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The use of wood ash as a soil amendment in afforestation and reforestation efforts is increasing. While most studies suggest benefits or neutral results on tree growth and survival, a few studies indicate adverse effects. Hybrid larch, jack pine and white spruce were studied at three northwestern Quebec plantation sites after they received wood ash at two application rates. Soil chemical properties, foliar nutrients and seedling growth and mortality were monitored over a period of eight years. The response of soil to ash application was mostly observed in the forest floor and was more pronounced in year 3 than year 8, likely due to the acidifying nature of the boreal soils studied. Jack pine growth increased linearly with wood ash application rates, white spruce growth showed an inconsistent and delayed positive response under the higher application rate, and hybrid larch growth and survival were either increased or decreased under the lower application rate depending of site but decreased at all sites under the higher application rate. The divergence in growth response between tree species underlines a trade-off between species with rapid acquisition of resources (e.g., pine, larch) to species that use more conservative strategies and store nutrients in their tissues for longer periods (e.g., spruce). In the case of hybrid larch, it accumulated larger amounts of Mn in its needles under the higher application rate and thus, the high bioavailabil - ity of Mn appears to have been detrimental to its survival and growth. Its higher sensitivity to Mn addition from ash is likely due to its highly acquisitive (nutrients) nature compared to other coniferous species as well as the initial levels of available Mn levels in the soil. The contrasted growth responses reported here under similar growing conditions highlight the importance of identifying suitable species, sites and application rates to maximize the benefits of wood ash amendments for future tree plantations in the boreal forest. [ABSTRACT FROM AUTHOR]

The increased pressure on timber supply due to a reduced forest land base urges the development of new approaches to fully capture the value of forest products. This paper investigates the effects of knowing the position of knots on lumber volume, value, and grade recoveries in curve sawing of 31 white spruce (Picea glauca (Moench) Voss) and 22 jack pine (Pinus banksiana Lamb.) trees. Internal knot position was evidenced by X-ray computed tomography (CT) imaging, followed by the application of a knot-detection algorithm allowing log reconstruction for use as input in the Optitek sawing simulation software. Comparisons of the three levels of sawing optimization (sweep up, shape optimized, and knot optimized) revealed that considering internal knots before log sawing (e.g., knot optimized) generated 23% more lumber value for jack pine and 15% more for white spruce compared with the traditional sweep-up sawing strategy. In terms of lumber quality, the knot-optimized strategy produced 38% more pieces of grade No. 2 and better in jack pine and 15% more such pieces in white spruce compared with the sweep-up strategy. These results indicate a great potential to increase manufacturing efficiency and profitability by implementing the CT scanning technology, which should aid in developing a strong bioeconomy based on an optimized use of wood. [ABSTRACT FROM AUTHOR]

Site index (SI) is a commonly used measure of forest site productivity and is affected by climate change. Therefore, climate effects on site productivity were analyzed and modeled for jack pine (Pinus banksiana Lamb.), black spruce (Picea mariana (Mill.) B.S.P.), red pine (Pinus resinosa Ait.), and white spruce (Picea glauca (Moench) Voss) plantations using annual/seasonal values of climate variables. Jack pine and black spruce trees were each sampled from 25 plantations (sites), and red pine and white spruce trees were sampled from 30 and 31 plantations, respectively, from across Ontario, Canada. Stem analysis data collected from 201 jack pine, 211 black spruce, 90 red pine, and 93 white spruce trees were used in this study. To analyze and model climatic effects on site productivity, parameters of the stand height models were expressed in terms of climate variables. A nonlinear mixed-effects modelling approach was applied to fit the stand height models. Climate effects on site productivity was evaluated by predicting stand heights in three areas (the central, eastern/southeastern, and western parts of Ontario) for the period 2021 to 2080 under three emissions trajectories (representative concentration pathways (RCP) 2.6, 4.5, and 8.5 watts m−2). Climate effects on site productivity depended on tree species and location. For jack pine, climate effects were positive and pronounced only in western Ontario under all emissions scenarios. The effects were negative and mild after breast height age (BHA) 50 in central Ontario for black spruce. Similarly, the effects were negative and more pronounced at all areas after BHA 35 for red pine. On the other hand, for white spruce the effects were negative and highly pronounced from a young age under all scenarios, mainly in the southeast. For all species except for jack pine, climate effects were more pronounced under RCP 8.5 than the other two scenarios. [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]

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

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

Mixed models combining random coefficient effect and covariance patterns were used to investigate mechanical property variations in jack pine ( Pinus banksiana Lamb.) and white spruce ( Picea glauca (Moench) Voss) trees. Modulus of elasticity (MOE) and modulus of rupture (MOR) were measured by conducting three-point bending tests on small defect-free samples selected from different radial positions and at a height of 2.5 m above ground within the stems. The objective of the paper was to build statistical predictive models describing the radial variations in stems for wood mechanical properties using easily measurable explanatory variables that are typically available in the wood manufacturing industry: distance from pith, tree height and diameter, and spacing. The explanatory variables integrated into the models explained MOE adequately, whereas MOR appeared harder to predict with only these variables and at this resolution. For white spruce, the best mixed-effects models explained 80% and 61% of the variation in MOE and MOR, respectively. For jack pine, it was 51% and 33% for the same response variables. These results are a step toward models that could be used in sawing simulation software designed to estimate the internal properties of sawlogs and, as a result, better predict lumber and pulp chip quality. [ABSTRACT FROM AUTHOR]

X-ray computed tomography (CT) of logs means possibilities for optimizing breakdown in sawmills. This depends on accurate detection of knots to assess internal quality. However, as logs are stored, they dry to some extent, and this drying affects the density variation in the log and therefore the X-ray images. For this reason, it is hypothetically difficult to detect log features in partially dried logs using X-ray CT. This paper investigates the effect of improper heartwood-sapwood border detection, possibly due to partial drying, on knot detection in jack pine ( Pinus banksiana Lamb.) and white spruce ( Picea glauca (Moench) Voss) logs from New Brunswick, Canada. An automatic knot detection algorithm was compared to manual reference knot measurements, and the results showed that knot detection was affected by detected heartwood shape. It was also shown that logs can be sorted into two groups based on how well the heartwood-sapwood border is detected to separate logs with a high knot detection rate from those with a low detection rate. In that way, a decision can be made whether or not to trust the knot models obtained from CT scanning. This can potentially aid both sawmills and researchers working with log models based on CT. [ABSTRACT FROM AUTHOR]

Oil sands mining in northeastern Alberta, Canada, generates tailings containing sand, silt, clay, water, and residual bitumen with hydrocarbons. The impact of tailings on revegetation is a major environmental concern and poses a significant land reclamation challenge. Oil sands companies have recently developed technologies that use thickeners in combination with carbon dioxide to produce non‐segregating tailings (NST), to accelerate the consolidation of tailings while sequestering greenhouse gases. Effects of these tailings on plant re‐establishment have yet to be determined. We investigated the impact of NST on biomass and physiology of 20 boreal woody plant species grown in environmentally controlled growth rooms. The seedlings were grown for 8 weeks in NST capped with boreal forest topsoil or peat‐mineral soil mix or petroleum coke in 50‐cm‐long polyvinyl chloride pipes. We found that the biomass of balsam fir, beaked hazelnut, blueberry, green alder, Labrador tea, lowbush cranberry, paper birch, and raspberry was severely reduced by NST, while the effects on balsam poplar, Bebb's willow, chokecherry, dogwood, saskatoon, and white spruce were relatively weak. This was also the case for jack pine, which showed poor survival in NST. The negative impact of NST on plants can be largely explained by elevated sodium and decreased foliar nutrient concentrations. The impact of NST capping with petroleum coke on plant growth was non‐significant. Differences among species in their survival and biomass responses to NST appeared to be partly a reflection of their natural habitats. Findings from this study can help guide revegetation oil sands reclamation strategies. [ABSTRACT FROM AUTHOR]

Compares the genetic diversity between white spruce Picea glauca and jack pine (Pinus banksiana). Absence of white spruce and jack pine alleles in seed orchards; Level of genetic identities of the specie; Effects of reducing the number of cloned specie on allelic density.

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]

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]

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

Black spruce ( Picea mariana), white spruce ( Picea glauca) and jack pine ( Pinus banksiana) were inoculated with Suillus tomentosus and subjected to potassium fluoride (1 m M KF and 5 m M KF) in the presence and absence of 60 m M NaCl. The NaCl and KF treatments reduced total dry weights in jack pine and black spruce seedlings, but they did not affect total dry weights in white spruce seedlings. The addition of 60 m M NaCl to KF treatment solutions alleviated fluoride-induced needle injury in ectomycorrhizal (ECM) black spruce and white spruce, but had little effect in jack pine seedlings. Both KF and 60 m M NaCl treatments reduced E values compared with non-treated control seedlings. However, with the exception of small reductions of Kr by NaCl treatments in black spruce, the applied KF and NaCl treatments had little effect on Kr in ECM plants. Chloride tissue concentrations in NaCl-treated plants were not affected by the presence of KF in treatment solutions. However, shoot F concentrations in ECM black spruce and white spruce treated with 5 m M KF + 60 m M NaCl were significantly reduced compared with the 5 m M KF treatment. The results point to a possible competitive inhibition of F transport by Cl. We also suggest that the possibility that aquaporins may be involved in the transmembrane transport of F should be further investigated. [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]

The purpose of this study was to develop an understanding of the pattern of variation in longitudinal, radial, and tangential shrinkage in two commercially important Canadian wood species using multivariate nonlinear mixed-effects models. Shrinkage data were measured in each growth ring at different heights on trees harvested from a mixed-species Nelder tree-spacing plot located in New Brunswick, Canada. Live crown base was reconstructed based on stem analysis. Cambial age, sampling height, crown characteristics (crown length, crown ratio, and distance to live crown base), and ring width at time of wood formation were used as prediction variables. The results indicated that shrinkage magnitude and pattern were closely related to crown dimensions and stem position at time of wood formation. Trees from wider tree spacings with larger crown lengths and ratios tended to have smaller tangential and radial shrinkage. Longitudinal shrinkage decreased nonlinearly from pith outwards with slower rate changes near the bottom of the trees. The model fixed effects accounted for more variation in jack pine ( Pinus banksiana Lamb.) than in white spruce ( Picea glauca (Moench) Voss) for shrinkage in the same anatomical direction. After further validation, the model developed can be used to provide shrinkage predictions for lumber distortion models within the framework of an individual tree growth model. [ABSTRACT FROM AUTHOR]

Compares the relative competitiveness of three early successional boreal forest species, trembling aspen (Populus tremuloides Michx.), fireweed (Epilobium angustifolium L.), and calamagrostis (Calamagrostis canadensis (Michx.) Beauv.), on 15N uptake and the growth response by containerized white spruce (Picea glauca (Moench) Voss) and jack pine (Pinus banksiana Lamb.) seedlings. Focus on belowground competition for nitrogen (N) between boreal forest species; Method; Findings; Conclusion.

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

Whole root systems of 2-yr-old containerized white spruce [Picea glauca (Moench) Voss], black spruce [Picea mariana (Mill.) B.S.P.] and jack pine (Pinus banksiana Lamb.) seedlings, with intact root plugs, were exposed to various frost temperatures, which a preliminary test indicated would induce approximately 0 (control), 20, 40, 60, 80 and nearly 100% frost damage. Damage to root systems was evaluated using: (1) two measures of electrolyte leakage (relative conductivity and total tissue leakage after autoclaving); (2) water loss after pressurization; (3) chlorophyll fluorescence (F[sub v]/[sub Fm], maximal PSII photochemical efficiency) measured 4, 21 and 30 days after the beginning of seedling regrowth and (4) live root dry mass measured 21 days after the artificial frost and 60 days after the beginning of regrowth. Seedling survival and growth after the artificial frost were evaluated using live root dry mass measured after 60 days of regrowth and new shoot length, stem diameter, and root and shoot dry mass. Live root dry mass, dead tissue leakage, jack pine root water loss and fluorescence measurements were all significantly correlated with one or more of the growth variables and the number of significant correlations varied with species. Dead tissue leakage measurements appear to be the most promising method for evaluating root damage to 2-yr-old well-developed root systems of these species. [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]

Although studies in the past have reported that the deeper planting of conifers has no effect on seedling performance, most planting guidelines in use today still recommend that seedlings be planted to the rootcollar. Past studies were mostly observational, used bareroot seedlings, and often reported early results from just one or two depths of planting treatments. Most of the results available regarding planting depth for boreal species are anecdotal, although they are planted by the hundreds of millions every year. The present study reports no short-term (1 year) or long-term (15 to 19 years) negative effect of planting depth on the survival and height and diameter growth of black spruce, white spruce, and jack pine seedlings over three large, replicated experiments in the boreal forest of eastern and northern Quebec (eastern Canada). Four different depth treatments were compared, from manual planting at the rootcollar to the deepest mechanical planting treatment at 10 cm or more, making this the largest, longest-lasting study of its kind. Although, as expected, important differences in growth were present between species, all three commonly planted conifers reacted similarly to the planting depth treatments (no effect). This result can in part be attributed to an almost perfect control of frost heaving in the deepest two treatments. Planting depth effects were assessed using analysis of variance, multiple Tukey honestly significant difference, and uncorrected pairwise one-tailed t-tests to increase the probability of detecting a negative effect. Absolute differences and effect sizes (generally small and often positive with greater depths) were also analyzed. [ABSTRACT FROM AUTHOR]

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

Responses of trembling aspen (Populus tremuloides), jack pine (Pinus banksiana), and white spruce (Picea glauca) seedlings to root zone pH ranging from 5 to 9 were studied in sand culture in the presence of two mineral nutrition levels. After eight weeks of treatments, effects of pH on plant dry weights varied between the plant species and were relatively minor in white spruce. Higher nutrient supply significantly increased dry weights only in trembling aspen subjected to pH 5 treatment. There was little effect of pH and nutrition level on net photosynthesis and transpiration rates in white spruce and jack pine, but net photosynthesis markedly declined in aspen at high pH. Chlorophyll concentrations in young foliage decreased the most in trembling aspen and jack pine. The effects of high pH treatments on the concentrations of Mg, P, Ca, Mn, Zn, and Fe in young foliage varied between the plant species with no significant decreases of Fe and Zn recorded in trembling aspen and white spruce, respectively. This was in contrast to earlier reports from the studies carried out in hydroponic culture. The sand culture system that we developed could be a more suitable alternative to hydroponics to study plant responses to pH in the root zone. Plant responses to high pH appear to involve complex events with a likely contribution of nutritional effects and altered water transport processes. [ABSTRACT FROM AUTHOR]

Significant reductions in needle water content were observed in white spruce (Picea glauca (Moench) Voss), black spruce (Picea mariana (Mill) B.S.P.), and jack pine (Pinus banksiana Lamb.) seedlings in response to a 10-day drought, although turgor was apparently maintained. When the seedlings were re-watered after the drought, jack pine needles regained their original saturated volume, whereas white spruce and black spruce needles did not. Significant drought-induced reductions in turgor-loss volume (i.e., tissue volume at the point of turgor loss) were observed in shoots of all three species, especially jack pine. Repeated exposure to 7 days of drought or treatment with the cytochrome P450 inhibitor, paclobutrazol ((2RS,3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-pentan-3-ol), reduced seedling height relative to that of untreated controls in all three species. The reductions in saturated and turgor-loss needle volumes in the paclobutrazol-treated seedlings were comparable with those of seedlings subjected to a 10-day drought. The treatment-induced reductions in shoot and needle water contents enabled seedlings to maintain turgor with tissue volumes close to, or below, the turgor-loss volume of untreated seedlings. Paclobutrazol-treated seedlings subsequently survived drought treatments that were lethal to untreated seedlings. [ABSTRACT FROM AUTHOR]

Ecological processes driving tree success in the early stages of succession are complex and often poorly understood, involving direct and indirect relationships among multiple agents modulated by legacies. Reclamation areas of open-pit mines provide a unique opportunity to study these relationships, as these sites are often homogeneous and have few ecological legacies. Our study evaluated the early performance of three boreal tree species planted at different densities over a large reclaimed landscape (57 ha) in northern Alberta, Canada, that varied in landscape topography, surface soils, and coarse woody material. A range of soil, topographical, and seedling characteristics were measured over five growing seasons. The two surface soils had stark differences in their physical and chemical properties. Overall, seedling survival was high (> 80%) for jack pine (Pinus banksiana) and white spruce (Picea glauca) and somewhat lower (60%) for trembling aspen (Populus tremuloides). All three species grew taller in the fine-textured than in the coarse-textured soils. Linear models identified simple relationships among some of the monitored variables. To further explore more complex relationships, we built a structural equation model for jack pine growth, 2 and 5 years after planting. On coarse-textured soil, the factors controlling pine growth shifted from intrinsic factors of seedling quality in the second growing season to more complex interactions in the fifth growing season, driven by soil nutrients, water availability and colonizing vegetation. We believe these models have the potential to be useful in forest reclamation, by identifying driving factors that could be monitored to indicate reclamation success. [ABSTRACT FROM AUTHOR]

We tested the effects of ectomycorrhizal (ECM) inoculation on greenhouse-grown white spruce (Picea glauca (Moench) Voss) and jack pine (Pinus banksiana L.) seedlings to be used for revegetation of salt-affected tailing sands resulting from the exploitation of oil sand in northeastern Alberta, Canada. White spruce and jack pine seedlings were inoculated with three ECM fungi selected for their in vitro tolerance to excess Na+ and Cl−: Hebeloma crustuliniforme (Bull) Quel. UAMH 5247, Laccaria bicolor Maire (Orton) UAMH 8232 and a Suillus tomentosus (Kauff.) Sing., Snell and Dick isolate from a salt-affected site. The physiological responses of the seedlings to a gradient of NaCl concentration (0, 50, 100 and 200 mM) were assessed over four weeks by: (1) Na+ accumulation and allocation; (2) chlorophyll a fluorescence; (3) growth, (4) water content; and (5) organic osmolyte accumulation. Jack pine seedlings were more sensitive than white spruce seedlings to increasing Na+ and Cl− concentrations. Both species showed decreasing biomass accumulation, and increasing concentrations of organic osmotica and Na with increasing NaCl concentration. White spruce seedlings inoculated with the S. tomentosus isolate had the best growth response at all NaCl concentrations tested. Although jack pine seedlings inoculated with the L. bicolor or S. tomentosus isolate exhibited the highest growth in the 50 and 100 mM NaCl treatments, both fungi increased the photochemical stress and dehydration of their hosts in the 200 mM NaCl treatment. At the latter concentration, jack pine seedlings inoculated with H. crustuliniforme showed the greatest tolerance to salt stress. Although the different fungi altered the physiological response of the host in different ways, inoculation with salt-stress-tolerant ECM fungi increased growth and reduced the negative effects of excess NaCl. Use of controlled mycorrhization may increase survival of coniferous seedlings used for revegetation of salt-affected sites. [ABSTRACT FROM PUBLISHER]

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Mineral soils exposed by fire are often covered by a layer of ash due to complete consumption of the forest floor (litter and duff). To assess the possible effects of ash on seed germination and viability of jack pine (Pinus banksiana Lamb.), black spruce (Picea mariana (Mill.) Britton, Sterns, Poggenb.), white spruce (Picea glauca (Moench) Voss), and balsam fir (Abies balsamea (L.) Mill.), a laboratory experiment was conducted using ash derived from three types of forest floor samples. The samples represented areas of high conifer concentration, high aspen concentration, and mixed aspen and conifer and were collected from five mature aspen (Populus tremuloides Michx.) – conifer mixedwood stands in southeastern Manitoba. Ash derived from each forest floor type neither prohibited nor delayed conifer germination, except that of balsam fir. Balsam fir had significantly less germination on ash derived from forest floor samples with high aspen concentration. When corrected for seed viability, balsam fir had significantly less germination on all three ash types compared with jack pine, black spruce, and white spruce. However, the impact of ash on balsam fir is unlikely to have meaningful ecological implications, as balsam fir is a climax species and will establish in undisturbed mature forests. Le sol minéral exposé par le feu est souvent recouvert d’une couche de cendre due à la combustion de la couverture morte (litière et humus). Les effets de la cendre sur la viabilité et la germination des graines de pin gris (Pinus banksiana Lamb.), d’épinette noire (Picea mariana (Mill.) Britton, Sterns, Poggenb.), d’épinette blanche (Picea glauca (Moench) Voss) et de sapin baumier (Abies balsamea (L.) Mill.) ont été évalués. Une expérience en laboratoire a été réalisée en utilisant de la cendre provenant de trois types d’échantillons de couverture morte, représentatifs de zones avec une concentration élevée de conifères (HC), de peupliers (LC) et d’un mélange de peupliers et de conifères (MC) prélevés dans cinq peuplements mixtes matures de peuplier faux-tremble (Populus tremuloides Michx.) dans le sud-est du Manitoba. La cendre provenant de chacun des types de couverture morte n’a ni inhibé ni retardé la germination des conifères à l’exception du sapin baumier. Les graines de sapin baumier germaient significativement moins bien sur la cendre provenant du type de couverture morte LC. Lorsqu’elle était corrigée pour la viabilité des graines, la germination du sapin baumier était significativement plus faible sur les trois types de cendre comparativement au pin gris, à l’épinette noire et à l’épinette blanche. L’impact de la cendre sur le sapin baumier a peu de chances d’avoir des implications écologiques significatives étant donné que le sapin baumier est une espèce climacique qui s’établira dans les forêts matures non perturbées. [ABSTRACT FROM AUTHOR]

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The root systems of 2-yr-old Picea glauca, Picea mariana and Pinus banksiana seedlings were submitted to various frost temperatures during an artificial frost to induce different levels of root damage. Frost-damaged and control seedlings were placed in a greenhouse under high and low soil moisture regimes. Seedling growth and physiology were evaluated periodically. Seedling survival was reduced when root damage reached levels of 60-80%. Root systems of all three species showed partial to total recovery by the end of the experiment. In general, root freezing damage caused reductions in seedling growth, with these reductions becoming less significant over time. Root damage had little to no effect on black spruce and jack pine seedling physiology, while white spruce CO[sub 2] uptake decreased with increasing root damage. Shoot nitrogen content of all three species decreased slightly with increasing root damage. [ABSTRACT FROM AUTHOR]

Leaf life span is an important plant trait associated with interspecific variation in leaf, organismal, and ecosystem processes. We hypothesized that intraspecific variation in gymnosperm needle traits with latitude reflects both selection and acclimation for traits adaptive to the associated temperature and moisture gradient. This hypothesis was supported, because across 127 sites along a 2,160-km gradient in North America individuals of Picea glauca Picea mariana, Pinus banksiana, and Abies balsamea had longer needle life span and lower tissue nitrogen concentration with decreasing mean annual temperature. Similar patterns were noted for Pinus syivestris across a north-south gradient in Europe. These differences highlight needle longevity as an adaptive feature important to ecological success of boreal conifers across broad climatic ranges. Additionally, differences in leaf life span directly affect annual foliage turnover rate, which along with needle physiology partially regulates carbon cycling through effects on gross primary production and net canopy carbon export. However, most, if not all, global land surface models parameterize needle longevity of boreal evergreen forests as if it were a constant. We incorporated temperature-dependent needle longevity and %nitrogen, and bio-mass allocation, into a land surface model. Community Atmosphere Biosphere Land Exchange, to assess their impacts on carbon cycling processes. Incorporating realistic parameterization of these variables improved predictions of canopy leaf area index and gross primary production compared with observations from flux sites. Finally, increasingly low foliage turnover and biomass fraction toward the cold far north indicate that a surprisingly small fraction of new biomass is allocated to foliage under such conditions. [ABSTRACT FROM AUTHOR]

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Determines the Michaelis?Menten kinetic parameters for white spruce (Picea glauca (Moench) Voss) and jack pine (Pinus banksiana Lamb.) seedlings, and three competitive common boreal forest early successional species: aspen (Populus tremuloides Michx.), fireweed (Epilobium angustifolium L.), and cala magrostis (Calamagrostis canadensis (Michx.) Beauv.). Uptake kinetics that were measured in hydroponic cultures and expressed as maximum uptake and ion affinity; Suggestion that silviculture practices that specifically reduce establishment of this grass should benefit the growth of planted seedlings.