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William L Baker - One of the best experts on this subject based on the ideXlab platform.
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disturbance and Stand Dynamics in ponderosa pine forests in rocky mountain national park usa
Ecological Monographs, 2003Co-Authors: Donna S Ehle, William L BakerAbstract:Fire is thought to be the dominant disturbance agent in pure ponderosa pine (Pinus ponderosa Laws.) forests, but fire severity and disturbances other than fire, and the effects of these events over time, have rarely been analyzed. We first created systematic criteria to (1) identify the causes of tree regeneration and mortality events and (2) classify the severity of these events. These criteria were then applied to underStand the effect of events on ponderosa pine forests in Rocky Mountain National Park (RMNP), Colorado. For each of nine intensive study plots sampled in the pure ponderosa pine zone of RMNP, we mapped and dated live and dead trees and the spatial extent of fire and non- fire events using dendrochronology. Events were identified using evidence of disturbance agents, such as blue-stain fungus in the case of mountain pine beetles, fire scars, and climatic reconstructions. Disturbance severity was classified based on amounts and spatial distri- bution of regeneration, mortality, and survivors. We studied the temporal and spatial re- lationships between events and tree age structures to determine historical and contemporary Stand Dynamics. We identified 103 events among the nine study plots; 97% of these events were fire. High-severity events were 7% of events, 2% of events were mixed-severity, and the other 70% were low-severity. The severity of 20% of events could not be determined. All but one of the high-severity events were fire. In seven plots, at least one crown fire occurred within the last 300 years. In RMNP, pre-EuroAmerican settlement crown fires led to dense, even-aged Stands. Subsequent surface fires killed some trees and facilitated the regeneration of others, leading to less dense, uneven-aged Stands after ;200-300 years. Climate may be the cause or co-cause of one or two regeneration pulses within the last 300 years, but most regeneration and mortality is associated with fire. The historical occurrence of crown fires, as well as surface fires, in pure ponderosa pine forests in RMNP indicates that the fire regime is more variable than previously thought. Suppression of crown fires, though not completely possible, would move the fire regime outside its historical range of natural variability.
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disturbance and Stand Dynamics in ponderosa pine forests in rocky mountain national park usa
Ecological Monographs, 2003Co-Authors: Donna S Ehle, William L BakerAbstract:Fire is thought to be the dominant disturbance agent in pure ponderosa pine (Pinus ponderosa Laws.) forests, but fire severity and disturbances other than fire, and the effects of these events over time, have rarely been analyzed. We first created systematic criteria to (1) identify the causes of tree regeneration and mortality events and (2) classify the severity of these events. These criteria were then applied to underStand the effect of events on ponderosa pine forests in Rocky Mountain National Park (RMNP), Colorado. For each of nine intensive study plots sampled in the pure ponderosa pine zone of RMNP, we mapped and dated live and dead trees and the spatial extent of fire and non- fire events using dendrochronology. Events were identified using evidence of disturbance agents, such as blue-stain fungus in the case of mountain pine beetles, fire scars, and climatic reconstructions. Disturbance severity was classified based on amounts and spatial distri- bution of regeneration, mortality, and survivors. We studied the temporal and spatial re- lationships between events and tree age structures to determine historical and contemporary Stand Dynamics. We identified 103 events among the nine study plots; 97% of these events were fire. High-severity events were 7% of events, 2% of events were mixed-severity, and the other 70% were low-severity. The severity of 20% of events could not be determined. All but one of the high-severity events were fire. In seven plots, at least one crown fire occurred within the last 300 years. In RMNP, pre-EuroAmerican settlement crown fires led to dense, even-aged Stands. Subsequent surface fires killed some trees and facilitated the regeneration of others, leading to less dense, uneven-aged Stands after ;200-300 years. Climate may be the cause or co-cause of one or two regeneration pulses within the last 300 years, but most regeneration and mortality is associated with fire. The historical occurrence of crown fires, as well as surface fires, in pure ponderosa pine forests in RMNP indicates that the fire regime is more variable than previously thought. Suppression of crown fires, though not completely possible, would move the fire regime outside its historical range of natural variability.
Andrej Boncina - One of the best experts on this subject based on the ideXlab platform.
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Stand Dynamics of silver fir abies alba mill european beech fagus sylvatica l forests during the past century a decline of silver fir
Forestry, 2011Co-Authors: Matija Klopcic, Andrej BoncinaAbstract:Summary Uneven-aged silver fi r-European beech forests in Slovenia were studied to investigate the Dynamics of their structure and composition in three different study areas over the last century, with a particular focus on silver fi r Dynamics. The study used current and archival data from forest inventories and historic forest management maps for a period of ~ 110 years. The Dynamics of several structural and compositional parameters of the forest Stands were also examined using a Stand volume index, the Gini coeffi cient and a recruitment rate index. Substantial changes in diameter growth at breast height structure, Stand volume, tree size diversity and tree species composition were documented during the observed period. Additionally, silver fi r underwent large-scale changes. Signifi cant differences, as well as some similarities, in forest Stand Dynamics were observed on a regional spatial scale. These Dynamics are underpinned by a complex array of natural and anthropogenic factors; past forest use and the silvicultural systems applied, the impact of large ungulates and site characteristics seem to play important roles.
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Stand Dynamics of dinaric old growth forest in slovenia are indirect human influences relevant
Plant Biosystems, 2010Co-Authors: Jurij Diaci, Dusan Rozenbergar, Andrej BoncinaAbstract:Abstract UnderStanding forest Stand structural change is crucial for forest ecosystem research and management. The aim of our research was to identify structural and compositional changes and possible natural and anthropogenic causes of these changes in an old‐growth silver fir‐beech forest in the Dinaric mountains of Slovenia. Data on Stand structure of the Rajhenavski Rog (51.14 ha) forest reserve originated from traditional methods, including five successive full callipering (1957–2007), two regeneration inventories and analysis of developmental phases (1984, 2007). A drastic decrease in the silver fir proportion in the last 50 years was probably caused by two indirect anthropogenic factors: polluted air and heavy browsing damage of silver fir regeneration. Nevertheless, other factors including reciprocal replacement of fir and beech and climate change also influenced the species composition, as similar processes were documented in the past with less air pollution. Furthermore, the alternation of fir a...
Donna S Ehle - One of the best experts on this subject based on the ideXlab platform.
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disturbance and Stand Dynamics in ponderosa pine forests in rocky mountain national park usa
Ecological Monographs, 2003Co-Authors: Donna S Ehle, William L BakerAbstract:Fire is thought to be the dominant disturbance agent in pure ponderosa pine (Pinus ponderosa Laws.) forests, but fire severity and disturbances other than fire, and the effects of these events over time, have rarely been analyzed. We first created systematic criteria to (1) identify the causes of tree regeneration and mortality events and (2) classify the severity of these events. These criteria were then applied to underStand the effect of events on ponderosa pine forests in Rocky Mountain National Park (RMNP), Colorado. For each of nine intensive study plots sampled in the pure ponderosa pine zone of RMNP, we mapped and dated live and dead trees and the spatial extent of fire and non- fire events using dendrochronology. Events were identified using evidence of disturbance agents, such as blue-stain fungus in the case of mountain pine beetles, fire scars, and climatic reconstructions. Disturbance severity was classified based on amounts and spatial distri- bution of regeneration, mortality, and survivors. We studied the temporal and spatial re- lationships between events and tree age structures to determine historical and contemporary Stand Dynamics. We identified 103 events among the nine study plots; 97% of these events were fire. High-severity events were 7% of events, 2% of events were mixed-severity, and the other 70% were low-severity. The severity of 20% of events could not be determined. All but one of the high-severity events were fire. In seven plots, at least one crown fire occurred within the last 300 years. In RMNP, pre-EuroAmerican settlement crown fires led to dense, even-aged Stands. Subsequent surface fires killed some trees and facilitated the regeneration of others, leading to less dense, uneven-aged Stands after ;200-300 years. Climate may be the cause or co-cause of one or two regeneration pulses within the last 300 years, but most regeneration and mortality is associated with fire. The historical occurrence of crown fires, as well as surface fires, in pure ponderosa pine forests in RMNP indicates that the fire regime is more variable than previously thought. Suppression of crown fires, though not completely possible, would move the fire regime outside its historical range of natural variability.
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disturbance and Stand Dynamics in ponderosa pine forests in rocky mountain national park usa
Ecological Monographs, 2003Co-Authors: Donna S Ehle, William L BakerAbstract:Fire is thought to be the dominant disturbance agent in pure ponderosa pine (Pinus ponderosa Laws.) forests, but fire severity and disturbances other than fire, and the effects of these events over time, have rarely been analyzed. We first created systematic criteria to (1) identify the causes of tree regeneration and mortality events and (2) classify the severity of these events. These criteria were then applied to underStand the effect of events on ponderosa pine forests in Rocky Mountain National Park (RMNP), Colorado. For each of nine intensive study plots sampled in the pure ponderosa pine zone of RMNP, we mapped and dated live and dead trees and the spatial extent of fire and non- fire events using dendrochronology. Events were identified using evidence of disturbance agents, such as blue-stain fungus in the case of mountain pine beetles, fire scars, and climatic reconstructions. Disturbance severity was classified based on amounts and spatial distri- bution of regeneration, mortality, and survivors. We studied the temporal and spatial re- lationships between events and tree age structures to determine historical and contemporary Stand Dynamics. We identified 103 events among the nine study plots; 97% of these events were fire. High-severity events were 7% of events, 2% of events were mixed-severity, and the other 70% were low-severity. The severity of 20% of events could not be determined. All but one of the high-severity events were fire. In seven plots, at least one crown fire occurred within the last 300 years. In RMNP, pre-EuroAmerican settlement crown fires led to dense, even-aged Stands. Subsequent surface fires killed some trees and facilitated the regeneration of others, leading to less dense, uneven-aged Stands after ;200-300 years. Climate may be the cause or co-cause of one or two regeneration pulses within the last 300 years, but most regeneration and mortality is associated with fire. The historical occurrence of crown fires, as well as surface fires, in pure ponderosa pine forests in RMNP indicates that the fire regime is more variable than previously thought. Suppression of crown fires, though not completely possible, would move the fire regime outside its historical range of natural variability.
Hans Pretzsch - One of the best experts on this subject based on the ideXlab platform.
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The social drift of trees. Consequence for growth trend detection, Stand Dynamics, and silviculture
European Journal of Forest Research, 2021Co-Authors: Hans PretzschAbstract:Recently, many studies worldwide tapped tree ring pattern for detection of growth events and trends caused by weather extremes and climate change. As long-term experiments with permanent survey of all trees are rare, growth trend analyses are mostly based on retrospective measurements of growth via increment coring or stem analyses of the remaining individual trees in older forest Stands. However, the growth of the survivor trees in older Stands may only unsufficiently represent the course of growth of the dominant trees throughout the Stand development. Here, the more than 100 years survey data of the European beech ( Fagus sylvatica L.) thinning experiment Fabrikschleichach in South Germany are used to show the long-term changes in social ranking of trees and their consequences for growth trend detection by retrospective tree ring analyses, for Stand Dynamics and silvicultural management. Firstly, a significant social upwards drift of initially medium-sized trees till 2010 is shown based on the trees' percentiles in the stem diameter distribution in 1904 versus 2010. The social climbing is stronger on the thinned compared to the unthinned plots. Secondly, we show that 40–60% of the 100 tallest trees in 1904 were replaced by social climbers and down-ranked below the 100 tallest trees till 2010. Linear mixed model analyses reveal that the long-term trend of the diameter growth of the 100 dominant survivors in 2010 was on average by 23% steeper than the trend of the 100 tallest starters in 1904. This indicates that the survivors had a steeper and longer lasting growth than the originally dominant trees. Thirdly, the diameter growth trend in the last 20 years, from 1990 to 2010, is analyzed in dependency on the current and past social position. A linear model shows that early subdominance or suppression can significantly steepen the growth trend a century later and vice versa. Finally, we discuss the implications of the social drift for the survivor-based growth trend analyses, for the Stand Dynamics, and silvicultural management.
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Stand Dynamics of mixed species Stands compared with monocultures
2017Co-Authors: Hans Pretzsch, David I ForresterAbstract:Based on well-established principles and using reference values for monocultures, this chapter examines how mixed-species Stands differ from monocultures in terms of Stand growth and yield, self-thinning, alien thinning, Stand density, and density-growth relationships. This chapter also considers how the species interactions and the resulting mixing effects on growth can vary spatially and temporarily in response to the prevailing environmental conditions.
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changes of forest Stand Dynamics in europe facts from long term observational plots and their relevance for forest ecology and management
Forest Ecology and Management, 2014Co-Authors: Hans Pretzsch, Peter Biber, Gerhard Schutze, Kamil BielakAbstract:Nearly one and a half centuries ago, far-sighted Central European forest scientists established a network of long-term observational plots, many of them being under observation up to the present day. Especially the untreated plots reveal significant anthropogenic impacts on the structure and Dynamics of forest ecosystems. Based on 14 observational plots, this study shows that tree size and Stand parameters of oak (sessile oak, Quercus petraea (MATT.) LIEBL. and pedunculate oak, Quercus robur L.) presently develop much faster than in the past, which is highly relevant for forestry in Central Europe. Thus, certain threshold sizes are reached decades earlier compared with the past. Due to the accelerated Stand development, stem numbers per unit area are presently lower than at the same Stand age in the past, while at the same time, Stand density is higher. As we can show, also the level of the tree growth rate vs. tree size allometry increased significantly. These changes have major consequences for forest ecology and management, forest modeling, and eco-monitoring.
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structural crown properties of norway spruce picea abies l karst and european beech fagus sylvatica l in mixed versus pure Stands revealed by terrestrial laser scanning
Trees-structure and Function, 2013Co-Authors: Dominik Bayer, Stefan Seifert, Hans PretzschAbstract:How tree morphology develops in mixed-species Stands is essential for underStanding and modelling mixed-Stand Dynamics. However, research so far focused on the morphological variation between tree species and neglected the variation within a species depending on intra- and interspecific competition. Our study, in contrast, addresses crown properties of nine mature Norway spruces (Picea abies [L.] Karst.) of a pure Stand and compares them with ten spruces growing in mixture with European beech (Fagus sylvatica [L.]). The same was done with 11 pure Stand beeches and 12 beeches growing in mixture with spruce. Through application of a terrestrial laser scanner and a new skeletonization approach, we deal with both species’-specific morphological traits such as branch angle, branch length, branch bending, crown volume and space occupation of branches within the crown, some of which were hardly accessible so far. Special attention is paid to distinct differences between trees growing in mixed and pure Stands: for spruce, our study reveals significantly longer branches and greater crown volumes in the mixed Stand when compared to the pure Stand. In case of European beech, individuals growing in mixture show flatter branch angles, more distinct ramification, greater crown volumes and a lower share of a single branch’s space occupation in the total crown volume. The results show that the presented methods yield detailed information on the morphological traits analyzed in this study and that interspecific competition on its own may have a significant impact on crown structures. Implications for production ecology and Stand Dynamics of mixed-species forests are discussed.
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forest Dynamics growth and yield
2010Co-Authors: Hans PretzschAbstract:The introduction points out the very specific system characteristics of trees and forest Stands which determine the approach and methods to analyse and model forest Stand Dynamics, growth and yield. Like other disciplines, forest science looks with an ever-increasing spatial and temporal resolution on the functions and structures of woodlands, forest Stands, trees, tree organs, plant cells…. This makes it necessary to discuss concepts for bridging the growing gap between an increasing amount of knowledge on structures and processes on temporarily and spatially highly resolved scales (chemical, biochemical, molecular-biological processes), and an information deficit on more strongly aggregated system levels (Stand, ecosystem, landscape scale). The reconciliation between progressing reductionism on the one hand and the demand for holistic system knowledge for forest ecosystem management on the other is a general challenge to forest science and other “green sciences”.
Yves Bergeron - One of the best experts on this subject based on the ideXlab platform.
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boreal mixedwood Stand Dynamics ecological processes underlying multiple pathways 1
Forestry Chronicle, 2014Co-Authors: Yves Bergeron, Norman C Kenkel, Albanie Leduc, Ellen S MacdonaldAbstract:The southern portions of the boreal region across Canada are dominated by boreal mixedwoods forests, which are character ized by varying canopy dominance of boreal broadleaf and conifer trees. This forest region encompasses a large east-to-west gradient of climate and disturbance regimes. Although the same major boreal tree species occur in all parts of the boreal mixedwood region, they vary greatly in relative abundance. This is a reflection of the interactions among the different abiotic and biotic components. As a result, there is considerable variation in post-disturbance Stand development, producing a wide variety of mixedwood forest conditions existing as a mosaic in time and space. Post-disturbance dominance by broadleaf species followed by a transition to conifers is the “classic” pathway in all regions. However, there is wide variation in the transition rate and the species sequence across the gradient depending on factors such as moisture, abundance of each species, fire cycle, climate and secondary disturbances (mainly insect outbreaks). Future changes in climate and disturbance regime could influ ence the nature of Stand Dynamics of boreal mixedwoods and the prominence of different pathways among regions. Focussing on the commonality of processes in mixedwood Stand development across the boreal is a promising way to address the management of this important forest ecosystem.
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the predominance of Stand composition and structure over direct climatic and site effects in explaining aspen populus tremuloides michaux site index within boreal and temperate forests of western quebec canada
Forest Ecology and Management, 2013Co-Authors: Kenneth A Anyomi, Yves Bergeron, Frederic Raulier, Daniel MaillyAbstract:Abstract Existing models that use the site-index concept (dominant canopy height of a tree species at a reference Stand age) are fundamentally Stand-level models that do not account for Stand Dynamics, limiting their use to only a part of successional trajectories. Given that Stand Dynamics is influenced by both large and fine scale processes, we took a multi-level look at aspen (Populus tremuloides Michaux) productivity by determining landscape- and plot-level factors related to productivity as rated with site index. The study area extends from latitude 45° to 50°N in western Quebec, from which were sampled 62 landscapes made up of 4948 plots, 25% of which had aspen as dominant and/co-dominants in the canopy. There, aspen is most often found in mixed Stands. A stepwise procedure with forward selection was used in building landscape- and plot-level models and models were then arranged hierarchically such that (a) predicted estimates of the landscape model were inputs to the plot-level model (top-down) and (b) significant landscape variables were added to selected plot level variables (bottom-up). For the plot-level model, none of the climate variables considered were selected but at the landscape level, annual sum of degree–days was only the third to enter. In both cases, aspen site index was more related to the proportion of spruce (Picea mariana (Mill.) B.S.P. and Picea glauca (Moench.) Voss). At the level of landscapes, this observation might be due to the existence of particular vegetation mosaics, of which spruce proportion could be a surrogate. At the level of plots, influence of spruce on aspen site index is probably indicative of niche sharing with aspen. A high random variability was associated with the plot-level model but not with the landscape-level model. The similarity in drivers of aspen site index at both levels and the fact that both top-down and bottom-up approaches provided the same information, suggest that the use of landscape variables when modelling site index in mixed Stands may help distinguish peculiarities shared by plots located in a landscape and improve the signal between site index and explanatory variables by reducing the random noise observed at the level of plots.
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Stand landscape integration in natural disturbance based management of the southern boreal forest
Forest Ecology and Management, 2002Co-Authors: Brian D Harvey, Sylvie Gauthier, Alain Leduc, Yves BergeronAbstract:Forest ecosystem management, based partly on a greater underStanding of natural disturbance regimes, has many variations but is generally considered the most promising approach to accommodating biodiversity concerns in managed forested regions. Using the Lake Duparquet Forest in the southeastern Canadian boreal forest as an example, we demonstrate an approach that attempts to integrate forest and Stand-level scales in biodiversity maintenance. The concept of cohorts is used to integrate Stand age, composition and structure into broad successional or Stand development phases. Mean forest age (MFA), because it partly incorporates historic variability of the regional fire cycle, is used as a target fire cycle. At the landscape level, forest composition and cohort objectives are derived from regional natural disturbance history, ecosystem classification, Stand Dynamics and a negative exponential age distribution based on a 140 year fire cycle. The resulting multi-cohort structure provides a framework for maintaining the landscape in a semi-natural age structure and composition. At the Stand level, the approach relies on diversifying interventions, using both even-aged and uneven-aged silviculture to reflect natural Stand Dynamics, control the passage (‘‘fluxes’’) between forest types of different cohorts and maintain forest-level objectives. Partial and selective harvesting is intended to create the structural and compositional characteristics of mid- to late-successional forest types and, as such, offers an alternative to increasing rotation lengths to maintain ecosystem diversity associated with overmature and old-growth forests. The approach does not however supplant the necessity for complementary strategies for maintaining biodiversity such as the creation of reserves to protect rare, old or simply natural ecosystems. The emphasis on maintaining the cohort structure and forest type diversity contrasts significantly with current even-aged management in the Canadian boreal forest and has implications for Stand-level interventions, notably in necessitating a greater diversification of silvicultural practices including more uneven-aged harvesting regimes. The approach also presents a number of operational challenges and potentially higher risks associated with multiply Stand entries, partial cutting and longer intervals between final harvests. There is a need for translating the conceptual model into a more quantitative silvicultural framework. Silvicultural Forest Ecology and Management 155 (2002) 369‐385
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using dendrochronology to reconstruct disturbance and forest Dynamics around lake duparquet northwestern quebec
Dendrochronologia, 2002Co-Authors: Yves Bergeron, Bernhard Denneler, Danielle Charron, Martinphilippe GirardinAbstract:Summary This paper presents a synthesis of the dendroecological work conducted in the area of Lake Duparquet in the southern boreal forest of northwestern Quebec (Canada) during the last 15 years. The topics of these syn- and autecological studies encompassed forest Dynamics and tree growth related to natural disturbances such as forest fires, insect outbreaks, and flooding, as well as the effects of climate change. Seven major fire events occurred around Lake Duparquet since 1720: 1760, 1797, 1823, 1847, 1870, 1916, and 1944. Post-fire Stand Dynamics, established by a chronosequence of over 200 years, are characterized by the gradual transition from broadleaf dominated Stands towards mixed and finally almost pure conifer Stands. After fire, insect outbreaks are the second most important disturbance type in the southern boreal forest. Spruce budworm, the predominating defoliating insect, but also forest tent caterpillar and larch sawfly have major impacts on growth and Stand Dynamics of their respective host species. Global warming since the end of Little Ice Age around 1850 coincided with increasing precipitation and, hence, decreasing droughts in the southeastern boreal area of North America. The accelerated radial growth of eastern white-cedar and black ash at Lake Duparquet is a direct effect of these wetter climatic conditions. Population Dynamics and forest composition, however, are rather indirectly affected by climate change through the alteration of the natural disturbance regimes, i. e., the decreased frequency and size of the forest fires and the increased frequency and amplitude of the spring floods. Potential consequences of future global warming on disturbance Dynamics and forest composition are briefly discussed. The results of the dendroecological studies contributed to the elaboration of a natural-disturbance based forest management model for the southern boreal forest of Quebec.
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species and Stand Dynamics in the mixed woods of quebec s southern boreal forest
Ecology, 2000Co-Authors: Yves BergeronAbstract:In order to test whether changes in forest composition observed while sam- pling portions of the landscape originating from different fires may be explained by Stand- level processes, I reconstructed species and Stand Dynamics for mesic sites in the mixed- boreal forests of Quebec. The Stands studied are located in the forest surrounding Lake Duparquet in northwestern Quebec and originated from eight successive fires representing a chronosequence of 230 yr. Tree composition and ecological characteristics were assessed in 313 quadrats distributed systematically within the burned areas; one representative Stand per fire, presenting the average species composition for clay soils with a moderate moisture regime, was selected for detailed dendroecological analysis. All living and dead stems (> 1 cm dbh) were mapped and cut down in a 20 x 20 m quadrat. Cross sections collected at the root collar and at every meter were analyzed using Standard dendrochronological techniques. The age of the Stand before the last fire was estimated using snags and logs located in, or in the vicinity of, each quadrat. A PCA (principal-components analysis) ordination of all quadrats shows a gradual change with time since fire from Stands dominated by hardwoods (aspen and paper birch), to mixed Stands with an important white spruce component, to coniferous Stands dominated by balsam fir and white cedar. Despite variations in the age and composition of the Stands before the last fire, they generally follow a common pattern characterized by post-fire hardwood dominance. Age structures show successive waves of aspen, birch, and fir re- cruitment, corresponding respectively to the post-fire cohort, the gradual dismissal of the first aspen cohort, and spruce budworm outbreaks. Each of these waves corresponds to a decrease in hardwoods and an increase in the conifer component of the Stand. Suppressed white spruce individuals, recruited primarily as part of the post-fire cohort, experienced growth releases following the dismissal of the first aspen cohorts. White cedar increased in abundance late in succession and tended to outcompete balsam fir in old coniferous Stands severely affected by spruce budworm outbreaks. The observed multi-cohort process contrasts with the simple replacement of hardwoods by conifers as suggested by observations of differential growth rates. The patchy distribution of conifer regeneration together with the poorer ability of conifers to rapidly fill gaps may explain why hardwoods are successfully recruited. This gradual rate of change, occurring over several generations, results in the maintenance of an important hardwood component in most Stands even in the absence of fire. After 230 yr, Stands are still mainly composed of trees originating from punctuated events such as fire, the gradual dismissal of the first aspen cohort, or spruce budworm outbreaks. This contrasts with old-growth boreal forests dominated by spruces in which a quasi-equilibrium is maintained by small canopy distur- bances. The study confirms that changes in forest composition observed while sampling portions of the landscape originating from different fires may be explained by simple processes occurring at the Stand level.