Uso do modelo century na dinâmica do carbono de solos do semiárido de Alagoas: cenários climáticos futuros em ambiente irrigado e de sequeiro

Abstract

Land use change, extensive land use and practices involving or not irrigation management are factors that contribute increasingly to soil organic matter quantity and quality (SOM) differential, important for the plant development and a major component for the mitigation of carbon in the atmosphere, one of the gases responsible for the global temperature increase and consequent phenomenon of climate change.In soil organic carbon (SOC) quantification, one of the components of SOM, several methodologies are adopted, among them the prediction of the SOC dynamics through mathematical models, indicating the CENTURY model as one of those that accurately estimate the contents of the SOC. In this context, the present study aimed to evaluate the dynamics of the COS in different soils of Alagoas semiarid, through the CENTURY 4.5 model, adapting and validating the model for the local conditions and simulating the COS dynamics in future scenarios with a rainfed and irrigated environment. The study was carried out with the CENTURY 4.5 model, with input data from three types of soils (Entisols Quartzipsamments, Entisols Psamments and Ultisols) in three municipalities of Alagoas State (Delmiro Gouveia, Pariconha and Inhapi). The study consisted of two stages: Step 1 - Stabilization, calibration and validation of CENTURY for different types of soil and land use systems (native vegetation, agriculture and pasture); and Step 2 - Simulation of future scenarios, considering the following conditions: a) Rainfed agriculture, assuming that there will be no increase in temperature and no increase in atmospheric CO2 concentration; b) rainfed agriculture, assuming that there will be an increase in temperature and an increase in atmospheric CO2 concentration; c) irrigated agriculture, assuming an increase in temperature and an environment rich in CO2. In Step 1, it was necessary to adapt the CENTURY model on SOC estimation, with the literature data. The adaptation was performed in two stages: i) model excution using the literature data; ii) modification of the parameters related to the decomposition rates of the SOC, adapting the model to the edaphoclimatic conditions of the study regions. In Step 2, simulations were carried out in conditions of future climate scenarios, using two climatic models (Eta-HadGem and Eta-MIROC5) and using the average data between the models, with radiative forcing of 4.5 W m-2 (RCP4.5) and 8.5 W m-2 (RCP8.5). According to the data obtained, the model was able to reach its main objectives, being adapted to the climate and soil conditions in the semiarid regions of Alagoas. The model was also able to simulate the dynamics of C in the rainfed and irrigated environment, in the different future climate scenarios, indicating that the dynamics of the SOC was influenced by the soil water management, as well as the climatic conditions.