HR: 0800h
AN: PP11A-1425    [Abstracts]
TI: Identifying the Oxygen Isotope Signature of Precipitation in Grass Cellulose and Phytoliths: Refining the Paleoclimate Model
AU: * Webb, E A
EM: ewebb5@uwo.ca
AF: The University of Western Ontario, Department of Earth Sciences, Biology and Geology Building, London, ON N6A 5B7 Canada
AU: Longstaffe, F J
EM: flongsta@uwo.ca
AF: The University of Western Ontario, Department of Earth Sciences, Biology and Geology Building, London, ON N6A 5B7 Canada
AB: The basis of using the oxygen-isotope composition of cellulose as a climate proxy is a reliable correlation between temperature and the oxygen-isotope composition of the precipitation feeding the plant. However, the isotopic composition of precipitation can be modified prior to its incorporation into cellulose via mixing and evaporation in the soil, leaf water oxygen-18 enrichment during transpiration and oxygen-isotope exchange between cellulose precursors and stem and/or leaf waters. Biogenic silica bodies (phytoliths) formed in the cells of terrestrial plants can also provide quantitative paleoclimate information as their oxygen-isotope compositions are dictated by growth temperature and the isotopic compositions of plant waters. These parameters, in turn, are dependent on the oxygen-isotope compositions of precipitation feeding the plants and climate conditions that influence transpiration rates. However, for both the cellulose and phytolith oxygen-isotope system, paleoclimate interpretations are limited by our ability to estimate the isotopic compositions of ancient plant water, which can fluctuate on a seasonal and daily basis and even differ between tissues of the same plant. We have compared the oxygen-isotope compositions of cellulose and silica phytoliths extracted from the leaves and stems of Calamovilfa longifolia, a C4 grass, grown under varying climatic conditions across the North American prairies, in order to independently deduce the oxygen-isotope compositions of leaf and soil water over the growing season. Their compositions can be ultimately linked to temperature, relative humidity and the oxygen-isotope compositions of precipitation.
DE: 0419 Biomineralization
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1818 Evapotranspiration
DE: 4853 Photosynthesis
DE: 4914 Continental climate records
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005