Search

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Herbivores affect plants via direct consumption, but also indirectly via changes in the vegetation. These indirect effects may only manifest after decades of exposure and, as a result, their impact is rarely accounted for. To better understand the direct and indirect impacts of a large herbivore, moose (Alces alces), on forests, we measured tree growth in areas that were both subjected to and excluded from herbivory for over 80 years. Growth data were gathered from five tree species, ranging from low to high palatability. We found that at small sizes, Betula papyrifera, a preferred species, benefited from herbivore exclusion. However, larger individuals grew more when exposed to herbivory, a response we attribute to lower competition in heavily browsed conditions. Populus tremuloides, a highly preferred tree, did not show any differences between levels of herbivory. Abies balsamea, a preferred winter browsed, was only marginally affected by browsing at smaller sizes. The two non-preferred species, Picea glauca and Picea mariana, did not show differential growth between herbivory levels. We conclude that herbivores can impact forests through both direct and indirect effects, that these effects are size specific, and that effects vary among species in ways not always predicted by consumption patterns. [ABSTRACT FROM AUTHOR]

The predictions of properties for wood disc average are seldom reported, and they are important for sorting out logs based on their quality. The minimum near infrared (NIR) spectra required to predict wood disc average properties would also be of critical importance. In this study, calibration and prediction models for wood disc average properties were developed using NIR spectral data for balsam fir (Abies balsamea (L.) Mill.) and black spruce (Picea mariana (Mill.) B.S.P.) samples collected from 14 different sites across Newfoundland, Canada. The calibration was done against area-weighted average wood properties determined by SilviScan. NIR spectra were collected in 18 mm increments from the radial-longitudinal face of green and oven-dried samples. Results showed that using NIR spectra from three spots per wood strip was sufficient for the modeling and prediction for density and module of elasticity (MOE). The coefficients of determination ranged from 0.76 (MOE of green wood samples) to 0.88 (density of oven-dried wood samples). However, the microfibril angle (MFA) cannot be well predicted from either green wood or oven-dried wood NIR spectra. Our results further showed that the NIR spectra collected from oven-dried wood samples gave better calibration and prediction than those collected from green wood samples. Les prédictions des propriétés moyennes des disques de bois sont rarement présentées, bien qu'elles soient importantes pour trier les billes en fonction de leur qualité. Les spectres minimum dans le proche infrarouge (PIR) qui sont nécessaires pour prédire les propriétés moyennes des disques de bois ont aussi une importance cruciale. Dans cette étude, des modèles de prédiction et de calibration des propriétés moyennes des disques de bois ont été développés à partir de données spectrales PIR d'échantillons de sapin baumier (Abies balsamea (L.) Mill.) et d'épinette noire (Picea mariana (Mill.) B.S.P.) prélevés dans 14 sites différents couvrant l'ensemble de la province de Terre-Neuve, au Canada. La calibration a été effectuée à partir des propriétés moyennes du bois déterminées à l'aide de SilviScan et pondérées par la superficie. Les spectres PIR ont été obtenus à tous les 18 mm le long de la face longitudinale-radiale d'échantillons verts et anhydres. Les résultats ont démontré que l'utilisation des spectres PIR provenant de trois points par barrette de bois était suffisante pour modéliser et prédire la densité et le module d'élasticité (MOE). Les coefficients de détermination variaient de 0,76 (MOE d'échantillons de bois à l'état vert) à 0,88 (densité d'échantillons de bois à l'état anhydre). Cependant, les spectres PIR du bois vert ou anhydre ne sont pas adéquats pour prédire l'angle des microfibrilles (AMF). Nos résultats ont de plus montré que les spectres PIR des échantillons de bois à l'état anhydre permettent d'obtenir une meilleure calibration et de faire de meilleures prédictions que ceux des échantillons de bois à l'état vert. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Mineral soils exposed by fire are often covered by a layer of ash due to complete consumption of the forest floor (litter and duff). To assess the possible effects of ash on seed germination and viability of jack pine (Pinus banksiana Lamb.), black spruce (Picea mariana (Mill.) Britton, Sterns, Poggenb.), white spruce (Picea glauca (Moench) Voss), and balsam fir (Abies balsamea (L.) Mill.), a laboratory experiment was conducted using ash derived from three types of forest floor samples. The samples represented areas of high conifer concentration, high aspen concentration, and mixed aspen and conifer and were collected from five mature aspen (Populus tremuloides Michx.) – conifer mixedwood stands in southeastern Manitoba. Ash derived from each forest floor type neither prohibited nor delayed conifer germination, except that of balsam fir. Balsam fir had significantly less germination on ash derived from forest floor samples with high aspen concentration. When corrected for seed viability, balsam fir had significantly less germination on all three ash types compared with jack pine, black spruce, and white spruce. However, the impact of ash on balsam fir is unlikely to have meaningful ecological implications, as balsam fir is a climax species and will establish in undisturbed mature forests. Le sol minéral exposé par le feu est souvent recouvert d’une couche de cendre due à la combustion de la couverture morte (litière et humus). Les effets de la cendre sur la viabilité et la germination des graines de pin gris (Pinus banksiana Lamb.), d’épinette noire (Picea mariana (Mill.) Britton, Sterns, Poggenb.), d’épinette blanche (Picea glauca (Moench) Voss) et de sapin baumier (Abies balsamea (L.) Mill.) ont été évalués. Une expérience en laboratoire a été réalisée en utilisant de la cendre provenant de trois types d’échantillons de couverture morte, représentatifs de zones avec une concentration élevée de conifères (HC), de peupliers (LC) et d’un mélange de peupliers et de conifères (MC) prélevés dans cinq peuplements mixtes matures de peuplier faux-tremble (Populus tremuloides Michx.) dans le sud-est du Manitoba. La cendre provenant de chacun des types de couverture morte n’a ni inhibé ni retardé la germination des conifères à l’exception du sapin baumier. Les graines de sapin baumier germaient significativement moins bien sur la cendre provenant du type de couverture morte LC. Lorsqu’elle était corrigée pour la viabilité des graines, la germination du sapin baumier était significativement plus faible sur les trois types de cendre comparativement au pin gris, à l’épinette noire et à l’épinette blanche. L’impact de la cendre sur le sapin baumier a peu de chances d’avoir des implications écologiques significatives étant donné que le sapin baumier est une espèce climacique qui s’établira dans les forêts matures non perturbées. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Evaluates the effects of careful logging on vegetation development in Canadian boreal forest. Growth in the densities of black spruce and balsam fir; Reduction of ericaceous cover in skid trails; Implications of the pattern of vegetation development for silvicultural decisions and stand modelling.