References of "Legrain, Xavier"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailDiachronical soil surveys: a way to quantify long term diffuse erosion
Pineux, Nathalie ULg; Michel, Brieuc ULg; Legrain, Xavier ULg et al

in Geophysical Research Abstracts (2015), 17

The loess belt of Western Europe is a high-risk area regarding diffuse erosion. It is due to the climate and the topography but also to the soil type. Loamy soils are naturally highly sensitive to diffuse ... [more ▼]

The loess belt of Western Europe is a high-risk area regarding diffuse erosion. It is due to the climate and the topography but also to the soil type. Loamy soils are naturally highly sensitive to diffuse erosion. Hence, these soils are very fertile. So, they are intensively cultivated which increases their sensitivity to erosion. Sheet erosion is an erosion type strongly represented in these regions. Contrarily to the concentrated form of erosion which happens more brutally, sheet erosion needs long-term observation time-scales, which remains rare. In Belgium, a soil map was established in 1956. This map is quite detailed and notably informs about the different horizons which are in the profile (ploughed horizon, eluvial horizon, clay included between the horizons, carbonate-free loess horizon, and all these were characterised by drainage class) and their depth. It was based on a dense augering network across the country (one point every 75 meters). A new augering campaign was done again in 2014. It consisted in one observation every 50 meters on an agricultural watershed of 124 hectares located in the centre of Belgium. This catchment has been cultivated since the 14th century and is representative of the local context (gentle slope (3-8%), plot size (mean value of 10 ha), …). We compared the two soil maps produced on this site with a 58years time lapse. Results show that the large majority of the watershed falls from upslope soils with weak erosion to slope soils with strong erosion. The soil thickness diminished in some zones to 1m10 (minimum estimation) of erosion. This comparison shows that very few upslope soils are preserved. On the other hand, the areas where colluviums were present to the full depth stay at the same place in the main thalweg of the watershed. Other areas on the watershed seem to be subject to a (minimum estimation) of 40cm of sediments deposition. Large areas in the watershed suffered from erosion and came to deposition areas as the clay horizon is no longer observed under the colluviums. It can be highlighted that soil depths were worryingly lost during 58 years of tillage and that some soils were converted to colluviums which is of lower agronomical quality than the original soils which had a clay horizon below to keep water. Diachronical soil survey offers an unique insight of long term diffuse erosion and should demonstrate the importance of preserving soils even in regions where agricultural yields are not (yet) affected by erosion. [less ▲]

Detailed reference viewed: 15 (2 ULg)
See detailLa Carte des Sols de la Belgique : un héritage à se réapproprier
Legrain, Xavier ULg; Michel, Brieuc ULg; Bock, Laurent ULg et al

Conference (2014, July 03)

Une cartographie systématique à grande échelle des sols de Belgique a été conduite entre 1947 et 1991. Les observations étaient effectuées au moyen de sondages à la tarière jusqu’à une profondeur standard ... [more ▼]

Une cartographie systématique à grande échelle des sols de Belgique a été conduite entre 1947 et 1991. Les observations étaient effectuées au moyen de sondages à la tarière jusqu’à une profondeur standard de 125 cm dans la mesure du possible, avec une densité moyenne de 2 sondages à l’hectare. Des plans cadastraux au 1/5 000 ont servi à noter les observations et à tracer les limites des plages cartographiques, généralisées par la suite par transcription sur fond de carte topographique au 1/10 000. La carte finale a été publiée par planchettes à l’échelle du 1/20 000, associées à des livrets explicatifs. La carte s’appuie sur une légende originale, basée majoritairement sur des critères morphologiques du sol, aisément identifiables sur le terrain, objectifs (sans a priori d’interprétation) et les plus permanents possibles. La combinaison de ces critères, transcrits en symboles alphanumériques, est à l’origine de la très grande richesse sémantique de la légende, forte de plus de 10 000 unités cartographiques de sols. La numérisation de la Carte des Sols de la Belgique et la structuration de l’information délivrée par la légende ont ouvert de nombreuses perspectives en terme d’applications. Mais au-delà du produit final qu’est la carte, le véritable héritage légué est l’extraordinaire connaissance experte accumulée par les cartographes durant la durée du projet. Si une part inestimable de ce savoir s’en est allée en même temps qu’eux, une part tangible est accessible à travers de nombreuses publications (livrets explicatifs, monographies, thèses, articles) ou parsème divers documents d’archive (notes de terrain, PV de réunion, rapports d’excursions). Ces derniers sont également une invitation à se replonger dans le contexte historique, scientifique et philosophique de l’époque des levés. Ils permettent de ce fait de mieux cerner la manière dont la légende a été pensée, élaborée, adaptée, remaniée. L’éclairage que ces publications et documents d’archive donnent sur la carte et sa légende laisse entrevoir une richesse d’information insoupçonnée. Se la réapproprier par une interprétation avertie de la carte est essentiel préalablement à toute valorisation. Cette communication se propose de justifier l’intérêt de cette démarche au travers de multiples exemples. Ils ont été choisis de manière (i) à présenter la diversité des cas rencontrés et (ii) à illustrer l’impact d’une telle interprétation sur la qualité des produits issus de 2 projets menés actuellement : la corrélation de la légende de la Carte des Sols de la Belgique avec le système de classification international World Reference Base et la contribution belge au projet mondial GlobalSoilMap. [less ▲]

Detailed reference viewed: 29 (7 ULg)
Peer Reviewed
See detailDecoding implicit information from the soil map of Belgium and implications for spatial modelling and soil classification
Dondeyne, Stefaan; Legrain, Xavier ULg; Colinet, Gilles ULg et al

Conference (2014, April 29)

A systematic soil survey of Belgium was conducted from 1948 to 1991. Field surveys were done at the detailed scale of 1:5000 with the final maps published at a 1:20,000 scale. Soil surveyors were ... [more ▼]

A systematic soil survey of Belgium was conducted from 1948 to 1991. Field surveys were done at the detailed scale of 1:5000 with the final maps published at a 1:20,000 scale. Soil surveyors were classifying soils in the field according to physical and morphogenetic characteristics such as texture, drainage class and profile development. Mapping units are defined as a combination of these characteristics but to which modifiers can be added such as parent material, stoniness or depth to substrata. Interpretation of the map towards predicting soil properties seems straight forward. Consequently, since the soil map has been digitized, it has been used for e.g. hydrological modelling or for estimating soil organic carbon content at sub-national and national level. Besides the explicit information provided by the legend, a wealth of implicit information is embedded in the map. Based on three cases, we illustrate that by decoding this information, properties pertaining to soil drainage or soil organic carbon content can be assessed more accurately. First, the presence/absence of fragipans affects the soil hydraulic conductivity. Although a dedicated symbol exits for fragipans (suffix “...m”), it is only used explicitly in areas where fragipans are not all that common. In the Belgian Ardennes, where fragipans are common, their occurrence is implicitly implied for various soil types mentioned in explanatory booklets. Second, whenever seasonal or permanent perched water tables were observed, these were indicated by drainage class “.h.” or “.i.”, respectively. Stagnic properties have been under reported as typical stagnic mottling – i.e. when the surface of soil peds are lighter and/or paler than the more reddish interior – were not distinguished from mottling due to groundwater gley. Still, by combining information on topography and the occurrence of substratum layers, stagnic properties can be inferred. Thirdly, soils with deep anthropogenic enriched organic matter (Anthrosols) are distinguished for their specific profile development (code “..m”). Obviously, when assessing soil organic carbon content these soil types need particular consideration. Soils in the Campine region with anthropogenic layers only 30 to 40 cm thick, not being Anthrosols, got a specific suffix code (“. . . 3”). Still, as these soils may have a buried Ah horizon of up to 20 cm, their soil organic carbon content can be comparable to those of Anthrosols. The buried Ah horizon is however not explicitly mapped; its presence needs to be inferred from other environmental information. In conclusion, conventional soil maps convey more information than what transpires from just the explicit legend’s semantics. Although a challenge, decoding the implicit information should be particularly useful for spatial modeling. The cases also point to the importance of classifying soil characteristics explicitly, wherever possible, and in particularly when soil maps are integrated into geographical information systems. [less ▲]

Detailed reference viewed: 19 (1 ULg)
Peer Reviewed
See detailSuitability of the soil map and legacy data in wallonia (BE) to support the GSM initiative
Legrain, Xavier ULg; Bock, Laurent ULg; Colinet, Gilles ULg

in Arrouays, Dominique; McKenzie, Neil; Hempel, Jon (Eds.) et al GlobalSoilMap - Basis of the global spatial soil information system (2014)

Belgium is covered with large-scale soil map and high density of historical profiles, now available in a numerical format. This papier first gives an overview of the soil properties which can be predicted ... [more ▼]

Belgium is covered with large-scale soil map and high density of historical profiles, now available in a numerical format. This papier first gives an overview of the soil properties which can be predicted from these documents, in combination with the legacy data, and of the uncertainty we can expect for now. The great potential of the soil map is highlighted, as well as its complexity. Example of the soil depth to rock points out the need of a thorough understanding of the soil map in order (i) to interpret correctly the information hidden behind each symbols or emerging from their combination and (ii) to take into account the sub-regional features. Expert knowledge seems essential, associated with historical and new hard data, in order to build a rich and confident map which respects the recommendations of the GlobalSoilMap.net project. [less ▲]

Detailed reference viewed: 17 (2 ULg)
Peer Reviewed
See detailSoil classification, map legends and GIS logic: experiences from converting the legend of the soil map of Belgium into WRB
Dondeyne, Stefaan; Legrain, Xavier ULg; Deckers, Jozef et al

Conference (2013, October 04)

A systematic soil survey of Belgium was conducted from 1948 to 1991. The purpose was to have a soil information base adequate for boosting agricultural production after the Second World War. Field surveys ... [more ▼]

A systematic soil survey of Belgium was conducted from 1948 to 1991. The purpose was to have a soil information base adequate for boosting agricultural production after the Second World War. Field surveys were done at the detailed scale of 1:5000, while the maps were published at a 1:20,000 scale. To enable soil surveyors to identify soils in the field, an original soil classification was developed based on readily observable physical and morphogenetic characteristics. Within the European Union, the World Reference Base (WRB) for Soil Resources (IUSS Working Group WRB, 2007), has been adopted as the common classification system. As soil surveys in most European countries were conducted independently, the challenge now is to convert the national legends into a common WRB legend. In Belgium, such a conversion is being implemented and we present some lessons learned in relation to classification and map legends. The legend of the soil map of Belgium is based primarily on soil texture, drainage status and profile development. “Soil series” are defined in an open and non-hierarchical structure by combining these three categorical variables, and to which modifiers can be added such as parent material, stoniness or depth to a substratum. The WRB-2007 classification is based on diagnostic features defined by morphological, physical and chemical properties. The conversion of the legend of the soil map of Belgium to WRB is based on insights gained from classifying, so far, more than 360 legacy soil profiles in combination with field observations. From these insights, heuristic rules have been deduced regrouping soil series into Reference Soil Groups (RSG) and for which some qualifiers could also be identified. Other qualifiers were determined by relying on databases of the legacy soil profiles. To take regional variability into account, the conversion is done by physiographic zone. Converting the legend of the soil map of Belgium to WRB actually leads to a regrouping of soil series into broader WRB categories and which can neatly be represented on 1:50,000 scale maps. Hence, it does not imply substituting one classification with another one. Users, who would need the detailed information, can still refer to the detailed symbols of the soil series. The regrouping of soil series has been made possible thanks to the flexibility of WRB for combining various qualifiers. However, as the WRB-2007 classification leads to a varying number of qualifiers it is less practical for constructing map legends. Therefore, the WRB-2010 guidelines (IUSS Working Group WRB, 2010) propose to organise qualifiers in main and optional ones with priority rules for the main qualifiers. As illustrated in Table 1, this approach may highlight, or hide, some qualifiers inconsistently. When for example only two qualifiers are retained in a map legend, the qualifier Endogleyic of stony, poorly drained Albic Podzols will not be indicated, while it will be indicated when such soils are not stony (Table 1). Moreover, the proposed hierarchy is sometimes also inconsistent when compared across Reference Soil Groups (RSG) as illustrated for the Arenosols and Regosols (Table 1). These drawbacks could be avoided if qualifiers would be organised into thematic groups ― such as profile development, texture, drainage, depth of substratum and fertility ― rather than by ranking them. Grouping qualifiers thematically would have the advantage to give more flexibility to the map user working with GIS, and indeed, it would render WRB a more “GIS logic” classification system. [less ▲]

Detailed reference viewed: 21 (0 ULg)
See detailProjet de Cartographie Numérique des Sols de Wallonie - Aperçu historique et missions actuelles de l'équipe de révision
Legrain, Xavier ULg; Michel, Brieuc ULg; Lejeune, Emilie et al

Conference given outside the academic context (2013)

Detailed reference viewed: 26 (3 ULg)
Full Text
Peer Reviewed
See detailRelationships between the P status of surface and deep horizons of agricultural soils under various cropping systems and for different soil types: a case study in Belgium
Renneson, Malorie ULg; Dufey, J.; Legrain, Xavier ULg et al

in Soil Use and Management (2013), 29(S1), 103--113

Application of phosphorus (P) fertilizers to agricultural soils should be based on sound knowledge about soil P reserves, availability and lability to optimize conditions for plant uptake while limiting P ... [more ▼]

Application of phosphorus (P) fertilizers to agricultural soils should be based on sound knowledge about soil P reserves, availability and lability to optimize conditions for plant uptake while limiting P transport to surface waters. This study investigated relationships between parent material (PM), land use and P fractions in agricultural soils at a regional scale. Surface and deep (100–120 cm) soil samples were collected from 120 agricultural sites (240 total samples) and analysed for three P forms (inorganic, organic and available) as well as for additional key properties. Land uses within the study area were continuous cropland, permanent pasture and temporary grassland. The area covered the 12 most common parent types in Wallonia. Mean total P contents were 904 and 401 mg/kg in surface and deep samples, respectively, with a 33% coefficient of variation for both horizons. The organic P fraction represented, on average, 30% of total P, while available P corresponded to 9% of total P. The influence of PM was apparent in both the surface and deep soil samples, while land use influenced only surface properties. The pattern in total P content relative to land use was pasture ≥ cropland ≥ temporary grassland. Correlation analyses highlighted significant relationships between edaphic parameters viz Alox, Feox, CEC, TOC, pH and P content, the main soil parameter being Alox which determines P sorption capacity. An enrichment factor was used to distinguish between geogenic sources and human activities in terms of topsoil P content. [less ▲]

Detailed reference viewed: 59 (24 ULg)
Full Text
Peer Reviewed
See detailCartographie du risque d’érosion hydrique à l’échelle parcellaire en soutien à la politique agricole wallonne (Belgique)
Maugnard, Alexandre; Bielders, Charles; Bock, Laurent ULg et al

in Étude et Gestion des Sols (2013), 20(2), 127-141

L’érosion hydrique des sols pose le problème de la protection de la ressource « sol » mais également de la prévention des impacts environnementaux et sociétaux qui y sont associés tels que la dégradation ... [more ▼]

L’érosion hydrique des sols pose le problème de la protection de la ressource « sol » mais également de la prévention des impacts environnementaux et sociétaux qui y sont associés tels que la dégradation de la qualité des eaux de surface, l’envasement des retenues d’eau et des bassins d’orage ou encore les inondations boueuses. Afin de cibler au mieux les mesures de lutte anti-érosives, il convient d’identifier les parcelles agricoles les plus à risque d’érosion. Mettant à profit la disponibilité d’importantes bases de données en matière de climat, sol, topographie, parcellaire et occupation du sol, une procédure automatisée de calcul de l’aléa érosion hydrique potentielle à l’échelle parcellaire, adaptée du modèle RUSLE, a été mise au point pour la Wallonie (Belgique). La carte de l’aléa érosion potentielle montre une sensibilité maximale à l’érosion hydrique en Ardenne et Haute-ardenne, en raison du relief accentué et d’une érosivité plus importante des pluies. Pour les principales zones agro-pédologiques de Wallonie, un suivi des principales cultures (céréales d’hiver, mais, betterave, pomme de terre, colza, lin) a également été réalisé, permettant d’estimer le facteur cultural C des principales successions culturales et ainsi l’érosion effective. La prise en compte de l’occupation du sol fait cette fois ressortir un aléa maximal dans les régions (sablo-)limoneuses et le Condroz, en raison des superficies importantes de grandes cultures industrielles. En Ardenne et Haute Ardenne, l’aléa d’érosion effective est faible en raison d’une couverture végétale dominée par les prairies permanentes. Enfin, sur base de la carte numériques des sols de Wallonie, une classification de la vulnérabilité des sols à l’érosion a été établie à partir du volume de sol pouvant être exploité par les racines. La vulnérabilité apparaît élevée sur une majorité du territoire wallon, à l’exception des Régions (sablo-)limoneuses et de la Région jurassique. Un indice d’érosion, calculé comme le rapport de l’érosion potentielle (aléa) sur l’érosion tolérable (vulnérabilité) permet de calculer le risque d’érosion hydrique et, par conséquent, de cibler au mieux les parcelles pour lesquelles l’érosion constitue une menace majeure pour leur valorisation durable. Une gestion appropriée de ces parcelles par un choix judicieux en termes d’occupation du sol (forêt, prairie, rotations culturales) et de pratiques culturales (p.ex., TCSL, inter-cultures) devrait permettre d’y réduire les risques de dégradation des sols par érosion hydrique. [less ▲]

Detailed reference viewed: 104 (29 ULg)
See detailProjet de Cartographie Numérique des Sols de Wallonie - Aperçu historique et missions actuelles de l'équipe de révision
Legrain, Xavier ULg; Michel, Brieuc ULg; Lejeune, Emilie et al

Conference given outside the academic context (2012)

Detailed reference viewed: 19 (4 ULg)