To improve the understanding of the long-term effect of forest potassium (K)-fertilization, I revived a 23-year-old base cation fertilization experiment in a sugar maple stand in southern Quebec (45°59.6'N 73°59.9'W). My main objectives were to determine (i) the long-term percent of K derived from fertilizer in the soil-plant system using the rubidium (Rb)/K reverse tracer method, (ii) if fertilization had altered the diversity of the understory plant community, and (iii) if there was still an effect on the growth and nutrient status of the sugar maple trees. In 1988, six 40 m × 40 m plots were delineated in a sugar maple stand. In June 1989, three of these plots received 500, 250, and 250 kg•ha-1 of K2SO4, CaMg(CO3)2, and CaCO3, respectively as fine particulate matter, and the other three were left as control. Mid-canopy leaves of sugar maple trees were sampled annually in August from 1988 to 1991 and 2011 to 2012. In 2012, understory species were surveyed using the Braun-Blanquet method and ten of the most abundant and ubiquitous species were sampled for leaf chemistry. Leaves of both understory and canopy sugar maple trees were digested for nutrient concentrations using trace metal grade HNO3. In 2012, two soil pits were dug in each plot and individual horizons were sampled. Soil was extracted with 1 M NH4Cl. K, Ca, Mg, and Rb concentrations were determined by inductively coupled plasma mass spectrometry (ICP-MS) for both digested and extracted samples. Growth of sugar maple trees was assessed using tree cores taken in 2012. Fertilization increased sugar maple leaf K two years following fertilization, but the effect was no longer detectable in 2011/2012. Only Ca and Mg showed increased concentrations in the leaves the fall of the year of fertilization. The percent of leaf K derived from fertilizer in 2011/12 is nearly what it was in the fall of 1989, two months after fertilization. There was no significant difference between control and fertilized plots in the concentration of K in the sapwood of the sugar maple trees, but there was 27 ± 2 % of K derived from fertilizer in the wood in 2012. There was no difference in relative growth of sugar maple, or understory vegetation diversity or species richness in fertilized plots. Nutrient analysis of understory vegetation showed no differences in concentrations of leaf K between treatments, but percent K from fertilizers amounted to over 25 % in several species. There was no effect of treatment on soil chemistry but there was a large proportion of the original fertilizer recovered in the soil profile. The total amount of K from fertilizer held in the soil-plant system was 54 kg•ha-1 or 24 % of the original 225 kg•ha-1 of fertilizer K applied. Overall, these results suggest: (i) a short-term improvement of K status following fertilization, (ii) efficient recycling of K fertilizer in the soil-plant system of maple forests, and (iii) no obvious long-term change in understory species composition following forest fertilization. / Pour améliorer notre compréhension de l'effet de la fertilisation en potassium (K) des forêts à long terme, nous avons remis en fonction une expérience de 23 ans de fertilisation en cations basiques dans un peuplement d'érable à sucre dans le sud du Québec (45°59.6'N 73°59.9'W). Nos objectifs étaient de déterminer (i) le pourcentage de potassium (K) provenant d'engrais dans le système sol-plante 23 ans après la fertilisation en utilisant méthode de traçage inverse du rubidium (Rb) / K, (ii) si la fertilisation a modifié la biodiversité de la communauté végétale des strates arbustives et herbacées, et (iii) s'il y avait encore un effet sur la croissance et l'état nutritionnel des érables à sucre.En 1988, six 40 x 40 m parcelles ont été délimitées dans un peuplement d'érable à sucre. En juin 1989, trois de ces parcelles ont reçu 500, 250 et 250 kg•ha- 1 de K2SO4, CaMg(CO3)2 et CaCO3, respectivement, sous forme de particules fines, et les trois autres parcelles n'ont pas été fertilisées (contrôle). Les feuilles en périphérie de la couronne d'érables à sucre ont été échantillonnées annuellement en août de 1988 à 1991 et 2011 à 2012. En 2012, les espèces du sous-étage ont été échantillonnés selon la méthode de Braun-Blanquet et dix espèces les plus communes ont été analysées pour la chimie des feuilles (digestion humide au HNO3). En 2012, deux pédons ont été creusés dans chaque parcelle et les horizons ont été échantillonnés jusqu'à une profondeur de 70 cm. Les sols ont été extraits au NH4Cl (1 M). Les concentrations de Rb, K, Ca, et Mg dans les feuilles et les sols ont été déterminées par spectrométrie de masse à plasma inductif (ICP-MS). La croissance des érables à sucre a été évaluée en utilisant des carottes d'arbres récoltées en 2012.La fertilisation a augmenté le K des feuilles d'érable à sucre deux ans après la fertilisation, mais l'effet n'était plus détectable en 2011/ 2012. Les concentrations en Ca et Mg ont augmenté à l'automne de l'année de la fertilisation. Le pourcentage du K foliaire provenant des engrais en 2011/12 est à peu près ce qu'il était à l'automne 1989. La fertilisation n'a pas augmenté la concentration de K de l'aubier des arbres d'érable à sucre, mais 27 ± 2% du K provenait des engrais en 2012. La croissance relative de l'érable à sucre, et la diversité et la richesse en espèces de la végétation du sous-étage dans les parcelles fertilisées n'ont pas été affectées par la fertilisation. L'analyse des éléments nutritifs de la végétation du sous-étage n'a montré aucune différence dans les concentrations en K des feuilles entre les traitements, mais le pourcentage en K dérivé des engrais s'élevaient à plus de 25% chez plusieurs espèces. Il n'y avait aucun effet du traitement sur la chimie du sol, mais il y avait une grande proportion de l'engrais récupéré dans le profil du sol. La masse totale de K dérivé des engrais dans le système sol-plante était de 54 kg•ha-1 ou 24 % des 225 kg•ha-1 d'engrais K appliqué. Ces résultats suggèrent: (i) une amélioration à court terme de la nutrition en K suivant la fertilisation, (ii) un recyclage efficace des engrais en K dans le système sol-plante de cette érablière, et (iii) aucun changement évident à long terme de la composition en espèces du sous-étage suivant la fertilisation du peuplement.

Understanding tree species distributions and dynamics in northern boreal forests is necessary for appropriate societal action and response to critical issues such as climate change, increased economic development of northern natural resources, and the collateral damage to cultures of indigenous communities. Northern tree species are expected to be sensitive to ongoing and anticipated climate change. Due to their remoteness and lack of a history of management-oriented research, information that is available for temperate areas, such as species distribution maps, soils, and climatology is often poorly quantified in the North. Consequently, our understanding of the factors controlling tree species northern distributional limits (NDL) and our ability to predict how future environmental change will affect their range distributions is limited. Moreover, very little attention has been devoted to understanding the dynamics of the few broadleaf tree species, such as trembling aspen, which are important components of northern boreal forest systems, from both an ecological and an economical perspective.This thesis was inspired by observations of aspen growing in uncharacteristic abundance near the extremes of its NDL in Quebec in conjunction with the pressing need to answer questions regarding how individual boreal tree species may respond to current and future environmental change. Here, I investigate the factors driving the variation in observable patterns of aspen distribution and abundance at regional and landscape scales in the James Bay area of northwestern Quebec, as well as the influence of a range of ecological conditions on aspen growth. The four specific objectives of this research were: (i) to map aspen's regional distribution and abundance using a combination of field, GIS, and remote sensing techniques, (ii) to determine how aspen height growth responds to change in environmental conditions across a broad latitudinal gradient from 46° to 54°N latitude, (iii) to determine the factors organizing vegetation community composition in and around aspen-dominated communities at the landscape scale, and (iv) to explore the influence of specific environmental factors on aspen abundance at the landscape scale near aspen's NDL.The key scientific merits of this thesis are: (i) creation of baseline data characterizing aspen's geographic range and associated land cover in northwestern Quebec to allow for more accurate comparative and quantitative studies now and in the future, (ii) development and application of a new method for rapid extraction of land cover classification data in remote areas, (iii) demonstration that the regional scale pattern of aspen occupancy in the James Bay area of QC appears influenced by anthropogenic driven disturbance, (iv) demonstration that aspen's NDL in QC is not predominately governed by harsh climate, thus highlighting the need for more in depth species specific research on determinants of range limits, and the subsequent factors most appropriate for use in predictive modelling of future tree species' distributions, and (v) demonstration that gradients related to soil moisture and soil fertility best characterize forest composition and structure at the landscape scale in the study area, while aspen abundance, in particular, is associated with soils high in K, and inland areas where fire events are more frequent than those on the coast. Together these tools and findings suggest that identifying and understanding species' distribution and abundance patterns is complex and a further grasp of change in species specific patterns across their entire ranges is necessary to make informed forest management decisions and predict future outcomes. / Une meilleure compréhension de la dynamique et de la répartition des espèces d'arbres en forêt boréale permettra d'intervenir socialement de façon plus appropriée face aux pressions exercées par les changements climatiques et par le développement accru du Nord, en plus de limiter les effets néfastes de ces pressions sur les communautés autochtones. Les espèces d'arbres nordiques peuvent s'avérer sensibles aux changements climatiques. Or, les données sur la répartition des espèces, la climatologie et les sols sont souvent manquantes en milieux nordiques étant donné l'isolement et le manque de recherche sur la gestion de ces milieux. En conséquence, notre compréhension des facteurs contrôlant les limites nordiques de répartition des espèces ligneuses et notre capacité à prédire les effets des changements environnementaux sur leurs aires de répartition sont limités. Les dynamiques des essences d'arbres feuillus tels que le peuplier faux-tremble ont été très peu étudiées malgré la très grande importance écologique et économique de ces espèces pour l'écosystème forestier boréal.Ce projet, initié suite à l'observation de quantités surprenantes de peupliers à la limite nordique de répartition de l'espèce au Québec, vise à améliorer les connaissances sur la réponse possible des espèces d'arbres boréales face aux changements environnementaux présents et futurs. J'étudie les facteurs contrôlant la répartition du peuplier dans la région de la Baie James du nord-ouest québécois et j'évalue l'influence d'un nombre de conditions écologiques sur la croissance du peuplier. Les objectifs de cette étude étaient de (i) cartographier, avec l'aide d'un SIG, la répartition et l'abondance régionale du peuplier en utilisant des données de terrain et de télédétection, (ii) déterminer de quelle façon la croissance du peuplier varie en fonction d'un large gradient de latitude (de 46° à 54°N), (iii) au niveau du paysage, déterminer les facteurs responsables de l'organisation et de la composition des communautés végétales dominées par le peuplier, et des communautés environnantes, (iv) explorer l'influence de facteurs environnementaux spécifiques au niveau du paysage sur l'abondance du peuplier près de la limite nordique de sa répartition. Les contributions scientifiques principales de cette thèse sont : (i) l'obtention de données sur la répartition géographique et la couverture terrestre du peuplier dans le nord-ouest du Québec qui pourront servir de base à des études comparatives et quantitatives plus précises, (ii) le développement et l'application d'une nouvelle méthode pour l'extraction rapide de classification de la couverture terrestre dans des régions éloignées, (iii) la démonstration que les patrons de répartition du peuplier à l'échelle régionale dans la région de la Baie James sont influencés par des perturbations anthropiques, (iv) la démonstration que la limite nord de répartition du peuplier au Québec n'est pas contrôlée principalement par le climat. Cette observation met en évidence le besoin d'effectuer des recherches plus approfondies sur les facteurs déterminant les limites de répartition, et d'évaluer lesquels permettront de prédire de façon précise la répartition future des espèces d'arbres, (v) la démonstration que les gradients liés à l'humidité et à la fertilité du sol caractérisent la composition et la structure de la forêt à l'échelle du paysage. De façon particulière, le peuplier est associé à des sols avec des teneurs élevées en potassium et à des sites éloignés des côtes où les feux sont moins fréquents. La mise en commun de ces outils et de ces résultats suggère que l'identification et la compréhension des patrons d'abondance et de répartition des espèces sont complexes. Plus de connaissances sur les patrons complets des aires de répartition spécifiques à chaque espèce sont nécessaires afin de prendre de meilleures décisions relatives à l'aménagement forestier et pour prédire les impacts futurs de ces décisions.

The Red-headed Woodpecker (Melanerpes erythrocephalus) is a widespread, once common but increasingly rare North American bird species. Consistent long-term population declines have resulted in the species' threatened status in Canada and several states in the United States. Throughout most of its range, Red-headed Woodpeckers occupy habitats that have been heavily influenced by human presence and activities. Yet, there is little research quantifying the potential drivers of the species' population decline, which constrains conservation or policy action. The overall objective of this research is to determine why the Red-headed Woodpecker, a once common, widespread species with apparently a high flexibility in habitat use is undergoing such large population declines. I hypothesize that rapid anthropogenic changes and ecological novelties are causing Red-headed Woodpecker fitness and its behavioural choices to have become disjointed. The specific objectives include: (1) to determine if Red-headed Woodpecker habitat use is adaptive or maladaptive, (2) to determine the influence of a non-native interference competitor, the European Starling (Sturnus vulgaris), on Red-headed Woodpecker breeding success, and (3) to compare the efficacy of global and local models of the relationships between Red-headed Woodpeckers and two possible competitor species over space and time, and explore local variations of these relationships. To test my hypothesis, I investigated Red-headed Woodpecker multi-scale habitat use and associations, and nest survival near the northern edge of the species range in southern Ontario, where populations are rapidly declining. In addition, I modelled interspecies abundance relationships across southern Canada and east-central United States using 45 years of survey data from the Breeding Bird Survey (BBS) for Red-headed Woodpeckers, European Starlings, and Red-bellied Woodpeckers (M. carolinus). Field-based results demonstrated that Red-headed Woodpeckers exhibit maladaptive habitat use at multiple scales, suggesting the potential for an ecological trap for the species. Specifically habitat characteristics that promoted feeding potential such as canopy openness and greater limb length were consistently associated with Red-headed Woodpecker occupancy from nest tree to woodlot scales, despite correlations with lower reproductive success. Further investigation into Red-headed Woodpecker nest survival by modelling a suite of abiotic, biotic, temporal, and habitat-based drivers showed that European Starling abundance near active woodpecker nest sites was the strongest factors influencing woodpecker nest survival. Logistic-exposure nest success assuming constant survival dropped significantly from 68% to 13% when starling abundance was considered. When interspecies abundance relationships were investigated at a larger spatial scale, they were found to be spatially structured, and suggested evidence for interspecific competition between Red-headed Woodpeckers and starlings, and niche differentiation between Red-headed and Red-bellied Woodpeckers. This research demonstrates the importance of multi-scale, multi-factor studies when determining threats for species-at-risk and will help in the development of conservation, management, and policy-making decisions for the species. / Le Pic à Tête Rouge (Melanerpes erythrocephalus) est une espèce d'oiseau répandue en Amérique du Nord, autrefois commune mais maintenant de plus en plus rare. Un déclin constant de la population dans les dernières décennies a mené l'espèce à être désignée menacée au Canada et dans plusieurs États américains. Dans la plupart de son aire de répartition, le Pic à Tête Rouge occupe des habitats fortement influencés par la présence et les activités humaines. Il y a cependant peu de recherche quantifiant les causes possibles du déclin de la population de l'espèce. Par conséquent, il manque d'information pour la conservation et l'action politique. L'objectif général de cette recherche est de déterminer pourquoi le Pic à Tête Rouge, une espèce autrefois commune et répandue avec une grande souplesse d'utilisation de l'habitat, connaît-il une diminution dramatique de ses populations. J'émets l'hypothèse que de rapides changements anthropiques et des nouveautés écologiques ont mené la valeur sélective et les choix comportementaux du Pic à Tête Rouge à être devenus disjoints. Les objectifs spécifiques incluent : (1) de déterminer si l'utilisation de l'habitat par le Pic à Tête Rouge est adaptatée ou mésadaptée, (2) de déterminer l'influence d'un compétiteur par interférence exotique, l'Étourneau Sansonnet (Sturnus vulgaris), sur le succès de reproduction du Pic à Tête Rouge, et (3) de comparer l'efficacité des modèles global et local du Pic à Tête Rouge versus deux compétiteurs potentiels pour l'espace et le temps, et explorer les variations locales des relations interspecifiques. Pour tester notre hypothèse, nous avons étudié l'utilisation et les associations multiéchelles de l'habitat du Pic à Tête Rouge, et la survie au nid près de la frontière nord de sa distribution dans le sud de l'Ontario, où les populations sont en rapide déclin. De plus, nous avons modélisé l'abondance interspécifique à travers le sud du Canada et le centre-est des États-Unis en utilisant 45 ans de données de recherche du Relevé des oiseaux nicheurs (BBS) pour le Pic à Tête Rouge et deux potentiels compétiteurs (Étourneau Sansonnet et Pic à Ventre Roux (M. carolinus). Des résultats basés sur la recherche sur le terrain ont démontré que le Pic à Tête Rouge présente une utilisation multiéchelles de l'habitat mésadaptée, ce qui suggère la possibilité d'un piège écologique pour l'espèce. De façon spécifique, les caractéristiques de l'habitat qui promouvaient le potentiel alimentaire tels que l'ouverture de la canopée et des membres plus longs étaient systématiquement associés à l'occupation de l'habitat à l'échelle de l'arbre du nid et du boisé par le Pic à Tête Rouge, malgré des corrélations avec un plus faible succès de reproduction. Une étude plus poussée de la survie au nid du Pic à Tête Rouge en modélisant une suite de pilotes abiotiques, biotiques, temporels et basés sur l'habitat a démontré que l'abondance de l'Étourneau Sansonnet près des sites de nids de pic actifs était le plus fort facteur influençant la survie au nid du pic. L'exposition logistique survie des nids en supposant une survie constante (68%) a chuté de façon significative lorsque l'abondance de l'Étourneau était considérée (13%). Lorsque les relations d'abondance interspécifiques ont été examinées à une plus grande échelle spatiale, elles se sont trouvées être structurées spatialement, et suggéraient une preuve de la compétition interspécifique entre le Pic à Tête Rouge et l'Étourneau et de la différentiation de niche entre les Pics à Tête Rouge et à Ventre Roux. Cette recherche démontre l'importance des études multiéchelles et à facteurs multiples lors de la détermination des menaces pour les espèces en péril, et aidera au développement de décisions relatives à la conservation, la gestion et l'élaboration des politiques pour cette espèce.

Single-tree selection harvesting is frequently used in the tolerant hardwood forests of North America but relatively little is known about how this silvicultural system affects wildlife, including many avian species. I investigated Rose-breasted Grosbeak (Pheucticus leudovicianus) habitat use, survival, and nestling provisioning behaviour in twelve hardwood stands in Algonquin Provincial Park which had been harvested by single-tree selection 0-5, 16-20, 21-25, and > 50 years previously. Density, pairing success, and the number of fledglings per successful nest were all significantly lower in the > 50 years post-harvest stands than in at least one other post-harvest treatment. Density and pairing success were significantly higher in the 16-20 year post-harvest stands than in other treatments. Neither nest nor fledgling survival differed significantly among post-harvest treatments, but all stands were population sinks except those cut 16-20 years previously. Nests that were initiated earlier in the season and built in areas with higher basal area were more likely to survive, whereas fledgling survival increased with days since fledging. Nest sites had higher cover from regenerative growth, saplings, and understory, and lower basal area than random locations. During their first week out of the nest, fledglings used locations with significantly higher cover from regenerative growth, saplings, small shrubs, and raspberry and elderberry bushes than were present at random locations. Habitat characteristics at nest and fledgling locations were significantly different, and estimates of nest and fledgling survival were not correlated among harvested stands. Nests attended by after-second-year (ASY) males were initiated significantly earlier, and territory density and productivity were significantly higher for ASY males than for second-year (SY) males. Nestling provisioning rates, male contribution to nestling provisioning and nest attendance, and mean nestling weights at the time of fledging were also significantly higher at nests attended by ASY males than at nests with SY males. This study found that single-tree selection did not have significant negative effects on Rose-breasted Grosbeaks breeding in a predominantly forested landscape, but like many other species of birds, experienced breeders were more successful than less experienced breeders were.

Single-tree selection harvesting is frequently used in the tolerant hardwood forests of North America but relatively little is known about how this silvicultural system affects wildlife, including many avian species. I investigated Rose-breasted Grosbeak (Pheucticus leudovicianus) habitat use, survival, and nestling provisioning behaviour in twelve hardwood stands in Algonquin Provincial Park which had been harvested by single-tree selection 0-5, 16-20, 21-25, and > 50 years previously. Density, pairing success, and the number of fledglings per successful nest were all significantly lower in the > 50 years post-harvest stands than in at least one other post-harvest treatment. Density and pairing success were significantly higher in the 16-20 year post-harvest stands than in other treatments. Neither nest nor fledgling survival differed significantly among post-harvest treatments, but all stands were population sinks except those cut 16-20 years previously. Nests that were initiated earlier in the season and built in areas with higher basal area were more likely to survive, whereas fledgling survival increased with days since fledging. Nest sites had higher cover from regenerative growth, saplings, and understory, and lower basal area than random locations. During their first week out of the nest, fledglings used locations with significantly higher cover from regenerative growth, saplings, small shrubs, and raspberry and elderberry bushes than were present at random locations. Habitat characteristics at nest and fledgling locations were significantly different, and estimates of nest and fledgling survival were not correlated among harvested stands. Nests attended by after-second-year (ASY) males were initiated significantly earlier, and territory density and productivity were significantly higher for ASY males than for second-year (SY) males. Nestling provisioning rates, male contribution to nestling provisioning and nest attendance, and mean nestling weights at the time of fledging were also significantly higher at nests attended by ASY males than at nests with SY males. This study found that single-tree selection did not have significant negative effects on Rose-breasted Grosbeaks breeding in a predominantly forested landscape, but like many other species of birds, experienced breeders were more successful than less experienced breeders were.

No description available.

The purpose of this thesis is to explain the spatial diffusion of lead in the forest vegetation along highway 417, around Limoges, Ontario. The analyses of samples taken along both sides of the highway 417 tells us that the wind is the main carrier of particulate lead. Knowing that the predominant winds are from WNW, we conclude that there is a greater concentration of lead north-east of the highway where most of the emanations fall. Lead particles that are carried by the winds settle on the tree foliage and are absorbed in very small quantities by the leaves stomates. The concentration of lead on foliage diminishes gradually with distance from the highway and distilled water will not wash it off. Lead also appears on the tree trunks. There again, the concentration is found to diminish with distance from the highway. The study also reveals that there is no correlation between the concentration of lead on the outside of the tree barks and the inside. Actually, this study cannot explain this phenomenon. (Abstract shortened by UMI.)

Variation in feeding behaviour was studied among young individuals of pumpkinseed (Lepomis gibbosus) and yellow perch (Perca flavescens). Three types of food, Drosophila, Daphnia and Artemia were used for the experiments. Eight individuals of pumpkinseed differed significantly in their number of feeding attempts, in time interval between feeding attempts (in the beginning, middle and towards the end of the experiment), feeding angle, number of unsuccessful attempts and regurgitations. Most of the differences in the time interval between feeding attempts were observed in the middle and towards the end of the experiment. When the experimental diet was composed of three types of foods (Drosophila, Daphnia and Artemia) in a mixture, the total number of feeding attempts in the experiment decreased. Mixing the food types also reduced the feeding efficiency of individuals which was evidenced by the increased time interval between the feeding attempts and the increased unsuccessful attempts and regurgitations. Individuals of pumpkinseed showed the highest preference for Daphnia. On the basis of the above feeding variables, groups of individuals of differing feeding patterns were identified. Similar patterns were observed for the eight individuals of yellow perch. Perch fed more efficiently on Artemia, however, two individuals of perch were more efficient on feeding on Daphnia. Effects of the presence of conspecifics and increasing population density were examined on the variation among individuals of the pumpkinseed and yellow perch, for two types of food, (Daphnia and Artemia), separately and in a mixture. The effects of conspecifics were not equal on each individual of pumpkinseed and yellow perch. Only the weaker individuals were affected more by the presence of other conspecifics than the stronger ones. The increasing population density of conspecifics increased the variation among the individuals of both species. The effect of the presence of heterospecifics (yellow perch) were also examined on individuals of pumpkinseed for similar food types and feeding variables. At low experimental densities the effects of the heterospecifics were not significant. However, at high densities yellow perch affected the feeding behaviour of pumpkinseed individuals significantly. The effects of conspecifics on pumpkinseed were always greater than heterospecifics. Yellow perch did not affect the feeding behaviour of all the individuals of pumpkinseed equally.

In this thesis, the environmental values of Canada and Sweden as they are embodied in the forest policy of these two countries are examined within the framework of Beck's theory of the risk society to discover whether there is evidence to support Beck's theory of the evolution of industrialised countries from primary to reflexive modernisation. The historical, cultural and social-structural conditions underlying the development of Canadian and Swedish forest policy are also investigated in order to situate those policies in their historical and comparative context.

This study provides detailed descriptions of 149 stands of the least disturbed, most mature forest communities in the Ottawa, Ontario region. For each of these sampled communities, a complete summary is provided of tree population structure, coverage and constancy of all vascular understory species and habitat data including topographic position, drainage class, and soil characteristics. Six widespread and five locally-distributed forest alliances, comprising 21 forest associations, are defined and described on the basis of presently-dominant tree species. A dichotomous key to the associations is provided. The successional trends exhibited by the present associations are integrated into a flowchart based on tree population structures, tree ages and habitat characteristics. A discussion of succession and climax theory, terminology, variability within and between associations, environmental controls and disturbance factors is provided with emphasis on comparisons with previous investigations in eastern North America.