Observações e estimativas de propriedades térmicas do solo sob floresta e pastagem no leste da Amazônia

Abstract

Temperature and heat flux variations in soils, at sites of the Caxiuanã native forest and a natural pasture in Marajó Island, were continuously monitored in the period between December, 2001 and February, 2005. The objective was to compare the thermal responses to the daily heating, of the soils of these two types of ecosystems present in eastern Amazonia, in order to subsidize regional climate models and the evaluation of deforestation effects. Besides the field measurements of the above mentioned variables, at three levels down to 0.50 m depth, this work presents estimates of the heat flux and soil properties such as: thermal diffusivity and conductivity, damping depth and propagation speed of the daily heating pulse, determined by analytical methods. The results showed the seasonal contrast and other significant differences between the responses of the two studied sites, especially regarding the role of the water contents on the vertical temperature profiles of each soil type. The observed fitting between the measurements and the computed values of the variables, indicates the possibility of generalization of the results to other similar ecosystems sites in Amazonia.