Search

Assisted gene flow according to expected climate gradients is considered as a forest management strategy to mitigate impacts of environmental change on forest growth. However, the effects of seed translocation on wood properties and lumber quality remain unknown. This study evaluated the effect of provenance origin on lumber production and quality at rotation age in two white spruce provenance trials established in contrasting environments in eastern Canada. Based on 108 sample trees, which resulted in 943 pieces of lumber, average volume production per tree at the southernmost site was twice that of the production at the northern site. Provenance had a significant influence on growth and lumber strength in the first sawlog but had no effect on lumber stiffness and wood density. Although visual grade yields of No. 2 and better were high in both trials (over 86%), the machine stress rated (MSR) grade potential and percentage of lumber that met the bending stiffness design values of the visual grades were generally low (12%–26%). Hence, plantation-grown lumber should preferably be machine stress rated to ensure its fitness for structural applications in buildings. Management strategies aiming to efficiently sequester carbon should primarily maximize volume productivity in northern sites, as moving seed sources north still reduces provenance productivity, while breeding programs should aim to prevent decrease in lumber stiffness due to augmented productivity and shortened rotation cycles. [ABSTRACT FROM AUTHOR]

Defoliation and tree species determine growth during spruce budworm outbreaks, with site showing inconsistent effects. We determined effects of artificial defoliation treatments (0%, 50%, 100%, 100%+bud) for 3 years on volume increment of 240 balsam fir, black spruce, and white spruce trees, initially 7–10 years old and 2.3–4.1 m tall, on four soil drainage/richness classes. Current annual increment was significantly affected by species × site and site × defoliation interactions, with DBH as covariate. Specific volume increment (SVI) was significantly affected by a species × site × defoliation treatment interaction. Combining species and sites, volume reductions after 3 years were 21%–28%, 43%–51%, and 55%–66% for 50% defoliation, 100% defoliation, and 100%+bud. SVI was negatively, linearly related to cumulative defoliation. Marginal r2 and conditional r2 showed that 64% of variance of SVI was explained by site, species, cumulative defoliation, and DBH, but 90% was explained by fixed and random variables. After 3 years of defoliation, SVI of white spruce was 21%–23% greater than balsam fir and black spruce, and SVI on rich was 55%–79% greater than on poor sites. Cumulative defoliation was a good predictor of growth, and soil richness had a stronger effect on growth after defoliation than in previous studies. [ABSTRACT FROM AUTHOR]

While deployment of white spruce (Picea glauca (Moench) Voss) from seed orchards is increasing in Alberta, genetic gain is only considered in pure spruce stands due to uncertainties in measuring yields in mixedwood stands. To better understand the performance of improved spruce in mixedwood stands, we compared the effects of interspecific competition on growth of improved (1.9% height gain at a 100-year rotation) and unimproved spruce in northeastern Alberta. By age 8 years the improved spruce showed no advantage over the unimproved spruce in either height (1.36 ± 0.36 m vs. 1.42 ± 0.38 m) or diameter (23.68 ± 7.33 mm vs. 25.65 ± 6.85 mm), and the largest diameter trees were found in a nutrient-poor subxeric site. A distance-independent Lorimer's index including tree size ratio, combined with a power function, accounted for most of the growth variation in diameter and height from 2016 to 2017. The unimproved and improved spruce had different growth-competition curves across ecosites, and their height growth was less sensitive to competition than diameter growth. These results highlight several considerations for managing improved spruce, including (i) deploying higher genetic worth seedlots, (ii) developing realized gain trials with a good statistical design, and (iii) developing growth and yield functions for improved spruce in mixedwood stands. [ABSTRACT FROM AUTHOR]

If the modern climate trend continues for an additional 20–40 years, forests along the southern border of Canadian taiga may shift into new ranges of annual temperature and precipitation that are similar to the modern climate of central New York State, United States. Here we investigate the possible future response of white spruce (Picea glauca (Moench) Voss) to a warmer climate by studying trees planted 90 years ago near the southern limit of their climate tolerance in central New York, 300 km south of the boreal forest where this species is prevalent. We employed high-frequency recording dendrometers to determine radial growth phenology of six mature white spruce trees during 2013–2017. The results demonstrate significant reductions in the length of radial growth periods inversely proportional to the number of hot days with air temperature exceeding 30 °C. During years with very hot summers, the start of radial growth began about 3 days earlier than the 2013–2017 average. However, in those same years, the end of radial growth was also about 17 days earlier resulting in a shorter (70 days versus 100 days) radial growth season. Abundant (350–500 mm) summer precipitation, which resulted in soil moisture values of 20%–30%, allowed us to dismiss drought as a factor. Instead, a likely cause of reduced radial growth was mean temperature that exceeded optimal growth ranges, exacerbated by temperature extremes in ranges that lead to photoinhibition. The latter case was evident in the two warmest growing seasons (2013 and 2017), marked by extended periods of high daytime temperature (>30 °C) followed by early cessation of radial growth independent of seasonal precipitation. [ABSTRACT FROM AUTHOR]

Populations of many tree species exhibit synchronous and highly temporally variable seed crops across years. This is called mast seeding, and there are two predominant hypotheses for this pattern of reproduction: pollination efficiency and seed-predator satiation. Mast seeding studies typically involve records of population-level reproduction, with less information on the characteristics of reproductive structures. Here, we use data across 6 years (2012–2017), spanning a range of population-level cone conditions, to characterize (i) white spruce (Picea glauca (Moench) Voss) cone lengths and seeds per cone, and (ii) levels of seed predation. We quantified population-level cone production and collected 1399 cones from a total of 38 trees in the Huron Mountains, Michigan, USA. Linear mixed models showed that mean and minimum cone lengths varied significantly across years; both being longest during the greatest cone production year. Larger cones had more seeds and the slopes of the relationships as well as the intercepts varied significantly across years. Generalized linear mixed models and Akaike's information criterion model selection showed that cones with insect predation damage was greatest when population-level reproduction was the lowest, with a mean proportion of cones damaged 0.82 in that year. Our findings show that white spruce cone characteristics and losses to insect seed predation vary temporally, and follow expectations based on mast seeding hypotheses. [ABSTRACT FROM AUTHOR]

Rapid establishment of closed canopy cover is a key goal in land reclamation. While re-establishment of understory vegetation is likely to positively contribute to this goal, native herbaceous species are not typically planted on reclaimed sites though it is an alternative to reliance on natural regeneration. The objective of the present study was to test the principle of hitchhiker production of a tree species with native herbaceous species on recently reclaimed industrial sites with the aim of (1) understanding growth tradeoffs when mixing these species in the same container and (2) if hitchhiking had negative growth and survival outcomes for white spruce (Picea glauca) seedlings compared with singly grown white spruce seedlings. White spruce seeds were sown in nursery containers of contrasting cavity sizes, followed by sowing a forb species (Eurybia conspicua or Chamerion angustifolium) at different time intervals or grown singly. Larger cavities and earlier sow dates were associated with higher persistence and growth of the forbs, while later sow dates were associated with larger white spruce seedlings. We observed no evidence to suggest that hitchhiked seedlings were at a competitive disadvantage in terms of growth or survival compared with singly grown seedlings that were initially similar in size. [ABSTRACT FROM AUTHOR]

Increasing the production of wood fibre from conifer species such as white spruce (Picea glauca (Moench) Voss) is one of many challenges in the management of boreal mixedwood forests. The effects of various competition measures on relative growth and relative growth rate variables were calculated for individual white spruce subject trees. Correlation analysis was used to explore relationships with competitor structural features, including the ratio of competitor basal area to subject tree basal area (CBAS), the ratio of competitor height to subject tree height (AHCS), and the proportion of softwood (FSW). Regression analysis was used to explore relationships with three distance-dependent competition indices. The ratio of subject tree height to diameter at breast height (DBH) (HDR), crown ratio (CR), and crown relative increment rate (CRIR) were significantly correlated with CBAS and AHCS. HDR, CR, CRIR, and DBH relative growth rate were all statistically significantly related to the competition indices. Results indicated that (i) relative growth and relative growth rate measures successfully captured a range of competition, (ii) crowns of trees with larger diameters used their horizontal growing space more efficiently to produce stemwood, and (iii) the proportion of softwood contributing to competition did not appear to influence subject tree production efficiency. Growth efficiency variables have the potential to improve our understanding of boreal mixedwood dynamics. [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]

White spruce (Picea glauca (Moench) Voss) plantations have historically been an important source of high-quality forest products in the Great Lakes Region of North America. Thinning in spruce plantations is a common silvicultural practice for reducing competition and promoting resiliency to forest health threats such as eastern spruce budworm (Choristoneura fumiferana Clemens), a native forest pest of eastern North America. Spruce budworm larvae feed on the foliage of trees, which reduces growth and potentially causes mortality during an outbreak. There has been continual spruce budworm defoliation in northern Minnesota, U.S.A., since the mid-1950s, with higher levels of defoliation in the late 1990s. This research modeled the diameter growth response of white spruce 18 years after initial thinning in stands that presently range between 44 and 64 years old. Some stands received a second thinning in recent years. We used generalized nonlinear least squares and nonlinear mixed-effects models to estimate annual diameter growth using common tree and stand metrics. Growth model performance was improved by including thinning and frequency of spruce budworm defoliation as modifiers of diameter growth. Results of this study highlight how thinning in combination with insect disturbance affect diameter growth in white spruce plantations of northern Minnesota. [ABSTRACT FROM AUTHOR]

Shifts in the extent of the boreal forest during past warm intervals and correlations between climate and the position of the forest–tundra ecotone suggest that recent temperature increases will facilitate forest expansion into tundra ecosystems. In this study, we used a unique set of high-resolution repeat photographs to characterize white spruce (Picea glauca (Moench) Voss) populations in 1980 and 2015 at 52 sites across the forest–tundra transition in the Northwest Territories, Canada. We also conducted field inventories at eight sites to examine mapping accuracy, construct age distributions, and assess cone production and seed viability. Our analysis shows that stand density in the forest–tundra has increased significantly since 1980 but that the density of spruce at sites in the tundra has not changed. Age distributions constructed from field sampling also indicate that recent recruitment has occurred in the forest–tundra but not at tundra sites. The nonlinear relationship between summer temperature and seed viability suggests that recent warming has facilitated recruitment in the northern Subarctic but that cold temperatures still limit recruitment at higher latitude tundra sites. Additional research to determine the extent of changes in forest density across the northern Subarctic should be conducted to determine if similar changes are occurring across this ecotone.

The onset of lifetime reproduction is central to processes of plant adaptation and population changes. The relative contributions of size and age to the onset of reproduction are important to predicting that key event in individuals. To estimate respective size and age effects on first reproduction in a conifer, I observed white spruce (Picea glauca (Moench) Voss) trees in forest stands in Alaska, United States, over ranges of cumulative growth rates. Age was estimated by counting annular growth rings, size was indicated by tree height, and reproductive status was indicated by seed cones. Multiple logistic regression showed the relative contributions of tree height and age, adjusted for each other, to statistical predictions of reproductive maturity. Trees selected for having little competition for light first produced cones at heights between 1 and 5 m with little additional effect of age. Tree height contributed approximately 50% to regression predictions of reproductive maturity. In contrast, tree age contributed ≤1.5% and bore little relation to reproductive maturity other than as a component of growth rate. This is among the first reports to partial the effect sizes of tree size and age on the commencement of lifetime reproduction in a conifer. [ABSTRACT FROM AUTHOR]

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

We compared three methods for estimating current-year spruce budworm (Choristoneura fumiferana (Clem.)) defoliation from 2014 to 2021 using a network of 99 permanent sample plots in central Gaspé Peninsula, Québec. Percent current-year defoliation was measured by assessing shoots from mid-crown branches, ocular ratings of all individual trees using binoculars, and provincial government aerial surveys. Ocular survey defoliation differed from branch sample defoliation in 5–6 out of 7 years, consistently underestimating defoliation, across the full range of defoliation severity observed. Nested mixed-effect models for fir–spruce combined, balsam fir, white spruce, and black spruce ocular survey defoliation bias resulted in marginal R2 of 0.40, 0.47, 0.82, and 0.86, respectively. Current defoliation severity and its interaction with previous year defoliation and weather conditions significantly affected ocular survey bias. Correspondence of aerial survey estimates and mean plot defoliation occurred in only 43% of all plot-years and ranged from 14%–58% in individual years. Differences between aerial survey defoliation and plot values mainly resulted from assigning an adjacent class (e.g., light <30% assigned as moderate 31%–70% defoliation) or misplaced defoliation polygon boundaries, suggesting that assignment of aerial survey defoliation to plots or specific ground areas needs ground truth sampling. [ABSTRACT FROM AUTHOR]

Survival and growth of planted white spruce (Picea glauca (Moench) Voss) were assessed at year 15 in boreal mixedwood stands of northern Alberta, Canada, in stands that were deciduous-dominated prior to logging or were conifer-dominated. Three overstory retention levels (0%, 50%, and 75% retention) and four site preparation treatments (mound, high speed mix, scalp, and no treatment) were evaluated. In deciduous-dominated stands, planted spruce performed best in the 50% retention; here, stem volume was at least double that of any other retention treatment after 15 years. In contrast, spruce had reduced growth in coniferous-dominated stands in both 50% and 75% retention treatments compared with the 0% retention. Survival of planted spruce was unaffected by level of retention, but survival was lower in coniferous-dominated stands than in deciduous-dominated stands; in the coniferous-dominated stands, survival was better with mounding and mixing and lowest with scalp treatments. All height variables tended to be greater in the mix and mound site preparation treatments. Finally, the best estimates of future total growth (regenerated spruce and deciduous combined) in the coniferous-dominated stands were in the clearcut treatment. In terms of regenerated spruce growth, the best estimates occurred in the deciduous-dominated – 50% retention stand planted with soil mixing–mounding treatments, where projected growth of spruce was comparable with that of open-grown and tended stands in Alberta's boreal forests. [ABSTRACT FROM AUTHOR]

Many plant species reproduce by cloning if environmental conditions are unfavorable for sexual reproduction. To test the alternative hypotheses, whether cloning is an "exit strategy" or caused by selection, clonal growth in white spruce (Picea glauca (Moench) Voss) was investigated in three stands in Alaska, each consisting of a core (closed forest) plot and an edge (tree-line) plot. In total, 2571 trees were mapped and genotyped with 11 single sequence repeat (SSR) markers. The proportion of clonal trees follows a moisture gradient and was lowest in the dry Interior basin (4.5%), followed by the sites at the Alaska Range (9.0%) and the Brooks Range (21.7%). At the two latter sites, clonal growth was more frequent in the edge plot. A comparison among 960 aged trees revealed that clonal growth becomes more likely with increasing age and continues over the life span of a tree. Genetic data do not indicate any genetic predisposition for cloning. Clonal growth in white spruce most likely takes place via layering and depends on environmental conditions. Because performance of the trees, and therefore likely plant reproductive success, is lower in plots with a high proportion of clones, selection for clonal growth seems to be highly unlikely. [ABSTRACT FROM AUTHOR]

A two-year field study was carried out to determine whether inoculating white spruce, Picea glauca (Moench) Voss, with a native endophytic fungus, Phialocephala scopiformis DAOM 229536 Kowalski & Kehr (Helotiales, Ascomycota), decreased the performance of eastern spruce budworm, Choristoneura fumiferana Clemens, developing on these trees. Second instars were reared at three densities in the mid crown and at one density in the lower, mid, and upper crown. Larval survival (i.e., survival of larvae to pupation) was lower on endophyte-inoculated trees than on control trees in the mid crown and especially the upper crown but was similar in the lower crown, resulting in a significant interaction between endophyte and crown level. A similar but marginally insignificant interaction was observed for overall survival up to adult emergence (i.e., total survival). Larval survival and total survival were approximately 22% and 19% lower, respectively, when developing in the upper crown of endophyte-inoculated trees than in control trees. Larval survival remained relatively constant, with increased density on control trees but decreased with density on endophyte-inoculated trees, resulting in a significant interaction between endophyte and larval density. Sex ratios of emerged adults and wing lengths of emerged females were not influenced by the endophyte. Our results suggest that endophytic fungi could be useful additions to integrated pest management programs. [ABSTRACT FROM AUTHOR]

Retention harvests may leave retention in aggregations evenly dispersed or in various combinations. Although the relative efficacy of aggregated and dispersed retention for biodiversity conservation is widely debated, there has been little study of combinations. We studied this question relative to saproxylic beetles that initially colonize horizontal and upright coarse woody material (CWM) of white spruce (Piceaglauca (Moench) Voss) in boreal mixedwood stands at the Ecosystem Management Emulating Natural Disturbance (EMEND) in northern Alberta 12–13 years after retention prescription. Neither species richness nor emergence of beetles differed among freshly cut bolts exposed as "horizontal" or "upright" in retention patches of two sizes (0.20 ha and 0.46 ha) that were surrounded by different levels of dispersed retention (2%, 20%, and 50%). However, species composition in retention patches differed significantly from those in unharvested controls, except in the larger patches surrounded by 50% dispersed retention, although patterns differed among feeding guilds. Both mycetophage and predator assemblages in patches were similar to those in unharvested controls, suggesting that even relatively small patches retain these guilds regardless of the surrounding matrix quality. Because species composition differed between horizontal and upright bolts, an appropriate mix of horizontal and upright CWM may contribute to conservation of saproxylic beetle faunas. [ABSTRACT FROM AUTHOR]

Given a seed source, the quality of available substrates is a key factor in determining the success of white spruce ( Picea glauca (Moench) Voss) natural regeneration. We examined the influence of substrate and competing vegetation on survival and growth of natural regeneration of white spruce up to 4 years following harvesting in deciduous-dominated upland boreal mixedwood sites. Feather moss, thick soil surface organic layers, litter, and solid wood were poor substrates for establishment. Early successional mosses establishing on mineral soil, thin organics, and rotten wood were generally favourable microsites but were not highly available on postharvest sites. Mineral soil substrates were not as suitable as expected, likely because on a postlogged site, they are associated with unfavourable environmental characteristics (e.g., low nutrient availability, exposure). There was some evidence that survival and growth of seedlings were improved by surrounding vegetation in the first years, but heavy competing vegetation had a negative impact on older seedlings. Burial by aspen litter greatly increased seedling mortality, especially when combined with a brief period of submergence due to heavy spring snowmelt. The results provide insight into conditions under which natural regeneration could be an option for establishing white spruce following harvesting of deciduous-dominated boreal mixedwood forests. [ABSTRACT FROM AUTHOR]

Picea × darwyniana Björk & Goward was recently proposed to replace Picea albertiana S. Brown as the representative taxon for the hybrid offspring of Picea glauca (Moench) Voss and Picea engelmannii Parry ex Engelm., but should be considered invalid for three reasons. First, the proponents failed to document in any way that the P. albertiana isotypes were Picea glauca × mariana Little & Pauley hybrids, as they claimed. Secondly, the P. albertiana isotypes lacked pubescent twigs, purple markings on their seed cones, and denticulate cone-scale margins, which are characteristics of P. glauca × mariana. This indicates a misinterpretation of the P. albertiana parentage. Lastly, P. × darwyniana appears to be an example of P. albertiana ssp. ogilviei Strong & Hills. As the latter is an earlier and validly published name, P. × darwyniana is an illegitimate replacement for plants within the P. glauca × engelmannii (=P.a. ssp. albertiana) and P. engelmannii × glauca (=P.a. ssp. ogilviei) circumscriptions based on naming priority. [ABSTRACT FROM AUTHOR]

We investigated the genetic makeup of Lutz spruce, a natural hybrid between white and Sitka spruce on the Kenai Peninsula, Alaska. Microsatellites indicate 72% of individuals sampled had predominantly white spruce ancestry, whereas 14% had predominantly Sitka spruce ancestry; some individuals classified as white spruce had Sitka spruce plastid genotypes. As Picea mitochondria are maternally inherited and plastids are paternally inherited, it appears that white spruce was the ancestral seed parent of nearly all spruce on the western peninsula, whereas Sitka spruce alleles originated from pollen. Pollen records show that white spruce colonized the western peninsula ∼8500 YBP from glacial refugium, whereas Sitka spruce arrived on the eastern peninsula ∼4000 YBP after migrating up the Pacific coast. Our data suggest that Sitka spruce colonization west of the Kenai Mountains may have occurred not via seed dispersal but by long distance transport of wind-borne pollen and subsequent hybridization with established white spruce populations. Hybridization was an important mechanism that allowed Sitka spruce to expand the leading edge of its range in response to historical climate change. As the climate continues to warm, climate envelope modeling suggests Lutz spruce may ultimately displace white spruce on the western peninsula even as Sitka spruce is constrained to the eastern peninsula where it will continue to hybridize. [ABSTRACT FROM AUTHOR]

White spruce ( Picea glauca (Moench) Voss) cone crops were measured at five regional centers in southern and central Yukon for 30 years at one site from 1986 to 2015 and at four other sites during 9 to 11 years to select the best climatic model that uses cues from growing season temperature and rainfall to predict the size of cone crops. We evaluated six climatic models that use summer temperature and rainfall of years t - 1 and t - 2 to predict cone crops in year t. July temperatures provided the best predictors of white spruce cone crops, and no rainfall variable was related to the size of cone crops. We explored three variants of July temperatures: mean temperature, degree-days > 5 °C, and maximum temperatures. For each of these, we used the Δ T model that uses the difference in the July temperature measures of years t - 1 and t - 2. We compared the resulting six models with corrected Akaike's information criterion (AICc) to determine their relative predictive performance. The best model combined Δ T measures of degree-days > 5 °C and the four highest daily maximum July temperatures with R2 = 0.65. By comparison, the Δ T model involving only mean July temperatures was less successful ( R2 = 0.49). There was good regional synchrony ( rp = 0.7 to 0.8) in high cone crops over southern and central Yukon during 1986 to 2015. [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]

Eastern dwarf mistletoe ( Arceuthobium pusillum Peck) parasitizes the branches of white spruce ( Picea glauca [Moench] Voss) and ultimately kills this host species. Previous studies of host needle physiology generally focused on trees experiencing infections of moderate severity; here, we expanded upon previous research to investigate the morphological, physiological, and biochemical properties of needles from white spruce trees experiencing the full range of infection severities. We found that the impact of parasitism on host needle parameters did not scale uniformly with infection severity. Rather, parasitism reduced host needle size distal to infection and resulted in more negative carbon isotope ratios across all infection severities. Reduced foliar nitrogen and chlorophyll content were only evident in trees with moderate or severe infection, while photosynthetic capacity was depressed in only severely infected trees. Furthermore, while some impacts were confined to infected host branches, others, such as smaller needles and reduced photosynthetic capacity, were also evident in branches showing no visible signs of infection. We conclude that symptoms of infection appearing only after infection worsened in severity or appearing in uninfected branches may in whole or in part also be manifestations of a decline in resource availability and vigor of the whole tree. [ABSTRACT FROM AUTHOR]

Site trees used to estimate site index are selected based on characteristics that ensure that the tree reflects the potential productivity of the site. Hidden leader damage can make it difficult to identify site trees. Using these trees as site trees could lead to erroneous estimates of site index and height growth trajectories. One hundred and fifteen white spruce ( Picea glauca (Moench) Voss) trees were selected, harvested, and split open to identify hidden damage and to quantify the effect of the damage on height growth and site index. A mixed-effects height growth model based on the Chapman-Richards function was formulated. A height growth modifier was included in the model to estimate the effect of leader damage on height growth. It was found that height growth was reduced by 28% in the year that the damage occurred and by 6% and 3% in the following two years. This results in a reduction of about 0.16 m in site index per incidence of damage on average, although this will depend on the age when the damage occurred and the timing between damage events. Since the damage is not outwardly visible, this creates problems when developing and applying site index models. [ABSTRACT FROM AUTHOR]

Mixed-species stands present a number of opportunities for and challenges to forest managers. Boreal mixedwood stands in eastern Canada are often characterized by a dominant canopy of shade-intolerant aspen ( Populus tremuloides Michx.) with more shade-tolerant conifers in the mid- to sub-canopy layers. Because the aspen and conifer components often attain optimal merchantable sizes at different moments in stand development, there is an interest in developing silvicultural practices that allow partial or total removal of aspen and favour accelerated growth of residual conifers. We tested four partial harvesting treatments in mixed aspen - white spruce ( Picea glauca (Moench.) Voss) stands in which different proportions of aspen (0%, 50%, 65%, and 100% basal area) were removed. Ten years after treatments, 72 spruce stems representing dominant, co-dominant, and suppressed social classes were destructively sampled for stem analysis. Using linear mixed effect models, we analyzed growth as a function of treatment intensity, time since treatment, social status, pretreatment growth rate, and neighbourhood competition. Relative to control stands, radial and volume growth responses were detected only in the extreme treatment of 100% aspen removal. In relative terms, suppressed trees showed the greatest magnitude of cumulative growth increase. Compared with control trees, average annual radial and volume increments were, respectively, 23.5% and 7.1% higher for dominant trees, 67.7% and 24.1% higher for co-dominant trees, and 115.8% and 65.6% higher for suppressed trees over the 10 years after treatment. Growth response was proportional to pretreatment growth rate, and among neighbouring trees, only coniferous neighbours had a negative effect on white spruce growth. Our results suggest that in similar mixed-stand conditions, relatively heavy removal of overstory aspen accompanied by thinning of crowded conifers would result in greatest growth response of residual spruce stems. [ABSTRACT FROM AUTHOR]

We examined modulus of elasticity (MoE) derived from SilviScan in white spruce ( Picea glauca (Moench) Voss) at the site, tree, and ring levels across the Boreal Plains ecozone in Canada. Area-weighted averages of MoE were calculated for juvenile and mature wood and were examined in relation to radial growth, climate, and location. Correlations indicated that there was a negative relationship between radial growth and MoE in the juvenile wood that was detectable at the site and tree levels; however, the relationship weakened in the mature wood, particularly at the site level. Few climate variables were correlated with MoE in juvenile wood, whereas multiple summer and fall climate variables showed a significant correlation with MOE in mature wood. A model describing the radial profile of MoE explained 58% of the variability in MoE, with 10% of the random variability attributed to between-tree differences. Elevation and summer water balance accounted for nearly all of the between-site variability. A decrease in MoE with increasing elevation was noted and has been previously linked to a decrease in cell wall thickness due to a shorter growing season at higher elevations. Integration of the MoE profile model into an individual-tree growth and yield simulator is the next logical step. [ABSTRACT FROM AUTHOR]

We examine the extent to which foliar monoterpenes are trapped in the epicuticular waxes as part of an investigation into their role in natural defense against folivores. We monitored concentrations in white spruce ( Picea glauca (Moench) Voss) previous-year foliage and expanding foliage and their epicuticular waxes over the 2010 (14 trees) and 2011 (25 trees) growing seasons. In 2010, concentrations were low in the spring and increased over the summer; in 2011, they stayed low. The monoterpene profile of individual trees was similar between years and showed a consistent pattern over the growing season; in expanding foliage, δ-3-carene was only present in spring, whereas bornyl acetate increased over the growing season. Individual wax monoterpene profiles correlated with those of foliage, but the total concentration showed a different phenological pattern. Total content remained constant throughout the growing season on previous-year foliage but decreased on expanding foliage. Electron microscopy suggests this is due to changes in stomatal wax plugs and their role in blocking evaporation from the stomata. These findings suggest that insects contacting the leaf surface will receive accurate information from the wax chemical composition about the monoterpene mix but not about overall monoterpene levels. [ABSTRACT FROM AUTHOR]

Phialocephala scopiformis Kowalski & Kehr is a foliar fungal endophyte of white spruce ( Picea glauca (Moench) Voss) that produces the anti-insect compound rugulosin and other compounds in lower amounts. Seedlings inoculated with this and other toxigenic endophytes have increased tolerance to the spruce budworm Choristoneura fumiferana (Clemens, 1865). The presence of rugulosin in the diet and in needles infected by P. scopiformis reduces the growth rate of the insect. One of 300 white spruce trees inoculated as a seedling in 2001 was chosen to investigate the distribution of P. scopiformis and its principal toxin rugulosin throughout the crown. To facilitate the detection of the fungus in small samples, a qPCR assay was developed based on the ITS region of fungal ribosomal DNA targeting a genetic polymorphism unique to P. scopiformis. The assay was specific, with a method limit of detection 100 ng mycelium per gram needle sample with high reproducibility and accuracy. We found that 11 years after inoculation, P. scopiformis DAOM 229536 and its toxin were detectable in needle samples distributed throughout the crown. Of the 109 samples tested, 100% of the rugulosin-positive samples also tested positive for P. scopiformis DAOM 229536 DNA in the qPCR assay. The mean and median needle rugulosin concentrations were >2 times that required to reduce the growth of spruce budworm. [ABSTRACT FROM AUTHOR]

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]

There is a growing interest in improving knowledge on wood quality of forest resources to allow for an end-product oriented supply for the wood-processing industry. We investigated the differences of white spruce ( Picea glauca (Moench) Voss) wood traits from 13 ecological regions of the eastern Canadian province of Quebec and identified climatic and geographic variables and tree characteristics that may help predict wood traits in novel approaches to forest inventories. One hundred and eleven wood disks were used to determine wood traits that are related to wood anatomy and to mechanical use of wood. Our results indicate significant differences between ecological regions for most of the investigated wood traits. Samples from several coastal regions showed, for example, wood anatomy that is advantageous for some pulp and paper grades, but they offer comparatively weak estimates for mechanical applications. Ordination and projection to latent structures allowed us to identify maximum temperature, degree days, geographic location, tree height, and tree diameter as important predictor variables for wood traits. The quality of models was variable and R2 values ranged from 0.13 to 0.59. Prediction errors in an independent sample were mostly below 10%, and bias was below 5%. Although the prediction of wood mechanics was less precise, the presented results are an encouraging step toward obtaining a wood trait signature for different environments. [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]

White spruce ( (Moench) Voss) cone crops were measured from 1986 to 2011 in the Kluane region of southwestern Yukon to test the hypothesis that the size of cone crops could be predicted from spring and summer temperature and rainfall of years t, t - 1, and t - 2 . We counted cones in the top 3 m of an average of 700 white spruce trees each year spread over 3-14 sites along 210 km of the Alaska Highway and the Haines Highway. We tested the conventional explanation for white spruce cone crops that implicates summer temperatures and rainfall in years t and t - 1 and rejected it, since it explained very little of the variation in our 26 years of data. We used exploratory data analysis with robust multiple regressions coupled with Akaike's information criterion corrected (AICc) analysis to determine the best statistical model to predict the size of cone crops. We could statistically explain 54% of the variation in cone crops from July and August temperatures of years t - 1 and t - 2 and May precipitation of year t - 2. There was no indication of a periodicity in cone crops, and years of large cone crops were synchronous over the Kluane region with few exceptions. This is the first quantitative model developed for the prediction of white spruce cone crops in the Canadian boreal forest and has the surprising result that weather conditions 2 years prior to the cone crop are the most significant predictors. [ABSTRACT FROM AUTHOR]

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.)

Early establishment of competing vegetation often presents an obstacle to the success of planted white spruce ( Picea glauca (Moench) Voss) seedlings. We followed growth and development of white spruce and associated vegetation for up to 17 years in Alaska's boreal forests to quantify roles of overtopping plant cover in suppressing conifers. The three study areas represented a range of site conditions of varying productivity and species of competing cover, different site preparation and release treatments, and different bare-root and container white spruce stock types. Herbaceous overtopping peaked early after planting and decreased as white spruce were able to outgrow competitors. Overtopping by shrubs and hardwoods, especially aspen ( Populus tremuloides Michx.) and resin birch ( Betula neoalaskana Sarg.) peaked somewhat later than herbaceous overtopping and decreased over time for most sites and treatments. In a model that combined all sites, vegetation management treatments, and years, overtopping and previous year's volume explained approximately 85% of the variation in volume growth. Increasing the size of planting stock helped reduce overtopping, hence suppression, even in treatments dominated by hardwood species. Results suggested that control of overtopping was essential for maximum growth and long-term or increasing levels of overtopping severely suppressed white spruce seedling growth. [ABSTRACT FROM AUTHOR]

Ongoing warming at high latitudes is expected to lead to large changes in the structure and function of boreal forests. Our objective in this research is to determine the climatic controls over the growth of white spruce ( Picea glauca (Moench) Voss) at the warmest driest margins of its range in interior Alaska. We then use those relationships to determine the climate variables most likely to limit future growth. We collected tree cores from white spruce trees growing on steep, south-facing river bluffs at five sites in interior Alaska, and analyzed the relationship between ring widths and climate using boosted regression trees. Precipitation and temperature of the previous growing season are important controls over growth at most sites: trees grow best in the coolest, wettest years. We identify clear thresholds in growth response to a number of variables, including both temperature and precipitation variables. General circulation model (GCM) projections of future climate in this region suggest that optimum climatic conditions for white spruce growth will become increasingly rare in the future. This is likely to cause short-term declines in productivity and, over the longer term, probably lead to a contraction of white spruce to the cooler, moister parts of its range in Alaska. [ABSTRACT FROM AUTHOR]

In the boreal plains of western Canada, white spruce ( Picea glauca (Moench) Voss) height−age and site index (SI) curves have been developed and applied to assess site productivity for white spruce without fully considering the competition that usually occurs between the spruce and taller deciduous trees. In this study, we evaluated the effects of deciduous removal on white spruce height growth potential using stem analysis on typical control spruce grown with deciduous neighbours and spruce that were released from deciduous competition ∼60 years prior. Due to the late application of the release treatments (at stand ages of 20-60 years), the observed site index of spruce was not affected by treatment. However, height growth in the 50 years following treatment was increased by 2.1 m. We present a height−age model to specifically estimate the change in SI required to achieve the observed height response following late release. The model indicated that the post-release SI estimate of white spruce would need to be on average 4.2 m higher than control SI to track the height response. This model is useful for estimating the true, competition-free SI for white spruce from the observed SI in natural mixed stands. [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]

Black spruce ( Picea mariana (Mill.) Britton, Sterns & Poggenb.) and white spruce ( Picea glauca (Moench) Voss) are phylogenetically proximal species that differ in productivity. Crown characteristics of these two species have not been extensively studied, in spite of the importance of these two species to the Canadian boreal forest and the importance of tree crowns for understanding and modelling tree growth. In this paper, we characterize and compare the crown lengths, crown profiles (i.e., radii), shapes, and surface areas of these two species using 65 white spruce and 57 black spruce trees destructively sampled in the provinces of Alberta, Ontario, and Quebec, Canada. Crown length was measured on every sample tree, while crown profile was obtained by reconstructing crowns from branch measurements. Our results showed that crown lengths did not differ between these two species given the same tree size and growth conditions. However, these two species establish under different growth conditions resulting in crown length differences. Further, differences in crown radii and profiles were found even under the same growth conditions. White spruce trees had wider crown radii and profiles changed from a parabola to a cone shape under increased density. As a result, differences in crown surface areas were found. [ABSTRACT FROM AUTHOR]