HR: 0800h
AN: B51D-0239    [Abstracts]
TI: Regional Reconstruction of Fire Regimes and Climate in Western Mongolia Over the Past 2000 Years
AU: * Umbanhowar, C E
EM: ceumb@stolaf.edu
AF: Saint Olaf College, 1520 St. Olaf Ave, Northfield, MN 55057 United States
AU: Johnson, E R
EM: johnsoer
AF: Saint Olaf College, 1520 St. Olaf Ave, Northfield, MN 55057 United States
AU: Tserenkhand, G
EM: tseren@chingis.com
AF: Institute of Botany Mongolian Academy of Sciences, 210351, Ulaanbaatar, 210351 Mongolia
AB: We conducted a multi-proxy (charcoal, LOI, magnetics, BSi), sediment-based study of 25 lakes in northwestern Mongolia to explore the hypothesis that fire intensity/frequency is positively correlated with precipitation-driven differences in primary productivity in semi-arid grasslands. Only 6 of 25 modern (0-5 cm) sediments samples contained charcoal, and these six samples were from sites that were surrounded by thick stands of Phragmites. This suggests only local burning and the virtual absence of fire in the modern upland landscape. Charcoal analysis of sediment cores from four sites reveals the presence of fire in the historic landscape and average charcoal influxes range from 0.007 to 0.121 mm² cm² yr^-1 over the last ~ 2000 years. Charcoal influxes were greatest from ~ 0-1200 cal yrs AD, dropping at three of the four sites by a factor of four or greater at ~ 1200-1400 AD. Magnetic concentrations (IRM) and BSi also change at ~ 1200-1400 AD, increasing at three sites and decreasing at the fourth, while LOI showed relatively little consistent change among sites. The drop in charcoal influx over the past ~ 600-800 years may indicate increasingly arid conditions, but may also reflect a grazing-driven reduction in fuels as observed in the southwestern U.S. over the last two centuries.
DE: 1815 Erosion
DE: 4815 Ecosystems, structure, dynamics, and modeling (0439)
SC: Biogeosciences [B]
MN: Fall Meeting 2005