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  • 1
    Online Resource
    Online Resource
    Interactions among herbivory, climate, topography and plant age shape riparian willow dynamics in northern Y ellowstone N ational P ark, USA
    Wiley ; 2014
    In:  Journal of Ecology Vol. 102, No. 3 ( 2014-05), p. 667-677
    Details
    In: Journal of Ecology, Wiley, Vol. 102, No. 3 ( 2014-05), p. 667-677
    Abstract: Understanding how the environmental context modifies the strength of trophic interactions within food webs forms a central challenge in community ecology. Here, we demonstrate the necessity of considering the influence of climate, landscape heterogeneity and demographics for understanding trophic interactions in a well‐studied food web in Y ellowstone N ational P ark, USA . We studied riparian willow ( S alix spp.) establishment and stem growth reconstructed from tree rings on the northern range of Y ellowstone over a 30‐year period that included the reintroduction of a top predator, the grey wolf ( C anis lupus ). We used climate variables (annual precipitation, stream flow and growing season length), herbivore abundance and landscape descriptors (elevation and topographic wetness index) to predict establishment and growth processes through time before and after the reintroduction of wolves. We fitted Bayesian hierarchical models to establishment data and time series of individual stem heights from 1980 to 2008. Explaining variability in establishment required models with stream flow, annual precipitation and elk abundance. Climate, trophic and landscape covariates interacted with stem age to determine stem height and growth rate through time. Growth rates of most stems ages (2+) declined after the reintroduction of wolves. However, stem growth rates naturally declined with age, and the decline we observed was coincident with faster growth rates for the youngest stems. Mean stem heights at age have remained relatively stable through time for most age classes. Estimated effects of landscape topography had approximately the same magnitude of effect on stem growth rate at age as elk abundance. Synthesis . We show that the effects of modification of a food web cannot be predicted by studying trophic dynamics in isolation. No single driver explained patterns of willow establishment and growth over the past three decades in Yellowstone. Instead, interactions among trophic forces, interannual climate variability and landscape topography together shaped how the ecosystem responded to perturbations. Top‐down effects of ungulates on riparian woody vegetation must be considered in the context of plant age, and climate and landscape heterogeneity.
    Type of Medium: Online Resource
    ISSN: 0022-0477 , 1365-2745
    URL: Issue
    URL: Article
    DOI: 10.1111/jec.2014.102.issue-3
    DOI: 10.1111/1365-2745.12225
    Language: English
    Publisher: Wiley
    Publication Date: 2014
    detail.hit.zdb_id: 3023-5
    detail.hit.zdb_id: 2004136-6
    SSG: 12
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    Online Resource
  • 2
    Online Resource
    Online Resource
    Experimental Comparisons of Diet Selection by Mountain Goats and Mountain Sheep in Colorado
    JSTOR ; 1984
    In:  The Journal of Wildlife Management Vol. 48, No. 3 ( 1984-07), p. 799-
    Details
    In: The Journal of Wildlife Management, JSTOR, Vol. 48, No. 3 ( 1984-07), p. 799-
    Type of Medium: Online Resource
    ISSN: 0022-541X
    URL: Article
    DOI: 10.2307/3801426
    Language: Unknown
    Publisher: JSTOR
    Publication Date: 1984
    detail.hit.zdb_id: 2066663-9
    SSG: 12
    SSG: 23
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    Online Resource
  • 3
    Online Resource
    Online Resource
    The effect of climate on population growth in a cold‐adapted ungulate at its equatorial range limit
    Wiley ; 2020
    In:  Ecosphere Vol. 11, No. 2 ( 2020-02)
    Details
    In: Ecosphere, Wiley, Vol. 11, No. 2 ( 2020-02)
    Abstract: Climatic changes are affecting the distribution and viability of species worldwide, and the effects may be greatest for heat‐sensitive organisms in populations situated near the species’ equatorial range limit. We studied the population dynamics of a cold‐adapted large herbivore, moose ( Alces alces shirasi ), in a population located at the extreme southern range limit of the species in Utah, USA , using a long‐term dataset of aerial counts conducted between 1958 and 2013. We used a modeling approach that acknowledges the uncertainty in the number of moose counted. To determine how climate influenced this population, we tested four models corresponding to different hypotheses suggested by previous studies of moose population dynamics: (1) High summer rainfall increases population growth, (2) severe winters reduce population growth, (3) high summer and winter temperatures cause heat stress which reduces population growth, and (4) snow conditions favorable to winter ticks reduce population growth. We then ranked these models against two additional hypotheses that tested the combined effects of the best‐performing models. The best‐supported model included summer rainfall and the number of days with snow cover in late winter, which described the conditions influencing winter tick numbers, a common parasite of moose in the region. Reproductive female ticks drop off their hosts at the end of winter to lay eggs, and fewer ticks survive in years with abundant snow cover. Positive effects of snow and rainfall indicated that moose population growth was higher following summers with more rainfall and late winters with more days of snow cover, the latter because those conditions likely reduced winter tick numbers. In accordance with global patterns in which altered precipitation regimes are influencing the dynamics of many species, the top‐performing model suggested that both summer and winter precipitation acted together to explain the most variation in moose population growth. Our analysis demonstrates the multiple pathways by which climate and population density can affect the dynamics of temperate species living at their equatorial range limits, including potential parasite‐mediated effects.
    Type of Medium: Online Resource
    ISSN: 2150-8925 , 2150-8925
    URL: Issue
    URL: Article
    DOI: 10.1002/ecs2.v11.2
    DOI: 10.1002/ecs2.3058
    Language: English
    Publisher: Wiley
    Publication Date: 2020
    detail.hit.zdb_id: 2572257-8
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  • 4
    Online Resource
    Online Resource
    Stream hydrology limits recovery of riparian ecosystems after wolf reintroduction
    The Royal Society ; 2013
    In:  Proceedings of the Royal Society B: Biological Sciences Vol. 280, No. 1756 ( 2013-04-07), p. 20122977-
    Details
    In: Proceedings of the Royal Society B: Biological Sciences, The Royal Society, Vol. 280, No. 1756 ( 2013-04-07), p. 20122977-
    Abstract: Efforts to restore ecosystems often focus on reintroducing apex predators to re-establish coevolved relationships among predators, herbivores and plants. The preponderance of evidence for indirect effects of predators on terrestrial plant communities comes from ecosystems where predators have been removed. Far less is known about the consequences of their restoration. The effects of removal and restoration are unlikely to be symmetrical because removing predators can create feedbacks that reinforce the effects of predator loss. Observational studies have suggested that the reintroduction of wolves to Yellowstone National Park initiated dramatic restoration of riparian ecosystems by releasing willows from excessive browsing by elk. Here, we present results from a decade-long experiment in Yellowstone showing that moderating browsing alone was not sufficient to restore riparian zones along small streams. Instead, restoration of willow communities depended on removing browsing and restoring hydrological conditions that prevailed before the removal of wolves. The 70-year absence of predators from the ecosystem changed the disturbance regime in a way that was not reversed by predator reintroduction. We conclude that predator restoration may not quickly repair effects of predator removal in ecosystems.
    Type of Medium: Online Resource
    ISSN: 0962-8452 , 1471-2954
    URL: Article
    DOI: 10.1098/rspb.2012.2977
    Language: English
    Publisher: The Royal Society
    Publication Date: 2013
    detail.hit.zdb_id: 1460975-7
    SSG: 12
    SSG: 25
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    Online Resource
  • 5
    Online Resource
    Online Resource
    Regulating overabundant ungulate populations: An example for elk in Rocky Mountain National Park, Colorado
    Elsevier BV ; 2008
    In:  Journal of Environmental Management Vol. 86, No. 3 ( 2008-2), p. 520-528
    Details
    In: Journal of Environmental Management, Elsevier BV, Vol. 86, No. 3 ( 2008-2), p. 520-528
    Type of Medium: Online Resource
    ISSN: 0301-4797
    URL: Article
    DOI: 10.1016/j.jenvman.2006.12.005
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2008
    detail.hit.zdb_id: 1469206-5
    SSG: 12
    SSG: 14
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  • 6
    Online Resource
    Online Resource
    Grazing in Herds: When are Nutritional Benefits Realized?
    University of Chicago Press ; 1988
    In:  The American Naturalist Vol. 131, No. 5 ( 1988-05), p. 760-764
    Details
    In: The American Naturalist, University of Chicago Press, Vol. 131, No. 5 ( 1988-05), p. 760-764
    Type of Medium: Online Resource
    ISSN: 0003-0147 , 1537-5323
    URL: Article
    DOI: 10.1086/284818
    RVK:
    WA 15000
    Language: English
    Publisher: University of Chicago Press
    Publication Date: 1988
    detail.hit.zdb_id: 1473832-6
    detail.hit.zdb_id: 207092-3
    detail.hit.zdb_id: 2669910-2
    SSG: 12
    SSG: 25
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    Online Resource
  • 7
    Online Resource
    Online Resource
    Fire and Grazing in the Tallgrass Prairie: Contingent Effects on Nitrogen Budgets
    Wiley ; 1991
    In:  Ecology Vol. 72, No. 4 ( 1991-08), p. 1374-1382
    Details
    In: Ecology, Wiley, Vol. 72, No. 4 ( 1991-08), p. 1374-1382
    Abstract: Fire and grazing occur together in many of the world's grasslands, but their effects on nutrient cycling have usually been studied as if they acted separately. We hypothesized that grazing by large herbivores results in conservation of nitrogen that would otherwise be lost from burned grasslands. We tested this hypothesis in a series of experiments on burned and unburned tallgrass prairie grazed by cattle. We manipulated grazing using exclosures and mowing. Combustion losses of N from ungrazed plots (1.8 g°m — 2 °yr — 1 ) burned in the spring were double those from similarly burned, grazed plots (0.9 g°m — 2 °yr — 1 ). These losses represented about half of the preburn, aboveground stocks of N. The magnitude of N loss was proportional to the standing crop biomass available for combustion. Fire temperatures and energy release were reduced by grazing. We used mowing to simulate locally heavy grazing in patches. In the absence of burning, mowing patches increased the likelihood that a patch would be regrazed and caused persistent reductions in the residual biomass remaining in a patch at the end of the growing season. Mowing did not influence patch utilization or residual biomass when pastures were burned. Thus, the effects of fire on grassland N budgets were modified by grazing, and the effects of grazing on the patch structure of grasslands were modified by fire. We conclude that accurately predicting volatile losses of nutrients from grassland ecosystems resulting from biomass burning may depend on understanding effects of grazing.
    Type of Medium: Online Resource
    ISSN: 0012-9658 , 1939-9170
    URL: Article
    DOI: 10.2307/1941109
    RVK:
    WA 15000
    Language: English
    Publisher: Wiley
    Publication Date: 1991
    detail.hit.zdb_id: 1797-8
    detail.hit.zdb_id: 2010140-5
    SSG: 12
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    Online Resource
  • 8
    Online Resource
    Online Resource
    AGE AND REPEATED BIOPSY INFLUENCE ANTEMORTEM PRP CWD TESTING IN MULE DEER ( ODOCOILEUS HEMIONUS ) IN COLORADO, USA
    Wildlife Disease Association ; 2015
    In:  Journal of Wildlife Diseases Vol. 51, No. 4 ( 2015-10), p. 801-810
    Details
    In: Journal of Wildlife Diseases, Wildlife Disease Association, Vol. 51, No. 4 ( 2015-10), p. 801-810
    Type of Medium: Online Resource
    ISSN: 0090-3558
    URL: Article
    DOI: 10.7589/2014-12-284
    Language: English
    Publisher: Wildlife Disease Association
    Publication Date: 2015
    detail.hit.zdb_id: 2162749-6
    SSG: 22
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  • 9
    Online Resource
    Online Resource
    Detecting stress responses in Rocky Mountain bighorn sheep ( Ovis canadensis canadensis ): reliability of cortisol concentrations in urine and feces
    Canadian Science Publishing ; 1991
    In:  Canadian Journal of Zoology Vol. 69, No. 1 ( 1991-01-01), p. 15-24
    Details
    In: Canadian Journal of Zoology, Canadian Science Publishing, Vol. 69, No. 1 ( 1991-01-01), p. 15-24
    Abstract: We evaluated the reliability of using cortisol concentrations in urine and feces to indicate stress responses in captive Rocky Mountain bighorn sheep (Ovis canadensis canadensis). Tests for parallelism and quantitative recovery of cortisol in bighorn plasma, urine, and fecal supernatant revealed that radioimmunoassay reliably measures cortisol in these media. High performance liquid chromatography confirmed the presence of cortisol in fecal extracts. In a randomized complete block experiment, we observed cortisol responses of eight bighorn sheep injected with either 0.0 or 0.50 U/kg of adrenocorticotrophic hormone (ACTH) gel delivered at 48 h intervals over a 29-day period. Treatment elevated (P  〈 0.01) cortisol in urine and fecal supernatant during 0–24 h following ACTH injections but levels dropped below those of controls during 24–48 h posttreatment. Magnitude of cortisol responses did not change with time during the experiment (time × treatment, P  〉  0.05). In a separate experiment, we observed short-term (0, 2, 4, 8, 12, 24 h) cortisol responses in plasma, urine, and feces from eight bighorns following a single challenge with 0.0, 0.25, 0.5, or 1.0 U/kg of repository corticotropin. Plasma cortisol concentrations rose within 2 h of treatment (P  〈 0.025) and remained elevated for at least 8 h. Urine cortisol excretion showed a similar trend with peak response delayed 2–6 h. Fecal cortisol trends resembled those of plasma and urine but were more variable. We failed to observe a dose response above the 0.5 U/kg level in any media. Concentrations of cortisol (ng/mL) in plasma correlated (r 2  = 0.76) with cortisol:creatinine ratios (ng/mg) in urine. We conclude that measuring cortisol in excreta of bighorn sheep offers promise as a noninvasive means of sampling their responses to environmental stressors.
    Type of Medium: Online Resource
    ISSN: 0008-4301 , 1480-3283
    URL: Article
    DOI: 10.1139/z91-003
    RVK:
    WA 15000
    Language: English
    Publisher: Canadian Science Publishing
    Publication Date: 1991
    detail.hit.zdb_id: 1490831-1
    SSG: 12
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  • 10
    Online Resource
    Online Resource
    Assessing impacts of large herbivores on shrubs: tests of scaling factors for utilization rates from shoot-level measurements : Scaling utilization estimates
    Wiley ; 2006
    In:  Journal of Applied Ecology Vol. 44, No. 1 ( 2006-11-20), p. 168-175
    Details
    In: Journal of Applied Ecology, Wiley, Vol. 44, No. 1 ( 2006-11-20), p. 168-175
    Type of Medium: Online Resource
    ISSN: 0021-8901 , 1365-2664
    URL: Issue
    URL: Article
    DOI: 10.1111/jpe.2007.44.issue-1
    DOI: 10.1111/j.1365-2664.2006.01245.x
    Language: English
    Publisher: Wiley
    Publication Date: 2006
    detail.hit.zdb_id: 2020408-5
    detail.hit.zdb_id: 410405-5
    SSG: 12
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