ABSTRACT: A Holocene-scale analysis of forest fire regimes near St. Lawrence Islands National Park, Ontario, using charcoal as a paleoindicator.

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Abstract

Parks Canada needs to assess past fire regimes of all national parks in order to implement effective fire and vegetation management techniques that maintain ecological integrity and biodiversity. This study looks to reconstruct the local fire regime around St.-Lawrence Islands National Park (SLINP), located in Southeastern Ontario. The region is mesic and characterized by mixed deciduous and coniferous forests that have not experienced natural fire for many decades. A species of particular interest is the rare fire-adapted species Pitch Pine (Pinus rigida), whose populations are limited to high bedrock outcrops and whose cones are serotinous. Since historic records of forest fire have only been kept for approximately the past 100 years and tree ring records show little evidence of fire, macroscopic charcoal contained within the sediment records of small lakes can provide information about local forest fires over the course of the Holocene. To begin this paleoecological assessment, sediment cores were taken from a small study lake, Little Black Lake (44º 32'45.20" N, 76º 03'12.06 W), located close to SLINP. Forest fire intervals were determined by counting macroscopic charcoal particles (>125 µm) at 0.5 cm intervals from a 0.5 m Glew core of surficial sediment, and a ~5 m piston core that encompasses the lake’s entire sedimentary record. A complete chronology for the Little Black Lake core was pieced together using 15 organic macrofossils that were AMS radiocarbon dated. The radiocarbon chronology was supplemented with 210Pb dates from the top 20 cm of the Glew core to accurately date the most recent sediment. From the charcoal counts and chronology, background levels of charcoal were determined and removed using a smoothing function, and local fire events were statistically identified from residual charcoal accumulation rates (CHAR). Large fire events were not identified in the charcoal record at this site for several hundred years before present. Using the fire interval information, we will make recommendations for appropriate land management practices for SLINP including: timely manual fuel reduction and planned ignition prescribed fires. In addition, the Little Black Lake charcoal records represent another contribution to a growing global charcoal database being used to investigate biomass burning and climate change.

Bibliography of Canadian Geomorphology