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Results for “Northwest Naturalist”

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27 records · Page 2Linked to original sources
USGS2002

Effects of cottonwood leaf beetle Chrysomela scripta (Coleoptera: Chrysomelidae) on survival and growth of Fremont cottonwood ( Populus fremontii ) in northwest Colorado

Greenhouse and field studies were used to assess the effects of a cottonwood leaf beetle ( Chrysomela scripta ) outbreak on growth and survivorship of Fremont cottonwood ( Populus fremontii ) along a segment of the Yampa River in northwestern Colorado. Exposure of greenhouse-reared seedlings to either 1 or 3 larvae reduced survivorship and the shoot and root masses of surviving seedlings. In the field sapling survivorship in unmanipulated, naturally established patches of saplings was inversely related to the intensity of beetle damage noted the previous year in both 1998–1999 and 1999–2000. Floodplain saplings treated with the insecticide esfenvalerate during two growing seasons added more height and radial growth than untreated saplings. Field observations in riparian stands along the Yampa River indicated that beetles preferentially oviposited and fed on cottonwood seedlings over saplings and mature trees during late summer. Taken together, the greenhouse and field studies suggest herbivory by C. scripta is a major determinant of Fremont cottonwood distribution and abundance at the Yampa River site. Repeated surveys detected few or no beetles in stands along the neighboring but regulated Green River. We hypothesize that flow regulation, by reducing P. fremontii seedling abundance, precludes C. scripta from reaching outbreak status along the Green River.

Colorado↗
USGS2010

Scale-dependent associations of Band-tailed Pigeon counts at mineral sites

The abundance of Band-tailed Pigeons ( Patagioenas fasciata monilis ) has declined substantially from historic numbers along the Pacific Coast. Identification of patterns and causative factors of this decline are hampered because habitat use data are limited, and temporal and spatial variability patterns associated with population indices are not known. Furthermore, counts are influenced not only by pigeon abundance but also by rate of visitation to mineral sites, which may not be consistent. To address these issues, we conducted mineral site counts during 2001 and 2002 at 20 locations from 4 regions in the Pacific Northwest, including central Oregon and western Washington, USA, and British Columbia, Canada. We developed inference models that consisted of environmental factors and spatial characteristics at multiple spatial scales. Based on information theory, we compared models within a final set that included variables measured at 3 spatial scales (0.03 ha, 3.14 ha, and 7850 ha). Pigeon counts increased from central Oregon through northern Oregon and decreased into British Columbia. After accounting for this spatial pattern, we found that pigeon counts increased 12% ± 2.7 with a 10% increase in the amount of deciduous forested area within 100 m from a mineral site. Also, distance from the mineral site of interest to the nearest known mineral site was positively related to pigeon counts. These findings provide direction for future research focusing on understanding the relationships between indices of relative abundance and complete counts (censuses) of pigeon populations by identifying habitat characteristics that might influence visitation rates. Furthermore, our results suggest that spatial arrangement of mineral sites influences Band-tailed Pigeon counts and the populations which those counts represent.

Pacific Northwest↗
USGS2006

Taxonomic and geographic variation in oviposition by tailed frogs ( Ascaphus spp )

Tailed frogs ( Ascaphus spp.) oviposit in cryptic locations in streams of the Pacific Northwest and Rocky Mountains. This aspect of their life history has restricted our understanding of their reproductive ecology. The recent split of A. montanus in the Rocky Mountains from A. truei was based on molecular differentiation, and comparisons of their ecology are limited. Our objectives were to provide a range-wide summary of information on Ascaphus oviposition, compare some aspects of the reproductive ecology of the 2 species, and examine geographic variation in their reproductive traits. Reproductive ecology of the 2 species differed. Ascaphus truei had smaller clutches, oviposited later in the summer, and had a longer duration of oviposition than A. montanus . A greater number of communal oviposition sites were attributed to A. montanus . These ecological differences support the recent taxonomic revision of Ascaphus and suggest that different management strategies may be necessary for each species where conservation is a priority.

Northwestern Naturalist↗
USGS2016

Flow regime effects on mature Populus fremontii (Fremont cottonwood) productivity on two contrasting dryland river floodplains

I compared riparian cottonwood ( Populus fremontii ) productivity-discharge relationships in a relictual stand along the highly regulated Green River and in a naturally functioning stand along the unregulated Yampa River in semiarid northwest Colorado. I used multiple regression to model flow effects on annual basal area increment (BAI) from 1982 to 2011, after removing any autocorrelation present. Each BAI series was developed from 20 trees whose mean size (67 cm diameter at breast height [DBH]) was equivalent in the two stands. BAI was larger in the Yampa River stand except in 2 y when defoliating leaf beetles were present there. I found no evidence for a Yampa flood-magnitude threshold above which BAI declined. Flow variables explained ∼45% of residual BAI variability, with most explained by current-year maximum 90-d discharge (Q M90 ) in the Yampa River stand and by a measure of the year-to-year change in Q M90 in the Green River stand. The latter reflects a management-imposed ceiling on flood magnitude—Flaming Gorge Dam power plant capacity—infrequently exceeded during the study period. BAI in the relictual stand began to trend upward in 1992 when flows started to mimic a natural flow regime. Mature Fremont cottonwoods appear to be ecologically resilient. Their productivity along regulated rivers might be optimized using multiyear environmental flow designs.

Southwestern Naturalist↗
USGS2026

Status and trend of white-cheeked geese wintering in coastal Nestucca Valley, Oregon

The status and trend of wintering goose populations along the coast of the Pacific Northwest is relatively unstudied. We estimated the status and trends of 6 subspecies of white-cheeked geese wintering in Nestucca Valley, Oregon, USA. Surveys conducted from 2007 to 2019 revealed significant variability in weekly counts among subspecies and years. Dusky ( Branta canadensis occidentalis ) and Cackling ( B . hutchinsii minima ) Geese typically arrived by mid-October and stayed until mid-April, while Aleutian Geese showed lower autumn numbers but doubled in spring. Trends indicated a significant delay in Dusky Geese arrival in recent years, with departure dates remaining constant. Total goose use-days averaged 903,899, with notable declines over the period for Aleutian ( B. h. leucopareia ), Taverner's ( B. h. taverneri )/Lesser ( B. c. parvipes ), and Western ( B. c. moffitti ) Geese. Supporting approximately 6000 geese daily, these results underscore the importance of Nestucca Bay National Wildlife Refuge and adjacent lands for wintering geese. These findings also highlight Nestucca Valley's role as a critical late-winter staging ground, particularly for Aleutian Geese, and emphasize that continued monitoring and adaptive management are essential to sustain these populations.

Oregon↗
USGS2017

Microhabitat selection of the Virginia Northern Flying Squirrel (Glaucomys sabrinus fuscus Miller) in the central Appalachians

Glaucomys sabrinus fuscus (Virginia Northern Flying Squirrel; VNFS) is a rare Sciurid that occurrs in the Allegheny Mountains of eastern West Virginia and northwest Virginia. Previous work on this subspecies has confirmed close associations with Picea rubens (Red Spruce) at the landscape and stand levels in the region. However, ongoing Red Spruce restoration actions using canopy-gap creation to release single or small groups of trees requires a better understanding of within-stand habitat selection of VNFS to assess potential short- and medium-term impacts. To address these questions, we conducted a microhabitat study using radio-collared squirrels in montane conifer and mixed conifer—hardwood stands. We used points obtained from telemetry surveys and randomly generated points within each squirrel's home range to compare microhabitat variables for 13 individuals. We found that VNFS preferentially selected plots with conifer-dominant overstories and deep organic-soil horizons. VNFS avoided plots with dense Red Spruce regeneration in the understory in stands with hardwood-dominated overstories—the types of areas targeted for Red Spruce restoration. We also opportunistically searched for hypogeal fungi at telemetry points and found 3 species of Elaphomyces during our surveys. Our results indicate that microhabitat selection is associated with Red Spruce-dominant forests. Efforts to restore Red Spruce where hardwoods dominate in the central Appalachians may improve the connectivity and extent of habitat of VNFS.

West Virginia↗
USGS2013

Effects of predators on fish and crayfish survival in intermittent streams

Predation from aquatic and terrestrial predators arc important factors structuring the size and depth distribution of aquatic prey. We conducted mesocosm and tethering experiments on Little Mulberry Creek in northwest Arkansas during low flows to examine the effects of predators on fish and crayfish survival in intermittent streams Using shallow artificial pools (10 cm deep) and predator exclusions, we tested the hypothesis that large-bodied fish are at greater risk from terrestrial predators in shallow habitats compared to small-bodied individuals. Twenty-four circular pools (12 open top. 12 closed top) were stocked with two size classes of Campostoma anomalum (Central Stonerller) and deployed systematically in a single stream pool. In addition, we used a crayfish tethering experiment to test the hypothesis that the survival of small and large crayfish is greater in shallow and deep habitats, respectively. We tethered two size classes of Orconectes meeki meeki (Meek's Crayfish) along shallow and deep transects in two adjacent stream pools and measured survival for 15 days. During both experiments, we monitored the presence or absence of predators by visual observation and from scat surveys. We demonstrated a negative effect of terrestrial predators on Central Stonerller survival in the artificial pools, and larger individuals were more susceptible to predation. In contrast, small crayfish experienced low survival at all depths and large crayfish were preyed upon much less intensively during the tethering study, particularly in the pool with larger substrate. More studies are needed to understand how stream drying and environmental heterogeneity influence the complex interactions between predator and prey populations in intermittent streams.

Arkansas↗
USGS2020

Occurrence of a suite of stream-obligate amphibians in timberlands of Mendocino County, California, examined using environmental DNA

Stream-obligate amphibians are important indicators of ecosystem health in the Pacific Northwest, but distributional information to improve forest management is lacking in many regions. We analyzed archived DNA extracted from water samples in 60 pools in streams on private timberlands in Mendocino County, California, for 3 California Species of Special Concern—Coastal Tailed Frogs ( Ascaphus truei ), Foothill Yellow-legged Frogs ( Rana boylii ), and Southern Torrent Salamanders ( Rhyacotriton variegatus )—to better understand their distributions in the region. Detection probabilities for eDNA of Foothill Yellow-legged Frogs and Coastal Tailed Frogs were positively influenced by water temperature. eDNA occurrence for both frogs was affected by whether silt or organic matter was a dominant substrate in the sampled pool, and Foothill Yellow-legged Frog eDNA occurrence was also affected by water temperature. Foothill Yellow-legged Frog eDNA occurrence had a strong, positive association with water temperature, with occurrence unlikely below 14°C and very likely above 16°C, and a positive association with silt or organic substrates in pools, which was likely an indicator of higher-order stream reaches. In contrast, Coastal Tailed Frogs had a negative association with silt or organic substrates. Historical visual detections were generally congruent with findings using eDNA, but differences highlight important areas for further study. We did not detect Southern Torrent Salamanders using eDNA at any sites. Our study reinforces that ecological relationships of these species are varied, and shows the importance of maintaining the integrity of streams with diverse characteristics for conserving stream amphibians.

California↗
USGS2019

Sharp savanna-forest transitions in the Midwest followed environmental gradients but are absent from the modern landscape

Historically, closed eastern forests transitioned into open savannas and prairies in the US Midwest, but this transition is poorly understood. To investigate the eastern boundary of the prairie-forest ecotone, we conducted a case study of historic and modern vegetation patterns of the Yellow River watershed in northwest Indiana. Historic vegetation came from the Public Land Survey notes collected in the early 1800s, whereas modern vegetation came from the Forest Inventory Analysis and USGS National Land Cover Database. We mapped historical survey vegetation data using GIS to reconstruct the region’s past and current forest composition and structure. We also mapped climate, topography, and soil composition across the watershed to investigate the relationship between historic vegetation and environmental gradients. We found a sharp transition in the presettlement forest structure and composition, with dense deciduous forests in the eastern portion of our study area and open oak savannas in the west. The savanna ecosystem dominated in sandy well-drained soils and was at a slightly lower elevation than the adjacent closed forest. Modest environmental changes accompanied major vegetation changes in the past, which might suggest fire and hydrological patterns helped maintain the sharp ecotone. By contrast, the modern forest shows no difference in tree density and composition across the watershed, which is consistent with major land use and hydrology changes in the watershed since settlement. On the modern landscape, land that was historically closed forest now has higher agricultural productivity compared to land that was historically savanna, whereas the historic savanna currently supports more mesic forest. These results suggest the environmental gradient continues to subtly shape the landscape. Though land use change has largely removed the closed mixed hardwood forests and oak savannas from this area, a better understanding of the historic vegetation and the conditions that supported it can help inform land management and restoration, as well as reveal ecological processes that drive vegetation transitions.

Indiana↗