Concentrações e fluxos de dióxido de carbono (CO2) sobre pastagem na região Amazônica

Abstract

Measures off luxes and concentration of Carbon dioxide (CO2) had been carried through in colon of measures, located in an pasture area in Ouro Preto D’Oeste/RO city (Nossa Senhora da Aparecida Farm), whose geographic coordinates are 10°45'S, 62°22'W and 293m above of the mean sea level. The period data-collection was of 04/15 to 05/21/99, characteristic period in the region as Begin of transition between the rainy station and the dries, what made the analyzes of extreme situations possible, with hard rains and without it occurrence. The CO2 release occurred from the pasture to the atmosphere with maximum of 6.53 umol m-2.s-1 during the nigh and a hard CO2 consumption with maximum of 21.04 umol m-2.s-1 during the daylight, the responsible for the consumption due the plants photosyntheses accomplishment, while the nocturnal period the plants and microorganisms breath is responsible for the deceased substance decomposition with consequent CO2 release. The daily average cycle of CO2 concentrations showed a maximum of 532,6 ppmv at 2 o’clock, and minimum at 15 o’clock with 367,4 ppmv (figure 21), where we can relate these values with the meteorological variable. Relative air humidity between 90-100% are related with high values of CO2 concentrations varying between 600-800 ppmv. The Wind speeds below of 1,5 m.s-1 are associates with CO2 concentrations between 350-400 ppmv. The measures of CO2 concentration carried through by LICOR (model Li-6262, Licoln, Nebraska, the USA) underestimate in 5,36% the measures of Tunable Diode Laser Spectrometer (TDLS), in which existed na excellent correlation enter the measures with R2=0,948 in a sample of 279 points. How much to the CO2 flow, for measures below 0umol m-2.s-1 the LICOR measured a lesser CO2 consumption and for measures above 0 umol m-2.s-1 the LICOR measured a lesser CO2 emission when compared to the measures of TDLS. The intention of this study aims at to compare the measures off luxes and CO2 concentration effected by instruments TDLS and LICOR, with emphasis in the determination of the hourly and daily cycles of the fluxes and concentration of CO2, relating them it the cycles of the meteorological variable.