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

Submitted to: II_ISC_LBA – 2 ND INTERNATIONAL SCIENTIFIC CONFERENCE OF LARGESCALE BIOSPHERE ATMOSPHERE EXPERIMENT IN AMAZÔNIA (LBA),MANAUS, AM, 07-10 JULY, 2002.DROUGHT EXPERIMENT IN EASTERN AMAZON – SOIL CO 2 DYNAMICS INCAXIUANÃ RAINFOREST, AMAZÔNIA, BRAZIL.1 IBW/University of Goettingen, GermanyContact; e-mail: esotta@bigfoot.com2 MPEG/CCTE, Belém, PA, Brazil.Eleneide Doff SOTTA 1 ; Edzo VELDKAMP 1 ; M. L. P. RUIVO 2 .ABSTRACTTemperature and precipitation variations coupled with increases in atmosphericCO 2 concentration may affect terrestrial carbon storage. Forest soils may release of ~1,4Pg of carbon in the first year after 0,5° C temperature increase, with most of the responseoccurring in the tropics 1 . Low rainfall reduces soil microbial and root activity and mayresult in unknown feedback mechanisms in the soil carbon dynamics. The EasternAmazon is susceptible to seasonal drought and the El Niño events can make seasonaldrought effects severe. To advance understanding of forest soil response to low rainfallwe are simulating a drought by excluding rain from the soil of an Eastern Amazon forest,Caxiuanã.Our objective was to find out how soil respiration will be affected by climatechange? Is there a critical value at which small changes in soil moisture strongly affectsoil respiration?The preliminary data on soil respiration did not show any difference betweencontrol (4.4 ± 0.2 µmol CO 2 . m -2 .s -1 , n=10) and treatment plot (4.2 ± 0.2 µmol CO 2 . m -2 .s -1 , n=10) after two months of water exclusion. No significant difference was measured forsoil temperature in control (21.8 ± 0.3 °C) and treatment (21.2 ± 0.3 °C). However soilmoisture had a significant difference, 0.20 ± 0.04 m 3 .m -3 (n=10) for the control and 0.08± 0.02 (n=10) for the treatment.We will report the first six months of soil respiration of the drought experiment.