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Red heartwood, a dark nonhomogenous discolouration in paper birch trees ( Marsh.), limits the applications and uses of sawn boards to nonvisible low-value products, thus resulting in substantial value loss. The occurrence and distribution of red heartwood were investigated in 12 paper birch trees grown in the province of Quebec, Canada. The youngest tree was 62 years old at breast height and the oldest 86 years old for an average of 75 years old. In this study, 225 occurrences of external traits, relating to branch scars and forks, previously proposed as initiation points for red heartwood were identified and measured. The distribution of red heartwood was digitally mapped and the effect of these external traits on the red heartwood surface and shape inside each tree was examined. Results show that red heartwood initiates from an external trait and that multiple external traits can contribute to the development of a red heartwood column following the longitudinal axis of the stem. Red heartwood appeared to initiate mainly from external traits at the base of the tree. A modelling exercise indicated that the width of the red heartwood column inside a standing tree can be estimated from branch scar width and height from the ground. Tree vigour could not be linked to the proportion of red heartwood inside standing trees. A three-dimensional analysis of log shape could potentially be used to detect red heartwood presence in a log before processing to optimize the log sawing pattern. [ABSTRACT FROM AUTHOR]

Normal paper birch (Betula papyrifera Marsh.) wood has a clear and uniform color. However, some paper birch trees contain reddish-brown-, discolored wood known as red heartwood. Its occurrence, proportion, and vertical distribution were investigated. One hundred and fifty trees were randomly sampled from three stands located at the Montmorency Forest, 75 km north of Quebec City, Quebec, Canada. A subsample of 18 trees showing occurrence of red heartwood at stump height were felled, and 5 cm thick disks were cut at every 0.5 m of height. Red heartwood volume, proportion, and vertical distribution were determined from the disks. Trees with larger diameter at breast height and lower tree height had a higher probability of red heartwood occurrence. Red heartwood starts occurring in 40-year-old trees on average in the stands studied. The volume of red heartwood was positively correlated with tree age, and the proportion of red heartwood was positively related to tree age, and negatively related to the amount of sunlight on the live crown. Red heartwood proportion was 13.3% of the tree merchantable volume, mostly located under the live crown. Le bois de bouleau à papier (Betula papyrifera Marsh.) est normalement clair et uniforme. Toutefois, le bois de couleur brun-rougeâtre présent chez certains bouleaux est appelé cœur rouge. Sa présence, sa proportion et sa distribution verticale dans l’arbre ont été étudiées. Cent cinquante arbres furent sélectionnés aléatoirement dans trois peuplements de la Forêt Montmorency à 75 km au nord de la ville de Québec, Québec, Canada. Un sous-échantillon de 18 arbres présentant du cœur rouge à hauteur de souche ont été abattus et découpés en disques de 5 cm d’épaisseur à tous les 5 m afin de mesurer le volume, la proportion et la distribution verticale du cœur rouge. La probabilité de présence de cœur rouge était plus élevée chez les arbres petits et de fort diamètre. Le cœur rouge était présent dans les arbres de 40 ans et plus en moyenne dans les peuplements étudiés. Le volume de cœur rouge était corrélé positivement avec l’âge de l’arbre. Sa proportion était corrélée positivement avec l’âge de l’arbre et négativement avec la quantité de lumière atteignant la cime vivante. La proportion moyenne de cœur rouge était 13,3 % du volume marchand de l’arbre et il était principalement situé sous la cime vivante. [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]

Quebec's forests represent 20% of Canadian forests and 2% of the world forests. Over the entire planet, forests play a major role in habitat preservation and in supplying goods and services to the population. However, climate change will have an impact on the forest through inter alia increased droughts, forest fires, warmer weather, and infestations. In this paper, we analyze the economic impact of climate change on the forest industry in Quebec over a 40-year period using a recursive dynamic computable general equilibrium model. We find that the climate change effects will be relatively weak on most macroeconomic variables as agents adjust their behavior over time and factors are reallocated across sectors. We find that climate change could generate losses in gross domestic product of up to Can$300 million (0.12% of gross domestic product) at the end of a 40-year period for Quebec's economy. However, we find relatively more important effects within the sectors of the forest industry, with losses ranging from 3% to 7.5%. [ABSTRACT FROM AUTHOR]

This paper presents development of a multivariate forest structural complexity index based on relationships between field-based structural variables and geospatial data. Remote sensing has been widely used to model individual forest structural attributes at many scales. As opposed to, or in addition to, individual structural parameters such as leaf area index or tree height, overall structural complexity information can enhance forest inventories and provide a variety of information to forest managers, including identifying damage and disturbance as well as indicators of habitat or biodiversity. In this study, a multivariate modelling technique, redundancy analysis, was implemented to derive a model incorporating both horizontal and vertical structural attributes as predicted by an ensemble of high-resolution multispectral airborne imagery and topographic variables. The first redundancy analysis axis of the final model explained 35% of the total variance of the field variables and was used as the complexity index. With a root mean squared error of 19.9%, the model was capable of differentiating four to five relative levels of complexity. This paper presents the forest ecological and modelling aspects of the research. A related paper presents the remote sensing aspects, including application of the model to map predicted structural complexity, map validation, and testing of the method at multiple scales. Cet article présente le développement d'un indice multivarié de complexité de la structure de la forêt basé sur les relations entre des variables structurales mesurées sur le terrain et des données géospatiales. La télédétection a été largement utilisée pour modéliser les attributs structuraux de la forêt à plusieurs échelles. Contrairement à, ou en plus, des paramètres structuraux individuels comme l'indice de surface foliaire ou la hauteur des arbres, une information globale au sujet de la complexité structurale peut améliorer les inventaires forestiers et fournir une variété de renseignements aux aménagistes forestiers, incluant l'identification des dommages et des perturbations aussi bien que des indicateurs d'habitat ou de biodiversité. Dans cette étude, une technique de modélisation multivariée, l'analyse de redondance, a été appliquée pour dériver un modèle qui incorpore des attributs, tant horizontaux que verticaux de la structure, prédits par un ensemble d'images aériennes multispectrales à haute résolution et des variables topographiques. Le premier axe de l'analyse de redondance du modèle final expliquait 35 % de la variance totale des variables terrain et a été utilisé comme indice de complexité. Avec une erreur quadratique moyenne de 19,9 %, le modèle était capable de différencier quatre à cinq niveaux de complexité. Cet article présente les aspects de la recherche reliés à la modélisation et à l'écologie forestière. Un autre article présente les aspects reliés à la télédétection, incluant l'application du modèle pour cartographier la complexité structurale prédite, la validation de la cartographie et l'essai de la méthode à plusieurs échelles. [ABSTRACT FROM AUTHOR]

To assess nutrient dynamics in decomposing logs of trembling aspen (Populus tremuloides Michx.), white birch (Betula papyrifera Marsh.), white spruce (Picea glauca (Moench) Voss), and jack pine (Pinus banksiana Lamb.), we monitored mass losses and changes in N and P contents in dead boles from a chronosequence of sites following stand-replacing disturbances. To assess the importance of wood decomposition to nutrient cycling, we compared net estimates of nutrient release from logs with net nutrient immobilization in live-tree biomass of stands as a function of time since disturbance. Mineralization rates were 0.060, 0.053, 0.038, and 0.020·year–1 for trembling aspen, white birch, white spruce, and jack pine logs, respectively. Trembling aspen boles released large quantities of N and P during the first year of decomposition (51 kg·ha–1 of N and 7 kg·ha–1 of P, assuming a bole volume of 150 m3·ha–1). White birch boles acted initially as a nutrient sink and delayed the release of immobilized nutrients until a period when the stand's net nutrient immobilization rates were highest. Jack pine boles appeared to be intermediate in terms of their contribution as a sink or a source of nutrients but, in mature stands, provided up to 40% of N and 26% of P immobilized annually in tree biomass. As pure stands of white spruce are rare in boreal Quebec, information on nutrient accumulation in white spruce stands was not available. [ABSTRACT FROM AUTHOR]

In many northern forest ecosystems, the postfire transition from a closed-crown forest to open woodland is often observed but poorly understood. This paper looks at the effect of interactions between surficial deposit, climate, and fire cycle on postfire forest recovery within a large territory (190 000 km2) of the boreal forest of eastern Canada. Postfire recovery was estimated using the time elapsed to move from the burnt stage to the regenerated stage and the young forest stage. The main objective was to determine if forests situated in dry regions (characterized by a high proportion of dry coarse surficial deposits, low precipitation, and short fire cycle) tend to reestablish more slowly after fire, obtaining a more open stand compared with wetter regions characterized by a longer fire cycle. To identify the best explanatory model for postfire recovery, multinomial logistic regressions with the Akaike information criterion were conducted using a combination of physicoclimatic factors. Our best model suggests that the most significant predictors of postfire recovery are time since fire (χ2 = 1370.06), surficial deposit type (χ2 = 651.95), the Canadian Drought Code (χ2 = 247.75), and the growing season precipitation (χ2 = 102.80). Fast recovery and dense forest regeneration are associated with subhydric till deposits only in the regions characterized by a long fire cycle (>500 years). Conversely, slow regeneration conducive to a sparse young forest was usually associated with regions characterized by a short fire cycle (<200 years) underlain by dry coarse deposits such as juxtaglacial but also mesic deposits in some cases. Our results also show that slow recovery and reduced forest regeneration are most likely to occur following fires that occurred in dry years, regardless of the deposit type and region. [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]

The main objective of this paper is to evaluate whether future climate change would trigger an increase in the fire activity of the Waswanipi area, central Quebec. First, we used regression analyses to model the historical (1973–2002) link between weather conditions and fire activity. Then, we calculated Fire Weather Index system components using 1961–2100 daily weather variables from the Canadian Regional Climate Model for the A2 climate change scenario. We tested linear trends in 1961–2100 fire activity and calculated rates of change in fire activity between 1975–2005, 2030–2060, and 2070–2100. Our results suggest that the August fire risk would double (+110%) for 2100, while the May fire risk would slightly decrease (–20%), moving the fire season peak later in the season. Future climate change would trigger weather conditions more favourable to forest fires and a slight increase in regional fire activity (+7%). While considering this long-term increase, interannual variations of fire activity remain a major challenge for the development of sustainable forest management. [ABSTRACT FROM AUTHOR]

Modelling volumes by log grades in standing hardwood trees is often hindered by the nature of the response variable. In this paper, we used a two-part conditional model to account for the excess of zero responses for some log grades. Moreover, this approach was used as a framework to compare three different tree classifications in their ability to predict volumes by log grades in standing yellow birch (Betula alleghaniensis Britton) and sugar maple (Acer saccharum Marsh.) trees. A tree grade classification was compared with two preharvest tree classifications based on mortality risk assessment. A cross-validation was also carried out to evaluate the two parts of the model. The results showed that the two-part conditional approach was efficient in this case study. Compared with a general model, the three classifications improved the maximum likelihood. According to the Akaike and Bayesian information criteria, the tree grade classification was the “best” one. All three classifications proved to be better able to distinguish log grade occurrence than log grade volume. Although it implies additional cost, the implementation of the tree grade classification into the preharvest inventories would improve the prediction of volumes by log grades for yellow birch and sugar maple trees. [ABSTRACT FROM AUTHOR]

This paper presents soil fluxes of methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2) from 12 sites located in four major forest types, black spruce (Picea mariana (Mill.) BSP), jack pine (Pinus banksiana Lamb.), aspen (Populus spp.), and alder (Alnus spp.) stands, in the Eastmain and Chibougamau regions of Quebec. Fluxes were determined with closed chambers during the snow-free period from May to October 2007. Well-drained black spruce, jack pine, and aspen forest soils were net sinks of atmospheric CH4 (–0.33 ± 0.11 mg·m–2·day–1), while alder-dominated wetland soils were sources of CH4 (0.45 ± 0.12 mg·m–2·day–1). The cut-over alder wetland soil produced 131 times more CH4 than the undisturbed wetland soil. Soil moisture and temperature mainly regulated CH4 fluxes. N2O fluxes from these forest soils were highly variable and smaller (1.6 ± 0.33 µg N·m–2·h–1) than those from deciduous forest soils. N2O emission from the cut-over black spruce forest soil was 2.7 times greater than that from the mature black spruce forest soil. Large C/N ratios (27 to 78) and slow soil N mineralization and nitrification rates in these forest soils may have led to small N2O fluxes. CO2 emissions from these forest soils, ranging from 0.20 to 2.7 g·m–2·day–1, were mainly controlled by soil temperature. [ABSTRACT FROM AUTHOR]

This paper examines structural changes and the dynamics of price relationships in the United States (US), British Columbia, Quebec, and Ontario lumber markets. With monthly price series from 1981 to 2002, I used Perron's method to identify structural shifts and the Johansen cointegration analysis and vector-error correction model to determine both short- and long-run price relationships. I found that because of restrictions on federal timber harvests in the Pacific Northwest, price instability experienced in 1992 has caused structural shifts for the US and Canadian lumber prices. I also found that the North American lumber market is indeed integrated, with the US price significantly affecting Canadian prices in both the short and long run. This further indicates that the US market plays a dominant role in price setting in the North American lumber market, as Canadian prices respond to the US price change, but the reverse situation does not occur. [ABSTRACT FROM AUTHOR]

We studied community development and mortality among tree species at multiple spatial scales in a 236-year mixedwood chronosequence at Lake Duparquet, Quebec. Spatial relationships, species associations, and understory–overstory replacement patterns were studied using spatial statistics, patch indices, G tests, and transition matrices. Results of these analyses showed that shade-intolerant and shade-tolerant tree communities formed increasingly fine-grained patches in midsuccession. These fine-grained associations appear to be partly due to suppressed stems being released into a slowly thinning canopy and partly due to new recruitment of shade-tolerant conifers. In 1-ha plots, tree species richness and evenness peaked in 25-, 100-, and 400-m2 subplots during midsuccession. Forest cover type diversity also peaked in midsuccessional landscapes assessed using aerial photographs. The oldest 1-ha plot was dominated by monospecific patches of eastern white cedar (Thuja occidentalis L.), which was the most likely replacement for live and dead trees and the most abundant species in the numerous subplots that were occupied by trees smaller than 8 cm DBH. In spite of this dominance, long-lived paper birch (Betula papyrifera Marsh.) and residual fir (Abies balsamea (L.) Mill.) seedlings may maintain the mixedwood character of this stand into the future. The implications of our findings for stand management and conservation are discussed. [ABSTRACT FROM AUTHOR]