## 1 Introduction  
The Brazilian Pampa biome covers an area of roughly 174,000 km\({}^{2}\) and is entirely situated in Rio Grande do Sul state (southern Brazil), corresponding to 63% of the state [1]. Biomes are characterized by its unique vegetation, soil, climate, and wildlife. The Pampa biome is located inside the Pasticzales del Rio de la Plata, which span over 700,000 km\({}^{2}\), covering southern Brazil, Uruguay, and northern Argentina (\(28^{\circ}\) S to \(38^{\circ}\) S, \(50^{\circ}\) W to \(61^{\circ}\) W). This Pasticzales is one of the world's most important temperate and subtropical natural grasslands due to their vast areas and the fact that they harbor a plethora of endemic plant and animal species. The natural landscape of the Brazilian Pampa biome is characterized by gently undulating relief and vegetation consisting of herbaceous plants, with a predominance of summer-growing grasses [2]. Trees are only found near water bodies in most areas. Due to these characteristics, the Pampa has been used for extensive cattle grazing. This economic activity originated with the Spanish Jesuit priests who colonized the region at the end of the seventeenth century [3]. In Brazil, the Pampa is a source of forage for roughly 5.5 million beef cattle. By preserving the natural vegetation, this ecosystem is home to rich biodiversity and formed by about 3000 species of plants, 100 species of mammals, and 500 species of birds [1; 4]. Recent evidence has shown that almost 30% of the natural vegetation in the Brazilian Pampa has been lost in the last two decades, mainly due to agriculture and forestry [5]. Large areas of natural pasture have been converted into soybean fields and eucalyptus afforestation [6]. For example, the annual loss of natural vegetation in the Brazilian Pampa increased from 500 hectares in 2019 to 3000 hectares in 2022 [7], consequently leading to soil degradation and biodiversity loss since these soils have predominantly sandy textures, making them susceptible to water and wind erosion [8]. Society has made great efforts to reduce the loss of natural pastures in the Pampa biome, and one of the alternatives is increasing the economic profitability of the traditional activity of raising animals [9; 10; 11; 3]; this is conducted by improving pasture and cattle management, increasing animal production per area [13]. Another alternative is acknowledging the value of meat produced in the Pampa biome through marketing since traditional production takes place with European beef breeds that produce high-quality meat (e.g., Hereford, Devon, Angus, etc.) and in natural pastures with high plant diversity, thereby contributing to a regional terroir. Additionally, environmental marketing can be employed if such production is neutral or sequesters C, since sustainability is an increasing concern for consumers willing to pay more for eco-friendly products [14]. However, the natural pastures in the Pampa biome have not yet been evaluated to assess whether they are a source of carbon or a carbon sink. Proper pasture management in cattle grazing can lead to carbon sequestration and mitigate greenhouse gas emissions from livestock [15]. Although pasture C exchange can be determined by changes in soil organic carbon stocks, this technique requires long assessment periods and cannot assess C dynamics at seasonal, annual, and interannual scales [16; 17]. Nevertheless, these limitations are overcome by employing the eddy covariance method (EC), which allows one to evaluate C dynamics in shorter periods [18]. This method measures the C fluxes (CO\({}_{2}\) and CH\({}_{4}\)) occurring between the ecosystem and atmosphere at the hectare scale by the covariance between continuous measurements of vertical wind speeds and gas concentrations. The CO\({}_{2}\) flux represents the net exchange due to the respiration of soil, plants, and animals and assimilation by photosynthesis, while the CH\({}_{4}\) flux is due to the enteric emission of cattle and generation/assimilation by soil microorganisms.