Since the late 1880's western juniper has expanded in range and
increased in density in sagebrush-bunchgrass, riparian, and forested plant
communities of the Pacific Northwest. Succession to western juniper
woodland has been shown to reduce the productivity and diversity of the
understory component, result in concentration of soil nutrients beneath...
The effect of anthropogenic disturbance on river systems is gaining attention, and concerns about the state of freshwater natural resources are increasing globally, as are efforts to restore habitat that has been degraded by disturbance. In rivers, non-point source pollution affects the physical characteristics of the habitat and the endemic...
We are at risk of losing the sagebrush steppe in the floristic Great Basin to the invasion of Bromus tectorum L., cheatgrass. The floristic Great Basin includes the Central Basin and Range, the Northern Basin and Range, and the Snake River Plain. The Great Basin receives most of its precipitation...
Large burrowing owl (Aihene cunicularia) populations exist in areas of intensive agriculture in California, and pesticide exposure has been identified as a potential threat to population persistence. I evaluated breeding season use of agricultural fields by adult male owls using radio telemetry, and examined egg contaminant residues to estimate population-level...
Fuelwood is a basic need for rural households in Malawi. However, deforestation has reduced the quantity of forest products such as fuelwood available to households. This has negatively affected rural Malawian quality of life, especially for women who are forced to walk long distances to collect fuelwood, prepare foods with...
Land use is one of the leading factors that cause environmental degradation, such as water pollution, open space contraction and habitat loss. This dissertation consists of three essays. First paper investigates the relationship between land use and water pollution. Combining land use choice model and water pollution data, I simulate...
There are over 35 known virus and virus-like diseases of sweet cherry (Prunus avium), some with potential to cause severe economic impact by reducing vegetative growth, vigor, and/or quality of fruit. Oregon is the second-ranked state for sweet cherry production in the United States with 13,000 acres and $70.8 million...
Bumble bees provide vital pollination services in both native and agricultural landscapes. However, in recent years, bumble bee populations have experienced global population declines. The primary causes of these declines have been attributed to the environmental impacts of pathogens, pesticide use and habitat fragmentation. While research has examined the impacts...
Crested wheatgrass (Agropyron cristatum [L] Gaertm), an introduced bunchgrass, has been seeded on over 5 million hectares of degraded rangeland in western North America because it establishes more readily than native bunchgrasses. Because crested wheatgrass stands are associated with native species displacement and low biological diversity, there is substantial interest...
Water availability is a critical limiting element in semi-arid ecosystem productivity and presents particular challenges in Sahelian countries such as Senegal. The landscapes are characterized by the presence of two common semi-arid shrubs (Piliostigma reticulatum and Guiera senegalensis), both of which may be important hydraulic regulators in these water-limited ecosystems....