Ranchers and resource managers have become concerned about the
role and spread of Cardaria draba (L.) Desv. (whitetop) in the sagebrush
steppe of Northeastern Oregon. This area is an important natural resource
for livestock production and big game winter range.
An area near Keating, Oregon was selected to study the...
In many areas of the Western U.S., diffuse knapweed (Centaurea diffusa Lam.)
has invaded into plant communities dominated by bluebunch wheatgrass
(Pseudomegnaria spicata [Pursh] A. Love). The objectives of this study were to compare
growth response of both species when grown under altered moisture and temperature
regimes while in the...
Cheatgrass (Bromus tectorum L.) and yellow starthistle (Centaurea
soistitialis L.) have invaded over 3 million ha of grasslands in the western U.S.
Future management will require an understanding of the conditions,
mechanisms, and processes which control species dominance, community
dynamics, and desirable plant establishment in these alien dominated annual
rangelands....
Yellow starthistle (Centaurea solstitialis L.) is an introduced Asteraceae that has become established on 10 million acres in the Pacific Northwest and California. This weed functions as an annual or short-lived perennial and depends on seeds for reproduction. Strategies of control that reduce plant fitness or lower seed production or...
From July 1985 to April 1987 the pelagic zooplankton community of Crater Lake, Oregon was studied to determine taxonomic structure, absolute and relative densities, and spatial and temporal distributional patterns. Samples were collected using vertically-towed zooplankton nets. The community structure consisted of two cladoceran and nine rotifer species, which were...
Carter Lake, a freshwater, coastal dune-margin lake,
was sampled at the beginning and end of the summer of 1986
to determine the sediment characteristics and benthic
macroinvertebrate abundance, biomass, variety, and
diversity. The distributions of major benthic habitats were
estimated by snorkeling in June and July, 1986. Water
temperature and...
Crater Lake, originally barren of fish, was stocked on an
irregular basis from 1888 through 1941 with several species of
salmonids. Two species occur in the lake today--kokanee salmon
(Oncorhynchus nerka) and rainbow trout (Salmo gairdneri). This
study was initiated in the summer of 1986 to evaluate the ecology of...
Ecologists have studied the responses of pelagic ecosystems
to varying levels of nutrient loading and fish predation on many
different scales ranging from small experimental enclosures to
whole lake systems. There are recurring patterns of response to
these two variables, which are generally predictable on the basis
of biogeographic, behavioral,...
Ten high mountain ponds in Mount Rainier National Park, Washington State, were
studied from June through September 1992 to investigate the influences of fluctuating
pond volumes on zooplankton communities. A temporary pond of short wet phase
duration was inhabited by zooplankton taxa with short generation times and a crustacean
taxa...
Distribution and life history characteristics of lacustrine-adfluvial bull trout (Salvelinus
confluentus) were described in the North Fork Skokomish River Basin (including Lake
Cushman, a reservoir) from 1994 to 1996. Day snorkeling was conducted in the river to
determine initiation of the bull trout spawning migration, abundance of spawners, and
duration...