335 pages / This thesis describes the river towns along the Willamette River in Oregon. River conditions, adaptation of the boats to the river, and steamboat routes shown at ten year intervals illustrate the degree of accessibility of the various towns. Reasons for success or failure in light of factors of site, situation, efforts of townsite promoters or lack thereof are evaluated. Increase in population is used as a measure of success. Orientation to the river was reflected in town plans and location of land uses as sh own in early maps and views.

This research consists of two related yet distinct studies: an observational study of the surface character of the penetration of marine air into the southern Willamette Valley and a climatological study of the summertime air masses of northwestern Oregon. For the observational study, temperature and estimated wind data were gathered by automobile. Mesoscale analysis of several cases indicate that the Marine Air Penetration (MAP) occurs regularly in approximately the same area and is strongly controlled by the topography. Qualitative observation and reasoning strongly suggests that the strong winds and increased stability at the top of the marine layer have an adverse effect upon agricultural field fires. Results of the climatological study indicated that the application of the partial collective method of analysis to July maximum temperature data from the U.S. Climatological Network yielded a meaningful air mass climatology for northwestern Oregon. To our knowledge, this is the first time that the partial collective method has been applied to a region with mountainous areas west of the Rocky Mountains or to the mesoscale. / Graduation date: 1981

Graduation date: 1997

Large scale disruption of natural habitats worldwide has led to concern over the effects of habitat fragmentation on wildlife populations. Small scale experiments may be a useful tool for discovering effects of fragmentation over larger landscape scales. I sought to explore the potential for using voles as an experimental model system, at a small scale, to discover mechanisms that may affect other species at different spatial scales. I compared over-winter demography of gray-tailed voles, Microtus canicaudus, in two experimental landscapes, consisting of fragmented and continuous habitat, to assess the effects of habitat fragmentation. I chose winter as the time frame of the experiment because it poses harsh conditions for voles and because seasonal bottlenecks may affect population persistence. Population size, population growth rates, reproduction, recruitment, survival and movements, were monitored using mark-recapture methods in 8, 0.2-ha enclosures planted with alfalfa. The habitat within the enclosures was manipulated into 2 configurations of equal area, 1 large continuous patch (625 m��), and a mosaic of 25 small patches (each 25 m��), prior to the introduction of 12 pairs of animals/enclosure. I hypothesized that population size and growth rates, reproduction, recruitment, and survival would be greater for vole populations in continuous habitats than for populations in fragmented habitats. Additionally, I hypothesized that movements would be more restricted within fragmented habitat because the voles would perceive the area between habitat patches as a barrier. I did not detect significant differences between vole populations in continuous and fragmented treatments. However, populations residing in fragmented habitat showed higher variability over the study period. Populations in both treatments decreased throughout the winter period and all became extinct by the end of the study. Reproduction occurred only during the fall period, and there were no significant differences between treatments. Movements were not different between treatments, or between male and female voles, but movements did increase over time. Survival appeared to be higher for male voles in continuous habitat than in fragmented habitat, but female vole survival was similar between treatments. Survival was influenced by weather conditions, and predation. These results contrast with a previous experiment during the summer season, and indicate that seasonal bottlenecks may be important to consider when studying habitat fragmentation. Extinction of populations in both treatments demonstrates that small populations are extremely vulnerable to both environmental and demographic stochastic events. / Graduation date: 1997

Fiber flax (Linum usitatissimum L.) production in the Willamette Valley ended in Oregon around 1957 before newly developed technology and fiber cultivars were available. The purpose of this research was to explore the use of modern methods and new cultivars. Field studies were conducted to evaluate cultivars and optimum cultural practices that would produce the highest yield and best fiber quality in the Willamette Valley on Woodburn silty clay loam. A study was conducted to assess the winter hardiness of fifty flax cultivars. The effect of four different pull dates on straw and fiber yield and fiber quality were investigated at two sites in 1995 and 1996. Pulling in stage 2, 3, or 4 resulted in an increase in straw yield over pulling in stage 1 in 1996. No differences were detected in fiber yield or caustic weight loss in response to pull date in either year. An acceptable pulling window is stages 1-3 (range of 900 to 1300 growing degree days). Retting took 13 weeks in both years. Rainfall during the retting period was 10.7 cm in 1995 and 6.9 cm in 1996. A field study was conducted in 1995 and 1996 to test the effect of three nitrogen (N) levels (50, 75, and 100 kg ha�����) and three fiber flax cultivars (Ariane, Cascade, and Viking) on straw yield. There was a significant increase in yield with increased N levels in 1996. Higher levels of N increased yield in all three cultivars in both years. Lodging of 'Cascade' increased with increased N levels in 1995. The effect of three planting dates on yield and stand density of Ariane fiber flax were investigated in 1995. The 31 March planting date produced the most retted straw (9704 kg ha�����). A fall-planted winter cultivar experiment was conducted during 1994-95 and 1995-96. In 1994-95, four varieties (Ariane, Texala, Viking, and Hyslop Cascade) had greater winter survival than Linore, the check variety. Only Linore withstood the second winter. / Graduation date: 1997

Graduation date: 1994

xiii, 67 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / The bedrock aquifer of the Southern Willamerte Basin, Oregon, USA, is contaminated with arsenic at concentrations as high as several ppm. Single-well push-pull tests were conducted to investigate how microbial metabolisms control arsenic occurrence and levels in the aquifer. Test solutions containing ethanol were injected into the aquifer; dissolved gases, groundwater, and sediments were then sampled to monitor the speciation of carbon, iron, sulfur, and arsenic. Ethanol amendment stimulated a series of microbial metabolisms, including arsenate reduction, iron reduction, and sulfate reduction. Arsenate reduction converts arsenate to arsenite; iron reduction produces ferrous iron; sulfate reduction releases sulfide. Arsenite and ferrous iron then combine with sulfide and form arsenic sulfide and iron sulfide minerals. Results of the experiments demonstrate that the interactions among microbial metabolisms and mineral precipitation influenced arsenic contamination in the aquifer. These results shed new light on potential bioremediation strategies in the area. / Committee in Charge: Dr. Qusheng Jin, Chair; Dr. Mark Reed; Dr. Samantha Hopkins

During the summer of 1974 chemical conditions in the lower reaches of the Willamette River, Oregon were similar to those in other rivers currently experiencing nuisance algal growth problems. Temperature and chemical nutrients are not limiting. Relatively high populations of phytoplankton and productivity values for upstream periphyton beds and surface waters suggest moderately eutrophic conditions. However, with increased depth in the lower river, and a constant euphotic zone, the amount of photosynthetically available light is reduced. With sufficient depth and complete mixing the critical depth is exceeded. Primary productivity rates are subsequently limited by low light availability in the lower river.

Hydrologic processes within mineral flat wetlands, along with their connections to groundwater and downstream surface water in lowland agricultural catchments are poorly understood, particularly under different land uses. In the three field studies included in this thesis, we examined infiltration, wetland hydroperiod, groundwater recharge dynamics, surface runoff generation, and water quality in mineral flat wetlands using a combination of soil and hydrometric measurements, stable isotope tracers, and water chemistry analysis. Our overarching objectives were to examine, for mineral flat wetlands under native prairie, farmed grassland, and restored prairie land cover: 1) how different land management influences infiltration and wetland hydroperiod at the plot scale, 2) the effects of land use on seasonal groundwater-surface water dynamics at the field scale, and 3) seasonal variation in runoff sources and nutrient transport from native prairie and farmed wetlands at the small catchment scale. At the plot scale, our results suggest that edaphic factors, particularly those related to soil structure, are strongly associated with wetland infiltration and overall hydroperiod across least-altered prairie, farmed, and restored prairie mineral flat wetlands. The hydroperiod metrics we examined were generally more sensitive to level of site disturbance than land use alone. At the field scale, our results indicate that, in spite of land use differences and slight variations in soil stratigraphy, many similarities exist in overall wetland hydroperiod, water sources and evaporation rates for mineral flat wetlands in the Willamette Valley lowlands. Isotopic evidence suggests that the greatest degree of groundwater-surface water mixing occurs in the upper 0.5 m of the saturated soil profile across sites under all land uses. Finally, at the small catchment scale, farmed wetland runoff was isotopically similar to field surface water for most of the wet season, indicating that saturation excess was an important runoff generation process. Prairie wetland runoff was isotopically similar to upstream water throughout the winter, and briefly similar to shallow groundwater and surface water within the wetland in mid-spring. Throughout the wet season, elevated nitrate, sulfate, and chloride concentrations were observed in groundwater and surface water at the farm site, and deeper groundwater at the prairie site. Upstream-downstream runoff chemistry remained similar throughout the wet season at the prairie site. Farm site runoff chemistry reflected the dominant water source within the farm field throughout the wet season. Our findings suggest that, while surface water pathways dominate runoff from wetland flats under farm land use, large wetland flat fields have a high potential to absorb, store, and process nutrients and agrochemicals from on-site and nearby off-site chemical inputs. Mineral flats that maintain wetland hydrology in spite of farm use represent a unique balance between agricultural production and preservation of some of the water storage and delay, and water quality-related ecosystem services once provided at a much larger scale in the Willamette Valley lowlands. We anticipate that results of this work will lead to better understanding of key site-scale edaphic and hydrologic factors to consider when prioritizing and managing sites for restoration, and how site disturbance under a variety of land uses may impact different hydrologic processes and components of the wetland hydroperiod. Additionally, our results provide a better understanding of how land use affects seasonal runoff generation processes in mineral flat wetlands, and the water quality implications of modifying groundwater and surface water connectivity between mineral flats and surrounding surface drainage networks. / Graduation date: 2012

Four key aspects of the relationship between predatory hoverflies and the aphid pest Brevicoryne brassicae L. on broccoli were investigated in the Willamette Valley, Oregon USA: 1) the relationship between aphid density and hoverfly oviposition, 2) the larval voracity of key hoverfly species, 3) the preferences of hoverflies and broccoli pests for candidate insectary plant species, and 4) the role of insectary plantings in enhancing hoverfly oviposition in aphid colonies in broccoli fields. Hoverfly oviposition at two commercial broccoli field sites increased at aphid densities greater than 50 aphids per plant, but did not peak at the highest aphid densities. A logistic regression model, selected with Akaike's Information Criterion, of the odds of oviposition in relation to aphid density included effects for sampling date and aphid species (B. brassicae and Myzus persicae (Suizer)). The magnitude of the response was similar for B. brassicae and M persicae. The oviposition response was greater in the upper part of the plant canopy, and different on individual leaves from that seen on whole plants. The voracity and development rate of Scaeva pyrastri (L.) were greater than those of Eupeodes fumipennis (Thomson), and both exceeded Syrphus opinator Osten Saken and Sphaerophoria suiphuripes (Thomson). Both E. fumipennis and S. opinator reduced aphid populations to low levels on plants over two weeks, but E. fumipennis spent much of the time foraging away form the caged plants. Alyssum (Lobularia maritima (L.) Desv.), coriander (Coriandrum sativa L.), buckwheat (Fagropyrum esculentum Moench), and phacelia (Phacelia tanacetifolia Benth.) were screened for arthropod visitation frequency. The three pest species Pieris rapae (L.), Diabrotica undecimpunctata undecimpunctata Mannerheim, and Lygus hesperus Knight visited phacelia the most frequently, while the hoverfly species visited mostly coriander, which was possibly influenced by competition from other foragers. Hoverfly oviposition was increased near within-field blocks of alyssum in broccoli fields at the end of the season however, hoverflies arriving at the field had pollen in their guts and were oviparous four to five weeks before their eggs were detected in aphid colonies. This late oviposition may have occurred because threshold densities for oviposition were not reached until this stage. / Graduation date: 2006