Histoire récente des épidémies de la Tordeuse des bourgeons de l'épinette au nord du lac Saint-Jean (Québec): une analyse dendrochronologique

Abstract

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 in the north and northwest of Lac Saint-Jean. Outbreaks began around 1974, 1944, 1909, and possibly, 1832. They are closely linked with those described in the Laurentide wildlife reserve. The frequency, duration and severity of growth rings suppression associated with outbreaks are similar to those registered during outbreaks in the southern forests, except for the 1974 outbreak, which was shorter and less severe. Other outbreaks registered in southern regions, where the proportion of balsam fir is higher, have reached this region where balsam fir populations are marginal. These results underline the importance of these ecological disturbances in the population dynamics of the host trees of the region.

Shift of Conifer Boreal Forest to Lichen–Heath Parkland Caused by Successive Stand Disturbances

“…Although spruce budworm feeds predominantly on balsam fir and white spruce (Picea glauca (Moench) Voss) trees (Greene and others 1999), black spruce was also heavily damaged by this insect during the three major infestations in this part of eastern Canada, in the 1910s, 1940s, and early 1970s to mid-1980s (Blais 1980, 1985Morin and Laprise 1990;Payette and others 2000;Simard and Payette 2001). The first outbreak seems to have had little effect on spruce growth at the study sites.…”

Can we reconstruct deer browsing history and how? Lessons from Gaultheria shallon Pursh

“…We suggest that the repetitive, irregular and partial defoliation by deer also explains the asynchronism observed in stem sections from deer-affected islands, in contrasts to the synchronism observed for sections collected on deer-free islands. Thus identifying, counting and dating abrupt growth changes in salal populations should allow to reconstruct the local history of deer browsing in a way similar to what has been done using adult tree rings [26] to reconstruct the history of insect outbreaks [31,32,42] or scars to reconstruct past caribou activity [33], porcupine expansion [36], beaver occupation [4] or changes in deer population [34,35].…”

“…Indeed, records of annual growth and wood density, age structure and morphological characteristics [13,25,27,43,56] are valuable signatures of past disturbances that have affected woody plants. Growth time series have been successfully used to infer spatial and temporal variations affecting several herbivore populations [31][32][33]36].…”

Croissance juvénile des arbres mères comparée à celle de jeunes semis d épinette noire (Picea Mariana (Mill) B S P ) issus de graines après un feu sur un même site

“…Badeau et al (1996), Mielikâinen et Sennov (1996), Schneider et Hartmann (1996), Spiecker et al (1996) (Raske et Sutton 1986;Basham 1994). De nombreuses études ont fait état du passage de la tbe au dix-neuvième et au vingtième siècle dans la région du Saguenay-Lac Saint-Jean (Biais 1965(Biais , 1985Morin 1994Morin , 1998Morin et Laprise 1990;DesRochers 1996;Lussier 1996;Fournier 1997;Krause 1997;Hardy 1998 Lussier (1996). Suite à la dernière épidémie, la plupart des tiges ont retrouvé une croissance semblable à celle qu'elles avaient avant l'épidémie, sauf pour les plus petites tiges du peuplement qui ont enregistré des baisses de croissance.…”

“…Au dix-neuvième siècle, trois périodes épidémiques ont été enregistrées dans l'est de l'Amérique du Nord, de l'Ontario au Nouveau-Brunswick et dans l'état du Maine aux États-Unis (Biais 1961(Biais , 1962(Biais , 1965(Biais , 1968Morin et Laprise 1990;Morin et al 1993;Krause 1996Krause , 1997. Au Québec, lorsque ces épidémies étaient retracées, elles étaient considérées comme légères (Biais 1968(Biais , 1985Morin et Laprise 1990).…”