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

Thermal and Hydric Behavior of Soil Beneath Pasture, in Marajó IslandJosé Ricardo S. de Souza, Julia C. P. Cohen, Antônio C.L. da Costa, Zilurdes F. LopesDepartment of MeteorologyFederal University of Pará, Belém, Brazile-mail : jricardo@ufpa.brABSTRACTSoil temperature and moisture were monitored within the upper 30 cm layer, beneatha natural pasture area in Soure, Marajo Island, Pará, Brazil. The data collected during an 18month observation period (Aug/2000 up to Jan/2002) inclued also the short wave incomingsolar radiation flux and pluviommetric precipitation, at that experimental site. Anautomatic station was used, with thermistor sonde, soil moisture reflectometer probe,silicon photodiode pyranometer and tipping bucket rain gage sensor systems.The results presented, include the monthly averages, hourly behavior and respectiveextremes, for those soil physical variables. Selected case studies are presented, to showsudden temperature falls and/or moisture recharging, associated with severe rainshowerevents or the transition between the local dry and rainy seasons.The soil temperatures observed at 20 cm depth were nearly 3 ºC above those measuredat the same depth, beneath other pasture sites in the Amazon Region (Souza et. al; 1996).This may be attributed to differences in soil composition and climatic conditions among thesites considered. The soil moisture values were within the range observed for shallowdepths, at other pasture sites, in Marabá, Manaus and Ji-Paraná (Hodnett et. al; 1996).The soil parameters measured, will be used to initialize regional weather andclimate numerical models, and serve as reference for comparisons with other ongoingexperiments, in soils beneath native forest and mangrove areas, as part of the AmazonianLarge Scale Biosphere – Atmosphere Experiment (LBA).Corresponding author address : Dr. José Ricardo S. de SOUZA.Departamento de Meteorologia - Centro de Geociências- UFPACP. 1611, Belém, Pará, Brasil CEP 66075-900.