Multi-scale dynamics of carbon dioxide flux and its environmental drivers in the Pantanal wetland

Abstract. Understanding carbon flux dynamics in tropical ecosystems is crucial for evaluating their role in global climate regulation. This study investigates the temporal variability of the net ecosystem exchange (NEE) of CO2 and its interactions with key meteorological variables in a tropical forest ecosystem of the Pantanal, Brazil. Using high-resolution hourly data from a flux tower, we apply Detrended Fluctuation Analysis (DFA) and Detrended Cross-Correlation Analysis (DCCA) to analyze diurnal to seasonal cycles of NEE, latent heat (LE), sensible heat (H), global radiation (Rg), air and soil temperature (Tair and Tsoil), relative humidity (RH), and vapor pressure deficit (VPD). The results reveal a strong diurnal coupling between solar radiation, temperature, and carbon fluxes, with peak CO2 uptake occurring at midday. A key novel finding is a marked shift to strong anti-persistence in NEE at the weekly scale during the dry season, a pattern supported by concurrent reductions in LE and RH and increases in H and VPD. This highlights that water limitation is a critical driver of carbon release and reveals a previously unidentified regulatory mechanism in the ecosystem's carbon cycle. These findings underscore the sensitivity of carbon dynamics to hydrometeorological conditions and underline the necessity of multi-scale analysis. Uncertainties remain regarding the role of extreme droughts and floods, as well as land-use dynamics, which merit further investigation.