Master of Science

thesisIn the field of ecology, regime shifts are often abrupt and catastrophic occurrences with far reaching effects on global and local ecosystems which result in distinct changes in the composition and function of an ecosystem. The boreal forest provides a long term stable ecosystem over the past 6000 years, with little anthropogenic influence, creating an ideal environment to study regime shifts with respect to regional and global climate changes. In the context of modern climate change, fire in the boreal forests appears to be expanding, however, little is understood concerning the impact of previous Holocene climate changes on fire regimes in the boreal forests. This study utilizes 14 long-term charcoal records from the boreal forests of Alaska to identify spatiotemporal patterns in regime shifts and identify possible climatic drivers and consequences of these shifts on the overall ecosystem. Regime shift patterns are identified by testing for structural change in linear regression models. Comparison of identified break points to existing paleoclimate and pollen records is then made to infer possible drivers of changes. Clusters of break points occur over the time interval associated with the expansion of the boreal forests, mid-Holocene climate changes, as well as smaller changes associated with the late-Holocene climate. Regional changes are seen to occur with shifts in vegetation and climate, while climate shifts tend to be more local and individual in nature