Garry oak savannah stand history and change in coastal southern British Columbia

Abstract

In this thesis I investigate the history of Garry oak (' Quercus garryana') savannah patches in coastal British Columbia and the changes to these ecosystems over recent centuries. Remnant Garry oak patches have been altered by agriculture, development, increased herbivory, exotic plants, and fire suppression. Identifying the historical stand structure and ecosystem processes is therefore critical for effective site management and restoration. In this study, tree-ring analysis was used to reconstruct the stand and disturbance history at eight Garry oak communities within and adjacent to the Gulf Islands National Park Reserve. Varying levels of disturbance and tree establishment were found to have occurred at the time of European settlement. After the initial colonization by Garry oak, Douglas-fir ('Pseudotsuga menziesii') recruitment increased and has been ongoing. Results from the smaller islands suggest that local environmental conditions, weather events, and competitive interactions are important controls of ecosystem dynamics on these sites.