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The effects of land use on mineral flat wetland hydrologic processes in lowland agricultural catchmentsMarshall, Sarah M. (Sarah Marie) 16 September 2011 (has links)
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
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Enhancing the predatory potential of hoverflies on aphids in Oregon broccoli fields with floral resourcesAmbrosino, Mario D. 13 March 2006 (has links)
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
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Trinexapac-ethyl and open-field burning in creeping red fescue (Festuca rubra L.) seed production in the Willamette ValleyZapiola, Maria Luz 22 October 2004 (has links)
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
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Effects of fire on seedling establishment in upland prairies in the Willamette Valley, OregonMaret, Mary P. 17 December 1996 (has links)
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
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Effects of ryegrass residue management on Dayton soil organic carbon content, distribution and related propertiesChapin, Michele F. 13 March 1992 (has links)
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
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The effect of nitrogen, irrigation, and cultivation on Pinot noir juice and wine composition from the Willamette Valley, OregonWall, Katherine Elizabeth 05 November 2003 (has links)
Graduation date: 2004
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Drivers of arbuscular mycorrhizal fungal community composition in roots : hosts, neighbors, and environmentPhillips, Wendy S. 06 September 2012 (has links)
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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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 OregonMini, Anne E. 11 October 2012 (has links)
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
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Determinants of off-farm labor supply among farm households in the north Willamette ValleyDoyle, Douglas J., 1963- 10 August 1987 (has links)
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
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The similarity of texted musical grammar to oral communication : exploring grammar, text and content with examples from fieldwork with Grupo KulturaHerrera, Tere Lynn 08 August 1997 (has links)
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
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