The modern global food system is the largest driver of nitrogen imbalances across the world. These problems are exacerbated by excessive and resource-intensive food demand prone to large amounts of loss and waste throughout the food system. Increasing international trade is shifting the burden and upstream nitrogen demand and downstream eutrophication impacts beyond national borders and moving beyond the safe regional boundaries for their presence in the environment. To better understand drivers and solutions to close nitrogen loops, we use the global food input-output model FABIO, which monitors the movement of biomass and the land utilized across global supply chains, encompassing 191 countries, and 130 agricultural and food products. We couple FABIO to nitrogen crop demand, livestock manure management systems, and agricultural surpluses to assess the consumption-based drivers for nitrogen emissions stemming from the agricultural system. A substantial amount of nitrogen losses can be attributed to traded commodities especially toward high-income nations. We further show how policy measures in a high-income nation (the Netherlands) related to the taxation of meat and carbon emissions from the food sector can lead to significant reduction of manure application (up to 20 kt N/yr) and nitrogen losses (over 1 kt N/yr) on a global scale. However, as the Dutch food system relies heavily on manure, there may be a concomitant increase in the need for synthetic fertilizers to account for the significant drop in manure of nearly (14 kt N/yr). We provide similar scenarios for various, more ambitious dietary changes (e.g. the EAT-Lancet diet) at the EU level that can help ameliorate global nitrogen losses, focusing in areas sensitive to terrestrial and aquatic eutrophication and acidification.
How to cite: Mogollón, J. M., Navarre, N., and Kevin Morgan-Rothschild, K.: Dutch and EU consumption-based assessments of nitrogen losses throughout the global food system, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18590, https://doi.org/10.5194/egusphere-egu25-18590, 2025.
Nitrogen holds a crucial place in maintaining the sustainability of the food-energy-water (FEW) nexus, essential pillars underpinning human society. Its vital role spans across food production, energy generation, and the preservation of water quality. Here based on CHANS model, we show that comprehensive nitrogen management strategies offer the dual benefits of satisfying China's food requirements and boosting nitrogen energy production from straw by 1 million tonnes (26%) compared to the baseline year of 2020. Simultaneously, these strategies could lead to a reduction of 8 million tonnes (-31%) in nitrogen fertilizer usage, a decrease of 3.8 million tonnes (-46%) in nitrogen-induced water pollution, and a halving of water consumption in agriculture, all relative to 2020 levels. These transformative changes within the FEW nexus could result in national societal gains of around US$140 billion, against a net investment of just US$8 billion. This emphasizes the cost-effectiveness of such strategies and highlights their significant potential in assisting China to meet multiple sustainable development goals, especially those related to hunger relief, clean energy advancement, and the protection of aquatic ecosystems.
How to cite: Chen, B.: Managing nitrogen to achieve sustainable food-energy-water nexus in China, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4076, https://doi.org/10.5194/egusphere-egu25-4076, 2025.
Anthropogenic activities have substantially enhanced the loadings of reactive nitrogen (Nr) in the Earth system since pre-industrial times, contributing to widespread eutrophication and air pollution. Increased Nr can also influence global climate through a variety of effects on atmospheric and land processes but the cumulative net climate effect is yet to be unravelled. Here we show that anthropogenic Nr causes a net negative direct radiative forcing of −0.34 [−0.20, −0.50] W m−2 in the year 2019 relative to the year 1850. This net cooling effect is not only as a result of the increased terrestrial carbon sequestration, but also led by short-lived Nr components and the associated atmospheric chemical reactions, including increased aerosol loading and reduced methane lifetime induced by nitrogen oxide (NOx). Such cooling effect is not offset by the warming effects of enhanced atmospheric nitrous oxide (N2O) and ozone (O3). However, despite the significant climate impacts of the short-lived nitrogen components, in particular, NOx, the associated soil biogeochemical processes remain poorly constrained, thus leading to varied responses to N fertilizer application as well as the estimates of global soil emissions among different approaches. Our results highlight the urgent necessities to integrate knowledge between atmospheric chemistry and soil biogeochemistry to improve the understanding of the Nr climatic effects.
How to cite: Gong, C., Tian, H., Liao, H., Kou-Giesbrecht, S., Vuichard, N., Wang, Y., and Zaehle, S. and the NMIP2 contributors: Global net cooling effects of anthropogenic reactive nitrogen: the unneglectable roles of short-lived nitrogen components, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10246, https://doi.org/10.5194/egusphere-egu25-10246, 2025.
Pollen is a critical component of the nitrogen (N) cycle in forests, but its role in N uptake, release and transformation during precipitation events remains poorly understood, contributing to uncertainties in N deposition estimates. In the frame of the COST Action CLEANFOREST a laboratory experiment was conducted to assess the biochemical activity of tree pollen and its effects on N compounds in precipitation. Pollen from green alder (Alnus viridis), pedunculate oak (Quercus robur), European beech (Fagus sylvatica), silver birch (Betula pendula), Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) was suspended in a synthetic nitrate (NO₃-) solution isotopically labelled with ¹⁵N under non-sterilized conditions and two sterilization treatments: addition of (i) thymol and (ii) a broad-spectrum antibiotic mixture (PSA) containing penicillin, streptomycin, and amphotericin B. Over one week, water samples were analysed daily for NO₃-, nitrite (NO₂-), ammonium (NH₄⁺) and total dissolved nitrogen (TDN) from which dissolved organic nitrogen (DON) was calculated. The results showed significant NO₃- removal from the solution in broadleaved species, particularly oak, beech, and alder, in all treatments, but most clearly in the non-sterilized treatment. Most species showed a significant decrease in DON during the first two-three days, in all treatments, but especially in the sterilized (PSA) treatment, which was subsequently converted into NH₄⁺ (mineralization). The use of 15N as a tracer clearly shows that the labelled N was actively taken up by the pollen in both the non-sterilized and PSA-treated samples. Notably, pollen from all tree species, predominantly the broadleaves, enzymatically transformed extracellular NO₃- into NO₂-, highlighting its active role in the N cycle. These findings offer valuable insights into N release, uptake, and transformation during precipitation events and reveal important interactions between pollen and microorganisms. The differences observed between sterilized and non-sterilized treatments underline the significant influence of microbial activity on N conversion. By expanding our understanding of canopy-level N processes, this research contributes to improving N deposition models and introduces innovative approaches to studying the forest N cycle. Further studies are essential to clarify the mechanisms by which pollen and microbial communities influence N transformations at ecosystem scales.
Keywords: Broadleaves; Conifers; Pollen; ¹⁵N; Ammonium; Nitrate; Nitrite
How to cite: Limić, I., Bodé, S., Boeckx, P., Bauters, M., Neirynck, J., Bruffaerts, N., Marković, S., Gottardini, E., and Verstraeten, A.: The role of tree pollen in forest nitrogen cycling: A laboratory perspective, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11830, https://doi.org/10.5194/egusphere-egu25-11830, 2025.
South Asian nations are facing the challenge of increasing nitrogen pollution with the Indo-Gangetic Plain having some of the highest levels of atmospheric ammonia pollution globally. However, there is a lack of in-country research to evaluate the possible impact of nitrogen-related pollutants on South Asian biodiversity. In the Himalayas, there is an opportunity to utilize lichens from natural habitats to establish field-based references for better future tracking of changes in ecosystem health relevant to the wider South Asian region. In this study, we assessed the natural chemical variability of two lichens (Usnea spp. and Hypotrachyna spp.) based on thallus nitrogen and metal ion contents along with their physico-chemical and oxidative responses in two 1-km long transects from two forests of Nepal representing local gradients. Our results revealed a moderate concentration of total Kjeldalh nitrogen (0.36-0.98 % DM in Chandragiri, KTM and 0.57-2.04 % DM in Ghorepani, ACA), as well as ammonium (40.42-159.84 mg/L in Chandragiri, KTM and 80.60-280.64 mg/L in Ghorepani, ACA) and considerable amount of metal ions in both lichens, though with the highest values for lichens collected from the Ghorepani, ACA (from Western Nepal). A noteworthy background concentration of atmospheric ammonia was also observed at both sites. The highest variation in physico-chemical responses, such as electrical conductivity, chlorophyll content, chlorophyll degradation, chlorophyll fluorescence, and phenolic content was observed in the lichens from the same area, consistent with the higher levels of air pollution. Moreover, there appeared to be associated impacts on oxidative responses such as radical scavenging and catalase activities. Furthermore, the metal ions in the lichen thalli were found to originate from both anthropogenic and natural sources in Chandragiri, KTM and few of the metal ions were deposited from long-range transport mechanisms in Ghorepani, ACA, which signifies the diverse sources of pollution in the study areas. The sampling line-wise variation in thallus chemistry signifies the local pollution gradient in both sites. Further, environmental covariables (slope, elevation, crown settings, wind pattern) were observed to affect the lichen abundance and accumulation of nitrogen and metal ions. In comparison, Hypotrachyna spp. showed greater potential to accumulate pollutants and variability in physico-chemical and oxidative responses. From this study, we conclude that a range of physico-chemical and biochemical responses of the target lichens can be used as proxies for the bioindication of nitrogen and metal ion pollution to assess lichen’s health and ecological functioning. Wider studies covering large spatial extent and cellular mechanisms of lichen response are now recommended to fully understand the functional biology explaining contrasting responses between lichen species in different geographic settings of Nepal and South Asia.
Keywords: Lichens; Bioindicators; Pollution; Ecosystem; Reference
How to cite: Pradhan, S. P., Bista, H., Lamsal, B., Pandey, B. P., Baniya, C. B., Deshpande, A., Sharma, S., and Sutton, M. A.: Contrasting physico-chemical and oxidative relationships to thalli nitrogen and metal ion contents in Usnea spp. and Hypotrachyna spp. from Himalayan forests of Nepal., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1999, https://doi.org/10.5194/egusphere-egu25-1999, 2025.
Global changes caused by anthropogenic activities are altering the cycling of nitrogen (N) in terrestrial ecosystems. For example, droughts of increasing frequency and severity can stimulate large emission pulses of nitrous oxide (N2O; a powerful greenhouse gas) when dry soils wet up. Further, increased fire frequency can favor the colonization of novel pyrophilous or “fire-loving” fungi on soils with the capacity to produce N2O, yet N2O isotopic ranges have been characterized in few fungal species, making generalizations difficult. To better understand how global changes are altering the N cycle, we studied drylands in southern California that can experience >6 months without rain, burned experimental “pyrocosms” to assess impacts of fire severity on soil biogeochemistry, and used a culture collection of pyrophilous fungi isolated from wildfire-burned soils to characterize their δ15N2Obulk,δN218Obulk, and δ15N2OSP values. Despite the hot and dry conditions known to hinder denitrification, isotope tracers and natural abundance isotopologues of N2O indicated NO3- was reduced within 15 minutes of wetting dry desert soils and that N2O reduction to N2 occurred. In post-fire environments, we found that while N2O isotope values for Neurospora discreta and Fusarium tricinctum closely matched literature values when grown with NO2-, Aspergillus fumigatus, Coniochaeta hoffmannii, Holtermaniella festucosa, and R. columbienses did not. Further, Fusarium sp. δ15N2Obulk and δN218Obulk values fell outside literature-derived values when grown with NO3-. Overall, we find that despite the hot and dry conditions known to make denitrification thermodynamically unfavorable in many drylands, denitrifiers can endure through hot and dry summers and are key to producing the surprisingly large N2O emissions when dry desert soils wet up. Further, we find that novel pyrophilous fungi present an opportunity to further characterize the isotopic composition of N2O as well as the factors controlling fungal denitrification as ecosystems are impacted by global changes.
How to cite: Homyak, P.: Drought, wildfires, and “fire-loving” fungi effects on ecosystem nitrogen cycling: Understanding global change effects on denitrification using N2O isotopologues, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12451, https://doi.org/10.5194/egusphere-egu25-12451, 2025.
Forests are integral to maintaining planetary health, serving as biodiversity reservoirs, carbon sink, and regulators of nutrient cycles, yet their capacity to sustain these functions is increasingly disrupted by global changes. Among them, the rise in atmospheric nitrogen (N) deposition, resulting from anthropogenic emissions of reactive N compounds during fertilizer production and fossil fuel combustion, occurs across terrestrial ecosystems and can alter microbial communities’ functional composition and diversity.
In this study, we evaluate the effects of long-term N fertilisation (simulating an increase in N deposition) on the taxonomic and functional diversity of soil microbial communities in a mature beech forest in Northern Italy. The experiment started in 2015, and it includes control (only ambient deposition, N0) and soil N addition (30 kg ha-1 yr-1, N30) each replicated in 3 plots. Soil biochemical variables including Nitrogen (N), Carbon (C) and Phosphorus (P) content and soluble ions were characterized for both treatments. In addition, GeoChip 5.0S, a microarray technology, was used to characterize the taxonomic and functional diversity of microbial communities.
Although no changes were detected in soil physicochemical characteristics between N30 and N0, there was a significant increase in the taxonomic richness and diversity (Shannon-Weiver and Simpson indices) in the fertilized plots. Moreover, the relative abundance of some functional genes related to the N, C and sulphur (S) cycles were significantly increased in N30 plots, whereas P cycling genes showed no significant changes between treatments. Preliminary results suggest a probable increase in the denitrification and assimilatory and dissimilatory nitrate reduction processes of the N-added soil microbiome. In addition, the results suggest an increase of both the C fixation and C degradation pathways in N30 plots. The higher stimulation of C degradation cycling genes in comparison to C fixation cycling genes, could be explained by the promotion of plant growth and the consequent increase in rhizosphere secretions and C input to the soil after N addition.
This study contributes to the description of microbial community dynamics and the resulting changes in soil biogeochemical processes in forests under increased N deposition conditions.
How to cite: López Sánchez, C., Ribas, À., Guerreri, R., Lei, J., Yang, Y., Zhou, J., and Mattana, S.: Effects of long-term nitrogen addition on changes in the functional composition of microbial communities after long-term N addition in a temperate beech forest, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18703, https://doi.org/10.5194/egusphere-egu25-18703, 2025.
High nitrogen (N) input in intensive cropping systems has resulted in significant nitrate (NO₃⁻) accumulation in agricultural soils of China. However, despite substantial N input (500-600 kg ha-1 y-1) in the Taihu Lake region, NO₃⁻ accumulation in soils and groundwater therein remains minimal with the mechanisms behind are unclear. Here, we investigated the spatiotemporal distribution and activity of dissimilatory nitrate reduction to ammonium (DNRA), anaerobic ammonium oxidation (anammox), and denitrification, and the associated microbial communities—in the vadose zones of rice-wheat, vegetable, and orchard fields of the Taihu Lake region. Results revealed NO₃⁻ content decreased progressively with soil depth, while NH₄⁺ levels increased, particularly in deeper soil layers. DNRA emerged as the primary pathway for NO₃⁻ reduction, contributing to over 50% of NO₃⁻ removal, especially in the 50–190 cm depth range. Seasonal variations indicated that DNRA activity was highest during spring and autumn, with lower rates observed in winter and summer. DNRA significantly contributed to NH₄⁺ accumulation, with rates strongly positively correlated with NH₄⁺ content, especially in rice-wheat rotation fields characterized by high OC/ NO₃⁻ ratios. Interestingly, DNRA rates were significantly negatively correlated with groundwater N₂O concentrations and the N₂O/(N₂ + N₂O) ratios. Microbial community analysis revealed that the nrfA gene, a marker for DNRA, exhibited higher diversity compared to genes related to denitrification. Additionally, the abundance of DNRA-specialist microbes was positively associated with DNRA rates, particularly in deep layer soils, emphasizing the role of microbial community composition in shaping DNRA activity. These findings demonstrate that DNRA plays a crucial role in facilitating NH₄⁺ accumulation, attenuating NO₃⁻ accumulation, and mitigating N₂O emission in the vadose zone of agricultural croplands in the Taihu Lake region.
How to cite: Shan, J., Wang, X., and Yan, X.: Hotspots and hot moments of DNRA in the Vadose Zone of Agricultural Croplands , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14072, https://doi.org/10.5194/egusphere-egu25-14072, 2025.
Nitric oxide (NO) and nitrous acid (HONO) are important reactive atmospheric trace gases. As part of the nitrogen (N) cycle, ammonia oxidizing nitrifiers in soils are recognized as key producers of these gases, impacting near-surface nitrogen oxide (NOx = NO + NO2) and ozone (O3) concentrations. The nitrification process results in the production of nitrite (NO2-), subsequently protonated in the liquid phase to form HONO, and NO, which are both emitted as gases. However, there is limited understanding of the coupled processes causing the simultaneous emission NO and HONO from drying soils incorporating ammonia oxidizing nitrifiers. Here, we combined experimental in-vitro studies of ammonia-oxidizing bacteria with a mechanistic modelling approach to investigate the mechanisms triggering gaseous NO and HONO emissions. We found out that several abiotic processes, such as NO auto-oxidation, Fe2+ catalysis, and soil moisture dynamics crucially influence the overall emission as well as the partitioning of reactive N. This, in turn, impacts the hydroxyl radical (OH) budget and soil N retention. Modelling allowed us to elucidate the interactions between biological and environmental processes under varying soil hydration conditions for different field scenarios, such as the effects of fertilization. This analysis suggests potential strategies for effectively managing the release of soil-derived NOx and OH emissions.
How to cite: Weber, B., Maier, S., Weber, J., Leiva, D., Zhou, M., Qian, X., Pöschl, U., Cheng, Y., Su, H., and Kim, M.: Mechanisms of soil emissions of NO and HONO produced by ammonia-oxidizing bacteria during drying, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15383, https://doi.org/10.5194/egusphere-egu25-15383, 2025.
Nitrogen is a crucial component of nutrient dynamics in the environment and exists in multiple oxidation states. Nitrate (NO3-) is the most stable form of all the reactive nitrogen species and has a higher residence time in groundwater. Sources of nitrate include mainly fertilizers, sewage, manure, soil organic matter, and rain. In a country like India, where agriculture covers an area of about 60% of the total land and population with 2nd rank globally, contributes a huge fertilizer and sewage component to the environment. Also, nitrate in groundwater deteriorates the potable water quality. So, optimization of nitrogen use and sources estimation of nitrate in groundwater and surface water is very essential. Hindon River basin in the western Indo-Gangetic plain provides an opportunity to study nitrate dynamics in a huge populated and extensive agricultural area. Nitrate concentration in groundwater has been found from 0.1 ppm to 80 ppm, far apart from the permissible limit. Pre-monsoon groundwater shows higher nitrate concentration than that of post-monsoon groundwater at most of the places suggesting the dilution effect of rainwater after monsoon. Fluctuations in δ15N and δ18O values seasonally suggest a rapid change in contribution of nitrate source in groundwater. Contribution from each source of nitrate was estimated by Stable Isotope Mixing Models in R (SIMMR). As the dual isotope plot shows denitrification trend, the actual fertilizers contribution shifted towards manure and sewage end members evidenced by higher sewage and manure contributions (60-75% in pre and post-monsoon respectively) need to be optimized for sustainability.
How to cite: Jakhar, M. and Sanyal, P.: Nitrate in water: Understanding the sources using δ15N and δ18O values, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20072, https://doi.org/10.5194/egusphere-egu25-20072, 2025.
Maintaining agricultural productivity while reducing soil organic carbon (SOC) loss, greenhouse gas emissions and groundwater contamination is a major challenge for European agriculture. Organic farming practices are expected to improve soil health and have increased their share of European cropland, but their effects on soil biogeochemical properties, biodiversity and nitrogen dynamics are mixed. This study uses the process-based ARMOSA crop model to assess the impact of conventional and organic farming practices on yield, SOC stock, nitrate (NO3) leaching, and nitrous oxide (N2O) emissions in both crop and livestock farms.
The research was carried out using simulations under current and projected future climate conditions in the South Savo region of Finland, which is characterised by a subarctic climate (Köppen-Geiger classification). The soil type was loamy sand (sand 76%, clay 4%, silt 20%) with a SOC content of 3.5%, a carbon-to-nitrogen ratio of 17, and a pH of 6.2 in the top 30 cm of the soil.
Five-year crop rotations that reflect prevalent practices in the area were designed for both crop and livestock production systems. Crop production rotations included cereals (with fodder peas in organic management), oilseed rape, and grass. Livestock farm rotations featured two years of cereals followed by a three-year fescue and timothy meadow (including clover in organic management). Nine scenarios were simulated to explore residue management and fertilisation strategies. Conventional systems used mineral fertilisers alone or combined with slurry. Organic systems used slurry, green manure, and a commercial organic fertiliser.
To evaluate the productivity and the environmental impact of these rotations, a fuzzy logic-based trade-off analysis was employed for each climate scenario. This analysis quantifies the trade-offs between crop yield, N2O emissions, NO3 leaching, and SOC stock changes. The result is a composite index known as the ∑ommit index. This index rates these trade-offs on a scale from 0 (poor) to 1 (excellent). To accommodate diverse evaluation criteria, alternative versions of this trade-off analysis were implemented. Each version varies the weightings assigned to the trade-off components to mirror the perspectives and priorities of different representative stakeholder categories.
Using the ∑ommit index to evaluate a five-year rotation, rather than analysing individual cropping cycles, offers a significant advantage. This approach takes into account the interconnected effects of each cycle and its interactions with preceding and subsequent cycles. By considering these cumulative effects, the index provides a more comprehensive view of the trade-off dynamics during crop transitions. This holistic perspective is essential for making informed decisions about sustainable farming practices and long-term crop rotation strategies.
How to cite: Calone, R., Valkama, E., Acutis, M., Perego, A., Botta, M., and Bregaglio, S.: Trade-off analysis of conventional and organic crop rotations under current and future climate scenarios in Finland, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9997, https://doi.org/10.5194/egusphere-egu25-9997, 2025.
Under European and International policies, organic soil amendments are highly promoted as a cost-efficient solution to improve soil C, quality, and agrosystem sustainability. Inorganic N application is an essential agronomic practice to increase and secure crop yields, however, its long-term application has led to serious environmental problems including deterioration of soil organic C, enhanced greenhouse gas emissions, and an overall decline in environmental quality. Consequently, the co-application of organic and inorganic fertilizers is advocated as a more effective and environmentally friendly fertilization regime. This study aims, to decipher the short-term N kinetics in agricultural soils amended with organic, inorganic, and a combined application of N fertilizer, with and without biochar, and to assess the trade-off balance of soil C and greenhouse gas emissions. Therefore, we investigated the short-term (90 d) soil N dynamics of sandy soil mesocosms (2 Kg) receiving municipal sewage sludge (MSS) amendments (50 t/ha), urea-N fertilization (U; 200 kg/ha), a combined application (MSS+U), without and with biochar (1.5% w/w). An unamended soil mesocosm was included as a control. The addition of urea-N (U), municipal sewage sludge (MSS), and their combined application (MSS+U) increased the availability of soil NH4+ by 3x, 5x and 12x times, relative to the control, respectively. Interestingly, we observed a tremendous release of soil NO2- only in the urea treatment (U; 128 mg kg-1), and not in the other remaining treatments. Throughout the incubation approx. 12.7x, 13.4x, and 19.7x more soil NO3- was observed for the U, MSS, and MSS+U treatment, relative to the control, respectively. Where biochar was applied, an approx. 40% reduction in soil available NO2- andNO3- was observed. Considering the gaseous emissions of CO2 and N2O, that are generally products of soil respiration, nitrification, and denitrification, the addition of MSS and its co-application (MSS+U), enhanced soil CO2 by 2.4x and 2.4x, and by 13.6x and 16.9x for soil N2O emissions, respectively. Though biochar addition reduced cumulative CO2 emissions by 24%, for all treatments except the control. Although biochar addition decreased cumulative N2O emission by 65% in the U, it had no effect on cumulative N2O emission for MSS and the combined treatment (MSS+U). Fertilization by U did not affect much soil CO2 (526 mg CO2-C kg-1) and N2O (1258 μg N2O-N kg-1) emissions when compared to the unamended soil treatment (C). The MSS+U reduced the N2O emission factor, by 5x when compared to MSS treatment, however, it was well above the IPPC emission factor of 1%. Municipal sewage sludge is a source of C, though we observed that MSS (74%) and the combined treatment (MSS+U, 96%) enhanced the CO2-equivalent emissions, indicating a complete loss of the added organic C through greenhouse gas emissions. Considering our key question, whether co-application of inorganic, and organic fertilizer with biochar is a double-edged sword, we conclude that co-application should be carefully evaluated case per case, as it affects several key soil parameters differently, and therefore we should seek new ways to minimize gaseous losses thus to improve sustainability in agrosystems.
How to cite: Giannopoulos, G., Pasvadoglou, E., Kourtidis, G., Diaz-Pines, E., Sgouridis, F., Boos, A., Duelli, G., Tzanakakis, V., Aschonitis, V., Arampatzis, G., and Anastopoulos, I.: Biochar as a sustainable amendment in fertilized agricultural soils; insights and trade-offs among nitrogen kinetics, carbon sequestration, and greenhouse gas emissions., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18764, https://doi.org/10.5194/egusphere-egu25-18764, 2025.
Cover crops are recognized as a climate-smart agricultural practice that increases soil organic carbon content (SOC). As carbon (C) and nitrogen (N) cycles are coupled, an increase in SOC can impact the N cycle and nitrous oxide (N2O) emissions. Another major driver affecting N cycling and N2O emissions is soil moisture. With the increasing risk of summer droughts and wetter conditions during the off-season in Northern Europe, it is important to understand how drying-wetting and agricultural practices together affect N cycling and N2O emissions.
To address this knowledge gap, we conducted a pot experiment with clay soil in controlled greenhouse conditions simulating summer drought with bare soil pots and oats sown either alone, with Italian ryegrass, or with alfalfa as plant treatments. The pots were initially watered to 70% degree of saturation to ensure that the plants start to grow, after which half the pots were let dry to 40% degree of saturation. The plants were grown for 36 days. At the end of the growth period, soil N2O emissions were measured over three days. Following this, the pots were sampled destructively, and total N in plants, roots, and soil, as well as mineral N in soil, were analysed. Additionally, a follow-up pool-dilution incubation experiment using 15N-labelling with bare soil and soil previously covered with oats was conducted to study the effect of moisture content and rewetting on gross N transformation rates.
Contrary to our expectations, the results from the pot experiment showed that N2O emissions in the plant treatments were higher in drought conditions than in moist conditions. This does not support our results from a cover crop field trial where reduced rainfall did not affect N2O emissions during the growing season. However, during off-season reduced rainfall in the field led to higher N2O emissions. Preliminary results from the incubation indicated lower N2O emissions under drought conditions, with increased emissions upon rewetting and the highest emissions under moist conditions. The presence of plants decreased soil N2O emissions in both experiments, but the plant species did not affect the emissions nor the total mineral N content in soil. As expected, in the pot experiment, total mineral N content in soil was higher in drought conditions than in moist soil as well as in bare soil compared with soil with growing plants. Results on the effects of drought and plants on gross N transformations during the incubation experiment with 15N labelling will be presented later.
How to cite: Turunen, P., Viinikainen, A., Koskinen, M., Simojoki, A., Karhu, K., and Pihlatie, M.: The effect of drought and rewetting on nitrogen cycling and nitrous oxide emissions in a controlled experiment with different cover crop species, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15354, https://doi.org/10.5194/egusphere-egu25-15354, 2025.
Soil microbial nitrous acid (HONO) production is an important source of atmospheric reactive nitrogen that affects air quality and climate. However, long-term global soil HONO emissions driven by climate change and fertilizer use have not been quantified. Here, we derive the global soil HONO emissions over the past four decades and evaluate their impacts on ozone (O3) and vegetation. Results show that climate change and the increased fertilizer use enhanced soil HONO emissions from 9.4 Tg N in 1980 to 11.5 Tg N in 2016. Chemistry-climate model simulations show that soil HONO emissions increased global surface O3 mixing ratios by 2.5% (up to 29%) and vegetation risk to O3, with increasing impact during 1980s-2016 in low-anthropogenic-emission regions. With future decreasing anthropogenic emissions, the soil HONO impact on air quality and vegetation is expected to increase. We thus recommend consideration of soil HONO emissions in strategies for mitigating global air pollution.
How to cite: Wang, Y., Li, Q., Treb, I., Wang, Y., Ren, C., Saiz-Lopez, A., Xue, L., and Wang, T.: Increasing soil nitrous acid emissions driven by climate and fertilization change aggravate global ozone pollution, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17830, https://doi.org/10.5194/egusphere-egu25-17830, 2025.
Mass emergence of periodic cicadas (Magicicada spp.) represents a unique ecosystem disturbance with potential impacts on forest soil biogeochemistry and greenhouse gas emissions. During the 2021 Brood X emergence in Indiana, USA, we investigated how cicada emergence and subsequent decomposition affected soil microbial communities and their production of nitrous oxide (N2O) and ammonia (NH3). Using a combination of field measurements and controlled laboratory experiments, we discovered that the interface between cicada carcasses and soil surfaces creates hotspots of enhanced microbial nutrient cycling, leading to significant pulses of N2O and NH3 after approximately 10-15 days. Our study revealed that dissimilatory nitrate reduction to ammonia (DNRA) was the primary mechanism driving these emissions, evidenced by increased abundance of DNRA taxa on cicada carcass surfaces (the necrobiome) coinciding with peak gas fluxes. Notably, the abundance of Serratia marcescens, a bacteria capable of both chitin degradation and DNRA, was significantly positively associated with N2O pulses. Analysis of 16S rRNA amplicon sequencing data showed distinct microbial community compositions between soil and cicada necrobiome samples, with significantly higher abundances of chitinolytic and DNRA taxa in the necrobiome. Time series decomposition experiments demonstrated that soil respiration rates and nitrogen cycling were significantly enhanced in cicada-amended soils. Quantitative PCR revealed that bacterial ammonia oxidisers dominated over archaeal counterparts in soil samples, while the cicada necrobiome was characterised by high abundances of heterotrophic nitrifiers. The emergence tunnels created by cicadas also influenced soil conditions, potentially creating microsites that favour DNRA over conventional denitrification. While individual emergence events may contribute relatively small amounts of nitrogen compared to annual atmospheric deposition, the predictable nature and geographic extent of cicada emergences suggest they may represent an overlooked yet significant contributor to forest nitrogen cycling and greenhouse gas emissions. Our findings provide new insights into the complex microbiological mechanisms driving biogeochemical pulses following mass mortality events and highlight the need to consider periodic ecosystem disturbances in climate change models.
How to cite: Mushinski, R., Purchase, M., Phillips, R., Raff, J., Phelps, A., Huenupi, E., and Lau, J.: Periodic Cicada Mass Mortality Events Drive Microbial-Mediated Gas Pulses from Forest Soils, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5842, https://doi.org/10.5194/egusphere-egu25-5842, 2025.
Tropical peatlands are crucial for global nitrogen (N) cycling because they store large amounts of carbon and N. This study, conducted in November 2023, investigated the dynamics of N2O emissions from Amazonian peatland forests in Peru. It focused specifically on two peatland forest sites in Iquitos: the Quistococha and Zungarococha forests. We conducted static chamber gas measurements to assess soil greenhouse gas (GHG) fluxes. Additionally, we took soil samples for physical and chemical properties and soil microbiome (DNA & RNA). In order to investigate the source processes for N2O production and consumption, we applied 15N isotopes as tracers in soil. We also took samples for natural abundance of 15N in N2O gas. Our results indicate that both forests exhibited different trends in soil GHG fluxes and N substrates. Quistococha had higher levels of soil nitrate and ammonium compared to Zungarococha, which correlated with increased N2O emissions from Quistococha. A similar pattern was observed for CO2 emissions, with Quistococha producing higher levels than Zungarococha. Contrastingly, Zungarococha had higher soil moisture levels, which aligned with its lower N2O emissions. This forest also showed greater soil N2 emissions, suggesting the potential for complete denitrification. However, this site was also a significant source of CH4 emissions due to its higher soil moisture, which supports methanogenic activity. Overall, the two sites demonstrated distinct behaviors: Quistococha was a source of N2O and CO2, influenced by intermediate soil moisture. Zungarococha emitted higher levels of CH4 and N2 due to its high soil moisture conditions. The patterns in N2O fluxes are further supported by 15N isotopic mapping, correlating N2O emissions with their source processes. The site preference values fall within the denitrification zone at Zungarococha and the nitrification zone, with some hybrid processes in Quistococha. The microbiome analyses show similar results, with denitrifying microbes dominating the Zungarococha soil and nitrifying microbes dominating the Quistococha soil.
How to cite: Masta, M., Kazmi, F. A., Espenberg, M., Pärn, J., Soosaar, K., and Mander, Ü.: Dynamics of N2O emissions from Amazonian tropical peat forest and partitioning N-processes using 15N isotopes., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6740, https://doi.org/10.5194/egusphere-egu25-6740, 2025.
Human activities have globally increased atmospheric nitrogen (N) deposition, which has enhanced the risk of ecosystem N losses. Phosphorus (P), as a macroelement required for life, is closely linked to the biogeochemical cycle of N. Therefore, quantifying how soil N cycle responds to different P supply levels is important. Here we examined the responses of soil N dynamics to altered P supply using a P addition experiment (+0, +25, +50, +100 kg P ha−1 yr−1) in an evergreen broadleaf mixed plantation in subtropical China. We found that P addition led to a more open soil N cycle in the forest ecosystem. The primary source of N2O emissions in the study plots was fungal denitrification, which accounted for 41%-52% of the total N2O emissions, based on δ18O-N2O, δ15Nα-N2O, δ15Nbulk-N2O and SP measurements. Nitrogen loss by gas or water and N assimilation by plants were found to be coupled processes at +25 kg P ha−1 yr−1 addition level. The δ15N-NO3− and δ18O-NO3− values in runoff and leaching water from different depths were all depleted from −10‰ to +0‰ in the wet season. This result indicates that soil N has a short residence time and rapid NO3−-N loss in the forest ecosystem, and with fewer nitrogen conversions according to the isotope fractionation theory. These observed varied responses of soil N transformation, gaseous loss, and liquid loss to different P supply levels provide new insights into our understanding of N-P relationships in broadleaf forest plantations.
How to cite: Ye, H., Lin, H., Ibrahim, M. M., Chen, L., Liu, Y., Bol, R., and Hou, E.: Phosphorus addition impacts on soil nitrogen dynamics in a subtropical plantation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16227, https://doi.org/10.5194/egusphere-egu25-16227, 2025.
Soil organic matter (SOM) provides crucial storage for carbon but also contains a majority of soil nitrogen. Land use intensity (LUI) may affect the particulate and mineral-associated SOM pools having repercussions on the carbon and nitrogen storage and cycling. Soil organic matter dynamics and composition plays a key role for the extent of these processes, yet its interactions remain poorly understood preventing targeted mitigation measures for carbon and nitrogen-related soil functions. Here we provide insights investigating how LUI and soil properties affect the storage of carbon and nitrogen in functional SOM pools in the topsoil (0-30 cm) of grassland soils across three different regions in Germany. Furthermore, we present a conceptual framework integrating biological, mineral, and organic nitrogen pools to disentangle nitrogen cycling processes and their interactions with organic matter dynamics.
Across the land use intensity gradient, we isolated particulate organic matter (POM), which is part of in the >20 μm fraction, and mineral associated organic matter (MOM) in the <20 μm fraction. Random forest and mixed model analysis showed that LUI did not significantly affect SOM storage, but led to reduced C/N ratios in POM and MOM, driven by increased N fertilization intensity. Rather than land use intensity, soil properties, such as clay and iron oxide content, and soil type diversity exerted most influence on SOM.
To reconcile the influences of soil properties on soil nitrogen cycling, we provide a novel conceptual framework integrating organic matter stabilization mechanisms, microbial N uptake and release as necromass, as well important processes catalyzed by the soil microbiome including biological nitrogen fixation pathways. Our integrative nitrogen cycling framework stimulates different disciplines towards a new perception of the nitrogen cycle in unlocking multiple organic nitrogen pools as mediated by soil type and climatic conditions.
How to cite: Schweizer, S. A., Böhm, A., Kepp, J., Kiese, R., Pacay-Barrientos, N. L., Ramm, E., Schloter, M., Schöning, I., Schrumpf, M., Schulz, S., and Dannenmann, M.: Cycling of nitrogen in soil organic matter pools in grasslands as influenced by land use intensity and soil diversity, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19982, https://doi.org/10.5194/egusphere-egu25-19982, 2025.
Reactive nitrogen (N) deposition presents significant environmental challenges in India, where approximately 24% of the land is forested and agriculture plays a vital role in the economy. As a major contributor from South Asia—a global reactive nitrogen emissions hotspot—India's policy actions, or inactions, have far-reaching implications. Despite ongoing clean air initiatives, the scientific community has largely neglected the effects of reactive nitrogen deposition on terrestrial ecosystems. This study aims to compile and assess the current research status on reactive nitrogen deposition in India, underscoring its importance given the country's unique geography and agricultural reliance.
The study will provide indirect estimations of reactive nitrogen deposition based on nitrogen concentration measurements from various regions across the country. While wet deposition studies offer a broader understanding, research on dry deposition remains limited. Recent efforts, such as the South Asia Nitrogen Hub project led by CEH UK, have studied the forest ecosystem to explore the impact of reactive nitrogen on lichens. However, comprehensive data on reactive nitrogen deposition across diverse ecosystems is still lacking.
This research seeks to identify existing gaps and stimulate discussion on future research directions essential for the effective management of reactive nitrogen in India's varied ecosystems. By addressing these issues, we aim to inform policy and practice to mitigate the adverse effects of reactive nitrogen deposition while promoting sustainable development in the region.
How to cite: Singh, S.: Reactive Nitrogen Deposition in India: Impacts on Terrestrial Ecosystems and Current Research Status, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17857, https://doi.org/10.5194/egusphere-egu25-17857, 2025.
The input of nitrogen (N) into forests through atmospheric deposition has been determined for the main forest types within the ICP Forests Level II monitoring network and the Swedish Throughfall Monitoring Network (SWETHRO) since the 1990s from measured concentrations in continuously collected precipitation (bulk deposition) and throughfall (below tree canopy) samples. Recently, aggregated data sets have been created, containing gap-filled monthly and annual bulk and throughfall depositions (including stemflow in beech stands) for more than 500 forest stands. Total deposition was calculated from throughfall deposition accounting for canopy exchange. Here, we present trends for throughfall deposition of inorganic N, including ammonium (NH4+-N) and nitrate (NO3--N), for plots with a complete time series, during the period 2000-2020 and in the first and last decade separately. Furthermore, we highlight and discuss spatial trends of total inorganic N deposition across Europe.
How to cite: Verstraeten, A., Schmitz, A., Marchetto, A., Clarke, N., Thimonier, A., Hilgers, C., Prescher, A.-K., Kirchner, T., Hansen, K., Jakovljević, T., Iacoban, C., de Vries, W., Ahrends, B., Meesenburg, H., Pihl Karlsson, G., Karlsson, P. E., and Waldner, P.: Trends of inorganic nitrogen deposition in European forests during the period 2000-2020, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3079, https://doi.org/10.5194/egusphere-egu25-3079, 2025.
Concentrated animal feeding operations (CAFOs) are emission hotspots of ammonia (NH3). The NH3 emitted from these hotspots can be locally recaptured by the surrounding vegetation, mainly due to dry deposition. This deposition can either have beneficial fertilizing effects for N-limited ecosystems or pose adverse impacts on sensitive ecosystems. However, there is a lack of direct measurements of NH3 deposition near hotspots. We conducted two field campaigns to investigate the landscape NH3 fluxes over the barley (winter), lentil (winter), and fallow (summer) fields adjacent to an intensive beef cattle feedlot in southeast Australia. The flux measurements were segregated into periods when the measurement location was upwind of the feedlot or downwind. Upwind of the feedlot, we observed upward fluxes (surface emissions) over the fallow and barley sites with daily means (± standard error) of 0.16 ± 0.02 and 0.007 ± 0.012 μg NH3 m-2 s-1, and downward fluxes (deposition) over the lentil site with a daily mean of -0.022 ± 0.007 μg NH3 m-2 s-1. These measurements indicated the NH3 compensation point for barley was approximately 6.2 μg m-3 (equivalent to the background atmospheric NH3 concentration), and the NH3 compensation point for lentils was lower than 3.4 μg m-3. Downwind of the feedlot, we observed downward fluxes at all sites with daily means of -0.57 ± 0.09 μg NH3 m-2 s-1 for the barley site, -1.26 ± 0.17 μg NH3 m-2 s-1 for the lentil site, and -0.58 ± 0.12 μg NH3 m-2 s-1 for the fallow site; the mean deposition velocities over the barley, lentil, and fallow sites were 0.74, 0.82 and 0.78 cm s-1. Based on the frequency of upwind and downwind periods, we estimate that the accumulated N inputs to the barley, lentil and fallow fields during each campaign were 4.5, 14.8 and 4.3 kg N ha-1, indicating that the deposition of NH3 emitted from the feedlot serves as a significant source of N input to its adjacent fields. Our study can provide valuable information on NH3 exchange between vegetation and atmosphere, and extend our understanding of the fate of NH3 emitted from hotspots.
How to cite: Wang, Q., Flesch, T. K., and Chen, D.: Landscape fluxes and dry deposition velocity of ammonia near a cattle feedlot using flux gradient approach, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10603, https://doi.org/10.5194/egusphere-egu25-10603, 2025.
Deposition of reactive nitrogen causes detrimental environmental effects, including biodiversity loss, eutrophication, and soil acidification. Measuring and modeling the biosphere-atmosphere exchange of ammonia, the most abundant reduced nitrogen species, is complex due to its high reactivity and solubility, often leading to systematic discrepancies between model predictions and observations. This study aims to determine whether three state-of-the-art exchange schemes for NH3 can accurately model NH3 exchange in a dune ecosystem and detect factors causing the uncertainties in these schemes. The selected schemes are DEPAC by Van Zanten et al. (2010), and the schemes by Massad et al. (2010) and Zhang et al. (2010). Validation against one year of gradient flux measurements revealed that the Zhang scheme represented the NH3 deposition at Solleveld best, whereas the DEPAC scheme overestimated the total deposition while the Massad scheme underestimated the total deposition. Yet, none of these schemes captured the emission events at Solleveld, pointing to considerable uncertainty in the compensation point parameterization and possibly in the modeling of NH3 desorption processes from wet surface layers. The sensitivity analysis further reinforced these results, showing how uncertainty in essential model parameters in the external resistance (Rw) and compensation point parameterization propagated into diverging model outcomes. These outcomes underscore the need to improve our mechanistic understanding of surface equilibria represented by compensation points, including the adsorption-desorption mechanism at the external water layer. Specific recommendations are provided for future modeling approaches and measurement setups to support this goal.
How to cite: Jongenelen, T., van Zanten, M., Dammers, E., Wichink Kruit, R., Hensen, A., Geers, L., and Erisman, J. W.: Validation and uncertainty quantification of three state-of-the-art ammonia surface exchange schemes using NH3 flux measurements in a dune ecosystem, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4177, https://doi.org/10.5194/egusphere-egu25-4177, 2025.
There are several nitrogen-sensitive areas in Europe, some more sensitive than others, and the Mediterranean climate zone is where many of the highly sensitive areas are. One of these areas is Portugal, where very few studies focus on this issue. The lack of infrastructure to monitor nitrogen concentrations and deposition in the country, as well as policies to enforce nitrogen emission reductions, poses a challenge, as ammonia is the most critical pollutant to fulfil Portugal's future emission goals.
Currently, modelling is the only cost-effective option to effectively study nitrogen deposition in the Mediterranean. Due to the extent of agriculture in these areas, nitrogen (N) deposition assessments have been conducted for many years in other countries, such as the Netherlands and Germany, using Chemistry Transport Models (CTMs) to assess the dry deposition of reduced and oxidised N. Among these CTMs, LOTOS-EUROS is regarded as one of the most advanced models that includes a compensation point parametrization for ammonia. However, applying this model to a Mediterranean area requires some adaptation since its deposition parameters are mostly based on studies from North-Western Europe. Since vegetation parameters influence the surface resistance of gas-phase deposition, and this resistance is crucial for gas deposition, using these models in climates different from where they were initially developed will likely lead to inaccurate results. Due to this, there is a need for a CTM that better represents different climate zones.
Here, we use a new version of the LOTOS-EUROS model incorporating a three-tiered vegetation approach. The three tiers considered are Tier 1—climate zones; Tier 2—land use classes; and Tier 3—vegetation type. This method incorporates 140 combinations of land use and vegetation types, allowing us to differentiate the Mediterranean from the standard temperate climate by changing vegetation parameters.
With this study, we aim to adapt and enhance the dry deposition module of LOTOS-EUROS by including specifications for the Mediterranean climate and vegetation. To achieve this goal, sensitivity runs were performed for multiple vegetation and climate-specific parameters to assess which are the most influential variables for the study region. Then, the most sensitive parameters were analysed to understand the variations.
This work found that adapting the maximum stomatal conductance is highly prone to introduce changes in the modelled deposition fluxes and concentrations of oxidised and reduced nitrogen and ozone. Maximum and minimum vapour pressure deficit and maximum, optimal and minimum temperature were also among the most susceptible to cause impacts in the model results over the Mediterranean. Also, the start and end of the growing season greatly impacted the modelled deposition fluxes since the growing season starts earlier and finishes later in the Mediterranean. Hence, adapting the deposition parameters to the Mediterranean climate and vegetation significantly impacts the modelled concentration and deposition fluxes of oxidised and reduced nitrogen compounds and ozone.
How to cite: Barreirinha, A., Banzhaf, S., Russo, M., Thürkow, M., Schaap, M., and Monteiro, A.: Investigating the sensitivity of modelled nitrogen inputs in the Mediterranean to dry deposition parameters, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1042, https://doi.org/10.5194/egusphere-egu25-1042, 2025.
Excessive nitrogen deposition from anthropogenic activities poses significant challenges to ecosystems and air quality.1 The atmospheric deposition of ammonium and nitrate plays a critical role in regulating ecosystem productivity and driving particulate matter formation, with impacts that vary across spatial and temporal scales.
In this study, high time-resolution measurements of gas-phase nitric acid (HNO3) and ammonia (NH3), as well as particulate nitrate and ammonium were conducted at an agricultural site in Switzerland. These measurements were complemented by 15 years of long-term monitoring data at the same site, providing a comprehensive record of changes in atmospheric gas and aerosol species over time. Aerosol pH was estimated using the ISORROPIA thermodynamic model2 and evaluated using a well-established approach based on the agreement between observed and predicted partition ratios of nitrogen species. The intensive measurement shows that the diurnal cycles of HNO3 and NH3 partitioning exhibited distinct patterns. HNO3 tended to partition into the particle phase during the night, driven by cooler temperatures, while NH3 remained predominantly in the gas phase throughout the day and night, regulated by high aerosol pH characteristics at the sampling site.
The dry deposition regimes of HNO3 and NH3 were investigated in relation to aerosol liquid water content and acidity following the approach of Nenes et al. (2021).3 The findings indicate that NH3 deposition is rapid, meaning it tends to deposit near its sources, raising concerns about its localized ecological impacts. Aerosol mass formation was found to be primarily sensitive to HNO3 concentrations. Long-term monitoring data spanning 15 years revealed that reduction in SO2 emissions did not lead to increases in aerosol pH owing to the buffering effect of NH3 in the NH3-rich environment. The decline in sulfate concentration has driven a clear shift in aerosol mass sensitivity, transitioning from NH3-sensitive to NH3 -insensitive regime. Comparative measurements at forested sites in Switzerland provide further insight into the diurnal cycle of aerosol pH and reactive nitrogen deposition, highlighting the influence of anthropogenic activities on nitrogen dynamics across different ecosystems. These findings show the complex interplay between rapidly fluctuating diurnal aerosol acidity and reactive nitrogen deposition, offering important reference for designing effective pollutant mitigation strategies.
References:
(1) Wim de Vries.: Impacts of nitrogen emissions on ecosystems and human health: A mini review, Current Opinion in Environmental Science & Health, 2021, 21:100249, DOI: 10.1016/j.coesh.2021.100249.
(2) Fountoukis, C. and Nenes, A.: ISORROPIA II: a computationally efficient thermodynamic equilibrium model for K+–Ca2+–Mg2+–NH4+–Na+–SO42−–NO3−–Cl−–H2O aerosols, Atmospheric Chemistry and Physics, 7, 4639–4659, DOI:10.5194/acp-7-4639-2007, 2007.
(3) Nenes, A., Pandis, S. N., Kanakidou, M., Russell, A. G., Song, S., Vasilakos, P., and Weber, R. J.: Aerosol acidity and liquid water content regulate the dry deposition of inorganic reactive nitrogen, Atmospheric Chemistry and Physics, 21, 6023–6033 DOI:10.5194/acp-21-6023-2021, 2021.
How to cite: Zhang, J., Waseem, A., Baccarini, A., Motos, G., Hüglin, C., Yue, S., Brem, B., Simon, L., Dada, L., Violaki, K., Gysel, M., Slowik, J., and Nenes, A.: Atmospheric reactive nitrogen and its dry deposition regimes under anthropogenic influence: Insights from intensive and long-term monitoring in Switzerland, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19168, https://doi.org/10.5194/egusphere-egu25-19168, 2025.
Particulate nitrate (pNO3-) and its precursor gas nitrogen oxide (NOx) are among the most significant reactive nitrogen species in the atmosphere. NOx emissions over the Indian sub-continent especially the Indo-Gangetic Plain (IGP) have increased rapidly over the past decades. NOx, an atmospheric gaseous pollutant, plays important roles in the formation of tropospheric ozone, recycling of hydroxyl radicals (OH), etc. It also serves as a precursor to pNO3- formation. This has significant implications for air quality, climate, and human health. Rapid accumulation of pNO3- can also increase PM load by aiding in secondary aerosol formations. Identification of the major sources of NOx and the formation pathways of pNO3- is crucial for improving the accuracy of air quality models and effective mitigation strategies. In the atmosphere, pNO3- is known to form mainly via four distinct pathways: (P1) oxidation of NO2 by OH in gas phase, (P2) hydrolysis of N2O5 on existing aerosols, (P3) reaction between NO3 radicals and VOCs, and (P4) reaction of NO3 radical and ClO. However, studies on the sources and formation pathways of pNO3- are limited pertaining to the Indian subcontinent as well as the globe. Dual isotopes (δ15N and δ18O) of pNO3- are an excellent tool to understand the formation mechanisms and sources of pNO3- precursor (NOx) in the atmosphere. In this study, diurnal samples of PM2.5 were collected over a semi-urban site (Patiala) in the IGP during a large-scale paddy residue burning period (October-November). Dual isotopes (δ15N and δ18O) of pNO3- along with other major ions were measured. Average δ18O and δ15N of pNO3- were 57.2 ± 8 ‰and -1.9 ± 5 ‰, respectively. Significant diurnal differences in δ18O-NO3- and δ15N-NO3- were observed. δ15N-NO3- and δ18O-NO3- were -5.0 ± 2.4‰, 52.1 ± 6.2‰ and -0.13 ± 5.7‰, 60.0 ± 8.4‰ during day and night-time respectively. Enriched δ15N-NO3- during night-time was due to enhanced gas-particle partitioning owing to lower temperature. A significant negative correlation between Nitrate Oxidation Ratio (NOR), and temperature further supported the above statement. Stable isotope mixing model (MixSIAR) was used to estimate the contribution of different pathways to pNO3- formation and sources. The major pathways contributing to the formation of pNO3- were P1(OH) (~ 92%) followed by P2 (N2O5) (~ 5%). P3 (VOCs) and P4 (ClO) had negligible contributions of ~1.3 and ~1.5% respectively. Relative contributions of P1 and P2 during day and night-time were calculated. P1 and P2 contributed to 95% and 5%, and 77% and 23% during day and night-time respectively. Presence of pNO3- formed via P1 during night-time could be due to the higher lifetime of pNO3- compared to sampling duration. Source apportionment showed biomass burning (32%) and traffic exhaust (35%) were the major contributors followed by combustion (18%) and soil emissions (15%) during the study period. Our study, first of its kind over India, is important for elucidating the formation mechanism of pNO3- from its precursor gas. Such studies are helpful in planning and developing mitigation strategies aiming to reduce NOx pollution over a specific region.
How to cite: Shaw, C., Mandal, R., Singh, A., Sanyal, P., and Rastogi, N.: Insights into the sources of precursor and formation pathways of particulate NO3- during paddy-residue burning period through dual isotope proxies, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-880, https://doi.org/10.5194/egusphere-egu25-880, 2025.
Human activities such as fertilization of agricultural lands and human-induced biomass burning strongly impact nitrogen (N) dynamics and losses, with many consequences on the environment. The quantification of N budgets (N inputs and outputs) between the surface and the atmosphere is a prerequisite to understand the N biogeochemical cycle, i.e. how N is transferred from the atmosphere to the biosphere, through the soil and back to the atmosphere from surface emissions. Sub Saharan Africa (SSA) is characterized by an increase in demography, with strong impacts on biodiversity, and on the sustainability of human activities including agriculture. In Africa, the increase in demography and the associated increased fertilizer inputs (to supply growing food and energy demands) will lead to increased emissions from amended soils, which will in turn increase atmospheric N deposition and induce feedbacks to the ecosystems and the atmosphere.
In this context, the NitroAfrica project (2023-2026) is designed to study the impact of N wet deposition on the soil – plant – atmosphere continuum. We make the hypothesis that changes of wet N deposition in West African ecosystems over the 21th centuries will induce important changes in biogenic emissions from the ecosystems to the atmosphere with impacts on regional atmospheric chemistry and further N deposition. Indeed, increasing trends of N wet deposition has already been observed, especially in the NH4+ form. Three ecoclimatic zones in West Africa are studied, in Guinean (Lamto, Côte d’Ivoire), Sudanese (Korhogo, Côte d’Ivoire) and Sahelian (Dahra, Senegal) zones, where solutions with different NH4+/NO3- partition are used to mimic the increase in N wet deposition.
Results on N (N2O, NO) and CO2 emissions from soils from plots amended with solutions as well as control plots will be presented. N wet deposition fluxes from recent years will also be presented within the context of existing long-term studies on N wet deposition. This comparison is particularly relevant for the Lamto station where the International Network to study Deposition and Atmospheric chemistry in Africa (INDAAF) is based and provides long-term data since 1995.
This study contributes to fill in the lack of studies in SSA, and to understand the processes involved in N emissions and deposition in tropical regions.
How to cite: Delon, C., Galy-Lacaux, C., Serça, D., Ossohou, M., Zouré, M., Barot, S., Le Roux, X., Ndiaye, O., Siélé, S., Kouassi, A., Gardrat, E., Dias-Alves, M., and Lenoir, O.: Impact of wet nitrogen deposition on soil nitrogen emissions in West African ecosystems, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12860, https://doi.org/10.5194/egusphere-egu25-12860, 2025.
Nitrogen (N) deposition generally reduces the temporal stability of plant community (community stability) across spatial scales. Theory predicts that community stability increases with sampling area, leading to a positive community stability–area relationship (CSAR). However, because atmospheric N deposition exhibits a temporal pattern, little is known about how the responses of community stability differ under seasonal N deposition, or whether seasonal N deposition alters the CSAR and its underlying mechanisms. Understanding this is crucial for assessing multi-scale ecological sustainability under global change. We conducted an experiment with N input during autumn, winter, or the growing season in a temperate grassland. Based on six years of survey data across nested spatial scales ranging from 0.01 to 16 m2, we explored the potential impacts of seasonal N enrichment on the CSAR. Our results showed that community stability increased with sampling area, regardless of N addition. Each of the three seasonal N inputs caused a significant reduction in the CSAR intercept, while N addition in winter or the growing season also reduced the CSAR slope. Biodiversity had a stronger effect than area in maintaining the positive CSAR, and mediated the relationship between area and stability. High biodiversity preserved community stability by maintaining population stability and compensatory dynamics. By validating and extending the CSAR theory under seasonal N input, our research showed that N input in winter or the growing season caused a greater reduction in plant community stability at larger spatial scales. As global N deposition continues to increase, small-scale studies may undervalue the adverse impact of N input on stability, while large-scale studies based only on N input during the growing season may overestimate this effect. These findings highlight the need to consider both spatial scales and seasonality of N deposition for accurately predicting ecosystem responses to atmospheric N deposition.
How to cite: Zhang, Y., Stevens, C. J., Lu, W., Chen, X., Ren, Z., and Zhang, Y.: Does nitrogen deposition affect plant community stability–area relationships? The role of biodiversity, area, and seasonal N addition, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21215, https://doi.org/10.5194/egusphere-egu25-21215, 2025.
Nitrogen policy in the Netherlands has a long history. Since the 70’s of the last century, various measures have been implemented in an attempt to reduce emissions of different nitrogen compounds. A few examples of a wide range of measures implemented since then are the introduction of catalytic converters removing nitrogen oxides from fossil fuel burning, shallow injection of manure into the soil reducing ammonia emissions to air and lowering of the manure application rates. In 2019, the European High Court judged that the Dutch nitrogen policy with respect to nitrogen deposition onto protected nature areas was not in accordance with the European Habitats Directive. All infrastructural developments came to a halt: building houses, roads, etc. stopped. With a new Minister on Nitrogen in place since 2021, the focus became a drastic reduction of nitrogen emissions to get the nitrogen deposition below the nitrogen critical loads for 74% of the protected (Natura 2000) nature areas, which is laid down in a nitrogen law. This requires a drastic change in activities in and around these nature areas, mainly (but not exclusively) focusing on the agricultural sector. This because the contribution to the total nitrogen deposition of this sector is on average 50% in the Netherlands. To help policymakers take measures as efficiently as possible, RIVM has developed a tool that maps the origin of the nitrogen deposition in each nature area. In this presentation, the tool will be presented and it will be shown how the tool can help the government, provinces and other stakeholders to take dedicated regional measures to reduce the nitrogen emissions and eventually reduce the nitrogen deposition in nature areas.
How to cite: Wichink Kruit, R., Brandt, K., Bleeker, A., and van der Maas, W.: Determining the origin of nitrogen deposition in nature areas, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1792, https://doi.org/10.5194/egusphere-egu25-1792, 2025.
Increased atmospheric nitrogen (N) deposition into sensitive ecosystems is leading to soil acidification, nutrient imbalances and biodiversity losses. Therefore, N depositions were quantified throughout Switzerland in 2000, 2014, 2019 and 2024 measuring the concentrations of seven different inorganic N compounds in wet and dry gravitational as well as in dry non-gravitational deposition. For data collection passive (diffusion tubes and bulk sampler) and active sampling systems (denuder and filter sampler) were used. From the obtained measurement data, N depositions were calculated. The wet and dry gravitational deposition was obtained directly from the bulk samples. The dry non-gravitational deposition was calculated using the inferential method. By summing up the gravitational and non-gravitational N deposition, the total N deposition was obtained and compared to the critical loads for N (CLN). The results show that N inputs in Switzerland are largely around or above the CLN, regardless of the sensitive ecosystems considered. Considerable exceedances have been found near intensive agriculture. In the long-term comparison, a decrease in oxidized N components was observed. However, the total N deposition remained stable over time. The most important processes for the N deposition are the precipitation and the dry deposition of ammonia (NH3). In summary, the atmospheric N inputs into sensitive ecosystems in Switzerland are largely too high and therefore further measures to reduce N emissions are necessary.
We would like to thank to the Swiss Federal Office for the Environment (FOEN), Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Ostluft, the Swiss cantons and the University of Basel for financial support of the measurement campaigns. A special thank goes to the Swiss Federal Laboratories for Materials Science and Technology (EMPA) for the valuable cooperation.
How to cite: Meier, M., Ehrenmann, Z., and Seitler, E.: Atmospheric nitrogen deposition in Switzerland, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18103, https://doi.org/10.5194/egusphere-egu25-18103, 2025.
Anthropogenic emissions of reactive nitrogen in Europe have increased significantly over the last two centuries. A large proportion of this reactive nitrogen is released into the atmosphere in the form of ammonia (NH3), which is generated from livestock farming activities and fertilizer use, and in the form of oxides of nitrogen (NOX) generated from the combustion of fossil fuels.
The atmospheric deposition of reactive nitrogen can adversely impact ecosystems and biodiversity. This is particularly relevant to the Iberian Peninsula where ecosystems that have a low threshold for eutrophication, and are therefore highly sensitive to nitrogen levels, are found.
In-situ measurements of reactive nitrogen species in this region are sparse and those that are available are measurements of NO2 concentrations and in some cases intermittent measurements of NHX & NOY wet deposition. This limitation in the availability of deposition data gives rise to a dearth of knowledge and a high degree of uncertainty in ascertaining the budget of nitrogen species in this region.
Several approaches have been developed to estimate emissions of NO2 and NH3 utilizing earth observation. Here we present the application of a multi-gaussian plume inversion method in combination with satellite observations of NH3 from the Cross-Track Infrared Sounder instrument and observations of NO2 from the TROPOMI sensor to validate concentration distributions simulated by the LOTOS-EUROS chemistry transport model.
Initially, a steady-state inversion scheme was applied over the Iberian Peninsula to derive spatial-temporal emission fields and evaluate these against inventory emissions and existing spatial and temporal distributions. An analysis of these results shows variations between the spatial distribution of inventory emissions and those obtained from the satellite observations. Then, the resulting emission fields are used within the LOTOS-EUROS model to simulate the concentration and deposition fields which will be evaluated with in-situ data.
How to cite: Helm, D., Dammers, E., Gama, C., Schaap, M., and Monteiro, A.: Emissions of ammonia and nitrogen dioxide over the Iberian Peninsula estimated with satellite observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1143, https://doi.org/10.5194/egusphere-egu25-1143, 2025.
Despite reduction of nitrogen emissions, deposition in German forests remain high. Eutrophication of ecosystems thus remains an important issue of scientific and socio-political interest. Here we analyse data from 78 intensive forest monitoring (Level II) sites operated by the forest research institutes of the German federal states as part of the ICP Forests network (International Co-operative Programme on Assessment and Monitoring of Air Pollution Effects on Forests). In the 2013-2022 period, mean annual bulk open field (inorganic + organic) deposition was between 4.4 and 13.5 kg N ha-1 a-1. Over the past twenty years, N deposition decreased by about 40 % which corresponds to a decrease of 2.5 % per year compared to the deposition in 2010. The decrease in N-NO3 (-3.1 % per year) was slightly higher than the decrease in N-NH4 (-2.7 %). Organic N deposition decreased by only 0.7 % per year. Canopy budget models show that N deposition (wet + dry + occult) to forest sites was between 10 and 31 kg N ha-1 a-1 over the same period.
The deposition data is used for reporting duties such as the German federal states’ core indicators of environmental quality (LIKI) and for scientific research e.g. to evaluate changes in biodiversity, dynamics of nutrient cycles and ensuing vulnerability of ecosystem services, or effects on tree vitality. We used the data to assess the impact of N deposition on foliar N concentrations, an import indicator of tree nutrition status. Tree nutrition influences vitality and trees’ resilience to climate extremes. A deterioration of foliar nutrients has been observed in forest ecosystems across Europe. At the German Level II sites, all main tree species (European beech, Norway spruce, Scots pine, sessile and pedunculate oak) show a significant decrease in foliar N concentration of 0.2-0.3 % per year. Besides nitrogen deposition, the reduction has been linked to various environmental factors, including increasing temperatures and changing precipitation patterns, as well as, the increase in atmospheric CO2 concentrations. At the spatial scale, nutrient availability can be explained by various site conditions such as parent material. Nonetheless, weak positive but significant relationships between mean foliar N and total N deposition for beech, oak, and pine for the 2013-2022 time period show that atmospheric deposition can explain part of the spatial variability between forest sites. The results indicate the importance of assessing deposition, trophy classes, and climate conditions at the same sites to fully understand their interaction.
How to cite: Krüger, I., Schmitz, A., Stadelmann, C., and Sanders, T.: Decreasing N deposition leads to significant decrease in foliar N concentrations in forest trees, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8269, https://doi.org/10.5194/egusphere-egu25-8269, 2025.
Advances in manufacturing and trade have reshaped global nitrogen deposition patterns, yet their dynamics and drivers remain unclear. Here, we compile a comprehensive global nitrogen deposition database spanning 1977–2021, aggregating 52,671 site-years of data from observation networks and published articles. This database show that global nitrogen deposition to land is 92.7 Tg N in 2020. Total nitrogen deposition increases initially, stabilizing after peaking in 2015. Developing countries at low and middle latitudes emerge as new hotspots. The gross domestic product per capita is found to be highly and non-linearly correlated with global nitrogen depositiondynamic evolution, and reduced nitrogen deposition peaks higher and earlier than oxidized nitrogen deposition. Our findings underscore the need for policies that align agricultural and industrial progress to facilitate the peak shift or reduction of nitrogen deposition in developing countries and to strengthen measures to address NH3 emission hotspots in developed countries.
How to cite: Zhu, J., Yu, G., and Wang, Q.: Changing patterns of global nitrogen deposition driven by socio-economic development, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15249, https://doi.org/10.5194/egusphere-egu25-15249, 2025.
We present a new Horizon Europe project titled GreenEO (2025-2029) as well as findings based on advances in modelling within the Nordic Nature & Nitrogen (Nordic Council of Ministers, 2021-2024) and the SEEDS (Horizon 2020, 2021-2023) projects. The ambition of GreenEO is to support governance approaches for the implementation of EU’s Green Deal. The implementation of which will rely on accessible, actionable environmental data for policymaking and monitoring. Success will be dependent on the usage of the latest observational data as well as on the level of uptake of these data by end-users. GreenEO addresses this by using observations from the Sentinel and newest meteorological (MTG and Metop-SG) satellites, and through co-creation with users of high-resolution services and novel indicators to directly meet user needs.
GreenEO will specifically address the environmental impacts of nitrogen deposition and advance the state of knowledge on this topic within the context of supporting the EU’s Green Deal and its ambition for protecting biodiversity.
Current data on nitrogen emissions, deposition, and biodiversity impacts are inconsistent and lack sufficient spatial resolution. GreenEO will therefore try to advance the state of knowledge in three areas:
- Using advanced satellite data, data assimilation, modeling, and ancillary data, GreenEO will estimate high-resolution nitrogen emissions (NH3, NOx). These high-resolution emissions will then be used in turn as a basis for modelling downstream impacts.
- GreenEO will advance the state of the art for nitrogen deposition modelling using findings from previous projects (Nordic Nature & Nitrogen and SEEDS projects). A bi-directional flux parameterization (Wichink-Kruit et al., 2012) was added to three regional scale air quality models (DEHM, MATCH, and EMEP) within the Nordic Nature and Nitrogen project. The findings were that this approach did not lead to consistent improvements in ambient concentration and flux modelling without commensurate improvements in land cover and vegetation data. For instance, bi-directional fluxes were shown to be highly sensitive to leaf area index (LAI) due to the dominating pathway being through external leaf water. Work within the SEEDS project to derive improved estimates of LAI by combining satellite observations of LAI in a land surface model using data assimilation, will serve as a basis for improving estimates of the bi-directional depositional fluxes of reactive nitrogen.
- GreenEO will combine these methods and data with regional scale air quality models (DEHM and EMEP) in order to model the distribution of nitrogen deposition with high accuracy. Specific attention will be paid to deposition within vulnerable habitats. Via this approach, GreenEO will improve the estimation of nitrogen deposition and critical load exceedances in vulnerable ecosystems. Collaborating with stakeholders, we will link these outputs to biodiversity indicators, like plant species richness and butterfly indices, to create a nitrogen sensitivity index. This will identify high-recovery areas and support sustainable agricultural practices.
Wichink Kruit, R. J., Schaap, M., Sauter, F. J., van Zanten, M. C., and van Pul, W. A. J.: Modeling the distribution of ammonia across Europe including bi-directional surface-atmosphere exchange, Biogeosciences, 9, 5261–5277, https://doi.org/10.5194/bg-9-5261-2012, 2012.
How to cite: Hamer, P., Frohn, L. M., Geels, C., Christensen, J., Denby, B. R., Simpson, D., Hutchings, N., Lopez-Aparicio, S., Schneider, P., Cao, T.-V., Jiminez, I., Fontenelle, T., van der A, R., Mijling, B., Ding, J., Trigo, I., Calvet, J.-C., Schante, J., Judes, T., and Tarrason, L. and the GreenEO Consortium: The GreenEO Project: Satellite-Based Services to Support Sustainable Land Use Practices Under the European Green Deal, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17316, https://doi.org/10.5194/egusphere-egu25-17316, 2025.
The German standard VDI 3782-5 "Deposition Parameters" (German/English, www.vdi.de) provides deposition velocities and washout rates for various gaseous substances and particles. It is applied in local and mesoscale dispersion modelling, for example in the context of the German regulation on Air Quality Control (TA Luft). The current version of the standard dates from 2006. It is based on findings from a limited number of studies that led to the implementation of relatively simple descriptions and only rough estimates of atmospheric nitrogen deposition. The standard is currently undergoing a rigorous scientific revision by the authors on behalf of the VDI.
The updated standard will specify, among others, a model for the calculation of surface resistances, including compensation points for NH3. The model is based on DEPAC (RIVM, Netherlands) and implemented in Java program (JDepac). JDepac allows parameter variations and time series calculations. Input parameters include date and time, geographical location, land use, meteorological data and, for NH3, information on current and past loads. Default options are provided for missing input. Output quantities are, among others, resistances, deposition velocities, and deposition fluxes of NH3, NO, NO2, HNO3, SO2, O3, Hg and particles.
JDepac is compared to various deposition measurements and results from mesoscale models. For NH3, effects of the compensation point on the resulting deposition velocities are investigated. JDepac is used to calculate temporal averages of deposition velocities for different land use classes. In combination with dispersion calculations, effective deposition velocities are derived from the calculated deposition fluxes and concentrations. These simpler parameters are straightforward to apply in local dispersion modelling. JDepac itself allows more sophisticated calculations and can be coupled to dispersion and chemical transport models.
The updated standard VDI 3782-5 and its OpenSource tool JDepac are intended to serve as a state-of-the art, practical, and transparent reference for both local and mesoscale calculations of nitrogen deposition. In addition, the standard contains descriptions for the calculation of deposition velocities and washout rates of particles, the calculation of deposition probabilities for Lagrangian particle models, and the effects of drop displacement in wet deposition.
The updated standard is expected to serve as a useful tool for example in the decision process of facility planning and its licensing procedure conducted by local authorities, which is especially critical for the impact assessment on ecosystems under the EU Habitats Directive. In addition, the updated standard is expected to support the harmonization of air pollution modelling within the implementation of the new (2024) EU Ambient Air Quality Directive.
How to cite: Janicke, U., Banzhaf, S., Brümmer, C., Gauger, T., Krämerkämper, T., Lorentz, H., Maßmeyer, K., Mohr, K., Moravek, A., Müller, W. J., Namyslo, J., Nickel, J., Prüeß, A., Rihm, B., Schaap, M., Schmitz, A., Tilgner, A., and Trukenmüller, A.: Standardization of a resistance model for the calculation of nitrogen deposition in the updated German standard VDI 3782-5, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11361, https://doi.org/10.5194/egusphere-egu25-11361, 2025.
In recent years, vehicle-based, multiple-gas mobile sensing platforms have been developed and extensively utilized for greenhouse gases (GHGs) and air pollutant emission studies. Closed-path analyzers are currently the primary equipment used for plume observations. However, the closed-path approach, poses sampling challenges for the species such as water vapor (H2O) and ammonia (NH3) that readily adsorb and desorb from the instrument inlets, tubings, and optical cells. Due to the different adsorption characteristics of each gas, the plume signals generated during the sampling process may become desynchronized. In addition, many mobile systems are deployed on fuel-powered vehicles, which emit exhaust that can contaminate the detected plume signals. These issues can increase the complexities in subsequent data processing tasks.
This work reports the field deployment of a multiple trace gas plume sensing platform, equipped with open-path N2O, CH₄, H2O and NH₃ quantum-cascade laser analyzers (model HT8500, HT8600P, HT8700, respectively) with a 10 Hz sampling time resolution. The plume monitoring system with a total power consumption of no more than 150W allows it to be easily driven by an electric vehicle. Utilizing the open-path N2O/CH4/H2O/NH3 gas analyzers eliminates the need for a pressure-controlled enclosed gas cell, the associated tubing systems, and power- hungry pump. The ambient air flows unrestricted through the optical path, enabling analyzers to achieve high temporal resolution, high response rates, and reduced sampling artifacts and power consumption compared to their closed-path gas analyzer counterparts. This open-path configuration not only eliminates the influence of exhaust emission signals from vehicles using fossil fuel engines, but also achieves perfect plume synchronization, which is crucial for the real-time identification of diffuse sources using correlations between different molecules in measured plumes.
The mobile platform has been field deployed in different field experiments including livestock farms, ammonia plants, cold storage facilities, wastewater treatment plants, and urban traffic roads in China. Our study has identified a substantial increase in ammonia concentrations adjacent to rivers, with an average increment of ~37 ppb relative to a few ppb background concentration. We observed that the peak methane concentration near a wastewater treatment plant reached 7539 ppb. Furthermore, the ratio of methane plume signal intensity to ammonia plume signal intensity in the vicinity of industrial areas is ~10, as opposed to non-industrial areas where this ratio is significantly reduced. The synchronized plume significantly enhances the efficiency of extracting effective plume data from the raw signals acquired from different gas analyzers.
How to cite: Hu, S., Shen, W., Jiang, R., Wilson, D., Lin, T.-J., and Wang, Y.: Synchronized N2O/CH4/H2O/NH3 plume mobile measurement system based on low-power open-path laser analyzers, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3928, https://doi.org/10.5194/egusphere-egu25-3928, 2025.
Atmospheric nitrogen (N) deposition is a significant driver of global change and disrupts the carbon and nitrogen cycles in ecosystems. Volatile Organic Compounds (VOCs) emitted by plants play an important role in regional air quality and the carbon cycle. This study investigates the effects of different forms and doses of N deposition on Biogenic Volatile Organic Compounds (BVOCs) emissions, photosynthesis, growth, and non-structural carbohydrate (NSC) accumulation in the widespread subtropical bamboo species-Moso bamboo (Phyllostachys edulis). A pot experiment was conducted with three N doses: 100 kg(N)·hm⁻²·a⁻¹ (L1), 200 kg(N)·hm⁻²·a⁻¹ (L2), and 0 kg(N)·hm⁻²·a⁻¹ (L0), using ammonium N (AN), nitrate N (NN), and a mixed N form (AN+NN). Dynamic headspace sampling was used to assess the effects of N deposition on BVOC emissions and the relationships between N deposition, photosynthesis, plant growth, and NSC distribution throughout the growing season.
The results indicated that N deposition increased BVOC emissions, with the highest emissions occurring under NN treatment at L1 during March and June. Isoprene (ISO) emissions were significantly enhanced under AN treatment, with L2 doses increasing ISO emissions by 99.20% compared to L1. The AN+NN treatment resulted in higher ISO emissions at L2, with increases of 76.02% and 141.69% compared to AN and NN alone, respectively. N form and dose also influenced photosynthetic pigments, with the highest total chlorophyll content observed under AN+NN at L1. Photosynthetic parameters, including net photosynthetic rate (Pn), stomatal conductance (Gs), and carboxylation efficiency (CE), were significantly higher under L1 compared to L0. A positive correlation was found between chlorophyll content and VOC emissions, with Pn, Gs, and CE strongly correlating with ISO emissions. Growth responses varied by N form. AN+NN treatment significantly promoted the growth of Phyllostachys edulis, particularly in above-ground biomass, while AN inhibited root and whip growth. Biomass of leaves and culms was significantly higher under L1 treatment, with increases of 85.60% and 38.14%, respectively, compared to L0 under AN treatment. Soluble sugar content in leaves, culms, and roots was highest at L1, with decreases observed as the N dose increased. Soluble sugars in leaves, culms, and buds increased by 24.85%, 24.92%, and 21.20% under L1 compared to L0. Starch content in leaves and culms increased initially but declined under higher N doses. AN and NN treatments at L2 reduced starch content in leaves and culms, with significant reductions observed in both N forms.
NSC content was positively correlated with ISO emissions, especially for soluble sugars. Total NSC content and soluble sugars were also positively correlated with BVOC emissions, suggesting that NSCs play a key role in plant responses to environmental stress. In conclusion, N deposition—particularly in mixed forms (AN+NN)—enhances BVOC emissions, especially ISO emissions, promotes biomass accumulation, and improves photosynthetic capacity. Lower N doses support higher ISO emissions and NSC accumulation. This study highlights that appropriate levels of N deposition can support bamboo growth and improve resilience to atmospheric changes.
How to cite: Li, L., Jiang, M., and Wang, X.: Effects of nitrogen deposition on VOCs emission and its relationship with photosynthesis, growth, accumulation and distribution of NSC in Moso bamboo tree (Phyllostachys edulis) , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14982, https://doi.org/10.5194/egusphere-egu25-14982, 2025.
Increasing the grassland proportion in the crop rotation has been considered as an effective approach to sequester carbon (C) in the soil. However, its climate mitigation benefits may be overestimated because the associated impact of long-term C sequestration on nitrous oxide (N2O) emissions remains uncertain. Mechanistic models, such as the DeNitrification and DeComposition model (DNDC v. CAN 9.5.0), are used to simulate changes in soil organic carbon (SOC) and N2O emissions. This provides the opportunity to estimate future emission trends and to enhance our understanding of the interactions between SOC and N2O emissions under different levels of grass/clover proportion in arable crop rotations. We hypothesize that increases in N2O emissions will offset the benefits from the increased SOC over time. The objectives of this study are to (1) calibrate and validate the DNDC model, and (2) estimate and predict the potential tipping point at which the negative climate forcing of N2O emissions offsets the benefits of C sequestration over long-term timescales. For this, we used long-term measurements of biomass, SOC, and N2O emissions from two crop rotations with either two or four years of grass-clover in a six-year rotation in Denmark. Preliminary results showed that the DNDC model simulated crop biomass production with fair to high accuracy as indicated by an index of agreement (d) of 0.98, a Nash-Sutcliffe efficiency (NSE) of 1, and a normalized root mean square error (nRMSE) of less than 30%. The simulated biomass was slightly underestimated as shown by a negative mean bias error (MBE). Conversely, the simulations for N2O fluxes and SOC exhibited poorer agreement, with d-values below 0.7 and nRMSE exceeding 30%. These findings suggest that while the DNDC model effectively predicts crop growth, including annual crops and grass/clover ley, its ability to simulate SOC and N2O fluxes requires substantial improvement. Our future efforts will focus on refining and optimizing model parameters for SOC and N2O, with an emphasis on calibration to enhance the model performance and the capacity to predict management-induced long-term dynamics under future climate scenarios. Results of these updated model simulations will be shown at the conference.
How to cite: Kong, M., Liu, H., Abalos, D., Grant, B. B., Smith, W. N., Zhartybayeva, A., Jensen, J. L., Eriksen, J., and Dold, C.: Estimating the Tipping Point between N2O Emissions and C Sequestration in Soil using the DNDC v. CAN Model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14338, https://doi.org/10.5194/egusphere-egu25-14338, 2025.
How to cite: Zamanian, K., Taghizadeh-Mehrjardi, R., Tao, J., Fan, L., Raza, S., Guggenberger, G., and Kuzyakov, Y.: Acidification of European croplands by nitrogen fertilization: Consequences for carbonate losses, and soil health, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2297, https://doi.org/10.5194/egusphere-egu25-2297, 2025.
Nitrogen-based inorganic fertilizers have been crucial in crop production globally. For a long time, SSA agriculture has been characterised by low fertilizer use and negative nutrient balances. However, recently fertilizer use has increased drastically. Unfortunately, increased use of synthetic N fertilizers alters soil properties directly and indirectly, and N losses to the ecosystem contribute to environmental degradation and climate change. Limited studies have focused on the effect of increased N application rates on agricultural soils in the tropical highlands. It is crucial to investigate and understand N flows in tropical soils to predict potential ecological impacts of increased synthetic N-fertilizer use while meeting the food demand in SSA.
This study aimed to investigate the effects of increasing N rates on soil N dynamics, chemical properties and N use efficiency in maize-monocrop systems in the tropical highlands of the Rift Valley region, Kenya. A field experiment consisting of six N-fertilizer rates (0, 25, 50, 75, 100 and 125 kg N ha-1) in triplicate was set up in Eldoret, Kenya. Soil samples were collected at depths of 0-20, 20-40 and 40-60 cm throughout the maize cropping season and analysed for mineral N (NH4+-N and NO3--N), soil organic carbon and pH. Results indicate a significant change in the soil chemistry due to fertilisation. The response magnitude varied across the three soil depths. For instance, NO3- -N increased with increased N application rate, which peaked at 14 (55.81 mg kg-1) and 42 (34.99 mg kg-1) days after treatment application in the top 20 cm and 20-40 cm depths, respectively. Similar trends were also observed in the NH4+-N concentration across different depths, with high N application rates tending to exhibit relatively high concentrations compared to treatments with lower N rates. We also observed a considerable decline in soil pH for plots treated with N fertilizer in the first 14 days, which then stabilized and rose gradually throughout the maize growing stages. However, the lower fertilizer plots tended to have higher pH in contrast to the other treatments. There was also a consistent increase in soil organic carbon (SOC), with slight fluctuations, throughout the cropping season.
These results indicated low mineral N movement below the effective root zone depth during the active growth phase of the crop. Thus, a clear indicator of increased plant uptake and implies a reduced risk of loss through leaching in Ferralsols. We also expect that meteorological conditions coupled with crop phenological processes to play a significant role in the soil chemistry variability, as exhibited by the differences in response to the treatments. We will therefore consider crop phenological processes and how they influence soil nutrient cycles. The results of this study will help to inform sustainable N use in maize cropping systems and further improve understanding of N cycle in tropical soils.
How to cite: Oluoch, K. C., Otinga, A., Njoroge, R., Mutua, S., Ouma, T., Agredazywczuk, P., Barthel, M., Six, J., Leitner, S., Oduor, C., and Harris, E.: Effects of N fertilization on soil chemistry dynamics in Ferralsols of the High Potential Maize Zone, Kenya , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-466, https://doi.org/10.5194/egusphere-egu25-466, 2025.
Reduced tillage is often considered as an agroecological practice that promotes soil organic carbon (SOC) sequestration in the topsoil, offering potential for climate change mitigation. However, effective mitigation requires a comprehensive understanding of trade-offs among SOC stocks, greenhouse gas emissions, and crop yields. As climate change alters carbon and nitrogen cycling, these trade-offs must be evaluated under current and experimentally induced extreme conditions to assess the effectiveness of reduced tillage in a changing climate. In this study, we measured crop yields, soil carbon stocks and soil CO2 and N2O fluxes in a conventional tillage (CT) vs. reduced tillage (RT) field trial in central Germany. The long-term trial runs since 1970 in a field with Luvisol soil (73% silt, 15% clay, and 6.6 pH). The mean annual precipitation is 611±120 mm and the mean annual temperature is 9.6±0.7°C. The field trial follows a randomized block design and consists of 16 plots: eight under CT with inversion ploughing to a depth of 27-30 cm, and eight under RT with non-inversion harrowing to a depth of 7-10 cm. In 2022-23 and in 2023-24 we cultivated winter wheat and winter barley respectively. In February 2023, rain-out shelters (area =2 m × 2 m) designed to intercept 50% of the precipitation were installed in half of the plots, and we initiated the soil flux measurements with static chambers over permanently installed rings and portable gas analyzers. We measured crop yields in both years, and SOC in samples from 0-90 cm at 10 cm intervals sampled in August 2023. SOC traits were examined with by-size fractionation to particulate and mineral-associated organic matter and an incubation experiment with an automated respirometer. Winter wheat yield did not differ between tillage and precipitation treatments but, in the second year of our experiment, winter barley yield was lower under rainfall exclusion than ambient precipitation in the RT fields only (50% precipitation: 0.26±0.05 kg m-2 vs. 100% precipitation: 0.52±0.02 kg m-2). Regarding SOC, we found that fields under RT had higher stocks in the 0-10 cm depth than under CT (RT: 1.93±0.03 kg m-2 vs. CT: 1.53±0.02 kg m-2), but the opposite occurred in the 20-30 cm depth (RT: 1.16±0.04 kg m-2 vs. CT: 1.58±0.06 kg m-2). Comparing SOC stocks at 0-90 cm, there was no difference between the two tillage systems. Field soil N2O fluxes did not differ significantly between tillage and precipitation treatments when considering block, plot and date as random effects. In contrast, field soil CO2 fluxes were significantly lower in RT than CT fields under ambient precipitation but this did not result in higher SOC stocks under RT. Rainfall exclusion led to higher soil CO2 fluxes both in the RT (in average, 50%: 32.0±1.0 mg CO2-C m-2 h-1 vs. 100%: 30.6±0.9 mg CO2-C m-2 h-1) and CT (in average, 50%: 30.1±1.1 mg CO2-C m-2 h-1 vs. 100%: 24.2±0.7 mg CO2-C m-2 h-1) fields. Based on the above, RT seems to have no climate change mitigation potential in a productive fine textured soil of temperate central Europe.
How to cite: Apostolakis, A., Englert, P., Daka, O. L., Siebert, S., and Meijide, A.: Trade-offs between crop yield, soil organic carbon and greenhouse gas emissions under reduced tillage and rainfall exclusion, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6623, https://doi.org/10.5194/egusphere-egu25-6623, 2025.
Soil organic matter (SOM) consists of carbon and nitrogen, both of which can contribute to the production of nitrous oxide (N2O). Currently, there is ample focus on increasing soil carbon content as a strategy for climate mitigation. Yet, the role of SOM on N2O production is poorly understood. We will present field flux N2O measurements from a hillslope cultivated to cereals with a natural gradient in SOM, pH and soil moisture. Additionally, eight rain exclusion shelters (~50% drought) were installed along the gradient, and N2O fluxes were measured both under 50% reduced and normal rainfall conditions. N2O fluxes have been measured for two growing seasons and will be presented alongside with soil and yield characteristics.
How to cite: Dörsch, P. and Kjær, S. T.: Influence of soil organic matter and reduced rainfall on nitrous oxide emissions along a cultivated hillslope , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7923, https://doi.org/10.5194/egusphere-egu25-7923, 2025.
The use of cover crops in agriculture is one of the climate-smart practices that have multiple benefits, such as increasing SOC, reducing N losses, and increasing biodiversity. Still the question whether cover crops and their diversity increase resilience against drought, and how the combined effects of cover crops, their diversity and drought affect N2O emissions, remain largely unknown. We study the combined effects of cover crop diversity and drought on cropland (oat) greenhouse gas emissions and belowground C and N processes in a field plot trial. The effect of drought on soil and crop C and N dynamics and greenhouse gas (CO2, N2O) emissions is studied with rainout shelters that remove 50% of incoming precipitation. The CO2 and N2O emissions are measured with the manual dark chamber method twice a week during the growing season and once a week during off-season, soil temperature and water content are measured continuously, and soil is sampled for mineral N and total C and N analysis seasonally.
The preliminary results show that reduced rainfall decreases CO2 emissions but does not affect N2O emissions significantly during the growing season. During off-season, reduced rainfall increases both CO2, and particularly N2O emissions irrespective of cover crop diversity treatments. During growing season there is a tendency of higher N2O emissions from diverse cover crop treatments compared to oat only treatment, and during off-season, a higher cover crop diversity significantly increases N2O emissions. Overall and in all treatments, off-season N2O emissions dominate the annual N2O balance. Our results highlight the need to include off-season measurements to the annual N2O balance estimation, and when assessing the effects of cover crops and future climate change scenarios such as summer drought on annual N2O emissions.
How to cite: Pihlatie, M., Turunen, P., Koskinen, M., Simojoki, A., Viinikainen, A., Virta, O., and Heinonsalo, J.: Cover crop diversity and summer drought increase off-season N2O emissions from Finnish agricultural soil , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15466, https://doi.org/10.5194/egusphere-egu25-15466, 2025.
Effective management of carbon (C) and nitrogen (N) in agricultural soils is crucial for mitigating greenhouse gas (GHG) emissions, particularly nitrous oxide (N2O) and carbon dioxide (CO2). This study investigates innovative dual C and N isotope-based methods to explore the mechanisms driving N2O and CO2 production and their potential mitigation, while maintaining soil fertility. By applying selectively labelled fertilizers with labelled in both fractions (15NH4NO3 or NH415NO3) the microbial transformations of N in soil are traced, allowing for the identification of conditions that promote N2O production or its reduction to the environmentally benign N gas (N2).
The impact of different labile and recalcitrant C sources on N cycling and GHG emissions is investigated by applying 13C-labelled maize-derived plant litter and biochar. The interaction between labile-C (e.g., plant litter) and recalcitrant C (e.g., biochar) with N in soils plays a critical role in regulating microbial processes and, consequently, GHG emissions. Plant litter, as a labile C source, stimulates microbial activity, (i) enhancing N-cycling and potentially increasing N2O emissions or, alternatively, (ii) stimulating microbial inorganic N immobilization thereby reducing N availability to gaseous and hydrological N loss processes. In contrast, recalcitrant C, such as biochar, provides a stable C form with long term C storage potential in soils. Biochar with its large specific surface area is recognized for its ability to sorb inorganic N such as ammonium and nitrate, reducing its availability for microbial processes that produce N2O and thereby may mitigate soil N2O emissions. However, how C inputs and N availability influence each other and affect microbial processes linked to GHG emissions remains poorly understood.
To address these challenges, a large-scale incubation study was initiated using soils sampled from a field experiment in Grabenegg, Austria, conducted by, The University of Natural Resources and Life Sciences, Vienna (BOKU) and Austrian Agency for Health and Food Safety, Vienna (AGES). One experimental soil was amended with NPK fertilizer, while the other received both NPK and hardwood- derived biochar since 2022. Soil samples were collected from the upper 10 cm of the root zone in October 2024 and used in a laboratory mesocosm experiment to trace litter-C and biochar-C processing and their effects on soil inorganic N cycling using 15N and 13C isotope tracing and isotope pool dilution measurements. Key measurements, including emissionsof 15N2O, 15N2, and 13CO2, 13C tracing into particulate organic 13C, mineral-associated organic 13C, and microbial biomass 13C and, 15N tracing in, mineral-N (15NH4, 15NO3) and microbial 15N will be performed at various intervals over one month, and data evaluated using numerical modelling. Findings from this study will greatly contribute to optimizing climate-smart soil management practices aimed at reducing GHG emissions from soil while maintaining its fertility.
How to cite: Bibi, S., Hafiza, B. S., Wanek, W., Vlasimsky, M., Rabello, M., Heiling, M., Dercon, G., Taru, S., Adelheid, S., and Hood-Nowotny, R.: Investigating Nitrous Oxide Pathways and Soil Carbon-Nitrogen Interactions Using Isotopic Techniques to Mitigate Greenhouse Gas Emission, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8306, https://doi.org/10.5194/egusphere-egu25-8306, 2025.
N2O is a potent greenhouse gas, with ~300 times the warming potential of carbon dioxide. The current trajectory for N2O emissions follows the highest warming RCP8.5 scenario, with agriculture accounting for ~70% of global emissions. As demand for food and livestock feed is expected to increase, mitigation measures which reduce agricultural N2O emissions and simultaneously increase nitrogen use efficiency (NUE) are urgently required to limit warming below the 2°C target set by the Paris Agreement.
The promotion of biological nitrogen fixation (BNF) in crop and forage systems via the incorporation of legumes has been advocated as a N2O mitigation strategy because it reduces synthetic N fertiliser application and increases NUE. However, novel strategies suggest that in addition to BNF, manipulation of the soil microbiota could hold the key to N2O mitigation. Soybean studies have successfully identified strains of symbiotic N-fixing rhizobia which can reduce N2O because they possess the gene encoding for nitrous oxide reductase (nosZ). The potential of N2O-reducing (NosZ+) rhizobia inoculums could therefore be critical to agricultural N2O emission mitigation; however, few studies have explored other legume-rhizobia associations for NosZ+ strains. Most notable is the complete lack of research on permanent grassland ecosystems, which cover 40% of global land surface and account for 54% of global N2O emissions.
This study aims to investigate the potential of clover-rhizobia associations to mitigate N2O emissions from UK grasslands and herbal leys under intercropping systems. Soils from five different land uses were sampled from FarmED (agroecology demonstration farm) and Pudlicote Farm in the Cotswolds, UK: unfertilised permanent pasture, unfertilised clover/grass sward, herbal ley (1st and 5th year) and conventionally farmed winter wheat. Native rhizobia present in the soil samples were selected by the growth and nodulation of Red Clover (Trifolium pratense) plants. Rhizobia extracted from the harvested root nodules were cultured on yeast mannitol agar to isolate individual strains. Strains then underwent gDNA extraction and whole-genome sequencing using the Illumina NovoSeq X platform to determine the presence of the nosZ gene. Biogeochemical analysis of the soils was related to the presence/absence of the nosZ gene to infer potential genotype environmental controls.
Finally, identified NosZ+ strains will undergo a phenotype assessment using a soil-plant-atmosphere mesocosm experiment, whereby N2O emissions from clover plants inoculated with NosZ+ strains will be monitored. Control strains; Rhizobium leguminosarum bv.trifolii T117 (nosZ+) and T132 (nosZ-) were obtained from the MIAE collection (INRAE, France) and will be tested alongside Bradyrhizobium diazoefficiens G49 (nosZ+) (soybean specific strain) and the identified native strains. The overall aim of the study is to create a rhizobia inoculum able to reduce N2O emissions when included in the intercropping sequence of leys and pastures, thus contributing to Net Zero global strategies.
How to cite: Weir, K., Williamson, C., Williams, T., and Sgouridis, F.: Rhizobia inoculation to mitigate nitrous oxide (N2O) emissions from UK grasslands and herbal leys under intercropping systems., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11640, https://doi.org/10.5194/egusphere-egu25-11640, 2025.
Root exudates account for up to 17% of the carbon fixed from photosynthesis and are allocated belowground, where they significantly influence microbial communities that drive nutrient cycling, particularly nitrogen in the rhizosphere. Root C exudation for nitrogen acquisition may differ between tree types. This study aimed to investigate how root exudates from English oak (Quercus robur) influence nitrogen cycling in rhizosphere soils compared to soils under alder (Alnus glutinosa). We hypothesized that oak root exudates would prime faster N transformation, given that alder tree roots host nodules for biological nitrogen fixation and thus will not invest exudate C in nitrogen acquisition. We experimented to measure gross and net nitrogen mineralization rates in soils subjected to simulated oak- and alder-specific carbon exudation rates. The study was designed using three artificial root exudate concentrations: 0, 77, and 359 µg C g⁻¹ soil day⁻¹ for alder, and 0, 187, and 814 µg C g⁻¹ soil day⁻¹ for oak. Soils were collected from the top 15 cm of the mineral layer from a four-year-old monoculture plantation of oak and alder trees in Staffordshire, England. The artificial root exudates were based on the actual root exudate rates from alder and oak trees collected during the Summer of 2022 and Spring of 2023 and contained carbohydrates, amino acids, and organic acids. Nitrogen transformation responses in the incubated soils were measured on days 15 and 30. On day 15, half of the soils were recovered from the incubation chambers and subjected to 15N-N tracer addition to determine gross N mineralization. The study revealed that higher concentrations of root exudate significantly (p<0.001) enhanced microbial activity. This was evidenced by increased soil respiration (21-fold in the oak simulation and 10-fold in the alder), microbial biomass carbon (3-fold in both tree species), and microbial biomass nitrogen (6-fold in oak and 2-fold in alder simulations) compared to the control after 30 days of incubation. These changes contributed to a 282% increase in total dissolved nitrogen in the oak and a 140% increase in the alder simulations. Root carbon inputs altered both gross and net mineralization and nitrification rates. Higher exudate concentrations over longer incubation periods elevated gross mineralization rates by up to 20-fold in the oak but reduced by up to fivefold in the alder compared to controls. Net mineralization rates increased with exudate concentration in both species. In gross nitrification, oak exudates enhanced tenfold, while alder exudates increased eightfold compared to controls after 15 days. Gross mineralization strongly correlated with net mineralization (R²oak=0.92, R²alder=0.76) but showed weaker correlations with net nitrification (R²oak = 0.30, R²alder = –0.47). Oak root exudates exhibited higher responses across gross mineralization (lnRR=3.08), net mineralization (lnRR=2.50), and gross nitrification (lnRR=1.57) compared to alder. Our results demonstrate that higher oak exudation rates enhanced nitrogen cycling compared to alder, underscoring the importance of species-specific traits in shaping carbon allocation strategies and nutrient cycling in the rhizosphere. This research highlights the critical role of root exudation in regulating soil nutrient dynamics and has broader implications for forest management.
How to cite: Kusumarini, N., Lynch, I., Cox, L., and Ullah, S.: Nitrogen transformation mediated by artificial root exudates derived from young alder and English oak trees, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9733, https://doi.org/10.5194/egusphere-egu25-9733, 2025.
Wetlands play a complex role as both sources of greenhouse gases (GHGs) and carbon sinks, making it essential to understand their dynamics and effects on biodiversity. The increasing pressures from climate change and human activities can disrupt the natural balance of these ecosystems, potentially resulting in elevated GHG emissions. The intricate abiotic and biotic interactions that govern these processes remain poorly understood. Therefore, there is an urgent need to enhance our understanding of the factors influencing GHG production in wetlands and to improve our capacity to model these emissions on a larger scale. In this study, we investigated the emissions of N2O, CO2 and CH4, with a particular focus on N2O, which is primarily produced through the microbial process of denitrification, and for which a satisfactory large-scale model formulation is lacking. The objective of this study was to evaluate these GHG emissions under optimal conditions for denitrification and to identify unifying abiotic factors. To achieve this, we selected contrasting study sites that varied by wetland type and climate zone, thereby gathering extensive data essential for our modelling efforts.
The research was conducted across multiple wetland sites involved in the ALFAwetlands project (https://alfawetlands.eu/), a European initiative dedicated to the study and restoration of both natural and managed wetlands. A total of 21 sites were selected across five European countries, encompassing a range of climate zones from Mediterranean to arctic. These included floodplains, alluvial forests, drained forests, peatlands, and mountain peatlands (with four sites each in France and Spain, three in Belgium, and five each in Finland and Estonia). For each location, three core samples (10 cm depth and 10 cm diameter) were collected and stored in the dark at 4°C prior to conducting mesocosm experiments. The samples were then placed in a custom-designed “GHG-aquacosm”, which simulates the effect of flooding on wetlands soils. During the experiments, soil cores were submerged in heated water enriched with nitrate. GHG emissions, soil moisture, and soil temperature were continuously monitored until stabilization or end of emission.
While CO2 and CH4 emissions were recorded, they have not yet been analysed, as this study primarily focuses on N2O emissions. The results indicated that N2O emissions varied significantly based on wetland type and initial soil water content. Drained forests, located in cool sub-arctic regions in Finland, demonstrated the highest N2O fluxes, ranging from 500 to 2000 µmol/m²·h. In contrast, floodplains and peatlands in Belgium and Estonia showed the lowest fluxes, between 5 and 150 µmol/m²·h. Significant variability was noted even among replicates, highlighting the considerable spatial heterogeneities of soils. Additionally, N2O emissions began immediately after nitrate addition, and for most sites ended 30 to 40 hours after, indicating the short temporal scale of N2O production and the challenges associated with in situ measurement. Ongoing data analysis and measurements are focused on further elucidating the spatial and temporal heterogeneities of denitrification processes, with the goal of effectively incorporating these factors into our modelling efforts.
How to cite: Crestey-Chury, T., Darnajoux, R., Kanaan, R., Aurela, M., Butlers, A., De Dobbelaer, T., Escarmena, L., Gandois, L., Jauhiainen, J., Juutinen, S., Larmola, T., Mander, Ü., Poblador, S., Raman, M., Sabater, F., Schindler, T., Soosaar, K., Ukonmaanaho, L., and Sánchez-Pérez, J.-M. and the French team (CRBE): Nitrous oxide emissions in natural and managed wetlands across Europe, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20384, https://doi.org/10.5194/egusphere-egu25-20384, 2025.
Temperature and oxygen content in soil are the well-known drivers of macronutrient cycling, as they influence the overall conditions that regulate microbial metabolism. However, the more detailed underlying aspects affecting nutrient cycling remain insufficiently understood.
This study focuses on different wetland forest types across Europe, aiming to investigate N cycling processes, the spatial distribution of N cycling genes and the linkage with soil greenhouse gas (GHG) emissions and relevant environmental parameters. The study sites were located in Finland, Estonia, and Latvia in Northern Europe, as well as in France and Spain in Southern Europe. The Northern Europe sites consisted of drained peatlands with varying management statuses, while the Southern Europe ones were alluvial forests. Soil samples were collected from three depths (0-10, 10-20, 20-40 cm) in autumn 2023, analysed using quantitative polymerase chain reaction (qPCR), and sequenced to assess processes and communities. In all samples, soil physico-chemical parameters were also determined and simultaneously with soil sampling, in-situ GHG emission measurements were done all as a part of Horizon Europe ALFAwetlands project.
Preliminary results of the quantification of N cycle genes revealed differences in the microbiome across wetland forest types in Europe. Ammonia-oxidizing archaea appeared to be the primary nitrifiers in the soils of the study sites, compared to ammonia-oxidizing bacteria. The alluvial forest soils revealed a higher genetic potential for the DNRA (Dissimilatory Nitrate Reduction to Ammonium) process in soil. The abundance of genes responsible for the comammox process—complete ammonia oxidation by a single microorganism—was also higher in the soils of the alluvial forests. In the rewetted peatland forest of Latvia, the soil exhibited a greater genetic potential for denitrification and DNRA processes compared to the drained peatland forests. The further analyses will be exploring the links between N cycle genes, GHG emissions, and soil physico-chemical properties.
How to cite: Kuusemets, L., Soosaar, K., Öpik, M., Aurela, M., Butlers, A., Escarmena, L., Jauhiainen, J., Juutinen, S., Kanaan, R., Larmola, T., Lazdiņš, A., Mander, Ü., Sánchez Pérez, J. M., Poblador, S., Sabater, F., Sauvage, S., Schindler, T., Ukonmaanaho, L., and Espenberg, M.: Microbial nitrogen cycling in wetland forests with varying management statuses across Europe, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17098, https://doi.org/10.5194/egusphere-egu25-17098, 2025.
Forests in Europe have been exposed to an increase in atmospheric deposition of nitrogen in the second half of the 20th century that potentially lead to nitrogen saturation and elevated leaching of nitrogen from forest soils potentially impacting water quality of drinking water resources. Nitrogen dynamics of forests, however, are complexe and still not fully understood.
Atmospheric deposition, soil solution, meteorology, soils, as well as stand and site characteristics have been continuously measured and analysed at several hundred intensive monitoring plots of the Level II plot network of the International Cooperative Programme on Assessment and Monitoring of Air Pollution Effects on Forests for many years.
We used the hydrological model LWFBrook90R to calculate water fluxes through the soils of these sites and calculated nitrogen input with atmospheric deposition and output fluxes with percolating soil water. We found high long-term variations on parts of the plots. Some of these variation patterns are in the time range of changes in the tree stands, e.g. mortality and subsequent biomass decomposition. We will discuss relations of found nitrate leaching patterns with nitrogen saturation indicators suggested in literature.
How to cite: Waldner, P., Raspe, S., Fleck, S., Zimmermann, L., Schmidt-Walter, P., Iacoban, C., De Vos, B., Cools, N., Deroo, H., Vanguelova, E., Galic, Z., Bourletsikas, A., Meesenburg, H., Schütt, T., Wohlgemuth, L., Schwärzel, K., Meusburger, K., and Nieminen, T.: Long-term variations in nitrate leaching from ICP Forests Level II plots, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19141, https://doi.org/10.5194/egusphere-egu25-19141, 2025.
Posters virtual: Wed, 30 Apr, 14:00–15:45 | vPoster spot A
EGU25-1233 | Posters virtual | VPS4
Identification of nitrification and denitrification along groundwater flow paths using dissolved N2, Ar, and N2O in typical groundwater flow systems in the Qingyi River basinWed, 30 Apr, 14:00–15:45 (CEST) | vPA.1
Seasonally different precipitation infiltration under monsoon humid areas may drive changes of groundwater flow systems and possible nitrate transformation processes in groundwater. In this study, dissolved greenhouse gases, noble gases concentrations (N2 and Ar) and isotopes of N2O were used to quantitively identify nitrification and denitrification to reveal spatial and temporal characterization of nitrate transformation in typical groundwater flow profiles in the Qingyi River basin, east China. In dry and wet seasons, the recharge altitudes of groundwater were distinctive and dominant nitrate transformation processes differed spatially and temporally. According to the N2-Ar estimation, the recharge altitudes of groundwater in dry season were higher than those in wet season, indicating obviously less proportion of precipitation from lower altitudes and relatively increased proportion of recharge from regional recharge areas in dry season, whereas local groundwater flow systems were preferentially developed in wet season. Denitrification is commonly observed in groundwater during the dry season, with positive Excess-N2 concentrations and phenomena that N2O concentrations initially accumulate with progress of denitrification but later decrease due to enhanced N2O reduction. In the wet season, nitrification is the dominant process in groundwater, with only a small portion of groundwater exhibiting denitrification, resulting in positive Excess-N2 concentrations. In this case, N2O concentrations initially increase during nitrification but later decline due to incomplete denitrification. Quantitative results based on δSP-N2O isotopes indicated that the maximum contribution of nitrification in groundwater during the wet season ranged from 52.8% to 100%, with an average of 77.3%. The contributions from denitrification and N2O reduction in wet season are limited, which is consistent with results identified by nitrate and ammonium isotopes. Spatially, due to more reducing redox environment in regional groundwater flow systems, the denitrification progress (DP) in most groundwater in discharge zones exceeds 99%, with denitrified NO3− concentrations reaching up to 25.72 mg/L, significantly higher than the average DP values in recharge zones (27.7%) and transition zones (31.6%).
How to cite: Huang, X.: Identification of nitrification and denitrification along groundwater flow paths using dissolved N2, Ar, and N2O in typical groundwater flow systems in the Qingyi River basin, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1233, https://doi.org/10.5194/egusphere-egu25-1233, 2025.
EGU25-2779 | ECS | Posters virtual | VPS4
Refining the nitrogen saturation hypothesis by accounting for microbial roles in nitrogen and phosphorus cyclingWed, 30 Apr, 14:00–15:45 (CEST) | vPA.3
Human activities have increased nitrogen (N) and phosphorus (P) deposition, disrupting microbial activity and altering N-P cycling. Understanding how nutrient limitations and additions affect soil microbes is critical for predicting ecosystem succession and mitigating greenhouse gas emissions. Leveraging long-term N-P addition experiments in a subtropical forest, we developed an enhanced Microbial-ENzyme Decomposition (MEND) model by incorporating an enzyme-mediated P module. Following rigorous calibration and validation with multi-source data, we found that N-P addition has antagonistic effects on main fluxes, with P application mitigating N stimulation of fluxes and partially reducing N₂O emissions. On this basis, we refined the nitrogen saturation hypothesis (NSH) for subtropical ecosystems by attributing divergent nitrification patterns to ammonia inhibition, and we expanded the hypothesis to encompass denitrification and N fixation. By integrating microbiome data, we demonstrated the intrinsic effects of N addition on N cycle through differential expression of genes due to community change, while P addition can counteract effects of N increase by alleviating microbial P limitations. Additionally, we highlight the significance of microbial-enzyme activities feedback in regulating P cycle to maintain ecological balance. Integrating microbially-enabled C-N-P model with diverse experimental data, particularly microbiome information, enhances interpretability and reveals ecosystem mechanisms beyond direct experimental observation.
How to cite: Lv, Z.: Refining the nitrogen saturation hypothesis by accounting for microbial roles in nitrogen and phosphorus cycling, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2779, https://doi.org/10.5194/egusphere-egu25-2779, 2025.
EGU25-20890 | ECS | Posters virtual | VPS4
Enhancing crop yield, carbon sequestration, and greenhouse gas mitigation through organic matter inputs: long-term grassland farming observations and DNDC model predictionsWed, 30 Apr, 14:00–15:45 (CEST) | vPA.2
Organic inputs in grasslands are known to enhance soil carbon sequestration. However, it remains unclear whether long-term organic inputs lead to greenhouse gas (GHG) emissions, specifically methane (CH4) from livestock and nitrous oxide (N2O) from soils, that outweigh the benefits of carbon sequestration. Addressing this issue is crucial, as it directly impacts the evaluation of organic farming practices for sustainable land management and climate change mitigation. In this study, we employed the process-based Denitrification-Decomposition (DNDC) model to estimate the fluxes of major greenhouse gases (GHGs) in a long-term grassland silage experiment established in 1969. The model was validated against measured data, effectively capturing the dynamics of N₂O emissions, soil temperature, biomass, and soil organic carbon (SOC). Simulations under different IPCC Shared Socioeconomic Pathway (SSP) scenarios of altered temperature, CO₂ concentrations, and radiative forcing were conducted. Treatments with high levels of cattle manure and pig manure under the SSP1-2.6 scenario exhibited a net GHG sink, whereas conventional fertilization resulted in a net GHG source under both SSP1-2.6 and SSP2-4.5. Grass yields decreased under conventional fertilization in both SSP2-4.5 and SSP5-8.5 scenarios. However, the application of organic matter inputs resulted in yield increases across all scenarios. These findings highlight the potential of organic farming practices, especially with high organic inputs, to mitigate GHG emissions and enhance productivity in grassland ecosystems. Therefore, adopting organic farming practices with adequate organic inputs could serve as a sustainable strategy for balancing food production and environmental conservation.
How to cite: Meng, X., Khalil, I., and Osborne, B.: Enhancing crop yield, carbon sequestration, and greenhouse gas mitigation through organic matter inputs: long-term grassland farming observations and DNDC model predictions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20890, https://doi.org/10.5194/egusphere-egu25-20890, 2025.
