different heights under various combinations of measures, and the benefits of several sand barrier and combined measures under different materials, slope positions, and specifications were compared and analyzed. The results showed wind speed reduction was highest for the 1 m × 1 m S. mongolica regenerative sand barrier and straw rope sand barrier (up to 80.29% and 78.49%). The effectiveness of wind prevention for the 3 m × 3 m combination of straw rope and PLA sand barriers was 58.14% and 57.88%, respectively. The reduction rate of sand transport was as follows: S. mongolica > straw rope > PLA, and the trend increased with the specification. The sand-blocking effect of S. mongolica regeneration sand barrier combined measures is more stable, while the other two measures are less stable. The microtopography inside the barrier is mainly controlled by the wind direction from NW to NNW under various measures, and the morphological characteristics varies with the type of sand barrier material. The overall erosion is dominant, and the relative depth of erosion in the barrier is the largest for straw rope sand barriers combination, and the PLA barrier is the next, and the S. mongolica regeneration sand barrier is weakly eroded in the range of -10-5 cm, but the relative depth of erosion decreases with the increase of specification and slope. Comprehensive analysis shows that the artificial sand fixation vegetation system of Salix mongolica sand barrier combined with sowing sand fixation plant species is the most stable, with the best benefit of wind prevention and sand fixation, and is a more suitable mobile sand dune sand barrier in Mu Us sandy land. It is a more suitable technical measure for flowing dune sand barriers to promote vegetation restoration in Mu Us sandy land. The other measures can be appropriately adopted according to the difficulty of obtaining sand barrier materials, transportation conditions, quicksand environment, and control.

The understanding of the evolution process of barchan dune and its movement rate is an important prerequisite for wind prevention and sand fixation and ecological construction in Minqin oasis. Based on field measurement and high-resolution remote sensing image analysis, The study discusses the relationship between the morphological parameters of barchan dune and its movement rate in the upwind edge of Minqin oasis. The results show that: (1) The aspect ratio of the dunes remains a constant value of 16 in 16 years. (2) The average annual moving distance of the tall dune is less than 3 m, which is a medium moving speed. The shape of the tall dune is basically unchanged, and the change is obvious only at the baseline, ridge line, and wing Angle of the windward slope. Low dunes move fast, with an average annual distance of more than 10 m, which is an extremely fast-moving speed. (3) The downwind velocity of the dune is inversely proportional to its width, and the proportionality constant is 718.52 m²·a^-1. In this area, the barchan dune is dominated by fast-moving speed, which is greater than 5 m·a^-1, accounting for 52.63%. (4) During the process of sand erosion on the windward slope and deposition on the leeward slope, large dunes maintain stable morphology and move slowly. Small dunes change dramatically and move rapidly, and the dunes tend to shrink in development.

Gravel is the product of various hydrological and erosion processes and is a symbol of grassland and soil degradation and ecosystem deterioration. Consequently, gravel also affects various erosion processes. Studying the spatial differentiation of gravel in the Northern Tibetan Plateau is of considerable importance for the restoration of regional ecological environments. In this paper, the size and spatial location of surface gravel were studied, and the spatial heterogeneity was systematically analyzed by Moran’s I index, spatial variogram, geographic detector, and regression analysis. The following results are presented. (1) The global Moran’s I index is 0.481, which shows a significant positive correlation. Meanwhile, the local Moran’s I index shows a high-high gravel accumulation pattern in the eastern part of the study area, low-low in the middle part, and mostly random distribution in the rest of the study area. (2) Gravel spatial heterogeneity is dominated by structural factors. However, some differences are found between the best fitting model of the variogram and the values of characteristic parameters; that is, certain anisotropy characteristics exist. (3) The geographic detector results showed that NDVI and land-use type were the main factors affecting the spatial heterogeneity of gravel size in the study area, while population density, vegetation type, and annual average precipitation were the secondary factors. (4) The results of regression analysis revealed that the optimal scale regression was the best regression model, and NDVI had the largest influence on gravel size, followed by land-use type, annual mean precipitation, and vegetation type.

Improving the disturbance resistance and restoration of ecologically fragile areas is an important part of ecological civilization construction. The key factors affecting ecological resilience were diagnosed with the help of coupling coordination model, correlation analysis, and obstacle model. Based on the economic, social, and natural multidimensional perspective of composite ecosystem resilience assessment model, using entropy method and GIS spatial analysis, in 2009-2019 Ningxia composite ecosystem resilience difference analysis was done. The results show that: (1) The resilience of Ningxia’s composite ecosystem is on the rise, but the overall level is low, and economic resilience grows the fastest. High economic resilience is densely distributed in the north, and high social resilience is centered in the city. High natural resilience is mainly distributed in the east, south, west, and north corners, and the northern composite ecosystem is more resilient than that in the central and southern regions. (2) The coupling degree of the composite ecosystem in Ningxia is relatively high, but the coordination degree is relatively low. The coupling and coordination degree improves slowly during the research period, and most districts and counties are still in a state of serious and moderate imbalance. (3) The economic structure shows a strong positive correlation with the economic potential, infrastructure, the improvement of people’s livelihood, and the natural environment. Population, environmental stress, and economic vitality in the criterion layer have a significant impact on the composite ecosystem’s resilience, while the index layer’s total energy consumption and the number of workers in the transportation, storage, and postal sectors have a significant impact on the resilience of the majority of districts and counties. In the future, it is necessary to actively play the positive synergistic effect of various influencing factors to rapidly improve the resilience of the composite ecosystem in Ningxia, to effectively help the ecological protection and the construction of a high-quality pilot zone in the Yellow River.

The ecological environment quality (based on the principles of space-time, ecology, integrity, and the dynamic changes) and water conservation in Fenhe River Basin in the past 20 years were analyzed by using the RSEI model and the InVEST model. The relationship between RSEI and water conservation was studied through the correlation analysis. The results showed that: (1) from 2000 to 2020, the area of a good grade RSEI increased by 23.6%, and the area of excellent grade (mainly distributed in the West and East of Fenhe River Basin) increased by 1.9% (2) In 2020, the total amount of water conservation would be 228.9 × 10⁸ mm (an increase of 23 × 10⁸ mm compared with 2000). High conservation capacity was mostly found in the upstream water supply, while the intermediate region of the middle and lower reaches had poor water conservation ability (3) The positive correlation between RSEI and water conservation was 78.42%. Conclusions: (1) The ecological environment of the Fenhe River Basin has been improving continuously for the past 20 years. The medium level shown a declining tendency after fluctuation, whereas the good and poor areas had both increased annually. (2) Over the past 20 years, the water conservation function of the Fenhe River Basin had been continuously improved. The water conservation capacity of the upstream water source areas had increased significantly, while the intermediate and lower reaches had less water conservation capacity. (3) The proportion of positive correlation between the ecological environment and water conservation in the Fenhe River Basin was the largest. The improvement of water conservation capacity could promote the improvement of ecological environment quality and vice versa. There are 21.58% of the regions with negative correlation, which was mainly related to the dominant factors of the two.

The ecological civilization construction in Inner Mongolia, an important ecological barrier in northern China, is important for national ecological security, the stability of the border areas, and the sustainable economic and societal development of the minority areas. In this study, we extracted four key indices based on long-term satellite observations to describe the quality of the ecosystem. We constructed the remote sensing ecological index (RSEI) through principal component analysis. Furthermore, we adopted the Mann-Kendall (M-K) trend test for analyzing the changes in ecological quality in the Hulunbuir grassland of Inner Mongolia from 1990 to 2021. The RSEI can comprehensively reflect the quality of the ecological environment, and results revealed that the quality of grassland in Inner Mongolia has improved in the past 30 years, with an increasing trend of 0.0037 every year (P < 0.01; R² = 0.39). The significant increasing trend of RSEI and the improved ecological quality from 2012 to 2021 was further verified through the M-K trend significance test. A single factor cannot fully characterize regional ecological quality so, four factors i.e., greenness, dryness, humidity, and heat were included in RSEI. The space quality showed a gradual improvement from west to east, with lower RSEI for grassland in the west compared with that for forest and farming areas in the east. A similar trend for quality was observed with the variation of the vegetation coverage. This study enriched the assessment methods of grassland ecological quality in Inner Mongolia, which can provide an important reference for the ecological protection, restoration, utilization, and sustainable development of meadow steppe in Inner Mongolia.