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Research about Willamette Valley

Source-linked reports with geographic coverage including Willamette Valley.

18 recordsLinked to original sources
USGS2022

Minimal diel vertical migration and consistent zooplankton capturability in low productivity reservoirs, Oregon

Diel migrations of zooplanktons occur in marine and freshwater systems and can complicate inferences from studies. If populations perform vertical or horizontal diel migrations, daytime-only sampling can mischaracterize distributions and abundances. Zooplanktons also often display reduced capture avoidance at night and occupy areas easier to sample near the surface and away from littoral structure and the benthos. We examined zooplankton abundance, water column position and taxonomic composition during daytime and nighttime new moon periods using discrete depth sampling in oligo-mesotrophic reservoirs in Oregon, USA. These reservoirs have limited littoral structures, but support populations of zooplanktivorous fishes that we expected to drive diel vertical migrations. Contrary to our expectations, at night, most zooplankton taxa were within 2 m of their daytime distributional peak and did not display differences in abundance from day to night sampling. We consider factors that may help predict whether diel vertical migration occurs in a system. Where daytime sampling is sufficient to characterize zooplankton densities and distributions, costs and risks specific to nighttime sampling may be avoided. Improving our knowledge of zooplankton dynamics, particularly in ecosystems with limited diurnal variability, is an important part of understanding lake and reservoir food webs and can optimize the efforts of future studies.

Oregon↗
USGS2019

Disentangling effects of invasive species and habitat while accounting for observer error in a long-term amphibian study

The invasive American bullfrog ( Lithobates catesbeianus ) and a variety of non‐native sport fish commonly co‐occur in lowland lentic habitats of the western United States. Both invasive taxa are implicated in declines of native amphibians in this region, but few long‐term studies of communities exist. Further, field studies of invasive–native interactions are complicated by confounding habitat modifications and observation errors. We surveyed amphibians and measured habitat characteristics for 12 yr across 38 wetland sites within the Willamette Valley, Oregon, USA. We assessed the influence of invasive species, habitat, and their interactions on the distributions of five native amphibian species using a multispecies dynamic occupancy model that accounted for false‐negative and false‐positive detections. In general, habitat characteristics—such as within‐pond vegetation cover, surrounding forest, and drought severity—were important for local persistence of native species when bullfrogs co‐occurred. We also found evidence of a cumulative negative effect of bullfrogs and non‐native fish (families Centrarchidae and Ictaluridae) on northern red‐legged frog ( Rana aurora ) local persistence that was mediated by the dominance of invasive reed canarygrass ( Phalaris arundinacea ). Non‐native fish and bullfrogs had variable effects on native amphibian species, but neither invasive taxon appears to be causing declines in occupied sites within our study area. Moreover, species relationships with habitat differed when invaders were present, indicating that certain habitats may increase persistence of native amphibians in the invaded landscape.

Oregon↗
USGS2017

Chronology and ecology of late Pleistocene megafauna in the northern Willamette Valley, Oregon

Since the mid-19th century, western Oregon's Willamette Valley has been a source of remains from a wide variety of extinct megafauna. Few of these have been previously described or dated, but new chronologic and isotopic analyses in conjunction with updated evaluations of stratigraphic context provide substantial new information on the species present, timing of losses, and paleoenvironmental conditions. Using subfossil material from the northern valley, we use AMS radiocarbon dating, stable isotope (δ 13 C and δ 15 N) analyses, and taxonomic dietary specialization and habitat preferences to reconstruct environments and to develop a local chronology of events that we then compare with continental and regional archaeological and paleoenvironmental data. Analysis of twelve bone specimens demonstrates the presence of bison, mammoth, horse, sloth, and mastodon from ~ 15,000–13,000 cal yr BP. The latest ages coincide with changing regional climate corresponding to the onset of the Younger Dryas. It is suggested that cooling conditions led to increased forest cover, and, along with river aggradation, reduced the area of preferred habitat for the larger bodied herbivores, which contributed to the demise of local megafauna. Archaeological evidence for megafauna–human interactions in the Pacific Northwest is scarce, limiting our ability to address the human role in causing extinction.

Oregon↗
USGS2016

Identification and distribution of the Olympic Shrew (Eulipotyphla: Soricidae), Sorex rohweri Rausch et al., 2007 in Oregon and Washington, based on USNM specimens

Review of specimens of long-tailed shrews (Mammalia, Soricidae, Sorex ) from the northwestern United States in the National Museum of Natural History (USNM), Washington, DC, has revealed the presence of the Olympic Shrew, Sorex rohweri Rausch et al., 2007, in the Coastal Range west of the Willamette Valley in Oregon. This determination nearly doubles the documented distribution for this species and increases the species diversity of soricids in Oregon to eleven. Sorex rohweri is relatively uncommon, but it occurs in a variety of forest successional stages and even clear cuts, as long as there is nearby forest and trees are allowed to regenerate. All USNM specimens from Washington formerly identified as S. cinereus streatori Merriam, 1895 are instead referable to the Olympic Shrew. The distribution of S. c. streatori is thereby restricted to the Pacific coasts of British Columbia north of the lower Frasier River and south central Alaska. Our study highlights the importance of taking and preserving high-quality voucher specimens in a collection where they are readily available for re-study.

Oregon↗
USGS2011

Non-native species impacts on pond occupancy by an anuran

Non‐native fish and bullfrogs ( Lithobates catesbeianus ) are frequently cited as contributing to the decline of ranid frogs in the western United States, so we hypothesized that non‐native species, habitat, or a combination of these relate to the probability of local extinction for northern red‐legged frogs ( Rana aurora ) in Oregon, USA. We also hypothesized that the probability of colonization relates to land use, wetland size, or riparian forest. In a 5‐yr study, we found no support for an effect of non‐native species on northern red‐legged frogs. Instead, probability of local extinction decreased with the extent of emergent vegetation and riparian forest. This finding suggests that managers consider the role of habitat when confronting non‐native species problems.

Oregon↗
USGS2011

Seasonal movement, residency, and migratory patterns of Wilson's Snipe (Gallinago delicata)

Cross-seasonal studies of avian movement establish links between geographically distinct wintering, breeding, and migratory stopover locations, or assess site fidelity and movement between distinct phases of the annual cycle. Far fewer studies have investigated individual movement patterns within and among seasons over an annual cycle. Within western Oregon's Willamette Valley throughout 2007, we quantified intra- and interseasonal movement patterns, fidelity (regional and local), and migratory patterns of 37 radiomarked Wilson's Snipe ( Gallinago delicata ) to elucidate residency in a region of breeding- and wintering-range overlap. Telemetry revealed complex regional population structure, including winter residents (74%), winter transients (14%), summer residents (9%), and one year-round resident breeder (3%). Results indicated a lack of connectivity between winter and summer capture populations, some evidence of partial migration, and between-season fidelity to the region (winter-resident return; subsequent fall). Across seasons, the extent of movements and use of multiple wetland sites suggested that Wilson's Snipe were capable of exploratory movements but more regularly perceived local and fine-scale segments of the landscape as connected. Movements differed significantly by season and residency; individuals exhibited contracted movements during late winter and more expansive movements during precipitation-limited periods (late spring, summer, fall). Mean home-range size was 3.5 ± 0.93 km 2 (100% minimum convex polygon [MCP]) and 1.6 ± 0.42 km 2 (95% fixed kernel) and did not vary by sex; however, home range varied markedly by season (range of 100% MCPs: 1.04–7.56 km 2 ). The results highlight the need to consider seasonal and interspecific differences in shorebird life histories and space-use requirements when developing regional wetland conservation plans.

Oregon↗
USGS2002

Residency and movement patterns of wintering dunlin in the Willamette Valley of Oregon

In the winters of 1998–1999 and 1999–2000, we tracked 67 radio-marked Dunlin ( Calidris alpina ) throughout the complex agricultural landscape of the Willamette Valley of Oregon. Individual birds were tracked across 8-week sampling periods and indicated a high degree of regional fidelity throughout the three winter sampling periods. Birds exhibited varied degrees of fidelity to specific wetland sites and were detected at an average of nine different sites. Distances traveled within the region were extensive and greatest during late winter. Females ranged farther from capture sites than males, and movement from capture sites for all birds was greatest during late winter. Mean home-range size (95% minimum convex polygons) of birds was 258.2 ± 44.8 km 2 (SE) and was greatest during late winter. Diurnal roosts were identified as centers of activities and daily movements were most pronounced during crepuscular periods. These data represent the most extensive documentation of winter movements for a shorebird at an inland site. Findings indicate Dunlin were winter residents, and extensive local movements suggest a high degree of functional connectivity of habitats.

Oregon↗
USGS2002

Regional fidelity and movement patterns of wintering killdeer in an agricultural landscape

Killdeer ( Charadrius vociferus ) is a common and widespread North American species for which there are few studies of residency patterns and movements. We quantified fidelity and movement patterns of 24 radio-tagged Killdeer in the Willamette Valley of Oregon during the winter of 1999-2000. Results from telemetry surveys and census efforts revealed that the group monitored was composed of winter residents (63%), winter transients (26%), and year-round residents (11%). Movements were localized with birds detected at an average distance of 5.15 ± 0.91 (SE) km from the site of capture. Mean home range size (95% kernel) was 7.73 ± 3.19 km 2 . However, results also indicated periodic exploratory movements, with some birds detected up to 30 km from marking sites. Overall, individuals exhibited a low degree of fidelity to specific sites and were detected at an average of 11.9 ± 1.1 sites. No differences were found in monthly movement patterns. In almost all cases, year-round residents were more sedentary than winter residents and winter transients. Results indicate a complex regional population structure and highlight the need to consider both migrant and resident birds, as well as seasonal differences in habitat needs and space use requirements, in future conservation planning efforts.

Oregon↗
USGS2001

Origin, extent, and thickness of quaternary geologic units in the Willamette Valley, Oregon

Stratigraphic and chronologic information collected for Quaternary deposits in the Willamette Valley, Oregon, provides a revised stratigraphic framework that serves as a basis for a 1:250,000-scale map, as well as for thickness estimates of widespread Quaternary geologic units. We have mapped 11 separate Quaternary units that are differentiated on the basis of stratigraphic, topographic, pedogenic, and hydrogeologic properties. In summation, these units reflect four distinct episodes in the Quaternary geologic development of the Willamette Valley: 1) Fluvial sands and gravels that underlie terraces flanking lowland margins and tributary valleys were probably deposited between 2.5 and 0.5 million years ago. They are the oldest widespread surficial Quaternary deposits in the valley. Their present positions and preservation are undoubtedly due to postdepositional tectonic deformation - either by direct tectonic uplift of valley margins, or by regional tectonic controls on local base level. 2) Tertiary and Quaternary excavation or tectonic lowering of the Willamette Valley accommodated as much as 500 m (meters) of lacustrine and fluvial fill. Beneath the lowland floor, much of the upper 10 to 50 m of fill is Quaternary sand and gravel deposited by braided channel systems in subhorizontal sheets 2 to 10 m thick. These deposits grade to gravel fans 40 to 100 m thick where major Cascade Range rivers enter the valley and are traced farther upstream as much thinner valley trains of coarse gravel. The sand and gravel deposits have ages that range from greater than 420,000 to about 12,000 years old. A widely distributed layer of sand and gravel deposited at about 12 ka (kiloannum, thousands of years before the present) is looser and probably more permeable than older sand and gravel. Stratigraphic exposures and drillers' logs indicate that this late Pleistocene unit is mostly between 5 and 20 m thick where it has not been subsequently eroded by the Willamette River and its major tributaries. 3) Between 15,000 and 12,700 years ago, dozens of floods from Glacial Lake Missoula flowed up the Willamette Valley from the Columbia River, depositing up to 35 m of gravel, sand, silt, and clay. 4) Subsequent to 12,000 years ago, Willamette River sediment and flow regimes changed significantly: the Pleistocene braided river systems that had formed vast plains of sand and gravel evolved to incised and meandering rivers that are constructing today's fine-grained floodplains and gravelly channel deposits. Sub-surface channel facies of this unit are loose and unconsolidated and are highly permeable zones of substantial groundwater flow that is likely to be well connected to surface flow in the Willamette River and major tributaries. Stratigraphic exposures and drillers' logs indicate that this unit is mostly between 5 and 15 m thick.

Oregon↗
USGS2000

Application of a modified harness design for attachment of radio transmitters to shorebirds

Radio transmitter attachment methodology is important to the design of radio telemetry studies. In 1998, we attached 5 transmitters to a captive population of Western Sandpipers ( Calidris mauri ) and 7 transmitters to wild Killdeer ( Charadriusv ociferus ) using a modified version of the Rappole and Tipton (1991) figure-8 leg-loop harness. Captive birds fitted with harnesses did not exhibit quantifiable differences in behavior relative to control birds. Based on initial success in using the leg-loop harnesses, we used harnesses to attach transmitters in the wild to 30 Killdeer and 49 Dunlin ( Calidris alpina ) during the winters of 1998-1999 and 1999-2000. This was part of a study on movements of wintering shorebirds in the Willamette Valley of Oregon, USA. Wild birds showed no adverse effects of the harnesses.Thus, the described harness is a practical method for attachment of transmitters to shorebirds. Advantages of this harness method include a reduction in handling time at capture, elimination of the need to clip feathers for attachment, and increased transmitter retention time.

Oregon↗
USGS1999

Integration of high-resolution seismic and aeromagnetic data for earthquake hazards evaluations: An example from the Willamette Valley, Oregon

Aeromagnetic and high-resolution seismic reflection data were integrated to place constraints on the history of seismic activity and to determine the continuity of the possibly active, yet largely concealed Mount Angel fault in the Willamette Valley, Oregon. Recent seismic activity possibly related to the 20-km-long fault includes a swarm of small earthquakes near Woodburn in 1990 and the magnitude 5.6 Scotts Mills earthquake in 1993. Newly acquired aeromagnetic data show several large northwest-trending anomalies, including one associated with the Mount Angel fault. The magnetic signature indicates that the fault may actually extend 70 km across the Willamette Valley to join the Newberg and Gales Creek faults in the Oregon Coast Range. We collected 24-fold high-resolution seismic reflection data along two transects near Woodburn, Oregon, to image the offset of the Miocene-age Columbia River Basalts ( CRB ) and overlying sediments at and northwest of the known mapped extent of the Mount Angel fault. The seismic data show a 100-200-m offset in the CRB reflector at depths from 300 to 700 m. Folded or offset sediments appear above the CRB with decreasing amplitude to depths as shallow as were imaged (approximately 40 m). Modeling experiments based on the magnetic data indicate, however, that the anomaly associated with the Mount Angel fault is not caused solely by an offset of the CRB and overlying sediments. Underlying magnetic sources, which we presume to be volcanic rocks of the Siletz terrane, must have vertical offsets of at least 500 m to fit the observed data. We conclude that the Mount Angel fault appears to have been active since Eocene age and that the Gales Creek, Newberg, and Mount Angel faults should be considered a single potentially active fault system. This fault, as well as other parallel northwest-trending faults in the Willamette Valley, should be considered as risks for future potentially damaging earthquakes.

Oregon↗
USGS1972

Ground-water data in the Corvallis-Albany area, central Willamette Valley, Oregon

THE CORVALLIS-ALBANY AREA IS PART OF THE ALLUVIAL PLAIN THAT LIES BETWEEN THE CASCADE AND COAST RANGES IN THE CENTRAL WILLAMETTE VALLEY IN NORTHWESTERN OREGON. THE ALLUVIAL DEPOSITS (SAND AND GRAVEL) OF THE VALLEY PLAIN CONTAIN THE MOST PRODUCTIVE AQUIFERS IN THE AREA AND ARE CONSIDERED TO BE THE ONLY UNITS FEASIBLE FOR LARGE-SCALE DEVELOPMENT OF GROUNDWATER SUPPLIES. DURING 1971 THE SEASONAL DECLINE OF WATER LEVELS FROM WINTER TO LATE SUMMER AVERAGED ABOUT 10 FEET FOR THE ALLUVIAL DEPOSITS. THE SEASONAL CHANGE OF STORAGE WAS ESTIMATED TO BE ABOUT 130,000 ACRE-FEET. OF THIS VOLUME, ABOUT 14,000 ACRE-FEET WAS PUMPED FROM WELLS; THE REST WAS DISCHARGED THROUGH SEEPS AND SPRINGS BY EVAPOTRANSPIRATION. THE DIFFERENCE BETWEEN PUMPAGE AND NATURAL DISCHARGE INDICATES THAT A GREAT QUANTITY OF ADDITIONAL WATER IS AVAILABLE FOR DEVELOPMENT. THE STORAGE CAPACITY OF THE ALLUVIAL AQUIFERS IS ESTIMATED TO BE ABOUT 750,000 ACRE-FEET BETWEEN DEPTHS OF 10 AND 100 FEET. WATER FROM THE ALLUVIAL DEPOSITS IS CHEMICALLY SUITABLE FOR ALL USES, AS IS MOST OF THE WATER FROM PERCHED-WATER BODIES IN THE OLDER SEDIMENTARY AND VOLCANIC ROCKS.

Oregon↗
USGS1968

Records of wells, water levels, and chemical quality of water in the lower Santiam River basin, middle Willamette Valley, Oregon

Basic water data on the lower Santiam River basin is preliminary to a comprehensive hydrologic study of this productive and intensely irrigated area where expanding population and industry increases the demand for water . Highest yielding wells are in shallow alluvial aquifers near the main streams; yields range from several hundred to more than a thousand gpm. Wells in lacustrine and older alluvial aquifers that underlie low, flat terraces have yields from a few tens to a few hundred gpm. Wells in the Salem Hills and in the Cascade Range foothills yield moderate to small quantities of water and tap a variety of geologic units. Tabulated material includes records of representative wells , drillers' logs, and chemical and spectrographic analyses of the ground water .

Oregon↗
USGS1965

Selected ground water data in the Eola-Amity Hills area, northern Willamette Valley, Oregon

Occurrence, quality, and availability of ground water differ considerably from place to place in the Eola - Amity Hills area because of the highly diversified geologic and hydrologic conditions. A table relates the geologic situation to the availability of ground water for four areas-- Eola - Amity Hills , east and west valley plains, and Willamette River flood plain. Tables show well and spring records, drillers' logs, and chemical analyses of ground water . The final interpretive report will be published by the U.S. Geological Survey.

Oregon↗