References of "Lejeune, Philippe"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailDiscrimination of deciduous tree species from time series of unmanned aerial system imagery
Lisein, Jonathan ULg; Michez, Adrien ULg; Claessens, Hugues ULg et al

in PLoS ONE (in press)

Technology advances can revolutionize Precision Forestry by providing accurate and fine forest information at tree level. This paper addresses the question of how and particularly when Unmanned Aerial ... [more ▼]

Technology advances can revolutionize Precision Forestry by providing accurate and fine forest information at tree level. This paper addresses the question of how and particularly when Unmanned Aerial System (UAS) should be used in order to efficiently discriminate deciduous tree species. A time series of high resolution UAS imagery was collected to cover the growing season from leaf flush to leaf fall. Full benefit was taken of the temporal resolution of UAS acquisition, one of the most promising features of small drones. The disparity in forest tree phenology is at the maximum during early spring and late autumn. But the phenology state that optimized the classification result is the one that minimizes the spectral variation within tree species groups and, at the same time, maximizes the phenologic differences between species. Sunlit tree crowns (5 deciduous species groups) were classified using a Random Forest approach for monotemporal, two-date and three-date combinations. The end of leaf flushing was the most efficient single-date time window. Multitemporal datasets definitely improve the overall classification accuracy. But single-date high resolution orthophotomosaics, acquired on optimal time-windows, result in a very good classification accuracy (overall out of bag error of 16%). [less ▲]

Detailed reference viewed: 41 (15 ULg)
Full Text
See detailGuide d'utilisation - Grille : Plugin de création de grilles d'échantillonnage pour le logiciel QGIS
Handerek, Daphné ULg; De Thier, Olivier ULg; Modave, Maxime et al

Learning material (2015)

Manuel d'utilisation du plugin grille pour QGIS.

Detailed reference viewed: 46 (4 ULg)
Full Text
See detailGrille : Plugin de création de grilles d'échantillonnage pour le logiciel QGIS
De Thier, Olivier ULg; Handerek, Daphné ULg; Modave, Maxime et al

Software (2015)

Le plugin Grille pour QGIS est destiné à définir et créer des grilles d’échantillonnage dans le cadre d’inventaires et de recensements appliqués à la gestion des ressources naturelles.

Detailed reference viewed: 43 (9 ULg)
Full Text
See detailForEstimator
Dedry, Laurent ULg; De Thier, Olivier ULg; Perin, Jérôme ULg et al

Software (2015)

ForEstimator est un plugin (une extension) QGIS qui permet d'estimer la hauteur dominante de peuplements résineux en Wallonie.

Detailed reference viewed: 80 (15 ULg)
Full Text
Peer Reviewed
See detailA novel procedure to measure shrinkage-free tree-rings from very large wood samples combining photogrammetry, high-resolution image processing, and GIS tools
Latte, Nicolas ULg; Beeckman, Hans; Bauwens, Sébastien ULg et al

in Dendrochronologia (2015), 34

We present a new procedure for wood sampling and tree-ring measurement that can be used for dendrochronological investigation on very large trees, specifically adapted for tropical rainforest species ... [more ▼]

We present a new procedure for wood sampling and tree-ring measurement that can be used for dendrochronological investigation on very large trees, specifically adapted for tropical rainforest species. This procedure takes advantage of the technological developments in computing, image processing, and geographic information systems (GIS) to overcome the technical limitations of the currently used methods. Two types of wood samples can be used (stem disks and/or bars) depending on tree diameter, and the difficulty of ring delineation and crossdating. Bars are an effective compromise between cores and disks. We developed an application combining several programs (Excel, R, ArcGIS, and MapWinGIS) in the Windows operating system for semi-automatic measurement of tree-rings from high-resolution images of the sanded cross-section. Using an innovative method to reverse the wood shrinkage resulting from the drying process, tree-ring measurement can be performed on shrinkage-free images, thus referring to the actual growth of the tree. [less ▲]

Detailed reference viewed: 31 (10 ULg)
Full Text
See detailDétection de l'érosion dans un bassin versant agricole par comparaison d'images multidates acquises par drone
Lisein, Jonathan ULg; Pineux, Nathalie ULg; Pierrot-Deseilligny, marc et al

Scientific conference (2015, March 26)

Detailed reference viewed: 35 (1 ULg)
Full Text
Peer Reviewed
See detailHow Tightly Linked Are Pericopsis elata (Fabaceae) Patches to Anthropogenic Disturbances in Southeastern Cameroon?
Bourland, Nils; Cerisier, François; Daïnou, Kasso ULg et al

in Forests (2015), 6(2), 293-310

While most past studies have emphasized the relationships between specific forest stands and edaphic factors, recent observations in Central African moist forests suggested that an increase of slash-and ... [more ▼]

While most past studies have emphasized the relationships between specific forest stands and edaphic factors, recent observations in Central African moist forests suggested that an increase of slash-and-burn agriculture since 3000–2000 BP (Before Present) could be the main driver of the persistence of light-demanding tree species. In order to examine anthropogenic factors in the persistence of such populations, our study focused on Pericopsis elata, an endangered clustered timber species. We used a multidisciplinary approach comprised of botanical, anthracological and archaeobotanical investigations to compare P. elata patches with surrounding stands of mixed forest vegetation (“out-zones”). Charcoal samples were found in both zones, but were significantly more abundant in the soils of patches. Eleven groups of taxa were identified from the charcoals, most of them also present in the current vegetation. Potsherds were detected only inside P. elata patches and at different soil depths, suggesting a long human presence from at least 2150 to 195 BP, as revealed by our charcoal radiocarbon dating. We conclude that current P. elata patches most likely result from shifting cultivation that occurred ca. two centuries ago. The implications of our findings for the dynamics and management of light-demanding tree species are discussed. [less ▲]

Detailed reference viewed: 9 (0 ULg)
Full Text
Peer Reviewed
See detailAgent-based modelling of the spatial pattern of leisure visitation in forests: A case study in Wallonia, south Belgium
Li, Sen; Colson, Vincent; Lejeune, Philippe ULg et al

in Environmental Modelling & Software (2015), 71

The leisure use of forests is a fast growing sector in European tourism. The difficulties in monitoring real usage pattern have hindered communications in tourism, conservation and public health in ... [more ▼]

The leisure use of forests is a fast growing sector in European tourism. The difficulties in monitoring real usage pattern have hindered communications in tourism, conservation and public health in forested areas. In this study, we present an agent-based model to approximate forest visit patterns at the regional level, based on the visitor, residential and forest attributes. The model was then adapted locally for Wallonia, south Belgium, to predict the daily distribution of forest visits and visitor flows. The results suggest high visit rates in urban forests. In highly attractive forests that are distant from major cities, the visit rates may greatly respond to the visitor-level and environmental changes. Future empirical investigations are encouraged to build a cross-contextual understanding on visitors' decision-making mechanisms and to identify how these mechanisms may be influenced by environmental factors operating at different spatio-temporal levels. [less ▲]

Detailed reference viewed: 36 (2 ULg)
Full Text
See detailNew technologies in conservation: monitoring African wildlife with UAS
Linchant, Julie ULg; Semeki, Jean; Lejeune, Philippe ULg et al

Conference (2014, December 13)

In the vast protected areas of Africa, traditional wildlife surveys performed by plane or foot are logistically difficult to implement due to the lack of means and appropriate materials. Moreover, the ... [more ▼]

In the vast protected areas of Africa, traditional wildlife surveys performed by plane or foot are logistically difficult to implement due to the lack of means and appropriate materials. Moreover, the possibilities of encountering poachers in the field pose a serious risk to the monitoring teams. Over the last decade, civilian UAS (Unmanned Aerial Systems) boomed in natural resource monitoring. One of the biggest challenges of the UAS is to replace traditional wildlife censuses for the application of wildlife conservation. Parameters have to be approached in a different way than before. We performed test flights in the open savannah of the Garamba National Park during the wet season using the Falcon Unmanned UAS. Both photos (Sony Nex7, 24Mp) and videos, including thermal infrared videos (Tamarisk 640x480), have been used. Flight altitude ranged from 50 to 200m and pictures showed that animals can be effectively detected at 100m. We spotted elephants, hippopotamus and buffaloes as well as other smaller species such as hartebeests, kobs and warthogs. Thermal videos gave medium quality results during the day due to the heat but performed well during the night. The limited range and endurance of the UAS suggest a rethink of the usual census protocols. We therefore tested new flight plans in a rosette shape to take advantage of the higher points in the park, with transects having the length of the maximal range. Twelve transects of 10km can be covered in half a day with pictures covering a 15.6km² area. Human activities could also be detected. Pictures showed areas burned by poachers and the thermal infrared camera allows the detection of fires from a high altitude. Future developments need to be investigated such as automatic detection to review the huge amount of data collected and statistical methods must be adapted to those challenging situations. [less ▲]

Detailed reference viewed: 41 (10 ULg)
Full Text
Peer Reviewed
See detailForest inventory with Terrestrial LiDAR: what about Hand-Held Mobile LiDAR?
Bauwens, Sébastien ULg; Bartholomeus, Harm; Piboule, Alexandre et al

Conference (2014, November 05)

For a decade, studies of the application of static Terrestrial Laser Scanner (TLS) in plotwise forest inventories are giving more and more effective results. In spite of the improvements occurring in ... [more ▼]

For a decade, studies of the application of static Terrestrial Laser Scanner (TLS) in plotwise forest inventories are giving more and more effective results. In spite of the improvements occurring in processing scan data to extract forest attributes, the occlusion effect is still limiting the processing efficiency. A multi-scan approach is recommended to reduce this effect. However, such approach needs pre-scan preparations (setting up the plot, targets positioning), it requires data registration and it comes at a higher data collection cost. In this study we explore the potential of a Hand-held mobile LiDAR System (HMLS) as new LiDAR tool to scan forest plots. HMLS data are compared to static TLS data (single and multi-scan) in terms of data acquisition, registration time and quality of automatic DBH extraction. The low weight, small size of the instrument and no targets requirements reduce the time of pre-scan preparations to the time needed for single scan which is 6 times less than scanning a plot with 5 scans. The registration time depends of the time spent to scan the plot and it is of the same magnitude than single scan. The resulting point cloud of the HMLS is noisier than TLS point clouds. Nevertheless, error on DBH estimations is similar to scanning a plot with a TLS positioned at 5 locations. RMSE is higher than multi-scan and close to single scan for trees detected by the both LiDAR technologies. This first study exhibits the high potential of HMLS by its simple use, which needs only one operator while presenting similar results in automatic DBH extraction than static TLS. Technology and registering method improvements of this type of mobile LiDAR will reduce the noise of the point cloud, which might reduce the DBH RMSE. [less ▲]

Detailed reference viewed: 88 (19 ULg)
Full Text
See detailHow to survey your hippos night and day? Follow them in bed with drones!
Linchant, Julie ULg; Lejeune, Philippe ULg; Vermeulen, Cédric ULg

Scientific conference (2014, October 20)

Detailed reference viewed: 46 (5 ULg)
Full Text
Peer Reviewed
See detailSeasonal variations of wild boar Sus scrofa distribution in agricultural landscapes: a species distribution modelling approach
Morelle, Kevin ULg; Lejeune, Philippe ULg

in European Journal of Wildlife Research (2014)

Seasonal changes in the distribution of animals can have an important impact on the ecosystem. In agricultural landscapes, the seasonal movement of the wild boar Sus scrofa towards field crops often ... [more ▼]

Seasonal changes in the distribution of animals can have an important impact on the ecosystem. In agricultural landscapes, the seasonal movement of the wild boar Sus scrofa towards field crops often results in damages and makes control of the population difficult. The plasticity of the species to cope with different habitats is largely proven, but the environmental and human drivers of this seasonal habitat shift at the population scale remain largely unknown. Using MaxEnt and two seasonally distinct presence datasets, we contrasted the distribution of wild boar in southern Belgium during the growing and hunting seasons to (i) analyse seasonal drivers of the distribution and (ii) forecast the potential spread of the species north to its current distribution. We demonstrated that during the growing season, wild boar range almost double, owing to the cover and food provided by agricultural areas, thereby enhancing the movement and spread of the species. We found that the seasonal distribution of wild boar in agricultural lands is mostly influenced by the search for cover and food provided alternatively by forest and field crops. Interestingly, it seems that this search for cover operates under the constraint of a threshold distance. Our results indeed reveal an increased probability of presence not only in the vicinity of forests but also above a threshold distance of 865 m from the forest edge, suggesting that wild boar can overcome the dependence to forest cover. The forecast distribution of wild boar highlighted a potential increase of the current range into suitable habitat between 63 and 168 km2. To counteract the potential spread of the species into agricultural habitats and the consecutive damages, we insist on the need for the development of integrated management strategies, combining land use spatial configuration and wild boar spatial behaviour. [less ▲]

Detailed reference viewed: 36 (17 ULg)
Full Text
See detailI know what you did last summer - High resolution mapping of wild boar damages with drones
Michez, Adrien ULg; Morelle, Kevin ULg; Lehaire, François ULg et al

Poster (2014, September 01)

Wild boar ability to cause important damages to agricultural lands is not anymore to be demonstrated. These damages often raise conflicts between farmers and hunters due to the associated economic losses ... [more ▼]

Wild boar ability to cause important damages to agricultural lands is not anymore to be demonstrated. These damages often raise conflicts between farmers and hunters due to the associated economic losses. Objective and accurate method for real impact assessment of losses suffered by farmers is thus needed. Currently,in Wallonia damage assessment is performed from the ground by experts, asked to evaluate precisely the area impacted. This task is time and man power consuming. Moreover, damaged areas are often large and consequently, sampling is mandatory and can induce accuracy issues. Recent development of unmanned aerial vehicle (UAV / drone) toghether with lower cost and better accessibility for civil society and scientific community, makes now possible the use of this technology for wildlife researches. Through photogrammetric 3D reconstruction of the field crop, UAV can allow to objectively and precisely measure the area impacted by wild boar damages. In a context of increasing issues caused by wild boar to agriculture, and the need for stakeholders for accurate impact assessment, we tested an innovative approach to estimate more effectively the area impacted by wild boar. [less ▲]

Detailed reference viewed: 124 (15 ULg)
Full Text
See detailLes drones au secours de la grande faune menacée de RDC
Linchant, Julie ULg; Lejeune, Philippe ULg; Vermeulen, Cédric ULg

in Parcs et Réserves (2014), 69(3), 5-13

Dans un contexte international de pressions de plus en plus intenses sur la faune sauvage, caractérisées notamment par une recrudescence intense du braconnage, le suivi régulier de la faune est essentiel ... [more ▼]

Dans un contexte international de pressions de plus en plus intenses sur la faune sauvage, caractérisées notamment par une recrudescence intense du braconnage, le suivi régulier de la faune est essentiel pour assurer sa conservation. La situation de la biodiversité en République Démocratique du Congo est particulièrement préoccupante suite aux nombreux conflits armés et aux pressions anthropiques qui en découlent, ainsi qu’au manque de moyens et d’investissement. Habituellement, le suivi de la faune est réalisé à l’aide d’inventaires pédestres et aériens. Cependant, ces méthodes font face à de nombreuses contraintes, notamment leur coût et la logistique importante qu’elles demandent. Elles sont aussi dangereuses pour les opérateurs, ces derniers risquant leur vie lors d’accidents de vol ou lors de rencontres avec des braconniers ou des animaux potentiellement dangereux. Dans ce contexte, l’utilisation des drones civils, actuellement en pleine expansion, représente une alternative aux méthodes classiques pour le suivi de la grande faune et la surveillance des aires protégées. En effet, cette nouvelle technologie présente un coût plus faible, une logistique facile et une prise en main rapide, ainsi qu’un minimum de risque pour les opérateurs. Néanmoins, elle en est à ses balbutiements et de nouvelles méthodes de suivi doivent être mises au point pour relever le défi imposé par les contraintes liées à ce matériel innovant, tels que la faible autonomie et le traitement de grands volumes de données. L’Université de Liège-Gembloux Agro-Bio Tech a bâti, en partenariat avec le CIFOR, le projet WiMUAS visant à développer ces nouvelles méthodes dans le cadre des aires protégées en RDC. Cet article s’appuie sur une revue bibliographique récente pour en présenter les trois principaux objectifs en regard des développements existants : - (i) la mise au point de nouvelles méthodes d’inventaire et de suivis ponctuels de la grande faune par analyse d’images et de vidéos obtenues par drone ; - (ii) la gestion des périphéries et activités illégales notamment grâce à la cartographie précise de ces activités qui peut être obtenue via l’imagerie drone ; - (iii) la lutte anti-braconnage qui pourrait être appuyée par une reconnaissance du terrain par drone pour rechercher et fournir des indices en limitant la mise en danger des gardes. [less ▲]

Detailed reference viewed: 99 (14 ULg)
Full Text
Peer Reviewed
See detailIs wild boar heading towards movement ecology? A review of trends and gaps
Morelle, Kevin ULg; Lehaire, François ULg; Lejeune, Philippe ULg

in Wildlife Biology (2014), 20(4), 196-205

Detailed reference viewed: 17 (10 ULg)
Full Text
Peer Reviewed
See detailKeep the nest clean: survival advantages of corpse removal in ants
Diez, Lise; Lejeune, Philippe ULg; Detrain, Claire

in Biology Letters (2014), 10(7),

Sociality increases exposure to pathogens. Therefore, social insects have developed a wide range of behavioural defences, known as ‘social immunity’. However, the benefits of these behaviours in terms of ... [more ▼]

Sociality increases exposure to pathogens. Therefore, social insects have developed a wide range of behavioural defences, known as ‘social immunity’. However, the benefits of these behaviours in terms of colony survival have been scarcely investigated. We tested the survival advantage of prophylaxis, i.e. corpse removal, in ants. Over 50 days, we compared the survival of ants in colonies that were free to remove corpses with those that were restricted in their corpse removal. From Day 8 onwards, the survival of adult workers was significantly higher in colonies that were allowed to remove corpses normally. Overall, larvae survived better than adults, but were slightly affected by the presence of corpses in the nest. When removal was restricted, ants removed as many corpses as they could and moved the remaining corpses away from brood, typically to the nest corners. These results show the importance of nest maintenance and prophylactic behaviour in social insects. [less ▲]

Detailed reference viewed: 29 (5 ULg)
Full Text
See detailDétection de l'érosion dans un bassin versant agricole par comparaison d'images multidates acquises par drone
Lisein, Jonathan ULg; Pineux, Nathalie ULg; Pierrot-Deseilligny, Marc et al

Conference (2014, June 26)

Detailed reference viewed: 81 (14 ULg)