Search Results (170)

Soil organic carbon (SOC) is central to terrestrial carbon cycling, soil health and sustainable land utilization. However, in Northeast China’s black soil region, the quantitative synergistic regulatory mechanisms of soil geochemical background, climate, and topography on SOC spatial heterogeneity remain poorly understood, limiting targeted sustainable soil carbon management. This study took the Hulan River Basin with a complete soil geochemical gradient as the study area. Based on eight major soil elements and pH data, we divided the basin into five geochemical zones via PCA and K-means clustering (cumulative variance contribution: 83.02%). SOC content differed significantly among zones, peaking in strongly acidic residual-slope zones and bottoming in alkaline saline–alkali alluvial zones. Geodetector results showed aridity (q = 0.57), mean annual temperature (q = 0.50), and geochemical zone (q = 0.46) dominated SOC differentiation. The non-linear interaction between geochemical zone and aridity exhibited the strongest explanatory power (q = 0.63), far exceeding individual effects, as revealed by the interaction detector. A dual regulatory mechanism was identified: iron–manganese oxides stabilize SOC via organo–mineral complexation, while high pH and base cations accelerate SOC decomposition by disrupting soil aggregates. This study clarifies the synergistic controls of pedogeochemistry, climate and topography on black soil SOC patterns, highlighting the underestimated dominant role of geochemical background. The findings support precise regional carbon stock assessment and differentiated carbon sequestration strategies. Full article

Microbial communities associated with fish mucosal tissues play important roles in host health and environmental adaptation. However, the effects of contrasting aquaculture conditions on the microorganisms of the large yellow croaker (Larimichthys crocea, L. crocea) remain poorly understood. In this study, 16S rRNA gene sequencing was used to compare the gut and gill microbiota of L. crocea cultured in a marine system and a saline–alkaline system, together with the corresponding surrounding water samples. The results showed that both host tissue type and rearing environment significantly influenced microbial community structure. Water samples generally exhibited higher alpha diversity than host-associated samples, whereas the gut and gill communities were clearly separated from the surrounding water microbial community. The intestine showed stronger culture system differentiation than the gill, suggesting greater niche selectivity, while the gill retained a closer association with the rearing water. Across multiple taxonomic levels, microbial composition differed markedly among water, gut, and gill samples, and the divergence between the marine culture and saline–alkaline culture system became more pronounced at finer taxonomic resolution. Differentially enriched taxa further revealed clear tissue- and habitat-associated microbial patterns. In addition, several dominant taxa were significantly correlated with environmental variables, especially salinity and nutrient-related factors, indicating that physicochemical heterogeneity contributed substantially to microbial community assembly. Overall, this study shows that host mucosal niche and rearing environment are associated with distinct gut and gill microbiota patterns in L. crocea and provides preliminary ecological information for future microbiome-informed aquaculture management, functional validation of candidate taxa, and the development of land-based culture systems for marine fish. Full article

Water quality in high-elevation agricultural river valleys is shaped by regional environmental gradients and localized hydrogeochemical conditions, but multi-year assessments often do not clearly separate routine hydrochemical variability from metal(loid) risk. This study evaluates a public multi-year dataset from the agricultural concentration area of the Yarlung Zangbo River and its two tributaries on the Qinghai–Tibet Plateau. The dataset includes 444 river-water, groundwater, and irrigation-water samples collected in 2019, 2020, 2021, 2023, and 2024. We combined water-type-specific standard assessment, normalized exceedance frequencies, spatial visualization, and descriptive correlation analysis with terrain, land-cover, soil, and climate-hydrological predictors. Because sampling coverage and hydrological-period classification differed among years, annual contrasts were interpreted descriptively rather than as fixed-site temporal trends. Most samples were neutral to weakly alkaline, whereas electrical conductivity (EC), total dissolved solids (TDS), and salinity varied more strongly across years and sampling locations. In total, 70 samples exceeded at least one evaluated criterion, but only 12 samples were flagged in the metal(loid) assessment. Eight samples exceeded the 0.05 mg/L As screening threshold, occurring only in 2023 and 2024 (3.25% and 2.92% of samples in those years, respectively), and were concentrated in a localized reach rather than distributed basin-wide. As was positively associated with Mo and Hg, whereas relationships with Fe, Mn, pH, EC, TDS, and salinity were weak or inconsistent; dissolved oxygen was not available for the high-As samples. These results distinguish broad dissolved-solute variability from localized As-dominated risk and show that the dataset supports regional screening and monitoring prioritization, but not definitive redox, speciation, or source-apportionment conclusions. Full article

Coastal saline–alkaline land has considerable potential for soil carbon sequestration, but how different land-use types affect microbial resource limitation and carbon-use efficiency (CUE) in coastal saline–alkaline soils remains unclear. Four representative land-use types, namely bare land (BL), wetland (WL), grassland (GL), and forest land (FL), were investigated in the coastal saline–alkaline soils of the Yellow River Delta. Soil physicochemical properties, microbial biomass, and extracellular enzyme activities were measured, and ecoenzymatic stoichiometry, microbial resource limitation, and CUE were subsequently calculated. Compared with BL, vegetated land-use types decreased electrical conductivity by 52.1–95.8%, while soil water content, soil nutrient indicators, and microbial biomass indicators increased by 47.1–77.5%, 2.6–136.8%, and 2.2–274.4%, respectively. WL was mainly phosphorus-limited, whereas BL, GL, and FL were primarily nitrogen-limited. Despite relatively high soil organic carbon and nutrient availability, GL showed the strongest N limitation and was the only land-use type showing C limitation. Model-estimated CUE ranged from 0.544 to 0.579 and followed the order FL > BL > WL > GL. Random forest analysis showed that soil physicochemical properties contributed most to CUE variation (42.9%). Structural equation modeling further indicated that soil physicochemical properties were indirectly associated with CUE, mainly through stoichiometric characteristics and microbial resource limitation, showing positive and negative associations, respectively. These findings provide microbial evidence for optimizing land-use patterns, vegetation restoration, and carbon-oriented ecological restoration in coastal saline–alkaline land. Full article

Soil microorganisms and plant residue decomposition are critical drivers of soil nutrient cycling and multifunctionality, yet their regulatory mechanisms in saline–alkali soils are not fully understood. This study selected bare land and forestland (shrub and tree stands) in Daqing, Heilongjiang, to investigate the effects of plant residue input on forest soil properties, microbial communities, keystone taxa, and multifunctionality using high-throughput sequencing and multivariate analysis. Results showed that plant residue cover significantly improved soil nutrients (SOC, TN, TP, TK, AN), enhanced alkaline phosphatase activity, and increased soil multifunctionality compared with bare land. Plant residues also increased bacterial α-diversity and shifted community composition, with elevated relative abundances of Proteobacteria, Bacteroidota, Planctomycetota, Patescibacteria, and key genera (Mycobacterium, Pseudonocardia, Bryobacter, Steroidobacter). Non-metric multidimensional scaling (NMDS) and correlation analysis revealed microbial communities and keystone taxa were closely correlated with soil nutrients and multifunctionality. Overall, plant residues enhance forest soil multifunctionality by improving soil organic matter, optimizing microbial community structure, and stimulating keystone taxa, providing a scientific basis for understanding microbial-driven nutrient cycling and vegetation restoration in degraded saline–alkali soils. Full article

Saline–alkaline land serves as a potential arable land reserve for augmenting agricultural productivity and safeguarding food security. However, long-term monitoring of saline–alkaline land conversion remains challenging because of vegetation recovery, surface changes, hydrological modification, and agricultural phenology. Compared with CCDC and LandTrendr, the proposed MK-based framework detects conversion occurrence and timing while reducing dependence on dense observations, parameter tuning, and annual classification. This study examines the spatiotemporal dynamics of saline–alkaline land converted into paddies in Da’an City, utilizing Landsat time-series data (2007–2021) from the Google Earth Engine (GEE) platform. The analysis employed Mann–Kendall (MK) trend and mutation tests to monitor conversion processes and analyze spatiotemporal dynamics. Point-biserial correlation analysis was applied to evaluate the sensitivity of various remote sensing indices in detecting land conversion. The top fifteen indices, including the Land Surface Water Index (LSWI), Salinity Index 4 (SI4), and Salinity Index 5 (SI5), demonstrated strong correlations (|r| = 0.788–0.885) and significant pre- and post-conversion spectral differences (p < 0.01). Validation via confusion matrix confirmed that the June SI5 index attained the highest detection accuracy (overall accuracy: 94.15%; Kappa coefficient: 0.86), supporting the MK trend test’s efficacy in monitoring conversion processes. The MK mutation test achieved 80.36% temporal accuracy in determining conversion timing. The spatiotemporal analyses identified heterogeneity in saline–alkaline land conversion patterns. Spatially, large contiguous paddy fields dominated the eastern region, whereas fragmented conversion characterized the west, with minimal activity in the central zone. Temporally, the conversion area expanded rapidly before 2015 and then gradually declined, reaching a cumulative converted area of 276.29 km² by 2021. This study elucidates spatiotemporal conversion dynamics to guide sustainable land use. Full article

Straw return and tillage practices can alter the soil properties and regulate the bacteria communities, which mediate nitrogen (N) transformation and accumulation. This study aims to elucidate the mechanisms of microbially driven N retention, providing a foundation for soil management strategies. A field experiment was conducted in 2019–2022, six treatments were set up, including rotary tillage with/without straw (RTSR and RTNS), deep tillage with/without straw (DTSR and DTNS), subsoiling with/without straw (STSR and STNS). Soil properties, N pools/fractions and bacterial communities were measured. The results showed that straw return and tillage practices ameliorated soil environment (reducing bulk density (by 7–8% via DTSR and STSR) and salinity (with 57% and 26% increase in DTSR and STSR compared with RTSR, while rotary tillage significantly reduced salinity), increasing soil organic matter (via RTSR treatment, with 5–16% significant increase in two years) and effectively promoting N accumulation. The number of OTUs and the α-diversity significantly increased in 2022 compared with 2021. Specifically, tillage was the main driver of bacterial α-diversity, but there was no significant influence on bacterial β-diversity. Mental test results showed that N availability is a pivotal environmental factor shaping the bacteria α- and β-diversity. Structural equation modeling revealed that SON accumulation directly drove N accumulation via the “environmental improvement–specific microbial community structure” pathway. STSR is the optimal treatment for promoting N accumulation by maintaining active SON levels, which is an effective strategy for sustainable N management in the Yellow River Delta (YRD). Full article

Pine wilt disease control often depends on reducing adult beetle activity, but how aerial spraying performs under operational forest management conditions remains poorly understood. We evaluated a 2022 operational aerial spray program in Pinus thunbergii stands in Shandong, China, by combining droplet deposition measurements, branch-feeding bioassays to assess acute and residual toxicity with Monochamus alternatus, and seasonal trap monitoring of both M. alternatus and Arhopalus rusticus, a relevant co-occurring cerambycid species. Spray cards showed that insecticide reached the stand in both spray rounds, although vertical differences between upper and lower strata were stronger during the second application. Branches collected immediately after spraying caused rapid mortality of M. alternatus, and both strata reached complete mortality within 72 h of exposure. In contrast, branches collected one month later caused little additional mortality beyond control levels, indicating that biologically effective exposure declined quickly and provided an insufficient window of protection relative to the full period of adult beetle activity. Trap data matched this pattern. After the first spray, M. alternatus captures dropped sharply during the immediate post-spray period but rebounded before the second spray. A. rusticus showed a similar short-term response, but its seasonal activity pattern differed from that of M. alternatus. Overall, the main limitation of the spray program was not weak initial toxicity, but the short duration of effective control relative to beetle activity in the field. This study shows that better aerial control of pine wilt vectors will depend on matching spray timing and residual persistence with local beetle phenology to improve the design and timing of aerial control programs in pine wilt management. Full article

The utilization of saline–alkali lands and the competition between medicinal plants and grain crops are urgent issues. This study aimed to evaluate the effects of combined biochar and phosphogypsum application on soil physicochemical properties, microbial communities, and safflower growth, yield, and bioactive component accumulation in moderately saline–alkali soil of western Jilin, and to identify key soil factors driving these responses. To achieve this, outdoor pot experiments were conducted using safflower (Carthamus tinctorius L.), with the application of 1% biochar + 1% phosphogypsum to moderately saline–alkali soil. The results showed that the amendment significantly reduced bulk density (BD), pH, sodium adsorption ratio (SAR), total alkalinity (TA), and exchangeable sodium percentage (ESP), while increasing soil water content (SWC), soil organic matter (SOM), nitrogen, phosphorus, potassium, and beneficial ions. Soil sucrase, urease, alkaline phosphatase, and catalase activities were enhanced. Copiotrophic taxa (Pseudomonadota, Sphingomonas, Vicinamibacter) increased, whereas oligotrophic taxa (Gemmatimonadetes, Longimicrobium, Luteitalea) decreased, with stronger effects on bacteria than fungi. Safflower growth indices improved; leaf Na⁺/K⁺ ratio, superoxide radicals, and malondialdehyde decreased; and soluble protein, proline, and antioxidant enzyme activities increased. Bioactive components (hydroxysafflor yellow A, kaempferol) and yield reached 1.41%, 0.056%, and 343.23 mg/plant, representing 1.74–27.68-fold increases over moderate and mild saline–alkali soils. Correlation analysis identified SOM, total nitrogen (TN), available phosphorus (AP), BD, SWC, pH, SAR, TA, and ESP as key factors. In conclusion, co-application of 1% biochar and 1% phosphogypsum improves soil physicochemical and microbial properties, alleviates saline–alkali stress, and enhances safflower quality and yield. Full article

Coastal land reclamation is widely implemented to support coastal development, yet its effects on microbial indicators in coupled surface water–groundwater systems remain poorly understood. This study examined the spatiotemporal variability of four microbial indicators and their environmental associations using 46 months of monthly monitoring (April 2016–January 2020) in eastern Guanghai Bay, China. Total bacterial counts, fecal coliforms, Escherichia coli, and total coliforms were analyzed using multivariate statistical methods. Surface water exhibited elevated levels of fecal indicators, with consistently higher pollution levels in the Xiaoma River than in the Dama River and clear seasonal variation associated with climatic and hydrological conditions. Groundwater showed pronounced spatial heterogeneity: Wells 1 and 2 exhibited relatively elevated microbial contamination, whereas Well 3 maintained persistently low microbial levels under high-salinity and high-alkalinity conditions. These patterns suggest that reclamation may be associated with groundwater microbial distribution through changes in groundwater transport pathways and hydrochemical conditions, while anthropogenic pressures also played an important role in shaping contamination patterns. These findings offer practical insights for groundwater protection and sustainable management in reclaimed coastal environments. Full article

Reclaiming saline–alkaline soil is critical for food security and land expansion. While paddy rice is the key pioneer crop for remediation, the soil fertility–yield relationship remains poorly understood. To optimize remediation strategies, this study evaluated soil fertility under 16 agronomic treatments—integrating irrigation quality, fertilizer regimes, and soil amendments—across three rice growth stages (tillering, heading, and maturity) in the Yellow River Delta using the minimum data set (MDS), integrated soil fertility index (SFI), and random forest models. Saline water irrigation increased soil salinity by 24.6%, while straw returning and desulfurization gypsum reduced salinity by 18.3% and 22.7%, respectively. Straw, biochar, and desulfurization gypsum significantly influenced soil organic carbon (SOC), total nitrogen (TN), inorganic nitrogen (NH₄⁺-N, NO₃⁻-N), and available phosphorus (AP), with effects varying across growth stages. Growth-stage-specific MDS indicators were significantly correlated with SFI based on the total data set (R² = 0.70, 0.65, and 0.81, p < 0.01), and stage-specific SFI was significantly positively related to rice yield. Notably, heading-stage SFI, although relatively low, explained the highest yield variance (R² = 0.51, p < 0.01) and prediction accuracy (%IncMSE = 25.22), especially under conventional NPK combined with full straw incorporation and desulfurization gypsum. These findings highlight the critical role of heading-stage soil fertility in regulating rice production, providing a targeted nutrient management blueprint for saline–alkaline paddy fields in the Yellow River Delta. Overall, this study offers a reliable scientific template to enhance yield and promote sustainable agriculture in comparable saline–alkaline paddy fields globally. Full article

Groundwater is a critical lifeline for ecosystems and human settlements in arid and semi-arid regions, yet it is increasingly vulnerable to the dual pressures of extreme climatic conditions and intensifying anthropogenic activities. This study investigated 24 groundwater and 4 river water samples to discuss the hydrogeochemical evolution and water quality suitability in the Tianjun Basin, a typical high-altitude arid basin on the northeastern Tibetan Plateau. The results indicate that groundwater is mildly alkaline (pH: 7.65–8.35) and predominantly fresh (TDS: 233.77–1061.42 mg/L). Hydrochemical facies evolve from HCO₃-Ca type in upstream areas to Mixed HCO₃-Na·Ca and Cl-Na types. Hydrochemical analysis suggests that silicate weathering and carbonate dissolution are the dominant natural processes, while cation exchange further modifies the ionic composition. Notably, anthropogenic nitrogen (NO₃⁻ and NH₄⁺) contamination, primarily from domestic sewage in the Tianjun Basin, has significantly impacted groundwater quality. Health risk assessment shows that infants are the most vulnerable group, with 16.67% of samples posing a non-carcinogenic risk via the oral pathway. Regarding irrigation suitability, while sodium hazards are generally low, a significant salinity hazard is identified due to elevated electrical conductivity in the arid environment. This poses a substantial risk of secondary soil salinization, necessitating strict salt management strategies to preserve long-term land productivity. These findings provide critical insights for the sustainable management of fragile groundwater resources in extreme arid environments. Full article

Grasslands are key terrestrial ecosystems in which root dynamics regulate soil carbon and nutrient cycling. Although grazing constitutes the predominant land use practice in grassland ecosystems, its impacts on root dynamics remain inadequately elucidated, particularly across a gradient of grazing intensities. In this two-year field experiment, an improved root window method was applied to investigate the effects of four grazing intensities (no grazing, light grazing, moderate grazing, heavy grazing) on root production, root mortality, root standing crop, root turnover, and root lifespan in the saline–alkaline grassland in northern China. The results showed that root production and root mortality exhibited pronounced seasonal dynamics, with peaks in June and August for root production and in September for root mortality. These seasonal patterns were primarily driven by precipitation and were not significantly altered by grazing intensity. Moderate grazing significantly increased root production by 51.2% through changes in soil bulk density and selective livestock grazing, supporting the intermediate disturbance hypothesis. Root turnover was predominantly shaped by plant community composition and interannual precipitation, as opposed to grazing intensity. Overall, these findings indicate that moderate grazing promotes root growth, providing important insights into the sustainable utilization of saline–alkali grassland resources. In other words, appropriate measures must be taken to effectively manage grazing activities in the fragile saline–alkaline grasslands of northern China. Full article

The development of bioenergy crops on saline–alkaline land has been recognized as a potential pathway for both land restoration and combating global warming. However, the role of soil organic carbon (SOC) dynamics under such conditions remains insufficiently quantified in long-term assessments. In this study, an exploratory assessment was conducted to evaluate the long-term soil carbon sequestration (SCS) potential and life-cycle greenhouse gas (GHG) emissions of sustainable aviation fuel (SAF) produced from Arundo donax in the Bohai Rim region of China. The CENTURY model was integrated with Long Short-Term Memory (LSTM) time series forecasting to simulate SOC dynamics under future climate scenarios (2024–2035). Compared with the original CENTURY simulation, the LSTM model yielded a substantially more conservative estimate of SOC accumulation, with an Ensemble Mean SCS rate of 0.032 t C/ha/a and a 95% confidence interval ranging from −0.079 to 0.143 t C/ha/a. This result indicates a positive regional average tendency toward soil carbon sequestration, while also suggesting that some locations may behave as carbon sources under less favorable climatic conditions. The total SCS potential across the study area was estimated at 0.615 Tg C. When these soil carbon benefits were incorporated into the life-cycle assessment of Fischer–Tropsch (F-T) SAF, the pathway could become potentially net-negative under the adopted assumptions, reaching −32.1 g CO₂e/MJ, which corresponds to a potential reduction of 136.1% relative to fossil aviation fuel. These results should be interpreted as exploratory and scenario-based, given that large-scale cultivation of Arundo donax has not yet been established in the Bohai Rim region and the assessment therefore relies on assumptions. Beyond GHG mitigation, the cultivation of Arundo donax on degraded saline–alkaline soils may also have potential relevance to broader sustainability objectives, including SDG 13 (Climate Action) and SDG 15 (Life on Land). These findings highlight the possible synergies among energy crop cultivation, soil restoration, and climate neutrality goals, and provide preliminary insights for integrating marginal land utilization into sustainable land management and low-carbon aviation strategies. Full article

Saline–alkaline water constitutes a vital strategic non-traditional fishery resource in China, characterized by high pH values, elevated carbonate alkalinity, and complex ionic compositions. These extreme environmental conditions impose significant stress on aquatic animals, mainly by inducing ionic toxicity and disrupting acid–base regulatory mechanisms. Such disruptions subsequently lead to osmotic imbalance, metabolic dysregulation, and immunosuppression, thus restricting the survival and growth of aquatic species in aquaculture systems. Consequently, the sustainable development of the saline–alkaline aquaculture is imperative for enhancing production efficiency and promoting the utilization of marginal land and water resources. This review comprehensively summarizes the current status of saline–alkaline aquaculture and highlights the stress-inducing impacts of salinity, alkalinity, and specific ionic ratios on teleost fishes and crustaceans. It further explores key adaptive mechanisms, including osmoregulatory and ionoregulatory strategies, bioenergetic trade-offs related to oxygen consumption and ammonia excretion, coordinated antioxidant and innate immune responses, as well as recent findings from multi-omics research. This review aims to offer a scientific foundation for the selection and breeding of saline–alkaline-tolerant strains, the precise regulation of aquaculture water environments, and the development of ecological aquaculture models in saline–alkaline regions, thereby facilitating the sustainable utilization of saline–alkaline land and water resources. Full article