Southeastern Oregon Research Articles

New species and records of Pyrgulopsis (Gastropoda: Hydrobiidae) from the Snake River basin, southeastern Oregon: further delineation of a highly imperiled fauna

Here we describe two new species from southeastern Oregon based on morphologic and molecular (mtCOI) evidence. Pyrgulopsis fresti n. sp., commonly known as the “Owyhee hot springsnail” and long considered to be distinct and critically imperiled, lives in thermal springs along a short reach of the Owyhee River above Three Forks. This snail differs from other regional species in its squat shell; penial ornament consisting of a large, disc-shaped ventral gland; absence of a seminal receptacle; and mtCOI sequences. Pyrgulopsis owyheensis n. sp. ranges among five disjunct groups of springs in the Owyhee and Malheur river drainages and is occasionally sympatric with P. fresti. This snail is closely similar to another regional congener, P. intermedia (Tryon, 1865), but is smaller and further differentiated by its typically disjunct inner shell lip, longer and narrower penial filament, more distally positioned ventral gland of penis, and mtCOI sequences. The type locality (Owyhee Spring) population of P. owyheensis is genetically differentiated from the other geographical subunits of this species (1.5–1.8% sequence divergence) and should perhaps be managed as a separate conservation unit. New records are provided for P. intermedia which extends the range of this conservation priority species into the lower Owyhee River basin. We also show that the “Malheur springsnail,” which has been listed in various conservation-related publications and documents, is the same as P. intermedia. This study provides critical information for the conservation of springsnails in southeastern Oregon and underscores the need for additional field surveys in the region.

Public information facilitates habitat selection of a territorial species: the eastern kingbird

The study of breeding habitat selection has focused mainly on physical characteristics of the environment such as nest sites and food abundance, both of which are required for successful reproduction. However, individuals may have limited time to make settlement decisions, and thus, their knowledge of resource availability may be incomplete. Furthermore, food abundance during settlement may not reflect levels later in the breeding season. An alternative perspective is that the most direct measure of habitat suitability is derived from social information such as the presence of conspecifics (conspecific attraction) or their reproductive performance (habitat copying). We tested resource and socially based hypotheses of habitat selection in a population of eastern kingbirds, Tyrannus tyrannus, at Malheur National Wildlife Refuge in southeastern Oregon, U.S.A. Kingbirds nested in areas with a greater proportion of suitable nest trees than what was generally available, but many areas with suitable numbers of trees went unused. Kingbirds also settled in areas of relatively high insect abundance, but only in years when overall abundance was low. We also found support for the socially based hypotheses. Relative to where they nested previously, kingbirds tended to settle in areas of higher conspecific density. But, we found stronger evidence in favour of habitat copying, suggesting that dispersing individuals settled in areas that produced more fledglings in the previous year. Kingbirds thus appeared to select breeding habitat based, in part, on resource availability, but dispersal decisions may be influenced by social information, primarily past reproductive success of conspecifics.

Comparison of Medusahead-Invaded and Noninvaded Wyoming Big Sagebrush Steppe in Southeastern Oregon

Medusahead (Taeniatherum caput-medusae [L.] Nevski) is an exotic, annual grass invading sagebrush steppe rangelands in the western United States. Medusahead invasion has been demonstrated to reduce livestock forage, but otherwise information comparing vegetation characteristics of medusahead-invaded to noninvaded sagebrush steppe communities is limited. This lack of knowledge makes it difficult to determine the cost–benefit ratio of controlling and preventing medusahead invasion. To estimate the impact of medusahead invasion, vegetation characteristics were compared between invaded and noninvaded Wyoming big sagebrush (Artemisia tridentata subsp. wyomingensis [Beetle & A. Young] S. L. Welsh) steppe communities that had similar soils, topography, climate, and management. Noninvaded plant communities had greater cover and density of all native herbaceous functional groups compared to medusahead-invaded communities (P < 0.01). Large perennial grass cover was 15-fold greater in the noninvaded compared to invaded plant communities. Sagebrush cover and density were greater in the noninvaded compared to the medusahead-invaded communities (P < 0.01). Biomass production of all native herbaceous functional groups was higher in noninvaded compared to invaded plant communities (P < 0.02). Perennial and annual forb biomass production was 1.9- and 45-fold more, respectively, in the noninvaded than invaded communities. Species richness and diversity were greater in the noninvaded than invaded plant communities (P < 0.01). The results of this study suggest that medusahead invasion substantially alters vegetation characteristics of sagebrush steppe plant communities, and thereby diminishes wildlife habitat, forage production, and ecosystem functions. Because of the broad negative influence of medusahead invasion, greater efforts should be directed at preventing its continued expansion. La cabeza de medusa (Taeniatherum caput-medusae [L.] Nevski) es una grama anual exótica que invade los pastizales de triguillo crestado en el oeste de los Estados Unidos. Se ha demostrado que la invasión de la cabeza de medusa reduce el forraje para el ganado, sin embargo otra información sobre las estepas de triguillo crestado invadida y no invadida por la cabeza de medusa es limitada. Esta ausencia de conocimiento hace difícil determinar la relación costo–beneficio para controlar y prevenir la invasión de la cabeza de medusa. Para estimar el impacto de la invasión de cabeza de medusa, se compararon las características vegetativas entre las comunidades de estepas de triguillo crestado grande de Wyoming (Artemisia tridentata subsp. wyomingensis [Beetle & A. Young] S. L. Welsh) invadida y no invadida con suelos, topografía, clima, y manejo similares. Las comunidades de plantas no invadidas tuvieron la mayor cobertura y densidad de todos los grupos funcionales de las herbáceas nativas comparadas a las comunidades de cabeza de medusa invadida (P < 0.01). La cobertura grande de grama perene fue 15 veces mayor en las comunidades no invadidas comparada con las comunidades de plantas invadidas. La cobertura del triguillo crestado fue mayor en las comunidades no invadidas comparada con las comunidades de cabeza de medusa invadidas (P < 0.01). La producción de biomasa de todos los grupos funcionales de herbáceas nativas fueron mayor en las no invadidas comparadas con las comunidades de plantas invadidas (P < 0.02). La producción de biomasa de la hierba anual y perene fue de 1.9 y 45 veces más, respectivamente, en las comunidades no invadidas que en las comunidades invadidas. La diversidad y la riqueza de especies fueron mayor en las comunidades no invadidas que en las comunidades de planta invadidas (P < 0.01). Los resultados de este estudio sugieren que la invasión de la cabeza de medusa altera sustancialmente las características vegetativas de las comunidades de estepas de triguillo crestado; y de ese modo, disminuye el hábitat de vida silvestre, la producción de forraje y las funciones del ecosistema. Debido a la amplia influencia negativa en la invasión de la cabeza de medusa mayores esfuerzos deben ser dirigidos para prevenir su continua expansión.

Regional conductivity structure of Cascadia: Preliminary results from 3D inversion of USArray transportable array magnetotelluric data

In conjunction with the USArray component of EarthScope, long period magnetotelluric (MT) data are being acquired in a series of arrays across the continental US. Initial deployments in 2006 and 2007 acquired data (10–10,000 s) at 110 sites covering the US Pacific Northwest, distributed with the same nominal spacing as the USArray seismic transportable array (∼75 km). The most striking and robust features revealed by initial three‐dimensional inversion of this dataset are extensive areas of high conductivity in the lower crust beneath all of southeastern Oregon, and beneath the Cascade Mountains, contrasting with very resistive crust in Siletzia and the Columbia Embayment. Significant variations in upper mantle conductivity are also revealed by the inversions, with the most conductive mantle beneath the Washington backarc, and the most resistive corresponding to subducting oceanic mantle.

Spatial Analysis of Water Use in Oregon, USA, 1985–2005

Water use patterns are not distributed evenly over space and time. Determining the amount of water used within a region, as well as the various ways in which water is used is important for making adequate and sustainable water management policies and determining future water availability. We examined differences in spatial trends in Oregon freshwater use (total, municipal, and agricultural water withdrawals), by county, between the years 1985 and 2005. We also explored biophysical and socioeconomic factors that explain spatial patterns using Moran’s I, local index of spatial autocorrelation (LISA), and spatial regression models. There was a moderate positive spatial autocorrelation among counties that had similar total and irrigation withdrawals. LISA analysis identified hot spots between certain arid agricultural counties in the southeastern Oregon and cold spots between certain humid northwestern counties, including within the Portland metro area. Annual precipitation and income are negatively associated with total water withdrawals. Summer temperature and farm size is positively associated with irrigation water withdrawals, while net cash return and income are negatively associated with irrigation water withdrawals. When compared to ordinary least square regression models, spatial error models that take into account spatial dependence provide a more comprehensive explanation of the variations of water use, suggesting that water resource planning and management should incorporate spatial and neighborhood effects to effective manage limited natural resources.

Range-wide phylogeographic analysis of the spotted frog complex ( Rana luteiventris and Rana pretiosa) in northwestern North America

The dynamic geological and climatic history of northwestern North America has made it a focal region for phylogeography. We conducted a range-wide phylogeographic analysis of the spotted frog complex ( Rana luteiventris and Rana pretiosa) across its range in northwestern North America to understand its evolutionary history and the distribution of clades to inform conservation of R. pretiosa and Great Basin R. luteiventris, candidates for listing under the US Endangered Species Act. Mitochondrial DNA sequence data from a segment of the cytochrome b gene were obtained from 308 R. luteiventris and R. pretiosa from 96 sites. Phylogenetic analysis revealed one main R. pretiosa clade and three main R. luteiventris clades, two of which overlapped in southeastern Oregon. The three R. luteiventris clades were separated from each other by high levels of sequence divergence (average of 4.75–4.97%). Two divergent clades were also uncovered within the Great Basin. Low genetic variation in R. pretiosa and the southeastern Oregon clade of R. luteiventris suggests concern about their vulnerability to extinction.

Ecophysiology and geochemistry of microbial arsenic oxidation within a high arsenic, circumneutral hot spring system of the Alvord Desert

Microbial metabolism of arsenic has gained considerable interest, due to the potential of microorganisms to drive arsenic cycling and significantly influence the geochemistry of naturally arsenic-rich or anthropogenically arsenic-polluted environments. Alvord Hot Spring in southeastern Oregon is a circumneutral hot spring with an average arsenic concentration of 4.5 mg L(-1) (60 microM). Hydrogeochemical analyses indicated significant arsenite oxidation, increased pH and decreased temperature along the stream channels flowing into Alvord Hot Spring. The dynamic range of pH and temperature over the length of three stream channels were 6.76-7.06 and 69.5-78.2 degrees C, respectively. Biofilm samples showed As(III) oxidation ex situ. 16S rRNA gene studies of sparse upstream biofilm indicated a dominance of bacteria related to Sulfurihydrogenibium, Thermus, and Thermocrinis. The lush downstream biofilm community included these same three groups but was more diverse with sequences related to uncultured OP10 bacterial phylum, uncultured Bacteroidetes, and an uncultured clade. Isolation of an arsenite oxidizer was conducted with artificial hot spring medium and yielded the isolate A03C, which is closely related to Thermus aquaticus based on 16S rRNA gene analysis. Thus, this study demonstrated the bacterial diversity along geochemical gradients of temperature, pH and As(III): As(V), and provided evidence of microbial arsenite oxidation within the Alvord Hot Spring system.

Atmospheric mercury near Salmon Falls Creek Reservoir in southern Idaho

Abstract Gaseous elemental mercury (GEM) and reactive gaseous mercury (RGM) were measured over 2-week seasonal field campaigns near Salmon Falls Creek Reservoir in south-central Idaho from the summer of 2005 through the fall of 2006 and over the entire summer of 2006 using automated Tekran Hg analyzers. GEM, RGM, and particulate Hg (HgP) were also measured at a secondary site 90 km to the west in southwestern Idaho during the summer of 2006. The study was performed to characterize Hg air concentrations in the southern Idaho area for the first time, estimate Hg dry deposition rates, and investigate the source of observed elevated concentrations. High seasonal variability was observed with the highest GEM (1.91 ± 0.9 ng m −3 ) and RGM (8.1 ± 5.6 pg m −3 ) concentrations occurring in the summer and lower values in the winter (1.32 ± 0.3 ng m −3 , 3.2 ± 2.9 pg m −3 for GEM, RGM, respectively). The summer-average HgP concentrations were generally below detection limit (0.6 ± 1 pg m −3 ). Seasonally averaged deposition velocities calculated using a resistance model were 0.034 ± 0.032, 0.043 ± 0.040, 0.00084 ± 0.0017 and 0.00036 ± 0.0011 cm s −1 for GEM (spring, summer, fall and winter, respectively) and 0.50 ± 0.39, 0.40 ± 0.31, 0.51 ± 0.43 and 0.76 ± 0.57 cm s −1 for RGM. The total annual RGM + GEM dry deposition estimate was calculated to be 11.9 ± 3.3 μg m −2 , or about 2/3 of the total (wet + dry) deposition estimate for the area. Periodic elevated short-term GEM (2.2–12 ng m −3 ) and RGM (50–150 pg m −3 ) events were observed primarily during the warm seasons. Back-trajectory modeling and PSCF analysis indicate predominant source directions to the SE (western Utah, northeastern Nevada) and SW (north-central Nevada) with fewer inputs from the NW (southeastern Oregon and southwestern Idaho).

The effect of grazing duration on forage quality and production of meadow foxtail

For the past 50 yr, meadow foxtail (Alopecurus pratensis L.) has been invading native flood meadows throughout the Harney Basin in southeastern Oregon. The expansion of this grass species has been the result of its broad climatic adaptation and ability to withstand drought while thriving in saturated soil conditions for a large part of the growing season. The growth of meadow foxtail starts as soon as adequate soil moisture exists. Managing this early-maturing hay species can prove to be a challenge because soil saturation and elevated water tables make it difficult to harvest hay when forage quality and yield are maximized. The purpose of this study was to evaluate whether planned grazing would retard maturation and thus prolong forage quality. Treatments included a non-grazed control and grazing durations of 2, 4, 6, and 8 wk. Grazing was initiated in May of 1998 and 1999 on six replications of each treatment arranged in a randomized block design. Within each treatment/replication combination, ten 0.2-m2 plots were clipped to ground level at about 2-wk intervals from May to August. The samples were weighed and dried for standing crop estimation and 4 of the 10 samples were selected at random and analyzed for acid detergent fiber (ADF), neutral detergent fiber (NDF), and crude protein (CP). We found that early spring grazing decreased forage yield significantly (P ≤ 0.05). Grazing tended to slow the seasonal decline in CP. The effects of grazing on the forage fiber components, however, were inconsistent. The relatively small increase in forage quality does not appear to compensate for the large decline in hay yield (a 40% decline in the shortest grazing duration treatment). We recommend that unfertilized meadow foxtail pastures be used for either haying or grazing, but not both in a given growing season. Key words: Grazing, beef cattle, regrowth, forage yield

Application of Terrestrial Laser Scanning in determining the pattern of late Pleistocene and Holocene fault displacement from the offset of pluvial lake shorelines in the Alvord extensional basin, northern Great Basin, USA

The northwardtrending Alvord extensional basin of southeastern Oregon lies along the northern margin of the Great Basin. The basin is nearly 200 km long and 15 km wide and is bound and internally dissected by a complex system of active normal faults. The faults cut Pleistocene wave-cut terraces that formed along successive shorelines of pluvial Lake Alvord. The wave-cut terraces are incised into late Tertiary volcanic and sedimentary rocks and unconsolidated Quaternary sediments. The terraces formed during stillstands of the ancient lake, during at least two cycles of lake fill and desiccation in the Pleistocene. Wave-cut terraces are divided into two sets, with the topographically higher and older Serrano terrace series consisting of three shorelines and the Alvord terrace series composed of the five topographically lower and younger shorelines. Shorelines are dated locally, and together with regional correlation to other pluvial lakes, the Serrano highstand is estimated as 200–130 ka and the Alvord highstand as 20–15 ka. High-resolution topographic images of the terrace morphology acquired by Terrestrial Laser Scanning georeferenced with the Global Positioning System allowed detailed analysis of shoreline altitudes where they are crosscut by faults. Variation in shoreline altitude measured across faults and on opposing sides of the basin indicates that fault slip occurred during and following periods of lake-level recession. The Serrano terrace highstand records a cumulative vertical displacement of 137.5 ± 3.6 m and the vertical offset of the younger Alvord terrace series highstand is 72.5 ± 2.8 m. Fault displacement is heterogeneously distributed across the basin. Faults along the western margin of the basin accommodated nearly 50% of the total displacement, with one fault accommodating over 20% of the total displacement budget. The residual displacement is distributed across the basin. As much as 30% of the cumulative offset is taken up by structures concealed beneath basin cover and 20% by structures exposed in the highlands along the eastern flank of the basin. Since formation of the Alvord shorelines, the rate of fault displacement was nonperiodic and the basin underwent elevated activity in the late Pleistocene and early Holocene. Vertical displacement rates vary through time, and offset of Alvord terraces occurred at 3.6–7.3 mm/yr, whereas displacement of the Serrano terraces ranged from 0.7 to 1.1 mm/yr. When the horizontal component of motion is calculated by using fault dips of 60°, the 104 yr time-scale rate determined from the Alvord terraces is as much as 2.4–4.2 mm/yr and exceeds the contemporary horizontal displacement across the basin of 1.75 mm/yr determined geodetically. The 105 yr horizontal displacement rate calculated for the Serrano highstand is substantially lower, 0.4–0.6 mm/yr. Spatial and temporal pattern of faulting within the Alvord basin illustrates the complexity of strain release within the basin and highlights the length- and time-scale dependence of deformation rate estimation within extensional basins.

LONG-TERM VEGETATION DYNAMICS IN A CUT WESTERN JUNIPER WOODLAND

Abstract Western juniper (Juniperus occidentalis spp. occidentalis Hook.) expansion in the northern Great Basin has reduced shrubsteppe productivity and diversity. Chainsaw cutting of western juniper woodlands is commonly applied to remove tree interference and restore sagebrush plant communities. Studies assessing understory response following cutting have been limited to early successional stages and have not evaluated the effects of western juniper debris on plant succession. Cutting western juniper produces a large amount of debris which is commonly left on site, occupying a significant portion of treated areas. This study evaluated successional dynamics spanning 13 years after western juniper cutting. Four 0.45-ha blocks were selected on Steens Mountain in southeastern Oregon. Western juniper cover averaged 26% and mature tree density averaged 250 trees · ha−1. Blocks were cut in late summer 1991. Understory standing crop, cover, and density were compared among 3 locations: old canopy litter mats (ca...

Morphological and textural diversity of the Steens Basalt lava flows, Southeastern Oregon, USA: implications for emplacement style and nature of eruptive episodes

This study focuses on Middle Miocene tholeiitic flood basalt lava flows from the Oregon Plateau, northwestern USA (Steens Basalt), and is the first to comprehensively document and evaluate their morphology. Field observations of flows from several sections within and proximal to the main exposures at Steens Mountain have been supplemented with textural and geochemical data, and are used to offer preliminary insights into their emplacement. Compound pahoehoe flows of variable thickness appear to be common throughout the study area, laterally and vertically. These tend to be plagioclase phyric and the morphology and disposition of constituent flow lobes are quite similar to those from other provinces such as Hawaii and the Snake River Plain. Classic a’a flows with brecciated upper and basal crusts are not abundant, but by no means uncommon. Flows with characters different from typical pahoehoe and a’a are also common. Such flows display a range in morphology; flows with preserved upper crusts but brecciated basal crusts, as well as those displaying well-developed flow-top breccias and preserved basal crusts (rubbly pahoehoe) are observed. The Steens Basalt appears to display greater morphological and textural diversity at the outcrop scale than that described for some other flood basalt provinces. The abundant compound pahoehoe flows (often rich in plagioclase phenocrysts) were likely emplaced during slow but sustained eruptive episodes; their constituent lobes show clear evidence for endogenous growth. The relatively aphyric flows with brecciated surfaces (including a’a) hint at higher strain rates and/or higher viscosity, probably caused by higher effusion rates. A couple of sections are characterized by compositionally similar, but morphologically different flows that were possibly part of the same eruption. While differences in pre-eruptive topography could explain this, it is also possible that certain physical parameters changed substantially and abruptly during eruption and that such changes were accompanied by differentiation processes within the plumbing system. It is possible that such observations indicate temporal fluctuations within complex magmatic and eruptive systems, and deserve closer scrutiny.

Starting a General Surgery Program at a Small Rural Critical Access Hospital: A Case Study From Southeastern Oregon

Surgical services are frequently unavailable in rural American communities. Therefore, rural residents often must travel long distances to receive surgical care. Rural hospitals commonly have difficulty providing surgical services despite potential economic benefits. The purpose of this project was to identify the key challenges and describe the initial outcomes experienced by Harney District Hospital (HDH), a rural critical access facility in Oregon, as it develops a surgical program. Since few models exist, this information will be valuable for those considering offering surgical services in a rural setting. This project employed a single case study design. Qualitative information was gathered from semi-structured interviews, a focus group, reviews of historical documents, and informal observations. Quantitative data sources included HDH financial and utilization records, US Census records, and economic and demographic statistics from the state of Oregon, Harney County, and the city of Burns. HDH is learning that initiating a change such as expanding surgical services within an organization is a challenging process requiring collaboration among the administration, staff, and community. Preliminary findings indicate that the new surgical program has resulted in significant financial gains for the hospital. While starting a rural surgery program is a complex undertaking, there are benefits for the hospital. If a rural hospital is to be successful in this mission, collaboration and adaptability must be key components of the process.

Landscape topography and the distribution of Lahontan cutthroat trout (Oncorhynchus clarki henshawi) in a high desert stream

Lahontan cutthroat trout, Oncorhynchus clarki henshawi, are currently limited in their distribution to a patchwork of small isolated populations, the result of habitat degradation and natural variation in landscape and in-stream conditions. The objectives of this study were to determine if landscape topography influences trout distribution, and if water temperatures control this response. The work was carried out in a sub-basin of the Quinn River system, McDermitt Creek, which drains the sagebrush desert of southeastern Oregon and northern Nevada. Headwater tributaries of this creek consist of alternating canyon-confined and valley bounded reaches. Trout within these systems are challenged by low discharge and high temperatures during the summer, and anchor ice during the winter. Contiguous whole stream surveys were used to look at trout distribution during the summer of 2003 and spring and fall of 2004. Our results suggested that topography can affect trout distribution. Trout numbers were highest in areas with greater numbers of nick-points (the transition zones between less confined and more confined valley segments) and greater valley confinement. Additionally, in the downstream portion of our headwater reaches, more trout were found in nick-points than expected based on the availability of this habitat type. Our data suggest that hyporheic inputs may be high in such areas, thus providing trout with shelter from warm water in the summer, anchor ice in the winter, and shallow stream depths during all seasons. Spatial occurrence of these areas of refugia can be taken into consideration when planning land use activities and restoration efforts. Further research is required to confirm that topography can affect the distribution of Lahontan cutthroat trout in other systems, and to better understand the mechanisms behind these patterns.

Revegetating Russian Knapweed (Acroptilon Repens) Infestations Using Morphologically Diverse Species and Seedbed Preparation

Highly degraded pastures and rangeland dominated by Russian knapweed (Acroptilon repens [L.] DC) are often devoid of desirable plants. Control efforts may be ephemeral because propagules of desirable species are not available to reoccupy niches made available by control procedures. Establishing desirable, competitive plants is essential for enduring management and restoration of Russian knapweed and other weed-infested plant communities. The objective of this study was to investigate the effectiveness of revegetating Russian knapweed–infested pastures with 3 nonnative, morphologically diverse species following 1 of 3 seedbed preparation treatments. In successive years, at 2 similar sites in southeastern Oregon, we sprayed Russian knapweed with glyphosate, then prepared the seedbed by burning, tilling, or leaving untreated. Following seedbed preparation, we seeded a perennial forb (alfalfa [Medicago sativa L.]), a bunchgrass (Siberian wheatgrass [Agropyron fragile {Roth} P. Candargy subsp. sibericum {Willd.} Melderis]), and a sod-forming grass (pubescent wheatgrass [Elytrigia intermedia {Host} Nevski subsp. trichophora {Link} Tvzel]) in monocultures and 2- and 3-species mixtures. We measured Russian knapweed and seeded-species density 1 and 2 years following seeding. The forb-seeding treatment decreased reinvasion of Russia knapweed by 50%–60% at 1 site, but otherwise, seeding treatment had little influence on total seeded-species density or Russian knapweed density. Tilling generally resulted in a 35%–40% reduction in Russian knapweed density compared with the control and resulted in the highest establishment of seeded species. Variability in annual precipitation appeared to influence seeded-species establishment between the sites. Our results suggest shallow tilling (10–15 cm) followed by drill-seeding desirable forbs and grasses may provide the best results when revegetating Russian knapweed infestations. Follow-up management should include strategies to enhance desirable species production while minimizing Russian knapweed reinvasion.

Unusual Barn Swallow Nest Placement in Southeastern Oregon

Abstract Barn Swallows (Hirundo rustica) historically nested along cliffs, in caves, and in other natural situations. Currently, nearly all reported nests of this species are on walls and beams of bridges, buildings, and other human-derived structures. Both natural and man-made nest sites typically share one thing in common: a horizontal surface for nest attachment. We describe a Barn Swallow nest that was constructed on a branch overhanging a river in southeastern Oregon. This is the first documented occurrence of this behavior by Barn Swallows and we believe it to be the result of high competition for a limited number of suitable nest sites in the study area.

Environmental and vegetation relationships of the Artemisia tridentata spp. wyomingensis alliance

The Artemisia tridentata spp. wyomingensis (Beetle & A. Young) S.L. Welsh alliance is the most extensive of the big sagebrush complex in the Intermountain West and is characterized by a wide range of environments and vegetation heterogeneity. The purpose of this study was to identify environmental factors driving variation in plant species composition and determine the potential for using environmental factors to explain vegetation characteristics of the A. tridentata spp. wyomingensis alliance. Seventeen environmental factors and seven vegetation response variables were measured on 107 relatively undisturbed, late seral A. tridentata spp. wyomingensis sites across southeastern Oregon and northern Nevada. Non-metric multidimensional scaling (NMS) was used to identify environmental factors correlated with plant species composition as indexed by canopy cover. Stepwise multiple linear regressions were used to develop models correlating plant cover and structural characteristics with environmental factors. Vegetation composition variation appears to be driven by soil characteristics. Canopy cover of perennial grasses and forbs was moderately correlated with direct incident radiation and soil characteristics, particularly soil texture in the upper 15 cm of the profile. Total herbaceous cover variation was better explained by environmental factors (soil water-holding capacity, incident radiation, depth to Bt horizon, and percent sand in the upper 15 cm of the soil profile) ( P<0.0001, R 2=0.52) than any other vegetation characteristic. Vegetation structural characteristics (e.g. sagebrush height, canopy volume and canopy cover, density, and plant visual obstruction) exhibited weak or no relationships with measured environmental variables. Limited correlation among environmental factors and some vegetation characteristics was likely due to the large ecological amplitudes and ecotypic variations expressed by many of the plant species in the sagebrush steppe. This study expands our understanding of the A. tridentata spp. wyomingensis alliance and elucidates the complexity of environmental–vegetation relationships.

INFLUENCE OF FIRE AND JUNIPER ENCROACHMENT ON BIRDS IN HIGH-ELEVATION SAGEBRUSH STEPPE

Abstract We examined relationships between high-elevation sagebrush (Artemisia spp.) steppe habitats altered by prescribed fire and western juniper (Juniperus occidentalis) encroachment on breeding distributions of Brewer's Sparrows (Spizella breweri), Vesper Sparrows (Pooecetes gramineus), Green-tailed Towhees (Pipilo chlorurus), and Sage Thrashers (Oreoscoptes montanus) on Steens Mountain in southeastern Oregon. In 2000 we conducted fixed-radius point count surveys at 172 sites encompassing burned and unburned sagebrush habitat and a range of juniper densities. For each bird species we developed habitat models using local variables measured in the field and landscape variables derived from remotely sensed data. Akaike's Information Criterion (AICc) was used to select the best-approximating model from a suite of a priori candidate models. Brewer's Sparrows, Sage Thrashers, and Green-tailed Towhees were positively related to increasing local sagebrush cover or percent sagebrush in the landscape, whereas V...

Late Pleistocene outburst flooding from pluvial Lake Alvord into the Owyhee River, Oregon

At least one large, late Pleistocene flood traveled into the Owyhee River as a result of a rise and subsequent outburst from pluvial Lake Alvord in southeastern Oregon. Lake Alvord breached Big Sand Gap in its eastern rim after reaching an elevation of 1292 m, releasing 11.3 km 3 of water into the adjacent Coyote Basin as it eroded the Big Sand Gap outlet channel to an elevation of about 1280 m. The outflow filled and then spilled out of Coyote Basin through two outlets at 1278 m and into Crooked Creek drainage, ultimately flowing into the Owyhee and Snake Rivers. Along Crooked Creek, the resulting flood eroded canyons, stripped bedrock surfaces, and deposited numerous boulder bars containing imbricated clasts up to 4.1 m in diameter, some of which are located over 30 m above the present-day channel. Critical depth calculations at Big Sand Gap show that maximum outflow from a 1292- to 1280-m drop in Lake Alvord was ∼ 10,000 m 3 s − 1 . Flooding became confined to a single channel approximately 40 km downstream of Big Sand Gap, where step-backwater calculations show that a much larger peak discharge of 40,000 m 3 s − 1 is required to match the highest geologic evidence of the flood in this channel. This inconsistency can be explained by (1) a single 10,000 m 3 s − 1 flood that caused at least 13 m of vertical incision in the channel (hence enlarging the channel cross-section); (2) multiple floods of 10,000 m 3 s − 1 or less, each producing some incision of the channel; or (3) an earlier flood of 40,000 m 3 s − 1 creating the highest flood deposits and crossed drainage divides observed along Crooked Creek drainage, followed by a later 10,000 m 3 s − 1 flood associated with the most recent shorelines in Alvord and Coyote Basins. Well-developed shorelines of Lake Alvord at 1280 m and in Coyote Basin at 1278 m suggest that after the initial flood, postflood overflow persisted for an extended period, connecting Alvord and Coyote Basins with the Owyhee River of the Columbia River drainage. Surficial weathering characteristics and planktonic freshwater diatoms in Lake Alvord sediment stratigraphically below Mt. St. Helens set Sg tephra, suggest deep open-basin conditions at ∼ 13–14 ka ( 14C yr) and that the flood and prominent shorelines date to about this time. But geomorphic and sedimentological evidence also show that Alvord and Coyote Basins held older, higher-elevation lakes that may have released earlier floods down Crooked Creek.

Regional Surficial Geochemistry of the Northern Great Basin

The regional distribution of arsenic and 20 other elements in stream-sediment samples in northern Nevada and southeastern Oregon was studied in order to gain new insights about the geologic framework and patterns of hydrothermal mineralization in the area. Data were used from 10,261 samples that were originally collected during the National Uranium Resource Evaluation (NURE) Hydrogeochemical and Stream Sediment Reconnaissance (HSSR) program in the 1970s. The data are available as U.S. Geological Survey Open-File Report 02-0227. The data were analyzed using traditional dot maps and interpolation between data points to construct highresolution raster images, which were correlated with geographic and geologic information using a geographic information system (GIS). Wavelength filters were also used to deconvolute the geochemical images into various textural components, in order to study features with dimensions of a few kilometers to dimensions of hundreds of kilometers. The distribution of arsenic, antimony, gold, and silver is different from distributions of the other elements in that they show a distinctive high background in the southeast part of the area, generally in areas underlain by the pre-Mesozoic craton. Arsenic is an extremely mobile element and can be used to delineate structures that served as conduits for the circulation of metal-bearing fluids. It was used to delineate large crustal structures and is particularly good for delineation of the Battle Mountain-Eureka mineral trend and the Steens lineament, which corresponds to a post-Miocene fault zone. Arsenic distribution patterns also delineated the Black Rock structural boundary, northwest of which the basement apparently consists entirely of Miocene and younger crust. Arsenic is also useful to locate district-sized hydrothermal systems and clusters of systems. Most important types of hydrothermal mineral deposit in the northern Great Basin appear to be strongly associated with arsenic; this is less so for low-sulfidation epithermal deposits. In addition to individual elements, the distribution of factor scores that resulted from principal component studies of the data was used. The strongest factor is characterized by Fe, Ti, V, Cu, Ni, and Zn and is used to map the distribution of distinctive basalts that are high in Cu, Ni, and Zn and that appear to be related to the Steens Basalt. The other important factor is related to hydrothermal precious metal mineralization and is characterized by Sb, Ag, As, Pb, Au, and Zn. The map of the distribution of this factor is similar in appearance to the one for arsenic, and we used wavelength filters to remove regional variations in the background for this factor score. The resulting residual map shows a very strong association with the most significant precious metal deposits and districts in the region. This residual map also shows a number of areas that are not associated with known mineral deposits, illustrating the utility of the method as a regional exploration tool. A number of these prospective areas are distant from known significant mineral deposits. The deconvolution of the spatial wavelength structure of geochemical maps, combined with the use of large regional geochemical data sets and GIS, permits new possibilities for the use of stream-sediment geochemistry in the study of large-scale crustal features as well as the isolation of mineral-district scale anomalies.