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

CO2 FLUXES OVER PANTANAL REGION UNDER DRY AND FLOODCONDITIONSPlinio Alvalá 1 , Celso von Randow 2,* , Antonio Manzi 2 , Amaury de Souza 31 Laboratório de Ozônio, Instituto Nacional de Pesquisas Espaciais2 Centro de Previsão de Tempo e Estudos Climáticos, Instituto Nacional de PesquisasEspaciais (CPTEC/INPE)3 Departamento de Física, Universidade Federal do Mato Grosso do Sul* Corresponding author: Celso von Randow, CPTEC/INPE, Rod. Pres. Dutra, km 40,Cachoeira Paulista, SP, 12630-000e-mail: randow@cptec.inpe.brABSTRACTThe Pantanal area, covering a large part of the center-western region of Brazil, ischaracterized by a strong seasonality throughout the year, with quite dry periods in thedry season and frequently flooded areas at the wet season. In May and June 2001, and inthe period from late November 2001 to April 2002, turbulent fluxes of carbon dioxide(CO 2 ) were measured at the micrometeorological tower of IPE project, using the eddycovariance technique. During the transition period from wet to dry season, the dailyaverage net ecosystem exchange (NEE) rate ranged from a sink of –1.0 ± 0.5 gC/m 2 /day in May to a situation close to the balance in June, with NEE of 0.1 ± 0.9 gC/m 2 /day. In the wet season, just before the flooding of the area around the tower,which happened on December 17, 2001, the daily NEE rate observed was –0.6 ± 1.1 gC/m 2 /day (carbon fixation). With a water layer of about 0.5 m height, the surface turnedinto a source of carbon, presenting a NEE average rate of +1.1 ± 0.5 g C/m 2 /day. Thiscondition lasted about 30 days, resulting on a carbon release of about 300 kg C / m 2 .After this period of large emission of carbon dioxide, the daily NEE rates were close tozero (daily uptake offset by nighttime losses) after some cold front passages whenemissions were lower and the water layer started to reduce. However, still there weredays with large emissions, leading to a release of about 50 kg C / m 2 on the next 30days. The daily NEE rates turn to negative values after that and the surface turns back toa sink of CO2, as the water layer dries out.