Holocene fire-climate-vegetation dynamics in Central Canadian Shield boreal forests of Northwestern Ontario, Canada / by Dominic Lafontaine-Senici.

Co-primary investigator of the original project proposal and outline: Dr. Adam Ali.The boreal forest is the largest terrestrial ecosystem in North America, one of the least disturbed by humans, and most disturbed by fire. This combination makes it an ideal system to explore the environmental controls on fire frequency, the relative importance of climatic and non-climatic factors, and the importance of fire in governing ecosystem processes at a large scale. Multiple vegetation and forest fire history records were established by analyzing Holocene-aged lake sediment stratigraphies collected in the central boreal shield region of northwestern Ontario, Canada. The stratigraphies were dated using [superscript14]C AMS. In the first research chapter macroscopic sedimentary charcoal and plant macroremains were analysed in order to investigate local fire frequency and tree abundance. The results show contrasting fire regime dynamics between a xeric and mesic landscape and highlight the influence of local factors as important drivers of fire frequency at centennial to millennial scales. The second research chapter examines spatial and temporal variations in fire frequency to evaluate the influence of some local non-climatic factors on the regional fire regime. The results show that sites within landscapes fragmented by high open-water lakes and wetland cover tended to have lower fire frequencies, and that this trend was stronger in the past. Results clarify some regional fire regime controls and imply climate-vegetation interactions will significantly affect future boreal fire regime dynamics. The third research chapter examines regional fire-vegetation interactions. The results show that millennial-scale species community diversity may not be driven by fire frequency variations. This study contributes to our knowledge of the varying spatial controls forest fire regimes in the central boreal forest region