Characterization of soil salinization and its driving factors in a typical irrigation area of Northwest China

Tomato Defenses Under Stress: The Impact of Salinity on Direct Defenses Against Insect Herbivores

Abiotic stressors, such as salt stress, can reduce crop productivity, and when combined with biotic pressures, such as insect herbivory, can exacerbate yield losses. However, salinity-induced changes to plant quality and defenses can in turn affect insect herbivores feeding on plants. This study investigates how salinity stress in tomato plants (Solanum Lycopersicum cv. Better Boy) impacts the behavior and performance of a devastating insect pest, the tomato fruitworm caterpillar (Helicoverpa zea). Through choice assays and performance experiments, we demonstrate that salt-stressed tomato plants are poor hosts for H. zea, negatively affecting caterpillar feeding preferences and growth rates. While changes in plant nutritional quality were observed, the primary factor influencing insect performance appears to be direct ionic toxicity, which significantly impairs multiple life history parameters of H. zea including survival, pupation, adult emergence, and fecundity. Plant defense responses show complex interactions between salt stress and herbivory, with two proteinase inhibitor genes - PIN2 and AspPI, showing a higher induced response to insect herbivory under salt conditions. However, plant defenses do not seem to be the main driver of reduced caterpillar performance on salt-treated plants. Furthermore, we report reduced oviposition by H. zea moths on salt-treated plants, which was correlated with altered volatile emissions. Our findings reveal that H. zea exhibits optimal host selection behaviours for both larval feeding and adult oviposition decisions, which likely contribute to its success as an agricultural pest. This research provides insights into the complex interactions between abiotic stress, plant physiology, and insect behaviour, with potential implications for pest management strategies in saline agricultural environments.

Spatial variation of soil quality limiting indicators in the North China

The identification of cultivated land obstacle indicators and their spatial distribution are preconditions to soil quality and productivity improvement. This study takes the North China as the objective, using principal component analysis (PCA), entropy TOPSIS and obstacle degree (OD) models to establish a systematic evaluation framework to identify the major limiting indicators. Results reveal that 17.0% of the cultivated land faces severe obstacles, 32.1% and 41.9% experience moderate and slight obstacles, respectively. Only 9.0% of the land shows no significant obstacles. Soil pH and the available potassium content (AK) emerged as the most critical limiting indicators, severely affecting 42.0% and 27.2% of the land, respectively. Other indicators like soil total nitrogen (TN), organic matter (OM) content and cultivated-layer thickness (CLT) exhibited slight obstacles, while AP and BD showed no significant limitations. Spatial analysis highlighted that the pH, AP and BD present notable obstacle incidences, followed by OM and TN. Furthermore, spatial overlap of multiple obstacle indicators was also revealed, 87.1% of the area were limited by more than 3 indicators in the North China. The systematic framework proposes an effective tool for guiding the accurate regional cultivated land quality improvement.

Synergistic effects of phytohormones and membrane transporters in plant salt stress mitigation

Plants are frequently exposed to high salinity, negatively affecting their development and productivity. This review examined the complex roles of membrane transporters (MTs) and phytohormones in mediating salt stress. MTs are crucial in capturing sodium ions (Na+) and maintaining a delicate balance between sodium (Na+) and potassium (K+), essential for supporting cellular homeostasis and enhancing overall plant health. These MTs were instrumental in regulating ion balance and promoting the absorption and segregation of vital nutrients, thereby enhancing salt stress tolerance. Various plant hormones, including abscisic acid, auxin, ethylene, cytokinin, and gibberellins, along with gaseous growth regulators such as nitric oxide and hydrogen sulfide, collaborate to regulate and synchronize numerous aspects of plant growth, development, and stress responses to environmental factors. These transporters and other phytohormones, including brassinosteroids, melatonin, and salicylic acid, also collaborated to initiate adaptation processes, such as controlling osmotic pressure, removing ions, and initiating stress signaling pathways. This study consolidated the advancements in understanding the molecular and physiological processes contributing to plant salt tolerance, emphasizing the intricate relationships between MTs and phytohormones. The aim was to elucidate these interactions to promote further research and develop strategies for enhancing plant salt tolerance.

Experiments to simulate the salinisation process of loess under a dynamic water cycle

Addressing loess salinisation is a crucial element in preserving ecological stability and fostering sustainable development in the northwest Loess Plateau. To investigate the impacts of salt solution on the properties of loess, independently designed salt solution-loess dynamic cyclic erosion equipment was used to soak the loess. Then, numerous tests were performed to analyse the variability of the effects of salt solution concentrations (SSC) and type, as well as the duration of soaking time, on these physico-mechanical properties. The results demonstrated that after being soaked in two different types of salt solutions for 3 days, the shear strength index of loess preliminary decreased and then increased. The compressibility preliminary increased and then declined when the SSC increased. After a 7-day soaking period, the cohesion of the loess did not change considerably, whereas the internal friction angle increased in proportion to the SSC. The compression of loess tended to initially decrease, subsequently increase, and eventually decrease. Loess can be slowed down in its disintegration process by salt solution, and disintegration duration can be effectively shortened with a prolonged soaking time. Finally, it is examined the evolutionary process of the impact of salt solution on loess microstructure. Moreover, the exchange of clay minerals with iron and aluminium ions is proposed to be the key element determining the water-loess chemical interaction. This study may function as an insightful guide for preventing and treating salinised loess on the Loess Plateau of Northwest China, while also serving as a reference for similar areas worldwide.

A comprehensive multicriteria decision analysis framework for shallow geothermal energy suitability evaluation in Yinchuan Area, China

Shallow geothermal energy (SGE) is a green, clean, and renewable energy source that is widely used for heating and cooling. However, hydrogeology conditions, thermophysical properties, geological environment conditions, and other factors influence the implementation of SGE projects. Making a suitability evaluation before implementing the SGE projects is necessary. The two most common methods of suitability evaluation are knowledge-driven and data-driven methods. The knowledge-driven method relies on expert experience. The data-driven method relies on criteria and lacks subjective analysis. To address this shortcoming, this study developed a comprehensive multicriteria decision analysis framework (CMCDAF) for SGE suitability evaluation. The framework comprehensively uses fuzzy analytic hierarchy process (FAHP), Shannon entropy, criteria importance through intercrieria correlation (CRITIC) and genetic algorithm to calulate weights. Then the technique for order preference by similarity to ideal solution (TOPSIS) and grey relation analysis(GRA) are used to rank the suitability of each node and select the most suitable area. To verify CMCDAF, the framework is used to evaluate the suitability of a ground-coupled heat pump (GCHP) system in the Yinchuan area. Results showed the evaluation framework is stable and effective. It has the advantages of avoiding the subjective and one-sided evaluation criteria weights, facilitating the selection of the most suitable areas. The evaluation framework also has the potential to be applied to other decision-making processes.

Effects of exogenous melatonin on the growth and photosynthetic characteristics of tomato seedlings under saline-alkali stress

Saline-alkali stress is a major abiotic stress factor that adversely affects the growth, development, and yield of crops by disrupting ion homeostasis, osmotic balance, and metabolic processes. This study was designed to explore the alleviating effect of melatonin on the growth and development of tomato plants under saline-alkali stress conditions and to screen for optimal concentrations to alleviate the stress. Tomato variety 'Condine Red' was used as the test material, and a total of six treatments were designed including no saline-alkali stress and no melatonin spray as control (CK), and foliar spraying of 0, 50, 100, 150, and 200 µmol·L- 1 melatonin under saline-alkali stress (75 mmol·L- 1), which were used to determine the growth and photosynthetic characteristics of tomato plants. The results showed that saline-alkali stress significantly inhibited plant height, stem diameter, root activity and biomass accumulation, significantly reduced the chlorophyll content of tomato leaves and the efficiency of photosynthetic electron transfer from primary quinone receptor QA to secondary quinone receptor QB, and caused significant deformation of the fast chlorophyll fluorescence induced kinetic curve (OJIP), inhibiting photosynthesis. Exogenous melatonin could improve tomato tolerance to saline-alkali stress, and the effect depended on the concentration. In this experiment, treatment with 100 µmol·L- 1 melatonin showed the strongest positive effect on the growth of tomato plants under saline-alkali stress according to the comprehensive evaluation of principal components. In addition, changes in photosynthetic chlorophyll fluorescence parameters and chlorophyll fluorescence induction curves after melatonin treatment highlighted that melatonin could improve the response of the photosynthetic system to saline-alkali stress by enhancing quenching of excess excitation energy and protecting the photosynthetic electron transport system. Collectively, exogenous melatonin pretreatment increased root activity, chlorophyll content and improved photosystem processes, thereby alleviating tomato growth under saline-alkali stress. The results of this study lay the foundation for the practical application of melatonin in saline-alkali stress.

Comprehensive evaluation of groundwater quality in population-dense and extensive agricultural regions and study on its relationship with agricultural production and human activities

Extensive agricultural regions commonly face issues of poor groundwater management, non-standard agricultural production practices, and unordered discharge of domestic pollution, leading to a continuous decline in groundwater quality and a sharp increase in risks. A comprehensive understanding of groundwater conditions and pollution is a crucial step in effectively addressing the water quality crisis. This study employs the Comprehensive Water Quality Index, Irrigation parameter, and Pollution Index to comprehensively investigate the groundwater quality in a typical agricultural area in Shandong, China, and assesses the suitability of groundwater for irrigation and the risks to human health. Furthermore, multivariate statistical analysis methods are utilized to analyze the relationship between groundwater quality and agricultural production and human activities. The results of the comprehensive quality evaluation indicate that the groundwater in the study area is primarily characterized as weakly alkaline hard freshwater and slightly brackish water, with a hydrochemical type of HCO3-Ca. 42% of the groundwater is unsuitable for drinking, with the main pollutants being TDS, TH, F-, and NO3-. The shallow groundwater level and high soil permeability provide favorable conditions for pollutant migration. Residual Sodium Carbonate (RSC) and Potential Salinity (PS) indicate that 37% of the water samples have excessive bicarbonate levels and 5% have excessive salinity, making them unsuitable for irrigation. Nitrate poses non-carcinogenic risks to all three age groups. Multivariate analysis results show that agricultural pollution dominates in the groundwater, with major pollutants including SO42-, NO3-, COD, NH4-N, F-, etc. Domestic pollution mainly increases the concentrations of ions such as Ca2+, Na+, Mg2+, and also contributes to Cl- and NO3-. The findings of this study contribute to enhancing the rational utilization of groundwater quality in agricultural areas, standardizing agricultural production activities, and promoting the sustainable development of green agriculture.

SORTING NEXIN1 facilitates SALT OVERLY SENSITIVE1 protein accumulation to enhance salt tolerance in Arabidopsis

The plasma membrane (PM)-localized Na+/H+ antiporter Salt Overly Sensitive1 (SOS1) is essential for plant salt tolerance through facilitating Na+ efflux; however, how SOS1 localization and protein accumulation is regulated in plants remains elusive. Here, we report that Sorting Nexin 1 (SNX1) is required for plant salt-stress tolerance through affecting endosomal trafficking of SOS1 in Arabidopsis (Arabidopsis thaliana). Disruption of SNX1 caused salt hypersensitivity with increased Na+ accumulation and decreased Na+ efflux in Arabidopsis when challenged with high salinity stress. SNX1 co-localized and interacted with SOS1 in endosomes, promoting its PM localization and protein stability in plants under saline conditions. SOS1 overexpression promoted salt tolerance in the wild-type, whereas such effect was greatly compromised in the snx1-2 mutant. Pharmaceutical results showed that SOS1 recycling from the cytosol to the PM was largely blocked while its vacuolar degradation was accelerated in the snx1-2 mutant. Furthermore, salt-induced SOS1 phosphorylation enhanced its interaction and co-localization with SNX1, which is required for SOS1 PM localization in plants. Our study elucidates that SNX1 facilitates SOS1 PM localization and protein accumulation through endosomal trafficking, thereby enhancing salt tolerance in plants.

The annual dynamic dataset of high-resolution crop water use in China from 1991 to 2019

Accurately quantifying agricultural water use is essential for protecting agricultural systems from the risk of water scarcity and promoting sustainable water management. While previous studies have innovatively provided spatially explicit analyses or datasets, they tend to have relatively coarse resolution (~8.3 km), and inadequately considered precise localization parameters. Here, we produced annual blue and green water use for 15 main crops with a resolution of 1 km for the years 1991-2019 in China. Firstly, we estimated the yearly crop blue and green water use at the site scale by incorporating more localized input parameters using a dynamic water balance model. Then, the random forest model was combined with site-scale simulation results to generate spatial predictions of blue and green water for each crop from 1991 to 2019. The resulting maps showed a high correlation with locally observed values at field stations (R2 = 0.95), statistics (R2 = 0.77), and exhibited some strengths compared with existing datasets that covered various scales. This dataset can play a key role in devising sustainable water management strategies.

SlNAC12, a novel NAC-type transcription factor, confers salt stress tolerance in tomato

KEY MESSAGE

SlNAC12 enhances salt stress tolerance of transgenic tomato by regulating ion homeostasis, antioxidant activity and flavonoids biosynthesis Soil salinization is a major environmental factor that adversely affects plant growth and development. NAC (NAM, ATAF1/2, and CUC2) is a large family of plant-specific transcription factors that play crucial roles in stress response. Here, we investigated the role of a novel NAC transcription factor, SlNAC12, in conferring salt stress tolerance in tomato (Solanum lycopersicum). Subcellular localization and yeast assays studies revealed that SlNAC12 is localized in the nucleus with weak transcriptional activity. SlNAC12 transcript was induced by salt stress in the leaves and roots of tomato seedlings. Overexpression of SlNAC12 in tomato led to significantly reduced plant height and root length. Transgenic tomato lines overexpressing of SlNAC12 (OE#1 and OE#3) exhibited enhanced tolerance to salinity, as evidenced by reduced the inhibitory effect of growth parameters under salt stress compared to wild type (WT). Overexpression of SlNAC12 in tomato affected Na+ and K+ homeostasis, leading to reduced Na+/K+ ratio, enhanced activity of antioxidant enzymes and decreased reactive oxygen species (ROS) accumulation under salt stress. Furthermore, the transcript levels of several genes involved in flavonoids metabolism and the levels of flavonoids accumulation were increased in SlNAC12-overexpressing tomato lines. Collectively, this study suggests that SlNAC12 transcription factor enhances salt stress tolerance in tomato is correlated with ion homeostasis, antioxidant enzyme systems, and flavonoids accumulation.

The influence of soil salinization, induced by the backwater effect of the Yellow River, on microbial community dynamics and ecosystem functioning in arid regions

Irrigation practices and groundwater levels are critical factors contributing to soil salinization in arid and semi-arid regions. However, the impact of soil salinization resulting from Yellow River water irrigation and recharge on microbial communities and their functions in the Huinong District has not been thoroughly documented. In this study, high-throughput sequencing technology was employed to analyze the diversity, composition, and structure of bacterial and fungal communities across a gradient of salinized soils. The results indicated that the alpha diversity of bacterial communities was significantly higher in slightly saline soils compared to highly saline soils. Soil salinization notably influenced the composition of both bacterial and fungal communities. Highly salinized soils were enriched with bacterial taxa such as Halomonas, Salinimicrobium, Pseudomonas, Solibacillus, and Kocuria, as well as fungal taxa including Emericellopsis, Alternaria, and Podospora. In these highly saline soils, bacterial taxa associated with iron respiration, sulfur respiration, and hydrocarbon degradation were more prevalent, whereas fungal taxa linked to functions such as soil animal pathogens, arbuscular mycorrhizal symbiosis, endophytes, dung saprotrophy, leaf saprotrophy, soil saprotrophy, fungal parasitism, and plant pathogenicity were less abundant. Random forest analysis identified nine bacterial and eighteen fungal taxa as potential biomarkers for salinity discrimination in saline soils. Symbiotic network analysis further revealed that soil salinization pressure reduced the overall complexity and stability of bacterial and fungal communities. Additionally, bacterial community assembly showed a tendency shift from stochastic to deterministic processes in response to increasing salinity, while fungal community assembly remained dominated by deterministic processes. provide robust evidence that soil salinity is a major inhibitor of soil biogeochemical processes in the Huinong District and plays a critical role in shaping bacterial and fungal communities, their symbiotic networks, and their assembly processes.

Evaluation of the microbial community in various saline alkaline-soils driven by soil factors of the Hetao Plain, Inner Mongolia

Soil microbial communities play a crucial role in maintaining diverse ecosystem functions within the saline-alkali soil ecosystems. Therefore, in this study, we collected various saline-alkaline soils from across the Inner Mongolia Hetao irrigation area. The soil chemical properties were analyzed, and the microbial diversity of bacteria and fungi was measured using 16 S rRNA and ITS rRNA amplicon sequencing. The dynamic relationship between the soil microbial community and soil factors was analyzed using the ABT (Aggregate Enhanced tree) model, the co-occurrence network, and the structural equation model. The results indicated that electrical conductivity (EC) was the biggest driving force of various saline-alkaline soils, affecting the community structure of bacteria (22.80%) and fungi (21.30%). The soil samples were categorized into three treatment levels based on their EC values: the low-salinity group (L, EC: 0-1 ms/cm, n = 10), the medium-salinity group (M, EC: 1-2 ms/cm, n = 8), and the high-salinity group (H, EC > 2 ms/cm, n = 6). The results demonstrated a negative correlation between microbial abundance and salinity-alkalinity, while revealing an enhanced interrelationship among species. The alterations in bacterial (12.36%) and fungal (22.92%) communities in various saline-alkali soils were primarily driven by saline-alkali ions, which served as the principal direct factors. The negative correlation between EC and SOM exhibited the highest magnitude, whereas the positive correlation between soil organic carbon and EC demonstrated the greatest strength. Therefore, it was further substantiated that EC played a pivotal role in shaping the distinct microbial communities in saline-alkali soils.

Comparative analysis of ecological sensitivity assessment using the coefficient of variation method and machine learning

Ecological sensitivity is an essential indicator for measuring the ecological environment's level, and its assessment results have significant reference value for regional ecological environment protection and resource development and utilization. Taking Xifeng County as the study area, we selected a total of 12 assessment factors in terms of ecological environment, geological environment, and human environment, including average annual rainfall, average annual temperature, average annual wind speed, river density, vegetation coverage, soil erodibility, elevation, slope, geological disaster susceptibility, road density, land use, and night light index, and explored the spatial distribution patterns of ecological sensitivities and the characteristics of the differences in the study area based on the coefficient of variation method and machine learning. The results show that the overall spatial distribution pattern of ecological sensitivity in Xifeng County shows a low sensitivity in the north and a high sensitivity in the south. 41.90% of the regional ecological sensitivity intensity is classified as very high and high sensitivity, mainly distributed in mountainous and hilly areas, while 35.51% is classified as very low and low sensitivity, mainly distributed in plains and low mountainous areas. The assessment results are consistent with the actual situation, enriching the ecological sensitivity assessment methods and models.

Salinity stress alters plant-mediated interactions between above- and below-ground herbivores

Below-ground herbivory impacts plant development and often induces systemic responses in plants that affect the performance and feeding behavior of above-ground herbivores. Meanwhile, pest-damaged root tissue can enhance a plant's susceptibility to abiotic stress such as salinity. Yet, the extent to which herbivore-induced plant defenses are modulated by such abiotic stress has rarely been studied. In this study, we examine whether root feeding by larvae of the turnip moth, Agrotis segetum (Lepidoptera: Noctuidae) affects the performance of the above-ground, sap-feeding aphid Aphis gossypii (Hemiptera: Aphididae) on cotton, and assess whether those interactions are modulated by salinity stress. In the absence of salinity stress, A. segetum root feeding does not affect A. gossypii development. On the other hand, under intense salinity stress (i.e., 600 mM NaCl), A. segetum root feeding decreases aphid development time by 16.1 % and enhances fecundity by 72.0 %. Transcriptome, metabolome and bioassay trials showed that root feeding and salinity stress jointly trigger the biosynthesis of amino acids in cotton leaves. Specifically, increased titers of valine in leaf tissue relate to an enhanced performance of A. gossypii. Taken together, salinity stress alters the interaction between above- and below-ground feeders by changing amino acid accumulation. Our findings advance our understanding of how plants cope with concurrent biotic and abiotic stressors, and may help tailor plant protection strategies to varying production contexts.

Response of Elymus nutans Griseb. seedling physiology and endogenous hormones to drought and salt stress

Elymus nutans Griseb. (E. nutans), a pioneer plant for the restoration of high quality pasture and vegetation, is widely used to establish artificial grasslands and ecologically restore arid and salinized soils. To investigate the effects of drought stress and salt stress on the physiology and endogenous hormones of E. nutans seedlings, this experiment configured the same environmental water potential (0 (CK), - 0.04, - 0.14, - 0.29, - 0.49, - 0.73, and - 1.02 MPa) of PEG-6000 and NaCl stress to investigate the effects of drought stress and salt stress, respectively, on E. nutans seedlings under the same environmental water potential. The results showed that although the physiological indices and endogenous hormones of the E. nutans seedlings responded differently to drought stress and salt stress under the same environmental water potential, the physiological indices of E. nutans shoots and roots were comprehensively evaluated using the genus function method, and the physiological indices of the E. nutans seedlings under the same environmental water potential exhibited better salt tolerance than drought tolerance. The changes in endogenous hormones of the E. nutans seedlings under drought stress were analyzed to find that treatment with gibberellic acid (GA3), gibberellin A7 (GA7), 6-benzyladenine (6-BA), 6-(y,y-dimethylallylaminopurine) (2.IP), trans-zeatin (TZ), kinetin (KT), dihydrozeatin (DHZ), indole acetic acid (IAA), and 2,6-dichloroisonicotininc acid (INA) was more effective than those under drought stress. By analyzing the amplitude of changes in the endogenous hormones in E. nutans seedlings, the amplitude of changes in the contents of GA3, GA7, 6-BA, 2.IP, TZ, KT, DHZ, IAA, isopentenyl adenosine (IPA), indole-3-butyric acid (IBA), naphthalene acetic acid (NAA), and abscisic acid was larger in drought stress compared with salt stress, which could be because the endogenous hormones are important for the drought tolerance of E. nutans itself. The amplitude of the changes in the contents of DHZ, TZR, salicylic acid, and jasmonic acid was larger in salt stress compared with drought stress. Changes in the content of melatonin were larger in salt stress compared with drought stress, which could indicate that endogenous hormones and substances are important for the salt tolerance of E. nutans itself.

Spatial analysis and mapping of intensity and types of agricultural salt-affected soils around Abaya and Chamo Lakes, South Ethiopia Rift Valley

Purpose

Salt-affected soils have significant enough salt concentrations to impact other land and soil resource uses, plant health, soil characteristics, and water quality. Consequently, a study was carried out in the South Ethiopian Rift Valley area around the lakes of Abaya and Chamo to determine the intensity and the types of salt-affected soil and map their spatial distributions.

Methods

At 0-20 cm depths, a grid soil sampling scheme was employed to gather data from agricultural soils affected by salt. An adequately spaced grid cell of 200 m*200 m or seven transects, with seven samples collected every 200 m on each sampling site, was generated by the QGIS software's Fishnet tool, and an auger collected 226 soil samples from the proposed 245 soil sampling points. The analysis and interpretation of the data were done using both statistical and geostatistical methods. The un-sampled surface was predicted and mapped from laboratory point data using the standard Kriging algorithm in QGIS.

Results

According to the results, the soil in the study area was rated as strongly alkaline and moderately alkaline in the reaction. The coefficient of variation (CV) was the lowest for soil pH. Except for the Ganta Kanchama site, low CV (<10 %) confirmed the similarity of pH values throughout all research areas. The EC values depicted that the study area is slightly saline except for the Ganta Kanchame site, which rated moderately saline to strongly saline. The variability of soil EC rated moderate to strong variation for the studied area. The exchangeable sodium percentage (ESP) values distribution between the study sites demonstrates considerable variability and difference. The area is dominated by low to high-risk rate soil sodicity, as evidenced by the soil ESP CV of the studied area, which was >100 % and showed significant variability among the samples. Out of 2274.65ha of the studied area, the type of salt 62.28 %, 26.09 %, 10.99 %, and 0.63 % were categorized as non-saline non-sodic, saline-sodic, sodic, and saline, respectively. Following saline-sodic, sodic, and saline soils, respectively, non-saline and non-sodic soils comprise most of the investigated areas.

Conclusions

The result indicates almost all the salt-affected areas were situated in relatively lower slope areas exhibiting a flat to almost flat slope (0-2%). The study's findings are that the studied area needs specific soil management strategies to boost the salinity and sodicity problems around the study area and recommended reclamation techniques as the extent of the problems.

The Multiple Promoting Effects of Suaeda glauca Root Exudates on the Growth of Alfalfa under NaCl Stress

Under abiotic stress, plant root exudates can improve plant growth performance. However, studies on the effect of root exudates on the stress resistance of another plant are insufficient. In this study, root exudates (REs) were extracted from Suaeda glauca to explore their effect on alfalfa seedlings under salt stress. The results showed that the plant height and fresh weight of alfalfa significantly increased by 47.72% and 53.39% after 7 days of RE treatment at a 0.4% NaCl concentration. Under 1.2% salt stress, REs reduced the Malondialdehyde content in alfalfa by 30.14% and increased the activity of its antioxidant enzymes (peroxidase and catalase) and the content of its osmotic regulators (soluble sugar and proline) by 60.68%, 52%, 45.67%, and 38.67%, respectively. Soil enzyme activity and the abundance of soil-beneficial bacteria were increased by REs. Spearman analysis showed that urease and neutral phosphatase were related to the richness of beneficial bacteria. Redundancy analysis confirmed that urease affected the composition of the soil bacterial community. The partial least squares structural equation model (PLS-SEM) revealed that REs had a direct positive effect on alfalfa growth under salt stress by regulating the plant's injury and antioxidant systems, and the soil bacterial community had an indirect positive effect on alfalfa growth through soil enzyme activity.

Multi-scale failure mechanisms of hydraulic engineering exposed to seasonally frozen salinization environment: Integrating SBAS-InSAR and mechanical experiments

Constructing hydraulic engineering ensures agricultural development and improves salinization environments. However, in seasonally frozen salinization regions, hydraulic engineering is prone to deformation failure. Leakage from canal raises the regional groundwater level, triggering secondary salinization environmental issues. Exploring the instability mechanisms is thus necessary for hydraulic engineering. Traditional deformation monitoring techniques and soil experiments are constrained by observation scale and timeliness. In this study, Sentinel-1B data from November 2017 to August 2019 were acquired. The small baseline subset (SBAS) InSAR approach was employed to interpret the seasonal deformation characteristics in both the vertical and slope directions of a damaged canal segment in Songyuan, Northeast China. The mechanical properties of saline-alkali soil under varying water contents were quantified by integrating unconfined compression experiment (UCE). In May, as the soil thawed downward, a frozen lenses with poor permeability formed at a depth of approximately 100 cm, causing the accumulation of meltwater and infiltrated precipitation between the frozen layer and the melting layer in the canal. The soil water content at a depth of 80 to 140 cm exceeded 22 %, reaching a threshold for rapid reduction in unconfined compression strength (UCS). Consequently, in spring, the low soil strength between the frozen layer and the melting layer resulted in interface sliding, with a displacement of -133.88 mm in the canal slope direction. Furthermore, the differential projection of freeze-thaw deformation in the slope direction caused continuous creep of the canal towards the free face, with a value of -23.27 mm, exacerbating the formation of the late spring landslide. Integrating InSAR and engineering geological analysis is beneficial for addressing deformation issues in hydraulic engineering. Ensuring the sustainable operation of hydraulic engineering holds important implications for mitigating the salinization process.

Study on the relationship between regional soil desertification and salinization and groundwater based on remote sensing inversion: A case study of the windy beach area in Northern Shaanxi

Soil desertification and salinization are important environmental concerns in arid regions, and their relationship with groundwater change must be further clarified. However, the relationships among soil desertification, salinization, and groundwater are difficult to investigate on a large spatiotemporal scale using traditional ground surveys. In the windy beach area in Northern Shaanxi (WBANS), desertification and salinization problems coexist; therefore, this area was selected as the study area. The feasibility of implementing large-scale remote sensing inversions to identify the degree of desertification and salinization was verified based on measured data, and the degree of influence of groundwater burial depth (GBD) on desertification and salinization was quantified using the geodetector and residual trend analysis methods. The results showed that the GBD in the WBANS presented an increasing trend and the degree of salinization showed a decreasing trend. Moreover, the joint influence of the unique natural environment and anthropogenic activities has led to increases in fractional vegetation cover and considerable improvements in the ecological environment. The intensity of desertification explained by GBD in the WBANS increased significantly (p < 0.01) at a rate of change of 0.0190/year, with high q-values above 0.66 for both Yuyang and Shenmu. The contribution rate of potential evapotranspiration and precipitation to salinization in Yuyang and Shenmu was >97 %, and the contribution rate of GBD to salinization in Dingbian, Jingbian, and Hengshan was 34.78 %, 31.15 %, and 29.41 %, respectively. Overall, the suitable GBD in the WBANS is 2-4 m. The study results provide a reference for research on the inversion, monitoring, and prevention of desertification and salinization dynamics on a large spatiotemporal scale and offer a scientific basis for rationally determining GBD.

Soil salinization in agriculture: Mitigation and adaptation strategies combining nature-based solutions and bioengineering

Soil salinization is among the most critical threats to agriculture and food security. Excess of salts adversely affects soil structure and fertility, plant growth, crop yield, and microorganisms. It is caused by natural processes, such as dry climates and low precipitations, high evaporation rate, poor waterlogging, and human factors, such as inappropriate irrigation practices, poor drainage systems, and excessive use of fertilizers. The growing extremization of climate with prolonged drought conditions is worsening the phenomenon. Nature-based solutions (NBS), combined with precision or conservation agriculture, represent a sustainable response, and offer benefits through revitalizing ecosystem services. This perspective explores NBS that can be adopted, along with their challenges and implementation limitations. We also argue that NBS could not be enough to combat hunger in the world's most vulnerable regions and fully achieve the Sustainable Development Goal - Zero Hunger (SDG2). We therefore discuss their possible combination with salt-tolerant crops based on bioengineering.

Analysis of spatial-temporal patterns and driving mechanisms of land desertification in China

Desertification is a major manifestation of land degradation in China. The monitoring and assessment of land desertification in China and the analysis of its driving mechanisms are crucial to the realization of the aspiration of "net zero land degradation" proposed by the United Nations Convention to Combat Desertification (UNCCD). An improved Mediterranean Desertification and Land Use (MEDALUS) model was applied to assess the multiyear spatial distribution of land desertification sensitivity across China in 2010, 2015, and 2020. A Principal Component Analysis (PCA) was used to evaluate the internal stability of the model. In addition, a Geographical Detector method was used to examine the driving mechanisms of desertification sensitivity in China. The results showed that extremely sensitive desertification areas were primarily concentrated within the Northwest Desert and Desertification Region, northern segment of the Qinghai-Tibet Plateau desert and desertification region, and western sector of the Inner Mongolia-Daxinganling Desert and Desertification Region. In addition, the proportion of land area showing an overall reduction in sensitivity (17.07 %) exceeded that showing an increase (16.56 %). This indicates an overall diminishing trend in sensitivity to land desertification across China. Land use intensity (LUI), drought resistance (DR), erosion protection (EP), and aridity index (AI) are consistently the most important drivers. From 2015 to 2020, the LUI emerged as the principal catalyst behind the transformation of land desertification sensitivity in China. Hence, emphasizing well-planned land use is vital for ensuring harmony between land utilization and ecological capacity. This study establishes a scientific basis for China's land desertification control strategy and serves as a quantitative analysis reference for the driving mechanisms.

Insights into plant salt stress signaling and tolerance

Soil salinization is an essential environmental stressor, threatening agricultural yield and ecological security worldwide. Saline soils accumulate excessive soluble salts which are detrimental to most plants by limiting plant growth and productivity. It is of great necessity for plants to efficiently deal with the adverse effects caused by salt stress for survival and successful reproduction. Multiple determinants of salt tolerance have been identified in plants, and the cellular and physiological mechanisms of plant salt response and adaption have been intensely characterized. Plants respond to salt stress signals and rapidly initiate signaling pathways to re-establish cellular homeostasis with adjusted growth and cellular metabolism. This review summarizes the advances in salt stress perception, signaling, and response in plants. A better understanding of plant salt resistance will contribute to improving crop performance under saline conditions using multiple engineering approaches. The rhizosphere microbiome-mediated plant salt tolerance as well as chemical priming for enhanced plant salt resistance are also discussed in this review.

The Roles of Calcineurin B-like Proteins in Plants under Salt Stress

Salinity stands as a significant environmental stressor, severely impacting crop productivity. Plants exposed to salt stress undergo physiological alterations that influence their growth and development. Meanwhile, plants have also evolved mechanisms to endure the detrimental effects of salinity-induced salt stress. Within plants, Calcineurin B-like (CBL) proteins act as vital Ca2+ sensors, binding to Ca2+ and subsequently transmitting signals to downstream response pathways. CBLs engage with CBL-interacting protein kinases (CIPKs), forming complexes that regulate a multitude of plant growth and developmental processes, notably ion homeostasis in response to salinity conditions. This review introduces the repercussions of salt stress, including osmotic stress, diminished photosynthesis, and oxidative damage. It also explores how CBLs modulate the response to salt stress in plants, outlining the functions of the CBL-CIPK modules involved. Comprehending the mechanisms through which CBL proteins mediate salt tolerance can accelerate the development of cultivars resistant to salinity.

Natural-human driving factors of groundwater salinization in a long-term irrigation area

Salinization of groundwater is a major challenge for groundwater management in long-term irrigation areas, decoupling its complex influencing factors can provide insights for the sustainable development of irrigation areas. In this study, the natural-human driving factors of groundwater salinization in the Yinchuan Plain, a typical irrigated area, were identified using isotope analysis, information entropy, and self-organizing map. Results show that groundwater in the study area is seriously salinized with obvious spatial heterogeneity. Multiple natural conditions and frequent human activities complicate the salinization characteristics of groundwater. On this basis, four typical natural influence units of groundwater were identified, namely, an evaporation and upward leakage zone, a runoff zone, an evaporation zone, and a runoff and upward leakage zone. Information entropy was proposed to quantify the complexity of groundwater resulting from human activities: The complexity difference between densely populated areas and natural dominant areas is mainly reflected in Na⁺, SO₄^2-, and Cl^-. Multiple human-made drivers of complex water environment were further separated into three patterns by the SOM model: blockage-evaporation type, leakage-evaporation type, and irrigation type. The blockage of drainage ditches and obstruction of salt discharge has the highest impact on the salinization of groundwater, followed by irrigation activities and transportation losses. Water excessive stagnation caused by blockage or irrigation is the root cause of groundwater salinization in the irrigated area, and its impact is greater than that of the traditional understanding of groundwater level rise. Based on the evaluation of irrigation water quality, management initiatives for irrigated areas should prioritize dredging and maintaining a healthy soil and groundwater environment in tandem.

Mining for salt-tolerant genes from halophyte Zoysia matrella using FOX system and functional analysis of ZmGnTL

Zoysia matrella is a salt-tolerant turfgrass grown in areas with high soil salinity irrigated with effluent water. Previous studies focused on explaining the regulatory mechanism of Z. matrella salt-tolerance at phenotypic and physiological levels. However, the molecular mechanism associated with salt tolerance of Z. matrella remained unclear. In this study, a high-efficient method named FOX (full-length cDNA overexpression) hunting system was used to search for salt-tolerant genes in Z. matrella. Eleven candidate genes, including several known or novel salt-tolerant genes involved in different metabolism pathways, were identified. These genes exhibited inducible expression under salt stress condition. Furthermore, a novel salt-inducible candidate gene ZmGnTL was transformed into Arabidopsis for functional analysis. ZmGnTL improved salt-tolerance through regulating ion homeostasis, reactive oxygen species scavenging, and osmotic adjustment. In summary, we demonstrated that FOX is a reliable system for discovering novel genes relevant to salt tolerance and several candidate genes were identified from Z. matrella that can assist molecular breeding for plant salt-tolerance improvement.