São Paulo state is the largest sugarcane cultivation area in Brazil and is the largest sugarcane producer in the world. However, the impact of sugarcane cultivation on carbon dynamics in tropical stream ecosystems remains poorly understood. We investigated CO2 emissions and concentrations in streams draining sugarcane fields and native vegetation catchments to elucidate the influence of sugarcane cultivation on CO2 dynamics in streams. Contrary to our hypothesis, streams from native vegetation catchments exhibited greater CO2 emissions and concentrations than those from draining sugarcane fields. This result can be attributed to the soil respiration, which are higher in native vegetation catchments due to higher organic matter inputs. Our findings underscore the significant role of tropical vegetation dynamics in shaping carbon dynamics in freshwater ecosystems and the connections between terrestrial and aquatic ecosystems in headwaters. Additionally, we observed higher CO2 emissions during the summer, attributable to increased temperatures, streamflow, and terrestrial organic matter inputs in soils and streams. The variables influencing CO2 concentrations were pH, conductivity, season, and methane concentration, highlighting the complex interplay of environmental factors. Future research should address critical gaps, including the effects of soil texture and liming on CO2 dynamics, and the quantification of the contributions of methane oxidation to CO2 emissions. Understanding these factors is vital for assessing the impact of sugarcane cultivation on freshwater carbon cycles, particularly in regions such as Brazil, which is a major contributor to global sugarcane production.
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