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

CO 2 AND ENERGY FLUXES IN AN AMAZONIAN MANGROVE ECOSYSTEMJ.M.N. da Costa 1 , A.C.L. da Costa 2 , J.C.P. Cohen 2 , Y. Malhi 3 , P. Meir 3 , J.Grace 3 , V.M.S.Andrade 2 , R.B.C. Silva 2 , R. F. da Costa 4 , P.J.O.P. de Souza 2 , M.H. Costa 1 , M.L. Ruivo 4and S. Almeida 41) Federal University of Vicosa, Agricultural and Environmental EngineeringDepartment, 36571-000 Vicosa, MG, Brazil. jmncosta@ufv.br2) Federal University of Para, Department of Meteorology3) University of Edinburgh, Institute of Ecology and Resource Management4) Para Museum Emilio GoeldiQuantification of fluxes of carbon dioxide, water vapor and sensible heat, measured on 15selected days, on January 2001, at a mangrove site, near Braganca-PA (1 o 3' S; 46 o 45' W),using the eddy covariance technique are presented. Relevant meteorological variables werealso measured. The dominant mangrove species at Braganca are Avicennia germinans andRhizophora racemosa. The mean midday CO 2 flux at the mangrove site reached a peak of –12.9 µmol.m -2 .s -1 , and the nocturnal CO 2 flux averaged about 4.0 µmol.m -2 .s -1 . At night,wind speed was in average 2.3 m.s -1 , with most of friction velocities values between 0.4and 0.6 m.s -1 . The magnitudes of CO 2 fluxes at the mangrove site were considerably lowerthan the CO 2 fluxes measured at an Amazonian forest site at the Ferreira Penna ScientificStation (ECFPn), in Caxiuana-PA (1° 42’ 30’’ S; 51° 31’ 45’’ W), for the same period. Themean CO 2 fluxes at the forest site reached a peak of about – 20 µmol.m -2 .s -1 , around noon,and the average nocturnal CO 2 flux was about 7 µmol.m -2 .s -1 . The dependence of thedaytime mangrove CO 2 flux on the incident solar radiation was very well established. Thedaily magnitude variations of CO 2 , water vapor and energy fluxes were also examinedbased on the pertinent meteorological variables.