References of "Beekkerk van Ruth, Jöran"
     in
Bookmark and Share    
Full Text
See detailTemporal variability of nitrous oxide fluxes from a fertilized grassland in Belgium: preliminary results from dynamic closed chambers.
Beekkerk van Ruth, Jöran ULg; Moureaux, Christine ULg; Degré, Aurore ULg et al

Poster (2013, April 09)

Presentation of preliminary results from N2O measurements over a grassland using dynamic closed chambers. See attached folders for more detail.

Detailed reference viewed: 15 (4 ULg)
Full Text
See detailTEMPORAL VARIABILITY OF N2O FLUXES FROM A FERTILIZED GRASSLAND: PRELIMINARY RESULTS FROM DYNAMIC CLOSED CHAMBERS
Beekkerk van Ruth, Jöran ULg; Moureaux, Christine ULg; Degré, Aurore ULg et al

Poster (2013, April 09)

This work presents preliminary results of nitrous oxide (N2O) fluxes measured by dynamic closed chambers from a fertilized grassland grazed by the Belgian Blue breed of cattle. It is part of a project ... [more ▼]

This work presents preliminary results of nitrous oxide (N2O) fluxes measured by dynamic closed chambers from a fertilized grassland grazed by the Belgian Blue breed of cattle. It is part of a project funded by the public service of Wallonia (SPW-DGARNE), whose objectives are to make a carbon/CO2 balance of the grassland (Jérôme et al., 2013) and to quantify CH4 (Dumortier et al., 2013) and N2O fluxes. The site is located in Dorinne (Dorinne Terrestrial Observatory), Belgium (50° 18’ 44” N; 4° 58’ 07” E; 248 m al.). It is a permanent grassland of ca. 4.2 ha with a moderate slope of 1 to 2 %. Mineral fertilisation took place in March and May 2012. Two cylindrical chambers of 19,2 cm diameter and 11,5 cm height were placed inside a protected area around a micrometeorological station. An infrared gas analyser (Thermofischer 46i) was used in order to measure the N2O concentrations inside of the chambers, closed by automatically controlled lids and ventilated by a constant air flow of 1liter/min. These devices were completed by adjacent soil humidity and temperature sensors. The first measurement campaign took place during June and July 2012. The chambers were installed in the field and N2O fluxes were followed without manipulation. N2O fluxes were characterised by a background emission (between 2 and 10 ngN.m2s􀀀1) on which intense but time limited peaks (between 50 and 300 ngN.m2s􀀀1) superimposed. Peaks were found to be mainly linked to fertilisation and driven by precipitation. Background fluxes were found to correlate positively with soil temperature. Secondly, a manipulation experiment took place in November 2012: two different fertilizer treatments were applied to the chambers. Doses of respectively 100 and 200 kg N/ha of ammonium nitrate were sprayed in the chambers (equivalent to a 8mmprecipitation). N2O fluxes peaked shortly after fertiliser application (respectively 300 and 550 ngN.m2s􀀀1), as well as after a posterior rain event (respectively 800 and 1500 ngN.m2s􀀀1). The peak dynamics suggests a complex interaction between soil humidity and nitrogen availability, which is under study. Dumortier et al., Geophysical Research Abstracts, Vol. 15, EGU2013-2083-1, 2013 Jérôme et al., Geophysical Research Abstracts Vol. 15, EGU2013-6989, 2013 [less ▲]

Detailed reference viewed: 85 (9 ULg)
Full Text
See detailImpact of grazing on carbon balance of an intensively grazed grassland in Belgium
Jerome, Elisabeth ULg; Beckers, Yves ULg; Beekkerk van Ruth, Jöran ULg et al

Poster (2013, April 09)

This work analyzes the impact of grazing on the carbon balance of a grassland grazed by the Belgian Blue breed of cattle. The research was run at the Dorinne terrestrial observatory (DTO). The ... [more ▼]

This work analyzes the impact of grazing on the carbon balance of a grassland grazed by the Belgian Blue breed of cattle. The research was run at the Dorinne terrestrial observatory (DTO). The experimental site is a permanent grassland of ca. 4.2 ha located in the Belgian Condroz (50° 18’ 44’’ N; 4° 58’ 07’’ E; 248 m asl.). Other studies are conducted at the DTO including measurements of methane (CH4) and nitrous oxide fluxes (Dumortier et al., Geophysical Research Abstracts, Vol. 15, EGU2013-2083-1, 2013; Beekkerk van Ruth et al., Geophysical Research Abstracts, Vol. 15, EGU2013-3211, 2013, respectively). Grassland carbon budget (Net Biome Productivity, NBP) was calculated from Net Ecosystem Exchange (NEE) measured by eddy covariance by taking imports and exports of organic C and losses of carbon as CH4 into account (Soussana et al., 2010). After 2 years of measurements (May 2010 - May 2012), the grassland behaved on average as a CO2 source (NEE = 73 ±31 g C m-2 y-1). After inclusion of all the C inputs and outputs the site was closed to equilibrium (NBP = 23 ±34 g C m-2 y-1). To analyze the impact of grazing on CO2 fluxes, we studied the temporal evolution of gross maximal photosynthetic capacity GPPmax and dark respiration Rd (deduced from the response of daytime fluxes to radiation over 5-day windows). We calculated GPPmax and Rd variation between the end and the beginning of grazing or non-grazing periods (∆GPPmax and ∆Rd, respectively). We observed a significant decrease of GPPmax during grazing periods and measured a ∆GPPmax dependence on the average stocking rate. This allows us to quantify the assimilation reduction due to grass consumption by cattle. On the contrary, no Rd decrease was observed during grazing periods. Moreover, we found that cumulated monthly NEE increased significantly with the average stocking rate. In addition, a confinement experiment was carried out in order to analyze livestock contribution to Total Ecosystem Respiration. Each experiment extended over two days: the first day, cattle was confined in the footprint of the eddy covariance set-up (1.76 ha, 27 LU ha-1) and the second day, it was removed from it. We compared filtered half-hourly data made at 24h intervals, in the presence or absence of cattle, considering that environmental conditions were equivalent (air temperature, wind speed, radiation and wind direction). Results showed that CO2 fluxes were significantly higher when cattle were on the plot. Livestock contribution estimation to CO2 fluxes was on average 6.6 µmol m-2 s-1. [less ▲]

Detailed reference viewed: 70 (16 ULg)
Full Text
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 ▲]

Detailed reference viewed: 194 (26 ULg)
Full Text
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 ▲]

Detailed reference viewed: 113 (30 ULg)
Full Text
Peer Reviewed
See detailImpact of thresholding techniques on X-ray soil microtomogram analyses
Beckers, Eléonore ULg; Léonard, Angélique ULg; Beekkerk van Ruth, Jöran ULg et al

in Geophysical Research Abstracts (2011), 13

Using X-ray microtomography, 3D soil structure can be visualised and analysed through useful factors like pore size distribution, shape, connectivity, orientation, etc. X-ray scans yield grey-level 2D ... [more ▼]

Using X-ray microtomography, 3D soil structure can be visualised and analysed through useful factors like pore size distribution, shape, connectivity, orientation, etc. X-ray scans yield grey-level 2D images, which can be recombined to form 3D structures. Treatments of the grey-level images can consist of either a binarization -distinguishing soil and pores- or a permeability level attribution directly linked to the grey-level values. The latter leads to problems in order to assign a permeability for each point (in soil a same grey level value can be assigned to points with a different permeability), as well as to analyse the 3D structure. On the other hand, treatment of black and white 3D structures is well-handled. However, the impact of the choice of one thresholding technique on the resulting images has already been demonstrated. Moreover, thresholding methods are various and numerous. Many of them are based on the image histogram analysis. But because of the soil complexity, the relevance of these techniques becomes debatable, with a risk of producing non reliable images. We propose to palliate this with a simple new algorithm based on physical measurements: it uses a loop fixing the threshold value in order to match the measured porosity for each sample. In this communication, our point is to highlight the impact of different thresholding techniques on the analysis and interpretation of our soil microtomograms. The underlying questions could be: Does the thresholding method influence our conclusions? Are the results depending on the sample itself or on the methodology? In order to answer these questions we tested the Otsu technique and our physically based algorithm. Soils samples were removed from the upper layer (Ap horizon) of a silty soil (Gentinnes, Brabant Walloon, Belgium) in plots with different management practices. In fact, since 2004, the field has been cultivated in conventional tillage (CT) or reduced tillage (RT). In order to empty the meso- and macroporosity, samples were placed under a 1.5 MPa pressure (Richards apparatus). Samples were then scanned by X-ray microtomography using a Skyscan-1172 high-resolution desktop micro-CT system (Skyscan, Kontich, Belgium). The cone beam source operated at 100 kV, using an aluminium filter. The detector configuration, i.e. 1048x2000 pixels with a 16-bit X-ray camera, and the distance source-object-camera were adjusted to produce images with a pixel size of 17 µm. Porosity was measured for each scanned sample. Then the threshold methods -the Otsu technique on one hand and our developed algorithm on the other - were applied, and morphological factors were calculated for both methods. A comparison of the first results shows a threshold influence on average porosity and number of pores, but also on connectivity factors and size distribution. The apparent porosity of the images, as well as connectivity, is underestimated with the Otsu technique. Despite the fact that the changes induced by thresholding are more important for RT than CT, global conclusions about the comparison of these agricultural practices are approximately the same in this case. However, differences between tillage systems are less important with the Otsu method, confirming the impact of choosing the adapted threshold method. [less ▲]

Detailed reference viewed: 77 (29 ULg)