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.CHARACTERISTICS OF VARIABILITY IN THE SOIL WATERVOLUMETRIC CONTENTS IN CAXIUANÃ RAINFOREST, AMAZÔNIA,BRAZIL.Rafael FERREIRA da COSTA 1 ; Patrick MEIR 2 ; P.J. OLIVEIRA 2 ; R. B. SILVA 3 ; A. C. L. COSTA 3 ;Y. MALHI 2 ; J. M. N. COSTA 4 ; M. L. P. RUIVO 1 and V. ANDRADE 3 .1 MPEG/CCTE, Belém, PA, Brazil.Contact; e-mail: rfcosta@museu-goeldi.br or rfcostampeg@bol.com.br2IERM/UEdin, Edinburgh, Scotland, UK.3 UFPA, Belém, PA, Brazil.4 UFV, Viçosa, MG, Brazil.ABSTRACTThe Caxiuanã National Forest, with an area of 330,000 hectares (1º43’ S; 51º32’W) belonging to the Museu Paraense Emílio Goeldi (MPEG), far from approximately400 km West of city of Belém, Para, Brazil. The experimental site was separated in threedifferent areas; Plot A, Plot B (with 1 ha each) and Plot T, where is installed themicrometeorological LBA’s tower. In the Plots A and B were made four trenches in eachone (with 1x2x5 meters width/length/depth each) where were installed the soil waterprobes, in two sides, at different levels, from surface to 5 meters deep. The Plot B isbeing used for the ESECAFLOR Experiment, and was covered by plastics panels, tosimulate a drought period in the forest for analysis of them influences. In the Plot T weremade two trenches like the others. The preliminary analysis indicated large variation inthe soil water volumetric contents among the plots A, B and T. The soils at Caxiuanã arewell drained to moderately drained, sandy to clay, acidic and poor of nutrients, with a pHranging from highly acidic (3.5) to moderately acidic (5.5). For the soil water contentmeasurements was used the TDR (Time-Domain Reflectometer) system, using Tektronic1502B/C equipment with WATTDR 3.11 software (Waterloo Centre for GroundwaterResearch). Monthly measurements are being made since September’2000. The Plot Ashowed values between 7.8% (Oct’2001) and 15.3% (May’2001). Plot B registered 6.5%(Oct’2001) and 15.7% (Jun’2001). The plot T showed 19.5 and 20% to Nov’2000 andNov’2001 respectively for minimums values and 27.3% (Mar’2001), 29.2% (Mar’2002).After to closed, in December of 2001, the plastic cover in the Plot B, this Plot reached–35.1% soil water content, when compared with Plot A. This characterisation isimportant for assessment of the soil in view of the expected changes in soil characteristicsduring and after the ESECAFLOR Experiment. It is very important to assess the impactof drought on water balance, carbon dioxide fluxes and carbon stock in the soil toinvestigate future sustainability of the Amazon forest ecosystem.Key words: Soil Water Content, Amazônia and Forest.