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Science 28 November 2003:
Vol. 302. no. 5650, pp. 1554 - 1557
DOI: 10.1126/science.1091165
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Reports

Carbon in Amazon Forests: Unexpected Seasonal Fluxes and Disturbance-Induced Losses

Scott R. Saleska,1* Scott D. Miller,2 Daniel M. Matross,1 Michael L. Goulden,2 Steven C. Wofsy,1 Humberto R. da Rocha,3 Plinio B. de Camargo,4 Patrick Crill,5{dagger} Bruce C. Daube,1 Helber C. de Freitas,3 Lucy Hutyra,1 Michael Keller,5,6 Volker Kirchhoff,7 Mary Menton,2 J. William Munger,1 Elizabeth Hammond Pyle,1 Amy H. Rice,1 Hudson Silva5

The net ecosystem exchange of carbon dioxide was measured by eddy covariance methods for 3 years in two old-growth forest sites near Santarém, Brazil. Carbon was lost in the wet season and gained in the dry season, which was opposite to the seasonal cycles of both tree growth and model predictions. The 3-year average carbon loss was 1.3 (confidence interval: 0.0 to 2.0) megagrams of carbon per hectare per year. Biometric observations confirmed the net loss but imply that it is a transient effect of recent disturbance superimposed on long-term balance. Given that episodic disturbances are characteristic of old-growth forests, it is likely that carbon sequestration is lower than has been inferred from recent eddy covariance studies at undisturbed sites.

1 Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138, USA.
2 University of California, Department of Earth System Science, Irvine, CA 92697, USA.
3 Department of Atmospheric Sciences, University of Sao Paulo, Sao Paulo 05508–900, Brazil.
4 Centro de Energia Nuclear na Agricultura, University of Sao Paulo, Piracicaba 13416–000, Brazil.
5 Complex Systems Research Center, University of New Hampshire, Durham, NH 03824, USA.
6 U.S. Department of Agriculture Forest Service, International Institute of Tropical Forestry, San Juan, PR 00926, USA.
7 Instituto Nacional De Pesquisas Espaciais (INPE), Sao Paulo 12227–010, Brazil.



{dagger} Present address: Department of Geologyand Geochemistry, Stockholm University, Stockholm 10691, Sweden.

* To whom correspondence should be addressed. E-mail: saleska{at}fas.harvard.edu

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