Seasonal dynamics of soil, litter, and ecosystem respiratory carbon dioxide fluxes as indicated by stable isotope analyses
Jean
Pierre
Ometto, CENA/USP, Univesity of Utah, jpometto@cena.usp.br
(Presenting)
James
R
Ehleringer, Univesity of Utah, jim@biology.utah.edu
Luiz
Antonio
Martinelli, CENA/USP, martinelli@cena.usp.br
Joseph
Berry, Carnegie Institution, joeberry@stanford.edu
Françoise
Yoko
Ishida, ESALQ/USP, yoko@lbaeco.com.br
Tomas
Ferreira
Domingues, Univesity of Utah, domingues@biology.utah.edu
Haroldo
Jackson
Silva, UFPA/Santarem, haroldo@lbaeco.com.br
Edmar
Mazzi, UNIMEP, eamazzi@cena.usp.br
Carbon (d13C) and oxygen (d18O) isotope ratios were measured to examine the seasonal changes in respiratory CO2 effluxes at the two forest sites (km 67 and km 83) in Santarem. We measured both the d13C values of leaf organic matter and the d13C and d18O values of the CO2 effluxing from the ecosystem, large dead wood, soil, and litter components. In addition, we quantified soil CO2 efflux rates in order to partition this flux into its soil and litter components. The d13C values of soil/litter and total ecosystem respiratory CO2 differed, with the respiratory values of soil/litter being 13C heavier than that of the entire ecosystem. When comparing the two forest sites, the observations suggest a year-long spike associated with the selected removal of trees at the km 83 site. Thereafter, the d13C values of total ecosystem respiration were again similar between the two forests and exhibited changes between dry and wet seasons. The CO2 efflux from litter and soil without litter differed in their d13C values allowing a quantitative estimate of the seasonal contribution of these two components to total soil/litter CO2 efflux. Furthermore, the CO2 efflux from large woody debris and of litter/soil differed in their d18O values allowing a quantitative partitioning of the two components to the overall CO2 efflux from the surface layer.
Submetido por Jean Pierre Ometto em 18-MAR-2004
Tema Científico do LBA: CD (Armazenamento e Trocas de Carbono)