Amping up soil carbon: soil carbon stocks in California rangelands under adaptive multi-paddock and conventional grazing management

Adaptive multi-paddock (AMP) grazing is gaining attention for its potential to increase soil organic carbon (SOC), yet its efficacy on arid and semi-arid rangelands remains debated. Given the adaptive nature of AMP, on-ranch studies are essential for measuring its applied outcomes. To assess AMP's impact on Mediterranean California rangelands, we collected 1,440 soil samples from four paired AMP and conventional (CONV) grazing sites across northern California. Three AMP ranches had significantly greater SOC stocks in surface soils (17% greater SOC at 0-10 cm), and two had greater SOC stocks to 100 cm (32% greater), compared to CONV ranches. The largest SOC differences occurred in the mineral-associated organic matter fraction, suggesting longer-term SOC storage. While plant community composition did not differ significantly, AMP ranches, on average, had slightly less bare ground, greater live plant cover, and two sites had 82% greater perennial grass cover. These factors may have contributed to SOC differences. Further research is needed to understand site-specific constraints, underlying mechanisms, and SOC changes over time under AMP grazing.