Variabilidade interanual das trocas de energia e CO2 em uma área remanescente do Bioma Caatinga sob condições extremas de precipitação

Abstract

Research focusing on energy, water vapor and CO2 exchanges over the Caatinga Biome is recent. For this reason, there are gaps on this topic that have limited our ability to understand and project interannual and long-term variations in the CO2 cycle in this environment. Thus, the objective of this study was to evaluate the behavior of the energy and CO2 balances of the Caatinga Biome when subjected to extreme precipitation conditions (extreme drought and intense precipitation) using the simulation of the SITE model (Simple Tropical Ecosystem Model) that was developed to study the response of tropical ecosystems to environmental conditions. Meteorological data from the years 2009 (heavy precipitation) and 2012 (extreme drought) from an INMET automatic station were used. Relationships between monthly GPP and NEE values and precipitation were also analyzed. The SITE model had already been previously calibrated for the region, but for our study it was necessary to adjust the calibration due to the extreme climatic values of the chosen years. The results show the effect of precipitation on energy and mass exchanges over the Caatinga, evidenced more strongly in the partitioning of the energy balance and in the CO2 balance. During the year 2009 (Intense precipitation) the portion of Rn converted into LE was almost 6% higher than the values observed during the year 2012 (extreme drought). Regarding CO2, it was found that the Caatinga behaved as a sink, even under extreme drought conditions (2012), whose annual average values were -1.86 µmol m-2 s-1 (2009) and -0.81 µmol m-2 s-1 (2012). Relationships between monthly GPP and NEE values and precipitation were also analyzed. These analyzes revealed that there is an asymptotic relationship between the aforementioned components of the CO2 balance and precipitation. It was evident that both the monthly values of GPP and NEE tend to stabilize from monthly precipitation volumes greater than 200 mm.