Millennial fire history reconstruction in the boreal forest of south-central Canada using lake-sediment charcoal, tree-ring and archival records By Justin M. Waito A thesis submitted to the Faculty of Graduate Studies of the University of Winnipeg in partial fulfillment of the Master of Science degree. Department of Biology Master of Science in Biology, Technology and Public Policy Program The University of Winnipeg Winnipeg, Manitoba, Canada October 2016 © 2016 Justin Waito Abstract The Canadian boreal forest has been developing since the end of the last glaciation approximately 10,000 years ago. During this time, fire has modified the development of the forest by altering species distribution, stand structure and forest regeneration. With future climate changes, the fire frequency and annual area burned (AAB) are expected to increase with increasing temperatures. It remains unclear what effect this increase in fire frequency will have on the forest. Current projections of future fire are often based on relatively short environmental records and longer records are needed to capture variability in fire occurrence over millennia. In this study, a multi-millennial fire history was reconstructed for eight lakes from the Lake of the Woods Ecoregion (LWE) within the boreal forest of central North America using a combination of archival, tree-ring and lake sediment charcoal records. The archival record provided fire dates and area burned information for the period 1920 to 2010. A tree-ring fire history reconstruction was developed around eight lakes for the period 1690-2010 from stand initiation dates and fire scars. The fire history reconstruction was extended through lake sediment charcoal records obtained from overlapping sediment cores collected from eight lakes. For each lake, the sediment fire history reconstruction was obtained from macroscopic charcoal particles with an area >150 micrometers. Calculation of the Charcoal Accumulation Rate (CHAR) and subsequent peak analysis of the CHAR record allowed for the examination of changes in fire regime dating back to 2500 BP (500 BCE). ii The archival and tree-ring records revealed recent large fires (>200 ha) in 1948, 1980 and 1989. An additional 17 fires were identified by the fire-scar record. Fire events in 1805, 1840, 1863, and the 1890’s were identified in numerous locations around multiple lakes suggesting that they were of large extents. In accordance with the tree-ring record, the CHAR peak record generally identified the major fires, with identification becoming less accurate for smaller fires and those in close succession. The CHAR record also tended to lag behind fires identified from tree-ring records by several decades. Within the LWE, the long-term charcoal record revealed that CHAR was higher for each lake in the earlier portion of the record followed by a progressive decrease towards the more recent record. Multi-millennial fluctuations in CHAR suggested that modern temperature increases could lead to higher fire frequency than that observed over the last two millennia. iii Acknowledgments This project has involved the efforts of many people and would not have been possible without them. A special acknowledgment goes out to Jacques Tardif for his support through all aspects of the project and guidance through the preparation of the manuscript. Special recognition also goes out to France Conciatori for countless hours of guidance and assistance with the preparation and analysis of samples in the laboratory. I would also like to thank Martin Girardin, Danny Blair and Adam Ali for participating as committee members and for providing valuable input throughout the project. For this project, there was a considerable amount of field and laboratory work involved and I would like to thank Adam Ali, Benoit Brandelet, Laurent Bremond, Benoit Brossier, Cody Clovenchok, France Conciatori, Karine Grotte, Johanna Hallmann, Kayla-Mae Hlushenko, Aurore Lucas, Renald Julien, Brian Moons, Nia Perron, Johanna Robson, Jacques Tardif, and Zabrina Yaremko for all of their assistance. I would like to thank the Schaeffer family at Cygnet Lake Camp in northwestern Ontario for providing us with lodging, logistical support and hospitality during our fieldwork in the area. My thanks also go out to the staff at Manitoba Conservation, Ontario Ministry of Natural Resources and Manitoba Hydro for providing support and assistance. I would also like to thank France Oris, Mycore Scientific and Beta Analytics for providing assistance with the isotope dating methods, Brad Russell for providing iv mapping support, Philip Higuera for assistance with MCAgeDepth software, and Olivier Blarquez for his assistance with the paleofire R package. Funding for this project was generously provided by Manitoba Hydro Forest Enhancement Program, Natural Sciences and Engineering Research Council of Canada (NSERC), the University of Winnipeg, GDRI Forêts Froides (CNRS, INEE), and the Canadian Forest Service research funds. To my family and friends, I thank you for your patience and support over the years. v Table of Contents Abstract ...................................................................................................................................... ii Acknowledgements .................................................................................................................... iv Table of Contents ....................................................................................................................... vi List of Figures ......................................................................................................................... viii List of Tables ............................................................................................................................. ix List of Appendices ...................................................................................................................... x 1.0 General Introduction ............................................................................................................. 1 1.1 Boreal forest dynamics ............................................................................................. 1 1.2 Disturbances in the North American boreal forest ................................................... 3 1.3 Methodological background ..................................................................................... 7 1.3.1 Archival records of fire in the boreal forest ............................................ 7 1.3.2 Dendroecological records ....................................................................... 8 1.3.3 Lake sediment records .......................................................................... 11 1.4 Boreal forest development during the Holocene .................................................... 18 1.4.1 Vegetation trends .................................................................................. 18 1.4.2 Fire during the Holocene ...................................................................... 20 1.4.3 Human influences ................................................................................. 23 1.5 Thesis rationale and objective ................................................................................. 25 2.0 Multi-proxy fire history fire history reconstruction in the boreal forest of South-Central Canada ......................................................................................................... 27 2.1 Introduction ............................................................................................................. 28 2.1.1 Fire in the boreal forest ......................................................................... 28 2.1.2 Fire history records ............................................................................... 29 2.1.2.1 Archival records ........................................................................ 29 2.1.2.2 Tree-ring records ....................................................................... 30 2.1.2.3 Lake sediment records .............................................................. 31 2.1.3 Post-glacial boreal forest development of central North America........ 32 2.1.4 The need for multi-proxy comparisons ................................................. 36 2.1.5 Objectives and Hypotheses ................................................................... 37 2.2 Materials and Methods ............................................................................................ 39 2.2.1 Study area.............................................................................................. 39 2.2.2 History of human activities ................................................................... 42 2.2.3 Lake sediment field and laboratory work ............................................. 44 2.2.3.1 Lake selection and sediment extraction .................................... 44 vi 2.2.3.2 Sediment dating (210Pb and 14C) and age-depth model ............. 48 2.2.3.3 Charcoal particle extraction, measurement and morphology ... 52 2.2.3.4 Merging sediment cores and general procedure for converting raw charcoal data to charcoal accumulation rate (CHAR) ..................................................................................... 57 2.2.3.5 Analysis of CHAR and identification of fires through peak analysis ...................................................................................... 61 2.2.4 Tree-ring records: field sampling and laboratory work ....................... 64