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See detailAre Christmas tree plantations a suitable habitat for farmland birds?
Gailly, Robin ULg; 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 ULg; 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 ULg; Perin, Jérôme ULg; 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 ULg; 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 ULg; Hebert, Jacques ULg; Lejeune, Philippe ULg 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 detailQuelques considérations pour adapter nos forêts aux changements climatiques
Claessens, Hugues ULg

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

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 detailMapping of riparian invasive species with supervised classification of Unmanned Aerial System (UAS) imagery
Michez, Adrien ULg; Piégay, Hervé; Lisein, Jonathan ULg 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 detailReview of shrubs and trees in intensive ruminant systems in temperate areas
Vandermeulen, Sophie ULg; Ramìrez-Restrepo, Carlos Alberto; Beckers, Yves ULg 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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See detailL'agroforesterie en Belgique : atouts et freins dans le paysage agricole moderne
Boutsen, Raphaël; Artru, Sidonie ULg; Claessens, Hugues ULg et al

in FORÊT.NATURE (2016), 138

L'agroforesterie associe la production ligneuse d'arbres avec d'autres cultures ou avec l'élevage. Si des formes traditionnelles d'agroforesterie se sont perpétuées jusqu'à nos jours, grâce notamment à ... [more ▼]

L'agroforesterie associe la production ligneuse d'arbres avec d'autres cultures ou avec l'élevage. Si des formes traditionnelles d'agroforesterie se sont perpétuées jusqu'à nos jours, grâce notamment à des aides indirectes de la PAC, une nouvelle génération est en train d'émerger. Des modèles plus complexes et novateurs tentent d'intégrer l'arbre à une réflexion globale sur le système de production. La prise en compte des processus sous-jacents aux fonctionnements des écosystèmes est au cœur de cette réflexion... [less ▲]

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See detailMaintaining the coexistence of tree species of different shade tolerances with uneven-aged silviculture
Ligot, Gauthier ULg; Balandier, Philippe; Courbaud, Benoît et al

Conference (2016)

Maintaining the coexistence of multiple tree species is one of the greatest issues of uneven-aged silviculture as it is of great interest, for example, to maintain biodiversity or increase resilience to ... [more ▼]

Maintaining the coexistence of multiple tree species is one of the greatest issues of uneven-aged silviculture as it is of great interest, for example, to maintain biodiversity or increase resilience to global changes. In many places, while forest managers have successfully maintained complex stand structure with uneven-aged silviculture, they have often faced difficulties in maintaining some desired species mixtures. Naturally, the composition of uneven-aged forests evolves so that a few species successfully regenerate and suppress the others. Since a continuous canopy cover is usually maintained by uneven-aged silviculture, when nutrients and moisture are not limiting, the availability of light in the understory is the driving factor of natural regeneration dynamics. The amount of transmitted radiation determines, at least partly, the composition of the regeneration layer because of interspecific differences in growth and survival in shade. In theory, shade-tolerant species generally dominate the regeneration under closed canopies whereas less shade-tolerant species dominate the regeneration under partially open canopies. We hypothesize that, along a gradient of light availability, shade-tolerant species suppress less shade-tolerant species in understory with low availability of light whereas the opposite situation occurs in understory with high availability of light. In addition, we expect that forest managers can effectively control understory light with appropriate modifications of forest structure and density. We examined mixtures of sessile oak (Quercus petraea (Matt.) Liebl.) and European beech (Fagus sylvatica L.) in the Belgian Ardennes. We selected 23 sites with favorable water and nutrient supply. Regeneration areas (100-6500m²) were fenced off to protect them from browsing by deer. Saplings were sampled in 241 subplots and their height growth was annually monitored during two years. Understory light transmittance was measured in each subplot using hemispherical photography. The height growth of beech and oak saplings was modeled with mixed non-linear models. In order to simulate various silvicultural treatments, we used a model of light interception by heterogeneous canopies (SAMSARALIGHT). We simulated selective thinnings of 5 different types: harvesting preferentially small trees, large trees, or trees of shade-tolerant species or creating circular gaps. Understory light was found to be a key parameter in the dynamics of uneven-aged stands, as it affects regeneration growth and composition. There were interspecific differences in growth response to light availability. The optimum height growth of beech and oak regenerations were reached at 10% and 20% of transmittance, respectively. Our simulations highlighted that various silvicultural treatments can effectively be used to control understory light as long as harvest intensity is adapted to the chosen strategy (Figure 1). The results of this study also underscore the problem that even under good light conditions (transmittance > 20 %), regeneration of less shade-tolerant species might not overcome the regeneration of shade-tolerant species. Contrary to our hypothesis, we found no rank reversal of the height growth of the two study species along a wide light gradient. Consequently, maintaining less shade-tolerant species in stands with shade-tolerant species might require silvicultural interventions jointly in the overstory and regeneration layers. [less ▲]

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See detailClassification of riparian forest species and health condition using multi-temporal and hyperspatial imagery from unmanned aerial system
Michez, Adrien ULg; Piégay, Hervé; Lisein, Jonathan ULg et al

in Environmental Monitoring and Assessment (2016), 188(3),

Riparian forests are critically endangered many anthropogenic pressures and natural hazards. The importance of riparian zones has been acknowledged by European Directives, involving multi-scale monitoring ... [more ▼]

Riparian forests are critically endangered many anthropogenic pressures and natural hazards. The importance of riparian zones has been acknowledged by European Directives, involving multi-scale monitoring. The use of this very high resolution and hyperspatial imagery in a multi-temporal approach is an emerging topic. The trend is reinforced by the recent and rapid growth of the use of the unmanned aerial system (UAS), which has prompted the development of innovative methodology. Our study proposes a methodological framework to explore how a set of multi-temporal images acquired during a vegetative period can differentiate some of the deciduous riparian forest species and their health conditions. More specifically, the developed approach intends to identify, through a process of variable selection, which variables derived from UAS imagery and which scale of image analysis are the most relevant to our objectives. The methodological framework is applied to two study sites to describe the riparian forest through two fundamental characteristics: the species composition and the health condition. These characteristics were selected not only because of their use as proxies for the riparian zone ecological integrity but also because of their use for river management. The comparison of various scales of image analysis identified the smallest OBIA objects (ca. 1 m²) as the most relevant scale. Variables derived from spectral information (bands ratio's) were identified as the most appropriate, followed by variables related to the vertical structure of the forest. Classification results show good overall accuracies for the species composition of the riparian forest (five classes, 79.5 and 84.1 % for Site 1 and Site 2). The classification scenario regarding the health condition of the black alders of the Site 1 performed the best (90.6 %). The quality of the classification models developed with a UAS-based, cost-effective, and semi-automatic approach competes successfully with those developed using more expensive imagery, such as multispectral and hyperspectral airborne imagery. The high overall accuracy results obtained by the classification of the diseased alders open the door to applications dedicated to monitoring of the health conditions of riparian forest. Our methodological framework will allow UAS users to manage large imagery metrics datasets derived from those dense time series. [less ▲]

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See detailVegetation classification and biogeography of European floodplain forests and alder carrs
Douda, Jan; Boublik, Karel; Slezak, Michal et al

in Applied Vegetation Science (2016)

Aim: Formalized classifications synthesizing vegetation data at the continental scale are being attempted only now, although they are of key importance for nature conservation planning. Therefore, we aim ... [more ▼]

Aim: Formalized classifications synthesizing vegetation data at the continental scale are being attempted only now, although they are of key importance for nature conservation planning. Therefore, we aim to provide a vegetation classification and to describe the main iogeographical patterns of floodplain forests and alder carrs in Europe. Location: Europe. Methods: A database of more than 40 000 vegetation plots of floodplain forests and alder carrs across Europe was compiled. After geographic stratification, 16 392 plots were available for classification, which was performed using the supervised method Cocktail. We also searched for new associations using semi-supervised K-means classification. The main biogeographic patterns and climate-related gradients in species composition were determined using detrended correspondence analysis and cluster analysis. Results: Thirty associations of floodplain forests and alder carrs were distinguished, which belong to five alliances. The Alnion incanae includes riparian, seepage and hardwood floodplain forests in the nemoral and hemiboreal zones (dominated by Alnus glutinosa and Fraxinus excelsior) and in the boreal zone (dominated by A. incana). The Osmundo-Alnion represents oceanic vegetation dominated by Alnus glutinosa, Fraxinus angustifolia and F. excelsior distributedmostly on the Iberian Peninsula and composed of species with Atlantic distribution and Iberian endemics. The Populion albae comprises floodplain forests frequently dominated by Fraxinus angustifolia, Populus alba and P. nigra that arewidespread in floodplains of large rivers under summer-dry climates in the Mediterranean region. The Platanion orientalis represents easternMediterranean floodplain forests dominated by Platanus orientalis. The Alnion glutinosae includes forest swamps dominated by Alnus glutinosa distributed mostly in the nemoral and hemiboreal zones. The main biogeographic patterns within European floodplain forests and alder carrs reflect the climatic contrasts between the Mediterranean, nemoral, boreal andmountain regions. Oceanic floodplain forests differ fromthose in the rest of Europe. The hydrological regime appears to be themost important factor influencing species compositionwithin regions. Conclusions: This study is the first applying a formalized classification at the association level for a broad vegetation type at the continental scale. The proposed classification provides the scientific basis for the necessary improvement of the habitat classification systems used in European nature conservation. [less ▲]

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See detailDendroécologie du hêtre en forêt de Soignes : Les cernes des arbres nous renseignent sur les changements récents et futurs
Latte, Nicolas ULg; Kint, Vincent; Drouet, Thomas et al

in FORÊT.NATURE (2015), 137(Octobre-Novembre-Décembre), 24-37

La dendroécologie combine la dendrochronologie et l’écologie forestière. Elle a permis d’analyser les cernes des hêtres de la forêt de Soignes et de comparer les tendances dans le contexte plus large des ... [more ▼]

La dendroécologie combine la dendrochronologie et l’écologie forestière. Elle a permis d’analyser les cernes des hêtres de la forêt de Soignes et de comparer les tendances dans le contexte plus large des hêtraies de Belgique. Depuis la fin des années ‘70, le hêtre devient de plus en plus sensible au climat, surtout en Soignes. L’augmentation de la fréquence et de l’intensité des sécheresses printanières et des canicules ont affecté négativement la croissance annuelle des hêtres. Les prévisions climatiques pour le 21e siècle présage une rapide aggravation. Les risques encourus par l’essence aboutissent à de nouvelles réflexions sur la gestion de la hêtraie de Soignes. Pour les peuplements existants : une sylviculture dynamique avec des éclaircies fortes et fréquentes afin de limiter la concurrence pour les ressources et favoriser la croissance individuelle des arbres. Pour la régénération des vieilles hêtraies : les remplacer par d’autres essences plus tolérantes ou favoriser le mélange et confiner le hêtre aux surfaces limitées des stations les plus fraîches. Un risque mesuré pourrait être pris en regard du rôle patrimonial des hêtraies cathédrales en Soignes. Toutefois, ce faciès peut être obtenu avec d’autres essences. [less ▲]

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See detailDosage de la lumière pour maintenir la coexistence d’espèces d’ombre et de demi-ombre dans la régénération de la futaie irrégulière
Ligot, Gauthier ULg; Balandier, Philippe; Courbaud, Benoît et al

in Revue Forestière Française (2015), 3

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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 (2015), 10(11),

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 ▲]

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See detailLa carte bioclimatique de Wallonie : un nouveau découpage écologique du territoire pour le choix des essences forestières
Van der Perre, Raphaèle; Bythell, Stephen; Bogaert, Patrick et al

in Forêt-Nature (2015), (135), 47-58

Dans le cadre de la révision du Fichier écologique des essences et du Guide de boisement, les deux principaux outils à disposition du gestionnaire pour la bonne adéquation essence-station, un nouveau ... [more ▼]

Dans le cadre de la révision du Fichier écologique des essences et du Guide de boisement, les deux principaux outils à disposition du gestionnaire pour la bonne adéquation essence-station, un nouveau découpage du territoire a été réalisé sur base de données climatiques actualisées et à la lumière des nouvelles connaissances en autécologie des essences. Dans un premier temps, les données de températures, de précipitations et de rayonnement solaire, de 1986 à 2005, ont été rassemblées et spatialisées sur une maille de 500 x 500 mètres. Le croisement de ces données avec les sensibilités écologiques des essences a permis d’aboutir à un nouveau découpage du territoire en dix zones bioclimatiques. Ces dix zones remplacent les territoires écologiques comme porte d’entrée du Guide de boisement. Elles permettent également de proposer des cartes de zones à risques pour les différentes essences en fonction de paramètres climatiques spécifiques et selon les quatre niveaux d’aptitude définis pour le nouveau Fichier écologique des essences (optimum, tolérance, tolérance élargie et exclusion). [less ▲]

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See detailIncreased tree-growth synchronization of beech (Fagus sylvatica L.) in response to climate change in northwestern Europe
Latte, Nicolas ULg; Lebourgeois, François; Claessens, Hugues ULg

in Dendrochronologia (2015), 33

To better understand how the radial growth of beech (Fagus sylvatica L.) high forests has responded to climate change, we selected 12 sites (137 trees) with optimal growing conditions along a W − E ... [more ▼]

To better understand how the radial growth of beech (Fagus sylvatica L.) high forests has responded to climate change, we selected 12 sites (137 trees) with optimal growing conditions along a W − E altitudinal gradient (67–590 m) in Belgium. We evaluated temporal changes in growth response to climate by using pointer year analysis, moving mean sensitivities (1860–2011), and moving bootstrapped correlation coefficients (1952–2011). The strongest driving climatic variables were identified by using the partial least squares method. The common patterns of growth trends, pointer years, and mean sensitivities among sites provided evidences for the impact of environmental changes operating at a regional scale. The results of growth–climate analysis indicated that these changes were strongly influenced by the climatic conditions of the previous year. The climate sensitivity of beech increased progressively in response to more frequent and intense heat waves and warming-related droughts, especially during recent decades, leading to remarkable inter-site synchronization. The changes were much more pronounced for sites located in lowlands (<300 m). The differences in growth responses along the altitudinal gradient and the consequences of warming for beech growth and physiology are discussed. [less ▲]

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