Search Results (1,066)

Mangrove ecosystems play a critical role in sequestering heavy metals pollutants, yet the dynamics of heavy metals accumulation during mixed litter decomposition remain poorly understood. This study investigated the seasonal and species-specific variations in heavy metals accumulation during the decomposition of Kandelia obovata (KO) and Avicennia marina (AM) leaf litter mixtures in a subtropical mangrove forest in the Jiulong River Estuary, Fujian, China. Using the litterbag technique, we monitored eight heavy metals (V, Cr, Ni, Cu, Zn, As, Se, Cd) across three mixing ratios (KO:AM = 1:2, 1:1, 2:1) in summer and winter. Results revealed that V concentrations were influenced by both season and litter ratio, with higher KO proportions enhancing V accumulation in summer but reducing it in winter. In contrast, Cr, Ni, Cu, As, Se, and Cd were primarily regulated by litter ratios: KO-dominated mixtures promoted Cr and Ni accumulation, while AM-dominated mixtures favored Cu, As, Se, and Cd. Zn exhibited the highest variability and was unaffected by season or ratio. Total organic carbon (TOC) and carbon/metal (C/M) ratios significantly correlated with reduced bioavailability of most heavy metals, whereas total nitrogen (TN) and C/N ratios showed no consistent relationship. The heavy metals accumulation index (MAI) indicated higher accumulation in summer than in winter, with the highest MAI observed in the KO:AM = 2:1 treatment group during summer (MAI = 1.36), whereas winter decomposition slowed accumulation rates. These findings highlight the dual regulatory roles of species composition and environmental factors in mangrove heavy metals cycling, offering critical insights for ecological risk assessment and contaminated soil remediation strategies in coastal ecosystems. Full article

Monitoring the soil–plant system in forest ecosystems is crucial for preserving their ecological functions and services. This study assessed carbon and nitrogen stable isotopes and ecoenzymatic stoichiometry as suitable indicators for characterizing the soil–plant system as a functional unit of ecological processes. To this end, in June 2021 six plots (1 m² each) were selected in two typical Mediterranean forest ecotypes: a coastal stone pine forest (Pinus pinea L., PF) and a meso-hygrophilous broadleaf forest (RV). Soil samples (0–15 and 15–30 cm depth) and litter samples (40 × 40 cm) were collected and characterized in terms of physical, chemical and biochemical properties. t-tests revealed significant differences between RV and PF, indicating distinct microbial nutrient acquisition strategies. The higher C:N ratio in PF suggested lower litter quality and greater recalcitrance to microbial decomposition. Consistently, RV showed a more pronounced ¹³C and ¹⁵N enrichment from litter to SOM down to a 30 cm depth, confirming faster organic matter decomposition and mineralization. Enzyme activity patterns supported these findings. The higher β-glucosidase and butyrate esterase activities in RV reflected its greater microbial potential to activate biogeochemical cycles. Both forests exhibited a higher microbial demand for C and P than for N to maintain ecological stoichiometric balance, with stronger C limitation at the surface and P limitation in the subsoil, particularly in RV soil. This integrated monitoring approach provides insights into nutrient cycling and ecosystem resilience and offers tools to evaluate ecosystem functionality under changing environmental conditions, supporting sustainable forest management. Full article

Precipitation pulses refer to discrete and intermittent precipitation events that significantly influence ecosystem carbon and nitrogen cycling processes. However, the mechanisms by which different vegetation types modulate the sensitivity of carbon dioxide (CO₂) and nitrous oxide (N₂O) fluxes to short-term rainfall pulses remain poorly elucidated. To address this knowledge gap, we conducted a controlled rainfall simulation experiment across four representative surface types (moss-dominated biological soil crusts, Artemisia-ordosica-dominated soil, Caragana-korshinskii-dominated soil, and bare sandy soil), applying two precipitation pulses (5 mm and 10 mm) to quantify soil CO₂ and N₂O flux responses. The results showed that: (1) CO₂ emissions increased significantly with precipitation intensity, with the 10 mm treatment producing higher mean fluxes than the 5 mm treatment. Emission peaks (1200–1600 mg m⁻² h⁻¹) occurred within 24 h after rainfall and returned to baseline levels within three days; (2) Surface cover exerted a strong regulatory effect on CO₂ emissions, with moss crust soils (~400 mg m⁻² h⁻¹) and A. ordosica soils (~350 mg m⁻² h⁻¹) exhibiting CO₂ fluxes 2.5–3 times higher than those of bare sandy soils (~120 mg m⁻² h⁻¹); (3) Structural equation modeling indicated that precipitation indirectly enhanced CO₂ emissions by increasing soil carbon availability, with total organic carbon emerging as the strongest direct driver. Together, these findings clarify the primary controls on precipitation-induced CO₂ emissions in restored desert systems and highlight the decoupled and weak short-term response of N₂O, providing critical insights for managing carbon–nitrogen processes under increasing precipitation variability. Full article

As a critical aquatic–terrestrial ecological transition zone, the lake littoral zone exhibits steep biogeochemical gradients and plays a vital role in regulating submerged microbial communities and their functions. This study aims to reveal how multi-scale environmental gradients influence microbial succession processes along desert lake littoral zones, as well as the distribution patterns of functional genes involved in carbon (C), nitrogen (N), and sulfur (S) cycling. The results demonstrated that microbial alpha-diversity in the vadose zone exhibited significant individual variability horizontally, while showing pronounced inter-group differences vertically. Horizontally, a distinct functional succession was observed from the shore to the water’s edge, with microbial potential shifting progressively from aerobic oxidative types toward anaerobic reductive types. Vertically, the root-intensive layer fostered more complex co-occurrence networks through enhanced interspecific interactions, suggesting higher functional resilience compared to other layers. Further analysis identified soil moisture as the primary environmental filter driving microbial composition, explaining 27.7% of the variation. Structural equation modeling (SEM) further elucidated that pH and Total Organic Carbon (TOC) were the key regulators of carbon fixation and sulfur oxidation genes, while Total Nitrogen (TN) dominated the distribution patterns of nitrogen cycling genes. These findings deepen the mechanistic understanding of microbial-mediated element cycling in desert lakeshore zones and provide a theoretical basis and data support for maintaining the functions of these fragile ecosystems. Full article

The field experiment was carried out in the fields of the Experimental Variety Testing Station in Chrząstów, belonging to the Central Research Centre for Cultivated Plants in Słupia Wielka. The aim of the present study was to determine the effect of residual nitrogen (N_res) remaining in the soil after cultivation of three varieties of common maize fertilized with different types of nitrogen fertilizers on nitrogen-use-efficiency indicators in subsequent crops of winter and spring common wheat. Nitrogen accumulation in both wheat cultivation systems showed a significant response to the interaction between maize varieties and the type of nitrogen fertilizer applied. Urea proved to be the most consistent source of nitrogen in the grain, regardless of the maize variety used as the preceding crop or the form of nitrogen applied. Variability in nitrogen accumulation under the U + N-Lock, Super N-46, and SG Stabilo treatments was primarily associated with a marked decrease in the SC maize variety. The SC + Roots Power maize variety left the soil in a condition highly favourable for nitrogen accumulation in wheat grain across two consecutive growing seasons. Maize variety was the primary factor influencing the proportion of fertilizer-derived nitrogen in the total nitrogen accumulated in the grain. The highest recovery of fertilizer nitrogen over the two-year production cycle was obtained in the SC + Roots Power treatment fertilized with SG Stabilo. Notably, urea demonstrated the strongest residual effect on nitrogen availability to winter wheat. Full article

This study investigated the effects of bio-organic fertilizer (BF) containing plant growth-promoting bacterium Bacillus velezensis SS-20 on soil properties, microbial community structure, and C/N cycle functional genes. The results showed that compared with chemical fertilizer (CF) and deactivated bio-organic fertilizer (BFD) treatments, BF significantly improved soil physicochemical properties. Soil pH, organic matter, total nitrogen, total potassium, and total phosphorus content under BF treatment were increased by 14.8%, 56.5%, 48.2%, 38.8%, and 58.4%, respectively, compared to the control; soil urease and sucrase activities increased by 3.5 and 2.4 times those of CF treatment, respectively. Meanwhile, BF increased pakchoi yield by 11.2% (vs. CF). BF treatment enhanced the relative abundance of beneficial bacteria Actinomycetota by 28.4% compared with the BFD treatment and raised that of fungi Ascomycota to 1.9 times that of the control. At the genus level, BF significantly enriched biocontrol-relevant genus Pseudogymnoascus, whose abundance reached three times that of CF treatment, while the abundance of potentially harmful genus Penicillium decreased by 82%. BF also led to a high degree of synergy in carbon and nitrogen cycles. Functional gene analysis indicated that BF down-regulated multiple carbon-degrading genes, increased organic nitrogen metabolism genes by 5.3%, and reduced denitrification genes by 13.3%. Overall, bio-organic fertilizer optimized the soil microenvironment, regulated the microbial community structure, and improved C/N use efficiency and plant growth by introducing functional microorganisms and organic matter. Full article

Aeroponics has emerged as a key technology for sustainable and resource-efficient food production, particularly under intensifying constraints on water availability, land use, and greenhouse gas (GHG) emissions. This review synthesizes recent advances in water–energy–nutrient integration, highlighting operational parameters—humidity (50–80%), temperature (18–25 °C), nutrient solution pH (5.5–6.5), and electrical conductivity (1.5–2.5 mS cm⁻¹)—that critically influence system performance. Evidence indicates that closed-loop water recirculation and AI-assisted monitoring for environmental control and nutrient dosing can stabilize system dynamics and reduce water consumption by more than 90%. Reported yield improvements ranged from 45% to 75% compared with conventional soil-based cultivation. Moreover, systems powered by renewable energy demonstrated up to an 80% reduction in GHG emissions. Life-cycle assessment studies further suggest that aeroponics, coupled with low-carbon electricity in controlled-environment agriculture (CEA), can outperform traditional agricultural supply chains in climate and resource efficiency metrics. Additional technological innovations—including multi-tier vertical rack architectures, optimized misting intervals, and micronutrient-enriched fertigation formulations containing N, P, Ca, Mg, and K—were found to enhance spatial productivity and crop quality. Overall, aeroponics represents a promising pathway toward net-zero, high-performance agricultural systems. Full article

Artificial cyanobacterial crusts (ACCs) are a potentially effective biological strategy for combating desertification. However, while functional microorganisms influence ACCs formation efficiency, research on their role is limited, and their underlying promotion mechanisms remain unclear. Here, we investigated the effects of three functional synthetic microbial communities (SynComs), each dominated by microorganisms specialized in exopolysaccharide (EPS) production (3 strains), siderophore production (3 strains), or nitrogen fixation (4 strains), on ACCs formation following inoculation with Microcoleus vaginatus. This study was carried out in a controlled laboratory setting with a 12 h light/dark cycle and a light intensity of 2400–2700 lux. Following a 24-day cultivation period, EPS-producing or nitrogen-fixing SynComs significantly increased the chlorophyll-a content by 16.0–16.3%. Except for the nitrogen-fixing bacteria treatment, other SynComs enhanced the soil organic matter content of ACCs by 9.1% to 27.3%. The content of EPS was significantly improved by all three SynComs by 14.1~19.2%. Urease activity rose by 6.7% when siderophore-producing bacteria were added. The impacts of SynComs on ammonium nitrogen (NH₄⁺-N) showed different temporal dynamics: nitrogen-fixing SynComs significantly increased NH₄⁺-N early (≤10 days), while EPS-producing and siderophore-producing SynComs enhanced accumulation later (17–24 days). SynComs inoculation markedly accelerated cyanobacterial and general microbial colonization and growth. In comparison to day 0, the 16S rRNA gene copy number of ACCs increased by 24.1% and 43.0%, respectively, in the EPS-producing and nitrogen-fixing SynComs. Additionally, correlation analysis showed that SynComs transformed the weak correlations in the control into a strong positive correlation between NH₄⁺-N and both Chl-a and microbial biomass. Our findings demonstrate SynComs, particularly the EPS-producing or nitrogen-fixing SynComs, enhance ACCs formation through elucidated mechanisms, providing a theoretical basis for optimizing ACCs-based desertification control strategies. Full article

Biological N₂ fixation (BNF) and ratoon rice growth are biological processes that mediate N and C cycling in rice paddy ecosystems, but their contributions to paddy soil fertility have rarely been evaluated in a quantitative and unified manner. In this study, we analyzed the contribution of BNF and ratoon rice growth to soil N fertility at six rice paddy sites in four prefectures of Japan, combining 2-year field monitoring and simulation using the DNDC-Rice biogeochemistry model. Across the sites and years, ratoon rice was found to accumulate up to 30 kg N ha⁻¹ without fertilization and irrigation after main rice harvest. BNF was not measured but estimated to be 33–63 kg N ha⁻¹ yr⁻¹ at the six sites, by applying a newly built BNF model after calibration against a literature dataset. Based on the simulations using DNDC-Rice under typical local management strategies, we estimated the following contributions of BNF and ratoon rice to soil N fertility, with variations based on the climate, soil properties, and management, as follows: (a) BNF and ratoon rice contributed 4–33% and 3–23% of the N supply from soil during the main rice season, respectively. (b) While BNF contributed 3–29% of the main rice N uptake, that from ratoon rice was much lower (6% or less), presumably because the decomposition of ratoon rice residue induced N immobilization during the main rice season. (c) Although the major part of N gain by BNF was being lost via denitrification and N leaching, BNF was contributing up to 6.6% of the organic N pool at the 0–30 cm soil layer. Ratoon rice was working to save N loss by reducing N leaching, consequently contributing up to 3.3% of the soil N pool. These findings provide quantitative insights into what roles BNF and ratoon rice play in paddy soil fertility. Full article

Rice–crab co-culture systems (RC) represent promising sustainable intensification approaches, yet their nitrogen (N) cycling and optimal fertilization strategies remain poorly characterized. In this study, we compared RC with rice monoculture system (RM) across four N gradients (0, 150, 210, and 270 kg N·hm⁻²), assessing N dynamics in field water and N distribution in soil. The results showed that field water ammonium nitrogen (NH₄⁺-N) concentrations increased nonlinearly, showing sharp increases beyond 210 kg N·hm⁻². Notably, crab activity in the RC altered the N transformation and transport processes, leading to a prolonged presence of nitrate nitrogen (NO₃⁻-N) in field water for two additional days after tillering fertilization compared to RM. This indicates a critical window for potential nitrogen loss risk, rather than enhanced retention, 15 days after basal fertilizer application. Compared to RM, RC exhibited enhanced nitrogen retention capacity, with NO₃⁻-N concentrations remaining elevated for an additional two days following tillering fertilization, suggesting a potential critical period for nitrogen loss risk. Post-harvest soil analysis revealed contrasting nitrogen distribution patterns: RC showed enhanced NH₄⁺-N accumulation in surface layers (0–2 cm) with minimal vertical NO₃⁻-N redistribution, while RM exhibited progressive NO₃⁻-N increases in subsurface layers (2–10 cm) with increasing fertilizer rates. The 210 kg N·hm⁻² rate proved optimal for the RC, producing a rice yield 12.08% higher than that of RM and sustaining high crab yields, while avoiding the excessive aqueous N levels seen at higher rates. It is important to note that these findings are based on a single-site, single-growing season field experiment conducted in Panjin, Liaoning Province, and thus the general applicability of the optimal nitrogen rate may require further validation across diverse environments. We conclude that a fertilization rate of 210 kg N·hm⁻² is the optimal strategy for RC, effectively balancing productivity and environmental sustainability. This finding provides a clear, quantitative guideline for precise N management in integrated aquaculture systems. Full article

Vehicle repeated passes over soft terrain alter the soil’s bearing and shear behavior, thereby affecting vehicle mobility and energy consumption. To address this issue, this study conducted cyclic compression and shear tests on beach sand with moisture contents of 5%, 15%, and 25%. A constitutive model incorporating the coupling effects of loading cycles (N) and moisture content (ω) was developed based on the Bekker and Janosi model framework. The model expresses compression parameters as functions of N and ω, and describes shear behavior through the strength evolution function k(N,ω) and deformation modulus function h(N,ω). Results show excellent agreement between the model predictions and experimental data (R² > 0.92). Furthermore, a vehicle–soil coupled dynamics model was established based on the proposed constitutive model, forming a comprehensive analytical framework that integrates soil meso-mechanics with full vehicle–terrain interaction. This work provides valuable theoretical and technical support for predicting vehicle trafficability on coastal soft soils and optimizing vehicle suspension systems. Full article

Waste valorisation has become a key strategy for applying circular economy principles in the agro-industrial field. This study investigated the territorial implementation of the waste composting on a territorial scale. The wastes considered were the post-processing orange waste, spent olive oil pomace, and spent wine grape pomace. Their potential use as soil amendments across the provinces of Sicily was assessed through a GIS-based analysis, taking into account nitrogen (N) application constraints. Moreover, a cascade valorisation scheme was also evaluated: post-processing orange waste was first used as animal feed, and the remaining fraction was directed to composting; olive pomace was first sent to pomace oil extraction mills, and the residual material was subsequently used for composting. Results indicate that N inputs derived from composted residues remain below legal thresholds in all provinces, with relative contributions ranging from 38% to 92% of the regulatory limits. Spatial variability in nitrogen availability reflects the territorial distribution of agro-industrial activities, highlighting the importance of localised management strategies. These findings demonstrate that composting, combined with cascade valorisation, is an effective pathway to close nutrient cycles, reduce waste generation, and support sustainable biomass management in regional agri-food systems. Full article

Atmospheric nitrogen deposition is increasing worldwide, with profound implications for plant nitrogen acquisition and ecosystem nutrient cycling, particularly in nitrogen-limited systems. In this study, we investigated how inorganic nitrogen form regulates nitrogen uptake in H. altissima through pot experiments by applying ammonium nitrogen, nitrate nitrogen, mixed nitrogen, and a nitrogen-free control in Songnen grassland ecosystems at the eastern end of Eurasia. Soil abiotic properties, root morphological traits, and nitrogen uptake dynamics were jointly quantified using integrative modeling in combination with ¹⁵N stable isotope tracing. Relative to the no-nitrogen control, both ammonium and nitrate nitrogen significantly altered soil physicochemical conditions and stimulated root development, with ammonium consistently exhibiting stronger effects. Ammonium and nitrate applications reduced soil pH by 4.83% and 6.25%, increased electrical conductivity by 2.01% and 1.17%, and enhanced inorganic nitrogen pools by 115.84% and 45.69%, respectively. Root morphological traits were significantly enhanced under ammonium, nitrate, and mixed nitrogen treatments. ¹⁵N tracing further demonstrated that ammonium nitrogen significantly increased root ¹⁵N uptake compared with the no-nitrogen control (p < 0.05) and promoted a 20.10% greater allocation of absorbed nitrogen to aboveground biomass than nitrate nitrogen. Collectively, these findings highlight nitrogen form as a key regulator of soil–plant nitrogen coupling, with ammonium nitrogen more effectively enhancing nitrogen acquisition and internal translocation than nitrate. Full article

To investigate the variation in shear strength of expansive soil under dry–wet cycles, laboratory direct shear tests were conducted on remolded soil from a foundation pit in the Chengdu area. The tests were performed under controlled drying and wetting paths, with systematic variations in water content (w), number of dry–wet cycles (N), and dry density (ρ). The characteristics and evolution of shear strength under these conditions were analyzed. Using a nonlinear multiple surface fitting method, empirical relationships were established between the soil’s shear strength parameters (cohesion c and internal friction angle φ) and the variables w and N. Furthermore, equations describing the attenuation of these parameters with respect to ρ and N were derived. Based on the experimental data and within the framework of the Mohr–Coulomb strength theory, a practical predictive model was developed for the shear strength of expansive soil under the coupled effects of dry–wet cycles, water content, and dry density. Verification results demonstrate that the model predictions are in good agreement with experimental measurements. The proposed model provides a practical reference for estimating the shear strength of similar expansive soils in the Chengdu area under cyclic drying and wetting conditions. Full article

Nitrogen (N) deposition poses a multi-pronged threat to the carbon (C)-regulating services of moss understories. For forest C-cycle modeling under increasing N deposition, failure to mechanistically incorporate the moss-mediated processes risks severely overestimating the C sink potential of global forests. To explore whether and how N input affects the moss-mediated CH₄ and carbon dioxide (CO₂) fluxes, a five-year field measurement was performed in the N manipulation experimental plots treated with 22.5 and 45 kg N ha⁻¹ yr⁻¹ as ammonium chloride for nine years under a well-drained temperate forest in northeastern China. In the presence of mosses, the average annual CH₄ uptake and CO₂ emission in all N-treated plots ranged from 0.96 to 1.48 kg C-CH₄ ha⁻¹ yr⁻¹ and from 4.04 to 4.41 Mg C-CO₂ ha⁻¹ yr⁻¹, respectively, with a minimum in the high-N-treated plots, which were smaller than those in the control (1.29–1.83 kg C-CH₄ ha⁻¹ yr⁻¹ and 4.82–6.51 Mg C-CO₂ ha⁻¹ yr⁻¹). However, no significant differences in annual cumulative CO₂ and CH₄ fluxes across all treatments occurred without moss cover. Based on the differences in C fluxes with and without mosses, the average annual moss-mediated CH₄ uptake and CO₂ emission in the control were 0.77 kg C-CH₄ ha⁻¹ yr⁻¹ and 2.40 Mg C-CO₂ ha⁻¹ yr⁻¹, respectively, which were larger than those in the two N treatments. The N effects on annual moss-mediated C fluxes varied with annual meteorological conditions. Soil pH, available N and C contents, and microbial activity inferred from δ¹³C shifts in respired CO₂ were identified as the main driving factors controlling the moss-mediated CH₄ and CO₂ fluxes. The results highlighted that this inhibitory effect of increasing N deposition on moss-mediated C fluxes in the context of climate change should be reasonably taken into account in model studies to accurately predict C fluxes under well-drained forest ecosystems. Full article