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We assessed the impacts of three approaches to thinning from below with varying spatial patterns on several stand and individual tree variables for interior Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco), interior spruce (Picea glauca (Moench) Voss × Picea engelmannii Engelm.), and lodgepole pine (Pinus contorta Dougl. Ex Loud. var. latifolia Englem.) in central British Columbia, Canada. The three thinning treatments were two experimental "clumped" treatments (3 m Clumped and 5 m Clumped) and the Standard (more uniform spacing) thinning treatment that was employed operationally at that time. We used long-term data from 24 plots measured five times over 21 years. Thinning increased stand basal area increment, with the plots that received the 5 m Clumped treatment having significantly higher periodic annual relative basal area increment than the unthinned Control plots. The responses for the two clumped treatments were not any lower than the Standard. The 3 m Clumped treatment was best if one is concerned about fast recovery of the growing space; however, the 5 m Clumped spacing treatment may be preferable if higher individual tree vigour is needed for resistance and resilience to fire, insects, and disease. [ABSTRACT FROM AUTHOR]

A significant portion of the harvested land base in western Canada is becoming old enough or entering a phase where thinning is a legitimate forest management option. A comprehensive review of the existing knowledge of commercial thinning (CT) treatments applied to pine and spruce-dominated stands in Alberta was conducted, with particular regard to the intensity, timing of interventions, method, and impacts on crop tree growth responses. Although the geographical focus of this review is Alberta, information on this topic is more complete in other areas of North America and Europe, where there is a long history of density management. In areas of eastern North America, our review revealed that CT from below, with tree removal levels from 27 to 43% of the basal area, could increase total merchantable wood produced from 11 to 60 m3 ha−1 over a rotation, depending on stand age and intensity of thinning. For Alberta conditions, and considering the risks, we conclude that commercial thinning basal area removal should be in the range of 25 to 40%, depending on a variety of factors such as species, wind firmness, and insect or disease incidence and risk. Thinning too aggressively and/or too late will increase the blowdown risk but the literature is fairly consistent in suggesting that live crown ratios should be >40% to maximize the chance of growth response and minimize the blowdown risk. In cases where stands are also threatened by stressors such as drought, wind, and insect or disease outbreaks, CT treatments likely offer the potential at limiting the overall risk, but localized knowledge and experience are critical. It is intended that the information presented may support ongoing and future research trials and growth and yield (G&Y) model development about potential CT treatments to apply and the likely results of practical application to commercial forestry. [ABSTRACT FROM AUTHOR]

The mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae), recently underwent a notable range-expansion event in western Canada, resulting in access to the novel host jack pine, Pinus banksiana Lamb. We assessed the suitability of jack pine for mountain pine beetle, as well as the historic host lodgepole pine, Pinus contorta Dougl. var. latifolia Engelm., and the non-Pinus host white spruce, Picea glauca (Moench) Voss, to help inform an assessment of the risk of future spread into Canada's boreal forest and to further our understanding of host use in bark beetles. Several performance traits we measured were similar between lodgepole pine and jack pine, but gallery length and productivity indicated that lodgepole pine was the more suitable host. Development appeared to be faster in jack pine; however, in contrast to previous studies, we attribute it to oviposition arresting earlier in the novel host compared to the other hosts and not a difference in development rate. Initial productivity was surprisingly high in spruce, but we found evidence of a delayed negative effect that manifested as reduced cold tolerance, delayed development, and high mortality of late-instar larvae. Although jack pine is a suitable host for the mountain pine beetle, our results indicate that the beetle's eruptive potential could be lower in jack pine compared to lodgepole pine, given all other factors are equal. Other factors that may also affect mountain pine beetle population dynamics require additional research and include the composition and structure of jack pine forests, environmental conditions, and biotic interactions. [ABSTRACT FROM AUTHOR]

Static bending tests to measure modulus of elasticity (MOEST) or wood stiffness provide an indicator of the structural performance of a finished product. These tests are however, slow and expensive. Tests to measure MOE using non-destructive testing (NDT) provide alternatives to MOEST tests; however, relationships between the different modes of measurement need to be established. Non-destructive testing MOE measured by two methods (SilviScan [MOESS] and time of flight [MOETOF]) have been compared with MOEST for lodgepole pine and white spruce. The relationships between stress wave speed (SWS) and MOEST have also been evaluated. Simple linear regressions of MOESS, MOETOF, and SWS had greater explanatory power (higher coefficients of determination (R2)) than did multiple linear regressions including growth rate or other wood fibre attributes. Simple linear regression from MOETOF and MOESS on MOEST had lower R2 for lodgepole pine than for white spruce; however, the converse was true for SWS. SWS had the highest R2 (89%) and MOESS the lowest R2 (47%) when regressed on MOEST in lodgepole pine. The results were tool and species specific, suggesting that R2 between MOEST and non-destructive testing MOE values must be validated separately for each commercial tree species and for each measurement technique. [ABSTRACT FROM AUTHOR]

Stand tending using glyphosate to promote coniferous overstory trees has been a common practice in the boreal forests of Alberta. However, there are concerns about the impact of this practice on biodiversity of understory species. This study examined the impact of broadcast glyphosate application during the active reforestation phase, two to several years post-harvest, on forest plant diversity 25 to 40 years post-harvest. Herbicide treatments had the desired effect of shifting tree layer dominance from deciduous to coniferous species, driven by a 25-fold reduction in the density of trembling aspen (3927 vs. 154 stems·ha−1, untreated and treated, respectively). However, understory plant diversity was not significantly different between treated and untreated sites as examined by the Shannon–Wiener (H) and evenness (E) indices. Shared plant species (beta) across sites was high. Of the seven site-indicator species examined, three had significantly lower cover on treated sites: Wild sarsaparilla, low bush-cranberry and oak fern. Total understory plant cover was significantly greater in the treated portion (98.0%) versus untreated (71.4%); however, this difference was not significant when bryophytes were excluded in the analysis. The establishment, maintenance and monitoring of larger long-term trials is strongly recommended. [ABSTRACT FROM AUTHOR]

As northern latitudes experience rapid winter warming, there is an urgent need to assess the effect of varying winter conditions on tree growth and forest carbon sequestration potential. We examined tree growth responses to variability in cold-season (November–- April) frequency of freeze days (FFD) over 1951 to 2018 using tree-ring data from 35,217 trees and 57 species at 4,375 sites distributed across Canada. We found that annual radial growth responses to FFD varied by species, with some commonalities across genera and clades. The growth of gymnosperms with late spring leaf-out strategies was negatively related to FFD; years with high FFD were most detrimental to the annual growth of Pinus banksiana, Pinus contorta, Larix lyalli, Abies amabilis, and Abies lasiocarpa. In contrast, the growth of angiosperms with early leaf-out strategies, namely, Populus tremuloides and Betula papyrifera, was better in the coldest years, and gymnosperms with intermediate leaf-out timing, such as widespread Picea mariana and Picea glauca, had no consistent relationship to FFD. Tree growth responses to FFD were further modulated by tree size, tree age, regional climate (i.e., mean cold-season temperature), and local site conditions. Overall, our results suggest that moderately warming winters may temporarily improve the growth of widespread pines and some high-elevation conifers in western Canada, whereas warming winters may be detrimental to the growth of widespread boreal angiosperms. Our findings also highlight the value of using species-specific climate-growth relationships to refine predictions of forest carbon dynamics. [ABSTRACT FROM AUTHOR]

Past research has shown that remotely sensed spectral information can be used to predict tree health and vitality. Recent developments in unmanned aerial vehicles (UAVs) have now made it possible to derive such information at the tree and stand scale from high-resolution imagery. We used visible and multispectral bands from UAV imagery to calculate a set of spectral indices for 52,845 individual tree crowns within 38 forest stands in western Canada. We then used those indices to predict the mortality of these canopy trees over the following year. We evaluated whether including multispectral indices leads to more accurate predictions than indices derived from visible wavelengths alone and how the performance varies among three different tree species (Picea glauca, Pinus contorta, Populus tremuloides). Our results show that spectral information can be effectively used to predict tree mortality, with a random forest model producing a mean area under the receiver operating characteristic curve (AUC) of 89.8% and a balanced accuracy of 83.3%. The exclusion of multispectral indices worsened the model performance, but only slightly (AUC = 87.9%, balanced accuracy = 81.8%). We found variation in model performance among species, with higher accuracy for the broadleaf species (balanced accuracy = 85.2%) than the two conifer species (balanced accuracy = 73.3% and 77.8%). However, all models overpredicted tree mortality by a major degree, which limits the use for tree mortality predictions on an individual level. Further improvements such as long-term monitoring, the use of hyperspectral data and cost-sensitive learning algorithms, and training the model with a larger and more balanced data set are necessary. Nevertheless, our results demonstrate that imagery from UAVs has strong potential for predicting annual mortality for individual canopy trees. [ABSTRACT FROM AUTHOR]

Mechanistically predicting the evolutionary response of tree species to climate change requires an understanding of genetic variation in relevant traits. Here we compared the phenotypic and genetic variation in the Leaf Economics Spectrum (LES) traits and the response of gas exchange to vapour pressure deficit (VPD) in lodgepole pine (Pico) and white spruce (Pigl), an early and a late successional species dominating the boreal forests of western Canada.We measured gas exchange, foliar nitrogen and lamina mass to area ratio in 697 c. 30‐year‐old trees in two field progeny trials. We analysed the response of gas exchange rates to VPD using a novel quantitative genetic model, the function‐valued trait approach.Pico showed greater phenotypic variation in the LES traits and greater genetic variation in photosynthetic rate than Pigl, but the species showed no significant difference in their phenotypic correlations between the LES traits. Pico showed a less sensitive stomatal response to VPD than Pigl and no significant genetic variation in stomatal sensitivity. In contrast, Pigl showed a positive correlation between the genetic values of stomatal sensitivity to VPD and stomatal conductance under low VPD.Our study region is projected to see an increase in VPD with climate change; the less sensitive and genetically diverse stomatal response to VPD in Pico could make this species more vulnerable to climate‐change‐induced droughts. A free Plain Language Summary can be found within the Supporting Information of this article. [ABSTRACT FROM AUTHOR]

In an attempt to comprehensively study the dynamics of non-structural carbon compounds (NCCs), we measured the seasonal changes of soluble sugars, starch, lipids and sugar alcohols in the leaves, branches, stem and roots of the fast-growing Pinus contorta (Loudon) (pine) and slow-growing Picea glauca (Moench) Voss (spruce) trees growing in a boreal climate. In addition to measuring the seasonal concentrations of these compounds, the relative contribution of these compounds to the total NCC pool within the organs of trees (~8 m tall) was estimated and compared across different phenological and growth stages. Both species showed large seasonal shifts from starch to sugars from spring to fall in nearly all organs and tissues; most likely an adaptation to the cold winters. For both species, the total fluctuation of sugar + starch across the year (i.e. the difference between the minimum and maximum observed across collection times) was estimated to be between 1.6 and 1.8 kg for all NCCs. The fluctuation, however, was 1.40 times greater than the minimum reserves in pine, while only 0.72 times the minimum reserves in spruce. By tissue type, NCC fluctuations were greatest in the roots of both species. Roots showed a large build-up of reserves in late spring, but these reserves were depleted over summer and fall. Storage reserves in needles and branches declined over the summer, and this decline may be linked to the sink strength of the stem during diameter growth. Some notable highlights of this holistic study: a late winter build-up of sugars in the stem xylem of both species, but especially spruce; and an increase in sugar alcohols in the bark of spruce in very late winter, which could indicate mobilization to support early growth in spring and high lipid reserves in the bark of pine, which appeared not to be impacted by seasonal changes between summer and winter. Collectively, these observations point toward a more conservative NCC reserve strategy in spruce compared with pine, which is consistent with its stress tolerance and greater longevity. [ABSTRACT FROM AUTHOR]

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Climate change may have spatially variable impacts on growth of trees in topographically diverse environments, making generalizing across broad spatial and temporal extents inappropriate. Therefore, topography must be considered when analyzing growth response to climate. We address these topo-climatic relationships in the Canadian Rocky Mountains, focusing on lodgepole pine (Pinus contorta Douglas ex Louden) and interior spruce (Picea glauca (Moench) Voss × Picea engelmannii hybrid Parry) growth response to climate, Palmer drought severity index (PDSI), aspect, and slope angle. Climate variables correlate with older lodgepole pine growth on south- and west-facing slopes, including previous August temperature, winter and spring precipitation, and previous late-summer and current spring PDSI, but younger lodgepole pine were generally less sensitive to climate. Climate variables correlate with interior spruce growth on all slope aspects, with winter temperature and PDSI important for young and old individuals. Numerous monthly growth–climate correlations are not temporally stable, with shifts over the past century, and response differs by slope aspect and angle. Both species are likely to be negatively affected by moisture stress in the future in some, but not all, topographic environments. Results suggest species-specific and site-specific spatiotemporally diverse climate–growth responses, indicating that climate change is likely to have spatially variable impacts on radial growth response in mountainous environments. [ABSTRACT FROM AUTHOR]

In the face of anticipated climate change, growth models require modifications to effectively model likely future growth and survival of trees and stands. To support incorporation of climate effects in the Mixedwood Growth Model (MGM), we developed climate-sensitive mixed effects models for lodgepole pine (Pinus contorta Douglas ex Loudon), jack pine (Pinus banksiana Lamb.), trembling aspen (Populus tremuloides Michx.), balsam poplar (Populus balsamifera L.) and white spruce (Picea glauca (Moench) Voss), and examined how tree size, intra- and interspecific competition and climate will influence individual-tree diameter growth. Remeasurement data from permanent growth and yield sample plots from across the western Canadian boreal forest were used for this study. Based on the model that we developed, tree size, competition and climate had varying effects on growth, among tree species. Although intraspecific competition had a stronger negative effect on growth for deciduous and white spruce trees, interspecific competition had a stronger negative effect on the growth of pine. Deciduous trees growing in stands having longer frost-free period experienced an increase in growth but a negative effect of frost-free period was observed for conifers. In addition, higher moisture was found to increase tree growth, but the influence of available moisture on growth was dependent on competition. Overall, these results suggest that, under climate warming, between-species differences in growth responses will contribute to our understanding of the stand dynamics in the western boreal region of Canada. Climate sensitive growth models developed in this study will be useful in the recalibration of MGM and other individual-tree models, and predictions will contribute to better-informed decisions about silvicultural treatments for these economically important boreal tree species. [ABSTRACT FROM AUTHOR]

Understanding the magnitude and cause of variation in tree growth and forest productivity is central to sustainable forest management. Measurements of annual growth rings allow assessments of individual-tree, tree population, and forest ecosystem vulnerabilities to drought stress or other changing forest disturbance regimes (insects, diseases, fire), which can be used to identify areas at greatest risk of forest losses. Given a heightened demand for tree-ring data, we consolidated and synthesized tree-ring studies and datasets gathered over the past 30 years in Canada by scientists with the Canadian Forest Service and research partners. We incorporated these datasets into a data repository that currently contains tree-ring measurements from 40 206 tree samples from 4594 sites and 62 tree species from all Canadian provinces and territories. Through our synthesis, we demonstrate the value of such large ensembles of tree-ring data for identifying patterns in tree growth over large spatial scales by mapping pan-Canadian drought sensitivity. Overall, we found high coherence in the samples analyzed; low coherence was generally limited to data-poor regions and species. Drought sensitivity was widespread across species and regions: 34% of sampled trees displayed a significant positive relationship between annual growth increment and summer soil moisture index. Dependence upon water availability in species Picea mariana (Mill.) BSP, Pinus banksiana Lamb., Pinus contorta Douglas ex Loudon, and Pseudotsuga menziesii (Mirb.) Franco was more strongly expressed in the warmest regions of the species' range; for species Picea glauca (Moench) Voss and Populus tremuloides Michx., drought sensitivity was stronger in the driest regions. This unprecedented consolidation and synthesis of tree-ring data will enable new research initiatives (e.g., meta-analyses) aimed at improved understanding of the drivers, patterns, and implications of changes in tree growth, as well as facilitating new research collaborations in earth and environmental sciences. Among other things, there is a need for expanding the spatial distribution of sites across Canada's northern regions, increasing the number of samples collected from older stands and angiosperm species, and integrating datasets from studies that evaluate the effects of silvicultural experiments, including provenance and progeny trials, on tree growth. [ABSTRACT FROM AUTHOR]

Understanding tree vulnerability to freezing temperatures will help resource managers to mitigate the effects of climatic variability. To test the effectiveness of tissue dehardening curves to represent whole seedling responses, we tested the cold tolerance of 4 conifer species to a range of freezing temperatures, − 15, − 25, and − 35 °C in late March, and − 5, − 10, and − 15 °C in early May. Results show that, after a 30-min exposure to freezing temperatures, needle mortality started at − 25 °C in late March (early spring dehardening) before budbreak activation and at − 10 °C in early May (late spring dehardening) when pine buds had flushed and white spruce (Picea glauca) buds had started swelling. Freezing temperatures delayed the timing of budbreak; increased needle, terminal bud, and seedling mortality; and reduced shoot growth and number of top laterals. White spruce and lodgepole pine (Pinus contorta) were more sensitive to freezing in terms of needle, terminal bud, and seedling mortality and growth reduction. The effects of March freezing were generally detected in the first year, whereas those of the May freezing were still evident in the second year on the shoot growth of black spruce (Picea mariana) and jack pine (Pinus banksiana). Although they seem relatively hardier based on first year post-freezing assessments (i.e., less immediate physical damage from freezing), black spruce and jack pine may have sustained more internal or physiological shock/damage. Our study results support the use of tissue cold hardiness–forcing temperature relationships to assess the risk of freezing damage for conifer seedlings. [ABSTRACT FROM AUTHOR]

Aims: The Sub-Boreal Pine-Spruce xeric-cold (SBPSxc) biogeoclimatic region in British Columbia, Canada is characterized by weakly-developed soils, thin organic forest floor and limited plant-available nitrogen. Yet, lodgepole pine trees are thriving in this region unaffected by these nitrogen-limitations, which led us to hypothesize that endophytic nitrogen-fixing bacteria could be playing a potential role in sustaining pine tree growth. Methods: We evaluated these endophytes in a yearlong greenhouse experiment with their native host (lodgepole pine) for in planta nitrogen-fixation (15N isotope dilution assay) and growth-promotion (length and biomass). These endophytes were also evaluated with a foreign host native to the SBPSxc region (hybrid white spruce) in another yearlong greenhouse trial. Results: Each bacterial strain considerably enhanced seedling length and biomass of pine and spruce along with fixing significant amount of nitrogen from atmosphere (15–50%). Notably, Caballeronia sordidicola HP-S1r strain fixed 49–50% of the host nitrogen from atmosphere and enhanced seedling length and biomass by up to 1.5-fold and 4-fold, respectively. Conclusions: Endophytic bacteria could be playing a crucial role in the survival of lodgepole pine trees in the SBPSxc region by providing them with significant amounts of fixed nitrogen. Their effectiveness with a foreign host (hybrid white spruce) shows the lack of plant x microbe specificity, indicating their potential role in supporting the growth of multiple boreal forest trees. [ABSTRACT FROM AUTHOR]

Lodgepole pine, a prominent Pinaceae tree species native to western North America, is well-known for its ability to thrive in highly disturbed and degraded areas. One such area is the Sub-Boreal Pine-Spruce xeric-cold (SBPSxc) region in British Columbia, Canada, which is characterized by weakly-developed, parched soils that lack an organic forest floor and essential plant-available nutrients. We hypothesized that plant growth-promoting bacteria could play a significant role in sustaining the growth of lodgepole pine trees in the SBPSxc region. Testing this hypothesis, we evaluated plant growth-promoting abilities of six endophytic bacterial strains previously isolated from lodgepole pine trees growing in this region. These bacterial strains significantly enhanced the length and biomass of their natural host (lodgepole pine) as well as a foreign host (hybrid white spruce) in a 540-day long greenhouse trial. This growth stimulation could be linked to the diverse plant growth-promoting (PGP) abilities detected in these strains using in vitro assays for inorganic/organic phosphate-solubilization, siderophore production IAA production, ACC deaminase activity, lytic enzymes (chitinase, β-1,3-glucanase, protease, and cellulase) activity, ammonia production and catalase activity. ACC deaminase activity was also detected in vivo for all strains using ethylene-sensitive plants–canola and tomato. Notably, strains belonging to the Burkholderiaceae family (HP-S1r, LP-R1r and LP-R2r) showed the greatest potential in all PGP assays and enhanced pine and spruce seedling length and biomass by up to 1.5-fold and 4-fold, respectively. Therefore, such bacterial strains with multifarious PGP abilities could be crucial for survival and growth of lodgepole pine trees in the SBPSxc region and could potentially be utilized as bioinoculant for Pinaceae trees in highly disturbed and nutrient-poor ecosystems. [ABSTRACT FROM AUTHOR]

Understanding interactions between competition and climate in relation to their effects on individual tree growth is crucial to the development of climate-sensitive growth models required for modelling boreal forest succession in a changing climate. We used data from permanent growth and yield sample plots in western Canada and Alaska to investigate the impact of competition within a regional gradient of climatic conditions for lodgepole pine (Pinus contorta Douglas ex Loudon), jack pine (Pinus banksiana Lamb.), trembling aspen (Populus tremuloides Michx.), balsam poplar (Populus balsamifera L.), white spruce (Picea glauca (Moench) Voss), and black spruce (Picea mariana (Mill.) Britton, Sterns & Poggenb.). We characterized the effects of competition (basal area of spruce–fir, deciduous, and pine trees larger than the focal tree) and climate (mean annual temperature and precipitation) and their interactions on basal area growth of individual trees using linear mixed-effects models. Our results indicated that intraspecific competition had stronger effects on growth than interspecific competition and climate. Moreover, significant interactions between intraspecific competition and climate suggest that an increase in intraspecific competition will lead to a reduction in tree growth for warmer regions (lodgepole pine, trembling aspen, balsam poplar, and white spruce) and wetter regions (jack pine). The manner in which interspecific competition altered tree growth responses to climate was variable, depending on tree species and competition type. These results indicate that the relationships between growth and climate may differ according to the degree of competition and the structure of the stand. [ABSTRACT FROM AUTHOR]

An emerging trend in tree-ring research is use of multiple species for reconstructing paleoclimates, but the possible simultaneous use of boreal-cordilleran species is untested. In this study, ring-width chronologies of sympatric Pinus contorta (lodgepole pine, n = 116 series) and Picea albertiana (western white spruce, n = 348 series) were constructed to assess their temporal (dis)similarities and correlative relationships with meteorological variables. Chronology construction was based on multiple Regional Curve Standardization. Most (97.5%) Pinus chronology values occurred within ±1 SD of their Picea counterparts, but Picea values tended to be slightly less (sign-test, p < 0.001, n = 201). Pinus ring widths were more frequently (16 versus 9) and more strongly correlated (U-test, p < 0.009) with 1942-2013 meteorological variables than Picea. Both species were correlated with moisture variables, but Picea was not correlated with those of temperature. Pinus and Picea ring-width variation was best explained by summer (r = -0.434) and annual (r = -0.426) heat-moisture index values (p < 0.001, n = 72) among tested variables, respectively. Although seldom used, P. contorta appears as suitable as conventionally-used P. albertiana based on chronology similarity, but a greater diversity of significant correlation outcomes suggest Pinus is potentially more useful for boreal-cordilleran paleoclimate reconstruction. [ABSTRACT FROM AUTHOR]

This study was conducted to quantify growth responses of three major commercial conifer species (lodgepole pine (Pinus contorta Douglas ex Loudon var. latifolia Engelm. ex S. Watson), interior Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. glauca (Beissn.) Franco), and spruce (white spruce (Picea glauca (Moench) Voss) and hybrid spruce (Picea engelmannii Parry ex. Engelm. × Picea glauca (Moench) Voss × Picea sitchensis (Bong.) Carrière))) to various fertilizer blends in interior British Columbia, Canada. Over 25 years, growth-response data were repeatedly collected across 46 installations. The fertilizer blends were classified into three groups: nitrogen only; nitrogen and sulfur combined; and nitrogen, sulfur, and boron combined. The growth responses for stand volume, basal area, and top height were calculated through absolute and relative growth rate ratios relative to a controlled group. Fertilizer blend, inverse years since fertilization, site index, stand density at fertilization, and their interactions with the fertilizer blend were used as explanatory variables. The magnitude and significance of volume and basal area growth responses to fertilization differed by species, fertilizer-blend groups, and stand-condition variables (i.e., site index and stand density). In contrast, the response in top height growth did not differ among fertilization blends, with the exception of the nitrogen and sulfur fertilizer subgroup for lodgepole pine. The models developed in this study will be incorporated into the current growth and yield fertilization module (i.e., Table Interpolation Program for Stand Yields (TIPSY)), thereby supporting guidance of fertilization applications in interior forests in British Columbia. [ABSTRACT FROM AUTHOR]

Mid-latitude forests commonly show increased productivity and ultimately produce larger trees on shaded, northern aspects compared with those on sunny, southern aspects. Little research has been conducted on this phenomenon at higher latitudes where solar radiation is less available. We examined patterns of canopy tree size in a set of 142 naturally regenerated, late-seral conifer stands in northwestern British Columbia, Canada, at latitudes of 54°N–56°N. The height, diameter, and total stem volume of three shade-tolerant conifers (western hemlock (Tsuga heterophylla (Raf.) Sarg.), subalpine fir (Abies lasiocarpa (Hook.) Nutt.), and hybrid spruce (Picea glauca × engelmannii (Moench) Voss)) and shade-intolerant lodgepole pine (Pinus contorta var. latifolia Engelm. ex S. Watson) were analyzed. In contrast to most previous studies, mean canopy tree height, diameter, and volume were greatest on southern aspects and lowest on northern aspects for the subset of sites with pronounced slopes (≥30%). There was some variation in patterns among species, with western hemlock responding most strongly to topography, and species-specific effects of topography on height–diameter allometry. We suggest that decreased levels of radiation at northern latitudes and increased light and warmer temperatures on steeper, southern aspects promote growth. In contrast, colder, shaded, northern aspects with increased snow accumulation, delayed snowmelt, and decreased nitrogen mineralization inhibit growth. Our results, together with published data, suggest that a latitudinal shift from higher forest productivity on northern aspects to higher productivity on southern aspects typically occurs between 40°N and 50°N. [ABSTRACT FROM AUTHOR]

• We assessed tree water stress from leaf temperature and changes in stem radius. • Both approaches revealed responses to similar environmental variables over the summer. • Pinus contorta was more sensitive to decreasing soil moisture than Picea glauca. • UAV-based thermal imagery can identify water stress in a natural forest environment. With a warming climate and greater evaporative demand, many forest ecosystems are increasingly affected by water limitation as prolonged water deficits reduce tree-level growth and survival. Water deficit can be monitored in several ways, including from daily measurements of sap flow or changes in stem radius from automated sensors mounted on individual trees. As an alternative approach, we evaluated the use of airborne thermal imagery from unmanned aerial vehicles as a rapid, scalable tool for assessing tree-level water stress. Plant water stress leads to higher leaf temperatures when soil moisture is low and evaporative demand is high. To detect this response, we modeled the difference between leaf and air temperature (∆T) as a function of local soil moisture, vapor pressure deficit, and wind speed for two tree species, lodgepole pine (Pinus contorta var. latifolia) and white spruce (Picea glauca). We used those same weather and soil conditions to model dendrometer-based measurements of daily changes in internal tree water deficit (∆TWD). While canopy leaf temperature and daily change in tree water deficit showed little direct correlation with one another, these variables both responded to soil moisture, vapor pressure deficit, and wind speed in a manner that reflects responses to water stress as soil became progressively drier over the summer months. The two species showed some differences related to species-specific strategies for drought avoidance. The application of thermal imagery to detect water stress in natural forest ecosystems can improve understanding of how trees experience water stress across species and environmental conditions. [ABSTRACT FROM AUTHOR]

Survival and growth of Siberian larch (SL, Larix sibirica Ledeb.) were compared with those of three conifer species native to Alberta, Canada: lodgepole pine (LP; Pinus contorta var. latifolia Engelm. ex S. Watson), white spruce (WS, Picea glauca (Moench) Voss), and jack pine (JP, Pinus banksiana Lamb.) at 12, 10, and 3 trial locations, respectively. The average data age was 18 years (range: 3 to 27 years). Survival of SL averaged 4.2% and 6.5% worse than LP and WS, respectively, while it was 5% better than JP. SL grew 25%, 94%, and 23% taller than LP, WS, and JP, respectively. Stem forking rates were similar between SL and LP, WS, and JP. The best seed sources for Alberta were mature trees established in Alberta and Saskatchewan of unknown initial provenances. The Russian Altai Mountain source grew well at high elevations, while the Finnish Raivola performed well in the northern, low-elevation area. Open-pollinated progeny tests of 58 families planted in five diverse locations yielded individual-tree narrow-sense heritabilities and family mean heritabilities for height at age 15 of 0.15 and 0.59, respectively. The type B between-site genetic correlation was 0.44, indicating a strong genotype × environment interaction. SL has performed well in Alberta, and its growth can be further improved by selection and breeding from appropriate seed sources. [ABSTRACT FROM AUTHOR]

Genomics-assisted tree breeding (GATB) is an emerging biotechnology method that has the potential to produce improved planting stock in selected traits, such as greater volume or higher wood quality, more quickly and effectively compared with traditional field-based breeding (TB) methods. In this study, we conducted an ex-ante stand-level financial benefit-cost analysis that is linked to a provincial tree growth and yield projection model to investigate the potential financial benefits of using improved white spruce (Picea glauca (Moench) Voss) and lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) planting stock identified via alternative tree improvement strategies (i.e. GATB vs. TB methods) for forest companies in the province of Alberta, Canada. With consideration of major tree breeding and establishment costs, expected sawlog price premiums at harvest, a shorter breeding cycle time, and additional genetic gain in volume achieved from using the GATB method relative to the TB method in the financial analysis; this study found that the use of GATB-selected third-generation planting stock was difficult to justify economically alone compared with TB-selected seedlings under the current sawlog market value and the current planting rate with improved stock in the province. However, results of our sensitivity analysis also revealed that the GATB method is: (1) more financially supported at lower discount rates; (2) strongly supported through decreased seedling costs with increased areas planted with improved stock; and (3) strongly supported through an increase in log price premiums at harvest resulting from potentially better wood quality and higher volume production relative to TB-selected stock. The findings of this study highlight several important market and biophysical factors that forest managers should take into account when adopting biotechnology in forestry. [ABSTRACT FROM AUTHOR]

Highlight • Black and white spruce increased in growth following mountain pine beetle outbreak. • White spruce had a higher growth rate than black spruce. • Spruce growth increases as initial tree size and understory light increases. • High spruce/fir competition led to a lower diameter growth but higher height growth. • Both species of spruce have the potential of replacing dead overstory pine trees. Abstract Advanced regeneration of black spruce and white spruce are common in lodgepole pine dominated stands of Alberta. These economically important species have the potential to replace lodgepole pine trees that are killed by mountain pine beetle (MPB). The growth responses of both species of spruce after overstory lodepole pine mortality were examined using data collected from seven sites in the lower foothills of western Alberta, Canada. We sampled understory black and white spruce (>1.3 m in height) and characterize competitive effect of surrounding trees on growth response. Diameter and height growth responses of both species were affected positively by overstory pine mortality with white spruce having a shorter delay in release response than black spruce. While higher mean growth responses were observed for white spruce, both species of spruce increased in growth as initial tree size and understory light increases. Spruce/fir competition around the focal trees resulted in increased height growth and a reduction in diameter growth of both spruces. Overall, our results demonstrate that advance regeneration of both species of spruce can increase in growth and potentially replace pine in the canopy that have been lost to MPB. [ABSTRACT FROM AUTHOR]

The effectiveness of nitrogen (N) fertilization in improving tree growth in saline forest soils is poorly understood. Hence, in this study, the interactive effect of N fertilization and salt stress on seedling physiology and growth was examined to improve our understanding of possible mechanisms for fertilization to mitigate salt stress. We compared physiological characteristics, growth, and foliar and root nutrient concentrations in lodgepole pine ( Pinus contorta ) and white spruce ( Picea glauca ) seedlings planted in a peat-mineral soil mix during a three months study with N fertilization (0 and 300 mg N seedling −1 ) and salinity (0, 50, 100, 150 mmol L −1 NaCl) in a greenhouse experiment. Nitrogen fertilization significantly increased net photosynthetic rates ( P n ) and N concentrations in needles and roots, resulting in improved seedling height and root collar diameter growth and total seedling biomass for both species when seedlings were subjected to low salinity (50 mmol L −1 NaCl), while it did not help tree growth under high salinity (150 mmol L −1 NaCl). The physiological responses to combined salt stress and N fertilization did not differ between the two species; however, fertilization improved the growth of pine seedlings more than that of spruce seedlings under different salinity levels. The results suggest that the effectiveness of N fertilization in mitigating the salinity effect on seedling growth was species specific. Our study demonstrates that N fertilization improves tree growth through enhanced photosynthesis and N nutrition under low salinity and provides valuable insights into strategies to manage N nutrition in saline boreal forest soils. [ABSTRACT FROM AUTHOR]

We investigated relationships between phosphorus (P) availability and fractionation and growth of lodgepole pine ( Pinus contorta var. latifolia Engelm. ex S. Watson) and white spruce ( Picea glauca (Moench) Voss) in the Athabasca oil sands region. The study sites had peat - mineral soil mix (PMM) as cover soil over a tailings sand substrate planted to pine or an overburden substrate planted to spruce. Available P was determined using a modified Kelowna extraction and sequentially extracted to obtain exchangeable, Fe- and Al-bound, Ca- and Mg-bound, organic, and residual P. The organic P content in PMM explained 83% and 65% of the variations in available P in the pine and spruce sites, respectively. Phosphorus bound to Fe and Al in PMM was also positively related to available P on pine sites ( p < 0.001) but not on spruce sites. Available P in PMM was correlated with aboveground biomass increment of spruce ( p < 0.05) and explained 78% of the variation in foliar P. Foliar P in both pine and spruce was lower than the adequate level for tree growth. Low foliar P and available P in PMM affect the successful establishment of pine and spruce trees on the reclaimed sites, and proper P nutrition management is important to overcome P limitation in reclaimed soils. [ABSTRACT FROM AUTHOR]

Conifer winter damage results primarily from loss of cold hardiness during unseasonably warm days in late winter and early spring, and such damage may increase in frequency and severity under a warming climate. In this study, the dehardening dynamics of lodgepole pine ( Pinus contorta Dougl. ex. Loud), jack pine ( Pinus banksiana Lamb.), white spruce ( Picea glauca (Moench) Voss), and black spruce ( Picea mariana (Mill.) B.S.P.) were examined in relation to thermal accumulation during artificial dehardening in winter (December) and spring (March) using relative electrolyte leakage and visual assessment of pine needles and spruce shoots. Results indicated that all four species dehardened at a similar rate and to a similar extent, despite considerably different thermal accumulation requirements. Spring dehardening was comparatively faster, with black spruce slightly hardier than the other conifers at the late stage of spring dehardening. The difference, however, was relatively small and did not afford black spruce significant protection during seedling freezing tests prior to budbreak in late March and early May. The dehardening curves and models developed in this study may serve as a tool to predict cold hardiness by temperature and to understand the potential risks of conifer cold injury during warming-freezing events prior to budbreak. [ABSTRACT FROM AUTHOR]

Losses in forest productivity through poor soil management are typically evaluated by changes in crop production, but conflicting growth responses among co-occurring species can challenge criteria for sustainability. In this study, we evaluate species response to compaction and organic matter removal by contrasting the growth and foliar attributes at age 20 of lodgepole pine ( Pinus contorta Dougl. ex Loud.) and hybrid white spruce ( Picea glauca × engelmannii (Moench) Voss) in sub-boreal forests of central British Columbia. Bole volume increment was stable for lodgepole pine, averaging a 6 % difference across treatments. White spruce, in contrast, often had large growth increases on forest floor retained - compacted plots (average of 63 % gain) but reductions in productivity on the forest floor removed - compacted plots (40 % decline). Foliar nitrogen concentrations converged across treatments for both species, despite the removal of over 50 % of the site N capital. Some key differences in species traits were suggested by foliar δ15N, attributed to deeper rooting of pine, and foliar δ13C, indicating possibly higher CO2 assimilation potential for spruce. The implication is that standard metrics of sustainable forestry are contingent upon tree autecology and that comprehensive assessments of land management require a measure of collective species response. [ABSTRACT FROM AUTHOR]

Key message : Early selection in tree breeding requires a credible age-age correlation. Modelling height growth in provenance and progeny trials, we can predict age-age correlations suitable for use in operational breeding as described in this article. Context : Tree breeding involves early selection, which is an indirect selection using a genetic correlation. This study describes a procedure of predicting an age-age phenotypic correlation as a surrogate for a genetic correlation. Although the predicted correlations are based on white spruce ( Picea glauca) and lodgepole pine ( Pinus contorta) data, they can be used in other coniferous species with similar mode of height growths. Aims : The aim of the study is to predict a correlation coefficient used to adjust breeding values at a measurement age to breeding values at a rotation age. This correlation is derived from the observed height growth trajectories of trees in progeny and provenance trials. Methods : Correlation prediction equations were developed using modelled height growth in provenance and progeny trials of lodgepole pine and white spruce. The time lag between successive tree ages was used as a correlation predictor variable. Results : Correlations differed between spruce and pine but the differences narrowed as trees grew older. For example, a correlation between 20 and 100 years was 0.607 for spruce and 0.470 for pine, whereas that of 30 and 100 was 0.826 for spruce and 0.832 for pine. Based on the age-age correlation, the optimum selection age for a 100-year rotation age is 40-50 years. Parameters of the tree height growth function exhibited significant genetic variance and genotype × environment interaction. Conclusion : After the age of 40 years, age-age correlation for height may be less important for selection and genetic gain prediction than the correlation between height and diameter, which is declining with tree age. [ABSTRACT FROM AUTHOR]

4 c An NBSK pulp comprised of a mixture of pine and spruce wood fibers SP 35 sp obtained from SCA from their Östand Mill (Sundsvall, Sweden). Corrections to: On two-phase modeling of dewatering pulp suspensions. [Extracted from the article]

The evolutionary and genomic determinants of sequence evolution in conifers are poorly understood, and previous studies have found only limited evidence for positive selection. Using RNAseq data, we compared gene expression profiles to patterns of divergence and polymorphism in 44 seedlings of lodgepole pine (Pinus contorta) and 39 seedlings of interior spruce (Picea glauca × engelmannii) to elucidate the evolutionary forces that shape their genomes and their plastic responses to abiotic stress. We found that rapidly diverging genes tend to have greater expression divergence, lower expression levels, reduced levels of synonymous site diversity, and longer proteins than slowly diverging genes. Similar patterns were identified for the untranslated regions, but with some exceptions. We found evidence that genes with low expression levels had a larger fraction of nearly neutral sites, suggesting a primary role for negative selection in determining the association between evolutionary rate and expression level. There was limited evidence for differences in the rate of positive selection among genes with divergent versus conserved expression profiles and some evidence supporting relaxed selection in genes diverging in expression between the species. Finally, we identified a small number of genes that showed evidence of site-specific positive selection using divergence data alone. However, estimates of the proportion of sites fixed by positive selection (a) were in the range of other plant species with large effective population sizes suggesting relatively high rates of adaptive divergence among conifers. [ABSTRACT FROM AUTHOR]

The distribution and characteristics of foliage are important aspects of tree structure and have implications for the productivity of individual trees and whole stands. We modelled foliage biomass and specific leaf area (SLA) using a sample of 60 lodgepole pine ( Pinus contorta ) and 60 white spruce ( Picea glauca ) that were destructively sampled in British Columbia, Canada. We modelled foliage biomass and SLA at three scales of organization: individual primary branches, annual shoots (all branches on an annual increment of the main stem), and the whole tree. We used a variety of independent variables that range in scale from the branch to plot level. Models of foliage biomass and SLA differ substantially between the two species even though their basic architectural design is quite similar. Models differed notably among levels of organization. For branch-level biomass, relevant variables for both species included branch diameter, length, age, distance to the crown base, and a measure of crown contact; however, at the annual-shoot level, relevant explanatory variables were mostly different between the species. At the whole tree-level, only crown length was common to both species and all other explanatory variables differed. SLA was higher in spruce than pine for all age classes and canopy positions. Overall, the models allow prediction of important crown properties for two major conifers at a range of scales, and can thus contribute to better prediction of stand growth and other properties. [ABSTRACT FROM AUTHOR]

A two-stage modelling approach was used for developing ingrowth models for four major tree species in Alberta: aspen, lodgepole pine, black spruce and white spruce. The probability of ingrowth presence was modelled first, followed by the modelling of annual amount of ingrowth conditional on ingrowth being present. To handle variable measurement intervals and plot sizes typical of repeatedly measured forestry data, two generalized logistic models were evaluated at the first stage: a traditional model with measurement interval length and plot size factor incorporated as an exponent of a standard logistic function and an alternative model with measurement interval length and plot size factor incorporated as a denominator. Two criteria were evaluated for defining optimal threshold values for plot classification: criterion 1 to maximize the summation of sensitivity and specificity and criterion 2 to maximize the overall rate of correct plot classification. It was found that criterion 1 was superior to criterion 2 for providing better plot classifications. The two ingrowth probability models behaved similarly based on model fitting and model validation results. Annual amount of ingrowth was modelled at the second stage by exponential functions. [ABSTRACT FROM AUTHOR]

Low nitrogen (N) availability may affect lodgepole pine ( Pinus contorta , Pl) and white spruce ( Picea glauca , Sw) growth in some reconstructed boreal forest soils in the Athabasca oil sands region in Alberta, Canada. The objective of this study was to investigate the effect of fertilization (N alone or complete fertilizer) on foliar nutrient concentrations in and growth of Pl (planted in soils with tailings sand as a substrate) and Sw (planted in soils with overburden material as a substrate) in a single-tree fertilization study. Two growing seasons after fertilization, both N alone and complete fertilizer treatments increased the height, diameter at breast height and aboveground biomass growth of Sw ( p = 0.005, 0.009 and 0.015, respectively). In contrast, fertilization did not affect Pl growth. Foliar N concentration and content in current-year needles of Sw were higher following fertilization than in the control treatment in 2012 ( p < 0.001 for both), but not in 2013. Foliar δ 15 N in current-year and 1-year-old needles was greater in the fertilization than in the control treatment for Sw ( p < 0.001 for both), in association with the increase of δ 15 N in soil NO 3 − -N. No fertilization effect on foliar micronutrients (Fe, Mn, Cu, Zn, B and Mo) or soil NH 4 + -N, NO 3 − -N or dissolved organic N was found in either Pl or Sw sites. We conclude that N was a limiting factor for tree growth in Sw but not in Pl sites and that N fertilization may be used to improve Sw growth in some reclaimed sites with overburden as a substrate in the oil sands region. [ABSTRACT FROM AUTHOR]

Peat-mineral soil mix (PMM) over tailings sand (TS) or overburden (OB) is a commonly used prescription for oil sands reclamation. The TS and OB (the substrates) often have unfavorable conditions such as high salinity, soil compaction, low nutrient availability in OB, and low nutrient and water availabilities in TS, which may limit tree growth. The objective of this study was to identify limiting factors for growth of lodgepole pine ( Pinus contorta ) on PMM over TS and white spruce ( Picea glauca ) on PMM over OB in the Athabasca oil sands region, Alberta, Canada. In the pine sites, mean annual growth of height (HG), diameter at breast height (DBHG) and aboveground biomass (ABG) were significantly correlated with volumetric water content (VWC) in PMM and foliar δ 13 C in current-year needles. Sites with high productivities had the lowest foliar δ 13 C relative to sites with low and medium productivities. The VWC and dissolved organic carbon (DOC) together explained 80% of the variation in both the current annual increment of height (HI) ( p = 0.007) and aboveground biomass (ABI) ( p = 0.008). In the spruce sites, foliar potassium (K) and foliar and soil nitrogen (N) concentrations were positively correlated with HG, DBHG and ABG, consistent with patterns in K and inorganic N (the sum of NH 4 + -N and NO 3 − -N) concentrations in PMM in those sites. Soil electrical conductivity (EC) and bulk density (Db) were greater in low than in medium and high productivity sites. The Db and inorganic N concentration together explained 67% of the variation in HI ( p = 0.037), while Db and EC together explained 79% of the variation in ABI ( p = 0.009). In conclusion, lodgepole pine trees planted on PMM over TS sites were limited by low water availability, while low soil N availability and high salinity limited the growth of white spruce trees planted on PMM over OB sites. Reclamation practices need to address water and nutrient limitations to ensure the success of reclaiming disturbed areas in the oil sands region. [ABSTRACT FROM AUTHOR]

• Short lodgepole pine trees were more likely to be dead when surrounded by tall trees. • Trembling aspen was more likely to be alive when surrounded by tall neighbours. • White spruce trees were more likely to be dead when surrounded conspecific trees. • Tree mortality can be studied by using unmanned aerial vehicles. Advances in unmanned aerial vehicle (UAV) technology have opened new opportunities for measuring canopy mortality processes through high-resolution aerial imagery. Unlike traditional plot-based sampling, UAVs can easily survey areas several hectares in size that encompass hundreds of canopy trees. The resulting imagery provides extensive data on the number and locations of dead trees (snags), which can be related to neighbourhood conditions and environmental factors that vary among stands. Here, we used a UAV to measure the relative proportions of live and dead canopy trees in stands varying in soil moisture across a mixed forest landscape. Crowns of live trees and snags were first segmented and classified to species from high-resolution canopy imagery. We then modeled whether crowns of each species were alive or dead as a function of tree height, neighbourhood competition, soil moisture, and the relative abundance of conspecifics. Short lodgepole pine (Pinus contorta var. latifolia) trees were more likely to be dead when surrounded by a tall canopy in sites with greater soil moisture, reflecting effects of competition on this shade-intolerant species. Trembling aspen (Populus tremuloides) was more likely to be alive when surrounded by tall neighbours, perhaps because this clonal species can benefit from facilitation through root connections with neighbouring aspen stems. There was a higher frequency of white spruce (Picea glauca) snags in sites where it had a high relative abundance, suggesting strong effects of intraspecific competition for this species. Soil moisture did not appear to have a direct effect on the snag frequency of any of these species, despite pronounced niche partitioning along an elevation-driven moisture gradient. Our models explained 39% and 33% of the variation in white spruce and lodgepole pine snag frequency, respectively, but did not have much predictive power for trembling aspen or total snag frequency. Our results reflect the important role of competition in determining tree mortality, but also indicate that stochastic or unexplained processes account for considerable variation in snag frequency among stands. As UAV technology becomes more widely used by ecologists, it may enable a better understanding of how biotic and abiotic processes produce local variation in canopy mortality. [ABSTRACT FROM AUTHOR]

Species respond to environmental stress through a combination of genetic adaptation and phenotypic plasticity, both of which may be important for survival in the face of climatic change., By characterizing the molecular basis of plastic responses and comparing patterns among species, it is possible to identify how such traits evolve. Here, we used de novo transcriptome assembly and RNAseq to explore how patterns of gene expression differ in response to temperature, moisture, and light regime treatments in lodgepole pine ( Pinus contorta) and interior spruce (a natural hybrid population of Picea glauca and Picea engelmannii)., We found wide evidence for an effect of treatment on expression within each species, with 6413 and 11 658 differentially expressed genes identified in spruce and pine, respectively. Comparing patterns of expression among these species, we found that 74% of all orthologs with differential expression had a pattern that was conserved in both species, despite 140 million yr of evolution. We also found that the specific treatments driving expression patterns differed between genes with conserved versus diverged patterns of expression., We conclude that natural selection has probably played a role in shaping plastic responses to environment in these species. [ABSTRACT FROM AUTHOR]

Next-generation sequencing (NGS) technologies are revolutionizing both medical and biological research through generation of massive SNP data sets for identifying heritable genome variation underlying key traits, from rare human diseases to important agronomic phenotypes in crop species. We evaluated the performance of genotyping-by-sequencing (GBS), one of the emerging NGS-based platforms, for genotyping two economically important conifer species, lodgepole pine ( Pinus contorta) and white spruce ( Picea glauca). Both species have very large genomes (>20,000 Mbp), are highly heterozygous, and lack reference sequences. From a small set (six accessions each) of independent replicated DNA samples and a 48-plex read depth, we obtained ~60,000 SNPs per species. After stringent filtering, we obtained 17,765 and 17,845 high-coverage SNPs without missing data for lodgepole pine and white spruce, respectively. Our results demonstrated that GBS is a robust and suitable method for genotyping conifers. The application of GBS to forest tree breeding and genomic selection is discussed. [ABSTRACT FROM AUTHOR]

We evaluated the Mixedwood Growth Model (MGM) at a whole model scale for pure and mixed species stands of aspen and white spruce in the western boreal forest. MGM is an individual tree-based, distance-independent growth model, designed to evaluate growth and yield implications relating to the management of white spruce, black spruce, aspen, lodgepole pine, and mixedwood stands in Alberta, British Columbia, Saskatchewan, and Manitoba. Our validation compared stand-level model predictions against re-measured data (volume, basal area, diameter at breast height (DBH), average and top height and density) from permanent sample plots using combined analysis of residual plots, bias statistics, efficiency and an innovative application of the equivalence test. For state variables, the model effectively simulated juvenile and mature stages of stand development for both pure and mixed species stands of aspen and white spruce in Alberta. MGM overestimates increment in older stands likely due to age-related pathology and weather-related stand damage. We identified underestimates of deciduous density and volume in Saskatchewan. MGM performs well for increment in postharvest stands less than 30 years of age. These results illustrate the comprehensive application of validation metrics to evaluate a complex model, and provide support for the use of MGM in management planning. [ABSTRACT FROM AUTHOR]

Sub-alpine environments consist of altitudinal gradients associated with dramatic changes in plant growth and community composition, but the role of soil feedbacks and microbe interactions is largely unknown. Here, we examine the influence of the overall soil microbial community, with a focus on ectomycorrhizal and dark septate endophytic root colonizing fungi, from low, mid, and high elevations on the growth of Pinus contorta and Picea glauca × engelmannii. The influence of the soil microbial community was tested on seedlings from the same three elevations in order to determine 'home' versus 'away' effects on conspecifics of differing elevations. The low elevation soil was the most fertile and harbored a soil microbial community with an overall negative effect on seedling growth. In contrast, the high elevation soil was the least fertile and had a microbial community that enhanced seedling growth. However, only the soil microbial community in the highest elevation soil resulted in a stronger influence on the native P. contorta seedlings than seedlings originating from lower elevations. Despite the overall influence of the soil microbial community, ectomycorrhizal colonization was significantly correlated with P. glauca × engelmannii growth rates, but colonization by dark septate endophytes showed no relationship with seedling growth. The results provide evidence that plant-soil microbial community relationships are dependent on soil environment. Moreover, our results provide further support for the importance of soil microbes in facilitating seedling growth toward the edge of their elevational range. [ABSTRACT FROM AUTHOR]

Site preparation and vegetation control can be used to mitigate climate change effects on early plantation growth in boreal forests. In this study, we explored growth of lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) and white spruce (Picea glauca (Moench) Voss) in relation to climate and site preparation using 20 years of data collected from studies in British Columbia. Results indicate that up to 45% of the variation in spruce growth and up to 37% of the variation in pine growth over this 20-year period can be explained by selected climatic variables. Monthly climate variables showed a stronger relationship to conifer growth than seasonal and annual variables. Climate variables related to the preceding year accounted for more than half of the variables in the final equations, indicating a lagged response in conifer growth. Future projections indicated that height growth of young lodgepole pine plantations in the sub-boreal zone could benefit (in the short term) from longer growing seasons by up to 12% on untreated stands. Untreated young white spruce plantations in the boreal zone may suffer height growth decreases of up to 10% due to increased drought stress. Vegetation control and mechanical site preparation treatments appear to mitigate effects of climate change to some extent. La préparation de terrain et la maîtrise de la végétation peuvent être utilisées pour atténuer les effets des changements climatiques sur la croissance de jeunes plantations en forêt boréale. Dans cette étude, nous évaluons la croissance du pin tordu latifolié (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) et de l'épinette blanche (Picea glauca (Moench) Voss) en fonction du climat et de la préparation de terrain à l'aide de données récoltées sur une période de 20 ans dans le cadre d'études réalisées en Colombie-Britannique. Les résultats indiquent que pendant cette période de 20 ans, jusqu'à 45 % de la variation de la croissance de l'épinette blanche et jusqu'à 37 % de la variation de la croissance du pin tordu peuvent être expliqués par des variables climatiques sélectionnées. Les variables climatiques mensuelles étaient davantage reliées à la croissance des conifères que les variables saisonnières et annuelles. Les variables climatiques reliées aux conditions de l'année précédente représentaient plus de la moitié des variables des équations finales, ce qui indique un décalage de la réaction de la croissance chez les conifères. Des projections indiquent que la croissance en hauteur des jeunes plantations de pin tordu de la zone subboréale pourrait, à court terme, être jusqu'à 12 % supérieure à celle de peuplements non traités si elles bénéficiaient de saisons de croissance plus longues. La croissance en hauteur des jeunes plantations non traitées d'épinette blanche dans la zone boréale pourrait diminuer jusqu'à 10 % à cause de l'augmentation des stress hydriques. La maîtrise de la végétation et la préparation mécanique de terrain semblent atténuer les effets des changements climatiques jusqu'à un certain point. [ABSTRACT FROM AUTHOR]

Abstract: This work aimed to compare radial growth–climate relationships among three coexisting coniferous tree species across a wide geographic and climate range from southern British Columbia (BC) to central Yukon, Canada. Tree-ring data were collected from 20 mature stands of white spruce (Picea glauca), lodgepole pine (Pinus contorta var. latifolia), and subalpine fir (Abies lasiocarpa). Linear relationships between annual growth variation and monthly and seasonal climate were quantified with correlation and regression analyses, and variation in climate–growth responses over a climatic gradient were quantified by regressing growth responses against local mean climatic conditions. Temperatures had more consistent and stronger correlations with growth for all three species than precipitation, but growth–climate responses varied among species and among sites. In particular, pine and fir populations showed different responses between BC and Yukon, whereas spruce showed a more consistent response across the study domain. Results indicate that (1) the response and sensitivity of trees to seasonal climate variables vary among species and sites and (2) winter temperatures prior to growth may have significant impacts on pine and fir growth at some sites. The capacity to adapt to climate change will likely vary among the study species and across climatic gradients, which will have implications for the future management of mixed-species forests in Yukon and BC. [Copyright &y& Elsevier]

In this study, compatible height and diameter increment models were fitted for lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.), trembling aspen (Populus tremuloides Michx.), and white spruce (Picea glauca (Moench) Voss), using the relationship between diameter and height growth. It was assumed that tree diameter increment is directly proportional to height increment, and the proportionality constant is a function of competition and site productivity. The results showed that the fit statistics are comparable with results of other studies, with adjusted R2 ranging from 30% to 50%. A validation test of the models, using independent permanent sample plots data, showed that the short-term predictions of the models for both pure and mixedwood stands are fairly unbiased. The models also gave reasonable average height growth and diameter growth trajectories for pure stands of the three species and also projected long-term mixedwood (aspen – white spruce mixture) volume growth dynamics reasonably well. The models also projected reasonably well (i) the effect of increasing initial stem density on average diameter and height, and (ii) the stand volume compared with an older version the Mixedwood Growth Model (ver. 2000A). It was concluded that explicitly linking tree height and diameter increment models does not only have a solid ecological basis, but it also results in a compatible prediction of tree growth and stand dynamics. [ABSTRACT FROM AUTHOR]

[Display omitted] • Exploration of producing energy-efficient nanocellulose by disc refining. • Novel quality index developed to compare between industrial crop and refiner type. • High quality development of nanocellulose (aspect ratio, fines, and tensile index). • Disc BEK quality index is fifty-eight times more energy efficient than PFI NBSK. • Fines resulted in improvement of aspect ratio, quality index, sheet strength. In the drive towards sustainable development, the growing application of renewable, biodegradable, green materials to substitute non-renewable resources has roused substantial interest. However, the very high electrical energy consumption typical of mechanical nanocellulose production is a significant drawback, from the point of view of both environmental impact and production cost. The aim of this study was to investigate the effect of fiber source, mechanical treatment mode and scale on the energy consumption for nanocellulose production. Nanocellulose (mechanically prepared fibers), also known as cellulose nanofibers, or CNF) from hardwood eucalyptus (Eucalyptus grandis) and northern bleached softwood which is believed to be a mix of lodgepole pine (Pinus contorta) and white spruce (Picea glauca) pulp was prepared using lab scale and pilot scale mechanical refiners. The rate of increase in fiber aspect ratio confirms that disc (pilot scale) refining is seven and thirty-three times more energy efficient than lab scale PFI (Papir Forsknings Institutet) mill refining for processing softwood and hardwood, respectively. A novel quality index (Q) is proposed which considers the percentage of fines, fiber diameter and relative bonded area in the sheet to demonstrate the production of high quality nanocellulose. When the energy required to reach equivalent values of Q were compared, it was found that pilot disc refining of hardwood is approximately fifty-eight times more energy efficient than laboratory PFI mill refining of softwood. Fines generation for hardwood and softwood was fifteen and eight times more energy efficient by disc refining as compared with PFI mill refining, respectively. The results indicate that disc refining of hardwood is the most energy efficient method of nanocellulose production, and this outcome can be applied to predict and minimise mechanical energy consumption, and therefore cost and environmental impacts, for nanocellulose production. [ABSTRACT FROM AUTHOR]

• Aridity exerted minimal to no selective pressure on wood density. • Wood density therefore did not reflect an ability to tolerate drought. • Wood quality is best assessed past cambial ages of 10 for spruce and 8 for pine. • Transition age out of juvenile wood production was not a heritable trait. • Five spruce and six pine families had above average wood density and volume. Climate driven tree mortality threatens the current performance and productivity of the temperate boreal forests. For economically important tree species, progeny trials provide an opportunity to assess variability in wood quality and growth traits and their associations with climatic stressors, such as water availability. Data from 3,152 34-year-old white spruce and lodgepole pine progeny, representing 120 half-sib families, were used to test the selective pressure of aridity on wood density and wood microfibril angle, two attributes that contribute to wood performance. Tree increment cores were further evaluated for correlations between time of transition out of juvenile wood production and the environment. Aridity at seed point of origin had minimal to no selective pressure on overall wood density or microfibril angle in the breeding populations represented in this study. Aridity at the progeny test sites had a greater effect on spruce wood density, however, similar effects on pine could not be assessed as sites were too climatically similar. Transition out of juvenile wood production was not found to be influenced by genetic differences across families in either species examined. These determinations are pivotal for breeding programs which seek to use heritable and economically important traits to select for adaptability in a changing climate. [ABSTRACT FROM AUTHOR]

The effect of seed water content (WC) (2-3, 5-6 and 22-25%, on a fresh weight basis), storage temperature (+4, -20, -80 and -196°C) and storage duration (6, 12, 24, 48 and 60 months) on the germination of white spruce (Picea glauca (Moench) Voss), black spruce (Picea mariana (Mill.) B.S.P.) and lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) seed was investigated. Germination of white spruce control (untreated) seeds and seeds adjusted to 2-3% and 5-6% WC declined after 48 months of storage at -80 and -196°C, with a further decline at 60 months at -20, -80, -196°C. Germination remained high when control white spruce seeds and seeds with 2-3, 5-6% WC were stored at +4°C, over all storage durations. Generally, black spruce and lodgepole pine exhibited high germination at all storage temperatures at 2-3% and 5- 6% WC as well as the control (untreated) seed, for up to 60 months in storage. Germination declined for all three species when seed was conditioned to 22-25% WC. This loss in germination was partially recovered in white spruce seed stored at +4, -20 and -80°C after storage durations of 24, 12 and 48 months, respectively, and in black spruce seeds stored at -20 and -196°C after storage durations of 24 months. Mean germination time (MGT) was relatively constant for all species, under all conditions, except for seed conditioned to 22-25% WC, where MGT increased for white spruce seed stored 48 months at -80 and -196°C, and for black spruce seed stored 24 months at +4 and -80°C and 60 months at -196°C. These results show that the optimal storage temperatures are 4°C for white spruce, and 4, -20, -80, and -196°C for black spruce and lodgepole pine, and 2-6% water content is optimal for all 3 species at these temperatures. [ABSTRACT FROM AUTHOR]