References of "Claessens, Hugues"
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See detailForest radiative transfer models: which approach for which application?
Ligot, Gauthier ULg; Balandier, Philippe; Courbaud, Benoît et al

in Canadian Journal of Forest Research = Journal Canadien de la Recherche Forestière (2014), 44(5), 385-397

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See detailLe nouveau fichier écologique des essences. Pourquoi et comment ?
Claessens, Hugues ULg; Bifolchi, Eva; Cordier, Sophie ULg et al

in Forêt Wallonne (2014), (129), 60-70

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See detailLa régénération naturelle des hêtraies-chênaies en lumière : approche expérimentale en forêt ardennaise
Ligot, Gauthier ULg; Claessens, Hugues ULg; Baudry, Olivier et al

in Forêt Wallonne (2014), (129), 19-21

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See detailNouvelles courbes de productivité harmonisées pour le douglas, l'épicéa et les mélèzes en wallonie
Perin, Jérôme ULg; De Thier, Olivier ULg; Claessens, Hugues ULg et al

in Forêt Wallonne (2014), 129(mars/avril),

Les courbes de productivité sont des outils de diagnostic précieux en gestion forestière. Elles permettent d'estimer le potentiel de production d'un peuplement de structure équienne d’âge connu à partir d ... [more ▼]

Les courbes de productivité sont des outils de diagnostic précieux en gestion forestière. Elles permettent d'estimer le potentiel de production d'un peuplement de structure équienne d’âge connu à partir d'une mesure ponctuelle de la hauteur dominante. Une nouvelle génération de modèles de productivité plus fiables ont été développés pour l'épicéa, le douglas et les mélèzes en Wallonie et ont été intégrés au sein d'un outil informatique de diagnostic simple et rapide d'utilisation. [less ▲]

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See detailInfluence du changement climatique sur l'accroissement du hêtre en Wallonie
Latte, Nicolas ULg; Claessens, Hugues ULg

Conference (2014, January 28)

Depuis quelques décennies, des signes d’affaiblissement de plus en plus marqués ont été observés sur le hêtre (Fagus sylvatica L.) un peu partout en Europe. L’inquiétude grandissante des gestionnaires ... [more ▼]

Depuis quelques décennies, des signes d’affaiblissement de plus en plus marqués ont été observés sur le hêtre (Fagus sylvatica L.) un peu partout en Europe. L’inquiétude grandissante des gestionnaires forestiers s’inscrit dans la problématique complexe du changement climatique. Une étude dendroécologique a donc été réalisée afin de mieux comprendre la relation entre l’accroissement du hêtre et son environnement. Des mesures de cernes ont été effectuées sur des échantillons de bois issus de 158 hêtres sélectionnés dans douze hêtraies (de 84 à 206 ans) situées le long du gradient climatique de Wallonie (de 67 à 590 m d’altitude). L’analyse de l’évolution temporelle de l’accroissement et de sa relation avec le climat a abouti à 3 résultats majeurs : (1) l’accroissement du hêtre a augmenté à partir des années 30 puis à diminuer de manière soutenue à partir des années 1980, (2) la sensibilité climatique des hêtraies a aussi fortement augmenté et cette augmentation est plus forte pour les peuplements de base altitude, et (3) les températures plus élevées en été et en début d’automne ont un impact négatif de plus en plus prononcé sur l’accroissement. Le réchauffement global rend les arbres de plus en plus dépendants de l’eau disponible (précipitation et sol). Les sécheresses et canicules plus fréquentes et intenses semblent progressivement affaiblir les arbres que puissent de plus en plus dans leur réserve. L’étude comprend une discussion complète intégrant l’interprétation écophysiologique des résultats mis en évidence. [less ▲]

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See detailLes forêts anciennes en Wallonie. 1ère partie : Concepts généraux
Jacquemin, Floriane ULg; Kervyn, Thierry; Branquart, Etienne et al

in Forêt Wallonne (2014), (131), 34-49

Au cours des siècles, la forêt wallonne a subi de profondes mutations qui marquent encore la structure et le fonctionnement des écosystèmes forestiers actuels. Néanmoins, certaines forêts ont été ... [more ▼]

Au cours des siècles, la forêt wallonne a subi de profondes mutations qui marquent encore la structure et le fonctionnement des écosystèmes forestiers actuels. Néanmoins, certaines forêts ont été relativement épargnées. Ces forêts, qualifiées de « forêts anciennes » en raison de la continuité temporelle de leur état forestier, s’avèrent d’un grand intérêt en matière de biodiversité, de naturalité de fonctionnement et de capacité d’adaptation aux changements globaux. Leur reconnaissance et leur identification sont utiles pour assurer une gestion responsable des territoires. [less ▲]

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See detailInfluence du changement climatique sur l'accroissement du hêtre en Wallonie
Latte, Nicolas ULg; Claessens, Hugues ULg

in Forêt Wallonne (2014), (129), 46-47

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See detailManaging understory light to maintain a mixture of species with different shade tolerance
Ligot, Gauthier ULg; Balandier, Philippe; Courbaud, Benoît et al

in Forest Ecology & Management (2014)

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See detailReprésentation du couvert forestier dans la modélisation hydrologique : Comparaison de dix modèles
Deraedt, Deborah ULg; Colinet, Gilles ULg; Claessens, Hugues ULg et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2014), 18(1), 83-96

There are many hydrological models, some of which can be used for forested environments. This review aims to compare ten of them (BILJOU, EPIC, BROOK90, SWAT, RHESSys, MIKE SHE, SHETRAN, WaSiM ETH, DHSVM ... [more ▼]

There are many hydrological models, some of which can be used for forested environments. This review aims to compare ten of them (BILJOU, EPIC, BROOK90, SWAT, RHESSys, MIKE SHE, SHETRAN, WaSiM ETH, DHSVM et Hydrus) to guide the choice. The compared fluxes are the interception, the transpiration and the root water uptake, the root distribution, the undercover effect, the tree growth and the model validation. The review underlines that each model deals with the forest fluxes in different ways. Most of the time, interception is similarly dealt by the models and the root distribution is used in the process of root water uptake. Understory and growth are seldom considered. [less ▲]

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See detailUtilisation des drones comme outil de suivi de travaux de restauration : génération de séries temporelles d'orthomosaïques à très haute résolution et de modèles numériques de surface
Michez, Adrien ULg; Lisein, Jonathan ULg; Geerts, Cédric ULg et al

Poster (2013, October 15)

D'une invention initialement militaire, les drones - et les applications qui dérivent de leurs utilisation - tendent à se banaliser au sein du domaine civil. En terme d'applications géographiques, les ... [more ▼]

D'une invention initialement militaire, les drones - et les applications qui dérivent de leurs utilisation - tendent à se banaliser au sein du domaine civil. En terme d'applications géographiques, les micro-drones (< 2 kg) occupent un segment nouveau dans les techniques d’acquisition d'informations, à mi-chemin entre deux segments plus classiques, représentés par les techniques d'acquisitions « terrain » (LiDAR terrestre, lever topographique, cartographie GPS, ..) et l'imagerie aérienne (caméra métrique, LiDAR aérien, imagerie satellitale). A l'aide d'un micro-drone X100 (Gatewing-Trimble), l'Unité GRFMN a effectué différents survols du projet de restauration du ruisseau du Morby, entrepris dans le cadre du projet Life+ Walphy. Les survols ont permis la réalisation d'orthomosaïques et de MNS (à l'aide d'Agisoft Photoscan) aux différentes étapes du chantier. Une évaluation de la qualité des MNS photogrammétriques générés est réalisée sur base de données LiDAR aérien disponible sur la zone. Une comparaison des coûts sera également réalisée entre les différentes techniques d'acquisition de données topographiques déployées sur le site lors du projet : MNS photogrammétriques UAV et caméra large format, LiDAR aérien. [less ▲]

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See detailHeight competition between Quercus petraea and Fagus sylvatica natural regeneration in mixed and uneven-aged stands
Ligot, Gauthier ULg; Balandier, Philippe; Fayolle, Adeline ULg et al

in Forest Ecology & Management (2013), 304

We monitored in situ natural regeneration in 23 uneven-aged stands. We modelled height growth in the regeneration of Quercus petraea and Fagus sylvatica. Beech saplings grew faster than oak saplings at ... [more ▼]

We monitored in situ natural regeneration in 23 uneven-aged stands. We modelled height growth in the regeneration of Quercus petraea and Fagus sylvatica. Beech saplings grew faster than oak saplings at all light levels. Oak gained greater benefit from direct radiation than did beech. Canopy opening is insufficient to promote oak over beech regeneration. [less ▲]

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See detailClassification of riparian forest species (individual tree level) using UAV-based Canopy Height Model and multi-temporal orthophotos (Vielsalm, Eastern Belgium)
Michez, Adrien ULg; Lisein, Jonathan ULg; Toromanoff, François ULg et al

Poster (2013, September 09)

Introduction : Despite their relatively low area coverage, riparian forests are central landscape features providing several ecosystem services. Nevertheless, they are critically endangered in European ... [more ▼]

Introduction : Despite their relatively low area coverage, riparian forests are central landscape features providing several ecosystem services. Nevertheless, they are critically endangered in European countries by human pressures (livestock grazing, land use conflicts, canalizations, waste water, ...) andalso by natural hazards such as the recent black alder (Alnus glutinosa) extensive decline caused by Phytophthora alni. In this study UAV is used to improve the characterization of riparian areas. Riparian forest species are identified at the individual tree level. The health condition of black alder is assessed. For this purpose a computer based approach has been developped, with low needs of specific operator ability or training. Methods : We used the Gatewing X100 to acquire 16 aerial photographs datasets (7 in classic RGB and 9 in RG NIR) during 5 days (form Augustus to October 2012). We processed a CHM in ArcGIS by combining a national Digital Terrain Model with a photogrammetric DSM generated from a single flight photographs dataset with the "MicMac" opensource platform. The 16 orthophotos were computed with Agisoft Photoscan. Based on the CHM and some basic vegetation index (mean NDVI), a classification/segmentation process was developped in eCognition allowing tree crown extraction. An amount of 113 metrics were computed in eCognition for every tree crown object. The metrics were both derived from the CHM raster and spectral information. Metrics were computed by band (object spectral mean and CHM mean, Harralick entropy, Skewness) but also with band combination (Green NDVI and NDVI). A reference dataset was also acquired through a field survey of 624 individual tree positions accurately localized. The health condition of the black alder was recorded during the field survey. A supervised classification algorithm was developed in R (Random Forest package). Results : Several classification trees were assessed trough global accuracy using the Out Of Bag (OOB) error. The best global accuracy (82%) was obtained when distinguishing the black alder (with no regards for health condition during field survey) from the rest of riparian forest objects. The global accuracy tended to decline when other species were added. When separating healthy black alders from those with symptoms, the global accuracy is 77%. Conclusions : Our study highlights the potential of UAV-based multitemporal orthophotos to identify riparian forest species and health conditions at the tree level. Future studies will focus on quick radiometrics corrections. This could improve global accuracy by reducing the variability caused by illumination conditions [less ▲]

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See detailSuivi de 27 régénérations de chêne sessile et de hêtre : résultats pour la période de 2007 à 2012
Ligot, Gauthier ULg; Mackels, Benoit ULg; Lehaire, François ULg et al

Report (2013)

En 2007, l’unité de Gestion des Ressources forestières et des Milieux naturels de la Faculté Universitaire des Sciences Agronomique de Gembloux (appartenant maintenant à l’Université de Liège, ULg) a ... [more ▼]

En 2007, l’unité de Gestion des Ressources forestières et des Milieux naturels de la Faculté Universitaire des Sciences Agronomique de Gembloux (appartenant maintenant à l’Université de Liège, ULg) a installé un vaste dispositif de suivi de la régénération naturelle de chêne et de hêtre en Ardenne. Ce document présente la synthèse des résultats pour la période de 2007 à 2012. Il a été rédigé suite à la demande des agents de terrain et des ingénieurs de cantonnement hébergeant les sites expérimentaux. [less ▲]

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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 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 detailRelevance of pedotopographical indicators in the assessment of spatial distributions of soil depth and soil water resources under forest stands : General Methodology
Ridremont, François ULg; Deraedt, Deborah ULg; Robert, Tanguy et al

Poster (2013, March)

Water resources constitute one of the most decisive factors of the adaptation of forest ecosystems facing climate changes. The assessment of soil water resources should lead a better understanding of ... [more ▼]

Water resources constitute one of the most decisive factors of the adaptation of forest ecosystems facing climate changes. The assessment of soil water resources should lead a better understanding of forest sites vulnerability to water stress and provide appropriate management recommendations for the choice of trees species and sylvicutlural techniques. This study aims to assess the relevance of pedotopographical indicators in the assessment of spatial distributions of soil depth and soil water resources under forest stands. The study area is located in the shale-slate stones pedological context of the Belgian Ardenne ecoregion. It falls within the constrasted relief of the Houille watershed and is 90% covered by forests. The estimation of spatial and profile distributions of water resources will be based on a multi-year monitoring of real time soil moisture content using TDR technology : subsurface (15 cm) on systematic sampling and profile (. 70 cm) on 32 local sites equipped with TDR pvc tubes. Additional laboratory analysis will be conducted to determine soil properties influencing soil water content (texture, organic matter content...). Directly impacting soil water content, soil depth and stoniness will be investigated in contrasting topographic conditions by (i) two traditional and destructive methods : 32 soil pits & 160 holes with auger soil; and (ii) an electromagnetic and non intrusive method : 5120m of Ground Penetrating Radar traces with 200 and 500 MHz antennas. The identification of soil and terrain attributes, able to explain distribution of soil water content and soil depth, will be done by digital cartographic resources exploitation : (i) Digital Elevation Model with different spatial resolutions (Lidar, 1 m2; Erruissol DEM, 100 m2; Aster DEM, 9.103m2) and (ii) Digital Soil Map of Wallonia. It is expected that the results could lead to the development of operational tools to ensure the forest site . tree species adequacy in order to increase resilience of forest ecosystems to ecological drifts. [less ▲]

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