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In peatlands, microtopography strongly affects understory plant communities. Disturbance can result in a loss of microtopographic variation, primarily through the loss of hummocks. To address this, mounding treatments can be used to restore microtopography. We examined the effects of mounding on the understory vegetation on seismic lines in wooded fens. Seismic lines are deforested linear corridors (~3 to 8 m wide) created for oil and gas exploration. Our objectives were to compare the recovery of understory communities on unmounded and mounded seismic lines and determine how recovery varies with microtopographic position. Recovery was evident in the unmounded seismic lines, with higher shrub and total understory cover at the 'tops' of the small, natural hummocks than at lower microtopographic positions--much like the trends in adjacent treed fens. In contrast, mounding treatments that artificially created hummocks on seismic lines significantly changed understory communities. Mounded seismic lines had higher forb cover, much lower bryophyte cover, less variation along the microtopographic gradient, and community composition less similar to that of the reference sites than unmounded seismic lines due to higher abundance of marsh-associated species. Our results suggest that mounding narrow seismic lines can be detrimental to the recovery of the understory communities in treed peatlands. Key words: moderate-rich fens, linear disturbances, mounding, restoration, understory vegetation. Dans les tourbieres, la microtopographie influence fortement les communautes vegetales de sous-etage. Une perturbation peut entrainer une baisse de variation de la microtopographie, surtout par la perte de monticules. Pour resoudre ce probleme, la creation de monticules peut etre utilisee pour restaurer la microtopographie. Nous avons etudie les effets de la creation de monticules sur la vegetation de sous-etage dans des lignes sismiques traversant des tourbieres boisees. Les lignes sismiques sont des couloirs lineaires deboises (environ 3 a 8 m de large), crees pour l'exploration petroliere et gaziere. Nos objectifs etaient de comparer le retablissement des communautes de sous-etage dans des lignes sismiques avec et sans creation de monticules, et de determiner comment le retablissement varie en fonction de la position microtopographique. Le retablissement etait manifeste dans les lignes sismiques sans creation de monticules, ou le recouvrement d'arbustes et de vegetation totale sur le dessus de petits monticules naturels etait plus grand qu'aux positions microtopographiques inferieures, ce qui tendait aussi a etre le cas dans les tourbieres boisees adjacentes. En revanche, la creation artificielle de monticules dans les lignes sismiques a considerablement change les communautes de plantes de sous-etage. Les lignes sismiques avec des monticules artificiels avaient un recouvrement de plantes herbacees plus eleve, un recouvrement de bryophytes beaucoup plus faible, moins de variation le long du gradient microtopographique, et une composition de la vegetation moins semblable a celle des stations de reference que celle des lignes sismiques non traitees, en raison d'une plus grande abondance d'especes associees aux marais. Nos resultats indiquent que la creation de monticules dans les lignes sismiques etroites peut nuire au retablissement des communautes de plantes de sous-etage dans les tourbieres boisees. [Traduit par la Redaction] Mots-cles: tourbieres moderement riches, perturbations lineaires, creation de monticules, restauration, vegetation de sous-etage., Introduction Forests across the world are experiencing increases in the levels of human disturbance that are influencing their ecological function and biodiversity (Haddad et al. 2015). In regions with oil [...]

Regionally fitted allometric equations for individual trees and root-to-shoot ratio values are normally used to estimate local aboveground and belowground forest biomass, respectively. However, uncertainties arising from such applications are poorly understood. We developed equations for both aboveground and belowground biomass using destructive sampling for three dominant upland boreal tree species in northwestern Alberta, Canada. Compared with our equations, the diameter-based national equations derived for use across Canada underestimated aboveground biomass for Picea glauca (Moench) Voss but gave reasonable estimates for Populus balsamifera L. and Populus tremuloides Michx. The national equations based on both tree diameter and height overestimated aboveground biomass for the Populus species but underestimated it for Picea glauca in our study area. The approach of root-to-shoot ratio proposed by the Intergovernmental Panel on Climate Change (IPCC) overestimated belowground biomass by 16%-41%, depending on forest cover type, in comparison with our values estimated directly on site, with the greatest bias in deciduous-dominated stands. When the general allometric equations for aboveground biomass and the root-toshoot ratio for belowground biomass were combined to estimate stand biomass, overestimation could be as high as 18% in our study area. The results of our study support the development of improved regional allometric equations for more accurate local-scale estimations. Incorporating intraspecific variation of important traits such as tree taper may be especially helpful. Key words: EMEND (Ecosystem Management Emulating Natural Disturbance), intraspecific trait variation, root-to-shoot ratio, tree taper, wood density. On utilise generalement des equations allometriques ajustees a l'echelle regionale pour les arbres individuels et des valeurs du rapport racines-tiges pour estimer respectivement la biomasse forestiere locale, aerienne et souterraine. Cependant, les incertitudes decoulant de telles applications sont mal comprises. Nous avons developpe des equations de biomasse aerienne et souterraine en utilisant un echantillonnage destructif pour trois especes d'arbres boreales dominantes dans les hautes terres du nord-ouest de l'Alberta, au Canada. Comparativement a nos equations, les equations nationales basees sur le diametre developpees pour etre utilisees partout au Canada sous-estimaient la biomasse aerienne de Picea glauca (Moench) Voss, mais donnaient des estimations raisonnables pour Populus balsamifera L. et Populus tremuloides Michx. Les equations nationales basees sur le diametre et la hauteur des arbres surestimaient la biomasse aerienne des especes de Populus L., mais la sous-estimaient pour Picea glauca dans notre zone d'etude. L'approche du rapport racines-tiges, proposee parle Groupe d'experts intergouvernemental sur l'evolution du climat (GIEC), a surestime la biomasse souterraine de 16 a 41% selon le type de couvert forestier par rapport a nos valeurs estimees directement sur le site, le biais le plus important etant observe dans les peuplements domines par les feuillus. En combinant les equations allometriques generales pour la biomasse aerienne et le rapport racines-tiges pour la biomasse souterraine pour estimer la biomasse du peuplement, la surestimation pouvait atteindre 18% dans notre zone d'etude. Les resultats de notre etude justifient le developpement d'equations allometriques regionales ameliorees pour des estimations plus precises a l'echelle locale. L'incorporation des variations intraspecifiques des attributs importants, tels que le defilement de la tige des arbres, peut etre particulierement utile. [Traduit par la Redaction] Mots-cles : amenagement ecosystemique, variations intraspecifiques des attributs, rapport racines-tiges, defilement de la tige, densite du bois., Introduction Increasing pressure to reduce net carbon dioxide (CO2) emissions in light of climate change is spurring development of global strategies such as carbon markets that encourage carbon offsets through [...]

The recent expansion of mountain pine beetle (MPB, Dendroctonus ponderosae) from its native range in western North America into northern boreal pine forests in Alberta, Canada has resulted in conditions for tree regeneration that are dramatically different from those after wildfire, the predominant natural disturbance in these forests. We assessed natural regeneration post-MPB for northern boreal lodgepole pine sites in Alberta, Canada via intensive surveys of small plots at 33 severely attacked pine stands and using data from 205 permanent sample plots representing various site types and levels of MPB mortality. We used model selection to identify factors explaining regeneration. Overall, pine regeneration was very poor 6–9 years post-MPB; only 42% of the 33 intensively surveyed plots and only 9% of the 205 permanent plots had pine seedlings. This poor regeneration is attributed to high levels of cone serotiny in these populations, unsuitable regeneration microsites due to undisturbed litter or feathermoss layers, and competition from the residual canopy and understory vegetation. Other species (aspen, birch, poplar, and black and white spruce) were found on most sites, either as post-attack regeneration or regeneration established in advance. Without intervention, many of these stands will likely transition away from pine, to broadleaf and other conifer species. [ABSTRACT FROM AUTHOR]

The first issue of the Canadian Journal of Forest Research (CJFR) was published in March 1971 by the National Research Council of Canada with J.L. Farrar, Faculty of Forestry at [...]

Wildfire is the predominant natural disturbance in the boreal forests of western Canada. Natural disturbance based forest management involves the use of retention harvesting to retain stand structural diversity after harvest; however, unlike fire, this partial harvesting technique does not cause combustion of the forest floor. Application of prescribed burning to areas treated with retention harvesting might emulate the influence of wildfires more effectively than harvesting alone. We compared understory vascular plant diversity, abundance, and composition between forest stands subjected to dispersed retention harvesting (10% retention) with and without prescribed burning 1, 6, and 11 or 12 years after burning. Untreated forest was included as a reference. Research was conducted in conifer-dominated, mixedwood, and deciduous-dominated boreal forest stands in northwestern Alberta, Canada. In deciduous-dominated stands, burned areas of retention harvested stands had higher species richness and greater cover than did unburned areas. In all three forest cover types, effects of harvest with and without burn on species richness, cover, and composition were still evident a decade after disturbance. Fire-adapted species benefited most from the prescribed burn treatment. The combination of prescribed burning with retention harvesting can be considered a useful option in forest management that aims to emulate natural disturbance. Key words: prescribed burning, retention harvesting, fire, understory vascular plants, boreal forest. Les perturbations qui dominent dans les forets boreales de l'ouest du Canada sont causees par les feux de foret. L'amenagement forestier qui s'inspire des perturbations naturelles inclut l'utilisation de la coupe avec retention pour conserver la diversite structurale a la suite de la recolte. Cependant, cette methode de coupe partielle n'entraine pas la combustion de la couverture morte comme c'est le cas avec le feu. Le recours au brulage dirige dans les zones soumises a une coupe avec retention pourrait imiter l'effet des feux de foret plus efficacement que la coupe seule. Nous avons compare la composition, l'abondance et la diversite des plantes vasculaires en sous-etage dans des peuplements forestiers soumis a une coupe avec retention des arbres disperses (10 % de retention) avec et sans brulage dirige 1, 6 et 11 ou 12 ans apres le brulage. Une foret non traitee a ete incluse comme reference. Cette etude a ete realisee dans le nord-ouest de l'Alberta, au Canada, dans des peuplements de foret boreale domines soit par des resineux soit par des feuillus et dans des peuplements mixtes. Dans les peuplements domines par des feuillus soumis a une coupe avec retention, la richesse en especes et la couverture etaient plus grandes dans les zones brulees que dans les zones non brulees. Dans les trois types de couvert forestier, les effets de la recolte avec et sans brulage sur la richesse en especes, la couverture et la composition etaient encore evidents 10 ans apres la perturbation. Les especes adaptees au feu ont le plus beneficie du brulage dirige. La combinaison du brulage dirige et de la coupe avec retention peut etre consideree comme une option utile pour l'amenagement forestier qui cherche a imiter les perturbations naturelles. [Traduit par la Redaction] Mots-cles: brulage dirige, coupe avec retention, feu, sous-etage, plantes vasculaires, foret boreale., Introduction Wildfire is the predominant stand-replacing natural disturbance in the boreal forest and it drives the region's vegetation dynamics (Johnson 1992; Payette 1992). The understory vegetation layer hosts most of [...]

The spatial effects of vegetation control on early tree growth were investigated in central Alberta, Canada, for four years after the establishment of hybrid poplar plantations including the two clones Walker (Populus deltoides x (P. laurifolia x P. nigra)) and its progeny Okanese (Walker x (P. laurifolia x P. nigra)). Tree survival and growth, herbaceous vegetation cover, soil nutrient availability, moisture, temperature, and light availability were assessed. Tree growth in the first two years after establishment was improved through selective in-row vegetation control close (within 50 cm) to trees for both aboveground (mechanical) and above- and below-ground (chemical) control. This was associated with increased light availability for trees. In contrast, growth in the third and fourth years benefitted from control of aboveground vegetation within 140 cm of the stem, and this was associated with increased nutrient availability. These findings suggest that the effects of neighbouring vegetation on trees shift from aboveground competition near the tree stem to belowground competition further (>50 cm) away; thus between-row vegetation control is more important starting in the third year after establishment. Okanese outperformed Walker poplar across all treatments and was more responsive to vegetation control, reflecting its superior performance, higher plasticity, and greater potential for short-rotation intensive-culture plantations. Key words: hybrid poplar, tree growth, aboveground and belowground competition, resource availability, vegetation management. Les effets de nature spatiale de la maitrise de la vegetation sur la croissance precoce des arbres ont ete etudies dans le centre de l'Alberta, au Canada, pendant quatre ans suivant l'etablissement de plantations de peupliers hybrides incluant les deux clones Walker (Populus deltoides x (P. laurifolia x P. nigra)) et sa descendance Okanese (Walker x (P. laurifolia x P. nigra)). La survie et la croissance des arbres, le couvert de vegetation herbacee, la disponibilite des nutriments dans le sol, l'humidite, la temperature, et la disponibilite de la lumiere ont ete evalues. Durant les deux premieres annees suivant l'etablissement, la croissance des arbres a ete amelioree par la maitrise selective de la vegetation dans les rangs pres (a moins de 50 cm) des arbres tant dans le cas de la maitrise aerienne (mecanique) qu'aerienne et souterraine (chimique). Cela etait associe a plus grande disponibilite de la lumiere pour les arbres. Par contre, durant les troisieme et quatrieme annees la croissance a beneficie de la maitrise aerienne de la vegetation en dedans de 140 cm de la tige et cela etait associe a une plus grande disponibilite des nutriments. Ces resultats indiquent que les effets de la vegetation avoisinante passent de la competition aerienne pres du tronc des arbres a la competition souterraine plus loin (>50 cm). Par consequent, la maitrise de la vegetation entre les rangs est plus importante a partir de la troisieme annee suivant l'etablissement. Le clone Okanese a ete plus performant que le clone Walker peu importe le traitement et reagissait mieux a la maitrise de la vegetation, refletant sa performance superieure, sa plus grande plasticite et son potentiel plus eleve pour les plantations a culture intensive et courte rotation. [Traduit par la Redaction] Mots-cles: peuplier hybride, croissance des arbres, competition aerienne et souterraine, disponibilite des ressources, gestion de la vegetation., Introduction Plantations of fast-growing hybrid poplar trees play a significant role in wood and fibre production and as a supplier of biomass for energy, alternative fodder sources, and ecosystem services [...]

Given a seed source, the quality of available substrates is a key factor in determining the success of white spruce (Picea glauca (Moench) Voss) natural regeneration. We examined the influence of substrate and competing vegetation on survival and growth of natural regeneration of white spruce up to 4 years following harvesting in deciduous-dominated upland boreal mixedwood sites. Feather moss, thick soil surface organic layers, litter, and solid wood were poor substrates for establishment. Early successional mosses establishing on mineral soil, thin organics, and rotten wood were generally favourable microsites but were not highly available on postharvest sites. Mineral soil substrates were not as suitable as expected, likely because on a postlogged site, they are associated with unfavourable environmental characteristics (e.g., low nutrient availability, exposure). There was some evidence that survival and growth of seedlings were improved by surrounding vegetation in the first years, but heavy competing vegetation had a negative impact on older seedlings. Burial by aspen litter greatly increased seedling mortality, especially when combined with a brief period of submergence due to heavy spring snowmelt. The results provide insight into conditions under which natural regeneration could be an option for establishing white spruce following harvesting of deciduous-dominated boreal mixedwood forests. Key words: natural regeneration, white spruce, substrate, seedling survival, competing vegetation, forest management. Pour une source de graines donnee, la qualite des substrats disponibles est un facteur cle pour le succes de la regeneration naturelle d'epinette blanche (Picea glauca (Moench) Voss). Nous avons etudie l'influence du substrat et de la vegetation concurrente sur la survie et la croissance de la regeneration naturelle d'epinette blanche jusqu'a 4 ans apres la coupe de peuplements mixtes boreaux domines par des especes decidues et etablis sur des stations bien drainees. Les mousses hypnacees, les couches epaisses de matiere organique sur le sol, la litiere et le bois massif constituaient de mauvais substrats pour l'etablissement des semis. Les mousses de debut de succession etablies sur le sol mineral, les couches minces de matiere organique sur le sol et le bois decompose constituaient generalement des microsites favorables, mais etaient peu disponibles sur les stations recoltees. Les substrats formes de sol mineral n'etaient pas aussi appropries que prevu, probablement parce que sur une station qui a ete recoltee, ils sont associes a des caracteristiques environnementales defavorables (p. ex.: faible disponibilite des nutriments, exposition). La survie et la croissance des semis ont montre des signes d'amelioration lies a la presence de vegetation environnante au cours des premieres annees, mais une forte competition exercee par cette vegetation a eu un impact negatif sur les plus vieux semis. L'ensevelissement des semis par la litiere de peuplier a considerablement augmente leur mortalite, particulierement lorsqu'il etait jumele a une breve periode d'immersion causee par une importante fonte des neiges au printemps. Les resultats donnent un apercu des conditions dans lesquelles la regeneration naturelle pourrait constituer une option pour l'etablissement de l'epinette blanche apres la recolte des forets mixtes boreales dominees par des especes decidues. [Traduit par la Redaction] Mots-cles: regeneration naturelle, epinette blanche, substrat, survie des semis, vegetation concurrente, amenagement forestier., Introduction White spruce (Picea glauca (Moench) Voss) is an economically and ecologically important conifer that is widely distributed across the boreal forests of North America. On upland mixedwood sites that [...]

: Terrestrial gastropods are important decomposers, herbivores, and prey items in forest systems and constitute a poorly understood element of forest biodiversity in Canada. We sampled terrestrial gastropod assemblages in northwestern Alberta, Canada, using board traps and forest floor sampling to examine their association with forest composition, structure, and environment (forest floor depth and moisture, coarse woody debris, understory vegetation cover) in four boreal mixedwood cover types: broadleaf (deciduous) dominated (DDOM), broadleaf (deciduous) dominated with coniferous understory (DDOMU), mixed conifer and broadleaf (MX), and conifer dominated (CDOM). The highest total gastropod abundance and richness occurred in the DDOM cover type. Furthermore, DDOM assemblages accumulated species more quickly (with sampling effort) and supported more gastropod species at higher levels of dominance than found in other cover types. The mix of coniferous and broadleaved trees influenced gastropod distributions within stands; however, associations observed between gastropod species and tree species differed among cover types, suggesting complex ecological contingency. For example, conifer basal area was an important driver of gastropod assemblage in DDOM and DDOMU forests, whereas broadleaf basal area was the most important driver in the CDOM forest type. We conclude that tree species mixture at a variety of scales sustains diversity of gastropod assemblages and that this understanding is significant for conservation of this taxon on mixedwood boreal forest landscapes. Key words: biodiversity, boreal forest, forest composition, gastropod assemblage, species dominance, gastropod sampling, Gastropoda, Pulmonata. Resume: Les gasteropodes terrestres sont d'importants decomposeurs, herbivores et proies dans les systemes forestiers et constituent un element peu connus de la biodiversite forestiere au Canada. Nous avons echantillonne les assemblages de gasteropodes terrestres dans le nord-ouest de l'Alberta, au Canada, en utilisant des pieges et l'echantillonnage de la couverture morte pour etudier leur association avec la composition, la structure et l'environnement de la foret (epaisseur et teneur en eau de la couverture morte, debris ligneux grossiers, couvert vegetal du sous-bois) dans quatre types de couvert forestier en foret boreale mixte: domine par les feuillus (DF), domine par les feuillus avec un sous-etage de coniferes (DFSEC), melange de coniferes et de feuillus (MCF) et domine par les coniferes (DC). L'abondance et la richesse les plus elevees de gasteropodes ont ete observees dans le type de couvert DF. De plus, les assemblages sous un couvert DF accumulaient les especes plus rapidement (avec l'effort d'echantillonnage) et supportaient plus d'especes de gasteropodes a des degres plus eleves de dominance que dans les autres types de couvert forestier. Le melange de coniferes et de feuillus influencait la repartition des gasteropodes dans les peuplements; cependant, les associations observees entre les especes de gasteropode et les especes d'arbre etaient differentes selon le type de couvert forestier, ce qui suppose une eventualite ecologique complexe. A titre d'exemple, la surface terriere des coniferes etait un facteur determinant pour les assemblages de gasteropodes dans les types de couvert forestier DF et DFSEC tandis que la surface terriere des feuillus etait le facteur le plus important dans le type de couvert forestier DC. Nous concluons que le melange des especes d'arbre a diverses echelles supporte la diversite des assemblages de gasteropodes et qu'il est important de compren-dre cela pour la conservation de ce taxon dans les paysages de foret boreale mixte. [Traduit par la Redaction] Mots-cles: biodiversite, foret boreale, composition forestiere, assemblage de gasteropodes, dominance des especes, echantillon-nage des gasteropodes, Gastropoda, Pulmonata., Introduction The boreal mixedwood forest is an intricate patchwork of broadleaved and coniferous trees produced and maintained by the local balance of disturbance events and successional development (Chen and Popadiouk [...]

In some boreal forests sites, there are considerable amounts of natural regeneration of white spruce (Picea glauca (Moench) Voss) after logging, even without silvicultural treatments to encourage establishment. We assessed the factors controlling the amount of this regeneration 8-15 years postharvest on previously aspen-dominated (Populus tremuloides Michx.) boreal mixedwood sites. We surveyed 162 transects across 81 cutovers, exploring the effects of mast years, season of harvest, distribution of seed trees, weather conditions around the time of harvest, and abundance of grass or woody vegetation on white spruce regeneration. Substantial amounts of naturally regenerated white spruce were found; however, sites with no seed trees had virtually no spruce regeneration. Average stocking was 7% (percentage of 9 m2 plots along a transect across a cutover that had at least one seedling), ranging from 0% to 62%. Stocking levels were higher in cutblocks that had been harvested in the summer, prior to seedfall of a mast year, and where there was a seed source within 60 m. Stocking was lower when conditions were cool and wet the year before and 2 years after harvest and when the site contained extensive cover of grass or woody vegetation. Resume: Sur certaines stations forestieres boreales, il y a une quantite considerable de semis naturels d'epinette blanche (Picea glauca (Moench) Voss) a la suite d'une coupe, meme sans traitement sylvicole visant a promouvoir leur etablissement. Nous avons evalue les facteurs qui determinent la quantite de cette regeneration sur des stations coupees il y a 8 a 15 ans et precedemment occupees par des peuplements mixtes boreaux domines par le peuplier faux-tremble (Populus tremuloides Michx.). Nous avons etabli 162 transects repartis dans 81 aires de coupe pour evaluer les effets des annees semencie res, de la saison durant laquelle la coupe a eu lieu, de la distribution des semenciers, des conditions climatiques a l'epoque de la coupe et de l'abondance de la vegetation herbacee et ligneuse sur la regeneration d'epinette blanche. Un nombre substantiel de semis naturels d'epinette blanche a ete inventorie. Cependant, les stations sans semenciers n'avaient pratiquement pas de regeneration d'epinette. Le coefficient de distribution de la regeneration etait en moyenne de 7 % (pourcentage de placettes de 9 [m.sup.2] le long d'un transect etabli dans une coupe ou il y avait au moins un semis) et variait de 0 % a 62 %. Le coefficient de distribution de la regeneration etait plus eleve sur les stations recoltees pendant l'ete, avant la pluie de graines d'une annee semenciere et ou il y avait une source de semences a moins de 60 m. Le coefficient de distribution de la regeneration etait plus faible lorsque les conditions climatiques durant l'annee precedant la coupe et deux ans apres la coupe etaient fraiches et humides et lorsque la station etait abondamment couverte de vegetation herbace e ou ligneuse. [Traduit par la Redaction], Introduction Boreal mixedwood forests composed of trembling aspen (Populus tremuloides Michx.) and white spruce (Picea glauca (Moench) Voss) are found on mesic and subhygric sites across large portions of North [...]

In mixedwood boreal forests of western Canada, stands classified as 'pure deciduous' by forest inventories sometimes contain a few large white spruce (Picea glauca (Moench) Voss) trees among or emerging from the canopy. These trees are important as regeneration seed sources and for habitat structure. Neither their abundance nor the characteristics of stands in which they occur have previously been quantified. Of 275 'pure aspen' stands in northeastern Alberta, 19.6% contained at least one such spruce detectable in an aerial photograph. These trees were found in stands across the range of sampled canopy heights, densities, age classes, and stand sizes and were often present in the interior of stands, not just on the perimeter. The frequency of 3 ha cells containing at least one spruce was related to (i) stand shape and size, (ii) amount of mature white spruce in adjacent forest, (iii) canopy height, (iv) stand age, and (v) stand density. We conclude that such trees are relatively abundant and widely distributed within the boreal mixedwood forests of Alberta. There is presently no provision to maintain this landscape element within managed forests. More information is needed to determine if or how they should be considered in forest management planning. Dans la foret boreale mixte de l'Ouest canadien, il arrive que les peuplements classes comme << feuillus purs >> dans les inventories forestiers contiennent quelques grosses tiges d'epinette blanche (Picea glauca (Moench) Voss) qui font partie ou emergent de la canopee. Ces arbres sont importants comme source de graines pour la regeneration et pour la structure de (habitat. Toutefois, leur abundance et les caracteristiques des peuplements dans lesquels ils sont presents n'ont jamais ete quantifiees. Parmi 275 << peupleraies pures >> du nord-est de (Alberta, 19,6 % contenaient au moms une telle epinette detectable a partir de photographies aeriennes. Ces arbres ont ete detectes dans des peuplements couvrant toute la gamme de hauteurs de canopee, de densites, de classes d'age et de tailles de peuplement echantillonnees; ils etaient souvent presents a finterieur des peuplements et non seulement en peripherie. La frequence des cellules de 3 ha a contenant au moms une epinette a ete reliee a (i) la forme et la taille du peuplement, (ii) la quantite d'epinettes blanches matures dans la foret adjacente, (iii) la hauteur de la canopee, (iv) Page du peuplement et (v) la density du peuplement. Nous concluons que de tels arbres sont relativement abondants et largement distrbbues dans la foret boreale mixte de l'Alberta. Il n'y a presentement aucune mesure visant a maintenir cet element du paysage dans les foress amenagees. Plus de renseignements sont necessaires pour determiner si ou comment ces arbres devraient etre consideres dans la planification de l'amenagement forestier. [Traduit par la Redaction], Introduction In the boreal mixedwood forests of western Canada, the canopies of upland mesic sites are dominated by some combination of Populus species (typically trembling aspen, Populus tremuloides Michx., but [...]

Abstract: We characterized the ectomycorrhizae (ECM) of planted white spruce (Picea glauca (Moench) Voss) seedlings as affected by mechanical site preparation (MSP) of clear-cut conifer-dominated boreal mixedwood forest. Relative abundance, [...]

We compared understory vegetation composition and richness in aspen-dominated boreal mixedwood forest stands in Alberta, Canada, that had been burned by wildfire with those that burned and were subsequently salvage logged. Stands were examined at early and midsuccessional (2 and 34 years after disturbance(s), respectively) developmental stages. In comparison with wildfire stands, understory communities of early successional salvage-logged stands were characterized by greater species richness, weedy species presence, higher shrub abundance, and lower abundances of fire- specialist seed bank species. In constrained ordination, the understory community of early successional wildfire stands was related to greater canopy cover, sapling density, and moss depth, whereas that of salvage- logged stands was related to greater light, volume of downed deadwood, and litter and organic matter. Longer term effects of salvage logging on the understory community were minimal and, instead, reflected the influence of forest canopy redevelopment. In midsuccessional stands, understory composition was related to conifer density, litter cover, soil moisture, organic layer depth, tall shrub density, and bryophyte-covered microsite cover. Postfire salvage logging can have substantial short- term effects on the postfire understory plant community; in the longer term, effects will depend to a large extent on the influence of harvesting and subsequent management on canopy redevelopment. Nous avons compare la composition et la richesse de la vegetation en sous-etage dans des peuplements de foret boreale mixte domines par le peuplier faux-tremble en Alberta, au Canada, qui avaient et. [Traduit par la Redaction], Introduction Early postfire forest stands are characterized by a distinctive combination of environmental and stand attributes that influence the initial establishment phase of the plant community and have important long-term [...]

Abstract: We compared prefire and postfire organic-layer depths in boreal forest types (14 fires) across Canada, and examined tree recruitment as a function of depth. There was extensive within-stand variation [...]

Abstract: This study assessed the dynamics of gap development in postharvest regeneration in five stands in northwestern Alberta dominated by trembling aspen (Populus tremuloides Michx.). The pattern of gap development [...]

Abstract: The timing of white spruce regeneration in aspen (Populus tremuloides Michx.)--white spruce (Picea glauca (Moench) Voss) boreal mixedwood stands is an important factor in stand development. We examined boreal [...]

Analyzes the effect of aging discrepancies of white spruce on the interpretation of static age structure (SAS) in boreal mixedwoods. Use of qualitative ring features and ring width chronologies in visual cross-dating; Occurrence of height variation among trees establishing at the same time; Difficulty of using SAS to infer regeneration dynamics.

Focuses on the use of generalized logistic model of individual tree mortality for trembling aspen, white spruce and lodgepole pine. Determination on the survival probability of an individual tree; Stand characteristics of trees; Estimation of species-specific site productivity index.