References of "Lejeune, Philippe"
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See detailModelling the top-height growth and site index of Norway spruce in Southern Belgium
Perin, Jérôme ULg; Hebert, Jacques ULg; Brostaux, Yves ULg et al

in Forest Ecology & Management (2013), 298

Top-height growth in even-aged stands of Norway spruce (Piceaabies (L.) Karst.) from Southern Belgium was modelled using functions which provide an algebraic solution for site index (SI) calculation. 16 ... [more ▼]

Top-height growth in even-aged stands of Norway spruce (Piceaabies (L.) Karst.) from Southern Belgium was modelled using functions which provide an algebraic solution for site index (SI) calculation. 16 well known growth model formulations were parameterized using a method which accounts for heterogeneous variance and autocorrelation on a dataset composed of stem analysis data completed by measuring the heights of all the branch whorls to allow for accurate height–age estimates. Comparison of the parameterized models showed that the oblique asymptotic function known as the Duplat and Tran-Ha III model was the most efficient on our dataset. Validation of the selected model on permanent sample plot data showed no evidence of bias over the full range of possible age, height, site index and densities encountered in Norway spruce stands of Southern Belgium. The new height growth model described represents a significant improvement over the previous model of Dagnelie et al. (1988), which was found to be unreliable and required the use of an iterative process to estimate SI. [less ▲]

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See detailGradient urbain-rural de la ville de Lubumbashi: dynamique entre 2002 et 2009
Andre, Marie ULg; Bogaert, Jan ULg; Mahy, Grégory ULg et al

in Ernoult, Aude (Ed.) Dynamiques écologiques des paysages: de l'agricole à l'urbain (2013, June 12)

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See detailDescription of a new procedure to estimate the carbon stocks of all forest pools and impact assessment of methodological choices on the estimates
Latte, Nicolas ULg; Colinet, Gilles ULg; Fayolle, Adeline ULg et al

in European Journal of Forest Research (2013), 132

Forest ecosystems play a major role in atmospheric carbon sequestration and emission. Comparable organic carbon stock estimates at temporal and spatial scales for all forest pools are needed for ... [more ▼]

Forest ecosystems play a major role in atmospheric carbon sequestration and emission. Comparable organic carbon stock estimates at temporal and spatial scales for all forest pools are needed for scientific investigations and political purposes. Therefore, we developed a new carbon stock (CS) estimation procedure that combines forest inventory and soil and litter geodatabases at a regional scale (southern Belgium). This procedure can be implemented in other regions and countries on condition that available external carbon soil and litter data can be linked to forest inventory plots. The presented procedure includes a specific CS estimation method for each of the following forest pools and subpools (in brackets): living biomass (aboveground and belowground), deadwood (dead trees and snags, coarse woody debris and stumps), litter, and soil. The total CS of the forest was estimated at 86 Tg (185 Mg ha-1). Soil up to 0.2 m depth, living biomass, litter, and deadwood CSs account, respectively, for 48, 47, 4, and 1 % of the total CS. The analysis of the CS variation within the pools across ecoregions and forest types revealed in particular that: (1) the living biomass CS of broadleaved forests exceeds that of coniferous forests, (2) the soil and litter CSs of coniferous forest exceed those of broadleaved forests, and (3) beech stands come at the top in carbon stocking capacity. Because our estimates differ sometimes significantly from the previous studies, we compared different methods and their impacts on the estimates. We demonstrated that estimates may vary highly, from -16 to ?12 %, depending on the selected methods. Methodological choices are thus essential especially for estimating CO2 fluxes by the stock change approach. The sources of error and the accuracy of the estimates were discussed extensively. [less ▲]

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See detailPrincipes de base de la télédétection et ses potentialités comme outil de caractérisation de la ressource forestière – II. LiDAR aérien
Bonnet, Stéphanie ULg; Toromanoff, François ULg; Bauwens, Sébastien ULg et al

in Forêt Wallonne (2013), (124), 28-41

La télédétection a déjà démontré, au travers de nombreuses études, son potentiel de caractérisation de la ressource forestière. En particulier, le développement du LiDAR aérien a ouvert la voie à de ... [more ▼]

La télédétection a déjà démontré, au travers de nombreuses études, son potentiel de caractérisation de la ressource forestière. En particulier, le développement du LiDAR aérien a ouvert la voie à de nouvelles perspectives. Cette technologie offre une vision tridimensionnelle de la forêt qui permet de récolter à large échelle des informations à l'intérieur même des peuplements. Après avoir présenté les grands principes de télédétection dans un premier article (Forêt Wallonne n°114), ce second volet présente quelques concepts de base pour se familiariser avec le LiDAR et illustre son intérêt pour la gestion des forêts et des milieux naturels aux travers de travaux de recherche menés sur une zone pilote constituée par le bassin versant de la Houille dans la région de Gedinne en Province de Namur. [less ▲]

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See detailSpecies delimitation and diversification in the widespread tree genus Milicia (Moraceae)
Daïnou, Kasso ULg; Mahy, Grégory ULg; Duminil, Jérôme et al

Conference (2013, June)

The long generation time and large effective size of widespread forest tree species can result in slow evolutionary rate and incomplete lineage sorting, complicating species delimitation. We addressed ... [more ▼]

The long generation time and large effective size of widespread forest tree species can result in slow evolutionary rate and incomplete lineage sorting, complicating species delimitation. We addressed this issue with the African timber tree genus Milicia that comprises two morphologically similar and often confounded species: M. excelsa, widespread from West to East Africa, and M. regia, endemic to West Africa. We combined information from nuclear microsatellites (nSSRs), nuclear and plastid DNA sequences, and morphological systematics to identify significant evolutionary units and infer their evolutionary and biogeographical history. We detected five geographically coherent genetic clusters using nSSRs and three levels of genetic differentiation. First, one West African cluster matched perfectly with the morphospecies M. regia, which formed a monophyletic clade at both DNA sequences. Second, a West African M. excelsa cluster formed a monophyletic group at plastid DNA and was more related to M. regia than to Central African M. excelsa, but shared many haplotypes with the latter at nuclear DNA. Third, three Central African clusters appeared little differentiated and shared most of their haplotypes. Although gene tree paraphyly could suggest a single species in Milicia following the Phylogenetic Species Concept, the existence of mutual haplotypic exclusivity and non-admixed genetic clusters in the contact area of the two taxa indicate strong reproductive isolation, and thus, two species following the Biological Species Concept. Molecular dating of the first divergence events showed that speciation in Milicia is ancient (Tertiary), indicating that long-living tree taxa exhibiting genetic speciation may remain similar morphologically. [less ▲]

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See detailLa photogrammétrie: un procédé pour mesurer les arbres à troncs irréguliers
Bauwens, Sébastien ULg; Fayolle, Adeline ULg; Nzenga, Alide Kidimbu et al

Conference (2013, April)

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See detailLes équations allométriques pan-tropicales plurispécifiques sont-elles valables en Afrique centrale ?
Fayolle, Adeline ULg; Doucet, Jean-Louis ULg; Gillet, Jean-François ULg et al

in Picard, Nicolas; Henry, Mathieu (Eds.) Compte-rendu de l'Atelier scientifique régional sur les équations allométriques en Afrique Centrale : PREREDD, Yaoundé 2-5 avril 2013 (2013, April)

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See detailCollisions entre véhicules et animaux en liberté : état des lieux à partir d'une enquête au sein de la police
Lehaire, François ULg; Morelle, Kevin ULg; Lejeune, Philippe ULg

in Forêt Wallonne (2013), 122

Les accidents de la route impliquant des animaux sauvages sont de plus en plus nombreux. En se basant sur les données recueillies par les zones de police en Wallonie, il est possible d’avoir une vision ... [more ▼]

Les accidents de la route impliquant des animaux sauvages sont de plus en plus nombreux. En se basant sur les données recueillies par les zones de police en Wallonie, il est possible d’avoir une vision plus claire de la problématique. Dans le cas du cerf et du sanglier, il apparaît clairement que la hausse des accidents est liée à l’augmentation de leurs populations. [less ▲]

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See detailUnmanned aerial survey of elephants
Vermeulen, Cédric ULg; Lejeune, Philippe ULg; Lisein, Jonathan ULg et al

in PLoS ONE (2013), 8(2),

The use of a UAS (Unmanned Aircraft System) was tested to survey large mammals in the Nazinga Game Ranch in the south of Burkina Faso. The Gatewing ×100™ equipped with a Ricoh GR III camera was used to ... [more ▼]

The use of a UAS (Unmanned Aircraft System) was tested to survey large mammals in the Nazinga Game Ranch in the south of Burkina Faso. The Gatewing ×100™ equipped with a Ricoh GR III camera was used to test animal reaction as the UAS passed, and visibility on the images. No reaction was recorded as the UAS passed at a height of 100 m. Observations, made on a set of more than 7000 images, revealed that only elephants (Loxodonta africana) were easily visible while medium and small sized mammals were not. The easy observation of elephants allows experts to enumerate them on images acquired at a height of 100 m. We, therefore, implemented an aerial strip sample count along transects used for the annual wildlife foot count. A total of 34 elephants were recorded on 4 transects, each overflown twice. The elephant density was estimated at 2.47 elephants/km2 with a coefficient of variation (CV%) of 36.10%. The main drawback of our UAS was its low autonomy (45 min). Increased endurance of small UAS is required to replace manned aircraft survey of large areas (about 1000 km of transect per day vs 40 km for our UAS). The monitoring strategy should be adapted according to the sampling plan. Also, the UAS is as expensive as a second-hand light aircraft. However the logistic and flight implementation are easier, the running costs are lower and its use is safer. Technological evolution will make civil UAS more efficient, allowing them to compete with light aircraft for aerial wildlife surveys. [less ▲]

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See detailTree allometry in Central Africa: Testing the validity of pantropical multi-species allometric equations for estimating biomass and carbon stocks
Fayolle, Adeline ULg; Doucet, Jean-Louis ULg; Gillet, Jean-François ULg et al

in Forest Ecology & Management (2013), (305), 29-37

There is a lot of uncertainty in the amount and spatial variations of above-ground biomass in Africa, partly because very few allometric equations are available. The aim of this study was to assess the ... [more ▼]

There is a lot of uncertainty in the amount and spatial variations of above-ground biomass in Africa, partly because very few allometric equations are available. The aim of this study was to assess the validity of using pan-tropical multispecies allometric equations developed by Chave et al. (2005) for estimating the above-ground biomass of trees in Central Africa and/or to develop site-specific equations. The study was conducted in lowland tropical forests of South-eastern Cameroon, at the edge between evergreen and semi-evergreen forests. Data of above-ground woody biomass were obtained from destructive sampling of 138 trees belonging to 47 taxa across a huge range of diameter (5.30–192.50 cm) and wood specific gravity (0.284–1.152 g cm 3). A set of local site-specific multi- and single-species models relating above-ground biomass to tree diameter and wood specific gravity were fitted to the data. The best model was selected using information criterion. Both tree diameter and wood specific gravity were important predictor to consider for the estimation of above-ground biomass at tree scale. Single-species models were not necessarily better than multi-species models including wood specific gravity as a predictor. The best local multi-species model had the same structure and parameters as the pan-tropical equation developed by Chave et al. (2005) for moist forests. The estimates from the pan-tropical multi-species equation were nearly as good as those of the local multi-species equation. Using wood specific gravity from the global data base only slightly increased the estimation errors, because for the study taxa wood specific gravity was highly correlated to wood specific gravity from the global data base. In this study, we showed that the pantropical multi-species allometric equation developped for moist forests can be used to produce accurate estimates of biomass and carbon stocks from diameter measurement in forest inventory and wood specific gravity from global data base at species level. These findings are especially timely given the urgent need to quantify biomass and carbon stocks in the tropics, and given the spatial extent of moist forests in Central Africa. [less ▲]

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See detailModeling recent bark stripping by red deer (Cervus elaphus) in South Belgium coniferous stands
Ligot, Gauthier ULg; Gheysen, Thibaut; Lehaire, François ULg et al

in Annals of Forest Science : a Multidisciplinary and International Journal (2013), 70(3),

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See detailRéviser les tarifs de cubage pour mieux gérer les forêts du Cameroun
Fayolle, Adeline ULg; Rondeux, Jacques ULg; Doucet, Jean-Louis ULg et al

in Bois et Forêts des Tropiques (2013), 317(3), 35-49

Volume tables are routinely used by forest planners and managers, but generally with no regard for the conditions in which they are applied (geographical zone, diameter range), which can cause errors in ... [more ▼]

Volume tables are routinely used by forest planners and managers, but generally with no regard for the conditions in which they are applied (geographical zone, diameter range), which can cause errors in estimations of timber volumes. The aim of this study is to test the validity of currently available volume tables, including those used by the government, for three commercial tree species in the forests of south-eastern Cameroon, and if required to propose tables suited to the study zone. The three species concerned are sapelli, Entandrophragma cylindricum, tali, Erythrophleum suaveolens, and assamela Pericopsis elata. Dendrometric data were collected by destructive sampling of 43 trees that were evenly distributed across the diameter range. Stemwood volume was calculated through successive butt-log measurements and linear and non-linear volume tables were adjusted by means of the weighted least-squares method. The results show that the best volume tables for all three species are non-linear. The equations used by the forests authority until now significantly under-estimate standing timber volumes and the estimation errors increase with the size of the trees. The proposed volume tables, once validated, should in future produce more accurate estimations of standing timber in the study zone. Given the international challenges involving Cameroon (FLEGT and REDD+), it is essential that it should have effective tools for estimating standing timber volumes. It is therefore important for Cameroon’s forests authority to conduct a large-scale programme to revise its volume tables. [less ▲]

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See detailWho brings out the dead ? Necrophoresis in the red ant, Myrmica rubra
Diez, Lise; Le Borgne, Hélène; Lejeune, Philippe ULg et al

in Animal Behaviour (2013)

The division of labour plays a major role in the success of social insects. For instance, through social prophylaxis, the spread of pathogens within the colony can be reduced if corpse removal is the ... [more ▼]

The division of labour plays a major role in the success of social insects. For instance, through social prophylaxis, the spread of pathogens within the colony can be reduced if corpse removal is the concern of a specialized group of ants. However, in relatively small colonies, the number of dead individuals and the amount of waste may be too low to justify a specialized group of corpse carriers. We examined the corpse removal habits of the common red ant, Myrmica rubra. Ants acting as corpse carriers were not strictly specialized in corpse management, but split their time between disposing of the dead and foraging. Some corpse-carrying individuals, however, developed a short-term specialization by making several successive corpse transports. Corpse carriers limited cross-contamination by remaining mostly outside the nest and congregating near the nest entrance when resting inside. [less ▲]

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See detailSpatio-temporal patterns of wildlife-vehicle collisions in a region with a high-density road network
Morelle, Kevin ULg; Lehaire, François ULg; Lejeune, Philippe ULg

in Nature Conservation (2013), (5), 53-73

This paper is the first to report data on wildlife-vehicle collisions (WVC) in Wallonia, southern Belgium, characterised by one of the densest road network worldwide. With the collaboration of police we ... [more ▼]

This paper is the first to report data on wildlife-vehicle collisions (WVC) in Wallonia, southern Belgium, characterised by one of the densest road network worldwide. With the collaboration of police we identified 3965 accidents involving “free ranging animal” between 2003 and 2011. We observed that these accidents with free ranging animals result in 13% of cases in injuries for the drivers or passengers, and in less than 1% of cases in fatalities (death). 78% of these casualties involve wild animals, among which wild boar take the largest part (39% ). During the covered period we observed an annual increase of WVC of 21%. For wild boar and red deer, this increase was significantly correlated with hunting statistics, used as an index of population density. The temporal analysis demonstrated an increase of WVC during night time with peak of accidents at dusk and dawn. Monthly distribution revealed the role of breeding, dispersal and hunting in shaping temporal patterns of accidents. Spatial analysis, focusing on wild boar, roe deer, red deer and red fox demonstrated clustering of accidents for all these species, until scale between 20 to 70 km. Mapping of accidents via Kernel density analysis permitted us to highlight areas with high risk of WVC risk. Our study suggests that the problem of car accidents due to wildlife is an increasing concern in Wallonia but results on spatial and temporal patterns should help for setting up mitigation measures in the most sensible areas. Moreover we suggest that police data source should be used for nationwide analysis and for comparison between countries. [less ▲]

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See detailEvaluation de la ressource en teck, Tectona grandis L.f., des plantations privées du Sud-Bénin
Atindogbé, Gilbert; Fonton, Noël, Houédougbé; Lejeune, Philippe ULg

in Bois et Forêts des Tropiques (2013), (316(2)), 93-103

Private teak plantations in southern Benin have been established at an increasing rate in the last thirty years. To remedy the lack of reliable information on this resource, a methodological approach was ... [more ▼]

Private teak plantations in southern Benin have been established at an increasing rate in the last thirty years. To remedy the lack of reliable information on this resource, a methodological approach was designed to quantify and characterise private teak plantations and gain a better understanding of the private owners involved in teak production in Benin. The method involves “snowball sampling” among three categories of players: forestry service agents, village chiefs and the owners of teak plantations or their representatives. The data collected are the socio-economic profiles of the owners, an overall description of their plantations and dendrometric characterisations of these plantations. In order to assess its performance, the snowball sampling technique was tested by the quadrant method. Snowball sampling identified 1,002 owners and 861.10 ha of Tectona grandis L.f. plantations. Almost 69 % of the plantations were less than 6 years of age, of which 12.4 % were young plantations and 56.7 % coppice. Stands more than 20 years of age accounted for only a very small proportion of these teak resources (0.2 %). With a very low overall afforestation rate, estimated at 3.58 %, and a snowball sampling detection rate of 68.6%, the total area planted with teak was estimated at 1,255.3 ha, within confidence limits of 1,084.5 ha and 1,574.2 ha. The geodatabase built up during the snowball sampling campaign in the Toffo municipality is clearly a promising start for the development of a network of players involved in teak production. The value of snowball sampling in the context of small-scale sylviculture warrants its application to the other municipalities concerned. [less ▲]

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See detailAnalyse de l'évolution de la surface de la forêt wallonne par interprétation d'images aériennes : un outil complémentaire à l'inventaire forestier régional
Lejeune, Philippe ULg; Alderweireld, Matthieu ULg; Lecomte, Hugues et al

in Forêt Wallonne (2013), (125), 27-35

L'analyse des images aériennes vient en complément des données recueillies par l'inventaire permanent des ressources forestières. L'objectif est d'obtenir des données plus fréquemment actualisées en ce ... [more ▼]

L'analyse des images aériennes vient en complément des données recueillies par l'inventaire permanent des ressources forestières. L'objectif est d'obtenir des données plus fréquemment actualisées en ce qui concerne les proportions et les surfaces de mises à blanc, l'âge d'exploitation et les surfaces de plantation. [less ▲]

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See detailG-Cube 2.0 : Un logiciel de cubage et de constitution de lots de bois
Handerek, Daphné ULg; Quevauvillers, Samuel ULg; Hebert, Jacques ULg et al

in Forêt Wallonne (2013), (124), 20-27

G-Cube, le logiciel de cubage et de constitution de lots de bois développé par Gembloux Agro-Bio Tech, fait peau neuve. Cette version 2.0 voit arriver des nouveautés parmi lesquelles : la géolocalisation ... [more ▼]

G-Cube, le logiciel de cubage et de constitution de lots de bois développé par Gembloux Agro-Bio Tech, fait peau neuve. Cette version 2.0 voit arriver des nouveautés parmi lesquelles : la géolocalisation des arbres cubés, le croisement des données avec des listes de prix personnelles ou standardisées, ou encore l’abandon de l’environnement Excel au profit d’une interface autonome. [less ▲]

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See detailLe Projet Léopard du Parc W : un Echange de Savoir Intra-Africain au Service de la Conservation de la Nature
Marchal, A.; Marchal, J.; Ouedraogo, M. et al

in Parcs & Réserves (2013), 67(4), 18-25

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See detailGame species monitoring using road–based distance sampling in association with thermal imagers: a covariate analysis
Morelle, Kevin ULg; Bouché, Philippe; Lehaire, François ULg et al

in Animal Biodiversity and Conservation (2012), 35(2), 253-265

Monitoring of game species populations is necessary to adequately assess culling by hunters in areas where natural large predators are absent. However, game managers have to control several species and ... [more ▼]

Monitoring of game species populations is necessary to adequately assess culling by hunters in areas where natural large predators are absent. However, game managers have to control several species and they often lack of an efficient and convenient survey design method. Monitoring several species at that same time over large areas could thus be cost– and time–effective. We tested the influence of several factors during monitoring of three common game species, (wild boar, roe deer and red fox, using road–based distance sampling in association with thermal imagers. This pilot survey based on 20 night counts in five contrasting sites studied the effect of several covariates (species, thermal imaging, observer, group size, and habitat type) on the detection probabilities. No differences were observed between thermal imagers and group sizes , but we found differences between observers . Expected differences were also observed between species and between habitat type. Our results show that the detectability of low cost thermal imaging equipment is similar to that of more expensive methods, highlighting new possibilities for the use of thermal imagery by game managers. Although adjustments should be made to the study design our findings suggest that large–scale multi–species monitoring could be an efficient method for common game species. [less ▲]

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