Flaherty E.A.,University of Wyoming |
Ben-David M.,University of Wyoming |
Smith W.P.,Pacific Northwest Research Station
Journal of Mammalogy | Year: 2010
Where dispersal is energetically expensive, feeding and food availability can influence dispersal success. The endemic Prince of Wales northern flying squirrel (Glaucomys sabrinus griseifrons) inhabits a landscape mosaic of old-growth, 2nd-growth, and clear-cut stands, with the latter 2 representing energetically expensive habitats. We estimated the diet of flying squirrels using stable isotope and fecal analyses, determined whether food availability varies among forest stands, and assessed the likelihood of foraging across a managed landscape given the distribution of foods on Prince of Wales Island (POW), Alaska. Both stable isotope and fecal analyses revealed that conifer seeds, lichens, and fungi were the main dietary items consumed and assimilated by flying squirrels. Similarly, soil macroinvertebrates were consumed by squirrels, whereas berries were not. Nonetheless, although examination of stable isotope data suggested that squirrels assimilated few nutrients from truffles, this food source was among the most frequent diet items in feces, probably because flying squirrels assimilate elements other than nitrogen from fungi. Our surveys showed that conifer seeds, truffles, and lichens were more prevalent in old-growth than 2nd-growth and clear-cut habitats. Thus, our results indicate that diet and availability of food items on POW may influence foraging success and dispersal movements of G. sabrinus across fragmented landscapes because of limited availability of food resources in the managed habitats. © 2010 American Society of Mammalogists.
Holloway G.L.,Fiera Biological Consulting |
Smith W.P.,Pacific Northwest Research Station
Journal of Wildlife Management | Year: 2011
Research on the impact of clearcut logging and partial harvesting practices on northern flying squirrels (Glaucomys sabrinus) has shown inconsistent and contrary results, limiting the use of this species as a management indicator species. Much of this variability in study results is due to the labor intensive nature of studying flying squirrels, resulting in small sampling sizes (average = 5.2 sites, n = 14) and high variation (CV = 0.59) across studies. We conducted a meta-analysis of relevant studies from North America to determine how forestry practices affect flying squirrel abundance. Mean effect size was -1.18 (P<0.001; n = 14) for all studies, indicating a strong difference between control stands and those regenerating postclearcut or following partial harvesting. Our results support the association of northern flying squirrels with mature, uncut forest and their suitability as ecological indicators of these vegetation types. © 2011 The Wildlife Society.
Geiser L.H.,U.S. Forest Service Pacific Northwest Region Air Resource Management Program |
Jovan S.E.,Pacific Northwest Research Station |
Glavich D.A.,U.S. Forest Service Pacific Northwest Region Air Resource Management Program |
Porter M.K.,Washington State University |
Porter M.K.,SLR International Corporation
Environmental Pollution | Year: 2010
Critical loads (CLs) define maximum atmospheric deposition levels apparently preventative of ecosystem harm. We present first nitrogen CLs for northwestern North America's maritime forests. Using multiple linear regression, we related epiphytic-macrolichen community composition to: 1) wet deposition from the National Atmospheric Deposition Program, 2) wet, dry, and total N deposition from the Communities Multi-Scale Air Quality model, and 3) ambient particulate N from Interagency Monitoring of Protected Visual Environments (IMPROVE). Sensitive species declines of 20-40% were associated with CLs of 1-4 and 3-9 kgNha-1 y-1 in wet and total deposition. CLs increased with precipitation across the landscape, presumably from dilution or leaching of depositional N. Tight linear correlation between lichen and IMPROVE data suggests a simple screening tool for CL exceedance in US Class I areas. The total N model replicated several US and European lichen CLs and may therefore be helpful in estimating other temperate-forest lichen CLs. © 2010 Elsevier Ltd.
Pattison R.R.,Pacific Northwest Research Station |
Pattison R.R.,University of Alaska Anchorage |
Welker J.M.,University of Alaska Anchorage
Oecologia | Year: 2014
Changes in winter precipitation that include both decreases and increases in winter snow are underway across the Arctic. In this study, we used a 14-year experiment that has increased and decreased winter snow in the moist acidic tussock tundra of northern Alaska to understand impacts of variation in winter snow depth on summer leaf-level ecophysiology of two deciduous shrubs and a graminoid species, including: instantaneous rates of leaf gas exchange, and δ13C, δ15N, and nitrogen (N) concentrations of Betula nana, Salix pulchra, and Eriophorum vaginatum. Leaf-level measurements were complemented by measurements of canopy leaf area index (LAI) and depth of thaw. Reductions in snow lowered summer leaf photosynthesis, conductance, and transpiration rates by up to 40 % compared to ambient and deep snow conditions for Eriophorum vaginatum, and reduced Salix pulchra conductance and transpiration by up to 49 %. In contrast, Betula nana exhibited no changes in leaf gas exchange in response to lower or deeper snow. Canopy LAI increased with added snow, while reduced winter snow resulted in lower growing season soil temperatures and reduced thaw depths. Our findings indicate that the spatial and temporal variability of future snow depth will have individualistic consequences for leaf-level C fixation and water flux by tundra species, and that these responses will be manifested over the longer term by changes in canopy traits, depth of thaw, soil C and N processes, and trace gas (CO2 and H2O) exchanges between the tundra and the atmosphere. © 2013 Springer-Verlag Berlin Heidelberg (outside the USA).
Zarnetske J.P.,Oregon State University |
Zarnetske J.P.,Yale University |
Haggerty R.,Oregon State University |
Wondzell S.M.,Pacific Northwest Research Station |
Baker M.A.,Utah State University
Journal of Geophysical Research: Biogeosciences | Year: 2011
We used an in situ steady state 15N-labeled nitrate ( 15NO3-) and acetate (AcO-) well-to-wells injection experiment to determine how the availability of labile dissolved organic carbon (DOC) as AcO- influences microbial denitrification in the hyporheic zone of an upland (third-order) agricultural stream. The experimental wells receiving conservative (Cl- and Br) and reactive (15NO3-) solute tracers had hyporheic median residence times of 7.0 to 13.1 h, nominal flowpath lengths of 0.7 to 3.7 m, and hypoxic conditions (<1.5 mg O2 L-1). All receiving wells demonstrated 15N2 production during ambient conditions, indicating that the hyporheic zone was an environment with active denitrification. The subsequent addition of AcO- stimulated more denitrification as evidenced by significant δ15N 2 increases by factors of 2.7 to 26.1 in receiving wells and significant decreases of NO3- and DO in the two wells most hydrologically connected to the injection. The rate of nitrate removal in the hyporheic zone increased from 218 kg ha-1 yr-1 to 521 kg ha-1 yr-1 under elevated AcO- conditions. In all receiving wells, increases of bromide and 15N2 occurred without concurrent increases in AcO-, indicating that 100% of AcO- was retained or lost in the hyporheic zone. These results support the hypothesis that denitrification in anaerobic portions of the hyporheic zone is limited by labile DOC supply. Copyright 2011 by the American Geophysical Union.