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

Soil Temperature and Moisture Variability, Beneath Forest, Pasture and MangroveAreas, in Eastern AmazoniaJosé 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 temperatures down to 50 cm depth, and volumetric moisture content within theupper 30 cm layer of soils, were measured with similar thermistor sonde and soil moisturereflectometer probe sensor systems, beneath natural forest (Caxiuanã), pasture (Soure) andmangrove (Bragança) areas, in Eastern Amazônia. The sites were selected along a 500 kmtransect, parallel to the equador, between latitudes of 0 and 2 degrees south.The climatic regimes at all three monitoring sites were quite similar and regulatedby the passage of the ITCZ over the equator, which determines the transition between theirdrier and rainy seasons. The soils temperature and moisture levels and variability, beforeand after the onset of the rainy season, were analysed considering the observed short waveincident solar radiation flux and pluviommetric precipitation, at each site.At the depths studied, the soil temperatures in general decreased in the sequence :pasture, mangrove and forest. On the other hand, the soil moisture beneath the forest washigh throughout the dry season.The soils vegetation coverage was found to be, the principal agent responsible forthe wide range of soil temperatures variability found among the studied sites.The waterstorage recharging beneath the pasture was intense and abrupt, just after the onset of therainy season. A smooth soil moisture transition was observed beneath the forest.Corresponding author address : Dr. José Ricardo S. de SOUZA.Departamento de Meteorologia - Centro de Geociências- UFPACP. 1611 , Belém Pará Brasil CEP 66075-900.