Disentangling microbial coupled fillers mechanisms for the permeable layer optimization process in multi-soil-layering systems.

The multi-soil-layering (MSL) systems is an emerging solution for environmentally-friendly and cost-effective treatment of decentralized rural domestic wastewater. However, the role of the seemingly simple permeable layer has been overlooked, potentially holding the breakthroughs or directions to addressing suboptimal nitrogen removal performance in MSL systems. In this paper, the mechanism among diverse substrates (zeolite, green zeolite and biological ceramsite) coupled microorganisms in different systems (activated bacterial powder and activated sludge) for rural domestic wastewater purification was investigated. The removal efficiencies performed by zeolite coupled with microorganisms within 3 days were 93.8% for COD, 97.1% for TP, and 98.8% for NH4+-N. Notably, activated sludge showed better nitrification and comprehensive performance than specialized nitrifying bacteria powder. Zeolite attained an impressive 89.4% NH4+-N desorption efficiency, with a substantive fraction of NH4+-N manifesting as exchanged ammonium. High-throughput 16S rRNA gene sequencing revealed that aerobic and parthenogenetic anaerobic bacteria dominated the reactor, with anaerobic bacteria conspicuously absent. And the heterotrophic nitrification-aerobic denitrification (HN-AD) process was significant, with the presence of denitrifying phosphorus-accumulating organisms (DPAOs) for simultaneous nitrogen and phosphorus removal. This study not only raises awareness about the importance of the permeable layer and enhances comprehension of the HN-AD mechanism in MSL systems, but also provides valuable insights for optimizing MSL system construction, operation, and rural domestic wastewater treatment.

Benefits and limits of biological nitrification inhibitors for plant nitrogen uptake and the environment.

Plant growth and high yields are secured by intensive use of nitrogen (N) fertilizer, which, however, pollutes the environment, especially when N is in the form of nitrate. Ammonium is oxidized to nitrate by nitrifiers, but roots can release biological nitrification inhibitors (BNIs). Under what conditions does root-exudation of BNIs facilitate nitrogen N uptake and reduce pollution by N loss to the environment? We modeled the spatial-temporal dynamics of nitrifiers, ammonium, nitrate, and BNIs around a root and simulated root N uptake and net rhizosphere N loss over the plant's life cycle. We determined the sensitivity of N uptake and loss to variations in the parameter values, testing a broad range of soil-plant-microbial conditions, including concentrations, diffusion, sorption, nitrification, population growth, and uptake kinetics. An increase in BNI exudation reduces net N loss and, under most conditions, increases plant N uptake. BNIs decrease uptake in the case of (1) low ammonium concentrations, (2) high ammonium adsorption to the soil, (3) rapid nitrate- or slow ammonium uptake by the plant, and (4) a slowly growing or (5) fast-declining nitrifier population. Bactericidal inhibitors facilitate uptake more than bacteriostatic ones. Some nitrification, however, is necessary to maximize uptake by both ammonium and nitrate transporter systems. An increase in BNI exudation should be co-selected with improved ammonium uptake. BNIs can reduce N uptake, which may explain why not all species exude BNIs but have a generally positive effect on the environment by increasing rhizosphere N retention.

Application of slow-controlled release fertilizer coordinates the carbon flow in carbon-nitrogen metabolism to effect rice quality.

Slow-controlled release fertilizers are experiencing a popularity in rice cultivation due to their effectiveness in yield and quality with low environmental costs. However, the underlying mechanism by which these fertilizers regulate grain quality remains inadequately understood. This study investigated the effects of five fertilizer management practices on rice yield and quality in a two-year field experiment: CK, conventional fertilization, and four applications of slow-controlled release fertilizer (UF, urea formaldehyde; SCU, sulfur-coated urea; PCU, polymer-coated urea; BBF, controlled-release bulk blending fertilizer). In 2020 and 2021, the yields of UF and SCU groups showed significant decreases when compared to conventional fertilization, accompanied by a decline in nutritional quality. Additionally, PCU group exhibited poorer cooking and eating qualities. However, BBF group achieved increases in both yield (10.8 t hm-2 and 11.0 t hm-2) and grain quality reaching the level of CK group. The adequate nitrogen supply in PCU group during the grain-filling stage led to a greater capacity for the accumulation of proteins and amino acids in the PCU group compared to starch accumulation. Intriguingly, BBF group showed better carbon-nitrogen metabolism than that of PCU group. The optimal nitrogen supply present in BBF group suitable boosted the synthesis of amino acids involved in the glycolysis/ tricarboxylic acid cycle, thereby effectively coordinating carbon-nitrogen metabolism. The application of the new slow-controlled release fertilizer, BBF, is advantageous in regulating the carbon flow in the carbon-nitrogen metabolism to enhance rice quality.

Redesigning and validation of fertilizer use in maize for variable plant densities in central rift valley and Jimma in Ethiopia.

Due to low adoption and sub-optimal fertilizer use and planting density recommendation in maize, redesigning and testing these technologies are required. The study was conducted to evaluate redesigned fertilizer use of maize in two pant densities (32,443 and 53,333 plants ha-1 in Central Rift Valley (CRV); 27724 and 62,000 plants ha-1 in Jimma) on farmers' fields in contrasting agro-ecologies of Ethiopia. The on-farm study was conducted in the 2017 and 2018 cropping seasons with 3 × 2 fertilizer and plant density, factors in both regions of Ethiopia. In redesigned fertilizer use, nutrients were estimated based on the target yield. In this study, 40.8, 0.0, and 12.2 kg ha-1 N, P, and K were estimated for the redesigned fertilizer use in CRV (50% of water-limited potential yield (Yw) = 3.1 t ha-1) whereas in Jimma (50% of Yw = 7.5 t ha-1) 149.8, 9, 130.6 kg ha-1 N, P and K were estimated to produce the 50% of Yw. Linear mixed modeling was used to assess the effect of fertilizer-plant density treatments on maize yield and nutrient use efficiency. The result revealed that the average estimated maize yield for WOF, FFU, and RDFU fertilizer treatments were 2.6, 3.6, and 4.5 t ha-1 under current plant density (32,443 plants ha-1) in CRV whereas the average yields of these treatments were 3.2, 4.5 and 4.5 t ha-1 respectively when maize was grown with redesigned plant density (53,333 plants ha-1) in the same location. The average maize yield with WOF, FFU, and RDFU were 3.0, 4.6, and 4.6 t ha-1 with 27,774 plants ha-1 plant density in Jimma whereas the average maize yields over the two seasons with the same treatments were 4.3, 6.0 and 8.0 t ha-1 respectively when the crop is planted with 62,000 plants ha-1 plant density. The RDFU and redesigned plant density resulted in significantly higher yield compared to their respective control CRV but RDFU significantly increased maize yield when it was planted at redesigned (62,000 plant ha-1) in Jimma. FFU and RDFU were economically viable and redesigned plant density was also a cheaper means of improving maize productivity, especially in the Jimma region. Soil organic carbon and N were closely related to the grain yield response of maize compared to other soil factors. In conclusion, this investigation gives an insight into the importance of redesigned fertilizer use and redesigned plant density for improving maize productivity and thereby narrowing the yield gaps of the crop in high maize potential regions in Ethiopia like Jimma.

High biomass yields of Chlorella protinosa with efficient nitrogen removal from secondary effluent in a membrane photobioreactor.

Further treatment of secondary effluents before their discharge into the receiving water bodies could alleviate water eutrophication. In this study, the Chlorella proteinosa was cultured in a membrane photobioreactor to further remove nitrogen from the secondary effluents. The effect of hydraulic retention time (HRT) on microalgae biomass yields and nutrient removal was studied. The results showed that soluble algal products concentration reduced in the suspension at low HRT, thereby alleviating microalgal growth inhibition. In addition, the lower HRT reduced the nitrogen limitation for Chlorella proteinosa's growth through the phase-out of nitrogen-related functional bacteria. As a result, the productivity for Chlorella proteinosa increased from 6.12 mg/L/day at an HRT of 24 hr to 20.18 mg/L/day at an HRT of 8 hr. The highest removal rates of 19.7 mg/L/day, 23.8 mg/L/day, and 105.4 mg/L/day were achieved at an HRT of 8 hr for total nitrogen (TN), ammonia, and chemical oxygen demand (COD), respectively. However, in terms of removal rate, TN and COD were the largest when HRT is 24 hr, which were 74.5% and 82.6% respectively. The maximum removal rate of ammonia nitrogen was 99.2% when HRT was 8 hr.

Enhanced nitrogen removal of the anaerobic ammonia oxidation process by coupling with an efficient nitrate reducing bacterium (Bacillus velezensis M3-1).

Bacillus velezensis M3-1 strain isolated from the sediment of Myriophyllum aquatium constructed wetlands was found to efficiently convert NO3--N to NO2--N, and the requirements for carbon source addition were not very rigorous. This work demonstrates, for the first time, the feasibility of using the synergy of anammox and Bacillus velezensis M3-1 microorganisms for nitrogen removal. In this study, the possibility of M3-1 that converted NO3--N produced by anammox to NO2--N was verified in an anaerobic reactor. The NO3--N reduction ability of M3-1 and denitrifying bacteria in coupling system was investigated under different C/N conditions, and it was found that M3-1 used carbon sources preferentially over denitrifying bacteria. By adjusting the ratio of NH4+-N to NO2--N, it was found that the NO2--N converted from NO3--N by M3-1 participated in the original anammox.The nitrogen removal efficacy (NRE) of the coupled system was increased by 12.1%, compared to the control group anammox system at C/N = 2:1. Functional gene indicated that it might be a nitrate reducing bacterium.This study shows that the nitrate reduction rate achieved by the Bacillus velezensis M3-1 can be high enough for removing nitrate produced by anammox process, which would enable improve nitrogen removal from wastewater.

Patterns and drivers of atmospheric nitrogen deposition retention in global forests.

Forests are the largest carbon sink in terrestrial ecosystems, and the impact of nitrogen (N) deposition on this carbon sink depends on the fate of external N inputs. However, the patterns and driving factors of N retention in different forest compartments remain elusive. In this study, we synthesized 408 observations from global forest 15N tracer experiments to reveal the variation and underlying mechanisms of 15N retention in plants and soils. The results showed that the average total ecosystem 15N retention in global forests was 63.04 ± 1.23%, with the soil pool being the main N sink (45.76 ± 1.29%). Plants absorbed 17.28 ± 0.83% of 15N, with more allocated to leaves (5.83 ± 0.63%) and roots (5.84 ± 0.44%). In subtropical and tropical forests, 15N was mainly absorbed by plants and mineral soils, while the organic soil layer in temperate forests retained more 15N. Additionally, forests retained more N 15 H 4 + $$ {}^{15}\mathrm{N}{\mathrm{H}}_4^{+} $$ than N 15 O 3 - $$ {}^{15}\mathrm{N}{\mathrm{O}}_3^{-} $$ , primarily due to the stronger capacity of the organic soil layer to retain N 15 H 4 + $$ {}^{15}\mathrm{N}{\mathrm{H}}_4^{+} $$ . The mechanisms of 15N retention varied among ecosystem compartments, with total ecosystem 15N retention affected by N deposition. Plant 15N retention was influenced by vegetative and microbial nutrient demands, while soil 15N retention was regulated by climate factors and soil nutrient supply. Overall, this study emphasizes the importance of climate and nutrient supply and demand in regulating forest N retention and provides data to further explore the impacts of N deposition on forest carbon sequestration.

The role of ruminant urine and faeces in the recycling of nutrients by forages.

This study addresses the effect of using animal excreta on the nutritional content of forages, focusing on macro- and micro-element concentrations (nitrogen; N, phosphorus; P, sulphur; S, copper; Cu, zinc; Zn, manganese; Mn, selenium; Se) from animal feed to excreta, soil, and plants. Data were collected from pot and field trials using separate applications of sheep or cattle urine and faeces. Key findings indicate that soil organic carbon (SOC) and the type of excreta significantly influences nutrient uptake by forages, with varied responses among the seven elements defined above. Although urine contributes fewer micronutrients compared to faeces (as applied at a natural volume/mass basis, respectively), it notably improves forage yield and micronutrient accumulation, thus potentially delivering positive consequences at the farm level regarding economic performance and soil fertility when swards upon clayey soil types receive said urine in temperate agro-climatic regions (i.e., South West England in the current context). In contrast, faeces application in isolation hinders Se and Mn uptake, once again potentially delivering unintended consequences such as micronutrient deficiencies in areas of high faeces deposition. As it is unlikely that (b)ovine grazing fields will receive either urine or faeces in isolation, we also explored combined applications of both excreta types which demonstrates synergistic effects on N, Cu, and Zn uptake, with either synergistic or dilution effects being observed for P and S, depending largely on SOC levels. Additionally, interactions between excreta types can result in dilution or antagonistic effects on Mn and Se uptake. Notably, high SOC combined with faeces reduces Mn and Se in forages, raising concerns for grazed ruminant systems under certain biotic situations, e.g., due to insufficient soil Se levels typically observed in UK pastures for livestock growth. These findings underscore the importance of considering SOC and excreta nutritional composition when designing forage management to optimize nutrient uptake. It should be noted that these findings have potential ramifications for broader studies of sustainable agriculture through system-scale analyses, as the granularity of results reported herein elucidate gaps in knowledge which could affect, both positively and negatively, the interpretation of model-based environmental impact assessments of cattle and sheep production (e.g., in the case of increased yields [beneficial] or the requirement of additional synthetic supplementation [detrimental]).

Analysis of the northern pitcher plant (Sarracenia purpurea L.) phytotelm bacteriome throughout a temperate region growing season.

The insectivorous Northern Pitcher Plant, Sarracenia purpurea, recruits a dynamic biotic community in the rainwater collected by its pitcher-shaped leaves. Insect capture and degradation within the pitcher fluid (phytotelma) has been well documented as a mechanism for supplementing the plant's nitrogen, phosphorous, and micronutrient requirements. Metagenomic studies have shown a diverse microbiome in this phytotelm environment, including taxa that contribute metabolically to prey digestion. In this investigation, we used high-throughput 16S rDNA sequencing and bioinformatics to analyze the S. purpurea phytotelm bacteriome as it changes through the growing season (May-September) in plants from the north-central region of the species' native range. Additionally, we used molecular techniques to detect and quantify bacterial nitrogenase genes (nifH) in all phytotelm samples to explore the hypothesis that diazotrophy is an additional mechanism of supplying biologically available nitrogen to S. purpurea. The results of this study indicate that while prokaryote diversity remains relatively stable in plants at different locations within our region, diversity changes significantly as the growing season progresses. Furthermore, nifH genes were detected at biologically significant concentrations in one hundred percent of samples, suggesting that nitrogen fixation may be an important contributor to the S. purpurea nutrient budget.

Improving denitrification estimation by joint inclusion of suspended particles and chlorophyll a in aquaculture ponds.

The denitrification process in aquaculture systems plays a crucial role in nitrogen (N) cycle and N budget estimation. Reliable models are needed to rapidly quantify denitrification rates and assess nitrogen losses. This study conducted a comparative analysis of denitrification rates in fish, crabs, and natural ponds in the Taihu region from March to November 2021, covering a complete aquaculture cycle. The results revealed that aquaculture ponds exhibited higher denitrification rates compared to natural ponds. Key variables influencing denitrification rates were Nitrate nitrogen (NO3--N), Suspended particles (SPS), and chlorophyll a (Chla). There was a significant positive correlation between SPS concentration and denitrification rates. However, we observed that the denitrification rate initially rose with increasing Chla concentration, followed by a subsequent decline. To develop parsimonious models for denitrification rates in aquaculture ponds, we constructed five different statistical models to predict denitrification rates, among which the improved quadratic polynomial regression model (SQPR) that incorporated the three key parameters accounted for 80.7% of the variability in denitrification rates. Additionally, a remote sensing model (RSM) utilizing SPS and Chla explained 43.8% of the variability. The RSM model is particularly valuable for rapid estimation in large regions where remote sensing data are the only available source. This study enhances the understanding of denitrification processes in aquaculture systems, introduces a new model for estimating denitrification in aquaculture ponds, and offers valuable insights for environmental management.

Pyric herbivory decreases soil denitrification despite increased nitrate availability in a temperate grassland.

Pyric herbivory, the combination of controlled burning and targeted grazing, is an effective strategy for restoring abandoned, shrub-encroached rangelands to open ecosystems. This practice may impact soil nitrogen pools by altering soil nitrification and denitrification rates, and may lead to an increase of nitrogen losses through nitrate leaching and N-gas emissions. This research, located in the south-western Pyrenees, investigated the effects of pyric herbivory on soil nitrification and denitrification potentials and mineral nitrogen content in a gorse-encroached temperate rangeland six months after the burning was implemented. The study included three treatments: high-severity burning plus grazing, low-severity burning plus grazing, and unburned and ungrazed areas (control). We measured soil nitrification and denitrification potentials (net and gross), the limitation of denitrifiers by nitrogen or organic carbon, and the abundance of nitrite- and nitrous oxide-reducing bacteria. Additional soil and vegetation data complemented these measurements. Results showed that pyric herbivory did not significantly affect nitrification potential, which was low and highly variable. However, it decreased gross denitrification potential and nitrous oxide reduction to dinitrogen in high-severely burned areas compared to the control. Denitrification rates directly correlated with microbial biomass nitrogen, soil organic carbon, soil water content and abundance of nirS-harbouring bacteria. Contrary to the expected, soil nitrate availability did not directly influence denitrification despite being highest in burned areas. Overall, the study suggests that pyric herbivory does not significantly affect mid-term nitrification rates in temperate open ecosystems, but may decrease denitrification rates in intensely burned areas. These findings highlight the importance of assessing the potential impacts of land management practices, such as pyric herbivory, on soil nutrient cycling and ecosystem functioning.

Development of an integrated fixed-film activated sludge (IFAS) reactor treating landfill leachate for the biological nitrogen removal through nitritation-denitritation.

The current work investigated the performance of an Integrated Fixed-Film Activated Sludge Sequencing Batch Reactor (IFAS-SBR) for Biological Nitrogen Removal (BNR) from mature landfill leachate through the nitritation-denitritation process. During the experimental period two IFAS-SBR configurations were examined using two different biocarrier types with the same filling ratio (50%). The dissolved oxygen (DO) concentration ranged between 2 and 3 mg/L and 4-6 mg/L in the first (baseline-IFAS) and the second (S8-IFAS) setup, respectively. Baseline-IFAS operated for 542 days and demonstrated a high and stable BNR performance maintaining a removal efficiency above 90% under a Nitrogen Loading Rate (NLR) up to 0.45 kg N/m3-d, while S8-IFAS, which operated for 230 days, was characterized by a limited and unstable BNR performance being unable to operate sufficiently under an NLR higher than 0.20 kg N/m3-d. It also experienced a severe inhibition period, when the BNR process was fully deteriorated. Moreover, S8-IFAS suffered from extensive biocarrier stagnant zones and a particularly poor sludge settleability. The attached biomass cultivated in both IFAS configurations had a negligible content of nitrifying bacteria, probably attributed to the insufficient DO diffusion through the biofilm, caused by the low DO concentration in the liquid in the baseline case and the extensive stagnant zones in the S8-IFAS case. As a result of the high biocarrier filling ratio, the S8-IFAS was unstable and low. This was probably attributed to the mass transfer limitations caused by the biocarrier stagnant zones, which hinder substrate and oxygen diffusion, thus reducing the biomass activity and increasing its vulnerability to inhibitory and toxic factors. Hence, the biocarrier filling fraction is a crucial parameter for the efficient operation of the IFAS-SBR and should be carefully selected taking into consideration both the media type and the overall reactor configuration.

Effect of Dietary Crude Protein and Apparent Metabolizable Energy Levels on Growth Performance, Nitrogen Utilization, Serum Parameter, Protein Synthesis, and Amino Acid Metabolism of 1- to 10-Day-Old Male Broilers.

This research compared how different levels of dietary crude protein (CP) and apparent metabolizable energy (AME) affect the growth performance, nitrogen utilization, serum parameters, protein synthesis, and amino acid (AA) metabolism in broilers aged 1 to 10 days. In a 4 × 3 factorial experimental design, the broilers were fed four levels of dietary CP (20%, 21%, 22%, and 23%) and three levels of dietary AME (2800 kcal/kg, 2900 kcal/kg, and 3000 kcal/kg). A total of 936 one-day-old male Arbor Acres broilers were randomly allocated to 12 treatments with 6 replications each. Growth performance, nitrogen utilization, serum parameter, gene expression of protein synthesis, and AA metabolism were evaluated at 10 d. The results revealed no interaction between dietary CP and AME levels on growth performance (p > 0.05). However, 22% and 23% CP enhanced body weight gain (BWG), the feed conversion ratio (FCR), total CP intake, and body protein deposition but had a detrimental effect on the protein efficiency ratio (PER) compared to 20% or 21% CP (p < 0.05). Broilers fed diets with 2800 kcal/kg AME showed increased feed intake (FI) and inferior PER (p < 0.05). Broilers fed diets with 3000 kcal/kg AME showed decreased muscle mRNA expression of mammalian target of the rapamycin (mTOR) and Atrogin-1 compared to those fed diets with 2800 kcal/kg and 2900 kcal/kg AME (p < 0.05). Increasing dietary CP level from 20% to 23% decreased muscle mTOR and increased S6K1 mRNA expression, respectively (p < 0.05). The muscle mRNA expression of Atrogin-1 was highest for broilers fed 23% CP diets (p < 0.05). The mRNA expression of betaine homocysteine methyltransferase (BHMT) and Liver alanine aminotransferase of the 22% and 23% CP groups were higher than those of 20% CP (p < 0.05). Significant interactions between dietary CP and AME levels were observed for muscle AMPK and liver lysine-ketoglutarate reductase (LKR) and branched-chain alpha-keto acid dehydrogenase (BCKDH) mRNA expression (p < 0.05). Dietary AME level had no effect on muscle AMPK mRNA expression for broilers fed 21% and 22% CP diets (p > 0.05), whereas increasing dietary AME levels decreased AMPK mRNA expression for broilers fed 23% CP diets (p < 0.05). The mRNA expression of LKR and BCKDH was highest for broilers fed the diet with 2800 kcal/kg AME and 22% CP, while it was lowest for broilers fed the diet with 3000 kcal/kg AME and 20% CP. The findings suggest that inadequate energy density hindered AA utilization for protein synthesis, leading to increased AA catabolism for broilers aged 1 to 10 days, and a dietary CP level of 22% and an AME level of 2900 to 3000 kcal/kg may be recommended based on performance and dietary protein utilization.

Effects of different carbon and nitrogen sources on liamocin production kinetics of Aureobasidium pullulans NBRC 100716 strain.

Liamocins are molecules with a polyol lipid structure produced by rare strains of Aureobasidium pullulans. In recent years, liamocins have attracted attention due to their antibacterial, anticancer and surface-active properties, and promising potential applications have been identified in the food, agriculture, medical and pharmaceutical industries. This study is the first to investigate the effects of different carbon and nitrogen sources on the growth and liamocin production kinetics of A. pullulans NBRC 100716 strain. This strain was selected among six different A. pullulans strains whose liamocin productions were tested by us for the first time. In fermentations carried out in shaking water baths, the carbon source that most supported the liamocin production of this strain was fructose, and the nitrogen source was peptone-yeast extract combination. In the medium containing fructose and the peptone-yeast extract mixture, A. pullulans NBRC 100716 produced 4.26 g liamocin L-1. The specific liamocin production rate (qp) of the strain in this medium was 0.0090 g liamocin/g mo.h. This study is also the first to produce liamocin with a fructophilic A. pullulans strain. Present findings in this research also demonstrated the excellent biosurfactant capacity of the liamocin produced by this strain. The obtained liamocin reduced the water surface tension to a degree that can compete with synthetic surfactants. Furthermore, this is the first report to reveal that the fatty acid profile of liamocin obtained from A. pullulans NBRC 100716 contains an appreciable amount of unsaturated fatty acids and is similar to the composition of vegetable oil.

ROS and Ca2+ signaling involved in important lipid changes of Chlorella pyrenoidosa under nitrogen stress conditions.

MAIN CONCLUSION: Nitrogen stress altered important lipid parameters and related genes in Chlorella pyrenoidosa via ROS and Ca2+ signaling. The mutual interference between ROS and Ca2+ signaling was also uncovered. The changed mechanisms of lipid parameters (especially lipid classes and unsaturation of fatty acids) in microalgae are not completely well known under nitrogen stress. Therefore, Chlorella pyrenoidosa was exposed to 0, 0.5, 1 and 1.5 g L-1 NaNO3 for 4 days. Then, the physiological and biochemical changes were measured. It was shown that the total lipid contents, neutral lipid ratios as well as their related genes (accD and DGAT) increased obviously while the polar lipid ratios, degrees of unsaturation as well as their related genes (PGP and desC) decreased significantly in nitrogen stress groups. The obvious correlations supported that gene expressions should be the necessary pathways to regulate the lipid changes in C. pyrenoidosa under nitrogen stress. The changes in ROS and Ca2+ signaling as well as their significant correlations with corresponding genes and lipid parameters were analyzed. The results suggested that ROS and Ca2+ may regulate these gene expressions and lipid changes in C. pyrenoidosa under nitrogen stress conditions. This was verified by the subordinate tests with an ROS inhibitor and calcium reagents. It also uncovered the clues of mutual interference between ROS and Ca2+ signaling. To summarize, this study revealed the signaling pathways of important lipid changes in microalgae under N stress.

Tropical root responses to global changes: A synthesis.

Tropical ecosystems face escalating global change. These shifts can disrupt tropical forests' carbon (C) balance and impact root dynamics. Since roots perform essential functions such as resource acquisition and tissue protection, root responses can inform about the strategies and vulnerabilities of ecosystems facing present and future global changes. However, root trait dynamics are poorly understood, especially in tropical ecosystems. We analyzed existing research on tropical root responses to key global change drivers: warming, drought, flooding, cyclones, nitrogen (N) deposition, elevated (e) CO2, and fires. Based on tree species- and community-level literature, we obtained 266 root trait observations from 93 studies across 24 tropical countries. We found differences in the proportion of root responsiveness to global change among different global change drivers but not among root categories. In particular, we observed that tropical root systems responded to warming and eCO2 by increasing root biomass in species-scale studies. Drought increased the root: shoot ratio with no change in root biomass, indicating a decline in aboveground biomass. Despite N deposition being the most studied global change driver, it had some of the most variable effects on root characteristics, with few predictable responses. Episodic disturbances such as cyclones, fires, and flooding consistently resulted in a change in root trait expressions, with cyclones and fires increasing root production, potentially due to shifts in plant community and nutrient inputs, while flooding changed plant regulatory metabolisms due to low oxygen conditions. The data available to date clearly show that tropical forest root characteristics and dynamics are responding to global change, although in ways that are not always predictable. This synthesis indicates the need for replicated studies across root characteristics at species and community scales under different global change factors.

Additive positive effect of warming and elevated nitrogen deposition on Sphagnum biomass production at mid-latitudes.

Global warming and increased atmospheric nitrogen (N) deposition can adversely impact Sphagnum moss populations and ecological functions in peatlands. Based on the anticipated increases in temperature and N levels at global scale, we investigated the effects of simultaneous warming and N treatment on growth and ecophysiological activity of Sphagnum papillosum, a predominant moss at mid-latitudes, utilizing a growth chamber experiment. Warming treatments increased the maximum yield of photosystem II (Fv/Fm) of S. papillosum while decreasing the stable carbon isotope ratio. However, warming treatment alone did not cause significant changes in the biomass increase from that of the control. Regarding N treatment, the low N treatment decreased Fv/Fm under the current temperature but did not affect the biomass increase. In contrast to these results, a simultaneous warming and high N treatment significantly enhanced the biomass production compared to that of the control, exhibiting additive effect of warming and high N treatment on Sphagnum biomass production. These responses were attributed to the improved photosynthetic performances by warming and N treatment. The results of this study contribute to the prediction of Sphagnum responses to warming and changes in N deposition.

Global leaf sulfur stoichiometry and the relationships with nitrogen and phosphorus: phylogeny, growth form and environmental controls.

Sulfur (S) is an essential bioelement with vital roles in serving regulatory and catalytic functions and tightly coupled with N and P in plants. However, globally stoichiometric patterns of leaf S and its relationships to leaf N and P are less well studied. We compiled 31 939 records of leaf-based data for 2600 plant species across 6652 sites worldwide. All plant species were divided into different phylogenetic taxa and growth forms. Standard major axis analysis was employed to fit the bivariate element relationships. A phylogenetic linear mixed-effect model and a multiple-regression model were used to partition the variations of bioelements into phylogeny and environments, and then to estimate the importance of environmental variables. Global geometric mean leaf S, N and P concentrations were 1.44, 15.70 and 1.27 mg g-1, respectively, with significant differences among plant groups. Leaf S-N-P positively correlated with each other, ignoring plant groups. The scaling exponents of LN-LS, LP-LS and LN-LP were 0.64, 0.76 and 0.79, respectively, for all species, but differed among plant groups. Both phylogeny and environments regulated the bioelements. The variability, rather than mean temperature, controlled the bioelements. Phylogeny explained more for the concentrations of all the three bioelements than environments, of which S was the one most affected by phylogenetic taxa.

More diverse rhizobial communities can lead to higher symbiotic nitrogen fixation rates, even in nitrogen-rich soils.

Symbiotic nitrogen (N) fixation (SNF) by legumes and their rhizobial partners is one of the most important sources of bioavailable N to terrestrial ecosystems. While most work on the regulation of SNF has focussed on abiotic drivers such as light, water and soil nutrients, the diversity of rhizobia with which individual legume partners may play an important but under-recognized role in regulating N inputs from SNF. By experimentally manipulating the diversity of rhizobia available to legumes, we demonstrate that rhizobial diversity can increase average SNF rates by more than 90%, and that high rhizobial diversity can induce increased SNF even under conditions of high soil N fertilization. However, the effects of rhizobial diversity, the conditions under which diversity effects were the strongest, and the likely mechanisms driving these diversity effects differed between the two legume species we assessed. These results provide evidence that biodiversity-ecosystem function relationships can occur at the scales of an individual plant and that the effects of rhizobial diversity may be as important as long-established abiotic factors, such as N availability, in driving terrestrial N inputs via SNF.

Soybean molasses can be used as a substitute for corn in grazing beef cattle supplements during the rainy season.

Soybean molasses (SBMO) is a byproduct derived from the production of soy protein concentrate, obtained through solubilization in water and alcohol. The utilization of SBMO as an animal feed ingredient shows promising potential, primarily due to its low cost and as a potential energy concentrate. This study aimed to assess the intake, digestibility, ruminal parameters (pH and ruminal ammonia - NH3), nitrogen retention (NR) and microbial protein synthesis in grazing beef cattle supplemented with SBMO as a substitute for corn during the rainy season. Five Nellore (10-month-old) bulls with an average initial weight of 246 ± 11.2 kg were utilized in a 5 × 5 Latin square design. The animals were housed in five paddocks, each consisting of 0.34 ha of Marandu grass (Urochloa brizantha). Five isonitrogenous protein-energy supplements (300 g crude protein [CP]/kg supplement) were formulated, with SBMO replacing corn at varying levels (0, 0.25, 0.50, 0.75, or 1.00 g-1 g). The supplements were provided daily at a quantity of 2.0 kg-1 animal. The inclusion of SBMO at any level of corn substitution did not significantly affect the intake of pasture dry matter or total dry matter (P > 0.10). Likewise, the intake of CP and, consequently, the ruminal concentration of NH3 did not differ among the SBMO levels. Increasing the inclusion of SBMO did not have a significant impact on NR (P > 0.10), indicating that animals receiving supplements containing 100% SBMO as a substitute for corn may perform similarly to animals receiving supplements with 100% corn (0% SBMO). Soybean molasses represents a viable alternative energy source for grazing beef cattle during the rainy season and can entirely replace corn without adversely affecting animal nutritional performance.