References of "Tychon, Bernard"
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See detailModeling heat stress under different environmental conditions
Carabano, Maria-Jesus; Logar, Betka; Bormann, Jeanne et al

in Journal of Dairy Science (2016)

Renewed interest in heat stress effects on livestock productivity derives from climate change, which is expected to increase temperatures and the frequency of extreme weather events. This study aimed at ... [more ▼]

Renewed interest in heat stress effects on livestock productivity derives from climate change, which is expected to increase temperatures and the frequency of extreme weather events. This study aimed at evaluating the effect of temperature and humidity on milk production in highly selected dairy cattle populations across three European regions differing in climate and production systems to detect differences and similarities that can be used to optimize heat stress (HS) effect modeling. Milk, fat and protein test day data from official milk recording for years 1999 to 2010 in four Holstein populations located in the Walloon Region of Belgium (BEL), Luxembourg (LUX), Slovenia (SLO) and Southern Spain (SPA) were merged with temperature and humidity data provided by the state meteorological agencies. After merging, the number of test day records/cows per trait ranged from 686,726/49,655 in SLO to 1,982,047/136,746 in BEL. Values for the daily average and maximum temperature and humidity index (THIavg and THImax) ranges for THIavg/THImax were largest in SLO (22-74/28-84) in SLO and shortest in SPA (39-76/46-83). Change point techniques were used to determine comfort thresholds, which differed across traits and climatic regions. Milk yield showed an inverted U shaped pattern of response across the THI scale with a HS threshold around 73 THImax units. For fat and protein, thresholds were lower than for milk yield and were shifted around 6 THI units towards larger values in SPA compared with the other countries. Fat showed lower HS thresholds than protein traits in all countries. The traditional broken line model was compared to quadratic and cubic fits of the pattern of response in production to increasing heat loads. A cubic polynomial model allowing for individual variation in patterns of response and THIavg as heat load measure showed the best statistical features. Higher/lower producing animals showed less/more persistent production (quantity and quality) across the THI scale. The estimated correlations between comfort and THIavg values of 70 (which represents the upper end of the THIavg scale in BEL-LUX) were lower for BEL-LUX (0.70 - 0.80) than for SPA (0.83 - 0.85). Overall, animals producing in the more temperate climates and semi-extensive grazing systems of BEL and LUX showed HS at lower heat loads and more re-ranking across the THI scale than animals producing in the warmer climate and intensive indoor system of SPA. [less ▲]

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See detailA KNOWLEDGE-BASED APPROACH FOR MAPPING LAND DEGRADATION IN THE ARID RANGELANDS OF NORTH AFRICA
Mahyou, Hamid; Tychon, Bernard ULg; Balaghi, Riad et al

in Land Degradation & Development (2015)

Rangelands cover about 82% of the arid area of Morocco. It is generally acknowledged that these areas are threatened by desertification. Monitoring desertification requires accurate knowledge about the ... [more ▼]

Rangelands cover about 82% of the arid area of Morocco. It is generally acknowledged that these areas are threatened by desertification. Monitoring desertification requires accurate knowledge about the current status of rangeland degradation. Remote sensing is widely used to assess changes in land cover, but its use in arid rangelands has limitations because of spectral confusion among various types of land cover. The objective of this study was to assess the severity and spatial extent of rangeland degradation in the high plateaus of eastern Morocco, using a knowledge-based approach combining remote sensing and ancillary data. This approach relies on analyzing datasets derived from Landsat TM satellite imagery, lithology, bioclimatic data and field measurements. The level of rangeland degradation was assessed using indicators such as vegetation parameters, grazing levels and cultivation intensity, which provided a high level of accuracy for mapping and monitoring the degradation of the arid rangelands. The results showed that the total area of degraded rangeland in the high plateaus of eastern Morocco is about 17,417 km², accounting for 48% in the studied area. [less ▲]

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See detailThe potential of OpenStreetMap for land use/land cover mapping
Minet, Julien ULg; Robert, Brieuc; Tychon, Bernard ULg

Conference (2015, October 29)

Land use and land cover (LULC) maps are important tools for the management of the environment, in particular for the modelling of biogeochemical cycles and climate. LULC maps are typically produced using ... [more ▼]

Land use and land cover (LULC) maps are important tools for the management of the environment, in particular for the modelling of biogeochemical cycles and climate. LULC maps are typically produced using supervised classification of satellite images supported by expert knowledge. Nowadays, the advance of the crowdsourced project OpenStreetMap (OSM) offers an alternative to official LULC maps. In OSM, LULC is usually mapped by manual digitalisation of satellite imagery and/or by the import of existing databases. We explored the potential of OSM to contribute to the improvement of an existing LULC map, Corine Land Cover (CLC), by comparing forest cover in Southern Belgium and Luxembourg. We focused on three forest types that were common to the two databases: coniferous, deciduous and mixed forest. Confusion matrices showed that the two databases differed in terms of classes over about one quarter of the forest area. Moreover, 9.9% and 8.0% of the forest area in OSM and CLC, respectively, were unmapped as forest area compared to the other database. Compared to CLC data, small patches of forest areas are mapped in OSM data. This study is a first attempt to show the potential of a crowdsourced project, i.e., OSM, to contribute to an official geodatabase. While current drawbacks of OSM such as the lack of completeness may limit its application in some operational applications, we claim that its large accessibility and its potentially high reactiveness makes OSM a serious alternative to existing geodatabase. [less ▲]

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See detailIrrigation Development Support Program - Agricultural water management in Burkina Faso
Traoré, Farid; Wellens, Joost ULg; Tychon, Bernard ULg et al

Poster (2015, October)

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See detailTrend analysis in ecological status and macrophytic characterization of watercourses: case of the Semois-Chiers basin, Belgium Wallonia
Sossey Alaoui, Khadija ULg; Rosillon, Francis ULg; Tychon, Bernard ULg

in Journal of Water Resource and Protection (2015), Vol.7 No.13 2015

In order to analyze the distribution and evolution of the aquatic vegetation and ecological status of the Semois-Chiers basin (Semois sub-basin and Chiers sub-basin), macrophyte surveys were conducted at ... [more ▼]

In order to analyze the distribution and evolution of the aquatic vegetation and ecological status of the Semois-Chiers basin (Semois sub-basin and Chiers sub-basin), macrophyte surveys were conducted at 48 sites in 2007 and 2013. Environmental parameters were also measured in order to characterize the waterbodies in terms of physico-chemical properties and anthropogenic pressure. The two-way clustering and indicator value (INDVAL) methods were used to assess groups of sites according to their macrophytic composition and species communities. The results showed a clear difference between streams in the Lorraine area (calcareous watercourses) and in the Ardennes (siliceous). Within each natural region, those with natural vegetation of high ecological status were separated from those dominated by resistant species. The Macrophytical Biological Index for Rivers (IBMR), was calculated for the sites visited in 2010 and 2013 and the results show a trend towards an increase of IBMR values of polluted sites. For the latter, the Wilcoxon test was performed to assess the significance of the difference in quality between 2010 and 2013. This showed a statistically significant difference (p-value= 0.035). Our results showed similarities with previous data, as well as some differences. The differences observed might indicate a gradual change in the composition of the vegetation in the study area, caused by changes in environmental conditions. They could also reflect a lack of information about the ecology of certain groups of plants, mainly bryophytes and macroalgae that were not considered in previous studies. Despite the measures implemented under the EU’s Water Framework Directive (WFD), the current vegetation of the Semois river differs little from that observed in 1996. There is a slight improvement in the headwaters of a Semois river, described in previous studies as polytrophic and devoid of vegetation, with the appearance of macrophytic species. In some parts of the Chiers sub-basin, however, resistant species observed in 1999 persist. [less ▲]

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See detailMonitoring surface water content using visible and short-wave infrared SPOT-5 data of wheat plots in irrigated semi-arid regions
Benabdelouahab, Tarik ULg; Balaghi, Riad; Hadria, Rachid et al

in International Journal of Remote Sensing (2015), 36(15), 4018-4036

Irrigated agriculture is an important strategic sector in arid and semi-arid regions. Given the large spatial coverage of irrigated areas, operational tools based on satellite remote sensing can ... [more ▼]

Irrigated agriculture is an important strategic sector in arid and semi-arid regions. Given the large spatial coverage of irrigated areas, operational tools based on satellite remote sensing can contribute to their optimal management. The aim of this study was to evaluate the potential of two spectral indices, calculated from SPOT-5 high-resolution visible (HRV) data, to retrieve the surface water content values (from bare soil to completely covered soil) over wheat fields and detect irrigation supplies in an irrigated area. These indices are the normalized difference water index (NDWI) and the moisture stress index (MSI), covering the main growth stages of wheat. These indices were compared to corresponding in situ measurements of soil moisture and vegetation water content in 30 wheat fields in an irrigated area of Morocco, during the 2012–2013 and 2013–2014 cropping seasons. NDWI and MSI were highly correlated with in situ measurements at both the beginning of the growing season (sowing) and at full vegetation cover (grain filling). From sowing to grain filling, the best correlation (R2 = 0.86; p < 0.01) was found for the relationship between NDWI values and observed soil moisture values. These results were validated using a k-fold cross-validation methodology; they indicated that NDWI can be used to estimate and map surface water content changes at the main crop growth stages (from sowing to grain filling). NDWI is an operative index for monitoring irrigation, such as detecting irrigation supplies and mitigating wheat water stress at field and regional levels in semi-arid areas. [less ▲]

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See detailEvaluation de la vulnérabilité et du risque associés à la sécheresse des nappes phréatiques en Belgique : simulation de la recharge au niveau des zones agricoles avec le modèle B-CGMS
Jacquemin, Ingrid ULg; Verbeiren, Boud; Uljee, Inge et al

Conference (2015, July 02)

Groundwater drought remains poorly studied under temperate climate. The GroWaDRISK project aims at covering this gap by studying the influencing factors and the drought-related impacts on the environment ... [more ▼]

Groundwater drought remains poorly studied under temperate climate. The GroWaDRISK project aims at covering this gap by studying the influencing factors and the drought-related impacts on the environment, water supply and agriculture in the area of the Dijle and Demer catchment. In order to evaluate the current recharge (1980-2012), both models B-CGMS and WetSpass are used under various land uses and land covers. Only BCGMS will be presented in this paper. The model will be adapted in order to be applied on agricultural land: for arable land (winter wheat, maize,…), orchards, horticulture and floriculture areas and for meadows and grassland classes. The use of this model can be justified by the precision, from both spatial and temporal, which allow us to propose a more accurate recharge assessment in function of the main crops of the study area. [less ▲]

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See detailFodder Biomass Monitoring in Sahelian Rangelands Using Phenological Metrics from FAPAR Time Series
Diouf, Abdoul Aziz; Brandt, Martin; Verger, Aleixandre et al

in Remote sensing (2015), 7(9122-9148),

Timely monitoring of plant biomass is critical for the management of forage resources in Sahelian rangelands. The estimation of annual biomass production in the Sahel is based on a simple relationship ... [more ▼]

Timely monitoring of plant biomass is critical for the management of forage resources in Sahelian rangelands. The estimation of annual biomass production in the Sahel is based on a simple relationship between satellite annual Normalized Difference Vegetation Index (NDVI) and in situ biomass data. This study proposes a new methodology using multi-linear models between phenological metrics from the SPOT-VEGETATION time series of Fraction of Absorbed Photosynthetically Active Radiation (FAPAR) and in situ biomass. A model with three variables—large seasonal integral (LINTG), length of growing season, and end of season decreasing rate—performed best (MAE = 605 kg·DM/ha; R2 = 0.68) across Sahelian ecosystems in Senegal (data for the period 1999–2013). A model with annual maximum (PEAK) and start date of season showed similar performances (MAE = 625 kg·DM/ha; R2 = 0.64), allowing a timely estimation of forage availability. The subdivision of the study area in ecoregions increased overall accuracy (MAE = 489.21 kg·DM/ha; R2 = 0.77), indicating that a relation between metrics and ecosystem properties exists. LINTG was the main explanatory variable for woody rangelands with high leaf biomass, whereas for areas dominated by herbaceous vegetation, it was the PEAK metric. The proposed approach outperformed the established biomass NDVI-based product (MAE = 818 kg·DM/ha and R2 = 0.51) and should improve the operational monitoring of forage resources in Sahelian rangelands. [less ▲]

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See detailQuantifying drought effects on groundwater recharge in a human-influenced catchment
Verbeiren, Boud; Huysmans, Marijke; Vanderhaegen, Sven et al

Conference (2015, June)

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See detailThe iPot Project: improved potato monitoring in Belgium using remote sensing and crop growth modelling
Piccard, I.; Nackaerts, K.; Gobin, A. et al

Poster (2015, April)

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See detailModelling carbon fluxes of forest and grassland ecosystems in Western Europe using the CARAIB dynamic vegetation model: evaluation against eddy covariance data.
Henrot, Alexandra-Jane ULg; François, Louis ULg; Dury, Marie ULg et al

in Geophysical Research Abstracts (2015, April), 17

Eddy covariance measurements are an essential resource to understand how ecosystem carbon fluxes react in response to climate change, and to help to evaluate and validate the performance of land surface ... [more ▼]

Eddy covariance measurements are an essential resource to understand how ecosystem carbon fluxes react in response to climate change, and to help to evaluate and validate the performance of land surface and vegetation models at regional and global scale. In the framework of the MASC project (« Modelling and Assessing Surface Change impacts on Belgian and Western European climate »), vegetation dynamics and carbon fluxes of forest and grassland ecosystems simulated by the CARAIB dynamic vegetation model (Dury et al., iForest - Biogeosciences and Forestry, 4:82-99, 2011) are evaluated and validated by comparison of the model predictions with eddy covariance data. Here carbon fluxes (e.g. net ecosystem exchange (NEE), gross primary productivity (GPP), and ecosystem respiration (RECO)) and evapotranspiration (ET) simulated with the CARAIB model are compared with the fluxes measured at several eddy covariance flux tower sites in Belgium and Western Europe, chosen from the FLUXNET global network (http://fluxnet.ornl.gov/). CARAIB is forced either with surface atmospheric variables derived from the global CRU climatology, or with in situ meteorological data. Several tree (e.g. Pinus sylvestris, Fagus sylvatica, Picea abies) and grass species (e.g. Poaceae, Asteraceae) are simulated, depending on the species encountered on the studied sites. The aim of our work is to assess the model ability to reproduce the daily, seasonal and interannual variablility of carbon fluxes and the carbon dynamics of forest and grassland ecosystems in Belgium and Western Europe. [less ▲]

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See detailunité: Eau-Environnement-Développement (ULg Campus Arlon): la télédétection au service de l'agriculture
Wellens, Joost ULg; Lang, Marie ULg; Benabdelouahab, Tarik et al

Diverse speeche and writing (2015)

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See detailRemote sensing enables high discrimination between organic and non-organic cotton for organic cotton certification in West Africa
Denis, Antoine ULg; Tychon, Bernard ULg

in Agronomy for Sustainable Development (2015)

One of the challenges of organic crop certification is the efficient targeting of the relatively small percentage of risk-sensitive fields that have to be controlled during the regulatory annual in situ ... [more ▼]

One of the challenges of organic crop certification is the efficient targeting of the relatively small percentage of risk-sensitive fields that have to be controlled during the regulatory annual in situ inspection. A previous study carried out on wheat and maize in Germany has shown that organic and non-organic crops can be efficiently distinguished by remote sensing. That study pointed to the possibility that these techniques could be used for helping organic crop certification bodies to better target risk-sensitive fields. This study is a first adaptation of that research on organic cotton in southwestern Burkina Faso, West Africa. This study assumed that organic and non-organic cotton, primarily because of their different approaches to fertilization and pest control, would result in bio-chemico-physical differences measurable by both in situ and remote sensing indicators. This study included 100 cotton fields, of which 50 were organic, 28 conventional, and 22 genetically modified. In situ indicators were derived from chlorophyll content, canopy cover, height, and spatial heterogeneity measurements. Remote sensing spectral and spatial heterogeneity indicators were derived from two SPOT 5 satellite images. Discriminant models were then computed. The results show statistically highly significant differences between organic and non-organic cotton fields for both in situ and satellite indicators, using univariate and multivariate linear models, with up to 86 % discrimination performance. This is the first time that the efficiency of using remote sensing to discriminate between organic and non-organic crops is evaluated in a developing country, particularly for cotton, with good discrimination being achieved. Pending further validation, it therefore seems that remote sensing could be used to enhance organic cotton certification in West Africa by enabling more efficient targeting of suspect fields and consequently could contribute to a better development of this sector. [less ▲]

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See detailLIVESTOCK SYSTEMS--TECHNICAL REPORT
Minet, Julien ULg; Diouf, Abdoul Aziz; Garba, Issa et al

Report (2015)

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See detailBayesian inversions of a dynamic vegetation model at four European grassland sites
Minet, Julien ULg; Laloy, Eric; Tychon, Bernard ULg et al

in Biogeosciences (2015), 12(9), 2809--2829

Eddy covariance data from four European grassland sites are used to probabilistically invert the CARAIB (CARbon Assimilation In the Biosphere) dynamic vegetation model (DVM) with 10 unknown parameters ... [more ▼]

Eddy covariance data from four European grassland sites are used to probabilistically invert the CARAIB (CARbon Assimilation In the Biosphere) dynamic vegetation model (DVM) with 10 unknown parameters, using the DREAM(ZS) (DiffeRential Evolution Adaptive Metropolis) Markov chain Monte Carlo (MCMC) sampler. We focus on comparing model inversions, considering both homoscedastic and heteroscedastic eddy covariance residual errors, with variances either fixed a priori or jointly inferred together with the model parameters. Agreements between measured and simulated data during calibration are comparable with previous studies, with root mean square errors (RMSEs) of simulated daily gross primary productivity (GPP), ecosystem respiration (RECO) and evapotranspiration (ET) ranging from 1.73 to 2.19, 1.04 to 1.56 g C m−2 day−1 and 0.50 to 1.28 mm day−1, respectively. For the calibration period, using a homoscedastic eddy covariance residual error model resulted in a better agreement between measured and modelled data than using a heteroscedastic residual error model. However, a model validation experiment showed that CARAIB models calibrated considering heteroscedastic residual errors perform better. Posterior parameter distributions derived from using a heteroscedastic model of the residuals thus appear to be more robust. This is the case even though the classical linear heteroscedastic error model assumed herein did not fully remove heteroscedasticity of the GPP residuals. Despite the fact that the calibrated model is generally capable of fitting the data within measurement errors, systematic bias in the model simulations are observed. These are likely due to model inadequacies such as shortcomings in the photosynthesis modelling. Besides the residual error treatment, differences between model parameter posterior distributions among the four grassland sites are also investigated. It is shown that the marginal distributions of the specific leaf area and characteristic mortality time parameters can be explained by site-specific ecophysiological characteristics. [less ▲]

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See detailDifferentiating between influencing factors land use and climate to assess drought effects on groundwater recharge in a temperate context
Verbeiren, Boud; Huysmans, Marijke; Vanderhaegen, Sven et al

Conference (2014, November)

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See detailOutcomes from the MACSUR grassland model inter-comparison with the model CARAIB
Minet, Julien ULg; Laloy, Eric; Tychon, Bernard ULg et al

Conference (2014, October 15)

Detailed reference viewed: 29 (5 ULg)