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...
Denitrifying bioreactors are an edge-of-field treatment technology particularly well suited for nitrate removal from subsurface (tile) drainage effluent of agricultural lands. The effectiveness of a proposed denitrifying bioreactor is site-specific and depends upon the complicated interplay of field and environmental parameters controlling discharge events, nitrate concentrations, subsurface temperatures, dissolved oxygen...
In intensively managed forest plantations in the northern Oregon Coast Range, herbicides are often applied during site preparation and early stand regeneration to reduce competition for resources for planted conifer seedlings. In addition to reducing competition for crop trees, herbicide applications may affect soil processes including decomposition and nutrient cycling,...
Soil food webs process the majority of terrestrial carbon, and influence overall ecosystem function. A primary distinction among soil food webs is based on fungal versus bacterial pathways of decomposition; these lead to fundamentally different soil function, and are expected to differ in dominance between meadows and forests. This assumption...
The role of the nonionic surfactant Tween 80 on the behavior of the therapeutic recombinant protein Factor VIII (rFVIII) was investigated at solid/liquid and air/water interfaces. In order to provide a model system to compare results obtained for the complicated rFVIII-Tween system, a well-characterized globular protein lysozyme was used. The...
Amphibian biodiversity is in rapid global decline, due in part to the fungal disease chytridiomycosis, caused by Batrachochytrium dendrobatidis (Bd). Susceptibility to Bd and chytridiomycosis varies between species and populations. Skin peptides and symbiotic skin bacteria appear to be important mechanisms of Bd resistance. However, not much is known about...
Biogeochemical mechanisms employed by key organisms, or symbiotic associations of organisms, transform the function and structure of their environment through processes recognized as ecosystem engineering. This dissertation seeks to investigate organism-ecosystem interactions that serve globally significant ecological functions in marine systems and impact how systems respond to environmental change. Using...
Many studies suggest that weedy plant species are most successful when
soil nitrogen in abundant. Consequently, I used soil nitrogen manipulations to
determine if altering nitrogen would affect the establishment of both weedy and
native plant species in a western Oregon wetland prairie. In two studies, we
added carbon amendments...
The Normalized Burn Ratio and Composite Burn Index were used to classify burn severity in three sites that experienced lightning-ignited wildfire in the year 2000. The effect of burn severity (unburned, low, moderate, and high severity classes) was investigated on vegetation and soil microbial community composition. Vegetation communities showed a...
The role of insect herbivores in the nutrient cycling dynamics of forest ecosystems remains poorly understood. Although past research in herbivory has focused primarily on the deleterious effects that insects can have on tree growth and mortality, the overall effects of herbivory are more complex. Herbivores have the potential to...