Hubert Morin

• Université du Québec à Chicoutimi

Intra-annual radial growth rates and durations in trees are reported to differ greatly in relation to species, site and environmental conditions. However, very similar dynamics of cambial activity and wood formation are observed in temperate and boreal zones. Here, we compared weekly xylem cell production and variation in stem circumference in the...

A high-resolution macrofossil analysis was conducted to reconstruct spruce budworm abundance in an 8600-year-old mire in Saguenay, Québec, Canada. Abundant spruce budworm (Choristoneura fumiferana [Clem.]) faeces recovered in the peat profile suggested endemic and epidemic presence of the insect in the study site since 8240 cal. BP. Important varia...

Earlywood (E) and latewood (L) are arbitrary concepts, by consequence, the E/L demarcation method is as well. The threshold method has been widely used in wood anatomy as well as wood density. Because of the presence of the intra-annual variation in tree-ring structure, however, the conventional threshold method needs adjustment in an objective and...

Tracheid production of balsam fir in the Qubec boreal forest (Canada) was studied by repeated cell analysis to investigate the influence of meteorological variables during the growing seasons 1998 to 2000. Wood micro-cores were extracted on a weekly basis throughout the growing season and sections were prepared in order to count the total number of...

SummaryDefoliation by spruce budworm (Choristoneura fumiferana Clem.) greatly affects balsam fir (Abies balsamea (L.) Mill.) by reducing needle mass and ring width and eventually resulting in tree death. We analyzed temporal patterns of radial growth in various stem sections of twenty balsam fir growing in two mature stands, one intermediate-aged,...

To assess daily relationships between xylem development and the environment, precise knowledge of tree-ring development is required. This includes accurate estimations of the rate and duration of the cell enlargement and wall thickening phases. This paper presents an application where the Gompertz equation is used to calculate cell number increase...

This study examines balsam fir (Abies balsamea (L.) Mill.) recruitment in old fir stands. Studying the regeneration of these stands is essential to understand the regeneration dynamic of the species in the absence of standdestroying disturbances. The objectives were (1) to obtain substrate-seedling associations for different age-classes and accordi...

Cell formation in growth rings of balsam fir (Abies balsamea (L.) Mill) in the boreal forest was studied to describe the timing of ring formation and the development patterns of earlywood and latewood. Wood micro-cores were extracted during the growing season from 1998 to 2000. The micro-cores were stained with cresyl fast violet to facilitate coun...

Daily stem radial growth of balsam fir [ Abies balsamea (L.) Mill.] was studied between 1998 and 2001 using automated point dendrometers to investigate meteorological influence. By dividing the dendrometer day-night variation, the diurnal growth pattern was resolved into the three phases of (1) contraction, (2) expansion and (3) stem radius increme...

Numerous researchers have suggested a causal relationship between low leaf biomass in suppressed trees and the lack of radial growth at the base of the trunk. The objective of this study was to verify this relationship with suppressed balsam fir (Abies balsamea (L.) Mill.) saplings found growing in an old-growth fir stand. A total of 29 saplings va...

The effects of recurrent spruce budworm (Choristoneura fumiferana (Clem.)) outbreaks on balsam fir (Abies balsamea (L.) Mill.) mortality have been extensively studied in Canada. Most studies report substantial seedling recruitment of balsam fir during outbreaks when reproductive trees are dying. According to previous research, this contradiction co...

This paper characterizes the growth and crown morphology of young balsam fir saplings naturally regenerated under a gradient of understory light environments and intraspecific competition densities for two size classes (50–100 cm and 100–200 cm). Most growth and crown morphological parameters investigated were strongly related to the natural light...

The age structure of balsam fir (Abies balsamea (L.) Mill.) regeneration is frequently used to investigate boreal forest dynamics of North America. Tree ages are usually estimated by counting annual growth rings at the shoot-root interface located above or close to the root system. Inaccurately locating the shoot-root interface could lead to imprec...

Following the 1995 mast year, we conducted detailed seedling demography surveys to characterize some ecological factors affecting germination and early establishment in understory balsam fir (Abies balsamea (L.) Mill.) seedling banks and verify if recruitment from a cohort can potentially renew the balsam fir seedling bank. Twenty-five seed traps p...

Résumé La compilation de toutes les chronologies publiées sur les épidémies de la tordeuse des bourgeons de l'épinette établies à partir de la largeur des cernes de croissance des arbres hôtes a été utilisée pour étudier l'évolution spatiale et temporelle des épidémies survenues au cours du XX e siècle dans l'est de l'Amérique du Nord et particuliè...

The compilation of published spruce budworm outbreaks chronology established using host trees' ring width was used to study the spatial and temporal evolution of outbreaks that occurred during the 20th century in Eastern North America and particularly in nordic regions. The study includes 19 chronologies and 1257 sampled trees. Data are numerous fo...

The seedling banks of 14 balsam fir (Abies balsamea (L.) Mill.) stands of various ages affected to different degrees by the last spruce budworm (Choristoneura fumiferana (Clem.)) outbreak were studied in the boreal zone north of Lake Saint-Jean, Quebec. The objectives of the study were to (1) characterize the age structure of fir seedling populatio...

The influence of spruce budworm (Choristoneura fumiferana (Clem.)) defoliation was analysed at different stem heights by counting the number of latewood tracheids and measuring tree-ring width. The total height of the tree was divided into three different equal parts: the lower, the middle, and the upper sections of the total stem length. However,...

Radial increment along the stems and the root systems of 20 balsam fir (Abies balsamea Mill.) was analysed as an indicator of resource allocation after a spruce budworm outbreak. The trees were located in a natural forest, 130 km north of Lake Saint Jean (Quebec) in the boreal forest zone. The dynamics of the forest were determined by fire and inse...

Balsam fir (Abies balsamea (L.) Mill.) mortality caused by the last spruce budworm (Choristoneura fumiferana (Clem.)) outbreak (1970-1987) was studied in 624 sites belonging to a complex natural forest mosaic originating from different fires in northwestern Quebec. Multiple regression analyses were used to assess the respective effects of stand str...

Age structures and growth curves were used to determine the origin and to follow the development of 17 balsam fir (Abies balsamea (L.) Mill.) stands in the middle of the Boreal Zone in the north of Lake Saint-Jean, Quebec. Every growth curve from the studied sites presented a more or less long period of suppression in the early growth of the balsam...

The chronology of eastern spruce budworm (Choristoneura fumiferana (Clem.)) outbreaks in the vicinity of Lake Duparquet in the Abitibi region, Quebec, was determined for a period of 200 years using dendroecological methods. Growth patterns of two budworm host species, balsam fir (Abies balsamea (L.) Mill.) and white spruce (Picea glauca (Moench) Vo...

A new automatic tree ring measurement system which uses computerized image processing and analysis techniques is presented. It is based on a line scan camera instead of a conventional TV camera so it can give high resolution images over long paths (many centimeters). On-line ring validation is possible by comparison with those on other radii. Also,...

Age, height and diameter distribution as well as height and diameter growth were studied in ten mesic black spruce stands originating from advance growth, forty years after cutting. All sampled stands showed a negative exponential type age structure. The majority of the trees were of layer origin established in the mature stands that were cut in th...

The chronology of spruce budworm (Choristoneurafumiferana (Clem.)) oubreaks for the past 200 years has been reconstructed by dendrochronological analysis of balsam fir (Abiesbalsamea (L.) Mill.) and white spruce (Piceaglauca (Moench) Voss) samples from virgin forests, unaffected by insecticide spraying programs and recently protected against fires...

The chronology of Choristoneura fumiferana outbreaks for the past 200 yr was reconstructed by dendrochronological analysis of balsam fir Abies balsamea and white spruce Picea glauca samples from virgin forests in the N and NW of Lac Saint-Jean. Outbreaks began around 1974, 1944, 1909 and possibly 1832. Frequency, duration and severity of growth rin...

RÉSUMÉ Deux types de combes à neige ont été répertoriés au lac à l'Eau Claire: 1) des combes à neige sur substrat minéral formées après le passage de feux dans les grandes îles ; 2) des combes à neige sur substrat tourbeux, localisées dans les petites îles envahies par des tourbières ombrotrophes dont l'existence est redevable au mésoclimat créé pa...

The number of Picea glauca seedlings decreased from 67/100m2 in the montane belt to approx 5/100m2 in the lower alpine belt. The age structure of the seedlings suggested that the regeneration was episodic in the subalpine and alpine belts. The germination percentage of the seeds formed the sampling year (1979) also declined with increasing altitude...

The ideas of community structure and the expression of dominance, that of bio-logical succession, and finally that of climax, are based largely upon the assumption of long-term stability in the physical habitat. Remove this assump-tion and the entire theoretical structure becomes a shambles. . . . Disturbances have been so frequent and so generally...