References of "Tychon, Bernard"
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See detailCan hyperspectral techniques improve estimates of carbon stocks in agricultural soils ?
Stevens, A.; van Wesemael, B.; Touré, Souleymane et al

in Proceedings of the Airborne imaging spectroscopy workshop : Belspo, Bruges 8 octobre 2004 (2004, October 08)

Soil organic carbon (SOC) represents one of the major pools in the global carbon cycle. However, fluxes of CO2 from soils into the atmosphere by respiration or inversely sequestration of CO2 through ... [more ▼]

Soil organic carbon (SOC) represents one of the major pools in the global carbon cycle. However, fluxes of CO2 from soils into the atmosphere by respiration or inversely sequestration of CO2 through photosynthesis and subsequent immobilisation in the form of humus are difficult to quantify. In principle changes in SOC stock over time reflect CO2 fluxes. The detection of these stock changes, however, require intensive sampling mainly due to the large spatial variability of SOC both within individual fields and larger units with similar soils and land use. The aim of this paper is to evaluate the potential of airborne-hyperspectral techniques using a CASI sensor and hand held Near Infrared Spectroscopy (NIRS) with an ASD spectrometer to conduct SOC inventories of individual parcels. During a field campaign in the Belgian Ardennes during Octobre 2003, more than 120 sites on a regular grid within 13 freshly ploughed fields were selected. At these sites, field spectra of the bare soil have been measured and samples from the topsoil were taken. SOC content (Walkley and Black), soil moisture and bulk density of these samples have been determined. As a first step, the soil reflectance has been transformed (log (1/R), Savitsky-Golay smoothing and derivative, gap derivative, moving average) in order to filter the spectral responses and to eliminate noise. Then, we used both stepwise and partial least square (PLS) regression analysis to relate these spectra to measured SOC contents. Regression models performed much better when the data were divided in two sub-groups representing different moisture conditions of the soil surface. These statistical model calibrations were validated on an independent data set. Standard Error of Prediction (SEP) ranged from 0.19 to 0.24 % carbon for the field spectra determined using the ASD depending on soil moisture of the surface layer. This is a little bit more than the reproducibility error inherent to the Walkley and Black analysis. Airborne CASI techniques performed less well mainly due to the narrow spectral range. Tests on airborne CASI+SASI hyperspectral data from a previous field campaign [1] showed better results. Overall, low bias allowed the use of spectral techniques to estimate population means with a high confidence level. The spectral techniques have a strong potential in determining changes in carbon tock change studies. The large within field variability of SOC content precludes the assessment, using conventional soil sampling, of SOC changes as a result of management (1 t C ha-1 yr-1) over a reasonable time period (5 years). Depending on the variance of the SOC content measured in the field ( 2 = 11-166 t C ha-1), we need 16-210 samples to detect a change. Since this number of samples is rarely available for individual fields, conventional sampling methods can only be used for larger spatial units containing many fields. In contrast, the airborne-hyperspectral technique and portable NIRS are able to supply these large amounts of data, and can thus improve the accuracy of SOC stock assessments of individual fields. This in turn will result in a smaller detection limit of SOC stock changes. [less ▲]

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See detailAirborne hyperspectral measurements and superficial soil organic matter
Touré, Souleymane; Tychon, Bernard ULg

in Proceedings of the Airborne Imaging Spectroscopy Workshop (2004, October 08)

Data acquired from field campaign and hyperspectral airborne sensors were processed to determine the surface soil organic matter of an agricultural area located in Southern Belgium. The method adopted was ... [more ▼]

Data acquired from field campaign and hyperspectral airborne sensors were processed to determine the surface soil organic matter of an agricultural area located in Southern Belgium. The method adopted was based on a forward stepwise multiple linear regression analysis linking soil organic matter and hyperspectral data from the CASI-2 (Compact Spectrographic Imager-2) airborne sensor working in the visible and near infrared domain. The results were validated successfully from an independent set of sampling points. However, disturbing factors effects are shown on the relationship between soil organic matter and spectral reflectance. It is concluded that the hyperspectral remote sensing approach is promising for soil organic matter prediction but it will require more study to better take account on the disturbing factors affecting the relationship. [less ▲]

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See detailBulletin agrométéorologique - Août 2004
Tychon, Bernard ULg; Ozer, Pierre ULg; Horion, S. et al

in Bulletin Agrométéorologique (2004), 3(5), 1-4

Le mois d’août a été caractérisé par des précipitations, des vitesses de vent et une humidité anormalement élevées. Les valeurs de rayonnement étaient par contre anormalement faibles. Les rendements ... [more ▼]

Le mois d’août a été caractérisé par des précipitations, des vitesses de vent et une humidité anormalement élevées. Les valeurs de rayonnement étaient par contre anormalement faibles. Les rendements prévus pour le maïs fourrager sont légèrement inférieurs à ceux observés au cours des cinq années antérieures. Par contre, concernant la betterave sucrière et la pomme de terre mi-hâtive, la tendance est inverse avec des estimations globalement supérieures à la moyenne des cinq dernières années. [less ▲]

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See detailBulletin agrométéorologique - Juillet 2004
Tychon, Bernard ULg; Ozer, Pierre ULg; Horion, S. et al

in Bulletin Agrométéorologique (2004), 3(4), 1-4

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See detailBulletin agrométéorologique - Juin 2004
Tychon, Bernard ULg; Ozer, Pierre ULg; Horion, S. et al

in Bulletin Agrométéorologique (2004), 3(3), 1-5

Les paramètres climatiques du mois de juin furent tous proches de la moyenne, exception faite de l'ensoleillement qui fut largement déficitaire sur l’est du pays. La situation des céréales d’hiver et de ... [more ▼]

Les paramètres climatiques du mois de juin furent tous proches de la moyenne, exception faite de l'ensoleillement qui fut largement déficitaire sur l’est du pays. La situation des céréales d’hiver et de la pomme de terre est globalement favorable laissant entrevoir des rendements généralement supérieurs à ceux de 2003. Par contre, les prévisions relatives au maïs fourrager et à la betterave sucrière montrent que ces cultures pourraient connaître, au niveau national, une légère baisse par rapport à l’année passée. [less ▲]

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See detailBulletin agrométéorologique - Mai 2004
Tychon, Bernard ULg; Ozer, Pierre ULg; Horion, S. et al

in Bulletin Agrométéorologique (2004), 3(2), 1-5

Les températures et l'ensoleillement du mois de mai furent légèrement inférieurs à la moyenne. En revanche, les précipitations déficitaires furent généralisées et les périodes sans pluie ont atteint près ... [more ▼]

Les températures et l'ensoleillement du mois de mai furent légèrement inférieurs à la moyenne. En revanche, les précipitations déficitaires furent généralisées et les périodes sans pluie ont atteint près de trois semaines en certaines régions. La situation des cultures est globalement favorable laissant entrevoir des rendements généralement semblables, voire supérieurs à ceux de 2003. [less ▲]

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See detailBulletin agrométéorologique - Avril 2004
Tychon, Bernard ULg; Ozer, Pierre ULg; Horion, S. et al

in Bulletin Agrométéorologique (2004), 3(1), 1-4

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See detailUse of remote sensing imagery for geotraceability in agriculture
Buffet, Dominique; Oger, Robert ULg; Tychon, Bernard ULg

Conference (2004, May 06)

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See detailAnalyse de la campagne agricole 2003 en terme de stress hydrique
De Longueville, Florence ULg; Horion, Stéphanie ULg; Tychon, Bernard ULg et al

in Bulletin de la Société Géographique de Liège (2004), 44

This article presents the evaluation of the crop water stress in 2003 using the Belgian Crop Growth Monitoring System (B-CGMS). The indicator used is the Relative Soil Moisture Index (RSMI), and is based ... [more ▼]

This article presents the evaluation of the crop water stress in 2003 using the Belgian Crop Growth Monitoring System (B-CGMS). The indicator used is the Relative Soil Moisture Index (RSMI), and is based on a calculation integrating soil moisture data. This index shows the differences between needed and effectively available soil water for different crop types. It is one of the outputs of the B-CGMS agrometeorological model. Based on a fixed threshold, days affected by water stress have been identified and computed for specific periods during which lack of soil water is likely to have dramatic impacts on crop production. The cumulative number of days affected by water stress indicator has then been integrated into a GIS to spatially represent the situation of winter wheat and maize during the 2003 crop season. Results suggest that only maize was affected by the water stress in northern and southern Belgium. In the latter area, the lack of water at key periods provoked a yield reduction ranging between 2 and 50%. [less ▲]

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See detailL’enseignement en gestion des risques naturels.
Ozer, Pierre ULg; Tychon, Bernard ULg; Ozer, André ULg et al

in Demarée, Gaston; De Dapper, Morgan; Alexandre, Jean (Eds.) Tropical Climatology, Meteorology and Hydrology: Climate-related risk analysis and sustainable development in tropical areas. (2004)

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See detailMonitoring drought stress in north-eastern China by means of rainfall data and diachrone indices derived from Pathfinder AVHRR-imagery.
Ozer, Pierre ULg; Tychon, Bernard ULg; Eerens, Herman

in Smits, Paul; Bruzzone, Lorenzo (Eds.) Analysis of Multi-Temporal Remote Sensing Images (2004)

For climatic stress detection and monitoring in the Heilongjiang Province, north-eastem China, an indicator on the interannual vegetation state was extracted from the AVHRR Pathfinder image set (1981-2000 ... [more ▼]

For climatic stress detection and monitoring in the Heilongjiang Province, north-eastem China, an indicator on the interannual vegetation state was extracted from the AVHRR Pathfinder image set (1981-2000) and compared to the rainfall variations over the growing season (June to August). The results show that the vegetation status does not closely depend on rainfall variations in this region. Temperatures, which showed a rapid augmentation in the northern high latitudes since the early 1980s, seem to be a more crucial limiting factor for vegetation growth. Rapid land cover change and large natural disasters are also likely to impact the relationship between rainfall and vegetation. [less ▲]

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See detailEstimation of surface soil organic matter by means of hyperspectral data analysis.
Touré, Souleymane; Tychon, Bernard ULg

Conference (2003, November 19)

Data acquired from field campaign and hyperspectral airborne sensors were processed to determine the surface soil organic matter of an agricultural area located in Southern Belgium. The method adopted was ... [more ▼]

Data acquired from field campaign and hyperspectral airborne sensors were processed to determine the surface soil organic matter of an agricultural area located in Southern Belgium. The method adopted was based on a forward stepwise multiple regression analysis linking soil organic matter and hyperspectral data from two airborne sensors working in the visible and infrared domain. The results were validated successfully from an independent set of sampling points. It is concluded that the hyperspectral remote sensing approach is promising for soil organic matter prediction. Furthermore, this approach could even be improved if disturbance factors are removed. [less ▲]

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See detailBulletin agrométéorologique - Septembre 2003
Tychon, Bernard ULg; Ozer, Pierre ULg; Eerens, H. et al

in Bulletin Agrométéorologique (2003)

Le mois de septembre a été caractérisé par des précipitations et des vitesses moyennes du vent faibles. Par contre, les températures et le rayonnement furent relativement élevés sur l’ensemble du pays ... [more ▼]

Le mois de septembre a été caractérisé par des précipitations et des vitesses moyennes du vent faibles. Par contre, les températures et le rayonnement furent relativement élevés sur l’ensemble du pays. Cette année, les rendements prévus pour les cultures de maï s fourrager et de betterave sucrière, sont respectivement équivalents et inférieurs à ceux observés en 2002. [less ▲]

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See detailBulletin agrométéorologique - Août 2003
Tychon, Bernard ULg; De Longueville, Florence ULg; Ozer, Pierre ULg et al

in Bulletin Agrométéorologique (2003)

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See detailEstimation of surface soil organic matter by means of hyperspectral data analysis.
Touré, Souleymane; Tychon, Bernard ULg

Conference (2003, September 04)

This presentation shows results from two different hyperspectral instruments for the assessment of soil organic content of agricultural soils in southern Belgium.

Detailed reference viewed: 5 (1 ULg)