Extreme climate events such as droughts and heat waves are intensifying under climate change, yet their combined effects on plant recovery remain unclear. In a 2-year outdoor mesocosm experiment, we tested how grassland species with contrasting growth strategies recover from summer drought under four warming regimes: ambient, constant warming (+2°C), periodic heat waves (+7°C), and their combination. Experimental communities of native fast- and slow-growing species plus the invasive Solidago canadensis were assessed for above-ground biomass and leaf traits (SLA, LDMC, chlorophyll content, stomatal conductance) at 1 and 4 months post-drought. Biomass fully recovered within 1 month in both growth strategies, but leaf traits showed transient shifts, over-recovery in SLA and under-recovery in LDMC, likely reflecting production of new leaf tissues. These deviations generally returned to control levels by 4 months, regardless of warming treatments. Solidago canadensis exhibited high tolerance to heat and drought, with early biomass and trait recovery, indicating potential for dominance under climate extremes. Biomass recovery was similar across growth strategies, suggesting that growth-related differences play a minimal role in short-term recovery; however, early regrowth was characterized by contrasting trait shifts. Such lagged trait recovery, combined with rapid invasive recovery, suggests potential for longer-term shifts in grassland composition and function. We recommend that incorporating trait-based recovery dynamics is essential for predicting ecosystem stability under compound climate extremes.
