The root systems of Douglas-fir trees infected with
Verticicladiella wagenerii and assigned by crown color and terminal
growth characteristics to several stages of decline were excavated at
three widely separated sites in the Coast Range of Oregon. Data were
gathered on insect species present, extent of colonization of the root...
Logs are seedbeds for trees in many Picea sitchensis-Tsuga
heterophylla forests of Washington and Oregon. Factors affecting this
close association, including seed retention and seedling establishment
on logs and successional changes in log characteristics, are explored
In this study.
Field and laboratory experiments indicated that competition with
vegetation on the...
This greenhouse study evaluates the influence of separately and
simultaneously imposed water stress, western spruce budworm (Choristorneura
occidentalis Freeman) defoliation, and inoculation with the root pathogen, Armillaria
ostoyae (Romagn.) Herink, on the growth and biochemical features of Abies .grandis
(Dougl.) Lindi. Seedling biomass, plant moisture status, bud phenology, and
allocation...
Concerns over the possibility of exotic pest
introductions from eastern Russia to the West Coast of the United States due to proposed log imports raises the question of the effectiveness of possible mitigation measures. Toxicity of methyl bromide to representative pathogenic fungi was tested by exposing Armillaria ostoyae, Heterobasidion annosum,...
Plantation forests on mountainous areas in Tanzania, East Africa, were successfully
established in the 1950's. Harvesting started in the 1970's to meet increased national
timber demand. Current problems of unharvested areas and potential environmental
degradation are associated with uncontrolled harvests, mismatch of harvest systems to
site needs, and post-harvest practices....
Basal area and height growth were analyzed for individual trees in uneven-aged ponderosa and lodgepole pine stands in central Oregon. Basal area growth was modeled as a function of other stand and tree variables to address five general objectives: 1) to compare the predictive ability of distance-dependent versus distance-independent stand...
The objective of this project was to investigate the fate of ponderosa pine regeneration from seed to established seedling, and to determine the relative influences of several important stand elements on those fates. The project was carried out in a series of observational and experimental recruitment studies in central Oregon....
While microbial colonization of wood is presumed to be characterized by a myriad of interactions between numerous organisms, studying these processes is often difficult owing to the opaque nature of the wood and the inability to readily distinguish among the many species colonizing the material. One method for enhancing the...
Phytophthora ramorum, a plant pathogen, is the cause of sudden oak death and ramorum blight and shoot die-back. It has a wide host range including many native forest species and common nursery plants. The lack of knowledge regarding infection biology of P. ramorum limits our understanding of its ecology and...
Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), a shade intolerant species, and western hemlock (Tsuga heterophylla (Raf.) Sarg.), a shade tolerant species, were compared to learn more about the temporal pattern of release from suppression in both species, whether hydraulic architecture or photosynthetic capacity constrain release and how wood functional properties change...
Interspecific hybridization was initiated between wild P. acutifolius accession G40199 and P. vulgaris to introgress resistance to Acanthoscelides obtectus (bean seed weevil). F1 interspecific hybrids were recovered by embryo rescue and maintained until flowering. Mostly sterile hybrids were backcrossed twice to common bean cultivar ICA Pijao to recover sufficient fertility...
This collection of six individual writings, both fiction and creative non-fiction, is an exploration in narrative first-person voices and multiple themes, such as the loss of innocence, modernization versus traditions/myths, the California Central Valley, death, creativity, language, change, and the pressures of the future. Though abstractly linked at times, these...
Coast redwood (Sequoia sempervirens) (D. Don) Endl. is a host for Phytophthora ramorum but it was unclear if the pathogen represents a significant disease risk to this tree species. In this study the susceptibility of coast redwood seedlings and the likelihood of sporulation on redwood were examined. Two methods were...
Tanoak (Lithocarpus densiflorus), along with some other members of Fagaceae, are susceptible to sudden oak death caused by the oomycete Phytophthora ramorum. Symptoms of the disease include dying crowns, bleeding cankers, and eventually death of infected trees. The cause of mortality is not well understood, but recent research indicates that...
Ponderosa pine is an important species both commercially and ecologically in western North America. This study considers the incidence of insect and disease pests on a series of replicated ponderosa pine research plantations in northern California. The studies, on an environmental gradient, contain a series of silvicultural treatments including vegetation...
Since around 1923 Port-Orford-cedar (Chamaecyparis lawsoniana (A. Murray) Parl.) has been affected by Phytophthora root disease caused by the virulent introduced pathogen Phytophthora lateralis. A systematic resistance testing and breeding program located at the USDA Forest Service Dorena Genetic Resource Center in Cottage Grove, Oregon was initiated in 1997 with...
Rubber without reinforcement has limited applications. The strength of reinforced rubber composites can be ten times stronger than that of unreinforced rubbers. Therefore, rubber composites are widely used in various applications ranging from automobile tires to seals, valves, and gaskets because of their excellent mechanical elastic properties. Silica and carbon...
Moisture intrusion in residential structures can lead to substantial fungal decay and this damage costs billions in repair/replacement costs. The extent of damage and the rate at which it occurs are primarily dependent on the wood moisture content and temperature in the structure. Determining the risk of decay for various...
Rhododendron species are host to many Phytophthora species and are an important crop in the nursery industry. The foliar epidemiology of twelve Phytophthora diseases on Rhododendron was studied in field and growth chamber experiments on two Rhododendron cultivars. The relative aggressiveness of Phytophthora spp. was assessed using disease incidence, severity,...
Phytophthora lateralis is the causal agent of cedar root rot, a fatal forest pathogen whose principal host is Chamaecyparis lawsoniana (Port-Orford-cedar), a predominantly riparian-restricted endemic tree species of ecological, economical, and cultural importance to coastal Oregon and California. Local scale distribution of P. lateralis is thought to be associated with...
Phytophthora ramorum, an oomycete plant pathogen, is the causal agent of sudden oak death, a serious disease of Fagaceous trees in California and Oregon over the last decade. Tanoak (Notholithocarpus densiflorus) is one of the most susceptible host species, but the cause of host mortality is poorly understood. Previous research...
Both transportation costs and market values of woody biomass are strongly linked to the amount of moisture in the woody biomass. Therefore, managing moisture in the woody biomass well can lead to significant advantages in the woody biomass energy business. In this study, two prediction models were developed to estimate...
Phytophthora pini Leonian, recently re-established from P. citricola
I, is a pathogen with a wide range of forest and nursery hosts. It causes foliar
infections in horticultural nurseries in Oregon, where recirculating irrigation
systems are common. Increased use of recirculating irrigation systems may
contribute to disease caused by waterborne plant...
Hypersensitive response-like (HR-like) needle reactions to infection by the white pine blister rust pathogen, Cronartium ribicola, have been reported for several species of five needle pines native to western North America. The best-studied examples are in Pinus monticola and P. lambertiana. In these species a "needle spot" phenotype has been...
Most parasites and their hosts live in a balance within their environment; however a disease outbreak can occur when either the parasite, host, or environment, are perturbed. Myxozoan parasites are associated with a wide variety of cultured and wild fish populations. Most myxozoans are relatively benign to their vertebrate host;...