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Peer Reviewed
See detailModelling agricultural strategies to protect groundwater resources in the Hesbaye aquifer (Belgium)
Sohier, Catherine ULg; Degré, Aurore ULg

in Fraters, Dico; Kovar, Karel (Eds.) International Interdisciplinary Conference on Land Use and Water Quality, Reducing Effects of Agriculture, The Hague, the Netherlands, 10-13 June 2013 (2013)

Groundwater quality is spoiled by various substances resulting from human activities. In addition to pesticides, one of the most problematic substances is nitrate. Pumping prevention areas are strategic ... [more ▼]

Groundwater quality is spoiled by various substances resulting from human activities. In addition to pesticides, one of the most problematic substances is nitrate. Pumping prevention areas are strategic zones in terms of struggle against diffuse pollution by nitrate. In order to reduce diffuse pollution of waters by nitrate, different strategies of agricultural practices can be implemented. Their impact can be evaluated either by monitoring water quality or using an agro-hydrological model. The advantage of modelling is to be able to test long term impacts of implemented measures and impacts of complementary measures. Using EPICgrid distributed agro-hydrological model, we reproduced the current agricultural practices. We calculated nitrate leaching but also the nitrate stock in the root zone. These results were validated through a comparison with a lot of nitrogen stock measurements. (These measurements are compulsory in the Walloon context.) The nitrate concentration in pumping wells was also used to assess the efficiency of the model. After this calibration phase, we modelled several scenarios of more water-protective agricultural practices. Indeed, the Hesbaye galleries represent an important source of drinking water in the Walloon region, it is therefore highly probable that further mitigation measures are going to be imposed in the pumping prevention area. An increase in the area cultivated with cereals, a strong limitation of mineral fertilisation as well as a conversion to grasslands were tested and combined. The results of these simulations show how some agricultural practices scenarios can lead to an important decrease in diffuse pollution by nitrate. Prospective simulations taking into account possible future climate evolution (global change scenarios) are carried out to assess nitrate concentrations near the groundwater table for the deadlines of the WFD (2015, 2021 and 2027). Due to the transfer time through the vadose zone (more than 20 years in some subregions), it is showed that an increase in groundwater nitrate concentrations will occur, in some areas, until at least 2030 before new agricultural practices can impact positively the groundwater quality. [less ▲]

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See detailModelling and optimization of an hydrogeological system to prevent groundwater pollution from a leaky landfill
Dassargues, Alain ULg

in Int. Symp. on Environmental Contamination, Budapest (1992)

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Peer Reviewed
See detailModelling and parameter estimation for heterogeneous cell populations
Waldherr, S; Hasenauer, J; Schliemann, Monica ULg et al

Poster (2009)

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See detailThe modelling and simulation of ocean's circulation on supercomputers
Beckers, Jean-Marie ULg

in Melli, P.; Zannetti, P. (Eds.) Environmental Modelling (1992)

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Peer Reviewed
See detailModelling and Simulation of Rat Swimming in a Water Maze Experiment
Fey, D.; Commins, Séan; Bullinger, Eric ULg

Poster (2009)

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See detailA modelling approach as an intermediate step for the study of protection zones in karstified limestones
Dassargues, Alain ULg; Derouane, Johan

in Leibundgut, Christian; Gunn, John; Dassargues, Alain (Eds.) Karst Hydrology (Proc. of Rabat Workshop W2) (1998)

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See detailA modelling approach of the Ross Sea plankton ecosystem
Hecq, Jean-Henri ULg; Guglielmo, Lillo; Goffart, Anne ULg et al

in Faranda, F.; Guglielmo, L.; Ianora, A. (Eds.) Ross Sea Ecology - ITALIANTARTIDE Expeditions (1987-1995) (1999)

See pdf file in attachment

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See detailModelling argon dynamics in first-year sea ice
Moreau, S.; Vancoppenolle, M; Zhou, Jiayun ULg et al

in Ocean Modelling (2014), 73

Abstract: Focusing on physical processes, we aim at constraining the dynamics of argon (Ar), a biogeochemically inert gas, within first year sea ice, using observation data and a one-dimensional halo ... [more ▼]

Abstract: Focusing on physical processes, we aim at constraining the dynamics of argon (Ar), a biogeochemically inert gas, within first year sea ice, using observation data and a one-dimensional halo-thermodynamic sea ice model, including parameterization of gas physics. The incorporation and transport of dissolved Ar within sea ice and its rejection via gas-enriched brine drainage to the ocean, are modeled following fluid transport equations through sea ice. Gas bubbles nucleate within sea ice when Ar is above saturation and when the total partial pressure of all three major atmospheric gases (N2, O2 and Ar) is above the brine hydrostatic pressure. The uplift of gas bubbles due to buoyancy is allowed when the brine network is connected with a brine volume above a given threshold. Ice-atmosphere Ar fluxes are formulated as a diffusive process proportional to the differential partial pressure of Ar between brine inclusions and the atmosphere. Two simulations corresponding to two case studies that took place at Point Barrow (Alaska, 2009) and during an ice-tank experiment (INTERICE IV, Hamburg, Germany, 2009) are presented. Basal entrapment and vertical transport due to brine motion enable a qualitatively sound representation of the vertical profile of the total Ar (i.e. the Ar dissolved in brine inclusions and contained in gas bubbles; TAr). Sensitivity analyses suggest that gas bubble nucleation and rise are of most importance to describe gas dynamics within sea ice. Ice-atmosphere Ar fluxes and the associated parameters do not drastically change the simulated TAr. Ar dynamics are dominated by uptake, transport by brine dynamics and bubble nucleation in winter and early spring; and by an intense and rapid release of gas bubbles to the atmosphere in spring. Important physical processes driving gas dynamics in sea ice are identified, pointing to the need for further field and experimental studies. [less ▲]

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Peer Reviewed
See detailModelling at the biological/biomechanical interface: fracture healing case studies
Geris, Liesbet ULg

in Exploring the biological/biomechanics interface (2009)

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See detailModelling atmospheric CO2 changes at geological timescales
François, Louis ULg; Grard, Aline ULg; Goddéris, Yves

in Carnets de Géologie = Notebooks on Geology (2005), M02/02(Memoir 2005/02), 11-14

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See detailModelling autotrophic and heterotrophic components of soil respiration in wheat fields
Delogu, Emilie; LeDantec, Valérie; Buysse, Pauline ULg et al

Conference (2012, April)

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See detailModelling Bark Thickness in the tree in relation to silviculturaltreatment
Jourez, Benoît ULg; Leclercq, André

Report (1993)

Based upon a sampling of 186 trees of Norway spruce, Sitka spruce and Douglas fir from Belgium (24 Norway spruce), Denmark (24 Norway spruce and 24 Sitka spruce), France (24 Norway spruce), Germany (24 ... [more ▼]

Based upon a sampling of 186 trees of Norway spruce, Sitka spruce and Douglas fir from Belgium (24 Norway spruce), Denmark (24 Norway spruce and 24 Sitka spruce), France (24 Norway spruce), Germany (24 Douglas fir), Great Britain (24 Sitka spruce) and Italy (24 Douglas fir) specially cut for the Project, this study which is a part (Task 6) of a larger ECC Project, has shown the effects of the tree, its Social position in the stand, the thinning intensity and the site productivity on bark thickness and bark volume. All along the stem, bark thickness has a particular profile characterized by a steep decrease from the bottom up to a given height variable from species to species, due to a bottom effect, then being relatively constant up to the living crown base level and finally decreasing slightly in the living crown part. The most important bottom effect has been observed on Douglas fir. Referring to a variance components analysis, variability in bark thickness is mainly due to the tree itself and the stand factor which globalized the cumulated effect of thinning intensity and site productivity. However, it appears that the trees selected by couple for each Social position in each stand are similar whatever the species could be, and may be considered, in fact, as true replicates. For each species, the Social position of the tree in the stand influences bark thickness in the same way. In all cases, dominant trees have indeed the thickest bark, whilst suppressed trees are always characterized by the thinnest bark and co-dominant trees range to this respect in an intermediate position. The effect of site productivity is not clear through this sampling, due to interferences of different factors, mainly the differences in tree age which let appear a significant effect of the country (differences in growing conditions and between productivity classes). Nevertheless, when tree age is almost the same in different countries, the general trends are going in the direction of a decrease of bark thickness when the site productivity becomes lower. The same general trends are observed in connection with the thinning intensity because bark thickness generally decreases when thinnings are less intense. In fact, bark thickness is far to be constant according to the stand selection criteria (site productivity, thinning intensity) but is noticeably affected by the tree selection criteria (Social position). Bark thickness, bark volume and amount of bark are mainly depending on the growing conditions with a major effect of the Social position compared to the thinning intensity and the site productivity. Unfortunately, a general model was unsuitable for an accurate prediction of bark thickness. The best predicted values of bark thickness was obtained in using common models, linear ones for Norway spruce and Sitka spruce but non linear ones for Douglas fir. [less ▲]

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See detailModelling BSE trend over time in europe, a risk assessment perspective
Ducrot, C.; Sala, C.; Ru, G. et al

in European Journal of Epidemiology (2010)

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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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Peer Reviewed
See detailModelling chemical weathering at river catchment scale: design and calibration of the WiTCh model
Probst, A.; Godderis, Y.; François, Louis ULg et al

in Geochimica et Cosmochimica Acta (2002), 66(15A), 615-615

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Peer Reviewed
See detailModelling chemo-hydro-mechanical behaviour of unsaturated clays: a feasibility study
Liu, Z.; Boukpeti, Nathalie; Li, Xikui ULg et al

in International Journal for Numerical and Analytical Methods in Geomechanics (2005), 29(9), 919-940

Effective capabilities of combined chemo-elasto-plastic and unsaturated soil models to simulate chemohydro-mechanical (CHM) behaviour of clays are examined in numerical simulations through selected ... [more ▼]

Effective capabilities of combined chemo-elasto-plastic and unsaturated soil models to simulate chemohydro-mechanical (CHM) behaviour of clays are examined in numerical simulations through selected boundary value problems. The objective is to investigate the feasibility of approaching such complex material behaviour numerically by combining two existing models. The chemo-mechanical effects are described using the concept of chemical softening consisting of reduction of the pre-consolidation pressure proposed originally by Hueckel (Can. Geotech. J. 1992; 29:1071-1086; Int. J. Numer. Anal. Methods Geomech. 1997; 21:43-72). An additional chemical softening mechanism is considered, consisting in a decrease of cohesion with an increase in contaminant concentration. The influence of partial saturation on the constitutive behaviour is modelled following Barcelona basic model (BBM) formulation (Geotech. 1990; 40(3):405-430; Can. Geotech. J. 1992; 29:1013-1032). The equilibrium equations combined with the CHM constitutive relations, and the governing equations for flow of fluids and contaminant transport, are solved numerically using finite element. The emphasis is laid on understanding the role that the individual chemical effects such as chemo-elastic swelling, or chemo-plastic consolidation, or finally, chemical loss of cohesion have in the overall response of the soil mass. The numerical problems analysed concern the chemical effects in response to wetting of a clay specimen with an organic liquid in rigid wall consolidometer, during biaxial loading up to failure, and in response to fresh water influx during tunnel excavation in swelling clay. Copyright (c) 2005 John Wiley [less ▲]

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See detailModelling Climate and Vegetation Interactions at the Middle Miocene with the Planet Simulator and CARAIB
Henrot, A.-J.; Munhoven, Guy ULg; François, Louis ULg et al

Conference (2011, January 18)

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See detailModelling climate change impacts on key tree species used by lion tamarins in the Brazilian Atlantic Forest
Raghunathan, Poornima ULg

Poster (2013, July 21)

We used 3 IPCC climate change scenarios (A1B, A2, B1) in a dynamic vegetation model (CARAIB), to determine the potential future distribution of biomes and 75 species of trees used as food sources or ... [more ▼]

We used 3 IPCC climate change scenarios (A1B, A2, B1) in a dynamic vegetation model (CARAIB), to determine the potential future distribution of biomes and 75 species of trees used as food sources or sleeping sites by endemic primates, the golden lion tamarin (Leontopithecus rosalia) and the golden-headed lion tamarin (L. chrysomelas), in the Brazilian Atlantic Forest (BAF). Habitat conservation is a vital part of strategies to protect endangered species, and this is an approach to understand how key plant species needed for faunal survival might be affected by climate change and what changes to their distribution are likely. CARAIB computes the main physiological reaction of plants, e.g. water absorption or photosynthesis, as a response to temperature, precipitation, or CO2 partial pressure. The model accurately predicted the current distribution of BAF vegetation types and for 66% of the individual tree species with 70% agreement obtained for presence. In the simulation experiments for the future, 72 out of 75 tree species maintained more than 95% of the original distribution and all species showed a range expansion. The results suggested that the trees may benefit from an increase in temperature, if and only if soil water availability is not altered significantly, as was the case with climate simulations that were used. However, the results must be coupled with current and planned land-uses to maximise the usefulness to conservation, as the BAF is subject to many threats. [less ▲]

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Peer Reviewed
See detailModelling climate control on cropland and grassland development using phenologically tuned variables
Horion, Stéphanie; Tychon, Bernard ULg; Cornet, Yves ULg

in Geophysical Research Abstracts (2010), 12

Many studies already investigated the impact of climate change and climate variability on vegetation at global and continental scales. Using time series of remote sensing and climate data, Nemani et al ... [more ▼]

Many studies already investigated the impact of climate change and climate variability on vegetation at global and continental scales. Using time series of remote sensing and climate data, Nemani et al. (2003) analyzed trends in Net Primary Production in relation with changes in climate and showed that, between 1982 and 1999, primary productivity increased by 6% globally in response to climate change. This study also stressed the need to take into account the spatial variability of climatic constraints to plant growth when analyzing the climate change impact on vegetation. Others authors described different phenomenon linked with climate change such as increases of seasonal NDVI amplitude and growing season duration in the Northern high latitude or changes in circumpolar photosynthetic activities. Understanding the interactions between climate and vegetation is also a key issue in our PhD research. Our objective is to identify the meteorological factors which limit the development of croplands and grasslands in relation with their geographical localization. For that purpose, we acquired 10-daily time series of the Normalized Difference Vegetation Index, NDVI, derived from SPOT-VEGETATION and 7 meteorological parameters (Tmean, Tmin, Tmax, Rain, Rad, ETP, Rain-ETP) derived from ERA40 re-analyses and the operational ECMWF (European Centre for Medium-Range Weather Forecast) atmospheric model. Cross-correlations between NDVI and each one of the meteorological parameters were analysed for a set of 25 regions over Europe and Africa: 15 agricultural regions and 10 regions covered by grassland or savannas. Unlike others studies, we did not consider the vegetation globally but we focussed on two types of vegetation: croplands and grasslands. This is quite important considering the role of phenology on the vegetation cycle and its relation with climate. Moreover the analysis was not realised using yearly estimates but using 10-daily products. In order to avoid stationarity related issue, a specific methodology was developed taking into account the phenological cycle of the vegetation under consideration. Preliminary results showed that the relation between a meteorological limiting factor, e.g. precipitation, and NDVI can not be considered as linear during the year or even during the growing season. Interactions must to be studied at a smaller time scale than the growing season in order to identify properly the limiting factors to plant growth taking into account its phenology. Moreover the main limiting factors are variable from a region to another. In our analysis we also considered the possibility of a delayed response of the vegetation or a cumulated effect of meteorological events (up to 3 months). Our methodology will be presented during the conference and results will be discussed and illustrated by some test cases. [less ▲]

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