This dissertation describes the epiphyte communities on tall shrubs in forests of
western Oregon, with a focus on potential effects of management practices on these
communities. Shrubs and other hardwoods have recently gained recognition as
hotspots of diversity for epiphytes in young conifer forests of the region. Yet little is...
Many studies suggest that weedy plant species are most successful when
soil nitrogen in abundant. Consequently, I used soil nitrogen manipulations to
determine if altering nitrogen would affect the establishment of both weedy and
native plant species in a western Oregon wetland prairie. In two studies, we
added carbon amendments...
Port-Orford-cedar (Chamaecyparis lawsoniana) is a forest tree native to
a small area of Oregon and California. A root disease caused by
Phytophthora lateralis causes widespread mortality of Port-Orford-cedar.
This dissertation examines three important elements of the Port-Orford-cedar
P. lateralis pathosystem related to breeding for disease resistance:
use of resistant rootstocks...
The diverse lichen flora of the Pacific Northwest is being impacted by
population growth and by forest management practices. Accumulating information
about our lichen flora will improve our conservation strategies. This dissertation first
collects information to improve our understanding of how lichen communities vary
among forests of differing structure, and...
This study was directed to improve our understanding of the ecology of Swiss needle cast (SNC) of Douglas-fir, a disease that produces extensive damage to forests and plantation in the coastal region of Oregon and Washington. A disease prediction model for the coastal area of Oregon was built by establishing...
The abundance and spatial heterogeneity of coarse woody debris (CWD) on the forest floor is a prominent feature of Pacific Northwest (PNW) forest ecosystems. The effect of CWD on soil solution chemistry, nutrient cycling and availability, soil physical structure and formation of soil organic matter, however, remains unknown. Therefore, studies...
Mycosphaerella graminicola (anamorph Septoria tritici) causes Septoria tritici blotch, a globally important disease of winter wheat. Resistance and pathogenicity generally vary quantitatively. The pathogen reproduces both sexually and asexually, and the pathogen population is highly genetically variable. Several unresolved questions about the epidemiology of this pathosystem are addressed by this...
A hierarchical series of studies, based mainly on molecular data, was conducted to elucidate the life history of the Douglas-fir Swiss needle cast pathogen Phaeocryptopus gaeumannii at macro- and micro-evolutionary scales. This information was then utilized to design and evaluate molecular diagnostic tools for use in studies on the epidemiology...
Reducing the cover of non-native species is one of the challenges of ecosystem restoration. The goal of this study is to identify native species traits that will increase native species cover and reduce non-native species cover in the first growing season at upland and wetland prairie restoration sites. Native and...
Astragalus oniciformis Barneby is a xerophyte of the sagebrush deserts of central Idaho. It is a narrow endemic of the upper Snake River Plains where it inhabits stabilized, aeolian sand deposits over Quaternary basalt flows. The objective of this study was to determine the levels and distribution of genetic differentiation...
Breeding Port-Orford-cedar for resistance to Phytophthora lateralis, a causal agent of root disease, begins by screening, through artificial inoculation, phenotypically resistant trees selected from natural stands. The successful program selected tolerant or resistant POC parent trees for the purpose of disease management. Candidate resistant POCs were used in my dissertation...
This thesis consists of three manuscripts describing ecophysiological research on the cyanolichen Lobaria oregana. The first manuscript includes a re-evaluation of the assumptions underlying past estimates of N fixation by this species and provides an estimate of annual N fixation at the Wind River Canopy Crane (WRCC). Based upon litterfall...
Before the arrival of Euro-Americans, the inland Pacific Northwest was settled by native
people whose frequent intentional burning of the landscape promoted open stands
dominated by large fire-resistant ponderosa pine. Fire suppression for nearly a century,
livestock grazing, and logging of the largest trees has resulted in forests characterized by...
Regulation of cell division and expansion are critical for plant development. The mechanisms that control these processes are not clearly understood in higher plants. In other eukaryotic models it has been shown that the highly conserved Rho family GTPases play a crucial role in these mechanisms. One distinct subset of...
Scientists and land managers realize that integrated weed management (IWM) strategies are needed to attain successful and lasting improvements of weed infested landscapes. At this time no broadly reliable and environmentally safe IWM strategy has been developed to control exotic annual grasses that dominate many ecosystems of the northern Great...
Cheatgrass (Bromus tectorum L.) is a widespread exotic weed in the Intermountain sagebrush steppe. An annual grass, it is highly prolific and very competitive with native perennial grass seedlings. A clipping experiment carried out at two cheatgrass-dominated sites (Lincoln Bench and Succor Creek) in eastern Oregon analyzed effects of defoliation...
Lichens are an important part of the biota in western Oregon forests, where
they perform valuable ecological roles and contribute significantly to biodiversity.
Lichens in western Oregon are threatened by a number of factors including air
pollution and land use practices. If we wish to maintain the persistence of lichens...
Transition matrix models are one of the most widely used tools for assessing population viability. The technique allows inclusion of environmental variability, thereby permitting estimation of probabilistic events, such as extinction. However, few studies use the technique to compare the effects of management treatments on population viability, and fewer still...
This dissertation describes patterns in epiphytic macrolichen community composition, diversity, and biomass across various stand types in the Blue River watershed of western Oregon. It first examines the relative importance of ecological factors such as stand age, remnant tree retention, and topography to lichen communities in the landscape. It then...
An experimental reintroduction was performed to determine the best method to create new populations of the tuberous species Perideridia erythrorhiza, a rare vascular plant endemic to southern Oregon. Only a handful of sites are currently present, and many of these are subject to other land uses such as urban development...