HR: 1340h
AN: PP43A-0616    [Abstracts]
TI: Annual growth bands in Hymenaea courbaril: implications for utilization in tropical paleoclimate reconstructions.
AU: * Westbrook, J A
EM: jaw94@cornell.edu
AF: Center for Isotope Geochemistry, Lawrence Berkeley National Lab, Berkeley, CA 94720 United States
AU: * Westbrook, J A
EM: jaw94@cornell.edu
AF: Dept. of Plant Biology, Cornell University, Ithaca, NY 14853 United States
AU: Guilderson, T
EM: tguilderson@llnl.gov
AF: Center for AMS, UC/LLNL L-397, Livermore, CA 94551 United States
AU: Colinvaux, P A
EM: pcolinva@mbl.edu
AF: Marine Biological Laboratories, 7 MBL Road, Woods Hole, MA 02543 United States
AU: D'Arrigo, R
EM: druidrd@ldeo.columbia.edu
AF: Lamont-Doherty Earth Obs., Rte. 9-W, Palisades, NY 10964 United States
AB: Instrumental records of environmental variables such as temperature and precipitation are necessary to understand climate patterns and variability. In general, such observations from the tropics do not exist prior to the late 19th century, and existing records contain large spatial and temporal gaps and are sparsely distributed. An important source of annual temperature and precipitation proxy-data comes from the regular annual growth rings of wood formed by trees. Tree growth rings occur in response to periodic seasonal changes in the environment. Although expansive and diverse in number and ecology, a vast majority of tropical trees do not produce distinct annual growth rings. Because of this, tropical dendrochronology and paleoclimate reconstructions have lagged behind their temperate and higher latitude cousins. Distinct secondary growth rings were investigated in a single individual of the tropical hardwood legume Hymenaea courbaril felled within the City of David, Republic of Panama. Rings that maintained circuitry were considered annual and were sampled for 14C. Radiocarbon values from the secondary growth rings from this specimen were compared with annual reference radiocarbon values from wood and air in North America, New Zealand and Germany. This comparison demonstrated that the secondary growth rings formed by H. courbaril were determined to be annual in nature in this one stem disk specimen. To confirm the consistency of the annual nature of the secondary growth rings in H. courbaril, nine (9) additional specimens were recovered from the small hamlet of San Carlos y Algarobbo in western Panama between the town of David and the cordillera approximately ~30km from the site of the first tree sample. Of the nine specimens, four were chosen for ring counts and isotope analyses. "Annual" rings were counted and samples corresponding to the equivalent time of the bomb-14C peak were sampled. In addition a small subset of years within one tree specimen were sub-annually sampled for d18O cellulose. Radiocarbon and 18Ocellulose are consistent with the secondary rings being annual. These results imply that H. courbaril may be suitable for extended paleoclimate reconstructions.
DE: 1040 Isotopic composition/chemistry
DE: 1620 Climate dynamics (3309)
DE: 0400 Biogeosciences
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting