Expansion of Juniperus occidentalis into the sagebrush steppe has resulted in significant changes in understory composition. A consequence of increased J. occidentalis dominance may be a depletion of the seed bank. The potential for depletion is problematic because a reduction in the amount of species available from the seed bank...
Fire has largely been excluded from many mountain big sagebrush communities. Managers are reluctant to
reintroduce fire, especially in communities without significant conifer encroachment, because of the decline in sagebrush-associated
wildlife. Given this management direction, a better understanding of fire exclusion and burning effects is
needed. We compared burned to...
This dataset consists of native and exotic plant species metrics, including cover, richness, relative abundance and responses to the exclusion of wild ungulates and herbivory. The data were used for the manuscript: "Synergistic effects of wild ungulates and management intensification suppress native plants and promote exotics", published in the journal...
In the tropics, widespread deforestation and conversion of primary forests to agricultural and pasture lands has resulted in losses of composition, structure, and functions of forest landscapes. Deforestation in the tropics is typically preformed via slash-and-burn practices; the byproducts from combustion have been identified as the second-highest form of anthropogenically...
A gene-ecological transplant study was made on populations of
the Crepis nana and C. elegans complex from the Arctic and Alpine of
North America. Transplants were collected from the Brooks Range,
Eagle Summit, and Alaska Range in Alaska, the Rocky Mountains in
Alberta, the Olympic Mountains in Washington, the Wallowa...
The evolutionary relationship between Frankia and actinorhizal plants was evaluated
by reconstructing molecular phylogenetic trees from nifH, 16S rDNA, and rbcL
nucleotide sequences. Subgroupings in Frankia phylogenetic trees reconstructed from
nifH and from 16S rDNA sequences were consistent in terms of plant origins of Frankia
strains. Although the branching order...
In this dissertation I study evolutionary patterns at genes encoding antimicrobial peptides (AMPs) in frogs. AMPs are short, amphipathic, cationic, secreted proteins that kill bacteria and other pathogens through a non-catalytic mechanism that involves
binding to and disrupting the microbial cell membrane. In many animal taxa, positive selection is much...
There is a new possibility of generating deep ultraviolet laser radiation from a solid-state source. With recent advances in material development, a new nonlinear optical crystal provides a greater damage threshold than current materials making higher conversion efficiencies possible.
This thesis examines the possibility of using this crystal to generate...
The sustainable use of natural resources, including the goods and services provided by pasturelands and rangelands, is of growing importance due to climatic uncertainty and population growth. Maintaining high productivity in livestock operations is necessary as land availability diminishes and global populations rise. The potential negative impacts to the environment...
Plagiobothrys hirtus (Boraginaceae) is a state and federally listed endangered plant found only in Douglas County, Oregon. This vernal pool endemic has historically been threatened by agricultural conversion of seasonal wetlands in the Sutherlin area, and is currently being eradicated as habitat is lost due to the rapid urban development...
The effects of fire severity on post-fire succession and shrub demography were quantified in shrub-steppe grasslands and subalpine forests in the Hells Canyon of the Payette National Forest, Idaho. Following the 1988 Eagle Bar Fire, species frequency, community diversity, fire adaptations, and stand ages were quantified at 12 plots in...
Agave salmiana is a native plant species harvested for the commercial production of mezcal (Agave spirits) in the highlands of central Mexico. The objective of this study was to identify vegetation changes in natural communities where A. salmiana has been differentially harvested for commercial purposes. Three plant community categories were...
Medusahead (Taeniatherum caput-medusae [L.] Nevski) is an exotic annual grass invading western rangelands. Successful
revegetation of invaded-plant communities can be prohibitively expensive because it often requires iterative applications of
integrated control and revegetation treatments. Prescribed burning has been used to control medusahead and prepare seedbeds
for revegetation, but burning has...
Crested wheatgrass (Agropyron cristatum (L.) Gaertn.) is a nonindigenous perennial grass that was introduced to North America to improve the condition of degraded rangelands. It has proven to be a successful revegetation species due to its superior ease of establishment, strong competitive ability, and ability to tolerate grazing. However, crested...
Most studies of plant disease epidemiology have focused on epidemics in host
populations composed of a single genotype. But crop plant diversity can be a useful
means of improving the deployment of resistance genes. In a series of experiments with wheat stripe rust and potato late blight, we studied factors...
The Arabidopsis Information Portal (AIP), a resource expected to provide access to all community data and combine outputs into
a single user-friendly interface, has emerged from community discussions over the last 23 months. These discussions began
during two closely linked workshops in early 2010 that established the International Arabidopsis Informatics...
Vegetation diversity in the Wyoming big sagebrush/Thurber needlegrass (Artemisia tridentata Nutt. ssp. wyomingensis Beetle & Young/Achnatherum thurberianum (Piper) Barkworth. syn. Stipa thurberiana Piper) plant association was studied across a condition class gradient in southeastern Oregon. All observable vascular plant species were counted during 6 seasons and 2 years and diversity...
The hump-shaped relationship that predicts highest species richness (species/unit area) at intermediate levels of productivity was examined for woody plants across the Pacific and Inland Northwest of the U.S. Many studies have examined this relationship at regional scales, but commonly use species range maps and surrogate measures of productivity (e.g....
These studies are part of the Demonstration of Ecosystem Management Options (DEMO) study, a program researching the effects of different levels and patterns of green-tree retention on ecological, economic, and social phenomena. We restricted our studies to the 15% basal area, evenly dispersed retention treatment. Our objectives were, first, to...