Search Results (5,124)

Soil erosion and nutrient loss degrade the soil resource base and water quality in dryland agricultural landscapes, yet optimal design of vegetation buffers for soil conservation under intensifying rainfall remains poorly quantified, particularly for nutrient retention. This study is novel in integrating event-scale rainfall-simulation experiments, Bayesian hierarchical modelling, Causal Forest analysis, and WEPP simulations to quantify how the sequential addition of biocrusts and grasses to shrub buffers shifts density thresholds for runoff, soil loss, and nutrient export across varying rainfall intensities. Experiments were conducted across a continuous shrub-density gradient (0–11,429 plants ha⁻¹) representing three configurations: shrub monoculture, shrub-biocrust, and shrub-biocrust-grass on agricultural hillslopes of the Chinese Loess Plateau. Runoff, soil loss, and exports of total nitrogen (TN) and total phosphorus (TP) were measured. Results demonstrate three main findings. First, multilayer shrub–biocrust–grass buffers exhibited lower soil loss than monocultures. Posterior estimates indicate reductions from approximately 3.8 t ha⁻¹ at moderate monoculture density to below 1.0 t ha⁻¹ at lower planting densities, with 94% of the highest-density intervals reflecting uncertainty in these estimates. Second, Causal Forest analysis reveals a functional separation of controls: rainfall intensity dominates soil loss (88% importance) and runoff (84%), whereas nutrient retention responds more strongly to buffer structure and density management. Third, WEPP simulations across rainfall intensities (50–180 mm h⁻¹) and slopes (10–30%) identify an optimal multilayer buffer density of 3800–5700 plants ha⁻¹, which delivers robust multifunctional benefits with 50–67% lower planting requirements than conventional high-density monocultures. These findings demonstrate that multilayer vegetation buffers enhance soil retention and reduce nitrogen and phosphorus losses from hillslopes, sustaining the soil resource base and protecting water quality in dryland agricultural landscapes. The integrated modelling framework provides transferable, evidence-based density recommendations for climate-resilient soil conservation in similar dryland regions. Full article

The Yangtze River, the largest river system in Asia, continues to receive substantial nitrogen loads despite the implementation of management measures. Within this vast and complex system, the spatial patterns and drivers of key nitrogen transformation processes, such as nitrification and denitrification, remain poorly constrained. In particular, systematic isotopic evidence from studies spanning the entire upstream–midstream–downstream continuum remains scarce. This study integrates multiple isotopes (δ¹⁵N-NO₃⁻, δ¹⁸O-NO₃⁻, δ¹⁵N-NH₄⁺) with hydrochemical techniques to elucidate the dominant controls on nitrogen transport and transformation and their spatial heterogeneity across the Yangtze River Basin. Results indicate that dissolved inorganic nitrogen (DIN) is the dominant form of nitrogen pollution in the basin. NO₃⁻ concentrations exhibited significant spatial variability, following the pattern downstream (2.86 mg/L) > upstream (1.83 mg/L) > midstream (1.75 mg/L). Isotopic signatures revealed that nitrification is the dominant process controlling the formation and transformation of NO₃⁻ throughout the basin. Most δ¹⁸O-NO₃⁻ values (−5.20‰ to +12.78‰) fell within or close to the theoretical range for nitrification, and a strong positive correlation was observed between δ¹⁵N-NO₃⁻ and δ¹⁵N-NH₄⁺ (R² = 0.72, p < 0.01), collectively confirming that the conversion of NH₄⁺ to NO₃⁻ is the primary pathway. Conversely, denitrification was significantly suppressed under the prevailing high dissolved oxygen conditions (mean 9.78 ± 2.46 mg/L), as further evidenced by the lack of a significant correlation between δ¹⁵N-NO₃⁻ and ln(NO₃⁻). Furthermore, preferential assimilation of NH₄⁺ by phytoplankton reduced the efficiency of nitrate removal via biological assimilation and influenced isotopic composition. These findings provide a scientific basis for identifying priority nitrogen sources and optimizing targeted nitrogen management strategies in the Yangtze River Basin. Full article

Improving crop yields while reducing environmental impacts remains a major challenge for smallholder agriculture, where heterogeneous management practices often limit the performance of technologies. This study developed a Select–Analyze–Design–Evaluate (SADE) framework to enhance the effectiveness of sustainable winter wheat technologies in smallholder farming systems. The framework was implemented in two villages on the North China Plain during a four-year field-based study (2017–2021), combining farmer follow-up surveys with field trials. During the Select stage, baseline data identified widely adopted technologies with substantial performance variability. Accordingly, delayed nitrogen application in Nanxia Village and precision seeding in Wangzhuang Village were selected as priority technologies for targeted diagnosis and improvement. During the Analyze stage, regression models identified key agronomic constraints: nutrient management in Nanxia, and sowing date and nitrogen management in Wangzhuang. Following this diagnosis, village-specific strategies were designed, implemented, and evaluated through multi-stakeholder collaboration. In Nanxia, yield, benefit–cost ratio, and nitrogen recovery efficiency increased by 7.9%, 21.5%, and 23.5%, respectively, while greenhouse gas emissions decreased by 21.5%. In Wangzhuang, the corresponding changes were 11.2%, 48.7%, 45.7%, and −22.9%, respectively. These findings demonstrate that SADE offers a practical pathway for sustainable smallholder agriculture. Full article

Although grazing is a key driver of nitrogen cycling in alpine meadow soils, a systematic understanding of how different grazing intensities shape the structure and functional potential of soil nitrogen-cycling microbial communities remains lacking. In this study, soil samples were collected under five grazing intensities (no grazing, light grazing, moderate grazing, heavy grazing, and extreme grazing) and metagenomic sequencing was employed to analyze variations in nitrogen-cycling microbial communities and functional genes. The results showed that bacteria were the dominant group in nitrogen-cycling communities (relative abundance: 93.99–98.98%), with significant community differentiation across grazing intensities. Light grazing maintained relatively high microbial diversity, whereas moderate and heavy grazing led to more pronounced differences in community composition. Functional gene analysis identified 41 nitrogen-cycling-related genes, primarily involved in denitrification, nitrate reduction, and ammonia assimilation. Light grazing enhanced nitrate reduction and glutamate synthesis; moderate grazing exhibited the strongest ammonia assimilation potential; heavy grazing significantly increased denitrification activity, indicating an elevated risk of nitrogen loss; and under extreme grazing, both the number and abundance of nitrogen-cycling functional genes declined markedly, with functional composition becoming simplified. Collectively, light grazing is more conducive to maintaining the balance between soil microbial diversity and nitrogen-cycling function in alpine meadows, whereas overgrazing disrupts the equilibrium between microbial communities and nitrogen metabolism. This study provides a microbiological basis for the restoration of degraded alpine meadows and sustainable grazing management. Full article

This study evaluates nitrogen (N) and phosphorus (P) pollution in the Ankara River Sub-basin, Türkiye, using the grey water footprint (GWF) approach. A Tier-1 GWF approach was applied, complemented by a sensitivity analysis to assess the influence of key parameters, including leaching–runoff fractions and water quality thresholds. The results should be interpreted as indicative rather than absolute values, as they depend on assumptions related to leaching fractions and background concentrations. By integrating data from agricultural diffuse sources and municipal wastewater treatment plants (WWTPs), the research identifies critical pollution hotspots and sectoral pressures on water resources, causing water quality degradation. The results reveal that P is the primary limiting pollutant governing GWF magnitudes across the sub-basin. The total GWF was estimated at 8294 million m³ yr⁻¹ in the sub-basin outlet. Approximately 10% and 31% of the basin-wide GWF were associated with fertilizer-based diffuse sources and WWTP1, respectively. The study demonstrates that regulatory compliance alone does not guarantee the protection of a river’s assimilative capacity. These results provide a basis for policy development, emphasizing the need to move beyond concentration-based regulations toward management frameworks that explicitly consider assimilative capacity and cumulative basin-scale impacts. Full article

The continuous monoculture in Populus × euramericana ‘Neva’ plantations is closely related to the accumulation of phenolic acids in the soil, and these phenolic compounds exert a certain influence on plant nitrogen uptake. Leguminous plants can replenish soil nitrogen through biological nitrogen fixation, which is of great significance for enhancing plant productivity. This study employed different concentrations of phenolic acid treatments (0T, 0.5T, 1.0T, 1.5T, 2.0T) to analyze the photosynthetic characteristics of five phenolic compounds in a poplar–soybean (Glycine max (L.) Merr.) intercropping system, thereby providing a basis for biological management strategies aimed at increasing the yield of poplar monoculture stands. The results indicate that (1) P_n in poplar monoculture, soybean monoculture, and soybean intercropping all decreased as phenolic acid concentration increased, whereas P_n in poplar intercropping increased with rising phenolic acid concentration. Under treatments ranging from 0T to 1.5T, the decrease in P_n in the pure poplar, pure soybean, and intercropped soybean systems was primarily due to stomatal limitations, whereas under treatments ranging from 1.5T to 2.0T, it was primarily due to non-stomatal limitations. (2) Poplar, soybean, and soybean-intercropped poplar adapted to environmental stress by dissipating excess light energy absorbed by PS II as heat. The intercropping system effectively optimized poplar fluorescence parameters and mitigated the damage caused by phenolic acid stress to its photosynthetic machinery. (3) Chlorophyll A, chlorophyll B, and total chlorophyll in poplar and soybean leaves were significantly inhibited. (4) The biomass of poplars grown in monoculture decreased as phenolic acid concentration increased, whereas the biomass of poplars in intercropping showed the opposite trend. It is evident that, under phenolic acid conditions, poplar–soybean intercropping can mitigate the effects of phenolic acid stress to a certain extent. Full article

Hyperspectral airborne data combined with machine learning has proven effective for characterizing plant nutritional quality. However, terrain, viewing geometry, and illumination can distort spectral signatures, leading to biased models with limited generalizability for large-scale mapping across farms with a heterogeneous landscape. In this study, we developed a framework for mapping pasture quality using airborne hyperspectral imaging while explicitly accounting for in-field acquisition and environmental effects. Nitrogen content (N%) and metabolizable energy (ME) were used as reference indicators across four hill country farms in New Zealand with contrasting environmental and management conditions. Ground truth was obtained using standard laboratory wet chemistry methods and paired with AisaFENIX airborne hyperspectral data, resulting in 1610 spectral samples derived from 161 spatially independent ground plots. Gaussian Process Regression (GPR) and a one-dimensional convolutional neural network (1D-CNN) were trained and evaluated on an independent test dataset. Both models achieved strong predictive performance (R² > 0.8); however, GPR provided more reliable estimates through predictive uncertainty. Using a 95% confidence interval threshold to mask uncertain predictions increased overall performance (R² > 0.9) and consequently improved the reliability of the mapped outputs. This approach enables spatially explicit pasture nutrient assessment to support precision land management for carbon and nitrogen. Full article

This study is the first to investigate volcanic ash (VA) as a soil amendment to mitigate nitrous oxide (N₂O) emissions, a potent greenhouse gas mainly produced through nitrification and denitrification processes in agricultural soils. The experiment assessed the effects of VA mixed with soil and combined with mineral (NH₄NO₃, N) or organic (poultry manure, O) fertilizer on N₂O emissions, soil mineral nitrogen (NO₃⁻ and NH₄⁺), trace metals (Zn, Cu, Mn), and crop yield in a 4-month pot experiment including treatments with and without VA. Results showed that VA reduced N₂O emissions by 55% in mineral fertilizer treatments and 71% in organic fertilizer treatments compared to soils without VA. This reduction was associated with significant changes in nitrogen availability. In mineral fertilizer treatments with VA, soil NO₃⁻ concentrations remained high, potentially limiting denitrifier activity, while in organic treatments VA appeared to inhibit nitrogen mineralization. Additionally, VA increased soil concentrations of Zn, Cu, and Mn, which were negatively correlated with N₂O emissions, suggesting an influence on microbial processes. Importantly, crop yields were not affected by VA application. Although promising, these preliminary findings highlight the need for further research to optimize application rates and evaluate long-term effects across soil types and management systems. Full article

Monoculture plantations often face challenges of soil degradation and declining ecosystem services. Intercropping is beneficial to improving soil quality; however, the long-term effects of intercropping woody plants with medicinal herbs on soil ecosystems remain unclear. This study aimed to investigate the temporal effects of different durations of poplar intercropping with Aralia elata on soil physicochemical properties, enzyme activities, and soil microbial community structure. Soil samples were collected from the 0–20 cm soil layer, with composite samples obtained by mixing four soil cores per plot. We determined soil physicochemical properties, including pH, total carbon (TC), total nitrogen (TN), and total phosphorus (TP); soil enzyme activities, including invertase, urease, phosphatase, and β-N-acetylglucosaminidase (NAG); and soil microbial community structure using high-throughput sequencing of the bacterial 16S rRNA gene and fungal ITS region. Intercropping significantly affected soil chemical properties and enzyme activities in poplar plantations. Compared with the monoculture control (Y), TN (p < 0.01) and TC (p < 0.01) contents increased significantly in the 3- and 7-year intercropping treatments. The activity of β-N-acetylglucosaminidase (NAG) was enhanced following poplar–Aralia elata intercropping. In addition, intercropping significantly changed the composition and structure of soil microbial communities. In summary, introducing Aralia elata into poplar plantations can effectively improve soil fertility and reshape soil microbial community structure. This positive effect is time-dependent and becomes more significant with a 7-year intercropping duration. Poplar–Aralia elata intercropping represents a feasible management strategy to enhance ecological sustainability and soil health in plantation ecosystems of Northeast China. Full article

Peanut (Arachis hypogaea L.) forms root nodules that host microbial communities influencing plant nutrition and stress tolerance, and herbicide use may act as an environmental filter altering the cultivable nodule microbiota. This study isolated and characterized bacteria from peanut nodules collected in fields with and without imazapic application in Jaboticabal, São Paulo, Brazil. Eight isolates were obtained, and one hemolytic strain was excluded after pathogenicity screening. Based on 16S rRNA gene sequencing and phylogenetic analysis, the isolates were identified as Bacillus aerophilus, Bacillus inaquosorum, Bacillus subtilis, Bradyrhizobium yuanmingense, Burkholderia lata, and Rhizobium tropici. Nodules from herbicide-treated plants yielded exclusively Bacillus spp., whereas those from non-treated plants showed greater taxonomic diversity. Molecular screening detected genes associated with biological nitrogen fixation (nifH) and nodulation (nodA, nodB, nodC, nodD), indicating potential functional capacity. In greenhouse assays, the isolates showed strain-dependent effects on early plant development, with pronounced responses in root growth and nodulation. Burkholderia lata and bacterial consortia enhanced root development and nodulation, with performance comparable to the commercial inoculant SEMIA 6144. Herbicide management shapes the cultivable nodule microbiota, and selected isolates show potential as bioinoculants for peanut production systems. Full article

Phosphogypsum (PG) stockpiles pose a persistent threat to regional water environments, yet their differential impacts on surface water and groundwater remain unclear. This study examined the pollution characteristics, sources, mechanisms, and model-predicted trends of PG-derived contaminants in both systems within a representative PG-affected region. Results showed that total phosphorus declined sharply from surface water to groundwater due to soil retention, whereas SO₄²⁻ and F⁻ remained comparable. Nitrogen species accumulated more in groundwater, indicating distinct transport and transformation processes. Arsenic was higher in surface water but rarely exceeded limits. In contrast, lead and manganese were significantly enriched in groundwater, exceeding standards by up to 27- and 11-fold, mainly due to reductive mobilization and subsurface geochemical processes. The Nemerow Index indicated heavy pollution in 35% of surface water and 43% of groundwater samples. Principal component analysis identified PG leachate as the dominant pollution source. Model predictions further suggested that increasing stockpile capacity would intensify contamination and pose long-term environmental risks. This study provided a scientific basis for understanding the distinct pollution mechanisms of PG stockpiles and offered guidance for targeted water environment management in PG-impacted areas. These findings have broader implications for regions globally facing similar challenges from industrial solid waste storage. Full article

Tree rings record environmental conditions and can serve as long-term biomonitors of urban pollution. This study evaluated the radial growth and chemical composition of Pinus greggii wood in three urban green areas of Mexico City: San Juan de Aragón Park (SJA), Sierra de Guadalupe State Park (GUAD), and Vivero Coyoacán National Park (COY). Tree ring chemical elements were analyzed at annual resolution for the period 2002 to 2022, and their relationships with atmospheric pollutant concentrations, including nitrogen oxides (NO_x), carbon monoxide (CO), ozone (O₃), and particulate matter (PM), of medium size or smaller than 10 µm, including the fractions PM_2.5 and PM₁₀, were assessed using a spatial scaling approach. Elemental concentrations were determined using X-ray fluorescence (XRF). Statistical analyses included analysis of variance (ANOVA), Theil–Sen trend estimation, and Pearson correlation with lag analysis (up to 3 years). The oldest trees were recorded in COY (52 years), while the youngest were recorded in GUAD (13 years). Distinct temporal patterns in elemental concentrations were detected among sites; for instance, peak concentrations of Fe (307 ppm), Cu (11 ppm), and Zn (51 ppm) occurred in GUAD in 2021, while Pb concentrations declined during 2019–2020 across all three sites. Significant correlations (p < 0.05) were identified between Cu, Fe, Zn, and Pb and the atmospheric pollutants (NO_x, PM_2.5, PM₁₀, O₃). Notably, O₃ showed significant positive correlations with Fe at SJA (up to r = 0.80) and GUAD (up to r = 0.46) with lags ranging from 0 to 3 years, suggesting delayed responses between atmospheric pollution and elemental deposition in tree rings. These findings highlight the sensitivity of P. greggii to urban atmospheric pollution and support its potential as a long-term biomonitoring tool, as well as its importance for informing policies aimed at improving air quality and promoting the sustainable management of urban green spaces. Full article

Acute kidney injury (AKI) is a frequent complication in critically ill patients and is associated with high morbidity, mortality, and an increased risk of progression to chronic kidney disease (CKD). In this context, nutritional management represents a key component of supportive therapy, as AKI is commonly characterized by hypercatabolism, negative nitrogen balance, and protein-energy wasting. Current nutritional strategies primarily focus on the quantity of protein intake required to compensate for catabolic losses, particularly in patients undergoing renal replacement therapy (RRT). However, growing evidence suggests that the quality and metabolic effects of dietary protein sources may also influence renal physiology and recovery. Plant-based proteins have recently gained attention as a potentially advantageous nutritional strategy in kidney disease. Compared with animal-derived proteins, plant-based proteins are associated with a lower dietary acid load, reduced production of gut-derived uremic toxins, and beneficial effects on the intestinal microbiota. In addition, their amino acid profile may modulate oxidative stress, inflammatory pathways, and renal hemodynamics. These characteristics may contribute to a more favorable metabolic environment in patients with AKI, potentially supporting renal recovery and reducing the risk of AKI-to-CKD transition. This review examines the pathophysiological mechanisms linking protein metabolism, renal injury, and nutritional support in AKI. Particular attention is given to the role of plant-based proteins, their amino acid composition, and their potential nephroprotective effects. Understanding the interaction between dietary protein sources, metabolic pathways, and the gut–kidney axis may help guide future nutritional strategies aimed at improving outcomes in critically ill patients with AKI. Full article

Improving the effluent quality of municipal wastewater treatment plants (WWTPs) is essential for sustainable water management and water quality protection in the Yellow River Basin. Many existing WWTPs in northern China were constructed under earlier discharge requirements and now face dual challenges of stricter effluent standards and poor low-temperature performance in winter. In this study, a municipal WWTP with a design capacity of 5 × 10⁴ m³/d in northern China was upgraded to improve winter treatment performance and support stable compliance with the discharge requirements of the Yellow River Basin. The original anaerobic + oxidation ditch process suffered from unstable effluent quality, excessive sludge loading, and insufficient pollutant removal under low-temperature conditions. A land-saving retrofit strategy was therefore proposed, involving oxidation ditch wall-height raising to extend the hydraulic retention time (HRT) and membrane bioreactor (MBR) integration to increase the mixed liquor suspended solids (MLSS) concentration. After the retrofit, the total HRT increased to 19.82 h, and the average MLSS concentration reached 7050 mg/L. The relative abundances of key nitrogen-removing bacteria, including Nitrospiraceae, Nitrosomonadaceae, and Rhodocyclaceae, increased markedly. Meanwhile, denitrification sludge loading and BOD₅ sludge loading decreased to 0.030 and 0.033 kg/(kg·d), respectively. Under low-temperature conditions, the theoretical removal capacities of total nitrogen (TN) and BOD₅ reached 44.32 and 286.19 mg/L, respectively, enabling stable effluent compliance. The results show that this retrofit strategy can improve WWTP effluent quality while avoiding large-scale land expansion, providing a practical and sustainable solution for upgrading cold-region WWTPs along the Yellow River Basin. Full article

Understanding the spatial distribution patterns and environmental drivers of plant communities is fundamental for biodiversity conservation and ecosystem management. Bombax ceiba is a widely distributed tree species that occurs in both humid tropical rainforests and drought-prone dry-hot valleys, representing two strongly contrasting ecological environments. However, the spatial patterns and environmental drivers of plant communities associated with B. ceiba across these habitats remain poorly understood. In this study, we investigated B. ceiba-associated plant communities in two representative habitats in Yunnan Province, Southwest China: a tropical rainforest in Mengla and a dry-hot valley in Yuanjiang. The species composition, community structure, and spatial coordinates of associated plants were recorded in replicated 20 m × 20 m plots. Spatial distribution patterns were analyzed using the pair-correlation function g(r), while environmental drivers were examined using Pearson correlation analysis and redundancy analysis (RDA). Species richness was substantially higher in the tropical rainforest (41 species from 33 families) than in the dry-hot valley (19 species from 14 families). Both communities contained a substantial proportion of tropical Asian floristic elements. Most dominant species exhibited aggregated spatial distributions at small spatial scales (0–7 m), indicating strong dispersal limitation and microhabitat heterogeneity. Spatial associations varied across scales: in the dry-hot valley, species associations alternated between positive and negative correlations at small scales (0–5 m) and shifted toward positive correlations at larger distances, whereas in the tropical rainforest negative associations were more common at small scales and positive associations increased at larger spatial scales. Environmental drivers differed markedly between habitats. In the dry-hot valley, community attributes were positively associated with slope, precipitation, and soil ammonium nitrogen, suggesting that community assembly is influenced by interactions between topography and water availability. In contrast, tropical rainforest communities were more strongly associated with soil phosphorus availability and temperature-related variables. These findings highlight distinct community assembly mechanisms in contrasting habitats and provide ecological insights for vegetation restoration in dry-hot valleys and biodiversity conservation in tropical rainforests. Full article