Winter wheat is commonly grown in rotation with leguminous and non-leguminous crops in the Willamette Valley. For agronomic, economic, and environmental reasons it is important to understand the influence of previous crops on availability of N and other nutrients. Objectives of this study were: (1) to evaluate the effects of long-term rotations on winter wheat response to N fertilizer, and (2) to evaluate the use of Plant Root Simulator���(PRS) probes for measuring soil N mineralization and N availability to winter wheat. Field experiments were conducted over three growing seasons in plots of `Stephens' soft white winter wheat at Hyslop farm. Plots receiving 0, 50, 100, 150 and 200 kg N ha����� at Feekes GS 4 were sampled to determine above ground N uptake, grain yield, and grain protein. In spring 1998, PRS probes were placed in 0 kg N ha����� plots and removed at one-week or two-week intervals. In autumn 1998, probes were placed in unfertilized plots and removed at 1-week, 4-week, and 8-week intervals. Probes measured the availability of NH������-N, NO������-N, K���, Ca�����, Mg�����, and P0��������-P. Grain yield and N uptake were greater for wheat following clover as compared to following oats. Three-year average fertilizer equivalent values calculated from N uptake and grain yield data were 44.5 kg N h����� and 49.0 kg N h�����, respectively. The similarity of these independent measurements suggest that differences in N availability were the primary reason for the rotation effect. PRS probes also detected rotational differences in N availability. Average N recovered by probes sampled at 1-week intervals indicated that there was 63% as much NO������-N available to wheat following oat as compared to clover. Wheat recovered 64% as much N following oats as compared to clover. This suggests that PRS probes are an effective method for predicting relative amounts of plant available N. PRS probes also detected rotational differences in plant available potassium. Agronomic responses are useful for assessing the availability of nutrients that are limiting plant growth. PRS probes, on the other hand, are effective for assessing the availability of both limiting and non-limiting nutrients. / Graduation date: 2000

This thesis studies the diffusion of architectural types and the rise of regionally distinct typologies in the Willamette Valley's settlement period (1840-1865) in Oregon. Using Geographic Information Systems (GIS) to analyze the dispersion of architectural types within the Willamette Valley revealed trends amongst the extant settlement architecture samples. Brownsville, Oregon, was identified to have a locally-specific architectural subtype, the closer study of which enabled deeper investigation of the development of architectural landscapes during the Willamette Valley's settlement period. Field and archival research revealed that the appearance of an architectural subtype, at least in Brownsville, was not directly connected to a shared provenance of settlers but rather came about through a number of regionally-specific circumstances, especially an active local carpenter community.

xii, 127 p. ： ill. (some col.) / I developed software to incorporate the FlamMap fire model into an agent-based model, Envision, to enable the exploration of relationships between wildfire, land use, climate change, and vegetation dynamics in the Willamette Valley. A dynamic-link library plug-in utilizing row-ordered compressed array lookup tables converts parameters between polygon-based Envision data and grid-based FlamMap data. Modeled fires are determined through Monte-Carlo draws against a set of possible fires by linking historic fire data to future climate projections. I used classification and regression tree (CART) and logistic regression to relate ignitions to human and land use factors in the Willamette Valley above the valley floor from 2000-2009. Both methods showed decreasing distance to major and minor roads as key factors that increase ignition probability for human ignitions but not for lightning ignitions. The resulting statistical model is implemented in the FlamMap plug-in to provide a dynamic ignition probability map over time. / Committee in charge: Dr. Bart Johnson， Co-Chair； Dr. Scott Bridgham ，Co-Chair； Dr. John Bolte； Member

Preservation of rare plant species often requires establishment of new populations. Survivorship surveys are the most common method of post-introduction monitoring. However, they provide an incomplete picture of establishment success. This study is an attempt to develop a model for determining establishment success by determining the factors affecting recruitment in introduced populations of a rare species. Erigeron decumbens is an endangered forb endemic to the Willamette Valley of western Oregon. Several populations of E. decumbens have been introduced by governmental and non-profit agencies. While there has been some monitoring of the survival of introduced plants, no systematic surveys have measured recruitment in the new populations. We monitored recruitment in five introduced populations, and compared abiotic and biotic characteristics in these and five stable natural populations. Seventy percent of introduced populations produced fewer than one recruit for every three survivors. Thirty percent produced at least one and one half recruits for every one survivor. The factors that affected recruitment were site specific. Low recruitment (less than one recruit per three survivors) was associated with dominance by exotic species (Dactylis glomerata, Rosa eglanteria, Vicia tetrasperma, and Leucanthemum vulgare), high litter cover, high soil electrical conductivity, and low silt levels. Recruitment was highest at sites with higher native plant species richness and soil characteristics falling within the variation of large natural populations. Viable seed number per individual had the strongest linear relationship with recruitment, demonstrating that seed viability could be a strong limitation for this species (r² = 0.83). The results of this study suggest numerous guidelines for future reintroductions of E. decumbens. This research also demonstrates the utility of recruitment surveys to determine factors important in the success of introduced populations of rare plant species. / Graduation date: 2013

671 pages / It is evident from a study of the history of these Indians, that the Warm Springs, together with other Oregon tribes, did not benefit greatly from the Government system of colonizing and reservations. It is true that they received the advantages of education and medical service furnished by the Government in accordance with treaty stipulations, and some protection from their enemies; but the value of these advantages may be questioned.

Graduation date: 2006 / Habitat loss causes a reduction in available resources for wildlife, alters the configuration of remaining habitat, and may isolate wildlife populations. White-breasted nuthatches (Sitta carolinensis) are experiencing long-term population declines in the Willamette Valley of Oregon, where they are historically associated with oak woodlands. As secondary cavity-nesters, white-breasted nuthatches may be limited by the availability of existing cavities for nesting and roosting. Oak vegetation in the Willamette Valley has changed since European-American settlement times from vast areas of open oak savanna to isolated closed-canopy stands separated by agricultural fields. We examined nuthatch density, nest cavity selection, and nest success in relation to oak woodland structure and landscape context. We conducted point transect surveys in 3 strata: woodland interiors, large woodland edges, and small woodlands. We located and monitored nuthatch nests and sampled vegetation at nest locations and matching random locations around each nest. Woodland structure and edge density were measured at a 178-m radius (home range) scale, and landscape context was measured using vegetation cover within a 1-km radius around point transects and nests. We used program DISTANCE to fit detection functions and calculate nuthatch densities. We used conditional logistic regression to compare nest locations with random locations, and analyzed nest success with Mayfield logistic regression. White-breasted nuthatch density was significantly higher in small woodlands than in edges of large woodlands, which had higher nuthatch density than woodland interiors. Density of nuthatches increased with a combination of oak cover within a 1-km radius of the point, edge density within a 178-m radius, and number of oak trees >50 cm diameter at breast height (dbh) within a 100-m radius. Nest cavities were situated in oak trees containing more cavities than random oak trees that had cavities, and oak trees used as nest trees had a larger dbh than oak trees within random plots. Local woodland structure at nest locations was characterized by larger trees, measured by greater mean dbh, canopy cover, and basal area of oaks than random locations within the home range. Nest success in natural cavities was 71% and was not predicted by attributes of nest cavities, nest trees, local woodland structure at nests, woodland structure at the home range scale, or landscape context. These results suggest that the most suitable habitat for white-breasted nuthatches in the Willamette Valley includes oak woodlands in close proximity to one another with a high proportion of edge and mature oak trees. Managers should preserve trees containing cavities and large oak trees whenever possible. Thinning of small oaks and removal of conifers in oak woodlands to create more open, savanna-like conditions may also promote the development of larger oaks with more spreading branches, providing more opportunities for cavities to form and more foraging surface area for nuthatches.