The language of regulations implementing the 1977 Clean Air Act Amendments distinguishes between humanly detectable visibility impairment in Class I Parks and Wilderness areas and the extent to which such impairment adversely affects a park visitor's visual experience. Two lines of environmental perception research have arisen from this distinction, one emphasizing the detectability of visibility impairment, and the other emphasizing a park visitor's experience. This study attempts to deal with issues relevant to both lines of research. Subjects were shown color slides depicting varying levels of visibility in Class I Parks and Wilderness areas under four treatment conditions. A sensitivity gradient emerged from these conditions: Subjects who rated repeated versions of selected vistas for visual air quality were most sensitive to changes in visibility, while subjects who rated a random series of scenes for scenic beauty were least sensitive. Other variables (i.e., scattering angle, and the particular vista being viewed) also proved to have substantial influence on perceptual ratings.

No description available.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. 11/30/2013. / A variety of mass movement and depositional geomorphic phenomena in the Golden Gate Highlands National Park have been described in the literature over the past few decades, yet notably, the prominent rockfalls remain understudied. The objective of the MSc study is to undertake detailed mapping of the GGHNP rockfalls, and in so doing ascertain a better understanding of their macro-morphologies, associated spatial-size dynamics and relationships to lithology, using both field-based and desktop image processing techniques. Ground truthing, using the highest possible resolution achievable through differential GPS (DGPS) and field measurements with an accuracy of cm to mm, serves to quantify the accuracy of mapping rockfall phenomena through 0.5 m GSD colour aerial imagery. In addition, field measurements are used as inputs for feature extraction, such that rockfalls associated with the Clarens, Elliot and Molteno Formation Sandstones may be defined using object orientated classification techniques. The dimensions, orientation and absolute coordinates of rockfalls for select representative sites were captured using both field based and desktop techniques. The rockfall coordinates were taken at the midpoint of each measured rock using a DGPS, with an accuracy of ~ 2 cm on the x, y and z axis. Object Based Image Analysis (OBIA) of Clarens and Molteno Fm. rockfalls was performed successfully using ground-truthed rockfall measurements to guide the creation of segmentation and classification rulesets. Multiple linear regression modelling can be used to model rockfall characteristics from ground-truthing with remotely sensed imagery, albeit to a very limited extent. Elliot Formation rockfalls could not be mapped and analysed mainly due to resolution limitations. Uni- and bi-variate statistics show promise in interpreting rockfall distribution and weighting with environmental variables derived from a DEM and geological vector. Point density analyses found that for the entire GGHNP ~2 and ~4 rockfalls are found per Km² of Clarens and Molteno Formation rockfall areas

No description available.

Includes appendices. Bibliography: p. 141-147.

Thesis (Ph.D.)--Texas Christian University, 2007. / Title from dissertation title page (viewed Dec. 10, 2007). Includes abstract. Includes bibliographical references.

Marine ecosystems can be exposed to natural and anthropogenic disturbances that can lead to ecological failures. Marine reserves have been lately suggested to protect marine populations and communities that have been affected by habitat destruction and harvest. This research evaluates the potential role of two marine reserves established in Oregon in 1967 (Whale Cove) and 1993 (Gregory Point). The red sea urchin (Strongylocentrotus franciscanus) was selected as indicator of population recovery since it is the only species that is commercially harvested. Changes in density, biomass, average size, size structure, growth and mortality rates were evaluated through time to assess population recovery. These parameters were also compared between reserves and adjacent exploited areas to evaluate the effect of exploitation. Results from Whale Cove (old reserve) indicate that the population in this area is fully recovered. On the contrary, the population in Gregory Point (new reserve) showed signs of recovery after six years of being protected. The importance of red urchins as source populations to provide larvae to adjacent areas was explored by the analysis of drifter's trajectories. Both reserves might be connected in a network where larvae produced in Whale Cove will provide recruits to Gregory Point and adjacent exploited areas, as well as populations in northern California. Gregory Point releases larvae that become recruits for Whale Cove only when spawning takes place in winter, otherwise larvae travel to central California. No clear trends were found in growth and mortality rates between reserves and non-reserves; differences were more related with food availability, competitors, and age specific mortality. We applied qualitative simulations to characterize and differentiate the community network inside reserves and exploited areas. Results suggest that communities from a particular site can be represented by a set of alternative models with consistent species interactions. Differences in predator-prey interactions as well as non-predatory relationships (interference competition, mutualism, amensalism) were found among sites. Each set of models represents a hypothesis of community organization that agreed with natural history information. Alternative models suggest that kelp forest communities are dynamic and can shift from one network configuration to another providing a buffer against a variable environment. / Graduation date: 2002

This thesis illustrates a process by which small organizations in the National Park Service can implement minor changes in current management and contracting practices to achieve measurable improvements in economy and efficiency by applying the principles and procedures outlined for competitive sourcing studies in Office of Management and Budget Circular A-76 (May 2003).

Thesis (M.S.)--Duke University, 2001. / Typescript. Includes bibliographical references (leaves 157-160). Also issued online.

Thesis (Ph. D.)--University of Oregon, 2003. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 453-468). Also available for download via the World Wide Web; free to University of Oregon users.