Short-duration, managed grazing system increases net ecosystem carbon uptake and water use efficiency on a working ranch

Grasslands are globally significant carbon (C) sinks, but data quantifying how multi-paddock, managed grazing sytems alter ecosystem fluxes and the annual C budget are limited. We hypothesized a high-intensity (150 cow-calf pair), short-duration (2 days), rotational grazing system targeting 50% utilization, followed by extended rest and recovery, could improve net C uptake (net ecosystem production; NEP), water use efficiency (WUE), and the net amount of C sequestered (C budget) by the ecosystem annually. We quantified water and C fluxes over two full years using eddy covariance and field-based measurements of C removed by grazers on a U.S. northern prairie working cattle ranch. Managed grazing nearly doubled annual NEP for both yearly cycles, as compared to ungrazed control. The net amount of C sequestered under managed grazing reached 1.01 and 0.37 Mg C ha⁻¹ yr⁻¹ in the first and second cycle, respectively—53% and 23% greater than ungrazed control. Grazing initially decreased leaf area index and daily C uptake, but the ecosystem gradually recovered through autumn, with elevated C uptake and resource-use efficiencies. Our findings demonstrate that improvements in grassland C uptake, C sequestration, and allocation of water to production can be achieved through inclusion of grazers and adaptive grassland management.