References of "Aubinet, Marc"
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See detailConstitutive versus heat and biotic stress induced BVOC emissions in Pseudotsuga menziesii
Joó, É.; Dewulf, J.; Amelynck, C. et al

in Atmospheric Environment (2011), 45(22), 3655-3662

Induced volatiles have been a focus of recent research, as not much is known of their emission behavior or atmospheric contribution. BVOC emissions were measured from Pseudotsuga menziesii saplings under ... [more ▼]

Induced volatiles have been a focus of recent research, as not much is known of their emission behavior or atmospheric contribution. BVOC emissions were measured from Pseudotsuga menziesii saplings under natural environmental conditions, using a dynamic branch enclosure system and GC-MS for their analysis. We determined temperature and light dependency of the individual compounds, studied seasonality of the emissions and discuss the effect of heat stress in comparison with two specific biotic stresses that occurred naturally on the trees. A standardized emission rate of 6.8 μg g (dw) -1 h -1 for monoterpenes under stressed conditions was almost a magnitude higher than that obtained for healthy trees (0.8 ± 0.2 μg g (dw) -1 h -1), with higher beta factors characterizing the stressed trees. The response of the emissions to light intensity was different for the individual compounds, suggesting a distinct minimum light intensity to reach saturation. Heat stress changed the relative contribution of specific volatiles, with larger extent of increase of sesquiterpenes, methyl salicylate and linalool emissions compared to monoterpenes. Biotic stress kept low the emissions of sesquiterpenes, (E)-4,8-dimethyl-1,3,7-nonatriene and methylbutenol isomers, and increased the level of methyl salicylate and monoterpenes. The ratio of β-pinene/α-pinene was also found to be significantly enhanced from 1.3 to 2.4 and 3.2 for non-stressed, heat stressed and combined biotic and heat stressed, respectively. [less ▲]

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See detailEffects of long term soil organic matter restitution mode on soil heterotrophic respiration and soil biological properties.
Buysse, Pauline ULg; Carnol, Monique ULg; Malchair, Sandrine ULg et al

Poster (2011, July)

Soil heterotrophic respiration (SHR) is the process by which CO2 is released during organic matter decomposition. It is generally expected that SHR can act as a positive feedback to global warming ... [more ▼]

Soil heterotrophic respiration (SHR) is the process by which CO2 is released during organic matter decomposition. It is generally expected that SHR can act as a positive feedback to global warming, therefore leading to more CO2 release into the atmosphere. It is thus important to better understand this process. Particularly, agricultural soils may behave as important CO2 sources that are strongly influenced by soil and crop management (e.g. organic matter restitution modes, hereafter “OM-RM”). The present study aimed at determining if, after more than 50 years of application of different OM-RM, (1) significant differences of SHR fluxes can be observed between treatments, (2) SHR responses to temperature and soil moisture content can be affected by the OM-RM and (3) the experimental design is suitable to assess potential differences between treatments. The experimental field is situated in Liroux, near Gembloux in Belgium. At that site, a long term experiment with different OM-RM runs from 1959 onwards. For the present study, three contrasted treatments were considered: (1) exportation of all residues after harvest, (2) addition of manure once every three to four years and (3) restitution of residues after harvest. SHR flux measurements were carried out manually on fourteen occasions from 2 April to 30 July 2010, using a dynamic closed chamber system. Temperature and soil moisture content at 5 cm depth were also measured manually. Results showed that after more than 50 years of OM-RM application, no significant differences could be observed between the three treatments in terms of SHR fluxes and SHR responses to temperature or soil moisture, while the soil organic carbon content did vary significantly between them. The sensitivity to temperature was quite low in all treatments, with a mean Q10 value of 1,36. Besides, SHR fluxes were seen to be more responsive to increases in soil water content than to absolute soil moisture content values. Indeed, when soil moisture content increased between two consecutive measurement dates, the ratio of the corresponding SHR fluxes was larger than 1. Particularly dry conditions in 2010 may actually have caused the fluxes to be very low, making the assessment of differences between treatments more difficult. Moreover, soil dryness is likely to be responsible for the SHR flux increases after rain events, as caused by re-solubilization of organic compounds. Also, an important spatial variability was observed, which may have obscured the assessment of potential differences between treatments. Further investigations will consist in performing a new flux measurement campaign in 2011 that will take the spatial variability issue into account, and in monitoring microbial and soil properties in the different treatments, such as microbial biomass, metabolic activity and labile carbon. [less ▲]

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See detailComparing monoterpenoid emissions and net photosynthesis of beech (Fagus sylvatica L.) in controlled and natural conditions
Šimpraga; Verbeeck, H.; Demarcke, M. et al

in Atmospheric Environment (2011), 45(17), 2922-2928

Although biogenic volatile organic compounds (BVOCs) only represent a very limited fraction of the plant's carbon (C) budget, they play an important role in atmospheric chemistry for example as a ... [more ▼]

Although biogenic volatile organic compounds (BVOCs) only represent a very limited fraction of the plant's carbon (C) budget, they play an important role in atmospheric chemistry for example as a precursor of tropospheric ozone. We performed a study comparing BVOC emissions of European beech (Fagus sylvatica L.) in controlled and natural environmental conditions. A young and adult beech tree was exposed to short-term temperature variations in growth room conditions and in an experimental forest, respectively. This study attempts to clarify how short-term temperature variations between days influenced the ratio between monoterpenoid (MT) emissions and net photosynthesis (Pn). Within a temperature range of 17-27 °C and 13-23 °C, the MT/Pn carbon ratio increased 10-30 fold for the growth room and forest, respectively. An exponential increasing trend between MT/Pn C ratio and air temperature was observed in both conditions. Beech trees re-emitted a low fraction of the assimilated C back into the atmosphere as MT: 0.01-0.12% and 0.01-0.30% with a temperature rise from 17 to 27 °C and 13-23 °C in growth room and forest conditions, respectively. However, the data showed that the MT/Pn C ratio of young and adult beech trees responded significantly to changes in temperature. [less ▲]

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See detailProduction de viande - réchauffement climatique
Beckers, Yves ULg; Jerome, Elisabeth ULg; Moureaux, Christine ULg et al

Article for general public (2011)

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See detailEffects of long term soil organic matter restitution mode on soil heterotrophic respiration and soil biological properties.
Buysse, Pauline ULg; Carnol, Monique ULg; Malchair, Sandrine ULg et al

Conference (2011, May 12)

For more than 50 years, an agricultural site divided in several plots is submitted to different organic matter restitution mode to the soil (crop residues, manure,...). The objectives of this study were ... [more ▼]

For more than 50 years, an agricultural site divided in several plots is submitted to different organic matter restitution mode to the soil (crop residues, manure,...). The objectives of this study were to determine (1) whether these different treatments may cause differences between treatments in terms of soil heterotrophic respiration, that would be of the same order of magnitude than differences in total soil organic carbon, (2) how temperature and soil moisture content affect soil heterotrophic respiration in the different treatments, and (3) how different soil biological properties (microbial biomass, metabolic diversity, labile carbon content) are affected in the different treatments. The results from a first measurement campaign carried out in 2010 are presented, together with the remaining questions at this stage of the study. [less ▲]

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See detailANALYSES DE PROPRIÉTÉS HYDROPHYSIQUES D’UN SOL AGRICOLE SOUMIS À DIFFÉRENTS TRAITEMENTS CULTURAUX DANS LE CADRE DU PROJET SOLRESIDUS
Beekkerk van Ruth, Jöran ULg; Beckers, Eléonore ULg; Aubinet, Marc ULg et al

Conference (2011, May 06)

Le projet SOLRESIDUS est une collaboration entre diverses unités au sein de GxABT. Il vise à analyser l’impact du mode de travail du sol (labour/non labour, restitution/exportation des pailles) sur divers ... [more ▼]

Le projet SOLRESIDUS est une collaboration entre diverses unités au sein de GxABT. Il vise à analyser l’impact du mode de travail du sol (labour/non labour, restitution/exportation des pailles) sur divers paramètres édaphiques/culturaux d’un champ de blé d’hiver (parcelles du Bordia). Le but du projet est de fournir une approche multidisciplinaire à l’analyse de systèmes agricoles. Afin de favoriser l’interaction entre les différentes unités, une base de données regroupant les différents résultats et méthodologies sera créée. Plus spécifiquement, les mesures touchant aux systèmes Eau-Sol (Unités d’Hydrologie et de Physique) incluent des courbes de rétention (pF), des évaluations d’infiltrabilité (tensio-infiltromètres, anneaux), des profils d’humidité (manuels et automatiques) et une caractérisation de la macro et microstructure porale (scan 3D par tomographie à rayons X). Ces mesures seront faites tout au long du projet (2 ans), afin d’établir une base solide à la compréhension du comportement hydrophysique d’un sol agricole limoneux. Ceci inclut un suivi des paramètres lors de l’évolution de la culture, mais également une comparaison entre les modalités. [less ▲]

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See detailCarbon exchange in a Belgian grassland with cattle
Jerome, Elisabeth ULg; Beckers, Yves ULg; Bodson, Bernard ULg et al

Poster (2011, April 08)

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See detailCarbon balance of crops: overview of 7 years of investigation
Moureaux, Christine ULg; Dufranne, Delphine ULg; Suleau, Marie ULg et al

in Geophysical Research Abstracts (2011, April 08), 13

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See detailManagement effects on net ecosystem carbon and GHG budgets at European crop sites
Ceschia, Eric; Béziat, Pierre; Dejoux, Jean-François et al

in Geophysical Research Abstracts (2011, April 08), 13

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See detailModeling soil heterotrophic respiration with an enzyme-based model: first comparison with field data and suggestions of improvements
Buysse, Pauline ULg; Longdoz, Bernard; Debacq, Alain ULg et al

in Geophysical Research Abstracts (2011, April 07), 13

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See detailIsoprene and monoterpene emissions from a mixed temperate forest
Laffineur, Quentin ULg; Heinesch, Bernard ULg; Amelynck, Crist et al

Poster (2011, April 07)

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See detailMeasurement and modeling of methanol deposition/emission in a mixed forest
Laffineur, Quentin ULg; Heinesch, Bernard ULg; Amelynck, Crist et al

in Geophysical Research Abstracts (2011, April 07), 13

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See detailMultilayer Analysis of Soil Respiration and its Isotopic Signature in Forest Ecosystem
Goffin, Stéphanie ULg; Longdoz, Bernard; Maier, Martin et al

in Geophysical Research Abstracts (2011, April 06), 13

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See detailANALYSING THE SOIL STRUCTURE UNDER DIFFERENT TILLAGE SYSTEMS USING X-RAY MICROTOMOGRAPHY AND PF CURVES
Beekkerk van Ruth, Jöran ULg; Degre, Aurore ULg; Aubinet, Marc ULg et al

Poster (2011, February 23)

Assessing soil structure is primordial when comparing tillage systems. Whilst most conventional techniques characterize global parameters, X-ray microtomography allows a characterization of the poral ... [more ▼]

Assessing soil structure is primordial when comparing tillage systems. Whilst most conventional techniques characterize global parameters, X-ray microtomography allows a characterization of the poral space at a µm-scale. These results, combined with data from pF curves, can form a solid basis in order to quantify soil physical fertility. Soil samples were taken from the organic topsoil on two Belgian experimental sites implementing both conventional tillage (CT, ploughing) and simplified tillage (ST, superficial works), without straw restitution: Gentinnes, Brabant Wallon (March 2010), and Gembloux, Namur (November 2010). On the Gentinnes site (Aba(b)1), CT and ST have been implemented since October 2005, with a beet/winter wheat rotation. On the Gembloux site (Aba(b)), CT and ST have been implemented since September 2008, with a winter wheat cultivation since end 2009. Tomography (10 samples for Gentinnes, 8 for Gembloux) and pF curves (10 samples for Gentinnes, 14 for Gembloux) were used for analysis. Pressure pans were used in order to obtain the pF curves on 100 cm³ undisturbed samples. Soil cores (3 cm diameter, 5 cm height) were scanned using a Skyscan-1172 µ-CT device. The conical beam, operating at 100 kV, produced images having a 17µm pixel size, using a 16-bit 1048×2000 pixels camera equipped with an aluminium filter. The raw images were then treated under Matlab® for binarization, using a thresholding loop to fit the measured and the calculated porosity of each sample (Beckers et al, 2011). The 2D binary images were then analyzed under Matlab® and Skyscan™ CT-analyzer. On the site of Gentinnes, pF analysis showed a greater available water content (between pF 4.2 and 2.5) for ST, and a greater efficient porosity (between saturation and pF 2.5) for CT. The differences in available water content, although not significant, were confirmed by site observation. Tomography analysis yielded the following: under ST, the pores are smaller and the anisotropy less developed. As for the poral connectivity, it was found greater in CT. On the site of Gembloux, however, no significant differences were found between the tillage systems concerning the pF curves. Tomography analysis showed smaller pores for simplified tillage, but the differences deduced by the tomographic analysis of the Gentinnes samples concerning connectivity and anisotropy were not found in this case. To conclude, from the results, the soil structure is found to differ between CT and ST. The pores tend to be smaller and less oriented in ST, whilst in CT pores are more connected. Soils undergoing a CT show a greater efficient porosity, whilst soils under ST display a greater available water content. However, these differences were mostly spotted on the Gentinnes site: in Gembloux, the differences between the samples were less marked. This could be due to the fact that the soil did not have time to differentiate yet (less than 3 years of tillage differentiation). More sampling is needed in any case before inferring general conclusions from these observations. A further analysis of the soil images, especially concerning pore orientation, will be done in order to fully exploit the tomography results. [less ▲]

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See detail11. Perspectives - Impact de la gestion culturale sur la respiration d'un sol agricole
Dufranne, Delphine ULg; Vancutsem, Françoise ULg; Aubinet, Marc ULg et al

in Livre Blanc: Céréales - Gembloux (2011, February 23)

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See detailFINAL REPORT PHASE II "Impact of Phenology and Environmental Conditions on BVOC Emissions from Forest Ecosystems" "IMPECVOC"
Dewulf, Jo; Joó, Eva; Van Langenhove, Herman et al

Report (2011)

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See detailEffect of seasonality and short-term light and temperature history on monoterpene emissions from European beech (Fagus sylvatica L.)
Demarcke, M.; Amelynck, Crist; Schoon, N. et al

in Hansel, Armin; Dunkl, Jürgen (Eds.) 5th International PTR-MS Conference on Proton Transfer Reaction Mass Spectrometry and its Applications (2011, January)

Branch enclosure measurements of monoterpene emision rates have been performed at different positions in the canopy of a European beech tree in natural environmental conditions. Strong and position ... [more ▼]

Branch enclosure measurements of monoterpene emision rates have been performed at different positions in the canopy of a European beech tree in natural environmental conditions. Strong and position-dependent standard emission rate variations were observed in the course of the growth season. By using the obtained dataset and a modified vesrion of the MEGAN algorithm, the response of the emissions to short-term light and temperature history was investigated [less ▲]

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See detailWhat can we learn from year-round BVOC disjunct eddycovariance measurements? A case example from a temperate forest
Laffineur, Quentin ULg; Heinesch, Bernard ULg; Schoon, N. et al

in Hansel, Armin; Dunkl, Jürgen (Eds.) 5th International PTR-MS Conference on Proton Transfer Reaction Mass Spectrometry and its Applications (2011, January)

Long term ecosystem-scale biogenic volatile organic compounds (BVOC) flux measurements by disjunct eddy-covariance are needed to determine and characterize the BVOC emissions/depositions from episodic ... [more ▼]

Long term ecosystem-scale biogenic volatile organic compounds (BVOC) flux measurements by disjunct eddy-covariance are needed to determine and characterize the BVOC emissions/depositions from episodic events (budburst, stress) as well as the continuous emission/deposition during vegetation growth and its seasonal evolution in interaction with climate and environment. If the data coverage is sufficient, this technique has the potential to provide a dataset covering the whole spectrum of meteorological and phenological conditions encountered by the studied ecosystem ending in a statistically more robust dataset than what can be provided by other BVOC measurement techniques. In addition, long term measurements allow in Oxygenated VOCs (OVOCs) depositions to be estimated in a realistic manner with is not the case with the enclosure technique. Here we present a year-round campaign of disjunct eddy-covariance BVOC fluxes above a mixed temperate forest performed in the frame of the IMPECVOC (Impact of Phenology and Environmental Conditions on BVOC Emissions from Forest Ecosystems) project. We will analyse the three main BVOC species (isoprene/monoterpenes and methanol) in order to illustrate the interest of long-term flux measurements by investigating the main driving variables and the underlying mechanisms of emission/deposition, how de novo carbon allocation to the isoprene/monoterpenes skeleton structure is altered through the time. For methanol, we will show the importance of deposition on a long-term basis and use an empirical model to discriminate the physical and physiological components of the exchange. [less ▲]

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