Grazing-related disturbance decouples aboveground and belowground responses in the Eurasian meadow steppe

Grazing is among the most pervasive disturbances in grasslands, yet it remains unclear whether the Intermediate Disturbance Hypothesis (IDH), which predicts peak biodiversity at intermediate disturbance, extends from plant to belowground multitrophic communities. Across a grazing-related disturbance gradient in the Eurasian meadow steppe, we show that plant communities followed the IDH, with unimodal responses in diversity, biomass, and stability, whereas soil multitrophic communities followed a different trajectory. Soil multitrophic α diversity was insensitive to disturbance, yet β diversity peaked under moderate disturbance, accompanied by reduced network complexity and a shift toward positive associations, indicating belowground community reorganization consistent with the stress-gradient hypothesis. These contrasting responses were associated with reduced plant-derived carbon subsidies, including lower dissolved organic carbon and a shift toward more recalcitrant dissolved organic matter. Our findings reveal that the IDH does not generalize across trophic compartments, calling for integration of belowground multitrophic dynamics into grassland resilience frameworks under global change.