Carbon and methane fluxes from typical pasture-based beef cattle production systems in the Southeastern USA.

Grazing lands covers approximately one-quarter of the global land surface and provides critical ecosystem services such as carbon (C) sequestration. In Florida, ~ 2 million hectares of native and cultivated pastures support a robust cattle industry. This 3-yr study evaluated net ecosystem C exchange (CO2 and CH4) in two representative pasture-based beef systems in the Southeastern USA: a native rangeland (low-intensity management) and a cultivated pasture (high-intensity management). The study captured broad climatic variability, including a hurricane event that resulted in prolonged wet conditions after an extended period of drought. Cultivated pasture exhibited significantly higher C uptake, with a mean annual net ecosystem productivity (NEP) of -4.91 ± 1.16 Mg C ha-1 yr-1, compared to -1.75 ± 0.26 Mg C ha-1 yr-1 for the native rangeland. Cumulative NEP over three years was -14.74 Mg C ha-1 for the pasture and - 5.25 Mg C ha-1 for the rangeland. Although methane emissions were considerably higher from the pasture (2.43 vs. 0.16 Mg C-CO2eqv ha-1), they were offset by greater CO₂ uptake, resulting in a more favorable total C balance (-6.26 vs. -3.55 Mg C-CO2eqv ha-1). However, native rangeland exhibited greater stability under climatic extremes, including both drought and hurricane, maintaining consistent NEP and total C balance. These findings underscore the importance of maintaining a mosaic of well-managed pastures and native rangelands. While cultivated pasture offers high productivity and C sequestration potential, native rangelands provide a more stable C sink under climatic extremes. Both systems demonstrated strong potential to mitigate GHG emissions while delivering essential environmental and societal benefits.