Timing of extreme drought events drives functional trait shifts and plasticity in dominant Inner Mongolian steppe grasses

Extreme droughts are intensifying, and their seasonal timing can reshape plant function. To evaluate such effects, we imposed spring, summer and autumn drought on three dominant steppe grasses (Leymus chinensis, Stipa krylovii, Cleistogenes squarrosa) in Inner Mongolia and measured 12 functional traits. Using a directional plasticity index (positive = higher than control) with univariate and multivariate analyses, we found that summer drought produced the strongest and most coordinated shifts. Leaf‐size traits (leaf area, width) were the most responsive across species, and leaf nitrogen concentration consistently increased in summer. Species strategies diverged: S. krylovii showed positive whole‐plant gains in spring–summer (biomass, coverage) followed by autumn declines in leaf dimensions; C. squarrosa exhibited predominantly negative whole‐plant plasticity (reductions in biomass, coverage, height) with limited compensatory leaf‐level increases; L. chinensis maintained low, near‐zero plasticity with modest summer increases and small spring/autumn structural reductions. Species identity and drought season jointly structured multivariate trait syndromes. Our results highlight that drought timing—not only intensity—governs functional reconfiguration, and that complementary species strategies, together with leaf‐size and LNC indicators, provide season‐aware metrics for monitoring and management to sustain steppe resilience under increasing climatic extremes.