Balsam fir mortality following the last spruce budworm outbreak in northwestern Quebec

1995 ◽  
Vol 25 (8) ◽  
pp. 1375-1384 ◽  
Author(s):  
Yves Bergeron ◽  
Alain Leduc ◽  
Claude Joyal ◽  
Hubert Morin
Keyword(s):  
Stand Structure ◽  
Management Strategies ◽  
Basal Area ◽  
Spruce Budworm ◽  
Balsam Fir ◽  
Forest Composition ◽  
Regression Analyses ◽  
Site Characteristics ◽  
Forest Mosaic ◽  
Independent Effects

Balsam fir (Abiesbalsamea (L.) Mill.) mortality caused by the last spruce budworm (Choristoneurafumiferana (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 structure, species composition, site characteristics, and the forest composition surrounding the stand on observed stand mortality. Mortality was observed to increase in relation to diameter of the trees, basal area of balsam fir, and the number of stands dominated by conifers in the forest mosaic. All of these factors showed significant independent effects, but 60% of the variance remained unexplained. Site characteristics, however, did not show a significant relationship to stand mortality. The results suggest that forest composition at both the stand and the forest mosaic levels may be responsible for differing degrees of defoliation that result in differences in stand mortality. Forest management strategies that favor the presence of mixed compositions both at the stand level and at the mosaic level may contribute to decreased stand vulnerability.

scholarly journals Impact of a spruce budworm outbreak in balsam fir and subsequent stand development over a 40-year period

2008 ◽  
Vol 84 (1) ◽  
pp. 60-69 ◽  
Author(s):  
David A MacLean ◽  
Allison R Andersen
Keyword(s):  
Stand Structure ◽  
Abies Balsamea ◽  
Basal Area ◽  
Stand Density ◽  
Spruce Budworm ◽  
Balsam Fir ◽  
Stand Development ◽  
Wide Range ◽  
Break Up ◽  
The Impact

Nine 0.04-ha plots were established in 1956 (age 35 years) in a balsam fir (Abies balsamea [L.] Mill.) stand in northwestern New Brunswick, Canada to determine the impact of an uncontrolled spruce budworm (Choristoneura fumiferana [Clem.]) outbreak on stand development. The plots were measured annually from 1956 to 1961 and at five-year intervals from 1965 to 1995. Moderate to severe defoliation occurred from 1951 to 1957 and again in 1975 to 1977, 1981, and 1986 to 1988. Budworm-caused mortality from 1956 to 1961 (age 35 to 40 years) varied considerably among plots, reducing volume by 35 to 113 m3/ha (34%-84%), and resulting in a wide range of post-outbreak plot densities. Plots were grouped into three post-budworm outbreak (1965, age 45 years) basal area classes, of ≤ 20 m2/ha, 21 to 27 m2/ha, and ≥ 28 m2/ha, to examine stand recovery. Recovery of volume up to age 60 years ranged from 72 to 132 m3/ha, in the lowest to highest basal area classes, respectively. From age 60 to 75 years, five plots declined in volume due to the onset of stand break-up and four plots increased in volume. By age 60 years, survivor growth was greatest in the high basal area plots, ranging from 6.2 to 9.0 m3/ha/yr in seven plots, versus 2.6 to 3.2 m3/ha/yr in two low basal area plots. From age 60 to 75 years, survivor growth averaged only 2.8 to 5.2 m3/ha/yr, and the stand exhibited major decline, with 63%, 74%, and 78% mortality of fir ≤ 15 cm DBH in the low to high basal area plots, respectively. Budworm-caused "thinning" in the 1950s largely determined subsequent stand development and the rate of stand break-up 25 to 35 years later. The timing and rate of natural stand decline was strongly influenced by post-outbreak stand density. Key words: budworm-caused mortality, stand structure, stand development, growth, mortality, stand density

scholarly journals SPRUCE BUDWORM DAMAGE TO BALSAM FIR IN IMMATURE STANDS, QUEBEC

1964 ◽  
Vol 40 (3) ◽  
pp. 372-383 ◽  
Author(s):  
R. J. Hatcher
Keyword(s):  
Minor Component ◽  
Basal Area ◽  
Spruce Budworm ◽  
Balsam Fir ◽  
Hardwood Forest ◽  
Cover Type ◽  
Area Reduction ◽  
A Minor ◽  
Very High ◽  
Diameter Classes

A study was made of the effect of the 1945-1957 spruce budworm infestation on 1,800 acres of spruce-fir and spruce-fir-hardwood forest logged for pulpwood about 15 years prior to the infestation.The number of fir trees was reduced 64 per cent between 1951 and 1961 in the main cover type representing 69 per cent of the forest; fir was reduced from a major stand component of 45 per cent by volume to a minor component of 11 per cent. The basal area reduction of fir varied directly with the fir basal area at the time of the outbreak. Losses were very high in stands containing over 20 sq. ft. of fir per acre.These young stands did not exhibit the degree of resistance to damage often observed in young stands elsewhere. But in spite of heavy losses through all diameter classes, the amount of spruce and fir regeneration that survived to 1961 is believed adequate to produce a pulpwood crop within 60 years.

One and two years impact of commercial thinning on spruce budworm feeding ecology and host tree foliage production and chemistry

1996 ◽  
Vol 72 (4) ◽  
pp. 393-398 ◽  
Author(s):  
Éric Bauce
Keyword(s):  
Choristoneura Fumiferana ◽  
Soluble Sugars ◽  
Abies Balsamea ◽  
Basal Area ◽  
Spruce Budworm ◽  
Balsam Fir ◽  
First Year ◽  
Commercial Thinning ◽  
Mill Stand ◽  
Second Year

Field rearing experiments of spruce budworm, Choristoneura fumiferana (Clem.), were conducted in conjunction with foliar chemical analyses, one and two years after a commercial thinning (removal of 25% stand basal area) in a 50-year-old balsam fir, Abies balsamea (L.) Mill., stand. The first year after thinning, spruce budworm larvae reared on the residual trees developed five days faster and removed 43% more foliage than those reared on control trees, but in the second year they developed two days faster and removed 37% more foliage. The increase in larval development rate was related to an increase in foliar soluble sugars while a reduction in foliar monoterpenes caused by the thinning apparently accounted for the greater amount of foliage ingested by the larvae. The first year after thinning, trees were more vulnerable to spruce budworm because there was no increase in foliage production and the trees were more heavily defoliated. However, in the second year trees were less vulnerable to the insect because there was an increase in foliage production that exceeded the increase in defoliation, hence a net gain in foliage. Results from this study showed that commercial thinning could reduce the vulnerability of balsam fir trees to spruce budworm if thinning is conducted two years prior to budworm outbreak, but the same silvicultural procedure could increase the vulnerability to the insect if it is conducted during an outbreak. Key words: spruce budworm, balsam fir, chemistry, thinning, defoliation

scholarly journals Spatial-Temporal Patterns of Spruce Budworm Defoliation within Plots in Québec

Forests ◽  
2019 ◽  
Vol 10 (3) ◽  
pp. 232 ◽  
Author(s):  
Mingke Li ◽  
David MacLean ◽  
Chris Hennigar ◽  
Jae Ogilvie
Keyword(s):  
Spatial Autocorrelation ◽  
Hot Spot ◽  
Basal Area ◽  
Temporal Patterns ◽  
Spruce Budworm ◽  
Balsam Fir ◽  
Tree Level ◽  
Cold Spot ◽  
Individual Tree ◽  
Tree Defoliation

We investigated the spatial-temporal patterns of spruce budworm (Choristoneura fumiferana (Clem.); SBW) defoliation within 57 plots over 5 years during the current SBW outbreak in Québec. Although spatial-temporal variability of SBW defoliation has been studied at several scales, the spatial dependence between individual defoliated trees within a plot has not been quantified, and effects of defoliation level of neighboring trees have not been addressed. We used spatial autocorrelation analyses to determine patterns of defoliation of trees (clustered, dispersed, or random) for plots and for individual trees. From 28% to 47% of plots had significantly clustered defoliation during the 5 years. Plots with clustered defoliation generally had higher mean defoliation per plot and higher deviation of defoliation. At the individual-tree-level, we determined ‘hot spot trees’ (highly defoliated trees surrounded by other highly defoliated trees) and ‘cold spot trees’ (lightly defoliated trees surrounded by other lightly defoliated trees) within each plot using local Getis-Ord Gi* analysis. Results revealed that 11 to 27 plots had hot spot trees and 27% to 64% of them had mean defoliation <25%, while plots with 75% to 100% defoliation had either cold spot trees or non-significant spots, which suggested that whether defoliation was high or low enough to be a hot or cold spot depended on the defoliation level of the entire plot. We fitted individual-tree balsam fir defoliation regression models as a function of plot and surrounding tree characteristics (using search radii of 3–5 m). The best model contained plot average balsam fir defoliation and subject tree basal area, and these two variables explained 80% of the variance, which was 2% to 5% higher than the variability explained by the neighboring tree defoliation, over the 3–5 m search radii tested. We concluded that plot-level defoliation and basal area were adequate for modeling individual tree defoliation, and although clustering of defoliation was evident, larger plots were needed to determine the optimum neighborhood radius for predicting defoliation on an individual. Spatial autocorrelation analysis can serve as an objective way to quantify such ecological patterns.

scholarly journals Vulnerability of Conifer Regeneration to Spruce Budworm Outbreaks in the Eastern Canadian Boreal Forest

Forests ◽  
2019 ◽  
Vol 10 (10) ◽  
pp. 850 ◽  
Author(s):  
Janie Lavoie ◽  
Miguel Montoro Girona ◽  
Hubert Morin
Keyword(s):  
Boreal Forests ◽  
Black Spruce ◽  
Choristoneura Fumiferana ◽  
Management Strategies ◽  
Abies Balsamea ◽  
Spruce Budworm ◽  
Balsam Fir ◽  
Insect Outbreaks ◽  
Spruce Stands ◽  
Canadian Boreal Forest

Spruce budworm (Choristoneura fumiferana) is the main defoliator of conifer trees in North American boreal forests, affecting extensive areas and causing marked losses of timber supplies. In 2017, spruce budworm affected more than 7 million ha of Eastern Canadian forest. Defoliation was particularly severe for black spruce (Picea mariana (Mill.) B.S.P.), one of the most important commercial trees in Canada. During the last decades, intensive forest exploitation practices have created vast stands of young balsam fir (Abies balsamea (L.) Mill.) and black spruce. Most research focused on the impacts of spruce budworm has been on mature stands; its effects on regeneration, however, have been neglected. This study evaluates the impacts of spruce budworm on the defoliation of conifer seedlings (black spruce and balsam fir) in clearcuts. We measured the cumulative and annual defoliation of seedlings within six clearcut black spruce stands in Quebec (Canada) that had experienced severe levels of defoliation due to spruce budworm. For all sampled seedlings, we recorded tree species, height class, and distance to the residual forest. Seedling height and species strongly influenced defoliation level. Small seedlings were less affected by spruce budworm activity. As well, cumulative defoliation for balsam fir was double that of black spruce (21% and 9%, respectively). Distance to residual stands had no significant effect on seedling defoliation. As insect outbreaks in boreal forests are expected to become more severe and frequent in the near future, our results are important for adapting forest management strategies to insect outbreaks in a context of climate change.

The influence of forest composition and climate on outbreak characteristics of the spruce budworm in eastern Canada

2013 ◽  
Vol 43 (12) ◽  
pp. 1181-1195 ◽  
Author(s):  
David R. Gray
Keyword(s):  
Black Spruce ◽  
Choristoneura Fumiferana ◽  
Basal Area ◽  
Spruce Budworm ◽  
Climate Scenario ◽  
Forest Composition ◽  
Eastern Canada ◽  
The North ◽  
Average Change ◽  
Maximum Temperatures

The spruce budworm (Choristoneura fumiferana Clemens) is perhaps the single most important disturbance agent in Canada’s eastern forests. Climate and forest composition are dominant factors in spruce budworm outbreak dynamics through their direct influences on the pest, its natural enemies, and its hosts, and through their influence on the multitrophic interactions that are important in outbreak dynamics. A combination of four climate variables, three forest composition variables, and one location variable explained 60% of the multivariate variability in outbreak characteristics (duration and severity) in eastern Canada. Outbreak duration was most strongly influenced by April–May accumulation of degree-days; outbreak severity was most strongly influenced by the extreme maximum temperatures of April–May. The basal area of balsam fir had a stronger influence than that of black spruce on duration and on severity. Both outbreak characteristics declined in more northerly locations. Under a projected future (2011–2040) climate scenario the largest increases in outbreak duration and severity are predicted to occur on the Gaspé Peninsula and the north shore of the St. Lawrence River (Quebec). The largest decreases in duration and severity are predicted to occur in southern Ontario and along the Bay of Fundy in New Brunswick and Nova Scotia. The predicted average change in outbreak duration is around –1.3 years. The predicted average change in outbreak severity is only slightly different from zero (around –1.5% defoliation).

Partial windthrow as a driving process of forest dynamics in old-growth boreal forests

2014 ◽  
Vol 44 (10) ◽  
pp. 1165-1176 ◽  
Author(s):  
François Girard ◽  
Louis De Grandpré ◽  
Jean-Claude Ruel
Keyword(s):  
Boreal Forest ◽  
Forest Dynamics ◽  
Boreal Forests ◽  
Tree Mortality ◽  
Stand Structure ◽  
Temporal Dynamics ◽  
Spruce Budworm ◽  
Climatic Conditions ◽  
Balsam Fir ◽  
Vegetation Development

As climate changes, boreal forest ecosystems may become subject to disturbances that were previously uncommon in some regions. In recent decades, large tracts of northeastern boreal forest of Canada have been affected by different types of climatic events causing a lot of partial and some total stand mortality. Since these disturbances may become more important drivers of forest dynamics, there is a need to document their impact on forest structure. The objectives of this study were to describe temporal dynamics of partial windthrows and determine the effect of partial windthrow on stand composition and understory vegetation. The study was conducted in the North-Shore region of Quebec (Canada). Eighteen plots in closed forests were paired with 18 adjacent windthrow areas, in which trees experienced similar edaphic and climatic conditions. Dendroecological analyses, combined with vegetation sampling, were conducted on each site to determine stand structure and vegetation development through time. Significant increases in balsam fir and shade-tolerant species were observed in windthrow gaps. Tree mortality in windthrown stands was a slow process until the mid-1990s, a period during which spruce budworm defoliation may have played a role in weakening trees and making them more vulnerable to partial windthrow. Greater mortality observed following the mid-1990s was most certainly related to a regional storm. The initial composition of stands plays an important role in driving postwindthrow succession, as balsam fir is more susceptible to treefall. As opposed to stand-replacing windthrow and spruce budworm outbreaks that generate various postdisturbance responses, partial windthrow appears to only create opportunities for pre-established balsam fir to undergo release in gaps.

scholarly journals Forest Succession Following a Spruce Budworm Outbreak in Minnesota

1985 ◽  
Vol 61 (2) ◽  
pp. 75-80 ◽  
Author(s):  
Harold O. Batzer ◽  
Michael P. Popp
Keyword(s):  
Forest Succession ◽  
Choristoneura Fumiferana ◽  
Abies Balsamea ◽  
Basal Area ◽  
Spruce Budworm ◽  
White Spruce ◽  
Balsam Fir ◽  
Red Maple ◽  
Shrub Species ◽  
Before And After

Plots in 24 spruce-fir stands in northeastern Minnesota studied throughout the period 1957 to 1962 at the time of a spruce budworm outbreak were remeasured in 1979. Composition of the overstory changed from an average of 79% of the basal area in host species before to 31% after the budworm outbreak. Twelve percent of the stands showed growth in nonhost species that more than offset the loss in balsam fir and white spruce. The understory was minimally stocked with balsam fir in two-thirds of the stands. Only 4% of the regeneration was spruce. Even so, some well-established white spruce seedlings were found in two-thirds of the stands. Red maple was the most abundant hardwood invader. Raspberry, hazel and mountain maple were the principal shrub species limiting balsam fir reproduction Shrubs were most abundant in stands where balsam fir mortality had exceeded 80%. Half of the stands had seedlings that originated both before and after the outbreak; 45% had seedlings that originated only after the outbreak; and 5% had seedlings that originated only before the outbreak. Stands having moderate mixture of nonhost species in the over-story prior to the budworm outbreak had the most balsam fir regeneration. This resulted from seed produced by surviving balsam fir trees after the outbreak. Key words: Choristoneura fumiferana, Abies balsamea, Balsam fir, spruce-fir shrubs

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