Search Results (31)

Carbonaceous–siliceous–argillaceous rock-type uranium deposits, a major uranium resource in China, pose significant environmental risks due to heavy metal contamination. Geochemical investigations in the former Zoige uranium mine revealed elevated As, Cd, Cr, Cu, Ni, U, and Zn concentrations in soils and sediments, particularly at river confluences and downstream regions, attributed to leachate migration from ore bodies and tailings ponds. Surface samples exhibited high Cd bioavailability. The integrated BCR and mineral analysis reveals that Acid-soluble and reducible fractions of Ni, Cu, Zn, As, and Pb are governed by carbonate dissolution and Fe-Mn oxide dynamics via silicate weathering, while residual and oxidizable fractions show weak mineral-phase dependencies. Positive Matrix Factorization identified natural lithogenic, anthropogenic–natural composite, mining-related sources. Pollution assessments using geo-accumulation index and contamination factor demonstrated severe contamination disparities: soils showed extreme Cd pollution, moderate U, As, Zn contamination, and no Cr, Pb pollution (overall moderate risk); sediments exhibited extreme Cd pollution, moderate Ni, Zn, U levels, and negligible Cr, Pb impacts (overall extreme risk). USEPA health risk models indicated notable non-carcinogenic (higher in adults) and carcinogenic risks (higher in children) for both age groups. Ecological risk assessments categorized As, Cr, Cu, Ni, Pb, and Zn as low risk, contrasting with Cd (extremely high risk) and sediment-bound U (high risk). These findings underscore mining legacy as a critical environmental stressor and highlight the necessity for multi-source pollution mitigation strategies. Full article

Given the worsening global climate change that drives drought frequency and irrigation water shortages, implementing water-conserving practices like alternate wetting and drying (AWD) is now critically urgent. Biochar is widely used for soil carbon sequestration. However, there is limited information on the effects of biochar on soil organic carbon (SOC) and its labile fractions in paddy fields, especially under AWD. A two-year field experiment was conducted with two irrigation regimes (CF: continuous flooding irrigation; AWD) as the main plots and 0 (B₀) and 20 t ha⁻¹ (B₁) biochar as sub-plots. AWD had no effect on the SOC and particulate organic carbon (POC) content, but increased the dissolved organic carbon (DOC), microbial biomass carbon (MBC), easily oxidizable organic carbon (EOC), light fraction organic carbon (LFOC), and carbon pool management index (CPMI) at 0–10 cm depths, by 24.4–56.4%, 12.6–17.7%, 9.2–16.8%, 25.6–28.1%, and 11.3–18.6%, respectively. Biochar increased SOC while also increasing DOC, MBC, EOC, LFOC, POC, and CPMI at 0–20 cm depths, by 18.4–53.3%, 14.7–70.2%, 17.4–22.3%, 10.2–27.6%, 95.2–188.3%, 46.6–224%, and 5.6–27.2, respectively, making SOC more labile under AWD. Our results highlight that biochar still holds great potential for improving soil quality and carbon sequestration under AWD, and the combination of biochar and AWD can achieve the synergistic optimization of the food–water–carbon sequestration trade-off, which is beneficial to sustainable agricultural production. Full article

Climate change and overgrazing significantly constrain the sustainability of meadow land and vegetation in the livestock industry on the Tibetan–Plateau ecosystem. In context of climate change mitigation, grassland soil C sequestration and forage sustainability, it is important to understand how manure regimes influence SOC stability, grassland soil, forage structure and nutritional quality. However, the responses of SOC fractions, soil and forage structure and quality to the influence of manure gradient practices remain unclear, particularly at Tianzhu belt, and require further investigation. A field study was undertaken to evaluate the soil bulk density, aggregate fractions and dynamics in SOC concentration, permanganate oxidizable SOC fractions, SOC stabilization and soil nutrients at the soil aggregate level under manure gradient practices. Moreover, the forage biodiversity, aboveground biomass and nutritional quality of alpine meadow plant communities were also explored. Four treatments, i.e., control (CK), sole sheep manure (SM), cow dung alone (CD) and a mixture of sheep manure and cow dung (SMCD) under five input rates, i.e., 0.54, 1.08, 1.62, 2.16 and 2.70 kg m⁻², were employed under randomized complete block design with four replications. Our analysis confirmed the maximum soil bulk density (BD) (0.80 ± 0.05 g cm⁻³) and micro-aggregate fraction (45.27 ± 0.77%) under CK, whilst the maximum macro-aggregate fraction (40.12 ± 0.54%) was documented under 2.70 kg m⁻² of SMCD. The SOC, very-labile C fraction (Cfrac₁), labile C fraction (Cfrac₂) and non-labile/recalcitrant C fraction (Cfrac₄) increased with manure input levels, being the highest in 2.16 kg m⁻² and 2.70 kg m⁻² applications of sole SM and the integration of 50% SM and 50% CD (SMCD), whereas the less-labile fraction (Cfrac₃) was highest under CK across aggregate fractions. However, manures under varying gradients improved SOC pools and stabilization for both macro- and micro-aggregates. A negative response of the carbon management index (CMI) in macro-aggregates was observed, whilst CMI in the micro-aggregate fraction depicted a positive response to manure addition with input rates, being the maximum under sole SM addition averaged across gradients. Higher SOC pools and CMI under the SM, CD and SMCD might be owing to the higher level of soil organic matter inputs under higher doses of manures. Moreover, the highest accumulation of soil nutrients,, for instance, TN, AN, TP, AP, TK, AK, DTPA extractable Zn, Cu, Fe and Mn, was recorded in SM, CD and SMCD under varying gradients over CK at both aggregate fractions. More nutrient accumulation was found in macro-aggregates over micro-aggregates, which might be credited to the physical protection of macro-aggregates. Overall, manure addition under varying input rates improved the plant community structure and enhanced meadow yield, plant community diversity and nutritional quality more than CK. Therefore, alpine meadows should be managed sustainably via the adoption of sole SM practice under a 2.16 kg m⁻² input rate for the ecological utilization of the meadow ecosystem. The results of this study deliver an innovative perspective in understanding the response of alpine meadows’ SOC pools, SOC stabilization and nutrients at the aggregate level, as well as vegetation structure, productivity and forage nutritional quality to manure input rate practices. Moreover, this research offers valuable information for ensuring climate change mitigation and the clean production of alpine meadows in the Qinghai–Tibetan Plateau area of China. Full article

To respond to China’s policies of “balancing and supplementing high-quality farmland, converting dryland to paddy fields” and of improving the quality of drylands, large-scale dryland conversion to paddy fields has been recently implemented to improve farmland quality and increase grain production capacity in China. However, the effects of the conversions on the soil carbon (C) pool remain unclear. Therefore, in a karst area of Guizhou Province, China, we selected farmland soils that had undergone dryland-to-paddy conversion and planted with rice for one year, ensuring that the historical management practices, soil parent material, and spatial proximity were consistent. We compared changes in and interactions between soil physicochemical properties, organic C components, and the C pool management index (CPMI) in pre-conversion drylands, post-conversion paddy fields, and reference unused lands. We found that dryland-to-paddy conversion suppressed most soil physicochemical properties in the short term. After dryland conversion to paddy fields, total C, total organic C, dissolved organic C, easily oxidizable organic C, inert organic C, microbial biomass C, and soil CPMI significantly decreased temporarily. With conversion, the proportion of easily oxidizable organic C decreased, whereas those of dissolved organic C, microbial biomass C, and inert organic C increased. Correlation and redundancy analyses indicated that bulk density was negatively correlated with organic C, its components, and the CPMI, whereas soil nitrogen (N), alkaline N, available phosphorus (P), and available potassium were significantly positively correlated with organic C. The carbon pool activity and CPMI were primarily influenced by easily oxidizable organic C, microbial biomass C, alkaline N, and available P. According to a partial least squares structural equation model, soil physicochemical properties and organic C and its components were the main drivers of C pool changes. Organic C and its components directly influenced C pool changes, whereas soil physicochemical properties mostly indirectly influenced C pool changes. Therefore, although dryland-to-paddy conversion can maintain a balance of arable land and ensure food security, such conversions may lead to short-term declines in organic C stability and C pool management index, indicating mitigation strategies, such as tailored N, P, and K fertilization regimes, should be developed to increase farmland C sequestration capacity. Full article

This study uses the Kherlen River as a case study to investigate the relationship between soil nutrients in riparian zones and water quality in inlet sections of lakes. Field sampling and experimental analyses were conducted during the high-water period (July) of 2023. An investigation was conducted on both the water quality of the river segments entering the lake and the soil nutrients. Methods such as the comprehensive water quality index (WQI), spatial heterogeneity analysis, and gray relational analysis were employed to assess water quality, soil nutrient characteristics, and their interrelationships, respectively. The results indicated that during the high-water period, the average concentrations of the permanganate index (COD_Mn), total nitrogen (TN), total phosphorus (TP), and dichromate oxidizability (COD_Cr) in the Kherlen River exceeded the Class V surface water quality standard thresholds. The overall WQI of the Kherlen River was 22.54, reflecting generally poor water quality, with a Global Moran’s I of 0.21, indicating a spatially clustered distribution. In the watershed, the Global Moran’s I values for pH values, TOC, TN, and TP at soil depths of 0–10 cm and 10–20 cm were 0.52, 0.90, 0.86, and 0.94 and 0.51, 0.57, 0.77, and 0.78, respectively. A significant positive correlation was found among soil nutrients, exhibiting a strong spatial aggregation characteristic, with nutrient concentrations decreasing with increasing soil depth. Moreover, the WQI of the Kherlen River demonstrated a significant correlation (R² > 0.6) with soil nutrient indicators, underscoring the substantial impact of riparian soil nutrients on river water quality. Based on these findings, targeted water management and ecological restoration measures are proposed to improve the water quality of the Kherlen River and Hulun Lake, providing new insights and scientific evidence for the restoration and sustainable development of lake ecosystems. Full article

Soil labile organic carbon (C) fractions play a key role in agricultural soil fertility. However, the effects of long-term organic substitution regimes on soil organic carbon (SOC), its labile fractions, stability, and vegetable yields as well as the relationships among these factors in the open-field are less well-studied. Hence, the objective of this study was to analyze the effects of long-term organic substitution regimes on SOC sequestration, labile C fractions [particulate organic C (POC), microbial biomass carbon (MBC), dissolved organic C (DOC), and readily oxidizable C (ROC)], SOC stability, the C pool management index (CMI), and vegetable yields in a long-term (13 years) open-field experiment. Five treatments were examined: 100% chemical nitrogen fertilizer (CN), substituting 25% of the chemical N with manure (MN) or straw (SN), and substituting 50% of the chemical N with manure (2MN) or manure plus straw (MSN). Compared to the CN, organic substitution treatments increased the average yields of vegetable, the SOC, the labile C fractions’ contents, and the C pool management index (CMI) to varying degrees, but only MSN reached significant levels for these factors. However, the MSN treatment had a significantly lower C stability index (SI) than the CN. ¹³C-NMR analyses also confirmed that organic substitution treatments increased the proportion of O-alkyl C and the OA/A, but reduced SOC stability. Pearson correlation analysis and the partial least squares path model indicated that labile C fractions were the mainly direct contributors to yield and SOC stability. Overall, substituting 50% of the chemical N with manure plus straw is a relatively ideal fertilization practice to improve vegetable yields and enhance C activity in an open field. Full article

The forest swamp ecosystem, as a special wetland ecosystem, is a key link in the material cycle and an important carbon sink in the carbon cycle. The global carbon cycle is of great significance, but the impact of forest swamp succession and soil depth on soil active organic matter and nematode community structure and diversity is unclear. This study used the “space instead of time” method to investigate the succession process of forest swamps from grasslands (WC) and shrubs (WG) to forests (WS) in national nature reserves. The results showed that during the forest succession process, the dominant nematode communities in the WC and WG stages were dominated by the genera Apis and Labroidei, while the dominant genera increased in the WS stage. The total abundance of nematodes increased, and the number of groups was ordered WG > WC > WS. The diversity in soil nematode communities according to Shannon–Wiener (H′), Pielou (J), and Trophic diversity (TD) was WS > WG > WC, which is related to vegetation, soil physical and chemical properties, and microbial community structure. The maturity index (MI) was WG > WS > WC. The soil food web was dominated by bacterial channels and had characteristics in forest metabolic activity and regulation ability. At different soil depths, there were significant differences in the community, with species such as the spiny cushioned blade genus being key. The number and group size of nematodes varied from 0–10 cm > 10–20 cm > 20–30 cm. The relative abundance of feeding nematodes changed with depth, while diversity indices such as H′, J, and TD decreased with depth. Ecological function indices such as MI and PPI showed depth variation patterns, while basic indices (BI) and channel indices (CI) showed significant differences. In terms of soil variables, during the forest succession stage, soil organic carbon (SOC), soluble organic nitrogen (DON), easily oxidizable organic carbon (ROC), microbial biomass carbon (MBC), and microbial biomass nitrogen (MBN) showed a gradually increasing trend with WC-WG-WS, while total nitrogen (TN), soluble organic carbon (DOC), soil temperature (ST), and soil moisture (SM) showed opposite changes. There were significant differences in soil ST, SM, and DON values with succession (p < 0.05). At different soil depths, except for DON and ROC, which increased first and then decrease with depth, the values of other physical and chemical factors and active carbon and nitrogen components at depths of 0–10 cm were higher than those at other depths and decreased with depth. An analysis of variance showed significant differences in MBC and MBN values at different soil depths (p < 0.05), which is of great significance for a deeper understanding of the mechanism of soil nematode community construction and its relationship with the environment. Full article

To amplify grain production capacity, a global trend is emerging in which many regions are transitioning from dependence on rainfall to irrigated agriculture. An illustrative example of this form of land consolidation is the conversion from dryland to paddy fields, which has changed the ecological environment of farmlands, resulting in significant effects on carbon fixation and emissions. However, there currently exists a deficiency in essential understanding regarding the short-term effects of dryland-to-paddy conversion on ecological processes tied to soil carbon-fixation bacteria and carbon emission efficiency (CEE). Therefore, field monitoring and high-throughput sequencing were carried out to monitor the changes in soil carbon emission efficiency and carbon-fixation bacteria before and after the conversion. Our results indicate that while conversion from dryland to paddy fields can boost grain yield, it also results in an increase in soil carbon emissions and a consequent decrease of 25.78% in carbon emission efficiency. This transition has resulted in an increased soil carbon-fixing bacterial alpha diversity index and enhanced network complexity. The structural equation model indicates that changes in soil environmental factors, especially soil moisture, soil organic carbon (SOC), readily oxidizable carbon (ROC), and carbon-fixing bacteria, are the primary drivers of CEE variation (p < 0.05). Given the critical role that the soil carbon cycle plays in global climate change, there is a pressing need for increased global attention towards the carbon emissions triggered by the transition from rainfed to irrigated agriculture. Full article

To remove oxidizable polyphenolic compounds from wines, fining treatments with products of various origins are applied before or after fermentation. Seeking alternatives to the treatments with animal proteins or synthetic materials such as polyvinylpolypyrrolidone (PVPP), vegetal and mineral products are tested. One of these alternative agents is pea protein (P), which can be combined with chitosan (K), yeast cell walls (Y), active carbon (C), and/or Ca-bentonite (B). Aside from the proven polyphenol removal effect, these products can also have an impact on aroma. This research evaluates the effect of P and ternary combinations with P on the volatile compounds of aromatic wines from the Tămâioasă românească variety. Several variants of treatments with P and with ternary mixtures involving P were prepared in triplicate with a total dose of 20 g/hL of fining agent applied during the pre-fermentative phase. Volatile profiles were determined using a flash gas chromatograph with two short columns of different polarities. The chromatographic peak areas for the identified ethylic esters, acetates and terpenes were used to compare the fining treatment effects. To test the significant differences between experimental variants, the Analysis of Similarity (ANOSIM) was used. The influences of P used alone and PVPP used alone were both significantly different compared to control (untreated), but based on the dissimilarity index R, PVPP affected the volatile profile about twice as much as P, showing that pea protein is a good alternative for PVPP. The ethyl esters were especially reduced by PVPP, while P especially reduced the terpenes. From all the tested pea protein ternary agents, those containing bentonite (PCB and PYB) showed a significant reducing effect on all classes of compounds and therefore are not recommended. The combinations containing yeast cell walls, PCY and PKY, are the most interesting alternatives to both PVPP and P used independently, PCY being the least aggressive of all treatments on overall aroma, preserving well the aroma compounds of all determined classes, including terpenes. Full article

Soil organic carbon (SOC) is a crucial indicator of soil quality and fertility. However, excessive nitrogen (N) application, while increasing Moso bamboo yield, may reduce SOC content, potentially leading to soil quality issues. The impact of N on SOC and its active fraction in Moso bamboo forests remains underexplored. Investigating these effects will elucidate the causes of soil quality decline and inform effective N management strategies. Four N application gradients were set: no nitrogen (0 kg·hm⁻²·yr⁻¹, N0), low nitrogen (242 kg·hm⁻²·yr⁻¹, N1), medium nitrogen (484 kg·hm⁻²·yr⁻¹, N2), and high nitrogen (726 kg·hm⁻²·yr⁻¹, N3), with no fertilizer application as the control (CK). We analyzed the changes in SOC, active organic carbon components, and the Carbon Pool Management Index (CPMI) under different N treatments. The results showed that SOC and its active organic carbon components in the 0~10 cm soil layer were more susceptible to N treatments. The N0 treatment significantly increased microbial biomass carbon (MBC) content but had no significant effect on SOC, particulate organic carbon (POC), dissolved organic carbon (DOC), and readily oxidizable organic carbon (ROC) contents. The N1, N2, and N3 treatments reduced SOC content by 29.36%, 21.85%, and 8.67%, respectively. Except for POC, N1,N2 and N3 treatments reduced MBC, DOC, and ROC contents by 46.29% to 71.69%, 13.98% to 40.4%, and 18.64% to 48.55%, respectively. The MBC/SOC ratio can reflect the turnover rate of SOC, and N treatments lowered the MBC/SOC ratio, with N1 < N2 < N3, indicating the slowest SOC turnover under the N1 treatment. Changes in the Carbon Pool Management Index (CPMI) illustrate the impact of N treatments on soil quality and SOC sequestration capacity. The N1 treatment increased the CPMI, indicating an improvement in soil quality and SOC sequestration capacity. The comprehensive evaluation index of carbon sequestration capacity showed N3 (−0.69) < N0 (−0.13) < CK (−0.05) < N2 (0.24) < N1 (0.63), with the highest carbon sequestration capacity under the N1 treatment and a gradual decrease with increasing N fertilizer concentration. In summary, although the N1 treatment reduced the SOC content, it increased the soil CPMI and decreased the SOC turnover rate, benefiting soil quality and SOC sequestration capacity. Therefore, the reasonable control of N fertilizer application is key to improving soil quality and organic carbon storage in Moso bamboo forests. Full article

Alpine grassland ecosystems are the most important ecosystem type, exhibiting a high sensitivity to anthropogenic nitrogen (N) and phosphorus (P) inputs into terrestrial ecosystems and significantly affecting the carbon (C) cycle within these ecosystems. However, the effects of N and P additions on soil C stability and the processes of organic C transformation remain unclear. This study measured the soil enzyme activities and oxidizable C fractions over a 9-year period following N and P additions to an alpine meadow in the Qinghai–Tibet Plateau. It included four treatments: control (CK), N addition, P addition, and combined N and P addition (NP), utilizing statistical methods such as analysis of variance (ANOVA), correlation analysis, and redundancy analysis. The findings indicated that NP addition significantly increased the non-labile soil oxidizable C fraction in the topsoil layer. Redundancy and correlation analyses revealed strong associations between the vegetation characteristics, C-cycling enzyme activities, soil-oxidized C fractions, and SOC stability index. These results underscore the role of NP addition in enhancing SOC accumulation and stability in grassland ecosystems, with the soil vegetation properties and C source enzyme activities serving as key regulators of the SOC stability. This study offers valuable insights into predicting the SOC dynamics amid rising N and P availability, thereby elucidating the effect of nutrient addition on soil C-cycling mechanisms. Full article

The present investigation was performed to evaluate the effects of various synthetic antioxidants (vitamin A, vitamin E, β-carotene, and BHT) on the oxidation of sunflower oil subjected to accelerated thermal storage at 60 °C for three months (12 weeks). The performance of the antioxidants studied was evaluated using several quality parameters: the free fatty acid value (FFA), primary oxidation (via the peroxide value (PV) and K232 value), secondary oxidation products (via the anisidine value (p-AV) and K270 value), and the total oxidation value (TOTOX). The fatty acid composition (FAC), oxidizability value (COX), iodine value (IV), and pigment content (chlorophyll and carotenoid) were also evaluated. The results revealed that the control sample of sunflower oil exhibited higher susceptibility to oxidative deterioration. Antioxidants at 200 ppm were more effective in preserving the oxidative stability of sunflower oil subjected to accelerated storage compared to the control oil. The smallest increases in all stability parameter indexes were recorded for antioxidant-supplemented sunflower oil. However, the IV and chlorophyll and carotenoid contents were reduced. At 200 ppm, vitamin E and β-carotene showed the greatest stability in sunflower oil, while their combination with vitamin A at 100 ppm of each showed the lowest stability. In addition, synthetic antioxidants provided greater protection against the degradation of polyunsaturated fatty acids (PUFAs). The highest level of PUFA degradation was recorded in the control oil, followed by the oil containing vitamin A. In conclusion, adding synthetic antioxidants to sunflower oil improves its stability during storage. However, some authors associated these molecules with a health risk due to carcinogenic effects as these molecules have been listed as “Generally Recognized As Safe” (GRAS). Full article

The excessive application of chemical fertilizers in rice fields exacerbates soil degradation and poses a threat to food security. Achieving an increase in rice production and minimizing environmental costs are inevitable requirements for achieving sustainable rice production. The synergistic utilization of rice straw (RS) and Chinese milk vetch (MV) is a sustainable measure to improve soil quality in Southern China. How this management strategy impacts agricultural productivity and soil carbon (C) sequestration under different fertilization conditions is unclear. Several treatments, including only chemical fertilizer (F), F + MV (FM), F + RS (FS), and F + MV + RS (FMS) under a standard rate of nitrogen (N₁₀₀) and 40% reduced nitrogen (N₆₀) levels were designed to explore changes in rice yields and soil organic carbon (SOC) concentrations, stocks, and soil labile organic C fractions (permanganate oxidizable C) during 2018–2020 in a double-rice-cropping system. The results show that the FMS treatment reduced soil bulk density to alleviate soil compaction and improved the soil carbon management index. The synergistic utilization of MV and RS replacing 40% of the chemical N fertilizer could still maintain the rice yield. Compared to the F treatment, the average annual grain yield was significantly increased by 9.82% and 5.84% in the FMS treatment; SOC concentration was increased by 16.05% and 19.98% on average (p < 0.05), and SOC stock was increased by 1.78 Mg C ha⁻¹ and 2.37 Mg C ha⁻¹ under the N₆₀ and N₁₀₀ levels, respectively. The random forest regression model and correlation analysis demonstrated that the inputs of chemical N, organic N and C, and appropriate C/N ratio promoted soil C accumulation. Furthermore, the structural equation model analysis exhibited that the C input affects the highly labile organic carbon (HLOC) and total labile organic carbon (LOC); the HLOC had a positive effect on SOC (p < 0.05). N input had a significant effect on LOC and yield. Our results suggest that the synergistic utilization of MV and RS plays an important role in ensuring stable grain production, improving soil C sequestration capacity, and maintaining soil environmental health in Southern China. Full article

Soil fungal communities play crucial roles in mediating the functional associations between above- and belowground components during forest restoration. Forest restoration shapes the alterations in plant and soil environments, which exerts a crucial effect on soil fungal assemblages. However, the changes, assembly processes, and driving factors of soil fungi communities during tropical forest restoration are still uncertain. We used Illumina high-throughput sequencing to identify the changes of soil fungal communities across a tropical secondary forest succession chronosequence (i.e., 12-, 42-, and 53-yr stages) in Xishuangbanna. During forest restoration, the dominant taxa of soil fungi communities shifted from r- to K-strategists. The relative abundance of Ascomycota (r-strategists) decreased by 10.0% and that of Basidiomycota (K-strategists) increased by 4.9% at the 53-yr restoration stage compared with the 12-yr stage. From the 12-yr to 53-yr stage, the operational taxonomic unit (OTU), abundance-based coverage estimator (ACE), Chao1, and Shannon index of fungal communities declined by 14.5–57.4%. Although the stochastic processes were relatively important in determining fungal assemblages at the late stage, the fungal community assembly was dominated by deterministic processes rather than stochastic processes. The shifts in soil properties resulting from tropical forest restoration exerted significant effects on fungal composition and diversity. The positive effects of microbial biomass carbon, readily oxidizable carbon, and soil water content explained 11.5%, 9.6%, and 9.1% of the variations in fungal community composition, respectively. In contrast, microbial biomass carbon (40.0%), readily oxidizable carbon (14.0%), and total nitrogen (13.6%) negatively contributed to the variations in fungal community diversity. Our data suggested that the changes in fungal composition and diversity during tropical forest restoration were primarily mediated by the positive or negative impacts of soil carbon and nitrogen pools. Full article

With rapid economic development, soil heavy metal (HM) pollution has emerged as a global environmental concern. Because the toxicity of HMs differs dramatically among various fractions, risk assessments based on these fractions are of great significance for environmental management. This study employed a modified Hakanson index approach to evaluate the possible ecological impacts of soil HMs in a gold mine tailings pond in Shaanxi Province, China. A modified Hakanson–Monte Carlo model was built to perform a probabilistic risk assessment. The results showed that: (1) the exceedance rates of chromium (Cr) and zinc (Zn) were 68.75% and 93.75%, respectively. Moreover, the overall concentrations of nickel (Ni), copper (Cu), arsenic (As), and lead (Pb) were higher than the background soil environmental values in China. (2) HMs with the lowest oxidizable fraction were mostly present in the residual fraction. The oxidizable portions of Cr, Cu, and Pb and the reducible and residual fractions of As were notably distinct. (3) The risk degrees of Cr, Ni, Cu, and Zn were low; those of As and Pb were very high and moderate; and the comprehensive ecological hazard index was very high. This study offers a solid scientific foundation for ecological risk notification and environmental management. Full article