Climate change and the increase in meteorological drought have generated global concern over the persistence of ecosystems already in decline from decreased moisture. Evidence suggests dryland ecosystems have been more impacted by drought because of their tightly coupled growth-water relationships and high sensitivity to environmental shift. Removal of competing vegetation...
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...
This thesis investigates the success of and challenges facing small farmers operating direct marketing farm businesses in Oregon's Willamette Valley. This qualitative study utilizes participatory methods to gain the unique perspectives of small farmers regarding their success and challenges. Small farms are important players in local food systems and ensuring...
The sagebrush steppe ecosystem of the Columbia Plateau has become degraded by a long history of alternative land use and associated perturbations. Protection of remnant stands of intact sagebrush steppe currently relies upon their preservation within the nation's network of parks and protected-areas. The John Day Fossil Beds National Monument,...
The spatial and temporal behavior of invasive species spread implies that optimal management strategies involve decisions over space and time. Dispersal and propagule pressure are two primary drivers of the spatial-temporal ecological process of species invasion. In the case of riparian communities, stream flow drives the dispersal of vegetation propagules....
Biological plant invasions are diminishing the ecological integrity and function of ecosystems worldwide. A primary example of this is in the Great Basin of the United States, where invasive annual grasses, like cheatgrass (Bromus tectorum L.) and medusahead (Taeniatherum caput-medusae L. Nevski), are dominating many sagebrush-steppe ecosystems. In these invaded...
Dalmatian toadflax (Linaria dalmatica) has become a prolific invasive plant of rangelands in Oregon since its arrival in the early 20th century. In 2001, the Oregon Department of Agriculture initiated a release program promoting the distribution of the stem-boring weevil, Mecinus janthinus as classical biological control agent to reduce densities...
Forty-six morphological characters were used in a study of Triticum turgidum ssp. carthlicum (2n = 28) and specimens of carthlicum-like forms of Triticum aestivum ssp. vulgare (2n = 42). The morphological variation patterns within these groups were examined using stepwise discriminant analysis. These results indicate that specimens studied could be...
Little is known about cactus nutrients, their
proportions in different species and the variability of
these proportions with season. In the scant literature
available on Opuntia species, no systematic survey has
been published to document and compare the nutritional
qualities of different species. Also, no studies have
been done to...
Quaking aspen (Populus tremuloides Michx.) is known to be a widely distributed, shade-intolerant and short-lived hardwood found in both seral, even-aged and stable, uneven aged stands. There have been reports of extensive aspen mortality, crown thinning, and branch dieback across North America that have been linked to the occurrence of...