Soil carbon fraction responses to grazing intensity and texture in a semiarid grassland

Soil organic carbon (SOC) in grasslands plays a central role in global carbon cycling, yet how long‐term grazing intensity (GI) and soil texture interact to affect SOC fractions remains unclear. We evaluated SOC partitioning into particulate organic matter carbon (POM‐C) and mineral‐associated organic matter carbon (MAOM‐C) after more than 80 years of cattle grazing in a semiarid mixed‐grass prairie in South Dakota. Soils (0–30 cm) were sampled across six pastures managed at high, medium, and low grazing intensities and stratified by texture (clay loam vs. silty clay). Bayesian mixed‐effects models accounting for pasture‐level variation revealed that while GI did not significantly affect MAOM‐C stocks, surface POM‐C (0–7.5 cm) was significantly higher under high and medium grazing in clay loam soils, with no significant grazing effects observed in silty clay soils. Across depths, POM:MAOM ratios were elevated in coarser soils and under heavier grazing, suggesting greater POM‐C accrual but also increased vulnerability to loss. Correlations showed only modest coupling ( r ≈ 0.3, p  < 0.001) between POM‐C and MAOM‐C, underscoring that these pools respond to distinct processes. Overall, our findings indicate that soil texture strongly modulates grazing effects on carbon fractions, with coarse‐textured soils favoring POM accumulation and finer soils maintaining more stable MAOM stocks. These results highlight the importance of accounting for soil physical context when evaluating grazing as a tool for enhancing grassland carbon sequestration.