Publications by L. De Grandpré

In Brief from the Canadian Forest Service, Laurentian Forestry Centre. 2012. No. 29.

Fri, 08 Jun 2012

Are mixed forest stands better carbon sinks than pure stands?

Does CO₂ have a fertilization effect on Canada's boreal forests?

Improving prediction of conifer growth in plantations.

Effects of small-scale disturbances in the boreal mixedwood forest.

Birds and post-fire salvage harvesting.

Forest genomics challenge: accelerating genetic selection.

Les Brèves du Service canadien des forêts, Centre de foresterie des Laurentides. No 29.

Fri, 08 Jun 2012

Are mixed forest stands better carbon sinks than pure stands?

Does CO₂ have a fertilization effect on Canada's boreal forests?

Improving prediction of conifer growth in plantations.

Effects of small-scale disturbances in the boreal mixedwood forest.

Birds and post-fire salvage harvesting.

Forest genomics challenge: accelerating genetic selection.

In Brief from the Canadian Forest Service, Laurentian Forestry Centre. Number 27.

Tue, 31 Jan 2012

The mountain pine beetle does not operate alone.

Reforestation of boreal forested peatlands.

Characterization of post-fire residual habitats.

Climate change: lichen woodlands to the rescue.

Good news for native poplars.

The pre-industrial forest landscape of Anticosti Island.

Les Brèves du Service canadien des forêts, Centre de foresterie des Laurentides. Numéro 27.

Tue, 31 Jan 2012

Seasonal shift in the climate responses of Pinus sibirica, Pinus sylvestris, and Larix sibirica trees from semi-arid, north-central Mongolia.

Tue, 19 Jul 2011

In light of a significant increase in the warming trend observed in recent decades in semi-arid Mongolia, tree-ring attributes and anomalies were analysed to detect potential changes in the growth–climate relationship. In a moisture-limited environment, an increase in temperature could cause a shift in the seasonal response of trees to climate. Chronologies were developed for the dominant tree species (Larix sibirica Ledeb., Pinus sibirica Du Tour, and Pinus sylvestris L.) from northcentral Mongolia. In addition to annual ring width, both earlywood and latewood width were measured, and tree-ring anomalies such as false rings and light rings were systematically identified. Earlywood width was mainly associated with precipitation in the year prior to ring formation and early growing season conditions. Temperature was associated with current year growth and mainly influenced latewood development. False rings were good indicators of early summer droughts, whereas light rings were mainly associated with a cold end of summer. A seasonal shift in the significance of monthly climate variables was observed in recent decades. This displacement presumably resulted from changes in the timing and duration of the growing season. Tree growth starts earlier in spring and is now affected by late summer to early autumn climate conditions.

Effects of small canopy gaps on boreal mixedwood understory vegetation dynamics.

Tue, 19 Jul 2011

Boreal mixedwood understory communities are highly dynamic because they are simultaneously influenced by canopy succession, small-scale environmental variation and disturbances. In such a system, fire initiates succession but canopy gaps, resulting from spruce budworm outbreaks or other disturbances, also affect forest dynamics during succession. In this study, we assessed the short-term response of understory communities along a canopy gap severity gradient in mature and old-growth forest stands. The objective was to determine if resource heterogeneity is driving understory community composition and diversity. We created artificial gaps of varying severities in stands of two late successional forest stages. Four treatments, i.e., total cut, conifer cut, girdling of conifers and a control treatment, were each applied over an area of 100 m2 and replicated three times in both types of forest stands. The cover of each understory species was measured before treatment application and 1, 2 and 11 years following it, in seven 1 m2 plots per replicate. Percent transmission of photosynthetic photon flux density and soil temperature were also measured on different occasions after the beginning of the experiment. Species richness, alpha diversity and total cover all increased following gap creation, and this increase was sustained up to 11 years. Increases were more pronounced in total cut than in other treatments. The increase in species richness and diversity was also more pronounced in old-growth stands, while total cover increase was greater in mature stands. Gap creation resulted in significant changes in abundance patterns that were associated with the resident species assemblages. The magnitude of changes in community composition did not significantly differ between mature and old-growth forests and differences in species composition among stands were maintained following gap creation. This study supports the evidence that resource heterogeneity resulting from small-scale disturbances will contribute to maintaining diversity among understory communities by allowing species more typical of early-successional communities to coexist with species from late-successional ones. Such a process may be essential for maintaining the species pool likely to re-invade the stands following major disturbances.

Service canadien des forêts. Points saillants sur la science. Comment la complexité structurelle de la forêt boréale de l'Est influence-t-elle la biodiversité?

Fri, 13 May 2011

Canadian Forest Service Science Highlights. How does the structural complexity of the eastern boreal forest affect biodiversity?

Fri, 13 May 2011

Service canadien des forêts. Points saillants sur la science. Comment les pays couverts par des zones de forêts boréales pourraient-ils échanger entre eux leurs pratiques exemplaires?

Tue, 10 May 2011

Canadian Forest Service Science Highlights. How can boreal forest countries learn best practices from each other?

Tue, 10 May 2011

In Brief from the Canadian Forest Service, Laurentian Forestry Centre. Number 25.

Wed, 06 Apr 2011

Decline in boreal forest productivity.

Beneficial effect of trembling aspen on soil fauna communities in boreal forests.

Rove beetles as indicators of forest disturbance.

Fewer nesting cavities for Barrow's Goldeneye.

Insect defoliators: periodic disturbances in boreal forest ecosystems.

Natural tree mortality in old-growth boreal forests.

Les Brèves du Service canadien des forêts, Centre de foresterie des Laurentides. Numéro 25.

Wed, 06 Apr 2011

Decline in boreal forest productivity.

Beneficial effect of trembling aspen on soil fauna communities in boreal forests.

Rove beetles as indicators of forest disturbance.

Fewer nesting cavities for Barrow's Goldeneye.

Insect defoliators: periodic disturbances in boreal forest ecosystems.

Natural tree mortality in old-growth boreal forests.

La recherche pour améliorer la compréhension.

Fri, 26 Apr 2013

Des solutions adaptées aux vieilles forêts.

Fri, 26 Apr 2013

L'aménagement forestier écosystémique : une approche pour préserver la biodiversité en forêt boréale

Mon, 24 Jan 2011

Preindustrial reconstruction of a perhumid midboreal landscape, Anticosti Island, Quebec

Wed, 22 Dec 2010

The knowledge of natural disturbance dynamics and preindustrial landscapes is essential to implement systainable forest management. Recent findings identify the lack of a forest dynamics model, different from the standard cyclic model of Baskerville (1975. For. Chron. 51: 138-140), for balsam fir (Abies balsamea (L.) Mill.) ecosystems of maritime eastern Canada. With the use of historical forest maps and dendrochronology, we reconstructed the range of variability of the preindustrial landscape (6798 km²) and inferred on the natural disturbance dynamics of the balsam fir forest of Anticosti Island. The preindustrial landscape was characterized by a forest matrix of overmature softwood stands with inclusions of younger softwood stands ranging from 0.1 to 7837 ha in size. Widespread stand-initiating events were apparently rare in the preindustrial landscape over the last 160 years. Since our results were not well represented by the cyclic model, which predicts the occurrence of a mosaic of stands in different age classes, we proposed an alternative forest dynamics model for eastern balsam fir ecosystems near the Gulf of St. Lawrence. Forest management inspired by this alternative model may be more appropriate to maintain or restore ecological characteristics of balsam fir forests of this region within their range of natural variability.

Changes in woody vegetation abundance and diversity after natural disturbances causing different levels of mortality

Wed, 22 Dec 2010

Questions: How does woody vegetation abundance and diversity differ after natural disturbances causing different levels of mortality?

Location: Abies balsamea–Betula papyrifera boreal mixed-wood stands of southeast Quebec, Canada.

Methods: Woody vegetation abundance and diversity were quantified and compared among three disturbance-caused mortality classes, canopy gap, moderate-severity disturbances, and catastrophic fire, using redundancy analysis, a constrained linear ordination technique, and diversity indices.

Results: Substantial changes in canopy tree species abundance and diversity only occurred after catastrophic fire. Shade-tolerant, late-successional conifer species remained dominant after canopy gap and moderate-severity disturbances, whereas shade-intolerant, early-successional colonizers dominated canopy tree regeneration after catastrophic fire. Density and diversity of mid-tolerant and shade-intolerant understory tree and shrub species increased as the impact of disturbance increased. Highest species richness estimates were observed after catastrophic fire, with several species establishing exclusively under these conditions. Relative abundance of canopy tree regeneration was most similar after canopy gap and moderate-severity disturbances. For the sub-canopy tree and shrub community, relative species abundances were most similar after moderate-severity disturbances and catastrophic fire. Vegetation responses to moderate- severity disturbances thus had commonalities with both extremes of the disturbance-caused mortality gradient, but for different regeneration layers.

Conclusions: Current spatio-temporal parameters of natural disturbances causing varying degrees of mortality promote the development of a complex, multi-cohort forest condition throughout the landscape. The projected increase in time intervals between catastrophic fires may lead to reduced diversity within the system.

Les vieilles forêts boréales : des forêts méconnues. L’éclaircie du Service canadien des forêts, Centre de foresterie des Laurentides. No. 59.

Wed, 06 Oct 2010

Although old-growth forests were once a dominant component of some pre-industrial forest landscapes, even-aged forest management in the boreal forest has led to a scarcity of old-growth stands. But what do we actually know about old-growth forests? Canadian Forest Service researchers are working to increase overall understanding of these forests and address certain misconceptions about them.

Old-growth boreal forests: unravelling the mysteries. Branching out from the Canadian Forest Service, Laurentian Forestry Centre. No. 59.

Wed, 06 Oct 2010

Fifty-seven years of composition change in the eastern boreal forest of Canada

Thu, 22 Jul 2010

Question: In the boreal forest of eastern Canada, how does forest vegetation change in the sustained absence of fire?

Location: Eastern boreal forest in Quebec’s North Shore region, Canada (49°30'–50°00'N; 67°30'–68°35'W).

Methods: Aerial photos from three different periods (1930, 1965 and 1987) were used to characterize changes in vegetation composition in 23 scenes of 200 ha. Time since fire, presence of secondary disturbances and data on soil and topographic variables were obtained. Ordination and clustering techniques were used to define compositional trajectories of change over the 57-yr period. These trajectories were further grouped into pathways based on compositional changes, time since fire and preferential deposit-drainage types.

Results: Among the 26 compositional trajectories, three successional pathways were distinguished. Two start post-fire succession with a dominance of intolerant hardwood. In one of these, this is followed by an increase in Abies balsamea, while in the second the importance of Picea mariana increases with time. In the third pathway P. mariana is an important component from the outset. In this pathway, we observed modest fluctuation in the relative dominance of P. mariana and A. balsamea and variation in stand structure.

Conclusion: The boreal forest vegetation of Eastern Canada is diverse and dynamic even in the absence of fire, notably under the influence of partial disturbances. Such disturbances can be associated with changes in composition or stand structure. The development of management strategies aimed at maintaining stand diversity by emulating a broader variety of partial and secondary disturbances should be encouraged.

Sustainable management of old-growth boreal forests: Myths, possible solutions and challenges

Fri, 09 Apr 2010

Old-growth boreal forests serve as focal points for many issues affecting the forest sector such as sustainable forest management and the development of a conservation network. They also challenge the implementation of an adaptive management framework and participative natural resources management. Old-growth boreal forests thus provide a good opportunity for the forest sector to develop transparent management that integrates the diversity of social values associated with old-growth boreal forests. In this paper, we review the different issues related to the sustainable management and conservation of old-growth boreal forests and present these issues in terms of myths and solutions. Finally, we identify and discuss the current limits of our understanding of these issues and we propose research priorities to bridge these knowledge gaps.

L’aménagement durable des vieilles forêts boréales : mythes, pistes de solutions et défis

Fri, 09 Apr 2010

Les mythes associés aux vieilles forêts boréales.

Fri, 26 Apr 2013

Ecosystem Management in the Boreal Forest.

Thu, 07 Jan 2010

Canopy gap characteristics and disturbance dynamics in old-growth Picea abies stands in northern Fennoscandia: Is the forest in quasi-equilibrium?

Fri, 02 Oct 2009

Emulating natural disturbances in managed forests has been suggested as a potential solution to maintain habitat conditions similar to those observed in old-growth forests. We examined the gap attributes and disturbance history of old-growth Picea abies-dominated stands in the norther boreal vegetation zone of the Pallas-Yllästunturi National Park in northwestern Finland to evaluate the influence of gaps on forest dynamics and the temporal patterns of gap creation. Six stands located at two sites were sampled along 400-m-long linear transects so that all intersected gaps were measured and dated. The average proportion of the forest area in the gaps was 43.1% ± 7.5%. An average gap size was estimated to be 221 m² ± 198 m², whereas the median gap size was 170.2 m². While only 20% of the gaps were smaller than 100 m², nearly 85% of them were smaller than 300 m² Gap creation was constant with no distinct peaks from 1965 to 2005. Thus, forest dynamics were driven by continuous small-scale disturbances and were characterized by quasi-equilibrium structure. However, the results of the growth release analysis indicated that more severe disturbance(s) may have occurred almost two centuries ago. Emulating this type of forest dynamics would imply selective or group harvesting of trees as the predominant methods, but larger-scale, more intensive cutting could also be carried out periodically.

Standing dead trees and their decay-class dynamics in the northeastern boreal old-growth forests of Quebec

Tue, 20 Jan 2009

In unmanaged boreal forests standing dead trees are an important component of stand structure, but knowledge on their quantities and dynamics is limited. We characterized the populations of standing dead trees, and modeled their decay-class dynamics in the northeastern boreal old-growth forests of Quebec, Canada. Using 40 m X 400 m plots, we sampled five Picea mariana-dominated, five mixed P. mariana-Abies balsamea, and five A. balsamea-dominated stands. We classified dead trees into five decay classes, extracted sample disks, and crossdated the year of death of 190 trees. Mean times since death in each decay class were used to construct a matrix model for transition dynamics between the classes. Standing dead trees were abundant in all stands, but with large between-stand variation (density, 89.4–229.4 trees ha^-1; volume, 8.3–49.2 m³ ha^-1). On average, dead trees represented 21.4% of the number of all standing trees in P. mariana-dominated stands, 34.0% in mixed P. mariana-A. balsamea stands, and 33.7% in A. balsamea-dominated stands. Modeling indicated lower transition rates between decay classes for P. mariana than for A. balsamea. Half-life as standing dead trees was 35–40 years for P. mariana and 30–35 years for A. balsamea. Our results showed that standing dead trees are an important and long-lasting structural component of the stands studied. To retain stand structural complexity and the associated species diversity in managed forests of this region, strategies for managing standing dead trees need to be developed.

Aménagement écosystémique en forêt boréale

Wed, 09 Jul 2008

Trees dying standing in the northeastern boreal old-growth forests of Quebec: spatial patterns, rates, and temporal variation

Wed, 23 May 2007

Spatial patterns, rates, and temporal variation of standing-tree mortality were studied in unmanaged boreal old-growth forests of northeastern Quebec. The study was carried out by sampling living and dead trees within 15 transects (400 m long, 40 m wide). The transects lay in stands that were classified according to their species composition in three types: dominated by black spruce. Picea mariana (Mill.) BSP; mixed P. mariana and balsam fir, Abies balsamea (L.) Mill.; and dominated by A. balsamea. Spatial patterns were analysed using Ripley's K function. The year of death was cross-dated using 190 sample discs extracted from dead standing A. balsamea and P. mariana to assess the rates and temporal variation of mortality. The spatial patterns of standing dead trees in P. mariana stands were predominantly clustered. The spatial patterns of large dead trees (>19 cm diameter at breast height (1.3 m height; DBH)) in mixed and A. balsamea-dominated stands were mainly random, with few stands showing clustered patterns. Small dead trees (9-19 cm DBH) in these stands were generally more clustered than larger trees. Tree mortality varied from year to year, though some mortality was observed in all the studied stand types for almost every year. Standing trees that had recently died accounted for 62%, 48%, and 51% of overall mortality in P. mariana-dominated, mixed, and A. balsamea-dominated stands, respectively. The results of this study indicate that mortality of standing trees outside of episodic mortality events (such as insect outbreaks) is an important process in the creation of structural complexity and habitat diversity in these stands.

In Brief from the Canadian Forest Service, Laurentian Forestry Centre. Number 9.

Tue, 29 May 2007

A tool for classifying stand structure

Developing models to measure forest productivity

FireSmart forest management: for the sustainable development of forest ecosystems

Forest vegetation simulator (FVS) growth model passes the test for Northern Ontario

Use of fluorescence for easier analysis of the growth rings of hardwoods

In Brief from the Canadian Forest Service, Laurentian Forestry Centre. Number 10.

Tue, 29 May 2007

A silvicultural approach more suited to boreal forests

Defining old-growth forests within boreal forests

Do ecological region and drainage have an impact on the site quality index of black spruce?

For a better understanding of the nitrification process in boreal forests

Gap dynamics and replacement patterns in gaps of the Northeastern boreal forest of Quebec

Landscape composition has an impact on plant succession in boreal forests

Changes in spatial pattern of trees and snags during structural development in Picea mariana boreal forests

Tue, 22 May 2007

Questions: How do gap abundance and the spatial pattern of trees and snags change throughout stand development in Picea mariana forests? Does spatial pattern differ among site types and structural components of a forest?

Location: Boreal forests dominated by Picea mariana, northern Quebec and Ontario, Canada.

Methods: Data on the abundance, characteristics and spatial location of trees, snags and gaps were collected along 200 m transects at 91 sites along a chronosequence. Spatial analyses included 3TLQV, NLV and autocorrelation analysis. Nonparametric analyses were used to analyse trends with time and differences among structural components and site types.

Results: Gaps became more abundant, numerous and more evenly distributed with time. At distances of 1-4 m, tree cover, sapling density and snag density became more heterogeneous with time. Tree cover appeared to be more uniform for the 10- 33 m interval, although this was not significant. Patch size and variance at 1 m were greater for overstorey than for understorey tree cover. Snags were less spatially variable than trees at 1 m, but more so at intermediate distances (4 - 8 m). Few significant differences were found among site types.

Conclusions: During stand development in P. mariana forest, gaps formed by tree mortality are filled in slowly due to poor regeneration and growth, leading to greater gap abundance and clumping of trees and snags at fine scales. At broader scales, patchy regeneration is followed by homogenization of forest stands as trees become smaller with low productivity due to paludification.

Les Brèves du Service canadien des forêts, Centre de foresterie des Laurentides. Numéro 9.

Fri, 03 Nov 2006

A tool for classifying stand structure

Developing models to measure forest productivity

FireSmart forest management: for the sustainable development of forest ecosystems

Forest vegetation simulator (FVS) growth model passes the test for Northern Ontario

Use of fluorescence for easier analysis of the growth rings of hardwoods

Les Brèves du Service canadien des forêts, Centre de foresterie des Laurentides. Numéro 10.

Fri, 03 Nov 2006

A silvicultural approach more suited to boreal forests

Defining old-growth forests within boreal forests

Do ecological region and drainage have an impact on the site quality index of black spruce?

For a better understanding of the nitrification process in boreal forests

Gap dynamics and replacement patterns in gaps of the Northeastern boreal forest of Quebec

Landscape composition has an impact on plant succession in boreal forests

Structural changes in coniferous stands along a chronosequence and a productivity gradient in the northeastern boreal forest of Québec

Tue, 24 Oct 2006

The influence of stand age and site conditions on the structure of coniferous stands was studied in the boreal forest of Québec’s Côte-Nord, a region with low fire recurrence. Stand diameter diversity was measured in 2202 forest inventory plots in black spruce (Picea mariana), balsam fir (Abies balsamea), and mixed stands using the Shannon-Wiener diversity index. A relative productivity index was developed based on the relationship between height and age of dominant trees. A stepwise regression analysis indicated that this productivity index best explains stand structure variation in all composition types, while stand age seems to influence structure more at the beginning of stand development. The results suggest that productive stands become uneven-sized earlier than unproductive stands and also maintain a greater diameter diversity. These contrasting structural dynamics may be explained by (i) a higher growth rate in richer stands that likely induces earlier senescence and thus an earlier passage to an uneven-sized structure and (ii) a restricted maximum tree diameter in poor stands caused by a scarcity of resources, which in turn reduces the diameter diversity of these stands, even after their break-up time.

Structural development following fire in black spruce boreal forest.

Fri, 13 Apr 2012

We investigated stand development along a chronosequence on organic, clay and sand sites in black spruce boreal forest in northwestern Quebec, Canada. Our objectives were: (1) to describe trends and stages of structural development following fire; (2) to compare trends and stages of development both in isolation from and in conjunction with species replacement. We tested the hypothesis that although trends in structural development are similar among site types, productivity and composition affect the timing of developmental stages. Data on live trees, snags and logs were collected at 91 sites. Trends with time since fire were analyzed using segmented piecewise linear regression. On organic sites, tree basal area and density increased continuously with time since fire, while deadwood abundance decreased and then increased. Live tree basal area, tree density and deadwood abundance generally followed expected S-, N- and U-shaped trends, respectively, on clay sites, but often with decreases in later stages due to paludification. Fewer trends were significant on sand sites, although tree basal area decreased likely due to a change in species composition. Older forests on all site types weremore structurally diverse. To estimate the timing of the stages of structural development, we introduce a new analysis technique which uses the breakpoints of the piecewise regressions. On organic sites, only three stages of stand development were evident, whereas a four-stage stand development model was appropriate for both clay and sand sites. We found that local conditions affected not only the timing of developmental stages, but also the number of stages and the trends themselves. We attributed these differences to changes in species composition and productivity. We refine the theory of structural development by representing patterns in both live and deadwood as two-stage trends with two possible outcomes for each stage. Our new method of determining the timing of the developmental stages using empirical data can be used to develop management practices that emulate structural development in order to conserve biodiversity on a landscape scale.

Gap dynamics and replacement patterns in gaps of the northeastern boreal forest of Quebec

Fri, 30 Jul 2004

The northeastern boreal forest of Quebec is characterized by a humid climate. Consequently, fires are less frequent and small-scale disturbances play an important role in forest dynamics. Natural mortality and nonfire disturbances such as insect outbreaks and windthrow lead to gap-driven processes. Changes in structure and species composition can result from gap dynamics. The objectives of this study were to characterize gaps and examine patterns of species replacement in gaps in old conifer stands. Line intersect sampling was used to sample stands dominated by balsam fir (Abies balsamea (L.) Mill.) and (or) black spruce (Picea mariana (Mill.) BSP). Results show that 54% of the forest was in expanded gaps and that canopy gaps are relatively small, since 87% of them were smaller than 100 m². The majority (94%) of the openings were caused by the mortality of less than 10 gap makers. Replacement probabilities show self-replacement of A. balsamea in Abies stands and of P. mariana in Picea stands. However, in Abies–Picea stands, there seems to be a reciprocal replacement of the two species. These results provide knowledge of the disturbance dynamics of the region as a basis for development of silvicultural practices that preserve the structural components of older forest stands.

Les Brèves du Service canadien des forêts, Centre de foresterie des Laurentides. Mars 2004 [No 4].

Wed, 28 Jul 2004

Insecticide resistance at what price?

Low genetic diversity in Canada yew

Post-fire evolution of the boreal forest

Productivity of trembling aspen and stand origin

Stepping stones to the development of resistant elms

Stimulating growth in balsam fir, even at age 60

In Brief from the Canadian Forest Service, Laurentian Forestry Centre. March 2004 [No 4].

Wed, 28 Jul 2004

Insecticide resistance at what price?

Low genetic diversity in Canada yew

Post-fire evolution of the boreal forest

Productivity of trembling aspen and stand origin

Stepping stones to the development of resistant elms

Stimulating growth in balsam fir, even at age 60

L'aménagement des forêts anciennes de la zone boréale de l'est du Canada : un exemple inspiré de la nature. Mémoire volontaire

Wed, 02 Jun 2004

Structure, composition and diversity of old-growth black spruce boreal forest of the Clay Belt region in Québec and Ontario

Wed, 02 Jun 2004

Old-growth black spruce (Picea mariana) boreal forest in the Clay Belt region of Ontario and Quebec is an open forest with a low canopy, quite different from what many consider to be “old growth”. Here, we provide an overview of the characteristics of old-growth black spruce forest for three different site types on organic, clay, and coarse deposits. Our objectives were (1) to identify the extent of older forests; (2) to describe the structure, composition, and diversity in different age classes; and (3) to identify key processes in old-growth black spruce forest. We sampled canopy composition, deadwood abundance, understorey composition, and nonvascular plant species in 91 forest stands along a chronosequence that extended from 20 to more than 250 years after fire. We used a peak in tree basal area, which occurred at 100 years on clay and coarse sites and at 200 years on organic sites, as a process-based means of defining the start of old-growth forest. Old-growth forests are extensive in the Clay Belt, covering 30–50% of the forested landscape. Black spruce was dominant on all organic sites, and in all older stands. Although there were fewer understorey species and none exclusive to old-growth, these forests were structurally diverse and had greater abundance of Sphagnum, epiphytic lichens, and ericaceous species. Paludification, a process characteristic of old-growth forest stands on clay deposits in this region, causes decreases in tree and deadwood abundance. Old-growth black spruce forests, therefore, lack the large trees and snags that are characteristic of other old-growth forests. Small-scale disturbances such as spruce budworm and windthrow are common, creating numerous gaps. Landscape and stand level management strategies could minimize structural changes caused by harvesting, but unmanaged forest in all stages of development must be preserved in order to conserve all the attributes of old-growth black spruce forest.

Composition and dynamics of the understory vegetation in the boreal forests of Quebec.

Tue, 01 Jun 2004

Les Brèves du Service canadien des forêts, Centre de foresterie des Laurentides. Décembre 2003 [No 3].

Fri, 30 Jan 2004

Biodiversity: Preserving lichen and bryophyte communities

Comparative study of black spruce stands originating after harvest or after fire

Does planting white pines under a canopy have an effect on weevil attacks?

Frost damage to seedling root systems and effects on growth

Yellow birch more vulnerable to ice damage than previously thought

In Brief from the Canadian Forest Service, Laurentian Forestry Centre. December 2003 [No 3].

Fri, 30 Jan 2004

Biodiversity: Preserving lichen and bryophyte communities

Comparative study of black spruce stands originating after harvest or after fire

Does planting white pines under a canopy have an effect on weevil attacks?

Frost damage to seedling root systems and effects on growth

Yellow birch more vulnerable to ice damage than previously thought

Développement d'un outil de classification de la structure des peuplements et comparaison de deux territoires de la pessière à mousses du Québec

Wed, 27 Aug 2003

Forest stand structure is an important element for biodiversity and, from a sustainable forest management perspective, uneven-sized stands should be managed in order to maintain the structural diversity over the landscape. The first objective of this study is to develop a statistical tool to characterize stand structure that can be used in forest management planning. The second objective is to classify the stand structure of two regions to illustrate a possible use for the tool. The statistical tool for characterizing stand structure has been developed from forest inventory data gathered by the ministère des Ressources naturelles du Québec, using discriminant analysis. The analysis makes it possible to classify the stands into three types of structure, even-sized, uneven-sized and inverse J-shaped, with an error rate estimated at only 7%. Proportions of different structure types in Quebec’s eastern black spruce forest region have been compared with those found in the western black spruce forest region. Nearly 90% of the western black spruce forest region is composed of pure black spruce stands, contrary to the eastern black spruce region, where there are more pure fir and mixed spruce-fir stands. Most of the western black spruce forest stands are even-sized (62%), while almost 70% of the eastern black spruce forest stands are uneven-sized or inverse J-shaped. Pure black spruce stands are more even-sized than pure fir stands, but regional differences are also found within pure black spruce stands. Our results show that it is possible to develop a robust tool that makes it possible to classify thousands of stands rapidly. Such tools are required if we want to consider stand structure for appropriate management prescriptions in the boreal forest.

Differences in forest composition in two boreal forest ecoregions of Quebec

Thu, 08 Aug 2002

In order to describe and compare the post-fire succession patterns of the two ecological regions (mixed-wood and coniferous ecoregions) of northwestern Quebec, 260 forest stands were sampled with the point-centred plot method. The mixed-wood ecological region belongs to the Abies balsamea-Betula papyrifera bioclimatic domain whereas the coniferous ecological region belongs to the Picea mariana-moss bioclimatic domain. In each plot, tree composition was described, surficial deposits and drainage were recorded, and fire history was reconstructed using standard dendro-ecological methods. Ordination techniques (Correspondence Analysis and Canonical Correspondence Analysis) were used to describe the successional patterns of forest vegetation and to correlate them with the explanatory variables. The results showed the importance of surficial deposits, the time since fire and the ecoregion in explaining the variation of stand composition. Abies balsamea tends to increase in importance with an increase in time since fire, and this trend is more pronounced in the mixed-wood region. Even when controlling both for surficial deposits and time since fire, differences in successional trends were observed between the two ecoregions. As all the species are present in both ecoregions and as they are all observed further north, our results suggest that both the landscape configuration and fire regime parameters such as fire size and fire intensity are important factors involved in these differences.

Early understory successional changes following clearcutting in the balsam fir-yellow birch forest

Wed, 07 Aug 2002

Community response to disturbance is influenced by species life history and the nature of disturbance. In this study we investigated the effects of clearcutting on the early successional changes of an understory species community in the balsam fir-yellow birch forest type of the Lower St. Lawrence Region of Québec, Canada. Clearcuts of 5, 10 and 20 years were sampled along with mature stands. In each of these communities, ten circular quadrats of 400 m² were established where the percent cover of herb, fern, and shrub species was estimated. Along a 150-m transect starting in the middle of each quadrat, the seedling density of commercial tree species was measured in ten 4-m² plots. Detrended Correspondence Analysis (DCA; cover values) was used to describe the early successional changes in the understory community and a Correspondence Analysis (CA) was used with presence/absence data to evaluate the compositional differences. The results revealed a time gradient associated with understory community changes, in which the first 10 years of successional changes are characterized by the dominance of shade intolerant species. A decrease in the floristic heterogeneity was associated with clearcut logging. Small herb species with a shallow root system were most affected by logging. For commercial tree seedlings, the changes following clearcutting were characterized by a decrease over time in the density and stocking of shade intolerant and mid-tolerant species (principally white and yellow birches). In the older clearcuts, sugar maple appeared to be the dominant commercial species in the seedling understory. The results suggested that clearcut logging in the balsam fir-yellow birch forest type may contribute to rapidly shifting the seedling understory composition towards dominance by shade tolerant species. This situation may be related to the dominance of mountain maple in the understory of old clearcuts that contribute to reducing the available light in the understory, thus increasing mortality of shade intolerant seedling species. Clearcutting may also have deleterious effects on some understory herb species that need particular conditions before re-establishing in a site. Logging tends to reduce micro-site heterogeneity over large extended areas'a situation that may preclude the re-establishment of some late successional herb species.

Long-term post-fire changes in the northeastern boreal forest of Quebec

Wed, 07 Aug 2002

Natural dynamics in the boreal forest is influenced by disturbances. Fire recurrence affects community development and landscape diversity. Forest development was studied in the northeastern boreal forest of Quebec. The objective was to describe succession following fire and to assess the factors related to the changes in forest composition and structure. The study area is located in northeastern Quebec, 50 km north of Baie-Comeau. We used the forest inventory data gathered by the Ministère des Ressources naturelles du Québec (MRNQ). In circular plots of 400 m², the diameter at breast height (DBH) of all stems of tree species greater than 10 cm was recorded and in 40 m² subplots, stems smaller than 10 cm were measured. A total of 380 plots were sampled in an area of 6000 km². The fire history reconstruction was done based on historical maps, old aerial photographs and field sampling. A time-since-fire class, a deposit type, slope, slope aspect and altitude were attributed to each plot. Each plot was also described according to species richness and size structure characteristics. Traces of recent disturbance were also recorded in each plot. Changes in forest composition were described using ordination analyses (NMDS and CCA) and correlated with the explanatory variables. Two successional pathways were observed in the area and characterized by the early dominance of intolerant hardwood species or Picea mariana. With time elapsed since the last fire, composition converged towards either Picea mariana, Abies balsamea or a mixture of both species and the size structure of the coniferous dominated stands got more irregular. The environmental conditions varied between stands and explained part of the variability in composition. Their effect tended to decrease with increasing time elapsed since fire, as canopy composition was getting more similar. Gaps may be important to control forest dynamics in old successional communities.

Diversity and stability of understorey communities following disturbance in the southern boreal forest

Tue, 22 Aug 2000

We investigated the response of boreal understorey communities to gap formation in order to evaluate the relationship between community stability and changes in community composition. We described the early changes in understorey species composition after gap formation and assessed some of the factors responsible for higher resistance to disturbance.
At six sites, in the southern boreal forest of north-western Québec, representing a successional gradient after fire, trees were cut and removed from an area of 400 m². In each experimental gap, we recorded the cover of the understorey species in four 4-m² permanent quadrats from before to 4 years after gap formation. We estimated resistance to disturbance in terms of changes in species composition and abundance.
Younger communities changed less than older ones after disturbance. Sites with more species changed less in composition after gap formation than less rich sites. Richer quadrats contained species that could react quickly to disturbance by increasing their cover and preventing invaders from dominating the understorey.
Stronger resistance of understorey species communities to gap formation can persist in older sites because of the particular disturbance regime. Gaps created by the spruce budworm in older sites dominated by balsam fir increase microsite heterogeneity and diversity by allowing the co-exitence of early and late successional species.