Recent history of fire and vegetation from laminated sediment of Greenleaf Lake, Algonquin Park, Ontario

Abstract

Laminated sediment (presumed varved) from Greenleaf Lake was examined for evidence of forest fires. A 500-year section dating approximately 770–1270 A.D. was analysed for influx of pollen, charcoal, aluminum, and vanadium using decadal samples. Intervals showing concurrent peaks in charcoal, aluminum, and vanadium influx, varve thickness, and charcoal:pollen ratio were interpreted as representing major fires within the drainage basin of Greenleaf Lake. By these criteria, six fires occurred within 500 years, or one fire approximately every 80 years. The pollen diagram indicates a stable forest composition for the past 1200 years. This, coupled with abundant charcoal fragments in all sediment samples, suggests that fire has been a frequent, natural phenomenon affecting the landscape during this period. There is a significant positive correspondence between peak charcoal influxes and peak influxes of aluminum and vanadium, indicating that increased soil erosion is responsible for their deposition.