References of "Claessens, Hugues"
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See detailAgroforestry for ruminants: a review of trees and shrubs as fodder in silvopastoral temperate and tropical production systems
Vandermeulen, Sophie; Ramirez Restrepo, Carlos; Beckers, Yves ULiege et al

in Animal production science (in press)

Among the oldest agroforestry systems, silvopastoralism uses shrubs and trees to feed ruminants. The practice is common in extensive livestock production systems, while the intensification of grass-based ... [more ▼]

Among the oldest agroforestry systems, silvopastoralism uses shrubs and trees to feed ruminants. The practice is common in extensive livestock production systems, while the intensification of grass-based systems in the past century has led to the removal of woody species from agricultural temperate landscapes. In Europe however, woody species are promoted again on grasslands through environment-friendly policies due to the ecosystem services they provide such as carbon sequestration, control of soil erosion, limitation of air-borne pollutants and biodiversity conservation. Positive effects of browse on rumen digestion and parasite control have also been documented across different plant species and regions. Under optimal conditions, feeding ruminants from woody fodder sustains animal production. Nonetheless, limitations can restrict the use of woody forage into animal diets, such as the presence of anti-nutritive and toxic compounds. The incorporation of this resource in ruminant feeding systems raises the question of the management of the interface between the plant and the animal. Various management systems are practiced. Temperate species such as Salix spp. and Populus spp. are fed to sheep and cattle in fodder blocks or by pruning trees in New Zealand, and Fraxinus spp. or Corylus avellana in hedgerows supply forage to livestock in Belgium, while Leucaena leucocepahala and Desmanthus spp. browsing is common in Australia. Nowadays, ensiling and pelleting techniques are being developed as a way to store browse forage. As the renewed interest in using shrubs and trees to feed ruminants is recent, especially in temperate regions, additional research about introducing optimally this resource within systems is needed. [less ▲]

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See detailCuriosité : le « curly birch ». Une figuration ondée, rare et recherchée du bois de bouleau
Dubois, Héloïse ULiege; Layon, José; Claessens, Hugues ULiege

in FORÊT.NATURE (2017), (145), 12-15

Nos forêts et leur gestion doivent s’adapter à de grands changements, qu’ils soient climatiques, socio-économiques ou sanitaires. De ce point de vue, le bouleau possède de nombreux atouts, tant en termes ... [more ▼]

Nos forêts et leur gestion doivent s’adapter à de grands changements, qu’ils soient climatiques, socio-économiques ou sanitaires. De ce point de vue, le bouleau possède de nombreux atouts, tant en termes écologiques qu’économiques et sylvicoles. De plus en plus abondant en Europe occidentale, il deviendra à l’avenir un facteur déterminant des décisions sylvicoles. Une recherche approfondie sur l’intérêt de l’essence pour la gestion forestière, ses filières économiques, sa croissance et, surtout, la sylviculture à lui apporter, est en cours à Gembloux Agro-Bio Tech (Liège Université) avec le financement de l’Accord-cadre de recherches et vulgarisation forestières. Elle a notamment été l’occasion de riches échanges avec la Finlande, pays le plus boisé d’Europe. Le bouleau y est une composante très importante des forêts, de l’économie du pays, de la construction et de l’ameublement. Cet article constitue un détour original afin de présenter une figuration rare du bois de bouleau, qui amusera les passionnés du bois et les curieux. Il s’agit du « curly birch », littéralement le « bouleau ondé », actuellement anecdotique mais très lucratif. [less ▲]

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See detailMulti-temporal monitoring of a regional riparian buffer network (>12,000 km) with LiDAR and photogrammetric point clouds
Michez, Adrien ULiege; Piégay, Hervé; Lejeune, Philippe ULiege et al

in Journal of Environmental Management (2017), 202(2), 424-436

Riparian buffers are of major concern for land and water resource managers despite their relatively low spatial coverage. In Europe, this concern has been acknowledged by different environmental ... [more ▼]

Riparian buffers are of major concern for land and water resource managers despite their relatively low spatial coverage. In Europe, this concern has been acknowledged by different environmental directives which recommend multi-scale monitoring (from local to regional scales). Remote sensing methods could be a cost-effective alternative to field-based monitoring, to build replicable “wall-to-wall” monitoring strategies of large river networks and associated riparian buffers. The main goal of our study is to extract and analyze various parameters of the riparian buffers of up to 12,000 km of river in southern Belgium (Wallonia) from three-dimensional (3D) point clouds based on LiDAR and photogrammetric surveys to i) map riparian buffers parameters on different scales, ii) interpret the regional patterns of the riparian buffers and iii) propose new riparian buffer management indicators. We propose different strategies to synthesize and visualize relevant information at different spatial scales ranging from local (<10 km) to regional scale (>12,000 km). Our results showed that the selected parameters had a clear regional pattern. The reaches of Ardenne ecoregion have channels with the highest flow widths and shallowest depths. In contrast, the reaches of the Loam ecoregion have the narrowest and deepest flow channels. Regional variability in channel width and depth is used to locate management units potentially affected by human impact. Riparian forest of the Loam ecoregion is characterized by the lowest longitudinal continuity and mean tree height, underlining significant human disturbance. As the availability of 3D point clouds at the regional scale is constantly growing, our study proposes reproducible methods which can be integrated into regional monitoring by land managers. With LiDAR still being relatively expensive to acquire, the use of photogrammetric point clouds combined with LiDAR data is a cost-effective means to update the characterization of the riparian forest conditions. [less ▲]

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See detailÉtude de la disponibilité des cavités pour les oiseaux cavernicoles dans la Région de Bruxelles-Capitale
Debois, Caroline; Claessens, Hugues ULiege; Paquet, Jean-Yves et al

in FORÊT.NATURE (2017), (144), 11-20

Selon une étude effectuée en 2002, le nord-ouest de Bruxelles possède une grande disponibilité en cavités pour les oiseaux cavernicoles malgré le fort développement depuis plusieurs décennies de deux ... [more ▼]

Selon une étude effectuée en 2002, le nord-ouest de Bruxelles possède une grande disponibilité en cavités pour les oiseaux cavernicoles malgré le fort développement depuis plusieurs décennies de deux perruches exotiques : la perruche à collier et la perruche alexandre. Suite à l’augmentation des effectifs des deux populations de perruches et suite au renouvellement des vieux peuplements forestiers bruxellois, une limitation du nombre de cavités disponibles pour la nidification des oiseaux cavernicoles est désormais possible. Une nouvelle étude a dès lors été réalisée sur l’ensemble des zones boisées de la Région de Bruxelles-Capitale à l’aide d’un réseau de placettes circulaires disposé aléatoirement dans trois zones distinctes. Dans ces placettes, un inventaire des arbres et des cavités a été effectué avant la période de feuillaison. Par la suite, l’occupation des cavités par les oiseaux cavernicoles a été déterminée. D’après les résultats, un grand nombre de cavités restent disponibles pour la nidification à Bruxelles comme cela avait été établi précédemment. Cela est confirmé par le peu d’interactions observées entre les espèces et par les tendances des populations de cavernicoles, qui sont stables ou en augmentation à Bruxelles de 1992 à 2015. [less ▲]

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See detailDistance-independent tree basal area growth models for Norway spruce, Douglas-fir and Japanese larch in Southern Belgium
Perin, Jérôme ULiege; Claessens, Hugues ULiege; Lejeune, Philippe ULiege et al

in European Journal of Forest Research (2017), 136(2),

This paper presents new harmonized distance independent individual tree basal area growth models for Norway spruce, Douglas-fir and Japanese larch in pure even-aged stands in Southern Belgium. The ... [more ▼]

This paper presents new harmonized distance independent individual tree basal area growth models for Norway spruce, Douglas-fir and Japanese larch in pure even-aged stands in Southern Belgium. The selected model was originally developed for Norway spruce and Douglas-fir in neighbouring France. New formulations are proposed for some of the model components in order to lower the number of fitted parameters and facilitate the fitting procedure. The resulting models integrate the most recent corresponding top-height growth models and use 4 simple and usually collected explanatory variables : stand age, top-height, total basal area and tree girth at breast height. The modified formulations maintain similar fitting performances and make it easier to interpret the influence of the explanatory variables on tree growth. Parameters estimates were fitted on thousands of growth measurements gathered from several monitoring plots, forest management inventories and silvicultural field experiments that represent the wide range of site conditions and of forest management scenarios applied to coniferous stands in Southern Belgium. Cross-validation of the models revealed no bias and highlighted their consistent behaviour over the entire range of girth at breast height, age, top-height, site index and density represented in our dataset. Combining utility and robust performances, these models represent useful forest management tools, purposely ideal for forest simulation software development. Moreover, the flexibility and generic capabilities of the model formulation should make it easily adjustable for other species in even-aged stands. [less ▲]

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See detailLe Fichier écologique des essences, version 2.0
Petit, S.; Claessens, Hugues ULiege; Vincke, C. et al

in FORÊT.NATURE (2017), (143), 12-19

Après plus de 25 ans d’utilisation, le Fichier écologique des essences méritait une révision en profondeur. Il a été remis au goût du jour grâce à l’Accord-cadre de recherches et vulgarisation forestières ... [more ▼]

Après plus de 25 ans d’utilisation, le Fichier écologique des essences méritait une révision en profondeur. Il a été remis au goût du jour grâce à l’Accord-cadre de recherches et vulgarisation forestières et par les équipes de recherches de l’Ulg-GxABT et de l’UCL, avec l’appui de Forêt Wallonne. Fruit d’une collaboration entre chercheurs et gestionnaires de terrain, il repose sur un large travail de recherche bibliographique, adapté au contexte wallon grâce aux membres d’un groupe de travail composé de scientifiques et de forestiers. Il a évolué pour répondre aux attentes de la société et prône une forêt multifonctionnelle et résiliente face aux changements climatiques. Disponible sous format web, il facilite la prise en main par les utilisateurs et les guide vers la meilleure adaptation entre les essences et les stations, gage d’un écosystème pleinement fonctionnel, résilient et répondant aux besoins actuels de la société. [less ▲]

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See detailCartographie de la disponibilité en eau et en éléments nutritifs des stations forestières de Wallonie
Wampach, Florent ULiege; Lisein, Jonathan; Cordier, Sophie ULiege et al

in FORÊT.NATURE (2017), avril-mai-juin(143), 47-60

Grâce aux données cartographiques de plus en plus nombreuses et disponibles, il est maintenant possible d'analyser l'adéquation essence-station à l'échelle d'un massif ou d'un cantonnement. A l'échelle ... [more ▼]

Grâce aux données cartographiques de plus en plus nombreuses et disponibles, il est maintenant possible d'analyser l'adéquation essence-station à l'échelle d'un massif ou d'un cantonnement. A l'échelle plus locale, cette nouvelle cartographie constitue un outil d'aide à l'interprétation des stations pour les gestionnaires, forestiers ou naturalistes. [less ▲]

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See detailLes peuplements à bouleau en forêt wallonne: reflet de la sylviculture du 20ème siècle
Dubois, Héloïse ULiege; Latte, Nicolas ULiege; Claessens, Hugues ULiege

in FORÊT.NATURE (2017), 142

Le bouleau est présent sous des formes diverses dans nos forêts. La place qu’il occupe en forêt wallonne est souvent le reflet d’une méconnaissance et du peu d’estime que lui portaient les sylviculteurs ... [more ▼]

Le bouleau est présent sous des formes diverses dans nos forêts. La place qu’il occupe en forêt wallonne est souvent le reflet d’une méconnaissance et du peu d’estime que lui portaient les sylviculteurs. Par une typologie des peuplements, l’article fait le tri parmi les contextes où se trouve le bouleau et discute de leurs potentialités sylvicoles dans un contexte changeant qui pourrait faire la part belle à cette essence vigoureuse et aux atouts variés. [less ▲]

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See detailEffects of the conversion of intensive grasslands into Christmas tree plantations on bird assemblages
Gailly, Robin ULiege; Paquet, Jean-Yves; Titeux, Nicolas et al

in Agriculture, Ecosystems & Environment (2017), 247

Over the last decade, the conversion of annual-rotation based crops or grassland areas into non-food perennial crops has been increasingly prevalent in European farming systems. This shift is associated ... [more ▼]

Over the last decade, the conversion of annual-rotation based crops or grassland areas into non-food perennial crops has been increasingly prevalent in European farming systems. This shift is associated with major changes in management practices and has created new environmental conditions and resources for wildlife. Impacts on birds have been examined for bioenergy agricultural systems, such as miscanthus plantations and short-rotation willow coppice. However, they remain largely unknown for Christmas tree plantations (CTPs) that have recently increased considerably in some European countries. We examined the extent to which CTPs alter bird species assemblages in the farmland areas of southern Belgium, where they mainly replace intensive grassland. The abundance of birds was recorded during the breeding season in randomly selected sites located in grassland and in CTP. Results show that introduction of CTP into landscapes dominated by grassland with low hedge densities locally increases bird species richness and abundance without leading to biotic homogenization. Differences in species richness and abundance between grassland and CTP decrease with increasing hedge densities. A community analysis indicates that the plantation of Christmas trees enriches the bird assemblage of intensive grassland areas. In intensive grassland with few hedges, small-size CTPs could constitute an option to increase structural heterogeneity and provide new potential breeding conditions for some farmland birds. However, questions remain about the genuine quality of the resources available in CTP and further research is needed to examine the breeding success and survival of birds that settle in this type of habitat. [less ▲]

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See detailPrès de 20 ans après sa grave crise sanitaire, où en est la hêtraie ardennaise?
Claessens, Hugues ULiege; Claessens, Laureline ULiege; Longrée, Charlotte et al

in FORÊT.NATURE (2017), 142(Janvier-Février-Mars), 30-36

La "maladie du hêtre", apparue au début des années 2000 suite au coup de froid de 1998, détruisit plus d'un million de mètres cubes de bois. Un suivi d'une vingtaine d'années a permis de faire le point ... [more ▼]

La "maladie du hêtre", apparue au début des années 2000 suite au coup de froid de 1998, détruisit plus d'un million de mètres cubes de bois. Un suivi d'une vingtaine d'années a permis de faire le point sur son évolution et son impact actuel, et de proposer quelques recommandations pour la gestion de la hêtraie. [less ▲]

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See detailLe bouleau, une essence qui s'impose. Description de la ressource dans son aire de distribution
Dubois, Héloïse ULiege; Latte, Nicolas ULiege; Lecomte, Hugues et al

in FORÊT.NATURE (2016), 140

L'essentiel de la ressource en bouleau (verruqueux et pubescent) se situe en Russie et en Scandinavie (15 milliards de m³) et cette ressource augmente graduellement depuis plusieurs années. Il y est ... [more ▼]

L'essentiel de la ressource en bouleau (verruqueux et pubescent) se situe en Russie et en Scandinavie (15 milliards de m³) et cette ressource augmente graduellement depuis plusieurs années. Il y est fortement valorisé en sciage, déroulage et trituration. En Europe de l'Ouest, cette croissance s'observe aussi, même si seulement 1 % de la ressource s'y concentre (dû notamment à la plus grande diversité d'essences commerciales présentes). En Wallonie, les évolutions du contexte socio-économique et environnemental jouent en faveur d'une augmentation de la présence du bouleau (parcelles non reboisées, entretien insuffisant, mélanges spontanés...). Le bouleau représente souvent une belle opportunité pour les mélanges, une excellente essence d'accompagnement et une diversification de la production. Mais, sans une sylviculture adaptée, les grumes sont généralement de faible dimension et présentent de nombreux défauts. C'est le cas de l'essentiel de la ressource actuelle en Wallonie. Aujourd'hui, les besoins sont de mieux le connaître, notamment les opportunités de valorisation, et d'aboutir à des recommandations sylvicoles. Il ne s'agit donc pas de vouloir faire du bouleau à tout prix mais plutôt de tirer profit d'une étape transitoire de la succession forestière. [less ▲]

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See detailAre Christmas tree plantations a suitable habitat for farmland birds?
Gailly, Robin ULiege; Paquet, Jean-Yves; Titeux, Nicolas et al

Conference (2016, September 06)

Over the last decade, nonfood perennial crops have been increasingly prevalent in European farming systems. Here, vegetation structure and crop management greatly differ from conventional crops and may ... [more ▼]

Over the last decade, nonfood perennial crops have been increasingly prevalent in European farming systems. Here, vegetation structure and crop management greatly differ from conventional crops and may likely impact farmland birds. Impacts on birds have been examined for bioenergy agricultural systems, such as miscanthus plantations and short rotation willow coppice. In Europe, the extend of Christmas tree plantations (CTP) has recently increased dramatically in farmland but their impacts on farmland birds remains largely unknown. We examined the extent to which CTP in southern Belgium alter bird species assemblages compared to traditional farmland. The presence and abundance of birds were recorded twice during a breeding season in randomly selected sites located in farmland areas with and without CTP. Results show that the conversion of traditional farmland into CTP modifies bird species assemblages and locally increases bird diversity and density without inducing biotic homogenization. This observed pattern indicates that CTP might constitute an interesting alternative habitat for farmland birds. However bird presence or abundance may be confounding indicator of habitat quality because individuals may be attracted to low-quality habitats in human modified landscapes. The European Stonechat Saxicola rubicola was chosen as a model species to investigate the quality of CTP as a breeding habitat in more details. Habitat quality in CTP was assessed with measures of reproductive success and survival. These measures were compared with those collected in traditional farmland. Although vegetation structure, field management and nest placement are highly different between habitat types, our first results suggest that CTP are not of lesser quality than traditional farmland for the European Stonechat. [less ▲]

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See detailAre Christmas tree plantations a suitable habitat for farmland birds?
Gailly, Robin ULiege; Paquet, Jean-Yves; Titeux, Nicolas et al

Poster (2016, September 06)

Over the last decade, nonfood perennial crops have been increasingly prevalent in European farming systems. Here, vegetation structure and crop management greatly differ from conventional crops and may ... [more ▼]

Over the last decade, nonfood perennial crops have been increasingly prevalent in European farming systems. Here, vegetation structure and crop management greatly differ from conventional crops and may likely impact farmland birds. Impacts on birds have been examined for bioenergy agricultural systems, such as miscanthus plantations and short rotation willow coppice. In Europe, the extend of Christmas tree plantations (CTP) has recently increased dramatically in farmland but their impacts on farmland birds remains largely unknown. We examined the extent to which CTP in southern Belgium alter bird species assemblages compared to traditional farmland. The presence and abundance of birds were recorded twice during a breeding season in randomly selected sites located in farmland areas with and without CTP. Results show that the conversion of traditional farmland into CTP modifies bird species assemblages and locally increases bird diversity and density without inducing biotic homogenization. This observed pattern indicates that CTP might constitute an interesting alternative habitat for farmland birds. However bird presence or abundance may be confounding indicator of habitat quality because individuals may be attracted to low-quality habitats in human modified landscapes. The European Stonechat Saxicola rubicola was chosen as a model species to investigate the quality of CTP as a breeding habitat in more details. Habitat quality in CTP was assessed with measures of reproductive success and survival. These measures were compared with those collected in traditional farmland. Although vegetation structure, field management and nest placement are highly different between habitat types, our first results suggest that CTP are not of lesser quality than traditional farmland for the European Stonechat. [less ▲]

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See detailMajor Changes in Growth Rate and Growth Variability of Beech (Fagus sylvatica L.) Related to Soil Alteration and Climate Change in Belgium
Latte, Nicolas ULiege; Perin, Jérôme ULiege; Kint, Vincent et al

in Forests (2016), 7(174),

Global change—particularly climate change, forest management, and atmospheric deposition—has significantly altered forest growing conditions in Europe. The influences of these changes on beech growth ... [more ▼]

Global change—particularly climate change, forest management, and atmospheric deposition—has significantly altered forest growing conditions in Europe. The influences of these changes on beech growth (Fagus sylvatica L.) were investigated for the past 80 years in Belgium, using non-linear mixed effects models on ring-width chronologies of 149 mature and dominant beech trees (87–186 years old). The effects of the developmental stage (i.e., increasing tree size) were filtered out in order to focus on time-dependent growth changes. Beech radial growth was divided into a low-frequency signal (=growth rate), mainly influenced by forest management and atmospheric deposition, and into a high-frequency variability (≈mean sensitivity), mainly influenced by climate change. Between 1930 and 2008, major long-term and time-dependent changes were highlighted. The beech growth rate has decreased by about 38% since the 1950–1960s, and growth variability has increased by about 45% since the 1970–1980s. Our results indicate that (1) before the 1980s, beech growth rate was not predominantly impacted by climate change but rather by soil alteration (i.e., soil compaction and/or nitrogen deposition); and (2) since the 1980s, climate change induced more frequent and intense yearly growth reductions that amplified the growth rate decrease. The highlighted changes were similar in the two ecoregions of Belgium, although more pronounced in the lowlands than in the uplands. [less ▲]

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See detailApport des nuages de points LiDAR et photogrammétriques pour le monitoring de 12000 km de cours d’eau en Wallonie (Belgique)
Michez, Adrien ULiege; Piégay, Hervé; Desteucq, Olivier et al

Conference (2016, June 10)

Sous l’impulsion de son administration, la Wallonie a entamé un processus de révision complète des modalités de la gestion des cours d’eau, notamment à travers le projet des Programmes d’Actions sur les ... [more ▼]

Sous l’impulsion de son administration, la Wallonie a entamé un processus de révision complète des modalités de la gestion des cours d’eau, notamment à travers le projet des Programmes d’Actions sur les Rivières par une approche Intégrée et Sectorisée (PARIS). Les PARIS ont pour but l'intégration dans le temps et dans l’espace de l’ensemble des mesures de gestion spécifiques au linéaire des cours d'eau en fonction d'enjeux prioritaires identifiés à l’échelle d’unités de gestion homogènes, les secteurs (6185 secteurs de gestion de 2 km de long en moyenne). La mise en place et le suivi de ces plans de gestion impliquent de facto le développement d'outils de suivi efficaces, permettant d'établir les états des lieux pour la planification des actes de gestion et à terme, d'évaluer l'efficacité desdits plans de gestion. Ces opérations doivent se réaliser sur près de 12000 km de cours d’eau et de bandes riveraines associées sur une base objective et commune à l’ensemble des gestionnaires de cours d’eau. Des données fines de télédétection étant disponibles et acquises de manière régulière par l’administration wallonne, des solutions dérivées de ces sources de données permettront de répondre partiellement aux besoins réguliers en information des plans de gestion PARIS pour un budget réduit. Pour atteindre cet objectif, un protocole a été établi sur base de nuages points LiDAR (densité ≈ 1 point « sol » / m²) complétés par des nuages de points photogrammétriques dérivés des images individuelles des couvertures ortho du territoire. Ces données ont été utilisées afin de caractériser la structure spatiale des bandes riveraines associées à l’ensemble du réseau hydrographique wallon (> 12 000 km) à travers 6 paramètres. Ces paramètres peuvent être d’ordre hydromorphologique (hauteur des berges, largeur et sinuosité du lit mineur), ou décrire la structure des forêts riveraines (hauteur moyenne, continuité longitudinale et ombrage du lit mineur). Une évaluation des patrons spatiaux de ces différents paramètres en lien avec les caractéristiques des territoires wallons (occupation du sol, régions naturelles) peut être ainsi réalisée. Différentes formes de visualisations de l’information peuvent ainsi appuyer le processus décisionnel des gestionnaires, de l’échelle locale (secteurs d’une masse d’eau DCE - Directive ‘Cadre-Eau’) à l’échelle régionale (354 masse d’eau DCE). L’acquisition des données sur l’ensemble du territoire wallon (15000 km²) a été sous-traitée à différentes compagnies privées, pour des montants approximatifs de 17 et 10 € / km² respectivement pour la donnée LiDAR et ortho. Une plateforme en ligne a récemment été lancée par la Direction des Cours d’Eau Non-Navigables du Service Public de Wallonie (DCENN) en tant que support du projet de plans de gestion PARIS. Les paramètres extraits dans le cadre de ce projet seront prochainement intégrés au sein de cette plateforme permettant leur visualisation à différentes échelles ainsi que l’encodage des actions par les gestionnaires. [less ▲]

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See detailNouvelles normes sylvicoles pour les peuplements purs équiennes d'épicéa et de douglas
Perin, Jérôme ULiege; Hebert, Jacques ULiege; Lejeune, Philippe ULiege et al

E-print/Working paper (2016)

Ces documents rassemblent les tables de production (version 2016) représentant les nouvelles normes sylvicoles recommandées pour les peuplements purs équiennes d'épicéa commun et de douglas. Un ensemble ... [more ▼]

Ces documents rassemblent les tables de production (version 2016) représentant les nouvelles normes sylvicoles recommandées pour les peuplements purs équiennes d'épicéa commun et de douglas. Un ensemble de 10 tables de production est présentée pour chaque essence, associant deux densités de plantation (2.5 x 2 m et 2 x 2 m) et 5 classes de productivité (0 à IV). [less ▲]

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See detailMapping of riparian invasive species with supervised classification of Unmanned Aerial System (UAS) imagery
Michez, Adrien ULiege; Piégay, Hervé; Lisein, Jonathan ULiege et al

in International Journal of Applied Earth Observation and Geoinformation (2016), 44

Riparian zones are key landscape features, representing the interface between terrestrial and aquatic ecosystems. Although they have been influenced by human activities for centuries, their degradation ... [more ▼]

Riparian zones are key landscape features, representing the interface between terrestrial and aquatic ecosystems. Although they have been influenced by human activities for centuries, their degradation has increased during the 20th century. Concomitant with (or as consequences of) these disturbances, the invasion of exotic species has increased throughout the world’s riparian zones. In our study, we propose a easily reproducible methodological framework to map three riparian invasive taxa using Unmanned Aerial Systems (UAS) imagery: Impatiens glandulifera Royle, Heracleum mantegazzianum Sommier and Levier, and Japanese knotweed (Fallopia sachalinensis (F. Schmidt Petrop.), Fallopia japonica (Houtt.) and hybrids). Based on visible and near-infrared UAS orthophoto, we derived simple spectral and texture image metrics computed at various scales of image segmentation (10,30, 45, 60 using eCognition software). Supervised classification based on the random forests algorithm was used to identify the most relevant variable (or combination of variables) derived from UAS imagery for mapping riparian invasive plant species. The models were built using 20% of the dataset, the rest of the dataset being used as a test set (80%). Except for H. mantegazzianum, the best results in terms of global accuracy were achieved with the finest scale of analysis (segmentation scale parameter = 10). The best values of overall accuracies reached 72%, 68%, and 97% for I. glandulifera, Japanese knotweed, and H. mantegazzianum respectively. In terms of selected metrics, simple spectral metrics (layer mean / camera brightness) were the most used. Our results also confirm the added value of texture metrics (GLCM derivatives) for mapping riparian invasive species. The results obtained for I. glandulifera and Japanese knotweed do not reach sufficient accuracies for operational applications. However, the results achieved for H. mantegazzianum are encouraging. The high accuracies values combined to relatively light model-inputs needed (delineation of a few umbels) make our approach a serious contender as a cost-effective tool to improve the field management of H. mantegazzianum. [less ▲]

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See detailQuelques considérations pour adapter nos forêts aux changements climatiques
Claessens, Hugues ULiege

in Silva Belgica (2016)

Au cœur d’une grande forêt naturelle comme celle d’Anlier, de Saint-Hubert ou de Daverdisse, le promeneur ressent souvent une impression de calme et de stabilité. Cela pourrait faire penser que la forêt ... [more ▼]

Au cœur d’une grande forêt naturelle comme celle d’Anlier, de Saint-Hubert ou de Daverdisse, le promeneur ressent souvent une impression de calme et de stabilité. Cela pourrait faire penser que la forêt est éternelle et sa forme immuable. Il n’en est rien, ce n’est qu’une question d’échelle temporelle, car depuis toujours, la forêt n’est que changement, dans sa surface, sa structure et sa composition, disparaissant parfois totalement pour recoloniser ensuite l’espace avec d’autres essences. [less ▲]

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Peer Reviewed
See detailGrowth partitioning within beech trees (Fagus sylvatica L.) varies in response to summer heat waves and related droughts
Latte, Nicolas ULiege; Lebourgeois, François; Claessens, Hugues ULiege

in Trees (2016), 30(1), 189-201

To characterize growth partitioning within the tree and its responses to climate, we studied 8 dominant beech trees (Fagus sylvatica L.) of a pure, even-aged 98-year-old stand in Belgium. We sampled 10 ... [more ▼]

To characterize growth partitioning within the tree and its responses to climate, we studied 8 dominant beech trees (Fagus sylvatica L.) of a pure, even-aged 98-year-old stand in Belgium. We sampled 10 disks along the stem from breast height to treetop and examined the inter-annual patterns of, and discrepancies between, ring-area and volume increments by performing detailed stem analysis and dendroecological investigations. Although the common inter-annual variation among all increment series was high, we observed increasing growth variability and climate sensitivity with height, leading to notable bole-crown discrepancies. Both the common inter-annual variation and bole-crown discrepancies were mainly driven by summer heat waves and related droughts of the previous year, and spring droughts of the current year. Despite these discrepancies, the radial growth at breast height can be considered a good estimate of the tree volume increment but not for the purpose of focusing on climatic effects of isolated years. Extreme climatic conditions increase the risk of inaccurate estimations. The results of the present study are discussed in relation to tree ecophysiology hypotheses. [less ▲]

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See detailReview of shrubs and trees in intensive ruminant systems in temperate areas
Vandermeulen, Sophie ULiege; Ramìrez-Restrepo, Carlos Alberto; Beckers, Yves ULiege et al

Conference (2016, January)

Using shrubs and trees as forage for ruminants is common in extensive production systems in the tropics, as well as the Mediterranean region and mountain areas. In temperate Europe, the intensification of ... [more ▼]

Using shrubs and trees as forage for ruminants is common in extensive production systems in the tropics, as well as the Mediterranean region and mountain areas. In temperate Europe, the intensification of agriculture led to a decline in the numbers of woody perennials on farmlands. A review of the potential uses of shrubs and trees in temperate intensive systems shows that this concept is rather recent. Few studies have been investigating the potential outputs and limitations of shrubs and trees forage in production systems, while in Belgium and other European countries, agro-environmental policies are promoting the establishment of hedgerows and woody strips that provide shelter to animals against variable climate conditions. Furthermore, it has been found that ruminant species browse the plants, or alternatively, the forage is harvested and fed fresh or preserved as hay, silages or pellets. In both cases, consequences on feed intake control, woody plant survival, dry matter (DM) production and forage quality in terms of crude protein content reduction have been documented. In addition, depending on the plant species and the preservation method, bio-active plant metabolites such as condensed tannins (CT) are also present in the range of less than 1 to more than 100 g/kg foliage DM. Overall, CT may reduce ruminal N degradation, methanogenesis and nematode parasites infestation, while enhancing microbial-protein synthesis, feed use efficiency and systemic animal physiology. Planting shrubs and trees into the agricultural landscape (i.e. silvopastoral system) can further improve biodiversity and environmental services. Nevertheless, agronomic practices, farm management or environmental policy limitations may reduce the use of this fodder resource. Therefore, although silvopastoral systems seem promising in temperate ruminant systems, the current knowledge to their introduction and efficient management need to be cautiously considered. [less ▲]

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