HR: 1340h
AN: B43A-0136    [Abstracts]
TI: Stable isotope analyses provide evidence of drought stress impacting plant function at the Seca Floresta
AU: * Ehleringer, J
EM: ehleringer@biology.utah.edu
AF: University of Utah, Department of Biology 257 South 1400 East, Salt Lake City, UT 84112 United States
AU: Ometto, J P
EM: jpometto@cena.usp.br
AF: University of Utah, Department of Biology 257 South 1400 East, Salt Lake City, UT 84112 United States
AU: Ometto, J P
EM: jpometto@cena.usp.br
AF: CENA-USP, Av. Centen rio 303 Cep 13416-000, Piracicaba, SP 13416-000 Brazil
AU: Yoko, F Y
EM: yoko@amazon.com.br
AF: CENA-USP, Av. Centen rio 303 Cep 13416-000, Piracicaba, SP 13416-000 Brazil
AU: Martinelli, L
EM: zebu@cena.usp.br
AF: CENA-USP, Av. Centen rio 303 Cep 13416-000, Piracicaba, SP 13416-000 Brazil
AU: Berry, J
EM: joeberry@globalecology.stanford.edu
AF: Carnegie Institution of Washington, 290 Panama Street, Stanford, CA 94305 United States
AU: Domingues, T
EM: domingues@biology.utah.edu
AF: University of Utah, Department of Biology 257 South 1400 East, Salt Lake City, UT 84112 United States
AU: Silva, H J
EM: haroldo@lbaeco.com.br
AF: CENA-USP, Av. Centen rio 303 Cep 13416-000, Piracicaba, SP 13416-000 Brazil
AU: Mazzi, E
EM: eamazzi@cena.usp.brN/A
AF: CENA-USP, Av. Centen rio 303 Cep 13416-000, Piracicaba, SP 13416-000 Brazil
AU: Nepstad, D
EM: dnepstad@whrc.org
AF: Woods Hole Research Center, P.O. Box 296, Woods Hole, MA 02543 United States
AB: Carbon and oxygen isotope ratios have been measured to examine the impacts of a long-term drought treatment at the Seca Floresta in Santarem, Para, Brazil. We measured the carbon isotope ratio values of leaf organic matter and on the carbon dioxide effluxing from soil and litter components in droughted and non-droughted plots. We measured the oxygen isotope ratios of leaf water throughout the day. In addition, we quantified soil carbon dioxide efflux rates in order to partition this flux into its soil and litter components. The observations suggest that a reduction in soil moisture availability resulted in increased carbon isotope ratio values of the leaf organic matter, increased carbon isotope ratio values of the soil carbon dioxide efflux, and increased oxygen isotope ratios of leaf water. Further examination of the data suggest that the carbon isotope ratio values of the soil carbon dioxide efflux can be partitioned into two components: a litter component that changed modestly its carbon isotope ratio value seasonally and a soil component that showed larger interseasonal fluctuations in carbon isotope ratio values. The seasonal fluctuations in both the leaf organic matter and the carbon dioxide efflux of the soil component were consistent with a photosynthetic activity reflecting significant reductions in stomatal conductance.
DE: 0315 Biosphere/atmosphere interactions
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting