Theme: East-West Interdisciplinary Boreal Forest Fire Experiment, Part 3 Moderator: A. Granström and G. Ivanova 8.8.1995 16:30 Room: U16
A 4500-Year Record of Fire and Vegetation Change in Central Siberia Based on Calibrated Sediment Charcoal Accumulation
Clark, James S., Hussey, Tristram
Sediment charcoal provides evidence of the long-term importance of fire. Unfortunately, there have been no comparisons of particle accumulation rates in sediments with fluxes to the ground that occur during burns. We determined the spatial pattern of charcoal accumulation at ground level in 340 cm2 traps during an experimetal burn in a Pinus sylvestris stand on Bor Forest Island, central Siberia, and compared it to charcoal accumulation in Bor Lake sediments of the last 4500 yr. The 50 ha island burned intensely, with convection column heights exceeding 5000 m. Twenty-four traps arrayed in transects extending upwind from the burn edge to a distance of 70 m were used to estimate fluxes that declined from >1 mm2cm2 at the burn edge to 5 mm) were restricted to the burn edge, but particles >1 mm occured in all traps. The intensity of the burn and column height led to windspread dispersion of small (aerosol) particles. Sediment pollen in Bor Lake shows an abupt shift from Betula to Pinus at 3200 yr BP. Charcoal particles accumulated at rates well below those obtained during the burn except for large “peaks” at 4300 yr BP and 500 yr BP. These samples contained order-of-magnitude higher values than observed during our experimental burn. Based on measured fluxes sediment data suggest fires occured in these years and that more detailed analysis of the core will permit a calibrated estimate of fire past fire frequency and a determination of whether fire mediated the transition from Betula to Pinus at 3200 yr BP.
Key words: Pinus sylvestris, fire history, lake sediment charcoal, aerosols, charcoal accumulation, pollen analysis.
Correspondence: James S. Clark and Tristram Hussey, Duke University, Department of Botany, USA-Durham, NC 27706