Frost damage to sapling size plantation Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco.] in the central interior of B.C. was identified as the major cause of dieback and canker through tree dissections. Prominent frost rings in the wood and frost damage to buds and shoots corresponded to the dates of dieback initiation and canker events throughout the history of the plantations. Frost rings and frost cankers were reproducible using an artificial freezing technique. Symptomatic frost-damaged buds and elongating shoots were described for Douglas-fir, white spruce [Picea glauca (Moench) Voss] and subalpine fir [Abies lasiocarpa (Hook.) Nutt.]. The effect of growing season frost was most noticeable on early flushing trees. Frost and dieback damage was most severe on concave and flat landforms, which are conducive to cold air pooling on nights with strong radiative cooling. Several pathogens isolated from recently killed stems were identified from fruiting bodies and culture. Leucocytospora kunzei (Sacc.) Urban was the pathogen most commonly isolated from the edge of expanding cankers and progressive dieback margins. Sclerophoma semenospora Funk was commonly found fruiting on dead stems and leaders killed by frost or by mechanical means. Cinara pseudotaxifoliae Wilson feeding caused latent cankers on one year old leaders of Douglas-fir, which are thought to be activated by frost. Boron levels of both healthy and severely affected trees were in the intermediate range, and were not considered to play an important role in frost or pathogen susceptibility for Douglas-fir in the interior. / Forestry, Faculty of / Graduate

Cell division was obtained from cultured microspores of Douglas-fir on medium supplemented with auxin, cytokinin, and sucrose, but without medium salts. Embryogenic callus was initiated from excised mature and immature zygotic embryos of Douglas-fir on media supplemented with cytokinin and auxin. Precotyledonary embryos produced most of the embryogenic calli in the cultures. Secondary embryogenic callus production, and subsequent subculturing, were required for the establishment of stable embryogenic callus lines for both mature and immature zygotic embryos. Somatic embryos at the precotyledonary stage were obtained in high frequency when Douglas-fir embryogenic callus was transferred onto hormone-free medium supplemented with 1% activated charcoal, while some cotyledonary somatic embryos were obtained from hormone-free medium supplemented with low ABA levels (0-10 uM). The level of ABA in the maturation medium significantly affected the quality of the somatic embryos produced. Cell suspensions were established from embryogenic calli and have been maintained for over one year. Protoplasts were isolated from suspension, cell colonies and calli were regenerated from protoplasts. GUS and CAT genes were successfully introduced into protoplasts of Douglas-fir via electroporation, and their transient expression was obtained 2-4 days after electroporation. The results so far indicate that the production of somatic embryos via embryogenesis in vitro is obtainable, and the application of direct gene transfer via electroporation for genetic engineering of trees in this species is promising. / Forestry, Faculty of / Graduate

An interlocking group of studies was carried out to address the concept of the free-to-grow seedling. This term is an attempt to define plantation establishment in a manner cognizant of early hazards from brush competition and other stresses. The studies were carried out on one- to five-year old Douglas-fir plantations on moist, rich sites in coastal British Columbia. Data were generated from field measurements and harvest sampling of the planted trees and their associated competing vegetation. On these productive sites, tree growth appears sensitive to interference from neighbouring brush species. An index implying competitive shading was derived and proved a useful measure of stress on the planted trees, particularly when measured as a relative production rate. Growth losses varied with the light environment at specific crown positions. Therefore, height growth was not affected by competition until the terminal leader was shaded. This allows height growth to remain independent of competition level until the tree is overtopped on these sites. The trees studied showed great ability to acclimate and survive relatively heavy shading by competing vegetation. After competition release treatment, trees were generally able to re-acclimate the current seasons growth to the increased light intensity. Growth following competition release was significantly improved by a chemical brush control treatment, while mechanical brushing resulted in little net change in competition levels after one year. The growth on these trees in the year following release from competition was also best measured as a relative production rate. The vegetation on untreated areas followed a strong successional trend during the period studied. The trend was a function of differences in height growth patterns between species modified by leaf area index. In general, woody species tend to succeed geophytes and microphanerophytes on these sites. A proposed free-to-grow definition in biological terms states that a tree must be free from competitive shading on the terminal leader and increasing in height relative to the competing vegetation. The free-to-grow status can be assessed by on a threshold value of the competition index and a predictive model for the comparative height increment of the tree and its competitors. / Forestry, Faculty of / Graduate

Variability in the relationship between tree leaf area (TLA) and selected stem measurements was examined in three Douglas-fir stands (Pseudotsuga menziesii (Mirb.) Franco, var. menziesii) that were less than 50 years-old, spaced to approximately 550 to 650 stems/ha, and differed in soil moisture and nutrients. Attention was given to the effect of mean annual ring width (MARW), cross-sectional area of the live bark (ALB - a surrogate measure of relative nutrient storage in the stem), and cross-sectional area of the most recent annual rings equal in number to the number of whorls in the live crown (ALC), on variability in the relationship between TLA and cross-sectional area of sapwood (ASW). At breast height, basal area, ASW, and cross-sectional area of sapwood plus live bark (ASWLB) were not linearly related to TLA, and linear regression equations using log transformed variables varied significantly between sites. Nonlinear regression equation for ASW at breast height was: TLA = 0.064ASẆ¹•³³ (I² = 0.856). Including D (the distance between breast height and the center of the live crown) in the nonlinear equation, did not significantly improve the regression. Tree leaf area prediction models using stem measures from the base of live crown (blc) had higher adjusted R² values than models using stem measures from breast height. At the blc, basal area, ASW, and ASWLB were linearly related to TLA (adjusted R² = 0.926, 0.908, and 0.934, respectively). Multiplying ASW by MARW did not improve the fit of the regression models. Multiplying ASW by ALB improved the linearity of the relationship of ASW at breast height to TLA. The best fitting TLA model overall used the product of ASW at blc and ALB at blc as the independent variable (adjusted R² = 0.967). The results indicate that research into the allometric relationship of TLA to stem measures should give consideration to more than hydraulic measures and include measures of bark function. At breast height and the blc, the independent variable ALC was linearly related to tree leaf area and had higher adjusted R² values than did ASW. In most trees the ALC stem measure was found to include a portion of heartwood area. The strong relationship between TLA and ALC suggests that a given transpiring leaf mass or area is related to a proportional amount of conducting stemwood and physical support stemwood. A quick alternative approach for estimating individual tree leaf area using photographs taken at fixed distance and angle from the target tree did not result in a reliable tree leaf area prediction technique. The difficulty of obtaining views of the tree crown which were not obstructed by adjacent tree crowns was the major obstacle. Using a fixed distance and camera angle was a problem because of variable tree heights. However, altering these fixed positions introduced additional variation into the tree leaf area estimation. Mean specific leaf area (SLA) varied significantly by site, needle age class, and crown position. Mean SLA per needle age class per branch can be predicted with 95% confidence and a 10% allowable error using six 10-needle samples. / Forestry, Faculty of / Graduate

Failure of pitched-tapered glulam beams in tension perpendicular to grain has been attributed to the inadequacy of the present method of calculating stresses. In this thesis, the factors of time and size for tension perpendicular to grain were investigated to determine how they would affect the allowable stresses. A total of 229 Douglas Fir glulam blocks of two sizes were loaded for ?0 days in uniform tension perpendicular to grain to investigate time effect. Test data were analyzed by developing estimates for the strength ratios. Results indicate that strength reductions increase at an increasing rate with the logarithm of time. The presently used time factors were shown to be conservative and could be increased for the 2-month, the 7-day and the 1-day durations. Experimental data also indicate that the present time factors may be non-conservative for load durations less than 5 minutes and more than ?0 days. In addition, short-term testing of 24-0 Southern Pine glulam blocks of three sizes was performed to investigate size effect. Results show that the relationship between specimen strength and volume is a straight line in a log.-log. plot, thus verifying the weakest-link model for Southern Pine. Comparison with Douglas Fir data taken from literature was also made. It was found that Southern Pine is definitely stronger than Douglas Fir In tension perpendicular to grain. Size effect, however, is almost identical for the two species. Significant difference was observed in the long-term test results between the two specimen volumes. This may be due to the effect of size, but it could also be caused by the different stress levels used for the two volumes. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

Recent bark beetle outbreaks have caused extensive tree mortality in conifer forests across western Northern America, which has altered forest fuels. These changes have raised concerns about forest health and wildfire risk. Studies focused on interactions between bark beetles, forests fuels, and changes in fire behavior have been primarily led in upper elevation forests characterized by high-severity fire regimes, principally in lodgepole pine (pinus contorta Douglas ex Loudon) and Engelmann spruce (Picea engelmannii Parry ex Engelm) forests. Few studies to date have addressed bark beetle fuel interactions in lower to middle montane forest characterized by a mixed-severity fire regime, with available research focused strictly on assessing fuel load conditions or stand structural changes. The goal of this research was to quantify and characterize surface and canopy fuel changes in middle montane interior Douglas-Fir (Pseudotsuga menziesii (Mirb.) Franco var. glauca (Beissn.)) forest infested by Douglas-fir beetle (Dendroctonus pseudotsugae Hopkins), while also measuring physical and chemical changes to foliage in terms of moisture content and terpenes, which are known to play important roles in foliage flammability. Our results revealed few changes in surface fuels following Douglas-fir beetle infestations aside from a significant increase in litter depth and loading in red stage sample plots. Substantial changes to canopy fuels were detected in the red stage of an outbreak with a significant reduction in foliar moisture content measured as tree crowns faded from a healthy green phase to red. During this period, volatile emissions and within-needle concentrations of terpenes increased, including some terpenes previously associated with increased foliage flammability in other tree species. Furthermore, aerial fuel parameters that estimate the likelihood of crown fire initiation, including canopy bulk density and canopy base height, showed a substantial reduction in gray stage sample plots. Based on our findings we judge the influence of Douglas-fir beetle activity on altering fuels is most pronounced in the aerial fuels complex. Our results suggest bark beetle affected interior Douglas-fir stands with a high percentage of trees in yellow and red crown phases could have an increased threshold for crown fire initiation based on higher levels of flammable monoterpenes and lower foliar moisture content.

Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (leaves 107-124).

The incidence of baculovirus disease in susceptible insect hosts may be used to estimate future host population sizes and estimate the relative defoliation of these populations for economically important insects. We developed an Enzyme-linked immunosorbent assay (ELISA) that was specific to two native baculovirus pathogens of the Douglas-fir tussock moth (DFTM), that was more sensitive and accurate (R2=0.99) than microscopic counts of virus polyhedron inclusion bodies, and more accurate than PCR or Southern hybridization for the direct detection of baculovirus disease. We also developed a field-based "dipstick" assay that was sensitive enough to detect virus disease prior to host mortality and did not require virus purification from macerated insect tissues, supporting its use for on-site field surveys. Finally, we used ELISA to establish, for the first time, a method to detect persistent sublethal baculovirus infections. Our work may contribute to more accurate understanding of the incidence and influence of persistent sublethal infections on insect hosts.

Thesis (M.S.)--Oregon State University, 1995. / Typescript (photocopy). Includes bibliographical references (leaves 50-58). Also available on the World Wide Web.

Concern about potential losses of biological diversity and productivity following clear-cut logging of old-growth forests in British Columbia led me to compare ectomycorrhizas in old-growth and mature stands of Douglas-fir. Two sites were selected, each with an old-growth (288-, 441-yr-old) and a mature stand (87-, 89-yr-old) well-matched in tree species, soil and topography. A total of 120 soil cores ≤15 cm deep by 5 cm diameter were taken at random from four 60 m square plots (one per stand). Samples were taken in spring and fall at each site. All morphological types of ectomycorrhizas in one half of each core were counted and characterized in detail. Ectomycorrhizal abundance and frequency was compared in logs, stumps, the forest floor over bedrock or gravel, the forest floor near the base of trees, the forest floor elsewhere, and mineral soil. Old-growth and mature stands were very similar in richness, diversity and types of ectomycorrhizas. Sixty-nine types of ectomycorrhizas were described. Nineteen types each accounted for more than one percent of the 17,500 ectomycorrhizal root tips examined, and eighteen types were found in five or more of the 120 soil cores. Extrapolation indicates a total richness of roughly 100 types in the four plots. Co-dominant fungi were Cenococcum geophilum Fr. (24% of all ectomycorrhizal root tips), a Rhizopogon Fr. of the section villosuli (10%), Hysterangium vitt. (9%), Lactarius deliciosus (Fr.) S.F.G. (6%), and Piloderma fallax (Libert) Stalpers (4%). Cenococcum geophilum, Rhizopogon Fr. and L. deliciosus were abundant in both mineral soil and organic substrates, Piloderma fallax was associated with decayed wood, and Hysterangium and type 27 were in organic substrates only. A bright greenish-yellow felty type was found in 5 cores in mineral soil only. The similarity of the ectomycorrhizal communities of old-growth and mature stands was probably due to their proximity ($<$200 m apart) and the similarity of their vegetation and soil. Differences may occur at some sites if ectomycorrhizal succession has been delayed or redirected as a result of frequent or severe disturbance, lack of old-growth legacies (logs and stumps), or lack of old-growth stands from which fungi can disperse. / Graduate