Publications
Filter Total Items: 1994
A hierarchical perspective of plant diversity
Predictive models of plant diversity have typically focused on either a landscapea??s capacity for richness (equilibrium models), or on the processes that regulate competitive exclusion, and thus allow species to coexist (nonequilibrium models). Here, we review the concepts and purposes of a hierarchical, multiscale model of the controls of plant diversity that incorporates the equilibrium model o
Authors
Daniel Sarr, D.E. Hibbs, M. Huston
Riparian communities associated with Pacific Northwest headwater streams: Assemblages, processes, and uniqueness
Riparian areas of large streams provide important habitat to many species and control many instream processes — but is the same true for the margins of small streams? This review considers riparian areas alongside small streams in forested, mountainous areas of the Pacific Northwest and asks if there are fundamental ecological differences from larger streams and from other regions and if there are
Authors
John S. Richardson, Robert J. Naiman, Frederick J. Swanson, David E. Hibbs
Tree species and size structure of old-growth Douglas-fir forests in central western Oregon, USA
We characterized the structure of 91 old-growth forests dominated by Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), using inventory data from recent (1985–1991) old-growth timber sales in western Oregon. The data were complete counts (i.e., censuses) of all live trees >20 cm diameter at breast height (dbh, measured at 1.4 m above the ground) over a mean area of 17.1 ha at each site. Across al
Authors
Nathan Poage, J. C. Tappeiner
Assessing uncertainty in ecological systems using global sensitivity analyses: A case example of simulated wolf reintroduction effects on elk
Often landmark conservation decisions are made despite an incomplete knowledge of system behavior and inexact predictions of how complex ecosystems will respond to management actions. For example, predicting the feasibility and likely effects of restoring top-level carnivores such as the gray wolf (Canis lupus) to North American wilderness areas is hampered by incomplete knowledge of the predator-
Authors
J. Fieberg, Kurt J. Jenkins
Monitoring temporal change in riparian vegetation of Great Basin National Park
Disturbance in riparian areas of semiarid ecosystems involves complex interactions of pulsed hydrologic flows, herbivory, fire, climatic effects, and anthropogenic influences. We resampled riparian vegetation within ten 10-m × 100-m plots that were initially sampled in 1992 in 4 watersheds of the Snake Range, east central Nevada. Our finding of significantly lower coverage of grasses, forbs, and s
Authors
Erik A. Beever, David A. Pyke, Jeanne C. Chambers, Fred Landau, S.D. Smith
Rana catesbeiana (American Bullfrog). Chytridiomycosis
No abstract available.
Authors
Christopher A. Pearl, D. E. Green
Observations of Interspecific amplexus between western North American ranid frogs and the introduced American bullfrog (Rana catesbeiana) and an hypothesis concerning breeding interference
Introduced American bullfrogs (Rana catesbeiana) come in contact with native amphibians on four continents and are well established in lowlands of western North America. To date, research on the effects of introduced bullfrogs on native frogs has focused on competition and predation, and is based largely on larval interactions. We present observations of interspecific amplexus between bullfrogs an
Authors
Christopher A. Pearl, M. P. Hayes, Russ Haycock, Joseph D. Engler, Jay Bowerman
Relationship between demographics and diet specificity of Imperial Eagles Aquila heliaca in Kazakhstan
The demographic consequences of within-population variability in predator foraging are not well understood. We assessed the relationship between the degree of diet specialization and two demographic parameters, population density and reproductive output, within a single population of Imperial Eagles Aquila heliaca at a nature reserve in north-central Kazakhstan. Nearest-neighbour distances between
Authors
Todd Katzner, Evgeny A. Bragin, Steven T. Knick, Andrew T. Smith
Population size and trend of Yellow-billed Loons in northern Alaska
The Yellow-billed Loon (Gavia adamsii) is of conservation concern due to its restricted range, small population size, specific habitat requirements, and perceived threats to its breeding and wintering habitat. Within the U.S., this species breeds almost entirely within the National Petroleum Reserve-Alaska, nearly all of which is open, or proposed to be opened, for oil development. Rigorous estima
Authors
Susan L. Earnst, Robert A Stehn, Robert Platte, William W. Larned, Edward J. Mallek
Evidence of decline for Bufo boreas and Rana luteiventris in and around the northern Great Basin
A method is described for the analysis of polychlorinated biphenyl (PCB) compounds in tissue samples. Cleanup by hexane-aceto-nitrile partitioning and Florisil column chromatography are performed on samples before oxidative treatment to convert DDE to DCBP. PCB components are then determined semi-quantitatively by TLC. No prior separation of PCB from chlorinated pesticides is required. The lower l
Authors
W. Wente, M. J. Adams, Christopher A. Pearl
Establishing native grasses in a big sagebrush-dominated site: An intermediate restoration step
Many semiarid rangelands in the Great Basin, U.S.A., are shifting dominance to woody species as a consequence of land degradation including intense livestock grazing and fire suppression. Whereas past rehabilitation efforts in Big sagebrush (Artemisia tridentata) steppes removed the shrub and added introduced forage grasses to successfully shift communities from shrublands to grasslands, current c
Authors
Elisabeth Huber-Sannwald, David A. Pyke
Available nitrogen: A time-based study of manipulated resource islands
Spatial and temporal heterogeneity of available nitrogen are critical determinants of the distribution and abundance of plants and animals in ecosystems. Evidence for the resource island theory suggests that soils below tree and shrub canopies contain higher amounts of resources, including available nitrogen, than are present in interspace areas. Disturbances, such as prescribed fire and tree remo
Authors
Michelle M. Stubbs, David A. Pyke