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We examined methods of linking density, dispersion, and stocking information from juvenile regeneration surveys with mortality estimates to predict future yield of white spruce (Picea glauca (Moench) Voss) in boreal mixedwoods. The study focused on data from 709 stands (7–150 years) and defined a stocked plot (10 m2) as having one or more acceptable trees. In juvenile surveys, ingress of natural spruce overwhelmed the regular planting pattern, creating clumped dispersion patterns, as indicated by the Morisita index. A function was developed to describe the relationship between stocking, density, and dispersion. In mature, permanent sample plots, only 30%–40% stocking of 10 m2 plots (700 stems·ha–1) was needed to achieve full yields. Mortality rates for planted spruce varied from 0.1% to 0.8% per year for juvenile stands and from 1.7% to 3.3% per year for mature stands. For rotation-length predictions in Alberta, 0.7% per year is likely a mean mortality loss. These findings were combined to generate stocking versus time curves at a range of mortality rates. The tallest spruce measured in each juvenile survey plot had the same mortality rate regardless of absolute size, and spruce mortality was reduced when associated with aspen. These findings call into question minimum height requirements and free-to-grow criteria in regeneration standards. [ABSTRACT FROM AUTHOR]

Formation of the shoot apical meristem (SAM) has been extensively investigated in zygotic embryos of flowering plants, where it follows a prolonged and dynamic developmental pattern underlined by precise temporal and spatial changes in gene expression. Studies conducted on the plant model system Arabidopsis have revealed that SAM formation is controlled by a genetic network and involves the participation of several regulatory genes expressed at different stages of development. As a general rule apical meristem development in vivo occurs very early; at the globular stage of development in flowering plants and in club-stage embryos of conifers. Once formed, meristems of zygotic embryos are stable structures that become reactivated at the onset of germination. Shoot apical meristem formation during in vitro embryogenesis is demarked by structural events similar to those described for zygotic embryos, although differences can be observed during the late phases of development, where cellular differentiation and formation of intercellular spaces disrupt the architecture of SAMs produced in culture. These events, which denote the “unstable” nature of SAMs of somatic embryos, often result in poor conversion frequency and reduced plant regeneration. By using Picea glauca (Moench) Voss (white spruce) somatic embryos and microspore-derived embryos of Brassica napus L. (canola) as model systems, this review provides methods for improving SAM formation through manipulations of the culture medium which alter the cellular redox status. Meristem marker genes from Arabidopsis, such as WUSCHEL (which is required for the acquisition of stem fate identity), represent a valuable tool for estimating the quality of SAM produced by microspore-derived embryos of canola. In spruce, the identification of two novel meristem marker genes, HBK1 and PgAGO, will allow similar studies in conifers. [ABSTRACT FROM AUTHOR]

The objectives of this study were to assess the change in organic carbon (C) stocks in aboveground biomass, litter, and soil in a 50 year chronosequence of white spruce (Picea glauca (Moench) Voss) plantations established on non-regenerated fallow land in Quebec, and to determine the effects of ploughing (furrows) on these C stocks. Woody aboveground biomass was determined from dendrometric surveys and the use of allometric equations. The litter was sampled as well as the underlying soil in layers 10 cm thick down to 50 cm depth. The plantations under study were C sinks over the 50 year period, since they accumulated 75 Mg·ha–1 during this period, with the highest rate of C accumulation occurring in the woody aboveground vegetation between 10 and 35 years. The soil at 0–30 cm depth was a C source, mainly until the plantations reached 22 years of age, with an annual loss of 0.8% over 50 years. No difference was observed among the controls and site-preparation treatments. These results suggest that 22-year-old white spruce plantations, the oldest considered for the first commitment period of the Kyoto Protocol (2008–2012), would be a small C sink (12 Mg·ha–1) in southeastern Quebec but would become a larger sink for subsequent commitment periods. [ABSTRACT FROM AUTHOR]

A total of 770 transgenic Bt white spruce needles were collected and plated on potato dextrose agar to determine their foliar endophyte diversity. The ribosomal internal transcribed spacer regions for 310 foliar endophytes were amplified by polymerase chain reaction (PCR) and digested using CfoI and MspI, which created 21 restriction groups. Isolates from each restriction group were sequenced and compared with reference sequences in GenBank. Eighteen sequence groups were obtained, of which five were identified at the species level. The most common endophytic fungi identified by PCR-RFLP was Lophodermium piceae (incidence of 74.5%). The second and third most common ones were Hypoxylon fragiforme (3.63%) and Lophodermium nitens (3.18%). A statistical analysis performed on the most common endophyte groups showed no statistical difference in endophyte frequency or distribution between the control white spruce needles (nontransgenic) and saplings with constructs containing the reporter gene GUS or the Bt Cry1A(b) gene and kanamycin. [ABSTRACT FROM AUTHOR]

The effects of six mechanical site preparation treatments, two stock-type treatments, and early chemical release on survival and growth of planted white spruce (Picea glauca (Moench) Voss) were studied in the BWBSmw1 biogeoclimatic zone of northeastern British Columbia. After 20 years, spruce height and diameter were larger in all mounding treatments than in the control. Early results suggested better spruce performance on large than small mounds, but after 20 years, growth was equally good on small mounds as on mounds with 20 cm mineral capping. Spruce planted on hinge positions in the Bräcke patch and blade scarification treatments did not survive or grow well. Early chemical release improved spruce growth equally as well as the mounding treatments. Twenty year spruce survival averaged 71% in the 14 and 20 cm mound treatments, 60% in the early chemical release treatment, and ≤35% in the Bräcke patch and blade scarification treatments. A large stock type was also planted in untreated ground and, after 20 years, had similar survival and growth as the standard stock type. Differences in survival had a large effect on basal area at age 20 years. Trend analysis showed that treatments diverged into two distinct groups with regard to spruce size during the 20 year span of the study. [ABSTRACT FROM AUTHOR]

To assess nutrient dynamics in decomposing logs of trembling aspen (Populus tremuloides Michx.), white birch (Betula papyrifera Marsh.), white spruce (Picea glauca (Moench) Voss), and jack pine (Pinus banksiana Lamb.), we monitored mass losses and changes in N and P contents in dead boles from a chronosequence of sites following stand-replacing disturbances. To assess the importance of wood decomposition to nutrient cycling, we compared net estimates of nutrient release from logs with net nutrient immobilization in live-tree biomass of stands as a function of time since disturbance. Mineralization rates were 0.060, 0.053, 0.038, and 0.020·year–1 for trembling aspen, white birch, white spruce, and jack pine logs, respectively. Trembling aspen boles released large quantities of N and P during the first year of decomposition (51 kg·ha–1 of N and 7 kg·ha–1 of P, assuming a bole volume of 150 m3·ha–1). White birch boles acted initially as a nutrient sink and delayed the release of immobilized nutrients until a period when the stand's net nutrient immobilization rates were highest. Jack pine boles appeared to be intermediate in terms of their contribution as a sink or a source of nutrients but, in mature stands, provided up to 40% of N and 26% of P immobilized annually in tree biomass. As pure stands of white spruce are rare in boreal Quebec, information on nutrient accumulation in white spruce stands was not available. [ABSTRACT FROM AUTHOR]

Although critical to monitoring forest ecosystems, inventories are expensive. This paper presents a generalizable method for using an integer programming model to examine tradeoffs between cost and estimation error for alternative measurement strategies in forest inventories. The method is applied to an example problem of choosing alternative height-modeling strategies for 1389 plots inventoried by field crews traveling within an 82.5 × 106 ha region of the west coast of North America during one field season. In the first part of the application, nonlinear regional height models were constructed for 38 common species using a development data set of 137 374 measured tree heights, with root mean square error varying from 6.7 to 2.1 m. In the second part of the application, alternative measurement strategies were examined using a minimal cost objective subject to constraints on travel time and estimation error. Reduced travel time for field crews can be a significant portion of the cost savings from modeling tree heights. The optimization model was used to identify a height-modeling strategy that, given assumptions made, resulted in <10% of maximum average plot volume error, >33% of potential measurement cost savings, and small bias for estimates of regional volume and associated sampling error (0.1% and 0.4%, respectively). [ABSTRACT FROM AUTHOR]

We examined the growth of understory conifers, following partial or complete deciduous canopy removal, in a field study established in two regions in Canada. In central British Columbia, we studied the responses of three species (Pseudotsuga menziesii var. glauca (Beissn.) Franco, Picea glauca (Moench) Voss × Picea engelmannii Parry ex Engelm., and Abies lasiocarpa (Hook.) Nutt.), and in northwestern Quebec, we studied one species (Abies balsamea (L.) Mill.). Stem and root diameter and height growth were measured 5 years before and 3 years after harvesting. Both root and stem diameter growth increased sharply following release but seedlings showed greater root growth, suggesting that in the short term, improvement in soil resource capture and transport, and presumably stability, may be more important than an increase in stem diameter and height growth. Response was strongly size dependent, which appears to reflect greater demand for soil resources as well as higher light levels and greater tree vigour before release for taller individuals. Growth ratios could not explain the faster response generally attributed to true fir species or the unusual swift response of spruces. Good prerelease vigour of spruces, presumably favoured by deciduous canopies, could explain their rapid response to release. [ABSTRACT FROM AUTHOR]

We examined jack pine (Pinus banksiana Lamb.), black spruce (Picea mariana (Mill.) BSP), and white spruce (Picea glauca (Moench) Voss) seed germination and seedling recruitment in aspen (Populus tremuloides Michx.) and conifer mixedwood stands following the 1999 Black River fire in southeastern Manitoba, Canada. Three postfire seedbed types were tested: scorched (surface litter only partially consumed), lightly burned (surface litter consumed with little or no duff consumption), and severely burned (complete consumption of litter and duff exposing mineral soil). Seeds were sown in 1999, 2000, and 2001, and each cohort was monitored for 3 years. In 1999, severely burned seedbeds had poor germination, while scorched seedbeds had the highest germination. The reverse was true in 2001. After the first growing season, continued survival of seedlings was greater on severely burned seedbeds for all three cohorts. However, better survival on severely burned seedbeds was not sufficient to overcome poor germination in 1999 and 2000. When using artificial seeding to promote conifer regeneration, we recommend a delay of one full year after a severe spring fire for jack pine and two full years for black spruce and white spruce on boreal aspen and conifer mixedwood sites. [ABSTRACT FROM AUTHOR]

White spruce (Picea glauca (Moench) Voss) and Engelmann spruce (Picea engelmannii Parry ex Engelm.) seed-cones from 676 sites in Canada and the northern United States were analyzed to determine the degree and spatial extent of interspecific hybridization. Fifteen cone-scale variables were analyzed, with percent free-scale and scale shape considered best for differentiating these taxa. The results show that putative Engelmann spruce and their hybrids occur mostly in the vicinity of the Rocky Mountains. Putative white spruce occurs across Canada east of the Rocky Mountains, whereas white × Engelmann hybrids occur eastward to Manitoba and northward to 68° latitude in northwest Canada. To explain the occurrence of the latter taxon hundreds of kilometres from an Engelmann spruce pollen source, it is hypothesized that palaeohybridization occurred during the Wisconsinan glacial period, probably in the southern Montana – Wyoming – Black Hills (South Dakota) region, with the resulting hybrids spreading north and northeastward into interior Canada following the retreat of the Laurentide glacier. White and Engelmann spruce have morphologically distinct cone-scales, whereas their hybrids have intermediate characteristics. An emended species (Picea albertiana) and two subspecies (P. albertiana subsp. albertiana and P. albertiana subsp. ogilviei) are proposed to account for morphological intermediates between the parent species. [ABSTRACT FROM AUTHOR]

During winter, boreal forest herbivores have access to only poor-quality forage. On Anticosti Island (Quebec, Canada), the ongoing reduction of balsam fir (Abies balsamea (L.) P. Mill.) owing to overbrowsing by white-tailed deer (Odocoileus virginianus (Zimmermann, 1780)) may force deer to include a higher proportion of white spruce (Picea glauca (Moench) Voss), a browse normally avoided, in their winter diet. We tested the hypotheses that (i) deer body condition during winter and (ii) the costs of detoxification of plant secondary metabolites in the winter diet could be estimated by monitoring the 3-methylhistidine / creatinine and glucuronic acid / creatinine ratios, respectively, in urine collected in snow from white-tailed deer fawns. Doubling the amount of white spruce in the winter diet of deer (from the current 20% under natural conditions to 40%) did not increase 3-methylhistidine / creatinine ratios but increased the glucuronic acid / creatinine ratio in urine, suggesting that a diet containing more spruce was more toxic. A weak positive relationship was observed between 3-methylhistidine and percent cumulative mass loss. There was no relationship between the 3-methylhistidine / creatinine ratio and the number of days left before death, as well as no relationship between the ratio of glucuronic acid / creatinine and percent cumulative mass loss. We conclude that the costs of detoxification of plant secondary metabolites in the winter diet of white-tailed deer in boreal forests could be monitored with glucuronic acid / creatinine ratios, but that 3-methylhistidine / creatinine ratios were weak indicators of deer body condition in winter. [ABSTRACT FROM AUTHOR]

The fragmentation of forests into small, isolated remnants may reduce pollen quantity and quality in natural plant populations. The reproductive success of white spruce (Picea glauca (Moench) Voss) was assessed in a landscape fragmented by agriculture in northern Ontario, Canada. We sampled a total of 23 stands and 104 white spruce trees from three different stand size classes. Each sampled stand was separated by 250–3000 m from the nearest neighbouring stand. Reproductive success, measured as the number of filled seeds per cone, increased with stand size. The total number of seeds per cone, a measure that includes both filled and aborted seeds, also increased with stand size, suggesting that pollen receipt limits the number of seeds in a cone. The proportion of empty seeds (postzygotic abortions) was highest in the two smallest stand size classes, suggesting that inbreeding levels were also highest in these stands. We detected no difference in germination success, seedling growth, and growth of trees up to 10 years from seeds produced by trees from different stand size classes. These results suggest that inbred individuals are largely eliminated during the seed development stage. We estimated that a threshold population size of 180 trees is needed to reduce the negative effects of pollen limitation and inbreeding and maintain seed yields observed in large contiguous stands. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the foliar endophyte biodiversity of white spruce (Picea glauca (Moench) Voss to establish a baseline for future comparative studies examining the impact of forestry practices. It identifies for the first time endophytic fungi living inside the needles of white spruce from 280 needles collected in seven natural stands in southern Québec. The endophyte colonization rate on surface sterilized needles was 53.2%. We performed a PCR-RFLP and sequence analysis on the ITS region of the nuclear ribosomal DNA to achieve molecular identification. Isolate ITS sequences were compared with data from GenBank presenting the best similarity and were analyzed by a maximum of parsimony and Bayesian inference. Relationships between morphological groups, digestion groups, and sequence groups were investigated. In all, 23 morphotypes were found to belong to 14 sequence groups and we demonstrated that morphological groups are poor indicators for estimating species diversity. This study is the first to establish species richness values for foliar endophytes. Among the 141 isolates in this study, 75.15% have a high sequence similarity with Lophodermium piceae, 10.95% with an unknown species of Mycosphaerella, and 5.5% with two species of the genus Hypoxylon. Distribution, incidence and biological significance of all the endophytes found in this study are discussed. [ABSTRACT FROM AUTHOR]

The number of cones produced by coniferous trees is commonly estimated by visual counts from the ground of a portion of the tree multiplied by a simple conversion factor. Linear conversion factors have been used to estimate total cone production by white spruce (Picea glauca (Moench) Voss). However, these conversion factors originate from other coniferous species and were often based on assumptions of cone visibility within the crown and not on empirical data. We propose a simple method for estimating the total number of cones produced by individual white spruce. We counted visible cones (an index of cone production, or cone index) on a total of 60 trees located in Alberta and Yukon, Canada, that were then felled and all cones were counted. We found that log(actual total cones) = 0.073 + 1.189 × log(cone index) is more accurate for estimating total cone numbers for white spruce than are other conversion factors (ranging from total cones = 1.5 × cone index to total cones = 3.35 × cone index), as determined using Akaike's information criterion with small sample bias adjustment and a validation data set. The relationship between the index of cone production and actual total cones produced is nonlinear, which is contrary to that proposed for various Pinus species. [ABSTRACT FROM AUTHOR]

Sustainable forest management that employs the emulation of natural disturbance paradigm develops plans based on disturbance-driven forest succession. However, most research on forest succession has focused primarily on postdisturbance species change, often ignoring predisturbance legacies. We used the FORECAST ecosystem management model and a newly created natural regeneration submodel to examine the interaction of fire severity, fire frequency, and natural regeneration to produce multicycle dynamics of white spruce (Picea glauca (Moench) Voss), lodgepole pine (Pinus contorta Dougl. ex Loud.), and trembling aspen (Populus tremuloides Michx.) in a western Canadian boreal forest. We simulated 19 different scenarios in a factorial disturbance experiment of three severities and six frequencies and a no-disturbance scenario. Our simulations resulted in a wide diversity of boreal forest community types, including trembling aspen dominated mixedwoods with high-frequency (75 year), high-severity (100% mortality) fires, and nearly pure lodgepole pine stands at midfrequency (100–125 year) and high-severity fires. With the unvarying disturbance regimes we used, a variety of different but recurring temporal patterns emerged. We show that the loss of seed source legacies reinforces the disturbance-driven species dominance, demonstrating community inertia. This study provides a long-term perspective to boreal forest management that demonstrates the role of disturbance and legacies in long-term dynamics. [ABSTRACT FROM AUTHOR]

Alterations in the chemical properties of the forest floor following clear-cut harvesting may have implications for forest productivity in boreal stands. We used proximate analysis, carbon-13 (13C) isotopic determination, and cross-polarization, magic-angle spinning (CPMAS) 13C nuclear magnetic resonance (NMR) spectroscopy to examine differences in the characteristics of the forest floors from uncut stands and clear-cut stands dominated by white spruce (Picea glauca (Moench) Voss; SPRUCE) and trembling aspen (Populus tremuloides Michx.; ASPEN) in northern Alberta. Proximate analysis revealed no difference in the chemical properties of forest floors from clear-cut and uncut stands in either stand type, but the acid-insoluble residue of forest floors from clear-cut ASPEN stands was enriched in 13C compared with those from uncut ASPEN stands. CPMAS 13C NMR spectroscopy revealed that forest floors from clearcuts were enriched in total aromatic C, particularly in ASPEN stands, and depleted in phenolic C, particularly in SPRUCE stands. These patterns indicate that forest floors from the clearcuts have become more humified, which may reflect stand-type differences in the amount of labile C available to the forest-floor microbial community and reductions in above- and below-ground inputs to the forest floor following clear-cutting in both stand types. Changes in the chemical properties of forest floors from clear-cut SPRUCE and ASPEN stands could exacerbate C limitation in these soils and alter patterns of nutrient cycling. [ABSTRACT FROM AUTHOR]

White spruce (Picea glauca (Moench) Voss) is a characteristic primary species of the Canadian boreal forest region, where it occurs in conifer-dominated and mixedwood forest types. Genetic diversity and population structure of white spruce may differ between the conifer-dominated and mixedwood forest types owing to the inherent differences in stand structure and dynamics. The objective of our study was to determine genetic diversity and population structure of pristine white spruce stands as they occur in conifer-dominated and mixedwood forest types at the EMEND (Ecosystem Management Emulating Natural Disturbance) study sites in northern Alberta. Nuclear microsatellite DNA markers were used to examine genetic diversity and population structure of 16 pristine natural old-growth (≥100 years) white spruce stands (subpopulations) of fire origin; 8 from conifer-dominated and 8 from neighboring mixedwood forest types. High levels of genetic diversity were observed, as expected. The genetic diversity and genetic constitution of white spruce were similar between the conifer-dominated and mixedwood forest types. Most of the genetic variation resided within subpopulations, with only about 2% genetic differentiation detected among 16 subpopulations as well as among 8 subpopulations within the same forest type. The mean genetic distances among subpopulations within and between the forest types were similar. Our study suggests that white spruce genetic resources are similar in the conifer-dominated and mixedwood forest types located in the EMEND study area in northern Alberta, and it provides the benchmarks for determining and monitoring the genetic diversity impacts of forest harvesting and forest fires. [ABSTRACT FROM AUTHOR]

Retaining organic matter and preventing soil compaction are important factors affecting the sustainability of managed forests. To assess how these factors affect short-term ecosystem dynamics, pre-treatment and 1 year and 5 year post-treatment soil properties and post-treatment tree growth responses were examined in a boreal trembling aspen (Populus tremuloides Michx.) dominated ecosystem in northeastern British Columbia, Canada. The experiment used a completely randomized design with three levels of organic matter removal (tree stems only; stems and slash; stems, slash, and forest floor) and three levels of soil compaction (none, intermediate (2-cm impression), heavy (5-cm impression)). Removal of the forest floor initially stimulated aspen regeneration and significantly reduced height growth of aspen and white spruce (Picea glauca (Moench) Voss). The compaction treatments had no effect on aspen regeneration density. At year 5, heights of both aspen and white spruce were negatively correlated (r2 > 0.31, p < 0.0001) with upper mineral soil bulk density and were lowest on forest floor removal treatments, where minimal recovery from compaction was observed. There was some evidence for recovery of soil properties to preharvest conditions where expansion of herbaceous vegetation increased soil organic matter. [ABSTRACT FROM AUTHOR]

This study assessed the impact of various harvesting practices (including those designed to emulate natural disturbances) on ectomycorrhizae (ECM) associated with white spruce (Picea glauca (Moench) Voss) in northwestern Alberta, Canada. Treatments included clearcuts, partial cuts (dispersed green-tree retention with 20%, 50%, and 75% residual live trees, and aggregated green-tree retention), unharvested control sites, and a burned stand. The percentage of active white spruce root tips and ECM richness and diversity, as observed in soil cores collected throughout the study site, all decreased with increasing disturbance intensity. Effects were particularly pronounced in clearcuts, machine corridors used for access by harvesting equipment in the dispersed green-tree retention stands, and in burned areas. Reductions in ECM biodiversity could be attributed to the sensitivity of late-stage ectomycorrhizae (e.g., Cortinarius spp., Lactarius spp., and Russula spp.) to soil disturbances and changes in microclimate associated with harvesting or burning. Areas of dispersed and aggregated green-tree retention were not dramatically different than unharvested forest in terms of root tip density and ECM richness, diversity, and composition. Harvesting practices that retain a percentage of residual live trees, either dispersed throughout the cutting unit or in aggregated patches, could be an effective means of maintaining ectomycorrhizal biodiversity at the stand level. [ABSTRACT FROM AUTHOR]

Picea glauca (white spruce) and P. engelmannii (Engelmann spruce) are so similar and integrated that it is impossible to distinguish between them and their hybrids using morphological characteristics. Although natural hybrids between P. glauca and P. mariana (black spruce) do not generally occur, even though the 2 species are sympatric in North America, a first-generation hybrid, called the Rosendahl spruce, has been reported in the literature. In this study, several inter-simple sequence repeat (ISSR) markers were developed, as were randomly amplified polymorphic DNA (RAPD) markers, to certify spruce trees and their hybrids. ISSR fingerprinting was more efficient than RAPD assay; it detected 70% polymorphic DNA markers among the spruce species analyzed, whereas RAPD fingerprinting detected only 53%. Species-diagnostic ISSR and RAPD markers differentiating P. glauca from P. engelmannii and P. mariana were cloned and sequenced. Molecular certification of the spruce samples analyzed confirmed that all the seeds from interior spruce populations were true hybrids of P. glauca and P. engelmannii. But the analysis of seeds derived from the putative Rosendahl spruce indicated that this tree is likely a pure P. glauca genotype, rather than a hybrid of P. glauca and P. mariana. These data were confirmed by cytological analyses. Further analysis, using a more sensitive DNA amplification method with designed primers flanking the species-diagnostic ISSR and RAPD markers, revealed that such sequences are not generally species-specific because they are present in other spruce species. [ABSTRACT FROM AUTHOR]

Experimental seeding of balsam fir (Abies balsamea (L.) Mill.) and white spruce (Picea glauca (Moench) Voss) was implemented in three mature trembling aspen (Populus tremuloides Michx.) stands in southeastern Manitoba to test (i) the effect of vegetation (light) competition and seedbed type (undisturbed forest floor, exposed mineral soil, and rotten logs) on seedling recruitment over the first 2 years and (ii) the effect of broadleaf litter exclusion on seedling mortality during the first winter. The study indicated that, with adequate seed supply, seedbed type was the most important factor limiting seedling recruitment, especially the recruitment of white spruce, in trembling aspen stands. Seedling recruitment on the best and the worst seedbeds differed by 1.8 times for balsam fir but by 19 times for white spruce. Significant differences in soil moisture and temperature were found between seedbed types. Broadleaf litter exclusion also facilitated the recruitment of balsam fir and white spruce, but only on undisturbed forest floor. Vegetation (light) competition, however, did not limit seedling recruitment. On the contrary, the presence of understory vegetation benefited seedling recruitment on rotten logs. Compared with white spruce, balsam fir is better adapted to regenerate in trembling aspen stands. Balsam fir was about 4, 12, and 36 times better than white spruce when regenerating on exposed mineral soil, rotten log, and undisturbed forest floor, respectively. [ABSTRACT FROM AUTHOR]

To investigate the feasibility of a spatially explicit, radiation-based regeneration model for the boreal forest, we tested the predictions of a three-dimensional simulator of photosynthetically active radiation transmission (%PAR), MIXLIGHT, and the growth response of understory Abies balsamea (L.) Mill. (balsam fir) and Picea glauca (Moench) Voss (white spruce) to %PAR in two large (>1 ha) mixed-species forest sites, one in eastern Canada at Lac Duparquet, Quebec, and one in western Canada at Calling Lake, Alberta. Overstory tree locations and dimensions were obtained from aerial photographs or ground measurements and allometric relationships. Seasonal %PAR calculated by MIXLIGHT for the Calling Lake site was very similar to seasonal %PAR measured by quantum sensors (n = 5, %PAR range = 15%–33%, r = 0.93). Daily measurements of %PAR were also predicted well by simulations at both sites (n = 34–36, %PAR range = 1%–45%, r ≥ 0.76). Functional relationships, designed to saturate at the maximum height growth potential of these sites, were developed to predict sapling height growth from simulated seasonal %PAR and initial height (R2 ≥ 0.74). These results demonstrate the potential of the MIXLIGHT simulator for estimating PAR at microsites within heterogeneous forests and for modeling understory tree growth. [ABSTRACT FROM AUTHOR]

We examined the growth of white spruce planted underneath a 33-year-old stand of trembling aspen following thinning and fertilization. Thinning the stand to 2000 stems·ha–1 resulted in increased light reaching spruce seedlings and significant increases in height and diameter growth of seedlings over that observed in either the unspaced or 3000 stems·ha–1 treatments. Fertilization (applied 3 years prior to planting) stimulated development of understory vegetation and did not benefit the planted spruce. While growth was improved by thinning, the benefits of the thinning treatment to establishment of white spruce appeared to be small, and amounted to increasing seedling height from 62 cm (unthinned) to 73 cm (thinned to 1000 or 2000 stems·ha–1) at the end of 5 years. Results indicated that when stands are thinned for the purpose of accelerating growth rates of underplanted spruce, residual basal areas above 25 m2·ha–1 should be retained to suppress growth of understory vegetation. Comparison of height at age 5 for seedlings planted under untended stands at Fort Nelson with three sites near Dawson Creek indicated no differences between locations, when height at the time of planting was included as a covariate. [ABSTRACT FROM AUTHOR]

This study investigated the genetic variation in veneer quality of white spruce (Picea glauca (Moench) Voss) and its correlation with tree growth and wood density. A total of 270 sample trees from 35 families were harvested from 36-year-old provenance-progeny trials at two sites through a thinning operation. A 36-cm long bolt was collected from each sample tree at an 8-foot (or 2.45 m) height for this veneer quality study. The results indicate that conversion of fast-grown white spruce into veneer and plywood may present some problems. Low wood density, numerous knots, and possibly a high proportion of juvenile wood appear to be major factors contributing to low veneer stress grading, resulting in a production of low-quality veneer. This study also showed that the environmental factors at the two sites played an important role in determining veneer quality and tree radial growth. The narrow-sense heritability for veneer density, veneer modulus of elasticity, and veneer roughness were 0.62, 0.13, and 0.14, respectively. The results revealed considerable phenotypic variation and relatively high additive genetic variation in the veneer modulus of elasticity. The phenotypic and genetic correlations between ring width and veneer density or veneer modulus of elasticity were negative. A positive phenotypic and genetic correlation was found between veneer density and veneer modulus of elasticity. This suggests that selection for tree volume growth in white spruce would lead to a decrease in wood density and veneer stiffness. [ABSTRACT FROM AUTHOR]

Previous laboratory and field studies have presented evidence for the existence of limestone ecotypes in white spruce (Picea glauca (Moench) Voss). Remeasurements of the range-wide 410 series of provenance trials were used for further evaluation of the existence of these ecotypes. In 2001, heights were measured of 23 provenances grown at four test sites in Ontario, all located south of 46°N. Bedrock classification for test sites and provenances by limestone or non-limestone parent material was done using a 1993 data set of the Ontario Geological Survey. Analysis of variance revealed significant differences among test sites and provenances only. No significant interactions consistent with the existence of limestone ecotypes were detected. This finding is in contrast to that of an earlier field study that detected a strong interaction between test site and provenance bedrock type (p < 0.001). Examination of the relative performance of individual provenances from limestone and non-limestone bedrock types revealed differences in performance at the four different test sites but few instances supporting the existence of limestone ecotypes. Although these more recent results generally support a pattern of between-stand variation in southern Ontario, they do not disprove the existence of limestone ecotypes, owing to the nature of the 410-series test design and the classification of provenances according to bedrock type instead of actual soil analyses. [ABSTRACT FROM AUTHOR]

Stem, branch, needle, and total aboveground biomass were assessed for three 9- to 12-year-old white spruce (Picea glauca (Moench) Voss) plantations, each subjected to three different stand tending options at age 4 to 7. Biomass components were predicted from measures of stem diameter with coefficients of variation between 24% and 29%. Diameter at breast height (DBH) generally provided lower prediction precision than did the lower stem measures tested (coefficient of variation > 35%). The addition of tree height in models reduced the standard error of the estimates for stem and total biomass by an average of 48% and 8%, respectively, and compensated for different height/diameter ratios imposed on the spruce by the stand tending treatments. Needle and branch biomass models were invariant to the tending treatments and, consequently, to the addition of height as an independent variable. Predictions from existing published white spruce equations suggest that extrapolation to this study area would have led to adequate stem biomass estimation but to serious (>55%) underestimates of branch, needle, and, correspondingly, total biomass. Slow self-pruning by plantation spruce, particularly before crown closure, is cited as a possible reason for these differences. [ABSTRACT FROM AUTHOR]

Temporal, spatial, and structural patterns of adult trembling aspen (Populus tremuloides Michx.) and white spruce (Picea glauca (Moench) Voss) mortality were studied in intact 150-year-old stands in the southwestern boreal forest of Quebec. For both species, mortality decreases (number of dead trees/total number of trees) with distance from the lake edge until 100–150 m, from which point it slightly increases. Strong peaks in mortality were found for 40- to 60-year-old aspen mainly between 1974 and 1992. Such mortality in relatively young aspen is likely related to competition for light from the dominant canopy trees. Also, the recruitment of this young aspen cohort is presumably the result of a stand breakup that occurred when the initial aspen-dominated stand was between 90 and 110 years old. For spruce, strong peaks in mortality were found in 110- to 150-year-old trees and they occurred mainly after 1980. No clear explanation could be found for these peaks, but we suggest that they may be related to senescence or weakening of the trees following the last spruce budworm outbreak. Suppressed and codominant aspen had a much higher mortality ratio than spruce in the same height class, while more surprisingly, no difference in mortality rate was found between dominant trees of the two species. Most spruce trees were found as standing dead, which leads us to reject the hypothesis that windthrow is an important cause of mortality for spruce in our forests. [ABSTRACT FROM AUTHOR]

The trembling aspen (Populus tremuloides Michx.) – white spruce (Picea glauca (Moench) Voss) mixed woods near Fort Nelson are distinguished by the large size of individual trees, longevity, and the low occurrence of internal decay in trembling aspen. The development of these forest ecosystems has had limited documentation and may be significantly different than those described in other portions of the boreal forest. At five study stands, stem analysis techniques were used to examine the patterns of height and radial growth over time according to species and structure type. There were two patterns of species establishment that were consistent with the stand structure. In codominant stands, recruitment periods for trembling aspen and white spruce overlapped. The stratified stands were consistently associated with a 29- to 58-year lag in white spruce recruitment. Spruce that were codominant with aspen at the time of sampling had sustained periods of rapid height and diameter growth. White spruce that were later to establish on site had slower rates of height and diameter growth. White spruce ages indicated that a dominant recruitment episode was more common than continuous recruitment. Height and diameter growth of trembling aspen were similar in both stand types. The differences in trembling aspen growth patterns between stands were due to site quality. The white spruce in codominant stands did not appear to go through a period of suppression and then release associated with stand-level trembling aspen mortality, as commonly described for other boreal mixedwoods. The vigor and longevity of trembling aspen in Fort Nelson appear to prolong the period of trembling aspen domination of mixed stands well beyond the time periods observed in other boreal ecosystems. [ABSTRACT FROM AUTHOR]

This study investigated the genetic variation of white spruce (Picea glauca (Moench) Voss) in decay resistance and its correlation with wood density and growth. Three fungi were examined, a brown-rot fungus (Gloeophyllum trabeum), a white-rot fungus (Trametes versicolor), and a standing-tree-decay fungus (Fomitopsis pinicola). The decay resistance was inversely related to the growth rate of the fungi on heartwood blocks. A total of 270 trees of 35 families were harvested from 36-year-old provenance–progeny trials at two sites through a thinning operation. The narrow-sense heritabilities of white spruce decay resistance to brown rot and white rot were 0.21 and 0.27, respectively. There were no significant differences in resistance to standing-tree-decay fungus among the families. The phenotypic and genetic correlations between the growth rate of brown rot on heartwood blocks and wood density were positive, but the genetic correlation between wood density and the growth rate of white rot on heartwood blocks was negative but not significant. The results indicate that the different species of fungi have different relationships with the annual growth of trees and wood density, and suggest that selection for wood density in white spruce might lead to an increase in resistance to white rot, but a decrease in resistance to brown rot. [ABSTRACT FROM AUTHOR]

Five years after spacing a young, 11 m tall paper birch (Betula papyrifera Marsh.) stand, we examine relationships between growth of understory white spruce (Picea glauca (Moench) Voss), subalpine fir (Abies lasiocarpa (Hook.) Nutt.), and level of birch retention. Our objectives were to evaluate the effectiveness of selected measures of competition for estimating the effects of the residual birch and to evaluate the influence of residual birch densities on growth responses of naturally regenerated subalpine fir and white spruce. Basal area of Scouler willow (Salix scouler iana Barratt) and birch were found to effectively predict light transmittance (diffuse noninterceptance). The best models for predicting 4-year volume growth of subalpine fir and white spruce incorporate initial crown volume of the subject trees and transmittance as independent variables. Lorimer's index and Hegyi's index gave similar results to those obtained using basal area and transmittance, suggesting that there is little benefit in including measurements of proximity in a competition index. For both species, the correlation between basal area increment and light was substantially stronger than observed for volume increment. However, height increment of both subalpine fir and spruce was only weakly correlated with measured light levels. The ratio of height increment to volume increment decreased with both increasing initial height and transmittance for subalpine fir and white spruce. [ABSTRACT FROM AUTHOR]

Investigates the growth recovery in young and plantation white spruce following artificial defoliation and pruning. Information on the four treatments applied for the artificial defoliation; Factors that influenced tree response to defoliation; Description of the two basic foliation systems; General features of conifers.

Discusses the results of a study, which explored the influence of partial harvesting and forest floor disturbance on nutrient availability and understory vegetation in boreal mixedwoods in Alberta. Factors that influence the establishment and growth of planted white spruce; Description of the forest floor disturbance treatments used in the study; Effects of harvest type on soil temperature, magnesium availability and plant density and cover.

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.

Reports that predation of white spruce (Picea glauca (Moench) Voss) cones by red squirrels (Tamiasciurus hudsonicus Erxleben) was quantified in the mixedwood boreal forest of Alberta in cutblocks with seed tree retention and in adjacent uncut forest. Percent cone loss that was quantified by comparison of paired pre- and post-caching photographs of tree crowns; Cone loss from seed trees in cutblocks that was significantly lower than from control trees in adjacent uncut forest; No corresponding increase in the percentage of cones that was harvested by squirrels; Percent cone loss that was significantly lower from single seed trees in cutblocks; Cone predation that significantly reduced the amount of seed available for natural regeneration using a seed tree system; White spruce seed trees as singles in cutblocks that may reduce the level of cone predation.

In this study we investigated quantitative genetic variation in tracheid characteristics in two genetic tests of British Columbia's interior spruce (the common name for white spruce, Picea glauca (Moench) Voss; Engelmann spruce, Picea engelmanni Parry ex Engelm.; and their hybrids). The study included 88 half-sib families from the East Kootenay and Prince George regions. We have developed a technique for quantitative assessment of tracheid characteristics by measuring cross-sectional dimensions. We obtained cell size, wall thickness and their ratio in early-, transition-, and late-wood classes within a growth ring. Tracheid length and microfibril angle were measured in the transition wood. A number of tracheid characteristics showed significant genetic variation, but heritability, phenotypic, and genetic correlation estimates varied across test sites within and outside regions of origin of parental trees. Ring width was determined, both phenotypically and genetically, by the number of tracheids and to a lesser extent by the by their mean size. On average, rings with larger tracheids did not have significantly thicker walls. Wider rings had lower mean wall to tracheid size ratio. Faster growth did not result in shorter tracheids in the transition wood. Longer tracheids had lower micro fibril angle. There were no particular benefits from considering the anatomical component traits for breaking the negative genetic correlation between growth and wood density. [ABSTRACT FROM AUTHOR]

A portable freezer was developed to apply frost to branches of large trees to study their growth and recuperation after frost application under natural conditions. The freezer measures 37.5 63.5 31.5 cm and weighs approximately 3 kg. It consists of two compartments, a freezing compartment and a dry ice compartment. The portable freezer provides a ramp-and-soak freezing pattern using a programmable controller. The nonfreezing temperature plateaus can be set from 1 to 6 C and maintained for 0 to 12 h. The cooling and warming rates can be programmed from 1 to 12 C h?1. Test temperatures can be maintained for a period of time ranging from 0 to 12 h at set temperatures. Freezers were tested without samples under controlled conditions at ambient temperatures of 0, ?5, ?10, 5, 15, 20, and 25 C. Under these conditions, the cooling and warming rates showed a deviation of less than -1 C h?1 at a set rate of 2 C h?1. The freezer provides test temperatures as low as ?38 C and ?47 C at ambient temperatures of 20 and ?10 C, respectively. Freezers were also tested under field conditions on attached branches in mature white spruce (Picea glauca (Moench) Voss) trees under hardening conditions. [ABSTRACT FROM AUTHOR]

Quantitative genetic variation in growth, latewood percentage, and wood density was investigated for British Columbia's interior spruce (the common name for white spruce, Picea glauca (Moench) Voss; Engelmann spruce, Picea engelmanni Parry ex Engelm.; and their hybrids). The study included 160 half-sib families from the East Kootenay and Prince George regions. At the time of sampling, progeny tests for those two regions were 20 and 22 years old, respectively. Univariate and multivariate restricted maximum likelihood (REML) estimates of genetic parameters were obtained. Estimates of genetic variances and heritabilities differed greatly across planting sites for the examined traits, especially after transplantation between the regions. Significant negative genetic correlation between overall growth and wood density was found for the East Kootenay progenies, while negative but nonsignificant genetic correlation between these traits was found for the Prince George progenies. Generally, there was no significant decrease in heritability for ring width and latewood percentage in successive growth rings. A general age trend for genetic correlation between those traits was not apparent, except that the correlation remained negative during the observed period. Our results show that it is not possible to select certain families as superior based on 1-year results because of the family by growing season interactions. Nevertheless, genetic age?age correlations for cumulative increments were high, having a decreasing trend with increasing difference in age. [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.

Analyzes the effect of aging discrepancies of white spruce on the interpretation of static age structure (SAS) in boreal mixedwoods. Use of qualitative ring features and ring width chronologies in visual cross-dating; Occurrence of height variation among trees establishing at the same time; Difficulty of using SAS to infer regeneration dynamics.

Examines the bark beetles and associated fungi colonizing subcortical tissues of white spruce Picea glauca in the Great Lakes Region. Percentage of the insects that emerged from the logs; Effects of time colonization on abundance and composition of insects; Correlations of specific fungi with specific bark beetles.

Low soil temperatures, common during the growing season in northern forests, have the potential to impede plant growth. In this study, water uptake, water relations, and growth characteristics were examined in aspen (Populus tremuloides) and white spruce (Picea glauca) seedlings that were inoculated with ectomycorrhizal fungi and grown at 20°C daytime air temperatures and low soil temperatures of 4°C and 8°C. Mycorrhizal associations had little effect on root and shoot biomass at both soil temperatures. Root hydraulic conductance (K[sub r] ) was higher in both mycorrhizal plant species compared to nonmycorrhizal plants, but there was no soil temperature effect on K[sub r] in either species. Mycorrhizae also increased shoot water potential (Ψ[sub w] ) in Populus tremuloides but had no effect on Ψ[sub w] in Picea glauca. The increases in K[sub r] and Ψ[sub w] were not reflected by changes in stomatal conductance (g[sub s] ) and transpiration rates (E), suggesting that the reduction of water flow in seedlings exposed to low soil temperature was not likely the factor limiting g[sub s] in both plant species.Key words: boreal forest, root hydraulic conductance, root growth, stomatal conductance, water uptake.Les basses températures du sol prévalant au cours de la saison de croissance dans les forêts nordiques, peuvent ralentir la croissance des plantes. Les auteurs ont examiné l'absorption de l'eau, les relations hydriques et les caractéristiques de croissance de plantules du peuplier faux-tremble (Populus tremuloides) et de l'épinette blanche (Picea glauca) préalablement inoculées avec des champignons ectomycorhiziens et cultivées à des températures diurnes de l'air de 20°C, et des températures basses du sol à 4°C et 8°C. L'association mycorhizienne a peu d'effet sur les biomasses racinaires et caulinaires, aux deux températures du sol. La conductance hydraulique (K[sub r] ) est plus élevée chez les deux espèces mycorhiziennes comparativement à des plantes nonmycorhiziennes, mais il n'y a pas d'effet de la température du sol chez aucune des deux espèces. Les mycorhizes augmentent également le potentiel hydrique de la tige (Ψ[sub w] ) chez le Populus tremuloides mais est sans effet sur le Ψ[sub w] du Picea glauca. Les augmentations du K[sub r] et du Ψ[sub w] ne se traduisent pas par des changements de la conductance stomatale (g[sub s] ) et des taux de transpiration (E), ce qui suggère que la réduction du transit de l'eau chez les plantules exposées à une basse température du sol n'est vraisemblablement pas le facteur limitant le g[sub s] chez ces deux plantes.Mots clés : forêt boréale, conductance hydraulique, croissance racinaire, conductance stomatale, absorption de l'eau.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Compares the overturning resistance of balsam fir and white spruce. Calculation of linear regressions using tree dendrometric data; Differences in height-diameter relationships; Indication of great resistance in white spruce.

Mean annual seed production is assumed to be proportional to basal area for canopy trees, but it is not known if subcanopy trees produce fewer seeds than expected (given their size) because of low light availability. Ovulate cone production was examined for balsam fir (Abies balsamea (L.) Mill.) and white spruce (Picea glauca (Moench) Voss) in 1998 and for balsam fir in 2000 in western Quebec using subcanopy stems, near or far from forest edges, or (at one site) planted white spruce trees in fully open conditions. A very simple light model for transmission through mature trembling aspen (Populus tremuloides Michx.) crowns and through boles near forest edges was developed to account for the effect of light receipt on cone production. The enhanced light near forest edges (e.g., recent clearcuts) leads to about a doubling of cone production for subcanopy stems. The minimum subcanopy height for cone production far from an edge is about 10 m for balsam fir and 14 m for white spruce, with these minima decreasing near edges. By contrast, the minimum height for white spruce in a plantation (full light) is about 3 m. Accounting for light receipt leads to an increase in the explained variance.Key words: balsam fir, cone production, light model, regressions, subcanopy stems, white spruce.La production annuelle moyenne de graines est proportionnelle à la surface terrière pour les arbres composant la canopée. Cependant, il reste à démontrer que des individus croissant sous couvert produisent moins de graines que prévu (en fonction de leur taille) en raison de la faible disponibilité de lumière. La production de cônes a été examinée pour le sapin baumier (Abies balsamea (L.) Mill.) et l'épinette blanche (Picea glauca (Moench) Voss) en 1998 et pour le sapin baumier en 2000 dans l'ouest du Québec. Les arbres étudiés poussaient sous couvert, près ou loin de la bordure forestière, ou (pour un site) faisaient partie d'une plantation. Un modèle très simple de transmission de la lumière à travers la canopée de peuplier faux-tremble (Populus tremuloides Michx.) et à travers les troncs en bordure de la forêt a été développé afin de quantifier l'effet de la disponibilité de lumière sur la production de cônes. L'augmentation de disponibilité de lumière près d'une bordure (par exemple une coupe forestière récente) entraîne un doublement de la production de cônes chez les arbres croissant sous couvert. La hauteur minimale pour la production de cônes chez des arbres croissant sous couvert et loin de la bordure forestière est d'environ 10 m pour le sapin baumier et 14 m pour l'épinette blanche, ces valeurs diminuant près de la bordure. En comparaison, la hauteur minimale pour la production de cônes pour les épinettes blanches d'une plantation (lumière = 100%) est d'environ 3 m. Une augmentation de la variance expliquée est obtenue en tenant compte de la disponibilité de lumière.Mots clés : sapin baumier, production de cônes, modèle de transmission de la lumière, régressions, arbres sous couvert, épinette blanche. [ABSTRACT FROM AUTHOR]

Presents a study of the anatomy of the resin canal system was observed on lateral branches of four host species of the white pine weevil (Pissodes strobi Peck) in relation to weevil performance. Host species that were studied were the Norway spruce (Picea abies (L.) Karst.), white spruce (Picea glauca (Moench) Voss), red spruce (Picea rubens Sarg.), and white pine (Pinus strobus L.); Survival, number, and mass of adult weevils that were measured on attacked terminal leaders collected before adult emergence; One uppermost lateral branch that was collected at the base of each attacked leader; Cross sections of these lateral branches that were observed to measure the number, diameter, depth, and density of inner and outer resin canals; Resin canal measurements that differed significantly among species, with white pine differing greatly from the other species with larger canals and lower canal density; Correlation analysis that demonstrated the anatomy of the resin canal system was principally related to adult mass, with the most important variable being the density of inner canals (r = ?0.54); Trees characterized by low density of large inner resin canals, like white pine, that seemed to favour mass gain in adult weevils; Study that suggests that a high density of inner resin canals constrains the insect to feed on canals early in larval development, which subsequently reduces weevil mass.

Examines the effects of cold temperatures on breakage of lodgepole pine and white spruce twigs. Use of a two-point bending test; Influence of temperature on crown friction; Dependence of shoot brittleness on the temperature.

Examines the effects of different humidity conditions on the growth, morphology and gas exchange of white spruce seedlings. Rate of seed germination; Response of white spruce seedlings to different humidity conditions; Comparison on the assimilation rate and stomatal conductance of trees under different humidity conditions.

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.

Focuses on the use of generalized logistic model of individual tree mortality for trembling aspen, white spruce and lodgepole pine. Determination on the survival probability of an individual tree; Stand characteristics of trees; Estimation of species-specific site productivity index.