HR: 0800h
AN: B41B-0101    [Abstracts]
TI: The Role of Fire History in Northern Latitude Organic Matter: Spatial and Temporal Patterns of C and Hg
AU: * Harden, J W
EM: jharden@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Rd ms962, Menlo Park, CA 94025 United States
AU: Turetsky, M R
EM: mrt@msu.edu
AF: U.S. Geological Survey, 345 Middlefield Rd ms962, Menlo Park, CA 94025 United States
AU: Friedli, H
EM: friedli@ucar.edu
AF: National Center for Atmospheric Research, Table Mesa Drive, Boulder, CO 80309 United States
AU: Crock, J
EM: jcrock@usgs.gov
AF: U.S. Geological Survey, Denver Federal Center, Denver, CO 80225 United States
AU: Radke, L
EM: radke@ucar.edu
AF: National Center for Atmospheric Research, Table Mesa Drive, Boulder, CO 80309 United States
AU: Robinson, J
EM: jrobins@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Rd ms962, Menlo Park, CA 94025 United States
AB: Fire history has dictated to a large extent the spatial occurrence and chemical composition of organic matter stored in postglacial peat and upland soils of northern latitudes. These regions are characterized by a unique co-occurrence of discontinuous permafrost and pervasive wetlands with large fires and large stocks of ground fuels. The distribution of combustible elements on the landscape is telltale of fire histories that have varied widely across these landscapes: Low C and Hg stocks in well drained uplands is consistent with modern radiocarbon signals in organic layers above mineral soil. Larger C and Hg stocks in poorly drained uplands are consistent with less frequent and/or less severe fire histories. Also, radiocarbon profiles demonstrate organic matter accumulation over the past 100 - 200 years. C and Hg in very poorly drained bogs and fens are highest of all systems, and high concentrations of Hg within 20 cm of the modern water table suggest that fires have occurred either infrequently or with low severity as compared to upland sites. Barring significant differences in losses to decomposition and leaching, fire emissions of C and Hg also must be dictated by landscape patterns of soil drainage and therefore by climate-drought-water table interactions. We project estimates of Hg emissions from Hg inventories of lowland and upland soils combined with landscape assessments of lowland and upland distributions and find that Hg likely varied by at least 5-fold as a result of temporal variations in drought, burn area, and water table depression. With the increasing threat of Hg toxicity in northern latitudes, questions of paleofire, paleoclimate, and past landscape distributions of fire and organic matter become increasingly important to our need for defining future Hg emissions, deposition, and redistribution on the landscape.
UR: http://carbon.wr.usgs.gov
DE: 4805 Biogeochemical cycles (1615)
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0315 Biosphere/atmosphere interactions
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting