RELATIONSHIPS BETWEEN CHARCOAL PARTICLES IN AIR AND SEDIMENTS IN WEST-CENTRAL SIBERIA

Production and size of charred particles determine transport and depos ition in lakes. Lack of such data is a principal obstacle to interpret ation of past fire from charcoal profiles. Our two-part analysis inclu des a calibration study, to assess charred-particle production and tra nsport during fire, and a study of charred particles in sediment. The calibration step establishes the magnitude and size distribution of pa rticle accumulation from traps during a controlled burn of Pinus sylve stris forest in west-central Siberia. This high-intensity fire consume d 3.71 kg m(-2) of fuels and produced 0.0729 kg m(-2) of airborne part icles. for an emission factor of 0.02 kg kg(-1). Particle flux to the ground was 1 to 3 mm(2)cm(-2) yr(-1) inside the burn; it declined shar ply within 5 m of the burn edge, and it was variable but without trend to a distance of 60 m. Particle-size distributions were conservative, with a slope of -2 on plots of log frequency versus log diameter, and sediment data suggest this slope may steepen as sources become more r emote and as large particles are progressively lost due to settling. D eposition from the plume is similar to accumulation rates in sediment, with apparent upward bias in sediments as expected from broad geograp hic patterns in charcoal distributions. During the mid-Holocene charre d-particle accumulation in lake sediments (10(1) mm(2)cm(-2) yr(-1) wa s greater than observed in particle traps within the experimental burn . Particles were larger, suggesting nearby sources. Rates decreased by 3800 BP to values lower than average rates in particle traps, and sam ples were depleted in large particles. Low rates and infrequent large particles indicate sources were distant. Accumulation rates and partic le sizes were again high from 3400 to 2800 and from 1400 to 700 BP. Cl ose correspondence between the accumulation rates during the experimen tal burn and in sediments and particle evidence for source area, as we ll as their agreement with particle-trap data from the experimental bu rn, suggest that, in this region, fire may have been more frequent and closer in the mid-Holocene than today. We cannot rule out the possibi lity, however, that changes in charred particle accumulation also refl ect changes in supply of sediment to the core sire.