[1] Tropical savanna (locally known as cerrado) composes 24% of Brazil and is characterized by high climatic variation; however, patterns of energy exchange are poorly understood, especially for mixed grasslands (locally known as campo sujo). We used eddy covariance to measure latent (L e ) and sensible (H) heat flux of a mixed grassland and linked meteorological and remote sensing data to determine the controls on these fluxes. We hypothesized that (1) seasonal variations in H and L e would be large due to variations in precipitation; (2) ecosystem phenology, estimated using the enhanced vegetation index (EVI), would be the best predictor of seasonal variation in L e ; and (3) cerrado, transitional, and humid evergreen forests would have similar rates of average annual L e despite large seasonal variation in cerrado L e . Our data suggest that campo sujo exhibits large seasonal fluctuations in energy balance that are driven by rainfall and that responses to rainfall pulses are rapid and dynamic, especially during the dry season. Path analysis indicated that temporal variations in the EVI did not significantly affect L e or G c , but this was because all three variables (EVI, L e , and G c ) responded similarly to temporal variations in surface water availability. Compared to other tropical ecosystems, wetter sites had higher rates of L e during the dry season but similar rates during the wet season when water was not limiting. Over annual time periods, average rates of L e increased significantly as average annual rainfall increased, due to dry-season water limitations in the more seasonal tropical ecosystems.

The savanna of Central Brazil (locally known as cerrado) has a long history of land cover change due to human activity. These changes have led to the degradation of cerrado forests and woodlands, leading to the expansion of grass-dominated cerrados and pastures. Thus, the aim of this study was to evaluate the temporal variation in energy flux in areas of degraded, grass-dominated cerrado (locally known as campo sujo) in Central Brazil. The amount of partitioned into H declined as monthly rainfall increased and reached a level of approximately 30% during the wet season, while the amount of partitioned into increased as monthly rainfall increased and reached a level of approximately 60% during the wet season. As a result, H was significantly higher than during the dry season, resulting in a Bowen ratio ( = H/ ) of 3-5, while Le was higher than H during the wet season, resulting in a ≈ 1. These data indicate that the energy partitioning of grass-dominated cerrado is relatively more sensitive to water availability than cerrado woodlands and forests, and have important implications for local and regional energy balance.

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Research involving the thermal soil dynamics of wetland areas has not yet been explored in a way that promotes a deeper understanding of the dynamics of this region. This makes it necessary for further studies to contribute to the understanding of this biome. In the present work, we studied the thermal dynamics of the soil contrasting seasonal conditions in the Vochysia Divergens Forest. The Fourier equation was used to analyze the influence of the thermal conductivity and thermal gradient on the soil heat flux. We determined how variable water content causes the system to behave differently in the four seasons, observing seasonality in soil when completely dry and when completely flooded.

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