HR: 0800h
AN: B41B-0100    [Abstracts]
TI: Charcoal Morphology, a Useful Indicator of Fire Signature in Prosser Lake, British Columbia, Canada.
AU: * Enache, M D
EM: enachem@biology.queensu.ca
AF: Queen's University, Dept. Biology, 116 Barrie St., Kingston, ON K7L 3N6 Canada
AU: Cumming, B F
EM: cummingb@biology.queensu.ca
AF: Queen's University, Dept. Biology, 116 Barrie St., Kingston, ON K7L 3N6 Canada
AB: Observations of charcoal particle size and morphology were used along with quantitative analysis to extract indications on fire events over the last century from Prosser Lake (49\deg45.05 N, 120\deg37.30 W), a mesotrophic and slightly meromictic lake from British Columbia, Canada. Charcoal particles $>$150$\mu$m were visually identified at a 0.5-3 years resolution in a laminated sedimentary sequence. According to their shape and structural features, charcoal particles were classified in seven morphologically distinct types and their abundances were assessed using Image Analysis techniques. Distributions of charcoal types were assessed as a proxy to fire events recorded between 1919-2000 and subsequent mechanisms of transportation-sedimentation to lake sediments. Frequent fires taking place before 1944, produced high amounts of charred particles, but strong fires that took place in 1939, 1940, 1958 and 1960 were poorly recorded by most of the charcoal types, whereas post-1944 periods of high precipitation levels without fire events increased their abundance. However, fragile-type fragments displaying high porosity walls showed a strong and significant correlation (R$^{2}$ = 0.7; p = 0.02) with historically recorded forest fire in the proximity of Prosser Lake. Those fragments, according to their shape and structure might originate from high fragmentation of wood burning at high temperatures or by burning of small branches and leaves. Being very fragile, particles of this type would be destroyed by eventual secondary transportation processes and would not occur in levels not related to fire events. The remaining types of charcoal from Prosser Lake sediments displayed distributions biased by secondary transportation-sedimentation processes. We propose that charcoal morphology can be a useful indicator of fire occurrence, proximity of source-area and transportation-sedimentation mechanisms.
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting