References of "Lejeune, Philippe"
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See detailQGIS, une alternative open source à ArcGIS?
Bonnet, Stéphanie ULg; Gheysen, Thibaut; Lejeune, Philippe ULg

Learning material (2010)

Séminaire d'introduction au logiciel Quantum GIS, dispensé dans le cadre du cours de télédétection appliquée (18 février 2010) à Gembloux Agro-Bio Tech.

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See detailModelling of Forest Trees Autecology. An applied research at the Walloon Region scale (Belgium).
Ridremont, François ULg; Claessens, Hugues ULg; Lejeune, Philippe ULg et al

in Hallet, Vincent; Vanclooster, Marnik (Eds.) ENVITAM and UNITER : PhD Student Day 2010 Proceedings (2010, January 12)

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See detailModelling of Forest Trees Autecology. An applied research at the Walloon Region scale (Belgium)
Ridremont, François ULg; Claessens, Hugues ULg; Lejeune, Philippe ULg et al

Poster (2010, January 12)

Three reasons have urged the Walloon Forest Administration (Walloon Public Service) on to solicit the help of forest researchers to bring practical responses to the adaptation of its current forests ... [more ▼]

Three reasons have urged the Walloon Forest Administration (Walloon Public Service) on to solicit the help of forest researchers to bring practical responses to the adaptation of its current forests management: (i) the progression of research in applied autecology, (ii) the development of software for the management and the analysis of georeferenced data (GIS technologies) and, (iii) the awareness of the potential negative impacts of climate change on forests. To answer to this request, this research aims to model the autecology of the main forest tree species at the Walloon Region scale (Beech, Oak, Norway Spruce, Douglas-fir and valuable broadleaves species). The results will be used to update current practical tools to assess the adequacy of forest tree species on sites, especially in the climate change context. The research is built into three main steps: • update the autecology knowledge for the targeted forest tree species through a state of the art; • compile and create different ecological parameters that can explain the major part of trees growth such as climatic, topographic, geologic, edaphic and phytosociological data gathered from forest plots or geodatabases. In the context of climate change, a particular attention will be brought on bioclimatic and soil moisture conditions because of their narrow link with the potential risk of trees ecophysiological stress; • model tree species reaction to environmental conditions with tree growth indicators. Three types of indicators with different spatio-temporal scales are foreseen: stand site index (30-50 years), periodic diameter growth (5-10 years) and tree-ring growth (1-3 years). The use of these three scales is justified by the interest presented by their cross-validations which are necessary for an accurate extrapolation of results to the entire region. Results should indicate the tree species behaviour, especially towards stress conditions. The integration of climatic data, provided by global climate models based on IPCC's climate scenarios, in autecological models could be used to assess the behaviour of forest stands in future climate conditions. From those results, we expect to identify and assess accurately the risky “sites-species pairs” to avoid in the context of a sustainable silviculture. Finally, results will be used to provide autecological synthesis and practical tools to help forest managers and foresters to identify the best “site-species pairs” (tree-site adequacy maps, sites catalogue and computer platform). [less ▲]

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See detailHas the final countdown to wildlife extinction in Northern Central African Republic begun ?
Bouché, Philippe ULg; Renaud, Pierre-Cyril; Lejeune, Philippe ULg et al

in African Journal of Ecology (2010), 48(4), 1-10

The wildlife populations of Northern Central African Republic experienced precipitous declines during the 1970s and 1980s. While anecdotes coming out of the region indicate that the wildlife populations ... [more ▼]

The wildlife populations of Northern Central African Republic experienced precipitous declines during the 1970s and 1980s. While anecdotes coming out of the region indicate that the wildlife populations remain under serious threat, little is known about their status. An aerial sample count was carried out in the Northern Central African Republic at the end of the dry season in June 2005 and covered an 85,000 km2 complex landscape containing national parks, hunting reserves and community hunting areas. Results show a dramatic decline of wildlife since the previous survey in 1985. In 20 years, large mammals’ numbers decreased by 65%, probably <br />because of poaching and diseases brought by illegal cattle transhumance. Elephant (Loxodonta africana) and Buffon kob (Kobus kob) populations showed the greatest decline (over 80% each), while buffalo (Syncerus caffer), roan antelope (Hippotragus equinus) and Giant Lord’s Derby Eland (Taurotragus derbianus) populations seem stable or increasing over these last 20 years. The analysis of the wildlife population distribution by status of the different types of protected areas (national parks, hunting areas) showed that individual encounter rates of elephant and buffalo were lower in national parks than in neighbouring hunting areas, while those for roan, giraffe (Giraffa camelopardalis) and Buffon kob were higher in the national parks. [less ▲]

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See detailAnts’ survival and waste management in Myrmica rubra nests
Diez, Lise; Lejeune, Philippe ULg; Detrain, Claire

Poster (2010)

Sociality increases risks of disease transmission as genetically related individuals live in a confined environment. Therefore, social insects developed specific defences against pathogens by showing ... [more ▼]

Sociality increases risks of disease transmission as genetically related individuals live in a confined environment. Therefore, social insects developed specific defences against pathogens by showing hygienic behaviours such as the rejection of cadavers and other wastes. We investigated if the undertaking and waste management is actually an efficient way of increasing ants’ survival and of limiting pathogens transmission. First, we observed the survival curve of ant colonies that were prevented from rejecting their dead nestmates outside the nest. Colonies that were forced to keep their dead inside the nest showed increased mortality of both adults and larvae in comparison to control nests, confirming that undertaking is an effective way for improving colony’s survival. Then, we compared the rejection dynamics of single waste items (ant cadavers, preys and clay pellet) introduced into ant nests. Clay pellets were quickly rejected within 12 ± 4 minutes, cadavers were dumped outside after 139 ± 28 min and preys were eaten and rejected only after 17.3 ± 0.3 hours. Spatial localisation inside the nest also differs between different items, as most cadavers stayed far from ants’ aggregate and larvae while preys were long-eaten close to larvae and inside ants’ aggregate. These results show that cadavers and preys are managed differently before becoming contagious, thus preventing effectively pathogens transmission inside the nest. [less ▲]

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See detailSpatio-temporal patterns of preys and wastes moved by ants within the nests
Diez, Lise; Lejeune, Philippe ULg; Deneubourg, Jean-Louis et al

Poster (2010)

Living in society in a restricted and confined nest implies important organisational issues. Ants have to control food supply for the whole colony as well as nest defence but they also have to manage ... [more ▼]

Living in society in a restricted and confined nest implies important organisational issues. Ants have to control food supply for the whole colony as well as nest defence but they also have to manage everyday life tasks such as waste rejection. Within the nest, ants are faced with different items that have to be used or rejected regarding colony needs. We study whether they can discriminate between three types of items (building material, nestmate cadaver or prey) and accordingly adapt the spatio-temporal distribution of these items. Therefore, we used colonies of the ant Myrmica rubra settled in a 2-dimensional space and introduced different items in the nest centre. We show that each item triggers a specific cascade of behaviour. We observed important differences in rejection time: building items were removed within a few minutes and cadavers after a few hours while preys could be kept in the nest for a day or more. Furthermore, the movement of items by ants leads to specific spatio-temporal patterns. Building items were removed with a straight trajectory from the centre to the exit of the nest. Ant cadavers that could bear pathogens showed a trajectory avoiding and moving away from larvae that are potentially more sensitive to diseases. The moving of preys headed an oscillating pattern: these items were alternatively taken on larvae for consumption and then moved away from them, until final rejection. This specific pattern may be due to the coupled effects of groups of ants acting alternatively to feed larvae and reject waste. In the case of cadavers and building items, only undertaking ants may be active. These results suggest that each ant is able to discriminate and interact with each other leading at the collective level to a complex cascade of behaviour. [less ▲]

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See detailDynamique spatiale de rejet des déchets au sein des fourmilières Myrmica rubra
Diez, Lise; Lejeune, Philippe ULg; Detrain, Claire

Conference (2010)

La vie en société de milliers d’individus apparentés dans un milieu confiné augmente le risque de transmission des pathogènes. Par le biais de comportements hygiéniques collectifs tels quel le rejet des ... [more ▼]

La vie en société de milliers d’individus apparentés dans un milieu confiné augmente le risque de transmission des pathogènes. Par le biais de comportements hygiéniques collectifs tels quel le rejet des déchets, les insectes sociaux ont développé des défenses spécifiques contre les pathogènes. Nous avons comparé la dynamique de rejet de différents types de déchets (cadavres, proies et morceaux de vermiculite) introduits dans des nids de Myrmica rubra. L’analyse vidéo, réalisée grâce à un programme original de suivi du déchet et de digitalisation des zones de couvain, a permis un suivi précis du déplacement de ces déchets au sein du nid. La vermiculite a été rapidement rejetée après 12 ± 4 minutes, les cadavres ont été éliminés après 139 ± 28 min et les proies ont été consommées puis rejetées après 17,3 ± 0,3 heures. L’analyse spatiale des déchets a montré un déplacement rapide des cadavres loin du couvain alors que les proies étaient fréquemment apportées près des larves pour la consommation. L’efficacité de la gestion des déchets a été testée par ailleurs en comparant la survie de colonies de fourmis ayant ou non la possibilité de rejeter leurs cadavres. La mortalité des adultes et des larves vivant dans des nids contraints de garder leurs cadavres est significativement supérieure à celle observée dans les colonies contrôles, confirmant l’importance de ce rejet pour la survie et le bon état sanitaire de la fourmilière. [less ▲]

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See detailEnrichment of logging gaps with moabi (Baillonella toxisperma Pierre) in a Central African rain forest
Doucet, Jean-Louis ULg; Kouadio, Y. L.; Monticelli, D. et al

in Forest Ecology & Management (2009), 258(11), 2407-2415

Studies of regeneration in African rain forests suggest that without silvicultural treatments, natural succession in logging gaps may not result in the establishment of timber species. In this paper we ... [more ▼]

Studies of regeneration in African rain forests suggest that without silvicultural treatments, natural succession in logging gaps may not result in the establishment of timber species. In this paper we present the results of an experimental enrichment planting with moabi (Baillonella toxisperma Pierre), a valuable and important timber species harvested in Central Africa. Although forest gaps are generally considered as favourable for the regeneration of this species, a survey conducted in a forest concession in southeastern Cameroon provided an estimate of only 12.7 seedlings ha 1, suggesting that the species was, in fact, poorly represented in logging gaps within the study area. To further investigate the dynamics of the moabi in logging gaps, 795 seeds were sown in 15 logging gaps and 410 nursery-raised seedlings were planted in 15 other gaps. A biannual monitoring program over a 30-month period showed a lower survival rate for seedlings from sowing (75.9%) compared to that of nursery-raised seedlings (95.3%). Planted seedlings reached on average 229.3 cm whereas seedlings from sowing were 167.5 cmtall, with the observed difference roughly corresponding to the average height of the nursery-raised seedlings at the time they were introduced to the logging gaps. After 30 months, the diameters of planted seedlings (16.8 mm) were also greater than those of the directly sown individuals (12.5 mm). Forest gap characteristics significantly influenced the growth of the plants. Factors accounting for the differences were total solar radiation, the soil content of coarse sand, the topographic position of the gap, the vegetation cover and the density of Macaranga spp. Whilst total solar radiation had a positive influence on growth, the remaining factors had impacted growth negatively. A streamlined technique was tested by planting 7 seedlings in 250 gaps. Without additional site maintenance, 29.3% of the moabi seedlings emerged naturally from the competing vegetation after 24 months. With biannual maintenance some 89.4% of seedlings became successfully established. Clearance operations had no significant influence on the height of plants whilst plant diameter was greater in cleared gaps. The total cost of the enrichment technique was 5.5 EUR per gap without maintenance and 7.5 EUR per gap with a single maintenance measure. Whilst long-term monitoring is needed, this study suggests a high survival rate of moabi introduced in logging gaps, and a growth rate 10 times higher than previously reported under canopy cover. These findings, combined with the low costs of the enrichment technique, support the use of silvicultural measures in logging gaps to restore the forest. [less ▲]

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See detailAirborne LiDAR forest inventory: from research to operational applications
Desclée, B.; Bemelmans, V.; Bonnet, Stéphanie ULg et al

Scientific conference (2009, October)

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See detailLa fonction récréative de la forêt wallonne : évaluation et pistes de réflexion pour son intégration optimale dans l'aménagement intégré des massifs
Colson, Vincent ULg; Lejeune, Philippe ULg; Rondeux, Jacques ULg

in Forêt Wallonne (2009), (101), 3-17

Dans le contexte d’une gestion multifonctionnelle de la forêt, il importe d’intégrer la fréquentation du public dans les démarches d’aménagement. Encore faut-il pouvoir se baser sur des éléments objectifs ... [more ▼]

Dans le contexte d’une gestion multifonctionnelle de la forêt, il importe d’intégrer la fréquentation du public dans les démarches d’aménagement. Encore faut-il pouvoir se baser sur des éléments objectifs. C’est ce que propose de cerner cette synthèse d’une thèse de doctorat menée à la Faculté universitaire des Sciences agronomiques de Gembloux qui a, entre autre, révélé l’ampleur et la valeur de la fonction récréative des forêts en Wallonie. [less ▲]

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See detailEvaluation de la fonction récréative des massifs forestiers wallons
Colson, Vincent ULg; Lejeune, Philippe ULg; Rondeux, Jacques ULg

Poster (2009, June 29)

Estimer la valeur économique des visites effectuées à des fins récréatives en forêt wallonne.

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See detailAn ArcGIS-based tool for the relational data management assistance of Natura 2000 habitat units in the Walloon Region, Belgium
Barbier, Yvan ULg; Lejeune, Philippe ULg; Dufrêne, Marc ULg et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2009), 13(2), 243-248

The Natura 2000 network designation stems from two important European conservation directives (79/409/EEC and 92/43/EEC). Each EU member state was instructed to draw up a national list of Natura 2000 ... [more ▼]

The Natura 2000 network designation stems from two important European conservation directives (79/409/EEC and 92/43/EEC). Each EU member state was instructed to draw up a national list of Natura 2000 conservation sites. This has largely been done. The next step is to specify what action has to be taken and what needs to be controlled in these sites by means of specific designation acts. In the Walloon Region in Belgium, the designation acts have to include a full description of the site and the habitats composing it. For this purpose, field biologists have been making a detailed inventory of all Natura 2000 sites. Land use and habitats are mapped into a Geographic Information System (ArcGIS) and a full description of them (including information needed to describe conservation states) is stored in a relational database (Access). The main problem is ensuring data integrity between the cartographic and database systems, which are completely separate. The technical solution that has been developed is an original set of tools integrated into the ArcGIS interface. These tools offer a variety of functions that enable users to create dynamic links between ArcGIS and Access. A tool will also carry out batch synchronization between the two systems. [less ▲]

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See detailLe suivi des bandes riveraines des cours d'eau de Wallonie
Claessens, Hugues ULg; Rondeux, Jacques ULg; Debruxelles, Natacha et al

in Revue Forestière Française (2009), 61(6), 595-610

Riparian forest buffers are environments that attract much ecological, economic and social interest. For the purposes of sustainable, multi-functional management, it is very important to have an initial ... [more ▼]

Riparian forest buffers are environments that attract much ecological, economic and social interest. For the purposes of sustainable, multi-functional management, it is very important to have an initial assessment and track changes in the situation. The article presents a monitoring system developed for the 24 000 kilometres of water courses that make up the Wallonia watershed. The system is based on a hierarchical sampling plan consisting of 1 064 sample units. Various items of information about each location were collected on practically linear plots (50 metres long and a few metres wides): landscape-related observations, description of the physical status of the shores and the streams, records of targeted vegetation and description of the riparian forest buffer where applicable. By way of example, the article describes some results that relate specifically to these strips (dendrology, tree and stand measurement, continuity and structure ) on various geographical scales. [less ▲]

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See detailMap and determinants of woodlands visiting in Wallonia
Colson, Vincent ULg; Garcia, S.; Rondeux, Jacques ULg et al

in Urban Forestry and Urban Greening (2009)

The Walloon forest taken as a whole can be regarded as typical of a rural area, although its proximity to densely populated areas gives it a peri-urban character. It is visited by the local population as ... [more ▼]

The Walloon forest taken as a whole can be regarded as typical of a rural area, although its proximity to densely populated areas gives it a peri-urban character. It is visited by the local population as well as by tourists (including from neighboring countries). To provide spatial information on the level of Wallonia woodland visitation, a survey was conducted among managers of Forest Service districts (also called ‘‘cantonnements’’). The aim was to map the woodlands to show spatial patterns of visitation levels, and analyze them qualitatively to determine the influence factors. This map identifies regional hubs of recreation woodlands and, conversely, areas where the recreational function is much less important. The level of visitation was scaled in four levels ranging from low to very high. The mapping was supplemented with a statistical analysis of data collected from the forest managers and also from different GIS-layers (slope, hydrology, land use, etc.). An equation using the level of visitation as a dependent variable was fitted to a set of characteristics of the woodland with an ordered Logit model. The results show that type of ownership, type of forest, and recreational facilities significantly influence the level of woodland visitation. They also show that woodland visitors prefer any type of forest to mainly coniferous woodland. These results and the analysis of the map are particularly useful for developing forest policy and tourism as well as managing the forest. [less ▲]

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See detailDesign of a watercourse and riparian strip monitoring system for environmental management
Debruxelles, N.; Claessens, Hugues ULg; Lejeune, Philippe ULg et al

in Environmental Monitoring & Assessment (2009), 156

Watercourses are complex ecosystems where numerous economic, ecological and heritage issues converge. To ensure their efficient management it is essential to have a full description of these ... [more ▼]

Watercourses are complex ecosystems where numerous economic, ecological and heritage issues converge. To ensure their efficient management it is essential to have a full description of these multifunctional ecosystems and to know their evolution over time. This paper describes a method for monitoring watercourses and their riparian strips developed in Wallonia (southern Belgium). It is based on an inventory constructed by stratified random sampling comprising 1,071 sampling plots distributed over a total length of 24,600 km of watercourses covered from their source. Each sampling plot is surveyed and measurements and fine observations are made on watercourse segments 50 m long. The method developed, which was applied on a regional scale, could easily be transposed to other entities, from large river basins, to an entire country. Examples of results obtained from a first inventory phase demonstrate the utility of this tool designed to supply qualitative and quantitative information to assist watercourse management. [less ▲]

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See detailL'apport d'un inventaire forestier par échantillonnage à la gestion de la forêt de Soignes
Lejeune, Philippe ULg; Alderweireld, Matthieu ULg; Rondeux, Jacques ULg

in Les amis de la forêt de Soignes, (Ed.) La forêt de Soignes. Connaissances nouvelles pour un patrimoine d'avenir (2009)

To keep up with the increase and diversity of constraints to which our forests are subjected, the forest managers need to have at their disposal a panel of information more and more complete, able to ... [more ▼]

To keep up with the increase and diversity of constraints to which our forests are subjected, the forest managers need to have at their disposal a panel of information more and more complete, able to offer objective guidance in making decisions. It is within this context that the Institut Bruxellois de Gestion de l’Environnement (IBGE), an institute responsible for local environmental management, chose to equip itself with a permanent inventory of forestry samples covering amongst it the 1657 ha of the Soignes forest near Brussels. This inventory was conceived and implemented in collaboration with the Gembloux Agricultural University. It is made up of a network of observation points distributed at regular intervals throughout the forest around Brussels. No less than 400 places (circular surfaces) of a few hundred square meters each are distributed within the forest and will be subject to precise and measurable observations at regular intervals (every 4 to 8 years). These measures not only record healthy trees, but also dead trees and the biodiversity they bring, also herbaceous plants, soil conditions, topography, animal wildlife, ... Thanks to a digital database specifically devised for this inventory, the information gathered will be treated and extrapolated to offer forest wide resource data. The continuing acquisition of this detailed information together with its spatial references ensure the completeness of the inventory and will enable an analytical study of its evolution of the different parameters studied. The inventory put in place here will constitute an important source of information to those who take part in the management and more widely to the improvements of our knowledge of the forestry heritage of the region Brussels Capital. [less ▲]

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See detailOutils et procédures pour l'inventaire de chablis
Riguelle, Simon ULg; Jourez, Benoît ULg; Hebert, Jacques ULg et al

Diverse speeche and writing (2008)

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See detailDevelopment of a decision support system for setting up a wind energy policy across the Walloon Region (southern Belgium)
Lejeune, Philippe ULg; Feltz, Claude ULg

in Renewable Energy : An International Journal (2008), 33

Wallonia (the region covering southern Belgium) is committed to making a significant increase in its wind-powered electricity production capacity by 2010. Therefore, a decision support system designed to ... [more ▼]

Wallonia (the region covering southern Belgium) is committed to making a significant increase in its wind-powered electricity production capacity by 2010. Therefore, a decision support system designed to evaluate and map environmental and landscape constraints fundamental to the building of wind farms was developed for the whole Walloon Region (17,000 km2). This system is a geodatabase using 40 criteria (landscape or environmental) corresponding to three constraint levels (exclusion, highly sensitive and sensitive). This geodatabase also has analysis functions developed in the ArcGIS 9 software environment that are used to update the overall constraints map, to analyse sensitivity with respect to constraint criteria-defining parameters as well as to perform full diagnostic studies on wind farm projects. [less ▲]

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