Spruce Zone Research Articles

Висотно-поясні особливості всихання ялинників на північно- східному мегасхилі Українських Карпат

Проаналізовано особливості поширення всихання ялинових насаджень у висотному діапазоні гір 350–1 400 м над рівнем моря на прикладі басейну річки Бистриця Солотвинська північно-східного мегасхилу Українських Карпат. Охарактеризовано кількість і площі осередків часткового та суцільного вс ихання для висотних поясів – передгірних ялицево-букових і гірських буково-ялицевих, буково-ялицево-ялинових і ялинових лісів. Наведено верхню межу поширення всихання. Розраховано емпіричні залежності площ осередків різних видів цього явища від гіпсометричних рівнів гірської системи. З’ясовано, що найбільш уразливою до всихання є ялина на висотах 400–900 м н. р. м. Оцінено вплив експозиції та крутизни гірських схилів на поширення процесів усихання. Виявлено, що в передгірних умовах важлива роль у стійкості похідних ялинників належить ландшафтно-лісівничим особливостям. У цих умовах процеси всихання насаджень найменш активно відбуваються в глибині лісових масивів, дещо активніше – на ділянках, що межують із галявинами, зрубами й молодняками, і сягають максимуму в смугах узлісся.

Spruce shows greater sensitivity to recent warming than Douglas‐fir in central British Columbia

AbstractThe effects of climate change on tree growth in ecosystems limited by cold temperature remain unclear. In some cases, growth may increase, but because warmer temperatures can increase water stress, growth may also decline. As climate changes in the sub‐boreal spruce (SBS) zone in central British Columbia, hybrid white spruce (Picea engelmannii × glauca)—a dominant but drought‐intolerant species of this region—is predicted to decline over much of its range, while species such as Douglas‐fir (Pseudotsuga menziesii var. glauca) are likely to replace spruce. To see whether these shifts are already evident, we examined recent trends in basal area increment (BAI) of these two species over the past 50 yr (1961–2010) and explored relationships with climate variables in the SBS zone across a range of sites varying in water availability due to differences in climate and soil moisture regimes. In addition, we analyzed wood δ13C during this period and root carbohydrate reserve (NSC) concentrations at the end of this period as indicators of water and carbon stress, respectively, to help interpret growth trends and climate relationships among sites. Spruce BAI was negatively associated with spring and/or summer temperature on all sites, but growth was never negatively correlated with temperature in Douglas‐fir. For both species, lower BAI on the driest site was accompanied by higher δ13C and lower root NSC reserve concentrations, particularly starch, consistent with drought stress reducing water and carbon availability for growth. However, there was no indication that the negative growth response to temperature was more pronounced on drier sites, as the only growth decline in spruce occurred on a mesic site with lower δ13C. We conclude that rising temperatures are likely to negatively impact the growth of spruce more than Douglas‐fir in the SBS zone, supporting predictions that spruce will decline and be replaced by other species like Douglas‐fir. And while rising temperatures may have already reduced growth on some sites, these declines are not clearly related to increasing drought stress but may relate to effects on the timing of snowmelt.

Swiss Needle Cast in Western Oregon Douglas-Fir Plantations: 20‐Year Monitoring Results

Swiss needle cast (SNC), a foliar disease specific to Douglas-fir (Pseudotsuga menziesii), is caused by an endemic Ascomycete fungus (Phaeocryptopus gaeumannii). In the late 1980s and early 1990s significant symptoms began to appear in coastal Oregon, and these have been associated with the planting of Douglas-fir in the Sitka spruce zone, leaf wetness during potential spore dispersal in May–August, and mild winter temperature. The first annual aerial survey was initiated in 1996 and has continued through 2015, which indicates a significant increase in area of visible symptoms from the air, increasing from 53,050 ha in 1996 to 238,705 ha in 2015. Monitoring plots in the NW Oregon Coast Range verified impacts of SNC on tree growth and productivity, with growth reductions averaging about 23% in the epidemic area linked to needle retention. A series of monitoring plots was set up in the western Cascade Mountains of Oregon and 590 10–23-year old Douglas-fir trees in 59 stands were tracked for 10 years, measured in 2001, 2006, and 2011. No measureable growth impacts were noted in this region of Oregon. A new plot network is being installed throughout the Oregon and southwest Washington coastal ranges as a means of monitoring future disease impact and providing framework for additional studies.

Soil fertility and charcoal as determinants of growth and allocation of secondary plant metabolites in seedlings of European beech and Norway spruce

Climate-change is predicted to drive a migration of European beech (Fagus sylvatica) into the boreal Norway spruce (Picea abies) zone. Still, the mechanisms underpinning beech success on novel soils is little understood. Further, projected increasing summer temperatures will increase risk of fire and subsequent charcoal deposition. Here we investigate how soil type and presence of charcoal affect growth and key plant traits of beech and spruce seedlings.Beech and spruce seedlings were grown in pots with forest soils of beech- or spruce origin to which beech- or spruce derived charcoal was added. Concentrations of phenolic compounds, carbon (C) and nitrogen (N) were analysed separately for root, stem, and leaf tissues.Our spruce forest soil contained more N than the beech forest soil, and both beech- and spruce seedlings grew bigger in spruce forest soil. Beech seedlings also had overall lower tissue concentrations of phenolic compounds when grown in spruce soil. For both species, shoots and roots displayed opposite phenolic responses. The addition of charcoal had no effect on growth, while effects on phenolic compounds were largely idiosyncratic.Our results indicate that beech expansion is not limited by soil factors in the study area, nor is it facilitated by increased levels of charcoal.

Climate‐induced changes in host tree–insect phenology may drive ecological state‐shift in boreal forests

Climate change is altering insect disturbance regimes via temperature‐mediated phenological changes and trophic interactions among host trees, herbivorous insects, and their natural enemies in boreal forests. Range expansion and increase in outbreak severity of forest insects are occurring in Europe and North America. The degree to which northern forest ecosystems are resilient to novel disturbance regimes will have direct consequences for the provisioning of goods and services from these forests and for long‐term forest management planning. Among major ecological disturbance agents in the boreal forests of North America is a tortricid moth, the eastern spruce budworm, which defoliates fir (Abiesspp.) and spruce (Piceaspp.). Northern expansion of this defoliator in eastern North America and climate‐induced narrowing of the phenological mismatch between the insect and its secondary host, black spruce (Picea mariana), may permit greater defoliation and mortality in extensive northern black spruce forests. Although spruce budworm outbreak centers have appeared in the boreal black spruce zone historically, defoliation and mortality were minor. Potential increases in outbreak severity and tree mortality raise concerns about the future state of this northern ecosystem. Severe spruce budworm outbreaks could decrease stand productivity compared with their occurrence in more diverse, southern balsam fir forest landscapes that have coevolved with outbreaks. Furthermore, depending on the proportion of balsam fir and deciduous species present and fire recurrence, changes in regeneration patterns and in nutrient cycling could alter ecosystem dynamics and replace black spruce by more productive mixed‐wood forest, or by less productive ericaceous shrublands. Long‐term monitoring, manipulative experiments, and process modeling of climate‐induced phenological changes on herbivorous insect pests, their host tree species, and natural enemies in northern forests are therefore crucial to predicting species range shifts and assessing ecological and economic impacts.

Interaction of Trembling Aspen and Lodgepole Pine in a Young Sub-Boreal Mixedwood Stand in Central British Columbia

Strategies for managing mixed broadleaf-conifer stands in British Columbia (BC) have been under review in recent years as the benefits of mixedwood management have been recognized. More has been learned about the role of broadleaves in forest ecosystems however ecosystem-specific knowledge about the competitive interactions between mixed broadleaf-conifer stands is still scarce. Therefore a competitive interactions study was conducted to facilitate ecosystem-specific management for lodgepole pine (Pinus contorta Dougl. Ex Loud. Var. latifolia Engelm.) and trembling aspen (Populus tremuloides Michx.) in the sub-boreal spruce (SBS) zone of central BC. The experiment was a completely randomized block design with six different aspen densities replicated three times. Each replicate was sampled three times between ages 14 to 19 years. Pine diameter and height growth were influenced by aspen density. Our current quantitative findings suggest that lodgepole pine growth was not impacted when growing with aspen densities up to 2500 stems ha-1. Considering free growing (FTG) and not free growing (NFTG) pine at the time of trial establishment, an insignificant difference was found for DBH, height and crown volume responses. Leaf area index (LAI) and diffuse non-interceptance (DIFN) radiation were also not significantly different between FTG or NFTG trees suggesting our results exceed the current BC’s free growing standard. Further work is recommended to determine whether or not the current free growing standards are appropriate for producing the desired crop outcome.

Quantification des changements récents à l'écotone forêt-toundra à partir de l'analyse numérique de photographies aériennes

RésuméLes écosystèmes arctiques situés à l'écotone forêt-toundra sont particulièrement sensibles aux changements induits par le réchauffement du climat. Plusieurs recherches récentes ont observé des modifications du couvert végétal, entre autres, une croissance accrue des arbustes. Nous avons évalué ces changements à une échelle locale près d'Umiujaq, Québec subarctique, Canada (56,55° N; 76,55° O) à l'aide de photographies aériennes en couleurs (1994 et 2010). En appliquant des méthodes semi-automatiques de classification par objet et en effectuant une analyse de changements, nous avons détecté des changements récents de la dominance du couvert végétal. Les résultats des classifications de 1994 et 2010 montrent un gain en superficie de 12 % des couverts arbustifs, une perte de près de 8 % des couverts lichéniques, une stabilité relative de la superficie occupée par les épinettes, ainsi que la disparition de près du quart des mares associées aux buttes de pergélisol en dégradation. De son côté, l'analyse de changements par superposition des classifications a montré que, pour chacune des classes de végétation présentes en 1994, le changement le plus important était celui du passage vers une dominance arbustive touchant 18 % de la zone étudiée. La carte « avant-après » montre bien l'arbustification générale en cours dans la région d'étude.

Improving site index estimates for pine and spruce plantations: a case study in the sub-boreal spruce zone in British Columbia

Site index (SI) expresses the growth potential for a species on a given site. Three SI determination methods were used for each managed stand sampled in the southern portion of the Prince George Timber Supply Area (TSA): forest inventory, calculated growth intercept or height over age, and site index biogeoclimatic ecosystem classification (SIBEC). Interior spruce and lodgepole pine leading stands were sampled in the Bowron Valley and only pine stands were sampled in the rest of the TSA. In the Bowron Valley for both species, calculated SI was greater than SIBEC SI, which was greater than inventory SI. Increases were greater for spruce. In the remaining pine areas sampled, the same relationship was observed. Pine yield model projections indicate mean annual increment (MAI) culmination occurred 5.7 and 16.4 years sooner for calculated SI compared with SIBEC and inventory SI, respectively, with yields increasing by 8% and 13%. The increases could be due to improved silviculture, tree response to climate change or a combination of the two. Differences could result in a mid-term timber supply available sooner or a greater yield at planned harvest age. This is particularly important in areas attacked by mountain pine beetle.

Shifting zonal patterns of the southern boreal forest in eastern Canada associated with changing fire regime during the Holocene

This research aims at uncovering the stand-scale Holocene fire history of balsam fir forest stands from two bioclimatic zones of the boreal forest and assessing the existence of a sub-continental shift in past fire activity that could have triggered a change in the Holocene zonal pattern. In eastern Canada, the extant closed-crown boreal forest corresponds to two ecological regions separated along 49°N, the northern black spruce zone and the southern balsam fir zone. We sampled balsam fir stands from the southern fir zone ( n = 7) and among the northernmost patches of fir forest located far beyond the fir zone boundary, into the spruce zone ( n = 6). Macrofossil analysis of charcoal in mineral soils was used to reconstruct both the stand-scale and regional Holocene fire histories. Data were interpreted in the context of published palaeoecological evidence. Stands of the balsam fir zone were submitted to recurrent fire disturbances between c. 9000 and 5000 cal. yr B.P. Local fire histories suggested that four sites within the fir zone escaped fire during the Holocene. Such fire protected sites allowed the continuous maintenance of the balsam fir forest in the southern boreal landscape. Stands of the spruce zone have been affected by recurrent fires from 5000 cal. yr B.P. to present. Local fire histories indicated that no site escaped fire in this zone. Published palaeoecological data suggested that balsam fir migrated to its current northern limit sometime between 7300 and 6200 cal. yr B.P. A change of the fire regime 5000 years ago caused the regional decline of an historical northern balsam fir forest and its replacement by black spruce forest. The consequence was a sub-continental reshuffling of the fir and spruce zones within the closed-crown boreal forest. The macrofossil analysis of charcoal in mineral soils was instrumental to the reconstruction of stand-scale Holocene fire history at sites where no other in situ fire proxies were available.

The Origin and Dynamics of Subalpine White Spruce and Balsam Fir Stands in Boreal Eastern North America

Associations among the few tree species in the North American boreal landscape are the result of complex interactions between climate, biota, and historical disturbances during the Holocene. The closed-crown boreal forest of eastern North America is subdivided into two ecological regions having distinct tree species associations; the balsam fir zone and the black spruce zone, south and north of 49°N, respectively. Subalpine old-growth stands dominated by trees species typical of the balsam fir forest flora (either balsam fir or white spruce) are found on high plateaus, some of which are isolated within the black spruce zone. Here we identified the ecological processes responsible for the distinct forest associations in the subalpine belt across the eastern boreal landscape. Extensive radiocarbon dating, species composition, and size structure analyses indicated contrasted origin and dynamics of the subalpine forests between the two ecological regions. In the black spruce zone, the subalpine belt is a mosaic of post-fire white spruce or balsam fir stands coexisting at similar elevation on the high plateaus. With increasing time without wildfire, the subalpine forests become structurally similar to the balsam fir forest of the fir zone. These results concur with the hypothesis that the subalpine forests of this area are protected remnants of an historical northern expansion of the fir zone. Its replacement by the fire-prone black spruce forest flora was caused by recurrent fires. In the subalpine belt of the fir zone, no fire was recorded for several millennia. Harsh climate at high altitude is the primary factor explaining white spruce dominance over balsam fir forming a distinct subalpine white spruce belt above the balsam fir dominated forest.

Planted stock performance 10 years after partial cutting in west-central British Columbia

Mature lodgepole pine (Pinus contorta) forests were harvested using group selection (GS) (0.02-ha openings) and irregular group shelterwood (IGS) (0.05-ha openings) systems to maintain arboreal and terrestrial lichens in the winter range of northern woodland caribou (Rangifer tarandus caribou). Ten years after planting, lodgepole pine showed excellent survival, but were smaller in the partial cut openings compared to the clearcuts. Pine grew less in the Sub-Boreal Pine–Spruce biogeoclimatic subzone (SBPSxc) than in the Montane Spruce subzone (MSxv), and trees were smaller in the GS versus IGS treatment within the MSxv subzone. Interior spruce (Picea glauca × engelmannii) grew best in the MSxv and partial cut treatments, but was significantly affected by summer frost in the clearcuts. In an operational-scale Adaptive Management trial, openings were enlarged to 0.15 ha, and both pine and spruce showed excellent survival, minimal frost damage, and 10-year size similar to clearcut conditions. This study suggests that lodgepole pine and interior spruce can be successfully regenerated in partial cut openings with acceptable growth in gaps of 0.15 ha. Key words: caribou, group selection, interior spruce, irregular group shelterwood, light level, lodgepole pine, Montane Spruce zone, partial harvest, soil moisture, soil temperature, Sub-Boreal Pine Spruce zone, summer frost

British Columbia's Northeastern Forests: Aspen Complex Stand Establishment Decision Aid

Aspen (Populus tremuloides) is the most widely distributed tree species in North America and can be found from the McKenzie Delta to northern Mexico. Its range in British Columbia is restricted to the Interior except for the east coast of Vancouver Island and along the Skeena, Kitimat, and Fraser rivers where it extends to the mouth of the river. In recent years, utilization of the species has increased dramatically, particularly in northeastern BC where aspen is the main fibre source for several OSB and veneer mills. Other aspen products include: dimension lumber, paper, molded wood composites, molding and trim, crates, pallets, pellets, chop sticks, fruit and vegetable boxes, furniture, fuel, and forage for livestock. The combined AAC for deciduous species in the Dawson Creek, Fort St. John, and Fort Nelson TSAs is almost 2 million m3/year. In 2006, the shipment value for OSB and aspen veneer produced in BC was $2.2 billion. Aspen can be an aggressive competitor for conifer species (particularly in the Black and White Boreal Spruce zone) but it also provides many non-timber services and is considered to be an acceptable crop tree and commercial species in a number of TSAs in the province. This Stand Establishment Decision Aid (SEDA) provides information to help forest managers in northern BC understand how to manage aspen for timber production as well as how to manage it when it is not regarded as a crop species. The following pages describe: the environmental conditions in which it is found; tree and stand regeneration; growth and yield; effects on crop trees and forest productivity; forest health considerations; management practices; and other values and benefits associated with aspen. The synopsis also includes a short list of references for further reading. For information on managing aspen in the Southern Interior of BC, see Swift and Turner (2004). Information in this document is based on a review of the pertinent literature and expert opinion.

Isotope and Cladocera data and interpretation from the Eemian optimum and postoptimum deposits, Kaliska palaeolake (Central Poland)

During the Eemian optimum, calcareous gyttja and lake marl accumulated. The characteristic feature of calcareous gyttja is an occurrence of fragments of diatoms and plants, while in lake marl they are absent. In the carbonate-rich deposits no Cladocera remains are preserved. Based on the results of stable isotope analyses of carbonates, the eight isotopic horizons (Is) were defined and characterised. In the studied deposits, 15 species of subfossil Cladocera were identified and 6 zones of fauna development were distinguished. The defined Cladocera species are similar to ones known from the other Eemian site in Poland. The faunal taxa indicate the low trophy status of the lake initially, followed by an increase to eutrophic status. The Cladocera and isotopic compositions suggest that the hornbeam zone (E5) was a period of higher density of macrophytes as well as of an increase of biological activity associated with the low water level. The fluctuations of the isotopic curves caused by a shallowing of the basin and a change of sediment lithology are characteristic for the spruce zone (E6). The palaeolake transformed into a peatbog during the pine zone (E7). During the Early Vistulian renewed carbonate accumulation and Cladocera development took place indicating the repeated reservoir existence.

Vegetational changes in the montane grassland zone of the High Bieszczady mountains (southeast Poland) during the last millennium—pollen records from deposits in hanging peat-bogs

The pollen analytical investigations of hanging peat bogs in the summit zone of the Polish east Carpathians show that the absence of the upper montane spruce zone in the western Bieszczady mountains is a phenomenon that has been historically stable at least for the last millennium and probably also in earlier times. At altitudes corresponding to the spruce zone in other parts of the Carpathians, dwarf beech woods form here a low-lying upper tree limit. The montane grassland zone occurring above this tree line did not result from human activities, although it has been extended by human activity. Besides, it is shown how far it is possible to reconstruct from a pollen diagram the differentiation of vegetation surrounding the site of profile collection located in the upper montane zone when the present-day local plant communities are well known, in spite of pollen from long distance transport always being present at the summits of mountain ranges.

Random acts of weevil: A spatial analysis of Hylobius warreni attack on Pinus contorta var. latifolia in the sub-boreal spruce zone of Northern British Columbia

The Warren root collar weevil ( Hylobius warreni) is a native pest of lodgepole pine ( Pinus contorta var. latifolia) in western North America. Damage caused by larval feeding at the root collar and roots often results in low to moderate levels of mortality in many regenerating lodgepole pine stands. We investigated the spatial distribution of lodgepole pine trees, weevil-attacked trees, and mortality due to attack. Stem maps of all lodgepole pine trees were generated in nine, 50-m × 50-m plots in six pine plantations infested by H. warreni. All trees in each plot were assessed for attack and mortality. In all plots, live-attacked trees were significantly larger than live-nonattacked trees. In each of three plantations, two contiguous plots were established to allow assessment of within-site variation and spatial structure variation at different scales. We used Ripley's univariate L( t) function to analyze the spatial distributions of all host trees, attacked host trees, and dead attacked host trees, respectively. The distribution of attacked trees generally coincided with the distribution of host trees. The distribution of attack did not change with increasing attack intensity among plots, but did so within plots. Trees killed by H. warreni were randomly distributed in all plots except one, and spatial distribution was not affected by attack intensity. Mortality increased as a function of attack. Our findings support that this insect does not aggregate, and that virtually all lodgepole pine are potentially susceptible to attack, i.e., host distribution alone largely explains distribution of both attack and mortality.

Soil and lodgepole pine foliar responses to two fertilizer sulphur forms in the Sub-Boreal Spruce zone, central interior British Columbia

Sulphur (S) fractions, total nitrogen (N) concentrations, and cumulative net S mineralization of forest floors and surface mineral soils (0-20 cm) were measured 13 years after an S-deficient lodgepole pine (Pinus contorta var. latifolia Engelm.) stand was fertilized (100 kg S·ha–1 + 400 kg N·ha–1) in 1990. Fertilizer treatments compared two S sources: elemental S (S0) and ammonium sulphate (AS). Total S and ester sulphate-S (SO4-S) concentrations and cumulative net S mineralization in forest floors were significantly higher in the S0 treatment than in the control and AS treatment. Except for a slight elevation of extractable SO4-S, such differences were absent in the mineral soils. Total S and SO4-S concentrations in current-year (2002) pine foliage from the S0 treatment were significantly higher than in foliage from the control and AS treatment, while foliar N concentrations indicated that all treatments had caused a return to N-deficiency. These results indicate that prolonged amelioration of S deficiencies in lodgepole pine stands in central interior British Columbia may be possible with single applications of S0.

A 1000-year record of forest fire, drought and lake-level change in southeastern British Columbia, Canada

High-resolution charcoal analysis of lake sediments and stand-age information were used to reconstruct a 1000-year fire history around Dog Lake, which is located in the montane spruce zone of southeastern British Columbia. Macroscopic charcoal (>125,um) accumulation rates (CHAR) from lake sediment were compared with a modern stand-origin map and fire-scar dates in the Kootenay Valley to determine the relative area and proximity of fires recorded as CHAR peaks. Small fires close to the lake and larger more distant fires appear as similar-sized peaks in the record. This information reinforces previous findings where CHAR peaks represent a complex spatial aggregation of local to extra-local fires around a lake site. CHAR peaks indicate frequent stand-destroying fires during the 'Mediaeval Warm Period' (-AD 1000-1300), and other significant fires at c. 1360, 1500, 1610 and 1800. We also present a proxy measure of lake-level changes based on a comparison of accumulation rates of Chara globulanis-type oospores over the last millennium and the present distribution of charophytes in the lake basin. Lower water levels, represented by few or no Chara oospores, correspond to times of regional drought and large forest fires around the lake. Higher lake levels, represented by increased Chara oospore accumulation rates, correspond to wetter climate periods during the Oort, Wolf, Sporer and Maunder solar sunspot minima, when little or no fire activity occurs around the lake.

Classification and ecology of the mid‐seral Picea mariana forests of British Columbia

Abstract. We sampled vegetation and soils of, and classified mid‐seral, even‐aged, fire‐origin, upland Picea mariana ecosystems in the Boreal White & Black Spruce and Sub‐boreal Spruce zones of British Columbia, Canada. We applied multi‐variate and tabular methods to analyse and synthesize the data from 121 plots according to the methods of biogeoclimatic ecosystem classification. We delineated seven basic vegetation units and described their vegetation and environmental features. However, the delineated units could not be related to neither of the taxonomies proposed for the North American boreal forest communities. Although species‐poor, the under‐storey vegetation in the sampled ecosystems provided for a sufficient floristic differentiation, which matched well the major edaphic differences between the units. The classification of mid‐seral boreal ecosystems may be more useful that based on old‐growth stands that are infrequent or lacking in the landscape due to wildfires.

Classification and ecology of the mid-seral Picea mariana forests of British Columbia

We sampled vegetation and soils of, and classified mid-seral, even-aged, fire-origin, upland Picea mariana eco- systems in the Boreal White & Black Spruce and Sub-boreal Spruce zones of British Columbia, Canada. We applied multi- variate and tabular methods to analyse and synthesize the data from 121 plots according to the methods of biogeoclimatic ecosystem classification. We delineated seven basic vegeta- tion units and described their vegetation and environmental features. However, the delineated units could not be related to neither of the taxonomies proposed for the North American boreal forest communities. Although species-poor, the under- storey vegetation in the sampled ecosystems provided for a sufficient floristic differentiation, which matched well the major edaphic differences between the units. The classifica- tion of mid-seral boreal ecosystems may be more useful that based on old-growth stands that are infrequent or lacking in the landscape due to wildfires.

Effects of clearcut edges on trees in the sub-boreal spruce zone of Northwest-Central British Columbia

Clearcut-forest boundaries were evaluated for their effects on mature and regenerating trees in the northern interior of British Columbia, Canada. Two hundred and eighteen rectangular plots measuring 200 m2 each were arrayed in transects across 12 cutblock edges created 9 to 21 years earlier, with the wall of standing timber facing either north or south. The density of canopy trees on the inner edge was found to be reduced by 19% (on north-facing edges) to 46% (on south-facing edges) from average densities found in forest interiors. This reduction was primarily due to windthrow after logging, which was elevated by 27% (over interior background levels) at north-facing edges, and by 216% at south-facing edges. Of the trees situated within 10 m of south-facing cutblock edges, 11% of the Pinus contorta, 18% of the Abies lasiocarpa, and 42% of the Picea engelmannii x glauca trees have apparently collapsed, primarily those having height-to-dbh ratios greater than 71:1. As a result, irradiance in the forest understory was elevated (over interior levels) at south-facing edges to distances of approximately 65 to 70 m into the forest. Increased irradiance from adjacent cutblocks enhanced the understory growth of Picea for approximately 60 m into the inner edge of forests, 75 m for Abies. Mature Pinus trees on south-facing edges showed an unexplained 48% decrease in radial growth compared to average growth rates in forest interiors, an effect that was detectable up to 45 m into the forest. Elevated densities of conifer seedlings were evident for up to approximately 70 m into clearcuts from north-facing forest edges. Seedling growth in clearcuts was largely unaffected by shade from stand edges. Though the extent of edge effects varies considerably with the statistical techniques used to detect them, it appears that opening effects on trees can extend between 40 and 120 m into this forest type, while canopy effects reach shorter distances into clearcuts.