Phosphorus Content Research Articles

Enhanced available phosphorus in paddy fields applying biochar and water-saving irrigation together: the role of alkaline phosphomonoesterase-harboring microorganisms

Organic phosphorus mineralization is one of the important pathways for phosphorus mobilization. However, the level of organic phosphorus mineralization in rice paddies under the coupling of water-saving irrigation and biochar has yet to be determined. To address this knowledge gap, we investigated the interplay between available phosphorus fractions, alkaline phosphomonoesterase activity, and bacterial communities encoding alkaline phosphomonoesterase in water-saving irrigated paddy fields subjected to different biochar applicated rates (0 t ha-1, 20 t ha-1, and 40 t ha-1), compared with a control (flooding irrigation with 0 t ha-1 biochar application). The findings revealed that changes in alkaline phosphomonoesterase activity were linked to variations in phoD gene numbers and the composition of phoD microbial communities. Water-saving irrigation, as opposed to flooding irrigation, notably enhanced the capacity of organic phosphorus mineralization in paddy fields. This enhancement was supported by a 27.94%–45.84% increase in alkaline phosphomonoesterase activity and a 23.00%–36.06% decrease in enzyme-extractable phosphorus in water-saving irrigated paddy fields vs. flooding irrigated paddy fields. Simultaneously, the important role of Firmicutes among phoD-harboring microorganism in water-saving irrigated rice paddies was detected. However, the increased capacity of microbes-mediated organic phosphorus mineralization under the condition of water-saving irrigation alone was insufficient to offset the resulting phosphorus depletion. Biochar could improve the available phosphorus content, which promoted competition among phoD-carrying microorganisms, raising the risk of phosphorus loss. The combined approach of water-saving irrigation and 40 t ha-1 biochar application enhanced the availability of phosphorus and simultaneously mitigated the risk of phosphorus loss, which is proved to be a more suitable field management strategy for paddy fields in southern China.

Evaluation of riboflavin, nanocurcumin, and hydrogen peroxide under light conditions: reduction of mature dental biofilms and enamel mineral loss

BackgroundBiofilms are a potential harbor for many microorganisms. The aim of this study was to test the efficacy of riboflavin (Rib), nano-micelle curcumin (NC), and hydrogen peroxide (HP), alone and in combination with the respective light (light-emitting diode (LED) or 980 nm diode laser) on the reduction of Streptococcus mutans and Lactobacillus acidophilus dual-species biofilms and their effect on the enamel mineral loss. Materials and methodsThe biofilms were formed on saliva-coated enamel slabs. Then, the biofilms were treated with antimicrobial photodynamic therapy (PDT) based on LED, Rib, and NC photosensitizers and with HP also based on a 980 nm diode laser (n = 8 per group). A crystal violet assay was performed to determine the reduction of the dual-species biofilms. The enamel slabs were analyzed for calcium and phosphorus content by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). ResultsWhile HP-PDT showed a reduction of 37% (p < 0.001), PDT with NC resulted in an even greater reduction of dual-species biofilms (40%, p < 0.001) than HP- and Rib-mediated PDT. In the EDX test, no significant difference was found between the control group and the treatment groups. ConclusionsThe use of natural photosensitizers such as NC in PDT has an effect that may be potentially important in reducing caries-causing bacteria.

Advanced data augmentation techniques coupled with enhanced particle swarm optimization for predicting total phosphorus concentrations in limited transmission spectra samples: A case study on the Yangtze River

Advanced data augmentation techniques coupled with enhanced particle swarm optimization for predicting total phosphorus concentrations in limited transmission spectra samples: A case study on the Yangtze River

Development of homemade oral nutrition supplements for individuals with kidney failure on hemodialysis: physicochemical properties, nutrient composition, and sensory evaluation

Purpose Protein-energy wasting is a common complication among patients with kidney failure undergoing dialysis. This study aims to develop a homemade oral nutrition supplement (ONS) to fulfill the energy and protein requirements of these patients. Design/methodology/approach Three formulations of homemade ONS were developed using soybean milk, whey protein isolates and canola oil. Two of these formulations were flavored with pineapple and honeydew juices, respectively. The energy and macronutrient contents were determined using proximate analyses, and mineral contents were determined using inductively coupled plasma optical emission spectroscopy. The acceptance of homemade ONS for five attributes, namely color, taste, odor, consistency and overall acceptability, was assessed using the nine-point hedonic scale. Findings The homemade ONS provided 198–212 kcal and 8.4–9.6 g protein per 100 mL, which were comparable to commercial products. Similarly, the sodium (45–65 mg/100 mL) and phosphorus (56–66 mg/100 mL) contents were on par with commercial products. However, the potassium content of homemade ONS was higher, ranging from 141 to 155 mg per 100 mL. The sensory evaluation indicated that the formulation added with honeydew juice had a similar degree of acceptance as the commercial ONS, while formulations containing pineapple juice and without added fruit juice were less favored. Originality/value A few studies have investigated the development of food products for individuals with kidney failure on dialysis. However, to the best of the authors’ knowledge, this is the first study to focus on developing a homemade ONS specifically tailored to meet the unique nutritional needs of hemodialysis patients. In addition, this research included a comprehensive assessment of the beverage’s nutritional content and sensory attributes.

Control system and process optimization for electroless nickel plating

A novel method based on mid-frequency vibration is proposed to eliminate coating defects such as bubbles during electroless nickel plating. An automated control system for the plating, enabling precise and stable measurements and adjustments of critical parameters such as plating solution temperature, pH, and nickel ion concentration, is also established, which significantly improves process efficiency and coating quality. Experimental results indicate that the system is capable of realizing stable operation over extended periods. A nonporous nickel–phosphorus coating with a thickness greater than 200 μm is successfully obtained, with high phosphorus content, robust adhesion, and superior machinability.

Investigation into Recycling of Iron Oxide Scale on H13 Steel by Low‐Temperature Carbothermal Reduction Method

The current method for recovering iron oxide scale in the steel industry is not economically optimal, especially for high‐alloy scales found in alloyed steel. This study focuses on iron oxide scale containing valuable metals like chromium (Cr), molybdenum (Mo), and vanadium (V). The required carbon addition is calculated based on the iron and chromium oxides in the scale. The effects of varying carbon additions and reduction temperatures on reduction efficiency are thoroughly examined. Kinetic studies show that as temperature and carbon increase, the rate‐limiting step shifts from interfacial diffusion to interfacial reaction. Reduction experiments assess carbon utilization, metallization rate, deoxidation rate, and removal of harmful elements. Results show that high temperatures hinder sulfur (S) and phosphorus (P) removal, and excess carbon reduces carbon utilization efficiency. Optimal conditions are a carbon ratio of 0.2174 and a temperature of 1150 °C. The carbothermic reduction product requires further refinement through conventional ladle slag systems to meet the quality standards for metallic materials. Over 65% of alloying elements are recovered, though phosphorus content remains slightly higher than in finished alloy steel. The materials from this study are suitable as high‐quality intermediates for alloy steel production.

Insights into the Acute Stress of Glutaraldehyde Disinfectant on Short-Term Wet Anaerobic Digestion System of Pig Manure: Dose Response, Performance Variation, and Microbial Community Structure

The outbreak of epidemics such as African swine fever has intensified the use of disinfectants in pig farms, resulting in an increasing residual concentration of disinfectants in environmental media; however, the high-frequency excessive use of disinfectants that damage pig farm manure anaerobic fermentation systems and their mechanisms has not attracted enough attention. Especially, the complex effects of residual disinfectants on anaerobic fermentation systems for pig manure remain poorly understood, thus impeding the application of disinfectants in practical anaerobic fermentation systems. Herein, we explored the effects of glutaraldehyde disinfectant on methane production, effluent physicochemical indices, and microbial communities in a fully automated methanogenic potential test system (AMPTSII). The results show that adding glutaraldehyde led to remarkable alterations in methane production, chemical oxygen demand (COD), volatile solids (VS), and polysaccharide and phosphorus concentrations. During the anaerobic process, the production of methane displayed a notable decrease of 5.0–98% in all glutaraldehyde treatments, and the trend was especially apparent for treatments containing high levels of glutaraldehyde. Comparisons of the effluent quality showed that in the presence of 0.002–0.04% glutaraldehyde, the COD and total phosphorus (TP) increased by 12–310% and 15–27%, respectively. Moreover, the addition of 0.01–0.08% glutaraldehyde decreased the ammonium (NH4+-N) concentration and VS degradation rate by 7.7–15% and 4.9–26.2%. Furthermore, microbiological analysis showed that the glutaraldehyde treatments had adverse effects on the microbial community. Notably, certain functional bacteria were restrained, as highlighted by the decreases in relative abundance and microbial diversity by 1.3–17% and 0.06–21%, respectively. This study provides a theoretical basis for the rational use of disinfectants in anaerobic fermentation systems.

Nutritional differences in eggs, chicken, and plantain from agroecological, conventional, and commercial systems: a case study in Valle del Cauca, Colombia

ABSTRACT This case study examines the nutritional differences between agroecological, conventional, and commercial products in Valle del Cauca, Colombia. Using a participatory methodology with local farmers, eggs, chicken, and plantain were selected for analysis. Moisture, protein, fat, ash, phosphorus, potassium, calcium, and magnesium contents were compared across the three production systems. Statistical analyses included ANOVA and MANOVA. Results indicate that agroecological products from the studied farms tended to have lower moisture content. Agroecological eggs showed higher fat content (11.09 g/100 g vs 9.32 g/100 g conventional and 8.45 g/100 g commercial). Agroecological chicken presented higher protein content (22.37 g/100 g vs 20.73 g/100 g conventional and 18.1 g/100 g commercial) and potassium (281 mg/100 g vs 298 mg/100 g conventional and 213 mg/100 g commercial). Agroecological plantain had higher ash content (0.85 g/100 g vs 0.77 g/100 g conventional and 0.79 g/100 g commercial) and calcium (8 mg/100 g vs 5 mg/100 g conventional and 6 mg/100 g commercial). These differences were statistically significant (p < 0.05). While these findings suggest potential nutritional benefits of agroecological production in this region, further studies with a larger number of replicates are needed to confirm these trends on a broader scale.

Effect of exogenous thermophilic biocontrol agent inoculum on the high temperature chicken manure composting

IntroductionAerobic composting is an effective method for utilizing chicken manure. However, its low carbon to nitrogen (C/N) ratio leads to slow heating and short high-temperature phases, which reduce composting efficiency and product quality.MethodsTo address this issue, splinted mushroom cultivation residues were added to adjust the C/N ratio, and exogenous thermophilic composting strains were introduced to increase composting temperature. This study analyzed the relationship between physicochemical metabolites and microbial community structure during high-temperature chicken manure composting.Results and discussionBased on metagenomic and physicochemical analyses, results showed that the exogenous microbial agents extended the thermophilic phase by three-times, reduced the heating phase duration by 75%, and increased nitrogen, phosphorus, potassium, and soluble organic carbon contents by 3.61, 21.63, 7.21, and 39.03%, respectively. Genes associated with amino acid metabolism were significantly enriched during the heating phase, while genes involved in the tricarboxylic acid cycle were more active in the thermophilic phase. During the thermophilic phase, bacterial diversity and richness decreased compared to the heating and cooling phases. Functional microbes such as Bacillus, Caldicoprobacter, and Virgibacillus showed a positive correlation with the key differential metabolites. While Actinomadura, Saccharomonospora, Paenibacillus, and Aneurinibacillus displayed an opposite correlation. Further experiments demonstrated that the increased temperature during the thermophilic phase triggered the upregulation of oleic acid metabolism and piperidine metabolism pathways in functional microorganisms, leading to the production of heat stabilizers and protective agents like oleic acid, gallic acid, and 2-piperidone. This phenomenon helped maintain microbial viability during the thermophilic phase and improved composting efficiency.

Inoculation with PGPR co-fermented broths promotes growth, yields and quality of pepper by increasing soil nutrients and changing soil bacterial community.

The purpose of this study was to explore impacts of different combinations of co-fermentation PGPR broth on the growth and yield of pepper. The effects of co-fermentation broth containing a random combination of two PGPR strains on the growth of pepper were analyzed. All inoculation treatments promoted growth, yield and quality of peppers. The relative abundance of the dominant Proteobacteria and Sphingomonas was significantly higher in the planted soil at the seedling and fruiting stages, and the soil available nitrogen, phosphorus, and potassium contents were correspondingly higher. In addition, the co-fermented broth of Bacillus velezensis HP9 and Burkholderia pyrrocinia P10 treatment had the most pronounced effect on plant growth, while the combination of Bacillus flexus HGD12 and P10 had the greatest impact on fruit nutritional indices. This is consistent with the highest enrichment of beneficial bacterial genera at the seedling stage in the HP9 and P10 treatment, and at the fruiting stage in the P10 and HGD12 treatment group, respectively. Different combinations of co-fermented bacterial broths increased soil nutrient contents and changed the bacterial community, which in turn promoted the growth, yield and quality of pepper.

Soil Microbial and Metabolomic Shifts Induced by Phosphate-Solubilizing Bacterial Inoculation in Torreya grandis Seedlings

Phosphorus is crucial for plant growth and development, but excess fertilizer not absorbed by plants often binds with metal ions like iron and manganese, forming insoluble compounds that contribute to soil environmental pollution. This study investigates the impact of Burkholderia sp., a phosphate-solubilizing bacterium utilized as a biofertilizer, on the fertility of T. grandis soil, alongside the associated shifts in soil metabolites and their relationship with microbial communities after inoculation. The soil microbial community structures and metabolite profiles were analyzed via amplicon sequencing and high-resolution untargeted metabolomics. The inoculation of phosphate-solubilizing bacteria led to a significant (p &lt; 0.05) enhancement in total phosphorus, potassium, and nitrogen concentrations in the soil, with a marked increase in available phosphorus in bulk soil (p &lt; 0.05). Moreover, the microbial community structure exhibited significant shifts, particularly in the abundance of bacterial phyla such as Acidobacteria, Chloroflexi, Proteobacteria, and the fungal phylum Ascomycota. Metabolomic analysis revealed distinct metabolites, including fatty acids, hormones, amino acids, and drug-related compounds. Key microbial taxa such as Chloroflexi, Proteobacteria, Acidobacteria, Verrucomicrobia, Mucoromycota, and Ascomycota indirectly contributed to soil phosphorus metabolism by influencing these differential metabolites. In conclusion, the application of phosphate-solubilizing bacteria offers an innovative approach to improving soil quality in T. grandis, promoting phosphorus utilization efficiency, and enhancing soil ecosystem health by optimizing microbial communities and metabolite compositions.

Temporal and Spatial Dynamics of Carbon, Nitrogen, and Phosphorus in a Subtropical Urban River (Tamanduateí River, São Paulo, Brazil)

Water quality in urban streams often reflects the broader environmental challenges posed by dense population centers, where pollution from untreated sewage and runoff can significantly degrade ecosystems. This study examines the spatial and temporal variations of carbon, nitrogen, and phosphorus concentrations in the Tamanduateí River, which runs through the Metropolitan Region of São Paulo, Brazil. Data were sourced from the annual reports of the Environmental Company of the State of São Paulo (CETESB) covering the period from 2011 to 2022. Between 2011 and 2017, carbon and phosphorus concentrations declined, likely due to sanitation improvements. However, since 2017, these concentrations have been rising again, indicating renewed pollution inputs, primarily from untreated sewage. Nitrogen levels remained consistently high, with elevated concentrations observed upstream, linked especially to domestic effluent discharges. The recent increase in phosphorus levels is also of concern. The absence of spatial variation in phosphorus suggests diffuse pollution from urban areas, while nitrogen decreases downstream, possibly due to biological assimilation. The study underscores the pressing need for enhanced sewage management. Drawing from the successful revitalization of the Cheonggyecheon stream in Seoul, implementing nature-based solutions and regular maintenance could effectively reduce nutrient pollution and improve water quality, facilitating the restoration of the Tamanduateí River.

Mapping Phosphorus Concentration in Lake Mainit, Philippines Using Landsat 8 OLI and GIS Techniques

Abstract. Lake Mainit is the fourth largest lake in the Philippines and water is one of the most important natural resources for humans and other living organisms. Sensors on satellites can measure the amount of solar radiation absorbed by surface water at different wavelengths, which can be compared with parameters of water quality. This study explored the use of Landsat 8 Operational Land Imager (OLI) and Geographic Information System (GIS) techniques for assessing the Phosphorus (P) content in the lake. Water quality data of Phosphorus from Environmental Management Bureau (EMB) was utilized to correlate with spectral values. Linear forward regression results yielded significant correlation with band combination B2/B4 with an R2 of 55% for Phosphorus (P). The model was then used to map the P content in the lake and was found out that the concentration ranges from 0.0228768 mg/L to 0.23145 mg/L. The study was effective in correlating P content and the bands of Landsat 8 OLI. In addition, GIS techniques were used in extracting spectral values of bands.

Long-term garlic‒maize rotation maintains the stable garlic rhizosphere microecology.

Crop rotation is a sophisticated agricultural practice that can modify the demographic structure and abundance of microorganisms in the soil, stimulate the growth and proliferation of beneficial microorganisms, and inhibit the development of harmful microorganisms. The stability of the rhizosphere microbiome is crucial for maintaining both soil ecosystem vitality and crop prosperity. However, the effects of extended garlic‒maize rotation on the physicochemical characteristics of garlic rhizosphere soil and the stability of its microbiome remain unclear. To investigate this phenomenon, soil samples from the garlic rhizosphere were collected across four different lengths of rotation in a garlic-maize rotation. There were notable positive associations between the total nitrogen and total phosphorus contents in the soil and the duration of rotation. Prolonged rotation could increase the maintenance of microbiome α diversity. The number of years of rotation and the soil organic carbon (SOC) content emerged as principal determinants impacting the evolution of the bacterial community structure, with the SOC content playing a pivotal role in sculpting the species diversity within the garlic rhizosphere bacterial community. Additionally, SOC remains predominant in shaping the root-associated bacterial community's β-nearest taxon index. However, these factors do not have a notable effect on the fungal community inhabiting the garlic rhizosphere. In comparison with monoculture, rotation can amplify the interconnectivity and intricacy of microbial ecological networks. Long-term rotation can further maintain the stability of both microbial ecological networks and interactions between bacterial and fungal communities. It can enlist a plethora of beneficial Bacillus species microorganisms within the garlic rhizosphere to form a biological barricade that aids in safeguarding garlic against encroachment by the pathogenic fungus Fusarium oxysporum, consequently diminishing disease incidence. This study provides a theoretical foundation for the sustainable development of garlic through long-term crop rotation with maize. Our research results indicate that long-term garlic‒maize rotation maintains stable garlic rhizosphere microecology. Our study provides compelling evidence for the role of long-term crop rotation in maintaining microbiota and community stability, emphasizing the importance of cultivating specific beneficial microorganisms to enhance rotation strategies for garlic farming, thereby promoting sustainability in agriculture.

Comparative Analysis of Sewage Sludge Characteristics After Natural Deposition, Accelerated Aging, and Composting

This study investigated treatment methods for urban wastewater sludge, specifically examining natural drying over five years, accelerated freeze–thaw–drying cycles, and composting with and without a zeolite additive. The findings reveal that composting effectively stabilized the sludge while retaining essential nutrients crucial for agriculture. Notably, with the addition of 2% zeolite by total mass, approximately 40% of the total nitrogen was preserved. Adequate aeration during composting maintained acceptable levels of phosphorus compounds, with the phosphorus content expressed as P2O5 showing significant retention compared with the natural drying methods. Composting also demonstrated a substantial reduction in petroleum hydrocarbon concentrations, which decreased from 30 mg/kg to 3 mg/kg, thereby showcasing its potential for processing contaminated sludge. The inclusion of zeolite enhanced the nitrogen retention by an additional 10–20% compared with the composting without zeolite, aligning with previous studies on its effectiveness. While composting and thermal treatments, like accelerated freeze–thaw cycles, influenced the physical properties of the sludge—such as reducing the moisture content and altering the volatile substance concentrations—they did not significantly affect the heavy metal levels. Natural drying over five years resulted in reduced metal quantities, which possibly reflected changes in the wastewater characteristics over time. Given that the heavy metal concentrations remained largely unchanged, additional treatment methods are recommended when the initial sludge contains high levels of these contaminants to ensure the safe use of the final product as fertilizer. This study underscored the significant role of biochemical and microbiological processes during composting and natural drying in transforming sludge properties. Future research should focus on establishing upper contamination thresholds and exploring microbiological safety measures to enhance the viability of sludge reuse in agriculture, balancing nutrient preservation with environmental safety.

Dietary Oregano Oil Supplementation Improved Egg Quality by Altering Cecal Microbiota Function in Laying Hens

Improving egg quality is one of the main objectives of the poultry industry. The objective of this study was to investigate the effects of dietary oregano oil supplementation with different concentrations on the egg quality, intestinal morphology and cecal microbiome of late-phase laying hens. A total of 300 55-week-old Snowy white laying hens were randomly divided into five groups and fed a basal diet (control) or basal diets supplemented with oregano oil at 25, 50, 75 and 100 mg/kg (O25, O50, O75 and O100) over a 100-day period. Compared with the control group, eggshell thickness and eggshell weight were increased significantly in eggs when oregano oil was added (p &lt; 0.05). The highest content of polyunsaturated fatty acids (PUFAs) and C18:2n6c was observed in yolks with 25 mg/kg supplement among 5 groups (p &lt; 0.05). The highest average content of riboflavin in egg yolk and thiamine in egg white was observed in the O25 group (p &lt; 0.05). When the supplemental levels of oregano oil were 25 mg/kg and 50 mg/kg, the selenium and phosphorus content in the egg was significantly increased (p &lt; 0.05). The ratio of villus height to crypt depth (V/C) and villus height of the small intestine was significantly increased compared with the chickens fed the basal diet (p &lt; 0.05). Compared with the control group, the abundance of Megamonas was increased in the O50 group (p &lt; 0.05). The unclassified_o__Bacteroidales in the O25 group were significantly higher than those in the other four groups (p &lt; 0.05). These differential microorganisms were significantly correlated with egg quality characteristics. Dietary supplementation of oregano oil can significantly improve egg quality via gut microbiota alteration in laying hens.

Integrative Transcriptomic and Metabolomic Analysis Reveals Quinoa Leaf Response Mechanisms to Different Phosphorus Concentrations During Filling Stage

Quinoa is an annual self-pollinating plant rich in polyphenols, flavonoids, saponins, and amino acids; its protein balance closely aligns with the ideal recommendation set by the Food and Agriculture Organization. Therefore, quinoa is considered the most suitable “all-nutrient food”. Phosphorus fertilization plays an important role in restricting the growth and development of quinoa; however, the effects of phosphorus fertilizer on quinoa growth remain unclear. Therefore, we conducted metabolome and transcriptome analyses on quinoa leaves during the filling stage, subjecting plants to different doses of phosphorus fertilizer. Overall, phosphorus treatment exerted a significant impact on the phenotypic characteristics of quinoa. Specifically, through a combined analysis of ultra-performance liquid chromatography–tandem mass spectrometry and transcriptome analysis, we identified the alteration and regulation of specific metabolites and genes within flavonoid biosynthesis pathways; this comprehensive evaluation helped elucidate the response mechanism of quinoa leaves during the grouting stage under various phosphorus conditions. Ultimately, the results of this study provide a reference for the selection of quinoa cultivars that exhibit tolerance to low- or high-phosphorus stress; additionally, we offer a theoretical basis for the rational application of phosphorus fertilizer and the enhancement of phosphorus utilization efficiency.

A Systematic Review and Meta-Analysis of the Sustainable Impact of Sewage Sludge Application on Soil Organic Matter and Nutrient Content

The increasing scarcity of natural resources makes the linear production model unsustainable, highlighting the need for more sustainable practices under the umbrella of circular economic principles. Sewage sludge emerges as a promising solution to provide soil organic matter (SOM) and nutrients. This meta-analysis evaluated the impacts of three levels of sludge application (low, medium, and high) on organic matter (OM), nitrogen (N), phosphorus (P), copper (Cu), and zinc (Zn) contents, considering different areas and experimental conditions worldwide. The analysis included 37 studies and 355 comparisons, after screening 7625 records, following the 2020 PRISMA protocol. The effects of sludge concentrations, continents, and types of experiment (field or greenhouse) were evaluated. Sewage sludge application significantly increased OM, N, Cu, and Zn levels, mainly at medium and high rates. The largest effects were observed in greenhouses, suggesting variation by location and environment. Moderators explained a part of the variation in the results, but the residual heterogeneity test revealed that there is still unexplained variability.

Carbon mineralization potential and nutrient dynamics in soils under vegetation types and soil depths at Luot mountain

Soil mineralization is a crucial soil process that improves soil physical properties, enhances carbon sequestration, and provides essential minerals and available nutrients for plant growth. This study was conducted at five vegetation types and soil depths at Luot mountain area, located in VNUF campus, Hanoi city. Samples were incubated in the dark at 25°C and measured at intervals of 1, 2, 5, 10, 15, 25, 35, and 40 days in the laboratory to determine C-CO2 respiration from soils. The study showed that CO2 emissions were highest in topsoils and decreased with deeper soil depths. Mineralized C-CO2 decreased from Shrubs &gt; Acacia + Native species (NS) &gt; Pinus + NS &gt; Native species &gt; Control. CO2 emissions peaked early in the incubation period and then stabilized in the 40-day incubation period. Larger aggregates (≥ 5mm) decreased significantly under most vegetation types, except for Shrubs, where the reduction was minimal. Aggregate size ≥3mm increased post-incubation, notably under Pinus + NS and Native species, with smaller aggregates also increasing slightly. Organic matter content was highest in the topsoil but decreased post-incubation due to microbial C mineralization. There was an increase in soil organic matter at 10-20 cm and 20-40 cm layers after incubation, especially under Shrubs. Available nitrogen slightly increased in soils post-incubation for most vegetation types. Phosphorus content increased post-incubation, peaking under Shrubs, while potassium levels were generally poor but increased during incubation. The study found that C-CO2 mineralization was strongly associated with soil porosity and pH, suggesting that higher porosity and optimal pH enhance mineralization, with organic matter content being crucial for available nutrient cycles in soils.

Vertical variations in enzymatic activity and C:N:P stoichiometry in forest soils under the influence of different tree species

Abstract Tree species play a crucial role in shaping soil properties, significantly influencing nutrient cycling and ecological dynamics within forest ecosystems. In this comprehensive study, we examined the influence of tree species on soil chemistry especially on C/N/P stoichiometry and enzymatic activities across soil profiles. We analyzed soil samples beneath eight distinct tree species at three vertical horizons of soil: organic (O), humus mineral (A), and mineral enrichment (B) horizons. Our study involved detailed assessment of soil carbon, nitrogen, and phosphorus contents, along with the activities of key enzymes: β-glucosidase, N-acetyl-β-glucosaminidase, and phosphatase. The study revealed pronounced vertical stratification in soil properties, significantly influenced by the tree species. General linear models (GLMs) highlighted differences in C: N:P stoichiometry and enzymatic activity across different soil horizons and among tree species. Enzymatic activity was strongly correlated with C, N and P content. The conducted research confirms the distinctiveness of coniferous and deciduous species in terms of C, N and P stoichiometry and the activity of the tested enzymes involved in the C, N and P circulation. These variations are indicative of the intricate interactions between tree species and soil processes. Our findings underscore the role of diversity of trees in modulating soil nutrient dynamics and enzyme-driven processes, which are crucial for understanding soil ecosystem functions and nutrient cycling. This study provides new insights into the role of tree species in shaping the soil environment, offering implications for forest management and conservation strategies. Taking into account the impact of individual tree species covered by the research on the soil, it is worth considering the cultivation of mixed stands.