Modeling the Effects of Livestock Rotation Frequency on Forage Production and Soil Carbon Using a Spatially Explicit Grazing Distribution

Livestock grazing strongly influences terrestrial ecosystems and plays a critical role in carbon dynamics, with outcomes highly dependent on grazing management. High-frequency rotation (HFR) grazing has been proposed to reduce the uneven spatial grazing distribution commonly associated with low-frequency rotation (LFR) grazing, potentially altering forage production and soil organic carbon (SOC). However, most ecosystem models used to assess SOC dynamics do not explicitly represent uneven grazing distribution, limiting their ability to evaluate management effects. To address this limitation, we enhanced the MEMS ecosystem model by incorporating a spatially explicit grazing distribution through the introduction of discrete spatial units and key environmental drivers, including forage availability and quality, and distance to water. Using remote sensing-derived enhanced vegetation index (EVI), we verified the simulated grazing distribution using an experimental rangeland site in Oklahoma. We tested the model’s sensitivity to grazing frequency under different management (stocking rate, timing, and duration) and climate (typical, dry, and wet) scenarios. Our results indicate that uneven grazing distribution leads to distinct spatial patterns of forage production and SOC. Notably, significant differences in field-average production and SOC between HFR and LFR emerged under heavy intensity grazing, where HFR sustained higher SOC stocks and productivity than LFR. These findings highlight the importance of spatially explicit modeling in understanding grazing distributions, suggesting that HFR grazing may be beneficial mostly under heavy intensity grazing. Our study offers actionable guidance for designing future grazing management experiments to address this critical knowledge gap and advance carbon management strategies.