Saline Soils Research Articles

Variation in microbial communities and network ecological clusters driven by soil organic carbon in an inshore saline soil amended with hydrochar in Yellow River Delta, China.

Char materials (e.g., hydrochar) can enhance carbon sequestration, improve soil quality and modulate soil microbial communities to recuperate soil health. However, little is known about the soil organic carbon (SOC) content, as well as the microbial communities and co-occurrence networks in response to hydrochar amendment in an inshore saline soil. Here, the effect of Sesbania cannabina (a halophyte) straw derived hydrochar (SHC) amendment on SOC and labile organic carbon (LOC) fractions and the potential associations among SOC content change, soil C-cycling enzyme activities and microbial communities were illustrated using a pot experiment. SHC effectively improved the contents of SOC and LOC, particularly particulate organic carbon (POC), and stimulated the activities of C-cycling enzymes. Furthermore, SHC induced shift in microbial community compositions and co-occurrence networks, result in decrease in relative abundance of Actinobacteriota and its corresponding ecological cluster, which may favor SOC accumulation. Functional annotation of prokaryotic taxa (FAPROTAX) analysis also revealed a decrease in microbial ecological function related to carbon degradation. These findings provided a deeper insight about the hydrochar-induced SOC enhancement and suggested an efficient approach to improve C sequestration and improve soil health in the coastal salt-affected soil.

Enhancing Photosynthetic Carbon Transport in Rice Plant Optimizes Rhizosphere Bacterial Community in Saline Soil

Saline soils exert persistent salt stress on plants that inhibits their ability to carry out photosynthesis and leads to photosynthetic carbon (C) scarcity in plant roots and the rhizosphere. However, it remains unclear how a rhizosphere environment is shaped by photosynthetic C partitioning under saline conditions. Given that sucrose is the primary form of photosynthetic C transport, we, respectively, created sucrose transport distorted (STD) and enhanced (STE) rice lines through targeted mutation and overexpression of the sucrose transporter gene OsSUT5. This approach allowed us to investigate different scenarios of photosynthate partitioning to the rhizosphere. Compared to the non-saline soil, we found a significant decrease in soil dissolved organic carbon (DOC) in the rhizosphere, associated with a reduction in bacterial diversity when rice plants were grown under moderate saline conditions. These phenomena were sharpened with STD plants but were largely alleviated in the rhizosphere of STE plants, in which the rhizosphere DOC, and the diversity and abundances of dominant bacterial phyla were measured at comparable levels to the wildtype plants under non-saline conditions. The complexity of bacteria showed a greater level in the rhizosphere of STE plants grown under saline conditions. Several salt-tolerant genera, such as Halobacteroidaceae and Zixibacteria, were found to colonize the rhizosphere of STE plants that could contribute to improved rice growth under persistent saline stresses, due to an increase in C deposition.

Monitoring soil salinization and waterlogging in the northeastern Nile Delta linked to shallow saline groundwater and irrigation water quality.

Soil salinization and waterlogging are critical environmental issues affecting agricultural productivity and cultural heritage preservation, particularly in arid regions. This study investigated soil degradation processes in the archaeologically and agriculturally significant northeastern Nile Delta of Egypt. The objective was to assess the severity of soil degradation and identify key drivers related to water resources and soil characteristics to aid in the development of management strategies. The research employed a multi-faceted approach, including hydrochemical analyses (of groundwater, irrigation water, and soil), water quality indices calculations, statistical analyses, and satellite data. The results revealed high levels of soil salinization in the northern and central areas, with 64% of soil samples classified as strongly and very strongly saline. Soil chemistry indicated salinization sources linked to sodium chloride dominance. Satellite data from Sentinel-2 images and SRTM digital elevation data showed widespread severe waterlogging in the northern lowlands. The Irrigation Water Quality Index (IWQI) values indicated that 87.5% of irrigation water samples posed severe restrictions due to high salinity and sodium hazards, which were mismatched with the low soil permeability observed in 81% of the collected samples exhibiting clay texture and covering most of the study area. Furthermore, shallow groundwater at depths of 0.5-3m with high salinity was detected, where total dissolved solids exceeded 20,000mg/L, and Na-Cl water types prevailed, indicating saltwater intrusion. A strong positive correlation (r > 0.83) was found between shallow saline groundwater and soil salinity. The combination of poor irrigation water quality, shallow saline groundwater tables, and low-permeability soils created a synergistic effect that severely compromised soil health and agricultural productivity. It also posed severe risks to the structural integrity of archaeological sites and buried artifacts through accelerated physical and chemical weathering processes. This necessitates an urgent mitigation strategy to combat soil degradation in this critical area.

Extreme soil salinity reduces N and P metabolism and related microbial network complexity and community immigration rate.

Soil microbiomes are well known to suffer from the effects of rising salinity. There are, however, no current understandings regarding its specific effects on microbial metabolic functions associated with nitrogen (N) and phosphorus (P) cycling, particularly in the Yellow River Delta (YRD), one of the largest estuaries in the world. This research examined soil microbiomes at 50 sites in the YRD region to analyze their co-occurrence networks and their relationship with N (nitrification, denitrification, dissimilatory, assimilatory, fixation, and mineralization) and P (solubilization, mineralization, transportation, and regulation) metabolism processes. Our findings indicate a notable reduction in soil multifunctionality as salinity levels increase, with Halofilum-ochraceum playing a significant role in nitrification, whereas Bacteroidetes-SB0662-bin-6 helps solubilize inorganic P in highly saline areas. High soil salinity negatively affected the amoA gene involved in nitrification and increased the nosZ gene involved in denitrification in extreme salinity soil with 8.2g/kg salt content. Extreme salinity significantly reduced the expression of genes involved in inorganic P solubilization, such as ppa and ppx. Additionally, the alkaline P gene phoD exhibited significant decreases in extremely saline soils, thereby impeding the mineralization of organic P. The neutral community models indicated that microbial community immigration rate showed a linear negative relationship with soil EC in the six N and four P processes. Salinization, however, displayed a nonlinear pattern with clearly defined thresholds on the community of microbes involved in N and P cycling. Reduced microbial diversity and interactions are causing a decline in soil multifunctionality, and the soil multifunctionality and network edges jointly limited the microbial community immigration rate involved in N and P cycling. It is crucial to preserve soil microbial functions to support nutrient cycling and predict the ecological effects of soil salinization.

Spatial heterogeneity response of soil salinization inversion cotton field expansion based on deep learning

Soil salinization represents a significant challenge to the ecological environment in arid areas, and digital mapping of soil salinization as well as exploration of its spatial heterogeneity with crop growth have important implications for national food security and salinization management. However, the machine learning models currently used are deficient in mining local information on salinity and do not explore the spatial heterogeneity of salinity impacts on crops. This study developed soil salinization inversion models using CNN (Convolutional Neural Network), LSTM (Long Short-Term Memory Network), and RF (Random Forest) models based on 97 field samples and feature variables extracted from Landsat-8 imagery. By evaluating the accuracy, the best-performing model was selected to map soil salinity at a 30m resolution for the years 2013 and 2022, and to explore the relationship between soil electrical conductivity (EC) values and the expansion of cotton fields as well as their spatial correlation. The results indicate that:(1) The CNN performs best in prediction, with an R2 of 0.84 for the training set and 0.73 for the test set, capable of capturing more local salinity information. (2) The expansion of cotton fields has reduced the level of soil salinization, with the area of severely salinized and saline soils in newly added cotton fields decreasing from 177.91 km2 and 381.46 km2 to 19.49 km2 and 1.12 km2, respectively. (3) Regions with long-term cotton cultivation and newly reclaimed cotton fields exhibit high sensitivity and vulnerability to soil salinity. This study explores the excellent performance of deep learning in salinity mapping and visualizes the spatial distribution of cotton fields that are highly sensitive to soil salinity, providing a scientific theoretical basis for accurate salinity management.

Reclamation and Improvement of Saline Soils Using Organo–Mineral–Natural Resources, Treated Saline Water, and Drip Irrigation Technology

Reclamation and management of saline soil in arid regions fundamentally require more consideration to attain sustainable agriculture. Experiments were conducted at Abo-Kalam Farm, South Sinai, Egypt. Split-split-plot design experiments were carried out to study the effect of treatments on saline soil hydrophysical properties, sorghum, and cv. ‘Dorado’ plants during the summer season. Pea cv. ‘Entsar 3’ plants were cultivated during the winter season for the residual effect of treatments. Organo–mineral amendment (rice straw compost + mineral sulfur at different rates) was assigned as the main factor, natural rock or artificial fertilizers were assigned as subfactors, and humic acid at different rates was the sub-subfactor. Results showed that organo–mineral amendments improved the hydrophysical properties of the soil, plant nutrient uptake, crop yield, and crop water productivity; however, it diminished by 10 tons/fed (4200 m2) of compost plus 700 kg/fed of mineral sulfur. Therefore, it is recommended that economically using the combination of applying organic–mineral amendments of 4 tons/fed of compost plus 400 kg/fed of mineral sulfur and 5 kg/fed of humic acid plus natural rock fertilizer is the best safe management for reclamation and improvement of saline soils using partially treated saline irrigation water and natural resources.

Crude Oil Biodegradation by a Biosurfactant-Producing Bacterial Consortium in High-Salinity Soil

Bioremediation is a promising strategy to remove crude oil contaminants. However, limited studies explored the potential of bacterial consortia on crude oil biodegradation in high salinity soil. In this study, four halotolerant strains (Pseudoxanthomonas sp. S1-2, Bacillus sp. S2-A, Dietzia sp. CN-3, and Acinetobacter sp. HC8-3S), with strong environmental tolerance (temperature, pH, and salinity), distinctive crude oil degradation, and beneficial biosurfactant production, were combined to construct a bacterial consortium. The inoculation of the consortium successfully degraded 97.1% of total petroleum hydrocarbons in 10 days, with notable removal of alkanes, cycloalkanes, branched alkanes, and aromatic hydrocarbons. Functional optimization showed that this consortium degraded crude oil effectively in a broad range of temperature (20–37 °C), pH (6–9), and salinity (0–100 g/L). In salt-enriched crude-oil-contaminated soil microcosms, the simultaneous treatment of bioaugmentation and biostimulation achieved the highest crude oil degradation rate of 568.6 mg/kg/d, compared to treatments involving abiotic factors, natural attenuation, biostimulation, and bioaugmentation after 60 days. Real-time PCR targeting the 16S rRNA and alkB genes showed the good adaptability and stability of this consortium. The degradation property of the constructed bacterial consortium and the engineered consortium strategy may have potential use in the bioremediation of crude oil pollution in high-salinity soil.

Positive impacts of compost and biochar from orange peel waste on Phaseolus vulgaris physio-biochemistry and productivity and soil properties under salinity stress

ABSTRACT Bioconversion of organic orange peel wastes into compost (OPC) or biochar (OPB) can help overcome the effects of soil salinity and maintain agricultural productivity. Effect of 1.0% OPC or 1.0% OPB as soil amendments on soil properties and performance of Phaseolus vulgaris plants under two salinity levels [5.60 dS m−1 (S-1) and 9.60 dS m−1 (S-2)] versus control [1.60 dS m−1 (S-0)] was investigated. Compared to the control, S-1 and S-2 increased soil sodium ion (Na+) content, while reducing soil organic matter (OM), macro- and micro-nutrients, cation exchange capacity (CEC), and enzyme (urease, acid phosphatase, and alkaline phosphatase) activities, reflecting decreased plant growth and yield. Under S-1 or S-2, OPC application exceeded OPB application, but both considerably enhanced soil OM content, nutrients, CEC, and enzyme activities. These positive results reflected decreased leaf electrolyte leakage and increased leaf-relative water content, pigments, nutrients, K+/Na+ ratio, antioxidant activity, plant growth, and yield. The beneficial impacts of 1.0% OPC were more pronounced under S-2 than S-1 or S-0. In conclusion, adding 1.0% OPC to saline soil (ECe of about 5–10 dS m−1) could mitigate the influences of soil salinity to improve Phaseolus vulgaris growth, physio-biochemistry, and yield.

Microencapsulated Microbial Seed Coating Could Improve Soil Environment and Maize Grain Yield in Saline Soil

Soil salinization is one of the major challenges for modern agriculture, posing a great threat to soil health and food security. Field experiments were conducted to evaluate the effect of seed coating on soil environment and maize growth in saline soils. Three treatments were applied to maize seeds: coating with a microencapsulated microbial agent (ME), coating with microbial only (MB), and no coating (CK). High-throughput sequencing of soil bacterial and fungal 16S and ITS rRNA genes was performed using the Illumina HiSeq platform to analyze the effects of these treatments on soil bacterial and fungal diversity and community structure. Additionally, the influence of different treatments on endogenous hormones and yield of maize were investigated. It was found that the coating with a microencapsulated microbial agent led to decreases in pH and electrical conductivity (EC), while increasing the content of soil available phosphorus. This coating improved soil microbial diversity, significantly increasing the relative abundance of the main bacteria genera, Bacillus (34.9%), and the main fungal genera, Mortierella (190.4%). The treatment also significantly enhanced indole-3-acetic acid (IAA) by 51.2%, contributing to improvements in resistance to salt stress. The germination rate increased by 22.9%, the 100-grain weight increased by 12.7%, and grain yield increased by 14.3%. The use of the microencapsulated microbial agent effectively mitigated the adverse effects of salt stress on maize plants. This approach is beneficial for promoting sustainable agriculture in saline soils.

Relationship between nutrient accumulation in broomcorn millet (Panicum miliaceum L.) and microbial community under different salinity soils

Relationship between nutrient accumulation in broomcorn millet (Panicum miliaceum L.) and microbial community under different salinity soils

Design and Testing of an Extruded Shaking Vibration-Type Peanut Digging and Harvesting Machine for Saline Soil

Design and Testing of an Extruded Shaking Vibration-Type Peanut Digging and Harvesting Machine for Saline Soil

Observing super-coarse carbonaceous aerosol particles containing chloride in a tropical savanna climate at an agro-forest site in Thailand.

Coarse aerosol particles containing chloride in tropical forests are significant for understanding biogeochemical cycles and atmospheric processes, with implications for environmental health and climate change mitigation. This study explored the sources of super-coarse carbonaceous aerosol particles containing chloride in a tropical savanna climate. Aerosol samples were collected from an agro-forest site in Thailand during the dry season and analyzed using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and Fourier-transform infrared (FTIR) spectroscopy. By examining the morphology and elemental compositions of individual aerosol particles, along with employing Positive Matrix Factorization (PMF) and backward trajectory analysis, potential sources were identified. The findings revealed two primary sources for the super-coarse aerosol particles: a mixture of biomass burning smoke and inorganic salts (likely from saline soil and sea salt), as well as halophilic fungal spores. FTIR analysis indicated the presence of compounds linked to biomass burning and clay minerals, influenced by prevailing northeast and southeast winds. Recommendations for future research include continued monitoring, correlation with meteorological parameters, and the application of transmission electron microscopy (TEM) for more detailed visualization and confirmation of aerosol sources.

The Optimum Mixed Cropping Ratio of Oat and Alfalfa Enhanced Plant Growth, Forage Yield, and Forage Quality in Saline Soil.

The forage shortage is more aggravating than ever before, with husbandry development accelerating and meat and dairy product demand increasing. Salinized soils are important reserve land encouraged to be used for forage production in China. However, the salt-tolerant cultivation techniques for forage crops are still inadequate. Therefore, a field experiment was conducted to study the effects of the mixed cropping ratio of oat and alfalfa on plant growth and physiological traits, forage yield, and forage quality in saline soils. Oat (Avena sativa L.) variety of Canadian Monopoly and alfalfa variety of WL525HQ were used, and five mixed cropping ratios (T1 = 100% oat + 0% alfalfa, CK, T2 = 75% oat + 25% alfalfa, T3 = 50% oat + 50% alfalfa, T4 = 25% oat + 75% alfalfa, and T5 = 0% oat + 100% alfalfa) were evaluated. The results showed that plant height, chlorophyll, soluble sugar, starch, antioxidant enzymes, and crude fat were increased firstly and then decreased prominently with decreased oats and increased alfalfa sowing rate; the maximum values showed under T2 but the minimum value under T5 at evaluated growth periods. On the contrary, malondialdehyde and acid detergent fiber were significantly decreased and then increased; the lowest contents were recorded under T2 and highest under T5. Furthermore, the relative growth rate, forage yield, neutral detergent fiber, and crude ash were decreased prominently with decreased oats and increased alfalfa sowing rate, and the highest and lowest values showed under T1 and T5, respectively. Oppositely, the contents of sucrose, proline, N, P, K, relative feeding value, and crude protein were all increased, with the highest contents generated under T2 and the lowest under T1. On the whole, the mixed cropping treatment of T2 showed the best performance in improving both biomass yield and forage quality by enhanced antioxidant enzyme activity, osmotic regulatory substances, and nutrient uptake and utilization. Therefore, this study indicates that 75% oat mixed cropping with 25% alfalfa can be recommended as a salt-tolerant cultivation technique for forage high-yield and high-quality production in moderately saline soil.

Effect of Salinity on Inorganic Phosphorus Fixation in Sara and Bajoa Soil Series of Ganges Tidal Floodplains

Soil salinity significantly impacts nutrient availability, especially phosphorus (P), in the southwestern regions of Bangladesh, where salinity is prevalent during the dry season. This study investigates the effect of varying salinity levels (2, 4, 8, and 12 dS m⁻¹) on phosphorus transformation and availability in two soil series, Bajoa and Sara, from the Ganges Floodplain. A laboratory incubation experiment was conducted with samples exposed to the salinity treatments over 0, 15, 30, and 60 days, followed by sequential extraction to quantify the phosphorus fractions. Results indicated that increased salinity led to a shift in phosphorus forms, with calcium-bound phosphorus (Ca-P) dominating over iron and aluminum-bound (Fe, Al-P) and reductant-soluble phosphorus (Rs-P) in both soil series. The Bajoa and Sara soils showed distinct responses, with a consistent reduction in bioavailable P as salinity levels increased. This fixation of phosphorus into less accessible forms has critical implications for nutrient management, as reduced P availability could limit crop productivity in saline soils. The study highlights the need for targeted phosphorus management strategies for saline-affected soils, emphasizing the importance of tailored fertilization practices to enhance sustainable agricultural productivity. Further research should explore adaptive management practices for phosphorus fertilization to mitigate the adverse effects of salinity on nutrient dynamics in affected regions.

Actinorhizal plants and Frankiaceae: The overlooked future of phytoremediation.

Bioremediation of degraded soils is increasingly necessary due to rising food demand, reductions in agricultural productivity, and limitations in total available arable area. Several bioremediation strategies could be utilized to combat soil degradation, with phytoremediation emerging as a standout option due to its in situ approach and low implementation and maintenance costs compared to other methods. Phytoremediation is also a sustainable solution, which is increasingly desirable to blunt the progression of global warming. Actinorhizal plants display several desirable traits for application in phytoremediation, including the ability to revegetate saline soil and sequester heavy metals with low foliar translocation. Additionally, when grown in association with Frankiaceae endophytes, these abilities are improved and expanded to include the degradation of anthropogenic pollutants and the restoration of soil fertility. However, despite this significant potential to remediate marginalized land, the actinorhizal-Frankiaceae symbiosis remains heavily understudied and underutilized. This review aims to collate the scattered studies that demonstrate these bioremediation abilities and explain the mechanics behind such abilities to provide the necessary insight. Finally, this review will conclude with proposed future directions for utilizing this symbiosis and how it can be optimized further to facilitate improved bioremediation outcomes.

Genome-Based Classification of 'Haloarcula aidinensis' and Description of Three Novel Halophilic Archaea Isolated from an Inland Saline Lake, Coastal Saline Soil, and a Marine Solar Saltern.

'Haloarcula aidinensis' was described by a pioneer Chinese scientist focused on halophilic archaea thirty years ago, and the type strain of 'Haloarcula aidinensis' was recently classified based on phylogenetic, phylogenomic, and comparative genomic analyses. Other three novel halophilic archaeal strains, CK38T, DT43T, and SYNS111T, isolated from diverse saline environments in China, were simultaneously subjected to polyphasic classification. 'Haloarcula aidinensis' A5 was found to be related to Haloarcula amylolytica, while strains CK38T, DT43T, and SYNS111T represented three novel species of Haloarcula based on phylogenetic, phylogenomic, and comparative genomic analyses. These strains can be distinguished from other species within the genus Haloarcula based on multiple phenotypic characteristics. The major phospholipids, phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, and phosphatidylglycerol sulfate can be detected in these strains, while the glycolipid profiles of these strains are diverse. Strains A5 and DT43T contained glucosyl mannosyl glucosyl diether and a diglycosyl diether, while other strains CK38T and SYNS111T had sulfated mannosyl glucosyl diether and mannosyl glucosyl diether. Thus, strain A5 should be a reference strain of Har. amylolytica and three novel species of Haloarcula, Haloarcula sediminis sp. nov., Haloarcula brevis sp. nov., and Haloarcula regularis sp. nov. are proposed to accommodate strains CK38T (= CGMCC 1.62732T = JCM 36675T), DT43T (= CGMCC 1.18924T = JCM 36146T), and SYNS111T (= CGMCC 1.62601T = JCM 36149T).

Impact of Salinity Stress on Morpho-physiology of Four Rice (Oryza sativa L.) Varieties

Abiotic stress, especially salinity, is one of the major restraints for attaining self-sufficiency in the food grain production. The saline soils affect the crop growth both directly and indirectly by interfering with plant metabolism resulting in reduction in yield potential of various crops. Rice (Oryza sativa L.), the staple food of much of the world’s population, is categorized as a salt-susceptible crop. Improving the salt tolerance of rice would increase the potential of saline-alkali land and ensure food security. To investigate the effect of different levels of salinity on morpho-physiological characters and yield of four rice variety viz. Pokkali, Narendra Ushar Dhan 3, IR 28 and IR 29. A pot experiment was conducted during Kharif 2011 and 2012 at the Department of Crop Physiology, Narendra Deva University of Agriculture and Technology, Kumarganj, Faizabad (U.P.) under normal soil and saline conditions with EC 6.0 and EC 10.0 dS/m. Gradual increase on plant height as well as biomass with the advancement in the age of crop up to dough grain in all the varities under both normal and salinity treatment. Maximum grain yield recorded in tolerant varieties Narendra Usar Dhan 3 followed by Pokkali, whereas minimum in IR 28. Under saline conditions regarding sink potential, the tolerant varieties recorded less reduction in yield attributes like length of panicle (cm), number of panicle per plant, number grain panicle-1 and grain yield plant-1 as compared to normal condition. The salinity tolerance capacity of tolerance varieties was associated with increased the activity of catalase and superoxide dismutase enzyme batter accumulation of proline and total carbohydrate as compared to normal condition.

Long-term rice cultivation enhances root development and yields by improving the structural properties of soil aggregates in saline–alkaline environments

Rice cultivation has the ability to improve saline soils. However, the effects of long-term rice cultivation on saline soil chemistry, salt ions, root characteristics, and aggregate formation remain unclear. In this study, the impact of different planting durations (1, 3, 5, 8, and 10 years) on the spatial and temporal transport of soil salts, soil chemical properties, distribution and stability of aggregates, root characteristics, and yields, were assessed. Long-term rice cultivation reduced soil pH, exchangeable sodium percentage (ESP), and EC in the 0-60cm soil layer compared to 1Y (5.45%, 61.57%, and 81.87% reduction in topsoil (0-20cm) and 8.54%, 72.82%, and 71.94 in subsoil (20-60cm), respectively). However, the soil organic matter (OM), alkaline nitrogen (AN), phosphorus (AP), and potassium (AK) increased (217.09%, 90.18%, 89.23%, and 179.18% increase in topsoil and 223.72%, 81.24%, 174.28%, and 172.57% increase in subsoil, respectively). Additionally, the Cl-, K+, and Na+ in the soil gradually leached downward with the increase in the duration of rice cultivation (55.87%、36.08%、59.80%). Simultaneously, the increased duration markedly elevated the soil macroaggregate content (11.43%-20.04% by dry-sieving and 53.48%-288.09% by wet-sieving), clayey grain content (59.17%-198.33%), and soil aggregate stability, especially for 8Y and 10Y. The improved soil structure and root characteristic under long-term rice cultivation conditions increased the yield (28.89-54.81%). Partial least squares path model displayed that rice cultivation affected the aggregate stability, root characteristics, and rice yield via the corresponding chemical properties (pH, EC, and ESP), nutrient contents (AN, AP, AK, and SOM), and salt ion contents (Cl-, K+, and Na+). These findings are critical to understanding aggregate formation in saline soils.

Salinity drives niche differentiation of soil bacteria and archaea in Hetao Plain, China

Soil salinization is a critical environmental issue that limits plant productivity and disrupts ecosystem functions. As important indicators of soil environment, soil microbes play essential roles in driving nutrient cycling and sustaining ecosystem services. Therefore, understanding how microbial communities and their functional potentials respond to varying levels of soil salinization across different land use types is crucial for the restoration and management of salt-affected ecosystems. In this study, we randomly selected 63 sites across the Hetao Plain, covering an area of ∼2500 km2. Our results showed that both salinity- and fertility-related soil parameters were significantly correlated with bacterial and archaeal diversities, with soil salinity emerging as the stronger predictor of prokaryotic diversity. Intriguingly, bacterial and archaeal communities were tightly interlinked but displayed opposite trends in response to environmental factors, indicating a clear microbial niche differentiation driven by soil salinity. Moreover, the generalist functions of bacteria and archaea (e.g., chemoheterotrophy) exhibited contrasting responses to environmental parameters, while their specialist functions (e.g., nitrification) responded consistently. These findings highlight the pivotal role of soil salinity in shaping the niche differentiation of bacterial and archaeal communities in saline soils, providing insights to guide salinity-centered restoration strategies for effective marginal land management.

Synergistic regulation of salinity and nutrients on organic carbon mineralization in a 700-year cultivated saline soil chronosequence

Long-term cultivation in reclaimed mudflats significantly impacts soil properties through changes in salinity and organic carbon (OC) inputs, which subsequently affect soil physical, chemical, and biological characteristics. In addition, long-term rice cultivation can help optimize soil health and fertility management in paddy fields, mitigate climate change, and enhance ecosystem services. However, the impact of long-term cultivation on OC mineralization across a salinity gradient remains unclear. During an 80-d incubation experiment, we assessed 13C-labeled glucose mineralization in soils cultivated for 5, 20, 200, and 700 years, each with varying salinity levels. Our results demonstrated that glucose mineralization declined linearly with increasing soil salinity, from 76 % in low-salinity soils to 31 % in high-salinity soils, reflecting a clear physical impact. This process was closely linked with chemical properties, showing a positive correlation with Olsen P and levels of microbial biomass carbon and nitrogen. Soil organic carbon (SOC) mineralization was primarily controlled by dissolved OC regardless of soil salinity. Further investigation revealed significant shifts in the biological properties, notably the bacterial community composition, which varied with the duration of soil cultivation. The bacterial Shannon index increased steadily from 50 to 700 years, forming distinct clusters, influenced primarily by electrical conductivity and pH in high-salinity soils and by soil-labile nutrients in low-salinity soils. The abundance of Acidobacteria, Proteobacteria, and Verrucomicrobia—dominant phyla in soil cultivated for 700 years—is negatively correlated with soil salinity and pH and positively with labile nutrients, glucose, and OC mineralization, whereas the opposite was true for Bacteroidetes and Firmicutes dominant phyla in soil cultivated for 5 years, was affected positively by soil salinity and pH and negatively by labile nutrients and glucose mineralization. In conclusion, soil salinity and nutrients synergistically regulate OC mineralization in a 700-year cultivated saline soil chronosequence. Addressing these factors is critical to enhancing microbial activity and OC accumulation in saline soils, underscoring the importance of integrating measures to reduce salt and increase the import and accumulation of exogenous organic matter.