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

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]

Long-term studies of vegetation succession can inform restoration of degraded forests. We examined resilience of a boreal mixedwood vegetation community, asking whether treatments employed to restore wood production in a degraded ecosystem could also restore diversity and composition of vegetation communities. The Inga Lake trial, established in 1987 in northeastern British Columbia, used mechanical, fire, and chemical and manual treatments, encompassing a gradient of restoration effort, and tree planting to restore a shrubland to white spruce (Picea glauca (Moench) Voss) forest. We monitored vascular plant, bryophyte, and macrolichen composition five times over 31 years on five to seven treatments replicated five times. We used mixed-effects models and nonmetric multidimensional scaling to compare diversity and composition among treatments and with mature reference forests. Low- to high-effort restoration created a gradient from broadleaf- to spruce-dominated overstories. Diversity increased with restoration effort. Four of 253 taxa occurred in mature forests only. There was no evidence that lower versus higher effort treatments followed divergent successional pathways toward broadleaved versus spruce reference communities. Our results suggest that these mixedwood vegetation communities lie within a broad domain of successional attraction that confers high ecological resilience to disturbance. Gap cuttings to stimulate understory re-initiation and provide woody debris are recommended to complete the restoration. [ABSTRACT FROM AUTHOR]

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

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

Background: The presupposition of genomic selection (GS) is that predictive accuracies should be based on population-wide linkage disequilibrium (LD). However, in species with large, highly complex genomes the limitation of marker density may preclude the ability to resolve LD accurately enough for GS. Here we investigate such an effect in two conifer species with ~ 20 Gbp genomes, Douglas-fir (Pseudotsuga menziesii Mirb. (Franco)) and Interior spruce (Picea glauca (Moench) Voss x Picea engelmannii Parry ex Engelm.). Random sampling of markers was performed to obtain SNP sets with totals in the range of 200–50,000, this was replicated 10 times. Ridge Regression Best Linear Unbiased Predictor (RR-BLUP) was deployed as the GS method to test these SNP sets, and 10-fold cross-validation was performed on 1,321 Douglas-fir trees, representing 37 full-sib F1 families and on 1,126 Interior spruce trees, representing 25 open-pollinated (half-sib) families. Both trials are located on 3 sites in British Columbia, Canada. Results: As marker number increased, so did GS predictive accuracy for both conifer species. However, a plateau in the gain of accuracy became apparent around 10,000–15,000 markers for both Douglas-fir and Interior spruce. Despite random marker selection, little variation in predictive accuracy was observed across replications. On average, Douglas-fir prediction accuracies were higher than those of Interior spruce, reflecting the difference between full- and half-sib families for Douglas-fir and Interior spruce populations, respectively, as well as their respective effective population size. Conclusions: Although possibly advantageous within an advanced breeding population, reducing marker density cannot be recommended for carrying out GS in conifers. Significant LD between markers and putative causal variants was not detected using 50,000 SNPS, and GS was enabled only through the tracking of relatedness in the populations studied. Dramatically increasing marker density would enable said markers to better track LD with causal variants in these large, genetically diverse genomes; as well as providing a model that could be used across populations, breeding programs, and traits. [ABSTRACT FROM AUTHOR]

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

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

• Statistical validation alone may yield unrealistic models; spatial validation is vital. • Weak genetic effects for interior spruce, hinting modest local adaptation. • Climate change, especially heat stress, threatens current interior spruce habitats. • Climate change may lead to upslope shift and lower interior spruce productivity. Ecological models, including various forms of population transfer and response functions, have been widely employed to predict the performance of forest trees under future climate conditions. However, the accuracy of model predictions remains a challenge due to the lack of systematic model optimization and validation processes. In this study, we explored a series of candidate universal response functions (URFs) based on comprehensive provenance trials for interior spruce, a tree hybrid complex of great ecological and economic importance in British Columbia. We first developed URFs with various numbers of climate variables and their combinations, then evaluated and validated these models with conventional statistical methods. Although these models showed high predictive power and performed well in statistical validation, the map visualizations of these models varied substantially. Therefore, we further conducted a pixel-wise spatial validation based on site productivity data to identify the model with the best performance. Finally, we analyzed the impact of climate change on interior spruce based on the final model. Our results revealed that: 1) a minimum number of independent climate variables is required to generate a reliable and informative ecological model; 2) spatial validation is critical to ensure the credibility of ecological models; 3) among-population variation resulting from local adaptation is relatively weak, indicating a potential for modest productivity gains from selecting well-adapted populations for stand establishment; and 4) most of the current interior spruce habitat is projected to be vulnerable to anthropogenic climate change, largely due to temperature rise, with a major upslope shift predicted. [ABSTRACT FROM AUTHOR]

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

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]

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

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

Abstract: A white spruce ring-width chronology was used to reconstruct June–July mean temperatures in the northern Canadian Rocky Mountains back to 1772 A.D. Samples were collected in an old growth subalpine forest in the remote Kwadacha Wilderness Provincial Park. Two chronologies were created, one using standard dendroclimatological methods and one through the use of principal components analysis. The ring-width chronologies both showed a strong positive relationship with minimum, maximum, and mean temperatures during the current growing season. The principal component based chronology was deemed superior for use as a proxy record due to its greater ability to explain the variance in the instrumental temperature record and stronger performance during reconstruction verification. Comparison of this reconstruction with other dendroclimatological reconstructions from western Canada revealed a coherent pattern of low-frequency variability, whereas comparisons at annual times-scales showed considerable temporal and spatial variability in the level of agreement between reconstructions. The northern Canadian Rocky Mountains reconstruction showed no evidence of the reduction in sensitivity to climatic variability that has been found in many other northern spruce chronologies during the late 20th century. [Copyright &y& Elsevier]

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

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

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Vertical and horizontal patterns of light within gaps and expansion of trees into gaps were examined in young stands dominated by trembling aspen (Populus tremuloides Michx.) in northeastern British Columbia and northwestern Alberta. Lateral growth of branches of aspen edge trees averaged 15.2 cm/year and was similar to crown expansion rates reported for edge trees in eastern North America. Branches growing into gaps were significantly longer than those growing away from gaps and are likely to lead to gap shrinkage and reductions in light within gaps. However, height growth of edge trees was not significantly different from that of trees within the surrounding stands. Models describing relationships between diffuse transmittance and locations within gaps and surrounding stand height were developed in this paper. Sky view angle (SVA) was found to be effective for predicting transmittance to different locations within gaps. When SVA values exceed 1.2 (at the B.C. sites), white spruce (Picea glauca (Moench) Voss) will receive <40% of full sunlight, which is less than optimal for spruce height growth. [ABSTRACT FROM AUTHOR]

The 19-20-year effects of mechanical site preparation, windrow burning, chemical site preparation, and postplanting vegetation control on survival and growth of planted white spruce are reported from two boreal sites in British Columbia, Canada. Survival differed between treatments at both sites, but was relatively good (≥77%) even in untreated plots. Current data regarding the proportion of spruce that were physically overtopped by vegetation and previous results from related soils and vegetation studies suggest that lasting reductions in tall shrub and aspen abundance were more important to spruce growth than early microenvironmental effects associated with manipulating the rooting environment. At Inga Lake, postplanting vegetation control produced a 13-fold increase in spruce volume over the control after 19 years, which was statistically equivalent to increases resulting from fine mixing, plow-inverting and windrow burning site preparation treatments. At Iron Creek, chemical site preparation and plow-inverting quadrupled spruce volume, whereas mounding, patch scarification and disc trenching were ineffective. Growth and yield simulations using treatment-specific site index curves for Inga Lake suggested that rotation length could be shortened by 12-16 years through the use of site preparation or postplanting vegetation control. However, untreated areas, due to the relatively good survival of white spruce at age 19, were predicted to produce equivalent volume if left to grow to mean annual increment culmination age. [ABSTRACT FROM AUTHOR]

Abstract: Establishing white spruce (Picea glauca (Moench) Voss) by planting it under established aspen (Populus tremuloides Michx.), stands has substantial potential as a technique for regenerating boreal mixedwood stands. The presence of an aspen overstory serves to ameliorate frost and winter injury problems and suppresses understory vegetation that may compete with white spruce. In this study we examine the growth of white spruce during the first 10 years after being planted underneath a 39-year-old stand of trembling aspen following thinning and fertilization. Results indicate successful establishment and reasonable growth rates of white spruce planted under thinned and unthinned aspen stands, even with aspen basal area of 51m2 ha−1. Thinning of overstory aspen to 1000 or 2000stemsha−1 did not increase light reaching seedlings, but did result in improvements in light above the shrub layer and in diameter and height growth of the underplanted seedlings. However, these increases in growth of underplanted spruce may not justify the expense of thinnings. Fertilization of these stands prior to planting had no effect on spruce growth. Growth of spruce underplanted at this site near Fort Nelson was similar to that at two other stands near Dawson Creek, B.C. Information on treatment effects on light, beam fraction, air temperature, and soil temperature are presented. Measurements of light obtained using LAI-2000 and hemispherical photography were compared with those obtained from hourly PPFD measurements. Results indicate that while both methods provide estimates of transmittance that are highly correlated with those provided by actual light measurements, they provide substantial underestimates of actual light levels. [Copyright &y& Elsevier]

Abstract: Establishing white spruce (Picea glauca (Moench) Voss) by planting it under established aspen (Populus tremuloides Michx.), stands has substantial potential as a technique for regenerating boreal mixedwood stands. The presence of an aspen overstory serves to ameliorate frost and winter injury problems and suppresses understory vegetation that may compete with white spruce. In this study we examine the growth of white spruce during the first 10 years after being planted underneath a 39 year-old stand of trembling aspen following thinning and fertilization. Results indicate successful establishment and reasonable growth rates of white spruce planted under thinned and unthinned aspen stands, even with aspen basal area of 51m2 ha−1. Thinning of overstory aspen to 1000 or 2000stemsha−1 did not increase light reaching seedlings, but did result in improvements in light above the shrub layer and in diameter and height growth of the underplanted seedlings. However, these increases in growth of underplanted spruce may not justify the expense of thinnings. Fertilization of these stands prior to planting had no effect on spruce growth. Growth of spruce underplanted at this site near Fort Nelson was similar to that at two other stands near Dawson Creek, B.C. Information on treatment effects on light, beam fraction, air temperature, and soil temperature are presented. Measurements of light obtained using LAI-2000 and hemispherical photography were compared with those obtained from hourly PPFD measurements. Results indicate that while both methods provide estimates of transmittance that are highly correlated with those provided by actual light measurements, they provide substantial underestimates of actual light levels. [Copyright &y& Elsevier]

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]

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]

A genetic analysis of the introgression zone between Sitka spruce (Picea sitchensis) and white spruce (P. glauca) in northwestern British Columbia was conducted to (1) quantify the contributions of parental species to introgressed populations; (2) characterize genetic patterns of variation across the introgression zone; and (3) address practical issues of gene resource management in this region. Seeds were sampled and seedlings grown from 57 putative hybrid parent trees from 16 locations across the introgression zone. Foliage samples were also obtained for allopatric Sitka and white spruce reference populations. Based on allele frequencies for sequence-tagged-site (STS) molecular markers, a hybrid index was developed that reflects the relative contribution of Sitka spruce to hybrid populations (0=white spruce, 1=Sitka spruce). Mean STS hybrid index estimates ranged from 0.46 to 0.95 for locations within the zone of introgression. Significant differences in hybrid index were observed among sampling locations. Hybrid indices decreased from the coast to the interior within the introgression zone in spite of large among-family variation within locations. Variation among locations in hybrid index was better explained by geographic variables than by climatic or ecological variables. Physical drainage distance along river valleys to the nearest marine inlet explained 78% of the variation in STS hybrid index. Concordant clines were obtained when the same analytical techniques were applied to published allozyme frequencies for seedlots originating from a wider geographic area across the introgression zone. Allozyme hybrid index estimates ranged from 0.01 to 0.98. The relatively steep cline observed in hybrid index across the maritime/continental climate ecotone is best managed by limiting longitudinal seed transfer for reforestation in this region. [Copyright &y& Elsevier]

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]

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]

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]

Reports on the measured rates of decomposition at three sites representing the major mixedwood forest types of British Columbia: (i) boreal forests of white spruce (Picea glauca (Moench) Voss) and trembling aspen (Populus tremuloides Michx.), (ii) coastal forests of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and red alder (Alnus rubra Bong.), and (iii) a wet interior forest of Douglas-fir, paper birch (Betula papyrifera Marsh.), and lodgepole pine (Pinus contorta Doug. ex Loud.). Mass loss of litter of each species (both pure and in combination with the other species) that was measured in forests of each species to determine (i) if broadleaf litter decomposed faster than needle litter, (ii) if litter decomposed faster in broadleaf or mixedwood forests than in coniferous forests, and (iii) if mixing with broadleaf hastened decomposition of needle litter; Broadleaf litters that decomposed faster than needles during the first year but, thereafter, decomposed more slowly; Litter that tended to decompose faster in the broadleaf forests than in the coniferous forests; No evidence to indicate that the addition of broadleaf litter hastened decomposition of needle litter; Results that indicate that the mixing of needle litter with broadleaf litter is unlikely to hasten decomposition in mixedwood forests of British Columbia.

The article discusses a paper that offer survival time analysis of a white spruce tree with respect to the attack by the white pine weevil. Topics discussed include investigation of survival times of resistant and susceptible trees during trial of white spruce in the interior of British Columbia, Canada, study of survivorship of resistant trees with respect to susceptible trees and identification of survival times of white spruce trees followed by a lognormal distribution.

Studies humus forms of trembling aspen ecosystems in a range of soil moisture and nutrient regimes in the Boreal Black and White Spruce of northeastern British Columbia. Intergrade between mors and moders; Methods applied in the study; Impact of higher temperature near the ground surface and aspen litter on the development of the upper soil fauna horizon.

Studies the relationship between concentrations of foliar nutrient with tree growth and soil nutrient amount for natural white spruce in British Columbia, Canada. Concentration of calcium and nitrogen found; Level of nutrients on wet to very wet sites; Correlation between nitrogen, phosphorus and potassium nutrients and stand age and height of tree; Needs for modification in standard applied to nutrient diagnosis.

Adaptive physiological changes were investigated in seven populations of Sitka (Picea sitchensis (Bong.) Carr.) × interior spruce (P. glauca (Moench) Voss × P. engelmannii Parry ex Engelm.) spanning the Nass–Skeena transition zone in British Columbia, Canada. Each population was represented by an Si rDNA index that was calculated from the relative optical densities on a gel autoradiogram of five ribosomal DNA bands characteristic of Sitka spruce and interior spruce. This index estimates the proportion of the genome contributed by interior spruce. Physiological adaptations were assessed by gas exchange parameters measured under both well-watered and drought conditions. Under well-watered conditions, Sitka spruce populations had higher maximal photosynthesis at saturating light and ambient CO2, higher quantum yield at the light compensation point, and higher dark respiration than interior spruce populations. Sitka spruce populations also reached maximal photosynthesis at lower photosynthetically active radiation and higher CO2 concentrations, and had higher stomatal densities that resulted in lower stomatal limitations to photosynthesis than interior spruce populations. In contrast, interior spruce populations exhibited greater drought tolerance than Sitka spruce populations. Their gas exchange rates declined at a slower rate in response to drought. They maintained higher gas exchange rates in response to moderate to severe drought (predawn plant water potentials = –1.5 MPa), and their photosynthetic rates recovered faster when they were rewatered after exposure to drought. Comparison of the seven populations indicated that physiological parameters were significantly related to the Si rDNA index. An increase in Si rDNA index was associated with proportional changes in physiological measurements, suggesting that genetic interchange among species with contrasting ecological adaptations can enhance the environmental adaptation of natural populations. [ABSTRACT FROM PUBLISHER]

Eight populations of Sitka spruce (Picea sitchensis (Bong.) Carr.) and interior spruce (Picea glauca (Moench) Voss × Picea engelmannii Parry ex. Engelm.) seedlings were sampled from a zone of Sitka–interior spruce introgression in British Columbia, Canada. Restriction fragment length polymorphisms of the nuclear ribosomal RNA genes (rDNA) were used to define species-specific hybridization patterns for the Sitka spruce and interior spruce populations. Hybridization was estimated from an index based on the relative abundance of polymorphic rDNA combining bands for each population. Sitka × interior hybrid seedlings had an index value for the relative abundance of interior spruce rDNA (Si-rDNA) ranging from 0.07 (Lower Nass; the most westerly collected source) to 0.95 (Bulkley Valley low-elevation seed orchard). During shoot elongation, osmotic potential at saturation (Ψsat) and turgor loss point (Ψtlp) increased, whereas total turgor (ΨPTotal) decreased. After bud set in the summer and throughout the fall, Ψsat and Ψtlp decreased, whereas ΨPTotal increased. At all times of year, populations with a higher Si-rDNA index had lower Ψtlp and Ψsat and higher ΨPTotal than populations with a lower Si-rDNA index. During the fall, Sitka × interior hybrid seedlings exhibited a seasonal decline in the temperature causing 50% needle electrolyte leakage (LT50) and in the critical temperature indicating the initial point of freezing injury. Seedlings with a higher Si-rDNA index had lower LT50 and critical temperature values indicating greater freezing tolerance in the fall. Throughout most of the year, seedling population Si-rDNA index was related to the degree of drought and freezing tolerance. [ABSTRACT FROM PUBLISHER]

Research Highlights: This research presents a novel approach for comparing structural carbon allocation to tree growth and to climate in a dendrochronological analysis. Increasing temperatures reduced the carbon proportion of wood in some cases. Background and Objectives: Our goal was to estimate the structural carbon content of wood within hybrid white spruce (Picea glauca (Moench) × engelmannii (Parry) grown in British Columbia, Canada, and compare the percent carbon content to wood properties and climate conditions of the region. Specific objectives included: (i) the determination of average incremental percent carbon, ring widths (RW), earlywood (EW) and latewood (LW) widths, cell wall thickness, and density over time; (ii) the determination of differences between percent carbon in individual forest stands and between regions; and (iii) the evaluation of the relationships between percent carbon and climate variation over time. Methods: Trees were sampled from twelve sites in northern British Columbia. Wood cores were analyzed with standard dendrochronology techniques and SilviScan analysis. Percent structural carbon was determined using acetone extraction and elemental analysis for 5 year increments. Individual chronologies of wood properties and percent carbon, and chronologies grouped by region were compared by difference of means. Temperature and precipitation values from the regions were compared to the carbon chronologies using correlation, regression, and visual interpretation. Results: Significant differences were found between the percent structural carbon of wood in individual natural and planted stands; none in regional aggregates. Some significant relationships were found between percent carbon, RW, EW, LW, and the cell wall thickness and density values. Percent carbon accumulation in planted stands and natural stands was found in some cases to correlate with increasing temperatures. Natural stand percent carbon values truncated to the last 30 years of growth was shown as more sensitive to climate variation compared to the entire time series. Conclusions: Differences between the stands in terms of structural carbon proportion vary by site-specific climate characteristics in areas of central interior British Columbia. Wood properties can be good indicators of variation in sequestered carbon in some stands. Carbon accumulation was reduced with increasing temperatures; however, warmer late-season conditions appear to enhance growth and carbon accumulation. [ABSTRACT FROM AUTHOR]

• Ecologically significant canopy leachates should be explored in undisturbed forests. • We used lichens to assess leachates from cottonwood/aspen and hybrid spruce canopy. • Standardized lichen transplants accumulated elements for 1 year in tree dripzones. • Base cations, soil pH and conifer bark pH was highest in cottonwood/aspen dripzones. • Lichen transplants are ecologically relevant indicators of throughfall chemistry. The importance of forest canopy settings for the elemental chemistry of epiphytic lichens in undisturbed forests is poorly understood despite its impact on epiphytes, understory vegetation and microbial soil communities. Here, we examine the elemental composition in standardized thalli of the cephalolichen Lobaria pulmonaria transplanted to the lower branches of Picea glauca x engelmannii in inland British Columbia. Transplants were attached to nets (avoiding direct contact with tree bark) exposed to natural canopy throughfall in three categories of natural forest stands: 1) within dripzones of Populus species in mixed stands always supporting L. pulmonaria ; 2) outside Populus dripzones, yet with L. pulmonaria and 3) outside Populus dripzones and without L. pulmonaria , which is the most common canopy setting. After one year, and with the exception of Fe and Al, the elemental content in lichen transplants changed within and between forest categories. Lichen transplants within Populus dripzones had more base cations (Ca, Mg, K) and less Mn than in the two categories outside dripzones. In Picea canopies outside Populus dripzones , lichen transplants had higher Ca, Na, Mo and lower C, S and Cu in trees with L. pulmonaria than without. The pH of Picea branches and soil within the rooting zone of trees with transplants were both approximately ten times more acidic outside Populus dripzones than within them. However, bark pH did not differ between the two categories of stands outside Populus dripzones. Based on our findings we conclude that canopy setting shapes the elemental composition of epiphytic lichen transplants, suggesting that such transplants might be used to monitor spatial variation in throughfall elements from forest canopies in unmanaged stands. We also conclude that elemental concentrations, Ca in particular, is a better predictor than bark pH for the occurrence of L. pulmonaria on Picea. [ABSTRACT FROM AUTHOR]

In natural ecosystems, plants associate with numerous microbes that play a crucial role in sustaining their growth and health on disturbed and nutrient-poor soils. The West Chilcotin in British Columbia, Canada is a secluded region having poorly-developed and coarse-textured soils containing extremely limited amounts of plant-available nutrients. However, natural forest stands of hybrid white spruce are thriving in this region unaffected by such nutrient-limited edaphic conditions. Looking for plant-growth-promoting bacteria that may be involved in supporting the growth of spruce trees in this region, several potential endophytic diazotrophic bacteria were previously isolated from spruce tissues. We analyzed the plant-growth-promoting potential of six selected bacterial strains in vitro using enzyme assays (qualitative and quantitative tests) and in vivo using 18-month long greenhouse growth trials. In lab-based enzyme assays, these bacterial strains showed significant ability to solubilize inorganic and organic phosphate and produce siderophores, indole-3-acetic acid, 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase enzyme and cell wall degrading enzymes – cellulase, protease, chitinase and β-1,3-glucanase. These bacteria also showed considerable in situ ACC deaminase activity by enhancing the root growth (84–479%) of canola and tomato (ethylene-sensitive plants). In addition, each bacterial strain was able to significantly enhance the length (>40%) and biomass (>90%) of not only its original host (hybrid white spruce) but also a foreign host (lodgepole pine) in the greenhouse growth trials. This plant growth promotion could be attributed to the rhizospheric and endophytic colonization observed for these bacterial strains in both tree species. Notably, one bacterial strain, Caballeronia sordidicola LS-S2r, showed the highest colonization ability (105–108 colony forming units/g tissue) in spruce and pine seedlings along with enhancing their biomass by 7-fold and 4.25-fold, respectively, which could be related to the highly significant in vitro plant growth promoting ability observed for this strain in all enzyme assays. In summary, the potential of these bacteria to form key ecological relationships with multiple tree hosts to promote their growth may explain the ability of trees to naturally regenerate on nutrient-poor soils. Moreover, these bacteria, particularly C. sordidicola LS-S2r, could potentially be used as comprehensive biofertilizers for boreal forest trees under highly disturbed and nutrient-poor edaphic conditions. • Plant growth promoting potential of bacteria associated with spruce trees was studied. • Their ability to acquire Fe and P as well as produce IAA, ACC deaminase and lytic enzymes was confirmed. • They significantly enhanced growth of spruce seedlings in 18-month long growth trial. • They provided similar benefits to a foreign host (lodgepole pine) in another growth trial. • So, these bacteria could be used as comprehensive biofertilizer for boreal forest trees. [ABSTRACT FROM AUTHOR]

Research Highlights: We investigated the competitive interactions among three tree species (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 multi-aged stands in central British Columbia, Canada. Background and Objectives: Understanding competitive interactions among tree species in mixed-species stands is fundamental to supporting silvicultural decision-making in such stands. Using the periodic annual basal area increment for single trees as our dependent variable, we investigated whether neighboring trees competed with subject trees independently of species identity. We also examined the differences in single-tree basal area growth among the three conifer species over time under different levels of competition. Materials and Methods: We developed several spatially explicit, single-tree basal area growth models for interior Douglas-fir, interior spruce, and lodgepole pine using data from 16 plots in two blocks of a long-term study (five measurements over a 21-year period) on the response to pre-commercial thinning. We compared these equations to assess whether intraspecific or interspecific competition predominated. We also examined the differences in basal area growth among the three conifer species over time under different levels of competition. Results: We found asymmetrical relationships between the conifer trees and their neighbors for all species, indicating that the main driver limiting growth in these stands is aboveground competition for light. There was evidence of higher intraspecific competition for small (<10.0 cm DBH) interior Douglas-fir in one block. However, there was no general pattern among larger subject trees with respect to the identity of neighborhood competitive effects and the equivalence of neighbors. We observed a higher level of basal area growth over time for interior Douglas-fir than for lodgepole pine and interior spruce, irrespective of the competition intensity and, not surprisingly, the growth rate declined with increasing competition levels for the three species. Conclusions: Our results provide an understanding of how interior Douglas-fir stands will develop over time and information on species interactions that could help forest managers explore different silvicultural options and their effects on individual tree growth in these complex stands. [ABSTRACT FROM AUTHOR]

The West Chilcotin region in British Columbia, Canada is located in the Sub-Boreal zone characterized by dry and weakly developed soils lacking essential plant nutrients, particularly nitrogen. Yet, hybrid white spruce (Picea glauca x engelmannii) trees thrive on such nitrogen-limited soils, raising a crucial question regarding their nitrogen sources. The presence of endophytic diazotrophic bacteria (nitrogen-fixing bacteria living inside the plant tissues) was reported in these spruce trees, previously. But, can these bacteria actually sustain tree growth on nitrogen-limited soils of this region? To answer this question, we tested six endophytic diazotrophic bacteria under nitrogen-poor conditions in a year-long greenhouse trial with their original host (i.e. hybrid white spruce). In a different year-long trial, we also tested these bacteria with another host native to the West Chilcotin region (i.e. lodgepole pine) to examine their interaction with a foreign host. Endophytic colonization, seedling growth promotion and the amount of nitrogen fixed in planta by each bacterium were examined. We found that each bacterium colonized one or more tissues of the spruce and pine seedlings (102–107 colonies per gram fresh tissue) and fixed significant (P < 0.05) amounts of nitrogen from the atmosphere (17–56% of the total plant nitrogen). In addition, bacteria-inoculated seedlings were considerably longer and accumulated significantly (P < 0.05) more biomass than non-inoculated controls after 12 months. Notably, the bacterium Caballeronia sordidicola LS-S2r fulfilled >50% of the nitrogen requirements of pine and spruce seedlings via nitrogen fixation, and enhanced seedling length and biomass by nearly 1.5-fold and 5-fold, respectively. Therefore, our results suggest that endophytic diazotrophic bacteria harboured by hybrid spruce trees can sustain their growth on nitrogen-limited soils via biological nitrogen fixation. These bacteria can also provide similar benefits to a foreign host - lodgepole pine, indicating their wide-range ecological applications in improving the N-supply of forest stands in this region and beyond. In particular, C. sordidicola LS-S2r holds strong potential to be possibly used as a biofertilizer in boreal forest stands, as an economical and eco-friendly alternative to chemical fertilizers. • Nitrogen-fixing bacteria formed endophytic colonies in multiple boreal forest trees. • They enhanced the length and biomass of trees in a yearlong greenhouse trial. • They provided significant amounts of nitrogen to trees via biological nitrogen fixation. • Presence of nifH gene and nitrogenase enzyme required to fix nitrogen was confirmed. • These bacteria could be crucial to sustain tree growth on highly nitrogen-poor soils. [ABSTRACT FROM AUTHOR]

On a silt-loam soil in the boreal white and black spruce (BWBS) zonein northern interior B.C., 50 root systems of 12-year-old planted white spruce (Picea glauca (Moench) Voss) seedlings were excavated; 25 from mounds (14cm of mineral soil over inverted organic matter) and 25 from untreated ground. Diameter, depth, and substrate of main structural roots were assessed at 10cm intervals from the stem. The total number of roots and the aggregate cross-sectional root area (CSA) exiting the mound or a 50-cm control radius in untreated ground were also determined. Seedlings on mounds had well-developed root systems that were equally as symmetric as those in untreated ground. Roots extended well beyond the mound, excepting those few that were surrounded by saturated soil conditions. Mound seedlings had more, and thicker, main lateral roots than seedlings in untreated ground. CSA of mound seedlings was approximately five times greater than for seedlings in untreated ground, and the total number of roots was 2.5 times greater. Beyond the mound, depth and substrate of main lateral roots was similar to that of seedlings in untreated ground. It was concluded that the potential for long-term mechanical stability of white spruce on such mounds would be no less than that of seedlings planted without sitepreparation. [ABSTRACT FROM AUTHOR]