The Pacific Coast form of Douglas-fir in natural forest succession
is an intermediate species thriving in the Coast Range and
Cascade Mountains of the Pacific Northwest. This species constitutes
26 percent of the standing timber in the United States, and 24 percent
of the nation's annual timber harvest. Characteristics of...
Cultivated lilies include many garden varieties in addition to
the Easter lily, Lilium longiflorum Thunb. A popular member of
the garden group is Lilium speciosum Thunb., whose leaves can be
discolored by a virus symptom described as streak mottle. This
disorder is characterized by dashes of chlorotic tissue interspersed
with...
The effects of dwarf mistletoe on fuel in precommercial ponderosa pine stands: Dwarf mistletoe and healthy stands were sampled by vertical planar intercept and whole tree biomass sampling techniques to measure
fuel loading in ground and crown fuels. Differences in size, distribution, and vitality of fuel were shown to depend...
Knowledge of post-dispersal seed fates and other regeneration characteristics is
crucial for predicting abundances and distributions of populations and, ultimately,
community species composition and diversity. Seed fate studies, however, are rare
primarily due to the difficulty of determining seed fates and causes of mortality.
This thesis investigated post-dispersal seed fates...
Crater Lake, located in the southern Cascade mountains of Oregon, is the seventh deepest lake in the world. Unlike a majority of the deepest lakes in the world, found in continental rift valleys, Crater Lake is in the caldera of a volcano. For the young at heart and mind, those...
The fungal ascomycete genus Otidea as represented in the Pacific Northwest of North America includes eight well known species and two poorly-known species. Cladistic analysis utilizing characters from ribosomal DNA and morphology allowed the development of a robust phylogenetic species concept for Otidea. The combination of characters from the ribosomal...
The hypothesis that inoculation of transplants with vesicular-arbuscular mycorrhizal (VAM) fungi before planting into saline soils would alleviate salt effects on growth and productivity was tested on lettuce (Lactuca sativa L.) and onion (Allium cepa L.). A secondary hypothesis was that the fungi isolated from a saline soil would be...
An important disease of Vitis vinifera production in Oregon and all other commercial growing regions is powdery mildew of grape, caused by the obligate fungal pathogen Uncinula necator (Schwein.) Burril. Grape production can be characterized as a long-term investment in the establishment and maintenance of the vineyard. Establishment times have...
Late blight, caused by Phytophthora infestans, is a devastating problem to potato production in many parts of the world. While the foliar phases of this disease are well characterized, tuber infection, leading to quality losses and disease perpetuation, is less well understood. Experiments were conducted during 1998 and 1999 in...
Active habitat management plays a key role in the preservation of native ecosystems and rare species, especially in the Willamette Valley of Oregon, where natural succession to woodlands threatens the few wetland prairies remaining after 150 years of agriculture and urbanization. Sidalcea nelsoniana, listed as threatened under the federal Endangered...
Cephalosporium stripe, caused by the soil-borne ascomycete Cephalosporium gramineum, is becoming an increasingly important disease of winter wheat (Triticum aestivum) in several areas of the world, especially where stubble mulch is practiced to maintain soil moisture and prevent erosion. As cultural control of the disease is infeasible and no fungicides...
I surveyed epiphytic macrolichens and bryophytes in six stands in each of seven riparian stand types in the Oregon Coast Range. This study (Chapter 2) describes the association of epiphytes with stand types and the corresponding potential of forest canopy conversions to affect epiphyte communities. Species composition, diversity, and representation...
Plagiobothrys hirtus (Boraginaceae) is a state and federally listed endangered plant found only in Douglas County, Oregon. This vernal pool endemic has historically been threatened by agricultural conversion of seasonal wetlands in the Sutherlin area, and is currently being eradicated as habitat is lost due to the rapid urban development...
The sensitive lichen Usnea longissima Ach., formerly a fairly common circumboreal species, has been extirpated from much of its range (e.g., Eastern Europe). Although the U.S. Pacific Northwest (PNW) remains a relative stronghold for the species, U longissima faces increasing pressure in the region from habitat loss, air pollution, and...
Riparian forests in the Idaho Panhandle, north of Whitebird, were surveyed for rare riparian lichen species. The region was stratified into nine geographic units and by stream size. Eighty-one plots were surveyed for lichen community, stand and river characteristics. Variables important to lichen community composition included regional differences, elevation, climatic...
Seed piece to plant transmission of the potato late blight pathogen, Phytophthora infestans, occurred with isolates of the clonal lineages US-8 in Oregon and US-11 in Washington in field trials. Average transmission rate across potato cultivars was 0.5 and 2.4% with US-8, and 0.8 and 1.0% with US-11 in 1999...
More than half of the recognized genera of positive strand RNA viruses employ polyprotein processing as one of the strategies for their genome expression. Normally, this processing is mediated by virus-encoded proteinases that belong to the trypsin-like or papain-like family. In particular, papain-like, leader proteinases were found in diverse families...
Forests in the Pacific Northwest receive very little nitrogen through atmospheric deposition and thus studying the nitrogen cycle in this region can provide insights into how the unpolluted nitrogen cycle functions. I examined the fate of organic nitrogen versus inorganic nitrogen and the effect of tamlins on N retention by...
Drought resistance among genotypes of Port-Orford-cedar (Chamaecyparis lawsoniana (A. Murr.) Pan., Cupressaceae) seedlings was evaluated both in the field and in the greenhouse. Field water potentials (Ψ) of 5-year-old seedlings were measured at two high-elevation plantation sites where summer drought occurs. Measurements of Ψ were compared to survival two years...
The primary goal of this dissertation research was to assess the use of compost for the control of several foliar and soil borne diseases commercially important in the Pacific Northwest. The use of compost teas to control of gray mold (Botrytis cinerea) on geraniums, powdery mildew (Podosphearapannosa var. rosae), rust...
In the canyon grasslands of Garden Creek Ranch Preserve in Idaho, where the threatened plant Silene spaldingii occurs and invasion by the exotic species Centaurea solstitialis and Bromus tectorum is proceeding rapidly, I examined environmental and community patterns of site invasion, and evaluated the apparent influence of invasion on Silene...
As large-scale restorations of degraded rangelands are initiated, land managers need to
understand how decades of dominance by the invasive annual grass, cheatgrass (Bromus tectorum
L.), have altered ecosystem processes. One way to assess such alterations is by observing
differences in decay rates, since decomposition is determined by factors such...
The focus of my thesis is ethnobotany which seeks to examine
botanical resources and their context within particular cultures. My ethnographic
research identifies and interprets the cultural processes woven into Oregon's
coastal basketry through spirituality, environmental habitats, and utilized plant
species. This is augmented with botanical research addressing the question...
In addition to its longstanding recognition as an influential evolutionary process, interspecific hybridization is increasingly regarded as a potential threat to the genetic integrity and survival of rare plant species, manifested through gamete wasting, increased pest and disease pressures, outbreeding depression, competitive exclusion, and genetic assimilation. Alternatively, hybridization has also...
This thesis examines factors limiting understory herb presence and flowering in young second-growth Douglas-fir (Pseudotsuga menziesii) forests on the west side of the Cascade Mountains, Oregon, USA. I studied the belowground effects of canopy trees on understory herbs and shrubs in old-growth forests using trenched plots from which tree roots...
Competitive exclusion has been the mechanism hypothesized to account for the biological control of fire blight disease of pear and apple by the bacterium Pseudomonas fluorescens A506 (A506). Recent laboratory assays demonstrated, however, that A506 produces an antibiotic that is toxic to the fire blight pathogen, Erwinia amylovora, when cultured...
For the past several years vegetable growers in Oregon's Willamette Valley
have experienced reduced yields in their sweet corn plantings. We conducted
studies to 1) describe the symptomology and etiology of the disease, 2) test a root
rot rating system we developed to evaluate factors in the disease syndrome, and...
A necrosis at the tip of cones was observed on hop (Humulus lupulus), cultivar "Nugget", grown in Oregon in the early 1990's. Fusarium sambucinum and F. avenaceum were recovered from symptomatic cones in 1998 and preliminary inoculation experiments suggested both Fusarium species could cause hop cone necrosis. Studies were carried...
The objective of this dissertation is to introduce low-cost processing methods for the fabrication of ZnO transparent thin-film transistors (TTFTs). A novel method for depositing ZnO body layers via spin-coating of a zinc nitrate-based spin solution is presented. The processing conditions of spin-coated ZnO are optimized to produce continuous and...
The sudden oak death pathogen, Phytophthora ramorum, is present in southwestern Oregon, and while an eradication effort is underway, the potential impact of the polyphagous pathogen on surrounding vegetation is unknown. Plant communities in the area are substantially different from those affected in California, although tanoak (Lithocarpus densiflorus), evergreen huckleberry...
In the wetland prairie of William L. Finley National Wildlife Refuge (FNWR) in western Oregon, we investigated the response of Delphinium pavonaceum Ewan (peacock larkspur, Ranunculaceae), an endangered perennial forb, to four unreplicated dormant season fire regimes of 0, 2, 4, or 10 fires that were applied over a 12-year...
Primary disease gradients of wheat stripe rust, caused by the aerially dispersed fungal pathogen Puccinia striformis, were measured in Madras and Hermiston, OR in the springs of 2002 and 2003. Disease foci were created by inoculating a 1.52m x 1.52m area in each of three replicate field plots (6.1m wide...
I studied the water relations traits, twig conductivity, C'3 isotopic composition,
and wood density of three conifer and five angiosperm species in western Oregon. This
study took place from spring 2002 to fall 2003 on four sites. Species were selected to
represent the diversity of drought tolerance of woody plants...
The unifying purpose of this dissertation was to describe, model, and map
relationships between epiphvtic macrolichen communities and air quality in Ibrests of
northern and central California. First, multivariate analyses were used to subdivide the
large study area into three model areas with similar climate, topography, and lichen
communities: the...
Foliar respiration forms a large component of the carbon balance of any coniferous forest. We examine seasonal, interannual, spatial and interspecific variation of foliar maintenance respiration in a forest in Washington, USA, with measurements made quarterly for >4 years on 400-year old trees of Pseudotsuga menziesii, Tsuga heterophylla and Thuja...
Fuel reduction treatments are being applied to public lands, affecting significant acreage at considerable expense. This study compares the short term effects on a chaparral plant community of two different fuel reduction methods, brush mastication and "hand piling and burning" (HPB). Ceanothus cuneatus dominated the southwestern Oregon study sites where...
In March 2005 the Oregon State University Herbarium launched its new, free online Oregon Vascular Plant Atlas for public use. This Atlas allows users to access location information from over 385,000 vascular plant specimen and observation records in the state of Oregon. The potential applications of such spatial information are...
Phytophthora ramorum, a plant pathogen, is the cause of sudden oak death and ramorum blight and shoot die-back. It has a wide host range including many native forest species and common nursery plants. The lack of knowledge regarding infection biology of P. ramorum limits our understanding of its ecology and...
Monophyly of the gomphoid-phalloid clade was confirmed based on multigene phylogenetic analyses. Four major subclades (Hysterangiales, Geastrales, Gomphales and Phallales) were also demonstrated to be monophyletic. The interrelationships among the subclades were, however, not resolved, and alternative topologies could not be rejected statistically. Nonetheless, most analyses showed that the Hysterangiales...
Cordyceps is a genus of perithecial ascomycetes. It includes over 400 species
that are pathogens of arthropods and parasites of the truffle genus Elaphomyces. Based
on the morphology of cylindrical asci, thickened ascus apices and filiform ascospores,
it is classified in the Clavicipitaceae (Hypocreales), which also includes endophytes
and epiphytes...
Golden paintbrush (Castilleja levisecta Greenman) historically inhabited the prairies of the Willamette Valley, Oregon. However, this Pacific Northwest endemic is currently restricted to eleven sites in the Puget Trough of Washington and British Columbia. Recovery criteria call for the establishment of new populations throughout the species historic range, including the...
The objective of this study was to characterize an unknown agent associated with decline in black raspberry (Rubus occidentalis) in Oregon. A virus was found consistently associated with decline symptoms of black raspberries and was named Black raspberry decline associated virus (BRDaV). Double stranded RNA extraction from BRDaV-infected black raspberry...
Soil organic matter (SOM) is the terrestrial biosphere's largest pool of organic carbon (C) and is an integral part of C cycling globally. Soil organic matter composition typically can be traced directly back to the type of detrital inputs; however, the stabilization of SOM results as a combination of chemical...
Torrubiella is a genus of entomopathogenic fungi in the Clavicipitaceae
(Ascomycota). Species of the genus produce superficial perithecia on a loose mat of
hyphae that forms directly on the host. The genus is estimated to contain about 70
species. Torrubiella is hypothesized to be a close relative of Cordyceps because...
In early 2000, unusual mortality of a native North American tree, golden chinquapin, was reported by the USDA-Forest Service. Dying trees exhibited girdling cankers in the inner bark of the lower bole, branch flagging and defoliation. Isolations from necrotic tissues and soil associated with diseased or killed trees yielded Phytophthora...
Pyrenophora tritici-repentis, causal agent of tan spot of wheat, produces multiple
host-selective toxins (HSTs), including Ptr ToxA, encoded for by ToxA, Ptr ToxB,
encoded for by ToxB, and Ptr ToxC. Variable distribution of these three HSTs among
different isolates of P. tritici-repentis, both singularly and in all possible combinations,
defines...
Data from nuclear ribosomal internal transcribed spacer regions (nrITS) and chloroplast DNA (cpDNA) have failed to resolve phylogenetic relationships in Pinus. To provide greater interspecific resolution, five low-copy nuclear genes were developed from mapped conifer anchor loci. Four genes were sequenced from species representing all Pinus subsections. Individual loci do...
In response to concerns about excessive stand densities and high-severity wildfires, land managers in the western United States are carrying out extensive programs of fuel reduction thinning. How will these sudden reductions in canopy cover and associated changes in habitat affect native and exotic herbaceous vegetation and canopy species regeneration?...
Prairies were once the dominant vegetation type in Oregon's Willamette Valley. Land use conversion, fire suppression, succession, and invasive species have reduced Willamette Valley prairies to less than 1% of their historical area. The remnant prairies that persist today are small in size and are highly fragmented. Marginal strips of...
