Doctor of Philosophy

dissertationDisturbances play an integral role in regeneration and succession of many forested ecosystems in the Intermountain West region of the western United States. However, changes in climate have been shown to alter the occurrence, duration, and frequency of disturbances. The research presented here uses a paleoecological approach using multiple proxies from sediment cores from three different sites from the Intermountain West in order to assess the linkages among disturbances, climate, and vegetation composition. From the first site in the central Rocky Mountains, a paleoenvironmental data documents the sensitivity of past quaking aspen occurrence to increased temperatures, while frequent wildfire activity led to the persistence of a quaking aspen. From the second site located in south central Utah, a paleoenvironmental data documents how changes in the position of the El Nio Southern Oscillation dipole transition zone affects moisture availability across the state of Utah, which ultimately influences vegetation composition and wildfire frequency. Lastly, from the third site located on the north slope of the Uinta Mountains in northeastern Utah, paleoenvironmental data assesses the long-term primary control on wildfire activity from the region. The results from this dissertation suggest that disturbance regimes have been in a state of constant change throughout the Holocene as a result of climate variability and in combination these led to changes in vegetation composition. The information contained in this dissertation will be important for natural resource planning and management because it provides context regarding the natural range of disturbance and vegetation variability for three distinctly different forested settings located in the Intermountain West. Forest managers can use paleoenvironmental records as analogs to help place context of how forested ecosystems will respond to climatic changes. By providing forest managers with long-term information about forest composition and disturbance regimes at multiple sites, this dissertation can be used to enhance resource policy making, planning and management