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See detailManaging understory light to maintain the coexistence of forest tree species with different shade tolerances
Ligot, Gauthier ULg

Doctoral thesis (2014)

Similar to the management of the other environmental resources, forest management has been questioned and more sustainable practices of forest management are being sought. New close-to-nature practices ... [more ▼]

Similar to the management of the other environmental resources, forest management has been questioned and more sustainable practices of forest management are being sought. New close-to-nature practices aim to favor natural processes over human interventions. Particularly, continuous-cover forestry has the goal of relying on natural regeneration, and maintaining irregular stand structure and tree species mixture. However, maintaining mixture of species with different shade tolerances appears arduous with such a silvicultural system. Successfully managing irregular and mixed forests, relying on natural processes, requires a strong knowledge of the ecology of natural regeneration. In particular, strong knowledge is required to predict the result of the interspecific competition in the understory depending upon light availability. The amount of radiation transmitted to the understory is indeed a critical factor determining regeneration dynamics. It determines, at least in part, regeneration composition because of interspecific differences of growth and survival under shade. Moreover, our quantitative understanding of understory light in uneven-aged and mixed stands remains incomplete. A better quantitative understanding of understory light is needed to provide quantitative guidelines for the management of understory light in uneven-aged and mixed stands and, hence, for the management of natural regeneration. The purpose of this thesis is to determine how close-to-nature forest management can maintain mixtures of species with contrasting shade tolerances. I consider ecological conditions with good water and nutrient supplies. In these conditions, partially closed canopy limits the amount of light that reaches the understory, and light is the major factor driving regeneration composition. Consequently, I study the dynamics of natural regeneration with regards to light availability as well as the interception of light by the canopy of heterogeneous stands. Studying the regeneration ecology of two species with contrasting shade tolerances (Fagus sylvatica L. and Quercus petraea (Matt.) Liebl.), I find that the shade-tolerant species outgrow the less shade-tolerant species in all light conditions. Even though the control of understory light with continuous-cover silviculture is required to sustain the growth of less shade-tolerant regenerations, it might not be sufficient to maintain the coexistence of species with contrasting shade tolerances. In order to examine the effects of canopy structure and composition on understory light availability, I use a model of light interception by heterogeneous canopies after synthesizing and discussing the approaches reported in the literature. The model predicts satisfactorily measures of transmitted light even though it is a relatively simple radiative transfer model. I next explore how various silvicultural treatments can be manipulated to provide favorable understory light conditions for natural regeneration. These silvicultural strategies correspond to selective thinnings of five different types, e.g., harvesting preferentially small trees, large trees, or trees of shade-tolerant species or creating circular gaps. The results underline that creating favorable understory light conditions for natural regeneration can be achieved with various regeneration treatments. However, the adequate reduction of stand density depends upon the chosen silvicultural strategies. In particular, creating gaps of about 500 m2 provides adequate light for small regeneration clumps. Harvesting preferentially small and trees of shade-tolerant species are also appropriate but required higher harvest intensity. Harvesting preferentially large trees slightly increases understory light and promotes more shade-tolerant species than less shade-tolerant species. In order to maintain the coexistence of species with contrasting shade tolerances, forest manager must control understory light and manually suppress the regeneration of the shade-tolerant species. The outcome of this study provides foresters with the necessary tools to evaluate how silvicultural treatments can be manipulated to create or maintain favorable light conditions for the regeneration of species of different shade tolerances. Guidelines are additionally proposed for forest managers wanting to maintain the coexistence of species with contrasting shade tolerances. [less ▲]

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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 detailDynamique des forêts irrégulières et mélangées: de la modélisation aux recommandations sylvicoles
Ligot, Gauthier ULg

Conference (2014, April 29)

Close-to-nature management of forests has been increasingly advocated and practiced. However forest managers often face difficulties in maintaining the mixture of species with different shade tolerance ... [more ▼]

Close-to-nature management of forests has been increasingly advocated and practiced. However forest managers often face difficulties in maintaining the mixture of species with different shade tolerance. We studied this issue in uneven-aged acidophile medio-European beech forests. In these forests, while forest management has achieved regular timber production, it has rarely succeeded in promoting a diversified natural regeneration. In view of this, our objective is to refine our knowledge about the dynamic of uneven-aged mixed forests using a modelling approach. A set of consistent models were carried out to describe stand dynamic with, in particular, models of regeneration growth and light interception. The models were then implemented in a simulator in order to perform prospective analysis. In contrast to expectations, we found that saplings of beech, the shade-tolerant species, had the highest height growth rate at all light levels. Beech saplings reached an optimum growth at transmittance of 10%, whereas oak saplings needed more than 20%. These results indicate that oak saplings are systematically outcompeted by beech saplings across the light gradient. Thus, the control of canopy opening is not sufficient to promote the natural regeneration of oak beneath a stand also containing beech. Taking into account these latter results, we compared cutting strategies varying in type and intensity. Creating gaps of about 500 m² provided adequate light for small regeneration clumps. Cutting from below, species-specific cutting and uniform cutting were also appropriate but uniform cutting required higher harvest intensity. Cutting from above weakly increased understory light and promoted rather shade tolerant species. Finally we provided indications on different strategies that promote the regeneration of less-shade tolerant species, depending on the spatial aggregation of saplings, and the desired post-harvest stand structure and composition. [less ▲]

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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 detailModélisation de la dynamique des peuplements irréguliers
Ligot, Gauthier ULg

Scientific conference (2014, February 18)

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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 detailLes indicateurs de la pression du cerf élaphe sur la végétation du sous-bois en forêts feuillues tempérées : synthèse bibliographique
Lehaire, François ULg; Ligot, Gauthier ULg; Morelle, Kevin ULg et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2014), 18(2), 262-272

During the last decades, the populations of large herbivores have increased. Consequently, their pressure on forest vegetation has been exacerbated and has reached in some forests levels that reduced the ... [more ▼]

During the last decades, the populations of large herbivores have increased. Consequently, their pressure on forest vegetation has been exacerbated and has reached in some forests levels that reduced the diversity of forest ecosystem services. Assessing the balance between timber production and hunting remains a crucial question for forest users (foresters, hunters) and requires reliable tools such as ecological indicators. This paper reviews the ecological indicators that characterize the pressure of red deer (Cervus elaphus L.) on understory vegetation in temperate deciduous forest. Such indicators monitor the cover, height, stem density, biomass and species diversity of different indicator plant groups. These plant groups embrace species belonging to herbaceous stratum, forest regeneration or particular species such as bilberry (Vaccinium myrtillus L.) and bramble (Rubus fruticosus L.). The choice of indicator plants, as it affects considerably the performance of the ecological indicator of deer pressure on understory vegetation, must be carried out with caution taking into account plant abundance and palatability. The reviewed indicators help to understand the relationships between biodiversity, carrying capacity and deer populations. They are intended to forest managers that would like to monitor red deer pressure in regards to forest management goals and forest sustainability. [less ▲]

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See detailANALYSE SPATIO-TEMPORELLE DES DÉGÂTS D’ÉCORCEMENT DANS LES PLANTATIONS RÉSINEUSES EN RÉGION WALLONNE
Ligot, Gauthier ULg; Lehaire, François ULg; Gheysen, Thibaut et al

in Forêt Wallonne (2013), 126

Les dégâts d’écorcement inquiètent de très nombreux gestionnaires forestiers. Depuis plus de 10 ans, des inventaires sont réalisés annuellement et des outils de diagnostic ont été développés afin d’en ... [more ▼]

Les dégâts d’écorcement inquiètent de très nombreux gestionnaires forestiers. Depuis plus de 10 ans, des inventaires sont réalisés annuellement et des outils de diagnostic ont été développés afin d’en quantifier l’ampleur en Région wallonne. L’examen de ces données met en évidence le rôle prépondérant des densités de cerfs ainsi que de la structure du paysage, de la rigueur des hivers et de la capacité d’accueil du milieu. [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 detailBioindicators for measurement of red deer pressure on understory vegetation in temperate deciduous forests
Lehaire, François ULg; Morelle, Kevin ULg; Ligot, Gauthier ULg et al

Poster (2013, August)

During the last decades, populations of large herbivores have largely increased. Consequently, their pressure on forest vegetation has been exacerbated, reaching in some cases levels that reduced the ... [more ▼]

During the last decades, populations of large herbivores have largely increased. Consequently, their pressure on forest vegetation has been exacerbated, reaching in some cases levels that reduced the diversity of forest ecosystem services. Assessing the balance between timber production and hunting activities remains a crucial question for forest managers who hence need reliable tools such as ecological indicators. Our aim was to review ecological indicators that characterize the pressure of red deer (Cervus elaphus L.) on understory vegetation in temperate deciduous forest ecosystem. The choice of plants on which the variables are measured is crucial to accurately characterize the deer pressure. This choice must take into account the feeding behavior of red deer, silvicultural objectives, ease of the measurement and the occurrence of these plants within the studied habitat. Generally, it is more appropriate to use common species with a wide ecological amplitude. The choice of indicator plants must take into account plant abundance and palatability, as they both affects considerably the performance of the ecological indicator. The variability of indicators generally increases with the scarcity of the chosen indicator plant. Therefore, choosing abundant plant species appear often the best solution as the resulting have a lower variability and hence enable better to detect changes of deer pressure. At low herbivore pressure, palatable species to offer quick response to the pressure variations. Palatable species are therefore reliable plant indicator especially if these is a good balance between game population and forestry. At excessive herbivore pressure, non-palatable species are preferred. In this case, the variability of ecological indicator is smaller with non palatable plant than with palatable plant. Ecological indicators of deer pressure help to understand the relationships between biodiversity, carrying capacity and deer populations. They are intended to forest managers that would like to monitor red deer pressure in regards to forest management goals and forest sustainability. [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 detailModélisation du transfert radiatif en forêts feuillues ardennaises : adaptation de la librairie Samsaralight
Ligot, Gauthier ULg; Jonard, Mathieu; de Coligny, François et al

Conference (2013, April 08)

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See detailQuel type de peuplement pour un renouvellement naturel du douglas?
Petit, Sébastien; Claessens, Hugues ULg; Ligot, Gauthier ULg

in Forêt Wallonne (2013), 122

L'article identifie les caractéristiques des peuplements de douglas qui favoriseraient l'obtention de régénération naturelle. Les seuils d'apparition de la régénération semble facilement atteint. L ... [more ▼]

L'article identifie les caractéristiques des peuplements de douglas qui favoriseraient l'obtention de régénération naturelle. Les seuils d'apparition de la régénération semble facilement atteint. L'article encourage donc les gestionnaires à renouveler leur peuplement de manière naturelle. [less ▲]

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

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

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See detailThe detection and characterization of broad-leaved forest canopy gaps: a regeneration perspective
Bonnet, Stéphanie ULg; Bauwens, Sébastien; Lehaire, François ULg et al

Poster (2012, September)

Canopy gaps are areas of high regeneration potential and, in uneven-aged forest, gaps are therefore places of particular care for the forest manager. Nevertheless the cartography and characterization of ... [more ▼]

Canopy gaps are areas of high regeneration potential and, in uneven-aged forest, gaps are therefore places of particular care for the forest manager. Nevertheless the cartography and characterization of canopy gaps are complex issues. This paper addresses the fundamental question of the canopy gap definition: what is the minimal area, the maximal height of vegetation, type of regeneration, etc? From a regeneration point of view, canopy gaps can be defined as holes in the forest cover where light conditions are suitable for recruitment. As an active sensor, LiDAR has made it possible to tackle the problems of shadows and penetration into the canopy, typical of aerial images. This study investigates the cartography and characterization of forest canopy gaps as areas of natural regeneration. [less ▲]

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See detailAssessing and Harmonizing Lying Deadwood Volume with Regional Forest Inventory Data in Wallonia (Southern Region of Belgium)
Ligot, Gauthier ULg; Lejeune, Philippe ULg; Rondeux, Jacques ULg et al

in Open Forest Science Journal (2012), 5

Using lying deadwood or coarse woody debris (CWD) is on the rise among national and local forest inventories. We compared two generally recommended methods for lying deadwood: line intersect sampling and ... [more ▼]

Using lying deadwood or coarse woody debris (CWD) is on the rise among national and local forest inventories. We compared two generally recommended methods for lying deadwood: line intersect sampling and fixed area sampling. We assessed both methods in plots of the regional forest inventory of Wallonia (southern region of Belgium) and we developed bridging functions that converts CWD volume estimates to estimates that would have been obtained with different thresholds. [less ▲]

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See detailSimuler la ressource forestière à l'échelle d'un massif : application de SIMMEM et GYMNOS
Ligot, Gauthier ULg; Vallet, Patrick; Perin, Jérôme ULg et al

Conference (2012, April 02)

Detailed reference viewed: 38 (13 ULg)