Biotic and abiotic controls in determining exceedingly variable responses of ecosystem functions to extreme seasonal precipitation in a mesophytic alpine grassland

•Responses of a mesophytic Tibetan grassland to extreme precipitation were simulated.•Completely divergent responses for growing season, plant functional types and organs.•Dominating species shift from sedges to forbs exaggerated grassland degradation.•Synergistic effects of soil temperature and water content were key abiotic factors.•Fairly high resilience contributed to the grassland acclimation and stability.