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

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 (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.

The Bouteloua curtipendula (Michx.) Torr. complex (BCC) is composed of 11 species and five varieties distributed in North and South America with its center of diversity in Mexico. It is characterized by tremendous morphological variation and taxonomic complexity that is most likely due to reticulate evolution, phenotypic plasticity, and the development of asexual reproduction (apomixis). Climate-induced range changes over evolutionary time may explain the origin of the morphologically diverse BCC as suites of species came into contact over time, hybridized, and created new species, cytotypes, and reproductive modes. I investigated the origins of the BCC by creating habitat suitability models based on present-day occurrence records for eight BCC taxa and hindcast these models to paleoclimate reconstructions for the Last Glacial Maximum and Last Interglacial. By estimating range dynamics over time, coupled with phylogenetic data, I inferred the locations of contact zones among taxa and identified likely progenitor taxa for various cytotypes found in the BCC. Species with large and environmentally heterogeneous distributions may have large ranges due to plastic responses to environmental variation for adaptive traits or they may maintain differently adapted ecotypes to specific habitats. I evaluated phenotypic plasticity for stolon and rhizome production in the three taxonomic varieties of B. curtipendula. My results indicate that expression of these traits is correlated with specific, local environmental conditions and not to broadly defined environments in geographic space and that phenotypic plasticity accounts for a greater proportion of trait expression than does total genetic variance. Apomixis, asexual reproduction via seed, most likely results from interploidy hybridization. There are many possible pathways that lead to asexual seed formation and understanding these pathways is important to understanding genetic diversity, demography, and evolutionary potential in apomictic and mixed apomictic-sexual populations. I discovered that B. curtipendula var. caespitosa, the only recognized apomictic taxon in the BCC, is pseudogamous, indicating that although fertilization is unnecessary to produce the embryo, it is necessary to produce the endosperm. These data also indicate that meiosis is highly irregular and results in sperm nuclei with variable chromosome numbers, which affects endosperm production, fertility and demographics in apomictic B. curtipendula.

In the effort to restore historic landscapes, it is necessary to first specify spatially explicit target vegetation communities. Previously, botanists or other local experts have used landscape and environmental factors, historical evidence, and evidence from remnant vegetation to define presettlement vegetation communities on the landscape. Once these communities are defined, they must be mapped in order to be truly understandable and useful. Efforts to map the location of these presettlement communities on a particular landscape are often laborious and time consuming. In this study, we discuss a rapid method for assessing the location of these vegetation communities using Geographic Information Systems (GIS) and the current science of fire behavior modeling. Fire behavior models are proven predictors of fire intensities across a landscape, considering vegetation, slope, aspect, wind, and weather. Our hypothesis was that these fire behavior models could be used to make inferences about presettlement vegetation community distributions in former frequent-fire landscapes. GIS software was used to find simple combinations of variables associated with vegetation distribution, including soil type, aspect, slope, and orientation to gradient winds. A conventional fire model (FlamMap) was then used to find areas that are distinctly fire sheltered. In a survey of 78 fire sheltered community sites visited on the study landscape, 91% of the areas were considered to be correctly identified based on the presence of remnant presettlement vegetation indicator species. Success in finding a single community as related to a specified range of fire behavior outputs suggests that there is potential for expanded utility of fire models in making inferences about vegetative distribution on the frequent-fire landscape. The fire model adds to the utility of the GIS by considering the effects of fire spread direction and variation in fuel moistures in conjunction with terrain variables. The resulting fire intensity outputs represent environmental effects on vegetation distribution that cannot be modeled solely with a GIS. A final presettlement vegetation layer was completed for the study site, located at Fort Bragg on the Southeastern coastal plain of North Carolina, and compared to a layer generated by an extensive 2-year study considered to be definitive. The results showed an overall map accuracy of 78 percent for the proposed procedure. This output may be used as a preliminary map that, in conjunction with ground-truthing, will shorten the process of mapping presettlement vegetation for use in the restoration of historic fire dependent communities.

The growth characteristics and habitat of the rare shrub Amorpha georgiana var. georgiana were studied by examining 19 documented groups of this Federal Species of Concern. These 19 groups occur along the Little River on the Fort Bragg Military Reservation in Cumberland, Hoke and Moore counties, North Carolina. Systematic field studies located and monitored the plants, and a modified version of the North Carolina Vegetation Survey protocol produced an inventory of surrounding plant communities. Results were used to modify knowledge of A. georgiana var. georgiana and correct errors in previous accounts: flowering commences in mid-April and ends in mid-May; seeds may persist on the plants until the following April; tree canopy densities range above 75 percent; and the plant inhabits transition zones on the dry side of wetland boundaries. A key to guide searches for the plant is presented along with recommendations for further research to resolve remaining questions about the protection status of Amorpha georgiana var. georgiana.