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...
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...
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...
Salvage-logging and artificial seeding of grass following wildfire are common practices in coniferous forests of the western United States, yet few studies have
quantified the ecological effects of these post-fire activities. The effects of post-wildfire salvage-logging and grass-seeding on vegetation composition, aboveground biomass, and growth and survival of Pinus ponderosa...
Three different ground cover management strategies were compared at the OSU research vineyard near Alpine, Oregon. Botanical diversity was actively increased in two diverse treatments. Another treatment was botanically uniform and contained creeping bentgrass (Agrostis stolonifera). The composition of the vineyard floor vegetation and grapevine performance as affected by the...
Corydalis aquae-gelidae is a large herbaceous perennial
in the Fumariaceae that has high habitat specificity. It is
endemic to the western Cascade Range of Oregon and
Washington, almost entirely on the Mt. Hood and Gifford
Pinchot National Forests. It is a federal C2 candidate
under the Endangered Species Act and...
The influence of loss of diversity on community dynamics and ecosystem functioning has recently received considerable attention. Although study of biodiversity has a long history within ecology, empirical investigations exploring consequences of loss have been rare. Because many factors confound diversity comparisons, experimental manipulations of diversity offer the most direct...
The objectives in this research were to assess whether Klebsiella planticola
SDF20 could survive in soil and result in ecological effects to soil foodweb
organisms and plant growth. Four experiments were conducted using soil
microcosms. Klebsiella planticola SDF20 has been genetically engineered to
produce ethanol from agricultural waste for use...
Mycorrhizal fungi in arid and semiarid rangelands have received little study in southwest Asia and north Africa, although they are important in food production and rangeland productivity. The desert truffles of the genera Terfezia and Tirmania form fruiting-bodies and mycorrhizae with rangeland plants. This thesis treats the taxonomy and the...
Forest stands were studied to determine if old-growth
forest structure could be mimicked in younger stands via
overstory manipulation. Cover and species composition of
understory plants were systematically sampled in sixteen
thinned second-growth stands and sixteen adjacent unthinned
second-growth Douglas fir (Pseudotsuga menziesii (Mirabel)
Franco.) stands. The stands were thinned...
The vegetation response of spring and fall prescribed fires in basin big sagebrush (Artemisia tridentata subsp. tridentata Nutt.)/Idaho fescue (Festuca idahoensis Elmer)--bluebunch wheatgrass (Agropyron spicatum Pursh. (Scribn. & Smith)) communities was measured at the John Day Fossil Beds National Monument in eastern Oregon. Objectives of the study were to quantify...
Considerable controversy exists about how fish assemblages are
organized. I explicitly took fish movement into account while I
studied the effects of disturbance, habitat complexity, and predation
at different times of the summer to understand the major factors
influencing assemblage structure in a high desert Oregon stream. The
effects of...
National Forest management in the Pacific Northwest is shifting
from a focus on commodity production to ecosystem management, in which
the health of the entire forest ecosystem is considered, rather than that
of a few key species. Ecosystem management includes retention of some
live trees following timber harvest (green-tree retention)...
Fires set by Native Americans were important in shaping and maintaining Willamette Valley prairie plant communities. With fire exclusion after Euro-American settlement in the 1840's, composition of the remaining prairies shifted toward shrub and tree dominance with a concomitant decline in endemic prairie plant populations. I hypothesize that by restoring...
The influence of overstory openness on the reproductive
ecology of Pacific yew (Taxus brevifolia Nutt.) was
investigated on 4 sites in western Oregon over 2 years. The
breeding system of T. brevifolia was found to deviate from
pure dioecy under a broad range of canopy and site
conditions. Production of...