Total Phosphorus Concentrations Research Articles

Optimization of a real municipal sewage treatment plant using CRFSMA algorithm and a mathematical model

This study presents the development, calibration, and validation of a mathematical model tailored for biological wastewater treatment at an actual urban sanitation facility. Utilizing multi-criteria optimization techniques, the research identified the most effective MCO algorithm by assessing Pareto optimal solutions. The model incorporated three primary performance measures energy consumption, overall volume, mean quality of effluent, and optimized 12 process parameters. Three algorithms, CRFSMA, particle swarm algorithm, and adaptive non-dominated sorting genetic algorithm III, were rigorously tested using MATLAB. The CRFSMA method emerged as superior, achieving enhanced Pareto optimal solutions for three-dimensional optimization. Quantitative improvements were observed with a 14.8 % increase in wastewater quality and reductions in total nitrogen (TN), chemical oxygen demand (COD), total phosphorus (TP), and ammonium nitrogen (NH4+-N) concentrations by 0.95, 2.38, 0.04, and 0.14 mg/L, respectively. Additionally, the total cost index and overall volume were decreased, contributing to an 18.27 % reduction in overall volume and an 18.83 % decrease in energy utilization. The adapted anaerobic-anoxic-Oxic (A2O) framework, based on real-world wastewater treatment plants, demonstrated compatibility with observed effluent variables, signifying the potential for energy savings, emission reductions, and urban sanitation enhancements.

Forms and Migration Mechanisms of Phosphorus in the Ice, Water, and Sediments of Cold and Arid Lakes.

Phosphorus (P) is a crucial nutrient in lake ecosystems and organic phosphorus (Po) is a significant component. However, the distribution characteristics and migration behaviour of Po in ice-water-sediment systems under freezing and thawing conditions in cold and arid regions remain unclear. This study aims to investigate the forms of Po and its contribution to endogenous P pollution. We selected three lakes (Dai, Hu, and Wu Lake) and employed phosphorus nuclear magnetic resonance (31P-NMR) techniques to analyse the following: (1) The total phosphorus (TP) content, which was the highest in the water from Dai Lake (0.16 mg/L), with substantial seasonal variation observed in Wu Lake, where P content was four times higher in summer than in winter because of farmland drainage. (2) Eutrophication analysis, which indicated that Dai Lake had significantly higher eutrophication levels than Wu Lake, with P being the controlling factor in Dai Lake and both N and P in Wu Lake. The proportion of Po in the TP content was 90%, 70%, and 55% for Wu, Dai, and Hu Lake, respectively, indicating that Po was the main component of eutrophic lakes. (3) 31P-NMR, which revealed that orthophosphate (Ortho-P) and monoester phosphate (Mon-P) were the main P components in the winter, with a higher P content in Dai Lake. Ortho-P has a higher content in ice, indicating that inorganic phosphorus (Pi) migration is the main factor in ice-water media. Mon-P showed multiple peaks in Dai Lake, indicating a complex composition of adenosine monophosphate and glucose-1-phosphate. (4) The ice-water phase change simulation experiments, which showed that phosphate was the least repelled in ice, while pyrophosphate (Pyro-P) and macromolecular P were more repelled. Adding sediment enhanced the migration of P but did not change the repulsion of macromolecular P, suggesting the molecular structure as the main influencing factor. These results provide important scientific evidence for the quantitative analysis of Po pollution in lake water environments, aiding in P load reduction and risk prevention and control.

Response of runoff N and P concentrations, losses, and stoichiometry to rainfall amount category, multisource fertilization, and straw return in sloping croplands

Nitrogen (N) and phosphorus (P) losses via runoff from sloping croplands are a major threat to the degradations of soil fertility and water quality worldwide. Rainfall amount category and agricultural practices, such as multisource fertilization and straw return, are key factors regulating nutrient loss via runoff in sloping croplands. Yet, the impacts of these factors on N and P losses via runoff remain elusive. This study investigated the responses of N and P in runoff to rainfall amount category, multisource fertilization, and the combination of multisource fertilization and straw return in sloping cropland with a radish and maize rotation during multiple natural rainfall events between 2019 and 2021. Three agricultural treatments (three replications for each), i.e., local traditional fertilization (CK), multisource fertilization (T1), and a combination of T1 and straw return (T2), were applied on nine 8 m × 3 m plots. The concentrations and losses of total nitrogen (TN), total phosphorus (TP), dissolved nitrogen (DN), dissolved phosphorus (DP), particulate nitrogen (PN) and particulate phosphorus (PP) and their paired stoichiometries in runoff were determined. The runoff depth during rainstorms was similar to that in large rainstorms and was 191.1 % and 178.7 % higher than in moderate and heavy rains, respectively (p < 0.05). The PN concentration was the highest during moderate rain, and the highest concentrations of TP and DP were observed during large rainstorms (p < 0.05). Rainstorms and large rainstorms produced higher runoff losses for PN, TP, DP, and PP than for other rainfall amount categories (p < 0.05). Compared to CK, the runoff depth was marginally reduced by 4.2 % and 12.7 % in T1 and T2, respectively, and the concentrations and losses of N and P in runoff also slightly increased in T1 and T2. The DN and DP losses accounted for 70.5 % and 59.8 % of the TN and TP losses across all treatments, respectively, indicating that the dissolved forms played a dominant role in nutrient loss via runoff. TN:TP (77:1) in runoff was higher than the Redfield ratio (16:1) across all treatments, implying a stoichiometric potential for P depletion in the runoff. Our results highlight the potential risk of N and P losses in dissolved form via runoff regulated by rainfall, multisource fertilization and straw return in sloping croplands.

Effects of mulching and flooding on soil nutrients and bacterial community structure under Phyllostachys praecox

Phyllostachys praecox is a shallow-rooted bamboo that often encounters hypoxia conditions which could be induced by long-term organic material mulching or flooding. It is important to uncover the effect of mulching and flooding on soil nutrient, ammonia-oxidizing microbes, and bacterial diversity. We set up field pot experiments with three treatments (control, mulching, and flooding) under P. praecox. Mulching or flooding altered soil conditions significantly, and both increased ammonium-nitrogen (NH4+-N), total phosphorus (TP), available P (AP), and available potassium (AK) concentrations, and decreased oxygen (O2) concentrations over control. Flooding increased pH and decreased nitrate-nitrogen (NO3−-N), while mulching decreased soil pH and NO3−-N. As O2 content decreased, archaeal 16S rRNA, amoA gene copies of ammonia-oxidizing archaea (AOA) and ammonia oxidizing bacteria (AOB) increased. Mulching and flooding decreased Shannon, ACE and Chao 1 diversity when compared with the control, and as the O2 contents decreased, bacterial diversity decreased. Redundancy Analysis revealed O2, NO3−-N, AK, AP, and pH were the major factors driving bacterial community structure. Correlation Analysis showed AK and O2 contents were highly correlated with bacterial community structure. In addition, structural equation modeling indicated that O2 facilitated efficient soil N use mainly through soil pH, AK content, and bacterial diversity. Mulching or flooding exerted great effects on environment factor and bacterial community structure, which could be exploited to facilitate the regulation of soil O2 conditions for sustainable P. praecox production.

Palaeoenvironmental and palaeoclimatic study of the Olazagutia (Spain) and Ten Mile Creek-Arbor Park (USA) sections during the Coniacian–Santonian interval

The mechanisms and palaeoenvironmental conditions leading to and occurring through the Coniacian–Santonian Ocean Anoxic Event 3 (OAE3) are poorly known, particularly with regard to the marine phosphorus cycle and the climatic conditions in general. To explore these issues further, two famous locations have been studied, Olazagutia (Spain) and Ten Mile Creek–Arbor Park (TX, USA), which are located in different palaeogeographical areas and deposited at different palaeodepths. The study of these two locations is based on mineralogy (bulk and clay), geochemistry (stable isotopes, organic matter, phosphorus and major element) and high-resolution biostratigraphy (nannofossils) to infer changes in climate and primary productivity across OAE3. The investigated sections were both previously proposed as candidates for the base Santonian global boundary stratotype section and point (GSSP). The Olazagutia section was ratified in 2013, where the base of the Santonian was defined by the first appearance datum of the inoceramid Platyceramus undulatoplicatus . Both sections, deposited in oxygenated conditions, record the δ 13 C patterns which characterized the Coniacian–Santonian OAE3 interval, in particular the positive carbon-isotope excursions comprising the K2, Michel Dean and Bedwell events. New nannofossil biostratigraphy for both sections is presented including new occurrences. Significant diachronism of marker taxa is observed between the Spanish and Texan sections. Based on a weathering index and mineralogy, similar climate changes are observed in all sections. The climate shifted synchronously from relatively drier to warmer and wetter conditions above the Coniacian–Santonian boundary from the Michel Dean event to above the Bedwell event during the early Santonian. Fluctuations in total phosphorus contents appear mainly to have been driven by changes in detrital input and consequently by climate change in Spain and Texas. Several bentonite layers were observed in Texas close to the Coniacian–Santonian boundary, but only one located 7 m above the Coniacian–Santonian boundary provided sufficient well-preserved zircon minerals, and gives an age of 86.24 ± 0.12 Ma based on U–Pb geochronology, consistent with an early Santonian age.

Effect of biochar and inorganic fertilizer on the quality of beetroot (Beta vulgaris L.) in Kenya

Despite its health benefits, the production and quality of beetroot is still low in Kenya due to the application of non-recommended rates of fertiliser and soil amendment. This research aimed at contributing to the improvement of the beetroot quality in Kenya. It was designed to determine the effects of biochar and NPK (17-17-17) on the quality of beetroot in Kenya. An RCBD factorial experiment was conducted at Egerton University farm, Kenya, for two seasons. Biochar (0, 5, 10 t/ha) and NPK (0, 200, 300 and 400 kg/ha) were applied together before planting. Data were collected on beetroot diameter, total phenolics, total soluble solids, calcium, iron and phosphorus contents and analysed using SAS statistical software. The co-application of biochar and NPK significantly (p≤0.05) increased the beetroot diameter, iron, calcium, phosphorus, TSS and phenolics content in season two and not in season one. The sole application of biochar showed a significant increase in the iron content of beetroot in season one. However, biochar did not have a significant effect on beetroot diameter, mineral content, TSS and phenolics content of beetroot in season two. The sole application of NPK at 200, 300 and 400 kg/ha significantly (p≤0.05) increased the diameter of beetroot and iron content in both seasons one and two and also significantly improved the calcium and phosphorus content in season two. These NPK levels were not statistically different from each other, but different from the control. It is therefore recommended to apply NPK and biochar for quality beetroot.

Split application of phosphorus fertilizer increased wheat grain weight under post-anthesis drought stress by delaying programmed cell death of endosperm

Drought is one of the important factors affecting wheat yield. However, the effect of split application of phosphorus fertilizer on the programmed cell death (PCD) of wheat endosperm cells under different post-anthesis water treatments is still unclear. In this study, three phosphorus fertilization methods (P1, all phosphorus fertilizer was applied at the spring green-up stage; P2, 50 % and 50 % of phosphorus fertilizer were applied at the spring green-up stage and jointing stage, respectively; P3, 40 %, 30 %, and 30 % of phosphorus fertilizer were applied at the spring green-up, jointing, and grain filling stages, respectively) were designed. Besides, two post-anthesis water treatments were designed: WT, full irrigation treatment; DT, drought stress treatment. Then, the effects of P1, P2, and P3 treatments on the endosperm cell development, nuclear number, nuclease activity, DNA fragmentation, DNA content, grain weight, and phosphorus content of winter wheat variety “Xindong 23” under WT and DT conditions were determined at different stages after anthesis. The results showed that under WT and DT conditions, the degree of nuclear deformation and nuclear membrane depression in P3 treatment was milder than that in P1 and P2 treatments. The ACPase amount in P3 treatment was more than that in P1 and P2 treatments. The number of endosperm nuclei in P3 treatment was higher than that in P1 and P2 treatments. Under DT condition, the endosperm DNA content of wheat grains collected 14–35 days post anthesis (DPA) in P3 treatment increased, and the peak time of genomic DNA fragmentation in P3 treatment was later, compared with those in P1 treatment. Under DT condition, the grain weight and grouting rate in P3 treatment were higher than those of P1 treatment at 7–28 DPA, and the 1000-grain weight of P3 was the highest under both WT and DT conditions, reaching 47.03 and 40.57 g, respectively. Under WT and DT conditions, compared with P1 treatment, the protein content change rate (3.16 % and 5.59 %, respectively) and the total phosphorus content change rate (34.36 % and 35.08 %, respectively) of wheat grains in P3 treatment were the highest. In summary, under the DT condition, split application of phosphorus fertilizer (P3, spring green-up stage stage: jointing stage: filling stage = 4: 3: 3) could increase the phosphorus uptake and utilization of wheat plants and grains, suppress the DNA fragmentation of endosperm cells, and delay the deformation and disintegration of nuclei, which ultimately delayed the PCD in endosperm and realized high grain weight and protein content.

Groundwater inputs could be a significant but often overlooked source of phosphorus in lake ecosystems

Freshwater lakes are severely threatened, due largely to excess inputs of nutrients and other contaminants. Phosphorus (P) is receiving renewed attention due to recent increases in toxic cyanobacteria blooms in lakes worldwide. We investigated groundwater seepage for its role in P loading dynamics at Oneida Lake, New York, USA—one of the most well-studied lakes globally. P loading was measured at representative sites along the 88 km shoreline over three summers by directly measuring groundwater flow using seepage meters and porewater samplers. Groundwater seepage was a continuous and significant source of dissolved P over the summer months, comparable to tributary sources to the lake during that time. This constant input has enriched the concentrations of P in the nearshore surface waters, significantly above levels in the pelagic zone. Pore Total Phosphorus (TP) concentrations and loads reached extremely high values (up to 100 mg/L), with inorganic P representing only ~ 10% of TP per site. Groundwater seepage flows and P loadings were highly variable across space and time, partially explained by adjacent land uses and precipitation. Our research concludes that groundwater seepage is a significant, but overlooked, source of dissolved P and a crucial factor driving summer primary production at Oneida Lake, and likely other temperate lakes.

Soil phosphorus cycling microbial functional genes of monoculture and mixed plantations of native tree species in subtropical China.

Transforming coniferous plantation into broadleaved or mixed broadleaved-coniferous plantations is the tendency of forest management strategies in subtropical China. However, the effects of this conversion on soil phosphorus (P) cycling microbial functional genes are still unknown. Soil samples were collected from 0-20, 20-40, and 40-60 cm (topsoil, middle layer, and subsoil, respectively) under coniferous Pinus massoniana (PM), broadleaved Erythrophleum fordii (EF), and their mixed (PM/EF) plantation in subtropical China. Used metagenomic sequencing to examine the alterations of relative abundances and molecular ecological network structure of soil P-cycling functional genes after the conversion of plantations. The composition of P-cycling genes in the topsoil of PM stand was significantly different from that of PM/EF and EF stands (p < 0.05), and total phosphorus (TP) was the main factor causing this difference. After transforming PM plantation into EF plantation, the relative abundances of P solubilization and mineralization genes significantly increased in the topsoil and middle layer with the decrease of soil TP content. The abundances of P-starvation response regulation genes also significantly increased in the subsoil (p < 0.05), which may have been influenced by soil organic carbon (SOC). The dominant genes in all soil layers under three plantations were phoR, glpP, gcd, ppk, and ppx. Transforming PM into EF plantation apparently increased gcd abundance in the topsoil (p < 0.05), with TP and NO3 --N being the main influencing factors. After transforming PM into PM/EF plantations, the molecular ecological network structure of P-cycling genes was more complex; moreover, the key genes in the network were modified with the transformation of PM plantation. Transforming PM into EF plantation mainly improved the phosphate solubilizing potential of microorganisms at topsoil, while transforming PM into PM/EF plantation may have enhanced structural stability of microbial P-cycling genes react to environmental changes.

Effects of different afforestation years on soil moisture and nutrient content in Maxian Mountain of the Loess Plateau

In the area of “returning farmland to forest” on the Loess Plateau in China, it is difficult to cultivate artificially planted trees into forests. In the current study, abandoned cultivated land after 10 years of natural restoration served as controls (CK), while the treatments included afforestation periods of 2, 4, 6, 8, and 10 years. Soil samples were collected from various depths: 0–20, 20–40, 40–60, 60–80, to 80–100 cm. The findings revealed that with increasing years of artificial afforestation, soil pH gradually increased, and soil moisture content rose in the 0–20 cm layer while declining in deeper layers (20–100 cm) in the Maxian Mountain region of the Loess Plateau. Moreover, the total carbon, nitrogen, phosphorus, and potassium content initially increased and then decreased with the duration of artificial afforestation, reaching peak values after 8 years. Contents of organic matter, ammonium nitrogen, nitrate nitrogen, available phosphorus, and available potassium in the same soil layer increased with each year of afforestation. However, upon reaching 10 years of artificial afforestation, the effective nutrient content in the 60–80 and 80–100 cm soil layers exhibited a decrease. The values of Integrated Fertility Index (IFI) in different afforestation years were ranked as follows: 8 years > 6 years > 10 years > 4 years > 2 year, but all of them were significantly smaller than those of natural restoration plot CK (P < 0.05). Overall, soil fertility in the Maxian Mountain area of the Loess Plateau increases with each additional year of artificial afforestation. However, when the artificial afforestation period is 10 years, soil fertility decreases and marking a shift from enhancement to decline beyond this duration.

Study on Soil Fertility Characteristics of Walnut Orchards with Different Parent Materials and Soil Types in Gyaca County, Tibet

Walnut trees on the Tibetan Plateau have sustainable and nutritious characteristics. They grow naturally without the use of any chemical fertilizers and pesticides. Therefore, the soil fertility of walnut orchards is a key factor influencing walnut yield and quality. This experiment measured and analyzed the basic soil nutrient content, microbial biomass carbon (MBC), nitrogen (MBN), phosphorus (MBP), and leaf nutrient indicators in five types of representative walnut orchard soil parent materials in Gyaca County to clarify the fertility characteristics of different soil types and their correlations with walnut nutrients, providing a basis for the sustainable development of the plateau walnut industry. The results showed that there were significant differences in soil organic matter (SOM), total nitrogen (TN), available nutrient contents, and microbial activity among soil types with different parent materials. The comprehensive representation of available nutrient levels in the soils is as follows: gray-cinnamon soil and calcareous alluvial soil &gt; mountain meadow soil &gt; plateau prairie soil and brush prairie soil. The average MBC, MBN, and MBP contents in the five soils were 368.8 mg/kg, 28.4 mg/kg, and 23.6 mg/kg, respectively, and the content in the topsoil (0–20 cm) was higher than that of the subsoil (20–40 cm). The total nitrogen (PN), total phosphorus (PP), and total potassium (PK) contents in walnut leaves were found to be closely related to the soil physicochemical properties and microbial activity, among which five indicators, including soil TN, available nitrogen (AN), SOM, MBC, and slowly available potassium (SAK), had the greatest impact on leaf nutrient levels. These findings are valuable for the future management and development of walnut orchards. Therefore, for different soil parent materials and soil types, improving the soil fertility and actively applying nitrogen-rich organic fertilizers should be prioritized to improve the yield and quality of Tibetan Plateau walnuts.

Study on the Effect of Magnesium Chloride-Modified Straw Waste Biochar on Acidic Soil Properties.

Soil biochar is a kind of organic matter rich in carbon, which is of great significance in soil fertility improvement, fertilizer type innovation and greenhouse gas emission reduction. In this paper, Mg-modified biochar was prepared by thermal cracking using rice straw and corn straw as raw materials. The Mg-modified biochar and unmodified biochar were fully mixed with prepared soil samples at the addition amounts of 0.5% (w/w), 1% (w/w) and 2% (w/w), respectively, and then simulated indoor soil cultivation experiments were carried out. The effects of magnesium ion-modified biochar and non-modified biochar on soil chemical properties and the effects of different amounts of biochar on soil properties were studied. The results showed that the yield of Mg-modified biochar from rice straw and corn straw, prepared by pyrolysis, was 65%, and the ash content was large. The pH of MG-modified corn stalk biochar (MCBC) is weakly basic (8.55), while the pH of MG-modified rice stalk biochar (MRBC) is basic (10.1), and their internal structures are slightly different. After the application of biochar prepared from rice straw and maize stover, soil indicators were determined. Compared to the control, the chemical properties of the treated soil samples were significantly improved, with an increase in soil pH, an increase in the content of effective nutrients, such as fast-acting potassium, fast-acting phosphorus and alkaline dissolved nitrogen, and an increase in the content of the total phosphorus and total nitrogen, as well as an increase in the content of organic matter. The Mg-modified biochar was generally superior to the unmodified biochar in improving soil fertility, at the same addition level. It was also found that the rice-straw biochar performed better than the corn-stover biochar and had a more obvious effect on soil improvement in terms of fast-acting potassium, ammonium nitrogen, nitrate nitrogen, total phosphorus and total nitrogen contents.

Interaction Effects of Vegetation and Soil Factors on Microbial Communities in Alpine Steppe Under Degradation

To clarify the regulating effect of vegetation and soil factors on microbial communities in the alpine steppe under degradation on the Qinghai-Xizang Plateau, the alpine steppe in the Sanjiangyuan area of the Qinghai-Tibet Plateau was chosen. We analyzed the differences in vegetation and soil factors in different stages of degradation （non-degradation, moderate degradation, and severe degradation） and detected the variations in microbial community characteristics in the alpine steppe under different degradation stages using high-throughput sequencing technology. Eventually, redundancy analysis （RDA） and multiple regression matrixes （MRM） based on the similarity or dissimilarity matrix were used to identify key environmental factors regulating microbial （bacterial and fungal） community changes under degradation. The results showed that the degradation of the alpine steppe significantly changed the community coverage, height, biomass, and important value of graminae； significantly reduced the contents of soil organic matter, total nitrogen, total phosphorus, and silt； and increased the soil bulk density and sand content. Degradation did not change the composition of bacteria and fungi, but their composition proportions changed and also resulted in the loss of microbial richness （Chao1 index and Richness index） but did not significantly change the microbial diversity （Shannon index）. With the occurrence of degradation, the vegetation characteristics, soil physicochemical properties, and microbial diversity showed a consistent change trend. Combined with the characteristics of the network topology changes （the number of nodes and clustering coefficient significantly decreased）, it was found that degradation of the alpine steppe led to the decline of interspecies interactions, decentralization of network, and homogenization of microorganisms, but the cooperation relations among the species were maintained （positive correlation connections accounted for more than 90% in all degradation stages）. Under the alpine steppe degradation, the vegetation-soil interaction had the greatest effect on soil bacterial community, whereas soil physicochemical properties had the greatest influence on soil fungal community. Specifically, vegetation community height, biomass, and soil bulk density were the mutual factors regulating soil microorganisms, whereas the vegetation Simpson index, important value of graminae, soil total phosphorus, total potassium, and silt content were the unique factors affecting the soil bacterial community, and soil pH and total nitrogen content were the particular factors affecting the soil fungal community.

Effects of Different Microbial Fertilizers on Soil Quality and Maize Yield in Coastal Saline Soil

Microbial fertilizers have the characteristics of high efficiency and environmental protection in improving saline soils, and the application of functional microbial fertilizers is of great significance for the green abatement of saline barriers and the improvement of soil quality in coastal areas. The experiment was based on moderately saline soil in the coastal area of Hebei Province, with corn as the indicator crop, on the basis of conventional chemical fertilizer application. Different microbial fertilizer treatments, namely, T1 （conventional chemical fertilizer 750 kg·hm-2 + compound microbial agent 75 kg·hm-2）, T2 （conventional chemical fertilizer 750 kg·hm-2 + Bacillus megaterium 300 kg·hm-2）, T3 （conventional chemical fertilizer 750 kg·hm-2 + B. mucilaginosus 300 kg·hm-2）, T4 （conventional chemical fertilizer 750 kg·hm-2 + organic silicon fertilizer 600 kg·hm-2）, T5 （conventional chemical fertilizer 750 kg·hm-2 + bio-organic fertilizer 600 kg·hm-2）, T6 （conventional fertilizer 750 kg·hm-2 + active microalgae 15 kg·hm-2）, and CK （only fertilizer 750 kg·hm-2）, were used for these seven treatments, to study the effects of different microbial fertilizers on soil nutrients, salinity, bacterial community, and corn yield and economic efficiency during two critical periods （V12 stage and maturity stage） of corn. The results showed that compared with that in CK, T1 significantly increased soil total nitrogen （TN） and available phosphorus （AP） contents during the whole growth period. Over the whole reproductive period, soil organic matter （OM） at maturity increased by 10.35% over the V12 stage compared to that in CK, but there was no significant difference between treatments. Compared with that in CK, T5 and T6 significantly reduced soil total salinity and Ca2+ content during the whole growth period by an average of 14.51%-18.48% and 24.25%-25.51%. T1 significantly increased the bacterial diversity index over the whole growth period by 45.16% compared to that in CK. The dominant soil phyla were Actinobacteria, Proteobacteria, Acidobacteria, and Chloroflexi, and the dominant genera were Bacillus and Geminicoccaceae. The most abundant functions of the bacterial community in the study area were chemoheterotrophy and aerobic chemoheterotrophy, with average relative abundances of 28.89% and 27.11%, and T3 and T6 significantly improved soil N cycling function. The results of redundancy analysis （RDA） indicated that Na+, SO42-, pH, and EC were important factors driving the structure of the bacterial community, and correlation heatmaps showed that Na+, SO42-, pH, and EC were significantly and positively correlated mainly with the phylum Planctomycetota, whereas soil OM and TN were significantly and positively correlated with Cyanobacteria. Compared with that in CK, T6 increased the relative abundance of Cyanobacteria and optimized the bacterial community structure during the whole growth period. Using recommended dosages of bacterial fertilizers T1 and T6 increased maize yield by 7.31%-24.83% and economic efficiency by 9.05%-23.23%, respectively. The preliminary results of soil chemical properties and yield correlation analysis revealed that EC, AP, HCO3-, and Mg2+ were the obstacle factors limiting soil productivity in coastal areas. In conclusion, the use of the compound bacterial agent （T1） and active microalgae （T6） at the recommended dosage can significantly enhance soil nutrients, reduce salinity, and improve the structural diversity of soil bacterial communities, which not only ensures the increase in maize yield and efficiency but also realizes the efficient use of microbial fertilizers and the improvement of soil quality.

Temporal Variations in Aboveground Biomass, Nutrient Content, and Ecological Stoichiometry in Young and Middle-Aged Stands of Chinese Fir Forests.

Understanding the ecological dynamics of forest ecosystems, particularly the influence of forest age structure on soil carbon (C), nitrogen (N), and phosphorus (P) content, is crucial for effective forest management and conservation. This study aimed to investigate the nutrient storage and ecological stoichiometry across different-aged stands of Chinese fir forests. Soil samples were collected from various depths (0-15 cm, 15-30 cm, and 30-45 cm) across four age groups of Chinese fir forests (8-year-old, 12-year-old, 20-year-old, and 25-year-old) in the Forest Farm, Pingjiang County, China. Soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) were measured, and their stoichiometries were calculated. The results showed that both individual tree biomass and stand biomass, along with SOC, TN, and TP content, increased with stand age, highlighting the significant importance of stand age on biomass production and nutrient accumulation in forests. Specifically, soil C and P contents significantly increased as the forest aged, while variation in N content was relatively minor. Soil C/N and C/P ratios exhibited variation corresponding to forest age, suggesting alterations in the ecological stoichiometry characteristics of the forests over time. These findings are crucial for understanding the dynamics of ecosystem functioning and nutrient cycling within Chinese fir forests and provide a solid scientific basis for the effective management and conservation of these vital forest ecosystems.

Biotic and Abiotic Factors Affecting Soil C, N, P and Their Stoichiometries under Different Land-Use Types in a Karst Agricultural Watershed, China

Comprehending the impacts of land-use type on soil nutrition and stoichiometry in watersheds is crucial for effective regional ecosystem management. However, a deeper understanding of the influence of land-use type on soil stoichiometry in karst agricultural watersheds is still lacking. Here, we analyzed the contents, stoichiometries, and drivers of topsoil C, N, and P in a karst agricultural watershed in China, focusing on six land-use types: paddy fields, dry farmland, tussock land, shrubland, shrubby tussock land, and woodland. We found that woodland exhibited significantly higher soil organic carbon (SOC) content than other land-use types except shrubland. Moreover, woodland exhibited the highest total nitrogen (TN) and total phosphorus (TP) contents compared with other land-use types. C/N and N/P ratios did not vary significantly with land-use type, whereas dry farmland (18.68) showed a significantly lower C/P ratio than woodland (39), shrubland (39.92), and paddy fields (34.87). In addition, our results revealed that soil pH, catalase and invertase activity, and bacterial and actinomycetes abundance significantly influenced C, N, and P content and stoichiometry. These findings reveal that interactions between multiple biotic and abiotic factors drive variability in soil stoichiometry, offering valuable insight for land improvement and ecological management in karst agricultural watersheds.

The role of deadwood substrates in promoting moss growth: Decay class and particle size effects

AbstractPlagiomnium acutum has a high value of landscape application and medicinal value, but there is a lack of related research on propagation and cultivation techniques. The deadwood substrate has rich nutrients and superior water retention properties, which will be conducive to promoting the growth of moss. Nevertheless, the underlying mechanisms by which deadwood influences moss growth are not yet fully unclear. In this study, we pulverized deadwood from five decay classes of Pinus massoniana into three distinct particle sizes. Through a pot experiment, we investigated the effects of decay class and physicochemical properties on the growth and physiology of Plagiomnium acutum, aiming to identify the most suitable growth substrate. The results indicated that both the decay class and particle diameter of deadwood significantly affect the substrate's physicochemical characteristics and the growth indexes of P. acutum, with the decay class exerting a more pronounced effect. The water‐holding porosity, water‐holding capacity, total nitrogen, total phosphorus, total potassium and lignin content of the substrate positively affected the growth of P. acutum, while the bulk density, void ratio, total carbon, carbon‐to‐nitrogen ratio, condensed tannin content and cellulose content had negative impacts. A comprehensive evaluation using a fuzzy membership function indicated that deadwood with higher decay classes (IV and V) was more conducive to the growth of P. acutum. Specifically, substrates from decay class IV with particle sizes of 10–20 mm provided the most favorable conditions for P. acutum and were recommended as the optimal cultivation substrate. The results of this study provide theoretical basis and technical support for the propagation and cultivation of P. acutum, and provide a foundation for further development of the industrial, pharmaceutical and environmental biotechnology potential of P. acutum.

Effects of rubber intercropping with native trees on litterfall and litter main nutrient return in Hainan Island, China

Understanding the process of litterfall production is crucial for sustainable development of plantations. However, the underlying dynamics of litterfall and its nutrient return in plantation agroforestry systems remain unclear. In this study, we investigated litterfall, including leaves, branches, flowers, and fruits, in three patterns: Hevea monoculture system (RM), Hevea–Michelia intercropping system (RAS1), and Hevea–Mytilaria intercropping system (RAS2) in Hainan Island, China. Our findings indicate that total litterfall was significantly higher in RAS1 (27,309 kg ha−1) and RAS2 (34,477 kg ha−1) than in RM (22,364 kg ha−1) and was predominantly composed of leaf litterfall in all three patterns, followed by branches, flowers, and fruits. The seasonal dynamics litterfall production of RM, RAS1, and RAS2 showed characteristic patterns. Litterfall nutrients exhibited peak and sub-peak monthly dynamics, peaking from February to March, during the dry season. Total nitrogen (TN), total phosphorus (TP), and total potassium (TK) content of annual litterfall in RAS1 significantly increased by 120 kg ha−1, 30 kg ha−1, and 139 kg ha−1, respectively, compared to those in RM, with percentage increases of 67.88%, 122.79% and 96.27%, respectively. Similarly, TN, TP, and TK content of annual litterfall in RAS2 significantly increased by 185 kg ha−1, 35 kg ha−1, and 170 kg ha−1, respectively, with percentage increases of 103.70%, 159.15% and 139.46%, respectively, for the abovementioned in RM. Litterfall showed a strong correlation with monthly average temperature, monthly minimum temperature, and monthly average wind speed, contributing 80.5%, 75.5%, 69.8%, and 69.6% to the total litterfall and its components, respectively. Further analysis indicated that monthly average temperature, monthly minimum temperature, and monthly average wind speed contributed 73.9%, 43.0%, and 66.6%, respectively, to TN, TP, and TK content of the annual litterfall, highlighting the significant influence of temperature and wind speed. These findings enhance our understanding of carbon and nutrient cycling and contribute to the sustainable management of tropical plantation ecosystems.

The development of fishery-photovoltaic complementary industry and the studies on its environmental, ecological and economic effects in China: A review

The fishery-photovoltaic complementary industry is an emerging industrial model in China that integrates aquaculture with the solar industry. This innovative model involves conducting aquaculture activities while installing photovoltaic modules on the water surface to harness solar energy for electricity generation. However, despite its rapid growth in China, this model lacks substantial scientific data support across various domains. Therefore, based on an analysis of relevant research literature, this study reviews the current development status, environmental and economic effects, as well as challenges faced by the fishery-photovoltaic complementary industry in China. The aim is to provide scientific references for promoting sustainable development within this sector. The findings reveal that existing fishery-photovoltaic complementary industry projects are primarily concentrated in the middle and lower reaches of the Yangtze River and Pearl River Basin. The geographical distribution of these projects is predominantly influenced by local aquaculture areas and available solar energy resources, with a greater impact observed from the former rather than the latter. During summer months when water is shaded by photovoltaic panels, a slight decrease in the average water quality parameters across cases was observed, such as a decrease of 0.2 units in pH, a decrease of 1.06 °C in water temperature, a decrease in dissolved oxygen levels of 0.8 mg/L, inorganic nitrogen content and total phosphorus concentration dropped by 0.08 mg/L and 0.02 mg/L respectively. Conversely, there is a moderate increase noted in total nitrogen and ammonia nitrogen levels. The conclusion of the effect on phytoplankton biomass is not uniform, but it will certainly reduce zooplankton biomass. The impact on the species diversity of the zooplankton community was minimal, and its direction, whether positive or negative, varied depending on the specific aquatic ecosystem. A certain degree of shade is advantageous for the cultivation of shade-loving fish. Through the strategic deployment of photovoltaic panels and the implementation of scientific stocking practices, it is possible to achieve sustained levels of fisheries production. This model also can reduce an average of 978.6 tons of CO2 emissions per megawatt per year through energy production, thus achieving the combined goals of energy conservation and emissions reduction, and ensuring the profitability of power generation. Additionally, compared with the land utilization area of 3.66 hm2 per megawatt of traditional ground-mounted photovoltaics, fishery-photovoltaic complementary only requires 1.64 hm2, which can significantly save land resources by utilizing water surfaces, which mitigates the conflict between land use for agriculture and renewable energy installations. At the same time, research also pointed out that the existence of fishery-photovoltaic complementary will inevitably have some negative impacts on bird communities. Economic analyses indicate that while initial infrastructure costs and long payback periods pose challenges, the overall economic feasibility is promising, especially with governmental support and technological advancements. However, several challenges need to be addressed for further development: these include difficulties associated with infrastructure construction and initial costs, long payback periods; insufficient experience and technical support; as well as a lack of research on ecological and environmental impacts - particularly an urgent need for comprehensive life cycle assessments encompassing both environmental and economic aspects. Future research should focus on life cycle assessments, improved PV technology integration, and optimized aquaculture practices.

Effect of pyrolysis temperature on the transformation of phosphorus forms in sludge biochar

ABSTRACT The Standards, Measurements, and Testing (SMT) phosphorus fractionation approach was used to measure the amounts of total phosphorus (TP), organic phosphorus (OP), inorganic phosphorus (IP), apatite inorganic phosphorus (AP), and non-apatite inorganic phosphorus (NAIP) in sludge biochar. Sludge biochar was characterized using methods such as X-ray diffraction, elemental analysis, and Fourier transform infrared spectroscopy. The findings showed that IP content increased significantly after pyrolysis, reaching up to 97% of TP content at the optimal temperature of 350 °C. Furthermore, when the pyrolysis temperature increased, the AP/IP ratio showed fluctuations between decreases and increases, maximum at 60%. The results of the correlation analysis indicate that IP has a positive correlation with yield, pH, and S elements (p &amp;lt; 0.05) and a negative correlation with N, C, and H elements (p &amp;lt; 0.01). OP, on the other hand, has a positive correlation with H elements (p &amp;lt; 0.05) and a negative correlation with yield (p &amp;lt; 0.01). Furthermore, TP, NAIP, and AP all show negative correlations with N, C, and H elements (p &amp;lt; 0.01), with TP and NAIP also displaying negative correlations with pH and S elements (p &amp;lt; 0.05).