Search Results (3,525)

The impact of arbuscular mycorrhiza fungi (AMF) on root–shoot scaling strategies under zinc and phosphorus deficiency remains poorly understood in maize. The aims of this study were (i) To quantify the effects of zinc/phosphorus deficiency on AMF colonization, (ii) to quantify biomass accumulation in different plant parts in the presence of AMF, and (iii) to characterize how AMF alter root–shoot allometric scaling under zinc/phosphorus deficiency. We conducted a pot experiment arranged in RCBD split plot with 6 replications. SUWAN 5819 maize seeds were grown for 22 days under five Hoagland’s solution-based nutrient regimes (+Zn+P, −Zn−P, +Zn−P, −Zn+P, and deionized water), with and without AMF. AMF colonization was highest (49.6%) under −Zn+P contrary to hypothesis 1 which predicted highest colonization under dual deficiency, while the deionized water treatment had the lowest colonization (30.1%). Phosphorus was the dominant factor affecting biomass accumulation with a 2–4-fold reduction in organ dry weights for phosphorus-deficient treatments compared to phosphorus-sufficient treatments. AMF colonization significantly reduced dry weights in +Zn+P by 8.6%, 19.0%, and 47.5% in the leaf, stem, and roots, respectively, consistent with mycorrhiza-induced growth depression (MGD). Nutrient deficiency resulted in root biomass accumulation, consistent with the optimal partitioning theory. AMF increased shoot mass fraction from 50% to 63% in +Zn+P, and from 41% to 52.5% in −Zn−P, suggesting AMF role in modulating biomass accumulation. Root–shoot scaling slopes derived from LMM revealed that zinc deficiency caused negative scaling trajectory, and AMF was associated with positive root–shoot scaling trajectory in the −Zn+P treatment, though the scaling relationship was not confirmed by SMA analysis. These findings highlight nutrient specific AMF-mediated growth dynamics in early vegetative stage. Full article

Alpine grasslands and alpine deserts represent two major ecosystems on the Tibetan Plateau. However, whether the two ecosystems differ in soil microbial community diversity and co-occurrence network structure remains poorly understood. This study assessed the composition and diversity of soil bacterial communities across alpine grasslands and alpine deserts on the Tibetan Plateau via 16S high-throughput sequencing, analysis of variance(ANOVA), mantel test, and other methods. Our results revealed that soil alkaline-hydrolyzable nitrogen (SAN), soil total nitrogen (STN), soil total phosphorus (STP), soil available phosphorus (SAP), and soil organic carbon (SOC) were significantly higher in grassland than in desert (p < 0.05). The microbial community composition and diversity differed significantly between alpine grasslands and alpine deserts. Analysis of microbial co-occurrence networks revealed that grassland systems possessed significantly more nodes, edges, and a higher average degree than desert systems, along with greater network robustness—indicating a more complex and stable microbial community structure. Correlation analysis further revealed that SOC and STN were positively correlated with microbial diversity, while electrical conductivity (EC), SOC, STN, and SAN showed positive associations with microbial community composition. In conclusion, alpine grasslands harbor greater soil microbial diversity and more stable microbial co-occurrence networks than alpine deserts, suggesting that alpine grasslands may hold greater ecological value than alpine deserts in maintaining soil biodiversity and ecosystem functioning. This study not only elucidates the distribution patterns and diversity of soil microbial communities across Tibetan grasslands, but also offers critical insights into the mechanisms governing ecosystem functioning, thereby informing ecological conservation and sustainable management strategies on the plateau. Full article

The development of sustainable and efficient plant growth substrates is crucial for modern agriculture. This study assessed the potential of plant pellets formulated from various lignocellulosic residues, either with or without bamboo biochar (BB-char) and arbuscular mycorrhizal fungi (AMF), to support seed germination and early seedling growth. Four types of residues, including coconut coir (CO), corn cob (CC), leaves from the genus Dipterocarpus (DL), and teak leaves (TL), were combined with soil and paper waste to produce eight pellet formulations, with commercial peat pellets serving as a control. Chemical analyses revealed significant variation among the pellet types, with pH values ranging from 6.40 to 7.65, electrical conductivity (EC) from 3.64 to 11.62 mS cm⁻¹, and differences in organic matter, carbon, and nutrient contents [nitrogen (N), phosphorus (P), potassium (K)], reflecting the influence of residue type and the addition of BB-char and AMF. Phytotoxicity screening using aqueous extracts demonstrated species-specific responses, with cucumber exhibiting high tolerance across treatments, whereas chili seeds were more sensitive. Final germination percentage (FGP) and seedling growth assays in greenhouse conditions showed that pellets derived from CC and CO, particularly when combined with BB-char and AMF (T6 and T7), enhanced shoot and root development in carrot, chili, cucumber, and tomato, approaching the performance of commercial peat pellets. In contrast, DL- and TL-based pellets resulted in lower germination and growth. These findings indicate that both the physicochemical properties of lignocellulosic wastes and the combination of BB-char and AMF are important factors influencing pellet efficacy, highlighting the potential of CC- and CO-based pellets as sustainable peat alternatives for early-stage plant cultivation. Full article

Rivers have always been essential to humankind. They are used for many purposes and, as a result, have been heavily modified. Human impacts, many of them still poorly understood, interfere with river ecosystems, making them vulnerable to disturbances. Amongst these, mega events along riverbanks are listed. We studied the effects of the “FM4 Frequency Festival,” which attracted more than 200,000 visitors, on microalgae in the channelized section of the River Traisen in St. Pölten, the capital of Lower Austria. During the festival, phosphorus, dissolved organic carbon, and chloride increased significantly during the whole study period compared with before and after. Although the overall epilithic biomass remained unchanged during the festival period, the phytobenthos community experienced an increase in taxonomic richness downstream of the festival area. Both the Shannon diversity (mean ± SD = 2.89 ± 0.34) and Pielou’s evenness (mean ± SD = 0.73 ± 0.08) did not differ significantly between the sampling dates before, during, and after the festival. We found a shift towards Achnanthidium minutissimum as the dominant species during the festival. Diatoma ehrenbergii, which is sensitive to nutrient enrichment and organic pollution, disappeared during the event. Overall, the biofilm shifted towards a community dominated by heterotrophs during the festival, likely due to high organic loading. Pelagic microalgae experienced a rise in the total taxa number during the festival, which was partly caused by resuspension of phytobenthos. Our results reflect significant impacts from visitors to the Traisen ecosystem. Not only short-term changes in the hydrochemical environment but also mechanical disturbances of the phytobenthos caused by visitors were demonstrated. We suggest continuous monitoring to verify that such events will not have long-term impacts on the system. Full article

Forest stand composition can regulate soil nutrient cycling by altering aggregate formation, nutrient partitioning and microbial extracellular enzyme activity. Here, we examined pure Pinus tabuliformis forest (YS), pure Quercus acutissima forest (ML) and mixed coniferous–broadleaved forest (HJ) in the Ziwuling forest region of the Chinese Loess Plateau. Soil aggregate composition, soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP) and extracellular enzyme activities were quantified across different aggregate-size fractions in the 0–100 cm soil profile. Except for the >5 mm aggregate fraction, the proportions of all other aggregate-size classes followed the order ML > HJ > YS, with ML and HJ showing increases of 19.94%–66.98% and 8.76%–35.01%, respectively, relative to YS. Mixed forest significantly promoted SOC content, with SOC contents 46.9% and 76.1% higher than those in YS and ML, respectively. In contrast, TN content was highest in YS and was 20.3% higher than that in HJ, whereas TP showed only small differences among forest types. SOC and TN were mainly enriched in smaller aggregate fractions, accounting for 49.7%–79.1% and 44.7%–81.3% of their total stocks, respectively, while TP was preferentially associated with larger aggregates, accounting for 54.9%–82.1%. Compared with YS, HJ increased EG, LAP, NAG and ACP activities by 42.2%, 14.9%, 18.0% and 42.5%, respectively. Compared with ML, HJ also showed generally higher extracellular enzyme activities, indicating that mixed forest favored the enhancement of most enzyme-mediated nutrient acquisition processes. Overall, forest stand type regulated extracellular enzyme activity by reshaping soil aggregate composition and aggregate-associated nutrient distribution. These findings help improve our understanding of aggregate-associated nutrient cycling processes in restored forest soils on the Loess Plateau and may provide a reference for future comparative studies on restoration effects among different forest types. Full article

Nitrogen (N), phosphorus (P), and potassium (K) are essential elements for plants and are also the main limiting elements in the growth process. In order to investigate the effects of fertilization on the nutrient content and stoichiometric ratio of Pinus yunnanensis seedlings, we implemented a complete 3 × 3 factorial design incorporating three nitrogen levels (0, 0.4, and 0.8 g·plant-1) and three phosphorus levels (0, 3, and 6 g·plant-1), yielding nine distinct treatment combinations. The contents of N, P, and K in different organs of P. yunnanensis were determined, and their stoichiometric ratios were calculated. N content ranked as needle > root > stem; P content was in the order of root > stem > needle; and K content showed the pattern of stem > needle > root. Fertilization did not alter the above nutrient distribution patterns; it significantly influenced nutrient concentrations and stoichiometry. Single applications of nitrogen fertilizer had the most significant effect on nutrient content; compared with the unfertilized control, single nitrogen application increased needle N content by 1.13-fold. Combined nitrogen and phosphorus application preferentially promoted the accumulation of N relative to P in stems; specifically, under combined N-P treatment, stem N content increased by 1.11-fold while stem P content increased by 1.03-fold, indicating a greater relative increase in N. In terms of stoichiometric ratio, fertilization increased N:P, particularly in the root and needle; root N:P increased by 1.19-fold under T8 (0.8 g N + 3 g P) and needle N:P increased by 1.17-fold under T2 (3 g P alone), both indicating a mitigation of N limitation. Consistent with the nutrient content results, single nitrogen application exerted the greatest effect on stoichiometric ratio, followed by nitrogen and phosphorus combined application, and single phosphorus application had the least effect. These findings suggest that fertilization can alter nutrient allocation and stoichiometric relationships in Pinus yunnanensis, which may affect its growth and metabolic processes, but further studies are needed to link these changes to seedling growth. Full article

Biological soil crusts (BSCs) play key roles in arid, semi-arid regions and ecological marginal habitats. This study focused on four types of sand-fixing plantations established in 1990 in alpine sandy land (Salix psammophila, SL; Caragana korshinskii, NT; Salix cheilophila, WL; Populus simonii, XYY). Soil samples were collected from bare sand, algae crusts, and moss crusts. Soil particle size distribution, physicochemical properties, and enzyme activity were determined. Then bacterial communities were analyzed using high-throughput (Illumina) sequencing and the correlations among these three factors were examined. The results showed that: (1) From bare sand to algae and moss crusts, the content of fine particles (clay + silt) gradually increased. (2) Soil water content (SWC), nutrients and enzyme activities increased progressively. (3) In the study area, the dominant bacterial phyla of BSCs included Pseudomonadota, Cyanobacteria, Actinobacteriota and Vibrionota. Principal Coordinates Analysis (PCoA) and Analysis of Similarities (ANOSIM) results showed that BSCs drive the differentiation of bacterial communities during succession, while forest stands influence their spatial distribution. (4) Spearman’s correlation and redundancy analysis (RDA) showed that available phosphorus (AP), alkaline hydrolyzable nitrogen (AN), soil organic matter (SOM), catalase (CAT), pH, soil water content (SWC), and alkaline phosphatase (ALP) are key physicochemical factors shaping the bacterial community structure of BSCs. Mantel’s test confirmed that these variables mediated BSCs’ bacterial community structure. This study elucidates the mechanisms underlying ecological restoration via BSCs and provides a theoretical basis for future restoration efforts in alpine sandy land. Full article

This study aimed to characterize the spatial patterns of soil nutrients and labile carbon in the 0–20 cm surface layer of a red-soil bench-terrace hillslope during the first year following cut-and-fill engineering. Soil nutrient redistribution is classically conceptualized as upslope depletion and downslope enrichment, yet whether this paradigm holds after bench terracing remains poorly documente d. On a granite-derived red-soil hillslope in Yudu County, Jiangxi Province, China, we established three replicated transects across four slope positions in May 2025, one year after cut-and-fill bench terracing combined with Camellia oleifera–Pinus massoniana mixed young-forest restoration. The 0–20 cm surface layer was sampled for pH, organic matter, total nitrogen, total phosphorus, water-soluble organic carbon, particulate organic carbon (POC), and mechanical composition. The results showed that organic matter, total nitrogen, and POC all peaked on the upper slope, with enrichment factors of 8.8×, 3.8×, and 5.1× relative to the hilltop, respectively; the slope base did not function as a nutrient sink. Texture displayed a monotonic downslope differentiation but decoupled from the nutrient gradient, and pH was significantly negatively correlated with organic matter and POC. The observed short-term post-restoration non-classical pattern is best interpreted as the spatially heterogeneous footprint of subsurface exposure and localized topsoil redistribution during cut-and-fill engineering, overlain by one year of incipient biological input, rather than the product of modified erosion–deposition dynamics. POC appears to be a particularly sensitive tracer of early biological activity under these short-term post-restoration conditions when superimposed on a depleted inverted-surface baseline, and the pronounced spatial heterogeneity implies that precision management based on high-resolution spatial diagnosis is warranted to address the substrate patchiness inherited from cut-and-fill operations. However, the temporal scope of this one-year baseline survey limits the inference of long-term indicator performance, and follow-up monitoring is needed to confirm whether POC retains this sensitivity as the surface layer matures. Full article

Chromium is an environmental pollutant with high toxicity and carcinogenicity. It can induce severe oxidative stress and DNA damage after entering the human body through the food chain. As a plant growth-promoting rhizobacterium (PGPR) with both heavy metal tolerance and plant growth-promoting properties, Klebsiella variicola has considerable potential for the remediation of chromium contamination. In this study, chicory served as the experimental plant to explore the mitigating impacts of K. variicola on stress induced by hexavalent chromium (Cr(VI)) at a concentration of 400 mg/kg. The results showed that chromium severely inhibited the growth of chicory. In contrast, K. variicola significantly reduced the soil chromium content. As the chromium content decreased, the activities of soil urease, sucrase, catalase, and alkaline phosphatase were restored, increasing by 32.60–53.69%. Accordingly, the contents of total phosphorus, available phosphorus, total nitrogen, available nitrogen, soil organic carbon, and available potassium also increased by 34.71–51.81%. In addition, K. variicola reversed the decline in microbial diversity induced by chromium stress, promoted the growth of beneficial bacteria such as Acidobacteriota and Chloroflexota, and enhanced the stability of soil ecosystem functions. Ultimately, the growth inhibition of chicory caused by chromium stress was alleviated, with fresh weight, root length, maximum leaf width, maximum leaf length, plant height, and stem diameter significantly increasing by 21.89–61.60%. This study enhances our comprehension of the various functions of PGPR when exposed to heavy metal stress, and provides support for the development of microbe–plant combined strategies in the remediation of chromium-contaminated soils. Full article

Swine wastewater, composed of farm effluents, is frequently applied as fertilizer, but repeated use can lead to eutrophication and contamination. This study investigated the improvement of swine wastewater quality by means of the electroflocculation technique using various alternative electrodes (aluminum, stainless steel, carbon, copper, and zinc) under very short exposure durations (3, 6, and 9 min) and low voltage conditions (12 V), aiming to optimize the process. After the treatments, both treated and control samples were analyzed in the laboratory for pollutants including turbidity, organic matter, phosphorus and other minerals. The results showed that zinc and stainless steel electrodes were particularly effective in reducing turbidity (47–67%), organic matter (23%), phosphorus (36–62%), calcium (24–54%), magnesium (34–52%) and sodium (19–38%) respectively in the effluent after only 6 or 9 min of current exposure. However, these electrodes released some heavy metals into the solution, which should be further reduced through a complementary treatment. Overall, electroflocculation using alternative electrode materials with short treatment times appears to be a suitable pre-treatment strategy for swine wastewater, reducing pollutant loads while maintaining low energy consumption and preserving nutrients for subsequent use as fertilizer. Full article

Northeast China’s black soil region serves as a critical cornerstone of national food security, yet accelerating soil degradation, characterized by declining soil organic matter (SOM) and rising bulk density (BD), threatens the productive capacity of its farmland. Understanding how soil physicochemical properties regulate crop yields in this ecologically heterogeneous landscape is essential for sustainable agricultural development. Here, 2916 soil samples from 201 counties across six ecological zones were analyzed in conjunction with county-level rice and maize yield records. Our findings revealed that crop yield determinants are fundamentally governed by regional resource endowment characteristics rather than uniform factors. In areas characterized by sandy soil texture, low precipitation (<400 mm yr⁻¹), and inherently low fertility, elevated bulk density (BD, >1.34 g cm⁻³) and alkaline soil conditions (pH > 7.0) constitute the primary constraints to productivity through restricting root development. Conversely, in regions with fertile mollisols and high baseline soil organic matter (SOM > 40 g kg⁻¹), nutrient dynamics emerge as the dominant yield-regulating factors. For volcanic soil landscapes with strong phosphorus fixation capacity, available phosphorus deficiency represents the critical bottleneck for maize production. Path analysis further demonstrates that BD and pH operate predominantly through indirect mechanisms, modulating SOM accumulation and nutrient cycling rather than directly constraining yield. Threshold analysis identified that BD exceeding 1.34 g cm⁻³ and SOM below 26 g kg⁻¹ markedly reduce productivity, while SOM levels above 40 g kg⁻¹ yield diminishing marginal returns. These findings advance our mechanistic understanding and provide scientific foundations for spatially differentiated soil conservation and precision nutrient management strategies essential for sustaining grain production capacity in northeast China’s black soil region. Full article

Fertilizer nitrogen-to-phosphorus (N/P) stoichiometry diverges between soil test recommendations and conventional farmer practices in tropical Asia; however, its associations with labile soil carbon fractions remain poorly characterized. This regional exploratory study quantified N/P input divergence and examined co-occurring soil carbon patterns across four cropping systems in northern Thailand. A fertilizer management dataset of 138 field records was combined with a complementary soil property dataset of 303 topsoil samples (101 plots × 3 management groups: App (soil test-based fertilizer recommendation), Farmer (conventional practice), and NF (No-Fertilizer control)). The two datasets were drawn from the same regional agroecosystem context but were not paired plot-by-plot; therefore, the results are interpreted as associations rather than direct cause–effect linkages. Soil properties included pH, macronutrients, total soil organic carbon (SOC), permanganate-oxidizable carbon (POXC), and oxidizable fractions (labile, less labile, and non-labile) quantified by wet oxidation. The App N/P mass ratios (kg N kg⁻¹ P) exceeded Farmer in all systems, with the greatest divergence in Rice (9.14 vs. 1.83) and Vegetables (7.62 vs. 2.24). Total SOC did not differ among management groups (p = 0.828), but labile carbon (LC) was significantly higher under Farmer (13.59 g kg⁻¹) than under App (7.46) and NF (3.34; p < 0.001), while POXC was elevated under NF and pH under App (both p < 0.001). Management associations were consistent across the soil orders and crop groups. LC and POXC appeared to be more sensitive short-term indicators than bulk SOC in this dataset. Because the soil property dataset is not paired plot-by-plot with the fertilizer dataset, and because management contrasts are also confounded with co-occurring differences in total fertilizer input, organic matter management, residue management, and environmental conditions, the observed associations cannot establish a direct causal role for the N/P ratio per se. The results suggest a possible association between low-N/P farmer fertilization and higher labile carbon in smallholder systems in northern Thailand; confirmation of causal mechanisms requires paired within-plot longitudinal studies. Full article

Biochar amendment is increasingly recognized as a promising strategy for enhancing soil carbon sequestration in cropland systems; however, the mechanisms governing its effects on root exudate-induced decomposition of native soil organic carbon (SOC) remain poorly understood. We conducted a controlled laboratory incubation experiment using ¹³C-labeled glucose as a proxy for root exudates to quantify native SOC decomposition in wheat soil with or without long-term biochar amendment. Glucose addition induced a strong positive priming effect in unamended control soils, increasing native SOC decomposition by 354.4 μg CO₂ g⁻¹ soil over 30 days, whereas biochar amendment substantially suppressed this response by 75.7%. This suppression was attributed to biochar-enhanced phosphorus availability and a shift in microbial community composition toward greater fungal dominance, which collectively reduced microbial nutrient mining from native SOC pools. Our findings demonstrate that biochar can effectively mitigate the priming effect through coordinated alterations in nutrient dynamics and microbial community structure, thereby promoting long-term SOC stabilization. These results strengthen the scientific basis for biochar application as a climate change mitigation strategy in agricultural ecosystems. 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

Cooling water systems of coastal nuclear power plants in China are frequently threatened by blockages caused by marine organisms. However, long-term studies on macrobenthic community dynamics and their associations with environmental factors are scarce, limiting the precise prevention of such blockage risks. This study conducted quantitative monitoring of macrobenthos and synchronous measurement of water environmental factors at 24 sampling stations in three functional areas (water intake, harbor basin, and drainage outlet) adjacent to the Northeast Fujian NPP from 2018 to 2024. Community structure characteristics were analyzed using the Shannon–Wiener and Margalef indices. The Grappler Method Risk Index (GMRI) was employed to screen species at risk of blocking cooling water systems, and the Mantel test and random forest models were applied to explore the associations between the macrobenthic community and environmental factors. A total of 161 macrobenthic species were identified. Polychaetes (71 species, accounting for 44.1%) were the absolute dominant group, followed by crustaceans (35 species) and Mollusks (30 species). The interannual fluctuation range of the polychaete proportion was 41.1–57.8%, reaching a peak in 2023. There were significant differences in community structure among different areas (PERMANOVA, p < 0.05), with the largest inter-regional difference in 2024 (R² = 0.36). The annual average number of species (9 species), density (155.25 ind./m²), and biomass (29.58 g/m²) in the drainage outlet were higher than those in the water intake and harbor basin. The GMRI identified Protankyra bidentata (spiny sea cucumber, GMRI values of 50.67% to 64.98% from 2019 to 2023) and Actiniaria sp. (sea anemone, a GMRI value of 54.63% in 2021) as medium-risk species for cooling water system blockage, while most other organisms were classified as low risk or extremely low risk. The Mantel test and random forest analysis confirmed that nitrogen nutrients (NO₃⁻) and phosphorus (PO₄³⁻) were significantly positively correlated with the polychaete community. Furthermore, NO₃⁻ and NH₄⁺ each explained 13.66% of the variation in the diversity index (H′), serving as key factors driving community structure. This study demonstrates the co-dominance of thermal and nutrient drivers in shaping macrobenthic communities over a multi-year scale, and identifies specific, morphologically suited taxa as potential blockage risks. The findings provide a scientific basis for targeted risk-species monitoring and support the integration of long-term ecological data into NPP cooling water system security management. Full article