ALEXANDRE MANIÇOBA DA ROSA FERRAZ JARDIM, UFRPEJOSÉ EDSON FLORENTINO DE MORAIS, UFRPE, Serra Talhada, PELUCIANA SANDRA BASTOS DE SOUZA, UFRPE, Serra Talhada, PEFABIO RICARDO MARIN, USPMAGNA SOELMA BESERRA DE MOURA, CPATSALEONOR PATRICIA CERDEIRA MORELLATO, UNESP, Rio Claro, SPABELARDO ANTÔNIO DE ASSUNÇÃO MONTENEGRO, UFRPEJEAN PIERRE HENRY BALBAUD OMETTO, INPEJOÃO L. M. P. DE LIMA, MARE—Marine and Environmental Sciences Centre, ARNET – Aquatic Research Network, Department of Civil Engineering, Faculty of Sciences and TechnologyJOSÉ CARLOS BATISTA DUBEUX JÚNIOR, North Florida Research and Education Center, University of FloridaTHIERES GEORGE FREIRE DA SILVA, Department of Agricultural Engineering, Federal Rural University of Pernambuco, Serra Talhada, PE.2026-07-07http://hdl.handle.net/123456789/503701Anthropogenic disturbances directly influence environmental processes and increase the concentration of carbon (C) in the atmosphere. Here, we compare the differences in the seasonality of the balance of carbon, energy, and radiation, as well as seek to identify the interrelationships between these environmental variables and their impact on the growth of Opuntia cactus. Data were acquired from an eddy covariance flux tower over a cactus crop agroecosystem (2019–2021) in the Brazilian semi-arid region. In addition, we use plant growth rates, carbon and nutrient stocks, evapotranspiration (ET) and water use efficiency (WUE), and radiation (RUE). We show that the closure of the surface energy balance was 71%, although there are minimal fluxes of available energy lost (29%) by unquantified processes. At all seasons, the highest net ecosystem CO2 exchange (NEE) rate was between 11:00–13:00 (�� 5.75 μmol m�� 2 s�� 1). During the dry and wet-dry season, there was the lowest daily gross primary productivity (GPP) (2.5 μmol m�� 2 s�� 1) and net radiation—Rn (217.97 W m�� 2). Ecosystem respiration was more expressive during the wet season (2.41 μmol m�� 2 s�� 1), and maximum diurnal value of 2.65 μmol m�� 2 s�� 1. Furthermore, the latent heat flux was higher during the wet season (114.68 W m�� 2) and lowered in the dry season (9.39 W m�� 2). The net assimilation rate showed higher values during the dry-wet transition. The dry season presented higher nutrient use efficiency and WUE (14.77 g m�� 2 mm�� 1). The highest ET occurred during the wet season (227 mm), and RUE was 81.48% higher than in the dry season. Overall, the cactus was a potential C sink during the three years of assessment (NEE: �� 377 g C m�� 2 year�� 1; GPP: 881 g C m�� 2 year�� 1). The results help us to understand that most of the Rn energy is used in the sensible heat flux (58% ratio).openAccessOpuntia cactusAgroecossistemaConcentração de carbonoCovariância de redemoinhoCacto de sequeiroTroca líquida de CO2Planta CAMSemiáridoSumidouro ou fonte de carbonoCaatingaCarbonoCactoEcossistemaEvapotranspiraçãoOpuntiaEvapotranspirationArtigo de periódico