Understanding the impact of climate change on water resources is important for developing regional adaptive water management strategies. This study investigated the impact of climate change on water resources in the Yarmouk River Basin (YRB) of Jordan by analyzing the historical trends and future projections of temperature, precipitation, and streamflow. Simple linear regression was used to analyze temperature and precipitation trends from 1989 to 2017 at Irbid, Mafraq, and Samar stations. The Statistical Downscaling Model (SDSM) was applied to predict changes in temperature and precipitation from 2018 to 2100 under three Representative Concentration Pathway (RCP) scenarios (i.e., RCP2.6, RCP4.5, and RCP8.5), and the Soil and Water Assessment Tool (SWAT) was utilized to estimate their potential impact on streamflow at Addasiyia station. Analysis of data from 1989 to 2017 revealed that mean maximum and minimum temperatures increased at all stations, with average rises of 1.62°C and 1.39°C, respectively. The precipitation trends varied across all stations, showing a significant increase at Mafraq station, an insignificant increase at Irbid station, and an insignificant decrease at Samar station. Historical analysis of streamflow data revealed a decreasing trend with a slope of -0.168. Significant increases in both mean minimum and mean maximum temperatures across all stations suggested that evaporation is the dominant process within the basin, leading to reduced streamflow. Under the RCP scenarios, projections indicated that mean maximum temperatures will increase by 0.32°C to 1.52°C, while precipitation will decrease by 8.5% to 43.0% throughout the 21^st century. Future streamflow projections indicated reductions in streamflow ranging from 8.7% to 84.8% over the same period. The mathematical model results showed a 39.4% reduction in streamflow by 2050, nearly double the SWAT model's estimate under RCP8.5 scenario. This research provides novel insights into the regional impact of climate change on water resources, emphasizing the urgent need to address these environmental challenges to ensure a sustainable water supply in Jordan.

Alluvial fans possess diverse geomorphological features and have a significant impact on soil characteristics and variations in ecological stoichiometry. However, it remains unclear how alluvial fans in arid mountainous areas influence the changes in ecological chemical stoichiometry and, consequently, indirectly affect ecosystem function. Alluvial fan, with its diverse topographical features, exerts a multifaceted influence on soil formation and characteristics. Limited information exists regarding the ecological stoichiometric characteristics of the alluvial fan in arid mountainous areas. This study investigated the soil physical-chemical characteristics, enzyme activities, soil ecological stoichiometries, and its driving factors of four types of micro-topographies (alluvial mesas, high floodplain, groove beach, and striated groove) in the foothills of eastern Helan Mountains, China. Results showed that soil physical and chemical properties in the 0-20 cm soil depth was consistently higher than those in the 20-40 cm soil depth, with no changes in pH, total nitrogen, and total potassium. C:P and N:P ratios in alluvial mesas, high floodplain, and striated groove were significantly higher than those in groove beach. Redundancy analysis showed that soil nutrients played the most significant role in the variation of soil ecological stoichiometry characteristics. Topography influenced soil stoichiometry indirectly, primarily through impacts on enzyme activity and soil nutrient elements. These findings elucidate the intricate interplay between soil ecological stoichiometric characteristics and environmental factors across diverse micro-topographies in alluvial fan, contributing to our understanding of the formation and development of soil in dryland.

Evapotranspiration is the most important expenditure item in the water balance of terrestrial ecosystems, and accurate evapotranspiration modeling is of great significance for hydrological, ecological, agricultural, and water resource management. Artificial forests are an important means of vegetation restoration in the western Loess Plateau, and accurate estimates of their evapotranspiration are essential to the management and development of water use strategies for artificial forests. This study estimated the soil moisture and evapotranspiration based on the HYDRUS-1D model for the artificial Platycladus orientalis (L.) Franco forest in western mountains of Loess Plateau, China from 20 April to 31 October, 2023. Moreover, the influence factors were identified by combining the correlation coefficient method and the principal component analysis (PCA) method. The results showed that HYDRUS-1D model had strong applicability in portraying hydrological processes in this area and revealed soil water surplus from 20 April to 31 October, 2023. The soil water accumulation was 49.64 mm; the potential evapotranspiration (ET_p) was 809.67 mm, which was divided into potential evaporation (E_p; 95.07 mm) and potential transpiration (T_p; 714.60 mm); and the actual evapotranspiration (ET_a) was 580.27 mm, which was divided into actual evaporation (E_a; 68.27 mm) and actual transpiration (T_a; 512.00 mm). From April to October 2023, the ET_p, E_p, T_p, ET_a, E_a, and T_a first increased and then decreased on both monthly and daily scales, exhibiting a single-peak type trend. The average ratio of T_a/ET_a was 0.88, signifying that evapotranspiration mainly stemmed from transpiration in this area. The ratio of ET_a/ET_p was 0.72, indicating that this artificial forest suffered from obvious drought stress. The ET_p was significantly positively correlated with ET_a, and the R² values on the monthly and daily scales were 0.9696 and 0.9635 (P<0.05), respectively. Furthermore, ET_a was significantly positively correlated with temperature, solar radiation, and wind speed, and negatively correlated with relative humidity and precipitation (P<0.05); and temperature exhibited the highest correlation with ET_a. Thus, ET_p and temperature were the decisive contributors to ET_a in this area. The findings provide an effective method for simulating regional evapotranspiration and theoretical reference for water management of artificial forests, and deepen understanding of effects of each influence factors on ET_a in arid areas.

The Chinese Loess Plateau has long been plagued by severe soil erosion and water scarcity. In this study, we proposed a technique involving the combined use of polymer SH and ryegrass and evaluated its effectiveness in modifying the water-holding characteristics of loess on the Chinese Loess Plateau (Chinese loess). We analysed the volumetric water content and water potential of untreated loess, treated loess with single polymer SH, treated loess with single ryegrass, and treated loess with both polymer SH and ryegrass using the loess samples collected from the Chinese Loess Plateau in July 2023. Moreover, fractal theory was used to analyse the fractal characteristics of the soil structure, and wet disintegration tests were conducted to assess the structural stability of both untreated and treated loess samples. The results showed that the loess samples treated with both polymer SH and ryegrass presented much higher volumetric water content and water potential than the untreated loess samples and those treated only with ryegrass or polymer SH. Moreover, the planting density of ryegrass affected the combined technique, since a relatively low planting density (20 g/m²) was conducive to enhancing the water-holding capacity of Chinese loess. The fractal dimension was directly correlated with both volumetric water content and water potential of Chinese loess. Specifically, since loess treated with both polymer SH and ryegrass was more saturated with moisture, its water potential increased, thus improving its water-holding capacity and fractal dimension. The combined technique better resisted disintegration than ryegrass alone but had slightly less resistance than polymer SH alone. This study provides insight into soil reinforcement and soil water management using polymetric materials and vegetation on the Chinese Loess Plateau.

Mangrove forests in southern Iran are of high ecological and economic importance. These forests are being threatened because of uncontrolled harvesting to provide fodder for livestock. The objective of this study is to provide recommendations for appropriate harvesting intensities by quantifying the effect of different harvesting intensities on vegetative and vigor characteristics of mangrove trees. This study was conducted using a randomized complete block design comprising four treatments (10.00%, 20.00%, and 30.00% trimming, along with a control) replicated three times. Vegetative characteristics were measured before and after trimming (five-year period) and analyzed using generalized linear model statistical analysis. The growths of the average diameter of canopy, canopy area, canopy volume, canopy height, tree height, and collar diameter in the control treatment were all significantly higher than those in the trimming treatments. In addition, there was a decreasing trend in leaf fresh and dry mass, leaf area index, total area of canopy leaves, and health status of tree in the trimming treatments. For example, the percentage change in fresh and dry leaf mass in the control treatment was positive (29.87% and 38.31%, respectively), whereas the trimming treatments of 10.00%, 20.00% and 30.00% had negative effects (-7.01% and -4.79%, -11.32% and -14.30%, and -15.84% and -17.29%, respectively). In addition, the changes in leaf area index in the control (4.95%) and 30.00% trimming (-24.57%) treatments were the highest and lowest, respectively. The percentage change in soil organic matter in the control, 10.00%, 20.00%, and 30.00% treatments were 22.94%, -9.90%, -16.91%, and -18.68%, respectively. The study demonstrated that gray mangrove trees were highly sensitive to canopy trimming, with even minimal trimming intensities negatively affecting vegetative growth and soil organic matter. Therefore, it is recommended that cutting and trimming of mangrove trees should be prevented even at low intensity to preserve mangrove ecosystem health and resilience against environmental stressors.

Film-stalk spaced dual mulching is a new type of cultivation measure that is increasingly highlighted in semi-arid areas in China. Despite its potential, there is limited understanding of how different mulching materials affect both soil quality and crop yield in these areas. To address this gap, we conducted a two-year (2020-2021) field experiment in central China to explore the yield-enhancing mechanisms and assess the impact of various mulching materials on soil and corn yield. The experiment comprised six treatments, i.e., plastic film-whole stalk spaced mulching in fall (PSF), plastic film-whole stalk spaced mulching in spring (PSS), black and silver plastic film-whole stalk spaced mulching in spring (BPSS), biodegradable film-whole stalk spaced mulching in spring (BSS), liquid film-whole stalk spaced mulching in spring (LSS), and non-mulching cultivation (CK). Results revealed that BPSS demonstrated the most significant yield increase, surpassing CK by a notable 10.0% and other mulching treatments by 2.4%-5.9%. The efficacy of BPSS lied in its provision of favorable hydrothermal conditions for corn cultivation, particularly during hot season. Its cooling effect facilitated the establishment of optimal temperature conditions relative to transparent mulching, leading to higher root growth indices (e.g., length and surface area), as well as higher leaf photosynthetic rate and dry matter accumulation per plant. Additionally, BPSS maintained higher average soil moisture content within 0-100 cm depth compared with biodegradable mulching and liquid mulching. As a result, BPSS increased activities of urease, catalase, and alkaline phosphatase, as well as the diversity and abundance of soil bacteria and fungi in the rhizosphere zone of corn, facilitating nutrient accessibility by the plant. These findings suggest that selecting appropriate mulching materials is crucial for optimizing corn production in drought-prone areas, highlighting the potential of BPSS cultivation.

Understanding the factors influencing the distribution of plant species is crucial for enhancing the management of endangered ecosystems. This study investigated the response of Hedysarum criniferum Boiss, an endemic and endangered species to 25 environmental variables within its habitats with an area of 2.95×10⁵ km² in arid and semi-arid rangelands of Iran. The purpose of this research is to identify the key environmental factors affecting the distribution and habitat preferences of H. criniferum for further conservation and restoration of the species. To predict the occurrence of H. criniferum and explore its relationship with environmental factors, we employed the best subset regression analysis, the hierarchical classification, and the extended Huisman-Olf-Fresco (eHOF) model. The results showed that four environmental variables, i.e., gravel content, pH, annual minimum temperature, and mean annual temperature showed significant correlations with the canopy cover of H. criniferum (P<0.05). The probability of H. criniferum occurrence increased with higher precipitation and elevation, while it decreased with higher mean annual temperature, annual minimum temperature, and gravel content. The species' response curves and their optimal values, as assessed by the eHOF model, indicated that the response to mean annual temperature, ranging from 12°C to 16°C, was optimal at 13°C. The response to mean annual precipitation, within a range of 150-650 mm, was optimal at 650 mm. Elevation responses, spanning from 1546 to 2450 m, showed an optimum at 2450 m. Regarding soil characteristics, the response to gravel content, ranging from 13.0%-48.0%, demonstrated an optimal value at 20.0%. The pH levels, varying from 7.5 to 8.2, prompted a sine-shaped response with an optimal pH of 8.0. These findings provide valuable insights for predicting species occurrence and identifying suitable locations for restoration programs. Our study underscores the importance of considering multiple environmental variables in habitat suitability assessments. By incorporating these broader considerations, we can further refine predictive models and enhance conservation efforts aimed at restoring habitats conducive to the luxuriance of endangered species like H. criniferum.

Biological invasion represents a major worldwide threat to native biodiversity and environmental stability. Haloxylon persicum was introduced to Tunisia (North Africa) with Saharan bioclimate in 1969 to fix sandy dunes. Since then, it has gained significant interest for its potential to colonize, proliferate, and become naturalized in Tunisia. Hence, understanding the seed germination response of H. persicum to abiotic conditions, including temperature, water stress, and salt stress, is crucial for predicting its future spread and adopting effective control strategies. Our work investigated the germination behavior of this invasive plant species by incubation at temperatures from 10.0°C to 35.0°C and at various osmotic potentials (-2.00, -1.60, -1.00, -0.50, and 0.00 MPa) of polyethylene glycol-6000 (PEG₆₀₀₀, indicating water stress) and sodium chloride (NaCl, indicating salt stress) solutions. Results showed remarkable correlations among the seed functional traits of H. persicum, indicating adaptive responses to local environmental constraints. The maximum germination rate was recorded at 25.0°C with a rate of 0.39/d. Using the thermal time model, the base temperature was recorded at 8.4°C, the optimal temperature was 25.5°C, and the ceiling temperature was found at 58.3°C. Besides, based on the hydrotime model, the base water potential showed lower values of -7.74 and -10.90 MPa at the optimal temperatures of 25.0°C and 30.0°C, respectively. Also, the species was found to have excellent tolerance to drought (water stress) compared to salt stress, which has implications for its potential growth into new habitats under climate change. Combining ecological and physiological approaches, this work elucidates the invasive potential of H. persicum and contributes to the protection of species distribution in Tunisian ecosystems.