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...
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...
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...
Disturbance and microclimate interact to play a central role influencing the composition and structure of plant communities. In this thesis, I examined plant community composition and structure twenty years after high severity wildfires with and without post-fire management (salvage logging, fuel treatment, tree planting, and shrub release) under contrasting microclimatic...
Pinyon-juniper woodlands throughout the western U.S. have expanded rapidly following European settlement during the late 19th century. In central and eastern Oregon, western juniper (Juniperus occidentalis var. occidentalis Hook.) encroachment has been previously documented in the sagebrush steppe and upper elevation aspen communities. While these vegetation changes and dynamics have...
Fire suppression in the last several decades has resulted in unprecedented accumulations of organic matter on the landscape, leading to an increase in large, intense wildfires. This study investigated the soil microbial community (using phospholipid fatty acid analysis) across recently burned forests on the eastern slope of the Cascade Range...
Fire exclusion has been associated with structural and compositional changes
in many upland forests of the western United States, but little is known about the
impacts on riparian forests, portions of the landscape protected for habitat and water
quality. For this study, I characterized the historic disturbance and tree recruitment...
Juniper is a native species to Oregon and confers ecological benefits to wildlife when it is at savannah and transitional densities. Its range and extent have fluctuated with climatic change, but the current range expansion is unprecedented in its extent. The range expansion has been associated with the degradation of...