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1
Keeler, Elizabeth Louise. "Willamette Valley River Towns and Steamboats." Thesis, University of Oregon, 1985. http://hdl.handle.net/1794/22967.
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335 pagesThis 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.
2
Ferreira, Gabriela Ribeiro de Sena. "Arsenic Mobilization from Silicic Volcanic Rocks in the Southern Willamette Valley." PDXScholar, 2016. http://pdxscholar.library.pdx.edu/open_access_etds/2752.
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Volcanic tuffs and tuffaceous sediments are frequently associated with elevated As groundwater concentrations even though their bulk As contents (~ 5 mg kg-1; Savoie, 2013) are only marginally greater than the average crustal abundance of 4.8 mg g-1 (Rudnick & Gao, 2003). Thus, As mobilization must be facilitated by conditions particular to these rocks. Alkaline desorption, anionic competition, reactive glass dissolution, and reductive dissolution of iron oxides are proposed processes of As release from volcanic rocks. Geogenic As contamination of groundwater in the southern Willamette Valley in western Oregon has been well-documented since the early 1960s, and previous studies have identified the Little Butte Volcanics Series and Fisher and Eugene Formations as the source of As contamination.
This study examines 19 samples from 10 units of ash flow tuffs and tuffaceous sediments within the Fisher Formation and Little Butte Volcanics Series, representing a range of weathering and devitrification, to determine conditions of mobilization and mineralogical constraints that control As release into solution. Leachate studies were conducted over a range of pH from 7 to 11, phosphate concentrations from 10 μM to 100 mM, and in time series from 4 to 196 hours. Results demonstrate that silicic volcanic tuffs are capable of mobilizing As in concentrations above regulatory limits at pH conditions produced naturally by the tuffs (pH 8-9) or with moderate concentrations of P (10-100 μM). Alteration products, e.g. zeolites and clays, appear to be the primary host phases for mobile As. Samples that do not contain these alteration products tend to produce concentrations of As well below regulatory limits and often below the instrument detection limits of this study. The type of alteration may influence As mobilization: tuffs containing more clays tend to mobilize As through surficial desorption, and tuffs containing more zeolites tend to mobilize As by dissolution or formation of colloids. Additionally, one volcaniclastic sample demonstrates that extremely elevated concentrations of As, up to 1000 μg/L are possible as a result of oxidative dissolution of As-bearing sulfide phases.
3
Gilmour, Daniel McGowan. "Chronology and Ecology of Late Pleistocene Megafauna in the Northern Willamette Valley, Oregon." PDXScholar, 2011. https://pdxscholar.library.pdx.edu/open_access_etds/416.
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This study is an investigation of the timing of extinction of late Pleistocene, large bodied mammalian herbivores (megafauna) and of the environment in which they lived. The demise of the megafauna near the end of the Pleistocene remains unexplained. Owing to potential human involvement in the extinctions, archaeologists have been particularly concerned to understand the causes for faunal losses. Our current lack of understanding of the timing and the causes of the extinctions in North America may result from a deficiency in understanding the histories of each individual species of extinct animal on a local level. Detailed regional chronologies of fauna are necessary for comparison with paleoenvironmental and archaeological data to help sort out causes for extinction. The Willamette Valley of western Oregon has long been noted for finds of megafauna, though records have not been synthesized since the early 20th century and these materials have remained largely unstudied. In this thesis, I first create a catalog of extinct megafauna recovered from the Willamette Valley. Next, using material from the northern valley, I employ AMS radiocarbon dating, stable isotope δ¹³C and δ¹⁵N analyses, and gross inferences based on the dietary specializations and habitat preferences of taxa in order to reconstruct environments and to develop a local chronology of events that is then arrayed against archaeological and paleoenvironmental data. The results of this study indicate that megafaunal populations in the northern Willamette Valley were contemporaneous with the earliest known human populations of the Pacific Northwest, as well as later populations associated with the Clovis Paleoindian Horizon. Consistent with the overkill hypothesis, radiocarbon ages span the length of the Clovis window, but no ages are younger than Clovis. Moreover, all radiocarbon ages are older than or contemporaneous to the onset of the Younger Dryas Stadial. No age ranges fall exclusively within the Younger Dryas. Comparison of megafaunal ages and paleoenvironmental records support the view that climate change contributed to local animal population declines. Prior to ~13,000 cal BP, the Willamette Valley was an open environment; herbivores mainly consumed C₃ vegetation. The timing of the loss of megafauna coincides with increased forested conditions as indicated by regional paleoenvironmental reconstruction. As the timing of megafaunal decline correlates with Clovis, the onset of the Younger Dryas, and increased forested conditions, it is not possible with the data currently available to distinguish the cause of extinction in the Willamette Valley. The age ranges of the fauna coupled with taphonomic and geologic context indicate that the fauna are autochthonous to the Willamette Valley; they do not represent ice rafted carcasses or isolated skeletal elements transported from elsewhere during late Pleistocene glacial outburst floods.
4
Chun, Nicholas. "Identifying Clusters of Non-Farm Activity within Exclusive Farm Use Zones in the Northern Willamette Valley." Thesis, Portland State University, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10600978.
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This thesis provides an extensive look at where permitted non-farm uses and dwellings have clustered within Exclusive Farm Use (EFU) zones in the Northern Willamette Valley in Oregon. There is a looming concern that non-farm related uses and dwellings, or non-farm development, are conflicting with agricultural preservation strategies. Specifically, non-farm developments can potentially undermine the critical mass of farmland needed to keep the agricultural economy sustainable, but until now, studies have lacked spatially precise data to systematically track these phenomena. This thesis offers methodological contributions towards analyzing these operations and presents a broad account of what has been occurring in the region. Using permit approval data from the Department of Land Conservation and Development (DLCD) and 2015 county tax lot shapefiles, I geocoded the locations of these uses and dwellings. I used location quotient and spatial autocorrelation coefficients to identify non-farm hotspots in the region and summarized different typologies that have developed. The findings reveal that viticulture operations have amassed near Dundee and Newberg in Yamhill County, while commercial activities and home occupations have clustered near the Salem-Keizer UGB. Concurrently, dwellings have clustered near the Yamhill-Polk County border. Finally, I offer suggestions to improve Oregon’s agricultural land use policy and data management process, as well as advocate for more intensive research in the future to generate narratives for our results.
5
Elder, J. Tait. "Exploring Prehistoric Salmon Subsistence in the Willamette Valley using Zooarchaeological Records and Optimal Foraging Theory." PDXScholar, 2010. https://pdxscholar.library.pdx.edu/open_access_etds/22.
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My research examines the prehistoric subsistence of native peoples of the Willamette Valley, Oregon through an analysis of the regional zooarchaeological records, and then modeling regional diet breadth. Through this analysis, I challenge commonly held stereotypes that the indigenous people of the Willamette Valley were strictly root eaters, and the basis for this claim, that salmon were not part of Native subsistence. The results of my research indicate that given the incomplete nature of the ethnohistoric record, very little can be said about expected cultural behaviors, such as salmon consumption, that appear to be absent in the Willamette Valley. In addition, since the faunal assemblage is so small in the Willamette Valley, zooarchaeological data are simply inadequate for studying the relationship between prehistoric peoples and their animal resources. Finally, optimal foraging modeling suggests that salmon is one of the higher ranked resources available to the Native People of the Willamette Valley.
6
Cody, Tia Rachelle. "LiDAR Predictive Modeling of Kalapuya Mound Sites in the Calapooia Watershed, Oregon." PDXScholar, 2019. https://pdxscholar.library.pdx.edu/open_access_etds/4863.
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Archaeologists grapple with the problematic nature of archaeological discovery. Certain types of sites are difficult to see even in the best environmental conditions (e.g., low-density lithic scatters) and performing traditional archaeological survey is challenging in some environments, such as the dense temperate rain forests of the Pacific Northwest. Archaeologists need another method of survey to assess large areas and overcome environmental and archaeological barriers to site discovery in regions like the Pacific Northwest. LiDAR (light detection and ranging) technology, a method for digitally clearing away swaths of vegetation and surveying the landscape, is one possible solution to some of these archaeological problems.
The Calapooia Watershed in the southern Willamette Valley in Oregon is an ideal area to focus LiDAR's unique archaeological capabilities, as the region is heavily wooded and known to contain hundreds of low-lying earthwork features or mounds. Modern Indigenous Communities, such as the Confederated Tribes of Grand Ronde, consider the Willamette Valley mound sites highly sensitive locations, as ethnographic accounts and limited archaeological work indicate that some are burial sites. However, these mounds have received little archaeological study. Land ownership (94 percent privately owned), dense vegetation that obscures mounds, and the sheer expanse of the landscape (234,000 acres) have impeded professional archaeological research.
The focus of this thesis is the development and the testing of a LiDAR and remote sensing predictive model to see if this type of model can detect where potential mound sites are located in the Calapooia Watershed, Oregon. The author created a LiDAR and remote sensing predictive model using ArcMap 10.5.1, LiDAR, and publicly available aerial imagery; manipulating data using standard hydrological tools in ArcMap. The resulting model was successful in locating extant previously identified mound sites. The author then conducted field work and determined that the model was also successful in identifying seven new, previously unrecorded mound sites in the watershed. The author also identified several possible patterns in mound location and characteristics through exploratory model analysis and fieldwork; this exploratory analysis highlights areas for future mound research.
This project has clearly established a method and a model appropriate for archaeological mound prospection in the Willamette Valley. This project also shows the efficacy of LiDAR predictive models and feature extraction methods for archaeological work, which can be modified for use in other regions of the Pacific Northwest and beyond. Furthermore, by identifying these mounds I have laid the groundwork for future studies that may continue to shed light on why and how people created these mounds, which will add valuable information to a poorly understood site type and cultural practice.
7
Barnard, Kathryn Nora. "The Terroir of Pinot Noir Wine in the Willamette Valley, Oregon : A Broad Analysis of Vineyard Soils, Grape Juice and Wine Chemistry." PDXScholar, 2016. http://pdxscholar.library.pdx.edu/open_access_etds/2941.
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Terroir is determined by a combination of factors in the vineyard including the grape varietal, geology and soil, soil hydrology, physiography, and climate. Although most studies have examined regional differences in wine flavors and associated provenance of wine based on chemistry, few have examined the chemistry of the soil and the ability to trace that chemistry to grape juice and, finally, to the wine. This dissertation examines what soil physical and chemical differences specific to this region might influence grape juice chemistry and wine chemistry.
Wine-grapes in the Willamette Valley, Oregon, are grown on three major soil parent materials: volcanic, marine sediments, and loess/volcanic. Winemakers have observed differences in the flavor of Pinot Noir wine made from grapes grown on these different parent materials. This dissertation examines differences in the soil properties and elemental chemistry of the soil parent materials at various vineyards to document their effect on wine chemistry as a step towards understanding differences in flavor. All aspects of the terroir are controlled by carefully selecting vineyards with similar exposure and elevation, the same grape varietal and wine making techniques, and only the soils vary. The hypothesis is that the chemistry of the grape juice and wine reflect the soil in which the grapes were grown and that the three parent materials have soils that can be distinguished by their physical and chemical characteristics.
Soil pits were excavated in 20 vineyards, soil properties were described in the field, and soil samples were later analyzed in the laboratory particle size, organic matter, color, pH, cation exchange capacity (ammonium acetate method), clay mineralogy (x-ray diffraction), and elemental chemistry (ICP-MS/AES). X-ray fluorescence was used to examine the pisolites. ICP-MS/AES was used for elemental analysis of grape juice and wines produced from these vineyards. Principal component analysis was used to compare soil physical and chemical characteristics, grape juice and wine chemistry.
The physical characteristics of soils from all the three parent materials indicate: they are old (>50,000 years) based on their high clay content, low cation exchange capacity, red colors, and high Fe and Al content. These features indicate enough time has passed to reduce organic matter and other cations at depth, leave behind insoluble Fe and Al, and develop pedogenic clays. In my study region, volcanic and marine sediment soils are more developed with slightly lower acidity than the loess/volcanic soils. A new finding for this region is the presence of pisolites (Fe/Mg concretions) in the volcanic and the loess/volcanic soils, but absent in the marine sediment soils. Winemakers hypothesized that pisolites were present only in loess soils and influenced wine flavor in some way.
Volcanic soils have the highest P, S, Fe, Co, Mn, and V concentrations and the lowest As and Sr values. Marine sediment soils have higher Cl and Sr and lower P, Co, Mn, Ba, and V concentrations than volcanic soils. Loess soils have the highest values of K and Mg and are similar to volcanic soils with higher P and V values and similar to marine sediment soils with higher Sr values. The main elements found to be significant in determining one parent material from another are V and Mn (volcanic soils), Mg and K (loess soils), and Sr (marine sediment or loess soils). Sr is slightly higher in grape juice and wine from vines grown on marine sediment parent material compared to volcanic and loess parent material, whereas Mn is higher in the juice and wine from grapes grown in volcanic parent material. P, S, Fe, Co, V, Cl, Ba, Mg, and K did not maintain their relative concentration levels from soil to grape juice to wine. The principal component analysis shows that soil and wine chemistry differs between parent material, but is inconclusive for grape juice chemistry.
8
Ulrich, Nathan D. 1977. "Restoring oak habitats in the Southern Willamette Valley, Oregon: A multi-objective tradeoffs analysis for landowners and managers." Thesis, University of Oregon, 2010. http://hdl.handle.net/1794/11087.
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xvii, 160 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.Restoring oak habitats is an emerging conservation priority in Oregon's Willamette Valley. Both private and public landowners face multiple challenges to conservation and restoration of oak habitats, including a lack of knowledge about the potential tradeoffs and constraints for achieving multiple priorities on a given site. This study simulated 25 alternative oak habitat restoration scenarios to develop estimates of outcomes related to six different restoration priorities: costs, income potential, habitat value, scenic quality, fire hazard reduction potential, and time requirements. Model results indicated that initial land conditions strongly influence a landowner's ability to optimize among these different priorities. To assist landowners with decision-making, model estimates were organized into a digital decision matrix that communicates advantages and tradeoffs associated with each alternative scenario. In doing so, it aims to help landowners choose restoration goals that better meet their broader needs and objectives.
Committee in Charge: Dr. Bart Johnson, Chair; Dr. Robert Ribe
9
Sheehan, Timothy J. "Modeling Wildfire and Ignitions for Climate Change and Alternative Land Management Scenarios in the Willamette Valley, Oregon." Thesis, University of Oregon, 2011. http://hdl.handle.net/1794/12184.
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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
10
Smith, Cessna R. "The Pursuit of Commerce: Agricultural Development in Western Oregon, 1825-1861." PDXScholar, 2011. https://pdxscholar.library.pdx.edu/open_access_etds/258.
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This thesis examines how the pursuit of commercial gain affected the development of agriculture in western Oregon's Willamette, Umpqua, and Rogue River Valleys. The period of study begins when the British owned Hudson's Bay Company began to farm land in and around Fort Vancouver in 1825, and ends in 1861--during the time when agrarian settlement was beginning to expand east of the Cascade Mountains. Given that agriculture in Oregon, as elsewhere, would eventually reach a standard of national development, and given that most of Oregon's immigrants arrived poor and lacked the farm implements needed for subsistence, the question this study asks is what methods and motivations guided Oregon's first agrarian settlers to improve their industry? It is the central premise of this study that commerce was the sine qua non of agricultural development, and that commercial gain was the incentive that underpinned the improvements necessary to its progress. The question itself necessarily involves physiographical and climatological conditions, existing and potential markets, and a merchant class whose commercial motivations were beyond doubt. Two additional matters that weigh substantially through most of this paper need to be mentioned: First, because not all farmers were commercially-oriented, the focus is on individuals, including merchants, whose entrepreneurial activities contributed the most to agriculture; second, the discovery of gold in California in 1848, and in southern Oregon in the early 1850s, had a huge and lasting influence on Oregon agriculture and on the overall economy.
11
Walsh, Megan Kathleen 1976. "Natural and Anthropogenic Influences on the Holocene Fire and Vegetation History of the Willamette Valley, Northwest Oregon and Southwest Washington." Thesis, University of Oregon, 2008. http://hdl.handle.net/1794/9488.
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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
12
Walsh, Megan Kathleen. "Natural and anthropogenic influences on the Holocene fire and vegetation history of the Willamette Valley, northwest Oregon and southwest Washington /." Connect to title online (Scholars' Bank) Connect to title online (ProQuest), 2008. http://hdl.handle.net/1794/9488.
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Blaisdell, Gretchen Kai 1974. "Introduced plant species, herbivores and pathogens, and the host-enemy relationships that accompany invasions." Thesis, University of Oregon, 2011. http://hdl.handle.net/1794/11227.
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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
14
Seter, Lisa M. "Geochemical characteristics of iron-manganese nodules in seasonally-saturated soils of the Willamette Valley, Oregon." Thesis, 1998. http://hdl.handle.net/1957/33609.
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Wall, Katherine Elizabeth. "The effect of nitrogen, irrigation, and cultivation on Pinot noir juice and wine composition from the Willamette Valley, Oregon." Thesis, 2003. http://hdl.handle.net/1957/25899.
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Chapin, Michele F. "Effects of ryegrass residue management on Dayton soil organic carbon content, distribution and related properties." Thesis, 1992. http://hdl.handle.net/1957/37280.
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Total organic carbon, total nitrogen, microbial respiration and enzyme
activity (β-glucosidase) were measured on several horizons of a Dayton silt loam
(fine, montmorillonitic, mesic, Typic Albaqualf) soil cropped to annual ryegrass
under two straw residue management systems. The study evaluated the effects
of annual burning of straw residues or annual incorporation of straw residues on
the content, distribution and bioavailability of soil organic carbon.
Four fields were selected to represent the burn management system which
have been annually burned for a minimum of 40 years. Four fields were selected
to represent the straw incorportated system (mold board plow) which had been
annually burned for approximately 30 years, followed by incorporation of straw
residues into soil for a minimum of 10 years. One native site was selected to
represent non-cultivation conditions.
Straw management system strongly influenced both the total organic C and
N and microbial activity the surface soil horizon. Soil organic C and N content
were significantly greater (p < 0.05) in the Ap horizons of soils under the plowed
management system than soils under the burned management system. The
collective evidence suggests, however, that the significant differences observed
between the two residue management systems are not due to greater losses of
soil organic C and N as a result of burning but rather that organic C levels have
increased as a result of a change in management. Soil C:N ratios are slightly
higher in the Ap horizons of soils as a result of straw residue incorporation in
comparison to burning of straw residues.
When expressed on a mass soil basis, both C0₂ evolution from microbial
respiration, during a 32 day incubation period, and enzyme activity were
significantly greater (p < 0.10) for the Ap horizon of soils where straw residue had
been incorporated than in soils where residues had been annually burned. When
expressed on a per gram C basis, neither C0₂ evolution from microbial respiration
or enzyme activity were significantly different between the two management
systems. These results indicate that long-term annual burning of straw residues
has not decreased the bioavailability of soil organic C.Graduation date: 1992
17
Gavilánez-Slone, Jenny M. "Pollination and pollinators of pumpkin and squash (Cucurbita maxima Duchesne) grown for seed production in the Willamette Valley of western Oregon." Thesis, 2000. http://hdl.handle.net/1957/32908.
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'Golden Delicious' winter squash (GDWS), Cucurbita maxima Duchesne,
provides significant amounts of pollen (24 mg) and nectar (236 μl), but with a low
reward of 14% nectar sugar. The quantity of nectar produced per GDWS flower
differed between sites and floral sex. The GDWS male flowers had 25% higher
sugar concentration than female flowers. There was no statistical difference in the
percent of nectar sugars per flower between sites, but the interaction between site
and floral sex was statistically significant for the amount of nectar and percent of
nectar sugars. Pollen production per flower differed significantly between sites
with the most productive site producing 27% more, and 45% more than the other
sites.
Pollination efficiency of honeybees and bumble bees was assessed with
field cages (1.8x1.8x1.8 m). No significant differences were found except for the
interaction between the bee treatment and year on number of fruit per cage. This
significant difference reflects the increase in fruit number produced by honey bees
in 1997.
The effect of distance from honey bee hives on fruit and seed quality was
tested, and found significant only for B- and C-seeds weight, which were both less
in the plots farthest from the nearest group of honey bee hives. Placement of honey
bee hives in fields of ≤120 ha appears not to be critical for adequate pollination of
GDWS. Other pollinators (excluding honey bees) were frequent visitors to the
squash flowers studied here - for example, Bombus spp., Megachilids, Halictids,
etc. These other pollinators, mostly bumble bees, accounted for 3.55% of all bee
visits.
Honey bees visited proportionately more female flowers in the morning,
and progressively switched to the more abundant male flowers in the afternoon.
This bias differed by site and year. Bumble bees visited proportionally slightly
more male GDWS flowers than did female flowers and did it in a similar rate
throughout the day. From 15 minute observations each hour of individual female
GDWS flower, we calculated that they received approximately 80 honey bee visits
per day.Graduation date: 2001
18
Hoinacki, Elisabeth V. "Sweet corn decline syndrome in Oregon's Willamette Valley." Thesis, 2003. http://hdl.handle.net/1957/29744.
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Davis-Born, Renee. "Influence of movement corridors on enclosed populations of the gray-tailed vole : do immigrants affect reproduction and dispersal of residents in a patchy environment?" Thesis, 1997. http://hdl.handle.net/1957/34238.
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I monitored demography, movement, and reproductive behavior of gray-tailed voles, Microtus canicaudus, in experimental habitat patches with and without corridors. I tested the hypotheses that reproductive rate, juvenile recruitment, and population size and growth rate would be affected negatively by immigrants that were introduced to resident groups (+ male and + female treatments). I hypothesized that "strangers" would commit infanticide thus decreasing juvenile recruitment. Second, I determined if movement corridors facilitated dispersal among habitat patches, thus potentially increasing infanticide, but decreasing reproductive inhibition of opposite-sex relatives by allowing them to separate (corridor treatment). Experiments were conducted in 12 0.2 ha enclosures planted with alfalfa that was fragmented into four patches (each 156 m��) separated by 12.5 m of bare ground. Introduction of unfamiliar conspecifics did not adversely affect reproductive rate, juvenile recruitment, population size, density, or growth rate. Corridors facilitated dispersal movements with males moving more than did females; however, corridors did not result in an even distribution of animals in the four patches. Unconnected habitat patches resulted in female- rather than the typical male-biased dispersal and females dispersed at lower body mass than in controls. Males that did not disperse from their natal patch exhibited a slight delay in sexual maturation.
I conclude that movement is deterred in patchy environments, enhanced with corridors, and differentially affects males and females. Behavioral factors that affect an individual's dispersal or reproductive pattern should be considered in landscape planning.Graduation date: 1997
20
Ambrosino, Mario D. "Enhancing the predatory potential of hoverflies on aphids in Oregon broccoli fields with floral resources." Thesis, 2006. http://hdl.handle.net/1957/29769.
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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
21
Maret, Mary P. "Effects of fire on seedling establishment in upland prairies in the Willamette Valley, Oregon." Thesis, 1996. http://hdl.handle.net/1957/33923.
Full textAbstract:
Prior to European settlement, native prairie dominated the landscape of the
Willamette Valley. Today, due to urbanization, agriculture, and the cessation of
burning, only isolated remnants of these grasslands still exist. In response to
conservation concerns, there has been a move to restore the remaining prairies in the
Willamette Valley, and prescribed burning and sowing native seed are often top
candidates for grassland restoration. However, the effects of burning on native seedling
establishment and the spread of weedy exotics are largely unknown.
In this study, I investigated how prescribed burning affects native and exotic
species seedling establishment on three upland prairie vegetation types in the Willamette
Valley. The general approach was to sow a known number of seeds from several native
and exotic grassland species into experimentally manipulated plots, designed to separate
the effects of litter removal from the other effects of burning, and to monitor seedling
densities. Germinability and dormancy characteristics of the sowed seeds were also
addressed. An additional study focused on the fire temperatures at soil surface in three
grassland vegetation types and two burn sizes.
Burning increased the establishment of most or all of the sown native species in
the two low quality, exotic grass sites. Exotic seedling establishment also tended to
increase, but did not differ significantly from unburned plots for most species tested. On
the higher quality, native bunchgrass site, burning did not significantly improve native species establishment, but did significantly increase the establishment of short-lived exotic species over those in unburned plots.
The germination and dormancy characteristics of the native and exotic species tested indicate that grasses, both native and exotic, are more likely than forbs to be non-dormant in the autumn following dispersal. Forbs, especially native forbs tend to require cold-stratification for maximum germinability.
During grassland fire, temperatures at soil surface were relatively cool. Fire temperature intensity was highest in the higher quality native bunchgrass vegetation. These burns reached higher temperatures significantly closer to the soil surface than the plot burns in lower quality sites dominated by annual or perennial exotic grasses. Average temperatures in a two hectare broadcast burn and in replicated 2m x 2.5m plot bums in an annual exotic grassland were very similar.
Prescribed burning can be an excellent tool for the restoration of low-quality upland prairies when combined with sowing native seeds in the fall. However, on high-quality prairie, prescribed burning may be a poor restoration choice for promoting native seedlings, as burning promoted weedy species without enhancing native seedling establishment.Graduation date: 1997
22
Lantz, Lisa E. "Population characteristics of exotic plants in a Willamette Valley native prairie." Thesis, 1997. http://hdl.handle.net/1957/33973.
Full text
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Zapiola, Maria Luz. "Trinexapac-ethyl and open-field burning in creeping red fescue (Festuca rubra L.) seed production in the Willamette Valley." Thesis, 2004. http://hdl.handle.net/1957/29428.
Full textAbstract:
Open-field burning has been an effective, economical, and widespread
method of post-harvest residue management in creeping red fescue seed
production in the Willamette Valley since the late 1940s. However, the use of field
burning has been legislatively restricted due to air quality and safety issues. The
foliar-applied plant growth regulator trinexapac-ethyl (TE), commercialized in the
USA as Palisade, has been accepted by producers as a yield enhancing agent
and is considered here as an alternative to open-field burning over a four-year
period.
The effects of open-field burning versus mechanical removal (flailing) of
post-harvest residue, and spring versus fall applications of TE on seed yield, dry
matter partitioning, and seed yield components were evaluated in a split-plot
design. The response to the different treatment combinations differed across
years. The young stand responded with a seed yield increase to spring TE
applications, regardless of residue management treatment. However, as the stand
aged, field burning became critical for maintaining high yields and, in 2003 and
2004, only spring TE applications resulted in seed yield increases in burned plots.
The higher potential seed yield achieved in burned plots over flailed plots,
as a result of a higher number of panicles per unit area and spikelets per panicle,
was critical for maintaining high seed yields as the stand aged. Spring
applications of TE, further increased seed yield over the untreated check by
increasing the number of florets per spikelet, reducing fertile tiller height and
lodging and consequently, favoring pollination and fertilization of the florets. Late
spring TE applications also increased 1000-seed weight in 2003 and 2004.
Although spring applications of TE were a promising alternative to open-field
burning early during the life of the stand, as the stand aged they did not
increase seed yield on flailed plots. Fall TE applications did not have a consistent
effect on seed yield, dry matter partitioning or seed yield components, and were
found not to be a viable management practice.Graduation date: 2005
24
Schumacher, Derek David. "Residue management and yield characteristics of fine fescue seed crops." Thesis, 2005. http://hdl.handle.net/1957/29436.
Full textAbstract:
Chewings fescue [Festuca rubra L. subsp. fallax (Thuill.) Nyman] is a desired
turfgrass with dense sod forming capabilities and superior shade tolerance. Thermal
residue management (open-field burning) has traditionally been used to remove post-harvest
residue and maintain seed yield over the life of the stand. However, alternative
non-thermal residue management practices have been observed to produce adequate
seed yields dependent upon cultivar.
Strong creeping red fescue (F. rubra L. subsp. rubra) is desired for
its prolific tillering capacity and creeping rhizomatous growth habit. In contrast to
Chewings fescue, maintenance of seed yield in strong creeping red fescue has only
been profitably produced under thermal residue management. Slender creeping red
fescue [F. rubra L. var. littoralis (Vasey)] is a desired turfgrass with a compact, less
rhizomatous growth habit, similar to Chewings fescue in desirable turf attributes.
However, little is known about the effects of post-harvest residue management in
slender creeping red fescue.
The objectives of this study were: 1) to evaluate seed yield and yield
components among different cultivars to thermal (open-burning), and non-thermal
(flail low and flail high) post-harvest residue management; 2) to evaluate harvest
index and percent cleanout to thermal and non-thermal residue management in
different cultivars; and 3) and to provide an economic analysis of thermal and non-thermal
residue management in all cultivars based on partial budgeting.
Three post-harvest residue management treatments (burn, flail low and flail
high) were applied over the course of two years. Seed yield components measured
included: total dry weight, fertile tiller number, spikelets per panicle, florets per
spikelet, and panicle length. Final seed yield in each cultivar and residue management
treatment method was determined after seed harvest and conditioning. Seed yield
component analysis was conducted over three production seasons.
Chewings fescue, strong creeping red fescue, and slender creeping red fescue
cultivars responded differently to residue management as indicated by a residue
management by cultivar interaction. In 2003 and 2004, residue management by
cultivar interactions were evident in seed number, seed weight, fertile tiller number,
percent cleanout, harvest index, and seed yield. Residue management by cultivar
interactions occurred in spikelets per panicle in 2003, whereas in 2004 a residue
management by cultivar interaction occurred in panicle length and florets per spikelet.
In 2004, non-thermal flail low, and thermal residue management resulted in
significantly greater spikelets per panicle in all cultivars. Thermal residue management
resulted in the greatest number of spikelets per panicle.
Results indicate that thermal residue management best maintained seed yield in
most subspecies and cultivars across both years. However, in 2003, non-thermal flail
low residue management produced profitable seed yield in only Marker slender
creeping red fescue. In contrast, thermal residue management resulted in poor seed
yields in Marker slender creeping red fescue and enhanced yields in Seabreeze slender
creeping red fescue in 2003. However, following the second year of thermal treatment
in 2004, Marker and Seabreeze both had lower seed yields, thus exhibiting the only
negative impact of thermal management among the cultivars tested in this study.
Moreover, upon review of an economic analysis, Marker slender red fescue was the
only cultivar that produced a positive net return of $78 and $4 ha⁻¹ under non-thermal
residue management in 2003 and 2004, respectively. Furthermore, in 2003, thermal
residue management net return increases ranged from $104 ha⁻¹ to -$996 ha⁻¹ in
Barnica and Shademark, respectively. In 2004, thermal residue management net return
increases ranged from $115 ha⁻¹ and $1,332 ha⁻¹ in Seabreeze and Shademark,
respectively.
Poor seed yields were observed in all strong creeping red fescue cultivars
under non-thermal residue management across both years of the study. This may be
attributed to an observed reduction in fertile tiller number and seed yield. In addition,
percent seed cleanout was increased with non-thermal residue management. In 2004,
as stand age increased, thermal residue management resulted in greater seed yields in
all cultivars and species, except both cultivars of slender creeping red fescue. Thus,
this study provided substantial evidence that thermal residue management has the
potential to maintain or increase fine fescue seed yield as stands age as well as to
maintain stand profitability.Graduation date: 2005
25
Qureshi, Maqsood Hassan. "Nitrogen available to winter wheat as influenced by previous crop in a moist xeric environment." Thesis, 1999. http://hdl.handle.net/1957/33521.
Full textAbstract:
Rotating wheat with other crops is a common practice in the Willamette Valley of
western Oregon. Depending upon previous crop and soil type, current N fertilizer
recommendations for wheat in the Willamette Valley vary widely. Excessive fertilizer
poses environmental risk, whereas lower N inputs than required by the crop represent
economic losses to growers. Growers and their advisors face the challenge to minimize
the environmental risk, and at the same time to maintain or increase economic returns.
Questions are often raised concerning the efficient use of N fertilizer and accurately
predicting the amount of N needed by wheat following different crops.
The first study measured growth, N uptake and N use efficiency (NUE) of winter
wheat grown after either a legume or oat for three years. In all three growing seasons,
winter wheat showed higher biomass, N uptake and NUE when grown after a legume
than after oat. The contribution of legume was evident before the wheat was fertilized in
spring, indicating that legume N had mineralized in fall or winter.
Contribution of soil N to wheat suggested that fertilizer N can be reduced by 44 kg N ha�����
if a legume is grown previously. Nitrogen use efficiency estimated 50 to 70 days after N
application by isotopic method (24 to 94%) was comparable with that estimated simply
by difference (21 to 94%) at the same time.
The second study predicted gross mineralization rates using analytical models.
Comparable N mineralization was predicted by a model assuming remineralization and a
model assuming no remineralization, suggesting that remineralization was negligible. In
the spring, mineralization-immobilization turnover was at a lower pace than expected in
both rotations. In two growing seasons, gross mineralization rates were higher where the
previous crop was legume (0.37 to 0.74 kg����� ha����� day�����) as compared to where oat was
grown previously (0.14 to 0.6 kg����� ha����� day). Negative net mineralization indicated that
fertilizer N was immobilized in the oat-wheat rotation.
The third study evaluated calibration and digestion techniques used to determine
elemental concentration in grasses. Use of a dry ashed standard to calibrate the ICP
spectrometer generated highly variable calibration curves and was not a viable calibration
method. Good agreement was found between chemical and microwave digested
standards. Dry ashing resulted in considerable S and Mn losses, whereas, perchloric acid
digestion and microwave digestion showed similar results. Our study suggests that if
routine analysis are to be performed for macro nutrients or involve trace level work, the
best method is microwave digestion with chemical standard calibration of ICP
spectrometer.Graduation date: 1999
26
Marx, Ernest S. "Evaluation of soil and plant analyses as components of a nitrogen monitoring program for silage corn." Thesis, 1995. http://hdl.handle.net/1957/34685.
Full text
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Kennedy, Ralph C. "Producing fiber flax using modern machinery and field retting." Thesis, 1996. http://hdl.handle.net/1957/34199.
Full textAbstract:
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
28
Hylton, Lindon B. "Peavy Arboretum : an archaeological and historical investigation of a Willamette Valley landscape." Thesis, 1998. http://hdl.handle.net/1957/35214.
Full textAbstract:
This thesis documents a period of ecological and cultural change on a Willamette
Valley, Oregon landscape. In particular, this study examines the Peavy Arboretum area
and the cultural changes that accompanied the transformation of the landscape from an
oak savannah in the mid-nineteenth century to a dense Douglas-fir forest in the early
twentieth century. Culturally, the inhabitants of this period included late-prehistoric
native people, Euro-American based fur industry personnel, and Euro-American
settlers.
As a student of history and archaeology, I have used a combination of methods and
sources for this study including surface surveys for cultural materials and features,
archaeological excavations and analysis, and documented materials. Knowledge gained as
a result of surveys and excavations are studied within the context of other Willamette
Valley archaeology, and likewise, documented materials concerning this landscape and its
historic features and people are compared against larger patterns in the history of the
American West.
Geographically, the study area was in a fortunate position to witness cultural
events. Located along the edge of the foothills of the Willamette Valley, its many
desirable features attracted both native people and the first white settlers. The study area was also located along a main route of travel that was used by natives, fur company personnel, travelers, and Euro-American settlers. The section of trail has been a part of regional travel routes known at different times as the Hudson's Bay Company Trail, the California Trail, the Southern Route (Scott-Applegate Trail), and the Territorial Road.
The objective of this thesis was to see what kind of information could be retrieved for a given landscape using a variety of methods practiced in history and archaeology. I believe such a multi-disciplinary approach allowed me to be more flexible and open to all pertinent sources of information. This type of investigation also provided an example of the type of work that could be done professionally when determining the cultural significance of a property. My fascination with the study of landscapes and their cultural features was also influential in my selection of a thesis topic.Graduation date: 1999
29
Mini, Anne E. "The role of body size in the foraging strategies and management of avian herbivores : a comparison of dusky Canada geese (Branta canadensis occidentalis) and cackling geese (B. hutchinsii minima) wintering in the Willamette Valley of Oregon." Thesis, 2012. http://hdl.handle.net/1957/35459.
Full textAbstract:
Body size explains much of the interspecific variation in the physiology, behavior, and morphology of birds, such as metabolic rate, diet selection, intake rate, gut size, and bill size. Based on mass-specific metabolic requirements and relative energetic costs of activities, being a certain body size has both advantages and disadvantages. In particular, avian herbivores such as geese possess a relatively simple digestive system, consume foods with low digestibility and poor nutrient content, and have increased energetic demands compared to other bird taxa; therefore, any effects of body size on foraging strategies should be readily apparent in this foraging guild. The influence of body size on the behavior and management of Canada Geese (Branta canadensis) and Cackling Geese (B. hutchinsii) as avian herbivores has not been well studied.
My dissertation explores the role of body size in comparative foraging behavior, habitat selection, and winter conservation planning for two congeneric geese, the Dusky Canada Goose (B. c. occidentalis; hereafter Duskys) and the Cackling Goose (B. h. minima; hereafter Cacklers). These two taxa share the same over-winter foraging environment (grass seed fields) in the same restricted geographic area (the Willamette Valley) during winter. Duskys and Cacklers differ by more than a factor of two in body size and have different relative bill sizes and social organization. Because of smaller body size, Cacklers have greater relative energy demands and less fasting endurance compared to Duskys; however, Cacklers have comparatively low energetic costs for flight and transport. Duskys, however, have higher total energy requirements than Cacklers. Additionally, Cacklers form large, high-density flocks and have a total over-wintering population size in the study area of about 200,000. Duskys occur in relatively small family groups and have a total over-wintering population size of about 13,000.
My study demonstrated that interspecific differences in body size between Cacklers and Duskys was associated with differences in foraging behavior, movements, and habitat selection. Cacklers foraged a greater percentage of time (30%) in all habitats and across the entire winter compared to Duskys. Cacklers had higher peck rates (up to 100 pecks min⁻¹ greater) than Duskys in all foraging habitats expect pasture. The pecking rate of Cacklers was greatest in fields of young grass (200 pecks min⁻¹), which may indicate that Cacklers had relatively high intake rates in this foraging habitat. Based on differences in foraging behavior among habitats, Cacklers may have the foraging strategy of energy intake maximizers, whereas the foraging strategy of Duskys is more towards time-energy expenditure minimizers, at least for part of the winter. Cacklers moved across the landscape very differently from
Duskys, exhibiting less site fidelity and greater commuting distances to foraging areas. Cacklers showed a preference for young grass during all periods of the winter, reaffirming that Cacklers are specialized grazers on short green forage, whereas Duskys preferred young grass and pasture. Fields of young grass were the preferred foraging habitat of Cacklers, had less standing crop biomass, and may have enabled higher foraging efficiencies, which may have led to higher intake rates.
The ability of the landscape to support wintering geese changed across the winter because total available plant biomass fluctuated with the rate of grass regrowth. The estimated carrying capacity of the landscape for geese decline by almost one-half during mid-winter (mid-December to mid-February) compared to early winter or late winter periods. Although Cacklers have lower individual energy requirements compared to Duskys, due to a much larger target population size, Cacklers required 89% more foraging habitat than Duskys. Forage requirements encountered a bottleneck during mid-winter, when grass regrowth rates were low and day length was short. Commensurate with this pattern of forage availability, goose body condition declined during the mid-winter period. To support Pacific Flyway target populations for geese, approximately 18,000 ha of total grazing habitat in young and mature grass is needed in the Willamette Valley to support a total over-wintering population composed of 340,000 geese belonging to four subspecies.
The role of body size in influencing the foraging behavior and decisions of over-wintering geese has important implications for conservation planning of goose populations. Small-bodied Cacklers are selective in field choice, yet more likely to
redistribute across the landscape. Disturbances (e.g., hunting, hazing, or predation) will have a disproportionate effect on the movements of smaller-bodied geese compared to larger geese. These characteristics of Cacklers will make conservation planning to retain geese on public land more difficult. Coordinated management with private landowners and farming practices that maximize preferred goose foraging habitat on public lands may attract geese to utilize protected areas and minimize conflicts with agriculture in the Willamette Valley. Availability of resources during critical periods in winter is an important factor affecting the distribution of geese, but may affect small and large bodied geese differently. Management could be targeted during these critical time periods. By considering the role of body size in the context of life history characteristics, foraging behavior and habitat selection, appropriate management strategies can be developed and implemented to reduce the effects of agricultural depredation by geese, while promoting the future conservation of wintering geese in the Willamette Valley.Graduation date: 2013
30
Marshall, Sarah M. (Sarah Marie). "The effects of land use on mineral flat wetland hydrologic processes in lowland agricultural catchments." Thesis, 2011. http://hdl.handle.net/1957/26310.
Full textAbstract:
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
31
Herrera, Tere Lynn. "The similarity of texted musical grammar to oral communication : exploring grammar, text and content with examples from fieldwork with Grupo Kultura." Thesis, 1997. http://hdl.handle.net/1957/28465.
Full textAbstract:
The goal of this study is to elucidate the similarities between the grammar of
oral folk music and oral language grammar through field examples from Grupo
Kultura, a group of neo-Latin American musicians in the mid-Willamette Valley area
of Oregon.
The linguistic analysis of oral folk music explores textual and contextual
issues which serve to highlight the need to include such forms of communication as
music in an expanded view of "language." It suggests both fluid and non-fluid
boundaries between spoken language and oral folk music. Of particular emphasis
are the potential ability of music to express deep emotional content in music and the
possible decoding of that content's musical meaning.
Data was collected through ethnographic interviews and participant
observation.Graduation date: 1998
32
Louhaichi, Mounir. "Methods to assess factors that influence grass seed yield." Thesis, 2002. http://hdl.handle.net/1957/30906.
Full textAbstract:
A greater than 10-fold increase in Canada goose (Branta canadensis)
populations over the past several years has resulted in concerns over grazing
impacts on grass seed production in the mid-Willamette Valley, Oregon. This
study was designed to develop methods to quantify and statistically analyze goose-grazing
impacts on seed yields of tall fescue (Festuca arundinacea Schreb.) and
perennial ryegrass (Lolium perenne L.). Yield-mapping-system equipped
combines, incorporating global positioning system (GPS) technology, were used to
measure and map yields. Image processing of ground-level photography to
estimate crop cover and other relevant observations were spatially located via GPS
to establish spatial-temporal goose grazing patterns. We sampled each field semi-monthly
from mid-winter through spring. Spatially located yield data, soils
information, exclosure locations, and grazing patterns were integrated via
geographical information system (GIS) technology. To avoid concerns about
autocorrelation, a bootstrapping procedure for subsampling spatially contiguous
seed yield data was used to organize the data for appropriate use of analysis of
variance. The procedure was used to evaluate grazing impacts on seed yield for
areas of fields with different soils and with differential timing and intensity of
goose grazing activity. We also used a standard paired-plot procedure, involving
exclosures and associated plots available for grazing. The combination of spatially
explicit photography and yield mapping, integrated with GIS, proved effective in
establishing cause-and-effect relationships between goose grazing and seed yield
differences. Exclosures were essential for providing nongrazed controls. Both
statistical approaches were effective in documenting goose-grazing impacts.
Paired-plots were restricted by small size and few numbers and did not capture
grazing impacts as effectively as comparison of larger areas to exclosures.
Bootstrapping to subsample larger areas of yield for comparison was an effective
method of avoiding autocorrelation of data while better representing impacts within
a field. Occasional yield increases, ranging from 1 to 5 percent, were recorded
following goose grazing. Goose grazing generally resulted in seed yield
reductions, ranging up to 20 percent. Later and more intensive grazing tended to
increase yield reductions. Newly seeded tall fescue tended to be the most sensitive
to grazing. Established perennial ryegrass tended to be more resilient.Graduation date: 2003
33
Doyle, Douglas J. 1963. "Determinants of off-farm labor supply among farm households in the north Willamette Valley." Thesis, 1987. http://hdl.handle.net/1957/26852.
Full textAbstract:
Financial stress in agriculture has been a concern over the past
century. Agrarian values and "love of the land" seem to yield public
conclusions for the support of the industry. Much of this support is
in the interest of preserving a viable food producing sector in an
volatile world climate. High interest rates, declining land values
and highly competitive export markets have spurred renewed concern
for farm survival in the past ten years.
One alternative to traditional price supports and tariffs for
farm household support is off-farm income. This may take many forms
including off-farm wages and salaries, rental income, interest and
dividend income and, retirement or pension funds. Central to the
analysis of nonfarm income generation is the allocation of time by
farm households. For farmers who place a high value on the farm
lifestyle, occupational choice is embedded in the time decision to
such an extent that the resource allocations based on economic efficiency
criteria may be altered.
Tobit techniques offer a new approach to the analysis of farm
household decisions on time allocation. The procedure allows the investigator
to estimate and evaluate parameters that may affect the
amount of off-farm work by farm household members. The Tobit
analysis is designed for censored data sets. The data in this study
were censored because there were missing observations on the quantity
of off-farm work for those individuals who did not work off-farm in
1986.
Results of Tobit analyses of off-farm work by farm operators and
spouses in three Oregon counties indicated that high levels of gross
farm income reduce the likelihood and extent of off-farm work.
Middle-aged operators worked off-farm more while the presence of
small children and elderly dependents in the farm household inhibited
off-farm work. The allocation decisions of the spouse and the
operator appeared to be independent; this supports a nonsimultaneous
Tobit specification like the one used in this research.Graduation date: 1988
34
Phillips, Wendy S. "Drivers of arbuscular mycorrhizal fungal community composition in roots : hosts, neighbors, and environment." Thesis, 2012. http://hdl.handle.net/1957/34446.
Full textAbstract:
The vast majority of terrestrial plant species live in symbiosis with arbuscular mycorrhizal fungi (AMF). AMF and plants live in complex networks, with roots of individual plants hosting multiple AMF, and single AMF colonizing multiple plants concurrently. Through the exchange of resources, the two partners of this symbiosis can have great effects on each other, effects which can ripple through both communities. What determines the patterns of associations between the partners is still largely unknown. In this dissertation, I examine a variety of factors, and in particular host identity, that could drive the community composition of AMF in roots.
I began by surveying the diversity of AMF in roots of 12 plant species at a remnant bunchgrass prairie in Oregon, U.S.A. (Chapter 2). To do that, I first designed new primers for use in polymerase chain reaction (PCR) to specifically amplify DNA from all Glomeromycota species. Using those primers, I found 36 distinct AMF phylogenetic groups, or operational taxonomic units (OTUs) in the roots from the
prairie. The proportion of OTUs in the basal order Archaeosporales was greater than in many other environmental surveys. I also conducted an in silico analysis to predict how effectively previously published primers would detect the whole diversity of OTUs I detected.
I then assayed AMF community composition in the roots of 50 plants from nine plant species (Chapter 3). To do that, I designed primers specific to 18 of the OTUs detected in the initial field survey and used them to test for the presence of each OTU in the roots individual plants. I used that data to test if AMF community composition in individual roots correlated with host identity, spatial distribution, or soil characteristics. I found host identity was associated with both the richness and the structure of root AMF communities, while spatial distribution and soil characteristics were not.
Finally, I performed an experimental test of the effect of host identity and community context on AMF community assembly (Chapter 4). I grew plants from four native perennial plant species, including two common and two federally endangered plants, either individually or in a community of four plants (with one plant of each species). I analyzed the AMF community composition in the roots of all plants after 12 weeks of growth with exposure to a uniform mix of field soil as inoculum. I found that host species identity affected root AMF richness and community composition, and community context affected AMF richness. Only one of the endangered species was highly colonized by AMF, and I did not detect unique AMF communities associated with it.
This dissertation provides information on the diversity of AMF at a remnant bunchgrass prairie, an ecosystem which has been the subject of very few studies of AMF. Although a complex mix of factors interact to determine AMF community composition in roots, this work provides strong evidence that host identity plays a major role in that process.Graduation date: 2013
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Gallagher, Katie J. (Katherine Jean). "Recruitment predictors of an endangered prairie species : a case study of Erigeron decumbens." Thesis, 2012. http://hdl.handle.net/1957/30472.
Full textAbstract:
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
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Klingensmith, Thomas S. "Civic agriculture : the successes, trials, and future of the local food movement in the Willamette Valley." Thesis, 2012. http://hdl.handle.net/1957/31349.
Full textAbstract:
This study investigated the local and sustainable food movements in the Willamette Valley of Oregon. The aim of the research was to better understand the current condition of the phenomenon, what it means to the communities studied and the future role it will play in the state. Other research objectives that were studied included the impact of demographics on food movements, successes and barriers to success and determining the motivations of people involved.
Key players in the city of Corvallis and Portland were interviewed to gather qualitative data about the movement. Interviewees were chosen based on criteria established through literature review that pointed towards groups that would be the most valuable on which to focus.
The study revealed a dynamic and progressive social movement that has profound and beneficial implications on the civic wellbeing of the communities studied both currently and for their future. In addition, through this work key goals were identified that can be transferred to other communities looking to work towards a more sustainable food system in order to better facilitate their growth and prosperity.Graduation date: 2013
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Jones, Katherine D. "Factors affecting establishment and germination of upland prairie species of conservation concern in the Willamette Valley, Oregon." Thesis, 2012. http://hdl.handle.net/1957/29047.
Full textAbstract:
Identifying mechanisms that determine who lives and dies is the first step in developing successful restoration techniques for rare species and endangered habitats. We studied interactions that affect establishment of native plant forbs of conservation concern at the seedling stage to support the theoretical basis for restoration activities in Pacific Northwest prairies. Specifically, we tested the hypothesis that seedling establishment is controlled by 1) competition with or 2) facilitation by existing vegetation and that the interaction is mediated in part by environmental stress.
We direct-seeded or planted vegetative plugs of Lupinus oreganus, Castilleja levisecta, Erigeron decumbens, Iris tenax and Sidalcea malviflora ssp. virgata into 20 plots with a range of community compositions in high-stress upland prairies at each of three sites. We counted seedlings and estimated cover of plant functional groups as well as litter, bare soil and disturbance then used linear regression to test for effects of these factors on seedling establishment.
We found evidence of indirect facilitation of grass on seedling establishment in the first year: higher accumulations of leaf litter increased seedling numbers at two sites. In the second year, there was evidence of facilitation by live vegetation and
litter on seedlings at one site, but no net effect of either competition or facilitation at the other two sites.
Overall, we found more evidence for positive interactions than we did for competition. In particular, litter appeared to have a positive effect on seedling establishment of L. oreganus and S. malviflora ssp. virgata. This is contrary to the common perception that litter inhibits plant establishment but supports the theory that facilitation is more common in high stress sites; practitioners should consider seeding into leaf litter at some sites.
To support a robust approach to conservation and reintroduction of species with dormant seed, we characterized dormancy types and developed germination protocols for S. malviflora ssp. virgata and I. tenax. S. malviflora ssp. virgata has physical dormancy and may have physiological dormancy. Scarification followed by four weeks of cold moist stratification was effective in initiating germination. I. tenax has morphophysiological dormancy which is overcome by four weeks of warm moist stratification followed by 6-12 weeks of cold stratification. We also conducted a meta-analysis of experiments that tested pre-sowing seed scarification of L. oreganus and conclude that breaking physical dormancy prior to direct seeding does not support higher establishment relative to unscarified seeds in this species.Graduation date: 2012
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Nelson, Natasha. "The effects of patch size and isolation on juvenile emigration in gray-tailed voles, Microtus canicaudus." Thesis, 1996. http://hdl.handle.net/1957/33978.
Full text
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Brunkal, Heidi L. "Over-winter demography of the gray-tailed vole (Microtus canicaudus) in fragmented and continuous habitats." Thesis, 1996. http://hdl.handle.net/1957/34000.
Full textAbstract:
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
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Kasana, Abdulmajid. "Developmental biology and phenology of the walnut husk fly, Rhagoletis completa Cresson (Diptera: Tephritidae) in the Willamette Valley of Oregon." Thesis, 1993. http://hdl.handle.net/1957/35640.
Full text
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Stepp, David. "Descriptive analysis of human remains from the Fuller and Fanning Mounds, Yamhill River, Willamette Valley, Oregon." Thesis, 1994. http://hdl.handle.net/1957/36847.
Full textAbstract:
The study presents the results of a descriptive analysis of the skeletal remains of 66
individuals recovered from the Fuller and Fanning Mound sites, located on the Yamhill River,
Willamette Valley, Oregon, excavated in 1941-42 by W. T. Edmundson and William S.
Laughlin. The literature and original field notes have been analyzed, and a description of burial
type, side, orientation, grave type, associations, original preservation, and other information has
been compiled for each individual. A tally of each of these burial attributes for the Yamhill
population as a whole is also completed. In addition, an assessment of age, sex, and stature, a
series of craniometric measurements, and non-metric traits, a dental analysis, and general
description of obvious pathologic and morphologic condition of each individual and the group
as a whole have been accomplished.
Differences in trade item associations between deformed and non-deformed individuals
suggest either a later arrival of cranial deformation practices (and possibly another cultural
group) to the area, and possibly a multiple occupation of the Fuller and Fanning sites, or an elite
class separation defined in part by artificial deformation of crania. Cranial deformation is also
associated with the frequency of certain cranial discrete traits. Sexual dimorphism was noted in
metric but not in non-metric analyses. Stature estimates indicate a population with mean stature
of 1636-1661 for males, and 1547-1574 for females, typical among prehistoric Oregon
populations. Mortality appears high for infants and adolescents when compared with other
prehistoric North American samples. Dental attrition and caries may indicate a heavier reliance
on plant than on animal foods. Single trait comparison to other regional populations shows
some significant differences and indicates a need for further analysis of biological relationships
using larger comparative samples and multivariate statistics.Graduation date: 1994
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Mower, Jennifer M. "Oregon outdoor garments : outdoor garments worn in the Willamette Valley and Eastern Oregon regions between 1880 to 1920." Thesis, 2006. http://hdl.handle.net/1957/28957.
Full textAbstract:
The purpose of this study was to describe women's outdoor garments
worn in Oregon from 1880 to 1920 to determine whether there were garment
differences between the Willamette Valley and Eastern Oregon. The question
addressed was: can garment differences be explained by the different Oregon
climates, geographic locations, and availability of goods throughout Oregon
during this time?
Harper's Bazar and The Ladies' Home Journal were used to identify
popular outdoor garment styles by date. A data collection instrument was
developed using other instruments and secondary sources as guides. The form
allowed collection of information about garment construction, fiber and fabric,
and style. Various historical societies and museums throughout Oregon were
visited and extant garments from various historical clothing collections were
analyzed, photographed, and drawn to scale. When available, information about
the original owner and use of the outdoor garments were collected.
The information was coded, and it was determined that the sample was too
small to statistically determine if there were regional outdoor garment differences.
Therefore, frequencies were analyzed and compared. There were some regional
garment differences, but they do not appear to be the result of climate and
geographic differences. Differences were most likely due to the availability of
ready-to-wear outdoor garments and materials. Some outdoor garments were
used only for special occasions, while others were worn by multiple family
members over a long period of time.Graduation date: 2006
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Louhaichi, Mounir. "Assessment of impacts of Canada geese on wheat production." Thesis, 1999. http://hdl.handle.net/1957/33615.
Full textAbstract:
Numbers of wild Canada geese (Branta canadensis) have increased dramatically during the past 30 years in the lower Columbia and Willamette Valley systems. The damage they cause by grazing and trampling plants can be substantial.
The objectives of this research were to:
1) Develop methods that provide reliable estimates of goose impact on wheat yield and quality, and 2) Develop methods to separate goose damage from other factors that lower
yield such as poor soil or waterlogging.
To document grazing impacts, color aerial photography was combined with Global Positioning System (GPS) and precision farming technology. Field-scale color aerial photographs (1:14,000 scale) were acquired four times during each growing season: in January, March, April, and just prior to harvest in July. Each flight was coupled with ground truth data collection to verify exact cause of spectral signature variation or variations in wheat cover. Such data included wheat height, number of goose droppings, and a relative rating of goose grazing intensity. At each sampling point a platform photograph and a GPS location were taken.
Wheat yield impact varied considerably as field size, shape and proximity to road varied. Yield maps revealed that, goose grazing had reduced grain yield by 25% or more in heavily grazed areas. At harvest time during the first year, wheat grain in the heavily grazed areas had higher moisture content due to delayed maturity. Therefore those areas were harvested two weeks later. Heavily grazed areas also had more weeds than ungrazed portions of the field. Late-season (April) grazing was more damaging to wheat yield than was earlier season grazing, but early season grazing did have an impact on yield. Intensely hazed fields had lower levels of damage than did fields or portions of fields that were not as vigorously guarded.
Our results illustrate very practical ways to combine image analysis capability, spectral observations, global positioning systems, precision farming and ground truth data collection to map and quantify field condition or crop damage from depredation, standing water, or other adversities. Image analysis of geopositioned color platform photographs can be used to stratify winter wheat fields into impact units according to grazing intensity. Ground-truth data, when collected in conjunction with a GPS, provided the information needed to locate and establish the spectral properties of impacted areas. Once the spectral properties of a representative area were identified, information could be extrapolated to other areas with the same characteristics. In addition, this method could be used in conjunction with aerial photography to verify areas of grazing. The combination of two or more of these tools would provide farm managers and agricultural consultants with a cost-effective method to identify problem areas associated with vegetation stress due to heavy grazing by geese or other factors.Graduation date: 1999
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Viste-Sparkman, Karen. "White-breasted nuthatch density and nesting ecology in oak woodlands of the Willamette Valley, Oregon." Thesis, 2005. http://hdl.handle.net/1957/890.
Full textAbstract:
Graduation date: 2006Habitat 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.
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Calkin, James D. "Distribution of Oligonychus (Oligonychus) ununguis (Jacobi) (Acari: Tetranychidae) and predator mite species (Acair: Phytoseiidae) on field-grown Douglas-fir (Pseudotsuga menziesii [Mirb] Franco) Christmas trees." Thesis, 1991. http://hdl.handle.net/1957/38054.
Full textAbstract:
The shake and wash technique (samples placed in a jar with alcohol added and
shaken to remove the mites) was effective in removing 100% of the predator mites, and adult
spruce spider mites from Douglas-fir foliage and 98% of the spruce spider mite nymphs.
Eighty-eight percent of the spruce spider mite eggs was removed. This technique was
considered efficient for removal of spruce spider mite and its predators from Douglas-fir
foliage. Sodium hypochlorite (0.84%) added to the alcohol did not increase the number of
spruce spider mites or phytoseiid mites removed from the foliage.
The intracanopy distribution of spruce spider mite and its predator mites was studied
on Douglas-fir Christmas trees in the Willamette Valley, Oregon. When overwintering
spruce spider mite egg densities populations were low (<5 eggs/19 cm of stem), significantly
more eggs were found on the current season's growth. No significant differences were
found between top and bottom halves of the tree or between compass directions.
Differences between current and previous season's growth were not found when egg
densities were high (>40 eggs/19 cm of stem), but significant differences were found
between levels for current season's growth with more eggs found in the upper portion of the
canopy. Quadri-directional differences did not exist with either low or high mite
populations. Sampling tip or basal stem-halves with low overwintering egg populations did
not bias population estimates.
Heavy spring rainfall appeared to reduce mite populations as has been reported
elsewhere by washing them off the tree and causing increased mortality. Spruce spider mite
disperse to the current season's growth shortly after budbreak. Population density rapidly
increased in late May and then abruptly declined in mid-July.Graduation date: 1991