Tropical pastures are one of the main land uses in Brazil, forming the backbone of the country's beef and milk production chain. Adopting sustainable management practices that increase the productivity of pastoral livestock systems is essential to mitigate environmental impacts and ensure food security. However, eddy covariance studies that contribute to understanding the influence of grazing management strategies on the ability of intensively grazed tropical pastures to absorb carbon remain scarce. Therefore, our main objective was to investigate the dynamics of CO2 and water vapor exchange and biomass production in a tropical C4 grass (Pennisetum purpureum Schum. cv. Cameroon) pasture under intermittent stocking management strategies from March 2021 to June 2023. We found that the pasture acted as a net source of CO2 to the atmosphere in both years studied. The annual NEE was 34 ± 14 g CO2-C m−2 yr−1 in 2021–2022 and 21 ± 12 g CO2-C m−2 yr−1 in 2022–2023. Reco, influenced by rising air and soil temperatures, increased rainfall, and higher incoming solar radiation levels, especially during spring and summer, played a crucial role in this result. The pasture absorbed more CO2, showed higher evapotranspiration, and produced more leaves in the rainy periods when the pasture structure was kept close to the previously established management targets. CO2 losses to the atmosphere prevailed in the dry periods and in wet periods where the pasture structure was far from the optimal limits for elephant grass.

中文翻译：

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巴西东南部热带集约化管理牧场 CO2 交换的季节性模式


热带牧场是巴西的主要土地用途之一，构成了该国牛肉和牛奶生产链的支柱。采用可持续管理实践来提高畜牧系统生产力，对于减轻环境影响和确保粮食安全至关重要。然而，有助于了解放牧管理策略对密集放牧热带牧场吸收碳能力影响的涡度相关研究仍然很少。因此，我们的主要目标是研究 2021 年 3 月至 2023 年 6 月间歇性放养管理策略下热带 C4 草 （Pennisetum purpureum Schum. cv. Cameroon） 牧场的 CO2 和水蒸气交换和生物量产生的动力学。我们发现，在研究的这两年中，牧场都是大气中二氧化碳的净来源。2021-2022 年的年平均排放当值为 34 ± 14 g CO2-C m-2 yr-1,2022-2023 年为 21 ± 12 g CO2-C m-2 yr-1。受空气和土壤温度升高、降雨量增加和入射太阳辐射水平升高的影响，尤其是在春季和夏季，Reco 对这一结果起着至关重要的作用。当牧场结构接近先前设定的管理目标时，牧场吸收了更多的 CO2，表现出更高的蒸散量，并在雨季产生了更多的叶子。CO2 流失到大气中的因素在干旱期和潮湿期普遍存在，因为牧场结构远非象草的最佳极限。