Canadian Boreal Forest Research Articles

Enzymatic demethylation of Kraft lignin for lignin-based phenol-formaldehyde resin applications

Wood-rot fungi from the Boreal Forest of Canada were studied for their ability to demethylate Kraft lignin (KL). Demethylation by the action of enzymes (O-demethylases) removed the O-methyl/methoxyl groups of lignin liberating methanol, and produced a demethylated KL enriched in vicinal-hydroxyl groups with potential to serve as lignin-based phenol-formaldehyde polymers. Screening experiments identified the liberation of methanol (measured by selected-ion flow-tube mass spectrometry), lignin-demethylating enzymes, alcohol oxidase, and other ligninolytic enzymes. Highest amounts of headspace methanol (parts-per-billion) were detected in the genus Aspergillus, Ctenomyces, Cunninghamella, Penicillium, and Sporobolomyces. Methanol generated from lignin demethylation induced alcohol oxidase activity, but which was higher in Aspergillus, Ctenomyces, Entoloma, and non-sporulating fungi. Among the fungi tested, three brown-rot, i.e., Fomitopsis pinicola and Galerina autumnalis and a mitosporic Aspergillus sp.3 BRI 270, were cultured solely on KL, and lignin model compounds (LMCs) to determine lignin demethylation. Various carbohydrate supplements added to nutrient media containing KL significantly influenced demethylating activity. Aspergillus sp.3 BRI 270 showed the highest degree of lignin demethylation (30.1%) which no evidence presented for this comment occurred when cultivated on KL media supplemented with birchwood xylan as analyzed by 1H NMR following O-acetylation of modified KLs. All fungi demonstrated considerable demethylating activity by utilizing softwood KL, but OrganoSolv lignins (poplar, willow, wheat straw, and mixed agricultural wastes), because of their harsh chemical treatments of extraction, affected the microbial and enzymatic demethylation. Extracellular demethylating enzymes from Aspergillus sp.3 BRI 270 generated high vicinal-diol content (measured by the pyrocatechol titanium(III)-nitrilotriacetate method) in LMCs: 4-hydroxy-3-methoxy cinnamaldehyde (326.00 μmol/mL), syringaldehyde (102.67 μmol/mL), and Kraft lignin (397.46 μmol/mL) as analyzed by 1H NMR analysis.

Decline of an ecotone forest: 50 years of demography in the southern boreal forest

AbstractVariation in tree recruitment, mortality, and growth can alter forest community composition and structure. Because tree recruitment and mortality events are generally infrequent, long‐time scales are needed to confirm trends in forests. We performed a 50‐yr demographic census of a forest plot located on the southern edge of the Canadian boreal forest, a region currently experiencing forest die‐back in response to direct and indirect effects of recent severe droughts. Here, we show that over the last 30 yr biomass, basal area, growth, and recruitment have decreased along with a precipitous rise in mortality across the dominant tree species. The stand experienced periods of drought in combination with multiple outbreaks of forest tent caterpillar (Malacosoma disstria) and bark beetles. These insect disturbances interacted to increase mortality rates within the stand and decrease stand density. The interaction of endogenous and exogenous factors may shift forests in this region onto novel successional trajectories with the possibility of changes in regional vegetation type.

Expanding and testing fluorescent amplified fragment length polymorphisms for identifying roots of boreal forest plant species.

Premise of the StudyIdentifying roots to species is challenging, but is a common problem in ecology. Fluorescent amplified fragment length polymorphisms (FAFLPs) can distinguish species within a mixed sample, are high throughput, and are inexpensive. To broaden the use of this tool across ecosystems, unique size profiles must be established for species, and its limits identified.MethodsFragments of three noncoding cpDNA regions were used to create size profiles for 193 species common to the western Canadian boreal forest. We compared detection success among congeners using FAFLPs and Sanger sequencing of the trnL intron. We also simulated and experimentally created communities to test the influence of species richness, cpDNA regions used, and extraction/amplification biases on detection success.ResultsOf the 193 species, 54% had unique size profiles. This value decreased when fewer cpDNA regions were used. In simulated communities, ambiguous species identifications were positively related to the species richness of the community. In mock communities, some species evaded detection owing to poor extraction or amplification. Sequencing did not increase detection success compared to FAFLPs for a subset of 24 species across nine genera.DiscussionWe recommend FAFLPs are best suited to confirm rather than discover species occurring belowground.

Assessment of Convolution Neural Networks for Wetland Mapping with Landsat in the Central Canadian Boreal Forest Region

Methods for effective wetland monitoring are needed to understand how ecosystem services may be altered from past and present anthropogenic activities and recent climate change. The large extent of wetlands in many regions suggests remote sensing as an effective means for monitoring. Remote sensing approaches have shown good performance in local extent studies, but larger regional efforts have generally produced low accuracies for detailed classes. In this research we evaluate the potential of deep-learning Convolution Neural Networks (CNNs) for wetland classification using Landsat data to bog, fen, marsh, swamp, and water classes defined by the Canada Wetland Classification System (CWCS). The study area is the northern part of the forested region of Alberta where we had access to two reference data sources. We evaluated ResNet CNNs and developed a Multi-Size/Scale ResNet Ensemble (MSRE) approach that exhibited the best performance. For assessment, a spatial extension strategy was employed that separated regions for training and testing. Results were consistent between the two reference sources. The best overall accuracy for the CWCS classes was 62–68%. Compared to a pixel-based random forest implementation this was 5–7% higher depending on the accuracy measure considered. For a parameter-optimized spatial-based implementation this was 2–4% higher. For a reduced set of classes to water, wetland, and upland, overall accuracy was in the range of 86–87%. Assessment for sampling over the entire region instead of spatial extension improved the mean class accuracies (F1-score) by 9% for the CWCS classes and for the reduced three-class level by 6%. The overall accuracies were 69% and 90% for the CWCS and reduced classes respectively with region sampling. Results in this study show that detailed classification of wetland types with Landsat remains challenging, particularly for small wetlands. In addition, further investigation of deep-learning methods are needed to identify CNN configurations and sampling methods better suited to moderate spatial resolution imagery across a range of environments.

Migrating silver-haired bats fine-tune torpor to save energy

Ultra-distance marathon runners are almost a race apart. Covering thousands of miles over weeks and even months, these extreme human athletes require mental stamina and physical endurance. Yet, many migratory species take these distances in their stride. ‘Some studies suggest that silver-haired bats spend their winters in southern USA and their summers in the Canadian boreal forest’, says Dylan Baloun, currently a graduate student at the University of Saskatchewan, Canada. But the bats that undertake these odysseys are at a natural disadvantage. ‘They are nocturnal, so daytime stopovers are mandatory’, says Baloun, who explains that stopovers can be extremely costly for some species – totalling ∼70% of the entire migration cost for some birds. But, the mini mammals have a nifty energy-saving trick up their sleeves. ‘Bats use torpor’, says Baloun, explaining that they drop their body temperature while they rest to conserve energy. However, no one had directly measured how much energy the torpid mammals conserve while hanging out during the day and how the roost temperature affects their energy saving. So, Baloun and PI Chris Guglielmo from the University of Western Ontario, Canada, packed up their lab and headed out to the Long Point Bird Observatory to catch bats in the act.‘It is difficult to bring and maintain state-of-the-art physiological equipment into the field, even with a mobile laboratory trailer to maintain a stable climate’, says Baloun, who ventured out into the near-by woods at night to retrieve silver-haired bats during their spring and autumn migrations. Back in the temporary lab, the duo weighed and scanned the animals using magnetic resonance to measure how much fat and muscle the animals were carrying. Then, after attaching a thermometer to each bat to track its body temperature, they snuggled the individual animals inside soft cloth bags where they could slip into torpor and slumber away at roost temperatures of 10, 17.0 or 25°C. Finally, when the bats were preparing to depart again during the following dusk, the duo repeated the body measurements before allowing the animals to continue on their way.Calculating how much fat and muscle the bats lost during their daytime stopover and converting the loss into the amount of energy consumed during their slumber, the duo could see that the animals used essentially the same amount of energy over the course of the day, regardless of the temperature in their roost. The team then calculated the total amount of torpor experienced by each animal and it was clear that the bats were fine tuning how cold they became and for how long, with the result that they all consumed similar amounts of energy during their stopover regardless of the air temperature. And when the duo calculated how much energy the bats consumed during their break, they were impressed to see that it was as low as 15–20% of the total migration energy cost. ‘By entering a state of torpor, bats save energy for future migratory and potentially reproductive costs’, says Baloun.However, the team also realised that some of the bats were conserving energy and using torpor in slightly different ways, with bats that carried more weight using less torpor at the warmer temperatures, while the heavier females consumed more energy during spring stopovers than the lighter males. ‘Body mass was a major determinant in how bats used torpor’, says Baloun.So, migrating bats have the ability to dramatically reduce their energy costs during enforced daytime stopovers and the study adds another piece to the puzzle of how these tiny mammals pull off extreme feats of endurance, at which most of us can only marvel.

Post-cutting Mortality Following Experimental Silvicultural Treatments in Unmanaged Boreal Forest Stands

Partial cutting has been recommended as an alternative harvesting method to ensure the sustainable management of boreal forests. The success of this approach is closely linked to the survival of residual trees as additional losses through mortality could affect post-cutting timber production at harvest. To better quantify post-cutting mortality in previously unmanaged boreal forests, we addressed two main questions: (1) what is the level of mortality ten years after cutting? and (2) what ecological factors are involved in this phenomenon? Even-aged black spruce [Picea mariana (Mill.) B.S.P.] stands in the Canadian boreal forest were subjected to three experimental shelterwood treatments, a seed-tree treatment and an untreated control. Tree status (live/dead) was recorded prior to cutting and ten years after cutting. Dead trees were classified as standing dead, overturned or broken. Ten years after experimental seed-tree treatment, 60% of residual trees were dead, compared to 30% for the shelterwood cuttings. Windthrow (overturned and broken trees) represented 80% of residual tree mortality; only the amount of overturning was influenced by treatment. Broken trees were associated with small-diameter trunks, stands having high growth prior to cutting, younger stands or forest plots located near to adjacent cuts (<200 m). Overturning was associated with a high harvesting intensity and large-diameter trees. Standing dead mortality was the most difficult to explain: it was related to untreated plots having suppressed and small-diameter trees. Based on these results, applying intermediate levels of harvest intensity could reduce post-cutting damage. Understanding tree mortality after cutting is essential to reduce economic losses, improve silvicultural planning and stand selection and ensure ultimately the sustainable harvest of North American boreal forests.

Increases in heat-induced tree mortality could drive reductions of biomass resources in Canada’s managed boreal forest

The Canadian boreal forest provides valuable ecosystem services that are regionally and globally significant. Despite its importance, the future of the Canadian boreal forest is highly uncertain because potential impacts of future climate change on ecosystem processes and biomass stocks are poorly understood. We investigate how anticipated climatic changes in coming decades could trigger abrupt changes in the biomass of dominant species in Canada’s boreal forests. Using the dynamic global vegetation model LPJ-LMfire, which was parameterized for the dominant tree genera in Canada’s boreal forests (Picea, Abies, Pinus, Populus) and driven by a large range of climate scenarios grouped by two forcing scenarios (RCP 4.5/8.5), we simulated forest composition, biomass, and the frequency of disturbance, including wildfire, from Manitoba to Newfoundland. Results suggest that responses of this region to a warmer future climate will be very important, especially in southern boreal areas and under the RCP 8.5 forcing scenario. In these areas, reductions of total aboveground biomass incurred by fire and heat-induced tree mortality events are projected; the fertilizing effect of increasing atmospheric CO2 on forest productivity is unlikely to compensate for these losses. Decreases in total forest stocks would likely be associated with forest cover loss and a shift in composition in particular from needleleaf evergreen (softwood) to broadleaf deciduous (hardwood) taxa. The simulated future reduction in softwood biomass suggests that forest management strategies will have to be adapted to maintain a sustainable level of forest harvest and tree density that meets demands for wood products, while maintaining other ecosystem services.

Wood quality attribute models and their utility when integrated into density management decision-support systems for boreal conifers

The objectives of this study were to (1) develop wood quality prediction models for a suite of commercially-relevant jack pine (Pinus banksiana Lamb.) fibre attributes (wood density (Wd), microfibril angle (Ma), modulus of elasticity (Me), fibre coarseness (Co), tracheid wall thickness (Wt), tracheid radial (Dr) and tangential (Dt) diameters and specific surface area (Sa)), (2) given (1), incorporate the parameterized equations within structural stand density management models (SSDMMs), and (3) given (2), exemplify their utility in silvicultural decision-making via the comparative assessment of attribute outcomes arising from operationally-relevant crop plans. Analytically, the equations were developed deploying Silviscan-determined attributes derived from transverse breast-height radial xylem sequences obtained from 61 trees sampled from 2 geographically-separated thinning experiments located in the central region of the Canadian Boreal Forest Region. Hierarchical mixed-effects regression modeling combined with cross-validation procedures were used to specify, parameterize and evaluate the attribute-specific prediction equations. Overall, the results revealed that the attribute trajectories were size-dependent and the resultant models were adequate in terms of their goodness-of-fit characteristics (e.g., I2 values of 75, 71, 71, 66, 60, 55, 49 and 38% for Co, Me, Wt, Sa, Wd, Ma, Dr and Dt respectively), lack-of-fit indicators (e.g., temporally invariant patterns of absolute and relative errors devoid of evidence of systematic bias), and predictive performance (e.g., 95% probability that 95% of all future relative Dt, Dr, Sa, Wd, Co, Wt, Me and Ma errors would be within ±5, ±9, ±11, ±12, ±12, ±13, ±35 and ±43% of their true values, respectively). Incorporating the jack pine equations along with a similar suite of functions previously developed for black spruce (Picea mariana (Mill) B.S.P) into the SSDMM analytical framework, yielded a pair of enhanced stand-type-specific (natural-origin and planted stands) decision-support systems for each species. These systems enabled the estimation of attribute-specific developmental trajectories for the rotational tree population from which diameter-class and stand-level wood quality performance measures were derived. As exemplified, the development of size-dependent fibre attribute prediction models and their subsequent integration within SSDMMs provides forest managers with a decision-support platform for evaluating and comparing end-product-related consequences of selected crop plans.

Carbon storage and net primary productivity in Canadian boreal mixedwood stands

Canadian boreal mixedwood forests are extensive, with large potential for carbon sequestration and storage; thus, knowledge of their carbon stocks at different stand ages is needed to adapt forest management practices to help meet climate-change mitigation goals. Carbon stocks were quantified at three Ontario boreal mixedwood sites. A harvested stand, a juvenile stand replanted with spruce seedlings and a mature stand had total carbon stocks (± SE) of 133 ± 13 at age 2, 130 ± 13 at age 25, and 207 ± 15 Mg C ha−1 at age 81 years. At the clear-cut site, stocks were reduced by about 40% or 90 Mg C ha−1 at harvest. Vegetation held 27, 34 and 62% of stocks, while detritus held 34, 29 and 13% of stocks at age 2, 25 and 81, respectively. Mineral soil carbon stocks averaged 51 Mg C ha−1, and held 38, 37 and 25% of stocks. Aboveground net primary productivity (± SE) in the harvested and juvenile stand was 2.1 ± 0.2 and 3.7 ± 0.3 Mg C ha−1 per annum (p.a.), compared to 2.6 ± 2.5 Mg C ha−1 p.a. in the mature stand. The mature canopies studied had typical boreal mixedwood composition and mean carbon densities of 208 Mg C ha−1, which is above average for managed Canadian boreal forest ecosystems. A comparison of published results from Canadian boreal forest ecosystems showed that carbon stocks in mixedwood stands are typically higher than coniferous stands at all ages, which was also true for stocks in vegetation and detritus. Also, aboveground net primary productivity was typically found to be higher in mixedwood than in coniferous boreal forest stands over a range of ages. Measurements from this study, together with those published from the other boreal forest stands demonstrate the potential for enhanced carbon sequestration through modified forest management practices to take advantage of Canadian boreal mixedwood stand characteristics.

Abundance and Impacts of Competing Species on Conifer Regeneration Following Careful Logging in the Eastern Canadian Boreal Forest

Managing competing vegetation is crucial in stand establishment strategies; forecasting the abundance, composition, and impact of competing vegetation after harvesting is needed to optimize silviculture scenarios and maintain long-term site productivity. Our main objective was to identify factors influencing the short-term abundance and composition of competing vegetation over a large area of the Canadian boreal forest. Our second objective was to better understand the mid-term evolution of the regeneration/competing vegetation complex in cases of marginal regeneration conditions. We used operational regeneration surveys of 4471 transects sampled ≈5 years after harvesting that contained data on regeneration, competing vegetation, elevation, ecological classification, soil attributes, and pre-harvest forest stands. We performed a redundancy analysis to identify the relationships between competing vegetation, harvesting and biophysical variables. We then estimated the probability of observing a given competing species cover based on these variables. In 2015, we re-sampled a portion of the sites, where conifer regeneration was marginal early after harvesting, to assess the temporal impact of different competing levels and species groups on the free-to-grow stocking, vigour and basal area of softwood regeneration. Results from the first inventory showed that, after careful logging around advance growth, ericaceous shrubs and hardwoods were not associated with the same sets of site attributes. Ericaceous shrubs were mainly found on low fertility sites associated with black spruce (Picea mariana (Mill.) BSP) or jack pine (Pinus banksiana Lamb.). The distinction between suitable environments for commercial shade-intolerant hardwoods and non-commercial hardwoods was less clear, as they responded similarly to many variables. Analysis of data from the second inventory showed a significant improvement in conifer free-to-grow stocking when commercial shade-intolerant hardwood competing levels were low (stocking 0%–40%) and when ericaceous shrubs competing levels were moderate (percent cover 26%–75%). In these conditions of marginal regeneration, the different types and intensities of competition did not affect the vigour or basal area of softwood regeneration, 9–14 years after harvesting.

Boreal Sand Hills are Areas of High Diversity for Boreal Ants (Hymenoptera: Formicidae)

The boreal forest in Canada comprises a wide variety of ecosystems, including stabilized (overgrown) sand dunes, often referred to as sand hills. Globally, sandy soils are known for supporting a high diversity of invertebrates, including ants, but little is known for boreal systems. We used pitfall trap sampling in sand hill, aspen parkland and peatland ecosystems to compare their ant diversity and test the prediction that areas with sandy soils have higher invertebrate diversity compared to more mesic/organic soils. Overall, sand hills had ~45% more ant species compared to other sampled ecosystems from Alberta. Similar to other studies, local canopy cover within sand hills was found to be inversely related to ant species richness and diversity. Although sand hills are rare across the region, they are high biodiversity areas for ants, with the sand hills of north-central Alberta having higher species richness of ants compared to other studied areas in Canada.

Rethinking the maps: A case study of knowledge incorporation in Canadian wildfire risk management and planning

As the natural fire regimes of Canada's Boreal forests have been transformed by dynamic social, economic, ecological and political drivers, wildfires have become a locus of increasingly complex land management decisions. But while, in Canada and elsewhere, social researchers have examined communities at risk of experiencing wildfire, the agencies and practitioners responsible for wildfire management have thus far been underrepresented in empirical inquiry. This article presents a case study of wildfire management in northern Alberta, examining how different forms of knowledge and experiences were incorporated into the creation of a new plan to support decision-making. Findings from interviews and a workshop confirm that ‘science’ in such applied contexts is not a pure entity. Instead, the objects represented internally and externally as ‘scientific’ have necessarily been shaped by the values and priorities of the individuals and institutions that have constructed them. Further, this case study revealed social factors that support the maintenance of institutional status quos, such as the commitment to total wildfire suppression policy, despite broad agreement amongst participants about superior alternatives. These findings support the need for further research on wildfire management agencies, and suggest that progress in wildfire management may be limited by mismatched expectations of ‘good’ policy between stakeholder groups and by practitioners' conceptions of their own institutional identity.

Changes in Spatiotemporal Patterns of 20th Century Spruce Budworm Outbreaks in Eastern Canadian Boreal Forests.

In scenarios of future climate change, there is a projectedincrease in the occurrence and severity of natural disturbances inboreal forests. Spruce budworm (Choristoneura fumiferana)(SBW) is the main defoliator of conifer trees in the North American boreal forests affecting large areas and causing marked losses of timber supplies. However, the impact and the spatiotemporal patterns of SBW dynamics at the landscape scale over the last century remain poorly known. This is particularly true for northern regions dominated by spruce species. The main goal of this study is to reconstruct SBW outbreaks during the 20th century at the landscape scale and to evaluate changes in the associated spatiotemporal patterns in terms of distribution area, frequency, and severity. We rely on a dendroecological approach from sites within the eastern Canadian boreal forest and draw from a large dataset of almost 4,000 trees across a study area of nearly 800,000 km2. Interpolation and analyses of hotspots determined reductions in tree growth related to insect outbreak periods and identified the spatiotemporal patterns of SBW activity over the last century. The use of an Ordinary Least Squares model including regional temperature and precipitation anomalies allows us to assess the impact of climate variables on growth reductions and to compensate for the lack of non-host trees in northern regions. We identified three insect outbreaks having different spatiotemporal patterns, duration, and severity. The first (1905–1930) affected up to 40% of the studied trees, initially synchronizing from local infestations and then migrating to northern stands. The second outbreak (1935–1965) was the longest and the least severe with only up to 30% of trees affected by SBW activity. The third event (1968–1988) was the shortest, yet it was also the most severe and extensive, affecting nearly up to 50% of trees and 70% of the study area. This most recent event was identified for the first time at the limit of the commercial forest illustrating a northward shift of the SBW distribution area during the 20th century. Overall, this research confirms that insect outbreaks are a complex and dynamic ecological phenomena, which makes the understanding of natural disturbance cycles at multiple scales a major priority especially in the context of future regional climate change.

A review of the intact forest landscape concept in the Canadian boreal forest: its history, value, and measurement

Loss of global forest, and in particular forest that has little human disturbance, is a standard against which we measure progress to conserve Earth’s forests. The value of intact forest landscapes has taken hold in the global psyche. We provide a brief history of the intact forest landscape concept and discuss how this has moved to an operational definition used as a global and regional metric of forest conservation. We distinguish between a conceptual intact forest landscape and an operational definition. For the purposes of this paper we will use the term IFL to mean the operational definition and intact forest landscapes to mean the conceptual idea. We provide an overview of the science that supports the value of intact forest landscapes in a Canadian boreal context and analyse issues with using a standard operationalized IFL definition to both measure and promote conservation of forests at global and regional scales. We found many arguments for protecting large, intact forest landscapes that are relevant to the Canadian boreal forest, including conservation of biodiversity, ecological processes and ecosystem services, existence values, application of the precautionary principle, and the need for scientific benchmarks. But it is clear that the standard operational IFL size threshold of 50 000 ha in the boreal forest is inadequate to meet these broad conservation objectives. However, the concept of intact forest being large enough to allow for all natural processes and biodiversity is likely not logistically feasible in Canada’s managed boreal forest. The scale at which the most extensive processes (e.g., fire and insects) occur and species (e.g., woodland caribou) function is likely too large. Management options incorporating local knowledge of conservation needs and the specifics of ecosystem function and composition are more likely to be effective in conservation than rigid IFL requirements. A standardized approach is useful for global tracking of IFLs but it is not the best approach to meet more regional forest conservation goals. Intact forest landscapes have exceptional value but should be managed in the context of integrated land use planning that includes protected areas, sustainable forest management, species at risk management, and ecosystem restoration.

Acoustic Velocity—Wood Fiber Attribute Relationships for Jack Pine Logs and Their Potential Utility

This study presents an acoustic-based predictive modeling framework for estimating a suite of wood fiber attributes within jack pine (Pinus banksiana Lamb.) logs for informing in-forest log-segregation decision-making. Specifically, the relationships between acoustic velocity (longitudinal stress wave velocity; vl) and the dynamic modulus of elasticity (me), wood density (wd), microfibril angle (ma), tracheid wall thickness (wt), tracheid radial and tangential diameters (dr and dt, respectively), fiber coarseness (co), and specific surface area (sa), were parameterized deploying hierarchical mixed-effects model specifications and subsequently evaluated on their resultant goodness-of-fit, lack-of-fit, and predictive precision. Procedurally, the data acquisition phase involved: (1) randomly selecting 61 semi-mature sample trees within ten variable-sized plots established in unthinned and thinned compartments of four natural-origin stands situated in the central portion the Canadian Boreal Forest Region; (2) felling and sectioning each sample tree into four equal-length logs and obtaining twice-replicate vl measurements at the bottom and top cross-sectional faces of each log (n = 4) from which a log-specific mean vl value was calculated; and (3) sectioning each log at its midpoint and obtaining a cross-sectional sample disk from which a 2 × 2 cm bark-to-pith radial xylem sample was extracted and subsequently processed via SilviScan-3 to derive annual-ring-specific attribute values. The analytical phase involved: (1) stratifying the resultant attribute—acoustic velocity observational pairs for the 243 sample logs into approximately equal-sized calibration and validation data subsets; (2) parameterizing the attribute—acoustic relationships employing mixed-effects hierarchical linear regression specifications using the calibration data subset; and (3) evaluating the resultant models using the validation data subset via the deployment of suite of statistical-based metrics pertinent to the evaluation of the underlying assumptions and predictive performance. The results indicated that apart from tracheid diameters (dr and dt), the regression models were significant (p ≤ 0.05) and unbiased predictors which adhered to the underlying parameterization assumptions. However, the relationships varied widely in terms of explanatory power (index-of-fit ranking: wt (0.53) &gt; me &gt; sa &gt; co &gt; wd &gt;&gt; ma (0.08)) and predictive ability (sa &gt; wt &gt; wd &gt; co &gt;&gt; me &gt;&gt;&gt; ma). Likewise, based on simulations where an acoustic-based wd estimate is used as a surrogate measure for a Silviscan-equivalent value for a newly sampled log, predictive ability also varied by attribute: 95% of all future predictions for sa, wt, co, me, and ma would be within ±12%, ±14%, ±15%, ±27%, and ±55% and of the true values, respectively. Both the limitations and potential utility of these predictive relationships for use in log-segregation decision-making, are discussed. Future research initiatives, consisting of identifying and controlling extraneous sources of variation on acoustic velocity and establishing attribute-specific end-product-based design specifications, would be conducive to advancing the acoustic approach in boreal forest management.

Root system origin and structure influence planting shock of black spruce seedlings in boreal microsites

Planting shock can last for several years during which seedling growth may significantly slow down. This duration depends upon the time that is required for the root system to acclimatize to its new environment. We hypothesized that characteristics of the root system are important factors for black spruce (Picea mariana [Mill.] BSP) seedling establishment. To test this hypothesis, we compared growth and physiology of three stock types: containerized seedlings, with a dense initial root system restricted to the volume of a root plug; deeply planted containerized seedlings, with the stem buried during production to develop dense adventitious and initial root systems; and bareroot seedlings, with a less developed but unrestricted initial root system. The three stock types were planted on three microsites that are typical of reforestation sites found in eastern Canadian boreal forest: (1) bare mineral soil; (2) in presence of ericaceous shrubs; or (3) in presence of Sphagnum spp. and ericaceous species. Labelled nitrogen fertilizer was added to half of the seedlings to compare nitrogen uptake. We measured seedling growth (height, diameter, above- and belowground biomass), nutrition (including 15N uptake) and 13C discrimination (as an indicator of water stress) at the end of the second growing season. Except at the root level, there were few interactions between stock types and microsites. For fertilized microsites, we speculate that ericaceous species captured most added nutrients since seedlings that were planted directly on mineral soil had greater height and diameter increments than seedlings with competing vegetation. In unfertilized microsites, Sphagnum spp. and ericaceous species had significant negative effects on seedling growth. For stock type, the presence of a root plug allowed containerized and deeply planted seedlings to have a lower δ13C, suggesting less water stress compared to bareroot seedlings. Strong initial root system development of containerized seedlings resulted in greater total biomass. We hypothesized that the presence of adventitious roots in deeply planted seedlings positively influenced nutrient uptake, particularly N. As nutrient availability is one of the most limiting factors in the boreal forest, we suggest using deeply planted containerized seedlings to reduce planting stress.

Boreal tree growth exhibits decadal‐scale ecological memory to drought and insect defoliation, but no negative response to their interaction

Abstract Interactions between drought and insect defoliation may dramatically alter forest function under novel climate and disturbance regimes, but remain poorly understood. We empirically tested two important hypotheses regarding tree responses to drought and insect defoliation: (a) trees exhibit delayed, persistent, and cumulative growth responses to these stressors; (b) physiological feedbacks in tree responses to these stressors exacerbate their impacts on tree growth. These hypotheses remain largely untested at a landscape scale, yet are critical for predicting forest function under novel future conditions, given the connection between tree growth and demographic processes such as mortality and regeneration. We developed a Bayesian hierarchical model to quantify the ecological memory of tree growth to past water deficits and insect defoliation events, derive antecedent variables reflecting the persistent and cumulative effects of these stressors on current growth, and test for their interactive effects. The model was applied to extensive tree growth, weather, and defoliation survey data from western and eastern regions of the Canadian boreal forest impacted by recent drought and defoliation events and characterized by contrasting tree compositions, climates, and insect defoliators. Results revealed persistent negative tree growth responses to past water (all trees) and defoliation (host trees) stress lasting 3–6 and 10–12 years, respectively, depending on study region. Accounting for the ecological memory of tree growth to water and defoliation stress allowed for detection of interactions not previously demonstrated. Contrary to expectations, we found evidence for positive interactions among non‐host trees likely due to reduced water stress following defoliation events. Regional differences in ecological memory to water stress highlight the role of climate in shaping forest responses to drought. Synthesis. Study results suggest negative feedbacks in tree responses to drought and insect attack may be weaker than predicted for defoliator‐dominated boreal forest systems. Instead, insect defoliation may offset the impacts of water deficit on boreal tree growth by reducing transpirational water demand. This offset mimics increased resistance to drought following forest thinning and may lessen growth and mortality losses due to increased aridity and more severe insect damage forecast for the boreal forest under global change.

Anthropocene futures: Linking colonialism and environmentalism in an age of crisis

The universal discourse of the Anthropocene presents a global choice that establishes environmental collapse as the problem of the future. Yet in its desire for a green future, the threat of collapse forecloses the future as a site for creatively reimagining the social relations that led to the Anthropocene. Instead of examining structures like colonialism, environmental discourses tend to focus instead on the technological innovation of a green society that “will have been.” Through this vision, the Anthropocene functions as a geophysical justification of structures of colonialism in the services of a greener future. The case of the Canadian Boreal Forest Agreement illustrates how this crisis of the future is sutured into mainstream environmentalism. Thus, both in the practices of “the environment in crisis” that are enabled by the Anthropocene and in the discourse of geological influence of the “human race,” colonial structures privilege whiteness in our environmental future. In this case, as in others, ecological protection has come to shape the political life of colonialism. Understanding this relationship between environmentalism and the settler state in the Anthropocene reminds us that the universal discourse of the Anthropocene is intertwined with the attempt to sustain whiteness into the future.

Roles of environmental and spatial factors in structuring assemblages of forest-floor Mesostigmata in the boreal region of Northern Alberta, Canada

ABSTRACTMesostigmatid mites (Arachnida: Parasitiformes) are a diverse, abundant group of soil predators; however, in comparison to some other groups of soil fauna (e.g. oribatid mites), little is known about environmental and spatial processes that influence local species richness and abundance. The main objective of our study was to identify factors strongly correlated with assemblages of Mesostigmata from boreal forests in northern Alberta, Canada. Soil and litter samples came from 62 sites with up to 4 samples per site (216 samples total), with a north–south range of ~800 km between sites. Environmental variables included ground cover type (e.g. moss, lichen, grass), disturbance intensity, precipitation, and temperature. From 3021 individual adult Mesostigmata, we identified 101 species/morphospecies from 21 families, the most species-rich being Ascidae, Zerconidae, and Digamasellidae. Redundancy analysis determined that the environmental variables that correlated most strongly with mite assemblages were precipitation, moss cover, and disturbance intensity. Spatial distance between sites had almost the same explanatory power, as environmental factors. Assemblages became more dissimilar with increasing spatial distance. This study showed the importance that particular environmental and spatial factors likely have on Mesostigmata composition in Canadian boreal forests; however, manipulative studies are required to be able to attribute causation to these correlations.

A value-added forest management policy reduces the impact of fire on timber production in Canadian boreal forests

When fire rates are sufficiently high, fire disturbances can have negative impacts on industrial timber supplies. One can mitigate such problems at the strategic level by accounting for potential fire losses in the timber supply planning process by reducing harvest levels to maintain a buffer stock of timber. With a forest planning model based on a timber volume maximizing policy, reducing the harvest level will lead to a reduction in the harvested timber volume and likely, of revenues. One possible solution is to change the policy to increase the value of the wood that is harvested so as to minimize such reductions with less risk. We have evaluated alternative policies for three commercially-managed forests that have different burn rates in northeastern Canada. When compared with a volume-maximization policy, a revenue-maximization policy that considers sustained production and the sale of sawmilling wood products (lumber, chips and sawdust) increased mean revenues by 130% (36–770%) with >0.90 probability and substantially decreased the area and volume harvested by 27% (11–38%) and 28% (14–36%), respectively. By reducing the harvest volume, the total number of jobs associated with forest operations decreased by 20% (10–27%) but the number of jobs per unit area harvested and volume increased. The policy also increased the harvest age and thereby enhanced the retention of a greater proportion of old-growth stands. Our study indicated that a tighter link between strategic planning and wood product processing helped identify better compromises between harvesting activities and revenues, despite the occurrence of natural disturbances.