Understanding the distribution and dynamics of glaciers is of great significance to the management and allocation of regional water resources and socio-economic development in arid regions of Northwest China. In this study, based on 36 Landsat images, we extracted the glacier boundaries in the Manas River Basin, Northwest China from 2000 to 2020 using eCognition combined with band operation, GIS (geographic information system) spatial overlay techniques, and manual visual interpretation. We further analyzed the distribution and variation characteristics of glacier area, and simulated glacial runoff using a distributed degree-day model to explore the regulation of runoff recharge. The results showed that glacier area in the Manas River Basin as a whole showed a downward trend over the past 21 a, with a decrease of 10.86% and an average change rate of -0.54%/a. With the increase in glacier scale, the number of smaller glaciers decreased exponentially, and the number and area of larger glaciers were relatively stable. Glacier area showed a normal distribution trend of increasing first and then decreasing with elevation. About 97.92% of glaciers were distributed at 3700-4800 m, and 48.11% of glaciers were observed on the northern and northeastern slopes. The retreat rate of glaciers was the fastest (68.82%) at elevations below 3800 m. There was a clear rise in elevation at the end of glaciers. Glaciers at different slope directions showed a rapid melting trend from the western slope to the southern slope then to the northern slope. Glacial runoff in the basin showed a fluctuating upward trend in the past 21 a, with an increase rate of 0.03×10⁸ m³/a. The average annual glacial runoff was 4.80×10⁸ m³, of which 33.31% was distributed in the ablation season (June-September). The average annual contribution rate of glacial meltwater to river runoff was 35.40%, and glacial runoff accounted for 45.37% of the total runoff during the ablation season. In addition, precipitation and glacial runoff had complementary regulation patterns for river runoff. The findings can provide a scientific basis for water resource management in the Manas River Basin and other similar arid inland river basins.

The eastern foothills of the Helan Mountains in China are a typical mountainous region of soil and gravel, where gravel could affect the water movement process in the soil. This study focused on the effects of different gravel contents on the water absorption characteristics and hydraulic parameters of stony soil. The stony soil samples were collected from the eastern foothills of the Helan Mountains in April 2023 and used as the experimental materials to conduct a one-dimensional horizontal soil column absorption experiment. Six experimental groups with gravel contents of 0%, 10%, 20%, 30%, 40%, and 50% were established to determine the saturated hydraulic conductivity (K_s), saturated water content (θ_s), initial water content (θ_i), and retention water content (θ_r), and explore the changes in the wetting front depth and cumulative absorption volume during the absorption experiment. The Philip model was used to fit the soil absorption process and determine the soil water absorption rate. Then the length of the characteristic wetting front depth, shape coefficient, empirical parameter, inverse intake suction and soil water suction were derived from the van Genuchten model. Finally, the hydraulic parameters mentioned above were used to fit the soil water characteristic curves, unsaturated hydraulic conductivity (K_θ) and specific water capacity (C(h)). The results showed that the wetting front depth and cumulative absorption volume of each treatment gradually decreased with increasing gravel content. Compared with control check treatment with gravel content of 0%, soil water absorption rates in the treatments with gravel contents of 10%, 20%, 30%, 40%, and 50% decreased by 11.47%, 17.97%, 25.24%, 29.83%, and 42.45%, respectively. As the gravel content increased, inverse intake suction gradually increased, and shape coefficient, K_s, θ_s, and θ_r gradually decreased. For the same soil water content, soil water suction and K_θ gradually decreased with increasing gravel content. At the same soil water suction, C(h) decreased with increasing gravel content, and the water use efficiency worsened. Overall, the water holding capacity, hydraulic conductivity, and water use efficiency of stony soil in the eastern foothills of the Helan Mountains decreased with increasing gravel content. This study could provide data support for improving soil water use efficiency in the eastern foothills of the Helan Mountains and other similar rocky mountainous areas.

Perennial grass-legume mixtures have been extensively used to restore degraded grasslands, increasing grassland productivity and forage quality. Tillage is crucial for seedbed preparation and sustainable weed management for the establishment of grass-legume mixtures. However, a common concern is that intensive tillage may alter soil characteristics, leading to losses in soil organic carbon (SOC). We investigated the plant community composition, SOC, soil microbial biomass carbon (MBC), soil enzyme activities, and soil properties in long-term perennial grass-legume mixtures under two different tillage intensities (once and twice) as well as in a fenced grassland (FG). The establishment of grass-legume mixtures increased plant species diversity and plant community coverage, compared with FG. Compared with once tilled grassland (OTG), twice tilled grassland (TTG) enhanced the coverage of high-quality leguminous forage species by 380.3%. Grass-legume mixtures with historical tillage decreased SOC and dissolved organic carbon (DOC) concentrations, whereas soil MBC concentrations in OTG and TTG increased by 16.0% and 16.4%, respectively, compared with FG. TTG significantly decreased the activity of N-acetyl-β-D-glucosaminidase (NAG) by 72.3%, whereas soil enzyme β-glucosidase (βG) in OTG and TTG increased by 55.9% and 27.3%, respectively, compared with FG. Correlation analysis indicated a close association of the increase in MBC and βG activities with the rapid decline in SOC. This result suggested that MBC was a key driving factor in soil carbon storage dynamics, potentially accelerating soil carbon cycling and facilitating biogeochemical cycling. The establishment of grass-legume mixtures effectively improves forage quality and boosts plant diversity, thereby facilitating the restoration of degraded grasslands. Although tillage assists in establishing legume-grass mixtures by controlling weeds, it accelerates microbial activity and organic carbon decomposition. Our findings provide a foundation for understanding the process and effectiveness of restoration management in degraded grasslands.

Soil salinization may affect biodiversity and species composition, leading to changes in the plant community structure. However, few studies have explored the spatial pattern of soil salinization and its effects on shrub community structure at the ecosystem scale. Therefore, we conducted a transect sampling of desert shrublands in Northwest China during the growing season (June-September) in 2021. Soil salinization (both the degree and type), shrub community structure (e.g., shrub density and height), and biodiversity parameters (e.g., Simpson diversity, Margalf abundance, Shannon-Wiener diversity, and Pielou evenness indices) were used to assess the effects of soil salinization on shrub community structure. The results showed that the primary degree of soil salinization in the study area was light salinization, with the area proportion of 69.8%. Whereas the main type of soil salinization was characterized as sulfate saline soil, also accounting for 69.8% of the total area. Notably, there was a significant reduction in the degree of soil salinization and a shift in the type of soil salinization from chloride saline soil to sulfate saline soil, with an increase in longitude. Regional mean annual precipitation (MAP), mean annual evapotranspiration (MAE), elevation, and slope significantly contributed to soil salinization and its geochemical differentiation. As soil salinization intensified, shrub community structure displayed increased diversity and evenness, as indicated by the increases in the Simpson diversity, Shannon-Wiener diversity, and Pielou evenness indices. Moreover, the succulent stems and leaves of Chenopodiaceae and Tamaricaceae exhibited clear advantages under these conditions. Furthermore, regional climate and topography, such as MAP, MAE, and elevation, had greater effects on the distribution of shrub plants than soil salinization. These results provide a reference for the origin and pattern of soil salinization in drylands and their effects on the community structure of halophyte shrub species.

The Keriya River Basin is located in an extremely arid climate zone on the southern edge of the Tarim Basin of Northwest China, exhibiting typical mountain-oasis-desert distribution characteristics. In recent decades, climate change and human activities have exerted significant impacts on the service functions of watershed ecosystems. However, the trade-offs and synergies between ecosystem services (ESs) have not been thoroughly examined. This study aims to reveal the spatiotemporal changes in ESs within the Keriya River Basin from 1995 to 2020 as well as the trade-offs and synergies between ESs. Leveraging the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) and Revised Wind Erosion Equation (RWEQ) using land use/land cover (LULC), climate, vegetation, soil, and hydrological data, we quantified the spatiotemporal changes in the five principal ESs (carbon storage, water yield, food production, wind and sand prevention, and habitat quality) of the watershed from 1995 to 2020. Spearman correlation coefficients were used to analyze the trade-offs and synergies between ES pairs. The findings reveal that water yield, carbon storage, and habitat quality exhibited relatively high levels in the upstream, while food production and wind and sand prevention dominated the midstream and downstream, respectively. Furthermore, carbon storage, food production, wind and sand prevention, and habitat quality demonstrated an increase at the watershed scale while water yield exhibited a decline from 1995 to 2020. Specifically, carbon storage, wind and sand prevention, and habitat quality presented an upward trend in the upstream but downward trend in the midstream and downstream. Food production in the midstream showed a continuously increasing trend during the study period. Trade-off relationships were identified between water yield and wind and sand prevention, water yield and carbon storage, food production and water yield, and habitat quality and wind and sand prevention. Prominent temporal and spatial synergistic relationships were observed between different ESs, notably between carbon storage and habitat quality, carbon storage and food production, food production and wind and sand prevention, and food production and habitat quality. Water resources emerged as a decisive factor for the sustainable development of the basin, thus highlighting the intricate trade-offs and synergies between water yield and the other four services, particularly the relationship with food production, which warrants further attention. This research is of great significance for the protection and sustainable development of river basins in arid areas.

Rising atmospheric CO₂ (carbon dioxide) concentrations and salinization are manifestations of climate change that affect plant growth and productivity. Species with an intermediate C₃-C₄ type of photosynthesis live in a wide range of precipitation, temperature, and soil quality, but are more often found in warm and dry habitats. One of the intermediate C₃-C₄ photosynthetic type is C₂ photosynthesis with a carbon concentration mechanism (CCM) that reassimilates CO₂ released via photorespiration. However, the ecological significance under which C₂ photosynthesis has advantages over C₃ and C₄ plants remains largely unexplored. Salt tolerance and functioning of CCM were studied in plants from two populations (P1 and P2) of Sedobassia sedoides (Pall.) Freitag & G. Kadereit Asch. species with C₂ photosynthesis exposed to 4 d and 10 d salinity (200 mM NaCl) at ambient (785.7 mg/m³, aCO₂) and elevated (1571.4 mg/m³, eCO₂) CO₂. On the fourth day of salinity, an increase in Na⁺ content, activity catalase, and superoxide dismutase was observed in both populations. P2 plants showed an increase in proline content and a decrease in photosynthetic enzyme content: rubisco, phosphoenolpyruvate carboxylase (PEPC), and glycine decarboxylase (GDC), which indicated a weakening of C₂ and C₄ characteristics under salinity. Treatment under 10 d salinity led to an increased Na⁺ content and activity of cyclic electron flow around photosystem I (PSI CEF), a decreased content of K⁺ and GDC in both populations. P1 plants showed greater salt tolerance, which was assessed by the degree of reduction in photosynthetic enzyme content, PSI CEF activity, and changes in relative growth rate (RGR). Differences between populations were evident under the combination of eCO₂ and salinity. Under long-term salinity and eCO₂, more salt-tolerant P1 plants had a higher dry biomass (DW), which was positively correlated with PSI CEF activity. In less salt-tolerant P2 plants, DW correlated with transpiration and dark respiration. Thus, S. sedoides showed a high degree of photosynthetic plasticity under the influence of salinity and eCO₂ through strengthening (P1 plants) and weakening C₄ characteristics (P2 plants).

The presence of invasive plant species poses a substantial ecological impact, thus comprehensive evaluation of their potential range and risk under the influence of climate change is necessary. This study uses maximum entropy (MaxEnt) modeling to forecast the likelihood of Leucaena leucocephala (Lam.) de Wit invasion in Saudi Arabia under present and future climate change scenarios. Utilizing the MaxEnt modeling, we integrated climatic and soil data to predict habitat suitability for the invasive species. We conducted a detailed analysis of the distribution patterns of the species, using climate variables and ecological factors. We focused on the important influence of temperature seasonality, temperature annual range, and precipitation seasonality. The distribution modeling used robust measures of area under the curve (AUC) and receiver-operator characteristic (ROC) curves, to map the invasion extent, which has a high level of accuracy in identifying appropriate habitats. The complex interaction that influenced the invasion of L. leucocephala was highlighted by the environmental parameters using Jackknife test. Presently, the actual geographic area where L. leucocephala was found in Saudi Arabia was considerably smaller than the theoretical maximum range, suggesting that it had the capacity to expand further. The MaxEnt model exhibited excellent prediction accuracy and produced reliable results based on the data from the ROC curve. Precipitation and temperature were the primary factors influencing the potential distribution of L. leucocephala. Currently, an estimated area of 216,342 km² in Saudi Arabia was at a high probability of invasion by L. leucocephala. We investigated the potential for increased invasion hazards in the future due to climate change scenarios (Shared Socioeconomic Pathways (SSPs) 245 and 585). The analysis of key climatic variables, including temperature seasonality and annual range, along with soil properties such as clay composition and nitrogen content, unveiled their substantial influence on the distribution dynamic of L. leucocephala. Our findings indicated a significant expansion of high risk zones. High-risk zones for L. leucocephala invasion in the current climate conditions had notable expansions projected under future climate scenarios, particularly evident in southern Makkah, Al Bahah, Madina, and Asir areas. The results, backed by thorough spatial studies, emphasize the need to reduce the possible ecological impacts of climate change on the spread of L. leucocephala. Moreover, the study provides valuable strategic insights for the management of invasion, highlighting the intricate relationship between climate change, habitat appropriateness, and the risks associated with invasive species. Proactive techniques are suggested to avoid and manage the spread of L. leucocephala, considering its high potential for future spread. This study enhances the overall comprehension of the dynamics of invasive species by combining modeling techniques with ecological knowledge. It also provides valuable information for decision-making to implement efficient conservation and management strategies in response to changing environmental conditions.

Savanna, semi-deserts, and hot deserts characterize the Saharo-Arabian region, which includes Morocco, Mauretania, Algeria, Tunisia, Libya, Egypt, Palestine, Kuwait, Saudi Arabia, Qatar, Bahrain, the United Arab Emirates, Oman, Yemen, southern Jordan, Syria, Iraq, Iran, Afghanistan, Pakistan, and northern India. Its neighboring regions, the Sudano-Zambezian region belonging to the Paleotropical Kingdom and the Mediterranean and Irano-Turanian regions included in the Holarctic Kingdom, share a large portion of their flora with the Saharo-Arabian region. Despite the widespread acknowledgment of the region's global importance for plant diversity, an up to date list of the Saharo-Arabian endemics is still unavailable. The available data are frequently insufficient or out of date at both the whole global and the national scales. Therefore, the present study aims at screening and verifying the Saharo-Arabian endemic plants and determining the phytogeographical distribution of these taxa in the Egyptian flora. Hence, a preliminary list of 429 Saharo-Arabian endemic plants in Egypt was compiled from the available literature. Indeed, by excluding the species that were recorded in any countries or regions outside the Saharo-Arabian region based on different literature, database reviews, and websites, the present study has reduced this number to 126 taxa belonging to 87 genera and 37 families. Regarding the national geographic distribution, South Sinai is the richest region with 83 endemic species compared with other eight phytogeographic regions in Egypt, followed by the Isthmic Desert (the middle of Sinai Peninsula, 53 taxa). Sahara regional subzone (SS1) distributes all the 126 endemic species, Arabian regional subzone (SS2) owns 79 taxa, and Nubo-Sindian subzone (SS3) distributes only 14 endemics. Seven groups were recognized at the fourth level of classification as a result of the application of the two-way indicator species analysis (TWINSPAN) to the Saharo-Arabian endemic species in Egypt, i.e., I Asphodelus refractus group, II Agathophora alopecuroides var. papillosa group, III Anvillea garcinii group, IV Reseda muricata group, V Agathophora alopecuroides var. alopecuroides group, VI Scrophularia deserti group, and VII Astragalus schimperi group. It's crucial to clearly define the Saharo-Arabian endemics and illustrate an updated verified database of these taxa for a given territory for providing future management plans that support the conservation and sustainable use of these valuable species under current thought-provoking devastating impacts of rapid anthropogenic and climate change in this region.