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Downed woody debris is important for biodiversity, forest regeneration, and carbon, nutrient, and water cycling, and past studies have examined how the coarse fraction is affected by climate or harvesting. In a field study in Douglas-fir dominated forests, we expand existing knowledge by investigating the interacting effects of climate and harvesting on downed woody debris of all sizes. Across a 900-km long latitudinal gradient in British Columbia, we found that coarse woody debris (CWD, >7.5 cm diameter) in humid climates contained 700% greater carbon stocks, had 500% greater volume, and was more diverse than in arid climates. Pre- and post-harvest, small and fine woody debris comprised a higher proportion of total woody debris carbon stocks in arid than moist climates, especially after clearcutting and seed tree treatments. Harvesting generally decreased total CWD volume, but it was not depleted on any site. Harvesting substantially reduced the volume of large, highly decomposed CWD except at the two most arid sites, and losses of large CWD increased with increasing tree removal. These losses were accompanied by a pulse of fresh, small diameter CWD and SWD which are short-term organic nutrient sources but have less habitat value than larger pieces and contribute to fuel loads. Because CWD was less abundant in arid than humid mature forests, care must be taken on arid sites to avoid its depletion during harvesting, especially clearcutting, where future woody debris inputs will not occur for decades. [ABSTRACT FROM AUTHOR]

Background: Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) plays a critical role in the ecology and economy of Western North America. This conifer species comprises two distinct varieties: the coastal variety (var. menziesii) along the Pacific coast, and the interior variety (var. glauca) spanning the Rocky Mountains into Mexico, with instances of inter-varietal hybridization in Washington and British Columbia. Recent investigations have focused on assessing environmental pressures shaping Douglas-fir's genomic variation for a better understanding of its evolutionary and adaptive responses. Here, we characterize range-wide population structure, estimate inter-varietal hybridization levels, identify candidate loci for climate adaptation, and forecast shifts in species and variety distribution under future climates., Results: Using a custom SNP-array, we genotyped 540 trees revealing four distinct clusters with asymmetric admixture patterns in the hybridization zone. Higher genetic diversity observed in coastal and hybrid populations contrasts with lower diversity in inland populations of the southern Rockies and Mexico, exhibiting a significant isolation by distance pattern, with less marked but still significant isolation by environment. For both varieties, we identified candidate loci associated with local adaptation, with hundreds of genes linked to processes such as stimulus response, reactions to chemical compounds, and metabolic functions. Ecological niche modeling revealed contrasting potential distribution shifts among the varieties in the coming decades, with interior populations projected to lose habitat and become more vulnerable, while coastal populations are expected to gain suitable areas., Conclusions: Overall, our findings provide crucial insights into the population structure and adaptive potential of Douglas-fir, with the coastal variety being the most likely to preserve its evolutionary path throughout the present century, which carry implications for the conservation and management of this species across their range., (© 2024. The Author(s).)

• Moisture deficit was the primary climatic influence of Douglas-fir radial growth. • Southernmost populations were most sensitive to annual climate moisture deficits. • Sensitivity to moisture deficit has decreased in all populations in recent decades. [ABSTRACT FROM AUTHOR]

Highlights • Mean BA and density of overstory Douglas-fir highest in patch-cut, group selection, and uncut sites. • Mean density of understory conifers highest in dispersed and aggregated retention sites. • Mean abundance and species richness of understory vegetation similar among sites. • Patch-cut and group selection sites were used by deer more than retention sites. Abstract Mule deer (Odocoileus hemionus) are a major mammal species in many interior Douglas-fir (Pseudotsuga menziesii) forest ecosystems in western North America. During winter in areas of relatively high snowpacks, mule deer seem to require older trees with large crowns for snow interception, but these forests are often targeted for harvest. Green-tree retention (GTR) may offer a solution to this conundrum. We tested three hypotheses (H) that, at 20–22 years after harvest, (H 1) abundance (e.g., basal area and density of residual trees and understory stand structure) of conifers, (H 2) abundance, species richness, and diversity of understory vegetation, and (H 3) relative habitat use by mule deer, will decline with lower levels of tree retention. Fecal pellet-groups of deer were counted in summer and winter periods for three years in replicated stands of dispersed retention, aggregated retention, patch-cut, group selection, and uncut forest in mixed Douglas-fir - lodgepole pine (Pinus contorta) forest in southern British Columbia, Canada. Mean basal area, density, and canopy closure of overstory Douglas-fir trees were generally greater in the patch-cut, group selection, and uncut forest sites than dispersed and aggregated retention sites, and hence supported the overstory part of H 1. Mean density of understory conifers did not support H 1 as the majority of these trees were in the dispersed and aggregated retention stands. There was no difference in mean abundance nor species richness of understory vegetation among treatment sites. Mean species diversity tended to be 1.4–1.8 times higher in the patch-cut and group selection than the other sites, and hence provided weak support for H 2. Patch-cut and group selection sites were dominated by Douglas-fir trees in both the overstory and understory, along with potential forage shrub species, and were used by deer more than the dispersed and aggregated retention stands in both summer and winter. Relative habitat use by deer in uncut forest was greater than the retention stands and generally similar to the patch-cut and group selection sites in both seasons. These results suggest that partial harvesting of these mixed Douglas-fir – lodgepole pine stands across a range of opening sizes (e.g., 0.1 to 2–5 ha) should provide suitable habitat for mule deer over time. [ABSTRACT FROM AUTHOR]

Highlights • Red alder density of up to 400 tph may be acceptable on nitrogen deficient sites. • Douglas-fir growth may be enhanced when red alder density is relatively low at age 15. • Competitive effects of red alder were lower than that of conifers in this study. • The effectiveness of competition indices varies with tree species. Abstract Red alder (Alnus rubra [Bong.]), is the most common broadleaf species in the Pacific Northwest, and is widely distributed as a component of mixed stands with conifers. It rapidly overtops associated juvenile conifers and is a strong competitor. However, red alder is also a symbiotic nitrogen fixer and can contribute to improvement in soil nitrogen, as well as serving other roles such as improving biodiversity and forest health. We examined data collected in mixed red alder-conifer plantations established between 1992 and 1999 to examine the effects of red alder on the growth of Douglas-fir (Pseudotsuga menziessi (Mirb.) Franco, Fd) and western redcedar (Thuja plicata Donn., Cw). Results suggest that densities of up to 400 alder trees per hectare may be acceptable and possibly desirable on nitrogen deficient sites. The growth of Fd may be enhanced when red alder density is relatively low at older ages. We found that the competitive effects of red alder on conifer growth were consistently lower than that of the conifers (Fd and Cw) while alder had stronger effects on light availability. The relationship between volume growth and competition indices varied between the two conifer species: (1) for Fd the highest correlations were obtained using a distance-dependent competition index based on the height differences, and (2) for Cw the highest correlations were with distance-independent Lorimer's index. As also expected due to Cw's greater shade tolerance, its volume growth showed less sensitivity to the presence of red alder than Fd. [ABSTRACT FROM AUTHOR]

• Soil rehabilitation, stumping, adding organic matter significant for soil chemistry. • The soil treatments significantly affected western white pine productivity. • Percent total disease significantly affected western white pine productivity. • Mineral soil chemistry covariates yielded significant effects on survival and growth. • Mineral soil chemistry covariates yielded significant effects on health agents. Soil disturbance amelioration affected tree survival, growth, health, mineral soil chemistry, and their covariation on five Long-Term Soil Productivity (LTSP) sites in southeastern British Columbia. The two most different LTSP treatments (baseline disturbance of no compaction / all organic matter left, versus most severe of heavy compaction / forest floor removed) were compared to five amelioration treatments: rehabilitation of most severe LTSP treatment (soil tillage with or without incorporation of removed forest floor [Rehab + FF]), root disease (Armillaria ostoyae (Romagn.) Herink) amelioration treatments (stump removal or biological with Hypholoma fasiculare), and enhancement of soil organic matter (tilling extra forest floor into mineral soil). Treatment significantly (p < 0.05) affected 10-year mineral soil carbon, nitrogen, sulfur, mineralizable nitrogen, and potassium, which were lower on forest floor removal treatments and higher on forest floor addition treatments (27 to 97% of baseline versus 78 to 183% of baseline, respectively). Western white pine (Pinus monticola Dougl. ex D.Don) 15-year productivity (m3/ha) was significantly affected by treatment (Rehab + FF yielding a 10 fold increase in productivity versus the poorly growing baseline treatment), with treatment also significant when total disease was a covariate and for average and total volume when mineral soil Ca:Al ratio was a marginally significant (p < 0.1) covariate, and for survival when the incidence of total disease or white pine blister rust (Cronartium ribicola) were significant covariates; or with mineral soil C:N ratio as a significant covariate. The incidence of blister rust and total disease were significantly influenced by treatment when C:N was a significant covariate. For 20-year lodgepole pine (Pinus contorta Dougl. Ex Loud) there were no direct relationships apparent, but western gall rust (Endocronartium harknessii) had treatment significant when total sulfur was a significant covariate. Fifteen- and twenty-year Douglas-fir (Pseudotsuga menziesii var. glauca [Beissn.] Franco) had no significant relationships. Results demonstrate that restoring or adding extra organic matter (forest floor) into mineral soil increased soil carbon and related nutrients and can increase above ground carbon (forest productivity). Conversely, removing forest floor lowered mineral soil carbon and generally lowered tree volume. Varied effects due to growth limiting factors like frost and competing vegetation affected results on a few plots. Recommendations include leaving or enhancing organic matter onsite for soil carbon, nutrients, forest health and site productivity. Further analysis with the larger LTSP dataset and ongoing monitoring is encouraged to determine if the results persist in the long-term and to better understand the significant covariate relationships. [ABSTRACT FROM AUTHOR]

This study examines spatially variable stand structure and fire-climate relationships at a low elevation forest-grassland ecotone in west central British Columbia, Canada. Fire history reconstructions were based on samples from 92 fire-scarred trees and stand demography from 27 plots collected over an area of about 7 km2. We documented historical chronologies of widespread fires and localized grassland fires between AD 1600 and 1900. Relationships between fire events, reconstructed values of the Palmer Drought Severity Index, and annual precipitation were examined using superposed epoch and bivariate event analyses. Widespread fires occurred during warm, dry years and were preceded by multiple anomalously dry, warm years. Localized fires that affected only grassland-proximal forests were more frequent than widespread fires. These localized fires showed a lagged, positive relationship with wetter conditions. The landscape pattern of forest structure provided further evidence of complex fire activity with multiple plots shown to have experienced low-, mixed-, and/or high-severity fires over the last four centuries. We concluded that this forest-grassland ecotone was characterized by fires of mixed severity, dominated by frequent, low-severity fires punctuated by widespread fires of moderate to high severity. This landscape-level variability in fire-climate relationships and patterns in forest structure has important implications for fire and grassland management in west central British Columbia and similar environments elsewhere. Forest restoration techniques such as prescribed fire and thinning are oftentimes applied at the forest-grassland ecotone on the basis that historically high frequency, low-severity fires defined the character of past fire activity. This study provides forest managers and policy makers with important information on mixed-severity fire activity at a low elevation forest-grassland ecotone, a crucial prerequisite for the effective management of these complex ecosystems. [ABSTRACT FROM AUTHOR]

Impaired soil quality due to compaction and organic matter removal following forest harvesting and mechanical site preparation is of concern, especially on calcareous soils which are believed to be particularly sensitive to disturbance. This study set out to determine the effects of organic matter removal and compaction on soil quality and seedling productivity on calcareous soils of a localized disturbance landscape (2.25 m 2 ). Here we report ten year post-establishment results of Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco) and lodgepole pine ( Pinus contorta var . latifolia Engelm.) seedlings across four sites in southern British Columbia, Canada with eight treatment levels incorporating different quantities of organic matter removal and soil compaction. Pine seedlings suffered high rates of mortality when planted in deposits across all sites while Douglas-fir seedling mortality was high when planted in compacted undisturbed treatments at two sites and in deposits on the remaining sites. Douglas-fir volume was greatest on the deposit treatment regardless of site but grew significantly better on the non-calcareous site. Pine seedlings outgrew Douglas-fir seedlings and, after ten years, seedlings were largest on a mildly calcareous site. Seedling growth was generally found to be negatively affected by calcareous soils and compaction; however, the specificity of results, in terms of species and site interaction and changing response as the seedlings aged, reinforced the importance of treatment effects on soil quality and forest productivity across the entire length of a stand rotation. [ABSTRACT FROM AUTHOR]

• Buprestid and cerambycid woodboring beetles are ubiquitous in post-fire Douglas-fir forests. • Highest rates of infestation occur in forests with moderate levels of scorch. • Woodborer infestation likelihood is driven by tree size and degree of fire injury. • Infestation is more likely in large than small trees with equal levels of fire injury. • Subcortical woodboring beetles kill trees which may otherwise survive fires. Warming temperatures and changing weather patterns are causing more frequent and severe disturbances in western North American forests. The increasing length and severity of recent wildfire seasons have annually caused widespread injury to millions of trees, facilitating the subsequent outbreak of various subcortical insect species that infest damaged hosts. The subcortical woodboring beetle assemblage (Coleoptera: Cerambycidae and Buprestidae) comprises insects that feed primarily within the phloem and sapwood of defensively compromised trees, often causing severe degradation of high value stands slated for post-fire salvage logging. We studied three 2017 fire complexes within mature Douglas-fir (Pseudotsuga menziesii) forests in southern British Columbia to investigate the post-fire infestation patterns of woodborers. We observed the highest levels of woodborer infestation in forests with moderate to high levels of fire injury, rather than in extremely burnt stands with greater tree mortality. We also found that woodborer infestation likelihood could be predicted from a combination of tree height and fire injury for individual trees. In addition, infestation was more likely in large (>13.1 m tall) rather than small trees (<13 m tall) with the same levels of fire injury. We conclude that the woodboring beetle assemblage present in dry interior Douglas-fir forests is more aggressive and ubiquitous than previously observed, and these insects actively attack and kill living trees that may otherwise survive after fires with both economic and ecological ramifications. Economically, post-fire salvage may be more effective in preventing woodborer population build-up and timber degradation by targeting moderately scorched stands immediately after wildfire. Ecologically, woodborer impacts to trees that would otherwise survive may compromise their biological legacy and impair the diversity and composition of future Douglas-fir stands. [ABSTRACT FROM AUTHOR]

Abstract: Many of the world''s forests are likely to face multiple stresses under a rapidly changing climate. Understanding the impact of climate change on tree species suitability is therefore crucial for forest management planning and policy development. We use the Douglas-fir and spruce (white spruce, Engelmann spruce, and interior spruce) forests of British Columbia as a case study. The impact of projected climate change on these forests was assessed using flexible bioclimatic envelope models appropriate for areas with sparse species locations records. Analysis of the model results focused on quantifying uncertainty due to differences between global climate models, emissions scenarios, and spatial resolution of climate data. To this end, future suitability was modelled using downscaled climate data from a collection of 10 climate projections that sampled across nine different global climate models and three different emissions scenarios (A2, A1B, and B1). All projections indicate a rapid shift in suitability for both spruce and Douglas-fir to higher elevations and latitudes relative to their current range. However, significant differences exist between the projections with regard to the pace, extent, and fine-scale details of these changes. This research was conducted as part of a collaborative interdisciplinary assessment involving both scientists and resource managers. [Copyright &y& Elsevier]

Abstract: A quantitative understanding of the effects complex residual forest structure has on the understorey light environment is useful in guiding strategies that facilitate regeneration in irregular stands. In this study we evaluate several methods for estimating the understorey light environment in an uneven-aged mixed conifer forest in the Interior Douglas-fir zone of south-eastern British Columbia, Canada. Measurements were collected 15years after selection harvesting, which was designed to create four different levels of residual basal area (8m2/ha, 16m2/ha, 24m2/ha and uncut). Understorey light availability was highly variable across all levels of residual basal area with estimates of stand structure, including density (N), basal area (G) and stand density index (SDI) explaining 37.2–52.1% of population level variation. While relatively large trees effectively reduced light levels below 40% open sky at a stand level; intermediate and smaller sized trees were found to have the greatest influence on light attenuation at the micro-site scale. Stand variables that heavily weighted the influence of larger trees on light attenuation were weak predictors of understorey light at the micro-site scale. Incorporating variables describing composition and inequality of tree size increased the predictive power of the models resulting in the ability to explain 55% of the variation in light levels. Small plot sizes used in this study are likely limiting the ability to describe variation in light levels and we recommend the use of larger plots (with a radius between 1.0 and 1.7times tree height) for future studies of this nature. The abundance and growth of natural regeneration was strongly related to both light (as influenced by overstorey) and understorey vegetation in these stands. [Copyright &y& Elsevier]

In this study, diameter growth models for three species growing in mixed-stands of Coastal British Columbia (BC), Canada, under a variety of silvicultural treatments were developed. The three species were: Douglas-fir (Pseudotsuga menziesii var. menziesii (Mirb.) Franco), western hemlock (Tsuga heterophylla (Raf.) Sarg.), and western redcedar (Thuja plicata Donn). A Box and Lucas model (1959) was initially fitted to the diameter growth series for each tree, as this model is very flexible and was based on processes reflective of the metabolic processes governing tree growth. Next, a random coefficients modelling approach (i.e., parameter prediction approach) was used to modify the estimated parameters for each species using functions of tree size and stage of development, site productivity, and inter-tree competition variables, while accounting for temporal correlation within trees. Impacts of fertilization on diameter growth were estimated by including the time since fertilization as an additional variable. Since state variables that are changed as a result of thinning were already in the model, accurate results post-thinning were obtained with no changes to the model. For the combined effects of thinning and fertilization, a two-step additive approach was used, where the state variables were changed following thinning and the diameter increment was modified for fertilization using the time since fertilization variable. Results indicated that multiple treatments sustain a change in growth for a longer time period following treatment than thinning or fertilization alone. [Copyright &y& Elsevier]

Abstract: Effective adaptation of forest management practices to climate change will require a good understanding of the ecological and climatic factors influencing tree sensitivities and responses to climate. Using tree-ring data collected from 33 stands of mature interior Douglas-fir (Pseudotsuga menziesii var. glauca) spanning a wide climatic range in British Columbia (BC), Canada, we present an approach combining high-resolution spatiotemporal climate data with traditional dendroecological analyses to quantify relationships between population climate–growth sensitivity and provenance (i.e., seed-source origin) climate. Key results showed that Douglas-fir climate–growth sensitivities were strongly linked to provenance climate and varied in coherent patterns across climatic gradients. Climate–growth sensitivities and responses were sometimes opposite between provenances from disparate climates. Perhaps most importantly, our results showed that Douglas-fir productivity across most of its range was sensitive to moisture limitations, and this sensitivity increased strongly with decreasing provenance mean annual precipitation and increasing heat-moisture index. Using geographic information systems, we visualize the link between provenance mean annual precipitation and climatic sensitivity of Douglas-fir across BC to identify “high risk” populations. By understanding the link between biological responses and climate, forest managers may be able to spatially identify sensitive populations using spatiotemporal climate data. [ABSTRACT FROM AUTHOR]

Abstract: Root pathogens are one of the principle factors affecting forest productivity in many forests, but few estimates of impact are available. Non-lethal root infections associated with Armillaria root disease were studied to determine their effect on stem volume yield in seven planted Douglas-fir stands and a naturally regenerated stand in British Columbia''s southern interior. Trees were removed from the soil and the infection date of a random selection of trees was determined. The volume reduction attributable to disease was determined as a comparison of diseased to disease-free trees over time since infection. Volume reductions per tree ranged from 0 to 30dm3 (0–27%) depending on the tree age and disease duration. Yield reduction reached 27m3/ha, averaging 15m3/ha for the three oldest planted sites by age 30 (7–15%), but was lower at the naturally regenerated site. Yield reduction at the site level correlated best with the number of diseased trees and an unknown site factor. Sites with slow juvenile growth had the least yield reduction owing to their lower incidence of disease over time. Yield was less affected by the proportion of diseased primary roots per tree than by the cumulative time since infection. A few of the diseased trees maintained growth rate after infection similar to disease-free trees; interestingly, these trees were smaller than average to begin with. Overall, trees suffer accumulating growth reduction without recovery. Root diseases prevent full expression of site potential even without mortality. Minimizing disease impact in respect to other forest management goals is also discussed. [Copyright &y& Elsevier]

Abstract: In southern British Columbia, juvenile trembling aspen is managed primarily as a competitor with conifers rather than for its ecological and economic value. As a result, brushing treatments have been applied on a widespread basis and this practice is likely to continue in the near future. Given the potential for climate change to affect our valuation of aspen, we require a better understanding of factors that affect its development, its competitive ability with conifers and its responses to brushing. We used data from 11 aspen management experiments to examine the influence of climate and site factors on aspen height, cover, and density in 17–24 year-old control stands and 9–16 years after manual cutting or girdling. Models explained 64% and 89% of the variation in aspen height in control and manually brushed stands, respectively, but were poor for girdling. Increasing length of the frost-free period was associated with increasing aspen height in control stands, whereas drier summer conditions on cool aspects favoured height growth of aspen suckers following manual cutting. We also examined the influence of climate and site factors on three simple competition indices that describe the height and density of aspen relative to conifer height, and then tested how well these indices predicted conifer growth. The density of aspen taller than conifers accounted for 39% of the variation in lodgepole pine diameter and the ratio of aspen/conifer height accounted for 33% of the variation in Douglas-fir height, suggesting that aspen competition was only moderately important to conifer growth. Our findings imply that aspen may become more productive with warmer summers provided it is not limited by summer moisture availability and that mixed stand management is a viable option in southern interior stands. [ABSTRACT FROM AUTHOR]

Abstract: Climate is a main driving factor of the formation of annual tree-rings, but which climatic variables are the most influential on radial growth may vary among species and sites. To explore these interactions, tree-ring chronologies along a major elevation gradient were examined for three tree species in southern interior British Columbia (Canada): Pseudotsuga menziesii, Pinus contorta, and Picea glauca × engelmannii. We used correlations and linear and multiple regressions to explore the relationships between tree-ring radial growth and climate variables in the area from 1922 to 1997. All correlation coefficients between ring chronologies and monthly climatic variables were medium to low (from −0.3 to 0.4); nevertheless, moderate but significant trends could be identified. Multivariate models explained up to 53%, 43% and 32% of radial growth variability for P. contorta, P. menziesii and P. glauca × engelmannii, respectively. All three species showed similar radial growth–climate patterns across the elevational gradient, but they had different details that made ring width–climate relationships species-specific. Precipitation-related variables were more related to radial growth at low-elevations, changing into temperature-related variables at high-elevations. Tree-ring width for all three species was primarily and significantly affected by climate variables from the year previous to the growing season and only secondly by current year conditions, but the critical months varied for different species and altitudes. Winter precipitation also affected radial growth, either as a source of water or as a possible agent of physical damage. Although our work showed significant climate influences on breast height tree radial growth, our results also indicated that other site factors such as microclimate or stand dynamics can be as or more important than climate variability. [Copyright &y& Elsevier]

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: We critically examine the hypothesis that dry forests in southern British Columbia evolved in the context of a low-severity fire-dominated disturbance regime, that fire suppression has led to ecological conditions which are radically different from the past, and that “restoration” initiatives are required to re-establish former ecological conditions. Four sources of information were used to infer historic disturbance regimes and forest condition and to quantify the nature of disturbance since the early 1900s: (1) patterns of annual and seasonal weather and lightning strikes, (2) topographic variability, (3) records of wildfire, insect attack, and timber harvesting practices, and (4) early systematic forest surveys. Our analyses consistently indicate that historic natural disturbances were likely diverse and episodic at multiple spatial and temporal scales. High seasonal and annual variability in weather and the number of lightning strikes in complex topography suggest that a widespread low-severity fire regime is very unlikely, with a mixed-severity disturbance regime more consistent with our analyses. Although the nature of disturbance has changed from one largely dominated by fire and insect attack historically to harvesting and insect attack since 1950, the area disturbed annually has not diminished. Several interacting factors including climate, extensive fires coincident with European settlement, harvesting, fire suppression and insect attack have been key drivers in creating the conditions observed today. A complex, mixed-severity disturbance regime creates uncertainty about what represents “natural” forest conditions, or what the target conditions for restoration activities are if the objective is to “restore natural conditions”. We conclude that dry forest ecosystems in British Columbia typically experienced mixed-severity disturbance regimes that included fire, bark beetles and defoliators. Trying to “restore” these forests with applications of frequent, low-severity fire is not an ecologically sound objective over large areas. Landscape management should focus on maintaining forest heterogeneity that would have existed historically under a mixed-severity disturbance regime. [Copyright &y& Elsevier]

Abstract: We examined the effects of competition from red alder (Alnus rubra Bong.) and paper birch (Betula papyrifera Marsh.) on the growth of western redcedar (Thuja plicata Donn), western hemlock (Tsuga heterophylla Sarg.), and Douglas-fir (Pseudotsuga menziesii Franco) at a site near Maple Ridge, British Columbia, Canada. At this site, the three coniferous species and two broadleaf species had been planted in 1999 as part of a long-term experiment examining effects of broadleaf density on conifer growth. Red alder and paper birch were planted alone and as a 50:50 mixture at four densities (0, 277, 556, and 1150stemsha−1). Red alder density was positively correlated with total available nitrogen in soil measured using ion-exchange membranes whereas density of paper birch was not. For Douglas-fir only, foliar N concentration was positively related to red alder density. Relationships between stem volume increment and competition indices varied between the three conifer species: (1) For Douglas-fir the highest correlations were obtained using a distance-independent competition index based on broadleaf crown surface area and diffuse transmittance (DIFN) measured using LAI-2000 plant canopy analyzers had the lowest R 2 of the competition measures tested; (2) for western redcedar the highest correlations were with DIFN and the second best competition measures were distance-dependent indices; (3) for western hemlock broadleaf competition did not have significant effects on growth. Height of each species at the time of measurement and crown surface area appear to be more important than shade tolerance in affecting conifer growth. At this site, significant reductions in stem volume (30%) of Douglas-fir and western redcedar occurred when red alder density exceeded 500stemsha−1 while paper birch was not detrimental to western redcedar growth until densities exceeded 1000stemsha−1 and birch density did not significantly affect Douglas-fir. The influence of red alder on soil N and foliar N of Douglas-fir may be leading to a weaker relationship between growth and DIFN for Douglas-fir compared to that for western redcedar. [Copyright &y& Elsevier]

The article reports on black stain root disease progression in coastal Douglas-fir in British Columbia. It states that periodic monitoring of black stain root disease provided intensification and mortality rates for this disease. Fifteen plots with Douglas-firs of varying ages and sizes and growing on sites with different conditions were established in 1989 and assessed in 1994 and 2000. Based on the data plot-level, the incidence of disease increased with an increase in elevation and in slope.

Abstract: We examined intra- and interspecific patterns of roost-site selection by females of three species of forest-dwelling bats (silver-haired, Lasionycteris noctivagans; big brown, Eptesicus fuscus; and California, Myotis californicus) in the Pend d’Oreille Valley in southern British Columbia. Roost-sites were located by outfitting reproductive and non-reproductive female bats with radio-transmitters and tracking them during the daytime. The tree and site characteristics of roost trees used by each bat species were then compared to those of randomly available trees with cavities, as well as to each other, using logistic regression. All three bat species selected roosts that were taller than cavity trees, and the majority of roost trees were emergent or canopy trees. In addition, tree species and the type of cavity were important predictors of whether trees were used as roosts in both intra- and interspecific analyses. The majority of silver-haired and big brown bat roost trees were in hollows in live trembling aspen trees (Populus tremuloides), but both species used small numbers of roosts on conifer snags. In contrast, the majority of California bat roosts were beneath loose bark on conifer snags, particularly Douglas-fir (Pseudotsuga menziesii), in intermediate stages of decay. In general, site characteristics were only weak predictors of differences between roost and random trees, and roost trees used by the three bat species, but roost trees were found in patches with lower percent canopy closure and greater density of available trees. These results suggest that while all three species of forest-dwelling bats use large trees, within this restricted range of trees there is considerable variation among species in the types of cavities and the tree species used. Maintaining stands containing mature trembling aspen is necessary to provide silver-haired and big brown bats with suitable roosting opportunities, but to meet the needs of California bats, areas rich in conifer snags must be protected. Thus, unique management strategies or silvicultural practices may be required to maintain suitable habitat for all bat species in a given area. [Copyright &y& Elsevier]

We examined the effect of harvesting intensity and pattern on red squirrels (Tamiasciurus buchonicus), northern flying squirrels (Glaucomys sabrinus), and yellow-pine chipmunks (Tarnias amoenus) in mature inland Douglas-fir (Pseudotsuga menziesiiglauca) forests in southcentral British Columbia, Canada. We sampled squirrels 1 year before harvesting through 4 years after harvesting and estimated population parameters using open-population models. Relative to unharvested stands, each of the 3 species showed a strong response to tree removal. From 2 years to 4 years after logging, red squirrel density was 40% (SE = 7.1) lower in stands with 50% basal-area tree removal. From 1 year and up to 4 years after logging, northern flying squirrel density averaged 60% (SE = 5.2) lower in harvested treatments regardless of intensity or pattern of logging. In contrast, density of yellow-pine chipmunks increased markedly with increased logging intensity. Beginning 3 years after logging, yellow-pine chipmunk density was 734% (SE = 269) greater in stands with 50% basal-area tree removal. In the short term, harvesting intensity was a more important determinant of squirrel density than harvesting pattern. Retaining >10 m² per ha of live residual stand structure in mature inland Douglas-fir forests maintained habitat for forest-dependent species such as red squirrels and northern flying squirrels, albeit at lower densities. [ABSTRACT FROM AUTHOR]

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To produce better habitat models, we analyzed a 1977 breeding bird data set with recently developed techniques. Our generalized linear models for specific bird species produced precise descriptions of bird-vegetation relationships, using visually obvious habitat features (e.g., grass, broad-leaved shrubs, and conifers of differing heights). This was, in general, confirmed by canonical correspondence analysis, which related the entire bird community to the vegetation across the successional stages. Nevertheless, our analyses produced some results that contradicted our expectations; ground-nesting species negatively associated with bunch grasses (species that grow in clumps within the Agropyron, Festuca, and Stipa genera), and cavity-nesting species negatively associated with stumps and snags. We speculate that those contrary relationships resulted from nest sites not being a limiting resource. We conclude that visually obvious vegetation features are sufficient to describe most breeding bird-habitat relationships. Further, appropriate landscape management for bird biodiversity requires that all successional stages are present. [ABSTRACT FROM AUTHOR]

The operational use of Bacillus thuringiensis subsp. kurstaki ( Btk ) to control the western spruce budworm in the mountainous terrain of British Columbia, Canada, gives variable results at the registered dose of 30 BIU ha  - 1 in 2.4 L ha  - 1 . Btk (Foray 48B®, 60 BIU ha  - 1 in 4.8 L ha  - 1 ) was applied experimentally in 1996 over 150-ha of western spruce budworm-infested Douglas-fir forest to determine if increasing both the dose and volume of Btk applications gives more uniform and effective control. We sampled native caterpillars on the shrub Ribes cereum Douglas in this and a similar, untreated area 2 km away from 1996 to 1998 to assess the impact of this high dose and volume Btk application on non-target Lepidoptera. The numerically dominant lepidopteran species were Euhyponomeutoides gracilariella Busck (52%) and Gelechia ribesella Chambers (32%). The remaining 16% of the guild was comprised of numerous sparsely distributed species. Total larval abundance was significantly lower on plants that were sprayed with Btk than on plants that were covered to exclude Btk within the treatment area in the year of application. Geometrids appeared to be less affected by the treatment than other taxa. Both G. ribesella and E. gracilariella appeared to make a full recovery by the second year post-treatment, but we did not find a full recovery of the sparsely distributed species. [ABSTRACT FROM AUTHOR]

Ringbarking is a girdling technique that is used prior to timber harvesting to reduce losses to Armillaria root disease in some parts of the world. The technique had not previously been evaluated in British Columbia, Canada. Small plots of primarily Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco) trees that were ringbarked prior to timber harvesting had approximately 50% lower levels of Armillaria root disease caused tree mortality in young trees after 15 years than plots of trees that were not ringbarked. Ringbarking did not reduce Armillaria root disease in this trial as much as has been reported in other research. This could be attributable to the centre of the small plots being within 5-10 m of live and dead Armillaria-infected trees in the surrounding forest. The treatment did reduce the severity of the disease by both statistically and biologically significant amounts and, therefore, warrants further investigation as a possible treatment where timber harvesting is conducted in Armillaria root disease affected stands. [ABSTRACT FROM AUTHOR]

• Tree height not impacted by compaction and organic matter removal treatments. • Tree height was greater in acidic soil as compared to calcareous soil conditions. • Reduced nutrients, but higher seedling survival with greatest OM removal (OM3) • Lodgepole pine survival after 15 years was 82% compared to 70% for Douglas-fir. • Year-15 foliar N and S deficiency in both species, especially with calcareous soils. Silviculture systems and associated forest harvesting practices that affect the level of soil compaction and organic matter retained on a site will cause changes to soil properties and processes that may affect the growth of planted trees. We present results for soil conditions and tree growth after 15 years for 6 Long-term Soil Productivity Study (LTSP) installations in 2 distinct regions of the Interior Douglas-fir (IDF) biogeoclimatic zone in southern British Columbia (BC). In a 3 × 3 factorial design, three levels of compaction and organic matter removal were replicated in two distinct IDF regions that varied in parent material, but with similar climates. Each treatment was then split and planted with two different species, Douglas-fir and lodgepole pine. In each region, three unique sites (block), all within a radius of 50 km from one other, were installed with the same combination of treatment and species for a total of six replicates, three in each of two regions. Across IDF regions, tree heights on calcareous soils in the Rocky Mountains of south-eastern BC were 36% lower for Douglas-fir and 23% lower for lodgepole pine than on more acidic soils on the Thompson Plateau. There were varying differences across treatments in soil and foliar nutrient concentrations between IDF regions, primarily from regional parent material differences. However, nutrient deficiencies were apparent in both regions and may have limited growth, especially on the more calcareous sites. Increases to soil bulk density (27%) 1 year after compaction did not impact tree survival, height at Year-15, or chemical properties in foliar tissue or soil. Fewer growing season frost events and increased soil water availability during the seedling establishment period was a likely reason for a 25% increase in Douglas-fir survival at Year-15 with the whole tree + forest floor removal (OM3) treatment. However, whole tree + forest floor removal (OM3) also produced a 13–19% reduction in soil N, S, K, and mineralizable N when compared to both stem-only (OM1) and whole tree (OM2) harvesting treatments that kept the forest floor intact. Effects on forest productivity from soil compaction after 15 years appear to be overshadowed by the more prominent effect of organic matter removal treatments during stand establishment and early growth. Future work at these installations focusing on nutrient budget, forest health, and ecosystem carbon stock differences across treatments will provide valuable insight into silviculture and harvesting practices for different species and regions in the dry forests of southern BC. [ABSTRACT FROM AUTHOR]

Forest fertilization is common in coastal British Columbia as a means to increase wood production and potentially enhance carbon sequestration. Generally, the effects of fertilization are determined by measuring sample plots pre- and post-treatment, resulting in fertilization effects being determined for a limited portion of the treatment area. Applications of remote sensing-based enhanced forest inventories have allowed for estimations to expand to the wider forested area. However, these applications have not focused on monitoring the effects of silvicultural treatments. The objective of this research was to examine if a multi-temporal application of the LiDAR area-based method can be used to detect the fertilization effects on volume, biomass, and height in a second-growth Douglas-fir (Pseudotsuga menziesii) stand. The study area on Vancouver Island was fertilized in January 2007, and sample plots were established in 2011. LiDAR acquisitions were made in 2004, prior to fertilization, and in 2008, 2011, and 2016, covering both treated and untreated areas. A total of 29 paired LiDAR blocks, comprised of four 20 m resolution raster cells, were selected on either side of the fertilization boundary for analysis of the effects across several different stand types differing in the percentage of Douglas-fir, site index, and age. Random forest (RF) plot-level models were developed to estimate total stem volume and total stem biomass for each year of LiDAR acquisition using an area-based approach. Plot level results showed an increase in stem volume by 13% fertilized over control from 2005 to 2011, which was similar to a 14% increase in above-ground carbon stocks estimated using a tree-ring stand reconstruction approach. Plot-level RF models showed R2 values of 0.86 (volume) and 0.92 (biomass) with relative cross-validated root mean square errors of 12.5% (volume) and 11.9% (biomass). For both the sample plots and LiDAR blocks, statistical results indicated no significant differences in volume or biomass between treatments. However, significant differences in height increments were detected between treatments in LiDAR blocks. The results from this research highlight the promising potential for the use of enhanced forest inventory methods to rapidly expand the assessment of treatment effects beyond sample plots to the stand, block, or landscape level. [ABSTRACT FROM AUTHOR]

• A mid-aged Douglas-fir stand was fertilized with urea at 200 kg ha−1 of N. • Fertilization increased NEP by an average value of 170 g m−2 y−1 of C over ten years. • Fertilization enhanced gross primary production only in the first two years. • Fertilization suppressed ecosystem respiration except in the first year after fertilization. • Fertilization caused water use to increase by an average of about 15%. Douglas-fir (Pseudotsuga menziesii) forests in the Pacific Northwest are the most productive managed forests in North America. Nitrogen (N) fertilizers are generally applied in this region to increase the rate of tree growth and consequently carbon (C) sequestration. However, the long-term effects of N fertilization on C and water exchanges of Douglas-fir forests are not clear. This study presents 15 years of eddy-covariance (EC) measurements of C and water fluxes above a pole-sapling-stage Douglas-fir stand on Vancouver Island, British Columbia, Canada, and determines how N fertilization with 200 kg ha−1 of urea-N affected these fluxes over the 10-year period after fertilization. A process-based forest growth model, 3-PG, was calibrated using EC-measured C and water fluxes during the 5 pre-fertilization years, and then used to predict these fluxes for the next 10 years assuming the stand was not fertilized. The modelled C and water fluxes for the pre-fertilization years agreed well with the measurements (with R2 values of 0.90, 0.89, and 0.89 for gross primary production (GPP), ecosystem respiration (R e) and evapotranspiration (ET), respectively) and only slightly underestimated GPP, R e , and ET by 4%, 1%, and 3%, respectively. The effects of N fertilization on C sequestration and water use (ET) were then obtained as differences between EC-measured (fertilized stand) and modelled (unfertilized stand) fluxes. Application of N fertilizer to this stand led to a short-term (first two years) increase in GPP followed by little change over the long term. R e increased over the short-term (first year), while it was appreciably suppressed over the long term. N fertilization resulted in an average increase in net ecosystem productivity by 170 g m−2 year−1 of C during 2007–2016 with interannual variation depending on annual weather conditions. N fertilization led to an average increase in annual water use of 15% (or 53 mm year−1). [ABSTRACT FROM AUTHOR]

Climatic and land use changes have significant consequences for the distribution of tree species, both through natural dispersal processes and following management prescriptions. Responses to these changes will be expressed most strongly in seedlings near current species range boundaries. In northern temperate forest ecosystems, where changes are already being observed, ectomycorrhizal fungi contribute significantly to successful tree establishment. We hypothesised that communities of fungal symbionts might therefore play a role in facilitating, or limiting, host seedling range expansion. To test this hypothesis, ectomycorrhizal communities of interior Douglas-fir and interior lodgepole pine seedlings were analysed in a common greenhouse environment following growth in five soils collected along an ecosystem gradient. Currently, Douglas-fir's natural distribution encompasses three of the five soils, whereas lodgepole pine's extends much further north. Host filtering was evident amongst the 29 fungal species encountered: 7 were shared, 9 exclusive to Douglas-fir and 13 exclusive to lodgepole pine. Seedlings of both host species formed symbioses with each soil fungal community, thus Douglas-fir did so even where those soils came from outside its current distribution. However, these latter communities displayed significant taxonomic and functional differences to those found within the host distribution, indicative of habitat filtering. In contrast, lodgepole pine fungal communities displayed high functional similarity across the soil gradient. Taxonomic and/or functional shifts in Douglas-fir fungal communities may prove ecologically significant during the predicted northward migration of this species; especially in combination with changes in climate and management operations, such as seed transfer across geographical regions for forestry purposes.

Limited tree size variation in coastal Oregon, Washington, and British Columbia Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) plantations makes them susceptible to developing high height to diameter ratios (H/D same units) in the dominant trees. The H/D of a tree is a relative measure of stability under wind and snow loads. Experimental plot data from three large studies was used to evaluate the impact ofinitial planting densities and thinning on plantation H/D values. The H/D predictions from the experimental plot data match spacing trialresults closely but are substantially different than distance-independent growth model predictions. The results suggest that plantation H/D values can be lowered and stability promoted through reduced planting densities or early thinning; however, later thinnings may not be effective in promoting stability, since they do not appear to lower H/D values. Higher initial planting densities shorten the time period during which thinning can be expected to effectively lower future H/Dvalues. Time-sensitive thinning requirements in dense plantations make their management inflexible. The flexibility with which a stand can be managed describes the rigidity of intervention requirements and (or) potential range of stand development pathways. [ABSTRACT FROM AUTHOR]

Abstract unavailable [ABSTRACT FROM AUTHOR]