Cumulative Mineralization Research Articles

Characteristics of organic amendments induce diverse microbial metabolisms for exogenous C turnover in Mollisols

The response of microbial community to organic amendments is closely related to the amendment-derived carbon (C) turnover, which in turn influences the enhancement of soil organic C, including the quantity and quality. The objective of this study was to quantify the decomposition and retention of exogenous C derived from amendments, and to identify the microbial regulatory mechanisms of exogenous C turnover in response to the characteristics of organic amendments. The 13C-labelled glucose, straw and biochar, characterizing organic amendments with high, medium and low labilities, respectively, were used to conduct a 90-day incubation experiment, in conjunction with stable isotope probing technology and amino sugar molecular biomarkers. It was found that the cumulative mineralization of amendment-derived C increased with increasing the corresponding lability of organic amendment, and the decompositions of the added glucose, straw and biochar, expressed as a percentage of the initially added C, were 53.6 %, 37.0 %, and 0.6 %, respectively. Among all treatments, the addition of straw significantly enhanced the total dissolved organic C (DOC) concentration and its ratio to total organic C by increasing the input of exogenous DOC and reducing the decomposition of native soil DOC. The exogenous C use efficiency by microorganisms was significantly enhanced with decreasing the amendment lability, and showed a positive correlation with the total amendment-derived C. However, the microbial growth efficiency was the highest when straw was added, and was closely related to the concentration of amendment-derived DOC. Different functional groups of soil microbes exhibited distinct capacities to metabolize various organic amendments. Generally, the incorporation of amendment-derived C into microbial biomass was significantly affected by fungi and gram-positive (G+) bacteria, while the relative contributions of microbial communities incorporating amendment-derived C into necromass were decreased in the order of gram-negative (G−) bacteria > fungi > actinomycetes > G+ bacteria. From the perspective of microbial metabolism, the larger incorporations of exogenous C into microbial biomass and necromass were observed in the soil with mediumly labile amendment, which contributed to enhance the quantity and quality of organic C in soil. These results would be informative to optimize the organic amendment strategy for integrated soil fertility management.

Physicochemical, Antimicrobial Properties and Mineral Content of Several Commercially Available Honey Samples

Ensuring food safety and protecting consumers are major aspects for commercialized products. Honey, the most prominent in the class of bee products, requires special regulations due to its origin as a natural product. Mislabeling, imitation, and adulteration represent a source of risks for human health. Specific determinations and analyses are essential for controlling the sector and preventing unfair competition. To compare and establish the correct labeling of several different honeys, melissopalynological, physicochemical, mineral content, and microbiological analyses were carried out on 18 samples commercially available in different countries, namely Türkiye, Romania, Bulgaria, and Northern Cyprus. The honey labels were in accordance with the determined pollen content. The physiochemical parameters showed high variability: 4.07–5.25 (pH), 79.95–83.45 (°Brix), 0.262–1.452 µS/cm (electrical conductivity), and 14.6–18.4% (moisture). The samples were quantitatively high in K, P, Na, and Ca, with the highest cumulative mineral content being found for honeys containing Fagaceae pollen. Additionally, the antimicrobial potential of the various honey samples was evaluated against selected bacteria, employing the disk diffusion and serial dilution methods. Results revealed that the honey samples exhibited increased antibacterial activity against Gram-negative bacteria, with notable activity against S. typhimurium, and moderate activity against Gram-positive S. aureus.

Lower crustal copper enrichment and mobilization indicated by Late Permian amphibole gabbros and granodiorites in the eastern Kunlun Orogen, northern Tibet

Lower crustal fractional crystallization accompanied by sulfide saturation in thick continental arcs has been viewed as an essential step in forming porphyry Cu systems. These processes are supposed to lock Cu in the lower crust and, therefore, can be unfavorable to the generation of ore-forming magmas. In this study, we present in situ mineral major-trace elements, pyrrhotite S isotopes, and zircon UPb ages, as well as whole-rock major-trace elements and SrNd isotopes for amphibole gabbros and contemporary granodiorites in the eastern Kunlun Orogen to elucidate Cu variations during the transcrustal magmatic evolution of these rocks. The amphibole gabbros can be divided into two types based on field relationships with the granodiorites. These rocks were derived from an oxidized metasomatic mantle in a steep subduction setting at ∼250 Ma and experienced a transcrustal magmatic evolution. Orthopyroxene relicts, resorbed clinopyroxene, calcic plagioclase, high-Al2O3 amphibole, and magnetite in the amphibole gabbros of the first type are lower crustal cumulate minerals. Pyrrhotite with minor amounts of chalcopyrite, interstitial to cumulate amphibole or as inclusions in magnetite from the amphibole gabbros of the first type, is lower crustal Ni-rich monosulfide solid solution (mss) crystallized from immiscible sulfide melts with residual Cu-rich sulfide liquids. These lines of evidence together with field, mineralogical, and geochemical data indicate that the Cu-rich parental magmas experienced lower crustal MASH (melting, assimilation, storage, and homogenization) processes and became Cu-depleted. The evolved magmas after lower crustal evolution became moderately oxidized and Cu-normal according to amphibole, biotite, zircon, and whole-rock compositions. The moderately oxidized magmas scavenged and mobilized Cu from Cu-rich sulfide liquids to the upper crustal magma chambers where degassing dispersed the Cu and thus was unfavorable to porphyry Cu mineralization.

Influence of nature reserve road traffic disturbance on soil carbon

PurposeRoad traffic has long been recognized as a considerable source of ecological disturbance, compromising the integrity of natural ecosystems from their pristine baseline state. Pollutant deposition from vehicular emissions significantly contributes to environmental contamination, while associated human activities exacerbate ecosystem disruptions. In designated conservation zones, including nature reserves, land-use practices such as pastoralism and agriculture are subject to regulation. Nevertheless, the influence of road traffic on ecosystem structure and processes, particularly concerning carbon (C) sequestration and its spatial heterogeneity, warrants further research. This consideration is critically relevant in the understanding the intricate C fractions and their dynamic interplay with environmental factors. Materials and methodsIn this study, we meticulously selected four distinct locations along a principal roadway within a national reserve. For each site, experimental measuring 2 m * 2 m were established at intervals of 2 m, 10 m, 20 m, 30 m, 40 m, and 50 m from the road's edge. Observational data were accrued during the peak of the vegetative growth seasons in August of both 2020 and 2021. Within each plot, soil and cut-ring samples were procured for comprehensive analysis of soil carbon fractions (Total Carbon, TC, g/kg; Carbon Density, g/m2; Readily Oxidizable Carbon, ROC, g/kg; Dissolved Organic Carbon, DOC, mg/kg; Microbial Biomass Carbon, MBC, mg/kg; Cumulative Mineralization Carbon, CMC, mg(CO2-C)*(kg*soil)−1; Soil Inorganic Carbon, SIC, g/kg), chemical properties (pH; Electrical Conductivity, EC, us/cm; Soil Organic Matter, SOM), and physical properties (Soil Water, SW, %; Bulk Density, BD, g/cm3; area conditions). Vegetation metrics, including above-ground biomass (AGB) and below-ground biomass (BGB), species composition, height, and coverage, were meticulously documented. The four sites were replicated, culminating in 24 uniformly oriented plots to mitigate wind influence. ResultsOur analysis revealed that C stock, as determined by TC and C density increased with distance from the road edge, reaching a peak at approximately 30 m (TC: 19.43 g/kg, C density: 39.26 g/m2, SOM: 27.57 g/kg), followed by a subsequent decline. At the 30 m distance, there was a 60.6 %, 41.2 %, and 38.7 % enhancement in TC, C density, and SOM, respectively, compared to the 2 m distance, and a 23.9 %, 25.9 %, and 19.8 % increase relative to the 50 m distance. Levels of DOC, MBC, and CMC exhibited an upward trend from the road edge to 50 m, suggesting more favorable microbiological conditions in less disturbed locales. SEM demonstrated that SIC is directly influenced by BGB (β = −0.31), pH (β = 0.46), and labile C components (β = 0.56), culminating in a reduction of total C storage (total effect, β = −0.28). The dynamic changes of soil C stocks were primarily explained directly by soil labile C (β = 0.475, p < 0.001), and indirectly by vegetation biomass (β = 0.460) and pH (β = −0.570), and were closely correlated with ROC (0.54, the highest eigenvalue among Labile_C). ConclusionThe findings suggest that the buffering effect of the roadside in these nature reserves up to a distance of 30 m has an signficant impact on C stock, and that C losses attributable to biochemical processes and laible soil C fractions may contribute to diminished C levels in less disturbed zones 50 m away from the road. Our findings also substantiate the moderate disturbance hypothesis, particularly in the milieu of road traffic within the Hulunbuir Nature Reserve, Mongolia. A moderate distance from roadways enhances soil C storage compared to areas near the road or undisturbed natural landscapes.

Effects of Incubation Temperature and Sludge Addition on Soil Organic Carbon and Nitrogen Mineralization Characteristics in Degraded Grassland Soil

Elucidating the characteristics and underlying mechanisms of soil organic carbon (SOC) and nitrogen mineralization in the context of sludge addition is vital for enhancing soil quality and augmenting the carbon sink capacity of soil. This study examined the chemical properties, enzyme dynamics, and organic carbon and nitrogen mineralization processes of soil from degraded grasslands on the Loess Plateau at various incubation temperatures (5, 15, 25, and 35 °C) and sludge addition rates (0%, 5.0%, 10.0%, and 20.0%) through a laboratory incubation experiment. The results showed that incubation temperature, sludge addition, and their interactive effects significantly altered the soil enzyme C:N, C:P, and N:P stoichiometries. The cumulative mineralization rates of SOC and nitrogen increased significantly with increasing incubation temperature and sludge addition rate. Principal component analysis revealed a significant linear correlation between cumulative SOC and nitrogen mineralization. Random forest analysis indicated that β-1,4-Glucosidase (BG), β-1,4-N-acetyglucosaminidase (NAG), cellobiohydrolase (CBH), ammonium nitrogen (NO3−), enzyme C:P ratio, alkaline phosphatase (ALP), and incubation temperature were crucial determinants of cumulative SOC mineralization. Structural equation modeling demonstrated that sludge addition, NO3−, NAG, ALP, and enzyme C:P positively impacted SOC mineralization, whereas dissolved organic carbon and BG had negative impacts. Conversely, incubation temperature negatively affected soil nitrogen mineralization, whereas NO3−, available phosphorus, and ALP contributed positively. Sludge addition and temperature indirectly modulated soil net nitrogen mineralization by altering soil chemical properties and enzyme activities. These findings underscore the role of SOC and nitrogen mineralization as indicators for evaluating soil nutrient retention capabilities.

Invasive Spartina alterniflora alters sediment organic carbon mineralization dynamics in a coastal wetland of Southeastern China

Invasive Spartina alterniflora has significant impacts on sediment carbon pool and turnover in the tidal wetlands of estuaries and coasts. Yet, how this exotic S. alterniflora affects sediment organic carbon mineralization dynamics remains poorly understood. In this study, sediment geochemical properties, organic carbon fractions, and mineralization dynamics were examined in a native Cyperus malaccensis habitat and three invasive S. alterniflora habitats (6-, 10-, and 14-year-old) in summer and winter. We found that invasive S. alterniflora generally increased sediment total organic carbon and their labile fraction contents. The organic carbon mineralization rates and cumulative carbon mineralization amounts were significantly influenced by invasive S. alterniflora, and their values increased with this exotic plant invasion chronosequences. The mineralization rates and cumulative mineralization amounts were also characterized by higher values in surface sediment (0 – 10 cm depth) compared to subsurface sediment (10 – 20 cm depth) and by seasonal variations with higher values in summer than in winter. The sediment organic carbon labile fractions, rather than total organic carbon, were the most important factor affecting carbon mineralization dynamics. The cumulative carbon mineralization amounts exhibited an excellent fit to the first-order kinetic equation (R2 ≥ 0.93). The changes in modeled kinetic parameters (potential carbon mineralization amounts (C0) and carbon mineralization rate constant (k)) among these four habitats were similar to carbon mineralization rates, implying invasive S. alterniflora promoted the availabilities of organic compounds for microbial respiration metabolism. Overall, our findings highlighted the importance of S. alterniflora invasion in accelerating organic carbon decomposition and carbon dioxide release potential, although it also increases carbon accumulation.

Vertical Distribution and Mineralization Dynamics of Organic Carbon in Soil and Its Aggregates in the Chinese Loess Plateau Driven by Precipitation

The mineralization of soil organic carbon (SOC) is a critical process in the soil carbon cycle. This study aimed to investigate the vertical distribution characteristics and mineralization dynamics of SOC in soils and their aggregates across different steppe types in the Loess Plateau (LP). Soil profiles from three steppe types under varying precipitation gradients were selected: meadow steppe (MS), typical steppe (TS), and desert steppe (DS). A 60-day controlled laboratory incubation study was conducted for carbon mineralization and the influence of climatic and soil properties on SOC mineralization was analyzed. The results showed that the SOC content and cumulative mineralization (CM) in 1–2 mm aggregates were higher than in other particle sizes; SOC content and CM followed the order MS &gt; TS &gt; DS and both decreased significantly with increasing soil depth. Correlation analysis revealed that precipitation significantly affected aggregate mineralization (p &lt; 0.001) and that mineralization in the 1–2 mm aggregates was more closely related to mean annual precipitation (MAP), SOC, and water-soluble organic carbon (SWOC). Precipitation primarily controlled SOC mineralization in the 0–50 cm soil layer, while SOC mineralization in the 50–100 cm layer was influenced by soil-related carbon content. Structural Equation Modeling indicated that precipitation influences the mineralization of organic carbon in topsoil indirectly through its direct impact on SOC. In the context of global warming, the SOC turnover rate in high-precipitation areas (MS) was faster than in low-precipitation areas (TS, DS), necessitating greater attention to soil carbon dynamics in these regions.

Effects of Land-Use Type and Salinity on Soil Carbon Mineralization in Coastal Areas of Northern Jiangsu Province

Sea level rise due to glacier melting caused by climate warming is a major global challenge, but the mechanism of the effect of salinity on soil carbon (C) mineralization in different land types is not clear. The pathways by which salinity indirectly affects soil carbon mineralization rates need to be investigated. Whether or not the response mode is consistent among different land-use types, as well as the intrinsic links and interactions between soil microbial resource limitation, environmental stress, microbial extracellular enzyme activity, and soil carbon mineralization, remain to be demonstrated. In this paper, three typical land-use types (wetland, forest, and agroforestry) were selected, and different salinity levels (0‰, 3‰, 6‰, and 32‰) were designed to conduct a 125-day laboratory incubation experiment to determine the soil CO2 release rate, soil physicochemical properties, and soil enzyme activities, and to correlate C mineralization with biotic and abiotic factors. A correlation analysis of soil physical and chemical properties, extracellular enzyme activities, and carbon mineralization rates was conducted to investigate their intrinsic linkages, and a multiple linear regression of C mineralization at different sites was performed to explore the variability of mineralization among different site types. Structural equation models were established in the pre- and post-incubation stages to study the pathways of soil C mineralization at different incubation times, and the mechanism of mineralization was further verified by enzyme stoichiometry. The results showed that, at the end of 125 days of incubation, the 32‰ salinity addition reduced the cumulative mineralization of forest and agroforestry types by 28.41% and 34.35%, respectively, compared to the 0‰ salinity addition. Soil C mineralization in the three different land-use types was highly correlated with the active C fractions of readily oxidizable C (ROC), dissolved organic C, and microbial biomass C (MBC) in the soil, with the standardized coefficients of multivariate linear regression reaching 0.67 for MBC in the wetland and −0.843 for ROC in the forest. Under long-term salinity additions, increased salinity would reduce the microbial respiratory quotient value by inhibiting β-glucosidase activity, thus indirectly affecting the rate of CO2 release. With added salinity, the mineralization of non-saline soil was more susceptible to the inhibitory effect of salinity, whereas the mineralization of salinized soil was more controlled by soil C pools.

Sulfur dynamics in saline sodic soils: The role of paddy cultivation and organic amendments

The phenomenon of sulfur (S) deficiency in Chinese soil is becoming increasingly severe, especially in the northeastern saline-sodic wasteland (WL). To determine the bioavailability of S in long-term cultivated paddy soil with or without organic amendment addition, the long-term field experiment site was established and incubation experiments were conducted. Compared to WL, soil properties have been continuously improved during the 15-year paddy field (PF) cultivation, ultimately enhancing the content of soil organic carbon (by 242.62 %), total nitrogen (by 126.49 %) and alkali-hydrolyzed nitrogen (by 28.07 %). Additionally, soil salinization has been decreasing, and the stock of total sulfur (TS) and available sulfur (AS) in the 0–60 cm soil layer have increased by 32.09 % and 293.52 % respectively. In contrast, organically-amended soil (OA) manifested superior TS and AS levels vs. PF. Additionally, water-soluble sulfur (WSS) was markedly elevated, registering post-annual increments of 227.31 % and 268.36 % in PF and OA, respectively, relative to WL. The key mechanistic impetus for the application of organic amendments was the enhancement of the soil's adsorptive and mineralization capabilities. As observed in our soil culture experiment, the maximum adsorption of sulfate ions and the cumulative mineralization of sulfur in the soil follow the pattern of OA > PF > WL. The Partial Least Squares Path Model (PLSPM) corroborated that both organic amendments and years of cultivation indirectly influenced total inorganic sulfur fractions. This influence is primarily mediated via structural soil enhancements and salinization amelioration, thereby elevating available quantities of sulfur in saline-sodic soil environments. In conclusion, from the perspective of soil sulfur biogeochemical cycling, we have confirmed that reclaiming saline-sodic wasteland for paddy field could be a beneficial and sustainable approach for soil management. These findings of this study can also provide an in-depth understanding of the bioavailability and influencing mechanism of sulfur in long-term saline-sodic paddy fields.

Geochemical diversity of continental arc basaltic mushy reservoirs driven by reactive melt infiltration

The reactive melt flow emerges as an important factor for diversification of basaltic magmatic reservoirs, but whether and how it influences continental arc basaltic mushes are enigmatic. Here, we used mineral and whole-rock geochemistry to examine the petrogenesis of a suit of mafic and intermediate plutons in western Yangtze Block, which were emplaced at continental arc crust and primarily had plagioclase and clinopyroxene as early cumulate mineral phases. We found the crystal mushes were infiltrated by externally-derived reactive melt with high δ18O and fertile crustal signatures, resulting in the changes of mineral phases (e.g., clinopyroxene transformed to hornblende) and bulk-rock geochemistry (including isotopes). Then, the reacted granitic melt was prone to either be extracted from or stall in the crystal mushes, generating quartz-poor (mafic) or quartz-rich (intermediate) plutons, respectively. This study supports the reactive melt infiltration may serve as an important engine for compositional diversity of basaltic mush system within continental arc settings.

Exploring the mechanical strength, antimicrobial performance, and bioactivity of 3D-printed silicon nitride-PEEK composites in cervical spinal cages

&amp;nbsp;In this study, our goal was to assess the suitability of a polyether-ether-ketone (PEEK) and silicon nitride (Si3N4) polymer composite for antimicrobial three-dimensional (3D)-printed cervical cages. Generic cage designs (PEEK and 15 vol.% Si3N4-PEEK) were 3D-printed, including solid and porous cage designs. Cages were tested in static compression, compression shear, and torsion per ASTM F2077. For antibacterial testing, virgin and composite filament samples were inoculated with Staphylococcus epidermidis and Escherichia coli. In vitro cell testing was conducted using MC3T3-E1 mouse preosteoblasts, where cell proliferation, cumulative mineralization, and osteogenic activity were measured. The 3D-printed PEEK and Si3N4-PEEK cages exhibited adequate mechanical strength for all designs, exceeding 14.7 kN in compression and 6.9 kN in compression shear. Si3N4-PEEK exhibited significantly lower bacterial adhesion levels, with a 93.9% reduction (1.21 log), and enhanced cell proliferation when compared to PEEK. Si3N4-PEEK would allow for custom fabrication of 3D-printed spinal implants that reduce the risk of infection compared to unfilled PEEK or metallic alloys. &amp;nbsp;

The potency of time series outliers in volatile models: An empirical analysis of fintech, and mineral resources

Understanding the importance of sustainability, the increasing ecological concerns need resource management under the cumulative mineral dependency. In this vein, prices of financial technology and mineral resources influence environmental sustainability; hence, sudden price variations must be evaluated carefully. For this, detecting outliers in financial and economic variables is gaining attention as economies are regionally integrated and influenced by external factors. Such peripheral events highly influence the statistical properties of model parameters and error distributions. In this vein, the current study proposed the method of outlier detection in various time series volatile models by extending the procedure of Frances and Ghijselse (1999) based on the framework of Chen and Liu (1993). The method is based on three phases: First, the outliers are detected, then the outliers are removed and estimated using the linear interpolation method, and third, the data values are forecasted by re-estimating the model with a corrected series. Forecasting accuracy has also been compared with and without outlier series to observe the impact of outlier presence in the series. For empirical analysis, the S&P Kensho Democratized Banking Index (USD), S&P 500 Environmental and Socially Responsible Index, and Gold price per Troy Ounce from July 15, 2013, to July 14, 2023. The outcomes retrieved from the proposed method suggest that the error distribution of volatile models is affected by outliers and manifestly forecasting performance is better with outlier corrected series. The diagnostic of the model is also analyzed. The study presents robust policy implications for outlier detection procedures in volatile models.

Soil pH determines microbial utilization strategy for straw-derived hydrophilic and hydrophobic fractions in a Ferralsol

Lime is commonly used to neutralize acidic soil in practical farmland management. This study aimed to examine the effect of soil pH change by liming in acidic soil on the mineralization and microbial assimilation of 13C-labelled maize straw-derived hydrophilic and hydrophobic fractions in a 60-d incubation experiment. Our results showed a higher cumulative mineralization of hydrophilic fraction in acidic (34.5%) than neutralized Ferralsol (22.3%), related to lower microbial substrate use efficiency under low soil pH. The cumulative mineralization of hydrophobic fraction was similar between acidic and neutralized Ferralsol. Soil pH affected substrate (hydrophilic and hydrophobic fractions) utilization by actinomycetes and bacteria, but not fungi. The utilization of hydrophilic fraction followed the order: bacteria (57–68%) > actinomycetes (10–19%) > fungi (4.2–5.5%). In contrast, utilization of hydrophobic fraction was the highest for fungi (24–38%), followed by bacteria (21–29%) and actinomycetes (3.2–15%). Actinomycetes showed a greater preference for hydrophilic fraction in neutralized than acidic Ferralsol; bacteria preferred to utilize hydrophilic fraction in both soils, while fungi favored hydrophobic fraction. Also, various substrate uses were found in specific phospholipid fatty acids, which showed that some individual species harbor particular organic C metabolization strategies. In conclusion, soil pH regulates the mineralization of hydrophilic fraction and variously determines the preferential utilization of hydrophilic and hydrophobic fractions by fungi, bacteria, and actinomycetes.Graphical

Siltation of check dams alters microbial communities and thus limits organic carbon mineralization

Check dam interception in the Loess Plateau leads to a buildup of silt-based deep soil reserves. These deep soils tend to be high in organic carbon (C), and could dramatically impact our estimates of terrestrial C storage. Despite a growing interest in the terrestrial C cycle, little work has focused on deep soil organic carbon (SOC) pools. In this study, we observed how soil depth and consequential oxygen concentration may influence the way in which microorganisms act on the SOC mineralization process. We found that the change from aerobic to anaerobic environment led to a decrease in cumulative mineralization from 1.37 mg to 1.06 mg and a significant decrease in mineralization rate, which had a limiting effect on SOC mineralization. The reduction of oxygen concentration (approximating depth) also led to changes in the dominant population of bacteria/fungi. Microorganisms with higher C metabolism capacity in aerobic conditions had higher utilization of C sources than that in anaerobic conditions, and vice versa. The limiting factors affecting the amount of SOC mineralization in aerobic soil were carbohydrate, Rokubacteria and Mortierellomycota, and that in anaerobic soil were Amino acid, Mortierellomycota and Ascomycota. Microorganisms with high C metabolism in anaerobic conditions have a weaker metabolism in aerobic conditions, and vice versa. We further quantified the direct and interactive contribution of each factor to SOC mineralization and found that when the soil was aerobic, the contribution of single factor to SOC mineralization was significantly lower (0.32) than the interactions (0.65). Conversely, when the soil was anaerobic, the contribution of single factor to SOC mineralization was much higher (0.76) than the interactions (0.20). When the soil is in anaerobic condition for a long time, the contribution of single factor will gradually increase and the interactions among factors will gradually weaken, further limiting SOC mineralization. In this study, the mechanism of SOC mineralization based on microbial activity in anaerobic and aerobic environment of check dam was reported for the first time, providing theoretical support for understanding the contribution of check dam construction to SOC pool on the Loess Plateau.

Mineralization mechanism of organic carbon in maize rhizosphere soil of soft rock and sand mixed soil under different fertilization modes.

This article endeavors to investigate the influence of various fertilization methods on the characteristics of rhizosphere soil and organic carbon mineralization in the mixed soil of Mu Us Sandy land under maize cultivation, with the objective of laying the groundwork for low-carbon agriculture and the development of high-quality farmland. The research focuses on soft rock and sand composite soil with a 1:2 ratio, and it comprises four treatments: no fertilization (CK), only chemical fertilization (CF), only cattle manure application (MF), and only oil residue application (DF). The findings revealed that the use of organic fertilizer substantially elevated nutrient content and enzyme activity in the maize rhizosphere soil. Furthermore, it had a notable influence on both soil aggregate diameter and stability. Specifically, the DF treatment led to a significant increase in both soil aggregate diameter and stability. The mineralization rate of organic carbon in the maize rhizosphere soil could be categorized into two distinct phases: a rapid initial decline followed by a slower release. By the end of the incubation period, the cumulative mineralization of organic carbon in the MF, DF, and CF treatments showed a significant increase of 119.87%, 57.57%, and 24.15%, respectively, in comparison to the CK treatment. Additionally, the mineralization rate constants of the DF and MF treatments experienced a substantial rise, with increments of 23.52% and 45.97%, respectively, when contrasted with the CK treatment. The bacterial phyla Actinobacteriota, Proteobacteria, Chloroflexi, Acidobacteriota, and Firmicutes were dominant in the rhizosphere soil bacterial community. Specific genera such as Nocardioides and Sphingomonas showed significant correlations with organic carbon mineralization. The application of different organic fertilizer can improve soil physical, chemical and biological properties, and promote the mineralization process of organic carbon in maize rhizosphere soil. Notably, the DF treatment exhibited the most favorable outcome, improving the overall quality of maize rhizosphere soil while incurring a minimal loss of unit organic carbon. These findings hold significant implications for optimizing field management practices and augmenting soil quality.

Phosphorus addition accelerates soil organic carbon mineralization by desorbing organic carbon and increasing microbial activity in subtropical forest soils

The magnitude and direction of soil organic carbon (SOC) mineralization are closely regulated by exogenous nutrient addition – and, especially, by limited nutrients such as phosphorus (P) – in tropical and subtropical ecosystems. However, the response of SOC decomposition to P addition and the underlying mechanisms operating in subtropical P-limited forest soils remain unclear. In this study, four subtropical forest soils (sandstone and granite soils planted with the chinkapin Castanopsis carlesii and Cunninghamia lanceolata (Chinese fir)) in Sanming City, Fujian Province, China were selected, and an incubation experiment with three levels (0, 0.1, 0.6 mg P g−1 soil) of P addition was conducted to explore the impact of P addition on SOC mineralization in subtropical forest soils. SOC mineralization, phospholipid fatty acids (PLFAs), enzymatic activities, and soil properties were determined. Results showed that P addition significantly increased the cumulative mineralization of SOC (P < 0.001). Additionally, the microbial biomass (e.g., fungal, bacterial, and total PLFAs) and the activities of C-cycling enzymes significantly increased (by 11.95 %–570.25 %) after P addition (P < 0.001), which suggests that exogenous P input enhanced microbial activity and thus accelerating SOC mineralization. P addition also significantly increased the concentration of dissolved organic C (DOC) (P < 0.001), thereby making soil C more available to microorganisms and allowing it to become quickly decomposed. A variance partitioning analysis (VPA) showed that DOC and fungal biomass acted as the predominant abiotic and biotic factors accelerating SOC mineralization under P addition. Using the results of a partial least squares path analysis (PLM-PM), we conclude that P addition stimulated the decomposition of SOC in these subtropical P-limited forest soils. Two processes help explain these results: (i) the enhancement of microbial activity in response to the alleviation of microbial P limitation and (ii) the fact that P addition desorbed the microbial inaccessible organic C and converting it into DOC, which is easily accessible to microbes, thereby contributing to SOC mineralization. Our study reveals how P input influences organic C mineralization in subtropical forest soils where P is limited. It also provides novel insight into the uncertainty of the global soil C sink, which might be partially attributable to exogenous nutrient inputs, especially in the case of limiting nutrients.

Soil aggregate-associated organic carbon mineralization and its driving factors in rhizosphere soil

Understanding the determinants of soil carbon mineralization at both the aggregate and rhizosphere levels is crucial for providing precise feedback on climate change. However, the specific patterns and relative contributions of rhizosphere effects on carbon mineralization at the aggregate scale remain unclear. To address this, we conducted an incubation experiment to examine the impact of warming on soil carbon mineralization. We also assessed variations in microbial activities and soil properties across different aggregates in both rhizosphere and non-rhizosphere soils, while exploring how the rhizosphere effects modulated the response of soil respiration to warming. Our findings revealed that rhizosphere soil provides a favorable environment for microbial activities through increased nutrient input and aggregate stability, leading to significant increases in microbial biomass and enzyme activity, thus promoting soil carbon mineralization. Moreover, the spatial heterogeneity of soil aggregates contributes to the differentiation and diversity of microbial community distribution, which further enhances the diversification of carbon mineralization at the aggregate level. Notably, macroaggregates play a significant role in soil carbon flux, making a substantial contribution to carbon turnover in the ecosystem. The partial least squares (PLS) path analysis indicated that the rhizosphere positively increased the contributions of soil properties and microbial variables to the overall amount of soil cumulative mineralization, with soil nutrients playing a crucial role among these factors. These findings highlight the complex regulatory role of substrate quality in soil carbon mineralization dynamics at the aggregate scale, underscoring its far-reaching implications for accurately predicting the feedback to climate change in soil carbon mineralization.

Effect of platy gangue minerals in sulfide flotation: Part I-transport rates

Observations from operating flotation plants suggest that the presence of the platy gangue mineral mica leads to significantly reduced concentrate grades. The combined effects of gangue particle shape (platy vs globular) and particle size on flotation has not been systematically investigated. Flotation tests were conducted on ground ore mixed with different amounts of sized mica (platy) or silica (globular) minerals. This essentially allowed us to alter the already present non-sulfide gangue (NSG) composition in a controlled manner and to investigate gangue size and shape effects on flotation recovery. The use of purposefully added mineral particles with narrow size distributions improved our ability to determine the different pathways by which hydrophilic particles of various sizes and shapes are transported through the froth. Cumulative mineral and water recovery data for each composition was used to calculate the degree of NSG entrainment for each ore plus adulterant (mica or silica). Analysis of the degree of entrainment vs adulterant particle size and shape showed that the addition of mica typically results in higher gangue recovery compared to when silica is added at comparable concentrations. The data for recovery when mica was added followed a trend associated with typical entrainment behavior, i.e., there was a decrease in the degree of entrainment with increasing mica particle size up to about 100μ. However, for greater mica size fractions, an increase in the degree of entrainment was observed. The reason for this behavior is discussed in the part II companion to this paper (Bhambhani, T., Farinato, R., Somasundaran, P., Nagaraj, D., 2022. Effect of play gangue minerals in sulfide flotation: Part 2: Mechanisms, Submitted to Minerals Engineering). The entrainment effects of mica were also evidenced to be concentration dependent. For coarser fractions of mica added to the ore pulp, where the degree of entrainment now increases with mica size, an increase in concentration of mica in that pulp resulted in a steeper increase in the degree of entrainment with mica particle size. This suggested second-order effects arising from particle-particle interactions. Similar results were seen with silica; however, deviations in the degree of entrainment vs particle size plots were less pronounced or required greater concentrations to be seen.

Effects of tillage management on cbbL-carrying bacteria and soil organic carbon dynamics across aggregate size classes in the farmland of North China Plain

Calvin-Benson-Bassham cycle (cbbL)-carrying bacteria in soil are essential to renew and circulate organic matter. However, the relation between cbbL-carrying bacteria and soil carbon dynamics under tillage managements, especially across the aggregate size remains unclear. Thus, in our study, soil organic carbon (SOC) storages, mineralization, and the cbbL-carrying bacterial community across five soil aggregate sizes were thoroughly investigated under four tillage treatments: conventional rotary tillage (CT), deep plowing (DP), subsoiling (SS), no-tillage (NT). We found macroaggregates (>2 mm) contributed most with regard to SOC stocks, whereas microaggregates (<0.25 mm) contributed the least among all the tillage managements (NT, DP, SS and CT). Macroaggregates (>1 mm) with the highest cumulative SOC mineralization were found in subsoiling, whereas microaggregates had the lowest cumulative mineralization under no-tillage. By physically protecting, no-tillage specifically inhibited carbon dioxide (CO2) emissions in macroaggregates (>1 mm), whereas increased SOC levels and encouraged CO2 releases across microaggregates. Shifts in the co-occurrence network demonstrated that subsoiling promoted the joint symbiotic function between cbbL-carrying bacteria, the efficiency of matter and energy, and information transfer. And the keystone species, the enhanced cooperation and stochastic processes of autotrophic microorganisms under subsoiling lead to increased carbon fixation and reduced CO2 emissions in microaggregates with limited oxygen and nutrients. Overall, our work verified physical protection of large aggregates under no-tillage and improvement of microbial interaction efficiency under subsoiling. This may offer a theoretical foundation for the choice of tillage practices in fluvo-aquic soil regions.

Geochemical internal variations of Salem Dolerite dykes from Southern Granulite Terrane: Implications of petrogenetic processes in the dyke conduits

&#x0D; &#x0D; &#x0D; Salem dolerites were collected across the dyke from various parts of the studied area for identifying the differentiation process of magma in the conduits from the compositional profile. The thick dolerites show NNW-SSE, NE-SW, and NW-SE trends. The studied dyke shows systematic composition increasing and decreasing in the chilled margin and centre of the dyke as the texture and concentration of plagioclase and pyroxene increase. Chilled margins show microcrystalline to intersertal, and the centre of the dyke show sub ophitic textures. The compatible oxide MgO, element Ni and the Mg number (100Mg/(Mg+FeT)) increased and the incompatible oxides TiO2, P2O5, and elements Zr decreased from the chilled margin to the centre of the dyke in the compositional profile show reverse fractionation trends (opposite to fractional crystallization) in the studied dykes except for Seeliyampatti dyke. The Seeliyampatti dolerites show opposite compositional variations indicating a normal fractionation trend from the other dykes of the study area. The reverse fractional trends in dykes resulting in the progressive increase of cumulate minerals growth against the dyke wall called the «cumulate process», however, the normal fractional trend in Seeliyampatti resulting in the progressive increase of more evolved magma successively removes the early chilled margin and fills the thick dyke with less compatible and more incompatible components toward the centre of the dyke. Although the normal trend in thick dyke considered the exceptional liquid process of magma differentiation that was formed more like fractional crystallization. Factor analysis also supports the differentiation process of magma. The first factor accounts total variance of 57.68% showing the positively loaded incompatible element and negatively loaded compatible elements.&#x0D; &#x0D; &#x0D;