HR: 0830h
AN: B21D-0741    [PDF]
TI: The Biogeochemistry of Silica in Grassland Ecosystems of the North American Great Plains
AU: * Kelly, E F
EM: pedoiso@lamar.colostate.edu
AF: Dept of Soil and Crop Sciences, Colorado State University, Fort Collins, CO 80523 United States
AU: Blecker, S W
AF: Dept of Soil and Crop Sciences, Colorado State University, Fort Collins, CO 80523 United States
AU: Chadwick, O A
EM: oac@geog.ucsb.edu
AF: Dept of Geography, University of California, Santa Barbara, CA 93106 United States
AU: Ziegler, K
EM: kziegler@geog.ucsb.edu
AF: Dept of Geography, University of California, Santa Barbara, CA 93106 United States
AU: Derry, L A
AF: Dept of Earth and Atmospheric Sciences Biogeochemistry and Environmental Biocomplexity, Cornell University, Ithaca, NY 14853 United States
AB: Over geologic timescales, biologically mediated weathering processes influence atmospheric CO2 content and global climate because the net effect of silicate weathering is the transfer of atmospheric CO2 to HCO-3 These weathering processes further influence atmospheric CO2 due to a net transfer of dissolved silica to the oceans which promotes diatom production and sedimentation there by adding carbon to the oceanic reservoir. There is a substantial body of evidence that suggests that plants may transform silica into more stable or labile forms thus acting as potential sinks or sources of silica. We are currently conducting research that investigates the changes in the biogeochemistry of silica along bioclimatic gradients and soil chronosequences in temperate grassland ecosystems. The goal of our research was to use a systematic approach to identify the possible effects of plant type and production on the losses, gains and compartmentalization of silica during soil development. To further quantify biological cycling of silica we present the initial results of field studies in which we utilized state factor analyses, constituent mass balance analyses, and mineralogical and geochemical characterization of soil and biogenic silica to quantify the role of plants in regulating the biogeochemistry of silica in terrestrial ecosystems. Our results suggest that grassland ecosystems have considerable variation in biogenic silica production and storage as a function of landscape age and bioclimatic conditions. In general Holocene aged soils of temperate grassland ecosystems have a net accumulation of silica while soils of Pleistocene age have experienced a net loss of Silica. However, all grassland systems accumulate biogenic silica. Shortgrass steppe ecosystems have greatest accumulations of biogenic silica in soil and the lowest storage in biomass, whereas, tall grass systems have greatest biomass silica and lowest Biogenic Si accumlation in soil and appear to show a "net transfer"of Silica to clay fraction of soils. Estimates of soil weathering rates need to include the influence of biogenic Si in "dampening" primary silicate weathering. Our studies demonstrate that biogenic Si derived from terrestrial systems may be important to consider when evaluating paleorecord of CO2 and climate change.
DE: 0330 Geochemical cycles
DE: 0400 Biogeosciences
DE: 1615 Biogeochemical processes (4805)
DE: 1625 Geomorphology and weathering (1824, 1886)
SC: Biogeosciences [B]
MN: 2003 Fall Meeting