BG3.25 | Gas exchange and emission mitigation options in agricultural and forest ecosystems
EDI
Gas exchange and emission mitigation options in agricultural and forest ecosystems
Convener: Christof Ammann | Co-conveners: Katerina Machacova, Christian Brümmer, Eliza Harris, Alexander Moravek, Laëtitia Brechet, Alex Valach
Orals
| Tue, 25 Apr, 08:30–12:30 (CEST)
 
Room 2.95
Posters on site
| Attendance Tue, 25 Apr, 16:15–18:00 (CEST)
 
Hall A
Orals |
Tue, 08:30
Tue, 16:15
Managed agricultural ecosystems (grassland and cropland) and forests are an important source and/or sink for the greenhouse gases (GHG) CO2, CH4, and N2O as well as for reactive trace gases. Representative measurements and modelling under typical conditions as well as for potential mitigation options are necessary as a basis for recommendations to policy makers, farmers, and foresters.
Due to the simultaneous influence of various environmental drivers and management activities (e.g. fertilizer application, harvest, grazing) the flux patterns are often complex and difficult to attribute to individual drivers. Moreover, management related mitigation options may often result in trade-offs between different GHG or between emission of GHG and reactive gases like NH3, NOx, or VOCs. To investigate these interactions, the session addresses experimentalists and modelers working on carbon and nitrogen cycling processes and related fluxes on plot, field, landscape, and regional scale. It is open to a wide range of studies including the development and application of new devices, methods, and model approaches as well as field observations and process studies. Particularly welcome are studies on multiple gases and on the full carbon, nitrogen or GHG budgets. We also encourage contributions about the applicability and overall potential of mitigation options.

Orals: Tue, 25 Apr | Room 2.95

Chairpersons: Katerina Machacova, Christof Ammann, Laëtitia Brechet
08:30–08:33
08:33–08:53
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EGU23-9990
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ECS
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solicited
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On-site presentation
Sunitha Pangala, Rodrigo Nunes-Sousa, Holly Blincow, Carla Gomez, and Leonardo Pequeno Reis

Methane emission from wetland trees is an overlooked source of methane, with poor resolution of their global significance and mechanisms. Our ongoing work in the Amazon basin has revealed that wetland trees are the largest source of methane, emitting the equivalent of all the methane emitted from the Arctic. Factors controlling and mechanisms driving these emissions remain unclear. Tree stem surfaces are no longer considered passive conduits for soil-produced methane; instead, they are active surfaces driving both methane production and oxidation.

Over the past five years, using methane flux measurements, wood incubation experiments, stable carbon isotopic composition of methane measurements and wood structure and traits analysis, we attempt to unravel the following questions:  Where is methane produced? How is methane transported and emitted from the tree stems? What controls the flux strength of methane eventually released at the stem surface?

So far, results suggest that soil is the predominant source of tree stem-released methane; however, certain tree species display strong internal methane production, increasing from the wet to dry season. The methane transport pathway is also tree species-specific, with some trees showing strong evidence of diel variability and others displaying minimal to zero diel variability. Internal wood methane concentration and stable isotopic measurements corroborate this. A strong presence of tree-methane oxidation was observed, which again was tree species-specific, despite the net fluxes measured at the stem surface always being positive. Methane oxidation within the tree stems was dominant, with methane oxidation in the bark only playing a minor role. Wood structure and traits analysis revealed that wood density could be used as a proxy to predict stem methane fluxes at an ecosystem level. However, species-level variability was controlled by other species-specific wood traits, making it harder to fully explain the variability we observe in methane emitted at the stem surface. 

How to cite: Pangala, S., Nunes-Sousa, R., Blincow, H., Gomez, C., and Reis, L. P.: Stem-methane emissions from the Amazon floodplains: controls and variability, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9990, https://doi.org/10.5194/egusphere-egu23-9990, 2023.

08:53–09:03
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EGU23-1783
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ECS
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On-site presentation
Holly Blincow, Sunitha Pangala, Niall McNamara, and Alison Hoyt

Trees are understood to emit large quantities of methane, particularly in tropical wetland environments; however, little is known about the source of tree methane emissions. We aim to understand the form of methanogenesis behind tree methane in the Brazilian Amazon and the source of this methane. In order to compare methanogenesis between different systems, isotope samples were taken from trees, soil and flood water at two sites. Initial isotopic analysis shows that there is no significant difference between soil and tree methane samples, whereas water-sampled methane was significantly different from both soil and tree samples. Hydrogen isotope analysis will further our understanding of the specific methanogenesis process in the soil-tree-atmosphere continuum. These preliminary results suggest tree methane is soil derived, which is critical in enhancing our understanding of both the global methane budget and the role trees play in methane emissions.

How to cite: Blincow, H., Pangala, S., McNamara, N., and Hoyt, A.: Tree methane: Getting to the root of it., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1783, https://doi.org/10.5194/egusphere-egu23-1783, 2023.

09:03–09:13
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EGU23-6417
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ECS
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On-site presentation
Natalia Kowalska, Georg Jocher, and Adam Bednařík

Floodplain forests as wetlands are characterized by methane (CH4) emission. Methane, after carbon dioxide (CO2) is the second main driver of global climate change. The magnitude of CH4 emission is site specific and depends on environmental factors like water table level and soil temperature. The standard method to quantify ecosystem-scale CH4 exchange is the eddy covariance (EC) method. Gap-filling procedures, however, are manifold and not standardized yet.

The main aim of our study was to quantify the CH4 emission on the floodplain forest ecosystem level using the EC method, with special emphasis on environmental conditions, turbulence development and footprint. Furthermore, the ecosystem-scale CH4 fluxes shall be analysed with regards to the CH4 emissions of water bodies within the EC footprint.

The studied floodplain forest represents nowadays relatively dry conditions. Consequently, we initially hypothesized that ecosystem-scale CH4 exchange will be negligible.

First results, however, showed, that the whole ecosystem is a small but constant CH4 source as we observed an average emission flux of 11.7 mg CH4 m-2 day-1 over the period June to December 2021.  In parallel, CH4 fluxes from a stream located within the footprint of the EC tower were measured using the floating chambers and bubble traps. Stream was substantial source of CH4 with mean CH4 fluxes of 260 ± 107 mg CH4 m-2 day-1, respectively, over the period from April to December 2021. Both, the EC and floating chamber measurements of CH4 were conducted also in 2022 and results will be presented.

In the future, the ecosystem-scale CH4 measurements shall be connected not only with the CH4 measurements from the water bodies, but also with stem CH4 efflux measurements conducted at the study site. Finally, an overview of all relevant CH4 sources in the studied ecosystem shall evolve including their relative importance for ecosystem CH4 exchange.

 

How to cite: Kowalska, N., Jocher, G., and Bednařík, A.: Ecosystem-scale floodplain forest methane exchange, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6417, https://doi.org/10.5194/egusphere-egu23-6417, 2023.

09:13–09:23
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EGU23-16027
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On-site presentation
Soil CH4 and N2O fluxes from drained nutrient-rich peatland forests in Estonia and Latvia
(withdrawn)
Muhammad Kamil Sardar Ali, Hanna Vahter, Thomas schindler, Andis Lazdins, Ain Kull, Ieva Licite, Ulo Mander, Aldis Butlers, Dovile Ciuldiene, Jyrki Jauhiainen, and Kaido Soosaar
09:23–09:25
09:25–09:35
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EGU23-9406
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ECS
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On-site presentation
Daniel Mika-Nsimbi Poultney, Yujia Liu, Per Ambus, Bo Elberling, Kristian Thorup-Kristensen, and Carsten W. Müller

Agricultural soils are a major source of the potent greenhouse gas nitrous oxide (N2O). However, these emissions have high spatial variability and are highly heterogeneous in their distribution in agricultural landscapes. In Eastern Denmark, N2O “hotspots” or disproportionately high emission zones, have been observed in the vicinity of glacial depressions. These depressions form a topographical slope, where the base of the slope is typically inundated for 1-3 months over the winter and spring seasons. Preliminary work showed that the highest N2O emissions have been observed at the base of the slope, along the perimeter of the ponding zone of these depressions. In the present study we now aim to identify the mechanistic drivers of these N2O hotspots.

N2O emissions were measured weekly at four positions along a gradient from upslope to the centre of a glacial depression over a winter to spring wheat growth season, at a farm in Eastern Denmark. The potential driving factors were  measured weekly along the slope: soil moisture at depths of 10 cm, 20 cm and 100 cm; soil solution nitrates and DOC at these same depths; and root growth using photographs at different depths using minirhizotrons to a depth of 100 cm. Additionally the groundwater level was monitored using a well and pressure logger. To underpin the results of this core site, further N2O measurements and soil samples were taken along the slope of three additional glacial depressions nearby with comparable topography and soil properties .

The N2O emissions were found to be highest at the base of the slope, around the perimeter of the depression. We were able to demonstrate that root growth is directly linked to the moisture regime and thus the overall fate of nitrate and N2O emissions.

Given the locally high N2O emissions of these hot spots, this study provides a lens into an important source of N2O emission heterogeneity in the Danish agricultural landscape.

How to cite: Poultney, D. M.-N., Liu, Y., Ambus, P., Elberling, B., Thorup-Kristensen, K., and Müller, C. W.: N2O emissions from emission hotspots in agricultural soils – linking crop root growth and distribution with soil moisture and nitrate dynamics, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9406, https://doi.org/10.5194/egusphere-egu23-9406, 2023.

09:35–09:45
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EGU23-15717
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ECS
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On-site presentation
James Benjamin Keane, Sarah Lee, Niall McNamara, Jeanette Whitaker, James Moir, Pete Levy, Sam Robinson, Stella Linnekogel, Hannah Walker, Kate Storer, Pete Berry, Mark Bentley, Steve Howarth, and Sylvia Toet

Nitrous oxide (N2O) is a potent greenhouse gas (GHG) with a global warming potential 265 times that of carbon dioxide (CO2) over 100 years. Contributing approximately 70% of global anthropogenic N2O emissions, agriculture represents the largest area of uncertainty for GHG reporting and the most challenging sector for emissions reduction: global N2O emissions are increasing at double the rate estimated by the Intergovernmental Panel on Climate Change (IPCC). The largest source of agricultural N2O emissions is from application of inorganic-N fertilisers, the manufacture of which produces more than 1% of global CO2 emissions and consumes 1% of global energy output.

However, typical crop N uptake efficiency (NupE) means approximately half the fertiliser doesn’t reach the target plant, causing further ecological problems, such as biodiversity loss from eutrophication and atmospheric deposition. The extent to which microbial immobilisation of fertiliser N contributes to the NupE value of ca. 60% is currently unknown. If N immobilisation is found to be a large contributor to reducing N available to crops, this offers new opportunities to better manage fertiliser N inputs. Critically, with a growing global population, it is vital that we can increase food crop yields, and more efficient use of water and nutrients could help close the 70% ‘yield gap’ between potential and actual crop yields. Finally, inorganic N is the largest single cost in gross margins for wheat production and prices are rising. Increased NupE therefore represents a key opportunity for farmers to increase their financial sustainability. 

 

We hypothesised that under the conventional management of three applications of inorganic N in the spring, crops do not have the ability to outcompete the fast-growing soil microbial community for N, and that by supplying N to the crop in a ‘little and often’ approach, we could increase NupE by reducing immobilisation, and consequentially reduce N2O emissions. We conducted a field study of a winter wheat crop on a northern UK farm to investigate this, which compared conventional N fertiliser management (220 kg N ha-1 over three applications) of ammonium nitrate, to a little and often approach (220 kg N ha-1 over six applications) and an untreated (0 kg N ha-1) control. We followed the crop until harvest, and continuously measured N2O emissions and net ecosystem exchange of CO2 using a skyline2D automated flux system and also measured C and N pools in soil, plants and microbial biomass to assess changes in N uptake and allocation.

We will present data which shows the outcome of plant-microbe competition for N in our agricultural system, and discuss the implications of different N fertiliser management for yield, profitability and GHG mitigation.

How to cite: Keane, J. B., Lee, S., McNamara, N., Whitaker, J., Moir, J., Levy, P., Robinson, S., Linnekogel, S., Walker, H., Storer, K., Berry, P., Bentley, M., Howarth, S., and Toet, S.: The outcome of plant-microbial competition for N in a wheat system and the implications for yield and N<sub>2</sub>O mitigation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15717, https://doi.org/10.5194/egusphere-egu23-15717, 2023.

09:45–09:55
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EGU23-9893
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ECS
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On-site presentation
Junyi Wang, Matthias Kuhnert, Mohamed Abdalla, Pete Smith, Weixin Ding, Xiaoyuan Yan, Jianwen Zou, Shiwei Guo, Jianling Fan, Yanbin Jiang, Ronggui Hu, Fusheng Li, Yanbin Guo, Zengming Chen, Xu Zhao, and Yingxin Xie

China contributes the largest share of cropland’s greenhouse gas (GHG) emissions globally. Processed-based biogeochemical models are useful tools to simulate GHG emissions from cropping systems. However, model comparisons are necessary to provide information for the application of models under different climate, soil, and crop conditions. In this study, two widely-used models (DayCent and DNDC) were evaluated and compared under four main cropping systems in China. The field observations from nine experiments were used for model calibration and validation.  The DayCent and DNDC models simulated daily and seasonal CH4 emissions from early rice-late rice and rice-wheat cropping systems reasonably well (r2≥0.49 for daily simulation and nRMSE≤52.9% for seasonal simulation). Both models were able to satisfactorily predict seasonal N2O emissions from maize-wheat fields (0.6≤d≤0.8), but overestimated most daily N2O fluxes at fertilisation and irrigation events. Significantly positive relationships were found between simulated and observed cumulative N2O fluxes in spring maize growing season (0.61≤ r2≤0.85). The DNDC showed smaller differences in simulated and observed cumulative GHG emissions for spring maize and double rice, while DayCent showed better performance on estimating N2O and CH4 for maize-wheat and rice-wheat. This study shows that both models have strengths and weaknesses under a variety of cropping systems and growing regions, which are important to consider when choosing a model for a crop/region-specific simulation.

How to cite: Wang, J., Kuhnert, M., Abdalla, M., Smith, P., Ding, W., Yan, X., Zou, J., Guo, S., Fan, J., Jiang, Y., Hu, R., Li, F., Guo, Y., Chen, Z., Zhao, X., and Xie, Y.: A comparison of DNDC and DayCent to evaluate GHG emissions from China’s main cropping systems, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9893, https://doi.org/10.5194/egusphere-egu23-9893, 2023.

09:55–10:05
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EGU23-14773
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ECS
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On-site presentation
Sonja Leitner, Victoria Carbonell, Klaus Butterbach-Bahl, Matti Barthel, Rangarirayi Lucia Mhindu, Paul Mutuo, Nina Buchmann, and Lutz Merbold

There is hot debate about whether grassland-based livestock production can be climate-smart or not. Greenhouse gas (GHG) emissions from livestock (primarily from enteric methane [CH4] and manure CH4 and nitrous oxide [N2O]) stand vis-à-vis vegetation CO2 uptake and soil carbon sequestration. In sub-Saharan Africa (SSA), livestock are a precious good that ensures the livelihoods of millions of people, which often belong to marginalized groups such as pastoralists. To protect their animals from predation and theft, livestock are secured in overnight enclosures (“bomas” in Kiswahili), which form the center of many pastoral settlements. However, in these enclosures manure accumulates for months or even years, making them a potential hotspot for GHG emissions. Here, we present the first year-long measurements of GHG emissions from active and inactive (abandoned) bomas from an African rangeland at the ILRI Kapiti Research Station in Kenya.

We found that active bomas were continuous sources for CO2, CH4 and N2O emissions, with flux peaks of up to 1940 mg CO2-C m‑2 h‑1, 1600 μg N2O-N m‑2 h‑1 , and 6690 μg CH4-C m‑2 h‑1. Even after their abandonment, fluxes from bomas continued to be elevated compared to savanna soil background emissions for all GHGs. When calculated over a full year and put in context with manure deposition rates into the bomas (GHG emission factors), we found that 12.6 ± 5.3 % manure-C was emitted as CO2, 2.4 ± 0.4 % manure-N was emitted as N2O, and 0.5 ± 0.1 % manure-C was emitted as CH4. GHG emissions from active bomas were not affected by rainfall seasonality or temperature, presumably because the moisture content of the fresh manure was always high due to urine input, and because temperature did not vary much during the year. In abandoned bomas, GHG emissions were driven by rainfall events that triggered emission pulses, leading to higher emissions during the wet season.

The high N2O and CH4 emissions we found have implications for global GHG inventories, which currently do not have a category for overnight livestock enclosures and therefore do not account for these emissions. Furthermore, hotspots for GHG emissions such as these livestock enclosures need to be included to assess the full GHG budget of pastoral livestock systems and to develop management interventions for low-emission livestock production in developing countries.

How to cite: Leitner, S., Carbonell, V., Butterbach-Bahl, K., Barthel, M., Mhindu, R. L., Mutuo, P., Buchmann, N., and Merbold, L.: Traditional livestock enclosures are greenhouse gas hotspots in the African savanna landscape: The case of a rangeland in Kenya, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14773, https://doi.org/10.5194/egusphere-egu23-14773, 2023.

10:05–10:15
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EGU23-8205
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On-site presentation
Cecilie Skov Nielsen, Nanna Schrøder Baggesen, Drishya Nair, Arezoo Taghizadeh-Toosi, and Ann Britt Værge

Nitrous oxide (N2O) is a strong greenhouse gas, and its atmospheric concentration is rising. Anthropogenic N2O emissions stem mostly from agricultural activities, especially the fertilization of fields. There is an urgent need to reduce the emissions of N2O from agriculture, but so far well documented mitigation options remain scarce.

Here we present data from the first year of a series of field trials which aim to test if N2O emissions from Danish winter wheat fields can be reduced by optimizing the fertilization strategy. The field trials were located at three different locations in Denmark with different soil types and climatic conditions. All treatments received 200 kg N/ha except the 0 N treatment (giving the background N2O emissions). The treatments were: (1) ammonium nitrate split in three applications, (2) ammonium nitrate coated with a nitrification inhibitor (3,4-Dimethylpyrazole phosphate, DMPP) split in three applications, (3) ammonium sulfate coated with DMPP split in three applications, (4) liquid fertilizer split in three applications, and (5) ammonium nitrate split in four applications. Nitrous oxide emissions were measured by manual chambers throughout the growing season in 2022 (22 days of measurements).

The highest emissions and cumulative emissions were observed in the treatment with liquid fertilizer, and in two of the trials the emissions from the liquid fertilizer treatment were higher than emissions from the treatment with ammonium sulfate coated with DMPP. However, the nitrification inhibitor did not significantly decrease N2O-emissions when compared to the same fertilizer type without inhibitor. In the treatment with ammonium nitrate split in four applications, we did not find significant reductions in N2O emissions. Generally, nitrous oxide emissions from all sites were low (cumulative fluxes of 0.14 – 0.31 kg N2O-N/ha for the growing season) due to a dry spring with a few peaks mainly due to precipitation events. Therefore a preliminary conclusion after the first year of field trials is that in a dry year, with low emissions, the selected fertilization strategies seem to have limited capacity for reducing N2O emissions.

How to cite: Skov Nielsen, C., Schrøder Baggesen, N., Nair, D., Taghizadeh-Toosi, A., and Værge, A. B.: Can improved fertilization strategies reduce N2O emissions from winter wheat?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8205, https://doi.org/10.5194/egusphere-egu23-8205, 2023.

Coffee break
Chairpersons: Christian Brümmer, Alexander Moravek, Alex Valach
10:45–10:47
10:47–10:57
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EGU23-17103
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ECS
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On-site presentation
Iris Feigenwinter, Lukas Johannes Hörtnagl, and Nina Buchmann

Agriculture is the main contributor to anthropogenic emissions of nitrous oxide (N2O) and methane (CH4). Greenhouse gas (GHG) mitigation options in agricultural ecosystems are therefore urgently needed. In contrast to carbon dioxide (CO2), continuous measurements of N2O and CH4 fluxes are still scarce. In this study, we investigated management and environmental drivers of N2O and CH4 fluxes, which were measured using eddy covariance in a predominantly mown temperate grassland. A N2O mitigation experiment took place at the site where two parcels surrounding the eddy station were managed differently: at the experimental parcel, organic fertilizer was replaced by an increased legume (clover) proportion while the other parcel was still fertilized with slurry. Random forest gap-filling models were able to capture intermittent emission peaks well, with a better performance for half-hourly N2O than for CH4 fluxes. The unfertilized clover parcel showed reduced N2O emissions (4.4 and 2.7 kg N2O-N ha-1 yr-1) compared to the fertilized parcel (6.9 and 5.9 kg N2O-N ha-1yr-1) over two years, which confirmed the results from the first years of the experiment. The net ecosystem CO2 exchange (NEE) showed high interannual variability, which had a substantial influence on the grassland GHG budget. Overall, reducing fertilization and increasing the legume proportion were effective N2O reduction measures. N2O and CH4 fluxes play an important role in the GHG budget of agricultural ecosystems as they can partly offset the ecosystem CO2 uptake.

How to cite: Feigenwinter, I., Hörtnagl, L. J., and Buchmann, N.: Greenhouse gas (CO2, N2O, CH4) fluxes from intensively managed grassland during a N2O mitigation experiment, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17103, https://doi.org/10.5194/egusphere-egu23-17103, 2023.

10:57–11:07
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EGU23-7822
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ECS
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On-site presentation
Laura Heimsch, Julius Vira, Istem Fer, Henriikka Vekuri, Juha-Pekka Tuovinen, Olli Nevalainen, Karla Kuvaja, Annalea Lohila, and Liisa Kulmala

Agricultural management has recently drawn substantial attention as regenerative practices are showing their potential in enhancing soil quality and fertility, biodiversity, and carbon uptake from the atmosphere into the soil. In Nordic countries, there is a great number of farmers farming regeneratively. However, they are still a minority, and we are lacking scientific studies on the effects of various improved practices and their combination and use in practice in northern growing conditions.

We conducted a long-term study of an agricultural grassland ecosystem in southern Finland where regenerative management practices were implemented from 2018 onwards. We monitored H2O and CO2 fluxes with the eddy covariance method, and additionally, CH4, N2O and CO2 with flux chambers. We also measured meteorological variables and several soil and vegetation parameters. We studied the impacts of different cutting heights for the silage grass on the ecosystem carbon sequestration. Furthermore, we utilised the data in model simulations with the grassland model BASGRA to study the carbon dynamics of the agricultural ecosystem in various weather conditions and with different management decisions. Our results indicate that the studied years, which were differing greatly from the long-term average weather, may have had a great impact on carbon dynamics on the grassland. Both empirical data and modelling demonstrated net carbon accumulation into the ecosystem under the selected improved practices.

How to cite: Heimsch, L., Vira, J., Fer, I., Vekuri, H., Tuovinen, J.-P., Nevalainen, O., Kuvaja, K., Lohila, A., and Kulmala, L.: Impact of weather and management practices on GHG dynamics on an agricultural grassland in southern Finland, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7822, https://doi.org/10.5194/egusphere-egu23-7822, 2023.

11:07–11:10
11:10–11:20
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EGU23-12920
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On-site presentation
Jesper Nørlem Kamp, Johanna Pedersen, Jan Huijsmans, Hannah Götze, Andreas Pacholski, and Sasha Hafner

Agricultural sources of atmospheric ammonia after slurry application vary over space and time, which makes it difficult to accurately quantify emissions. Different methods for concentration and emission estimation have been used by different institutions for many years, and these differences may contribute to variability in measurements. There is an need for commonly acceptable and reliable measurement methods.

Ammonia emission measurements show a strong connection to the group that conducted them, suggesting effects of local soil properties, application techniques, or measurement method biases. The aim of this work was to clarify one source of these institutional effects related to applied measurement methods. Emission measurements with several common measurement methods were compared by three different research institutions simultaneously in the same field plots. This approach eliminates any variation from soil properties and application technique, making it possible to obtain new insight into the effect of measurement technique on model ammonia flux estimates.

Two joint experiments were conducted at Research Center Foulum, Aarhus University (AU), Denmark, and one at Wageningen University and Research (WUR), the Netherlands. The four measurement methods included in the first experiment in Denmark were the backwards Lagrangian model (bLS) with online concentration measurement and wind tunnel measurements conducted by a AU group, while a group from Thünen Institute for Climate-Smart Agriculture conducted measurements with the Dräger Tube Method (DTM) and ALPHA passive diffusion samplers combined with bLS. The second experiment in the Netherlands included the integrated horizontal flux (IHF) method conducted by a WUR group using impingers as ammonia traps, while AU conducted bLS and wind tunnel measurements again. Furthermore, emission from both experiments were also estimated with the ALFAM2 model (v2.10, https://github.com/sashahafner/ALFAM2) based on the specific slurry and climatic parameters after slurry application.

The difference in season and application method between the two experiments caused large differences in emissions as expected. The low time resolution measurements methods (DTM, ALPHA samplers with bLS, and IHF) tended to have lower emissions compared to the online and high time resolution methods (bLS and WT). More comparative measurements are needed to allow for more complete assessment of different methods.

How to cite: Kamp, J. N., Pedersen, J., Huijsmans, J., Götze, H., Pacholski, A., and Hafner, S.: Measurement methods for ammonia emissions after field application of slurry, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12920, https://doi.org/10.5194/egusphere-egu23-12920, 2023.

11:20–11:30
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EGU23-12913
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ECS
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On-site presentation
Anna Holm Støckler, Johanna Pedersen, Jesper Nørlem Kamp, Anders Feilberg, and Sasha D. Hafner

Emission of ammonia from agriculture is a problem due to the negative effects on human health and natural ecosystems. Additionally, ammonia is a precursor for production of N2O in the atmosphere and is therefore an indirect greenhouse gas. A large part of ammonia emissions from agriculture originate from manure handling, which also reduces manure fertilizer value. Therefore, more knowledge on emissions from different types of manure and the effect of manure treatments are necessary to develop new measures to reduce ammonia emissions. Separating liquid manure (slurry) into a liquid and solid fraction can be used as a reduction technique for field application. The lower dry matter content of the liquid fraction may increase infiltration and decrease emission. Because separation might influence emissions during the storage period, this period must be considered along with the potential increased emissions from field application of the fiber fraction, when assessing the ammonia mitigation effect of separation. Here, data on ammonia emissions from storage and field application of raw and separated manure is presented. The manure types investigated were anaerobically digested manure and pig manure. Ammonia emissions from storage were measured with 1 m3 tanks constructed as dynamic flow chambers, and emissions after field application were measured with wind tunnels. Online measurements of ammonia concentrations were done with cavity ring-down spectrometry.   
    How the fiber fraction from the manure separation is utilized is important for the overall ammonia loss. Fiber can be stored in a pile and subsequently spread in the field. Another way to treat the fiber is to pyrolyze it into biochar which can be incorporated into the field as a strategy for long term carbon sequestration. It has been suggested to mix the biochar and manure prior to field application to limit operating costs with field driving. Therefore, during the field application experiments, a treatment with biochar added to the liquid fraction of manure was also investigated.

How to cite: Holm Støckler, A., Pedersen, J., Nørlem Kamp, J., Feilberg, A., and D. Hafner, S.: Effect of manure separation on ammonia emission during storage and subsequent field application., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12913, https://doi.org/10.5194/egusphere-egu23-12913, 2023.

11:30–11:40
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EGU23-11378
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On-site presentation
Nicola Dal Ferro, Marta Mencaroni, Giorgia Fabbri, Flaviana Gottardo, Barbara Lazzaro, and Francesco Morari

Concerns about ammonia (NH3) emission from agriculturre have increased in recent years due to its contribution to atmospheric fine particulate matter formation (PM2.5 and PM10). To reduce NH3 losses a wide range of techniques has been reported, from the management of livestock and storage of excreted animal manure to the types and methods of application of organic and mineral fertilizers. The successful implementation of such techniques requires following a collaborative bottom-up approach that engages farmers and practitioners to the full technology valuation. Bayesian Belief Networks (BBNs) are probabilistic models that represent expert knowledge in any particular situation –e.g. in the agroecosystem– and evaluate the potential effects of different management scenarios. By linking multiple variables in a cause-and-effect relationship, BBNs can provide both diagnosis and prognosis aiding the decision-making process. In this work, a BBN was built to integrate quantitative experimental data and quali-quantitative stakeholder assessment. The aim was to provide recommendations to policy makers and practitioners about the most promising best available techniques (BAT) that combine environmental effectiveness in reducing NH3 emissions with economic and sociocultural acceptability by farmers at the regional scale. The variability of the livestock sector (swine, cattle and dairy cows) and agricultural systems (climate, soils, crops, etc.) across the Veneto region, NE Italy, was included in the BBN model. For the livestock sector management practices such as those related to feeding (e.g., precision feeding), overcrowding (e.g., breeding density), healthcare (e.g., infirmary spaces), etc. were considered. Estimates of NH3 losses from N fertilizer application techniques (e.g., closed slot injection Vs. surface distribution, N fertilizer in conservation vs conventional tillage) came from the integration of experimental, literature, and modelling data by using the modified version of DNDC v.CAN biogeochemical model. Stakeholders were engaged in evaluating the NH3 mitigation effectiveness of the proposed techniques. Perceptions about economic attractiveness and sociocultural acceptability were enquired, and results were introduced in the BBN as utility nodes to determine BATs. Results showed that the BBN model was able to embed into a single network quantitative outcomes from technical solutions with quali-quantitative assessment by stakeholders. By combining social and economic valuation with the technical potential of NH3 reduction, the BBN model acted as an effective tool to recommend the most promising BAT that should be supported by policy makers. The greatest room for improvement was found in the livestock supply chain, from the stable management to the manure distribution in the field. In contrast, stakeholders were unfamiliar with the most innovative techniques (e.g. precision farming, closed slot injection of mineral fertilizers), whose uncertainty in the costs and difficulties in the implementation would hinder their application despite their environmental benefits.

How to cite: Dal Ferro, N., Mencaroni, M., Fabbri, G., Gottardo, F., Lazzaro, B., and Morari, F.: How to select Best Available Techniques to reduce NH3 emissions from the agricultural sector? Results from integrating the pillars of sustainability into a Bayesian Belief Network model, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11378, https://doi.org/10.5194/egusphere-egu23-11378, 2023.

11:40–11:50
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EGU23-1139
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On-site presentation
Antonio Rafael Sánchez-Rodríguez, Elena Gómez-Álvarez, Jose María Méndez, Ute Skiba, Davey L Jones, Dave R Chadwick, María del Carmen del Campillo, Raphael BA Fernandes, Jörg Kleffmann, and Vidal Barrón

Trace gases of nitrogen (N), such as NOx (nitric oxide, NO + nitrogen dioxide, NO2) have a negative impact on human health and the environment. Although NOx are naturally produced in volcanic eruptions, forest fires and biotic nitrification and denitrification in soils, human activity is a major source of these contaminants via e.g. the combustion of fossil fuels. Additionally, N fertilization in agricultural soils is also an important source of NOx emissions. These emissions involve a loss of soil N to the atmosphere and have a negative impact in air quality. The abiotic part of the N cycle in terrestrial ecosystems has not received as much attention as the biotic part and certain abiotic reactions could play a key role in regulating NOx emissions. Photocatalysis is an example as this is used to abate NOx gases in urban and industrial areas. This reaction requires the presence of a catalyst (e.g. titanium oxide), oxygen, water, and energy from the sun (UV-visible light) to transform NO from the atmosphere into innocuous inorganic N forms (mainly nitrate, NO3-). There is a continuous investment in the production of catalysts by the industry. However, a variety of soil minerals such as anatase or rutile (titanium oxides), hematite and goethite (iron oxides), are found in soils and they could act as catalysts; however, the occurrence of photocatalysis in soils has not been evaluated so far. In this study, we assess (i) the potential of a selection of soils with different mineralogy and a wide variety of soil properties to fix or emit NOx through photocatalysis, and (ii) the possible alterations in the fixation or emission of other N gases from the soil, i.e., nitrous oxide (N2O) and ammonia (NH3), when photocatalysis is induced. Around thirty agricultural soils were selected to meet the first objective and irradiated for 1 hour with UV-visible light under a constant flux of air and NO (100 ppm). Similar experiments were carried out with a selection of soils, whose potential to fix NO was different and tested in the previous experiment, to satisfy the second objective. However, only air (without NO) was pumped within the soil chamber in this case and the soils were previously fertilized with different N fertilisers (urea or KNO3-) and rates (0 to 250 mg N kg-1 soil). Our experiments show that weathered soils (with a high content in titanium and iron oxides) were able to fix more atmospheric NO through photocatalysis (objective i), and that NO and NH3 fixation and emissions after N fertilization depended not only on the N fertilizer and rate but also on soil properties, mainly soil pH and N content (objective ii). Soil mineralogy and properties play a key role in soil photocatalysis, and this abiotic reaction should be considered in order to design more sustainable strategies for agriculture.

How to cite: Sánchez-Rodríguez, A. R., Gómez-Álvarez, E., Méndez, J. M., Skiba, U., Jones, D. L., Chadwick, D. R., del Campillo, M. C., Fernandes, R. B., Kleffmann, J., and Barrón, V.: Photocatalysis in agricultural soils: Mineralogy and soil properties control the fixation and emission of NOx and other trace gases of N, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1139, https://doi.org/10.5194/egusphere-egu23-1139, 2023.

11:50–12:00
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EGU23-7381
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ECS
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On-site presentation
Jasper H. Fabius, Burcu Celikkol, Upasna Rai, Jan Vonk, Remco Suer, and Shaojie Zhuang

Nitrogen compounds such as nitrogen dioxide (NO2) and ammonia (NH3) contribute significantly to air pollution and environmental degradation. Fine-grained networks of sensors for ambient nitrogen compounds can be used to inform policy makers and farmers about the effectiveness of techniques to reduce emissions of nitrogen compounds. We are developing a low-cost self-sustaining sensor system that can be deployed outdoors in large numbers in and around agricultural areas to measure the concentration of NH3, NO2, temperature and humidity with a high spatiotemporal resolution. We use off-the-shelf electrochemical sensors to measure nitrogen compounds. A preliminary comparison between the NH3 measurements taken by our sensor system and by a differential optical absorption spectroscopy instrument (miniDOAS) demonstrate encouraging results. After calibration, the measurements from our system show fairly good agreement with hourly-averaged miniDOAS measurements, at concentrations down to ~20 µg/m3. We are currently setting up a larger validation study to further assess the performance and robustness of our system in different outdoor agricultural environments. Our sensor system has the potential to greatly expand the availability and affordability of NH3 monitoring across wide areas, enabling farmers and policymakers to gain insights on the effectiveness of potential nitrogen reduction measures.

How to cite: Fabius, J. H., Celikkol, B., Rai, U., Vonk, J., Suer, R., and Zhuang, S.: Low-cost sensor system for measuring ambient nitrogen compounds in agricultural areas, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7381, https://doi.org/10.5194/egusphere-egu23-7381, 2023.

12:00–12:10
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EGU23-4564
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On-site presentation
Pascale Chelin, Sylvain Caville, Nadir Guendouz, Vincent Michoud, Antonin Bergé, Alain Fortineau, Céline Decuq, Pauline Buysse, Benjamin Loubet, Baptiste Esnault, Sophie Génermont, Raluca Ciuraru, Michel Burban, Jérémie Depuydt, Brigitte Durand, Camille Viatte, Cristelle Cailteau-Fischbach, Jean-Eudes Petit, Sabine Crunaire, Pablo Espina, Nathalie Redon, Lilian Joly, Julien Cousin, Florian Parent, Jean-Louis Bonne, Christophe Flechard, Yannick Fauvel, Anne-Claude Romain, and Marie Scheuren

Ammonia is an atmospheric pollutant precursor of inorganic fine particles (sulphate and ammonium nitrate particles) that are particularly harmful to human health. Ammonia and particulate matter (PM) are responsible for severe pollution outbreaks over Europe (LCSQA, LCSQA 2019), during springtime of 2012 (Kutzner et al., 2021), 2014 (Fortems-Cheiney et al., 2016), 2015 (Petit et al., 2017), 2016 (Tournadre et al., 2020: Viatte et al., 2020) and 2020 (Viatte et al., 2021). Despite this major societal and scientific interest, there is a crucial lack of routine ammonia and aerosol speciation observations. One of the scientific reasons comes from the difficulty to measure atmospheric ammonia due to its sticky, volatile, and reactive nature (von Bobrutzki et al., 2010).

The objective of the Multi-Instrumental Analysis of Ammonia Concentrations (AMICA) project is to compare the response of different available systems for measuring atmospheric ammonia at a rural site in the Île-de-France region. The 14 instruments based on different NH3 measurement techniques are compared over a wide range of ammonia concentrations from ambient atmospheric to boosted concentrations (10 to 600 ppbv) using an innovative 400 m2 ammonia emission system. They are all synchronized with a cross-correlation function based on the median value. At elevated concentrations all inlet-based instruments sampling to the same manifold performed very well on precision, even at high temporal resolution monitoring (1 min) that highlights a great progress for current in situ NH3 analysers. By comparing with the data from a mini Differential Optical Absorption Spectrometer (miniDOAS) and a sequential acid trap-IC (ROSAA), we demonstrated that inlet design perturbs the response time of the instruments connected to the manifold, which was already mentioned in literature. This measurement campaign is part of a series of ammonia projects that have recently taken place in France.

References

Fortems-Cheiney, A., et al., Geophys. Res. Lett., 43, 5475–5482, https://doi.org/10.1002/2016GL069361, 2016.

Kutzner, R. D., et al., Atmos. Chem. Phys., 21, 12091–12111, https://doi.org/10.5194/acp-21-12091-2021, 2021.

LCSQA, Le Laboratoire Central de Surveillance de la Qualité de l'Air, Bilan des travaux 2018-2019 du programme CARA, Ref. INERIS : DRC-19-181155-02828A, 2019.

Petit, J.-E. , et al., T, Atmospheric Environment, Volume 155, 2017, Pages 68-84, ISSN 1352-2310, https://doi.org/10.1016/j.atmosenv.2017.02.012.

Tournadre, B., et al., Atmos. Meas. Tech., 13, 3923–3937, https://doi.org/10.5194/amt-13-3923-2020, 2020.

Viatte, C., et al., Atmos. Chem. Phys., 20, 577–596, https://doi.org/10.5194/acp-20-577-2020, 2020.

Viatte C., et al., Atmosphere, 2021, 12, 160, https://doi.org/10.3390/atmos12020160.

von Bobrutzki, et al., Atmos. Meas. Tech., 3, 91–112, https://doi.org/10.5194/amt-3-91-2010, 2010.

 

 

How to cite: Chelin, P., Caville, S., Guendouz, N., Michoud, V., Bergé, A., Fortineau, A., Decuq, C., Buysse, P., Loubet, B., Esnault, B., Génermont, S., Ciuraru, R., Burban, M., Depuydt, J., Durand, B., Viatte, C., Cailteau-Fischbach, C., Petit, J.-E., Crunaire, S., Espina, P., Redon, N., Joly, L., Cousin, J., Parent, F., Bonne, J.-L., Flechard, C., Fauvel, Y., Romain, A.-C., and Scheuren, M.: Measurements of ammonia in ambient air and over a controlled artificial source during the AMICA field campaign at a rural site in the Ile-de-France region, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4564, https://doi.org/10.5194/egusphere-egu23-4564, 2023.

12:10–12:20
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EGU23-11693
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On-site presentation
Anders Feilberg, Yolanda Maria Lemes, Jesper Nørlem Kamp, and Johanna Pedersen

Non-methane volatile organic compounds are important air pollutants that contribute to tropospheric ozone production in combination with nitrogen oxides (NOx) and sunlight. Ozone is an important but often overlooked greenhouse gas with adverse effects on human health and crop yields as well as climate. Due to these indirect effects, there is a need for knowledge on emissions and potential mitigation strategies for NMVOC from key sources. Agricultural activities have recently been assessed to be a major source of non-methane volatile organic compounds (NMVOC) with particular importance in regions with intensive livestock production and manure management. In e.g. Denmark, recent assessments indicate that agriculture is the dominant source of NMVOC exceeding emissions from industry, transportation and residential heating. However, estimates of NMVOC emissions from agriculture are based on very limited realistic data and obtained by e.g. indirect calculations relative to ammonia. According to estimates for 2020 (EMEP Centre on Emission Inventories and Projections), around 25% of NMVOC in EU are from agriculture with livestock production and manure management being the dominant sources. These emission inventories are, however, quite uncertain and only based on measured data to a very low degree. Only very few studies have actually attempted to quantitatively measure NMVOC emissions from agricultural facilities and activities. In addition, little is known about the NMVOC composition and how composition varies with sources and conditions. Here, data on emissions from field application of manure based on a number of wind tunnel experiments are presented and used to estimate the contribution to national NMVOC emissions. NMVOC were quantified by proton-transfer-reaction mass spectrometry (PTR-MS) and simultaneous measurement of ammonia was used to achieve national emission estimates from field application of manure. Measurements were performed by placing a series of wind tunnels with realistic air flow rates in agricultural fields following application of liquid manure (slurry) and analyzing emissions over one week with a time resolution of typically 1 – 2 hours. The results demonstrate that emissions are significant and consist mainly of carboxylic acids with smaller contributions from phenols. Highly dynamic diurnal variations are identified. Impacts of different source types and manure treatments are discussed together with recommendations for future investigations.

How to cite: Feilberg, A., Lemes, Y. M., Kamp, J. N., and Pedersen, J.: Emissions of NMVOC from field application of manure measured by PTR-MS, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11693, https://doi.org/10.5194/egusphere-egu23-11693, 2023.

12:20–12:30
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EGU23-5752
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ECS
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On-site presentation
Auriane Voyard, Raluca Ciuraru, Michael Staudt, Benjamin Loubet, and Frédéric Rees

Plants are the primary worldwide source of Volatile Organic Compounds (VOCs) on Earth and therefore play a significant role in the atmosphere's gas composition. While emissions from foliage have been well documented for decades, emissions from soils with living roots and associated microorganisms are not well understood. In particular, field studies show a wide and inconsistent range of soil-derived VOC net fluxes, possibly due to the variable abiotic and biotic conditions during measurements. In order to figure out the main drivers of soil VOC exchanges, studies under controlled experimental conditions are necessary. 

We developed a new experimental dynamic chamber, allowing to monitor the gas emissions from 1-9 plants simultaneously, both in the aboveground and belowground compartments. Aside from providing controlled experimental conditions, this setup allows to compare the net VOC, CO2, and H2O flux dynamics from soil to that from the aboveground plant organs at a high time resolution.

Using a Proton Transfer Reaction – Time Of Fly – Mass Spectrometer, constitutive emissions from soil-grown rapeseed and tomato plants were recorded over 24h. Methanol was the main VOC emitted by both species, followed by, at one order of magnitude lower, methanethiol and monoterpenes for rapeseed and tomato plants, respectively. Although root-derived VOC emissions were generally much lower than shoot-derived ones, belowground DMDS emissions from rapeseed plants were twice higher than those from aboveground.  Interestingly, a negative correlation was observed between several root-derived VOC and root/soil respiration, suggesting a shift in the carbon allocation to specific metabolic pathways in roots or root-associated microorganisms. This experimental approach opens new perspectives for understanding the specific contributions of VOC emissions from soils and roots in agricultural ecosystems, and how these emissions may be linked to plant carbon budget.

How to cite: Voyard, A., Ciuraru, R., Staudt, M., Loubet, B., and Rees, F.: Are crops significant sources of Volatile Organic Compounds? A bi-compartmented chamber setup for investigating VOC emissions from aboveground and belowground, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5752, https://doi.org/10.5194/egusphere-egu23-5752, 2023.

Posters on site: Tue, 25 Apr, 16:15–18:00 | Hall A

Chairpersons: Katerina Machacova, Christian Brümmer, Christof Ammann
Reactive trace gas exchange
A.302
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EGU23-14139
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ECS
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Clément Dumont, Bert Verreyken, Niels Schoon, Crist Amelynck, and Bernard Heinesch

Volatile organic compounds (VOCs) play a key role in atmospheric chemistry. These gases impact air quality by participating in the formation of ozone and secondary organic aerosols and extend the lifetime of methane in the atmosphere. Approximately 90% of global VOC emissions are biogenic (BVOCs), and since forests are the main emitters of BVOCs, these ecosystems deserve special attention in order to better characterize BVOCs exchanges with the atmosphere.          

Traditionally, flux measurements were mainly limited to a few dominant BVOC species, such as isoprene, terpenes and methanol, due to technical measurement limitations. Most of the measured species were found to be emitted by vegetation, but some studies detected significant net depositions of compounds such as methanol, driven by environmental factors favouring the formation of surface wetness. This observation supports the need for a more detailed and complete picture of BVOC bidirectional exchanges at forest sites as well as the mechanisms controlling these fluxes, which are essential to better characterize the in-canopy atmospheric chemistry.

To address this gap, BVOC fluxes were measured in spring-summer 2022 using a PTR-TOF-MS instrument (PTR-TOF-4000, Ionicon Analytik GmbH) over a mixed temperate forest in the Belgian Ardenne (Vielsalm), which is part of the ICOS network. The use of a PTR-TOF-MS instrument, deployed at Vielsalm in the framework of ACTRIS, allows for the simultaneous detection of a very wide range of VOC-related ion masses with increased sensitivity (especially for ions at high m/z ratios) and higher mass resolving power compared to conventional PTR-Quad-MS instruments. O3 fluxes were also simultaneously acquired using fast and slow ozone analysers in order to complete the BVOC fluxes dataset and BVOC+O3 concentration profiles were frequently measured at seven levels along the flux tower from ground level up to 51 m.

(Un)calibrated BVOC mixing ratios were first derived from results of the Ionicon Data Analyzer software (IDA, Ionicon Analytik GmbH) obtained on a near-daily basis, and these concentrations were then used in a computational tool based on InnFLUX (Atmospheric Physics and Chemistry Group, University of Innsbruck) to compute fluxes by eddy covariance. Along with these fluxes, uncertainties and limits of detection (LODs) were estimated, and quality control statistical tests were performed. During the whole measurement campaign, about 570 m/z peaks were detected by the IDA software.

Based on this extensive dataset, our goals are to: (1) perform spectral analysis (which often turns out to be trickier for low signal-to-noise ratios), (2) determine the significant fluxes based on LODs, (3) analyse their response to meteorological variables, phenology and O3 concentrations/fluxes, (4) attempt compound attribution based on scientific literature and site-related information, and (5) establish the budget of BVOC emissions and depositions for the forest site. The obtained results will be compared to BVOC studies previously conducted at the Vielsalm ICOS forest site with a PTR-Quad-MS instrument and should improve our previous BVOC budget estimates at the site.

How to cite: Dumont, C., Verreyken, B., Schoon, N., Amelynck, C., and Heinesch, B.: Study of biogenic volatile organic compound emissions and depositions over a mixed temperate forest by PTR-TOF-MS and eddy covariance, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14139, https://doi.org/10.5194/egusphere-egu23-14139, 2023.

A.303
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EGU23-13229
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ECS
Emma Galloway, Adrien Gandolfo, Julien Kammer, and John Wenger

The use of animal-based fertilizers in the forms of manure and slurry is widespread throughout Europe. The process of spreading manure and slurry results in large emissions of greenhouse gases as well as inorganic gases and volatile organic compounds (VOCs). The non-methane VOCs emitted from manure and slurry are not well characterized, even though they are expected to result in the formation of important secondary pollutants such as ozone and secondary organic aerosols (SOA).

 

In this study, we conducted an initial small-scale laboratory measurement of VOCs emitted by cattle slurry using a Time of Flight Chemical Ionisation Mass Spectrometer. Dry purified air was passed through a small chamber containing the slurry and into the instrument, which was operated using both C6H6+ and I- as reagent ions in order to detect a large range of oxygenated and hydrocarbon VOCs.

 

Using the I- reagent ion, a number of low molecular weight carboxylic acids were detected, along with some phenolic compounds and hydrogen disulfide. A much larger number of compounds was detected using the C6H6+reagent ion, including the same phenolic compounds and a range of nitrogen-containing species. The timescales of the emitted species showed considerable variation, with some, e.g. hydrogen disulfide, being very intense and short-lived, and others, e.g. phenol, being continuously emitted at a roughly constant rate for several hours. Further work is currently underway to understand the factors controlling the nature of these emissions, their reactivity and SOA formation.

How to cite: Galloway, E., Gandolfo, A., Kammer, J., and Wenger, J.: Analysis of Emissions from Cattle Slurry using Time of FlightChemical Ionisation Mass Spectrometry (TOF-CIMS), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13229, https://doi.org/10.5194/egusphere-egu23-13229, 2023.

A.304
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EGU23-17146
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ECS
Pascal Wintjen, Jeremy Rüffer, Liv Offermanns, Christof Ammann, and Christian Brümmer

Drained agriculturally used peatlands are hotspots of greenhouse gas emissions. Their exchange of reactive nitrogen (Nr) with the atmosphere, however, has been less investigated, mainly due to challenges in accurate and feasible flux measurements. In this study, we present data from a two-year field campaign on intensively managed grassland on bog peat soil. We used a modified custom-built converter called TRANC with fast time response connected to a dual-channel chemiluminescence detector (CLD) for eddy flux measurements of total reactive nitrogen (∑Nr) and total odd nitrogen (NOy). The difference of the two channels was taken for an estimation of reduced nitrogen (NHx). We found good agreement between time-integrated Nr concentrations from TRANC and a DELTA denuder sampler system. Over the two-year observation period, roughly two thirds of all recorded half-hourly ∑Nr and NHx fluxes were positive, i.e. indicating ecosystem Nr loss to the atmosphere. Emission peaks occurred after fertilization events and mainly during the warmer months. Monthly median ∑Nr fluxes were ranging between -8 to 57 ng N m-2 s-1. We further found an enhancement of emissions under dry conditions and clear diurnal patterns in all Nr fluxes with peaks occurring around noon and close-to-neutral exchange during nighttime. The net loss of ∑Nr to the atmosphere was calculated to reach 9.3 kg N ha-1 in 2020 and 6.7 kg N ha-1 in 2021. Our setup allowed for an estimation of NHx emission factors, at least for the organic inputs. Taking one week after each fertilization into account by summing up all recorded and gap-filled fluxes, emission factors for NHx were in the range of 1.2 to 2.5% of added fertilizer nitrogen. Our study demonstrates the applicability of the modified TRANC converter for eddy flux measurements and provides useful data for understanding N cycling in agroecosystems to derive sustainable management options for farmers and conservationists.

How to cite: Wintjen, P., Rüffer, J., Offermanns, L., Ammann, C., and Brümmer, C.: Substantial net emissions of reactive nitrogen from intensively managed grassland on bog peat soil, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17146, https://doi.org/10.5194/egusphere-egu23-17146, 2023.

A.305
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EGU23-12677
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ECS
Johanna Pedersen, Sasha D. Hafner, Valthor Ingi Karlsson, Andreas Pacholski, Rodrigo Labouriau, and Jesper N Kamp

Liquid animal manure (slurry) can be utilized as a valuable nutrient source for crop production but is also a significant source of ammonia (NH3) emissions, which negatively affect the environment and human health.

Emission depends on several factors, including application technique, climatic conditions, and slurry and soil properties. Despite increased knowledge there are still important effects and interactions that are not quantitatively understood. Reliable emission measurements and assessment of new low-emission application technologies are needed for emission inventories and research aimed at reducing emission.

Different methods can be used to measure NH3 emission after field application of slurry and can roughly be sorted into two categories: micrometeorological and enclosure methods. Micrometeorological methods yield accurate flux measurements and slurry can be applied by full-scale farm machinery, but replication is impractical and usually omitted, making statistical comparisons difficult. In contrast enclosure methods, such as dynamic chambers, only require a small plot area, making replication possible. However, most dynamic chamber designs can only be used with manual application of the slurry, which is not always representative of application of full-scale machinery, especially when there is an interaction between the slurry application aggregate and the soil.  

A new design of dynamic chambers enabling application of slurry both manually and by full-scale farm machinery has been developed. The dynamic chambers are connected to a cavity ring-down spectrometer for online measurements of NH3, allowing for high time-resolution measurements with a low detection limit, high recovery, and relatively low variation among chambers.

Several configurations of the design were investigated in silico with computational fluid dynamic (CFD) in order to optimize airflow through the chamber and the configuration to ensure turbulence homogeneity of the emitting surface and sufficient mixing of the air within the chamber.

The new dynamic chambers were tested in three field trials where a different method of applying the slurry was used in each trial: manual application, application with a field trial system with 3-m slurry boom, and application by a 30-m farm-scale slurry boom. Statistical power analysis was performed to estimate the number of replicates required for detecting several effect sizes for each application method. Furthermore, the flux measurements from the new chambers will be compared with wind tunnel measurements (manual application) and the backward Lagrangian Stochastic (bLS) dispersion technique (3-m and 30-m boom application).

This new design allows for representative measurements of NH3 flux after application of slurry in the field, making it possible to statistically assess the effect of individual variables affecting flux dynamics and thereby further increase knowledge on NH3 emissions mitigation options.

How to cite: Pedersen, J., Hafner, S. D., Karlsson, V. I., Pacholski, A., Labouriau, R., and Kamp, J. N.: Optimized design of flux chambers for online measurement of NH3 emission after field application of slurry with full-scale farm machinery, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12677, https://doi.org/10.5194/egusphere-egu23-12677, 2023.

A.306
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EGU23-14615
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ECS
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Geng Li, Peng Xu, and Jimmy C.H. Fung

Mitigating NH3 emission from cropland soil is crucial for further improving air quality. Despite crop-specific emission factors (EFs) being provided by several studies, the lack of high-resolution EFs under different human management practices limits the further exploration of global cropland NH3 mitigation potential. Agricultural NH3 mitigation potential varies widely depending on where emissions are released. Thus, comprehensively and systematically assessing impacts on a fine scale is useful when developing strategies to efficiently mitigate the effects of NH3 emission. In this study, we performed several machine learning models on a global NH3 emission factors response dataset to find the relationship between EFs and climate conditions, soil properties, and human management. The random forest (RF) model with an R2 of 0.78 and an RMSE of 0.88 showed the best estimation ability. Our data-driven approach indicated that the EFs were mainly affected by temperature, water input, N placement, crop type, and fertilizer type. The combine-effect of N application rate and temperature need to be further studied since these two variables interacted most in our RF model. Using the RF model, we provided five-arcminute high-resolution NH3 emission factor maps under different management practices. The results showed that under proper management, the global NH3 emission of rice, wheat, and maize production has a reduction potential of 44%, 34%, and 37%, respectively. The effects of different human management practices vary everywhere due to the interaction of environmental conditions and management. Our management-specific EFs can provide insights for fine-scale NH3 emission control.

How to cite: Li, G., Xu, P., and Fung, J. C. H.: Fine-scale agricultural fertilizer management promotes global NH3 emission reduction, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14615, https://doi.org/10.5194/egusphere-egu23-14615, 2023.

A.307
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EGU23-14100
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ECS
Sina Kukowski, Hannah Götze, Pascal Wintjen, Jeremy Rüffer, Andreas Pacholski, Heinz Flessa, and Christian Brümmer

Ammonia (NH3)emissions stem mainly from agricultural sources and affect environment, climate and human health, thereby concomitantly reducing fertilizer nitrogen use efficiency. Reliable and representative measurements for typical field conditions as well as for potential mitigation options are needed as a basis for recommendations to policy makers and farmers. However, there is still uncertainty about the reliability of different NH3 measurement methods for emissions from low intensity sources, such as synthetic fertilizers, and a lack of data on simultaneous comparative evaluations of different methods. The joint research project NH3-Min aims at comparing combinations of different NH3 samplers and sensors (e. g. acid traps, dynamic chamber, laser-based techniques), flux calculation approaches (e. g. IHF, ZINST, bLs-Windtrax, eddy covariance), and scales (small scale multi-plots, field scale) to accurately quantify emissions and evaluate mitigation options (e. g. use of inhibitors, injection, form of nitrogen).

This poster focuses primarily on the quantification of NH3 concentrations and fluxes determined by a quantum cascade laser spectrometer (QCL) within an eddy covariance setup and the comparison to low-cost approaches, such as ALPHA passive diffusion samplers in combination with backwards Lagrangian stochastic (bLs) modelling (Windtrax). Measurements were carried out in Central Germany during the vegetation period in 2021 and 2022 in a winter wheat crop field, which received 3 urea fertilizer applications (to a total of 170 kg N) per year.

First results showed that under high ambient NH3 concentrations, time-integrated QCL values compared fairly well with those from ALPHA samplers. Under a low concentration regime, however, a significant underestimation of ALPHA values was observed, thereby providing a basis for an estimation of the method-specific detection limit. High-frequency losses using a co-spectral method in the process of eddy flux calculation were estimated to be in the range of 25 to 30%. We found clear diurnal flux courses and emission peaks after each urea application. The net loss of NH3 summed up to 3.6 kg N ha-1 over the whole measurement period (March – July). In further steps, we will evaluate the performance of the Windtrax model for estimating NH3 losses from field-scale fertilizer applications and investigate the sensitivity of differences in input concentrations on modelled NH3 emissions. Our study is a step towards better comparability and integration of different NH3 measurement techniques and is expected to provide useful tools for robust estimations of NH3 emission factors for synthetic fertilizer applications.

The project is supported by funds of the German Government‘s Special Purpose Fund held at Landwirtschaftliche Rentenbank.

How to cite: Kukowski, S., Götze, H., Wintjen, P., Rüffer, J., Pacholski, A., Flessa, H., and Brümmer, C.: Quantification of ammonia losses from winter wheat using eddy covariance and low-cost samplers, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14100, https://doi.org/10.5194/egusphere-egu23-14100, 2023.

Agricultural greehouse gas exchange
A.308
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EGU23-15905
Christian Brümmer, Frederik Schrader, Olaf Kolle, Mathias Herbst, Antje Lucas-Moffat, and Werner Kutsch

Agriculture plays an important role in the land surface-atmosphere exchange of greenhouse gases and terrestrial carbon cycling. The determination of carbon budgets with varying system boundaries has been in the focus of environmental research, particularly at agricultural sites, which occupy roughly 50% of the global land surface. Accurate carbon balancing at crop sites is subjected to a number of uncertainties, for example through variations in vegetation cover development, carbon imports and exports by fertilization, harvest, and recurring disturbance by soil and plant management. Since 2001, continuous observations of CO2 and water vapour net ecosystem exchange, meteorological parameters, and field operations have been carried out at the ICOS Class-1 station Gebesee (DE-Geb), located in the Thuringian Basin, Germany, making it the longest operating agricultural eddy-covariance site in Europe. In this contribution, we present two decades of flux measurements under the given land management and bioclimatic conditions. We found two opposing trends between net ecosystem and net biome production, called NEP and NBP, respectively. While the net CO2 exchange resulted in an average annual ecosystem carbon gain of ca. 2.2 t C ha-1 (NEP), including lateral fluxes from harvest and fertilization turned the site into a substantial deficit, indicating a loss of ca. 1.6 t C ha-1 (NBP) per year. The mean values in repeated measurements of soil organic carbon (SOC) stocks in 2004 and 2019, however, did not show any significant changes in any of the soil horizons. Taking conservative uncertainty estimations from all components into account, the carbon loss revealed in the NBP trend over 21 years barely matched the outer ranges of the SOC uncertainty in the 0-60 cm layer. As the soil type at DE-Geb is a black earth with high carbonate content, we speculate that a certain amount of the emitted CO2 is of inorganic origin and may partly explain the site’s carbon imbalance. An additional experiment investigating the δ13C signature of the emitted CO2 to potentially prove this assumption is still ongoing. Our study highlights the importance of long-term continuous biosphere-atmosphere observations within research infrastructures like ICOS for understanding carbon cycling in agricultural landscapes, but also emphasizes the importance of site-specific knowledge to improve sustainable land management.

How to cite: Brümmer, C., Schrader, F., Kolle, O., Herbst, M., Lucas-Moffat, A., and Kutsch, W.: The enigma of a massive carbon imbalance – Two decades of cropland eddy flux measurements at Gebesee, Thuringia, Germany, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15905, https://doi.org/10.5194/egusphere-egu23-15905, 2023.

A.309
|
EGU23-10270
|
ECS
Samuel Munyaka Kimani, Putu Oki Bimantara, Valensi Kautsar, Satoshi Hattori, Keitaro Tawaraya, Shigeto Sudo, Takeshi Tokida, and Weiguo Cheng

Azolla, a common aquatic fern has been used successfully as a dual crop with lowland rice. It grows rapidly and fixes atmospheric nitrogen for rice paddy. However, its ecological significance especially on greenhouse gases emissions remains unclear. Three independent experiments -two pot (2016 and 2017), and one field in 2019- were conducted to investigate the effects Azolla (A. filiculoides Lam.) either or both as dual cropping and green manure along with rice plant on simultaneous methane (CH4) and nitrous oxide (N2O) emissions from constantly flooded paddy soil. Under pot setups, dual cropping Azolla as a cover with rice plant significantly decreased seasonal CH4 emission by 34.7%, with no effect on N2O emissions. Suppressed CH4 emission was likely due to an increase in dissolved oxygen concentration and redox potential at the soil-water interface simulating CH4 oxidation. However, incorporation of Azolla as green manure into the soil plus dual crop in conjunction with chemical fertilizers significantly increased CH4 emission by 37.5% but decreased N2O emission by 74.5%. The significantly higher CH4 and lower N2O emissions were attributed to the readily decomposable incorporated Azolla, acting both as a source of CH4 production and N2O reduction. Contrary to the pot observations, application of Azolla as a dual crop in conjunction with chemical fertilizer or incorporated as green manure plus dual cropping in the field did not significantly affect seasonal CH4 emissions, but significantly increased cumulative N2O emissions at the middle rice growth stages by 645%—816%, and the total seasonal emission 3.4-fold. The higher N2O emissions were partly attributed to large quantities of exogenous organic carbon resulting from the accelerated growth and subsequent senescence of Azolla cover applied as a dual crop as impacted by higher summer air temperatures. Our observations suggest that dual cropping of Azolla with rice has the potential to reduce CH4 emissions from flooded rice paddies. Conversely, incorporation of Azolla as green manure into the paddy soil plus dual cropping in conjunction with or without chemical fertilizers indicates an inconsistent relationship between CH4 and N2O emissions. Long-term studies are needed to evaluate the relationship between leguminous cover crops and their effects on factors influencing CH4 and N2O emissions from continuously flooded rice paddies.

How to cite: Kimani, S. M., Bimantara, P. O., Kautsar, V., Hattori, S., Tawaraya, K., Sudo, S., Tokida, T., and Cheng, W.: Influence of Azolla incorporation and/or dual cropping on CH4 and N2O emissions from flooded rice paddy systems, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10270, https://doi.org/10.5194/egusphere-egu23-10270, 2023.

A.310
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EGU23-3397
|
ECS
Elizabeth Wangari, Ricky Mwanake, David Kraus, Christian Werner, Gretchen Gettel, Ralf Kiese, Lutz Breuer, Klaus Butterbach-Bahl, and Tobias Houska

Accurate quantification of landscape soil greenhouse gas (GHG) exchange from chamber
measurements is challenging due to the high spatial-temporal variability of fluxes, which results in large
uncertainties in upscaled regional and global flux estimates. We quantified landscape-scale (6 km2 in central
Germany) soil/ecosystem respiration (SR/ER-CO2), methane (CH4), and nitrous oxide (N2O) fluxes at
stratified sites with contrasting landscape characteristics using the fast-box chamber technique. We assessed
the influence of land use (forest, arable, and grassland), seasonality (spring, summer, and autumn), soil
types, and slope on the fluxes. We also evaluated the number of chamber measurement locations required to
estimate landscape fluxes within globally significant uncertainty thresholds. The GHG fluxes were strongly
influenced by seasonality and land use rather than soil type and slope. The number of chamber measurement
locations required for robust landscape-scale flux estimates depended on the magnitude of fluxes, which varied
with season, land use, and GHG type. Significant N2O-N flux uncertainties greater than the global mean
flux (0.67 kg ha−1 yr−1) occurred if landscape measurements were done at <4 and <22 chamber locations
(per km2) in forest and arable ecosystems, respectively, in summer. For CO2 and CH4 fluxes, uncertainties
greater than the global median CO2-C flux (7,500 kg ha−1 yr−1) and the global mean forest CH4-C uptake rate
(2.81 kg ha−1 yr−1) occurred at <2 forest and <6 arable chamber locations. This finding suggests that more
chamber measurement locations are required to assess landscape-scale N2O fluxes than CO2 and CH4, based on
these GHG-specific uncertainty thresholds.

How to cite: Wangari, E., Mwanake, R., Kraus, D., Werner, C., Gettel, G., Kiese, R., Breuer, L., Butterbach-Bahl, K., and Houska, T.: Number of Chamber Measurement Locations for Accurate Quantification of Landscape-Scale Greenhouse Gas Fluxes: Importance of Land Use, Seasonality, and Greenhouse Gas Type, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3397, https://doi.org/10.5194/egusphere-egu23-3397, 2023.

A.311
|
EGU23-9734
|
ECS
Elpida Pasvadoglou, George Kourtidis, Andreas Mamolos, George Menexes, Efimia Papatheodorou, and Georgios Giannopoulos

Agriculture is the second-largest contributor of greenhouse gasses (GHGs) globally, after fossil fuels combustion. The excessive application of mineral fertilizers and the inadequate disposal of large amounts of livestock waste in agricultural soils result in elevated N2O and CO2 emissions, which surpass 17% of the global GHG emissions.

Approximately 1.4 billion tons of cow manure (CM) are produced every year in the EU and current EU policies promote CM incorporation into the soil, as a cost-efficient and sustainable agronomic practice. The European Green Deal urges a 20% reduction in chemical fertilization by 2030 and reuse of organic fertilizers, i.e. cow manure The beneficial use of CM is linked to enhanced soil fertility, soil organic matter content and carbon sequestration. However, soil organic amendments may fuel soil nutrient transformations and potentially increase nutrient losses i.e. GHG emissions.

To test the short-term effects of combined organic and inorganic fertilization on GHG emissions, we conducted a mesocosm experiment using two soil types (Sandy-loam (SL) & Loamy (L)) and including five treatments: Control (C: No fertilization), Urea as Chemical Fertilization in two rates (100U:200 kg/ha & 80U:160 kg/ha), Cow Manure (CM:50 Mg/ha) and the combination of 80U and CM (80U-CM:160 kg/ha Urea & 50 Mg/ha Cow Manure). During a 90-days incubation period, CO2 and N2O flux rates and soil NO-3, NO-2 and NH+4 were measured regularly. 

Soil type was the only significant factor (p≤0.05) driving cum. CO2 emissions. A 20% increase of cum. CO2 was found for L soil treatments than SL. The combined treatment 80U-CM had similar emissions to conventional fertilization (100U) that were on average 762 mg/kg C-CO2, approx. 28.5% greater than C (591 mg/kg). CM incorporation led to 19% increase in cum. CO2 emissions than C.

Contrary to CO2, soil (p<0.001), fertilization (p<0.001) and their interaction (p=0.002) were significant factors explaining cum. N2O emissions. The SL soil had 60% higher cum. N2O emissions compared to L. The use of CM in L soil decreased (39%), while in SL soil increased (5%) cum N2O emissions, relative to C. A 20% reduction in urea application resulted in 90% and 19% reduction for SL and L soil, respectively when compared to 100U. The combined application 80U-CM increased cum. N2O emissions than CM and 80U and had lower cum. N2O emissions than 100U, for both soils. Soil, fertilization, and their interaction were accounted for statistically significant (p≤0.05) differences in soil NO3- , NO2- and NH4+ availability (AUC) .

According to our study, the combined application of 80U-CM cannot be an effective alternative to conventional fertilization (100U), as it generates similar levels of GHG emissions and has lower nutrient (N) supply potential. Furthermore, our preliminary research indicates the need to further quantify the effects of different organic amendments on GHG soil emissions and soil microbial communities.

Funding: The BSc and MSc research work by George Kourtidis and Elpida Pasvadoglou, respectively, was supported in part by the Hellenic Foundation for Research and Innovation (HFRI) Post-Doctoral Grant #1053 awarded to Principal Investigator Dr. Georgios Giannopoulos.

How to cite: Pasvadoglou, E., Kourtidis, G., Mamolos, A., Menexes, G., Papatheodorou, E., and Giannopoulos, G.: Combined application of urea and cow manure results in similar cumulative N2O emissions relative to conventional fertilization, in two types of soil., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9734, https://doi.org/10.5194/egusphere-egu23-9734, 2023.

A.312
|
EGU23-11584
|
ECS
Heidi Aaltonen, Noora Manninen, Markku Koskinen, Saana Hakkola, Virpi Kling, Juha Nousiainen, and Mari Pihlatie

Agricultural grasslands may act as carbon sinks, counteracting emissions caused by agricultural practices. Contrastingly, grasslands may also act as sources of Nitrous oxide (N2O). For example, in Finland, N2O emissions from grasslands total up to 30 % of the climate impact of milk production. The N2O emissions from grasslands are induced by the use of nitrogen fertilizers, crop management and various environmental factors. However, the dynamics of N2O production are complex and not yet fully understood. Successful mitigation of N2O fluxes from agricultural soils calls for better understanding of these dynamics and the finding of practical solutions for farmers.

We measured greenhouse gas fluxes (N2O, carbon dioxide (CO2) and methane (CH4)) in May-September on five Finnish grasslands with varying soil types (organic and mineral) and vegetation (perennial grasses) in 2022. The grasslands were harvested and fertilized twice during the measurement period. Each grassland had a fertilized and nonfertilized plot. The fluxes were measured every second week, with a dark chamber method by using online gas analysers, from both plots and adjacent soil samples were collected each time for chemical analysis. Soil parameters (temperature, moisture and conductivity) were measured continuously on each plot.

The measured N2O fluxes varied from -22.6 to 928 µg N2O m-2 h-1. All measured grasslands were N2O sources over the measurement period, with organic soils showing higher emissions. Statistical analysis showed that N2O fluxes were affected by soil moisture, soil type and pH, whereas the effect of fertilizers and harvests was not as clear. However, the harvests and fertilizers seemed to have a more profound effect on CO2 respiration. The results indicate, that environmental factors govern the changes of N2O fluxes in these agricultural grasslands, but there is a need for long term, continuous measurements.

How to cite: Aaltonen, H., Manninen, N., Koskinen, M., Hakkola, S., Kling, V., Nousiainen, J., and Pihlatie, M.: Nitrous oxide flux dynamics on agricultural grasslands in Western Finland, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11584, https://doi.org/10.5194/egusphere-egu23-11584, 2023.

A.313
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EGU23-948
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ECS
|
Alexandra Lugo-Arroyo, Giampaolo Zanin, Aaron Thompson, Carmelo Maucieri, and Maurizio Borin

Covering building rooftops with vegetation [Green roofs (GR)] holds promise for lowering building temperatures, reducing stormwater runoff, and other ecosystem services, but it is unclear how this will impact greenhouse gas (GHG) emissions. GHG emissions may also be influenced by vegetation type, substrate depth, and irrigation level and we sought to test this by comparing daytime greenhouse gas (GHG) emissions (CH4, CO2, and N2O) and daily temperatures, from 48 GR microcosms in North-eastern Italy during a dry-hot summer season (June to September). The microcosms were planted with Sedum spp., cold season grasses, warm season grasses, or wildflowers to a substrate depth of 8 cm or 14 cm, and with an average irrigation level of 1 or 2 mm d-1 for a total of 16 treatments with 3 replicates. We found that vegetation type had a significant effect on temperature [median temp. of 24.8 °C (Sedum) vs 25.5 °C (warm season grasses)] and CH4, CO2, and N2O emissions. While all species emitted net CO2 (median values from 147 to 671 mg m-2  h-1) and captured net N2O (median values were negative from -0.06 to -0.28 mg m-2  h-1)— highlighting a potential GR ecosystem service with a beneficial effect on the environment— CH4 had net negative values (capture) only in microcosms with wildflowers (-0.07 mg m-2  h-1) whereas other treatments had a median emission of 0.09 mg m-2  h-1 . Substrate depth significantly affected CO2 and N2O fluxes with deeper substrate leading to higher CO2 emission (+ 60.7%) and greater N2O uptake (+ 30.8%). Irrigation level only significantly influenced N2O fluxes with a significantly higher uptake supplying 2 mm  (-0.20 mg m-2  h-1) than in the 1 mm  (-0.09 mg m-2  h-1) irrigation treatments. Our study suggests that, in a hot summer season, GRs can improve N2O and CH4 capture, but will likely increase CO2 emissions and that vegetation type and substrate depth can significantly alter emissions and are thus important design parameters.

How to cite: Lugo-Arroyo, A., Zanin, G., Thompson, A., Maucieri, C., and Borin, M.: Diurnal greenhouse gas emissions and substrate temperatures from green roofs in north-eastern Italy during summer season, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-948, https://doi.org/10.5194/egusphere-egu23-948, 2023.

Forest greenhouse gas exchange
A.314
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EGU23-2632
German Cabrera Carillo, Sergio Aranda-Barranco, Daniel Agea, Enrique Echeverría-Martín, Enrique P Sánchez-Cañete, Penelope Serrano-Ortiz, Cecilio Oyonarte, Luis Villagarcía, and Francisco Domingo

For the last decade there has been a continuous increase in atmospheric methane. Methane (CH4) is the second most important greenhouse gas (after carbon dioxide, CO2). However, despite the recent international effort to quantify global CH4 fluxes, such information is still limited, with a significant source of uncertainty (from 51% to 82%) mainly attributed to emissions from wetlands and other inland waters. On the other hand, some research in arid ecosystems (drylands) has shown that they play an important role in the CH4 cycle as CH4 sinks. These uncertainties in quantifying potential methane sinks highlight the need to increase our understanding of this effect of dryland ecosystems.


In this study we have quantified the capacity of two Mediterranean ecosystems as methane sinks. A lowland site located at 200 m.a.s.l and 6 km from the coast, in Cabo de Gata Natural Park (Almería, Spain; N36°56′26.0″, W2°01′58.8). This lowland is dominated by Stipa tenacissima at 60 % cover. And a subalpine site located at 1,600 m.a.s.l. and 25 km from the coast, in Sierra de Gádor (Almería; 36º55′41.7″N; 2º45′ 1.7″W). This site is a shrubland plateau derived from an open forest and its climate is Mediterranean with hot summers. Both study sites are included in the international network FLUXNET (https://fluxnet.org/about/).


For this purpose, two techniques have been used, the Eddy covariance technique to measure CH4 fluxes at the ecosystem scale and a standardized camera system composed by an infrared gas analyser (LI-7810, Li-Cor, Lincoln, NE, USA) connected to a Smart Chamber (8200-01S, Li-Cor, Lincoln, NE, USA), to measure soil CH4 fluxes in intensive campaigns. The Eddy covariance technique was applied for several weeks during the dry season, while the camera system was used to measure fluxes during the rainy season and in the middle of the growing season. Thanks to this study we will be able to establish an approximate range of CH4 assimilation by these ecosystems, comparing this value with those obtained in other studies; additionally, we will analyse the effect of the different soil conditions (humidity, temperature, porosity, texture...) on CH4 fluxes in these "drylands".

This work was supported by the projects P20_00016 (BAGAMET) and LifeWatch-2019-10-UGR-01, co-funded by the MICINN through the FEDER funds.

How to cite: Cabrera Carillo, G., Aranda-Barranco, S., Agea, D., Echeverría-Martín, E., Sánchez-Cañete, E. P., Serrano-Ortiz, P., Oyonarte, C., Villagarcía, L., and Domingo, F.: Analysing the capacity of two Mediterranean semiarid ecosystems located in the southeast Spain as methane sinks, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2632, https://doi.org/10.5194/egusphere-egu23-2632, 2023.

A.315
|
EGU23-12510
|
ECS
Carl-Fredrik Johannesson, Klaus Steenberg Larsen, Jenni Nordén, and Hanna Silvennoinen

Methane (CH4) is the second largest contributor to global warming and the importance of reducing net CH4 emissions was recently highlighted through the 2021 Global Methane Pledge. Upland forest soils are most often acting as CH4 sinks, but forest management – for example clear cutting and nitrogen (N) fertilization – carry the potential to turn CH4 sinks into CH4 sources. However, little is currently known about the underlying mechanisms and to what extent forest management affects the fluxes. Furthermore, the role of deadwood in the CH4 cycle is poorly understood and quantified but has recently received increased attention. Deadwood, like soils, can act both as a sink and a source of CH4 and the few available studies indicate that tree species, decay class and wood density are important regulators of CH4 cycling in deadwood.

In the ForBioFunCtioN-project, we utilize state-of-the-art technology (LI-7810 Trace Gas Analyzer, LI-COR®) for in situ measurements of soil-atmosphere and deadwood-atmosphere exchange of CO2 and CH4 in an extensive climate and management manipulation experiment. Treatments include warming with open-top chambers, increased precipitation (on average 25 mm/year during the snow-free period), N fertilization (NH4NO3 150 kg/ha) and biochar addition (10 t/ha) in a total of 12 treatment combinations (n = 144) across five Norwegian spruce dominated bilberry forest sites spanning from a recent clear-cut to mature managed (80 years) and old unmanaged (140 years) stands.

Here, we present the experimental setup of ForBioFunCtioN and soil and deadwood CH4 flux measurements from the snow-free period in 2021 and 2022. Initial results showed that N fertilization decreased net soil CH4 consumption and that, while at rare occasions functioning as a sink, the Norwegian spruce deadwood was almost exclusively a source of CH4. The source strength of deadwood differed substantially between sites but CH4 efflux from deadwood increased by biochar addition at all sites.

How to cite: Johannesson, C.-F., Larsen, K. S., Nordén, J., and Silvennoinen, H.: Forest soil and deadwood CH4 fluxes in response to warming, increased precipitation, nitrogen fertilization and biochar addition across a Norwegian spruce age-management gradient, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12510, https://doi.org/10.5194/egusphere-egu23-12510, 2023.

A.316
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EGU23-8790
|
ECS
|
Katharina Scholz, Albin Hammerle, and Georg Wohlfahrt

Forests play an important role in the exchange of greenhouse gases like CO2 and CH4 between the biosphere and the atmosphere. Although fluxes vary depending on biotic and abiotic factors like ecosystem composition and climatic conditions, forests generally are a sink for CO2. For CH4, forests with well-drained soils are considered a sink due to the oxidation of CH4 within those soils. However, recent study results indicate that CH4 emissions from trees may offset this soil CH4 sink, resulting in a lower sink strength or even source at the ecosystem level.

To quantify the net CH4 ecosystem exchange of a temperate needleleaf forest, we started CH4 flux measurements above a Scots Pine forest at the ‘FAIR’ research site in Austria in August 2022 using the eddy covariance method. The results show very small fluxes with nighttime fluxes close to zero while fluxes during the day are more variable. Overall, the site is a very small sink for CH4 at most. This site is temporally snow-covered during winter. As snowmelt increases soil moisture, we hypothesize that snowmelt in spring may further reduce the ecosystem CH4 sink strength. Here, besides presenting flux results, we will also discuss methodical challenges of measuring very small fluxes.

How to cite: Scholz, K., Hammerle, A., and Wohlfahrt, G.: Methane flux measurements above a Scots Pine forest in Austria, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8790, https://doi.org/10.5194/egusphere-egu23-8790, 2023.

A.317
|
EGU23-11731
|
ECS
Measuring methane emissions from tree shoots: challenges and advances
(withdrawn)
Salla Tenhovirta, Lukas Kohl, Markku Koskinen, Tatu Polvinen, Iikka Haikarainen, and Mari Pihlatie
A.318
|
EGU23-2693
Katerina Machacova, Kaido Soosaar, Reti Ranniku, and Hannes Warlo

Floodplain forests play an important role in the exchange of greenhouse gases - methane (CH4) and nitrous oxide (N2O) - with the atmosphere. However, due to climate change and anthropogenic activities related i.a. to the construction of retention basins, the water regime of these forests has often changed (groundwater table lowering, severe decrease in flood events). Resulting alternations of various environmental parameters can also affect the greenhouse gas exchange.

Soils are well-known as substantial sources and sinks of CH4 and N2O. However, besides soils, tree stems can also emit or take up these greenhouse gases under certain conditions. But due to limited knowledge of the role of trees in forest CH4 and especially N2O fluxes under varying conditions, the calculations of the forest ecosystems CH4 and N2O exchange have mostly been limited to trace gas exchange at the level of soil–atmosphere interface, thus excluding the exchange activity of trees. This approach can lead to a severe under- or overestimation of the CH4 and N2O ecosystem fluxes.

We aimed to investigate the contribution of trees to the CH4 and N2O exchange of floodplain forests in danger of gradual drying. We determined CH4 and N2O fluxes of stems of mature European hornbeam (Carpinus betulus), and adjacent soil in a temperate floodplain forest in Southern Moravia, Czech Republic, in May and June 2022, using non-steady-state chamber methods and spectroscopic gas analysis. The measurements were accompanied by a parallel determination of stem and soil CO2 exchange and numerous tree and environmental characteristics (internal heartwood concentrations of CH4, N2O and CO2; soil CH4, N2O, CO2,and O2 concentrations and water content in vertical soil profiles; soil and air temperature).

Our preliminary results identified hornbeam stems as net sinks of CH4 (−6.83 ± 0.53 µg CH4 m−2 stem area h−1, mean ± standard error) and very low net emitters of N2O (0.241 ± 0.337 µg N2O m−2 h−1). The adjacent soil was a strong sink of CH4 (−41.8 ± 2.96 µg CH4 m−2 soil area h−1) and a source of N2O (2.16 ± 0.95 µg N2O m−2 h−1). Even though the forest is classified as a floodplain forest, the soil volumetric water content was very low (0.281 ± 0.012 m3 m−3) and the soil O2 concentration was similar to the ambient concentration (19.1 ± 0.095%; both parameters at 10 cm soil depth).

The European hornbeam, a native and widely spread tree species in Central Europe, seems to contribute markedly to the CH4 uptake of the studied floodplain forest under low soil water content.

 

 Acknowledgement

This research was supported by the Ministry of Education, Youth and Sports of CR within the CzeCOS program (LM2018123) and project SustES - Adaptation strategies for sustainable ecosystem services and food security under adverse environmental conditions (CZ.02.1.01/0.0/0.0/16_019/0000797). We thank Marian Pavelka and Manuel Acosta for field station access.

How to cite: Machacova, K., Soosaar, K., Ranniku, R., and Warlo, H.: Stems of mature European hornbeam trees are low consumers of methane and low emitters of nitrous oxide, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2693, https://doi.org/10.5194/egusphere-egu23-2693, 2023.

A.319
|
EGU23-17518
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Laëtitia M. Bréchet, Roberto L. Salomόn, Warren Daniel, Clément Stahl, Benoît Burban, Jean-Yves Goret, Kathy Steppe, Joost van Haren, Scott Saleska, and Ivan A. Janssens

Methane (CH4) and nitrous oxide (N2O), critical climate-forcing trace gases, are rising sharply in the atmosphere. The estimate for their natural emissions remains uncertain because of mismatches between bottom-up (from flux measurements to process-based models) and top-down (from satellites to inversion models) approaches. Besides soils, trees can exchange CH4 and N2O with the atmosphere (either emitting or taking up), potentially acting as conduits for transporting large amounts of soil-produced CH4 and N2O. However, tree CH4 and N2O fluxes are not included yet in models, mainly because of a lack of detailed understanding of the sources and drivers of their temporal variation. This holds particularly true in tropical forests where high-frequency measurements are rare.

We first hypothesized that, although on well-aerated upland forest soils, trees contribute to ecosystem CH4 and N2O fluxes, with seasonal CH4 and N2O flux dynamics being reversed between the stems and soil. Second, we postulated that, at the daily scale, circadian rhythms of tree physiology affect stem CH4 and N2O fluxes. We investigated these hypotheses by examining the high-temporal-resolution fluxes of CH4 and N2O of three tropical trees. We measured fluxes from their stems (and adjacent soils) with an automated chamber system and tree and environmental variables (i.e. tree growth, sap flux density, tree water deficit, stem and soil temperature, stem and soil water content) over 20 months in a tropical forest, in French Guiana.

Long-term series of stem CH4 and N2O fluxes not only revealed that stems emitted CH4 and consumed N2O but also that flux variability was greater between tree individuals than seasons. We also found that stem CH4 and N2O fluxes were not linked to soil fluxes and exhibited diurnal patterns, with stems being greater emitters of CH4 and lower consumers of N2O in the early morning than at midday. CH4 and N2O peaks at sunrise suggest that gases accumulated in the stem at night when there was no gas flow and were vented out as soon as the pressurized flow started, following daily tree water dynamics. These preliminary results showed clear evidence of the need for continuous CH4 and N2O flux measurements in tropical forests to disentangle tree-mediated CH4 and N2O transport; more study is required to determine the relative importance of wood microbial organisms and tree traits for regulating gas transport through their aboveground parts.

How to cite: Bréchet, L. M., Salomόn, R. L., Daniel, W., Stahl, C., Burban, B., Goret, J.-Y., Steppe, K., van Haren, J., Saleska, S., and Janssens, I. A.: Insights into the daily emissions and consumptions of methane and nitrous oxide from tropical tree stem surfaces, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17518, https://doi.org/10.5194/egusphere-egu23-17518, 2023.