Search

Forest plantations play an increasingly important role in meeting global demand for wood. They usually have higher yield than naturally regenerated forests. Thus, plantations can support economically viable wood production, enable forest conservation elsewere, help mitigate climate change by contributing to carbon sequestration and increase forest resilience and resistance to biotic and abiotic stressors. If yield of plantations is not as high as anticipated, then their use could generate important sustainability issues. There are still major gaps in our understanding of the factors that influence yield, even with respect to black spruce, white spruce, and jack pine, three of the most commonly planted tree species in northeastern North America. Our objective was to evaluate the yield of forest plantations of these species over a 416 000 km2 region that was representative of northeastern North American forests. Contrary to our prediction, realized yield of operational plantations was consistently lower than anticipated. Site index and competition both played a significant role in determining the yield of plantations. In the context of uncertain realized yield of operational plantations, we emphasize the necessity of relying on adaptive management to determine harvest levels that are compatible with sustainable management objectives. [ABSTRACT FROM AUTHOR]

Short-term experimental studies provided evidence that plant diversity increases ecosystem resilience and resistance to drought events, suggesting diversity to serve as a nature-based solution to address climate change. However, it remains unclear whether the effects of diversity are momentary or still hold over the long term in natural forests to ensure that the sustainability of carbon sinks. By analyzing 57 years of inventory data from dryland forests in Canada, we show that productivity of dryland forests decreased at an average rate of 1.3% per decade, in concert with the temporally increasing temperature and decreasing water availability. Increasing functional trait diversity from its minimum (monocultures) to maximum value increased productivity by 13%. Our results demonstrate the potential role of tree functional trait diversity in alleviating climate change impacts on dryland forests. While recognizing that nature-based climate mitigation (e.g., planting trees) can only be partial solutions, their long-term (decadal) efficacy can be improved by enhancing functional trait diversity across the forest community. [ABSTRACT FROM AUTHOR]

Copyright of Forestry Chronicle is the property of Canadian Institute of Forestry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Forest productivity is a key driver of forest growth and yield and a critical information need for forest management and planning. Traditionally, this information has come from field plots, but these are expensive to measure and have limited coverage. Remote sensing, on the other hand, can provide forest inventory attributes on landscape scales and with a relatively low cost. A common predictor of forest productivity is site index (SI), traditionally estimated from age and height. In plantations, age can often be treated as a known quantity, but in natural-origin forests (of which Canada has vast swaths), age is often unknown and must be estimated, requiring expensive field work and resulting in a high level of error which, in turn, introduces error into SI estimates. The objective of this study is to generate estimates of SI from two successive LiDAR captures. The 99th percentiles (p99) of LiDAR returns from two successive captures 13 years apart were used along with species-specific SI curves to estimate SI. The results were compared to field-based estimates of SI for two major boreal species, jack pine and black spruce in managed and unmanaged conditions. Overall, the difference between the LiDAR-based SI and the field estimate was 2% with a relative mean squared error of 18%. For the few situations in which the height change was small or negative (less than 0.5%/year), SI was estimated from the average p99 and an assumed age of 100. The advantage of this method is that it does not require field sampling or estimates of age. Using two successive LiDAR captures, wall to wall estimates of SI can be generated at the grid cell level (e.g., 20 × 20 m), a level of detail generally not found in inventories. Overall, our results demonstrate the excellent potential for estimating SI from LiDAR alone, without age, to provide detailed productivity information for forest management and inventory that has been lacking in most large-scale inventories until now. [ABSTRACT FROM AUTHOR]

Copyright of Forestry Chronicle is the property of Canadian Institute of Forestry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Natural disturbances exacerbated by novel climate regimes are increasing worldwide, threatening the ability of forest ecosystems to mitigate global warming through carbon sequestration and to provide other key ecosystem services. One way to cope with unknown disturbance events is to promote the ecological resilience of the forest by increasing both functional trait and structural diversity and by fostering functional connectivity of the landscape to ensure a rapid and efficient self-reorganization of the system. We investigated how expected and unexpected variations in climate and biotic disturbances affect ecological resilience and carbon storage in a forested region in southeastern Canada. Using a process-based forest landscape model (LANDIS-II), we simulated ecosystem responses to climate change and insect outbreaks under different forest policy scenarios--including a novel approach based on functional diversification and network analysis--and tested how the potentially most damaging insect pests interact with changes in forest composition and structure due to changing climate and management. We found that climate warming, lengthening the vegetation season, will increase forest productivity and carbon storage, but unexpected impacts of drought and insect outbreaks will drastically reduce such variables. Generalist, non-native insects feeding on hardwood are the most damaging biotic agents for our region, and their monitoring and early detection should be a priority for forest authorities. Higher forest diversity driven by climate-smart management and fostered by climate change that promotes warm-adapted species, might increase disturbance severity. However, alternative forest policy scenarios led to a higher functional and structural diversity as well as functional connectivity--and thus to higher ecological resilience--than conventional management. Our results demonstrate that adopting a landscape-scale perspective by planning interventions strategically in space and adopting a functional trait approach to diversify forests is promising for enhancing ecological resilience under unexpected global change stressors. [ABSTRACT FROM AUTHOR]

• Patterns of summer forest productivity were examined in the context of winter snow and summer rain. • The GPP season was longer in years with earlier snowmelt. • Total GPP was higher for a longer GPP season in sites with wetter summer climate. • Total GPP was lower for a longer GPP season in sites with drier summer climate. • These patterns were weaker in forests with snow as a higher annual fraction of precipitation. Seasonal snow cover is important in shaping ecosystem carbon uptake across many regions of the world, however forest responses to projected declines in snowpack remain uncertain. We studied the response of forest gross primary productivity (GPP) during the photosynthetically active season to interannual and spatial variability in snow water equivalent (SWE), timing of snowmelt, and length of the active season. We combined carbon flux and weather data from 14 temperate deciduous and evergreen forests in the US and southeast Canada with SWE and precipitation from the Snow Data Assimilation System to test these hypotheses: 1) earlier snowmelt leads to a longer active season; 2) a longer active season is associated with higher total GPP, and 3) GPP during the active season is dependent on peak SWE and timing of snowmelt the previous winter. Regression and correlation analyses did not reveal meaningful environmental predictors of interannual variability in GPP, so linear mixed effects models were used to analyze broader scale spatiotemporal patterns. We found that active season length was negatively correlated with total active season GPP in forests with drier summers on average (based on mean annual summer climatic water deficit), but positively correlated in areas with typically wetter summers. The magnitude of these effects decreased at forests with a higher percentage of annual precipitation falling as snow. Our results showed that the capacity for plants to gain more carbon during a longer active season appears to be dependent on soil water status determined by long-term climate, rather than interannual fluctuations in weather. We found no evidence that the magnitude of total snowfall or peak SWE had a legacy effect on subsequent active season GPP. Finally, we highlight that there was large interannual variability both within and between sites that was not well explained by seasonal climate or phenology. [ABSTRACT FROM AUTHOR]

Objectives: The purpose of this study was to determine the relationship between gender, research productivity, academic rank, and departmental leadership positions of pathology faculty in North America.Methods: The online information presented for the faculty members in all American- and Canadian-accredited pathology residency programs' official websites and Elsevier's SCOPUS were queried to assess research productivity, academic ranks, and leadership positions.Results: Among 5,228 academic pathologists included in our study, there were 3,122 (59.7%) males and 2,106 (40.3%) females. Male faculty held higher academic ranks (being professor) and leadership positions (chair/program director) (P < .0001). Males were more likely to hold combined MD-PhD degrees (P < .0001) than females. The median h-index for the male faculty was 17 vs 9 for the female faculty (P = .023).Conclusions: Gender has a significant influence on leadership positions, academic ranks, and research productivity among pathology faculty members in North America. [ABSTRACT FROM AUTHOR]

Tree‐ring data have become widely used to model tree growth responses to climate variability and gain insight about the potential effects of global warming on forests. We capitalized on a rare opportunity to develop growth–climate models using tree‐ring data collected from all trees (>4 cm in diameter at breast height) within 50 × 50 m plots established in subalpine old‐growth forests of western Canada. Our objective was to determine how tree growth responses to climate vary among tree size classes, species, and sites. We modeled relationships between times series of annual basal area increment (ΔBA) and yearly climate variables for individual trees; this approach obviated key statistical criticisms of "traditional" tree‐ring analysis methods. Time series of annual basal area increment were detrended a priori for size, age, legacy, and competition effects. We found that the overall climate signal in our time series of ΔBA was weak; <6% of the interannual variance was explained by climate variables. Nevertheless, there were clear patterns in climate–growth relationships related to tree size and species. Relationships between ΔBA and five climate variables increased in strength with tree size class; large trees were most sensitive to annual climate fluctuations and accounted for ~71% of the overall climate effect on growth across all trees and sites. In all stands, ΔBA variance explained by climate variables was stable over the 20th century for large trees but decreased in the 1940s for small trees, indicating a temporal reduction in sensitivity to annual fluctuations in five climate variables. In coastal forests, relationships between ΔBA and climate for Callitropsis nootkatensis were significantly different in direction and magnitude than those of co‐occurring Pinaceae species. The effect of climate on tree growth was idiosyncratic among stands and could not be discriminated by forest type (coastal vs. interior). Our individual‐tree modeling approach adds to a growing body of research providing novel insights about the complexities of tree growth responses to climate variability and the challenges associated with predicting future tree growth and forest productivity using tree‐ring data. [ABSTRACT FROM AUTHOR]

Old‐growth forests are optimal habitats for many woodpeckers, which are often themselves excellent indicators of deadwood‐associated biodiversity. Old‐growth forests are, however, heterogeneous ecosystems in terms of structure, composition, and deadwood characteristics, thus implying a varied use of these forests by woodpeckers. In boreal landscapes, old‐growth stands are threatened by forest harvesting; however, there is little information in regard to the consequences for biodiversity with the loss of specific types of old‐growth forests. This study aimed to assess how the black‐backed woodpecker (Picoides arcticus), a biodiversity indicator species associated with old‐growth forest attributes, uses different types of old‐growth forests for its foraging needs. We identified woodpecker foraging marks in 24 boreal old‐growth forest stands in eastern Canada that were dominated by black spruce (Picea mariana), located within the home range of eight black‐backed woodpeckers. We identified the various old‐growth forest types using a typology based on the structural attributes of old‐growth stands. We classified the sampled stands into four old‐growth forest types, corresponding to different successional stages (recent or old, relative to the onset of the old‐growth stage), composition (pure black spruce or mixed black spruce–balsam fir [Abies balsamea]), and productivity (ongoing paludification or not). The black‐backed woodpecker foraged in all types of old‐growth forests, but favored dense old‐growth forests that were not paludified and that showed a high temporal continuity (i.e., old‐growth dynamics probably started more than a century ago). The temporal continuity of the old‐growth state allows for the continuous supply of large, slightly decayed snags, the preferred foraging substrates of the black‐backed woodpecker. The old‐growth forest type most favored by this woodpecker is, however, also the forest type most often targeted first by logging operations. Protecting the biodiversity associated with recent deadwood in managed areas thus requires maintaining a sufficient area and density of dense, old‐growth black spruce‐dominated forests in managed areas. [ABSTRACT FROM AUTHOR]

[Display omitted] • Climate zone shifts of northeastern US and maritime Canada delineated and characterized. • Based on differing spatial resolutions, optimal zones of 3, 9, 15, and 21 were determined. • Current high diversity of distinct climate zones in region is anticipated to decrease. • Projected shifts have important implications for regional forest structure and productivity. Climate zones play a significant role in shaping the forest ecosystems located within them by influencing multiple ecological processes, including growth, disturbances, and species interactions. Therefore, delineation of current and future climate zones is essential to establish a framework for understanding and predicting shifts in forest ecosystems. In this study, we developed and applied an efficient approach to delineate regional climate zones in the northeastern United States and maritime Canada, aiming to characterize potential shifts in climate zones and discuss associated changes in forest ecosystems. The approach comprised five steps: climate data dimensionality reduction, sampling scenario design, cluster generation, climate zone delineation, and zone shift prediction. The climate zones in the study area were delineated into four different orders, with increasing subzone resolutions of 3, 9, 15, and 21. Furthermore, projected climate normals under Shared Socioeconomic Pathways 4.5 and 8.5 scenarios were used to predict the shifts in climate zones until 2100. Our findings indicate that climate zones characterized by higher temperatures and lower precipitation are expected to become more prevalent, potentially becoming the dominant climate condition across the entire region. Thes changes are likely to alter regional forest composition, structure, and productivity. In short, such shifts in climate underscore the significant impact of environmental change on forest ecosystem dynamics and carbon sequestration potential. [ABSTRACT FROM AUTHOR]

Questions: The relationships between biodiversity and ecosystem functioning (BEF) vary largely across natural ecosystems, with a unimodal, monotonous linear or no relationship. However, it remains unclear how BEF relationships vary under global change. Given future predicted changes in precipitation and nitrogen (N) deposition, it is crucial to determine how precipitation change and N deposition affect grassland biodiversity and productivity, and regulate their relationships. Location: A Dry Mixed-Grass Prairie of western Canada. Methods: We established a manipulative field experiment of increased precipitation (water addition with approximately 15% and 30% more monthly precipitation) and N addition (10 g/m² ) using a randomized complete block design, including six treatments, each replicated five times (30 plots). We conducted vegetation sampling with a 1 m × 1 m quadrat in each plot from 2016 to 2017, to examine the individual and interactive effects of water and N addition on plant diversity, functional group composition, above- and below-ground productivity, and the diversity–productivity relationships. Results: We found a positive linear diversity–above-ground biomass (AGB) relationship under increased precipitation, which was attributed to the water-induced increase in the abundance of forbs in the plant community, further promoting the positive effect of plant diversity on AGB. However, N addition caused a negative linear diversity–AGB relationship by increasing AGB and reducing plant diversity. The effects of N on diversity and productivity can be further strengthened under increased precipitation, which was due to the increase of C3 rhizomatous grasses with high above- and below-ground biomass and the decrease of forbs with high richness. Conclusions: Our results suggest that changes in functional group composition determine the plant species’ diversity, productivity, and their relationships under increasing precipitation and N deposition, which has significant implications for understanding and modelling ecosystem productivity in the context of global change. [ABSTRACT FROM AUTHOR]

Background: Assessing cumulative effects of anthropogenic and natural disturbances on forest carbon (C) stocks and fluxes, because of their relevance to climate change, is a requirement of environmental impact assessments (EIAs) in Canada. However, tools have not been developed specifically for these purposes, and in particular for the boreal forest of Canada, so current forest C assessments in EIAs take relatively simple approaches. Here, we demonstrate how an existing tool, the Generic Carbon Budget Model (GCBM), developed for national and international forest C reporting, was used for an assessment of the cumulative effects of anthropogenic and natural disturbances to support EIA requirements. We applied the GCBM to approximately 1.3 million ha of upland forest in a pilot study area of the oil sands region of Alberta that has experienced a large number of anthropogenic (forestry, energy sector) and natural (wildfire, insect) disturbances. Results: Over the 28 years, 25% of the pilot study area was disturbed. Increasing disturbance emissions, combined with declining net primary productivity and reductions in forest area, changed the study area from a net C sink to a net C source. Forest C stocks changed from 332.2 Mt to 327.5 Mt, declining by 4.7 Mt at an average rate of 0.128 tC ha−1 yr−1. The largest cumulative areas of disturbance were caused by wildfire (139,000 ha), followed by the energy sector (110,000 ha), insects (33,000 ha) and harvesting (31,000 ha) but the largest cumulative disturbance emissions were caused by the energy sector (9.5 Mt C), followed by wildfire (5.5 Mt C), and then harvesting (1.3 Mt C). Conclusion: An existing forest C model was used successfully to provide a rigorous regional cumulative assessment of anthropogenic and natural disturbances on forest C, which meets requirements of EIAs in Canada. The assessment showed the relative importance of disturbances on C emissions in the pilot study area, but their relative importance is expected to change in other parts of the oil sands region because of its diversity in disturbance types, patterns and intensity. Future assessments should include peatland C stocks and fluxes, which could be addressed by using the Canadian Model for Peatlands. [ABSTRACT FROM AUTHOR]

Trees provide vital global ecosystem services, including carbon sequestration and biodiversity conservation, among others. Further, trees play an important role in regulating climate because of their role in complex water and carbon cycles, and other climate feedback mechanisms. Thus, understanding influences on their growth and productivity is important for gaining insight into current and future climatic conditions. Research has shown that tree height within forests is a significant indicator of the tree's health as well as overall forest productivity. This study aims to add to understanding of how stress factors might influence tree growth and how trees might adapt to stressed conditions by comparing two sites in Canada's sub-Arctic, near Schefferville, Quebec. The methodology involved collecting and analyzing tree core samples taken from trees in the two sites: one 'stressed' and a second 'ideal' or 'non-stressed.' Analysis of the tree cores found no statistically significant difference in trunk circumference (or diameter) growth between the stressed and ideal forests. This arguably indicates that trees in both plots had similar amounts of water to facilitate their annual growth. However, comparisons of annual average tree height and vertical growth found highly statistically significant differences. Trees in the stressed forest grew slower vertically (but not in thickness) than trees in the ideal forest, and they reached lower total height--by a factor of almost two. If it is assumed that the stressed forest under study constitutes a random sample of trees that comes from a population of "all stressed forests," and similarly for the "ideal forest," then we may conclude that stressed forests--ones exposed to heavy winds and facing unreliable water supply--tend to produce shorter and slower-growing trees than forests under "ideal" conditions. Equally, the non-significance of the width-growth variable can indicate that it is not necessarily true that tree-width and tree-width-growth-rate are adversely affected by a stressed environment. [ABSTRACT FROM AUTHOR]

Copyright of Forestry Chronicle is the property of Canadian Institute of Forestry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The claim that changes in atmospheric composition and climate have enhanced the growth rate of trees is prevalent in science, yet it is not supported by many recent tree ring studies. In this study, we analyzed historical time trends in stemwood biomass growth derived from black spruce (Picea mariana (Mill.) BSP) trees at 248 plots across Canada. The sample consisted of trees that were live and dominant at the time of sampling (LDS). Observations of stemwood biomass of LDS trees at a reference age of 75 years (Bsw75,LDS) increased by 154 to 321% over 1901–2001 depending on the method of trend estimation. Simulations from a calibrated individual‐based Growth and Yield model—forced with varying degrees of hypothetical trend in tree growth—were used to estimate the proportion of trend that could be attributed to intrinsic factors, including artefacts introduced by sampling from LDS trees instead of from the population of trees. Imposing no time trend in simulated tree growth, stemwood biomass of 75‐year‐old LDS trees (Bsw75,LDS,Model) increased by 63% (41 to 85% CI). We conclude that the remaining variation in growth of LDS trees (154 to 321% minus 63% = 91 to 258%) can be attributed to net extrinsic forcing. The scaling relationship between LDS and population trees further suggested that stemwood biomass growth of the population (Gsw75,POP) increased by 47 to 82%. By accounting for both natural dynamics and artefacts of the sampling design in estimation of net intrinsic forcing, we gained confidence that growth rate of black spruce trees across Canada increased significantly over 1901–2001. While growth enhancement is consistent with beneficial effects of increasing levels of reactive nitrogen, carbon dioxide, and warming, there remains uncertainty in the degree that applied procedures fully account for known sampling artefacts. Key Points: Tree ring observations indicate that growth of black spruce trees increased between 1901 and 2001 over boreal forests of CanadaSamples represent trees that were live and dominant at time of sampling, which confounds the attribution of trend to environmental changeAdjusting trends in growth to account for natural dynamics suggested that environmental changes collectively drove an increase in growth of 47–82% [ABSTRACT FROM AUTHOR]

Landscape‐scale reconstruction and prescription of soil cover systems following oil sands mining is challenging due to the quality of available reclamation materials and the subhumid climate of the Boreal Plains of Canada. In an experimental reclaimed watershed (Sandhill Fen Watershed), basin‐scale upland landforms (i.e., hummocks) were designed to provide groundwater to adjacent lowlands, necessitating adequate recharge following establishment of forest vegetation. Volumetric water contents, soil water pressure heads, and groundwater levels were monitored for four years throughout the watershed and used to calibrate and verify numerical models in HYDRUS. Using a variably saturated two‐dimensional domain, we identified a threshold‐like relationship between recharge (or upflux) and upland hummock height, where upland hummocks not tall enough to limit root water uptake from the saturated zone decreased recharge or resulted in net upflux. Recharge varied with soil cover texture (higher in coarser‐textured) and associated soil hydraulic parameters. Furthermore, scenario tests indicated the importance and relative influence that maximum rooting depths, forest floor placement thicknesses, and leaf area indices (all associated with forest development) had on recharge. Simulations utilizing a historical climate record indicated that interannual climatic variability was as influential as variation in soil cover texture in determining recharge. Reclamation practitioners should recognize that the water balances of reconstructed landscapes are largely influenced by the trade‐off between optimizing forest productivity and sourcing water to downgradient landscape positions. Key Points: A tradeoff exists between optimizing forest productivity and facilitating groundwater recharge at reclaimed mines in sub‐humid regionsRecharge exhibited a threshold‐like relationship to landform height, driven by the distance between the water table and rooting zone.Factors associated with forest development, such as maximum rooting depth, were key controls on recharge over the long‐term. [ABSTRACT FROM AUTHOR]

Abstract: Community and ecosystem changes are happening in the pristine boreal forest ecosystem of the Yukon for 2 reasons. First, climate change is affecting the abiotic environment (temperature, rainfall and growing season) and driving changes in plant productivity and predator–prey interactions. Second, simultaneously change is occurring because of mammal species reintroductions and rewilding. The key ecological question is the impact these faunal changes will have on trophic dynamics. Primary productivity in the boreal forest is increasing because of climatic warming, but plant species composition is unlikely to change significantly during the next 50–100 years. The 9–10‐year population cycle of snowshoe hares will persist but could be reduced in amplitude if winter weather increases predator hunting efficiency. Small rodents have increased in abundance because of increased vegetation growth. Arctic ground squirrels have disappeared from the forest because of increased predator hunting efficiency associated with shrub growth. Reintroductions have occurred for 2 reasons: human reintroductions of large ungulates and natural recolonization of mammals and birds extending their geographic ranges. The deliberate rewilding of wood bison (Bison bison) and elk (Cervus canadensis) has changed the trophic structure of this boreal ecosystem very little. The natural range expansion of mountain lions (Puma concolor), mule deer (Odocoileus hemionus) and American marten (Martes americana) should have few ecosystem effects. Understanding potential changes will require long‐term monitoring studies and experiments on a scale we rarely deem possible. Ecosystems affected by climate change, species reintroductions and human alteration of habitats cannot remain stable and changes will be critically dependent on food web interactions. [ABSTRACT FROM AUTHOR]

Forest age is an important variable for assessments of biodiversity and habitat, sustainable forest and land management, as well as forest carbon science and modeling. Tree and stand age are typically measured directly on site, or estimated through visual photo interpretation, with spatially explicit maps of forest age not often produced over large areas. Remote sensing enables the generation of wall-to wall, spatially explicit maps of disturbance events within the satellite record; however, as disturbance is relatively rare on the landscape in a given year, additional means of determining forest age are required. As reviewed herein, the estimation of forest age using optical Earth observation data is challenging due to the limited spectral link to the attribute of interest, especially as forests get older. The temporally dictated multi-method approach to forest age estimation outlined herein acknowledges these limitations, by applying the approach that is best suited to the quality of the information available, depending on the epoch of interest. In this research, we combine three approaches to estimate forest age at a 30-m spatial resolution using Landsat data. The first approach uses change detection protocols to detect disturbance from 1985 to 2019, with time since disturbance used as a proxy for forest age. The second approach uses Landsat surface reflectance composites to identify pixels exhibiting evidence of recovery from a disturbance that occurred within the twenty years prior to 1985, allowing for the extension of forest age estimates to 1965. Finally, given an understanding of the linkage between forest age and canopy height, inverted allometric equations are coupled with maps of forest structure and productivity metrics to model forest age for those pixels that show no evidence of disturbance or recovery to a maximum of 150 years, acknowledging that uncertainty in age estimate increases with increasing age. Combining these three approaches, forest age estimates are made for every treed pixel found within the 650 Mha forested ecosystems of Canada. Nationwide, mean estimated forest age for forests ≤150 years old (representing 94.1% of treed area) was 70 years (standard deviation = 32.1 years). For confidence building, forest age estimates were compared to reported forest age in the National Forest Inventory (NFI) both spatially and aspatially. Nationally, 5.9% of the forested area was estimated to be older than 150 years, while 9.5% of area within in the NFI sample was recorded as older than 150 years. The median estimated forest age for forested pixels ≤150 years old was 68 years while median forest age reported in the NFI was 73 years, with regional variability matching expectations related to disturbance regimes and productivity. Spatially explicit maps of forest age provide important information for understanding forest ecosystems and can be used to inform a wide range of policy, science, and management needs. • Forest age was estimated at 30-m scale across all of Canada's forested ecosystems. • Three approaches were used to estimate age depending on temporal era. • Agreement with forest inventory recorded age decreased as estimated age increased. • Nationally, mean estimated age for forests <150 years old was 70 years. • 5.9% of Canada's forested area has an age of >150 years. [ABSTRACT FROM AUTHOR]

Ecosystem-based management advocates that forestry disturbances should aim to emulate natural disturbances to mitigate the landscape-level impact of forest management. This study compares the impact of clear-cuts followed by a prescribed burn (CCPB) with clear-cuts alone (CC) and current careful logging practices (CLAAG: 'careful logging around advanced growth') on understory composition within black spruce ( Picea mariana Miller (BSP)) paludified forest stands at the plot, site, and treatment levels using a functional-type approach. Vascular and nonvascular taxa showed significant differences in composition at the plot level among treatments. We found that pioneer taxa occurred mainly in CCPB sites, while late-successional taxa characterized CC sites. CLAAG sites had higher taxa richness than CCPB and CC sites, and we found that CCPB treatments were most likely to promote vascular taxa compositions that are more similar to those observed after natural disturbances. Additionally, the relative abundance of Sphagnum spp., responsible for paludification, was significantly reduced in sites treated by prescribed burning. This study therefore presents results suggesting that prescribed burning might represent a sustainable alternative to current harvesting techniques in the Clay Belt of eastern Canada that could help in preserving biodiversity (in terms of understory species assemblage) while maintaining or even enhancing forest productivity. [ABSTRACT FROM AUTHOR]

Some regenerating stands of the boreal forest exhibit low juvenile growth after major disturbances, which compromises sustainable forest management objectives. In black spruce - feather moss stands of eastern Canada subject to paludification, careful logging methods could decrease stand productivity with time by preventing a beneficial reduction in organic soil thickness. The aim of this project was to confirm decreases in juvenile growth between stands originating from careful logging and the former stands originating from old fires on the same sites. Stem analyses showed that stands originating from CPRS had significantly better juvenile height growth than the former stands but significantly lower growth than stands originating from recent fire in the study region. If organic matter thickness apparently played a role in the growth differences observed between fire and harvesting, it was not the only factor determining stand productivity. According to our results, cohort status, climatic regime, and quality of the residual organic matter are other factors that seem to drive productivity. Our results show that postharvest management approaches (e.g., site preparation) should be used to increase yields after harvest for the sites to express their full growth potential. [ABSTRACT FROM AUTHOR]

The recovery of forests following stand-replacing disturbance is of widespread interest; however, there is both a lack of definitional clarity for the term “recovery” and a dearth of empirical data on the rates of forest recovery associated with different disturbance types. We conducted a quantitative review of literature to determine recovery times following wildfire and timber harvest and to evaluate variation in recovery rates across Canada’s diverse forest ecosystems. Recovery was assessed according to the rate of change associated with certain forest structural attributes that have traditionally been used as indicators of forest growth and productivity. The recovery of forest canopy cover, tree height, and stand basal area varied at rates that depended on disturbance type, forest biome, and ecozone. We found that, on average, it took 5–10 years, depending on factors such as location and species, for most forest ecosystems of Canada to attain a benchmark canopy cover of 10% after wildfire or harvest. Similarly, regenerating stands in Canada’s boreal forests were capable of attaining average heights of 5 m within five to ten years after wildfire or harvest. Stands in the Boreal Plains ecozone post-harvest reached stand basal area, benchmarked at 10 m 2 ha −1 , faster than those in the Boreal Shield, attributable to differences in tree species composition and the rich mineral deposits of the Boreal Plains. Overall, recovery of canopy cover, tree height, and stand basal area was similar or more rapid following wildfire than harvest. Our review provides temporal benchmarks for gauging recovery times after disturbance. Building upon these temporal benchmarks, and conditioned by disturbance type, site conditions, and location, we present opportunities for using dense time series of remotely sensed data to inform on regional and national trends in forest recovery following disturbance. [ABSTRACT FROM AUTHOR]

• Context: The Canadian forest industry is turning its attention towards the unmanaged areas at higher latitudes, where the forest resource is still poorly understood because of lack of accessibility. Despite a lower productivity in terms of volume, northern stands are expected to produce wood of higher quality, which may make these areas attractive for management and production. • Aims: This study aims to test the hypothesis that trees at high latitudes produce wood with better basic properties than trees at lower latitudes. • Methods: Growth and wood characteristics were assessed according to cambial age in 25 black spruce ( Picea mariana) trees from five sites located along an alti-latitudinal gradient in Quebec. • Results: Sites at higher latitudes and altitudes exhibited slower growth rates and lower stem volume. Wood density and mechanical properties were higher in the sites located at lower latitudes or altitudes. Fiber size had higher values in southern sites, but only at younger ages. Principal component analysis confirmed these results, with the northernmost site being the one where growth, density and mechanical properties were generally lowest. • Conclusion: The reduction in growth was not compensated by increases in the basic properties of wood. More extensive samplings are needed to validate the results at larger scale. [ABSTRACT FROM AUTHOR]

This study estimates the potential physical amounts and financial costs of post-harvest forest residue biomass supply in Canada. The analyses incorporate the locations of harvest activities in Canada, the geographical variation of forest productivity patterns and the costs associated with the extraction and transportation of residue feedstock to bioenergy facilities. We estimated the availability of harvest residues within the extent of industrial forest management operations in Canadian forests. Our analyses focused on the extraction of biomass from roadside harvest residues that involve four major cost components: pre-piling and aggregation, loading, chipping and transportation. The estimates of residue extraction costs also included representation of basic ecological sustainability and technical accessibility constraints. Annual supply of harvestable residual biomass with these ecological sustainability constraints were estimated to be approximately 19.2–23.3 Tg * year −1 and 16.5–20.0 Tg * year −1 in scenarios that included both ecological and technical accessibility limitations. These estimates appear to be less than other similar studies, due to the higher level of spatial details on inventories and ecological and operational constraints in our analyses. The amount of residual biomass available in baseline scenarios at a supply cost of $60 ODT −1 and $80 ODT −1 were 1.08 and 1.38 Tg year −1 and 7.82 and 10.14 Tg year −1 respectively. Decreasing residue extraction costs by 35% increased the amount of residues available at a $60 ODT −1 and $80 ODT −1 supply price by ∼5.5–5.7 and ∼1.5–1.6 times respectively. The assessment methodology is generic and could be extended to examine residue supplies for specialized biomass markets such as lignocellulosic ethanol production. [ABSTRACT FROM AUTHOR]

Understanding boreal/hemi-boreal forest growth sensitivity to seasonal variations in temperature and water availability provides important basis for projecting the potential impacts of climate change on the productivity of these ecosystems. Our best available information currently comes from a limited number of field experiments and terrestrial biosphere model (TBM) simulations of varying predictive accuracy. Here, we assessed the sensitivity of annual boreal/hemi-boreal forest growth in Canada to yearly fluctuations in seasonal climate variables using a large tree-ring dataset and compared this to the climate sensitivity of annual net primary productivity (NPP) estimates obtained from fourteen TBMs. We found that boreal/hemi-boreal forest growth sensitivity to fluctuations in seasonal temperature and precipitation variables changed along a southwestern to northeastern gradient, with growth limited almost entirely by temperature in the northeast and west and by water availability in the southwest. We also found a lag in growth climate sensitivity, with growth largely determined by the climate during the summer prior to ring formation. Analyses of NPP sensitivity to the same climate variables produced a similar southwest to northeast gradient in growth climate sensitivity for NPP estimates from all but three TBMs. However, analyses of growth from tree-ring data and analyses of NPP from TBMs produced contrasting evidence concerning the key climate variables limiting growth. While analyses of NPP primarily indicated a positive relationship between growth and seasonal temperature, tree-ring analyses indicated negative growth relationships to temperature. Also, the positive effect of precipitation on NPP derived from most TBMs was weaker than the positive effect of precipitation on tree-ring based growth: temperature had a more important limiting effect on NPP than tree-ring data indicated. These mismatches regarding the key climate variables limiting growth suggested that characterization of tree growth in TBMs might need revision, particularly regarding the effects of stomatal conductance and carbohydrate reserve dynamics., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Forest productivity is driven by a suite of direct climatic and non-climatic factors that are transient or permanent. The kind of productivity driver and the nature of their effects vary by species, and scale dependencies potentially complicate these relationships. This study explored productivity-driver relations in eastern Boreal Canada and determined spatial effects in productivity control when expressed with stand dominant height at a reference age (site index). Data from 4,217 temporary sample plots obtained from boreal mixedwood and conifer bioclimatic domains, and with varied species composition, were used in this study. A single-level global model that assumes equal sensitivities across spatial scales was calibrated and compared with three alternative models reflecting different hypotheses on possible spatial heterogeneities. Alternative models were calibrated by plot-level soil deposit types (microscale), landscape dominant deposits (mesoscale) and bioclimatic domains (macroscale). A marked difference between the global and alternative models was observed, suggesting that a single global model does not sufficiently reflect existing heterogeneity in productivity-driver relationships. A combination of macro- and microscale models provided the best explanation of site index. Results further showed that site index is mainly driven by species composition (complementarity effects of aspen and jack pine compositions) and stand diameter structural diversity effects. It is concluded that successional changes, more than direct climatic effects, drive productivity. [ABSTRACT FROM AUTHOR]

The structure and productivity of boreal forests are key components of the global carbon cycle and impact the resources and habitats available for species. With this research, we characterized the relationship between measurements of forest structure and satellite-derived estimates of gross primary production (GPP) over the Canadian boreal. We acquired stand level indicators of canopy cover, canopy height, and structural complexity from nearly 25,000 km of small-footprint discrete return Light Detection and Ranging (Lidar) data and compared these attributes to GPP estimates derived from the MODerate resolution Imaging Spectroradiometer (MODIS). While limited in our capacity to control for stand age, we removed recently disturbed and managed forests using information on fire history, roads, and anthropogenic change. We found that MODIS GPP was strongly linked to Lidar-derived canopy cover ( r = 0.74, p < 0.01), however was only weakly related to Lidar-derived canopy height and structural complexity as these attributes are largely a function of stand age. A relationship was apparent between MODIS GPP and the maximum sampled heights derived from Lidar as growth rates and resource availability likely limit tree height in the prolonged absence of disturbance. The most structurally complex stands, as measured by the coefficient of variation of Lidar return heights, occurred where MODIS GPP was highest as productive boreal stands are expected to contain a wider range of tree heights and transition to uneven-aged structures faster than less productive stands. While MODIS GPP related near-linearly to Lidar-derived canopy cover, the weaker relationships to Lidar-derived canopy height and structural complexity highlight the importance of stand age in determining the structure of boreal forests. We conclude that an improved quantification of how both productivity and disturbance shape stand structure is needed to better understand the current state of boreal forests in Canada and how these forests are changing in response to changing climate and disturbance regimes. [ABSTRACT FROM AUTHOR]

Simultaneous biometric measurements of aboveground net primary production (ANPP) and eddy-covariance measurements of gross primary production (GPP) were made at 18 forest stands with 80 site-years of data across Canada – to assess the fraction of photosynthesis that is used to produce plant tissues and the consistency of carbon allocation patterns across forest ecosystems. The stands included boreal and temperate forests and spanned very young to mature stand ages. Across all sites, ANPP averaged 298±138gCm−2 yr−1 (mean±1 s.d.), with the highest values for temperate white pine plantations (307–630gCm−2 yr−1) and harvested Douglas-fir stands (219–459gCm−2 yr−1), and the lowest values for boreal harvested jack pine stands (97–185gCm−2 yr−1). ANPP more than doubled from newly established (≤12 years) to young (13–25 years) stands, then stabilized in young to mature (≥51 years) stands but with diverging trends among species. Inter-site variations in ANPP and GPP were closely related to site characteristics, in particular, to leaf area index, which explained 66% of the variation in ANPP and 80% of the variation in GPP, and absorbed photosynthetically active radiation, which explained 80% of the variation in ANPP and 82% of the variation in GPP. Both ANPP and GPP were also positively correlated with mean annual air temperature, mean annual precipitation, and total soil nitrogen in the upper 10cm of the mineral soil. ANPP was strongly, positively correlated with GPP and the ANPP/GPP ratio was relatively constant (0.29±0.06), with no consistent differences among species or age classes. The results support the use of a constant ANPP/GPP ratio as a reasonable assumption in models of forest productivity for boreal and northern temperate forests. A similar conclusion is reached for the NPP/GPP ratio when published values of belowground NPP are considered. [ABSTRACT FROM AUTHOR]

Attack by the white pine weevil has notably reduced Sitka spruce productivity in British Columbia (BC) (Canada) and western US. By the 1970s, the BC Ministry of Forests established provenance trials of Sitka spruce with the objective of detecting usable genetic resistance to weevil. These early trials reported significant weevil resistance and allowed the production of the first (F1) controlled-cross progeny generation with demonstrable weevil resistance (R) or susceptibility (S). This study reports results of the screening for weevil resistance and the levels of constitutive defenses of this F1 Sitka spruce progeny. Progeny from resistant parents (R × R progeny) sustained significantly fewer weevil attacks than progeny from susceptible parents (S × S progeny) or progeny with one resistant and one susceptible parent (R × S progeny). Individual and family heritability estimates of the weevil resistance were 0.5 and 0.9, respectively. Constitutive defenses, measured by resin canal and sclereid cell density in the cortex, were significantly higher in R × R progeny than in R × S or S × S progeny. We observed a negative correlation between the percentage of trees attacked in each cross and the average density of the resin canals or sclereid cells for each cross. [ABSTRACT FROM AUTHOR]

Copyright of Forestry Chronicle is the property of Canadian Institute of Forestry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: The increasing commercial interest and advancing exploitation of new remote territories of the boreal forest require deeper knowledge of the productivity of these ecosystems. Canadian boreal forests are commonly assumed to be evenly aged, but recent studies show that frequent small-scale disturbances can lead to uneven-aged class distributions. However, how age distribution affects tree growth and stand productivity at high latitudes remains an unanswered question. Dynamics of tree growth in even- and uneven-aged stands at the limit of the closed black spruce (Picea mariana) forest in Quebec (Canada) were assessed on 18 plots with ages ranging from 77 to 340 years. Height, diameter and age of all trees were measured. Stem analysis was performed on the 10 dominant trees of each plot by measuring tree-ring widths on discs collected each meter from the stem, and the growth dynamics in height, diameter and volume were estimated according to tree age. Although growth followed a sigmoid pattern with similar shapes and asymptotes in even- and uneven-aged stands, trees in the latter showed curves more flattened and with increases delayed in time. Growth rates in even-aged plots were at least twice those of uneven-aged plots. The vigorous growth rates occurred earlier in trees of even-aged plots with a culmination of the mean annual increment in height, diameter and volume estimated at 40–80 years, 90–110 years earlier than in uneven-aged plots. Stand volume ranged between 30 and 238m3 ha−1 with 75% of stands showing values lower than 120m3 ha−1 and higher volumes occurring at greater dominant heights and stand densities. Results demonstrated the different growth dynamics of black spruce in single- and multi-cohort stands and suggested the need for information on the stand structure when estimating the effective or potential growth performance for forest management of this species. [Copyright &y& Elsevier]

Abstract: The utility of site index as a predictor variable in models for complex, mixed species stands is limited because the site index concept is not well suited for these stand types. Additionally, there is no standard protocol of estimating site index for uneven-aged mixed species stands, which is evident in permanent sample plot (PSP) and co-operative (COOP) data sets available from the Province of Ontario, Canada. Under such circumstances, an alternative to site index in a basal area increment model was explored, using a combination of climate and Forest Ecosystem Classification (FEC) variables from the Ontario boreal region. Among the four candidate climate variables chosen, mean annual temperature (MAT) explained the most variability in basal area increment for the four selected tree species – trembling aspen (Populus tremuloides Michx.), balsam fir (Abies balsamea (L.) Mill.), jack pine (Pinus banksiana Lamb.), and black spruce (Picea mariana (Mill.) B.S.P.). Our results indicated that a combination of the climate variable, MAT, and FEC explained a substantially higher proportion of variation in the basal area increment than site index alone. Thus, climate and FEC variables are superior substitutes in the basal area increment model even when error-free site index values are possible to obtain. [Copyright &y& Elsevier]

In many northern forest ecosystems, soil organic matter accumulation can lead to paludification and forest productivity losses. Paludification rate is primarily influenced by topography and time elapsed since fire, two factors whose influence is often confounded and whose discrimination would help forest management. This study, which was conducted in the black spruce (Picea mariana (Mill.) BSP) boreal forest of northwestern Quebec (Canada), aimed to (1) quantify the effect of slope and time since fire on paludification rates, (2) determine whether soil organic layer depth could be estimated by surface variables that can potentially be remotely sensed, and (3) relate the degree of paludification to tree productivity. In this study, soil organic layer depth was used as an estimator of the degree of paludification. Slope and postfire age strongly affected paludification dynamics. Young stands growing on steep slopes had thinner organic layers and lower organic matter accumulation rates compared with young stands growing on flat sites. Black spruce basal area and Sphagnum cover were strong predictors of organic layer depth, potentially allowing mapping of paludification degree across the landscape. Tree productivity was negatively related to organic layer depth (R2 = 0.57). The equations developed here can be used to quantify forest productivity decline in stands that are undergoing paludification, as well as potential productivity recovery given appropriate site preparation techniques. [ABSTRACT FROM AUTHOR]

Aim Comparisons of the biotas in the Palaearctic and Nearctic have focused on limited portions of the two regions. The purpose of this study was to assess the geographic pattern in the abundance, species richness, and importance of different migration patterns of the boreal forest avifauna of Eurasia from Europe to East Asia as well as their relationship to climate and forest productivity. We further examine data from two widely separated sites in the New World to see how these conform to the patterns found in the Eurasian system. Location Boreal forest sites in Russia and Canada. Methods Point counts were conducted in two to four boreal forest habitats at each of 14 sites in the Russian boreal forest from near to the Finnish border to the Far East, as well as at two sites in boreal Canada. We examined the abundance and species richness of all birds, and specific migratory classes, against four gradients (climate, primary productivity, latitude, and longitude). We tested for spatial autocorrelation in both dependent and independent variables using Moran’s I to develop spatial correlograms. For each migratory class we used maximum likelihood to fit models, first assuming uncorrelated residuals and then assuming spatially autocorrelated residuals. For models assuming unstructured residuals we again generated correlograms on model residuals to determine whether model fitting removed spatial autocorrelation. Models were compared using Akaike’s information criterion, adjusted for small sample size. Results Overall abundance was highest at the eastern and western extremes of the survey region and lowest at the continent centre, whereas the abundance of tropical and short-distance migrants displayed an east–west gradient, with tropical migrants increasing in abundance in the east (and south), and short-distance migrants in the west. Although overall species richness showed no geographic pattern, richness within migratory classes showed patterns weaker than, but similar to, their abundance patterns described above. Overall abundance was correlated with climate variables that relate to continentality. The abundances of birds within different migration strategies were correlated with a second climatic gradient – increasing precipitation from west to east. Models using descriptors of location generally had greater explanatory value for the abundance and species-richness response variables than did those based on climate data and the normalized difference vegetation index (NDVI). Main conclusions The distribution patterns for migrant types were related to both climatic and locational variables, and thus the patterns could be explained by either climatic regime or the accessibility of winter habitats, both historically and currently. Non-boreal wintering habitat is more accessible from both the western and eastern ends than from the centre of the boreal forest belt, but the tropics are most accessible from the eastern end of the Palaearctic boreal zone, in terms of distance and the absence of geographical barriers. Based on comparisons with Canadian sites, we recommend that future comparative studies between Palaearctic and Nearctic faunas be focused more on Siberia and the Russian Far East, as well as on central and western Canada. [ABSTRACT FROM AUTHOR]

This study examines the long-term effects of experimental conifer monocultures on stem volume and soil chemistry. Replicated plots of black spruce (Picea mariana), white spruce (Picea glauca), and red pine (Pinus resinosa) were planted in 1950 at three spacings (1.8, 2.7, and 3.6 m) on a briefly cultivated agricultural field on glaciolacustrine sandy loam soil near Thunder Bay, Ontario, Canada. Stem volumes per hectare and per tree were measured in 2002 (52 years after planting). Surface organic (i.e., forest floor) and mineral soil fertility in terms of pH, total N and P, and extractable NH4-N and P were measured in 2000 (50 years after planting). Of the three species red pine had the highest volume per hectare at all the three spacing followed by white spruce and black spruce; volume for all three species peaked at the 1.8-m spacing. The effects of conifer species on soil physical and chemical properties were more pronounced than spacing effects and the changes were mainly confined to forest floor layer. Few changes in mineral soil properties occurred because of the species and spacing treatments. Per hectare forest floor nutrient pools were higher under white spruce and red pine than black spruce, a pattern likely driven by higher litterfall and forest floor accumulation. It appears that toward the end of first rotation the higher productivity of red pine compared with the other conifers did not come at the cost of reduced soil pools of available NH4, P04, or K, but it was associated with reduced Ca levels in the forest floor. [ABSTRACT FROM AUTHOR]

Measuring net primary productivity of trees requires the measurement of total wood production of branches. Recent work on balsam fir (Abies balsamea) has shown that branch-wood production can be estimated as a function of foliage production. We extend the analysis to four other species found in the Canadian forest: black spruce (Picea mariana), jack pine (Pinus banksiana), Douglas-fir (Pseudotsuga menziesii), and trembling aspen (Populus tremuloides). Results show that the ratio of annual branch-wood production to annual foliage production is about 1.0 for conifer species (between 0.86 and 1.12) and 0.56 for aspen during a nondrought year. An analysis using field measurements of litterfall and stem-diameter increment from selected forested sites shows that branch-wood production accounts for a smaller proportion of aboveground net primary productivity in trembling aspen (15%–20%) than in conifer species (25%). Also, litterfall capture of small branches (<1 cm diameter) accounts for only 33% of branch detritus production in conifers and 50% in trembling aspen. This study supports the use of an alternative method for estimating branch-wood production that reduces the potential bias in field estimates of net primary productivity. [ABSTRACT FROM AUTHOR]

Copyright of Forestry Chronicle is the property of Canadian Institute of Forestry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Compares the response of net ecosystem productivity (NEP) and evaporation in a boreal aspen forest and a black spruce forest in Canada. Relationship between carbon dioxide uptake and evaporation; Strength of carbon source of black spruce forest in warm condition; Basis of the carbon balance of both forests.

Quantifies the relationship between mean age and net primary productivity (NPP) of black spruce stands in Ontario using practical methodology. Definition of mean age-NPP relationship; Approach in reducing uncertainty in NPP estimates; Possibility of measuring NPP components.

Copyright of Forest Ecology & Management is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

As a result of a Class Environmental Assessment, the Ontario Ministry of Natural Resources (OMNR) was mandated to design and implement a research project pertaining to the effects of fulltree harvesting on long-term site productivity. This project, initiated in 1991, was designed to focus on ecosystem processes and the changes occurring to these processes after harvesting (e.g., quantifying the disruption and recovery) for the black spruce working group. A series of replicated, experimental harvest treatments with varying degrees of biomass removal were conducted on nine core study sites, representing different black spruce ecosites located in northwestern Ontario, Canada. The harvest treatments included: uncut — controls, tree length — delimbed at the stump, full tree — delimbed at the roadside, full-tree chipping chipped debris was returned to the harvest plot, and whole tree — complete removal of vegetation and forest floor. Each site consisted of 16 plots, three replicates of the four harvest treatments (30 m × 30 m plots) and four replicates of the control plots (50 m × 50 m plots). Work on this project is anticipated to continue for a minimum of fifteen years to detail the early and most dynamic stages of post-harvest recovery. [ABSTRACT FROM AUTHOR]

ECOLEAP is a Canadian Forest Service research project that is aimed at improving our understanding of the environmental controls on boreal and sub-boreal forest productivity and at developing tools for predicting stand-level forest productivity over large areas. This interdisciplinary project combines, in a coordinated manner, ecophysiological and soils research, remote sensing research, development of scaling up procedures and process modelling of net primary productivity on a common set of field sites. The process research is carried out in different forest types across large climatic and productivity gradients. Remote sensing provides timely stand information such as composition, leaf area, and absorbed radiation that are not currently available in existing spatial databases. A geographic information system is used to integrate the diverse sources of data. Models serve both as integrators of knowledge and as vehicles for the transfer of the information and methodologies to resource managers. Currently there are three interrelated modelling exercises being carried out within ECOLEAP to address different objectives of the project: an empirical, spatially explicit model of site index, a site-specific process model of productivity, and a spatially explicit process model of productivity. Application of the spatially explicit models will be conducted on extensive pilot regions, the first of which is located north of Quebec City. [ABSTRACT FROM AUTHOR]

Highlights the connection between productivity, good work and environmental sustainability on the forest industry in Canada. Status of Canada as exporter of forest products in the world; Discussion on clearcutting; Conclusion.

Climate change is threatening our ability to manage forest ecosystems sustainably. Despite strong consensus on the need for a broad portfolio of options to face this challenge, diversified management options have yet to be widely implemented. Inspired by functional zoning, a concept aimed at optimizing biodiversity conservation and wood production in multiple-use forest landscapes, we present a portfolio of management options that intersects management objectives with forest vulnerability to better address the wide range of goals inherent to forest management under climate change. Using this approach, we illustrate how different adaptation options could be implemented when faced with impacts related to climate change and its uncertainty. These options range from establishing ecological reserves in climatic refuges, where self-organizing ecological processes can result in resilient forests, to intensive plantation silviculture that could ensure a stable wood supply in an uncertain future. While adaptation measures in forests that are less vulnerable correspond to the traditional functional zoning management objectives, forests with higher vulnerability might be candidates for transformative measures as they may be more susceptible to abrupt changes in structure and composition. To illustrate how this portfolio of management options could be applied, we present a theoretical case study for the eastern boreal forest of Canada. Even if these options are supported by solid evidence, their implementation across the landscape may present some challenges and will require good communication among stakeholders and with the public. [ABSTRACT FROM AUTHOR]

Assisted migration of forest tree populations through reforestation and restoration is a climate change adaptation strategy under consideration in many jurisdictions. Matching climates in which seed sources evolved with near future climates projected for plantation sites should help reduce maladaptation and increase plantation health and productivity. For threatened tree species, assisted migration outside of the species range could help avert extinction. Here, we examine lessons, limitations, and challenges of assisted migration through the lens of three assisted migration field trials of conifers in Canada and Mexico: Pinus albicaulis Engelm., an endangered subalpine tree species in the mountains of western North America; the Picea glauca (Moench) Voss × P. engelmannii Parry ex Engelm hybrid complex, of great economic and ecological importance in western Canada, and Abies religiosa (Kunth) Schltdl. & Cham., a tree species that provides overwintering sites for the monarch butterfly. We conclude that: (a) negative impacts of climate change on productivity of Picea glauca × P. engelmannii may be mitigated by planting seed sources from locations that are 3 °C mean coldest month temperature warmer than the plantation; (b) it is possible to establish Pinus albicaulis outside of its current natural distribution at sites that have climates that are within the species' modelled historic climatic niche, although developing disease-resistant trees through selective breeding is a higher priority in the short term; (c) Abies religiosa performs well when moved 400 m upward in elevation and local shrubs (such as Baccharis conferta Kunth) are used as nurse plants; (d) new assisted migration field trials that contain populations from a wide range of climates tested in multiple disparate climates are needed, despite the costs; and (e) where naturalization of a migrated tree species in recipient ecosystem is viewed as undesirable, the invasive potential of the tree species should be assessed prior to large scale establishment, and stands should be monitored regularly following establishment. [ABSTRACT FROM AUTHOR]

• Trees that regenerate after fire tend to produce higher-stiffness wood. • The growth efficiency index is the best predictor of wood traits in the first post-fire cohort. • Time elapsed since the last stand-replacing fire is the best predictor of wood traits in subsequent cohorts. In boreal forests where the fire return interval is long, the high structural variability of stands may affect wood traits. Here, we build on earlier work that revealed a difference in wood mechanical traits of black spruce between regular (regenerated from fire in the last 200 years) and irregular (undisturbed by fire for at least 200 years) stands. This study aimed to identify the ecological drivers of this variation in wood traits. To do so, we first sought to corroborate existing results on the effects of stand structure induced by the time since the last stand-replacing fire (TSLF) on wood mechanical stiffness in the eastern boreal forest of Canada. Results confirmed that black spruce from regular stands tend to produce wood with higher modulus of elasticity (MOE) than those from irregular stands. For both regular and irregular stands, we compared a set of linear models that were defined a priori to determine the structural and site productivity variables having the largest influence on MOE. The 'growth efficiency index' (aboveground woody biomass production per unit leaf area) was the best predictor of MOE variation among regular stands. For irregular stands, the model with TSLF as the sole explanatory variable was a better predictor of MOE than any other candidate model. However, we did not find strong evidence of a direct relationship between TSLF and wood traits, since our best models explained a relatively small proportion of the variance. Our results suggest that differences in wood traits could be attributable to the seed or layer origin of the trees and/or to the length of time trees remain in the understory. We propose that intensive wood production strategies focus on stands of the first post-fire cohort. [ABSTRACT FROM AUTHOR]

Over the past two decades, partial harvesting has been increasingly used in boreal forests as an alternative to clearcutting to promote irregular stand structures and maintain a balance between biodiversity preservation and continued timber production. However, relatively little is still known about the silvicultural potential of partial harvesting in Canada's boreal forest, especially in areas prone to organic matter accumulation (paludification), and most prior research has focused on biodiversity responses. In this study, we assess the effects of partial harvesting on stand development (recruitment, growth, and mortality) ten years after harvesting in previously unmanaged black spruce stands and quantify its effectiveness in reducing the impacts on ecosystem structures. Our analyses revealed that pre-harvest stand structure and site characteristics, especially initial basal area, sapling density, tree diameter, and organic layer thickness (OLT) were major factors involved in stand development ten years following these partial harvesting treatments. Depending on pre-harvest structure and site characteristics, partial harvesting can result in either an increase in post-harvest tree recruitment and growth or a loss of stand volume because of standing tree mortality. To increase the chances of partial harvesting success in ensuring an increase in decennial stand yield after harvest in black spruce forest stands, sites prone to paludification (i.e., where OLT >17 cm) should be left unharvested. This study illustrates the importance of taking into account pre-existing structure and site characteristics in the selection of management strategies to maximize the potential of partial harvesting to achieve sustainable forest management in black spruce stands. [ABSTRACT FROM AUTHOR]

• We modeled how tree mortality will affect wood supply in three regions of Canada. • We project strong declines in biomass due to increased drought and wildfire. • Maintaining long-term sustainable harvesting levels will be extremely challenging. • Canada's future wood supply is highly vulnerable to changes in climate. Climate change poses a serious risk to long-term sustainable forest management, particularly when projecting future wood supply for forestry operations. However, few studies have accounted for the cumulative and interacting impacts of climate change on forest productivity and natural disturbances; even fewer have considered drought impacts when projecting wood supply. We modeled how disturbance- and drought-induced tree mortality will affect wood supply in three regions of Canada's boreal forest over a 200-year period under three climate-forcing scenarios. We project strong declines in overall aboveground biomass due to increases in mortality caused mainly by increased drought and wildfire, particularly in drier, western regions. Using two management strategies, we show that maintaining current long-term sustainable harvesting levels will be extremely challenging depending on the level of anthropogenic climate forcing. Increased wildfire activity under severe climate forcing will strongly decrease the availability of harvestable stands. In western areas that are already water-limited, harvesting levels will need to be low to remain sustainable. Our results show that Canada's future wood supply and sustainable forest management practices are highly vulnerable to changes in climate; hence adaptation actions are needed to lower these vulnerabilities. [ABSTRACT FROM AUTHOR]

• Standard forest inventory methods underestimate tree and stand age in western Canadian boreal forests. • Dendrochronological procedures including ring measurement and cross dating improve age estimates. • Oldest tree in a subsample is better estimate of time since last disturbance than the average age of the subsample. • Reducing uncertainty in tree and stand age critical for several important forest policies and for improving forest models. Tree and stand age are critical information needed for understanding forest ecosystems. Tree age estimates are usually derived from ring counts, but these are not dendrochronological estimates unless procedures like ring measurement and cross-dating are used. Stand age is usually estimated from the mean ring count on a sample of trees. However, the oldest trees may better represent time since stand replacing disturbance. Using a forest inventory dataset from Manitoba, Canada, standard ring counts were found to underestimate true ring counts obtained using dendrochronological procedures for all black spruce (Picea mariana) trees, and older jack pine (Pinus banksiana) and trembling aspen (Populus tremuloides) trees. Data from whole stand reconstruction plots for these same species demonstrated that mean ring counts from a sample of trees underestimate the time since last stand replacing disturbance, particularly for black spruce stands where ring counts at breast height were highly variable among individuals. The evidence in this study, and from similar existing studies, suggests that tree age, stand age, and time since last stand replacing disturbance are more likely underestimated than overestimated in the boreal forest of western Canada. Dendrochronological procedures can improve both the precision and accuracy of tree age estimates, but some aspects of age uncertainty may be irreducible, especially in older stands. Age uncertainty should be more widely acknowledged and where possible incorporated into forest science models. [ABSTRACT FROM AUTHOR]

The article focuses on Canadian Minister of Industry and Networks of Centers of Excellence head Maxime Bernier's announcement of a $3.3 million investment over three years in cutting-edge sustainable forest management projects in British Columbia, Alberta, Ontario and New Brunswick. Bernier also announced a continued investment of $1.2 million in Quebec research projects. According to Bernier, these investments will further improve the productivity and competitiveness for the forest sector. Through this plan, the government is also safeguarding the way of life of forest-dependent communities.