Species' distributions across the landscape are perhaps the least understood yet most conspicuous features of life on earth. Ecologists have long studied species' distributions; yet, many questions remain about why species occur where they do. Such questions persist largely because species' distributions are complex systems with challenging properties like non-linearity,...
Whitebark pine (Pinus albicaulis) is an iconic North American high-elevation tree species currently threatened by climate change, mountain pine beetle, and white pine blister rust (WPBR), a lethal disease caused by the non-native fungal pathogen Cronartium ribicola. In collaboration with the USDA Forest Service Dorena Genetic Resource Center, germplasm was...
Cyanobacterial harmful algae blooms (cyanoHABs) are a growing concern worldwide due to damage of ecosystems and threats to human health. Previous research indicates that plant humics from aquatic and wetland vascular plants are effective inhibitors of cyanobacterial metabolism and growth and may be useful as control agents for mitigating cyanoHABs....
The two most economically important plant pathogens in the Pseudoperonospora (Peronosporaceae) genus are P. cubensis, causal agent of cucurbit downy mildew, and P. humuli, causal agent of hop downy mildew. These organisms have been shown to be very closely related phylogenetically and morphologically. In 2005, researchers in Korea proposed that...
Rhizopogon vesiculosus is a common ectomycorrhizal (EM) symbiont of Pseudotusga menziesii (Douglas-fir) in the coast range of the Pacific Northwest. The species has been studied for its systematics, genet size, population structure, and competitive ability in several field and experimental studies. This thesis seeks to provide a more thorough characterization...
The antibiotics, streptomycin sulfate and oxytetracycline, are used widely for fire blight suppression in the Pacific Northwest region of the United States. The efficacy of streptomycin, however, is compromised by widespread streptomycin-resistance in E. amylovora populations, and oxytetracycline is only partially effective. Consequently, for several years, the aminoglycoside antibiotic, kasugamycin...
A multi-year field study was conducted in Oregon and Washington to evaluate the influence of nitrogen fertilization rate and timing on cone quality, nitrate accumulation in cones, severity of powdery mildew (caused by Podosphaera macularis), arthropod pests, and the stability of conservation biological control of the twospotted spider mite (Tetranychus...
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3.1 Cone yield A,E, and I; alpha-acids B, F, and J; total oil C, G, and K; and cone color
D
Purposeful introductions of exotic species for rehabilitation efforts following wildfire are common on rangelands in the western U.S., though potential ecological impacts of introduced species in novel environments are often poorly understood. One such introduced species, Kochia prostrata (L.) Schrad (forage kochia) has been seeded on over 200,000 ha throughout...
Hypersensitive response-like (HR-like) needle reactions to infection by the white pine blister rust pathogen, Cronartium ribicola, have been reported for several species of five needle pines native to western North America. The best-studied examples are in Pinus monticola and P. lambertiana. In these species a "needle spot" phenotype has been...
Rhizopogon is a large genus of ectomycorrhizal (EM) fungi that grows in association with host trees of the family Pinaceae. We have conducted a series of studies investigating the ecology and evolutionary biology of the EM symbiosis shared between R. subgenus Villosuli and trees of the genus Pseudotsuga. Two members...