14 results on '"Flechard, Christophe R."'
Search Results
2. Validation of a Short-Range Dispersion and Deposition Model Using Field-Scale Ammonia and Methane Release Experiments
- Author
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Häni, Christoph, primary, Neftel, Albrecht, additional, Flechard, Christophe R., additional, Ammann, Christof, additional, Valach, Alex, additional, and Kupper, Thomas, additional
- Published
- 2024
- Full Text
- View/download PDF
3. Detection and Attribution of an Anomaly in Terrestrial Photosynthesis in Europe During the Covid-19 Lockdown
- Author
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Tang, Angela C. I., primary, Flechard, Christophe R., additional, Arriga, Nicola, additional, Papale, Dario, additional, Stoy, Paul. C., additional, Buchmann, Nina, additional, Cuntz, Matthias, additional, Douros, John, additional, Fares, Silvano, additional, Knohl, Alexander, additional, Šigut, Ladislav, additional, Simioni, Guillaume, additional, Timmermans, Renske, additional, Grünwald, Thomas, additional, Ibrom, Andreas, additional, Loubet, Benjamin, additional, Mammarella, Ivan, additional, Belelli Marchesini, Luca, additional, Nilsson, Mats B., additional, Peichl, Matthias, additional, Rebmann, Corinna, additional, Schmidt, Marius, additional, Bernhofer, Christian, additional, Berveiller, Daniel, additional, Cremonese, Edoardo, additional, El-Madany, Tarek S., additional, Gharun, Mana, additional, Gianelle, Damiano, additional, Hörtnagl, Lukas, additional, Roland, Marilyn, additional, Varlagin, Andrej, additional, Fu, Zheng, additional, Heinesch, Bernard, additional, Janssens, Ivan A., additional, Kowalska, Natalia, additional, Dušek, Jiří, additional, Gerosa, Giacomo, additional, Mölder, Meelis, additional, Tuittila, Eeva-Stiina, additional, and Loustau, Denis, additional
- Published
- 2023
- Full Text
- View/download PDF
4. Turbulent exchange of ammonia above vegetation
- Author
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Flechard, Christophe R.
- Subjects
628.53 ,Air pollution & emissions & acid rain - Published
- 1998
5. Modeling N2O emissions of complex cropland management in Western Europe using DayCent: Performance and scope for improvement
- Author
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dos Reis Martins, Marcio, primary, Necpalova, Magdalena, additional, Ammann, Christof, additional, Buchmann, Nina, additional, Calanca, Pierluigi, additional, Flechard, Christophe R., additional, Hartman, Melannie D., additional, Krauss, Maike, additional, Le Roy, Philippe, additional, Mäder, Paul, additional, Maier, Regine, additional, Morvan, Thierry, additional, Nicolardot, Bernard, additional, Skinner, Colin, additional, Six, Johan, additional, and Keel, Sonja G., additional
- Published
- 2022
- Full Text
- View/download PDF
6. Fluxes of total reactive atmospheric nitrogen (ΣNr) using eddy covariance above arable land
- Author
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Brümmer, Christian, Marx, Oliver, Kutsch, Werner, Ammann, Christof, Wolff, Veronika, Flechard, Christophe R., and Freibauer, Annette
- Subjects
agricultural land ,fertilization ,ecosystem N saturation ,eddy covariance ,Agricultural land ,Biosphere-atmosphere exchange ,Converter ,Ecosystem N saturation ,Eddy covariance ,Fertilization ,N budget ,TRANC ,Total reactive nitrogen (∑Nr) exchange ,lcsh:Meteorology. Climatology ,Atmospheric chemistry ,Biogeosciences ,Micrometeorology ,lcsh:QC851-999 ,converter ,total reactive nitrogen (ΣNr) exchange ,biosphere–atmosphere exchange - Abstract
The amount and timing of reactive nitrogen exchange between agricultural land and the atmosphere play a key role in evaluating ecosystem productivity and in addressing atmospheric nitrogen budgets and transport. With the recent development of the Total Reactive Atmospheric Nitrogen Converter (TRANC) apparatus, a methodology has been provided for continuous measurement of the sum of all airborne nitrogen containing species (ΣNr) allowing for diurnal and seasonal investigations. We present ΣNr concentration and net flux data from an 11-month field campaign conducted at an arable field using the TRANC system within an eddy-covariance setup. Clear diurnal patterns of both ΣNr concentrations and fluxes with significant dependencies on atmospheric stability and stomatal regulation were observed in the growing season. TRANC data were compared with monthly-averaged concentrations and dry deposition rates of selected Nr compounds using DELTA denuders and ensemble-averages of four inferential models, respectively. Similar seasonal trends were found for Nr concentrations from DELTA and TRANC measurements with values from the latter being considerably higher than those of DELTA denuders. The variability of the difference between these two systems could be explained by seasonally changing source locations of NOx contributions to the TRANC signal. As soil and vegetation Nr emissions to the atmosphere are generally not treated by inferential (dry deposition) models, TRANC data showed lower monthly deposition rates than those obtained from inferential modelling. Net ΣNr exchange was almost neutral (~0.072 kg N ha−1) at the end of the observation period. However, during most parts of the year, slight but permanent net ΣNr deposition was found. Our measurements demonstrate that fertilizer addition followed by substantial ΣNr emissions plays a crucial role in a site's annual atmospheric nitrogen budget. As long-term Nr measurements with high temporal resolution are usually cost and labour-intensive, field application of the TRANC helps improve the understanding of ecosystem functioning, atmospheric transport and revising definitions of ecosystem-specific critical loads at a relatively moderate operational cost level.Keywords: agricultural land; biosphere–atmosphere exchange; converter; ecosystem N saturation; eddy covariance; fertilization; N budget; TRANC; total reactive nitrogen (ΣNr) exchange(Published: 25 February 2013)Citation: Tellus B 2013, 65, 19770, http://dx.doi.org/10.3402/tellusb.v65i0.19770
- Published
- 2013
7. Surface–atmosphere exchange of ammonia over peatland using QCL-based eddy-covariance measurements and inferential modeling
- Author
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Zöll, Undine, primary, Brümmer, Christian, additional, Schrader, Frederik, additional, Ammann, Christof, additional, Ibrom, Andreas, additional, Flechard, Christophe R., additional, Nelson, David D., additional, Zahniser, Mark, additional, and Kutsch, Werner L., additional
- Published
- 2016
- Full Text
- View/download PDF
8. Surface-atmosphere exchange of ammonia over peatland using QCL-based eddy covariance measurements and inferential modeling
- Author
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Richter, Undine, primary, Brümmer, Christian, additional, Schrader, Frederik, additional, Ammann, Christof, additional, Ibrom, Andreas, additional, Flechard, Christophe R., additional, Nelson, David D., additional, Zahniser, Mark, additional, and Kutsch, Werner L., additional
- Published
- 2016
- Full Text
- View/download PDF
9. Surface-atmosphere exchange of ammonia over peatland using QCL-based eddy covariance measurements and inferential modeling.
- Author
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Richter, Undine, Brümmer, Christian, Schrader, Frederik, Ammann, Christof, Ibrom, Andreas, Flechard, Christophe R., Nelson, David D., Zahniser, Mark, and Kutsch, Werner L.
- Abstract
Recent advances in laser spectrometry offer new opportunities to investigate ecosystem-atmosphere exchange of environmentally relevant trace gases. In this study, we demonstrate the applicability of a quantum cascade laser (QCL) absorption spectrometer to continuously measure ammonia concentrations at a high time resolution and thus to quantify the net exchange between a semi-natural peatland ecosystem and the atmosphere based on the eddy-covariance approach. Changing diurnal patterns of both ammonia concentration and fluxes were found during different periods of the campaign. We observed a clear tipping point in early spring with decreasing deposition velocities and increasingly bi-directional fluxes that occurred after the switch from dormant vegetation to CO
2 uptake, but was triggered by a significant weather change. While several biophysical parameters such as temperature, radiation, and surface wetness were identified to partially regulate ammonia exchange at the site, the seasonal concentration pattern was clearly dominated by agricultural practices in the surrounding area. Comparing the results of a compensation point model with our measurement-based flux estimates showed considerable differences in some periods of the campaign due to overestimation of non-stomatal resistances caused by low acid ratios. The total cumulative campaign exchange of ammonia after nine weeks, however, differed only in a 6 % deviation with 911 and 857 g NH3-N ha-1 deposition being found by measurements and modeling, respectively. Extrapolating our findings to an entire year, ammonia deposition was lower than reported by Hurkuck et al. (2014) for the same site in previous years using denuder systems. This was likely due to a better representation of the emission component in the net signal of eddy-covariance fluxes as well as better adapted site-specific parameters in the model. Our study not only stresses the importance of high-quality measurements for studying and assessing land surface-atmosphere interactions, but also demonstrates the potential of QCL spectrometers for continuous observation of reactive nitrogen species as important additional instruments within long-term monitoring research infrastructures such as ICOS or NEON. [ABSTRACT FROM AUTHOR]- Published
- 2016
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10. Bi‐directional soil/atmosphere N 2 O exchange over two mown grassland systems with contrasting management practices
- Author
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FLECHARD, CHRISTOPHE R., primary, NEFTEL, ALBRECHT, additional, JOCHER, MARKUS, additional, AMMANN, CHRISTOF, additional, and FUHRER, JÜRG, additional
- Published
- 2005
- Full Text
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11. Fluxes of total reactive atmospheric nitrogen (∑Nr) using eddy covariance above arable land.
- Author
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Brümmer, CHRISTIAN, Marx, OLIVER, Kutsch, WERNER, Ammann, CHRISTOF, Wolff, VERONIKA, Flechard, CHRISTOPHE R., and Freibauer, ANNETTE
- Subjects
ATMOSPHERIC nitrogen ,ATMOSPHERIC transport ,ANALYSIS of covariance ,ARABLE land ,PLANT fertilization ,ATMOSPHERIC deposition - Abstract
The amount and timing of reactive nitrogen exchange between agricultural land and the atmosphere play a key role in evaluating ecosystem productivity and in addressing atmospheric nitrogen budgets and transport. With the recent development of the Total Reactive Atmospheric Nitrogen Converter (TRANC) apparatus, a methodology has been provided for continuous measurement of the sum of all airborne nitrogen containing species (∑N
r ) allowing for diurnal and seasonal investigations. We present ∑Nr concentration and net flux data from an 11-month field campaign conducted at an arable field using the TRANC system within an eddy-covariance setup. Clear diurnal patterns of both ∑Nr concentrations and fluxes with significant dependencies on atmospheric stability and stomatal regulation were observed in the growing season. TRANC data were compared with monthly-averaged concentrations and dry deposition rates of selected Nr compounds using DELTA denuders and ensemble-averages of four inferential models, respectively. Similar seasonal trends were found for Nr concentrations from DELTA and TRANC measurements with values from the latter being considerably higher than those of DELTA denuders. The variability of the difference between these two systems could be explained by seasonally changing source locations of NOx contributions to the TRANC signal. As soil and vegetation Nr emissions to the atmosphere are generally not treated by inferential (dry deposition) models, TRANC data showed lower monthly deposition rates than those obtained from inferential modelling. Net ∑Nr exchange was almost neutral (~0.072 kg N ha-1 ) at the end of the observation period. However, during most parts of the year, slight but permanent net ∑Nr deposition was found. Our measurements demonstrate that fertilizer addition followed by substantial ∑Nr emissions plays a crucial role in a site's annual atmospheric nitrogen budget. As long-term Nr measurements with high temporal resolution are usually cost and labour-intensive, field application of the TRANC helps improve the understanding of ecosystem functioning, atmospheric transport and revising definitions of ecosystem-specific critical loads at a relatively moderate operational cost level. [ABSTRACT FROM AUTHOR]- Published
- 2013
- Full Text
- View/download PDF
12. Modeling Carbon and Water Fluxes of Managed Grasslands: Comparing Flux Variability and Net Carbon Budgets between Grazed and Mowed Systems.
- Author
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Puche, Nicolas, Senapati, Nimai, Flechard, Christophe R., Klumpp, Katia, Kirschbaum, Miko U.F., and Chabbi, Abad
- Subjects
ROTATIONAL grazing ,GRASSLANDS ,DAIRY cattle ,RESPIRATION ,FLUX (Energy) ,NITROGEN cycle ,CARBON cycle - Abstract
The CenW ecosystem model simulates carbon, water, and nitrogen cycles following ecophysiological processes and management practices on a daily basis. We tested and evaluated the model using five years eddy covariance measurements from two adjacent but differently managed grasslands in France. The data were used to independently parameterize CenW for the two grassland sites. Very good agreements, i.e., high model efficiencies and correlations, between observed and modeled fluxes were achieved. We showed that the CenW model captured day-to-day, seasonal, and interannual variability observed in measured CO
2 and water fluxes. We also showed that following typical management practices (i.e., mowing and grazing), carbon gain was severely curtailed through a sharp and severe reduction in photosynthesizing biomass. We also identified large model/data discrepancies for carbon fluxes during grazing events caused by the noncapture by the eddy covariance system of large respiratory losses of C from dairy cows when they were present in the paddocks. The missing component of grazing animal respiration in the net carbon budget of the grazed grassland can be quantitatively important and can turn sites from being C sinks to being neutral or C sources. It means that extra care is needed in the processing of eddy covariance data from grazed pastures to correctly calculate their annual CO2 balances and carbon budgets. [ABSTRACT FROM AUTHOR]- Published
- 2019
- Full Text
- View/download PDF
13. Are ammonia emissions from field-applied slurry substantially over-estimated in European emission inventories?
- Author
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Sintermann, Jörg, Neftel, Albrecht, Ammann, Christoph, Häni, Christoph, Hensen, Arjan, Loubet, Benjamin, and Flechard, Christophe R.
- Subjects
13. Climate action - Abstract
The EMEP/EEA guidebook 2009 for agricultural emission inventories reports an average ammonia (NH3) emission factor (EF) by volatilisation of 55% of the applied total ammoniacal nitrogen (TAN) content for cattle slurry, and 35% losses for pig slurry, irrespective of the type of surface or slurry characteristics such as dry matter content and pH. In this review article, we compiled over 350 measurements of EFs published between 1991 and 2011. The standard slurry application technique during the early years of this period, when a large number of measurements were made, was spreading by splash plate, and as a result reference EFs given in many European inventories are predominantly based on this technique. However, slurry application practices have evolved since then, while there has also been a shift in measurement techniques and investigated plot sizes. We therefore classified the available measurements according to the flux measurement technique or measurement plot size and year of measurement. Medium size plots (usually circles between 20 to 50 m radius) generally yielded the highest EFs. The most commonly used measurement setups at this scale were based on the Integrated Horizontal Flux method (IHF or the ZINST method (a simplified IHF method)). Several empirical models were published in the years 1993 to 2003 predicting NH3 EFs as a function of meteorology and slurry characteristics (Menzi et al., 1998; Søgaard et al., 2002). More recent measurements show substantially lower EFs which calls for new measurement series in order to validate the various measurement approaches against each other and to derive revised inputs for inclusion into emission inventories., Biogeosciences, 9 (5), ISSN:1726-4170
14. Fluxes of total reactive atmospheric nitrogen (Sigma N-r) using eddy covariance above arable land
- Author
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Brümmer, Christian, Marx, Oliver, Kutsch, Werner L., Ammann, Christof, Wolff, Veronika, Flechard, Christophe R., and Freibauer, Annette
- Subjects
2. Zero hunger ,Zotal reactive nitrogen (Sigma N-r) exchange ,13. Climate action ,Agricultural land ,Fertilization ,biosphere-atmosphere exchange ,Converter ,Eddy covariance ,15. Life on land ,TRANC ,Ecosystem N saturation ,N budget - Abstract
The amount and timing of reactive nitrogen exchange between agricultural land and the atmosphere play a key role in evaluating ecosystem productivity and in addressing atmospheric nitrogen budgets and transport. With the recent development of the Total Reactive Atmospheric Nitrogen Converter (TRANC) apparatus, a methodology has been provided for continuous measurement of the sum of all airborne nitrogen containing species (ΣNr) allowing for diurnal and seasonal investigations. We present ΣNr concentration and net flux data from an 11-month field campaign conducted at an arable field using the TRANC system within an eddy-covariance setup. Clear diurnal patterns of both ΣNr concentrations and fluxes with significant dependencies on atmospheric stability and stomatal regulation were observed in the growing season. TRANC data were compared with monthly-averaged concentrations and dry deposition rates of selected Nr compounds using DELTA denuders and ensemble-averages of four inferential models, respectively. Similar seasonal trends were found for Nr concentrations from DELTA and TRANC measurements with values from the latter being considerably higher than those of DELTA denuders. The variability of the difference between these two systems could be explained by seasonally changing source locations of NOx contributions to the TRANC signal. As soil and vegetation Nr emissions to the atmosphere are generally not treated by inferential (dry deposition) models, TRANC data showed lower monthly deposition rates than those obtained from inferential modelling. Net ΣNr exchange was almost neutral (~0.072 kg N ha−1) at the end of the observation period. However, during most parts of the year, slight but permanent net ΣNr deposition was found. Our measurements demonstrate that fertilizer addition followed by substantial ΣNr emissions plays a crucial role in a site's annual atmospheric nitrogen budget. As long-term Nr measurements with high temporal resolution are usually cost and labour-intensive, field application of the TRANC helps improve the understanding of ecosystem functioning, atmospheric transport and revising definitions of ecosystem-specific critical loads at a relatively moderate operational cost level., Tellus B: Chemical and Physical Meteorology, 65 (1), ISSN:0280-6509, ISSN:1600-0889
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