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Yield tables are used to identify trends in growing space efficiency (GSE) and to relate GSE to self-tolerance and intraspecific competition. The method is useful when data specifically collected for this purpose are not available. Plonski's normal yield tables for jack pine (Pinus banksiana Lamb.), paper birch (Betula papyrifera Marshall), trembling aspen (Populus tremuloides Michx.), and black spruce (Picea mariana (Mill.) B.S.P.) are used. An exponential volume-age function was partitioned into volume-area and area-age functions. The exponents of these two components form the B/D ratio, which is used to determine the mode of the stand at a given time, e.g., if B/D is <3/2, then the stand is in area occupation mode, and if B/D is >3/2, then the stand is in area exploitation mode. The dominant mode is the one most responsive to availability of growth resources, showing greater acceleration when resources are plentiful and more rapid deceleration when resources are scarce. Jack pine and paper birch are identified as area occupiers, whereas trembling aspen and black spruce are area exploiters and are therfore self-tolerant. Asymmetric competition was deemed to be present for paper birch throughout the life of the stand on site class I and for trembling aspen on all sites prior to senescence. Les tables de production sont utilisées pour identifier les tendances de l'efficacité à utiliser l'espace de croissance (EEC) et pour relier l'EEC à l'auto-tolérance et à la compétition intraspécifique. La méthode est utile lorsque des données spécifiquement récoltées à cette fin ne sont pas disponibles. Les tables normales de production de Plonski pour le pin gris (Pinus banksiana Lamb.), le bouleau à papier (Betula papyrifera Marshall), le peuplier faux-tremble (Populus tremuloides Michx.) et l'épinette noire (Picea mariana (Mill.) B.S.P.) ont été utilisées. Une fonction exponentielle reliant le volume à l'âge a été séparée en fonctions reliant le volume à la surface et la surface à l'âge. Les exposants de ces deux composantes forment le rapport entre B et D qui est utilisé pour déterminer le mode du peuplement à un temps donné; p. ex. si B/D est plus petit que 3/2, le peuplement est dans un mode d'occupation de la surface et, si B/D est plus grand que 3/2, le peuplement est dans un mode d'exploitation de la surface. Le mode dominant est celui qui réagit le plus à la disponibilité des ressources qui supportent la croissance; il est associé à une plus forte accélération quand les ressources sont abondantes et à une plus forte décélération lorsque les ressources sont rares. Le pin gris et le bouleau à papier sont identifiés comme des occupants de la surface alors que le peuplier faux-tremble et l'épinette noire sont des exploitants et sont, par conséquent, auto-tolérants. Nous avons jugé qu'une compétition asymétrique était présente dans le cas du bouleau à papier tout au long de la vie d'un peuplement établi sur une station de qualité I et, dans le cas du peuplier, sur toutes les stations avant la période de sénescence. [ABSTRACT FROM AUTHOR]

Ecosystem management requires good knowledge of preindustrial ecosystems and their dynamics. However, in most regions of Québec, the original forested landscape has been altered by human activities. To validate the ecosystem management conducted in the lower Mauricie region, the preindustrial landscape of the high hills of the lower Saint-Maurice region was characterized from the study of 18 historical forest surveys conducted by the pulp and paper industry in the early 20th century. The analysis of these surveys showed the predominance of irregular mature stands. Two-thirds of these stands were of mixedwood type, while a very small proportion was of hardwood type. Softwood volume was mainly constituted of balsam fir (Abies balsamea (L.) Mill.) and red (Picea rubens Sarg.) and black spruces (Picea mariana (Mill.) BSP). Lastly, the analysis of these inventories showed the occurrence, in the preindustrial landscape, of a mixed disturbance regime, where severe fires and insect outbreaks coexisted with gap dynamics. From a broader perspective, we can fully appreciate with this study the importance and usefulness for ecosystem management of conserving forest inventory archives, because in many cases they are the only references to the preindustrial landscape. [ABSTRACT FROM AUTHOR]

A shadow fraction method was developed previously for mapping forest attributes of northern black spruce ( Picea mariana (Mill.) Britton, Sterns & Poggenb.) forests. This paper evaluates application of the method for ( i) balsam fir stands ( Abies balsamea (L.) Mill.), ( ii) stands with higher volume and biomass than those of previous studies, and ( iii) stands with a higher composition of deciduous trees and steeper slopes. Models developed for new test sites in ( i) central Labrador and ( ii) western Newfoundland were not statistically different from previous models for biomass, volume, and basal area. Relative root mean square errors (RMSEr) for central Labrador were slightly lower than those found in other test sites (RMSEr: 24%-29%) but higher for western Newfoundland (RMSEr = 37%-43%), attributed to the higher upper limit of measured attributes and increased presence of deciduous trees. Results suggest that reasonable estimates can be generated for conifer forests of northeastern Canada; however, an alternative solution is needed where mixed and deciduous stands are prevalent. Measurement of ground plots over a wider range of species composition and forest structure is recommended for broader application to northern boreal forests and to further assess the potential role of the shadow fraction method in national-scale inventory programs. [ABSTRACT FROM AUTHOR]

Black spruce ( Picea mariana (Mill.) Britton, Sterns & Poggenb.) and white spruce ( Picea glauca (Moench) Voss) are phylogenetically proximal species that differ in productivity. Crown characteristics of these two species have not been extensively studied, in spite of the importance of these two species to the Canadian boreal forest and the importance of tree crowns for understanding and modelling tree growth. In this paper, we characterize and compare the crown lengths, crown profiles (i.e., radii), shapes, and surface areas of these two species using 65 white spruce and 57 black spruce trees destructively sampled in the provinces of Alberta, Ontario, and Quebec, Canada. Crown length was measured on every sample tree, while crown profile was obtained by reconstructing crowns from branch measurements. Our results showed that crown lengths did not differ between these two species given the same tree size and growth conditions. However, these two species establish under different growth conditions resulting in crown length differences. Further, differences in crown radii and profiles were found even under the same growth conditions. White spruce trees had wider crown radii and profiles changed from a parabola to a cone shape under increased density. As a result, differences in crown surface areas were found. [ABSTRACT FROM AUTHOR]

As many insect outbreak reconstructions are typically based on targeted single-site sampling, researchers have often been limited in their ability to draw conclusions about regional trends as opposed to local trends in the data. The results of this paper demonstrate the value of a systematic sampling design when studying spatio-temporal processes that can vary greatly within large continuous areas of forest. Many single-site research programs have been conducted to reconstruct the history of larch sawfly (Pristiphora erichsonii Htg.) outbreaks in the eastern boreal region of North America. However, no such research has yet been conducted in the region of Labrador. In an attempt to illustrate the strength of a systematic gridded sampling protocol over a single-site study, we sampled a 12-site grid in western Labrador. Dominant and codominant species were sampled at each grid point, resulting in 24 master chronologies. Six eastern larch (Larix laricina (Du Roi) K. Koch) chronologies (host) and a regional black spruce (Picea mariana (Mill.) Britton, Sterns, Poggenb.) chronology (nonhost) were used to establish a host–nonhost analysis of past sawfly outbreaks on a regional scale. Both regional and localized larch sawfly outbreaks were identified, but in general, larch sawfly outbreaks in western Labrador appeared to be spatially synchronous and regional in scale. [ABSTRACT FROM AUTHOR]

The boreal forest of higher latitudes constitutes a reservoir of trees of great ecological importance and unknown economic potential, but the stand dynamics in these regions still remain essentially unexplored. This paper examines the change in age and size structures during stand development on the northern border of the natural closed boreal forest in Quebec, Canada. Height, diameter, and age of trees were measured in 18 plots with stand ages between 77 and 340 years. The occurrence, size, and origin (layer or seed) of seedlings and saplings were assessed in subplots. Tree density ranged from 600 to 3750 trees·ha–1. Picea mariana (Mill.) BSP was the dominant species, mainly originating by layering. A cluster analysis segregated plots into even-aged and uneven-aged stands according to tree age, but size distribution of trees, saplings, and seedlings did not differ statistically between the two groups. Even-aged stands exhibited a 60% probability of assuming an uneven-aged structure between 120 and 200 years after stand initiation. At high latitudes, the closed boreal forest of P. mariana appears homogeneously sized, with similar distributions of diameter and height across all stages of stand development. [ABSTRACT FROM AUTHOR]

Xylem production was studied by repeatedly taking microcore samples from the stems of six tree species growing on the “réserve écologique des Vieux-Arbres”, on Lake Duparquet, Québec, throughout the 1999 growing season. Species examined were paper birch (Betula papyrifera Marsh.), white spruce (Picea glauca (Moench) Voss), black spruce (Picea mariana (Mill.) BSP), jack pine (Pinus banksiana Lamb.), red pine (Pinus resinosa Ait.), and eastern white cedar (Thuja occidentalis L.). Onset of xylem cell production was observed in all species by 22 May 1999, and ended as early as mid-July and early August for white spruce and eastern white cedar, respectively. Xylem cell production in the remaining species ended between late August and mid-September. In general, the onset of latewood production ranged from the start of July to the first week of August. Typical sigmoidal curves were characteristic of ring width, number of cells, and number of earlywood cells over the growing season. Completion of the annual growth increment was quickest for white spruce and eastern white cedar, while it continued longest in both pine species. Numerous similarities in xylem production and tree ring formation over the course of the growing season were observed among the six species, suggesting that weather, along with photoperiod, plays a critical role in xylem production. [ABSTRACT FROM AUTHOR]

Symbiotic fungi’s role in providing nitrogen to host plants is well-studied in tundra at Toolik Lake, Alaska, but little-studied in the adjoining boreal forest ecosystem. Along a 570 km north-south transect from the Yukon River to the North Slope of Alaska, the 15N content was strongly reduced in ectomycorrhizal and ericoid mycorrhizal plants including Betula, Salix, Picea mariana (P. Mill.) B.S.P., Picea glauca Moench (Voss), and ericaceous plants. Compared with the 15N content of soil, the foliage of nonmycorrhizal plants (Carex and Eriophorum) was unchanged, whereas content of the ectomycorrhizal fungi was very much higher (e.g., Boletaceae, Leccinum and Cortinarius). It is hypothesized that similar processes operate in tundra and boreal forest, both nitrogen-limited ecosystems: (i) mycorrhizal fungi break down soil polymers and take up amino acids or other nitrogen compounds; (ii) mycorrhizal fungi fractionate against 15N during production of transfer compounds; (iii) host plants are accordingly depleted in 15N; and (iv) mycorrhizal fungi are enriched in 15N. Increased N availability for plant roots or decreased light availability to understory plants may have decreased N allocation to mycorrhizal partners and increased δ15N by 3‰-4‰ for southern populations of Vaccinium vitis-idaea L. and Salix. Fungal biomass, measured as ergosterol, correlated strongly with soil organic matter and attained amounts similar to those in temperate forest soils. [ABSTRACT FROM AUTHOR]

The predictions of properties for wood disc average are seldom reported, and they are important for sorting out logs based on their quality. The minimum near infrared (NIR) spectra required to predict wood disc average properties would also be of critical importance. In this study, calibration and prediction models for wood disc average properties were developed using NIR spectral data for balsam fir (Abies balsamea (L.) Mill.) and black spruce (Picea mariana (Mill.) B.S.P.) samples collected from 14 different sites across Newfoundland, Canada. The calibration was done against area-weighted average wood properties determined by SilviScan. NIR spectra were collected in 18 mm increments from the radial-longitudinal face of green and oven-dried samples. Results showed that using NIR spectra from three spots per wood strip was sufficient for the modeling and prediction for density and module of elasticity (MOE). The coefficients of determination ranged from 0.76 (MOE of green wood samples) to 0.88 (density of oven-dried wood samples). However, the microfibril angle (MFA) cannot be well predicted from either green wood or oven-dried wood NIR spectra. Our results further showed that the NIR spectra collected from oven-dried wood samples gave better calibration and prediction than those collected from green wood samples. Les prédictions des propriétés moyennes des disques de bois sont rarement présentées, bien qu'elles soient importantes pour trier les billes en fonction de leur qualité. Les spectres minimum dans le proche infrarouge (PIR) qui sont nécessaires pour prédire les propriétés moyennes des disques de bois ont aussi une importance cruciale. Dans cette étude, des modèles de prédiction et de calibration des propriétés moyennes des disques de bois ont été développés à partir de données spectrales PIR d'échantillons de sapin baumier (Abies balsamea (L.) Mill.) et d'épinette noire (Picea mariana (Mill.) B.S.P.) prélevés dans 14 sites différents couvrant l'ensemble de la province de Terre-Neuve, au Canada. La calibration a été effectuée à partir des propriétés moyennes du bois déterminées à l'aide de SilviScan et pondérées par la superficie. Les spectres PIR ont été obtenus à tous les 18 mm le long de la face longitudinale-radiale d'échantillons verts et anhydres. Les résultats ont démontré que l'utilisation des spectres PIR provenant de trois points par barrette de bois était suffisante pour modéliser et prédire la densité et le module d'élasticité (MOE). Les coefficients de détermination variaient de 0,76 (MOE d'échantillons de bois à l'état vert) à 0,88 (densité d'échantillons de bois à l'état anhydre). Cependant, les spectres PIR du bois vert ou anhydre ne sont pas adéquats pour prédire l'angle des microfibrilles (AMF). Nos résultats ont de plus montré que les spectres PIR des échantillons de bois à l'état anhydre permettent d'obtenir une meilleure calibration et de faire de meilleures prédictions que ceux des échantillons de bois à l'état vert. [ABSTRACT FROM AUTHOR]