Desertification is a global crucial ecological and environmental issue, and China is among the countries most seriously affected by desertification. In recent decades, numerous independent studies on desertification dynamics have been carried out using remote sensing technology, but there has been a lack of systematic research on desertification trends in China. This study employed the meta-analysis to integrate the findings of 140 published research cases and examined the dynamics of desertification in the eight major deserts, four major sandy lands, and their surrounding areas in China from 1970 to 2019, with a comparative analysis of differences between the eastern (including the Mu Us Sandy Land, the Otindag Sandy Land, the Hulunbuir Sandy Land, the Horqin Sandy Land, and the Hobq Desert) and western (including the Taklimakan Desert, the Gurbantunggut Desert, the Kumtagh Desert, the Ulan Buh Desert, the Qaidam Basin Desert, the Badain Jaran Desert, and the Tengger Desert) regions. The results revealed that from 1970 to 2019, desertification first expanded and then reversed in the whole region. Specifically, desertification expanded from 1980 to 1999 and reversed after 2000. The desertification trend exhibited distinct spatio-temporal variations between the eastern and western regions. From 1970 to 2019, the western region experienced relatively minor changes in desertified land area compared to the eastern region. In the context of global climate change, beneficial climatic conditions and ecological construction projects played a crucial role in reversing desertification. These findings provide valuable insights for understanding the development patterns of desertification in the most representative deserts and sandy lands in China and formulating effective desertification control strategies.

Climate change in High Mountain Asia (HMA) is characterized by elevation dependence, which results in vertical zoning of vegetation distribution. However, few studies have been conducted on the distribution patterns of vegetation, the response of vegetation to climate change, and the key climatic control factors of vegetation along the elevation gradient in this region. In this study, based on the Normalized Difference Vegetation index (NDVI), we investigated the evolution pattern of vegetation in HMA during 2001-2020 using linear trend and Bayesian Estimator of Abrupt change, Seasonality, and Trend (BEAST) methods. Pearson correlation analysis and partial correlation analysis were used to explore the response relationship between vegetation and climatic factors along the elevation gradient. Path analysis was employed to quantitatively reveal the dominant climatic factors affecting vegetation distribution along the elevation gradient. The results showed that NDVI in HMA increased at a rate of 0.011/10a from 2001 to 2020, and the rate of increase abruptly slowed down after 2017. NDVI showed a fluctuating increase at elevation zones 1-2 (<2500 m) and then decreased at elevation zones 3-9 (2500-6000 m) with the increase of elevation. NDVI was most sensitive to precipitation and temperature at a 1-month lag. With the increase of elevation, the positive response relationship of NDVI with precipitation gradually weakened, while that of NDVI with temperature was the opposite. The total effect coefficient of precipitation (0.95) on vegetation was larger than that of temperature (0.87), indicating that precipitation is the dominant control factor affecting vegetation growth. Spacially, vegetation growth is jointly influenced by precipitation and temperature, but the influence of precipitation on vegetation growth is dominant at each elevation zone. The results of this study contribute to understanding how the elevation gradient effect influences the response of vegetation to climate change in alpine ecosystems.

Water quality is a pressing issue affecting the sustainable development of lakes. To elucidate the spatial and temporal characteristics of water quality in Bosten Lake, China, this study constructed a comprehensive water quality index (CWQI) based on key water quality indicators, utilizing water quality data collected from 17 sampling sites spaning from 2011 to 2019. Key water quality indicators were determined using factor analysis, and the spatial and temporal characteristics of key water quality indicators and the CWQI were examined using multivariate statistical analysis. The key water quality indicators included pH, chemical oxygen demand (COD), water transparency (SD), NO₃^-, total dissolved solids (TDS), Cl^-, SO₄^2-, and electrical conductivity (EC). Furthermore, the contribution rates of all water quality indicators to the water quality were quantitatively elucidated using the SHapley Additive exPlanations (SHAP) values, thereby validating the factor analysis outcomes. Among the eight key water quality indicators, the COD had the most significant influence on the water quality of Bosten Lake. The water quality condition of Bosten Lake has remained at Class III from 2011 to 2019 (CWQI ranging from 3.19 to 3.90). The water quality of Bosten Lake was characterized by distinct regional differences that arose from hydrodynamic processes within the lake and upstream water quality. The southwestern region exhibited the best water quality (mean CWQI of 3.47), whereas the northwestern region exhibited the worst (mean CWQI of 3.58). It is crucial to acknowledge that alongside the increase in industrial and agricultural effluent discharge monitoring, a series of ecological restoration projects for the lake basin have been initiated. Over time, the water quality of Bosten Lake showed gradual improvement (improvement rate of CWQI at 0.05/a). This study provides a critical scientific basis for enhancing the understanding and effective management of water quality in the Bosten Lake Basin through a comprehensive analysis of its spatial and temporal evolution and driving mechanisms.

Tree growth is extremely vulnerable to climate change, especially in semi-arid areas. Although the response of stem radial growth (SRG) to climate change has been extensively studied, the intra-annual regulatory mechanisms of SRG in trees with different water use strategies and life types remain poorly understood. This study calculated the SRG of four native species in the semi-arid area of the Loess Plateau, China, including two isohydric species (Pinus tabuliformis Carrière and Populus × hopeiensis Hu & Chow) and two anisohydric species (Prunus sibirica L. and Platycladus orientalis (L.) Franco). The results revealed that the intra-annual SRG of all the four tree species exhibited a single peak, and greater SRG was found in anisohydric species. Principal component analysis and structural equation model revealed that atmospheric water, particularly relative humidity, was the main factor affecting the SRG of coniferous species (P. tabuliformis and P. orientalis), whereas the SRG was mainly affected by soil water content in broadleaf species (P. sibirica and P. × hopeiensis). These findings suggested that water use strategies and life types play important roles in SRG and environmental response of trees in semi-arid area. Considering the high climate sensitivity of wood formation in trees, our results highlight the importance of water use strategies and life types of trees in SRG prediction in the context of future climate change in arid and semi-arid areas.

Land desertification severely compromises the core function of ecosystem and significantly disrupts biodiversity. Caragana korshinskii Kom. plays a pivotal role as a critical plant resource in the restoration and ecological reconstruction of desertified areas in Northwest China. Kytorhinus immixtus Motschulsky is the primary pest responsible for causing substantial damage to the seeds of C. korshinskii. In this study, field surveys were utilized in three distinct desertified types (lightly, moderately, and severely desertified areas) in north central Ningxia Hui Autonomous Region, Northwest China. This research was focused on investigating the population dynamics and damage rates of K. immixtus, with an emphasis on examining the relationships among K. immixtus distribution, levels of soil desertification, and associated environmental factors. The results revealed marked variations in the population distribution and abundance of K. immixtus across habitats with different degrees of desertification. Due to the sand-fixing ability of C. korshinskii, the severity of soil desertification decreased progressively from severe to moderate and light with C. korshinskii establishment. This reduction in desertification, along with habitat restoration and an increase in plant diversity, was correlated with a gradual increase in K. immixtus population size and damage rate. Generalized linear mixed model analysis revealed significantly positive correlations of soil total potassium, C. korshinskii height, maximum temperature during the survey, precipitation, and the plant species richness index with K. immixtus population. In contrast, the soil total phosphorus content, organic matter content, minimum temperature during the survey, C. korshinskii canopy width, and branch number were significantly and negatively correlated with K. immixtus population. Due to the sand-fixing capacity of C. korshinskii, the plant mitigated soil desertification, but as desertification severity decreased, habitat restoration and increased plant diversity drove a gradual increase in the population and damage rate of K. immixtus. Both biotic and abiotic factors in the habitat significantly influenced K. immixtus occurrence. To achieve the sustainable restoration of desert ecosystem, optimization of plant community structure with soil nutrient management in ecological rehabilitation is necessary to balance the benefits of sand fixation with pest risks.

The rhizosphere bacteria play crucial roles in plant health and growth as they are involved in assimilating nutrients and resisting adverse conditions such as nutrient stress, drought, and wind erosion. Agriophyllum squarrosum (L.) Moq. is a pioneer plant used in sand fixation due to its strong resistance to drought and wind erosion. However, the bacterial community characteristics and ecological function in the rhizosphere of A. squarrosum are poorly understood. In this study, soil samples were collected from different developmental stages (seedling stage, vegetative stage, reproductive stage, and withering stage) of A. squarrosum. Illumina Miseq sequencing was used to detect differences in soil bacterial abundance. The Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) program was used to predict bacterial functions, and the relationships among bacteria, functional populations, and soil nutrients were examined using a heatmap analysis. The results showed that the Shannon and Sobs indices of rhizosphere bacteria were significantly higher during the reproductive stage than during the other stages. Pantoea sp. (7.03%) was the dominant genus during the seedling stage; Arthrobacter sp. was the dominant genus during the vegetative (13.94%), reproductive (7.57%), and withering (12.30%) stages. The relative abundances of Chloroflexi, Acidobacteria, and Gemmatimonadetes were significantly high during the reproductive stage. According to the PICRUSt analysis, membrane transport, signal transduction, and environmental adaptation of the bacterial functional population occurred during the seedling stage. Carbohydrate metabolism increased during the vegetative stage, while energy metabolism, lipid metabolism, and biosynthesis of other secondary metabolites of the bacterial functional population significantly increased during the reproductive stage. The abundances of bacterial communities, functional genes, and soil nutrients were synergistically altered during various developmental stages. Our findings suggest that the developmental stages of A. squarrosum play a significant role in defining the composition and structure of bacterial communities in the rhizosphere. The results will provide a basis for better prediction and understanding of soil bacterial metabolic potential and functions of A. squarrosum rhizosphere in sandy areas.

In recent years, intensive human activities have increased the intensity of desertification, driving continual desertification process of peripheral meadows. To investigate the effects of restoration on soil microbial communities, we analyzed vegetation-soil relationships in the Hulun Buir Sandy Land, northern China. Through the use of high-throughput sequencing, we examined the structure and diversity in the bacterial and fungal communities within the 0-20 cm soil layer after 9-15 a of restoration. Different slope positions were analyzed and spatial heterogeneity was assessed. The results showed progressive improvements in soil properties and vegetation with the increase of restoration duration, and the following order was as follows: bottom slope>middle slope>crest slope. During the restoration in the Hulun Buir Sandy Land, the bacterial communities were dominated by Proteobacteria, Actinobacteria, and Acidobacteria, whereas the fungal communities were dominated by Ascomycota and Basidiomycota. Eutrophic bacterial abundance increased with the restoration duration, whereas oligotrophic bacterial and fungal abundance levels decreased. The soil bacterial abundance significantly increased with the increasing restoration duration, whereas the fungal diversity decreased after 11 a of restoration, except that at the crest slope. Redundancy analysis showed that pH, soil moisture content, total nitrogen, and vegetation-related factors affected the bacterial community structure (45.43% of the total variance explained). Canonical correspondence analysis indicated that pH, total phosphorus, and vegetation-related factors shaped the bacterial community structure (31.82% of the total variance explained). Structural equation modeling highlighted greater bacterial responses (R²=0.49-0.79) to changes in environmental factors than those of fungi (R²=0.20-0.48). The soil bacterial community was driven mainly by pH, soil moisture content, electrical conductivity, plant coverage, and litter dry weight. The abundance and diversity of the soil fungal community were mainly driven by plant coverage, litter dry weight, and herbaceous aboveground biomass, while there was no significant correlation between the soil fungal community structure and environmental factors. These findings highlighted divergent microbial succession patterns and environmental sensitivities during sandy grassland restoration.

Crude oil pollution is a significant global environmental challenge. The eastern Gansu Province on the Loess Plateau, an important agricultural region containing the Changqing Oilfield, is facing increasing crude oil contamination. Understanding how microbial communities respond to varying pollution levels is critical for developing effective bioremediation strategies. This study examined how different concentrations of crude oil affect soil properties and microbial communities in Qingyang City, eastern Gansu Province, China by comparing lightly polluted (1895.84-2696.54 mg/kg total petroleum hydrocarbons (TPH)), heavily polluted (4964.25-7153.61 mg/kg TPH), and uncontaminated (CK) soils. Results revealed that petroleum contamination significantly increased total organic carbon (TOC), pH, C:N:P ratio, and the activities of dehydrogenase (DHA) and polyphenol oxidase (PPO), while reducing total nitrogen (TN), available nitrogen (AN), total phosphorus (TP), available phosphorus (AP), available potassium (AK), soil organic matter (SOM), soil water content (SWC), the activities of urease (URE) and alkaline phosphatase (APA), and microbial alpha diversity (P<0.050). Light pollution (LP) soils demonstrated an increase in culturable microorganisms, whereas heavy pollution (HP) soils exhibited increased hydrocarbon-degrading microbes and higher expression of key functional genes, such as alkane monooxygenase (AlkB), cytochrome P450 alkane hydroxylases (P450), catechol 2,3-dioxygenase (C23O), and naphthalene dioxygenase (Nah) (P<0.050). Non-metric multidimensional scaling (NMDS) and redundancy analysis (RDA) indicated evident variations in microbial community structure across different oil contamination levels. LP soils were dominated by bacterial genera Pseudoxanthomonas and Solimonadaceae, whereas Pseudomonas, Nocardioides, and hydrocarbon-degrading genera (Marinobacter, Idiomarina, and Halomonas) were predominant in HP soils. The fungal genus Pseudallescheria exhibited the most pronounced abundance shift between LP and HP soils (P<0.050). Environmental factor analysis identified AN, SWC, TN, SOM, and alpha diversity indices (Shannon index and Chao1 index) as the key differentiators of CK soils, whereas the pollutant levels and metal content were characterized in HP soils. Hydrocarbon-degrading microbial abundance was a defining trait of HP soils. Metabolic pathway analysis revealed enhanced aromatic hydrocarbon degradation in HP soils, indicating microbial adaptation to severe contamination. These findings demonstrated that crude oil pollution suppressed soil nutrients while reshaping the structure and function of microbial communities. Pollution intensity directly affected microbial composition and degradation potential. This study offers valuable insights into microbial responses across contamination gradients and supports the development of targeted bioremediation strategies for oil-contaminated loess soils.