Four Utah populations of Drosophila pseudoobscura from the Wasatch Mountains in Utah were sampled and characterized for third chromosome gene arrangements. The original samples in this area were taken in 1940 and 1950. At that time the populations were essentially monomorphic for the Arrowhead arrangement, with small percentages of Pikes Peak and Chiricahua also found. The current samples show these populations to contain eight third chromosome arrangements; seven previously described (AR, PP, CH, ST, TL, OL, EP) and a newly discovered endemic arrangement (American Fork, AF), with breakpoints 63E and 70D. The frequency of AR had decreased to 25% in certain areas; the highest frequency found being 63%. The observed array of arrangements is very similar to the Rocky Mountain populations of Colorado, and repeated sampling from one of the Utah localities seems to show a seasonal variation of the AR chromosome resembling that of the Colorado area. Due to the diversity and extent of the changes observed it is improbable that any one mechanism or event could account for these changes.

No description available.

In the Northwest Great Basin, aspen (Populus tremuloides) communities uniquely contribute to the biodiversity of a semi-arid, sagebrush-dominated landscape. In this same region, western juniper (Juniperus occidentalis) is encroaching into aspen stands. This study determined the timing, extent, and some of the effects of this expansion. Aspen stands below 2,133 m elevation were sampled in northwest Nevada, northeast California, and southeast Oregon for density, canopy cover, age, stand structure, and recruitment of western juniper and aspen. Soils and tree litter from both species were collected to analyze the effects of western juniper in areas previously influenced by aspen. Additionally, two large aspen complexes in southeast Oregon were intensively aged to determine disturbance (fire) frequencies. Western juniper encroachment into aspen stands peaked from 1920 to 1939 with 77% of all juniper trees sampled establishing during this period. Five percent were greater than 100 years and none exceeded 145 years. Three-fourths of aspen stands sampled have established populations of western juniper. Twenty-three percent have a dominant canopy of western juniper. Twelve percent of aspen stands sampled were completely replaced by western juniper. Average density of western juniper was 1,573 trees per hectare of aspen. Seventy percent of aspen stands sampled had zero recruitment of new aspen. Within the study area aspen stands averaged 98 years old. Forty-eight percent of stands were greater than 100 years old. There was an inverse correlation between aspen canopy cover and western juniper canopy cover (r��=.80, p=.0001). Soils influenced by western juniper had a higher C:N ratio and pH; higher amounts of salts, lime, and sulfate; and lower amounts of magnesium, iron, copper, and manganese (p<.05). Aspen litter had a lower C:N ratio than western juniper litter (p<.05). Prior to 1870, the two major aspen complexes sampled had mean fire return intervals of 10 and 11 years. However, the most recent disturbance in either complex was 80 to 90 years ago. This lack of disturbance (fire) coupled with aspen stand decadence and low recruitment levels leaves aspen communities in the Northwest Great Basin vulnerable to western juniper encroachment and replacement. / Graduation date: 2000

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 300-330). Also available via the Internet.

This paper presents a refined methodology for distinguishing the stone points of arrows from the stone points of spear thrower darts in archaeological assemblages from the Great Basin. The methodology was developed from a sample of 111 complete stone points collected during the archaeological reconnaissance and testing of the Malheur National Wildlife Refuge, Harney County, Oregon, 1971-1974. The points were measured for five metric variables and frequency histograms of each variable were generated by computer. The effectiveness of each variable as an index of functional class (i.e., arrow point vs. dart point) was judged on the basis of the apparent bimodality of its curve and the t-test. The variables of weight and neck width showed significant bimodality, confirming the work of previous researchers. A new variable, stem thickness, also showed significant bimodality. All three can be considered useful indices of functional class. They also appear to be functionally independent. An attempt was made at developing a multivariable index of point function, using a multivariable clustering analysis, the K-means test. Results of the K-means test were inconclusive but showed promise for further development.

The processes by which plant spatial patterns are formed, and the effects of those patterns on plant community dynamics, remain important areas of research in plant ecology. Plant spatial pattern formation has been linked to many ecological processes that act to structure plant communities at different spatiotemporal scales. Past studies of pattern formation are common, but recent methodological advances in data collection and analysis have permitted researchers to conduct more advanced observational studies of pattern formation in space and time. While studies of the effects of plant spatial patterns were formally rare, they have increased in the last decade as new types of experiments and analysis have been developed to better understand the myriad effects of plant patterns on community dynamics. My dissertation research examined both the causes and consequences of plant spatial patterns in the context of natural and experimental Great Basin semi-arid plant communities. In both cases, I implemented novel methodologies for data collection, experimental design, and data analysis in an attempt to address current gaps in knowledge related to the processes by which plant spatial patterns are formed, as well as the effect of plant spatial patterns on community dynamics. The results inform both basic and applied plant ecology, and set the stage for further research on the causes and consequences of plant spatial patterns in semi-arid plant communities.

Three Macroterrain Landtype Association classification models were developed to stratify and categorize Utah's West Desert. These models approached terrain segmentation using an energy-flow paradigm from erosional to transitional to depositional landscape. One model was developed as a slope-backed deterministic model that used slope-threshold limits to discriminate between Landtype Associations. A second model was developed as a stochastic, training-data driven supervised classification, using comparative t-values to classify the landscape to the most similar landtype class. The third model was a probabilistic algorithm, which classified the landscape to the most probable class based on multiple iterations of the stochastic model. These models were assessed for performance against Macroterrain Landtype Association classifications from three independent geographical datasets. The performance assessment involved calculating model-to-reference agreement, a piecewise assessment of errors for each Macroterrain Landtype Association class, and a measure of the modeI-to-reference performance relative to that performance expected from random chance.

The inputs and losses of nitrogen from Great Basin arid soils were studied using the acetylene reduction and 15N techniques. Filamentous blue-green algae were observed to be the predominant algal group in the soil crusts. The bacterial association with this group of algae suggest a phycosphere-like effect, thus allowing heterotrophic nitrogen fixation and denitrification to occur. Up to 17.5 mg N/100 g soil was found to have been fixed in surface soils (0 to 3 em) during a three week incubation period, while 45.9 mg N/100 g soil was fixed in a five week incubation period. Ammonium sulfate and ammonium sulfate plus plant material amendments reduced the gain in nitrogen by 41 to 100 percent. 15 + 15 - Fifty to sixty percent of the applied NH4-N and N0 3-N was denitrified during the first week of incubation while 70 to 80 percent of the NH 4-N was lost in a three- to five-week incubation period. These data suggest that a potential for heterotrophic nitrogen fixation exists, and under optimal conditions, significant gains in soil nitrogen may be achieved. However, in the presence of allelochemic agents, the potential gain in soil nitrogen may be reduced or inhibited. In addition, the denitrification potentials of these soils may also limit the input of nitrogen. The application of protein ( casein) to these soils resulted in an ammonification rate of 50 to 60 percent. 15 Fixed N2 indicated a 21 to 48.8 percent ammonification rate, thus suggesting that the mineraliztion of NH 4 was the rate limiting step for nitrogen loss. Ammonia volatilization accounted for less than a five percent nitrogen loss, regardless of experimental conditions. The inhibitory effects of plant material and litter extracts, and ''N-Serve" on heterotrophic nitrogen fixation has been assessed. The data suggest that the nitrogen fixing population is sensitive to the inhibitory effects of such agents .

The supply of market milk in the Great Basin marketing area has been increasing more rapidly than the demand for fluid milk and cream. During the last four years, supply of market milk increased 35 million pounds, while fluid use increased only 15 million pounds.

Intact sagebrush communities in the Great Basin are rapidly disappearing due to invasion of non-native plants, large wildfires, and encroachment of pinyon pine and juniper woodlands. Land management options include the use of prescribed fire, grazing, herbicides and mechanical treatments to reduce the potential for wildfire and restore plant communities. Land managers in the region face a complex and interrelated set of ecological, economic, and social challenges to the implementation of these management practices. Effective restoration strategies require consideration of citizens in the region and their acceptance of management practices, as well as their trust in the agencies that implement them. This longitudinal panel study (2006-2010) examines the social acceptability of management options for rangeland restoration and public trust in agencies to carry out these options in three urban and three rural regions of the Great Basin. Most similar studies in this region have been largely place-based and cross-sectional, focusing on communities at one point in time. Results from this study can be used to evaluate the success of management programs, predict support for different treatments, determine the impact of agency outreach efforts, and identify important factors for building trust between communities and agencies across the region. The study uses data from a mail-back questionnaire sent to residents in 2006 and again in 2010. Overall, 698 respondents comprise the panel of interest. Results suggest landscape scale events such as wildfire, as well as agency management and outreach programs, had little influence on respondents' perceptions of agencies or management options over the study period. Several key findings have persisted throughout the study: (1) acceptance is high for the use of prescribed fire, grazing, felling, and mowing, but low for chaining and herbicide use, though there are (2) low levels of public trust and confidence in agencies to implement these management options, and (3) there are salient differences between the region's rural and urban residents with important implications for agency communication strategies. Most changes in response over the study period were subtle, though the direction and strength of these changes highlight noteworthy trends: (1) Great Basin residents are becoming more aware of key threats facing rangelands, (2) they seem more interested in having a role in making management decisions, and (3) they are slightly more positive about their interactions with agency personnel. Finally, findings suggest many residents have had little experience with agency outreach programs. Trust and confidence in management agencies are key factors in garnering support for restoration activities. While knowledge of management activities and confidence in managers' ability to competently implement them certainly play a role, findings strongly suggest sincerity factors (e.g., good communication or the perception that agencies share citizens' goals, thoughts, or values) have the greatest influence on acceptance of management practices in the Great Basin. Results suggest it would be beneficial for agencies to take a more active role in building trust with residents across the region. Differing levels of knowledge and interest, as well as different concerns, found among rural and urban residents highlight the need to tailor outreach strategies for use in specific communities. / Graduation date: 2012