Balanços de radiação e energia em área reflorestada com algaroba no seridó do Rio Grande do Norte.

Abstract

The present research was conducted in two areas located near the city of the Serra Negra do Norte - RN. one covered with native vegetation - caatinga (6 0 35 ' 49 " S; 37 ° 14 ' 54 " W) and the other reforested with algaroba (6° 36 ' 08 " S; 37 ° 18 ' 31 , : W). The objective of this study was to compare the radiation and energy balance of the algaroba area with that of the caatinga area, during two extreme seasons: in summer, period of 01 to 31 of October, 1999 (dry period - where the algaroba remains green) and in the rainy period of March 09 to April 08, 2000 (when both the areas were completely green). For this purpose, two micrometeorological towers were built: one of 08 m in the caatinga area and another of 14 m in the algaroba area. The data were acquired with data loggers (Campbell 2IX) programmed to collect data at one second intervals and averaging it over a period of ten minutes. The results showed that, even though the two canopies had very different surfaces in summer, the ratio of the net radiation (Rn) to the global solar radiation (K.4-), piactically didn't show any difference: in the dry period over the caatinga and algaroba, Rn represented 76.0 and 77.0% of K l respectively, and during the rainy period the ratios were 77.1 and 78.3%. The increase in humidity of the soil in the algaroba area during the rainy period, contributed to the decrease in albedo. The latent heat flux in the dry period represented 96.7 and 104.2% of the net radiation over the caatinga and algaroba, respectively, and in the rainy period 84.5 and 94.2%. There was contribution of energy due to advection of sensible heat during whole dry period, over both the areas. The regressions between the net radiation and global solar radiation and between the net radiation and the latent heat flux, for the two periods studied, presented large correlation coefficients.