Impactos da substituição da mata Atlântica por canavial no balanço de ondas longas e sua variabilidade sazonal no litoral alagoano

Abstract

The Atlantic Forest is composed of a set of forest formations, of which only 12,4% of the forest that originally existed remains. In Alagoas, the main substitution was for agricultural crops such as sugarcane, where on average 432 thousand hectares are planted, corresponding to approximately 15,55% of the state's area. This degradation causes significant impacts, especially on the Longwave Radiation Balance (BOL), an important variable for climate and microclimate studies, as this balance is intrinsically related to the thermal balance and energy exchange between surface and atmosphere. Knowledge of BOL is important for determining the energy exchanges that occur in the surface-atmosphere system. Microclimatic studies are scarce, mainly related to long wave radiation (OL) on Atlantic Forest. Given this, the main objective of this work is to characterize the seasonal variability and the impact of the replacement of Atlantic Forest by sugarcane in the BOL, as well as to verify the influence of micrometeorological variables (precipitation, cloudiness, solar radiation incident on the terrestrial surface (Rg), Atmospheric Longwave Radiation (Ra) and Terrestrial Longwave Radiation (Rs)) over the BOL. Data were collected in an Atlantic Forest (10 ° 00'37 ”S, 36 ° 17'60” W) in Coruripe – AL and a Sugarcane (09º28'03''S, 35º49'49''W) located at the Center for Agricultural Sciences of the Federal University of Alagoas in Rio Largo-AL. Long and short wave radiation measurements were obtained by a model radiometer CNR1 from Kipp and Zonen (Delft, the Netherlands). Precipitation was recorded by a TE 525 rain gauge (Texas Instruments, USA). The study periods at both sites were in the dry season (November-December) and rainy season (May-June), the months with the lowest and highest rainfall records, respectively. After data acquisition and treatment, the atmospheric transmissivity index (Kt) and the descriptive statistics of the data were calculated. In the dry season the precipitation was below or above the normal climate, but had little influence on Rg that was attenuated only on specific days with higher rainfall records. The same thing happened with Ra, but a slight increase. The Rs had a 3,95% increase in the daytime in the replacement of Atlantic Forest with sugarcane. As a result, on average, during the dry season, it impacted a 26,07% decrease in BOL in the daytime and increase in BOL night periods with a 22,99%. In the rainy season the precipitation was also below or above normal and, therefore, influenced the Rg which had a difference of 13,03% between the two sites. But the difference in precipitation did not influence Ra which had a difference of only 1,89% in its average. Already Rs had the impact of deforestation reduced in the rainy season due to lower Rg and canopy growth of sugarcane. Thus, Rs was the main variable that influenced BOL.