Ecophysiological Responses to Seasonal Variation at the Ecosystem Scale in the Amazon Basin: An Isotopic Approach
Ishida, University of São Paulo, firstname.lastname@example.org
Camargo, University of São Paulo, email@example.com
P. H. B.
Ometto, University of São Paulo, firstname.lastname@example.org
Martinelli, University of São Paulo, email@example.com
Ehleringer, Utah University, firstname.lastname@example.org
This study was conducted in 2003 and 2004 at the km 67 old growth forest in the Tapajós National Forest (2,85°S; 54,05°W). The objective was to measure the carbon isotope ratio (δ13C/12C) of respired CO2 from the entire ecosystem and leaf isotopic composition along profiles through the canopy. We used the Keeling plot technique and Farquhar’s leaf model to examine the physiological drivers of the isotopic composition of several components in the system as well as the seasonal response for these components. Variations of respired δ13C CO2 by the ecosystem was related with precipitation variation, but not significantly different either seasonally or temporally. The δ13C of leaf organic matter showed a clear stratification along the vertical profile with significant seasonal variation. A positive correlation was found between photosynthetically active radiation (PAR) and δ13C of leaves from the top of the canopy where high PAR favored photosynthetic activity. The ci/ca ratio values did not show significant differences between heights and seasons. Our study indicated that the isotopic composition of respired CO2 and leaf organic matter was sensitive to microclimatic variations.