Nitrogen Ratio Research Articles

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.

Impact of chemical oxygen demand to nitrogen ratio on ANAMMOX bacterial growth in an up-flow anaerobic sludge blanket reactor

Impact of chemical oxygen demand to nitrogen ratio on ANAMMOX bacterial growth in an up-flow anaerobic sludge blanket reactor

Nuclear burning in an accretion flow around a stellar-mass black hole embedded within an AGN disk

Abstract A stellar-mass black hole, embedded within the accretion disk of an active galactic nuclei (AGN), has the potential to accrete gas at a rate that can reach approximately ∼109 times the Eddington limit. This study explores the potential for nuclear burning in the rapidly accreting flow towards this black hole and studies how nucleosynthesis affects metal production. Using numerical methods, we have obtained the disk structure while considering nuclear burning and assessed the stability of the disk. In contrast to gas accretion onto the surface of a neutron star or white dwarf, the disk remains stable against the thermal and secular instabilities because advection cooling offsets the nuclear heating effects. The absence of a solid surface for a black hole prevents excessive mass accumulation in the inner disk region. Notably, nuclear fusion predominantly takes place in the inner disk region, resulting in substantial burning of $\rm ^{12}C$ and $\rm ^{3}He$, particularly for black holes around M = 10 M⊙ with accretion rates exceeding approximately ∼107 times the Eddington rate. The ejection of carbon-depleted gas through outflows can lead to an increase in the mass ratio of oxygen or nitrogen to carbon, which may be reflected in observed line ratios such as $\rm N\, V/C\, IV$ and $\rm O\, IV/C\, IV$. Consequently, these elevated spectral line ratios could be interpreted as indications of super-solar metallicity in the broad line region.

Enhancing soil ecosystem multifunctionality through combined conservation tillage and legume-based crop rotation in the North China Plain

Conservation agriculture (CA), based on principles of conservation tillage (CT) and crop rotations, has been adopted as a solution to global climate change. However, interactions between these principles and their cumulative effects on soil functions and crop productivity are not yet fully understood. Herein, a 4-year filed experiment was conducted to assess the impact of CA on soil ecosystem multifunctionality (EMF) in the North China Plain (NCP). The results showed that CA improved EMF by up to 532 % compared to traditional agriculture (rotary tillage under wheat and maize rotation system). This enhancement is mainly driven by a 12.3 % increase in soil organic carbon (SOC) storage, an 8.3 % reduction in soil carbon to nitrogen ratio (C: N), a 68.3 % boost in soil enzyme activities index (SEI), and a 59.7 % increase in available phosphorus (AP) under legume-based crop rotations (LBCR) compared to maize-wheat-maize-wheat (MWMW). The principle of CT improved soil physical structure, enhancing soil aggregate stability by up to 38.1 % compared to rotary tillage (RT). Although, the benefits of CT on crop yield were not always observed, positive interactions on crop yield occurred under LBCR combined with CT. For instance, the soybean-wheat-soybean-wheat (SWSW) rotation produced 40.8 % higher yields than the MWMW rotation under CT. Overall, benefits of CT in improving soil structure, along with the increased diversity crop residues, adjustments in soil nutrient stoichiometric ratios, and enhanced soil enzyme activity under LBCR, led to improved SOC sequestration, crop yield and EMF under CA. The positive interactions between the principles of CA demonstrate its ability to enhance ecosystem multifunctionality. As a result, the combination of CT and LBCR within CA is recommended to sustain the productivity in NCP and other regions with similar conditions.

Nitrogen Storage in Rice: Analysis of Physical Quality by Respiration, Weight, and Storage According to Nitrogen Ratio

Various studies have been conducted to minimize the damage and loss of stored grain. For safe storage, the moisture content must be reduced, or respiration must be suppressed. In this study, grain respiration rates were analyzed under various nitrogen atmospheric conditions, and the quality of stored rice was evaluated. As the nitrogen content of the storage space increases, the respiration rate of the grain decreases accordingly. In this study, the effect of the modified atmospheric nitrogen concentration on reducing respiration was determined. When predicting weight loss due to respiration, low moisture content, and high nitrogen concentration could reduce loss. Quality analysis was performed to compare different respiration rate conditions and showed that lower oxygen concentration and moisture content were associated with safer storage. Our results indicate that changes in atmospheric conditions depending on climate and storage conditions can be considered for the safe storage of harvested rice.

Feedstock optimization with low carbon to nitrogen ratio during algal sludge aerobic composting: Quality and gaseous emissions

This study investigated compost quality and gaseous emissions during the algal sludge composting. The experiment explored the feasibility of low initial carbon to nitrogen (C/N) ratio composting by using different volume ratios of algal sludge and spent mushroom substrates (1:1, 1:2, 1:3, and 1:4, corresponding to C/N ratios of 9.5, 12.3, 14.6, 16.0, respectively). The results showed that increasing the proportion of algal sludge in the initial material led to a longer maturation time and higher nitrogen losses but also enhanced the mineralization of organic nitrogen (converted to NH4+ and NO3-) and reduced carbon losses. The addition of carbon-rich bulking agents within a certain range improved the diversity and interactions of bacterial communities during algal sludge composting. In conclusion, considering the nitrogen and carbon lost, retained, and made available across the four treatments, treatment 3 (C/N = 14.6) appears to be the optimal choice for low C/N composting.

Model-based study of Yarrowia lipolytica cultivation on crude glycerol under different fermentation modes: Development of a membrane bioreactor process.

Batch fermentations of the wild type Yarrowia lipolytica MUCL 28849 were performed in a bench-top bioreactor to assess crucial operating conditions. A setup of carbon to nitrogen (mol/mol) ratio equal to 34, pH = 6.0 and 52 g/L of crude glycerol showed increased lipid production and complete glycerol consumption at t = 24 h, thus, selected for further process improvement. Α semi-continuous process was implemented, where a pH drop to 4.0 at 24 h, interrupted citric acid secretion without affecting lipid production. An in-situ membrane module was employed for membrane bioreactor fermentations, where yeast cells were successfully retained with minimum fouling. The membrane bioreactor fed-batch process, resulted in a high-cell-density culture reaching 49.8 g/L of dry biomass and 4.9 g/L of lipids. An unstructured model was developed and successfully simulated operation under all fermentation modes, distinguishing diverse physiological shifts.

Different nitrogen conditions regulating extracellular polymeric substances and erosion resistance of sewer sediment: Mechanism of microbial metabolism and molecular response

Nitrogen biotransformation plays a vital role in the metabolism of microbial communities in sewers. Extracellular polymeric substances (EPS) secreted by microbial communities can form gel-like sewer sediments, causing clogging of the sewer. However, knowledge on the effects of varying nitrogen conditions on the erosion resistance of sewer sediments and EPS produced by sewer microorganisms is limited. In this study, two typical organic/inorganic nitrogen ratios of sewage were reproduced in simulated sewer reactors, i.e., 3/7 (R1 group) and 7/3 (R2 group). Higher organic nitrogen (ON) concentrations were found to increase the critical erosion shear stress by 26.43%; this was ascribed to increased particle diameter, weakened electrostatic repulsion of sediments and stimulated EPS secretion in the R2 group. The protein and polysaccharide contents of the R2 group were 48.84% and 34.25% higher than those of the R1 group, respectively, which was supported by increased gene abundances for aromatic amino acid synthesis, general secretory pathways of protein, and synthesis of precursors and polysaccharides. Tightly-bound EPS in R2 group exhibited increased contents of hydrophobic protein secondary structures and intermolecular hydrogen bonds, thereby promoting the formation of gel-like sediment structures with enhanced erosion resistance. However, the microbial diversity and the abundance of key genes involved in EPS generation and secretion (e.g., tyrB, yajC, secB, gumF, and gumH) obviously decreased in the R1 group. Moreover, high ON concentrations increased microbial diversity and enhanced microbial glycolysis, tricarboxylic acid cycle and ammonium assimilation. This study reveals the formation mechanisms of EPS in sewer sediments under different nitrogen conditions and their effects on sediment erosion resistance, which contributed to improved sewer system operation and sewer sediment control.

Impact of tetracycline on mixotrophic denitrification process under different sulfur to nitrogen ratios

The sulfur-based autotrophic-heterotrophic denitrification, i.e., mixotrophic denitrification, is suitable for the nitrate and antibiotics removal in aquaculture tailwater at a low COD to nitrogen (C/N) ratio. This study focused on the effect of tetracycline (TC) on mixotrophic denitrification under different S/N ratios. Two bioreactors were simultaneously operated with or without dosing tetracycline under different sulfur to nitrogen (S/N) ratios of 3.94, 4.64 and 5.94. The results showed that the removal rate of total inorganic nitrogen (TIN) increased from 0.25 to 0.69 mg N L−1 min−1 with the rise of S/N ratio, while TC dosage significantly declined the removal efficiency of TIN. Dissimilatory nitrogen reduction to ammonia (DNRA) bacteria was detected when exposing to TC, indicating that DNRA presented more resistance to TC. The removal efficiency of TC in the denitrification system reached the maximum of 22.87 % at S/N of 4.64. Meanwhile the genus Marinicella was detected at this phase, which was conducive to the degradation of organic pollutants. This study found that TC promoted the accumulation of ammonia nitrogen, and had a great effect on sulfur autotrophic bacteria at S/N of 5.94. The removal of TC mainly depended on microbial co-metabolism, and there was a significant correlation between the reduction of TC concentration and the decrease of sulfur compounds (p < 0.05). 4.64 is the best S/N ratio for the mixotrophic denitrification process, which revealed maximum nitrate and TC removal rates.

Benthic foraminifera as bio-indicators of natural and anthropogenic conditions in Roscoff Aber Bay (Brittany, France).

Living benthic foraminifera, known as environmental bio-indicators of both natural and anthropogenic conditions in marine environments, were investigated in the coastal environment of Roscoff Aber Bay (Brittany, France). Eight sampling sites subject to natural variations (freshwater inputs, tides) and/or anthropogenic impacts (pollution, eutrophication) were studied over four seasons in 2021-2022 (November, February, May, August). We sought to understand the spatial distribution of foraminiferal populations within and between sampling sites over the different seasons and to identify sensitive species and those tolerant to anthropogenic impacts. To this end, sedimentary and biogeochemical characteristics of the sediments were examined by measuring grain size, temperature, oxygen, salinity, pH, environmental pigment concentration (chl a and phaeopigments), total organic carbon (TOC), isotopic ratios of carbon (δ13C), nitrogen (δ15N) and sulfide (δ34S), and chl a fluorescence. Considering these parameters as potential driving factors, four environments were distinguished among the sampling sites: open water, terrestrial, oligotrophic and eutrophic. These showed an increasing gradient of organic supply as well as very different microbial activities, highlighted by carbon and sulfide isotopic ratios. Foraminiferal population study revealed the dominant species characterising these main environments. The lowest abundance but highest diversity of foraminifera was found in the harbour site, associated with the dominance of Haynesina germanica, suggesting this species is tolerant to eutrophic environments and anthropogenic impacts. Open water was dominated by Ammonia beccarii and Elphidium crispum, while Quinqueloculina seminula was the most abundant species in the site with the greatest terrestrial influence. Interestingly, the observed organic enrichment of the harbour due to anthropogenic activities (fisheries, waste deposits, etc.) does not seem to significantly affect foraminiferal diversity. Overall, the benthic foraminiferal species in Roscoff Aber Bay appear to be an excellent proxy for marine environmental conditions under various natural and anthropogenic influences.

Kitchen Waste Digestate and Digestate Biochar Fertilizer for Turfgrass Management and Nutrient Leaching

Slow-release fertilizer is generally used in turfgrass management to maintain quality turf without inducing excess vertical growth, to avoid frequent mowing. This study was designed to verify whether kitchen waste digestate and digestate biochar could serve as slow-release fertilizers to promote turf quality and reduce nutrient leaching risk in two turfgrass species over two years in controlled pot experiments. The results showed that the nutrient release of granular fertilizers made from kitchen waste digestate and digestate biochar was a two-phase process (an initial rapid phase, followed by a slow-release phase). The kitchen waste digestate showed higher nitrogen and phosphorus release ratios than the biochar and sheep manure. Compared to the reference sheep manure, fertilization with kitchen waste digestate and biochar increased the leaf chlorophyll content by 48.6% and 27.9%, and reduced senescent leaves by 15.6% and 11.1%, respectively, at 23 d after fertilization, leading to higher turf quality. Fertilization with kitchen waste digestate biochar significantly reduced the nutrient leaching risk compared to fertilization with kitchen waste digestate and sheep manure. Our results demonstrated the potential of reusing kitchen waste digestate and digestate biochar as slow-release fertilizers for promoting turf quality in turfgrass management.

Microstructure evolution and mechanical properties of martensitic stainless bearing steels with different carbon nitrogen ratios

This study investigates the effect of adjusting the carbon nitrogen ratio on the microstructure and mechanical properties of martensitic stainless bearing steels, keeping the equivalent total carbon and nitrogen content. The results demonstrate that the sample with nearly equal weight percentages of C and N exhibits optimal comprehensive performance, achieving impressive yield strength, ultimate tensile strength, and uniform elongation of up to 1806.5 MPa, 2279.3 MPa, and 4.5%, respectively. Distinct phase ratios and morphologies observed across the three C/N ratios after identical heat treatment process suggest varying intrinsic mechanisms due to differences in C and N solid solubility in the matrix. The specimen with almost balanced C and N shows the highest interstitial atom solubility in the austenite phase, stabilizing austenite and lowering stacking fault energy. Abundant fine twins in martensite and stacking faults in austenite contribute to increased elongation without compromising strength. In contrast, specimen with higher N/C ratio exhibits numerous nitrides, limiting N atom solid solution in austenite during austenization, resulting in martensite with twins and dislocations. Specimen with higher C/N ratio shows extensive carbide precipitation and mainly dislocation-type martensite. The study deepens the understanding of C and N interactions in advanced bearing steels and provides a foundation for improving mechanical properties of such steels.

Seasonal and long-term variations of nutrients in Liaodong Bay, China: Influencing factors and ecological effects

Nutrients are essential for marine primary productivity and have a critical role in maintaining the structure and function of marginal. Variations in nutrient levels in sea ecosystems can influence ecological disturbances significantly. The Liaodong Bay (LDB) is a semi-enclosed marginal sea in northern China. It has experienced severe eutrophication since the 1990s, leading to considerable environmental challenges. Understanding of seasonal and long-term nutrient dynamics in the LDB is limited. We examined seasonal datasets collected in May (spring), August (summer), November (autumn), and March (winter) of 2019, and analyzed long-term trends through historical records spanning multiple decades. Nutrients accumulated during autumn/winter but were depleted during spring/summer. A low concentration of dissolved inorganic phosphate led to an increased nitrogen ratio exceeding the Redfield ratio (>16) during winter, spring, and summer, driven by phytoplankton growth. In late-autumn, nutrient concentrations increased, with ratios approaching the Redfield ratio. Phosphorus limitation prevailed in spring, summer, and winter, while silicon limitation dominated in autumn. Dissolved inorganic nitrogen and nitrogen ratios in the LDB increased sharply since the 1980s, peaking before declining after 2013. Dissolved silica and silicon ratios decreased steadily, stabilizing in recent years. These trends imply a shift from nitrogen-to-phosphorus limitation, influenced by riverine inputs and atmospheric deposition. These nutrient fluctuations may have significant ecological effects, including dinoflagellate abundance, algal blooms, and jellyfish blooms. Our analyses highlight the complexity of nutrient dynamics and positive impact of local nutrient-reduction policies implemented in recent years in improving the environmental quality of the LDB.

Four birds with one stone: applying nitrification inhibitor on the basis of percarbamide restores yield, decreases fungicide residue, enhances soil multifunctionality and stimulates bacterial community.

Fungicide residues were frequently detected in vegetables and soils, which severely affected crop yields and qualities. Reasonable nitrogen management might promote yields and decrease fungicide carbendazim residues in plant-soil systems. Current study explores comprehensive relationships among carbendazim residues, crop yields, soil multifunctionalities and endophytic and soil bacterial communities after applying nitrification inhibitors (3,4-dimethylpyrazole phosphate and dicyandiamide) and percarbamide to different soils. Combined nitrification inhibitor and percarbamide additions produced multi-effects on restoring yields, declining fungicide residues, promoting soil multifunctionalities and stimulating bacterial communities. Relative to the control, percarbamide application promoted carbendazim dissipations in upland soils but decreased bacterial community diversities and stabilities in different soils. Compared to exclusive percarbamide, extra dicyandiamide applications decreased carbendazim residues by 25.8% in upland soils and 70.2% in paddy soils, declined carbendazim residues in carrots via improving soil pH, ammonium nitrogen (NH4 +-N) and Proteobacteria ratios. Relative to percarbamide application alone, extra dicyandiamide addition promoted the dry carrot yields by 133.2% in upland soils and 33.5% in paddy soils via promoting soil NH4 +-N, Acidobacteriota and Actinobacteriota ratios and bacterial community diversities and stabilities. Upland soil multifunctionality improvements diminished soil carbendazim residues via promoting soil pH and NH4 +-N, and paddy soil multifunctionalities and endophytic bacterial community structures generated negative influences on carrot carbendazim residues. Our study suggested that nitrification inhibitor on the basis of percarbamide generated multi-effects on the different crop-soil systems: restoring carrot yields, reducing carbendazim contents, promoting soil multifunctionalities and stimulating bacterial community diversities and stabilities. © 2024 Society of Chemical Industry.

Stable isotope ratios indicate trophic niche overlap in three sympatric delphinid species in the Eastern Ionian Sea

AbstractStudying the sympatric ecology of closely related marine top predator species is of interest both from an ecological and conservation standpoint, because it provides insights into ecosystem functioning, how such species avoid competitive exclusion, and how human stressors may impact these patterns. In this study, we examine the isotopic niche of three sympatric dolphin species that inhabit the eastern Ionian Sea: the common dolphin (Delphinus delphis), the striped dolphin (Stenella coeruleoalba), and the common bottlenose dolphin (Tursiops truncatus). We used carbon, nitrogen, and sulfur isotope ratios to construct three‐dimensional isotope niches and calculate niche sizes and their overlaps among the three species to study interspecific competition for resources. Common dolphin niche overlapped with that of the striped dolphin by 77%, suggesting potential resource competition between these two species. The niche overlap between striped/common dolphins and bottlenose dolphins was much lower (47%). Large differences in isotopic ratios were found between the bottlenose dolphins of the Ionian Sea and those of a largely isolated population in the adjacent semienclosed Gulf of Ambracia, further corroborating the previously documented isolation between the two populations.

Multifactorial effects of warming, low irradiance, and low salinity on Arctic kelps

Abstract. The Arctic is projected to warm by 2 to 5 °C by the end of the century. Warming causes melting of glaciers, shrinking of the areas covered by sea ice, and increased terrestrial runoff from snowfields and permafrost thawing. Warming, decreasing coastal underwater irradiance, and lower salinity are potentially threatening polar marine organisms, including kelps, that are key species of hard-bottom shallow communities. The present study investigates the physiological responses of four kelp species (Alaria esculenta, Laminaria digitata, Saccharina latissima, and Hedophyllum nigripes) to these environmental changes through a perturbation experiment in ex situ mesocosms. Kelps were exposed for 6 weeks to four experimental treatments: an unmanipulated control; a warming condition under the CO2 emission scenario SSP5-8.5; and two multifactorial conditions combining warming, low salinity, and low irradiance reproducing the future coastal Arctic exposed to terrestrial runoff under two CO2 emission scenarios (SSP2-4.5 and SSP5-8.5). The physiological effects on A. esculenta, L. digitata, and S. latissima were investigated, and gene expression patterns of S. latissima and H. nigripes were analyzed. Across all species and experimental treatments, growth rates were similar, underlying the acclimation potential of these species to future Arctic conditions. Specimens of A. esculenta increased their chlorophyll a content when exposed to low irradiance conditions, suggesting that they may be resilient to an increase in glacier and river runoff with the potential to become more dominant at greater depths. S. latissima showed a lower carbon : nitrogen (C : N) ratio under the SSP5-8.5 multifactorial conditions' treatment, suggesting tolerance to coastal erosion and permafrost thawing. In contrast, L. digitata showed no response to the conditions tested on any of the investigated physiological parameters. The down-regulation of genes coding for heat-shock proteins in H. nigripes and S. latissima underscores their ability to acclimate to heat stress, which portrays temperature as a key influencing factor. Based on these results, it is expected that kelp communities will undergo changes in species composition that will vary at local scale as a function of the changes in environmental drivers.

Effect of probiotics 'Bio-health' and foliar fertilization with zinc sulfate on growth and yield of okra (Abelmoschus esculentus (L.) Moench)

The experiment was conducted in a private field in Jaflawiya, Al-Mishkhab District, Najaf Governorate, for the spring season 2021, to study the effect of soil application with probiotics Bio health and foliar fertilization with aqueous zinc sulfate on some vegetative growth characteristics and yield of okra Husainawia variety. The experiment was a factorial experiment according to Randomized Complete Block Design (R.C.B.D.) with 2 factors and 3 replicates. The first factor was ground application with probiotics Bio health at 3 levels (0, 2500, 5000 g ha-1) and the second factor is the foliar spraying of zinc in (ZnSO4.7H20) using 3 concentrations (0, 75 and 150 mg L-1). Both factors were applied 3 times during the growing season. The first application was in the stage of 4 true leaves and zinc was sprayed a week later. The second and third were 30 and 60 days after the first addition respectively. Analysis of variance (ANOVA) was performed and the averages were compared using the least significant difference test. Least Significant Difference Test (L.S.D.) at 0.05 probability level. The highest results were recorded in the treatment of adding the Bio health at a level of 5000 g ha-1, which led to the highest rates of vegetative growth indicators, quantitative and qualitative yield and chemical indicators, including plant height, leaf area, knot ratio, number of pods, total yield, nitrogen and phosphorous ratio in pods, zinc content in pods and protein % in pods. In general, the ground application of Bio health at 5000 g ha-1 with zinc 150 mg L-1 significantly outperformed most of the single and interaction treatments. It gave the highest significant increase in vegetative growth indicators, yield, chemical and qualitative indicators.

Utilization of stable isotopes in teeth to investigate pygmy sperm whales (Kogia breviceps) in the southeastern United States

AbstractThe pygmy sperm whale (Kogia breviceps) is currently the second‐most stranded cetacean in the southeastern United States (SEUS), but information concerning their population structure is severely limited. This study used stable isotope analysis to investigate the isotopic niches and population structure of K. breviceps among three regions in the SEUS determined by the distance of the continental shelf break and a fourth region in the Gulf of Mexico. Teeth from stranded individuals were subsampled via dental drill at four separate areas on each tooth, representing four different age classes: calf, juvenile, subadult, and adult. Stable isotope ratios of carbon and nitrogen were measured in the organic component of 42 teeth, and oxygen isotope ratios were measured in the inorganic (hydroxyapatite) component of 19 teeth. No differences were found in δ13C, δ15N, or δ18O values between regions. However, differences between age classes were significant for adults and subadults for δ13C and adults and juveniles for δ15N. Differences between males and females were also significant for δ15N. Results from this study provide the first carbon and nitrogen isotope values from different age classes of pygmy sperm whales as well as the first reported oxygen isotope values for this species.

Seasonal states and carbon dynamics in key areas of the carbon polygon in the Chechen Republic, Russia

The aim of the work was to analyze the relationship between carbon dynamics and changes in the states of natural territorial complexes in two key areas of the carbon polygon in the Chechen Republic from the standpoint of landscape and landscape‐geophysical approaches. The work was carried out at two sites of the carbon polygon in the Chechen Republic: in Chernorechye (the Chechen plain under water‐protective broad‐leaved forests, about 169 m above sea level) and Roshni‐Chu (low‐ mountain broad‐leaved forests, about 450 m above sea level).Methods: landscape‐geophysical description of geomasses, geohorizons and vertical structures in key areas, detailed microclimatic studies using installed loggers with temperature and humidity sensors, observations of the state of the vegetation cover, biomass dynamics, determination of mortmass fractions on the soil surface, as well as humus and basic nutrients.The relationship between carbon dynamics and changes in seasonal states of natural‐territorial complexes is expressed in changes in landscape‐ geophysical parameters: the ratio of geomasses, geohorizons and vertical structures. Seven seasonal states of natural‐territorial complexes with different carbon dynamics have been identified. Two of them are key to understanding the long‐term carbon balance. These states are determined by the dynamics of accumulation and decomposition of mortmass. The ways of changing the intensity of carbon deposition based on the creation of new phytocenoses, increasing soil fertility, including by optimising the carbon and nitrogen ratio have been identified. A more radical way – mortmass utilisation – requires detailed research and consideration of environmental consequences.

Drought Stress, Elevated CO2 and Their Combination Differentially Affect Carbon and Nitrogen in Different Organs of Six Spring Wheat Genotypes

This study aimed to analyze the combined impact of CO2 and drought stress at the flowering stage on carbon (C), nitrogen (N), and CN ratios in leaves, stem, and grains of bread wheat. Six diverse bread wheat genotypes, comprised of two commercial checks, two landraces, and two synthetics derivatives, were grown at two levels of CO2, i.e., 400 ppm and 800 ppm, and drought stress was imposed at the flowering stage through progressive soil drying. Stem, leaf, and grain samples were taken at maturity and concentrations of C and N were determined. Our results indicate that the threshold value of fraction of transpirable soil water (CFTSW) at which it diverges towards closure of stomata was different among genotypes and a higher range of values was estimated under elevated CO2. Drought significantly increased C levels in leaves and N levels in grains but decreased N levels in leaves, which increased CN ratios in leaves. In contrast, drought significantly reduced CN ratios in grains. Genotypes differed significantly in N content in grains, where the landrace derivative L2 maintained the highest N content. Moreover, pronounced changes in leaf N and CN ratios were induced by the combination of elevated CO2 and drought stress. Additionally, combined correlation and biplot analyses indicate a strong positive association of grain CN (GCN) with grain number, weight, and grain yield. These effects possibly interact with drought to strongly interfere with the impact of elevated CO2. The differential performance of the tested genotypes shows that selection of appropriate germplasm is essential to maintain agricultural production.