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Wood discoloration was investigated in 721 paper birch (Betula papyrifera Marsh.) trees from 146 sites across the managed forest of Quebec, Canada. Discoloration was present at breast height in 85% of trees, but its impact was limited in terms of tree basal area and volume, with proportions of 6.4% and 3.6%, respectively. These two measures were strongly correlated. Discoloration changed wood appearance but had no effect on microfibril angle and modulus of elasticity. Discolored wood was nevertheless denser, probably due to the accumulation of colored extractives. Predictive models were also developed and applied to 415 711 paper birch trees from 51 689 inventory plots across the province to study regional variation. Higher proportions of discolored basal area were obtained in the southwestern areas of the province where the climate is warmer and drier. In these areas, paper birch trees are larger and, likely, support bigger branches which can cause larger columns of discoloration when broken. Lower proportions were found in eastern regions where snowfall is more abundant. Smaller, more flexible branches in trees growing in these areas could explain this result. This study confirms the feasibility of large-scale mapping of wood discoloration in standing trees based on forest inventory and climate data.

We use a dynamic, global computable general equilibrium (CGE) model to capture the economic impacts of internet adoption, modeled through reduced demand in the newsprint and printing and writing paper (pulp and paper) industries. Global newsprint consumption is estimated to fall dramatically by 2030. We rely on estimates from another study that captures the change in global pulp and paper consumption using the global forest products model (GFPM), based on two scenarios: (i) full per capita internet adoption by 2100 and (ii) more rapid full internet adoption by 2050. We incorporate reductions in pulpwood consumption into a global multiregional dynamic CGE model to estimate economy-wide impacts in Canadian provinces, the United States, and the rest of the world. Results indicated that the year 2050 internet adoption scenario would result in a reduction in cumulative discounted gross domestic product (GDP) by as much as 17% in some regions of Canada, reduce GDP by 5.8% in the United States, and increase GDP by 3.3% in the rest of the world from 2006 to 2030. These findings highlight the costs of internet adoption, leaving net benefit analysis of adoption to future work.

We analyze the total factor productivity (TFP) of the pulp and paper industry in three Canadian provinces (British Columbia, Ontario, and Quebec) and in three United States (US) states that are contiguously located south of the border (Washington, Illinois, and Maine) over the period of 1971 to 2005. We find that the industry in the three Canadian provinces had much higher TFP growth rates in the era following the Free-Trade Agreement (FTA) signed in 1988. In terms of productivity level, this relative TFP surge allowed the industry in Ontario and British Columbia to move ahead of Illinois and Washington, respectively; however, Quebec trailed further Maine, which is the overall leader in the sample. Our results in this particular case reveal that the Canadian pulp and paper industry did not contribute to the overall Canada–US productivity gap.

Technological growth in production and efficient utilization of input factors are the two biggest contributors to total factor productivity (TFP). TFP of the four major forest industries (logging, pulp and paper, sawmill, and veneer and plywood industries) of Ontario are compared by analyzing their production structures using duality theory in production and costs. The study uses annual data of output and four inputs — labour, capital, energy and materials — from 1967 to 2003. Different restrictions on the translog cost function are applied to each industry to determine the cost function that best describes each industry’s technology, which is further used to estimate Morishima elasticities of substitution, own-price and cross-price elasticities, rate of technological change, and TFP. The production structure of sawmill and veneer and plywood industries is found to be linear homogeneous and homothetic, and that of logging and pulp and paper industries is non-homothetic. Further, Hicks neutral technological change for all four industries is rejected, indicating that the production structure in all four industries is biased in favour of certain inputs and against others. This suggests that policies that improve the efficiency of each industry should focus on input-saving factors of that industry, thereby improving its competitive position.

Better pulp quality control, especially relating to product sheet strength, can offer an important means to improve the market superiority of a pulp. However, aside from lignin content, few pulp properties can be easily measured in a timely manner for process control. The present report proves a principle on a novel Raman system and a systematic chemometric approach, allowing for rapid spectral data acquisition and definitive spectrochemical analysis of wet pulp under harsh manufacturing conditions. By incorporating sophisticated chemometrics strategies that combine wavelet transform with a template-oriented genetic algorithm feature selection and partial least squares multivariate classification, this instrument system extracts maximum analytical information from raw Raman spectra to accurately predict the physicomechanical properties of sheet products. Our work has tested and refined these routines by drawing upon the systematic analysis of 26 bleached softwood kraft pulps formulated to yield challenges representative of those encountered in common pulp fibre and sheet analyses. Satisfactory calibration results suggest that a Raman gauge can be developed that has the capacity to continuously assay pulp to predict the physicomechanical properties of sheet paper in real time.

Partial and total measures of factor productivity are presented for the pulp and paper industries of the United States and Canada, from 1959 to 1987. Total factor productivity was measured with (1) a Tornqvist–Theil index, (2) a nonparametric index with translating hypothesis, and (3) a nonparametric index with distance functions. Method 1 implied a constant return to scale translog production function. Methods 2 and 3 removed any assumption on the functional form of the production function. Furthermore, method 3 allowed for fully disaggregated outputs. Methods 1 and 3 gave similar results within countries: an increase in total factor productivity of 0.7% per year in the United States and of 0.5% per year in Canada. Method 2 gave rates of growth of total factor productivity that were twice as high, but unreliable because of the assumptions of the method. From 1961 to 1984, when comparable data are available, methods 1 and 3 gave growth rates of total factor productivity that were significantly higher, statistically, in the United States than in Canada. Nevertheless, the differences seem to be too small to be of economic significance.

Although jack pine (Pinusbanksiana Lamb.), which represents 20% of the total softwood volume, is one of the most abundant commercial softwood species in Canada, its rate of utilization in pulping is surprisingly low. This paper reviews the literature concerning the physical and chemical properties as well as the pulping characteristics of this species by mechanical, thermomechanical, chemithermomechanical, chemimechanical, and chemical processes to better understand its potential use in papermaking. The objective is to identify the problems related to the use of jack pine so that solutions might be sought to promote its usage. Some recommendations are put forth concerning future research.

This paper analyzes the productivity performance of the Canadian pulp and paper industry for the 1963–1984 period. The industry's productivity is first measured, then its sources are analyzed. Total factor productivity is used to measure industry productivity, and statistical estimation of neoclassical cost functions are used to determine sources of the productivity changes. In addition to decomposing the productivity changes into technical changes and changing the scale of the industry's output and capacity utilization, an attempt is also made to assess the impact of pollution control expenditures. The paper finds that although labour productivity grew at 2.5% per year (modest in comparison to other industries), the gross total factor productivity grew only by 1.2% per year. This is largely due to the fact that capital investment raises labour productivity but retards overall productivity. Of the 1.2% growth in total factor productivity, 0.88% was due to the increased scale of the industry output and 0.32% to technical change. Although there is no statistically conclusive evidence, the point estimate indicates that pollution control expenditures may have retarded productivity growth. However, this subject requires further investigation.

Red heartwood, a dark nonhomogenous discolouration in paper birch trees ( Betula papyrifera 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.

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.

A continually increasing demand for energy and concerns about climate change, greenhouse gas emissions and peak oil have prompted countries to develop policies that promote renewable energy including forest-based bioenergy. In Europe, fuelwood-driven changes in forestry are likely to impact habitat conditions for forest biodiversity. We conducted a systematic literature overview based on 88 papers to synthesize research findings and gaps in knowledge. At the stand scale, but also on a landscape scale, deadwood availability and profile are altered by several practices: whole-tree harvesting and postharvest recovery of logging residues and stumps, for instance. Large-scale fuelwood removal may, on a landscape scale, jeopardize the amounts and diversity of substrate that saproxylic organisms require as food and habitat. Besides, bioenergy-related forest practices also affect nonsaproxylic biodiversity through physical (e.g., soil compaction and disturbance) and chemical changes in soil properties associated with fuelwood removal and increased machine traffic. Moreover, the extended density of internal edges threatens interior forest species populations. Important effects differ substantially between boreal and nemoral forests because of contrasts in management systems, structure of forest ownership, and ecological properties. Developing relevant operational guidelines to partially mitigate ecological damage on biodiversity should be based on our compiled cautionary statements but require further large-scale and long-term research.

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 (

Natural disturbance emulation (NDE) has been proposed as a general approach to ecologically sustainable forest management. We reviewed the concepts, theories, and strategies related to NDE in boreal forest management. We also reviewed publications that discussed NDE in the boreal forest in general and those that specifically compared NDE-based management with conventional even-aged management. The papers generally focused on northern North America and landscape-scale wildfire as the main disturbance factor, whereas information from Eurasia was exclusively theoretical. Within this limited scope, NDE was generally found to have a positive effect on biodiversity in terms of forest structure and species diversity when compared with conventional even-aged management. Studies on timber supply and social implications of NDE were so few that they preclude generalizations. We conclude that the ecological and economic performance of NDE as a management approach still remains poorly examined. To advance the development of NDE, particular attention should be given to (1) augmenting the knowledge base on natural range of variability of unmanaged forest ecosystems and evaluating the validity of this information in a changing climate, (2) fostering multidisciplinary research with better integration of ecological theory to both integrative and analytical research on NDE, and (3) better integration of socioeconomic concerns, adaptive management schemes, and international collaboration into NDE initiatives.

This paper studies substitution between main categories of imported pulp and paper products and between im- ported and domestic pulp and paper products in the US market. A restricted translog subcost function approach was em- ployed to derive the elasticity of substitution. The results suggest that Canadian pulp and paper products are competitive and have maintained their competitiveness in the US market, and therefore, the challenges faced by the Canadian pulp and paper industry are not because of the loss of its product competitiveness but are due to other reasons such as declining de- mand for paper products in the United States. It seems that if the Canadian pulp and paper industry wants to retain its dominant position in the world market place, it will have to create global reach and develop new markets. Resume´ : Cet article s'interesse a la substitution entre les principales categories de produits de pates et papiers et entre les produits de pates et papiers importes et domestiques sur le marcheamericain. Une approche basee sur une fonction trans- log restreinte de sous-coutaeteutilisee pour determiner l'elasticitede substitution. Les resultats indiquent que les produits de pates et papiers canadiens sont competitifs, qu'ils ont maintenu leur competitivitesur le marcheamericain et que les defis rencontres par l'industrie canadienne des pates et papiers ne sont pas dus aune perte de competitivitede ses produits mais plutotad'autres facteurs tels que la diminution de la demande pour les produits du papier aux Etats-Unis. Il semble que si l'industrie canadienne des pates et papiers desire maintenir sa position dominante sur le marchemondial, elle devra adopter une perspective globale et developper de nouveaux marches. (Traduit par la Redaction)

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.

Forest edge length is important for landscape ecological analysis, including the analysis of fragmentation. In this paper, we estimate forest edge length using field sample data from the German National Forest Inventory as an example. The complex plot design of many large-area forest inventories allows for the estimation of forest edge length at different spatial resolutions. As expected, estimates depend on the spatial resolution: longer estimated edge lengths resulted from observations at finer spatial resolutions. From the comparison of estimated edge lengths at different spatial resolutions, conclusions about the irregularity of forest edges can be drawn: more irregular forest boundaries resulted in greater differences between the estimated lengths for different spatial resolutions. One conclusion is of particular relevance: reported forest edge length values are meaningless unless their spatial resolution is also reported. The analysis presented is an add-on to the standard estimations from a forest inventory, producing additional, ecologically meaningful information. It is contended that many more nonstandard analyses of forest inventory data are possible either immediately or with minor modifications to the plot design.

In forest inventories, regression models are often applied to predict quantities such as biomass at the level of sampling units. In this paper, we propose a model-based inference framework for combining sampling and model errors in the variance estimation. It was applied to airborne laser (LiDAR) data sets from Hedmark County, Norway, where the model error proportion of the total variance was found to be large for both scanning (airborne laser scanning) and profiling LiDAR when biomass was estimated. With profiling LiDAR, the model error variance component for the entire county was as large as 71% whereas for airborne laser scanning, it was 43% of the total variance. Partly, this reflects the better accuracy of the pixel-based regression models estimated from scanner data as compared with the models estimated from profiler data. The framework proposed in our study can be applied in all types of sample surveys where model-based predictions are made at the level of individual sampling units. Especially, it should be useful in cases where model-assisted inference cannot be applied due to the lack of a probability sample from the target population or due to problems of correctly matching observations of auxiliary and target variables.

Following centuries of deforestation, Ireland has undergone a substantial afforestation programme in the last 40 years. This paper presents the results of a case study undertaken to examine local response to afforestation. The study is set in Arigna, a region in northwestern Ireland that has traditionally depended on agriculture but has experienced relatively high rates of afforestation in recent decades. Relying on documentary evidence and in-depth qualitative interviews conducted with local stakeholders, the results suggest more local resistance to afforestation than one might expect in a country that has historically experienced such massive deforestation. Among the reasons uncovered for this resistance is the history of land tenure in rural Ireland, the institutional means by which afforestation has been conducted, the tree species used, and the aesthetic appearance of the forest stands once established. Underlying all of this is an apparently widespread local perception that forestry has benefited outsiders more than locals. Yet, the study also documents local perceptions that those responsible for afforestation have responded to concerns and that resistance to afforestation may be declining, as well as the reasons for this decline. The paper concludes with a discussion of the importance of local history and community involvement in developing socially acceptable forestry.

This paper integrates dendrochronological, demographic, and experimental perspectives to improve understanding of the response of white spruce ( Picea glauca (Moench) Voss) tree growth to climatic variability in interior Alaska. The dendrochronological analyses indicate that climate warming has led to widespread declines in white spruce growth throughout interior Alaska that have become more prevalent during the 20th century. Similarly, demographic studies show that white spruce tree growth is substantially limited by soil moisture availability in both mid- and late-successional stands. Interannual variability in tree growth among stands within a landscape exhibits greater synchrony than does growth of trees that occupy different landscapes, which agrees with dendrochronological findings that the responses depend on landscape position and prevailing climate. In contrast, the results from 18 years of a summer moisture limitation experiment showed that growth in midsuccessional upland stands was unaffected by moisture limitation and that moisture limitation decreased white spruce growth in floodplain stands where it was expected that growth would be less vulnerable because of tree access to river water. Taken together, the evidence from the different perspectives analyzed in this study clearly indicates that white spruce tree growth in interior Alaska is vulnerable to the effects of warming on plant water balance.

This paper outlines molecular analyses of soil fungi within the Bonanza Creek Long Term Ecological Research program. We examined community structure in three studies in mixed upland, black spruce (Picea mariana (Mill.) BSP), and white spruce (Picea glauca (Moench) Voss) forests and examined taxa involved in cellulose degradation at one upland site. We found that soil horizon was the factor by which fungal communities were most strongly structured and that pre- dictable turnover in upland fungal species occurred through succession. Communities from consecutive summers were not significantly different, indicating that interannual variation was small in relation to differences between forest types and soil horizons, yet the community at a seasonal study site underwent significant changes within a year. In each study, my- corrhizal fungi dominated the community. Fungi rather than bacteria appeared to dominate ( 13 C)cellulose degradation, with strongest growth in taxa that were not dominant members of the untreated community, including members of the ge- nus Sebacina. Overall, our results point to considerable interannual resilience juxtaposed with narrow niche partitioning and the capacity of individual taxa in these hyperdiverse communities to respond strongly to resource inputs and changes in other abiotic environmental parameters such as temperature. Our data double the cumulative total of fungal sequences in GenBank and together achieve a better picture of fungal communities here than for any other ecosystem on earth at this time. Resume´ : Cet article decrit les analyses moleculaires effectuees sur les champignons du sol dans le cadre du programme de recherche a long terme en ecologie de Bonanza Creek. Nous avons etudiela structure des communautes par le biais de trois etudes portant sur des forets mixtes en milieu sec, d'epinette noire (Picea mariana (Mill.) BSP) et d'epinette blanche (Picea glauca (Moench) Voss) et nous avons etudieles taxons impliques dans la degradation de la cellulose dans une sta- tion seche. Nous avons trouveque l'horizon du sol etait le facteur preponderant dans la structuration des communautes fongiques et que le renouvellement previsible des especes fongiques en milieu sec se produisait par l'entremise de la suc- cession. Les communautes presentes d'un eteal'autre n'etaient pas significativement differentes indiquant que la variation interannuelle etait faible comparativement aux differences entre les types de foret et les horizons du sol. Par contre, la communautepresente sur le site d'une etude saisonniere a subi des changements significatifs a l'interieur d'une annee. Dans chaque etude, les champignons mycorhiziens dominaient la communaute ´. Les champignons plutot que les bacteries semblaient dominer la degradation de la ( 13 C)cellulose; la plus forte croissance a eteobservee parmi les taxons qui n'etaient pas des membres dominants de la communautenon traitee, incluant des membres du genre Sebacina. Globale- ment, nos resultats font ressortir la grande resilience interannuelle juxtaposeead'etroites niches ecologiques ainsi que la capacitede taxons particuliers dans ces communautes hyper diversifiees de reagir fortement aux apports de ressources et a la variation d'autres parametres environnementaux. Nos donnees viennent doubler le total cumulatif de sequences fongi- ques dans GenBank et ensemble donnent ace jour une meilleure image des communautes fongiques ici que dans n'im- porte quel autre ecosysteme ailleurs dans le monde. (Traduit par la Redaction)

Deadwood-associated insects and saprotrophic fungi are principal agents of wood decomposition in boreal forest. Silvicultural treatments that alter microclimate and availability of deadwood likely affect composition and growth rates of both insect and fungal communities, leading to changes in wood decomposition rates. Here, we relate both saproxylic beetle and dominant polypore assemblages with woody decomposition rates and environmental variables in experimental partial cuts, clearcuts, and uncut controls using a series of causal models to determine the relationship between stand structure, biodiversity, and ecosystem function in black spruce ( Picea mariana (Mill.) BSP) forests. Overall beetle and fungal composition differed between uncut stands and harvested stands. Main effects of harvesting included large increases in wood-feeding beetles and the fungus Gloeophyllum sepiarium (Wul.:Fr.) Karst. We suggest that these species were promoted by specific alterations in microhabitat conditions of deadwood. Within clearcuts specifically, changes in species composition and significantly more fungal degree-days resulted in significantly higher decomposition rates. We concluded that levels of partial cutting in the range of 15%–20% retention were not sufficient to maintain predisturbance communities but were sufficient to maintain wood decomposition rates similar to uncut stands.

Forest owners are confronted with contradictory views on the importance of deadwood. Environmentalists argue that it should be left in the forest to conserve biodiversity, provide a habitat for specific fauna and flora, and maintain soil quality through wood decay. Conversely, industrial stakeholders, and some public decision makers, advocate harvesting deadwood. Based on a sociological survey and qualitative interviews, we first analyzed the detailed environmental opinions and values of four groups of French foresters as well as their attitudes towards biodiversity, in particular regarding deadwood conservation. We identified various types of attitudes towards deadwood, which could be seen as waste, an unprofitable by-product, a meaningless entity, or a key part of the ecosystem. We then studied the arguments leading them to choose between deadwood conservation and deadwood harvesting for bioenergy production. On one hand, foresters are interested in short-term profitability and pest control, while others fear potential loss of fertility. Finally, the article shows that specific approaches to deadwood conservation ought to be negotiated at a local scale, pending further scientific investigation into the impact of deadwood on biodiversity and the development of more positive attitudes toward ecological concerns in the forest owners’ community.

Modification of forest attributes and structural components like downed wood (DW) during forest harvest can lead to local species loss. Epixylic bryophytes have been proposed as good indicators of such changes. Unharvested control, variable canopy retention, and single pass harvest represent a gradient in forest harvest impact and can be used to test the response of epixylic bryophytes to different levels of environmental change. The objective of this study was to see if variable canopy retention attenuates environmental change associated with harvesting, consequently maintaining an epixylic community more similar to unharvested stands than single pass harvesting. Environmental conditions and DW characteristics were sampled on 225 DW pieces distributed in 45 permanent plots. Results showed that treatment affected epixylic richness through its impact on canopy openness and DW diameter and decomposition class. Fewer species were found in more open habitats and more species were found on bigger and more decomposed DW. Most epixylic species were more commonly found on the forest floor than on the DW. In conclusion, variable canopy retention harvest offered microclimatic conditions and DW availability and quality more suitable for epixylic species than single pass harvest, which was less suitable for epixylic species.

Decaying wood contribution to the heterogeneity of forest soils could depend on tree species and wood decay stage. The study was conducted in an 85-year-old trembling aspen ( Populus tremuloides Michx.) – jack pine ( Pinus banksiana Lamb.) forest in northwestern Quebec, Canada. Trees, snags, logs, and forest floor originating from wood buried within the forest floor (lignic FF) and from fine litter (alignic FF) were inventoried in fifteen 400 m2 plots (nine jack pine and six trembling aspen). Chemical properties of alignic and lignic FF and logs were measured and relative nutrient availability in the mineral soil assessed under logs and under lignic and alignic FF using PRS probes. No significant differences between forest covers were found for the proportion of C and nutrients contained in deadwood (snags, logs, and lignic FF) relative to tree biomass plus necromass (deadwood plus alignic FF) content. Lignic FF was characterized by a higher C/N ratio and exchangeable acidity than alignic FF and its nutrient concentrations were between those of alignic FF and logs. Differences in wood characteristics may explain some of the differences in forest floor properties observed between trembling aspen and jack pine. Nutrient availability in the mineral soil was affected by the overlaying materials and could reflect differences in the dynamics of individual nutrients.

Because quantitative data on the distribution of whole microhabitat sets are still lacking to indirectly assess taxonomic biodiversity in forests, we studied the distribution of seven key microhabitat types in 10 montane European beech ( Fagus sylvatica L.) – silver fir ( Abies alba Mill.) forests (Pyrénées, France) that had not been harvested for several decades. We examined 2105 live trees and 526 snags. Frequencies of cavities and dendrothelms were significantly higher on live beech than on fir. Sap runs were strictly found on live fir. Frequencies of cracks and saproxylic fungi were significantly higher on snags than on live trees. Seventy percent of live beeches but only 18% of firs carried one or more microhabitats. For both beech and fir and for each microhabitat type, we found, using the recursive partitioning method, one to three diameter thresholds that each corresponded to a significant change in the probability of microhabitat presence. When considering the whole microhabitat set, the most significant diameter thresholds were 42, 60, 73, and 89 cm for beech and 99 cm for fir. We suggest that forest managers conserve (i) mixed stands and (ii) beech with a diameter at breast height >90 cm and fir >100 cm. These rules should be adapted for each forest ecosystem.

In the boreal forest, establishment of tree regeneration is tightly linked to both mast years and the availability of adequate germination beds for seedlings. We took advantage of a mast year (2006) in the eastern boreal mixedwood to compare seedling establishment in 2007 and seedling survival 2 and 4 years later on sections of fallen logs and equivalent areas of adjacent forest floor. Several factors that could explain establishment of seedlings on logs were measured, including wood resistance, density, moisture content, and C/N ratio. Our results show that small-seeded species, such as white birch ( Betula papyrifera Marsh.) and white spruce ( Picea glauca (Moench) Voss), establish preferentially on logs whereas balsam fir ( Abies balsamea (L.) Mill.), a relatively large-seeded species, establishes more often on the forest floor. Using logistic regressions, we confirmed that the probability of seedling establishment on logs declines with wood resistance, while the survival probability is inversely proportional to stand deciduous basal area. Survival rate was similar for seedlings established on the forest floor and on logs. However, none of the white birch seedlings established on the forest floor in 2007 were alive by 2011. Even following an exceptional mast year, log occurrence in eastern mixedwood stands would not suffice to obtain adequate white spruce stocking levels.

Under the auspices of ecosystem-based management, historical disturbance patterns are promoted as a means of providing benchmarks for ecosystem sustainability. The associated research in support of this strategy in the boreal forest has substantially increased our understanding of frequencies, sizes, shapes, and severities of wildfires. However, despite the fact that different spatial definitions of wildfires exist in both research and practice, we have not considered the significance or impact of those differences on observed patterns. This study addresses this gap by conducting a sensitivity analysis on the influence of 11 spatial definitions of a wildfire on six pattern metrics for 24 wildfires in the Foothills Natural Region of Alberta. The results suggest that all pattern metrics were sensitive to changes to wildfire delineation, but in particular the total amount of remnants, wildfire shape, and the relationship between pre-burn fuel types and the probability of burning. The results also suggest that simple mortality maps do not necessarily identify multiple disturbed patches within wildfires, an attribute undocumented by previous research. These pattern differences potentially correspond to some fundamental differences in perception of how and why wildfires burn and our understanding of the associated processes and biological responses.

Observed modifications of ectomycorrhizal (ECM) communities have been connected to the increased N depositions of the 20th century. Because of their narrow niche width, small disturbances of soil conditions can produce greater effects on the fungal species than on their host trees. This study investigated the ECM community in a black spruce ( Picea mariana (Mill.) BSP) stand subjected to long-term additions of 9 and 30 kg N·ha–1·year–1 of ammonium nitrate, representing 3 and 10 times the atmospheric N deposition at the site, respectively. Root tip vitality and ECM presence were detected on samples collected from the organic horizon and ECM were classified into morphotypes according to their morphological and anatomical characters. In the control, 80.6% of the root tips were vital, 76.5% of them showing ECM colonization. Higher root tip vitality and mycorrhization were observed in the treated plots. Forty-one morphotypes were identified, most of them detected at the higher N inputs. Results diverging from the expectations of a reduction in ECM presence and diversity could be related to a higher growth rate of the trees following fertilization. The repeated application of small N doses could have been a better imitation of natural inputs from atmospheric deposition and could have provided more reliable responses of ECM to treatment.

It is argued that spruce budworm (Choristoneura fumiferana (Clemens)) (SBW) outbreaks have tended to be more frequent, severe, and spatially synchronized since the beginning of the 20th century. However, few studies have as- sessed the long-term (>200 years) variations in SBW outbreak dynamics. We reconstructed the SBW outbreak history at the northern limit of the temperate forest in southern Quebec using dendrochronological material from old buildings and five old-growth stands. Our regional tree-ring chronology (1551-1995) represents one of the longest and most replicated insect outbreak reconstructions in North America. Nine potential outbreaks were identified (1976-1991, 1946-1959, 1915-1929, 1872-1903, 1807-1817, 1754-1765, 1706-1717, 1664-1670, and 1630-1638) with three additional uncertain outbreaks (1647-1661, 1606-1619, and 1564-1578). Results suggested that southern Quebec has experienced frequent and synchron- ized outbreaks throughout the last 400 years. Although outbreak frequency was higher during the 20th century (approxi- mately 30 years) as compared with the 1660-1850 period (approximately 50 years), similar or even higher outbreak frequency might have occurred prior to 1660 (approximately 28 years). We did not find any evidence that the recent out- break dynamics in southern Quebec is outside its historical range of the last 400 years. Previous studies based on living trees may have underestimated outbreak frequency and synchrony prior to 1900. Resume : Les epidemies de tordeuse des bourgeons de l'epinette (Choristoneura fumiferana (Clemens)) (TBE) tendent a etre plus frequentes, severes et synchrones depuis le debut du 20 e siecle. Cependant, peu d'etudes ont analyse les variations

The predicted climate warming and more frequent and longer droughts are expected to produce potentially severe water stresses in the boreal forest. The aim of this experiment was to study the effect of a summer drought on xylem phenology and anatomy of mature black spruce ( Picea mariana (Mill.) BSP) trees in their natural environment. The trees were excluded from rain during June–September 2010 by the installation of under-canopy roofs in four sites of the boreal forest of Quebec. Xylem phenology, stem radius variations, and physiological traits of treated and control trees were monitored at short time resolution. At the end of the growth season, cell characteristics were measured. The rain exclusion reduced the cell area of the xylem, but no significant change was observed in cell wall thickness, cell production, or phenology. Stem radius variations of the treated trees were lower but followed the same pattern as the control. After removal of the exclusion, trees and soil quickly recovered their normal water status. One summer of drought led to the formation of smaller tracheids but showed that black spruce is resistant to this rain exclusion treatment. This is likely due to the ability to collect water from sources other than the superficial soil horizon.

Forest management inspired from natural disturbances is often claimed to have more benign effects on biodiversity than more traditional approaches but this premise has rarely been tested. In the northern hardwood forest, selection harvesting could be seen as a surrogate for the combined effects of windthrow, moderate ice storms, and senescence. Here, we quantified the response of two focal species of forest birds (Brown Creeper ( Certhia americana (Bonaparte, 1838)) and Ovenbird ( Seiurus aurocapilla (Linnaeus, 1766))) to this treatment (30%–40% basal area removal) in the first 5 years post-harvest using a replicated field experiment. We tested the possibility that selection harvesting creates ecological traps whereby individuals show a preference for a habitat type where their fitness is lower. We found that both focal species actually seemed to prefer control plots, where they reached a higher density than in treated plots. There was no evidence for a treatment effect on per capita productivity in either species. Hence, there was no evidence for an ecological trap. However, large-scale application of selection harvesting may have ecologically significant effects on productivity of the focal species per unit area of habitat. Future studies should test whether selection harvesting creates ecological traps for species naturally associated with canopy gaps.

Spruce budworm ( Choristoneura fumiferana (Clemens)) defoliation is known to regularly produce radial growth decrease in black spruce ( Picea mariana (Mill.) Britton, Sterns & Poggenb.) in the boreal forest of Quebec. Some studies have already shown that the first year of defoliation does not induce growth losses in the stem but could occur in other tree parts. We therefore examined the timing and duration of the growth reduction caused by the last outbreak in black spruce by also considering the branches. More than 79% of branches and 65% of stems exhibited a >40% growth decrease.The reduction was first registered in the upper part of the stem before being detected lower in the stem in 87% of the trees. Probabilities of growth reduction in the upper part of the stem were highest in 1976 and 1977. In the lower stem, the probabilities were highest in 1978. An interesting finding was that in 69% of the studied stands, the probability of growth reduction started earlier (1–2 years) in the branches than in the stem at 1.3 m. Branch analysis should be considered whenever questions arise in regard to the evolution of spruce budworm defoliation as well as the timing of observed growth reduction in black spruce.

When species are introduced into new regions, there is great uncertainty whether the trait differences of the intro- duced species or regional factors, such as climate or edaphic properties, will serve as the dominant control of ecosystem properties or processes. In this study, we examined whether the introduction of Pinus contorta Douglas ex Loudon into Sweden has altered forest floor properties and processes or whether these properties are more strongly controlled by re- gional factors. We compared forest floor pH, potential N mineralization rates, bulk density, litter and forest floor depths, C and N concentrations and pool sizes, C:N ratios, and soil microbial communities using substrate-induced respiration and phospholipid fatty acid analysis among stands of introduced P. contorta (SwPc), native Swedish Pinus sylvestris L. (SwPs), and native Canadian P. contorta (CaPc). For most forest floor properties (pH, net NH4 + mineralization, bulk density, N mass, and the microbial phospholipid fatty acid community structure), SwPc sites were more similar to SwPs than to CaPc, whereas litter and forest floor depth were significantly higher in SwPc than the two other forest types. Our findings suggest that regional factors exerted a stronger control on most forest floor properties and processes than did species differences be- tween the two Pinus species for the regions we studied. Resume : Lorsque des especes sont introduites dans de nouvelles regions, il y a une grande incertitude quand a savoir si les proprietes et les processus de l'ecosysteme seront surtout determines par les differences de caracteristiques des especes in- troduites ou par les facteurs regionaux, tels que le climat ou les proprietes du sol. Dans cette etude, nous examinons si l'in

Since plant growth in the boreal forest is often considered to be limited by low temperatures and low N availability and these variables are projected to increase due to climate warming and increased anthropogenic activities, it is important to understand whether and to what extent these disturbances may affect the growth of boreal trees. In this study, the hypotheses that wood phenology and anatomy were affected by increased soil temperatures and N depositions have been tested in two mature black spruce ( Picea mariana (Mill.) BSP) stands at different altitudes in Quebec, Canada. For 3 years, soil temperature was increased by 4 °C during the first part of the growing season and precipitations containing three times the current N concentration were added in the field by frequent canopy applications. Soil warming resulted in earlier onsets of xylogenesis and interacted with N addition producing longer durations of xylogenesis for the treated trees. The effect of warming was especially marked in the phenology of roots, while wood production, in terms of number of tracheids, was not affected by the treatment. Xylem anatomy and soil and needle chemistry showed no effect of the treatments, except for an increase of cell wall thickness in earlywood of treated trees. This short-term experiment with black spruce suggested that previous fertilization studies that used large and unrealistic rates of N addition may have overestimated the impact of N depositions on boreal forest productivity.