The phantom midges (Diptera: Chaoboridae) are a relatively small fly family composed of 50 extant species in six genera. Larvae are of interest to limnologists and ecologists because of their tolerance to toxicants, predatory avoidance strategies, and the role chaoborids play in zooplankton community dynamics. Relative to mosquitoes, systematists have...
Variations in heat treatments have significant effects on the microstructure of tool steels. For CPM-M4 tool steel, the changes in microstructure and mechanical properties were observed based off of variations in temperature. Five heat treatments with constant exposure time and variable austenitizing and tempering temperatures were performed on samples of...
The search for and discovery of early archaeological sites is an inherently geoarchaeological problem. Archaeological sites of late Pleistocene-age are known to be located in the Intermountain West, however, the record of these early sites remains limited to only a few examples. In the lower Salmon River canyon (LSRC), the...
The dynamics of a field population of the cinnabar moth, Tyria
jacobaeae L., were studied near Jordan, Linn County, Oregon. In
both 1970 and 1971 larval populations were so large that all foliage of
the host weed, tansy ragwort, Senecio jacobaea L., was consumed.
The ensuing starvation accounted for the...
Changes in forest ecosystem conditions in the region have prompted federal resource agencies to target the health of ecosystems in an effort to learn more about cause and effect relationships, develop plans for restoring healthy forest conditions, and communicate with citizens about treatment alternatives and potential outcomes. Because of the...
Wind flow on vegetated coastal foredunes adapts to the local canopy drag, resulting in spatial gradients in bed shear stresses which contribute to the formation of localized bedforms (e.g., nebkha, shadow dunes). Numerous morphological properties of the plants, including canopy height and density, affect the wind flow dynamics and therefore...
I tested a theoretical model proposing that anemia
favors transmission of blood-borne parasites to vectors
by accelerating the blood-feeding rate. Using Aedes
aegypti, the yellow fever mosquito, initially, I was not
able to confirm this phenomenon either in an artificial
or a live system; anemia did not correlate with blood-feeding...
Epichloë typhina (Ascomycetes: Clavicipitaceae) is an endophytic fungus that
infects perennial Pooid grasses and is the causal agent of choke disease. It is endemic
to Europe and was inadvertently introduced into orchardgrass seed production fields in
western Oregon. Choke disease, which was first recorded in Oregon in 1996, currently
infects...
Pheromones are chemical cues produced by organisms that affect the behavior and/or physiology of conspecifics. The orchestration of reproductive behaviors in many animals depends on the expression of sex pheromones. In insects, intraspecific variation in sex pheromone expression is commonly observed and often influences social interactions between individuals. To what...
Marine sediments are vast sources and reservoirs of methane, a potent greenhouse gas. Most of this methane is anaerobically oxidized by archaea before it can reach the overlying ocean, though the efficiency of this process often depends on methane fluxes and mechanisms of fluid transport. Anaerobic methanotrophic archaea, or ANME,...
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Frederick S. Colwell
Abstract
Marine sediments are vast sources and reservoirs of methane
Intimate associations with reactive metal species permanently protect soil organic matter (SOM) from microbial access and oxidation, contributing to the build-up of organic carbon (C) stocks in soils. It is increasingly recognized, however, that such associations can be reversible and that reactive metal species might even facilitate the oxidation of...
The effects of burial by tephra (volcanic aerial ejecta) on
forest understory plants were examined northeast of Mount St. Helens,
Washington, in the area where the 18 May 1980 eruption deposited
tephra but did not destroy canopy trees. At six sites along a tephra
depth gradient from 2-15 cm, understory...
Continental shelves located along eastern boundary currents occupy relatively small volumes of the world’s oceans, yet are responsible for a large proportion of global primary production. The Oregon coast is among these ecosystems. Recent analyses of dissolved oxygen at shallow depths in the water column has suggested increasing episodes of...
Habitat selection behavior was investigated as a proximate mechanism influencing spatial distributions of three species of anuran larvae. Rana cascadae, Hyla regilla, and Bufo boreas overlap in distribution in lakes and ponds of the Cascade Mts. and were chosen to provide a comparative basis for analyzing habitat selection behavior. Major...
Land use alters the physical and biological structure of stream ecosystems and potentially alters their capacity to process nitrogen (N), an essential nutrient that has nearly doubled in abundance on the biosphere
during the past century from human activities. In this dissertation, I quantified uptake and transformation of nitrate (NO₃⁻)...
Piliostigma reticulatum and Guiera senegalensis are two native shrubs that
coexist with row crops in parkland systems of the Sahel of Africa. Although
permanently green all year around in soil depleted in nutrients and dry for a nine-month
period, these shrubs have been largely overlooked. Conventional management of these
shrubs...