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As forest managers increasingly seek to implement partial-harvest silviculture systems in complex forests, more data are required on the potential development of the residual stand following treatment. In this study, we present 25-year data from a long-term silvicultural study of tree- and stand-level responses to differing levels of basal area following partial harvest in a complex spruce–fir forest in central British Columbia, Canada. Reducing stand basal area elicited stronger basal area increment response in fir than spruce; however, spruce productivity was overall higher than fir across all treatments. Smaller trees increased their size proportionally more than larger trees, and thinning resulted in increased recruitment of smaller trees into larger diameter classes. At the stand-level, basal area reductions to well below 20 m2/ha resulted in higher volume and basal area growth over the length of this study, and suggest that optimum stand-level growth may be achieved at lower basal areas than suggested in prior literature. We also found a positive relationship between stand-level residual basal area and mortality. In central British Columbia, stand structure, species composition, and growth rates in complex spruce–fir forests can be maintained through partial-harvest silviculture treatments. [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]

Climate change is expected to increase winter temperatures in boreal climates. White spruce ( Picea glauca (Moench) Voss) is vulnerable to spring frost damage due to its habit of early budbreak, which may be exacerbated or lessened with increasingly warm winters at its southern range edge. We tested the effects of episodic warming during the quiescent stage on budbreak time and growth of seven seed sources grown in a common garden setting in Minnesota, USA. Treatment plots were warmed with infrared lamps for 4 days each in February, March, or February and March to simulate a midwinter thaw. Control plots for each treatment and an overall control were included for comparison. Trees warmed in February experienced a slight delay in spring budbreak, but differences in budbreak time were generally not significant. Terminal growth was significantly and negatively correlated with time of budbreak but not with time to growth cessation. Our results suggest that white spruce is relatively resilient to the effects of intermittent warming but that warming early in the season may delay budbreak time, which is expected to reduce terminal growth. [ABSTRACT FROM AUTHOR]

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

We assessed whether commercially thinning (CT) spruce ( Picea spp.) plantations (40% basal area removal) can cause structural changes in fine woody debris (FWD) and understory vegetation to improve habitat quality for small rodents in northwestern New Brunswick, Canada. We created three contrasting environments (FWD rich - understory vegetation rich, FWD poor - understory vegetation rich, and FWD poor - understory vegetation poor) by establishing CT with debris retention (merchantable trunk removal), CT with all debris removed (full tree removal), and non-CT (plantation without CT) in six midrotation white spruce ( Picea glauca (Moench) Voss) plantations. We live-trapped small mammals in each plantation during spring and summer of 2011 and 2012 and estimated animal density and survival with capture-recapture models. Southern red-backed vole ( Myodes gapperi (Vigors, 1830)) density was two to three times greater in CT with debris retention than in either non-CT or CT with debris removal, and their survival rate was twice that in CT with debris removal. Woodland jumping mouse ( Napaeozapus insignis (Miller, 1891)) density was two to five times greater in non-CT than in either CT treatment. Deer mice ( Peromyscus maniculatus (Wagner, 1845)) did not show any treatment effect. Productivity and demographics were not affected by CT treatment for any species. We found evidence that midrotation spruce plantations are used differently by small mammal species based on stand condition and recommend that managers maintain plantations in CT and non-CT states. [ABSTRACT FROM AUTHOR]

Radial patterns of modulus of elasticity (MOE) were examined for white spruce ( Picea glauca (Moench) Voss) and trembling aspen ( Populus tremuoides Michx.) from 19 mature, uneven-aged stands in the boreal mixedwood region of northern Alberta, Canada. The main objectives were to (1) evaluate the relationship between pith-to-bark changes in MOE and cambial age or distance from pith; (2) develop species-specific models to predict pith-to-bark changes in MOE; and (3) to test the influences of radial growth, relative vertical height, and tree slenderness (tree height/DBH) on MOE. For both species, cambial age was selected as the best explanatory variable with which to build pith-to-bark models of MOE. For white spruce and trembling aspen, the final nonlinear mixed-effect models indicated that an augmented rate of increase in MOE occurred with increasing vertical position within the tree. For white spruce trees, radial growth and slenderness were found to positively influence maximum estimated MOE. For trembling aspen, there was no apparent effect of vertical position or radial growth on maximum MOE. The results shed light on potential drivers of radial patterns of MOE and will be useful in guiding silvicultural prescriptions. [ABSTRACT FROM AUTHOR]

We characterized the ectomycorrhizae (ECM) of planted white spruce (Picea glauca (Moench) Voss) seedlings as affected by mechanical site preparation (MSP) of clear-cut conifer-dominated boreal mixedwood forest. Relative abundance, richness, and composition of the ECM community were compared among untreated control, mixed, mounded, and scalped site preparation treatments. On >11 000 root tips, we observed 16 ECM morphotypes. Those common to the nursery in which the seedlings were raised were most abundant (Thelephora americana, Wilcoxina-like (E-strain), Amphinema byssoides, Phialocephala-like (MRA)). Seedlings in the untreated controls had lower abundances of these, but higher abundances of other ECM, which were not present in the nursery of origin but were indigenous to these forest stands. In terms of ECM composition, the “mixed” treatment was most similar to the untreated control, while the “scalped” and “mound” treatments showed significantly different ECM communities than the controls. Our results suggest that MSP may facilitate continued dominance by ECM that establish on seedlings in the nursery while slowing the natural succession towards the natural forest ECM. MSP treatments that leave some surface organic matter relatively intact may impact ECM less than those that remove or bury the organic layer. Nous avons caractérisé les ectomycorhizes (ECM) de plants d’épinette blanche (Picea glauca (Moench) Voss) affectés par la préparation mécanisée de terrain (PMT) à la suite d’une coupe à blanc dans une forêt mixte dominée par des résineux. L’abondance relative, la richesse et la composition de la communauté d’ECM a été comparée entre un témoin non traité et des traitements de préparation de terrain mixtes, d’aménagement de buttes et de scalpage. Nous avons observé 16 morphotypes d’ECM sur plus de 11 000 apex racinaires. Ceux qui étaient communs dans la pépinière où les semis avaient été produits étaient les plus abondants (Thelephora americana, le type Wilcoxina (souche E), Amphinema byssoides, le type Phialocephala (MRA)). L’abondance de ces ECM était plus faible chez les semis des témoins non traités qui comportaient, cependant, une plus forte abondance d’autres ECM qui n’étaient pas présentes dans la pépinière d’origine, mais qui étaient indigènes à ces peuplements forestiers. En termes de composition en ECM, le traitement mixte était le plus semblable au témoin non traité alors que le scalpage et l’aménagement de buttes étaient associés à des communautés d’ECM significativement différentes de celle du témoin. Nos résultats indiquent que la PMT peut faciliter le maintien de la dominance des ECM établies sur les plants en pépinière tout en ralentissant la succession naturelle vers les ECM de la forêt naturelle. Les traitements de PMT qui laissent des superficies relativement intactes de matière organique peuvent avoir moins d’impact sur les ECM que ceux qui enlèvent ou enfouissent la couche de matière organique. [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]

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]

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.

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]

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.