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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.)

Individual tree diameter at breast height (DBH) distribution is an important information for forest management planning. Forest managers obtain the DBH data either by field measurements or estimations using predictive models. However, probability distribution models are still lacking or need improvement. Therefore, we aimed to construct and fit diameter distribution models that reflect forest structure and composition change. We evaluated gamma, log-normal, and Weibull probability distribution functions (PDFs) for two commercially important tree species, black spruce (Picea mariana (Mill) B.S.P.) and jack pine (Pinus banksiana Lamb), grown in natural stands across Ontario, Canada. We modelled the parameters of the distributions as a function of stand-level variables for these species. We used DBH data from 735 permanent sample plots. Our results showed that all three evaluated PDFs reflected observed DBH distribution. We demonstrated that the moment-based recovered parameters could represent the maximum likelihood-estimated parameters precisely, and parameters of the PDFs can be modelled as a function of stand-level dynamic covariates. The models unbiasedly predicted the PDF parameters DBH means and DBH classes. The R2 of the model fit ranged between 0.35 and 0.98 for the predicted parameters and 0.90 and 0.97 for the predicted DBH. [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.)

Non-industrial wood ash may be an effective forest soil nutrient supplement but its use in Canada is largely restricted because of unknown concentrations of trace metal contaminants. Sugar maple (Acer saccharum Marshall) is particularly sensitive to low soil calcium (Ca) levels, and though maple syrup is of great economic importance in Canada, it is unknown how wood ash could affect sap chemistry. Non-industrial wood ash (NIWA; 6 Mg·ha−1) applied to experimental plots in Muskoka, Ontario was rich in Ca (27%), while metal concentrations were well below provincial regulatory limits. One-year post-application, significant increases were observed in the treated plots in the soil pH and base cations (Ca, K, and Mg) in the surface soil horizons, and metal concentrations in the litter. Sap yield in the control plots was significantly lower in the first-year post-application than in the second year, but no other differences were found. In both tapping years, sap sweetness remained similar and differences in nutrient and metal concentrations between treatments were generally small and inconsistent. Foliar chemistry remained largely unchanged 1 year following application, except for K that was twice as high in the treated plots. Ultimately, NIWA is unlikely to significantly alter sugar maple sap chemistry, indicating that it is a viable nutrient supplement that can enhance soil fertility in sugar bushes with no impact on sap sweetness. [ABSTRACT FROM AUTHOR]

Fungi are primary agents of coarse woody debris (CWD) decay in boreal forests, playing an essential role in nutrient cycling and carbon storage. We compared fungal community assemblages using alpha and beta diversity metrics, and physical and chemical properties of CWD across three tree species (trembling aspen [Populus tremuloides], black spruce [Picea mariana], and jack pine [Pinus banksiana]), five decay classes, and two stand development stages, differing in time since stand replacing disturbance in Ontario's boreal forest region. We sampled 180 individual CWD logs from 6 independent stands, with 3 replicates per each species × decay class combination at each site. Using high-throughput sequencing of marker DNA, we found that fungal community structure significantly differed across tree species, decay stage, and stand age. Fungal diversity was highest in decay class 4 CWD. We found that Mn and K concentrations, total carbon, C/N ratio, N/P ratio, and moisture content were important predictors of fungal composition across CWD species and/or decay stage. This study suggests that forest management guidelines that consider both deadwood quantity and quality will support a broader range of fungal species and communities through post-disturbance stand development. [ABSTRACT FROM AUTHOR]

This analysis quantifies projected carbon (C) storage in harvested wood products (HWP) from Ontario’s Crown forests. The large-scale forest C budget model, FORCARB-ON, was applied to estimate HWP C stock changes using the production approach defined by the Intergovernmental Panel on Climate Change. Harvested wood volume was converted to C mass and allocated to four HWP end-use categories: in use, landfill, energy, and emission. The redistribution of C over time among HWP end-use categories was calculated using a product age-based C-distribution matrix. Carbon emissions for harvest, transport, and manufacturing, as well as emission reductions from the use of wood in place of other construction materials and fossil fuels were not accounted for. Considering the wood harvested from Ontario Crown forests from 1951 to 2000 and the projected harvest from 2001 to 2100, C storage in HWP in use and in landfills is projected to increase by 3.6 Mt·year–1 during 2001–2100, with an additional 1.2 Mt·year–1 burned for energy. Annual additions of C projected for HWP far outweighs the annual increase of C storage in Ontario’s Crown forests managed for harvest, which is projected to increase by 0.1 Mt·year–1 during the same period. These projections indicate that regulated harvest in Ontario results in a steadily increasing C sink in HWP and forests. Uncertainties in HWP C estimation are also discussed. Cette analyse quantifie la séquestration prévue du carbone (C) dans les produits du bois provenant des forêts publiques de l’Ontario. Le modèle de bilan à grande échelle de C de la forêt, FORCARB-ON, a été utilisé pour estimer les changements dans les stocks de carbone associés aux produits du bois à l’aide de l’approche de production définie par le « Intergovernmental Panel on Climate Change ». Le bois récolté a été converti en masse de C et alloué à quatre catégories d’utilisation ultime des produits du bois : en usage, enfouissement, énergie et émission. La redistribution de C dans le temps parmi les catégories d’utilisation ultime des produits du bois a été calculée à l’aide d’une matrice de distribution de C basée sur l’âge des produits. Les émissions de C engendrées par la récolte, le transport et la transformation ainsi que la réduction des émissions due à l’utilisation du bois à la place d’autres matériaux de construction et des combustibles fossiles n’ont pas été comptabilisées. En tenant compte du bois récolté sur les terres publiques de l’Ontario de 1951 à 2000 et de la récolte prévue de 2001 à 2100, la séquestration de C dans les produits du bois en usage et dans les enfouissements devrait augmenter de 3,6 Mt·an–1 de 2001 à 2100 et l’utilisation du bois à des fins énergétiques devrait générer 1,2 Mt·an–1 de plus. Les prévisions d’ajout annuel de C dans les produits du bois dépassent largement l’augmentation annuelle de la séquestration de C dans les forêts publiques aménagées de l’Ontario qui devrait atteindre 0,1 Mt·an–1 pendant la même période. Ces projections indiquent que la récolte réglementée en Ontario se traduit par un puits de C qui augmente régulièrement dans les produits du bois et les forêts. Les incertitudes associées à l’estimation de C dans les produits du bois sont également abordées dans la discussion. [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.)

Airtankers are commonly used for initial attack (IA) to reduce the likelihood of wildland fires escaping containment efforts. We examined IA airtanker dispatch decisions for forest fires in Ontario, Canada, through an analysis of historical fire records from 2001 to 2019. A hurdle modelling approach that predicts the probability of airtanker(s) being dispatched and then the number of airtankers sent was used. Two different hurdle models were considered depending on the timing of the information available to the decision maker: a "fire report model" based upon the information available when a fire is first reported, and an "initial attack model" using information available at the time IA action began. Both models indicated that the most influential covariates for airtanker dispatch are the fire weather index, fuel volatility, observed fire rate of spread, fire size at IA, and cause of ignition. When evaluating the predictive ability of the models on a validation data set, the "initial attack model" performed better than the "fire report model". Our models generally perform well when predicting none, one, or two airtankers on IA, but they generally underpredict when more than two airtankers are dispatched, which suggests risk-averse decision-making in fire management resource dispatching. [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.)

Stand structure diversity is hypothesized (i) to increase with stand development and (ii) to be greater in mixedwood stands than in conifer and broadleaf stands. We examined the effects of time since stand-replacing fire (TSF) and overstory type on stand volume, stand density, and tree-size variability, which is measured using Shannon’s diversity index (H′) and coefficient of variation, in fire-origin boreal forest stands. We sampled 36 stands representing conifer, mixedwood, and broadleaf overstory types, ranging in ages from 72 to 201 years TSF on upland mesic sites in northwestern Ontario, Canada. Stand volume decreased in older mixedwood and broadleaf stands, but followed a U-shaped pattern in conifer stands with TSF. Diameter-at-breast-height-based H′ followed an inverse U-shaped pattern with TSF for all overstory types. Height-based H′ decreased with TSF in conifer and mixedwood stands but peaked at the intermediate age class in broadleaf stands. Diameter-at-breast-height- and height-based coefficient of variation indices followed an inverse U-shaped distribution with TSF. Our results partially supported the two hypotheses, as (i) the 124- to 139-year-old stands were most diverse and (ii) mixedwood stands were more than or as equally diverse as conifer and broadleaf stands, depending on stand development stage and the diversity indices used. Nous posons les hypothèses que (i) la diversité de la structure des peuplements augmente au fil de leur développement et (ii) cette diversité est plus grande dans les peuplements mixtes que dans les peuplements résineux et feuillus. Dans des peuplements boréaux issus de feu, nous avons étudié les effets du temps écoulé depuis le dernier feu (TDF) et de la composition du couvert dominant sur le volume et la densité du peuplement et sur la variabilité de la taille des arbres, déterminée à l’aide de l’indice de diversité de Shannon (H′) et du coefficient de variation. Sur des stations mésiques et bien drainées du nord-ouest de l’Ontario, au Canada, nous avons échantillonné 36 peuplements représentant des peuplements résineux, mixtes et feuillus pour lesquels le TDF variait de 72 à 201 ans. Le volume à l’hectare diminuait dans les vieux peuplements mixtes et feuillus, mais la relation entre le volume et le TDF suivait une trajectoire en U dans les peuplements résineux. La relation entre la valeur de H′ basée sur le diamètre à hauteur de poitrine et le TDF suivait une trajectoire en U inversé pour tous les types de peuplement. La valeur de H′ basée sur la hauteur diminuait avec une augmentation du TDF pour les peuplements résineux et mixtes, mais a atteint un sommet à la classe d’âge intermédiaire dans les peuplements feuillus. Les relations entre le TDF et la valeur du coefficient de variation basée sur le diamètre à hauteur de poitrine et sur la hauteur suivaient des trajectoires en U inversé. Nos résultats n’ont que partiellement supporté les deux hypothèses puisque (i) les peuplements de 124 à 139 ans étaient les plus diversifiés et (ii) la diversité des peuplements mixtes était supérieure ou égale à celle des peuplements résineux et feuillus, dépendamment du stade de développement des peuplements et de l’indice de diversité utilisé. [ABSTRACT FROM AUTHOR]

Presents further discussion of a study concerning the effects of fire suppression in the boreal forest in Ontario. Impact of suppression on fire size; Evidence on the increase in the fire-return interval; Disclosure on the average annual burn fractions for protected and unprotected forests.

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.)

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.)

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.)

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.)

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.)

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.)

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.)

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.)

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.)

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.)

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.)

In an environment of uncertain climatic change, there is an urgent need to develop robust reserve networks, i.e., networks that conserve species across multiple climatic futures. Using climatic envelopes based on multiple future climatic scenarios, we first estimate the impacts that these scenarios might have on the distributions of 63 native tree species in the Province of Ontario. Next, an optimization model is applied to expand an existing system of reserves in this province by determining the minimum number of optimal locations for additional reserves both with and without the need for migration. The optimization model formulated differs from previous work in that it meets the need for present and future distributions to occur in the same reserve and accommodates multiple differing climate change scenarios rather than a single scenario. The reserve selection approach described here can be applied anywhere that species' distributions and environmental grids are available. Although this approach is designed to produce a robust solution to the uncertainties over future climatic scenarios, it does not eliminate these uncertainties because the proposed solutions inherit the uncertainties of the global climate change models. Dans un contexte d'incertitude face au changement climatique, il est urgent de mettre sur pied des réseaux robustes de réserves, c.-à-d. des réseaux qui préservent les espèces face à un éventail d'avenirs climatiques plausibles. À l'aide d'enveloppes climatiques basées sur un ensemble de scénarios climatiques futurs, nous estimons d'abord l'impact que ces scénarios pourraient avoir sur la répartition géographique de 63 espèces indigènes arborescentes dans la province d'Ontario. Ensuite, un modèle d'optimisation est appliqué pour étendre le système existant de réserves dans cette province en déterminant le nombre minimum de localisations optimales pour des réserves additionnelles avec et sans besoin de migration. Le modèle d'optimisation qui a été développé diffère des modèles précédents en ce qu'il répond à la nécessité que les répartitions actuelle et future se retrouvent dans la même réserve et qu'il tient compte de plusieurs scénarios de changement climatique différents plutôt que d'un seul. L'approche présentée ici pour choisir des réserves peut être appliquée partout où la répartition des espèces et des grilles environnementales sont disponibles. Bien que cette approche soit conçue pour produire une solution robuste aux incertitudes inhérentes aux scénarios climatiques futurs, elle n'élimine pas ces incertitudes parce que les solutions proposées héritent des incertitudes des modèles de changement climatique planétaire. [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.)

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.)

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.)

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.)

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.)

Preindustrial forest composition for >180 000 km2 throughout central and northeastern Ontario was recreated from Ontario Crown land survey notes (1816–1955) and compared with existing forest composition derived from current Forest Resource Inventories (1998–2009) in each of Site Regions 3E, 4E, and 5E. A validation analysis was performed using the Forest Resource Inventory data to test the assumption that sampling the land survey tree species composition along township boundaries is adequate in describing the composition of the whole forest. The majority of tree species in each of the three site regions validated successfully. A binary logistic regression model allowed birch genera to be classified at the species level to aid in the interpretation of survey notes. All analyses showed significant reductions in conifers (especially red pine (Pinus resinosa Ait.), white pine (Pinus strobus L.), and eastern larch (Larix laricina (Du Roi) K. Koch)) and significant increases in maple (Acer spp.), oak (Quercus spp.), white birch (Betula papyrifera Marsh.), and poplar (Populus spp.). La composition forestière préindustrielle d’une aire de plus de 180 000 km2 dans le centre et le nord-est de l’Ontario a été reconstituée à partir de notes d’inventaire des terres publiques de l’Ontario (1816–1955) et comparée à la composition forestière actuelle déterminée à partir des inventaires des ressources forestières (1998–2009) dans chacune des régions écologiques 3E, 4E et 5E. Une analyse de validation a été effectuée avec des données de l’inventaire des ressources forestières pour tester l’hypothèse que l’échantillonnage de la composition forestière de l’inventaire des terres le long des limites de comté est adéquat pour décrire la composition de l’ensemble de la forêt. La majorité des espèces d’arbre dans chacune des trois régions écologiques ont été validés avec succès. Un modèle de régression logistique binaire a permis de classifier les bouleaux à l’espèce pour faciliter l’interprétation des notes d’inventaire. Toutes les analyses ont montré qu’il y avait une réduction significative des conifères (en particulier le pin rouge (Pinus resinosa Ait.), le pin blanc (Pinus strobus L.) et le mélèze laricin (Larix laricina (Du Roi) K. Koch)) et une augmentation significative des érables (Acer spp.), des chênes (Quercus spp.), du bouleau à papier (Betula papyrifera Marsh.) et des peupliers (Populus spp.). [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.)

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.)

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.)

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.)

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.)

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.)

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.)

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.)

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.)

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.)

The 20-year successional development of understory vegetation was investigated in jack pine (Pinus banksiana Lamb.) and black spruce (Picea mariana (Mill.) BSP) plantations in northern Ontario, in relation to stand species composition, species diversity, and the rate of change in stands of different post-disturbance ages. Detrended correspondence analysis (DCA) ordination of plantation stands using species composition data from 1978 and 1998 indicated variation among stands in directions and rates of change in species composition over time. Rank correlations of environmental variables with the DCA axes suggested a light–moisture gradient along the first axis, driven by soil texture and overstory species, and a gradient representing time since disturbance and stand development along the second axis. Although overall beta diversity among stands remained constant over time, some convergence was found among a smaller group of stands, and divergence was noted between spruce and pine stands. Species composition also became more highly correlated with environmental variables through time. From 1978 to 1998, species richness increased in young, dry pine stands; decreased in older, dry pine stands; and decreased in young spruce stands. The understory vegetation in stands on mesic sites was more diverse than that on dry, sandy sites at both times. The rate of change in understory species composition slowed with time after disturbance, indicating an increasing stability in micro en vi ron men tal conditions as the influence of harvesting disturbance became weaker with time.Le développement sur une période de 20 ans de la succession de la végétation de sous-étage a été étudié dans des plantations de pin gris (Pinusbanksiana Lamb.) et d'épinette noire (Piceamariana (Mill.) BSP) situées dans le Nord de l'Ontario en lien avec la composition en espèces du peuplement, la diversité des espèces et le taux de changement dans des peuplements d'âge différent issus de perturbations. L'ordination des plantations par l'analyse de correspondance en utilisant les données de composition en espèces de 1978 et de 1998 indiquait une variation entre les peuplements dans la direction et le taux de changement dans la composition en espèces en fonction du temps. Les corrélations de rang des variables environnementales avec les axes associés à l'analyse de correspondance suggèrent l'ex istence d'un gradient de lumière et d'humidité le long du premier axe, déterminé par les espèces de l'étage dominant et la texture du sol, ainsi qu'un gradient représentant le développement du peuplement et le temps écoulé depuis la perturbation le long du deuxième axe. Bien que dans l'ensemble la diversité bêta parmi les peuplements soit demeurée constante dans le temps, une certaine convergence a été observée parmi un plus petit groupe de peuplements et une divergence a été notée entre les peuplements d'épinette et de pin. Avec le temps, la composition en espèce est également devenue plus étroitement corrélée avec les variables environnementales. De 1978 à 1998, la richesse en espèces a augmenté dans les jeunes peuplements secs de pin et a diminué dans les plus vieux peuplements secs de pin et les jeunes peuplements d'épinette. La végétation de sous-étage dans les peuplements sur des stations mésiques était plus diversifiée que sur les stations sèches et sableuses aux deux moments. Le taux de changement dans la composition en espèces de sous-étage a diminué avec le temps après la perturbation, reflétant la stabilité croissante des conditions en vironnementales à mesure que l'influence de la perturbation due à la récolte s'atténuait.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Describes the spatial and temporal patterns associated with canopy interception, throughfall and net forest water along a black spruce topo-sequence situated in northwestern Ontario. Detection of downward shifts in the potential of hydrogen ions for throughfall; Demographic profile of the study area; Modal conditions for three discrete vegetative communities.

Quantifies the relationship between mean age and net primary productivity (NPP) of black spruce stands in Ontario using practical methodology. Definition of mean age-NPP relationship; Approach in reducing uncertainty in NPP estimates; Possibility of measuring NPP components.

Examines the influence of root and butt rots on windfall and mortality of residual trees following partial cutting in Ontario. Measurement of decay at stump level made on cross-sectional discs; Use of laboratory culturing procedures in identifying causal fungi; Association between root rot and windfall.

Analyzes the effects of silvicultural disturbances on cryptogam diversity in the boreal-mixedwood forest in Ontario. Essence of cryptogams in forest ecosystem and diversity; Conifer release treatments performed; Contribution of forest management in the loss of species and species diversity from forest ecosystems.

Investigates the species, geographic distribution, host range and site relationships Armillaria in Ontario. Identification of species by polymerase chain reaction and diploid-haploid pairings; Preference for calcareous soils; Association between Armillaria species and soil texture.