Boreal Forest Of Quebec Research Articles

Latitudinal variation in tree-ring and wood cell characteristics of Picea mariana across the continuous boreal forest in Quebec

Wood anatomical features measured in tree-rings are useful indicators of environmental change and wood quality. The effect of latitude on the wood anatomy of mature black spruce ( Picea mariana (Mill.) BSP) was investigated along a 500 km transect from 47°N to 52°N across the continuous boreal forest in Quebec, Canada. Total tree-ring width, earlywood width, latewood width, latewood proportion, cell numbers, tracheid length, radial diameter, lumen diameter, and cell wall thickness were measured using image analysis on samples from 15 mature stands. Our results suggest that tree-ring, earlywood, and latewood widths, cell numbers, latewood radial cell diameter, and cell wall thickness decrease with latitude. No significant trend was observed for latewood proportion, despite a slight increase with latitude (p = 0.0856). However, the high variability in radial growth seen along the gradient might explain the absence of a significant relationship. Latitude and the associated growth rate reduction had no effect on tracheid length. The existence of a latitudinal pattern of variation in black spruce wood anatomy may be the result of tree adaptation to differing environmental conditions along the gradient.

Fire return intervals and tree species succession in the North Shore region of eastern Quebec

We evaluated geographic variations in mean fire return intervals and postfire forest succession within a 66 497 km2 land area located in the eastern Quebec boreal forest. Fire return intervals were calculated using a time since last fire map for 1800–2000, and forest dynamics were studied by superimposing 3204 forest inventory plots onto the fire map. Mean fire return interval proved significantly shorter in the western part of the study area, at 270 years, compared with the eastern part, where it was probably more than 500 years. The two main tree species in the study area were balsam fir ( Abies balsamea (L.) P. Mill.) and black spruce ( Picea mariana (Mill.) BSP). Balsam fir abundance increased progressively as a function of time since fire, whereas black spruce abundance increased during the first 90 years after fire and then declined. Balsam fir was significantly more abundant in the southeastern portion of the study area, which we attribute to the combined limitations imposed by temperature along the north–south axis and by fire along the east–west axis. Large forest patches (i.e., ≥200 km2) dominated by early successional tree species, within a matrix of irregular black spruce – balsam fir mixtures, are an important feature of preindustrial forest landscapes in this region.

Influence of fire intensity on structure and composition of jack pine stands in the boreal forest of Quebec: Live trees, understory vegetation and dead wood dynamics

North American jack pine ( Pinus banksiana Lamb.) stands are generally characterized by an even-aged structure resulting from high intensity fires (HIF). However, non-lethal fires of moderate intensity (MIF), which leave behind surviving trees, have also been reported. The objectives of this study were two-fold: (1) assess the concurrent dynamics of live trees, understory vegetation and different types of coarse woody debris (CWD) during succession after HIF; and (2) document how MIF affects stand structure component dynamics compared to HIF. Stands affected by both HIF and MIF were selected. Tree characteristics and age structure, understory biomass, and CWD volume were assessed. Our results suggest that the structural succession of jack pine stands following HIF comprises three stages: young stands (<48 years), premature and mature stands (58–100 years) and old stands (>118 years). Canopy openness and jack pine density significantly decreased with time since HIF, while black spruce density and CWD volume significantly increased. The highest structural diversity was measured in the premature and mature stands. Compared to HIF, MIF increased mean jack pine basal area, decreased average stand density, delayed the replacement of jack pine by black spruce replacement in the canopy, decreased CWD volume, and significantly increased bryophytes mass. MIF increased the diversity of live trees and generally decreased CWD structural diversity. The study confirms the diversity of natural disturbance magnitude and successional processes thereby initiated. Thereafter, it appeared to be relevant for adjustment of disturbance emulating forest-management systems.

Stem deformation in young plantations of black spruce ( Picea mariana (Mill.) B.S.P.) and jack pine ( Pinus banksiana Lamb.) in the boreal forest of Quebec, Canada

Stem deformation has often been observed in young black spruce ( Picea mariana (Mill.) B.S.P.) and jack pine ( Pinus banksiana Lamb.) plantations. Whenever important stem deformations are observed at the time of harvesting, timber value is negatively affected especially during the wood transformation process. The present work was undertaken to quantify and qualify the importance of stem deformation of black spruce and jack pine in the boreal forest of central Quebec at the stand and tree levels. In 30 black spruce and jack pine plantations, approximately 22% of spruce trees and 27% of pine trees exhibited stem deformation. The proportion of deformed trees was higher in the youngest plantations and decreased with the age of the plantations. Stem deformation caused the formation of compression wood which is another factor that can reduce the value of wood products. Thirty-nine black spruces and 34 jack pines were analysed at the tree level. On average, compression wood represented 14% and 20% of stem volume in 7- and 10-year old black spruce plantations, respectively. These proportions ranged from 18% in the youngest jack pine plantation to 26% in the oldest one. Stems of both species classified as normal contained a lower volume of compression wood than stems classified as deformed or very deformed. Annual percentages of compression wood and annual shoot length increased significantly with tree age ( p < 0.0001 for both variables). Statistically significant correlations were also found between the range of displacement of the stem and the percentage of compression wood. The fewer number of trees with deformed stems in older plantations combined with high compression wood formation suggests that, over time, a deformed tree can become normal and straight in appearance.

Dendroclimatic inference of wildfire activity in Quebec over the 20th century and implications for natural disturbance-based forest management at the northern limit of the commercial forest

We examined the fire–climate relationship at the northern limit of commercial forest in western Quebec, a region where forest management is currently competing with fires for mature stands. The main objective was to determine if a particular climate signal would control the fire activity in this region when compared with other parts of the Quebec boreal forest. We used 500-hPa spatial correlation maps to compare the atmospheric patterns associated with the annual area burned (AAB) in the study area, the entire province of Quebec, the intensive (southern Quebec), and the restricted (northern Quebec) fire management zones. Next, dendroclimatic analyses were used to obtain tree-ring estimates of the AAB back to 1904 and to investigate the temporal stability of the fire–climate relationship. The climate controls associated with the AAB of the study area are intermediate between those associated with the AAB of the intensive and restricted fire management zones. The 500-hPa correlation patterns for the 1948–71 and 1972–2001 periods were relatively stable through time for the study area and for the restricted fire management zone. Our results provide a plausible mechanism for explaining the link between sea surface temperature and regional fire activity established in previous studies. They also provide information complementary to the Canadian fire danger rating system that uses daily weather data.

Black spruce (Picea mariana) foliage hosts numerous and potentially endemic fungal endophytes

Fungal foliar endophytes (hereinafter endophytes) were isolated on malt agar from black spruce ( Picea mariana (Mill.) BSP) needles from the Quebec boreal forest during 2 successive years to study their distribution along a latitudinal transect. Twenty sites were sampled in 2002, 8 of which were sampled again in 2003, in an area located between 47°N and 54°N in the province of Quebec. The endophytes were named whenever possible, using homologies of ITS rDNA sequences from GenBank. In 2002, 232 morphotypes were classified in 40 operational taxonomic units (OTUs), and in 2003, 93 morphotypes were classified in 16 OTUs, for a total of 44 OTUs. Isolation frequencies of the most common endophyte species were 28% for Lophodermium piceae (Fuchel) Höhn., 17% for Darkera parca Whitney, Reid &amp; Piroz, and 9% for Dwayaangam colodena Sokolski &amp; Bérubé. Of the 44 OTUs identified, 18 were unique to P. mariana and found on one site only, possibly constituting rare endemic species. There was some evidence that needles colonized with rare endophyte species were more abundant in the western and southern regions than in the northern region. This supports our hypothesis that as the diversity of tree species surrounding the P. mariana decrease from the southern region to the northern region, the diversity of endophytes also decreases.

Postfire Succession of Saproxylic Arthropods, with Emphasis on Coleoptera, in the North Boreal Forest of Quebec

Saproxylic succession in fire-killed black spruce [Picea mariana (Mill.) B.S.P.] coarse woody debris (CWD) in northern Quebec is estimated in this study using a 29-yr postfire chronosequence. Sampling was performed using both trunk-window traps and rearing from snag and log sections. A total of 37,312 arthropods (>220 taxa) were collected from both sampling methods. Two distinct colonization waves were identified. The onset of initial colonization occurs the year of the fire, whereas the second colonization phase begins only once debris falls to the ground. The initial colonization step is influenced by fire-associated species including subcortical predators, xylophages, and ascomycetes feeders. Abundance of most early colonizer species decline with time since fire with the disappearance of subcortical habitat. No noticeable species turnover occurred in snags thereafter. Lack of succession in snags is related to very low decomposition rates for postfire CWD because this substrate is unsuitable for species associated with highly decayed wood. Snag falling triggers fungal growth and concomitant saproxylic succession toward micro- and saprophagous species and increases accessibility for soil-dwelling organisms. Because the position of woody debris greatly influences overall physical properties of dead wood, the fall of burned CWD plays a major role in saproxylic community shift after fire.

Historical fire regime shifts related to climate teleconnections in the Waswanipi area, central Quebec, Canada

The synchrony of regional fire regime shifts across the Quebec boreal forest, eastern Canada, suggests that regional fire regimes are influenced by large-scale climate variability. The present study investigated the relationship of the forest-age distribution, reflecting the regional fire activity, to large-scale climate variations. The interdecadal variation in forest fire activity in the Waswanipi area, north-eastern Canada, was reconstructed over 1720–2000. Next, the 1880–2000 reconstructed fire activity was analysed using different proxies of the Pacific Decadal Oscillation (PDO) and the North Atlantic Oscillation (NAO) and the Atlantic Multidecadal Oscillation (AMO). We estimated the global fire cycle around 132–153 years, with a major lengthening of the fire cycle from 99 years before 1940, to 282 years after 1940. Correlations between decadal fire activity and climate indices indicated a positive influence of the PDO. The positive influence of PDO on regional fire activity was also validated using t-tests between fire years and non-fire years between 1899 and 1996. Our results confirmed recent findings on the positive influence of the PDO on the fire activity over northern Quebec and the reinforcing role of the NAO in this relationship.

Identification of two genera of N2-fixing cyanobacteria growing on three feather moss species in boreal forests of Quebec, Canada

The recent discovery that N2fixation rates by the feather moss carpet of boreal Scandinavian forests increases with stand maturity has put into question the paradigm that N2fixation is negligible in mature boreal forest. The N2fixation was attributed to a previously unknown association between Nostoc sp., a N2-fixing cyanobacteium and Pleurozium schreberi (Brid.) Mitt., a feather moss that is abundant worldwide in the boreal forest. Here we report for the first time that this association also exists in the Canadian boreal forest. We discovered, however, that Nostoc was found growing not only on Pleurozium but also on two other moss species ( Hylocomnium splendens (Hedw.) Br. Eur. and Ptillium crista-castrensis (Hedw.) De Not.). In addition, the N2-fixing cyanobacterium Stigonema sp. was observed on the three moss species mentioned above, indicating the existence of six different associations. At least one of the six associations was found at 9 of 13 sites that are representative of a large area of the Quebec boreal forest. These findings suggest possibilities for further research, aimed at measuring the unaccounted for N2-fixing potential of the feather moss carpet in Canadian boreal forests.

Factors Responsible for the Co-occurrence of Forested and Unforested Rock Outcrops in the Boreal Forest

Rock outcrops in the boreal forest of Quebec can show either of two different states: a forested state with >25% tree cover, and an unforested state (<25% tree cover). We tested three different hypotheses that might explain the co-occurrence of forested and unforested rock outcrops: (1) differences in bedrock geology, with unforested outcrops associated to bedrock types inimical to tree growth; (2) unforested outcrops as recently disturbed sites undergoing secondary succession towards a forested state; (3) unforested outcrops as an alternative stable state to forested outcrops, induced by post-fire regeneration failure. Digitized forest inventory maps were used along with bedrock geology maps and time-since-fire maps to compare forested and unforested outcrops for bedrock geology type and date of the last fire. Field surveys were conducted on 28 outcrops (14 forested, 14 unforested) to gather information regarding tree species composition and site characteristics (thickness of the organic matter layer, percent cover of lichens, mosses and ericaceous shrubs). None of the three hypotheses explain the co-occurrence of forested and unforested rock outcrops in the boreal forest of Quebec. Both outcrop types occur on the same bedrock geology types. Unforested outcrops are not recently disturbed sites in early-successional states, as no clear distinction could be made in tree species composition and date of the last fire between the two outcrop types. Forested and unforested outcrops are not alternative stable states, as unforested outcrops are unstable and cannot maintain themselves through time in the prolonged absence of fire. Hence, unforested rock outcrops could be viewed as degraded, diverging post-fire types maintained by the late Holocene disturbance regime, characterized by high fire frequencies.

Adventive-root development in mature black spruce and balsam fir in the boreal forests of Quebec, Canada

Black spruce (Picea mariana (Mill.) BSP) and balsam fir (Abies balsamea (L.) Mill.) are the two main tree species in the boreal forests of Quebec, Canada, and both show adventive-root formation. Little is known about the dynamics of adventive-root initiation and the pattern of length growth. To gain a better understanding of root growth, the root systems of 30 mature black spruce and 30 mature balsam fir were excavated until the root diameter had decreased to 2 cm. Tree ages ranged from 100 to more than 250 years. All trees showed only adventive roots; this was confirmed by dating the root–shoot interface. The youngest lateral roots were located close to ground level, whereas the oldest ones occurred lower in the stump, suggesting a process of renewal for the latter. Reconstruction of the development of the root system revealed a specific root-growth pattern. Adventive roots grew, on average, more than 60% of their total length in the year of initiation, whereas more than 93% of lateral-root elongation was recorded in the first 10 years after adventive roots were initiated. This growth pattern was found to be similar in the two tree species in terms of lateral-root development (p = 0.68). More variability was observed for the ramified adventive roots. However, two patterns emerged. First, around 10% of total elongation was completed in the same year as that of the corresponding lateral roots. Second, several ramified adventive roots were initiated in the same calendar year but delayed by several years relative to lateral adventive root initiation. No significant differences were observed between black spruce and balsam fir (p = 0.1).

The adaptive capacity of forest management to changing fire regimes in the boreal forest of Quebec

Climate influences natural processes at multiple spatial and temporal scales. Consequently, climate change raises many challenges for sustainable forest management; among them, the integration of fire and forest management is increasingly discussed. We propose here an evaluation of the adaptive capacity of forest management under changing forest fire regimes under climate change in the boreal forest of Quebec. Adaptation begins by reinterpreting current practices dealing with climatically driven variability. Among them, fire suppression, and regeneration enhancement can contribute to coping with some impacts of climate change. However, there is an increasing need to develop more integrative and spatially explicit management strategies to decrease the vulnerability of forest management to changing fire risk. Some developing management strategies, such as fuel management or the triad approach (zoning system for conservation, intensive, and extensive forest management), present an interesting potential for integrating the fire risk in management plans. While fuel management and fire suppression are indicated for particularly severe fire regimes, protection against insects, and maintaining a shorter disturbance cycle using forest management represent the preferred adaptation options where the fire cycle is lengthening under climate change. Key words: forest fire, fire risk, climate change, vulnerability, impacts, adaptation strategy, adaptation options, sustainable forest management, fire management

Fire disturbance of larch woodlands in string fens in northern Québec

In this study, dendrochronology was used to reconstruct the fire history and associated dynamics of the last 350 years in three larch (Larix laricina [Du Roi] K. Koch) woodlands in string fens of the northern boreal forest of Quebec. Fire scars were also sampled to reconstruct the fire history across the surrounding uplands. Our results show that string fens are more likely to experience partial disturbance than complete removal of the tree cover during fire. Although large fires burned across the studied landscape in 1733, 1787, 1865, and 1941, no stand-replacing fire has occurred in any of the studied woodlands. At all sites, the oldest larch trees became established around 1640–1680, and several individuals survived each fire identified across the uplands. However, partial disturbance during the most recent 1941 fire, which was associated with severe fire weather, decreased tree density and released the growth of several trees. Although signs of previous fire may have been lost through wood decay, no fire impacted larch growth as severely as the 1941 fire, further emphasizing the modest influence of fire in string fens as compared with uplands. The low fire influence in these minerotrophic peatlands helps explain the high occurrence of the fire-sensitive eastern larch.Key words: boreal forest, fire disturbance, larch woodland, Larix laricina, northern Quebec, string fen.

Landscape-level variability in the age underestimation of understory black spruce in the northern boreal forest of Quebec

This study examines the variability of the potential aging error for saplings (height ≤1.5 m) of black spruce (Picea mariana (Mill.) B.S.P.) in mature fire-dominated stands (n = 14 stands) of the northern boreal forest of northwestern Quebec. Age underestimation was determined by counting the number of underground bud scars of saplings. The magnitude and variability of age underestimation was compared within and among stands. The relationship between corrected ages (the sum of age underestimation and the number of growth rings at ground level) and ground-level ages was strongly linear and was therefore described with simple linear regression models. To evaluate landscape-level variability in this relationship, the regressions were compared among stands using mixed models. Despite high variability in age underestimation at the stand level, the relationship between corrected and ground-level age was highly significant (p &lt; 0.0001) for all stands except one. However, there were many significant statistical differences between these regressions, indicating high landscape-level variability. The magnitude of age underestimation was found to be highly site specific (means of 7–26 years), the phenomenon being more marked and variable in older stands. Given high landscape-level variability, age underestimation of understory black spruce saplings in northern boreal stands must be documented for every sampled stand to apply a valid age correction in studies that involve multiple stands.

Wet Heartwood Distribution in the Stem, Stump, and Root Wood of Black Spruce in the Quebec Boreal Forest, Canada

Abstract Wet heartwood has been studied since the beginning of the 20th century. The present work focused on wet heartwood of 44 black spruces (Picea mariana (Mill.) B.S.P.) from boreal forest swampy sites Quebec, Canada. Trees were studied to characterize their tree crown shape, quickly identify them in the field, measure their moisture content, establish their moisture content distribution pattern, evaluate the wet heartwood volume inside their stem, and find the possibility of water entrance in this species. Black spruces with wet heartwood were characterized by a typical tree shape with a small number of living branches, short branches, and a clump of green needles at the top of the tree. The wet heartwood was characterized by high moisture content at the stem base and decreased with stem height. Wet heartwood was observed as high as 5 m above stem base for trees around 10.5 m in height. Moisture content of sapwood along the stem varied from 81 to 161%, whereas in dry heartwood, it was around 43% but reached more than 100% in the wet heartwood. Wet heartwood volume in the first 3.25 m of black spruce stems averaged 13% with variations between 2 and 35% per study site. Twelve stumps had wet heartwood moisture contents reaching 143% or higher. Moisture content of wet heartwood in root sections closest to the stump varied along a gradient: lower or absent at ground level and increasing with depth up to a maximum value before decreasing again. North. J. Appl. For. 22(1):12–18.

Response of beaver, moose, and snowshoe hare to clear-cutting in a Quebec boreal forest: a reassessment 10 years after cut

We studied the response of beaver (Castor canadensis Kuhl), moose (Alces alces L.), and snowshoe hare (Lepus americanus Erxl.) to clear-cutting in three blocks that had been logged 10 years ago. In a previous study, these species had been surveyed in the same blocks 2 years before and 2 years after logging. We also surveyed an uncut block of the initial experimental design that was logged more recently. Over the 10-year period, the shrub layer and available browse have improved markedly in clear-cut areas. As compared with logged coniferous stands, logged mixed stands had higher lateral cover (62% vs. ≈55%) and taller regeneration (&gt;4 m vs. &lt;3 m). Beaver density did not change over the period because its feeding habitat remained unchanged in the riparian forest strips. Moose densities increased 54%–87% in two harvested blocks as a result of both logging and stricter hunting regulations (selective hunting). Based on the rate of increase observed in a control block, we estimate that a 25% density increase in the mixed forest block can be related to logging, while selective hunting can solely be responsible for the change in the coniferous forest block. Snowshoe hare have started to reoccupy logged coniferous stands, but their relative density still remained less than half that of uncut stands. We conclude that, after 10 years, logged mixed stands already offer good habitat conditions for moose and snowshoe hare. Conversely, in logged black spruce (Picea mariana (Mill.) BSP) stands, habitat conditions still remain poor for snowshoe hare because of a lack of cover.

Intra-annual tracheid production in balsam fir stems and the effect of meteorological variables

Tracheid production of balsam fir in the Quebec boreal forest (Canada) was studied by repeated cell analysis to investigate the influence of meteorological variables during the growing seasons 1998 to 2000. Wood micro-cores were extracted on a weekly basis throughout the growing season and sections were prepared in order to count the total number of cells produced. From the weekly cell number obtained, the rate of tracheid production was calculated and correlated with meteorological variables. The average total number of cells produced per year was reasonably uniform, increasing only from 36.6 in 1998, to 41.1 in 2000. However, different cell production rates were noted during the growing season. Regression analysis revealed that the cell production rate was largely dependent on minimum air and soil temperature during most of the cell production period. Mean and maximum temperature had less influence on cell production. Moreover, the influence of temperature was higher during earlywood production mainly from the end of May to mid-July. Lagging the weather data by 1–5 days decreased the relationship between temperature and cell production, showing the high correspondence with the same interval where cell production was measured. These results suggest a fast response of the cambium to temperature variation during tree-ring formation.

Productivity of black spruce and Jack pine stands in Quebec as related to climate, site biological features and soil properties

The relationships between site quality indices (SQI) (estimated height at age 50) of black spruce and Jack pine and site characteristics were investigated over a large territory in the boreal forest of Quebec. The relationships with degree-days (DD) and parent material, which are considered as permanent site factors, were significant for both species. Linear regressions with these two parameters as independent variables explained about 40% of the variability in site quality indices for black spruce and Jack pine. The addition of soil chemistry and biological data to this model indicated a significant contribution of exchangeable Mg concentrations or Al:CEC molar ratios in the forest floor and lichen cover to the prediction of site quality indices. Inclusion of these variables increased the model R 2 up to 60% for both species. Whether these variables reflect permanent site conditions or conditions related to the history of the sites is unknown.

Temporal, spatial, and structural patterns of adult trembling aspen and white spruce mortality in Quebec's boreal forest

Temporal, spatial, and structural patterns of adult trembling aspen (Populus tremuloides Michx.) and white spruce (Picea glauca (Moench) Voss) mortality were studied in intact 150-year-old stands in the southwestern boreal forest of Quebec. For both species, mortality decreases (number of dead trees/total number of trees) with distance from the lake edge until 100–150 m, from which point it slightly increases. Strong peaks in mortality were found for 40- to 60-year-old aspen mainly between 1974 and 1992. Such mortality in relatively young aspen is likely related to competition for light from the dominant canopy trees. Also, the recruitment of this young aspen cohort is presumably the result of a stand breakup that occurred when the initial aspen-dominated stand was between 90 and 110 years old. For spruce, strong peaks in mortality were found in 110- to 150-year-old trees and they occurred mainly after 1980. No clear explanation could be found for these peaks, but we suggest that they may be related to senescence or weakening of the trees following the last spruce budworm outbreak. Suppressed and codominant aspen had a much higher mortality ratio than spruce in the same height class, while more surprisingly, no difference in mortality rate was found between dominant trees of the two species. Most spruce trees were found as standing dead, which leads us to reject the hypothesis that windthrow is an important cause of mortality for spruce in our forests.

Croissance et statut nutritif de marcottes, de semis naturels et de plants d'épinette noire à la suite du scarifiage : résultats de 10 ans

Careful logging around advance growth (CLAAG) and tree planting following site preparation or not (fill planting) are widely used to regenerate black spruce (Picea mariana (Mill.) BSP) stands in the boreal forest of Quebec, Canada. However, few mid-term studies have compared these different regeneration modes. In this study, we examined height growth and nutrient status of black spruce layers, natural seedlings, and planted seedlings over a 10-year period, in an experimental design combining CLAAG, natural seeding, planting, and two types of scarification (cones and disks). Without scarification, growth of planted seedlings (5.8 cm·year–1) was slightly greater than that of layers (4.4 cm·year–1) and natural seedlings (4.1 cm·year–1). Scarification improved growth of the three types of regeneration, but the treatment was more beneficial for planted seedlings (+7.1 cm·year–1) than for natural seedlings (+1.6 cm·year–1) and layers (+1,0 cm·year–1). Five years after treatment, scarification had increased the current-year needle N concentration of the three types of regeneration, but this beneficial effect on N was still detectable only in foliage of layers after 10 years. The effect of the treatment was variable for P and K contents, for which natural regeneration seems to have taken advantage more than plants. Our results indicate that scarification can improve the initial growth and nutrient status of both natural and artificial regeneration of black spruce and thus accelerate site recovery after cutting in the boreal forest. Furthermore, fill planting without site preparation appeared to be clearly less efficient than planting combined with scarification.