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Juvenile tree survival will play an important role in the persistence of coniferous forests and woodlands in the southwestern United States (SWUS). Vulnerability to climatic and environmental stress declines as trees grow, such that larger, more deeply rooted juveniles are less likely to experience mortality. It is unclear how juvenile conifers partition the aboveground and belowground components of early growth, if growth differs between species and ecosystem types, and what environmental factors influence juvenile carbon allocation above‐ or belowground. We developed a novel data set for four juvenile conifer groups (junipers, piñon pines, ponderosa pines, firs; 1121 juveniles sampled, 221 destructively) in three height classes (

The U.S. Forest Service is reconsidering policies that limit the size of trees that can be removed in the course of restoration treatments in dry forests of eastern Oregon. To evaluate the effects of diameter limits on the ability of managers to meet restoration objectives, we used an existing network of long‐term research plots to summarize historical and contemporary structure and composition of mixed‐conifer forests within a one million‐ha study area in eastern Oregon. Then, we used a novel thinning simulation procedure to quantify the degree to which thinning using different diameter limits restored stands to historical conditions. Contemporary mixed‐conifer forests within the study area are significantly denser, have more basal area, and have a greater proportion of shade‐tolerant species than historical conditions. Our simulations of thinning under current policy that prohibits cutting of trees ≥53 cm show that a quarter of mixed‐conifer stands cannot be restored to within the historical range of basal area or density. Those stands that could be restored to within historical basal area ranges still had a substantially higher component of shade‐tolerant trees than historical stands. Permitting larger shade‐tolerant trees to be removed allowed restoration of all or most of stands to within historical structural and compositional ranges. Forest conditions in the late 1800s may not necessarily provide the best template for management because climate and disturbance projections suggest that eastern Oregon forests will be less well suited to shade‐tolerant species in the future. Adapting stands to future conditions will require robust monitoring of forest structural and compositional response to restoration treatments.

Following a wildfire, regeneration to forest can take decades to centuries and is no longer assured in many western U.S. environments given escalating wildfire severity and warming trends. After large fire years, managers prioritize where to allocate scarce planting resources, often with limited information on the factors that drive successful forest establishment. Where occurring, long‐term effects of postfire salvage operations can increase uncertainty of establishment. Here, we collected field data on postfire regeneration patterns within 13‐ to 28‐yr‐old burned patches in eastern Washington State. Across 248 plots, we sampled tree stems

Clark's nutcracker (Nucifraga columbiana) functions as a keystone seed disperser and ecological mobile link for many western conifers. The bird is the primary seed disperser for limber pine (Pinus flexilis), which is an important seed resource for the bird. In the Southern Rocky Mountains, annual variation in limber pine cone production and growing threats, such as exotic disease, require that nutcrackers rely on additional conifer seed resources. We investigated the utilization of limber pine, ponderosa pine (Pinus ponderosa), and Douglas‐fir (Pseudotsuga menziesii) as seed resources by nutcrackers to determine how temporal variation in seed production and maturation drives nutcracker seed resource and habitat use decisions. Working in Rocky Mountain National Park (RMNP) during three field seasons, we examined (1) cone production in limber pine, ponderosa pine, and Douglas‐fir, and seed energy availability across the RMNP landscape; (2) timing and likelihood of nutcracker seed harvest and caching behavior for each conifer species; and (3) predictors of nutcracker visitation to the different forest stand types. Each year starting in mid‐ to late August, nutcrackers foraged on limber pine seeds. In 2014 and 2015, nutcrackers transitioned from limber pine to harvesting ponderosa pine seeds. In 2016, a year of low ponderosa pine cone production but exceptionally high Douglas‐fir cone production, they transitioned from limber pine to Douglas‐fir seeds. Cone density was a significant predictor of nutcracker counts in every negative binomial regression model in which it was used. However, the best overall model, which included interaction effects, indicated that stand type, year, and month were better predictors. We interpret these three predictors as reflecting temporal variation in patterns of cone production and maturation among the three conifers but also in habitat use by nutcrackers. In all three years of study, limber pine alone did not provide sufficient energy resources for foraging and caching, and nutcrackers used an additional conifer seed resource. With potential future limber pine losses, these other seed resources may be essential to sustain a nutcracker population. We suggest that Douglas‐fir and especially ponderosa pine will serve as increasingly important food resources as limber pine declines across the montane West.

Dendroecological studies of historical tree recruitment patterns suggest mixed‐severity fire effects are common in Douglas‐fir/western hemlock forests of the Pacific Northwest (PNW), USA, but empirical studies linking observed fire severity to tree regeneration response are needed to expand our understanding into the functional role of fire in this forest type. Recent increases in mixed‐severity fires offered this opportunity, so we quantified the abundance, spatial distribution, species richness, and community composition of regenerating trees across a mixed‐severity fire gradient (unburned–high‐severity fire) 10 and 22 yr post‐fire, and use our results to inform a discussion of fire's functional role in western Oregon Cascades Douglas‐fir forests. Regeneration abundance was unimodal across the fire severity gradient such that the greatest mean abundance followed moderate‐severity fire (25–75% basal area mortality). Similarly, the greatest number of species was present within the most 25‐m2 regeneration quadrants (most extensive distribution) following moderate‐severity fire, relative to any other fire severity class. On average, species richness also exhibited a unimodal distribution across the severity gradient, increasing by 100% in stands that experienced moderate‐severity fire relative to unburned forests or following high‐severity fire, as predicted by the Intermediate Disturbance Hypothesis. Several distinct regeneration communities emerged across the fire severity gradient, including early seral tree communities indicative of those observed in initial and relay floristics successional models for this forest type. Most significantly, moderate‐severity fire alters successional trajectories and facilitates the establishment of a more diverse tree regeneration community than observed following low‐ or high‐severity fire. These communities are reflective of the diverse overstory communities commonly encountered throughout this forest type. The emergence of these diverse forests is unlikely to develop or persist in the absence of moderate‐severity fire effects, and may be perpetuated longer by recurring moderate‐severity fire relative to experiencing stand replacing fire. Therefore, moderate‐severity fire may be the most functionally important fire effect in Douglas‐fir forests and should be better represented in successional models and more prominent in ecologically based fire and forest management.

We developed an observational study to (1) examine differences in the structure of mature Douglas‐fir stands representing thinned, structural retention harvest and unmanaged conditions, and (2) assess the extent to which active management in mature stands expedites development of old‐growth structure, relative to two old‐growth indices. Time since treatment averaged 38 and 22 yr in thinned and retention harvest conditions, respectively, and stand age ranged from 106 to 193 yr when sampled. Differences in stand structure were apparent between all three management conditions, with attributes associated with stumps, live tree diameter diversity, understory vegetation, and vertical foliage structure being the strongest individual drivers of these differences. Mean old‐growth index scores were lower than expected of true old‐growth for each of the management conditions examined here, but were not significantly different between thinned and unmanaged stands. Our results suggest thinning in mature stands may promote certain elements of old‐growth structure, including foliage height diversity, but also indicate the need for provisions against the depletion of dead wood resources. Stumps are an understudied dead wood structure, and in actively managed mature stands, our results imply that stumps may provide a degree of functional substitution where down log availability is low.

Forest soil carbon represents a large, but slowly changing pool of carbon in forests. Understanding the response of soil carbon to forest management, including harvesting, is critical for determining overall stand and/or landscape carbon balance. This longitudinal study on nine randomly selected sites was designed to detect a 5% or greater change in mineral soil carbon storage following harvest. Soil samples were collected both pre-harvest and 3 to 3.5 yr post-harvest at 300 sample points on a fixed grid from each stand. A forest floor sample and mineral soil samples in depth increments of 0 to 15 and 15 to 30 cm were collected at every point. A soil sample at 30 to 100 cm (or 30–60 cm at two sites) was collected at 200 points. Each mineral soil depth fraction was separated into size fractions of

A review is presented to the article "A transdisciplinary framework for SLA in a multilingual world," published in a previous issue of the journal, on second language learning.

• Processes governing the fixation, partitioning, and mineralization of carbon in soils are under increasing scrutiny as we develop a more comprehensive understanding of global carbon cycling. Here we examined fixation by Douglas-fir seedlings and transfer to associated ectomycorrhizal fungi, soil microbes, and full-sibling or non-sibling neighbouring seedlings. • Stable isotope probing with 99% 13C-CO2 was applied to trace 13C-labelled photosynthate throughout plants, fungi, and soil microbes in an experiment designed to assess the effect of relatedness on 13C-transfer between plant pairs. The fixation and transfer of 13C-label to plant, fungal, and soil microbial tissue was examined in biomass and PLFAs. • After a 6-day chase period, approximately 26.8% of the 13C remaining in the system was translocated belowground. Enrichment was proportionally greatest in ectomycorrhizal biomass. The presence of mesh barriers (0.5 or 35 µm) between seedlings did not restrict 13C-transfer. • Fungi were the primary recipients of 13C-labelled photosynthate throughout the system, representing 60–70% of total 13C-enriched phospholipids. Full-sibling pairs exhibited significantly greater 13C-transfer to recipient roots in two of four Douglas-fir families, representing 3- and 4-fold increases (+ approx. 4 µg excess 13C) compared to non-sibling pairs. The existence of a root/mycorrhizal exudation – hyphal uptake pathway was supported.

Plant lesions affect disease impact, progression and host resistance. Root lesions caused by Armillaria ostoyae (Romagn.) Herink were inspected on 24‐ to 34‐year‐old planted Douglas‐fir (Pseudotsuga menziesii (Mirb.) Franco) pulled from the soil in five locations. Four hundred seventy‐nine lesions were measured for length (mm), expansion rate (mm/year) and lesion type. Lesion types were patch lesions on a root side, girdled lesions covering the root circumference and root collar lesions on the stem below ground. Non‐linear mixed modelling revealed that fungal lesion length at girdled and collar lesions increased but the expansion rate slowed as a power function of time, indicating increasing secondary inoculum and host resistance. Average fungal lesion expansion rate in girdled root and collar lesions was 127 mm the first year which then declined non‐linearly to 26 mm/year after 10 years. Fungal lesion length in patch lesions showed little change after the first year of infection. For girdled and collar lesions, fungal lesion length increased with tree size at the time of infection. Sites with a longer frost‐free period had shorter girdled root and stem lesions, probably because of more active host defence. Results indicate that mortality would be rare from one infection event. Furthermore, patch lesions pose a lower risk of mortality than other lesions because of a lower fungal lesion expansion rate and secondary inoculum. Tree size, lesion position, lesion type and fungal lesion expansion rate need to be considered when assessing the risk of lesions to individual tree survival. Techniques to minimize the disease impact are discussed.

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

Summary Climatic adaptations are the foundation of conifer genecology, but populations also display variation in traits for nitrogen (N) utilization, along with some heritable specificity for ectomycorrhizal fungi (EMF). We examined soil and EMF influences on assisted migration of Douglas-fir (Pseudotsuga menziesii var. menziesii) by comparing two contrasting maritime populations planted up to 400 km northward in southwestern British Columbia. Soil N availability and host N status (via δ15N) were assessed across 12 maritime test sites, whereas EMF on local and introduced hosts were quantified by morphotyping with molecular analysis. Climatic transfer effects were only significant with soil N concentrations of test sites as a covariate, and illustrated how height growth was compromised for populations originating from relatively dry or cool maritime environments. We also found evidence for EMF maladaptation, where height declined by up to 15% with the extent of dissimilarity in EMF communities of southern populations relative to local hosts. The results demonstrate how geographic structure in belowground environments can contribute to conifer genecology. Differences in the inherent growth potential of conifers may be partly related to nutritional adaptations arising under native soil fertility, and optimization of this growth potential likely requires close affiliation with local EMF communities.

Interior Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] is an economically and ecologically important forest tree species in the Inland Northwest that is universally limited by nutrient availability. A variety of other site conditions also limit forest growth and vigor that complicate our understanding of Douglas-fir nutrition in the region. In this report, we summarize existing scientific information on nutrition of interior Douglas-fir and draw conclusions about best management practices. A general N deficiency was confirmed through universal increases in tree growth and nutrient uptake following N fertilization. However, water availability and other nutrients, such as K, S, and B, frequently limit the response to N fertilization. Increasing the probability of a strong fertilizer response within the region requires critical information on site moisture availability, parent material, and foliar K, sulfate-S, and B concentrations. Such stand and site characteristics should guide management prescriptions, including appropriate harvest operations, slash management, site preparation, fertilization, and stocking levels. Synthesis of the available information on interior Douglas-fir nutrition and site characteristics provides a set of management guidelines and recommendations.

Forests dominated by Douglas-fir and western hemlock in the Pacific Northwest of the United States have strongly influenced concepts and policy concerning old-growth forest conservation. Despite the attention to their old-growth characteristics, a tendency remains to view their disturbance ecology in relatively simple terms, emphasizing infrequent, stand-replacing (SR) fire and an associated linear pathway toward development of those old-growth characteristics. This study uses forest stand- and age-structure data from 124 stands in the central western Cascades of Oregon to construct a conceptual model of stand development under the mixed-severity fire regime that has operated extensively in this region. Hierarchical clustering of variables describing the age distributions of shade-intolerant and shade-tolerant species identified six groups, representing different influences of fire frequency and severity on stand development. Douglas-fir trees400 years old were found in 84% of stands, yet only 18% of these stands (15% overall) lack evidence of fire since the establishment of these old trees, whereas 73% of all stands show evidence of at least one non-stand-replacing (NSR) fire. Differences in fire frequency and severity have contributed to multiple development pathways and associated variation in contemporary stand structure and the successional roles of the major tree species. Shade-intolerant species form a single cohort following SR fire, or up to four cohorts per stand in response to recurring NSR fires that left living trees at densities up to 45 trees/ha. Where the surviving trees persist at densities of 60-65 trees/ha, the postfire cohort is composed only of shade-tolerant species. This study reveals that fire history and the development of old-growth forests in this region are more complex than characterized in current stand-development models, with important implications for maintaining existing old-growth forests and restoring stands subject to timber management.

Under projected changes in global climate, the growth and survival of existing forests will depend on their ability to adjust physiologically in response to environmental change. Quantifying their capacity to adjust and whether the response is species- or population-specific is important to guide forest management strategies. New analyses of historic provenance tests data are yielding relevant insights about these responses. Yet, differences between the objectives used to design the experiments and current objectives impose limitations to what can be learned from them. Our objectives are (i) to discuss the possibilities and limitations of using such data to quantify growth responses to changes in climate and (ii) to present a modeling approach that creates a species- and population-specific model. We illustrate the modeling approach for Larix occidentalis Nutt. We conclude that the reanalysis of historic provenance tests data can lead to the identification of species that have population-specific growth responses to changes in climate, provide estimates of optimum transfer distance for populations and species, and provide estimates of growth changes under different climate change scenarios. Using mixed-effects modeling techniques is a sound statistical approach to overcome some of the limitations of the data.

Summary Fusarium species can cause damping-off and root rot of young conifer seedlings, resulting in severe crop and economic losses in forest nurseries. Disease control within tree nurseries is difficult because of the inability to characterize and quantify Fusarium spp. populations with regard to disease potential because of high variability in isolate virulence. Fusarium isolates were collected from healthy and diseased seedlings of Douglas-fir (Pseudotsuga menziesii) and western white pine (Pinus monticola) from a nursery in Idaho, USA. Molecular markers such as DNA sequences (mitochondrial small subunit and nuclear translation elongation factor 1-alpha) and amplified fragment length polymorphism were used to identify isolates as either F. oxysporum or F. commune. In addition, diagnostic primers were developed to detect and distinguish F. commune from F. oxysporum. In vitro and greenhouse virulence tests were completed on Douglas-fir germinants and seedlings. For Douglasfir germinants and seedlings, F. oxysporum isolates generally caused less severe symptoms, whereas most F. commune isolates caused mortality through damping-off. This is the first report of direct evidence that F. commune can cause damping-off disease on Douglas-fir seedlings under greenhouse conditions.

Facilitation of tree establishment by ectomycorrhizal (EM) networks (MNs) may become increasingly important as drought stress increases with climate change in some forested regions of North America. The objective of this study was to determine (1) whether temperature, CO2 concentration ([CO2]), soil moisture, and MNs interact to affect plant establishment success, such that MNs facilitate establishment when plants are the most water stressed, and (2) whether transfer of C and water between plants through MNs plays a role in this. We established interior Douglas-fir (Pseudotsuga menziesiivar.glauca) seedlings in root boxes with and without the potential to form MNs with nearby conspecific seedlings that had consistent access to water via their taproots. We varied temperature, [CO2], and soil moisture in growth chambers. Douglas-fir seedling survival increased when the potential existed to form an MN. Growth increased with MN potential under the driest soil conditions, but decreased with temperature at 800 ppm [CO2]. Transfer of 13C to receiver seedlings was unaffected by potential to form an MN with donor seedlings, but deuterated water (D2O) transfer increased with MN potential under ambient [CO2]. Chlorophyll fluorescence was reduced when seedlings had the potential to form an MN under high [CO2] and cool temperatures. We conclude that Douglas-fir seedling establishment in laboratory conditions is facilitated by MN potential where Douglas-fir seedlings have consistent access to water. Moreover, this facilitation appears to increase as water stress potential increases and water transfer via networks may play a role in this. These results suggest that conservation of MN potential may be important to forest regeneration where drought stress increases with climate change.

Summary Results are presented from several studies on the epidemiology of Armillaria ostoyae in Douglas-fir plantations in the interior cedar-hemlock (ICH) biogeoclimatic zone of British Columbia. Two plantations were monitored for mortality by A. ostoyae and other agents for 35 years after establishment. In these and other plantations ranging in age from 7 to 32 years, one or more of the following factors were determined: source of inoculum, mode of spread and characteristics of lesions on roots of excavated trees; symptom expression in relation to tree age and damage to the root system and years from initial infection to death on trees killed by the fungus. Mortality from A. ostoyae began in both plantations about 5 years after planting, reaching 30% in one and 11% in the other after 35 years. The spatial pattern of mortality was similar to that reported from New Zealand, France and South Africa; however, the temporal pattern differed, beginning later and, instead of declining, continuing at a nearly constant rate to the present. To age 10, nearly all infections were initiated by rhizomorphs; as plantations aged, the proportion of infections occurring at root–root contacts increased. In seven plantations, in moist and wet subzones of the ICH, from 23 to 52% of Douglas-firs had root lesions, with the higher incidences occurring on moist sites. The occurrence of aboveground symptoms, reduced leader growth and basal resinosis, was related to the percentage of root length colonized by A. ostoyae on trees with more than 30% of root length killed. Average time from infection to death increased from 1 to 2 years at age 6 to 22 years at age 33. The outlook for timber yield from Douglas-fir plantations in the cedar-hemlock zone is discussed. Management alternatives for reducing damage from A. ostoyae when regenerating sites are reviewed.

Commercial-aged Douglas-fir trees mechanically damaged during commercial thinning activities were investigated to quantify fungal taxa present 14years after thinning. A total of 235 wood cores from 18 damaged and 18 non-damaged control trees were obtained. Fungi were isolated on malt extract agar and molecular methods were used to identify 48 taxa. Damaged Douglas-fir trees were more than twice as likely to contain wood-inhabiting fungi as undamaged trees (p=0.07) and contained more than 2.5 times more fungi (p=0.006). However, typical Douglas-fir stem-decay fungi were not isolated. Fungi present were mostly endophytes and no significant differences were found in frequencies of decay/non-decay soft-rot fungi between damaged and control trees (p=0.67). Likewise, no significant differences were found for the trend in number of fungi isolates over radial depth into the stem between damaged and control trees (p=0.29). Frequency of fungal isolates was non-linearly related to depth in the tree bole. Significant differences between damaged and control trees (p=0.03) was influenced by the data in the outermost 3mm. With the exception of these data, there were no significant differences between damaged and control trees in the radial trend in fungal frequency (p=0.37). Results of this study suggest that wounding in commercial-aged Douglas-fir may not contribute significantly to occurrence and species composition of wood inhabiting fungi over the period of a short-rotation final harvest. However, damage mitigation is recommended supported by a related study showing vertical discolouration affecting all wounded stems. © 2010 Blackwell Verlag GmbH.

The identity of a reported Dendroctonus pseudotsugae attractant, 3-methyl-2-cyclohexen-1-ol (MCH-ol), was confirmed by GLC/MS analysis of volatiles collected over live attractive female. In bioassay with previously known attractants, MCH-ol synergistically evoked male arrestment and stridulation in the laboraotry and high attraction predominantly of males in the field. Verbenone was similarly identified and was synergistically active to a lesser degree. The known double effect of the antiaggragetive pheromone 3-methyl-2-cyclohexen-1-one (MCH) was confirmed, at it repressed response to the attractants at high concentration but at very low concentration it increased response to MCH-ol and frontalin. The highest field response occurred to these three components together. Comparative GLC of feces and volatiles from pairs supports the belief that fecal release of MCH with the other attractants is quantitatively less than the release stimulated by the presence of the male and/or its sonic signal. Zusammenfassung Weitere Komponenten des Aggregations-Pheromons von Dendroctonus pseudotsugae (Col., Scolyt.) Aus den Duftstoffen lebender Kafer von Dendroctonus pseudotsugae wurde 3-methyl-2-cyclohexen-1-ol (MCH-ol) gewonnen und seine Identitat chromatographisch sowie auch massenspektrometrisch bestatigt. In Laborversuchen bewirkte MCH-ol, in Verbindung mit den schon bekannten Pheromonen, eine stark zunehmende Anlockung sowie Stridulation der Mannchen. Auch in Freilandversuchen lockte dieses Pheromon die fliegenden Borkenkafer, vor allem die Mannchen, stark an. Als weiteres Pheromon wurde Verbenone aus den lebenden Borkenkafern gewonnen, doch war es synergistisch weniger aktiv. Die bekannte Doppelwirkung des antiaggregativen Pheromons 3-methyl-2-cyclohexen-1-one (MCH) wurde bestatigt: eine hohere Konzentration des MCH blockierte die Anlockung an die attraktiven Stoffe ganzlich, wahrend es in sehr geringer Konzentration die Anlockung an Frontalin und MCH-ol erheblich vergroserte. Die groste Anlockung wurde im Felde erzielt, wenn die drei Pheromone zusammen angeboten wurden. Vergleichende chromatographische Untersuchungen des Borkenkaferfrasses, des Kotes und der Duftstoffe zeigten, das die Freisetzung von MCH aus Borkenkaferkot quantitativ bedeutend geringer ist als die Freigabe, die durch die Anwesenheit des Mannchens und seine Stridulation stimuliert wird.

Observations on field populations of Adelges cooleyi sistentes showed that two redistribution phases occurred. The first phase took place in the short period between egg hatch and diapause, the second during mild periods in the winter after diapause had terminated. The resultant movement of sistentes on to previously uncolonised needles and needle upper surfaces was correlated with density and enabled the insects to exploit the needle cortex with less competition from neighbouring sistentes. On the lower surface the sistentes probed through the stomata. On the upper surface the vast majority settled in the median groove which necessitated intercellular probing through the epidermis and sub-epidermal sclerotized cells. Despite this difference in the mode of stylet penetration no differences in rate of development or egg production were observed. This was attributed to the single entry probe made by each sistens, the cortical cells being exploited by movement of the long stylets within the cortex. The rate of dislodgement was higher for sistentes in diapause on the upper surface. Dislodgement was minimised by the reduced movement to the upper surface in response to sistens density in the first redistribution phase, in comparison with the second, and by the tendency of the sistentes to settle in the sheltered median groove. The more pronounced second phase resulted in large numbers of sistentes moving on to the terminal lateral shoots where dislodgement by wind would have been greater during diapause. Zusammenfassung Die Art der Niederlassung der Douglasienwollaus-Sistenten auf reifen Nadeln der Douglasfichte Beobachtungen von Gebietsbestanden der Douglasienwollaus-Sistenten im Freien haben das Auftreten von zwei Neuverteilungsphasen erkennen lassen. Die erste Phase fand in dem kurzen Zeitabschnitt zwischen dem Eiausschlupfen und der Diapause statt, die zweite wahrend milder Wetterperioden im Winter nach Abschlus der Diapause. Die sich ergebende Fortbewegung der Sistenten auf bisher unbesiedelte Nadeln und Nadeloberflachen war der Dichte entsprechend und ermoglichte den Insekten, die Nadelrinde mit weniger Konkurrenz von benachbarten Sistenten auszubeuten. Auf der Nadelunterflache drangen die Sistenten durchs Stoma. Auf der Oberflache lies sich die vorwiegende Mehrheit in der Mittelspalte nieder, was das Durchdringen vom Zellgewebe der Epidermis und der sklerosen Zellen der unteren Epidermis erforderte. Trotz dieser Differenz in der Art der Stilettdurchdringung konnten keine Unterschiede in der Entwicklungsgeschwindigkeit oder Eierproduktion festgestellt werden. Dies wurde auf den Einzeleindrang jedes Sistenten zuruckgefuhrt, bei dem die Rindenzellen durch Bewegung des langen Stiletts innerhalb der Rinde ausgebeutet werden. Die Verlagerungsquote lag bei Sistenten in der Diapause auf der oberen Nadelflachehoher. Verlagerung wurde durch verringerte Bewegung auf der Oberflache auf Grund von Sistenten-Dichte in der ersten Neuverteilungsphase - im Vergleich zur zweiten - reduziert sowie durch die Tendenz der Sistenten zur Niederlassung in der geschutzten Mittelspalte. Die ausgepragtere zweite Phase hatte die Fortbewegung groser Mengen von Sistenten zu den seitlichen Endsprossen zur Folge, wo die Verlagerung durch Wind wahrend der Diapause groser gewesen ware.

The Douglas fir beetle antiaggregative pheromone, 3-methyl-2-cyclohexen-1-one (MCH), was identified as the major fraction of the antiaggregative pheromone of the spruce beetle. A slow-release granular formulation of MCH, which was field tested on downed Douglas fir and Sitka spruce trees in western Oregon, reduced attack only briefly with Douglas fir beetle but by 93.3% for five weeks with the spruce beetle. As in previous tests, glass vials of liquid MCH almost totally prevented attack on both species. Practical use of a granular formulation appears feasible but the rate of release must be improved for the Douglas fir beetle. Zusammenfassung Methylcyclohexenone-Granulat, ein Antiaggregations-Pheromon von Dendroctonus-Arten Das anti-aggregative Pheromon des Douglasien-Borkenkafers (Dendroctonus pseudotsugae Hopk.), 3-Methyl-2-cyclohexen-1-one (MCH) wurde auch als der wichtigste Teil des anti-aggregativen Pheromons des Fichten-Borkenskafers {Dendroctonus rufipennis Kirby) identifiziert. MCH wurde in Kornchen inkorporiert, die dieses Material langsam freigeben. Diese Kornchen wurden in Freilandversuchen auf liegende Fichten und Douglasien gestreut. Gegen den Fichtenkafer wurde auch flussiges MCH langs der Stamme in Glasrorchen angewendet. Das granulose MCH schutzte die Fichten gegen den Fichten-Borkenkafer fur 5 Wochen, dagegen Douglasienstamme gegen den Douglasien-Borkenkafer nur fur wenige Tage. Das Ausbringen von flussigem MCH auf den Fichtenstammen ergab jedoch volligen Schutz. Es scheint, als ob eine praktische Anwendung des MCH in granuloser Form gegen die beiden Borkenkaferarten moglich ist. Die Freigabe des MCH vom Praparat mus aber noch verbessert werden, um wahrend der ganzen Flugzeit des Kafers wirksam zu sein.

Five insect molt inhibitors (MI's) were mixed with artificial diet and fed to 3rd and 6th stage western spruce budworm (Choristoneura occidentalis) larvae and 2nd stage Douglas-fir tussock moth (Orgyia pseudotsugata) larvae. In general, tussock moth larvae were more susceptible than western spruce budworm larvae to these MI's. SIR 6874 was by far the most toxic to 3rd and 6th stage western spruce budworm, and diflubenzuron the least toxic. TH 75331 and EL-494 both showed substantial activity against this insect, while SIR 8514 was relatively less active but was still at least 3 times as toxic as diflubenzuron. Except for EL-494, there were no large differences in toxicity of these compounds to 2nd stage tussock moth larvae; EL-494 was 30–90 times less toxic than the others at the LC50. The other four MI's caused at least 50% mortality of 2nd stage tussock moth which were fed a diet containing less than 0.1 ppm of the MI's. Zusammenfassung Uber letale Wirkungen von funf an Choristoneura occidentalis Free. (Lep.: Tortricidae) und Orgyia pseudotsugata (McDonn.) (Lep.: Lymantriidae) verfutterten Hautungshemmstoffen TH 75331 und SIR 6874 zeigten eine sehr gute Wirkung auf beide Insektschadlinge. Auch SIR 8514 wirkte gut. Diflubenzuron zeigte sich als bester auf Orgyia pseudotsugata wirkender Chitinsynthesehemmer, war aber bei Choristoneura occidentalis weniger wirksam. Umgekehrt wirkte EL-494 ziemlich stark auf C. occidentalis, war aber bei O. pseudotsugata eines der schwachsten Praparate. TH 75331, der dem Diflubenzuron ahnlichste Chitinsynthesehemmer, zeigte sich wirksamer auf O. pseudotsugata als jener SIR 6874 war der starkste Hemmstoff bei C. occidentalis. Unsere Versuche bestatigten die Spezifitat aller 5 Praparate. Diflubenzuron ist im Begriff, in den USA registriert zu werden. Es ist sehr wirksam gegen O. pseudotsugata, aber nicht anzuwenden gegen C. occidentalis (Gillette et al. 1977; Granett et al. 1980). Unsere Versuche zeigten, das gewisse Chitinsynthesehemmer-Praparate wirksamer als Diflubenzuron gegen C. occidentalis sind. SIR 6874 benotigt vor dem Erscheinen auf dem Handelsmarkt weitere Untersuchungen mit C. occidentalis. Die Untersuchungen weisen nachdrucklich darauf hin, das man nie die toxikologischen Eigenschaften verwandter Praparate gegen verschiedene Insektenarten innerhalb derselben Ordnung verallgemeinern soll.

Polyethylene envelopes containing 3-methylcyclohex-2-en-1-one sorbed on filter paper were tested as a deployment technique to prevent attack by Dendroctonus pseudotsugae on single trees or groups of trees of high value. Test logs were protected by all three release rates tested, estimated at 0.46–0.12 mg/hr. Zusammenfassung Kontrolliertes Freigabesystem von anti-attraktivem Pheromon 3,2-MCH des Douglasien-Borkenkafers Das anti-attraktive Pheromon des Douglasien-Borkenkafers, 3-methylcyclohex-2-en-1-one (kurz 3,2-MCH genannt), wurde in Filterpapier absorbiert und in Polyathylenumschlagen eingeschlossen, in Freilandversuchen als eine kontrollierte Freigabetechnik gegen den Befall einzelner wertvoller Baume (in Parkanlagen etc.) durch den Kafer getestet. Das Pheromon wurde in drei verschiedenen Freigabe-Raten, namlich 0,48 mg, 0,24 mg und 0,12 mg per Stunde in Polyathylenumschlag freigesetzt. Die Versuchsstamme wurden durch die Freigabe des Pheromons in diesen drei Konzentrationen vor Borkenkaferbefall vollig geschutzt.

Zusammenfassung Ergebnisse der Freilanduntersuchungen, die in den nordamerikanischen Douglasien waldern an der Kuste des Stillen Ozeans durchgefuhrt wurden, haben gezeigt, das die Holz- und Borkenkafer durch die fluchtigen Harzsubstanzen des Wirtbaumes (Alpha- und Betapinen, Limonen, Camphen, Geraniol und Alpha-terpineol) zu ihren Brutstammen gelockt werden. Diese Anlokkung wird als Primar- oder Wirtsanlockung bezeichnet, da sie durch den Wirt verursacht wird und vor der sekundaren Massenanlockung stattfindet. Sie ist besonders auffallend bei Kafern, die frisch gefallene Douglasien bevorzugen, wie z. B. Dendroctonus pseudotsugae, Gnathotrichus sulcatus und Pseudohylesinus nebulosus. Sobald die Kafer in die Wirtpflanze eingedrungen sind und mit dem Fras begonnen haben, produzieren die Weibchen einen Geruchsstoff, der eine starke sekundare Anlockung zur Folge hat, wie es bei D. pseudotsugae, Trypodendron lineatum und wahrscheinlich auch bei den beiden Pseudohylesinus-Arten der Fall ist. Gewisse Unterschiede in dem Geruchsverhalten und in der Pheromonproduktion der Kafer sind erkennbar, die zu weiteren Unterschieden in der Kafer-biologie zu korrespondieren scheinen. Wahrend bei den monogamen Arten gewohnlich die Weibchen zuerst in die Wirtpflanze eindringen (Trypodendron, Dendroctonus) und dann Pheromone abgeben, sind es bei den polygamen Ips die Mannchen. Bei D. pseudotsugae findet die Kopulation im Frasgang statt, der Lockstoff wird vom unbefruchteten Weibchen abgegeben, nach der Begattung jedoch in stark vermindertem Mas. Mit Beginn der zweiten Brut-periode sezernieren die Weibchen erneut den Lockstoff. Diese Pheromon-sekretion steht wahrscheinlich in Beziehung zur Wiederaktivierung der Ovarien. Die Kopulation des linierten Nutzholzborkenkafers dagegen findet auf der Stammoberflache statt; das Pheromon wird nur durch die befruchteten Weibchen produziert. Im Gegensatz zu D. pseudotsugae dauert die Anlokkung wahrend der ganzen Flugperiode des Kafers an.

Western spruce budworm rarely reach epidemic status west of the Cascade Mountain's Crest in Oregon while in the eastern portion of the state outbreaks occur periodically. Foliage from westside Douglas-fir var. menziesii seedlings grown in a common garden caused no significant larval mortality but some pupal mortality was noted when bioassayed with a laboratory colony of spruce budworm. Conversely, foliage from seedlings of the Douglas-fir var. glauca grown in the same garden caused a wide range of larval mortality ranging from nearly 100% mortality to no significant killing. Pupal mortality was significantly higher than control (artificial diet with var. menziesii foliage supplement) and peaked at 40%. Two year old foliage taken from mature trees of var. glauca gave highly variable bioassay results. In the 1981 foliage collections trees varied significantly in the larval mortality they produced, and in the 1982 collections there was significant variation in both larval and pupal mortality. There was also variation in time. In one stand 9 of 10 trees produced higher larval mortality, and lower pupal mortality, in 1982 than in 1981. Control mortality remained relatively constant between the two years. This change in foliage defenses was coincident with the very early stages of a budworm outbreak in the vicinity of the stand, though we detected no budworm in our sampled trees. In the continental environments occupied by var. glauca, environmental stress such as drought may alter the trees ability to produce allelochemics, and thus play a key role in regulating eastside spruce budworm populations. The apparent lack of constitutive defensive chemicals in the foliage of var. menziesii populations suggests that inducible defenses may play a role. Our results did not show the latter to be important, however, this may be due to our experimental technique. Alternatively, in the mesic, species-rich, ecosystems occupied by var. menziesii, predators and parasites may act to maintain budworm populations at relatively low levels. Zusammenfassung Genetische und umweltbedingte Einflusse auf die Resistenz der Wirtspflanze gegen Blatt- und Nadelfras: Douglasie und Triebwickler Der Triebwickler Choristoneura occidentalis tritt in Oregon westlich vom Kamm der Kaskaden fast nie epidemisch auf, wahrend ostlich davon haufig Massenvermehrungen vorkommen. Nadel-material von Samlingen der im Westen vorkommen Douglasie var. menziesii verursachte im Laborversuch bei Larven des Triebwicklers kaum, bei Puppen nur wenig Mortalitat. Dagegen fuhrte Nadelmaterial von Samlingen der Varietat glauca (die im gleichen Garten aufgewachsen waren), zu unterschiedlichen Mortalitatsraten zwischen 0 und 100%. Die Puppenmortalitat war signifikant hoher als in unbehandelten Vergleichszuchten (Kunstfutter mit Zusatz von menziesii-Nadeln) und hatte ihr Maximum bei 40%. Zwei Jahre alte Nadeln von Altbaumen der var. glauca fuhrten zu sehr variablen Ergebnissen. Verschiedene Nadelherkunfte des Jahres 1981 unterschieden sich signifikant hinsichtlich der von ihnen verursachten Larvenmortalitat, 1982 waren signifikante Unterschiede fur Larven- und Puppenmortalitat festzustellen. Daneben ergaben sich zeitliche Unterschiede: in einem Bestand fuhrten 9 von 10 Baumen 1982 zu hoherer Larven- und geringerer Puppenmortalitat als 1981. Die Mortalitatsraten der Vergleichszuchten blieben demgegenuber in beiden Jahren relativ konstant. Dieser Wechsel in der Nadelqualitat fiel zusammen mit den Anfangen einer Triebwickler-Massenvermehrung in der Nahe des Versuchsbestandes; doch wurden in den Testbaumen keine Larven gefunden. In den kontinentalen Lagen der var. glauca wird moglicherweise durch umweltbedingte Stresfaktoren die Fahigkeit der Baume zur Produktion von Signal- und Wehrstoffen verandert; dies konnte der Schlusselfaktor fur die Dichteregulierung der im Osten Oregons vorkommenden Triebwickler-Populationen sein. Offensichtlich fehlen primare Wehrsubstanzen in den Nadeln der Douglasien-Varietat menziesii im Westen Oregons; es wird vermutet, das sekundare Abwehr-mechanismen eine Rolle spielen. Die Versuchsergebnisse geben hierfur zwar keinen Hinweis; dies mag aber an der Methodik liegen. Moglicherweise werden aber auch in den artenreichen Okosystemen, in welchen die var. menziesii vorkommt, die Triebwickler-Populationen durch Rauber und Parasiten auf ihrem geringen Dichteniveau gehalten.

Hydraulic vulnerability of Douglas-fir (Pseudotsuga menziesii) branchlets decreases with height, allowing shoots at greater height to maintain hydraulic conductance (K shoot) at more negative leaf water potentials (Psi l). To determine the basis for this trend shoot hydraulic and tracheid anatomical properties of foliage from the tops of Douglas-fir trees were analysed along a height gradient from 5 to 55 m. Values of Psi l at which K shoot was substantially reduced, declined with height by 0.012 Mpa m(-1). Maximum K shoot was reduced by 0.082 mmol m(-2) MPa(-1) s(-1) for every 1 m increase in height. Total tracheid lumen area per needle cross-section, hydraulic mean diameter of leaf tracheid lumens, total number of tracheids per needle cross-section and leaf tracheid length decreased with height by 18.4 microm(2) m(-1), 0.029 microm m(-1), 0.42 m(-1) and 5.3 microm m(-1), respectively. Tracheid thickness-to-span ratio (tw/b)2 increased with height by 1.04 x 10(-3) m(-1) and pit number per tracheid decreased with height by 0.07 m(-1). Leaf anatomical adjustments that enhanced the ability to cope with vertical gradients of increasing xylem tension were attained at the expense of reduced water transport capacity and efficiency, possibly contributing to height-related decline in growth of Douglas fir.

Seventy trees from seven stands 50–650 years old were selected for this investigation of crown structural development in Pseudotsuga menziesii. All branches, limbs, and trunks were nondestructively measured for size, structure, and location while climbing the trees with ropes. These data were used to generate a computer model of each tree's crown that was error-checked trigonometrically. Leaves, bark, cambium, and wood were quantified by using limited destructive sampling to develop predictive equations that were applied to the complete inventory of structures in each tree's crown. Summations of these values yielded whole-tree estimates of several structural variables. A second set of equations was then developed to predict these whole-tree parameters from simple, ground-based measurements. Principal components analysis of 24 tree-level variables revealed two orthogonal dimensions of structure that accounted for 71.3% and 12.4% of total variation in the 70 trees. The first dimension represented a gradient...