Phellinus weirli (Murr.) Gilbertson is an important root rot of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) in western North America. The effect of site and tree species on the growth of P. weirii along roots can be measured by inoculation using naturally infected root material or P. weirii cultured on sterile wood. This thesis reports the development of an inoculation technique using naturally infected root material to infect Douglas-fir and western hemlock (Tsuga heterophylla (Raf.) Sarg.). Intact naturally infected root sections of Douglas-fir used as an inoculum source resulted in P. weirii growing on approximately 87% of roots inoculated. Further inoculations were made using infected root sections split longitudinally with the exposed wood surface placed in contact with the host root. Subsequently an attempt was made to evaluate the influence of xeric, submesic and hygric sites, within the Demonstration area of the UBC Research Forest, Maple Ridge, on inoculation and growth of P. weirii along roots of Douglas-fir and western hemlock. Dry soil conditions experienced during the summer of 1978 reduced the expected number of successful infections of host roots to approximately 20%, 26 weeks after installation. All inoculations of a third series established after heavy rains in the late summer infected the roots of both Douglas-fir and western hemlock, verifying that the technique was successful when conditions were cool and moist. P. weirii inoculum used was collected from two sources, Haney and Surrey. Laboratory studies indicated incompatibility between the two sources when raised on agar media and field results indicated a longer retention of viable P. weirii in inoculum blocks from the Surrey source. / Forestry, Faculty of / Graduate

Cytokinin levels were determined by bioassay on a seasonal basis, for two species of dwarf mistletoes (Arceuthobium douglasii and Arceuthobium tsugense) and their respective hosts, Douglas-fir (pseudotsuga menziesii) and western hemlock (Tsuga heterophylla). The highest cytokinin levels occurred in early Spring for all of the samples studied. However, with the exception of the first growth segments of Douglas-fir, the levels of cytokinins detected were significantly greater in infected tissue and aerial shoots of the mistletoe than in the healthy tissue. Further studies were carried out on Spring and Winter samples to determine the kinds of cytokinins present. High performance thin layer chromatography and gas liquid chromatography results showed that zeatin riboside (ZR) was the only detectable cytokinin in Winter samples. ZR was also detected in all Spring samples excepting the aerial shoots of A. douglasii. Two other cytokinins were also detectable in Spring samples. Zeatin was present in aerial shoots from both dwarf mistletoes and in the infected fifth growth segments from Douglas-fir and in infected western hemlock tissue. Zeatin occurred in the healthy tissue only in first growth segments of Douglas-fir. The 2iPA was detectable in the aerial shoots of the dwarf mistletoe, in the fifth grmvth segments of Douglas-fir, and in the infected tissue from western hemlock. These results are discussed with particular reference to the role of cytokinins in the physiological interactions between the host and the parasite.

The structuring of canopy arthropod communities was reviewed and investigated in relation to tree species diversity and its component factors, interspersion of different species and density of each tree species. Fifteen treatments of Douglas-fir (Pseudotsuga menziesii) and red alder (Alnus rubra) (various densities and proportions of each) were randomly assigned to 0.073 ha plots, replicated three-fold at each of two locations in Western Oregon: the Cascade Head Experimental Forest and the H.J. Andrews Experimental Forest. The six treatments used in this study were two densities of Douglas-fir and red alder monoculture (1000 trees/ha and 500 trees/ha), and mixtures of Douglas-fir and red alder (500 trees/ha of each) planted simultaneously or red alder planted 6 years after the Douglas-fir. Trees were initially planted in 1985-1986. The arthropod communities were sampled in the summer of 1998 by bagging and pruning branches from the mid-canopy of both tree species. Multivariate analyses distinguished the arthropod communities found on each tree species and geographical location, but not among the different diversity and density treatments. Many arthropod taxa and functional groups residing on a single tree species had significantly different abundances between locations. The most commonly encountered taxon, Adelges cooleyi Gillette (Homoptera: Adelgidae), was most abundant on Douglas-firs in the 500 trees/ha monoculture and the mixture with younger red alder, and least abundant in the mixture with both species planted simultaneously (the 1000 trees/ha Douglas-fir monoculture was intermediate). Adelgids showed no significant response to location, but did respond to combinations of location x treatment. The functional group of sap-feeders was dominated by adelgids, and showed similar treatment differences on Douglas-fir. Defoliators on red alder responded in abundance to location, treatment (most abundant in the 500 trees/ha monoculture and even-aged mixture, least abundant in the 1000 trees/ha monoculture), and location x treatment. This study demonstrated that tree species and geographical location are the primary determinants of forest arthropod community composition at this spatial scale. However, tree species diversity and density can affect the abundance of certain arthropod taxa, apparently through some combination of resource quality and plant apparency. / Graduation date: 2000

Aphids are a widespread family of plant pests, whose abilities to suppress shoot and root growth are well documented for many terrestrial plants. Only a few studies have been conducted on conifer aphids of the genus Cinara. Cinara pseudotsugae are known to attack Douglas-fir seedlings, an important crop in the Pacific Northwest. Douglas-fir are most susceptible to aphid damage as seedlings, especially in nurseries where conditions favor aphid outbreaks. A parasitoid wasp (Pauesia sp.) attacks C. pseudotsugae, and may be useful as a biological control agent. Studies of its natural history and host interactions are needed to assess its potential as a bio-control agent. This study examined the effects of an experimental range of aphid densities on the growth of total shoot and root volume and biomass and shoot morphology of Douglas-fir seedlings. Eighteen-week tests explored short term effects of different aphid feeding intensities in both the greenhouse and field. Long term effects were tested by exposing greenhouse seedlings to 16 months of aphid feeding. The ability of the plants to recover was tested by allowing one set of seedlings to grow aphid free for one year, after being exposed to aphid feeding for 18 weeks. The success rate of parasitoids over an 18 week period was compared to aphid density in both greenhouse and field tests. Increasing aphid destiny was significantly related to decreasing root and shoot dry weights in greenhouse tests. Growth suppression increased slightly during the second year of testing, regardless of whether or not aphid feeding continued. The results for root and shoot volumes were highly variable. However, root tissue density was significantly reduced after the second year of testing. Few shoot characteristics showed consistently significant aphid effects among the trials. Stem diameter and height decreased and needle density of new buds increased significantly with aphid feeding in most tests. Root and shoot growth of field plants did not show any significant aphid effects. Percentage of parasitoid success was independent of aphid density except at the lowest aphid densities. There was a block effect on parasitoid success in the field test, that may have been a result of varying environmental conditions. These results indicate that even short term aphid feeding can have long lasting effects on plant growth and structure. The effect on shoot and root growth was small, but there were no signs of recovery. The long term effects of the reduced root tissue density on Douglas-fir is unknown. / Graduation date: 1998

No description available.

Two study plots containing Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) newly infested by Douglas-fir beetle (Dendroctonus pseudotsugae Hopk.) were established and photographed with large-scale (1:1000), colour infrared film on July 29. 1979 - approximately three months after possible insect attack. Ground checking confirmed attacked trees and also showed that at the time of photography all trees had visually green, healthy-appearing foliage. All trees, both attacked and non-attacked in each plot were matched to their photographic images, and visual photo interpretation for damage types and densitometric analysis of the original transparencies were done. For each tree-crown image included, the yellow, magenta and cyan dye layer density measurements were taken and these values plus three ratios derived from them were tested statistically using analysis of variance and stepwise discriminant analysis. Significant differences were found between the optical density values of the images of healthy and attacked trees. The ratio values had much smaller variances than did the individual dye layer densities and all three ratios showed significant differences between healthy and attacked trees. Stepwise discriminant analysis produced significant separation of damage classes. Two-thirds of the successfully attacked trees were correctly classified and were confirmed by a second ground check in January, 1980. It is concluded that successfully beetle-attacked trees have a unique spectral signature than can be detected on colour infrared air photos approximately three months after initial attack when the trees still support visually green, healthy-appearing foliage. / Forestry, Faculty of / Graduate