Thesis (M.S.) in Ecology and Environmental Science--University of Maine, 2003. / Includes vita. Includes bibliographical references (leaves 75-86).

Thesis--Harvard University, 1926. / Includes bibliographical references and index.

Boston University. University Professors Program Senior theses. / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / 2031-01-02

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Section 1: Introduction, Section 2: Physical Features, Section 3: Biological Resources, Section 4: Social/Economic Characteristics, Section 5: Important Resources, Section 6: Watershed Classification, Section 7: Watershed Management, Section 8: Local Watershed Planning, Section 9: Nine Key Elements, Appendix A: Water Quality Data and Assessments, Appendix B: Selected References, Appendix C: RUSLE, Appendix D: AGWA

This study identifies the biogeographic factors that structure small mammal communities on mountains of the Colorado Plateau and adjacent regions. Forty six isolated ranges were characterized across a 5-state study area encompassing the Colorado Plateau, including the central high plateaus of Utah and the Basin and Range Province (i.e. the Great Basin and mountains of Arizona and New Mexico). Presence/absence data of 25 montane mammal species were used to explore the interactions between historical and ecological processes affecting local and regional diversity patterns. Multivariate analyses, such as non-metric dimensional scaling, were used to explore factors which influence community composition. Results of these analyses revealed the Colorado River as a significant biogeographic barrier that affects montane mammal community structure. MtDNA cytochrome b sequence variation was analyzed among populations of the long-tailed vole, Microtus longicaudus, sampled from five interior ranges of the Colorado Plateau- Abajo, LaSal, Henry, and Chuska Mts., and Boulder Mountain of the Aquarius Plateau-and analyzed using traditional phylogenetic approaches (parsimony and likelihood) as well as nested clade analysis. Results support previous documentation of a major east-west phylogeographic break occurring between populations southeast of the Colorado River (eastern Arizona, Colorado, Wyoming and New Mexico) and all other western populations, which include a central clade, a northwest clade, and an Alaskan island clade. Evidence also supports differentiation of a 'southern Rockies' clade and a distinct 'southwest island' clade. Populations of M. longicaudus north and west of the Colorado River (Boulder and Henry Mts.) share two haplotypes, form a well-supported subclade with populations from the Kaibab plateau, and are closely related to the Northwest clade. Past approaches to studying montane mammal communities utilizing theory based on island biogeography have overemphasized area and isolation as the only forces structuring insular communities. As a result, there has been a lack of recognition of the influences of environmental factors, species turnover, and barriers that create and maintain regional diversity on the Colorado Plateau and adjacent areas.

Between 2000 and 2014, annual Colorado River flows averaged 19% below the 1906-1999 average, the worst 15-year drought on record. At least one-sixth to one-half (average at one-third) of this loss is due to unprecedented temperatures (0.9 degrees C above the 1906-1999 average), confirming model-based analysis that continued warming will likely further reduce flows. Whereas it is virtually certain that warming will continue with additional emissions of greenhouse gases to the atmosphere, there has been no observed trend toward greater precipitation in the Colorado Basin, nor are climate models in agreement that there should be a trend. Moreover, there is a significant risk of decadal and multidecadal drought in the coming century, indicating that any increase in mean precipitation will likely be offset during periods of prolonged drought. Recently published estimates of Colorado River flow sensitivity to temperature combined with a large number of recent climate model-based temperature projections indicate that continued business-as-usual warming will drive temperature-induced declines in river flow, conservatively -20% by midcentury and -35% by end-century, with support for losses exceeding -30% at midcentury and -55% at end-century. Precipitation increases may moderate these declines somewhat, but to date no such increases are evident and there is no model agreement on future precipitation changes. These results, combined with the increasing likelihood of prolonged drought in the river basin, suggest that future climate change impacts on the Colorado River flows will be much more serious than currently assumed, especially if substantial reductions in greenhouse gas emissions do not occur. Plain Language Summary Between 2000 and 2014, annual Colorado River flows averaged 19% below the 1906-1999 average, the worst 15-year drought on record. Approximately one-third of the flow loss is due to high temperatures now common in the basin, a result of human caused climate change. Previous comparable droughts were caused by a lack of precipitation, not high temperatures. As temperatures increase in the 21st century due to continued human emissions of greenhouse gasses, additional temperature-induced flow losses will occur. These losses may exceed 20% at mid-century and 35% at end-century. Additional precipitation may reduce these temperature-induced losses somewhat, but to date no precipitation increases have been noted and climate models do not agree that such increases will occur. These results suggest that future climate change impacts on the Colorado River will be greater than currently assumed. Reductions in greenhouse gas emissions will lead to lower future temperatures and hence less flow loss.

An investigation of the life history of the western chuckwalla, Sauromalus obesus, was undertaken in the Colorado Desert of southeastern California during a 7-year period. The study provided for a test of current life history theory and the modeling of population dynamics from environmental parameters. Colorado Desert S. obesus were mainly active February through September, but feeding occurred throughout the year. Coyotes were this species' primary predator. Home range sizes of males and females were correlated with adult female activity and nutrient requirements, respectively. The breeding status of females was determined by the presence of preovulatory follicles, oviductal eggs and copora lutea. The breeding status of males was best determined by the presence of sperm in the vas deferens and by levels of spermatogenic activity. Adult females always oviposited during the first half of July. Size at reproductive maturity for both sexes was about 125 mm snoutvent length. Age at maturity for males and females was 2 and 3 years, respectively. Mean annual reproductive frequency was 51%. Reproduction occurred in 6 of 7 years. Mean clutch size was 6.9 eggs. Clutch masses and egg masses averaged 34.3% and 5.3% of total body mass, respectively. For a given body size, there was no annual variation in clutch size, egg mass, or reproductive effort. The consistency of these traits indicates adaptation to a predictable environment. Relatively high egg masses are an adaptation to counter the harsh environment. Annual recruitment was about 20%, almost exclusively due to reproduction. First year and subsequent annual survivorship rates averaged 40% and 75%, respectively. Most individuals lived no longer than 10 years. Compared with Mojave Desert populations, Colorado Desert S. obesus demonstrated earlier maturity, higher reproductive rates, higher first year survival and lower adult survivorship. High reproductive rates and first year survival were attributable to the predictability of mild winters and summer rainfall. Such conditions promoted lower adult survivorship because of associated costs of reproduction and predation. Attempts were made to predict population age class structure from winter precipitation regression models. Such a procedure appears reliable for predicting age-specific fecundity and therefore is a useful tool for management practices.

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