Subarctic Quebec Research Articles

Recent Fluctuations of the Lichen-Spruce Forest Limit in Subarctic Quebec

1 Black spruce (Picea mariana) experienced increased radial growth and stem height over the last 100 years at treeline in subarctic Quebec, suggesting warmer and snowier conditions. We tested if recent climate change also induced a shift from forest to krummholz during the Little Ice Age and stand reversion from krummholz to forest during the 1900s. Whether the shifts caused measurable displacements of the forest limit were also examined. 2 Growth forms of living and dead spruces were compared in five lichen-spruce stands located 0, 2, 4, 6 and 8 km south of the krummholz limit. The age structure of supranival shoots (stems standing above the snow cover) at each site was also determined. 3 A reversion from lichen-spruce forest to krummholz probably occurred during the mid-1800s. Since the late 1800s, the forest limit moved 4 km northward most likely in response to milder winter conditions. Krummholz changed progressively to forest as spruce height and frequency of the tree growth form increased. Thus the northward advance of the forest limit resulted from structural changes of pre-established spruces, whereas there was no evidence for a recent spruce establishment in the tundra.

Variations in rooting ability of cuttings and in seed characteristics of five populations of Juniperus communis var. depressa from subarctic Quebec

Juniperus communis var. depressa is a species with potential for site restoration in the Canadian subarctic and low arctic. We assessed this potential by evaluating the rooting ability of cuttings and the seed quality of five populations of the species along the east coast of Hudson Bay, in subarctic Quebec. Cuttings of male and female plants were sampled from each site. Cones were collected, and seeds were extracted, weighed, and then tested for viability. Cuttings from female plants rooted more easily than those from male plants. At high indolyl-3-butyric acid concentration, rooting of female cuttings was inhibited. Among-population differences in rooting ability were large: cuttings from the northernmost population rooted more easily than those from sites further south. Seed number per cone and seed mass and viability also varied significantly among sites. Of the populations studied, the northernmost one produced the lightest seeds and the southernmost one produced the heaviest seeds. Juniperus presents some potential for restoration, but transplant (cutting or seedling) performance in the field should be evaluated before any definite recommendations are made. There is some evidence that seed quality and rooting ability are characteristics that are negatively related in Juniperus, although the basis of such a trade-off has not been investigated. Key words: gender differences in rooting ability, indolyl-3-butyric acid, restoration, Whapmagoostui-Kuujjuaraapik.

Temporal variations in the rooting ability of cuttings of Populusbalsamifera and Salixplanifolia from natural clones–populations of subarctic Quebec

Temporal variations in the rooting ability of cuttings from five clones of Populusbalsamifera L. and five populations of Salixplanifolia Pursh from the Great Whale River valley in subarctic Quebec were determined. Cuttings were sampled monthly from May through October and rooted in a greenhouse. Root number and length of the longest root per cutting were determined 35 days after planting. There were significant variations among the six sampling dates in the rooting potential of cuttings of both species. A higher percentage of cuttings formed adventitious roots in May and June before or shortly after bud break than later, during the growing season; root number and length followed a similar trend. There was an increase in the rooting ability of cuttings of both species towards the fall period. Salixplanifolia produced more roots per cutting than P. balsamifera early in the season (i.e., May and June), but later in the season the differences between the two species were not great; root length showed no such trend. Differences among clones–populations in the rooting potential of cuttings were large for both species. Coefficients of variation for root number were lower in spring than later, during the growing season, for both P. balsamifera and S. planifolia. Seasonal trends in coefficients of variation for root length were not as evident as for root number. These results have significant implications for site restoration in the Subarctic. To optimize the rooting ability of cuttings and minimize the differences among clones–populations in rooting potential, cuttings should be sampled early in the season before bud break or shortly thereafter.

Defoliation of tamarack by outbreak populations of larch sawfly in subarctic Quebec: measuring the impact on tree growth

In conjunction with other major perturbations, outbreaks of specialist insect defoliators could play a key role in the long-term evolution of northern forest communities. Sawfly oviposition marks up to 20 years old in shoots of tamarack, Larixlaricina (Du Roi) K. Koch, provide a direct record of a large-scale epidemic cycle of the larch sawfly, Pristiphoraerichsonii (Htg.), during the 1980s in the Grande Rivière de la Baleine region, northern Quebec. Because no significant tree mortality was noted in the years following peak defoliator populations in 1985–1986, a study was undertaken to determine whether insect population changes during the outbreak period were correlated with growth changes under various climatic and soil conditions in three coastal sites and one continental sampling site. The fluctuations with time in the density of oviposition marks on trees indicated that the epidemic cycle was synchronous at all sites. However, the defoliator's density was significantly higher at the inland site, located 150 km from Hudson Bay, than at the coastal sites, where climatic conditions may be less favorable to insect activity and survival. No significant effects on tree growth were detected at the coastal sites, whereas larch from the inland site recorded a significant reduction in radial growth in 1984, the 1st year of outbreak conditions. Larch from this site also showed significant effects on foliage development after 4 years of defoliation (1988), when a virtual stop on elongative growth became apparent. Larch trees reproduced actively during the outbreak, with peak reproductive effort in 1984 and 1987 correlating with lows in elongative growth. Delayed or minimal effects of this outbreak characterized by the presence of hundreds of sawfly colonies per tree and defoliation levels comparable to those observed in the boreal forest during similar outbreaks indicate that subarctic larch may be highly tolerant to prolonged defoliation by the larch sawfly.

Air temperature, tree growth, and the northern and southern range limits to Picea mariana

Abstract. Many models that simulate the long‐term response of forests to climatic change use the assumption that northern and southern range limits are caused by the deleterious effects of cold and hot air temperatures, respectively, on individual tree growth and that growth declines symmetrically with air temperatures above and below some optimal value in between these extremes. To test the validity of this assumption, we combined physiological data for black spruce, Picea mariana, growing near the treeline in subarctic Quebec with a model of the biophysical and biochemical effects of temperature on photosynthesis. The physiological conditions allow black spruce to grow over a wider range of air temperatures than is reflected in its geographic distribution. In particular, the physiological data suggest that the northern range limit of black spruce is not caused by the direct effects of cold growing‐season air temperatures on tree growth and that growth is optimal, with respect to temperature, at the southern range limit. While pollen data indicate large geographic changes in spruce abundance with past climatic changes, the current analyses suggest that the direct effect of air temperature on individual tree growth has not caused these changes. Until we better understand the effects of air temperature on ecological processes, the efficacy of climatic change analyses must be evaluated in terms of model assumptions.

Black Spruce Growth Forms as a Record of a Changing Winter Environment at Treeline, Quebec, Canada

The environmental conditions prevailing at treeline in subarctic Quebec have been reconstructed over the past 400 yr through a comparative analysis of tree rings and growth forms of black spruce (Picea mariana (Mill.) B.S.P.). Because black spruce growth forms are closely associated with the winter environment, they are a direct response to conditions of low temperature and windblown snow abrasion affecting living tissues at the snow-air interface. The age structure of supranival shoot populations was closely associated with periods of higher stem survival in winter most likely under snowier and windless conditions. Spruce growth on slopes and in the valley revealed periods of low tree-ring growth between 1601 and 1663 and between 1700 and 1904, respectively. A long-lasting period of low radial growth 1697 and 1939 prevailed in the hilltop site. During the 20th century, spruce height increased from 0.8 to 1.6 m on slopes and in the valley, while the basal level of abrasion from windblown snow increased from 0.1 to 0.5 m, suggesting an increasing trend towards warmer and snowier conditions. Abraded spruces growing during the Little Ice Age (1570-1880) were replaced by symmetrical trees during the 20th century. Supranival skirted and whorled spruces which dominated on themore » hilltop site during the 16th century reverted to infranival cushion and mat growth forms during the Little Ice Age. These stunted spruces were unable to recover during the recent warming because of their inability to catch enough drifting snow to allow vertical growth.« less

A dendroecological analysis of eastern larch (Larixlaricina) in subarctic Quebec

Two new dendrochronological series of eastern larch (Larixlaricina (Du Roi) K. Koch) from subarctic Quebec extend from 1710 to 1987 (Whapmagoostui–Kuujjuarapik, eastern Hudson Bay) and from 1596 to 1978 (Rivière aux Feuilles, western Ungava). In both regions, the tree-ring series show similar long-term variations. Generally, conditions were more favorable for growth at the end of the 19th century and during the 20th century than before. A comparison of several larch and white spruce (Piceaglauca (Moench) Voss) tree-ring series from northern Quebec indicates significant shared variance between regions and species. Larch chronologies show two important depressions during the 20th century, between 1905–1908 and 1940–1946, which are more obvious in the two series from the southern forest–tundra than in the series from Ungava. These may be caused by outbreaks of the larch sawfly, Pristiphoraerichsonii (Htg.).

Spatial and temporal variations of methane flux from subarctic/northern boreal fens

Emissions of CH4 were measured by a static chamber technique (five chambers/site) at 23 sites in four fens near Schefferville, subarctic Quebec. At three intensively‐monitored sites along a transect from fen margin to central and flooded sites, mean CH4 fluxes from June to August, 1989 were 65, 125, and 36 mg m−2 d−1, respectively. Pore water CH4 concentrations in the peat profiles to a depth of l m averaged 125 to 200 μM, with lower concentrations (generally <50 μM) at 0.1 m. Total, depth‐integrated storage of CH4 in the peat profiles ranged from 3.5 to 4.3 g m−2. Although CH4 flux was only weakly correlated with either peat temperature at 0.1 m or water table position within each site, there was a strong association of flux and these variables among the three sites, indicating the value of ecological attributes in identifying patterns of CH4 flux. A pulse of CH4 was recorded at two of the three sites in mid‐August, associated with a degassing of the peat profile, based on pore water CH4 concentrations. This pulse appeared to be initiated by the lowering of the water table by between 5 and 10 cm during a 3‐week period of low rainfall and is estimated to have contributed 18 to 65% of the seasonal CH4 emission, depending on the location of the site. An estimate of the regional CH4 flux from 130 km2 of the Schefferville area was based on CH4 flux measurements at 23 sites in the area, stratified by fen type (forested margin, margin, central, flooded, ridge, and pool). June to August regional CH4 flux was 18 mg m−2 d−1, for an area in which fen coverage was 29%. When extrapolated to the global scale, these results indicate that northern fens may contribute about 14 Tg yr−1, somewhat lower than other recent estimates.

Postfire black spruce establishment in subarctic and boreal Quebec

Forest regeneration in areas burned during the 1950s in northern Quebec was studied along topographic and climatic gradients, from the northern Boreal Forest to the northern Forest–Tundra. Regenerated plant communities are mostly dominated by Cladinamitis in well-drained uplands and by hygrophilous shrub species in moister lowlands. The age structure of 23 stands, as they were immediately before and about 30 years after the 1950s fires, was used to analyze the patterns of establishment and development of black spruce (Piceamariana (Mill.) B.S.P.) populations associated with fire disturbance. Postfire black spruce establishment was active during the first 20 years of vegetation recovery, then it decreased rapidly. Three older populations originating from 1936 and 1922 fires showed a rapid postfire tree establishment, whereas a long delay of recolonization was observed in the 1906 fire. Along the topographical gradient, postfire regeneration was more rapid in hill sites, whereas spruce recruitment was more abundant in lowland sites. Along a northward latitudinal gradient, prefire populations showed an increasing trend in age range, mean age, and mean age of youngest individuals. This gradient coincided also with an increasing fire rotation period from south to north. The proportion of stunted individuals in postfire populations was often more important than in prefire populations on the same sites, suggesting more rigorous growth conditions associated with forest removal. Because most black spruce seedling establishment is occurring during a short period in this area, it is suggested that stand density is determined by regeneration conditions, including seed input and seedbed quality, soon after the fire. Therefore, comparisons between prefire and 30-year-old postfire populations can be used as an index to evaluate fire impact on stand density.

Frost bursting: a violent expression of frost action in rock

The breakdown of rock by forces attributable to the freezing of water is one of the various weathering processes included under the general term "frost action." Field observations in the Guillaume–Delisle Gulf area, subarctic Quebec, suggest that under certain conditions the process can be rapid, even explosive. By analogy to rockbursting, the term "frost bursting" is proposed as the equivalent to the French term "éclatement". Frost bursting is the process by which intact and massive rock is shattered when water saturated and submitted to intense and rapid freezing. Hydrostatic pressure developed either in pore spaces or rock cracks allows strain energy to be stored in the freezing rock. Frost bursting will occur if the material is stiff and strong enough to exhibit release of a large quantity of stored strain energy.

Patterns of dissolved organic matter in subarctic peatlands

AbstractSamples of water from poor to very rich fens in the Schefferville region of subarctic Quebec revealed strong spatial and temporal variations in dissolved organic carbon (DOC), ranging from 2 to 40 mg 1−1. Concentrations of DOC tend to increase during the summer and decrease in the autumn, at most sites, which probably reflects increased plant tissue decomposition and higher rates of evapotranspiration. Principal components analysis revealed that DOC is strongly associated with Fe, NO−3‐N and NO−2‐N, but essentially independent of other chemical properties of the peat water, such as pH, Ca, Mg, K, P, and NH+4‐N. Based on observed concentrations of DOC and estimates of summer runoff (June to September), export of DOC from four peatlands ranges from 1·1 to 4·9 gCm−2, with the lowest values for peatlands underlain by dolomite. Molecular weight fractionation of four samples revealed significant differences in the dissolved organic matter (DOM), with the largest fractions (GF/C to 10 000 nmw) being dominant in the more acid samples. The ratio of absorbance at 400 and 600 nm wavelengths (E4:E6) has been used as a simple indicator of differences in DOM type, ranging from 3 to 15. There is a strong seasonal pattern of increasing E4:E6 ratio during the summer at many sites, though this ratio is essentially independent of other chemical properties of peat waters.

EFFETS SUR LA DERIVE DES INSECTES AQUATIQUES D'UN TRAITEMENT AU TEMEPHOS CONTRE LES LARVES DE MOUSTIQUES DANS LE QUEBEC SUBARCTIQUE

RésuméEn mai 1980, on a étudié pendant 5 j la dérive des insectes aquatiques dans 3 ruisseaux drainant des tourbières traitées au téméphos granulé pour le contrôle des larves de moustiques, à Gagnon (51°52′ N, 68°10′ O) dans le Québec subarctique. Dans les tourbières l'activité résiduelle du téméphos contre les larves de moustiques est passée de 100% à 0% en 5 j. Alors qu'un ruisseau témoin ne montrait aucun changement, la dérive a augmenté en moyenne de 6.4 fois dans les 3 ruisseaux exposés pendant les 3 j suivant l'épandage. L'augmentation de dérive a été significative pour les Plécoptères (11.8 fois), les Ephéméroptères (4.7 fois) et les Diptères (3 fois), mais pas pour les Trichoptères ni les autres insectes. Pour chaque ordre respectivement, cette augmentation est due à Podmosta macdunnoughi (Nemouridae), aux Baetis spp. (Baetidae) et aux Chironomidae. Une analyse en composantes principales distingue les échantillons traités des échantillons avant traitement ou témoins (facteur 1) et groupe les échantillons selon le ruisseau d'origine (facteur 2). Les données montrent que le téméphos, lorsqu'appliqué contre les larves de moustiques dans les tourbières, augmente la dérive des insectes aquatiques dans les ruisseaux drainant celles-ci, et que P. macdunnoughi est particulièrement sensible à cet insecticide or-ganophosphoré.

Manual on protection and control of coastal erosion in India

Erosional and depositional features produced by lake ice occur in many lakes of temperate and cold regions. Ice-push ridges, grooves with a boulder at their head, ice-rafted sediments, boulder ridges, stone pavements, beach micro-relief, and destruction of shore vegetation, are features common to many lakes in the James Bay area, subarctic Quebec. However, the ice cover offers good protection against shore erosion by waves, during six months per year, permitting varve sedimentation. Ice-push ridges and grooves with a boulder at their head are the two most common ice-made features: 95 ice-push ridges, up to 7 m high, have been observed in 35 lakes, and grooves, up to 300 m long have been found in 81 sites from 69 lakes. These features resulted from ice movements caused either by ice expansion and wind action, at breakup. A review of the literature indicates that several factors must be considered in any investigation of ice action in the lacustrine environment.

Ice action in the lacustrine environment. A review with particular reference to subarctic Quebec, Canada

Erosional and depositional features produced by lake ice occur in many lakes of temperate and cold regions. Ice-push ridges, grooves with a boulder at their head, ice-rafted sediments, boulder ridges, stone pavements, beach micro-relief, and destruction of shore vegetation, are features common to many lakes in the James Bay area, subarctic Quebec. However, the ice cover offers good protection against shore erosion by waves, during six months per year, permitting varve sedimentation. Ice-push ridges and grooves with a boulder at their head are the two most common ice-made features: 95 ice-push ridges, up to 7 m high, have been observed in 35 lakes, and grooves, up to 300 m long have been found in 81 sites from 69 lakes. These features resulted from ice movements caused either by ice expansion and wind action, at breakup. A review of the literature indicates that several factors must be considered in any investigation of ice action in the lacustrine environment.

Radiocarbon dates on peat and tree remains from James Bay area, subarctic Quebec

14C dates on peat and tree remains from the southern part of James Bay Lowlands, subarctic Quebec, indicate that forests and peatland conditions began at least 1000 years after the deglaciation of the area. Inception of forest and organic deposition in bogs varies within the main geological events of the late-glacial and postglacial times in the area: the drainage of glacial Lake Ojibway, the Tyrrell Sea transgression, and the emergence. The oldest age recorded for the beginning of peat deposition is 6890 ± 120 years before present (BP) at an elevation of 240 m and the youngest age is 3830 ± 120 years BP at an elevation of 60 m. A delay ranging from 400 to 900 years between forest occupation and the establishment of bog conditions is recorded.

Aboveground Biomass of Black Spruce Stands in Subarctic Quebec

Aboveground biomass and tree density data are presented for three spruce–lichen woodland and three spruce–moss forest sites (Piceamariana dominant). Based on regressions of oven-dry weight on diameter breast height, spruce biomass values of 10 000–29 000 and 78 000–163 300 kg•ha−1 were obtained from the woodland and forest sites, respectively. Tree densities ranged from 1270 to 3080 and 4840 to 5350 per hectare for the two associations.