Center for Engineering, Modelling and Applied Social Sciences, Federal University of ABC, Santo Andre, SP, Brazil; Center for Limnology, University of Wisconsin-Madison, Madison, WI, USA.
Departamento de Hidráulica e Saneamento, Escola de Engenharia de São Carlos, Universidade de São Paulo, São Carlos, SP, Brazil.
Sci Total Environ. 2022 Oct 20;844:157238. doi: 10.1016/j.scitotenv.2022.157238. Epub 2022 Jul 8.
Tropical streams have been intensively impacted by agricultural activities. Among the most important agricultural activities in Brazil, sugarcane production represents a large impact for economic development and for environmental conditions. Permeating sugarcane fields, several headwater streams can be affected by sugarcane cultivation, in special, aquatic biogeochemical cycles because of the deforestation, fertilization, crop residues and higher temperatures in the tropics. In this study, we analyzed the effects of sugarcane cultivation on methane fluxes and concentrations, assuming that carbon cycles are influenced by agricultural activities in headwater streams. Our study aimed to (1) measure methane fluxes and concentrations in tropical streams located in Southeastern Brazil, (2) Analyze whether seasonal cycles influence methane fluxes and concentrations, (3) Evaluate the influence of sugarcane cultivation on methane fluxes and (4) Analyze the association between water chemistry in the methane concentrations in tropical streams. We found mean fluxes of CH of 0.280 mmol m d, with higher fluxes during the summer and in streams draining preserved catchments. The average CH concentrations were 0.695 μmol L, with higher values during the summer and in streams draining preserved catchments. Methane concentrations in the studied streams was influenced by dissolved oxygen (negatively), dissolved organic carbon (negatively), water velocity (positively) and conductivity (negatively). Methane concentrations were significantly higher than concentrations found in Temperate Grasslands, Savannas & Shrublands and similar to concentrations found in other tropical biomes (excluding Tropical & Subtropical Moist Broadleaf Forests which receives large amounts of organic inputs). We conclude that sugarcane influence methane concentrations and fluxes in tropical streams by reducing the organic matter availability provided by the native vegetation in soil and water.
热带溪流受到农业活动的强烈影响。在巴西最重要的农业活动中，甘蔗生产对经济发展和环境条件具有重要影响。在甘蔗地中，几条源头溪流可能会受到甘蔗种植的影响，特别是在热带地区，由于森林砍伐、施肥、作物残茬和更高的温度，水生生物地球化学循环会受到影响。在这项研究中，我们分析了甘蔗种植对甲烷通量和浓度的影响，假设碳循环会受到源头溪流农业活动的影响。我们的研究旨在：(1)测量位于巴西南部的热带溪流中的甲烷通量和浓度；(2)分析季节性周期是否会影响甲烷通量和浓度；(3)评估甘蔗种植对甲烷通量的影响；(4)分析热带溪流中水质与甲烷浓度之间的关系。我们发现 CH 的平均通量为 0.280mmol m d，夏季和流经保护流域的溪流通量更高。CH 的平均浓度为 0.695 μmol L，夏季和流经保护流域的溪流浓度更高。研究溪流中的甲烷浓度受到溶解氧（负相关）、溶解有机碳（负相关）、水速度（正相关）和电导率（负相关）的影响。与温带草原、稀树草原和灌木丛和其他热带生物群系（不包括热带和亚热带湿润阔叶林，这些生物群系接收大量有机输入）相比，研究溪流中的甲烷浓度明显更高。我们得出结论，甘蔗通过减少土壤和水中原生植被提供的有机物可用性，影响热带溪流中的甲烷浓度和通量。
