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Recent studies of natural regeneration dynamics in ponderosa pine (Pinus ponderosa var. ponderosa Dougl. ex Laws.) forests of central Oregon's Cascade Range reveal positive associations between shrubs and the survival of new tree seedlings. To shed light on the potential mechanisms of this possible facilitative relationship, we conducted a simple experiment in which ambient air temperature, relative humidity, soil temperature, and shrub-canopy light penetration were recorded beneath shrub-shaded and shrub-free locations during a typical mid-summer day in four stands at two sites. Air temperature and relative humidity were unaffected by shrubs, but soil temperatures were 6.2 °C to 6.6 °C lower beneath shrubs between 12 pm and 4 pm. Percent shading by shrubs averaged 2.3 to 3.0 times that of adjacent shrub-free locations. Amelioration of midday soil temperature appears to be one of the mechanisms involved in theorized shrub-seedling facilitations in this region.
The EPA's Environmental Monitoring and Assessment Program large-river assessment protocol was applied to assess the ecological condition, major stressors, and likely human disturbances of the mainstem Malheur River, OR. We used inflatable rafts to allow launching and retrieving from difficult access points and to sample river reaches inaccessible to most other boat types or wading crews, including areas with river obstacles such as rapids and small dams. Electrofishing twenty-four 1–2 km long reaches within the lower 150 km of the river during the summers of 2006 and 2007 revealed: (1) the absence of native mountain whitefish Prosopium williamsoni; (2) the presence of previously undocumented endemics, mountain sucker Catostomus platyrhynchus and leopard dace Rhinichthys falcatus; (3) the existence of previously undocumented aliens, flathead catfish Pylodictis olivaris, tadpole madtom Noturus gyrinus, pumpkinseed Lepomis gibbosus, fathead minnow Pimephales promelas, and western mosquitofish Gambusia affinis; (4) possible range extensions into the main river by two alien basin-reservoir inhabitants, largemouth bass Micropterus salmoides and yellow perch Perca flavescens; and (5) index of biological integrity scores that declined from a high of 53 for an upstream site to 0.5 for a site 6 km from the river mouth. Regular standardized direct assessments of large-river fish assemblages can provide important information used to update river-basin management plans and inform water-resource managers.
Past riparian microclimate studies have measured changes horizontally from streams, but not vertically through the forest canopy. We recorded temperature and relative humidity for a year along a two-dimensional grid of 24 data-loggers arrayed up to 40 m height in four trees 2 – 30 m slope distance from a perennial second order stream in the Sierra Nevada. Our objective was to quantify diurnal and seasonal changes in vertical and horizontal microclimate gradients. Our data suggest a dynamic zone of riparian influence on microclimate that fluctuates diurnally and seasonally. Stream influence on microclimate was limited (statistically significant < 5.0 m vertically, < 7.5 m horizontally). In summer and winter, mean daily temperature and vapor pressure deficit (VPD) increased horizontally and vertically from the stream. Maximum absolute differences in temperature and VPD between upland and streamside conditions were greater in summer than winter. Winter diurnal ranges of temperature and VPD were dampened near the stream, increasing with distance, while summer diurnal ranges were greater near the stream and decreased with distance. Microclimate change was markedly greater vertically above the stream than horizontally. Such steep gradients of air temperature and moisture through the vertical forest profile likely affect arboreal habitat conditions that influence epiphytes and their animal communities.
Limited information exists on the ecology and habitat requirements of the pallid bat (Antrozous pallidus) inhabiting forested ecosystems at the northern limits of its range. We used mist netting, radiotelemetry, and emergence counts at roosts to identify foraging and roosting habitat of pallid bats on the Plumas National Forest in northern California during summer 2007. Pallid bats used a variety of structures for day and night roosting, including live trees and snags, a rock crevice, and a building. Live trees and snags used for roosting were consistently tall in height, large in diameter, and located in mature stands in micro-sites with low percentages of overstory and mid-story cover. The height of roosting sites used by pallid bats in live trees and snags was low relative to the height of the stems selected for roosting. Size of foraging areas varied among sex and reproductive classes of pallid bats, with lactating females (1.56 km2 ± 0.88 SE) exhibiting the smallest foraging areas and post-lactating females (5.97 km2 ± 2.69 SE) having the largest foraging areas. Sierran mixed conifer and white fir habitats comprised significantly larger proportions of the available habitat within foraging areas of adult females than other habitats. Long distance movements during nightly foraging, > 2 km, were common for all sex and reproductive classes of pallid bats. These data indicate that pallid bats inhabiting coniferous forests choose alternate habitats in which to forage and roost from those typically used by the species in other regions of its distribution.
Forest stands of trembling aspen (Populus tremuloides) have been shown to support relatively abundant and diverse faunal communities, but this potential has not been extensively explored within the dry interior forests of British Columbia, Canada. These forests are primarily composed of conifers, particularly stands of Douglas-fir (Pseudotsuga menziesii), with only a small proportion consisting of trembling (or quaking) aspen. During 2005 and 2006, we live-trapped and compared small mammal assemblages within rare aspen stands to those in neighboring Douglas-fir and mixed-wood (aspen Douglas-fir) stands. We captured a total of 4246 individuals of 10 small mammal species during 15,761 trap nights—with 54% of individuals captured in aspen stands. Commonly captured species included the deer mouse (Peromyscus maniculatus), southern red-backed vole (Myodes gapperi), long-tailed vole (Microtus longicaudus), montane vole (Microtus montanus), meadow vole (Microtus pennsylvanicus), yellow-pine chipmunk (Tamias amoenus), and common shrew (Sorex cinereus). Small mammal densities were most often higher within aspen stands than mixed-wood and Douglas-fir stands, as were species richness indices. Aspen stand communities also had consistently higher mean proportions of reproductive adult females and a higher proportion of juveniles. These results illustrate the importance of aspen stands as small mammal “hotspots” within dry forests, such as those found in British Columbia.
Wildlife managers of the twentieth century generally accepted south central Washington as the southernmost range of indigenous mountain goats (Oreamnos americanus) occurring in the coastal and Cascade mountains of North America. We reviewed historical publications to provide twenty-first century managers a more complete review of native mountain goat distribution. We encountered many misidentified or fictitious accounts of mountain goats during our review. Criteria used to dismiss non-credible material included physical descriptions, behavior, biology, and habitat of the animal discussed as well as incorrect geographic descriptions, history, or inconsistent documentation of other fauna. Archaeological evidence and a number of historical documents published during the 1800s and early 1900s place the mountain goat further south into Oregon. Small isolated populations occurring in Oregon were likely extirpated by the middle of the nineteenth century as a result of over harvest. The absence of physical evidence seems to be the primary reason that most modern day authors exclude Oregon from their description of historical mountain goat distribution. Based on our interpretation of the literature and understanding of mountain goat ecology, we suggest that mountain goats were native in historical times at least as far south as the central Cascades, and the northeast mountains of Oregon.
Western gray squirrels (Sciurus griseus griseus Ord) are rare in western Washington and population distribution information has proven difficult to gather. A variety of standard survey methods employed on the Fort Lewis Military Reservation in southern Puget Sound in 1998–99 yielded limited results, likely due to the squirrel's elusive behavior and low-density population. We tried a new survey approach in 2004 using hair-snare tubes, which proved successful in providing information on the distribution of habitat used by western gray squirrels and eastern gray squirrels, the latter previously unknown to be resident in the interior woodlands. The hair-snare tubes also contributed information on habitat use by western and eastern gray squirrels during management actions such as timber cutting and eastern gray squirrel trapping. Knowledge of squirrel distribution allowed managers to strategically allocate resources to improve habitat. Hair-snare tubes are relatively inexpensive to construct and easy to install, and have the potential to provide distribution information on squirrel populations that are widely distributed or occur at low densities, and difficult to detect visually. At the same time, interpretation of results obtained from hair-snare devices are constrained by unknowns regarding numbers of individuals depositing hair samples, and inter- and intra-specific behavioral interactions that influence hair deposition patterns. Despite the drawbacks, knowledge gained from hair-snares can serve as a basis for management planning and lead to the application of other direct study techniques, such as radio-telemetry, that are likely to yield more detailed information.
Bridge Creek is a low-gradient stream in the John Day River basin of eastern Oregon. After decades of grazing, riparian vegetation along a 31.7 km reach was sparse and low in diversity, vegetated floodplains were typically narrow, and the stream was relatively wide and shallow. Cattle grazing within this reach was reduced in 1988, irrigation diversion ditches were replaced with culverts in 1989, and beaver (Castor canadensis) trapping was discontinued after 1991. Between 1988 and 2004, we inventoried beaver dams and ponds twice a year and estimated their dimensions. Field notes and photographs were used to document habitat use and better understand the potential role of beaver with regard to channel morphology and riparian plant communities. The annual number of beaver dams present in the study reach ranged from 9 to 103. On average, dams were nearly 8 m in length with ponds extending upstream 26 m. We also found that beaver dams/ponds, over time, typically accumulated sediment, improved conditions for establishment and growth of riparian plants, and altered channels. Dams that breached during periods of high flow often contributed to long-term increases in channel complexity through the formation of new meanders, pools, and riffles. Exposed sediment deposits associated with breached dams provided fresh seedbeds for regeneration of willows (Salix spp.), black cottonwood (Populus balsamifera ssp. trichocarpa), and other riparian plants. Although portions of the study reach were periodically abandoned by beaver following heavy utilization of streamside vegetation, within a few years dense stands of woody plants normally occupied a larger portion of the floodplain. Observations over a period of 17 yrs indicate that beaver facilitated recovery of riparian vegetation, floodplain functions, and stream channels.
A total of 556 hearts from free-ranging coyotes (Canis latrans) in eastern and central Washington State were examined for heart-worms (Dirofilaria immitis) during 2005–2007. Sampling occurred in fall and winter and only heart tissues were examined. No immature or adult heartworms were detected, indicating that heartworm infection is either not currently present in eastern and central Washington, or the prevalence is very low. These data do not support the concept of heartworm transmission in eastern or central Washington State at this time.