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Research about Oregon, Washington

Source-linked reports with geographic coverage including Oregon, Washington.

At least 217 records · Page 12Linked to original sources
USGS2001

Mountain hemlock growth responds to climatic variability at annual and decadal time scales

Improved understanding of tree growth responses to climate is needed to model and predict forest ecosystem responses to current and future climatic variability. We used dendroecological methods to study the effects of climatic variability on radial growth of a subalpine conifer, mountain hemlock ( Tsuga mertensiana ). Tree-ring chronologies were developed for 31 sites, spanning the latitudinal and elevational ranges of mountain hemlock in the Pacific Northwest. Factor analysis was used to identify common patterns of interannual growth variability among the chronologies, and correlation and regression analyses were used to identify climatic factors associated with that variability. Factor analysis identified three common growth patterns, representing groups of sites with different climate–growth relationships. At high-elevation and midrange sites in Washington and northern Oregon, growth was negatively correlated with spring snowpack depth, and positively correlated with growth-year summer temperature and the winter Pacific Decadal Oscillation index (PDO). In southern Oregon, growth was negatively correlated with spring snowpack depth and previous summer temperature, and positively correlated with previous summer precipitation. At the low-elevation sites, growth was mostly insensitive to annual climatic variability but displayed sensitivity to decadal variability in the PDO opposite to that found at high-elevation sites. Mountain hemlock growth appears to be limited by late snowmelt, short growing seasons, and cool summer temperatures throughout much of its range in the Pacific Northwest. Earlier snowmelt, higher summer temperatures, and lower summer precipitation in southern Oregon produce conditions under which growth is limited by summer temperature and/or soil water availability. Increasing atmospheric CO 2 concentrations could produce warmer temperatures and reduced snowpack depths in the next century. Such changes would likely increase mountain hemlock growth and productivity throughout much of its range in Washington and northern Oregon. Increased summer drought stress and reduced productivity would be likely, however, in mountain hemlock forests of southern Oregon and near the species lower elevation limit at some sites.

Oregon, Washington↗
USGS2001

Data-collection methods, quality-assurance data, and site considerations for total dissolved gas monitoring, lower Columbia River, Oregon and Washington, 2000

Excessive total dissolved gas pressure can cause gas-bubble trauma in fish downstream from dams on the Columbia River. In cooperation with the U.S. Army Corps of Engineers, the U.S. Geological Survey collected data on total dissolved gas pressure, barometric pressure, water temperature, and probe depth at eight stations on the lower Columbia River from the John Day forebay (river mile 215.6) to Camas (river mile 121.7) in water year 2000 (October 1, 1999, to September 30, 2000). These data are in the databases of the U.S. Geological Survey and the U.S. Army Corps of Engineers. Methods of data collection, review, and processing, and quality-assurance data are presented in this report.

Oregon, Washington↗
USGS2001

Predation by northern pikeminnow on juvenile salmonids in The Dalles Dam tailrace: field, laboratory, and habitat modeling studies (FY2000)

Predation by resident fish is known to be a substantial cause of juvenile salmonid mortality, especially in dam tailraces and outfall locations. Conditions in The Dalles Dam tailrace are unique compared to other projects on the Columbia or Snake rivers, having a complex basin with a series of downriver islands where predators are known to reside. In May-June of 1999, northern pikeminnow and smallmouth bass were sampled in the tailrace of The Dalles Dam during periods immediately following the release of PIT-tagged juvenile salmonids for survival studies. Over twice as many smallmouth bass (N = 101) were collected as northern pikeminnow (N = 40), but none of the predators had PIT tags within their gut. A laboratory study was conducted to estimate the time required for PIT tags in juvenile salmonids to be evacuated from the gut of northern pikeminnow after consuming a tagged preyfish. Evacuation rate was sensitive to temperature, with median evacuation time being 21 h at 18 oC and 30 h at 14 oC. These results suggest that field studies to estimate predator population sizes, feeding rates, or predation on specific release groups would require considerably more effort than we allocated during 1999.

Oregon, Washington↗
USGS2000

Models of downdip frictional coupling for the Cascadia Megathrust

We have developed models of downdip frictional coupling along two transects across the Cascadia subduction zone in northern Washington and central Oregon. The models involve complicated downdip coupling profiles. Although not unique, our models closely predict available GPS shortening rates and vertical uplift data. We are able to explain relatively low horizontal shortening rates along the Washington coast and small vertical uplift rates in central Oregon. Our models depart from previous models by inclusion of a deeply coupled region assumed to be related to mafic rocks in both the upper and lower plates of the thrust.

Oregon, Washington↗
USGS2000

Liquefaction evidence for the strength of ground motions resulting from Late Holocene Cascadia subduction earthquakes, with emphasis on the event of 1700 A.D.

During the past decade, paleoseismic studies done by many researchers in the coastal regions of the Pacific Northwest have shown that regional downdropping and subsequent tsunami inundation occurred in response to a major earthquake along the Cascadia subduction zone. This earthquake occurred almost certainly in 1700 A.D., and is believed by many to have been of M 8.5-9 or perhaps larger. In order to characterize the severity of ground motions from this earthquake, we report on a field search and analysis of seismically induced liquefaction features. The search was conducted chiefly along the banks of islands in the lowermost Columbia River of Oregon and Washington and in stream banks along smaller rivers throughout southwestern Washington. To a lesser extent, the investigation included rivers in central Oregon. Numerous small- to moderate-sized liquefaction features from the earthquake of 1700 A.D. were found in some regions, but there was a notable lack of liquefaction features in others. The regional distribution of liquefaction features is evaluated as a function of geologic and geotechnical factors in different field settings near the coast. Our use of widely different field settings, each in which we independently assess the strength of shaking and arrive at the same conclusion, enhances the credibility of our interpretations. Our regional inventory of liquefaction features and preliminary geotechnical analysis of liquefaction potential provide substantial evidence for only moderate levels of ground shaking in coastal Washington and Oregon during the subduction earthquake of 1700 A.D. Additionally, it appears that a similar conclusion can be reached for an earlier subduction earthquake that occurred within the past 1100 years, which also has been characterized by others as being M 8 or greater. On the basis of more limited data for older events collected in our regional study, it appears that seismic shaking has been no stronger throughout Holocene time. Our interpreted levels of shaking are considerably lower than current estimates in the technical literature that use theoretical and statistical models to predict ground motions of subduction earthquakes in the Cascadia region. Because of the influence of estimated ground motions from Cascadia subduction-zone earthquakes on seismic hazard evaluations, more paleoliquefaction and geotechnical field studies are needed to definitively bracket the strength of shaking. With further work, it should be possible to extend the record of seismic shaking through much of Holocene time in large portions of Washington and Oregon.

Oregon, Washington↗
USGS1999

Three-dimensional velocity structure of Siletzia and other accreted terranes in the Cascadia forearc of Washington

Eocene mafic crust with high seismic velocities underlies much of the Oregon and Washington forearc and acts as a backstop for accretion of marine sedimentary rocks from the obliquely subducting Juan de Fuca slab. Arc-parallel migration of relatively strong blocks of this terrane, known as Siletzia, focuses upper crustal deformation along block boundaries, which are potential sources of earthquakes. In a three-dimensional velocity model of coastal Washington, we have combined surface geology, well data, and travel times from earthquakes and controlled source seismic experiments to resolve the major boundaries of the Siletz terrane with the adjacent accreted sedimentary prism and volcanic arc. In southern Washington and northern Oregon the Siletz terrane appears to be a thick block (???20 km) that extends west of the coastline and makes a high-angle contact with the offshore accreted sedimentary prism. On its east flank the high-velocity Siletz terrane boundary coincides with an en echelon zone of seismicity in the arc. In northern Washington the western edge of Siletzia makes a lower-angled, fault-bound contact with the accretionary prism. In addition, alternating, east-west trending uplifts and downwarps of the Siletz terrane centered on the antiformal Olympic Mountains may reflect focusing of north-south compression in the northern part of the Siletz terrane. This compressional strain may result from northward transport and clockwise rotation of the Siletz terrane into the relatively fixed Canadian Coast Mountains restraining bend along the coast.

Oregon, Washington↗
USGS1999

Butyltin compounds in river otters (Lutra canadensis) from the northwestern United States

Butyltin compounds, including mono-, di-, and tributyltin (MBT, DBT, and TBT) were measured in livers of 40 adult river otters ( Lutra canadensis ) collected from rivers and coastal bays in Washington and Oregon, USA. Butyltins were found in all the river otters, at a concentration range of 8.5–2,610 ng/g, WW. The greatest concentration of total butyltins of 2,610 ng/g, WW, was found in a river otter collected in Puget Sound from Fort Ward, Washington. River otters collected near areas with major shipping activities, such as the Puget Sound, contained significantly greater concentrations (geometric mean: 367 ng/g, WW) of butyltins than those from rivers. Among butyltin compounds, MBT and DBT predominated in livers. The concentrations of butyltins in river otters ranged from comparable (Puget Sound) to less (rivers) than what was found in coastal cetaceans.

Oregon, Washington↗
USGS1999

Health evaluation of Columbian white-tailed deer on Julia Butler Hansen Refuge for the Columbian white-tailed deer

The Columbian white-tailed deer ( Odocoileus virginianus leucurus) was designated an endangered species in 1968. At that time the estimated population along the lower Columbia River of Washington and Oregon was 300 to 400 deer (Gavin, 1984). The Julia Butler Hansen Refuge for the Columbian White-tailed Deer was established in 1972 to protect Columbian white-tailed deer and associated habitat Currently, an estimated 600 deer are present in several separate populations. The total refuge population is estimated at 200 animals. Of those, the mainland population consists of approximately 60 animals while the largest refuge island (Tenasillahe.Island) supports about 120 animals. The remaining 420 deer are present on private lands near the refuge (AI Clark, pers. com.). Higher than expected deer mortality on Tenasillahe Island in the spring of 1996 prompted refuge personnel to request assistance from the National Wildlife Health Center (NWHC) for diagnostic evaluation to determine the cause of the mortalities. The mortality event occurred in the wake of extraordinary .flooding that reduced the availability and quality of forage on the island. It is estimated that 50% of the deer population on the refuge died during this time period. The basic finding of emaciation attributable to probable starvation raised concerns regarding the health status of the deer herd, available food resources, and current population levels. A health evaluation was conducted on free-ranging deer from the refuge in February, 1998. This evaluation was an analysis of physiologic parameters obtained from live deer in an attempt to determine the health of individual animals and, with adequate sampling, the health of the population. This study was conducted during February to examine individual animal health during the seasonal period when the deer are in their poorest physical condition. The late winter period prior to spring green-up is a time when the effects ofbreeding and winter stress are most evident (Venne and Ozoga, 1971). The objectives of this study were to: (1) gather baseline physiologic data on a subset of the population, (2) evaluate the data to determine the health of the animals sampled, (3) if possible, identify causes of poor health and, ( 4) provide refuge personnel with information that will aid them in managing the population.

Oregon, Washington↗