A Look at Amazon Basin Seasonal Dynamics with the Biophysical ...

ISOPRENOID FLUXES AND PHOTOSYNTHETIZED CARBON MESURED OVER THETROPICAL RAINFOREST NEAR MANAUS DURING DRY SEASON 2001P. Stefani 1 , A.C. de Araujo 2 , A. D. Nobre 2 , P. Ciccioli 3 , E. Brancaleoni 3 , M. Frattoni 3 , U.Kuhn 4 , J. Kesselmeier 4 , C. Corradi 1 , R. Valentini 11-Dipartimento di Scienze dell’Ambiente Forestale e delle sue Risorse, Università della Tuscia, Via C. de Lellis,CAP 01100 Viterbo ITALY (e-mail: pstefani@unitus.it)2-Instituto Nacional de Pesquisas da Amazonia, C.P. 478 Manaus, Amazonas, Brasil 69011-9703-Istituto sull’Inquinamento Atmosferico del CNR area delle ricerche di Roma Via Salaria km 29.300 CP10CAP 00016 Monterotondo Scalo Italy4-Max Planck Institute for Chemistry, Biogeochemistry Dept.,P.O. Box 3060, D55020 Mainz GERMANYAlthough small when compared to the GPP, the amount of carbon released in the atmosphere by terrestrial by terrestrialvegetation exceeds by an order of magnitude the one produced by man-made activities. Although the largest portion ofthis emission is concentrated in tropical regions, only recently systematic investigations have been undertaken in thisportion of the earth surface. Among them, particularly interesting are the data that have been collected in Brazil duringthe previous LBA- EUSTACH experiments, where an integrated approach was followed to quantify reduced carbonemission from terrestrial vegetation and to assess its possible conversion of emitted VOC into secondary products(gases and aerosols). During these experiments, first attempts were also made to quantify the fluxes of biogenic VOCby REA. These preliminary data have been recently complemented with those collected in the LBA-CLAIRE 2001 andLBA-CARBONSINK field studies performed in the tropical rain forest near Manaus. As a part of these projects, VOCfluxes were measured during the dry season (July 2001) using a REA system installed in the K34 tower located insidethe ZF2 reserve managed by INPA: More than two weeks of data were collected. For some of them diel trends werefollowed. Data confirmed the preliminary observations made during the wet season. Isoprene was the dominantcomponent even though the emission of monoterpenes was not negligible (30-40% of reduced carbon emission).The relationship between carbon emitted as VOC and carbon fixed from photosynthetic activity will be presented anddiscussed.