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Population dynamics of Fraxinus nigra in response to flood-level variations, in northwestern Quebec


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Tardif, Jacques et Bergeron, Yves (1999). Population dynamics of Fraxinus nigra in response to flood-level variations, in northwestern Quebec. Ecological Monographs , 69 (1). p. 107-125. doi:10.1890/0012-9615(1999)069[0107:PDOFNI]2.0.CO;2 Repéré dans Depositum à

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Population dynamics of black ash (Fraxinus nigra) were investigated in five stands with different exposures to spring flooding at the southwestern limit of Quebec's boreal forest. Fifty-four 100-m2 plots were sampled along 25 transects laid out perpendicular to Lake Duparquet. In each plot, all black ash >5 cm in diameter at breast height (dbh) were aged using dendrochronological methods. An age-height regression was used to calculate the age of those individuals <5 cm in dbh. Stump sprouts had a significantly faster height and diameter growth rate than individuals established from sexual origin. Two stands in this study showed deficits in sexual recruitment. One stand, located on a deep organic layer, also showed recent colonization by F. nigra that may have started during the 1930s. This stand had the highest stem density, and sprouting was restricted to the younger age classes. Ordination analysis of dispersion indices characterizing the age distribution of F. nigra indicated a definite pattern toward higher sexual recruitment in plots and stands that were less exposed to flooding. In contrast, poor sexual recruitment was observed on more exposed sites. However, this situation was compensated for by abundant vegetative recruitment. Analysis of the periods of growth release and suppression of 153 trees revealed that F. nigra population dynamics are not regulated by major disturbance events. A general upward trend in radial growth and F. nigra expansion toward higher elevation sites observed since the end of the 19th century may be due to changes in Lake Duparquet's hydrological regime. Increases in the severity of flooding events may result in the decrease in seedling abundance observed in the more exposed stands. F. nigra populations were found to be resistant to long-term natural water fluctuations due to their ability to regenerate both by seeds and by sprouts.

Type de document: Article
Mots-clés libres: Black ash; Boreal forest; Dendrochronology; Flood exposure, effects on black ash demography; Fraxinus nigra, Marsh.; Lake Duparquet (Quebec, Canada); Population dynamics of black ash; Radial growth, release and suppression; Regeneration, sexual vs. vegetative
Divisions: Forêts
Date de dépôt: 14 mai 2020 14:08
Dernière modification: 14 mai 2020 14:08

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