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To evaluate impacts of competitive conditions in tree neighborhoods on growth responses as influenced by moisture availability and local environmental conditions, we sampled 102 codominant 40- to 70-year-old coastal Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) in regions with relatively high and low moisture availability. We quantified local environmental conditions (topographic position index, heat load, and soil depth), and the annual basal area increment and climate moisture deficits during two growth periods: a five-year period prior to commercial thinning and years six to 10 after thinning. In both regions and growth periods, tree growth was higher for trees growing in local neighborhoods with lower competition. The density/growth relationships differed by region and by growth period in the moist regions, but they were not influenced by climate moisture deficit. Furthermore, including topographic position index, heat load, or soil depth did not improve model support. Our results highlight the importance of managing local competition and indicate that environmental factors such as soil depth, heat load, and topography may be less likely to warrant consideration when developing thinning prescriptions. This could allow foresters to accommodate other ecosystem services when designing density management treatments, at least within typical growing conditions.

Productive Norway spruce forests in mountainous growing areas are expected to be affected by increasing climate-driven disturbances, which will most likely result in a reduction of their economic performance. This study seeks to compare the potential of currently discussed management options aiming to maintain the economic performance on typical sites of spruce under a changing climate. For this purpose, we used a combined approach of tree mortality simulation and portfolio optimization to assess the management options: (1) including a deciduous species, (2) establishing mixed stands, (3) shortening the rotation periods, (4) forest protection measures focusing on bark beetles and (5) introducing another highly productive species. As a novel feature, we also compared the effect of combined management strategies on the return and risk of stand management. In our simulation and optimization approach, the inclusion of an alternative, highly productive tree species, such as Douglas fir, into the tree species portfolio outcompeted the forest protection measure of intensive bark beetle monitoring with timely sanitation fellings in terms of balancing risks and returns. The adaptation gain of introducing Douglas fir was further enhanced when combined with additional management options such as adapted rotation periods. The resulting synergies were able to overcompensate for the adverse economic effects of climate change. On the contrary, including beech did not only reduce the risks but also the return in a magnitude which was clearly outcompeted by Douglas fir, even with the assumption of high mortality risks for Douglas fir. These results prove the importance of a proactive tree species selection in relation to more reactive forest protection measures for climate change adaptation. They also advise a careful consideration of expected market demands when selecting an additional species for the portfolio.

Concerns about long-term pollinator declines have made assessing bee communities a priority in nonagricultural ecosystems, including managed forests. We assessed wild bee communities in Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) stands one to 15 years after clearcut harvest in western Oregon, USA, testing the hypothesis that bee diversity would be high initially and then decline with time-dependent reductions in floral resources. We captured 2,009 individual bees that represented 67 distinct species/morphospecies in 20 genera and five families. Asymptotic estimators of bee diversity representing Shannon and Simpson diversity were greater in communities during the second half of the early seral period, indicating older early seral stands were less diverse and contained more common and dominant bee species. In addition, observed species richness and bee abundance peaked at approximately three years postharvest and declined thereafter by 20% and 30% per year, respectively. Because floral resources declined in concert with reductions in bee diversity as stands aged, food appears to be a key driver of forest bee communities. Our results indicate that postharvest Douglas-fir stands supported a diversity of bees, including important crop pollinators, but their value to bees was restricted to a relatively short window at the beginning of the early seral period.

Swiss needle cast (SNC), caused by Nothophaeocryptopus gaeumannii, is a foliage disease of Douglas-fir (Pseudotsuga menziesii), that reduces growth in native stands and exotic plantations worldwide. An outbreak of SNC began in coastal Oregon in the mid-1990s and has persisted since that time. Here we review the current state of knowledge after 24 years of research and monitoring, with a focus on Oregon, although the disease is significant in coastal Washington and has recently emerged in southwestern British Columbia. We present new insights into SNC distribution, landscape patterns, disease epidemiology and ecology, host-pathogen interactions, trophic and hydrologic influences, and the challenges of Douglas-fir plantation management in the presence of the disease. In Oregon, the SNC outbreak has remained geographically contained but has intensified. Finally, we consider the implications of climate change and other recently emerged foliage diseases on the future of Douglas-fir plantation management.

Tree improvement programs are critical to establishing high yield seed sources while maintaining genetic diversity and developing sustainable plantation forests. Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) is commonly used in improvement programs due to its superior strength and stiffness properties. Progeny testing trials in British Columbia (BC), Canada aim to increase stem volume without sacrificing wood quality. As genetically improved stock in BC is entering its fourth generation, wood quality and branch attributes are becoming more important as selection criteria evolve. This study investigates the utility of Airborne Laser Scanning (ALS) to produce metrics that describe branch attributes, and test whether these attributes showed differences in trees of three different genetic gain levels (GL); Wild-Stand (WS), Mid-Gain (MG) and Top-Cross (TC), planted at two different spacings (2.9 m and 4.0 m) in a realized-gain trial. New methods were developed to utilize ALS data to estimate metrics such as branch angle, length and volume using a point clustering approach. The relative impact of GL and spacing on branch attributes were assessed. Spacing was significant for branch angle (2.9 m = 73.53°, 4.0 m = 72.46°), whereas GL (WS = 0.861 m, MG = 0.917 m, TC = 0.948 m) and spacing (2.9 m = 0.884, 4.0 m = 0.942) were significant for length. For all metrics, TC trees at 4.0 m spacing were consistently significantly different whenever GL or the interaction effect was significant. This data provide an insight into how ALS can be used to model branch attributes, whereas the ability to analyse trees by plot, individual tree and individual branch attributes further allows researchers and foresters to maximize the value of ALS data. Findings from this research can be integrated into large-scale programs not just for monitoring trees, but also for identifying new trees that can display attributes associated with larger volumes and increased value.

Substantial growth losses in Douglas-fir can be the result of Swiss needle cast, a foliar disease caused by the fungus Nothophaeocryptopus gaeumannii. Although the disease is native to western North America, it is expected to become increasingly problematic in regions where climates become warmer in winter and wetter in spring, such as in coastal British Columbia (BC), Canada. Previous research suggests that tolerance to this disease is under partial genetic control. We therefore aim to screen for tolerance and resistance to the disease in the tree breeding population of coastal Douglas-fir (Pseudotsuga menziesii var. menziesii) in BC. We evaluated if early screening for resistance or tolerance to this disease is possible. We worked with 32 families grown for 18-years on two full-sibling genetic field trial sites representing different climates. We assessed >900 trees for disease signs and symptoms from 2017 to 2019. Needle retention was assessed in the field. In the laboratory, the proportion of stomata occluded with pseudothecia was measured, deoxyribonucleic acid (DNA) was extracted, and the proportion of fungal DNA in the needles was assessed using quantitative polymerase chain reaction. Strong differences were observed among families for needle retention, stomatal occlusion and fungal load. The milder and wetter site closer to the coast was generally more severely affected. Families showed rank changes between the two sites for all response variables. Higher needle retention was correlated with increased tree volume. No correlation was found between the proportion of stomata occluded with pseudothecia, fungal DNA load and needle retention. These results indicate that a more complex pathology is involved in causing needle loss. We conclude that screening for Swiss needle cast tolerance in the coastal BC Douglas-fir breeding population is possible if needle retention can be assessed and that area-specific deployment strategies may be needed given family rank changes in different environments.

The 1912 Douglas-Fir Heredity Study is one of the first studies undertaken by the US Forest Service, and one of the first forest genetics studies in North America. The study considers provenance variation of 120 parent trees from 13 seed sources planted at five test sites in the Pacific Northwest. The unique, long-term nature of the study makes it valuable to revisit and consider its biological and historical significance. This analysis considers how far climatically Douglas-fir populations may be moved without incurring unacceptable declines in growth and survival. Results indicate that Douglas-fir seed sources may be moved at least 2° C cooler or warmer and still retain good long-term survival and productivity. However, projected future climate change beyond 2° C may lead to lower survival and productivity. One option to address these concerns is assisted migration; however, if seed sources are moved beyond 2–3° C to a cooler climate in anticipation of warming, or from a more continental to a maritime climate, we are likely to see increased mortality and associated losses in productivity in the near-term. Lessons from this study include: (1) pay attention to good experimental design; we were able to overcome limitations from the design by using new statistical approaches; (2) maladaptation may take time to develop; poorer survival was not evident until more than two decades after planting; and (3) long-term studies may have value for addressing new, unforeseen issues in the future.

This study aimed to investigate the effects of juvenile spacing (precommercial thinning), thinning, and fertilization on Douglas-fir butt log (first 4.9 m) and second log (4.9–10 m) quality attributes: juvenile wood percentage, heartwood percentage, rings per inch, specific gravity, and modulus of elasticity. A 41-year-old, 36.6 m site index Douglas-fir stand in western Oregon, USA was selected as the first stand to explore. Nine common silviculture pathway treatments of juvenile spacing, thinning, and fertilization were applied to independent 0.404-hectare plots. Ninety-nine trees were felled and disks cut at five heights along the stem. Wood properties were measured and calculated from the disks for log quality attributes. There was no effect of silvicultural treatments on log heartwood percentage, but significant effects on other log quality attributes were observed. Juvenile wood percentage and rings per inch declined with stand density control and fertilization treatment. Responses to thinning and fertilization in log specific gravity depend on juvenile spacing. Also, thinning and juvenile spacing were shown to have impacts on log modulus of elasticity.

Swiss needle cast (SNC) is a foliage disease of Douglas-fir (Pseudotsuga menziesii) caused by Nothophaeocryptopus gaeumannii, an ascomycete fungus (Mycosphaerellaceae) that causes tree growth reductions in the Pacific Northwest. The epidemiology of the fungus is generally well known, but the relations between disease expression and foliar nutrition are unclear. In this study, we used data from the Swiss Needle Cast Cooperative research and monitoring plot network in western Oregon and SW Washington to assess associations between SNC severity, carbon, and nine foliage nutrients (nitrogen, Na, K, P, Ca, Mg, Mn, Al, S). Foliage samples were collected from midcrown of selected Douglas-firs from each plot. SNC severity was determined on 2-year-old needles by multiplying disease incidence and fungal reproductive (pseudothecia) density. Disease severity and nutrient relations were determined using linear mixed models. SNC severity showed statistically significant positive trends with concentrations of carbon, nitrogen, Na, K, and S, no relation with concentrations of Ca, Mg, or Al, and slightly negative trends that were not significant for P and Mn. This is the first such analysis of associations between a conifer foliage disease and foliage nutrients across a landscape; subsequently, there is little published literature on how or why these nutrients may interact with disease.

We applied a range of bole and root damage treatments to young Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) trees. Significant natural damage occurred to tree crowns over the course of the 10-year study allowing for an analysis of how damage severity to tree boles, tree roots, and tree tops impacts growth and cumulative survival of trees. Tree bole damage severity, measured by percent bole circumference removed, exponentially reduced cumulative survival across the study period, whereas damage to tree roots had no significant impact on survival. Bole damage had different impacts on survival depending on the relative size of trees that were damaged. At higher levels of bole damage, trees with larger relative diameters had accelerated mortality rates compared with trees with smaller relative diameters. Tree crown height loss averaged at the treatment within stand level reduced the impacts of bole damage on tree cumulative survival response. Increasing bole, root, and tree crown damage severity led to reductions in estimated maximum diameter and height. Bole damage and damage to tree crowns hastened the decline of diameter growth rates and delayed the decline of height growth rates.

Westernhemlock(Tsugaheterophylla(Raf.)Sarg.)isamajorcommercialtreespeciesinwesternOregonandWashingtonandisoftenassociatedwithcoastDouglas-fir(Pseudotsugamenziesii(Mirb.)Francovarmenziesii)andother species in coniferous forests of the Coast Ranges and Cascade Mountains. Growth of Douglas-fir in many coastal forestshasbeennegativelyaffectedbySwissneedlecast (SNC),afoliardiseasecausedbytheascomycetePhaeocryptopusgaeumannii(T.Rohde)Petr.andcharacterizedbyprematurefoliagelossonseverelyinfectedDouglas-fir trees.TheeffectofSNConstanddynamicsinmixedDouglas-fir-westernhemlockstandswastestedbyconstructingadiameterincrementmodelforwesternhemlockthatquantifieditsgrowthresponsetovaryingSNCseverityin Douglas-fir. Diameter increment of western hemlock in any given growth period increased with increasing initial SNC severity as measured by Douglas-fir foliage retention (FR), here defined as the number of annual needle cohorts held by the tree. Furthermore, a decline in Douglas-fir FR during the growth period was associated with an additional increase in diameter increment of western hemlock trees. Assuming no change in FR over the growthperiod,westernhemlocktreesinstandswithseverelyimpactedDouglas-fir(initialFR ≤1.5years)averaged 79 per cent greater diameter growth than that in relatively healthy stands (initial Douglas-fir FR ≥3.5 years). The implied annual diameter growth response of a western hemlock with initial diameter at breast height of 10, 20, 30 or 40 cm was 0.29, 0.52, 0.65 and 0.68 cm year 21 , respectively. Compensatory growth by western hemlock inmixed-speciesstandsaltersstanddynamicsbyallowingthisspeciestosurpassthegrowthofDouglas-firexperiencing severe SNC.

In coastal forests of the Pacific Northwest, young coniferous plantations typically contain a mixture of planted and natural Douglas-fir (Pseudotsuga menziesii) and western hemlock (Tsuga heterophylla). Swiss needle cast (SNC) disease inhibits the growth of Douglas-fir to varying degrees in these stands, depending on SNC severity. In addition to the value differential between Douglas-fir and western hemlock, foresters must account for differences in growth potential (tree size, competitive position, site characteristics, disease pressure) when selecting trees for retention during thinning operations. Diameter increment models for Douglas-fir and western hemlock were developed from permanent plot data collected for the SNC growth impact study (GIS), precommercial thinning study (PCT), commercial thinning study (CT), and retrospective commercial thinning study (RCT). Predictor variables represent tree size, competitive position, site characteristics, and SNC severity. SNC severity was indexed by foliage retention, defined as the number of annual needle cohorts held by a tree. Foliage retention was positively correlated with Douglas-fir diameter increment and negatively correlated with western hemlock diameter increment. Charts developed from the diameter growth models provide a field tool for assessing the relative basal area growth of adjacent Douglas-fir and western hemlock of a given initial diameter in a stand of given SNC severity. In a stand with severe SNC (foliage retention 1.5 years) the basal area growth of a 6-in. western hemlock tree will exceed the basal area growth of any Douglas-fir tree up to 7.7 in. in DBH. In a relatively healthy stand (foliage retention 3.0 years) the basal area growth of 6 in. Douglas-fir and western hemlock trees will be approximately equivalent.

•In recent years, interest has increased in silvicultural systems and harvest cuts that retain partial overstories, but there are few data available on the growth of the understory trees in such stands. We studied the response of overstory trees and underplanted seedlings, Douglas-fir (Pseudofsugo menziesii), western hemlock (Tsuga heferaphylla), and western redcedar (Thuja plicafa), to a range of residual overstory densities. Forty to 70-year-old Douglas-fir stands in western Washington were harvested, leaving retention levels of 0, 8, 16, 24, 32, and 40% of full stocking. The 9-year response of the understory seedlings was species-dependent wnh Douglas-fir the largest in diameter (mean diameter 6.4 cm and mean height 3.8 m), western hemlock the tallest (mean diameter 5.5 cm and mean height 5.4 m), and redcedar the smallest (mean diameter 1.5 cm and mean height 1.5 m), in port because it was heavily browsed. Douglas-fir and western redcedar showed the greatest growth in the lowest retention levels (0 and 8%), and western hemlock responded best at the middle retention levels (8 and 16%).

The timing of periodic life cycle events in plants (phenology) is an important factor determining how species and populations will react to climate change. We evaluated annual patterns of basal-area and height growth of coast Douglas-fir (Pseudotusga menziesii var. menziesii (Mirb.) Franco) seedlings from four seed sources that were planted in four diverse environments as part of the Douglas-fir Seed-Source Movement Trial. Stem diameters and heights were measured periodically during the 2010 growing season on 16 open-pollinated families at each study installation. Stem diameters were measured on a subset of trees with electronic dendrometers during the 2010 and 2011 growing seasons. Trees from the four seed sources differed in phenology metrics that described the timing of basal-area and height-growth initiation, growth cessation and growth rates. Differences in the height-growth metrics were generally larger than differences in the basal-area growth metrics and differences among installations were larger than differences among seed sources, highlighting the importance of environmental signals on growth phenology. Variations in the height- and basal-area growth metrics were correlated with different aspects of the seed-source environments: precipitation in the case of height growth and minimum temperature in the case of basal-area growth. The detailed dendrometer measurements revealed differences in growth patterns between seed sources during distinct periods in the growing season. Our results indicate that multiple aspects of growth phenology should be considered along with other traits when evaluating adaptation of populations to future climates.

An instantaneous puff dispersion model was used to assess concentration fields of the Douglas-fir beetle, Dendroctonus pseudotsugae Hopkins, antiaggregation pheromone, 3-methylcyclohex-2-en-1-one (MCH), within a 1-ha circular plot. Several combinations of MCH release rate and releaser spacing were modeled to theoretically analyze optimal deployment strategies. The combinations of MCH release rate and releaser spacing used in the modeling exercise were based on results of previous field studies of treatment efficacy. Analyses of model results suggest that a release rate up to six times the initial standard, at a correspondingly wider spacing to keep the total amount of pheromone dispersed per unit area constant, may be effective at preventing Douglas-fir beetle infestation. The model outputs also provide a visual representation of pheromone dispersion patterns that can occur after deployment of release devices in the field. These results will help researchers and practitioners design more effective deployment strategies.

Foliar diagnostic tools have been used with varying success to identify limiting nutrients in Douglas-fir (Pseudotsuga menziesii [Mirab.] Franco var. glauca [Beissn.] Franco). The mechanisms of sulfur and nitrogen metabolism in plants enable the measurement of nutrient fractions that may yield more informative results. Measurements of sulfate-sulfur in conifer foliage have shown potential as a diagnostic tool for predicting tree response to nitrogen fertilization. Using archived samples and data from previously established fertilizer trials in northern Idaho, we tested the relationship between foliar sulfate-sulfur concentrations in unfertilized trees and 2-year growth response to nitrogen fertilization in Rocky Mountain Douglas-fir (P. menziesii [Mirab.] Franco var. glauca [Beissn.] Franco). Sulfate-sulfur concentrations explained 42% of the variability in growth response, compared with 17% for the total nitrogen to sulfur ratio. Sulfate-sulfur concentrations were variable within sites, presenting a challenge to the feasibility of sampling. Our results suggest that further controlled research would aid in development of sulfate-sulfur as a foliar diagnostic tool.

Interest in managing Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) forests in the Pacific Northwest under silvicultural systems other than traditional clearcutting has prompted research on the efficacy of alternative systems for successful regeneration and sustained timber productivity of Douglas-fir. The College of Forestry Integrated Research Project, implemented by Oregon State University, was established to compare various ecosystem responses and public perceptions among treatments implemented under clearcutting, shelterwood-with-reserves, and group selection silvicultural systems. The objective of this analysis was to quantify the following three responses of planted Douglas-fir seedlings to initial regeneration cuts: cumulative 13-year height growth (H13yr; 1992–2004), cumulative 13-year diameter growth (D13yr; 1992–2004), and most recent 5-year height growth (ΔH5yr; 2000–2004). Differences in variability of overstory density at the treatment level led to significant differences in the variance of understory growth responses. After accounting for heterogeneous variance, analysis of variance indicated significant treatment effects for all three responses. Treatment effects were explained by the decline in H13yr, D13yr, and ΔH5yr with increasing overstory competition as represented by basal area of residual trees immediately after harvesting (initial basal area). Predicted height:diameter ratio of Douglas-fir seedlings increased as IBA increased. Under regeneration methods that retain a portion of the overstory, a residual overstory with basal area

Summary In this study, we examined density–size relationships for Sitka spruce (Picea sitchensis (Bong.) Carr.) and Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) using data collected in stands in Great Britain (GB) and Western Canada. These two conifers are native to Western North America and have been widely planted in GB. Results indicate differences between stands in Canada and GB in both the intercept and slope of the log maximum density–log size boundary lines. In GB, the slope (b) of the relationship between log of stand density (number of trees per hectare) and log of quadratic mean diameter (Dq) is steeper than the theoretical value of −1.605 (−2.063 for Sitka spruce and −1.864 for Douglas-fir). Values of b are lower in Canada (−1.437 for Sitka spruce and −1.241 for Douglas-fir) than in GB . Within each region, b is similar for the two species. However, the intercept term differs for Sitka spruce and Douglas-fir in GB. These differences provide additional evidence that density–size boundary line relationships are influenced by environmental and other factors and indicate the need for development of density–size relationships for each species and for each region where the species is grown. Maximum stand density index (SDI) values calculated using these relationships are 1868 and 2073 for Sitka spruce and 1491 and 1815 for Douglas-fir in GB and Canada, respectively. Differences in maximum SDI between these two regions may be related to differences in climate, provenance, stand history and other factors. Maximum density–size relationships presented in this paper can be used as a starting point for managing stand density for both even-aged and continuous cover stands and for identifying potential maximum stocking in stands of these species in GB and Canada.

Growth models for coast Douglas-fir (Pseudotsuga menziesii var. menziesii [Mirb.] Franco) are generally based on measurements of stands that are genetically unimproved (or woods-run); therefore, they cannot be expected to accurately project the development of stands that originate from improved seedlots. In this report, we demonstrate how early expected gain and genetic-gain multipliers can be incorporated into growth projection, and we also summarize projected volume gains and other aspects of stand development under different levels of genetic gain, site productivity, and initial planting density. Representative tree lists that included three levels of productivity (site index = 100, 125, and 150 ft; base = 50 years)and three initial planting densities (302, 435, and 602 trees/ac) were projected from ages 10 to 60 years under three scenarios using two regional growth models (Stand Management Cooperative version of ORGANON and the Pacific Northwest variant of the Forest Vegetation Simulator). The two models projected similar percentage volume gains for improved seedlots. Seedlots with a genetic worth (GW) of 5% for height and diameter growth were projected to have volume gains of 3.3–5.8% over woods-run stands at 40 years and 2.1–3.2% at 60 years. Volume gains were projected to approximately double when GW was increased from 5 to 10%.

Bear activity resulting in injury to Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) trees has been documented as early as the mid-1850s in the Pacific Northwest. The study reported in this article was designed to help managers decide whether the common practice of removing the damaged but potentially valuable butt section of the bottom log and leaving it in the woods is warranted. Thirty-four damaged and 28 undamaged trees were selected from three sites in western Washington where bear damage has been a persistent problem. Trees were felled and bucked into 16-ft lengths. The damaged trees in the sample had been injured at ages between 10 and 15 years at two sites and between 10 and 65 years at the third site. The primary scaling deductions were for ring and scar defects. The 16-ft butt logs from the damaged and undamaged trees were sawn into dimension lumber. Bear-damaged logs were found to have lower cubic volume recovery than undamaged logs having the same small-end diameters. Lumber grade recovery was also influenced by bear damage; logs from damaged trees had a lower percentage of high-value lumber. The analysis suggests that the optimal harvesting policy is to haul the entire butt log to the mill rather than leaving the damaged portion in the woods. Although the value of the damaged portion is lower, most of the lumber recovered from that section can be used, with only a modest reduction in grade and value.

Made available in DSpace on 2022-04-28T20:59:27Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-01-01 Aboveground biomass predictive equations were developed for a highly productive 47-year-old mixed Douglas-fir and western hemlock stand in southwest Washington State to characterize the preharvest stand attributes for the Fall River Long-Term Site Productivity Study. The equations were developed using detailed biomass data taken from 31 Douglas-fir and 11 western hemlock trees within the original stand. The stand had an average of 615 live trees per hectare, with an average dbh of 35.6 cm (39.1 cm for Douglas-fir and 33.3 cm for western hemlock) and an average total tree height of 31.6 m (32.8 m for Douglas-fir and 30.2 m for western hemlock). Equations developed were of the form ln Y = b1 + b2 ln dbh, where Y = biomass in kg, dbh = diameter in cm at 1.3 m height, b1 = intercept, and b2 = slope of equation. Each tree part was estimated separately and also combined into total aboveground biomass. The total aboveground biomass estimation equations were ln Y=-0.9950 + 2.0765 ln dbh for Douglas-fir, and ln Y=-1.6612 + 2.2321 ln dbh for western hemlock. The estimate of the aboveground live-tree biomass was of 395 Mg ha-1 (235 Mg ha-1 for Douglas-fir and 160 Mg ha-1 for western hemlock), with 9.5, 29.3, 12.9, 308, and 32.7 Mg ha-1 in the foliage, live branches, dead branches, stem wood, and stem bark, respectively. When compared with biomass estimates from six other studies, ranging in age from 22 to 110 years and from 96.3 to 636 Mg ha-1, the biomass of the Fall River site was relatively high for its age, indicating very high productivity. Copyright © 2009 by the Society of American Foresters. Soil and Environment Sciences Forest Resources University of Washington Box 352100, Seattle, WA 98195-2100 Department of Biological Sciences University of Denver, Denver, CO 80208 USAID Regional Development Mission for Asia Regional Environment Office, 93/1 Wireless Road, Bangkok 10330 Western Forestry Research Weyerhauser Company, Centralia, WA 98513 Faculdade de Ciencias Agronomicas Dep. de Ciencias do Solo UNESP, 18600-000 Botucatu-SP, Brasil Department of Ecology and Evolutionary Biology Cornell University, E343 Corson Hall, Ithaca, NY 14853 College of Forest Resources University of Washington, Box 352100, Seattle, WA 98195-2100 The Nature Conservancy, 1001 West Yakima Ave., Yakima, WA 98902 Philips US Fleet, 22100 Bothell Everett Highway, Bothell, WA98021 Faculdade de Ciencias Agronomicas Dep. de Ciencias do Solo UNESP, 18600-000 Botucatu-SP, Brasil

We studied the potential for stand density management treatments to increase growth rates of advanced regeneration in the understory of 50- to 70-year-old Douglas-fir (Pseudotsuga menziesii) forests. Study sites in Oregon included a mesic coastal site, a moderate coast range site, and a drier coast range foothills site. Commercial thinning treatments in 1974–1984 led to the establishment of Douglas-fir and western hemlock (Tsuga heterophylla) in the understory and, in 1997, parts of these same stands were thinned for a second time to release this advanced regeneration and promote two-story structure. Both species responded positively where overstory was reduced to 30–40 m2/ha, but western hemlock saplings grew 30–80% more rapidly than Douglas-fir. Average annual height growth of all western hemlock saplings that were more than 1.0 m tall in 1999 was 23–30 cm/year in twice-thinned stands but only 13 cm/year in denser, once-thinned stands. About one-half of all western hemlock saplings doubled or tripled their height in 4 years after a second overstory treatment; the largest 10% of these saplings grew 74–93 cm/year and now represents midstory structure. The response of Douglas-fir saplings to a partial overstory removal was limited. Repeated density management treatments in these Douglas-fir forests can accelerate growth of understory saplings, resulting in the development of two or more canopy layers over time; however, repeated and/or heavy thinning will be required for Douglas-fir sapling growth. Furthermore, because of western hemlock's potential for rapid height growth, some reduction of hemlock sapling density may be needed to maintain vigorous Douglas-fir.

This study describes soil horizon depth and fine root distribution in cores collected at two distances from the boles of Douglas-fir and ponderosa pine trees at a study site in a central Idaho forest. Concentration and content of fine roots extracted from soil cores were compared among species, soil horizons, tree size, and distance from bole. Approximately 80% of litter and humus samples contained no fine roots. The highest fine root content and concentrations of fine roots occurred in deep mineral soil for both species (1.24 g and 2.82 g/l for Douglas-fir and 0.98g and 2.24 g/l for ponderosa pine, respectively). No statistically significant differences were found in fine root content or concentration between species in any of the four soil horizons. Tree size was not a significant factor in fine root distribution in this study. Significant variables were horizon, distance from bole, and interactions among tree size, location of sample, and soil horizon. This study, which was part of a larger US Forest Service study to develop a predictive model of postfire tree mortality, provides baseline information that may be useful in predicting postfire damage to fine roots.

For nearly 20 years, foresters in the Oregon Coast Range have been witnessing a substantial decease in Douglas-fir (Pseudotsuga menziesii var. menziesii [Mirb.] Franco.) vigor and volume, caused by Swiss needle cast (SNC) disease. Currently, there are no solutions and disease severity is expected to worsen in coming years, but there is hope that aerially applied treatments of sulfur may be able to alleviate the effects of SNC. In this trial, volume, taper, and other attributes were examined on 120 Douglas-fir trees heavily infected with SNC for response to treatments of (1) sulfur, (2) sulfur + nutrients, and (3) control, which received no treatment. Tree attributes such as crown ratio, crown width, and sapwood area at crown base showed no statistically significant differences between treatments. Means of both foliage mass and years of needle retention also were not different between sulfur and control treatments. However, both of these attributes were different between the sulfur + nutrient and control treatments (P = 0.0599, 0.0205). Using a modified Kozak's (1988) variable exponent model form, taper analysis indicated that the taper of trees within the sulfur treatment was not significantly different from the taper of the control, while the sulfur + nutrient treatment showed decreased taper compared with the control (P =

Relationships between growing space per tree and tree growth components (dbh, height, percentage of live crown, height-diameter ratio, tree volume, and tree biomass) were studied in three single-species, 20-year-old Nelder plots in the Sierra Nevada. Study species included ponderosa pine (Pinus ponderosa [P.&C. Lawson]), coast Douglas-fir (Pseudotsuga menziesii var. menziesii [Mirb.] Franco) and giant sequoia (Sequoiadendron giganteum [Lindl.] Buchh.). Spacing distance between trees varied from 1.77 to 17.78 ft, and growing space per tree varied from 4.1 to 411.0 ft2 (computed using Thiessen polygons). Relationships between growing space and tree height, tree diameter, and percentage of live crown were all significant and showed increasing trends as growing space per tree increased. Height:diameter ratios were high at close spacing and decreased with increasing growing space. Volume growth and biomass per tree increased, whereas stand volume and stand biomass decreased with increased growing space. Ponderosa pine produced the most stand volume and biomass of the three species.

Changes in plant hormones and metabolites in long-shoot stems of interior Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco) during cone induction by gibberellic acid (GA) treatment were analyzed by high performance liquid chromatography-electrospray ionization tandem mass spectrometry in multiple reaction monitoring mode. A mixture of GA(4) and GA(7), including small amounts of GA(3) and GA(1), was stem-injected into each tree in amounts of 0, 4, 40 or 400 mg. One week after injection, concentrations of GA(4), GA(7) and GA(3) were elevated in all GA-treated samples. The ratio of GA(4) to GA(7) decreased significantly at Week 3. Absolute concentrations of all gibberellins declined sharply at Week 3 after GA application. After 5 weeks, GA(1) and GA(4) were below detection limits in all samples, and GA(7) and GA(3) were found only in the samples from trees treated with 40 or 400 mg of GA. Endogenous indole-3-acetic acid (IAA) concentrations increased following GA injection, and peaked at Week 2 or Week 3 in the trees treated with 40 or 400 mg GA, respectively. Injection of 400 mg of GA brought about a twofold increase in IAA concentration compared with control values. Injection of 40 and 400 mg of GA caused significant increases in stem dry mass in Week 5. Seed orchard data revealed that injection of either 40 or 400 mg GA enhanced female cone formation, whereas male cone formation was enhanced only by 400 mg GA. Slight decreases in concentrations of abscisic acid (ABA) and isopentenyl adenosine were observed after GA application. No significant changes were detected in the concentrations of ABA metabolites except for a slight decrease in the concentration of 7'-hydroxy ABA. The concentration of ABA declined during the growing season and the concentration of ABA glucose ester increased correspondingly.

We tested the ability of individual tree seedling protectors to deter mountain beavers from damaging Douglas-fir seedlings. Using captive mountain beavers in field pens, we tested 20 products representative of a wide range of barriers suitable for protecting individual tree seedlings from rodent damage. Eleven products protected 95% or more of seedlings from damage. Tree shelters and fabric shelters provided the most protection; 98 and 95% of seedlings were undamaged, respectively. Rigid mesh protector tubes protected 81% of seedlings, and protection netting protected 55% of seedlings. Purchase prices varied widely; protection netting was least expensive, followed by rigid mesh tubes, fabric shelters, and tree shelters. Seedling growth was greatest within fabric shelters and plastic tree shelters. Materials used to construct 15 of the 20 tree protectors were tested using captive mountain beavers in small sheltered pens. Here, samples of barrier materials were used to block access to a favored food. The four materials that excluded all test animals in all trials were from unvented tree shelters with solid seamless walls. Seven materials failed to exclude any animals in the sheltered-pen trials.

Aerial applications of chorothalonil fungicide were carried out annually over 5 consecutive years, 1996–2000, on three sets of paired, 2-ha units in a Douglas-fir plantation affected by Swiss needle cast in the Oregon Coast Range. The effect of treatment on disease control was evaluated annually from 2001 to 2004. One- and 2-year-old foliage in the fungicide-treated units had fewer fruiting bodies of the pathogen Phaeocryptopus gaeumannii compared with the unsprayed units for foliage sampled in 2001. Total needle retention was also greater in the fungicide-treated units after five consecutive annual fungicide applications. Reduced P. gaeumannii infection in the fungicide-treated units persisted for foliage produced in 2001, which did not receive direct fungicide treatment. Reduced infection levels in the 2001 foliage cohort in the treated units was presumed to be due to the effect of disease control on inoculum production. At 4 years following the final treatment application, infection levels averaged over four foliage cohorts (2000–2003) remained significantly smaller for the fungicide-treated units. Trees in fungicide-treated units retained 10–50% of the 2000 needle cohort (4-year-old needles) and 25–60% of the 2001 cohort in May 2004. However, there was no detectable effect of treatment on infection for 2002 foliage sampled in 2003 or for 2003 foliage sampled in 2004 (1-year-old needles), suggesting that the duration of disease control was relatively brief.

Laminated root rot caused by Phellinus weirii is a significant disease of western conifers; it is important to understand the effects of the disease on tree growth and survival and, for some management objectives, to develop treatments that will reduce those effects. This study was conducted in a 47-year-old Douglas-fir (Pseudotsuga menziesii) stand in northwest Oregon. First, we evaluated the effects of root system infection on diameter and height growth. Growth rates were lowest in trees with high infection levels; root infection level affected diameter growth more than height growth. Second, we evaluated the effects of fumigation treatments on tree growth. The nine treatments were as follows: three dosages of methylisothiocyanate (MITC), four dosages of chloropicrin (trichloronitromethane), one dosage of Vorlex [20% MITC, 80% chlorinated C3 hydrocarbons (v/v)], and a control. The fumigants were applied by inserting them into holes drilled into the base of live trees. After nine growing seasons, all three of the treatments applying different dosages of MITC and the treatment applying the lowest dosage of chloropicrin had higher tree survival rates than the untreated control, and the growth rates in those four fumigation treatments were not significantly different from growth in the surviving control trees.

We examined the microsite characteristics of 6,048 Douglas-fir seedlings at three regeneration sites in Washington state. Our objective was to determine the microsite characteristics that were most influential on seedling growth change over time. We analyzed microsite influences both individually and in concert with one another through regression-based techniques. Microsite parameters included soil impedance, topographic, and physical parameter measurements that were recorded at each seedling's location. Akaike's information criterion (AIC) was used to determine combinations of microsite parameters that were most strongly correlated with seedling growth. Multiparameter models explained between 15 and 39 percent of the variance in diameter growth. Prevalent terms from the strongest multiparameter models included soil penetration, log presence, stump presence, skid road presence, and topography. Individual microsite parameters for each regeneration site were also assessed for importance in explaining diameter growth using two additional methods. The first approach was to isolate the parameters that appeared in the strongest multiparameter models and to sum and contrast the AIC weights of all models in which they appeared. The second approach was to regress single parameters against seedling diameter growth. Results varied by site for both methods. AIC weight sums revealed that topographical depression and berms, the presences of logs and stumps, and soil penetration (pounds per square inch) as measured by a penetrometer were most influential, with values ranging from 0.31 (berm) to 0.82 (log). Regression analysis revealed that topographical depression, log presence, and soil penetration were significantly related to diameter growth, explaining between 6 and 29 percent of the variance in diameter growth. Combined results from the three regeneration sites suggest that preferred planting locations are near berms, in the transition zone associated with skid roads, and in soil that is neither too loose nor too compacted. Results from the Randle and Orting sites indicate that planting in topographical depressions should be avoided. Results from Orting indicate that seedlings should not be placed near logs, and Randle findings suggest not planting next to stumps.

Heartwood extractives (nonstructural wood components) are believed to be formed from a combination of compounds present in the adjacent sapwood and materials imported from the phloem. The roles of local compounds and imported material in heartwood formation could have important implications for the wood quality of species having naturally durable wood. Stable isotope composition (delta(13)C) was analyzed to assess radial variation in sapwood extractives, and to estimate the relative importance of adjacent sapwood extractives and imported photosynthate in the formation of heartwood extractives. Cellulose and extractives from the outer 39 annual rings of six Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) trees were isolated and their delta(13)C composition determined. Although the extractives and the cellulose showed different absolute delta(13)C values, the patterns of change over time (as represented by the annual rings) were similar in most cases. Within an annual ring, carbon isotope ratios of extractives were correlated with the cellulose isotope ratio (R2 = 0.33 in sapwood, R2 = 0.34 in heartwood for aqueous acetone-soluble extractives; R2 = 0.41 in sapwood for hot-water-soluble extractives). These data suggest that some sapwood extractives are formed when the wood ring forms, and remain in place until they are converted to heartwood extractives many years later. Sapwood extractives appear to be important sources of materials for the biosynthesis of heartwood extractives in Douglas-fir.

Coastal Douglas-fir (Pseudotsuga menziesii spp. menziesii (Mirb.) Franco) occurs over a wide range of environmental conditions on Vancouver Island, British Columbia. Although ecological zones have been drawn, no formal spatial analysis of environmental limitations on tree growth has been carried out. Such an exercise is desirable to identify areas that may warrant intensive management and to evaluate the impacts of predicted climate change this century. We applied a physiologically based forest growth model, 3-PG (Physiological Principles Predicting Growth), to interpret and map current limitations to Douglas-fir growth across Vancouver Island at 100-m cell resolution. We first calibrated the model to reproduce the regional productivity estimates reported in yield table growth curves. Further analyses indicated that slope exposure is important; southwest slopes of 30 degrees receive 40% more incident radiation than similarly inclined northeast slopes. When combined with other environmental differences associated with aspect, the model predicted 60% more growth on southwest exposures than on northeast exposures. The model simulations support field observations that drought is rare in the wetter zones, but common on the eastern side of Vancouver Island at lower elevations and on more exposed slopes. We illustrate the current limitations on growth caused by suboptimal temperature, high vapor pressure deficits and other factors. The modeling approach complements ecological classifications and offers the potential to identify the most favorable sites for management of other native tree species under current and future climatic conditions.

Purportedly, large Douglas-fir trees in the American Pacific Northwest use water stored in bole tissues to ameliorate the effects of seasonal summer drought, the water content of bole tissues being drawn down over the summer months and replenished during the winter. Continuous monitoring of bole relative water content (RWC) in two 110-120-year-old Douglas-fir trees with ThetaProbe impedance devices provided an integrated measure of phloem-sapwood water content over 4 years. Seasonal changes in RWC closely tracked cambial activity and wood formation, but lagged changes in soil water content by 2-3 months. The RWC in the combined phloem and sapwood markedly increased during earlywood production in the late spring and early summer to maximum values of 64-77% as plant available soil water (ASW) decreased by approximately 60%. With transition and latewood formation, RWC decreased to minimum values of 59-72%, even as ASW increased in the fall. The difference between minimum RWC in the fall and maximum RWC in midsummer was only approximately 5%. Seasonal changes in bole RWC corresponded to cambial phenology, although decreasing AWS appeared to trigger the shift from earlywood to latewood formation.

We consider tree and stand response to low, crown, and no thinningof well-differentiated, naturally regenerated even-aged Douglas-firstands over 15 years on a moderately productive Cascade Mountains siteand over 10 years on a highly productive Oregon Coast Range site.Regardless of treatment, trees in dominant and codominant crown classescontinued growing at preinitiation rates and contributed 92–100% ofstand growth 5–15 years later. Most leave trees in suppressed crownclasses died during the first 10 years and suppressed and intermediatecrown classes contributed little to stand growth because survivorscontinued to grow slowly. Low thinning remains the most reliablethinning method for increasing stand volume in high-quality trees.Crown or selection thinning may be used to achieve certain objectivesif managers carefully use information about response of trees invarious crown classes. Growth rates of residual stands will depend onthe amount of residual growing stock and the degree to which it iscomprised of vigorously growing dominant and codominant trees.Residual subordinate trees may provide snags but few living trees insmall-diameter classes. Implications for management of the Douglas-firare discussed.

Silvicultural regimes are becoming more intensive in the US Pacific Northwest, incorporating a multitude of treatments over the length of the rotation. Therefore, there is a need to understand not only how individual treatments affect forest productivity, but also how these treatments interact to determine productivity. To help launch the Planted Forest Productivity and Value Enhancement Program at Oregon State University, an extensive literature search was conducted over 9 different classes of silvicultural treatments and 10 different categories of measured responses. The objective was to examine the scope of our current knowledge base about intensive silvicultural practices in the Pacific Northwest, particularly the mechanisms by which various treatment combinations or regimes control the productivity of coastal Douglas-fir stands. The literature, 1984 through 2004, shows that studies were more likely to focus on a combination of silvicultural treatments or practices if they were applied during similar times of stand development. Very little documented research addressed the interactive effects of treatments applied sequentially over the rotation. Although most studies monitored growth, yield, and tree mortality, fewer studies investigated environmental, physiological, and morphological responses that are key to understanding and predicting how both tested and untested silvicultural regimes will affect forest productivity.

Douglas-fir beetle (DFB), Dendroctonus pseudotsugae, risk rating systems were developed for four USDA Forest Service ranger districts in northern Idaho. Risk rating systems were developed using a geographic information system, USDA Forest Service aerial detection survey maps, and nearest neighbor distances. Years where epidemic populations of DFB occurred over the four ranger districts were selected and risk rating systems were developed for each district. Nearest neighbor distances for between-year (t + 1) and between-2-year (t + 2) infestations were measured. Percentiles of nearest neighbor distances were determined and used to estimate distances at which 50, 75, and 90% of infestations occurred. On average, there was a 50% chance of an infestation occurring within 176 m from previous year infestations, 75% chance from within 517 m, and 90% chance from within 1,188 m. The between-2-year risk rating determined that there is a 50% chance of infestation occurring on average within 249 m, 75% within 627 m, and 90% within 1,332 m from infestations that occurred 2 years earlier. West. J. Appl. For. 21(4):173–177.

Douglas-fir beetle populations were monitored before and after thinning and felling of trees to create down wood in an 88-year-old Douglas-fir plantation in the Oregon Coast Range. Treatments included an unthinned control, thinning to a target of 75 trees/ha, and thinning to a target of 150 trees/ha. Actual mean tree densities on the plots after thinning were 406, 102, and 154, for the control, 75 trees/ha, and 150 trees/ha treatments, respectively. Fifty trees/ha were felled and left on all thinned plots to create down wood for ecological values. Catches in pheromone-baited traps indicated that the local beetle population increased for 1 year in response to felling and leaving large diameter trees in partial shade. Douglas-fir beetle entrance holes and brood were significantly more abundant on the sides of felled trees and wood borers were significantly more abundant on the upper surface suggesting that treatments that provide maximum exposure of felled trees will create the least favorable habitat for Douglas-fir beetles. However, there were no differences in Douglas-fir beetle entrance holes or brood densities in felled trees between the two thinning intensities. Douglas-fir beetle-caused tree mortality was significantly higher on thinned plots with residual felled trees compared with unthinned controls, although infestation levels were low on all plots (

Mean curves of increment and yield in gross total cubic volume and net merchantable cubic volume were derived from seven installations of the regional cooperative Levels-of-Growing-Stock Study (LOGS) in Douglas-fir. The technique used reduces the seven curves for each treatment for each variable of interest to a single set of readily interpretable mean curves. To a top height of 100 ft and corresponding average age of 45 years, volume growth and yield are strongly related to stocking level, being highest at the highest stocking levels. At that point, current annual increment is still far greater than mean annual increment. Thinning has accelerated diameter growth of the largest 40 trees per acre as well as of the stand average. Maximum volume production would be obtained at stand relative densities approaching the zone of competition-related mortality, although in practice considerations of feasibility of frequent entries and wildlife and amenity considerations would make somewhat lower average levels necessary.