Differential Responses of Flowering Functional Groups to Species Loss Altered Community Flowering-Date Synchrony and Reduced Temporal Stability in an Alpine Meadow

Understanding how biodiversity loss alters flowering patterns in plant communities is crucial for predicting species coexistence, community dynamics, and ecosystem functioning under global change. Using phenological records from 2017 to 2023 within a 12-year species removal experiment in a Tibetan alpine meadow, we examined responses of early-, mid-, and late-flowering functional groups and changes in community flowering-date synchrony and temporal stability. Species removal tended to advance first flowering but more consistently delayed last flowering and extended flowering duration, with differential responses among flowering functional groups leading to contrasting changes in community flowering-date synchrony: forb removal decreased synchrony, whereas grass and dominant-sedge removal increased synchrony. Forb removal, grass removal, and proportional thinning also reduced the temporal stability of community first and last flowering dates. Declining species richness and lower richness stability were associated with increased phenological divergence among flowering functional groups, which predicted 88% and 85% of the variation in community-wide dispersion of first and last flowering dates, respectively. Greater dispersion was associated with lower temporal stability only for first flowering. These findings suggest a temporal-niche pathway through which species loss may reorganize community flowering phenology and help predict long-term changes in floral resource availability and ecosystem functioning in alpine meadows.