At regional scales climate patterns (e.g., interannual wet-dry cycles) result in high spatial fire synchrony among Southwest forests. However, in the "Sky Island" forests of southeastern Arizona spatial and temporal patterns of fire history and tree age structure at landscape levels (i.e., within mountain ranges) are relatively unknown and therefore the focus of this study. In the Santa Catalina Mountains we reconstructed the fire history on a 2,900-hectare study area with two distinct landscapes, Butterfly Peak (BP) and Rose Canyon (RC) using 2-hectare "points" (i.e., collection areas). The RC landscape was dominated by shallow south-facing aspects and BP was dominated by steep north-facing aspects. Within each landscape, point mean fire intervals (PMFIs) were not significantly different between aspect classes. However, pooled PMFIs were significantly shorter in RC compared to BP. These results show that the fire history at any given point (i.e., 2 hectares or less) was primarily controlled by the broad-scale topography of the encompassing landscape, rather than by the fine-scale topography at that point.Using similar methods we also reconstructed the fire history on Rincon Peak, which is a small isolated mountain range with very step topography. The fire history of the 310-hectare forest area was a mixture of frequent low severity surface fires (from AD 1648 to 1763) and infrequent mixed-severity fires (from AD 1763 to 1867). This mixed-fire regime was probably due to a combination of climatic variability, the small area and rugged topography of this mountain range, and complex fuel arrangements. The distinct fire histories from these two study areas provided natural age structure experiments that indicated tree age cohorts (i.e., higher than expected tree establishment pulses) occurred during periods of reduced fire frequencies. In some instances these periods were likely caused by climatic variability (e.g., a wet and/or cool early 1800s) creating synchronous age cohorts across the region. At other times, extended fire intervals were a function of local topography (e.g., 1763-1819 in the northern half of Rincon Peak). Overall, these studies demonstrated that landscape and climatic variations combine to produce complex spatial and temporal variations in fire history and tree age structures.

This work was a case study of historical ecological change in Tintic Valley, Juab County, Utah, an area historically impacted by mining and ranching activities common to much of the American West. The temporal framework for the study was approximately 120 years, the period of direct Euroamerican influence. In recognition of the ecological implications of cultural change, however, the impacts of prehistoric and protohistoric human activity on study area landscape patterns and processes were also explicitly addressed. The study included a narrative description of historic land uses and ecological change in Tintic Valley, and examined the changes in landscape patterns and processes so revealed within the context of the state and transition model of rangeland dynamics. The case of Tintic Valley thus served as a test of the heuristic utility of the theory of self-organization in ecological systems, within which the state and transition model is embedded. This theoretical framework in turn was used to gain insight into the present state of the Tintic landscape, how that state has changed over time, and the nature of those forces leading to transitions between system states in the historic period. The study employed archival research, personal interviews, repeat photography, field surveys, aerial photographs, and a geographic information system (GIS) to identify, describe, and quantify historic-era change in Tintic Valley landscape level patterns and processes. The analysis revealed dramatic change in both the landscape vegetation mosaic and the channel network of the study area over time. Evidence was found for direct anthropogenic influence in precipitating those changes, primarily through tree harvesting associated with mining and ranching activities and through the effects of historic roads and railroads on the Tintic Valley gully network. Results supported the working hypothesis of a change in system state in the Tintic Valley landscape in the historic period. Taken together, historical narrative and theoretical context permitted a degree of prediction with respect to potential future conditions for the study area under different management scenarios. Future research directions and implications of the research results for ecosystem management are also discussed.