HR: 17:45h
AN: B12F-08    [PDF]
TI: Wetland ecosystem hydroperiods: long-term variability reconstruction using isotopic signatures from tree rings
AU: * Anderson, W T
EM: andersow@fiu.edu
AF: Earth Science Department and the Southeast Environmental Research Center, Florida International University, Miami, FL 33199 United States
AU: Sternberg, L O
EM:
AF: Biology Department, University of Miami, Coral Gables, FL 33124 United States
AU: Pinzon, M C
EM:
AF: Biology Department and the Southeast Environmental Research Center, Florida International University, Miami, FL 33199
AB: In order to restore altered wetlands to their natural state and/or water levels an independent measure of past water depths will be necessary where no historical documents/data exist. Presently the United States Geological Survey (USGS), SFWMD, and the National Parks Service (NPS) maintain an extensive network of gauge stations through out South Florida, but locally, theses stations typically have data only going back for the last 20 to 30 years (and more typically only 10 years). We propose to investigate the stable isotopic signatures within ring forming tree species in several wetland settings in South Florida including Everglades National Park (ENP) and within Big Cypress National Preserve, in order to reconstruct past changes in water levels/precipitation. Our preliminary work has demonstrated that the $\delta^{13}$C values from the annual rings of Pond Cypress ({\it Taxodium ascendens}) trees in the C-111 basin (Tayler Slough, south-east Everglades) has a positive correlation with rain fall amount (Fig. 2). Therefore as the amount of precipitation increases, accompanied by a relative increase in water level adjacent and around the plant, a physical drought may occur, causing a change in stomatal conductance, resulting in an increase in intercelluar $^{13}$C/$^{12}$C ratios. As water levels increase the plant experiences a stress which affects the $\delta^{13}$C values of its fixed sugars, and this signal is in turn transferred to the trunk/annual rings. Note, this relationship is the opposite of terrestrial trees, where decreases in relative precipitation are normally correlated with increasing $\delta^{13}$C of plant material, water-stress or -limitation.
DE: 1615 Biogeochemical processes (4805)
DE: 1815 Erosion and sedimentation
DE: 1854 Precipitation (3354)
DE: 1890 Wetlands
DE: 4870 Stable isotopes
SC: Biogeosciences [B]
MN: 2003 Fall Meeting