Thesis (M.S.)--Oregon State University, 1990. / Typescript (photocopy). Includes bibliographical references (leaves 89-96). Also available via the World Wide Web.

Thesis (M.S.)--University of Wyoming, 2008. / Title from PDF title page (viewed on June 25, 2009). Includes bibliographical references (p. 52-55).

Thesis (M.S.)--Oregon State University, 2006. / Printout. Includes bibliographical references (leaves 85-90). Also available on the World Wide Web.

Thesis (Ph. D.)--University of Wyoming, 2007. / Title from PDF title page (viewed on July 15, 2008). Includes bibliographical references.

Ranchers and resource managers have become concerned about the role and spread of Cardaria draba (L.) Desv. (whitetop) in the sagebrush steppe of Northeastern Oregon. This area is an important natural resource for livestock production and big game winter range. An area near Keating, Oregon was selected to study the influence of environmental conditions on whitetop seed germination, mode of spread and species displacement by whitetop. Whitetop seeds were placed in the field at four different topographical positions (toe slope, mid-slope, north slope and south slope) and placed at three different locations in the soil profile (0, 1, and 3 cm). Seed placed on the toe slope position at 0 cm had the greatest germination. At the south aspect greater germination occurred at lower soil profile locations. Increases in whitetop populations were evaluated by establishing permanent transects in two locations in the study area. Whitetop shoot density increased during the three year study. Whitetop density increase was restricted to previously infested plots and was due to vegetative reproduction. In whitetop infested areas, crested wheatgrass density was less than in non-infested areas. Whitetop germination at different topographical positions was apparently related to moisture conditions. Once established, whitetop populations increase through vegetative reproduction. This phenomenon is reflected in a reduction of crested wheatgrass density and production as the level of whitetop infestation increases. / Graduation date: 1992

Thesis (M.S.)--Brigham Young University. Dept. of Plant and Animal Sciences, 2006. / Includes bibliographical references (p. 14-21).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1963. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Bibliography: leaves 102-105.

No description available.

Water potential, leaf conductance, growth, nitrogen content, and seedling survival of Wyoming Big Sagebrush (Artemisia tridentata ssp. wyomingensis) following defoliation of the herbaceous understory were assessed during two growing seasons. Precipitation was 107% and 63% of the long-term mean (283 mm) in 1989 and 1990, respectively, which presented an opportunity to study impacts during a drought and a non-drought year. Response of Artemisia was measured on a site seeded to Agropyron desertorum in the late 1960s, and a native site with Stipa thurberiana, Festuca idahoensis and Poa sandbergii in the understory. The two sites were analyzed as separate experiments. The dry year had a significant effect on plant water relations and growth of Artemisia on both sites. Pre-dawn water potentials averaged 1.23 MPa more negative on the seeded site and 1.22 MPa more negative on the native site in 1990 compared to the previous year. Mid-day water potential averaged 1.22 MPa more negative on the seeded site and 1.13 MPa more negative on the native site in 1990 compared to 1989. Morning leaf conductance in 1990 was 61% lower on the seeded site and 51% lower on the native site than in 1989. Mean afternoon leaf conductance in the drought year was 62% less on the seeded site and 63% less on the native site. Nitrogen content in current year's growth was reduced 29% on the seeded site and 18% on the native site from 1989 to 1990. Vegetative and reproductive shoot (stem plus leaves) weights were reduced by over 80% in 1990 compared to 1989. Other production variables showed similar reductions in the drought year. Nitrogen content was 11% greater in current year's growth from shrubs on control as opposed to defoliated plots on the native site in 1989. Shrubs on control plots had 8% heavier reproductive stems per unit of canopy, and 7% longer vegetative stems than shrubs on defoliated plots in 1989 on the seeded site. Shrubs on control plots had 18% fewer annual leaves per unit of vegetative shoot, but 12% more primary ephemeral leaves per vegetative shoot than shrubs on defoliated plots in 1990 on the seeded site. In 1990, shrubs on control plots on the seeded site had 11% more ephemeral leaves per vegetative shoot while shrubs on the control plots on the native site had 8% fewer ephemeral leaves per vegetative shoot. Large shrubs generally had more and heavier leaves, and longer and heavier stems than medium shrubs. Exceptions included large shrub lateral stems were 30% shorter than those of medium shrubs, and large shrubs had 37% fewer annual leaves per vegetative shoot than medium shrubs in 1989 on the seeded site. Drought had substantial negative impact on water relations and growth of Wyoming big sagebrush, while defoliation of understory vegetation had little effect. / Graduation date: 1993

Thesis (M.S.)--Oregon State University, 1989. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.