Ecosystems responses to seasonal variation and different land use in Amazon Basin using the isotope approach
Francoise
Yoko
Ishida, Esalq (CENA/USP), fyishida@cena.usp.br
(Presenting)
Jean
Ometto, CENA/USP, jpometto@cena.usp.br
Jim
Ehleringer, University of Utah, ehleringer@biology.utah.edu
Tomas
Domingues, University of Utah, domingues@biology.utah.edu
Luiz
Antonio
Martinelli, CENA/USP, martinelli@cena.usp.br
Plínio
Barbosa de
Camargo, CENA/USP, pcamargo@cena.usp.br
Joe
Berry, University of Stanford, joeberry@stanford.edu
Edmar
Mazzi, CENA/USP, eamazzi@cena.usp.br
Haroldo
Jackson
Silva, Federal Univesity of Para, haroldo@lbaeco.com.br
This study was conducted in four different sites in Santarém region (PA)that characterize two distinct physiological group of plants (C4 and C3) and different land use: pasture; primary forest, primary forest with logging, and primary forest with simulation of El Niño/La Niña events, respectively. Carbon and oxygen isotope ratio (13C/12C and 18O/16O) of CO2 were measured in the canopy vertical profile, soil respiration (with and without litter), dead wood decomposition and leaf organic composition were also collected monthly during the year of 2003. Keeling plot technique and Farquhar’s leaf model were used to distinguish the physiological drives to changes in the isotopic composition of the several components in the system as well as the response of this components associate to the land cover. The carbon isotopic ratio of the leaf organic matter was similar at lower canopy and understory in all forest sites, but upper canopy has shown heavier signal associated to the water exclusion treatment at the Seca, which reflects on the ci/ca ratio of theses leaves. The seasonal variation of the respired CO2 is higher than the forests intrasite comparison, and at the pasture (C4 grass) the variation can be associated to a neighbor forest. Litter input is an important component on the isotopic signal of the soil efflux CO2.