Grazing and Plateau Zokor Disturbance Exert Non-additive Effects on Soil Carbon Pools in Alpine Meadows of the Qinghai-Tibet Plateau

Grazing and plateau zokor ( Eospalax baileyi ) activities constitute critical biotic disturbances influencing soil carbon pool dynamics in the alpine meadows of the Qinghai-Tibet Plateau. However, their synergistic mechanisms remain poorly understood. Through dual-season sampling (July and October), this study utilized linear mixed models (LMM) and structural equation modeling (SEM) to evaluate soil carbon-nitrogen metrics (SOC, TIC, TC, TN) and physicochemical parameters (SBD, pH) across four treatments: undisturbed control (CK), grazing-only (G), zokor-only (Z), and combined disturbances (G×Z). The results revealed that: (1) Grazing effects elevated SOC, TN, and SBD (+15-30%) throughout the soil profile ( p <0.05), while concurrently suppressing TIC concentrations; (2) Zokor dynamics demonstrated seasonal stratification, with rainy-season SOC enrichment in surface soils (0-10 cm) contrasting with dry-season carbon-nitrogen retention in subsurface layers (20-30 cm); (3) Interaction mechanisms exhibited antagonistic suppression of TIC and non-additive responses of SOC and TN, which were potentially mediated by microbial mineralization thresholds. These results delineate the hierarchical regulation of biotic disturbances on soil carbon sequestration and offer mechanistic insights for alpine meadow carbon management under global change scenarios.