Western juniper (Juniperus occidentalis) poses both a challenge and an opportunity for natural resource management in the rangelands of the northern Great Basin. The continued expansion of western juniper on the rangelands of the interior Northwest will likely continue as there are currently no practical options for returning this area...
Greater Sage-grouse (Centrocercus urophasianus) habitat research has historically focused on fine-scale (0.007 - 0.032 ha) vegetation structure and composition immediately surrounding sites selected by birds. However, little work has evaluated vegetation attributes important for Greater Sage-grouse at a landscape-scale or identified landscape attributes that influence habitat use patterns. Habitat use...
Greater sage-grouse (Centrocercus urophasianus), a sagebrush obligate species, has contracted in extent by nearly half its original distribution. This is primarily due to habitat loss and degradation over the past 150 years. During winter, sage-grouse depend completely on sagebrush habitat for food and cover, yet sage-grouse winter ecology has been...
This study examines the long-term role of interference on stand development of Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) and red alder (Alnus rubra Bong.) planted mixtures in the Central Cascades of Oregon, USA. The two species are common associates in naturally regenerated and planted conifer stands in the Pacific Northwest. Due...
Silvicultural canopy gaps are emerging as an alternative management tool to accelerate development of complex forest structure in young, even-aged forests of the Pacific Northwest. I investigated patterns of nitrogen (N) availability along transects through 0.1 and 0.4 ha silvicultural gaps in three 50-70 year old Douglas-fir forests of western...
While damages due to ponding are common and expensive, provisions for design and
construction of flat roof systems lack guidance regarding these loads. The goal of this research is
to present methods of designing or building flat roofs that are less vulnerable to this condition. An
investigation of the literature,...
Wildtype sunflower typically produces 12-24% oleic acid (18:1) and 70-82%
linoleic acid (18:2). High-oleic sunflower, by contrast, produces up to 80-94% oleic
acid. The monounsaturated oleic acid has a greater oxidative stability than the
polyunsaturated linoleic acid, predominant in wildtype sunflower, and has greater
nutritional benefits than polyunsaturated and saturated...
Cultivated meadowfoam (Limnanthes alba Benth.) is an annual oil seed crop native to southern Oregon. California and British Columbia. The genus Limnanthes is composed of nine species and divided into two sections, Inflexae and Reflexae. The seed oil of meadowfoam is a rich source of erucic acid and several novel...
Tocopherols are plant secondary metabolites that are known collectively as
vitamin E. Tocopherol compounds act as potent antioxidants by quenching free
radicals and protecting fatty acids from oxidative damage. In humans (in vivo)
tocopherols protect membrane lipids from breaking down, while in oils (in vitro)
tocopherols protect fatty acids from...
The cultivated sunflower (Helianthus annuus L., x=17) is one of the most important annual oilseed crops in the world. There are very few publicly shared sequence-based DNA markers and genetic maps in sunflower, even though molecular DNA markers and genetic maps have become widely used in all areas of genetic...
Understanding how N availability influences base cation stores is critical for long-term ecosystem sustainability. Indices of nitrogen (N) availability and the distribution of nutrients in plant biomass, soil, and soil water were examined across ten young, unpolluted Douglas-fir (Pseudotsuga menziesii) stands in the Oregon Coast Range spanning a three-fold soil...
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Steven S. Perakis
Understanding how N availability influences base cation stores is
Although previous research in central Oregon has shown soil compaction can lead to a decline in site productivity, the subject is not understood well enough to predict the growth changes resulting from a given level of soil compaction. A study was initiated to relate the basal area, height and volume...
Single nucleotide polymorphisms (SNPs) are the most common DNA polymorphisms in plant and animal genomes. SNPs were identified in the allele sequences of up to 12 sunflower (Helianthus annuus L.) genotypes for a genome-wide sample of 81 loci originally mapped using restriction fragment length polymorphism (RFLP) markers. The RFLP loci...
Medium chain fatty acids (MCFAs) are important industrial feedstocks for
soaps, detergents and surfactants. Interspecific lines derived from Cuphea lanceolata
and Cup hea viscosissima are being domesticated as a temperate source of MCFAs.
These species also serve as model organisms for understanding the biosynthesis of
MCFAs in seeds. Various markers...
Microsatellites or simple sequence repeats (SSRs) are highthroughput sequence based DNA markers that have been exploited as tools for measuring genetic distance and diversity in evolutionary studies, protection of intellectual property, genetic resource conservation management, cultivar identification and molecular breeding of crop plants. We isolated and sequenced 1095 clones from...
Black rockfish (Sebastes melanops) is an important marine recreational species throughout the Pacific Northwest. Recent catch data indicate a trend of age-truncation in the black rockfish population off the Oregon coast, with older females rapidly disappearing from the population. In populations with broad age distributions, older fish may contribute disproportionately...
Meadowfoam (Limnanthes alba Bentham; Order: Brassicales; Family: Limnanthaceae) is a self-compatible, predominantly allogamous, insect pollinated species. Meadowfoam oil is a source of novel unsaturated very-long-chain (VLC) seed oils (C₂₀ and C₂₂) with low concentrations of saturated fatty acids (typically less than 2%) and outstanding oxidative stability. Here we report the...
The mechanisms of substrate recognition by regulatory proteases are not well understood. Presently, two opposing models have arisen to describe E. coil Lon's ability to discriminate between substrates: one suggests the N-terminus involvement while the second suggests the C-terminus involvement. In this project, the role of the C-terminal domain as...
Fire is a major disturbance process in many forests. Long-term studies of the biogeochemical effects of fires, especially on soils, are very rare.
Consequently, long-term effects of fire on soils are often hypothesized from
short-term effects. In a chronosequence study, I studied 24 western Cascades
(Oregon) forest stands thought to...
To reduce the environmental impacts caused by gene flow from transgenic trees, reproductive sterility genes have been developed that use a floral regulatory element linked to a cell toxin. This results in dysfunction or ablation of floral tissues, causing sterility. However, floral promoters often permit low levels of expression in...
Plant form is a compromise between resource gathering, reproduction and
the tolerance to physical demands of the abiotic and biotic environment. In
an agricultural field in addition to the natural factors causing stress, humans
also introduce physical and mechanical stresses, and chemical pesticides
into the environment. Many of these factors...
The warm pool region of the western tropical Pacific is of particular interest to atmospheric dynamics because it represents a significant source of energy to the atmosphere. A better understanding of heat transfer driven by mesoscale and turbulent circulations within this region could lead to improved global circulation models, and...
Tree species directly and indirectly affect soil nutrient cycles. I sought to characterize soils and foliage associated with four common canopy tree species (Douglas-fir, western hemlock, western redcedar, and bigleaf maple) in mixed-species old-growth forests of the Oregon Coast Range and to determine whether and how soils differ among the...
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Steven S. Perakis
Tree species directly and indirectly affect soil nutrient cycles. I
Western juniper has rapidly expanded into sagebrush steppe communities in the Intermountain West during the past 120 years. This expansion has occurred across a wide range of soil types and topographic positions. These plant communities, however, are typically treated in current peer-reviewed literature generically. The focus of this research is...
Society uses massive quantities of wood fiber in production of paper, and demand for fiber is projected to increase further as production of biofuels from fermentation of plant cellulosic materials increases. Because these end uses generally require the costly step of removing of lignin, wood with reduced or more easily...
Phylogeographic studies of six Pacific Northwest forest-associated
salamanders provide insight into historical and contemporary processes on
population genetic structure. Among Larch Mountain Salamanders (Plethodon
larselli), cytochrome b mitochondrial (mtDNA) sequences (381 bp) and random
amplified polymorphic DNA (RAPDs; 34 loci) supported separate Management
Units for northern and southern populations (12...
During two cruises in February and June of 2003, the erodibility of sediment along the western Adriatic Sea was measured using a "Gust erosion chamber". In addition, the surficial sediment properties were characterized through a suite physical and biological measurements including porosity, grain-size, inorganic carbon, organic carbon and colloidal carbohydrate....
Radiotelemetry was used to study the seasonal movements and habitat use of adult westslope cutthroat trout Oncorhynchus clarki lewisi in Roberts
Creek and Rail Creek, headwater tributaries of the John Day River, Oregon,
from September 2000 to December 2001. The objectives were to (1)
describe adult cutthroat trout life history...
In addition to its longstanding recognition as an influential evolutionary process, interspecific hybridization is increasingly regarded as a potential threat to the genetic integrity and survival of rare plant species, manifested through gamete wasting, increased pest and disease pressures, outbreeding depression, competitive exclusion, and genetic assimilation. Alternatively, hybridization has also...
Upper Klamath Lake (UKL) and Agency Lake in south-central Oregon are hypereutrophic due to phosphorus (P) loading from both geologic and agricultural sources in the watershed. Restoring historic lake-fringe wetlands to provide P sinks around the lakes has been accepted as a favorable means of reducing lake P levels and...
In modern on-chip memories, an increasing demand for higher performance, lower power, reduced area, and improved robustness creates a rising need for advanced microarchitecture and circuit design techniques. Particularly in large-signal multi-ported register files, these advanced design techniques include: (i) multi-banked arrays, (ii) multi-frequency arrays, (iii) multi-bit width gating, (iv)...
Technology is a key determinant of comparative advantage among nations. As information technology improves and the nations of the world become economically integrated, concern arises over the dissipation of high-income economies’ technological advantage. The three essays in this dissertation explore the trade and technology relationship, which is essential to economic...
Beetle diversity and habitat associations of five
prevalent riparian plant communities were examined along
the lower reaches of Big Beaver Creek Research Natural
Area, North Cascades National Park, Washington. These
communities were defined by dominant tree species, and
included Alder Swamps, Cedar-Hemlock Forests, Douglas-fir
Forests, Gravel Bars, and Willow-Sedge Swamps....
Riparian zone vegetation can influence terrestrial and aquatic food webs through variations in the amounts, timing, and nutritional content of leaf and other litter inputs. Differences in vegetation composition and density, as well as riparian topography, may modulate the strength and quality of these inputs. Changes in inputs to small...
From 1996 through 1998 I collected mature female black rockfish off Oregon and examined ovaries and otoliths to estimate weekly, age-specific larval production. In all reproductive seasons, older black rockfish extruded larvae earlier in the season, followed by progressively younger fish. Each year, beginning in May, I collected young-of-the-year (YOY)...
I examined factors regulating decomposition rates of red alder (Alnus rubra)) and Douglas-fir (Pseudotsuga menziesii) leaf litter in Coast Range riparian areas in western Oregon. Overall, this study was designed to examine the influence that leaf litter quality characteristics and decomposition site treatment have on decomposition rates, to provide a...
The overall purpose of this study was to examine the root and shoot development of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings at two distinct time periods in seedling establishment (after I and 3 growing seasons) in response to fertilizer, stock size, vegetation control, and soil moisture treatments. Two separate experiments...
The Uruguay Round Agreement on Agriculture in 1994 initiated multilateral
reform of the agricultural sector to better integrate global markets. The implementation of
the agreement has occurred at a time when agricultural commodity prices have
significantly declined. These two events reveal that many countries maintained different
thresholds in terms of...
Relatively recent increases in ponderosa pine abundance have effected unprecedented changes to ecosystem structure and function. Efforts to restore ponderosa pine systems are often focused on the manipulation of tree structure and the re-introduction of a more natural fire regime. Successful restoration should also incorporate understory components but information addressing...
Tag and recovery programs can provide valuable information on population size and exploitation rates in fishes. Passive integrated transponder (PIT) tags are ideal for use in such programs because they provide identification of individual fish and are invisible to anglers, circumventing problems with nonreporting of tags. Our objective was to...
A fossil-calibrated phylogenetic framework based on exemplars from each of the four taxonomic sections within Pinus was created using multiple nuclear and chloroplast loci. Calibration at the well-defined subgeneric split within Pinus with either fossil leaves and cones (ca. 45 million years ago) or fossil wood (ca. 85 million years...
Remote sensing and Geographic Information Systems (GIS) are well known tools for the study of time change analysis in natural systems. However, long-term studies of riparian systems using large-scale aerial photography are less common. The purpose of this project was to combine large scale aerial photography, GIS, Global Positioning Systems...
This thesis focuses on the application of the cosmogenic nuclide Beryllium-10 (10Be) in an effort to better constrain the thickness history of the Fennoscandian Ice Sheet (FIS) at the Last Glacial Maximum (LGM) and into the Holocene, as well as begin to answer the long-standing question regarding the age
and...
This research was undertaken to provide barley growers, processors, and consumers with quality food barley. Because all currently available varieties of food barley are of spring growth habit, the first phase of the research involved agronomic assessment of these varieties under Oregon conditions. Because winter barley usually yields more than...
Myxobacteria represent an interesting class of Gram-negative soil bacteria. These bacteria utilize organic materials from the environment as a food source by the action of their extracellular hydrolytic enzymes. They grow vegetatively in the presence of adequate nutrients. During starvation conditions, however, they aggregate and form multicellular structures called fruiting...
The Disney Company is an inescapable force in American life that is often detached from the stigma of big business and instead viewed as something particularly valuable, the United States’ foremost storyteller. In addition to the stories that the Disney Company
produces through its animated and live-action productions, there is...
Article 1: Behavior of Epoxy Injected Diagonally Cracked Full-Scale CRC Deck-Girders.
Many cast-in place reinforced concrete deck-girder bridges (RCDG) remain in the national inventory and exhibit diagonal cracking. Epoxy injection has been in use for several decades as a method for sealing diagonal cracks, but the effects on girder behavior...
Ponding of water on roof systems leading to collapse causes expensive damage and jeopardizes the life safety of building occupants. Current building codes and design specifications for flat roof systems offer minimal guidance in designing for ponding loads. The present research investigated ponding load effects on a long span, lightweight...
The relationships among stand structure, Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) branch characteristics, and red alder (Alnus rubra (Bong.)) stem form attributes were explored for 10- to 15-year-old trees growing in mixed Douglas-fir – red alder plantations. Treatments included a range of species proportions, and red alder was either planted simultaneously...