The recovery of degraded pastures and the increase in their capacity for storing carbon is a key strategy in Brazil's commitment to meeting its Nationally Determined Contribution (NDC) to the international effort to halt global warming. Here we report the fluxes of CO2, N2O and CH4 gasses and their balances, obtained by the eddy covariance method, from a representative pasture area in southeast Brazil. The measurements covered more than five years, starting with the old degraded pasture, covering the renewal process and then the re-establishment of pasture. The latter only received nitrogen fertilization once after the renewal – the common practice. The net ecosystem carbon balance (NECB), which considered the sum of the net ecosystem exchange (NEEpasture) of CO2 and methane (FCH4pasture) without the cattle respiration and enteric fermentation, as well the export/import of carbon by grazing and as feces (stocking rates of 1.8 to 3.3 AU ha−1), was positive in the old pasture (236 ± 104 g CO2m−2 year−1) representing a source to the atmosphere, but a sink (negative) during the first year of the renewal (-1603 ± 122 g CO2m−2 year−1) when it was fertilized and the recorded rainfall was normal. In the following two years it was neutral (77 ± 93 and 5 ± 100 g CO2m−2 year−1), partially a consequence of the lower rainfall received. In the fourth year it was a sink again (-736 ± 131 g CO2m−2 year−1). On average the cumulative fluxes of CH4 (42 ± 19 g CO2 eq. m−2 year−1) without the animals’ enteric fermentation and N2O (20 ± 10 g CO2 eq. m−2 year−1) were small and positive, being offset by the net carbon gain. The NECB for this site covering the period of measurements was an overall source of 671 ± 254 g CO2m−2.

中文翻译：

---

在巴西东南部更新的牧场中观察到的温室气体涡流协方差通量


恢复退化牧场并提高其碳储存能力是巴西承诺实现其对遏制全球变暖的国际努力的国家自主贡献（NDC）的一项关键战略。在这里，我们报告了巴西东南部代表性牧场地区的 CO2、N2O 和 CH4 气体通量及其平衡，通过涡流协方差方法获得。测量历时五年多，从退化的老牧场开始，到更新过程，再到牧场的重建。后者在更新后只接受一次氮肥——这是常见的做法。净生态系统碳平衡（NECB），考虑了没有牛呼吸和肠道发酵的二氧化碳和甲烷（FCH4pasture）的净生态系统交换（NEEpasture）的总和，以及通过放牧和粪便排出/进口的碳（载畜率为 1.8 至 3.3 AU ha−1)，在旧牧场为正值（236 ± 104 g CO2m−2 年−1），代表大气源，但在更新的第一年为汇（负值） (-1603 ± 122 g CO2m−2year−1) 施肥时记录的降雨量正常。在接下来的两年里，它是中性的（77±93和5±100克CO2m−2年−1），部分原因是降雨量减少。第四年又出现了汇（-736 ± 131 g CO2m−2 年−1）。平均而言，没有动物肠道发酵的 CH4（42 ± 19 g CO2 eq. m−2year−1）和 N2O（20 ± 10 g CO2 eq. m−2year−1）的累积通量较小且为正值，被净碳增量抵消。该站点覆盖测量期间的 NECB 总来源为 671 ± 254 g CO2m−2。