Thesis (M.A.)--University of California, Dec. 1918. / Typewritten (carbon copy). Bibliography: vi p. at end.

Based on thesis, University of California. / Bibliography: p. 195-213.

Based on thesis, University of California. / Bibliography: p. 195-213.

Thesis (M.A.)--University of California, Dec. 1918. / Typewritten (carbon copy). Bibliography: vi p. at end.

In the desert areas of southwestern United States the Coleoptera, family Tenebrionidae, constitute a conspicuous part of the ground-dwelling insects. Most species are black or dull chestnut-brown. They are primarily nocturnal and during the day can be found under rocks, debris, loose bark, or in rodent burrows. On cloudy days they may be seen lumbering along the desert floor. Most tenebrionids feed on plant materials of various sorts. In August, 1959, Brigham Young University initiated an ecological study at the Nevada Test Site near Mercury in Nye County, Nevada. As part of that study, emphasis was given to the ground-dwelling arthropods. One of the largest resulting collections was of tenebrionids. The purpose of this study is to provide descriptions of and keys to the beetles of this family found at the Nevada Test Site with notes on their relative abundance, seasonal occurrence, and plant community relationships. The results reported here deal with the tenebrionids collected between August, 1959 and July, 1962.

Graduation date: 2003 / Presentation date: 2002-06-03

No description available.

No description available.

The study of the subsurface flow and distribution of water is critical to the evaluation of the unsaturated zone for a potential geologic high-level radioactive waste repository. This site is located at Yucca Mountain, Nevada in the northern Mojave Desert. and was chosen on the basis of its low precipitation, deep unsaturated zone, and layered volcanic rocks providing the potential for natural hydraulic barriers to reduce the downward percolation of water through the waste storage area. The detailed characterization of hydrologic properties is necessary to evaluate the mechanisms responsible for the distribution and flow of water in the unsaturated zone. Analyses in this study have provided detailed hydrogeologic units with unique hydrologic properties and hydraulic parameters. Porosity was determined to be a useful physical property for predicting hydraulic parameters, as it relates to the largescale deterministic processes that created the volcanic rocks. The detailed property dataset, along with field measurements of moisture status, temperature, and chemistry, were used to evaluate the potential for lateral diversion in the rocks above the potential repository. It was determined that lateral diversion is a small-scale process in this natural system. On the basis of analyses performed in this study, it is suggested that large-scale diversion is not likely to occur at this site. This mechanism should not, therefore, be relied upon to perform as a natural hydraulic barrier to flow reducing percolation through the unsaturated zone. / Graduation date: 2002

The biogeography and ecology of P. balfouriana, a subalpine conifer endemic to California, were studied. Direct gradient-analysis, classification, and ordination were combined to identify the primary factors controlling the tree community in the southern Sierra Nevada. Competition, disturbance, and temperature were inferred as the most important factors regulating the tree community. Pinus balfouriana responded strongly to variation in soil drainage, distrubance, and temperature. Wildfire was the most important chronic disturbance agent in southwestern Inyo National Forest. Stochastic models of wildfire probability in space and time were developed. Evidence of thunderstorm genesis zones in the vicinity of Overlook Mountain and Ball Mountain in the Golden Trout Wilderness was found. A gradient in wildfire ignition probability was identified. Wildfire ignition is most likely at 2700 m elevation on submesic sites. Wildfire return interval is long enough to permit the coexistence of P. balfouriana and P. murrayana; and, short enough that it has important fitness consequences for P. balfouriana. Wildfire disturbance may limit the geographic range of the species in the southern Sierra Nevada. There was a close negative correlation between the abundance of P. balfouriana near the lower-forest-border and the wildfire disturbance gradient. However, the northern range boundary is probably not determined solely by wildfire disturbance. The canopies of mature P. balfouriana were found to be highly elliptic (when viewed from above) with the major axis of the ellipse oriented exactly north-to-south. This trait permits maximum photosynthesis in the early morning and late afternoon. It simultaneously minimizes evaporative demands during midday. Elliptic canopies minimize solar interception during winter and maximize it during summer. This is important for carbon-balance since the photosynthetic apparatus is only active for a brief period during mid-summer. The lower-forest-border was accurately predicted with a carbon-balance model strongly suggesting carbon-balance limitations. The dispersal potential of P. balfouriana, in the absence of vertebrate seed dispersers, was studied. Anemochory under modern climatic conditions would permit closure of the disjunction in P. balfouriana within a single (120,000 year) glacial cycle.