HR: 16:50h
AN: B24A-04    [Abstracts]
TI: Flood Pulse Influence on Export of Terrestrial Organic Matter
AU: * Dalzell, B J
EM: dalzell@purdue.edu
AF: Purdue University Dept. of Earth and Atmospheric Sciences, 550 Stadium Mall Drive, West Lafayette, IN 47907-1397 United States
AU: Harbor, J M
EM: jharbor@purdue.edu
AF: Purdue University Dept. of Earth and Atmospheric Sciences, 550 Stadium Mall Drive, West Lafayette, IN 47907-1397 United States
AU: Filley, T R
EM: filley@purdue.edu
AF: Purdue University Dept. of Earth and Atmospheric Sciences, 550 Stadium Mall Drive, West Lafayette, IN 47907-1397 United States
AB: While much attention has been placed on characterizing Terrestrial Organic Matter (TOM) export from large rivers, recent research has shown that in-stream processing of TOM in smaller streams and rivers over shorter time scales can be an important upland component of regional carbon budgets not detected at the outlets of large rivers. With predictions of climate change accompanied by more intense rainfall patterns in some areas, it is important to understand the linkage between flood events and watershed export of TOM. To this end, we have collected water samples from Big Pine Creek watershed, an 850km2 watershed located in west central Indiana. Organic carbon in dissolved, colloidal, and particulate size fractions has been described with molecular and stable carbon isotope techniques to track source, quantity, and compositional changes of TOM over changing flow conditions. Results from these samples show that flood conditions export dramatically more TOM; not only from increases in discharge, but also from increases in concentration of terrestrial organic carbon to all size fractions. While molecular biomarkers show increases in terrestrial organic matter, bulk stable carbon isotope values show that the sources of TOM do not remain constant. Rather, relative contributions from C4 plants (corn in this study area) increase during flood conditions by up to 40 percent. Finally, increases in rainfall intensity are likely to disproportionately increase organic carbon export from terrestrial systems, especially from smaller watersheds where short duration and high intensity flow events dominate annual discharge.
DE: 1694 Instruments and techniques
DE: 1860 Runoff and streamflow
DE: 1030 Geochemical cycles (0330)
DE: 1615 Biogeochemical processes (4805)
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting