xvi, 109 p. : ill. / Invasions by introduced plant species cost billions of dollars each year in the United States and threaten native habitat. The primary goal of my dissertation research was to examine the role that natural enemies (pathogens and herbivores) play in these invasions in both unmanaged and restored plant communities. In two related studies in seasonal wetland prairies in the Willamette Valley, Oregon, USA, I surveyed natural enemy attack on common native and introduced plant species in a restoration experiment designed to test the effects of site preparation techniques on plant community composition. Restoration treatments had little influence on enemy attack rates. Attack rates depended on idiosyncratic differences in the relationships between host species and plant community characteristics, suggesting that existing theories concerning these relationships have limited predictive power. Another field experiment tested the potential for enemy spillover from introduced to native species and dilution of natural enemy attack on introduced species by native species. I examined natural enemy attack on three native and three perennial grasses that commonly co-occur in the Willamette Valley. The native species are commonly used in restoration. The introduced species are common throughout North America and potentially harbor enemies that could affect both crops and natural communities. There was no compelling evidence of enemy spillover from the introduced to the native species, but dilution of enemies on the introduced species by the native species was evident in year 2 and even stronger in year 3 for two of the three introduced species. Using the same three introduced species from the spillover/dilution study, I tested the enemy release hypothesis, which proposes that introduced species lose natural enemies upon introduction and are thus "released" from population control. I surveyed populations of the three grass species across a wide geographic area in their native and naturalized ranges in Europe and the United States, respectively. I also compared my results to those of a previously published literature survey. My field survey supported release from herbivores but not from fungal pathogens. In contrast, the literature survey found evidence of release from fungal pathogens. This dissertation includes unpublished co-authored material. / Committee in charge: Brendan Bohannan, Chairperson; Bitty Roy, Co-Advisor; Scott Bridgham, Co-Advisor; Eric Seabloom, Member; Robert Mauro, Outside Member

The Willamette is a gravel-bed river that drains ~28,800 square kilometers between the Coast Range and Cascade Range in northwestern Oregon before entering the Columbia River near Portland. In the last 150 years, natural and anthropogenic drivers have altered the sediment transport regime, drastically reducing the geomorphic complexity of the river. The purpose of this research is to assess longitudinal trends in sediment transport within the modern flow regime. Sediment transport rates are highly discrete in space, exhibit similar longitudinal patters across flows and increase non-linearly with flow. The highest sediment transport rates are found where the channel is confined due to disconnection of the floodplain and the river runs against high resistance terraces. The spatial distributions of sediment transport rates and active gravel are tightly linked. Sediment sampling revealed slight downstream fining in the surface grain size. Sediment size did not correlate with stream power.

In a profession such as social work, where one is responsible for dealing with the ills of society and meeting the needs of other individuals, such emotional detachment and estrangement from others is antithetical to the purpose of the field and eminently destructive to those seeking and needing assistance. With the current push for accountability, factors such as burnout or alienation from one's work become of crucial importance. In addition, burnout leads to a high rate of absenteeism and job turnover (Minihan, 1980). This too decreases cost effectiveness and the quality of service, matters of extreme concern in a field designed to serve the needs of individuals in society and to do so on limited funds and resources. Thus, alienation is of paramount importance to the field of social services and can no longer be ignored or relegated to a back seat in terms of study and research. Current literature in the field of social work deals only with the subjective expression of alienation; it has omitted linking the psychological with the social-structural aspects of alienation: indeed, with linking burnout to alienation itself. This study proposes to begin to fill this gap. What conditions in the structure of the work place and/or society cause or are correlated with the expression of alienation? It is this question which we endeavor to pursue.

The lack of suitable nest sites may be a limiting factor for Western Bluebird populations inhabiting the upper Willamette Valley. Nest box trails have been established on the hills surrounding the Portland metropolitan area. Since their placement, approximately 25% of the boxes available have been used by Western Bluebirds as nest cavities. This study was undertaken to identify factors which might determine the selection of a nest box by Western Bluebirds and the subsequent nest success or failure. The breeding biology of Western Bluebirds using the nest box trail located on Parrett Mountain, Oregon in 1979 was investigated. Breeding season, mean clutch size, average incubation and nestling periods, and level of nest success were determined. Nest box dimensions, placement, and surrounding habitat features were quantified. Potentially important nest site characteristics were examined and tested for association with Western Bluebird nest box use and reproductive success. Western Bluebird nest box selection was random with regard to all of the characteristics studied except Solar Index and Nest Box Density. No correlation was seen between nest box characteristics and bluebird nest success.

Recent work indicates that microorganisms present in soils can remove carbon monoxide from the atmosphere and as such constitutes a major sink. B.E.T. adsorption studies were carried out on representative soils from the Willamette Valley River Basin in order to determine their adsorptive characteristics for carbon monoxide and other gases. Attempts were made to isolate, through a non-soildestructive sterilization, the adsorptive characteristics of the soil microorganisms as well as of the test soil. The carbon monoxide studies show physical adsorption equivalent to the coverage of a few per cent of the surface area at 25.0° and 76 cm-Hg. Adsorption studies also shows that the soil rather then the microorganisms adsorbs most of the carbon monoxide. On sterilized soil, chemical sorption of oxygen was present and was probably caused by the oxidation of dead or damaged soil microorganisms. Hysteresis effects were present in all adsorption studies at 25.0° and appears to be a characteristic of the constituents of the soil and represents a new and as yet unexplained phenomenon.

Aquatic ecosystems continue to be increasingly affected by climate warming. For salmonids in the Pacific Northwest of North America, increasing temperatures pose tighter thermal constraints on their habitat use as well as aspects of their individual performance, such as disease resistance. This thesis examines the effect of temperature on the phenology of the Ceratomyxa shasta life cycle, the effect of thermal refugia on disease risk in juvenile salmonids in the Klamath River, CA, and the spatial and temporal distribution of C. shasta in the Willamette River, OR. We developed a biological model that predicts an acceleration of the C. shasta life cycle development due to climate shifts in the Klamath River, resulting in more generations per year and earlier seasonal parasite occurrence. We showed that in early summer the Beaver Creek-Klamath River confluence provides juvenile Chinook and coho salmon an area of lower parasite doses and cooler temperatures than the main stem, thus lessening disease risk. By accelerating the development of C. shasta in its hosts, increasing temperatures will result in earlier parasite transmission to juvenile salmonids and a longer season of infectivity. These fish may find disease refuge at cold tributary inflows to the main stem of the Klamath River in early summer, further adding to the benefit of these important thermal habitats. To determine if similar disease patterns occur in other rivers with the parasite, we described spatial and temporal occurrence of C. shasta in the Willamette River. By collecting weekly water sampling at four sites over 28 months we characterize seasonal and annual differences of parasite abundance, which varies with weekly temperature. We also collected samples along the length of the main stem and its tributaries and identified spatial differences in C. shasta spore densities. Identification of spatial and temporal variation of C. shasta in the Willamette River provides a foundation for understanding future patterns of disease occurrence in this river where conservation of anadromous fisheries is also of concern. This thesis identifies likely responses of C. shasta to climate warming in the Klamath River, with useful application to other rivers in the Pacific Northwest. / Graduation date: 2013

xvii, 382 p. : ill. (some col.), maps. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / The debate concerning the role of natural versus anthropogenic burning in shaping the prehistoric vegetation patterns of the Willamette Valley of Oregon and Washington remains highly contentious. To address this, pollen and high-resolution charcoal records obtained from lake sediments were analyzed to reconstruct the Holocene fire and vegetation history, in order to assess the relative influence of climate variability and anthropogenic activity on those histories. Two sites provided information on the last 11,000 years. At one site at the northern margin of the Willamette Valley, shifts in fire activity and vegetation compared closely with millennial- and centennial-time scale variations in climate, and there was no evidence that anthropogenic burning affected the natural fire-climate linkages prior to Euro-American arrival. In contrast, the fire and vegetation history at a site in the central Willamette Valley showed relatively little vegetation change in response to both millennial- and centennial-scale climate variability, but fire activity varied widely in both frequency and severity. A comparison of this paleoecological reconstruction with archaeological evidence suggests that anthropogenic burning near the site may have influenced middle- to late-Holocene fire regimes. The fire history of the last 1200 years was compared at five sites along a north-south transect through the Willamette Valley. Forested upland sites showed stronger fire-climate linkages and little human influence, whereas lowland sites located in former prairie and savanna showed temporal patterns in fire activity that suggest a significant human impact. A decline in fire activity at several sites in the last 600 years was attributed to the effects of a cooling climate as well as the decline of Native American populations. The impacts of Euro-American settlement on the records include dramatic shifts in vegetation assemblages and large fire events associated with land clearance. The results of this research contribute to our understanding of long-term vegetation dynamics and the role of fire, both natural- and human-ignited, in shaping ecosystems, as well as provide an historical context for evaluating recent shifts in plant communities in the Willamette Valley. / Advisers: Cathy Whitlock, Patrick J. Bartlein

Humans make decisions within ecosystems to enhance their well-being, but choices can lead to unintended consequences. The ecosystem services (ES) approach supports decision-making that considers all environmental goods and services. Many challenges remain in the implementation of the ES approach like how specific ES vary through space and time. We address this research problem using the Tualatin and Yamhill river basins in northwestern Oregon as a study area. Freshwater ES are quantified and mapped with the spatially-explicit ES modeling tool, Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST). In chapter II, we develop a simple urban land cover change modeling approach with selected stakeholder input. The products of this analysis are used in part to answer the question of how the freshwater ES of water yield, nutrient retention, and sediment retention will change in the future, and how their distribution potentially will change? In chapter III, these ES are modeled in InVEST using the land cover scenarios and three downscaled global climate models. The base period is 1981 to 2010 and the future period is 2036 to 2065. The models are calibrated to empirical estimates, and display different sensitivities to inputs. Water yield increases with higher rainfall but decreases with the highest temperature scenario. Nutrient export and retention estimates are positively correlated. In the Tualatin basin, more urban lands generally lead to increases in nutrient exports and retention. The effect is reversed in the Yamhill basin from much larger agricultural exports. Sediment exports and retention increase with higher winter rainfall but are negatively spatially correlated due to topographic effects. Simulation of a landscape scale installation of riparian buffers leads to decreases in exports and increases in retention. The distribution of the provision of freshwater ES remains unchanged throughout the scenarios. With few parameters in each InVEST model, all display a high degree of sensitivity. Parameterization is subject to high uncertainty even with calibrated values. We discuss the assumptions and limitations of InVEST's freshwater models. The spatially explicit nature of InVEST is its main advantage. This work coupled with other analyses in the study area can facilitate the identification of tradeoffs amongst ES leading to better ecosystem management.

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.

Precipitation changes and urban growth are two factors altering the state of water quality. Changes in precipitation will alter the amount and timing of flows, and the corresponding sediment and nutrient dynamics. Meanwhile, densification associated with urban growth will create more impervious surfaces which will alter sediment and nutrient loadings. Land and water managers often rely on models to develop possible future scenarios and devise management responses to these projected changes. We use the Soil and Water Assessment Tool (SWAT) to assess the sensitivities of stream flow, sediment, and nutrient loads in two urbanizing watersheds in Northwest Oregon, USA to various climate and urbanization scenarios. We evaluate the spatial patterns climate change and urban growth will have on water, sediment and nutrient yields. We also identify critical source areas (CSAs) and investigate how implementation of vegetative filter strips (VFS) could ameliorate the effects of these changes. Our findings suggest that: 1) Water yield is tightly coupled to precipitation. 2) Large increases in winter and spring precipitation provide enough sub-surface storage to increase summertime water yields despite a moderate decrease in summer precipitation. 3) Expansion of urban areas increases surface runoff and has mixed effects on sediment and nutrients. 4) Implementation of VFS reduces pollutant loads helping overall watershed health. This research demonstrates the usefulness of SWAT in facilitating informed land and water management decisions.