Personne : Ruel, Jean-Claude
En cours de chargement...
Date de naissance
Projets de recherche
Nom de famille
Université Laval. Département des sciences du bois et de la forêt
Résultats de recherche
Voici les éléments 1 - 5 sur 5
- PublicationAccès libreVérification d'une méthode d'inventaire écologique de la frange urbaine : application aux sites forestiers de l'Étang du Moulin, à Beauport(1983) Ruel, Jean-ClaudeAfin de répondre aux besoins des aménagistes du milieu forestier périurbain (Bélanger et Pineau, 1983), Bélanger et al. (1984) proposent une méthode d'inventaire écologique qui tente d'intégrer le facteur humain dans la description du milieu. Cette méthode utilise quatre niveaux de perception écologique de l'espace: la région écologique, le sous-système écologique, le type écologique et la phase écologique. Le présent travail consiste à vérifier cette méthode en l'appliquant à un territoire précis : les environs de l’Étang du Moulin, à Beauport. Avant de procéder à la description écologique du milieu étudié, il a fallu procéder à quelques études préliminaires, notamment pour permettre de définir des groupements végétaux forestiers. Six cas types ont été retenus pour un examen plus poussé : l'évaluation du potentiel récréatif de la zone étudiée, l'expansion du développement résidentiel du secteur Courville, l'aménagement du boisé de l’Étang du Moulin et du parc linéaire des Marches Naturelles, la gestion du camping municipal de Beauport, ainsi que la réhabilitation d'une sablière désaffectée située en face du cimetière de Villeneuve. L'examen de ces cas types a permis de répondre à une bonne part des besoins d'information identifiés. Des améliorations sont proposées, toutefois, pour augmenter l'efficacité de la méthode. C'est ainsi que sont proposées une redéfinition de la phase écologique de façon à définir l'occupation par l'utilisation et l'état actuels du site, l'introduction au sein du type écologique d'un critère de discrimination supplémentaire, la perturbation du sol, ainsi que l'identification d'un niveau plus fin de perception écologique, dénommé provisoirement la sous-phase écologique.
- PublicationAccès libreThe motion of trees in the wind : a data synthesis(Göttingen Copernicus, 2021-07-06) Jackson, Toby D.; Sethi, Sarab; Dellwik, Ebba; Angelou, Nikolas; Bunce, Amanda; Emmerik, Tim van; Duperat, Marine; Ruel, Jean-Claude; Wellpott, Axel; Bloem, Skip Van; Achim, Alexis; Kane, Brian; Ciruzzi, Dominick M.; Loheide, Steven P.; James, Ken; Burcham, Daniel; Moore, John; Schindler, Dirk; Kolbe, Sven; Wiegmann, Kilian; Rudnicki, Mark; Lieffers, Victor J.; Selker, John; Gougherty, Andrew V.; Newson, Tim; Koeser, Andrew; Miesbauer, Jason; Samelson, Roger; Wagner, Jim; Ambrose, Anthony R.; Detter, Andreas; Rust, Steffen; Coomes, David; Gardiner, BarryInteractions between wind and trees control energy exchanges between the atmosphere and forest canopies. This energy exchange can lead to the widespread damage of trees, and wind is a key disturbance agent in many of the world’s forests. However, most research on this topic has focused on conifer plantations, where risk management is economically important, rather than broadleaf forests, which dominate the forest carbon cycle. This study brings together tree motion time-series data to systematically evaluate the factors influencing tree responses to wind loading, including data from both broadleaf and coniferous trees in forests and open environments. Wefoundthatthetwomostdescriptive features of tree motion were (a) the fundamental frequency, which is a measure of the speed at which a tree sways and is strongly related to tree height, and (b) the slope of the power spectrum, which is related to the efficiency of energy transfer from wind to trees. Intriguingly, the slope of the power spectrum was found to remain constant from medium to high wind speeds for all trees in this study. This suggests that, contrary to some predictions, damping or amplification mechanisms do not change dramatically at high wind speeds, and therefore wind damage risk is related, relatively simply, to wind speed. Conifers from forests were distinct from broadleaves in terms of their response to wind loading. Specifically, the fundamental frequency of forest conifers was related to their size according to the cantilever beam model (i.e. vertically distributed mass), whereas broadleaves were better approximated by the simple pendulum model (i.e. dominated by the crown). Forest conifers also had a steeper slope of the power spectrum. We interpret these finding as being strongly related to tree architecture; i.e. conifers generally have a simple shape due to their apical dominance, whereas broadleaves exhibit a much wider range of architectures with more dominant crowns.
- PublicationRestreintEffect of thinning on the relationship between mean ring density and climate in black spruce (Picea mariana (Mill.) BSP).(London Milford, 2017-09-23) Ruel, Jean-Claude; Gauthray-Guyénet, Vincent; Pothier, David; Schneider, Robert; Achim, Alexis; Franceschini, TonyRelationships between wood density and climatic variables have generally been developed from unmanaged stands near the treeline. Using black spruce (Picea mariana (Mill.) B.S.P.) samples from the managed boreal zone in Canada, we investigated whether the relationship between mean ring density (MRD) and climatic variables is altered by silvicultural practices. We analysed the MRD of 10 384 growth rings from 72 trees sampled among 18 stands (nine thinned, nine controls) across Quebec, Canada. We constructed a mixed-effects model relating MRD to cambial age and ring width (RW). Model residuals (εM1), i.e. the difference between observed and predicted MRD, were then related to monthly temperature and precipitation of the year of ring formation and the year before. After thinning, RW slightly increased while MRD remained constant, thus lowering the strength of the relationship between MRD and RW. εM1 were positively related to spring temperatures and negatively related to summer temperatures and precipitation. No effect of thinning on the relationship between εM1 and climatic variables was observed. The sample trees grew in less limiting conditions than at the treeline so the reduced strength of the relationship between MRD and growth rate in thinned stands may result from a higher photosynthetic capacity. Such results may have implications in forest management as thinning could increase the value of black spruce wood.
- PublicationRestreintWood degradation after windthrow in a northern environment(Forest Products Society, 2010-01-31) Ruel, Jean-Claude; Cloutier, Alain; Espinoza-Herrera, Raul; Achim, Alexis; Brossier, BenoîtSevere windthrows often require salvage operations that can lead to increased costs. Given these extra costs, it is of paramount importance to make sure that wood degradation does not become so advanced that significant value loss is incurred. The rate at which wood deteriorates is a function of many factors, including species and climate. The study was conducted in a northern area affected by two partial windthrows. Logs from the damaged area were collected for two species, balsam fir (Abies balsamea) and black spruce (Picea mariana). Logs were classified into one of three degradation classes based on visual assessments. A sample of logs from standing trees was also collected. In total, 167 logs were sampled. Each log was sawn and one piece of lumber was selected from each to determine the bending strength and stiffness and the visual grade. The time since tree death, as determined from dendrochronology, ranged from 1 to 31 years. The visual grade of the lumber was not affected after 1 year but severe downgrades were observed after 4 years. Moisture content decreased rapidly for both species during the first year and continued to decrease until 4 years after mortality. No clear decrease in bending stiffness was identified even though such a tendency was noticed for older black spruce windthrows. Bending strength became variable after 4 years for balsam fir and was reduced after 4 years for black spruce. Windthrows older than 7 years will produce low visual grade timber of reduced bending strength and possibly of lower bending stiffness.
- PublicationRestreintRelating mechanical strength at the stem level to values obtained from defect-free wood samples(2010-08-22) Ruel, Jean-Claude; Cloutier, Alain; Espinoza-Herrera, Raul; Achim, AlexisStem or branch failure is a recurrent problem in silviculture and arboriculture. The risk of rupture varies with species in relation to the inherent mechanical properties of the species and the presence of defects. In general, calculations of critical loads for breakage are based on mechanical properties determined from defect-free samples and adjustment factors that try to scale up to full trees that include defects. This study aims at developing an objective method to scale up mechanical resistance to breakage from defect-free samples to full trees, including different types of defects. It combines two approaches. In the first one, a correction factor is determined from a meta-analysis of various tree-pulling studies involving balsam fir [Abies balsamea (L.) Mill.], white spruce [Picea glauca (Moench) Voss], jack pine [Pinus banksiana Lamb.], and black spruce [Picea mariana (Mill.) B.S.P.]. The second approach consists in obtaining empirical data from three-point bending tests using 8-foot (2.44 m) logs with various amounts of decay. Results show that the correction required varies according to the species and the presence of some defects. For balsam fir, which was the species showing the most important difference between whole log and small sample values, differences in correction factors were found between tree-pulling tests and three-point bending tests. Data from winching tests tend to underestimate the stem’s resistance to breakage since they likely represent the weakest trees among those tested. No relationship was found between the adjustment factors and different indices used in arboriculture to account for decay, showing the complexity of mechanical resistance at the stem level.