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  • 1
    Article
    Article
    2018
    ISSN: 0347-0520 
    Language: English
    In: The Scandinavian journal of economics, 2018-01, Vol.120 (1), p.242-267
    Description: In this paper, I study how occupational segregation affects the allocation of talent in a competitive labour market. I propose a model of occupational choice in which heterogeneous workers must rely on their social contacts to acquire job‐vacancy information. While occupational segregation implies benefits in terms of job‐finding probability, it also leads to allocative inefficiencies. Efficient and equilibrium outcomes differ due to a network externality that leads workers to segregate too little, and a pecuniary externality that leads workers to segregate too much. Which effect dominates depends on the elasticity of wages to changes in the degree of occupational segregation.
    Subject(s): Allocation of talent ; occupational choice ; social networks ; Social networks ; Segregation ; Career choice ; Analysis
    ISSN: 0347-0520
    E-ISSN: 1467-9442
    Source: Business Source Ultimate
    Source: EconLit with Full Text
    Source: Alma/SFX Local Collection
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  • 2
    Language: English
    In: Canadian journal of forest research, 2008-06-01, Vol.38 (6), p.1621-1633
    Description: We evaluated geographic variations in mean fire return intervals and postfire forest succession within a 66497km2 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 3204forest inventory plots onto the fire map. Mean fire return interval proved significantly shorter in the western part of the study area, at 270years, compared with the eastern part, where it was probably more than 500years. 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 90years 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., ≥200km2) 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.Nous avons évalué les variations géographiques dans les intervalles de retour moyens des feux, ainsi que la succession forestière après feu, au sein d'un territoire de 66497km2 localisé dans la forêt boréale de l'est du Québec. Les intervalles de retour moyens ont été calculés à partir d'une carte du temps depuis le dernier feu pour la période 1800-2000, et la dynamique forestière a été étudiée en superposant 3204placettes d'inventaire à cette carte. L'intervalle de retour des feux était significativement plus courts dans la partie ouest de l'aire d'étude, à 270ans, comparativement avec la partie est, où l'intervalle moyen dépassait probablement 500ans. Les deux principales espèces d'arbre dans l'aire d'étude étaient le sapin baumier (Abies balsamea (L.) P. Mill.) et l'épinette noire (Picea mariana (Mill.) BSP). L'abondance du sapin baumier augmentait progressivement en fonction du temps depuis le dernier feu, alors que l'abondance de l'épinette noire augmentait durant les 90premières années, puis déclinait subséquemment. Le sapin baumier était significativement plus bondant dans la partie sud-est de l'aire d'étude, ce que nous attribuons aux limitations imposées par la température le long de l'axe nord-sud, et par les feux le long de l'axe est-ouest. De grands massifs forestiers (par exemple, ≥200km2), dominés par de espèces de début de succession au sein d'une matrice dominée par des peuplements mélangés irréguliers de sapin baumier et d'épinette noire, représentent une caractéristique importante des paysages forestiers pré-industriels dans cette région.
    Subject(s): Fundamental and applied biological sciences. Psychology ; Forest and land fires ; Synecology ; Terrestrial ecosystems ; Animal, plant and microbial ecology ; Forestry ; Biological and medical sciences ; Stand types and stand dynamics. Silvicultural treatments. Tending of stands. Natural regeneration ; Phytopathology. Animal pests. Plant and forest protection ; Animal and plant ecology ; Forest management. Stand types and stand dynamics. Silvicultural treatments. Tending of stands. Natural regeneration ; Weather damages. Fires ; Canada ; Forestry research ; Research ; Forest fires ; Forest dynamics
    ISSN: 0045-5067
    E-ISSN: 1208-6037
    Source: Academic Search Ultimate
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  • 3
    Language: English
    In: Ecosystems (New York), 2014-09-01, Vol.17 (6), p.1053-1067
    Description: Fire is considered as a major driver of ecosystem processes of the boreal forest with important effects on soil and forest productivity. When the interval between successive forest fires is long, a thick organic layer can develop and eventually interfere with processes involved in tree nutrient uptake. We thus hypothesized that the organic layer of well-drained boreal stands increases with time since last fire and that thick organic layers are associated with low values of soil temperature, nutrient availability, and site productivity. This was tested on a chronosequence composed of 90 boreal stands ranging from 1 to more than 2000 years after fire within which we measured organic layer thickness (OLT), mineral soil and foliage nutrient concentrations, soil temperature, ground cover of Sphagnum sp. and Ericaceae sp., leaf area index, aboveground biomass production, and growth efficiency index (GEI). The OLT increased during the first 64 years after fire but stayed statistically constant thereafter. This initial increase in OLT was accompanied by an increase in the C/N ratio and decreases in soil temperature, foliar N, and GEI. The absence of a significant decrease in productivity from 80 to 2000 years post-fire suggests that these characteristics reach a steady state early in the chronosequence that persists in the absence of major disturbances or changes in site conditions. These results imply that management practices may not be necessary to maintain boreal forest productivity in the absence of fire on well-drained sites.
    Subject(s): Productivity ; Trees ; Boreal forests ; Forest stands ; Mineral soils ; Organic foods ; Leaf area ; Chronosequences ; Soil temperature ; Forest soils ; Hydrology/Water Resources ; Zoology ; boreal forest ; Ecology ; leaf area index ; organic layer thickness ; post-fire chronosequence ; Life Sciences ; Geoecology/Natural Processes ; soil nutrient concentrations ; soil temperature ; site productivity ; Plant Sciences ; Environmental Management ; Ecosystems ; Analysis ; Forest fires
    ISSN: 1432-9840
    E-ISSN: 1435-0629
    Source: Alma/SFX Local Collection
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  • 4
    Language: English
    In: Oecologia, 2016-07, Vol.181 (3), p.831-840
    Description: As the impact of anthropogenic activities intensifies worldwide, an increasing proportion of landscape is converted to early successional stages every year. To understand and anticipate the global effects of the human footprint on wildlife, assessing short-term changes in animal populations in response to disturbance events is becoming increasingly important. We used isodar habitat selection theory to reveal the consequences of timber harvesting on the ecological processes that control the distribution dynamics of a small mammal, the red-backed vole (Myodes gapperi). The abundance of voles was estimated in pairs of cut and uncut forest stands, prior to logging and up to 2 years afterwards. A week after logging, voles did not display any preference between cut and uncut stands, and a non-significant isodar indicated that their distribution was not driven by density-dependent habitat selection. One month after harvesting, however, juvenile abundance increased in cut stands, whereas the highest proportions of reproductive females were observed in uncut stands. This distribution pattern appears to result from interference competition, with juveniles moving into cuts where there was weaker competition with adults. In fact, the emergence of source-sink dynamics between uncut and cut stands, driven by interference competition, could explain why the abundance of red-backed voles became lower in cut (the sink) than uncut (the source) stands 1–2 years after logging. Our study demonstrates that the influences of density-dependent habitat selection and interference competition in shaping animal distribution can vary frequently, and for several months, following anthropogenic disturbance.
    Subject(s): Life Sciences ; Hydrology/Water Resources ; Ecology ; Isodar ; Red-backed vole ; Habitat selection ; Plant Sciences ; Interference competition ; Anthropogenic disturbances ; Forests ; Reproduction ; Animals ; Ecosystem ; Arvicolinae ; Old growth forests ; Timber ; Index Medicus
    ISSN: 0029-8549
    E-ISSN: 1432-1939
    Source: Alma/SFX Local Collection
    Source: © ProQuest LLC All rights reserved〈img src="https://exlibris-pub.s3.amazonaws.com/PQ_Logo.jpg" style="vertical-align:middle;margin-left:7px"〉
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  • 5
    Language: English
    In: Land degradation & development, 2020-05-15, Vol.31 (8), p.1039-1049
    Description: In arid and semiarid forests and rangelands, native ranchers and farmers frequently use fire as a tool to improve soil fertility and vegetation composition, and to facilitate soil tilling. Investigating changes in ecosystem characteristics after these measures is of great importance for establishing management and recovery strategies. This study aimed to investigate spatial–temporal changes in the understory heterogeneity, diversity and composition after fires of different severities in a Brant's oak (Quercus brantii Lindl.) forest. Vegetation sampling was monitored in 14 patches including unburned sites (UBN), burned sites with low fire severity after 1, 5, and 10 years (LFSO, LFSF, and LFST, respectively), and burned sites with high fire severity after 1, 5, and 10 years (HFSO, HFSF, and HFST, respectively). Fire severity and time since fire significantly affected diversity indices with the lowest values of richness, evenness and diversity in high‐severity fires, while the highest values were observed in low‐severity fires. Time since fire did not significantly affect the understory evenness in both fire severities. However, species diversity and richness in low‐severity fires decreased with time since fire while the reverse was observed in high‐severity fires. The results of a detrended correspondence analysis indicated that the severity and time since fire significantly changed vegetation composition. The largest changes in vegetation composition compared to control sites were observed in HFSO, and then in HFSF and HFST. Both fire severity and time since fire caused changes in the heterogeneity of plant communities. We concluded that the use of low‐severity fires can be suitable for maintaining and increasing the heterogeneity of understory vegetation in semiarid forest ecosystems. However, low‐severity fires have also slightly, while not significantly, increased evenness and can therefore potentially reduce the ecosystem functions of dominant species in such semiarid regions. This could mitigate the positive effect of fire on vegetation heterogeneity and necessitate further investigations.
    Subject(s): evenness ; MRPP ; vegetation ; recovery ; anthropogenic fires
    ISSN: 1085-3278
    E-ISSN: 1099-145X
    Source: Alma/SFX Local Collection
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  • 6
    Language: English
    In: Canadian journal of forest research, 2010-01-01, Vol.40 (1), p.86-94
    Description: We evaluated spruce budworm (Choristoneura fumiferana (Clem.)) outbreak effects in nine study areas (60-86ha each) located in the boreal forest of eastern Quebec (Canada). In each area, spruce budworm outbreak effects were measured from vegetation plots, dominant canopy and understory tree age structures, retrospective analysis of aerial photographs, defoliation records, and host tree growth reductions (dendrochronology). Large-scale synchronous outbreaks were detected across the region around the years 1880, 1915, 1950, and 1980. Overall, contrarily to what was expected for a region where host species (balsam fir (Abies balsamea (L.) Mill.), Picea spp.) content is relatively high, these spruce budworm outbreaks seemed to have a relatively minor influence on stand dynamics, with the exception of the most recent outbreak (1980). This outbreak resulted in major stand mortality in the southern part of the region and favored the establishment of extensive tracts of young even-aged stands with few residual mature trees. This very abrupt increase in outbreak severity compared with earlier outbreaks, perhaps due to climatic or random factors, suggests that historical trends in successive outbreak severity should be extrapolated very cautiously and that the study of several outbreak cycles is needed to establish a range of natural variability that can be used to develop an ecosystem forest management strategy.Nous avons évalué les effets des épidémies de tordeuse des bourgeons de l'épinette (Choristoneura fumiferana (Clem.)) dans neuf aires d'étude (de 60-86ha chaque) situées dans la forêt boréale de l'est du Québec, au Canada. Dans chaque aire d'étude, les effets des épidémies de tordeuse des bourgeons de l'épinette ont été mesurés à partir de placettes de végétation, de la structure d'âge des arbres de la canopée dominante et du sous-bois, d'une analyse rétrospective de photographies aériennes, de relevés de défoliation et des réductions de croissance des arbres hôtes (dendrochronologie). Des épidémies synchrones ont été détectées sur l'ensemble de la région autour des années 1880, 1915, 1950 et 1980. Contrairement à ce qui était anticipé dans une région où les espèces hôtes (sapin baumier (Abies balsamea (L.) Mill.), Picea spp.) sont relativement abondantes, ces épidémies de tordeuse des bourgeons de l'épinette semblent avoir eu un impact relativement limité sur la dynamique des peuplements, à l'exception de l'épidémie la plus récente (1980). Cette épidémie a causé une forte mortalité dans les peuplements situés dans la partie sud de la région et a favorisé l'établissement, sur de vastes étendues, de jeunes peuplements équiennes contenant peu d'arbres matures résiduels. La hausse très abrupte de l'intensité de cette épidémie comparativement aux épidémies précédentes est probablement attribuable à des facteurs climatiques ou aléatoires et indique que les tendances historiques de l'intensité des épidémies successives devraient être extrapolées avec beaucoup de prudence. Ce résultat indique aussi qu'il faut étudier plusieurs cycles épidémiques pour définir les limites de la variabilité naturelle qui peuvent être utilisées pour mettre au point une stratégie d'aménagement forestier écosystémique.
    Subject(s): Fundamental and applied biological sciences. Psychology ; Biological and medical sciences ; Stand types and stand dynamics. Silvicultural treatments. Tending of stands. Natural regeneration ; Forest management. Stand types and stand dynamics. Silvicultural treatments. Tending of stands. Natural regeneration ; Forestry ; Trees ; Canada ; Influence ; Forests and forestry ; Research ; Spruce budworm
    ISSN: 0045-5067
    E-ISSN: 1208-6037
    Source: Academic Search Ultimate
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  • 7
    Language: English
    In: Journal of vegetation science, 2015-11-01, Vol.26 (6), p.1225-1237
    Description: Questions: What are the relative roles of disturbance type and canopy composition on understorey plant assemblages? Are these two environmental filters of equal importance in driving understorey patterns? Does a trait-based approach improve understanding of plant assemblage responses in disturbed boreal forests? Location: Eastern boreal forests of North America, Québec, Canada. Methods: We sampled understorey plant assemblages in ca. 30-yr-old forest stands originating from three types of disturbance (clear-cutting, fire and spruce budworm outbreak) and two dominant canopy compositions (coniferous and deciduous). For each disturbance × canopy combination, at least eight stands were sampled. The results were analysed with a combination of multivariate (RDA, PERMANOVA), univariate (IndVal) and trait-based (fourth-comer) approaches. Results: Overall, canopy composition was a more important driver than disturbance type for understorey plant communities. Species richness and particularly the abundance of herbaceous species were highest under deciduous canopies, whereas bryophytes and lichens were more diverse and abundant under coniferous canopies. Light-demanding species with abundant seed production were mostly restricted to deciduous canopies. Some patterns were also explained by disturbance type, but these were mostly associated with the presence/absence of non-abundant species or species groups such as lichens. Conclusions: We propose that the higher effect of canopy composition compared with disturbance type can be explained by two factors. First, the effect of canopy composition tends to remain present for decades during stand development, whereas the effect of the disturbance type tends to dissipate progressively after the stand-initiating disturbance. Second, in boreal forests, most understorey plant species possess reproduction strategies (such as vegetative reproduction) that make them well adapted to persist in stands affected by any type of disturbance. At the landscape level, maintaining the right proportion of deciduous and coniferous stands through forest management could ensure that understorey ecosystem processes and plant diversity are maintained. However, creating or maintaining specific post-disturbance attributes could be important for the conservation of species affiliated with specific substrates.
    Subject(s): Understorey plants ; Boreal forests ; Clear‐cutting ; Canopy composition ; Disturbances ; Environmental filters ; Fire ; Functional traits ; Coniferous stands ; Spruce budworm ; Deciduous stands
    ISSN: 1100-9233
    E-ISSN: 1654-1103
    Source: Academic Search Ultimate
    Source: Alma/SFX Local Collection
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  • 8
    Language: English
    In: Landscape ecology, 2017-02, Vol.32 (2), p.377-395
    Description: Sustained timber harvesting conflicts with the long-term viability of boreal caribou (Rangifer tarandus caribou) populations. The spatial arrangement of harvest blocks in the landscape could mitigate the impact of logging on caribou populations. For the forest industry, however, these measures represent constraints that reduce the annual allowable cut (AAC).Estimate the long-term impacts of spatial constraints to harvesting, applied alone or in combination, on AAC and boreal caribou populations.We divided a 30,000 km2 region into 20 harvest block sizes varying from 50 to 1000 km2, and modeled the implementation of spatially explicit harvest schedule plans in combination with wildfire and caribou population dynamics. We then evaluated the probability of persistence of boreal caribou populations.The probability of maintaining an AAC target declined with increasing target AAC, increasing size of operating area, and increasing adjacency constraints. In contrast, the probability of maintaining caribou populations declined with increasing AAC, decreasing size of operating areas, and decreasing adjacency constraints. An increase in operating area size from 50 to 300 km2 produced a considerable gain in AAC for all adjacency constraints.Because adjacency constraints led only to a small increase in the probability of maintaining caribou populations, we recommend adopting less constraining landscape management actions, such as a 70-year period between two consecutive harvests in the same ~300-km2 operating area.
    Subject(s): Caribou population dynamics ; Timber supply optimization ; Annual allowable cut ; Landscape/Regional and Urban Planning ; Landscape Ecology ; Sustainable Development ; Ecology ; Landscape disturbance ; Life Sciences ; Landscape dynamics ; Nature Conservation ; Harvesting scenarios ; Environmental Management ; Wildfires ; Harvesting ; Analysis ; Timber ; Population biology ; Reindeer ; Caribou
    ISSN: 0921-2973
    E-ISSN: 1572-9761
    Source: Alma/SFX Local Collection
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  • 9
    Language: English
    In: Canadian journal of forest research, 2013, Vol.43 (3), p.278-287
    Description: Stems of sugar maple (Acer saccharum Marsh.) and yellow birch (Betula alleghaniensis Britt.) trees often contain a column of discoloured wood known as red heartwood, which reduces lumber value. To quantify the regional-scale variation in red heartwood, 192 trees of each species were sampled in 12 locations across the temperate forest zone of southern Quebec, Canada. Large regional variation in the radial proportion of red heartwood (RHP) at breast height (1.3 m) was observed in both species. Statistical modeling showed that such variation was mainly attributable to factors related to tree development. Cambial age had a strong positive effect on RHP in both species, suggesting that the occurrence of red heartwood ultimately might be unavoidable. There was also a positive effect of ring area increment at the limit of the discoloured zone. In the case of sugar maple, there was an added effect of the trend in ring area increments observed in the same zone, with a negative trend being generally indicative of a larger RHP. Further variability in this species was also associated with the annual minimum temperature of the sampling locations. The models developed for each species explained around 60% of the variance in RHP and could be used to improve forest management and wood procurement decisions.
    Subject(s): Fundamental and applied biological sciences. Psychology ; Biological and medical sciences ; Forestry ; Trees ; Forest management ; Observations ; Sustainable forestry ; Analysis
    ISSN: 0045-5067
    E-ISSN: 1208-6037
    Source: Academic Search Ultimate
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  • 10
    Language: English
    In: Annals of forest science., 2019-06, Vol.76 (2), p.1-13
    Description: Wood properties were generally similar in unmanaged even-aged and uneven-aged black spruce stands. In contrast, in managed forests, wood density was higher in even-aged than in uneven-aged stands. As ring width is the discriminant factor, forest management should regulate the intensity of partial cutting to maintain a high wood density. North American boreal forests experience recurrent disturbances, such as fire and insect outbreaks, that shape the structure of even-aged and uneven-aged stands. Ecosystem-based forest management practices, such as partial cutting, aim to increase timber yields, and these forest harvesting approaches are being applied more frequently. Although the influence of these practices on tree growth is well known, few studies have examined their impact on anatomy and density of the resulting wood.This research studied the relationships between wood properties and ring width and tree heights in even- and uneven-aged black spruce (Picea mariana (Mill.) BSP) stands and how these relationships are modified following partial cutting.Wood density (ring, earlywood, latewood, and maximum density) and anatomical traits (lumen area, cell-wall thickness, and tracheid length) were measured at breast height on the stem of black spruce trees. The measured wood properties were then correlated with ring width and stem height.The model demonstrated significant correlations between most measured wood parameters and ring width with only small differences between even- and uneven-aged unmanaged stands. Five wood properties were influenced by tree height in even-aged and uneven-aged unmanaged plots. Partial cutting increased the number of significant relationships between wood properties (ring, latewood, maximum density, early- and latewood lumen area, tracheid length) and tree height. We detected differences in wood properties between even- and uneven-aged plots. Although we detected no change in average ring density, the variation of intra-annual density increased, due to changes in earlywood and latewood density that resulted in more heterogeneous rings.Partial cutting should take into consideration the age structure of the stand when the density of wood products matters.
    Subject(s): Life Sciences ; Environment, general ; Even- and uneven-aged forest ; Wood Science & Technology ; Wood properties ; Forestry ; Forestry Management ; Wood anatomy ; Wood density ; Tree Biology ; Picea mariana ; Managed and unmanaged forest ; Trees ; Forests ; Wood ; Change detection ; Harvesting ; Timber ; Boreal forests ; Forest management ; Environmental changes ; Outbreaks ; Forest ecosystems ; Wall thickness ; Density ; Pest outbreaks ; Properties (attributes) ; Insects ; Ecosystem management ; Correlation analysis ; Wood products ; Forest harvesting ; Herbivores ; Age composition
    ISSN: 1286-4560
    E-ISSN: 1297-966X
    Source: Alma/SFX Local Collection
    Source: © ProQuest LLC All rights reserved〈img src="https://exlibris-pub.s3.amazonaws.com/PQ_Logo.jpg" style="vertical-align:middle;margin-left:7px"〉
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