References of "Heinesch, Bernard"
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See detailN2O eddy covariance fluxes : from field measurements to flux analysis
Lognoul, Margaux ULg; Debacq, Alain ULg; Heinesch, Bernard ULg et al

Poster (2017, April 28)

N2O eddy covariance data were collected for a complete season of sugar beet crop (from first fertilization to harvest). Data treatment and preliminary results are presented.

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See detailImpact of tillage on greenhouse gas emissions by an agricultural crop and dynamics of N2O fluxes: Insights from automated closed chamber measurements
Lognoul, Margaux ULg; Theodorakopoulos, Nicolas ULg; Hiel, Marie-Pierre ULg et al

in Soil & Tillage Research (2017), 167

Our experiment aimed at studying the impact of long term tillage treatments – reduced tillage (RT) and conventional tillage (CT), on CO2 and N2O emissions by soil and at describing the dynamics of N2O ... [more ▼]

Our experiment aimed at studying the impact of long term tillage treatments – reduced tillage (RT) and conventional tillage (CT), on CO2 and N2O emissions by soil and at describing the dynamics of N2O fluxes. Gas measurements were performed from June to October 2015 in a Belgian maize crop, with homemade automated closed chambers, allowing continuous measurement at a high temporal resolution. After 7 years of treatment, CO2 and N2O average emissions were significantly larger in the RT parcel than in the CT parcel. This observation was attributed to the effect of tillage on the distribution of crop residues within the soil profile, leading to higher soil organic C and total N contents and a greater microbial biomass in the upper layer in RT. A single N2O emission peak triggered by a sudden increase of water- filled pore space (WFPS) was observed in the beginning of the measuring campaign. The absence of large emission afterwards was most likely due to a decreasing availability of N as crop grew. N2O background fluxes showed to be significantly correlated to CO2 fluxes but not to WFPS, while the influence of soil temperature remained unclear. Our results question the suitability of reduced tillage as a “climate-smart” practice and suggest that more experiments be conducted on conservation practices and their potent negative effect on environment. [less ▲]

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See detailMethane balance of an intensively grazed pasture and estimation of the enteric methane emissions from cattle
Dumortier, Pierre ULg; Aubinet, Marc ULg; Beckers, Yves ULg et al

in Agricultural and Forest Meteorology (2017), 232

The methane turbulent fluxes of an intensively grazed pasture were measured continuously from June 2012 to December 2013 at the Dorinne Terrestrial Observatory (DTO) in Belgium. During grazing periods ... [more ▼]

The methane turbulent fluxes of an intensively grazed pasture were measured continuously from June 2012 to December 2013 at the Dorinne Terrestrial Observatory (DTO) in Belgium. During grazing periods, the fluxes were dominated by enteric fermentation and were found to be strongly related to cow stocking density. In 2013, total emission from the pasture was found between 9 and 11 g CH4 m−2, 97% of which being emitted during grazing periods. Emission per LU (livestock unit) was estimated in a non-invasive way by integrating eddy covariance fluxes over large periods and by assuming a homogeneous average cattle disposition on the pasture. This estimate was compared to the one obtained during confinement periods, where cows were confined in a small part of the pasture. The emission per LU varied between 104 and 134 g CH4 LU−1 day−1 (13 and 17 g CH4 kg DMI−1), depending on the dataset and the computation method used. Diel course was characterized by two emission peaks, one in the morning and a larger one in the afternoon. For rest periods (no cattle on the pasture), small emissions were observed (median and mean values of 0.5 and 1.5 mg CH4 m−2 day−1, respectively). [less ▲]

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See detailMethanol emissions from maize: Ontogenetic dependence to varying light conditions and guttation as an additional factor constraining the flux
Mozaffar, Ahsan ULg; Schoon, N.; Digrado, Anthony ULg et al

in Atmospheric Environment (2017), 152

Because of its high abundance and long lifetime compared to other volatile organic compounds in the atmosphere, methanol (CH3OH) plays an important role in atmospheric chemistry. Even though agricultural ... [more ▼]

Because of its high abundance and long lifetime compared to other volatile organic compounds in the atmosphere, methanol (CH3OH) plays an important role in atmospheric chemistry. Even though agricultural crops are believed to be a large source of methanol, emission inventories from those crop ecosystems are still scarce and little information is available concerning the driving mechanisms for methanol production and emission at different developmental stages of the plants/leaves. This study focuses on methanol emissions from Zea mays L. (maize), which is vastly cultivated throughout the world. Flux measurements have been performed on young plants, almost fully grown leaves and fully grown leaves, enclosed in dynamic flow-through enclosures in a temperature and light-controlled environmental chamber. Strong differences in the response of methanol emissions to variations in PPFD (Photosynthetic Photon Flux Density) were noticed between the young plants, almost fully grown and fully grown leaves. Moreover, young maize plants showed strong emission peaks following light/dark transitions, for which guttation can be put forward as a hypothetical pathway. Young plants’ average daily methanol fluxes exceeded by a factor of 17 those of almost fully grown and fully grown leaves when expressed per leaf area. Absolute flux values were found to be smaller than those reported in the literature, but in fair agreement with recent ecosystem scale flux measurements above a maize field of the same variety as used in this study. [less ▲]

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See detailIncreased expression of bacterial amoA during an N2O emission peak in an agricultural field
Theodorakopoulos, Nicolas ULg; Lognoul, Margaux ULg; Degrune, Florine ULg et al

in Agriculture, Ecosystems & Environment (2017), 236

Levels of N-cycle gene transcripts (nirK, nirS, nosZ, amoA) were measured during an N2O emission peak in an agricultural soil. Automated dynamic closed chambers were used to monitor an N2O emission peak ... [more ▼]

Levels of N-cycle gene transcripts (nirK, nirS, nosZ, amoA) were measured during an N2O emission peak in an agricultural soil. Automated dynamic closed chambers were used to monitor an N2O emission peak on a maize crop after a natural rainfall. The peak occurred rapidly after the rainfall began. Spatial and temporal variability in N2O emission was observed between chambers. An analysis of N-cycle gene transcript levels revealed an increase in bacterial amoA gene transcripts (but not in archaeal amoA transcripts), correlating strongly with N2O emission. This suggests the involvement of nitrification enzymes, despite a high water-filled pore space (80%). Reverse transcription of bacterial 16S rRNA followed by partial sequencing of the resulting cDNAs revealed few rainfall-induced changes in the potentially active bacterial community, and notably no significant change in the relative abundance of 16S rRNAs from the nitrifier genus Nitrosospira. Expression of the amoA gene appears as a possible proxy for monitoring the N2O emission peak. To our knowledge, this is the first experiment to evaluate the expression of N-cycle genes during an N2O emission peak on an agricultural field. [less ▲]

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See detailSensitivity of the annual net ecosystem exchange to the cospectral model used for high frequency loss corrections at a grazed grassland site
Mamadou, Ossenatou; Gourlez de la Motte, Louis ULg; De Ligne, Anne ULg et al

in Agricultural and Forest Meteorology (2016), 228-229

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See detailCarbon balance of an intensively grazed grassland in southern Belgium
Gourlez de la Motte, Louis ULg; Jérôme, Elisabeth; Mamadou, Ossénatou et al

in Agricultural and Forest Meteorology (2016), 228-229

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See detailChamber-based continuous measurement of N2O fluxes in a winter wheat field: comparison of tillage treatments and identification of emission peak dynamic
Broux, François ULg; Theodorakopoulos, Nicolas; Heinesch, Bernard ULg et al

Scientific conference (2016, September 27)

Agriculture is the first anthropogenic source of N2O, notably through fertilized croplands. Though, few publications have studied through continuous measurement the N2O emissions in cultivated lands. We ... [more ▼]

Agriculture is the first anthropogenic source of N2O, notably through fertilized croplands. Though, few publications have studied through continuous measurement the N2O emissions in cultivated lands. We conducted this study to assess the effect of farming practices and climate on N2O emissions from a winter wheat crop. The experiment was held in an experimental field in the loamy region in Belgium from March 2016 till crop harvest in August 2016. The N2O fluxes are measured on two nearby parcels in a winter wheat field with restitution of the residues from previous crop. For the past 8 years, one parcel was subjected to a reduced tillage (RT, 10 cm depth) and the other one to a conventional tillage (CT, 25 cm depth). On each parcel, the N2O emissions were assessed with homemade automated closed chambers. Measurement continuity and good temporal resolution (one mean flux every 4 hours) of the system allowed a fine detection and quantification of the emission peaks which usually represent the major part of N2O fluxes. In addition to gas fluxes, soil water content at various depths and surface temperature were measured continuously. Soil samples were taken regularly to determine soil pH, soil organic carbon and nitrogen pools (total, NO3- and NH4+) and study microbial diversity and nitrification/denitrification gene expression. Measurements are still in progress. First results suggested that fluxes were about 3 times larger in the RT parcel than in the CT parcel. Several emissions peaks were observed during the measurement period. The peaks occurred after fertilization events and seemed to be triggered by an elevation of soil water content. A comparison of the emissions between RT and CT and a discussion on peak temporal dynamics, focusing on their intensity, duration and starting time will be presented. [less ▲]

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See detailClimatic and management drivers of CO2 exchanges by a production crop: Analysis over three successive 4-year crop rotation cycles
Buysse, Pauline ULg; Manise, Tanguy ULg; De Ligne, Anne ULg et al

Poster (2016, September 27)

Carbon dioxide (CO2) exchanges between crops and the atmosphere are influenced by both climatic and crop management drivers. The investigated crop, situated at the Lonzée Terrestrial Observatory (LTO ... [more ▼]

Carbon dioxide (CO2) exchanges between crops and the atmosphere are influenced by both climatic and crop management drivers. The investigated crop, situated at the Lonzée Terrestrial Observatory (LTO, candidate ICOS site) in Belgium and managed for more than 70 years using conventional farming practices, was monitored over three complete sugar beet/winter wheat/potato/winter wheat rotation cycles from 2004 to 2016. Continuous eddy-covariance measurements and regular biomass samplings were performed in order to obtain the daily and seasonal Net Ecosystem Exchange (NEE), Gross Primary Productivity (GPP), Total Ecosystem Respiration (TER), Net Primary Productivity (NPP), and Net Biome Production (NBP). Meteorological data and crop management practices were also recorded. Over the 12 years, NEE was negative (-4.34 kg C m-2) but NBP was positive (1.05 kg C m-2), i.e. as soon as carbon exportation by harvest and carbon importation (manure, slimes) are included in the budget, the site behaves as a carbon source. At the crop rotation scale (4 years) it was quite remarkable to observe that NBP was very similar over the three rotations (0.30-0.36 kg C m-2), despite climatic and management differences between years. Crop type impacted carbon exchanges, with sugar beet and winter wheat crops leading to higher net carbon sequestration than seed potato crops. For one given crop, larger growth length and cumulated global radiation drove larger cumulated NEE. Net carbon emissions were observed during intercrops, but growing mustard during these periods reduced their rates and provided carbon residues to the soil. NBP values suggest that one sixth of the total soil organic carbon stock at LTO (6.23 ± 0.16 kg C m-2 in [0, 60] cm) would be lost in 12 years. Large uncertainties (mostly due to biomass measurements) affect NBP estimates, but still, this figure is huge and should encourage cultural practices returning carbon to the soil. [less ▲]

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See detailRéduction des émissions de gaz à effet de serre en exploitation agricole : quelles mesures ?
Heinesch, Bernard ULg

Conference given outside the academic context (2016)

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See detailNos écosystèmes sont-ils des alliés pour lutter contre le changement climatique?
Heinesch, Bernard ULg

Conference given outside the academic context (2016)

Les écosystèmes terrestres jouent un rôle dans le changement climatique. Ils peuvent notamment échanger des gaz à effet de serre avec l’atmosphère. Ils peuvent par exemple émettre ou séquestrer du CO2, du ... [more ▼]

Les écosystèmes terrestres jouent un rôle dans le changement climatique. Ils peuvent notamment échanger des gaz à effet de serre avec l’atmosphère. Ils peuvent par exemple émettre ou séquestrer du CO2, du CH4 et du N2O en fonction du type d’écosystème, de la façon dont l’homme les exploite et des conditions climatiques. Dans cet exposé, des exemples concrets d’expériences menées sur des forêts, des cultures ou des prairies wallonnes seront utilisés pour illustrer les avancées scientifiques récentes dans le domaine et apporter des réponses à des questions du type: «Est-ce qu’une grande culture permet de stocker du carbone ? Et une prairie ? Que devient le bilan si la prairie est pâturée par du bétail ? Quelles pratiques d’exploitation pourraient améliorer le bilan ?» Des exemples de projets menés au sein des écoles secondaires et associant les élèves et des chercheurs seront aussi présentés. [less ▲]

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See detailDisentangling soil from plant methanol exchanges in a maize field: a first step
Bachy, Aurélie ULg; Mozaffar, Ahsan ULg; Aubinet, Marc ULg et al

Poster (2016, June)

This poster presents the current research done in order to disentangle soil from plant methanol exchanges in a maize field. Methanol exchanges were calculated at ecosystem-scale (therefore including both ... [more ▼]

This poster presents the current research done in order to disentangle soil from plant methanol exchanges in a maize field. Methanol exchanges were calculated at ecosystem-scale (therefore including both components). It bases on the following observation: methanol exchanges on bare soil (measured when maize was at germination stage) were as important as when plants were fast growing (and thereby, when the highest methanol plant methanol emissions were expected), and this under similar weather conditions. The goal of this poster is thus to understand why emissions were similar at these two periods. First, it addresses the question of the actual contribution of maize plants in methanol exchanges, by comparing up-scaled methanol exchanges measured on maize at leaf-scale (Mozaffar A.) to those measured at ecosystem-scale. Then, it investigates methanol exchanges mechanisms in order to evaluate how did soil methanol emissions evolve along the maize growing season. At the end of this poster, the hypothesis of decreasing soil methanol emissions along the maize growing season is proposed. [less ▲]

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See detailVingt ans de mesures des échanges de CO2 et de vapeur d'eau à l'Observatoire Terrestre de Vielsalm
Aubinet, Marc ULg; Vincke, Caroline; Heinesch, Bernard ULg et al

Article for general public (2016)

La séquestration du carbone via l'assimilation nette de CO2 par les écosystèmes terrestres varie fortement d'une année à l'autre. La compréhension plus fine de ce phénomène est nécessaire pour pouvoir ... [more ▼]

La séquestration du carbone via l'assimilation nette de CO2 par les écosystèmes terrestres varie fortement d'une année à l'autre. La compréhension plus fine de ce phénomène est nécessaire pour pouvoir prédire si les écosystèmes continueront à se comporter comme des puits de carbone ou si la séquestration va diminuer voire s'inverser complètement, transformant les écosystèmes en source de carbone. Pour mesurer les échanges nets de CO2, des chercheurs ont installé un "Observatoire Terrestre" dans une forêt à Vielsalm qui a permis de mettre en évidence les dynamiques journalière, saisonnière et interannuelle de la séquestration en carbone. La mesure simultanée de l'évapotranspiration réelle permet de plus d'évaluer la consommation en eau des espèces présentes. Les mesures effectuées durant 20 ans montrent que la forêt se comporte comme un puits de carbone. [less ▲]

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See detailAre BVOC exchanges in agricultural ecosystems overestimated? Insights from fluxes measured in a maize field over a whole growing season
Bachy, Aurélie ULg; Aubinet, Marc ULg; Schoon, Niels et al

in Atmospheric Chemistry and Physics (2016), 16(8),

Although maize is the second most important crop worldwide, and the most important C4 crop, no study on biogenic volatile organic compounds (BVOCs) has yet been conducted on this crop at ecosystem scale ... [more ▼]

Although maize is the second most important crop worldwide, and the most important C4 crop, no study on biogenic volatile organic compounds (BVOCs) has yet been conducted on this crop at ecosystem scale and over a whole growing season. This has led to large uncertainties in cropland BVOC emission estimations. This paper seeks to fill this gap by presenting, for the first time, BVOC fluxes measured in a maize field at ecosystem scale (using the disjunct eddy covariance by mass scanning technique) over a whole growing season in Belgium. The maize field emitted mainly methanol, although exchanges were bi-directional. The second most exchanged compound was acetic acid, which was taken up mainly in the growing season. Bi-directional exchanges of acetaldehyde, acetone and other oxygenated VOCs also occurred, whereas the terpenes, benzene and toluene exchanges were small, albeit significant. Surprisingly, BVOC exchanges were of the same order of magnitude on bare soil and on well developed vegetation, suggesting that soil is a major BVOC reservoir in agricultural ecosystems. Quantitatively, the maize BVOC emissions observed were lower than those reported in other maize, crops and grasses studies. The standard emission factors (SEFs) estimated in this study (231 ± 19 µg m−2 h−1 for methanol, 8 ± 5 µg m−2 h−1 for isoprene and 4 ± 6 µg m−2 h−1 for monoterpenes) were also much lower than those currently used by models for C4 crops, particularly for terpenes. These results suggest that maize fields are small BVOC exchangers in north-western Europe, with a lower BVOC emission impact than that modelled for growing C4 crops in this part of the world. They also reveal the high variability in BVOC exchanges across world regions for maize and suggest that SEFs should be estimated for each region separately. [less ▲]

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See detailImpact of tillage on CO2 and N2O efflux in an agricultural crop
Lognoul, Margaux ULg; Theodorakopoulos, Nicolas ULg; Hiel, Marie-Pierre ULg et al

Poster (2016, April 20)

CO2 and N2O fluxes exchanged by a maize crop were measured from June to Octboer 2015 using a homemade automated system of dynamic closed chambers. We studied the impact of tillage (reduced and ... [more ▼]

CO2 and N2O fluxes exchanged by a maize crop were measured from June to Octboer 2015 using a homemade automated system of dynamic closed chambers. We studied the impact of tillage (reduced and conventional) on greenhouse gas emissions and nitrous oxide flux dynamics. [less ▲]

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See detailAre BVOC exchanges in agricultural ecosystems overestimated? Insights from fluxes measured in a maize field over a whole growing season
Bachy, Aurélie ULg; Aubinet, Marc ULg; Schoon, Niels et al

Conference (2016, April 18)

This oral communication aims to present the main outputs of the BVOC (Biogenic Volatile Organic Compounds) flux measurement campaign performed on a maize field in Belgium. It begins by highligthing the ... [more ▼]

This oral communication aims to present the main outputs of the BVOC (Biogenic Volatile Organic Compounds) flux measurement campaign performed on a maize field in Belgium. It begins by highligthing the interest of investigating BVOC exchanges on maize; then measurement techniques are briefly presented. The second half of the communication aims to present and discuss the main outputs of this measurement campaign (similar BVOC composition, lower exchange rate than other maize and cropland/grassland studies, significant importance of soil in ecosystem exchanges, strong differences between exchanges rates observed in this study and those used by up-scaling models). [less ▲]

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