Search

The sources and sinks of nitrous oxide, as control emissions to the atmosphere, are generally poorly constrained for most environmental systems. Initial depth-resolved analysis of nitrous oxide flux from observation wells and the proximal surface within a nitrate contaminated aquifer system revealed high subsurface production but little escape from the surface. To better understand the environmental controls of production and emission at this site, we used a combination of isotopic, geochemical, and molecular analyses to show that chemodenitrification and bacterial denitrification are major sources of nitrous oxide in this subsurface, where low DO, low pH, and high nitrate are correlated with significant nitrous oxide production. Depth-resolved metagenomes showed that consumption of nitrous oxide near the surface was correlated with an enrichment of Clade II nitrous oxide reducers, consistent with a growing appreciation of their importance in controlling release of nitrous oxide to the atmosphere. Our work also provides evidence for the reduction of nitrous oxide at a pH of 4, well below the generally accepted limit of pH 5.

Global potent greenhouse gas nitrous oxide (N2O) emissions from soil are accelerating, with increases in the proportion of reactive nitrogen emitted as N2O, i.e., N2O emission factor (EF). Yet, the primary controls and underlying mechanisms of EFs remain unresolved. Based on two independent but complementary global syntheses, and three field studies determining effects of acidity on N2O EFs and soil denitrifying microorganisms, we show that soil pH predominantly controls N2O EFs and emissions by affecting the denitrifier community composition. Analysis of 5438 paired data points of N2O emission fluxes revealed a hump-shaped relationship between soil pH and EFs, with the highest EFs occurring in moderately acidic soils that favored N2O-producing over N2O-consuming microorganisms, and induced high N2O emissions. Our results illustrate that soil pH has a unimodal relationship with soil denitrifiers and EFs, and the net N2O emission depends on both the N2O/(N2O + N2) ratio and overall denitrification rate. These findings can inform strategies to predict and mitigate soil N2O emissions under future nitrogen input scenarios.

Methane (CH4) and nitrous oxide (N2O) are major greenhouse gases that are predominantly generated by microbial activities in anoxic environments. N2O inhibition of methanogenesis has been reported, but comprehensive efforts to obtain kinetic information are lacking. Using the model methanogen Methanosarcina barkeri strain Fusaro and digester sludge-derived methanogenic enrichment cultures, we conducted growth yield and kinetic measurements and showed that micromolar concentrations of N2O suppress the growth of methanogens and CH4 production from major methanogenic substrate classes. Acetoclastic methanogenesis, estimated to account for two-thirds of the annual 1 billion metric tons of biogenic CH4, was most sensitive to N2O, with inhibitory constants (KI) in the range of 18-25 μM, followed by hydrogenotrophic (KI, 60-90 μM) and methylotrophic (KI, 110-130 μM) methanogenesis. Dissolved N2O concentrations exceeding these KI values are not uncommon in managed (i.e. fertilized soils and wastewater treatment plants) and unmanaged ecosystems. Future greenhouse gas emissions remain uncertain, particularly from critical zone environments (e.g. thawing permafrost) with large amounts of stored nitrogenous and carbonaceous materials that are experiencing unprecedented warming. Incorporating relevant feedback effects, such as the significant N2O inhibition on methanogenesis, can refine climate models and improve predictive capabilities.

Optimum soil moisture and high crop residue return (RR) can increase the active pool of soil organic carbon and nitrogen, thus modulating the magnitude of greenhouse gas (GHG) fluxes. To determine the effect of soil moisture on the threshold level of RR for the wheat production system, we analyzed the relationship between GHG fluxes and RR at four levels, namely 0, 5, 10, and 15 Mg ha−1 (R0, R5, R10, and R15) under two soil moisture content (80% FC and 100% FC) and three levels of nutrient management (NS0: no nutrient; NS1, NS2= 3x NS1). Nutrient input (N and P) in NS1 balanced the residue C/nutrient stoichiometry to achieve 30% stabilization of the residue C input in RR (R5). All RR treatments (cf. R0) were found to significantly reduce N2O emission in moderate soil moisture content (80% FC) by 22–56% across nutrient management due to enhanced soil C mineralization, microbial biomass carbon, and N immobilization. However, averaged across nutrient management, a linear increase in N2O emission was observed with increasing RR under 100% FC soil moisture. A significant decrease in CH4 emission by ca. 46% in most RR treatments was observed in 100% FC compared with the R0. The N2O emission was negatively correlated (p = <0.001) with nutrient stoichiometry. Partial least square (PLS) regression indicated that GHG emissions were more responsive (values > 0.8) to management variables (RR rate, nitrogen (N) input rate, soil moisture, and nutrient stoichiometry of C: N) and post-incubation soil properties (SMBC and NO3-N) in Alfisols. This study demonstrated that the mechanisms responsible for RR effects on soil N2O, CH4 fluxes, and carbon mineralization depend on soil moisture and nutrient management, shifting the nutrient stoichiometry of residue C: N: P. [ABSTRACT FROM AUTHOR]

Agriculture is the dominant source of anthropogenic nitrous oxide (N2O) –a greenhouse gas and a stratospheric ozone depleting substance. The US Corn Belt is a large global N2O source, but there remain large uncertainties regarding its source attribution and biogeochemical pathways. Here, we interpret high frequency stable N2O isotope observations from a very tall tower to improve our understanding of regional source attribution. We detected significant seasonal variability in δ15Nbulk (6.47–7.33‰) and the isotope site preference (δ15NSP = δ15Nα–δ15Nβ, 18.22–25.19‰) indicating a predominance of denitrification during the growing period but of nitrification during the snowmelt period. Isotope mixing models and atmospheric inversions both indicate that indirect emissions contribute substantially (>35%) to total N2O emissions. Despite the relatively large uncertainties, the upper bound of bottom‐up indirect emission estimates are at the lower bound of the isotopic constraint, implying significant discrepancies that require further investigation. Plain Language Summary: Increasing use of synthetic nitrogen fertilizers for agricultural production is causing higher atmospheric nitrous oxide (N2O) concentrations. Nitrous oxide is a long‐lived greenhouse gas and degrades the protective stratospheric ozone layer. Using tall tower N2O isotope observations from within the US Corn Belt, we examine how different processes (denitrification vs. nitrification) and sources (corn fields vs. wetlands, rivers, and streams) contribute to variations in atmospheric N2O. The findings indicate that a substantial amount of nitrogen leakage from agricultural crops contributes to N2O emissions via indirect sources such as drainage networks. These findings can help inform mitigation strategies targeting nitrogen use and leakage pathways from agricultural systems. Key Points: Seasonality of N2O isotope fingerprint driven by snowmelt and fertilizer inputSnowmelt and growing season emissions dominated by nitrification versus denitrification pathwaysIsotope fingerprints were used to constrain direct and indirect N2O emissions [ABSTRACT FROM AUTHOR]

Our understanding of how rapid Arctic warming and permafrost thaw affect global climate dynamics is restricted by limited spatio-temporal data coverage due to logistical challenges and the complex landscape of Arctic regions. It is therefore crucial to make best use of the available observations, including the integrated data analysis across disciplines and observational platforms. To alleviate the data compilation process for syntheses, cross-scale analyses, earth system models, and remote sensing applications, we introduce ARGO, a new meta-dataset comprised of greenhouse gas observations from various observational platforms across the Arctic and boreal biomes within the polar region of the northern hemisphere. ARGO provides a centralised repository for metadata on carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) measurements linked with an interactive online tool (https://www.bgc-jena.mpg.de/argo/). This tool offers prompt metadata visualisation for the research community. Here, we present the structure and features of ARGO, underscoring its role as a valuable resource for advancing Arctic climate research and guiding synthesis efforts in the face of rapid environmental change in northern regions. The ARGO meta-dataset is openly available for download at Zenodo (https://doi.org/10.5281/zenodo.13870390) (Vogt et al., 2024). [ABSTRACT FROM AUTHOR]

Ammonia-oxidizing archaea (AOA) are key players in the nitrogen cycle and among the most abundant microorganisms in the ocean, thriving even in oxygen-depleted ecosystems. AOA produce the greenhouse gas nitrous oxide (N2O) as a byproduct of ammonia oxidation. Additionally, the recent discovery of a nitric oxide dismutation pathway in the AOA isolate Nitrosopumilus maritimus points toward other N2O production and consumption pathways in AOA. AOA that perform NO dismutation when exposed to oxygen depletion, produce oxygen and dinitrogen as final products. Based on the transient accumulation of N2O coupled with oxygen accumulation, N2O has been proposed as an intermediate in this novel archaeal pathway. In this study, we spiked N2O to oxygen-depleted incubations with pure cultures of two marine AOA isolates that were performing NO dismutation. By using combinations of N compounds with different isotopic signatures (15NO2− pool +44N2O spike and 14NO2− pool +46N2O spike), we evaluated the N2O spike effects on the production of oxygen and the isotopic signature of N2 and N2O. The experiments confirmed that N2O is an intermediate in NO dismutation by AOA, distinguishing it from similar pathways in other microbial clades. Furthermore, we showed that AOA rapidly reduce high concentrations of spiked N2O to N2. These findings advance our understanding of microbial N2O production and consumption in oxygen-depleted settings and highlight AOA as potentially important key players in N2O turnover. [ABSTRACT FROM AUTHOR]

Flooded rice (Oryza sativa L.) systems are critical for global food security but contribute significantly to anthropogenic greenhouse gas (GHG) emissions due to high methane (CH4) emissions from anaerobic soils. Drill‐seeding (DS) rice, which in California includes early‐season irrigation flushes to establish the rice, has been shown to reduce CH4 emissions compared to water‐seeded (WS) systems. The effect of these early‐season flushes on nitrogen (N) fertilizer losses and nitrous oxide (N2O) emissions, however, is not well understood. In a 2‐year study, we quantitatively compared DS to WS systems with respect to their global warming potential (GWP) (CH4 + N2O in CO2 eq.), nitrate (NO3−) accumulation during flushes, and crop N‐uptake. Despite 0.68 kg ha−1 more N2O–N emissions in the DS system, GWP was 3700 CO2 eq. kg ha−1, a 42% reduction compared to 6340 CO2 eq. kg ha−1 in the WS system. This was due to a 46% reduction in CH4 in the DS (94.5 CH4–C kg ha−1) relative to the WS (175.7 CH4–C kg ha−1) system. Nitrate accumulation in the DS system amounted to 26.2 kg NO3–N ha−1, and subsequent N losses via denitrification likely contributed to the 22.4 kg N ha−1 less crop N‐uptake in the DS system. These results suggest that DS rice has potential for improved environmental impact via GWP reductions but will require increased N inputs. Future efforts should focus on reducing N losses, which have a negative economic impact for the farmer and contribute to N2O emissions. [ABSTRACT FROM AUTHOR]

A process for the catalytic reduction of nitrous oxide using NHC‐ligated copper(I) tert‐butoxide precatalysts and B2pin2 as the reductant is reported. These reactions proceed under mild conditions via copper(I)‐boryl intermediates which react with N2O by facile O‐atom insertion into the Cu−B bond and liberate N2. Turnover numbers >800 can be achieved at 80 °C under 1 bar N2O. [ABSTRACT FROM AUTHOR]

Le protoxyde d'azote est découvert par hasard à la fin du XVIIIe siècle. Dès les premières décennies d'utilisation, ce gaz a suscité l'intérêt pour ses propriétés psychodysleptiques, mais aussi de l'inquiétude, pour les cas de folie et les décès qu'il a pu provoquer. Bien qu'il soit bénéfique en médecine pour prévenir la douleur, il fait parler de lui aujourd'hui pour une utilisation excessive sous sa forme pure chez certains jeunes, menant à des complications graves sur le plan somatique et psychiatrique. Tout son potentiel addictogène s'est révélé au fil de ses usages et des découvertes de ses mécanismes d'action. Il agit très vite, provoque une tolérance, et des signes de sevrage apparaissent dès l'arrêt de l'inhalation. Certains se remettent à consommer malgré une période d'abstinence et malgré leurs difficultés à marcher ou à faire face à leurs obligations (travail, études). Ces dernières années, il revient donc sur le devant de la scène médiatique, poussant le pouvoir législatif, judiciaire et les institutions médicales à s'adapter encore à ce vieux gaz. Nitrous oxide (N 2 O) was discovered by chance at the end of the 18th century. While working on nitric acid, the English chemist Joseph Priestley forgot a gas he called "nitrous air" for two months in contact with mercury and iron nails. He thus discovered a new gas which supports combustion, but which is fatal for animals. At that time, few instruments existed, and scientists tasted and inhaled their discoveries to study them. Writers were called upon to test Priestley's air and find the most accurate words to describe its extraordinary effects on the human mind. Humphry Davy, a young English chemist, was passionate about nitrous oxide. He synthesized it late in the evening at the Pneumatic Institute and inhaled it regularly, sometimes with other substances, including wine. In his book Researches, Chemical and Philosophical, chiefly concerning Nitrous Oxide and its Respiration, he specified that his health had deteriorated with the repetition of these experiments from April 1799 to June 1800, evoking disorders similar to what we observe today with the recreational use of N 2 O cartridges. This gas will subsequently inspire poets and philosophers and become popular in circuses and fairs, where it was used to entertain crowds. In the 19th century, in France, a first wave of concern about the use of Nitrous oxide appeared following cases of death and madness among users. In the 20th century, recreational use remained scattered until the 1990s. It circulated at this time, mainly on the party and techno scene where it was inhaled from whipped cream siphon cartridges, using balloons, alone or in combination, to enhance the effect of other substances such as ecstasy for example. Its ability to block NMDA receptor activity makes it a product that modifies perceptions and the coherence of thought: an effect similar to that caused by ketamine. Its medical potential first came to light in dentistry. Horace Wells, an American dentist, attended a public "laughing gas" demonstration. A man who had just inhaled it fell and injured his calf. He showed no pain. The dentist then had the idea of testing it on himself by inhaling nitrous oxide and having his assistant pull out a tooth, with success. Then he used it on his patients for pain-free care. In France, it was Apolloni Pierre Préterre who developed the use of nitrous oxide for dental care. In 1866, he filed a patent for his invention, which synthesized and administered N 2 O for anesthetic purposes. He developed a mask that allowed for the inhalation through the mouth and nose: the use of anesthesia was quickly adopted. However, during the Franco-Prussian War in the 1870s and the subsequent great demand for anesthesia, nitrous oxide was abandoned in favor of chloroform, which was easier to use. Today, its place is essential and unique among the therapeutic options against pain. Its action is rapid, with few side effects. The patient does not need to fast and can quickly return to their usual activities. It is used during painful treatments or in obstetrics instead of or while waiting for an epidural injection to take effect. Currently, several targets have been identified in the body. Nitrous oxide is an agonist of opioid receptors and gabaergic receptors, and an antagonist of glutamate receptors (NMDA receptors). It is therefore both anxiolytic, analgesic and disrupts memory. It is an essential tool for the prevention of pain induced by medical procedures (dental but also sutures, mobilizations, painful washing of children as well as adults and the elderly). Its use in anesthesia makes it possible to limit the use of opioids. However, its effect on climate change is considerable (300 times greater than CO2), and that fact is currently taken into account and it is used less and less in the operating room out of concern for the environment. If Humphry Davy appears to be the first to have used N 2 O to relieve withdrawal symptoms (from alcohol), there is a detailed case in 1972 of a woman suffering from chronic pain and dependent on pentazocine (a powerful synthetic opioid) who was weaned from taking it thanks to N 2 O. From the 1980s on, it was used in alcohol withdrawal by Gillman, but also for cannabis and cocaine addiction. In 2006, the American dentist Alan Blanton described his relationship with nitrous oxide as an addiction. He details in his testimony the phenomenon of tolerance, i.e. the need to increase the dosage to obtain the same effect, and the schemes he put in place to hide his consumption for thirteen years. Contemporary recreational use eventually became part of many students' lives. In 2015, in Lyon, a 22 years old medical student was treated in a Center for Care and Support and Prevention in Addictology. He presented the eleven criteria of the DSM 5 defining substance use disorder. The beginning of its consumption was festive, then for analgesic purposes in the context of an irritable bowel syndrome. His medical history includes several depressive episodes: a vulnerability, which probably favored his addiction to nitrous oxide. This antidepressant effect of N 2 O has been particularly studied by Peter Nagele, in the USA. In 2018, Bourbon estimates that 49% of medical students had experimented with N 2 O. In a study published in April 2021, 77% of the medical students surveyed said they had already inhaled it. In recent years, new modes of delivery have appeared: canisters of around 600 grams of liquefied gas is the most common model. The complications linked to the inhalation of this pure gas in large quantities are increasing. They are neurological, psychiatric but also vascular with thromboses and cases of substance use disorders appearing. Tolerance to this gas develops quickly, as early as 30 minutes, and signs of withdrawal may appear as soon as inhalation stops. Among users who present a first episode of neurological complications, some resume consuming with ensuing cravings, thus demonstrating the addictive power of this substance. Finally, in France and in many other countries, a paradox exists regarding the sale of nitrous oxide. In its pure form used for whipped cream, it is accessible over the counter while the medical form, mixed with oxygen, was included on list 1 of toxic substances and treated similarly to the legislation on narcotics. Legislation on toxic substances therefore had to be adapted. Since 2019, several mayors in France have issued municipal decrees to try to regulate the sale of nitrous oxide to minors and its use on public roads. Then in 2021, under law No. 2021-695 of June 1, its sale is prohibited to minors, and the incitation of a minor to misuse the product to obtain a psychoactive effect is punishable with a fine of €15,000. Finally, since January 2024, sales to individuals are limited to 8.6 g cartridges in packaging not to exceed a total of ten cartridges. On the health front, new recommendations from the ANSM (National Medicines Safety Agency) were disseminated at the beginning of 2023, to improve detection of the use of N 2 O and to manage serious complications arising from its use, and to insist on an assessment of an addictive disorder. [ABSTRACT FROM AUTHOR]

Despite recent advances in treatment options, stroke remains a highly prevalent and devastating condition with significant socioeconomic impact. Recanalization therapies, including intravenous thrombolysis and endovascular treatments, have revolutionized stroke management and prognosis, providing a promising framework for exploring new therapeutic strategies. Endothelial dysfunction plays a critical role in the pathophysiology, progression, and prognosis of stroke. This review aims to synthesize the current evidence regarding the involvement of the nitric oxide (NO)/endothelium pathway in ischemic stroke, with a particular focus on aging, response to recanalization therapies, and therapeutic approaches. While significant progress has been made in recent years in understanding the relationship between endothelial dysfunction and stroke, many uncertainties persist, and although treatments targeting this pathway are promising, they have yet to demonstrate clear clinical benefits. [ABSTRACT FROM AUTHOR]

Manure treatment technologies are of interest to dairy operations to improve nutrient management, although there are little data related to nutrient availability and environmental impacts of these manure‐based fertilizer products. This field trial experiment investigated the impact of two manure‐based fertilizer sources (phosphorus enriched solids [PE] and mechanical vapor recompression solids [VR]) on soil nutrients, crop yields, and N2O emissions in a forage rotation. The study was a factorial random complete block design, with two main factors: manure history (with [M]; without [NM]) and manure‐based fertilizer product (control [Con], PE, VR), under a continuous corn and triticale rotation. M had greater soil organic carbon, total carbon, total nitrogen, and M3‐P (30%–128%) and reduced NH4‐N (15%) than NM, with no other treatment differences. Corn silage yields were greater in NM versus M (7%) treatments only in 2021, while in 2022 VRNM was 17% greater than ConNM only. Triticale yields were 14% greater in M plots versus NM treatments only in 2021. In 2022, triticale yields were 1.7 times lower in ConNM versus all other treatments, and PENM was 71% greater than ConM. The greatest N2O fluxes occurred in May, June, and July with M having 69% greater average cumulative fluxes than NM, while average VR cumulative fluxes were 102% greater than PE and Con. Over both years, net loss of Napplied as N2O‐N was 1.9%–2.2% for VR and 0.4%–0.8% for PE solids. While manure‐based fertilizers performed well as a nutrient source, their susceptibility to N2O loss needs to be considered in management strategies. Core Ideas: Solid manure application had greater effect on soil C and N and crop yields compared to manure‐based fertilizers.Annual cumulative N2O emissions from mechanical recompression solids were 53%–153% greater than other treatments.Average N2O emission factor was greater for mechanical recompression solids (>1.6%) versus P‐enriched solids (<1.0%). Plain Language Summary: Manure treatment technologies can improve nutrient management, though there is little data related to crop and environmental impacts of manure byproducts. We investigated two manure‐based fertilizer sources (Phosphorus Enriched Solids [PE] and Mechanical Vapor Recompression Solids [VR]), and application of solid dairy manure, on soil nutrients, crop yields and N2O emissions. Application of solid dairy manure had greater soil carbon, nitrogen and phosphorus in the topsoil compared to manure‐based fertilizers. There were slight differences in corn silage and triticale yields which were greater in treatments with previous manure application. Over two years, net loss of N applied as N2O‐N was 1.9–2.2% for VR and 0.4–0.8% for PE solids. Nutrient extraction technologies produce manure‐based fertilizer products that are beneficial for crops but may be susceptible to N2O losses, which need to be considered when managing these products. [ABSTRACT FROM AUTHOR]

The Australian dairy industry contributes significantly to the rural economy, but must reduce its greenhouse-gas emissions to remain competitive in a global market that is starting to prioritise a low carbon footprint. Demand for improved environmental, social and governance performance from supply chains creates an imperative for research to deliver options for farmers to make reductions in their environmental footprint. Given the rapidly evolving nature of greenhouse-gas abatement research, this critical review provides an update on the state of the research relevant to Australian dairy systems and identifies research gaps that must be addressed if there is to be widespread on-farm adoption. Current research suggests that Australian dairy farms could theoretically abate enteric methane by 40-50%, with about another 5-10% reduction in wholefarm greenhouse-gas emissions being possible by flocculating or covering stored effluent. Fertiliserand urine-patch management strategies could substantially reduce direct and indirect nitrous oxide emissions, but by variable amounts subject to local conditions. However, few abatement options are currently cost-effective for farmers. Significantly more research investment is required to facilitate the on-farm adoption of strategies, particularly to reduce enteric methane and improve the efficiency of nitrogen cycling. Improved understanding is required of the influences on each strategy's abatement potential and interactions with economically important traits in grazing systems, the effect of combining abatement strategies, and systems by which strategies can be implemented cost-effectively on farms. The challenge for research is to consider how the implementation of cost-effective abatement options can be refined for grazing dairy systems to maintain the position of Australian dairy in the global market. [ABSTRACT FROM AUTHOR]

The interaction of biochar with mineral fertilization has attracted attention as a strategy to reduce N losses and enhance nitrogen use efficiency. In this study, we investigated the coapplication of biochar with two optimized fertilization strategies based on split urea and a microbial inoculant (Azospirillum brasilense) in a commercial pointed white cabbage crop. Additionally, we evaluated a third optimized N fertilization alternative, a biochar‐based fertilizer (BBF) enriched in plant‐available N, which was developed from the same biochar. We assessed environmental impacts such as greenhouse gasses (GHG) and NH3 emissions, yield‐scaled N2O emissions, and global warming potential (GWP). Additionally, we evaluated agronomical outcomes such as crop yield, plant N, and chlorophyll concentration. Moreover, we examined the N‐fixing gene's total and relative abundance (nifH and nifH/16S). Biochar and BBF exhibited similar crop yield, GHG, and NH3 emissions compared to split applications of the synthetic fertilizer. The main difference was associated with the higher soil C sequestration in biochar and BBF treatments that reduced the associated GWP of these fertilization strategies. Finally, biochar favored the activity of the N‐fixing bacteria spread, compared to the sole application of bacteria and BBF demonstrated a promoting effect in the soil's total abundance of natural N‐fixing bacteria. [ABSTRACT FROM AUTHOR]

Background: Many prehospital emergency patients receive suboptimal treatment for their moderate to severe pain. Various factors may contribute. We aim to systematically review literature pertaining to prehospital emergency adult patients with acute pain and the pain‐reducing effects, adverse events (AEs), and safety issues associated with inhaled analgetic agents compared with other prehospital analgesic agents. Methods: As part of an initiative from the Scandinavian Society of Anaesthesia and Intensive Care Medicine, we conducted a systematic review (PROSPERO CRD42018114399), applying the PRISMA guidelines, Grading of Recommendations Assessment, Development, and Evaluation (GRADE), and Cochrane methods, searching the Cochrane Library, Epistemonikos, Centre for Reviews and Dissemination, PubMed, and EMBASE databases (updated March 2024). Inclusion criteria were the use of inhaled analgesic agents in adult patients with acute pain in the prehospital emergency care setting. All steps were performed by minimum of two individual researchers. The primary outcome was pain reduction; secondary outcomes were speed of onset, duration of effect, and relevant AEs. Results: We included seven studies (56,535 patients in total) that compared inhaled agents (methoxyflurane [MF] and nitrous oxide [N2O]) to other drugs or placebo. Study designs were randomized controlled trial (1; n = 60), randomized non‐blinded study (1; n = 343), and randomized open‐label study (1; n = 270). The remaining were prospective or retrospective observational studies. The evidence according to GRADE was of low or very low quality. No combined meta‐analysis was possible. N2O may reduce pain compared to placebo, but not compared to intravenous (IV) paracetamol, and may be less effective compared to morphine and MF. MF may reduce pain compared to paracetamol, ketoprofen, tramadol, and fentanyl. Both agents may be associated with marked but primarily mild AEs. Conclusion: We found low‐quality evidence suggesting that both MF and N2O are safe and may have a role in the management of pain in the prehospital setting. There is low‐quality evidence to support MF as a short‐acting single analgesic or as a bridge to IV access and the administration of other analgesics. There may be occupational health issues regarding the prehospital use of N2O. [ABSTRACT FROM AUTHOR]

We investigated the potential of earthworm casts to emit N2O, hypothesizing that emission levels are influenced by the species of earthworm and their ecological category. This study examined casts a broad taxonomic and ecological coverage of tropical earthworms, i.e., 16 different species across four ecological categories. We quantified the potential nitrification, N2O production and consumption as well as the abundance of N-related microbial functional groups, including ammonia-oxidizers, nitrite-reducers, and distinct clades of N2O-reducers, along with casts chemical properties to determine cast organic matter quality and substrate availability. Earthworm casts exhibited significantly higher concentrations of carbon, nitrogen, and nitrate compared to control soil, while humification index were lower. A negative correlation between humification index and potential N₂O production suggests that more labile substrates in the casts promote higher N₂O flux. Net potential N₂O emissions were higher in the casts of 7 out of 16 species compared to control soil, and all species' casts showed higher gross potential N₂O production, with substantial interspecific variability. The abundance of nitrite and N₂O reducers was significantly higher in the casts and positively correlated with potential N₂O emissions. Casts from epigeic and mixed categories displayed higher carbon and nitrogen content, abundance of nitrite and N₂O reducers, ammonia-oxidizing bacteria, and potential N₂O production compared to anecic and endogeic categories, which exhibited higher values of humification index. Structural equation modeling indicated that gross potential N₂O production was primarily explained by the abundance of nitrite reducers and substrate availability indicators such as humification index and nitrate concentration. Our study demonstrates significant interspecific variability in N₂O potential emissions from a broad range of tropical earthworm casts, influenced by species feeding behavior, microbial communities, and substrate availability. [ABSTRACT FROM AUTHOR]

Recreational use of nitrous oxide (N2O) has become a major health issue worldwide, with a high number of clinical events, especially in neurology and cardiology. It is essential to be able to detect and monitor N2O abuse to provide effective care and follow-up to these patients. Current recommendations for detecting N2O in cases of recreational misuse and consumption markers are lacking. We aimed to update current knowledge through a review of the literature on N2O measurement and kinetics. We reviewed the outcomes of experiments, whether in preclinical models (in vitro or in vivo), or in humans, with the aim to identify biomarkers of intoxication as well as biomarkers of clinical severity, for laboratory use. Because N2O is eliminated 5 min after inhalation, measuring it in exhaled air is of no value. Many studies have found that urine and blood matrices concentrations are connected to ambient concentrations, but there is no similar data for direct exposure. There have been no studies on N2O measurement in direct consumers. Currently, patients actively abusing N2O are monitored using effect biomarkers (biomarkers related to the effects of N2O on metabolism), such as vitamin B12, homocysteine and methylmalonic acid. [ABSTRACT FROM AUTHOR]

Le protoxyde d'azote (N 2 O) est un gaz utilisé en médecine pour ses propriétés anesthésiques et analgésiques et dans l'industrie comme gaz comburant ou propulseur. Ce gaz est également disponible pour un usage alimentaire à la vente en libre-service. Depuis quelques années, son utilisation est de plus en plus détournée pour un usage récréatif. Entre 2020 et 2021, le nombre de cas graves d'intoxications a augmenté de 320 % en France, démontrant une préoccupation majeure de santé publique. De plus, c'est un problème pour la sécurité routière avec une augmentation du nombre d'accidents de la route en lien avec la consommation de ce gaz. Le protoxyde d'azote provoque des effets à court terme (euphorie, désorientations, etc.) et à long terme (troubles neurologiques sensitifs et moteurs, thrombose). Ce gaz agit sur le système nerveux central, induisant des effets anxiolytique, anesthésique, antidépresseur et analgésique. Le dosage du protoxyde d'azote est difficile à cause de son élimination rapide. L'exploration biologique repose ainsi sur les anomalies secondaires liées à l'inactivation de la vitamine B12 : augmentation du taux d'acide méthylmalonique et d'homocystéine. Cependant ces deux marqueurs biologiques ne sont pas spécifiques à l'intoxication au protoxyde d'azote. Pour permettre une meilleure prise en charge des patients, il est nécessaire de trouver de nouveaux marqueurs biologiques plus spécifiques des intoxications au protoxyde d'azote. Nitrous oxide (N 2 O) is a gas used in medicine for its anesthetic and analgesic properties, and in industry as an oxidizing gas or propellant. This gas is also available on self-service for food use. In recent years, its use has been increasingly diverted to recreational purposes. Between 2020 and 2021, the number of serious cases of intoxication increased by 320% in France, demonstrating a major public health concern. It is also a problem for road safety, with an increase in the number of road accidents linked to the consumption of this gas. Nitrous oxide causes both short-term effects (euphoria, disorientation, etc.) and long-term effects (sensory and motor neurological disorders and thrombosis). This gas acts on the central nervous system, inducing anxiolytic, anesthetic, antidepressant and analgesic effects. Nitrous oxide is difficult to quantify because of its rapid elimination. Biological investigation is thus based on secondary anomalies linked to vitamin B12 inactivation: increased methylmalonic acid and homocysteine levels. However, these two biological markers are not specific to nitrous oxide intoxication. To improve patient support, we need to find new biological markers that are more specific to nitrous oxide intoxication. [ABSTRACT FROM AUTHOR]

Due to the carbon dioxide (CO2) content in biogas, using biogas is relatively limited in many industrial applications. Hydrogen (H2) is a highly reactive gas that is used extensively to enhance the burning rate of biogas, on the other hand, nitrous oxide (N2O) is a powerful oxidizer that can improve the burning rate of biogas. The laminar burning velocities of biogas-hydrogen-air and biogas-N2O mixtures at various equivalence ratios were investigated experimentally using the spherical flame methodology. It was found that the laminar burning velocities were enhanced in biogas-hydrogen-air and biogas-N2O mixtures. However, the enhanced laminar burning velocities of biogas-N2O showed a more significant increase than biogas-hydrogen-air due to the significant energy released by the N2O decomposition reaction. The flame thickness of the biogas-N2O mixture indicated lower values than biogas-hydrogen-air mixtures, suggesting a higher flame instability of the biogas-N2O mixture than biogas-hydrogen-air mixtures. The Lewis number of biogas-N2O mixture showed lower values than all biogas-hydrogen mixtures, indicating higher diffusive-thermal instability influence on biogas' flame. The reactions of H + O2⇔ OH + O and H + CH3(+M) ⇔ CH4(+M) represented the most significant reactions influencing the laminar burning velocities of biogas-hydrogen mixtures, while the N2O + H⇔N2 + OH, and N2O(+M) ⇔ N2 + O(+M) reactions represented the most important reactions in biogas-N2O combustion. [ABSTRACT FROM AUTHOR]

The burning of agricultural straw is a pressing environmental issue, and identifying effective strategies for the rational utilization of straw resources is decisive for achieving sustainable development. Owing to its high carbon content and exceptional stability, straw biochar produced via pyrolysis has emerged as a key focus in multidisciplinary research. However, the efficacy of biochar in mitigating nitrous oxide (N2O) emissions from paddy soils is not consistent. A 2-year field experiment was conducted and investigated the impact of biochar derived from two feedstocks (rice straw and wheat straw, pyrolyzed at 450 °C) on N2O emissions, global warming potential (GWP), greenhouse gas intensity (GHGI), nitrogen use efficiency (NUE), crop yield, and soil quality. The static chamber technique was used for collecting N2O gas samples, and concentrations were analyzed through gas chromatography methods. The treatment combinations included BR0 (control), BR1 (NPK at the recommended dose, 120:60:40 kg ha−1), BR2 (wheat straw biochar, 5 t ha−1), and BR3 (rice straw biochar, 5 t ha−1). The results exhibited that cumulative N2O emissions from BR2 and BR3 treatments decreased by 10.55% and 13.75% respectively, compared to BR1. Lower GWP and GHGI were observed under both biochar treatments compared with BR1. The highest rice grain yield (3.48 Mg ha−1) and NUE (76.72%) were recorded from BR3, which also exhibited the lowest yield-scaled N2O emission. We observed positive correlations between soil nitrate, ammonia and water-filled pore spaces, while NUE showed negative correlations with N2O emissions. Significant (p < 0.05) improvements in soil quality were also detected in both the biochar treated plots, indicated by increased soil pH, water holding capacity, porosity, and nutrient contents. Overall, the results suggest that applying biochar at a rate of 5 t ha−1 in paddy soil is a viable nutrient management strategy with the potential to reduce reliance on inorganic fertilizers, mitigate N2O emissions, and contribute to sustainable food production. [ABSTRACT FROM AUTHOR]

Globally, ammonia (NH3) is one of the key air pollutants and reducing NH3 emissions and the associated indirect emission of the greenhouse gas nitrous oxide remains challenging for the agricultural sector. During the past three decades, a number of urease inhibitors have been placed on the market with the goal of reducing NH3 loss from urea containing fertilisers. N-(n-butyl) thiophosphoric triamide (NBPT), N-(2-nitrophenyl) phosphoric triamide (2-NPT), a 3:1 ratio of NBPT + N-(n-propyl) thiophosphoric triamide (NPPT) and the maleic and itaconic acid co-polymer (MIP) are registered urease inhibitors under the European Commission Fertilising Products Regulation (FPR). However, the availability of several inhibitor options has raised questions from farmers, policymakers and emissions inventory compiling authorities regarding the field efficacy of the different options available for reducing NH3 loss. Despite many disparate NH3 field studies existing for NBPT, 2-NPT, NBPT + NPPT and MIP there is presently no review that brings these results together, a significant and important knowledge gap. This review addresses the gap by summarising the published field trial literature on NH3 volatilisation mitigation offered by NBPT, 2- NPT, NBPT + NPPT and MIP. Our review identified 48 peer reviewed studies where NH3 loss mitigation was measured in a field setting, giving 256 replicated comparisons. The synthesised literature results revealed that NBPT + NPPT reduced NH3 loss by 75% (95% CI = 58-82% n = 32), 2-NPT reduced NH3 loss by 70% (95% CI = 63-76% n = 19) and NBPT reduced NH3 loss by 61% (95% CI = 57-64% n = 165), giving on average a 69% reduction by these three urease inhibitors. In contrast, MIP increased NH3 loss by 0.3% on average (95% CI = -8-9% n = 40). The results presented in this review broaden the understanding of urease inhibitor efficacy in field conditions and demonstrate that not all products behave the same in terms of field NH3 reduction efficacy. This review is important for farmers, policymakers, emission inventory compilers and other stakeholders. [ABSTRACT FROM AUTHOR]

The diiron‐containing YtfE protein in Escherichia coli is pivotal in counteracting nitrosative stress, a critical barrier to bacterial viability. This study delves into the biochemical complexity governing YtfE's conversion of nitric oxide (NO) to nitrous oxide, a key process for alleviating nitrosative stress. Through site‐directed mutagenesis, we explored YtfE's molecular structure, with a particular focus on two internal transport tunnels important for its activity. Our findings illuminate Tunnel 1 as the primary conduit for substrate transport, regulated by conformational shifts within the N‐terminal domain that enable substrate access to the diiron core in the C‐terminal domain. Tunnel 2 emerges as a secondary, supportive route, activated when Tunnel 1 is compromised. This result challenges a previous model of distinct tunnels for substrate entry and product exit, suggesting both tunnels are capable of transporting substrates and products. Our engineering efforts enhanced the role of Tunnel 2, enabling a synergistic operation with Tunnel 1 and tripling YtfE's enzymatic activity compared to its wild‐type form. This research not only deepens our understanding of YtfE's regulatory mechanism for NO reduction but also introduces a strategy to amplify its enzymatic efficiency. The outcomes offer new ravenues for modulating bacterial stress responses. [ABSTRACT FROM AUTHOR]

Meta-analyses show an overall decrease in soil N2O emissions after biochar (BC) amendment. Nonetheless, N2O mitigation with BC cannot be extrapolated to every BC-soil combination, inasmuch as an increase in soil N2O release has been occasionally reported. We hypothesized that BC characteristics are key, and performed two microcosm experiments to advance in the understanding of the properties associated. We first investigated how 22 well-characterized BCs affect N2O emissions in a calcareous soil under denitrification conditions. Whereas most BCs decreased N2O emissions, some substantially increased N2O emissions. In a second experiment, we selected and further characterized eight of the 22 previous BCs. We applied the 15N-gas-flux method to study how these BCs affect denitrification products (N2O and N2) in the same soil. Results indicate that the interaction between BC and the denitrification process depends on the temperature of pyrolysis. Whereas BCs produced at 400 °C tended to increase total denitrification (N2O+N2) by an average of 28%, BCs produced at 600 °C significantly reduced total denitrification by 53%. Nevertheless, this decline in overall denitrification did not result in a decrease of N2O emissions, as there was a strong shift in the N2O/(N2+N2O) ratio favoring N2O. A redundancy analysis revealed a direct correlation between carboxylic groups on BCs surface and N2O emissions. This research enhances our understanding of the interaction of BC with denitrification, particularly concerning the relevance of the temperature of pyrolysis, and opens up new paths for investigation, crucial for optimizing the application of BCs in different soil environments. Highlights: High concentration of –COO- groups on BCs surface correlated with the highest N2O emissions. Biochars produced at 600 °C decreased total denitrification (N2O+N2). Biochars with high electrical conductivity and pH increased NO2−/NO3− ratios. [ABSTRACT FROM AUTHOR]

In flooded paddy fields, peak greenhouse gas nitrous oxide (N2O) emission after rewetting the dry soils is widely recognised. However, the relative contribution of biotic and abiotic factors to this emission remains uncertain. In this study, we used the isotope technique (δ18O and δ15NSP) and molecular-based microbial analysis in an anoxic incubation experiment to evaluate the contributions of bacterial, fungal, and chemical denitrification to N2O emissions. We collected eight representative paddy soils across southern China for an incubation experiment. Results show that during the 10-day incubation period, the net N2O emissions were mainly produced by fungal denitrification, which accounted for 58–77% in six of the eight investigated flooded paddy soils. In contrast, bacterial denitrification contributed 6–15% of the net N2O emissions. Moreover, around 11–35% of the total N2O emissions were derived from chemical denitrification in all soil types. Variation partitioning analysis (VPA) and principal component analysis (PCA) demonstrated that initial soil organic carbon (OC) concentrations were the primary regulator of N2O source patterns. Soils with relatively lower OC concentration (7–15 mg g−1) tend to be dominated by fungal denitrification, which accounted for the net N2O production at the end of the incubation period. Overall, these findings highlight the dominance of the fungal denitrification pathway for N2O production in flooded paddy soils, which predominates in soils with relatively lower OC content. This suggests that fungal contribution should be considered when optimizing agricultural management system timing to control N2O emissions in flooded paddy soil ecosystems, and for the relevant establishment of predictive numerical models in the future. [ABSTRACT FROM AUTHOR]

Agricultural intensification has increased the consumption of inputs, mainly fertilizers, which may increase emissions of greenhouse gases (GHG). The improvement of our knowledge on GHG dynamics in the soil is mandatory to optimize the use of fertilizers and reduce environmental impacts. We developed an electronic sensor prototype based on Arduino to monitor concentrations of carbon dioxide (CO2), ethylene (C2H4), ammonia (NH3), and nitrogen oxides (N2O/NOx) in the soil air in a greenhouse experiment with soybean (Glycine max L.) under two treatments: single inoculation (Bradyrhizobium spp.) or triple co-inoculation (Bradyrhizobium spp. Azospirillum brasilense and Pseudomonas fluorescens) in a completely randomized design. One-way analysis of variance, as well as correlation between plant traits at 35 days of emergence and the average daily concentration of gases in the soil air were performed. Although not affecting plant growth or yield-related traits, co-inoculation increased CO2, while decreased NOx concentrations compared with single inoculation, whereas C2H4 emission changed with the plant growth stage. Although co-inoculation increased respiration, decreased N losses by denitrification, mitigating the total emissions of GHG. The prototype showed to be efficient for monitoring GHG across the experiment at a low cost and easy use, contributing for monitoring GHG concentrations in the soil air. [ABSTRACT FROM AUTHOR]

Shallow lakes and ponds play a crucial role in the processing of carbon and other nutrients. However, many lakes and ponds worldwide are affected by climate change and nutrient pollution. How these pressures affect the emission of the greenhouse gas nitrous oxide (N2O) is unclear. Warming and eutrophication are expected to increase the production and emission of N2O in lakes and ponds, but changes in ecological structure and function may complicate these seemingly straightforward relationships. In this study, we used the world's longest running, mesocosm‐based, freshwater climate change experiment to disentangle the effect of nutrient enrichment and warming on N2O emissions. We gathered a large dataset on N2O concentrations and ancillary variables, comprising three sampling campaigns between 2011 and 2020 and a total of 687 individual mesocosm measurements. Our results demonstrated that nutrient enrichment increased N2O emissions, while warming (+2.5–4.0°C and +3.75–6.0°C) had no discernable effect. Our study indicates that curtailing nitrogen influxes into lakes and ponds is the most effective strategy to minimize N2O emissions, and while warming may influence N2O emissions, it does not appear to be a direct driver. These findings underscore the importance of prioritizing nitrogen mitigation efforts to curb N2O emissions from shallow lakes and ponds. [ABSTRACT FROM AUTHOR]

The relaxed eddy accumulation (REA) method is a widely‐known technique that measures turbulent fluxes of scalar quantities. The REA technique has been used to measure turbulent fluxes of various compounds, such as methane, ethene, propene, butene, isoprene, nitrous oxides, ozone, and others. The REA method requires the accumulation of scalar concentrations in two separate compartments that conditionally sample updrafts and downdraft events. It is demonstrated here that the assumptions behind the conventional or two‐compartment REA approach allow for one‐compartment sampling, therefore called a one compartment or 1‐C‐REA approach, thereby expanding its operational utility. The one‐compartment sampling method is tested across various land cover types and atmospheric stability conditions, and it is found that the one‐compartment REA can provide results comparable to those determined from conventional two‐compartment REA. This finding enables rapid expansion and practical utility of REA in studies of surface‐atmosphere exchanges, interactions, and feedbacks. Plain Language Summary: Estimates of emission inventory of chemical compounds from the biosphere remain an indispensable tool in air quality and climate science research. Such inventory requires the measurements of the number of molecules flowing from the biosphere to the atmosphere, or vice‐versa, per unit ground area per unit time. What makes these measurements challenging is that such molecules are being transported rapidly by gusts and swirling (i.e., turbulent) motion in the atmosphere. In theory, this vertical exchange can be measured by a rapidly sampled covariance between vertical velocity and concentration variations. The main drawback is that such covariance requires rapid concentration measurements that are difficult to conduct for a large number of chemical species, although it is standard practice and easier to obtain for carbon dioxide, water vapor, and air temperature. The work here offers an alternative and efficient approach that necessitates measuring the accumulation of molecules in a single compartment, supplemented by knowledge of the velocity statistics. Both velocity and accumulated concentration measurements can be conducted with available instrumentation. Thus, the work here offers a blueprint for efficient sampling of emission rates across the biosphere‐atmosphere interface that can be deployed in upcoming experiments. Key Points: Relaxed eddy accumulation (REA) is used to estimate turbulent fluxes of numerous chemical speciesThe original REA relies on sampling concentrations in two compartmentsA single‐compartment REA is proposed with no loss in accuracy [ABSTRACT FROM AUTHOR]

Nitrous oxide (N2O) emissions from croplands contribute substantially to the climate impact of agriculture. Emissions of N2O are controlled by both anthropogenic and environmental factors and can vary by orders of magnitude over short times and distances. This nature of emissions is difficult to capture with models and presents an observational challenge. In the 2021 and 2022 growing season, we collected airborne measurements of N2O over Iowa to characterize N2O emissions at the farm to multi‐county spatial scales across days. We link our airborne observations to surface emissions using a Lagrangian particle dispersion model and quantify emissions using a Bayesian inversion framework. We find emissions magnitudes across Iowa, showing greater skew than modeled predictions, with a small fraction of fields contributing disproportionately to the total [25% of the domain contributing to 52%–77% of total emissions]. In addition to the high spatial variation, we find high temporal variability between flight days by a factor of 2 at the 100 km scale, and an order of magnitude at the 2 km scale], with peak emissions occurring at median soil moisture. This work illustrates the importance of transient, intense emissions from concentrated areas in explaining total cropland emissions, and demonstrates how airborne measurements can provide insights into variation that may be missed by other observational systems. Investigation into environmental factors highlights the need for observations, models and their input data to be spatiotemporally resolved to enable direct comparison, facilitating evaluation of predicted and reported emissions and providing guidance and feedback on mitigation strategies. Plain Language Summary: Nitrous oxide (N2O) is an important greenhouse gas, and rising atmospheric concentrations due to human‐driven emissions contribute to warming temperatures. The largest source of N2O comes from fertilized croplands. Soil microbial processes naturally emit N2O into the atmosphere, and soils treated with nitrogen‐based fertilizers have more nitrogen available and thus higher emissions. Environmental variables that regulate N2O emissions (e.g., temperature, moisture content, management practices) can lead to variations in output that span several orders of magnitude across brief intervals and small areas. This variability makes it difficult to accurately represent emissions in models and observe with measurements. Here, we use an aircraft to measure N2O over farmlands in the U.S. Midwest. We use inverse modeling tools to determine N2O emissions and emission variability across the U.S. Corn Belt. We observed large emission variability in both time and space. We frequently find a small fraction of the region contributes disproportionately to total emissions, highlighting the challenge to observe representative emission behavior and the importance of these small areas for mitigation. This study shows how aircraft observations can provide insight into emissions at fine scales and play a critical role in developing policies and management techniques to monitor and mitigate N2O emissions. Key Points: Airborne measurements combined with inverse modeling enables investigation of nitrous oxide emissions variation spanning 1–100 km across daysEmissions are highly skewed, with a small fraction of the domain explaining the bulk of emissions, with large day‐to‐day varianceObservations, models and geophysical input data need to be spatially/temporally resolved to enable direct comparison and evaluation [ABSTRACT FROM AUTHOR]

Objective: The purpose of this study is to identify and visualize from different perspectives the topic on occupational exposure in operating room (OEOR). Methods: In the Web of Science Core Collection (WoSCC), all the half-century data were retrieved from January 1st, 1973 to December 31st, 2022. CiteSpace, VOSviewer and Excel 2019 were employed to analyze and visualize data, based on publications, countries, institutions, journals, authors, keywords. Result: A total of 336 journal papers were found. The increase of publications virtually started in 1991, peaked in 2020 and has been slowing down ever since. USA played most significant part among all the 49 countries/regions, while Universidade Estadual Paulista out of 499 institutions published the most papers. International Archives of Occupational and Environmental Health bears the most documents and citations in all the 219 retrieved journals. There are 1847 authors found, among whom Hoerauf K is the most influential one. "Occupational exposure", "nitrous oxide" and "operating room personnel" are the top 3 co-occurrences keywords. Conclusion: The trend in the field lies in "anaesthetic gas", "blood borne pathogen", "radiation" and "aerosol", while "surgical smoke" and "occupational safety" are the recently researching hot spots in this study. Accurate recognize and effective protection are always essential subjects for researchers. [ABSTRACT FROM AUTHOR]

In recent years, the arctic tundra has been subject to more frequent stochastic biotic or extreme weather events (causing plant dieback) and warmer summer air temperatures. However, the combined effects of these perturbations on the tundra ecosystem remain uninvestigated. We experimentally simulated plant dieback by cutting vegetation and increased summer air temperatures (ca. +2°C) by using open‐top chambers (OTCs) in an arctic heath tundra, West Greenland. We quantified surface greenhouse gas fluxes, measured soil gross N transformation rates, and investigated all ecosystem compartments (plants, soils, microbial biomass) to utilize or retain nitrogen (N) upon application of stable N‐15 isotope tracer. Measurements from three growing seasons showed an immediate increase in surface CH4 and N2O uptake after the plant dieback. With time, surface N2O fluxes alternated between emission and uptake, and rates in both directions were occasionally affected, which was primarily driven by soil temperatures and soil moisture conditions. Four years after plant dieback, deciduous shrubs recovered their biomass but retained significantly lower amounts of 15N, suggesting the reduced capacity of deciduous shrubs to utilize and retain N. Among four plant functional groups, summer warming only increased the biomass of deciduous shrubs and their 15N retention, while following plant dieback deciduous shrubs showed no response to warming. This suggests that deciduous shrubs may not always benefit from climate warming over other functional groups when considering plant dieback events. Soil gross N mineralization (~ −50%) and nitrification rates (~ −70%) significantly decreased under both ambient and warmed conditions, while only under warmed conditions immobilization of NO3− significantly increased (~ +1900%). This explains that plant dieback enhanced N retention in microbial biomass and thus bulk soils under warmed conditions. This study underscores the need to consider plant dieback events alongside summer warming to better predict future ecosystem‐climate feedback. [ABSTRACT FROM AUTHOR]

The application of intelligent process-based crop model parameter optimization algorithms can effectively improve both the model simulation accuracy and applicability. Based on measured values of soil N2O emission flux in wheat fields from 2020 to 2022, and meteorological data from 1971 to 2022, five parameters of the N2O emission flux module in the APSIM model were optimized using the variable step Fruit Fly algorithm (VSS-FOA). The optimized parameters were the soil nitrification potential, the range of concentrated KNH4 of ammonia and nitrogen at semi-maximum utilization efficiency, the proportion of nitrogen loss to N2O during the nitrification process, the denitrification coefficient, and the Power term P for calculating the denitrification water coefficient. Contrasting the optimized parameters using the VSS-FOA algorithm versus the default values supplied with the model substantially improved the goodness-of-fit to field measurements with the overall R2 increasing from 0.41 to 0.74, and a decrease in NRMSE from 17.1% to 11.4%. This work demonstrates that the VSS-FOA algorithm affords a straightforward mechanism for the optimization of parameters in models such as APSIM to enhance the accuracy of model N2O emission flux estimates. [ABSTRACT FROM AUTHOR]