Thesis (M.S.)--Humboldt State University, 2007. / Includes bibliographical references (leaves 40-43). Also available via Humboldt Digital Scholar.

Thesis (Ph. D.)--University of Queensland, 2002. / Includes bibliographical references.

Thesis (Ph. D.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 314-348).

Thesis (Ph. D.)--Oregon State University, 2005. / Printout. Includes bibliographical references (leaves 134-153). Also available on the World Wide Web.

Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (leaves 84-90).

Thesis (M.A.)--Carleton University, 2004. / Includes bibliographical references (p. 156-164). Also available in electronic format on the Internet.

Thesis (Ed.D.)--Teachers College, Columbia University. / Typescript; issued also on microfilm. Sponsor: Frederick Fitzpatrick. Dissertation Committee: Willard Jacobson, Phil Lange. Includes bibliographical references (leaves 124-144) and a ten-page bibliography of films available on conservation.

The climate of the Southwestern United States and northwestern Mexico is marked by a bimodal precipitation regime with the majority of moisture arriving during (1) the cool season via intermittent frontal storm systems (November to February) and (2) intense, convective storms during the North American Monsoon (NAM) (July to September). Fire season in the region occurs primarily during the arid fore-summer in May and early June prior to the arrival of the NAM. Most long-term tree-ring based studies of fire-climatology in the region have evaluated only the role of winter precipitation. We used tree-ring width based reconstructions of both winter and monsoon precipitation, coupled with fire scar based tree-ring reconstructions of fire history from twelve mountain ranges in the US and Mexico at the northwestern margin of the NAM to quantify the historical role of both seasons of precipitation in modulating widespread fire years. Winter precipitation was the primary driver of widespread fire years in the region, but years with drought in both seasons had the highest fire frequency and most widespread fires. The timing and amount of monsoon precipitation can be important factors in ending the most severe fire weather conditions. Monsoon drought coupled with earlier snow melt in the spring appears to contribute to an extension of fire weather for longer periods, leading to more and larger fires.

The main purpose of this report is to develop an economic theory, along the lines of the Bergson- Samuelson social welfare theory, to regulate the utilization of natural resources in the long -term interest of a political- economic group of individuals and firms. The theory, called Collective Utility, qualifies as a "systems approach" because of its inherent flexibility, generality, and comprehensiveness. Collective Utility is a function of individual satisfactions and firm revenues, which are, in general, contingent upon the actions of other individuals and /or firms. Such interactions are called externalities. It is the contention of this report that efficient management of natural resources will follow from efficient control of externalities. A taxation - subsidy structure is suggested as an efficient control and the complete mathematics of determining and implementing such a structure are provided. Finally, the idea of externalities is integrated within the framework of Collective Utility to form an optimal policy for the utilization of natural resources using the techniques of calculus of variations.

Disturbances are key processes that alter environmental conditions which have consequences for species interactions; therefore, disturbances are important to maintenance of biological diversity. Climate, fire, livestock grazing, introduction of nonnative species, and humans all influence semi-desert grasslands of the southwestern United States. In southeast Arizona, a nonnative perennial grass, Lehmann lovegrass (Eragrostis lehmanniana), was introduced in the 1930s in an effort to restore degraded rangelands. I quantified annual fluctuations of Lehmann lovegrass and the response of native plants along a gradient of dominance by this nonnative grass. Biomass and richness of native plants declined with increasing dominance by Lehmann lovegrass. Substantial increases in biomass by Lehmann lovegrass in response to above-average rainfall did not result in decreases in native plants. Fire is an important disturbance in semi-desert grasslands. Herbaceous plants are favored over trees and shrubs in areas with frequent fires, therefore fire maintains grassland physiognomy. Humans have manipulated natural fire regimes however, by altering their frequency, season, and spatial extent. I experimentally investigated the possibility of a positive feedback cycle in grasslands invaded by Lehmann lovegrass by assessing whether the presence of Lehmann lovegrass was enhanced by fire to the detriment of native plants. In the two years post-fire, the proportion of Lehmann lovegrass on burned sites did not increased compared to unburned sites or to pre-fire conditions. I also detected no changes in species richness, diversity, or biomass of native plants in response to fire for 2-3 years after fires. Changes in biomass of all plants varied among years, especially due to exceptionally wet conditions during spring 2001, and varied if fires were set in spring versus summer. Lastly, I investigated the response of Agave palmeri to fire, a species that provides forage for a migratory bat that is federally endangered. Survival of agave varied with soil type, fire season, and size of the plant. In general, agave can tolerate up to 85% damage before mortality. Germination of agave seed was decreased by fire. Based on my research, I recommend setting fire at natural frequency and season for the maintenance of semi-desert grasslands.