Population Dynamics of Fraxinus nigra in Response to Flood-Level Variations, in Northwestern Quebec

Abstract

Population dynamics of black ash (Fraxinus nigra) were investigated in five stands with different exposures to spring flooding at the southwestern limit of Québec's boreal forest. Fifty-four 100-m 2 plots were sampled along 25 transects laid out perpendicular to Lake Duparquet. In each plot, all black ash Ͼ5 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 Ͻ5 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.

Evaluating Adaptive Management Options for Black Ash Forests in the Face of Emerald Ash Borer Invasion

“…The importance of overstory tree cover in regulating water table dynamics during recruitment events has also been reinforced by examinations of the age structure of old-growth examples for these two habitat types, which indicate these systems are strongly multi-aged with historic development influenced primarily by gap-scale disturbances (Figure 1; D'Amato et al in prep). A similar multi-aged population structure was also documented across numerous old-growth black ash riparian forests in the Lake Duparquet region of Quebec [26]. Age structure for two old-growth black ash forests in Minnesota.…”

Variations in levels of clonality among Populus nigra L. stands of different ages

“…One might expect, therefore, considerable spatio-temporal heterogeneity in levels of genotypic diversity both within and between populations of the same species where resources/disturbances are themselves not equally distributed in space and time (Held, 1983;Rood et al, 1994;McKay, 1996;Gom and Rood, 1999;Tardif and Bergeron, 1999;Barsoum, 2002). Clearly defined relationships between levels of sprouting in clonal woody species (as reflected by levels of genotypic diversity) and environmental factors that promote sprouting are, nevertheless, very difficult to establish.…”

Characteristics and distribution of potential ash tree hosts for emerald ash borer

“…The elmred maple-black ash type grades into an almost pure black ash type on poorly drained sites with organic peat and muck soils, where it has been considered as the climax species (Erdmann et al, 1987). Tardif and Bergerson (1999) noted pure stands of black ash in the northern portion of its range, along lakes and rivers. Black ash communities on boreal forest floodplains were identified by Tardif and Bergeron (1992), who used a cluster analysis to produce four vegetation types: (1) black ash/speckled alder (Alnus rugosa)/bog willow (Salix pedicellaris), (2) black ash/balsam poplar (Populus balsamifera)/ostrich fern (Matteuccia struthiopteris), (3) black ash/pussy willow (Salix discolor)/sensitive fern (Onoclea sensibilis), and (4) black ash/speckled alder/sensitive fern.…”